Anionic Photopolymerization of Methyl-2-Cyanoacrylate and Simultaneous Color Formation

DTIC Science & Technology

2000-11-15

Anionic polymerization of methyl 2-cyanoacrylate initiated by photoinduced heterolysis of crystal violet leuconitrile (CVCN) and of malachite green leucohydroxide (MGOH) is demonstrated. Polymerization is accompanied by color formation.

Synthesis and polymerization of vinyl triazolium ionic liquids

DOEpatents

Luebke, David; Nulwala, Hunaid; Matyjaszewski, Krzysztof; Adzima, Brian

2018-05-15

Herein, we describe polymerized ionic liquids, demonstrate the synthesis of polymerized ionic liquids, and demonstrate the polymerization of triazolium monomers. One embodiment shows the polymeriazation of the triazolium monomers with bis(trifluoromethanesulfonyl)imide anions. In another embodiment we show the feasibility of copolymerizing with commodity monomers such as styrene using free radical polymerization techniques.

Tetrahedrality and hydrogen bonds in water

NASA Astrophysics Data System (ADS)

Székely, Eszter; Varga, Imre K.; Baranyai, András

2016-06-01

We carried out extensive calculations of liquid water at different temperatures and pressures using the BK3 model suggested recently [P. T. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)]. In particular, we were interested in undercooled regions to observe the propensity of water to form tetrahedral coordination of closest neighbors around a central molecule. We compared the found tetrahedral order with the number of hydrogen bonds and with the partial pair correlation functions unfolded as distributions of the closest, the second closest, etc. neighbors. We found that contrary to the number of hydrogen bonds, tetrahedrality changes substantially with state variables. Not only the number of tetrahedral arrangements increases with lowering the pressure, the density, and the temperature but the domain size of connecting tetrahedral structures as well. The difference in tetrahedrality is very pronounced between the two sides of the Widom line and even more so between the low density amorphous (LDA) and high density amorphous (HDA) phases. We observed that in liquid water and in HDA, the 5th water molecule, contrary to ice and LDA, is positioned between the first and the second coordination shell. We found no convincing evidence of structural heterogeneity or regions referring to structural transition.

Covalent Polymers Containing Discrete Heterocyclic Anion Receptors

PubMed Central

Rambo, Brett M.; Silver, Eric S.; Bielawski, Christopher W.; Sessler, Jonathan L.

2010-01-01

This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions. PMID:20871791

Functional Materials from Polymeric Ionic Liquids

NASA Astrophysics Data System (ADS)

Segalman, Rachel; Sanoja, Gabriel; Michenfelder-Schauser, Nicole; Mitragotri, Samir; Seshadri, Ram

Ionic liquids (IL's) have been suggested for applications as diverse as solubilizing cellulose, antimicrobial treatments, and electrolytes in batteries due to their molten salt properties. A polymeric cation (such as imidazolium) is an excellent host for any associated anion. As a result, polymerized ionic liquids are not just solid counterparts to IL's, but are shown to be vectors for the inclusion of a wide variety of functionalities ranging from multi-valent ions to magnetic anions. Moreover, PIL block copolymers allow orthogonal control over mechanical and morphological properties, ultimately leading to a conceptual framework for processable, tunable, multifunctional materials.

Layered double hydroxide/polyethylene terephthalate nanocomposites. Influence of the intercalated LDH anion and the type of polymerization heating method

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

Herrero, M.; Martinez-Gallegos, S.; Labajos, F.M.

2011-11-15

Conventional and microwave heating routes have been used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate had been previously intercalated in the LDH. PXRD and TEM were used to detect the degree of dispersion of the filler and the type of the polymeric composites obtained, and FTIR spectroscopy confirmed that the polymerization process had taken place. The thermal stability of these composites, as studied by thermogravimetric analysis, was enhanced when the microwave heating method was applied. Dodecyl sulphate wasmore » more effective than terephthalate to exfoliate the samples, which only occurred for the terephthalate ones under microwave irradiation. - Graphical abstract: Conventional and microwave heating routes were used to prepare PET-LDH (polyethylene terephthalate-layered double hydroxide) composites with 1-10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate was previously intercalated into the LDH. The microwave process improves the dispersion and the thermal stability of nanocomposites due to the interaction of the microwave radiation and the dipolar properties of EG and the homogeneous heating. Highlights: > LDH-PET compatibility is enhanced by preintercalation of organic anions. > Dodecylsulphate performance is much better than that of terephthalate. > Microwave heating improves the thermal stability of the composites. > Microwave heating improves as well the dispersion of the inorganic phase.« less

Glomerular disease augments kidney accumulation of synthetic anionic polymers.

PubMed

Liu, Gary W; Prossnitz, Alexander N; Eng, Diana G; Cheng, Yilong; Subrahmanyam, Nithya; Pippin, Jeffrey W; Lamm, Robert J; Ngambenjawong, Chayanon; Ghandehari, Hamidreza; Shankland, Stuart J; Pun, Suzie H

2018-06-02

Polymeric drug carriers can alter the pharmacokinetics of their drug cargoes, thereby improving drug therapeutic index and reducing side effects. Understanding and controlling polymer properties that drive tissue-specific accumulation is critical in engineering targeted drug delivery systems. For kidney disease applications, targeted drug delivery to renal cells that reside beyond the charge- and size-selective glomerular filtration barrier could have clinical potential. However, there are limited reports on polymer properties that might enhance kidney accumulation. Here, we studied the effects of molecular weight and charge on the in vivo kidney accumulation of polymers in health and disease. We synthesized a panel of well-defined polymers by atom transfer radical polymerization to answer several questions. First, the biodistribution of low molecular weight (23-27 kDa) polymers composed of various ratios of neutral:anionic monomers (1:0, 1:1, 1:4) in normal mice was determined. Then, highly anionic (1:4 monomer ratio) low molecular and high molecular weight (47 kDa) polymers were tested in both normal and experimental focal segmental glomerulosclerosis (FSGS) mice, a model that results in loss of glomerular filtration selectivity. Through these studies, we observed that kidney-specific polymer accumulation increases with anionic monomer content, but not molecular weight; experimental FSGS increases kidney accumulation of anionic polymers; and anionic polymers accumulate predominantly in proximal tubule cells, with some distribution in kidney glomeruli. These findings can be applied to the design of polymeric drug carriers to enhance or mitigate kidney accumulation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Streaming simplification of tetrahedral meshes.

