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Articles 991 - 1020 of 2524

Full-Text Articles in Physical Sciences and Mathematics

Photochemical Cycling Of Iron Mediated By Dicarboxylates: Special Effect Of Malonate, Zhaohui Wang, Chen Xi, Hongwei Ji, Wanghong Ma, Chuncheng Chen, Jincai Zhao Sep 2013

Photochemical Cycling Of Iron Mediated By Dicarboxylates: Special Effect Of Malonate, Zhaohui Wang, Chen Xi, Hongwei Ji, Wanghong Ma, Chuncheng Chen, Jincai Zhao

Dr Zhaohui Wang

Photochemical redox cycling of iron coupled with oxidation of malonate (Mal) ligand has been investigated under conditions that are representative of atmospheric waters. Malonate exhibited significantly different characteristics from oxalate and other dicarboxylates (or monocarboxylates). Both strong chelating ability with Fe(III) and strong molar absorptivities, but much low efficiency of Fe(II) formation (ΦFe(II) = 0.0022 ± 0.0009, 300−366 nm) were observed for Fe(III)−Mal complexes (FMCs). Fe(III) speciation calculation indicated that Mal is capable of mediating the proportion between two photoactive species of Fe(III)−OH complexes and FMCs by changing the Mal concentration. Spin-trapping electron spin resonance (ESR) experiments proved the formation …

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Adsorption Behavior Of Glucose On Pyrite Surface Investigated By Tg, Ftir And Xrd Analyses, Zhaohui Wang, Xuehui Xie, Shengmu Xiao, Jianshe Liu Sep 2013

Adsorption Behavior Of Glucose On Pyrite Surface Investigated By Tg, Ftir And Xrd Analyses, Zhaohui Wang, Xuehui Xie, Shengmu Xiao, Jianshe Liu

Dr Zhaohui Wang

The interaction of glucose with pyrite has been investigated by a series of surface analyses, such as amounts adsorbed, TG, FTIR and XRD measurements. The adsorption experiment reveals that glucose would rapidly adsorb on the pyrite surface within 60 min. However, physical adhesion characterized as multi-molecular layer adsorption may occur based on adsorption isotherm type. All results obtained by TG and FTIR suggest that no adsorption took place after several times of washing. XRD results indicate that crystal structure of pyrite was not obviously destructed after glucose was added. The interplane distances of (111), (400) after interaction between glucose and …

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Photochemical Coupling Reactions Between Fe(Iii)/Fe(Ii), Cr(Vi)/Cr(Iii) And Polycarboxylates: Inhibitory Effect Of Cr Species, Zhaohui Wang, Wanhong Ma, Chuncheng Chen, Jincai Zhao Sep 2013

Photochemical Coupling Reactions Between Fe(Iii)/Fe(Ii), Cr(Vi)/Cr(Iii) And Polycarboxylates: Inhibitory Effect Of Cr Species, Zhaohui Wang, Wanhong Ma, Chuncheng Chen, Jincai Zhao

Dr Zhaohui Wang

The roles of chromium species on photochemical cycling of iron and mineralization of polycarboxylates are examined in the presence of Cr(VI) or Cr(III) at pH 2.2−4.0. Under UV irradiation, Cr(III) altered the redox equilibrium of iron species, leading to the shift of the photosteady state toward Fe(II). After a longer time of illumination, total organic carbon (TOC) approached a steady state in the presence of Cr(III) or Cr(VI), whereas oxalate was thoroughly mineralized in the absence of Cr species. The TOC of steady state was closely related to the kind of polycarboxylates, Cr species dosages, pH and O2 atmosphere, but …

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Probing Paramagnetic Species In Titania-Based Heterogeneous Photocatalysis By Electron Spin Resonance (Esr) Spectroscopy- A Mini Review, Zhaohui Wang, Wanhong Ma, Chuncheng Chen, Hongwei Ji, Jincai Zhao Sep 2013

