Sample records for accelerator-based surface chemistry

  1. Laser polishing for topography management of accelerator cavity surfaces

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhao, Liang; Klopf, J. Mike; Reece, Charles E.

    2015-07-20

    Improved energy efficiency and reduced cost are greatly desired for advanced particle accelerators. Progress toward both can be made by atomically-smoothing the interior surface of the niobium superconducting radiofrequency accelerator cavities at the machine's heart. Laser polishing offers a green alternative to the present aggressive chemical processes. We found parameters suitable for polishing niobium in all surface states expected for cavity production. As a result, careful measurement of the resulting surface chemistry revealed a modest thinning of the surface oxide layer, but no contamination.

  2. Impact of surface chemistry

    PubMed Central

    Somorjai, Gabor A.; Li, Yimin

    2011-01-01

    The applications of molecular surface chemistry in heterogeneous catalyst technology, semiconductor-based technology, medical technology, anticorrosion and lubricant technology, and nanotechnology are highlighted in this perspective. The evolution of surface chemistry at the molecular level is reviewed, and the key roles of surface instrumentation developments for in situ studies of the gas–solid, liquid–solid, and solid–solid interfaces under reaction conditions are emphasized. PMID:20880833

  3. Effect of accelerated weathering on surface chemistry of modified wood

    NASA Astrophysics Data System (ADS)

    Temiz, Ali; Terziev, Nasko; Eikenes, Morten; Hafren, Jonas

    2007-04-01

    In this study, the effects of UV-light irradiation and water spray on colour and surface chemistry of scots pine sapwood samples were investigated. The specimens were treated with chromated copper arsenate (CCA), a metal-free propiconazol-based formulation, chitosan, furfuryl alcohol and linseed and tall oils. The weathering experiment was performed by cycles of 2 h UV-light irradiation followed by water spray for 18 min. The changes at the surface of the weathered samples were characterised by Fourier transform infrared spectroscopy (FT-IR); colour characterizations were performed by measuring CIELab parameters. The results show that all treatment methods except chitosan treatment provided lower colour changes than the control groups after 800 h exposure in weathering test cycle, but differences between chitosan and control were also small. The lowest colour changes were found on linseed oil (full cell process) and CCA treated wood. FT-IR results show that oil treatment (linseed and tall oil) decreased the intensities of a lignin specific peak (1500-1515 cm -1). Absorption band changes at 1630-1660 cm -1 were reduced by all treatments.

  4. A Smart Superwetting Surface with Responsivity in Both Surface Chemistry and Microstructure.

    PubMed

    Zhang, Dongjie; Cheng, Zhongjun; Kang, Hongjun; Yu, Jianxin; Liu, Yuyan; Jiang, Lei

    2018-03-26

    Recently, smart surfaces with switchable wettability have aroused much attention. However, only single surface chemistry or the microstructure can be changed on these surfaces, which significantly limits their wetting performances, controllability, and applications. A new surface with both tunable surface microstructure and chemistry was prepared by grafting poly(N-isopropylacrylamide) onto the pillar-structured shape memory polymer on which multiple wetting states from superhydrophilicity to superhydrophobicity can be reversibly and precisely controlled by synergistically regulating the surface microstructure and chemistry. Meanwhile, based on the excellent controllability, we also showed the application of the surface as a rewritable platform, and various gradient wettings can be obtained. This work presents for the first time a surface with controllability in both surface chemistry and microstructure, which starts some new ideas for the design of novel superwetting materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Next Steps Forward in Understanding Martian Surface and Subsurface Chemistry

    NASA Astrophysics Data System (ADS)

    Carrier, Brandi L.

    2017-09-01

    The presence of oxidants such as hydrogen peroxide (H2O2) and perchlorate (ClO4-), which have been detected on Mars, has significant implications for chemistry and astrobiology. These oxidants can increase the reactivity of the Martian soil, accelerate the decomposition of organic molecules, and depress the freezing point of water. The study by Crandall et al. "Can Perchlorates be Transformed to Hydrogen Peroxide Products by Cosmic Rays on the Martian Surface" reveals a new formation mechanism by which hydrogen peroxide and other potential oxidants can be generated via irradiation of perchlorate by cosmic rays. This study represents an important next step in developing a full understanding of Martian surface and subsurface chemistry, particularly with respect to degradation of organic molecules and potential biosignatures.

  6. Modeling the acid-base surface chemistry of montmorillonite.

    PubMed

    Bourg, Ian C; Sposito, Garrison; Bourg, Alain C M

    2007-08-15

    Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we show that the apparent discrepancy between titration data sets results in large part from the widespread use of an erroneous assumption of zero specific net proton surface charge at the onset of titration. Using a novel simulation scheme involving a surface chemistry model to simulate both pretreatment and titration, we find that montmorillonite edge surface chemistry models that account for the "spillover" of electrostatic potential from basal onto edge surfaces and for the stabilization of deprotonated Al-Si bridging sites through bond-length relaxation at the edge surface can reproduce key features of the best available experimental titration data (the influence of pretreatment conditions on experimental results, the absence of a point of zero salt effect, buffer capacity in the acidic pH range). However, no combination of current models of edge surface structure, reactivity and electrostatics can quantitatively predict, without fitted parameters, the experimental titration data over the entire range of pH (4.5 to 9) and ionic strength (0.001 to 0.5 mol dm(-3)) covered by available data.

  7. Surface chemistry of InP ridge structures etched in Cl{sub 2}-based plasma analyzed with angular XPS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bouchoule, Sophie, E-mail: sophie.bouchoule@lpn.cnrs.fr; Cambril, Edmond; Guilet, Stephane

    2015-09-15

    Two x-ray photoelectron spectroscopy configurations are proposed to analyze the surface chemistry of micron-scale InP ridge structures etched in chlorine-based inductively coupled plasma (ICP). Either a classical or a grazing configuration allows to retrieve information about the surface chemistry of the bottom surface and sidewalls of the etched features. The procedure is used to study the stoichiometry of the etched surface as a function of ridge aspect ratio for Cl{sub 2}/Ar and Cl{sub 2}/H{sub 2} plasma chemistries. The results show that the bottom surface and the etched sidewalls are P-rich, and indicate that the P-enrichment mechanism is rather chemically driven.more » Results also evidence that adding H{sub 2} to Cl{sub 2} does not necessarily leads to a more balanced surface stoichiometry. This is in contrast with recent experimental results obtained with the HBr ICP chemistry for which fairly stoichiometric surfaces have been obtained.« less

  8. Organic chemistry on solid surfaces

    NASA Astrophysics Data System (ADS)

    Ma, Zhen; Zaera, Francisco

    2006-07-01

    Chemistry on solid surfaces is central to many areas of practical interest such as heterogeneous catalysis, tribology, electrochemistry, and materials processing. With the development of many surface-sensitive analytical techniques in the past decades, great advances have been possible in our understanding of such surface chemistry at the molecular level. Earlier studies with model systems, single crystals in particular, have provided rich information about the adsorption and reaction kinetics of simple inorganic molecules. More recently, the same approach has been expanded to the study of the surface chemistry of relatively complex organic molecules, in large measure in connection with the selective synthesis of fine chemicals and pharmaceuticals. In this report, the chemical reactions of organic molecules and fragments on solid surfaces, mainly on single crystals of metals but also on crystals of metal oxides, carbides, nitrides, phosphides, sulfides and semiconductors as well as on more complex models such as bimetallics, alloys, and supported particles, are reviewed. A scheme borrowed from the organometallic and organic chemistry literature is followed in which key examples of representative reactions are cited first, and general reactivity trends in terms of both the reactants and the nature of the surface are then identified to highlight important mechanistic details. An attempt has been made to emphasize recent advances, but key earlier examples are cited as needed. Finally, correlations between surface and organometallic and organic chemistry, the relevance of surface reactions to applied catalysis and materials functionalization, and some promising future directions in this area are briefly discussed.

  9. Computational Materials Science and Chemistry: Accelerating Discovery and Innovation through Simulation-Based Engineering and Science

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Crabtree, George; Glotzer, Sharon; McCurdy, Bill

    This report is based on a SC Workshop on Computational Materials Science and Chemistry for Innovation on July 26-27, 2010, to assess the potential of state-of-the-art computer simulations to accelerate understanding and discovery in materials science and chemistry, with a focus on potential impacts in energy technologies and innovation. The urgent demand for new energy technologies has greatly exceeded the capabilities of today's materials and chemical processes. To convert sunlight to fuel, efficiently store energy, or enable a new generation of energy production and utilization technologies requires the development of new materials and processes of unprecedented functionality and performance. Newmore » materials and processes are critical pacing elements for progress in advanced energy systems and virtually all industrial technologies. Over the past two decades, the United States has developed and deployed the world's most powerful collection of tools for the synthesis, processing, characterization, and simulation and modeling of materials and chemical systems at the nanoscale, dimensions of a few atoms to a few hundred atoms across. These tools, which include world-leading x-ray and neutron sources, nanoscale science facilities, and high-performance computers, provide an unprecedented view of the atomic-scale structure and dynamics of materials and the molecular-scale basis of chemical processes. For the first time in history, we are able to synthesize, characterize, and model materials and chemical behavior at the length scale where this behavior is controlled. This ability is transformational for the discovery process and, as a result, confers a significant competitive advantage. Perhaps the most spectacular increase in capability has been demonstrated in high performance computing. Over the past decade, computational power has increased by a factor of a million due to advances in hardware and software. This rate of improvement, which shows no sign of

  10. Ferroelectric based catalysis: Switchable surface chemistry

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2015-03-01

    We describe a new class of catalysts that uses an epitaxial monolayer of a transition metal oxide on a ferroelectric substrate. The ferroelectric polarization switches the surface chemistry between strongly adsorptive and strongly desorptive regimes, circumventing difficulties encountered on non-switchable catalytic surfaces where the Sabatier principle dictates a moderate surface-molecule interaction strength. This method is general and can, in principle, be applied to many reactions, and for each case the choice of the transition oxide monolayer can be optimized. Here, as a specific example, we show how simultaneous NOx direct decomposition (into N2 and O2) and CO oxidation can be achieved efficiently on CrO2 terminated PbTiO3, while circumventing oxygen (and sulfur) poisoning issues. One should note that NOx direct decomposition has been an open challenge in automotive emission control industry. Our method can expand the range of catalytically active elements to those which are not conventionally considered for catalysis and which are more economical, e.g., Cr (for NOx direct decomposition and CO oxidation) instead of canonical precious metal catalysts. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  11. Deconvoluting the effects of surface chemistry and nanoscale topography: Pseudomonas aeruginosa biofilm nucleation on Si-based substrates.

    PubMed

    Zhang, Jing; Huang, Jinglin; Say, Carmen; Dorit, Robert L; Queeney, K T

    2018-06-01

    The nucleation of biofilms is known to be affected by both the chemistry and topography of the underlying substrate, particularly when topography includes nanoscale (<100 nm) features. However, determining the role of topography vs. chemistry is complicated by concomitant variation in both as a result of typical surface modification techniques. Analyzing the behavior of biofilm-forming bacteria exposed to surfaces with systematic, independent variation of both topography and surface chemistry should allow differentiation of the two effects. Silicon surfaces with reproducible nanotopography were created by anisotropic etching in deoxygenated water. Surface chemistry was varied independently to create hydrophilic (OH-terminated) and hydrophobic (alkyl-terminated) surfaces. The attachment and proliferation of Psuedomonas aeruginosa to these surfaces was characterized over a period of 12 h using fluorescence and confocal microscopy. The number of attached bacteria as well as the structural characteristics of the nucleating biofilm were influenced by both surface nanotopography and surface chemistry. In general terms, the presence of both nanoscale features and hydrophobic surface chemistry enhance bacterial attachment and colonization. However, the structural details of the resulting biofilms suggest that surface chemistry and topography interact differently on each of the four surface types we studied. Copyright © 2018 Elsevier Inc. All rights reserved.

  12. Surface water geochemical and isotopic variations in an area of accelerating Marcellus Shale gas development.

    PubMed

    Pelak, Adam J; Sharma, Shikha

    2014-12-01

    Water samples were collected from 50 streams in an area of accelerating shale gas development in the eastern U.S.A. The geochemical/isotopic characteristics show no correlation with the five categories of Marcellus Shale production. The sub-watersheds with the greatest density of Marcellus Shale development have also undergone extensive coal mining. Hence, geochemical/isotopic compositions were used to understand sources of salinity and effects of coal mining and shale gas development in the area. The data indicates that while some streams appear to be impacted by mine drainage; none appear to have received sustained contribution from deep brines or produced waters associated with shale gas production. However, it is important to note that our interpretations are based on one time synoptic base flow sampling of a few sampling stations and hence do account potential intermittent changes in chemistry that may result from major/minor spills or specific mine discharges on the surface water chemistry. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Synchronized chaotic targeting and acceleration of surface chemistry in prebiotic hydrothermal microenvironments

    PubMed Central

    Priye, Aashish; Yu, Yuncheng; Hassan, Yassin A.; Ugaz, Victor M.

    2017-01-01

    Porous mineral formations near subsea alkaline hydrothermal vents embed microenvironments that make them potential hot spots for prebiotic biochemistry. But, synthesis of long-chain macromolecules needed to support higher-order functions in living systems (e.g., polypeptides, proteins, and nucleic acids) cannot occur without enrichment of chemical precursors before initiating polymerization, and identifying a suitable mechanism has become a key unanswered question in the origin of life. Here, we apply simulations and in situ experiments to show how 3D chaotic thermal convection—flows that naturally permeate hydrothermal pore networks—supplies a robust mechanism for focused accumulation at discrete targeted surface sites. This interfacial enrichment is synchronized with bulk homogenization of chemical species, yielding two distinct processes that are seemingly opposed yet synergistically combine to accelerate surface reaction kinetics by several orders of magnitude. Our results suggest that chaotic thermal convection may play a previously unappreciated role in mediating surface-catalyzed synthesis in the prebiotic milieu. PMID:28119504

  14. A functionalized poly(ethylene glycol)-based bioassay surface chemistry that facilitates bio-immobilization and inhibits non-specific protein, bacterial, and mammalian cell adhesion

    PubMed Central

    Harbers, Gregory M.; Emoto, Kazunori; Greef, Charles; Metzger, Steven W.; Woodward, Heather N.; Mascali, James J.; Grainger, David W.; Lochhead, Michael J.

    2008-01-01

    This paper describes a new bioassay surface chemistry that effectively inhibits non-specific biomolecular and cell binding interactions, while providing a capacity for specific immobilization of desired biomolecules. Poly(ethylene glycol) (PEG) as the primary component in nonfouling film chemistry is well-established, but the multicomponent formulation described here is unique in that it (1) is applied in a single, reproducible, solution-based coating step; (2) can be applied to diverse substrate materials without the use of special primers; and (3) is readily functionalized to provide specific attachment chemistries. Surface analysis data are presented, detailing surface roughness, polymer film thickness, and film chemistry. Protein non-specific binding assays demonstrate significant inhibition of serum, fibrinogen, and lysozyme adsorption to coated glass, indium tin oxide, and tissue culture polystyrene dishes. Inhibition of S. aureus and K. pneumoniae microbial adhesion in a microfluidic flow cell, and inhibition of fibroblast cell adhesion from serum-based cell culture is shown. Effective functionalization of the coating is demonstrated by directing fibroblast adhesion to polymer surfaces activated with an RGD peptide. Batch-to-batch reproducibility data are included. The in situ cross-linked PEG-based coating chemistry is unique in its formulation, and its surface properties are attractive for a broad range of in vitro bioassay applications. PMID:18815622

  15. Acceleration of the chemistry solver for modeling DI engine combustion using dynamic adaptive chemistry (DAC) schemes

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Liang, Long; Ge, Hai-Wen; Reitz, Rolf D.

    2010-03-01

    Acceleration of the chemistry solver for engine combustion is of much interest due to the fact that in practical engine simulations extensive computational time is spent solving the fuel oxidation and emission formation chemistry. A dynamic adaptive chemistry (DAC) scheme based on a directed relation graph error propagation (DRGEP) method has been applied to study homogeneous charge compression ignition (HCCI) engine combustion with detailed chemistry (over 500 species) previously using an R-value-based breadth-first search (RBFS) algorithm, which significantly reduced computational times (by as much as 30-fold). The present paper extends the use of this on-the-fly kinetic mechanism reduction scheme to model combustion in direct-injection (DI) engines. It was found that the DAC scheme becomes less efficient when applied to DI engine simulations using a kinetic mechanism of relatively small size and the accuracy of the original DAC scheme decreases for conventional non-premixed combustion engine. The present study also focuses on determination of search-initiating species, involvement of the NOx chemistry, selection of a proper error tolerance, as well as treatment of the interaction of chemical heat release and the fuel spray. Both the DAC schemes were integrated into the ERC KIVA-3v2 code, and simulations were conducted to compare the two schemes. In general, the present DAC scheme has better efficiency and similar accuracy compared to the previous DAC scheme. The efficiency depends on the size of the chemical kinetics mechanism used and the engine operating conditions. For cases using a small n-heptane kinetic mechanism of 34 species, 30% of the computational time is saved, and 50% for a larger n-heptane kinetic mechanism of 61 species. The paper also demonstrates that by combining the present DAC scheme with an adaptive multi-grid chemistry (AMC) solver, it is feasible to simulate a direct-injection engine using a detailed n-heptane mechanism with 543 species

  16. Isotachophoresis-Based Surface Immunoassay.

    PubMed

    Paratore, Federico; Zeidman Kalman, Tal; Rosenfeld, Tally; Kaigala, Govind V; Bercovici, Moran

    2017-07-18

    In the absence of amplification methods for proteins, the immune-detection of low-abundance proteins using antibodies is fundamentally limited by binding kinetic rates. Here, we present a new class of surface-based immunoassays in which protein-antibody reaction is accelerated by isotachophoresis (ITP). We demonstrate the use of ITP to preconcentrate and deliver target proteins to a surface decorated with specific antibodies, where effective utilization of the focused sample is achieved by modulating the driving electric field (stop-and-diffuse ITP mode) or applying a counter flow that opposes the ITP motion (counterflow ITP mode). Using enhanced green fluorescent protein (EGFP) as a model protein, we carry out an experimental optimization of the ITP-based immunoassay and demonstrate a 1300-fold improvement in limit of detection compared to a standard immunoassay, in a 6 min protein-antibody reaction. We discuss the design of buffer chemistries for other protein systems and, in concert with experiments, provide full analytical solutions for the two operation modes, elucidating the interplay between reaction, diffusion, and accumulation time scales and enabling the prediction and design of future immunoassays.

  17. Covalent-Bond Formation via On-Surface Chemistry.

    PubMed

    Held, Philipp Alexander; Fuchs, Harald; Studer, Armido

    2017-05-02

    In this Review article pioneering work and recent achievements in the emerging research area of on-surface chemistry is discussed. On-surface chemistry, sometimes also called two-dimensional chemistry, shows great potential for bottom-up preparation of defined nanostructures. In contrast to traditional organic synthesis, where reactions are generally conducted in well-defined reaction flasks in solution, on-surface chemistry is performed in the cavity of a scanning probe microscope on a metal crystal under ultrahigh vacuum conditions. The metal first acts as a platform for self-assembly of the organic building blocks and in many cases it also acts as a catalyst for the given chemical transformation. Products and hence success of the reaction are directly analyzed by scanning probe microscopy. This Review provides a general overview of this chemistry highlighting advantages and disadvantages as compared to traditional reaction setups. The second part of the Review then focuses on reactions that have been successfully conducted as on-surface processes. On-surface Ullmann and Glaser couplings are addressed. In addition, cyclodehydrogenation reactions and cycloadditions are discussed and reactions involving the carbonyl functionality are highlighted. Finally, the first examples of sequential on-surface chemistry are considered in which two different functionalities are chemoselectively addressed. The Review gives an overview for experts working in the area but also offers a starting point to non-experts to enter into this exciting new interdisciplinary research field. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Surface and Interface Chemistry for Gate Stacks on Silicon

    NASA Astrophysics Data System (ADS)

    Frank, M. M.; Chabal, Y. J.

    This chapter addresses the fundamental silicon surface science associated with the continued progress of nanoelectronics along the path prescribed by Moore's law. Focus is on hydrogen passivation layers and on ultrathin oxide films encountered during silicon cleaning and gate stack formation in the fabrication of metal-oxide-semiconductor field-effect transistors (MOSFETs). Three main topics are addressed. (i) First, the current practices and understanding of silicon cleaning in aqueous solutions are reviewed, including oxidizing chemistries and cleans leading to a hydrogen passivation layer. The dependence of the final surface termination and morphology/roughness on reactant choice and pH and the influence of impurities such as dissolved oxygen or metal ions are discussed. (ii) Next, the stability of hydrogen-terminated silicon in oxidizing liquid and gas phase environments is considered. In particular, the remarkable stability of hydrogen-terminated silicon surface in pure water vapor is discussed in the context of atomic layer deposition (ALD) of high-permittivity (high-k) gate dielectrics where water is often used as an oxygen precursor. Evidence is also provided for co-operative action between oxygen and water vapor that accelerates surface oxidation in humid air. (iii) Finally, the fabrication of hafnium-, zirconium- and aluminum-based high-k gate stacks is described, focusing on the continued importance of the silicon/silicon oxide interface. This includes a review of silicon surface preparation by wet or gas phase processing and its impact on high-k nucleation during ALD growth, and the consideration of gate stack capacitance and carrier mobility. In conclusion, two issues are highlighted: the impact of oxygen vacancies on the electrical characteristics of high-k MOS devices, and the way alloyed metal ions (such as Al in Hf-based gate stacks) in contact with the interfacial silicon oxide layer can be used to control flatband and threshold voltages.

  19. Low temperature surface chemistry and nanostructures

    NASA Astrophysics Data System (ADS)

    Sergeev, G. B.; Shabatina, T. I.

    2002-03-01

    The new scientific field of low temperature surface chemistry, which combines the low temperature chemistry (cryochemistry) and surface chemistry approaches, is reviewed in this paper. One of the most exciting achievements in this field of science is the development of methods to create highly ordered hybrid nanosized structures on different organic and inorganic surfaces and to encapsulate nanosized metal particles in organic and polymer matrices. We consider physical and chemical behaviour for the systems obtained by co-condensation of the components vapours on the surfaces cooled down to 4-10 and 70-100 K. In particular the size effect of both types, the number of atoms in the reactive species structure and the thickness of growing co-condensate film, on the chemical activity of the system is analysed in detail. The effect of the internal mechanical stresses on the growing interfacial co-condensate film formation and on the generation of fast (explosive) spontaneous reactions at low temperatures is discussed. The examples of unusual chemical interactions of metal atoms, clusters and nanosized particles, obtained in co-condensate films on the cooled surfaces under different conditions, are presented. The examples of highly ordered surface and volume hybrid nanostructures formation are analysed.

  20. Anisotropic surface chemistry properties and adsorption behavior of silicate mineral crystals.

    PubMed

    Xu, Longhua; Tian, Jia; Wu, Houqin; Fang, Shuai; Lu, Zhongyuan; Ma, Caifeng; Sun, Wei; Hu, Yuehua

    2018-03-07

    Anisotropic surface properties of minerals play an important role in a variety of fields. With a focus on the two most intensively investigated silicate minerals (i.e., phyllosilicate minerals and pegmatite aluminosilicate minerals), this review highlights the research on their anisotropic surface properties based on their crystal structures. Four surface features comprise the anisotropic surface chemistry of minerals: broken bonds, energy, wettability, and charge. Analysis of surface broken bond and energy anisotropy helps to explain the cleavage and growth properties of mineral crystals, and understanding surface wettability and charge anisotropy is critical to the analysis of minerals' solution behavior, such as their flotation performance and rheological properties. In a specific reaction, the anisotropic surface properties of minerals are reflected in the adsorption strengths of reagents on different mineral surfaces. Combined with the knowledge of mineral crushing and grinding, a thorough understanding of the anisotropic surface chemistry properties and the anisotropic adsorption behavior of minerals will lead to the development of effective relational models comprising their crystal structure, surface chemistry properties, and targeted reagent adsorption. Overall, such a comprehensive approach is expected to firmly establish the connection between selective cleavage of mineral crystals for desired surfaces and designing novel reagents selectively adsorbed on the mineral surfaces. As tools to characterize the anisotropic surface chemistry properties of minerals, DLVO theory, atomic force microscopy (AFM), and molecular dynamics (MD) simulations are also reviewed. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Ab Initio-Based Predictions of Hydrocarbon Combustion Chemistry

    DTIC Science & Technology

    2015-07-15

    There are two prime objectives of the research. One is to develop and apply efficient methods for using ab initio potential energy surfaces (PESs...31-Mar-2015 Approved for Public Release; Distribution Unlimited Final Report: Ab Initio -Based Predictions of Hydrocarbon Combustion Chemistry The...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 hydrocarbon combustion, ab initio quantum chemistry, potential energy surfaces, chemical

  2. Operando chemistry of catalyst surfaces during catalysis.

    PubMed

    Dou, Jian; Sun, Zaicheng; Opalade, Adedamola A; Wang, Nan; Fu, Wensheng; Tao, Franklin Feng

    2017-04-03

    Chemistry of a catalyst surface during catalysis is crucial for a fundamental understanding of mechanism of a catalytic reaction performed on the catalyst in the gas or liquid phase. Due to the pressure- or molecular density-dependent entropy contribution of gas or liquid phase of the reactants and the potential formation of a catalyst surface during catalysis different from that observed in an ex situ condition, the characterization of the surface of a catalyst under reaction conditions and during catalysis can be significant and even necessary for understanding the catalytic mechanism at a molecular level. Electron-based analytical techniques are challenging for studying catalyst nanoparticles in the gas or liquid phase although they are necessary techniques to employ. Instrumentation and further development of these electron-based techniques have now made in situ/operando studies of catalysts possible. New insights into the chemistry and structure of catalyst nanoparticles have been uncovered over the last decades. Herein, the origin of the differences between ex situ and in situ/operando studies of catalysts, and the technical challenges faced as well as the corresponding instrumentation and innovations utilized for characterizing catalysts under reaction conditions and during catalysis, are discussed. The restructuring of catalyst surfaces driven by the pressure of reactant(s) around a catalyst, restructuring in reactant(s) driven by reaction temperature and restructuring during catalysis are also reviewed herein. The remaining challenges and possible solutions are briefly discussed.

  3. Investigation into the effect of water chemistry on corrosion product formation in areas of accelerated flow

    NASA Astrophysics Data System (ADS)

    McGrady, John; Scenini, Fabio; Duff, Jonathan; Stevens, Nicholas; Cassineri, Stefano; Curioni, Michele; Banks, Andrew

    2017-09-01

    The deposition of CRUD (Chalk River Unidentified Deposit) in the primary circuit of a Pressurised Water Reactor (PWR) is known to preferentially occur in regions of the circuit where flow acceleration of coolant occurs. A micro-fluidic flow cell was used to recreate accelerated flow under simulated PWR conditions, by flowing water through a disc with a central micro-orifice. CRUD deposition was reproduced on the disc, and CRUD Build-Up Rates (BUR) in various regions of the disc were analysed. The effect of the local environment on BUR was investigated. In particular, the effect of flow velocity, specimen material and Fe concentration were considered. The morphology and composition of the deposits were analysed with respect to experimental conditions. The BUR of CRUD was found to be sensitive to flow velocity and Fe concentration, suggesting that mass transfer is an important factor. The morphology of the deposit was affected by the specimen material indicating a dependence on surface/particle electrostatics meaning surface chemistry plays an important role in deposition. The preferential deposition of CRUD in accelerated flow regions due to electrokinetic effects was observed and it was shown that higher Fe concentrations in solution increased BURs within the orifice whereas increased flow velocity reduced BURs.

  4. Why surface chemistry matters for QD–QD resonance energy transfer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hoffman, Jacob B.; Alam, Rabeka; Kamat, Prashant V.

    Resonance energy transfer (RET) has been shown to occur in films of semiconductor quantum dots (QDs) with variation in QD composition and size. When coupled with charge carrier transfer, RET could provide a complementary strategy for light harvesting in QD based solid state photovoltaic devices. Due to a direct dependence on the optical properties of the donor and acceptor, QD surface chemistry plays a drastic role in determining the efficiency of RET. Here, the impact of QD surface chemistry on RET in QD films was investigated using a pair of different sized CdSe QDs spin-cast onto a glass substrate. Themore » effects of QD surface passivation on RET were studied by removing surface ligands through QD washing and adding an insulating ZnS shell. In addition, QD films were subjected to solid state ligand exchanges with thiolated ligands in order to mimic a layer-by-layer deposition method commonly used in the construction of QD photovoltaics. These solid state ligand exchanges exhibit drastic quenching of RET in the films. As a result, these experiments highlight the importance of understanding surface chemistry when designing photovoltaics that utilize RET.« less

  5. Why surface chemistry matters for QD–QD resonance energy transfer

    DOE PAGES

    Hoffman, Jacob B.; Alam, Rabeka; Kamat, Prashant V.

    2017-01-12

    Resonance energy transfer (RET) has been shown to occur in films of semiconductor quantum dots (QDs) with variation in QD composition and size. When coupled with charge carrier transfer, RET could provide a complementary strategy for light harvesting in QD based solid state photovoltaic devices. Due to a direct dependence on the optical properties of the donor and acceptor, QD surface chemistry plays a drastic role in determining the efficiency of RET. Here, the impact of QD surface chemistry on RET in QD films was investigated using a pair of different sized CdSe QDs spin-cast onto a glass substrate. Themore » effects of QD surface passivation on RET were studied by removing surface ligands through QD washing and adding an insulating ZnS shell. In addition, QD films were subjected to solid state ligand exchanges with thiolated ligands in order to mimic a layer-by-layer deposition method commonly used in the construction of QD photovoltaics. These solid state ligand exchanges exhibit drastic quenching of RET in the films. As a result, these experiments highlight the importance of understanding surface chemistry when designing photovoltaics that utilize RET.« less

  6. Surface chemistry in photodissociation regions

    NASA Astrophysics Data System (ADS)

    Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.

    2016-06-01

    Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

  7. Nonlinear friction dynamics on polymer surface under accelerated movement

    NASA Astrophysics Data System (ADS)

    Aita, Yuuki; Asanuma, Natsumi; Takahashi, Akira; Mayama, Hiroyuki; Nonomura, Yoshimune

    2017-04-01

    Nonlinear phenomena on the soft material surface are one of the most exciting topics of chemical physics. However, only a few reports exist on the friction phenomena under accelerated movement, because friction between two solid surfaces is considered a linear phenomenon in many cases. We aim to investigate how nonlinear accelerated motion affects friction on solid surfaces. In the present study, we evaluate the frictional forces between two polytetrafluoroethylene (PTFE) resins using an advanced friction evaluation system. On PTFE surfaces, the normalized delay time δ, which is the time lag in the response of the friction force to the accelerated movement, is observed in the pre-sliding friction process. Under high-velocity conditions, kinetic friction increases with velocity. Based on these experimental results, we propose a two-phase nonlinear model including a pre-sliding process (from the beginning of sliding of a contact probe to the establishment of static friction) and a kinetic friction process. The present model consists of several factors including velocity, acceleration, stiffness, viscosity, and vertical force. The findings reflecting the viscoelastic properties of soft material is useful for various fields such as in the fabrication of clothes, cosmetics, automotive materials, and virtual reality systems as well as for understanding friction phenomena on soft material surfaces.

  8. The Role of Surface Chemistry in Adhesion and Wetting of Gecko Toe Pads

    PubMed Central

    Badge, Ila; Stark, Alyssa Y.; Paoloni, Eva L.; Niewiarowski, Peter H.; Dhinojwala, Ali

    2014-01-01

    An array of micron-sized setal hairs offers geckos a unique ability to walk on vertical surfaces using van der Waals interactions. Although many studies have focused on the role of surface morphology of the hairs, very little is known about the role of surface chemistry on wetting and adhesion. We expect that both surface chemistry and morphology are important, not only to achieve optimum dry adhesion but also for increased efficiency in self-cleaning of water and adhesion under wet conditions. Here, we used a plasma-based vapor deposition process to coat the hairy patterns on gecko toe pad sheds with polar and non-polar coatings without significantly perturbing the setal morphology. By a comparison of wetting across treatments, we show that the intrinsic surface of gecko setae has a water contact angle between 70–90°. As expected, under wet conditions, adhesion on a hydrophilic surface (glass) was lower than that on a hydrophobic surface (alkyl-silane monolayer on glass). Surprisingly under wet and dry conditions the adhesion was comparable on the hydrophobic surface, independent of the surface chemistry of the setal hairs. This work highlights the need to utilize morphology and surface chemistry in developing successful synthetic adhesives with desirable adhesion and self-cleaning properties. PMID:25323067

  9. The Role of Surface Chemistry in Adhesion and Wetting of Gecko Toe Pads

    NASA Astrophysics Data System (ADS)

    Badge, Ila; Stark, Alyssa Y.; Paoloni, Eva L.; Niewiarowski, Peter H.; Dhinojwala, Ali

    2014-10-01

    An array of micron-sized setal hairs offers geckos a unique ability to walk on vertical surfaces using van der Waals interactions. Although many studies have focused on the role of surface morphology of the hairs, very little is known about the role of surface chemistry on wetting and adhesion. We expect that both surface chemistry and morphology are important, not only to achieve optimum dry adhesion but also for increased efficiency in self-cleaning of water and adhesion under wet conditions. Here, we used a plasma-based vapor deposition process to coat the hairy patterns on gecko toe pad sheds with polar and non-polar coatings without significantly perturbing the setal morphology. By a comparison of wetting across treatments, we show that the intrinsic surface of gecko setae has a water contact angle between 70-90°. As expected, under wet conditions, adhesion on a hydrophilic surface (glass) was lower than that on a hydrophobic surface (alkyl-silane monolayer on glass). Surprisingly under wet and dry conditions the adhesion was comparable on the hydrophobic surface, independent of the surface chemistry of the setal hairs. This work highlights the need to utilize morphology and surface chemistry in developing successful synthetic adhesives with desirable adhesion and self-cleaning properties.

  10. What's on the Surface? Physics and Chemistry of Delta-Doped Surfaces

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael

    2011-01-01

    Outline of presentation: 1. Detector surfaces and the problem of stability 2. Delta-doped detectors 3. Physics of Delta-doped Silicon 4. Chemistry of the Si-SiO2 Interface 5. Physics and Chemistry of Delta-doped Surfaces a. Compensation b. Inversion c. Quantum exclusion. Conclusions: 1. Quantum confinement of electrons and holes dominates the behavior of delta-doped surfaces. 2. Stability of delta-doped detectors: Delta-layer creates an approx 1 eV tunnel barrier between bulk and surface. 3. At high surface charge densities, Tamm-Shockley states form at the surface. 4. Surface passivation by quantum exclusion: Near-surface delta-layer suppresses T-S trapping of minority carriers. 5. The Si-SiO2 interface compensates the surface 6. For delta-layers at intermediate depth, surface inversion layer forms 7. Density of Si-SiO2 interface charge can be extremely high (>10(exp 14)/sq cm)

  11. Modeling the Acceleration of Global Surface Temperture

    NASA Astrophysics Data System (ADS)

    Jones, B.

    2017-12-01

    A mathematical projection focusing on the changing rate of acceleration of Global Surface Temperatures. Using historical trajectory and informed expert near-term prediction, it is possible to extend this further forward drawing a reference arc of acceleration. Presented here is an example of this technique based on data found in the Summary of Findings of A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011 and that same team's stated prediction to 2050. With this, we can project a curve showing future acceleration: Decade (midpoint) Change in Global Land Temp Degrees C Known Slope Projected Trend 1755 0.000 1955 0.600 0.0030 2005 1.500 0.0051 2045 3.000 0.0375 2095 5.485 0.0497 2145 8.895 0.0682 2195 13.488 0.0919 Observations: Slopes are getting steeper and doing so faster in an "acceleration of the acceleration" or an "arc of acceleration". This is consistent with the non-linear accelerating feedback loops of global warming. Such projected temperatures threaten human civilization and human life. This `thumbnail' projection is consistent with the other long term predictions based on anthropogenic greenhouse gases. This projection is low when compared to those whose forecasts include greenhouse gases released from thawing permafrost and clathrate hydrates. A reference line: This curve should be considered a point of reference. In the near term and absent significant drawdown of greenhouse gases, my "bet" for this AGU session is that future temperatures will generally be above this reference curve. For example, the decade ending 2020 - more than 1.9C and the decade ending 2030 - more than 2.3C - again measured from the 1750 start point. *Caveat: The long term curve and prediction assumes that mankind does not move quickly away from high cost fossil fuels and does not invent, mobilize and take actions drawing down greenhouse gases. Those seeking a comprehensive action plan are directed to drawdown.org

  12. Surface Functionalization of Exosomes Using Click Chemistry

    PubMed Central

    2015-01-01

    A method for conjugation of ligands to the surface of exosomes was developed using click chemistry. Copper-catalyzed azide alkyne cycloaddition (click chemistry) is ideal for biocojugation of small molecules and macromolecules to the surface of exosomes, due to fast reaction times, high specificity, and compatibility in aqueous buffers. Exosomes cross-linked with alkyne groups using carbodiimide chemistry were conjugated to a model azide, azide-fluor 545. Conjugation had no effect on the size of exosomes, nor was there any change in the extent of exosome adherence/internalization with recipient cells, suggesting the reaction conditions were mild on exosome structure and function. We further investigated the extent of exosomal protein modification with alkyne groups. Using liposomes with surface alkyne groups of a similar size and concentration to exosomes, we estimated that approximately 1.5 alkyne groups were present for every 150 kDa of exosomal protein. PMID:25220352

  13. Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Not Available

    1990-03-01

    Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

  14. Development of a Detailed Surface Chemistry Framework in DSMC

    NASA Technical Reports Server (NTRS)

    Swaminathan-Gopalan, K.; Borner, A.; Stephani, K. A.

    2017-01-01

    Many of the current direct simulation Monte Carlo (DSMC) codes still employ only simple surface catalysis models. These include only basic mechanisms such as dissociation, recombination, and exchange reactions, without any provision for adsorption and finite rate kinetics. Incorporating finite rate chemistry at the surface is increasingly becoming a necessity for various applications such as high speed re-entry flows over thermal protection systems (TPS), micro-electro-mechanical systems (MEMS), surface catalysis, etc. In the recent years, relatively few works have examined finite-rate surface reaction modeling using the DSMC method.In this work, a generalized finite-rate surface chemistry framework incorporating a comprehensive list of reaction mechanisms is developed and implemented into the DSMC solver SPARTA. The various mechanisms include adsorption, desorption, Langmuir-Hinshelwood (LH), Eley-Rideal (ER), Collision Induced (CI), condensation, sublimation, etc. The approach is to stochastically model the various competing reactions occurring on a set of active sites. Both gas-surface (e.g., ER, CI) and pure-surface (e.g., LH, desorption) reaction mechanisms are incorporated. The reaction mechanisms could also be catalytic or surface altering based on the participation of the bulk-phase species (e.g., bulk carbon atoms). Marschall and MacLean developed a general formulation in which multiple phases and surface sites are used and we adopt a similar convention in the current work. Microscopic parameters of reaction probabilities (for gas-surface reactions) and frequencies (for pure-surface reactions) that are require for DSMC are computed from the surface properties and macroscopic parameters such as rate constants, sticking coefficients, etc. The energy and angular distributions of the products are decided based on the reaction type and input parameters. Thus, the user has the capability to model various surface reactions via user-specified reaction rate

  15. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

    PubMed

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

    2016-03-14

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

  16. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    PubMed Central

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  17. Surface chemistry driven actuation in nanoporous gold

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Biener, J; Wittstock, A; Zepeda-Ruiz, L

    Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry driven actuation can be realized in high surface area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes in the order of a few tenths of a percent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into amore » mechanical response thus opening the door to surface-chemistry driven actuator and sensor technologies.« less

  18. Surface chemistry of carbon dioxide revisited

    NASA Astrophysics Data System (ADS)

    Taifan, William; Boily, Jean-François; Baltrusaitis, Jonas

    2016-12-01

    This review discusses modern developments in CO2 surface chemistry by focusing on the work published since the original review by H.J. Freund and M.W. Roberts two decades ago (Surface Science Reports 25 (1996) 225-273). It includes relevant fundamentals pertaining to the topics covered in that earlier review, such as conventional metal and metal oxide surfaces and CO2 interactions thereon. While UHV spectroscopy has routinely been applied for CO2 gas-solid interface analysis, the present work goes further by describing surface-CO2 interactions under elevated CO2 pressure on non-oxide surfaces, such as zeolites, sulfides, carbides and nitrides. Furthermore, it describes additional salient in situ techniques relevant to the resolution of the interfacial chemistry of CO2, notably infrared spectroscopy and state-of-the-art theoretical methods, currently used in the resolution of solid and soluble carbonate species in liquid-water vapor, liquid-solid and liquid-liquid interfaces. These techniques are directly relevant to fundamental, natural and technological settings, such as heterogeneous and environmental catalysis and CO2 sequestration.

  19. Unravelling the surface chemistry of metal oxide nanocrystals, the role of acids and bases.

    PubMed

    De Roo, Jonathan; Van den Broeck, Freya; De Keukeleere, Katrien; Martins, José C; Van Driessche, Isabel; Hens, Zeger

    2014-07-09

    We synthesized HfO2 nanocrystals from HfCl4 using a surfactant-free solvothermal process in benzyl alcohol and found that the resulting nanocrystals could be transferred to nonpolar media using a mixture of carboxylic acids and amines. Using solution (1)H NMR, FTIR, and elemental analysis, we studied the details of the transfer reaction and the surface chemistry of the resulting sterically stabilized nanocrystals. As-synthesized nanocrystals are charge-stabilized by protons, with chloride acting as the counterion. Treatment with only carboxylic acids does not lead to any binding of ligands to the HfO2 surface. On the other hand, we find that the addition of amines provides the basic environment in which carboxylic acids can dissociate and replace chloride. This results in stable, aggregate-free dispersions of HfO2 nanocrystals, sterically stabilized by carboxylate ligands. Moreover, titrations with deuterated carboxylic acid show that the charge on the carboxylate ligands is balanced by coadsorbed protons. Hence, opposite from the X-type/nonstoichiometric nanocrystals picture prevailing in literature, one should look at HfO2/carboxylate nanocrystals as systems where carboxylic acids are dissociatively adsorbed to bind to the nanocrystals. Similar results were obtained with ZrO2 NCs. Since proton accommodation on the surface is most likely due to the high Brønsted basicity of oxygen, our model could be a more general picture for the surface chemistry of metal oxide nanocrystals with important consequences on the chemistry of ligand exchange reactions.

  20. Tunnel flexibility effect on the ground surface acceleration response

    NASA Astrophysics Data System (ADS)

    Baziar, Mohammad Hassan; Moghadam, Masoud Rabeti; Choo, Yun Wook; Kim, Dong-Soo

    2016-09-01

    Flexibility of underground structures relative to the surrounding medium, referred to as the flexibility ratio, is an important factor that influences their dynamic interaction. This study investigates the flexibility effect of a box-shaped subway tunnel, resting directly on bedrock, on the ground surface acceleration response using a numerical model verified against dynamic centrifuge test results. A comparison of the ground surface acceleration response for tunnel models with different flexibility ratios revealed that the tunnels with different flexibility ratios influence the acceleration response at the ground surface in different ways. Tunnels with lower flexibility ratios have higher acceleration responses at short periods, whereas tunnels with higher flexibility ratios have higher acceleration responses at longer periods. The effect of the flexibility ratio on ground surface acceleration is more prominent in the high range of frequencies. Furthermore, as the flexibility ratio of the tunnel system increases, the acceleration response moves away from the free field response and shifts towards the longer periods. Therefore, the flexibility ratio of the underground tunnels influences the peak ground acceleration (PGA) at the ground surface, and may need to be considered in the seismic zonation of urban areas.

  1. Surface chemistry: Key to control and advance myriad technologies

    PubMed Central

    Yates, John T.; Campbell, Charles T.

    2011-01-01

    This special issue on surface chemistry is introduced with a brief history of the field, a summary of the importance of surface chemistry in technological applications, a brief overview of some of the most important recent developments in this field, and a look forward to some of its most exciting future directions. This collection of invited articles is intended to provide a snapshot of current developments in the field, exemplify the state of the art in fundamental research in surface chemistry, and highlight some possibilities in the future. Here, we show how those articles fit together in the bigger picture of this field. PMID:21245359

  2. Electron acceleration by surface plasma waves in double metal surface structure

    NASA Astrophysics Data System (ADS)

    Liu, C. S.; Kumar, Gagan; Singh, D. B.; Tripathi, V. K.

    2007-12-01

    Two parallel metal sheets, separated by a vacuum region, support a surface plasma wave whose amplitude is maximum on the two parallel interfaces and minimum in the middle. This mode can be excited by a laser using a glass prism. An electron beam launched into the middle region experiences a longitudinal ponderomotive force due to the surface plasma wave and gets accelerated to velocities of the order of phase velocity of the surface wave. The scheme is viable to achieve beams of tens of keV energy. In the case of a surface plasma wave excited on a single metal-vacuum interface, the field gradient normal to the interface pushes the electrons away from the high field region, limiting the acceleration process. The acceleration energy thus achieved is in agreement with the experimental observations.

  3. Water at surfaces with tunable surface chemistries

    NASA Astrophysics Data System (ADS)

    Sanders, Stephanie E.; Vanselous, Heather; Petersen, Poul B.

    2018-03-01

    Aqueous interfaces are ubiquitous in natural environments, spanning atmospheric, geological, oceanographic, and biological systems, as well as in technical applications, such as fuel cells and membrane filtration. Where liquid water terminates at a surface, an interfacial region is formed, which exhibits distinct properties from the bulk aqueous phase. The unique properties of water are governed by the hydrogen-bonded network. The chemical and physical properties of the surface dictate the boundary conditions of the bulk hydrogen-bonded network and thus the interfacial properties of the water and any molecules in that region. Understanding the properties of interfacial water requires systematically characterizing the structure and dynamics of interfacial water as a function of the surface chemistry. In this review, we focus on the use of experimental surface-specific spectroscopic methods to understand the properties of interfacial water as a function of surface chemistry. Investigations of the air-water interface, as well as efforts in tuning the properties of the air-water interface by adding solutes or surfactants, are briefly discussed. Buried aqueous interfaces can be accessed with careful selection of spectroscopic technique and sample configuration, further expanding the range of chemical environments that can be probed, including solid inorganic materials, polymers, and water immiscible liquids. Solid substrates can be finely tuned by functionalization with self-assembled monolayers, polymers, or biomolecules. These variables provide a platform for systematically tuning the chemical nature of the interface and examining the resulting water structure. Finally, time-resolved methods to probe the dynamics of interfacial water are briefly summarized before discussing the current status and future directions in studying the structure and dynamics of interfacial water.

  4. A facile route to steady redox-modulated nitroxide spin-labeled surfaces based on diazonium chemistry.

    PubMed

    Cougnon, Charles; Boisard, Séverine; Cador, Olivier; Dias, Marylène; Levillain, Eric; Breton, Tony

    2013-05-18

    A TEMPO derivative was covalently grafted onto carbon and gold surfaces via the diazonium chemistry. The acid-dependent redox properties of the nitroxyl group were exploited to elaborate electro-switchable magnetic surfaces. ESR characterization demonstrated the reversible and permanent magnetic character of the material.

  5. Quantification of air plasma chemistry for surface disinfection

    NASA Astrophysics Data System (ADS)

    Pavlovich, Matthew J.; Clark, Douglas S.; Graves, David B.

    2014-12-01

    Atmospheric-pressure air plasmas, created by a variety of discharges, are promising sources of reactive species for the emerging field of plasma biotechnology because of their convenience and ability to operate at ambient conditions. One biological application of ambient-air plasma is microbial disinfection, and the ability of air plasmas to decontaminate both solid surfaces and liquid volumes has been thoroughly established in the literature. However, the mechanism of disinfection and which reactive species most strongly correlate with antimicrobial effects are still not well understood. We describe quantitative gas-phase measurements of plasma chemistry via infrared spectroscopy in confined volumes, focusing on air plasma generated via surface micro-discharge (SMD). Previously, it has been shown that gaseous chemistry is highly sensitive to operating conditions, and the measurements we describe here extend those findings. We quantify the gaseous concentrations of ozone (O3) and nitrogen oxides (NO and NO2, or NOx) throughout the established ‘regimes’ for SMD air plasma chemistry: the low-power, ozone-dominated mode; the high-power, nitrogen oxides-dominated mode; and the intermediate, unstable transition region. The results presented here are in good agreement with previously published experimental studies of aqueous chemistry and parameterized models of gaseous chemistry. The principal finding of the present study is the correlation of bacterial inactivation on dry surfaces with gaseous chemistry across these time and power regimes. Bacterial decontamination is most effective in ‘NOx mode’ and less effective in ‘ozone mode’, with the weakest antibacterial effects in the transition region. Our results underscore the dynamic nature of air plasma chemistry and the importance of careful chemical characterization of plasma devices intended for biological applications.

  6. Microbially-accelerated consolidation of oil sands tailings. Pathway I: changes in porewater chemistry

    PubMed Central

    Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Arkell, Nicholas; Young, Rozlyn; Li, Carmen; Guigard, Selma; Underwood, Eleisha; Foght, Julia M.

    2014-01-01

    Dispersed clay particles in mine tailings and soft sediments remain suspended for decades, hindering consolidation and challenging effective management of these aqueous slurries. Current geotechnical engineering models of self-weight consolidation of tailings do not consider microbial contribution to sediment behavior, however, here we show that microorganisms indigenous to oil sands tailings change the porewater chemistry and accelerate consolidation of oil sands tailings. A companion paper describes the role of microbes in alteration of clay chemistry in tailings. Microbial metabolism in mature fine tailings (MFT) amended with an organic substrate (hydrolyzed canola meal) produced methane (CH4) and carbon dioxide (CO2). Dissolution of biogenic CO2 lowered the pH of amended MFT to pH 6.4 vs. unamended MFT (pH 7.7). About 12% more porewater was recovered from amended than unamended MFT during 2 months of active microbial metabolism, concomitant with consolidation of tailings. The lower pH in amended MFT dissolved carbonate minerals, thereby releasing divalent cations including calcium (Ca2+) and magnesium (Mg2+) and increasing bicarbonate (HCO−3) in porewater. The higher concentrations increased the ionic strength of the porewater, in turn reducing the thickness of the diffuse double layer (DDL) of clay particles by reducing the surface charge potential (repulsive forces) of the clay particles. The combination of these processes accelerated consolidation of oil sands tailings. In addition, ebullition of biogenic gases created transient physical channels for release of porewater. In contrast, saturating the MFT with non-biogenic CO2 had little effect on consolidation. These results have significant implications for management and reclamation of oil sands tailings ponds and broad importance in anaerobic environments such as contaminated harbors and estuaries containing soft sediments rich in clays and organics. PMID:24711805

  7. Microbially-accelerated consolidation of oil sands tailings. Pathway I: changes in porewater chemistry.

    PubMed

    Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Arkell, Nicholas; Young, Rozlyn; Li, Carmen; Guigard, Selma; Underwood, Eleisha; Foght, Julia M

    2014-01-01

    Dispersed clay particles in mine tailings and soft sediments remain suspended for decades, hindering consolidation and challenging effective management of these aqueous slurries. Current geotechnical engineering models of self-weight consolidation of tailings do not consider microbial contribution to sediment behavior, however, here we show that microorganisms indigenous to oil sands tailings change the porewater chemistry and accelerate consolidation of oil sands tailings. A companion paper describes the role of microbes in alteration of clay chemistry in tailings. Microbial metabolism in mature fine tailings (MFT) amended with an organic substrate (hydrolyzed canola meal) produced methane (CH4) and carbon dioxide (CO2). Dissolution of biogenic CO2 lowered the pH of amended MFT to pH 6.4 vs. unamended MFT (pH 7.7). About 12% more porewater was recovered from amended than unamended MFT during 2 months of active microbial metabolism, concomitant with consolidation of tailings. The lower pH in amended MFT dissolved carbonate minerals, thereby releasing divalent cations including calcium (Ca(2+)) and magnesium (Mg(2+)) and increasing bicarbonate (HCO(-) 3) in porewater. The higher concentrations increased the ionic strength of the porewater, in turn reducing the thickness of the diffuse double layer (DDL) of clay particles by reducing the surface charge potential (repulsive forces) of the clay particles. The combination of these processes accelerated consolidation of oil sands tailings. In addition, ebullition of biogenic gases created transient physical channels for release of porewater. In contrast, saturating the MFT with non-biogenic CO2 had little effect on consolidation. These results have significant implications for management and reclamation of oil sands tailings ponds and broad importance in anaerobic environments such as contaminated harbors and estuaries containing soft sediments rich in clays and organics.

  8. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  9. Surface functionalization of two-dimensional metal chalcogenides by Lewis acid-base chemistry

    NASA Astrophysics Data System (ADS)

    Lei, Sidong; Wang, Xifan; Li, Bo; Kang, Jiahao; He, Yongmin; George, Antony; Ge, Liehui; Gong, Yongji; Dong, Pei; Jin, Zehua; Brunetto, Gustavo; Chen, Weibing; Lin, Zuan-Tao; Baines, Robert; Galvão, Douglas S.; Lou, Jun; Barrera, Enrique; Banerjee, Kaustav; Vajtai, Robert; Ajayan, Pulickel

    2016-05-01

    Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti4+ to form planar p-type [Ti4+n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B3+, Al3+ and Sn4+) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

  10. Can we accelerate medicinal chemistry by augmenting the chemist with Big Data and artificial intelligence?

    PubMed

    Griffen, Edward J; Dossetter, Alexander G; Leach, Andrew G; Montague, Shane

    2018-03-22

    AI comes to lead optimization: medicinal chemistry in all disease areas can be accelerated by exploiting our pre-competitive knowledge in an unbiased way. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Chemistry of the surface and lower atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Fegley, B., Jr.; Treiman, A.

    1992-01-01

    A comprehensive overview of the chemical interactions between the atmosphere and surface of Venus is presented. Earth-based, earth-orbital, and spacecraft data on the composition of the atmosphere and surface of Venus are presented and applied to quantitative evaluations of the chemical interactions between carbon, hydrogen, sulfur, chlorine, fluorine, and nitrogen-containing gases and possible minerals on the Venus surface. The calculation results are used to predict stable minerals and mineral assemblages on the Venus surface to determine which, if any, atmospheric gases are buffered by mineral assemblages on the surface, and to critically review and assess prior work on atmosphere-surface chemistry on Venus. It is concluded that the CO2 pressure on Venus is comparable to the CO2 equilibrium partial pressure developed by the calcite + wollastonite + quartz assemblage at the mean Venus surface temperature of 740 K.

  12. Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

    NASA Astrophysics Data System (ADS)

    Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M.; Ke, Pu Chun; Ding, Feng

    2014-06-01

    Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and

  13. Engineered microtopographies and surface chemistries direct cell attachment and function

    NASA Astrophysics Data System (ADS)

    Magin, Chelsea Marie

    topographically modified surface (R2=0.82). Functionalized PEGDMA hydrogels significantly reduced attachment and attachment strength of Navicula and C. marina. These hydrogels also reduced attachment of zoospores of Ulva compared to PDMSe. Attachment of Ulva to microtopographies in PDMSe and PEGDMA-co-HEMA negatively correlated with ERIII*Re (R2 = 0.94 and R2 = 0.99, respectively). Incorporating a surface energy term into this equation created a correlation between the attachment densities of cells from two evolutionarily diverse groups on substrates of two surface chemistries with an equation that describes the various microtopographies and surface chemistries in terms of surface energy (R2 = 0.80). The current Attachment Model can now be used to design engineered antifouling surface microtopographies and chemistries that inhibit the attachment of organisms from three evoluntionarily diverse groups. Hydrogels based on PEGDMA were also chosen as a substratum material for mammalian cell culture. Capturing endothelial progenitor cells (EPCs) and inducing differentiation into the endothelial cell (EC) phenotype is the ideal way to re-endothelialize a small-diameter vascular graft. Substratum elasticity has been reported to direct stem cell differentiation into specific lineages. Functionalized PEGDMA hydrogels provided good compliance, high fidelity of topographic features and sites for surface modification with biomolecules. Fibronectin grafting and topography both increased EC attachment. This combination of adjustable elasticity, surface chemistry and topography has the potential to promote the capture and differentiation of EPCs into a confluent EC monolayer. Engineered microtopographies replicated in PDMSe directed elongation and alignment of human coronary artery endothelial cells (HCAECs) and human coronary artery smooth muscle cells (HCASMCs) compared to smooth surfaces. Engineered cellular micro-environments were created with specific surface energies defined by chemistry

  14. The impact of surface chemistry on the performance of localized solar-driven evaporation system

    PubMed Central

    Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

    2015-01-01

    This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation. PMID:26337561

  15. The impact of surface chemistry on the performance of localized solar-driven evaporation system.

    PubMed

    Yu, Shengtao; Zhang, Yao; Duan, Haoze; Liu, Yanming; Quan, Xiaojun; Tao, Peng; Shang, Wen; Wu, Jianbo; Song, Chengyi; Deng, Tao

    2015-09-04

    This report investigates the influence of surface chemistry (or wettability) on the evaporation performance of free-standing double-layered thin film on the surface of water. Such newly developed evaporation system is composed of top plasmonic light-to-heat conversion layer and bottom porous supporting layer. Under solar light illumination, the induced plasmonic heat will be localized within the film. By modulating the wettability of such evaporation system through the control of surface chemistry, the evaporation rates are differentiated between hydrophilized and hydrophobized anodic aluminum oxide membrane-based double layered thin films. Additionally, this work demonstrated that the evaporation rate mainly depends on the wettability of bottom supporting layer rather than that of top light-to-heat conversion layer. The findings in this study not only elucidate the role of surface chemistry of each layer of such double-layered evaporation system, but also provide additional design guidelines for such localized evaporation system in applications including desalination, distillation and power generation.

  16. Measuring restoration progress using pore- and surface-water chemistry across a chronosequence of formerly afforested blanket bogs.

    PubMed

    Gaffney, Paul P J; Hancock, Mark H; Taggart, Mark A; Andersen, Roxane

    2018-08-01

    During the restoration of degraded bogs and other peatlands, both habitat and functional recovery can be closely linked with nutrient cycling, which is reflected in pore- and surface-water chemistry. Several peatland restoration studies have shown that the time required for recovery of target conditions is slow (>10 years); for heavily-impacted, drained and afforested peatlands of northern Scotland, recovery time is unknown. We monitored pore- and surface-water chemistry across a chronosequence of formerly drained, afforested bog restoration sites spanning 0-17 years, using a space-for-time substitution, and compared them with open blanket bog control sites. Our aims were to measure rate of recovery towards bog conditions and to identify the best suite of water chemistry variables to indicate recovery. Our results show progress in recovery towards bog conditions over a 0-17 year period post-restoration. Elements scavenged by trees (Mg, Na, S) completely recovered within that period. Many water chemistry variables were affected by the restoration process itself, but recovered within 11 years, except ammonium (NH 4 + ), Zn and dissolved organic carbon (DOC) which remained elevated (when compared to control bogs) 17 years post restoration. Other variables did not completely recover (water table depth (WTD), pH), exhibiting what we term "legacy" effects of drainage and afforestation. Excess N and a lowered WTD are likely to slow the recovery of bog vegetation including key bog plants such as Sphagnum mosses. Over 17 years, we measured near-complete recovery in the chemistry of surface-water and deep pore-water but limited progress in shallow pore-water. Our results suggest that at least >17 years are required for complete recovery of water chemistry to bog conditions. However, we expect that newer restoration methods including conifer harvesting (stem plus brash) and the blocking of plough furrows (to increase the WTD) are likely to accelerate the restoration process

  17. Effects of surface chemistry on the optical properties and cellular interaction of lanthanide-based nanoparticles

    NASA Astrophysics Data System (ADS)

    Pedraza, Francisco J.; Avalos, Julio C.; Mimun, Lawrence C.; Yust, Brian G.; Tsin, Andrew; Sardar, Dhiraj K.

    2015-03-01

    Fluorescent nanoparticles (NPs) such as KYb2F7:Tm3+ potential in biomedical applications due to their ability to absorb and emit within the biological window, where near infrared light is less attenuated by soft tissue. This results in less tissue damage and deeper tissue penetration making it a viable candidate in biological imaging. Another big factor in determining their ability to perform in a biological setting is the surface chemistry. Biocompatible coatings, including polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), pluronic and folic acid are commonly used because they pose several advantages such as ease of functionalization, better dispersion, and higher cellular uptake. To study the effects of the NP surface chemistry, KYb2F7:Tm3+ a solvothermal method using PEG, PVP, pluronic acid, and folic acid as a capping agent, followed by thorough optical characterizations. Optical changes were thoroughly studied and compared using absorption, emission, and quantum yield data. Cell viability was obtained by treating Rhesus Monkey Retinal Endothelial cells (RhREC) with KYb2F7:Tm3+ and counting viable cells following a 24 hour uptake period. The work presented will compare the optical properties and toxicity dependency on the surface chemistry on KYb2F7:Tm3+. The results will also indicate that KYb2F7:Tm3+ nanoparticles are viable candidates for various biomedical applications.

  18. Surface Chemistry in Heterogeneous Catalysis: An Emerging Discipline.

    ERIC Educational Resources Information Center

    White, J. M.; Campbell, Charles T.

    1980-01-01

    Provides background data on surface chemistry as an emerging discipline. Highlights the important role which surfaces play in catalysis by focusing on the catalyzed oxidation of carbon monoxide. Provides a demonstration of how surfaces exert their influences in heterogeneous phenomena and illustrates how experimental problems in this field are…

  19. Transport of oxidized multi-walled carbon nanotubes through silica based porous media: influences of aquatic chemistry, surface chemistry, and natural organic matter.

    PubMed

    Yang, Jin; Bitter, Julie L; Smith, Billy A; Fairbrother, D Howard; Ball, William P

    2013-12-17

    This paper provides results from studies of the transport of oxidized multi-walled carbon nanotubes (O-MWCNTs) of varying surface oxygen concentrations under a range of aquatic conditions and through uniform silica glass bead media. In the presence of Na(+), the required ionic strength (IS) for maximum particle attachment efficiency (i.e., the critical deposition concentration, or CDC) increased as the surface oxygen concentration of the O-MWCNTs or pH increased, following qualitative tenets of theories based on electrostatic interactions. In the presence of Ca(2+), CDC values were lower than those with Na(+) present, but were no longer sensitive to surface oxygen content, suggesting that Ca(2+) impacts the interactions between O-MWCNTs and glass beads by mechanisms other than electrostatic alone. The presence of Suwannee River natural organic matter (SRNOM) decreased the attachment efficiency of O-MWCNTs in the presence of either Na(+) or Ca(2+), but with more pronounced effects when Na(+) was present. Nevertheless, low concentrations of SRNOM (<4 mg/L of dissolved organic carbon) were sufficient to mobilize all O-MWCNTs studied at CaCl2 concentrations as high as 10 mM. Overall, this study reveals that NOM content, pH, and cation type show more importance than surface chemistry in affecting O-MWCNTs deposition during transport through silica-based porous media.

  20. The surface chemistry of multi-oxide silicates

    NASA Astrophysics Data System (ADS)

    Oelkers, Eric H.; Golubev, Sergey V.; Chairat, Claire; Pokrovsky, Oleg S.; Schott, Jacques

    2009-08-01

    The surface chemistry of natural wollastonite, diopside, enstatite, forsterite, and albite in aqueous solutions was characterized using both electrokinetic techniques and surface titrations performed for 20 min in batch reactors. Titrations performed in such reactors allow determination of both proton consumption and metal release from the mineral surface as a function of pH. The compositions, based on aqueous solution analysis, of all investigated surfaces vary dramatically with solution pH. Ca and Mg are preferentially released from the surfaces of all investigated divalent metal silicates at pH less than ˜8.5-10 but preferentially retained relative to silica at higher pH. As such, the surfaces of these minerals are Si-rich and divalent metal poor except in strongly alkaline solutions. The preferential removal of divalent cations from these surfaces is coupled to proton consumption. The number of protons consumed by the preferential removal of each divalent cation is pH independent but depends on the identity of the mineral; ˜1.5 protons are consumed by the preferential removal of each Ca atom from wollastonite, ˜3 protons are consumed by the preferential removal of each Mg or Ca atom from diopside or enstatite, and ˜4 protons are consumed by the preferential removal of each Mg from forsterite. These observations are interpreted to stem from the creation of additional 'internal' adsorption sites by the preferential removal of divalent metal cations which can be coupled to the condensation of partially detached Si. Similarly, Na and Al are preferentially removed from the albite surface at 2 > pH > 11; mass balance calculations suggest that three protons are consumed by the preferential removal of each Al atom from this surface over this entire pH range. Electrokinetic measurements on fresh mineral powders yield an isoelectric point (pH IEP) 2.6, 4.4, 3.0, 4.5, and <1, for wollastonite, diopside, enstatite, forsterite, and albite, respectively, consistent with

  1. A Simple "Boxed Molecular Kinetics" Approach To Accelerate Rare Events in the Stochastic Kinetic Master Equation.

    PubMed

    Shannon, Robin; Glowacki, David R

    2018-02-15

    The chemical master equation is a powerful theoretical tool for analyzing the kinetics of complex multiwell potential energy surfaces in a wide range of different domains of chemical kinetics spanning combustion, atmospheric chemistry, gas-surface chemistry, solution phase chemistry, and biochemistry. There are two well-established methodologies for solving the chemical master equation: a stochastic "kinetic Monte Carlo" approach and a matrix-based approach. In principle, the results yielded by both approaches are identical; the decision of which approach is better suited to a particular study depends on the details of the specific system under investigation. In this Article, we present a rigorous method for accelerating stochastic approaches by several orders of magnitude, along with a method for unbiasing the accelerated results to recover the "true" value. The approach we take in this paper is inspired by the so-called "boxed molecular dynamics" (BXD) method, which has previously only been applied to accelerate rare events in molecular dynamics simulations. Here we extend BXD to design a simple algorithmic strategy for accelerating rare events in stochastic kinetic simulations. Tests on a number of systems show that the results obtained using the BXD rare event strategy are in good agreement with unbiased results. To carry out these tests, we have implemented a kinetic Monte Carlo approach in MESMER, which is a cross-platform, open-source, and freely available master equation solver.

  2. Bactericidal effects of plasma-modified surface chemistry of silicon nanograss

    NASA Astrophysics Data System (ADS)

    Ostrikov, Kola; Macgregor-Ramiasa, Melanie; Cavallaro, Alex; (Ken Ostrikov, Kostya; Vasilev, Krasimir

    2016-08-01

    The surface chemistry and topography of biomaterials regulate the adhesion and growth of microorganisms in ways that are still poorly understood. Silicon nanograss structures prepared via inductively coupled plasma etching were coated with plasma deposited nanometer-thin polymeric films to produce substrates with controlled topography and defined surface chemistry. The influence of surface properties on Staphylococcus aureus proliferation is demonstrated and explained in terms of nanograss substrate wetting behaviour. With the combination of the nanograss topography; hydrophilic plasma polymer coatings enhanced antimicrobial activity while hydrophobic coatings reduced it. This study advances the understanding of the effects of surface wettability on the bactericidal properties of reactive nano-engineered surfaces.

  3. Graduate Student Program in Materials and Engineering Research and Development for Future Accelerators

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Spentzouris, Linda

    The objective of the proposal was to develop graduate student training in materials and engineering research relevant to the development of particle accelerators. Many components used in today's accelerators or storage rings are at the limit of performance. The path forward in many cases requires the development of new materials or fabrication techniques, or a novel engineering approach. Often, accelerator-based laboratories find it difficult to get top-level engineers or materials experts with the motivation to work on these problems. The three years of funding provided by this grant was used to support development of accelerator components through a multidisciplinary approachmore » that cut across the disciplinary boundaries of accelerator physics, materials science, and surface chemistry. The following results were achieved: (1) significant scientific results on fabrication of novel photocathodes, (2) application of surface science and superconducting materials expertise to accelerator problems through faculty involvement, (3) development of instrumentation for fabrication and characterization of materials for accelerator components, (4) student involvement with problems at the interface of material science and accelerator physics.« less

  4. Surface-Enhanced Raman Spectroscopy as a Probe of the Surface Chemistry of Nanostructured Materials.

    PubMed

    Dick, Susan; Konrad, Magdalena P; Lee, Wendy W Y; McCabe, Hannah; McCracken, John N; Rahman, Taifur M D; Stewart, Alan; Xu, Yikai; Bell, Steven E J

    2016-07-01

    Surface-enhanced Raman spectroscopy (SERS) is now widely used as a rapid and inexpensive tool for chemical/biochemical analysis. The method can give enormous increases in the intensities of the Raman signals of low-concentration molecular targets if they are adsorbed on suitable enhancing substrates, which are typically composed of nanostructured Ag or Au. However, the features of SERS that allow it to be used as a chemical sensor also mean that it can be used as a powerful probe of the surface chemistry of any nanostructured material that can provide SERS enhancement. This is important because it is the surface chemistry that controls how these materials interact with their local environment and, in real applications, this interaction can be more important than more commonly measured properties such as morphology or plasmonic absorption. Here, the opportunity that this approach to SERS provides is illustrated with examples where the surface chemistry is both characterized and controlled in order to create functional nanomaterials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Preparation and measurement methods for studying nanoparticle aggregate surface chemistry.