PubMed

Vo, Huy T; Callahan, Steven P; Lindstrom, Peter; Pascucci, Valerio; Silva, Cláudio T

2007-01-01

Unstructured tetrahedral meshes are commonly used in scientific computing to represent scalar, vector, and tensor fields in three dimensions. Visualization of these meshes can be difficult to perform interactively due to their size and complexity. By reducing the size of the data, we can accomplish real-time visualization necessary for scientific analysis. We propose a two-step approach for streaming simplification of large tetrahedral meshes. Our algorithm arranges the data on disk in a streaming, I/O-efficient format that allows coherent access to the tetrahedral cells. A quadric-based simplification is sequentially performed on small portions of the mesh in-core. Our output is a coherent streaming mesh which facilitates future processing. Our technique is fast, produces high quality approximations, and operates out-of-core to process meshes too large for main memory.

Polymerization Initiated at the Sidewalls of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Tour, James M.; Hudson, Jared L.

2011-01-01

A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

Hoop/column and tetrahedral truss electromagnetic tests

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1987-01-01

The distortion of antennas was measured with a metric camera system at discrete target locations on the surface. Given are surface distortion for hoop column reflector antennas, for tetrahedral truss reflector antennas, and distortion contours for the tetrahedral truss reflector. Radiation patterns at 2.27-GHz, 4.26-GHz, 7.73-GHz and 11.6-GHz are given for the hoop column antenna. Also given are radiation patterns at 4.26-GHz and 7.73-GHz for the tetrahedral truss antenna.

Neutrino Mixing and the Double Tetrahedral Group

NASA Astrophysics Data System (ADS)

Bentov, Yoni; Zee, A.

2013-11-01

In the spirit of a previous study of the tetrahedral group T ≃A4, we discuss a minimalist scheme to derive the neutrino mixing matrix using the double tetrahedral group T‧, the double cover of T. The new features are three distinct two-dimensional representations and complex Clebsch-Gordan coefficients, which can result in a geometric source of CP violation in the neutrino mass matrix. In an appendix, we derive explicitly the relevant group theory for the tetrahedral group T and its double cover T‧.

A fluorescent molecular sensor for pH windows in traditional and polymeric biocompatible micelles: comicellization of anionic species to shift and reshape the ON window.

PubMed

Cavallaro, Gennara; Giammona, Gaetano; Pasotti, Luca; Pallavicini, Piersandro

2011-09-12

A new approach is presented to obtain fluorescent sensors for pH windows that work in water and under biomimetic conditions. A single molecule that features all-covalently linked components is used, thus making it capable of working as a fluorescent sensor with an OFF/ON/OFF response to pH value. The components are a tertiary amine, a pyridine, and a fluorophore (pyrene). The forms with both protonated bases or both neutral bases quench the pyrene fluorescence, whereas the form with the neutral pyridine and protonated amine groups is fluorescent. The molecular sensor is also equipped with a long alkyl chain to make it highly hydrophobic in all its protonated and unprotonated forms, that is, either when neutral or charged. Accordingly, it can be confined at any pH value either in traditional (i.e., low-molecular-weight) nonionic surfactant micelles or inside polymeric, biocompatible micellar containers. Relevant for future applications in vivo, thanks to its strong hydrophobicity, no leakage of the molecular sensor is observed from the polymeric biocompatible micelles. Due to the proximity of the pyridine and amine functions in the molecular structure and the poor hydration inside the micelles, the observed pK(a) values are low so that the ON window is positioned at very low pH values. However, the window can be shifted to biologically relevant values by comicellization of anionic species. In particular, in the micelles of the nonionic surfactant TritonX-100, a shift of the ON window to pH 4-6 is obtained by addition of the anionic sodium dodecyl sulphate surfactant, whose negative charge promotes the stability of the protonated forms of the pyridine and amine fragments. In the case of the polymeric micelles, we introduce the use of the amphiphilic polystyrene sulfonate anionic polyelectrolyte, the comicellization of which induces a shift and sharpening of the ON window that is centered at pH 4. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation of Polymer Particles by Direct Polymerization on the Surface of a Supramolecular Template.

PubMed

Schmuck, Carsten; Li, Mao; Zellermann, Elio

2018-04-06

Formation of polymeric materials on the surface of supramolecular assemblies is rather challenging due to the often weak non-covalent interactions between the self-assembled template and the monomers before polymerization. We herein describe that the introduction of a supramolecular anion recognition motif, the guanidiniocarbonyl pyrrole cation (GCP), into a short Fmoc-dipeptide 1 leads to self-assembled spherical nanoparticles in aqueous solution. Onto the surface of these nanoparticles negatively charged diacetylene monomers can be attached which after UV polymerization lead to the formation of a polymer shell around the self-assembled template. The hybrid supramolecular and polymeric nanoparticles demonstrated intriguing thermal hysteresis phenomenon. The template nanoparticle could be disassembled through the treatment with organic base which cleaved the Fmoc moiety on 1. This strategy thus showed that a supramolecular anion recognition motif allows the post-assembly formation of polymeric nanomaterials from anionic monomers around a cationic self-assembled template. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pu Anion Exchange Process Intensification

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

Taylor-Pashow, Kathryn M. L.

This research is focused on improving the efficiency of the anion exchange process for purifying plutonium. While initially focused on plutonium, the technology could also be applied to other ion-exchange processes. Work in FY17 focused on the improvement and optimization of porous foam columns that were initially developed in FY16. These foam columns were surface functionalized with poly(4-vinylpyridine) (PVP) to provide the Pu specific anion-exchange sites. Two different polymerization methods were explored for maximizing the surface functionalization with the PVP. The open-celled polymeric foams have large open pores and large surface areas available for sorption. The fluid passes through themore » large open pores of this material, allowing convection to be the dominant mechanism by which mass transport takes place. These materials generally have very low densities, open-celled structures with high cell interconnectivity, small cell sizes, uniform cell size distributions, and high structural integrity. These porous foam columns provide advantages over the typical porous resin beads by eliminating the slow diffusion through resin beads, making the anion-exchange sites easily accessible on the foam surfaces. The best performing samples exceeded the Pu capacity of the commercially available resin, and also offered the advantage of sharper elution profiles, resulting in a more concentrated product, with less loss of material to the dilute heads and tails cuts. An alternate approach to improving the efficiency of this process was also explored through the development of a microchannel array system for performing the anion exchange.« less

New Gel-Like Polymers as Selective Weak-Base Anion Exchangers

PubMed Central

Gierczyk, Błażej; Cegłowski, Michał; Zalas, Maciej

2015-01-01

A group of new anion exchangers, based on polyamine podands and of excellent ion-binding capacity, were synthesized. The materials were obtained in reactions between various poly(ethyleneamines) with glycidyl derivatives of cyclotetrasiloxane. The final polymeric, strongly cross-linked materials form gel-like solids. Their structures and interactions with anions adsorbed were studied by spectroscopic methods (CP-MAS NMR, FR-IR, UV-Vis). The sorption isotherms and kinetic parameters were determined for 29 anions. Materials studied show high ion capacity and selectivity towards some important anions, e.g., selenate(VI) or perrhenate. PMID:25946220

Sterically shielded diboron-containing metallocene olefin polymerization catalysts

DOEpatents

Marks, Tobin J.; Ja, Li; Yang, Xinmin

1995-09-05

A non-coordinating anion, preferably containing a sterically shielded diboron hydride, if combined with a cyclopenta-dienyl-substituted metallocene cation component, such as a zirconocene metallocene, is a useful olefin polymerization catalyst component. The anion preferably has the formula ##STR1## where R is branched lower alkyl, such as t-butyl.