Probing Paramagnetic Species In Titania-Based Heterogeneous Photocatalysis By Electron Spin Resonance (Esr) Spectroscopy- A Mini Review, Zhaohui Wang, Wanhong Ma, Chuncheng Chen, Hongwei Ji, Jincai Zhao

Dr Zhaohui Wang

Many paramagnetic species such as active surface sites, reactive oxygen species (ROS) and organic radicals derived from the photodegradation of organics were involved in the heterogeneous photocatalysis. Identification and characterization of these paramagnetic species are essentially conducted using electron spin resonance (ESR) techniques, which can provide a detailed understanding of the radical composition and structure on the basis of the unique feature of g, hyperfine, and superhyperfine tensors for each kind of radicals of interest. In the present review, the basic theoretical principles of the ESR technique and its application in the field of TiO2-based heterogeneous photocatalysis are generally summarized. …

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Degradation Of Reactive Dyes By Contact Glow Discharge Electrolysis In The Presence Of Cl− Ions: Kinetics And Aox Formation, Sadiqua Ramjaum, Ruixia Yuan, Zhaohui Wang, Jianshe Liu Sep 2013

Degradation Of Reactive Dyes By Contact Glow Discharge Electrolysis In The Presence Of Cl− Ions: Kinetics And Aox Formation, Sadiqua Ramjaum, Ruixia Yuan, Zhaohui Wang, Jianshe Liu

Dr Zhaohui Wang

The plasma generated around the anode during contact glow discharge electrolysis (CGDE) is a rich source of hydroxyl (OH) radicals that can efficiently degrade organic contaminants in aqueous solutions. The degradation of textile azo dyestuffs, Reactive Yellow 176 (Y3RS), Reactive Red 239 (R3BS) and Reactive Black 5 (B5), by anodic CGDE was investigated in the presence of chloride (Cl−) ions. The degradation kinetics of the dyes was dependent on the concentration of Cl− ions and on the respective dye being treated. R3BS degradation was inhibited by Cl− ions in the range of 0–0.01 M. When the …

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Effects Of Chloride Ions On Bleaching Of Azo Dyes By Co2+/Oxone Regent: Kinetic Analysis, Zhaohui Wang, Ruxia Yuan, Yaoguang Guo, Lei Xu, Jinashe Liu Sep 2013

Effects Of Chloride Ions On Bleaching Of Azo Dyes By Co2+/Oxone Regent: Kinetic Analysis, Zhaohui Wang, Ruxia Yuan, Yaoguang Guo, Lei Xu, Jinashe Liu

Dr Zhaohui Wang

Orange II (Org II), one of the most common used azo dyes, was taken as a model to investigate the effects of chloride ion on dye decoloration in cobalt/peroxymonosulfate (Co/PMS) system. A significant decrease in the rate of Org II decoloration was observed upon addition of Cl− (0.05–10 mM), but further addition of Cl− (>50 mM) apparently accelerated dyes degradation. This dual effect of chloride on dyes bleaching was also observed as other halide ions (e.g. Br−, I−) or other azo dyes were present in Co/PMS system. In the Co-free PMS solutions, the …

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Improving Processor Efficiency By Statically Pipelining Instructions, Ian Finlayson, Brandon Davis, Peter Gavin, Gang-Ryung Uh, David Whalley, Magnus Själander, Gary Tyson Sep 2013

Improving Processor Efficiency By Statically Pipelining Instructions, Ian Finlayson, Brandon Davis, Peter Gavin, Gang-Ryung Uh, David Whalley, Magnus Själander, Gary Tyson

Gang-Ryung Uh

A new generation of applications requires reduced power consumption without sacrificing performance. Instruction pipelining is commonly used to meet application performance requirements, but some implementation aspects of pipelining are inefficient with respect to energy usage. We propose static pipelining as a new instruction set architecture to enable more efficient instruction flow through the pipeline, which is accomplished by exposing the pipeline structure to the compiler. While this approach simplifies hardware pipeline requirements, significant modifications to the compiler are required. This paper describes the code generation and compiler optimizations we implemented to exploit the features of this architecture. We show that …