    PubMed

    Szakal, Christopher; McCarthy, James A; Ugelow, Melissa S; Konicek, Andrew R; Louis, Kacie; Yezer, Benjamin; Herzing, Andrew A; Hamers, Robert J; Holbrook, R David

    2012-07-01

    Despite best efforts at controlling nanoparticle (NP) surface chemistries, the environment surrounding nanomaterials is always changing and can impart a permanent chemical memory. We present a set of preparation and measurement methods to be used as the foundation for studying the surface chemical memory of engineered NP aggregates. We attempt to bridge the gap between controlled lab studies and real-world NP samples, specifically TiO(2), by using well-characterized and consistently synthesized NPs, controllably producing NP aggregates with precision drop-on-demand inkjet printing for subsequent chemical measurements, monitoring the physical morphology of the NP aggregate depositions with scanning electron microscopy (SEM), acquiring "surface-to-bulk" mass spectra of the NP aggregate surfaces with time-of-flight secondary ion mass spectrometry (ToF-SIMS), and developing a data analysis scheme to interpret chemical signatures more accurately from thousands of data files. We present differences in mass spectral peak ratios for bare TiO(2) NPs compared to NPs mixed separately with natural organic matter (NOM) or pond water. The results suggest that subtle changes in the local environment can alter the surface chemistry of TiO(2) NPs, as monitored by Ti(+)/TiO(+) and Ti(+)/C(3)H(5)(+) peak ratios. The subtle changes in the absolute surface chemistry of NP aggregates vs. that of the subsurface are explored. It is envisioned that the methods developed herein can be adapted for monitoring the surface chemistries of a variety of engineered NPs obtained from diverse natural environments.

  6. Molecular-level chemistry of model single-crystal oxide surfaces with model halogenated compounds

    NASA Astrophysics Data System (ADS)

    Adib, Kaveh

    Synchrotron-based X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD) and low energy electron diffraction (LEED) have been used to investigate, at a molecular level, the chemistry of different terminations of single crystal iron-oxide surfaces with probe molecules (CCl4 and D2O). Comparisons of the reactivity of these surfaces towards CCl4, indicate that the presence of an uncapped surface Fe cation (strong Lewis acid site) and an adjacent oxygen site capped by that cation can effect the C-Cl bond cleavage in CCl4, resulting in dissociatively adsorbed Cl-adatoms and carbon-containing fragments. If in addition to these sites, an uncapped surface oxygen (Lewis base) site is also available, the carbon-containing moiety can then move that site, coordinate itself with that uncapped oxygen, and stabilize itself. At a later step, the carbon-containing fragment may form a strong covalent bond with the uncapped oxygen and may even abstract that surface oxygen. On the other hand, if an uncapped oxygen is not available to stabilize the carbon-containing fragment, the surface coordination will not occur and upon the subsequent thermal annealing of the surface the Cl-adatoms and the carbon-containing fragments will recombine and desorb as CCl4. Finally, the presence of surface deuteroxyls blocking the strong Lewis acid and base sites of the reactive surface, passivates this surface. Such a deuteroxylated surface will be unreactive towards CCl 4. Such a molecular level understanding of the surface chemistry of metal-oxides will have applications in the areas of selective catalysis, including environmental catalysis, and chemical sensor technology.

  7. Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels

    PubMed Central

    Syverud, Kristin

    2014-01-01

    Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. PMID:24713295

  8. Magmatic and fragmentation controls on volcanic ash surface chemistry

    NASA Astrophysics Data System (ADS)

    Ayris, Paul M.; Diplas, Spyros; Damby, David E.; Hornby, Adrian J.; Cimarelli, Corrado; Delmelle, Pierre; Scheu, Bettina; Dingwell, Donald B.

    2016-04-01

    The chemical effects of silicate ash ejected by explosive volcanic eruptions on environmental systems are fundamentally mediated by ash particle surfaces. Ash surfaces are a composite product of magmatic properties and fragmentation mechanisms, as well as in-plume and atmospheric alteration processes acting upon those surfaces during and after the eruption. Recent attention has focused on the capacity of alteration processes to shape ash surfaces; most notably, several studies have utilised X-ray photoelectron spectroscopy (XPS), a technique probing the elemental composition and coordination state of atoms within the top 10 nm of ash surfaces, to identify patterns of elemental depletions and enrichments relative to bulk ash chemical composition. Under the presumption of surface and bulk equivalence, any disparities have been previously attributed to surface alteration processes, but the ubiquity of some depletions (e.g., Ca, Fe) across multiple ash studies, irrespective of eruptive origin, could suggest these to be features of the surface produced at the instant of magma fragmentation. To investigate this possibility further, we conducted rapid decompression experiments at different pressure conditions and at ambient and magmatic temperature on porous andesitic rocks. These experiments produced fragmented ash material untouched by secondary alteration, which were compared to particles produced by crushing of large clasts from the same experiments. We investigated a restricted size fraction (63-90 μm) from both fragmented and crushed materials, determining bulk chemistry and mineralogy via XRF, SEM-BSE and EPMA, and investigated the chemical composition of the ash surface by XPS. Analyses suggest that fragmentation under experimental conditions partitioned a greater fraction of plagioclase-rich particles into the selected size fraction, relative to particles produced by crushing. Trends in surface chemical composition in fragmented and crushed particles mirror that

  9. A label-free colorimetric sensor for Pb2+ detection based on the acceleration of gold leaching by graphene oxide.

    PubMed

    Shi, Xinhao; Gu, Wei; Zhang, Cuiling; Zhao, Longyun; Peng, Weidong; Xian, Yuezhong

    2015-03-14

    In this work, we developed a novel, label-free, colorimetric sensor for Pb(2+) detection based on the acceleration of gold leaching by graphene oxide (GO) at room temperature. Gold nanoparticles (AuNPs) can be dissolved in a thiosulfate (S2O3(2-)) aqueous environment in the presence of oxygen; however, the leaching rate is very slow due to the high activation energy (27.99 kJ mol(-1)). In order to enhance the reaction rate, some accelerators should be added. In comparison with the traditional accelerators (metal ions or middle ligands), we found that GO could efficiently accelerate the gold leaching reaction. Kinetic data demonstrate that the dissolution rate of gold in the Pb(2+)-S2O3(2-)-GO system is 5 times faster than that without GO at room temperature. In addition, the effects of surface modification and the nanoparticle size on the etching of AuNPs were investigated. Based on the GO-accelerated concentration-dependent colour changes of AuNPs, a colorimetric sensor for Pb(2+) detection was developed with a linear range from 0.1 to 20 μM and the limit of detection (LOD) was evaluated to be 0.05 μM. This colorimetric assay is simple, low-cost, label-free, and has numerous potential applications in the field of environmental chemistry.

  10. Surface chemistry, microstructure and friction properties of some ferrous-base metallic glasses at temperatures to 750 C

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analysis, transmission electron microscopy, diffraction studies, and sliding friction experiments were conducted with ferrous-base metallic glasses in sliding contact with aluminum oxide at temperatures from room to 750 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on the friction properties, surface chemistry, and microstructure of metallic glasses. The relative concentrations of the various constituents at the surface of the sputtered specimens were very different from the normal bulk compositions. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and silicon oxide at 350 C and boron nitride above 500 C. The coefficient of friction increased with increasing temperature to 350 C. Above 500 C the coefficient of friction decreased rapidly. The segregation of contaminants may be responsible for the friction behavior.

  11. Engineering of Surface Chemistry for Enhanced Sensitivity in Nanoporous Interferometric Sensing Platforms.

    PubMed

    Law, Cheryl Suwen; Sylvia, Georgina M; Nemati, Madieh; Yu, Jingxian; Losic, Dusan; Abell, Andrew D; Santos, Abel

    2017-03-15

    We explore new approaches to engineering the surface chemistry of interferometric sensing platforms based on nanoporous anodic alumina (NAA) and reflectometric interference spectroscopy (RIfS). Two surface engineering strategies are presented, namely (i) selective chemical functionalization of the inner surface of NAA pores with amine-terminated thiol molecules and (ii) selective chemical functionalization of the top surface of NAA with dithiol molecules. The strong molecular interaction of Au 3+ ions with thiol-containing functional molecules of alkane chain or peptide character provides a model sensing system with which to assess the sensitivity of these NAA platforms by both molecular feature and surface engineering. Changes in the effective optical thickness of the functionalized NAA photonic films (i.e., sensing principle), in response to gold ions, are monitored in real-time by RIfS. 6-Amino-1-hexanethiol (inner surface) and 1,6-hexanedithiol (top surface), the most sensitive functional molecules from approaches i and ii, respectively, were combined into a third sensing strategy whereby the NAA platforms are functionalized on both the top and inner surfaces concurrently. Engineering of the surface according to this approach resulted in an additive enhancement in sensitivity of up to 5-fold compared to previously reported systems. This study advances the rational engineering of surface chemistry for interferometric sensing on nanoporous platforms with potential applications for real-time monitoring of multiple analytes in dynamic environments.

  12. Laboratory Activity Worksheet to Train High Order Thinking Skill of Student on Surface Chemistry Lecture

    NASA Astrophysics Data System (ADS)

    Yonata, B.; Nasrudin, H.

    2018-01-01

    A worksheet has to be a set with activity which is help students to arrange their own experiments. For this reason, this research is focused on how to train students’ higher order thinking skills in laboratory activity by developing laboratory activity worksheet on surface chemistry lecture. To ensure that the laboratory activity worksheet already contains aspects of the higher order thinking skill, it requires theoretical and empirical validation. From the data analysis results, it shows that the developed worksheet worth to use. The worksheet is worthy of theoretical and empirical feasibility. This conclusion is based on the findings: 1) Assessment from the validators about the theoretical feasibility aspects in the category is very feasible with an assessment range of 95.24% to 97.92%. 2) students’ higher thinking skill from N Gain values ranges from 0.50 (enough) to 1.00 (high) so it can be concluded that the laboratory activity worksheet on surface chemistry lecture is empirical in terms of worth. The empirical feasibility is supported by the responses of the students in very reasonable categories. It is expected that the laboratory activity worksheet on surface chemistry lecture can train students’ high order thinking skills for students who program surface chemistry lecture.

  13. Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels.

    PubMed

    Chinga-Carrasco, Gary; Syverud, Kristin

    2014-09-01

    Nanocellulose from wood is a promising material with potential in various technological areas. Within biomedical applications, nanocellulose has been proposed as a suitable nano-material for wound dressings. This is based on the capability of the material to self-assemble into 3D micro-porous structures, which among others have an excellent capacity of maintaining a moist environment. In addition, the surface chemistry of nanocellulose is suitable for various applications. First, OH-groups are abundant in nanocellulose materials, making the material strongly hydrophilic. Second, the surface chemistry can be modified, introducing aldehyde and carboxyl groups, which have major potential for surface functionalization. In this study, we demonstrate the production of nanocellulose with tailor-made surface chemistry, by pre-treating the raw cellulose fibres with carboxymethylation and periodate oxidation. The pre-treatments yielded a highly nanofibrillated material, with significant amounts of aldehyde and carboxyl groups. Importantly, the poly-anionic surface of the oxidized nanocellulose opens up for novel applications, i.e. micro-porous materials with pH-responsive characteristics. This is due to the swelling capacity of the 3D micro-porous structures, which have ionisable functional groups. In this study, we demonstrated that nanocellulose gels have a significantly higher swelling degree in neutral and alkaline conditions, compared to an acid environment (pH 3). Such a capability can potentially be applied in chronic wounds for controlled and intelligent release of antibacterial components into biofilms. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  14. NOx Binding and Dissociation: Enhanced Ferroelectric Surface Chemistry by Catalytic Monolayers

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2013-03-01

    NOx molecules are regulated air pollutants produced during automotive combustion. As part of an effort to design viable catalysts for NOx decomposition operating at higher temperatures that would allow for improved fuel efficiency, we examine NOx chemistry on ferroelectric perovskite surfaces. Changing the direction of ferroelectric polarization can modify surface electronic properties and may lead to switchable surface chemistry. Here, we describe our recent work on potentially enhanced surface chemistry using catalytic RuO2 monolayers on perovskite ferroelectric substrates. In addition to thermodynamic stabilization of the RuO2 layer, we present results on the polarization-dependent binding of NO, O2, N2, and atomic O and N. We present results showing that one key problem with current catalysts, involving the difficulty of releasing dissociation products (especially oxygen), can be ameliorated by this method. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  15. Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana

    The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

  16. Role of Surface Chemistry on Catalyst/Ionomer Interactions for Transition Metal–Nitrogen–Carbon Electrocatalysts

    DOE PAGES

    Artyushkova, Kateryna; Workman, Michael J.; Matanovic, Ivana; ...

    2017-12-18

    The role of the interaction between doped carbon-based materials and ionic conductors is essential in multiple technologies, from fuel cells and energy storage devices to conductive polymer composites. In this paper, we report how the surface chemistry of transition metal–nitrogen–carbon (MNC) electrocatalysts affects catalyst–ionomer interaction and the resulting structure of cathodes. The cathode structure resulting from these interactions is directly related to the performance in membrane electrode assembly (MEA) fuel cells. To advance the development of platinum group metal (PGM)-free electrodes for the oxygen reduction reaction it is necessary to understand the structure of the catalyst layers with focus onmore » chemistry and distribution of active sites and ionomer morphology. To assess catalyst interaction with an ionomer, X-ray photoelectron spectroscopy is applied to study the chemistry of catalyst layers while density functional theory (DFT) is used to calculate adsorption energies of the ionomer side chain on different nitrogen species. We report that a high surface concentration of hydrogenated nitrogen at the surface of MNC catalysts causes inefficient ionomer morphology, while an abundance of surface oxides promotes both an efficient distribution of active sites and an optimal ionomer–catalyst interface. The critical role of protonation of nitrogen within catalytic layers in inhibiting proton transport during fuel cell operation is also suggested. As a result, this is the first report of the effect the surface chemistry of MNC catalysts, in the presence of the ionomer, has on the structure and performance of MEA electrodes.« less

  17. Organic Chemistry in Two Dimensions: Surface-Functionalized Polymers and Self-Assembled Monolayer Films

    DTIC Science & Technology

    1988-09-01

    surfaces as components of materials . In particular, we hope to develop the ability to rationalize and predict the macroscooic properties of surfaces...of much of the current research in areas such as materials science, condensed matter and device physics, and polymer physical chemistry. Surface...6 Underlying our program in surface chemistry is a broad interest in the prop- erties of organic surfaces as components of materials . In particular

  18. Effect of non-equilibrium flow chemistry and surface catalysis on surface heating to AFE

    NASA Technical Reports Server (NTRS)

    Stewart, David A.; Henline, William D.; Chen, Yih-Kanq

    1991-01-01

    The effect of nonequilibrium flow chemistry on the surface temperature distribution over the forebody heat shield on the Aeroassisted Flight Experiment (AFE) vehicle was investigated using a reacting boundary-layer code. Computations were performed by using boundary-layer-edge properties determined from global iterations between the boundary-layer code and flow field solutions from a viscous shock layer (VSL) and a full Navier-Stokes solution. Surface temperature distribution over the AFE heat shield was calculated for two flight conditions during a nominal AFE trajectory. This study indicates that the surface temperature distribution is sensitive to the nonequilibrium chemistry in the shock layer. Heating distributions over the AFE forebody calculated using nonequilibrium edge properties were similar to values calculated using the VSL program.

  19. Unraveling the Reaction Chemistry of Icy Ocean World Surfaces

    NASA Astrophysics Data System (ADS)

    Hudson, R.; Loeffler, M. J.; Gerakines, P.

    2017-12-01

    The diverse endogenic chemistry of ocean worlds can be divided among interior, surface, and above-surface process, with contributions from exogenic agents such as solar, cosmic, and magnetospheric radiation. Bombardment from micrometeorites to comets also can influence chemistry by both delivering new materials and altering pre-existing ones, and providing energy to drive reactions. Geological processes further complicate the chemistry by transporting materials from one environment to another. In this presentation the focus will be on some of the thermally driven and radiation-induced changes expected from icy materials, primarily covalent and ionic compounds. Low-temperature conversions of a few relatively simple molecules into ions possessing distinct infrared (IR) features will be covered, with an emphasis on such features as might be identified through either orbiting spacecraft or landers. The low-temperature degradation of a few bioorganic molecules, such as DNA nucleobases and some common amino acids, will be used as examples of the more complex, and potentially misleading, chemistry expected for icy moons of the outer solar system. This work was supported by NASA's Emerging Worlds and Outer Planets Research programs, as well as the NASA Astrobiology Institute's Goddard Center for Astrobiology.

  20. REGIONAL RELATIONSHIPS BETWEEN GEOMORPHIC/HYDROLOGIC PARAMETERS AND SURFACE WATER CHEMISTRY RELATIVE TO ACIDIC DEPOSITION

    EPA Science Inventory

    We determined geomorphic and hydrologic parameters for 144 forested, lake watersheds in the Northeast (NE) of the United States based primarily on measurements from topographic maps. hese parameters were used to test for relationships with selected surface water chemistry relevan...

  1. On the use of SPM to probe the interplay between polymer surface chemistry and polymer surface mechanics

    NASA Astrophysics Data System (ADS)

    Brogly, Maurice; Noel, Olivier; Awada, Houssein; Castelein, Gilles

    2007-03-01

    Adhesive properties of a polymer surface results from the complex contribution of surface chemistry and activation of sliding and dissipating mechanisms within the polymer surface layer. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between the surface viscoelastic properties of the polymer, the surface chemistry of functionalized polymer surfaces and the adhesive forces, as determined by C-AFM experiments. Indeed we are interested in the measurements of local attractive or adhesive forces in AFM contact mode, of controlled chemical and mechanical model substrates. In order to investigate the interplay between mechanical or viscoelastic mechanisms and surface chemistry during the tip - polymer contact, we achieved force measurements on model PDMS polymer networks, whose surfaces are chemically controlled with the same functional groups as before (silicon substrates). On the basis of AFM nano-indentation experiments, surface Young moduli have been determined. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. We propose an original model, which express the local adhesion force to the energy dissipated within the contact and the surface properties of the material (thermodynamic work of adhesion). Moreover we show that the dissipation function is related to Mc, the mass between crosslinks of the network.

  2. Elementary photocatalytic chemistry on TiO2 surfaces.

    PubMed

    Guo, Qing; Zhou, Chuanyao; Ma, Zhibo; Ren, Zefeng; Fan, Hongjun; Yang, Xueming

    2016-07-07

    Photocatalytic hydrogen production and pollutant degradation provided both great opportunities and challenges in the field of sustainable energy and environmental science. Over the past few decades, we have witnessed fast growing interest and efforts in developing new photocatalysts, improving catalytic efficiency and exploring the reaction mechanism at the atomic and molecular levels. Owing to its relatively high efficiency, nontoxicity, low cost and high stability, TiO2 becomes one of the most extensively investigated metal oxides in semiconductor photocatalysis. Fundamental studies on well characterized single crystals using ultrahigh vacuum based surface science techniques could provide key microscopic insight into the underlying mechanism of photocatalysis. In this review, we have summarized recent progress in the photocatalytic chemistry of hydrogen, water, oxygen, carbon monoxide, alcohols, aldehydes, ketones and carboxylic acids on TiO2 surfaces. We focused this review mainly on the rutile TiO2(110) surface, but some results on the rutile TiO2(011), anatase TiO2(101) and (001) surfaces are also discussed. These studies provided fundamental insights into surface photocatalysis as well as stimulated new investigations in this exciting field. At the end of this review, we have discussed how these studies can help us to develop new photocatalysis models.

  3. Subglottal Impedance-Based Inverse Filtering of Voiced Sounds Using Neck Surface Acceleration

    PubMed Central

    Zañartu, Matías; Ho, Julio C.; Mehta, Daryush D.; Hillman, Robert E.; Wodicka, George R.

    2014-01-01

    A model-based inverse filtering scheme is proposed for an accurate, non-invasive estimation of the aerodynamic source of voiced sounds at the glottis. The approach, referred to as subglottal impedance-based inverse filtering (IBIF), takes as input the signal from a lightweight accelerometer placed on the skin over the extrathoracic trachea and yields estimates of glottal airflow and its time derivative, offering important advantages over traditional methods that deal with the supraglottal vocal tract. The proposed scheme is based on mechano-acoustic impedance representations from a physiologically-based transmission line model and a lumped skin surface representation. A subject-specific calibration protocol is used to account for individual adjustments of subglottal impedance parameters and mechanical properties of the skin. Preliminary results for sustained vowels with various voice qualities show that the subglottal IBIF scheme yields comparable estimates with respect to current aerodynamics-based methods of clinical vocal assessment. A mean absolute error of less than 10% was observed for two glottal airflow measures –maximum flow declination rate and amplitude of the modulation component– that have been associated with the pathophysiology of some common voice disorders caused by faulty and/or abusive patterns of vocal behavior (i.e., vocal hyperfunction). The proposed method further advances the ambulatory assessment of vocal function based on the neck acceleration signal, that previously have been limited to the estimation of phonation duration, loudness, and pitch. Subglottal IBIF is also suitable for other ambulatory applications in speech communication, in which further evaluation is underway. PMID:25400531

  4. Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

    NASA Astrophysics Data System (ADS)

    Zonca, Michael R., Jr.

    Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a

  5. The Chemistry of Inorganic Precursors during the Chemical Deposition of Films on Solid Surfaces.

    PubMed

    Barry, Seán T; Teplyakov, Andrew V; Zaera, Francisco

    2018-03-20

    The deposition of thin solid films is central to many industrial applications, and chemical vapor deposition (CVD) methods are particularly useful for this task. For one, the isotropic nature of the adsorption of chemical species affords even coverages on surfaces with rough topographies, an increasingly common requirement in microelectronics. Furthermore, by splitting the overall film-depositing reactions into two or more complementary and self-limiting steps, as it is done in atomic layer depositions (ALD), film thicknesses can be controlled down to the sub-monolayer level. Thanks to the availability of a vast array of inorganic and metalorganic precursors, CVD and ALD are quite versatile and can be engineered to deposit virtually any type of solid material. On the negative side, the surface chemistry that takes place in these processes is often complex, and can include undesirable side reactions leading to the incorporation of impurities in the growing films. Appropriate precursors and deposition conditions need to be chosen to minimize these problems, and that requires a proper understanding of the underlying surface chemistry. The precursors for CVD and ALD are often designed and chosen based on their known thermal chemistry from inorganic chemistry studies, taking advantage of the vast knowledge developed in that field over the years. Although a good first approximation, however, this approach can lead to wrong choices, because the reactions of these precursors at gas-solid interfaces can be quite different from what is seen in solution. For one, solvents often aid in the displacement of ligands in metalorganic compounds, providing the right dielectric environment, temporarily coordinating to the metal, or facilitating multiple ligand-complex interactions to increase reaction probabilities; these options are not available in the gas-solid reactions associated with CVD and ALD. Moreover, solid surfaces act as unique "ligands", if these reactions are to be

  6. Estimating the Analytical and Surface Enhancement Factors in Surface-Enhanced Raman Scattering (SERS): A Novel Physical Chemistry and Nanotechnology Laboratory Experiment

    ERIC Educational Resources Information Center

    Pavel, Ioana E.; Alnajjar, Khadijeh S.; Monahan, Jennifer L.; Stahler, Adam; Hunter, Nora E.; Weaver, Kent M.; Baker, Joshua D.; Meyerhoefer, Allie J.; Dolson, David A.

    2012-01-01

    A novel laboratory experiment was successfully implemented for undergraduate and graduate students in physical chemistry and nanotechnology. The main goal of the experiment was to rigorously determine the surface-enhanced Raman scattering (SERS)-based sensing capabilities of colloidal silver nanoparticles (AgNPs). These were quantified by…

  7. Grain Surface Chemistry and the Composition of Interstellar Ices

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.

    2006-01-01

    Submicron sized dust grains are an important component of the interstellar medium. In particular they provide surface where active chemistry can take place. At the low temperatures (-10 K) of the interstellar medium, colliding gas phase species will stick, diffuse, react, and form an icy mantle on these dust grains. This talk will review the principles of grain surface chemistry and delineate important grain surface routes, focusing on reactions involving H, D, and O among each other and with molecules such as CO. Interstellar ice mantles can be studied through the fundamental vibrations of molecular species in the mid-infrared spectra of sources embedded in or located behind dense molecular clouds. Analysis of this type of data has provided a complex view of the composition of these ices and the processes involved. Specifically, besides grain surface chemistry, the composition of interstellar ices is also affected by thermal processing due to nearby newly formed stars. This leads to segregation between different ice components as well as outgassing. The latter results in the formation of a so-called Hot Core region with a gas phase composition dominated by evaporated mantle species. Studies of such regions provide thus a different view on the ice composition and the chemical processes involved. Interstellar ices can also be processed by FUV photons and high energy cosmic ray ions. Cosmic ray processing likely dominates the return of accreted species to the gas phase where further gas phase reactions can take place. These different chemical routes towards molecular complexity in molecular clouds and particularly regions of star formation will be discussed.

  8. Accelerating proof of concept for small molecule drugs using solid-state chemistry.

    PubMed

    Byrn, Stephen R; Zografi, George; Chen, Xiaoming Sean

    2010-09-01

    In this perspective we have shown that the process of "proof of concept" (POC) in the early part of drug development can be greatly accelerated by close attention to the underlying solid-state chemistry (SSC) of a new chemical entity. POC seeks data that provide confidence in the therapeutic activity and safety of a new chemical entity, which can rapidly lead to a key "GO/NO-GO" decision point for further development. Due to the high cost of the development of new chemical entities and the current low overall productivity of obtaining successful candidates, the pharmaceutical industry is being required to develop accelerated POC strategies. The success of accelerated approaches to POC depends on a full understanding of the SSC of drugs in relation to solubility and stability. Dissolution-limited absorption due to poor solubility of drug substances is particularly important because it can lead to low exposure in animals and undesired bioavailability in humans. Choosing a desirable solid form with sufficient solubility and acceptable stability is essential in developing formulations for POC with superior quality. In this perspective we present an approach that utilizes SSC as part of a novel 2-year development strategy for reaching the pivotal clinical trial stage of development.

  9. Analysis of temporal evolution of quantum dot surface chemistry by surface-enhanced Raman scattering.

    PubMed

    Doğan, İlker; Gresback, Ryan; Nozaki, Tomohiro; van de Sanden, Mauritius C M

    2016-07-08

    Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions.

  10. Giant magnetoresistive biosensors for molecular diagnosis: surface chemistry and assay development

    NASA Astrophysics Data System (ADS)

    Yu, Heng; Osterfeld, Sebastian J.; Xu, Liang; White, Robert L.; Pourmand, Nader; Wang, Shan X.

    2008-08-01

    Giant magnetoresistive (GMR) biochips using magnetic nanoparticle as labels were developed for molecular diagnosis. The sensor arrays consist of GMR sensing strips of 1.5 μm or 0.75 μm in width. GMR sensors are exquisitely sensitive yet very delicate, requiring ultrathin corrosion-resistive passivation and efficient surface chemistry for oligonucleotide probe immobilization. A mild and stable surface chemistry was first developed that is especially suitable for modifying delicate electronic device surfaces, and a practical application of our GMR biosensors was then demonstrated for detecting four most common human papillomavirus (HPV) subtypes in plasmids. We also showed that the DNA hybridization time could potentially be reduced from overnight to about ten minutes using microfluidics.

  11. Accelerator-based BNCT.

    PubMed

    Kreiner, A J; Baldo, M; Bergueiro, J R; Cartelli, D; Castell, W; Thatar Vento, V; Gomez Asoia, J; Mercuri, D; Padulo, J; Suarez Sandin, J C; Erhardt, J; Kesque, J M; Valda, A A; Debray, M E; Somacal, H R; Igarzabal, M; Minsky, D M; Herrera, M S; Capoulat, M E; Gonzalez, S J; del Grosso, M F; Gagetti, L; Suarez Anzorena, M; Gun, M; Carranza, O

    2014-06-01

    The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases. © 2013 Elsevier Ltd. All rights reserved.

  12. The role of "inert" surface chemistry in marine biofouling prevention.

    PubMed

    Rosenhahn, Axel; Schilp, Sören; Kreuzer, Hans Jürgen; Grunze, Michael

    2010-05-07

    The settlement and colonization of marine organisms on submerged man-made surfaces is a major economic problem for many marine industries. The most apparent detrimental effects of biofouling are increased fuel consumption of ships, clogging of membranes and heat exchangers, disabled underwater sensors, and growth of biofoulers in aquaculture systems. The presently common-but environmentally very problematic-way to deal with marine biofouling is to incorporate biocides, which use biocidal products in the surface coatings to kill the colonizing organisms, into the surface coatings. Since the implementation of the International Maritime Organization Treaty on biocides in 2008, the use of tributyltin (TBT) is restricted and thus environmentally benign but effective surface coatings are required. In this short review, we summarize the different strategies which are pursued in academia and industry to better understand the mechanisms of biofouling and to develop strategies which can be used for industrial products. Our focus will be on chemically "inert" model surface coatings, in particular oligo- and poly(ethylene glycol) (OEG and PEG) functionalized surface films. The reasons for choosing this class of chemistry as an example are three-fold: Firstly, experiments on spore settlement on OEG and PEG coatings help to understand the mechanism of non-fouling of highly hydrated interfaces; secondly, these studies defy the common assumption that surface hydrophilicity-as measured by water contact angles-is an unambiguous and predictive tool to determine the fouling behavior on the surface; and thirdly, choosing this system is a good example for "interfacial systems chemistry": it connects the behavior of unicellular marine organisms with the antifouling properties of a hydrated surface coating with structural and electronic properties as derived from ab initio quantum mechanical calculations using the electronic wave functions of oxygen, hydrogen, and carbon. This short

  13. Surface chemistry of liquid metals

    NASA Technical Reports Server (NTRS)

    Mann, J. Adin, Jr.; Peebles, Henry; Peebles, Diamond; Rye, Robert; Yost, Fred

    1993-01-01

    The fundamental surface chemistry of the behavior of liquid metals spreading on a solid substrate is not at all well understood. Each of these questions involves knowing the details of the structure of interfaces and their dynamics. For example the structure of a monolayer of tin oxide on pure liquid tin is unknown. This is in contrast to the relatively large amount of data available on the structure of copper oxide monolayers on solid, pure copper. However, since liquid tin has a vapor pressure below 10(exp -10)torr for a reasonable temperature range above its melting point, it is possible to use the techniques of surface science to study the geometric, electronic and vibrational structures of these monolayers. In addition, certain techniques developed by surface chemists for the study of liquid systems can be applied to the ultra-high vacuum environment. In particular we have shown that light scattering spectroscopy can be used to study the surface tension tensor of these interfaces. The tin oxide layer in particular is very interesting in that the monolayer is rigid but admits of bending. Ellipsometric microscopy allows the visualization of monolayer thick films and show whether island formation occurs at various levels of dosing.

  14. "Turn-on" fluorescence detection of lead ions based on accelerated leaching of gold nanoparticles on the surface of graphene.

    PubMed

    Fu, Xiuli; Lou, Tingting; Chen, Zhaopeng; Lin, Meng; Feng, Weiwei; Chen, Lingxin

    2012-02-01

    A novel platform for effective "turn-on" fluorescence sensing of lead ions (Pb(2+)) in aqueous solution was developed based on gold nanoparticle (AuNP)-functionalized graphene. The AuNP-functionalized graphene exhibited minimal background fluorescence because of the extraordinarily high quenching ability of AuNPs. Interestingly, the AuNP-functionalized graphene underwent fluorescence restoration as well as significant enhancement upon adding Pb(2+), which was attributed to the fact that Pb(2+) could accelerate the leaching rate of the AuNPs on graphene surfaces in the presence of both thiosulfate (S(2)O(3)(2-)) and 2-mercaptoethanol (2-ME). Consequently, this could be utilized as the basis for selective detection of Pb(2+). With the optimum conditions chosen, the relative fluorescence intensity showed good linearity versus logarithm concentration of Pb(2+) in the range of 50-1000 nM (R = 0.9982), and a detection limit of 10 nM. High selectivity over common coexistent metal ions was also demonstrated. The practical application had been carried out for determination of Pb(2+) in tap water and mineral water samples. The Pb(2+)-specific "turn-on" fluorescence sensor, based on Pb(2+) accelerated leaching of AuNPs on the surface of graphene, provided new opportunities for highly sensitive and selective Pb(2+) detection in aqueous media.

  15. Density functional theory in surface chemistry and catalysis

    PubMed Central

    Nørskov, Jens K.; Abild-Pedersen, Frank; Studt, Felix; Bligaard, Thomas

    2011-01-01

    Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future challenges. PMID:21220337

  16. Modulation of terrestrial ion escape flux composition /by low-altitude acceleration and charge exchange chemistry/

    NASA Technical Reports Server (NTRS)

    Moore, T. E.

    1980-01-01

    Motivated by recent observations of highly variable hot plasma composition in the magnetosphere, control of the ionospheric escape flux composition by low-altitude particle dynamics and ion chemistry has been investigated for an e(-), H(+), O(+) ionosphere. It is found that the fraction of the steady state escape flux which is O(+) can be controlled very sensitively by the occurrence of parallel or transverse ion acceleration at altitudes below the altitude where the neutral oxygen density falls rapidly below the neutral hydrogen density and the ionospheric source of O(+) tends to be rapidly converted by charge exchange to H(+). The acceleration is required both to overcome the gravitational confinement of O(+) and to violate charge exchange equilibrium so that the neutral hydrogen atmosphere appears 'optically' thin to escaping O(+). Constraints are placed on the acceleration processes, and it is shown that O(+) escape is facilitated by observed ionospheric responses to magnetic activity.

  17. Nanoporous Gold as a Neural Interface Coating: Effects of Topography, Surface Chemistry, and Feature Size

    DOE PAGES

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; ...

    2015-02-23

    We report that designing neural interfaces that maintain close physical coupling of neurons to an electrode surface remains a major challenge for both implantable and in vitro neural recording electrode arrays. Typically, low-impedance nanostructured electrode coatings rely on chemical cues from pharmaceuticals or surface-immobilized peptides to suppress glial scar tissue formation over the electrode surface (astrogliosis), which is an obstacle to reliable neuron–electrode coupling. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a promising candidate to reduce astrogliosis solely through topography by taking advantage of its tunable length scale. In the present in vitro study on np-Au’s interactionmore » with cortical neuron–glia co-cultures, we demonstrate that the nanostructure of np-Au achieves close physical coupling of neurons by maintaining a high neuron-to-astrocyte surface coverage ratio. Atomic layer deposition-based surface modification was employed to decouple the effect of morphology from surface chemistry. Additionally, length scale effects were systematically studied by controlling the characteristic feature size of np-Au through variations in the dealloying conditions. In conclusion, our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage and may enhance neuron–electrode coupling through nanostructure-mediated suppression of scar tissue formation.« less

  18. Endothelial cell behaviour on gas-plasma-treated PLA surfaces: the roles of surface chemistry and roughness.

    PubMed

    Shah, Amita; Shah, Sarita; Mani, Gopinath; Wenke, Joseph; Agrawal, Mauli

    2011-04-01

    Glow-discharge gas-plasma (GP) treatment has been shown to induce surface modifications such that cell adhesion and growth are enhanced. However, it is not known which gas used in GP treatment is optimal for endothelial cell function. Polylactic acid (PLA) films treated oxygen, argon, or nitrogen GP were characterized using contact angles, scanning electron microscopy, atomic force microscopy, optical profilometry, and x-ray photoelectron spectroscopy. All three GP treatments decreased the carbon atomic concentration and surface roughness and increased the oxygen atomic concentration. Human umbilical vein endothelial cells were cultured on the PLA films for up to 7 days. Based on proliferation and live/dead assays, surface chemistry was shown to have the greatest effect on the attachment, proliferation, and viability of these cells, while roughness did not have a significant influence. Of the different gases, endothelial cell viability, attachment and proliferation were most significantly increased on PLA surfaces treated with oxygen and argon gas plasma. Copyright © 2010 John Wiley & Sons, Ltd.

  19. Metal-composite adhesion based on diazonium chemistry.

    PubMed

    Oweis, Yara; Alageel, Omar; Kozak, Paige; Abdallah, Mohamed-Nur; Retrouvey, Jean-Marc; Cerruti, Marta; Tamimi, Faleh

    2017-11-01

    Composite resins do not adhere well to dental alloys. This weak bond can result in failure at the composite-metal interface in fixed dental prostheses and orthodontic brackets. The aim of this study was to develop a new adhesive, based on diazonium chemistry, to facilitate chemical bonding between dental alloys and composite resin. Samples of two types of dental alloys, stainless steel and cobalt chromium were primed with a diazonium layer in order to create a surface coating favorable for composite adhesion. Untreated metal samples served as controls. The surface chemical composition of the treated and untreated samples was analyzed by X-ray photoelectron spectroscopy (XPS) and the tensile strength of the bond with composite resin was measured. The diazonium adhesive was also tested for shear bond strength between stainless steel orthodontic brackets and teeth. XPS confirmed the presence of a diazonium coating on the treated metals. The coating significantly increased the tensile and shear bond strengths by three and four folds respectively between the treated alloys and composite resin. diazonium chemistry can be used to develop composite adhesives for dental alloys. Diazonium adhesion can effectively achieve a strong chemical bond between dental alloys and composite resin. This technology can be used for composite repair of fractured crowns, for crown cementation with resin based cements, and for bracket bonding. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  20. Interaction between carbon fibers and polymer sizing: Influence of fiber surface chemistry and sizing reactivity

    NASA Astrophysics Data System (ADS)

    Moosburger-Will, Judith; Bauer, Matthias; Laukmanis, Eva; Horny, Robert; Wetjen, Denise; Manske, Tamara; Schmidt-Stein, Felix; Töpker, Jochen; Horn, Siegfried

    2018-05-01

    Different aspects of the interaction of carbon fibers and epoxy-based polymer sizings are investigated, e.g. the wetting behavior, the strength of adhesion between fiber and sizing, and the thermal stability of the sizing layer. The influence of carbon fiber surface chemistry and sizing reactivity is investigated using fibers of different degree of anodic oxidation and sizings with different number of reactive epoxy groups per molecule. Wetting of the carbon fibers by the sizing dispersion is found to be specified by both, the degree of fiber activation and the sizing reactivity. In contrast, adhesion strength between fibers and sizing is dominated by the surface chemistry of the carbon fibers. Here, the number of surface oxygen groups seems to be the limiting factor. We also find that the sizing and the additional functionalities induced by anodic oxidation are removed by thermal treatment at 600 °C, leaving the carbon fiber in its original state after carbonization.

  1. Influence of surface structure and chemistry on water droplet splashing.

    PubMed

    Koch, Kerstin; Grichnik, Roland

    2016-08-06

    Water droplet splashing and aerosolization play a role in human hygiene and health systems as well as in crop culturing. Prevention or reduction of splashing can prevent transmission of diseases between animals and plants and keep technical systems such as pipe or bottling systems free of contamination. This study demonstrates to what extent the surface chemistry and structures influence the water droplet splashing behaviour. Smooth surfaces and structured replicas of Calathea zebrina (Sims) Lindl. leaves were produced. Modification of their wettability was done by coating with hydrophobizing and hydrophilizing agents. Their wetting was characterized by contact angle measurement and splashing behaviour was observed with a high-speed video camera. Hydrophobic and superhydrophilic surfaces generally showed fewer tendencies to splash than hydrophobic ones. Structuring amplified the underlying behaviour of the surface chemistries, increasing hydrophobic surfaces' tendency to splash and decreasing splash on hydrophilic surfaces by quickly transporting water off the impact point by capillary forces. The non-porous surface structures found in C. zebrina could easily be applied to technical products such as plastic foils or mats and coated with hydrophilizing agents to suppress splash in areas of increased hygiene requirements or wherever pooling of liquids is not desirable.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

  2. Ferroelectrics: A pathway to switchable surface chemistry and catalysis

    NASA Astrophysics Data System (ADS)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

    2016-08-01

    It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

  3. Colloid Surface Chemistry Critically Affects Multiple Particle Tracking Measurements of Biomaterials

    PubMed Central

    Valentine, M. T.; Perlman, Z. E.; Gardel, M. L.; Shin, J. H.; Matsudaira, P.; Mitchison, T. J.; Weitz, D. A.

    2004-01-01

    Characterization of the properties of complex biomaterials using microrheological techniques has the promise of providing fundamental insights into their biomechanical functions; however, precise interpretations of such measurements are hindered by inadequate characterization of the interactions between tracers and the networks they probe. We here show that colloid surface chemistry can profoundly affect multiple particle tracking measurements of networks of fibrin, entangled F-actin solutions, and networks of cross-linked F-actin. We present a simple protocol to render the surface of colloidal probe particles protein-resistant by grafting short amine-terminated methoxy-poly(ethylene glycol) to the surface of carboxylated microspheres. We demonstrate that these poly(ethylene glycol)-coated tracers adsorb significantly less protein than particles coated with bovine serum albumin or unmodified probe particles. We establish that varying particle surface chemistry selectively tunes the sensitivity of the particles to different physical properties of their microenvironments. Specifically, particles that are weakly bound to a heterogeneous network are sensitive to changes in network stiffness, whereas protein-resistant tracers measure changes in the viscosity of the fluid and in the network microstructure. We demonstrate experimentally that two-particle microrheology analysis significantly reduces differences arising from tracer surface chemistry, indicating that modifications of network properties near the particle do not introduce large-scale heterogeneities. Our results establish that controlling colloid-protein interactions is crucial to the successful application of multiple particle tracking techniques to reconstituted protein networks, cytoplasm, and cells. PMID:15189896

  4. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes.

    PubMed

    Nady, Norhan

    2016-04-18

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled "green surface modification". This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers-ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)-is presented.

  5. PES Surface Modification Using Green Chemistry: New Generation of Antifouling Membranes

    PubMed Central

    Nady, Norhan

    2016-01-01

    A major limitation in using membrane-based separation processes is the loss of performance due to membrane fouling. This drawback can be addressed thanks to surface modification treatments. A new and promising surface modification using green chemistry has been recently investigated. This modification is carried out at room temperature and in aqueous medium using green catalyst (enzyme) and nontoxic modifier, which can be safely labelled “green surface modification”. This modification can be considered as a nucleus of new generation of antifouling membranes and surfaces. In the current research, ferulic acid modifier and laccase bio-catalyst were used to make poly(ethersulfone) (PES) membrane less vulnerable to protein adsorption. The blank and modified PES membranes are evaluated based on e.g., their flux and protein repellence. Both the blank and the modified PES membranes (or laminated PES on silicon dioxide surface) are characterized using many techniques e.g., SEM, EDX, XPS and SPM, etc. The pure water flux of the most modified membranes was reduced by 10% on average relative to the blank membrane, and around a 94% reduction in protein adsorption was determined. In the conclusions section, a comparison between three modifiers—ferulic acid, and two other previously used modifiers (4-hydroxybenzoic acid and gallic acid)—is presented. PMID:27096873

  6. GPU Linear Algebra Libraries and GPGPU Programming for Accelerating MOPAC Semiempirical Quantum Chemistry Calculations.

    PubMed

    Maia, Julio Daniel Carvalho; Urquiza Carvalho, Gabriel Aires; Mangueira, Carlos Peixoto; Santana, Sidney Ramos; Cabral, Lucidio Anjos Formiga; Rocha, Gerd B

    2012-09-11

    In this study, we present some modifications in the semiempirical quantum chemistry MOPAC2009 code that accelerate single-point energy calculations (1SCF) of medium-size (up to 2500 atoms) molecular systems using GPU coprocessors and multithreaded shared-memory CPUs. Our modifications consisted of using a combination of highly optimized linear algebra libraries for both CPU (LAPACK and BLAS from Intel MKL) and GPU (MAGMA and CUBLAS) to hasten time-consuming parts of MOPAC such as the pseudodiagonalization, full diagonalization, and density matrix assembling. We have shown that it is possible to obtain large speedups just by using CPU serial linear algebra libraries in the MOPAC code. As a special case, we show a speedup of up to 14 times for a methanol simulation box containing 2400 atoms and 4800 basis functions, with even greater gains in performance when using multithreaded CPUs (2.1 times in relation to the single-threaded CPU code using linear algebra libraries) and GPUs (3.8 times). This degree of acceleration opens new perspectives for modeling larger structures which appear in inorganic chemistry (such as zeolites and MOFs), biochemistry (such as polysaccharides, small proteins, and DNA fragments), and materials science (such as nanotubes and fullerenes). In addition, we believe that this parallel (GPU-GPU) MOPAC code will make it feasible to use semiempirical methods in lengthy molecular simulations using both hybrid QM/MM and QM/QM potentials.

  7. Advances in understanding the surface chemistry of lignocellulosic biomass via time-of-flight secondary ion mass spectrometry

    DOE PAGES

    Tolbert, Allison K.; Ragauskas, Arthur J.

    2016-12-12

    Overcoming the natural recalcitrance of lignocellulosic biomass is necessary in order to efficiently convert biomass into biofuels or biomaterials and many times this requires some type of chemical pretreatment and/or biological treatment. While bulk chemical analysis is the traditional method of determining the impact a treatment has on biomass, the chemistry on the surface of the sample can differ from the bulk chemistry. Specifically, enzymes and microorganisms bind to the surface of the biomass and their efficiency could be greatly impacted by the chemistry of the surface. Therefore, it is important to study and understand the chemistry of the biomassmore » at the surface. Time-of- flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool that can spectrally and spatially analyze the surface chemistry of a sample. This review discusses the advances in understanding lignocellulosic biomass surface chemistry using the ToF-SIMS by addressing the instrument parameters, biomass sample preparation, and characteristic lignocellulosic ion fragmentation peaks along with their typical location in the plant cell wall. Furthermore, the use of the ToF-SIMS in detecting chemical changes due to chemical pretreatments, microbial treatments, and physical or genetic modifications is discussed along with possible future applications of the instrument in lignocellulosic biomass studies.« less

  8. Advances in understanding the surface chemistry of lignocellulosic biomass via time-of-flight secondary ion mass spectrometry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tolbert, Allison K.; Ragauskas, Arthur J.

    Overcoming the natural recalcitrance of lignocellulosic biomass is necessary in order to efficiently convert biomass into biofuels or biomaterials and many times this requires some type of chemical pretreatment and/or biological treatment. While bulk chemical analysis is the traditional method of determining the impact a treatment has on biomass, the chemistry on the surface of the sample can differ from the bulk chemistry. Specifically, enzymes and microorganisms bind to the surface of the biomass and their efficiency could be greatly impacted by the chemistry of the surface. Therefore, it is important to study and understand the chemistry of the biomassmore » at the surface. Time-of- flight secondary ion mass spectrometry (ToF-SIMS) is a powerful tool that can spectrally and spatially analyze the surface chemistry of a sample. This review discusses the advances in understanding lignocellulosic biomass surface chemistry using the ToF-SIMS by addressing the instrument parameters, biomass sample preparation, and characteristic lignocellulosic ion fragmentation peaks along with their typical location in the plant cell wall. Furthermore, the use of the ToF-SIMS in detecting chemical changes due to chemical pretreatments, microbial treatments, and physical or genetic modifications is discussed along with possible future applications of the instrument in lignocellulosic biomass studies.« less

  9. Turbulent Mixing Chemistry in Disks

    NASA Astrophysics Data System (ADS)

    Semenov, D.; Wiebe, D.

    2006-11-01

    A gas-grain chemical model with surface reaction and 1D/2D turbulent mixing is available for protoplanetary disks and molecular clouds. Current version is based on the updated UMIST'95 database with gas-grain interactions (accretion, desorption, photoevaporation, etc.) and modified rate equation approach to surface chemistry (see also abstract for the static chemistry code).

  10. The physics of water droplets on surfaces: exploring the effects of roughness and surface chemistry

    NASA Astrophysics Data System (ADS)

    Eid, K. F.; Panth, M.; Sommers, A. D.

    2018-03-01

    This paper explores the fluid property commonly called surface tension, its effect on droplet shape and contact angle, and the major influences of contact angle behaviour (i.e. surface roughness and surface chemistry). Images of water droplets placed on treated copper surfaces are used to measure the contact angles between the droplets and the surface. The surface wettability is manipulated either by growing a self-assembled monolayer on the surface to make it hydrophobic or by changing the surface roughness. The main activities in this experiment, then, are (1) preparing and studying surfaces with different surface wettability and roughness; (2) determining the shape and contact angles of water droplets on these surfaces; and (3) demonstrating the spontaneous motion of water droplets using surface tension gradients.

  11. Surface chemistry and mineralogy. [of planet Mars

    NASA Technical Reports Server (NTRS)

    Banin, A.; Clark, B. C.; Waenke, H.

    1992-01-01

    The accumulated knowledge on the chemistry and mineralogy of Martian surface materials is reviewed. Pertinent information obtained by direct analyses of the soil on Mars by the Viking Landers, by remote sensing of Mars from flyby and orbiting spacecraft, by telescopic observations from earth, and through detailed analyses of the SNC meteorites presumed to be Martian rocks are summarized and analyzed. A compositional model for Mars soil, giving selected average elemental concentrations of major and trace elements, is suggested. It is proposed that the fine surface materials on Mars are a multicomponent mixture of weathered and nonweathered minerals. Smectite clays, silicate mineraloids similar to palagonite, and scapolite are suggested as possible major candidate components among the weathered minerals.

  12. Click chemistry approach to conventional vegetable tanning process: accelerated method with improved organoleptic properties.

    PubMed

    Krishnamoorthy, Ganesan; Ramamurthy, Govindaswamy; Sadulla, Sayeed; Sastry, Thotapalli Parvathaleswara; Mandal, Asit Baran

    2014-09-01

    Click chemistry approaches are tailored to generate molecular building blocks quickly and reliably by joining small units together selectively and covalently, stably and irreversibly. The vegetable tannins such as hydrolyzable and condensed tannins are capable to produce rather stable radicals or inhibit the progress of radicals and are prone to oxidations such as photo and auto-oxidation, and their anti-oxidant nature is well known. A lot remains to be done to understand the extent of the variation of leather stability, color variation (lightening and darkening reaction of leather), and poor resistance to water uptake for prolonged periods. In the present study, we have reported click chemistry approaches to accelerated vegetable tanning processes based on periodates catalyzed formation of oxidized hydrolysable and condensed tannins for high exhaustion with improved properties. The distribution of oxidized vegetable tannin, the thermal stability such as shrinkage temperature (T s) and denaturation temperature (T d), resistance to collagenolytic activities, and organoleptic properties of tanned leather as well as the evaluations of eco-friendly characteristics were investigated. Scanning electron microscopic analysis indicates the cross section of tightness of the leather. Differential scanning calorimetric analysis shows that the T d of leather is more than that of vegetable tanned or equal to aldehyde tanned one. The leathers exhibited fullness, softness, good color, and general appearance when compared to non-oxidized vegetable tannin. The developed process benefits from significant reduction in total solids and better biodegradability in the effluent, compared to non-oxidized vegetable tannins.

  13. Advances on Aryldiazonium Salt Chemistry Based Interfacial Fabrication for Sensing Applications.

    PubMed

    Cao, Chaomin; Zhang, Yin; Jiang, Cheng; Qi, Meng; Liu, Guozhen

    2017-02-15

    Aryldiazonium salts as coupling agents for surface chemistry have evidenced their wide applications for the development of sensors. Combined with advances in nanomaterials, current trends in sensor science and a variety of particular advantages of aryldiazonium salt chemistry in sensing have driven the aryldiazonium salt-based sensing strategies to grow at an astonishing pace. This review focuses on the advances in the use of aryldiazonium salts for modifying interfaces in sensors and biosensors during the past decade. It will first summarize the current methods for modification of interfaces with aryldiazonium salts, and then discuss the sensing applications of aryldiazonium salts modified on different transducers (bulky solid electrodes, nanomaterials modified bulky solid electrodes, and nanoparticles). Finally, the challenges and perspectives that aryldiazonium salt chemistry is facing in sensing applications are critically discussed.

  14. The role of surface chemistry in the cytotoxicity profile of graphene.

    PubMed

    Majeed, Waqar; Bourdo, Shawn; Petibone, Dayton M; Saini, Viney; Vang, Kieng Bao; Nima, Zeid A; Alghazali, Karrer M; Darrigues, Emilie; Ghosh, Anindya; Watanabe, Fumiya; Casciano, Daniel; Ali, Syed F; Biris, Alexandru S

    2017-04-01

    Graphene and its derivative, because of their unique physical, electrical and chemical properties, are an important class of nanomaterials being proposed as foundational materials in nanomedicine as well as for a variety of industrial applications. A major limitation for graphene, when used in biomedical applications, is its poor solubility due to its rather hydrophobic nature. Therefore, chemical functionalities are commonly introduced to alter both its surface chemistry and biochemical activity. Here, we show that surface chemistry plays a major role in the toxicological profile of the graphene structures. To demonstrate this, we chemically increased the oxidation level of the pristine graphene and compared the corresponding toxicological effects along with those for the graphene oxide. X-ray photoelectron spectroscopy revealed that pristine graphene had the lowest amount of surface oxygen, while graphene oxide had the highest at 2.5% and 31%, respectively. Low and high oxygen functionalized graphene samples were found to have 6.6% and 24% surface oxygen, respectively. Our results showed a dose-dependent trend in the cytotoxicity profile, where pristine graphene was the most cytotoxic, with decreasing toxicity observed with increasing oxygen content. Increased surface oxygen also played a role in nanomaterial dispersion in water or cell culture medium over longer periods. It is likely that higher dispersity might result in graphene entering into cells as individual flakes ~1 nm thick rather than as more cytotoxic aggregates. In conclusion, changes in graphene's surface chemistry resulted in altered solubility and toxicity, suggesting that a generalized toxicity profile would be rather misleading. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  15. Adsorption of Dyes in Studying the Surface Chemistry of Ultradispersed Diamond

    NASA Astrophysics Data System (ADS)

    Khokhlova, T. D.; Yunusova, G. R.; Lanin, S. N.

    2018-05-01

    The effect the surface chemistry of ultradispersed diamond (UDD) has on the adsorption of watersoluble dyes is considered. A comparison is made to adsorption on graphitized thermal carbon black (GTCB), which has a homogeneous and nonporous surface. The adsorption isotherms of dyes and the dependence of the adsorption on the pH of solutions are measured. It is found that UDD adsorbs acid (anionic) dyes—acid orange (AO) and acid anthraquinone blue (AAB)—but barely adsorbs a basic (cationic) dye, methylene blue (MB), because of the predominance of positively charged basic groups on the surface of UDD. The maximum adsorption of AO is much lower on UDD than on GTCB, while the maximum adsorption of AAB is similar for both surfaces. The adsorption of AO on UDD depends strongly on the pH of the solution, while the adsorption of AAB is independent of this parameter. It is suggested that the adsorption of AAB is determined not only by ionic and hydrophobic interactions but also by coordination interactions with impurity metal ions on a UDD surface. It is concluded that the adsorption of dyes characterizes the chemistry of a UDD surface with high sensitivity.

  16. Block copolymer-templated chemistry on Si, Ge, InP, and GaAs surfaces.

    PubMed

    Aizawa, Masato; Buriak, Jillian M

    2005-06-29

    Patterning of semiconductor surfaces is an area of intense interest, not only for technological applications, such as molecular electronics, sensing, cellular recognition, and others, but also for fundamental understanding of surface reactivity, general control over surface properties, and development of new surface reactivity. In this communication, we describe the use of self-assembling block copolymers to direct semiconductor surface chemistry in a spatially defined manner, on the nanoscale. The proof-of-principle class of reactions evaluated here is galvanic displacement, in which a metal ion, M+, is reduced to M0 by the semiconductor, including Si, Ge, InP, and GaAs. The block copolymer chosen has a polypyridine block which binds to the metal ions and brings them into close proximity with the surface, at which point they undergo reaction; the pattern of resulting surface chemistry, therefore, mirrors the nanoscale structure of the parent block copolymer. This chemistry has the added advantage of forming metal nanostructures that result in an alloy or intermetallic at the interface, leading to strongly bound metal nanoparticles that may have interesting electronic properties. This approach has been shown to be very general, functioning on a variety of semiconductor substrates for both silver and gold deposition, and is being extended to organic and inorganic reactions on a variety of conducting, semiconducting, and insulating substrates.

  17. Regulating Biocompatibility of Carbon Spheres via Defined Nanoscale Chemistry and a Careful Selection of Surface Functionalities

    NASA Astrophysics Data System (ADS)

    Misra, Santosh K.; Chang, Huei-Huei; Mukherjee, Prabuddha; Tiwari, Saumya; Ohoka, Ayako; Pan, Dipanjan

    2015-10-01

    A plethora of nanoarchitectures have been evaluated preclincially for applications in early detection and treatment of diseases at molecular and cellular levels resulted in limited success of their clinical translation. It is important to identify the factors that directly or indirectly affect their use in human. We bring a fundamental understanding of how to adjust the biocompatibility of carbon based spherical nanoparticles (CNPs) through defined chemistry and a vigilant choice of surface functionalities. CNPs of various size are designed by tweaking size (2-250 nm), surface chemistries (positive, or negatively charged), molecular chemistries (linear, dendritic, hyperbranched) and the molecular weight of the coating agents (MW 400-20 kDa). A combination of in vitro assays as tools were performed to determine the critical parameters that may trigger toxicity. Results indicated that hydrodynamic sizes are potentially not a risk factor for triggering cellular and systemic toxicity, whereas the presence of a highly positive surface charge and increasing molecular weight enhance the chance of inducing complement activation. Bare and carboxyl-terminated CNPs did present some toxicity at the cellular level which, however, is not comparable to those caused by positively charged CNPs. Similarly, negatively charged CNPs with hydroxyl and carboxylic functionalities did not cause any hemolysis.

  18. Friction and surface chemistry of some ferrous-base metallic glasses

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    The friction properties of some ferrous-base metallic glasses were measured both in argon and in vacuum to a temperature of 350 C. The alloy surfaces were also analyzed with X-ray photoelectron spectroscopy to identify the compounds and elements present on the surface. The results of the investigation indicate that even when the surfaces of the amorphous alloys, or metallic glasses, are atomically clean, bulk contaminants such as boric oxide and silicon dioxide diffuse to the surfaces. Friction measurements in both argon and vacuum indicate that the alloys exhibit higher coefficients of friction in the crystalline state than they do in the amorphous state.

  19. Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

    NASA Technical Reports Server (NTRS)

    Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

    2009-01-01

    Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

  20. The Effect of Solution Chemistry on Nucleation of Nesquehonite

    NASA Astrophysics Data System (ADS)

    Zhao, L.; Zhu, C.; Wang, Z.

    2016-12-01

    The interfaces between minerals and aqueous solutions are key to important Earth surface processes, including chemical weathering, mineral dissolution/precipitation, and pollutant absorption/release. Mineral surface properties, such as the surface structure and the surface energy, determine the outcomes of many geochemical reactions. Several factors could affect surface energy, but the effect of solution chemistry, particularly the solution stoichiometry, on the surface energy and nucleation process is poorly understood. The goal of this study is to understand the effect of solution chemistry on the nucleation of nesquehonite. Nesquehonite nucleation experiments were conducted in aqueous solutions having similar Mg2+/ CO32- activity ratios, but different saturation states and solution pH. The experimental results show that induction-time estimates from our precipitation experiments with similar Mg2+/CO32- activity ratios are consistent with classical nucleation theory (CNT), while the surface energy derived from CNT varies with Mg2+/CO32- activity ratios. Our observations can be explained by the different absorption behaviors of Mg2+ and CO32- and and/or reduced Gibbs free energies through better screening of the electric double layer. A surface energy model involving solution composition is developed that combines surface complexation with electrostatic models. The new model takes into account how surface charge may affect surface energy. It implies that the highest surface energy may occur around the point of zero charge (p.z.c), where the nucleation is fastest (or conversely, where the induction time is shortest) under low saturation states, but not under high saturation states. An accelerated attachment rate of monomers at the p.z.c. is consistent with high surface energy, since it represents higher reactivity of surface ions and less work needed to break the solvated water molecules. This study provides deeper insights into mechanisms of nesquehonite

  1. Surface chemistry of gold nanorods: origin of cell membrane damage and cytotoxicity

    NASA Astrophysics Data System (ADS)

    Wang, Liming; Jiang, Xiumei; Ji, Yinglu; Bai, Ru; Zhao, Yuliang; Wu, Xiaochun; Chen, Chunying

    2013-08-01

    We investigated how surface chemistry influences the interaction between gold nanorods (AuNRs) and cell membranes and the subsequent cytotoxicity arising from them in a serum-free cell culture system. Our results showed that the AuNRs coated with cetyl trimethylammonium bromide (CTAB) molecules can generate defects in the cell membrane and induce cell death, mainly due to the unique bilayer structure of CTAB molecules on the surface of the rods rather than their charge. Compared to CTAB-capped nanorods, positively charged polyelectrolyte-coated, i.e. poly(diallyldimethyl ammonium chloride) (PDDAC), AuNRs show improved biocompatibility towards cells. Thus, the present results indicate that the nature of surface molecules, especially their packing structures on the surface of AuNRs rather than surface charge, play a more crucial role in determining cytotoxicity. These findings about interfacial interactions could also explain the effects of internalized AuNRs on the structures or functions of organelles. This study will help understanding of the toxic nature of AuNRs and guide rational design of the surface chemistry of AuNRs for good biocompatibility in pharmaceutical therapy.

  2. The physics and chemistry of graphene-on-surfaces.

    PubMed

    Zhao, Guoke; Li, Xinming; Huang, Meirong; Zhen, Zhen; Zhong, Yujia; Chen, Qiao; Zhao, Xuanliang; He, Yijia; Hu, Ruirui; Yang, Tingting; Zhang, Rujing; Li, Changli; Kong, Jing; Xu, Jian-Bin; Ruoff, Rodney S; Zhu, Hongwei

    2017-07-31

    Graphene has demonstrated great potential in next-generation electronics due to its unique two-dimensional structure and properties including a zero-gap band structure, high electron mobility, and high electrical and thermal conductivity. The integration of atom-thick graphene into a device always involves its interaction with a supporting substrate by van der Waals forces and other intermolecular forces or even covalent bonding, and this is critical to its real applications. Graphene films on different surfaces are expected to exhibit significant differences in their properties, which lead to changes in their morphology, electronic structure, surface chemistry/physics, and surface/interface states. Therefore, a thorough understanding of the surface/interface properties is of great importance. In this review, we describe the major "graphene-on-surface" structures and examine the roles of their properties and related phenomena in governing the overall performance for specific applications including optoelectronics, surface catalysis, anti-friction and superlubricity, and coatings and composites. Finally, perspectives on the opportunities and challenges of graphene-on-surface systems are discussed.

  3. Bacterial response to different surface chemistries fabricated by plasma polymerization on electrospun nanofibers.

    PubMed

    Abrigo, Martina; Kingshott, Peter; McArthur, Sally L

    2015-12-06

    Control over bacterial attachment and proliferation onto nanofibrous materials constitutes a major challenge for a variety of applications, including filtration membranes, protective clothing, wound dressings, and tissue engineering scaffolds. To develop effective devices, the interactions that occur between bacteria and nanofibers with different morphological and physicochemical properties need to be investigated. This paper explores the influence of fiber surface chemistry on bacterial behavior. Different chemical functionalities were generated on the surface of electrospun polystyrene nanofibers through plasma polymerization of four monomers (acrylic acid, allylamine, 1,7-octadiene, and 1,8-cineole). The interactions of Escherichia coli with the surface modified fibers were investigated through a combination of scanning electron microscopy and confocal laser scanning microscopy. Fiber wettability, surface charge, and chemistry were found to affect the ability of bacterial cells to attach and proliferate throughout the nanofiber meshes. The highest proportion of viable cells attachment occurred on the hydrophilic amine rich coating, followed by the hydrophobic octadiene. The acrylic acid coating rich in carboxyl groups showed a significantly lower attraction of bacterial cells. The 1,8-cineole retained the antibacterial activity of the monomer, resulting with a high proportion of dead isolated cells attached onto the fibers. Results showed that the surface chemistry properties of nanofibrous membranes can be strategically tuned to control bacterial behavior.

  4. Accelerator-based Neutrino Physics at Fermilab

    NASA Astrophysics Data System (ADS)

    Dukes, Edmond

    2008-10-01

    The discovery of neutrino mass has excited great interest in elucidating the properties of neutrinos and their role in nature. Experiments around the world take advantage of solar, atmospheric, reactor, and accelerator sources of neutrinos. Accelerator-based sources are particularly convenient since their parameters can be tuned to optimize the measurement in question. At Fermilab an extensive neutrino program includes the MiniBooNE, SciBooNE, and MINOS experiments. Two major new experiments, MINERvA and NOvA, are being constructed, plans for a high-intensity neutrino source to DUSEL are underway, and an R&D effort towards a large liquid argon detector is being pursued. The NOvA experiment intends to search for electron neutrino appearance using a massive surface detector 811 km from Fermilab. In addition to measuring the last unknown mixing angle, theta(13), NOvA has the possibility of seeing matter-antimatter asymmetries in neutrinos and resolving the ordering of the neutrino mass states.

  5. Final Report: Rational Design of Anode Surface Chemistry in Microbial Fuel Cells for Improved Exoelectrogen Attachment and Electron Transfer

    DTIC Science & Technology

    2015-12-21

    SECURITY CLASSIFICATION OF: The overall goal of this project is to determine how electrode surface chemistry can be rationally designed to decrease...2015 Approved for Public Release; Distribution Unlimited Final Report: Rational Design of Anode Surface Chemistry in Microbial Fuel Cells for...ABSTRACT Final Report: Rational Design of Anode Surface Chemistry in Microbial Fuel Cells for Improved Exoelectrogen Attachment and Electron Transfer

  6. Fabrication of a platform to isolate the influences of surface nanotopography from chemistry on bacterial attachment and growth.

    PubMed

    Pegalajar-Jurado, Adoracion; Easton, Christopher D; Crawford, Russell J; McArthur, Sally L

    2015-03-26

    Billions of dollars are spent annually worldwide to combat the adverse effects of bacterial attachment and biofilm formation in industries as varied as maritime, food, and health. While advances in the fabrication of antifouling surfaces have been reported recently, a number of the essential aspects responsible for the formation of biofilms remain unresolved, including the important initial stages of bacterial attachment to a substrate surface. The reduction of bacterial attachment to surfaces is a key concept in the prevention or minimization of biofilm formation. The chemical and physical characteristics of both the substrate and bacteria are important in understanding the attachment process, but substrate modification is likely the most practical route to enable the extent of bacterial attachment taking place to be effectively controlled. The microtopography and chemistry of the surface are known to influence bacterial attachment. The role of surface chemistry versus nanotopography and their interplay, however, remain unclear. Most methods used for imparting nanotopographical patterns onto a surface also induce changes in the surface chemistry and vice versa. In this study, the authors combine colloidal lithography and plasma polymerization to fabricate homogeneous, reproducible, and periodic nanotopographies with a controllable surface chemistry. The attachment of Escherichia coli bacteria onto carboxyl (plasma polymerized acrylic acid, ppAAc) and hydrocarbon (plasma polymerized octadiene, ppOct) rich plasma polymer films on either flat or colloidal array surfaces revealed that the surface chemistry plays a critical role in bacterial attachment, whereas the effect of surface nanotopography on the bacterial attachment appears to be more difficult to define. This platform represents a promising approach to allow a greater understanding of the role that surface chemistry and nanotopography play on bacterial attachment and the subsequent biofouling of the surface.

  7. The Impact of Nanoparticle Surface Chemistry on Biological Systems

    NASA Astrophysics Data System (ADS)

    Thorn, Angie Sue Morris

    because they are easy to synthesize and their properties (such as size, porosity and surface chemistry) can be fine-tuned. Silica nanoparticles can be found in thousands of commercially available products such as toothpastes, cosmetics and detergents and are currently being developed for biomedical applications such as drug delivery and biomedical imaging. Our findings herein indicate that the surface chemistry of silica nanoparticles can have an effect on lung inflammation after exposure. Specifically, amine-modified silica NPs are considered to be less toxic compared to bare silica nanoparticles. Together, these studies provide insight into the role that material properties have on toxicity and allow for a better understanding of their impact on human and environmental health. The final aim of this thesis was to develop surface-modified nanoparticles for drug delivery applications. For this, biodegradable, polymeric NPs were used due to their inert nature and biocompatibility. Furthermore, polymeric NPs are excellent for loading drugs and using them as drug delivery vehicles. In this work, poly (lactic-co-glycolic acid) (PLGA) NPs were loaded with a therapeutic peptide. These NPs were then coated with chitosan (a mucoadhesive polymer) for the treatment of allergic asthma or coated with a small cationic mitochondrial targeting agent for the treatment of ischemia/reperfusion injury. Taken as a whole, this thesis sheds light on the impact of NPs on human health. First by providing useful toxological data for CuO and silica NPs as well as highlighting the potential of surface-modified polymeric NPs to be used in drug delivery-based applications.

  8. Electron acceleration and high harmonic generation by relativistic surface plasmons

    NASA Astrophysics Data System (ADS)

    Cantono, Giada; Luca Fedeli Team; Andrea Sgattoni Team; Andrea Macchi Team; Tiberio Ceccotti Team

    2016-10-01

    Intense, short laser pulses with ultra-high contrast allow resonant surface plasmons (SPs) excitation on solid wavelength-scale grating targets, opening the way to the extension of Plasmonics in the relativistic regime and the manipulation of intense electromagnetic fields to develop new short, energetic, laser-synchronized radiation sources. Recent theoretical and experimental studies have explored the role of SP excitation in increasing the laser-target coupling and enhancing ion acceleration, high-order harmonic generation and surface electron acceleration. Here we present our results on SP driven electron acceleration from grating targets at ultra-high laser intensities (I = 5 ×1019 W/cm2, τ = 25 fs). When the resonant condition for SP excitation is fulfilled, electrons are emitted in a narrow cone along the target surface, with a total charge of about 100 pC and energy spectra peaked around 5 MeV. Distinguishing features of the resonant process were investigated by varying the incidence angle, grating type and with the support of 3D PIC simulations, which closely reproduced the experimental data. Open challenges and further measurements on high-order harmonic generation in presence of a relativistic SP will also be discussed.

