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Sample records for magnesia-supported pd clusters

  1. Structure and Mobility of Metal Clusters in MOFs: Au, Pd, and AuPd Clusters in MOF-74

    DEFF Research Database (Denmark)

    Vilhelmsen, Lasse; Walton, Krista S.; Sholl, David S.

    2012-01-01

    is just as important for nanocluster adsorption as open Zn or Mg metal sites. Using the large number of clusters generated by the GA, we developed a systematic method for predicting the mobility of adsorbed clusters. Through the investigation of diffusion paths a relationship between the cluster......Understanding the adsorption and mobility of metal–organic framework (MOF)-supported metal nanoclusters is critical to the development of these catalytic materials. We present the first theoretical investigation of Au-, Pd-, and AuPd-supported clusters in a MOF, namely MOF-74. We combine density...... functional theory (DFT) calculations with a genetic algorithm (GA) to reliably predict the structure of the adsorbed clusters. This approach allows comparison of hundreds of adsorbed configurations for each cluster. From the investigation of Au8, Pd8, and Au4Pd4 we find that the organic part of the MOF...

  2. The effect of gamma-Al{sub 2}O{sub 3} support on the NO adsorption on Pd{sub 4} cluster

    Energy Technology Data Exchange (ETDEWEB)

    Prates, Letícia M.; Cruz, Maurício T.M., E-mail: cruzmtm@uerj.br [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Departamento de Química Geral e Inorgânica; Ferreira, Glaucio B.; Carneiro, José W.M.; Almeida, Wagner B. de [Universidade Federal Fluminense (UFF), Niterói, RJ (Brazil). Departamento de Química Inorgânica; Carauta, Alexandre N.M. [Fundação Técnico-Educacional Souza Marques, Rio de Janeiro, RJ (Brazil); Correia, Julio C.G. [Centro de Tecnologia Mineral (CETEM), Rio de Janeiro, RJ (Brazil)

    2016-07-01

    The effect of γ-Al{sub 2}O{sub 3} support on the NO adsorption on Pd{sub 4} clusters was investigated by means of density functional theory (DFT) calculations. Pd4 adsorbed on γ-Al{sub 2}O{sub 3} (represented by a Al{sub 14}O{sub 24}H{sub 6} cluster) changes its preferential geometry from tetrahedral to a distorted planar structure. The alumina support promotes a higher dispersion in the palladium catalyst and reduces the NO adsorption energy to - 25.6 kcal mol{sup -1} (computed at B3LYP/LANL2DZ/6-311+G(d)), in close agreement with the experimental value of - 27.2 kcal mol{sup -1}. On the bare planar Pd{sub 4} cluster the NO molecule adsorbs in a bridge arrangement, with adsorption energy of - 41.2 kcal mol{sup -1}. Adsorption on the tetrahedral Pd{sub 4} cluster occur preferentially in an atop mode, with adsorption energy of - 30.6 kcal mol{sup -1}. Charge density analysis show that the electron flux between the NO molecule and Pd{sub 4} depends on the adsorption form, with back-donation being stronger in the bridge adsorption mode. (author)

  3. Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

    KAUST Repository

    Song, Hyon Min

    2015-01-13

    The synthesis and magnetic behavior of matrix-supported Pd and PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal columnal packing is selected as a template, and the impregnation method with thermal annealing is used to obtain supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary to the general belief that smaller Pd NPs or cluster size particles have higher magnetization, matrix-supported Pd NPs in this study maintain the highest magnetization with room temperature ferromagnetism when the size is the largest. (2) Twin boundaries along with stacking faults are more pronounced in these large Pd NPs and are believed to be the reason for this high magnetization. Similarly, supported PdO NPs were prepared under air conditions with different heating rates. Their phase is tetragonal (P42/mmc) with cell parameters of a = 3.050 Å and c = 5.344 Å, which are slightly larger than in the bulk phase (a = 3.03 Å, c = 5.33 Å). Faster heating rate of 30 °C/min also produces larger particles and larger magnetic hysteresis loop, although magnetization is smaller and few twin boundaries are observed compared to the supported metallic Pd NPs.

  4. The effect of CNTs on structures and catalytic properties of AuPd clusters for H2O2 synthesis.

    Science.gov (United States)

    Yang, Hua-feng; Xie, Peng-yang; Yu, Hui-you; Li, Xiao-nian; Wang, Jian-guo

    2012-12-28

    The structures and catalytic properties of AuPd clusters supported on carbon nanotubes (CNTs) for H(2)O(2) synthesis have been investigated by means of density functional theory calculations. Firstly, the structures of AuPd clusters are strongly influenced by CNTs, in which the bottom layers are mainly composed of Pd and the top layers are a mix of Au and Pd due to the stronger binding of Pd than Au on CNTs. Especially, it is found that O(2) adsorption on the Pd/CNTs interfacial sites is much weaker than that on the only Pd sites, which is in contrast to transition metal oxide (for example TiO(2), Al(2)O(3), CeO(2)) supported metal clusters. Furthermore, Pd ensembles on the interfacial sites have far superior catalytic properties for H(2)O(2) formation than those away from CNT supports due to the changes in electronic structures caused by the CNTs. Therefore, our study provides a physical insight into the enhanced role of carbon supports in H(2)O(2) synthesis over supported AuPd catalysts.

  5. Thermodynamics of Pore Filling Metal Clusters in Metal Organic Frameworks: Pd in UiO-66

    DEFF Research Database (Denmark)

    Vilhelmsen, Lasse; Sholl, David S.

    2012-01-01

    Metal organic frameworks (MOFs) have experimentally been demonstrated to be capable of supporting isolated transition-metal clusters, but the stability of these clusters with respect to aggregation is unclear. In this letter we use a genetic algorithm together with density functional theory...... calculations to predict the structure of Pd clusters in UiO-66. The cluster sizes examined are far larger than those in any previous modeling studies of metal clusters in MOFs and allow us to test the hypothesis that the physically separated cavities in UiO-66 could stabilize isolated Pd clusters. Our...... calculations show that Pd clusters in UiO-66 are, at best, metastable and will aggregate into connected pore filling structures at equilibrium....

  6. Dynamics diffusion behaviors of Pd small clusters on a Pd(1 1 1) surface

    International Nuclear Information System (INIS)

    Liu, Fusheng; Hu, Wangyu; Deng, Huiqiu; He, Rensheng; Yang, Xiyuan; Lu, Kuilin; Deng, Lei; Luo, Wenhua

    2010-01-01

    Using molecular dynamics, nudged elastic band and modified analytic embedded atom methods, the self-diffusion dynamics properties of palladium atomic clusters up to seven atoms on the Pd (1 1 1) surface have been studied at temperatures ranging from 300 to 1000 K. The simulation time varies from 20 to 75 ns according to the cluster sizes and the temperature ranges. The heptamer and trimer are more stable than the other neighboring clusters. The diffusion coefficients of the clusters are derived from the mean square displacement of the cluster's mass-center, and the diffusion prefactors D 0 and activation energies E a are derived from the Arrhenius relation. The activation energy of the clusters increases with the increasing atom number in the clusters, especially for Pd 6 to Pd 7 . The analysis of trajectories shows the noncompact clusters diffuse by the local diffusion mechanism but the compact clusters diffuse mainly by the whole gliding mechanism, and some static energy barriers of the diffusion modes are calculated. From Pd 2 to Pd 6 , the prefactors are in the range of the standard value 10 −3  cm 2  s −1 , and the prefactor of Pd 7 cluster is 2 orders of magnitude greater than that of the single Pd adatom because of a large number of nonequivalent diffusion processes. The heptamer can be the nucleus in the room temperature range according to nucleation theory

  7. Direct atomic imaging and density functional theory study of the Au24Pd1 cluster catalyst.

    Science.gov (United States)

    Bruma, A; Negreiros, F R; Xie, S; Tsukuda, T; Johnston, R L; Fortunelli, A; Li, Z Y

    2013-10-21

    In this study we report a direct, atomic-resolution imaging of calcined Au24Pd1 clusters supported on multiwall carbon nanotubes by employing aberration-corrected scanning transmission electron microscopy. Using gold atoms as mass standards, we confirm the cluster size to be 25 ± 2, in agreement with the Au24Pd1(SR)18 precursor used in the synthesis. Concurrently, a Density-Functional/Basin-Hopping computational algorithm is employed to locate the low-energy configurations of free Au24Pd1 cluster. Cage structures surrounding a single core atom are found to be favored, with a slight preference for Pd to occupy the core site. The cluster shows a tendency toward elongated arrangements, consistent with experimental data. The degree of electron transfer from the Pd dopant to Au is quantified through a Löwdin charge analysis, suggesting that Pd may act as an electron promoter to the surrounding Au atoms when they are involved in catalytic reactions.

  8. Defluoridation of water using magnesia/chitosan composite

    Energy Technology Data Exchange (ETDEWEB)

    Sairam Sundaram, C. [Department of Science and Humanities, Karaikal Polytechnic College, Karaikal 609609, Puducherry (India)], E-mail: sairam_adithya@yahoo.com; Viswanathan, Natrayasamy [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Tamilnadu (India)], E-mail: natrayasamy_viswanathan@rediffmail.com; Meenakshi, S. [Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Tamilnadu (India)], E-mail: drs_meena@rediffmail.com

    2009-04-30

    Magnesia (MgO) is a well-known adsorbent showing extremely high defluoridation capacity (DC). In order to over come the limitations of MgO for field applications, an attempt has been made to modify magnesia with abundant biomaterial chitosan to form magnesia/chitosan (MgOC) composite in a usable form and its merits over conventional magnesia and raw chitosan is established. Removal of fluoride from aqueous solution with MgO and MgOC composite was studied with batch equilibrium experiments. At equilibrium, MgOC composite has a DC of 4440 mg F{sup -}/kg while for magnesia it is only 2175 mg F{sup -}/kg. The physicochemical properties of the synthesised MgOC composite were analyzed with FTIR and SEM with EDAX studies. The equilibrium data were fitted with isotherm and kinetic models. Thermodynamic parameters viz, {delta}G{sup o}, {delta}H{sup o} and {delta}S{sup o} were calculated to understand the nature of sorption. Field studies were carried out to find the suitability of these sorbents at field conditions.

  9. The Effect of Alumina and Magnesia Supported Germanium Nanoparticles on the Growth of Carbon Nanotubes in the Chemical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    Ghazaleh Allaedini

    2015-01-01

    Full Text Available The effect of alumina and magnesia supported germanium (Ge nanoparticles on the synthesis of carbon nanotubes (CNTs using the chemical vapor deposition (CVD method in atmospheric pressure was investigated. The TEM micrographs confirmed the formation of carbon nanotubes, and the field emission scanning electron microscopy (FESEM analysis suggested a tip-growth mechanism for the grown carbon nanotubes. The X-ray diffraction (XRD pattern indicated a graphitic nature of the carbon nanotubes. The obtained CNTs using Ge nanoparticles supported by MgO resulted in a higher degree of graphitization than the CNTs obtained using Ge nanoparticles supported by Al2O3. Raman spectroscopy analysis of the CNTs confirmed the presence of radial breathing modes (RBM, which verified the formation of CNTs. High frequency Raman analysis demonstrated that the degree of graphitization of the synthesized CNTs using magnesia supported Ge nanoparticles is higher than that of the alumina supported Ge nanoparticles with the values of (ID/IG ratios equal to 0.45 and 0.73, respectively.

  10. Geometric, stability, and electronic properties of gold-doped Pd clusters (Pd{sub n}Au, n = 3~20)

    Energy Technology Data Exchange (ETDEWEB)

    Huan, Hao; Chen, Yan; Wang, Tao; Ye, Xiang, E-mail: yexiang@shnu.edu.cn [Shanghai Normal University, Department of Physics (China); Gu, Xiao, E-mail: gx@cqu.edu.cn [Chongqing University, Department of Applied Physics (China)

    2016-11-15

    The structure, stability, and electronic properties of Pd{sub n}Au (n = 3~20) clusters are studied by density functional theory. The results show that the clusters studied here prefer three-dimensional structures even with very small atom number. It is found that the binding energies of Pd{sub n}Au clusters are higher than the corresponding pure Pd{sub n} clusters with the same atom number. Most Pd{sub n}Au clusters studied here are magnetic with magnetic moments ranging from 1.0 to 7.0 μ{sub B.} The dissociation energies of Pd atoms are lower than the doped gold atom, that is the doped Au atom will increase the mother clusters stability and activity.

  11. Effect of magnesia on properties and microstructure of alkali-activated slag cement

    Directory of Open Access Journals (Sweden)

    Yong-hao Fang

    2011-12-01

    Full Text Available The effect of magnesia burnt at 800-950°C on the properties, especially the shrinkage, of alkali-activated slag cement (AASC was experimentally studied. Experimental results show that, although adding 4%-8% lightly-burnt magnesia may shorten the setting time and slightly reduce the compressive strength of AASC, it can remarkably reduce the shrinkage of AASC. The results also show that the setting time of AASC with a certain amount of magnesia increases with the burning temperature, and that the flexural and compressive strengths of AASC decrease with the increase of the additive amount of magnesia. Generally, the adverse effect of magnesia decreases with the increase of the burning temperature, and the shrinkage-reducing effect of magnesia increases with the additive amount of magnesia. X-ray diffraction (XRD and scanning electron microscopy (SEM analyses show that some magnesia particles in the hardened AASC paste at a 28-d age remained unhydrated, and that the compactness decreased a little as magnesia was added. We can also conclude that magnesia burnt at 850-950°C can be used to reduce the shrinkage of AASC only when its additive amount does not exceed 8%; otherwise, the setting time may be too short, and the flexural and compressive strengths may severely decrease.

  12. Efficient Decarbonylation of Furfural to Furan Catalyzed by Zirconia-Supported Palladium Clusters with Low Atomicity.

    Science.gov (United States)

    Ishida, Tamao; Kume, Kurumi; Kinjo, Kota; Honma, Tetsuo; Nakada, Kengo; Ohashi, Hironori; Yokoyama, Takushi; Hamasaki, Akiyuki; Murayama, Haruno; Izawa, Yusuke; Utsunomiya, Masaru; Tokunaga, Makoto

    2016-12-20

    Decarbonylation of furfural to furan was efficiently catalyzed by ZrO 2 -supported Pd clusters in the liquid phase under a N 2 atmosphere without additives. Although Pd/C and Pd/Al 2 O 3 have frequently been used for decarbonylation, Pd/ZrO 2 exhibited superior catalytic performance compared with these conventional catalysts. Transmission electron microscopy and X-ray absorption fine structure measurements revealed that the size of the Pd particles decreased with an increase in the specific surface area of ZrO 2 . ZrO 2 with a high surface area immobilized Pd as clusters consisting of several (three to five) Pd atoms, whereas Pd aggregated to form nanoparticles on other supports such as carbon and Al 2 O 3 despite their high surface areas. The catalytic activity of Pd/ZrO 2 was enhanced with a decrease in particle size, and the smallest Pd/ZrO 2 was the most active catalyst for decarbonylation. When CeO 2 was used as the support, a decrease in Pd particle size with an increase in surface area was also observed. Single Pd atoms were deposited on CeO 2 with a high surface area, with a strong interaction through the formation of a Pd-O-Ce bond, which led to a lower catalytic activity than that of Pd/ZrO 2 . This result suggests that zero-valent small Pd clusters consisting of more than one Pd atom are the active species for the decarbonylation reaction. Recycling tests proved that Pd/ZrO 2 maintained its catalytic activity until its sixth use. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Density functional calculations on 13-atom Pd12M (M = Sc—Ni) bimetallic clusters

    International Nuclear Information System (INIS)

    Tang Chun-Mei; Chen Sheng-Wei; Zhu Wei-Hua; Tao Cheng-Jun; Zhang Ai-Mei; Gong Jiang-Feng; Zou Hua; Liu Ming-Yi; Zhu Feng

    2012-01-01

    The geometric structures, electronic and magnetic properties of the 3d transition metal doped clusters Pd 12 M (M = Sc—Ni) are studied using the semi-core pseudopots density functional theory. The groundstate geometric structure of the Pd 12 M cluster is probably of pseudoicosahedron. The I h -Pd 12 M cluster has the most thermodynamic stability in five different symmetric isomers. The energy gap shows that Pd 12 M cluster is partly metallic. Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd 12 M cluster. The magnetic moment of Pd 12 M varies from 0 to 5 μ B , implying that it has a potential application in new nanomaterials with tunable magnetic properties

  14. 75 FR 56556 - Certain Magnesia Carbon Bricks From China and Mexico

    Science.gov (United States)

    2010-09-16

    ...)] Certain Magnesia Carbon Bricks From China and Mexico Determinations On the basis of the record \\1... from China and Mexico of certain magnesia carbon bricks, provided for in subheadings 6902.10.10, 6902... the Act (19 U.S.C. 1671b(b)) and that imports of certain magnesia carbon bricks from China and Mexico...

  15. Using Mortar Mixing Pump for Magnesia Mortars Preparing and Transporting

    Science.gov (United States)

    Kiyanets, A. V.

    2017-11-01

    The article is devoted to the problem of preparation and transportation of magnesia mortars with the help of screw mortar mixing pumps. The urgency of the wide use of mortars on magnesia binders (Sorel’s cement) in construction is substantiated due to their high characteristics: strength, hardening speed, wear resistance, possibility of using organic and mineral aggregates, ecological purity and economic efficiency. The necessity for the development of a technique for calculating the main parameters of a mortar mixing pump for its application in the technology of preparation and transportation of magnesia mortars is demonstrated. The analysis of various types of modern mortar mixing pumps is given. The conclusions are drawn about the advantages and disadvantages of standard schemes. The description of the experiment for determination of the productivity of a mortar mixing pump is described depending on the plasticity (mobility) of the used magnesia mortar. The graph and description of the mathematical dependency of the productivity of the mortar mixing pump on the magnesia mortar plasticity are given. On the basis of the obtained dependency, as well as the already known formulas given in the article, a new method is proposed for calculating the main parameters of the screw mortar mixing pump in preparation and transportation of magnesia mortar: productivity, feed range, supply pressure, drive power.

  16. Investigating unexpected magnetism of mesoporous silica-supported Pd and PdO nanoparticles

    KAUST Repository

    Song, Hyon Min; Zink, Jeffrey I.; Khashab, Niveen M.

    2015-01-01

    supported Pd and PdO NPs. The heating rate and the annealing conditions determine the particle size and the phase of the NPs, with a fast heating rate of 30 °C/min producing the largest supported Pd NPs. Unusual magnetic behaviors are observed. (1) Contrary

  17. Cluster size matters: Size-driven performance of subnanometer clusters in catalysis, electrocatalysis and Li-air batteries

    Science.gov (United States)

    Vajda, Stefan

    2015-03-01

    This paper discusses the strongly size-dependent performance of subnanometer cluster based catalysts in 1) heterogeneous catalysis, 2) electrocatalysis and 3) Li-air batteries. The experimental studies are based on I. fabrication of ultrasmall clusters with atomic precision control of particle size and their deposition on oxide and carbon based supports; II. test of performance, III. in situand ex situ X-ray characterization of cluster size, shape and oxidation state; and IV.electron microscopies. Heterogeneous catalysis. The pronounced effect of cluster size and support on the performance of the catalyst (catalyst activity and the yield of Cn products) will be illustrated on the example of nickel and cobalt clusters in Fischer-Tropsch reaction. Electrocatalysis. The study of the oxygen evolution reaction (OER) on size-selected palladium clusters supported on ultrananocrystalline diamond show pronounced size effects. While Pd4 clusters show no reaction, Pd6 and Pd17 clusters are among the most active catalysts known (in in terms of turnover rate per Pd atom). The system (soft-landed Pd4, Pd6, or Pd17 clusters on an UNCD Si coated electrode) shows stable electrochemical potentials over several cycles, and the characterization of the electrodes show no evidence for evolution or dissolution of either the support Theoretical calculations suggest that this striking difference may be a demonstration that bridging Pd-Pd sites, which are only present in three-dimensional clusters, are active for the oxygen evolution reaction in Pd6O6. Li-air batteries. The studies show that sub-nm silver clusters have dramatic size-dependent effect on the lowering of the overpotential, charge capacity, morphology of the discharge products, as well as on the morphology of the nm size building blocks of the discharge products. The results suggest that by precise control of the active surface sites on the cathode, the performance of Li-air cells can be significantly improved

  18. Density functional study of structural and catalytic properties of free and supported metal nano cluster; Dichtefunktionalstudie der strukturellen und katalytischen Eigenschaften freier und getraegerter Metallnanocluster

    Energy Technology Data Exchange (ETDEWEB)

    Huber, B.

    2007-04-11

    The structural and catalytic properties of metal clusters were determined in the framework of density functional theory. The first part of this work investigates the electronic and geometrical structure of sodium clusters with up to 309 atoms. The ground-state structures of the clusters are determined and the corresponding electronic density of states is compared to experimental photoelectron spectras. The excellent agreement to the experimental results indicates that the correct growth motive of the sodium clusters was found. Small clusters from Na{sup -}{sub 20} to Na{sup -}{sub 42} prefer pentagonal and icosahedral structures with anti-Mackay overlayers, while clusters larger than Na{sup -}{sub 50} prefer icosahedral structures with Mackay overlayers. Clusters between the closed-shell Mackay Clusters often exhibit a twist deformation with respect to the regular Mackay positions. The second part of this work investigates the catalytic properties of free and supported palladium clusters. For both cases the oxidation of small Pd{sub N} clusters (N {<=} 9) was studied. It turned out that MgO supported Pd-clusters dissociate oxygen with a significant lower reaction energy than free clusters or supported systems with particles consisting of several thousands of atoms. The reaction with oxygen transforms the non-crystalline Pd-clusters into crystalline Pd{sub x}O{sub y} nano-oxide clusters that are in epitaxy with the underlying support. Simulations of the CO oxidation on the Pd{sub x}O{sub y} cluster predict a low-temperature reaction mechanism. By calculating the electronic density of states and CO stretch frequencies, different ways of verifying the results experimentally are discussed. (orig.)

  19. Application of a parallel genetic algorithm to the global optimization of medium-sized Au-Pd sub-nanometre clusters

    Science.gov (United States)

    Hussein, Heider A.; Demiroglu, Ilker; Johnston, Roy L.

    2018-02-01

    To contribute to the discussion of the high activity and reactivity of Au-Pd system, we have adopted the BPGA-DFT approach to study the structural and energetic properties of medium-sized Au-Pd sub-nanometre clusters with 11-18 atoms. We have examined the structural behaviour and stability as a function of cluster size and composition. The study suggests 2D-3D crossover points for pure Au clusters at 14 and 16 atoms, whereas pure Pd clusters are all found to be 3D. For Au-Pd nanoalloys, the role of cluster size and the influence of doping were found to be extensive and non-monotonic in altering cluster structures. Various stability criteria (e.g. binding energies, second differences in energy, and mixing energies) are used to evaluate the energetics, structures, and tendency of segregation in sub-nanometre Au-Pd clusters. HOMO-LUMO gaps were calculated to give additional information on cluster stability and a systematic homotop search was used to evaluate the energies of the generated global minima of mono-substituted clusters and the preferred doping sites, as well as confirming the validity of the BPGA-DFT approach.

  20. H{sub 2} dissociation on γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms: A DFT investigation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongtao [College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Chen, Lijuan [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Lv, Yongkang, E-mail: lykang@tyut.edu.cn [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China); Ren, Ruipeng, E-mail: s2003wht@126.com [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, Shanxi (China)

    2014-01-30

    The density functional theory (DFT) was applied to investigate the promotion effects of single Cu and Pd atoms deposition on γ-Al{sub 2}O{sub 3} surface for the adsorption and dissociation of H{sub 2} molecule, which is of importance for many catalysis reactions. Due to its strong Lewis acidity, the tri-coordinated surface Al site was identified to be the most preferable site for both Cu and Pd location. The inner surface electrons rearrangement from O to Al of alumina was found to be a key factor to stabilize the Cu/Pd adsorption configurations, rather than the total electrons transfer between Cu/Pd and the surface. It was found that the supported Cu and Pd atoms are more active for H{sub 2} dissociation than the clean γ-Al{sub 2}O{sub 3} surface. The supported Pd is more active than Cu for H{sub 2} dissociation. In addition, the metal–support interaction of the γ-Al{sub 2}O{sub 3} supported Cu/Pd atoms are more favored than the metal–metal interaction of the metal clusters for the H{sub 2} dissociated adsorption.

  1. Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Guenter; Muenzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

    2011-01-01

    Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier. - Research highlights: → Transport properties of Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions. → Tunnel barrier consists of MgO, Al-Ox, or MgO/Al-Ox bilayer systems. → Limitation of TMR-ratio in composite barrier tunnel junctions to Al-Ox values. → Limitation indicates that Al-Ox layer is causing incoherent tunneling.

  2. Au and Pd nanoparticles supported on CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} oxides

    Energy Technology Data Exchange (ETDEWEB)

    Nascente, P.A.P., E-mail: nascente@ufscar.br [Federal University of Sao Carlos, Department of Materials Engineering, Sao Carlos, SP (Brazil); Maluf, S.S.; Afonso, C.R.M. [Federal University of Sao Carlos, Department of Materials Engineering, Sao Carlos, SP (Brazil); Landers, R. [State University of Campinas, Institute of Physics, Department of Applied Physics, Campinas, SP (Brazil); Pinheiro, A.N.; Leite, E.R. [Federal University of Sao Carlos, Department of Chemistry, Sao Carlos, SP (Brazil)

    2014-10-01

    Highlights: • CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supported Au and Pd nanoparticles. • Additions of 0.5 wt% of Au and Pd onto CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supports. • Characterization by XRD, XPS, EDS, TEM, HRTEM, STEM, and EFTEM. - Abstract: Gold and palladium nanoparticles were incorporated on CeO{sub 2}, TiO{sub 2}, and Mn{sub 2}O{sub 3} supports prepared by a sol–gel method. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution TEM (HRTEM), scanning TEM (STEM) in high angle annular dark field mode (HAADF), and energy filtered TEM (EFTEM) using electron energy loss spectroscopy (EELS). The XRD diffractograms presented sharp and intense peaks indicating that the samples are highly crystalline, but it did not detected any peak corresponding to Au or Pd phases. This indicates that the Au and Pd NPs were incorporated into the structures of the oxides. It was not possible to obtain an Au 4f spectrum for Au/Mn{sub 2}O{sub 3} due to an overlap with the Mn 3p spectrum. The XPS Au 4f spectra for Au/CeO{sub 2} and Au/TiO{sub 2} present negative chemical shifts that could be attributed to particle-size-related properties. The XPS Pd 3d spectra indicate that for both CeO{sub 2} and TiO{sub 2} substrates, the Pd NPs were in the metallic state, while for the Mn{sub 2}O{sub 3} substrate, the Pd NPs were oxidized. The HRTEM results show the formation of nanocrystalline oxides having particles sizes between 50 and 200 nm. TEM micrographs show that the addition of Au caused the formation of Au clusters in between the CeO{sub 2} NPS, formation of Au NPs for the TiO{sub 2} support, and homogeneous distribution of Au clusters for the Mn{sub 2}O{sub 3} support. The addition of Pd yielded a homogeneous dispersion throughout the CeO{sub 2} and TiO{sub 2}, but caused the formation of Pd clusters for the Mn{sub 2}O

  3. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Mokkath, Junais Habeeb, E-mail: Junais.Mokkath@kaust.edu.sa

    2014-01-15

    The structural, electronic and magnetic properties of small Co{sub m}Pd{sub n}(N=m+n=8,m=0−N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ{sup ¯}{sub N} increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin–orbit interactions on the cluster properties is also discussed. - Highlights: • This work analyses the structural and magnetic properties of CoPd nanoclusters. • The magnetic order is found to be ferromagnetic-like for all the ground-state structures. • The average magnetic moment per atom increases approximately linearly with Co content. • The influence of spin–orbit interactions on the cluster properties is discussed.

  4. Liquid phase catalytic hydrodebromination of tetrabromobisphenol A on supported Pd catalysts

    International Nuclear Information System (INIS)

    Wu, Ke; Zheng, Mengjia; Han, Yuxiang; Xu, Zhaoyi; Zheng, Shourong

    2016-01-01

    Highlights: • Pd catalysts supported on TiO_2, CeO_2, Al_2O_3 and SiO_2 were prepared. • Deposition-precipitation method resulted in positively charged smaller Pd particle. • Complete debromination of tetrabromobisphenol A could be achieved on Pd/TiO_2. • Pd/TiO_2 prepared by the deposition-precipitation method was more active. - Abstract: Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant and reductive debromination is an effective method for the abatement of TBBPA pollution. In this study, Pd catalysts supported on TiO_2, CeO_2, Al_2O_3 and SiO_2 were prepared by the impregnation (the resulting catalyst denoted as im-Pd/support), deposition-precipitation (the resulting catalyst denoted as dp-Pd/support), and photo-deposition (the resulting catalyst denoted as pd-Pd/support) methods. The catalysts were characterized by N_2 adsorption-desorption isotherm, X-ray diffraction, transmission electron microscopy, measurement of zeta potential, CO chemisorption, and X-ray photoelectron spectroscopy. The results showed that at an identical Pd loading amount (2.0 wt.%) Pd particle size in dp-Pd/TiO_2 was much smaller than those in im-Pd/TiO_2 and pd-Pd/TiO_2. Pd particle size of the dp-Pd/TiO_2 catalyst increased with Pd loading amount. Additionally, Pd particles in the dp-Pd/TiO_2 catalysts were positively charged due to the strong metal-support interaction, whereas the cationization effect was gradually attenuated with the increase of Pd loading amount. For the liquid phase catalytic hydrodebromination (HDB) of TBBPA, tri-bromobisphenol A (tri-BBPA), di-bromobisphenol A (di-BBPA), and mono-bromobisphenol A (mono-BBPA) were identified as the intermediate products, indicative of a stepwise debromination process. The catalytic HDB of TBBPA followed the Langmuir-Hinshelwood model, reflecting an adsorption enhanced catalysis mechanism. At an identical Pd loading amount, the Pd catalyst supported on TiO_2 exhibited a much higher catalytic activity

  5. Liquid phase catalytic hydrodebromination of tetrabromobisphenol A on supported Pd catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ke [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Zheng, Mengjia [Kuang Yaming Honors School, Nanjing University, Nanjing 210023 (China); Han, Yuxiang [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Xu, Zhaoyi, E-mail: zhaoyixu@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China); Zheng, Shourong [State Key Laboratory of Pollution Control and Resource Reuse, Jiangsu Key Laboratory of Vehicle Emissions Control, School of the Environment, Nanjing University, Nanjing 210023 (China)

    2016-07-15

    Highlights: • Pd catalysts supported on TiO{sub 2}, CeO{sub 2}, Al{sub 2}O{sub 3} and SiO{sub 2} were prepared. • Deposition-precipitation method resulted in positively charged smaller Pd particle. • Complete debromination of tetrabromobisphenol A could be achieved on Pd/TiO{sub 2}. • Pd/TiO{sub 2} prepared by the deposition-precipitation method was more active. - Abstract: Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant and reductive debromination is an effective method for the abatement of TBBPA pollution. In this study, Pd catalysts supported on TiO{sub 2}, CeO{sub 2}, Al{sub 2}O{sub 3} and SiO{sub 2} were prepared by the impregnation (the resulting catalyst denoted as im-Pd/support), deposition-precipitation (the resulting catalyst denoted as dp-Pd/support), and photo-deposition (the resulting catalyst denoted as pd-Pd/support) methods. The catalysts were characterized by N{sub 2} adsorption-desorption isotherm, X-ray diffraction, transmission electron microscopy, measurement of zeta potential, CO chemisorption, and X-ray photoelectron spectroscopy. The results showed that at an identical Pd loading amount (2.0 wt.%) Pd particle size in dp-Pd/TiO{sub 2} was much smaller than those in im-Pd/TiO{sub 2} and pd-Pd/TiO{sub 2}. Pd particle size of the dp-Pd/TiO{sub 2} catalyst increased with Pd loading amount. Additionally, Pd particles in the dp-Pd/TiO{sub 2} catalysts were positively charged due to the strong metal-support interaction, whereas the cationization effect was gradually attenuated with the increase of Pd loading amount. For the liquid phase catalytic hydrodebromination (HDB) of TBBPA, tri-bromobisphenol A (tri-BBPA), di-bromobisphenol A (di-BBPA), and mono-bromobisphenol A (mono-BBPA) were identified as the intermediate products, indicative of a stepwise debromination process. The catalytic HDB of TBBPA followed the Langmuir-Hinshelwood model, reflecting an adsorption enhanced catalysis mechanism. At an identical Pd

  6. Capability of defective graphene-supported Pd{sub 13} and Ag{sub 13} particles for mercury adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Meeprasert, Jittima; Junkaew, Anchalee; Rungnim, Chompoonut; Kunaseth, Manaschai [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Wangchan, Rayong 21210 (Thailand); Namuangruk, Supawadee, E-mail: supawadee@nanotec.or.th [National Nanotechnology Center, NSTDA, 111 Thailand Science Park, Klong Luang, Pathum Thani 12120 Thailand (Thailand)

    2016-02-28

    Graphical abstract: Defective graphene (DG) supported Ag{sub 13} and Pd{sub 13} nanoparticles acts as sorbents for elementary mercury (Hg{sup 0}) adsorption. Hg is inert to DG surface, but it moderately adsorbs on deposited Ag{sub 13}-DG and strongly adsorbs on deposited Pd{sub 13}-DG. - Highlights: • Pd{sub 13}-DG composite has highest stability. • Pd{sub 13}-DG composite is the most reactive sorbent for Hg{sup 0} adsorption. • Hg{sup 0} adsorption abilities of Pd-DG composites are relatively higher than those of Ag-DG composites. • The d-band center of deposited metal is an adsorption descriptor of composite models. - Abstract: Reactivity of single-vacancy defective graphene (DG) and DG-supported Pd{sub n} and Ag{sub n} (n = 1, 13) for mercury (Hg{sup 0}) adsorption has been studied using density functional theory calculation. The results show that Pd{sub n} binds defective site of DG much stronger than the Ag{sub n}, while metal nanocluster binds DG stronger than single metal atom. Metal clustering affects the adsorption ability of Pd composite while that of Ag is comparatively less. The binding strength of −8.49 eV was found for Pd{sub 13} binding on DG surface, indicating its high stability. Analyses of structure, energy, partial density of states, and d-band center (ε{sub d}) revealed that the adsorbed metal atom or cluster enhances the reactivity of DG toward Hg adsorption. In addition, the Hg adsorption ability of M{sub n}-DG composite is found to be related to the ε{sub d} of the deposited M{sub n}, in which the closer ε{sub d} of M{sub n} to the Fermi level correspond to the higher adsorption strength of Hg on M{sub n}-DG composite. The order of Hg adsorption strength on M{sub n}-DG composite are as follows: Pd{sub 13} (−1.68 eV) >> Ag{sub 13} (−0.67 eV) ∼ Ag{sub 1} (−0.69 eV) > Pd{sub 1} (−0.62 eV). Pd{sub 13}-DG composite is therefore more efficient sorbent for Hg{sup 0} removal in terms of high stability and high adsorption

  7. Enhanced quantum coherence in graphene caused by Pd cluster deposition

    International Nuclear Information System (INIS)

    Qin, Yuyuan; Han, Junhao; Du, Yongping; Li, Zhaoguo; Wan, Xiangang; Han, Min; Song, Fengqi; Guo, Guoping; Song, You; Pi, Li; Wang, Xuefeng

    2015-01-01

    We report on the unexpected increase in the dephasing lengths of a graphene sheet caused by the deposition of Pd nanoclusters, as demonstrated by weak localization measurements. The dephasing lengths reached saturated values at low temperatures. Theoretical calculations indicate the p-type charge transfer from the Pd clusters, which contributes more carriers. The saturated values of dephasing lengths often depend on both the carrier concentration and mean free path. Although some impurities are increased as revealed by decreased mobilities, the intense charge transfer leads to the improved saturated values and subsequent improved dephasing lengths

  8. Effect of the strong metal-support interaction on hydrogen sorption kinetics of Pd-capped switchable mirrors

    NARCIS (Netherlands)

    Borgschulte, A.; Westerwaal, R.J.; Rector, J.H.; Dam, B.; Griessen, R.P.; Schoenes, J.

    2004-01-01

    The morphology and electronic structure of Pd clusters grown on oxidized yttrium surfaces are investigated by scanning tunneling microscopy and ultraviolet photoelectron spectroscopy. The hydrogen sorption mediated by the Pd clusters is determined from the optically monitored switching kinetics of

  9. Highly Active, Carbon-supported, PdSn Nano-core, Partially ...

    African Journals Online (AJOL)

    Carbon-supported, Pt partially covered, PdSn alloy nanoparticles (Pt-PdSn/C) were synthesized via a metathetical reaction of PdSn alloy nanoparticles, and a platinum precursor. The electrochemical activity was evaluated by methanol oxidation. The Pt-PdSn/C catalysts were characterized by transmission electron ...

  10. Preparation of supported Au–Pd and Cu–Pd by the combined strong ...

    Indian Academy of Sciences (India)

    BOONTIDA PONGTHAWORNSAKUN

    2017-10-25

    Oct 25, 2017 ... Bimetallic catalyst; Au–Pd/TiO2; Cu–Pd/TiO2; strong electrostatic adsorption; electroless deposition .... The liquid samples .... composition and gas mixture product at the outlet of reactor ... the TiO2 support (no change in the deposition curve of. TiO2). ..... TrimmDL1980In Design of Industrial Catalysts (Ams-.

  11. Theoretical analysis of microdosimetric spectra and cluster formation for 103Pd and 125I photon emitters

    International Nuclear Information System (INIS)

    Reniers, B; Vynckier, S; Verhaegen, F

    2004-01-01

    In this work we have compared 125 I or 103 Pd from a microdosimetric point of view. The photon spectra at different positions around the seeds have first been calculated using EGSnrc Monte Carlo (MC) code. These photon spectra are used as input for the event-by-event MC code TRION to calculate the microdosimetric lineal energy (y) distribution for each isotope. The microdosimetric dose average lineal energy, y D , calculated in a sphere of 1 μm is 3.5 keV μm -1 for 125 I and 4.0 keV μm -1 for 103 Pd, agreeing well with values reported in the literature. y D in a 1 μm sphere diminishes slightly with the distance from the seed for 103 Pd. This is due to the spectral hardening caused by the presence of a gamma-ray of 357.5 keV in the initial spectrum of 103 Pd. In parallel with the calculation of the microdosimetric spectra, we have analysed the distribution of the size of the energy deposition clusters generated by these low energy photons in structures of 2 and 10 nm of radius. Due to Compton interactions, the fraction of very low energy electrons ( 125 I photons is 51%, whereas it is only 27% for 103 Pd. As these electrons deposit their energy very locally, the pattern of energy depositions contains more clusters of a few nm of radius for 125 I than for 103 Pd; the mean cluster orders are respectively 3.3 and 3.0 for 10 nm clusters. This is in opposition with the prediction based on the microdosimetric spectrum and the parameter y D and could be of importance for the damage to the cells

  12. Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes

    Directory of Open Access Journals (Sweden)

    Luis M. Rivera Gavidia

    2017-05-01

    Full Text Available Direct methanol fuel cells (DMFCs are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM and X-ray techniques such as photoelectron spectroscopy (XPS, diffraction (XRD and energy dispersive spectroscopy (EDX. The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M and temperatures (60 °C and 90 °C. The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm−2 at 90 °C with 10 M methanol, higher than supported Pd and Pt commercial catalysts, demonstrating that Fe addition yields structural changes to Pd crystal lattice that reduce the crossover effects in DMFC operation.

  13. A randomized, prospective, comparison study of polyethylene glycol 3350 without electrolytes and milk of magnesia for children with constipation and fecal incontinence.

    Science.gov (United States)

    Loening-Baucke, Vera; Pashankar, Dinesh S

    2006-08-01

    Our aim was to compare 2 laxatives, namely, polyethylene glycol 3350 without electrolytes and milk of magnesia, evaluating the efficacy, safety, acceptance, and 1-year outcomes. Seventy-nine children with chronic constipation and fecal incontinence were assigned randomly to receive polyethylene glycol or milk of magnesia and were treated for 12 months in tertiary care pediatric clinics. Children were counted as improved or recovered depending on resolution of constipation, fecal incontinence, and abdominal pain after 1, 3, 6, and 12 months. An intent-to-treat analysis was used. Safety was assessed with evaluation of clinical adverse effects and blood tests. Thirty-nine children were assigned randomly to receive polyethylene glycol and 40 to receive milk of magnesia. At each follow-up visit, significant improvement was seen in both groups, with significant increases in the frequency of bowel movements, decreases in the frequency of incontinence episodes, and resolution of abdominal pain. Compliance rates were 95% for polyethylene glycol and 65% for milk of magnesia. After 12 months, 62% of polyethylene glycol-treated children and 43% of milk of magnesia-treated children exhibited improvement, and 33% of polyethylene glycol-treated children and 23% of milk of magnesia-treated children had recovered. Polyethylene glycol and milk of magnesia did not cause clinically significant side effects or blood abnormalities, except that 1 child was allergic to polyethylene glycol. In this randomized study, polyethylene glycol and milk of magnesia were equally effective in the long-term treatment of children with constipation and fecal incontinence. Polyethylene glycol was safe for the long-term treatment of these children and was better accepted by the children than milk of magnesia.

  14. A Real-Time Embedded Control System for Electro-Fused Magnesia Furnace

    Directory of Open Access Journals (Sweden)

    Fang Zheng

    2013-01-01

    Full Text Available Since smelting process of electro-fused magnesia furnace is a complicated process which has characteristics like complex operation conditions, strong nonlinearities, and strong couplings, traditional linear controller cannot control it very well. Advanced intelligent control strategy is a good solution to this kind of industrial process. However, advanced intelligent control strategy always involves huge programming task and hard debugging and maintaining problems. In this paper, a real-time embedded control system is proposed for the process control of electro-fused magnesia furnace based on intelligent control strategy and model-based design technology. As for hardware, an embedded controller based on an industrial Single Board Computer (SBC is developed to meet industrial field environment demands. As for software, a Linux based on Real-Time Application Interface (RTAI is used as the real-time kernel of the controller to improve its real-time performance. The embedded software platform is also modified to support generating embedded code automatically from Simulink/Stateflow models. Based on the proposed embedded control system, the intelligent embedded control software of electro-fused magnesium furnace can be directly generated from Simulink/Stateflow models. To validate the effectiveness of the proposed embedded control system, hardware-in-the-loop (HIL and industrial field experiments are both implemented. Experiments results show that the embedded control system works very well in both laboratory and industry environments.

  15. Clean fuel-magnesia bonded coal briquetting

    Energy Technology Data Exchange (ETDEWEB)

    Tosun, Yildirim I. [S. Demirel University Eng., Arch. Faculty Mining Eng. Department, Isparta (Turkey)

    2007-10-15

    Benefaction from coal fines as solid fuel in Turkey is very much important for economical development. Beneficiation from washed coal fines in the industry using solid fuel at lump size and in the municipal areas as an household solid fuel may be only provided by hot briquetting of the coal fines. The most practical common way of that benefication from coal fines in our country have been hot binding by sulfite liquor-sulfite liquor-melas and lime mixtures. Harmful the flue content of sulfite liquor-melas may only be eliminated by lime, a type of solid additive. However, cold bonded briquettes produced from coal fines are environmentally free. Just ash contents of these briquettes increase at a certain degree and heat content of them decrease at a certain extent. By using magnesia binder showed in this study, Tuncbilek lignite fines have been briquetted by cold and hot briquetting techniques. The qualities of briquettes produced by cold binders were compared with to those produced by other hot binding methods As a result, magnesia binder showed the similar characteristics with those of the briquettes produced by only cold bonded gypsum. Use of magnesite mixture and gypsum just as only cold binder was not suitable for the requirements from the coal briquettes to be used as solid fuels, particularly from household fuels, but just only as cold additive should be used. (author)

  16. Support Policies in Clusters: Prioritization of Support Needs by Cluster Members According to Cluster Life Cycle

    Directory of Open Access Journals (Sweden)

    Gulcin Salıngan

    2012-07-01

    Full Text Available Economic development has always been a moving target. Both the national and local governments have been facing the challenge of implementing the effective and efficient economic policy and program in order to best utilize their limited resources. One of the recent approaches in this area is called cluster-based economic analysis and strategy development. This study reviews key literature and some of the cluster based economic policies adopted by different governments. Based on this review, it proposes “the cluster life cycle” as a determining factor to identify the support requirements of clusters. A survey, designed based on literature review of International Cluster support programs, was conducted with 30 participants from 3 clusters with different maturity stage. This paper discusses the results of this study conducted among the cluster members in Eskişehir- Bilecik-Kütahya Region in Turkey on the requirement of the support to foster the development of related clusters.

  17. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, electronic and magnetic properties of small ComPdn (N=m+n=8,m=0-N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ̄N increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin-orbit interactions on the cluster properties is also discussed. © 2013 Elsevier B.V.

  18. Cytotoxicity of Pd nanostructures supported on PEN: Influence of sterilization on Pd/PEN interface

    Energy Technology Data Exchange (ETDEWEB)

    Polívková, M., E-mail: polivkoa@vscht.cz [Department of Solid State Engineering, University of Chemistry and Technology Prague, 166 28 Prague (Czech Republic); Siegel, J. [Department of Solid State Engineering, University of Chemistry and Technology Prague, 166 28 Prague (Czech Republic); Rimpelová, S. [Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, 166 28 Prague (Czech Republic); Hubáček, T. [Institute of Hydrobiology, Biology Centre of the AS CR, 370 05 Ceske Budejovice (Czech Republic); Kolská, Z. [Materials Centre of Usti n. L., J.E. Purkyne University, 400 96 Usti nad Labem (Czech Republic); Švorčík, V. [Department of Solid State Engineering, University of Chemistry and Technology Prague, 166 28 Prague (Czech Republic)

    2017-01-01

    Non-conventional antimicrobial agents, such as palladium nanostructures, have been increasingly used in the medicinal technology. However, experiences uncovering their harmful and damaging effects to human health have begun to appear. In this study, we have focused on in vitro cytotoxicity assessment of Pd nanostructures supported on a biocompatible polymer. Pd nanolayers of variable thicknesses (ranging from 1.1 to 22.4 nm) were sputtered on polyethylene naphthalate (PEN). These nanolayers were transformed by low-temperature post-deposition annealing into discrete nanoislands. Samples were characterized by AFM, XPS, ICP-MS and electrokinetic analysis before and after annealing. Sterilization of samples prior to cytotoxicity testing was done by UV irradiation, autoclave and/or ethanol. Among the listed sterilization techniques, we have chosen the gentlest one which had minimal impact on sample morphology, Pd dissolution and overall Pd/PEN interface quality. Cytotoxic response of Pd nanostructures was determined by WST-1 cell viability assay in vitro using three model cell lines: mouse macrophages (RAW 264.7) and two types of mouse embryonic fibroblasts (L929 and NIH 3T3). Finally, cell morphology in response to Pd/PEN was evaluated by means of fluorescence microscopy. - Highlights: • Annealing of Pd nanolayers on PEN resulted to Pd aggregation and formation of discrete nanoislands. • UV treatment was found as the gentlest sterilization method in term of physicochemical properties of Pd/PEN interface. • Autoclaving and chemical sterilization by ethanol resulted into remarkable changes of Pd/PEN interface. • Cytotoxicity of Pd samples was insignificant. • Pd nanostructures are potentially applicable as health-unobjectionable antibacterial coatings of medical devices.

  19. Carbon supported Pd-Sn and Pd-Ru-Sn nanocatalysts for ethanol electro-oxidation in alkaline medium

    CSIR Research Space (South Africa)

    Modibedi, RM

    2011-04-01

    Full Text Available Carbon supported Pd-Sn and Pd-Ru-Sn nanocatalysts were prepared by the chemical reduction method, using sodium borohydride and ethylene glycol mixture as the reducing agent. The catalytic activity towards ethanol electro-oxidation in alkaline medium...

  20. Crystal-field and clustering effects in the specific heat of Dy in Pd

    International Nuclear Information System (INIS)

    Devine, R.A.B.; Jacques, P.; Poirier, M.

    1975-01-01

    Recent results of specific-heat measurements on dilute alloys of Dy in Pd are reanalyzed. Assuming the ionic ground state found from paramagnetic-resonance measurements, the Schottky-anomaly and cluster contributions are segregated and the crystal-field splitting of the ground and first-excited states is found to be in reasonable agreement with theoretical predictions. The nature of the cluster contribution is discussed and an upper limit to the range of the Ruderman-Kittel-Kasuya-Yosida interaction deduced

  1. Comparison of bacterial cells and amine-functionalized abiotic surfaces as support for Pd nanoparticle synthesis

    DEFF Research Database (Denmark)

    De Corte, Simon; Bechstein, Stefanie; Lokanathan, Arcot R.

    2013-01-01

    An increasing demand for catalytic Pd nanoparticles has motivated the search for sustainable production methods. An innovative approach uses bacterial cells as support material for synthesizing Pd nanoparticles by reduction of Pd(II) with e.g. hydrogen or formate. Nevertheless, drawbacks...... nanoparticles, and that abiotic surfaces could support the Pd particle synthesis as efficiently as bacteria. In this study, we explore the possibility of replacing bacteria with amine-functionalized materials, and we compare different functionalization strategies. Pd nanoparticles formed on the support...... on these surfaces was higher than for Pd particles formed on Shewanella oneidensis cells. Smaller Pd nanoparticles generally have better catalytic properties, and previous studies have shown that the particle size can be lowered by increasing the amount of support material used during Pd particle formation. However...

  2. Carbon supported Pd-Ni and Pd-Ru-Ni nanocatalysts for the alkaline direct ethanol fuel cell (DEFC)

    CSIR Research Space (South Africa)

    Mathe, MK

    2011-08-01

    Full Text Available Carbon supported Pd-Ni and Pd-Ru-Ni nanocatalysts were prepared by the chemical reduction method, using sodium borohydride and ethylene glycol mixture as the reducing agent. The catalytic activity towards ethanol electro-oxidation in alkaline medium...

  3. Pulse-driven micro gas sensor fitted with clustered Pd/SnO2 nanoparticles.

    Science.gov (United States)

    Suematsu, Koichi; Shin, Yuka; Ma, Nan; Oyama, Tokiharu; Sasaki, Miyuki; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

    2015-08-18

    Real-time monitoring of specific gas concentrations with a compact and portable gas sensing device is required to sense potential health risk and danger from toxic gases. For such purposes, we developed an ultrasmall gas sensor device, where a micro sensing film was deposited on a micro heater integrated with electrodes fabricated by the microelectromechanical system (MEMS) technology. The developed device was operated in a pulse-heating mode to significantly reduce the heater power consumption and make the device battery-driven and portable. Using clustered Pd/SnO2 nanoparticles, we succeeded in introducing mesopores ranging from 10 to 30 nm in the micro gas sensing film (area: ϕ 150 μm) to detect large volatile organic compounds (VOCs). The micro sensor showed quick, stable, and high sensor responses to toluene at ppm (parts per million) concentrations at 300 °C even by operating the micro heater in a pulse-heating mode where switch-on and -off cycles were repeated at one-second intervals. The high performance of the micro sensor should result from the creation of efficient diffusion paths decorated with Pd sensitizers by using the clustered Pd/SnO2 nanoparticles. Hence we demonstrate that our pulse-driven micro sensor using nanostructured oxide materials holds promise as a battery-operable, portable gas sensing device.

  4. Nanostructured carbon-supported Pd electrocatalysts for ethanol oxidation: synthesis and characterization

    Science.gov (United States)

    Gacutan, E. M.; Climaco, M. I.; Telan, G. J.; Malijan, F.; Hsu, H. Y.; Garcia, J.; Fulo, H.; Tongol, B. J.

    2012-12-01

    The need to lower the construction cost of fuel cells calls for the development of non-Pt based electrocatalysts. Among others, Pd has emerged as a promising alternative to Pt for fuel cell catalysis. This research aims to investigate the synthesis and characterization of nanostructured Pd-based catalysts dispersed on carbon support as anode materials in direct ethanol fuel cells. For the preparation of the first Pd-based electrocatalyst, palladium nanoparticles (NPs) were synthesized via oleylamine (OAm)-mediated synthesis and precursor method with a mean particle size of 3.63 ± 0.59 nm as revealed by transmission electron microscopy (TEM). Carbon black was used as a supporting matrix for the OAm-capped Pd NPs. Thermal annealing and acetic acid washing were used to remove the OAm capping agent. To evaluate the electrocatalytic activity of the prepared electrocatalyst towards ethanol oxidation, cyclic voltammetry (CV) studies were performed using 1.0 M ethanol in basic medium. The CV data revealed the highest peak current density of 11.05 mA cm-2 for the acetic acid-washed Pd/C electrocatalyst. Meanwhile, the fabrication of the second Pd-based electrocatalyst was done by functionalization of the carbon black support using 3:1 (v/v) H2SO4:HNO3. The metal oxide, NiO, was deposited using precipitation method while polyol method was used for the deposition of Pd NPs. X-ray diffraction (XRD) analysis revealed that the estimated particle size of the synthesized catalysts was at around 9.0-15.0 nm. CV results demonstrated a 36.7% increase in the catalytic activity of Pd-NiO/C (functionalized) catalyst towards ethanol oxidation compared to the non-functionalized catalyst.

  5. 75 FR 21346 - Certain Magnesia Carbon Bricks From China and Mexico

    Science.gov (United States)

    2010-04-23

    ...)] Certain Magnesia Carbon Bricks From China and Mexico AGENCY: United States International Trade Commission... of subsidized imports from China or less-than-fair-value imports from China or Mexico of certain... bricks from China and Mexico are being sold in the United States at less than fair value within the...

  6. Session 6: Catalytic hydro-dehalogenation of halon 1211 (CBrClF{sub 2}) over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Hai, Yu; Kennedy, E.M.; Md Azhar, Uddin; Dlugogorski, B.Z. [Newcastle Univ., Process Safety and Environment Protection Group, School of Engineering, Callaghan, NSW (Australia)

    2004-07-01

    In the current study, we present the result of our investigation on the hydro-dehalogenation of halon 1211 with hydrogen over carbon supported Pd-Fe, Pd-Co and Pd-Ni bimetallic catalysts. In addition to dissociatively adsorbing hydrogen, Fe, Co and Ni themselves can facilitate cleavage of C-halogen bonds. The effect of the interaction of a second metal (Fe, Co and Ni) with Pd on the conversion of halon 1211 and selectivity to CH{sub 2}F{sub 2} for the catalytic hydro-dehalogenation of halon 1211 is discussed. Activated carbon is chosen as support in order to minimize the interaction of support with the metals. The obtained experimental results show that the introduction of Fe, Co and Ni to Pd catalysts has a significant influence on the catalytic hydro-dehalogenation of halon 1211, especially with respect to the selectivity to CH{sub 2}F{sub 2}. The presence of Fe increases the amount of halon 1211 adsorbed on the surface of catalysts and enhances the cleavage of C-halogen bonds in halon 1211, resulting in a higher halon 1211 conversion level and selectivity to hydrocarbons. Higher selectivity to CHBrF{sub 2} is ascribed to the secondary reaction: CF{sub 2} + HBr {yields} CHBrF{sub 2}. (authors)

  7. Effects of Cu over Pd based catalysts supported on silica or niobia

    Directory of Open Access Journals (Sweden)

    Roma M.N.S.C.

    2000-01-01

    Full Text Available Palladium and palladium-copper catalysts supported on silica and niobia were characterized by H2 chemisorption and H2-O2 titration. Systems over silica were also analyzed by transmission electron microscopy and EXAFS. The metallic dispersion decreased from 20% to 7% when the content of Pd was increased from 0.5wt.-% to 3wt.-% in monometallic catalysts. The addition of 3 wt.-% Cu to obtain Pd-Cu catalysts caused a remarkable capacity loss of hydrogen chemisorption. TPR analysis suggested an interaction between the two metals and EXAFS characterization of the catalyst supported on silica confirmed the formation of Pd-Cu alloy. Pd/Nb2O5 catalysts showed turnover numbers higher than those obtained with the Pd/SiO2 systems in the cyclohexane dehydrogenation. However, the bimetallic catalysts showed very low turnover numbers.

  8. Determination of the structures of small gold clusters on stepped magnesia by density functional calculations.

    Science.gov (United States)

    Damianos, Konstantina; Ferrando, Riccardo

    2012-02-21

    The structural modifications of small supported gold clusters caused by realistic surface defects (steps) in the MgO(001) support are investigated by computational methods. The most stable gold cluster structures on a stepped MgO(001) surface are searched for in the size range up to 24 Au atoms, and locally optimized by density-functional calculations. Several structural motifs are found within energy differences of 1 eV: inclined leaflets, arched leaflets, pyramidal hollow cages and compact structures. We show that the interaction with the step clearly modifies the structures with respect to adsorption on the flat defect-free surface. We find that leaflet structures clearly dominate for smaller sizes. These leaflets are either inclined and quasi-horizontal, or arched, at variance with the case of the flat surface in which vertical leaflets prevail. With increasing cluster size pyramidal hollow cages begin to compete against leaflet structures. Cage structures become more and more favourable as size increases. The only exception is size 20, at which the tetrahedron is found as the most stable isomer. This tetrahedron is however quite distorted. The comparison of two different exchange-correlation functionals (Perdew-Burke-Ernzerhof and local density approximation) show the same qualitative trends. This journal is © The Royal Society of Chemistry 2012

  9. Effect of Ferrous Additives on Magnesia Stone Hydration

    Science.gov (United States)

    Zimich, V.

    2017-11-01

    The article deals with the modification of the magnesia binder with additives containing two- and three-valent iron cations which could be embedded in the chloromagnesium stone structure and also increase the strength from 60 MPa in a non-additive stone to 80MPa, water resistance from 0.58 for clear stone to 0.8 and reduce the hygroscopicity from 8% in the non-additive stone to 2% in the modified chloromagnesium stone. It is proposed to use the iron hydroxide sol as an additive in the quantities of up to 1% of the weight of the binder. The studies were carried out using the modern analysis methods: the differentialthermal and X-ray phase analysis. The structure was studied with an electron microscope with an X-ray microanalyzer. A two-factor plan-experiment was designed which allowed constructing mathematical models characterizing the influence of variable factors, such as the density of the zatcher and the amount of sol in the binder, on the basic properties of the magnesian stone. The result of the research was the magnesia stone with the claimed properties and formed from minerals characteristic for magnesian materials as well as additionally formed from amachenite and goethite. It has been established that a highly active iron hydroxide sol the ion sizes of which are commensurate with magnesium ions is actively incorporated into the structure of pentahydroxychloride and magnesium hydroxide changing the habit of crystals compacting the structure of the stone and changing its hygroscopicity.

  10. Nanostructured carbon-supported Pd electrocatalysts for ethanol oxidation: synthesis and characterization

    International Nuclear Information System (INIS)

    Gacutan, E M; Tongol, B J; Climaco, M I; Telan, G J; Malijan, F; Hsu, H Y; Garcia, J; Fulo, H

    2012-01-01

    The need to lower the construction cost of fuel cells calls for the development of non-Pt based electrocatalysts. Among others, Pd has emerged as a promising alternative to Pt for fuel cell catalysis. This research aims to investigate the synthesis and characterization of nanostructured Pd-based catalysts dispersed on carbon support as anode materials in direct ethanol fuel cells. For the preparation of the first Pd-based electrocatalyst, palladium nanoparticles (NPs) were synthesized via oleylamine (OAm)-mediated synthesis and precursor method with a mean particle size of 3.63 ± 0.59 nm as revealed by transmission electron microscopy (TEM). Carbon black was used as a supporting matrix for the OAm-capped Pd NPs. Thermal annealing and acetic acid washing were used to remove the OAm capping agent. To evaluate the electrocatalytic activity of the prepared electrocatalyst towards ethanol oxidation, cyclic voltammetry (CV) studies were performed using 1.0 M ethanol in basic medium. The CV data revealed the highest peak current density of 11.05 mA cm −2 for the acetic acid-washed Pd/C electrocatalyst. Meanwhile, the fabrication of the second Pd-based electrocatalyst was done by functionalization of the carbon black support using 3:1 (v/v) H 2 SO 4 :HNO 3 . The metal oxide, NiO, was deposited using precipitation method while polyol method was used for the deposition of Pd NPs. X-ray diffraction (XRD) analysis revealed that the estimated particle size of the synthesized catalysts was at around 9.0–15.0 nm. CV results demonstrated a 36.7% increase in the catalytic activity of Pd–NiO/C (functionalized) catalyst towards ethanol oxidation compared to the non-functionalized catalyst. (paper)

  11. Enhanced Activity and Selectivity of Carbon Nanofiber Supported Pd Catalysts for Nitrite Reduction

    KAUST Repository

    Shuai, Danmeng; Choe, Jong Kwon; Shapley, John R.; Werth, Charles J.

    2012-01-01

    Pd-based catalyst treatment represents an emerging technology that shows promise to remove nitrate and nitrite from drinking water. In this work we use vapor-grown carbon nanofiber (CNF) supports in order to explore the effects of Pd nanoparticle size and interior versus exterior loading on nitrite reduction activity and selectivity (i.e., dinitrogen over ammonia production). Results show that nitrite reduction activity increases by 3.1-fold and selectivity decreases by 8.0-fold, with decreasing Pd nanoparticle size from 1.4 to 9.6 nm. Both activity and selectivity are not significantly influenced by Pd interior versus exterior CNF loading. Consequently, turnover frequencies (TOFs) among all CNF catalysts are similar, suggesting nitrite reduction is not sensitive to Pd location on CNFs nor Pd structure. CNF-based catalysts compare favorably to conventional Pd catalysts (i.e., Pd on activated carbon or alumina) with respect to nitrite reduction activity and selectivity, and they maintain activity over multiple reduction cycles. Hence, our results suggest new insights that an optimum Pd nanoparticle size on CNFs balances faster kinetics with lower ammonia production, that catalysts can be tailored at the nanoscale to improve catalytic performance for nitrite, and that CNFs hold promise as highly effective catalyst supports in drinking water treatment. © 2012 American Chemical Society.

  12. Enhanced Activity and Selectivity of Carbon Nanofiber Supported Pd Catalysts for Nitrite Reduction

    KAUST Repository

    Shuai, Danmeng

    2012-03-06

    Pd-based catalyst treatment represents an emerging technology that shows promise to remove nitrate and nitrite from drinking water. In this work we use vapor-grown carbon nanofiber (CNF) supports in order to explore the effects of Pd nanoparticle size and interior versus exterior loading on nitrite reduction activity and selectivity (i.e., dinitrogen over ammonia production). Results show that nitrite reduction activity increases by 3.1-fold and selectivity decreases by 8.0-fold, with decreasing Pd nanoparticle size from 1.4 to 9.6 nm. Both activity and selectivity are not significantly influenced by Pd interior versus exterior CNF loading. Consequently, turnover frequencies (TOFs) among all CNF catalysts are similar, suggesting nitrite reduction is not sensitive to Pd location on CNFs nor Pd structure. CNF-based catalysts compare favorably to conventional Pd catalysts (i.e., Pd on activated carbon or alumina) with respect to nitrite reduction activity and selectivity, and they maintain activity over multiple reduction cycles. Hence, our results suggest new insights that an optimum Pd nanoparticle size on CNFs balances faster kinetics with lower ammonia production, that catalysts can be tailored at the nanoscale to improve catalytic performance for nitrite, and that CNFs hold promise as highly effective catalyst supports in drinking water treatment. © 2012 American Chemical Society.

  13. Oxidative conversion of propane over lithium-promoted magnesia catalyst. I. Kinetics and mechanism

    NARCIS (Netherlands)

    Leveles, L.; Seshan, Kulathuiyer; Lercher, J.A.; Lefferts, Leonardus

    2003-01-01

    Oxidative conversion of lower alkanes over lithium-promoted magnesia catalysts offers a viable alternative for propene and ethene production. The catalytic performance of propane oxidative dehydrogenation and cracking shows yields up to 50% of olefin (propene and ethene). The reaction kinetics were

  14. TPO characterization of ethanol reduced Pd nanoparticles supported on SiO$_{2}$

    CERN Document Server

    Horváth, A; Sarkany, A; Guczi, L

    2002-01-01

    Silica-supported Pd catalysts were prepared at 298-353 K from Pd(II) chloride or Pd(II) acetate in suspension of SiO/sub 2/ and ethanol- water or ethanol-toluene mixtures, respectively. Reduction of Pd ions diffusing from liquid phase was ensured in an ethanol-rich adsorption layer covering the SiO/sub 2/ particles. Temperature-programmed oxidation (TPO) measurements were performed to characterize the organic impurities retained by solid phase. Vapour phase reduction /adsorption experiments with ethanol confirmed that under the reported reduction conditions, the Pd nanoparticles decompose ethanol and the CO formed remains chemisorbed on the Pd sites. Upon contacting the samples with air during the drying process to eliminate the solvent, the CO molecules are immediately removed from Pd sites by O/sub 2/, and thereby, a significant fraction (22-34%) of Pd sites becomes accessible for catalytic reactions. (33 refs).

  15. Catalytic activity of bimetal-containing Co,Pd systems in the oxidation of carbon monoxide

    Science.gov (United States)

    Oleksenko, L. P.; Lutsenko, L. V.

    2013-02-01

    The catalytic activity of low-percentage Co,Pd systems on ZSM-5, ERI, SiO2, and Al2O3 supports in the oxidation of CO was studied. The activity of bimetal-containing catalysts was shown to depend on the nature of the catalyst and the amount and ratio of their active components. According to the results of thermoprogrammed reduction with H2 (H2 TPR) and X-ray photoelectron spectroscopy (XPS) data, the metals are distributed as isolated cations or Coδ+-O-Pdδ+ clusters with cobalt and palladium cations surrounded by off-lattice oxygen in Co,Pd systems. The 0.8% Co,0.5% Pd-ZSM-5 bimetal catalysts were found to be more active due to the presence of clusters.

  16. Preparation of new composite ceramics based on gadolinium-doped ceria and magnesia nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jingying; Schelter, Matthias; Zosel, Jens; Oelssner, Wolfram [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Mertig, Michael [Kurt-Schwabe-Institut fuer Mess- und Sensortechnik e.V. Meinsberg, Waldheim (Germany); Physikalische Chemie, Mess- und Sensortechnik, Technische Universitaet Dresden (Germany)

    2017-09-15

    To achieve solid electrolyte materials for electrochemical energy storage devices with very high oxygen ion conductivity, composites of gadolinium-doped ceria (GDC) and magnesia (MgO) are developed in this study. Three different preparation methods are used to prepare nanoparticles from these two components. According to the characterization results, the self-propagating high-temperature synthesis is best suited for the preparation of both nanometer-sized GDC powder as solid electrolyte and MgO powder as insulator. The structures of the prepared nanometer-sized powders have been characterized by X-ray diffraction and transmission electron microscopy. They show narrow size distributions in the lower nanometer range. Then, dense composite ceramics are prepared from a MgO-GDC mixture by sintering. The size of the crystallite domains in the sintered ceramic is in the upper nanometer range. TEM and TEM-EDX images of a new composite ceramic based on gadolinium-doped ceria and magnesia nanoparticles. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Preparation of new composite ceramics based on gadolinium-doped ceria and magnesia nanoparticles

    International Nuclear Information System (INIS)

    Yao, Jingying; Schelter, Matthias; Zosel, Jens; Oelssner, Wolfram; Mertig, Michael

    2017-01-01

    To achieve solid electrolyte materials for electrochemical energy storage devices with very high oxygen ion conductivity, composites of gadolinium-doped ceria (GDC) and magnesia (MgO) are developed in this study. Three different preparation methods are used to prepare nanoparticles from these two components. According to the characterization results, the self-propagating high-temperature synthesis is best suited for the preparation of both nanometer-sized GDC powder as solid electrolyte and MgO powder as insulator. The structures of the prepared nanometer-sized powders have been characterized by X-ray diffraction and transmission electron microscopy. They show narrow size distributions in the lower nanometer range. Then, dense composite ceramics are prepared from a MgO-GDC mixture by sintering. The size of the crystallite domains in the sintered ceramic is in the upper nanometer range. TEM and TEM-EDX images of a new composite ceramic based on gadolinium-doped ceria and magnesia nanoparticles. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Structural Characterizations of Palladium Clusters Prepared by Polyol Reduction of [PdCl4]2− Ions

    Directory of Open Access Journals (Sweden)

    Loredana Schiavo

    2016-01-01

    Full Text Available Palladium nanoparticles are of great interest in many industrial fields, ranging from catalysis and hydrogen technology to microelectronics, thanks to their unique physical and chemical properties. In this work, palladium clusters have been prepared by reduction of [PdCl4]2− ions with ethylene glycol, in the presence of poly(N-vinyl-2-pyrrolidone (PVP as stabilizer. The stabilizer performs the important role of nucleating agent for the Pd atoms with a fast phase separation, since palladium atoms coordinated to the polymer side-groups are forced at short distances during nucleation. Quasispherical palladium clusters with a diameter of ca. 2.6 nm were obtained by reaction in air at 90°C for 2 hours. An extensive materials characterization by transmission electron microscopy (TEM, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and other characterizations (TGA, SEM, EDS-SEM, and UV-Vis has been performed in order to evaluate the structure and oxidation state of nanopalladium.