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Uncertainty Associated With Modeling The Global Ionosphere, Janelle Jenniges, Ariel Acebal, Larry Gardner, Robert Schunk, Lie Zhu Sep 2013

Uncertainty Associated With Modeling The Global Ionosphere, Janelle Jenniges, Ariel Acebal, Larry Gardner, Robert Schunk, Lie Zhu

Janelle V Jenniges

A study has been conducted of the effect that different physical assumptions have on global models of the electron density distribution. The study was conducted with the Ionosphere Forecast Model (IFM) and the Ionosphere Plasmasphere Model (IPM) developed by Utah State University. Both physics-based, time-dependent, global models use the same empirical models for the neutral atmosphere (MSIS) and neutral wind (Horizontal Wind Model, HWM), but the altitude range, thermal structure, number of ion species, and magnetic 2ield are different. The IFM covers the altitude range from 90-1400 km, calculates the densities for four ions (NO+, O2+, N2+, O+), has a …

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Exploiting Redundancy To Boost Performance In A Raid-10 Style Cluster-Based File System, Yifeng Zhu, Hong Jiang, Xiao Qin, Dan Feng, David Swanson Sep 2013

Exploiting Redundancy To Boost Performance In A Raid-10 Style Cluster-Based File System, Yifeng Zhu, Hong Jiang, Xiao Qin, Dan Feng, David Swanson

Yifeng Zhu

While aggregating the throughput of existing disks on cluster nodes is a cost-effective approach to alleviate the I/O bottleneck in cluster computing, this approach suffers from potential performance degradations due to contentions for shared resources on the same node between storage data processing and user task computation. This paper proposes to judiciously utilize the storage redundancy in the form of mirroring existed in a RAID-10 style file system to alleviate this performance degradation. More specifically, a heuristic scheduling algorithm is developed, motivated from the observations of a simple cluster configuration, to spatially schedule write operations on the nodes with less …

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Amp: An Affinity-Based Metadata Prefetching Scheme In Large-Scale Distributed Storage Systems, Lin Li, Xuemin Li, Hong Jiang, Yifeng Zhu Sep 2013

Amp: An Affinity-Based Metadata Prefetching Scheme In Large-Scale Distributed Storage Systems, Lin Li, Xuemin Li, Hong Jiang, Yifeng Zhu

Yifeng Zhu

Prefetching is an effective technique for improving file access performance, which can reduce access latency for I/O systems. In distributed storage system, prefetching for metadata files is critical for the overall system performance. In this paper, an Affinity-based Metadata Prefetching (APM) scheme is proposed for metadata servers in large-scale distributed storage systems to provide aggressive metadata prefetching. Through mining useful information about metadata assesses from past history, AMP can discover metadata file affinities accurately and intelligently for prefetching. Compared with LRU and some of the latest file prefetching algorithms such as NEXUS and C-miner, trace-driven simulations show that AMP can …

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Hba: Distributed Metadata Management For Large Cluster-Based Storage Systems, Yifeng Zhu, Hong Jiang, Jun Wang, Feng Xian Sep 2013

Hba: Distributed Metadata Management For Large Cluster-Based Storage Systems, Yifeng Zhu, Hong Jiang, Jun Wang, Feng Xian

Yifeng Zhu

An efficient and distributed scheme for file mapping or file lookup is critical in decentralizing metadata management within a group of metadata servers. This paper presents a novel technique called Hierarchical Bloom Filter Arrays (HBA) to map filenames to the metadata servers holding their metadata. Two levels of probabilistic arrays, namely, the Bloom filter arrays with different levels of accuracies, are used on each metadata server. One array, with lower accuracy and representing the distribution of the entire metadata, trades accuracy for significantly reduced memory overhead, whereas the other array, with higher accuracy, caches partial distribution information and exploits the …

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Smartstore: A New Metadata Organization Paradigm With Semantic-Awareness For Next-Generation File Systems, Yu Hua, Hong Jiang, Yifeng Zhu, Dan Feng, Lei Tian Sep 2013