  9. Effects of soot-induced snow albedo change on snowpack and hydrological cycle in western U.S. based on WRF chemistry and regional climate simulations

    NASA Astrophysics Data System (ADS)

    Qian, Y.; Gustafson, W. I.; Leung, R.; Ghan, S. J.

    2008-12-01

    Radiative forcing induced by soot on snow is an important anthropogenic forcing affecting the global climate. In this study we simulated the deposition of soot aerosol on snow and the resulting impact on snowpack and the hydrological cycle in the western United States. A yearlong simulation was performed using the chemistry version of the Weather Research and Forecasting model (WRF-Chem) to determine the soot deposition, followed by three simulations using WRF in meteorology-only mode, with and without the soot-induced snow albedo perturbations. The chemistry simulation shows large spatial variability in soot deposition that reflects the localized emissions and the influence of the complex terrain. The soot-induced snow albedo perturbations increase the surface net solar radiation flux during late winter to early spring, increase the surface air temperature, and reduce the snow accumulation and spring snowmelt. These effects are stronger over the central Rockies and southern Alberta, where soot deposition and snowpack overlap the most. The indirect forcing of soot accelerates snowmelt and alters stream flows, including a trend toward earlier melt dates in the western United States. The soot-induced albedo reduction initiates a positive feedback process whereby dirty snow absorbs more solar radiation, heating the surface and warming the air. This warming causes reduced snow depth and fraction, which further reduces the regional surface albedo for the snow covered regions. For a doubled snow albedo perturbation, the change to surface energy and temperature is around 50-80%, however, snowpack reduction is nonlinearly accelerated.

  10. Nanoporous Anodic Alumina Platforms: Engineered Surface Chemistry and Structure for Optical Sensing Applications

    PubMed Central

    Kumeria, Tushar; Santos, Abel; Losic, Dusan

    2014-01-01

    Electrochemical anodization of pure aluminum enables the growth of highly ordered nanoporous anodic alumina (NAA) structures. This has made NAA one of the most popular nanomaterials with applications including molecular separation, catalysis, photonics, optoelectronics, sensing, drug delivery, and template synthesis. Over the past decades, the ability to engineer the structure and surface chemistry of NAA and its optical properties has led to the establishment of distinctive photonic structures that can be explored for developing low-cost, portable, rapid-response and highly sensitive sensing devices in combination with surface plasmon resonance (SPR) and reflective interference spectroscopy (RIfS) techniques. This review article highlights the recent advances on fabrication, surface modification and structural engineering of NAA and its application and performance as a platform for SPR- and RIfS-based sensing and biosensing devices. PMID:25004150

  11. Desorption of 1,3,5-Trichlorobenzene from Multi-Walled Carbon Nanotubes: Impact of Solution Chemistry and Surface Chemistry

    PubMed Central

    Ma, Xingmao; Uddin, Sheikh

    2013-01-01

    The strong affinity of carbon nanotubes (CNTs) to environmental contaminants has raised serious concern that CNTs may function as a carrier of environmental pollutants and lead to contamination in places where the environmental pollutants are not expected. However, this concern will not be realized until the contaminants are desorbed from CNTs. It is well recognized that the desorption of environmental pollutants from pre-laden CNTs varies with the environmental conditions, such as the solution pH and ionic strength. However, comprehensive investigation on the influence of solution chemistry on the desorption process has not been carried out, even though numerous investigations have been conducted to investigate the impact of solution chemistry on the adsorption of environmental pollutants on CNTs. The main objective of this study was to determine the influence of solution chemistry (e.g., pH, ionic strength) and surface functionalization on the desorption of preloaded 1,3,5-trichlorobenzene (1,3,5-TCB) from multi-walled carbon nanotubes (MWNTs). The results suggested that higher pH, ionic strength and natural organic matter in solution generally led to higher desorption of 1,3,5-TCB from MWNTs. However, the extent of change varied at different values of the tested parameters (e.g., pH < 7 vs. pH > 7). In addition, the impact of these parameters varied with MWNTs possessing different surface functional groups, suggesting that surface functionalization could considerably alter the environmental behaviors and impact of MWNTs. PMID:28348336

  12. The contribution of inflammasome components on macrophage response to surface nanotopography and chemistry

    NASA Astrophysics Data System (ADS)

    Christo, Susan; Bachhuka, Akash; Diener, Kerrilyn R.; Vasilev, Krasimir; Hayball, John D.

    2016-05-01

    Implantable devices have become an established part of medical practice. However, often a negative inflammatory host response can impede the integration and functionality of the device. In this paper, we interrogate the role of surface nanotopography and chemistry on the potential molecular role of the inflammasome in controlling macrophage responses. To achieve this goal we engineered model substrata having precisely controlled nanotopography of predetermined height and tailored outermost surface chemistry. Bone marrow derived macrophages (BMDM) were harvested from genetically engineered mice deficient in the inflammasome components ASC, NLRP3 and AIM2. These cells were then cultured on these nanoengineered substrata and assessed for their capacity to attach and express pro-inflammatory cytokines. Our data provide evidence that the inflammasome components ASC, NLRP3 and AIM2 play a role in regulating macrophage adhesion and activation in response to surface nanotopography and chemistry. The findings of this paper are important for understanding the inflammatory consequences caused by biomaterials and pave the way to the rational design of future implantable devices having controlled and predictable inflammatory outcomes.

  13. Surface and interfacial chemistry of high-k dielectric and interconnect materials on silicon

    NASA Astrophysics Data System (ADS)

    Kirsch, Paul Daniel

    Surfaces and interfaces play a critical role in the manufacture and function of silicon based integrated circuits. It is therefore reasonable to study the chemistries at these surfaces and interfaces to improve existing processes and to develop new ones. Model barium strontium titanate high-k dielectric systems have been deposited on ultrathin silicon oxynitride in ultrahigh vacuum. The resulting nanostructures are characterized with secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). An interfacial reaction between Ba and Sr atoms and SiOxNy was found to create silicates, BaSixOy or SrSi xOy. Inclusion of N in the interfacial oxide decreased silicate formation in both Ba and Sr systems. Furthermore, inclusion of N in the interfacial oxide decreased the penetration of Ba and Sr containing species, such as silicides and silicates. Sputter deposited HfO2 was studied on nitrided and unnitrided Si(100) surfaces. XPS and SIMS were used to verify the presence of interfacial HfSixOy and estimate its relative amount on both nitrided and unnitrided samples. More HfSixOy formed without the SiNx interfacial layer. These interfacial chemistry results are then used to explain the electrical measurements obtained from metal oxide semiconductor (MOS) capacitors. MOS capacitors with interfacial SiNx exhibit reduced leakage current and increased capacitance. Lastly, surface science techniques were used to develop a processing technique for reducing thin films of copper (II) and copper (I) oxide to copper. Deuterium atoms (D*) and methyl radicals (CH3*) were shown to reduce Cu 2+ and/or Cu1+ to Cu0 within 30 min at a surface temperature of 400 K under a flux of 1 x 1015 atoms/cm2s. Temperature programmed desorption experiments suggest that oxygen leaves the surface as D2O and CO2 for the D* and CH3* treated surfaces, respectively.

  14. Surface modification of model hydrogel contact lenses with hyaluronic acid via thiol-ene "click" chemistry for enhancing surface characteristics.

    PubMed

    Korogiannaki, Myrto; Zhang, Jianfeng; Sheardown, Heather

    2017-10-01

    Discontinuation of contact lens wear as a result of ocular dryness and discomfort is extremely common; as many as 26% of contact lens wearers discontinue use within the first year. While patients are generally satisfied with conventional hydrogel lenses, improving on-eye comfort continues to remain a goal. Surface modification with a biomimetic, ocular friendly hydrophilic layer of a wetting agent is hypothesized to improve the interfacial interactions of the contact lens with the ocular surface. In this work, the synthesis and characterization of poly(2-hydroxyethyl methacrylate) surfaces grafted with a hydrophilic layer of hyaluronic acid are described. The immobilization reaction involved the covalent attachment of thiolated hyaluronic acid (20 kDa) on acrylated poly(2-hydroxyethyl methacrylate) via nucleophile-initiated Michael addition thiol-ene "click" chemistry. The surface chemistry of the modified surfaces was analyzed by Fourier transform infrared spectroscopy-attenuated total reflectance and X-ray photoelectron spectroscopy. The appearance of N (1s) and S (2p) peaks on the low resolution X-ray photoelectron spectroscopy spectra confirmed successful immobilization of hyaluronic acid. Grafting hyaluronic acid to the poly(2-hydroxyethyl methacrylate) surfaces decreased the contact angle, the dehydration rate, and the amount of nonspecific sorption of lysozyme and albumin in comparison to pristine hydrogel materials, suggesting the development of more wettable surfaces with improved water-retentive and antifouling properties, while maintaining optical transparency (>92%). In vitro testing also showed excellent viability of human corneal epithelial cells with the hyaluronic acid-grafted poly(2-hydroxyethyl methacrylate) surfaces. Hence, surface modification with hyaluronic acid via thiol-ene "click" chemistry could be useful in improving contact lens surface properties, potentially alleviating symptoms of contact lens related dryness and discomfort during

  15. Global transcriptomic analysis of model human cell lines exposed to surface-modified gold nanoparticles: the effect of surface chemistry

    NASA Astrophysics Data System (ADS)

    Grzincic, E. M.; Yang, J. A.; Drnevich, J.; Falagan-Lotsch, P.; Murphy, C. J.

    2015-01-01

    Gold nanoparticles (Au NPs) are attractive for biomedical applications not only for their remarkable physical properties, but also for the ease of which their surface chemistry can be manipulated. Many applications involve functionalization of the Au NP surface in order to improve biocompatibility, attach targeting ligands or carry drugs. However, changes in cells exposed to Au NPs of different surface chemistries have been observed, and little is known about how Au NPs and their surface coatings may impact cellular gene expression. The gene expression of two model human cell lines, human dermal fibroblasts (HDF) and prostate cancer cells (PC3) was interrogated by microarray analysis of over 14 000 human genes. The cell lines were exposed to four differently functionalized Au NPs: citrate, poly(allylamine hydrochloride) (PAH), and lipid coatings combined with alkanethiols or PAH. Gene functional annotation categories and weighted gene correlation network analysis were used in order to connect gene expression changes to common cellular functions and to elucidate expression patterns between Au NP samples. Coated Au NPs affect genes implicated in proliferation, angiogenesis, and metabolism in HDF cells, and inflammation, angiogenesis, proliferation apoptosis regulation, survival and invasion in PC3 cells. Subtle changes in surface chemistry, such as the initial net charge, lability of the ligand, and underlying layers greatly influence the degree of expression change and the type of cellular pathway affected.Gold nanoparticles (Au NPs) are attractive for biomedical applications not only for their remarkable physical properties, but also for the ease of which their surface chemistry can be manipulated. Many applications involve functionalization of the Au NP surface in order to improve biocompatibility, attach targeting ligands or carry drugs. However, changes in cells exposed to Au NPs of different surface chemistries have been observed, and little is known about how

  16. Clathrin to Lipid Raft-Endocytosis via Controlled Surface Chemistry and Efficient Perinuclear Targeting of Nanoparticle.

    PubMed

    Chakraborty, Atanu; Jana, Nikhil R

    2015-09-17

    Nanoparticle interacts with live cells depending on their surface chemistry, enters into cell via endocytosis, and is commonly trafficked to an endosome/lysozome that restricts subcellular targeting options. Here we show that nanoparticle surface chemistry can be tuned to alter their cell uptake mechanism and subcellular trafficking. Quantum dot based nanoprobes of 20-30 nm hydrodynamic diameters have been synthesized with tunable surface charge (between +15 mV to -25 mV) and lipophilicity to influence their cellular uptake processes and subcellular trafficking. It is observed that cationic nanoprobe electrostatically interacts with cell membrane and enters into cell via clathrin-mediated endocytosis. At lower surface charge (between +10 mV to -10 mV), the electrostatic interaction with cell membrane becomes weaker, and additional lipid raft endocytosis is initiated. If a lipophilic functional group is introduced on a weakly anionic nanoparticle surface, the uptake mechanism shifts to predominant lipid raft-mediated endocytosis. In particular, the zwitterionic-lipophilic nanoprobe has the unique advantage as it weakly interacts with anionic cell membrane, migrates toward lipid rafts for interaction through lipophilic functional group, and induces lipid raft-mediated endocytosis. While predominate or partial clathrin-mediated entry traffics most of the nanoprobes to lysozome, predominate lipid raft-mediated entry traffics them to perinuclear region, particularly to the Golgi apparatus. This finding would guide in designing appropriate nanoprobe for subcellular targeting and delivery.

  17. Atomic scale characterization and surface chemistry of metal modified titanate nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    Kukovecz, Ákos; Kordás, Krisztián; Kiss, János; Kónya, Zoltán

    2016-10-01

    Titanates are salts of polytitanic acid that can be synthesized as nanostructures in a great variety concerning crystallinity, morphology, size, metal content and surface chemistry. Titanate nanotubes (open-ended hollow cylinders measuring up to 200 nm in length and 15 nm in outer diameter) and nanowires (solid, elongated rectangular blocks with length up to 1500 nm and 30-60 nm diameter) are the most widespread representatives of the titanate nanomaterial family. This review covers the properties and applications of these two materials from the surface science point of view. Dielectric, vibrational, electron and X-ray spectroscopic results are comprehensively discussed first, then surface modification methods including covalent functionalization, ion exchange and metal loading are covered. The versatile surface chemistry of one-dimensional titanates renders them excellent candidates for heterogeneous catalytic, photocatalytic, photovoltaic and energy storage applications, therefore, these fields are also reviewed.

  18. Surface topography and chemistry shape cellular behavior on wide band-gap semiconductors.

    PubMed

    Bain, Lauren E; Collazo, Ramon; Hsu, Shu-Han; Latham, Nicole Pfiester; Manfra, Michael J; Ivanisevic, Albena

    2014-06-01

    The chemical stability and electrical properties of gallium nitride make it a promising material for the development of biocompatible electronics, a range of devices including biosensors as well as interfaces for probing and controlling cellular growth and signaling. To improve the interface formed between the probe material and the cell or biosystem, surface topography and chemistry can be applied to modify the ways in which the device interacts with its environment. PC12 cells are cultured on as-grown planar, unidirectionally polished, etched nanoporous and nanowire GaN surfaces with and without a physisorbed peptide sequence that promotes cell adhesion. While cells demonstrate preferential adhesion to roughened surfaces over as-grown flat surfaces, the topography of that roughness also influences the morphology of cellular adhesion and differentiation in neurotypic cells. Addition of the peptide sequence generally contributes further to cellular adhesion and promotes development of stereotypic long, thin neurite outgrowths over alternate morphologies. The dependence of cell behavior on both the topographic morphology and surface chemistry is thus demonstrated, providing further evidence for the importance of surface modification for modulating bio-inorganic interfaces. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  19. Problem-based learning on quantitative analytical chemistry course

    NASA Astrophysics Data System (ADS)

    Fitri, Noor

    2017-12-01

    This research applies problem-based learning method on chemical quantitative analytical chemistry, so called as "Analytical Chemistry II" course, especially related to essential oil analysis. The learning outcomes of this course include aspects of understanding of lectures, the skills of applying course materials, and the ability to identify, formulate and solve chemical analysis problems. The role of study groups is quite important in improving students' learning ability and in completing independent tasks and group tasks. Thus, students are not only aware of the basic concepts of Analytical Chemistry II, but also able to understand and apply analytical concepts that have been studied to solve given analytical chemistry problems, and have the attitude and ability to work together to solve the problems. Based on the learning outcome, it can be concluded that the problem-based learning method in Analytical Chemistry II course has been proven to improve students' knowledge, skill, ability and attitude. Students are not only skilled at solving problems in analytical chemistry especially in essential oil analysis in accordance with local genius of Chemistry Department, Universitas Islam Indonesia, but also have skilled work with computer program and able to understand material and problem in English.

  20. Surface chemistry of Ti6Al4V components fabricated using selective laser melting for biomedical applications.

    PubMed

    Vaithilingam, Jayasheelan; Prina, Elisabetta; Goodridge, Ruth D; Hague, Richard J M; Edmondson, Steve; Rose, Felicity R A J; Christie, Steven D R

    2016-10-01

    Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM-AF surface was observed to be porous with an average surface roughness (Ra) of 17.6±3.7μm. The surface chemistry of the SLM-AF was significantly different to the FGD-MP surface with respect to elemental distribution and their existence on the outermost surface. Sintered particles on the SLM-AF surface were observed to affect depth profiling of the sample due to a shadowing effect during argon ion sputtering. Surface heterogeneity was observed for all three surfaces; however, vanadium was witnessed only on the mechanically polished (SLM-MP and FGD-MP) surfaces. The direct and indirect 3T3 cell cytotoxicity studies revealed that the cells were viable on the SLM fabricated Ti6Al4V parts. The varied surface chemistry of the SLM-AF and SLM-MP did not influence the cell behaviour. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  1. High capacity Li-ion battery anodes: Impact of crystallite size, surface chemistry and PEG-coating

    DOE PAGES

    Minnici, Krysten; Kwon, Yo Han; Huie, Matthew M.; ...

    2017-12-06

    Battery electrodes are complex mesoscale systems comprised of an active material, conductive agent, current collector, and polymeric binder. Previous work showed that introduction of poly [3-(potassium-4-butanoate) thiophene] (PPBT) as a binder component coupled with a polyethylene glycol (PEG) surface coating on magnetite (Fe 3O 4) nanoparticles enhanced electron and ion transport in the high capacity anode system. Here, the impact of Fe 3O 4 crystallite size (10 nm vs. 20 nm) and surface chemistry were explored to evaluate their effects on interfacial interactions within the composite PEG/PPBT based electrodes and resultant battery performance. The Fe 3O 4 synthesis methods inevitablymore » lead to differences in surface chemistry. For instance, the Fe 3O 4 particles synthesized using ammonium hydroxide appeared more dispersed, and afforded improved rate capability performance. Notably, chemical interactions between the active nanoparticles and PPBT binder were only seen with particles synthesized using triethylamine. Capacity retention and cycling performance were unaffected. Thus, this study provides fundamental insights into the significant impact of active material synthesis on the design and fabrication of composite battery electrodes.« less

  2. High capacity Li-ion battery anodes: Impact of crystallite size, surface chemistry and PEG-coating

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Minnici, Krysten; Kwon, Yo Han; Huie, Matthew M.

    Battery electrodes are complex mesoscale systems comprised of an active material, conductive agent, current collector, and polymeric binder. Previous work showed that introduction of poly [3-(potassium-4-butanoate) thiophene] (PPBT) as a binder component coupled with a polyethylene glycol (PEG) surface coating on magnetite (Fe 3O 4) nanoparticles enhanced electron and ion transport in the high capacity anode system. Here, the impact of Fe 3O 4 crystallite size (10 nm vs. 20 nm) and surface chemistry were explored to evaluate their effects on interfacial interactions within the composite PEG/PPBT based electrodes and resultant battery performance. The Fe 3O 4 synthesis methods inevitablymore » lead to differences in surface chemistry. For instance, the Fe 3O 4 particles synthesized using ammonium hydroxide appeared more dispersed, and afforded improved rate capability performance. Notably, chemical interactions between the active nanoparticles and PPBT binder were only seen with particles synthesized using triethylamine. Capacity retention and cycling performance were unaffected. Thus, this study provides fundamental insights into the significant impact of active material synthesis on the design and fabrication of composite battery electrodes.« less

  3. Hoof accelerations and ground reaction forces of Thoroughbred racehorses measured on dirt, synthetic, and turf track surfaces.

    PubMed

    Setterbo, Jacob J; Garcia, Tanya C; Campbell, Ian P; Reese, Jennifer L; Morgan, Jessica M; Kim, Sun Y; Hubbard, Mont; Stover, Susan M

    2009-10-01

    To compare hoof acceleration and ground reaction force (GRF) data among dirt, synthetic, and turf surfaces in Thoroughbred racehorses. 3 healthy Thoroughbred racehorses. Forelimb hoof accelerations and GRFs were measured with an accelerometer and a dynamometric horseshoe during trot and canter on dirt, synthetic, and turf track surfaces at a racecourse. Maxima, minima, temporal components, and a measure of vibration were extracted from the data. Acceleration and GRF variables were compared statistically among surfaces. The synthetic surface often had the lowest peak accelerations, mean vibration, and peak GRFs. Peak acceleration during hoof landing was significantly smaller for the synthetic surface (mean + or - SE, 28.5g + or - 2.9g) than for the turf surface (42.9g + or - 3.8g). Hoof vibrations during hoof landing for the synthetic surface were < 70% of those for the dirt and turf surfaces. Peak GRF for the synthetic surface (11.5 + or - 0.4 N/kg) was 83% and 71% of those for the dirt (13.8 + or - 0.3 N/kg) and turf surfaces (16.1 + or - 0.7 N/kg), respectively. The relatively low hoof accelerations, vibrations, and peak GRFs associated with the synthetic surface evaluated in the present study indicated that synthetic surfaces have potential for injury reduction in Thoroughbred racehorses. However, because of the unique material properties and different nature of individual dirt, synthetic, and turf racetrack surfaces, extending the results of this study to encompass all track surfaces should be done with caution.

  4. Particle acceleration at shocks with surface ripples

    NASA Technical Reports Server (NTRS)

    Decker, R. B.

    1990-01-01

    The present treatment of superthermal-ion acceleration on the surface of a fast-mode hydromagnetic shock gives attention to (1) small-amplitude surface ripples characterized by width L and amplitude A that are large relative to the energetic-ion gyroradius, and (2) shocks which are on average quasi-perpendicular. An investigation is made of the effects of the confinement, evolving geometry, and finite shock curvature associated with the ripple, by integrating along the orbits of the proton test particles. As an upstream magnetic field line convects through the surface ripple, it intersects the shock at two points, thereby forming a temporary magnetic trap. Flux-line profiles and angular distributions in a given ripple differ substantially, depending on the path it takes through the ripple and its distance from the shock.

  5. Chemistry of acetylene on platinum (111) and (100) surfaces

    PubMed Central

    Muetterties, E. L.; Tasi, M.-C.; Kelemen, S. R.

    1981-01-01

    An ultra-high vacuum experimental study of acetylene chemisorption on Pt(111) and Pt(100) and of the reaction of hydrogen with the acetylene adsorbate has established distinguishing features of carbon-hydrogen bond breaking and making processes as a function of pressure, temperature, and surface crystallography. The rates for both processes are substantially higher on the Pt(100) surface. Net acetylene-hydrogen processes, in the temperature range of 20°C to ≈130°C, are distinctly different on the two surfaces: on Pt(100) the net reaction is hydrogen exchange (1H-2H exchange) and on Pt(111) the only detectable reaction is hydrogenation. Stereochemical differences in the acetylene adsorbate structure are considered to be a contributing factor to the differences in acetylene chemistry on these two surfaces. Images PMID:16593110

  6. The behavior of MC3T3-E1 cells on chitosan/poly-L-lysine composite films: effect of nanotopography, surface chemistry, and wettability.

    PubMed

    Zheng, Zhenhuan; Zhang, Ling; Kong, Lijun; Wang, Aijun; Gong, Yandao; Zhang, Xiufang

    2009-05-01

    In the present work, a series of composite films were produced from chitosan/poly-L-lysine blend solutions. The surface topography, chemistry, and wettability of composite films were characterized by atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and contact angle assay, respectively. For all composite films, blending with poly-L-lysine induced changes in surface chemistry and wettability. Interestingly, it was also found that increasing poly-L-lysine weight fraction in blend solutions could result in different nanoscaled surface topographic features, which displayed particle-, granule-, or fiber-dominant morphologies. MC3T3-E1 osteoblast-like cells were cultured on all composite films to evaluate the effects of surface nanotopography, chemistry, and wettability on cell behavior. The observations indicated that MC3T3-E1 cell behavior was affected by surface topography, chemistry, and wettability simultaneously and that cells showed strong responses to surface topography. On fiber-dominant surface, cells fully spread with obvious cytoskeleton organization and exhibited significantly higher level of adhesion and proliferation compared with particle- or granule-dominant surfaces. Furthermore, fiber-dominant surface also induced greater expression of mature osteogenic marker osteocalcin and higher mineralization based on RT-PCR and von Kossa staining. The results suggest that topographic modification of chitosan substratum at the nanoscale may be exploited in regulating cell behavior for its applications in tissue engineering.

  7. Roles of surface chemistry on safety and electrochemistry in lithium ion batteries.

    PubMed

    Lee, Kyu Tae; Jeong, Sookyung; Cho, Jaephil

    2013-05-21

    Motivated by new applications including electric vehicles and the smart grid, interest in advanced lithium ion batteries has increased significantly over the past decade. Therefore, research in this field has intensified to produce safer devices with better electrochemical performance. Most research has focused on the development of new electrode materials through the optimization of bulk properties such as crystal structure, ionic diffusivity, and electric conductivity. More recently, researchers have also considered the surface properties of electrodes as critical factors for optimizing performance. In particular, the electrolyte decomposition at the electrode surface relates to both a lithium ion battery's electrochemical performance and safety. In this Account, we give an overview of the major developments in the area of surface chemistry for lithium ion batteries. These ideas will provide the basis for the design of advanced electrode materials. Initially, we present a brief background to lithium ion batteries such as major chemical components and reactions that occur in lithium ion batteries. Then, we highlight the role of surface chemistry in the safety of lithium ion batteries. We examine the thermal stability of cathode materials: For example, we discuss the oxygen generation from cathode materials and describe how cells can swell and heat up in response to specific conditions. We also demonstrate how coating the surfaces of electrodes can improve safety. The surface chemistry can also affect the electrochemistry of lithium ion batteries. The surface coating strategy improved the energy density and cycle performance for layered LiCoO2, xLi2MnO3·(1 - x)LiMO2 (M = Mn, Ni, Co, and their combinations), and LiMn2O4 spinel materials, and we describe a working mechanism for these enhancements. Although coating the surfaces of cathodes with inorganic materials such as metal oxides and phosphates improves the electrochemical performance and safety properties of

  8. Sol-gel chemistry-based Ucon-coated columns for capillary electrophoresis.

    PubMed

    Hayes, J D; Malik, A

    1997-07-18

    A sol-gel chemistry-based novel approach for the preparation of a Ucon-coated fused-silica capillary column in capillary electrophoresis is presented. In this approach the sol-gel process is carried out inside 25 microm I.D. fused-silica capillaries. The sol solution contained appropriate quantities of an alkoxide-based sol-gel precursor, a polymeric coating material (Ucon), a crosslinking reagent, a surface derivatizing reagent, controlled amounts of water and a catalyst dissolved in a suitable solvent system. The coating procedure involves filling a capillary with the sol solution and allowing the sol-gel process to proceed for an optimum period. Hydrolysis of the alkoxide precursor and polycondensation of the hydrolyzed products with the surface silanol groups and the hydroxy-terminated Ucon molecules lead to the formation of a surface-bonded sol-gel coating on the inner walls of the capillary. The thickness of the coated film can be controlled by varying the reaction time, coating solution composition and experimental conditions. Commercial availability of high purity sol-gel precursors (e.g., TEOS 99.999%), the ease of coating, run-to-run and column-to-column reproducibility, and long column lifetimes make sol-gel coating chemistry very much suitable for being applied in analytical microseparations column technology. Test samples of basic proteins and nucleotides were used to evaluate the column performance. These results show that the sol-gel coating scheme has allowed for the generation of bio-compatible surfaces characterized by high separation efficiencies in CE. For different types of solutes, the sol-gel coated Ucon column consistently provided migration time R.S.D. values of the order of 0.5%.

  9. Role of nanoparticle size, shape and surface chemistry in oral drug delivery.

    PubMed

    Banerjee, Amrita; Qi, Jianping; Gogoi, Rohan; Wong, Jessica; Mitragotri, Samir

    2016-09-28

    Nanoparticles find intriguing applications in oral drug delivery since they present a large surface area for interactions with the gastrointestinal tract and can be modified in various ways to address the barriers associated with oral delivery. The size, shape and surface chemistry of nanoparticles can greatly impact cellular uptake and efficacy of the treatment. However, the interplay between particle size, shape and surface chemistry has not been well investigated especially for oral drug delivery. To this end, we prepared sphere-, rod- and disc-shaped nanoparticles and conjugated them with targeting ligands to study the influence of size, shape and surface chemistry on their uptake and transport across intestinal cells. A triple co-culture model of intestinal cells was utilized to more closely mimic the intestinal epithelium. Results demonstrated higher cellular uptake of rod-shaped nanoparticles in the co-culture compared to spheres regardless of the presence of active targeting moieties. Transport of nanorods across the intestinal co-culture was also significantly higher than spheres. The findings indicate that nanoparticle-mediated oral drug delivery can be potentially improved with departure from spherical shape which has been traditionally utilized for the design of nanoparticles. We believe that understanding the role of nanoparticle geometry in intestinal uptake and transport will bring forth a paradigm shift in nanoparticle engineering for oral delivery and non-spherical nanoparticles should be further investigated and considered for oral delivery of therapeutic drugs and diagnostic materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Accelerated sampling by infinite swapping of path integral molecular dynamics with surface hopping

    NASA Astrophysics Data System (ADS)

    Lu, Jianfeng; Zhou, Zhennan

    2018-02-01

    To accelerate the thermal equilibrium sampling of multi-level quantum systems, the infinite swapping limit of a recently proposed multi-level ring polymer representation is investigated. In the infinite swapping limit, the ring polymer evolves according to an averaged Hamiltonian with respect to all possible surface index configurations of the ring polymer and thus connects the surface hopping approach to the mean-field path-integral molecular dynamics. A multiscale integrator for the infinite swapping limit is also proposed to enable efficient sampling based on the limiting dynamics. Numerical results demonstrate the huge improvement of sampling efficiency of the infinite swapping compared with the direct simulation of path-integral molecular dynamics with surface hopping.

  11. Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

    NASA Astrophysics Data System (ADS)

    Jones, A. P.

    2016-12-01

    Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of `polar ice' mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm `carbonyl' absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes.

  12. Controlling the Surface Chemistry of Graphite by Engineered Self-Assembled Peptides

    PubMed Central

    Khatayevich, Dmitriy; So, Christopher R.; Hayamizu, Yuhei; Gresswell, Carolyn; Sarikaya, Mehmet

    2012-01-01

    The systematic control over surface chemistry is a long-standing challenge in biomedical and nanotechnological applications for graphitic materials. As a novel approach, we utilize graphite-binding dodecapeptides that self-assemble into dense domains to form monolayer thick long-range ordered films on graphite. Specifically, the peptides are rationally designed through their amino acid sequences to predictably display hydrophilic and hydrophobic characteristics while maintaining their self-assembly capabilities on the solid substrate. The peptides are observed to maintain a high tolerance for sequence modification, allowing the control over surface chemistry via their amino acid sequence. Furthermore, through a single step co-assembly of two different designed peptides, we predictably and precisely tune the wettability of the resulting functionalized graphite surfaces from 44 to 83 degrees. The modular molecular structures and predictable behavior of short peptides demonstrated here give rise to a novel platform for functionalizing graphitic materials that offers numerous advantages, including non-invasive modification of the substrate, bio-compatible processing in an aqueous environment, and simple fusion with other functional biological molecules. PMID:22428620

  13. Tuning filler shape, surface chemistry and ion content in nanofilled polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Ganapatibhotla, Lalitha V. N. R.

    We investigate how nanofiller surface chemistry and aspect ratio affect the performance of nanofilled solid polymer electrolytes. Polymer-based electrolytes are an attractive alternative to the organic electrolytes currently used in lithium ion batteries. We characterize acidic nanoparticle filled electrolytes and compare them to neutral particle-filled electrolytes previously measured in our lab. Dielectric spectroscopy measurements indicate that the highest increase in conductivity occurs at the eutectic composition (EO/Li=10) and is independent of filler surface chemistry. We measure PEO dynamics using quasi-elastic neutron scattering and do not observe any change in polymer dynamics with particle surface chemistry. When we examine the elastic incoherent structure factor associated with the rotational process, fillers are found to restrict the rotation of the highly conducting PEO6:LiClO4 tunnels. At the eutectic composition, these tunnels are stabilized at the filler surface even above PEO melting temperature. Marginal stability theory predicts formation of alternating layers of coexisting phases at the eutectic composition. We propose a new mechanism, via stabilization of alternating layers of PEO and highly conducting PEO 6:LiClO4 tunnels at the filler surface. When compared to spherical particles, more such structures would be stabilized at a filler surface with high aspect ratio. Consistent with this hypothesis, neutral gamma-Al2O3 nanowhiskers (2-4 nm in diameter and 200-400 nm in length) intensify the effect of neutral gamma-Al 2O3 nanoparticles. The diameters of the two fillers are similar, but the change in aspect ratio (1 to 100) improves conductivity by a factor of 5. This enhancement occurs at battery operation temperatures! Although the change in aspect ratio does not affect thermal transitions and segmental dynamics at optimal whisker loading, the rotation of PEO6 remnants is distinct at the eutectic composition. Because the mechanism by which

  14. Comparative Evaluation of Conventional and Accelerated Castings on Marginal Fit and Surface Roughness.

    PubMed

    Jadhav, Vivek Dattatray; Motwani, Bhagwan K; Shinde, Jitendra; Adhapure, Prasad

    2017-01-01

    The aim of this study was to evaluate the marginal fit and surface roughness of complete cast crowns made by a conventional and an accelerated casting technique. This study was divided into three parts. In Part I, the marginal fit of full metal crowns made by both casting techniques in the vertical direction was checked, in Part II, the fit of sectional metal crowns in the horizontal direction made by both casting techniques was checked, and in Part III, the surface roughness of disc-shaped metal plate specimens made by both casting techniques was checked. A conventional technique was compared with an accelerated technique. In Part I of the study, the marginal fit of the full metal crowns as well as in Part II, the horizontal fit of sectional metal crowns made by both casting techniques was determined, and in Part III, the surface roughness of castings made with the same techniques was compared. The results of the t -test and independent sample test do not indicate statistically significant differences in the marginal discrepancy detected between the two casting techniques. For the marginal discrepancy and surface roughness, crowns fabricated with the accelerated technique were significantly different from those fabricated with the conventional technique. Accelerated casting technique showed quite satisfactory results, but the conventional technique was superior in terms of marginal fit and surface roughness.

  15. Investigations of nitrogen oxide plasmas: Fundamental chemistry and surface reactivity and monitoring student perceptions in a general chemistry recitation

    NASA Astrophysics Data System (ADS)

    Blechle, Joshua M.

    Part I of this dissertation focuses on investigations of nitrogen oxide plasma systems. With increasing concerns over the environmental presence of NxOy species, there is growing interest in utilizing plasma-assisted conversion techniques. Advances, however, have been limited because of the lack of knowledge regarding the fundamental chemistry of these plasma systems. Understanding the kinetics and thermodynamics of processes in these systems is vital to realizing their potential in a range of applications. Unraveling the complex chemical nature of these systems, however, presents numerous challenges. As such, this work serves as a foundational step in the diagnostics and assessment of these NxOy plasmas. The partitioning of energy within the plasma system is essential to unraveling these complications as it provides insight into both gas and surface reactivity. To obtain this information, techniques such as optical emission spectroscopy (OES), broadband absorption spectroscopy (BAS), and laser induced fluorescence (LIF) were utilized to determine species energetics (vibrational, rotational, translational temperatures). These temperature data provide mechanistic insight and establish the relationships between system parameters and energetic outcomes. Additionally, these data are also correlated to surface reactivity data collected with the Imaging of Radicals Interacting with Surfaces (IRIS) technique. IRIS data demonstrate the relationship between internal temperatures of radicals and their observed surface scatter coefficients (S), the latter of which is directly related to surface reactivity (R) [R = 1-S]. Furthermore, time-resolved (TR) spectroscopic techniques, specifically TR-OES, revealed kinetic trends in NO and N2 formation from a range of precursors (NO, N2O, N2/O2). By examining the rate constants associated with the generation and destruction of various plasma species we can investigate possible mechanistic implications. All told, such data provides

  16. Challenges in Teaching "Colloid and Surface Chemistry"--A Danish Experience

    ERIC Educational Resources Information Center

    Kontogeorgis, Georgios M.; Vigild, Martin E.

    2009-01-01

    Seven years ago we were asked, as one of our first teaching duties at the Technical University of Denmark (DTU), to teach a 5 ECTS point course on "Colloid and Surface Chemistry". The topic is itself at the same time exciting and demanding, largely due to its multidisciplinary nature. Several "local" requirements posed…

  17. Surface design for controlled crystallization: the role of surface chemistry and nanoscale pores in heterogeneous nucleation.

    PubMed

    Diao, Ying; Myerson, Allan S; Hatton, T Alan; Trout, Bernhardt L

    2011-05-03

    Current industrial practice for control of primary nucleation (nucleation from a system without pre-existing crystalline matter) during crystallization from solution involves control of supersaturation generation, impurity levels, and solvent composition. Nucleation behavior remains largely unpredictable, however, due to the presence of container surfaces, dust, dirt, and other impurities that can provide heterogeneous nucleation sites, thus making the control and scale-up of processes that depend on primary nucleation difficult. To develop a basis for the rational design of surfaces to control nucleation during crystallization from solution, we studied the role of surface chemistry and morphology of various polymeric substrates on heterogeneous nucleation using aspirin as a model compound. Nucleation induction time statistics were utilized to investigate and quantify systematically the effectiveness of polymer substrates in inducing nucleation. The nucleation induction time study revealed that poly(4-acryloylmorpholine) and poly(2-carboxyethyl acrylate), each cross-linked by divinylbenzene, significantly lowered the nucleation induction time of aspirin while the other polymers were essentially inactive. In addition, we found the presence of nanoscopic pores on certain polymer surfaces led to order-of-magnitude faster aspirin nucleation rates when compared with surfaces without pores. We studied the preferred orientation of aspirin crystals on polymer films and found the nucleation-active polymer surfaces preferentially nucleated the polar facets of aspirin, guided by hydrogen bonds. A model based on interfacial free energies was also developed which predicted the same trend of polymer surface nucleation activities as indicated by the nucleation induction times.

  18. Influence of biocompatible metal ions (Ag, Fe, Y) on the surface chemistry, corrosion behavior and cytocompatibility of Mg-1Ca alloy treated with MEVVA.

    PubMed

    Liu, Yang; Bian, Dong; Wu, Yuanhao; Li, Nan; Qiu, Kejin; Zheng, Yufeng; Han, Yong

    2015-09-01

    Mg-1Ca samples were implanted with biocompatible alloy ions Ag, Fe and Y respectively with a dose of 2×10(17)ionscm(-2) by metal vapor vacuum arc technique (MEVVA). The surface morphologies and surface chemistry were investigated by SEM, AES and XPS. Surface changes were observed after all three kinds of elemental ion implantation. The results revealed that the modified layer was composed of two sublayers, including an outer oxidized layer with mixture of oxides and an inner implanted layer, after Ag and Fe ion implantation. Y ion implantation induced an Mg/Ca-deficient outer oxidized layer and the distribution of Y along with depth was more homogeneous. Both electrochemical test and immersion test revealed accelerated corrosion rate of Ag-implanted Mg-1Ca and Fe-implanted Mg-1Ca, whereas Y ion implantation showed a short period of protection since enhanced corrosion resistance was obtained by electrochemical test, but accelerated corrosion rate was found by long period immersion test. Indirect cytotoxicity assay indicated good cytocompatibility of Y-implanted Mg-1Ca. Moreover, the corresponding corrosion mechanisms involving implanting ions into magnesium alloys were proposed, which might provide guidance for further application of plasma ion implantation to biodegradable Mg alloys. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Microstructure and surface chemistry of amorphous alloys important to their friction and wear behavior

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    An investigation was conducted to examine the microstructure and surface chemistry of amorphous alloys, and their effects on tribological behavior. The results indicate that the surface oxide layers present on amorphous alloys are effective in providing low friction and a protective film against wear in air. Clustering and crystallization in amorphous alloys can be enhanced as a result of plastic flow during the sliding process at a low sliding velocity, at room temperature. Clusters or crystallines with sizes to 150 nm and a diffused honeycomb-shaped structure are produced on the wear surface. Temperature effects lead to drastic changes in surface chemistry and friction behavior of the alloys at temperatures to 750 C. Contaminants can come from the bulk of the alloys to the surface upon heating and impart to the surface oxides at 350 C and boron nitride above 500 C. The oxides increase friction while the boron nitride reduces friction drastically in vacuum.

  20. Contribution of Surface Chemistry to the Shear Thickening of Silica Nanoparticle Suspensions.

    PubMed

    Yang, Wufang; Wu, Yang; Pei, Xiaowei; Zhou, Feng; Xue, Qunji

    2017-01-31

    Shear thickening is a general process crucial for many processed products ranging from food and personal care to pharmaceuticals. Theoretical calculations and mathematical simulations of hydrodynamic interactions and granular-like contacts have proved that contact forces between suspended particles dominate the rheological characteristic of colloidal suspensions. However, relevant experimental studies are very rare. This study was conducted to reveal the influence of nanoparticle (NP) interactions on the rheological behavior of shear-thickening fluids (STFs) by changing the colloidal surface chemistries. Silica NPs with various surface chemical compositions are fabricated and used to prepare dense suspensions. Rheological experiments are conducted to determine the influence of NP interactions on corresponding dense suspension systems. The results suggest that the surface chemistries of silica NPs determine the rheological behavior of dense suspensions, including shear-thickening behavior, onset stress, critical volume fraction, and jamming volume fraction. This study provides useful reference for designing effective STFs and regulating their characteristics.

  1. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerone C.; Kolody, Mark R.

    2011-01-01

    Evaluation of metal-based structures has long relied on atmospheric exposure test sites to determine corrosion resistance in marine environments. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions of the corrosive environment. Their success for correlation to atmospheric exposure is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated laboratory testing, which often focuses on the electrochemical reactions that occur during corrosion conditions, has yet to be universally accepted as a useful tool in predicting the long term service life of a metal despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard and their use is imperative, a method that correlates timescales from atmospheric exposure to accelerated testing would be very valuable. This work uses surface chemistry to interpret the chemical changes occurring on low carbon steel during atmospheric and accelerated corrosion conditions with the objective of finding a correlation between its accelerated and long-term corrosion performance. The current results of correlating data from marine atmospheric exposure conditions at the Kennedy Space Center beachside corrosion test site, alternating seawater spray, and immersion in typical electrochemical laboratory conditions, will be presented. Key words: atmospheric exposure, accelerated corrosion testing, alternating seawater spray, marine, correlation, seawater, carbon steel, long-term corrosion performance prediction, X-ray photoelectron spectroscopy.

  2. Reacting Chemistry Based Burn Model for Explosive Hydrocodes

    NASA Astrophysics Data System (ADS)

    Schwaab, Matthew; Greendyke, Robert; Steward, Bryan

    2017-06-01

    Currently, in hydrocodes designed to simulate explosive material undergoing shock-induced ignition, the state of the art is to use one of numerous reaction burn rate models. These burn models are designed to estimate the bulk chemical reaction rate. Unfortunately, these models are largely based on empirical data and must be recalibrated for every new material being simulated. We propose that the use of an equilibrium Arrhenius rate reacting chemistry model in place of these empirically derived burn models will improve the accuracy for these computational codes. Such models have been successfully used in codes simulating the flow physics around hypersonic vehicles. A reacting chemistry model of this form was developed for the cyclic nitramine RDX by the Naval Research Laboratory (NRL). Initial implementation of this chemistry based burn model has been conducted on the Air Force Research Laboratory's MPEXS multi-phase continuum hydrocode. In its present form, the burn rate is based on the destruction rate of RDX from NRL's chemistry model. Early results using the chemistry based burn model show promise in capturing deflagration to detonation features more accurately in continuum hydrocodes than previously achieved using empirically derived burn models.

  3. Dust evolution, a global view: III. Core/mantle grains, organic nano-globules, comets and surface chemistry

    PubMed Central

    2016-01-01

    Within the framework of The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS), this work explores the surface processes and chemistry relating to core/mantle interstellar and cometary grain structures and their influence on the nature of these fascinating particles. It appears that a realistic consideration of the nature and chemical reactivity of interstellar grain surfaces could self-consistently and within a coherent framework explain: the anomalous oxygen depletion, the nature of the CO dark gas, the formation of ‘polar ice’ mantles, the red wing on the 3 μm water ice band, the basis for the O-rich chemistry observed in hot cores, the origin of organic nano-globules and the 3.2 μm ‘carbonyl’ absorption band observed in comet reflectance spectra. It is proposed that the reaction of gas phase species with carbonaceous a-C(:H) grain surfaces in the interstellar medium, in particular the incorporation of atomic oxygen into grain surfaces in epoxide functional groups, is the key to explaining these observations. Thus, the chemistry of cosmic dust is much more intimately related with that of the interstellar gas than has previously been considered. The current models for interstellar gas and dust chemistry will therefore most likely need to be fundamentally modified to include these new grain surface processes. PMID:28083090

  4. Effect of Surface Chemistry on the Fluorescence of Detonation Nanodiamonds.

    PubMed

    Reineck, Philipp; Lau, Desmond W M; Wilson, Emma R; Fox, Kate; Field, Matthew R; Deeleepojananan, Cholaphan; Mochalin, Vadym N; Gibson, Brant C

    2017-11-28

    Detonation nanodiamonds (DNDs) have unique physical and chemical properties that make them invaluable in many applications. However, DNDs are generally assumed to show weak fluorescence, if any, unless chemically modified with organic molecules. We demonstrate that detonation nanodiamonds exhibit significant and excitation-wavelength-dependent fluorescence from the visible to the near-infrared spectral region above 800 nm, even without the engraftment of organic molecules to their surfaces. We show that this fluorescence depends on the surface functionality of the DND particles. The investigated functionalized DNDs, produced from the same purified DND as well as the as-received polyfunctional starting material, are hydrogen, hydroxyl, carboxyl, ethylenediamine, and octadecylamine-terminated. All DNDs are investigated in solution and on a silicon wafer substrate and compared to fluorescent high-pressure high-temperature nanodiamonds. The brightest fluorescence is observed from octadecylamine-functionalized particles and is more than 100 times brighter than the least fluorescent particles, carboxylated DNDs. The majority of photons emitted by all particle types likely originates from non-diamond carbon. However, we locally find bright and photostable fluorescence from nitrogen-vacancy centers in diamond in hydrogenated, hydroxylated, and carboxylated detonation nanodiamonds. Our results contribute to understanding the effects of surface chemistry on the fluorescence of DNDs and enable the exploration of the fluorescent properties of DNDs for applications in theranostics as nontoxic fluorescent labels, sensors, nanoscale tracers, and many others where chemically stable and brightly fluorescent nanoparticles with tailorable surface chemistry are needed.

  5. Micromotors for "Chemistry-on-the-Fly".

    PubMed

    Karshalev, Emil; Esteban-Fernández de Ávila, Berta; Wang, Joseph

    2018-03-21

    This perspective reviews mobile micro/nanomotor scaffolds for performing "chemistry-on-the-fly". Synthetic nano/micromotors offer great versatility and distinct advantages in diverse chemical applications owing to their efficient propulsion and facile surface functionalization that allow these mobile platforms to move and disperse reactive materials across the solution. Such dynamic microreactors have led to accelerated chemical processes, including organic pollutant degradation, metal chelation, biorecognition, redox chemistry, chemical "writing", and a variety of other chemical transformations. Representative examples of such micromotor-enhanced chemical reactions are discussed, focusing on the specific chemical role of these mobile microreactors. The advantages, gaps and limitations of using micromotors as mobile chemical platforms are discussed, concluding with the future prospects of this emerging field. We envision that artificial nano/micromotors will become attractive dynamic tools for speeding up and enhancing "on-the-fly" chemical reactions.

  6. Massive Thermal Acceleration of the Emergence of Primordial Chemistry, the Incidence of Spontaneous Mutation, and the Evolution of Enzymes*

    PubMed Central

    Wolfenden, Richard

    2014-01-01

    Kelvin considered it unlikely that sufficient time had elapsed on the earth for life to have reached its present level of complexity. In the warm surroundings in which life first appeared, however, elevated temperatures would have reduced the kinetic barriers to reaction. Recent experiments disclose the profound extent to which very slow reactions are accelerated by elevated temperatures, collapsing the time that would have been required for early events in primordial chemistry before the advent of enzymes. If a primitive enzyme, like model catalysts and most modern enzymes, accelerated a reaction by lowering its enthalpy of activation, then the rate enhancement that it produced would have increased automatically as the environment cooled, quite apart from any improvements in catalytic activity that arose from mutation and natural selection. The chemical events responsible for spontaneous mutation are also highly sensitive to temperature, furnishing an independent mechanism for accelerating evolution. PMID:25210030

  7. Surface-Accelerated Decomposition of δ-HMX.

    PubMed

    Sharia, Onise; Tsyshevsky, Roman; Kuklja, Maija M

    2013-03-07

    Despite extensive efforts to study the explosive decomposition of HMX, a cyclic nitramine widely used as a solid fuel, explosive, and propellant, an understanding of the physicochemical processes, governing the sensitivity of condensed HMX to detonation initiation is not yet achieved. Experimental and theoretical explorations of the initiation of chemistry are equally challenging because of many complex parallel processes, including the β-δ phase transition and the decomposition from both phases. Among four known polymorphs, HMX is produced in the most stable β-phase, which transforms into the most reactive δ-phase under heat or pressure. In this study, the homolytic NO2 loss and HONO elimination precursor reactions of the gas-phase, ideal crystal, and the (100) surface of δ-HMX are explored by first principles modeling. Our calculations revealed that the high sensitivity of δ-HMX is attributed to interactions of surfaces and molecular dipole moments. While both decomposition reactions coexist, the exothermic HONO-isomer formation catalyzes the N-NO2 homolysis, leading to fast violent explosions.

  8. Effects of soot-induced snow albedo change on snowpack and hydrological cycle in western United States based on Weather Research and Forecasting chemistry and regional climate simulations

    NASA Astrophysics Data System (ADS)

    Qian, Yun; Gustafson, William I.; Leung, L. Ruby; Ghan, Steven J.

    2009-02-01

    Radiative forcing induced by soot on snow is an important anthropogenic forcing affecting the global climate. In this study we simulated the deposition of soot aerosol on snow and the resulting impact on snowpack and the hydrological cycle in the western United States. A year-long simulation was performed using the chemistry version of the Weather Research and Forecasting model (WRF-Chem) to determine the soot deposition, followed by three simulations using WRF in meteorology-only mode, with and without the soot-induced snow albedo perturbations. The chemistry simulation shows large spatial variability in soot deposition that reflects the localized emissions and the influence of the complex terrain. The soot-induced snow albedo perturbations increase the surface net solar radiation flux during late winter to early spring, increase the surface air temperature, and reduce the snow accumulation and spring snowmelt. These effects are stronger over the central Rockies and southern Alberta, where soot deposition and snowpack overlap the most. The indirect forcing of soot accelerates snowmelt and alters stream flows, including a trend toward earlier melt dates in the western United States. The soot-induced albedo reduction initiates a positive feedback process whereby dirty snow absorbs more solar radiation, heating the surface and warming the air. This warming causes reduced snow depth and fraction, which further reduces the regional surface albedo for the snow-covered regions. For a doubled snow albedo perturbation, the change to surface energy and temperature is around 50-80%; however, snowpack reduction is nonlinearly accelerated.

  9. Modelling interstellar physics and chemistry: implications for surface and solid-state processes.

    PubMed

    Williams, David; Viti, Serena

    2013-07-13

    We discuss several types of regions in the interstellar medium of the Milky Way and other galaxies in which the chemistry appears to be influenced or dominated by surface and solid-state processes occurring on or in interstellar dust grains. For some of these processes, for example, the formation of H₂ molecules, detailed experimental and theoretical approaches have provided excellent fundamental data for incorporation into astrochemical models. In other cases, there is an astrochemical requirement for much more laboratory and computational study, and we highlight these needs in our description. Nevertheless, in spite of the limitations of the data, it is possible to infer from astrochemical modelling that surface and solid-state processes play a crucial role in astronomical chemistry from early epochs of the Universe up to the present day.

  10. Comparative Evaluation of Conventional and Accelerated Castings on Marginal Fit and Surface Roughness

    PubMed Central

    Jadhav, Vivek Dattatray; Motwani, Bhagwan K.; Shinde, Jitendra; Adhapure, Prasad

    2017-01-01

    Aims: The aim of this study was to evaluate the marginal fit and surface roughness of complete cast crowns made by a conventional and an accelerated casting technique. Settings and Design: This study was divided into three parts. In Part I, the marginal fit of full metal crowns made by both casting techniques in the vertical direction was checked, in Part II, the fit of sectional metal crowns in the horizontal direction made by both casting techniques was checked, and in Part III, the surface roughness of disc-shaped metal plate specimens made by both casting techniques was checked. Materials and Methods: A conventional technique was compared with an accelerated technique. In Part I of the study, the marginal fit of the full metal crowns as well as in Part II, the horizontal fit of sectional metal crowns made by both casting techniques was determined, and in Part III, the surface roughness of castings made with the same techniques was compared. Statistical Analysis Used: The results of the t-test and independent sample test do not indicate statistically significant differences in the marginal discrepancy detected between the two casting techniques. Results: For the marginal discrepancy and surface roughness, crowns fabricated with the accelerated technique were significantly different from those fabricated with the conventional technique. Conclusions: Accelerated casting technique showed quite satisfactory results, but the conventional technique was superior in terms of marginal fit and surface roughness. PMID:29042726

  11. Staging of RF-accelerating Units in a MEMS-based Ion Accelerator

    NASA Astrophysics Data System (ADS)

    Persaud, A.; Seidl, P. A.; Ji, Q.; Feinberg, E.; Waldron, W. L.; Schenkel, T.; Ardanuc, S.; Vinayakumar, K. B.; Lal, A.

    Multiple Electrostatic Quadrupole Array Linear Accelerators (MEQALACs) provide an opportunity to realize compact radio- frequency (RF) accelerator structures that can deliver very high beam currents. MEQALACs have been previously realized with acceleration gap distances and beam aperture sizes of the order of centimeters. Through advances in Micro-Electro-Mechanical Systems (MEMS) fabrication, MEQALACs can now be scaled down to the sub-millimeter regime and batch processed on wafer substrates. In this paper we show first results from using three RF stages in a compact MEMS-based ion accelerator. The results presented show proof-of-concept with accelerator structures formed from printed circuit boards using a 3 × 3 beamlet arrangement and noble gas ions at 10 keV. We present a simple model to describe the measured results. We also discuss some of the scaling behaviour of a compact MEQALAC. The MEMS-based approach enables a low-cost, highly versatile accelerator covering a wide range of currents (10 μA to 100 mA) and beam energies (100 keV to several MeV). Applications include ion-beam analysis, mass spectrometry, materials processing, and at very high beam powers, plasma heating.

  12. Staging of RF-accelerating Units in a MEMS-based Ion Accelerator

    DOE PAGES

    Persaud, A.; Seidl, P. A.; Ji, Q.; ...

    2017-10-26

    Multiple Electrostatic Quadrupole Array Linear Accelerators (MEQALACs) provide an opportunity to realize compact radio- frequency (RF) accelerator structures that can deliver very high beam currents. MEQALACs have been previously realized with acceleration gap distances and beam aperture sizes of the order of centimeters. Through advances in Micro-Electro-Mechanical Systems (MEMS) fabrication, MEQALACs can now be scaled down to the sub-millimeter regime and batch processed on wafer substrates. In this paper we show first results from using three RF stages in a compact MEMS-based ion accelerator. The results presented show proof-of-concept with accelerator structures formed from printed circuit boards using a 3more » × 3 beamlet arrangement and noble gas ions at 10 keV. We present a simple model to describe the measured results. We also discuss some of the scaling behaviour of a compact MEQALAC. The MEMS-based approach enables a low-cost, highly versatile accelerator covering a wide range of currents (10 μA to 100 mA) and beam energies (100 keV to several MeV). Applications include ion-beam analysis, mass spectrometry, materials processing, and at very high beam powers, plasma heating.« less

  13. Staging of RF-accelerating Units in a MEMS-based Ion Accelerator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Persaud, A.; Seidl, P. A.; Ji, Q.

    Multiple Electrostatic Quadrupole Array Linear Accelerators (MEQALACs) provide an opportunity to realize compact radio- frequency (RF) accelerator structures that can deliver very high beam currents. MEQALACs have been previously realized with acceleration gap distances and beam aperture sizes of the order of centimeters. Through advances in Micro-Electro-Mechanical Systems (MEMS) fabrication, MEQALACs can now be scaled down to the sub-millimeter regime and batch processed on wafer substrates. In this paper we show first results from using three RF stages in a compact MEMS-based ion accelerator. The results presented show proof-of-concept with accelerator structures formed from printed circuit boards using a 3more » × 3 beamlet arrangement and noble gas ions at 10 keV. We present a simple model to describe the measured results. We also discuss some of the scaling behaviour of a compact MEQALAC. The MEMS-based approach enables a low-cost, highly versatile accelerator covering a wide range of currents (10 μA to 100 mA) and beam energies (100 keV to several MeV). Applications include ion-beam analysis, mass spectrometry, materials processing, and at very high beam powers, plasma heating.« less

  14. ATR-FTIR Spectroscopy in the Undergraduate Chemistry Laboratory: Part II--A Physical Chemistry Laboratory Experiment on Surface Adsorption

    ERIC Educational Resources Information Center

    Schuttlefield, Jennifer D.; Larsen, Sarah C.; Grassian, Vicki H.

    2008-01-01

    Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. The use of FTIR-ATR spectroscopy in organic and inorganic chemistry laboratory courses as well as in undergraduate research was presented…

  15. Accelerated aging effects on surface hardness and roughness of lingual retainer adhesives.

    PubMed

    Ramoglu, Sabri Ilhan; Usumez, Serdar; Buyukyilmaz, Tamer

    2008-01-01

    To test the null hypothesis that accelerated aging has no effect on the surface microhardness and roughness of two light-cured lingual retainer adhesives. Ten samples of light-cured materials, Transbond Lingual Retainer (3M Unitek) and Light Cure Retainer (Reliance) were cured with a halogen light for 40 seconds. Vickers hardness and surface roughness were measured before and after accelerated aging of 300 hours in a weathering tester. Differences between mean values were analyzed for statistical significance using a t-test. The level of statistical significance was set at P < .05. The mean Vickers hardness of Transbond Lingual Retainer was 62.8 +/- 3.5 and 79.6 +/- 4.9 before and after aging, respectively. The mean Vickers hardness of Light Cure Retainer was 40.3 +/- 2.6 and 58.3 +/- 4.3 before and after aging, respectively. Differences in both groups were statistically significant (P < .001). Following aging, mean surface roughness was changed from 0.039 microm to 0.121 microm and from 0.021 microm to 0.031 microm for Transbond Lingual Retainer and Light Cure Retainer, respectively. The roughening of Transbond Lingual Retainer with aging was statistically significant (P < .05), while the change in the surface roughness of Light Cure Retainer was not (P > .05). Accelerated aging significantly increased the surface microhardness of both light-cured retainer adhesives tested. It also significantly increased the surface roughness of the Transbond Lingual Retainer.

  16. Photografting of perfluoroalkanes onto polyethylene surfaces via azide/nitrene chemistry

    NASA Astrophysics Data System (ADS)

    Siegmann, Konstantin; Inauen, Jan; Villamaina, Diego; Winkler, Martin

    2017-02-01

    The purpose of this study is to render polyethylene surfaces strongly and permanently hydrophobic. Polyethylene is a common plastic and, because of its inertness, difficult to graft. We chose polyethylene as example because of its ubiquity and model character. As graft chains linear perfluoroalkyl residues (-C4F9, -C6F13, -C8F17 and -C10F21) were chosen, and photografting was selected as grafting method. Photolytically generated nitrenes can insert into carbon-hydrogen bonds and are therefore suited for binding to polyethylene. Hydrophobic photo reactive surface modifiers based on azide/nitrene chemistry are designed, synthesized in high yield and characterized. Four new molecules are described. Water contact angles exceeding 110° were achieved on grafted polyethylene. One problem is to demonstrate that the photografted surface modifiers are bound covalently to the polyethylene. Abrasion tests show that all new molecules, when photografted to polyethylene, have a higher abrasion resistance than a polyethylene surface coated with a long-chain perfluoroalkane. Relative abrasion resitances of 1.4, 2.0, 2.1 and 2.5 compared to the fluoroalkane coating were obtained for the four compounds. An abrasion model using ice is developed. Although all four compounds have the same λmax of 266 nm in acetonitrile solution, their molar extincition coefficients increase from 1.6·104 to 2.2·104 with increasing length of the fluorotelomer chain. Exitonic coupling of the chromophores of the surface modifiers is observed for specific molecules in the neat state. A linear correlation of water contact angle with fluorine surface content, as measured by photoelectron spectroscopy, in grafted polyethylene surfaces is established.

  17. Static Chemistry in Disks or Clouds

    NASA Astrophysics Data System (ADS)

    Semenov, D.; Wiebe, D.

    2006-11-01

    This FORTRAN77 code can be used to model static, time-dependent chemistry in ISM and circumstellar disks. Current version is based on the OSU'06 gas-grain astrochemical network with all updates to the reaction rates, and includes surface chemistry from Hasegawa & Herbst (1993) and Hasegawa, Herbst, and Leung (1992). Surface chemistry can be modeled either with the standard rate equation approach or modified rate equation approach (useful in disks). Gas-grain interactions include sticking of neutral molecules to grains, dissociative recombination of ions on grains as well as thermal, UV, X-ray, and CRP-induced desorption of frozen species. An advanced X-ray chemistry and 3 grain sizes with power-law size distribution are also included. An deuterium extension to this chemical model is available.

  18. Bioadhesion of mussels and geckos: Molecular mechanics, surface chemistry, and nanoadhesives

    NASA Astrophysics Data System (ADS)

    Lee, Haeshin

    The adhesive strategies of living creatures are diverse, ranging from temporary to permanent adhesions with various functions such as locomotion, self-defense, communication, colony formation, and so on. The classic example of temporary adhesion is the gecko, which is known for its ability to walk along vertical and even inverted surfaces; this remarkable adhesion arises from the interfacial weak interactions of van der Waals and capillary forces. In contrast, a celerbrated example of permanent adhesion is found in marine mussels which secrete protein adhesives that function in aqueous environments without mechanical failure against turbulent conditions on the seashore. In addition, mussel adhesives stick to virtually all inorganic and organic surfaces. However, most commonly used man-made adhesives lack such unique adhesion properties compared to their natural counterparts. For example, many commercial adhesives quickly lose their adhesive strength when exposed to solvents, particularly water. The first part of this thesis focused on adhesion mechanics of mussels at a single-molecule level, in which the adhesive molecule showed surprisingly strong yet reversible adhesion on inorganic surfaces but exhibited irreversible covalent bond formation on organic surfaces. Strong and reversible adhesion on mucin surfaces was found, indicating potential application for drug delivery via mucus layers. Next, inspired by the mussel's versatile adhesion on a wide variety of material surfaces, a material-independent surface modification chemistry called 'polydopamine coating' is described. This concept was subsequently adapted to develop a surface-independent polymeric primer for layer-by-layer assembly of multifunctional coatings. Finally, a new bio-hybrid adhesive 'geckel' was developed by the functional combination of adhesion strategies of geckos and mussels. The new bio-inspired adhesive and material-independent surface chemistry can revolutionize the research areas such as

  19. A Study on Advanced Lithium-Based Battery Cell Chemistries to Enhance Lunar Exploration Missions

    NASA Technical Reports Server (NTRS)

    Reid, Concha M.; Bennett, William R.

    2010-01-01

    NASAs Exploration Technology Development Program (ETDP) Energy Storage Project conducted an advanced lithium-based battery chemistry feasibility study to determine the best advanced chemistry to develop for the Altair Lunar Lander and the Extravehicular Activities (EVA) advanced Lunar surface spacesuit. These customers require safe, reliable batteries with extremely high specific energy as compared to state-of-the-art. The specific energy goals for the development project are 220 watt-hours per kilogram (Wh/kg) delivered at the battery-level at 0 degrees Celsius ( C) at a C/10 discharge rate. Continuous discharge rates between C/5 and C/2, operation between 0 and 30 C and 200 cycles are targeted. Electrode materials that were considered include layered metal oxides, spinel oxides, and olivine-type cathode materials, and lithium metal, lithium alloy, and silicon-based composite anode materials. Advanced cell chemistry options were evaluated with respect to multiple quantitative and qualitative attributes while considering their projected performance at the end of the available development timeframe. Following a rigorous ranking process, a chemistry that combines a lithiated nickel manganese cobalt oxide Li(LiNMC)O2 cathode with a silicon-based composite anode was selected as the technology that can potentially offer the best combination of safety, specific energy, energy density, and likelihood of success.

  20. Structure-based classification and ontology in chemistry

    PubMed Central

    2012-01-01

    Background Recent years have seen an explosion in the availability of data in the chemistry domain. With this information explosion, however, retrieving relevant results from the available information, and organising those results, become even harder problems. Computational processing is essential to filter and organise the available resources so as to better facilitate the work of scientists. Ontologies encode expert domain knowledge in a hierarchically organised machine-processable format. One such ontology for the chemical domain is ChEBI. ChEBI provides a classification of chemicals based on their structural features and a role or activity-based classification. An example of a structure-based class is 'pentacyclic compound' (compounds containing five-ring structures), while an example of a role-based class is 'analgesic', since many different chemicals can act as analgesics without sharing structural features. Structure-based classification in chemistry exploits elegant regularities and symmetries in the underlying chemical domain. As yet, there has been neither a systematic analysis of the types of structural classification in use in chemistry nor a comparison to the capabilities of available technologies. Results We analyze the different categories of structural classes in chemistry, presenting a list of patterns for features found in class definitions. We compare these patterns of class definition to tools which allow for automation of hierarchy construction within cheminformatics and within logic-based ontology technology, going into detail in the latter case with respect to the expressive capabilities of the Web Ontology Language and recent extensions for modelling structured objects. Finally we discuss the relationships and interactions between cheminformatics approaches and logic-based approaches. Conclusion Systems that perform intelligent reasoning tasks on chemistry data require a diverse set of underlying computational utilities including algorithmic

  1. Developing the Surface Chemistry of Transparent Butyl Rubber for Impermeable Stretchable Electronics.

    PubMed

    Vohra, Akhil; Carmichael, R Stephen; Carmichael, Tricia Breen

    2016-10-11

    Transparent butyl rubber is a new elastomer that has the potential to revolutionize stretchable electronics due to its intrinsically low gas permeability. Encapsulating organic electronic materials and devices with transparent butyl rubber protects them from problematic degradation due to oxygen and moisture, preventing premature device failure and enabling the fabrication of stretchable organic electronic devices with practical lifetimes. Here, we report a methodology to alter the surface chemistry of transparent butyl rubber to advance this material from acting as a simple device encapsulant to functioning as a substrate primed for direct device fabrication on its surface. We demonstrate a combination of plasma and chemical treatment to deposit a hydrophilic silicate layer on the transparent butyl rubber surface to create a new layered composite that combines Si-OH surface chemistry with the favorable gas-barrier properties of bulk transparent butyl rubber. We demonstrate that these surface Si-OH groups react with organosilanes to form self-assembled monolayers necessary for the deposition of electronic materials, and furthermore demonstrate the fabrication of stretchable gold wires using nanotransfer printing of gold films onto transparent butyl rubber modified with a thiol-terminated self-assembled monolayer. The surface modification of transparent butyl rubber establishes this material as an important new elastomer for stretchable electronics and opens the way to robust, stretchable devices.

  2. Centrifugal accelerator, system and method for removing unwanted layers from a surface

    DOEpatents

    Foster, Christopher A.; Fisher, Paul W.

    1995-01-01

    A cryoblasting process having a centrifugal accelerator for accelerating frozen pellets of argon or carbon dioxide toward a target area utilizes an accelerator throw wheel designed to induce, during operation, the creation of a low-friction gas bearing within internal passages of the wheel which would otherwise retard acceleration of the pellets as they move through the passages. An associated system and method for removing paint from a surface with cryoblasting techniques involves the treating, such as a preheating, of the painted surface to soften the paint prior to the impacting of frozen pellets thereagainst to increase the rate of paint removal. A system and method for producing large quantities of frozen pellets from a liquid material, such as liquid argon or carbon dioxide, for use in a cryoblasting process utilizes a chamber into which the liquid material is introduced in the form of a jet which disintegrates into droplets. A non-condensible gas, such as inert helium or air, is injected into the chamber at a controlled rate so that the droplets freeze into bodies of relatively high density.

  3. Genotoxic capacity of Cd/Se semiconductor quantum dots with differing surface chemistries

    PubMed Central

    Manshian, Bella B.; Soenen, Stefaan J.; Brown, Andy; Hondow, Nicole; Wills, John; Jenkins, Gareth J. S.; Doak, Shareen H.