  19. Pd supported on carbon containing nickel, nitrogen and sulfur for ethanol electrooxidation.

    Science.gov (United States)

    Yang, Zi-Rui; Wang, Shang-Qing; Wang, Jing; Zhou, Ai-Ju; Xu, Chang-Wei

    2017-11-13

    Carbon material containing nickel, nitrogen and sulfur (Ni-NSC) has been synthesized using metal-organic frameworks (MOFs) as precursor by annealing treatment with a size from 200 to 300 nm. Pd nanoparticles supported on the Ni-NSC (Pd/Ni-NSC) are used as electrocatalysts for ethanol oxidation in alkaline media. Due to the synergistic effect between Pd and Ni, S, N, free OH radicals can form on the surface of Ni, N and S atoms at lower potentials, which react with CH 3 CO intermediate species on the Pd surface to produce CH 3 COO - and release the active sites. On the other hand, the stronger binding force between Pd and co-doped N and S is responsible for enhancing dispersion and preventing agglomeration of the Pd nanoparticles. The Pd(20 wt%)/Ni-NSC shows better electrochemical performance of ethanol oxidation than the traditional commercial Pd(20 wt%)/C catalyst. Onset potential on the Pd(20 wt%)/Ni-NSC electrode is 36 mV more negative compared with that on the commercial Pd(20 wt%)/C electrode. The Pd(20 wt%)/Ni-NSC in this paper demonstrates to have excellent electrocatalytic properties and is considered as a promising catalyst in alkaline direct ethanol fuel cells.

  20. Robust Pseudo-Hierarchical Support Vector Clustering

    DEFF Research Database (Denmark)

    Hansen, Michael Sass; Sjöstrand, Karl; Olafsdóttir, Hildur

    2007-01-01

    Support vector clustering (SVC) has proven an efficient algorithm for clustering of noisy and high-dimensional data sets, with applications within many fields of research. An inherent problem, however, has been setting the parameters of the SVC algorithm. Using the recent emergence of a method...... for calculating the entire regularization path of the support vector domain description, we propose a fast method for robust pseudo-hierarchical support vector clustering (HSVC). The method is demonstrated to work well on generated data, as well as for detecting ischemic segments from multidimensional myocardial...

  1. clusters

    Indian Academy of Sciences (India)

    environmental as well as technical problems during fuel gas utilization. ... adsorption on some alloys of Pd, namely PdAu, PdAg ... ried out on small neutral and charged Au24,26,27, Cu,28 ... study of Zanti et al.29 on Pdn (n = 1–9) clusters.

  2. Investigation of Supported Pd-Based Electrocatalysts for the Oxygen Reduction Reaction: Performance, Durability and Methanol Tolerance

    Directory of Open Access Journals (Sweden)

    Carmelo Lo Vecchio

    2015-11-01

    Full Text Available Next generation cathode catalysts for direct methanol fuel cells (DMFCs must have high catalytic activity for the oxygen reduction reaction (ORR, a lower cost than benchmark Pt catalysts, and high stability and high tolerance to permeated methanol. In this study, palladium catalysts supported on titanium suboxides (Pd/TinO2n–1 were prepared by the sulphite complex route. The aim was to improve methanol tolerance and lower the cost associated with the noble metal while enhancing the stability through the use of titanium-based support; 30% Pd/Ketjenblack (Pd/KB and 30% Pd/Vulcan (Pd/Vul were also synthesized for comparison, using the same methodology. The catalysts were ex-situ characterized by physico-chemical analysis and investigated for the ORR to evaluate their activity, stability, and methanol tolerance properties. The Pd/KB catalyst showed the highest activity towards the ORR in perchloric acid solution. All Pd-based catalysts showed suitable tolerance to methanol poisoning, leading to higher ORR activity than a benchmark Pt/C catalyst in the presence of low methanol concentration. Among them, the Pd/TinO2n–1 catalyst showed a very promising stability compared to carbon-supported Pd samples in an accelerated degradation test of 1000 potential cycles. These results indicate good perspectives for the application of Pd/TinO2n–1 catalysts in DMFC cathodes.

  3. Designing Pd-based supported bimetallic catalysts for environmental applications

    OpenAIRE

    Nowicka, Ewa; Meenakshisundaram, Sankar

    2018-01-01

    Supported bimetallic nanoparticulate catalysts are an important class of heterogeneous catalysts for many reactions including selective oxidation, hydrogenation/hydrogenolysis, reforming, biomass conversion reactions, and many more. The activity, selectivity, and stability of these catalysts depend on their structural features including particle size, composition, and morphology. In this review, we present important structural features relevant to supported bimetallic catalysts focusing on Pd...

  4. Molecular dynamics computer simulation study of Pd{sub n} (n=13, 19, 38 and 55) clusters

    Energy Technology Data Exchange (ETDEWEB)

    Karabacak, M [Afyon Kocatepe University, Department of Physics, Afyon (Turkey); Oezcelik, S [Gazi University, Department of Physics, Ankara (Turkey); Guevenc, Z B [Cankaya University, Department of Electronics and Communication Engineering, Ankara (Turkey)

    2002-07-01

    Using constant-energy molecular dynamics and thermal quenching simulations, we have studied minimum-energy structures and energetics, Pd{sub n} (n=13, 19, 38, and 55) clusters employing the Voter and Chen's version of parameterisation of the embedded-atom potential surface. Isomer statistics for Pdn ( n = 13 and 19 ) is obtained from 10000 initial independent configurations, which have been generated along high-energy trajectories (chosen energy values are high enough to melt the clusters). The thermal quenching technique is employed to remove the internal kinetic energy of the clusters. The locally stable isomers are separated from metastable ones. Probabilities belonging to sampling the basins of attractions of each isomers are computed, and then, isomers' energy spectra are analyzed.

  5. Structural studies of supported tin catalysts

    Science.gov (United States)

    Nava, Noel; Viveros, Tomás

    1999-11-01

    Tin oxide was supported on aluminium oxide, titanium oxide, magnesium oxide and silicon oxide, and the resulting interactions between the components in the prepared samples and after reduction were characterized by Mössbauer spectroscopy. It was observed that in the oxide state, tin is present as SnO2 on alumina, magnesia and silica, but on titania tin occupies Ti sites in the structure. After hydrogen treatment at high temperatures, tin is reduced from Sn(4) to Sn(2) on alumina and titania; it is reduced from Sn(4) to Sn(0) on silica, and is practically not reduced on magnesia. These results reveal the degree of interaction between tin and the different supports studied.

  6. Structural studies of supported tin catalysts

    International Nuclear Information System (INIS)

    Nava, Noel; Viveros, Tomas

    1999-01-01

    Tin oxide was supported on aluminium oxide, titanium oxide, magnesium oxide and silicon oxide, and the resulting interactions between the components in the prepared samples and after reduction were characterized by Moessbauer spectroscopy. It was observed that in the oxide state, tin is present as SnO 2 on alumina, magnesia and silica, but on titania tin occupies Ti sites in the structure. After hydrogen treatment at high temperatures, tin is reduced from Sn(4) to Sn(2) on alumina and titania; it is reduced from Sn(4) to Sn(0) on silica, and is practically not reduced on magnesia. These results reveal the degree of interaction between tin and the different supports studied

  7. Synthesis and characterization of carbon supported PdNi nanocatalysts for electroreduction of oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Muhammad Sufaid; Milian, Rosendo Parra, E-mail: sufaidkhan1984@gmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Química; Gallo, Irã Borges Coutinho; Villullas, Hebe Mercedes [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sao Paulo, SP (Brazil). Instituto de Química

    2016-07-01

    Full text: In this work, PdNi nanoparticles were prepared by a modified polyol method [1] with different Pd:Ni nominal ratios (80:20, 70:30 and 50:50, in atoms) and then supported on carbon (Vulcan XC-72). The structural properties of all materials were characterized by X-ray diffraction (XRD). Data show the formation PdNi alloys, as indicated by the decreased of the Pd lattice parameter compared Pd/C. The Pd 4d band electronic occupancy was assessed by X-ray Absorption Spectroscopy measurements that were carried out around the Pd L3 edge. Results evidenced that the presence of Ni decreases the electronic vacancy of the Pd 4d band. The electrocatalytic activity for the oxygen reduction reaction (ORR) was studied using the rotating disk electrode technique in O{sub 2}-saturated H{sub 2}SO{sub 4} and NaOH solutions. Overall, all PdNi materials presented better catalytic performance for the ORR than pure Pd, in both acidic and alkaline media. The production of H{sub 2}O{sub 2} was quantified using the rotating ring-disk technique, which allowed detecting this reaction intermediate by oxidizing it at the ring electrode. In all cases, data indicate low production of H{sub 2}O{sub 2}, which suggests that the ORR occurs mainly through the 4 electron mechanism on all catalysts studied in this work. Additionally, all prepared materials were submitted to stability tests by continuous potential cycling up to 1.0 V (vs. RHE). These studies evidenced that stability of Pd against dissolution is affected by the presence of Ni, with significant improvement for the PdNi alloys containing 20 and 30% Ni. Acknowledgments. Thanks are due to FAPESP (2014/12255-6) and CNPq (407143/2013-0) for financial support, and to the Brazilian Synchrotron Light Laboratory (LNLS) for the XAS experiments. References [1] S. Sun, C.B. Murray, D. Weller, L. Folks, A. Moser. Science 287, 1989 (2000). (author)

  8. Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Changwei; Cheng, Liqiang; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Shen, Peikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2007-05-15

    Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells. (author)

  9. Adsorption characteristics of lithium in sea water with coprecipitated alumina-magnesia gel

    International Nuclear Information System (INIS)

    Kaneko, Shoji; Takahashi, Wataru

    1988-01-01

    Alumina-magnesia mixed-oxide gel exhibited adsorptive ability for lithium in sea water attributed to weak acidic sites and micropores of diameter 20-30 A. The adsorption of lithium proceeded predominantly by the mechanism of ion-exchange, on which the facility was shown in the order of Na + > H + > NH 4 + . The elution of lithium adsorbed on the gel was complete with dilute hydrochloric acid. (author)

  10. One step electrochemical synthesis of bimetallic PdAu supported on nafion–graphene ribbon film for ethanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Shendage, Suresh S., E-mail: sureshsshendage@gmail.com; Singh, Abilash S.; Nagarkar, Jayashree M., E-mail: jm.nagarkar@ictmumbai.edu.in

    2015-10-15

    Highlights: • Electrochemical deposition of bimetallic PdAu NPs. • Highly loaded PdAu NPs are obtained. • Nafion–graphene supported PdAu NPs shows good activity for ethanol electrooxidation. - Abstract: A nafion–graphene ribbon (Nf–GR) supported bimetallic PdAu nanoparticles (PdAu/Nf–GR) catalyst was prepared by electrochemical codeposition of Pd and Au at constant potential. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The average particle size of PdAu nanoparticles (NPs) determined from XRD was 3.5 nm. The electrocatalytic activity of the PdAu/Nf–GR catalyst was examined by cyclic voltametry. It was observed that the as prepared catalyst showed efficient activity and good stability for ethanol electrooxidation in alkaline medium.

  11. The effect of sintering time on recycled magnesia brick from kiln of the cement plant

    Science.gov (United States)

    Aji, B. B.; Rosalina, D.; Azhar; Amin, M.

    2018-01-01

    This research aim was to investigate the effect of sintering time on reuse waste of magnesia brick from the rotary kiln of the cement plant. Reuse of the magnesia brick was carried out by mixed the kaolin as the binder. Spent refractory was used as aggregate with the composition of 85% spent refractory and 15% kaolin clay, respectively. The reuse brick then was molded with the size of 5x5x5 cm using hydraulic press under a load of 10 tons in order to forms green body. Green body then dried and sintered at 1200 °C with time variation of 2 hours, 4 hours, 6 hours, 8 hours and 10 hours, respectively. Thus, for comparison reuse brick was tested to its apparent porosity, the bulk density, and Cold Crushing Strength (CCS). The effect of kaolin addition as binder was also discussed.

  12. Pd nanoparticles supported on ultrahigh surface area honeycomb-like carbon for alcohol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Zaoxue; He, Guoqiang; Zhang, Guanghui; Meng, Hui; Shen, Pei Kang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2010-04-15

    The honeycomb-like porous carbon was prepared using glucose as carbon source and solid core mesoporous shell (SCMS) silica as templates. The material was characterized by physical and electrochemical methods. The results showed that the honeycomb-like porous carbon was consisted of hollow porous carbon (HPC) which gave an ultrahigh BET surface area of 1012.97 m{sup 2} g{sup -1} and pore volume of 2.19 cm{sup 3} g{sup -1}. The porous walls of the HPC were formed in the mesoporous shells of the silica templates. The HPC was used as the support to load Pd nanoparticles (Pd/HPC) for alcohol electrooxidation. It was highly active for methanol, ethanol and isopropanol electrooxidation. The peak current density for ethanol electrooxidation on Pd/HPC electrode was five times higher than that on Pd/C electrode at the same Pd loadings. The mass activity for ethanol electrooxidation was 4000 A g{sup -1} which is much higher compared to the data reported in the literature. The highly porous structure of such HPC can be widely used as support for uniform dispersing metal nanoparticles to increase their utilization as electrocatalysts. (author)

  13. Ultra-low Pt decorated PdFe Alloy Nanoparticles for Formic Acid Electro-oxidation

    International Nuclear Information System (INIS)

    Zhou, Yawei; Du, Chunyu; Han, Guokang; Gao, Yunzhi; Yin, Geping

    2016-01-01

    Highlights: • A cost-efficient way is used to prepare transition-noble metal alloy nanoparticles. • The Pd 50 Fe 50 /C catalyst shows excellent activity for formic acid oxidation (FAO). • Much activity enhancement of FAO is acquired by ultra-low Pt decorated Pd 50 Fe 50 . • A synergistic mechanism between Pt clusters and PdFe is proposed during the FAO. - Abstract: Palladium (Pd), has demonstrated promising electro-catalytic activity for formic acid oxidation, but suffers from extremely low abundance. Recently alloying with a transition metal has been considered as an effective approach to reducing the loading of Pd and enhancing the activity of Pd-based catalysts simultaneously. Herein, carbon supported PdFe nanoparticles (NPs) are synthesized at room temperature by using sodium borohydride as reducing agent and potassium ferrocyanide as Fe precursor. The Pd 50 Fe 50 alloy sample annealed at 900 °C for 1 h shows the best catalytic activity among Pd x Fe 1-x (x = 0.2, 0.4, 0.5, 0.6, and 0.8) towards formic acid oxidation. To further improve both catalytic activity and stability, the ultra-low Pt (0.09 wt %) decorated Pd 50 Fe 50 NPs (PtPd/PdFe) are prepared via the galvanic replacement reaction. Compared with Pd 50 Fe 50 /C, the PtPd/PdFe/C Exhibits 1.52 times higher catalytic activity and lower onset potential (−0.12 V). The significant enhancements of formic acid oxidation can be attributed to the accelerated dehydrogenation reaction of formic acid by Pt atomic clusters. Moreover, the PtPd/PdFe/C also demonstrates better tolerance to poisons during formic acid oxidation.

  14. Enhancing the biofuel upgrade performance for Pd nanoparticles via increasing the support hydrophilicity of metal-organic frameworks.

    Science.gov (United States)

    Sun, Qi; Chen, Meng; Aguila, Briana; Nguyen, Nicholas; Ma, Shengqian

    2017-09-08

    In this work, the influence of the hydrophilic/hydrophobic nature of metal-organic framework (MOF) materials on the catalytic performance of supported Pd nanoparticles for biofuel upgrade was studied. We show that the introduction of hydrophilic groups on a MOF can greatly enhance the performance of the resultant catalyst. Specifically, Pd nanoparticles supported on MIL-101-SO 3 Na with superhydrophilicity (Pd/MIL-101-SO 3 Na) far outperforms pristine MIL-101 and the benchmark catalyst Pd/C in the hydrodeoxygenation reaction of vanillin, a model component of pyrolysis oil derived from the lignin fraction. This is attributed to a favorable mode of adsorption of the highly water soluble reactants on the more hydrophilic support in the vicinity of the catalytically active Pd nanoparticles, thereby promoting their transformation.

  15. One-Pot Synthesis of Hierarchical Flower-Like Pd-Cu Alloy Support on Graphene Towards Ethanol Oxidation

    Science.gov (United States)

    Zhang, Jingyi; Feng, Anni; Bai, Jie; Tan, Zhibing; Shao, Wenyao; Yang, Yang; Hong, Wenjing; Xiao, Zongyuan

    2017-09-01

    The synergetic effect of alloy and morphology of nanocatalysts play critical roles towards ethanol electrooxidation. In this work, we developed a novel electrocatalyst fabricated by one-pot synthesis of hierarchical flower-like palladium (Pd)-copper (Cu) alloy nanocatalysts supported on reduced graphene oxide (Pd-Cu(F)/RGO) for direct ethanol fuel cells. The structures of the catalysts were characterized by using scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS). The as-synthesized Pd-Cu(F)/RGO nanocatalyst was found to exhibit higher electrocatalytic performances towards ethanol electrooxidation reaction in alkaline medium in contrast with RGO-supported Pd nanocatalyst and commercial Pd black catalyst in alkaline electrolyte, which could be attributed to the formation of alloy and the morphology of nanoparticles. The high performance of nanocatalyst reveals the great potential of the structure design of the supporting materials for the future fabrication of nanocatalysts.

  16. Near death by milk of magnesia.

    Science.gov (United States)

    Alaini, Ahmed; Roldan, Carlos A; Servilla, Karen; Colombo, Elizabeth Sage

    2017-03-21

    We report a case of hypermagnesemia associated with the use of milk of magnesia in a male patient with end-stage renal disease. After experiencing nausea and vomiting, he developed severe bradycardia and then asystole. Resuscitation efforts were successful; however, he developed atrial fibrillation with severe widening of the QRS and diffuse ST elevation, hypothermia, hypotension and apnoea requiring intubation. Initial diagnoses included ST-elevation myocardial infarction, cardiogenic and/or septic shock and hyperkalaemia. However, serum magnesium was later found to be >4.1 mmol/L (equivalent to >10 mg/dL). He underwent haemodialysis (HD) to remove serum magnesium with remarkable overall improvement. Severe hypermagnesemia can manifest with severe bradycardia and asystole, shock, hypothermia and respiratory failure and can mimic acute coronary syndromes complicated with cardiogenic shock or septic shock. Therefore, clinicians should be aware of this life-threatening condition in patients with significant renal dysfunction. Timely treatment with HD is highly effective and lifesaving. 2017 BMJ Publishing Group Ltd.

  17. Promising SiC support for Pd catalyst in selective hydrogenation of acetylene to ethylene

    Science.gov (United States)

    Guo, Zhanglong; Liu, Yuefeng; Liu, Yan; Chu, Wei

    2018-06-01

    In this study, SiC supported Pd nanoparticles were found to be an efficient catalyst in acetylene selective hydrogenation reaction. The ethylene selectivity can be about 20% higher than that on Pd/TiO2 catalyst at the same acetylene conversion at 90%. Moreover, Pd/SiC catalyst showed a stable catalytic life at 65 °C with 80% ethylene selectivity. With the detailed characterization using temperature-programmed reduction (H2-TPR), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption/desorption analysis, CO-chemisorption and thermo-gravimetric analysis (TGA), it was found that SiC owns a lower surface area (22.9 m2/g) and a broad distribution of meso-/macro-porosity (from 5 to 65 nm), which enhanced the mass transfer during the chemical process at high reaction rate and decreased the residence time of ethylene on catalyst surface. Importantly, SiC support has the high thermal conductivity, which favored the rapid temperature homogenization through the catalyst bed and inhabited the over-hydrogenation of acetylene. The surface electronic density of Pd on Pd/SiC catalyst was higher than that on Pd/TiO2, which could promote desorption of ethylene from surface of the catalyst. TGA results confirmed a much less coke deposition on Pd/SiC catalyst.

  18. Effect of ion implantation on thermal shock resistance of magnesia and glass

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Williams, J.S.; Watt, A.J.

    1995-01-01

    Monocrystals of magnesia together with glass samples have been subjected to ion implantation prior to thermal shock testing in an impulse plasma of continuously varied intensity. Measurements of the separation between fragments have been used to estimate the surface temperature. Fracture and deformation characteristics of the surface layer are measured in ion implanted and unimplanted samples using optical and scanning electron microscopy. Implantation-induced near-surface damage is analysed by ion channeling using 2 MeV He + ions. Ion implantation is shown to modify the near-surface structure of magnesia samples by introducing damage, which makes crack initiation easier under thermal stresses. The fracture threshold and maximum crack density are shifted towards the lower temperature range. Ion implanted MgO crystals show a ten fold increase in surface crack density. An increased crack density results in a decreased degree of damage characterised by the depth of crack penetration. The thermal stress resistance parameter of glass samples is increased at relatively small doses and decreased at higher doses. The results suggest that crack density and the degree of fracture damage in brittle ceramics operating under thermal shock conditions can be effectively controlled by ion implantation which provides crack initiating defects in the near-surface region. 23 refs., 7 figs

  19. Investigation of Carbon Monoxide Adsorption on Cationic Gold- Palladium Clusters

    Science.gov (United States)

    Chen, Yang-Mei; Kuang, Xiao-Yu; Sheng, Xiao-Wei; Wang, Huai-Qian; Shao, Peng; Zhong, Min-Ming

    2013-11-01

    Density functional calculations have been performed for the carbon monoxide molecule adsorption on AunPd+m(n+m ≤ 6) clusters. In the process of CO adsorption, small Au clusters and Pd clusters tend to be an Au atom and three Pd atoms adsorption, respectively. For the mixed Au-Pd clusters, an Au atom, a Pd atom, two atoms consisted of an Au atom and a Pd atom, two Pd atoms, and three Pd atoms adsorption structures are displayed. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps and natural bond orbital charge population are calculated. Moreover, CO adsorption energy, CO stretching frequency, and CO bond length (upon adsorption) are also analysed in detail. The results predict that the adsorption strength of Au clusters with CO and the C-O vibration strength is enhanced and reduced after doping of Pd in the AunPdmCO+ complexes, respectively

  20. Fabrication of Pd Micro-Membrane Supported on Nano-Porous Anodized Aluminum Oxide for Hydrogen Separation.

    Science.gov (United States)

    Kim, Taegyu

    2015-08-01

    In the present study, nano-porous anodized aluminum oxide (AAO) was used as a support of the Pd membrane. The AAO fabrication process consists of an electrochemical polishing, first/second anodizing, barrier layer dissolving and pores widening. The Pd membrane was deposited on the AAO support using an electroless plating with ethylenediaminetetraacetic acid (EDTA) as a plating agent. The AAO had the regular pore structure with the maximum pore diameter of ~100 nm so it had a large opening area but a small free standing area. The 2 µm-thick Pd layer was obtained by the electroless plating for 3 hours. The Pd layer thickness increased with increasing the plating time. However, the thickness was limited to ~5 µm in maximum. The H2 permeation flux was 0.454 mol/m2-s when the pressure difference of 66.36 kPa0.5 was applied at the Pd membrane under 400 °C.

  1. Catalytic oxidation of dichloromethane over sol-gel oxides supported Pd or Ni

    International Nuclear Information System (INIS)

    Martinez; Leidy Marcela; Montes, Consuelo

    2004-01-01

    Several supported Pd or Ni catalysts were synthesized by the sol-gel method using y-alumina, silica, sulfated zirconium and sulfated titanium as carriers. The resulting catalysts were characterized by XRD and nitrogen adsorption, and evaluated in the catalytic oxidation of dichloromethane. The effect of different parameters were determined, i.e. method of synthesis, temperature and the type of support. The durability of the best catalyst (0,5% Pd impregnated over sulfated titanium) was tested between 300 degrades Celsius and 350 degrades Celsius during 48 h. Under the conditions of this study, impregnated catalysts exhibited higher activity than those prepared by cogelation. Pd loaded catalysts showed higher conversion into CO 2 and HCl. Catalyst activity also increased with increasing temperature. Y-Alumina and sulfated titanium showed good activity but the formation of CO is favored instead of CO 2 . Therefore, bifunctional catalysts, i.e. containing metallic and acid sites appear to be required for the decomposition of methylene chloride into CO 2 and HCI

  2. Catalytic reduction of 4-nitrophenol over Ni-Pd nanodimers supported on nitrogen-doped reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lijun, E-mail: liulj@wtu.edu.cn [College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073, People' s Republic of China (China); Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Chen, Ruifen; Liu, Weikai [College of Chemistry and Chemical Engineering, Wuhan Textile University, Wuhan 430073, People' s Republic of China (China); Wu, Jiamin [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Gao, Di, E-mail: gaod@pitt.edu [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

    2016-12-15

    Catalytic reduction of toxic 4-nitrophenol to 4-aminophenol over magnetically recoverable nanocatalysts has attracted much attention. Herein, we report a Ni-Pd/NrGO catalyst through the growth of Ni-Pd nanodimers (NDs) on nitrogen-doped reduced graphene oxide (NrGO). The Ni-Pd NDs show a heterogeneous nanostructure with Ni and Pd subparts contacting with each other, remarkably different from the frequently-observed core/shell nanoparticles (NPs) or nanoalloy. The formation of Ni-Pd NDs follows an initial deposition of Pd NPs on the graphene and in-situ catalytic generation of Ni subparts over the newly-generated Pd NPs. The resulting Ni-Pd/NrGO exhibits a superior catalytic activity towards the reduction of 4-nitrophenol at room temperature with a high rate constant (3400 s{sup -1} g{sup -1}) and a low activated energy (29.1 kJ mol{sup -1}) as compared to unsupported Ni-Pd NDs and supported monometallic catalysts. The conversion rate of 4-NP is calculated to be 99.5% and the percent yield (%) of 4-AP is as high as 99.1%. A synergistic catalysis mechanism is rationally proposed, which is ascribed to the electronic modification of Ni-Pd metals due to the strong metal/support interaction (SMSI) effect as well as the electron transfer between Ni and Pd. The hybrid catalyst shows soft ferromagnetic properties and can be magnetically separated and recycled without obvious loss of activity.

  3. Collagen fiber with surface-grafted polyphenol as a novel support for Pd(0) nanoparticles: Synthesis, characterization and catalytic application

    International Nuclear Information System (INIS)

    Wu Hao; Wu Chao; He Qiang; Liao Xuepin; Shi Bi

    2010-01-01

    The aim of this study is to use collagen fiber (CF) as a natural polymeric support to synthesize a novel palladium (Pd) nanoparticle catalyst. To achieve a stable immobilization of Pd on CF support, epigallocatechin-3-gallate (EGCG), a typical plant polyphenol, was grafted onto CF surface, acting both as dispersing and stabilizing agent for Pd nanoparticles. Scanning electron microscopy showed that this catalyst was in ordered fibrous state with high flexibility. The presence of EGCG grafted on CF and the interaction mechanism of Pd ions with support was investigated by X-ray photoelectron spectroscopy. X-ray diffraction and transmission electron microscopy offered evidence that the well-dispersed Pd nanoparticles were generated on the outer surface of CF. By using the hydrogenation of allyl alcohol as a model reaction, the synthesized catalyst presented remarkably improved activity, selectivity and reusability as compared with the Pd catalyst supported by CF without grafting of EGCG.

  4. Corrosion improvement of the non-silica-alumina-graphite quality of the material for long nozzle by the magnesia addition. Maguneshia tenka ni yoru rongu nozuru suragkurain yo nonshirikaarumina [center dot] gurafuaito zaishitsu no taishokusei kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Ogata, R. (Krosaki Corp., Fukuoka (Japan))

    1999-02-01

    The non silica AG quality of the material that a 10 mass percent added the magnesia of the inside grain was applied to the slag line of the long nozzle, and an actual opportunity was used on the condition of the re-use without heat. The food that a slag line was the same was about two times in comparison with the non silica AG quality of the material not to add a magnesia, and the corrosion of the long nozzle improved as that result. And, the quality of the material that magnesia was added examines the reason why an elasticity rate decreases after heating with the formation of the micro-space due to the disappearance of the magnesia due to the magnesia, carbon response and the spinel formation. But, because it is in the relations who oppose it, as for the top of the corrosion character, this mechanism wants to expect the analysis, which it stepped into more. (translated by NEDO)

  5. Corrosion improvement of the non-silica-alumina-graphite quality of the material for long nozzle by the magnesia addition; Maguneshia tenka ni yoru rongu nozuru suragkurain yo nonshirikaarumina {center_dot} gurafuaito zaishitsu no taishokusei kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Ogata, R. [Krosaki Corp., Fukuoka (Japan)

    1999-02-01

    The non silica AG quality of the material that a 10 mass percent added the magnesia of the inside grain was applied to the slag line of the long nozzle, and an actual opportunity was used on the condition of the re-use without heat. The food that a slag line was the same was about two times in comparison with the non silica AG quality of the material not to add a magnesia, and the corrosion of the long nozzle improved as that result. And, the quality of the material that magnesia was added examines the reason why an elasticity rate decreases after heating with the formation of the micro-space due to the disappearance of the magnesia due to the magnesia, carbon response and the spinel formation. But, because it is in the relations who oppose it, as for the top of the corrosion character, this mechanism wants to expect the analysis, which it stepped into more. (translated by NEDO)

  6. 75 FR 4528 - Certain Magnesia Carbon Bricks From the People's Republic of China: Alignment of Final...

    Science.gov (United States)

    2010-01-28

    ... the PRC and Mexico. See Certain Magnesia Carbon Bricks from the People's Republic of China: Initiation... Bricks from the People's Republic of China and Mexico: Initiation of Antidumping Duty Investigations, 74... Bricks From the People's Republic of China: Alignment of Final Countervailing Duty Determination With...

  7. Structural, electronic and magnetic properties of small bimetallic zirconium–palladium clusters: Ab initio study

    International Nuclear Information System (INIS)

    Bezi Javan, Masoud

    2015-01-01

    Highlights: • Electronic and magnetic properties of small Zr n Pd m (n + m ⩽ 5) have been investigated. • Binding energies of the Zr n clusters are significantly higher than Pd n clusters. • Binding energy of the Pd n clusters increase with substituting one or more Zr atom. • HOMO–LUMO gap of the Zr n Pd m clusters increase in comparison with pure states. - Abstract: Structural, electronic and magnetic properties of small bimetallic zirconium–palladium clusters, Zr n Pd m (n + m ⩽ 5), have been investigated using density functional theory with considering generalized gradient approximation and PBE functional. We have determined the ground state conformations of the bimetallic zirconium–palladium clusters by substitution of Zr and Pd atoms in the optimized lowest energy structures of pure zirconium and palladium clusters. Results reveal that binding energies of the pure Zr n clusters are significantly higher than Pd n clusters with the same number of atoms. Also it is found that binding energy of the Zr n and Pd n clusters increase with growth of the number of consisting atoms in the clusters. Results indicate that, for both Zr n and Pd n clusters the binding energy of planar forms is lower than three-dimensional structures. We have also found that the binding energy of the Pd n clusters increase with substituting one or more Zr atoms in these clusters. We have also studied the HOMO–LUMO energy gap and magnetic moment of the pure and combined Zr and Pd clusters. The energy gap analysis of the pure and combined Pd and Zr clusters show that in generally the HOMO–LUMO gap of the bimetallic Zr n Pd m clusters increase in comparison with their corresponding pure clusters with the same number of atoms. According to the spin polarization DFT calculations all of the Zr n Pd m (n + m ⩽ 5) have net magnetic moments as instance the Zr 2 , Pd 2 and ZrPd clusters show a total magnetic moment value of 2 μ B . Some more discussions around charge population

  8. Spontaneously Bi decorated carbon supported Pd nanoparticles for formic acid electro-oxidation

    International Nuclear Information System (INIS)

    Bauskar, Akshay S.; Rice, Cynthia A.

    2013-01-01

    Highlights: • Selective decoration of Bi onto commercial Pd/C is carried out by a simple gas controlled surface potential modulation technique. • Bi decorated Pd/C catalyst exhibits higher and sustained formic acid oxidation activity presumably via the electronic effect. • Shielding of Pd atoms by Bi increases long term stability. • Formic acid electro-oxidation current increased by 121% at 0.2 V vs. RHE. -- Abstract: The activity and stability of carbon supported palladium (Pd/C) nanoparticles decorated with a submonolayer of bismuth (Bi) for formic acid (FA) electro-oxidation was investigated herein. The FA electro-oxidation activity enhancement of Bi decorated Pd/C was evaluated electrochemically using a rotating disk electrode configuration by linear sweep voltammetric and chronoamperometric measurements. Commercial Pd/C was decorated by irreversible adsorption of Bi via a simple gas controlled surface potential modulation technique, and the coverage of Bi adatoms as measured by cyclic voltammetry was controlled in the range of 30–87%. An optimal Bi coverage was observed to be 40%, resulting in a favorable decrease in the FA onset potential by greater than 0.1 V and increase in electro-oxidation current density from 0.25 mA cm −2 SA to 0.55 mA cm −2 SA at 0.2 V vs. RHE, compared to commercial Pd/C. The results indicate that Bi decorated Pd nanoparticles have excellent properties for the electro-oxidation of FA, i.e. high electro-catalytic activity and excellent stability, due to sustained promotion of dehydrogenation pathway attributed to the electronic effect, thereby promoting FA adsorption in the CH-down orientation. Based on no significant shifting in the CO stripping peak position, minimal impact of Bi on the Pd-CO bond strength is observed. Chronoamperometry results show much better long-term electro-catalytic activity for Bi decorated Pd nanoparticles attributed to shielding of surface Pd atoms by Bi and reducing Pd dissolution

  9. 75 FR 57442 - Certain Magnesia Carbon Bricks from the People's Republic of China: Countervailing Duty Order

    Science.gov (United States)

    2010-09-21

    ... and Mexico. See Certain Magnesia Carbon Bricks from China and Mexico (Investigation Nos. 701- TA-468... Bricks from the People's Republic of China: Countervailing Duty Order AGENCY: Import Administration... the People's Republic of China (PRC). On September 8, 2010, the ITC notified the Department of its...

  10. Cu assisted synthesis of self-supported PdCu alloy nanowires with enhanced performances toward ethylene glycol electrooxidation

    Science.gov (United States)

    Yan, Bo; Xu, Hui; Zhang, Ke; Li, Shujin; Wang, Jin; Shi, Yuting; Du, Yukou

    2018-03-01

    Self-supported PdCu alloy nanowires fabricated by a facile one-pot method have been reported, which copper assists in the morphological transformation from graininess to nanowires. The copper incorporated with palladium to form alloy structures cannot only cut down the usage of noble metal but also enhance their catalytic performances. The catalysts with self-supported structure and proper ratio of palladium to copper show great activity and long-term stability for the electrooxidation of ethylene glycol in alkaline solution. Especially for Pd43Cu57, its mass activity reaches to 5570.83 mA mg-1, which is 3.12 times as high as commercial Pd/C. This study highlights an accessible strategy to prepare self-supported PdCu alloy nanowires and their potential applications in renewable energy fields.

  11. Utilization of Magnesium Hydroxide Produced by Magnesia Hydration as Fire Retardant for Nylon 6-6,6

    Directory of Open Access Journals (Sweden)

    Rocha Sônia D.F.

    2001-01-01

    Full Text Available The present work investigates the use of magnesium hydroxide, produced by magnesia hydration, as a fire retardant in polymers. The hydration was carried out in an autoclave, at temperature of 130°C for 1 hour, and the product was further submitted to cominution in a jet mill. The solids were characterized with regard to their chemical composition, particle size distribution, surface area and morphology. The performance evaluation of the hydroxide as a flame retardant for a copolymer of nylon 6-6,6 was carried out according to the UL94 specifications for vertical burning tests. V-0 flammability rating at 1.6 mm (60% magnesium hydroxide-filled nylon composite and at 3.2 mm (40% magnesium hydroxide filled nylon composite were achieved. Mechanical properties were maintained at the desired values. These results indicate that the hydroxide obtained from magnesia hydration can be successfully employed as a fire retardant for nylon 6-6,6.

  12. Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose

    This thesis presents a fundamental study of the sintering of supported nanoparticles in relation to diesel oxidation catalysts. The sintering of supported nanoparticles is an important challenge in relation to this catalyst, as well as many other catalyst systems, and a fundamental understanding...... of Pt, Pd and bimetallic Pt-Pd nanoparticles supported on a flat and homogeneous Al2O3 or SiO2 surface. By using in situ TEM on the planar model catalysts it was possible to directly monitor the detailed dynamical changes of the individual nanoparticles during exposure to oxidizing conditions...

  13. Preparation and electrochemistry of graphene nanosheets–multiwalled carbon nanotubes hybrid nanomaterials as Pd electrocatalyst support for formic acid oxidation

    International Nuclear Information System (INIS)

    Yang Sudong; Shen Chengmin; Lu Xiangjun; Tong Hao; Zhu Jiajia; Zhang Xiaogang; Gao Hongjun

    2012-01-01

    Highlights: ► Graphene nanosheets–MWCNTs (GNS–CNTs) composites as Pd electrocatalysts support were synthesized by in situ reduction method. ► The direct electrooxidation of HCOOH is improved on the GNS–CNTs based catalyst. ► Both activity and durability of GNS–CNTs based catalyst are improved greatly. ► Pd/GNS–CNTs catalysts exhibit excellent performance when the mass ratio of GO to CNTs is 5:1. - Abstract: Graphene nanosheets–MWCNTs (GNS–CNTs) composites were synthesized by in situ reduction method, and then palladium nanoparticles (NPs) were supported on the GNS–CNTs by a microwave-assisted polyol process. Microstructure measurements showed that the graphene nanosheets and the CNTs formed a uniform nanocomposite with CNTs absorbed on the graphene nanosheets surface and/or filled between the graphene nanosheets. Compared to Pd/Vulcan XC-72R carbon, Pd/GNS, or Pd/CNTs catalysts, the Pd/GNS–CNTs catalysts exhibit excellent electrocatalytic activity and stability for formic acid electro-oxidation when the mass ratio of GO to CNTs is 5:1. The superior performance of Pd/GNS–CNTs catalysts may arise from large surface area utilization for NPs and enhanced electronic conductivity of the supports. Therefore, the GNS–CNTs composite should be a promising carbon material for application as electrocatalyst support in fuel cells.

  14. Direct synthesis of graphene nanosheets support Pd nanodendrites for electrocatalytic formic acid oxidation

    Institute of Scientific and Technical Information of China (English)

    杨苏东; 陈琳

    2015-01-01

    We report a solvothermal method preparation of dendritic Pd nanoparticles (DPNs) and spherical Pd nanoparticles (SPNs) supported on reduced graphene oxide (RGO). Drastically different morphologies of Pd NPs with nanodendritic structures or spherical structures were observed on graphene by controlling the reduction degree of graphene oxide (GO) un-der mild conditions. In addition to being a commonplace substrate, GO plays a more important role that relies on its surface groups, which serves as a shape-directing agent to direct the dendritic growth. As a result, the obtained DPNs/RGO catalyst exhibits a significantly enhanced electro-catalytic behavior for the oxidation of formic acid compared to the SPNs/RGO catalyst.

  15. Effect of the dispersants on Pd species and catalytic activity of supported palladium catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yue [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Yang, Xiaojun, E-mail: 10100201@wit.edu.cn [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Cao, Shuo, E-mail: cao23@email.sc.edu [North America R& D Center, Clariant BU Catalysts, Louisville, 40209, KY (United States); Zhou, Jie [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Wu, Yuanxin [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Han, Jinyu [School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Yan, Zhiguo [Key Laboratory for Green Chemical Process of Ministry of Education, School of Chemical Engineering and Pharmacy, Wuhan Institute of Technology, Wuhan 430205 (China); Zheng, Mingming [Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Hubei Key Laboratory of Oilcrops Lipid Chemistry and Nutrition, Wuhan 430062 (China)

    2017-04-01

    Highlights: • Polyvinyl alcohol (PVA) inhibited the sintering and reduction of Pd nanoparticles. • Activity was improved for supported Pd catalysts with PVA modified method. • PVA modified method minimized the catalyst deactivation. • This work provides an insight of the regeneration strategies for Pd catalysts. - Abstract: A series of supported palladium catalysts has been prepared through the precipitation method and the reduction method, using polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) as dispersants. The effects of the dispersants on the properties of catalysts were evaluated and the catalytic performance of the new materials was investigated for the oxidative carbonylation of phenol to diphenyl carbonate (DPC). The catalysts as prepared were also characterized by the X-ray diffraction (XRD), transmission electron microscope (TEM), Brunner-Emmet-Teller (BET) measurements and X-ray photoelectron spectroscopy (XPS) techniques. The results show that the addition of the dispersants had no effect on the crystal phase of the catalysts. However, the dispersion of Pd particles was improved when the dispersants were used. Moreover, the particle sizes of Pd nanoparticles modified by PVA were smaller than those modified by PVP. The catalysts prepared using the dispersants gave better yields of DPC than the catalysts prepared without the dispersants. The highest yield of DPC was 17.9% with the PVA-Red catalyst. The characterization results for the used catalysts showed that the Pd species in the PVA-Red catalyst remained mostly divalent and the lattice oxygen species were consumed during the reaction, which could lead to the higher catalytic activity of the PVA-Red catalyst. The experimental results confirm that PVA effectively inhibited the sintering and reduction of active Pd species in the oxidative carbonylation of phenol.

  16. 75 FR 45467 - Certain Magnesia Carbon Bricks From the People's Republic of China: Final Determination of Sales...

    Science.gov (United States)

    2010-08-02

    ... the People's Republic of China: Verification of Fengchi Import & Export Co., Ltd. of Haicheng City... Certain Magnesia Carbon Bricks from the People's Republic of China and Mexico: Initiation of Antidumping... from the People's Republic of China; Final Determination of Sales at Less Than Fair Value and Critical...

  17. 75 FR 57257 - Certain Magnesia Carbon Bricks From Mexico and the People's Republic of China: Antidumping Duty...

    Science.gov (United States)

    2010-09-20

    ... Carbon Bricks From Mexico and the People's Republic of China: Antidumping Duty Orders AGENCY: Import... China and Mexico (Investigation Nos. 701-TA-468 and 731-TA-1166-1167 (Final), USITC Publication 4182... from Mexico Prelim); and Certain Magnesia Carbon Bricks from the People's Republic of China...

  18. Mesoporous silica nanoparticle supported PdIr bimetal catalyst for selective hydrogenation, and the significant promotional effect of Ir

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hui; Huang, Chao; Yang, Fan [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Du, Li [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China)

    2015-12-01

    Graphical abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction caused by the addition of Ir. - Highlights: • Mesoporous nanoparticles were synthesized and used as support for metal catalyst. • PdIr bimetallic catalyst exhibited significantly improved hydrogenation activity. • The strong promotion of Ir was recognized firstly and investigated intensively. • PdIr exhibits 18 times higher activity than Pd to the hydrogenation of nitrobenzene. - Abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction

  19. Functional clay supported bimetallic nZVI/Pd nanoparticles used for removal of methyl orange from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ting [School of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Fujian Key Laboratory of Pollution Control and Resource Reuse, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Su, Jin [School of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Jin, Xiaoying [School of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Fujian Key Laboratory of Pollution Control and Resource Reuse, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Chen, Zuliang, E-mail: Zuliang.chen@unisa.edu.au [School of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, Fujian Province (China); Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia); Megharaj, Mallavarapu; Naidu, Ravendra [Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes, SA 5095 (Australia)

    2013-11-15

    Highlights: • Functional clay supported bimetallic nZVI/Pd was synthesized. • Methyl orange (MO) was degraded using B-nZVI/Pd. • 93.75% of MO in wastewater was removed. • The functions of clay, nZVI and Pd were observed. -- Abstract: Bentonite supported Fe/Pd nanoparticles (B/nZVI/Pd) were synthesized as composites that exhibit functionalities assisting in the removal of methyl orange (MO) from aqueous solution. The results showed that 91.87% of MO was removed using B/nZVI/Pd, while only 85% and 1.41% of MO were removed using nZVI/Pd and bentonite after 10 min, respectively. The new findings include that the presence of bentonite decreased the aggregation of nZVI/Pd and nZVI in the composite played its role as a reductant, while Pd{sup 0} acted as the catalyst to enhance the degradation of MO, which were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis analysis and the batch experiments. The increase in B/nZVI/Pd loading led to greater removal efficiency, while decolorization efficiency declined in the presence of anions such as nitrate, sulfite and carbonate, especially nitrate, which decreased the apparent rate constant k{sub obs} almost 17.06-fold. The kinetics study indicated that the degradation of MO fitted well to the pseudo-first-order model, where the k{sub obs} was 0.0721 min{sup −1}. Finally, the reactivity of aged B/nZVI/Pd was investigated, and the application of B/nZVI/Pd in wastewater indicated a removal efficiency higher than 93.75%. This provided a new environmental pollution management option for dyes-contaminated sites.

  20. Preparation and characterization of metallic supported thin Pd-Ag membranes for hydrogen separation

    OpenAIRE

    Fernandez, Ekain; Medrano, Jose Antonio; Melendez, Jon; Parco, Maria; Viviente, J.L.; van Sint Annaland, Martin; Gallucci, Fausto; Pacheco Tanaka, David A.

    2015-01-01

    This paper reports the preparation and characterization of thin-film (4-5 µm thick) Pd-Ag metallic supported membranes for high temperature applications. Various thin film membranes have been prepared by depositing a ceramic interdiffusion barrier layer prior to the simultaneous Pd-Ag electroless plating deposition. Two deposition techniques for ceramic layers (made of zirconia and alumina) have been evaluated: atmospheric plasma spraying and dip coating of a powder suspension. Initially, the...

  1. Preparation of Bimetallic Pd-Co Nanoparticles on Graphene Support for Use as Methanol Tolerant Oxygen Reduction Electrocatalysts

    Directory of Open Access Journals (Sweden)

    R. N. Singh

    2012-12-01

    Full Text Available Graphene-supported (40-x wt% Pd x wt% Co (0≤x≤13.33 alloys/composites have been prepared by a microwave-assisted polyol reduction method and been investigated for their structural and electrocatalytic properties for the oxygen reduction reaction (ORR in 0.5 M H2SO4 at 298 K. The study demonstrated that the bimetallic Pd-Co composite nanoparticles are, in fact, alloy nanoparticles with fcc crystalline structure. Partial substitution of Pd by Co (from 3.64 to 13.33 wt% in 40 wt% Pd/graphene decreases the lattice parameter as well as the crystallite size and increases the apparent catalytic activity, the latter, however, being the greatest with 8 wt% Co. The ORR activity of the active 32 wt% Pd 8wt% Co is found to be considerably low when it was deposited on the support multiwall carbon nanotubes under similar conditions. The rotating disk electrode study indicated that the ORR on 32 wt% Pd 8 wt% Co/GNS in 0.5 M H2SO4 follows approximately the four-electron pathway.

  2. Time-resolved QXAFS studies on the formation and dynamic behavior of the highly active Pd catalyst

    International Nuclear Information System (INIS)

    Okumura, Kazu

    2009-01-01

    The stepwise growth of Pd in USY zeolite was followed by in situ scanning quick X-ray absorption fine structure (QXAFS) spectroscopy involving repeated alternating exposures to H 2 and O 2 flows at room temperature. During the first reduction of 0.4 wt%-Pd/USY with 8% H 2 , Pd clusters of 13 atoms with a coordination number (CN) of 5.1 formed within 20 min in the supercage of USY. The growth followed first-order kinetics with respect to the concentration of Pd 2+ and the CN of Pd-Pd. The clusters were stable up to 443 K. The clusters were partially oxidized in less than 2 min on exposure to 8% O 2 , and then quickly reduced with 8% H 2 (second reduction) to afford larger Pd clusters of 26 atoms. The clusters continued to increase in size in a stepwise fashion on further alternate exposures to O 2 and H 2 . The finely dispersed Pd 0 species exhibited extremely high activity in the Suzuki-Miyaura coupling reactions when the o-xylene solution was activated with H 2 -bubbling. (author)

  3. Diatomite-supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts for selective hydrogenation of long-chain aliphatic esters.

    Science.gov (United States)

    Huang, Changliang; Zhang, Hongye; Zhao, Yanfei; Chen, Sha; Liu, Zhimin

    2012-11-15

    Diatomite supported Pd-M (M=Cu, Co, Ni) bimetal nanocatalysts with various metal compositions were prepared and characterized by means of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the metal nanoparticles were uniformly distributed on the support, and their size was centered around 8 nm with a relatively narrow size distribution. The catalysts were used to catalyze hydrogenation of long-chain aliphatic esters, including methyl palmitate, methyl stearate, and methyl laurate. It was indicated that the all diatomite-supported Pd-based bimetal catalysts were active to the selective hydrogenation of long-chain esters to corresponding alcohols at 270°C, originated from the synergistic effect between the metal particles and the diatomite support. For the selective hydrogenation of methyl palmitate, Pd-Cu/diatomite with metal loading of 1% and Pd/Cu=3 displayed the highest performance, giving a 1-hexadecanol yield of 82.9% at the substrate conversion of 98.8%. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Hot corrosion behavior of magnesia-stabilized ceramic material in a lithium molten salt

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Soo-Haeng, E-mail: nshcho1@kaeri.re.kr [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kim, Sung-Wook [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kim, Dae-Young [Graduate School of Energy Science and Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Lee, Jong-Hyeon, E-mail: jonglee@cnu.ac.kr [Graduate School of Energy Science and Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Graduate School of Advanced Materials Engineering, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Rapidly Solidified Materials Research Center, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Hur, Jin-Mok [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of)

    2017-07-15

    The isothermal and cyclic corrosion behaviors of magnesia-stabilized zirconia in a LiCl-Li{sub 2}O molten salt were investigated at 650 °C in an argon atmosphere. The weights of as-received and corroded specimens were measured and the microstructures, morphologies, and chemical compositions were analyzed by scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffraction. For processes where Li is formed at the cathode during electrolysis, the corrosion rate was about five times higher than those of isothermal and thermal cycling processes. During isothermal tests, the corrosion product Li{sub 2}ZrO{sub 3} was formed after 216 h. During thermal cycling, Li{sub 2}ZrO{sub 3} was not detected until after the completion of 14 cycles. There was no evidence of cracks, pores, or spallation on the corroded surfaces, except when Li was formed. We demonstrate that magnesia-stabilized zirconia is beneficial for increasing the hot corrosion resistance of structural materials subjected to high temperature molten salts containing Li{sub 2}O. - Highlights: •Corrosion mechanism of MSZin LiCl-Li{sub 2}O molten salt is proposed. •Formation of Li{sub 2}ZrO{sub 3}is main corrosion mechanism. •There were no cracks, pores and spallation after corrosion test. •MSZ shows high corrosion resistance to LiCl-Li{sub 2}O molten salt.

  5. Thermogravimetry for optimization of chloride pyro hydrolytic separations in zirconia-magnesia matrix

    International Nuclear Information System (INIS)

    Pires, M.A.F.; Dantas, E.S.K.

    1992-08-01

    A fast and accurate method for chloride ion determination in zirconia-magnesia matrix was studied the method consists in the pyro hydrolysis of the oxides at 900 o C, using a quartz apparatus, during thirty minutes and further determination of the chloride ion collected by means of either ion-selective electrode or ion chromatography. The thermogravimetric curves (TG curves) of the metal oxides and oxychlorides provide all the information about the chloride ion evolution temperature and the influence of pyro hydrolytic accelerators (U 3 O 8 ) on ion evolution. (author)

  6. Carbon-Nanotubes-Supported Pd Nanoparticles for Alcohol Oxidations in Fuel Cells: Effect of Number of Nanotube Walls on Activity.

    Science.gov (United States)

    Zhang, Jin; Lu, Shanfu; Xiang, Yan; Shen, Pei Kang; Liu, Jian; Jiang, San Ping

    2015-09-07

    Carbon nanotubes (CNTs) are well known electrocatalyst supports due to their high electrical conductivity, structural stability, and high surface area. Here, we demonstrate that the number of inner tubes or walls of CNTs also have a significant promotion effect on the activity of supported Pd nanoparticles (NPs) for alcohol oxidation reactions of direct alcohol fuel cells (DAFCs). Pd NPs with similar particle size (2.1-2.8 nm) were uniformly assembled on CNTs with different number of walls. The results indicate that Pd NPs supported on triple-walled CNTs (TWNTs) have the highest mass activity and stability for methanol, ethanol, and ethylene glycol oxidation reactions, as compared to Pd NPs supported on single-walled and multi-walled CNTs. Such a specific promotion effect of TWNTs on the electrocatalytic activity of Pd NPs is not related to the contribution of metal impurities in CNTs, oxygen-functional groups of CNTs or surface area of CNTs and Pd NPs. A facile charge transfer mechanism via electron tunneling between the outer wall and inner tubes of CNTs under electrochemical driving force is proposed for the significant promotion effect of TWNTs for the alcohol oxidation reactions in alkaline solutions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. The role of the poet in Plato's ideal cities of Callipolis and Magnesia

    OpenAIRE

    Gerard Naddaf

    2008-01-01

    Plato's attitude toward the poets and poetry has always been a flashpoint of debate, controversy and notoriety, but most scholars have failed to see their central role in the ideal cities of the Republic and the Laws, that is, Callipolis and Magnesia. In this paper, I argue that in neither dialogue does Plato "exile" the poets, but, instead, believes they must, like all citizens, exercise the expertise proper to their profession, allowing them the right to become full-fledged participants in ...

  8. Improving the electrocatalytic properties of Pd-based catalyst for direct alcohol fuel cells: effect of solid solution.

    Science.gov (United States)

    Wen, Cuilian; Wei, Ying; Tang, Dian; Sa, Baisheng; Zhang, Teng; Chen, Changxin

    2017-07-07

    The tolerance of the electrode against the CO species absorbed upon the surface presents the biggest dilemma of the alcohol fuel cells. Here we report for the first time that the inclusion of (Zr, Ce)O 2 solid solution as the supporting material can significantly improve the anti-CO-poisoning as well as the activity of Pd/C catalyst for ethylene glycol electro-oxidation in KOH medium. In particular, the physical origin of the improved electrocatalytic properties has been unraveled by first principle calculations. The 3D stereoscopic Pd cluster on the surface of (Zr, Ce)O 2 solid solution leads to weaker Pd-C bonding and smaller CO desorption driving force. These results support that the Pd/ZrO 2 -CeO 2 /C composite catalyst could be used as a promising effective candidate for direct alcohol fuel cells application.

  9. STUDY OF CHEMICAL INTERACTION OF MAGNESIA CEMENT WITH HIGH CONCENTRATION MAGNESIUM CHLORIDE SOLUTIONS

    Directory of Open Access Journals (Sweden)

    DEREVIANKO V. N.

    2015-10-01

    Full Text Available Problem statement. In activating MgO by electrolyte salts, as a result of formation of non water-resist magnesium silicate hydrate are obtained the durable cement stone having the low water-resist. I. P. Vyrodov considers [9; 5], that magnesia cement curing in mixing with sufficiently concentrated (C > 20 % solutions MgCl2 is caused with the crystallization of oxyhydrochloride composition: 3MgO∙MgCl2∙11Н2О, 5MgO∙MgCl2∙13Н2О and 7MgO∙MgCl2∙15Н2О. In the lower concentration parts of MgCl2 solution is formed a transitional compound of Mg[(OHnCl2-n] with isomorphous Mg(OH2 structure. At very low Cl concentration only Mg(OH2 is practically formed. Purpose. The Formation of water-resist magnesium silicate hydrates for obtaining of fast curing and solid structure of the magnesia stone. Conclusion. The dependence of the formation of the magnesia stone from the ratio (MgO/MgCl2 of the magnesia cement (MgO and the magnesium chloride solution (MgCl2 of different density has been identified in order to obtain the best content for oxyhydrochloride 3MgO•MgCl2•11Н2О, 5MgO•MgCl2•13Н2О and magnesium hydroxide (Mg(OH2. In putting into the system MgO∙–∙H2О of the silicic acid or fine ground quartz grains with size of less than 20 – 30 microns, over 1 month for the magnesium silicate hydrates formation is needed, where from 2 to 5 % of the total number of newgrowths are created. The study is proved by the expert opinion, that magnesium silicate hydrates do not have binding properties, unlike calcium silicate hydrates, and the main role in the system curing is played with the Mg(OH2 gel recrystallization, which provides the acceptable stone strength (R ≈ 30MPa in a few years. It has been also established, that in mixing of cement with low concentration MgO solutions of less than 1,5 mol/l (or 13% 1,1g/sm3, the final product in the stone structure is Mg(OH2. With increasing the sealer (MgCl2 solution there is formed by turn in

  10. Facile synthesis of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide with enhanced electrocatalytic properties

    Science.gov (United States)

    Li, Shan-Shan; Zheng, Jie-Ning; Ma, Xiaohong; Hu, Yuan-Yuan; Wang, Ai-Jun; Chen, Jian-Rong; Feng, Jiu-Ju

    2014-05-01

    A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media.A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media. Electronic supplementary information (ESI) available: Experimental section, Fig. S1-S12 and Tables S1 and S2. See DOI: 10.1039/c3nr06808k

  11. Performance of carbon nanofiber supported Pd-Ni catalysts for electro-oxidation of ethanol in alkaline medium

    Science.gov (United States)

    Maiyalagan, T.; Scott, Keith

    Carbon nanofibers (CNF) supported Pd-Ni nanoparticles have been prepared by chemical reduction with NaBH 4 as a reducing agent. The Pd-Ni/CNF catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical voltammetry analysis. TEM showed that the Pd-Ni particles were quite uniformly distributed on the surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of the Pd-Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential was 200 mV lower and the peak current density four times higher for ethanol oxidation for Pd-Ni/CNF compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 °C had a great effect on increasing the ethanol oxidation activity.

  12. Estimation of breast percent density in raw and processed full field digital mammography images via adaptive fuzzy c-means clustering and support vector machine segmentation

    International Nuclear Information System (INIS)

    Keller, Brad M.; Nathan, Diane L.; Wang Yan; Zheng Yuanjie; Gee, James C.; Conant, Emily F.; Kontos, Despina

    2012-01-01

    Purpose: The amount of fibroglandular tissue content in the breast as estimated mammographically, commonly referred to as breast percent density (PD%), is one of the most significant risk factors for developing breast cancer. Approaches to quantify breast density commonly focus on either semiautomated methods or visual assessment, both of which are highly subjective. Furthermore, most studies published to date investigating computer-aided assessment of breast PD% have been performed using digitized screen-film mammograms, while digital mammography is increasingly replacing screen-film mammography in breast cancer screening protocols. Digital mammography imaging generates two types of images for analysis, raw (i.e., “FOR PROCESSING”) and vendor postprocessed (i.e., “FOR PRESENTATION”), of which postprocessed images are commonly used in clinical practice. Development of an algorithm which effectively estimates breast PD% in both raw and postprocessed digital mammography images would be beneficial in terms of direct clinical application and retrospective analysis. Methods: This work proposes a new algorithm for fully automated quantification of breast PD% based on adaptive multiclass fuzzy c-means (FCM) clustering and support vector machine (SVM) classification, optimized for the imaging characteristics of both raw and processed digital mammography images as well as for individual patient and image characteristics. Our algorithm first delineates the breast region within the mammogram via an automated thresholding scheme to identify background air followed by a straight line Hough transform to extract the pectoral muscle region. The algorithm then applies adaptive FCM clustering based on an optimal number of clusters derived from image properties of the specific mammogram to subdivide the breast into regions of similar gray-level intensity. Finally, a SVM classifier is trained to identify which clusters within the breast tissue are likely fibroglandular, which

  13. Impact of Personality Disorder Cluster on Depression Outcomes Within Collaborative Care Management Model of Care.

    Science.gov (United States)

    George, Merit P; Garrison, Gregory M; Merten, Zachary; Heredia, Dagoberto; Gonzales, Cesar; Angstman, Kurt B

    2018-01-01

    Previous studies have suggested that having a comorbid personality disorder (PD) along with major depression is associated with poorer depression outcomes relative to those without comorbid PD. However, few studies have examined the influence of specific PD cluster types. The purpose of the current study is to compare depression outcomes between cluster A, cluster B, and cluster C PD patients treated within a collaborative care management (CCM), relative to CCM patients without a PD diagnosis. The overarching goal was to identify cluster types that might confer a worse clinical prognosis. This retrospective chart review study examined 2826 adult patients with depression enrolled in CCM. The cohort was divided into 4 groups based on the presence of a comorbid PD diagnosis (cluster A/nonspecified, cluster B, cluster C, or no PD). Baseline clinical and demographic variables, along with 6-month follow-up Patient Health Questionnaire-9 (PHQ-9) scores were obtained for all groups. Depression remission was defined as a PHQ-9 score cluster A or nonspecified PD diagnosis, 122 patients (4.3%) had a cluster B diagnosis, 35 patients (1.2%) had a cluster C diagnosis, and 2610 patients (92.4%) did not have any PD diagnosis. The presence of a cluster A/nonspecified PD diagnosis was associated with a 62% lower likelihood of remission at 6 months (AOR = 0.38; 95% CI 0.20-0.70). The presence of a cluster B PD diagnosis was associated with a 71% lower likelihood of remission at 6 months (AOR = 0.29; 95% CI 0.18-0.47). Conversely, having a cluster C diagnosis was not associated with a significantly lower likelihood of remission at 6 months (AOR = 0.83; 95% CI 0.42-1.65). Increased odds of having PDS at 6-month follow-up were seen with cluster A/nonspecified PD patients (AOR = 3.35; 95% CI 1.92-5.84) as well as cluster B patients (AOR = 3.66; 95% CI 2.45-5.47). However, cluster C patents did not have significantly increased odds of experiencing persistent depressive symptoms at 6-month

  14. Microbially supported synthesis of catalytically active bimetallic Pd-Au nanoparticles

    DEFF Research Database (Denmark)

    Hosseinkhani, Baharak; Søbjerg, Lina Sveidal; Rotaru, Amelia-Elena

    2012-01-01

    Transformation (FFT) analyses confirmed that the nanoparticles indeed were bimetallic. The bimetallic nanoparticles did not have a core-shell structure, but were superior to monometallic particles at reducing p-nitrophenol to p-aminophenol. Hence, formation of microbially supported nanoparticles may be a cheap......(II) to the bio-supported particles resulted in increased particle size. UV-Vis spectrophotometry and HR-TEM analyses indicated that the previously monometallic nanoparticles had become fully or partially covered by Au(0) or Pd(0), respectively. Furthermore, Energy Dispersive Spectrometry (EDS) and Fast Fourier...

  15. Performance of carbon nanofiber supported Pd-Ni catalysts for electro-oxidation of ethanol in alkaline medium

    Energy Technology Data Exchange (ETDEWEB)

    Maiyalagan, T.; Scott, Keith [School of Chemical Engineering and Advanced Materials, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2010-08-15

    Carbon nanofibers (CNF) supported Pd-Ni nanoparticles have been prepared by chemical reduction with NaBH{sub 4} as a reducing agent. The Pd-Ni/CNF catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical voltammetry analysis. TEM showed that the Pd-Ni particles were quite uniformly distributed on the surface of the carbon nanofiber with an average particle size of 4.0 nm. The electro-catalytic activity of the Pd-Ni/CNF for oxidation of ethanol was examined by cyclic voltammetry (CV). The onset potential was 200 mV lower and the peak current density four times higher for ethanol oxidation for Pd-Ni/CNF compared to that for Pd/C. The effect of an increase in temperature from 20 to 60 C had a great effect on increasing the ethanol oxidation activity. (author)

  16. Low-Temperature Pd/Zeolite Passive NO x Adsorbers: Structure, Performance, and Adsorption Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Yang [Institute for Integrated; Kovarik, Libor [Institute for Integrated; Engelhard, Mark H. [Institute for Integrated; Wang, Yilin [Institute for Integrated; Wang, Yong [Institute for Integrated; Gao, Feng [Institute for Integrated; Szanyi, János [Institute for Integrated

    2017-07-14

    Pd/zeolite passive NOx adsorber (PNA) materials were prepared with solution ion-exchange between NH4/zeolites (Beta, ZSM-5 and SSZ-13) and PdCl2 solutions. The nature of Pd (dispersion, distribution and oxidation states) in these materials was characterized with Na+ ion-exchange, TEM imaging, CO titration with FTIR and in situ XPS. The NOx trapping and release properties were tested using feeds with different compositions. It is concluded that multiple Pd species coexist in these materials: atomically dispersed Pd in the cationic sites of zeolites, and PdO2 and PdO particles on the external surfaces. While Pd is largely atomically dispersed in ZSM-5, the small pore opening for SSZ-13 inhibits Pd diffusion such that the majority of Pd stays as external surface PdO2 clusters. NOx trapping and release are not simple chemisorption and desorption events, but involve rather complex chemical reactions. In the absence of CO in the feed, cationic Pd(II) sites with oxygen ligands and PdO2 clusters are reduced by NO to Pd(I) and PdO clusters. These reduced sites are the primary NO adsorption sites. In the presence of H2O, the as-formed NO2 desorb immediately. In the presence of CO in the feed, metallic Pd, “naked” Pd2+, and Pd+ sites are responsible for NO adsorption. For Pd adsorption sites with the same oxidation states but in different zeolite frameworks, NO binding energies are not expected to vary greatly. However, NO release temperatures do vary substantially with different zeolite structures. This indicates that NO transport within these materials play an important role in determining release temperatures. Finally, some rational design principles on efficient PNA materials are suggested. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a

  17. Pd enhanced WC catalyst to promote heterogeneous methane combustion

    International Nuclear Information System (INIS)

    Terracciano, Anthony Carmine; De Oliveira, Samuel; Siddhanti, Deepti; Blair, Richard; Vasu, Subith S.; Orlovskaya, Nina

    2017-01-01

    Highlights: • Pd enhanced WC catalyst particles were synthesized via mechanochemical alloying. • Catalyst was characterized by XRD, XRF, SEM, and EDS. • Catalyst was deposited on porous ZrO_2 and evaluated in heterogeneous combustion. • During combustion temperature profiles and spectral emissions were collected. - Abstract: The efficiency of combustion for low cost heat production could be greatly enhanced if an active and low cost catalyst would be used to facilitate the chemical reactions occurring during combustor operation. Within this work an experimental study of palladium (Pd) enhanced tungsten carbide (WC) catalyst, synthesized via high energy ball milling and deposited by dip coating onto a magnesia partially stabilized zirconia (MgO-ZrO_2) porous matrix of 10 ppin was evaluated in heterogeneous methane combustion. The synthesized powder was characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) analysis, as well as by X-ray Fluorescence (XRF); and the morphology of the deposited WC-Pd coating was also characterized using SEM and EDS. Performance evaluation of the heterogeneous combustor with WC-Pd coated MgO-ZrO_2 porous media was conducted at constant air flow rate and various equivalence ratios of methane/air gaseous mixtures, while monitoring axial temperature profiles within the combustion chamber using thermocouples, as well as thermal radiative and acoustic emissions from the combustor exhaust using an externally placed CCD camera and a microphone. It was found that there is a strong dependence of flame position and maximum temperature on equivalence ratio (φ) over the range of 0.47 ± 0.02 ⩽ φ ⩽ 0.75 ± 0.02. Additionally it was found that over the same equivalence ratio range, there is a characteristic 4 peak acoustic signature between 200 and 500 Hz. It was found that at higher equivalence ratios 0.51 ± 0.02 ⩽ φ ⩽ 0.75 ± 0.02 the performance of combustor

  18. Adsorption behavior and electronic properties of Pdn (n ≤ 10) clusters on silicon carbide nanotubes: a first-principles study

    International Nuclear Information System (INIS)

    Wang Jianguang; Ma Li; Wang Guanghou

    2013-01-01

    First-principles calculations have been carried out to investigate the adsorption of Pd n (n ≤ 10) clusters on the single-walled (8, 0) and (5, 5) SiC nanotubes (SiCNTs). We find that the Pd n clusters can be stably adsorbed on the outer surfaces of both SiCNTs through an exothermic adsorption process. The adsorption energies of the Pd n clusters on the (8, 0) SiCNT are generally larger than those of clusters on the (5, 5) SiCNT. The number of bonds between the Pd n clusters and the SiCNTs increases with increasing cluster size. The Pd atoms adjacent to the SiCNTs adsorb preferentially on the bridge sites over an axial Si–C bond. The adsorption leads to elongation of the Pd–Pd bond lengths and structural reconstruction for the Pd n clusters. Moreover, the adsorbed Pd n clusters show two-layered structures at the cluster size n ≥ 4. We also find that the adsorbed Pd n clusters induce some impurity states within the band gap of the pristine SiCNTs and the strong pd hybridization near the Fermi level, thereby reducing the band gap. The charge transfer from the SiCNTs to the Pd atoms that occurs is observed for all the systems considered. Due to the strong interactions between the Pd n clusters and the SiCNTs, most adsorbed Pd n clusters exhibit zero magnetic moment. (paper)

  19. Pd adsorption on Si(1 1 3) surface: STM and XPS study

    International Nuclear Information System (INIS)

    Hara, Shinsuke; Yoshimura, Masamichi; Ueda, Kazuyuki

    2008-01-01

    Pd-induced surface structures on Si(1 1 3) have been studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In the initial process of the Pd adsorption below 0.10 ML, Pd silicide (Pd 2 Si) clusters are observed to form randomly on the surface. By increasing the Pd coverage to 0.10 ML, the clusters cover the entire surface, and an amorphous layer is formed. After annealing the Si(1 1 3)-Pd surface at 600 deg. C, various types of islands and chain protrusions appears. The agglomeration, coalescence and crystallization of these islands are observed by using high temperature (HT-) STM. It is also found by XPS that the islands correspond to Pd 2 Si structure. On the basis of these results, evolution of Pd-induced structures at high temperatures is in detail discussed

  20. Clustering Categories in Support Vector Machines

    DEFF Research Database (Denmark)

    Carrizosa, Emilio; Nogales-Gómez, Amaya; Morales, Dolores Romero

    2017-01-01

    The support vector machine (SVM) is a state-of-the-art method in supervised classification. In this paper the Cluster Support Vector Machine (CLSVM) methodology is proposed with the aim to increase the sparsity of the SVM classifier in the presence of categorical features, leading to a gain in in...