Smartstore: A New Metadata Organization Paradigm With Semantic-Awareness For Next-Generation File Systems, Yu Hua, Hong Jiang, Yifeng Zhu, Dan Feng, Lei Tian

Yifeng Zhu

Existing storage systems using hierarchical directory tree do not meet scalability and functionality requirements for exponentially growing datasets and increasingly complex queries in Exabyte-level systems with billions of files. This paper proposes semantic-aware organization, called SmartStore, which exploits metadata semantics of files to judiciously aggregate correlated files into semantic-aware groups by using information retrieval tools. Decentralized design improves system scalability and reduces query latency for complex queries (range and top-k queries), which is conducive to constructing semantic-aware caching, and conventional filename-based query. SmartStore limits search scope of complex query to a single or a minimal number of semantically related groups …

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Assessing Occupant Comfort In An Iconic Sustainable Education Building, Rick Best, Brian Purdey Sep 2013

Assessing Occupant Comfort In An Iconic Sustainable Education Building, Rick Best, Brian Purdey

Rick Best

The building that houses the Mirvac School of Sustainable Development at Bond University is the first educational building to achieve a six Green Star rating from the Green Building Council of Australia. It has won numerous awards since opening in August 2008 including being judged the RICS (Royal Institution of Chartered Surveyors) Sustainable Building of 2009. After more than two years in use a post-occupancy evaluation study was carried out to assess the performance of the building from the viewpoint of the users; both resident staff and transient students. Results for factors such as lighting, thermal comfort, noise and air …

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Valuing Water: Variability And The Lake Eyre Basin, Central Australia, Leah Gibbs Sep 2013

Valuing Water: Variability And The Lake Eyre Basin, Central Australia, Leah Gibbs

Leah Maree Gibbs

'Environmental values' form an increasingly important component of natural resource management, but use of the term 'value' is dominated by a narrow and limiting utility-based definition. In this paper I consider theories of value and practices of valuing water in the arid and semi-arid Lake Eyre Basin, central Australia. While value is the subject of diverse meanings - both within a range of academic disciplines and as understood by people in specific places - methods of valuing water in natural resource management are limited by reductionism, anthropocentrism and cultural specificity. This conceptualisation of value does not adequately capture what people …

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Evolution Of Enzymatic Activities In The Enolase Superfamily: L-Rhamnonate Dehydratase, John Rakus, Alexander Fedorov, Elena Fedorov, Margaret Glasner, Brian Hubbard, Joseph Delli, Patricia Babbitt, Steven Almo, John Gerlt Sep 2013

Evolution Of Enzymatic Activities In The Enolase Superfamily: L-Rhamnonate Dehydratase, John Rakus, Alexander Fedorov, Elena Fedorov, Margaret Glasner, Brian Hubbard, Joseph Delli, Patricia Babbitt, Steven Almo, John Gerlt

John F. Rakus

The L-rhamnonate dehydratase (RhamD) function was assigned to a previously uncharacterized family in the mechanistically diverse enolase superfamily that is encoded by the genome of Escherichia coli K-12. We screened a library of acid sugars to discover that the enzyme displays a promiscuous substrate specificity: L-rhamnonate (6-deoxy-L-mannonate) has the “best” kinetic constants, with L-mannonate, L-lyxonate, and D-gulonate dehydrated less efficiently. Crystal structures of the RhamDs from both E. coli K-12 and Salmonella typhimurium LT2 (95% sequence identity) were obtained in the presence of Mg2+; the structure of the RhamD from S. typhimurium was also obtained in the presence of 3-deoxy-L-rhamnonate …

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Parcel Subdivision Automation For Agent-Based Land Use Modelling, Rohan Wickramasuriya, Laurie Chisholm, Marji Puotinen, Nicholas Gill, Peter Klepeis Sep 2013

Parcel Subdivision Automation For Agent-Based Land Use Modelling, Rohan Wickramasuriya, Laurie Chisholm, Marji Puotinen, Nicholas Gill, Peter Klepeis

Rohan Wickramasuriya, Ph.D.