Metal-chelating polymers by anionic ring-opening polymerization and their use in quantitative mass cytometry.

PubMed

Illy, Nicolas; Majonis, Daniel; Herrera, Isaac; Ornatsky, Olga; Winnik, Mitchell A

2012-08-13

Metal-chelating polymers (MCPs) are important reagents for multiplexed immunoassays based on mass cytometry. The role of the polymer is to carry multiple copies of individual metal isotopes, typically as lanthanide ions, and to provide a reactive functionality for convenient attachment to a monoclonal antibody (mAb). For this application, the optimum combination of chain length, backbone structure, end group, pendant groups, and synthesis strategy has yet to be determined. Here we describe the synthesis of a new type of MCP based on anionic ring-opening polymerization of an activated cyclopropane (the diallyl ester of 1,1-cyclopropane dicarboxylic acid) using a combination of 2-furanmethanethiol and a phosphazene base as the initiator. This reaction takes place with rigorous control over molecular weight, yielding a polymer with a narrow molecular weight distribution, reactive pendant groups for introducing a metal chelator, and a functional end group with orthogonal reactivity for attaching the polymer to the mAbs. Following the ring-opening polymerization, a two-step transformation introduced diethylenetriaminepentaacetic acid (DTPA) chelating groups on each pendant group. The polymers were characterized by NMR, size exclusion chromatography (SEC), and thermogravimetric analysis (TGA). The binding properties toward Gd(3+) as a prototypical lanthanide (Ln) ion were also studied by isothermal titration calorimetry (ITC). Attachment to a mAb involves a Diels-Alder reaction of the terminal furan with a bismaleimide, followed by a Michael addition of a thiol on the mAb, generated by mild reduction of a disulfide bond in the hinge region. Polymer samples with a number average degree of polymerization of 35, with a binding capacity of 49.5 ± 6 Ln(3+) ions per chain, were loaded with 10 different types of Ln ions and conjugated to 10 different mAbs. A suite of metal-tagged Abs was tested by mass cytometry in a 10-plex single cell analysis of human adult peripheral blood

Polymerization as a Model Chain Reaction

ERIC Educational Resources Information Center

Morton, Maurice

1973-01-01

Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

Video Vectorization via Tetrahedral Remeshing.

PubMed

Wang, Chuan; Zhu, Jie; Guo, Yanwen; Wang, Wenping

2017-02-09

We present a video vectorization method that generates a video in vector representation from an input video in raster representation. A vector-based video representation offers the benefits of vector graphics, such as compactness and scalability. The vector video we generate is represented by a simplified tetrahedral control mesh over the spatial-temporal video volume, with color attributes defined at the mesh vertices. We present novel techniques for simplification and subdivision of a tetrahedral mesh to achieve high simplification ratio while preserving features and ensuring color fidelity. From an input raster video, our method is capable of generating a compact video in vector representation that allows a faithful reconstruction with low reconstruction errors.

Vibrational Spectra of Tetrahedral Fullerenes.

PubMed

Cheng; Li; Tang

1999-01-01

From the topological structures of the following classes of tetrahedral fullerenes-(1) Cn(h, h; -i, i), Cn(h, 0; -i, 2i), Cn(2h + i, -h + i; i, i), Cn(h - i, h + 2i; -i, 2i), and Cn(h, i; 0, i) for Td symmetry; (2) Cn(h, k; k, h), Cn(h, k; -h - k, k), and Cn(h, k; -h, h + k) for Th symmetry; (3) Cn(h, k; i, j) for T symmetry-we have obtained theoretically the formulas for the numbers of their IR and Raman active modes for all of the tetrahedral fullerenes through the decomposition of their nuclear motions into irreducible representations by means of group theory. Copyright 1999 Academic Press.

High temperature thermoplastic elastomers synthesized by living anionic polymerization in hydrocarbon solvent at room temperature

DOE PAGES

Schlegel, Ralf; Williams, Katherine; Voyloy, Dimitry; ...

2016-03-30

We present the synthesis and characterization of a new class of high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene (FIF) triblock copolymers. All copolymers were prepared by living anionic polymerization in benzene at room temperature. Homopolymerization and effects of additives on the glass transition temperature (T g) of polybenzofulvene (PBF) were also investigated. Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390 ± 66% from tensile tests. The stress–strain curves of FIF-10 and 14 were analyzed by a statistical molecular approach using amore » nonaffine tube model to estimate the thermoplastic elastomer behavior. Dynamic mechanical analysis showed that the softening temperature of PBF in FIF was 145 °C, much higher than that of thermoplastic elastomers with polystyrene hard blocks. Microphase separation of FIF triblock copolymers was observed by small-angle X-ray scattering, even though long-range order was not achieved under the annealing conditions employed. Additionally, the microphase separation of the resulting triblock copolymers was examined by atomic force microscopy.« less

High temperature thermoplastic elastomers synthesized by living anionic polymerization in hydrocarbon solvent at room temperature

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

Schlegel, Ralf; Williams, Katherine; Voyloy, Dimitry

We present the synthesis and characterization of a new class of high temperature thermoplastic elastomers composed of polybenzofulvene–polyisoprene–polybenzofulvene (FIF) triblock copolymers. All copolymers were prepared by living anionic polymerization in benzene at room temperature. Homopolymerization and effects of additives on the glass transition temperature (T g) of polybenzofulvene (PBF) were also investigated. Among all triblock copolymers studied, FIF with 14 vol % of PBF exhibited a maximum stress of 14.3 ± 1.3 MPa and strain at break of 1390 ± 66% from tensile tests. The stress–strain curves of FIF-10 and 14 were analyzed by a statistical molecular approach using amore » nonaffine tube model to estimate the thermoplastic elastomer behavior. Dynamic mechanical analysis showed that the softening temperature of PBF in FIF was 145 °C, much higher than that of thermoplastic elastomers with polystyrene hard blocks. Microphase separation of FIF triblock copolymers was observed by small-angle X-ray scattering, even though long-range order was not achieved under the annealing conditions employed. Additionally, the microphase separation of the resulting triblock copolymers was examined by atomic force microscopy.« less

Tetrahedral bonding in amorphous carbon

NASA Astrophysics Data System (ADS)

McKenzie, D. R.