  1. Study of the cubic - to - monoclinic transformation in magnesia partially stabilized zirconia

    International Nuclear Information System (INIS)

    Muccillo, R.

    1988-01-01

    The transformation of the cubic phase to the stable monoclinic phase in ZrO 2 : 3%MgO quenched from 1450 0 C to RT has been studied by X-ray diffractometry in order to explain the thermal hysteresis in the electrical conductivity. The monoclinic-to-cubic ratio has been measured for samples annealed in the 500 0 C-1000 0 C temperature range. The results show that the decrease in the cubic phase content is the main responsible for the thermal hysteresis in the electrical conductivity of the magnesia partially stabilized zirconia solid electrolytes. (author) [pt

  2. Synthesis of Au-Pd Nanoflowers Through Nanocluster Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianguang [Duke University; Howe, Jane Y [ORNL; Chi, Miaofang [ORNL; Wilson, Adria [Duke University; Rathmall, Aaron [Duke University; Wiley, Benjamin J [ORNL

    2011-01-01

    Reduction of Pd ions by hydroquinone in the presence of gold nanoparticles and polyvinylpyrrolidone resulted in the formation of nanoflowers with a Au core and Pd petals. Addition of HCl to the synthesis halted the reduction by hydroquinone and enabled the acquisition of snapshots of the nanoflowers at different stages of growth. TEM images of the reaction after 10 s show that the nanoflower morphology resulted from the homogeneous nucleation of Pd clusters in solution and their subsequent attachment to gold seeds coated with a thin (0.8 {+-} 0.1 nm) shell of Pd. UV-visible spectra also indicate Pd clusters formed in the early stages of the reaction and disappeared as the nanoflowers grew. The speed at which this reaction can be halted is useful not only for producing a variety of bimetallic nanostructures with precisely controlled dimensions and morphologies but also for understanding the growth mechanism of these structures. The ability of the AuPd core-shell structure to catalyze the Suzuki coupling reaction of iodobenzene to phenylboronic acid was probed and compared against the activity of Pd nanocubes and thin-shelled AuPd core-shell nanoparticles. The results of this study suggest that Suzuki coupling was not affected by the surface structure or subsurface composition of the nanoparticles, but instead was primarily catalyzed by molecular Pd species that leached from the nanostructures.

  3. Synthesis and Catalytic Properties of Au Pd Nanoflowers

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianguang [Department of Chemistry, Duke University; Wilson, Adria [Duke University; Howe, Jane Y [ORNL; Chi, Miaofang [ORNL; Wiley, Benjamin J [Duke University

    2011-01-01

    Reduction of Pd ions by hydroquinone in the presence of gold nanoparticles and polyvinylpyrrolidone resulted in the formation of nanoflowers with a Au core and Pd petals. Addition of HCl to the synthesis halted the reduction by hydroquinone and enabled the acquisition of snapshots of the nanoflowers at different stages of growth. TEM images of the reaction after 10 s show that the nanoflower morphology resulted from the homogeneous nucleation of Pd clusters in solution and their subsequent attachment to gold seeds coated with a thin (0.8 0.1 nm) shell of Pd. UV visible spectra also indicate Pd clusters formed in the early stages of the reaction and disappeared as the nanoflowers grew. The speed at which this reaction can be halted is useful not only for producing a variety of bimetallic nanostructures with precisely controlled dimensions and morphologies but also for understanding the growth mechanism of these structures. The ability of the AuPd core shell structure to catalyze the Suzuki coupling reaction of iodobenzene to phenylboronic acid was probed and compared against the activity of Pd nanocubes and thin-shelled AuPd core shell nanoparticles. The results of this study suggest that Suzuki coupling was not affected by the surface structure or subsurface composition of the nanoparticles, but instead was primarily catalyzed by molecular Pd species that leached from the nanostructures.

  4. Synthesis and catalytic properties of Au-Pd nanoflowers.

    Science.gov (United States)

    Xu, Jianguang; Wilson, Adria R; Rathmell, Aaron R; Howe, Jane; Chi, Miaofang; Wiley, Benjamin J

    2011-08-23

    Reduction of Pd ions by hydroquinone in the presence of gold nanoparticles and polyvinylpyrrolidone resulted in the formation of nanoflowers with a Au core and Pd petals. Addition of HCl to the synthesis halted the reduction by hydroquinone and enabled the acquisition of snapshots of the nanoflowers at different stages of growth. TEM images of the reaction after 10 s show that the nanoflower morphology resulted from the homogeneous nucleation of Pd clusters in solution and their subsequent attachment to gold seeds coated with a thin (0.8 ± 0.1 nm) shell of Pd. UV-visible spectra also indicate Pd clusters formed in the early stages of the reaction and disappeared as the nanoflowers grew. The speed at which this reaction can be halted is useful not only for producing a variety of bimetallic nanostructures with precisely controlled dimensions and morphologies but also for understanding the growth mechanism of these structures. The ability of the AuPd core-shell structure to catalyze the Suzuki coupling reaction of iodobenzene to phenylboronic acid was probed and compared against the activity of Pd nanocubes and thin-shelled AuPd core-shell nanoparticles. The results of this study suggest that Suzuki coupling was not affected by the surface structure or subsurface composition of the nanoparticles, but instead was primarily catalyzed by molecular Pd species that leached from the nanostructures. © 2011 American Chemical Society

  5. Selective Reduction of Nitrite to Nitrogen with Carbon-Supported Pd-AOT Nanoparticles

    NARCIS (Netherlands)

    Perez-Coronado, A. M.; Calvo, L.; Baeza, J.A.; Palomar, J.; Lefferts, L.; Rodriguez, J-C.; Gilarranz, M.A.

    2017-01-01

    The catalytic reduction of nitrite in water with hydrogen has been studied using a new strategy to control selectivity. The catalysts used are based on size-controlled Pd-AOT nanoparticles, synthesized via sodium bis[2-ethylhexyl] sulfosuccinate (AOT)/isooctane reverse microemulsion, supported on

  6. 78 FR 28194 - Certain Magnesia Carbon Bricks From the People's Republic of China: Notice of Correction to the...

    Science.gov (United States)

    2013-05-14

    ... Bricks From the People's Republic of China: Notice of Correction to the Final Results of the 2010-2011... of Commerce, 14th Street and Constitution Avenue NW., Washington, DC 20230; telephone: (202) 482-4047... duty order on certain magnesia carbon bricks from the People's Republic of China.\\1\\ The period of...

  7. Metal-support interaction: The key factor governing activity of Pd/SnO2 catalyst for denitration of ground water

    Directory of Open Access Journals (Sweden)

    Bošković Goran C.

    2008-01-01

    Full Text Available Two mesoporous nanocristalline Pd/SnO2 catalysts were prepared by modified solgel technique differing in the pH conditions (pH = 2 and 9.5 of the synthesis of their supports. Samples achieved different activity and selectivity in water denitration reaction using hydrogen. XPS results of reduced samples indicate a strong interaction between the Pd and the Sn possibly as a result of electron shift from Sn to Pd. The solid solution of Pd2+ and SnO2 is formed by taking O from the surface of the support. In such a way some SnO2-X species may stay onto the surface and be responsible for its pronounced activity.

  8. Interaction of hydrogen with palladium clusters deposited on graphene

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Julio A.; Granja, Alejandra; Cabria, Iván; López, María J. [Departamento de Física Teórica, Atómica y Optica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2015-12-31

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H{sub 2} on Pd{sub 6} anchored on a graphene vacancy has been studied in detail.

  9. Interaction of hydrogen with palladium clusters deposited on graphene

    Science.gov (United States)

    Alonso, Julio A.; Granja, Alejandra; Cabria, Iván; López, María J.

    2015-12-01

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H2 on Pd6 anchored on a graphene vacancy has been studied in detail.

  10. A DFT study of arsine adsorption on palladium doped graphene: Effects of palladium cluster size

    International Nuclear Information System (INIS)

    Kunaseth, Manaschai; Mudchimo, Tanabat; Namuangruk, Supawadee; Kungwan, Nawee; Promarak, Vinich; Jungsuttiwong, Siriporn

    2016-01-01

    Graphical abstract: The relationship between charge difference and adsorption strength demonstrates that charge migration from Pd_n-SDG to AsH_x significantly enhanced adsorption strength, the Pd_6 clusters doped SDG with a steep slope is recommended as a superior adsorbent material for AsH_3 removal from gas stream. - Highlights: • Pd atom and Pd clusters bind strongly onto the defective graphene surface. • Larger size of Pd cluster adsorbs arsine and its hydrogenated products stronger. • Order of adsorption strength on Pd_n doped graphene: As > AsH > AsH_2 > > AsH_3. • Charge migration characterizes the strong adsorption of AsH_2, AsH, and As. • Pd cluster doped graphene is thermodynamically preferable for arsine removal. - Abstract: In this study, we have investigated the size effects of palladium (Pd) doped single-vacancy defective graphene (SDG) surface to the adsorption of AsH_3 and its dehydrogenated products on Pd using density functional theory calculations. Here, Pd cluster binding study revealed that Pd_6 nanocluster bound strongest to the SDG surface, while adsorption of AsH_x (x = 0–3) on the most stable Pd_n doped SDG showed that dehydrogenated arsine compounds adsorbed onto the surface stronger than the pristine AsH_3 molecule. Charge analysis revealed that considerable amount of charge migration from Pd to dehydrogenated arsine molecules after adsorption may constitute strong adsorption for dehydrogenated arsine. In addition, study of thermodynamic pathways of AsH_3 dehydrogenation on Pd_n doped SDG adsorbents indicated that Pd cluster doping on SDG adsorbent tends to be thermodynamically favorable for AsH_3 decomposition than the single-Pd atom doped SDG. Hence, our study has indicated that Pd_6 clusters doped SDG is more advantageous as adsorbent material for AsH_3 removal.

  11. Pd nanoparticles supported on three-dimensional graphene aerogels as highly efficient catalysts for methanol electrooxidation

    International Nuclear Information System (INIS)

    Liu, Mingrui; Peng, Cheng; Yang, Wenke; Guo, Jiaojiao; Zheng, Yixiong; Chen, Peiqin; Huang, Tingting; Xu, Jing

    2015-01-01

    Well-dispersed Pd nanoparticles supported on three-dimensional graphene aerogels (Pd/3DGA) were successfully prepared via a facile and efficient hydrothermal method without surfactant and template. The morphology and structure of the as-prepared Pd/3DGA nanocomposites were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM showed that the Pd nanoparticles with a small average diameter and narrow size distribution were uniformly deposited on the surface of the self-assembled three-dimensional graphene aerogels. Raman spectra revealed the surface properties of 3DGA and its interaction with metallic nanoparticles. Cyclic voltammetric (CV) and chronoamperometric (CA) experiments further exhibited its superior catalytic activity and stability for the electro-oxidation of methanol in alkaline media, making it a promising anodic catalyst for direct alkaline alcohol fuel cells (DAAFCs).

  12. Poly (pyrrole-co-aniline) hollow nanosphere supported Pd nanoflowers as high-performance catalyst for methanol electrooxidation in alkaline media

    International Nuclear Information System (INIS)

    Fard, Leyla Abolghasemi; Ojani, Reza; Raoof, Jahan Bakhsh; Zare, Ehsan Nazarzadeh; Lakouraj, Moslem Mansour

    2017-01-01

    In this work, first poly (pyrrole-co-aniline) (PPCA) hollow nanosphere (HN) as a catalyst support material is fabricated through in-situ emulsion polymerization. Then we reported a one-step and template-free approach to fabricate Pd NFs on a PPCA HN coated glassy carbon electrode by a facile electrochemical approach. Several techniques such as FTIR (Fourier transform infrared spectroscopy), SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) were utilized for the characterization of the synthesized materials. The catalytic performance of Pd NFs/PPCA HN catalyst is evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy toward methanol oxidation as a model reaction in alkaline media. The comparison of specific activities for Pd NFs/PPCA HN (1.79 mA cm"−"2), Pd NFs/PPy (1.28 mA cm"−"2), Pd NFs/PANI (0.93 mA cm"−"2) and Pd NFs (0.78 mA cm"−"2) shows that the PPCA supported Pd NFs with high surface area exhibits the excellent electrocatalytic activity than other electrodes for the electro-oxidation reaction in alkaline media. This might be due to the easier charge transfer at conductive copolymer interfaces, higher electrochemically accessible surface areas and electronic conductivity. This strategy provides a promising platform for direct methanol fuel cells. - Highlights: • Pd nanoflowers supported on poly (pyrrole-co-aniline) hollow nanosphere is prepared by a facile electrochemical approach. • The as-prepared nanocatalyst displays the enhanced electrocatalytic activity and stability for methanol oxidation. • The high performance is attributed to facile electron transfer on poly (pyrrole-co-aniline) hollow nanosphere substrate.

  13. DFT study on stability and H{sub 2} adsorption activity of bimetallic Au{sub 79−n}Pd{sub n} (n = 1–55) clusters

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xuejing [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Tian, Dongxu, E-mail: tiandx@dlut.edu.cn [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Meng, Changgong [State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

    2013-03-29

    Highlights: ► Stability of Pd substitution type is face > mid-edge > corner > edge. ► H{sub 2} adsorption activity is in contrast with the stability of Pd substitution type. ► Non-activated dissociation of H{sub 2} occurs in Au{sub 36}Pd{sub 43−3} with high thermal stability. ► ε{sub d} agrees with that Pd at edge and corner are more active than face and mid-edge. - Abstract: The stability and H{sub 2} adsorption activity of bimetallic Au{sub 79−n}Pd{sub n} (n = 1–55) clusters were studied by density functional theory with GGA-PW91 functional. The stability order for four Pd substitution types is face > mid-edge > corner > edge, and the stability is improved with increasing Pd content. In contrast with the stability order, H{sub 2} adsorption activity is corner ≈ edge > mid-edge > face. The Au{sub 36}Pd{sub 43} (3) with Au:Pd ≈ 1:1 ratio and twenty-four Pd substitutions at (1 1 1) facets and nineteen Pd substitutions at subshell sites shows high stability and H{sub 2} non-activated dissociation activity. The partial density of d-states and d band center revealed that the electronic properties are closely associated with the geometric characteristic and adsorption activity. Correlating the d band center ε{sub d} and the adsorption energies, the ε{sub d} order agrees with the adsorption activity that the Pd substitution at edge and corner sites are more active than at face and mid-edge sites.

  14. Effective adsorption/electrocatalytic degradation of perchlorate using Pd/Pt supported on N-doped activated carbon fiber cathode

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Fubing; Zhong, Yu [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yang, Qi, E-mail: yangqi@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wang, Dongbo, E-mail: dongbowang@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Chen, Fei; Zhao, Jianwei; Xie, Ting; Jiang, Chen; An, Hongxue; Zeng, Guangming; Li, Xiaoming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

    2017-02-05

    Highlights: • Pd/Pt-NACF served as an adsorption/electrocatalysis electrode to reduce perchlorate. • The possible mechanisms involved in the reaction process were explained. • The reusability and stability of Pd/Pt-NACF bifunctional material was evaluated. - Abstract: In this work, Pd/Pt supported on N-doped activated carbon fiber (Pd/Pt-NACF) was employed as the electrode for electrocatalytic degradation of perchlorate through adsorption/electroreduction process. Perchlorate in solution was firstly adsorbed on Pd/Pt-NACF and then reduced to non-toxic chloride by the catalytic function of Pd/Pt at a constant current (20 mA). Compared with Pd/Pt-ACF, the adsorption capacity and electrocatalytic degradation efficiency of Pd/Pt-NACF for perchlorate increased 161% and 28%, respectively. Obviously, positively charged N-functional groups on NACF surface enhanced the adsorption capacity of Pd/Pt-NACF, and the dissociation of hydrogen to atomic H* by the Pd/Pt nanostructures on the cathode might drastically promote the electrocatalytic reduction of perchlorate. The role of atomic H* in the electroreduction process was identified by tertiary butanol inhibition test. Meanwhile, the perchlorate degradation performance was not substantially lower after three successive adsorption/electrocatalytic degradation experiments, demonstrating the electrochemical reusability and stability of the as-prepared electrode. These results showed that Pd/Pt-NACF was effective for electrocatalytic degradation of perchlorate and had great potential in perchlorate removal from water.

  15. Electrocatalytic oxidation of ethylene glycol at palladium-bimetallic nanocatalysts (PdSn and PdNi) supported on sulfonate-functionalised multi-walled carbon nanotubes

    CSIR Research Space (South Africa)

    Ramulifho, T

    2013-04-01

    Full Text Available Electrocatalytic oxidation of ethylene glycol (EG) in alkaline medium using nano-scaled palladium-based bimetallic catalysts (PdM, where M = Ni and Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) is compared. The bimetallic...

  16. A DFT study of arsine adsorption on palladium doped graphene: Effects of palladium cluster size

    Energy Technology Data Exchange (ETDEWEB)

    Kunaseth, Manaschai, E-mail: manaschai@nanotec.or.th [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA) , Pathum Thani 12120 (Thailand); Mudchimo, Tanabat [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand); Namuangruk, Supawadee [National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA) , Pathum Thani 12120 (Thailand); Kungwan, Nawee [Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Promarak, Vinich [Department of Material Science and Engineering, School of Molecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21201 (Thailand); Jungsuttiwong, Siriporn, E-mail: siriporn.j@ubu.ac.th [Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190 (Thailand)

    2016-03-30

    Graphical abstract: The relationship between charge difference and adsorption strength demonstrates that charge migration from Pd{sub n}-SDG to AsH{sub x} significantly enhanced adsorption strength, the Pd{sub 6} clusters doped SDG with a steep slope is recommended as a superior adsorbent material for AsH{sub 3} removal from gas stream. - Highlights: • Pd atom and Pd clusters bind strongly onto the defective graphene surface. • Larger size of Pd cluster adsorbs arsine and its hydrogenated products stronger. • Order of adsorption strength on Pd{sub n} doped graphene: As > AsH > AsH{sub 2} > > AsH{sub 3}. • Charge migration characterizes the strong adsorption of AsH{sub 2}, AsH, and As. • Pd cluster doped graphene is thermodynamically preferable for arsine removal. - Abstract: In this study, we have investigated the size effects of palladium (Pd) doped single-vacancy defective graphene (SDG) surface to the adsorption of AsH{sub 3} and its dehydrogenated products on Pd using density functional theory calculations. Here, Pd cluster binding study revealed that Pd{sub 6} nanocluster bound strongest to the SDG surface, while adsorption of AsH{sub x} (x = 0–3) on the most stable Pd{sub n} doped SDG showed that dehydrogenated arsine compounds adsorbed onto the surface stronger than the pristine AsH{sub 3} molecule. Charge analysis revealed that considerable amount of charge migration from Pd to dehydrogenated arsine molecules after adsorption may constitute strong adsorption for dehydrogenated arsine. In addition, study of thermodynamic pathways of AsH{sub 3} dehydrogenation on Pd{sub n} doped SDG adsorbents indicated that Pd cluster doping on SDG adsorbent tends to be thermodynamically favorable for AsH{sub 3} decomposition than the single-Pd atom doped SDG. Hence, our study has indicated that Pd{sub 6} clusters doped SDG is more advantageous as adsorbent material for AsH{sub 3} removal.

  17. Efficient Aerobic Oxidation of 5-Hydroxymethylfurfural in Aqueous Media with Au-Pd Supported on Zinc Hydroxycarbonate

    DEFF Research Database (Denmark)

    Gui, Zhenyou; Cao, Wenrong; Shunmugavel, Saravanamurugan

    2016-01-01

    Bimetallic catalysts with Au–Pd supported on zinc hydroxycarbonate (ZOC) were synthesized by a simple deposition–precipitation method and analyzed by transmission electron microscopy to have a narrow-size distribution of predominantly 1–2 nm. The prepared Au–Pd/ZOC catalysts exhibited excellent...... activity towards 5-hydoxymethylfurfural (HMF) oxidation in water in the presence of the base NaHCO3 at benign conditions of 80 °C and 3 bar O2, resulting in quantitative yield of 2,5-furandicarboxylic acid (FDCA). The addition of base not only enhanced the yield of FDCA but also stabilized the support ZOC...

  18. Magnetotransport in Pd-rich PdFe alloys

    Czech Academy of Sciences Publication Activity Database

    Kudrnovský, Josef; Drchal, Václav; Turek, Ilja

    2013-01-01

    Roč. 26, č. 5 (2013), s. 1749-1752 ISSN 1557-1939 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional support: RVO:68378271 ; RVO:68081723 Keywords : galvanomagnetic transport * Pd-rich PdFe * long-range order * effect of temperature * anisotropic magnetoresistance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.930, year: 2013

  19. Carbon supported Pd-Co-Mo alloy as an alternative to Pt for oxygen reduction in direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Ch. Venkateswara [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India); Viswanathan, B., E-mail: bvnathan@acer.iitm.ernet.i [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India)

    2010-03-01

    Carbon black (CDX975) supported Pd and Pd-Co-Mo alloy nanoparticles are prepared by the reduction of metal precursors with hydrazine in reverse microemulsion of water/Triton-X-100/propanol-2/cyclohexane. The as-synthesized Pd-Co-Mo/CDX975 is heat treated at 973, 1073 and 1173 K to promote alloy formation. The prepared materials are characterized by powder XRD and EDX. Face-centred cubic structure of Pd is evident from XRD. The chemical composition of the respective elements in the catalysts is evaluated from the EDX analysis and observed that it is in good agreement with initial metal precursor concentrations. Oxygen reduction measurements performed by linear sweep voltammetry indicate the good catalytic activity of Pd-Co-Mo alloys compared to Pd. This is due to the suppression of (hydr)oxy species on Pd surface by the presence of alloying elements, Co and Mo. Among the investigated catalysts, heat-treated Pd-Co-Mo/CDX975 at 973 K exhibited good ORR activity compared to the catalysts heat treated at 1073 and 1173 K. This is due to the small crystallite size and high surface area. Rotating disk electrode (RDE) measurements indicated the comparable ORR activity of heat-treated Pd-Co-Mo/CDX975 at 973 K with that of commercial Pt/C. Kinetic analysis reveals that the ORR on Pd-Co-Mo/CDX975 follows the four-electron pathway leading to water. Moreover, Pd-Co-Mo/CDX975 exhibited substantially higher ethanol tolerance during the ORR than Pt/C. Good dispersion of metallic nanoparticles on the carbon support is observed from HRTEM images. Single-cell direct ethanol fuel cell tests indicated the comparable performance of Pd-Co-Mo/CDX975 with that of commercial Pt/C. Stability under DEFC operating conditions for 50 h indicated the good stability of Pd-Co-Mo/CDX975 compared with that of Pt/C.

  20. Facile synthesis of porous Pt-Pd nanospheres supported on reduced graphene oxide nanosheets for enhanced methanol electrooxidation

    Science.gov (United States)

    Li, Shan-Shan; Lv, Jing-Jing; Hu, Yuan-Yuan; Zheng, Jie-Ning; Chen, Jian-Rong; Wang, Ai-Jun; Feng, Jiu-Ju

    2014-02-01

    In this study, a simple, facile, and effective wet-chemical strategy was developed in the synthesis of uniform porous Pt-Pd nanospheres (Pt-Pd NSs) supported on reduced graphene oxide nanosheets (RGOs) under ambient temperature, where octylphenoxypolye thoxyethanol (NP-40) is used as a soft template, without any seed, organic solvent or special instruments. The as-prepared nanocomposites display enhanced electrocatalytic activity and good stability toward methanol oxidation, compared with commercial Pd/C and Pt/C catalysts. This strategy may open a new route to design and prepare advanced electrocatalysts for fuel cells.

  1. Formation mechanism of solute clusters under neutron irradiation in ferritic model alloys and in a reactor pressure vessel steel: clusters of defects

    International Nuclear Information System (INIS)

    Meslin-Chiffon, E.

    2007-11-01

    The embrittlement of reactor pressure vessel (RPV) under irradiation is partly due to the formation of point defects (PD) and solute clusters. The aim of this work was to gain more insight into the formation mechanisms of solute clusters in low copper ([Cu] = 0.1 wt%) FeCu and FeCuMnNi model alloys, in a copper free FeMnNi model alloy and in a low copper French RPV steel (16MND5). These materials were neutron-irradiated around 300 C in a test reactor. Solute clusters were characterized by tomographic atom probe whereas PD clusters were simulated with a rate theory numerical code calibrated under cascade damage conditions using transmission electron microscopy analysis. The confrontation between experiments and simulation reveals that a heterogeneous irradiation-induced solute precipitation/segregation probably occurs on PD clusters. (author)

  2. MIS gas sensors based on porous silicon with Pd and WO{sub 3}/Pd electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Solntsev, V.S. [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine); Gorbanyuk, T.I., E-mail: tatyanagor@mail.r [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine); Litovchenko, V.G.; Evtukh, A.A. [Institute of Semiconductor Physics, National Academy of Science of Ukraine, 03028, Kiev (Ukraine)

    2009-09-30

    Pd and WO{sub 3}/Pd gate metal-oxide-semiconductor (MIS) gas sensitive structures based on porous silicon layers are studied by the high frequency C(V) method. The chemical compositions of composite WO{sub 3}/Pd electrodes are characterized by secondary-ion mass spectrometry (SIMS). The atomic force microscopy (AFM) was used for morphologic studies of WO{sub 3}/Pd films. As shown in the experiments, WO{sub 3}/Pd structures are more sensitive and selective to the adsorption of hydrogen sulphide compared to Pd gate. The analyses of kinetic characteristics allow us to determine the response and characteristic times for these structures. The response time of MIS-structures with thin composite WO{sub 3}/Pd electrodes (the thickness of Pd is about 50 nm with WO{sub 3} clusters on its surface) is slower compared to the structures with Pd electrodes. Slower sensor responses of WO{sub 3}-based gas sensors may be associated with different mechanism of gas sensitivity of given structures. The enhanced sensitivity and selectivity to H{sub 2}S action of WO{sub 3}/Pd MIS-structures can also be explained by the chemical reaction that occurs at the catalytic active surface of gate electrodes. The possible mechanisms of enhanced sensitivity and selectivity to H{sub 2}S adsorption of MIS gas sensors with WO{sub 3}/Pd composite gate electrodes compared to pure Pd have been analyzed.

  3. Estimation of breast percent density in raw and processed full field digital mammography images via adaptive fuzzy c-means clustering and support vector machine segmentation

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Brad M.; Nathan, Diane L.; Wang Yan; Zheng Yuanjie; Gee, James C.; Conant, Emily F.; Kontos, Despina [Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Applied Mathematics and Computational Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2012-08-15

    Purpose: The amount of fibroglandular tissue content in the breast as estimated mammographically, commonly referred to as breast percent density (PD%), is one of the most significant risk factors for developing breast cancer. Approaches to quantify breast density commonly focus on either semiautomated methods or visual assessment, both of which are highly subjective. Furthermore, most studies published to date investigating computer-aided assessment of breast PD% have been performed using digitized screen-film mammograms, while digital mammography is increasingly replacing screen-film mammography in breast cancer screening protocols. Digital mammography imaging generates two types of images for analysis, raw (i.e., 'FOR PROCESSING') and vendor postprocessed (i.e., 'FOR PRESENTATION'), of which postprocessed images are commonly used in clinical practice. Development of an algorithm which effectively estimates breast PD% in both raw and postprocessed digital mammography images would be beneficial in terms of direct clinical application and retrospective analysis. Methods: This work proposes a new algorithm for fully automated quantification of breast PD% based on adaptive multiclass fuzzy c-means (FCM) clustering and support vector machine (SVM) classification, optimized for the imaging characteristics of both raw and processed digital mammography images as well as for individual patient and image characteristics. Our algorithm first delineates the breast region within the mammogram via an automated thresholding scheme to identify background air followed by a straight line Hough transform to extract the pectoral muscle region. The algorithm then applies adaptive FCM clustering based on an optimal number of clusters derived from image properties of the specific mammogram to subdivide the breast into regions of similar gray-level intensity. Finally, a SVM classifier is trained to identify which clusters within the breast tissue are likely

  4. Supported Pd nanoclusters for the hydrogen mitigation application in severe accidents

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Zhengfeng; Zhu, Hongzhi; Zhang, Zhi; Zheng, Zhenghua [China Academy of Engineering Physics, P. O. Box 919-71, Mianyang 621700 (China); Ma, Guohua [University of Science and Technology of Southwest, Mianyang 621010 (China); Lai, Xinchun; Li, Rong; Tang, Tao; Fu, Jun [China Academy of Engineering Physics, P. O. Box 919-71, Mianyang 621700 (China); Gao, Bo, E-mail: gaobo@caep.cn [China Academy of Engineering Physics, P. O. Box 919-71, Mianyang 621700 (China)

    2017-05-15

    Highlights: • Pd catalysts were prepared by electroless deposition path with no extra reduction agents. • The Pd catalysts not only have good hydrogen-oxygen recombination efficiency, but also have good stability. • The catalysts were proved to have good resistance to poisoning. • Pd catalysts could be supposed to be used for PARs in severe accidents. - Abstract: Accidents at TMI, USA and Fukushima, Japan have emphasized the need for hydrogen mitigation during nuclear plant accidental conditions, especially during severe accidents which will be no power, massive hydrogen, high temperature, long-term operation, and poisoning environment. Passive autocatalytic recombiners with catalyst sheets are the promising way to deal with the situation in severe accidents. Here we report a new kind of catalyst sheets based on stainless steel supported Pd nanoclusters prepared by electroless deposition route. The catalyst sheets were characterised for morphology and composition of surface by SEM and EDS. The catalytic activity of the catalyst sheets has been evaluated under the conditions of higher temperature, long-term operation and poisoning environments. The catalyst sheets showed high activity and good stability either operating above 500 °C for 24 h or continuous operating for 25 days. For the obtained catalyst sheets after exposed to methanal, iodine vapor and BaSO{sub 4} aerosol respectively with corresponding concentrations higher than SA conditions, the start-up time for H{sub 2}-O{sub 2} recombination reaction was less than 1 min and the catalytic efficiency was more than 90%. These results indicate the potential application of this type of catalyst sheets for hydrogen mitigation in severe accidents.

  5. Methanol steam reforming over Pd/ZnO and Pd/CeO{sub 2} catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ranganathan, Easwar S.; Bej, Shyamal K.; Thompson, Levi T. [University of Michigan, Department of Chemical Engineering, 3026 H.H. Dow Building, 2300 Hayward Avenue, Ann Arbor, MI 48109-2136 (United States)

    2005-08-10

    The goal of work described in this paper was to better understand the methanol steam reforming (MSR) activity and selectivity patterns of ZnO and CeO{sub 2} supported Pd catalysts. This reaction is being used to produce H{sub 2}-rich gas for a number of applications including hydrogen fuel cells. The Pd/ZnO catalysts had lower MSR rates but were more selective for the production of CO{sub 2} than the Pd/CeO{sub 2} catalysts. The CH{sub 3}OH conversion rates were proportional to the H{sub 2} chemisorption uptake suggesting that the rate determining step was catalyzed by Pd. The corresponding turnover frequencies averaged 0.8+/-0.3s{sup -1} and 0.4+/-0.2s{sup -1} at 230{sup o}C for the Pd/ZnO and Pd/CeO{sub 2} catalysts, respectively. The selectivities are explained based on the reaction pathways, and characteristics of the support. The key surface intermediate appeared to be a formate. The ZnO supported catalysts had a higher density of acidic sites and favored pathways where the intermediate was converted to CO{sub 2} while the CeO{sub 2} supported catalysts had a higher density of basic sites and favored the production of CO.

  6. Study of methods to increase cluster/dislocation loop densities in electrodes

    Science.gov (United States)

    Yang, Xiaoling; Miley, George H.

    2009-03-01

    Recent research has developed a technique for imbedding ultra-high density deuterium ``clusters'' (50 to 100 atoms per cluster) in various metals such as Palladium (Pd), Beryllium (Be) and Lithium (Li). It was found the thermally dehydrogenated PdHx retained the clusters and exhibited up to 12 percent lower resistance compared to the virginal Pd samplesootnotetextA. G. Lipson, et al. Phys. Solid State. 39 (1997) 1891. SQUID measurements showed that in Pd these condensed matter clusters approach metallic conditions, exhibiting superconducting propertiesootnotetextA. Lipson, et al. Phys. Rev. B 72, 212507 (2005ootnotetextA. G. Lipson, et al. Phys. Lett. A 339, (2005) 414-423. If the fabrication methods under study are successful, a large packing fraction of nuclear reactive clusters can be developed in the electrodes by electrolyte or high pressure gas loading. This will provide a much higher low-energy-nuclear- reaction (LENR) rate than achieved with earlier electrodeootnotetextCastano, C.H., et al. Proc. ICCF-9, Beijing, China 19-24 May, 2002..

  7. Catalytic activity of bimetallic AuPd alloys supported MgO and MnO2 nanostructures and their role in selective aerobic oxidation of alcohols

    Directory of Open Access Journals (Sweden)

    Hamed Alshammari

    2017-10-01

    Full Text Available The use of metal oxides as supports for gold and palladium (Au-Pd nano alloys constitutes new horizons to improve catalysts materials for very important reactions. From the literatures, Pd-based bimetallic nanostructures have great properties and active catalytic performance. In this study, nanostructures of magnesium oxide (MgO and manganese dioxide (MnO₂ were synthesised and utilized as supports for Au-Pd nanoparticle catalysts. Gold and palladium were deposited on these supports using sol-immobilisation method. The MgO and MnO2 supported Au-Pd catalysts were evaluated for the oxidation of benzyl alcohol and 1-octanol, respectively. These catalysts were found to be more selective, active and reusable than the corresponding monometallic Au and Pd catalysts. The effect of base supports on the disproportionation reaction during the oxidation process was investigated. The results show that MgO stopped the disproportionation reaction for both aromatic and aliphatic alcohols while MnO₂ stopped it in the case of benzyl alcohol only. The outcomes of this work shed light on the selective aerobic oxidation of alcohols using bimetallic Au-Pd nanoalloys and pave the way to a complete investigation of more basic metal oxides for various aliphatic alcohols.

  8. Reversing Size-Dependent Trends in the Oxidation of Copper Clusters through Support Effects: Reversing Size-Dependent Trends in the Oxidation of Copper Clusters through Support Effects

    Energy Technology Data Exchange (ETDEWEB)

    Mammen, Nisha [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, -560064 Bangalore India; Spanu, Leonardo [Shell Technology Center, Shell India Markets Private Limited, -560048 Bangalore India; Tyo, Eric C. [Materials Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Yang, Bing [Materials Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Halder, Avik [Materials Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Seifert, Sönke [X-ray Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Vajda, Stefan [Materials Science Division, Argonne National Laboratory, 60439 Argonne IL USA; Institute for Molecular Engineering, The University of Chicago, 60637 Chicago IL USA; Narasimhan, Shobhana [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, -560064 Bangalore India

    2017-12-22

    Having the ability to tune the oxidation state of Cu nanoparticles is essential for their utility as catalysts. The degree of oxidation that maximizes product yield and selectivity is known to vary, depending on the particular reaction. Using first principles calculations and XANES measurements, we show that for subnanometer sizes in the gas phase, smaller Cu clusters are more resistant to oxidation. However, this trend is reversed upon deposition on an alumina support. We are able to explain this result in terms of strong cluster-support interactions, which differ significantly for the oxidized and elemental clusters. The stable cluster phases also feature novel oxygen stoichiometries. Our results suggest that one can tune the degree of oxidation of Cu catalysts by optimizing not just their size, but also the support they are deposited on.

  9. Al-doped TiO{sub 2} mesoporous material supported Pd with enhanced catalytic activity for complete oxidation of ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Jing, E-mail: mlczjsls123@163.com; Mu, Wentao, E-mail: mwt15035687833@163.com; Su, Liqing, E-mail: suliqing0163@163.com; Li, Xingying, E-mail: lixingying0479@link.tyut.edu.cn; Guo, Yuyu, E-mail: guoyuyu0455@link.tyut.edu.cn; Zhang, Shen, E-mail: zhangshen0472@link.tyut.edu.cn; Li, Zhe, E-mail: lizhe@tyut.edu.cn

    2017-04-15

    Pd catalysts supported on Al-doped TiO{sub 2} mesoporous materials were evaluated in complete oxidation of ethanol. The catalysts synthesized by wet impregnation based on evaporation-induced self-assembly were characterized by X-ray diffraction, measurement of pore structure, XPS, FT-IR, temperature programmed reduction and TEM. Characteristic results showed that the aluminium was doped into the lattice of mesoporous anatase TiO{sub 2} to form Al-O-Ti defect structure. Catalytic results revealed that Al-doped catalysts were much more active than the pristine one, especially at low temperature (≤200 °C). This should be ascribed to the introduction of aluminium ions that suppressed the strong metal-support interaction and increased the active sites of Pd oxides, enhanced the stabilized anatase TiO{sub 2}, improved well dispersed high valence palladium species with high reducibility and enriched chemisorption oxygen. - Graphical abstract: Al-doped Pd/TiO{sub 2} exhibited optimal catalytic performance for ethanol oxidation and CO{sub 2} yield by the suppression of SMSI. - Highlights: • Palladium catalysts supported on Al-doped TiO{sub 2} mesoporous materials were studied. • The introduction of Al can enhance anatase stabilization and increase defect TiO{sub 2}. • The Pd/Al-TiO{sub 2} catalysts show higher ethanol conversion and CO{sub 2} yield than Pd/TiO{sub 2}. • The influence of Al on SMSI and catalytic performance were evaluated by TPR and XPS.

  10. Oxide-supported metal clusters: models for heterogeneous catalysts

    International Nuclear Information System (INIS)

    Santra, A K; Goodman, D W

    2003-01-01

    Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead. (topical review)

  11. Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

    CSIR Research Space (South Africa)

    Ramulifho, T

    2012-01-01

    Full Text Available The preparation of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated multi-walled carbon nanotubes (SF-MWCNTs) using a very rapid microwave-assisted solvothermal strategy has been described. Electrocatalytic behaviour of the SF...

  12. Pd-PEPPSI-IPent-SiO2 : A Supported Catalyst for Challenging Negishi Coupling Reactions in Flow.

    Science.gov (United States)

    Price, Gregory A; Hassan, Abbas; Chandrasoma, Nalin; Bogdan, Andrew R; Djuric, Stevan W; Organ, Michael G

    2017-10-16

    A silica-supported precatalyst, Pd-PEPPSI-IPent-SiO 2 , has been prepared and evaluated for its proficiency in the Negishi cross-coupling of hindered and electronically deactivated coupling partners. The precatalyst Pd-PEPPSI-IPent loaded onto packed bed columns shows high catalytic activity for the room-temperature coupling of deactivated/hindered biaryl partners. Also for the first time, the flowed Csp 3 -Csp 2 coupling of secondary alkylzinc reagents to (hetero)aromatics has been achieved with high selectivity with Pd-PEPPSI-IPent-SiO 2 . These couplings required residence times as short as 3 minutes to effect completion of these challenging transformations with excellent selectivity for the nonrearranged product. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

    International Nuclear Information System (INIS)

    Zhao, Chunjiang; Wu, Huarui

    2017-01-01

    Highlights: • PNG can be acted as micro-sensor for monitoring heavy metal in agriculture. • The most favorable adsorption site of Pd atom or cluster on PNG is the vacancy site. • The Pd atom or cluster enhance the reactivity of PNG toward Hg and AsH_3 adsorption. • The efficiency of a sorbent can be tuned by tailoring the ε_d of adsorbed metals. - Abstract: Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd_n (n = 1–6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH_3 adsorption on PNG. The adsorption ability of Hg on Pd_n decorated PNG is found to be related to the d-band center (ε_d) of the Pd_n, in which the closer ε_d of Pd_n to the Fermi level, the higher adsorption strength for Hg on Pd_n decorated PNG. Moreover, the charge transfer between Pd_n and arsenic may constitute arsenic adsorption on Pd_n decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ε_d of adsorbed metals.

  14. Molecular Dynamics Simulation of Solidification of Pd-Ni Clusters with Different Nickel Content

    Directory of Open Access Journals (Sweden)

    Chen Gang

    2014-01-01

    Full Text Available Molecular dynamics simulation has been performed for investigating the glass transition of Pd-Ni alloy nanoparticles in the solidification process. The results showed that the Pd-Ni nanoparticles with composition far from pure metal should form amorphous structure more easily, which is in accordance with the results of the thermodynamic calculation. There are some regular and distorted fivefold symmetry in the amorphous Pd-Ni alloy nanoparticles. The nanoclusters with bigger difference value between formation enthalpies of solutions and glasses will transform to glass more easily than the other Pd-Ni alloy nanoclusters.

  15. Titania Supported Pt and Pt/Pd Nano-particle Catalysts for the Oxidation of Sulfur Dioxide

    DEFF Research Database (Denmark)

    Koutsopoulos, Sotiris; Johannessen, Tue; Eriksen, Kim Michael

    2006-01-01

    Several types of titania (anatase) were used as supports for pure platinum and Pt–Pd bimetallic alloy catalysts. The preparation methods, normal wet impregnation technique and flame aerosol synthesis, obtained metal loadings of 2% by weight. The prepared catalysts were tested for SO2 oxidation...... activity at atmospheric pressure in the temperature range 250–600 °C. The SO2 to SO3 conversion efficiency of the Pt–Pd alloy was significantly higher than that of the individual metals. The effects of the preparation method and the titania type used on the properties and activity of the resulting catalyst...

  16. Ligand-protected gold clusters: the structure, synthesis and applications

    Science.gov (United States)

    Pichugina, D. A.; Kuz'menko, N. E.; Shestakov, A. F.

    2015-11-01

    Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Aun with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au15 and Au25) and on anchorage to a support surface (Au25/SiO2, Au20/C, Au10/FeOx) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR)n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters MxAunLm (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR)x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active sites. The bibliography includes 345 references.

  17. Supported silver clusters as nanoplasmonic transducers for protein sensing

    DEFF Research Database (Denmark)

    Fojan, Peter; Hanif, Muhammad; Bartling, Stephen

    2015-01-01

    Transducers for optical sensing of proteins are prepared using cluster beam deposition on quartz substrates. Surface plasmon resonance phenomenon of the supported silver clusters is used for the detection. It is shown that surface immobilisation procedure providing adhesion of the silver clusters...... stages and protein immobilisation scheme the sensing of protein of interest can be assured using a relatively simple optical spectroscopy method....... an enhancement of the plasmon absorption band used for the detection. Atomic force microscopy study allows to suggest that immobilisation of antibodies on silver clusters has been achieved, thus giving a possibility to incubate and detect an antigen of interest. Hence, by applying the developed preparation...

  18. Synthesis of a carbon-coated NiO/MgO core/shell nanocomposite as a Pd electro-catalyst support for ethanol oxidation

    International Nuclear Information System (INIS)

    Mahendiran, C.; Maiyalagan, T.; Scott, K.; Gedanken, A.

    2011-01-01

    Highlights: → Carbon coated on NiO/MgO in a core/shell nanostructure is synthesized by RAPET. → The carbon-coated NiO/MgO is supported by Pd. → The electrocatalytic properties of the Pd/(NiO/MgO-C) catalyst for ethanol oxidation studied. - Abstract: Carbon coated on NiO/MgO in a core/shell nanostructure was synthesized by the single-step RAPET (reaction under autogenic pressure at elevated temperatures) technique, and the obtained formation mechanism of the core/shell nanocomposite was presented. The carbon-coated NiO/MgO and its supported Pd catalyst, Pd/(NiO/MgO-C), were characterized by SEM, HR-TEM, XRD and cyclic voltammetry. The X-ray diffraction patterns confirmed the face-centered cubic crystal structure of NiO/MgO. Raman spectroscopy measurements provided structural evidence for the formation of a NiO/MgO composite and the nature of the coated carbon shell. The high-resolution transmission electron microscopy images showed the core and shell morphologies individually. The electrocatalytic properties of the Pd/(NiO/MgO-C) catalyst for ethanol oxidation were investigated in an alkaline solution. The results indicated that the prepared Pd-NiO/MgO-C catalyst has excellent electrocatalytic activity and stability.

  19. Total oxidation of VOCs on Pd and/or Au supported on TiO2/ZrO2 followed by ''operando'' Drift

    International Nuclear Information System (INIS)

    Hosseini, M.; Siffert, St.; Cousin, R.; Aboukais, A.; Hadj-Sadok, Z.; Bao-Lian, Su

    2009-01-01

    Catalytic performances of nano-structured meso-porous TiO 2 -ZrO 2 mixed oxides impregnated by Pd and/or Au were studied in toluene total oxidation in a fixed bed micro-reactor and with 'operando' DRIFT. Meso-porous TiO 2 -ZrO 2 mixed oxides with various Ti:Zr mole ratio of 80/20, 50/50 and 20/80, high surface areas were synthesised using a mixture of zirconium prop-oxide and titanium iso-prop-oxide as Zr and Ti sources and also CTMABr as surfactant. The new supports are impregnated by 0.5 or 1.5 wt% of palladium and 1 wt% of gold using impregnation and Deposition-Precipitation methods. The catalytic activity for the nano-structured meso-porous TiO 2 -ZrO 2 mixed oxides varies depending on the molar ratio of Ti:Zr and also for all series of the studied catalysts impregnated by Pd and/or Au, when the gold is loaded firstly the activity in toluene complete oxidation is higher than when Pd was deposited firstly (PdAu/TZ ≥ 1.5Pd/TZ ≥ AuPd/TZ ≥ Pd/TZ ≥ Au/TZ ≥ TZ). The highest activity of PdAu/TZ (80/20) can be related to the higher acid sites density of the support and also to the presence of a synergetic effect between palladium and gold. 'Operando' DRIFT allowed following the VOCs oxidation but also suggesting an interaction between the adsorbed molecule and the catalyst which decreases when the activity for oxidation reaction increases. (authors)

  20. PERBANDINGAN QUANTUM CLUSTERING DAN SUPPORT VECTOR CLUSTERING UNTUK DATA MICROARRAY EXPRESSION YEAST CELL DALAM RUANG SINGULAR VALUE DECOMPOSITION (SVD)

    OpenAIRE

    ., Riwinoto

    2013-01-01

    Sekarang ini, metode clustering telah diimplementasikan dalam riset DNA. Data dari DNA didapat melalui teknik microarray. Dengan menggunakan metode teknik SVD, dimensi data dikurangi sehingga mempermudah proses komputasi. Dalam paper ini, ditampilkan hasil clustering tanpa pengarahan terhadap gen-gen dari data bakteri ragi dengan menggunakan metode quantum clustering. Sebagai pembanding, dilakukan juga clustering menggunakan metoda Support Vector Clustering. Selain itu juga ditampilkan data h...

  1. Density functional investigation of mercury and arsenic adsorption on nitrogen doped graphene decorated with palladium clusters: A promising heavy metal sensing material in farmland

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chunjiang, E-mail: zhaocj_nercita@163.com [National Engineering Research Center for Information Technology in Agriculture, Beijing 100097 (China); Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097 (China); Key Laboratory for Information Technologies in Agriculture, Ministry of Agriculture, Beijing100097 (China); Wu, Huarui, E-mail: wuhrnercita@163.com [National Engineering Research Center for Information Technology in Agriculture, Beijing 100097 (China); Beijing Research Center for Information Technology in Agriculture, Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097 (China); Key Laboratory for Information Technologies in Agriculture, Ministry of Agriculture, Beijing100097 (China)

    2017-03-31

    Highlights: • PNG can be acted as micro-sensor for monitoring heavy metal in agriculture. • The most favorable adsorption site of Pd atom or cluster on PNG is the vacancy site. • The Pd atom or cluster enhance the reactivity of PNG toward Hg and AsH{sub 3} adsorption. • The efficiency of a sorbent can be tuned by tailoring the ε{sub d} of adsorbed metals. - Abstract: Density functional theory calculations are carried out to study the adsorption of mercury and arsenic on Pd{sub n} (n = 1–6) supported on pyridine-like nitrogen doped graphene (PNG). Owing to the promising sensitivity in trace amounts of atoms or molecules, PNG can be acted as micro-sensor for sensing heavy metals in agriculture soils. Through the analyses of structural and electronic properties of pristine PNG and Pd atom decorated PNG, we find that the most favorable adsorption site for Pd atom is the vacancy site. The analyses of structural and electronic properties reveal that the Pd atom or clusters can enhance the reactivity for Hg and AsH{sub 3} adsorption on PNG. The adsorption ability of Hg on Pd{sub n} decorated PNG is found to be related to the d-band center (ε{sub d}) of the Pd{sub n}, in which the closer ε{sub d} of Pd{sub n} to the Fermi level, the higher adsorption strength for Hg on Pd{sub n} decorated PNG. Moreover, the charge transfer between Pd{sub n} and arsenic may constitute arsenic adsorption on Pd{sub n} decorated PNG. Further design of highly efficient carbon based sorbents for heavy metals removal should be focused on tailoring ε{sub d} of adsorbed metals.

  2. A green method to prepare Pd-Ag nanoparticles supported on reduced graphene oxide and their electrochemical catalysis of methanol and ethanol oxidation

    Science.gov (United States)

    Li, Lingzhi; Chen, Mingxi; Huang, Guanbo; Yang, Nian; Zhang, Li; Wang, Huan; Liu, Yu; Wang, Wei; Gao, Jianping

    2014-10-01

    Bimetallic palladium-silver nanoparticles (NPs) supported on reduced oxide graphene (RGO) with different Pd/Ag ratios (Pd-Ag/RGO) were prepared by an easy green method which did not use any additional reducing agents or a dispersing agent. During the process, simultaneous redox reactions between AgNO3, K2PdCl4 and graphene oxide (GO) led to bimetallic Pd-Ag NPs. The morphology and composition of the Pd-Ag/RGO were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman spectroscopy. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of these Pd-Ag/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. Among the different Pd/Ag ratios, the Pd-Ag (1:1)/RGO had the best catalytic activities and stability. So it is a promising catalyst for direct alcohol fuel cell applications.

  3. Architecture of Pd-Au bimetallic nanoparticles in sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles as investigated by X-ray absorption spectroscopy.

    Science.gov (United States)

    Chen, Ching-Hsiang; Sarma, Loka Subramanyam; Chen, Jium-Ming; Shih, Shou-Chu; Wang, Guo-Rung; Liu, Din-Goa; Tang, Mau-Tsu; Lee, Jyh-Fu; Hwang, Bing-Joe

    2007-09-01

    In this study, we demonstrate the unique application of X-ray absorption spectroscopy (XAS) as a fundamental characterization tool to help in designing and controlling the architecture of Pd-Au bimetallic nanoparticles within a water-in-oil microemulsion system of water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane. Structural insights obtained from the in situ XAS measurements recorded at each step during the formation process revealed that Pd-Au bimetallic clusters with various Pd-Au atomic stackings are formed by properly performing hydrazine reduction and redox transmetalation reactions sequentially within water-in-oil microemulsions. A structural model is provided to explain reasonably each reaction step and to give detailed insight into the nucleation and growth mechanism of Pd-Au bimetallic clusters. The combination of in situ XAS analysis at both the Pd K-edge and the Au L(III)-edge and UV-vis absorption spectral features confirms that the formation of Pd-Au bimetallic clusters follows a (Pd(nuclei)-Au(stack))-Pd(surf) stacking. This result further implies that the thickness of Au(stack) and Pd(surf) layers may be modulated by varying the dosage of the Au precursor and hydrazine, respectively. In addition, a bimetallic (Pd-Au)(alloy) nanocluster with a (Pd(nuclei)-Au(stack))-(Pd-Au(alloy))(surf) stacking was also designed and synthesized in order to check the feasibility of Pd(surf) layer modification. The result reveals that the Pd(surf) layer of the stacked (Pd(nuclei)-Au)(stack) bimetallic clusters can be successfully modified to form a (Au-Pd alloy)(surf) layer by a co-reduction of Pd and Au ions by hydrazine. Further, we demonstrate the alloying extent or atomic distribution of Pd and Au in Pd-Au bimetallic nanoparticles from the derived XAS structural parameters. The complete XAS-based methodology, demonstrated here on the Pd-Au bimetallic system, can easily be extended to design and control the alloying extent or atomic distribution, atomic

  4. Efectos de la magnesia sobre la combinación de la cal en el clínker

    Directory of Open Access Journals (Sweden)

    Hesselljerg Christenssen, Niels

    1979-06-01

    Full Text Available El autor se propone, en este muy apreciable artículo, poner de manifiesto que la magnesia en el clínker de portland no es un constituyente "traza" sino que tiene efectos pequeños pero distintos en la calcinación del clínker, diferentes del efecto perjudicial que ejercería en la estabilidad del hormigón, motivo de su limitación al 6% en la mayoría de las normas qué condicionan al cemento portland.

  5. Fuzzy Modeled K-Cluster Quality Mining of Hidden Knowledge for Decision Support

    OpenAIRE

    S. Parkash  Kumar; K. S. Ramaswami

    2011-01-01

    Problem statement: The work presented Fuzzy Modeled K-means Cluster Quality Mining of hidden knowledge for Decision Support. Based on the number of clusters, number of objects in each cluster and its cohesiveness, precision and recall values, the cluster quality metrics is measured. The fuzzy k-means is adapted approach by using heuristic method which iterates the cluster to form an efficient valid cluster. With the obtained data clusters, quality assessment is made by predictive mining using...

  6. Pd-NiO decorated multiwalled carbon nanotubes supported on reduced graphene oxide as an efficient electrocatalyst for ethanol oxidation in alkaline medium

    Science.gov (United States)

    Rajesh, Dhanushkotti; Indra Neel, Pulidindi; Pandurangan, Arumugam; Mahendiran, Chinnathambi

    2018-06-01

    The synthesis of Pd-NiO nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) on reduced graphene oxide (rGO) for ethanol electrooxidation is reported. NiO nanoparticles (NPs) were deposited on functionalized MWCNTs by wet impregnation method. Pd nanoparticles were formed on NiO-MWCNTs by the addition of PdCl2 and its reduction using NaBH4. The Pd-NiO/MWCNTs nanocomposite then deposited on rGO support using ultrasound irradiation which led to the formation of the Pd-NiO/MWCNTs/rGO electrocatalyst. The prepared electrocatalysts were characterized by XRD, SEM, HR-TEM and XPS analysis. Electrochemical measurements demonstrate that as synthesized Pd-NiO/MWCNTs/rGO electrocatalyst exhibit higher catalytic activity (90.89 mA/cm2) than either Pd/MWCNTs/rGO (43.05 mA/cm2) or Pd/C (28.0 mA/cm2) commercial catalyst. Chronoamperometry study of Pd-NiO/MWCNTs/rGO electrocatalyst showed long-term electrochemical stability. The enhanced catalytic activity of Pd-NiO/MWCNTs/rGO electrocatalyst for electrooxidation of ethanol can be attributed to the synergistic effect between Pd & NiO active sites.

  7. K-means clustering for support construction in diffractive imaging.

    Science.gov (United States)

    Hattanda, Shunsuke; Shioya, Hiroyuki; Maehara, Yosuke; Gohara, Kazutoshi

    2014-03-01

    A method for constructing an object support based on K-means clustering of the object-intensity distribution is newly presented in diffractive imaging. This releases the adjustment of unknown parameters in the support construction, and it is well incorporated with the Gerchberg and Saxton diagram. A simple numerical simulation reveals that the proposed method is effective for dynamically constructing the support without an initial prior support.

  8. Cluster A personality pathology in social anxiety disorder: a comparison with panic disorder.

    Science.gov (United States)

    O'Toole, Mia Skytte; Arendt, Mikkel; Fentz, Hanne Nørr; Hougaard, Esben; Rosenberg, Nicole K

    2014-10-01

    Social anxiety disorder (SAD) has been associated with cluster A personality disorder (PD) traits, mainly paranoid and schizoid traits. The aim of the study was to further investigate cluster A personality pathology in patients with SAD. Self-reported PD traits were investigated in a clinical sample of 161 participants with SAD and in a clinical comparison group of 145 participants with panic disorder with or without agoraphobia (PAD). A diagnosis of SAD was associated with more paranoid and schizotypal PD traits, and an association between depression and personality pathology could indicate a state-effect of depression on PD traits. Patients with SAD had more cluster A personality pathology than patients with PAD, with the most solid indication for paranoid personality pathology.

  9. Barium oxide, calcium oxide, magnesia, and alkali oxide free glass

    Science.gov (United States)

    Lu, Peizhen Kathy; Mahapatra, Manoj Kumar

    2013-09-24

    A glass composition consisting essentially of about 10-45 mole percent of SrO; about 35-75 mole percent SiO.sub.2; one or more compounds from the group of compounds consisting of La.sub.2O.sub.3, Al.sub.2O.sub.3, B.sub.2O.sub.3, and Ni; the La.sub.2O.sub.3 less than about 20 mole percent; the Al.sub.2O.sub.3 less than about 25 mole percent; the B.sub.2O.sub.3 less than about 15 mole percent; and the Ni less than about 5 mole percent. Preferably, the glass is substantially free of barium oxide, calcium oxide, magnesia, and alkali oxide. Preferably, the glass is used as a seal in a solid oxide fuel/electrolyzer cell (SOFC) stack. The SOFC stack comprises a plurality of SOFCs connected by one or more interconnect and manifold materials and sealed by the glass. Preferably, each SOFC comprises an anode, a cathode, and a solid electrolyte.

  10. Application of affinity propagation algorithm based on manifold distance for transformer PD pattern recognition

    Science.gov (United States)

    Wei, B. G.; Huo, K. X.; Yao, Z. F.; Lou, J.; Li, X. Y.

    2018-03-01

    It is one of the difficult problems encountered in the research of condition maintenance technology of transformers to recognize partial discharge (PD) pattern. According to the main physical characteristics of PD, three models of oil-paper insulation defects were set up in laboratory to study the PD of transformers, and phase resolved partial discharge (PRPD) was constructed. By using least square method, the grey-scale images of PRPD were constructed and features of each grey-scale image were 28 box dimensions and 28 information dimensions. Affinity propagation algorithm based on manifold distance (AP-MD) for transformers PD pattern recognition was established, and the data of box dimension and information dimension were clustered based on AP-MD. Study shows that clustering result of AP-MD is better than the results of affinity propagation (AP), k-means and fuzzy c-means algorithm (FCM). By choosing different k values of k-nearest neighbor, we find clustering accuracy of AP-MD falls when k value is larger or smaller, and the optimal k value depends on sample size.

  11. Recombinant human G6PD for quality control and quality assurance of novel point-of-care diagnostics for G6PD deficiency.

    Directory of Open Access Journals (Sweden)

    Maria Kahn

    Full Text Available A large gap for the support of point-of-care testing is the availability of reagents to support quality control (QC of diagnostic assays along the supply chain from the manufacturer to the end user. While reagents and systems exist to support QC of laboratory screening tests for glucose-6-phosphate dehydrogenase (G6PD deficiency, they are not configured appropriately to support point-of-care testing. The feasibility of using lyophilized recombinant human G6PD as a QC reagent in novel point-of-care tests for G6PD deficiency is demonstrated.Human recombinant G6PD (r-G6PD was expressed in Escherichia coli and purified. Aliquots were stored at -80°C. Prior to lyophilization, aliquots were thawed, and three concentrations of r-G6PD (representing normal, intermediate, and deficient clinical G6PD levels were prepared and mixed with a protective formulation, which protects the enzyme activity against degradation from denaturation during the lyophilization process. Following lyophilization, individual single-use tubes of lyophilized r-G6PD were placed in individual packs with desiccants and stored at five temperatures for one year. An enzyme assay for G6PD activity was used to ascertain the stability of r-G6PD activity while stored at different temperatures.Lyophilized r-G6PD is stable and can be used as a control indicator. Results presented here show that G6PD activity is stable for at least 365 days when stored at -80°C, 4°C, 30°C, and 45°C. When stored at 55°C, enzyme activity was found to be stable only through day 28.Lyophilized r-G6PD enzyme is stable and can be used as a control for point-of-care tests for G6PD deficiency.

  12. The role of the poet in Plato's ideal cities of Callipolis and Magnesia

    Directory of Open Access Journals (Sweden)

    Gerard Naddaf

    2008-01-01

    Full Text Available Plato's attitude toward the poets and poetry has always been a flashpoint of debate, controversy and notoriety, but most scholars have failed to see their central role in the ideal cities of the Republic and the Laws, that is, Callipolis and Magnesia. In this paper, I argue that in neither dialogue does Plato "exile" the poets, but, instead, believes they must, like all citizens, exercise the expertise proper to their profession, allowing them the right to become full-fledged participants in the productive class. Moreover, attention to certain details reveals that Plato harnesses both positive and negative factors in poetry to bring his ideal cities closer to a practical realization. The status of the poet and his craft in this context has rarely to my knowledge been addressed.

  13. Dual-functional Pt-on-Pd supported on reduced graphene oxide hybrids: peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic.

    Science.gov (United States)

    Zhang, Xiahong; Wu, Genghuang; Cai, Zhixiong; Chen, Xi

    2015-03-01

    In this study, a facile hydrothermal method was developed to synthesize Pt-on-Pd supported on reduced graphene oxide (Pt-on-Pd/RGO) hybrids. Because of the synergistic effect between Pt-on-Pd and RGO, the obtained Pt-on-Pd/RGO had superior peroxidase-mimic activities in H2O2 reduction and TMB oxidation. The reaction medium was optimized and a sensing approach for H2O2 was developed with a linear range from 0.98 to 130.7 μM of H2O2. In addition, the characteristic of electrocatalytic oxidation of methanol was investigated. The peak current density value, j(f), for the Pt-on-Pd/RGO hybrid (328 mA mg(Pt)(-1)) was about 1.85 fold higher than that of commercial Pt black (177 mA mg(Pt)(-1)) and, also, more durable electrocatalytic activity could be obtained. For the first time, the dual-functional Pt-on-Pd/RGO with peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic was reported. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Hydrogenation of tetralin in the presence of dibenzothiophene and quinoline on Pt-Pd/SiO{sub 2}-Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, O.Y.; Yu, Y.; Jentys, A.; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center

    2012-07-01

    Three Pt-Pd catalysts with 0.3 and 0.5 wt.% of Pt and Pd, respectively, were supported on amorphous silica alumina with Al{sub 2}O{sub 3}:SiO{sub 2} wt.% ratios of 20:80, 30:70 and 55:45. The materials were characterized by physisorption of N{sub 2}, TEM, X-ray absorption spectroscopy and adsorption of pyridine and CO followed by IR spectroscopy. The EXAFS fitting and IR characterization showed that bimodal distributions of monometallic Pd and bimetallic Pt-Pd particles. The bimetallic particles in all catalysts have a Pt-rich core and a Pd-rich shell. However, the degree of alloying and proportion of exposed Pt increases with increasing concentration of Lewis acid sites (LAS) in the support, probably because the LAS are good anchoring sites for Pt species. The activity of the catalysts for the hydrogenation of tetralin in the presence of DBT and quinoline, and the corresponding selectivity to cis-decalin increase with the proportion of exposed Pt. Therefore, in the presence of DBT and quinoline the morphology of bimetallic clusters is the parameter determining its hydrogenation performance. (orig.)

  15. Carbon-supported PdM (M = Au and Sn) nanocatalysts for the electrooxidation of ethanol in high pH media

    Science.gov (United States)

    He, Qinggang; Chen, Wei; Mukerjee, Sanjeev; Chen, Shaowei; Laufek, František

    Carbon-supported Pd 4Au- and Pd 2.5Sn-alloyed nanoparticles were prepared by a chemical reduction method, and characterized by a wide array of experimental techniques including mass spectrometry, transmission electron microscopy, and X-ray diffraction spectroscopy. Ethanol electrooxidation on the as-synthesized catalysts and commercial Pt/C was then investigated and compared in alkaline media by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy studies at room temperature. Voltammetric and chronoamperometric measurements showed higher current density and longer term stability in ethanol oxidation with the palladium alloy nanocatalysts than with the commercial one. Electrochemical impedance spectroscopy and Tafel plots were employed to examine the charge-transfer kinetics of ethanol electrooxidation. The results suggest that whereas the reaction kinetics might be somewhat more sluggish on the Pd-based alloy catalysts than on commercial Pt/C, the former appeared to have a higher tolerance to surface poisoning. Overall, the Pd-based alloy catalysts represent promising candidates for the electrocatalytic oxidation of ethanol, and Pd 4Au/C displays the best catalytic activity among the series for the ethanol oxidation in alkaline media.

  16. Ligand-protected gold clusters: the structure, synthesis and applications

    International Nuclear Information System (INIS)

    Pichugina, D A; Kuz'menko, N E; Shestakov, A F

    2015-01-01

    Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Au n with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au 15 and Au 25 ) and on anchorage to a support surface (Au 25 /SiO 2 , Au 20 /C, Au 10 /FeO x ) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR) n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters M x Au n L m (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR) x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active

  17. Shape-controlled synthesis of Pd polyhedron supported on polyethyleneimine-reduced graphene oxide for enhancing the efficiency of hydrogen evolution reaction

    Science.gov (United States)

    Li, Jing; Zhou, Panpan; Li, Feng; Ma, Jianxin; Liu, Yang; Zhang, Xueyao; Huo, Hongfei; Jin, Jun; Ma, Jiantai

    2016-01-01

    The catalytic activity of noble-metal nanoparticles (NPs) often has closely connection with their sizes and geometric shape. In the work, polyhedral NPs of palladium (Pd) with controlled sizes, shapes, and different proportions of {100} to {111} facets on the surface were prepared by a seed-mediated approach. Electrochemical experiment demonstrates that the catalytic performance of the Pd nanocubes (NCs) enclosed by {100} facets is more active than Pd octahedrons enclosed by {111} facets for the hydrogen evolution reaction (HER), which is consistent with density functional theory (DFT) calculation results. Meanwhile, with the assistance of a polyethyleneimine-reduced graphene oxide (PEI-rGO) support, the examined Pd cube/PEI-rGO50:1 (10 wt. %) electrocatalyst presents outstanding HER activity comparable with that of commercial Pt/C catalyst. This correlation between the HER catalytic activity and surface structure will contribute to the reasonable design of Pd catalysts for HER with high efficiency and low metal loading.

  18. Fischer–Tropsch Synthesis at a Low Pressure on Subnanometer Cobalt Oxide Clusters: The Effect of Cluster Size and Support on Activity and Selectivity

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sungsik; Lee, Byeongdu; Seifert, Sönke; Winans, Randall E.; Vajda, Stefan

    2015-05-21

    In this study, the catalytic activity and changes in the oxidation state during the Fischer Tropsch (FT) reaction was investigated on subnanometer size-selected cobalt clusters deposited on oxide (Al2O3, MgO) and carbon-based (ultrananocrystalline diamond UNCD) supports by temperature programmed reaction (TPRx) combined with in-situ grazing-incidence X-ray absorption characterization (GIXAS). The activity and selectivity of ultrasmall cobalt clusters exhibits a very strong dependence on cluster size and support. The evolution of the oxidation state of metal cluster during the reaction reveals that metal-support interaction plays a key role in the reaction.

  19. Hydrocracking of α-Cellulose Using Co, Ni, and Pd Supported on Mordenite Catalysts

    Directory of Open Access Journals (Sweden)

    Wega Trisunaryanti

    2018-02-01

    Full Text Available Hydrocracking of α-cellulose has been conducted in a semi-batch reactor at 400, 450, and 500 °C with hydrogen flow (30 mL/min. for 4 h. Mordenite (MOR and Co, Ni and Pd metal supported on the MOR were used as solid catalysts. The catalysts were characterized using X-ray Diffractometer (XRD, Fourier Transform Infrared (FTIR spectroscopy, and Scanning Electron Microscopy (SEM to evaluate the physical-chemical properties. Energy Dispersive X-ray (EDX and Inductively Coupled Plasma (ICP were used to analyze the amount of metal impregnated on the catalysts. The liquid product was analyzed using Gas Chromatograph-Mass Spectroscopy (GC-MS. Thermal hydrocracking was also conducted at 450 °C with the amount of liquid product was 37.86 wt.%. The highest liquid conversion obtained by mordenite catalyst was 94.66 wt.% at 450 °C and the highest liquid conversion (98.08 wt.% was reached by Pd/MOR catalyst at 400 °C.