To a significant extent rural Australia is transforming into multifunctional landscapes. Amenity migration (i.e. movement of people from metropolitan to rural settings) is a major driving force of this transition in many areas. However, the effects of amenity migration on the receiving landscapes are not yet fully understood. Agent-based land use modelling helps unravel the complex spatio-temporal relationships that affect landscape response to change from amenity migration. A land subdivision module is essential for a complete agent-based land use model developed for these landscapes because the land sold to in-migrants are lots that are subdivided from much larger tracts. In …

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A Pedagogical Evaluation Of New State Model Diagrams For Teaching Internetwork Technologies, Stanislaw Maj, Gurpreet Kohli, Tony Fetherston Sep 2013

A Pedagogical Evaluation Of New State Model Diagrams For Teaching Internetwork Technologies, Stanislaw Maj, Gurpreet Kohli, Tony Fetherston

Tony Fetherston

Curriculum based on internetworking devices is primarily based on the Command Line Interface (CLI) and case studies. However a single CLI command may produce output that is not only hierarchical but must also be interpreted - both represent learning difficulties for novices. It should also be noted that device status requires many different CLI commands. Internetworking curriculum also typically defines devices as 'black boxes' - this is not a good teaching strategy. New state models were designed that diagrammatically integrated relevant output from different CLI commands with protocol finite state information and protocol stacks by means of tables. The diagrams …

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Preparation And Characterization Of 3 Nm Magnetic Niau Nanoparticles, Bethany Auten, Benjamin Hahn, Ganesh Vijayaraghavan, Keith Stevenson, Bert Chandler Sep 2013

Preparation And Characterization Of 3 Nm Magnetic Niau Nanoparticles, Bethany Auten, Benjamin Hahn, Ganesh Vijayaraghavan, Keith Stevenson, Bert Chandler

Bert D Chandler

Using PAMAM dendrimers as nanoparticle templates, a synthetic route to prepare 3 nm magnetic NiAu nanoparticles was developed. Aqueous solutions of hydroxyl-terminated generation 5 PAMAM dendrimers in 25 mM NaClO4 were shown to bind aqueous NiII. Coreduction of NiII and AuIII salts yielded bimetallic dendrimer stabilized nanoparticles, which were extracted into toluene with decanethiol. Characterization of the resulting monolayer protected clusters (MPCs) with transmission electron microscopy and UV-visible, atomic absorption, and X-ray photoelectron spectroscopies suggested that the MPCs had substantial surface enrichment in Au. Superconducting quantum interference device (SQUID) measurements at 5 K show the bimetallic MPCs to have low …

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Synthesis And Characterization Of Dendrimer Templated Supported Bimetallic Pt-Au Nanoparticles, Huifang Lang, Stephen Maldonado, Keith Stevenson, Bert Chandler Sep 2013

Synthesis And Characterization Of Dendrimer Templated Supported Bimetallic Pt-Au Nanoparticles, Huifang Lang, Stephen Maldonado, Keith Stevenson, Bert Chandler

Bert D Chandler

Bimetallic dendrimer-stabilized nanoparticles (DSNs) were used to prepare supported Pt-Au catalysts within the bulk miscibility gap for this binary system. Hydroxy-terminated generation 5 PAMAM dendrimers were used to prepare Cu0 nanoparticles (NPs). The Cu0 NPs were subsequently used to reduce K2PtCl4 and HAuCl4, preparing stabilized bimetallic Pt-Au NPs with a 1:1 stoichiometry. The stabilized NPs were adsorbed onto a high surface area silica support and thermally activated to remove the dendrimers. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and infrared spectroscopy of adsorbed CO showed that this preparation route resulted in NPs in which the two metals are intimately …

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Adsorption Of Co On Supported Gold Nanoparticle Catalysts: A Comparative Study, Heather Hartshorn, Christopher Pursell, Bert Chandler Sep 2013