1996-12-01

Electron configurations close to the tetrahedral 0034-4885/59/12/002/img1 hybridization are found in pure amorphous carbon at a concentration which depends on preparation conditions. Tetrahedral bonding at levels of approximately 80% is found in amorphous carbons formed from beams of carbon ions with energies in a `window' between 20 eV and approximately 500 eV. Suitable techniques for its formation include cathodic arc deposition, ion beam deposition and laser ablation. Similar material appears to be formed by pressure treatment of fullerene precursors and by displacement damage in diamond. Highly tetrahedral forms of amorphous carbon (ta-C) show electronic, optical and mechanical properties which approach those of diamond and are quite different from amorphous carbons with low 0034-4885/59/12/002/img1 content. Useful techniques for determining the 0034-4885/59/12/002/img1 content include electron energy loss spectroscopy, electron and neutron diffraction and Raman spectroscopy. Considerable progress has been made in the understanding of this material by simulating its structure in the computer with a range of techniques from empirical potentials to ab initio quantum mechanics. The structure shows departures from an idealized glassy state of diamond which would have a random tetrahedral network structure as used to describe amorphous silicon and germanium. A surprising feature of the structure simulated using ab initio methods is the presence of small rings containing three or four 0034-4885/59/12/002/img1 carbon atoms. The electronic and optical properties are strongly influenced by the residual of 0034-4885/59/12/002/img5 carbon. Applications to electronic devices are at an early stage with the demonstration of photoconductivity and some simple junction devices. Applications as a wear resistant coating are promising, since the theoretically predicted high values of elastic constants, comparable to but less than those of diamond, are achieved experimentally

Polymerization initated at sidewalls of carbon nanotubes

NASA Technical Reports Server (NTRS)

Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

2011-01-01

The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

An 8-node tetrahedral finite element suitable for explicit transient dynamic simulations

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

Key, S.W.; Heinstein, M.W.; Stone, C.M.

1997-12-31

Considerable effort has been expended in perfecting the algorithmic properties of 8-node hexahedral finite elements. Today the element is well understood and performs exceptionally well when used in modeling three-dimensional explicit transient dynamic events. However, the automatic generation of all-hexahedral meshes remains an elusive achievement. The alternative of automatic generation for all-tetrahedral finite element is a notoriously poor performer, and the 10-node quadratic tetrahedral finite element while a better performer numerically is computationally expensive. To use the all-tetrahedral mesh generation extant today, the authors have explored the creation of a quality 8-node tetrahedral finite element (a four-node tetrahedral finite elementmore » enriched with four midface nodal points). The derivation of the element`s gradient operator, studies in obtaining a suitable mass lumping and the element`s performance in applications are presented. In particular, they examine the 80node tetrahedral finite element`s behavior in longitudinal plane wave propagation, in transverse cylindrical wave propagation, and in simulating Taylor bar impacts. The element only samples constant strain states and, therefore, has 12 hourglass modes. In this regard, it bears similarities to the 8-node, mean-quadrature hexahedral finite element. Given automatic all-tetrahedral meshing, the 8-node, constant-strain tetrahedral finite element is a suitable replacement for the 8-node hexahedral finite element and handbuilt meshes.« less

Screening of anionic-modified polymers in terms of stability, disintegration, and swelling behavior.

PubMed

Laffleur, Flavia; Ijaz, Muhammad; Menzel, Claudia

2017-11-01

This study aimed to screen the stability, disintegration, and swelling behavior of chemically modified anionic polymers. Investigated polymers were well-known and widely used staples of the pharmaceutical and medical field, namely, alginate (AL), carboxymethyl cellulose (CMC), polycarbophil (PC), and hyaluronic acid (HA). On the basis of amide bond formation between the carboxylic acid moieties of anionic polymers and the primary amino group of the modification ligand cysteine (CYS), the modified polymers were obtained. Unmodified polymers served as controls throughout all studies. With the Ellman's assay, modification degrees were determined of synthesized polymeric excipients. Stability assay in terms of erosion study at physiological conditions were performed. Moreover, water uptake of compressed polymeric discs were evaluated and further disintegration studies according to the USP were carried out to define the potential ranking. Results ranking figured out PCCYS > CMCCYS > HACYS > ALCYS in terms of water uptake capacity compared to respective controls. Cell viability assays on Caco-2 cell line as well as on RPMI 2650 (ATTC CCL30) proved modification not being harmful to those. Due to the results of this study, an intense screening of prominent anionic polymer derivate was performed in order to help the pharmaceutical research for the best choice of polymeric excipients for developments of controlled drug release systems.

Polymerized Paired Ions as Polymeric Ionic Liquid-Proton Conductivity.

PubMed

Gu, Hong; Yan, Feng; Texter, John

2016-07-01

A new polymerized ionic liquid has been derived by photopolymerization of a stimuli-responsive ionic liquid surfactant, ILAMPS, which is composed of polymerizable, paired ions. The cation is 1-methyl-3-[11-(acryloyloxy)undecyl] imidazolium (IL), and the anion is 2-acrylamido-2-methyl-1-propanesulfonate (AMPS). This ion combination is a new ionic liquid. The resulting hygroscopic resins are highly polarizable, suitable for sensor design and for ultracapacitor fabrication and proton conducting. Interactions of imidazolium with anions provide basis for stimuli-responsiveness, and are used to promote proton transport. Doping with one equivalent of HPF6 at 0% relative humidity produces a 100-fold increase in proton conductivity at 100-125 °C and activation energies for proton transport lower than those of Nafion at water loadings less than 5 per sulfonate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Anion permselective membrane

NASA Technical Reports Server (NTRS)

Hodgdon, R. B.; Waite, W. A.

1982-01-01

The synthesis and fabrication of polymeric anion permselective membranes for redox systems are discussed. Variations of the prime candidate anion membrane formulation to achieve better resistance and/or lower permeability were explored. Processing parameters were evaluated to lower cost and fabricate larger sizes. The processing techniques to produce more membranes per batch were successfully integrated with the fabrication of larger membranes. Membranes of about 107 cm x 51 cm were made in excellent yield. Several measurements were made on the larger sample membranes. Among the data developed were water transport and transference numbers for these prime candidate membranes at 20 C. Other work done on this system included characterization of a number of specimens of candidate membranes which had been returned after service lives of up to sixteen months. Work with new polymer constituents, with new N.P.'s, catalysts and backing fabrics is discussed. Some work was also done to evaluate other proportions of the ingredients of the prime candidate system. The adoption of a flow selectivity test at elevated temperature was explored.