  20. Ab initio random structure search for 13-atom clusters of fcc elements

    International Nuclear Information System (INIS)

    Chou, J P; Hsing, C R; Wei, C M; Cheng, C; Chang, C M

    2013-01-01

    The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. The global minima were searched for by the ab initio random structure searching method. In addition to some new lowest-energy structures for Pd 13 and Au 13 , we found that the effective coordination numbers of the lowest-energy clusters would increase with the ratio of the dimer-to-bulk bond length. This correlation, together with the electronic structures of the lowest-energy clusters, divides the 13-atom clusters of these fcc elements into two groups (except for Au 13 , which prefers a two-dimensional structure due to the relativistic effect). Compact-like clusters that are composed exclusively of triangular motifs are preferred for elements without d-electrons (Al) or with (nearly) filled d-band electrons (Ni, Pd, Cu, Ag). Non-compact clusters composed mainly of square motifs connected by some triangular motifs (Rh, Ir, Pt) are favored for elements with unfilled d-band electrons. (paper)

  1. Oxidation of CO and Methanol on Pd-Ni Catalysts Supported on Different Chemically-Treated Carbon Nanofibers

    Directory of Open Access Journals (Sweden)

    Juan Carlos Calderón

    2016-10-01

    Full Text Available In this work, palladium-nickel nanoparticles supported on carbon nanofibers were synthesized, with metal contents close to 25 wt % and Pd:Ni atomic ratios near to 1:2. These catalysts were previously studied in order to determine their activity toward the oxygen reduction reaction. Before the deposition of metals, the carbon nanofibers were chemically treated in order to generate oxygen and nitrogen groups on their surface. Transmission electron microscopy analysis (TEM images revealed particle diameters between 3 and 4 nm, overcoming the sizes observed for the nanoparticles supported on carbon black (catalyst Pd-Ni CB 1:2. From the CO oxidation at different temperatures, the activation energy Eact for this reaction was determined. These values indicated a high tolerance of the catalysts toward the CO poisoning, especially in the case of the catalysts supported on the non-chemically treated carbon nanofibers. On the other hand, apparent activation energy Eap for the methanol oxidation was also determined finding—as a rate determining step—the COads diffusion to the OHads for the catalysts supported on carbon nanofibers. The results here presented showed that the surface functional groups only play a role in the obtaining of lower particle sizes, which is an important factor in the obtaining of low CO oxidation activation energies.

  2. Structure sensitivity in the nonscalable regime explored via catalysed ethylene hydrogenation on supported platinum nanoclusters

    Science.gov (United States)

    Crampton, Andrew S.; Rötzer, Marian D.; Ridge, Claron J.; Schweinberger, Florian F.; Heiz, Ueli; Yoon, Bokwon; Landman, Uzi

    2016-01-01

    The sensitivity, or insensitivity, of catalysed reactions to catalyst structure is a commonly employed fundamental concept. Here we report on the nature of nano-catalysed ethylene hydrogenation, investigated through experiments on size-selected Ptn (n=8-15) clusters soft-landed on magnesia and first-principles simulations, yielding benchmark information about the validity of structure sensitivity/insensitivity at the bottom of the catalyst size range. Both ethylene-hydrogenation-to-ethane and the parallel hydrogenation-dehydrogenation ethylidyne-producing route are considered, uncovering that at the =10) clusters at T>150 K, with maximum room temperature reactivity observed for Pt13. Structure insensitivity, inherent for specific cluster sizes, is induced in the more active Pt13 by a temperature increase up to 400 K leading to ethylidyne formation. Control of sub-nanometre particle size may be used for tuning catalysed hydrogenation activity and selectivity.

  3. TiO2/C composite as a support for Pd-nanoparticles toward the electrocatalytic oxidation of methanol in alkaline media

    International Nuclear Information System (INIS)

    Estudillo-Wong, L.A.; Vargas-Gómez, A.M.; Arce-Estrada, E.M.; Manzo-Robledo, A.

    2013-01-01

    The electro-oxidation of methanol was studied in alkaline solution on Pd nanoparticles supported on carbon black (XC-72R, C) and TiO 2 /C composite. The materials were prepared via organic colloid route at 170 °C with 5 wt% of Pd. X-ray diffraction (XRD), PdO monolayer reduction (PdO red ) and CO-stripping was employed to characterize both structure and electrochemical properties. According to this, the lattice parameter decreases from 0.3991 to 0.3905 nm due to a possible formation of Pd–Ti alloy. This modification is linked with the electrochemical active surface area (ECSA) decreasing from 22 to 18 m 2 g −1 . On the other hand, studies as a function of temperature and alcohol concentration indicated that the current for methanol electro-oxidation is higher and more stable at Pd/TiO 2 –C, with E a = 44.042 kJ mol −1 . Then, it is highly possible that at Pd/TiO 2 –C, the OH − /OH ads couple is adsorbed at the TiO 2 sites, increasing the kinetic of methanol oxidation reaction at the catalyst surface

  4. RHEED and EELS study of Pd/Al bimetallic thin film growth on different α-Al 2O 3 substrates

    Science.gov (United States)

    Moroz, V.; Rajs, K.; Mašek, K.

    2002-06-01

    Pd/Al bimetallic thin films were grown by molecular beam epitaxy on single-crystalline α-Al 2O 3(0 0 0 1) and (1 1 2¯ 0) surfaces. Substrate and deposit crystallographic structures and evolution of deposit lattice parameter during the growth were studied by reflection high-energy electron diffraction. The electron energy loss spectroscopy was used as an auxiliary method for chemical analysis. The bimetallic films were prepared by successive deposition of both Pd and Al metals. The structure of Pd and Al deposits in early stages of the growth and its dependence on the preparation conditions were studied. Two phases of Pd clusters covered by Al overlayer have been found. The formation of Al overlayer strongly influenced the lattice parameter of Pd clusters.

  5. Magneto-structural properties and magnetic anisotropy of small transition-metal clusters: a first-principles study

    International Nuclear Information System (INIS)

    Blonski, Piotr; Hafner, Juergen

    2011-01-01

    Ab initio density-functional calculations including spin-orbit coupling (SOC) have been performed for Ni and Pd clusters with three to six atoms and for 13-atom clusters of Ni, Pd, and Pt, extending earlier calculations for Pt clusters with up to six atoms (2011 J. Chem. Phys. 134 034107). The geometric and magnetic structures have been optimized for different orientations of the magnetization with respect to the crystallographic axes of the cluster. The magnetic anisotropy energies (MAE) and the anisotropies of spin and orbital moments have been determined. Particular attention has been paid to the correlation between the geometric and magnetic structures. The magnetic point group symmetry of the clusters varies with the direction of the magnetization. Even for a 3d metal such as Ni, the change in the magnetic symmetry leads to small geometric distortions of the cluster structure, which are even more pronounced for the 4d metal Pd. For a 5d metal the SOC is strong enough to change the energetic ordering of the structural isomers. SOC leads to a mixing of the spin states corresponding to the low-energy spin isomers identified in the scalar-relativistic calculations. Spin moments are isotropic only for Ni clusters, but anisotropic for Pd and Pt clusters, orbital moments are anisotropic for the clusters of all three elements. The magnetic anisotropy energies have been calculated. The comparison between MAE and orbital anisotropy invalidates a perturbation analysis of magnetic anisotropy for these small clusters.

  6. Improvement of oxidation resistance in magnesia-graphite material for casting nozzle; Chuzo nozuru yo maguneshia-kokuen zaishitsu no tai sankasei kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Rikimaru, Yasushi.; Iitsuka, Shoji.; Harada, Tsutomu.; Ando, Hideyuki.; Yamato, Tsugio. [Kurosaki Corp., Fukuoka (Japan). Technical Research Center

    1999-08-01

    As for the alumina black lead quality of the material, it knows that loss grows big caused by CaO from steel and the formation of the low melting point material due to the response with the alumina in the refractories at the time of the Ca-Si management steel cast. Because of this, it was exchanged with the AG quality of the material for the nozzle union department that emphasis could specially cut abrasion and corrosion, and the application of the magnesia black lead quality of the material was examined. Slag caused by the disappearance that black lead on the operating side oxidizes and the permeation of the metal were recognized as the improvement in the corrosion though it was recognized when an actual opportunity checked a ceremony nozzle in the Ca-Si management steel while MG quality of the material was applied to the union part. The decline of the durability due to the disappearance that black lead oxidizes from not forming it was recognized on the operating side in the bone material and the steel the low melting point material layer due to the response with the element because a magnesia was high melting point material when a nozzle was usually used for the steel again. (NEDO)

  7. The effect of alkylating agents on model supported metal clusters

    Energy Technology Data Exchange (ETDEWEB)

    Erdem-Senatalar, A.; Blackmond, D.G.; Wender, I. (Pittsburgh Univ., PA (USA). Dept. of Chemical and Petroleum Engineering); Oukaci, R. (CERHYD, Algiers (Algeria))

    1988-01-01

    Interactions between model supported metal clusters and alkylating agents were studied in an effort to understand a novel chemical trapping technique developed for identifying species adsorbed on catalyst surfaces. It was found that these interactions are more complex than had previously been suggested. Studies were completed using deuterium-labeled dimethyl sulfate (DMS), (CH{sub 3}){sub 2}SO{sub 4}, as a trapping agent to interact with the supported metal cluster ethylidyne tricobalt enneacarbonyl. Results showed that oxygenated products formed during the trapping reaction contained {minus}OCD{sub 3} groups from the DMS, indicating that the interaction was not a simple alkylation. 18 refs., 1 fig., 3 tabs.

  8. Carbon-supported PdM (M = Au and Sn) nanocatalysts for the electrooxidation of ethanol in high pH media

    Energy Technology Data Exchange (ETDEWEB)

    He, Qinggang; Mukerjee, Sanjeev [Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115 (United States); Chen, Wei; Chen, Shaowei [Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); Laufek, Frantisek [Czech Geological Survey (Czech Republic)

    2009-02-15

    Carbon-supported Pd{sub 4}Au- and Pd{sub 2.5}Sn-alloyed nanoparticles were prepared by a chemical reduction method, and characterized by a wide array of experimental techniques including mass spectrometry, transmission electron microscopy, and X-ray diffraction spectroscopy. Ethanol electrooxidation on the as-synthesized catalysts and commercial Pt/C was then investigated and compared in alkaline media by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy studies at room temperature. Voltammetric and chronoamperometric measurements showed higher current density and longer term stability in ethanol oxidation with the palladium alloy nanocatalysts than with the commercial one. Electrochemical impedance spectroscopy and Tafel plots were employed to examine the charge-transfer kinetics of ethanol electrooxidation. The results suggest that whereas the reaction kinetics might be somewhat more sluggish on the Pd-based alloy catalysts than on commercial Pt/C, the former appeared to have a higher tolerance to surface poisoning. Overall, the Pd-based alloy catalysts represent promising candidates for the electrocatalytic oxidation of ethanol, and Pd{sub 4}Au/C displays the best catalytic activity among the series for the ethanol oxidation in alkaline media. (author)

  9. Predicting catalyst-support interactions between metal nanoparticles and amorphous silica supports

    Science.gov (United States)

    Ewing, Christopher S.; Veser, Götz; McCarthy, Joseph J.; Lambrecht, Daniel S.; Johnson, J. Karl

    2016-10-01

    Metal-support interactions significantly affect the stability and activity of supported catalytic nanoparticles (NPs), yet there is no simple and reliable method for estimating NP-support interactions, especially for amorphous supports. We present an approach for rapid prediction of catalyst-support interactions between Pt NPs and amorphous silica supports for NPs of various sizes and shapes. We use density functional theory calculations of 13 atom Pt clusters on model amorphous silica supports to determine linear correlations relating catalyst properties to NP-support interactions. We show that these correlations can be combined with fast discrete element method simulations to predict adhesion energy and NP net charge for NPs of larger sizes and different shapes. Furthermore, we demonstrate that this approach can be successfully transferred to Pd, Au, Ni, and Fe NPs. This approach can be used to quickly screen stability and net charge transfer and leads to a better fundamental understanding of catalyst-support interactions.

  10. Significant promotion effect of carbon nanotubes on the electrocatalytic activity of supported Pd NPs for ethanol oxidation reaction of fuel cells: the role of inner tubes.

    Science.gov (United States)

    Zhang, Jin; Cheng, Yi; Lu, Shanfu; Jia, Lichao; Shen, Pei Kang; Jiang, San Ping

    2014-11-18

    The inner tubes of carbon nanotubes (CNTs) have a significant promotion effect on the electrocatalytic activity of Pd nanoparticles (NPs) for the ethanol oxidation of direct alcohol fuel cells (DAFCs) and Pd NPs supported on CNTs with 3-7 walls show a much higher activity as compared to that supported on typical single-walled and multi-walled CNTs.

  11. Aqueous phase hydrogenation of phenol catalyzed by Pd and PdAg on ZrO 2

    Energy Technology Data Exchange (ETDEWEB)

    Resende, Karen A.; Hori, Carla E.; Noronha, Fabio B.; Shi, Hui; Gutierrez, Oliver Y.; Camaioni, Donald M.; Lercher, Johannes A.

    2017-11-01

    Hydrogenation of phenol in aqueous phase was studied over a series of ZrO2-supported Pd catalysts in order to explore the effects of particle size and of Ag addition on the activity of Pd. Kinetic assessments were performed in a batch reactor, on monometallic Pd/ZrO2 samples with different Pd loadings (0.5%, 1% and 2%), as well as on a 1% PdAg/ZrO2 sample. The turnover frequency (TOF) increases with the Pd particle size. The reaction orders in phenol and H2 indicate that the surface coverages by phenol, H2 and their derived intermediates are higher on 0.5% Pd/ZrO2 than on other samples. The activation energy was the lowest on the least active sample (0.5% Pd/ZrO2), while being identical on 1% and 2% Pd/ZrO2 catalysts. Thus, the significantly lower activity of the small Pd particles (1-2 nm on average) in 0.5%Pd/ZrO2 is explained by the unfavorable activation entropies for the strongly bound species. The presence of Ag increases considerably the TOF of the reaction by decreasing the Ea and increasing the coverages of phenol and H2.

  12. A Density Functional Theory Investigation of Nin , Pdn , and Ptn Clusters (n=1-4) Adsorbed on Buckminsterfullerene.

    Science.gov (United States)

    Pham, Nguyet N T; Le, Hung M

    2017-05-19

    In this study, we examine the adsorptions of Ni, Pd, and Pt clusters on C 60 by using a computational approach. Our calculation results show that the base structure of C 60 can host Ni n /Pd n /Pt n (n=1-4) clusters with good adsorption stability and the complexes establish either two or no unpaired electrons. The binding energy of Pd and Pt clusters increases as the number of metal atoms increases, implying that the coverage of C 60 with Pd or Pt preferentially establishes a large-size metal cluster. A single metal atom favorably occupies the C-C bridge site. For dimer clusters, the three metals of interest share a similar binding fashion, in which two metal atoms establish direct interactions with the C-C bridge sites. For trimer adsorptions, the formation of linear and triangular structures is observed. Both Pt 3 and Ni 3 preferably constitute isosceles triangles on C 60 , whilst Pd 3 favorably establishes a linear shape. Finally, for each of the Ni 4 and Pd 4 adsorption cases, we observed three stable binding configurations: rhombus, tetrahedron, and Y-form. Whereas Ni 4 establishes a tetrahedral form, Pd 4 attains the most stable form with the Y-shape geometry on C 60 . Overall, we observe that the trend of Pd binding to C 60 tends to go beyond the fashion of Ni and Pt. In terms of magnetic alignment, the Pd n -C 60 systems seem to be non-magnetic in most cases, unlike the Ni and Pt cases, the structures of which possess magnetic moments of 2 μB in their most stable forms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Glycerol electro-oxidation in alkaline medium using Pd/C and PdSn/C electrocatalysts prepared by electron beam irradiation

    International Nuclear Information System (INIS)

    Geraldes, Adriana Napoleao; Silva, Dionisio Fortunato da; Pino, Eddy Segura; Spinace, Estevan Vitorio; Oliveira Neto, Almir; Linardi, Marcelo; Santos, Mauro Coelhos dos

    2013-01-01

    Carbon-supported metal nanoparticles were prepared for fuel cell applications by radiation-induced reduction of metal ions precursors. Pd/C and PdSn/C electrocatalysts (Pd:Sn atomic ratio 90:10), prepared by using electron beam irradiation, were tested for glycerol electro-oxidation in single alkaline direct glycerol fuel cell (ADGFC). EDX analysis showed that the Pd:Sn atomic ratio is very similar to the nominal one. X-ray diffractograms of PdSn/C electrocatalyst showed the presence of Pd (fcc) phase. Cyclic voltammetry (CV) indicated that Pd/C and PdSn/C electrocatalysts have good activity for glycerol electro-oxidation, at room temperature. Experiments with single ADGFC were carried out from 60 to 90 deg C, using Pd/C and PdSn/C electrocatalysts and glycerol 2.0 mol.L -1 , as fuel. The best performance was obtained at 85 deg C, for both electrocatalysts. The Pd/C and PdSn/C electrocatalysts showed similar performance (34 mW cm -2 ), at 85 deg C. (author)

  14. Enhancing the Activity of Pd on Carbon Nanofibers for Deoxygenation of Amphiphilic Fatty Acid Molecules through Support Polarity

    NARCIS (Netherlands)

    Gosselink, R.W.; Xia, W.; Muhler, M.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    The influence of support polarity on Pd/CNF for the deoxygenation of fatty acids was studied. Catalysts with a low (O/C = 3.5 × 10–2 at/at from X-ray photoelectron spectroscopy (XPS)) and a high (O/C = 5.9 × 10–2 at/at from XPS) amount of oxygen containing groups on the support were prepared. The

  15. Atomic Layer Deposition of Pd Nanoparticles on TiO₂ Nanotubes for Ethanol Electrooxidation: Synthesis and Electrochemical Properties.

    Science.gov (United States)

    Assaud, Loïc; Brazeau, Nicolas; Barr, Maïssa K S; Hanbücken, Margrit; Ntais, Spyridon; Baranova, Elena A; Santinacci, Lionel

    2015-11-11

    Palladium nanoparticles are grown on TiO2 nanotubes by atomic layer deposition (ALD), and the resulting three-dimensional nanostructured catalysts are studied for ethanol electrooxidation in alkaline media. The morphology, the crystal structure, and the chemical composition of the Pd particles are fully characterized using scanning and transmission electron microscopies, X-ray diffraction, and X-ray photoelectron spectroscopy. The characterization revealed that the deposition proceeds onto the entire surface of the TiO2 nanotubes leading to the formation of well-defined and highly dispersed Pd nanoparticles. The electrooxidation of ethanol on Pd clusters deposited on TiO2 nanotubes shows not only a direct correlation between the catalytic activity and the particle size but also a steep increase of the response due to the enhancement of the metal-support interaction when the crystal structure of the TiO2 nanotubes is modified by annealing at 450 °C in air.

  16. Rapid preparation of ceramic moulds for medium-sized superalloy castings with magnesia-phosphate-bonded bauxite-mullite investments

    Directory of Open Access Journals (Sweden)

    Li Tingzhong

    2010-11-01

    Full Text Available Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI, a series of experiments were conducted, including modification of the workable time of slurry by liquid(mL/powder(g(L/P ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP as strengthening agent, and adjustment of bauxite (g/mullite(g(B/M ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.

  17. Supported quantum clusters of silver as enhanced catalysts for reduction

    Directory of Open Access Journals (Sweden)

    Leelavathi Annamalai

    2011-01-01

    Full Text Available Abstract Quantum clusters (QCs of silver such as Ag7(H2MSA7, Ag8(H2MSA8 (H2MSA, mercaptosuccinic acid were synthesized by the interfacial etching of Ag nanoparticle precursors and were loaded on metal oxide supports to prepare active catalysts. The supported clusters were characterized using high resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and laser desorption ionization mass spectrometry. We used the conversion of nitro group to amino group as a model reaction to study the catalytic reduction activity of the QCs. Various aromatic nitro compounds, namely, 3-nitrophenol (3-np, 4-nitrophenol (4-np, 3-nitroaniline (3-na, and 4-nitroaniline (4-na were used as substrates. Products were confirmed using UV-visible spectroscopy and electrospray ionization mass spectrometry. The supported QCs remained active and were reused several times after separation. The rate constant suggested that the reaction followed pseudo-first-order kinetics. The turn-over frequency was 1.87 s-1 per cluster for the reduction of 4-np at 35°C. Among the substrates investigated, the kinetics followed the order, SiO2 > TiO2 > Fe2O3 > Al2O3.

  18. Metal clusters on supported argon layers; Metallcluster auf dielektrischen Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Faber, Bernhard

    2011-10-21

    The deposition of small sodium clusters on supported Ar(001)-surfaces is simulated. Theoretical description is achieved by a hierarchical model consisting of time-dependent DFT and molecular dynamics. The valence electrons of the sodium atoms are considered by Kohn-Sham-Scheme with self interaction correction. The interaction of argon atoms and sodium ions is described by atom-atom potentials whereas the coupling to the QM electrons is done by local pseudo-potentials. A decisive part of the model is the dynamical polarizability of the rare-gas atoms. The optional metal support is considered by the method of image charges. The influence of the forces caused by image charges and the influence of the number of argon monolayers on structure, optical response and deposition dynamics of Na{sub 6} and Na{sub 8} is investigated. There is very little influence on cluster structure and only a small shift of the cluster perpendicular to the surface. Concerning optical response the position of the Mie plasmon peak stays robust whereas the details of spectral fragmentation react very sensitively to changes. The forces caused by image charges of the metal support play only a little role with the dynamics of deposition while the thickness of the argon surface strongly influences the dissipation. (orig.)

  19. (Electronic structure and reactivities of transition metal clusters)

    Energy Technology Data Exchange (ETDEWEB)

    1992-01-01

    The following are reported: theoretical calculations (configuration interaction, relativistic effective core potentials, polyatomics, CASSCF); proposed theoretical studies (clusters of Cu, Ag, Au, Ni, Pt, Pd, Rh, Ir, Os, Ru; transition metal cluster ions; transition metal carbide clusters; bimetallic mixed transition metal clusters); reactivity studies on transition metal clusters (reactivity with H{sub 2}, C{sub 2}H{sub 4}, hydrocarbons; NO and CO chemisorption on surfaces). Computer facilities and codes to be used, are described. 192 refs, 13 figs.

  20. Support Vector Data Descriptions and k-Means Clustering: One Class?

    Science.gov (United States)

    Gornitz, Nico; Lima, Luiz Alberto; Muller, Klaus-Robert; Kloft, Marius; Nakajima, Shinichi

    2017-09-27

    We present ClusterSVDD, a methodology that unifies support vector data descriptions (SVDDs) and k-means clustering into a single formulation. This allows both methods to benefit from one another, i.e., by adding flexibility using multiple spheres for SVDDs and increasing anomaly resistance and flexibility through kernels to k-means. In particular, our approach leads to a new interpretation of k-means as a regularized mode seeking algorithm. The unifying formulation further allows for deriving new algorithms by transferring knowledge from one-class learning settings to clustering settings and vice versa. As a showcase, we derive a clustering method for structured data based on a one-class learning scenario. Additionally, our formulation can be solved via a particularly simple optimization scheme. We evaluate our approach empirically to highlight some of the proposed benefits on artificially generated data, as well as on real-world problems, and provide a Python software package comprising various implementations of primal and dual SVDD as well as our proposed ClusterSVDD.

  1. A Self-Organizing Spatial Clustering Approach to Support Large-Scale Network RTK Systems.

    Science.gov (United States)

    Shen, Lili; Guo, Jiming; Wang, Lei

    2018-06-06

    The network real-time kinematic (RTK) technique can provide centimeter-level real time positioning solutions and play a key role in geo-spatial infrastructure. With ever-increasing popularity, network RTK systems will face issues in the support of large numbers of concurrent users. In the past, high-precision positioning services were oriented towards professionals and only supported a few concurrent users. Currently, precise positioning provides a spatial foundation for artificial intelligence (AI), and countless smart devices (autonomous cars, unmanned aerial-vehicles (UAVs), robotic equipment, etc.) require precise positioning services. Therefore, the development of approaches to support large-scale network RTK systems is urgent. In this study, we proposed a self-organizing spatial clustering (SOSC) approach which automatically clusters online users to reduce the computational load on the network RTK system server side. The experimental results indicate that both the SOSC algorithm and the grid algorithm can reduce the computational load efficiently, while the SOSC algorithm gives a more elastic and adaptive clustering solution with different datasets. The SOSC algorithm determines the cluster number and the mean distance to cluster center (MDTCC) according to the data set, while the grid approaches are all predefined. The side-effects of clustering algorithms on the user side are analyzed with real global navigation satellite system (GNSS) data sets. The experimental results indicate that 10 km can be safely used as the cluster radius threshold for the SOSC algorithm without significantly reducing the positioning precision and reliability on the user side.

  2. Ethanol electro-oxidation in alkaline medium using Pd/c and PdRh/C electrocatalysts prepared by electron beam irradiation

    International Nuclear Information System (INIS)

    Silva, Dionisio Furtunato da; Geraldes, Adriana Napoleao; Pino, Eddy Segura; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Linardi, Marcelo

    2013-01-01

    In this study, carbon-supported Pd (Pd/C) and bimetallic PdRh (Pd:Rh 90:10 atomic ratio) (PdRh/C) electrocatalysts were prepared using electron beam irradiation. The morphology and composition of the obtained materials were characterized by Cyclic voltammetry (VC), Chronoamperometry (CA), Energy dispersive X-ray (EDX), X-ray Diffraction (XRD) and Thermo-gravimetric analysis (TGA). The catalytic activities of the electrocatalysts toward the ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC), in a range temperature of 50 to 85 deg C. The best performances were obtained at 85 deg C (25 mW.cm -2 ) and 75 deg C (38 mW.cm -2 ) for Pd/C and PdRh/C electrocatalysts, respectively. The XRD of the PdRh/C electrocatalyst showed the presence of Pd-rich (fcc) phase. CV and CA experiments showed that PdRh/C electrocatalyst demonstrated superior activity toward ethanol electro-oxidation at room temperature, compared to Pd/C electrocatalyst. (author)

  3. Pd nanoparticles Supported on Cellulose as a catalyst for vanillin conversion in aqueous media.

    Science.gov (United States)

    Li, Dan-Dan; Zhang, Jia-Wei; Cai, Chun

    2018-05-17

    Palladium nanoparticles were firstly anchored on modified biopolymer as an efficient catalyst for biofuel upgradation. Fluorinated compounds was grafted onto cellulose to obtain amphiphilic supports for on water reactions. Pd catalyst was prepared by straightforward deposition of metal nanoparticles on modified cellulose. The catalyst exhibited excellent catalytic activity and selectivity in hydrodeoxygenation of vanillin (a typical model compound of lignin) to 2-methoxy-4-methylphenol under atmospheric hydrogen pressure in neat water without any other additives under mild conditions.

  4. Promotion of Phenol Photodecomposition over TiO2 Using Au, Pd, and AuPd Nanoparticles

    DEFF Research Database (Denmark)

    Su, Ren; Tiruvalam, Ramchandra; He, Qian

    2012-01-01

    Noble metal nanoparticles (Au, Pd, AuPd alloys) with a narrow size distribution supported on nanocrystalline TiO2 (M/TiO2) have been synthesized via a sol-immobilization route. The effect of metal identity and size on the photocatalytic performance of M/TiO2 has been systematically investigated u...

  5. Cluster pattern analysis of energy deposition sites for the brachytherapy sources 103Pd, 125I, 192Ir, 137Cs, and 60Co.

    Science.gov (United States)

    Villegas, Fernanda; Tilly, Nina; Bäckström, Gloria; Ahnesjö, Anders

    2014-09-21

    Analysing the pattern of energy depositions may help elucidate differences in the severity of radiation-induced DNA strand breakage for different radiation qualities. It is often claimed that energy deposition (ED) sites from photon radiation form a uniform random pattern, but there is indication of differences in RBE values among different photon sources used in brachytherapy. The aim of this work is to analyse the spatial patterns of EDs from 103Pd, 125I, 192Ir, 137Cs sources commonly used in brachytherapy and a 60Co source as a reference radiation. The results suggest that there is both a non-uniform and a uniform random component to the frequency distribution of distances to the nearest neighbour ED. The closest neighbouring EDs show high spatial correlation for all investigated radiation qualities, whilst the uniform random component dominates for neighbours with longer distances for the three higher mean photon energy sources (192Ir, 137Cs, and 60Co). The two lower energy photon emitters (103Pd and 125I) present a very small uniform random component. The ratio of frequencies of clusters with respect to 60Co differs up to 15% for the lower energy sources and less than 2% for the higher energy sources when the maximum distance between each pair of EDs is 2 nm. At distances relevant to DNA damage, cluster patterns can be differentiated between the lower and higher energy sources. This may be part of the explanation to the reported difference in RBE values with initial DSB yields as an endpoint for these brachytherapy sources.

  6. Synthesis of coin-like hollow carbon and performance as Pd catalyst support for methanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Dingsheng [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); State Key Laboratories of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Xu, Changwei; Liu, Yingliang; Tan, Shaozao [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Wang, Xin [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wei, Zidong [School of Chemical Engineering, Chongqing University, Chongqing 400044 (China); Shen, Pei Kang [State Key Laboratories of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

    2007-10-15

    The coin-like hollow carbon (CHC) has been synthesized by only using ethanol as the carbon source with a novel Mg/NiCl{sub 2} catalytic system via a facile solvothermal method for the first time. The CHC synthesized at optimized conditions shows an average thickness of less than 154 nm and the coin diameter of 1-3 {mu}m. The CHC is characterized by SEM, TEM, XRD and electrochemical techniques. Pd on CHC (denotes as Pd/CHC) electrocatalysts are prepared for methanol oxidation in alkaline media. The Pd/CHC electrocatalyst gives a mass activity of 2930 A g{sup -1} Pd for methanol oxidation against 870 A g{sup -1} Pd on Pd/C electrocatalyst. One main reason for the higher mass activity of the Pd/CHC is the higher electrochemical active surface area (EASA) of the Pd/CHC. (author)

  7. A Self-Organizing Spatial Clustering Approach to Support Large-Scale Network RTK Systems

    Directory of Open Access Journals (Sweden)

    Lili Shen

    2018-06-01

    Full Text Available The network real-time kinematic (RTK technique can provide centimeter-level real time positioning solutions and play a key role in geo-spatial infrastructure. With ever-increasing popularity, network RTK systems will face issues in the support of large numbers of concurrent users. In the past, high-precision positioning services were oriented towards professionals and only supported a few concurrent users. Currently, precise positioning provides a spatial foundation for artificial intelligence (AI, and countless smart devices (autonomous cars, unmanned aerial-vehicles (UAVs, robotic equipment, etc. require precise positioning services. Therefore, the development of approaches to support large-scale network RTK systems is urgent. In this study, we proposed a self-organizing spatial clustering (SOSC approach which automatically clusters online users to reduce the computational load on the network RTK system server side. The experimental results indicate that both the SOSC algorithm and the grid algorithm can reduce the computational load efficiently, while the SOSC algorithm gives a more elastic and adaptive clustering solution with different datasets. The SOSC algorithm determines the cluster number and the mean distance to cluster center (MDTCC according to the data set, while the grid approaches are all predefined. The side-effects of clustering algorithms on the user side are analyzed with real global navigation satellite system (GNSS data sets. The experimental results indicate that 10 km can be safely used as the cluster radius threshold for the SOSC algorithm without significantly reducing the positioning precision and reliability on the user side.

  8. Ethanol electro-oxidation in alkaline medium using Pd/c and PdRh/C electrocatalysts prepared by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Furtunato da; Geraldes, Adriana Napoleao; Pino, Eddy Segura; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Linardi, Marcelo, E-mail: dfsilva@ipen.br, E-mail: drinager@ig.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    In this study, carbon-supported Pd (Pd/C) and bimetallic PdRh (Pd:Rh 90:10 atomic ratio) (PdRh/C) electrocatalysts were prepared using electron beam irradiation. The morphology and composition of the obtained materials were characterized by Cyclic voltammetry (VC), Chronoamperometry (CA), Energy dispersive X-ray (EDX), X-ray Diffraction (XRD) and Thermo-gravimetric analysis (TGA). The catalytic activities of the electrocatalysts toward the ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC), in a range temperature of 50 to 85 deg C. The best performances were obtained at 85 deg C (25 mW.cm{sup -2}) and 75 deg C (38 mW.cm{sup -2}) for Pd/C and PdRh/C electrocatalysts, respectively. The XRD of the PdRh/C electrocatalyst showed the presence of Pd-rich (fcc) phase. CV and CA experiments showed that PdRh/C electrocatalyst demonstrated superior activity toward ethanol electro-oxidation at room temperature, compared to Pd/C electrocatalyst. (author)

  9. Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

    Directory of Open Access Journals (Sweden)

    Sonia Gil

    2015-04-01

    Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

  10. Phase diagrams of two dimensional Pd{sub x}Ag{sub 1-x}/Pd(111) and Pt{sub x}Ag{sub 1-x}/Pt(111) surface alloys

    Energy Technology Data Exchange (ETDEWEB)

    Engstfeld, Albert K.; Roetter, Ralf T.; Bergbreiter, Andreas; Hoster, Harry E.; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University (Germany)

    2011-07-01

    The distribution of Ag and Pd or Pt in Ag{sub x}Pd{sub 1-x}/Pd(111) and Ag{sub x}Pt{sub 1-x}/Pt(111) surface alloys was studied by high resolution UHV-STM. The alloys were prepared by evaporating Ag on the respective substrate and subsequent annealing to 800 K. From quantitative 2D atom distributions we can show that AgPt tends towards two dimensional clustering and AgPd towards a 'quasi' random distribution, with small deviations for low and high coverages. From effective pair interactions, we are able to calculate the surface mixing energy and determine 2D phase diagrams. Furthermore we will elucidate whether the size mismatch or the differences in the intermetallic bonding are the dominant factor for the respective distribution in the surface alloy.

  11. First-principles study of the Pd–Si system and Pd(0 0 1)/SiC(0 0 1) hetero-structure

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P.E.A. [Lawrence Livermore National Laboratory (L-352), 7000 East Avenue, Livermore, CA 94551 (United States); Ivashchenko, V.I. [Institute of Problems of Materials Science, NAS of Ukraine, Krzhyzhanovsky str. 3, 03142 Kyiv (Ukraine)

    2014-11-15

    Highlights: • A large atomic mixing at the Pd/Si interface occurs at 1500–1800 K. • The Pd/C interface remains sharp even at the highest temperature of 2100 K. • At the Pd/C interface, voids and a graphite-like clustering are detected. • At the Pd/Si interface C22-Pd{sub 2}Si and D0{sub 11}-Pd{sub 3}Si fragments form, in agreement with experiment. - Abstract: First-principles molecular dynamics simulations of the Pd(0 0 1)/3C–SiC(0 0 1) nano-layered structure were carried out at different temperatures ranging from 300 to 2100 K. Various PdSi (Pnma, Fm3{sup ¯}m, P6{sup ¯}m2, Pm3{sup ¯}m), Pd{sub 2}Si (P6{sup ¯}2m, P6{sub 3}/mmc, P3{sup ¯}m1, P3{sup ¯}1m) and Pd{sub 3}Si (Pnma, P6{sub 3}22, Pm3{sup ¯}m, I4/mmm) structures under pressure were studied to identify the structure of the Pd/Si and Pd/C interfaces in the Pd/SiC systems at high temperatures. It was found that a large atomic mixing at the Pd/Si interface occurred at 1500–1800 K, whereas the Pd/C interface remained sharp even at the highest temperature of 2100 K. At the Pd/C interface, voids and a graphite-like clustering were detected. Palladium and silicon atoms interact at the Pd/Si interface to mostly form C22-Pd{sub 2}Si and D0{sub 11}-Pd{sub 3}Si fragments, in agreement with experiment.

  12. High stability and high activity Pd/ITO-CNTs electrocatalyst for direct formic acid fuel cell

    International Nuclear Information System (INIS)

    Qu, Wei-Li; Gu, Da-Ming; Wang, Zhen-Bo; Zhang, Jing-Jia

    2014-01-01

    Graphical abstract: The addition of ITO in Pd/CNTs catalyst significantly improves the activity and stability of catalyst for formic acid electrooxidation due to excellent stability and high electrical conductivity of ITO, and metal-support interaction between Pd nanoparticles and ITO. - Highlights: • Pd catalyst with ITO and CNTs as a mixture support for DFAFC was first prepared by microwave-assisted polyol process. • The activity and stability of Pd/ITO-CNTs catalyst is significantly higher than those of Pd/CNTs. • When ITO content is 50% of ITO/CNTs support mass, Pd/ITO-CNTs exhibits the best performance. - Abstract: Indium tin oxide (ITO) and carbon nanotube hybrid has been explored as a support for Pd catalyst. Pd/ITO-CNTs catalysts with different ITO contents were prepared by the microwave-assisted polyol process. The as-prepared Pd/ITO-CNTs catalysts were characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and electrochemical measurements in this work. The TEM results show that Pd particle size distribution in the Pd/ITO-CNTs catalyst is more uniform than that in Pd/CNTs, indicating that the ITO can promote the dispersion of Pd nanoparticles. It is found that there is metal-support interaction between Pd nanoparticles and ITO in the Pd/ITO-CNTs catalyst through XPS test. The results of electrochemical tests prove that the Pd/ITO-CNTs catalysts exhibit higher electro-catalytic activity and stability than Pd/CNTs toward formic acid electrooxidation. When the ITO content is 50% of ITO-CNTs support mass, the Pd/ITO-CNTs catalyst has the best catalytic performance for formic acid electrooxidation. The peak current density of formic acid electrooxidation on the Pd/ITO-CNTs50% electrode is 1.53 times as high as that on Pd/CNTs, 2.31 times higher than that on Pd/ITO. The results of aging

  13. [Electronic and structural properties of individual nanometer-size supported metallic clusters

    International Nuclear Information System (INIS)

    Reifenberger, R.

    1993-01-01

    This report summarizes the work performed under contract DOE-FCO2-84ER45162. During the past ten years, our study of electron emission from laser-illuminated field emission tips has taken on a broader scope by addressing problems of direct interest to those concerned with the unique physical and chemical properties of nanometer-size clusters. The work performed has demonstrated that much needed data can be obtained on individual nanometer-size clusters supported on a wide-variety of different substrates. The work was performed in collaboration with R.P. Andres in the School of Chemical Engineering at Purdue University. The Multiple Expansion Cluster Source developed by Andres and his students was essential for producing the nanometer-size clusters studied. The following report features a discussion of these results. This report provides a motivation for studying the properties of nanometer-size clusters and summarizes the results obtained

  14. Evaluation of colloidal Pd and Pd-alloys as anode electrocatalysts for direct borohydride fuel cells applications

    Energy Technology Data Exchange (ETDEWEB)

    Atwan, M.H. [General Motors R and D Technical Center, Warren, MI (United States); Gyenge, E.L. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Northwood, D.O. [Windsor Univ., ON (Canada). Dept. of Mechanical, Automotive and Materials Engineering

    2010-07-01

    An evaluation was conducted to assess the use of colloidal palladium (Pd) and Pd alloys as anode electrocatalysts for direct borohydride fuel cell applications. A modified Bonneman method was used to investigate borohydride oxidation on supported Pd and Pd-alloy nano-electrocatalysts. Cyclic voltammetry (CV), rotating disk electrode (RDE) voltammetry, and single fuel cell test stations were used to determine Tafel slopes, exchange current densities, oxidation peak potentials, and fuel cell performance. The study also investigated the influence of temperature and oxidant flow and fuel flow rates on fuel cell performance. The study showed that the current density of the fuel cell increased with increases in temperature for all the investigated Pd electrocatalysts. However, the increase in current density was not as high as expected when fuel flow rates were increased. A current density of 50 mA cm{sup -2} was observed at 298 K with a Pd-Ir anode catalyst operating at a cell voltage of 0.5 V. 28 refs., 1 tab., 15 figs.

  15. Ethanol electro-oxidation in an alkaline medium using Pd/C, Au/C and PdAu/C electrocatalysts prepared by electron beam irradiation

    International Nuclear Information System (INIS)

    Geraldes, Adriana Napoleão; Furtunato da Silva, Dionisio; Pino, Eddy Segura; Martins da Silva, Júlio César; Brambilla de Souza, Rodrigo Fernando; Hammer, Peter; Spinacé, Estevam Vitório; Neto, Almir Oliveira; Linardi, Marcelo; Coelho dos Santos, Mauro

    2013-01-01

    Carbon-supported Pd, Au and bimetallic PdAu (Pd:Au 90:10, 50:50 and 30:70 atomic ratios) electrocatalysts were prepared using electron beam irradiation. The obtained materials were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their catalytic activities toward ethanol electro-oxidation were evaluated in an alkaline medium using electrochemical techniques, in situ attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) analysis and a single alkaline direct ethanol fuel cell (ADEFC). EDX analyses showed that the actual Pd:Au atomic ratios were very similar to the nominal ones. X-ray diffractograms of PdAu/C electrocatalysts evidenced the presence of Pd-rich (fcc) and Au-rich (fcc) phases. TEM analysis showed a homogeneous dispersion of nanoparticles on the carbon support, with an average size in the range of 3–5 nm and broad size distributions. Cyclic voltammetry (CV) and chronoamperometry (CA) experiments revealed the superior ambient activity toward ethanol electro-oxidation of PdAu/C electrocatalysts with Pd:Au ratios of 90:10 and 50:50. In situ ATR-FTIR spectroscopy measurements have shown that the mechanism for ethanol electro-oxidation is dependent on catalyst composition, leading to different reaction products, such as acetaldehyde and acetate, depending on the number of electrons transferred. Experiments on a single ADEFC were conducted between 50 and 90 °C, and the best performance of 44 mW cm −2 in 2.0 mol L −1 ethanol was obtained at 85 °C for the Pd:Au 90:10 catalysts. This superior performance is most likely associated with enhancement of ethanol adsorption on Pd, oxidation of the intermediates, the presence of gold oxide-hydroxyl species, low mean particle diameters and better distribution of particles on the support

  16. Subtypes of borderline personality disorder patients: a cluster-analytic approach.

    Science.gov (United States)

    Smits, Maaike L; Feenstra, Dine J; Bales, Dawn L; de Vos, Jasmijn; Lucas, Zwaan; Verheul, Roel; Luyten, Patrick

    2017-01-01

    The borderline personality disorder (BPD) population is notably heterogeneous, and this has potentially important implications for intervention. Identifying distinct subtypes of patients may represent a first step in identifying which treatments work best for which individuals. A cluster-analysis on dimensional personality disorder (PD) features, as assessed with the SCID-II, was performed on a sample of carefully screened BPD patients ( N  = 187) referred for mentalization-based treatment. The optimal cluster solution was determined using multiple indices of fit. The validity of the clusters was explored by investigating their relationship with borderline pathology, symptom severity, interpersonal problems, quality of life, personality functioning, attachment, and trauma history, in addition to demographic and clinical features. A three-cluster solution was retained, which identified three clusters of BPD patients with distinct profiles. The largest cluster ( n  = 145) consisted of patients characterized by "core BPD" features, without marked elevations on other PD dimensions. A second "Extravert/externalizing" cluster of patients ( n  = 27) was characterized by high levels of histrionic, narcissistic, and antisocial features. A third, smaller "Schizotypal/paranoid" cluster ( n  = 15) consisted of patients with marked schizotypal and paranoid features. Patients in these clusters showed theoretically meaningful differences in terms of demographic and clinical features. Three meaningful subtypes of BPD patients were identified with distinct profiles. Differences were small, even when controlling for severity of PD pathology, suggesting a strong common factor underlying BPD. These results may represent a stepping stone toward research with larger samples aimed at replicating the findings and investigating differential trajectories of change, treatment outcomes, and treatment approaches for these subtypes. The study was retrospectively registered 16 April 2010

  17. Tailoring the synthesis of supported Pd catalysts towards desired structure and size of metal particles.

    Science.gov (United States)

    Suresh, Gatla; Radnik, Jörg; Kalevaru, Venkata Narayana; Pohl, Marga-Martina; Schneider, Matthias; Lücke, Bernhard; Martin, Andreas; Madaan, Neetika; Brückner, Angelika

    2010-05-14

    In a systematic study, the influence of different preparation parameters on phase composition and size of metal crystallites and particles in Pd-Cu/TiO(2) and Pd-Sb/TiO(2) catalyst materials has been explored. Temperature and atmosphere of thermal pretreatment (pure He or 10% H(2)/He), nature of metal precursors (chlorides, nitrates or acetates) as well as of ammonium additives (ammonium sulfate, nitrate, carbonate) and urea were varied with the aim of tailoring the synthesis procedure for the preferential formation of metal particles with similar size and structure as observed recently in active catalysts after long-term equilibration under catalytic reaction conditions in acetoxylation of toluene to benzylacetate. Among the metal precursors and additives, the chloride metal precursors and (NH(4))(2)SO(4) were most suitable. Upon thermal pretreatment of Pd-Sb or Pd-Cu precursors, chloroamine complexes of Pd and Cu are formed, which decompose above 220 degrees C to metallic phases independent of the atmosphere. In He, metallic Pd particles were formed with both the co-components. In H(2)/He flow, Pd-Cu precursors were converted to core-shell particles with a Cu shell and a Pd core, while Sb(1)Pd(1) and Sb(7)Pd(20) alloy phases were formed in the presence of Sb. Metal crystallites of about 40 nm agglomerate to particles of up to 150 nm in He and to even larger size in H(2)/He.

  18. Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Support Distribution Machines

    Science.gov (United States)

    Ntampaka, Michelle; Trac, Hy; Sutherland, Dougal; Fromenteau, Sebastien; Poczos, Barnabas; Schneider, Jeff

    2018-01-01

    We study dynamical mass measurements of galaxy clusters contaminated by interlopers and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create two mock catalogs from Multidark’s publicly available N-body MDPL1 simulation, one with perfect galaxy cluster membership infor- mation and the other where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power-law scaling relation to infer cluster mass from galaxy line-of-sight (LOS) velocity dispersion. Assuming perfect membership knowledge, this unrealistic case produces a wide fractional mass error distribution, with a width E=0.87. Interlopers introduce additional scatter, significantly widening the error distribution further (E=2.13). We employ the support distribution machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to distributions of galaxy observables such as LOS velocity and projected distance from the cluster center, SDM yields better than a factor-of-two improvement (E=0.67) for the contaminated case. Remarkably, SDM applied to contaminated clusters is better able to recover masses than even the scaling relation approach applied to uncon- taminated clusters. We show that the SDM method more accurately reproduces the cluster mass function, making it a valuable tool for employing cluster observations to evaluate cosmological models.

  19. Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, Masato; Beard, Kevin D.; Ma Shuguo; Blom, Douglas A.; St-Pierre, Jean; Van Zee, John W. [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Monnier, John R., E-mail: monnier@cec.sc.ed [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

    2010-10-01

    Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt. The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.

  20. A Kondo cluster-glass model for spin glass Cerium alloys

    International Nuclear Information System (INIS)

    Zimmer, F M; Magalhaes, S G; Coqblin, B

    2011-01-01

    There are clear indications that the presence of disorder in Ce alloys, such as Ce(Ni,Cu) or Ce(Pd,Rh), is responsible for the existence of a cluster spin glass state which changes continuously into inhomogeneous ferromagnetism at low temperatures. We present a study of the competition between magnetism and Kondo effect in a cluster-glass model composed by a random inter-cluster interaction term and an intra-cluster one, which contains an intra-site Kondo interaction J k and an inter-site ferromagnetic one J 0 . The random interaction is given by the van Hemmen type of randomness which allows to solve the problem without the use of the replica method. The inter-cluster term is solved within the cluster mean-field theory and the remaining intra-cluster interactions can be treated by exact diagonalization. Results show the behavior of the cluster glass order parameter and the Kondo correlation function for several sizes of the clusters, J k , J 0 and values of the ferromagnetic inter-cluster average interaction I 0 . Particularly, for small J k , the magnetic solution is strongly dependent on I 0 and J 0 and a Kondo cluster-glass or a mixed phase can be obtained, while, for large J k , the Kondo effect is still dominant, both in good agreement with experiment in Ce(Ni,Cu) or Ce(Pd,Rh) alloys.

  1. Rapid Reduction of Alkenes and Alkynes over Pd Nanoparticles Supported on Sulfonated Porous Carbon

    Directory of Open Access Journals (Sweden)

    Arash Shokrolahi

    2013-01-01

    Full Text Available A novel method has been introduced for rapid reduction of alkenes and alkynes, which may be attractive for chemical industries. This method has some advantages such as simplicity and low cost of reactants. Pd supported on sulfonated porous carbon (SPC was used as a new catalyst for reduction of alkenes and alkynes to the corresponding alkanes using sodium borohydride. The heterogeneous reaction was conducted in open air at room temperature to produce the desired saturated compounds in high yields (over 96% and in short reaction time (15 minutes.

  2. Generation and oxidation of aerosol deposited PdAg nanoparticles

    Science.gov (United States)

    Blomberg, S.; Gustafson, J.; Martin, N. M.; Messing, M. E.; Deppert, K.; Liu, Z.; Chang, R.; Fernandes, V. R.; Borg, A.; Grönbeck, H.; Lundgren, E.

    2013-10-01

    PdAg nanoparticles with a diameter of 10 nm have been generated by an aerosol particle method, and supported on a silica substrate. By using a combination of X-ray Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy it is shown that the size distribution of the particles is narrow and that the two metals form an alloy with a mixture of 75% Pd and 25% Ag. Under oxidizing conditions, Pd is found to segregate to the surface and a thin PdO like oxide is formed similar to the surface oxide previously reported on extended PdAg and pure Pd surfaces.

  3. Atomic Structure of Au−Pd Bimetallic Alloyed Nanoparticles

    KAUST Repository

    Ding, Yong

    2010-09-08

    Using a two-step seed-mediated growth method, we synthesized bimetallic nanoparticles (NPs) having a gold octahedron core and a palladium epitaxial shell with controlled Pd-shell thickness. The mismatch-release mechanism between the Au core and Pd shell of the NPs was systematically investigated by high-resolution transmission electron microscopy. In the NPs coated with a single atomic layer of Pd, the strain between the surface Pd layer and the Au core is released by Shockley partial dislocations (SPDs) accompanied by the formation of stacking faults. For NPs coated with more Pd (>2 nm), the stacking faults still exist, but no SPDs are found. This may be due to the diffusion of Au atoms into the Pd shell layers to eliminate the SPDs. At the same time, a long-range ordered L11 AuPd alloy phase has been identified in the interface area, supporting the assumption of the diffusion of Au into Pd to release the interface mismatch. With increasing numbers of Pd shell layers, the shape of the Au-Pd NP changes, step by step, from truncated-octahedral to cubic. After the bimetallic NPs were annealed at 523 K for 10 min, the SPDs at the surface of the NPs coated with a single atomic layer of Pd disappeared due to diffusion of the Au atoms into the surface layer, while the stacking faults and the L11 Au-Pd alloyed structure remained. When the annealing temperature was increased to 800 K, electron diffraction patterns and diffraction contrast images revealed that the NPs became a uniform Au-Pd alloy, and most of the stacking faults disappeared as a result of the annealing. Even so, some clues still support the existence of the L11 phase, which suggests that the L11 phase is a stable, long-range ordered structure in Au-Pd bimetallic NPs. © 2010 American Chemical Society.

  4. Synthesis of PdO/MCM-41 nanocomposites using trans-[PdCl2(PEt3)2] as the source of metal

    International Nuclear Information System (INIS)

    Hernandez-Pineda, Jessica; Rio, Jose Manuel del; Carreto, Enrique; Terres, Eduardo; Montoya, J. Asencion; Zuniga-Gonzalez, Maria de Jesus; Morgado, Jorge

    2009-01-01

    Three PdO/MCM-41 nanocomposites containing PdO species that are dispersed on an MCM-41 support have been prepared using trans-[PdCl 2 (PEt 3 ) 2 ] as the source of metal. Thermal gravimetric analysis of the decomposition of this complex in air reveals a remarkable mass loss of all nonmetallic elements centered at 300 deg. C. The materials were characterized with X-ray powder diffraction (XRPD), nitrogen sorption and TEM, which showed that the PdO nanoparticles were present inside the pores of MCM-41. XRPD analysis confirms formation of PdO (palladinite) nanocrystals, as the sole crystalline phase present in the nanocomposites.

  5. Formation mechanism of solute clusters under neutron irradiation in ferritic model alloys and in a reactor pressure vessel steel: clusters of defects; Mecanismes de fragilisation sous irradiation aux neutrons d'alliages modeles ferritiques et d'un acier de cuve: amas de defauts

    Energy Technology Data Exchange (ETDEWEB)

    Meslin-Chiffon, E

    2007-11-15

    The embrittlement of reactor pressure vessel (RPV) under irradiation is partly due to the formation of point defects (PD) and solute clusters. The aim of this work was to gain more insight into the formation mechanisms of solute clusters in low copper ([Cu] = 0.1 wt%) FeCu and FeCuMnNi model alloys, in a copper free FeMnNi model alloy and in a low copper French RPV steel (16MND5). These materials were neutron-irradiated around 300 C in a test reactor. Solute clusters were characterized by tomographic atom probe whereas PD clusters were simulated with a rate theory numerical code calibrated under cascade damage conditions using transmission electron microscopy analysis. The confrontation between experiments and simulation reveals that a heterogeneous irradiation-induced solute precipitation/segregation probably occurs on PD clusters. (author)

  6. Surface, segregation profile for Ni50Pd50(100)

    DEFF Research Database (Denmark)

    Christensen, Asbjørn; Ruban, Andrei; Skriver, Hans Lomholt

    1997-01-01

    A recent dynamical LEED study [G.N. Derry, C.B. McVey, P.J. Rous, Surf. Sci. 326 (1995) 59] reported an oscillatory surface segregation profile in the Ni50Pd50(100) system with the surface layer enriched by Pd. We have performed ab-initio total-energy calculations for the surface of this alloy...... system using the coherent potential approximation and obtain an oscillatory segregation profile, in agreement with experiments. We discuss the energetic origin of the oscillatory segregation profile in terms of effective cluster interactions. We include relaxation effects by means of the semi...

  7. Analysis of microstructures for Co/Pd multilayer perpendicular magnetic recording media with carbon underlayer

    International Nuclear Information System (INIS)

    Asahi, T.; Kuramochi, K.; Kawaji, J.; Onoue, T.; Osaka, T.; Saigo, M.

    2001-01-01

    The effect of amorphous carbon underlayer thickness on the microstructure of the Co/Pd multilayer perpendicular magnetic recording media was investigated. From the magnetic force microscopy observation in the AC-demagnetized state of the Co/Pd multilayer media, the magnetic cluster size was observed to effectively decrease with an increase in carbon underlayer thickness, where the higher coercivity and the higher S/N ratio of the Co/Pd multilayer media were obtained with the thicker underlayer. Furthermore, the distribution of [1 1 1] orientation of FCC-Pd became broader, and the grain size decreased with an increase in the carbon underlayer thickness. These effects caused the magnetic exchange decoupling of Co/Pd multilayer media. We suggested that the change of microstructure was directly related to the surface roughness of the amorphous carbon underlayer

  8. Review of Supported Pd-Based Membranes Preparation by Electroless Plating for Ultra-Pure Hydrogen Production.

    Science.gov (United States)

    Alique, David; Martinez-Diaz, David; Sanz, Raul; Calles, Jose A

    2018-01-23

    In the last years, hydrogen has been considered as a promising energy vector for the oncoming modification of the current energy sector, mainly based on fossil fuels. Hydrogen can be produced from water with no significant pollutant emissions but in the nearest future its production from different hydrocarbon raw materials by thermochemical processes seems to be more feasible. In any case, a mixture of gaseous compounds containing hydrogen is produced, so a further purification step is needed to purify the hydrogen up to required levels accordingly to the final application, i.e., PEM fuel cells. In this mean, membrane technology is one of the available separation options, providing an efficient solution at reasonable cost. Particularly, dense palladium-based membranes have been proposed as an ideal chance in hydrogen purification due to the nearly complete hydrogen selectivity (ideally 100%), high thermal stability and mechanical resistance. Moreover, these membranes can be used in a membrane reactor, offering the possibility to combine both the chemical reaction for hydrogen production and the purification step in a unique device. There are many papers in the literature regarding the preparation of Pd-based membranes, trying to improve the properties of these materials in terms of permeability, thermal and mechanical resistance, poisoning and cost-efficiency. In this review, the most relevant advances in the preparation of supported Pd-based membranes for hydrogen production in recent years are presented. The work is mainly focused in the incorporation of the hydrogen selective layer (palladium or palladium-based alloy) by the electroless plating, since it is one of the most promising alternatives for a real industrial application of these membranes. The information is organized in different sections including: (i) a general introduction; (ii) raw commercial and modified membrane supports; (iii) metal deposition insights by electroless-plating; (iv) trends in

  9. The Cladistic Basis for the Phylogenetic Diversity (PD Measure Links Evolutionary Features to Environmental Gradients and Supports Broad Applications of Microbial Ecology’s “Phylogenetic Beta Diversity” Framework

    Directory of Open Access Journals (Sweden)

    Rob Knight

    2009-11-01

    Full Text Available The PD measure of phylogenetic diversity interprets branch lengths cladistically to make inferences about feature diversity. PD calculations extend conventional specieslevel ecological indices to the features level. The “phylogenetic beta diversity” framework developed by microbial ecologists calculates PD-dissimilarities between community localities. Interpretation of these PD-dissimilarities at the feature level explains the framework’s success in producing ordinations revealing environmental gradients. An example gradients space using PD-dissimilarities illustrates how evolutionary features form unimodal response patterns to gradients. This features model supports new application of existing species-level methods that are robust to unimodal responses, plus novel applications relating to climate change, commercial products discovery, and community assembly.

  10. Calix[4]arene supported clusters: a dimer of [Mn(III)Mn(II)] dimers

    DEFF Research Database (Denmark)

    Taylor, Stephanie M; McIntosh, Ruaraidh D; Beavers, Christine M

    2011-01-01

    Phosphinate ligands allow for the transformation of a calix[4]arene supported [Mn(III)(2)Mn(II)(2)] tetramer cluster motif into an unusual [Mn(III)Mn(II)](2) dimer of dimers; the clusters self-assemble in the crystal to form bi-layer arrays reminiscent of the typical packing of calixarene solvates....

  11. First-principles study of the Pd–Si system and Pd(001)/SiC(001) hetero-structure

    Energy Technology Data Exchange (ETDEWEB)

    Turchi, P.E.A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ivashchenko, V.I. [National Academy of Sciences of Ukraine (NASU), Kiev (Ukraine)

    2014-11-01

    First-principles molecular dynamics simulations of the Pd(001)/3C–SiC(001) nano-layered structure were carried out at different temperatures ranging from 300 to 2100 K. Various PdSi (Pnma, Fm3m, P6m2, Pm3m), Pd2Si (P6⁻2m, P63/mmc, P3m1, P3⁻1m) and Pd3Si (Pnma, P6322, Pm3m, I4/mmm) structures under pressure were studied to identify the structure of the Pd/Si and Pd/C interfaces in the Pd/SiC systems at high temperatures. It was found that a large atomic mixing at the Pd/Si interface occurred at 1500–1800 K, whereas the Pd/C interface remained sharp even at the highest temperature of 2100 K. At the Pd/C interface, voids and a graphite-like clustering were detected. Palladium and silicon atoms interact at the Pd/Si interface to mostly form C22-Pd2Si and D011-Pd3Si fragments, in agreement with experiment.

  12. Clustering Algorithm As A Planning Support Tool For Rural Electrification Optimization

    Directory of Open Access Journals (Sweden)

    Ronaldo Pornillosa Parreno Jr

    2015-08-01

    Full Text Available Abstract In this study clustering algorithm was developed to optimize electrification plans by screening and grouping potential customers to be supplied with electricity. The algorithm provided adifferent approach in clustering problem which combines conceptual and distance-based clustering algorithmsto analyze potential clusters using spanning tree with the shortest possible edge weight and creating final cluster trees based on the test of inconsistency for the edges. The clustering criteria consists of commonly used distance measure with the addition of household information as basis for the ability to pay ATP value. The combination of these two parameters resulted to a more significant and realistic clusters since distance measure alone could not take the effect of the household characteristics in screening the most sensible groupings of households. In addition the implications of varying geographical features were incorporated in the algorithm by using routing index across the locations of the households. This new approach of connecting the households in an area was applied in an actual case study of one village or barangay that was not yet energized. The results of clustering algorithm generated cluster trees which could becomethetheoretical basis for power utilities to plan the initial network arrangement of electrification. Scenario analysis conducted on the two strategies of clustering the households provideddifferent alternatives for the optimization of the cost of electrification. Futhermorethe benefits associated with the two strategies formulated from the two scenarios was evaluated using benefit cost ratio BC to determine which is more economically advantageous. The results of the study showed that clustering algorithm proved to be effective in solving electrification optimization problem and serves its purpose as a planning support tool which can facilitate electrification in rural areas and achieve cost-effectiveness.

  13. Bimetallic Ag-Pt Sub-nanometer Supported Clusters as Highly Efficient and Robust Oxidation Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Negreiros, Fabio R. [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Halder, Avik [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Yin, Chunrong [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Singh, Akansha [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Barcaro, Giovanni [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Sementa, Luca [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Tyo, Eric C. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Pellin, Michael J. [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Bartling, Stephan [Institut für Physik, Universität Rostock, Rostock Germany; Meiwes-Broer, Karl-Heinz [Institut für Physik, Universität Rostock, Rostock Germany; Seifert, Sönke [X-ray Science Division, Argonne National Laboratory, Lemont IL USA; Sen, Prasenjit [Harish-Chandra Research Institute, HBNI, Chhatnag Road Jhunsi Allahabad 211019 India; Nigam, Sandeep [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Majumder, Chiranjib [Chemistry Division, Bhabha Atomic Research Centre, Trombay Mumbai- 400 085 India; Fukui, Nobuyuki [East Tokyo Laboratory, Genesis Research Institute, Inc., Ichikawa Chiba 272-0001 Japan; Yasumatsu, Hisato [Cluster Research Laboratory, Toyota Technological Institute: in, East Tokyo Laboratory, Genesis Research Institute, Inc. Ichikawa, Chiba 272-0001 Japan; Vajda, Stefan [Materials Science Division, Argonne National Laboratory, Lemont IL USA; Nanoscience and Technology Division, Argonne National Laboratory, Lemont IL USA; Institute for Molecular Engineering, University of Chicago, Chicago IL USA; Fortunelli, Alessandro [CNR-ICCOM & IPCF, Consiglio Nazionale delle Ricerche, Pisa Italy; Materials and Process Simulation Center, California Institute of Technology, Pasadena CA USA

    2017-12-29

    A combined experimental and theoretical investigation of Ag-Pt sub-nanometer clusters as heterogeneous catalysts in the CO -> CO2 reaction (COox) is presented. Ag9Pt2 and Ag9Pt3 clusters are size-selected in the gas phase, deposited on an ultrathin amorphous alumina support, and tested as catalysts experimentally under realistic conditions and by first-principles simulations at realistic coverage. Insitu GISAXS/TPRx demonstrates that the clusters do not sinter or deactivate even after prolonged exposure to reactants at high temperature, and present comparable, extremely high COox catalytic efficiency. Such high activity and stability are ascribed to a synergic role of Ag and Pt in ultranano-aggregates, in which Pt anchors the clusters to the support and binds and activates two CO molecules, while Ag binds and activates O-2, and Ag/Pt surface proximity disfavors poisoning by CO or oxidized species.

  14. A cinematic magnetic resonance imaging study of milk of magnesia laxative and an antiflatulent diet to reduce intrafraction prostate motion.

    Science.gov (United States)

    Nichol, Alan M; Warde, Padraig R; Lockwood, Gina A; Kirilova, Anna K; Bayley, Andrew; Bristow, Robert; Crook, Juanita; Gospodarowicz, Mary; McLean, Michael; Milosevic, Michael; Rosewall, Tara; Jaffray, David A; Catton, Charles N

    2010-07-15

    To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia. Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of the prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen. The mean rectal area was: 13.5 cm(2) at MRI-BL, 12.7 cm(2) at MRI-CT, and 12.3 cm(2) at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89). For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion. Copyright 2010 Elsevier Inc. All rights reserved.

  15. A Cinematic Magnetic Resonance Imaging Study of Milk of Magnesia Laxative and an Antiflatulent Diet to Reduce Intrafraction Prostate Motion

    International Nuclear Information System (INIS)

    Nichol, Alan M.; Warde, Padraig R.; Lockwood, Gina A.

    2010-01-01

    Purpose: To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia. Methods and Materials: Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of the prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen. Results: The mean rectal area was: 13.5 cm 2 at MRI-BL, 12.7 cm 2 at MRI-CT, and 12.3 cm 2 at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89). Conclusion: For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion.

  16. Fusion of 110Pd with 110Pd

    International Nuclear Information System (INIS)

    Morawek, W.

    1991-07-01

    In the framework of this thesis the excitation functions of the systems 110 Pd + 110 Pd and 110 Pd + 104 Ru could be measured. The evaporation-residual-nucleus cross sections is deviating from lighter systems dominated by channels, which arise from evaporation of α particles. In the reaction 110 Pd + 110 Pd no xn channels were observed. In comparison to other reactions qualitatively a strong fusion hindrance of this system is shown. (orig./HSI) [de

  17. The role of destabilization of palladium hydride in the hydrogen uptake of Pd-containing activated carbons

    International Nuclear Information System (INIS)

    Bhat, V V; Contescu, C I; Gallego, N C

    2009-01-01

    This paper reports on differences in stability of Pd hydride phases in palladium particles with various degrees of contact with microporous carbon supports. A sample containing Pd embedded in activated carbon fibre (2 wt% Pd) was compared with commercial Pd nanoparticles deposited on microporous activated carbon (3 wt% Pd) and with support-free nanocrystalline palladium. The morphology of the materials was characterized by electron microscopy, and the phase transformations were analysed over a large range of hydrogen partial pressures (0.003-10 bar) and at several temperatures using in situ x-ray diffraction. The results were verified with volumetric hydrogen uptake measurements. Results indicate that higher degrees of Pd-carbon contacts for Pd particles embedded in a microporous carbon matrix induce efficient 'pumping' of hydrogen out of β- PdH x . It was also found that thermal cleaning of carbon surface groups prior to exposure to hydrogen further enhances the hydrogen pumping power of the microporous carbon support. In brief, this study highlights that the stability of β- PdH x phase supported on carbon depends on the degree of contact between Pd and carbon and on the nature of the carbon surface.

  18. Strong paramagnon scattering in single atom Pd contacts

    DEFF Research Database (Denmark)

    Schendel, V.; Barreteau, Cyrille; Brandbyge, Mads

    2017-01-01

    Pd contacts shows a reduction with increasing bias, which gives rise to a peculiar Lambda-shaped spectrum. Supported by theoretical calculations, we correlate this finding with the lifetime of hot quasiparticles in Pd, which is strongly influenced by paramagnon scattering. In contrast to this, Co...

  19. Carbon nanotube-supported Au-Pd alloy with cooperative effect of metal nanoparticles and organic ketone/quinone groups as a highly efficient catalyst for aerobic oxidation of amines.

    Science.gov (United States)

    Deng, Weiping; Chen, Jiashu; Kang, Jincan; Zhang, Qinghong; Wang, Ye

    2016-05-21

    Functionalised carbon nanotube (CNT)-supported Au-Pd alloy nanoparticles were highly efficient catalysts for the aerobic oxidation of amines. We achieved the highest turnover frequencies (>1000 h(-1)) for the oxidative homocoupling of benzylamine and the oxidative dehydrogenation of dibenzylamine. We discovered a cooperative effect between Au-Pd nanoparticles and ketone/quinone groups on CNTs.