Adsorption Of Co On Supported Gold Nanoparticle Catalysts: A Comparative Study, Heather Hartshorn, Christopher Pursell, Bert Chandler

Bert D Chandler

The adsorption of CO on three different gold nanoparticle catalysts supported on high surface area TiO2 was studied using infrared transmission spectroscopy at room temperature and CO pressures typically used in CO oxidation reactions. The three, real-world catalysts were Au catalysts synthesized in our laboratory from thiol monolayer protected clusters (MPCs) and two commercial catalysts from the World Gold Council (WGC and AuTEK). Within experimental reproducibility, the adsorption data for the three catalysts are indistinguishable. While showing approximately Langmuir behavior, the adsorption data also show coverage dependence, as others have observed for many catalyst systems. Two approaches were used to …

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Air And Water Free Solid-Phase Synthesis Of Thiol Stabilized Au Nanoparticles With Anchored, Recyclable Dendrimer Templates, John Gilbertson, Ganesh Vijayaraghavan, Keith Stevenson, Bert Chandler Sep 2013

Air And Water Free Solid-Phase Synthesis Of Thiol Stabilized Au Nanoparticles With Anchored, Recyclable Dendrimer Templates, John Gilbertson, Ganesh Vijayaraghavan, Keith Stevenson, Bert Chandler

Bert D Chandler

Solid-phase synthetic templates for Au nanoparticles were developed using Merrifield resins and polyamidoamine (PAMAM) dendrimers. This synthetic scheme affords the opportunity to prepare metal nanoparticles in the absence of air and water, and it does not necessitate phase transfer agents that can be difficult to remove in subsequent steps. Amine-terminated generation 5 PAMAM (G5NH2) dendrimers were grafted to anhydride functionalized polystyrene resin beads and alkylated with 1,2-epoxydodecane to produce G5C12anch. The anchored dendrimers bound both CoII and AuIII salts from toluene solutions at ratios comparable to those of solution phase alkyl-terminated PAMAM dendrimers. The encapsulated AuIII salts could be reduced …

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Kinetic Evaluation Of Highly Active Supported Gold Catalysts Prepared From Monolayer-Protected Clusters: An Experimental Michaelis-Menten Approach For Determining The Oxygen Binding Constant During Co Oxidation Catalysis, Cormac Long, John Gilbertson, Ganesh Vijayaraghavan, Keith Stevenson, Christopher Pursell, Bert Chandler Sep 2013

Kinetic Evaluation Of Highly Active Supported Gold Catalysts Prepared From Monolayer-Protected Clusters: An Experimental Michaelis-Menten Approach For Determining The Oxygen Binding Constant During Co Oxidation Catalysis, Cormac Long, John Gilbertson, Ganesh Vijayaraghavan, Keith Stevenson, Christopher Pursell, Bert Chandler

Bert D Chandler

Thiol monolayer-protected Au clusters (MPCs) were prepared using dendrimer templates, deposited onto a high-surface-area titania, and then the thiol stabilizers were removed under H2/N2. The resulting Au catalysts were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy of adsorbed CO. The Au catalysts prepared via this route displayed minimal particle agglomeration during the deposition and activation steps. Structural data obtained from the physical characterization of the Au catalysts were comparable to features exhibited from a traditionally prepared standard Au catalyst obtained from the World Gold Council (WGC). A differential kinetic study of CO oxidation catalysis by the …

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Enhanced Oxygen Activation Over Supported Bimetallic Au-Ni Catalysts, Bert Chandler, Cormac Long, John Gilbertson, Christopher Pursell, Ganesh Vijayaraghavan, Keith Stevenson Sep 2013

Enhanced Oxygen Activation Over Supported Bimetallic Au-Ni Catalysts, Bert Chandler, Cormac Long, John Gilbertson, Christopher Pursell, Ganesh Vijayaraghavan, Keith Stevenson