    2016-01-01

    Quantum dots (QD) have unique electronic and optical properties promoting biotechnological advances. However, our understanding of the toxicological structure–activity relationships remains limited. This study aimed to determine the biological impact of varying nanomaterial surface chemistry by assessing the interaction of QD with either a negative (carboxyl), neutral (hexadecylamine; HDA) or positive (amine) polymer coating with human lymphoblastoid TK6 cells. Following QD physico-chemical characterisation, cellular uptake was quantified by optical and electron microscopy. Cytotoxicity was evaluated and genotoxicity was characterised using the micronucleus assay (gross chromosomal damage) and the HPRT forward mutation assay (point mutagenicity). Cellular damage mechanisms were also explored, focusing on oxidative stress and mitochondrial damage. Cell uptake, cytotoxicity and genotoxicity were found to be dependent on QD surface chemistry. Carboxyl-QD demonstrated the smallest agglomerate size and greatest cellular uptake, which correlated with a dose dependent increase in cytotoxicity and genotoxicity. Amine-QD induced minimal cellular damage, while HDA-QD promoted substantial induction of cell death and genotoxicity. However, HDA-QD were not internalised by the cells and the damage they caused was most likely due to free cadmium release caused by QD dissolution. Oxidative stress and induced mitochondrial reactive oxygen species were only partially associated with cytotoxicity and genotoxicity induced by the QD, hence were not the only mechanisms of importance. Colloidal stability, nanoparticle (NP) surface chemistry, cellular uptake levels and the intrinsic characteristics of the NPs are therefore critical parameters impacting genotoxicity induced by QD. PMID:26275419

  4. Biodegradable polyester-based microcarriers with modified surface tailored for tissue engineering.

    PubMed

    Privalova, A; Markvicheva, E; Sevrin, Ch; Drozdova, M; Kottgen, C; Gilbert, B; Ortiz, M; Grandfils, Ch

    2015-03-01

    Microcarriers have been proposed in tissue engineering, namely for bone, cartilage, skin, vascular, and central nervous system. Although polyester-based microcarriers have been already used for this purpose, their surface properties should be improved to provide better cell growth. The goal of this study was to prepare microbeads based on poly(D,L-lactide) acid, poly(L-lactide) acid, and to study cell behavior (adhesion, spreading, growth, and proliferation) in function of microbead topography and surface chemistry. To improve L-929 fibroblasts adhesion, microbead surface has been modified with three polycations: chitosan, poly(2-dimethylamino ethylmethacrylate) (PDMAEMA), or chitosan-g-oligolactide copolymer (chit-g-OLA). Although modification of the microbead surface with chitosan and PDMAEMA was performed through physical adsorption on the previously prepared microbeads, chit-g-OLA copolymer was introduced directly during microbead processing. This simple approach (1) bypass the use of an emulsifier (polyvinyl alcohol, PVA); (2) avoid surface "contamination" with PVA molecules limiting a control of the surface characteristics. In vitro study of the growth of mouse fibroblasts on the microbeads showed that both surface topography and chemistry affected cell attachment, spreading, and proliferation. Cultivation of L-929 fibroblasts for 7 days resulted in the formation of a 3D cell-scaffold network. © 2014 Wiley Periodicals, Inc.

  5. Anisotropic wetting of microstructured surfaces as a function of surface chemistry.

    PubMed

    Neuhaus, Sonja; Spencer, Nicholas D; Padeste, Celestino

    2012-01-01

    In order to study the influence of surface chemistry on the wetting of structured surfaces, microstructures consisting of grooves or squares were produced via hot embossing of poly(ethylene-alt-tetrafluoroethylene) ETFE substrates. The structured substrates were modified with polymer brushes, thereby changing their surface functionality and wettability. Water droplets were most strongly pinned to the structure when the surface was moderately hydrophilic, as in the case of poly(4-vinylpyridine) (P4VP) or poly(vinyl(N-methyl-2-pyridone) (PVMP) brush-modified substrates. As a result, the droplet shape was determined by the features of the microstructure. The water contact angles (CA) were considerably higher than on flat surfaces and differed, in the most extreme case, by 37° when measured on grooved substrates, parallel and perpendicular to the grooves. On hydrophobic substrates (pristine ETFE), the same effects were observed but were much less pronounced. On very hydrophilic sampes (those modified with poly(N-methyl-vinylpyridinium) (QP4VP)), the microstructure had no influence on the drop shape. These findings are explained by significant differences in apparent and real contact angles at the relatively smooth edges of the embossed structures. Finally, the highly anisotropic grooved microstructure was combined with a gradient in polymer brush composition and wettability. In the case of a parallel alignment of the gradient direction to the grooves, the directed spreading of water droplets could be observed. © 2011 American Chemical Society

  6. Fragment-Based Drug Design Facilitated by Protein-Templated Click Chemistry: Fragment Linking and Optimization of Inhibitors of the Aspartic Protease Endothiapepsin.

    PubMed

    Mondal, Milon; Unver, M Yagiz; Pal, Asish; Bakker, Matthijs; Berrier, Stephan P; Hirsch, Anna K H

    2016-10-10

    There is an urgent need for the development of efficient methodologies that accelerate drug discovery. We demonstrate that the strategic combination of fragment linking/optimization and protein-templated click chemistry is an efficient and powerful method that accelerates the hit-identification process for the aspartic protease endothiapepsin. The best binder, which inhibits endothiapepsin with an IC 50 value of 43 μm, represents the first example of triazole-based inhibitors of endothiapepsin. Our strategy could find application on a whole range of drug targets. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  7. A Self Consistent RF Discharge, Plasma Chemistry and Surface Model for Plasma Enhanced Chemical Vapor Deposition

    DTIC Science & Technology

    1988-06-30

    consists of three submodels for the electron kinetics, plasma chemistry , and surface deposition kinetics for a-Si:H deposited from radio frequency...properties. Plasma enhanced, Chemical vapor deposition, amorphous silicon, Modeling, Electron kinetics, Plasma chemistry , Deposition kinetics, Rf discharge, Silane, Film properties, Silicon.

  8. Effect of chitosan and cationic starch on the surface chemistry properties of bagasse paper.

    PubMed

    Ashori, Alireza; Cordeiro, Nereida; Faria, Marisa; Hamzeh, Yahya

    2013-07-01

    The use of non-wood fibers in the paper industry has been an economical and environmental necessity. The application of dry-strength agents has been a successful method to enhance the strength properties of paper. The experimental results evidencing the potential of chitosan and cationic starch utilization in bagasse paper subjected to hot water pre-extraction has been presented in this paper. The research analyzes the surface properties alterations due to these dry-strength agents. Inverse gas chromatography was used to evaluate the properties of surface chemistry of the papers namely the surface energy, active sites, surface area as well as the acidic/basic character. The results of the study revealed that the handsheets process causes surface arrangement and orientation of chemical groups, which induce a more hydrophobic and basic surface. The acid-base surface characteristics after the addition of dry-strength agents were the same as the bagasse handsheets with and without hot water pre-extraction. The results showed that the dry-strength agent acts as a protecting film or glaze on the surfaces of bagasse paper handsheets. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Atomic Scale Structure-Chemistry Relationships at Oxide Catalyst Surfaces and Interfaces

    NASA Astrophysics Data System (ADS)

    McBriarty, Martin E.

    Oxide catalysts are integral to chemical production, fuel refining, and the removal of environmental pollutants. However, the atomic-scale phenomena which lead to the useful reactive properties of catalyst materials are not sufficiently understood. In this work, the tools of surface and interface science and electronic structure theory are applied to investigate the structure and chemical properties of catalytically active particles and ultrathin films supported on oxide single crystals. These studies focus on structure-property relationships in vanadium oxide, tungsten oxide, and mixed V-W oxides on the surfaces of alpha-Al2O3 and alpha-Fe2O 3 (0001)-oriented single crystal substrates, two materials with nearly identical crystal structures but drastically different chemical properties. In situ synchrotron X-ray standing wave (XSW) measurements are sensitive to changes in the atomic-scale geometry of single crystal model catalyst surfaces through chemical reaction cycles, while X-ray photoelectron spectroscopy (XPS) reveals corresponding chemical changes. Experimental results agree with theoretical calculations of surface structures, allowing for detailed electronic structure investigations and predictions of surface chemical phenomena. The surface configurations and oxidation states of V and W are found to depend on the coverage of each, and reversible structural shifts accompany chemical state changes through reduction-oxidation cycles. Substrate-dependent effects suggest how the choice of oxide support material may affect catalytic behavior. Additionally, the structure and chemistry of W deposited on alpha-Fe 2O3 nanopowders is studied using X-ray absorption fine structure (XAFS) measurements in an attempt to bridge single crystal surface studies with real catalysts. These investigations of catalytically active material surfaces can inform the rational design of new catalysts for more efficient and sustainable chemistry.

  10. The hydrochemistry of glacial Ebba River (Petunia Bay, Central Spitsbergen): Groundwater influence on surface water chemistry

    NASA Astrophysics Data System (ADS)

    Dragon, Krzysztof; Marciniak, Marek; Szpikowski, Józef; Szpikowska, Grażyna; Wawrzyniak, Tomasz

    2015-10-01

    The article presents the investigation of surface water chemistry changes of the glacial Ebba River (Central Spitsbergen) during three melting seasons of 2008, 2009 and 2010. The twice daily water chemistry analyses allow recognition of the surface water chemistry differentiation. The surface water chemistry changes are related to the river discharge and changes in the influence of different water balance components during each melting season. One of the most important process that influence river water component concentration increase is groundwater inflow from active layer occurring on the valley area. The significance of this process is the most important at the end of the melting season when temperatures below 0 °C occur on glaciers (resulting in a slowdown of melting of ice and snow and a smaller recharge of the river by the water from the glaciers) while the flow of groundwater is still active, causing a relatively higher contribution of groundwater to the total river discharge. The findings presented in this paper show that groundwater contribution to the total polar river water balance is more important than previously thought and its recognition allow a better understanding of the hydrological processes occurring in a polar environment.

  11. Mass Spectrometric Analysis of the Cell Surface N-Glycoproteome by Combining Metabolic Labeling and Click Chemistry

    NASA Astrophysics Data System (ADS)

    Smeekens, Johanna M.; Chen, Weixuan; Wu, Ronghu

    2015-04-01

    Cell surface N-glycoproteins play extraordinarily important roles in cell-cell communication, cell-matrix interactions, and cellular response to environmental cues. Global analysis is exceptionally challenging because many N-glycoproteins are present at low abundances and effective separation is difficult to achieve. Here, we have developed a novel strategy integrating metabolic labeling, copper-free click chemistry, and mass spectrometry (MS)-based proteomics methods to analyze cell surface N-glycoproteins comprehensively and site-specifically. A sugar analog containing an azido group, N-azidoacetylgalactosamine, was fed to cells to label glycoproteins. Glycoproteins with the functional group on the cell surface were then bound to dibenzocyclooctyne-sulfo-biotin via copper-free click chemistry under physiological conditions. After protein extraction and digestion, glycopeptides with the biotin tag were enriched by NeutrAvidin conjugated beads. Enriched glycopeptides were deglycosylated with peptide- N-glycosidase F in heavy-oxygen water, and in the process of glycan removal, asparagine was converted to aspartic acid and tagged with 18O for MS analysis. With this strategy, 144 unique N-glycopeptides containing 152 N-glycosylation sites were identified in 110 proteins in HEK293T cells. As expected, 95% of identified glycoproteins were membrane proteins, which were highly enriched. Many sites were located on important receptors, transporters, and cluster of differentiation proteins. The experimental results demonstrated that the current method is very effective for the comprehensive and site-specific identification of the cell surface N-glycoproteome and can be extensively applied to other cell surface protein studies.

  12. An Acid-Base Chemistry Example: Conversion of Nicotine

    NASA Astrophysics Data System (ADS)

    Summerfield, John H.

    1999-10-01

    The current government interest in nicotine conversion by cigarette companies provides an example of acid-base chemistry that can be explained to students in the second semester of general chemistry. In particular, the conversion by ammonia of the +1 form of nicotine to the easier-to-assimilate free-base form illustrates the effect of pH on acid-base equilibrium. The part played by ammonia in tobacco smoke is analogous to what takes place when cocaine is "free-based".

  13. Influence of chemistry on wetting dynamics of nanotextured hydrophobic surfaces.

    PubMed

    Di Mundo, Rosa; Palumbo, Fabio; d'Agostino, Riccardo

    2010-04-06

    In this work, the role of a chemical parameter, such as the degree of fluorination, on the wetting behavior of nanotextured hydrophobic surfaces is investigated. Texture and chemistry tuning of the surfaces has been accomplished with single batch radiofrequency low-pressure plasma processes. Polystyrene substrates have been textured by CF(4) plasma etching and subsequently covered by thin films with a tunable F-to-C ratio, obtained in discharges fed with C(4)F(8)-C(2)H(4). Measurements of wetting dynamics reveal a regime transition from adhesive-hydrophobic to slippery-superhydrophobic, i.e., from wet to non wet states, as the F-to-C rises at constant topography. Such achievements are strengthened by calculation of the solid fraction of surface water contact area applying Cassie-Baxter advancing and receding equations to water contact angle data of textured and flat reference surfaces.

  14. Using Chemistry Teaching Aids Based Local Wisdom as an Alternative Media for Chemistry Teaching and Learning

    ERIC Educational Resources Information Center

    Priyambodo, Erfan; Wulaningrum, Safira

    2017-01-01

    Students have difficulties in relating the chemistry phenomena they learned and the life around them. It is necessary to have teaching aids which can help them to relate between chemistry with the phenomena occurred in everyday life, which is chemistry's teaching aids based on local wisdom. There are 3 teaching aids which used in chemistry…

  15. Interfaces in heterogeneous catalytic reactions: Ambient pressure XPS as a tool to unravel surface chemistry

    DOE PAGES

    Palomino, Robert M.; Hamlyn, Rebecca; Liu, Zongyuan; ...

    2017-04-27

    In this paper we provide a summary of the recent development of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and its application to catalytic surface chemistry. The methodology as well as significant advantages and challenges associated with this novel technique are described. Details about specific examples of using AP-XPS to probe surface chemistry under working reaction conditions for a number of reactions are explained: CO oxidation, water-gas shift (WGS), CO 2 hydrogenation, dry reforming of methane (DRM) and ethanol steam reforming (ESR). In conclusion, we discuss insights into the future development of the AP-XPS technique and its applications.

  16. Interfaces in heterogeneous catalytic reactions: Ambient pressure XPS as a tool to unravel surface chemistry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Palomino, Robert M.; Hamlyn, Rebecca; Liu, Zongyuan

    In this paper we provide a summary of the recent development of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and its application to catalytic surface chemistry. The methodology as well as significant advantages and challenges associated with this novel technique are described. Details about specific examples of using AP-XPS to probe surface chemistry under working reaction conditions for a number of reactions are explained: CO oxidation, water-gas shift (WGS), CO 2 hydrogenation, dry reforming of methane (DRM) and ethanol steam reforming (ESR). In conclusion, we discuss insights into the future development of the AP-XPS technique and its applications.

  17. Saturn Magnetospheric Impact on Surface Molecular Chemistry and Astrobiological Potential of Enceladus

    NASA Technical Reports Server (NTRS)

    Cooper, Paul D.; Cooper, John F.; Sittler, Edward C.; Burger, Matthew H.; Sturner, Steven J.; Rymer, Abigail M.

    2008-01-01

    The active south polar surface of Enceladus is exposed to strong chemical processing by direct interaction with charged plasma and energetic particles in the local magnetospheric environment of this icy moon. Chemical oxidation activity is suggested by detection of H202 at the surface in this region and less directly by substantial presence of C02, CO, and N2 in the plume gases. Molecular composition of the uppermost surface, including ejecta from plume activity, is radiolytically transformed mostly by penetrating energetic electrons with lesser effects from more depleted populations of energetic protons. The main sources of molecular plasma ions and E-ring dust grains in the magnetospheric environment are the cryovolcanic plume emissions from Enceladus. These molecular ions and the dust grains are chemically processed by magnetospheric interactions that further impact surface chemistry on return to Enceladus. For example, H20 neutrals dominating the emitted plume gas return to the surface mostly as H30+ ions after magnetospheric processing. Surface oxidant loading is further increased by return of radiolytically processed ice grains from the E-ring. Plume frost deposition and micrometeoroid gardening protect some fraction of newly produced molecular species from destruction by further irradiation. The evident horizontal and vertical mobility of surface ices in the south polar region drive mixing of these processed materials into the moon interior with potential impacts on deep ice molecular chemistry and plume gas production. Similarly as suggested previously for Europa, the externally driven source of radiolytic oxidants could affect evolution of life in any subsurface liquid water environments of Enceladus.

  18. Modeling of thermalization phenomena in coaxial plasma accelerators

    NASA Astrophysics Data System (ADS)

    Subramaniam, Vivek; Panneerchelvam, Premkumar; Raja, Laxminarayan L.

    2018-05-01

    Coaxial plasma accelerators are electromagnetic acceleration devices that employ a self-induced Lorentz force to produce collimated plasma jets with velocities ~50 km s‑1. The accelerator operation is characterized by the formation of an ionization/thermalization zone near gas inlet of the device that continually processes the incoming neutral gas into a highly ionized thermal plasma. In this paper, we present a 1D non-equilibrium plasma model to resolve the plasma formation and the electron-heavy species thermalization phenomena that take place in the thermalization zone. The non-equilibrium model is based on a self-consistent multi-species continuum description of the plasma with finite-rate chemistry. The thermalization zone is modelled by tracking a 1D gas-bit as it convects down the device with an initial gas pressure of 1 atm. The thermalization process occurs in two stages. The first is a plasma production stage, associated with a rapid increase in the charged species number densities facilitated by cathode surface electron emission and volumetric production processes. The production stage results in the formation of a two-temperature plasma with electron energies of ~2.5 eV in a low temperature background gas of ~300 K. The second, a temperature equilibration stage, is characterized by the energy transfer between the electrons and heavy species. The characteristic length scale for thermalization is found to be comparable to axial length of the accelerator thus putting into question the equilibrium magnetohydrodynamics assumption used in modeling coaxial accelerators.

  19. Roles of Bulk and Surface Chemistry in the Oxygen Exchange Kinetics and Related Properties of Mixed Conducting Perovskite Oxide Electrodes

    PubMed Central

    Perry, Nicola H.; Ishihara, Tatsumi

    2016-01-01

    Mixed conducting perovskite oxides and related structures serving as electrodes for electrochemical oxygen incorporation and evolution in solid oxide fuel and electrolysis cells, respectively, play a significant role in determining the cell efficiency and lifetime. Desired improvements in catalytic activity for rapid surface oxygen exchange, fast bulk transport (electronic and ionic), and thermo-chemo-mechanical stability of oxygen electrodes will require increased understanding of the impact of both bulk and surface chemistry on these properties. This review highlights selected work at the International Institute for Carbon-Neutral Energy Research (I2CNER), Kyushu University, set in the context of work in the broader community, aiming to characterize and understand relationships between bulk and surface composition and oxygen electrode performance. Insights into aspects of bulk point defect chemistry, electronic structure, crystal structure, and cation choice that impact carrier concentrations and mobilities, surface exchange kinetics, and chemical expansion coefficients are emerging. At the same time, an understanding of the relationship between bulk and surface chemistry is being developed that may assist design of electrodes with more robust surface chemistries, e.g., impurity tolerance or limited surface segregation. Ion scattering techniques (e.g., secondary ion mass spectrometry, SIMS, or low energy ion scattering spectroscopy, LEIS) with high surface sensitivity and increasing lateral resolution are proving useful for measuring surface exchange kinetics, diffusivity, and corresponding outer monolayer chemistry of electrodes exposed to typical operating conditions. Beyond consideration of chemical composition, the use of strain and/or a high density of active interfaces also show promise for enhancing performance. PMID:28773978

  20. Saltwater icephobicity: Influence of surface chemistry on saltwater icing

    PubMed Central

    Carpenter, Katherine; Bahadur, Vaibhav

    2015-01-01

    Most studies on icephobicity focus on ice formation with pure water. This manuscript presents studies to understand the influence of surfaces on saltwater ice nucleation and propagation. Experiments are conducted to quantify the influence of surface chemistry on saltwater ice nucleation and to understand the utility of superhydrophobic surfaces for saltwater icephobicity. These experiments are conducted with pure water and two sodium chloride solutions, which represent the salinity of seawater and briny produced water. It is seen that the presence of salt slows down the ice front propagation velocity significantly. Saltwater droplet impact dynamics on superhydrophobic surfaces are also different from pure water. Saltwater droplets retract more and a greater fraction of impacting liquid is repelled from the superhydrophobic surface. It is seen that the greater bounciness of saltwater droplets is a result of slower ice nucleation propagation kinetics. These experiments indicate that superhydrophobic surfaces will have better resistance to impact icing with saltwater than pure water and can remain useful at temperatures as low as −40 °C. Overall, this work is a starting point for further studies on heterogeneous nucleation in saltwater and serves as a bridge between the widely studied freshwater icephobic surfaces and saltwater-related applications. PMID:26626958

  1. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

    NASA Astrophysics Data System (ADS)

    Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr2. Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr2. Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr2.

  2. Surface Mass Balance Contributions to Acceleration of Antarctic Ice Mass Loss during 2003- 2013

    NASA Astrophysics Data System (ADS)

    Seo, K. W.; Wilson, C. R.; Scambos, T. A.; Kim, B. M.; Waliser, D. E.; Tian, B.; Kim, B.; Eom, J.

    2015-12-01

    Recent observations from satellite gravimetry (the GRACE mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6±7.2 GTon/yr2. Of this total, we find that the surface mass balance component is -8.2±2.0 GTon/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8±5.8 GTon/yr2. Correcting for this yields an ice discharge acceleration of -15.1±6.5 GTon/yr2.

  3. A new AMS facility at Inter University Accelerator Centre, New Delhi

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Chopra, S.; Pattanaik, J. K.; Ojha, S.; Gargari, S.; Joshi, R.; Kanjilal, D.

    2015-10-01

    Inter University Accelerator Centre (IUAC), a national facility of government of India, is having a 15UD Pelletron accelerator for multidisciplinary ion beam based research programs. Recently, a new accelerator mass spectrometry (AMS) facility has been developed after incorporating many changes in the existing 15UD Pelletron accelerator. A clean chemistry laboratory for 10Be and 26Al with all the modern facilities has also been developed for the chemical processing of samples. 10Be measurements on sediment samples, inter laboratory comparison results and 26Al measurements on standard samples are presented in this paper. In addition to the 10Be and 26Al AMS facilities, a new 14C AMS facility based on a dedicated 500 kV tandem ion accelerator with two cesium sputter ion sources, is also being setup at IUAC.

  4. A Thematic Review of Studies into the Effectiveness of Context-Based Chemistry Curricula

    NASA Astrophysics Data System (ADS)

    Ültay, Neslihan; Çalık, Muammer

    2012-12-01

    Context-based chemistry education aims at making connections between real life and the scientific content of chemistry courses. The purpose of this study was to evaluate context-based chemistry studies. In looking for the context-based chemistry studies, the authors entered the keywords `context-based', `contextual learning' and `chemistry education' in well-known databases (i.e. Academic Search Complete, Education Research Complete, ERIC, Springer LINK Contemporary). Further, in case the computer search by key words may have missed a rather substantial part of the important literature in the area, the authors also conducted a hand search of the related journals. To present a detailed thematic review of context-based chemistry studies, a matrix was used to summarize the findings by focusing on insights derived from the related studies. The matrix incorporates the following themes: needs, aims, methodologies, general knowledge claims, and implications for teaching and learning, implications for curriculum development and suggestions for future research. The general knowledge claims investigated in this paper were: (a) positive effects of the context-based chemistry studies; (b) caveats, both are examined in terms of students' attitudes and students' understanding/cognition. Implications were investigated for practice in context- based chemistry studies, for future research in context- based chemistry studies, and for curriculum developers in context- based chemistry studies. Teachers of context-based courses claimed that the application of the context-based learning approach in chemistry education improved students' motivation and interest in the subject. This seems to have generated an increase in the number of the students who wish to continue chemistry education at higher levels. However, despite the fact that the majority of the studies have reported advantages of context-based chemistry studies, some of them have also referred to pitfalls, i.e. dominant

  5. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.

    2012-01-01

    Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

  6. Controls on surface water chemistry in the upper Merced River basin, Yosemite National Park, California

    USGS Publications Warehouse

    Clow, D.W.; Mast, M.A.; Campbell, D.H.

    1996-01-01

    Surface water draining granitic bedrock in Yosemite National Park exhibits considerable variability in chemical composition, despite the relative homogeneity of bedrock chemistry. Other geological factors, including the jointing and distribution of glacial till, appear to exert strong controls on water composition. Chemical data from three surface water surveys in the upper Merced River basin conducted in August 1981, June 1988 and August 1991 were analysed and compared with mapped geological, hydrological and topographic features to identify the solute sources and processes that control water chemistry within the basin during baseflow. Water at most of the sampling sites was dilute, with alkalinities ranging from 26 to 77 ??equiv. 1-1. Alkalinity was much higher in two subcatchments, however, ranging from 51 to 302 ??equiv. 1-1. Base cations and silica were also significantly higher in these two catchments than in the rest of the watershed. Concentrations of weathering products in surface water were correlated to the fraction of each subcatchment underlain by surficial material, which is mostly glacial till. Silicate mineral weathering is the dominant control on concentrations of alkalinity, silica and base cations, and ratios of these constituents in surface water reflect the composition of local bedrock, Chloride concentrations in surface water samples varied widely, ranging from <1 to 96 ??equiv. 1-1. The annual volume-weighted mean chloride concentration in the Merced River at the Happy Isles gauge from 1968 to 1990 was 26 ??equiv. 1-1, which was five times higher than in atmospheric deposition (4-5 ??equiv. 1-1), suggesting that a source of chloride exists within the watershed. Saline groundwater springs, whose locations are probably controlled by vertical jointing in the bedrock, are the most likely source of the chloride. Sulphate concentrations varied much less than most other solutes, ranging from 3 to 14 ??equiv. 1-1. Concentrations of sulphate in

  7. Accelerator-based neutrino oscillation experiments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harris, Deborah A.; /Fermilab

    2007-12-01

    Neutrino oscillations were first discovered by experiments looking at neutrinos coming from extra-terrestrial sources, namely the sun and the atmosphere, but we will be depending on earth-based sources to take many of the next steps in this field. This article describes what has been learned so far from accelerator-based neutrino oscillation experiments, and then describe very generally what the next accelerator-based steps are. In section 2 the article discusses how one uses an accelerator to make a neutrino beam, in particular, one made from decays in flight of charged pions. There are several different neutrino detection methods currently in use,more » or under development. In section 3 these are presented, with a description of the general concept, an example of such a detector, and then a brief discussion of the outstanding issues associated with this detection technique. Finally, section 4 describes how the measurements of oscillation probabilities are made. This includes a description of the near detector technique and how it can be used to make the most precise measurements of neutrino oscillations.« less

  8. Surface microstructure and chemistry of polyimide by single pulse ablation of picosecond laser

    NASA Astrophysics Data System (ADS)

    Du, Qifeng; Chen, Ting; Liu, Jianguo; Zeng, Xiaoyan

    2018-03-01

    Polyimide (PI) surface was ablated by the single pulse of picosecond laser, and the effects of laser wavelength (λ= 355 nm and 1064 nm) and fluence on surface microstructure and chemistry were explored. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the concave of concentric ring and the convex of porous circular disk, were generated by 355 nm and 1064 nm picosecond laser ablation, respectively. X-ray photoelectron spectroscopy (XPS) characterization indicated that due to the high peak energy density of picosecond laser, oxygen and nitrogen from the ambient were incorporated into the PI surface mainly in the form of Cdbnd O and Csbnd Nsbnd C groups. Thus, both of the O/C and N/C atomic content ratios increased, but the increase caused by 1064 nm wavelength laser was larger. It inferred that the differences of PI surface microstructures and chemistry resulted from different laser parameters were related to different laser-matter interaction effects. For 355 nm picosecond laser, no obvious thermal features were observed and the probable ablation process of PI was mainly governed by photochemical effect; while for 1064 nm picosecond laser, obvious thermal feature appeared and photothermal effect was thought to be dominant.

  9. Effect of accelerated ageing and surface sealing on the permanent deformation of auto-polymerising soft linings.

    PubMed

    da Silva, Joaquim; Takahashi, Jessica; Nuňez, Juliana; Consani, Rafael; Mesquita, Marcelo

    2012-09-01

    To compare the effects of different ageing methods on the permanent deformation of two permanent soft liners. The materials selected were auto-polymerising acrylic resin and silicone-based reliners. Sealer coating was also evaluated. Sixty specimens of each reliner were manufactured (12.7 mm diameter and 19 mm length). Specimens were randomly distributed into 12 groups (n = 10) and submitted to one of the accelerated ageing processes. Permanent deformation tests were conducted with a mechanical device described within the American Dental Association specification number 18 with a compressive load of 750 gf applied for 30 s. All data were submitted for statistical analysis. Mann-Whitney test compared the effect of the surface sealer on each material and the permanent deformation of the materials in the same ageing group (p = 0.05). Kruskal-Wallis and Dunn tests compared all ageing groups of each material (p = 0.05). The silicone-based reliner presented a lower permanent deformation than the acrylic resin-based reliner, regardless of the ageing procedure. The surface sealer coating was effective only for the thermocycled silicone group and the accelerated ageing processes affected only the permanent deformation of the acrylic resin-based material. The silicone-based reliner presented superior elastic properties and the thermocycling was more effective in ageing the materials. © 2010 The Gerodontology Society and John Wiley & Sons A/S.

  10. An in situ accelerator-based diagnostic for plasma-material interactions science on magnetic fusion devices.

    PubMed

    Hartwig, Zachary S; Barnard, Harold S; Lanza, Richard C; Sorbom, Brandon N; Stahle, Peter W; Whyte, Dennis G

    2013-12-01

    This paper presents a novel particle accelerator-based diagnostic that nondestructively measures the evolution of material surface compositions inside magnetic fusion devices. The diagnostic's purpose is to contribute to an integrated understanding of plasma-material interactions in magnetic fusion, which is severely hindered by a dearth of in situ material surface diagnosis. The diagnostic aims to remotely generate isotopic concentration maps on a plasma shot-to-shot timescale that cover a large fraction of the plasma-facing surface inside of a magnetic fusion device without the need for vacuum breaks or physical access to the material surfaces. Our instrument uses a compact (~1 m), high-current (~1 milliamp) radio-frequency quadrupole accelerator to inject 0.9 MeV deuterons into the Alcator C-Mod tokamak at MIT. We control the tokamak magnetic fields--in between plasma shots--to steer the deuterons to material surfaces where the deuterons cause high-Q nuclear reactions with low-Z isotopes ~5 μm into the material. The induced neutrons and gamma rays are measured with scintillation detectors; energy spectra analysis provides quantitative reconstruction of surface compositions. An overview of the diagnostic technique, known as accelerator-based in situ materials surveillance (AIMS), and the first AIMS diagnostic on the Alcator C-Mod tokamak is given. Experimental validation is shown to demonstrate that an optimized deuteron beam is injected into the tokamak, that low-Z isotopes such as deuterium and boron can be quantified on the material surfaces, and that magnetic steering provides access to different measurement locations. The first AIMS analysis, which measures the relative change in deuterium at a single surface location at the end of the Alcator C-Mod FY2012 plasma campaign, is also presented.

  11. The relative effect of surface strontium chemistry and super-hydrophilicity on the early osseointegration of moderately rough titanium surface in the rabbit femur.

    PubMed

    Park, Jin-Woo; Kwon, Tae-Geon; Suh, Jo-Young

    2013-06-01

    It is unclear whether surface bioactive chemistry or hydrophilicity plays a more dominant role in the osseointegration of micro-structured titanium implants having the same surface topography at the micrometer and submicrometer scales. To understand their comparative effect on enhancing the early osseointegration of micro-rough-surfaced implants, this study compared the bone healing-promoting effect of surface strontium (Sr) chemistry that has been shown in numerous studies to super-hydrophilicity in the early osseointegration of moderately rough-surfaced clinical oral implants (SLA(®) implant) in rabbit cancellous bone. Hydrothermal treatment was performed to incorporate Sr ions into the surface of clinical SLA implants (SLA/Sr implant). The surface characteristics were evaluated by using field emission-scanning electron microscopy, X-ray photoelectron spectroscopy and optical profilometry. Twenty screw implants (10 control and 10 experimental) were placed in the femoral condyles of 10 New Zealand White rabbits. The early osseointegration of the SLA/Sr implant was compared with a chemically modified super-hydrophilic SLA implant (SLActive(®) implant) by histomorphometric and resonance frequency analysis after 2 weeks of implantation. The SLA/Sr and SLActive implants exhibited an identical surface topography and average R(a) values at the micron and submicron scales. The SLA/Sr implant displayed a high amount of surface Sr content (15.6 at.%). There was no significant difference in the implant stability quotient (ISQ) values between the two groups. However, histomorphometric analysis revealed a significantly higher bone-to-implant contact percentage in the SLA/Sr implants compared with the SLActive implants in rabbit cancellous bone (P < 0.01). The results indicate that the surface Sr chemistry surpasses the effect of super-hydrophilicity in promoting the early bone apposition of moderately rough Ti surface in cancellous bone. © 2012 John Wiley & Sons A/S.

  12. Laser-plasma accelerator and femtosecond photon sources-based ultrafast radiation chemistry and biophysics

    NASA Astrophysics Data System (ADS)

    Gauduel, Y. A.

    2017-02-01

    The initial distribution of energy deposition triggered by the interaction of ionizing radiations (far UV and X rays, electron, proton and accelerated ions) with molecular targets or integrated biological systems is often decisive for the spatio-temporal behavior of radiation effects that take place on several orders of magnitude. This contribution deals with an interdisciplinary approach that concerns cutting-edge advances on primary radiation events, considering the potentialities of innovating strategies based on ultrafast laser science, from femtosecond photon sources to laser-driven relativistic particles acceleration. Recent advances of powerful TW laser sources (~ 1019 Wcm-2) and laser-plasma interactions providing ultrashort relativistic particle beams in the energy domain 2.5-150 MeV open exciting opportunities for the development of high-energy radiation femtochemistry (HERF). Early radiation damages being dependent on the survival probability of secondary electrons and radial distribution of short-lived radicals inside ionization clusters, a thorough knowledge of these processes involves the real-time probing of primary events in the temporal range 10-14-10-11 s. In the framework of a closed synergy between low-energy radiation femtochemistry (LERF) and the emerging domain of HERF, the paper focuses on early phenomena that occur in the prethermal regime of low-energy secondary electrons, considering very short-lived quantum effects in aqueous environments. A high dose-rate delivered by femtosecond electron beam (~ 1011-1013 Gy s-1) can be used to investigate early radiation processes in native ionization tracks, down to 10-12 s and 10-9 m. We explain how this breakthrough favours the innovating development of real-time nanodosimetry in biologically relevant environments and open new perspectives for spatio-temporal radiation biophysics. The emerging domain of HERF would provide guidance for understanding the specific bioeffects of ultrashort particle

  13. A Thematic Review of Studies into the Effectiveness of Context-Based Chemistry Curricula

    ERIC Educational Resources Information Center

    Ultay, Neslihan; Calik, Muammer

    2012-01-01

    Context-based chemistry education aims at making connections between real life and the scientific content of chemistry courses. The purpose of this study was to evaluate context-based chemistry studies. In looking for the context-based chemistry studies, the authors entered the keywords "context-based", "contextual learning" and "chemistry…

  14. Adsorption of dyes by ACs prepared from waste tyre reinforcing fibre. Effect of texture, surface chemistry and pH.

    PubMed

    Acevedo, Beatriz; Rocha, Raquel P; Pereira, Manuel F R; Figueiredo, José L; Barriocanal, Carmen

    2015-12-01

    This paper compares the importance of the texture and surface chemistry of waste tyre activated carbons in the adsorption of commercial dyes. The adsorption of two commercial dyes, Basic Astrazon Yellow 7GLL and Reactive Rifafix Red 3BN on activated carbons made up of reinforcing fibres from tyre waste and low-rank bituminous coal was studied. The surface chemistry of activated carbons was modified by means of HCl-HNO3 treatment in order to increase the number of functional groups. Moreover, the influence of the pH on the process was also studied, this factor being of great importance due to the amphoteric characteristics of activated carbons. The activated carbons made with reinforcing fibre and coal had the highest SBET, but the reinforcing fibre activated carbon samples had the highest mesopore volume. The texture of the activated carbons was not modified upon acid oxidation treatment, unlike their surface chemistry which underwent considerable modification. The activated carbons made with a mixture of reinforcing fibre and coal experienced the largest degree of oxidation, and so had more acid surface groups. The adsorption of reactive dye was governed by the mesoporous volume, whilst surface chemistry played only a secondary role. However, the surface chemistry of the activated carbons and dispersive interactions played a key role in the adsorption of the basic dye. The adsorption of the reactive dye was more favored in a solution of pH 2, whereas the basic dye was adsorbed more easily in a solution of pH 12. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Ground- and Surface-Water Chemistry of Handcart Gulch, Park County, Colorado, 2003-2006

    USGS Publications Warehouse

    Verplanck, Philip L.; Manning, Andrew H.; Kimball, Briant A.; McCleskey, R. Blaine; Runkel, Robert L.; Caine, Jonathan S.; Adams, Monique; Gemery-Hill, Pamela A.; Fey, David L.

    2008-01-01

    As part of a multidisciplinary project to determine the processes that control ground-water chemistry and flow in mineralized alpine environments, ground- and surface-water samples from Handcart Gulch, Colorado were collected for analysis of inorganic solutes and water and dissolved sulfate stable isotopes in selected samples. The primary aim of this study was to document variations in ground-water chemistry in Handcart Gulch and to identify changes in water chemistry along the receiving stream of Handcart Gulch. Water analyses are reported for ground-water samples collected from 12 wells in Handcart Gulch, Colorado. Samples were collected between August 2003 and October 2005. Water analyses for surface-water samples are reported for 50 samples collected from Handcart Gulch and its inflows during a low-flow tracer injection on August 6, 2003. In addition, water analyses are reported for three other Handcart Gulch stream samples collected in September 2005 and March 2006. Reported analyses include field parameters (pH, specific conductance, temperature, dissolved oxygen, and Eh), major and trace constituents, oxygen and hydrogen isotopic composition of water and oxygen and sulfur isotopic composition of dissolved sulfate. Ground-water samples from this study are Ca-SO4 type and range in pH from 2.5 to 6.8. Most of the samples (75 percent) have pH values between 3.3 and 4.3. Surface water samples are also Ca-SO4 type and have a narrower range in pH (2.7?4.0). Ground- and surface-water samples vary from relatively dilute (specific conductance of 68 ?S/cm) to concentrated (specific conductance of 2,000 ?S/cm).

  16. On the Hiatus in the Acceleration of Tropical Upwelling Since the Beginning of the 21st Century

    NASA Technical Reports Server (NTRS)

    Aschmann, J.; Burrows, J. P.; Gebhardt, C.; Rozanov, A.; Hommel, R.; Weber, M.; Thompson, A. M.

    2014-01-01

    Chemistry-climate models predict an acceleration of the upwelling branch of the Brewer-Dobson circulation as a consequence of increasing global surface temperatures, resulting from elevated levels of atmospheric greenhouse gases. The observed decrease of ozone in the tropical lower stratosphere during the last decades of the 20th century is consistent with the anticipated acceleration of upwelling. However, more recent satellite observations of ozone reveal that this decrease has unexpectedly stopped in the first decade of the 21st century, challenging the implicit assumption of a continuous acceleration of tropical upwelling. In this study we use three decades of chemistry transport-model simulations (1980-2013) to investigate this phenomenon and resolve this apparent contradiction. Our model reproduces the observed tropical lower stratosphere ozone record, showing a significant decrease in the early period followed by a statistically robust trend-change after 2002. We demonstrate that this trend-change is correlated with corresponding changes in the vertical transport and conclude that a hiatus in the acceleration of tropical upwelling occurred during the last decade.

  17. Bacterial resistance of self-assembled surfaces using PPOm-b-PSBMAn zwitterionic copolymer - concomitant effects of surface topography and surface chemistry on attachment of live bacteria.

    PubMed

    Hsiao, Sheng-Wen; Venault, Antoine; Yang, Hui-Shan; Chang, Yung

    2014-06-01

    Three well-defined diblock copolymers made of poly(sulfobetaine methacrylate) (poly(SBMA)) and poly(propylene oxide) (PPO) groups were synthesized by atom transfer radical polymerization (ATRP) method. They were physically adsorbed onto three types of surfaces having different topography, including smooth flat surface, convex surface, and indented surface. Chemical state of surfaces was characterized by XPS while the various topographies were examined by SEM and AFM. Hydrophilicity of surfaces was dependent on both the surface chemistry and the surface topography, suggesting that orientation of copolymer brushes can be tuned in the design of surfaces aimed at resisting bacterial attachment. Escherichia coli, Staphylococcus epidermidis, Streptococcus mutans and Escherichia coli with green fluorescent protein (E. coli GFP) were used in bacterial tests to assess the resistance to bacterial attachment of poly(SBMA)-covered surfaces. Results highlighted a drastic improvement of resistance to bacterial adhesion with the increasing of poly(SBMA) to PPO ratio, as well as an important effect of surface topography. The chemical effect was directly related to the length of the hydrophilic moieties. When longer, more water could be entrapped, leading to improved anti-bacterial properties. The physical effect impacted on the orientation of the copolymer brushes, as well as on the surface contact area available. Convex surfaces as well as indented surfaces wafer presented the best resistance to bacterial adhesion. Indeed, bacterial attachment was more importantly reduced on these surfaces compared with smooth surfaces. It was explained by the non-orthogonal orientation of copolymer brushes, resulting in a more efficient surface coverage of zwitterionic molecules. This work suggests that not only the control of surface chemistry is essential in the preparation of surfaces resisting bacterial attachment, but also the control of surface topography and orientation of antifouling

  18. Soil Studies: Applying Acid-Base Chemistry to Environmental Analysis.

    ERIC Educational Resources Information Center

    West, Donna M.; Sterling, Donna R.

    2001-01-01

    Laboratory activities for chemistry students focus attention on the use of acid-base chemistry to examine environmental conditions. After using standard laboratory procedures to analyze soil and rainwater samples, students use web-based resources to interpret their findings. Uses CBL probes and graphing calculators to gather and analyze data and…

  19. Response of surface water chemistry to reduced levels of acid precipitation: Comparison of trends in two regions of New York, USA

    USGS Publications Warehouse

    Burns, Douglas A.; McHale, M.R.; Driscoll, C.T.; Roy, K.M.

    2006-01-01

    In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984-2001 and 1992-2001) and surface water chemistry (1992-2001) were determined in two of the most acid-sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO42-), nitrate (NO3-), and base cation (CB) concentrations and increasing pH during 1984-2001, but few significant trends during 1992-2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO42- concentrations at all sites, and decreasing trends in NO3-, CB, and H+ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid-neutralizing capacity (ANC increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO42- trends, but it caused several significant non-flow-corrected trends in NO3- and ANC to become non-significant, suggesting that trend results for flow-sensitive constituents are affected by flow-related climate variation. SO42- concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation-surface water comparisons, reflecting a strong link between S emissions, precipitation SO42- concentrations, and the processes that affect S cycling within these regions. NO3- and H+ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation-surface water comparisons, indicating that variation in local-scale processes driven by factors such as climate are affecting trends in acid-base chemistry in these two regions. Copyright ?? 2005 John Wiley & Sons, Ltd.

  20. Surface Chemistry and Nano-/Microstructure Engineering on Photocatalytic In2S3 Nanocrystals.

    PubMed

    Berestok, Taisiia; Guardia, Pablo; Portals, Javier Blanco; Estradé, Sònia; Llorca, Jordi; Peiró, Francesca; Cabot, Andreu; Brock, Stephanie L

    2018-06-05

    Colloidal nanocrystals (NCs) compete with molecular catalysts in the field of homogenous catalysis, offering easier recyclability and a number of potentially advantageous functionalities, such as tunable band gaps, plasmonic properties, or a magnetic moment. Using high-throughput printing technologies, colloidal NCs can also be supported onto substrates to produce cost-effective electronic, optoelectronic, electrocatalytic, and sensing devices. For both catalytic and technological application, NC surface chemistry and supracrystal organization are key parameters determining final performance. Here, we study the influence of the surface ligands and the NC organization on the catalytic properties of In 2 S 3 , both as a colloid and as a supported layer. As a colloid, NCs stabilized by inorganic ligands show the highest photocatalytic activities, which we associate with their large and more accessible surfaces. On the other hand, when NCs are supported on a substrate, their organization becomes an essential parameter determining performance. For instance, NC-based films produced through a gelation process provided five-fold higher photocurrent densities than those obtained from dense films produced by the direct printing of NCs.

  1. Electrospray Charging of Minerals: Surface Chemistry and Applications to High-Velocity Microparticle Impacts

    NASA Astrophysics Data System (ADS)

    Daly, T.; Call, S.; Austin, D. E.

    2010-12-01

    Electrospray is a soft ionization technique commonly used to charge large biomolecules; it has, however, also been applied to inorganic compounds. We are extending this technique to mineral microparticles. Electrospray-charged mineral microparticles are interesting in the context of surface science because surface chemistry dictates where and how charge carriers can bond to mineral surfaces. In addition, using electrospray to charge mineral particles allows these particles to be electrostatically accelerated as projectiles in high- and hyper-velocity impacts. Since current techniques for producing high- and hyper-velocity microparticle impacts are largely limited to metal or metal-coated projectiles, using minerals as projectiles is a significant innovation. Electrospray involves three steps: creation of charged droplets containing solute/particles, evaporation and bifurcation of droplets, and desolvation of the solute/particles. An acidified solution is slowly pumped through a needle in a strong DC field, which causes the solution to break into tiny, charged droplets laden with protons. Solvent evaporates from the electrosprayed droplets as they move through the electric field toward a grounded plate, causing the charge on the droplet to increase relative to its mass. When the electrosprayed droplet’s charge becomes such that the droplet is no longer stable, it bifurcates, and each of the resulting droplets carries some of the original droplet’s charge. Evaporation and bifurcation continues until the solute particle is completely desolvated. The result is a protonated solute molecule or particle. We built an instrument that electrosprays particles into vacuum and measures them using an image charge detector. Mineral microparticles were prepared by grinding natural mineral samples to ~2 µm diameter. These microparticles are then added to a 4:1 methanol:water solution to create a 0.005% w/v suspension. The suspension is electrosprayed into vacuum, where the

  2. Insight into Chemistry on Cloud/Aerosol Water Surfaces.

    PubMed

    Zhong, Jie; Kumar, Manoj; Francisco, Joseph S; Zeng, Xiao Cheng

    2018-05-15

    Cloud/aerosol water surfaces exert significant influence over atmospheric chemical processes. Atmospheric processes at the water surface are observed to follow mechanisms that are quite different from those in the gas phase. This Account summarizes our recent findings of new reaction pathways on the water surface. We have studied these surface reactions using Born-Oppenheimer molecular dynamics simulations. These studies provide useful information on the reaction time scale, the underlying mechanism of surface reactions, and the dynamic behavior of the product formed on the aqueous surface. According to these studies, the aerosol water surfaces confine the atmospheric species into a specific orientation depending on the hydrophilicity of atmospheric species or the hydrogen-bonding interactions between atmospheric species and interfacial water. As a result, atmospheric species are activated toward a particular reaction on the aerosol water surface. For example, the simplest Criegee intermediate (CH 2 OO) exhibits high reactivity toward the interfacial water and hydrogen sulfide, with the reaction times being a few picoseconds, 2-3 orders of magnitude faster than that in the gas phase. The presence of interfacial water molecules induces proton-transfer-based stepwise pathways for these reactions, which are not possible in the gas phase. The strong hydrophobicity of methyl substituents in larger Criegee intermediates (>C1), such as CH 3 CHOO and (CH 3 ) 2 COO, blocks the formation of the necessary prereaction complexes for the Criegee-water reaction to occur at the water droplet surface, which lowers their proton-transfer ability and hampers the reaction. The aerosol water surface provides a solvent medium for acids (e.g., HNO 3 and HCOOH) to participate in reactions via mechanisms that are different from those in the gas and bulk aqueous phases. For example, the anti-CH 3 CHOO-HNO 3 reaction in the gas phase follows a direct reaction between anti-CH 3 CHOO and HNO 3

  3. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013.

    PubMed

    Seo, Ki-Weon; Wilson, Clark R; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr 2 . Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr 2 . However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr 2 . Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr 2 .

  4. Surface chemistry of rare-earth oxide surfaces at ambient conditions: reactions with water and hydrocarbons

    NASA Astrophysics Data System (ADS)

    Külah, Elçin; Marot, Laurent; Steiner, Roland; Romanyuk, Andriy; Jung, Thomas A.; Wäckerlin, Aneliia; Meyer, Ernst

    2017-03-01

    Rare-earth (RE) oxide surfaces are of significant importance for catalysis and were recently reported to possess intrinsic hydrophobicity. The surface chemistry of these oxides in the low temperature regime, however, remains to a large extent unexplored. The reactions occurring at RE surfaces at room temperature (RT) in real air environment, in particular, in presence of polycyclic aromatic hydrocarbons (PAHs), were not addressed until now. Discovering these reactions would shed light onto intermediate steps occurring in automotive exhaust catalysts before reaching the final high operational temperature and full conversion of organics. Here we first address physical properties of the RE oxide, nitride and fluoride surfaces modified by exposure to ambient air and then we report a room temperature reaction between PAH and RE oxide surfaces, exemplified by tetracene (C18H12) on a Gd2O3. Our study evidences a novel effect - oxidation of higher hydrocarbons at significantly lower temperatures (~300 K) than previously reported (>500 K). The evolution of the surface chemical composition of RE compounds in ambient air is investigated and correlated with the surface wetting. Our surprising results reveal the complex behavior of RE surfaces and motivate follow-up studies of reactions between PAH and catalytic surfaces at the single molecule level.

  5. Anticorrelation between Surface and Subsurface Point Defects and the Impact on the Redox Chemistry of TiO2(110)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yoon, Yeohoon; Du, Yingge; Garcia, Juan C.

    2015-02-02

    Using combination of STM, DFT and SIMS, we explored the interplay and relative impact of surface vs. subsurface defects on the surface chemistry of rutile TiO2. STM results show that surface O vacancies (VO’s) are virtually absent in the vicinity of positively-charged subsurface point-defects. This observation is consistent with DFT calculations of impact of subsurface defect proximity on VO formation energy. To monitor the influence of such lateral anticorrelation on surface redox chemistry, a test reaction of the dissociative adsorption of O2 is employed, which is observed to be suppressed around them. DFT results attribute this to a perceived absencemore » of the intrinsic (Ti) (and likely extrinsic) interstitials in the nearest subsurface layer beneath “inhibited” areas. We also postulate that the entire nearest subsurface region could be voided of any charged point-defects, whereas prevalent VO’s are largely responsible for mediation of the redox chemistry at reduced TiO2(110) surface.« less

  6. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    NASA Astrophysics Data System (ADS)

    Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.

    2016-02-01

    The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent data set for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total data set of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regionally representative locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This data set is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily 8-hour average (MDA8), sum of means over 35 ppb (daily maximum 8-h; SOMO35), accumulated ozone exposure above a threshold of 40 ppbv (AOT40), and metrics related to air quality regulatory thresholds. Gridded data sets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi: 10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  7. Gridded global surface ozone metrics for atmospheric chemistry model evaluation

    NASA Astrophysics Data System (ADS)

    Sofen, E. D.; Bowdalo, D.; Evans, M. J.; Apadula, F.; Bonasoni, P.; Cupeiro, M.; Ellul, R.; Galbally, I. E.; Girgzdiene, R.; Luppo, S.; Mimouni, M.; Nahas, A. C.; Saliba, M.; Tørseth, K.; Wmo Gaw, Epa Aqs, Epa Castnet, Capmon, Naps, Airbase, Emep, Eanet Ozone Datasets, All Other Contributors To

    2015-07-01

    The concentration of ozone at the Earth's surface is measured at many locations across the globe for the purposes of air quality monitoring and atmospheric chemistry research. We have brought together all publicly available surface ozone observations from online databases from the modern era to build a consistent dataset for the evaluation of chemical transport and chemistry-climate (Earth System) models for projects such as the Chemistry-Climate Model Initiative and Aer-Chem-MIP. From a total dataset of approximately 6600 sites and 500 million hourly observations from 1971-2015, approximately 2200 sites and 200 million hourly observations pass screening as high-quality sites in regional background locations that are appropriate for use in global model evaluation. There is generally good data volume since the start of air quality monitoring networks in 1990 through 2013. Ozone observations are biased heavily toward North America and Europe with sparse coverage over the rest of the globe. This dataset is made available for the purposes of model evaluation as a set of gridded metrics intended to describe the distribution of ozone concentrations on monthly and annual timescales. Metrics include the moments of the distribution, percentiles, maximum daily eight-hour average (MDA8), SOMO35, AOT40, and metrics related to air quality regulatory thresholds. Gridded datasets are stored as netCDF-4 files and are available to download from the British Atmospheric Data Centre (doi:10.5285/08fbe63d-fa6d-4a7a-b952-5932e3ab0452). We provide recommendations to the ozone measurement community regarding improving metadata reporting to simplify ongoing and future efforts in working with ozone data from disparate networks in a consistent manner.

  8. Control of Surface Chemistry, Substrate Stiffness, and Cell Function in a Novel Terpolymer Methacrylate Library

    PubMed Central

    Joy, Abraham; Cohen, Daniel M.; Luk, Arnold; Anim-Danso, Emmanuel; Chen, Christopher; Kohn, Joachim

    2011-01-01

    A focused library of methacrylate terpolymers was synthesized to explore the effects of varying surface chemistry and adhesive peptide ligands on cell function. The chemical diversity of methacrylate monomers enabled construction of a library of polymers in which one can systematically vary the chemical composition to achieve a wide range of contact angle, Young's modulus, and Tg values. Furthermore, the materials were designed to allow surface immobilization of bioactive peptides. We then examined the effects of these material compositions on protein adsorption and cell attachment, proliferation, and differentiation. We observed that chemical composition of the polymers was an important determinant for NIH 3T3 cell attachment and proliferation, as well as human mesenchymal stem cell differentiation, and correlated directly with the ability of the polymers to adsorb proteins that mediate cell adhesion. Importantly, functionalization of the methacrylate terpolymer library with an adhesive GRGDS peptide normalized cellular responses. RGD-functionalized polymers uniformly exhibited robust attachment, proliferation, and differentiation irrespective of the underlying substrate chemistry. These studies provide a library-based approach to rapidly explore the biological functionality of biomaterials with a wide range of compositions, and highlights the importance of cell and protein cell adhesion in predicting their performance. PMID:21226505

  9. Implementation of Problem-Based Learning in Environmental Chemistry

    ERIC Educational Resources Information Center

    Jansson, Stina; So¨derstro¨m, Hanna; Andersson, Patrik L.; Nording, Malin L.

    2015-01-01

    Environmental Chemistry covers a range of topics within the discipline of chemistry, from toxicology to legislation, which warrants interdisciplinary study. Consequently, problem-based learning (PBL), a style of student-centered learning which facilitates the integration of multiple subjects, was investigated to determine if it would be a more…

  10. Chemistry and catalysis at the surface of nanomaterials

    NASA Astrophysics Data System (ADS)

    White, Brian Edward

    This thesis will delve into three main areas of nanomaterials research: (I) Designing, building, and utilizing a chemical vapor deposition (CVD) system for the growth of CNTs; (II) Aqueous suspensions of carbon nanotubes (CNT) solubilized by various surfactants, and the oxidative chemistry that can occur at CNT surfaces; (III) Catalytic CO oxidation over supported Cu2O nanoparticle systems. An introduction to nanomaterials in general, with a particular emphasis on carbon nanotubes and nanoparticles will be given in Chapter one. Chapter two provides a summary of common techniques used to grow carbon nanotubes, and introduces a new method we have developed. This method is based on previous chemical vapor deposition techniques, but uses liquids, specifically ethanol, as the carbon source. Using ethanol has several advantages, including ease of use and safety, as well as chemical benefits. Our new process affords long, aligned, single-walled nanotubes, with a relatively narrow diameter distribution. This method can also be used to grow CNTs across slits, which can then be studied spectroscopically. In Chapter three CNT-surfactant aqueous suspensions will be discussed in depth, including a new robust polymer surfactant. Poly(maleic acid/octyl vinyl ether) (PMAOVE) is stable over a large range of temperatures and pH values, and is well suited for the study of the oxidative chemistry that can occur on SWNT surfaces. Our aqueous suspensions were found to be quite stable by zeta potential studies and their emissive properties exhibited a pH dependence, quenching at higher concentrations of H+. We attribute this dependence to chemisorbed oxygen and its protonation at lower pH values. By heating the suspensions of SWNTs, O2 can be driven off, thus eliminating the dependence on pH. We also reproducibly add oxygen back into the system in the form of 1DeltaO2 , obtained from an endoperoxide. This method allows us to calculate the number of oxygen molecules needed for

  11. Influence of changing water sources and mineral chemistry on the everglades ecosystem

    USGS Publications Warehouse

    McCormick, P.V.; Harvey, J.W.; Crawford, E.S.

    2011-01-01

    Human influences during the previous century increased mineral inputs to the Florida Everglades by changing the sources and chemistry of surface inflows. Biogeochemical responses to this enrichment include changes in the availability of key limiting nutrients such as P, the potential for increased turnover of nutrient pools due to accelerated plant decomposition, and increased rates of mercury methylation associated with sulfate enrichment. Mineral enrichment has also been linked to the loss of sensitive macrophyte species, although dominant Everglades species appear tolerant of a broad range of mineral chemistry. Shifts in periphyton community composition and function provide an especially sensitive indicator of mineral enrichment. Understanding the influence of mineral chemistry on Everglades processes and biota may improve predictions of ecosystem responses to ongoing hydrologic restoration efforts and provide guidelines for protecting remaining mineral-poor areas of this peatland. Copyright ?? 2011 Taylor & Francis Group, LLC.

  12. IMMUNOBLOT ANALYSIS OF PROTEINS ASSOCIATED WITH SELF-ASSEMBLED MONOLAYER SURFACES OF DEFINED CHEMISTRIES

    PubMed Central

    Cornelius, Rena M.; Shankar, Sucharita P.; Brash, John L.; Babensee, Julia E.

    2011-01-01

    Intact and fragmented proteins, eluted from self assembled monolayer (SAM) surfaces of alkanethiols of different chemistries (-CH3, -OH, -COOH, -NH2 ), following exposure to human plasma (HP) or human serum (HS), were examined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting techniques. The SAM surfaces were incubated for 1 hour with 10% (v/v) sterile-filtered heat-inactivated (h.i.) HS or 1% (v/v) sterile-filtered h.i. HP preparations [both in phosphate buffered saline (PBS)]. Adsorbed proteins were eluted using 10% SDS/2.3% dithioerythritol for characterization of protein profiles. The type of incubating medium may be an important determinant of adsorbed protein profiles, since some variations were observed in eluates from filtered versus control unfiltered h.i. 10% HS or 1% HP. Albumin and apolipoprotein A1 were consistently detected in both filtered h.i 10% HS and 1% HP eluates from all SAM surfaces and from control tissue culture-treated polystyrene (TCPS). Interestingly, Factor H and Factor I, antithrombin, prothrombin, high molecular weight kininogen (HMWK) and IgG were present in eluates from OH, COOH and NH2 SAM surfaces and in eluates from TCPS, but not in eluates from CH3 SAM surfaces, following exposure to filtered h.i. 10% HS. These results suggest that CH3 SAM surfaces were the least pro-inflammatory of all SAM surfaces. Overall, similar trends were observed in the profiles of proteins eluted from surfaces exposed to filtered 10% HS or 1% HP. However the unique profiles of adsorbed proteins on different SAM surface chemistries may be related to their differential interactions with cells, including immune/inflammatory cells. PMID:21509932

  13. Modulation of Protein Fouling and Interfacial Properties at Carbon Surfaces via Immobilization of Glycans Using Aryldiazonium Chemistry

    PubMed Central

    Zen, Federico; Angione, M. Daniela; Behan, James A.; Cullen, Ronan J.; Duff, Thomas; Vasconcelos, Joana M.; Scanlan, Eoin M.; Colavita, Paula E.

    2016-01-01

    Carbon materials and nanomaterials are of great interest for biological applications such as implantable devices and nanoparticle vectors, however, to realize their potential it is critical to control formation and composition of the protein corona in biological media. In this work, protein adsorption studies were carried out at carbon surfaces functionalized with aryldiazonium layers bearing mono- and di-saccharide glycosides. Surface IR reflectance absorption spectroscopy and quartz crystal microbalance were used to study adsorption of albumin, lysozyme and fibrinogen. Protein adsorption was found to decrease by 30–90% with respect to bare carbon surfaces; notably, enhanced rejection was observed in the case of the tested di-saccharide vs. simple mono-saccharides for near-physiological protein concentration values. ζ-potential measurements revealed that aryldiazonium chemistry results in the immobilization of phenylglycosides without a change in surface charge density, which is known to be important for protein adsorption. Multisolvent contact angle measurements were used to calculate surface free energy and acid-base polar components of bare and modified surfaces based on the van Oss-Chaudhury-Good model: results indicate that protein resistance in these phenylglycoside layers correlates positively with wetting behavior and Lewis basicity. PMID:27108562

  14. Modulation of Protein Fouling and Interfacial Properties at Carbon Surfaces via Immobilization of Glycans Using Aryldiazonium Chemistry

    NASA Astrophysics Data System (ADS)

    Zen, Federico; Angione, M. Daniela; Behan, James A.; Cullen, Ronan J.; Duff, Thomas; Vasconcelos, Joana M.; Scanlan, Eoin M.; Colavita, Paula E.

    2016-04-01

    Carbon materials and nanomaterials are of great interest for biological applications such as implantable devices and nanoparticle vectors, however, to realize their potential it is critical to control formation and composition of the protein corona in biological media. In this work, protein adsorption studies were carried out at carbon surfaces functionalized with aryldiazonium layers bearing mono- and di-saccharide glycosides. Surface IR reflectance absorption spectroscopy and quartz crystal microbalance were used to study adsorption of albumin, lysozyme and fibrinogen. Protein adsorption was found to decrease by 30-90% with respect to bare carbon surfaces; notably, enhanced rejection was observed in the case of the tested di-saccharide vs. simple mono-saccharides for near-physiological protein concentration values. ζ-potential measurements revealed that aryldiazonium chemistry results in the immobilization of phenylglycosides without a change in surface charge density, which is known to be important for protein adsorption. Multisolvent contact angle measurements were used to calculate surface free energy and acid-base polar components of bare and modified surfaces based on the van Oss-Chaudhury-Good model: results indicate that protein resistance in these phenylglycoside layers correlates positively with wetting behavior and Lewis basicity.

  15. Effect of Gold Nanorod Surface Chemistry on Cellular Interactions In Vitro

    DTIC Science & Technology

    2010-09-01

    properties of GNRs on cells. Previous studies on the cytotoxicity of various nanoparticles indicated that surface chemistry has a strong influence on cell...supplemented with 10% fetal bovine serum (FBS, ATCC) and 1% penicillin/streptomycin (pen/strep, Sigma). For nanoparticle exposure, media was supplemented...reagent ( phenazine ethosulfate; PES). Metabolically active cells reduce the MTS compound into a colored formazan product that is soluble in tissue

  16. Rapid in situ generation of two patterned chemoselective surface chemistries from a single hydroxy-terminated surface using controlled microfluidic oxidation.

    PubMed

    Pulsipher, Abigail; Westcott, Nathan P; Luo, Wei; Yousaf, Muhammad N

    2009-06-10

    In this work, we develop a new, rapid and inexpensive method to generate spatially controlled aldehyde and carboxylic acid surface groups by microfluidic oxidation of 11-hydroxyundecylphosphonic acid self-assembled monolayers (SAMs) on indium tin oxide (ITO) surfaces. SAMs are activated and patterned using a reversibly sealable, elastomeric polydimethylsiloxane cassette, fabricated with preformed micropatterns by soft lithography. By flowing the mild oxidant pyridinium chlorochromate through the microchannels, only selected areas of the SAM are chemically altered. This microfluidic oxidation strategy allows for ligand immobilization by two chemistries originating from a single SAM composition. ITO is robust, conductive, and transparent, making it an ideal platform for studying interfacial interactions. We display spatial control over the immobilization of a variety of ligands on ITO and characterize the resulting oxime and amide linkages by electrochemistry, X-ray photoelectron spectroscopy, contact angle, fluorescence microscopy, and atomic force microscopy. This general method may be used with many other materials to rapidly generate patterned and tailored surfaces for studies ranging from molecular electronics to biospecific cell-based assays and biomolecular microarrays.

  17. Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

    NASA Technical Reports Server (NTRS)

    Martin, Randall V.; Fiore, Arlene M.; VanDonkelaar, Aaron

    2004-01-01

    We present a novel capability in satellite remote sensing with implications for air pollution control strategy. We show that the ratio of formaldehyde columns to tropospheric nitrogen dioxide columns is an indicator of the relative sensitivity of surface ozone to emissions of nitrogen oxides (NO(x) = NO + NO2) and volatile organic compounds (VOCs). The diagnosis from these space-based observations is highly consistent with current understanding of surface ozone chemistry based on in situ observations. The satellite-derived ratios indicate that surface ozone is more sensitive to emissions of NO(x) than of VOCs throughout most continental regions of the Northern Hemisphere during summer. Exceptions include Los Angeles and industrial areas of Germany. A seasonal transition occurs in the fall when surface ozone becomes less sensitive to NOx and more sensitive to VOCs.

  18. Surface chemistry associated with the cooling and subaerial weathering of recent basalt flows

    USGS Publications Warehouse

    White, A.F.; Hochella, M.F.

    1992-01-01

    The surface chemistry of fresh and weathered historical basalt flows was characterized using surface-sensitive X-ray photoelectron spectroscopy (XPS). Surfaces of unweathered 1987-1990 flows from the Kilauea Volcano, Hawaii, exhibited variable enrichment in Al, Mg, Ca, and F due to the formation of refractory fluoride compounds and pronounced depletion in Si and Fe from the volatilization of SiF4 and FeF3 during cooling. These reactions, as predicted from shifts in thermodynamic equilibrium with temperature, are induced by diffusion of HF from the flow interiors to the cooling surface. The lack of Si loss and solid fluoride formation for recent basalts from the Krafla Volcano, Iceland, suggest HF degassing at higher temperatures. Subsequent short-term subaerial weathering reactions are strongly influenced by the initial surface composition of the flow and therefore its cooling history. Successive samples collected from the 1987 Kilauea flow demonstrated that the fluoridated flow surfaces leached to a predominantly SiO2 composition by natural weathering within one year. These chemically depleted surfaces were also observed on Hawaiian basalt flows dating back to 1801 AD. Solubility and kinetic models, based on thermodynamic and kinetic data for crystalline AlF3, MgF2, and CaF2, support observed elemental depletion rates due to chemical weathering. Additional loss of alkalis from the Hawaiian basalt occurs from incongruent dissolution of the basalt glass substrate during weathering. ?? 1992.

  19. Ethers on Si(001): A Prime Example for the Common Ground between Surface Science and Molecular Organic Chemistry.

    PubMed

    Pecher, Lisa; Laref, Slimane; Raupach, Marc; Tonner, Ralf

    2017-11-20

    By using computational chemistry it has been shown that the adsorption of ether molecules on Si(001) under ultrahigh vacuum conditions can be understood with classical concepts of organic chemistry. Detailed analysis of the two-step reaction mechanism-1) formation of a dative bond between the ether oxygen atom and a Lewis acidic surface atom and 2) nucleophilic attack of a nearby Lewis basic surface atom-shows that it mirrors acid-catalyzed ether cleavage in solution. The O-Si dative bond is the strongest of its kind, and the reactivity in step 2 defies the Bell-Evans-Polanyi principle. Electron rearrangement during C-O bond cleavage has been visualized with a newly developed method for analyzing bonding, which shows that the mechanism of nucleophilic substitutions on semiconductor surfaces is identical to molecular S N 2 reactions. Our findings illustrate how surface science and molecular chemistry can mutually benefit from each other and unexpected insight can be gained. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Chemically active colloids near osmotic-responsive walls with surface-chemistry gradients

    NASA Astrophysics Data System (ADS)

    Popescu, M. N.; Uspal, W. E.; Dietrich, S.

    2017-04-01

    Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g. the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility. Employing an approximate ‘point-particle’ analysis, we show analytically that—owing to this kind of induced active response (chemi-osmosis) of the wall—such chemically active colloids can align with, and follow, gradients in the surface chemistry of the wall. In this sense, these artificial ‘swimmers’ exhibit a primitive form of thigmotaxis with the meaning of sensing the proximity of a (not necessarily discontinuous) physical change in the environment. We show that the alignment with the surface-chemistry gradient is generic for chemically active colloids as long as they exhibit motility in an unbounded fluid, i.e. this phenomenon does not depend on the exact details of the propulsion mechanism. The results are discussed in the context of simple models of chemical activity, corresponding to Janus particles with ‘source’ chemical reactions on one half of the surface and either ‘inert’ or ‘sink’ reactions over the other half.