  20. The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO{sub 2} by radiolytic method

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Marek [Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology, 80-233 Gdansk (Poland); Institute of Fluid-Flow Machinery, Polish Academy of Sciences, 80-231 Gdansk (Poland); Nadolna, Joanna, E-mail: joanna.nadolna@ug.edu.pl [Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology, 80-233 Gdansk (Poland); Department of Environmental Technology, University of Gdansk, 80-308 Gdansk (Poland); Gołąbiewska, Anna [Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology, 80-233 Gdansk (Poland); Mazierski, Paweł [Department of Environmental Technology, University of Gdansk, 80-308 Gdansk (Poland); Klimczuk, Tomasz [Department of Solid State Physics, Faculty of Applied Physics and Mathematics, Gdansk University of Technology, 80-233 Gdansk (Poland); Remita, Hynd [Laboratoire de Chimie Physique, CNRS-UMR 8000, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); CNRS, Laboratoire de Chimie Physique, UMR 8000, 91405 Orsay (France); Zaleska-Medynska, Adriana [Department of Chemical Technology, Faculty of Chemistry, Gdansk University of Technology, 80-233 Gdansk (Poland); Department of Environmental Technology, University of Gdansk, 80-308 Gdansk (Poland)

    2016-08-15

    Highlights: • Pd-Pt decorated TiO{sub 2} shows the highest activity under visible light among all. • Concurrent addition of metal precursors results in rise of BNPs size and Vis-activity. • Subsequent addition of metal precursors enhances UV–vis stability of modified TiO{sub 2}. • Superoxide radicals are responsible for pollutants degradation over BNPs-TiO{sub 2}. - Abstract: TiO{sub 2} (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV–vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO{sub 2} co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15–30 nm) on TiO{sub 2} surface and enhances the Vis-induced activity of Ag/Pd-TiO{sub 2} up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV–vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for

  1. Agentes ligantes e seus efeitos em concretos refratários alumina-magnésia Binders and their effects on alumina-magnesia refratory castables

    Directory of Open Access Journals (Sweden)

    M. A. L. Braulio

    2010-12-01

    Full Text Available Concretos refratários alumina-magnésia são comumente ligados por cimentos de aluminato de cálcio. Estes materiais apresentam, em temperaturas elevadas, uma reação de caráter expansivo decorrente da espinelização in-situ (MgAl2O4. Quando ligados por cimentos, reações adicionais (formação de CA2 e CA6 contribuem para a expansão. Uma alternativa para controlar a estabilidade volumétrica é a substituição do cimento tipicamente utilizado (~30%-p CaO por outro de menor teor de cálcio (~20%-p CaO ou por alumina hidratável. Tais substituições podem afetar as propriedades dos concretos, como a resistência mecânica a frio, a hidratação da magnésia e as propriedades durante e após a sinterização. Deste modo, o objetivo deste trabalho é avaliar o impacto destes ligantes no processamento de concretos alumina-magnésia. Sendo assim, pretende-se utilizar a fonte de ligante como uma ferramenta para a obtenção de concretos refratários com expansão engenheirada, visando-se aumentar a flexibilidade na seleção de materiais aplicados em panelas de siderurgia.The usual binder of alumina-magnesia castables is the calcium aluminate cement. Due to in-situ spinel (MgAl2O4 formation at high temperatures, these materials present an expansive behavior. When bonded with cement, further reactions (CA2 and CA6 formation also contribute to the overall expansion. Changing the most common cement used (~ 30 wt.% CaO for other containing less calcia (~ 20 wt.% CaO or for hydratable alumina are suitable alternatives for controlling the castables' volumetric stability. Nevertheless, the binder replacement may affect castables properties, such as cold mechanical strength, MgO hydration degree and properties during and after sintering. Therefore, the objective of the present paper is to analyze the effects of these binders on the alumina-magnesia castables processing. As a result, the binder systems can be used as a tool for designing the alumina-magnesia

  2. Catalytic hydrodechlorination of trichloroethylene in a novel NaOH/2-propanol/methanol/water system on ceria-supported Pd and Rh catalysts.

    Science.gov (United States)

    Cobo, Martha; Becerra, Jorge; Castelblanco, Miguel; Cifuentes, Bernay; Conesa, Juan A

    2015-08-01

    The catalytic hydrodechlorination (HDC) of high concentrations of trichloroethylene (TCE) (4.9 mol%, 11.6 vol%) was studied over 1%Pd, 1%Rh and 0.5%Pd-0.5%Rh catalysts supported on CeO2 under conditions of room temperature and pressure. For this, a one-phase system of NaOH/2-propanol/methanol/water was designed with molar percentages of 13.2/17.5/36.9/27.6, respectively. In this system, the alcohols delivered the hydrogen required for the reaction through in-situ dehydrogenation reactions. PdRh/CeO2 was the most active catalyst for the degradation of TCE among the evaluated materials, degrading 85% of the trichloroethylene, with alcohol dehydrogenation rates of 89% for 2-propanol and 83% for methanol after 1 h of reaction. Fresh and used catalysts were characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric analysis (TGA). These results showed important differences of the active phase in each catalyst sample. Rh/CeO2 had particle sizes smaller than 1 nm and the active metal was partially oxidized (Rh(0)/Rh(+δ) ratio of 0.43). This configuration showed to be suitable for alcohols dehydrogenation. On the contrary, Pd/CeO2 showed a Pd completed oxidized and with a mean particle size of 1.7 nm, which seemed to be unfavorable for both, alcohols dehydrogenation and TCE HDC. On PdRh/CeO2, active metals presented a mean particle size of 2.7 nm and more reduced metallic species, with ratios of Rh(0)/Rh(+δ) = 0.67 and Pd(0)/Pd(+δ) = 0.28, which showed to be suitable features for the TCE HDC. On the other hand, TGA results suggested some deposition of NaCl residues over the catalyst surfaces. Thus, the new reaction system using PdRh/CeO2 allowed for the degradation of high concentrations of the chlorinated compound by using in situ hydrogen liquid donors in a reaction at room temperature and pressure. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. The emergence of nonbulk properties in supported metal clusters: negative thermal expansion and atomic disorder in Pt nanoclusters supported on gamma-Al2O3.

    Science.gov (United States)

    Sanchez, Sergio I; Menard, Laurent D; Bram, Ariella; Kang, Joo H; Small, Matthew W; Nuzzo, Ralph G; Frenkel, Anatoly I

    2009-05-27

    The structural dynamics-cluster size and adsorbate-dependent thermal behaviors of the metal-metal (M-M) bond distances and interatomic order-of Pt nanoclusters supported on a gamma-Al(2)O(3) are described. Data from scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) studies reveal that these materials possess a dramatically nonbulklike nature. Under an inert atmosphere small, subnanometer Pt/gamma-Al(2)O(3) clusters exhibit marked relaxations of the M-M bond distances, negative thermal expansion (NTE) with an average linear thermal expansion coefficient alpha = (-2.4 +/- 0.4) x 10(-5) K(-1), large static disorder and dynamical bond (interatomic) disorder that is poorly modeled within the constraints of classical theory. The data further demonstrate a significant temperature-dependence to the electronic structure of the Pt clusters, thereby suggesting the necessity of an active model to describe the cluster/support interactions mediating the cluster's dynamical structure. The quantitative dependences of these nonbulklike behaviors on cluster size (0.9 to 2.9 nm), ambient atmosphere (He, 4% H(2) in He or 20% O(2) in He) and support identity (gamma-Al(2)O(3) or carbon black) are systematically investigated. We show that the nonbulk structural, electronic and dynamical perturbations are most dramatically evidenced for the smallest clusters. The adsorption of hydrogen on the clusters leads to an increase of the Pt-Pt bondlengths (due to a lifting of the surface relaxation) and significant attenuation of the disorder present in the system. Oxidation of these same clusters has the opposite effect, leading to an increase in Pt-Pt bond strain and subsequent enhancement in nonbulklike thermal properties. The structural and electronic properties of Pt nanoclusters supported on carbon black contrast markedly with those of the Pt/gamma-Al(2)O(3) samples in that neither NTE nor comparable levels of atomic disorder are observed. The Pt

  4. Improvement of sulfur resistance of Pd/Ce-Zr-Al-O catalysts for CO oxidation

    Science.gov (United States)

    Shin, Haebin; Baek, Minsung; Ro, Youngsoo; Song, Changyeol; Lee, Kwan-Young; Song, In Kyu

    2018-01-01

    Two kinds of mesoporous ceria-zirconia-alumina supports were prepared by a single-step epoxide-driven sol-gel method (SGCZA) and by a co-precipitation method (PCZA). Palladium catalysts supported on these materials were then prepared by a wet impregnation method (Pd/SGCZA and Pd/PCZA). The prepared catalysts were applied to the CO oxidation reaction before and after sulfur aging. XRD and N2 adsorption-desorption analyses revealed that these two catalysts retained different physicochemical properties. Pd/SGCZA had higher surface area and larger pore volume than Pd/PCZA before and after sulfur aging. TPR (Temperature-programmed reduction), CO chemisorption, FT-IR, and XPS analyses showed that the catalysts were differently influenced by sulfur species. Pd/SGCZA formed less sulfate and retained higher palladium dispersion than Pd/PCZA after sulfur aging. In the CO oxidation, Pd/PCZA showed better activity than Pd/SGCZA before sulfur aging. However, Pd/SGCZA showed higher CO conversion than Pd/PCZA after sulfur aging. We concluded that Pd/SGCZA was less poisoned by sulfur species than Pd/PCZA.

  5. Finite Size Effects in Submonolayer Catalysts Investigated by CO Electrosorption on PtsML/Pd(100).

    Science.gov (United States)

    Yuan, Qiuyi; Doan, Hieu A; Grabow, Lars C; Brankovic, Stanko R

    2017-10-04

    A combination of scanning tunneling microscopy, subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS), and density functional theory (DFT) is used to quantify the local strain in 2D Pt clusters on the 100 facet of Pd and its effect on CO chemisorption. Good agreement between SNIFTIRS experiments and DFT simulations provide strong evidence that, in the absence of coherent strain between Pt and Pd, finite size effects introduce local compressive strain, which alters the chemisorption properties of the surface. Though this effect has been widely neglected in prior studies, our results suggest that accurate control over cluster sizes in submonolayer catalyst systems can be an effective approach to fine-tune their catalytic properties.

  6. Ethanol electro-oxidation in alkaline medium using Pd/MWCNT and PdAuSn/MWCNT electrocatalysts prepared by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Geraldes, Adriana Napoleao; Silva, Dionisio Furtunato da; Andrade e Silva, Leonardo Gondin de; Spinace, Estevam Vitorio; Oliveira Neto, Almir, E-mail: drinager@ig.com.br, E-mail: dfsilva@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Santos, Mauro Coelho dos [Universidade Federal do ABC (LEMN/CCNH/UFABC), Santo Andre, SP (Brazil)

    2015-07-01

    Environmental problems and the world growing demand for energy has mobilized the scientific community in finding of clean and renewable energy sources. In this context, fuel cells appear as appropriate technology for generating electricity through alcohols electro-oxidation. Multi Wall Carbon Nanotubes (MWCNT)-supported Pd and trimetallic PdAuSn (Pd:Au:Sn 50:10:40 atomic ratio) electrocatalysts were prepared using electron beam irradiation. The obtained materials were characterized by VC, Chronoamperometry, EDX, TEM and XRD. The catalytic activities of electrocatalysts toward ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC) in a range temperature 60 to 90 deg C. The best performances were obtained at 85 deg C: 33 mW.cm{sup -2} and 31 mW.cm{sup -2} for Pd/ MWCNT and PdAuSn/MWCNT electrocatalysts, respectively. X-ray diffractograms of electrocatalysts showed the presence of Pd-rich (fcc) and Au-rich (fcc) phases. Cyclic voltammetry and chronoamperometry experiments showed that PdAuSn/MWCNT electrocatalyst demonstrated similar activity toward ethanol electro-oxidation at room temperature, compared to electrocatalyst Pd/MWCNT. (author)

  7. Ethanol electro-oxidation in alkaline medium using Pd/MWCNT and PdAuSn/MWCNT electrocatalysts prepared by electron beam irradiation

    International Nuclear Information System (INIS)

    Geraldes, Adriana Napoleao; Silva, Dionisio Furtunato da; Andrade e Silva, Leonardo Gondin de; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Santos, Mauro Coelho dos

    2015-01-01

    Environmental problems and the world growing demand for energy has mobilized the scientific community in finding of clean and renewable energy sources. In this context, fuel cells appear as appropriate technology for generating electricity through alcohols electro-oxidation. Multi Wall Carbon Nanotubes (MWCNT)-supported Pd and trimetallic PdAuSn (Pd:Au:Sn 50:10:40 atomic ratio) electrocatalysts were prepared using electron beam irradiation. The obtained materials were characterized by VC, Chronoamperometry, EDX, TEM and XRD. The catalytic activities of electrocatalysts toward ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC) in a range temperature 60 to 90 deg C. The best performances were obtained at 85 deg C: 33 mW.cm -2 and 31 mW.cm -2 for Pd/ MWCNT and PdAuSn/MWCNT electrocatalysts, respectively. X-ray diffractograms of electrocatalysts showed the presence of Pd-rich (fcc) and Au-rich (fcc) phases. Cyclic voltammetry and chronoamperometry experiments showed that PdAuSn/MWCNT electrocatalyst demonstrated similar activity toward ethanol electro-oxidation at room temperature, compared to electrocatalyst Pd/MWCNT. (author)

  8. Community detection in complex networks using proximate support vector clustering

    Science.gov (United States)

    Wang, Feifan; Zhang, Baihai; Chai, Senchun; Xia, Yuanqing

    2018-03-01

    Community structure, one of the most attention attracting properties in complex networks, has been a cornerstone in advances of various scientific branches. A number of tools have been involved in recent studies concentrating on the community detection algorithms. In this paper, we propose a support vector clustering method based on a proximity graph, owing to which the introduced algorithm surpasses the traditional support vector approach both in accuracy and complexity. Results of extensive experiments undertaken on computer generated networks and real world data sets illustrate competent performances in comparison with the other counterparts.

  9. Factors influencing the charge distribution on Pd x Pt y bimetallic nanoparticles

    Directory of Open Access Journals (Sweden)

    Carlos M. Celis-Cornejo

    2013-12-01

    Full Text Available We performed quantum mechanics calculations to elucidate the electronic behavior of Pd-Pt bimetallic nanoparticles, using density functional theory, in response to particle size and stoichiometric composition. Using neutrally charged nanoparticles and the Bader charge analysis, we found that external Pd atoms were positively charged, which agrees with previous XPS observations of supported Pd-Pt nanoparticles. From the calculations, unsupported nanoparticles exhibit an electron transfer from Pd to Pt. This result supports the idea that Pd electron-deficient species are possibly responsible of the hydrogenating function of these catalysts, in the hydrodesulfurization of dibenzothiophene. Additionally, it was found that the particle size does not affect the electronic charge distribution and the stoichiometric composition is the factor that greatly influences this property in nanoparticles.

  10. Atomic structure of a decagonal Al-Pd-Mn phase

    Science.gov (United States)

    Mihalkovič, Marek; Roth, Johannes; Trebin, Hans-Rainer

    2017-12-01

    We present a detailed structure solution for the 16 -Å decagonal quasicrystal in the Al-Pd-Mn system by means of cluster decoration and ab initio energy minimization. It is based on structure models of the ɛ and other approximant phases. The ɛ phases can be represented as subsets of a hexagon-boat-star (HBS) tiling. The decagonal phase comprises further HBS tiles. We have constructed several fictitious HBS approximants and optimized their structures individually. All tiles are decorated by two types of atomic clusters: the pseudo-Mackay icosahedron (PMI) and the large bicapped pentagonal prism (LBPP). It turns out that, whereas the PMI clusters can be kept essentially unchanged, the LBPP clusters must be adjusted in occupancy with Al atoms depending on their positions in the various tiles. In this way we obtain cluster decorations for all tiles of the decagonal quasicrystal. The calculations were confirmed by evaluation of an effective tile Hamiltonian.

  11. Palladium clusters deposited on the heterogeneous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Kun, E-mail: cqdxwk@126.com [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China); Liu, Juanfang, E-mail: juanfang@cqu.edu.cn [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China); Chen, Qinghua, E-mail: qhchen@cqu.edu.cn [College of Power Engineering, Chongqing University, Chongqing 400044 (China); Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing 400044 (China)

    2016-07-15

    Graphical abstract: The site-exchange between the substrate and cluster atoms can result in the formation of the surface alloys and the reconstruction of the cluster structure before the collision system approaching the thermal equilibrium. The deposited cluster adjusted the atom arrangement as possibly as to match the substrate lattice arrangement from bottom to up. The structural reconstruction is accompanied by the system potential energy minimization. - Highlights: • The deposition process can divide explicitly into three stages: adsorption, collision, relaxation. • The local melt does not emerge inside the substrate during the deposition process. • Surface alloys are formed by the site-exchange between the cluster and substrate atoms. • The cluster reconstructs the atom arrangement following as the substrate lattice arrangement from bottom to up. • The structural reconstruction ability and scope depend on the cluster size and incident energy. - Abstract: To improve the performance of the Pd composite membrane prepared by the cold spraying technology, it is extremely essential to give insights into the deposition process of the cluster and the heterogeneous deposition of the big Pd cluster at the different incident velocities on the atomic level. The deposition behavior, morphologies, energetic and interfacial configuration were examined by the molecular dynamic simulation and characterized by the cluster flattening ratio, the substrate maximum local temperature, the atom-embedded layer number and the surface-alloy formation. According to the morphology evolution, three deposition stages and the corresponding structural and energy evolution were clearly identified. The cluster deformation and penetrating depth increased with the enhancement of the incident velocity, but the increase degree also depended on the substrate hardness. The interfacial interaction between the cluster and the substrate can be improved by the higher substrate local temperature

  12. CO-induced Pd segregation and the effect of subsurface Pd on CO adsorption on CuPd surfaces

    International Nuclear Information System (INIS)

    Padama, A A B; Villaos, R A B; Albia, J R; Diño, W A; Nakanishi, H; Kasai, H

    2017-01-01

    We report results of our study on the adsorption of CO on CuPd surfaces with bulk stoichiometric and nonstoichiometric layers using density functional theory (DFT). We found that the presence of Pd atoms in the subsurface layer promotes the adsorption of CO. We also observed CO-induced Pd segregation on the CuPd surface and we attribute this to the strong CO–Pd interaction. Lastly, we showed that the adsorption of CO promotes Pd–Pd interaction as compared to the pristine surface which promotes strong Cu–Pd interaction. These results indicate that CO adsorption on CuPd surfaces can be tuned by taking advantage of the CO-induced segregation and by considering the role of subsurface Pd atoms. (paper)

  13. Basal cell carcinoma: PD-L1/PD-1 checkpoint expression and tumor regression after PD-1 blockade.

    Science.gov (United States)

    Lipson, Evan J; Lilo, Mohammed T; Ogurtsova, Aleksandra; Esandrio, Jessica; Xu, Haiying; Brothers, Patricia; Schollenberger, Megan; Sharfman, William H; Taube, Janis M

    2017-01-01

    Monoclonal antibodies that block immune regulatory proteins such as programmed death-1 (PD-1) have demonstrated remarkable efficacy in controlling the growth of multiple tumor types. Unresectable or metastatic basal cell carcinoma, however, has largely gone untested. Because PD-Ligand-1 (PD-L1) expression in other tumor types has been associated with response to anti-PD-1, we investigated the expression of PD-L1 and its association with PD-1 expression in the basal cell carcinoma tumor microenvironment. Among 40 basal cell carcinoma specimens, 9/40 (22%) demonstrated PD-L1 expression on tumor cells, and 33/40 (82%) demonstrated PD-L1 expression on tumor-infiltrating lymphocytes and associated macrophages. PD-L1 was observed in close geographic association to PD-1+ tumor infiltrating lymphocytes. Additionally, we present, here, the first report of an objective anti-tumor response to pembrolizumab (anti-PD-1) in a patient with metastatic PD-L1 (+) basal cell carcinoma, whose disease had previously progressed through hedgehog pathway-directed therapy. The patient remains in a partial response 14 months after initiation of therapy. Taken together, our findings provide a rationale for testing anti-PD-1 therapy in patients with advanced basal cell carcinoma, either as initial treatment or after acquired resistance to hedgehog pathway inhibition.

  14. In Situ Generation of Pd-Pt Core-Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins.

    Science.gov (United States)

    Goswami, Anandarup; Rathi, Anuj K; Aparicio, Claudia; Tomanec, Ondrej; Petr, Martin; Pocklanova, Radka; Gawande, Manoj B; Varma, Rajender S; Zboril, Radek

    2017-01-25

    Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (>98%), excellent selectivity (>98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core-shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions.

  15. Optimised photocatalytic hydrogen production using core–shell AuPd promoters with controlled shell thickness

    DEFF Research Database (Denmark)

    Jones, Wilm; Su, Ren; Wells, Peter

    2014-01-01

    of these materials towards the reforming of alcohols for hydrogen production. The core–shell structured Au–Pd bimetallic nanoparticle supported on TiO2 has being of interest as it exhibited extremely high quantum efficiencies for hydrogen production. However, the effect of shell composition and thickness...... of the nanoparticles by a combination of X-ray absorption fine structure and X-ray photoelectron spectroscopy. Photocatalytic ethanol reforming showed that the core–shell structured Au–Pd promoters supported on TiO2 exhibit enhanced activity compared to that of monometallic Au and Pd as promoters, whilst the core......–shell Au–Pd promoters containing one ML equivalent Pd provide the optimum reactivity....

  16. Molecular mechanism of PD-1/PD-L1 blockade via anti-PD-L1 antibodies atezolizumab and durvalumab.

    Science.gov (United States)

    Lee, Hyun Tae; Lee, Ju Yeon; Lim, Heejin; Lee, Sang Hyung; Moon, Yu Jeong; Pyo, Hyo Jeong; Ryu, Seong Eon; Shin, Woori; Heo, Yong-Seok

    2017-07-17

    In 2016 and 2017, monoclonal antibodies targeting PD-L1, including atezolizumab, durvalumab, and avelumab, were approved by the FDA for the treatment of multiple advanced cancers. And many other anti-PD-L1 antibodies are under clinical trials. Recently, the crystal structures of PD-L1 in complex with BMS-936559 and avelumab have been determined, revealing details of the antigen-antibody interactions. However, it is still unknown how atezolizumab and durvalumab specifically recognize PD-L1, although this is important for investigating novel binding sites on PD-L1 targeted by other therapeutic antibodies for the design and improvement of anti-PD-L1 agents. Here, we report the crystal structures of PD-L1 in complex with atezolizumab and durvalumab to elucidate the precise epitopes involved and the structural basis for PD-1/PD-L1 blockade by these antibodies. A comprehensive comparison of PD-L1 interactions with anti-PD-L1 antibodies provides a better understanding of the mechanism of PD-L1 blockade as well as new insights into the rational design of improved anti-PD-L1 therapeutics.

  17. Interfacial processes in the Pd/a-Ge:H system

    Science.gov (United States)

    Edelman, F.; Cytermann, C.; Brener, R.; Eizenberg, M.; Weil, R.; Beyer, W.

    1993-06-01

    The kinetics of phase transformation has been studied in a two-layer structure of Pd/a-Ge:H after vacuum annealing at temperatures from 180 to 500°C. The a-Ge:H was deposited at 250°C on both c-Si and cleaved NaCl substrates in an RF glow discharge from a GeH 4/H 2 mixture. It was found that, similarly to the Pd/c-Ge and the Pd/a-Ge (e-gun deposited) systems, in the case of 0.15-0.2 μm Pd/0.6-1.0 μm a-Ge:H interfacial germanides formed first through the production of Pd 2Ge (plus a small amount of PdGe), and then PdGe was produced. The growth of both compounds was found to be diffusion-controlled. The nonreacted a-Ge:H layer beneath the germanide overlayer crystallized at 400-500°C. A reverse sequence of germanides formation was revealed in the case of 50 nm Pd/30 nm a-Ge:H, studied by in situ heat treatment in the TEM utilizing non-supported samples. The first germanide detected was PdGe and then, as a result of PdGe and Ge reaction or the PdGe decomposition, Pd 2Ge formed. The temperature dependence of the incubation time before the first ˜ 10 nm PdGe grains formed, followed an Arrhenius curve with an activation energy of 1.45 eV.

  18. Targeting PD-1/PD-L1 in lung cancer: current perspectives

    Directory of Open Access Journals (Sweden)

    González-Cao M

    2015-07-01

    Full Text Available María González-Cao,1 Niki Karachaliou,1 Santiago Viteri,1 Daniela Morales-Espinosa,1 Cristina Teixidó,2 Jesús Sánchez Ruiz,3 Miquel Ángel Molina-Vila,2 Mariacarmela Santarpia,4 Rafael Rosell1,2,5,61Translational Cancer Research Unit, Instituto Oncológico Dr Rosell, Quirón Dexeus University Hospital, Barcelona, Spain; 2Pangaea Biotech SL, Barcelona, Spain; 3Centro Nacional de Investigación Oncología (CNIO, Madrid, Spain; 4Medical Oncology Unit, Human Pathology Department, University of Messina, Messina, Italy; 5Cancer Biology and Precision Medicine Program, Catalan Institute of Oncology, Germans Trias i Pujol Health Sciences Institute and Hospital, Campus Can Ruti, Badalona, Barcelona, Spain; 6Fundación Molecular Oncology Research, Barcelona, SpainAbstract: Increased understanding of tumor immunology has led to the development of effective immunotherapy treatments. One of the most important advances in this field has been due to pharmacological design of antibodies against immune checkpoint inhibitors. Anti-PD-1/PD-L1 antibodies are currently in advanced phases of clinical development for several tumors, including lung cancer. Results from Phase I–III trials with anti-PD-1/PD-L1 antibodies in non-small-cell lung cancer have demonstrated response rates of around 20% (range, 16%–50%. More importantly, responses are long-lasting (median duration of response, 18 months and fast (50% of responses are detected at time of first tumor evaluation with very low grade 3–4 toxicity (less than 5%. Recently, the anti-PD-1 antibody pembrolizumab received US Food and Drug Administration (FDA breakthrough therapy designation for treatment of non-small-cell lung cancer, supported by data from a Phase Ib trial. Another anti-PD-1 antibody, nivolumab, has also been approved for lung cancer based on survival advantage demonstrated in recently released data from a Phase III trial in squamous cell lung cancer.Keywords: immunotherapy, immunoncology

  19. Evaluation of artillery equipment maintenance support capability based on grey clustering

    Science.gov (United States)

    Zhai, Mei-jie; Gao, Peng

    2017-12-01

    This paper, the theory and method of evaluating the capability of equipment maintenance support in China and abroad are studied, from the point of view of the combat task of artillery troops and the strategic attachment in the future military struggle. This paper establishes the framework of the evaluation Index system of the equipment maintenance support capability of the artillery units, and applies the grey clustering method to the evaluation of the equipment maintenance support capability of the artillery units, and finally evaluates the equipment maintenance and support capability of the artillery brigade as an example, and analyzes the evaluation results. This paper finds out the outstanding problems existing in the maintenance and support of military equipment, and puts forward some constructive suggestions, in order to improve the status of military equipment maintenance and support and improve the level of future equipment maintenance.

  20. An algebraic model for three-cluster giant molecules

    International Nuclear Information System (INIS)

    Hess, P.O.; Bijker, R.; Misicu, S.

    2001-01-01

    After an introduction to the algebraic U(7) model for three bodies, we present a relation of a geometrical description of three-cluster molecule to the algebraic U(7) model. Stiffness parameters of oscillations between each of two clusters are calculated and translated to the model parameter values of the algebraic model. The model is applied to the trinuclear system l32 Sn+ α + ll6 Pd which occurs in the ternary cold fission of 252 Cf. (Author)

  1. Synthesis and characterization of bulky mesoporous silica Pd-MCM-41

    International Nuclear Information System (INIS)

    Nagata, Hidezumi; Nakahira, Atsushi; Hirao, Norie; Baba, Yuji; Onoki, Takamasa; Yamasaki, Yuki

    2008-01-01

    Bulky palladium catalyst supported on mesoporous silica MCM-41 (Pd-MCM-41) was successfully synthesized by hydrothermal hot-pressing method. In this study, the structure of the palladium species in Pd-MCM-41 bulk before and after heat-treatment process was revealed by X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and transmission electron microscopy (TEM). Also, the microstructure and mesoporous property of Pd-MCM-41 bulk was discussed. As a result, it was revealed that these dense Pd-MCM-41 bulks possessed a high surface area of over 1000 m 2 /g and the structure of palladium of Pd-MCM-41 bulk is almost equal to palladium (0) metal. (author)

  2. Morphology and N₂ Permeance of Sputtered Pd-Ag Ultra-Thin Film Membranes.

    Science.gov (United States)

    Fernandez, Ekain; Sanchez-Garcia, Jose Angel; Viviente, Jose Luis; van Sint Annaland, Martin; Gallucci, Fausto; Tanaka, David A Pacheco

    2016-02-10

    The influence of the temperature during the growth of Pd-Ag films by PVD magnetron sputtering onto polished silicon wafers was studied in order to avoid the effect of the support roughness on the layer growth. The surfaces of the Pd-Ag membrane films were analyzed by atomic force microscopy (AFM), and the results indicate an increase of the grain size from 120 to 250-270 nm and film surface roughness from 4-5 to 10-12 nm when increasing the temperature from around 360-510 K. After selecting the conditions for obtaining the smallest grain size onto silicon wafer, thin Pd-Ag (0.5-2-µm thick) films were deposited onto different types of porous supports to study the influence of the porous support, layer thickness and target power on the selective layer microstructure and membrane properties. The Pd-Ag layers deposited onto ZrO₂ 3-nm top layer supports (smallest pore size among all tested) present high N₂ permeance in the order of 10(-6) mol·m(-2)·s(-1)·Pa(-1) at room temperature.

  3. [Electronic and structural properties of individual nanometer-size supported metallic clusters]. Final performance report

    Energy Technology Data Exchange (ETDEWEB)

    Reifenberger, R.

    1993-09-01

    This report summarizes the work performed under contract DOE-FCO2-84ER45162. During the past ten years, our study of electron emission from laser-illuminated field emission tips has taken on a broader scope by addressing problems of direct interest to those concerned with the unique physical and chemical properties of nanometer-size clusters. The work performed has demonstrated that much needed data can be obtained on individual nanometer-size clusters supported on a wide-variety of different substrates. The work was performed in collaboration with R.P. Andres in the School of Chemical Engineering at Purdue University. The Multiple Expansion Cluster Source developed by Andres and his students was essential for producing the nanometer-size clusters studied. The following report features a discussion of these results. This report provides a motivation for studying the properties of nanometer-size clusters and summarizes the results obtained.

  4. Water-dispersable hybrid Au-Pd nanoparticles as catalysts in ethanol oxidation, aqueous phase Suzuki-Miyaura and Heck reactions

    KAUST Repository

    Song, Hyon Min; Moosa, Basem; Khashab, Niveen M.

    2012-01-01

    The catalytic activities of water-dispersable Au@Pd core-shell nanoparticles (NPs) and Au-Pd alloy NPs were examined. There is growing interest in Au-Pd hybridized NPs in a supported matrix or non-supported forms as catalysts in various reactions

  5. Anti-tumor immunotherapy by blockade of the PD-1/PD-L1 pathway with recombinant human PD-1-IgV.

    Science.gov (United States)

    Zhang, C; Wu, S; Xue, X; Li, M; Qin, X; Li, W; Han, W; Zhang, Y

    2008-01-01

    Blockade of the programmed death-1 (PD-1)/PD-ligand 1 (PD-L1) pathway can delay tumor growth and prolong the survival of tumor-bearing mice. The extracellular immunoglobulin (Ig) V domain of PD-1 is important for the interaction between PD-1 and PD-L1, suggesting that PD-1-IgV may be a potential target for anti-tumor immunotherapy. The extracellular sequence of human PD-1-IgV (hPD-1-IgV) was expressed in Escherichia coli and purified. The anti-tumor effect of hPD-1-IgV on tumor-bearing mice was tested. hPD-1-IgV recombinant protein could bind PD-L1 at molecular and cellular levels and enhance Cytotoxic T Lymphocyte (CTL) activity and anti-tumor effect on tumor-bearing mice in vivo. The percentage of CD4(+)CD25(+) T cells in tumor-bearing mice was decreased compared with control mice after administration of the recombinant protein. Our results suggest that inhibition of the interaction between PD-1 and PD-L1 by hPD-1-IgV may be a promising strategy for specific tumor immunotherapy.

  6. Pd nanoparticles supported on functionalized multi-walled carbon nanotubes (MWCNTs) and electrooxidation for formic acid

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Sudong; Mi, Hongyu; Ye, Xiangguo [Institute of Applied Chemistry, Xinjiang University, Urumqi 830046 (China); Zhang, Xiaogang [College of Material Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2008-01-03

    To improve the utilization and activity of anodic catalysts for formic acid electrooxidation, palladium (Pd) particles were loaded on the MWCNTs, which were functionalized in a mixture of 96% sulfuric acid and 4-aminobenzenesulfonic acid, using sodium nitrite to produce intermediate diazonium salts from substituted anilines. The composition, particle size, and crystallinity of the Pd/f-MWCNTs catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) measurements. The electrocatalytic properties of the Pd/f-MWCNTs catalysts for formic acid oxidation were investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 0.5 mol L{sup -1} H{sub 2}SO{sub 4} solution. The results demonstrated that the catalytic activity was greatly enhanced due to the improved water-solubility and dispersion of the f-MWCNTs, which were facile to make the small particle size (3.8 nm) and uniform dispersion of Pd particles loading on the surface of the MWCNTs. In addition, the functionalized MWCNTs with benzenesulfonic group can provide benzenesulfonic anions in aqueous solution, which may combine with hydrogen cation and then promote the oxidation of formic acid reactive intermediates. So the Pd/f-MWCNTs composites showed excellent electrocatalytic activity for formic acid oxidation. (author)

  7. Active sites and mechanisms for H2O2 decomposition over Pd catalysts

    Science.gov (United States)

    Plauck, Anthony; Stangland, Eric E.; Dumesic, James A.; Mavrikakis, Manos

    2016-01-01

    A combination of periodic, self-consistent density functional theory (DFT-GGA-PW91) calculations, reaction kinetics experiments on a SiO2-supported Pd catalyst, and mean-field microkinetic modeling are used to probe key aspects of H2O2 decomposition on Pd in the absence of cofeeding H2. We conclude that both Pd(111) and OH-partially covered Pd(100) surfaces represent the nature of the active site for H2O2 decomposition on the supported Pd catalyst reasonably well. Furthermore, all reaction flux in the closed catalytic cycle is predicted to flow through an O–O bond scission step in either H2O2 or OOH, followed by rapid H-transfer steps to produce the H2O and O2 products. The barrier for O–O bond scission is sensitive to Pd surface structure and is concluded to be the central parameter governing H2O2 decomposition activity. PMID:27006504

  8. Clusters - Tourism Activity Increase Competitiveness Support

    Directory of Open Access Journals (Sweden)

    Carmen IORDACHE

    2010-05-01

    Full Text Available Tourism represents one of those areas with the greatest potential of global expansion. Tourism development strategy in terms of maximizing its positive effects on regional economic increase and implicitly on the national one starts from the premise that in global economy value is created in regions which are defined as particular geographical entities, separated by geographical reasons and not as political-administrative structures, and economic increase is centrally cumulated and valued according to the economic policy and the national legal system.Regional economic system approach based on “cluster” concept is explained by the fact that the regional activities portfolio is based on an inter and intra-industry networking grouped by cluster, in which is created the value that increases as the activity results are leading to the final consumers.This type of communication aims to highlight the tourism role as a factor in regional development, the clustering process significance in obtaining some competitiveness advantages, clusters development in tourism beginnings, and also the identification methodology used to select one touristic area to create the cluster.

  9. Carbon Supported Oxide-Rich Pd-Cu Bimetallic Electrocatalysts for Ethanol Electrooxidation in Alkaline Media Enhanced by Cu/CuOx

    Directory of Open Access Journals (Sweden)

    Zengfeng Guo

    2016-04-01

    Full Text Available Different proportions of oxide-rich PdCu/C nanoparticle catalysts were prepared by the NaBH4 reduction method, and their compositions were tuned by the molar ratios of the metal precursors. Among them, oxide-rich Pd0.9Cu0.1/C (Pd:Cu = 9:1, metal atomic ratio exhibits the highest electrocatalytic activity for ethanol oxidation reaction (EOR in alkaline media. X-ray photoelectron spectroscopy (XPS and high resolution transmission electron microscopy (HRTEM confirmed the existence of both Cu and CuOx in the as-prepared Pd0.9Cu0.1/C. About 74% of the Cu atoms are in their oxide form (CuO or Cu2O. Besides the synergistic effect of Cu, CuOx existed in the Pd-Cu bimetallic nanoparticles works as a promoter for the EOR. The decreased Pd 3d electron density disclosed by XPS is ascribed to the formation of CuOx and the spill-over of oxygen-containing species from CuOx to Pd. The low Pd 3d electron density will decrease the adsorption of CH3COads intermediates. As a result, the electrocatalytic activity is enhanced. The onset potential of oxide-rich Pd0.9Cu0.1/C is negative shifted 150 mV compared to Pd/C. The oxide-rich Pd0.9Cu0.1/C also exhibited high stability, which indicated that it is a candidate for the anode of direct ethanol fuel cells (DEFCs.

  10. Positive XPS binding energy shift of supported Cu{sub N}-clusters governed by initial state effects

    Energy Technology Data Exchange (ETDEWEB)

    Peters, S.; Peredkov, S. [Technische Universität Berlin, IOAP, Strasse des 17. Juni 135, 10623 Berlin (Germany); Al-Hada, M. [Department of Physics, College of Education and Linguistics, University of Amran (Yemen); Neeb, M., E-mail: matthias.neeb@helmholtz-berlin.de [Helmholtz-Zentrum Berlin, Wilhelm-Conrad-Röntgen-Campus Adlershof, Elektronenspeicherring BESSY II, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Eberhardt, W. [Technische Universität Berlin, IOAP, Strasse des 17. Juni 135, 10623 Berlin (Germany); DESY, Center for Free Electron Laser Science (CFEL), Notkestr. 85, 22607 Hamburg (Germany)

    2014-01-01

    Highlights: • Size dependent initial and final state effects of mass-selected deposited clusters. • Initial state effect dominates positive XPS shift in supported Cu-clusters. • Size dependent Coulomb correlation shift in the Auger final state of Cu cluster. • Size-dependent Auger parameter analysis. • Positive XPS shift differs from negative surface core level shift in crystalline copper. - Abstract: An initial state effect is established as origin for the positive 2p core electron binding energy shift found for Cu{sub N}-clusters supported by a thin silica layer of a p-doped Si(1 0 0) wafer. Using the concept of the Auger parameter and taking into account the usually neglected Coulomb correlation shift in the Auger final state (M{sub 4,5}M{sub 4,5}) it is shown that the initial state shift is comparable to the measured XPS shift while the final state relaxation shift contributes only marginally to the binding energy shift. The cluster results differ from the negative surface core-level shift of crystalline copper which has been explained in terms of a final state relaxation effect.

  11. A DFT study of Ru, Rh, Pd, Os, Ir, and Pt clusters as catalysts for methane dissociation in a direct methane fuel cell (DMHFC)

    Energy Technology Data Exchange (ETDEWEB)

    Psofogiannakisa, G. [Ottawa Univ., Ottawa, ON (Canada). Dept. of Chemical Engineering; Ottawa, Univ., Ottawa, ON (Canada). Centre for Catalysis Research and Innovation; St-Amant, A. [Ottawa Univ., Ottawa, ON (Canada). Dept. of Chemistry; Ternan, M. [Ottawa Univ., Ottawa, ON (Canada). Centre for Catalysis Research and Innovation; EnPross Inc., Ottawa, ON (Canada)

    2008-07-01

    The rate limiting step in a direct methane hydrocarbon fuel cell (DMHFC) is the dissociative chemisorption of methane. Quantum mechanical computations were used to examine the terrace, kink, and step sites on 6 different clusters of group 8 transition metals, notably Ru, Rh, Pd, Os, Ir, and Pt. The computations involved the anodic reaction of a DMHFC with a polymer electrolyte that operates at atmospheric pressure and temperatures higher than 120 degrees C. The interaction between molecular fragments and a surface (Pt) were described and density functional theory (DFT) calculations were performed using Guassian software. The geometries of 5 different platinum clusters were examined along with their electronic energy barriers. The biggest contribution to the stabilization energy came from the overlap between the sigma bond in methane and unoccupied sd hybrid orbitals in the Pt bonding atom. The study showed that when relaxation was allowed, the displacement of the bonding metal atom was 0.36 to 0.52 A. The electronic energy barrier often increased as d-orbital occupancy increased. For the kink surface sites, the energy barriers were considerably smaller for the 5d transition metals than for the 4d transition metals. 5 refs., 1 tab.

  12. Crystal structure and transport properties of Pd5HgSe

    Czech Academy of Sciences Publication Activity Database

    Laufek, F.; Vymazalová, A.; Drábek, M.; Navrátil, Jiří; Plecháček, T.; Drahokoupil, Jan

    2012-01-01

    Roč. 14, č. 10 (2012), s. 1476-1479 ISSN 1293-2558 R&D Projects: GA ČR GAP108/10/1315 Institutional support: RVO:61389013 ; RVO:68378271 Keywords : Pd5HgSe * Pd-Hg-Se system * crystal structure Subject RIV: CA - Inorganic Chemistry Impact factor: 1.671, year: 2012

  13. Study of Pd-Au/MWCNTs formic acid electrooxidation catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Mikolajczuk, Anna; Borodzinski, Andrzej; Kedzierzawski, Piotr; Lesiak, Beata [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa (Poland); Stobinski, Leszek [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa (Poland); Faculty of Materials Science and Engineering, Warsaw University of Technology, ul. Woloska 141, 02-507 Warsaw (Poland); Koever, Laszlo; Toth, Jozsef [Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI), P. O. Box 51, 4001 Debrecen (Hungary); Lin, Hong-Ming [Department of Materials Engineering, Tatung University, 40, Chungshan N. Rd., 3rd Sec, 104, Taipei (China)

    2010-12-15

    The Pd-Au multiwall carbon nanotubes (MWCNTs) supported catalyst exhibits higher power density in direct formic acid fuel cell (DFAFC) than similar Pd/MWCNTs catalyst. The Pd-Au/MWCNTs catalyst also exhibits higher activity and is more stable in electrooxidation reaction of formic acid during cyclic voltammetry (CV) measurements. After preparation by polyol method, the catalyst was subjected to two type of treatments: (I) annealing at 250 C in 100% of Ar, (II) reducing in 5% of H{sub 2} in Ar atmosphere at 200 C. It was observed that the catalyst after treatment I was completely inactive, whereas after treatment II exhibited high activity. In order to explain this effect the catalysts were characterized by electron spectroscopy methods. The higher initial catalytic activity of Pd-Au/MWCNTs catalyst than Pd/MWCNTs catalyst in reaction of formic acid electrooxidation was attributed to electronic effect of gold in Pd-Au solution, and larger content of small Au nanoparticles of 1 nm size. The catalytic inactivity of Pd-Au/MWCNTs catalysts annealed in argon is attributed to carbon amorphous overlayer covering of Pd oxide shell on the metallic nanoparticles. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Synthesis and Characterization of a Triphos Ligand Derivative and the Corresponding Pd II Complexes: Triphos Ligand Derivative and Corresponding Pd II Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Deanna L.; Boro, Brian J.; Grubel, Katarzyna; Helm, Monte L.; Appel, Aaron M.

    2015-11-16

    The synthesis of the new bis(2-(diphenylphosphino)ethyl)methylhydroxyphosphine tridentate phosphine ligand, LCH2OH/Ph, is reported. The ligand reacts with [Pd(Cl)2(PhCN)2 to form [Pd(LCH2OH/Ph)Cl]Cl. Exchange of the chloride ions for triflate (OTf–) using AgOTf yielded pure [Pd(LCH2OH/Ph)OTf]OTf. In addition to spectral characterization the free ligand, LCH2OH/Ph, and Pd(II) complex, [Pd(LCH2OH/Ph)OTf]OTf, are structurally characterized. This research was supported by the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences, and Geosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for DOE.

  15. NNΔ resonance and pd → 3He πo reaction

    International Nuclear Information System (INIS)

    Ueda, T.

    1988-01-01

    On the basis of the I = 1, JP = 2+ resonant NΔ interaction (the pp 1D2 dibaryon), one argues that in NNΔ system a three-body resonance is generated. With a clustering binding energy of a few 10 MeV between the N and the Δ making the dibaryon and another binding energy of about 10 MeV between the NΔ cluster and the spectator N due to the attractive interaction of the Δ exchange between the cluster and spectator, the NNΔ system is bound about 40 - 60 MeV below the NNΔ threshold. Because of the Δ decay width the NNΔ bound state is actually a resonant state. The case where the spins of all the particles align in the same direction is most favorable to be bound, since the driving term is largest here. Assigning the zero orbital angular momenta, the spin-parity of the NNΔ resonance is JP = (5/2)+ . The resonance couples with NNN system through NN(1D2)-NΔ(5S2). Thus the total spin of the NNN system which couples easily with the NNΔ resonance is 1/2. Namely the spin doublet pd channel creates the NNΔ resonance. Similar argument applies to NΔΔ system. Then one summarize: NNΔ resonance : M = 3.07 GeV, JP = (5/2)+. NΔΔ resonance : M = 3.36 GeV, JP = (7/2)+. Both are easy to couple with the spin-doublet pd channel. Assuming the NNΔ and NΔΔ resonance terms, combined with the background ones which are mild in the energy dependence, one analyses the differential cross section and the deuteron tensor polarization of pd → 3 He π o at deuteron incident energy 410 ∼ 2200 MeV at θ = 0 and π. The remarkable energy-dependent structure of the tensor polarization is fairly explained by the existence of the NNΔ and NΔΔ resonances. (author)

  16. Tools for predicting the PK/PD of therapeutic proteins.

    Science.gov (United States)

    Diao, Lei; Meibohm, Bernd

    2015-07-01

    Assessments of the pharmacokinetic/pharmacodynamic (PK/PD) characteristics are an integral part in the development of novel therapeutic agents. Compared with traditional small molecule drugs, therapeutic proteins possess many distinct PK/PD features that necessitate the application of modified or separate approaches for assessing their PK/PD relationships. In this review, the authors discuss tools that are utilized to describe and predict the PK/PD features of therapeutic proteins and that are valuable additions in the armamentarium of drug development approaches to facilitate and accelerate their successful preclinical and clinical development. A variety of state-of-the-art PK/PD tools is currently being applied and has been adjusted to support the development of proteins as therapeutics, including allometric scaling approaches, target-mediated disposition models, first-in-man dose calculations, physiologically based PK models and empirical and semi-mechanistic PK/PD modeling. With the advent of the next generation of biologics including bioengineered antibody constructs being developed, these tools will need to be further refined and adapted to ensure their applicability and successful facilitation of the drug development process for these novel scaffolds.

  17. PdRu/C catalysts for ethanol oxidation in anion-exchange membrane direct ethanol fuel cells

    Science.gov (United States)

    Ma, Liang; He, Hui; Hsu, Andrew; Chen, Rongrong

    2013-11-01

    Carbon supported PdRu catalysts with various Pd:Ru atomic ratios were synthesized by impregnation method, and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electrochemical half-cell tests, and the anion-exchange membrane direct ethanol fuel cell (AEM-DEFC) tests. XRD results suggest that the PdRu metal exists on carbon support in an alloy form. TEM study shows that the bimetallic PdRu/C catalysts have slightly smaller average particle size than the single metal Pd/C catalyst. Lower onset potential and peak potential and much higher steady state current for ethanol oxidation in alkaline media were observed on the bimetallic catalysts (PdxRuy/C) than on the Pd/C, while the activity for ethanol oxidation on the pure Ru/C was not noticeable. By using Pd/C anode catalysts and MnO2 cathode catalysts, AEM-DEFCs free from the expensive Pt catalyst were assembled. The AEM DEFC using the bimetallic Pd3Ru/C anode catalyst showed a peak power density as high as 176 mW cm-2 at 80 °C, about 1.8 times higher than that using the single metal Pd/C catalyst. The role of Ru for enhancing the EOR activity of Pd/C catalysts is discussed.

  18. Cluster analysis of spontaneous preterm birth phenotypes identifies potential associations among preterm birth mechanisms.

    Science.gov (United States)

    Esplin, M Sean; Manuck, Tracy A; Varner, Michael W; Christensen, Bryce; Biggio, Joseph; Bukowski, Radek; Parry, Samuel; Zhang, Heping; Huang, Hao; Andrews, William; Saade, George; Sadovsky, Yoel; Reddy, Uma M; Ilekis, John

    2015-09-01

    We sought to use an innovative tool that is based on common biologic pathways to identify specific phenotypes among women with spontaneous preterm birth (SPTB) to enhance investigators' ability to identify and to highlight common mechanisms and underlying genetic factors that are responsible for SPTB. We performed a secondary analysis of a prospective case-control multicenter study of SPTB. All cases delivered a preterm singleton at SPTB ≤34.0 weeks' gestation. Each woman was assessed for the presence of underlying SPTB causes. A hierarchic cluster analysis was used to identify groups of women with homogeneous phenotypic profiles. One of the phenotypic clusters was selected for candidate gene association analysis with the use of VEGAS software. One thousand twenty-eight women with SPTB were assigned phenotypes. Hierarchic clustering of the phenotypes revealed 5 major clusters. Cluster 1 (n = 445) was characterized by maternal stress; cluster 2 (n = 294) was characterized by premature membrane rupture; cluster 3 (n = 120) was characterized by familial factors, and cluster 4 (n = 63) was characterized by maternal comorbidities. Cluster 5 (n = 106) was multifactorial and characterized by infection (INF), decidual hemorrhage (DH), and placental dysfunction (PD). These 3 phenotypes were correlated highly by χ(2) analysis (PD and DH, P cluster 3 of SPTB. We identified 5 major clusters of SPTB based on a phenotype tool and hierarch clustering. There was significant correlation between several of the phenotypes. The INS gene was associated with familial factors that were underlying SPTB. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Expression of PD-1 and PD-L1 in poorly differentiated neuroendocrine carcinomas of the digestive system: a potential target for anti-PD-1/PD-L1 therapy.

    Science.gov (United States)

    Roberts, Jordan A; Gonzalez, Raul S; Das, Satya; Berlin, Jordan; Shi, Chanjuan

    2017-12-01

    Poorly differentiated neuroendocrine carcinoma of the digestive system has a dismal prognosis with limited treatment options. This study aimed to investigate expression of the PD-1/PD-L1 pathway in these tumors. Thirty-seven patients with a poorly differentiated neuroendocrine carcinoma of the digestive system were identified. Their electronic medical records, pathology reports, and pathology slides were reviewed for demographics, clinical history, and pathologic features. Tumor sections were immunohistochemically labeled for PD-1 and PD-L1, and expression of PD-1 and PD-L1 on tumor and tumor-associated immune cells was analyzed and compared between small cell and large cell neuroendocrine carcinomas. The mean age of patients was 61 years old with 18 men and 19 women. The colorectum (n=20) was the most common primary site; other primary sites included the pancreaticobiliary system, esophagus, stomach, duodenum, and ampulla. Expression of PD-1 was detected on tumor cells (n=6, 16%) as well as on tumor-associated immune cells (n=23, 63%). The 6 cases with PD-1 expression on tumor cells also had the expression on immune cells. Expression of PD-L1 was visualized on tumor cells in 5 cases (14%) and on tumor-associated immune cells in 10 cases (27%). There was no difference in PD-1 and PD-L1 expression between small cell and large cell neuroendocrine carcinomas. In conclusion, PD-1/PD-L1 expression is a frequent occurrence in poorly differentiated neuroendocrine carcinomas of the digestive system. Checkpoint blockade targeting the PD-1/PD-L1 pathway may have a potential role in treating patients with this disease. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Synthesis of hybrid interfacial silica-based nanospheres composite as a support for ultra-small palladium nanoparticle and application of PdNPs/HSN in Mizoroki-Heck reaction

    Science.gov (United States)

    Rostamnia, Sadegh; Kholdi, Saba

    2017-12-01

    The silica based hollow nanosphere (silica-HNS) containing polymer of polyaniline was synthesized and chosen as a promising support for PdNPs. Then it was applied as a green catalyst in the reaction of Heck coupling with high yield. TEM and SEM-EDX/mapping images were used to study the structure and morphology. FT-IR spectroscopy, Thermal gravimetry analysis (TGA), and BET were used to characterize and investigate the catalyst. Also, the amounts of Pd loading were characterized by ICP-AES technique. Catalyst recyclability showed 5 successful runs for the reaction.

  1. Oxidation-induced spin reorientation in Co adatoms and CoPd dimers on Ni/Cu(100)

    Science.gov (United States)

    Chen, K.; Beeck, T.; Fiedler, S.; Baev, I.; Wurth, W.; Martins, M.

    2016-04-01

    Ultrasmall magnetic clusters and adatoms are of strong current interest because of their possible use in future technological applications. Here, we demonstrate that the magnetic coupling between the adsorbates and the substrate can be significantly changed through oxidation. The magnetic properties of Co adatoms and CoPd dimers deposited on a remanently magnetized Ni/Cu(100) substrate have been investigated by x-ray absorption and x-ray magnetic circular dichroism spectroscopy at the Co L2 ,3 edges. Using spectral differences, pure and oxidized components are distinguished, and their respective magnetic moments are determined. The Co adatoms and the CoPd dimers are coupled ferromagnetically to the substrate, while their oxides, Co-O and CoPd-O, are coupled antiferromagnetically to the substrate. Along with the spin reorientation from the pure to the oxidized state, the magnetic moment of the adatom is highly reduced from Co to Co-O. In contrast, the magnetic moment of the dimer is of similar order for CoPd and CoPd-O.

  2. Size-dependent effects in supported highly dispersed Fe2O3 catalysts, doped with Pt and Pd

    International Nuclear Information System (INIS)

    Cherkezova-Zheleva, Zara; Shopska, Maya; Mitov, Ivan; Kadinov, Georgi

    2010-01-01

    Series of Fe and Fe–Me (Me = Pt or Pd) catalyst supported on γ-Al 2 O 3 , TiO 2 (anatase) or diatomite were prepared by the incipient wetness impregnation method. The metal loading was 8 wt.% Fe and 0.7 wt.% noble metal. The preparation and pretreatment conditions of all studied samples were kept to be the same. X-ray diffraction, Moessbauer spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction are used for characterization of the supports and the samples at different steps during their treatment and catalytic tests. The catalytic activity of the samples was tested in the reaction of total benzene oxidation. The physicochemical and catalytic properties of the obtained materials are compared with respect of the different chemical composition, dispersion of used carriers and of the supported phases. Samples with the same composition prepared by mechanical mixing are studied as catalysts for comparison and for clearing up the presence of size-dependent effect, also.

  3. Enhancement in the Catalytic Activity of Pd/USY in the Heck Reaction Induced by H2 Bubbling

    Directory of Open Access Journals (Sweden)

    Miki Niwa

    2010-12-01

    Full Text Available Pd was loaded on ultra stable Y (USY zeolites prepared by steaming NH4-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H2 bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc2. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H2O gave the highest activity (TOF = 61,000 h−1, which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OHstrong generated as a result of steaming had a profound effect on the catalytic activity of Pd.

  4. Enhancement in the catalytic activity of Pd/USY in the heck reaction induced by H2 bubbling.

    Science.gov (United States)

    Okumura, Kazu; Tomiyama, Takuya; Moriyama, Sayaka; Nakamichi, Ayaka; Niwa, Miki

    2010-12-24

    Pd was loaded on ultra stable Y (USY) zeolites prepared by steaming NH(4)-Y zeolite under different conditions. Heck reactions were carried out over the prepared Pd/USY. We found that H₂ bubbling was effective in improving not only the catalytic activity of Pd/USY, but also that of other supported Pd catalysts and Pd(OAc)₂. Moreover, the catalytic activity of Pd/USY could be optimized by choosing appropriate steaming conditions for the preparation of the USY zeolites; Pd loaded on USY prepared at 873 K with 100% H₂O gave the highest activity (TOF = 61,000 h⁻¹), which was higher than that of Pd loaded on other kinds of supports. The prepared Pd/USY catalysts were applicable to the Heck reactions using various kinds of substrates including bromo- and chloro-substituted aromatic and heteroaromatic compounds. Characterization of the acid properties of the USY zeolites revealed that the strong acid site (OH(strong)) generated as a result of steaming had a profound effect on the catalytic activity of Pd.

  5. Preparation technology of 103Pd-110Agm composite alloy membranes

    International Nuclear Information System (INIS)

    Liu Zhuo; Chen Daming; Jin Xiaohai; Li Zhongyong; Guo Feihu; Qin Hongbin

    2012-01-01

    The preparation of 103 Pd- 110 Ag m alloy membranes was the basis for the production of 103 Pd- 125 I composite sources. Taking 103 Pd and 110 Ag m as trace elements, the method of non-electrolytical plating was chosen to prepare the alloy membrane. A γ-detector and electron microscope (SEM) were used for quantitative and qualitative analysis, respectively. The pre-treatment of the support before the preparation of Palladium-silver composite membranes was discussed in detail. It was found that when the concentration of PdCl 2 was between 0.5 and 2.0 mmol/L the result was good. The effects of various factors were investigated, including the proportion of Pd and Ag, the concentrations of the total metal, ammonium hydroxide hydrazine and ethylenediaminetetraacetic acid, temperature, the time, and the rotation speed. By improving the reaction conditions the alloy membrane with metallic luster was obtained. Besides, the presence of Pd and Ag was observed in the alloy membranes by qualitative analysis. (authors)

  6. Empowering Patients: PD in Healthcare

    DEFF Research Database (Denmark)

    Kensing, Finn; Strand, Dixi Louise; Bansler, Jørgen P.

    2004-01-01

    In this paper, we discuss PD issues and concerns in the context of a national initiative the purpose of which is to provide IT support for the communication and collaboration within a heterogeneous network of patients/citizens and health care professionals. We present the notion of patient empowe...

  7. CHARACTERIZATION OF YTTRIA AND MAGNESIA PARTIALLY STABILIZED ZIRCONIA BIOCOMPATIBLE COATINGS DEPOSITED BY PLASMA SPRAYING

    Directory of Open Access Journals (Sweden)

    Roşu R. A.

    2013-09-01

    Full Text Available Zirconia (ZrO2 is a biocompatible ceramic material which is successfully used in medicine to cover the metallic implants by various methods. In order to avoid the inconvenients related to structural changes which may appear because of the temperature treatment while depositing the zirconia layer over the metallic implant, certain oxides are added, the most used being Y2O3, MgO and CaO. This paper presents the experimental results regarding the deposition of yttria (Y2O3 and magnesia (MgO partially stabilized zirconia layers onto titanium alloy substrate by plasma spraying method. X ray diffraction investigations carried out both on the initial powders and the coatings evidenced the fact that during the thermal spraying process the structure has not been significantly modified, consisting primarily of zirconium oxide with tetragonal structure. Electronic microscopy analyses show that the coatings are dense, uniform and cracks-free. Adherence tests performed on samples whose thickness ranges between 160 and 220 μm showed that the highest value (23.5 MPa was obtained for the coating of ZrO2 - 8 wt. % Y2O3 with 160 μm thickness. The roughness values present an increasing tendency with increasing the coatings thickness.

  8. Hydrogenolysis of α-methylbenzyl alcohol to ethylbenzene over Pd/C catalyst

    Science.gov (United States)

    Feng, J.; Zhong, Y. H.; Dai, S. H.

    2018-01-01

    The hydrogenolysis of α-methylbenzyl alcohol (MBA) to ethylbenzene (EB) over Pd/C catalyst was studied. The XRD and TEM results show that Pd nanoparticles are well dispersed on the carbon support with good crystallinity. There is no 1-cyclohexylethanol or ethylcyclohexane in the products, indicating that Pd/C is excellent for inhibiting the hydrogenation of the aromatic ring. Alcohol solvents are beneficial to increase the catalytic activity because of their strong polarity and good solubility.

  9. Immobilized Pd-Ag bimetallic nanoparticles on polymeric nanofibers as an effective catalyst: effective loading of Ag with bimetallic functionality through Pd nucleated nanofibers

    Science.gov (United States)

    Shanmugam Ranjith, Kugalur; Celebioglu, Asli; Uyar, Tamer

    2018-06-01

    Here, we present a precise process for synthesizing Pd-Ag bimetallic nanoparticles (NPs) onto polymeric nanofibers by decorating Pd-NPs through atomic layer deposition followed by a chemical reduction process for tagging Ag nanostructures with bimetallic functionality. The results show that Pd-NPs act as a nucleation platform for tagging Ag and form Pd-Ag bimetallic NPs with a monodisperse nature with significant catalytic enhancement to the reaction rate over the bimetallic nature of the Pd-Ag ratio. A Pd-NP decorated polymeric nanofibrous web acts as an excellent platform for the encapsulation or interaction of Ag, which prevents agglomeration and promotes the interaction of Ag ions only on the surface of the Pd-NPs. We observed an effective reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by sodium borohydride (NaBH4) to access the catalytic activity of Pd-Ag bimetallic NPs on a free-standing flexible polymeric nanofibrous web as a support. The captive formation of the polymeric nanofibrous web with Pd-Ag bimetallic functionality exhibited superior and stable catalytic performance with reduction rates of 0.0719, 0.1520, and 0.0871 min‑1 for different loadings of Ag on Pd decorated nanofibrous webs such as Pd/Ag(0.01), Pd/Ag(0.03), and Pd/Ag(0.05), respectively. The highly faceted Pd-Ag NPs with an immobilized nature improves the catalytic functionality by enhancing the binding energy of the 4-NP adsorbate to the surface of the NPs. With the aid of bimetallic functionality, the nanofibrous web was demonstrated as a hybrid heterogeneous photocatalyst with a 3.16-fold enhancement in the reaction rate as compared with the monometallic decorative nature of NaBH4 as a reducing agent. The effective role of the monodisperse nature of Pd ions with an ultralow content as low as 3 wt% and the tunable ratio of Ag on the nanofibrous web induced effective catalytic activity over multiple cycles.

  10. Pd and S binding energies and Auger parameters on a model silica-supported Suzuki–Miyaura catalyst: Insights into catalyst activation

    International Nuclear Information System (INIS)

    Hanif, Mohammad A.; Ebralidze, Iraklii I.; Horton, J. Hugh

    2013-01-01

    Model Suzuki–Miyaura reaction catalysts have been developed by immobilizing palladium on a mercaptopropyltrimethoxysilane (MPTMS) functionalized Si substrate. Two types of Pd species were found on the fresh catalysts that may be attributed to a S-bound Pd (II) species and Pd nanoparticles. The binding energy of the nanoparticles is strongly size dependent, and is higher than that of metallic Pd. A sulfur species that has not been previously reported on this class of catalysts has also been observed. A systematic investigation of various palladium/sulfur complexes using XPS was carried out to identify this species, which may be assigned to high oxidation state sulfur formed by oxidation of thiol during the reduction of the Pd(OAc) 2 used to load the catalyst with Pd. Shifts in binding energy observed for both Pd and S spectra of the used catalysts were examined in order to probe the change of electronic environment of reactive palladium center and the thiol ligand during the reaction. Electron and atomic force microscopic imaging of the surfaces demonstrates the formation of Pd nanoparticles on fresh catalysts and subsequent size reduction of the Pd nano-particles following reaction.

  11. Novel Fe-Pd/SiO2 catalytic materials for degradation of chlorinated organic compounds in water

    Science.gov (United States)

    Novel reactive materials for catalytic degradation of chlorinated organic compounds in water at ambient conditions have been prepared on the basis of silica-supported Pd-Fe nanoparticles. Nanoscale Fe-Pd particles were synthesized inside porous silica supports using (NH4

  12. Adsorption of small palladium clusters on the relaxed α-Al2O3(0001) surface

    DEFF Research Database (Denmark)

    Gomes, J.R.B.; Lodziana, Zbiegniew; Illas, F.

    2003-01-01

    of supported Pd-3 is largely distorted from the gas-phase equilibrium geometry whereas the structure of supported Pd-4 is less distorted and reminiscent of the most stable gas-phase isomer. Consequently, the adhesion energy of Pd-3 on the relaxed alpha-Al2O3(0001) surface is smaller than that of Pd-4...... adsorption on other oxide surfaces, there are no preferred adsorption sites for Pd deposited on the corundum surface....

  13. Catalytic reduction of nitrate and nitrite ions by hydrogen : investigation of the reaction mechanism over Pd and Pd-Cu catalysts

    NARCIS (Netherlands)

    Ilinitch, OM; Nosova, LV; Gorodetskii, VV; Ivanov, VP; Trukhan, SN; Gribov, EN; Bogdanov, SV; Cuperus, FP

    2000-01-01

    The catalytic behavior of mono- and bimetallic catalysts with Pd and/or Cu supported over gamma-Al2O3 in the reduction of aqueous nitrate and nitrite ions by hydrogen was investigated. The composition of the supported metal catalysts was analysed using secondary ion mass spectroscopy (SIMS) and

  14. Morphology and N2 Permeance of Sputtered Pd-Ag Ultra-Thin Film Membranes

    Directory of Open Access Journals (Sweden)

    Ekain Fernandez

    2016-02-01

    Full Text Available The influence of the temperature during the growth of Pd-Ag films by PVD magnetron sputtering onto polished silicon wafers was studied in order to avoid the effect of the support roughness on the layer growth. The surfaces of the Pd-Ag membrane films were analyzed by atomic force microscopy (AFM, and the results indicate an increase of the grain size from 120 to 250–270 nm and film surface roughness from 4–5 to 10–12 nm when increasing the temperature from around 360–510 K. After selecting the conditions for obtaining the smallest grain size onto silicon wafer, thin Pd-Ag (0.5–2-µm thick films were deposited onto different types of porous supports to study the influence of the porous support, layer thickness and target power on the selective layer microstructure and membrane properties. The Pd-Ag layers deposited onto ZrO2 3-nm top layer supports (smallest pore size among all tested present high N2 permeance in the order of 10−6 mol·m−2·s−1·Pa−1 at room temperature.

  15. Controlled Clustering of Gold Nanoparticles using Solid-support for Surface-enhanced Raman Spectroscopic Probes

    International Nuclear Information System (INIS)

    Chang, Hyejin; Chae, Jinjoo; Jeong, Hong; Kang, Homan; Lee, Yoonsik

    2014-01-01

    We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature

  16. Controlled Clustering of Gold Nanoparticles using Solid-support for Surface-enhanced Raman Spectroscopic Probes

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hyejin; Chae, Jinjoo; Jeong, Hong [Department of Chemistry Education, Seoul (Korea, Republic of); Kang, Homan; Lee, Yoonsik [Interdisciplinary Program in Nano-Science and Technology, Pohang (Korea, Republic of)

    2014-03-15

    We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature.

  17. Biosupported Bimetallic Pd Au Nanocatalysts for Dechlorination of Environmental Contaminants

    Energy Technology Data Exchange (ETDEWEB)

    De Corte, S.; Fitts, J.; Hennebel, T.; Sabbe, T.; Bliznuk, V.; Verschuere, S.; van der Lelie, D.; Verstraete, W.; Boon, N.

    2011-08-30

    Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichloroethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L{sup -1} and reduced simultaneously by Shewanella oneidensis in the presence of H{sub 2}, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.

  18. Stabilization of Palladium Nanoparticles on Nanodiamond-Graphene Core-Shell Supports for CO Oxidation.

    Science.gov (United States)

    Zhang, Liyun; Liu, Hongyang; Huang, Xing; Sun, Xueping; Jiang, Zheng; Schlögl, Robert; Su, Dangsheng

    2015-12-21

    Nanodiamond-graphene core-shell materials have several unique properties compared with purely sp(2) -bonded nanocarbons and perform remarkably well as metal-free catalysts. In this work, we report that palladium nanoparticles supported on nanodiamond-graphene core-shell materials (Pd/ND@G) exhibit superior catalytic activity in CO oxidation compared to Pd NPs supported on an sp(2) -bonded onion-like carbon (Pd/OLC) material. Characterization revealed that the Pd NPs in Pd/ND@G have a special morphology with reduced crystallinity and are more stable towards sintering at high temperature than the Pd NPs in Pd/OLC. The electronic structure of Pd is changed in Pd/ND@G, resulting in weak CO chemisorption on the Pd NPs. Our work indicates that strong metal-support interactions can be achieved on a non-reducible support, as exemplified for nanocarbon, by carefully tuning the surface structure of the support, thus providing a good example for designing a high-performance nanostructured catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Ni-Pd-Al2O3 catalyst supported on reticulated ceramic foam for dry methane reforming

    Directory of Open Access Journals (Sweden)

    Vesna Nikolić

    2015-03-01

    Full Text Available In the present study, Ni-Pd/Al2O3 catalyst supported on α-Al2O3 based foam was prepared and evaluated in the dry methane reforming process. Corresponding metal chlorides were deposited to the foam surface by impregnation of the foam with ultrasonically aerosolized salt solutions at 473 K and drying at that temperature. Calcination step was excluded and the catalyst was reduced at very low temperature – 533 K. The reforming experiment lasted for 3 h, with standing time of 1 h at the following temperatures: 873, 973 and 1023 K. Conclusions on selectivity, catalytic activity and stability were reached on the basis of CO and H2 yields.

  20. Effect of chlorine on performance of Pd catalysts prepared via colloidal immobilization

    NARCIS (Netherlands)

    Zhao, Yingnan; Liang, Wanwei; Li, Yongdan; Lefferts, Leon

    2017-01-01

    This contribution shows the effect of residual chlorine on the catalytic performance of a Pd-based catalyst in the hydrogenation of nitrite for cleaning of drinking water. The catalyst was prepared via immobilization a colloidal Pd nanoparticles using activated carbon as support. Different amount of

  1. Coarsening of Pd nanoparticles in an oxidizing atmosphere studied by in situ TEM

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose; Chorkendorff, Ib; Dahl, Søren

    2016-01-01

    The coarsening of supported palladium nanoparticles in an oxidizing atmosphere was studied in situ by means of transmission electron microscopy (TEM). Specifically, the Pd nanoparticles were dispersed on a planar and amorphous Al2O3 support and were observed during the exposure to 10 mbar technical...... for the Ostwald ripening process indicates that the observed change in the particle size distribution can be accounted for by wetting of the Al2O3 support by the larger Pd nanoparticles....