Binding of anions in triply interlocked coordination catenanes and dynamic allostery for dehalogenation reactions.

PubMed

Yang, Linlin; Jing, Xu; An, Bowen; He, Cheng; Yang, Yang; Duan, Chunying

2018-01-28

By synergistic combination of multicomponent self-assembly and template-directed approaches, triply interlocked metal organic catenanes that consist of two isolated chirally identical tetrahedrons were constructed and stabilized as thermodynamic minima. In the presence of suitable template anions, the structural conversion from the isolated tetrahedral conformers into locked catenanes occurred via the cleavage of an intrinsically reversible coordination bond in each of the tetrahedrons, followed by the reengineering and interlocking of two fragments with the regeneration of the broken coordination bonds. The presence of several kinds of individual pocket that were attributed to the triply interlocked patterns enabled the possibility of encapsulating different anions, allowing the dynamic allostery between the unlocked/locked conformers to promote the dehalogenation reaction of 3-bromo-cyclohexene efficiently, as with the use of dehalogenase enzymes. The interlocked structures could be unlocked into two individual tetrahedrons through removal of the well-matched anion templates. The stability and reversibility of the locked/unlocked structures were further confirmed by the catching/releasing process that accompanied emission switching, providing opportunities for the system to be a dynamic molecular logic system.

Bidentate urea derivatives of p-tert-butyldihomooxacalix[4]arene: neutral receptors for anion complexation.

PubMed

Marcos, Paula M; Teixeira, Filipa A; Segurado, Manuel A P; Ascenso, José R; Bernardino, Raul J; Michel, Sylvia; Hubscher-Bruder, Véronique

2014-01-17

Three new bidentate ureidodihomooxacalix[4]arene derivatives (phenyl 5a, n-propyl 5b, and tert-butyl 5c) were synthesized in four steps from the parent compound p-tert-butyldihomooxacalix[4]arene and obtained in the cone conformation, as shown by NMR studies. The binding ability of these neutral receptors toward spherical, linear, trigonal planar, and tetrahedrical anions was assessed by (1)H NMR and UV-vis titrations. The structures and complexation energies of some complexes were also studied by DFT methods. The data showed that the association constants are strongly dependent on the nature of the substituent (aryl/alkyl) at the urea moiety. In general, for all the receptors, the association constants decrease with decrease of anion basicity. Ph-urea 5a is the best anion receptor, showing the strongest complexation for F(-) (log K(assoc) = 3.10 in CDCl3) and also high binding affinity for the carboxylates AcO(-) and BzO(-). Similar results were obtained by UV-vis studies and were also corroborated by DFT calculations.

Bimetallic complexes and polymerization catalysts therefrom

DOEpatents

Patton, Jasson T.; Marks, Tobin J.; Li, Liting

2000-11-28

Group 3-6 or Lanthanide metal complexes possessing two metal centers, catalysts derived therefrom by combining the same with strong Lewis acids, Bronsted acid salts, salts containing a cationic oxidizing agent or subjected to bulk electrolysis in the presence of compatible, inert non-coordinating anions and the use of such catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers are disclosed.

Tetrahedrality and structural order for hydrophobic interactions in a coarse-grained water model

NASA Astrophysics Data System (ADS)

Chaimovich, Aviel; Shell, M. Scott

2014-02-01

The hydrophobic interaction manifests two separate regimes in terms of size: Small nonpolar bodies exhibit a weak oscillatory force (versus distance) while large nonpolar surfaces exhibit a strong monotonic one. This crossover in hydrophobic behavior is typically explained in terms of water's tetrahedral structure: Its tetrahedrality is enhanced near small solutes and diminished near large planar ones. Here, we demonstrate that water's tetrahedral correlations signal this switch even in a highly simplified, isotropic, "core-softened" water model. For this task, we introduce measures of tetrahedrality based on the angular distribution of water's nearest neighbors. On a quantitative basis, the coarse-grained model of course is only approximate: (1) While greater than simple Lennard-Jones liquids, its bulk tetrahedrality remains lower than that of fully atomic models; and (2) the decay length of the large-scale hydrophobic interaction is less than has been found in experiments. Even so, the qualitative behavior of the model is surprisingly rich and exhibits numerous waterlike hydrophobic behaviors, despite its simplicity. We offer several arguments for the manner in which it should be able to (at least partially) reproduce tetrahedral correlations underlying these effects.

Tetrahedrality and structural order for hydrophobic interactions in a coarse-grained water model.

PubMed

Chaimovich, Aviel; Shell, M Scott

2014-02-01

The hydrophobic interaction manifests two separate regimes in terms of size: Small nonpolar bodies exhibit a weak oscillatory force (versus distance) while large nonpolar surfaces exhibit a strong monotonic one. This crossover in hydrophobic behavior is typically explained in terms of water's tetrahedral structure: Its tetrahedrality is enhanced near small solutes and diminished near large planar ones. Here, we demonstrate that water's tetrahedral correlations signal this switch even in a highly simplified, isotropic, "core-softened" water model. For this task, we introduce measures of tetrahedrality based on the angular distribution of water's nearest neighbors. On a quantitative basis, the coarse-grained model of course is only approximate: (1) While greater than simple Lennard-Jones liquids, its bulk tetrahedrality remains lower than that of fully atomic models; and (2) the decay length of the large-scale hydrophobic interaction is less than has been found in experiments. Even so, the qualitative behavior of the model is surprisingly rich and exhibits numerous waterlike hydrophobic behaviors, despite its simplicity. We offer several arguments for the manner in which it should be able to (at least partially) reproduce tetrahedral correlations underlying these effects.

Modulation of chondrocyte motility by tetrahedral DNA nanostructures.