  1. Effects of activated carbon surface chemistry and pore structure on the adsorption of trace organic contaminants from aqueous solution

    NASA Astrophysics Data System (ADS)

    Li, Lei

    The objectives were (1) to identify activated pore structure and surface chemistry characteristics that assure the effective removal of trace organic contaminants from aqueous-solution, and (2) to develop a procedure to predict the adsorption capacity of activated carbons from fundamental adsorbent and adsorbate properties. A matrix of activated carbon fibers (ACFs) (with three activation levels and four surface chemistry levels) and three commercially available granular activated carbons (GACs) served as the adsorbents. BET surface area, pore size distribution, elemental composition, point of zero charge and infrared spectroscopy data were obtained to characterize the adsorbents. The adsorption of relative hydrophilic methyl tertiary-butyl ether (MTBE) and relative hydrophobic trichloroethene (TCE) were conducted in both ultrapure water and Sacramento-San Joaquin Delta water. The results showed that an effective adsorbent for the removal of micropollutants from water requires (1) a large volume of micropores with widths that are about 1.5 times larger than the kinetic diameter of the target adsorbate, (2) a micropore size distribution that extends to widths that are approximately twice the kinetic diameter of the target adsorbate to prevent pore blockage by NOM, and (3) a hydrophobic pore surface chemistry with the sum of oxygen and nitrogen contents less than 2 to 3 mmol/g. A procedure based on the Polanyi Potential Theory (PPT) was developed to predict the adsorption capacities of activated carbons from fundamental adsorbent and adsorbate properties. A correlation between the coalescing factor for water adsorption and adsorbent oxygen content was developed. Based on this correlation, the PPT yielded reasonable estimates of aqueous phase adsorption capacities for both relatively polar and non-polar adsorbates on both relatively hydrophobic and hydrophilic activated carbons. With the developed procedure, the adsorption capacities of organic compounds that are

  2. 3D Printed Potential and Free Energy Surfaces for Teaching Fundamental Concepts in Physical Chemistry

    ERIC Educational Resources Information Center

    Kaliakin, Danil S.; Zaari, Ryan R.; Varganov, Sergey A.

    2015-01-01

    Teaching fundamental physical chemistry concepts such as the potential energy surface, transition state, and reaction path is a challenging task. The traditionally used oversimplified 2D representation of potential and free energy surfaces makes this task even more difficult and often confuses students. We show how this 2D representation can be…

  3. Untangling the Chemical Evolution of Titan's Atmosphere and Surface -- From Homogeneous to Heterogeneous Chemistry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kaiser, Ralf I.; Maksyutenko, Pavlo; Ennis, Courtney

    The arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and a thick atmosphere with a pressure of 1.4 atm at surface level - in 2004 opened up a new chapter in the history of Solar System exploration. The mission revealed Titan as a world with striking Earth-like landscapes involving hydrocarbon lakes and seas as well as sand dunes and lava-like features interspersed with craters and icy mountains of hitherto unknown chemical composition. The discovery of a dynamic atmosphere and active weather system illustrates further themore » similarities between Titan and Earth. The aerosol-based haze layers, which give Titan its orange-brownish color, are not only Titan's most prominent optically visible features, but also play a crucial role in determining Titan's thermal structure and chemistry. These smog-like haze layers are thought to be very similar to those that were present in Earth's atmosphere before life developed more than 3.8 billion years ago, absorbing the destructive ultraviolet radiation from the Sun, thus acting as 'prebiotic ozone' to preserve astrobiologically important molecules on Titan. Compared to Earth, Titan's low surface temperature of 94 K and the absence of liquid water preclude the evolution of biological chemistry as we know it. Exactly because of these low temperatures, Titan provides us with a unique prebiotic 'atmospheric laboratory' yielding vital clues - at the frozen stage - on the likely chemical composition of the atmosphere of the primitive Earth. However, the underlying chemical processes, which initiate the haze formation from simple molecules, have been not understood well to date.« less

  4. Kinetics and Chemistry of Ionization Wave Discharges Propagating Over Dielectric Surfaces

    NASA Astrophysics Data System (ADS)

    Petrishchev, Vitaly

    Experimental studies of near-surface ionization wave electric discharges generated by high peak voltage (20-30 kV), nanosecond duration pulses (full width at half-maximum 50-100 ns) of positive and negative polarity and propagating over dielectric surfaces have been performed. A novel way to sustain diffuse, reproducible, ns pulse surface plasmas at a liquid-vapor interface is demonstrated at buffer gas pressures ranging from 10 to 200 Torr. Generation of surface ionization waves well reproduced shot-to-shot and sustaining diffuse near-surface plasmas is one of the principal advantages of the use of ns pulse discharge waveforms. This makes possible characterization of these plasmas in repetitively pulsed experiments. Numerous applications of these plasmas include low-temperature plasma assisted combustion, plasma fuel reforming, plasma flow control, plasma materials processing, agriculture, biology, and medicine. The objectives of the present work are (i) to demonstrate that surface ionization wave discharge plasmas sustained at a liquid-vapor interface can be used as an experimental platform for studies of near-surface plasma chemical reaction kinetics, at the conditions when the interface acts as a high-yield source of radical species, and (ii) to obtain quantitative insight into dynamics, kinetics and chemistry of surface ionization wave discharges and provide experimental data for validation of kinetic models, to assess their predictive capability. Generation of the initial radical pool may trigger a number of plasma chemical processes leading to formation of a variety of stable product species, depending on the initial composition of the liquid and the buffer gas flow. One of the products formed and detected during surface plasma / liquid water interaction is hydroxyl radical, which is closely relevant to applications of plasmas for biology and medicine. The present work includes detailed studies of surface ionization wave discharges sustained in different

  5. Review: Impacts of permafrost degradation on inorganic chemistry of surface fresh water

    NASA Astrophysics Data System (ADS)

    Colombo, Nicola; Salerno, Franco; Gruber, Stephan; Freppaz, Michele; Williams, Mark; Fratianni, Simona; Giardino, Marco

    2018-03-01

    Recent studies have shown that climate change is impacting the inorganic chemical characteristics of surface fresh water in permafrost areas and affecting aquatic ecosystems. Concentrations of major ions (e.g., Ca2 +, Mg2 +, SO42 -, NO3-) can increase following permafrost degradation with associated deepening of flow pathways and increased contributions of deep groundwater. In addition, thickening of the active layer and melting of near-surface ground ice can influence inorganic chemical fluxes from permafrost into surface water. Permafrost degradation has also the capability to modify trace element (e.g., Ni, Mn, Al, Hg, Pb) contents in surface water. Although several local and regional modifications of inorganic chemistry of surface fresh water have been attributed to permafrost degradation, a comprehensive review of the observed changes is lacking. The goal of this paper is to distil insight gained across differing permafrost settings through the identification of common patterns in previous studies, at global scale. In this review we focus on three typical permafrost configurations (pervasive permafrost degradation, thermokarst, and thawing rock glaciers) as examples and distinguish impacts on (i) major ions and (ii) trace elements. Consequences of warming climate have caused spatially-distributed progressive increases of major ion and trace element delivery to surface fresh water in both polar and mountain areas following pervasive permafrost degradation. Moreover, localised releases of major ions and trace elements to surface water due to the liberation of soluble materials sequestered in permafrost and ground ice have been found in ice-rich terrains both at high latitude (thermokarst features) and high elevation (rock glaciers). Further release of solutes and related transport to surface fresh water can be expected under warming climatic conditions. However, complex interactions among several factors able to influence the timing and magnitude of the impacts

  6. Impact of plasma chemistry versus titanium surface topography on osteoblast orientation.

    PubMed

    Rebl, Henrike; Finke, Birgit; Lange, Regina; Weltmann, Klaus-Dieter; Nebe, J Barbara

    2012-10-01

    Topographical and chemical modifications of biomaterial surfaces both influence tissue physiology, but unfortunately little knowledge exists as to their combined effect. There are many indications that rough surfaces positively influence osteoblast behavior. Having determined previously that a positively charged, smooth titanium surface boosts osteoblast adhesion, we wanted to investigate the combined effects of topography and chemistry and elucidate which of these properties is dominant. Polished, machined and corundum-blasted titanium of increasing microroughness was additionally coated with plasma-polymerized allylamine (PPAAm). Collagen I was then immobilized using polyethylene glycol diacid and glutar dialdehyde. On all PPAAm-modified surfaces (i) adhesion of human MG-63 osteoblastic cells increased significantly in combination with roughness, (ii) cells resemble the underlying structure and melt with the surface, and (iii) cells overcome the restrictions of a grooved surface and spread out over a large area as indicated by actin staining. Interestingly, the cellular effects of the plasma-chemical surface modification are predominant over surface topography, especially in the initial phase. Collagen I, although it is the gold standard, does not improve surface adhesion features comparably. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  7. An investigation into the effectiveness of problem-based learning in a physical chemistry laboratory course

    NASA Astrophysics Data System (ADS)

    Gürses, Ahmet; Açıkyıldız, Metin; Doğar, Çetin; Sözbilir, Mustafa

    2007-04-01

    The aim of this study was to investigate the effectiveness of a problem-based learning (PBL) approach in a physical chemistry laboratory course. The parameters investigated were students’ attitudes towards a chemistry laboratory course, scientific process skills of students and their academic achievement. The design of the study was one group pre-test post-test. Four experiments, covering the topics adsorption, viscosity, surface tension and conductivity were performed using a PBL approach in the fall semester of the 2003/04 academic year at Kazim Karabekir Education Faculty of Atatürk University. Each experiment was done over a three week period. A total of 40 students, 18 male and 22 female, participated in the study. Students took the Physical Chemistry Laboratory Concept Test (PCLCT), Attitudes towards Chemistry Laboratory (ATCL) questionnaire and Science Process Skills Test (SPST) as pre and post-tests. In addition, the effectiveness of the PBL approach was also determined through four different scales; Scales Specific to Students’ Views of PBL. A statistically significant difference between the students’ academic achievement and scientific process skills at p

  8. Surface chemistry and mechanical property changes of wood-flour/high-density-polyethylene composites after accelerated weathering

    Treesearch

    Nicole M. Stark; Laurent M. Matuana

    2004-01-01

    Although wood–plastic composites have become more accepted and used in recent years and are promoted as low-maintenance, high-durability building products, they do experience a color change and a loss in mechanical properties with accelerated weathering. In this study, we attempted to characterize the modulus-of-elasticity (MOE) loss of photostabilized high- density...

  9. Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

    PubMed Central

    Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

    2017-01-01

    Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the band edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications. PMID:28508866

  10. Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

    DOE PAGES

    Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; ...

    2017-05-16

    Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the bandmore » edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. As a result, we expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.« less

  11. Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.

    Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the bandmore » edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. As a result, we expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.« less

  12. Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

    NASA Astrophysics Data System (ADS)

    Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

    2017-05-01

    Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the band edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.

  13. Biocompatible Surface Chemistry Manipulation of Gold Nanorods Preserves Optical Properties for Bio-Imaging Applications

    DTIC Science & Technology

    2015-12-18

    3. DATES COVERED (From - To) March 2014 – Sept 2014 4. TITLE AND SUBTITLE Biocompatible surface chemistry manipulation of gold nanorods preserves...Due to their anisotropic shape, gold nanorods (GNRs) possess a number of advantages for biosystem use including, enhanced surface area and tunable...intracellular aggregation of MTAB-TA GNRs, and identify them as prime andidates for use in nanobased bio-imaging applications. 15. SUBJECT TERMS Gold

  14. Emphasizing the role of surface chemistry on hydrophobicity and cell adhesion behavior of polydimethylsiloxane/TiO2 nanocomposite films.

    PubMed

    Yousefi, Seyedeh Zahra; Tabatabaei-Panah, Pardis-Sadat; Seyfi, Javad

    2018-07-01

    Improving the bioinertness of materials is of great importance for developing biomedical devices that contact human tissues. The main goal of this study was to establish correlations among surface morphology, roughness and chemistry with hydrophobicity and cell adhesion in polydimethylsiloxane (PDMS) nanocomposites loaded with titanium dioxide (TiO 2 ) nanoparticles. Firstly, wettability results showed that the nanocomposite loaded with 30 wt.% of TiO 2 exhibited a superhydrophobic behavior; however, the morphology and roughness analysis proved that there was no discernible difference between the surface structures of samples loaded with 20 and 30 wt.% of nanoparticles. Both cell culture and MTT assay experiments showed that, despite the similarity between the surface structures, the sample loaded with 30 wt.% nanoparticles exhibits the greatest reduction in the cell viability (80%) as compared with the pure PDMS film. According to the X-ray photoelectron spectroscopy results, the remarkable reduction in cell viability of the superhydrophobic sample could be majorly attributed to the role of surface chemistry. The obtained results emphasize the importance of adjusting the surface properties especially surface chemistry to gain the optimum cell adhesion behavior. Copyright © 2018 Elsevier B.V. All rights reserved.

  15. Physics and Chemistry on Well-Defined Semiconductor and Oxide Surfaces

    NASA Astrophysics Data System (ADS)

    Chen, Peijun

    High resolution electron energy loss spectroscopy (HREELS) and other surface spectroscopic techniques have been employed to investigate the following two classes of surface/interface phenomena on well-defined semiconductor and oxide surfaces: (i) the fundamental physical and chemical processes involved in gas-solid interaction on silicon single crystal surfaces, and (ii) the physical and chemical properties of metal-oxide interfaces. The particular systems reported in this dissertation are: NH_3, PH_3 and B_ {10}H_{14} on Si(111)-(7 x 7); NH_3 on Si(100) -(2 x 1); atomic H on Si(111)-(7 x 7) and boron-modified Si(111); Al on Al_2O_3 and Sn on SiO_2.. On silicon surfaces, the surface dangling bonds function as the primary adsorption sites where surface chemical processes take place. The unambiguous identification of surface species by vibrational spectroscopy allows the elementary steps involved in these surface chemical processes to be followed on a molecular level. For adsorbate molecules such as NH_3 and PH_3, the nature of the initial low temperature (100 -300 K) adsorption is found to be dissociative, while that for B_{10}H_ {14} is non-dissociative. This has been deduced based upon the presence (or absence) of specific characteristic vibrational mode(s) on surface. By following the evolution of surface species as a function of temperature, the elementary steps leading to silicon nitride thin film growth and doping of silicon are elucidated. In the case of NH_3 on Si(111)-(7 x 7) and Si(100)-(2 x 1), a detailed understanding on the role of substrate surface structure in controlling the surface reactivity has been gained on the basis of a Si adatom backbond-strain relief mechanism on the Si(111) -(7 x 7). The electronic modification to Si(111) surface by subsurface boron doping has been shown to quench its surface chemistry, even for the most aggressive atomic H. This discovery is potentially meaningful to the technology of gas-phase silicon etching. The

  16. How Do Undergraduate Students Conceptualize Acid-Base Chemistry? Measurement of a Concept Progression

    ERIC Educational Resources Information Center

    Romine, William L.; Todd, Amber N.; Clark, Travis B.

    2016-01-01

    We developed and validated a new instrument, called "Measuring Concept progressions in Acid-Base chemistry" (MCAB) and used it to better understand the progression of undergraduate students' understandings about acid-base chemistry. Items were developed based on an existing learning progression for acid-base chemistry. We used the Rasch…

  17. Manipulating the Surface Chemistry of Quantum Dots for Sensitive Ratiometric Fluorescence Detection of Sulfur Dioxide.

    PubMed

    Li, Huihui; Zhu, Houjuan; Sun, Mingtai; Yan, Yehan; Zhang, Kui; Huang, Dejian; Wang, Suhua

    2015-08-11

    Herein, we report a novel approach to the rapid visual detection of gaseous sulfur dioxide (SO2) by manipulating the surface chemistry of 3-aminopropyltriethoxysilane (APTS)-modified quantum dots (QDs) using fluorescent coumarin-3-carboxylic acid (CCA) for specific reaction with SO2. The CCA molecules are attached to the surface amino groups of the QDs through electrostatic attraction, thus the fluorescence of CCA is greatly suppressed because of the formation of an ion-pair complex between the ATPS-modified QDs and CCA. Such an interaction is vulnerable to SO2 because SO2 can readily react with surface amino groups to form strong charge-transfer complexes and subsequently release the strongly fluorescent CCA molecules. The mechanism has been carefully verified through a series of control experiments. Upon exposure to different amounts of SO2, the fluorescent color of the nanoparticle-based sensor displays continuously changes from red to blue. Most importantly, the approach owns high selectivity for SO2 and a tolerance of interference, which enables the sensor to detect SO2 in a practical application. Using this fluorescence-based sensing method, we have achieved a visual detection limit of 6 ppb for gaseous SO2.

  18. Perchlorate Formation on Mars Through Surface Radiolysis-Initiated Atmospheric Chemistry: A Potential Mechanism

    NASA Technical Reports Server (NTRS)

    Wilson, Eric H.; Atreya, Sushil K.; Kaiser, Ralf I.; Mahaffy, Paul R.

    2016-01-01

    Recent observations of the Martian surface by the Phoenix lander and the Sample Analysis at Mars indicate the presence of perchlorate (ClO4). The abundance and isotopic composition of these perchlorates suggest that the mechanisms responsible for their formation in the Martian environment may be unique in our solar system. With this in mind, we propose a potential mechanism for the production of Martian perchlorate: the radiolysis of the Martian surface by galactic cosmic rays, followed by the sublimation of chlorine oxides into the atmosphere and their subsequent synthesis to form perchloric acid (HClO4) in the atmosphere, and the surface deposition and subsequent mineralization of HClO4 in the regolith to form surface perchlorates. To evaluate the viability of this mechanism, we employ a one-dimensional chemical model, examining chlorine chemistry in the context of Martian atmospheric chemistry. Considering the chlorine oxide, OClO, we find that an OClO flux as low as 3.2 x 10(exp 7) molecules/sq cm/s sublimated into the atmosphere from the surface could produce sufficient HClO4 to explain the perchlorate concentration on Mars, assuming an accumulation depth of 30 cm and integrated over the Amazonian period. Radiolysis provides an efficient pathway for the oxidation of chlorine, bypassing the efficient Cl/HCl recycling mechanism that characterizes HClO4 formation mechanisms proposed for the Earth but not Mars.

  19. Adsorption of pentacene on (100) vicinal surfaces: role of coordination, surface chemistry and vdWs effects

    NASA Astrophysics Data System (ADS)

    Matos, Jeronimo; Kara, Abdelkader

    2015-03-01

    In contrast to low miller index surfaces, vicinal surfaces are characterized by steps and step edges that not only present an interesting atomic landscape for the adsorption organic molecules, but also a unique electronic structure resulting in part from the low coordinated atoms at the step edges. The adsorption of pentacene on the stepped (511), (711), (911) surfaces (respectively 3, 4 and 5-atom wide terraces) of Cu and Ag (coinage transition metals); Pt (reactive transition metal); and Ni (reactive, magnetic transition metal) are studied using density functional theory, in order to investigate the support effects arising from differing surface chemistry. We compare the adsorption energy, adsorption geometry and electronic structure predicted by the PBE functional with those obtained from one of the optimized vdW-DF methods: optB88-vdW. Work supported by the U.S. Department of Energy Basic Energy Science under Contract No. DE-FG02-11ER16243.

  20. Early osteoblast responses to orthopedic implants: Synergy of surface roughness and chemistry of bioactive ceramic coating.

    PubMed

    Aniket; Reid, Robert; Hall, Benika; Marriott, Ian; El-Ghannam, Ahmed

    2015-06-01

    Pro-osteogenic stimulation of bone cells by bioactive ceramic-coated orthopedic implants is influenced by both surface roughness and material chemistry; however, their concomitant impact on osteoblast behavior is not well understood. The aim of this study is to investigate the effects of nano-scale roughness and chemistry of bioactive silica-calcium phosphate nanocomposite (SCPC50) coated Ti-6Al-4V on modulating early bone cell responses. Cell attachment was higher on SCPC50-coated substrates compared to the uncoated controls; however, cells on the uncoated substrate exhibited greater spreading and superior quality of F-actin filaments than cells on the SCPC50-coated substrates. The poor F-actin filament organization on SCPC50-coated substrates is thought to be due to the enhanced calcium uptake by the ceramic surface. Dissolution analyses showed that an increase in surface roughness was accompanied by increased calcium uptake, and increased phosphorous and silicon release, all of which appear to interfere with F-actin assembly and osteoblast morphology. Moreover, cell attachment onto the SCPC50-coated substrates correlated with the known adsorption of fibronectin, and was independent of surface roughness. High-throughput genome sequencing showed enhanced expression of extracellular matrix and cell differentiation related genes. These results demonstrate a synergistic relationship between bioactive ceramic coating roughness and material chemistry resulting in a phenotype that leads to early osteoblast differentiation. © 2014 Wiley Periodicals, Inc.

  1. Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bernal, Susan A., E-mail: s.bernal@sheffield.ac.uk; Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD; Provis, John L., E-mail: j.provis@sheffield.ac.uk

    2013-11-15

    Binders formed through alkali-activation of slags and fly ashes, including ‘fly ash geopolymers’, provide appealing properties as binders for low-emissions concrete production. However, the changes in pH and pore solution chemistry induced during accelerated carbonation testing provide unrealistically low predictions of in-service carbonation resistance. The aluminosilicate gel remaining in an alkali-activated slag system after accelerated carbonation is highly polymerised, consistent with a decalcification mechanism, while fly ash-based binders mainly carbonate through precipitation of alkali salts (bicarbonates at elevated CO{sub 2} concentrations, or carbonates under natural exposure) from the pore solution, with little change in the binder gel identifiable by nuclearmore » magnetic resonance spectroscopy. In activated fly ash/slag blends, two distinct gels (C–A–S–H and N–A–S–H) are formed; under accelerated carbonation, the N–A–S–H gel behaves comparably to fly ash-based systems, while the C–A–S–H gel is decalcified similarly to alkali-activated slag. This provides new scope for durability optimisation, and for developing appropriate testing methodologies. -- Highlights: •C-A-S-H gel in alkali-activated slag decalcifies during accelerated carbonation. •Alkali-activated fly ash gel changes much less under CO{sub 2} exposure. •Blended slag-fly ash binder contains two coexisting gel types. •These two gels respond differently to carbonation. •Understanding of carbonation mechanisms is essential in developing test methods.« less

  2. Surface chemistry and moisture sorption properties of wood coated with multifunctional alkoxysilanes by sol-gel process

    Treesearch

    Mandla A. Tshabalala; Peter Kingshott; Mark R. VanLandingham; David Plackett

    2003-01-01

    Sol-gel surface deposition of a hydrophobic polysiloxane coating on wood was accomplished by using a mixture of a low molecular weight multifunctional alkoxysilane, methyltrimethoxysilane (MTMOS), and a high molecular weight multifunctional alkoxysilane, hexadecyltrimethoxysilane (HDTMOS). Investigation of the surface chemistry and morphology of the wood specimens by...

  3. Surface chemistry and corrosion behavior of Inconel 625 and 718 in subcritical, supercritical, and ultrasupercritical water

    NASA Astrophysics Data System (ADS)

    Rodriguez, David; Merwin, Augustus; Karmiol, Zachary; Chidambaram, Dev

    2017-05-01

    Corrosion behavior of Inconel 625 and 718 in subcritical, supercritical and ultrasupercritical water was studied as a function of temperature and time. The change in the chemistry of the as-received surface film on Inconel 625 and 718 after exposure to subcritical water at 325 °C and supercritical water at 425 °C and 527.5 °C for 2 h was studied. After exposure to 325 °C subcritical water, the CrO42- based film formed; however minor quantities of NiFexCr2-xO4 spinel compounds were observed. The oxide film formed on both alloys when exposed to supercritical water at 425 °C consisted of NiFexCr2-xO4 spinel. The surface films on both alloys were identified as NiFe2O4 when exposed to supercritical water at 527.5 °C. To characterize the fully developed oxide layer, studies were conducted at test solution temperatures of 527.5 and 600 °C. Samples were exposed to these temperatures for 24, 96, and 200 h. Surface chemistry was analyzed using X-ray diffraction, as well as Raman and X-ray photoelectron spectroscopies. Inconel 718 exhibited greater mass gain than Inconel 625 for all temperatures and exposure times. The differences in corrosion behavior of the two alloys are attributed to the lower content of chromium and increased iron content of Inconel 718 as compared to Inconel 625.

  4. Effectiveness of Case-Based Learning Instruction on Pre-Service Teachers' Chemistry Motivation and Attitudes toward Chemistry

    ERIC Educational Resources Information Center

    Çam, Aylin; Geban, Ömer

    2017-01-01

    Background: The development of primary pre-service teachers' chemistry motivation and attitudes toward chemistry were examined in order to develop their science literacy using case-based learning. Students' ideas were emphasized, real-life situations were discussed, and students could share their ideas and knowledge with peers; as a result,…

  5. Impact of water chemistry on surface charge and aggregation of polystyrene microspheres suspensions.

    PubMed

    Lu, Songhua; Zhu, Kairuo; Song, Wencheng; Song, Gang; Chen, Diyun; Hayat, Tasawar; Alharbi, Njud S; Chen, Changlun; Sun, Yubing

    2018-07-15

    The discharge of microplastics into aquatic environment poses the potential threat to the hydrocoles and human health. The fate and transport of microplastics in aqueous solutions are significantly influenced by water chemistry. In this study, the effect of water chemistry (i.e., pH, foreign salts and humic acid) on the surface charge and aggregation of polystyrene microsphere in aqueous solutions was conducted by batch, zeta potentials, hydrodynamic diameters, FT-IR and XPS analysis. Compared to Na + and K + , the lower negative zeta potentials and larger hydrodynamic diameters of polystyrene microspheres after introduction of Mg 2+ were observed within a wide range of pH (2.0-11.0) and ionic strength (IS, 0.01-500mmol/L). No effect of Cl - , HCO 3 - and SO 4 2- on the zeta potentials and hydrodynamic diameters of polystyrene microspheres was observed at low IS concentrations (<5mmol/L), whereas the zeta potentials and hydrodynamic diameters of polystyrene microspheres after addition of SO 4 2- were higher than that of Cl - and HCO 3 - at high IS concentrations (>10mmol/L). The zeta potentials of polystyrene microspheres after HA addition were decreased at pH2.0-11.0, whereas the lower hydrodynamic diameters were observed at pH<4.0. According to FT-IR and XPS analysis, the change in surface properties of polystyrene microspheres after addition of hydrated Mg 2+ and HA was attributed to surface electrostatic and/or steric repulsions. These investigations are crucial for understanding the effect of water chemistry on colloidal stability of microplastics in aquatic environment. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Surface Chemistry in Cobalt Phosphide-Stabilized Lithium-Sulfur Batteries.

    PubMed

    Zhong, Yiren; Yin, Lichang; He, Peng; Liu, Wen; Wu, Zishan; Wang, Hailiang

    2018-01-31

    Chemistry at the cathode/electrolyte interface plays an important role for lithium-sulfur batteries in which stable cycling of the sulfur cathode requires confinement of the lithium polysulfide intermediates and their fast electrochemical conversion on the electrode surface. While many materials have been found to be effective for confining polysulfides, the underlying chemical interactions remain poorly understood. We report a new and general lithium polysulfide-binding mechanism enabled by surface oxidation layers of transition-metal phosphide and chalcogenide materials. We for the first time find that CoP nanoparticles strongly adsorb polysulfides because their natural oxidation (forming Co-O-P-like species) activates the surface Co sites for binding polysulfides via strong Co-S bonding. With a surface oxidation layer capable of confining polysulfides and an inner core suitable for conducting electrons, the CoP nanoparticles are thus a desirable candidate for stabilizing and improving the performance of sulfur cathodes in lithium-sulfur batteries. We demonstrate that sulfur electrodes that hold a high mass loading of 7 mg cm -2 and a high areal capacity of 5.6 mAh cm -2 can be stably cycled for 200 cycles. We further reveal that this new surface oxidation-induced polysulfide-binding scheme applies to a series of transition-metal phosphide and chalcogenide materials and can explain their stabilizing effects for lithium-sulfur batteries.

  7. Accelerated weathering of wood surfaces coated with multifunctional allkoxysilanes by sol-gel deposition

    Treesearch

    Mandla A. Tshabalala; John E. Gangstad

    2003-01-01

    Accelerated weathering of wood surfaces coated with hexadecyltrimethoxysilane (HDTMOS) in the presence of methyltrimethoxysilane (MTMOS) by the sol-gel process was investigated. The sol-gel process allowed the deposition of a covalently bound thin layer of polysiloxane networks on the wood surface that was resistant to water sorption and water leaching. The rate of...

  8. The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

    NASA Technical Reports Server (NTRS)

    Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

    1994-01-01

    Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

  9. [Computational chemistry in structure-based drug design].

    PubMed

    Cao, Ran; Li, Wei; Sun, Han-Zi; Zhou, Yu; Huang, Niu

    2013-07-01

    Today, the understanding of the sequence and structure of biologically relevant targets is growing rapidly and researchers from many disciplines, physics and computational science in particular, are making significant contributions to modern biology and drug discovery. However, it remains challenging to rationally design small molecular ligands with desired biological characteristics based on the structural information of the drug targets, which demands more accurate calculation of ligand binding free-energy. With the rapid advances in computer power and extensive efforts in algorithm development, physics-based computational chemistry approaches have played more important roles in structure-based drug design. Here we reviewed the newly developed computational chemistry methods in structure-based drug design as well as the elegant applications, including binding-site druggability assessment, large scale virtual screening of chemical database, and lead compound optimization. Importantly, here we address the current bottlenecks and propose practical solutions.

  10. CuAAC click chemistry accelerates the discovery of novel chemical scaffolds as promising protein tyrosine phosphatases inhibitors.

    PubMed

    He, X-P; Xie, J; Tang, Y; Li, J; Chen, G-R

    2012-01-01

    Protein tyrosine phosphatases (PTPs) are crucial regulators for numerous biological processes in nature. The dysfunction and overexpression of many PTP members have been demonstrated to cause fatal human diseases such as cancers, diabetes, obesity, neurodegenerative diseases and autoimmune disorders. In the past decade, considerable efforts have been devoted to the production of PTPs inhibitors by both academia and the pharmaceutical industry. However, there are only limited drug candidates in clinical trials and no commercial drugs have been approved, implying that further efficient discovery of novel chemical entities competent for inhibition of the specific PTP target in vivo remains yet a challenge. In light of the click-chemistry paradigm which advocates the utilization of concise and selective carbon-heteroatom ligation reactions for the modular construction of useful compound libraries, the Cu(I)-catalyzed azidealkyne 1,3-dipolar cycloaddition reaction (CuAAC) has fueled enormous energy into the modern drug discovery. Recently, this ingenious chemical ligation tool has also revealed efficacious and expeditious in establishing large combinatorial libraries for the acquisition of novel PTPs inhibitors with promising pharmacological profiles. We thus offer here a comprehensive review highlighting the development of PTPs inhibitors accelerated by the CuAAC click chemistry.

  11. A context based approach using Green Chemistry/Bio-remediation principles to enhance interest and learning of organic chemistry in a high school AP chemistry classroom

    NASA Astrophysics Data System (ADS)

    Miller, Tricia

    The ability of our planet to sustain life and heal itself is not as predictable as it used to be. Our need for educated future scientists who know what our planet needs, and can passionately apply that knowledge to find solutions should be at the heart of science education today. This study of learning organic chemistry through the lens of the environmental problem "What should be done with our food scraps?" explores student interest, and mastery of certain concepts in organic chemistry. This Green Chemistry/ Bio-remediation context-based teaching approach utilizes the Nature MillRTM, which is an indoor food waste composting machine, to learn about organic chemistry, and how this relates to landfill reduction possibilities, and resource production. During this unit students collected food waste from their cafeteria, and used the Nature MillRTM to convert food waste into compost. The use of these hands on activities, and group discussions in a context-based environment enhanced their interest in organic chemistry, and paper chromatography. According to a one-tailed paired T-test, the result show that this context-based approach is a significant way to increase both student interest and mastery of the content.

  12. Human Fetal Osteoblast Response on Poly(Methyl Methacrylate)/Polystyrene Demixed Thin Film Blends: Surface Chemistry Vs Topography Effects.

    PubMed

    D'Sa, Raechelle A; Raj, Jog; Dickinson, Peter J; McCabe, Fiona; Meenan, Brian J

    2016-06-22

    Recent advances in materials sciences have allowed for the development and fabrication of biomaterials that are capable of providing requisite cues to instigate cells to respond in a predictable fashion. We have developed a series of poly(methyl methacrylate)/polystyrene (PMMA/PS) polymer demixed thin films with nanotopographies ranging from nanoislands to nanopits to study the response of human fetal osteoblast cells (hFOBs). When PMMA was in excess in the blend composition, a nanoisland topography dominated, whereas a nanopit topography dominated when PS was in excess. PMMA was found to segregate to the top of the nanoisland morphology with PS preferring the substrate interface. To further ascertain the effects of surface chemistry vs topography, we plasma treated the polymer demixed films using an atmospheric pressure dielectric barrier discharge reactor to alter the surface chemistry. Our results have shown that hFOBs did not have an increased short-term cellular response on pristine polymer demixed surfaces. However, increasing the hydrophilicty/wettability of the surfaces by oxygen functionalization causes an increase in the cellular response. These results indicate that topography alone is not sufficient to induce a positive cellular response, but the underlying surface chemistry is also important in regulating cell function.

  13. Molecular Studies of Complex Soil Organic Matter Interactions with Metal Ions and Mineral Surfaces using Classical Molecular Dynamics and Quantum Chemistry Methods

    NASA Astrophysics Data System (ADS)

    Andersen, A.; Govind, N.; Laskin, A.

    2017-12-01

    Mineral surfaces have been implicated as potential protectors of soil organic matter (SOM) against decomposition and ultimate mineralization to small molecules which can provide nutrients for plants and soil microbes and can also contribute to the Earth's elemental cycles. SOM is a complex mixture of organic molecules of biological origin at varying degrees of decomposition and can, itself, self-assemble in such a way as to expose some biomolecule types to biotic and abiotic attack while protecting other biomolecule types. The organization of SOM and SOM with mineral surfaces and solvated metal ions is driven by an interplay of van der Waals and electrostatic interactions leading to partitioning of hydrophilic (e.g. sugars) and hydrophobic (e.g., lipids) SOM components that can be bridged with amphiphilic molecules (e.g., proteins). Classical molecular dynamics simulations can shed light on assemblies of organic molecules alone or complexation with mineral surfaces. The role of chemical reactions is also an important consideration in potential chemical changes of the organic species such as oxidation/reduction, degradation, chemisorption to mineral surfaces, and complexation with solvated metal ions to form organometallic systems. For the study of chemical reactivity, quantum chemistry methods can be employed and combined with structural insight provided by classical MD simulations. Moreover, quantum chemistry can also simulate spectroscopic signatures based on chemical structure and is a valuable tool in interpreting spectra from, notably, x-ray absorption spectroscopy (XAS). In this presentation, we will discuss our classical MD and quantum chemistry findings on a model SOM system interacting with mineral surfaces and solvated metal ions.

  14. Aromatic, Alphatic, Enigmatic: The Chemistry of Titan

    NASA Astrophysics Data System (ADS)

    Horst, Sarah

    2017-10-01

    The extraordinary complexity of Titan’s atmospheric chemistry far surpasses that of any other solar system atmosphere. With its thick N2 atmosphere and stable bodies of liquid on its surface, Titan also possesses many physical processes that are similar to those that occur on Earth. The connection between Titan’s surface and atmosphere is unique in our solar system; atmospheric chemistry produces materials that are deposited on the surface and subsequently altered by surface-atmosphere interactions such as aeolian and fluvial processes resulting in the formation of extensive dune fields and expansive lakes and seas. Titan’s atmosphere is favorable for organic haze formation, which combined with the presence of some oxygen-bearing molecules indicates that Titan’s atmosphere may produce molecules of prebiotic interest. The combination of organics and liquid, in the form of water in a subsurface ocean and methane/ethane in the surface lakes and seas, means that Titan may be the ideal place in the solar system to test ideas about habitability, prebiotic chemistry, and the ubiquity and diversity of life in the universe. I will review our current understanding of chemistry on Titan forged from the powerful combination of Earth-based observations, remote sensing and in situ spacecraft measurements, laboratory experiments, and models. I will conclude with some of the questions that remain after Cassini-Huygens.

  15. EDITORIAL: Laser and Plasma Accelerators Workshop, Kardamyli, Greece, 2009 Laser and Plasma Accelerators Workshop, Kardamyli, Greece, 2009

    NASA Astrophysics Data System (ADS)

    Bingham, Bob; Muggli, Patric

    2011-01-01

    -resolved radiobiology or chemistry. Such laser-generated beams will form the basis of the fifth generation light sources and will be compact versions of the much more expensive fourth generation XFEL, such as LCLS light sources. Laser-driven ion acceleration is also making rapid headway; one of the goals in these experiments is to produce protons and carbon ions of hundreds of MeV for oncology. These experiments are carried out using solid-target-laser interactions. There is still a number of issues to be resolved in these experiments including the origin of light ions. The paper by Willingale et al addresses this issue and demonstrates that deuteron ions originating from the front surface can gain comparable energies as those from the rear surface. Furthermore, from two-dimensional simulations they show that a proton-rich contamination layer over the surface is detrimental to deuteron ion acceleration from the rear surface but not detrimental to the front surface acceleration mechanism. Studies of different laser polarizations on ion acceleration at the rear surface were reported by Antici et al. It was shown that no real enhancement using a particular polarization was found. At higher radiation intensities, especially with the multi-petawatt lasers being planned, radiation reaction becomes important. This was reported by Chen et al who found that radiation reaction effects on ion acceleration in laser-foil interactions impeded the backward moving electrons, which enhanced the ion acceleration. An interesting new development is the use of ultra-relativistic proton beams to drive plasma wakefields. This is similar to the SLAC electron-beam-driven wakefields. However, unlike the SLAC electron beam, which is of the order of 30 fs long and matches the period of the plasma wave necessary to create the blowout or bubble regime, the ion beam is very much longer. To create shorter ion beams a magnetic compression scheme is investigated in the paper by Caldwell et al, and results for proton

  16. Carbohydrate CuAAC click chemistry for therapy and diagnosis.

    PubMed

    He, Xiao-Peng; Zeng, Ya-Li; Zang, Yi; Li, Jia; Field, Robert A; Chen, Guo-Rong

    2016-06-24

    Carbohydrates are important as signaling molecules and for cellular recognition events, therefore offering scope for the development of carbohydrate-mimetic diagnostics and drug candidates. As a consequence, the construction of carbohydrate-based bioactive compounds and sensors has become an active research area. While the advent of click chemistry has greatly accelerated the progress of medicinal chemistry and chemical biology, recent literature has seen an extensive use of such approaches to construct functionally diverse carbohydrate derivatives. Here we summarize some of the progress, covering the period 2010 to mid-2015, in Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition CuAAC "click chemistry" of carbohydrate derivatives, in the context of potential therapeutic and diagnostic tool development. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Testing grain-surface chemistry in massive hot-core regions

    NASA Astrophysics Data System (ADS)

    Bisschop, S. E.; Jørgensen, J. K.; van Dishoeck, E. F.; de Wachter, E. B. M.

    2007-04-01

    Aims:We study the chemical origin of a set of complex organic molecules thought to be produced by grain surface chemistry in high mass young stellar objects (YSOs). Methods: A partial submillimeter line-survey was performed toward 7 high-mass YSOs aimed at detecting H2CO, CH3OH, CH2CO, CH3CHO, C2H5OH, HCOOH, HNCO and NH2CHO. In addition, lines of CH3CN, C2H5CN, CH3CCH, HCOOCH3, and CH3OCH3 were observed. Rotation temperatures and beam-averaged column densities are determined. To correct for beam dilution and determine abundances for hot gas, the radius and H2 column densities of gas at temperatures >100 K are computed using 850 μm dust continuum data and source luminosity. Results: Based on their rotation diagrams, molecules can be classified as either cold (<100 K) or hot (>100 K). This implies that complex organics are present in at least two distinct regions. Furthermore, the abundances of the hot oxygen-bearing species are correlated, as are those of HNCO and NH2CHO. This is suggestive of chemical relationships within, but not between, those two groups of molecules. Conclusions: .The most likely explanation for the observed correlations of the various hot molecules is that they are "first generation" species that originate from solid-state chemistry. This includes H2CO, CH3OH, C2H5OH, HCOOCH3, CH3OCH3, HNCO, NH2CHO, and possibly CH3CN, and C2H5CN. The correlations between sources implies very similar conditions during their formation or very similar doses of energetic processing. Cold species such as CH2CO, CH3CHO, and HCOOH, some of which are seen as ices along the same lines of sight, are probably formed in the solid state as well, but appear to be destroyed at higher temperatures. A low level of non-thermal desorption by cosmic rays can explain their low rotation temperatures and relatively low abundances in the gas phase compared to the solid state. The CH3CCH abundances can be fully explained by low temperature gas phase chemistry. No cold N

  18. Plants and Chemistry: A Teaching Course Based on the Chemistry of Substances of Plant Origin

    NASA Astrophysics Data System (ADS)

    Andreoli, Katia; Calascibetta, Franco; Campanella, Luigi; Favero, Gabriele; Occhionero, Francesca

    2002-08-01

    Over the past few years, we developed an idea about the teaching of chemistry by determining the links between theory and the real world. The principles, concepts, and experimental procedures of chemistry were illustrated through an original approach based on useful substances obtained from plants. The starting point was substances that have always been obtained from trees and vegetables. The approach was implemented during many refresher courses for secondary school teachers of chemistry. The courses were divided into sections, each called "Plants and ...", dedicated to colors, odors, tastes, medicines and drugs, fibers, soaps, and alcoholic beverages. Each section consisted of a theoretical lesson followed by a laboratory session.

  19. Characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems.

    PubMed

    Bryant, M; Ward, M; Farrar, R; Freeman, R; Brummitt, K; Nolan, J; Neville, A

    2014-04-01

    This study presents the characterisation of the surface topography, tomography and chemistry of fretting corrosion product found on retrieved polished femoral stems. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FI-IR) were utilised in order to assess the surface morphology of retrieved Metal-on-Metal Total Hip Replacements and surface chemistry of the films found on the surface. Gross slip, plastic deformation and directionality of the surface were extensively seen on the proximal surfaces of the retrievals. A more corrosive phenomenon was observed in the distal regions of the stem, demonstrating a seemingly intergranular attack. Tribochemical reactions were seen to occur within the stem-cement interfaces with tribofilms being observed on the femoral stem and counterpart PMMA bone cement. XPS, TEM-EDX and FT-IR analyses demonstrated that the films present in the stem surfaces were a complex mixture of chromium oxide and amorphous organic material. A comparison between current experimental and clinical literature has been conducted and findings from this study demonstrate that the formation and chemistry of films are drastically influenced by the type of wear or degradation mechanism. Films formed in the stem-cement interface are thought to further influence the biological environment outside the stem-cement interface due to the formation of Cr and O rich films within the interface whilst Co is free to migrate away. © 2013 Elsevier Ltd. All rights reserved.

  20. Near-ambient pressure XPS of high-temperature surface chemistry in Sr2Co2O5 thin films

    DOE PAGES

    Hong, Wesley T.; Stoerzinger, Kelsey; Crumlin, Ethan J.; ...

    2016-02-11

    Transition metal perovskite oxides are promising electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells, but a lack of fundamental understanding of oxide surfaces impedes the rational design of novel catalysts with improved device efficiencies. In particular, understanding the surface chemistry of oxides is essential for controlling both catalytic activity and long-term stability. Thus, elucidating the physical nature of species on perovskite surfaces and their catalytic enhancement would generate new insights in developing oxide electrocatalysts. In this article, we perform near-ambient pressure XPS of model brownmillerite Sr 2Co 2O 5 (SCO) epitaxial thin films with different crystallographic orientations. Detailedmore » analysis of the Co 2p spectra suggests that the films lose oxygen as a function of temperature. Moreover, deconvolution of the O 1s spectra shows distinct behavior for (114)-oriented SCO films compared to (001)-oriented SCO films, where an additional bulk oxygen species is observed. These findings indicate a change to a perovskite-like oxygen chemistry that occurs more easily in (114) SCO than (001) SCO, likely due to the orientation of oxygen vacancy channels out-of-plane with respect to the film surface. This difference in surface chemistry is responsible for the anisotropy of the oxygen surface exchange coefficient of SCO and may contribute to the enhanced ORR kinetics of La 0.8Sr 0.2CoO 3-δ thin films by SCO surface particles observed previously.« less

  1. Students' Understanding of Acids/Bases in Organic Chemistry Contexts

    ERIC Educational Resources Information Center

    Cartrette, David P.; Mayo, Provi M.

    2011-01-01

    Understanding key foundational principles is vital to learning chemistry across different contexts. One such foundational principle is the acid/base behavior of molecules. In the general chemistry sequence, the Bronsted-Lowry theory is stressed, because it lends itself well to studying equilibrium and kinetics. However, the Lewis theory of…

  2. WATER CHEMISTRY ASSESSMENT METHODS

    EPA Science Inventory

    This section summarizes and evaluates the surfce water column chemistry assessment methods for USEPA/EMAP-SW, USGS-NAQA, USEPA-RBP, Oho EPA, and MDNR-MBSS. The basic objective of surface water column chemistry assessment is to characterize surface water quality by measuring a sui...

  3. Effectiveness of case-based learning instruction on pre-service teachers' chemistry motivation and attitudes toward chemistry

    NASA Astrophysics Data System (ADS)

    Çam, Aylin; Geban, Ömer

    2017-01-01

    Background: The development of primary pre-service teachers' chemistry motivation and attitudes toward chemistry were examined in order to develop their science literacy using case-based learning. Students' ideas were emphasized, real-life situations were discussed, and students could share their ideas and knowledge with peers; as a result, students were active in the learning process.

  4. Surface engineering approaches to micropattern surfaces for cell-based assays.

    PubMed

    Falconnet, Didier; Csucs, Gabor; Grandin, H Michelle; Textor, Marcus

    2006-06-01

    The ability to produce patterns of single or multiple cells through precise surface engineering of cell culture substrates has promoted the development of cellular bioassays that provide entirely new insights into the factors that control cell adhesion to material surfaces, cell proliferation, differentiation and molecular signaling pathways. The ability to control shape and spreading of attached cells and cell-cell contacts through the form and dimension of the cell-adhesive patches with high precision is important. Commitment of stem cells to different specific lineages depends strongly on cell shape, implying that controlled microenvironments through engineered surfaces may not only be a valuable approach towards fundamental cell-biological studies, but also of great importance for the design of cell culture substrates for tissue engineering. Furthermore, cell patterning is an important tool for organizing cells on transducers for cell-based sensing and cell-based drug discovery concepts. From a material engineering standpoint, patterning approaches have greatly profited by combining microfabrication technologies, such as photolithography, with biochemical functionalization to present to the cells biological cues in spatially controlled regions where the background is rendered non-adhesive ("non-fouling") by suitable chemical modification. The focus of this review is on the surface engineering aspects of biologically motivated micropatterning of two-dimensional (flat) surfaces with the aim to provide an introductory overview and critical assessment of the many techniques described in the literature. In particular, the importance of non-fouling surface chemistries, the combination of hard and soft lithography with molecular assembly techniques as well as a number of less well known, but useful patterning approaches, including direct cell writing, are discussed.

  5. Present status of Accelerator-Based BNCT

    PubMed Central

    Kreiner, Andres Juan; Bergueiro, Javier; Cartelli, Daniel; Baldo, Matias; Castell, Walter; Asoia, Javier Gomez; Padulo, Javier; Suárez Sandín, Juan Carlos; Igarzabal, Marcelo; Erhardt, Julian; Mercuri, Daniel; Valda, Alejandro A.; Minsky, Daniel M.; Debray, Mario E.; Somacal, Hector R.; Capoulat, María Eugenia; Herrera, María S.; del Grosso, Mariela F.; Gagetti, Leonardo; Anzorena, Manuel Suarez; Canepa, Nicolas; Real, Nicolas; Gun, Marcelo; Tacca, Hernán

    2016-01-01

    Aim This work aims at giving an updated report of the worldwide status of Accelerator-Based BNCT (AB-BNCT). Background There is a generalized perception that the availability of accelerators installed in hospitals, as neutron sources, may be crucial for the advancement of BNCT. Accordingly, in recent years a significant effort has started to develop such machines. Materials and methods A variety of possible charged-particle induced nuclear reactions and the characteristics of the resulting neutron spectra are discussed along with the worldwide activity in suitable accelerator development. Results Endothermic 7Li(p,n)7Be and 9Be(p,n)9B and exothermic 9Be(d,n)10B are compared. In addition to having much better thermo-mechanical properties than Li, Be as a target leads to stable products. This is a significant advantage for a hospital-based facility. 9Be(p,n)9B needs at least 4–5 MeV bombarding energy to have a sufficient yield, while 9Be(d,n)10B can be utilized at about 1.4 MeV, implying the smallest possible accelerator. This reaction operating with a thin target can produce a sufficiently soft spectrum to be viable for AB-BNCT. The machines considered are electrostatic single ended or tandem accelerators or radiofrequency quadrupoles plus drift tube Linacs. Conclusions 7Li(p,n)7Be provides one of the best solutions for the production of epithermal neutron beams for deep-seated tumors. However, a Li-based target poses significant technological challenges. Hence, Be has been considered as an alternative target, both in combination with (p,n) and (d,n) reactions. 9Be(d,n)10B at 1.4 MeV, with a thin target has been shown to be a realistic option for the treatment of deep-seated lesions. PMID:26933390

  6. Present status of Accelerator-Based BNCT.

    PubMed

    Kreiner, Andres Juan; Bergueiro, Javier; Cartelli, Daniel; Baldo, Matias; Castell, Walter; Asoia, Javier Gomez; Padulo, Javier; Suárez Sandín, Juan Carlos; Igarzabal, Marcelo; Erhardt, Julian; Mercuri, Daniel; Valda, Alejandro A; Minsky, Daniel M; Debray, Mario E; Somacal, Hector R; Capoulat, María Eugenia; Herrera, María S; Del Grosso, Mariela F; Gagetti, Leonardo; Anzorena, Manuel Suarez; Canepa, Nicolas; Real, Nicolas; Gun, Marcelo; Tacca, Hernán

    2016-01-01

    This work aims at giving an updated report of the worldwide status of Accelerator-Based BNCT (AB-BNCT). There is a generalized perception that the availability of accelerators installed in hospitals, as neutron sources, may be crucial for the advancement of BNCT. Accordingly, in recent years a significant effort has started to develop such machines. A variety of possible charged-particle induced nuclear reactions and the characteristics of the resulting neutron spectra are discussed along with the worldwide activity in suitable accelerator development. Endothermic (7)Li(p,n)(7)Be and (9)Be(p,n)(9)B and exothermic (9)Be(d,n)(10)B are compared. In addition to having much better thermo-mechanical properties than Li, Be as a target leads to stable products. This is a significant advantage for a hospital-based facility. (9)Be(p,n)(9)B needs at least 4-5 MeV bombarding energy to have a sufficient yield, while (9)Be(d,n)(10)B can be utilized at about 1.4 MeV, implying the smallest possible accelerator. This reaction operating with a thin target can produce a sufficiently soft spectrum to be viable for AB-BNCT. The machines considered are electrostatic single ended or tandem accelerators or radiofrequency quadrupoles plus drift tube Linacs. (7)Li(p,n)(7)Be provides one of the best solutions for the production of epithermal neutron beams for deep-seated tumors. However, a Li-based target poses significant technological challenges. Hence, Be has been considered as an alternative target, both in combination with (p,n) and (d,n) reactions. (9)Be(d,n)(10)B at 1.4 MeV, with a thin target has been shown to be a realistic option for the treatment of deep-seated lesions.

  7. How accelerated biological aging can affect solar reflective polymeric based building materials

    NASA Astrophysics Data System (ADS)

    Ferrari, C.; Santunione, G.; Libbra, A.; Muscio, A.; Sgarbi, E.

    2017-11-01

    Among the main issues concerning building materials, in particular outdoor ones, one can identify the colonization by microorganisms referred to as biological aggression. This can affect not only the aesthetical aspect but also the thermal performance of solar reflective materials. In order to improve the reliability of tests aimed to assess the resistance to biological aggression and contextually reduce the test duration, an accelerated test method has been developed. It is based on a lab reproducible setup where specific and controlled environmental and boundary conditions are imposed to accelerate as much as possible biological growth on building materials. Due to their widespread use, polymeric materials have been selected for the present analysis, in the aim of reaching an advanced bio-aged level in a relatively short time (8 weeks or less) and at the same time comparatively evaluate different materials under a given set of ageing conditions. Surface properties before, during and after ageing have been investigated by surface, microstructural and chemical analyses, as well as by examination of time progressive images to assess bacterial and algal growth rate.

  8. Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions

    NASA Astrophysics Data System (ADS)

    Sodeau, J.; Oriordan, B.

    2003-04-01

    CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

  9. THE INTEGRATED USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY, AND VIRTUAL REALITY TO PREDICT THE CHEMICAL REACTIVITY OF ENVIRONMENTAL SURFACES

    EPA Science Inventory

    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

  10. Factors Influencing NO2 Adsorption/Reduction on Microporous Activated Carbon: Porosity vs. Surface Chemistry

    PubMed Central

    Ghouma, Imen; Limousy, Lionel; Bennici, Simona

    2018-01-01

    The textural properties and surface chemistry of different activated carbons, prepared by the chemical activation of olive stones, have been investigated in order to gain insight on the NO2 adsorption mechanism. The parent chemical activated carbon was prepared by the impregnation of olive stones in phosphoric acid followed by thermal carbonization. Then, the textural properties and surface chemistry were modified by chemical treatments including nitric acid, sodium hydroxide and/or a thermal treatment at 900 °C. The main properties of the parent and modified activated carbons were analyzed by N2-adsorption, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques, in order to enlighten the modifications issued from the chemical and thermal treatments. The NO2 adsorption capacities of the different activated carbons were measured in fixed bed experiments under 500 ppmv NO2 concentrations at room temperature. Temperature programmed desorption (TPD) was applied after adsorption tests in order to quantify the amount of the physisorbed and chemisorbed NO2. The obtained results showed that the development of microporosity, the presence of oxygen-free sites, and the presence of basic surface groups are key factors for the efficient adsorption of NO2. PMID:29670008

  11. Controlling Short-Range Interactions by Tuning Surface Chemistry in HDPE/Graphene Nanoribbon Nanocomposites.

    PubMed

    Sadeghi, Soheil; Zehtab Yazdi, Alireza; Sundararaj, Uttandaraman

    2015-09-03

    Unique dispersion states of nanoparticles in polymeric matrices have the potential to create composites with enhanced mechanical, thermal, and electrical properties. The present work aims to determine the state of dispersion from the melt-state rheological behavior of nanocomposites based on carbon nanotube and graphene nanoribbon (GNR) nanomaterials. GNRs were synthesized from nitrogen-doped carbon nanotubes via a chemical route using potassium permanganate and some second acids. High-density polyethylene (HDPE)/GNR nanocomposite samples were then prepared through a solution mixing procedure. Different nanocomposite dispersion states were achieved using different GNR synthesis methods providing different surface chemistry, interparticle interactions, and internal compartments. Prolonged relaxation of flow induced molecular orientation was observed due to the presence of both carbon nanotubes and GNRs. Based on the results of this work, due to relatively weak interactions between the polymer and the nanofillers, it is expected that short-range interactions between nanofillers play the key role in the final dispersion state.

  12. Surface disturbances: their role in accelerating desertification

    USGS Publications Warehouse

    Belnap, Jayne

    1995-01-01

    Maintaining soil stability and normal water and nutrient cycles in desert systems is critical to avoiding desertification. These particular ecosystem processes are threatened by trampling of livestock and people, and by off-road vehicle use. Soil compaction and disruption of cryptobiotic soil surfaces (composed of cyanobacteria, lichens, and mosses) can result in decreased water availability to vascular plants through decreased water infiltration and increased albedo with possible decreased precipitation. Surface disturbance may also cause accelerated soil loss through wind and water erosion and decreased diversity and abundance of soil biota. In addition, nutrient cycles can be altered through lowered nitrogen and carbon inputs and slowed decomposition of soil organic matter, resulting in lower nutrient levels in associated vascular plants. Some cold desert systems may be especially susceptible to these disruptions due to the paucity of surface-rooting vascular plants for soil stabilization, fewer nitrogen-fixing higher plants, and lower soil temperatures, which slow nutrient cycles. Desert soils may recover slowly from surface disturbances, resulting in increased vulnerability to desertification. Recovery from compaction and decreased soil stability is estimated to take several hundred years. Re-establishment rates for soil bacterial and fungal populations are not known. The nitrogen fixation capability of soil requires at least 50 years to recover. Recovery of crusts can be hampered by large amounts of moving sediment, and re-establishment can be extremely difficult in some areas. Given the sensitivity of these resources and slow recovery times, desertification threatens million of hectares of semiarid lands in the United States.

  13. Surface chemistry from wettability and charge for the control of mesenchymal stem cell fate through self-assembled monolayers.

    PubMed

    Hao, Lijing; Fu, Xiaoling; Li, Tianjie; Zhao, Naru; Shi, Xuetao; Cui, Fuzhai; Du, Chang; Wang, Yingjun

    2016-12-01

    Self-assembled monolayers (SAMs) of alkanethiols on gold are highly controllable model substrates and have been employed to mimic the extracellular matrix for cell-related studies. This study aims to systematically explore how surface chemistry influences the adhesion, morphology, proliferation and osteogenic differentiation of mouse mesenchymal stem cells (mMSCs) using various functional groups (-OEG, -CH 3 , -PO 3 H 2 , -OH, -NH 2 and -COOH). Surface analysis demonstrated that these functional groups produced a wide range of wettability and charge: -OEG (hydrophilic and moderate iso-electric point (IEP)), -CH 3 (strongly hydrophobic and low IEP), -PO 3 H 2 (moderate wettability and low IEP), -OH (hydrophilic and moderate IEP), -NH 2 (moderate wettability and high IEP) and -COOH (hydrophilic and low IEP). In terms of cell responses, the effect of wettability may be more influential than charge for these groups. Moreover, compared to -OEG and -CH 3 groups, -PO 3 H 2 , -OH, -NH 2 and -COOH functionalities tended to promote not only cell adhesion, proliferation and osteogenic differentiation but also the expression of α v and β 1 integrins. This finding indicates that the surface chemistry may guide mMSC activities through α v and β 1 integrin signaling pathways. Model surfaces with controllable chemistry may provide insight into biological responses to substrate surfaces that would be useful for the design of biomaterial surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. A New Project-Based Lab for Undergraduate Environmental and Analytical Chemistry

    ERIC Educational Resources Information Center

    Adami, Gianpiero

    2006-01-01

    A new project-based lab was developed for third year undergraduate chemistry students based on real world applications. The experience suggests that the total analytical procedure (TAP) project offers a stimulating alternative for delivering science skills and developing a greater interest for analytical chemistry and environmental sciences and…

  15. Influence of surface chemistry of carbon materials on their interactions with inorganic nitrogen contaminants in soil and water.

    PubMed

    Sumaraj; Padhye, Lokesh P

    2017-10-01

    Inorganic nitrogen contaminants (INC) (NH 4 + , NO 3 - , NO 2 - , NH 3 , NO, NO 2 , and N 2 O) pose a growing risk to the environment, and their remediation methods are highly sought after. Application of carbon materials (CM), such as biochar and activated carbon, to remediate INC from agricultural fields and wastewater treatment plants has gained a significant interest since past few years. Understanding the role of surface chemistry of CM in adsorption of various INC is highly critical to increase adsorption efficiency as well as to assess the long term impact of using these highly recalcitrant CM for remediation of INC. Critical reviews of adsorption studies related to INC have revealed that carbon surface chemistry (surface functional groups, pH, Eh, elemental composition, and mineral content) has significant influence on adsorption of INC. Compared to basic functional groups, oxygen containing surface functional groups have been found to be more influential for adsorption of INC. However, basic sites on carbon materials still play an important role in chemisorption of anionic INC. Apart from surface functional groups, pH, Eh and pH zpc of CM and elemental and mineral composition of its surface are important properties capable of altering INC interactions with CM. This review summarizes our current understanding of INC interactions with CM's surface through the known chemisorption mechanisms: electrostatic interaction, hydrogen bonding, electron donor-acceptor mechanism, hydrophobic and hydrophilic interaction, chemisorption aided by minerals, and interactions influenced by pH and elemental composition. Change in surface chemistry of CM in soil during aging is also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Controlled surface chemistry of diamond/β-SiC composite films for preferential protein adsorption.

    PubMed

    Wang, Tao; Handschuh-Wang, Stephan; Yang, Yang; Zhuang, Hao; Schlemper, Christoph; Wesner, Daniel; Schönherr, Holger; Zhang, Wenjun; Jiang, Xin

    2014-02-04

    Diamond and SiC both process extraordinary biocompatible, electronic, and chemical properties. A combination of diamond and SiC may lead to highly stable materials, e.g., for implants or biosensors with excellent sensing properties. Here we report on the controllable surface chemistry of diamond/β-SiC composite films and its effect on protein adsorption. For systematic and high-throughput investigations, novel diamond/β-SiC composite films with gradient composition have been synthesized using the hot filament chemical vapor deposition (HFCVD) technique. As revealed by scanning electron microscopy (SEM), the diamond/β-SiC ratio of the composite films shows a continuous change from pure diamond to β-SiC over a length of ∼ 10 mm on the surface. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed to unveil the surface termination of chemically oxidized and hydrogen treated surfaces. The surface chemistry of the composite films was found to depend on diamond/β-SiC ratio and the surface treatment. As observed by confocal fluorescence microscopy, albumin and fibrinogen were preferentially adsorbed from buffer: after surface oxidation, the proteins preferred to adsorb on diamond rather than on β-SiC, resulting in an increasing amount of proteins adsorbed to the gradient surfaces with increasing diamond/β-SiC ratio. By contrast, for hydrogen-treated surfaces, the proteins preferentially adsorbed on β-SiC, leading to a decreasing amount of albumin adsorbed on the gradient surfaces with increasing diamond/β-SiC ratio. The mechanism of preferential protein adsorption is discussed by considering the hydrogen bonding of the water self-association network to OH-terminated surfaces and the change of the polar surface energy component, which was determined according to the van Oss method. These results suggest that the diamond/β-SiC gradient film can be a promising material for biomedical applications which

  17. Bioorthogonal chemistry: applications in activity-based protein profiling.

    PubMed

    Willems, Lianne I; van der Linden, Wouter A; Li, Nan; Li, Kah-Yee; Liu, Nora; Hoogendoorn, Sascha; van der Marel, Gijs A; Florea, Bogdan I; Overkleeft, Herman S

    2011-09-20

    of chemical biology research include contributions from many areas of the multifaceted discipline of chemistry, and particularly from organic chemistry. Researchers apply knowledge inherent to organic chemistry, such as reactivity and selectivity, to the manipulation of specific biomolecules in biological samples (cell extracts, living cells, and sometimes even animal models) to gain insight into the biological phenomena in which these molecules participate. In this Account, we highlight some of the recent developments in chemical biology research driven by organic chemistry, with a focus on bioorthogonal chemistry in relation to activity-based protein profiling. The rigorous demands of bioorthogonality have not yet been realized in a truly bioorthogonal reagent pair, but remarkable progress has afforded a range of tangible contributions to chemical biology research. Activity-based protein profiling, which aims to obtain information on the workings of a protein (or protein family) within the larger context of the full biological system, has in particular benefited from these advances. Both activity-based protein profiling and bioorthogonal chemistry have been around for approximately 15 years, and about 8 years ago the two fields very profitably intersected. We expect that each discipline, both separately and in concert, will continue to make important contributions to chemical biology research. © 2011 American Chemical Society

  18. Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

    PubMed

    Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

    2015-08-18

    Energy dissipation at surfaces and interfaces is mediated by excitation of elementary processes, including phonons and electronic excitation, once external energy is deposited to the surface during exothermic chemical processes. Nonadiabatic electronic excitation in exothermic catalytic reactions results in the flow of energetic electrons with an energy of 1-3 eV when chemical energy is converted to electron flow on a short (femtosecond) time scale before atomic vibration adiabatically dissipates the energy (in picoseconds). These energetic electrons that are not in thermal equilibrium with the metal atoms are called "hot electrons". The detection of hot electron flow under atomic or molecular processes and understanding its role in chemical reactions have been major topics in surface chemistry. Recent studies have demonstrated electronic excitation produced during atomic or molecular processes on surfaces, and the influence of hot electrons on atomic and molecular processes. We outline research efforts aimed at identification of the intrinsic relation between the flow of hot electrons and catalytic reactions. We show various strategies for detection and use of hot electrons generated by the energy dissipation processes in surface chemical reactions and photon absorption. A Schottky barrier localized at the metal-oxide interface of either catalytic nanodiodes or hybrid nanocatalysts allows hot electrons to irreversibly transport through the interface. We show that the chemicurrent, composed of hot electrons excited by the surface reaction of CO oxidation or hydrogen oxidation, correlates well with the turnover rate measured separately by gas chromatography. Furthermore, we show that hot electron flows generated on a gold thin film by photon absorption (or internal photoemission) can be amplified by localized surface plasmon resonance. The influence of hot charge carriers on the chemistry at the metal-oxide interface are discussed for the cases of Au, Ag, and Pt

  19. MEMS-based, RF-driven, compact accelerators

    NASA Astrophysics Data System (ADS)

    Persaud, A.; Seidl, P. A.; Ji, Q.; Breinyn, I.; Waldron, W. L.; Schenkel, T.; Vinayakumar, K. B.; Ni, D.; Lal, A.

    2017-10-01

    Shrinking existing accelerators in size can reduce their cost by orders of magnitude. Furthermore, by using radio frequency (RF) technology and accelerating ions in several stages, the applied voltages can be kept low paving the way to new ion beam applications. We make use of the concept of a Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) and have previously shown the implementation of its basic components using printed circuit boards, thereby reducing the size of earlier MEQALACs by an order of magnitude. We now demonstrate the combined integration of these components to form a basic accelerator structure, including an initial beam-matching section. In this presentation, we will discuss the results from the integrated multi-beam ion accelerator and also ion acceleration using RF voltages generated on-board. Furthermore, we will show results from Micro-Electro-Mechanical Systems (MEMS) fabricated focusing wafers, which can shrink the dimension of the system to the sub-mm regime and lead to cheaper fabrication. Based on these proof-of-concept results we outline a scaling path to high beam power for applications in plasma heating in magnetized target fusion and in neutral beam injectors for future Tokamaks. This work was supported by the Office of Science of the US Department of Energy through the ARPA-e ALPHA program under contracts DE-AC02-05CH11231.

  20. Theme-Based Bidisciplinary Chemistry Laboratory Modules

    NASA Astrophysics Data System (ADS)

    Leber, Phyllis A.; Szczerbicki, Sandra K.

    1996-12-01

    A thematic approach to each of the two introductory chemistry laboratory sequences, general and organic chemistry, not only provides an element of cohesion but also stresses the role that chemistry plays as the "central science" and emphasizes the intimate link between chemistry and other science disciplines. Thus, in general chemistry the rubric "Environmental Chemistry" affords connections to the geosciences, whereas experiments on the topic of "Plant Assays" bridge organic chemistry and biology. By establishing links with other science departments, the theme-based laboratory experiments will satisfy the following multidisciplinary criteria: (i) to demonstrate the general applicability of core methodologies to the sciences, (ii) to help students relate concepts to a broader multidisciplinary context, (iii) to foster an attitude of both independence and cooperation that can transcend the teaching laboratory to the research arena, and (iv) to promote greater cooperation and interaction between the science departments. Fundamentally, this approach has the potential to impact the chemistry curriculum significantly by including student decision-making in the experimental process. Furthermore, the incorporation of GC-MS, a powerful tool for separation and identification as well as a state-of-the-art analytical technique, in the modules will enhance the introductory general and organic chemistry laboratory sequences by making them more instrument-intensive and by providing a reliable and reproducible means of obtaining quantitative analyses. Each multifaceted module has been designed to meet the following criteria: (i) a synthetic protocol including full spectral characterization of products, (ii) quantitative and statistical analyses of data, and (iii) construction of a database of results. The database will provide several concrete functions. It will foster the idea that science is a continuous incremental process building on the results of earlier experimentalists

  1. Rapid changes in surface water carbonate chemistry during Antarctic sea ice melt

    NASA Astrophysics Data System (ADS)

    Jones, Elizabeth M.; Bakker, Dorothee C. E.; Venables, Hugh J.; Whitehouse, Michael J.; Korb, Rebecca E.; Watson, Andrew J.

    2010-11-01

    ABSTRACT The effect of sea ice melt on the carbonate chemistry of surface waters in the Weddell-Scotia Confluence, Southern Ocean, was investigated during January 2008. Contrasting concentrations of dissolved inorganic carbon (DIC), total alkalinity (TA) and the fugacity of carbon dioxide (fCO2) were observed in and around the receding sea ice edge. The precipitation of carbonate minerals such as ikaite (CaCO3.6H2O) in sea ice brine has the net effect of decreasing DIC and TA and increasing the fCO2 in the brine. Deficits in DIC up to 12 +/- 3 μmol kg-1 in the marginal ice zone (MIZ) were consistent with the release of DIC-poor brines to surface waters during sea ice melt. Biological utilization of carbon was the dominant processes and accounted for 41 +/- 1 μmol kg-1 of the summer DIC deficit. The data suggest that the combined effects of biological carbon uptake and the precipitation of carbonates created substantial undersaturation in fCO2 of 95 μatm in the MIZ during summer sea ice melt. Further work is required to improve the understanding of ikaite chemistry in Antarctic sea ice and its importance for the sea ice carbon pump.