  2. Linear and nonlinear surface spectroscopy of supported size selected metal clusters and organic adsorbates

    Energy Technology Data Exchange (ETDEWEB)

    Thaemer, Martin Georg

    2012-03-08

    The spectroscopic investigation of supported size selected metal clusters over a wide wavelength range plays an important role for understanding their outstanding catalytic properties. The challenge which must be overcome to perform such measurements is the difficult detection of the weak spectroscopic signals from these samples. As a consequence, highly sensitive spectroscopic methods are applied, such as surface Cavity Ringdown Spectroscopy and surface Second Harmonic Generation Spectroscopy. The spectroscopic apparatus developed is shown to have a sensitivity which is high enough to detect sub-monolayer coverages of adsorbates on surfaces. In the measured spectra of small supported silver clusters of the sizes Ag{sub 4}2, Ag{sub 2}1, Ag{sub 9}, and Ag atoms a stepwise transition from particles with purely metallic character to particles with molecule-like properties can be observed within this size range.

  3. Hybrid NiCoOx adjacent to Pd nanoparticles as a synergistic electrocatalyst for ethanol oxidation

    Science.gov (United States)

    Wang, Wei; Yang, Yan; Liu, Yanqin; Zhang, Zhe; Dong, Wenkui; Lei, Ziqiang

    2015-01-01

    To improve the electrocatalytic activity of Pd for ethanol oxidation, hybrid NiCoOx adjacent to Pd catalyst (Pd-NiCoOx/C) is successfully synthesized. Physical characterization shows NiCoOx is closely adjacent to Pd nanoparticles in Pd-NiCoOx/C catalyst, which leads to Strong Metal-Support Interactions (SMSI) between the NiCoOx and Pd nanoparticles, in favor of the electrocatalytic properties. The Pd-NiCoOx/C catalyst is estimated to own larger electrochemically active surface area than Pd/C and Pd-NiO/C catalysts. Moreover, compared to Pd/C catalyst, the onset potential of Pd-NiCoOx/C catalyst is negative 40 mV for ethanol oxidation. Noticeably, the current density of Pd-NiCoOx/C catalyst is 2.05 and 1.43 times higher contrasted to Pd/C and Pd-NiO/C catalysts accordingly. Importantly, the Pd-NiCoOx/C catalyst exhibits better stability during ethanol oxidation, which is a promising electrocatalyst for application in direct alkaline alcohol fuel cells.

  4. PD-1/PD-L signaling pathway in chronic hepatitis B

    Directory of Open Access Journals (Sweden)

    TAO Lilin

    2016-12-01

    Full Text Available Hepatitis B is one of the major diseases that affect the health of Chinese people, and chronic hepatitis B virus (HBV infection can lead to disease progression. Programmed death-1 (PD-1 discovered in recent years is an important coordinated stimulus molecule which belongs to the B7/CD28 family. After its binding with programmed death ligand (PD-L, it can regulate the activation, differentiation, and proliferation of T lymphocytes. PD-1 and its ligand are differently expressed in different stages of chronic HBV infection. The interaction between PD-1 and its ligand in different immune cells induces immune tolerance in human body and finally leads to the chronicity of HBV infection. Blocking the PD-1/PD-L signaling pathway through different ways can improve T cell exhaustion, suggesting that this might be one of the directions of antiviral therapy in future.

  5. Impulse control disorder in PD: A lateralized monoaminergic frontostriatal disconnection syndrome?

    Science.gov (United States)

    Premi, E; Pilotto, A; Garibotto, V; Bigni, B; Turrone, R; Alberici, A; Cottini, E; Poli, L; Bianchi, M; Formenti, A; Cosseddu, M; Gazzina, S; Magoni, M; Bertoli, M; Paghera, B; Borroni, B; Padovani, A

    2016-09-01

    Impulse Control Disorder symptoms (ICD) in Parkinson's disease (PD) has been recently associated by magnetic Resonance imaging with impaired cortico-striatal connectivity, especially between left putamen and frontal associative areas. 84 patients entered the study (21 PD-ICD+ and 64 PD-ICD-) and underwent DATSCAN imaging. The striatal tracer uptake was evaluated using BRASS software (Hermes, Sweden). The whole-brain analysis was performed with Statistical Parametric Mapping (SPM). PD-ICD+ showed a significant reduction of left putaminal and left inferior frontal gyrus tracer uptake compared to PD-ICD-. Functional covariance analysis using left putamen as the seed point showed that, in contrast to ICD-patients, ICD+ patients had no functional covariance with contralateral basal ganglia and ipsilateral cingulate cortex, as index of an impaired inter- and intra-hemispheric dopamine binding in PD-ICD+. the results support and expand the concept of a functional disconnection syndrome linked to ICD symptoms in PD patients through an asymmetric molecular frontostriatal network breakdown with left basal ganglia as central hub. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Formic Acid Oxidation over Hierarchical Porous Carbon Containing PtPd Catalysts

    Directory of Open Access Journals (Sweden)

    Elena Pastor

    2013-10-01

    Full Text Available The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500 with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes.

  7. Validation of FFM PD counts for screening personality pathology and psychopathy in adolescence.

    Science.gov (United States)

    Decuyper, Mieke; De Clercq, Barbara; De Bolle, Marleen; De Fruyt, Filip

    2009-12-01

    Miller and colleagues (Miller, Bagby, Pilkonis, Reynolds, & Lynam, 2005) recently developed a Five-Factor Model (FFM) personality disorder (PD) count technique for describing and diagnosing PDs and psychopathy in adulthood. This technique conceptualizes PDs relying on general trait models and uses facets from the expert-generated PD prototypes to score the FFM PDs. The present study corroborates on the study of Miller and colleagues (2005) and investigates in Study 1 whether the PD count technique shows discriminant validity to describe PDs in adolescence. Study 2 extends this objective to psychopathy. Results suggest that the FFM PD count technique is equally successful in adolescence as in adulthood to describe PD symptoms, supporting the use of this descriptive method in adolescence. The normative data and accompanying PD count benchmarks enable to use FFM scores for PD screening purposes in adolescence.

  8. Valence band electronic structure of Nb{sub 2}Pd{sub 1.2}Se{sub 5} and Nb{sub 2}Pd{sub 0.95}S{sub 5} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Lohani, H. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India); Mishra, P. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Goyal, R.; Awana, V.P.S. [National Physical Laboratory(CSIR), Dr. K. S. Krishnan Road, New Delhi 110012 (India); Sekhar, B.R., E-mail: sekhar@iopb.res.in [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085 (India)

    2017-03-15

    We present a comparative study of our valence band photoemission results on Nb{sub 2}Pd{sub 1.2}Se{sub 5} and Nb{sub 2}Pd{sub 0.95}S{sub 5} superconductors which are supported by our DFT based electronic structure calculations. We observe that the VB spectra of both the compounds are qualitatively similar, except for some slight differences in the binding energy positions of all the features. This could be due to the unequal electronegativities of Se and S atom. The calculated density of states (DOS) reveals that the VB features are mainly composed of Pd-Se/S hybridized states. The nature of DOS originating from the distinctly coordinated Pd atoms is different. Further, various Pd-4d and Nb-4d states crossing the Fermi level (E{sub f}) signifies the multiband character of these compounds. In addition, we find a temperature dependent pseudogap in Nb{sub 2}Pd{sub 0.95}S{sub 5} which is absent in Nb{sub 2}Pd{sub 1.2}Se{sub 5}.

  9. A novel method for synthesis of phosphomolybdic acid-modified Pd/C catalysts for oxygen reduction reaction

    Science.gov (United States)

    Zhu, Mingyuan; Gao, Xiaoling; Luo, Guangqin; Dai, Bin

    2013-03-01

    This manuscript reports a convenient method for immobilizing phosphomolybdic acid (HPMo) on polyaniline (PAN-) functionalized carbon supports. The obtained HPMo-PAN-C sample is used as the support to prepare a Pd/HPMo-PAN-C catalyst. The samples are characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray diffraction analysis. The results suggest that HPMo retains its Keggin structure and that the presence of HPMo reduces the average particle size of the Pd nano-particles in the obtained Pd/HPMo-PAN-C catalyst. Electro-chemical measurements in 0.5 M HClO4 solution reveal that the Pd/HPMo-PAN-C catalyst has higher catalytic activity for oxygen reduction reactions than does a Pd/C catalyst prepared using a similar procedure. The stability of the Pd/HPMo-PAN-C catalyst is evaluated by multiple-cycle voltammetry techniques; the mass catalytic activity decreases by only 10% after 100 scanning cycles.

  10. Preparation of Pd-Diimine@SBA-15 and Its Catalytic Performance for the Suzuki Coupling Reaction

    Directory of Open Access Journals (Sweden)

    Jiahuan Yu

    2016-11-01

    Full Text Available A highly efficient and stable Pd-diimine@SBA-15 catalyst was successfully prepared by immobilizing Pd onto diimine-functionalized mesoporous silica SBA-15. With the help of diimine functional groups grafted onto the SBA-15, Pd could be anchored on a support with high dispersion. Pd-diimine@SBA-15 catalyst exhibited excellent catalytic performance for the Suzuki coupling reaction of electronically diverse aryl halides and phenylboronic acid under mild conditions with an ultralow amount of Pd (0.05 mol % Pd. When the catalyst amount was increased, it could catalyze the coupling reaction of chlorinated aromatics with phenylboronic acid. Compared with the catalytic performances of Pd/SBA-15 and Pd-diimine@SiO2 catalysts, the Pd-diimine@SBA-15 catalyst exhibited higher hydrothermal stability and could be repeatedly used four times without a significant decrease of its catalytic activity.

  11. Recovery of high-purity metallic Pd from Pd(II)-sorbed biosorbents by incineration.

    Science.gov (United States)

    Won, Sung Wook; Lim, Areum; Yun, Yeoung-Sang

    2013-06-01

    This work reports a direct way to recover metallic palladium with high purity from Pd(II)-sorbed polyethylenimine-modified Corynebacterium glutamicum biosorbent using a combined method of biosorption and incineration. This study is focused on the incineration part which affects the purity of recovered Pd. The incineration temperature and the amount of Pd loaded on the biosorbent were considered as major factors in the incineration process, and their effects were examined. The results showed that both factors significantly affected the enhancement of the recovery efficiency and purity of the recovered Pd. SEM-EDX and XRD analyses were used to confirm that Pd phase existed in the ash. As a result, the recovered Pd was changed from PdO to zero-valent Pd as the incineration temperature was increased from 600 to 900°C. Almost 100% pure metallic Pd was recovered with recovery efficiency above 99.0% under the conditions of 900°C and 136.9 mg/g. Copyright © 2013 Elsevier Ltd. All rights reserved.

  12. Theoretical analysis of hydrogen chemisorption on Pd(111), Re(0001) and PdML/Re(0001), ReML/Pd(111) pseudomorphic overlayers

    DEFF Research Database (Denmark)

    Pallassana, Venkataraman; Neurock, Matthew; Hansen, Lars Bruno

    1999-01-01

    not appear to provide an independent parameter for assessing surface reactivity. The weak chemisorption of hydrogen on the Pd-ML/Re(0001) surface relates to substantial lowering of the d-band center of Pd, when it is pseudomorphically deposited as a monolayer on a Re substrate. [S0163-1829(99)00331-2].......Gradient-corrected density-functional theory (DFT-GGA) periodic slab calculations have been used to analyze the binding of atomic hydrogen on monometallic Pd(111), Re(0001), and bimetallic Pd-mL/Re(0001) [pseudomorphic monolayer of Pd(111) on Re(0001)] and Re-ML/Pd(111) surfaces. The computed...

  13. The influence of nanoscale morphology on the resistivity of cluster-assembled nanostructured metallic thin films

    International Nuclear Information System (INIS)

    Barborini, E; Bertolini, G; Repetto, P; Leccardi, M; Vinati, S; Corbelli, G; Milani, P

    2010-01-01

    We have studied in situ the evolution of the electrical resistivity of Fe, Pd, Nb, W and Mo cluster-assembled films during their growth by supersonic cluster beam deposition. We observed resistivity of cluster-assembled films several orders of magnitude larger than the bulk, as well as an increase in resistivity by increasing the film thickness in contrast to what was observed for atom-assembled metallic films. This suggests that the nanoscale morphological features typical of ballistic films growth, such as the minimal cluster-cluster interconnection and the evolution of surface roughness with thickness, are responsible for the observed behaviour.

  14. PD-1/PD-L1 Inhibitors for Immuno-oncology: From Antibodies to Small Molecules.

    Science.gov (United States)

    Geng, Qiaohong; Jiao, Peifu; Jin, Peng; Su, Gaoxing; Dong, Jinlong; Yan, Bing

    2018-02-12

    The recent regulatory approvals of immune checkpoint protein inhibitors, such as ipilimumab, pembrolizumab, nivolumab, atezolizumab, durvalumab, and avelumab ushered a new era in cancer therapy. These inhibitors do not attack tumor cells directly but instead mobilize the immune system to re-recognize and eradicate tumors, which endows them with unique advantages including durable clinical responses and substantial clinical benefits. PD-1/PD-L1 inhibitors, a pillar of immune checkpoint protein inhibitors, have demonstrated unprecedented clinical efficacy in more than 20 cancer types. Besides monoclonal antibodies, diverse PD- 1/PD-L1 inhibiting candidates, such as peptides, small molecules have formed a powerful collection of weapons to fight cancer. The goal of this review is to summarize and discuss the current PD-1/PD-L1 inhibitors including candidates under clinical development, their molecular interactions with PD-1 or PD-L1, the disclosed structureactivity relationships of peptides and small molecules as inhibitors. Current PD-1/PD-L1 inhibitors under clinical development are exclusively dominated by antibodies. The molecular interactions of therapeutic antibodies with PD-1 or PD-L1 have been gradually elucidated for the design of novel inhibitors. Various peptides and traditional small molecules have been investigated in preclinical model to discover novel PD-1/PD-L1 inhibitors. Peptides and small molecules may play an important role in immuno-oncology because they may bind to multiple immune checkpoint proteins via rational design, opening opportunity for a new generation of novel PD-1/PD-L1 inhibitors. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  15. Multiplexed Immunofluorescence Reveals Potential PD-1/PD-L1 Pathway Vulnerabilities in Craniopharyngioma.

    Science.gov (United States)

    Coy, Shannon; Rashid, Rumana; Lin, Jia-Ren; Du, Ziming; Donson, Andrew M; Hankinson, Todd C; Foreman, Nicholas K; Manley, Peter E; Kieran, Mark W; Reardon, David A; Sorger, Peter K; Santagata, Sandro

    2018-03-02

    Craniopharyngiomas are neoplasms of the sellar/parasellar region that are classified into adamantinomatous (ACP) and papillary (PCP) subtypes. Surgical resection of craniopharyngiomas is challenging, and recurrence is common, frequently leading to profound morbidity. BRAF V600E mutations render PCP susceptible to BRAF/MEK inhibitors, but effective targeted therapies are needed for ACP. We explored the feasibility of targeting the PD-1/PD-L1 immune checkpoint pathway in ACP and PCP. We mapped and quantified PD-L1 and PD-1 expression in ACP and PCP resections using immunohistochemistry, immunofluorescence, and RNA in situ hybridization. We used tissue-based cyclic immunofluorescence (t-CyCIF) to map the spatial distribution of immune cells and characterize cell cycle and signaling pathways in ACP tumor cells which intrinsically express PD-1. All ACP (15±14% of cells, n=23, average±S.D.) and PCP (35±22% of cells, n=18) resections expressed PD-L1. In ACP, PD-L1 was predominantly expressed by tumor cells comprising the cyst-lining. In PCP, PD-L1 was highly-expressed by tumor cells surrounding the stromal fibrovascular cores. ACP also exhibited tumor cell-intrinsic PD-1 expression in whorled epithelial cells with nuclear-localized beta-catenin. These cells exhibited evidence of elevated mTOR and MAPK signaling. Profiling of immune populations in ACP and PCP showed a modest density of CD8+ T-cells. ACP exhibit PD-L1 expression in the tumor cyst-lining and intrinsic PD-1 expression in cells proposed to comprise an oncogenic stem-like population. In PCP, proliferative tumor cells express PD-L1 in a continuous band at the stromal-epithelial interface. Targeting PD-L1 and/or PD-1 in both subtypes of craniopharyngioma might therefore be an effective therapeutic strategy.

  16. Spontaneous dispersion of PdO onto acid sites of zeolites studied by in situ DXAFS

    CERN Document Server

    Okumura, K; Niwa, M; Yokota, S; Kato, K; Tanida, H; Uruga, T

    2003-01-01

    The generation of highly dispersed PdO over zeolite supports was studied using in situ energy-dispersive XAFS (DXAFS) technique. From the comparison with the Na-ZSM-5, it was found that the oxidation as well as the spontaneous dispersion of Pd was promoted through the interaction between PdO and acid sites of H-form zeolites. (author)

  17. Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability.

    Science.gov (United States)

    Sun, Wuzhu; Yang, Weiyi; Xu, Zhengchao; Li, Qi; Shang, Jian Ku

    2016-01-27

    Superparamagnetic nanocatalysts could minimize both the external and internal mass transport limitations and neutralize OH(-) produced in the reaction more effectively to enhance the catalytic nitrite reduction efficiency with the depressed product selectivity to undesirable ammonium, while possess an easy magnetic separation capability. However, commonly used qusi-monodispersed superparamagnetic Fe3O4 nanosphere is not suitable as catalyst support for nitrite reduction because it could reduce the catalytic reaction efficiency and the product selectivity to N2, and the iron leakage could bring secondary contamination to the treated water. In this study, protective shells of SiO2, polymethylacrylic acid, and carbon were introduced to synthesize Fe3O4@SiO2/Pd, Fe3O4@PMAA/Pd, and Fe3O4@C/Pd catalysts for catalytic nitrite reduction. It was found that SiO2 shell could provide the complete protection to Fe3O4 nanosphere core among these shells. Because of its good dispersion, dense structure, and complete protection to Fe3O4, the Fe3O4@SiO2/Pd catalyst demonstrated the highest catalytic nitrite reduction activity without the detection of NH4(+) produced. Due to this unique structure, the activity of Fe3O4@SiO2/Pd catalysts for nitrite reduction was found to be independent of the Pd nanoparticle size or shape, and their product selectivity was independent of the Pd nanoparticle size, shape, and content. Furthermore, their superparamagnetic nature and high saturation magnetization allowed their easy magnetic separation from treated water, and they also demonstrated a good stability during the subsequent recycling experiment.

  18. Evaluation of Pd Nanoparticle-Decorated CeO2-MWCNT Nanocomposite as an Electrocatalyst for Formic Acid Fuel Cells

    Science.gov (United States)

    Saleem, Junaid; Safdar Hossain, SK.; Al-Ahmed, Amir; Rahman, Ateequr; McKay, Gordon; Hossain, Mohammed M.

    2018-04-01

    In this work, CeO2-modified Pd/CeO2-carbon nanotube (CNT) electrocatalyst for the electro-oxidation of formic acid has been investigated. The support CNT was first modified with different amounts (5-30 wt.%) of CeO2 using a precipitation-deposition method. The electrocatalysts were developed by dispersing Pd on the CeO2-CNT supports using the borohydride reduction method. The synthesized electrocatalysts were analyzed for composition, morphology and electronic structure using x-ray diffraction (XRD), scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) techniques. The formation of Pd nanoparticles on the CeO2-CNT support was confirmed using TEM. The activity of Pd/CeO2-CNT and of Pd-CNT samples upon oxidation of formic acid was evaluated by using carbon monoxide stripping voltammetry, cyclic voltammetry, and chronoamperometry. The addition of moderate amounts of cerium oxide (up to 10 wt.%) significantly improved the activity of Pd/CeO2-CNT compared to the unmodified Pd-CNT. Pd/10 wt.% CeO2-CNT showed a current density of 2 A mg-1, which is ten times higher than that of the unmodified Pd-CNT (0.2 A mg-1). Similarly, the power density obtained for Pd/10 wt.% CeO2-CNT in an air-breathing formic acid fuel cell was 6.8 mW/cm2 which is two times higher than Pd-CNT (3.2 mW/cm2), thus exhibiting the promotional effects of CeO2 to Pd/CeO2-CNT. A plausible justification for the improved catalytic performance and stability is provided in the light of the physical characterization results.

  19. Water-dispersable hybrid Au-Pd nanoparticles as catalysts in ethanol oxidation, aqueous phase Suzuki-Miyaura and Heck reactions

    KAUST Repository

    Song, Hyon Min

    2012-01-01

    The catalytic activities of water-dispersable Au@Pd core-shell nanoparticles (NPs) and Au-Pd alloy NPs were examined. There is growing interest in Au-Pd hybridized NPs in a supported matrix or non-supported forms as catalysts in various reactions that are not limited to conventional Pd-related reactions. Four different Au@Pd core-shell NPs in this study were prepared at room temperature with help from the emulsion phase surrounding the Au core NPs. Au-Pd alloy NPs were prepared over 90 °C, and underwent phase transfer to aqueous medium for their catalytic use. Au@Pd core-shell NPs show catalytic activity in ethanol oxidation reactions as electrocatalysts, and both core-shell and alloy NPs are good to excellent catalysts in various Suzuki-Miyaura and Heck reactions as heterogeneous catalysts. Specifically, Au@Pd core-shell NPs with sharp branched arms show the highest yield in the reactions tested in this study. A relatively small amount (0.25 mol%) was used throughout the catalytic reactions. © 2012 The Royal Society of Chemistry.

  20. Pd-nanoparticles cause increased toxicity to kiwifruit pollen compared to soluble Pd(II)

    International Nuclear Information System (INIS)

    Speranza, Anna; Leopold, Kerstin; Maier, Marina; Taddei, Anna Rita; Scoccianti, Valeria

    2010-01-01

    In the present study, endpoints including in vitro pollen performance (i.e., germination and tube growth) and lethality were used as assessments of nanotoxicity. Pollen was treated with 5-10 nm-sized Pd particles, similar to those released into the environment by catalytic car exhaust converters. Results showed Pd-nanoparticles altered kiwifruit pollen morphology and entered the grains more rapidly and to a greater extent than soluble Pd(II). At particulate Pd concentrations well below those of soluble Pd(II), pollen grains experienced rapid losses in endogenous calcium and pollen plasma membrane damage was induced. This resulted in severe inhibition and subsequent cessation of pollen tube emergence and elongation at particulate Pd concentrations as low as 0.4 mg L -1 . Particulate Pd emissions related to automobile traffic have been increasing and are accumulating in the environment. This could seriously jeopardize in vivo pollen function, with impacts at an ecosystem level. - Nanoparticulate Pd - which resembles emissions from automobile catalysts - affects pollen to a higher extent than soluble Pd.

  1. Pd-nanoparticles cause increased toxicity to kiwifruit pollen compared to soluble Pd(II)

    Energy Technology Data Exchange (ETDEWEB)

    Speranza, Anna, E-mail: anna.speranza@unibo.i [Dipartimento di Biologia, Universita di Bologna, via Irnerio 42, 40126 Bologna (Italy); Leopold, Kerstin, E-mail: kerstin.leopold@lrz.tu-muenchen.d [Arbeitsgruppe fuer Analytische Chemie, Technische Universitaet Muenchen, Garching (Germany); Maier, Marina, E-mail: marina.maier@ch.tum.d [Arbeitsgruppe fuer Analytische Chemie, Technische Universitaet Muenchen, Garching (Germany); Taddei, Anna Rita, E-mail: artaddei@unitus.i [CIME, Universita della Tuscia, Viterbo (Italy); Scoccianti, Valeria, E-mail: valeria.scoccianti@uniurb.i [Dipartimento di Scienze dell' Uomo, dell' Ambiente e della Natura, Universita di Urbino ' Carlo Bo' , Urbino (Italy)

    2010-03-15

    In the present study, endpoints including in vitro pollen performance (i.e., germination and tube growth) and lethality were used as assessments of nanotoxicity. Pollen was treated with 5-10 nm-sized Pd particles, similar to those released into the environment by catalytic car exhaust converters. Results showed Pd-nanoparticles altered kiwifruit pollen morphology and entered the grains more rapidly and to a greater extent than soluble Pd(II). At particulate Pd concentrations well below those of soluble Pd(II), pollen grains experienced rapid losses in endogenous calcium and pollen plasma membrane damage was induced. This resulted in severe inhibition and subsequent cessation of pollen tube emergence and elongation at particulate Pd concentrations as low as 0.4 mg L{sup -1}. Particulate Pd emissions related to automobile traffic have been increasing and are accumulating in the environment. This could seriously jeopardize in vivo pollen function, with impacts at an ecosystem level. - Nanoparticulate Pd - which resembles emissions from automobile catalysts - affects pollen to a higher extent than soluble Pd.

  2. A Facile Synthesis of Hollow Palladium/Copper Alloy Nanocubes Supported on N-Doped Graphene for Ethanol Electrooxidation Catalyst

    OpenAIRE

    Zhengyu Bai; Rumeng Huang; Lu Niu; Qing Zhang; Lin Yang; Jiujun Zhang

    2015-01-01

    In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG) is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG) and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO) are also prepared using the similar synthesis conditions for comparison. It is f...

  3. Adsorption behaviour of SF6 decomposed species onto Pd4-decorated single-walled CNT: a DFT study

    Science.gov (United States)

    Cui, Hao; Zhang, Xiaoxing; Zhang, Jun; Tang, Ju

    2018-07-01

    Metal nanocluster decorated single-walled carbon nanotubes (SWCNT) with improved adsorption behaviour towards gaseous molecules compared with intrinsic ones, have been widely accepted as a workable media for gas interaction due to their strong catalysis. In this work, Pd4 cluster is determined as a catalytic centre to theoretically study the adsorption property of Pd4-decorated SWCNT upon SF6 decomposed species. Results indicate that Pd4-SWCNT possessing good responses and sensitivities towards three composed species of SF6 could realise selective detection for them according to the different conductivity changes resulting from the varying adsorption ability. The response of Pd4-SWCNT upon three molecules in order is SOF2 > H2S > SO2, and the conductivity of the proposed material is about to increase in SOF2 and H2S systems, while declining in SO2 system. Such conclusions would be helpful for experimentalists to explore novel SWCNT-based sensors in evaluating the operating state of SF6 insulation devices.

  4. First-principles studies on graphene-supported transition metal clusters

    International Nuclear Information System (INIS)

    Sahoo, Sanjubala; Khanna, Shiv N.; Gruner, Markus E.; Entel, Peter

    2014-01-01

    Theoretical studies on the structure, stability, and magnetic properties of icosahedral TM 13 (TM = Fe, Co, Ni) clusters, deposited on pristine (defect free) and defective graphene sheet as well as graphene flakes, have been carried out within a gradient corrected density functional framework. The defects considered in our study include a carbon vacancy for the graphene sheet and a five-membered and a seven-membered ring structures for graphene flakes (finite graphene chunks). It is observed that the presence of defect in the substrate has a profound influence on the electronic structure and magnetic properties of graphene-transition metal complexes, thereby increasing the binding strength of the TM cluster on to the graphene substrate. Among TM 13 clusters, Co 13 is absorbed relatively more strongly on pristine and defective graphene as compared to Fe 13 and Ni 13 clusters. The adsorbed clusters show reduced magnetic moment compared to the free clusters

  5. Pd-RuSe/C as ORR specific catalyst in alkaline solution containing methanol

    Energy Technology Data Exchange (ETDEWEB)

    Maheswari, S.; Sridhar, P.; Pitchumani, S. [CSIR-Central Electrochemical Research Institute-Madras Unit, CSIR Complex, Chennai 600 113 (India)

    2012-12-15

    Carbon supported RuSe (RuSe/C) catalyst in varying atomic ratios of Ru to Se, namely, 1:1, 2:1, and 3:1 were prepared and their performances were compared with carbon supported Ru (Ru/C). Based on the performance, Palladium was incorporated into as prepared RuSe(2:1)/C and heat treated HTRuSe(2:1)/C. Ru/C, RuSe/C, and Pd-RuSe/C were characterized by X-ray diffraction (XRD) and transmission electron microscopy techniques. The XRD analyses of Ru/C, RuSe/C and Pd-HTRuSe/C show the formation of the hcp structure of Ru particles and the mean particle size was obtained from Ru(101) peak. The electrochemical characterizations of Ru/C, RuSe/C, Pd-HTRuSe(2:1)/C and Pd-RuSe(2:1)/C were conducted by cyclic voltammetry. Linear Sweep Voltammetric studies showed that incorporation of Pd in HTRu-Se(2:1)/C resulted in better catalytic activity toward oxygen reduction with resistance to methanol oxidation. The quantity of hydrogen peroxide produced was obtained from rotating ring disk electrode studies. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Characterization and electrocatalytic properties of sonochemical synthesized PdAg nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Godinez-Garcia, Andres, E-mail: agodinez@qro.cinvestav.mx [Depto. Materiales, Centro de Investigacion y de Estudios Avanzados del IPN, Libramiento norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230 Santiago de Queretaro, Qro. (Mexico); Perez-Robles, Juan Francisco [Depto. Materiales, Centro de Investigacion y de Estudios Avanzados del IPN, Libramiento norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230 Santiago de Queretaro, Qro. (Mexico); Martinez-Tejada, Hader Vladimir [Grupo de Energia y Termodinamica, Universidad Pontificia Bolivariana, Medellin, Antioquia C.P. 050031 (Colombia); Solorza-Feria, Omar [Depto. Quimica, CINVESTAV-IPN, Av. IPN 2508, A. P. 14-740, 07360 D.F. Mexico (Mexico)

    2012-06-15

    High intensity ultrasound was used in the synthesis of PdAg nanoparticles. PdAg nanoparticles were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), scanning transmission electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM). Catalytic properties for oxygen reduction reaction (ORR) were determined by electrochemical techniques of cyclic voltammetry (CV) and thin-film rotating disk electrode (TF-RDE). Finally the electrocatalyst was tested as a cathode in a single polymer electrolyte membrane fuel cell (PEMFC). Sonochemical synthesis (SS) decreased the overpotential required for the ORR and increased the double-layer capacitance (DLC) respect to the sodium borohydride reduction method due to a better distribution on vulcan carbon support. The electrocatalytic activity of the nanometric bimetallic electrocatalyst for the ORR in acid media showed a favorable multielectron charge transfer process (n = 4e{sup -}) to water formation. The performance of the membrane electrode assembly (MEA) prepared with dispersed PdAg/C as a cathode catalyst in a single PEMFC is lower in comparison to platinum. - Highlights: Black-Right-Pointing-Pointer Sonochemical synthesized PdAg nanoparticles supported on carbon were produced. Black-Right-Pointing-Pointer The material showed catalytic properties for the oxygen reduction reaction (ORR). Black-Right-Pointing-Pointer The ORR favored the pathway to water formation.

  7. Syngas upgrading in a membrane reactor with thin Pd-alloy supported membrane

    NARCIS (Netherlands)

    Brunetti, A.; Caravella, A.; Fernandez Gesalaga, E.; Pacheco Tanaka, D. A.; Gallucci, F.; Drioli, E.; Curcio, E.; Viviente, J. L.; Barbieri, G.

    2015-01-01

    In hydrogen production, the syngas streams produced by reformers and/or coal gasification plants contain a large amount of H2 and CO in need of upgrading. To this purpose, reactors using Pd-based membranes have been widely studied as they allow separation and recovery of a pure hydrogen stream.

  8. Size-dependent effects in supported highly dispersed Fe{sub 2}O{sub 3} catalysts, doped with Pt and Pd

    Energy Technology Data Exchange (ETDEWEB)

    Cherkezova-Zheleva, Zara; Shopska, Maya, E-mail: shopska@ic.bas.bg; Mitov, Ivan; Kadinov, Georgi [Bulgarian Academy of Sciences, Institute of Catalysis (Bulgaria)

    2010-06-15

    Series of Fe and Fe-Me (Me = Pt or Pd) catalyst supported on {gamma}-Al{sub 2}O{sub 3}, TiO{sub 2} (anatase) or diatomite were prepared by the incipient wetness impregnation method. The metal loading was 8 wt.% Fe and 0.7 wt.% noble metal. The preparation and pretreatment conditions of all studied samples were kept to be the same. X-ray diffraction, Moessbauer spectroscopy, X-ray photoelectron spectroscopy and temperature-programmed reduction are used for characterization of the supports and the samples at different steps during their treatment and catalytic tests. The catalytic activity of the samples was tested in the reaction of total benzene oxidation. The physicochemical and catalytic properties of the obtained materials are compared with respect of the different chemical composition, dispersion of used carriers and of the supported phases. Samples with the same composition prepared by mechanical mixing are studied as catalysts for comparison and for clearing up the presence of size-dependent effect, also.

  9. Selective hydrogenation of 4-isobutylacetophenone over a sodium-promoted Pd/C catalyst

    International Nuclear Information System (INIS)

    Cho, Hong-Baek; Lee, Bae Uk; Nakayama, Tadachika; Park, Yeung-Ho; Ryu, Chung-Han

    2013-01-01

    The effect of sodium promotion on the selective hydrogenation of 4-isobutylacetophenone, 4-IBAP, was investigated over a Pd/C catalyst. A precipitation and deposition method was used to prepare the catalyst, and sodium was promoted on the Pd/C catalyst via post-impregnation while varying the sodium content. The sodium-promoted Pd/C catalyst resulted in a significantly improved yield greater than 96% of the desired product, 1-(4-isobutylphenyl) ethanol (4-IBPE), compared with the non-patented literature results under a mild hydrogenation condition. A detailed hydrogenation network over the Pd/C catalyst was suggested. The reaction mechanism for the yield and selectivity enhancement of 4-IBPE induced-by the promoted Pd/C was elucidated in relation to the geometric and electronic effects of reactant molecules in the microporous support depending on the reaction steps

  10. Ab Initio Density Functional Calculations and Infra-Red Study of CO Interaction with Pd Atoms on θ-Al2O3 (010) Surface.

    Science.gov (United States)

    Narula, Chaitanya K; Allard, Lawrence F; Wu, Zili

    2017-07-24

    The ab initio density functional theoretical studies show that energetics favor CO oxidation on single Pd atoms supported on θ-alumina. The diffuse reflectance infra-red spectroscopy (DRIFTS) results show that carbonates are formed as intermediates when single supported Pd atoms are exposed to a gaseous mixture of CO + O 2 . The rapid agglomeration of Pd atoms under CO oxidation conditions even at 6 °C leads to the presence of Pd particles along with single atoms during CO oxidation experiments. Thus, the observed CO oxidation has contributions from both single Pd atoms and Pd particles.

  11. Highly active Pd-In/mesoporous alumina catalyst for nitrate reduction.

    Science.gov (United States)

    Gao, Zhenwei; Zhang, Yonggang; Li, Deyi; Werth, Charles J; Zhang, Yalei; Zhou, Xuefei

    2015-04-09

    The catalytic reduction of nitrate is a promising technology for groundwater purification because it transforms nitrate into nitrogen and water. Recent studies have mainly focused on new catalysts with higher activities for the reduction of nitrate. Consequently, metal nanoparticles supported on mesoporous metal oxides have become a major research direction. However, the complex surface chemistry and porous structures of mesoporous metal oxides lead to a non-uniform distribution of metal nanoparticles, thereby resulting in a low catalytic efficiency. In this paper, a method for synthesizing the sustainable nitrate reduction catalyst Pd-In/Al2O3 with a dimensional structure is introduced. The TEM results indicated that Pd and In nanoparticles could efficiently disperse into the mesopores of the alumina. At room temperature in CO2-buffered water and under continuous H2 as the electron donor, the synthesized material (4.9 wt% Pd) was the most active at a Pd-In ratio of 4, with a first-order rate constant (k(obs) = 0.241 L min(-1) g(cata)(-1)) that was 1.3× higher than that of conventional Pd-In/Al2O3 (5 wt% Pd; 0.19 L min(-1) g(cata)(-1)). The Pd-In/mesoporous alumina is a promising catalyst for improving the catalytic reduction of nitrate. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. The Role of Mg(OH)2 in the So-Called "Base-Free" Oxidation of Glycerol with AuPd Catalysts.

    Science.gov (United States)

    Fu, Jile; He, Qian; Miedziak, Peter J; Brett, Gemma L; Huang, Xiaoyang; Pattisson, Samuel; Douthwaite, Mark; Hutchings, Graham J

    2018-02-16

    Mg(OH) 2 - and Mg(OH) 2 -containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH) 2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH) 2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH) 2 added under base-free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH) 2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH) 2 , physically mixed (AuPd/C+Mg(OH) 2 ) and (AuPd/C+NaHCO 3 ) was obtained and compared. Furthermore, NaOH and Mg(OH) 2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH) 2 supported catalysts in base-free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. PD-1/PD-L blockade in gastrointestinal cancers: lessons learned and the road toward precision immunotherapy

    Directory of Open Access Journals (Sweden)

    Junyu Long

    2017-08-01

    Full Text Available Abstract Gastrointestinal (GI malignancies are the most prevalent tumors worldwide, with increasing incidence and mortality. Although surgical resection, chemotherapy, radiotherapy, and molecular targeted therapy have led to significant advances in the treatment of GI cancer patients, overall survival is still low. Therefore, alternative strategies must be identified to improve patient outcomes. In the tumor microenvironment, tumor cells can escape the host immune response through the interaction of PD-1 and PD-L, which inhibits the function of T cells and tumor-infiltrating lymphocytes while increasing the function of immunosuppressive T regulatory cells. The use of an anti-PD-1/PD-L blockade enables reprogramming of the immune system to efficiently identify and kill tumor cells. In recent years, the efficacy of PD-1/PD-L blockade has been demonstrated in many tumors, and this treatment is expected to be a pan-immunotherapy for tumors. Here, we review the signaling pathway underlying the dysregulation of PD-1/PD-L in tumors, summarize the current clinical data for PD-1/PD-L inhibitors in GI malignancies, and discuss road toward precision immunotherapy in relation to PD-1/PD-L blockade. The preliminary data for PD-1/PD-L inhibitors are encouraging, and the precision immunotherapy of PD-1/PD-L inhibitors will be a viable and pivotal clinical strategy for GI cancer therapy.

  14. PD-1/PD-L blockade in gastrointestinal cancers: lessons learned and the road toward precision immunotherapy.

    Science.gov (United States)

    Long, Junyu; Lin, Jianzhen; Wang, Anqiang; Wu, Liangcai; Zheng, Yongchang; Yang, Xiaobo; Wan, Xueshuai; Xu, Haifeng; Chen, Shuguang; Zhao, Haitao

    2017-08-03

    Gastrointestinal (GI) malignancies are the most prevalent tumors worldwide, with increasing incidence and mortality. Although surgical resection, chemotherapy, radiotherapy, and molecular targeted therapy have led to significant advances in the treatment of GI cancer patients, overall survival is still low. Therefore, alternative strategies must be identified to improve patient outcomes. In the tumor microenvironment, tumor cells can escape the host immune response through the interaction of PD-1 and PD-L, which inhibits the function of T cells and tumor-infiltrating lymphocytes while increasing the function of immunosuppressive T regulatory cells. The use of an anti-PD-1/PD-L blockade enables reprogramming of the immune system to efficiently identify and kill tumor cells. In recent years, the efficacy of PD-1/PD-L blockade has been demonstrated in many tumors, and this treatment is expected to be a pan-immunotherapy for tumors. Here, we review the signaling pathway underlying the dysregulation of PD-1/PD-L in tumors, summarize the current clinical data for PD-1/PD-L inhibitors in GI malignancies, and discuss road toward precision immunotherapy in relation to PD-1/PD-L blockade. The preliminary data for PD-1/PD-L inhibitors are encouraging, and the precision immunotherapy of PD-1/PD-L inhibitors will be a viable and pivotal clinical strategy for GI cancer therapy.

  15. CO Oxidation by Subnanometer AgxAu3–x Supported Clusters via Density Functional Theory Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Negreiros, Fabio R.; Sementa, Luca; Barcaro, Giovanni; Vajda, S.; Apra, Edoardo; Fortunelli, Alessandro

    2012-09-07

    The activity of AgxAu3–x/MgO(100) clusters in CO oxidation is investigated computationally via systematic sampling techniques. It is found that these subnanometer species transform after ligand adsorption into reaction complexes which catalyze CO oxidation through a variety of different mechanisms, occurring via both Langmuir–Hinshelwood and Eley–Rideal paths and in some cases directly involving the oxide support. The alloyed Ag2Au1 cluster is proposed as the best catalyst in terms of efficiency and robustness.

  16. Exploring the Potential of Different-Sized Supported Subnanometer Pt Clusters as Catalysts for Wet Chemical Applications

    KAUST Repository

    Rondelli, Manuel

    2017-05-10

    The use of physicochemical preparation techniques of metal clusters in the ultrahigh vacuum (UHV) allows for high control of cluster nuclearity and size distribution for fundamental studies in catalysis. Surprisingly, the potential of these systems as catalysts for organic chemistry transformations in solution has not been explored. To this end, single Pt atoms and Pt clusters with two narrow size distributions were prepared in the UHV and applied for the hydrogenation of p-chloronitrobenzene to p-chloroaniline in ethanol. Following the observation of very high catalytic turnovers (approaching the million molecules of p-nitroaniline formed per Pt cluster) and of size-dependent activity, this work addresses fundamental questions with respect to the suitability of these systems as heterogeneous catalysts for the conversion of solution-phase reagents. For this purpose, we employ scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS) characterization before and after reaction to assess the stability of the clusters on the support and the question of heterogeneity versus homogeneity in the catalytic process.

  17. Elaboration and characterisation of Pd-Cr alloys for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Souleymane, B.; Fouda-Onana, F.; Savadogo, O. [Ecole Polytechnique de Montreal, Montreal, PQ (Canada). Laboratoire de nouveaux materiaux pour l' energie et l' electrochimie

    2008-07-01

    Palladium (Pd) alloys have been considered as alternative catalyst cathodes for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, particularly in liquid fuel cells. The purpose of this study was to investigate the ORR on various Pd-Cr alloys. Pd-Cr alloys were deposited on glassy carbon support and the electrocatalytic parameters for the ORR were determined in acid medium. The effect of the Pd-Cr alloy deposition parameters on its composition and electrocatalytic behaviour were determined. The study showed that there is a relationship between the composition of the alloy and the power of the Pd and Cr cathode. The parameters of the ORR were correlated to the alloy chemical and physical properties. EDS and XPS analysis revealed a segregation of Cr in the alloy.The variation of the work function (W) of the alloy with the alloy composition has shown a minimum value of W of 0.287 for a composition of the alloy of 70 per cent of Pd and 30 per cent of Cr. The electrochemically active surface area and the exchange current density of the ORR indicated that the mechanism of the ORR on Pd-Cr is similar to that on platinum. 9 refs., 2 figs.

  18. 48 CFR 726.7102 - PD 20 provision.

    Science.gov (United States)

    2010-10-01

    ..., Internationally Recognized Workers' Rights 726.7102 PD 20 provision. Relocation of U.S. Businesses, Assistance to Export Processing Zones, Internationally Recognized Workers' Rights (JAN 1994) No funds or other support... may be used in an activity which contributes to the violation of internationally recognized rights of...

  19. Experimental study on the surface characteristics of Pd-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiang; Sun, Bingli [School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001 (China); National Center for International Joint Research of Micro-nano Molding Technology, Zhengzhou University, Zhengzhou 450001 (China); Key Laboratory for Micro Molding Technology of Henan Province, Zhengzhou University, Zhengzhou, 450001 (China); Zhao, Na [National Center for International Joint Research of Micro-nano Molding Technology, Zhengzhou University, Zhengzhou 450001 (China); Key Laboratory for Micro Molding Technology of Henan Province, Zhengzhou University, Zhengzhou, 450001 (China); National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002 (China); Li, Qian, E-mail: qianli@zzu.edu.cn [School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001 (China); National Center for International Joint Research of Micro-nano Molding Technology, Zhengzhou University, Zhengzhou 450001 (China); Key Laboratory for Micro Molding Technology of Henan Province, Zhengzhou University, Zhengzhou, 450001 (China); National Engineering Research Center for Advanced Polymer Processing Technology, Zhengzhou University, Zhengzhou 450002 (China); Hou, Jianhua; Feng, Weina [School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001 (China); National Center for International Joint Research of Micro-nano Molding Technology, Zhengzhou University, Zhengzhou 450001 (China); Key Laboratory for Micro Molding Technology of Henan Province, Zhengzhou University, Zhengzhou, 450001 (China)

    2014-12-01

    Highlights: • Wetting behavior of four polymer melts on Pd-based bulk metallic glass was investigated. • From results, in general, the contact angle of polymer on Pd-based BMG decreases with temperature increasing. • We find a critical temperature for each polymer, above this temperature, contact angle on Pd-based BMG does not decrease with temperature increasing. • Surface free energy of Pd-based BMG was estimated by Owens–Wendt method. - Abstract: The metallic glass has many unique and desirable physical and chemical characteristics for their long-range disordered atomic structure, among them the interfacial properties of the metallic glasses are crucial for their applications and manufacturing. In this work, the contact wetting angles between the polymer melts and Pd{sub 40}Cu{sub 30}Ni{sub 10}P{sub 20} bulk metallic glass (Pd-BMG) with four kinds of roughness were analyzed. Experiments show the order of four polymers wettability on Pd-BMG was PP > HDPE > COC > PC. The surface free energy of Pd-BMG was estimated by Owens–Wendt method using the contact angles of three testing liquids. Neumann method was also used to further evidence the surface free energy of Pd-BMG comparing with PTFE, mold steels NAK80 and LKM2343ESR. The results provide theoretical and technical supports for the fabrication of metallic glass micro mold and the parameter optimization of polymer micro injection molding.

  20. TreeCluster: Massively scalable transmission clustering using phylogenetic trees

    OpenAIRE

    Moshiri, Alexander

    2018-01-01

    Background: The ability to infer transmission clusters from molecular data is critical to designing and evaluating viral control strategies. Viral sequencing datasets are growing rapidly, but standard methods of transmission cluster inference do not scale well beyond thousands of sequences. Results: I present TreeCluster, a cross-platform tool that performs transmission cluster inference on a given phylogenetic tree orders of magnitude faster than existing inference methods and supports multi...

  1. Specific brainstem and cortico-spinal reflex abnormalities in coexisting essential tremor and Parkinson's disease (ET-PD).

    Science.gov (United States)

    Yavuz, D; Gündüz, A; Ertan, S; Apaydın, H; Şifoğlu, A; Kiziltan, G; Kiziltan, M E

    2015-05-01

    We aimed to analyze functional changes at brainstem and spinal levels in essential tremor (ET), Parkinson's disease (PD) and coexisting essential tremor and Parkinson's disease (ET-PD). Age- and gender-matched patients with tremor (15 ET, 7 ET with resting tremor, 25 ET-PD and 10 PD) and 12 healthy subjects were enrolled in the study. Diagnosis was established according to standardized clinical criteria. Electrophysiological studies included blink reflex (BR), auditory startle reaction (ASR) and long latency reflex (LLR). Blink reflex was normal and similar in all groups. Probability of ASR was significantly lower in ET-PD group whereas it was similar to healthy subjects in ET and PD (PET, PD and ET-PD groups. LLR III was far more common in the PD group (n=3, 13.6% in ET; n=4, 16.0% in ET-PD and n=7, 46.7% in PD; p=0.037). Despite the integrity of BR pathways, ASR and LLR show distinctive abnormalities in ET-PD. In our opinion, our electrophysiological findings support the hypothesis that ET-PD is a distinct entity. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  2. Government Support, FDI Clustering and Semiconductor Sustainability in China: Case Studies of Shanghai, Suzhou and Wuxi in the Yangtze Delta

    Directory of Open Access Journals (Sweden)

    Tsu-Lung Chou

    2014-08-01

    Full Text Available With reference to the case studies of Shanghai, Suzhou, and Wuxi, in the Yangtze Delta, China, this paper demonstrates the local possibilities and various development paths for developing an indigenous semiconductor industry, using the government support within foreign direct investment (FDI-dominated clusters for the New Industrializing Countries (NICs. Two important policy lessons are identified. The first is that the government may attract FDI and develop high-tech clustering by using policy support, but it does not necessarily provide conducive and positive influences on the sustainable development of domestic semiconductors. The second lesson is that the sustainability of the domestic semiconductor industry in the FDI cluster may start from three connected elements: (1 a pragmatic goal of government support; (2 complementarities of the domestic semiconductors with international leading firms in the market, technology and equipment linkages; and (3 a sustainable capacity of technical learning to drive local developments.

  3. Structure characterization of Pd/Co/Pd tri-layer films epitaxially grown on MgO single-crystal substrates

    Energy Technology Data Exchange (ETDEWEB)

    Tobari, Kousuke, E-mail: tobari@futamoto.elect.chuo-u.ac.jp; Ohtake, Mitsuru; Nagano, Katsumasa; Futamoto, Masaaki

    2011-09-30

    Pd/Co/Pd tri-layer films were prepared on MgO substrates of (001), (111), and (011) orientations at room temperature by ultra high vacuum rf magnetron sputtering. The detailed film structures around the Co/Pd and the Pd/Co interfaces are investigated by reflection high energy electron diffraction. Pd layers of (001){sub fcc}, (111){sub fcc}, and (011){sub fcc} orientations epitaxially grow on the respective MgO substrates. Strained fcc-Co(001) single-crystal layers are formed on the Pd(001){sub fcc} layers by accommodating the fairly large lattice mismatch between the Co and the Pd layers. On the Co layers,, Pd polycrystalline layers are formed. When Co films are formed on the Pd(111){sub fcc} and the Pd(011){sub fcc} layers, atomic mixing is observed around the Co/Pd interfaces and fcc-CoPd alloy phases are coexisting with Co crystals. The Co crystals formed on the Pd(111){sub fcc} layers consist of hcp(0001) + fcc(111) and Pd(111){sub fcc} epitaxial layers are formed on the Co layers. Co crystals epitaxially grow on the Pd(011){sub fcc} layers with two variants, hcp(11-bar 00) and fcc(111). On the Co layers, Pd(011){sub fcc} epitaxial layers are formed.

  4. Self-assembled metal clusters on an alumina nanomesh

    International Nuclear Information System (INIS)

    Buchsbaum, A.

    2012-01-01

    Template mediated growth of metals has attracted much interest due to the remarkable magnetic and catalytic properties of clusters in the nanometer range and provides the opportunity to grow clusters with narrow size distributions. When the Ni3Al(111) surface is exposed to oxygen at elevated temperature a thin oxide film with a well-defined structure and uniform thickness grows and covers the alloy surface completely. The structure of the alumina film has been solved mainly by the help of scanning tunneling microscopy (STM) combined with density functional theory (DFT) calculations. The structure of the approx. 0.5 nm thick oxide film has sixfold symmetry and exhibits holes with a diameter of approx. 400 pm reaching down to the metal substrate at the corners of the (Sqrt(67) x Sqrt(67))R12.2° unit cell. The side length of the unit cell is 4.1 nm. The driving force for the formation of the oxide nanomesh is the reduction of the metal/oxide interface energy by the formation of energetically favorable Al-Ni bonds at the interface. Due to better wetting of metal on metal surfaces than on oxide surfaces, metal atoms prefer to bind to the substrate in the hole, not to the oxide. Therefore the oxide forms a template with a hexagonal 4.1 nm lattice for the growth of well-ordered metal clusters. Nevertheless, the growth of most metal clusters on top of the corner holes is not straightforward. Fe and Co atoms cannot jump into the corner holes due to a barrier for diffusion and nucleate at their second favorable adsorption site. However, Pd atoms trapped in these corner holes reduce the barrier for diffusion and create metallic nucleation sites where Fe as well as Co clusters can nucleate and form a well-ordered hexagonal arrangement on the oxide nanomesh. We have studied these Fe and Co clusters and applied different methods like STM and surface x-ray diffraction (SXRD) to determine the morphology and crystallography of the clusters. For Fe we found cluster growth with

  5. PD Lab

    NARCIS (Netherlands)

    Bilow, Marcel; Entrop, Alexis Gerardus; Lichtenberg, Jos; Stoutjesdijk, Pieter

    2015-01-01

    PD Lab explores the applications of building sector related product development. PD lab investigates and tests digital production technologies like CNC milled wood connections. It will also act as a platform in its wider meaning to investigate the effects and influences of file to factory

  6. A Facile Synthesis of Hollow Palladium/Copper Alloy Nanocubes Supported on N-Doped Graphene for Ethanol Electrooxidation Catalyst

    Directory of Open Access Journals (Sweden)

    Zhengyu Bai

    2015-04-01

    Full Text Available In this paper, a catalyst of hollow PdCu alloy nanocubes supported on nitrogen-doped graphene support (H-PdCu/ppy-NG is successfully synthesized using a simple one-pot template-free method. Two other catalyst materials such as solid PdCu alloy particles supported on this same nitrogen-doped graphene support (PdCu/ppy-NG and hollow PdCu alloy nanocubes supported on the reduced graphene oxide support (H-PdCu/RGO are also prepared using the similar synthesis conditions for comparison. It is found that, among these three catalyst materials, H-PdCu/ppy-NG gives the highest electrochemical active area and both the most uniformity and dispersibility of H-PdCu particles. Electrochemical tests show that the H-PdCu/ppy-NG catalyst can give the best electrocatalytic activity and stability towards the ethanol electrooxidation when compared to other two catalysts. Therefore, H-PdCu/ppy-NG should be a promising catalyst candidate for anodic ethanol oxidation in direct ethanol fuel cells.

  7. Nitrite reduction mechanism on a Pd surface.

    Science.gov (United States)

    Shin, Hyeyoung; Jung, Sungyoon; Bae, Sungjun; Lee, Woojin; Kim, Hyungjun

    2014-11-04

    Nitrate (NO3-) is one of the most harmful contaminants in the groundwater, and it causes various health problems. Bimetallic catalysts, usually palladium (Pd) coupled with secondary metallic catalyst, are found to properly treat nitrate-containing wastewaters; however, the selectivity toward N2 production over ammonia (NH3) production still requires further improvement. Because the N2 selectivity is determined at the nitrite (NO2-) reduction step on the Pd surface, which occurs after NO3- is decomposed into NO2- on the secondary metallic catalyst, we here performed density functional theory (DFT) calculations and experiments to investigate the NO2- reduction pathway on the Pd surface activated by hydrogen. Based on extensive DFT calculations on the relative energetics among ∼100 possible intermediates, we found that NO2- is easily reduced to NO* on the Pd surface, followed by either sequential hydrogenation steps to yield NH3 or a decomposition step to N* and O* (an adsorbate on Pd is denoted using an asterisk). Based on the calculated high migration barrier of N*, we further discussed that the direct combination of two N* to yield N2 is kinetically less favorable than the combination of a highly mobile H* with N* to yield NH3. Instead, the reduction of NO2- in the vicinity of the N* can yield N2O* that can be preferentially transformed into N2 via diverse reaction pathways. Our DFT results suggest that enhancing the likelihood of N* encountering NO2- in the solution phase before combination with surface H* is important for maximizing the N2 selectivity. This is further supported by our experiments on NO2- reduction by Pd/TiO2, showing that both a decreased H2 flow rate and an increased NO2- concentration increased the N2 selectivity (78.6-93.6% and 57.8-90.9%, respectively).

  8. Detection of sensor degradation using K-means clustering and support vector regression in nuclear power plant

    International Nuclear Information System (INIS)

    Seo, Inyong; Ha, Bokam; Lee, Sungwoo; Shin, Changhoon; Lee, Jaeyong; Kim, Seongjun

    2011-01-01

    In a nuclear power plant (NPP), periodic sensor calibrations are required to assure sensors are operating correctly. However, only a few faulty sensors are found to be rectified. For the safe operation of an NPP and the reduction of unnecessary calibration, on-line calibration monitoring is needed. In this study, an on-line calibration monitoring called KPCSVR using k-means clustering and principal component based Auto-Associative support vector regression (PCSVR) is proposed for nuclear power plant. To reduce the training time of the model, k-means clustering method was used. Response surface methodology is employed to efficiently determine the optimal values of support vector regression hyperparameters. The proposed KPCSVR model was confirmed with actual plant data of Kori Nuclear Power Plant Unit 3 which were measured from the primary and secondary systems of the plant, and compared with the PCSVR model. By using data clustering, the average accuracy of PCSVR improved from 1.228×10 -4 to 0.472×10 -4 and the average sensitivity of PCSVR from 0.0930 to 0.0909, which results in good detection of sensor drift. Moreover, the training time is greatly reduced from 123.5 to 31.5 sec. (author)

  9. Catalytic hydrodechlorination of triclosan using a new class of anion-exchange-resin supported palladium catalysts.

    Science.gov (United States)

    Han, Bing; Liu, Wen; Li, Jingwen; Wang, Jin; Zhao, Dongye; Xu, Rui; Lin, Zhang

    2017-09-01

    We prepared a new class of anion-exchange-resin supported Pd catalysts for efficient hydrodechlorination of triclosan in water. The catalysts were prepared through an initial ion-exchange uptake of PdCl 4 2- and subsequent reduction of Pd(II) to Pd(0) nanoparticles at ambient temperature. Two standard strong-base anion exchange resins (IRA-900 and IRA-958) with different matrices (polystyrene and polyacrylic) were chosen as the supports. SEM and TEM images showed that Pd(0) nanoparticles were evenly attached on the resin surface with a mean size of 3-5 nm. The resin supported Pd catalysts (Pd@IRA-900 and Pd@IRA-958) were able to facilitate rapid and complete hydrodechlorination of triclosan. At a Pd loading of 2.0 wt.%, the observed pseudo first-order rate constant (k obs ) was 1.25 ± 0.06 and 1.6 ± 0.1 L/g/min for Pd@IRA-900 and Pd@IRA-958, respectively. The catalysts were more resistant to Cl - poisoning and natural organic matter fouling than other supported-Pd catalysts. The presence of 10 mM NaCl suppressed the k obs value by 31% and 23% for Pd@IRA-900 and Pd@IRA-958, whereas the presence of humic acid at 30 mg/L as TOC lowered the rates by 28% and 27%, respectively. The better performance of Pd@IRA-958 was attributed to the polymeric matrix properties (i.e., hydrophobicity, pore size, and surface area) as well as Pd particle size. GC/MS analyses indicated that very low concentrations of chlorinated intermediates were detected in the early stage of the hydrodechlorination process, with 2-phenoxyphenol being the main byproduct. The catalysts can be repeatedly used in multiple operations without significant bleeding. The catalysts eliminate the need for calcination in preparing conventional supported catalysts, and the resin supports conveniently facilitate control of Pd loading and material properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Evaluation of Potential Locations for Siting Small Modular Reactors near Federal Energy Clusters to Support Federal Clean Energy Goals

    Energy Technology Data Exchange (ETDEWEB)

    Belles, Randy J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Omitaomu, Olufemi A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2014-09-01

    Geographic information systems (GIS) technology was applied to analyze federal energy demand across the contiguous US. Several federal energy clusters were previously identified, including Hampton Roads, Virginia, which was subsequently studied in detail. This study provides an analysis of three additional diverse federal energy clusters. The analysis shows that there are potential sites in various federal energy clusters that could be evaluated further for placement of an integral pressurized-water reactor (iPWR) to support meeting federal clean energy goals.

  11. Pd-Pt alloys nanowires as support-less electrocatalyst with high synergistic enhancement in efficiency for methanol oxidation in acidic medium.

    Science.gov (United States)

    Rana, Moumita; Patil, Pramod K; Chhetri, Manjeet; Dileep, K; Datta, Ranjan; Gautam, Ujjal K

    2016-02-01

    In a facile approach, Pd73Pt27 alloy nanowires (NWs) with large aspect ratios were synthesized in high yield by using sacrificial templates. Unlike majority of processes, our synthesis was carried out in aqueous solution with no intermittent separating stages for the products, while maintaining the NW morphology up to ∼30% of Pt. Upon evaporation of their dispersion, the NWs transform into a stable porous membrane due to self-entanglement and can be directly lifted and employed for electrocatalytic applications without external catalyst supports. We show that the NW membranes exhibit efficient electrocatalytic performance for methanol oxidation reaction (MOR) with 10 times higher mass activity and 4.4 times higher specific activity in acidic media as compared to commercial Pt catalysts. The membrane electrocatalysts is robust and exhibited very good stability with retention of ∼70% mass-activity after 4000 potential cycles. Since Pd was found to be inert towards MOR in acidic medium, our investigation provides a direct estimate of synergistic enhancement of efficiency. Over 10 times increment of mass activity appears to be significantly higher than previous investigations in various other reaction media. Copyright © 2015 Elsevier Inc. All rights reserved.

  12. Preparation of Pd-Loaded Hierarchical FAU Membranes and Testing in Acetophenone Hydrogenation

    Directory of Open Access Journals (Sweden)

    Raffaele Molinari

    2016-03-01

    Full Text Available Pd-loaded hierarchical FAU (Pd-FAU membranes, containing an intrinsic secondary non-zeolitic (mesoporosity, were prepared and tested in the catalytic transfer hydrogenation of acetophenone (AP to produce phenylethanol (PE, an industrially relevant product. The best operating conditions were preliminarily identified by testing different solvents and organic hydrogen donors in a batch hydrogenation process where micron-sized FAU seeds were employed as catalyst support. Water as solvent and formic acid as hydrogen source resulted to be the best choice in terms of conversion for the catalytic hydrogenation of AP, providing the basis for the design of a green and sustainable process. The best experimental conditions were selected and applied to the Pd-loaded FAU membrane finding enhanced catalytic performance such as a five-fold higher productivity than with the unsupported Pd-FAU crystals (11.0 vs. 2.2 mgproduct gcat−1·h−1. The catalytic performance of the membrane on the alumina support was also tested in a tangential flow system obtaining a productivity higher than that of the batch system (22.0 vs. 11.0 mgproduct gcat−1·h−1.

  13. Preparation of Pd-Loaded Hierarchical FAU Membranes and Testing in Acetophenone Hydrogenation.

    Science.gov (United States)

    Molinari, Raffaele; Lavorato, Cristina; Mastropietro, Teresa F; Argurio, Pietro; Drioli, Enrico; Poerio, Teresa

    2016-03-22

    Pd-loaded hierarchical FAU (Pd-FAU) membranes, containing an intrinsic secondary non-zeolitic (meso)porosity, were prepared and tested in the catalytic transfer hydrogenation of acetophenone (AP) to produce phenylethanol (PE), an industrially relevant product. The best operating conditions were preliminarily identified by testing different solvents and organic hydrogen donors in a batch hydrogenation process where micron-sized FAU seeds were employed as catalyst support. Water as solvent and formic acid as hydrogen source resulted to be the best choice in terms of conversion for the catalytic hydrogenation of AP, providing the basis for the design of a green and sustainable process. The best experimental conditions were selected and applied to the Pd-loaded FAU membrane finding enhanced catalytic performance such as a five-fold higher productivity than with the unsupported Pd-FAU crystals (11.0 vs. 2.2 mgproduct gcat(-1)·h(-1)). The catalytic performance of the membrane on the alumina support was also tested in a tangential flow system obtaining a productivity higher than that of the batch system (22.0 vs. 11.0 mgproduct gcat(-1)·h(-1)).

  14. Efficiency of bimetallic PtPd on polydopamine modified on various carbon supports for alcohol oxidations

    Science.gov (United States)

    Pinithchaisakula, A.; Ounnunkad, K.; Themsirimongkon, S.; Promsawan, N.; Waenkaew, P.; Saipanya, S.

    2017-02-01

    In this work, the preparation, characterization, and electrocatalytic analysis of the catalysts on various carbon substrates for direct alcohol fuel cells were studied. Selected carbons were modified with/without polydopamine (labelled as PDA-C and C) and further metal electrodeposited incorporated onto the glassy carbon (labelled as 5Pt1Pd/PDA-C and 5Pt1Pd/C). Four various carbon materials were used e.g. graphite (G), carbon nanotube (CNT), graphene (GP) and graphene oxide (GO) and the carbons were modified with PDA denoted as PDA-G, PDA-CNT, PDA-GP and PDA-GO, respectively. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) experimental observation showed narrow size distribution of metal anchored on the PDA-C and C materials. Chemical compositions and oxidation states of the catalysts were determined by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The catalytic performances for small organic electro-oxidation (e.g. methanol and ethanol) were measured by cyclic voltammetry (CV). Among different PDA-C and C catalysts, monometallic Pt showed less activity than the bimetallic catalysts. Among catalysts with PDA, the 5Pt1Pd/PDA-GO catalyst facilitated methanol and ethanol oxidations with high oxidation currents and If/Ib value and stability with low potentials while among catalysts without PDA, the 5Pt1Pd/CNT provides highest activity and stability. It was found that the catalysts with PDA provided high activity and stability than the catalysts without PDA. The improved catalytic performance of the prepared catalysts could be related to the higher active surface area from polymer modification and bimetallic catalyst system in the catalyst composites.

  15. High-temperature stability of Au/Pd/Cu and Au/Pd(P)/Cu surface finishes

    Science.gov (United States)

    Ho, C. E.; Hsieh, W. Z.; Lee, P. T.; Huang, Y. H.; Kuo, T. T.

    2018-03-01

    Thermal reliability of Au/Pd/Cu and Au/Pd(4-6 wt.% P)/Cu trilayers in the isothermal annealing at 180 °C were investigated by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and transmission electron microscopy (TEM). The pure Pd film possessed a nanocrystalline structure with numerous grain boundaries, thereby facilitating the interdiffusion between Au and Cu. Out-diffusion of Cu through Pd and Au grain boundaries yielded a significant amount of Cu oxides (CuO and Cu2O) over the Au surface and gave rise to void formation in the Cu film. By contrast, the Pd(P) film was amorphous and served as a good diffusion barrier against Cu diffusion. The results of this study indicated that amorphous Pd(P) possessed better oxidation resistance and thermal reliability than crystalline Pd.

  16. Device for supporting a fuel pin cluster within a nuclear reactor fuel assembly wrapper

    International Nuclear Information System (INIS)

    Marmonier, P.; Mesnage, B.; Teulon, J.; Vayra, J.; Venobre, H.

    1976-01-01

    A supporting member for an array of parallel rails each carrying one row of slidably mounted pins of a fuel cluster is placed coaxially at the lower end of a vertical fuel assembly wrapper. Each parallel rail is provided at each end with a downward extension and terminal lug which engages in a lateral groove formed in the periphery of the supporting member in order to lock and maintain the rails and the fuel pins in uniformly spaced relation within the fuel assembly wrapper. 10 claims, 8 figures

  17. Atomically precise cluster catalysis towards quantum controlled catalysts

    International Nuclear Information System (INIS)

    Watanabe, Yoshihide

    2014-01-01

    Catalysis of atomically precise clusters supported on a substrate is reviewed in relation to the type of reactions. The catalytic activity of supported clusters has generally been discussed in terms of electronic structure. Several lines of evidence have indicated that the electronic structure of clusters and the geometry of clusters on a support, including the accompanying cluster-support interaction, are strongly correlated with catalytic activity. The electronic states of small clusters would be easily affected by cluster–support interactions. Several studies have suggested that it is possible to tune the electronic structure through atomic control of the cluster size. It is promising to tune not only the number of cluster atoms, but also the hybridization between the electronic states of the adsorbed reactant molecules and clusters in order to realize a quantum-controlled catalyst. (review)

  18. Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

    International Nuclear Information System (INIS)

    Zhou, Juan; Chen, Huan; Chen, Quanyuan; Huang, Zhaolu

    2016-01-01

    Graphical abstract: 2,4-Dichlorophenol can be converted to phenol via the catalytic HDC method over Pd-Au/CNTs and the catalytic activity first increased and then decreased with Au content. - Highlights: • Bimetallic catalysts had smaller metal particles and larger number of exposed active site than the monometallic catalysts. • The cationization of Pd particles increased with Au content in the bimetallic catalysts. • The bimetallic catalysts exhibited higher catalytic activities for HDC of 2,4-DCP than the monometallic counterparts. • The concerted pathway for HDC of 2,4-DCP was more predominant with increasing Au content in the bimetallic catalyst. - Abstract: Monometallic and bimetallic Pd-Au catalysts supported on multi-walled carbon nanotubes (CNTs) with varied Au cooperation amounts were prepared using the complexing-reduction method in the presence of tetrahydrofuran (THF). The liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP) was investigated over these bimetallic catalysts. The catalysts were characterized by N 2 adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H 2 chemisorption. Characterization results showed that the co-reduction of Pd and Au mainly formed alloy-like structure. The bimetallic catalysts had smaller metal particles and larger numbers of exposed active site than that of monometallic catalysts. In addition, compared with Pd(1.7)/CNTs and Au(0.4)/CNTs, the binding energies of Pd 3d 5/2 shifted to higher positions while that of Au 4f 7/2 had negative shifts in the Pd-Au bimetallic catalysts, which can be ascribed to the electrons transferred from metal Pd to Au and the cationization of Pd particles was enhanced. Accordingly, the bimetallic Pd-Au particles with different Au contents in the catalysts exhibited varied synergistic effects for the catalytic HDC of 2,4-DCP, with Pd(1.8)Au(0.4)/CNTs having the highest catalytic activity

  19. Morphology and magnetism of Fe monolayers and small Fen clusters (n 2-19) supported on the Ni(111) surface

    International Nuclear Information System (INIS)

    Longo, R C; MartInez, E; Dieguez, O; Vega, A; Gallego, L J

    2007-01-01

    Using the modified embedded atom model in conjunction with a self-consistent tight-binding method, we investigated the lowest-energy structures of Fe monolayers and isolated Fe n clusters (n = 2-19) supported on the Ni(111) surface. In keeping with experimental findings, our calculations predict that the atoms of the monolayer occupy face-centred cubic (fcc) rather than hexagonal close-packed (hcp) sites. Likewise in agreement with experiment we found that Fe layers stack with a pseudomorphic fcc structure up to two monolayers, beyond which they stack as bcc(110). The structures of supported Fe clusters are predicted to be two-dimensional islands maximizing the number of nearest-neighbour bonds among the adsorbed Fe atoms, and their average magnetic moments per atom decrease towards that of the supported Fe monolayer almost monotonically as n increases. Finally, a pair of Fe 3 clusters on Ni(111) were found to exhibit virtually no interaction with each other even when separated by only one atomic row, i.e. so long as they do not coalesce they retain their individual magnetic properties

  20. One-pot synthesis of Pd-Pt@Pd core-shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

    KAUST Repository

    Yuan, Qiang; Huang, Dabing; Wang, Honghui; Zhou, Zhiyou; Wang, Qingxiao

    2014-01-01

    Well-defined Pd-Pt@Pd core-shell nanocrystals with a Pd-Pt alloy core and a conformal Pd shell of ~2-3 nm were directly synthesized through a one-pot, aqueous solution approach without any preformed Pd or Pt seeds. These Pd-Pt@Pd core

  1. Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

    KAUST Repository

    Zwaschka, Gregor; Rondelli, Manuel; Krause, Maximilian; Rö tzer, Marian David; Hedhili, Mohamed N.; Heiz, Ulrich; Basset, Jean-Marie; Schweinberger, Florian; D'Elia, Valerio

    2018-01-01

    The preparation of organic ligands-free, isolated tantalum oxide atoms (Ta1) and small clusters (Tan>1) on flat silicate supports was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air. The resulting surface complexes were thoroughly characterized and tested as supported catalysts for the epoxidation of cycloalkenes. The observed catalytic performance highlights the potential of the applied method for the production of active catalysts and the study of well-defined, ligand-free metal oxide moieties.