PubMed

Shi, Sirong; Lin, Shiyu; Shao, Xiaoru; Li, Qianshun; Tao, Zhang; Lin, Yunfeng

2017-10-01

Contemporarily, a highly increasing attention was paid to nanoconstructs, particularly DNA nanostructures possessing precise organization, functional manipulation, biocompatibility and biodegradability. Amongst these DNA nanomaterials, tetrahedral DNA nanostructures (TDNs) are a significantly ideal bionanomaterials with focusing on the property that can be internalized into cytoplasm in the absence of transfection. Therefore, the focus of this study was on investigating the influence of TDNs on the chondrocytes locomotion. Tetrahedral DNA nanostructures was confirmed by 6% polyacrylamide gel electrophoresis (PAGE) and dynamic light scattering (DLS). Subsequently, the effect of TDNs on chondrocyte locomotion was investigated by real-time cell analysis (RTCA) and wound healing assay. The variation of relevant genes and proteins was detected by quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence respectively. We demonstrated that tetrahedral DNA nanostructures have positive influence on chondrocytes locomotion and promoted the expression of RhoA, ROCK2 and vinculin. Additionally, upon exposure to TDNs with the concentration of 250 nmol L -1 , the chondrocytes were showed the highest motility via both RTCA and wound healing assay. Meanwhile, the mRNA and protein expression of RhoA, ROCK2 and vinculin were also significantly enhanced with the same concentration. It can be concluded that the TDNs with the optimal concentration of 250 nmol L -1 could extremely promoted the chondrocytes locomotion through facilitating the expression of RhoA, ROCK2 and vinculin. These results seemed to reveal that this special three-dimensional DNA tetrahedral nanostructures may be applied to cartilage repair and treatment in the future. © 2017 John Wiley & Sons Ltd.

H-Bonding Assisted Self-Assembly of Anionic and Neutral Ligand on Metal: A Comprehensive Strategy To Mimic Ditopic Ligands in Olefin Polymerization.

PubMed

Mote, Nilesh R; Patel, Ketan; Shinde, Dinesh R; Gaikwad, Shahaji R; Koshti, Vijay S; Gonnade, Rajesh G; Chikkali, Samir H

2017-10-16

Self-assembly of two neutral ligands on a metal to mimic bidentate ligand coordination has been frequently encountered in the recent past, but self-assembly of an anionic ligand on a metal template alongside a neutral ligand remains an elusive target. Such a self-assembly is hampered by additional complexity, wherein a highly negatively charged anion can form intermolecular hydrogen bonding with the supramolecular motif, leaving no scope for self-assembly with neutral ligand. Presented here is the self-association of anionic ligand 3-ureidobenzoic acid (2a) and neutral ligand 1-(3-(diphenylphosphanyl)phenyl)urea (1a) on a metal template to yield metal complex [{COOC 6 H 4 NH(CO)NH 2 }{Ph 2 PC 6 H 4 NH(CO)NH 2 }PdMeDMSO] (4a). The identity of 4a was established by NMR and mass spectroscopy. Along the same lines, 3-(3-phenylureido)benzoic acid (2b) and 1-(3-(diphenylphosphanyl)phenyl)-3-phenylurea (1b) self-assemble on a metal template to produce palladium complex [{COOC 6 H 4 NH(CO)NHPh}{Ph 2 PC 6 H 4 NH(CO)NHPh}PdMePy] (5c). The existence of 5c was confirmed by Job plot, 1-2D NMR spectroscopy, deuterium labeling, IR spectroscopy, UV-vis spectroscopy, model complex synthesis, and DFT calculations. These solution and gas phase investigations authenticated the presence of intramolecular hydrogen bonding between hydrogen's of 1b and carbonyl oxygen of 2b. The generality of the supramolecular approach has been validated by preparing six complexes from four monodentate ligands, and their synthetic utility was demonstrated in ethylene polymerization. Complex 4a was found to be the most active, leading to the production of highly branched polyethylene with a molecular weight of 55700 g/mol and melting temperature of 112 °C.

The effects of non-ionic polymeric surfactants on the cleaning of biofouled hydrogel materials.

PubMed

Guan, Allan; Li, Zhenyu; Phillips, K Scott

2015-01-01

Block co-polymer surfactants have been used for cleaning hydrogel medical devices that contact the body (e.g., contact lenses) because of their biocompatibility. This work examined the relationship between concentration and detergency of two non-ionic polymeric surfactants (Pluronic F127 and Triton X-100) for cleaning protein soil, with anionic surfactants (sodium dodecyl sulfate and sodium laureth sulfate) as positive controls. Surface plasmon resonance was used to quantify removal of simulated tear soil from self-assembled monolayer surfaces, and a microplate format was used to study the removal of fluorescently labeled soil proteins from contact lenses. While detergency increased as a function of concentration for anionic surfactants, it decreased with concentration for the two polymeric surfactants. The fact that the protein detergency of some non-ionic polymeric surfactants did not increase with concentration above the critical micelle concentration could have implications for optimizing the tradeoff between detergency and biocompatibility.

Nucleophilically assisted and cationic ring-opening polymerization of tin-bridged [1]ferrocenophanes.

PubMed

Baumgartner, Thomas; Jäkle, Frieder; Rulkens, Ron; Zech, Gernot; Lough, Alan J; Manners, Ian

2002-08-28

To obtain mechanistic insight, detailed studies of the intriguing "spontaneous" ambient temperature ring-opening polymerization (ROP) of tin-bridged [1]ferrocenophanes Fe(eta-C(5)H(4))(2)SnR(2) 3a (R = t-Bu) and 3b (R = Mes) in solution have been performed. The investigations explored the influence of non-nucleophilic additives such as radicals and radical traps, neutral and anionic nucleophiles, Lewis acids, protic species, and other cationic electrophiles. Significantly, two novel methodologies and mechanisms for the ROP of strained [1]ferrocenophanes are proposed based on this study. First, as the addition of amine nucleophiles such as pyridine was found to strongly accelerate the polymerization rate in solution, a new nucleophilicallyassisted ROP methodology was proposed. This operates at ambient temperature in solution even in the presence of chlorosilanes but, unlike the anionic polymerization of ferrocenophanes, does not involve cyclopentadienyl anions. Second, the addition of small quantities of the electrophilic species H(+) and Bu(3)Sn(+) was found to lead to a cationic ROP process. These studies suggest that the "spontaneous" ROP of tin-bridged [1]ferrocenophanes may be a consequence of the presence of spurious, trace quantities of Lewis basic or acidic impurities. The new ROP mechanisms reported are likely to be of general significance for the ROP of other metallocenophanes (e.g., for thermal ROP in the melt) and for other metallacycles containing group 14 elements.

Lipase-catalyzed ring-opening polymerization of lactones to polyesters and its mechanistic aspects.