  2. Improving Pharmacy Students' Understanding and Long-term Retention of Acid-Base Chemistry

    PubMed Central

    2007-01-01

    Despite repeated exposure to the principles underlying the behavior of organic acids and bases in aqueous solution, some pharmacy students remain confused about the topic of acid-base chemistry. Since a majority of organic drug molecules have acid-base character, the ability to predict their reactivity and the extent to which they will ionize in a given medium is paramount to students' understanding of essentially all aspects of drug action in vivo and in vitro. This manuscript presents a medicinal chemistry lesson in the fundamentals of acid-base chemistry that many pharmacy students have found enlightening and clarifying PMID:19503706

  3. Soft X-ray absorption spectroscopy investigation of the surface chemistry and treatments of copper indium gallium diselenide (CIGS)

    DOE PAGES

    Schwartz, Craig; Nordlund, Dennis; Sokaras, Dimosthenis; ...

    2017-02-01

    The surface and near surface structure of copper-indium-gallium-selenide (CIGS) absorber layers is integral to the producing a high-quality photovoltaic junction. By using X-ray absorption spectroscopy (XAS) and monitoring multiple elemental absorption edges with both theory and experiment, we are able to identify several features of the surface of CIGS as a function of composition and surface treatments. The XAS data shows trends in the near surface region of oxygen, copper, indium and gallium species as the copper content is varied in the films. The oxygen surface species are also monitored through a series of experiments that systematically investigates the effectsmore » of water and various solutions of: ammonium hydroxide, cadmium sulfate, and thiourea. These being components of cadmium sulfide chemical bath deposition (CBD). Characteristics of the CBD are correlated with a restorative effect that produces as normalized, uniform surface chemistry as measured by XAS. This surface chemistry is found in CIGS solar cells with excellent power conversion efficiency (<19%). The results provide new insight for CIGS processing strategies that seek to replace CBD and/or cadmium sulfide.« less

  4. Soft X-ray absorption spectroscopy investigation of the surface chemistry and treatments of copper indium gallium diselenide (CIGS)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schwartz, Craig; Nordlund, Dennis; Sokaras, Dimosthenis

    The surface and near surface structure of copper-indium-gallium-selenide (CIGS) absorber layers is integral to the producing a high-quality photovoltaic junction. By using X-ray absorption spectroscopy (XAS) and monitoring multiple elemental absorption edges with both theory and experiment, we are able to identify several features of the surface of CIGS as a function of composition and surface treatments. The XAS data shows trends in the near surface region of oxygen, copper, indium and gallium species as the copper content is varied in the films. The oxygen surface species are also monitored through a series of experiments that systematically investigates the effectsmore » of water and various solutions of: ammonium hydroxide, cadmium sulfate, and thiourea. These being components of cadmium sulfide chemical bath deposition (CBD). Characteristics of the CBD are correlated with a restorative effect that produces as normalized, uniform surface chemistry as measured by XAS. This surface chemistry is found in CIGS solar cells with excellent power conversion efficiency (<19%). The results provide new insight for CIGS processing strategies that seek to replace CBD and/or cadmium sulfide.« less

  5. Correlation between surface chemistry and ion energy dependence of the etch yield in multicomponent oxides etching

    NASA Astrophysics Data System (ADS)

    Bérubé, P.-M.; Poirier, J.-S.; Margot, J.; Stafford, L.; Ndione, P. F.; Chaker, M.; Morandotti, R.

    2009-09-01

    The influence of surface chemistry in plasma etching of multicomponent oxides was investigated through measurements of the ion energy dependence of the etch yield. Using pulsed-laser-deposited CaxBa(1-x)Nb2O6 (CBN) and SrTiO3 thin films as examples, it was found that the etching energy threshold shifts toward values larger or smaller than the sputtering threshold depending on whether or not ion-assisted chemical etching is the dominant etching pathway and whether surface chemistry is enhancing or inhibiting desorption of the film atoms. In the case of CBN films etched in an inductively coupled Cl2 plasma, it is found that the chlorine uptake is inhibiting the etching reaction, with the desorption of nonvolatile NbCl2 and BaCl2 compounds being the rate-limiting step.

  6. Collaborative routes to clarifying the murky waters of aqueous supramolecular chemistry.

    PubMed

    Cremer, Paul S; Flood, Amar H; Gibb, Bruce C; Mobley, David L

    2017-12-19

    On planet Earth, water is everywhere: the majority of the surface is covered with it; it is a key component of all life; its vapour and droplets fill the lower atmosphere; and even rocks contain it and undergo geomorphological changes because of it. A community of physical scientists largely drives studies of the chemistry of water and aqueous solutions, with expertise in biochemistry, spectroscopy and computer modelling. More recently, however, supramolecular chemists - with their expertise in macrocyclic synthesis and measuring supramolecular interactions - have renewed their interest in water-mediated non-covalent interactions. These two groups offer complementary expertise that, if harnessed, offer to accelerate our understanding of aqueous supramolecular chemistry and water writ large. This Review summarizes the state-of-the-art of the two fields, and highlights where there is latent chemical space for collaborative exploration by the two groups.

  7. Collaborative routes to clarifying the murky waters of aqueous supramolecular chemistry

    NASA Astrophysics Data System (ADS)

    Cremer, Paul S.; Flood, Amar H.; Gibb, Bruce C.; Mobley, David L.

    2018-01-01

    On planet Earth, water is everywhere: the majority of the surface is covered with it; it is a key component of all life; its vapour and droplets fill the lower atmosphere; and even rocks contain it and undergo geomorphological changes because of it. A community of physical scientists largely drives studies of the chemistry of water and aqueous solutions, with expertise in biochemistry, spectroscopy and computer modelling. More recently, however, supramolecular chemists -- with their expertise in macrocyclic synthesis and measuring supramolecular interactions -- have renewed their interest in water-mediated non-covalent interactions. These two groups offer complementary expertise that, if harnessed, offer to accelerate our understanding of aqueous supramolecular chemistry and water writ large. This Review summarizes the state-of-the-art of the two fields, and highlights where there is latent chemical space for collaborative exploration by the two groups.

  8. Modification of heterogeneous chemistry by complex substrate morphology

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Henson, B.F.; Buelow, S.J.; Robinson, J.M.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Chemistry in many environmental systems is determined at some stage by heterogeneous reaction with a surface. Typically the surface exists as a dispersion or matrix of particulate matter or pores, and a determination of the heterogeneous chemistry of the system must address the extent to which the complexity of the environmental surface affects the reaction rates. Reactions that are of current interest are the series of chlorine nitrate reactions important in polar ozone depletion. The authors have applied surfacemore » spectroscopic techniques developed at LANL to address the chemistry of chlorine nitrate reactions on porous nitric and sulfuric acid ice surfaces as a model study of the measurement of complex, heterogeneous reaction rates. The result of the study is an experimental determination of the surface coverage of one adsorbed reagent and a mechanism of reactivity based on the dependence of this coverage on temperature and vapor pressure. The resulting mechanism allows the first comprehensive modeling of chlorine nitrate reaction probability data from several laboratories.« less

  9. Relationship of wood surface energy to surface composition

    Treesearch

    Feipeng P. Liu; Timothy G. Rials; John Simonsen

    1998-01-01

    The wood cell wall is composed of cellulose, lignin, hemicelluloses, and extractives. Thus, the surface energy of the wood material must be some combination of the surface energies of these components. The influence of extractives on wood surface chemistry can be important in diverse industrial applications, such as coating, pulping, and wood-based composites. In this...

  10. Assessment of surface hardness of acrylic resins submitted to accelerated artificial aging.

    PubMed

    Tornavoi, D C; Agnelli, J A M; Lepri, C P; Mazzetto, M O; Botelho, A L; Soares, R G; Dos Reis, A C

    2012-06-01

    The aim of this study was to assess the influence of accelerated artificial aging (AAA) on the surface hardness of acrylic resins. The following three commercial brands of acrylic resins were tested: Vipi Flash (autopolymerized resin), Vipi Wave (microwave heat-polymerized resin) and Vipi Cril (conventional heat-polymerized resin). To perform the tests, 21 test specimens (65x10x3 mm) were made, 7 for each resin. Three surface hardness readings were performed for each test specimen, before and after AAA, and the means were submitted to the following tests: Kolmogorov-Smirnov (P>0.05), Levene Statistic, Two-way ANOVA, Tukey Post Hoc (P<0.05) with the SPSS Statistical Software 17.0. The analysis of the factors showed significant differences in the hardness values (P<0.05). Before aging, the autopolymerized acrylic resin Vipi Flash showed lower hardness values when compared with the heat-polymerized resin Vipi Cril (P=0.001). After aging, the 3 materials showed similar performance when compared among them. The Vipi Cril was the only one affected by AAA and showed lower hardness values after this procedure (Pp=0.003). It may be concluded that accelerated artificial aging influenced surface hardness of heat-polymerized acrylic resin Vipi Cril.

  11. The Design and Testing of a Dual Fiber Textile Matrix for Accelerating Surface Hemostasis

    PubMed Central

    Fischer, Thomas H.; Vournakis, John N.; Manning, James E.; McCurdy, Shane L.; Rich, Preston B.; Nichols, Timothy C.; Scull, Christopher M.; McCord, Marian G.; Decorta, Joseph A.; Johnson, Peter C.; Smith, Carr J.

    2011-01-01

    The standard treatment for severe traumatic injury is frequently compression and application of gauze dressing to the site of hemorrhage. However, while able to rapidly absorb pools of shed blood, gauze fails to provide strong surface (topical) hemostasis. The result can be excess hemorrhage-related morbidity and mortality. We hypothesized that cost-effective materials (based on widespread availability of bulk fibers for other commercial uses) could be designed based on fundamental hemostatic principles to partially emulate the wicking properties of gauze while concurrently stimulating superior hemostasis. A panel of readily available textile fibers was screened for the ability to activate platelets and the intrinsic coagulation cascade in vitro. Type E continuous filament glass and a specialty rayon fiber were identified from the material panel as accelerators of hemostatic reactions and were custom woven to produce a dual fiber textile bandage. The glass component strongly activated platelets while the specialty rayon agglutinated red blood cells. In comparison with gauze in vitro, the dual fiber textile significantly enhanced the rate of thrombin generation, clot generation as measured by thromboelastography, adhesive protein adsorption and cellular attachment and activation. These results indicate that hemostatic textiles can be designed that mimic gauze in form but surpass gauze in ability to accelerate hemostatic reactions. PMID:19489008

  12. Generation of attosecond electron packets via conical surface plasmon electron acceleration

    PubMed Central

    Greig, S. R.; Elezzabi, A. Y.

    2016-01-01

    We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129

  13. The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running.

    PubMed

    Boey, Hannelore; Aeles, Jeroen; Schütte, Kurt; Vanwanseele, Benedicte

    2017-06-01

    Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

  14. Hybrid quantum and molecular mechanics embedded cluster models for chemistry on silicon and silicon carbide surfaces

    NASA Astrophysics Data System (ADS)

    Shoemaker, James Richard

    Fabrication of silicon carbide (SiC) semiconductor devices are of interest for aerospace applications because of their high-temperature tolerance. Growth of an insulating SiO2 layer on SiC by oxidation is a poorly understood process, and sometimes produces interface defects that degrade device performance. Accurate theoretical models of surface chemistry, using quantum mechanics (QM), do not exist because of the huge computational cost of solving Schrodinger's equation for a molecular cluster large enough to represent a surface. Molecular mechanics (MM), which describes a molecule as a collection of atoms interacting through classical potentials, is a fast computational method, good at predicting molecular structure, but cannot accurately model chemical reactions. A new hybrid QM/MM computational method for surface chemistry was developed and applied to silicon and SiC surfaces. The addition of MM steric constraints was shown to have a large effect on the energetics of O atom adsorption on SiC. Adsorption of O atoms on Si-terminated SiC(111) favors above surface sites, in contrast to Si(111), but favors subsurface adsorption sites on C- terminated SiC(111). This difference, and the energetics of C atom etching via CO2 desorption, can explain the observed poor performance of SiC devices in which insulating layers were grown on C-terminated surfaces.

  15. Rapidly accelerating Mathieu and Weber surface plasmon beams.

    PubMed

    Libster-Hershko, Ana; Epstein, Itai; Arie, Ady

    2014-09-19

    We report the generation of two types of self-accelerating surface plasmon beams which are solutions of the nonparaxial Helmholtz equation in two dimensions. These beams preserve their shape while propagating along either elliptic (Mathieu beam) or parabolic (Weber beam) trajectories. We show that owing to the nonparaxial nature of the Weber beam, it maintains its shape over a much larger distance along the parabolic trajectory, with respect to the corresponding solution of the paraxial equation-the Airy beam. Dynamic control of the trajectory is realized by translating the position of the illuminating free-space beam. Finally, the ability of these beams to self-heal after blocking obstacles is demonstrated as well.

  16. Fluorination of vertically aligned carbon nanotubes: from CF4 plasma chemistry to surface functionalization.

    PubMed

    Struzzi, Claudia; Scardamaglia, Mattia; Colomer, Jean-François; Verdini, Alberto; Floreano, Luca; Snyders, Rony; Bittencourt, Carla

    2017-01-01

    The surface chemistry of plasma fluorinated vertically aligned carbon nanotubes (vCNT) is correlated to the CF 4 plasma chemical composition. The results obtained via FTIR and mass spectrometry are combined with the XPS and Raman analysis of the sample surface showing the dependence on different plasma parameters (power, time and distance from the plasma region) on the resulting fluorination. Photoemission and absorption spectroscopies are used to investigate the evolution of the electronic properties as a function of the fluorine content at the vCNT surface. The samples suffer a limited ageing effect, with a small loss of fluorine functionalities after two weeks in ambient conditions.

  17. Fluorination of vertically aligned carbon nanotubes: from CF4 plasma chemistry to surface functionalization

    PubMed Central

    Scardamaglia, Mattia; Colomer, Jean-François; Verdini, Alberto; Floreano, Luca; Snyders, Rony; Bittencourt, Carla

    2017-01-01

    The surface chemistry of plasma fluorinated vertically aligned carbon nanotubes (vCNT) is correlated to the CF4 plasma chemical composition. The results obtained via FTIR and mass spectrometry are combined with the XPS and Raman analysis of the sample surface showing the dependence on different plasma parameters (power, time and distance from the plasma region) on the resulting fluorination. Photoemission and absorption spectroscopies are used to investigate the evolution of the electronic properties as a function of the fluorine content at the vCNT surface. The samples suffer a limited ageing effect, with a small loss of fluorine functionalities after two weeks in ambient conditions. PMID:28904833

  18. Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

    NASA Astrophysics Data System (ADS)

    Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna; Nowakowska, Maria; Szczubiałka, Krzysztof

    2014-12-01

    Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2

  19. Osteoinductive activity of insulin-functionalized cell culture surfaces obtained using diazonium chemistry

    PubMed Central

    Mikulska, Anna; Filipowska, Joanna; Osyczka, Anna M.; Nowakowska, Maria; Szczubiałka, Krzysztof

    2015-01-01

    Polymeric surfaces suitable for cell culture (DR/Pec) were constructed from diazoresin (DR) and pectin (Pec) in a form of ultrathin films using the layer-by-layer (LbL) technique. The surfaces were functionalized with insulin using diazonium chemistry. Such functionalized surfaces were used to culture human mesenchymal stem cells (hMSCs) to assess their suitability for bone tissue engineering and regeneration. The activity of insulin immobilized on the surfaces (DR/Pec/Ins) was compared to that of insulin dissolved in the culture medium. Human MSC grown on insulin-immobilized DR/Pec surfaces displayed increased proliferation and higher osteogenic activity. The latter was determined by means of alkaline phosphatase (ALP) activity, which increases at early stages of osteoblasts differentiation. Insulin dissolved in the culture medium did not stimulate cell proliferation and its osteogenic activity was significantly lower. Addition of recombinant human bone morphogenetic protein 2 (rhBMP-2) to the culture medium further increased ALP activity in hMSCs indicating additive osteogenic action of immobilized insulin and rhBMP-2. PMID:25629028

  20. Chemistry and temperature-assisted dehydrogenation of C60H30 molecules on TiO2(110) surfaces

    NASA Astrophysics Data System (ADS)

    Sánchez-Sánchez, Carlos; Martínez, José Ignacio; Lanzilotto, Valeria; Biddau, Giulio; Gómez-Lor, Berta; Pérez, Rubén; Floreano, Luca; López, María Francisca; Martín-Gago, José Ángel

    2013-10-01

    The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited, under ultra-high vacuum, a submonolayer coverage of C60H30 and studied, by a combination of experimental techniques (STM, XPS and NEXAFS) and theoretical methods, the different chemical on-surface interaction stages induced by the increasing temperature. We show that room temperature adsorbed molecules exhibit a weak interaction and freely diffuse on the surface, as previously reported for other aromatics. Nevertheless, a slight annealing induces a transition from this (meta)stable configuration into chemisorbed molecules. This adsorbate-surface interaction deforms the C60H30 molecular structure and quenches surface diffusion. Higher annealing temperatures lead to partial dehydrogenation, in which the molecule loses some of the hydrogen atoms and LUMO levels spread in the gap inducing a net total energy gain. Further annealing, up to around 750 K, leads to complete dehydrogenation. At these temperatures the fully dehydrogenated molecules link between them in a bottom-up coupling, forming nanodomes or fullerene-like monodisperse species readily on the dielectric surface. This work opens the door to the use of on-surface chemistry to generate new bottom-up tailored structures directly on high-K dielectric surfaces.The thermal induced on-surface chemistry of large polycyclic aromatic hydrocarbons (PAHs) deposited on dielectric substrates is very rich and complex. We evidence temperature-assisted (cyclo)dehydrogenation reactions for C60H30 molecules and the subsequent bottom-up formation of assembled nanostructures, such as nanodomes, on the TiO2(110) surface. To this aim we have deposited

  1. Computer-based, Jeopardy™-like game in general chemistry for engineering majors

    NASA Astrophysics Data System (ADS)

    Ling, S. S.; Saffre, F.; Kadadha, M.; Gater, D. L.; Isakovic, A. F.

    2013-03-01

    We report on the design of Jeopardy™-like computer game for enhancement of learning of general chemistry for engineering majors. While we examine several parameters of student achievement and attitude, our primary concern is addressing the motivation of students, which tends to be low in a traditionally run chemistry lectures. The effect of the game-playing is tested by comparing paper-based game quiz, which constitutes a control group, and computer-based game quiz, constituting a treatment group. Computer-based game quizzes are Java™-based applications that students run once a week in the second part of the last lecture of the week. Overall effectiveness of the semester-long program is measured through pretest-postest conceptual testing of general chemistry. The objective of this research is to determine to what extent this ``gamification'' of the course delivery and course evaluation processes may be beneficial to the undergraduates' learning of science in general, and chemistry in particular. We present data addressing gender-specific difference in performance, as well as background (pre-college) level of general science and chemistry preparation. We outline the plan how to extend such approach to general physics courses and to modern science driven electives, and we offer live, in-lectures examples of our computer gaming experience. We acknowledge support from Khalifa University, Abu Dhabi

  2. Turkish Prospective Chemistry Teachers' Alternative Conceptions about Acids and Bases

    ERIC Educational Resources Information Center

    Boz, Yezdan

    2009-01-01

    The purpose of this study was to obtain prospective chemistry teachers' conceptions about acids and bases concepts. Thirty-eight prospective chemistry teachers were the participants. Data were collected by means of an open-ended questionnaire and semi-structured interviews. Analysis of data indicated that most prospective teachers did not have…

  3. Life-Cycle Analysis and Inquiry-Based Learning in Chemistry Teaching

    ERIC Educational Resources Information Center

    Juntunen, Marianne; Aksela, Maija

    2013-01-01

    The purpose of this design research is to improve the quality of environmental literacy and sustainability education in chemistry teaching through combining a socio-scientific issue, life-cycle analysis (LCA), with inquiry-based learning (IBL). This first phase of the cyclic design research involved 20 inservice trained chemistry teachers from…

  4. Physico-chemical changes of ZnO nanoparticles with different size and surface chemistry under physiological pH conditions.

    PubMed

    Gwak, Gyeong-Hyeon; Lee, Won-Jae; Paek, Seung-Min; Oh, Jae-Min

    2015-03-01

    We studied the physico-chemical properties of ZnO nanoparticles under physiological pH conditions (gastric, intestinal and plasma) as functions of their size (20 and 70 nm) and surface chemistry (pristine, L-serine, or citrate coating). ZnO nanoparticles were dispersed in phosphate buffered saline under physiological pH conditions and aliquots were collected at specific time points (0.5, 1, 4, 10 and 24 h) for further characterization. The pH values of the aqueous ZnO colloids at each condition were in the neutral to slightly basic range and showed different patterns depending on the original size and surface chemistry of the ZnO nanoparticles. The gastric pH condition was found to significantly dissolve ZnO nanoparticles up to 18-30 wt%, while the intestinal or plasma pH conditions resulted in much lower dissolution amounts than expected. Based on the X-ray diffraction patterns and X-ray absorption spectra, we identified partial phase transition of the ZnO nanoparticles from wurtzite to Zn(OH)2 under the intestinal and plasma pH conditions. Using scanning electron microscopy, we verified that the overall particle size and morphology of all ZnO nanoparticles were maintained regardless of the pH. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

    NASA Astrophysics Data System (ADS)

    Zeng, Shibi; Nguyen, Luan; Cheng, Fang; Liu, Lacheng; Yu, Ying; Tao, Franklin (Feng)

    2014-11-01

    Near surface alloy (NSA) model catalyst Pt/Cu/Pt(1 1 1) was prepared on Pt(1 1 1) through a controlled vapor deposition of Cu atoms. Different coordination environments of Pt atoms of the topmost Pt layer with the underneath Cu atoms in the subsurface result in different local electronic structures of surface Pt atoms. Surface structure and chemistry of the NAS model catalyst in Torr pressure of CO were studied with high pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In Torr pressure of CO, the topmost Pt layer of Pt/Cu/Pt(1 1 1) is restructured to thin nanoclusters with size of about 1 nm. Photoemission feature of O 1s of CO on Pt/Cu/Pt(1 1 1) suggests CO adsorbed on both edge and surface of these formed nanoclusters. This surface is active for CO oxidation. Atomic layers of carbon are formed on Pt/Cu/Pt(1 1 1) at 573 K in 2 Torr of CO.

  6. Experienced Teachers' Pedagogical Content Knowledge of Teaching Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Drechsler, Michal; Van Driel, Jan

    2008-01-01

    We investigated the pedagogical content knowledge (PCK) of nine experienced chemistry teachers. The teachers took part in a teacher training course on students' difficulties and the use of models in teaching acid-base chemistry, electrochemistry, and redox reactions. Two years after the course, the teachers were interviewed about their PCK of (1)…

  7. Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well.

    PubMed

    Mille, Caroline; Debarnot, Dominique; Zorzi, Willy; El Moualij, Benaïssa; Coudreuse, Arnaud; Legeay, Gilbert; Quadrio, Isabelle; Perret-Liaudet, Armand; Poncin-Epaillard, Fabienne

    2012-04-18

    The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic-phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface.

  8. Increasing the Detection Limit of the Parkinson Disorder through a Specific Surface Chemistry Applied onto Inner Surface of the Titration Well

    PubMed Central

    Mille, Caroline; Debarnot, Dominique; Zorzi, Willy; Moualij, Benaïssa El; Coudreuse, Arnaud; Legeay, Gilbert; Quadrio, Isabelle; Perret-Liaudet, Armand; Poncin-Epaillard, Fabienne

    2012-01-01

    The main objective of this paper was to illustrate the enhancement of the sensitivity of ELISA titration for neurodegenerative proteins by reducing nonspecific adsorptions that could lead to false positives. This goal was obtained thanks to the association of plasma and wet chemistries applied to the inner surface of the titration well. The polypropylene surface was plasma-activated and then, dip-coated with different amphiphilic molecules. These molecules have more or less long hydrocarbon chains and may be charged. The modified surfaces were characterized in terms of hydrophilic—phobic character, surface chemical groups and topography. Finally, the coated wells were tested during the ELISA titration of the specific antibody capture of the α-synuclein protein. The highest sensitivity is obtained with polar (Θ = 35°), negatively charged and smooth inner surface. PMID:24955533

  9. Tuning Wettability and Adhesion of Structured Surfaces

    NASA Astrophysics Data System (ADS)

    Badge, Ila

    Structured surfaces with feature size ranging from a few micrometers down to nanometers are of great interest in the applications such as design of anti-wetting surfaces, tissue engineering, microfluidics, filtration, microelectronic devices, anti-reflective coatings and reversible adhesives. A specific surface property demands particular roughness geometry along with suitable surface chemistry. Plasma Enhanced Chemical Vapor Deposition (PECVD) is a technique that offers control over surface chemistry without significantly affecting the roughness and thus, provides a flexibility to alter surface chemistry selectively for a given structured surface. In this study, we have used PECVD to fine tune wetting and adhesion properties. The research presented focuses on material design aspects as well as the fundamental understanding of wetting and adhesion phenomena of structured surfaces. In order to study the effect of surface roughness and surface chemistry on the surface wettability independently, we developed a model surface by combination of colloidal lithography and PECVD. A systematically controlled hierarchical roughness using spherical colloidal particles and surface chemistry allowed for quantitative prediction of contact angles corresponding to metastable and stable wetting states. A well-defined roughness and chemical composition of the surface enabled establishing a correlation between theory predictions and experimental measurements. We developed an extremely robust superhydrophobic surface based on Carbon-Nanotubes (CNT) mats. The surface of CNTs forming a nano-porous mesh was modified using PECVD to deposit a layer of hydrophobic coating (PCNT). The PCNT surface thus formed is superhydrophobic with almost zero contact angle hysteresis. We demonstrated that the PCNT surface is not wetted under steam condensation even after prolonged exposure and also continues to retain its superhydrophobicity after multiple frosting-defrosting cycles. The anti

  10. Rail accelerator research at Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Kerslake, W. R.; Cybyk, B. Z.

    1982-01-01

    A rail accelerator was chosen for study as an electromagnetic space propulsion device because of its simplicity and existing technology base. The results of a mission feasibility study using a large rail accelerator for direct launch of ton-size payloads from the Earth's surface to space, and the results of initial tests with a small, laboratory rail accelerator are presented. The laboratory rail accelerator has a bore of 3 by 3 mm and has accelerated 60 mg projectiles to velocities of 300 to 1000 m/s. Rail materials of Cu, W, and Mo were tested for efficiency and erosion rate.

  11. Extending Halogen-based Medicinal Chemistry to Proteins

    PubMed Central

    El Hage, Krystel; Pandyarajan, Vijay; Phillips, Nelson B.; Smith, Brian J.; Menting, John G.; Whittaker, Jonathan; Lawrence, Michael C.; Meuwly, Markus; Weiss, Michael A.

    2016-01-01

    Insulin, a protein critical for metabolic homeostasis, provides a classical model for protein design with application to human health. Recent efforts to improve its pharmaceutical formulation demonstrated that iodination of a conserved tyrosine (TyrB26) enhances key properties of a rapid-acting clinical analog. Moreover, the broad utility of halogens in medicinal chemistry has motivated the use of hybrid quantum- and molecular-mechanical methods to study proteins. Here, we (i) undertook quantitative atomistic simulations of 3-[iodo-TyrB26]insulin to predict its structural features, and (ii) tested these predictions by X-ray crystallography. Using an electrostatic model of the modified aromatic ring based on quantum chemistry, the calculations suggested that the analog, as a dimer and hexamer, exhibits subtle differences in aromatic-aromatic interactions at the dimer interface. Aromatic rings (TyrB16, PheB24, PheB25, 3-I-TyrB26, and their symmetry-related mates) at this interface adjust to enable packing of the hydrophobic iodine atoms within the core of each monomer. Strikingly, these features were observed in the crystal structure of a 3-[iodo-TyrB26]insulin analog (determined as an R6 zinc hexamer). Given that residues B24–B30 detach from the core on receptor binding, the environment of 3-I-TyrB26 in a receptor complex must differ from that in the free hormone. Based on the recent structure of a “micro-receptor” complex, we predict that 3-I-TyrB26 engages the receptor via directional halogen bonding and halogen-directed hydrogen bonding as follows: favorable electrostatic interactions exploiting, respectively, the halogen's electron-deficient σ-hole and electronegative equatorial band. Inspired by quantum chemistry and molecular dynamics, such “halogen engineering” promises to extend principles of medicinal chemistry to proteins. PMID:27875310

  12. Surface chemistry and microstructure of metallic biomaterials for hip and knee endoprostheses

    NASA Astrophysics Data System (ADS)

    Jenko, Monika; Gorenšek, Matevž; Godec, Matjaž; Hodnik, Maxinne; Batič, Barbara Šetina; Donik, Črtomir; Grant, John T.; Dolinar, Drago

    2018-01-01

    The surface chemistry and microstructures of titanium alloys (both new and used) and CoCrMo alloys used for hip and knee endoprostheses were determined using SEM (morphology), EBSD (phase analysis), AES and XPS (surface chemistry). Two new and two used endoprostheses were studied. The SEM SE and BE images showed their microstructures, while the EBSD provided the phases of the materials. During the production of the hip and knee endoprostheses, these materials are subject to severe thermomechanical treatments and physicochemical processes that are decisive for CoCrMo alloys. The AES and XPS results showed that thin oxide films on (a) Ti6Al4V are primarily a mixture of TiO2 with a small amount of Al2O3, while the V is depleted, (b) Ti6Al7Nb is primarily a mixture of TiO2 with a small amount of Al2O3 and Nb2O5, and (c) the CoCrMo alloy is primarily a mixture of Cr2O3 with small amounts of Co and Mo oxides. The thin oxide film on the CoCrMo alloy should prevent intergranular corrosion and improve the biocompatibility. The thin oxide films on the Ti alloys prevent further corrosion, improve the biocompatibility, and affect the osseointegration.

  13. Gas-filled capillaries for plasma-based accelerators

    NASA Astrophysics Data System (ADS)

    Filippi, F.; Anania, M. P.; Brentegani, E.; Biagioni, A.; Cianchi, A.; Chiadroni, E.; Ferrario, M.; Pompili, R.; Romeo, S.; Zigler, A.

    2017-07-01

    Plasma Wakefield Accelerators are based on the excitation of large amplitude plasma waves excited by either a laser or a particle driver beam. The amplitude of the waves, as well as their spatial dimensions and the consequent accelerating gradient depend strongly on the background electron density along the path of the accelerated particles. The process needs stable and reliable plasma sources, whose density profile must be controlled and properly engineered to ensure the appropriate accelerating mechanism. Plasma confinement inside gas filled capillaries have been studied in the past since this technique allows to control the evolution of the plasma, ensuring a stable and repeatable plasma density distribution during the interaction with the drivers. Moreover, in a gas filled capillary plasma can be pre-ionized by a current discharge to avoid ionization losses. Different capillary geometries have been studied to allow the proper temporal and spatial evolution of the plasma along the acceleration length. Results of this analysis obtained by varying the length and the number of gas inlets will be presented.

  14. Constraints on the Early Terrestrial Surface UV Environment Relevant to Prebiotic Chemistry.

    PubMed

    Ranjan, Sukrit; Sasselov, Dimitar D

    2017-03-01

    The UV environment is a key boundary condition to abiogenesis. However, considerable uncertainty exists as to planetary conditions and hence surface UV at abiogenesis. Here, we present two-stream multilayer clear-sky calculations of the UV surface radiance on Earth at 3.9 Ga to constrain the UV surface fluence as a function of albedo, solar zenith angle (SZA), and atmospheric composition. Variation in albedo and latitude (through SZA) can affect maximum photoreaction rates by a factor of >10.4; for the same atmosphere, photoreactions can proceed an order of magnitude faster at the equator of a snowball Earth than at the poles of a warmer world. Hence, surface conditions are important considerations when computing prebiotic UV fluences. For climatically reasonable levels of CO 2 , fluence shortward of 189 nm is screened out, meaning that prebiotic chemistry is robustly shielded from variations in UV fluence due to solar flares or variability. Strong shielding from CO 2 also means that the UV surface fluence is insensitive to plausible levels of CH 4 , O 2 , and O 3 . At scattering wavelengths, UV fluence drops off comparatively slowly with increasing CO 2 levels. However, if SO 2 and/or H 2 S can build up to the ≥1-100 ppm level as hypothesized by some workers, then they can dramatically suppress surface fluence and hence prebiotic photoprocesses. H 2 O is a robust UV shield for λ < 198 nm. This means that regardless of the levels of other atmospheric gases, fluence ≲198 nm is only available for cold, dry atmospheres, meaning sources with emission ≲198 (e.g., ArF excimer lasers) can only be used in simulations of cold environments with low abundance of volcanogenic gases. On the other hand, fluence at 254 nm is unshielded by H 2 O and is available across a broad range of [Formula: see text], meaning that mercury lamps are suitable for initial studies regardless of the uncertainty in primordial H 2 O and CO 2 levels. Key Words: Radiative

  15. Development and Assessment of Green, Research-Based Instructional Materials for the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Cacciatore, Kristen L.

    2010-01-01

    This research entails integrating two novel approaches for enriching student learning in chemistry into the context of the general chemistry laboratory. The first is a pedagogical approach based on research in cognitive science and the second is the green chemistry philosophy. Research has shown that inquiry-based approaches are effective in…

  16. Multifunctional Surface Modification of Nanodiamonds Based on Dopamine Polymerization.

    PubMed

    Zeng, Yun; Liu, Wenyan; Wang, Zheyu; Singamaneni, Srikanth; Wang, Risheng

    2018-04-03

    Surface functionalization of nanodiamonds (NDs), which is of great interest in advanced material and therapeutic applications, requires the immobilization of functional species, such as nucleic acids, bioprobes, drugs, and metal nanoparticles, onto NDs' surfaces to form stable nanoconjugates. However, it is still challenging to modify the surface of NDs due to the complexity of their surface chemistry and the low density of each functional group on the surfaces of NDs. In this work, we demonstrate a general applicable surface functionalization approach for the preparation of ND-based core-shell nanoconjugates using dopamine polymerization. By taking advantage of the universal adhesion and versatile reactivity of polydopamine, we have effectively conjugated DNA and silver nanoparticles onto NDs. Moreover, the catalytic activity of ND-supported silver nanoparticle was characterized by the reduction of 4-nitrophenol, and the addressability of NDs was tested through DNA hybridization that formed satellite ND-gold nanorod conjugation. This simple and robust method we have presented may significantly improve the capability for attaching various functionalities onto NDs and open up new platforms for applications of NDs.

  17. The surface chemistry of cerium oxide

    DOE PAGES

    Mullins, David R.

    2015-01-29

    Our review covers the structure of, and chemical reactions on, well-defined cerium oxide surfaces. Ceria, or mixed oxides containing ceria, are critical components in automotive three-way catalysts due to their well-known oxygen storage capacity. Ceria is also emerging as an important material in a number of other catalytic processes, particularly those involving organic oxygenates and the water–gas shift reaction. Ceria's acid–base properties, and thus its catalytic behavior, are closely related to its surface structure where different oxygen anion and cerium cation environments are present on the low-index structural faces. The actual structure of these various faces has been the focusmore » of a number of theoretical and experimental investigations. Ceria is also easily reducible from CeO 2 to CeO 2-X. The presence of oxygen vacancies on the surface often dramatically alters the adsorption and subsequent reactions of various adsorbates, either on a clean surface or on metal particles supported on the surface. We conducted surface science studies on the surfaces of thin-films rather than on the surfaces of bulk single crystal oxides. The growth, characterization and properties of these thin-films are also examined.« less

  18. Materials Chemistry and Performance of Silicone-Based Replicating Compounds.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brumbach, Michael T.; Mirabal, Alex James; Kalan, Michael

    Replicating compounds are used to cast reproductions of surface features on a variety of materials. Replicas allow for quantitative measurements and recordkeeping on parts that may otherwise be difficult to measure or maintain. In this study, the chemistry and replicating capability of several replicating compounds was investigated. Additionally, the residue remaining on material surfaces upon removal of replicas was quantified. Cleaning practices were tested for several different replicating compounds. For all replicating compounds investigated, a thin silicone residue was left by the replica. For some compounds, additional inorganic species could be identified in the residue. Simple solvent cleaning could removemore » some residue.« less

  19. Optical Diagnostics for Plasma-based Particle Accelerators

    NASA Astrophysics Data System (ADS)

    Muggli, Patric

    2009-05-01

    One of the challenges for plasma-based particle accelerators is to measure the spatio-temporal characteristics of the accelerated particle bunch. ``Optical'' diagnostics are particularly interesting and useful because of the large number of techniques that exits to determine the properties of photon pulses. The accelerated bunch can produce photons pulses that carry information about its characteristics for example through synchrotron radiation in a magnet, Cherenkov radiation in a gas, and transition radiation (TR) at the boundary between two media with different dielectric constants. Depending on the wavelength of the emission when compared to the particle bunch length, the radiation can be incoherent or coherent. Incoherent TR in the optical range (or OTR) is useful to measure the transverse spatial characteristics of the beam, such as charge distribution and size. Coherent TR (or CTR) carries information about the bunch length that can in principle be retrieved by standard auto-correlation or interferometric techniques, as well as by spectral measurements. A measurement of the total CTR energy emitted by bunches with constant charge can also be used as a shot-to-shot measurement for the relative bunch length as the CTR energy is proportional to the square of the bunch population and inversely proportional to its length (for a fixed distribution). Spectral interferometry can also yield the spacing between bunches in the case where multiple bunches are trapped in subsequent buckets of the plasma wave. Cherenkov radiation can be used as an energy threshold diagnostic for low energy particles. Cherenkov, synchrotron and transition radiation can be used in a dispersive section of the beam line to measure the bunch energy spectrum. The application of these diagnostics to plasma-based particle accelerators, with emphasis on the beam-driven, plasma wakefield accelerator (PWFA) at the SLAC National Accelerator Laboratory will be discussed.

  20. Fifty years of accelerator based physics at Chalk River

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McKay, John W.

    1999-04-26

    The Chalk River Laboratories of Atomic Energy of Canada Ltd. was a major centre for Accelerator based physics for the last fifty years. As early as 1946, nuclear structure studies were started on Cockroft-Walton accelerators. A series of accelerators followed, including the world's first Tandem, and the MP Tandem, Superconducting Cyclotron (TASCC) facility that was opened in 1986. The nuclear physics program was shut down in 1996. This paper will describe some of the highlights of the accelerators and the research of the laboratory.

  1. Chemistry of surface nanostructures in lead precursor-rich PbZr0.52Ti0.48O3 sol-gel films

    NASA Astrophysics Data System (ADS)

    Gueye, I.; Le Rhun, G.; Gergaud, P.; Renault, O.; Defay, E.; Barrett, N.

    2016-02-01

    We present a study of the chemistry of the nanostructured phase at the surface of lead zirconium titanate PbZr0.52Ti0.48O3 (PZT) films synthesized by sol-gel method. In sol-gel synthesis, excess lead precursor is used to maintain the target stoichiometry. Surface nanostructures appear at 10% excess whereas 30% excess inhibits their formation. Using the surface-sensitive, quantitative X-ray photoelectron spectroscopy and glancing angle X-ray diffraction we have shown that the chemical composition of the nanostructures is ZrO1.82-1.89 rather than pyrochlore often described in the literature. The presence of a possibly discontinuous layer of wide band gap ZrO1.82-1.89 could be of importance in determining the electrical properties of PZT-based metal-insulator-metal heterostructures.

  2. Surface modification of pitch-based spherical activated carbon by CVD of NH 3 to improve its adsorption to uric acid

    NASA Astrophysics Data System (ADS)

    Liu, Chaojun; Liang, Xiaoyi; Liu, Xiaojun; Wang, Qin; Zhan, Liang; Zhang, Rui; Qiao, Wenming; Ling, Licheng

    2008-08-01

    Surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by chemical vapor deposition of NH 3 (NH 3-CVD) to improve the adsorption properties of uric acid. The texture and surface chemistry of PSAC were studied by N 2 adsorption, pH PZC (point of zero charge), acid-base titration and X-ray photoelectron spectroscopy (XPS). NH 3-CVD has a limited effect on carbon textural characteristics but it significantly changed the surface chemical properties, resulting in positive effects on uric acid adsorption. After modification by NH 3-CVD, large numbers of nitrogen-containing groups (especially valley-N and center-N) are introduced on the surface of PSAC, which is responsible for the increase of pH PZC, surface basicity and uric acid adsorption capacity. Pseudo-second-order kinetic model can be used to describe the dynamic adsorption of uric acid on PSAC, and the thermodynamic parameters show that the adsorption of uric acid on PSAC is spontaneous, endothermic and irreversible process in nature.

  3. The Path to High Q-Factors in Superconducting Accelerating Cavities: Flux Expulsion and Surface Resistance Optimization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martinello, Martina

    Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatmentmore » capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity

  4. Inhibition of bacterial and leukocyte adhesion under shear stress conditions by material surface chemistry.

    PubMed

    Patel, Jasmine D; Ebert, Michael; Stokes, Ken; Ward, Robert; Anderson, James M

    2003-01-01

    Biomaterial-centered infections, initiated by bacterial adhesion, persist due to a compromised host immune response. Altering implant materials with surface modifying endgroups (SMEs) may enhance their biocompatibility by reducing bacterial and inflammatory cell adhesion. A rotating disc model, which generates shear stress within physiological ranges, was used to characterize adhesion of leukocytes and Staphylococcus epidermidis on polycarbonate-urethanes and polyetherurethanes modified with SMEs (polyethylene oxide, fluorocarbon and dimethylsiloxane) under dynamic flow conditions. Bacterial adhesion in the absence of serum was found to be mediated by shear stress and surface chemistry, with reduced adhesion exhibited on materials modified with polydimethylsiloxane and polyethylene oxide SMEs. In contrast, bacterial adhesion was enhanced on materials modified with fluorocarbon SMEs. In the presence of serum, bacterial adhesion was primarily neither material nor shear dependent. However, bacterial adhesion in serum was significantly reduced to < or = 10% compared to adhesion in serum-free media. Leukocyte adhesion in serum exhibited a shear dependency with increased adhesion occurring in regions exposed to lower shear-stress levels of < or = 7 dyne/cm2. Additionally, polydimethylsiloxane and polyethylene oxide SMEs reduced leukocyte adhesion on polyether-urethanes. In conclusion, these results suggest that surface chemistry and shear stress can mediate bacterial and cellular adhesion. Furthermore, materials modified with polyethylene oxide SMEs are capable of inhibiting bacterial adhesion, consequently minimizing the probability of biomaterial-centered infections.

  5. Bioorthogonal chemistry: strategies and recent development

    PubMed Central

    Ramil, Carlo P.; Lin, Qing

    2013-01-01

    The use of covalent chemistry to track biomolecules in their native environment—a focus of bioorthogonal chemistry—has received considerable interests recently among chemical biologists and organic chemists alike. To facilitate wider adoption of bioorthogonal chemistry in biomedical research, a central effort in the last few years has been focused on the optimization of a few known bioorthogonal reactions, particularly with respective to reaction kinetics improvement, novel genetic encoding systems, and fluorogenic reactions for bioimaging. During these optimizations, three strategies have emerged, including the use of ring strain for substrate activation in the cycloaddition reactions, the discovery of new ligands and privileged substrates for accelerated metal-catalysed reactions, and the design of substrates with pre-fluorophore structures for rapid “turn-on” fluorescence after selective bioorthogonal reactions. In addition, new bioorthogonal reactions based on either modified or completely unprecedented reactant pairs have been reported. Finally, increasing attention has been directed toward the development of mutually exclusive bioorthogonal reactions and their applications in multiple labeling of a biomolecule in cell culture. In this feature article, we wish to present the recent progress in bioorthogonal reactions through the selected examples that highlight the above-mentioned strategies. Considering increasing sophistication in bioorthogonal chemistry development, we strive to project several exciting opportunities where bioorthogonal chemistry can make a unique contribution to biology in near future. PMID:24145483

  6. A Gas-Surface Interaction Model based on Accelerated Reactive Molecular Dynamics for Hypersonic Conditions including Thermal Conduction

    DTIC Science & Technology

    2012-02-28

    Interaction Model based on Accelerated Reactive Molecular Dynamics for Hypersonic conditions including Thermal Conduction FA9550-09-1-0157 Schwartzentruber...Dynamics for Hypersonic Conditions including Thermal Conduction Grant/Contract Number: FA9550-09-1-0157 Program Manager: Dr. John Schmisseur PI...through the boundary layer and may chemically react with the vehicle’s thermal protection system (TPS). Many TPS materials act as a catalyst for the

  7. Electrostatic accelerators with high energy resolution

    NASA Astrophysics Data System (ADS)

    Uchiyama, T.; Agawa, Y.; Nishihashi, T.; Takagi, K.; Yamakawa, H.; Isoya, A.; Takai, M.; Namba, S.

    1991-05-01

    Several models of electrostatic accelerators based on rotating disks (Disktron) have been manufactured for various ion beam applications like surface analyses and implantation. The high voltage terminal of the Disktron with a terminal voltage of up to 500 kV is open in air, while the generator part is enclosed in FRP (fiber reinforced plastics) or a ceramic vessel filled with sf 6 gas. The 1 MV model is completely enclosed in a steel vessel. A compact tandem accelerator of the pellet chain type with a terminal voltage of 1.5 MV has also been manufactured. The good energy stability of these accelerators, typically in the range of 10 -4, has proved to be quite favorable for applications in precise studies of material surfaces, including the use of microbeam techniques.

  8. Demonstration of a high-intensity neutron source based on a liquid-lithium target for Accelerator based Boron Neutron Capture Therapy.

    PubMed

    Halfon, S; Arenshtam, A; Kijel, D; Paul, M; Weissman, L; Berkovits, D; Eliyahu, I; Feinberg, G; Kreisel, A; Mardor, I; Shimel, G; Shor, A; Silverman, I; Tessler, M

    2015-12-01

    A free surface liquid-lithium jet target is operating routinely at Soreq Applied Research Accelerator Facility (SARAF), bombarded with a ~1.91 MeV, ~1.2 mA continuous-wave narrow proton beam. The experiments demonstrate the liquid lithium target (LiLiT) capability to constitute an intense source of epithermal neutrons, for Accelerator based Boron Neutron Capture Therapy (BNCT). The target dissipates extremely high ion beam power densities (>3 kW/cm(2), >0.5 MW/cm(3)) for long periods of time, while maintaining stable conditions and localized residual activity. LiLiT generates ~3×10(10) n/s, which is more than one order of magnitude larger than conventional (7)Li(p,n)-based near threshold neutron sources. A shield and moderator assembly for BNCT, with LiLiT irradiated with protons at 1.91 MeV, was designed based on Monte Carlo (MCNP) simulations of BNCT-doses produced in a phantom. According to these simulations it was found that a ~15 mA near threshold proton current will apply the therapeutic doses in ~1h treatment duration. According to our present results, such high current beams can be dissipated in a liquid-lithium target, hence the target design is readily applicable for accelerator-based BNCT. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System Version 5 (GEOS-5)

    NASA Technical Reports Server (NTRS)

    Li, Feng; Vikhliaev, Yury V.; Newman, Paul A.; Pawson, Steven; Perlwitz, Judith; Waugh, Darryn W.; Douglass, Anne R.

    2016-01-01

    Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer's evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. In this study we investigate the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960-2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model's climatology is evaluated using observations and reanalysis. Comparison of the 1979-2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November-December-January. It enhances stratosphere-troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean Meridional Overturning Circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

  10. Canonical Pedagogical Content Knowledge by Cores for Teaching Acid-Base Chemistry at High School

    ERIC Educational Resources Information Center

    Alvarado, Clara; Cañada, Florentina; Garritz, Andoni; Mellado, Vicente

    2015-01-01

    The topic of acid-base chemistry is one of the oldest in general chemistry courses and it has been almost continuously in academic discussion. The central purpose of documenting the knowledge and beliefs of a group of ten Mexican teachers with experience in teaching acid-base chemistry in high school was to know how they design, prepare and…

  11. Influence of Partial Solar Eclipse 2016 on the surface gravity acceleration using photogate sensor on Kater's reversible pendulum

    NASA Astrophysics Data System (ADS)

    Nugraha, M. G.; Saepuzaman, D.; Sholihat, F. N.; Ramayanti, S.; Setyadin, A. H.; Ferahenki, A. R.; Samsudin, A.; Utama, J. A.; Susanti, H.; Kirana, K. H.

    2016-11-01

    This study was conducted to determine the Earth's surface gravitational acceleration (g) prior to, during, and after a partial solar eclipse. Data was collected in Basic Physics Laboratory Universitas Pendidikan Indonesia, Bandung with coordinates S 6°51'48", E 107°35'40" for three days on March 8 - 10, 2016, in time interval measurement from 6 a.m. to 9 a.m. This research used a standard pendulum, Kater's reversible pendulum, which deviated less than 3° so that the motion can be regarded harmonics oscillation. The period of pendulum oscillation motion is measured by a light sensor (photogate sensor) with accuracy until 10-13 seconds. The data analysis shows that there is small difference value of gravity acceleration at the Earth's surface from three days of observation, i.e. in the order of 10-3 ms-2. It means, there is a changes in the Earth's surface gravitational acceleration (g) due to the partial solar eclipse but not significant.

  12. Surface degradation of polymer insulators under accelerated climatic aging in weather-ometer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xu, G.; McGrath, P.B.; Burns, C.W.

    1996-12-31

    Climatic aging experiments were conducted on two types of outdoor polymer insulators by using a programmable weather-ometer. The housing materials for the insulators were silicone rubber (SR) and ethylene propylene diene monomer (EPDM). The accelerated aging stresses were comprised of ultraviolet radiation, elevated temperature, temperature cycling, thermal shock and high humidity. Their effects on the insulator surface conditions and electrical performance wee examined through visual inspection and SEM studies, contact angle measurements, thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS) analysis, and 50% impulse flashover voltage tests. The results showed a significant damage on the insulator surface caused by some ofmore » the imposed aging stresses. The EDS analysis suggested a photooxidation process that happened on the insulator surface during the aging period.« less

  13. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    NASA Astrophysics Data System (ADS)

    Sych, N. V.; Trofymenko, S. I.; Poddubnaya, O. I.; Tsyba, M. M.; Sapsay, V. I.; Klymchuk, D. O.; Puziy, A. M.

    2012-11-01

    Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (SBET = 2081 m2/g, Vtot = 1.1 cm3/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  14. New Perspectives on Context-Based Chemistry Education: Using a Dialectical Sociocultural Approach to View Teaching and Learning

    ERIC Educational Resources Information Center

    King, Donna

    2012-01-01

    Context-based chemistry education aims to improve student interest and motivation in chemistry by connecting canonical chemistry concepts with real-world contexts. Implementation of context-based chemistry programmes began 20 years ago in an attempt to make the learning of chemistry meaningful for students. This paper reviews such programmes…

  15. Ethanol surface chemistry on MBE-grown GaN(0001), GaOx/GaN(0001), and Ga2O3(2¯01).

    PubMed

    Kollmannsberger, Sebastian L; Walenta, Constantin A; Winnerl, Andrea; Knoller, Fabian; Pereira, Rui N; Tschurl, Martin; Stutzmann, Martin; Heiz, Ueli

    2017-09-28

    In this work, ethanol is used as a chemical probe to study the passivation of molecular beam epitaxy-grown GaN(0001) by surface oxidation. With a high degree of oxidation, no reaction from ethanol to acetaldehyde in temperature-programmed desorption experiments is observed. The acetaldehyde formation is attributed to a mechanism based on α-H abstraction from the dissociatively bound alcohol molecule. The reactivity is related to negatively charged surface states, which are removed upon oxidation of the GaN(0001) surface. This is compared with the Ga 2 O 3 (2¯01) single crystal surface, which is found to be inert for the acetaldehyde production. These results offer a toolbox to explore the surface chemistry of nitrides and oxynitrides on an atomic scale and relate their intrinsic activity to systems under ambient atmosphere.

  16. Nitrate pollution and surface water chemistry in Shimabara, Nagasaki Prefecture, Japan

    NASA Astrophysics Data System (ADS)

    Nakagawa, K.; Amano, H.

    2017-12-01

    Shimabara city has been experiencing serious nitrate pollution in groundwater. To evaluate nitrate pollution and water chemistry in surface water, water samples were collected at 42 sampling points in 15 rivers in Shimabara including a part of Unzen city from January to February 2017. Firstly, spatial distribution of water chemistry was assessed by describing stiff and piper-trilinear diagrams using major ions concentrations. Most of the samples showed Ca-HCO3 or Ca-(NO3+SO4) water types. It corresponds to groundwater chemistry. Some samples were classified into characteristic water types such as Na-Cl, (Na+K)-HCO3, and Ca-Cl. These results indicate sea water mixing and anthropogenic pollution. At the upstream of Nishi-river, although water chemistry showed Ca-HCO3, ions concentrations were higher than that of the other rivers. It indicates that this site was affected by the peripheral anthropogenic activities. Secondly, nitrate-pollution assessment was performed by using NO3-, NO2-, coprostanol (5β(H)-Cholestan-3β-ol), and cholestanol (5α(H)-Cholestan-3β-ol). NO2-N was detected at the 2 sampling points and exceeded drinking standard 0.9 mg L-1 for bottle-fed infants (WHO, 2011). NO3-N + NO2-N concentrations exceeded Japanese drinking standard 10 mg L-1 at 18 sampling points. The highest concentration was 27.5 mg L-1. Higher NO3-N levels were observed in the rivers in the northern parts of the study area. Coprostanol has been used as a fecal contamination indicator, since it can be found in only feces of higher animals. Coprostanol concentrations at 8 sampling points exceeded 700 ng L-1 (Australian drinking water standard). Coprostanol has a potential to distinguish the nitrate pollution sources between chemical fertilizer or livestock wastes, since water samples with similar NO3-N + NO2-N concentration showed distinct coprostanol concentration. The sterols ratio (5β/ (5β+5α)) exceeded 0.5 at 18 sampling points. This reveals that fecal pollution has occurred.

  17. Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

    NASA Astrophysics Data System (ADS)

    Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

    2017-06-01

    Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

  18. Application of Intel Many Integrated Core (MIC) accelerators to the Pleim-Xiu land surface scheme

    NASA Astrophysics Data System (ADS)

    Huang, Melin; Huang, Bormin; Huang, Allen H.

    2015-10-01

    The land-surface model (LSM) is one physics process in the weather research and forecast (WRF) model. The LSM includes atmospheric information from the surface layer scheme, radiative forcing from the radiation scheme, and precipitation forcing from the microphysics and convective schemes, together with internal information on the land's state variables and land-surface properties. The LSM is to provide heat and moisture fluxes over land points and sea-ice points. The Pleim-Xiu (PX) scheme is one LSM. The PX LSM features three pathways for moisture fluxes: evapotranspiration, soil evaporation, and evaporation from wet canopies. To accelerate the computation process of this scheme, we employ Intel Xeon Phi Many Integrated Core (MIC) Architecture as it is a multiprocessor computer structure with merits of efficient parallelization and vectorization essentials. Our results show that the MIC-based optimization of this scheme running on Xeon Phi coprocessor 7120P improves the performance by 2.3x and 11.7x as compared to the original code respectively running on one CPU socket (eight cores) and on one CPU core with Intel Xeon E5-2670.

  19. Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.

    PubMed

    Lanthony, Cloé; Guiltat, Mathilde; Ducéré, Jean Marie; Verdier, Agnes; Hémeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estève, Alain

    2014-09-10

    The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species.

  20. Elucidating the role of surface chemistry on cationic phosphorus dendrimer-siRNA complexation.

    PubMed

    Deriu, Marco A; Tsapis, Nicolas; Noiray, Magali; Grasso, Gianvito; El Brahmi, Nabil; Mignani, Serge; Majoral, Jean-Pierre; Fattal, Elias; Danani, Andrea

    2018-06-14

    In the field of dendrimers targeting small interfering RNA (siRNA) delivery, dendrimer structural properties, such as the flexibility/rigidity ratio, play a crucial role in the efficiency of complexation. However, advances in organic chemistry have enabled the development of dendrimers that differ only by a single atom on their surface terminals. This is the case for cationic phosphorus dendrimers functionalized with either pyrrolidinium (DP) or morpholinium (DM) terminal groups. This small change was shown to strongly affect the dendrimer-siRNA complexation, leading to more efficient anti-inflammatory effects in the case of DP. Reasons for this different behavior can hardly be inferred only by biological in vitro and in vivo experiments due to the high number of variables and complexity of the investigated biological system. However, an understanding of how small chemical surface changes may completely modify the overall dendrimer-siRNA complexation is a significant breakthrough towards the design of efficient dendrimers for nucleic acid delivery. Herein, we present experimental and computational approaches based on isothermal titration calorimetry and molecular dynamics simulations to elucidate the molecular reasons behind different efficiencies and activities of DP and DM. Results of the present research highlight how chemical surface modifications may drive the overall dendrimer-siRNA affinity by influencing enthalpic and entropic contributions of binding free energy. Moreover, this study elucidates molecular reasons related to complexation stoichiometry that may be crucial in determining the dendrimer complexation efficiency.

  1. General Dialdehyde Click Chemistry for Amine Bioconjugation.

    PubMed

    Elahipanah, Sina; O'Brien, Paul J; Rogozhnikov, Dmitry; Yousaf, Muhammad N

    2017-05-17

    The development of methods for conjugating a range of molecules to primary amine functional groups has revolutionized the fields of chemistry, biology, and material science. The primary amine is a key functional group and one of the most important nucleophiles and bases used in all of synthetic chemistry. Therefore, tremendous interest in the synthesis of molecules containing primary amines and strategies to devise chemical reactions to react with primary amines has been at the core of chemical research. In particular, primary amines are a ubiquitous functional group found in biological systems as free amino acids, as key side chain lysines in proteins, and in signaling molecules and metabolites and are also present in many natural product classes. Due to its abundance, the primary amine is the most convenient functional group handle in molecules for ligation to other molecules for a broad range of applications that impact all scientific fields. Because of the primary amine's central importance in synthetic chemistry, acid-base chemistry, redox chemistry, and biology, many methods have been developed to efficiently react with primary amines, including activated carboxylic acids, isothiocyanates, Michael addition type systems, and reaction with ketones or aldehydes followed by in situ reductive amination. Herein, we introduce a new traceless, high-yield, fast click-chemistry method based on the rapid and efficient trapping of amine groups via a functionalized dialdehyde group. The click reaction occurs in mild conditions in organic solvents or aqueous media and proceeds in high yield, and the starting dialdehyde reagent and resulting dialdehyde click conjugates are stable. Moreover, no catalyst or dialdehyde-activating group is required, and the only byproduct is water. The initial dialdehyde and the resulting conjugate are both straightforward to characterize, and the reaction proceeds with high atom economy. To demonstrate the broad scope of this new click

  2. Surveys of research in the Chemistry Division, Argonne National Laboratory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grazis, B.M.

    1992-01-01

    Research reports are presented on reactive intermediates in condensed phase (radiation chemistry, photochemistry), electron transfer and energy conversion, photosynthesis and solar energy conversion, metal cluster chemistry, chemical dynamics in gas phase, photoionization-photoelectrons, characterization and reactivity of coal and coal macerals, premium coal sample program, chemical separations, heavy elements coordination chemistry, heavy elements photophysics/photochemistry, f-electron interactions, radiation chemistry of high-level wastes (gas generation in waste tanks), ultrafast molecular electronic devices, and nuclear medicine. Separate abstracts have been prepared. Accelerator activites and computer system/network services are also reported.

  3. Surveys of research in the Chemistry Division, Argonne National Laboratory

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Grazis, B.M.

    1992-11-01

    Research reports are presented on reactive intermediates in condensed phase (radiation chemistry, photochemistry), electron transfer and energy conversion, photosynthesis and solar energy conversion, metal cluster chemistry, chemical dynamics in gas phase, photoionization-photoelectrons, characterization and reactivity of coal and coal macerals, premium coal sample program, chemical separations, heavy elements coordination chemistry, heavy elements photophysics/photochemistry, f-electron interactions, radiation chemistry of high-level wastes (gas generation in waste tanks), ultrafast molecular electronic devices, and nuclear medicine. Separate abstracts have been prepared. Accelerator activites and computer system/network services are also reported.

  4. INLAND DISSOLVED SALT CHEMISTRY: STATISTICAL EVALUATION OF BIVARIATE AND TERNARY DIAGRAM MODELS FOR SURFACE AND SUBSURFACE WATERS

    EPA Science Inventory

    We compared the use of ternary and bivariate diagrams to distinguish the effects of atmospheric precipitation, rock weathering, and evaporation on inland surface and subsurface water chemistry. The three processes could not be statistically differentiated using bivariate models e...

  5. The EPA Comptox Chemistry Dashboard: A Web-Based Data ...

    EPA Pesticide Factsheets

    The U.S. Environmental Protection Agency (EPA) Computational Toxicology Program integrates advances in biology, chemistry, and computer science to help prioritize chemicals for further research based on potential human health risks. This work involves computational and data driven approaches that integrate chemistry, exposure and biological data. As an outcome of these efforts the National Center for Computational Toxicology (NCCT) has measured, assembled and delivered an enormous quantity and diversity of data for the environmental sciences including high-throughput in vitro screening data, in vivo and functional use data, exposure models and chemical databases with associated properties. A series of software applications and databases have been produced over the past decade to deliver these data but recent developments have focused on the development of a new software architecture that assembles the resources into a single platform. A new web application, the CompTox Chemistry Dashboard provides access to data associated with ~720,000 chemical substances. These data include experimental and predicted physicochemical property data, bioassay screening data associated with the ToxCast program, product and functional use information and a myriad of related data of value to environmental scientists. The dashboard provides chemical-based searching based on chemical names, synonyms and CAS Registry Numbers. Flexible search capabilities allow for chemical identificati

  6. Students' Perceptions of Teaching in Context-based and Traditional Chemistry Classrooms: Comparing content, learning activities, and interpersonal perspectives

    NASA Astrophysics Data System (ADS)

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2014-07-01

    Context-based curriculum reforms in chemistry education are thought to bring greater diversity to the ways in which chemistry teachers organize their teaching. First and foremost, students are expected to perceive this diversity. However, empirical research on how students perceive their teacher's teaching in context-based chemistry classrooms, and whether this teaching differs from traditional chemistry lessons, is scarce. This study aims to develop our understanding of what teaching looks like, according to students, in context-based chemistry classrooms compared with traditional chemistry classrooms. As such, it might also provide a better understanding of whether teachers implement and attain the intentions of curriculum developers. To study teacher behaviour we used three theoretical perspectives deemed to be important for student learning: a content perspective, a learning activities perspective, and an interpersonal perspective. Data were collected from 480 students in 24 secondary chemistry classes in the Netherlands. Our findings suggest that, according to the students, the changes in teaching in context-based chemistry classrooms imply a lessening of the emphasis on fundamental chemistry and the use of a teacher-centred approach, compared with traditional chemistry classrooms. However, teachers in context-based chemistry classrooms seem not to display more 'context-based' teaching behaviour, such as emphasizing the relation between chemistry, technology, and society and using a student-centred approach. Furthermore, students in context-based chemistry classrooms perceive their teachers as having less interpersonal control and showing less affiliation than teachers in traditional chemistry classrooms. Our findings should be interpreted in the context of former and daily experiences of both teachers and students. As only chemistry is reformed in the schools in which context-based chemistry is implemented, it is challenging for both students and teachers to

  7. Study of the Effect of Grafting Method on Surface Polarity of Tempo-Oxidized Nanocellulose Using Polycaprolactone as the Modifying Compound: Esterification versus Click-Chemistry

    PubMed Central

    Benkaddour, Abdelhaq; Jradi, Khalil; Robert, Sylvain; Daneault, Claude

    2013-01-01

    Esterification and click-chemistry were evaluated as surface modification treatments for TEMPO-oxidized nanocelluloses (TONC) using Polycaprolactone-diol (PCL) as modifying compound in order to improve the dispersion of nanofibers in organic media. These two grafting strategies were analyzed and compared. The first consists of grafting directly the PCL onto TONC, and was carried out by esterification between hydroxyl groups of PCL and carboxyl groups of TONC. The second strategy known as click-chemistry is based on the 1,3-dipolar cycloaddition reaction between azides and alkyne terminated moieties to form the triazole ring between PCL and TONC. The grafted samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetry analysis (TGA). Further, the effects of the two treatments on the surface hydrophobization of TONC were investigated by contact angle measurements. The results show that both methods confirm the success of such a modification and the click reaction was significantly more effective than esterification. PMID:28348357

  8. Assessing College Students' Understanding of Acid Base Chemistry Concepts

    ERIC Educational Resources Information Center

    Wan, Yanjun Jean

    2014-01-01

    Typically most college curricula include three acid base models: Arrhenius', Bronsted-Lowry's, and Lewis'. Although Lewis' acid base model is generally thought to be the most sophisticated among these three models, and can be further applied in reaction mechanisms, most general chemistry curricula either do not include Lewis' acid base model, or…

  9. Color and surface chemistry changes of extracted wood flour after heating at 120 °C

    Treesearch

    Yao Chen; Mandla A. Tshabalala; Jianmin Gao; Nicole M. Stark

    2013-01-01

    To investigate the effect of heat on color and surface chemistry of wood flour (WF), unextracted, extracted and delignified samples of commercial WF were heated at 120 °C for 24 h and analyzed by colorimetry, diffuse reflectance visible (DRV), attenuated total reflectance Fourier transform infrared (ATR-FTIR) and Fourier transform Raman (FT-Raman) spectroscopies....

  10. Model-based Acceleration Control of Turbofan Engines with a Hammerstein-Wiener Representation

    NASA Astrophysics Data System (ADS)

    Wang, Jiqiang; Ye, Zhifeng; Hu, Zhongzhi; Wu, Xin; Dimirovsky, Georgi; Yue, Hong

    2017-05-01

    Acceleration control of turbofan engines is conventionally designed through either schedule-based or acceleration-based approach. With the widespread acceptance of model-based design in aviation industry, it becomes necessary to investigate the issues associated with model-based design for acceleration control. In this paper, the challenges for implementing model-based acceleration control are explained; a novel Hammerstein-Wiener representation of engine models is introduced; based on the Hammerstein-Wiener model, a nonlinear generalized minimum variance type of optimal control law is derived; the feature of the proposed approach is that it does not require the inversion operation that usually upsets those nonlinear control techniques. The effectiveness of the proposed control design method is validated through a detailed numerical study.

  11. JAERI R & D on accelerator-based transmutation under OMEGA program

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takizuka, T.; Nishida, T.; Mizumoto, M.

    1995-10-01

    The overview of the Japanese long-term research and development program on nuclide partitioning and transmutation, called {open_quotes}OMEGA,{close_quotes} is presented. Under this national program, major R&D activities are being carried out at JAERI, PNC, and CRIEPI. Accelerator-based transmutation study at JAERI is focused on a dedicated transmutor with a subcritical actinide-fueled subcritical core coupled with a spallation target driven by a high intensity proton accelerator. Two types of system concept, solid system and molten-salt system, are discussed. The solid system consists of sodium-cooled tungsten target and metallic actinide fuel. The molten-salt system is fueled with molten actinide chloride that acts alsomore » as a target material. The proposed plant transmutes about 250 kg of minor actinide per year, and generates enough electricity to power its own accelerator. JAERI is proposing the development of an intense proton linear accelerator ETA with 1.5 GeV-10 mA beam for engineering tests of accelerator-based transmutation. Recent achievements in the accelerator development are described.« less

  12. Effectiveness of Case-Based Learning Instruction on Epistemological Beliefs and Attitudes Toward Chemistry

    NASA Astrophysics Data System (ADS)

    Çam, Aylin; Geban, Ömer

    2011-02-01

    The purpose of the study was to investigate the effectiveness of case-based learning instruction over traditionally designed chemistry instruction on eleventh grade students' epistemological beliefs and their attitudes toward chemistry as a school subject. The subjects of this study consisted of 63 eleventh grade students from two intact classes of an urban high school instructed with same teacher. Each teaching method was randomly assigned to one class. The experimental group received case-based learning and the control group received traditional instruction. At the experimental group, life cases were presented with small group format; at the control group, lecturing and discussion was carried out. The results showed that there was a significant difference between the experimental and control group with respect to their epistemological beliefs and attitudes toward chemistry as a school subject in favor of case-based learning method group. Thus, case base learning is helpful for development of students' epistemological beliefs and attitudes toward chemistry.

  13. Surface trimming of silicon photonics devices using controlled reactive ion etching chemistry

    NASA Astrophysics Data System (ADS)

    Chandran, S.; Das, B. K.

    2015-06-01

    Surface trimming of rib waveguides fabricated in 5-μm SOI substrate has been carried out successfully without any significant increase of propagation losses. A reactive ion etching chemistry has been optimized for trimming and an empirical model has been developed to obtain the resulting waveguide geometries. This technique has been used to demonstrate smaller footprint devices like multimode interference based power splitters and ring resonators after defining them photolithographically with relatively large cross-section rib waveguides. We have been also successful to fabricate 2D tapered spot-size converter useful for monolithic integration of waveguides with varying heights and widths. The taper length is again precisely controlled by photolithographic definition. Minimum insertion loss of such a spot-size converter integrated between waveguides with 3-μm height difference has been recorded to be ∼2 dB. It has been also shown that the overall fiber-to-chip coupling loss can be reduced by >3 dB by using such spot-size converters at the input/output side of the waveguides.