  2. Supported sub-nanometer Ta oxide clusters as model catalysts for the selective epoxidation of cyclooctene

    KAUST Repository

    Zwaschka, Gregor

    2018-01-22

    The preparation of organic ligands-free, isolated tantalum oxide atoms (Ta1) and small clusters (Tan>1) on flat silicate supports was accomplished by ultra-high vacuum (UHV) techniques followed by oxidation in air. The resulting surface complexes were thoroughly characterized and tested as supported catalysts for the epoxidation of cycloalkenes. The observed catalytic performance highlights the potential of the applied method for the production of active catalysts and the study of well-defined, ligand-free metal oxide moieties.

  3. Electronic Absorption and MCD Spectra for Pd(AuPPh(3))(8)(2+), Pt(AuPPh(3))(8)(2+), and Related Platinum-Centered Gold Cluster Complexes.

    Science.gov (United States)

    Adrowski, Michael J.; Mason, W. Roy

    1997-03-26

    Electronic absorption and 7.0 T magnetic circular dichroism (MCD) spectra in the UV-vis region, 1.6 to approximately 4.0 &mgr;m(-)(1) (1 &mgr;m(-)(1) = 10(4) cm(-)(1)) are reported for [Pd(AuPPh(3))(8)](NO(3))(2) and [Pt(AuPPh(3))(8)](NO(3))(2) in acetonitrile solutions at room temperature. The MCD spectra are better resolved than the absorption spectra and consist of both A and B terms. The spectra are interpreted in terms of D(4)(d)() skeletal geometry and MO's that are approximated by 5s and 6s orbitals for Pd and Pt/Au atoms, respectively. The lowest energy excited configurations and states are attributed to intraframework (IF) Au(8)(2+) transitions. Evidence is also presented for Pt 5d --> Au 6s transitions in the MCD spectra for Pt(AuPPh(3))(8)(2+). Acetonitrile solution absorption and MCD spectra for the related Pt-centered cluster complexes [Pt(CO)(AuPPh(3))(8)](NO(3))(2), [Pt(AuP(p-tolyl)(3))(8)](NO(3))(2), [Pt(CuCl)(AuPPh(3))(8)](NO(3))(2), [Pt(AgNO(3))(AuPPh(3))(8)](NO(3))(2), [Pt(Hg)(2)(AuPPh(3))(8)](NO(3))(2), [Pt(HgCl)(2)(AuPPh(3))(8)](BF(4))(2), and [Pt(HgNO(3))(2)(AuPPh(3))(8)](BF(4))(2) are also reported and interpreted within the context of the model developed for the M(AuPPh(3))(8)(2+) complexes.

  4. Neonatal nucleated red blood cells in G6PD deficiency.

    Science.gov (United States)

    Yeruchimovich, Mark; Shapira, Boris; Mimouni, Francis B; Dollberg, Shaul

    2002-05-01

    The objective of this study is to study the absolute number of nucleated red blood cells (RBC) at birth, an index of active fetal erythropoiesis, in infants with G6PD deficiency and in controls. We tested the hypothesis that hematocrit and hemoglobin would be lower, and absolute nucleated RBC counts higher, in the G6PD deficient and that these changes would be more prominent in infants exposed passively to fava bean through maternal diet. Thirty-two term infants with G6PD deficiency were compared with 30 term controls. Complete blood counts with manual differential counts were obtained within 12 hours of life. Absolute nucleated RBC and corrected leukocyte counts were computed from the Coulter results and the differential count. G6PD deficient patients did not differ from controls in terms of gestational age, birth weight, or Apgar scores or in any of the hematologic parameters studied, whether or not the mother reported fava beans consumption in the days prior to delivery. Although intrauterine hemolysis is possible in G6PD deficient fetuses exposed passively to fava beans, our study supports that such events must be very rare.

  5. Catalytic characterization of bi-functional catalysts derived from Pd ...

    Indian Academy of Sciences (India)

    Unknown

    1995; Lyubovsky and Pfefferle 1999; Sales et al 1999;. Hill et al 2000). ... For a catalytic system, whose activity ... catalytic systems containing Pd, supported on various acid- ..... Further studies are needed to optimize a balance between.

  6. Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al_2O_3 templates

    International Nuclear Information System (INIS)

    Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.

    2016-01-01

    Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L1_0 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment. - Highlights: • CoPd and FePd antidots were fabricated on porous anodic aluminum oxide templates. • CoPd antidot arrays have perpendicular magnetic anisotropy. • FePd antidot arrays revealed isotropic magnetic behavior. • The complex morphology of nanoporous template resulted in a complex magnetic domains image.

  7. Cyanogel-derived N-doped C nanosheets immobilizing Pd-P nanoparticles: One-pot synthesis and enhanced hydrogenation catalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hao; Yan, Xiaohong; Huang, Yundi; Zhang, Mengru; Tang, Yawen; Sun, Dongmei; Xu, Lin, E-mail: njuxulin@gmail.com; Wei, Shaohua, E-mail: weishaohua@njnu.edu.cn

    2017-02-28

    Highlights: • Cyanogel-bridged approach was developed for the synthesis of Pd-P@N-Cnanosheets. • Pd-P@N-C nanosheets exhibit high activity and stability for reduction of 4-NP. • Compositional and structural advantages account for the high catalytic activity. • The feasible synthesis could be extendable to other carbon-based nanohybrids. - Abstract: For Pd-based nanocatalysts, stabilization of Pd nanoparticles on carbon support could not only effectively avoid particle aggregation and maintain catalytic stability during catalytic processes, but also facilitate enhancing the catalytic activity due to the synergy between Pd nanoparticles and carbon support. Furthermore, the incorporation of non-metal of phosphorus (P) into Pd could effectively modulate the electronic structure of Pd and thus help to boost the catalytic properties. However, one-pot synthesis of such nanohybrids remains a great challenge due to the distinct physiochemical properties of Pd, P and C components. Herein, we demonstrate a one-pot and scalable synthesis of highly dispersed PdP alloy nanoparticle-immobilized on N-doped graphitic carbon nanosheets (abbreviated as Pd-P@N-C nanosheets) by using inorganic-organic hybrid cyanogel as a reaction precursor. In virtue of both compositional and structural advantages, the as-synthesized Pd-P@N-C nanosheets manifest a superior catalytic activity and stability toward the hydrogenation of 4-nitrophenol (4-NP). We believe that the present work will provide a feasible and versatile strategy for the development of efficient catalysts for environmental remediation and can also be extendable to other carbon-based nanohybrids with desirable functionalities.

  8. Effects of training and weight support on muscle activation in Parkinson's disease.

    Science.gov (United States)

    Rose, Martin H; Løkkegaard, Annemette; Sonne-Holm, Stig; Jensen, Bente R

    2013-12-01

    The aim of this study was to investigate the effect of high-intensity locomotor training on knee extensor and flexor muscle activation and adaptability to increased body-weight (BW) support during walking in patients with Parkinson's disease (PD). Thirteen male patients with idiopathic PD and eight healthy participants were included. The PD patients completed an 8-week training program on a lower-body, positive-pressure treadmill. Knee extensor and flexor muscles activation during steady treadmill walking (3 km/h) were measured before, at the mid-point, and after training. Increasing BW support decreased knee extensor muscle activation (normalization) and increased knee flexor muscle activation (abnormal) in PD patients when compared to healthy participants. Training improved flexor peak muscle activation adaptability to increased (BW) support during walking in PD patients. During walking without BW support shorter knee extensor muscle off-activation time and increased relative peak muscle activation was observed in PD patients and did not improve with 8 weeks of training. In conclusion, patients with PD walked with excessive activation of the knee extensor and flexor muscles when compared to healthy participants. Specialized locomotor training may facilitate adaptive processes related to motor control of walking in PD patients. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. One-pot synthesis of Pd-Pt@Pd core-shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

    KAUST Repository

    Yuan, Qiang

    2014-01-01

    Well-defined Pd-Pt@Pd core-shell nanocrystals with a Pd-Pt alloy core and a conformal Pd shell of ~2-3 nm were directly synthesized through a one-pot, aqueous solution approach without any preformed Pd or Pt seeds. These Pd-Pt@Pd core-shell nanocrystals show an enhanced electrocatalytic activity for formic acid oxidation compared with commercial Pd black. This journal is © 2014 The Royal Society of Chemistry.

  10. Green synthesis of Pt-on-Pd bimetallic nanodendrites on graphene via in situ reduction, and their enhanced electrocatalytic activity for methanol oxidation

    International Nuclear Information System (INIS)

    Cai, Zhi-xiong; Liu, Cong-cong; Wu, Geng-huang; Chen, Xiao-mei; Chen, Xi

    2014-01-01

    Graphical abstract: - Highlights: • Porous 3D dendrite-like structure of Pt-on-Pd bimetallic nanostructures supported on graphene were prepared. • The surface of nanostructures was very “clean” because of the surfactant-free formation process and the use of green reagent. • The hetero-nanostructures showed excellent electrocatalytic performance in methanol oxidation. - Abstract: A green synthesis of Pt-on-Pd bimetallic nanodendrites supported on graphene (GPtPdNDs) with a Pd interior and a dendrite-like Pt exterior was achieved using a two-step preparation, mixing graphene and PdCl 4 2− first, then adding PtCl 4 2− and ethanol without any other solvent. The morphology, structure and composition of the thus-prepared GPtPdNDs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Because no halide ions (refer in particular to Br - , I − ) or surfactant was involved in the synthesis, the prepared GPtPdNDs were directly modified onto a glassy carbon electrode and showed excellent electrocatalytic performance in methanol oxidation without any pretreatments. Moreover, with the special structure of PtPdNDs and the synergetic effects of Pt and Pd and the enhanced electron transfer by graphene, the GPtPdNDs composites exhibited higher electrocatalytic activity and better tolerance to Pt nanoparticles supported on graphene (GPtNPs) and Pt/C for methanol oxidation

  11. Pd-Cu/poly(o-Anisidine) nanocomposite as an efficient catalyst for formaldehyde oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Sayed Reza, E-mail: r.hosseini@umz.ac.ir [Nanochemistry Research Laboratory, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of); Raoof, Jahan-Bakhsh [Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of); Ghasemi, Shahram; Gholami, Zahra [Nanochemistry Research Laboratory, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar (Iran, Islamic Republic of)

    2016-08-15

    Highlights: • o-Anisidine monomer was electro-polymerized at the pCPE surface in acid medium. • Palladium/copper NPs were prepared by galvanic replacement method at the POA/pCPE. • Pd-Cu NPs showed excellent electrocatalytic activity towards formaldehyde oxidation. • The bimetallic Pd-Cu NPs/POA nanocomposite showed satisfactory long-term stability. - Abstract: In this work, for the first time, the electrocatalytic oxidation of formaldehyde in 0.5 M sulfuric acid solution at spherical bimetallic palladium-copper nanoparticles (Pd-Cu NPs) deposited on the poly (o-Anisidine) film modified electrochemically pretreated carbon paste electrode (POA/pCPE) has been investigated. Highly porous POA film prepared by electropolymerization onto the pCPE was used as a potent support for deposition of the Pd-Cu NPs. The Pd-Cu NPs were prepared through spontaneous and irreversible reaction via galvanic replacement between Pd{sup II} ions and the Cu{sup 0} particles. The prepared Pd-Cu NPs were characterized by scanning electron microscopy, energy dispersive spectroscopy and electrochemical methods. The obtained results showed that the utilization of Cu nanoparticles and pretreatment technique enhances the electrocatalytic activity of the modified electrode towards formaldehyde oxidation. The influence of several parameters on formaldehyde oxidation as well as stability of the Pd-Cu/POA/pCPE has been investigated.

  12. The structure of nano-palladium deposited on carbon-based supports

    International Nuclear Information System (INIS)

    Pikna, Ľubomír; Milkovič, Ondrej; Saksl, Karel; Heželová, Mária; Smrčová, Miroslava; Puliš, Pavel; Michalik, Štefan; Gamcová, Jana

    2014-01-01

    Nano-palladium catalysts, prepared using the same procedure with the same metal content (3 wt%) and two different supports, activated carbon (Pd/C) and activated carbon—multiwalled carbon nanotubes (Pd/C/CNT), are discussed. The simple technique of deposition reduction was applied in the preparation of these two types of Pd catalysts. TEM, XRD analysis, EXAFS signal analysis, and XANES were used for sample characterization. In both samples, transmission electron microscopy identified nanosized Pd particles with nearly spherical morphology but different sizes. The mean diameters of the particles on Pd/C and Pd/C/CNT were estimated to be 5.4 nm and 7.8 nm, respectively. The EXAFS signal analysis showed that Pd atoms on the particle surfaces were coordinated by 4 oxygens to form a PdO monolayer covering a metallic core. The XANES signal analysis indicated a smaller particle size for Pd/C (∅ 5 nm) than for Pd/C/CNT (∅ 10 nm), in good agreement with the TEM observations. - Graphical abstract: Visualization of metallic core (left), oxide monolayer (middle) and nanoparticle of diameter 5 nm (right). - Highlights: • Pd catalysts were prepared on two types of supports: carbon and carbon nanotubes. • BET, TEM, XRD characterization of prepared catalysts. • XAFS: Concentration of Pd in samples Pd/C and Pd/C/CNT. • EXAFS and XANES signal analysis of catalysts. • Visualisation of atoms arrangement at the Pd nanoparticle surface

  13. Atomic structure of graphene supported heterogeneous model catalysts

    International Nuclear Information System (INIS)

    Franz, Dirk

    2017-04-01

    the Ir clusters show equal ratio of ABC and ACB stacking. Pt/Rh clusters show mainly (∝75 %) ABC stacking and Ir/Pd clusters show exclusively ABC stacking - note the Ir(111) substrate stacking is chosen to be ABC-like. During gas exposure the clusters gain in height, while simultaneously the ordering of the cluster lattice decreases. The order of ACB stacked Pt/Rh clusters decreases more rapidly, so that a weakening of the cluster binding due to ACB stacking is proposed. In addition a size reduction of the lowest cluster layer to a hexagonal arrangement of 19 atoms was observed, which seems to be the energetically favoured interface area between graphene/Ir(111) and the investigated metal clusters. Platinum clusters containing fewer than 40 atoms have been investigated with surface sensitive X-ray diffraction. The cluster height could be determined and a reduced atom distance among the cluster was observed. CO exposure decreased the in-plane atom distance even more. This effect could be reverted by a subsequent oxygen exposure (2CO + O_2 → 2 CO_2). For Pt/Rh clusters with fewer than 60 atoms the element distribution was investigated and revealed an enrichment of Rh at the two topmost cluster layers. This element distribution was found for co-deposition and sequential deposition of the material and is therefore independent of the order of deposition. Oxygen exposure led to the formation of a rhodium surface oxide, which could be prevented by preceding CO exposure. In case of Ir/Pd clusters containing ∝60 atoms we found preferences for a core/shell structure with iridium atoms at core sites. Exposure to p(H_2)=1 bar did not result in the formation of the palladium β-phase, so that a reduced hydrogen solubility of graphene/Ir(111) supported palladium clusters is assumed. The reduced hydrogen solubility is probably a consequence of substrate induced strain among the cluster atoms.

  14. Atomic structure of graphene supported heterogeneous model catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Franz, Dirk

    2017-04-15

    , whereupon the Ir clusters show equal ratio of ABC and ACB stacking. Pt/Rh clusters show mainly (∝75 %) ABC stacking and Ir/Pd clusters show exclusively ABC stacking - note the Ir(111) substrate stacking is chosen to be ABC-like. During gas exposure the clusters gain in height, while simultaneously the ordering of the cluster lattice decreases. The order of ACB stacked Pt/Rh clusters decreases more rapidly, so that a weakening of the cluster binding due to ACB stacking is proposed. In addition a size reduction of the lowest cluster layer to a hexagonal arrangement of 19 atoms was observed, which seems to be the energetically favoured interface area between graphene/Ir(111) and the investigated metal clusters. Platinum clusters containing fewer than 40 atoms have been investigated with surface sensitive X-ray diffraction. The cluster height could be determined and a reduced atom distance among the cluster was observed. CO exposure decreased the in-plane atom distance even more. This effect could be reverted by a subsequent oxygen exposure (2CO + O{sub 2} → 2 CO{sub 2}). For Pt/Rh clusters with fewer than 60 atoms the element distribution was investigated and revealed an enrichment of Rh at the two topmost cluster layers. This element distribution was found for co-deposition and sequential deposition of the material and is therefore independent of the order of deposition. Oxygen exposure led to the formation of a rhodium surface oxide, which could be prevented by preceding CO exposure. In case of Ir/Pd clusters containing ∝60 atoms we found preferences for a core/shell structure with iridium atoms at core sites. Exposure to p(H{sub 2})=1 bar did not result in the formation of the palladium β-phase, so that a reduced hydrogen solubility of graphene/Ir(111) supported palladium clusters is assumed. The reduced hydrogen solubility is probably a consequence of substrate induced strain among the cluster atoms.

  15. Progress of PD-1/PD-L1 Inhibitors in Non-small Cell Lung Cancer

    Directory of Open Access Journals (Sweden)

    Zhansheng JIANG

    2017-02-01

    Full Text Available Pembrolizumab, an inhibitor target programmed death 1 (PD-1, was approved into the first line therapy in advanced non-small cell lung cancer (NSCLC. It was a milestone that immune checkpoints drugs have played an important role in the treatment system of NSCLC. The results of clinical trials revealed the superiority of PD-1/programmed death ligand 1 (PD-L1 inhibitors compared with chemotherapy in first-line, second-line and multidrug resistance phase therapy. Objective response rate (ORR was up to 80% with pembrolizumab plus chemotherapy, and progression-free survival (PFS with single pembrolizumab in first line was nearly 1 year (10.3 months, the hazard ratio for death fell by 40%. Overall survival (OS was more or less 1 year with single drug pembrolizumab, nivolumab and atezolizumab for second line therapy. PD-L1 expression was a predictor of PD-1/PD-L1 inhibitors. The positive rate of PD-L1 (more than 1% in advanced NSCLC was about 60% with little difference between the tissue types. However, there was no gold standard test of PD-L1 expression.

  16. Improved ethanol electrooxidation performance by shortening Pd-Ni active site distance in Pd-Ni-P nanocatalysts

    Science.gov (United States)

    Chen, Lin; Lu, Lilin; Zhu, Hengli; Chen, Yueguang; Huang, Yu; Li, Yadong; Wang, Leyu

    2017-01-01

    Incorporating oxophilic metals into noble metal-based catalysts represents an emerging strategy to improve the catalytic performance of electrocatalysts in fuel cells. However, effects of the distance between the noble metal and oxophilic metal active sites on the catalytic performance have rarely been investigated. Herein, we report on ultrasmall (~5 nm) Pd-Ni-P ternary nanoparticles for ethanol electrooxidation. The activity is improved up to 4.95 A per mgPd, which is 6.88 times higher than commercial Pd/C (0.72 A per mgPd), by shortening the distance between Pd and Ni active sites, achieved through shape transformation from Pd/Ni-P heterodimers into Pd-Ni-P nanoparticles and tuning the Ni/Pd atomic ratio to 1:1. Density functional theory calculations reveal that the improved activity and stability stems from the promoted production of free OH radicals (on Ni active sites) which facilitate the oxidative removal of carbonaceous poison and combination with CH3CO radicals on adjacent Pd active sites.

  17. Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

    Directory of Open Access Journals (Sweden)

    Qinghe Zheng

    2015-10-01

    Full Text Available The Pd component in the automotive three way catalyst (TWC experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C–1050 °C air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I, reduction via in situ steam reforming (SR of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd+/Pd0 and Ce3+/Ce4+ couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance.

  18. Influence of Pd-precursor on the acetoxylation activity of Pd-Sb/TiO{sub 2} catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ben-homeid, A. [Benghazi Univ. (Libyan Arab Jamahiriya). Chemistry Dept.; Kalevaru, V.N.; Radnik, J.; Luecke, B.; Martin, A. [Leibniz-Institut fuer Katalyse e.V. an der Universitaet Rostock (Germany)

    2013-11-01

    The impact of palladium precursors (e.g. chloride-PdCl{sub 2}; acetate-Pd(OAc){sub 2}; nitrate-Pd(NO{sub 3}){sub 2}) on the catalytic properties of Pd-Sb/TiO{sub 2} catalysts used for acetoxylation of toluene has been investigated. The catalysts were characterized by different techniques such as N{sub 2}-adsorption (BET-surface area and pore volume), XRD, TEM, CO-Chemisorption and XPS for better understanding of the catalytic properties of the catalysts. The acetate and nitrate-type precursors exhibited higher surface areas, pore volumes and higher dispersion of Pd, but displayed poor performance compared to chloride precursor. TEM analysis indicated that the size of Pd particles depended upon the nature of Pd-precursor. Among the three, chloride precursor exhibited bigger Pd particles. XPS results revealed that all the fresh catalysts irrespective of Pd-precursor contained Pd in oxidized state (i.e. Pd{sup +2}), while in the spent catalysts such oxidized Pd species were reduced. The catalytic performance was found to depend strongly on the nature of precursor used. Among the three, the catalysts prepared from chloride-type precursor showed much higher overall catalytic activity (68%) than those of nitrate and/or acetate type precursors. Moreover, these two precursors (acetate and nitrate) gave higher total oxidation products due to oxidative decomposition of mainly acetic acid. Furthermore, the catalyst prepared from Cl-precursor revealed easy deactivation due to coke deposition and also due to loss of Pd in the near-surface-region. (orig.)

  19. High throughput screening of Pd-alloys for H2 separation membranes studied by hydrogenography and CVM

    Energy Technology Data Exchange (ETDEWEB)

    Westerwaal, R.J.; Dam, B. [Delft University of Technology, Department of Chemical Engineering, Materials for Energy Conversion and Storage, Julianaweg 136, 2628 BL Delft (Netherlands); Den Besten, C.; Slaman, M. [Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Nanuc, D.E.; Boettger, A.J. [Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Haije, W.G. [Energy research Centre of The Netherlands, Westerduinweg 3, 1755 LE Petten (Netherlands)

    2011-01-15

    The search for and development of stable Pd-based membranes for hydrogen separation applications with resistance to hydrogen embrittlement and cracking is a challenging and time-consuming task. Membrane failure is most often caused by the occurrence of the {alpha}-{beta} phase transition during hydrogen absorption and desorption by the Pd-alloy below the critical temperature. By finding a suitable alloy with a critical temperature below room temperature, the membrane lifetime can be extended tremendously. Here we present a combinatorial approach that enables the fast screening of phase transitions in multi-component Pd-alloys for hydrogen separation membranes by experiments and thermodynamic calculations. The method is applied to the well-documented Pd-Cu alloy compositions. Hydrogenography, a compositional gradient thin film technique, is used to experimentally investigate the alloy compositions. Using a new phenomenological method to determine the critical temperature from hydrogenography measurements, we show that the experimental results and the calculations, using the Cluster Variation Method (CVM), agree well with the phase boundaries and critical temperatures reported in literature. Our results show that the combined capabilities of hydrogenography and CVM enable an efficient screening of promising multi-component alloys for which thermodynamic data are scarce or absent.

  20. Controlled synthesis of pompon-like self-assemblies of Pd nanoparticles under microwave irradiation

    International Nuclear Information System (INIS)

    Tong Xia; Zhao Yanxi; Huang Tao; Liu Hanfan; Liew, Kong Yong

    2009-01-01

    Pd nanoparticles with uniform, self-assembled pompon-like nanostructure were synthesized by thermal decomposition of palladium acetate under microwave irradiation with methyl isobutyl ketone (MIBK) as a solvent in the presence of a little amount of ethylene glycol (EG) and KOH without using any special stabilizers. The as-synthesized Pd nano-pompons were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. The results show that the as-prepared Pd nano-pompons with the average diameters in the range of 28-81 nm were self-assemblies organized by hundreds of smaller primary nanoparticles with an average dimension of about 2.4 nm. The sizes of Pd nano-pompons can be well controlled by adjusting the concentration of palladium acetate. A little amount of EG and KOH also plays an important role in controlling the size, uniformity and dispersion of Pd nano-pompons. The Pd nano-pompons can be easily supported on γ-Al 2 O 3 and their catalytic activity was examined preliminarily.

  1. Predictive Maintenance (PdM) Centralization for Significant Energy Savings

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Dale

    2010-09-15

    Cost effective predictive maintenance (PdM) technologies and basic energy calculations can mine energy savings form processes or maintenance activities. Centralizing and packaging this information correctly empowers facility maintenance and reliability professionals to build financial justification and support for strategies and personnel to weather global economic downturns and competition. Attendees will learn how to: Systematically build a 'pilot project' for applying PdM and tracking systems; Break down a typical electrical bill to calculate energy savings; Use return on investment (ROI) calculations to identify the best and highest value options, strategies and tips for substantiating your energy reduction maintenance strategies.

  2. Electrocatalytic Reduction-oxidation of Chlorinated Phenols using a Nanostructured Pd-Fe Modified Graphene Catalyst

    International Nuclear Information System (INIS)

    Shi, Qin; Wang, Hui; Liu, Shaolei; Pang, Lei; Bian, Zhaoyong

    2015-01-01

    A Pd-Fe modified graphene (Pd-Fe/G) catalyst was prepared by the Hummers oxidation method and bimetallic co-deposition method. The catalyst was then characterized by various characterization techniques and its electrochemical property toward the electrocatalytic reduction-oxidation of chlorinated phenols was investigated by using cyclic voltammetry and differential pulse voltammetry. The results of the characterization show that the Pd-Fe/G catalyst in which the weight proportion of Pd and Fe is 1:1 has an optimal surface performance. The diameter of the Pd-Fe particles is approximately 5.2 ± 0.3 nm, with a uniform distribution on the supporting graphene. This is smaller than the Pd particles of a Pd-modified graphene (Pd/G) catalyst. The Pd-Fe/G catalyst shows a higher electrocatalytic activity than the Pd/G catalyst for reductive dechlorination when feeding with hydrogen gas. The reductive peak potentials of −0.188 V, −0.836 V and −0.956 V in the DPV curves are attributed to the dechlorination of ortho-Cl, meta-Cl, and para-Cl in 2-chlorophenol, 3-chlorophenol and 4-chlorophenol, respectively. In accordance with an analysis of the frontier orbital theory, the order of ease of dechlorination with Pd-Fe/G catalyst is 2-chlorophenol > 3-chlorophenol > 4-chlorophenol. The Pd-Fe/G catalyst has a greater activity than the Pd/G catalyst in accelerating the two-electron reduction of O_2 to H_2O_2, which is attributed to the higher current of the reduction peak at approximately −0.40 V when feeding with oxygen gas. Therefore, the Pd-Fe/G catalyst exhibits a higher electrocatalytic activity than the Pd/G catalyst for the reductive dechlorination and acceleration of the two-electron reduction of O_2 to H_2O_2.

  3. Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

    Directory of Open Access Journals (Sweden)

    Vineetha Mukundan

    2014-03-01

    Full Text Available Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2 alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C. The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.

  4. Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation.

    Science.gov (United States)

    Narula, Chaitanya K; Allard, Lawrence F; Moses-DeBusk, Melanie; Stocks, G Malcom; Wu, Zili

    2017-04-03

    New convenient wet-chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms, however, the single supported atoms on inert substrates (e.g. alumina) are limited to adatoms and cations of Pt, Pd, and Ru. Previously, we have found that single supported Pt atoms are remarkable NO oxidation catalysts. In contrast, we report that Pd single atoms are completely inactive for NO oxidation. The diffuse reflectance infra-red spectroscopy (DRIFTS) results show the absence of nitrate formation on catalyst. To explain these results, we explored modified Langmuir-Hinshelwood type pathways that have been proposed for oxidation reactions on single supported atom. In the first pathway, we find that there is energy barrier for the release of NO 2 which prevent NO oxidation. In the second pathway, our results show that there is no driving force for the formation of O=N-O-O intermediate or nitrate on single supported Pd atoms. The decomposition of nitrate, if formed, is an endothermic event.

  5. Efficient Pd@MIL-101(Cr) hetero-catalysts for 2-butyne-1,4-diol hydrogenation exhibiting high selectivity

    KAUST Repository

    Yin, Dongdong

    2017-01-05

    Pd@MIL-101(Cr) hetero-catalysts have been successfully prepared using the metal-organic chemical vapour deposition (MOCVD) approach, by choosing [Pd(η-CH)(η-CH)] as a volatile precursor, and the hydrothermally stable metal-organic framework, MIL-101(Cr) as a support. The prepared Pd@MIL-101(Cr) hetero-catalysts characterized with various analytical techniques, exhibited highly monodispersed immobilized Pd nanoparticles in the MIL-101(Cr) cavities, while retaining the pristine crystallinity and porosity. The intact hybrid Pd@MIL-101(Cr) has been demonstrated to be an efficient catalyst for 2-butyne-1,4-diol hydrogenation with excellent activity, stability and selectivity (2-butene-1,4-diol (>94%)).

  6. Improved resection and prolonged overall survival with PD-1-IRDye800CW fluorescence probe-guided surgery and PD-1 adjuvant immunotherapy in 4T1 mouse model

    Directory of Open Access Journals (Sweden)

    Du Y

    2017-11-01

    Full Text Available Yang Du,1,2,* Ting Sun,3,* Xiaolong Liang,4,* Yuan Li,3 Zhengyu Jin,3 Huadan Xue,3 Yihong Wan,5 Jie Tian1,2 1CAS Key Laboratory of Molecular Imaging, 2The State Key Laboratory of Management and Control for Complex Systems, Institute of Automation, Chinese Academy of Sciences, 3Department of Radiology, Peking Union Medical College Hospital, 4Department of Ultrasound, Peking University Third Hospital, Beijing, China; 5Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA *These authors contributed equally to this work Abstract: An intraoperative technique to accurately identify microscopic tumor residuals could decrease the risk of positive surgical margins. Several lines of evidence support the expression and immunotherapeutic effect of PD-1 in breast cancer. Here, we sought to develop a fluorescence-labeled PD-1 probe for in vivo breast tumor imaging and image-guided surgery. The efficacy of PD-1 monoclonal antibody (PD-1 mAb as adjuvant immunotherapy after surgery was also assessed. PD-1-IRDye800CW was developed and examined for its application in tumor imaging and image-guided tumor resection in an immunocompetent 4T1 mouse tumor model. Fluorescence molecular imaging was performed to monitor probe biodistribution and intraoperative imaging. Bioluminescence imaging was performed to monitor tumor growth and evaluate postsurgical tumor residuals, recurrences, and metastases. The PD-1-IRDye800CW exhibited a specific signal at the tumor region compared with the IgG control. Furthermore, PD-1-IRDye800CW-guided surgery combined with PD-1 adjuvant immunotherapy inhibited tumor regrowth and microtumor metastases and thus improved survival rate. Our study demonstrates the feasibility of using PD-1-IRDye800CW for breast tumor imaging and image-guided tumor resection. Moreover, PD-1 mAb adjuvant immunotherapy reduces cancer recurrences and metastases emanating from tumor residuals. Keywords: PD-1, programmed cell

  7. Bimetallic Au-decorated Pd catalyst for the liquid phase hydrodechlorination of 2,4-dichlorophenol

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Juan [School of the Environment, Donghua University, Shanghai 201620 (China); Chen, Huan, E-mail: hchen404@njust.edu.cn [Key Laboratory of Jiangsu Province for Chemical Pollution Control and Resources Reuse, School of Environmental & Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Chen, Quanyuan; Huang, Zhaolu [School of the Environment, Donghua University, Shanghai 201620 (China)

    2016-11-30

    Graphical abstract: 2,4-Dichlorophenol can be converted to phenol via the catalytic HDC method over Pd-Au/CNTs and the catalytic activity first increased and then decreased with Au content. - Highlights: • Bimetallic catalysts had smaller metal particles and larger number of exposed active site than the monometallic catalysts. • The cationization of Pd particles increased with Au content in the bimetallic catalysts. • The bimetallic catalysts exhibited higher catalytic activities for HDC of 2,4-DCP than the monometallic counterparts. • The concerted pathway for HDC of 2,4-DCP was more predominant with increasing Au content in the bimetallic catalyst. - Abstract: Monometallic and bimetallic Pd-Au catalysts supported on multi-walled carbon nanotubes (CNTs) with varied Au cooperation amounts were prepared using the complexing-reduction method in the presence of tetrahydrofuran (THF). The liquid phase catalytic hydrodechlorination (HDC) of 2,4-dichlorophenol (2,4-DCP) was investigated over these bimetallic catalysts. The catalysts were characterized by N{sub 2} adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and H{sub 2} chemisorption. Characterization results showed that the co-reduction of Pd and Au mainly formed alloy-like structure. The bimetallic catalysts had smaller metal particles and larger numbers of exposed active site than that of monometallic catalysts. In addition, compared with Pd(1.7)/CNTs and Au(0.4)/CNTs, the binding energies of Pd 3d{sub 5/2} shifted to higher positions while that of Au 4f{sub 7/2} had negative shifts in the Pd-Au bimetallic catalysts, which can be ascribed to the electrons transferred from metal Pd to Au and the cationization of Pd particles was enhanced. Accordingly, the bimetallic Pd-Au particles with different Au contents in the catalysts exhibited varied synergistic effects for the catalytic HDC of 2,4-DCP, with Pd(1.8)Au(0.4)/CNTs having the highest

  8. Study of Pd-Sn/Al{sub 2}O{sub 3} catalysts prepared by an oxide colloidal route; Etude de catalyseurs Pd-Sn/Al{sub 2}O{sub 3} prepares par voie colloidale oxyde

    Energy Technology Data Exchange (ETDEWEB)

    Verdier, St.

    2001-09-01

    The oxide colloidal route, developed in the laboratory for mono-metallic catalysts, consists in preparing a metallic oxide hydro-sol which leads to the supported catalyst after deposition onto a support and an activation stage. In this work, this method has been adapted to the preparation of alumina supported bimetallic Pd-Sn catalysts to determine its interest for the control of the properties of the bimetallic phase (size, composition and structure). In the preliminary study concerning tin oxide sols, SnO{sub 2} (size=2,3 nm) and Sn{sub 6}O{sub 4}(OH){sub 4} (size = 25 nm) nano-particles were synthesized by neutralization respectively for tin(IV) and tin(H). The control through the pH of the aggregation of the PdO and SnO{sub 2} particles revealed that increasing oxide solubility promotes integral re-dispersion of the oxide particles. To synthesize oxide bimetallic sols, three strategies were defined. Copolymerization (formation of a mixed oxide nano-sol by cross condensation of both metals) does not lead to a mixed oxide Pd-Sn phase. Surface precipitation (neutralization of the second metal in the presence of the first oxide sol) yields nano-particles of both oxides in close interaction. Adsorption (adsorption of the second metal onto the first oxide sol) significantly occurs when contacting tin with a basic PdO sol (hydrolytic adsorption). The characterization and the assessment of the catalytic properties (selective hydrogenation of buta-1,3-diene) of the catalysts prepared by deposition of oxide bimetallic sols showed that the oxide colloidal route allows the control of the properties of the supported bimetallic phase. Moreover, our results display that both Pd-Sn alloy formation and,aggregation of the metallic particles contribute to increase the selectivity for this reaction. (author)

  9. Ultrahigh-sensitive detection of molecules produced in catalytic reactions by uni-atomic-composition bi-element clusters supported on solid substrate

    International Nuclear Information System (INIS)

    Yasumatsu, H; Fukui, N

    2013-01-01

    An apparatus has been developed for measuring catalytic activities of uni-atomic-composition bi-element clusters supported on a solid substrate. The cluster sample is prepared by irradiating a cluster-ion beam having the uni-atomic composition onto the substrate on a soft-landing condition in an ultra-high vacuum. The catalytic activity is measured by temperature-programmed desorption (TPD) mass analysis. Molecules at a density as low as 3 cm −3 have been detected with an ultrahigh-sensitive TPD mass spectrometer consisting of a cylindrical electron gun, a quadrupole mass filter and a micro-channel-plate ion-detector. The high reproducibility has been achieved by careful calibration of the TPD mass spectrometer. As a benchmark example, thermal oxidation of CO catalysed on Pt 30 disks supported on a silicon surface was studied. The CO 2 products have been successfully observed at the Pt 30 density as low as 3 × 10 12 clusters in a circular area of 8 mm in diameter at the ramping rate of the sample temperature as low as 0.3 K s −1 .

  10. Crystal clear: visualizing the intervention mechanism of the PD-1/PD-L1 interaction by two cancer therapeutic monoclonal antibodies

    Directory of Open Access Journals (Sweden)

    Shuguang Tan

    2016-11-01

    Full Text Available Abstract Antibody-based PD-1/PD-L1 blockade therapies have taken center stage in immunotherapies for cancer, with multiple clinical successes. PD-1 signaling plays pivotal roles in tumor-driven T-cell dysfunction. In contrast to prior approaches to generate or boost tumor-specific T-cell responses, antibody-based PD-1/PD-L1 blockade targets tumor-induced T-cell defects and restores pre-existing T-cell function to modulate antitumor immunity. In this review, the fundamental knowledge on the expression regulations and inhibitory functions of PD-1 and the present understanding of antibody-based PD-1/PD-L1 blockade therapies are briefly summarized. We then focus on the recent breakthrough work concerning the structural basis of the PD-1/PD-Ls interaction and how therapeutic antibodies, pembrolizumab targeting PD-1 and avelumab targeting PD-L1, compete with the binding of PD-1/PD-L1 to interrupt the PD-1/PD-L1 interaction. We believe that this structural information will benefit the design and improvement of therapeutic antibodies targeting PD-1 signaling.

  11. Interaction of Pd single atoms with different CeO2 crystal planes: A first-principles study

    Science.gov (United States)

    He, Bingling; Wang, Jinlong; Ma, Dongwei; Tian, Zhixue; Jiang, Lijuan; Xu, Yan; Cheng, Sujun

    2018-03-01

    The adsorption of single Pd atoms on the various CeO2 surfaces, including (111), (110), and (100), has been studied based on the first-principles calculations. It is found that, according to the calculated adsorption energy, interaction strength between Pd and the three CeO2 surfaces follows the order of (100) > (110) > (111). Interestingly, the effect of the electron localization on the surface Ce ions due to the Pd adsorption on its adsorption stability is more significant for the (110) surface than that for the (111) and (100) surfaces. We also find that the formal oxidation states of Pd0, Pdδ+ (δ < 1) and Pd1+ may appear on the CeO2 (111) surface, and Pdδ+ (δ < 1) and Pd1+ could coexist on the CeO2 (100) surfaces. However, under suitable conditions the CeO2 (110) surface may be covered with Pd2+ ions. Present theoretical results clearly suggest that the interaction between Pd and CeO2 nanocrystals significantly depends on the crystal planes of CeO2. It is expected that our study will give useful insights into the effect of CeO2 crystal plane on the physicochemical and catalytic properties of CeO2 supported Pd catalyst.

  12. Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al2O3 templates

    Science.gov (United States)

    Maximenko, A.; Fedotova, J.; Marszałek, M.; Zarzycki, A.; Zabila, Y.

    2016-02-01

    Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L10 structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment.

  13. Effects of training and weight support on muscle activation in Parkinson's disease

    DEFF Research Database (Denmark)

    Rose, Martin Høyer; Løkkegaard, Annemette; Sonne-Holm, Stig

    2013-01-01

    The aim of this study was to investigate the effect of high-intensity locomotor training on knee extensor and flexor muscle activation and adaptability to increased body-weight (BW) support during walking in patients with Parkinson's disease (PD). Thirteen male patients with idiopathic PD and eight...... healthy participants were included. The PD patients completed an 8-week training program on a lower-body, positive-pressure treadmill. Knee extensor and flexor muscles activation during steady treadmill walking (3km/h) were measured before, at the mid-point, and after training. Increasing BW support...... decreased knee extensor muscle activation (normalization) and increased knee flexor muscle activation (abnormal) in PD patients when compared to healthy participants. Training improved flexor peak muscle activation adaptability to increased (BW) support during walking in PD patients. During walking without...

  14. Personality traits related to juvenile myoclonic epilepsy: MRI reveals prefrontal abnormalities through a voxel-based morphometry study.

    Science.gov (United States)

    de Araújo Filho, Gerardo Maria; Jackowski, Andrea Parolin; Lin, Katia; Guaranha, Mirian S B; Guilhoto, Laura M F F; da Silva, Henrique Hattori; Caboclo, Luís Otávio Sales Ferreira; Júnior, Henrique Carrete; Bressan, Rodrigo Affonseca; Yacubian, Elza Márcia T

    2009-06-01

    Studies involving juvenile myoclonic epilepsy (JME) patients have demonstrated an elevated prevalence of cluster B personality disorders (PD) characterized as emotional instability, immaturity, unsteadiness, lack of discipline, and rapid mood changes. We aimed to verify a possible correlation between structural brain abnormalities in magnetic resonance image (MRI) and the PD in JME using voxel-based morphometry (VBM). Sixteen JME patients with cluster B PD, 38 JME patients without psychiatric disorders, and 30 healthy controls were submitted to a psychiatric evaluation through SCID I and II and to a MRI scan. Significant reduction in thalami and increase in mesiofrontal and frontobasal regions' volumes were observed mainly in JME patients with PD. Structural alterations of the orbitofrontal cortex (OFC), involved in regulation of mood reactivity, impulsivity, and social behavior, were also observed. This study supports the hypothesis of frontobasal involvement in the pathophysiology of cluster B PD related to JME.

  15. Measurement of benzenethiol adsorption to nanostructured Pt, Pd, and PtPd films using Raman spectroelectrochemistry.

    Science.gov (United States)

    Pomfret, Michael B; Pietron, Jeremy J; Owrutsky, Jeffrey C

    2010-05-04

    Raman spectroscopy and electrochemical methods were used to study the behavior of the model adsorbate benzenethiol (BT) on nanostructured Pt, Pd, and PtPd electrodes as a function of applied potential. Benzenethiol adsorbs out of ethanolic solutions as the corresponding thiolate, and voltammetric stripping data reveal that BT is oxidatively removed from all of the nanostructured metals upon repeated oxidative and reductive cycling. Oxidative stripping potentials for BT increase in the order Pt oxidizing potentials via cleavage of the Pt-S bond. In contrast, on nanoscale Pd and PtPd, BT is irreversibly lost due to cleavage of BT C-S bonds at oxidizing potentials, which leaves adsorbed sulfur oxides on Pd and PtPd films and effects the desulfurization of BT. While Pd and PtPd films are less sulfur-resistant than Pt films, palladium oxides, which form at higher potentials than Pt oxides, oxidatively desulfurize BT. In situ spectroelectrochemical Raman spectroscopy provides real-time, chemically specific information that complements the cyclic voltammetric data. The combination of these techniques affords a powerful and convenient method for guiding the development of sulfur-tolerant PEMFC catalysts.

  16. Towards Cluster-Assembled Materials of True Monodispersity in Size and Chemical Environment: Synthesis, Dynamics and Activity

    Science.gov (United States)

    2016-10-27

    thermodynamic and kinetic cluster size control on periodically wet - table surfaces, new questions came up concerning the link between diffusivity and...from ring-hollow (H,F) to ring-bridge (B). Left: STM annealing series (50×50 nm2), Moiré cell scheme and cluster position evaluation. Pd clus- ters...growth at T>700 K. Below: Measured and theoretically simulated (insets) STM images of various stages in the dehydrogenation process upon annealing

  17. Electro-deposition of Pd on Carbon paper and Ni foam via surface limited redox-replacement reaction for oxygen reduction reaction

    International Nuclear Information System (INIS)

    Modibedi, Remegia M.; Mathe, Mkhulu K.; Motsoeneng, Rapelang G.; Khotseng, Lindiwe E.; Ozoemena, Kenneth I.; Louw, Eldah K.

    2014-01-01

    Pd nanostructured catalysts were electrodeposited by surface-limited redox replacement reactions using the electrochemical atomic layer deposition technique. Carbon paper and Ni foam were used as substrates for the electrodeposition of the metal. Supported nanostructured Pd electrodes were characterized using electrochemical methods and scanning electron microscopy. Carbon paper and Ni foam produced good quality deposits with some agglomeration on Ni foam. The EDX profiles confirmed the presence of Pd particles. Cyclic voltammograms of the electrodeposited Pd on substrates showed features characteristic of polycrystalline Pd electrodes. In the acidic electrolyte a very weak oxygen reduction reaction (ORR) activity was observed on Pd/Carbon paper electrode when compared to Pd/Ni foam electrode. The Pd/Ni foam electrode showed improved ORR activity in alkaline medium

  18. Structural Biology of the Immune Checkpoint Receptor PD-1 and Its Ligands PD-L1/PD-L2

    NARCIS (Netherlands)

    Zak, Krzysztof M.; Grudnik, Przemyslaw; Magiera, Katarzyna; Dömling, Alexander; Dubin, Grzegorz; Holak, Tad A.

    2017-01-01

    Cancer cells can avoid and suppress immune responses through activation of inhibitory immune checkpoint proteins, such as PD-1, PD-L1, and CTLA-4. Blocking the activities of these proteins with monoclonal antibodies, and thus restoring T cell function, has delivered breakthrough therapies against

  19. Cooperative Data Sharing: Simple Support for Clusters of SMP Nodes

    Science.gov (United States)

    DiNucci, David C.; Balley, David H. (Technical Monitor)

    1997-01-01

    Libraries like PVM and MPI send typed messages to allow for heterogeneous cluster computing. Lower-level libraries, such as GAM, provide more efficient access to communication by removing the need to copy messages between the interface and user space in some cases. still lower-level interfaces, such as UNET, get right down to the hardware level to provide maximum performance. However, these are all still interfaces for passing messages from one process to another, and have limited utility in a shared-memory environment, due primarily to the fact that message passing is just another term for copying. This drawback is made more pertinent by today's hybrid architectures (e.g. clusters of SMPs), where it is difficult to know beforehand whether two communicating processes will share memory. As a result, even portable language tools (like HPF compilers) must either map all interprocess communication, into message passing with the accompanying performance degradation in shared memory environments, or they must check each communication at run-time and implement the shared-memory case separately for efficiency. Cooperative Data Sharing (CDS) is a single user-level API which abstracts all communication between processes into the sharing and access coordination of memory regions, in a model which might be described as "distributed shared messages" or "large-grain distributed shared memory". As a result, the user programs to a simple latency-tolerant abstract communication specification which can be mapped efficiently to either a shared-memory or message-passing based run-time system, depending upon the available architecture. Unlike some distributed shared memory interfaces, the user still has complete control over the assignment of data to processors, the forwarding of data to its next likely destination, and the queuing of data until it is needed, so even the relatively high latency present in clusters can be accomodated. CDS does not require special use of an MMU, which

  20. Highly active carbon supported ternary PdSnPtx (x=0.1-0.7) catalysts for ethanol electro-oxidation in alkaline and acid media.

    Science.gov (United States)

    Wang, Xiaoguang; Zhu, Fuchun; He, Yongwei; Wang, Mei; Zhang, Zhonghua; Ma, Zizai; Li, Ruixue

    2016-04-15

    A series of trimetallic PdSnPtx (x=0.1-0.7)/C catalysts with varied Pt content have been synthesized by co-reduction method using NaBH4 as a reducing agent. These catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperometry (CA). The electrochemical results show that, after adding a minor amount of Pt dopant, the resultant PdSnPtx/C demonstrated more superior catalytic performance toward ethanol oxidation as compared with that of mono-/bi-metallic Pd/C or PdSn/C in alkaline solution and the PdSnPt0.2/C with optimal molar ratio reached the best. In acid solution, the PdSnPt0.2/C also depicted a superior catalytic activity relative to the commercial Pt/C catalyst. The possible enhanced synergistic effect between Pd, Sn/Sn(O) and Pt in an alloyed state should be responsible for the as-revealed superior ethanol electro-oxidation performance based upon the beneficial electronic effect and bi-functional mechanism. It implies the trimetallic PdSnPt0.2/C with a low Pt content has a promising prospect as anodic electrocatalyst in fields of alkali- and acid-type direct ethanol fuel cells. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Effect of the nanosized TiO2 particles in Pd/C catalysts as cathode materials in direct methanol fuel cells.

    Science.gov (United States)

    Choi, Mahnsoo; Han, Choonsoo; Kim, In-Tae; Lee, Ji-Jung; Lee, Hong-Ki; Shim, Joongpyo

    2011-07-01

    Pd-TiO2/C catalysts were prepared by impregnating titanium dioxide (TiO2) on carbon-supported Pd (Pd/C) for use as the catalyst for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). Transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried to confirm the distribution, morphology and structure of Pd and TiO2 on the carbon support. In fuel cell test, we confirmed that the addition of TiO2 nanoparticles make the improved catalytic activity of oxygen reduction. The electrochemical characterization of the Pd-TiO2/C catalyst for the ORR was carried out by cyclic voltammetry (CV) in the voltage window of 0.04 V to 1.2 V with scan rate of 25 mV/s. With the increase in the crystallite size of TiO2, the peak potential for OH(ads) desorption on the surface of Pd particle shifted to higher potential. This implies that TiO2 might affect the adsorption and desorption of oxygen molecules on Pd catalyst. The performance of Pd-TiO2/C as a cathode material was found to be similar to or better performance than that of Pt/C.

  2. Structure and magnetism of ultrathin Co and Fe films epitaxially grown on Pd/Cu(0 0 1)

    International Nuclear Information System (INIS)

    Lu, Y.F.; Przybylski, M.; Yan, L.; Barthel, J.; Meyerheim, H.L.; Kirschner, J.

    2005-01-01

    A contribution originating from the Co/Pd and Fe/Pd interfaces to the magneto-optical Kerr effect (MOKE) rotation is analyzed for Co and/or Fe films grown on a Pd-buffer-monolayer on Cu(0 0 1). A clear increase of the MOKE signal in comparison to the Co(Fe) films grown directly on Cu(0 0 1) is detected. An interpretation is supported by similar observations for Co films grown on Pd(1 1 0) and Pd(0 0 1). In particular, the sign reversal of the Kerr loops with increasing thickness of the Co(Fe) films is discussed. Magneto-optical effects are separated from the real magnetization and its dependence on the film thickness

  3. The PD-1/PD-L1 complex resembles the antigen-binding Fv domains of antibodies and T cell receptors

    Energy Technology Data Exchange (ETDEWEB)

    Lin, David Yin-wei; Tanaka, Yoshimasa; Iwasaki, Masashi; Gittis, Apostolos G.; Su, Hua-Poo; Mikami, Bunzo; Okazaki, Taku; Honjo, Tasuku; Minato, Nagahiro; Garboczi, David N. (NIH); (Kyoto)

    2008-07-29

    Signaling through the programmed death 1 (PD-1) inhibitory receptor upon binding its ligand, PD-L1, suppresses immune responses against autoantigens and tumors and plays an important role in the maintenance of peripheral immune tolerance. Release from PD-1 inhibitory signaling revives 'exhausted' virus-specific T cells in chronic viral infections. Here we present the crystal structure of murine PD-1 in complex with human PD-L1. PD-1 and PD-L1 interact through the conserved front and side of their Ig variable (IgV) domains, as do the IgV domains of antibodies and T cell receptors. This places the loops at the ends of the IgV domains on the same side of the PD-1/PD-L1 complex, forming a surface that is similar to the antigen-binding surface of antibodies and T cell receptors. Mapping conserved residues allowed the identification of residues that are important in forming the PD-1/PD-L1 interface. Based on the structure, we show that some reported loss-of-binding mutations involve the PD-1/PD-L1 interaction but that others compromise protein folding. The PD-1/PD-L1 interaction described here may be blocked by antibodies or by designed small-molecule drugs to lower inhibitory signaling that results in a stronger immune response. The immune receptor-like loops offer a new surface for further study and potentially the design of molecules that would affect PD-1/PD-L1 complex formation and thereby modulate the immune response.

  4. RuPd, RuCo, PdCo and RuPdCo materials as candidates for cathode catalyzers in PEM fuel cells; Materiales RuPd, RuCo, PdCo y RuPdCo como candidatos a catalizadores catodicos en celdas de combustible tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Leyva Noyola, Fatima; Solorza Feria, Omar [Centro de Investigacion y Estudios Superiores del IPN, Mexico, D.F. (Mexico)]. E-mail: fleyva@cinvestav.mx

    2009-09-15

    This work reports on the catalytic activity of RuPd, RuCo, PdCo and RuPdCo material for oxygen reduction reaction (ORR). These materials were synthesized using chemical reduction with NaBH{sub 4} as a reducing agent in THF, in ambient temperature and pressure conditions. The evaluation of the catalytic activity was done using cyclic voltamperometry (CV) and rotary disc electrode (RDE) in H{sub 2}SO{sub 4} 0.5 M. The kinetic results showed that the electrochemical reaction involves 4 electrons and the transfer of the first electron is the determinant stage. The values of {alpha}, i0 and the Tafel slope were very similar for the four materials studied, around 0.4, 5x10{sup -6} mA cm{sup -2} and 60 mV dec-1, respectively. Although these values are less than those reported for nanostructured platinum, they are better than those reported for other materials such as pure Pd, which enables them to be considered as cathode catalysts for a proton exchange membrane fuel cell. [Spanish] En este trabajo se reporta la actividad catalitica de los materiales RuPd, RuCo, PdCo y RuPdCo para la reaccion de reduccion de oxigeno (RRO). Estos materiales fueron sintetizados por el metodo de reduccion quimica, usando NaBH{sub 4} como agente reductor en THF, en condiciones de temperatura y presion ambiental. La evaluacion de la actividad catalitica fue realizada usando Voltamperometria Ciclica (VC) y Electrodo Disco Rotatorio (EDR) en H{sub 2}SO{sub 4} 0.5 M. Los resultados cineticos mostraron que la reaccion electroquimica procede por la via de 4 electrones y la etapa determinante es la transferencia del primer electron. Los valores de {alpha}, i0 y pendiente de Tafel fueron muy similares para los 4 materiales estudiados, siendo estos de alrededor de 0.4, 5x10{sup -6} mA cm{sup -2} y 60 mV dec{sup -1}, respectivamente. Sin embargo, aun cuando estos valores son menores que los reportados para platino nanoestructurado, son mejores que los reportados para otros materiales como el Pd puro

  5. Feasibility test for production and separation of 103Pd

    International Nuclear Information System (INIS)

    Szuecs, Z.; Takacs, S.; Hunyadi, M.; Gacsi, Z.; Zeevaart, J.R.

    2011-01-01

    Complete text of publication follows. 103 Pd as a well-known Auger-emitter is commonly employed in brachytherapy, but the ultra-short range stopping of Auger-electrons can be more potentially exploited in applications of targeted radionuclide therapy in the future. The no-carrier-added production of 103 Pd is practically possible through charged particle induced reactions. However, separation techniques of 103 Pd from the target material (typically Rh), as well as its recovery by wet chemistry are expensive, and yields high amounts of radioactive waste. An alternative and more efficient procedure, called drydistillation method (DDM), is based on differences between the isothermal vapor pressures of the radionuclide element and the target element. In an appropriately selected temperature region the diffusion and out-gassing rates of radionuclides from the solid matrix of the target material are enhanced. Optimal irradiation parameters were determined in previous experiments at ATOMKI. Separation of 103 Pd was demonstrated at the Isotope Separator Laboratory with an evaporating-condensing system (Fig. 1). Figure 1. Evaporation-condensation system at the Isotope Separator Laboratory of ATOMKI. The irradiated Rh foil was kept above 1800?C in vacuum for several hours. The evaluation of γ-spectra of the Rh foil and the 103 Pd condensed on a low-temperature substrate (Fig. 2). The analysis resulted in a radiochemical yield of about 99.5% for 103 Pd and a radionuclidic purity of better than 99% with respect to the level of 101 Rh in the end product. Acknowledgement. The work was partly supported by the Hungarian TeT Bilateral Cooperation (OMFB- 00138/2009) and by the South African NRF (UID 68768).

  6. Electrocatalytic oxidation of hydrazine and hydroxylamine by graphene oxide-Pd nanoparticle-modified glassy carbon electrode.

    Science.gov (United States)

    Lee, Eunhee; Kim, Daekun; You, Jung-Min; Kim, Seul Ki; Yun, Mira; Jeon, Seungwon

    2012-12-01

    Pd nanoparticle catalysts supported by thiolated graphene oxide (tGO) on a glassy carbon electrode (GCE), and denoted as tGO-Pd/GCE, are used in this study for the electrochemical determination of hydroxylamine and hydrazine. The physicochemical properties of tGO-Pd were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). They showed strong catalytic activity toward the oxidation of hydroxylamine and hydrazine. Cyclic voltammetry (CV) and amperometry were used to characterize the sensors' performances. The detection limits of hydroxylamine and hydrazine by tGO-Pd/GCE were 0.31 and 0.25 microM (s/n = 3), respectively. The sensors' sensitivity, selectivity, and stability were also investigated.

  7. The role of the poet in Plato's ideal cities of Callipolis and Magnesia

    Directory of Open Access Journals (Sweden)

    Gerard Naddaf

    2007-12-01

    Full Text Available Plato's attitude toward the poets and poetry has always been a flashpoint of debate, controversy and notoriety, but most scholars have failed to see their central role in the ideal cities of the Republic and the Laws, that is, Callipolis and Magnesia. In this paper, I argue that in neither dialogue does Plato "exile" the poets, but, instead, believes they must, like all citizens, exercise the expertise proper to their profession, allowing them the right to become full-fledged participants in the productive class. Moreover, attention to certain details reveals that Plato harnesses both positive and negative factors in poetry to bring his ideal cities closer to a practical realization. The status of the poet and his craft in this context has rarely to my knowledge been addressed.A atitude de Platão com relação aos poetas e à poesia tem sempre sido um ponto de debate, controvérsia e notoriedade, mas a maioria dos estudiosos não consegue ver seu papel central nas cidades ideais da República e das Leis, ou seja, Callipolis e Magnésia. Neste artigo, defendo que em nenhum dos dois diálogos Platão exila os poetas, mas, ao contrário, acredita que eles devem, como todos os cidadãos, exercitar a competência própria à sua profissão, permitindo-lhes o direito de se tornarem participantes com todos os direitos da classe produtora. Principalmente, se prestarmos a atenção devida em certos detalhes, veremos que Platão controla tanto os fatores positivos, como os negativos na poesia, para aproximar mais suas cidades ideais da realização prática. A meu ver, o estatuto do poeta e de sua habilidade, nesse contexto, foram raramente estudados.

  8. Pd-Pt Catalysts on Mesoporous SiO2-Al2O3 with Superior Activity for HDS of 4,6-Dimethyldibenzothiophene: Effect of Metal Loading and Support Composition

    Czech Academy of Sciences Publication Activity Database

    Vít, Zdeněk; Gulková, Daniela; Kaluža, Luděk; Kupčík, Jaroslav

    2015-01-01

    Roč. 179, DEC 2015 (2015), s. 44-53 ISSN 0926-3373 R&D Projects: GA ČR GAP106/11/0902 Institutional support: RVO:67985858 ; RVO:61388980 Keywords : Pd-Pt catalyst * mesoporous silica-alumina * 4,6-DMDBT Subject RIV: CF - Physical ; Theoretical Chemistry ; CA - Inorganic Chemistry (UACH-T) Impact factor: 8.328, year: 2015

  9. CO tolerance of PdPt/C and PdPtRu/C anodes for PEMFC

    International Nuclear Information System (INIS)

    Garcia, Amanda C.; Paganin, Valdecir A.; Ticianelli, Edson A.

    2008-01-01

    The performance of H 2 /O 2 proton exchange membrane fuel cells (PEMFCs) fed with CO-contaminated hydrogen was investigated for anodes with PdPt/C and PdPtRu/C electrocatalysts. The physicochemical properties of the catalysts were characterized by energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD) and 'in situ' X-ray absorption near edge structure (XANES). Experiments were conducted in electrochemical half and single cells by cyclic voltammetry (CV) and I-V polarization measurements, while DEMS was employed to verify the formation of CO 2 at the PEMFC anode outlet. A quite high performance was achieved for the PEMFC fed with H 2 + 100 ppm CO with the PdPt/C and PdPtRu/C anodes containing 0.4 mg metal cm -2 , with the cell presenting potential losses below 200 mV at 1 A cm -2 , with respect to the system fed with pure H 2 . For the PdPt/C catalysts no CO 2 formation was seen at the PEMFC anode outlet, indicating that the CO tolerance is improved due to the existence of more free surface sites for H 2 electrooxidation, probably due to a lower Pd-CO interaction compared to pure Pd or Pt. For PdPtRu/C the CO tolerance may also have a contribution from the bifunctional mechanism, as shown by the presence of CO 2 in the PEMFC anode outlet

  10. Electronic structure of metal clusters

    International Nuclear Information System (INIS)

    Wertheim, G.K.

    1989-01-01

    Photoemission spectra of valence electrons in metal clusters, together with threshold ionization potential measurements, provide a coherent picture of the development of the electronic structure from the isolated atom to the large metallic cluster. An insulator-metal transition occurs at an intermediate cluster size, which serves to define the boundary between small and large clusters. Although the outer electrons may be delocalized over the entire cluster, a small cluster remains insulating until the density of states near the Fermi level exceeds 1/kT. In large clusters, with increasing cluster size, the band structure approaches that of the bulk metal. However, the bands remain significantly narrowed even in a 1000-atom cluster, giving an indication of the importance of long-range order. The core-electron binding-energy shifts of supported metal clusters depend on changes in the band structure in the initial state, as well as on various final-state effects, including changes in core hole screening and the coulomb energy of the final-state charge. For cluster supported on amorphous carbon, this macroscopic coulomb shift is often dominant, as evidenced by the parallel shifts of the core-electron binding energy and the Fermi edge. Auger data confirm that final-state effects dominate in cluster of Sn and some other metals. Surface atom core-level shifts provide a valuable guide to the contributions of initial-state changes in band structure to cluster core-electron binding energy shifts, especially for Au and Pt. The available data indicate that the shift observed in supported, metallic clusters arise largely from the charge left on the cluster by photoemission. As the metal-insulator transition is approached from above, metallic screening is suppressed and the shift is determined by the local environment. (orig.)

  11. The Electrochemical Atomic Layer Deposition of Pt and Pd nanoparticles on Ni foam for the electrooxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2012-10-01

    Full Text Available Electrodeposition of Pt and Pd metal by surface limited redox replacement reactions was performed using the electrochemical atomic layer deposition. Carbon paper and Ni foam were used as substrates for metal deposition. Supported Pt and Pd...

  12. Pd Alloy Membranes for Hydrogen Separation from Coal-Derived Syngas

    National Research Council Canada - National Science Library

    Alptekin, Gokhan O; DeVoss, Sarah; Amalfitano, Bob; Way, Douglas; Thoen, Paul; Lusk, Mark

    2006-01-01

    TDA Research Inc., in collaboration with Colorado School of Mines (CSM) is developing a sulfur and CO-tolerant membrane to produce the clean hydrogen from syngas using Pd membrane films prepared on a variety of supports (e.g...

  13. Influence of the preparation conditions of Pd-ZrO.sub.2./sub. and AuPd-ZrO.sub.2./sub. nanoparticle-decorated functionalised MWCNTs: Electron spectroscopy study aided with the QUASES

    Czech Academy of Sciences Publication Activity Database

    Lesiak, B.; Zemek, Josef; Jiříček, Petr; Malolepszy, A.; Stobinski, L.

    2017-01-01

    Roč. 49, č. 11 (2017), s. 1124-1134 ISSN 0142-2421 R&D Projects: GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : AuPd-ZrO2/f-MWCNTs * high pressure microwave reactor * Pd-ZrO2/f-MWCNTs * XPS * QUASES Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.132, year: 2016

  14. Aerobic oxidation of alcohols in visible light on Pd-grafted Ti cluster

    Data.gov (United States)

    U.S. Environmental Protection Agency — The titanium cluster with the reduced band gap has been synthesized having the palladium nanoparticles over the surface, which not only binds to the atmospheric...

  15. Stroke localization and classification using microwave tomography with k-means clustering and support vector machine.

    Science.gov (United States)

    Guo, Lei; Abbosh, Amin

    2018-05-01

    For any chance for stroke patients to survive, the stroke type should be classified to enable giving medication within a few hours of the onset of symptoms. In this paper, a microwave-based stroke localization and classification framework is proposed. It is based on microwave tomography, k-means clustering, and a support vector machine (SVM) method. The dielectric profile of the brain is first calculated using the Born iterative method, whereas the amplitude of the dielectric profile is then taken as the input to k-means clustering. The cluster is selected as the feature vector for constructing and testing the SVM. A database of MRI-derived realistic head phantoms at different signal-to-noise ratios is used in the classification procedure. The performance of the proposed framework is evaluated using the receiver operating characteristic (ROC) curve. The results based on a two-dimensional framework show that 88% classification accuracy, with a sensitivity of 91% and a specificity of 87%, can be achieved. Bioelectromagnetics. 39:312-324, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

  16. Dynamic stabilities of icosahedral-like clusters and their ability to form quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Xiaogang; Hamid, Ilyar; Duan, Haiming, E-mail: dhm@xju.edu.cn [College of Physics Science and Technology. Xinjiang University, Urumqi 830046 (China)

    2016-06-15

    The dynamic stabilities of the icosahedral-like clusters containing up to 2200 atoms are investigated for 15 metal elements. The clusters originate from five different initial structures (icosahedron, truncated decahedron, octahedron, closed-shell fragment of an HCP structure, and non-closed-shell fragment of an HCP structure). The obtained order of the dynamic stabilities of the icosahedral-like clusters can be assigned to three groups, from stronger to weaker, according to the size ranges involved: (Zr, Al, Ti) > (Cu, Fe, Co, Ni, Mg, Ag) > (Pb, Au, Pd, Pt, Rh, Ir), which correspond to the predicted formation ability of the quasicrystals. The differences of the sequences can be explained by analyzing the parameters of the Gupta-type many-body inter-atomic potentials.

  17. Endohedral gallide cluster superconductors and superconductivity in ReGa5.

    Science.gov (United States)

    Xie, Weiwei; Luo, Huixia; Phelan, Brendan F; Klimczuk, Tomasz; Cevallos, Francois Alexandre; Cava, Robert Joseph

    2015-12-22

    We present transition metal-embedded (T@Gan) endohedral Ga-clusters as a favorable structural motif for superconductivity and develop empirical, molecule-based, electron counting rules that govern the hierarchical architectures that the clusters assume in binary phases. Among the binary T@Gan endohedral cluster systems, Mo8Ga41, Mo6Ga31, Rh2Ga9, and Ir2Ga9 are all previously known superconductors. The well-known exotic superconductor PuCoGa5 and related phases are also members of this endohedral gallide cluster family. We show that electron-deficient compounds like Mo8Ga41 prefer architectures with vertex-sharing gallium clusters, whereas electron-rich compounds, like PdGa5, prefer edge-sharing cluster architectures. The superconducting transition temperatures are highest for the electron-poor, corner-sharing architectures. Based on this analysis, the previously unknown endohedral cluster compound ReGa5 is postulated to exist at an intermediate electron count and a mix of corner sharing and edge sharing cluster architectures. The empirical prediction is shown to be correct and leads to the discovery of superconductivity in ReGa5. The Fermi levels for endohedral gallide cluster compounds are located in deep pseudogaps in the electronic densities of states, an important factor in determining their chemical stability, while at the same time limiting their superconducting transition temperatures.