Bert D Chandler

New bimetallic Ni-Au supported nanoparticle catalysts were prepared by using dendrimer templated nanoparticles. Amine-terminated generation 5 polyamidoamine (PAMAM) dendrimers were anchored to a commercial silica with a siloxane linked anhydride. The dendrimer was then alkylated and used to template Ni-Au nanoparticles, which were subsequently extracted into organic solution as thiol monolayer protected clusters (MPCs). Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) indicated bimetallic nanoparticles of about 2 nm in size. Nanoparticles were deposited onto P-25 TiO2, and the capping thiol ligands were removed under flowing H2. DRIFTS infrared spectra of adsorbed CO showed only Au on the catalyst …

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Low-Temperature Activation Conditions For Pamam Dendrimer Templated Pt Nanoparticles, Anil Singh, Bert Chandler Sep 2013

Low-Temperature Activation Conditions For Pamam Dendrimer Templated Pt Nanoparticles, Anil Singh, Bert Chandler

Bert D Chandler

Surface immobilized polyamidoamine (PAMAM) dendrimer templated Pt nanoparticles were employed as precursors to heterogeneous catalysts. CO oxidation catalysis and in situ infrared spectroscopy were used to evaluate conditions for dendrimer removal. Infrared spectroscopy showed thatPAMAMdendrimer amide bonds begin decomposing at temperatures as low as 75 °C. Although the amide stretches are completely removed after 3 h of oxidation at 300 °C, 16 h were required to reach maximum catalytic activity. Further treatment under oxidizing or reducing atmospheres did not cause substantial changes in activity. Infrared spectroscopy of the activated materials indicated that organic residues, probably surface carboxylates, are formed during …

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Origin Of Enantioselection In Chiral Alcohol Oxidation Catalyzed By Pd[(-)-Sparteine]Cl2, Jaime Mueller, Anne Cowell, Bert Chandler, Matthew Sigman Sep 2013

Origin Of Enantioselection In Chiral Alcohol Oxidation Catalyzed By Pd[(-)-Sparteine]Cl2, Jaime Mueller, Anne Cowell, Bert Chandler, Matthew Sigman

Bert D Chandler

A kinetic investigation into the origin of enantioselectivity for the Pd[(-)-sparteine]Cl2-catalyzed aerobic oxidative kinetic resolution (OKR) is reported. A mechanism to account for a newly discovered chloride dissociation from Pd[(-)-sparteine]Cl2 prior to alcohol binding is proposed. The mechanism includes (1) chloride dissociation from Pd[(-)-sparteine]Cl2 to form cationic Pd(-)-sparteine]Cl, (2) alcohol binding, (3) deprotonation of Pd-bound alcohol to form a Pd-alkoxide, and (4) â-hydride elimination of Pd-alkoxide to form ketone product and a Pd-hydride. Utilizing the addition of (-)-sparteine HCl to control the [Cl-] and [H+] and the resulting derived rate law, the key microscopic kinetic and thermodynamic constants were extracted …

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Ultrafast Optical Study Of Small Gold Monolayer Protected Clusters: A Closer Look At Emission, Sung Hei Yau, Oleg Varnavski, John Gilbertson, Bert Chandler, Guda Ramakrishna, Theodore Goodson Sep 2013

Ultrafast Optical Study Of Small Gold Monolayer Protected Clusters: A Closer Look At Emission, Sung Hei Yau, Oleg Varnavski, John Gilbertson, Bert Chandler, Guda Ramakrishna, Theodore Goodson

Bert D Chandler

Monolayer-protected metal nanoclusters (MPCs) were investigated to probe their fundamental excitation and emission properties. In particular, gold MPCs were probed by steady-state and time-resolved spectroscopic measurements; the results were used to examine the mechanism of emission in relation to the excited states in these systems. In steady-state measurements, the photoluminescence of gold clusters in the range of 25 to 140 atoms was considerably stronger relative to larger particle analogues. The increase in emission efficiency (for Au25, Au55, and Au140 on the order of 10-5) over bulk gold may arise from a different mechanism of photoluminescence, as suggested by measurements on …

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Mathematical Reasoning: Writing And Proof, Ted Sundstrom Sep 2013