  14. Assessment of mean-field microkinetic models for CO methanation on stepped metal surfaces using accelerated kinetic Monte Carlo

    NASA Astrophysics Data System (ADS)

    Andersen, Mie; Plaisance, Craig P.; Reuter, Karsten

    2017-10-01

    First-principles screening studies aimed at predicting the catalytic activity of transition metal (TM) catalysts have traditionally been based on mean-field (MF) microkinetic models, which neglect the effect of spatial correlations in the adsorbate layer. Here we critically assess the accuracy of such models for the specific case of CO methanation over stepped metals by comparing to spatially resolved kinetic Monte Carlo (kMC) simulations. We find that the typical low diffusion barriers offered by metal surfaces can be significantly increased at step sites, which results in persisting correlations in the adsorbate layer. As a consequence, MF models may overestimate the catalytic activity of TM catalysts by several orders of magnitude. The potential higher accuracy of kMC models comes at a higher computational cost, which can be especially challenging for surface reactions on metals due to a large disparity in the time scales of different processes. In order to overcome this issue, we implement and test a recently developed algorithm for achieving temporal acceleration of kMC simulations. While the algorithm overall performs quite well, we identify some challenging cases which may lead to a breakdown of acceleration algorithms and discuss possible directions for future algorithm development.

  15. Atmospheric Constraints on the Surface UV Environment of Mars at 3.9 Ga Relevant to Prebiotic Chemistry.

    PubMed

    Ranjan, Sukrit; Wordsworth, Robin; Sasselov, Dimitar D

    2017-08-01

    Recent findings suggest that Mars may have been a clement environment for the emergence of life and may even have compared favorably to Earth in this regard. These findings have revived interest in the hypothesis that prebiotically important molecules or even nascent life may have formed on Mars and been transferred to Earth. UV light plays a key role in prebiotic chemistry. Characterizing the early martian surface UV environment is key to understanding how Mars compares to Earth as a venue for prebiotic chemistry. Here, we present two-stream, multilayer calculations of the UV surface radiance on Mars at 3.9 Ga to constrain the surface UV environment as a function of atmospheric state. We explore a wide range of atmospheric pressures, temperatures, and compositions that correspond to the diversity of martian atmospheric states consistent with available constraints. We include the effects of clouds and dust. We calculate dose rates to quantify the effect of different atmospheric states on UV-sensitive prebiotic chemistry. We find that, for normative clear-sky CO 2 -H 2 O atmospheres, the UV environment on young Mars is comparable to young Earth. This similarity is robust to moderate cloud cover; thick clouds (τ cloud  ≥ 100) are required to significantly affect the martian UV environment, because cloud absorption is degenerate with atmospheric CO 2 . On the other hand, absorption from SO 2 , H 2 S, and dust is nondegenerate with CO 2 , meaning that, if these constituents build up to significant levels, surface UV fluence can be suppressed. These absorbers have spectrally variable absorption, meaning that their presence affects prebiotic pathways in different ways. In particular, high SO 2 environments may admit UV fluence that favors pathways conducive to abiogenesis over pathways unfavorable to it. However, better measurements of the spectral quantum yields of these pathways are required to evaluate this hypothesis definitively. Key Words: Radiative

  16. Influence of porous texture and surface chemistry on the CO₂ adsorption capacity of porous carbons: acidic and basic site interactions.

    PubMed

    Sánchez-Sánchez, Angela; Suárez-García, Fabián; Martínez-Alonso, Amelia; Tascón, Juan M D

    2014-12-10

    Doped porous carbons exhibiting highly developed porosity and rich surface chemistry have been prepared and subsequently applied to clarify the influence of both factors on carbon dioxide capture. Nanocasting was selected as synthetic route, in which a polyaramide precursor (3-aminobenzoic acid) was thermally polymerized inside the porosity of an SBA-15 template in the presence of different H3PO4 concentrations. The surface chemistry and the porous texture of the carbons could be easily modulated by varying the H3PO4 concentration and carbonization temperature. Porous texture was found to be the determinant factor on carbon dioxide adsorption at 0 °C, while surface chemistry played an important role at higher adsorption temperatures. We proved that nitrogen functionalities acted as basic sites and oxygen and phosphorus groups as acidic ones toward adsorption of CO2 molecules. Among the nitrogen functional groups, pyrrolic groups exhibited the highest influence, while the positive effect of pyridinic and quaternary functionalities was smaller. Finally, some of these N-doped carbons exhibit CO2 heats of adsorption higher than 42 kJ/mol, which make them excellent candidates for CO2 capture.

  17. Zwitterion-Coated Iron Oxide Nanoparticles: Surface Chemistry and Intracellular Uptake by Hepatocarcinoma (HepG2) Cells.

    PubMed

    Mondini, Sara; Leonzino, Marianna; Drago, Carmelo; Ferretti, Anna M; Usseglio, Sandro; Maggioni, Daniela; Tornese, Paolo; Chini, Bice; Ponti, Alessandro

    2015-07-07

    Nanoparticles (NPs) have received much attention in recent years for their diverse potential biomedical applications. However, the synthesis of NPs with desired biodistribution and pharmacokinetics is still a major challenge, with NP size and surface chemistry being the main factors determining the behavior of NPs in vivo. Here we report on the surface chemistry and in vitro cellular uptake of magnetic iron oxide NPs coated with zwitterionic dopamine sulfonate (ZDS). ZDS-coated NPs were compared to similar iron oxide NPs coated with PEG-like 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEA) to investigate how surface chemistry affects their in vitro behavior. ZDS-coated NPs had a very dense coating, guaranteeing high colloidal stability in several aqueous media and negligible interaction with proteins. Treatment of HepG2 cells with increasing doses (2.5-100 μg Fe/mL) of ZDS-coated iron oxide NPs had no effect on cell viability and resulted in a low, dose-dependent NP uptake, inferior than most reported data for the internalization of iron oxide NPs by HepG2 cells. MEEA-coated NPs were scarcely stable and formed micrometer-sized aggregates in aqueous media. They decreased cell viability for dose ≥50 μg Fe/mL, and were more efficiently internalized than ZDS-coated NPs. In conclusion, our data indicate that the ZDS layer prevented both aggregation and sedimentation of iron oxide NPs and formed a biocompatible coating that did not display any biocorona effect. The very low cellular uptake of ZDS-coated iron NPs can be useful to achieve highly selective targeting upon specific functionalization.

  18. Effect of surface chemistries and characteristics of Ti6Al4V on the Ca and P adsorption and ion dissolution in Hank's ethylene diamine tetra-acetic acid solution.

    PubMed

    Chang, E; Lee, T M

    2002-07-01

    This study examined the influence of chemistries and surface characteristics of Ti6Al4V on the adsorption of Ca and P species and ion dissolution behavior of the material exposed in Hank's solution with 8.0 mM ethylene diamine tetra-acetic acid at 37 degrees C. The variation of chemistries of the alloy and nano-surface characteristics (chemistries of nano-surface oxides, amphoteric OH group adsorbed on oxides, and oxide thickness) was effected by surface modification and three passivation methods (34% nitric acid passivation. 400 degrees C heated in air, and aged in 100 degrees C water). X-ray photoelectron spectroscopy and Auger electron spectroscopy were used for surface analyses. The chemistries of nano-surface oxides in a range studied should not change the capability of Ca and P adsorption. Nor is the capability affected significantly by amphoteric OH group and oxide thickness. However, passivations influence the surface oxide thickness and the early stage ion dissolution rate of the alloy. The rate-limiting step of the rate can be best explained by metal-ion transport through the oxide film, rather than hydrolysis of the film. Variation of the chemistries of titanium alloy alters the electromotive force potential of the metal, thereby affecting the corrosion and ion dissolution rate.

  19. Surface Chemistry, Microstructure, and Tribological Properties of Cubic Boron Nitride Films

    NASA Technical Reports Server (NTRS)

    Watanabe, Shuichi; Wheeler, Donald R.; Abel, Phillip B.; Street, Kenneth W.; Miyoshi, Kazuhisa; Murakawa, Masao; Miyake, Shojiro

    1998-01-01

    This report deals with the surface chemistry, microstructure, bonding state, morphology, and friction and wear properties of cubic boron nitride (c-BN) films that were synthesized by magnetically enhanced plasma ion plating. Several analytical techniques - x-ray photoelectron spectroscopy, transmission electron microscopy and electron diffraction, Fourier transform infrared spectroscopy, atomic force microscopy, and surface profilometry - were used to characterize the films. Sliding friction experiments using a ball-on-disk configuration were conducted for the c-BN films in sliding contact with 440C stainless-steel balls at room temperature in ultrahigh vacuum (pressure, 10(exp -6), in ambient air, and under water lubrication. Results indicate that the boron-to-nitrogen ratio on the surface of the as-deposited c-BN film is greater than 1 and that not all the boron is present as boron nitride but a small percentage is present as an oxide. Both in air and under water lubrication, the c-BN film in sliding contact with steel showed a low wear rate, whereas a high wear rate was observed in vacuum. In air and under water lubrication, c-BN exhibited wear resistance superior to that of amorphous boron nitride, titanium nitride, and titanium carbide.

  20. How do video-based demonstration assessment tasks affect problem-solving process, test anxiety, chemistry anxiety and achievement in general chemistry students?

    NASA Astrophysics Data System (ADS)

    Terrell, Rosalind Stephanie

    2001-12-01

    Because paper-and-pencil testing provides limited knowledge about what students know about chemical phenomena, we have developed video-based demonstrations to broaden measurement of student learning. For example, students might be shown a video demonstrating equilibrium shifts. Two methods for viewing equilibrium shifts are changing the concentration of the reactants and changing the temperature of the system. The students are required to combine the data collected from the video and their knowledge of chemistry to determine which way the equilibrium shifts. Video-based demonstrations are important techniques for measuring student learning because they require students to apply conceptual knowledge learned in class to a specific chemical problem. This study explores how video-based demonstration assessment tasks affect problem-solving processes, test anxiety, chemistry anxiety and achievement in general chemistry students. Several instruments were used to determine students' knowledge about chemistry, students' test and chemistry anxiety before and after treatment. Think-aloud interviews were conducted to determine students' problem-solving processes after treatment. The treatment group was compared to a control group and a group watching video demonstrations. After treatment students' anxiety increased and achievement decreased. There were also no significant differences found in students' problem-solving processes following treatment. These negative findings may be attributed to several factors that will be explored in this study.

  1. Mimicking the surface and prebiotic chemistry of early Earth using flow chemistry.

    PubMed

    Ritson, Dougal J; Battilocchio, Claudio; Ley, Steven V; Sutherland, John D

    2018-05-08

    When considering life's aetiology, the first questions that must be addressed are "how?" and "where?" were ostensibly complex molecules, considered necessary for life's beginning, constructed from simpler, more abundant feedstock molecules on primitive Earth. Previously, we have used multiple clues from the prebiotic synthetic requirements of (proto)biomolecules to pinpoint a set of closely related geochemical scenarios that are suggestive of flow and semi-batch chemistries. We now wish to report a multistep, uninterrupted synthesis of a key heterocycle (2-aminooxazole) en route to activated nucleotides starting from highly plausible, prebiotic feedstock molecules under conditions which mimic this scenario. Further consideration of the scenario has uncovered additional pertinent and novel aspects of prebiotic chemistry, which greatly enhance the efficiency and plausibility of the synthesis.

  2. Double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor.

    PubMed

    Qi, Honglan; Li, Min; Zhang, Rui; Dong, Manman; Ling, Chen

    2013-08-20

    A double electrochemical covalent coupling method based on click chemistry and diazonium chemistry for the fabrication of sensitive amperometric immunosensor was developed. As a proof-of-concept, a designed alkyne functionalized human IgG was used as a capture antibody and a HRP-labeled rabbit anti-goat IgG was used as signal antibody for the determination of the anti-human IgG using the sandwich model. The immunosensor was fabricated by electrochemically grafting a phenylazide on the surface of a glassy carbon electrode, and then, by coupling the alkyne functionalized human IgG with the phenylazide group through an electro-click chemistry in the presence of Cu(II). The amperometric measurement for the determination of the anti-human IgG was performed after the fabricated immunosensor was incubated with the target anti-human IgG and then with the HRP-labeled anti-goat IgG at -0.25V in 0.10M PBS (pH 7.0) containing 0.1mM hydroquinone and 2.0mM H2O2. The results showed that the increased current was linear with the logarithm of the concentration of the anti-human IgG in the range from 1.0×10(-10)g mL(-1) to 1.0×10(-8)g mL(-1) with a detection limit of 3×10(-11)g mL(-1). Furthermore, the feasibility of the double electrochemical covalent coupling method proposed in this work for fabricating the amperometric immunosensor array was explored. This work demonstrates that the double electrochemical covalent coupling method is a promising approach for the fabrication of the immunosensor and immunosensor array. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. Substantial difference in target surface chemistry between reactive dc and high power impulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Greczynski, G.; Mráz, S.; Schneider, J. M.; Hultman, L.

    2018-02-01

    The nitride layer formed in the target race track during the deposition of stoichiometric TiN thin films is a factor 2.5 thicker for high power impulse magnetron sputtering (HIPIMS), compared to conventional dc processing (DCMS). The phenomenon is explained using x-ray photoelectron spectroscopy analysis of the as-operated Ti target surface chemistry supported by sputter depth profiles, dynamic Monte Carlo simulations employing the TRIDYN code, and plasma chemical investigations by ion mass spectrometry. The target chemistry and the thickness of the nitride layer are found to be determined by the implantation of nitrogen ions, predominantly N+ and N2+ for HIPIMS and DCMS, respectively. Knowledge of this method-inherent difference enables robust processing of high quality functional coatings.

  4. Particle acceleration in pulsar magnetospheres

    NASA Technical Reports Server (NTRS)

    Baker, K. B.

    1978-01-01

    The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must occur. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration occurred at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to occur nearer to the surface of the star.

  5. Atmospheric Constraints on the Surface UV Environment of Mars at 3.9 Ga Relevant to Prebiotic Chemistry

    NASA Astrophysics Data System (ADS)

    Ranjan, Sukrit; Wordsworth, Robin; Sasselov, Dimitar D.

    2017-08-01

    Recent findings suggest that Mars may have been a clement environment for the emergence of life and may even have compared favorably to Earth in this regard. These findings have revived interest in the hypothesis that prebiotically important molecules or even nascent life may have formed on Mars and been transferred to Earth. UV light plays a key role in prebiotic chemistry. Characterizing the early martian surface UV environment is key to understanding how Mars compares to Earth as a venue for prebiotic chemistry. Here, we present two-stream, multilayer calculations of the UV surface radiance on Mars at 3.9 Ga to constrain the surface UV environment as a function of atmospheric state. We explore a wide range of atmospheric pressures, temperatures, and compositions that correspond to the diversity of martian atmospheric states consistent with available constraints. We include the effects of clouds and dust. We calculate dose rates to quantify the effect of different atmospheric states on UV-sensitive prebiotic chemistry. We find that, for normative clear-sky CO2-H2O atmospheres, the UV environment on young Mars is comparable to young Earth. This similarity is robust to moderate cloud cover; thick clouds (τcloud ≥ 100) are required to significantly affect the martian UV environment, because cloud absorption is degenerate with atmospheric CO2. On the other hand, absorption from SO2, H2S, and dust is nondegenerate with CO2, meaning that, if these constituents build up to significant levels, surface UV fluence can be suppressed. These absorbers have spectrally variable absorption, meaning that their presence affects prebiotic pathways in different ways. In particular, high SO2 environments may admit UV fluence that favors pathways conducive to abiogenesis over pathways unfavorable to it. However, better measurements of the spectral quantum yields of these pathways are required to evaluate this hypothesis definitively.

  6. Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry

    PubMed Central

    Kim, Hyun-Ha; Ogata, Atsushi

    2011-01-01

    This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed. PMID:22163781

  7. Accelerators for Discovery Science and Security applications

    NASA Astrophysics Data System (ADS)

    Todd, A. M. M.; Bluem, H. P.; Jarvis, J. D.; Park, J. H.; Rathke, J. W.; Schultheiss, T. J.

    2015-05-01

    Several Advanced Energy Systems (AES) accelerator projects that span applications in Discovery Science and Security are described. The design and performance of the IR and THz free electron laser (FEL) at the Fritz-Haber-Institut der Max-Planck-Gesellschaft in Berlin that is now an operating user facility for physical chemistry research in molecular and cluster spectroscopy as well as surface science, is highlighted. The device was designed to meet challenging specifications, including a final energy adjustable in the range of 15-50 MeV, low longitudinal emittance (<50 keV-psec) and transverse emittance (<20 π mm-mrad), at more than 200 pC bunch charge with a micropulse repetition rate of 1 GHz and a macropulse length of up to 15 μs. Secondly, we will describe an ongoing effort to develop an ultrafast electron diffraction (UED) source that is scheduled for completion in 2015 with prototype testing taking place at the Brookhaven National Laboratory (BNL) Accelerator Test Facility (ATF). This tabletop X-band system will find application in time-resolved chemical imaging and as a resource for drug-cell interaction analysis. A third active area at AES is accelerators for security applications where we will cover some top-level aspects of THz and X-ray systems that are under development and in testing for stand-off and portal detection.

  8. Impact of surface ozone interactions on indoor air chemistry: A modeling study.

    PubMed

    Kruza, M; Lewis, A C; Morrison, G C; Carslaw, N

    2017-09-01

    An INdoor air Detailed Chemical Model was developed to investigate the impact of ozone reactions with indoor surfaces (including occupants), on indoor air chemistry in simulated apartments subject to ambient air pollution. The results are consistent with experimental studies showing that approximately 80% of ozone indoors is lost through deposition to surfaces. The human body removes ozone most effectively from indoor air per square meter of surface, but the most significant surfaces for C 6 -C 10 aldehyde formation are soft furniture and painted walls owing to their large internal surfaces. Mixing ratios of between 8 and 11 ppb of C 6 -C 10 aldehydes are predicted to form in apartments in various locations in summer, the highest values are when ozone concentrations are enhanced outdoors. The most important aldehyde formed indoors is predicted to be nonanal (5-7 ppb), driven by oxidation-derived emissions from painted walls. In addition, ozone-derived emissions from human skin were estimated for a small bedroom at nighttime with concentrations of nonanal, decanal, and 4-oxopentanal predicted to be 0.5, 0.7, and 0.7 ppb, respectively. A detailed chemical analysis shows that ozone-derived surface aldehyde emissions from materials and people change chemical processing indoors, through enhanced formation of nitrated organic compounds and decreased levels of oxidants. © 2017 The Authors. Indoor Air Published by John Wiley & Sons Ltd.

  9. Ethanol surface chemistry on MBE-grown GaN(0001), GaOx/GaN(0001), and Ga2O3(2 \\xAF 01 )

    NASA Astrophysics Data System (ADS)

    Kollmannsberger, Sebastian L.; Walenta, Constantin A.; Winnerl, Andrea; Knoller, Fabian; Pereira, Rui N.; Tschurl, Martin; Stutzmann, Martin; Heiz, Ueli

    2017-09-01

    In this work, ethanol is used as a chemical probe to study the passivation of molecular beam epitaxy-grown GaN(0001) by surface oxidation. With a high degree of oxidation, no reaction from ethanol to acetaldehyde in temperature-programmed desorption experiments is observed. The acetaldehyde formation is attributed to a mechanism based on α -H abstraction from the dissociatively bound alcohol molecule. The reactivity is related to negatively charged surface states, which are removed upon oxidation of the GaN(0001) surface. This is compared with the Ga2O3(2 ¯ 01 ) single crystal surface, which is found to be inert for the acetaldehyde production. These results offer a toolbox to explore the surface chemistry of nitrides and oxynitrides on an atomic scale and relate their intrinsic activity to systems under ambient atmosphere.

  10. Accelerating spirocyclic polyketide synthesis using flow chemistry.

    PubMed

    Newton, Sean; Carter, Catherine F; Pearson, Colin M; de C Alves, Leandro; Lange, Heiko; Thansandote, Praew; Ley, Steven V

    2014-05-05

    Over the past decade, the integration of synthetic chemistry with flow processing has resulted in a powerful platform for molecular assembly that is making an impact throughout the chemical community. Herein, we demonstrate the extension of these tools to encompass complex natural product synthesis. We have developed a number of novel flow-through processes for reactions commonly encountered in natural product synthesis programs to achieve the first total synthesis of spirodienal A and the preparation of spirangien A methyl ester. Highlights of the synthetic route include an iridium-catalyzed hydrogenation, iterative Roush crotylations, gold-catalyzed spiroketalization and a late-stage cis-selective reduction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Trends in Surface Water Chemistry in Acidified Areas in Europe and North America from 1990 to 2008

    EPA Science Inventory

    Acidification of lakes and rivers is still an environmental concern despite reduced emissions of acidifying compounds. We analyzed trends in surface water chemistry of 173 acid-sensitive sites from 12 regions in Europe and North America. In 11 of 12 regions, non-marine sulphate (...

  12. Component-based integration of chemistry and optimization software.

    PubMed

    Kenny, Joseph P; Benson, Steven J; Alexeev, Yuri; Sarich, Jason; Janssen, Curtis L; McInnes, Lois Curfman; Krishnan, Manojkumar; Nieplocha, Jarek; Jurrus, Elizabeth; Fahlstrom, Carl; Windus, Theresa L

    2004-11-15

    Typical scientific software designs make rigid assumptions regarding programming language and data structures, frustrating software interoperability and scientific collaboration. Component-based software engineering is an emerging approach to managing the increasing complexity of scientific software. Component technology facilitates code interoperability and reuse. Through the adoption of methodology and tools developed by the Common Component Architecture Forum, we have developed a component architecture for molecular structure optimization. Using the NWChem and Massively Parallel Quantum Chemistry packages, we have produced chemistry components that provide capacity for energy and energy derivative evaluation. We have constructed geometry optimization applications by integrating the Toolkit for Advanced Optimization, Portable Extensible Toolkit for Scientific Computation, and Global Arrays packages, which provide optimization and linear algebra capabilities. We present a brief overview of the component development process and a description of abstract interfaces for chemical optimizations. The components conforming to these abstract interfaces allow the construction of applications using different chemistry and mathematics packages interchangeably. Initial numerical results for the component software demonstrate good performance, and highlight potential research enabled by this platform.

  13. Dragonfly: In Situ Exploration of Titan's Organic Chemistry and Habitability

    NASA Astrophysics Data System (ADS)

    Turtle, E. P.; Barnes, J. W.; Trainer, M. G.; Lorenz, R. D.

    2017-12-01

    Titan's abundant complex carbon-rich chemistry, interior ocean, and past presence of liquid water on the surface make it an ideal destination to study prebiotic chemical processes and document the habitability of an extraterrestrial environment. Titan exploration is a high science priority due to the level of organic synthesis that it supports. Moreover, opportunities for organics to have interacted with liquid water at the surface (e.g., in impact melt sheets) increase the potential for chemical processes to progress further, providing an unparalleled opportunity to investigate prebiotic chemistry, as well as to search for signatures of potential water-based or even hydrocarbon-based life. The diversity of Titan's surface materials and environments drives the scientific need to be able to sample a variety of locations, thus mobility is key for in situ measurements. Titan's atmosphere is 4 times denser than Earth's reducing the wing/rotor area required to generate a given amount of lift, and the low gravity reduces the required magnitude of lift, making heavier-than-air mobility highly efficient. Dragonfly is a rotorcraft lander mission proposed to NASA's New Frontiers Program to take advantage of Titan's unique natural laboratory to understand how far chemistry can progress in environments that provide key ingredients for life. Measuring the compositions of materials in different environments will reveal how far organic chemistry has progressed. Surface material can be sampled into a mass spectrometer to identify the chemical components available and processes at work to produce biologically relevant compounds. Bulk elemental surface composition can be determined by a neutron-activated gamma-ray spectrometer. Meteorology measurements can characterize Titan's atmosphere and diurnal and spatial variations therein. Geologic features can be characterized via remote-sensing observations, which also provide context for samples. Seismic sensing can probe subsurface

  14. Effect of Porosity Parameters and Surface Chemistry on Carbon Dioxide Adsorption in Sulfur-Doped Porous Carbons.

    PubMed

    Wang, En-Jie; Sui, Zhu-Yin; Sun, Ya-Nan; Ma, Zhuang; Han, Bao-Hang

    2018-05-22

    In this work, a series of highly porous sulfur-doped carbons are prepared through physical activation methods by using polythiophene as a precursor. The morphology, structure, and physicochemical properties are revealed by a variety of characterization methods, such as scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and nitrogen sorption measurement. Their porosity parameters and chemical compositions can be well-tuned by changing the activating agents (steam and carbon dioxide) and reaction temperature. These sulfur-doped porous carbons possess specific surface area of 670-2210 m 2 g -1 , total pore volume of 0.31-1.26 cm 3 g -1 , and sulfur content of 0.6-4.9 atom %. The effect of porosity parameters and surface chemistry on carbon dioxide adsorption in sulfur-doped porous carbons is studied in detail. After a careful analysis of carbon dioxide uptake at different temperatures (273 and 293 K), pore volumes from small pore size (less than 1 nm) play an important role in carbon dioxide adsorption at 273 K, whereas surface chemistry is the key factor at a higher adsorption temperature or lower relative pressure. Furthermore, sulfur-doped porous carbons also possess good gas adsorption selectivity and excellent recyclability for regeneration.

  15. The Australian methane budget: Interpreting surface and train-borne measurements using a chemistry transport model

    NASA Astrophysics Data System (ADS)

    Fraser, Annemarie; Chan Miller, Christopher; Palmer, Paul I.; Deutscher, Nicholas M.; Jones, Nicholas B.; Griffith, David W. T.

    2011-10-01

    We investigate the Australian methane budget from 2005-2008 using the GEOS-Chem 3D chemistry transport model, focusing on the relative contribution of emissions from different sectors and the influence of long-range transport. To evaluate the model, we use in situ surface measurements of methane, methane dry air column average (XCH4) from ground-based Fourier transform spectrometers (FTSs), and train-borne surface concentration measurements from an in situ FTS along the north-south continental transect. We use gravity anomaly data from Gravity Recovery and Climate Experiment to describe the spatial and temporal distribution of wetland emissions and scale it to a prior emission estimate, which better describes observed atmospheric methane variability at tropical latitudes. The clean air sites of Cape Ferguson and Cape Grim are the least affected by local emissions, while Wollongong, located in the populated southeast with regional coal mining, samples the most locally polluted air masses (2.5% of the total air mass versus <1% at other sites). Averaged annually, the largest single source above background of methane at Darwin is long-range transport, mainly from Southeast Asia, accounting for ˜25% of the change in surface concentration above background. At Cape Ferguson and Cape Grim, emissions from ruminant animals are the largest source of methane above background, at approximately 20% and 30%, respectively, of the surface concentration. At Wollongong, emissions from coal mining are the largest source above background representing 60% of the surface concentration. The train data provide an effective way of observing transitions between urban, desert, and tropical landscapes.

  16. A qualitative study of high school students' pre- and post-instructional conceptions in acid-base chemistry

    NASA Astrophysics Data System (ADS)

    Sheppard, Keith

    This study investigated high school students' understanding of acid-base chemistry, prior to and after formal chemistry instruction. Sixteen students enrolled in a regular chemistry course were interviewed three times during the school year; before and after studying the topic of acids and bases and then while conducting a titration using a microcomputer-based laboratory (MBL). Oral, pictorial and graphical data were collected in a variety of acid-base practical tasks. The data were analyzed in two parts; first, common themes, ideas and alternative conceptions that students held were identified; second, profiles of each students were made to determine changes in their conceptions due to instruction. The findings showed that students had considerable difficulty with several areas of acid-base chemistry and did not develop an integrated conceptual understanding of the topic. Students were unable to describe acid-base concepts accurately and revealed a number of alternative conceptions, which remained unchanged by instruction. Specific areas of difficulty included the concepts of pH, neutralization, strength and the theoretical descriptions of acids and bases. Further, most students could not relate the concepts to actual solutions and were unable to describe acid-base phenomena at a sub-microscopic level. Student difficulties stemmed from a lack of understanding of some underlying and fundamental chemistry, such as the nature of chemical change and the particulate nature of matter. A number of factors were identified as contributing to these difficulties, and included the overstuffed nature of introductory chemistry itself, the emphasis in instruction on solving numerical problems and the dominant role played by the textbook. Further, the conceptual density of acid-base chemistry, the confusing nature of acid-base terminology and the lack of agreement about what material should be included in the chemistry curriculum were viewed as problematic. The study calls for a

  17. Effects of Chemistry on Blunt-Body Wake Structure

    NASA Technical Reports Server (NTRS)

    Dogra, Virendra K.; Moss, James N.; Wilmoth, Richard G.; Taylor, Jeff C.; Hassan, H. A.

    1995-01-01

    Results of a numerical study are presented for hypersonic low-density flow about a 70-deg blunt cone using direct simulation Monte Carlo (DSMC) and Navier-Stokes calculations. Particular emphasis is given to the effects of chemistry on the near-wake structure and on the surface quantities and the comparison of the DSMC results with the Navier-Stokes calculations. The flow conditions simulated are those experienced by a space vehicle at an altitude of 85 km and a velocity of 7 km/s during Earth entry. A steady vortex forms in the near wake for these freestream conditions for both chemically reactive and nonreactive air gas models. The size (axial length) of the vortex for the reactive air calculations is 25% larger than that of the nonreactive air calculations. The forebody surface quantities are less sensitive to the chemistry than the base surface quantities. The presence of the afterbody has no effect on the forebody flow structure or the surface quantities. The comparisons of DSMC and Navier-Stokes calculations show good agreement for the wake structure and the forebody surface quantities.

  18. Towards "Bildung"-Oriented Chemistry Education

    ERIC Educational Resources Information Center

    Sjöström, Jesper

    2013-01-01

    This paper concerns "Bildung"-oriented chemistry education, based on a reflective and critical discourse of chemistry. It is contrasted with the dominant type of chemistry education, based on the mainstream discourse of chemistry. "Bildung"-oriented chemistry education includes not only content knowledge in chemistry, but also…

  19. Connecting Acids and Bases with Encapsulation... and Chemistry with Nanotechnology

    ERIC Educational Resources Information Center

    Criswell, Brett

    2007-01-01

    The features and the development of various new acids and bases activity sets that combines chemistry with nanotechnology are being described. These sets lead to the generation of many nanotechnology-based pharmaceuticals for the treatment of various diseases.

  20. Electrostatic design and beam transport for a folded tandem electrostatic quadrupole accelerator facility for accelerator-based boron neutron capture therapy.

    PubMed

    Vento, V Thatar; Bergueiro, J; Cartelli, D; Valda, A A; Kreiner, A J

    2011-12-01

    Within the frame of an ongoing project to develop a folded Tandem-Electrostatic-Quadrupole (TESQ) accelerator facility for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT), we discuss here the electrostatic design of the machine, including the accelerator tubes with electrostatic quadrupoles and the simulations for the transport and acceleration of a high intensity beam. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Ensemble Manifold Rank Preserving for Acceleration-Based Human Activity Recognition.

    PubMed

    Tao, Dapeng; Jin, Lianwen; Yuan, Yuan; Xue, Yang

    2016-06-01

    With the rapid development of mobile devices and pervasive computing technologies, acceleration-based human activity recognition, a difficult yet essential problem in mobile apps, has received intensive attention recently. Different acceleration signals for representing different activities or even a same activity have different attributes, which causes troubles in normalizing the signals. We thus cannot directly compare these signals with each other, because they are embedded in a nonmetric space. Therefore, we present a nonmetric scheme that retains discriminative and robust frequency domain information by developing a novel ensemble manifold rank preserving (EMRP) algorithm. EMRP simultaneously considers three aspects: 1) it encodes the local geometry using the ranking order information of intraclass samples distributed on local patches; 2) it keeps the discriminative information by maximizing the margin between samples of different classes; and 3) it finds the optimal linear combination of the alignment matrices to approximate the intrinsic manifold lied in the data. Experiments are conducted on the South China University of Technology naturalistic 3-D acceleration-based activity dataset and the naturalistic mobile-devices based human activity dataset to demonstrate the robustness and effectiveness of the new nonmetric scheme for acceleration-based human activity recognition.

  2. A New Approach for Detection Improvement of the Creutzfeldt-Jakob Disorder through a Specific Surface Chemistry Applied onto Titration Well

    PubMed Central

    Mille, Caroline; Debarnot, Dominique; Zorzi, Willy; Moualij, Benaissa El; Quadrio, Isabelle; Perret-Liaudet, Armand; Coudreuse, Arnaud; Legeay, Gilbert; Poncin-Epaillard, Fabienne

    2012-01-01

    This work illustrates the enhancement of the sensitivity of the ELISA titration for recombinant human and native prion proteins, while reducing other non-specific adsorptions that could increase the background signal and lead to a low sensitivity and false positives. It is achieved thanks to the association of plasma chemistry and coating with different amphiphilic molecules bearing either ionic charges and/or long hydrocarbon chains. The treated support by 3-butenylamine hydrochloride improves the signal detection of recombinant protein, while surface modification with the 3,7-dimethylocta-2,6-dien-1-diamine (geranylamine) enhances the sensitivity of the native protein. Beside the surface chemistry effect, these different results are associated with protein conformation. PMID:25586034

  3. Surface-enhanced redox chemistry of polysulphides on a metallic and polar host for lithium-sulphur batteries.

    PubMed

    Pang, Quan; Kundu, Dipan; Cuisinier, Marine; Nazar, L F

    2014-08-26

    The lithium-sulphur battery relies on the reversible conversion between sulphur and Li2S and is highly appealing for energy storage owing to its low cost and high energy density. Porous carbons are typically used as sulfur hosts, but they do not adsorb the hydrophilic polysulphide intermediates or adhere well to Li2S, resulting in pronounced capacity fading. Here we report a different strategy based on an inherently polar, high surface area metallic oxide cathode host and show that it mitigates polysulphide dissolution by forming an excellent interface with Li2S. Complementary physical and electrochemical probes demonstrate strong polysulphide/Li2S binding with this 'sulphiphilic' host and provide experimental evidence for surface-mediated redox chemistry. In a lithium-sulphur cell, Ti4O7/S cathodes provide a discharge capacity of 1,070 mAh g(-1) at intermediate rates and a doubling in capacity retention with respect to a typical conductive carbon electrode, at practical sulphur mass fractions up to 70 wt%. Stable cycling performance is demonstrated at high rates over 500 cycles.

  4. Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification

    USGS Publications Warehouse

    Lawrence, Gregory B.; Dukett, James E; Houck, Nathan; Snyder, Phillip; Capone, Susan B.

    2013-01-01

    Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

  5. Increases in dissolved organic carbon accelerate loss of toxic Al in Adirondack lakes recovering from acidification.

    PubMed

    Lawrence, Gregory B; Dukett, James E; Houck, Nathan; Snyder, Phil; Capone, Sue

    2013-07-02

    Increasing pH and decreasing Al in surface waters recovering from acidification have been accompanied by increasing concentrations of dissolved organic carbon (DOC) and associated organic acids that partially offset pH increases and complicate assessments of recovery from acidification. To better understand the processes of recovery, monthly chemistry from 42 lakes in the Adirondack region, NY, collected from 1994 to 2011, were used to (1) evaluate long-term changes in DOC and associated strongly acidic organic acids and (2) use the base-cation surplus (BCS) as a chemical index to assess the effects of increasing DOC concentrations on the Al chemistry of these lakes. Over the study period, the BCS increased (p < 0.01) and concentrations of toxic inorganic monomeric Al (IMAl) decreased (p < 0.01). The decreases in IMAl were greater than expected from the increases in the BCS. Higher DOC concentrations that increased organic complexation of Al resulted in a decrease in the IMAl fraction of total monomeric Al from 57% in 1994 to 23% in 2011. Increasing DOC concentrations have accelerated recovery in terms of decreasing toxic Al beyond that directly accomplished by reducing atmospheric deposition of strong mineral acids.

  6. Accelerator based epithermal neutron source

    NASA Astrophysics Data System (ADS)

    Taskaev, S. Yu.

    2015-11-01

    We review the current status of the development of accelerator sources of epithermal neutrons for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. Particular attention is given to the source of epithermal neutrons on the basis of a new type of charged particle accelerator: tandem accelerator with vacuum insulation and lithium neutron-producing target. It is also shown that the accelerator with specialized targets makes it possible to generate fast and monoenergetic neutrons, resonance and monoenergetic gamma-rays, alpha-particles, and positrons.

  7. Modifying Surface Chemistry of Metal Oxides for Boosting Dissolution Kinetics in Water by Liquid Cell Electron Microscopy.

    PubMed

    Lu, Yue; Geng, Jiguo; Wang, Kuan; Zhang, Wei; Ding, Wenqiang; Zhang, Zhenhua; Xie, Shaohua; Dai, Hongxing; Chen, Fu-Rong; Sui, Manling

    2017-08-22

    Dissolution of metal oxides is fundamentally important for understanding mineral evolution and micromachining oxide functional materials. In general, dissolution of metal oxides is a slow and inefficient chemical reaction. Here, by introducing oxygen deficiencies to modify the surface chemistry of oxides, we can boost the dissolution kinetics of metal oxides in water, as in situ demonstrated in a liquid environmental transmission electron microscope (LETEM). The dissolution rate constant significantly increases by 16-19 orders of magnitude, equivalent to a reduction of 0.97-1.11 eV in activation energy, as compared with the normal dissolution in acid. It is evidenced from the high-resolution TEM imaging, electron energy loss spectra, and first-principle calculations where the dissolution route of metal oxides is dynamically changed by local interoperability between altered water chemistry and surface oxygen deficiencies via electron radiolysis. This discovery inspires the development of a highly efficient electron lithography method for metal oxide films in ecofriendly water, which offers an advanced technique for nanodevice fabrication.

  8. Bacterial filamentation accelerates colonization of adhesive spots embedded in biopassive surfaces

    NASA Astrophysics Data System (ADS)

    Möller, Jens; Emge, Philippe; Avalos Vizcarra, Ima; Kollmannsberger, Philip; Vogel, Viola

    2013-12-01

    Sessile bacteria adhere to engineered surfaces and host tissues and pose a substantial clinical and economical risk when growing into biofilms. Most engineered and biological interfaces are of chemically heterogeneous nature and provide adhesive islands for bacterial attachment and growth. To mimic either defects in a surface coating of biomedical implants or heterogeneities within mucosal layers (Peyer's patches), we embedded micrometre-sized adhesive islands in a poly(ethylene glycol) biopassive background. We show experimentally and computationally that filamentation of Escherichia coli can significantly accelerate the bacterial surface colonization under physiological flow conditions. Filamentation can thus provide an advantage to a bacterial population to bridge non-adhesive distances exceeding 5 μm. Bacterial filamentation, caused by blocking of bacterial division, is common among bacterial species and can be triggered by environmental conditions or antibiotic treatment. While great awareness exists that the build-up of antibiotic resistance serves as intrinsic survival strategy, we show here that antibiotic treatment can actually promote surface colonization by triggering filamentation, which in turn prevents daughter cells from being washed away. Our combined microfabrication and computational approaches provide quantitative insights into mechanisms that enable biofouling of biopassive surfaces with embedded adhesive spots, even for spot distances that are multiples of the bacterial length.

  9. Chemistry for Student Nurses: Applications-Based Learning

    ERIC Educational Resources Information Center

    El-Farargy, Nancy

    2009-01-01

    New chemistry materials were devised for pre university National Certificate (NC) nursing students studying chemistry at a further education college. Previously, preliminary work showed that students felt that the chemistry taught to them was irrelevant, boring and difficult. It was hoped that through an applications-led style curriculum…

  10. Surface chemistry of gold nanoparticles determines the biocorona composition impacting cellular uptake, toxicity and gene expression profiles in human endothelial cells.

    PubMed

    Chandran, Parwathy; Riviere, Jim E; Monteiro-Riviere, Nancy A

    2017-05-01

    This study investigated the role of nanoparticle size and surface chemistry on biocorona composition and its effect on uptake, toxicity and cellular responses in human umbilical vein endothelial cells (HUVEC), employing 40 and 80 nm gold nanoparticles (AuNP) with branched polyethyleneimine (BPEI), lipoic acid (LA) and polyethylene glycol (PEG) coatings. Proteomic analysis identified 59 hard corona proteins among the various AuNP, revealing largely surface chemistry-dependent signature adsorbomes exhibiting human serum albumin (HSA) abundance. Size distribution analysis revealed the relative instability and aggregation inducing potential of bare and corona-bound BPEI-AuNP, over LA- and PEG-AuNP. Circular dichroism analysis showed surface chemistry-dependent conformational changes of proteins binding to AuNP. Time-dependent uptake of bare, plasma corona (PC) and HSA corona-bound AuNP (HSA-AuNP) showed significant reduction in uptake with PC formation. Cell viability studies demonstrated dose-dependent toxicity of BPEI-AuNP. Transcriptional profiling studies revealed 126 genes, from 13 biological pathways, to be differentially regulated by 40 nm bare and PC-bound BPEI-AuNP (PC-BPEI-AuNP). Furthermore, PC formation relieved the toxicity of cationic BPEI-AuNP by modulating expression of genes involved in DNA damage and repair, heat shock response, mitochondrial energy metabolism, oxidative stress and antioxidant response, and ER stress and unfolded protein response cascades, which were aberrantly expressed in bare BPEI-AuNP-treated cells. NP surface chemistry is shown to play the dominant role over size in determining the biocorona composition, which in turn modulates cell uptake, and biological responses, consequently defining the potential safety and efficacy of nanoformulations.

  11. Compact Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

  12. CCl 4 chemistry on the magnetite selvedge of single-crystal hematite: competitive surface reactions

    NASA Astrophysics Data System (ADS)

    Adib, K.; Camillone, N., III; Fitts, J. P.; Rim, K. T.; Flynn, G. W.; Joyce, S. A.; Osgood, R. M., Jr.

    2002-01-01

    Temperature programmed reaction/desorption (TPR/D) studies were undertaken to characterize the surface chemistry which occurs between CCl 4 and the Fe 3O 4 (1 1 1) selvedge of single crystal α-Fe 2O 3 (0 0 0 1). Six separate desorption events are clearly observed and four desorbing species are identified: CCl 4, OCCl 2, C 2Cl 4 and FeCl 2. It is proposed that OCCl 2, CCl 4 and C 2Cl 4 are produced in reactions involving the same precursor, CCl 2. Three reaction paths compete for the CCl 2 precursor: oxygen atom abstraction (for OCCl 2), molecular recombinative desorption (for CCl 4) and associative desorption (for C 2Cl 4). During the TPR/D temperature ramp, the branching ratio is observed to depend upon temperature and the availability of reactive sites. The data are consistent with a rich site-dependent chemistry.

  13. Development and Assessment of a Chemistry-Based Computer Video Game as a Learning Tool

    ERIC Educational Resources Information Center

    Martinez-Hernandez, Kermin Joel

    2010-01-01

    The chemistry-based computer video game is a multidisciplinary collaboration between chemistry and computer graphics and technology fields developed to explore the use of video games as a possible learning tool. This innovative approach aims to integrate elements of commercial video game and authentic chemistry context environments into a learning…

  14. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2006-04-18

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  15. Conducting water chemistry of the secondary coolant circuit of VVER-based nuclear power plant units constructed without using copper containing alloys

    NASA Astrophysics Data System (ADS)

    Tyapkov, V. F.

    2014-07-01

    The secondary coolant circuit water chemistry with metering amines began to be put in use in Russia in 2005, and all nuclear power plant units equipped with VVER-1000 reactors have been shifted to operate with this water chemistry for the past seven years. Owing to the use of water chemistry with metering amines, the amount of products from corrosion of structural materials entering into the volume of steam generators has been reduced, and the flow-accelerated corrosion rate of pipelines and equipment has been slowed down. The article presents data on conducting water chemistry in nuclear power plant units with VVER-1000 reactors for the secondary coolant system equipment made without using copper-containing alloys. Statistical data are presented on conducting ammonia-morpholine and ammonia-ethanolamine water chemistries in new-generation operating power units with VVER-1000 reactors with an increased level of pH. The values of cooling water leaks in turbine condensers the tube system of which is made of stainless steel or titanium alloy are given.

  16. Surface chemistry relevant to material processing for semiconductor devices

    NASA Astrophysics Data System (ADS)

    Okada, Lynne Aiko

    Metal-oxide-semiconductor (MOS) structures are the core of many modern integrated circuit (IC) devices. Each material utilized in the different regions of the device has its own unique chemistry. Silicon is the base semiconductor material used in the majority of these devices. With IC device complexity increasing and device dimensions decreasing, understanding material interactions and processing becomes increasingly critical. Hsb2 desorption is the rate-limiting step in silicon growth using silane under low temperature conditions. Activation energies for Hsb2 desorption measured during Si chemical vapor deposition (CVD) versus single-crystal studies are found to be significantly lower. It has been proposed that defect sites on the silicon surface could explain the observed differences. Isothermal Hsb2 desorption studies using laser induced thermal desorption (LITD) techniques have addressed this issue. The growth of low temperature oxides is another relevant issue for fabrication of IC devices. Recent studies using 1,4-disilabutane (DSB) (SiHsb3CHsb2CHsb2SiHsb3) at 100sp°C in ambient Osb2 displayed the successful low temperature growth of silicon dioxide (SiOsb2). However, these studies provided no information about the deposition mechanism. We performed LITD and Fourier transform infrared (FTIR) studies on single-crystal and porous silicon surfaces to examine the adsorption, decomposition, and desorption processes to determine the deposition mechanism. Titanium nitride (TiN) diffusion barriers are necessary in modern metallization structures. Controlled deposition using titanium tetrachloride (TiClsb4) and ammonia (NHsb3) has been demonstrated using atomic layered processing (ALP) techniques. We intended to study the sequential deposition method by monitoring the surface intermediates using LITD techniques. However, formation of a Cl impurity source, ammonium chloride (NHsb4sp+Clsp-), was observed, thereby, limiting our ability for effective studies. Tetrakis

  17. Reactions at surfaces in the atmosphere: integration of experiments and theory as necessary (but not necessarily sufficient) for predicting the physical chemistry of aerosols.

    PubMed

    Finlayson-Pitts, Barbara J

    2009-09-28

    While particles have significant deleterious impacts on human health, visibility and climate, quantitative understanding of their formation, composition and fates remains problematic. Indeed, in many cases, even qualitative understanding is lacking. One area of particular uncertainty is the nature of particle surfaces and how this determines interactions with gases in the atmosphere, including water, which is important for cloud formation and properties. The focus in this Perspective article is on some chemistry relevant to airborne particles and especially to reactions occurring on their surfaces. The intent is not to provide a comprehensive review, but rather to highlight a few selected examples of interface chemistry involving inorganic and organic species that may be important in the lower atmosphere. This includes sea salt chemistry, nitrate and nitrite ion photochemistry, organics on surfaces and heterogeneous reactions of oxides of nitrogen on proxies for airborne mineral dust and boundary layer surfaces. Emphasis is on the molecular level understanding that can only be gained by fully integrating experiment and theory to elucidate these complex systems.

  18. The nucleation rate surfaces design over diagram of phase equilibria and their applications for computational chemistry

    NASA Astrophysics Data System (ADS)

    Anisimov, M. P.

    2016-12-01

    One can find in scientific literature a pretty fresh idea of the nucleation rate surfaces design over the diagrams of phase equilibria. That idea looks like profitable for the nucleation theory development and for various practical applications where predictions of theory have no high enough accuracy for today. The common thermodynamics has no real ability to predict parameters of the first order phase transition. Nucleation experiment can be provided in very local nucleation conditions even the nucleation takes place from the critical line (in two-component case) down to the absolute zero temperature limit and from zero nucleation rates at phase equilibria up to the spinodal conditions. Theory predictions have low reliability as a rule. The computational chemistry has chance to make solution of that problem easier when a set of the used axiomatic statements will adapt enough progressive assumptions [1]. Semiempirical design of the nucleation rate surfaces over diagrams of phase equilibria have a potential ability to provide a reasonable quality information on nucleation rate for each channel of nucleation. Consideration and using of the nucleation rate surface topologies to optimize synthesis of a given phase of the target material can be available when data base on nucleation rates over diagrams of phase equilibria will be created.

  19. Chemistry Modeling for Aerothermodynamics and TPS

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Stallcop, James R.; Dateo, Christopher e.; Schwenke, David W.; Halicioglu, Timur; Huo, winifred M.

    2005-01-01

    Recent advances in supercomputers and highly scalable quantum chemistry software render computational chemistry methods a viable means of providing chemistry data for aerothermal analysis at a specific level of confidence. Four examples of first principles quantum chemistry calculations will be presented. Study of the highly nonequilibrium rotational distribution of a nitrogen molecule from the exchange reaction N + N2 illustrates how chemical reactions can influence rotational distribution. The reaction C2H + H2 is one example of a radical reaction that occurs during hypersonic entry into an atmosphere containing methane. A study of the etching of a Si surface illustrates our approach to surface reactions. A recently developed web accessible database and software tool (DDD) that provides the radiation profile of diatomic molecules is also described.

  20. Chemistry Modeling for Aerothermodynamics and TPS

    NASA Technical Reports Server (NTRS)

    Wang, Dun-You; Stallcop, James R.; Dateo, Christopher E.; Schwenke, David W.; Haliciogiu, Timur; Huo, Winifred

    2004-01-01

    Recent advances in supercomputers and highly scalable quantum chemistry software render computational chemistry methods a viable means of providing chemistry data for aerothermal analysis at a specific level of confidence. Four examples of first principles quantum chemistry calculations will be presented. The study of the highly nonequilibrium rotational distribution of nitrogen molecule from the exchange reaction N + N2 illustrates how chemical reactions can influence the rotational distribution. The reaction C2H + H2 is one example of a radical reaction that occurs during hypersonic entry into a methane containing atmosphere. A study of the etching of Si surface illustrates our approach to surface reactions. A recently developed web accessible database and software tool (DDD) that provides the radiation profile of diatomic molecules is also described.

  1. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons.

    PubMed

    Nakatsutsumi, M; Sentoku, Y; Korzhimanov, A; Chen, S N; Buffechoux, S; Kon, A; Atherton, B; Audebert, P; Geissel, M; Hurd, L; Kimmel, M; Rambo, P; Schollmeier, M; Schwarz, J; Starodubtsev, M; Gremillet, L; Kodama, R; Fuchs, J

    2018-01-18

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5  T at laser intensities ~10 21  W cm -2 ) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.

  2. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

    DOE PAGES

    Nakatsutsumi, M.; Sentoku, Y.; Korzhimanov, A.; ...

    2018-01-18

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the targetmore » surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5 T at laser intensities ~10 21 W cm –2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.« less

  3. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakatsutsumi, M.; Sentoku, Y.; Korzhimanov, A.

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the targetmore » surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5 T at laser intensities ~10 21 W cm –2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.« less

  4. Adsorption of benzene and toluene from aqueous solutions onto activated carbon and its acid and heat treated forms: influence of surface chemistry on adsorption.

    PubMed

    Wibowo, N; Setyadhi, L; Wibowo, D; Setiawan, J; Ismadji, S

    2007-07-19

    The influence of surface chemistry and solution pH on the adsorption of benzene and toluene on activated carbon and its acid and heat treated forms were studied. A commercial coal-based activated carbon F-400 was chosen as carbon parent. The carbon samples were obtained by modification of F-400 by means of chemical treatment with HNO3 and thermal treatment under nitrogen flow. The treatment with nitric acid caused the introduction of a significant number of oxygenated acidic surface groups onto the carbon surface, while the heat treatment increases the basicity of carbon. The pore characteristics were not significantly changed after these modifications. The dispersive interactions are the most important factor in this adsorption process. Activated carbon with low oxygenated acidic surface groups (F-400Tox) has the best adsorption capacity.

  5. Surface Chemistry of La0.99Sr0.01NbO4-d and Its Implication for Proton Conduction.

    PubMed

    Li, Cheng; Pramana, Stevin S; Ni, Na; Kilner, John; Skinner, Stephen J

    2017-09-06

    Acceptor-doped LaNbO 4 is a promising electrolyte material for proton-conducting fuel cell (PCFC) applications. As charge transfer processes govern device performance, the outermost surface of acceptor-doped LaNbO 4 will play an important role in determining the overall cell performance. However, the surface composition is poorly characterized, and the understanding of its impact on the proton exchange process is rudimentary. In this work, the surface chemistry of 1 atom % Sr-doped LaNbO 4 (La 0.99 Sr 0.01 NbO 4-d , denoted as LSNO) proton conductor is characterized using LEIS and SIMS. The implication of a surface layer on proton transport is studied using the isotopic exchange technique. It has shown that a Sr-enriched but La-deficient surface layer of about 6-7 nm thick forms after annealing the sample under static air at 1000 °C for 10 h. The onset of segregation is found to be between 600 and 800 °C, and an equilibrium surface layer forms after 10 h annealing. A phase separation mechanism, due to the low solubility of Sr in LaNbO 4 , has been proposed to explain the observed segregation behavior. The surface layer was concluded to impede the water incorporation process, leading to a reduced isotopic fraction after the D 2 16 O wet exchange process, highlighting the impact of surface chemistry on the proton exchange process.

  6. NOTE: Acceleration of Monte Carlo-based scatter compensation for cardiac SPECT

    NASA Astrophysics Data System (ADS)

    Sohlberg, A.; Watabe, H.; Iida, H.

    2008-07-01

    Single proton emission computed tomography (SPECT) images are degraded by photon scatter making scatter compensation essential for accurate reconstruction. Reconstruction-based scatter compensation with Monte Carlo (MC) modelling of scatter shows promise for accurate scatter correction, but it is normally hampered by long computation times. The aim of this work was to accelerate the MC-based scatter compensation using coarse grid and intermittent scatter modelling. The acceleration methods were compared to un-accelerated implementation using MC-simulated projection data of the mathematical cardiac torso (MCAT) phantom modelling 99mTc uptake and clinical myocardial perfusion studies. The results showed that when combined the acceleration methods reduced the reconstruction time for 10 ordered subset expectation maximization (OS-EM) iterations from 56 to 11 min without a significant reduction in image quality indicating that the coarse grid and intermittent scatter modelling are suitable for MC-based scatter compensation in cardiac SPECT.

  7. Deep learning for computational chemistry.

    PubMed

    Goh, Garrett B; Hodas, Nathan O; Vishnu, Abhinav

    2017-06-15

    The rise and fall of artificial neural networks is well documented in the scientific literature of both computer science and computational chemistry. Yet almost two decades later, we are now seeing a resurgence of interest in deep learning, a machine learning algorithm based on multilayer neural networks. Within the last few years, we have seen the transformative impact of deep learning in many domains, particularly in speech recognition and computer vision, to the extent that the majority of expert practitioners in those field are now regularly eschewing prior established models in favor of deep learning models. In this review, we provide an introductory overview into the theory of deep neural networks and their unique properties that distinguish them from traditional machine learning algorithms used in cheminformatics. By providing an overview of the variety of emerging applications of deep neural networks, we highlight its ubiquity and broad applicability to a wide range of challenges in the field, including quantitative structure activity relationship, virtual screening, protein structure prediction, quantum chemistry, materials design, and property prediction. In reviewing the performance of deep neural networks, we observed a consistent outperformance against non-neural networks state-of-the-art models across disparate research topics, and deep neural network-based models often exceeded the "glass ceiling" expectations of their respective tasks. Coupled with the maturity of GPU-accelerated computing for training deep neural networks and the exponential growth of chemical data on which to train these networks on, we anticipate that deep learning algorithms will be a valuable tool for computational chemistry. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  8. Progression towards optimization of viscosity of highly concentrated carbonaceous solid-water slurries by incorporating and modifying surface chemistry parameters with and without additives

    NASA Astrophysics Data System (ADS)

    Mukherjee, Amrita

    electrostatic interaction energy, and the van der Waals interaction energy, was clearly the dominant interaction energy for such a system. Hydrophobic interactions lead to the formation of aggregation networks of solids in the suspensions, entrapping a part of the bulk water, whereas hydrophilic interactions result in the formation of hydration layers around carbonaceous solids. Both of these phenomena cause a loss of bulk water from the slurry and increase the effective solid volume fraction, resulting in an increase in slurry viscosity. The water in the bulk of the slurry, responsible for the fluidity of the slurry is called free water. The amount of free water was determined using thermogravimetric analysis and was observed to increase with an increase in the O/C ratio of a carbonaceous solid (up to ˜20%). The free water to total water ratio was observed to be constant for the slurry of a particular carbonaceous solid for various loadings of solids (44 wt.% to 67 wt.%). The increase in the effective solid volume fractions of slurries was determined using viscosity measurements. A relationship between the effective solid volume fraction and the O/C ratio of the carbonaceous solid was developed. This correlation was then incorporated into the existing equation for viscosity prediction (developed based on particle size distribution and solid volume fraction), to account for the surface chemistry of the carbonaceous solid and hence improve the predictive capabilities. This modified equation was validated using three concentrated carbonaceous slurries with different particle size distributions and was observed to significantly improve accuracy of prediction (deviation of predicted results decreased from up to 96% to 25%). The validation was performed with a lignite, bituminous coal and a petcoke-all with low ash yield. Additives modify the surface chemistry of the carbonaceous solids, thereby affecting the interfacial interactions. Through this research, the effects of additives

  9. Facile Synthesis of Nitrogen Doped Graphene Oxide from Graphite Flakes and Powders: A Comparison of Their Surface Chemistry.

    PubMed

    Yokwana, Kholiswa; Ray, Sekhar C; Khenfouch, Mohammad; Kuvarega, Alex T; Mamba, Bhekie B; Mhlanga, Sabelo D; Nxumalo, Edward N

    2018-08-01

    Nitrogen-doped graphene oxide (NGO) nanosheets were prepared via a facile one-pot modified Hummer's approach at low temperatures using graphite powder and flakes as starting materials in the presence of a nitrogen precursor. It was found that the morphology, structure, composition and surface chemistry of the NGO nanosheets depended on the nature of the graphite precursor used. GO nanosheets doped with nitrogen atoms exhibited a unique structure with few thin layers and wrinkled sheets, high porosity and structural defects. NGO sheets made from graphite powder (NGOp) exhibited excellent thermal stability and remarkably high surface area (up to 240.53 m2 ·g-1) compared to NGO sheets made from graphite flakes (NGOf) which degraded at low temperatures and had an average surface area of 24.70 m2 ·g-1. NGOf sheets had a size range of 850 to 2200 nm while NGOp sheets demonstrated obviously small sizes (460-1600 nm) even when exposed to different pH conditions. The NGO nanosheets exhibited negatively charged surfaces in a wide pH range (1 to 12) and were found to be stable above pH 6. In addition, graphite flakes were found to be more suitable for the production of NGO as they produced high N-doping levels (0.65 to 1.29 at.%) compared to graphite powders (0.30 to 0.35 at.%). This study further demonstrates that by adjusting the amount of N source in the host GO, one can tailor its thermal stability, surface morphology, surface chemistry and surface area.

  10. Acceleration ramps along high operating speed roadways.

    DOT National Transportation Integrated Search

    2010-11-01

    Until recently, guidelines for the geometric design of acceleration lanes used for the : successful merge of an entering vehicle into a high-speed surface transportation system : through-traffic lane have been based upon concepts and vehicle characte...

  11. Development and Implementation of a Two-Semester Introductory Organic-Bioorganic Chemistry Sequence: Conclusions from the First Six Years

    ERIC Educational Resources Information Center

    Goess, Brian C.

    2014-01-01

    A two-semester second-year introductory organic chemistry sequence featuring one semester of accelerated organic chemistry followed by one semester of bioorganic chemistry is described. Assessment data collected over a six-year period reveal that such a course sequence can facilitate student mastery of fundamental organic chemistry in the first…

  12. Flying fish accelerate at 5 G to leap from the water surface

    NASA Astrophysics Data System (ADS)

    Yang, Patricia; Phonekeo, Sulisay; Xu, Ke; Chang, Shui-Kai; Hu, David

    2013-11-01

    Flying fish can both swim underwater and glide in air. Transitioning from swimming to gliding requires penetration of the air-water interface, or breaking the ``surface tension barrier,'' a formidable task for juvenile flying fish measuring 1 to 5 cm in length. In this experimental investigation, we use high-speed videography to characterize the kinematics of juvenile flying fish as they leap from the water surface. During this process, which lasts 0.05 seconds, flying fish achieve body accelerations of 5 times earth's gravity and gliding speeds of 1.3 m/s, an order of magnitude higher than their steady swimming speed. We rationalize this anomalously high speed on the basis of the hydrodynamic and surface tension forces and torques experienced by the fish. Specifically, leaping fish experience skin friction forces only on the submerged part of their body, permitting them to achieve much higher speeds than in steady underwater swimming. We also perform experiments using a towed flying fish mimc to determine optimality of various parameters in this process, including body angle and start position with respect to the water surface.

  13. Managing oils pumplessly on open surfaces

    NASA Astrophysics Data System (ADS)

    Ghosh, Aritra; Morrissette, Jared; Mates, Joseph; Megaridis, Constantine

    2017-11-01

    Passive management of low-surface-tension liquids (e.g. oils) can be achieved by tuning curvature of liquid volumes (Laplace pressure) on juxtaposed oleophobic/oleophilic domains. Recent advancements in material chemistry in repelling low-surface-tension liquids has enabled researchers to fabricate surfaces and transport oils without the aid of gravity or using a pump. Liquid transport on such surfaces harnesses the force arising from the spatial contrast of surface energy on the substrate, providing rapid fluid actuation. In this work, we demonstrate and study the liquid transport dynamics (velocity, acceleration) in open air for several oils of interest (Jet A, hexadecane, mineral oil) with varying surface tension and viscosity. High-speed image analysis of the motion of the bulk liquid is performed using a droplet-shape tracking algorithm; dominant forces are identified and model predictions are compared with experimental data. Experimental and analytical tools offer new insight on a problem that is relevant to open-surface passive oil transport devices like propellant management devices, oil tankers and many more. Office of Naval Research, Air Force Research Laboratory.

  14. Surface Redox Chemistry of Immobilized Nanodiamond: Effects of Particle Size and Electrochemical Environment

    NASA Astrophysics Data System (ADS)

    Gupta, S.; McDonald, B.; Carrizosa, S. B.

    2017-07-01

    The size of the diamond particle is tailored to nanoscale (nanodiamond, ND), and the ND surface is engineered targeting specific (electrochemical and biological) applications. In this work, we investigated the complex surface redox chemistry of immobilized ND layer on conductive boron-doped diamond electrode with a broad experimental parameter space such as particle size (nano versus micron), scan rate, pH (cationic/acidic versus anionic/basic), electrolyte KCl concentration (four orders of magnitude), and redox agents (neutral and ionic). We reported on the significant enhancement of ionic currents while recording reversible oxidation of neutral ferrocene methanol (FcMeOH) by almost one order of magnitude than traditional potassium ferricyanide (K3Fe(CN)6) redox agent. The current enhancement is inversely related to ND particle diameter in the following order: 1 μm << 1000 nm < 100 nm < 10 nm ≤ 5 nm < 2 nm. We attribute the current enhancement to concurrent electrocatalytic processes, i.e. the electron transfer between redox probes and electroactive surface functional (e.g. hydroxyl, carboxyl, epoxy) moieties and the electron transfer mediated by adsorbed FcMeOH+ (or Fe(CN) 6 3+ ) ions onto ND surface. The first process is pH dependent since it depends upon ND surface functionalities for which the electron transfer is coupled to proton transfer. The adsorption mediated process is observed most apparently at slower scan rates owing to self-exchange between adsorbed FcMeOH+ ions and FcMeOH redox agent molecules in diffusion-limited bulk electrolyte solution. Alternatively, it is hypothesized that the surface functionality and defect sites ( sp 2-bonded C shell and unsaturated bonds) give rise to surface electronic states with energies within the band gap (midgap states) in undoped ND. These surface states serve as electron donors (and acceptors) depending upon their bonding (and antibonding) character and, therefore, they can support electrocatalytic redox

  15. Surface-Enhanced Resonance Raman Scattering and Visible Extinction Spectroscopy of Copper Chlorophyllin: An Upper Level Chemistry Experiment

    ERIC Educational Resources Information Center

    Schnitzer, Cheryl S.; Reim, Candace Lawson; Sirois, John J.; House, Paul G.

    2010-01-01

    Advanced chemistry students are introduced to surface-enhanced resonance Raman scattering (SERRS) by studying how sodium copper chlorophyllin (CuChl) adsorbs onto silver colloids (CuChl/Ag) as a function of pH. Using both SERRS and visible extinction spectroscopy, the extent of CuChl adsorption and colloidal aggregation are monitored. Initially at…

  16. Accelerating Multiple Compound Comparison Using LINGO-Based Load-Balancing Strategies on Multi-GPUs.

    PubMed

    Lin, Chun-Yuan; Wang, Chung-Hung; Hung, Che-Lun; Lin, Yu-Shiang

    2015-01-01

    Compound comparison is an important task for the computational chemistry. By the comparison results, potential inhibitors can be found and then used for the pharmacy experiments. The time complexity of a pairwise compound comparison is O(n (2)), where n is the maximal length of compounds. In general, the length of compounds is tens to hundreds, and the computation time is small. However, more and more compounds have been synthesized and extracted now, even more than tens of millions. Therefore, it still will be time-consuming when comparing with a large amount of compounds (seen as a multiple compound comparison problem, abbreviated to MCC). The intrinsic time complexity of MCC problem is O(k (2) n (2)) with k compounds of maximal length n. In this paper, we propose a GPU-based algorithm for MCC problem, called CUDA-MCC, on single- and multi-GPUs. Four LINGO-based load-balancing strategies are considered in CUDA-MCC in order to accelerate the computation speed among thread blocks on GPUs. CUDA-MCC was implemented by C+OpenMP+CUDA. CUDA-MCC achieved 45 times and 391 times faster than its CPU version on a single NVIDIA Tesla K20m GPU card and a dual-NVIDIA Tesla K20m GPU card, respectively, under the experimental results.

  17. Influence of surface sealing on color stability and roughness of composite submitted to ultraviolet-accelerated aging.

    PubMed

    Catelan, Anderson; Suzuki, Thaís Yumi Umeda; Becker, Francisco; Briso, André Luiz Fraga; Dos Santos, Paulo Henrique

    2017-05-01

    In the present study, we evaluated the influence of surface sealing on color stability and surface roughness of a composite resin after accelerated artificial aging. Thirty-two specimens of a composite were prepared. After 24 h, the specimens were polished and divided into four groups (n = 8), according to the surface sealant used, including the control, which had no sealant application. Baseline color was measured according to the CIELab system using a reflection spectrophotometer. Surface roughness was determined using a profilometer with a cut-off of 0.25 mm. After these tests, specimens were aged for 252 h in an ultraviolet (UV)-accelerated aging chamber. Color stability was determined by difference between coordinates obtained before and after the aging procedure. Data of color change and roughness were evaluated by anova and Fisher's exact test (α = 0.05). The results showed that the unsealed group had the highest color change compared to other groups (P = 0.0289), and there was no significant difference between groups sealed with surface sealant (P > 0.05). The artificial aging caused an increase in roughness values independent of the experimental group studied (P = 0.0015). The sealed composites showed lower color change after UV aging, but all groups showed clinically-acceptable color change, and only liquid polish decreased roughness. © 2016 John Wiley & Sons Australia, Ltd.

  18. A QR accelerated volume-to-surface boundary condition for finite element solution of eddy current problems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    White, D; Fasenfest, B; Rieben, R

    2006-09-08

    We are concerned with the solution of time-dependent electromagnetic eddy current problems using a finite element formulation on three-dimensional unstructured meshes. We allow for multiple conducting regions, and our goal is to develop an efficient computational method that does not require a computational mesh of the air/vacuum regions. This requires a sophisticated global boundary condition specifying the total fields on the conductor boundaries. We propose a Biot-Savart law based volume-to-surface boundary condition to meet this requirement. This Biot-Savart approach is demonstrated to be very accurate. In addition, this approach can be accelerated via a low-rank QR approximation of the discretizedmore » Biot-Savart law.« less

  19. Population-Based Pediatric Reference Intervals in General Clinical Chemistry: A Swedish Survey.

    PubMed

    Ridefelt, Peter

    2015-01-01

    Very few high quality studies on pediatric reference intervals for general clinical chemistry and hematology analytes have been performed. Three recent prospective community-based projects utilising blood samples from healthy children in Sweden, Denmark and Canada have substantially improved the situation. The Swedish survey included 701 healthy children. Reference intervals for general clinical chemistry and hematology were defined.

  20. Quantifying the pattern of microbial cell dispersion, density and clustering on surfaces of differing chemistries and topographies using multifractal analysis.

    PubMed

    Wickens, David; Lynch, Stephen; West, Glen; Kelly, Peter; Verran, Joanna; Whitehead, Kathryn A

    2014-09-01

    The effects of surface topography on bacterial distribution across a surface are of extreme importance when designing novel, hygienic or antimicrobial surface coatings. The majority of methods that are deployed to describe the pattern of cell dispersion, density and clustering across surfaces are currently qualitative. This paper presents a novel application of multifractal analysis to quantitatively measure these factors using medically relevant microorganisms (Staphylococcus aureus or Staphylococcus epidermidis). Surfaces (medical grade 316 stainless steel) and coatings (Ti-ZrN, Ti-ZrN/6.0%Ag, Ti-ZrN/15.6%Ag, TiZrN/24.7%Ag) were used in microbiological retention assays. Results demonstrated that S. aureus displayed a more heterogeneous cell dispersion (∆αAS<1) whilst the dispersion of S. epidermidis was more symmetric and homogeneous (∆αAS≥1). Further, although the surface topography and chemistry had an effect on cell dispersion, density and clustering, the type of bonding that occurred at the surface interface was also important. Both types of cells were influenced by both surface topographical and chemical effects; however, S. aureus was influenced marginally more by surface chemistry whilst S. epidermidis cells was influenced marginally more by surface topography. Thus, this effect was bacterially species specific. The results demonstrate that multifractal analysis is a method that can be used to quantitatively analyse the cell dispersion, density and clustering of retained microorganisms on surfaces. Using quantitative descriptors has the potential to aid the understanding the effect of surface properties on the production of hygienic and antimicrobial coatings. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Learning to detect vocal hyperfunction from ambulatory neck-surface acceleration features: initial results for vocal fold nodules.