  18. Nickel group cluster anion reactions with carbon monoxide: Rate coefficients and chemisorption efficiency

    Science.gov (United States)

    Hintz, Paul A.; Ervin, Kent M.

    1994-04-01

    Reactions of Ni-n(n=3-10), Pd-n(n=3-8), and Pt-n(n=3-7) with CO are studied in a flow tube reactor. Bimolecular rate coefficients are measured for the association reaction of CO adsorbing on the cluster surface. The rate coefficients range from about 10% of the collision rate for the trimer anions to near the collision rate for clusters larger than four atoms. The maximum number of CO molecules that bind to each cluster is determined. Whereas the saturation limits for nickel are typical for an 18 electron transition metal, the limits for platinum are lower, reflecting the electron deficient structures observed in condensed phase chemistry. The CO saturated palladium clusters represent the first examples of saturated binary palladium carbonyl compounds. Comparisons are made to similar studies on metal cation and neutral clusters and also to surface scattering studies of nickel group metals.

  19. Magnetic characteristics of CoPd and FePd antidot arrays on nanoperforated Al{sub 2}O{sub 3} templates

    Energy Technology Data Exchange (ETDEWEB)

    Maximenko, A., E-mail: Alexey.Maximenko@ifj.edu.pl [The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego Str. 152, 31-342 Krakow (Poland); Research Institute for Nuclear Problems of Belarusian State University, Bobruiskaya Str. 11, 220030 Minsk (Belarus); Fedotova, J. [Research Institute for Nuclear Problems of Belarusian State University, Bobruiskaya Str. 11, 220030 Minsk (Belarus); Marszałek, M.; Zarzycki, A.; Zabila, Y. [The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego Str. 152, 31-342 Krakow (Poland)

    2016-02-15

    Hard magnetic antidot arrays show promising results in context of designing of percolated perpendicular media. In this work the technology of magnetic FePd and CoPd antidot arrays fabrication is presented and correlation between surface morphology, structure and magnetic properties is discussed. CoPd and FePd antidot arrays were fabricated by deposition of Co/Pd and Fe/Pd multilayers (MLs) on porous anodic aluminum oxide templates with bowl-shape cell structure with inclined intercellular regions. FePd ordered L1{sub 0} structure was obtained by successive vacuum annealing at elevated temperatures (530 °C) and confirmed by XRD analysis. Systematic analysis of magnetization curves evidenced perpendicular magnetic anisotropy of CoPd antidot arrays, while FePd antidot arrays revealed isotropic magnetic anisotropy with increased out-of-plane magnetic contribution. MFM images of antidots showed more complicated contrast, with alternating magnetic dots oriented parallel and antiparallel to tip magnetization moment. - Highlights: • CoPd and FePd antidots were fabricated on porous anodic aluminum oxide templates. • CoPd antidot arrays have perpendicular magnetic anisotropy. • FePd antidot arrays revealed isotropic magnetic behavior. • The complex morphology of nanoporous template resulted in a complex magnetic domains image.

  20. Comparing PD results with visual inspection

    International Nuclear Information System (INIS)

    Rossi, A.; Stone, G.C.

    2005-01-01

    ENEL is the main generation utility in Italy, with more than 200 hydro units and 120 turbine generators, totaling 39,000 MW of capacity. To help identify the maintenance needs of the stator windings in these units, ENEL has been gradually equipping the generators with partial discharge (PD) sensors that facilitate an on-line measurement of the PD. The paper describes results from several machines that have PD. In all cases, the high PD was confirmed by visual inspections. Although PD usually found the units with severe insulation problems, it was not always possible to determine the causes of the deterioration from the PD pattern. (author)

  1. Physical properties of the GaPd2 intermetallic catalyst in bulk and nanoparticle morphology

    DEFF Research Database (Denmark)

    Wencka, M.; Schwerin, J.; Klanjšek, M.

    2015-01-01

    Intermetallic compound GaPd2 is a highly selective catalyst material for the semi-hydrogenation of acetylene. We have determined anisotropic electronic, thermal and magnetic properties of a GaPd2 monocrystal along three orthogonal orthorhombic directions of the structure. By using 69Ga and 71Ga NMR...... properties of the GaPd2 phase on going from the bulk material to the nanoparticles morphology, we have synthesized GaPd2/SiO2 supported nanoparticles and determined their electronic DOS at εF from the 71Ga NMR spin-lattice relaxation rate. The electronic DOS of the GaPd2 was also studied theoretically from...... spectroscopy, we have determined the electric-field-gradient tensor at the Ga site in the unit cell and the Knight shift, which yields the electronic density of states (DOS) at the Fermi energy εF. The DOS at εF was determined independently also from the specific heat. To see the change of electronic...

  2. Performance of the PdNi and PdNiSe as cathodes in PEM fuel cells; Desempeno de PdNi y PdNiSe como catodos en celdas de combustible tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Santana, A.; Ramos-Sanchez, G.; Vazquez, G.; Solorza-Feria, O. [Centro de Investigaciones y de Estudios Avanzados del IPN, Mexico D.F. (Mexico)]. E-mail: gramos@cinvestav.mx

    2009-09-15

    The search for new materials capable of catalyzing oxygen reactions in low temperature fuel cells continues to be one of the key issues in the development of a hydrogen economy. Electrochemical and physical characterization studies have demonstrated that the PdNi and PdNiSe catalysts have adequate properties for use as cathodes in fuel cells. Nevertheless, the performance of the materials in proton exchange membrane (PEM) fuel cells depends not only on the catalytic properties but also on the adequate preparation of the electrocatalyst membrane interface (EMI). This work presents the results of the search for optimal conditions to prepare the EMIs with PdNi and PdNiSe cathodes. There are many variables for handling the preparation of the interfaces, nevertheless our search focuses on two: catalyst ratio/Vulcan Carbon® and the catalyst amount. Interfaces were prepared with an active area of 5 cm{sup 2} with PdNi and PdNiSe cathodes and carbon fabric anode with Pt E-tek®. These interfaces were tested with an ElectroChem model under different gas pressure and temperature conditions. The optimization method was carried out using a simplex method with the variables mentioned above and power density per unit mass and catalyst area as response variables. [Spanish] La busqueda de nuevos materiales capaces de catalizar la Reaccion de Oxigeno (RRO) en celdas de combustible de baja temperatura, sigue siendo uno de los temas clave para el desarrollo de una Economia del Hidrogeno. Estudios electroquimicos y de caracterizacion fisica han demostrado que los catalizadores PdNi y PdNiSe, tienen las propiedades adecuadas para poder ser utilizados como catodos en celdas de combustible; sin embargo el desempeno de los materiales en celdas de combustible de membrana de intercambio protonico (PEM), no solo depende de las propiedades del catalizador, sino tambien de la preparacion adecuada del Ensamble Membrana Electrocatalizador (EME). En este trabajo se presentan los resultados de la

  3. PD Lab

    Directory of Open Access Journals (Sweden)

    Marcel Bilow

    2015-08-01

    Full Text Available PD Lab explores the applications of building sector related product development.  PD lab investigates and tests digital production technologies like CNC milled wood connections. It will also act as a platform in its wider meaning to investigate the effects and influences of file to factory production, to explore the potential in the field of sustainability, material use, logistics and the interaction of stakeholders within the chain of the building process.

  4. The role of Pd in the transport of Ag in SiC

    International Nuclear Information System (INIS)

    Olivier, E.J.; Neethling, J.H.

    2013-01-01

    This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

  5. The role of Pd in the transport of Ag in SiC

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, E.J., E-mail: jolivier@nmmu.ac.za [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa); Neethling, J.H. [Centre for High Resolution Transmission Electron Microscopy, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2013-01-15

    This paper presents results in support of a newly proposed transport mechanism to account for the release of Ag from intact TRISO particles during HTR reactor operation. The study reveals that the migration of Ag in polycrystalline SiC can occur in association with Pd, a relatively high yield metallic fission product. The migration takes place primarily along grain boundary routes, seen in the form of distinct Pd, Ag and Si containing nodules. Pd is known to rapidly migrate to the SiC and iPyC interface within TRISO particles during operation. It has been shown to chemically corrode the SiC to form palladium silicides. These palladium silicides are found present along SiC grain boundaries in nodule like form. It is suggested that Ag penetrates these nodules together with the palladium silicide, to form a Pd, Ag and Si solution capable of migrating along SiC grain boundaries over time.

  6. ALTERNATIVE MATERIALS TO PD MEMBRANES FOR HYDROGEN PURIFICATION

    Energy Technology Data Exchange (ETDEWEB)

    Korinko, P; T. Adams

    2008-09-12

    Development of advanced hydrogen separation membranes in support of hydrogen production processes such as coal gasification and as front end gas purifiers for fuel cell based system is paramount to the successful implementation of a national hydrogen economy. Current generation metallic hydrogen separation membranes are based on Pd-alloys. Although the technology has proven successful, at issue is the high cost of palladium. Evaluation of non-noble metal based dense metallic separation membranes is currently receiving national and international attention. The focal point of the reported work was to evaluate two different classes of materials for potential replacement of conventional Pd-alloy purification/diffuser membranes. Crystalline V-Ni-Ti and Amorphous Fe- and Co-based metallic glass alloys have been evaluated using gaseous hydrogen permeation testing techniques.

  7. Polystyrene-Supported Acyclic Diaminocarbene Palladium Complexes in Sonogashira Cross-Coupling: Stability vs. Catalytic Activity

    Directory of Open Access Journals (Sweden)

    Vladimir N. Mikhaylov

    2018-04-01

    Full Text Available Two types of immobilized on the amino-functionalized polystyrene-supported acyclic diaminocarbene palladium complexes (ADC-PdII are investigated under Sonogashira cross-coupling conditions. Depending on substituents in the diaminocarbene fragment immobilized ADC-PdII, systems are found to have different catalytic activity and stability regarding Pd-leaching. PdII-diaminocarbenes possessing protons at both nitrogen atoms smoothly decompose into Pd0-containing species providing a catalytic “cocktail system” with high activity and ability to reuse within nine runs. Polymer-supported palladium (II complex bearing NBn–Ccarbene–NH-moiety exhibits greater stability while noticeably lower activity under Sonogashira cross-coupling. Four molecular ADC-PdII complexes are also synthesized and investigated with the aim of confirming proposed base-promoted pathway of ADC-PdII conversion through carbodiimide into an active Pd0 forms.

  8. Threshold selection for classification of MR brain images by clustering method

    Energy Technology Data Exchange (ETDEWEB)

    Moldovanu, Simona [Faculty of Sciences and Environment, Department of Chemistry, Physics and Environment, Dunărea de Jos University of Galaţi, 47 Domnească St., 800008, Romania, Phone: +40 236 460 780 (Romania); Dumitru Moţoc High School, 15 Milcov St., 800509, Galaţi (Romania); Obreja, Cristian; Moraru, Luminita, E-mail: luminita.moraru@ugal.ro [Faculty of Sciences and Environment, Department of Chemistry, Physics and Environment, Dunărea de Jos University of Galaţi, 47 Domnească St., 800008, Romania, Phone: +40 236 460 780 (Romania)

    2015-12-07

    Given a grey-intensity image, our method detects the optimal threshold for a suitable binarization of MR brain images. In MR brain image processing, the grey levels of pixels belonging to the object are not substantially different from the grey levels belonging to the background. Threshold optimization is an effective tool to separate objects from the background and further, in classification applications. This paper gives a detailed investigation on the selection of thresholds. Our method does not use the well-known method for binarization. Instead, we perform a simple threshold optimization which, in turn, will allow the best classification of the analyzed images into healthy and multiple sclerosis disease. The dissimilarity (or the distance between classes) has been established using the clustering method based on dendrograms. We tested our method using two classes of images: the first consists of 20 T2-weighted and 20 proton density PD-weighted scans from two healthy subjects and from two patients with multiple sclerosis. For each image and for each threshold, the number of the white pixels (or the area of white objects in binary image) has been determined. These pixel numbers represent the objects in clustering operation. The following optimum threshold values are obtained, T = 80 for PD images and T = 30 for T2w images. Each mentioned threshold separate clearly the clusters that belonging of the studied groups, healthy patient and multiple sclerosis disease.

  9. Fast optimization of binary clusters using a novel dynamic lattice searching method

    International Nuclear Information System (INIS)

    Wu, Xia; Cheng, Wen

    2014-01-01

    Global optimization of binary clusters has been a difficult task despite of much effort and many efficient methods. Directing toward two types of elements (i.e., homotop problem) in binary clusters, two classes of virtual dynamic lattices are constructed and a modified dynamic lattice searching (DLS) method, i.e., binary DLS (BDLS) method, is developed. However, it was found that the BDLS can only be utilized for the optimization of binary clusters with small sizes because homotop problem is hard to be solved without atomic exchange operation. Therefore, the iterated local search (ILS) method is adopted to solve homotop problem and an efficient method based on the BDLS method and ILS, named as BDLS-ILS, is presented for global optimization of binary clusters. In order to assess the efficiency of the proposed method, binary Lennard-Jones clusters with up to 100 atoms are investigated. Results show that the method is proved to be efficient. Furthermore, the BDLS-ILS method is also adopted to study the geometrical structures of (AuPd) 79 clusters with DFT-fit parameters of Gupta potential

  10. Synthesis and characterization of Pd-Ni nanoalloy electrocatalysts for oxygen reduction reaction in fuel cells

    International Nuclear Information System (INIS)

    Zhao, Juan; Sarkar, Arindam; Manthiram, Arumugam

    2010-01-01

    Carbon-supported Pd-Ni nanoalloy electrocatalysts with different Pd/Ni atomic ratios have been synthesized by a modified polyol method, followed by heat treatment in a reducing atmosphere at 500-900 deg. C. The samples have been characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), rotating disk electrode (RDE) measurements, and single-cell proton exchange membrane fuel cell (PEMFC) tests for oxygen reduction reaction (ORR). XRD and TEM data reveal an increase in the degree of alloying and particle size with increasing heat-treatment temperature. XPS data indicate surface segregation with Pd enrichment on the surface of Pd 80 Ni 20 after heat treatment at ≥500 deg. C, suggesting possible lattice strains in the outermost layers. Electrochemical data based on CV, RDE, and single-cell PEMFC measurement show that Pd 80 Ni 20 heated at 500 deg. C has the highest mass catalytic activity for ORR among the Pd-Ni samples investigated, with stability and catalytic activity significantly higher than that found with Pd. With a lower cost, the Pd-Ni catalysts exhibit higher tolerance to methanol than Pt, offering an added advantage in direct methanol fuel cells (DMFC).

  11. Understanding the structural properties and thermal stabilities of Au–Pd–Pt trimetallic clusters

    International Nuclear Information System (INIS)

    Zhao, Zheng; Li, Mingjiang; Cheng, Daojian; Zhu, Jiqin

    2014-01-01

    Highlights: • Structural properties of Au–Pd–Pt clusters are studied by Monte Carlo simulation. • Melting of Au–Pd–Pt clusters is studied by molecular dynamics simulation. • Au atoms are systematically segregated on the surface of the Au–Pd–Pt clusters. • Linear decrease in cluster melting point with the inverse cluster diameter. - Abstract: In this work, surface segregation phenomena of Au–Pd–Pt trimetallic clusters are investigated by using semi-grand Monte Carlo simulations based on the Gupta potential. It is found that Au atoms are systematically segregated on the surface of the Au–Pd–Pt clusters (6–24 at.% higher than the overall Au concentration), due to the competition among the surface energies of Au, Pd, and Pt. The melting properties of Au–Pd–Pt trimetallic clusters with different composition and size are investigated by using molecular dynamics simulations, based on the same Gupta potential. It is found that the Au–Pd–Pt trimetallic cluster with the highest melting point corresponds to the one with the most stable structure. In addition, linear decrease in cluster melting point with the inverse cluster diameter is predicted for both pure and trimetallic clusters, which is well-known as the Pawlow’s law

  12. The Emerging Role of PD-1/PD-L1-Targeting Immunotherapy in the Treatment of Metastatic Urothelial Carcinoma.

    Science.gov (United States)

    Gwynn, Morgan E; DeRemer, David L

    2018-01-01

    To summarize and evaluate immunotherapy agents targeting programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) recently approved for the treatment of metastatic urothelial carcinomas (UC). A literature review was performed using PubMed (2012 to June 2017), the American Society of Clinical Oncology abstract databases (2012 to June 2017 Annual Meetings/symposia), and the America Association for Cancer Research symposia (2012 to June 2017). A search using clinicaltrials.gov was conducted to identify studies for atezolizumab, avelumab, durvalumab, nivolumab, and pembrolizumab. English language phase I to III studies assessing PD-1 and PD-L1 in UC were incorporated. Atezolizumab, avelumab, durvalumab, nivolumab, and pembrolizumab have demonstrated clinical efficacy with tolerable toxicities in patients with metastatic UC with disease progression following platinum-based chemotherapy. Anti-PD-1/PD-L1 therapies may provide overall survival advantage; these are currently being evaluated in ongoing phase 3 studies. Greater objective response rates seem to be observed in PD-L1-positive patients versus PD-L1-negative patients, but methodologies in this assessment differ among clinical trials. The identification of biomarkers that provide greater insight into patients who positively respond to PD-1/PD-L1 therapies are needed. Treatment options for metastatic UC have expanded to include PD-1/PD-L1 therapies. These agents should be strongly considered as second-line therapy over single-agent chemotherapy for patients who fail or progress after platinum-based treatment.

  13. Aerobic oxidation of alcohols in visible light on Pd-grafted Ti cluster

    Science.gov (United States)

    The titanium cluster with the reduced band gap has been synthesized having the palladium nanoparticles over the surface, which not only binds to the atmospheric oxygen but also catalyzes the oxidation of alcohols under visible light.

  14. Targeting immune co-stimulatory effects of PD-L1 and PD-L2 might represent an effective therapeutic strategy in stroke

    Directory of Open Access Journals (Sweden)

    Sheetal eBodhankar

    2014-08-01

    Full Text Available Stroke outcome is worsened by the infiltration of inflammatory immune cells into ischemic brains. Our recent study demonstrated that PD-L1- and to a lesser extent PD-L2-deficient mice had smaller brain infarcts and fewer brain-infiltrating cells vs. WT mice, suggesting a pathogenic role for PD-Ligands in experimental stroke. We sought to ascertain PD-L1 and PD-L2-expressing cell types that affect T-cell activation, post-stroke in the context of other known co-stimulatory molecules. Thus, cells from male WT and PD-L-deficient mice undergoing 60 min of middle cerebral artery occlusion (MCAO followed by 96h of reperfusion were treated with neutralizing antibodies to study co-stimulatory and co-inhibitory interactions between CD80, CTLA-4, PD-1 and PD-Ls that regulate CD8+ and CD4+ T-cell activation. We found that antibody neutralization of PD-1 and CTLA-4 signaling post-MCAO resulted in higher proliferation in WT CD8+ and CD4+ T-cells, confirming an inhibitory role of PD-1 and CTLA-4 on T-cell activation. Also, CD80/CD28 interactions played a prominent regulatory role for the CD8+ T-cells and the PD-1/PD-L2 interactions were dominant in controlling the CD4+ T-cell responses in WT mice after stroke. A suppressive phenotype in PD-L1-deficient mice was attributed to CD80/CTLA-4 and PD-1/PD-L2 interactions. PD-L2 was crucial in modulating CD4+ T-cell responses, whereas PD-L1 regulated both CD8+ and CD4+ T-cells. To establish the contribution of PD-L1 and PD-L2 on regulatory B-cells (Bregs, infarct volumes were evaluated in male PD-L1- and PD-L2-deficient mice receiving IL-10+ B-cells 4h post-MCAO. PD-L2- but not PD-L1-deficient recipients of IL-10+ B-cells had markedly reduced infarct volumes, indicating a regulatory role of PD-L2 on Bregs. These results imply that PD-L1 and PD-L2 differentially control induction of T- and Breg-cell responses after MCAO, thus suggesting that selective targeting of PD-L1 and PD-L2 might represent a valuable therapeutic

  15. Alkaline Ionic Liquid Modified Pd/C Catalyst as an Efficient Catalyst for Oxidation of 5-Hydroxymethylfurfural

    Directory of Open Access Journals (Sweden)

    Zou Bin

    2018-01-01

    Full Text Available Conversion of HMF into FDCA was carried out by a simple and green process based on alkaline ionic liquid (IL modified Pd/C catalyst (Pd/C-OH−. Alkaline ionic liquids were chosen to optimize Pd/C catalyst for special hydrophilicity and hydrophobicity, redox stability, and unique dissolving abilities for polar compounds. The Pd/C-OH− catalyst was successfully prepared and characterized by SEM, XRD, TG, FT-IR, and CO2-TPD technologies. Loading of alkaline ionic liquid on the surface of Pd/C was 2.54 mmol·g−1. The catalyst showed excellent catalytic activity in the HMF oxidation after optimization of reaction temperature, reaction time, catalyst amount, and solvent. Supported alkaline ionic liquid (IL could be a substitute and promotion for homogeneous base (NaOH. Under optimal reaction conditions, high HMF conversion of 100% and FDCA yield of 82.39% were achieved over Pd/C-OH− catalyst in water at 373 K for 24 h.

  16. Size selected metal clusters

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. The Optical Absorption Spectra of Small Silver Clusters (5-11) ... Soft Landing and Fragmentation of Small Clusters Deposited in Noble-Gas Films. Harbich, W.; Fedrigo, S.; Buttet, J. Phys. Rev. B 1998, 58, 7428. CO combustion on supported gold clusters. Arenz M ...

  17. DFT study of the structures and energetics of 98-atom AuPd clusters.

    Science.gov (United States)

    Bruma, Alina; Ismail, Ramli; Paz-Borbón, L Oliver; Arslan, Haydar; Barcaro, Giovanni; Fortunelli, Alessandro; Li, Z Y; Johnston, Roy L

    2013-01-21

    The energetics, structures and segregation of 98-atom AuPd nanoclusters are investigated using a genetic algorithm global optimization technique with the Gupta empirical potential (comparing three different potential parameterisations) followed by local minimizations using Density Functional Theory (DFT) calculations. A shell optimization program algorithm is employed in order to study the energetics of the highly symmetric Leary Tetrahedron (LT) structure and optimization of the chemical ordering of a number of structural motifs is carried out using the Basin Hopping Monte Carlo approach. Although one of the empirical potentials is found to favour the LT structure, it is shown that Marks Decahedral and mixed FCC-HCP motifs are lowest in energy at the DFT level.

  18. PD-L1 expression associated with worse survival outcome in malignant pleural mesothelioma.

    Science.gov (United States)

    Nguyen, Bella Hai; Montgomery, Renn; Fadia, Mitali; Wang, Jiali; Ali, Sayed

    2018-02-01

    There is currently a need to identify prognostic biomarkers to assist in a risk adopted approach in treatment of malignant pleural mesothelioma (MPM). Expression of programmed death ligand 1 (PD-L1) has been studied as a prognostic biomarker in a number of tumors given its central role in antitumoral immune response evasion. Four previously published analyses found PD-L1 positivity to be an adverse survival prognostic factor in MPM. This study aims to further investigate the relationship between PD-L1 expression in mesothelioma tissues and survival outcome. Clinical data of MPM patients from a single institution between 2006 and 2016 were reviewed. Patient's archived tissues were stained with PD-L1 (Clone Ventana SP263). PD-L1 positivity was defined as > 1% membranous staining regardless of intensity. Data from fifty eight patients were analyzed. Median age was 73, majority was male (49, 84%) and had ECOG between 0 and 2 (46, 79%). Most common histopathological subtype was epithelioid (42, 72%), 9 (16%) biphasic subtype and 7 (12%) sarcomatoid. Thirty one patients (53%) received best supportive care and twenty seven patients (47%) received chemotherapy or combination treatment. Forty-two patients had positive PD-L1 expression (72.4%). The median survival time for PD-L1 negative group is 15.5 months and 6 months for the positive group. Positive PD-L1 expression is independently correlated with worse prognosis (HR = 2.02; 95% CI, 1.005-4.057; P-value = 0.0484). Our analysis found a higher percentage of MPM patients with positive PD-L1 (> 1%) compared to other studies. Highly positive PD-L1 expression was associated with statistically significantly lower median survival time. © 2017 John Wiley & Sons Australia, Ltd.

  19. UV Light-Assisted Synthesis of Highly Efficient Pd-Based Catalyst over NiO for Hydrogenation of o-Chloronitrobenzene.

    Science.gov (United States)

    Jiang, Weidong; Xu, Bin; Fan, Guangyin; Zhang, Kaiming; Xiang, Zhen; Liu, Xiaoqiang

    2018-04-14

    Supported Pd-based catalyst over active nickel oxide (NiO) was repared using the impregnation method companying with UV-light irradiation. Moreover, the catalytic performance of the obtained Pd-based catalysts was evaluated towards the hydrogenation of o -chloronitrobenzene ( o -CNB). Observations indicate that the as-prepared UV-irradiated Pd/NiO catalyst with a mole fraction 0.2% (0.2%Pd/NiO) has higher activity and selectivity in the o -CNB hydrogenation. Especially, UV-light irradiation played a positive role in the improvement of catalytic activity of 0.2%Pd/NiO catalyst, exhibiting an excess 11-fold activity superiority in contrast with non-UV-irradiated 0.2%Pd/NiO catalyst. In addition, it was investigated that effects of varied factors (i.e., reaction time, temperature, o -CNB/Pd ratio, Pd loading, hydrogen pressure) on the selective hydrogenation of ο -CNB catalyzed by UV-irradiated 0.2%Pd/NiO catalyst. Under the reaction conditions of 60 °C, 0.5 h, 1 MPa H₂ pressure, 100% conversion of o -CNB, and 81.1% o -CAN selectivity were obtained, even at high molar ratio (8000:1) of o -CNB to Pd.

  20. Plot Description (PD)

    Science.gov (United States)

    Robert E. Keane

    2006-01-01

    The Plot Description (PD) form is used to describe general characteristics of the FIREMON macroplot to provide ecological context for data analyses. The PD data characterize the topographical setting, geographic reference point, general plant composition and cover, ground cover, fuels, and soils information. This method provides the general ecological data that can be...

  1. Size control and catalytic activity of bio-supported palladium nanoparticles.

    Science.gov (United States)

    Søbjerg, Lina Sveidal; Lindhardt, Anders T; Skrydstrup, Troels; Finster, Kai; Meyer, Rikke Louise

    2011-07-01

    The development of nanoparticles has greatly improved the catalytic properties of metals due to the higher surface to volume ratio of smaller particles. The production of nanoparticles is most commonly based on abiotic processes, but in the search for alternative protocols, bacterial cells have been identified as excellent scaffolds of nanoparticle nucleation, and bacteria have been successfully employed to recover and regenerate platinum group metals from industrial waste. We report on the formation of bio-supported palladium (Pd) nanoparticles on the surface of two bacterial species with distinctly different surfaces: the gram positive Staphylococcus sciuri and the gram negative Cupriavidus necator. We investigated how the type of bacterium and the amount of biomass affected the size and catalytic properties of the nanoparticles formed. By increasing the biomass:Pd ratio, we could produce bio-supported Pd nanoparticles smaller than 10nm in diameter, whereas lower biomass:Pd ratios resulted in particles ranging from few to hundreds of nm. The bio-supported Pd nanoparticle catalytic properties were investigated towards the Suzuki-Miyaura cross coupling reaction and hydrogenation reactions. Surprisingly, the smallest nanoparticles obtained at the highest biomass:Pd ratio showed no reactivity towards the test reactions. The lack of reactivity appears to be caused by thiol groups, which poison the catalyst by binding strongly to Pd. Different treatments intended to liberate particles from the biomass, such as burning or rinsing in acetone, did not re-establish their catalytic activity. Sulphur-free biomaterials should therefore be explored as more suitable scaffolds for Pd(0) nanoparticle formation. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness

    Science.gov (United States)

    Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E.; Huang, Yu

    2012-01-01

    Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications.Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more

  3. Microenvironment effects in electrocatalysis: ionic-liquid-like coating on carbon nanotubes enhances the Pd-electrocatalytic alcohol oxidation.

    Science.gov (United States)

    Li, Shuwen; Dong, Zhengping; Yang, Honglei; Guo, Shujing; Gou, Galian; Ren, Ren; Zhu, Zhejun; Jin, Jun; Ma, Jiantai

    2013-02-11

    A new catalyst consisting of ionic liquid (IL)-functionalized carbon nanotubes (CNTs) obtained through 1,3-dipolar cycloaddition support-enhanced electrocatalytic Pd nanoparticles (Pd@IL(Cl(-))-CNTs) was successfully fabricated and applied in direct ethanol alkaline fuel cells. The morphology, structure, component and stability of Pd@IL(Cl(-))-CNTs were systematic characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectra, thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The new catalyst exhibited higher electrocatalytic activity, better tolerance and electrochemical stability than the Pd nanoparticles (NPs) immobilized on CNTs (Pd@CNTs), which was ascribed to the effects of the IL, larger electrochemically active surface area (ECSA), and greater processing performance. Cyclic voltammograms (CVs) at various scan rates illustrated that the oxidation behaviors of ethanol at all electrodes were controlled by diffusion processes. The investigation of the different counteranions demonstrated that the performance of the IL-CNTs hybrid material was profoundly influenced by the subtly varied structures of the IL moiety. All the results indicated that the Pd@IL(Cl(-))-CNTs catalyst is an efficient anode catalyst, which has potential applications in direct ethanol fuel cells and the strategy of IL functionalization of CNTs could be available to prepare other carbonaceous carrier supports to enhance the dispersivity, stability, and catalytic performance of metal NPs as well. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Design of Pd/PANI/Pd sandwich-structured nanotube array catalysts with special shape effects and synergistic effects for ethanol electrooxidation.

    Science.gov (United States)

    Wang, An-Liang; Xu, Han; Feng, Jin-Xian; Ding, Liang-Xin; Tong, Ye-Xiang; Li, Gao-Ren

    2013-07-24

    Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

  5. Molecular dynamics computer simulation study of Pdn (n=13, 19, 38 and 55) clusters

    International Nuclear Information System (INIS)

    Karabacak, M.; Oezcelik, S.; Guevenc, Z.B.

    2002-01-01

    Using constant-energy molecular dynamics and thermal quenching simulations, we have studied minimum-energy structures and energetics, Pd n (n=13, 19, 38, and 55) clusters employing the Voter and Chen's version of parameterisation of the embedded-atom potential surface. Isomer statistics for Pdn ( n = 13 and 19 ) is obtained from 10000 initial independent configurations, which have been generated along high-energy trajectories (chosen energy values are high enough to melt the clusters). The thermal quenching technique is employed to remove the internal kinetic energy of the clusters. The locally stable isomers are separated from metastable ones. Probabilities belonging to sampling the basins of attractions of each isomers are computed, and then, isomers' energy spectra are analyzed

  6. Effect of preparation method on the surface characteristics and activity of the Pd/OMS-2 catalysts for the oxidation of carbon monoxide, toluene, and ethyl acetate

    Science.gov (United States)

    Liu, Lisha; Song, Yong; Fu, Zhidan; Ye, Qing; Cheng, Shuiyuan; Kang, Tianfang; Dai, Hongxing

    2017-02-01

    The cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2)-supported Pd (0.5 wt% Pd/OMS-2-DP, 0.5 wt% Pd/OMS-2-PI, and 0.5 wt% Pd/OMS-2-EX) catalysts were prepared by the deposition-precipitation, pre-incorporation, and ion-exchanging strategies, respectively. It is shown that the preparation method exerted an important effect on the physicochemical property of the sample. Among the OMS-2-supported Pd catalysts, 0.5 wt% Pd/OMS-2-DP possessed the highest surface (Mn2+ + Mn3+)/Mn4+ atomic ratio and the highest surface Pd loading and acid sites. The 0.5 wt% Pd/OMS-2 catalysts outperformed the Pd-free counterpart, among which 0.5 wt% Pd/OMS-2-DP presented the best catalytic activity (T50% and T90% were 25 and 55 °C for CO oxidation, 240 and 285 °C for toluene oxidation, and 160 and 200 °C for ethyl acetate oxidation, respectively). We believe that the high Pd surface loading, high surface atomic ratio of (Mn2+ + Mn3+)/Mn4+, and good low-temperature reducibility, good oxygen mobility, and high acidity were responsible for the excellent performance of the 0.5 wt% Pd/OMS-2-DP catalyst.

  7. Preparation of 103Pd seed-molecular plating of 103Pd onto silver rod

    International Nuclear Information System (INIS)

    Zhang Chunfu; Wang Yongxian; Tian Haibin; Yin Duanzhi

    2002-01-01

    A method for 103 Pd 'molecular plating' onto the surface of a silver rod is reported. The optimal composition of the plating bath is as follows: palladium chloride 0.1 mol/l, formaldehyde 2 mol/l, nitric acid 1 mol/l, and formic acid 0.4 mol/l. The 103 Pd molecular plating procedure will last 25 min at 30 deg. C. This article provides a valuable experience for the preparation of 103 Pd brachytherapy seed

  8. Domain structures and magnetization reversal in Co/Pd and CoFeB/Pd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Sbiaa, R., E-mail: rachid@squ.edu.om [Department of Physics, Sultan Qaboos University, P.O. Box 36, PC 123 (Oman); Ranjbar, M. [Physics Department, University of Gothenburg, 412 96 Gothenburg (Sweden); Åkerman, J. [Physics Department, University of Gothenburg, 412 96 Gothenburg (Sweden); Materials Physics, School of ICT, Royal Institute of Technology (KTH), 164 40 Kista (Sweden)

    2015-05-07

    Domain structures and magnetization reversal of (Co/Pd) and (CoFeB/Pd) multilayers with 7 and 14 repeats were investigated. The Co-based multilayers show much larger coercivities, a better squareness, and a sharper magnetization switching than CoFeB-based multilayers. From magnetic force microscopy observations, both structures show strong reduction in domains size as the number of repeats increases but the magnetic domains for Co-based multilayers are more than one order of magnitude larger than for CoFeB-based multilayers. By imaging domains at different times, breaks in the (CoFeB/Pd) multilayer stripes were observed within only few hours, while no change could be seen for (Co/Pd) multilayers. Although CoFeB single layers are suitable for magnetoresistive devices due to their large spin polarization and low damping constants, their lamination with Pd suffers mainly from thermal instability.

  9. Classification of Autism Spectrum Disorder Using Random Support Vector Machine Cluster

    Directory of Open Access Journals (Sweden)

    Xia-an Bi

    2018-02-01

    Full Text Available Autism spectrum disorder (ASD is mainly reflected in the communication and language barriers, difficulties in social communication, and it is a kind of neurological developmental disorder. Most researches have used the machine learning method to classify patients and normal controls, among which support vector machines (SVM are widely employed. But the classification accuracy of SVM is usually low, due to the usage of a single SVM as classifier. Thus, we used multiple SVMs to classify ASD patients and typical controls (TC. Resting-state functional magnetic resonance imaging (fMRI data of 46 TC and 61 ASD patients were obtained from the Autism Brain Imaging Data Exchange (ABIDE database. Only 84 of 107 subjects are utilized in experiments because the translation or rotation of 7 TC and 16 ASD patients has surpassed ±2 mm or ±2°. Then the random SVM cluster was proposed to distinguish TC and ASD. The results show that this method has an excellent classification performance based on all the features. Furthermore, the accuracy based on the optimal feature set could reach to 96.15%. Abnormal brain regions could also be found, such as inferior frontal gyrus (IFG (orbital and opercula part, hippocampus, and precuneus. It is indicated that the method of random SVM cluster may apply to the auxiliary diagnosis of ASD.

  10. Cluster management.

    Science.gov (United States)

    Katz, R

    1992-11-01

    Cluster management is a management model that fosters decentralization of management, develops leadership potential of staff, and creates ownership of unit-based goals. Unlike shared governance models, there is no formal structure created by committees and it is less threatening for managers. There are two parts to the cluster management model. One is the formation of cluster groups, consisting of all staff and facilitated by a cluster leader. The cluster groups function for communication and problem-solving. The second part of the cluster management model is the creation of task forces. These task forces are designed to work on short-term goals, usually in response to solving one of the unit's goals. Sometimes the task forces are used for quality improvement or system problems. Clusters are groups of not more than five or six staff members, facilitated by a cluster leader. A cluster is made up of individuals who work the same shift. For example, people with job titles who work days would be in a cluster. There would be registered nurses, licensed practical nurses, nursing assistants, and unit clerks in the cluster. The cluster leader is chosen by the manager based on certain criteria and is trained for this specialized role. The concept of cluster management, criteria for choosing leaders, training for leaders, using cluster groups to solve quality improvement issues, and the learning process necessary for manager support are described.

  11. Catalysts for selective hydrogenation of furfural derived from the double complex salt [Pd(NH 3 ) 4 ](ReO 4 ) 2 on γ-Al 2 O 3

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Simon T.; Lamb, H. Henry

    2017-06-01

    The double complex salt [Pd(NH3)4](ReO4)2 was employed as precursor of supported bimetallic catalysts for selective hydrogenation of furfural. Direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 in flowing H2 at 400 °C yields bimetallic nanoparticles 1–2 nm in size that exhibit significant interaction between the metals, as evidenced by temperature-programmed hydride decomposition (complete suppression of β-PdHx formation), extended X-ray absorption fine structure spectroscopy at the Pd K and Re LIII edges (PdRe distance = 2.72 Å), and scanning transmission electron microscopy with energy dispersive X-ray analysis. In contrast, calcination of [Pd(NH3)4](ReO4)2 on γ-Al2O3 at 350 °C in air and subsequent reduction in H2 at 400 °C results in metal segregation and formation of large (>50 nm) supported Pd particles; Re species cover the Pd particles and γ-Al2O3 support. A PdRe 1:2 catalyst prepared by sequential impregnation and calcination using HReO4 and [Pd(NH3)4](NO3)2 has a similar morphology. The catalyst derived by direct reduction of [Pd(NH3)4](ReO4)2 on γ-Al2O3 exhibits remarkably high activity for selective hydrogenation of furfural to furfuryl alcohol (FAL) at 150 °C and 1 atm. Suppression of H2 chemisorption via elimination of Pd threefold sites, as evidenced by CO diffuse-reflectance infrared Fourier transform spectroscopy, correlates with increased FAL selectivity.

  12. Configurational energies and effective cluster interactions in substitutionally disordered binary alloys

    International Nuclear Information System (INIS)

    Gonis, A.; Zhang, X.h.; Freeman, A.J.; Turchi, P.; Stocks, G.M.; Nicholson, D.M.

    1987-01-01

    The determination of configurational energies in terms of effective cluster interactions in substitutionally disordered alloys from a knowledge of the alloy electronic structure is examined within the methods of concentration waves (CW) and the generalized perturbation method (GPM), and for the first time within the embedded-cluster method (ECM). It is shown that the ECM provides the exact summation to all orders of the effective cluster interaction expansions obtained in the partially renormalized GPM. The connection between the various methods (CW, GPM, and ECM) is discussed and illustrated by means of numerical calculations for model one-dimensional tight-binding (TB) systems and for TB Hamiltonians chosen to describe Pd-V alloys. These calculations, and the formal considerations presented in the body of the paper, show the complete equivalence of converged GPM summations within specific clusters and the ECM. In addition, it is shown that an exact expansion of the configurational energy can be obtained in terms of fully renormalized effective cluster interactions. In principle, these effective cluster interactions can be used in conjunction with statistical models to determine stable ordered structures at low temperatures and alloy phase diagrams

  13. DFT study on stability and H2 adsorption activity of bimetallic Au79−nPdn (n = 1–55) clusters

    International Nuclear Information System (INIS)

    Liu, Xuejing; Tian, Dongxu; Meng, Changgong

    2013-01-01

    Highlights: ► Stability of Pd substitution type is face > mid-edge > corner > edge. ► H 2 adsorption activity is in contrast with the stability of Pd substitution type. ► Non-activated dissociation of H 2 occurs in Au 36 Pd 43−3 with high thermal stability. ► ε d agrees with that Pd at edge and corner are more active than face and mid-edge. - Abstract: The stability and H 2 adsorption activity of bimetallic Au 79−n Pd n (n = 1–55) clusters were studied by density functional theory with GGA-PW91 functional. The stability order for four Pd substitution types is face > mid-edge > corner > edge, and the stability is improved with increasing Pd content. In contrast with the stability order, H 2 adsorption activity is corner ≈ edge > mid-edge > face. The Au 36 Pd 43 (3) with Au:Pd ≈ 1:1 ratio and twenty-four Pd substitutions at (1 1 1) facets and nineteen Pd substitutions at subshell sites shows high stability and H 2 non-activated dissociation activity. The partial density of d-states and d band center revealed that the electronic properties are closely associated with the geometric characteristic and adsorption activity. Correlating the d band center ε d and the adsorption energies, the ε d order agrees with the adsorption activity that the Pd substitution at edge and corner sites are more active than at face and mid-edge sites

  14. Single-Trial Classification of Bistable Perception by Integrating Empirical Mode Decomposition, Clustering, and Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Hualou Liang

    2008-04-01

    Full Text Available We propose an empirical mode decomposition (EMD- based method to extract features from the multichannel recordings of local field potential (LFP, collected from the middle temporal (MT visual cortex in a macaque monkey, for decoding its bistable structure-from-motion (SFM perception. The feature extraction approach consists of three stages. First, we employ EMD to decompose nonstationary single-trial time series into narrowband components called intrinsic mode functions (IMFs with time scales dependent on the data. Second, we adopt unsupervised K-means clustering to group the IMFs and residues into several clusters across all trials and channels. Third, we use the supervised common spatial patterns (CSP approach to design spatial filters for the clustered spatiotemporal signals. We exploit the support vector machine (SVM classifier on the extracted features to decode the reported perception on a single-trial basis. We demonstrate that the CSP feature of the cluster in the gamma frequency band outperforms the features in other frequency bands and leads to the best decoding performance. We also show that the EMD-based feature extraction can be useful for evoked potential estimation. Our proposed feature extraction approach may have potential for many applications involving nonstationary multivariable time series such as brain-computer interfaces (BCI.

  15. Using social media to support cluster development

    NARCIS (Netherlands)

    Manickam, Anu; de Graaf, Frank Jan

    2012-01-01

    Developing European transnational clusters is a cornerstone in current EU-policies towards a sustainable competitive and open European economy. Within this conceptual paper relates these objectives to new developments in the application of network IT or, in popular terms, the rise of social media.

  16. Polymer-supported CuPd nanoalloy as a synergistic catalyst for electrocatalytic reduction of carbon dioxide to methane.

    Science.gov (United States)

    Zhang, Sheng; Kang, Peng; Bakir, Mohammed; Lapides, Alexander M; Dares, Christopher J; Meyer, Thomas J

    2015-12-29

    Developing sustainable energy strategies based on CO2 reduction is an increasingly important issue given the world's continued reliance on hydrocarbon fuels and the rise in CO2 concentrations in the atmosphere. An important option is electrochemical or photoelectrochemical CO2 reduction to carbon fuels. We describe here an electrodeposition strategy for preparing highly dispersed, ultrafine metal nanoparticle catalysts on an electroactive polymeric film including nanoalloys of Cu and Pd. Compared with nanoCu catalysts, which are state-of-the-art catalysts for CO2 reduction to hydrocarbons, the bimetallic CuPd nanoalloy catalyst exhibits a greater than twofold enhancement in Faradaic efficiency for CO2 reduction to methane. The origin of the enhancement is suggested to arise from a synergistic reactivity interplay between Pd-H sites and Cu-CO sites during electrochemical CO2 reduction. The polymer substrate also appears to provide a basis for the local concentration of CO2 resulting in the enhancement of catalytic current densities by threefold. The procedure for preparation of the nanoalloy catalyst is straightforward and appears to be generally applicable to the preparation of catalytic electrodes for incorporation into electrolysis devices.

  17. Convex Clustering: An Attractive Alternative to Hierarchical Clustering

    Science.gov (United States)

    Chen, Gary K.; Chi, Eric C.; Ranola, John Michael O.; Lange, Kenneth

    2015-01-01

    The primary goal in cluster analysis is to discover natural groupings of objects. The field of cluster analysis is crowded with diverse methods that make special assumptions about data and address different scientific aims. Despite its shortcomings in accuracy, hierarchical clustering is the dominant clustering method in bioinformatics. Biologists find the trees constructed by hierarchical clustering visually appealing and in tune with their evolutionary perspective. Hierarchical clustering operates on multiple scales simultaneously. This is essential, for instance, in transcriptome data, where one may be interested in making qualitative inferences about how lower-order relationships like gene modules lead to higher-order relationships like pathways or biological processes. The recently developed method of convex clustering preserves the visual appeal of hierarchical clustering while ameliorating its propensity to make false inferences in the presence of outliers and noise. The solution paths generated by convex clustering reveal relationships between clusters that are hidden by static methods such as k-means clustering. The current paper derives and tests a novel proximal distance algorithm for minimizing the objective function of convex clustering. The algorithm separates parameters, accommodates missing data, and supports prior information on relationships. Our program CONVEXCLUSTER incorporating the algorithm is implemented on ATI and nVidia graphics processing units (GPUs) for maximal speed. Several biological examples illustrate the strengths of convex clustering and the ability of the proximal distance algorithm to handle high-dimensional problems. CONVEXCLUSTER can be freely downloaded from the UCLA Human Genetics web site at http://www.genetics.ucla.edu/software/ PMID:25965340

  18. On formation mechanism of Pd-Ir bimetallic nanoparticles through thermal decomposition of [Pd(NH3)4][IrCl6

    Science.gov (United States)

    Asanova, Tatyana I.; Asanov, Igor P.; Kim, Min-Gyu; Gerasimov, Evgeny Yu.; Zadesenets, Andrey V.; Plyusnin, Pavel E.; Korenev, Sergey V.

    2013-10-01

    The formation mechanism of Pd-Ir nanoparticles during thermal decomposition of double complex salt [Pd(NH3)4][IrCl6] has been studied by in situ X-ray absorption (XAFS) and photoelectron (XPS) spectroscopies. The changes in the structure of the Pd and Ir closest to the surroundings and chemical states of Pd, Ir, Cl, and N atoms were traced in the range from room temperature to 420 °C in inert atmosphere. It was established that the thermal decomposition process is carried out in 5 steps. The Pd-Ir nanoparticles are formed in pyramidal/rounded Pd-rich (10-200 nm) and dendrite Ir-rich (10-50 nm) solid solutions. A d charge depletion at Ir site and a gain at Pd, as well as the intra-atomic charge redistribution between the outer d and s and p electrons of both Ir and Pd in Pd-Ir nanoparticles, were found to occur.

  19. PD-L1-specific T cells

    DEFF Research Database (Denmark)

    Ahmad, Shamaila Munir; Borch, Troels Holz; Hansen, Morten

    2016-01-01

    -specific T cells that recognize both PD-L1-expressing immune cells and malignant cells. Thus, PD-L1-specific T cells have the ability to modulate adaptive immune reactions by reacting to regulatory cells. Thus, utilization of PD-L1-derived T cell epitopes may represent an attractive vaccination strategy...... for targeting the tumor microenvironment and for boosting the clinical effects of additional anticancer immunotherapy. This review summarizes present information about PD-L1 as a T cell antigen, depicts the initial findings about the function of PD-L1-specific T cells in the adjustment of immune responses...

  20. The relationship between the PD-1/PD-L1 pathway and DNA mismatch repair in cervical cancer and its clinical significance

    Directory of Open Access Journals (Sweden)

    Feng YC

    2018-01-01

    Full Text Available Yang-chun Feng,1,2 Wen-li Ji,3 Na Yue,3 Yan-chun Huang,2 Xiu-min Ma1 1Clinical Laboratory Center, The First Affiliated Hospital of Xinjiang Medical University, 2Clinical Laboratory Center, 3Clinical Pathology Center, Tumor Hospital Affiliated to Xinjiang Medical University, Urumqi, People’s Republic of China Background: According to recent clinical observations, deficient DNA mismatch repair (dMMR is capable of improving antitumor effects of the PD-1/PD-L1 pathway, suggesting that dMMR may act as a prognostic indicator of PD-1/PD-L1 antibody drugs. In this study, we examined the dMMR and PD-1/PD-L1 expression, as well as explored the correlation of dMMR status with PD-1/PD-L1 expression in cervical cancer patients, in order to optimize cervical cancer patient selection for PD-1/PD-L1 antibody drug treatment, which is helpful to avoid adverse effects and keep costs manageable. Methods: Sixty-six tissue samples from patients with squamous cell carcinoma were collected, and data of their clinical characteristics were also gathered. Based on these samples, the expression levels of MLH1, MSH2, and PD-L1 in cancer cells were tested by immunohistochemical assay (IHC. Moreover, PD-1/PD-L1 expression in tumor-invading lymphocytes (TILs was detected by IHC as well. Six single-nucleotide-repeat markers of microsatellite instability (MSI, including NR-27, MONO-27, BAT-25, NR-24, NR-21, and BAT-26, were tested by capillary electrophoresis sequencer analysis. According to expression of MLH1, MSH2 and the MSI test, all 66 cases were divided into dMMR or proficient DNA mismatch repair (pMMR groups. The comparisons of dMMR and PD-L1 in cancer cells and of PD-1/PD-L1 in TILs were conducted categorized by age, childbearing history, history of abortion, ethnicity, and cancer cell differentiation subgroup. Furthermore, PD-L1 levels in cancer cells and PD-1/PD-L1 in TILs were analyzed and compared in both dMMR and pMMR subgroups. Results: Of the patient samples, 25

  1. Alternative splice variants of the human PD-1 gene

    DEFF Research Database (Denmark)

    Nielsen, Christian; Ohm-Laursen, Line; Barington, Torben

    2005-01-01

    PD-1 is an immunoregulatory receptor expressed on the surface of activated T cells, B cells, and monocytes. We describe four alternatively spliced PD-1 mRNA transcripts (PD-1Deltaex2, PD-1Deltaex3, PD-1Deltaex2,3, and PD-1Deltaex2,3,4) in addition to the full length isoform. PD-1Deltaex2 and PD-1...... and flPD-1 upon activation suggests an important interplay between the putative soluble PD-1 and flPD-1 possibly involved in maintenance of peripheral self-tolerance and prevention of autoimmunity....

  2. PD-L1 expression and the immune microenvironment in primary invasive lobular carcinomas of the breast.

    Science.gov (United States)

    Thompson, Elizabeth D; Taube, Janis M; Asch-Kendrick, Rebecca J; Ogurtsova, Aleksandra; Xu, Haiying; Sharma, Rajni; Meeker, Alan; Argani, Pedram; Emens, Leisha A; Cimino-Mathews, Ashley

    2017-11-01

    Tumor-infiltrating lymphocytes and immune checkpoint proteins such as PD-L1 are potential prognostic factors and therapeutic targets in breast cancer. Most studies characterizing the breast tumor immune microenvironment have focused on ductal carcinomas. Here we investigate the tumor microenvironment of primary invasive lobular carcinomas. Previously constructed tissue microarrays of 47 lobular carcinomas were labeled by immunohistochemistry for PD-L1, CD8, CD20, and FoxP3. The stromal immune infiltrate density was qualitatively scored as a percentage of tumor area: 1+ (50%). The average immune cell subtype per high-power field was quantitatively scored. The percentage PD-L1 labeling on tumor-infiltrating lymphocytes was scored as none, focal (lobular carcinomas contained PD-L1 + tumor-infiltrating lymphocytes with the majority showing 1+ immune infiltrates with focal-moderate PD-L1 labeling. PD-L1 was expressed by tumor cells in 17% of lobular carcinomas. In contrast to ductal carcinomas, there was no correlation between the immune infiltrate density, the PD-L1 expression by lobular carcinoma cells, tumor grade, or the expression of estrogen receptor or human epidermal growth factor receptor-2. However, both the tumor-infiltrating lymphocyte density and the average CD8 + T-cell counts correlated with immune cell PD-L1 status (P=0.004 and 0.03, respectively). Similar to breast ductal carcinomas, PD-L1 + lobular breast carcinomas had higher numbers of PD-L1 + tumor-infiltrating lymphocytes (63%) than PD-L1 - lobular carcinomas (23%; P=0.04). These data show that a subset of primary breast lobular carcinomas both express PD-L1 on tumor cells and contain PD-L1 + tumor-infiltrating lymphocytes, suggesting the possibility of both constitutive and adaptive PD-L1 expression. Together, these results support immunotherapy as a potential treatment for a subset of patients with primary invasive lobular breast carcinomas.

  3. Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

    International Nuclear Information System (INIS)

    Patel, Hasmukh A.; Bajaj, Hari C.; Jasra, Raksh Vir

    2008-01-01

    This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM

  4. The Pd distribution and Cu flow pattern of the Pd-plated Cu wire bond and their effect on the nanoindentation

    International Nuclear Information System (INIS)

    Lin, Yu-Wei; Wang, Ren-You; Ke, Wun-Bin; Wang, I-Sheng; Chiu, Ying-Ta; Lu, Kuo-Chang; Lin, Kwang-Lung; Lai, Yi-Shao

    2012-01-01

    Highlights: ► Pd distribution in Pd-plated Cu wires reveals the whirlpool flow pattern of Cu. ► The mechanisms of the Cu flow behavior and Pd distribution are proposed. ► At Pd-rich phases, small voids formed and followed the direction of Cu flow. ► Nanoindentation studies show the Cu ball bond is harder in regions with Pd. - Abstract: The Pd plating on the 20 μm Cu wire dissolves in the free air ball (FAB) and the Cu ball bond during the wire bonding process without forming intermetallic compounds. The limiting supply of Pd and the short bonding process, 15 ms of thermosonic bonding, result in uneven distribution of Pd in the as produced Cu ball bond. Also, the Pd-rich phase may accompany small voids formed within the FAB and the wire bond, and following the direction of semi-solid Cu flow. The Pd distribution, as evidenced by the focused ion beam (FIB) and wavelength dispersive X-ray spectroscopy (WDS) mapping, reveals the whirlpool flow pattern of Cu within the FAB and the ball bond. Pd distributes within the copper ball through convective transport by the copper flow. Additionally, hardness measurements by nanoindentation testing show that the Cu ball bond is harder in the regions where Pd exists.

  5. Dimensional representations of DSM-IV cluster B personality disorders in a population-based sample of Norwegian twins: a multivariate study.

    Science.gov (United States)

    Torgersen, S; Czajkowski, N; Jacobson, K; Reichborn-Kjennerud, T; Røysamb, E; Neale, M C; Kendler, K S

    2008-11-01

    The personality disorders (PDs) in the 'dramatic' cluster B [antisocial (ASPD), histrionic (HPD), narcissistic (NPD) and borderline (BPD)] demonstrate co-morbidity. However, the degree to which genetic and/or environmental factors influence their co-occurrence is not known and, with the exception of ASPD, the relative impact of genetic and environmental risk factors on liability to the cluster B PDs has not been conclusively established. PD traits were assessed in 1386 Norwegian twin pairs between the age of 19 and 35 years using the Structured Interview for DSM-IV Personality Disorders (SIDP-IV). Using the statistical package Mx, multivariate twin models were fitted to dimensional representations of the PDs. The best-fitting model, which did not include sex or shared family environment effects, included common genetic and environmental factors influencing all four dramatic PD traits, and factors influencing only ASPD and BPD. Heritability was estimated at 38% for ASPD traits, 31% for HPD traits, 24% for NPD traits and 35% for BPD traits. BPD traits had the lowest and ASPD traits the highest disorder-specific genetic variance. The frequently observed co-morbidity between cluster B PDs results from both common genetic and environmental influences. Etiologically, cluster B has a 'substructure' in which ASPD and BPD are more closely related to each other than to the other cluster B disorders.

  6. Impulsivity and Cluster B Personality Disorders.

    Science.gov (United States)

    Turner, Daniel; Sebastian, Alexandra; Tüscher, Oliver

    2017-03-01

    Impulsivity is a multifaceted construct and an important personality trait in various mental health conditions. Among personality disorders (PDs), especially cluster B PDs are affected. The aims of this review are to summarize the relevant findings of the past 3 years concerning impulsivity in cluster B PDs and to identify those subcomponents of self-reported impulsivity and experimentally measured impulse control that are most affected in these disorders. All studies referred to antisocial (ASPD) or borderline PD (BPD), and none were found for narcissistic or histrionic PD. In ASPD as well as BPD, self-report scales primarily revealed heightened impulsivity compared to healthy controls. In experimental tasks, ASPD patients showed impairments in response inhibition, while fewer deficits were found in delay discounting. BPD patients showed specific impairments in delay discounting and proactive interference, while response inhibition was less affected. However, after inducing high levels of stress, deficits in response inhibition could also be observed in BPD patients. Furthermore, negative affect led to altered brain activation patterns in BPD patients during impulse control tasks, but no behavioral impairments were found. As proposed by the DSM-5 alternative model for personality disorders, heightened impulsivity is a core personality trait in BPD and ASPD, which is in line with current research findings. However, different components of experimentally measured impulse control are affected in BPD and ASPD, and impulsivity occurring in negative emotional states or increased distress seems to be specific for BPD. Future research could be focused on measures that assess impulsive behaviors on a momentary basis as this is a promising approach especially for further ecological validation and transfer into clinical practice.

  7. Thermogravimetric study on the hydration of reactive magnesia and silica mixture at room temperature

    International Nuclear Information System (INIS)

    Jin, Fei; Al-Tabbaa, Abir

    2013-01-01

    Highlights: • The characteristics of reactive MgO vary significantly in terms of their impurity content and reactivity depending on their sources and calcination conditions. • The synthesis of magnesium silicate hydrate (MSH) is affected by the characteristics of the precursors, i.e., MgO and silica. • The reaction process in the MgO–SiO 2 –H 2 O system can be followed by TGA, and is essential to develop MSH-based materials. - Abstract: The synthesis of magnesium silicate hydrate (MSH), which has wide applications in both construction and environmental fields, has been studied for decades. However, it is known that the characteristics of magnesia (MgO) vary significantly depending on their calcination conditions, which is expected to affect their performance in the MgO–SiO 2 –H 2 O system. This paper investigated the effect of different MgO and silica sources on the formation of magnesium silicate hydrate (MSH) at room temperature. The hydration process was studied by mixing commercial reactive MgO and silica powders with water and curing for 1, 7 and 28 days. The hydration products were analysed with the help of X-ray diffraction (XRD) and thermogravimatric analysis (TGA). The results showed the continuous consumption of MgO and the existence of MSH and brucite and other minor phases such as magnesite and calcite. It is found that the Mg and Si sources have significant effect on the hydration process of MgO–SiO 2 –H 2 O system. The reaction degree is controlled by the availability of dissolved Mg and Si in the solution. The former is determined by the reactivity of MgO and the latter is related to the reactivity of the silica as well as the pH of the system

  8. The PD1:PD-L1/2 Pathway from Discovery to Clinical Implementation.

    Science.gov (United States)

    Bardhan, Kankana; Anagnostou, Theodora; Boussiotis, Vassiliki A

    2016-01-01

    The immune system maintains a critically organized network to defend against foreign particles, while evading self-reactivity simultaneously. T lymphocytes function as effectors and play an important regulatory role to orchestrate the immune signals. Although central tolerance mechanism results in the removal of the most of the autoreactive T cells during thymic selection, a fraction of self-reactive lymphocytes escapes to the periphery and pose a threat to cause autoimmunity. The immune system evolved various mechanisms to constrain such autoreactive T cells and maintain peripheral tolerance, including T cell anergy, deletion, and suppression by regulatory T cells (T Regs ). These effects are regulated by a complex network of stimulatory and inhibitory receptors expressed on T cells and their ligands, which deliver cell-to-cell signals that dictate the outcome of T cell encountering with cognate antigens. Among the inhibitory immune mediators, the pathway consisting of the programed cell death 1 (PD-1) receptor (CD279) and its ligands PD-L1 (B7-H1, CD274) and PD-L2 (B7-DC, CD273) plays an important role in the induction and maintenance of peripheral tolerance and for the maintenance of the stability and the integrity of T cells. However, the PD-1:PD-L1/L2 pathway also mediates potent inhibitory signals to hinder the proliferation and function of T effector cells and have inimical effects on antiviral and antitumor immunity. Therapeutic targeting of this pathway has resulted in successful enhancement of T cell immunity against viral pathogens and tumors. Here, we will provide a brief overview on the properties of the components of the PD-1 pathway, the signaling events regulated by PD-1 engagement, and their consequences on the function of T effector cells.

  9. The PD1: PD-L1/2 pathway from discovery to clinical implementation

    Directory of Open Access Journals (Sweden)

    Kankana Bardhan

    2016-12-01

    Full Text Available The immune system has the difficult challenge of discerning and defending against a diversity of microbial pathogens, while simultaneously avoiding self-reactivity. T lymphocytes function as effectors and regulators of the immune system. While central tolerance mechanism results in deletion of the majority of self-reactive T lymphocytes during thymic selection, a fraction of self reactive lymphocytes escapes to the periphery and retains the potential to inflict destructive autoimmune pathology. The immune system evolved various mechanisms to restrain such auto-reactive T cells and maintain peripheral tolerance, including T cell anergy, deletion, and suppression by regulatory T cells (TRegs. These effects are regulated by a complex network of stimulatory and inhibitory receptors expressed on T cells and their ligands, which deliver cell-to-cell signals that dictate the outcome of T cell encountering with cognate antigens. Among the inhibitory immune mediators, the pathway consisting of the programmed cell death 1 (PD-1 receptor (CD279 and its ligands PD-L1 (B7-H1, CD274 and PD-L2 (B7-DC; CD273 plays a vital role in the induction and maintenance of peripheral tolerance and for the maintenance of T cell homeostasis. In contrast to its beneficial role in self-tolerance, the PD-1: PD-L1/L2 pathway mediates potent inhibitory signals that prevent the expansion and function of T effector cells and have detrimental effects on antiviral and antitumor immunity. Therapeutic targeting of this pathway has resulted in successful enhancement of T cell immunity against viral pathogens and tumors. Here, we will provide a brief overview on the properties of the components of the PD-1 pathway, the signaling events that are regulated by PD-1 triggering, and their consequences on the function of T effector cells.

  10. Enhancement of Degradation and Dechlorination of Trichloroethylene via Supporting Palladium/Iron Bimetallic Nanoparticles onto Mesoporous Silica

    Directory of Open Access Journals (Sweden)

    Jianjun Wei

    2016-07-01

    Full Text Available This study is aimed to prevent the agglomeration of Pd/Fe bimetallic nanoparticles and thus improve the efficiency toward degradation and dechlorination of chlorinated organic contaminants. A mesoporous silica with a primary pore diameter of 8.3 nm and a specific surface area of 688 m2/g was prepared and used as the host of Pd/Fe nanoparticles. The Pd/Fe nanoparticles were deposited onto or into the mesoporous silica by reduction of ferrous ion and hexachloropalladate ion in aqueous phase. Batch degradation and dechlorination reactions of trichloroethylene were conducted with initial trichloroethylene concentration of 23.7 mg/L, iron loading of 203 or 1.91 × 103 mg/L and silica loading of 8.10 g/L at 25 °C. Concentration of trichloroethylene occurs on the supported Pd/Fe nanoparticles, with trichloroethylene degrading to 56% and 59% in 30 min on the supported Pd/Fe nanoparticles with weight percentage of palladium to iron at 0.075% and 0.10% respectively. The supported Pd/Fe nanoparticles exhibit better dechlorination activity. When the supported Pd/Fe nanoparticles with a weight percentage of palladium to iron of 0.10% were loaded much less than the bare counterpart, the yield of ethylene plus ethane in 10 h on them was comparable, i.e., 19% vs. 21%. This study offers a future approach to efficiently combine the reactivity of supported Pd/Fe nanoparticles and the adsorption ability of mesoporous silica.

  11. Deposition and characterization of plasma sprayed Ni-5A1/ magnesia stabilized zirconia based functionally graded thermal barrier coating

    International Nuclear Information System (INIS)

    Baig, M N; Khalid, F A

    2014-01-01

    Thermal barrier coatings (TBCs) are employed to protect hot section components in industrial and aerospace gas turbine engines. Conventional TBCs frequently fail due to high residual stresses and difference between coefficient of thermal expansion (CTE) of the substrate and coatings. Functionally graded thermal barrier coatings (FG-TBCs) with gradual variation in composition have been proposed to minimize the problem. In this work, a five layered functionally graded thermal barrier coating system was deposited by atmospheric plasma spray (APS) technique on Nimonic 90 substrates using Ni-5Al as bond coat (BC) and magnesia stabilized zirconia as top coat (TC). The coatings were characterized by SEM, EDS, XRD and optical profilometer. Microhardness and coefficient of thermal expansion of the five layers deposited as individual coatings were also measured. The deposited coating system was oxidized at 800°C. SEM analysis showed that five layers were successfully deposited by APS to produce a FG-TBC. The results also showed that roughness (Ra) of the individual layers decreased with an increase in TC content in the coatings. It was found that microhardness and CTE values gradually changed from bond coat to cermet layers to top coat. The oxidized coated sample revealed parabolic behavior and changes in the surface morphology and composition of coating

  12. Colloidal lithography nanostructured Pd/PdO x core–shell sensor for ppb level H2S detection

    Science.gov (United States)

    Benedict, Samatha; Lumdee, Chatdanai; Dmitriev, Alexandre; Anand, Srinivasan; Bhat, Navakanta

    2018-06-01

    In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdO x ) core–shell sensor for ppb level H2S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H2S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H2S at the optimum operating temperature of 200 °C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H2S sensing characteristics. The nanostructured Pd/PdO x sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15 s and 100 s, respectively) compared to the unstructured Pd/PdO x counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdO x sensors is done using UV–vis spectroscopy and x-ray photoemission spectroscopy.

  13. Tackling Cancer Resistance by Immunotherapy: Updated Clinical Impact and Safety of PD-1/PD-L1 Inhibitors

    Directory of Open Access Journals (Sweden)

    Shifaa M. Abdin

    2018-01-01

    Full Text Available Cancer therapy has been constantly evolving with the hope of finding the most effective agents with the least toxic effects to eradicate tumors. Cancer immunotherapy is currently among the most promising options, fulfilling this hope in a wide range of tumors. Immunotherapy aims to activate immunity to fight cancer in a very specific and targeted manner; however, some abnormal immune reactions known as immune-related adverse events (IRAEs might occur. Therefore, many researchers are aiming to define the most proper protocols for managing these complications without interfering with the anticancer effect. One of these targeted approaches is the inhibition of the interaction between the checkpoint protein, programmed death-receptor 1 (PD-1, and its ligand, programmed death-ligand 1 (PD-L1, via a class of antibodies known as PD-1/PD-L1 inhibitors. These antibodies achieved prodigious success in a wide range of malignancies, including those where optimal treatment is not yet fully identified. In this review, we have critically explored and discussed the outcome of the latest PD-1 and PD-L1 inhibitor studies in different malignancies compared to standard chemotherapeutic alternatives with a special focus on the clinical efficacy and safety. The approval of the clinical applications of nivolumab, pembrolizumab, atezolizumab, avelumab, and durvalumab in the last few years clearly highlights the hopeful future of PD-1/PD-L1 inhibitors for cancer patients. These promising results of PD-1/PD-L1 inhibitors have encouraged many ongoing preclinical and clinical trials to explore the extent of antitumor activity, clinical efficacy and safety as well as to extend their applications.

  14. Tackling Cancer Resistance by Immunotherapy: Updated Clinical Impact and Safety of PD-1/PD-L1 Inhibitors.

    Science.gov (United States)

    Abdin, Shifaa M; Zaher, Dana M; Arafa, El-Shaimaa A; Omar, Hany A

    2018-01-25

    Cancer therapy has been constantly evolving with the hope of finding the most effective agents with the least toxic effects to eradicate tumors. Cancer immunotherapy is currently among the most promising options, fulfilling this hope in a wide range of tumors. Immunotherapy aims to activate immunity to fight cancer in a very specific and targeted manner; however, some abnormal immune reactions known as immune-related adverse events (IRAEs) might occur. Therefore, many researchers are aiming to define the most proper protocols for managing these complications without interfering with the anticancer effect. One of these targeted approaches is the inhibition of the interaction between the checkpoint protein, programmed death-receptor 1 (PD-1), and its ligand, programmed death-ligand 1 (PD-L1), via a class of antibodies known as PD-1/PD-L1 inhibitors. These antibodies achieved prodigious success in a wide range of malignancies, including those where optimal treatment is not yet fully identified. In this review, we have critically explored and discussed the outcome of the latest PD-1 and PD-L1 inhibitor studies in different malignancies compared to standard chemotherapeutic alternatives with a special focus on the clinical efficacy and safety. The approval of the clinical applications of nivolumab, pembrolizumab, atezolizumab, avelumab, and durvalumab in the last few years clearly highlights the hopeful future of PD-1/PD-L1 inhibitors for cancer patients. These promising results of PD-1/PD-L1 inhibitors have encouraged many ongoing preclinical and clinical trials