Mathematical Reasoning: Writing And Proof, Ted Sundstrom

Ted Sundstrom, Professor of Mathematics

Mathematical Reasoning: Writing and Proof is designed to be a text for the first course in the college mathematics curriculum that introduces students to the processes of constructing and writing proofs and focuses on the formal development of mathematics. The primary goals of the text are to help students: • Develop logical thinking skills and to develop the ability to think more abstractly in a proof oriented setting. • Develop the ability to construct and write mathematical proofs using standard methods of mathematical proof including direct proofs, proof by contradiction, mathematical induction, case analysis, and counterexamples. • Develop the ability …

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Query-Oriented Keyphrase Extraction, Minghui Qiu, Yaliang Li, Jing Jiang Sep 2013

Query-Oriented Keyphrase Extraction, Minghui Qiu, Yaliang Li, Jing Jiang

Minghui QIU

People often issue informational queries to search engines to find out more about some entities or events. While a Wikipedia-like summary would be an ideal answer to such queries, not all queries have a corresponding Wikipedia entry. In this work we propose to study query-oriented keyphrase extraction, which can be used to assist search results summarization. We propose a general method for keyphrase extraction for our task, where we consider both phraseness and informativeness. We discuss three criteria for phraseness and four ways to compute informativeness scores. Using a large Wikipedia corpus and 40 queries, our empirical evaluation shows that …

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Characterization Of (C)-Riordan Arrays, Gegenbauer-Humbert-Type Polynomial Sequences, And (C)-Bell Polynomials, Tian-Xiao He, Henry Gould Aug 2013

Characterization Of (C)-Riordan Arrays, Gegenbauer-Humbert-Type Polynomial Sequences, And (C)-Bell Polynomials, Tian-Xiao He, Henry Gould

Tian-Xiao He

Here presented are the definitions of (c)-Riordan arrays and (c)-Bell polynomials which are extensions of the classical Riordan arrays and Bell polynomials. The characterization of (c)-Riordan arrays by means of the A- and Z-sequences is given, which corresponds to a horizontal construction of a (c)-Riordan array rather than its definition approach through column generating functions. There exists a one-to-one correspondence between Gegenbauer-Humbert-type polynomial sequences and the set of (c)-Riordan arrays, which generates the sequence characterization of Gegenbauer-Humbert-type polynomial sequences. The sequence characterization is applied to construct readily a (c)-Riordan array. In addition, subgrouping of (c)-Riordan arrays by using the characterizations …

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Computation-Facilitated Assignment Of The Function In The Enolase Superfamily: A Regiochemically Distinct Galactarate Dehydratase From Oceanobacillus Iheyensis, John Rakus, Chakrapani Kalyanaraman, Alexander Fedorov, Elena Fedorov, Fiona Mills-Groninger, Rafael Toro, Jeffrey Bonanno, Kevin Bain, J. Sauder, Stephen Burley, Steven Almo, Matthew Jacobson, John Gerlt Aug 2013

Computation-Facilitated Assignment Of The Function In The Enolase Superfamily: A Regiochemically Distinct Galactarate Dehydratase From Oceanobacillus Iheyensis, John Rakus, Chakrapani Kalyanaraman, Alexander Fedorov, Elena Fedorov, Fiona Mills-Groninger, Rafael Toro, Jeffrey Bonanno, Kevin Bain, J. Sauder, Stephen Burley, Steven Almo, Matthew Jacobson, John Gerlt

John F. Rakus

The structure of an uncharacterized member of the enolase superfamily from Oceanobacillus iheyensis(GI 23100298, IMG locus tag Ob2843, PDB entry 2OQY) was determined by the New York SGX Research Center for Structural Genomics (NYSGXRC). The structure contained two Mg2+ ions located 10.4 A˚ from one another, with one located in the canonical position in the (β/R) 7 β-barrel domain (although the ligand at the end of the fifth β-strand is His, unprecedented in structurally characterized members of the superfamily); the second is located in a novel site within the capping domain. In silico docking of a library of mono- and …

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