PubMed

Namekawa, S; Suda, S; Uyama, H; Kobayashi, S

1999-01-01

Lipase catalysis induced a ring-opening polymerization of lactones with different ring-sizes. Small-size (four-membered) and medium-size lactones (six- and seven-membered) as well as macrolides (12-, 13-, 16-, and 17-membered) were subjected to lipase-catalyzed polymerization. The polymerization behaviors depended primarily on the lipase origin and the monomer structure. The macrolides showing much lower anionic polymerizability were enzymatically polymerized faster than epsilon-caprolactone. The granular immobilized lipase derived from Candida antartica showed extremely efficient catalysis in the polymerization of epsilon-caprolactone. Single-step terminal functionalization of the polyester was achieved by initiator and terminator methods. The enzymatic polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics.

Implementation of tetrahedral-mesh geometry in Monte Carlo radiation transport code PHITS

NASA Astrophysics Data System (ADS)

Furuta, Takuya; Sato, Tatsuhiko; Han, Min Cheol; Yeom, Yeon Soo; Kim, Chan Hyeong; Brown, Justin L.; Bolch, Wesley E.

2017-06-01

A new function to treat tetrahedral-mesh geometry was implemented in the particle and heavy ion transport code systems. To accelerate the computational speed in the transport process, an original algorithm was introduced to initially prepare decomposition maps for the container box of the tetrahedral-mesh geometry. The computational performance was tested by conducting radiation transport simulations of 100 MeV protons and 1 MeV photons in a water phantom represented by tetrahedral mesh. The simulation was repeated with varying number of meshes and the required computational times were then compared with those of the conventional voxel representation. Our results show that the computational costs for each boundary crossing of the region mesh are essentially equivalent for both representations. This study suggests that the tetrahedral-mesh representation offers not only a flexible description of the transport geometry but also improvement of computational efficiency for the radiation transport. Due to the adaptability of tetrahedrons in both size and shape, dosimetrically equivalent objects can be represented by tetrahedrons with a much fewer number of meshes as compared its voxelized representation. Our study additionally included dosimetric calculations using a computational human phantom. A significant acceleration of the computational speed, about 4 times, was confirmed by the adoption of a tetrahedral mesh over the traditional voxel mesh geometry.

Implementation of tetrahedral-mesh geometry in Monte Carlo radiation transport code PHITS.

PubMed

Furuta, Takuya; Sato, Tatsuhiko; Han, Min Cheol; Yeom, Yeon Soo; Kim, Chan Hyeong; Brown, Justin L; Bolch, Wesley E

2017-06-21

A new function to treat tetrahedral-mesh geometry was implemented in the particle and heavy ion transport code systems. To accelerate the computational speed in the transport process, an original algorithm was introduced to initially prepare decomposition maps for the container box of the tetrahedral-mesh geometry. The computational performance was tested by conducting radiation transport simulations of 100 MeV protons and 1 MeV photons in a water phantom represented by tetrahedral mesh. The simulation was repeated with varying number of meshes and the required computational times were then compared with those of the conventional voxel representation. Our results show that the computational costs for each boundary crossing of the region mesh are essentially equivalent for both representations. This study suggests that the tetrahedral-mesh representation offers not only a flexible description of the transport geometry but also improvement of computational efficiency for the radiation transport. Due to the adaptability of tetrahedrons in both size and shape, dosimetrically equivalent objects can be represented by tetrahedrons with a much fewer number of meshes as compared its voxelized representation. Our study additionally included dosimetric calculations using a computational human phantom. A significant acceleration of the computational speed, about 4 times, was confirmed by the adoption of a tetrahedral mesh over the traditional voxel mesh geometry.

Untemplated nonenzymatic polymerization of 3',5'cGMP: a plausible route to 3',5'-linked oligonucleotides in primordia.

PubMed

Šponer, Judit E; Šponer, Jiří; Giorgi, Alessandra; Di Mauro, Ernesto; Pino, Samanta; Costanzo, Giovanna

2015-02-19

The high-energy 3',5' phosphodiester linkages conserved in 3',5' cyclic GMPs offer a genuine solution for monomer activation required by the transphosphorylation reactions that could lead to the emergence of the first simple oligonucleotide sequences on the early Earth. In this work we provide an in-depth characterization of the effect of the reaction conditions on the yield of the polymerization reaction of 3',5' cyclic GMPs both in aqueous environment as well as under dehydrating conditions. We show that the threshold temperature of the polymerization is about 30 °C lower under dehydrating conditions than in solution. In addition, we present a plausible exergonic reaction pathway for the polymerization reaction, which involves transient formation of anionic centers at the O3' positions of the participating riboses. We suggest that excess Na(+) cations inhibit the polymerization reaction because they block the anionic mechanism via neutralizing the negatively charged O3'. Our experimental findings are compatible with a prebiotic scenario, where gradual desiccation of the environment could induce polymerization of 3',5' cyclic GMPs synthesized in liquid.

Preparation of a surface-grafted imprinted ceramic membrane for selective separation of molybdate anion from water solutions.

PubMed

Zeng, Jianxian; Dong, Zhihui; Zhang, Zhe; Liu, Yuan

2017-07-05

A surface-grafted imprinted ceramic membrane (IIP-PVI/CM) for recognizing molybdate (Mo(VI)) anion was prepared by surface-initiated graft-polymerization. Firstly, raw alumina ceramic membrane (CM) was deposited with SiO 2 active layer by situ hydrolysis deposition method. Subsequently, γ-methacryloxy propyl trimethoxyl silane (MPS) was used as a coupling agent to introduce double bonds onto the SiO 2 layer (MPS-CM). Then, 1-vinylimidazole (VI) was employed as a functional monomer to graft-polymerization onto the MPS-CM (PVI-CM). During the graft-polymerization, the influence factors of grafting degree of PVI were investigated in detail. Under optimum conditions (monomer concentration 20wt%, temperature 70°C, initiator amount 1.1wt% and reaction time 8h), the grafting degree of 20.39g/100g was obtained. Further, Mo(VI) anion was used as a template to imprint in the PVI-CM by employing 1,6-dibromohexane as a cross-linking agent, and then Mo(VI) was removed, obtaining the IIP-PVI/CM with many imprinted cavities for Mo(VI). Thereafter, static adsorption and dynamic separation properties of IIP-PVI/CM for Mo(VI) were studied. Results indicate that IIP-PVI/CM shows a specific selectivity for Mo(VI) with the adsorption capacity of 0.69mmol/100g, and the selectivity coefficient of IIP-PVI/CM is 7.48 for molybdate to tungstate anions. During the dynamic separation, IIP-PVI/CM has also good selectivity for separation of Mo(VI) and W(VI) anions. Copyright © 2017 Elsevier B.V. All rights reserved.

Covalent bonding of polycations to small polymeric particles

NASA Technical Reports Server (NTRS)

Rembaum, A.