    PubMed

    Ghassemi, Marzyeh; Van Stan, Jarrad H; Mehta, Daryush D; Zañartu, Matías; Cheyne, Harold A; Hillman, Robert E; Guttag, John V

    2014-06-01

    Voice disorders are medical conditions that often result from vocal abuse/misuse which is referred to generically as vocal hyperfunction. Standard voice assessment approaches cannot accurately determine the actual nature, prevalence, and pathological impact of hyperfunctional vocal behaviors because such behaviors can vary greatly across the course of an individual's typical day and may not be clearly demonstrated during a brief clinical encounter. Thus, it would be clinically valuable to develop noninvasive ambulatory measures that can reliably differentiate vocal hyperfunction from normal patterns of vocal behavior. As an initial step toward this goal we used an accelerometer taped to the neck surface to provide a continuous, noninvasive acceleration signal designed to capture some aspects of vocal behavior related to vocal cord nodules, a common manifestation of vocal hyperfunction. We gathered data from 12 female adult patients diagnosed with vocal fold nodules and 12 control speakers matched for age and occupation. We derived features from weeklong neck-surface acceleration recordings by using distributions of sound pressure level and fundamental frequency over 5-min windows of the acceleration signal and normalized these features so that intersubject comparisons were meaningful. We then used supervised machine learning to show that the two groups exhibit distinct vocal behaviors that can be detected using the acceleration signal. We were able to correctly classify 22 of the 24 subjects, suggesting that in the future measures of the acceleration signal could be used to detect patients with the types of aberrant vocal behaviors that are associated with hyperfunctional voice disorders.

  2. Architecture and Surface Chemistry of Compound Nanoclusters

    DTIC Science & Technology

    2012-08-01

    spectroscopy of metal carbonyls and carbocations: Inorganic and organic chemistry in the gas phase," Molecular Dynamics Seminar, Fritz Haber Institute...Disclosures none Pi Honors/Awards Alexander von Humboldt Fellowship ( Fritz Haber Institute, Berlin), 2007-present American Chemical Society

  3. Supramolecular chemistry at interfaces: host-guest interactions for fabricating multifunctional biointerfaces.

    PubMed

    Yang, Hui; Yuan, Bin; Zhang, Xi; Scherman, Oren A

    2014-07-15

    CONSPECTUS: Host-guest chemistry can greatly improve the selectivity of biomolecule-ligand binding on account of recognition-directed interactions. In addition, functional structures and the actuation of supramolecular assemblies in molecular systems can be controlled efficiently through various host-guest chemistry. Together, these highly selective, strong yet dynamic interactions can be exploited as an alternative methodology for applications in the field of programmable and controllable engineering of supramolecular soft materials through the reversible binding between complementary components. Many processes in living systems such as biotransformation, transportation of matter, and energy transduction begin with interfacial molecular recognition, which is greatly influenced by various external stimuli at biointerfaces. Detailed investigations about the molecular recognition at interfaces can result in a better understanding of life science, and further guide us in developing new biomaterials and medicines. In order to mimic complicated molecular-recognition systems observed in nature that adapt to changes in their environment, combining host-guest chemistry and surface science is critical for fabricating the next generation of multifunctional biointerfaces with efficient stimuli-responsiveness and good biocompatibility. In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host-guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments

  4. Muscle activation patterns in acceleration-based phases during reach-to-grasp movement.

    PubMed

    Tokuda, Keisuke; Lee, Bumsuk; Shiihara, Yasufumi; Takahashi, Kazuhiro; Wada, Naoki; Shirakura, Kenji; Watanabe, Hideomi

    2016-11-01

    [Purpose] An earlier study divided reaching activity into characteristic phases based on hand velocity profiles. By synchronizing muscle activities and the acceleration profile, a phasing approach for reaching movement, based on hand acceleration profiles, was attempted in order to elucidate the roles of individual muscle activities in the different phases of the acceleration profile in reaching movements. [Subjects and Methods] Ten healthy volunteer subjects participated in this study. The aim was to electromyographically evaluate muscles around the shoulder, the upper trapezius, the anterior deltoid, the biceps brachii, and the triceps brachii, most of which have been used to evaluate arm motion, as well as the acceleration of the upper limb during simple reaching movement in the reach-to-grasp task. [Results] Analysis showed the kinematic trajectories of the acceleration during a simple biphasic profile of the reaching movement could be divided into four phases: increasing acceleration (IA), decreasing acceleration (DA), increasing deceleration (ID), and decreasing deceleration (DD). Muscles around the shoulder showed different activity patterns, which were closely associated with these acceleration phases. [Conclusion] These results suggest the important role of the four phases, derived from the acceleration trajectory, in the elucidation of the muscular mechanisms which regulate and coordinate the muscles around the shoulder in reaching movements.

  5. Ion Beam Facilities at the National Centre for Accelerator based Research using a 3 MV Pelletron Accelerator

    NASA Astrophysics Data System (ADS)

    Trivedi, T.; Patel, Shiv P.; Chandra, P.; Bajpai, P. K.

    A 3.0 MV (Pelletron 9 SDH 4, NEC, USA) low energy ion accelerator has been recently installed as the National Centre for Accelerator based Research (NCAR) at the Department of Pure & Applied Physics, Guru Ghasidas Vishwavidyalaya, Bilaspur, India. The facility is aimed to carried out interdisciplinary researches using ion beams with high current TORVIS (for H, He ions) and SNICS (for heavy ions) ion sources. The facility includes two dedicated beam lines, one for ion beam analysis (IBA) and other for ion implantation/ irradiation corresponding to switching magnet at +20 and -10 degree, respectively. Ions with 60 kV energy are injected into the accelerator tank where after stripping positively charged ions are accelerated up to 29 MeV for Au. The installed ion beam analysis techniques include RBS, PIXE, ERDA and channelling.

  6. Host-guest chemistry of dendrimer-drug complexes. 2. Effects of molecular properties of guests and surface functionalities of dendrimers.

    PubMed

    Hu, Jingjing; Cheng, Yiyun; Wu, Qinglin; Zhao, Libo; Xu, Tongwen

    2009-08-06

    The host-guest chemistry of dendrimer-drug complexes is investigated by NMR techniques, including (1)H NMR and 2D-NOESY studies. The effects of molecular properties of drug molecules (protonation ability and spatial steric hindrance of charged groups) and surface functionalities of dendrimers (positively charged amine groups and negatively charged carboxylate groups) on the host-guest interactions are discussed. Different interaction mechanisms between dendrimers and drug molecules are proposed on the basis of NMR results. Primary amine- and secondary amine-containing drugs preferentially bind to negatively charged dendrimers by strong electrostatic interactions, whereas tertiary amine and quaternary ammonium-containing drugs have weak binding ability with dendrimers due to relatively low protonation ability of the tertiary amine group and serious steric hindrance of the quaternary ammonium group. Positively charged drugs locate only on the surface of negatively charged dendrimers, whereas negatively charged drugs locate both on the surface and in the interior cavities of positively charged dendrimers. The host-guest chemistry of dendrimer-drug complexes is promising for the development of new drug delivery systems.

  7. Architecture and Surface Chemistry of Compound Nanoclusters

    DTIC Science & Technology

    2012-07-31

    Inorganic and organic chemistry in the gas phase," Molecular Dynamics Seminar, Fritz Haber Institute, Berlin, Germany, June 2010. 12. "Infrared...Patent Disclosures none Pi Honors/Awards Alexander von Humboldt Fellowship ( Fritz Haber Institute, Berlin), 2007-present American Chemical

  8. Superoxide (Electro)Chemistry on Well-Defined Surfaces in Organic Environments

    DOE PAGES

    Genorio, Bostjan; Staszak-Jirkovský, Jakub; Assary, Rajeev S.; ...

    2016-02-09

    Efficient chemical transformations in energy conversion and storage systems depend on understanding superoxide anion (O 2 –) electrochemistry at atomic and molecular levels. Here, in this work, a combination of experimental and theoretical techniques are used for rationalizing, and ultimately understanding, the complexity of superoxide anion (electro)chemistry in organic environments. By exploring the O 2 + e – ↔ O 2 – reaction on well-characterized metal single crystals (Au, Pt, Ir), Pt single crystal modified with a single layer of graphene (Graphene@Pt(111)), and glassy carbon (GC) in 1,2 dimethoxyethane (DME) electrolytes, we demonstrate that (i) the reaction is an outer-spheremore » process; (ii) the reaction product O 2 – can “attack” any part of the DME molecule, i.e., the C–O bond via nucleophilic reaction and the C–H bond via radical hydrogen abstraction; (iii) the adsorption of carbon-based decomposition products and the extent of formation of a “solid electrolyte interface” (“SEI”) increases in the same order as the reactivity of the substrate, i.e., Pt(hkl)/Ir(hkl) » Au(hkl)/GC > Gaphene@Pt(111); and (iv) the formation of the “SEI” layer leads to irreversible superoxide electrochemistry on Pt(hkl) and Ir(hkl) surfaces. In conclusion, we believe this fundamental insight provides a pathway for the rational design of stable organic solvents that are urgently needed for the development of a new generation of reliable and affordable battery systems.« less

  9. A Study on Advanced Lithium-Based Battery Cell Chemistries to Enhance Lunar Exploration Missions

    NASA Technical Reports Server (NTRS)

    Reid, Concha; Bennett, William

    2009-01-01

    NASA's Exploration Technology Development Program (ETDP) Energy Storage Project conducted an advanced lithium-based battery chemistry feasibility study to determine the best advanced chemistry to develop for the Altair lunar lander and the Extravehicular Activities (EVA) advanced lunar surface spacesuit. These customers require safe, reliable energy storage systems with extremely high specific energy as compared to today's state-of-the-art batteries. Based on customer requirements, the specific energy goals for the development project are 220 watt-hours per kilogram (Wh/kg) delivered at the battery level at 0 degrees Celsius (degrees Celcius) at a C/10 discharge rate. Continuous discharge rates between C/5 and C/2, operation over 0 to 30 degrees C, and 200 cycles are targeted. The team, consisting of members from NASA Glenn Research Center, Johnson Space Center, and Jet Propulsion laboratory, surveyed the literature, compiled information on recent materials developments, and consulted with other battery experts in the community to identify advanced battery materials that might be capable of achieving the desired results with further development. A variety of electrode materials were considered, including layered metal oxides, spinel oxides, and olivine-type cathode materials, and lithium metal, lithium alloy, and silicon-based composite anode materials. lithium-sulfur systems were also considered. Hypothetical cell constructs that combined compatible anode and cathode materials with suitable electrolytes, separators, current collectors, headers, and cell enclosures were modeled. While some of these advanced materials are projected to obtain the desired electrical performance, there are risks that also factored into the decision making process. The risks include uncertainties due to issues such as safety of a system containing some of these materials, ease of scaling-up of large batches of raw materials, adaptability of the materials to processing using established

  10. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo 2C) for the deoxygenation of acetic acid,more » an abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo 2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.« less

  11. Experimental and computational investigation of acetic acid deoxygenation over oxophilic molybdenum carbide: Surface chemistry and active site identity

    DOE PAGES

    Schaidle, Joshua A.; Blackburn, Jeffrey; Farberow, Carrie A.; ...

    2016-01-21

    Ex situ catalytic fast pyrolysis (CFP) is a promising route for producing fungible biofuels; however, this process requires bifunctional catalysts that favor C–O bond cleavage, activate hydrogen at near atmospheric pressure and high temperature (350–500 °C), and are stable under high-steam, low hydrogen-to-carbon environments. Recently, early transition-metal carbides have been reported to selectively cleave C–O bonds of alcohols, aldehydes, and oxygenated aromatics, yet there is limited understanding of the metal carbide surface chemistry under reaction conditions and the identity of the active sites for deoxygenation. In this study, we evaluated molybdenum carbide (Mo 2C) for the deoxygenation of acetic acid,more » an abundant component of biomass pyrolysis vapors, under ex situ CFP conditions, and we probed the Mo 2C surface chemistry, identity of the active sites, and deoxygenation pathways using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations.« less

  12. Final Technical Report. Reactivity of Iron-Bearing Minerals and CO 2 Sequestration and Surface Chemistry of Pyrite. An Interdisciplinary Approach

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Strongin, Daniel

    2014-12-31

    Over the course of the scientific program, two areas of research were pursued: reactions of iron oxides with supercritical CO 2 and sulfide and surface reactivity of pyrite. The latter area of interest was to understand the chemistry that results when supercritical CO 2 (scCO 2 ) with H 2 S and/or SO 2 in deep saline formations (DFS) contacts iron bearing minerals. Understanding the complexities the sulfur co-injectants introduce is a critical step in developing CO 2 sequestration as a climate-mitigating strategy. The research strategy was to understand macroscopic observations of this chemistry with anmore » atomic/molecular level view using surface analytical techniques. Research showed that the exposure of iron (oxyhdr)oxides (which included ferrihydrite, goethite, and hematite) to scCO 2 in the presence of sulfide led to reactions that formed siderite (FeCO 3). The results have important implications for the sequestration of CO 2 via carbonation reactions in the Earth’s subsurface. An earlier area of focus in the project was to understand pyrite oxidation in microscopic detail. This understanding was used to understand macroscopic observations of pyrite reactivity. Results obtained from this research led to a better understanding how pyrite reacts in a range of chemical environments. Geochemical and modern surface science techniques were used to understand the chemistry of pyrite in important environmental conditions. The program relied on a strong integration the results of these techniques to provide a fundamental understanding to the macroscopic chemistry exhibited by pyrite in the environment. Major achievements during these studies included developing an understanding of the surface sites on pyrite that controlled its reactivity under oxidizing conditions. In particular sulfur anion vacancies and/or ferric sites were sites of reactivity. Studies also showed that the adsorption of phospholipid on the surface to selectively suppress the reactivity of

  13. Accelerator boom hones China's engineering expertise

    NASA Astrophysics Data System (ADS)

    Normile, Dennis

    2018-02-01

    In raising the curtain on the China Spallation Neutron Source, China has joined just four other nations in having mastered the technology of accelerating and controlling beams of protons. The $277 million facility, set to open to users this spring in Dongguan, is expected to yield big dividends in materials science, chemistry, and biology. More world class machines are on the way, as China this year starts construction on four other major accelerator facilities. The building boom is prompting a scramble to find enough engineers and technicians to finish the projects. But if they all come off as planned, the facilities would position China to tackle the next global megaproject: a giant accelerator that would pick up where Europe's Large Hadron Collider leaves off.

  14. Structure-to-property relationships in fuel cell catalyst supports: Correlation of surface chemistry and morphology with oxidation resistance of carbon blacks

    NASA Astrophysics Data System (ADS)

    Artyushkova, Kateryna; Pylypenko, Svitlana; Dowlapalli, Madhu; Atanassov, Plamen

    2012-09-01

    Linking durability of carbon blacks, expressed as their oxidation resistance, used in PEMFCs as catalyst supports, with their chemistry and morphology is an important task towards designing carbon blacks with desired properties. Structure-to-property relationship between surface chemistry determined by X-ray photoelectron spectroscopy (XPS), morphological structure determined by digital image processing of scanning electron microscopy (SEM) images, physical properties, and electrochemical corrosion behavior determined in an air-breathing gas-diffusion electrode is studied for several un-altered and several modified carbon blacks. We are showing that surface chemistry, graphitic content and certain physical characteristics such as Brunauer-Emmett-Teller (BET) surface area and pore volume, determined by nitrogen adsorptions are not sufficient to explain high corrosion instability of types of carbon blacks. Inclusion of morphological characteristics, such as roughness, texture and shape parameters provide for more inclusive description and therefore more complete structure-to-property correlations of corrosion behavior of carbon blacks. This paper presents the first direct statistically-derived structure-to-property relationship, developed by multivariate analysis (MVA) that links chemical and physical structural properties of the carbon blacks to their critical properties as supports for PEMFC catalysts. We have found that balance between electrocatalytic activity and high resistance towards oxidation and corrosion is achieved by balance between amount of graphitic content and surface oxide coverage, smaller overall roughness and, finally, larger amount of big elongated and loose, and, hypothetically, more hydrophobic pores.

  15. Chemistry and Photochemistry at the Surface of Urban Road Dust and Photoactive Minerals

    NASA Astrophysics Data System (ADS)

    Styler, S. A.; Abou-Ghanem, M.; Wickware, B.

    2017-12-01

    Each year, over a billion tons of dust are released into the atmosphere from arid regions. After its emission, dust can undergo efficient long-range transport to urban centres, where it can interact with local pollution sources. Another source of dust in urban regions is road dust resuspension, which is the largest anthropogenic source of primary particulate matter in both Canada and the United States. Since dust contains light-absorbing components, including iron- and titanium-containing minerals, dust-catalyzed photochemical processes have the potential to influence both the lifetime of pollutants present at the dust surface and the composition of the surrounding atmosphere. To date, most studies of dust photochemistry have focused on TiO2-mediated processes, and no studies have explored trace gas uptake at the surface of road dust. Here, we present first results from aerosol and coated-wall flow tube investigations of ozone uptake at the surface of a suite of titanium-containing minerals and road dust collected in Edmonton, Alberta. Together, this work represents a significant advance in our understanding of chemistry and photochemistry at realistic environmental interfaces.

  16. Insulin adsorption on crystalline SiO2: Comparison between polar and nonpolar surfaces using accelerated molecular-dynamics simulations

    NASA Astrophysics Data System (ADS)

    Nejad, Marjan A.; Mücksch, Christian; Urbassek, Herbert M.

    2017-02-01

    Adsorption of insulin on polar and nonpolar surfaces of crystalline SiO2 (cristobalite and α -quartz) is studied using molecular dynamics simulation. Acceleration techniques are used in order to sample adsorption phase space efficiently and to identify realistic adsorption conformations. We find major differences between the polar and nonpolar surfaces. Electrostatic interactions govern the adsorption on polar surfaces and can be described by the alignment of the protein dipole with the surface dipole; hence spreading of the protein on the surface is irrelevant. On nonpolar surfaces, on the other hand, van-der-Waals interaction dominates, inducing surface spreading of the protein.

  17. Properties Data for Adhesion and Surface Chemistry of Aluminum: Sapphire-Aluminum, Single-Crystal Couple

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Pohlchuck, Bobby; Whitle, Neville C.; Hector, Louis G., Jr.; Adams, Jim

    1998-01-01

    An investigation was conducted to examine the adhesion and surface chemistry of single-crystal aluminum in contact with single-crystal sapphire (alumina). Pull-off force (adhesion) measurements were conducted under loads of 0. I to I mN in a vacuum of 10(exp -1) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) at room temperature. An Auger electron spectroscopy analyzer incorporated directly into an adhesion-measuring vacuum system was primarily used to define the chemical nature of the surfaces before and after adhesion measurements. The surfaces were cleaned by argon ion sputtering. With a clean aluminum-clean -sapphire couple the mean value and standard deviation of pull-off forces required to separate the surfaces were 3015 and 298 micro-N, respectively. With a contaminated aluminum-clean sapphire couple these values were 231 and 241 micro-N. The presence of a contaminant film on the aluminum surface reduced adhesion by a factor of 13. Therefore, surfaces cleanliness, particularly aluminum cleanliness, played an important role in the adhesion of the aluminum-sapphire couples. Pressures on the order of 10(exp -8) to 10(exp -9) Pa (approx. 10(exp -10) to 10(exp -11) torr) maintained a clean aluminum surface for only a short time (less then 1 hr) but maintained a clean sapphire surface, once it was achieved, for a much longer time.

  18. Surface chemistry dependent immunostimulative potential of porous silicon nanoplatforms.

    PubMed

    Shahbazi, Mohammad-Ali; Fernández, Tahia D; Mäkilä, Ermei M; Le Guével, Xavier; Mayorga, Cristobalina; Kaasalainen, Martti H; Salonen, Jarno J; Hirvonen, Jouni T; Santos, Hélder A

    2014-11-01

    Nanoparticles (NPs) have been suggested for immunotherapy applications in order to optimize the delivery of immuno-stimulative or -suppressive molecules. However, low attention towards the impact of the NPs' physicochemical properties has presented a major hurdle for developing efficient immunotherapeutic agents. Here, the effects of porous silicon (PSi) NPs with different surface chemistries were evaluated on human monocyte-derived dendritic cells (MDDCs) and lymphocytes in order to highlight the importance of the NPs selection in immuno-stimulative or -suppressive treatment. Although all the PSi NPs showed high biocompatibility, only thermally oxidized PSi (TOPSi) and thermally hydrocarbonized PSi (THCPSi) NPs were able to induce very high rate of immunoactivation by enhancing the expression of surface co-stimulatory markers of the MDDCs (CD80, CD83, CD86, and HLA-DR), inducing T-cell proliferation, and also the secretion of interleukins (IL-1β, IL-4, IL-6, IL-10, IL-12, IFN-γ, and TNF-α). These results indicated a balanced increase in the secretion of Th1, Th2, and Treg cytokines. Moreover, undecylenic acid functionalized THCPSi, as well as poly(methyl vinyl ether-alt-maleic acid) conjugated to (3-aminopropyl)triethoxysilane functionalized thermally carbonized PSi and polyethyleneimine conjugated undecylenic acid functionalized THCPSi NPs showed moderate immunoactivation due to the mild increase in the above-mentioned markers. By contrast, thermally carbonized PSi (TCPSi) and (3-aminopropyl)triethoxysilane functionalized TCPSi NPs did not induce any immunological responses, suggesting that their application could be in the delivery of immunosuppressive molecules. Overall, our findings suggest all the NPs containing more nitrogen or oxygen on the outermost backbone layer have lower immunostimulatory effect than NPs with higher C-H structures on the surface. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Monitoring the Surface Chemistry of Functionalized Nanomaterials with a Microfluidic Electronic Tongue.

    PubMed

    Shimizu, Flavio M; Pasqualeti, Anielli M; Todão, Fagner R; de Oliveira, Jessica F A; Vieira, Luis C S; Gonçalves, Suely P C; da Silva, Gabriela H; Cardoso, Mateus B; Gobbi, Angelo L; Martinez, Diego S T; Oliveira, Osvaldo N; Lima, Renato S

    2018-03-23

    Advances in nanomaterials have led to tremendous progress in different areas with the development of high performance and multifunctional platforms. However, a relevant gap remains in providing the mass-production of these nanomaterials with reproducible surfaces. Accordingly, the monitoring of such materials across their entire life cycle becomes mandatory to both industry and academy. In this paper, we use a microfluidic electronic tongue (e-tongue) as a user-friendly and cost-effective method to classify nanomaterials according to their surface chemistry. The chip relies on a new single response e-tongue with association of capacitors in parallel, which consisted of stainless steel microwires coated with SiO 2 , NiO 2 , Al 2 O 3 , and Fe 2 O 3 thin films. Utilizing impedance spectroscopy and a multidimensional projection technique, the chip was sufficiently sensitive to distinguish silica nanoparticles and multiwalled carbon nanotubes dispersed in water in spite of the very small surface modifications induced by distinct functionalization and oxidation extents, respectively. Flow analyses were made acquiring the analytical readouts in a label-free mode. The device also allowed for multiplex monitoring in an unprecedented way to speed up the tests. Our goal is not to replace the traditional techniques of surface analysis, but rather propose the use of libraries from e-tongue data as benchmark for routine screening of modified nanomaterials in industry and academy.

  20. Smaller to larger biomolecule detection using a lab-built surface plasmon resonance based instrument

    NASA Astrophysics Data System (ADS)

    Lukose, J.; Kulal, V.; Chidangil, S.; Sinha, R. K.

    2016-10-01

    We have developed a low-cost surface plasmon resonance (SPR) instrument based on the Kretschmann configuration for biosensing applications. The fabricated instrument is capable of operating in both angular and intensity interrogation schemes. The proposed sensor has proved enormously versatile by detecting a range of analytes with low to high molecular weights. The refractive index based sensor has been used for detecting the variation in the concentration of the aqueous solution of glucose and glycerine. Real time immobilization of protein molecules, bovine serum albumin on a gold (Au) film surface, has also been detected using the SPR imaging technique. Alkanethiol functionalization of the Au surface was performed, and bovine serum albumin was immobilized onto the carboxyl functionalized surface using amine reactive cross linker chemistry. In future, the present approach can also be utilized for the selective detection of a wide range of target biomolecules with the help of specific capture probes, as well as for monitoring protein-drug interactions.

  1. Observation of the controlled assembly of preclick components in the in situ click chemistry generation of a chitinase inhibitor

    PubMed Central

    Hirose, Tomoyasu; Maita, Nobuo; Gouda, Hiroaki; Koseki, Jun; Yamamoto, Tsuyoshi; Sugawara, Akihiro; Nakano, Hirofumi; Hirono, Shuichi; Shiomi, Kazuro; Watanabe, Takeshi; Taniguchi, Hisaaki; Sharpless, K. Barry; Ōmura, Satoshi; Sunazuka, Toshiaki

    2013-01-01

    The Huisgen cycloaddition of azides and alkynes, accelerated by target biomolecules, termed “in situ click chemistry,” has been successfully exploited to discover highly potent enzyme inhibitors. We have previously reported a specific Serratia marcescens chitinase B (SmChiB)-templated syn-triazole inhibitor generated in situ from an azide-bearing inhibitor and an alkyne fragment. Several in situ click chemistry studies have been reported. Although some mechanistic evidence has been obtained, such as X-ray analysis of [protein]–[“click ligand”] complexes, indicating that proteins act as both mold and template between unique pairs of azide and alkyne fragments, to date, observations have been based solely on “postclick” structural information. Here, we describe crystal structures of SmChiB complexed with an azide ligand and an O-allyl oxime fragment as a mimic of a click partner, revealing a mechanism for accelerating syn-triazole formation, which allows generation of its own distinct inhibitor. We have also performed density functional theory calculations based on the X-ray structure to explore the acceleration of the Huisgen cycloaddition by SmChiB. The density functional theory calculations reasonably support that SmChiB plays a role by the cage effect during the pretranslation and posttranslation states of selective syn-triazole click formation. PMID:24043811

  2. Accelerated Compressed Sensing Based CT Image Reconstruction.

    PubMed

    Hashemi, SayedMasoud; Beheshti, Soosan; Gill, Patrick R; Paul, Narinder S; Cobbold, Richard S C

    2015-01-01

    In X-ray computed tomography (CT) an important objective is to reduce the radiation dose without significantly degrading the image quality. Compressed sensing (CS) enables the radiation dose to be reduced by producing diagnostic images from a limited number of projections. However, conventional CS-based algorithms are computationally intensive and time-consuming. We propose a new algorithm that accelerates the CS-based reconstruction by using a fast pseudopolar Fourier based Radon transform and rebinning the diverging fan beams to parallel beams. The reconstruction process is analyzed using a maximum-a-posterior approach, which is transformed into a weighted CS problem. The weights involved in the proposed model are calculated based on the statistical characteristics of the reconstruction process, which is formulated in terms of the measurement noise and rebinning interpolation error. Therefore, the proposed method not only accelerates the reconstruction, but also removes the rebinning and interpolation errors. Simulation results are shown for phantoms and a patient. For example, a 512 × 512 Shepp-Logan phantom when reconstructed from 128 rebinned projections using a conventional CS method had 10% error, whereas with the proposed method the reconstruction error was less than 1%. Moreover, computation times of less than 30 sec were obtained using a standard desktop computer without numerical optimization.

  3. Accelerated Compressed Sensing Based CT Image Reconstruction

    PubMed Central

    Hashemi, SayedMasoud; Beheshti, Soosan; Gill, Patrick R.; Paul, Narinder S.; Cobbold, Richard S. C.

    2015-01-01

    In X-ray computed tomography (CT) an important objective is to reduce the radiation dose without significantly degrading the image quality. Compressed sensing (CS) enables the radiation dose to be reduced by producing diagnostic images from a limited number of projections. However, conventional CS-based algorithms are computationally intensive and time-consuming. We propose a new algorithm that accelerates the CS-based reconstruction by using a fast pseudopolar Fourier based Radon transform and rebinning the diverging fan beams to parallel beams. The reconstruction process is analyzed using a maximum-a-posterior approach, which is transformed into a weighted CS problem. The weights involved in the proposed model are calculated based on the statistical characteristics of the reconstruction process, which is formulated in terms of the measurement noise and rebinning interpolation error. Therefore, the proposed method not only accelerates the reconstruction, but also removes the rebinning and interpolation errors. Simulation results are shown for phantoms and a patient. For example, a 512 × 512 Shepp-Logan phantom when reconstructed from 128 rebinned projections using a conventional CS method had 10% error, whereas with the proposed method the reconstruction error was less than 1%. Moreover, computation times of less than 30 sec were obtained using a standard desktop computer without numerical optimization. PMID:26167200

  4. Accurate fluid force measurement based on control surface integration

    NASA Astrophysics Data System (ADS)

    Lentink, David

    2018-01-01

    Nonintrusive 3D fluid force measurements are still challenging to conduct accurately for freely moving animals, vehicles, and deforming objects. Two techniques, 3D particle image velocimetry (PIV) and a new technique, the aerodynamic force platform (AFP), address this. Both rely on the control volume integral for momentum; whereas PIV requires numerical integration of flow fields, the AFP performs the integration mechanically based on rigid walls that form the control surface. The accuracy of both PIV and AFP measurements based on the control surface integration is thought to hinge on determining the unsteady body force associated with the acceleration of the volume of displaced fluid. Here, I introduce a set of non-dimensional error ratios to show which fluid and body parameters make the error negligible. The unsteady body force is insignificant in all conditions where the average density of the body is much greater than the density of the fluid, e.g., in gas. Whenever a strongly deforming body experiences significant buoyancy and acceleration, the error is significant. Remarkably, this error can be entirely corrected for with an exact factor provided that the body has a sufficiently homogenous density or acceleration distribution, which is common in liquids. The correction factor for omitting the unsteady body force, {{{ {ρ f}} {1 - {ρ f} ( {{ρ b}+{ρ f}} )}.{( {{{{ρ }}b}+{ρ f}} )}}} , depends only on the fluid, {ρ f}, and body, {{ρ }}b, density. Whereas these straightforward solutions work even at the liquid-gas interface in a significant number of cases, they do not work for generalized bodies undergoing buoyancy in combination with appreciable body density inhomogeneity, volume change (PIV), or volume rate-of-change (PIV and AFP). In these less common cases, the 3D body shape needs to be measured and resolved in time and space to estimate the unsteady body force. The analysis shows that accounting for the unsteady body force is straightforward to non

  5. Designing durable icephobic surfaces

    PubMed Central

    Golovin, Kevin; Kobaku, Sai P. R.; Lee, Duck Hyun; DiLoreto, Edward T.; Mabry, Joseph M.; Tuteja, Anish

    2016-01-01

    Ice accretion has a negative impact on critical infrastructure, as well as a range of commercial and residential activities. Icephobic surfaces are defined by an ice adhesion strength τice < 100 kPa. However, the passive removal of ice requires much lower values of τice, such as on airplane wings or power lines (τice < 20 kPa). Such low τice values are scarcely reported, and robust coatings that maintain these low values have not been reported previously. We show that, irrespective of material chemistry, by tailoring the cross-link density of different elastomeric coatings and by enabling interfacial slippage, it is possible to systematically design coatings with extremely low ice adhesion (τice < 0.2 kPa). These newfound mechanisms allow for the rational design of icephobic coatings with virtually any desired ice adhesion strength. By using these mechanisms, we fabricate extremely durable coatings that maintain τice < 10 kPa after severe mechanical abrasion, acid/base exposure, 100 icing/deicing cycles, thermal cycling, accelerated corrosion, and exposure to Michigan wintery conditions over several months. PMID:26998520

  6. Do sediment type and test durations affect results of laboratory-based, accelerated testing studies of permeable pavement clogging?

    PubMed

    Nichols, Peter W B; White, Richard; Lucke, Terry

    2015-04-01

    Previous studies have attempted to quantify the clogging processes of Permeable Interlocking Concrete Pavers (PICPs) using accelerated testing methods. However, the results have been variable. This study investigated the effects that three different sediment types (natural and silica), and different simulated rainfall intensities, and testing durations had on the observed clogging processes (and measured surface infiltration rates) of laboratory-based, accelerated PICP testing studies. Results showed that accelerated simulated laboratory testing results are highly dependent on the type, and size of sediment used in the experiments. For example, when using real stormwater sediment up to 1.18 mm in size, the results showed that neither testing duration, nor stormwater application rate had any significant effect on PICP clogging. However, the study clearly showed that shorter testing durations generally increased clogging and reduced the surface infiltration rates of the models when artificial silica sediment was used. Longer testing durations also generally increased clogging of the models when using fine sediment (<300 μm). Results from this study will help researchers and designers better anticipate when and why PICPs are susceptible to clogging, reduce maintenance and extend the useful life of these increasingly common stormwater best management practices. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Effectiveness of Case-Based Learning Instruction on Epistemological Beliefs and Attitudes toward Chemistry

    ERIC Educational Resources Information Center

    Cam, Aylin; Geban, Omer

    2011-01-01

    The purpose of the study was to investigate the effectiveness of case-based learning instruction over traditionally designed chemistry instruction on eleventh grade students' epistemological beliefs and their attitudes toward chemistry as a school subject. The subjects of this study consisted of 63 eleventh grade students from two intact classes…

  8. Influence of the carrier-envelope phase of few-cycle pulses on ponderomotive surface-plasmon electron acceleration.

    PubMed

    Irvine, S E; Dombi, P; Farkas, Gy; Elezzabi, A Y

    2006-10-06

    Control over basic processes through the electric field of a light wave can lead to new knowledge of fundamental light-matter interaction phenomena. We demonstrate, for the first time, that surface-plasmon (SP) electron acceleration can be coherently controlled through the carrier-envelope phase (CEP) of an excitation optical pulse. Analysis indicates that the physical origin of the CEP sensitivity arises from the electron's ponderomotive interaction with the oscillating electromagnetic field of the SP wave. The ponderomotive electron acceleration mechanism provides sensitive (nJ energies), high-contrast, single-shot CEP measurement capability of few-cycle laser pulses.

  9. Surface defect chemistry and oxygen exchange kinetics in La2-xCaxNiO4+δ

    NASA Astrophysics Data System (ADS)

    Tropin, E. S.; Ananyev, M. V.; Farlenkov, A. S.; Khodimchuk, A. V.; Berenov, A. V.; Fetisov, A. V.; Eremin, V. A.; Kolchugin, A. A.

    2018-06-01

    Surface oxygen exchange kinetics and diffusion in La2-xCaxNiO4+δ (x = 0; 0.1; 0.3) have been studied by the isotope exchange method with gas phase equilibration in the temperature range of 600-800 °C and oxygen pressure range 0.13-2.5 kPa. Despite an enhanced electrical conductivity of La2-xCaxNiO4+δ theirs oxygen surface exchange (k*) and oxygen tracer diffusion (D*) coefficients were significantly lower in comparison with La2NiO4+δ. The rates of the elementary stages of oxygen exchange have been calculated. Upon Ca doping the change of the rate-determining stage was observed. The surface of the oxides was found to be inhomogeneous towards oxygen exchange process according to the recently developed model. The reasons of such inhomogeneity are discussed as well as Ca influence on the surface defect chemistry and oxygen surface exchange and diffusivity.

  10. Water chemistry controlled aggregation and photo-transformation of silver nanoparticles in environmental waters.

    PubMed

    Yin, Yongguang; Yang, Xiaoya; Zhou, Xiaoxia; Wang, Weidong; Yu, Sujuan; Liu, Jingfu; Jiang, Guibin

    2015-08-01

    The inevitable release of engineered silver nanoparticles (AgNPs) into aquatic environments has drawn great concerns about its environmental toxicity and safety. Although aggregation and transformation play crucial roles in the transport and toxicity of AgNPs, how the water chemistry of environmental waters influences the aggregation and transformation of engineered AgNPs is still not well understood. In this study, the aggregation of polyvinylpyrrolidone (PVP) coated AgNPs was investigated in eight typical environmental water samples (with different ionic strengths, hardness, and dissolved organic matter (DOM) concentrations) by using UV-visible spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the interaction of DOM with the surface of AgNPs. Further, the photo-transformation and morphology changes of AgNPs in environmental waters were studied by UV-visible spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The results suggested that both electrolytes (especially Ca(2+) and Mg(2+)) and DOM in the surface waters are key parameters for AgNP aggregation, and sunlight could accelerate the morphology change, aggregation, and further sedimentation of AgNPs. This water chemistry controlled aggregation and photo-transformation should have significant environmental impacts on the transport and toxicity of AgNPs in the aquatic environments. Copyright © 2015. Published by Elsevier B.V.

  11. Applications of laser wakefield accelerator-based light sources

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Albert, Felicie; Thomas, Alec G. R.

    Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons inmore » the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. Here, we first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science.« less

  12. Applications of laser wakefield accelerator-based light sources

    DOE PAGES

    Albert, Felicie; Thomas, Alec G. R.

    2016-10-01

    Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons inmore » the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. Here, we first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science.« less

  13. Thai Grade 11 Students' Alternative Conceptions for Acid-Base Chemistry

    ERIC Educational Resources Information Center

    Artdej, Romklao; Ratanaroutai, Thasaneeya; Coll, Richard Kevin; Thongpanchang, Tienthong

    2010-01-01

    This study involved the development of a two-tier diagnostic instrument to assess Thai high school students' understanding of acid-base chemistry. The acid-base diagnostic test (ABDT) comprising 18 items was administered to 55 Grade 11 students in a science and mathematics programme during the second semester of the 2008 academic year. Analysis of…

  14. Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors

    NASA Astrophysics Data System (ADS)

    Mazur, Mykola; Barras, Alexandre; Kuncser, Victor; Galatanu, Andrei; Zaitzev, Vladimir; Turcheniuk, Kostiantyn V.; Woisel, Patrice; Lyskawa, Joel; Laure, William; Siriwardena, Aloysius; Boukherroub, Rabah; Szunerits, Sabine

    2013-03-01

    The synthesis of multifunctional magnetic nanoparticles (MF-MPs) is one of the most active research areas in advanced materials as their multifunctional surfaces allow conjugation of biological and chemical molecules, thus making it possible to achieve target-specific diagnostic in parallel to therapeutics. We report here a simple strategy to integrate in a one-step reaction several reactive sites onto the particles. The preparation of MF-MPs is based on their simultaneous modification with differently functionalized dopamine derivatives using simple solution chemistry. The formed MF-MPs show comparable magnetic properties to those of naked nanoparticles with almost unaltered particle size of around 25 nm. The different termini, amine, azide and maleimide functions, enable further functionalization of MF-MPs by the grafting-on approach. Michael addition, Cu(i) catalyzed « click » chemistry and amidation reactions are performed on the MF-MPs integrating subsequently 6-(ferrocenyl)-hexanethiol, horseradish peroxidase (HRP) and mannose.

  15. Gold nanoparticles: role of size and surface chemistry on blood protein adsorption

    NASA Astrophysics Data System (ADS)

    Benetti, F.; Fedel, M.; Minati, L.; Speranza, G.; Migliaresi, C.

    2013-06-01

    Material interaction with blood proteins is a critical issue, since it could influence the biological processes taking place in the body following implantation/injection. This is particularly important in the case of nanoparticles, where innovative properties, such as size and high surface to volume ratio can lead to a behavioral change with respect to bulk macroscopic materials and could be responsible for a potential risk for human health. The aim of this work was to compare gold nanoparticles (AuNP) and planar surfaces to study the role of surface curvature moving from the macro- to the nano-size in the process of blood protein adsorption. In the course of the study, different protocols were tested to optimize the analysis of protein adsorption on gold nanoparticles. AuNP with different size (10, 60 and 200 nm diameter) and surface coatings (citrate and polyethylene glycol) were carefully characterized. The stabilizing action of blood proteins adsorbed on AuNP was studied measuring the variation of size and solubility of the nanoparticles following incubation with single protein solutions (human serum albumin and fibrinogen) and whole blood plasma. In addition, we developed a method to elute proteins from AuNP to study the propensity of gold materials to adsorb plasma proteins in function of dimensional characteristics and surface chemistry. We showed a different efficacy of the various eluting media tested, proving that even the most aggressive agent cannot provide a complete detachment of the protein corona. Enhanced protein adsorption was evidenced on AuNP if compared to gold laminae (bare and PEGylated) used as macroscopic control, probably due to the superior AuNP surface reactivity.

  16. Inorganic Chemistry Solutions to Semiconductor Nanocrystal Problems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alvarado, Samuel R.; Guo, Yijun; Ruberu, T. Purnima A.

    2014-03-15

    The optoelectronic and chemical properties of semiconductor nanocrystals heavily depend on their composition, size, shape and internal structure, surface functionality, etc. Available strategies to alter these properties through traditional colloidal syntheses and ligand exchange methods place a premium on specific reaction conditions and surfactant combinations. In this invited review, we apply a molecular-level understanding of chemical precursor reactivity to reliably control the morphology, composition and intimate architecture (core/shell vs. alloyed) of semiconductor nanocrystals. We also describe our work aimed at achieving highly selective, low-temperature photochemical methods for the synthesis of semiconductor–metal and semiconductor–metal oxide photocatalytic nanocomposites. In addition, we describemore » our work on surface modification of semiconductor nanocrystal quantum dots using new approaches and methods that bypass ligand exchange, retaining the nanocrystal's native ligands and original optical properties, as well as on spectroscopic methods of characterization useful in determining surface ligand organization and chemistry. Using recent examples from our group and collaborators, we demonstrate how these efforts have lead to faster, wider and more systematic application of semiconductor nanocrystal-based materials to biological imaging and tracking, and to photocatalysis of unconventional substrates. We believe techniques and methods borrowed from inorganic chemistry (including coordination, organometallic and solid state chemistry) have much to offer in reaching a better understanding of the synthesis, functionalization and real-life application of such exciting materials as semiconductor nanocrystals (quantum dots, rods, tetrapods, etc.).« less

  17. Precipitation chemistry - Atmospheric loadings to the surface waters of the Indian River lagoon basin by rainfall

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.; Madsen, Brooks C.; Maull, Lee A.; Hinkle, C. R.; Knott, William M., III

    1990-01-01

    Rain volume and chemistry monitoring as part of the Kennedy Space Center Long Term Environmental Monitoring Program included the years 1984-1987 as part of the National Atmospheric Deposition Program. Atmospheric deposition in rainfall consisted primarily of sea salt and hydrogen ion, sulfate, nitrate, and ammonium ions. The deposition of nitrogen (a principal plant nutrient) was on the order of 200-300 metric tons per year to the surface waters.

  18. Laser-ablation-based ion source characterization and manipulation for laser-driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Sommer, P.; Metzkes-Ng, J.; Brack, F.-E.; Cowan, T. E.; Kraft, S. D.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

    2018-05-01

    For laser-driven ion acceleration from thin foils (∼10 μm–100 nm) in the target normal sheath acceleration regime, the hydro-carbon contaminant layer at the target surface generally serves as the ion source and hence determines the accelerated ion species, i.e. mainly protons, carbon and oxygen ions. The specific characteristics of the source layer—thickness and relevant lateral extent—as well as its manipulation have both been investigated since the first experiments on laser-driven ion acceleration using a variety of techniques from direct source imaging to knife-edge or mesh imaging. In this publication, we present an experimental study in which laser ablation in two fluence regimes (low: F ∼ 0.6 J cm‑2, high: F ∼ 4 J cm‑2) was applied to characterize and manipulate the hydro-carbon source layer. The high-fluence ablation in combination with a timed laser pulse for particle acceleration allowed for an estimation of the relevant source layer thickness for proton acceleration. Moreover, from these data and independently from the low-fluence regime, the lateral extent of the ion source layer became accessible.

  19. A compact linear accelerator based on a scalable microelectromechanical-system RF-structure

    NASA Astrophysics Data System (ADS)

    Persaud, A.; Ji, Q.; Feinberg, E.; Seidl, P. A.; Waldron, W. L.; Schenkel, T.; Lal, A.; Vinayakumar, K. B.; Ardanuc, S.; Hammer, D. A.

    2017-06-01

    A new approach for a compact radio-frequency (RF) accelerator structure is presented. The new accelerator architecture is based on the Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) structure that was first developed in the 1980s. The MEQALAC utilized RF resonators producing the accelerating fields and providing for higher beam currents through parallel beamlets focused using arrays of electrostatic quadrupoles (ESQs). While the early work obtained ESQs with lateral dimensions on the order of a few centimeters, using a printed circuit board (PCB), we reduce the characteristic dimension to the millimeter regime, while massively scaling up the potential number of parallel beamlets. Using Microelectromechanical systems scalable fabrication approaches, we are working on further reducing the characteristic dimension to the sub-millimeter regime. The technology is based on RF-acceleration components and ESQs implemented in the PCB or silicon wafers where each beamlet passes through beam apertures in the wafer. The complete accelerator is then assembled by stacking these wafers. This approach has the potential for fast and inexpensive batch fabrication of the components and flexibility in system design for application specific beam energies and currents. For prototyping the accelerator architecture, the components have been fabricated using the PCB. In this paper, we present proof of concept results of the principal components using the PCB: RF acceleration and ESQ focusing. Ongoing developments on implementing components in silicon and scaling of the accelerator technology to high currents and beam energies are discussed.

  20. A compact linear accelerator based on a scalable microelectromechanical-system RF-structure.

    PubMed

    Persaud, A; Ji, Q; Feinberg, E; Seidl, P A; Waldron, W L; Schenkel, T; Lal, A; Vinayakumar, K B; Ardanuc, S; Hammer, D A

    2017-06-01

    A new approach for a compact radio-frequency (RF) accelerator structure is presented. The new accelerator architecture is based on the Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) structure that was first developed in the 1980s. The MEQALAC utilized RF resonators producing the accelerating fields and providing for higher beam currents through parallel beamlets focused using arrays of electrostatic quadrupoles (ESQs). While the early work obtained ESQs with lateral dimensions on the order of a few centimeters, using a printed circuit board (PCB), we reduce the characteristic dimension to the millimeter regime, while massively scaling up the potential number of parallel beamlets. Using Microelectromechanical systems scalable fabrication approaches, we are working on further reducing the characteristic dimension to the sub-millimeter regime. The technology is based on RF-acceleration components and ESQs implemented in the PCB or silicon wafers where each beamlet passes through beam apertures in the wafer. The complete accelerator is then assembled by stacking these wafers. This approach has the potential for fast and inexpensive batch fabrication of the components and flexibility in system design for application specific beam energies and currents. For prototyping the accelerator architecture, the components have been fabricated using the PCB. In this paper, we present proof of concept results of the principal components using the PCB: RF acceleration and ESQ focusing. Ongoing developments on implementing components in silicon and scaling of the accelerator technology to high currents and beam energies are discussed.

  1. Students' Perceptions of Teaching in Context-Based and Traditional Chemistry Classrooms: Comparing Content, Learning Activities, and Interpersonal Perspectives

    ERIC Educational Resources Information Center

    Overman, Michelle; Vermunt, Jan D.; Meijer, Paulien C.; Bulte, Astrid M. W.; Brekelmans, Mieke

    2014-01-01

    Context-based curriculum reforms in chemistry education are thought to bring greater diversity to the ways in which chemistry teachers organize their teaching. First and foremost, students are expected to perceive this diversity. However, empirical research on how students perceive their teacher's teaching in context-based chemistry classrooms,…

  2. Effects of Computer Based Learning on Students' Attitudes and Achievements towards Analytical Chemistry

    ERIC Educational Resources Information Center

    Akcay, Hüsamettin; Durmaz, Asli; Tüysüz, Cengiz; Feyzioglu, Burak

    2006-01-01

    The aim of this study was to compare the effects of computer-based learning and traditional method on students' attitudes and achievement towards analytical chemistry. Students from Chemistry Education Department at Dokuz Eylul University (D.E.U) were selected randomly and divided into three groups; two experimental (Eg-1 and Eg-2) and a control…

  3. Surface chemistry governs cellular tropism of nanoparticles in the brain

    NASA Astrophysics Data System (ADS)

    Song, Eric; Gaudin, Alice; King, Amanda R.; Seo, Young-Eun; Suh, Hee-Won; Deng, Yang; Cui, Jiajia; Tietjen, Gregory T.; Huttner, Anita; Saltzman, W. Mark

    2017-05-01

    Nanoparticles are of long-standing interest for the treatment of neurological diseases such as glioblastoma. Most past work focused on methods to introduce nanoparticles into the brain, suggesting that reaching the brain interstitium will be sufficient to ensure therapeutic efficacy. However, optimized nanoparticle design for drug delivery to the central nervous system is limited by our understanding of their cellular deposition in the brain. Here, we investigated the cellular fate of poly(lactic acid) nanoparticles presenting different surface chemistries, after administration by convection-enhanced delivery. We demonstrate that nanoparticles with `stealth' properties mostly avoid internalization by all cell types, but internalization can be enhanced by functionalization with bio-adhesive end-groups. We also show that association rates measured in cultured cells predict the extent of internalization of nanoparticles in cell populations. Finally, evaluating therapeutic efficacy in an orthotopic model of glioblastoma highlights the need to balance significant uptake without inducing adverse toxicity.

  4. Atomic-scale simulation of dust grain collisions: Surface chemistry and dissipation beyond existing theory

    NASA Astrophysics Data System (ADS)

    Quadery, Abrar H.; Doan, Baochi D.; Tucker, William C.; Dove, Adrienne R.; Schelling, Patrick K.

    2017-10-01

    The early stages of planet formation involve steps where submicron-sized dust particles collide to form aggregates. However, the mechanism through which millimeter-sized particles aggregate to kilometer-sized planetesimals is still not understood. Dust grain collision experiments carried out in the environment of the Earth lead to the prediction of a 'bouncing barrier' at millimeter-sizes. Theoretical models, e.g., Johnson-Kendall-Roberts and Derjaguin-Muller-Toporov theories, lack two key features, namely the chemistry of dust grain surfaces, and a mechanism for atomic-scale dissipation of energy. Moreover, interaction strengths in these models are parameterized based on experiments done in the Earth's environment. To address these issues, we performed atomic-scale simulations of collisions between nonhydroxylated and hydroxylated amorphous silica nanoparticles. We used the ReaxFF approach which enables modeling chemical reactions using an empirical potential. We found that nonhydroxylated nanograins tend to adhere with much higher probability than suggested by existing theories. By contrast, hydroxylated nanograins exhibit a strong tendency to bounce. Also, the interaction between dust grains has the characteristics of a strong chemical force instead of weak van der Waals forces. This suggests that the formation of strong chemical bonds and dissipation via internal atomic vibration may result in aggregation beyond what is expected based on our current understanding. Our results also indicate that experiments should more carefully consider surface conditions to mimic the space environment. We also report results of simulations with molten silica nanoparticles. It is found that molten particles are more likely to adhere due to viscous dissipation, which supports theories that suggest aggregation to kilometer scales might require grains to be in a molten state.

  5. A New Chemistry Course for Non-Chemistry Majors.

    ERIC Educational Resources Information Center

    Ariel, Magda; And Others

    1982-01-01

    A two-semester basic chemistry course for nonchemistry engineering majors is described. First semester provides introductory chemistry for freshmen while second semester is "customer-oriented," based on a departmental choice of three out of six independent modules. For example, aeronautical engineering "customers" would select…

  6. Thai Grade 11 students' alternative conceptions for acid-base chemistry

    NASA Astrophysics Data System (ADS)

    Artdej, Romklao; Ratanaroutai, Thasaneeya; Coll, Richard Kevin; Thongpanchang, Tienthong

    2010-07-01

    This study involved the development of a two-tier diagnostic instrument to assess Thai high school students' understanding of acid-base chemistry. The acid-base diagnostic test (ABDT) comprising 18 items was administered to 55 Grade 11 students in a science and mathematics programme during the second semester of the 2008 academic year. Analysis of students' responses from this study followed the methodology outlined by Çalik and Ayas. The research findings suggest that the ABDT, the multiple choice diagnostic instrument, enables researchers and teachers to classify students' understanding at different levels. Most students exhibited alternative conceptions for several concepts: acid-base theory, dissociation of strong acids or bases, and dissociation of weak acids/bases. Interestingly, one of the concepts that students appeared to find most difficult, and for which they exhibited the most alternative conceptions, was acid-base theory. Some alternative conceptions revealed in this study differ from earlier reports, such as the concept of electrolyte and non-electrolyte solutions as well as the concentration changes of H3O+and OH- in water. These research findings present valuable information for facilitating better understanding of acid-base chemistry by providing insight into the preventable and correctable alternative conceptions exhibited by students.

  7. Spectroscopic measurements of plasma emission light for plasma-based acceleration experiments

    NASA Astrophysics Data System (ADS)

    Filippi, F.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Zigler, A.

    2016-09-01

    Advanced particle accelerators are based on the excitation of large amplitude plasma waves driven by either electron or laser beams. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of high brightness electron beams through the so-called resonant Plasma Wakefield Acceleration scheme in which a train of electron bunches (drivers) resonantly excites wakefields into a preformed hydrogen plasma; the last bunch (witness) injected at the proper accelerating phase gains energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The measurements of plasma density of the order of 1016-1017 cm-3 can be performed with spectroscopic measurements of the plasma-emitted light. The measured density distribution for hydrogen filled capillary discharge with both Balmer alpha and Balmer beta lines and shot-to-shot variation are here reported.

  8. Wideband Motion Control by Position and Acceleration Input Based Disturbance Observer

    NASA Astrophysics Data System (ADS)

    Irie, Kouhei; Katsura, Seiichiro; Ohishi, Kiyoshi

    The disturbance observer can observe and suppress the disturbance torque within its bandwidth. Recent motion systems begin to spread in the society and they are required to have ability to contact with unknown environment. Such a haptic motion requires much wider bandwidth. However, since the conventional disturbance observer attains the acceleration response by the second order derivative of position response, the bandwidth is limited due to the derivative noise. This paper proposes a novel structure of a disturbance observer. The proposed disturbance observer uses an acceleration sensor for enlargement of bandwidth. Generally, the bandwidth of an acceleration sensor is from 1Hz to more than 1kHz. To cover DC range, the conventional position sensor based disturbance observer is integrated. Thus, the performance of the proposed Position and Acceleration input based disturbance observer (PADO) is superior to the conventional one. The PADO is applied to position control (infinity stiffness) and force control (zero stiffness). The numerical and experimental results show viability of the proposed method.

  9. Effects of surface chemistry and microstructure of electrolyte on oxygen reduction kinetics of solid oxide fuel cells

    DOE PAGES

    Park, Joong Sun; An, Jihwan; Lee, Min Hwan; ...

    2015-11-01

    In this study, we report systematic investigation of the surface properties of yttria-stabilized zirconia (YSZ) electrolytes with the control of the grain boundary (GB) density at the surface, and its effects on electrochemical activities. The GB density of thin surface layers deposited on single crystal YSZ substrates is controlled by changing the annealing temperature (750-1450 °C). Higher oxygen reduction reactions (ORR) kinetics is observed in samples annealed at lower temperatures. The higher ORR activity is ascribed to the higher GB density at the YSZ surface where 'mobile' oxide ion vacancies are more populated. Meanwhile, oxide ion vacancies concurrently created withmore » yttrium segregation at the surface at the higher annealing temperature are considered inactive to oxygen incorporation reactions. Our results provide additional insight into the interplay between the surface chemistry, microstructures, and electrochemical activity. They potentially provide important guidelines for engineering the electrolyte electrode interfaces of solid oxide fuel cells for higher electrochemical performance.« less

  10. Acceleration modules in linear induction accelerators

    NASA Astrophysics Data System (ADS)

    Wang, Shao-Heng; Deng, Jian-Jun

    2014-05-01

    The Linear Induction Accelerator (LIA) is a unique type of accelerator that is capable of accelerating kilo-Ampere charged particle current to tens of MeV energy. The present development of LIA in MHz bursting mode and the successful application into a synchrotron have broadened LIA's usage scope. Although the transformer model is widely used to explain the acceleration mechanism of LIAs, it is not appropriate to consider the induction electric field as the field which accelerates charged particles for many modern LIAs. We have examined the transition of the magnetic cores' functions during the LIA acceleration modules' evolution, distinguished transformer type and transmission line type LIA acceleration modules, and re-considered several related issues based on transmission line type LIA acceleration module. This clarified understanding should help in the further development and design of LIA acceleration modules.

  11. Effects of TEA·HCl hardening accelerator on the workability of cement-based materials

    NASA Astrophysics Data System (ADS)

    Pan, Wenhao; Ding, Zhaoyang; Chen, Yanwen

    2017-03-01

    The aim of the test is to research the influence rules of TEA·HCl on the workability of cement paste and concrete. Based on the features of the new hardening accelerator, an experimental analysis system were established through different dosages of hardening accelerator, and the feasibility of such accelerator to satisfy the need of practical engineering was verified. The results show that adding of the hardening accelerator can accelerate the cement hydration, and what’s more, when the dosage was 0.04%, the setting time was the shortest while the initial setting time and final setting time were 130 min and 180 min, respectively. The initial fluidity of cement paste of adding accelerator was roughly equivalent compared with that of blank. After 30 min, fluidity loss would decrease with the dosage increasing, but fluidity may increase. The application of the hardening accelerator can make the early workability of concrete enhance, especially the slump loss of 30 min can improve more significantly. The bleeding rate of concrete significantly decreases after adding TEA·HCl. The conclusion is that the new hardening accelerator can meet the need of the workability of cement-based materials in the optimum dosage range.

  12. IN-PACKAGE CHEMISTRY ABSTRACTION

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    E. Thomas

    2005-07-14

    This report was developed in accordance with the requirements in ''Technical Work Plan for Postclosure Waste Form Modeling'' (BSC 2005 [DIRS 173246]). The purpose of the in-package chemistry model is to predict the bulk chemistry inside of a breached waste package and to provide simplified expressions of that chemistry as a function of time after breach to Total Systems Performance Assessment for the License Application (TSPA-LA). The scope of this report is to describe the development and validation of the in-package chemistry model. The in-package model is a combination of two models, a batch reactor model, which uses the EQ3/6more » geochemistry-modeling tool, and a surface complexation model, which is applied to the results of the batch reactor model. The batch reactor model considers chemical interactions of water with the waste package materials, and the waste form for commercial spent nuclear fuel (CSNF) waste packages and codisposed (CDSP) waste packages containing high-level waste glass (HLWG) and DOE spent fuel. The surface complexation model includes the impact of fluid-surface interactions (i.e., surface complexation) on the resulting fluid composition. The model examines two types of water influx: (1) the condensation of water vapor diffusing into the waste package, and (2) seepage water entering the waste package as a liquid from the drift. (1) Vapor-Influx Case: The condensation of vapor onto the waste package internals is simulated as pure H{sub 2}O and enters at a rate determined by the water vapor pressure for representative temperature and relative humidity conditions. (2) Liquid-Influx Case: The water entering a waste package from the drift is simulated as typical groundwater and enters at a rate determined by the amount of seepage available to flow through openings in a breached waste package.« less

  13. Development and assessment of a chemistry-based computer video game as a learning tool

    NASA Astrophysics Data System (ADS)

    Martinez-Hernandez, Kermin Joel

    The chemistry-based computer video game is a multidisciplinary collaboration between chemistry and computer graphics and technology fields developed to explore the use of video games as a possible learning tool. This innovative approach aims to integrate elements of commercial video game and authentic chemistry context environments into a learning experience through gameplay. The project consists of three areas: development, assessment, and implementation. However, the foci of this study were the development and assessment of the computer video game including possible learning outcomes and game design elements. A chemistry-based game using a mixed genre of a single player first-person game embedded with action-adventure and puzzle components was developed to determine if students' level of understanding of chemistry concepts change after gameplay intervention. Three phases have been completed to assess students' understanding of chemistry concepts prior and after gameplay intervention. Two main assessment instruments (pre/post open-ended content survey and individual semi-structured interviews) were used to assess student understanding of concepts. In addition, game design elements were evaluated for future development phases. Preliminary analyses of the interview data suggest that students were able to understand most of the chemistry challenges presented in the game and the game served as a review for previously learned concepts as well as a way to apply such previous knowledge. To guarantee a better understanding of the chemistry concepts, additions such as debriefing and feedback about the content presented in the game seem to be needed. The use of visuals in the game to represent chemical processes, game genre, and game idea appear to be the game design elements that students like the most about the current computer video game.

  14. Improving density functional tight binding predictions of free energy surfaces for peptide condensation reactions in solution

    NASA Astrophysics Data System (ADS)

    Kroonblawd, Matthew; Goldman, Nir

    First principles molecular dynamics using highly accurate density functional theory (DFT) is a common tool for predicting chemistry, but the accessible time and space scales are often orders of magnitude beyond the resolution of experiments. Semi-empirical methods such as density functional tight binding (DFTB) offer up to a thousand-fold reduction in required CPU hours and can approach experimental scales. However, standard DFTB parameter sets lack good transferability and calibration for a particular system is usually necessary. Force matching the pairwise repulsive energy term in DFTB to short DFT trajectories can improve the former's accuracy for chemistry that is fast relative to DFT simulation times (<10 ps), but the effects on slow chemistry and the free energy surface are not well-known. We present a force matching approach to increase the accuracy of DFTB predictions for free energy surfaces. Accelerated sampling techniques are combined with path collective variables to generate the reference DFT data set and validate fitted DFTB potentials without a priori knowledge of transition states. Accuracy of force-matched DFTB free energy surfaces is assessed for slow peptide-forming reactions by direct comparison to DFT results for particular paths. Extensions to model prebiotic chemistry under shock conditions are discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Accelerating Multiple Compound Comparison Using LINGO-Based Load-Balancing Strategies on Multi-GPUs

    PubMed Central

    Lin, Chun-Yuan; Wang, Chung-Hung; Hung, Che-Lun; Lin, Yu-Shiang

    2015-01-01

    Compound comparison is an important task for the computational chemistry. By the comparison results, potential inhibitors can be found and then used for the pharmacy experiments. The time complexity of a pairwise compound comparison is O(n 2), where n is the maximal length of compounds. In general, the length of compounds is tens to hundreds, and the computation time is small. However, more and more compounds have been synthesized and extracted now, even more than tens of millions. Therefore, it still will be time-consuming when comparing with a large amount of compounds (seen as a multiple compound comparison problem, abbreviated to MCC). The intrinsic time complexity of MCC problem is O(k 2 n 2) with k compounds of maximal length n. In this paper, we propose a GPU-based algorithm for MCC problem, called CUDA-MCC, on single- and multi-GPUs. Four LINGO-based load-balancing strategies are considered in CUDA-MCC in order to accelerate the computation speed among thread blocks on GPUs. CUDA-MCC was implemented by C+OpenMP+CUDA. CUDA-MCC achieved 45 times and 391 times faster than its CPU version on a single NVIDIA Tesla K20m GPU card and a dual-NVIDIA Tesla K20m GPU card, respectively, under the experimental results. PMID:26491652

  16. Titanium surface bio-functionalization using osteogenic peptides: Surface chemistry, biocompatibility, corrosion and tribocorrosion aspects.

    PubMed

    Trino, Luciana D; Bronze-Uhle, Erika S; Ramachandran, Amsaveni; Lisboa-Filho, Paulo N; Mathew, Mathew T; George, Anne

    2018-05-01

    Titanium (Ti) is widely used in biomedical devices due to its recognized biocompatibility. However, implant failures and subsequent clinical side effects are still recurrent. In this context, improvements can be achieved by designing biomaterials where the bulk and the surface of Ti are independently tailored. The conjugation of biomolecules onto the Ti surface can improve its bioactivity, thus accelerating the osteointegration process. Ti was modified with TiO 2 , two different spacers, 3-(4-aminophenyl) propionic acid (APPA) or 3-mercaptopropionic acid (MPA) and dentin matrix protein 1 (DMP1) peptides. X-ray photoelectron spectroscopy analysis revealed the presence of carbon and nitrogen for all samples, indicating a success in the functionalization process. Furthermore, DMP1 peptides showed an improved coverage area for the samples with APPA and MPA spacers. Biological tests indicated that the peptides could modulate cell affinity, proliferation, and differentiation. Enhanced results were observed in the presence of MPA. Moreover, the immobilization of DMP1 peptides through the spacers led to the formation of calcium phosphate minerals with a Ca/P ratio near to that of hydroxyapatite. Corrosion and tribocorrosion results indicated an increased resistance to corrosion and lower mass loss in the functionalized materials, showing that this new type of functional material has attractive properties for biomaterials application. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. Enhanced Surface Warming and Accelerated Snow Melt in the Himalayas and Tibetan Plateau Induced by Absorbing Aerosols

    NASA Technical Reports Server (NTRS)

    Lau, William K.; Kim, Maeng-Ki; Kim, Kyu-Myong; Lee, Woo-Seop

    2010-01-01

    Numerical experiments with the NASA finite-volume general circulation model show that heating of the atmosphere by dust and black carbon can lead to widespread enhanced warming over the Tibetan Plateau (TP) and accelerated snow melt in the western TP and Himalayas. During the boreal spring, a thick aerosol layer, composed mainly of dust transported from adjacent deserts and black carbon from local emissions, builds up over the Indo-Gangetic Plain, against the foothills of the Himalaya and the TP. The aerosol layer, which extends from the surface to high elevation (approx.5 km), heats the mid-troposphere by absorbing solar radiation. The heating produces an atmospheric dynamical feedback the so-called elevated-heat-pump (EHP) effect, which increases moisture, cloudiness, and deep convection over northern India, as well as enhancing the rate of snow melt in the Himalayas and TP. The accelerated melting of snow is mostly confined to the western TP, first slowly in early April and then rapidly from early to mid-May. The snow cover remains reduced from mid-May through early June. The accelerated snow melt is accompanied by similar phases of enhanced warming of the atmosphere-land system of the TP, with the atmospheric warming leading the surface warming by several days. Surface energy balance analysis shows that the short-wave and long-wave surface radiative fluxes strongly offset each other, and are largely regulated by the changes in cloudiness and moisture over the TP. The slow melting phase in April is initiated by an effective transfer of sensible heat from a warmer atmosphere to land. The rapid melting phase in May is due to an evaporation-snow-land feedback coupled to an increase in atmospheric moisture over the TP induced by the EHP effect.

  18. Changing Groundwater-Surface Water Interactions Impact Stream Chemistry and Ecology at the Arctic-Boreal Transition in Western Alaska

    NASA Astrophysics Data System (ADS)

    Koch, J. C.; Carey, M.; O'Donnell, J.; Sjoberg, Y.; Zimmerman, C. E.

    2016-12-01

    The arctic-boreal transition zone of Alaska is experiencing rapid change related to unprecedented warming and subsequent loss of permafrost. These changes in turn may affect groundwater-surface water (GW-SW) interactions, biogeochemical cycling, and ecosystem processes. While recent field and modeling studies have improved our understanding of hydrology in watersheds underlain by thawing permafrost, little is known about how these hydrologic shifts will impact bottom-up controls on stream food webs. To address this uncertainty, we are using an integrative experimental design to link GW-SW interactions to stream biogeochemistry and biota in 10 first-order streams in northwest Alaska. These study streams drain watersheds that span several gradients, including elevation, aspect, and vegetation (tundra vs. forest). We have developed a robust, multi-disciplinary data set to characterize GW-SW interactions and to mechanistically link GW-SW dynamics to water quality and the stream ecosystem. Data includes soil hydrology and chemistry; stream discharge, temperature, and inflow rates; water chemistry (including water isotopes, major ions, carbon concentration and isotopes, nutrients and chlorophyll-a), and invertebrate and fish communities. Stream recession curves indicate a decreasing rate later in the summer in some streams, consistent with seasonal thaw in lower elevation and south-facing catchments. Base cation and water isotope chemistry display similar impacts of seasonal thaw and also suggest the dominance of groundwater in many streams. Coupled with estimates of GW-SW exchange at point, reach, and catchment scales, these results will be used to predict how hydrology and water quality are likely to impact fish habitat and growth given continued warming at the arctic-boreal transition.

  19. Advocating for Grade-Based Acceleration

    ERIC Educational Resources Information Center

    Guilbault, Keri M.

    2014-01-01

    Parents often struggle with the decision to accelerate their child and may worry about social and emotional issues, although research indicates positive effects on the social and emotional adjustment of carefully selected accelerants. As children's advocates, parents can work effectively with a school system to secure an appropriate academic…

  20. Regional warming of hot extremes accelerated by surface energy fluxes consistent with drying soils

    NASA Astrophysics Data System (ADS)

    Donat, M.; Pitman, A.; Seneviratne, S. I.

    2017-12-01

    Strong regional differences exist in how hot temperature extremes increase under global warming. Using an ensemble of coupled climate models, we examine the regional warming rates of hot extremes relative to annual average warming rates in the same regions. We identify hotspots of accelerated warming of model-simulated hot extremes in Europe, North America, South America and Southeast China. These hotspots indicate where the warm tail of a distribution of temperatures increases faster than the average and are robust across most CMIP5 models. Exploring the conditions on the specific day the hot extreme occurs demonstrates the hotspots are explained by changes in the surface energy fluxes consistent with drying soils. Furthermore, in these hotspot regions we find a relationship between the temperature - heat flux correlation under current climate conditions and the magnitude of future projected changes in hot extremes, pointing to a potential emergent constraint for simulations of future hot extremes. However, the model-simulated accelerated warming of hot extremes appears inconsistent with observations of the past 60 years, except over Europe. The simulated acceleration of hot extremes may therefore be unreliable, a result that necessitates a re-evaluation of how climate models resolve the relevant terrestrial processes.