1975-01-01

Process produces small spherical polymeric particles which have polycations bound to them. In emulsion form, particles present large positively charged surface which is available to absorb polyanions. This properly can be used in removing heparin from blood or bile acids from the digestive tract. Other anions, such as DNA and RNA, can also be removed from aqueous solutions.

Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl: Interesting size effects originated from the tetrahedral anions

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

Pan, Ming-Yan; Xia, Sheng-Qing, E-mail: shqxia@sdu.edu.cn; Liu, Xiao-Cun

2014-11-15

Two new barium chalcogenides, Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl, were synthesized by using high temperature solid-state reactions and their structures were determined by single-crystal X-ray diffraction technique. Despite the similar chemical formula, the structures of Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl are subtly different due to the size effects originated from the tetrahedral anions. Ba{sub 3}GeS{sub 5} crystallizes in the orthorhombic space group Pnma (no. 62) with cell parameters of a=12.0528(9) Å, b=9.5497(7) Å and c=8.5979(6) Å, while Ba{sub 3}InS{sub 4}Cl adopts a different tetragonal system (space group: I4/mcm, no. 140, a=b=8.3613(6) Å, c=14.3806(18) Å). The measuredmore » optical band gap of Ba{sub 3}GeS{sub 5} is 3.0 eV, a little smaller than the value of 3.42 eV in Ba{sub 3}InS{sub 4}Cl. Theoretical calculations by Wien2k are provided as well in order to better understand these results. - Graphical abstract: The polyhedral structure view for Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl in which Ba, S and Cl atoms are plotted in purple, red and green spheres. - Highlights: • Two new barium chalcogenides, Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl, were synthesized from the BaCl{sub 2}-flux reactions. • Their crystal structures feature discrete [MS{sub 4}] tetrahedra which embody interesting size effects. • Both compounds exhibit a band gap around 3.0 eV. • They are thermally stable up to 1073 K.« less

Thin Robust Anion Exchange Membranes for Fuel Cell Applications

DTIC Science & Technology

2014-01-01

water diffsuion. Here we use a Polyphenylene Oxide dibock polymer co-polymerized with polyvinyl benzyl trimethyl ammonium blocks ( PPO -b-PVBTMA[F...in PPO -b-PVBTMA[F-] AEM under saturated humidity environment ECS Transactions, 64 (3) 1185-1194 (2014) 1191 Conductivity of this membrane was...makes it a promising material for applications in anion exchange membrane fuel cells. Figure 5: Conductivity of PPO -b-PVBTMA[F-] under 95% Relative

Lattice Cleaving: A Multimaterial Tetrahedral Meshing Algorithm with Guarantees

PubMed Central

Bronson, Jonathan; Levine, Joshua A.; Whitaker, Ross

2014-01-01

We introduce a new algorithm for generating tetrahedral meshes that conform to physical boundaries in volumetric domains consisting of multiple materials. The proposed method allows for an arbitrary number of materials, produces high-quality tetrahedral meshes with upper and lower bounds on dihedral angles, and guarantees geometric fidelity. Moreover, the method is combinatoric so its implementation enables rapid mesh construction. These meshes are structured in a way that also allows grading, to reduce element counts in regions of homogeneity. Additionally, we provide proofs showing that both element quality and geometric fidelity are bounded using this approach. PMID:24356365

A review of defects and disorder in multinary tetrahedrally bonded semiconductors [Defects and disorder in multinary tetrahedrally bonded semiconductors studied by experiment and theory

DOE PAGES

Baranowski, Lauryn L.; Zawadzki, Pawel; Lany, Stephan; ...

2016-11-10

Defects are critical to understanding the electronic properties of semiconducting compounds, for applications such as light-emitting diodes, transistors, photovoltaics, and thermoelectrics. In this review, we describe our work investigating defects in tetrahedrally bonded, multinary semiconductors, and discuss the place of our research within the context of publications by other groups. We applied experimental and theory techniques to understand point defects, structural disorder, and extended antisite defects in one semiconductor of interest for photovoltaic applications, Cu 2SnS 3. We contrast our findings on Cu 2SnS 3 with other chemically related Cu-Sn-S compounds, as well as structurally related compounds such as Cumore » 2ZnSnS 4 and Cu(In,Ga)Se 2. We find that evaluation of point defects alone is not sufficient to understand defect behavior in multinary tetrahedrally bonded semiconductors. In the case of Cu 2SnS 3 and Cu 2ZnSnS 4, structural disorder and entropy-driven cation clustering can result in nanoscale compositional inhomogeneities which detrimentally impact the electronic transport. Therefore, it is not sufficient to assess only the point defect behavior of new multinary tetrahedrally bonded compounds; effects such as structural disorder and extended antisite defects must also be considered. Altogether, this review provides a framework for evaluating tetrahedrally bonded semiconducting compounds with respect to their defect behavior for photovoltaic and other applications, and suggests new materials that may not be as prone to such imperfections.« less

A review of defects and disorder in multinary tetrahedrally bonded semiconductors [Defects and disorder in multinary tetrahedrally bonded semiconductors studied by experiment and theory

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

Baranowski, Lauryn L.; Zawadzki, Pawel; Lany, Stephan

Defects are critical to understanding the electronic properties of semiconducting compounds, for applications such as light-emitting diodes, transistors, photovoltaics, and thermoelectrics. In this review, we describe our work investigating defects in tetrahedrally bonded, multinary semiconductors, and discuss the place of our research within the context of publications by other groups. We applied experimental and theory techniques to understand point defects, structural disorder, and extended antisite defects in one semiconductor of interest for photovoltaic applications, Cu 2SnS 3. We contrast our findings on Cu 2SnS 3 with other chemically related Cu-Sn-S compounds, as well as structurally related compounds such as Cumore » 2ZnSnS 4 and Cu(In,Ga)Se 2. We find that evaluation of point defects alone is not sufficient to understand defect behavior in multinary tetrahedrally bonded semiconductors. In the case of Cu 2SnS 3 and Cu 2ZnSnS 4, structural disorder and entropy-driven cation clustering can result in nanoscale compositional inhomogeneities which detrimentally impact the electronic transport. Therefore, it is not sufficient to assess only the point defect behavior of new multinary tetrahedrally bonded compounds; effects such as structural disorder and extended antisite defects must also be considered. Altogether, this review provides a framework for evaluating tetrahedrally bonded semiconducting compounds with respect to their defect behavior for photovoltaic and other applications, and suggests new materials that may not be as prone to such imperfections.« less

Finite Element Simulation of Articular Contact Mechanics with Quadratic Tetrahedral Elements

PubMed Central

Maas, Steve A.; Ellis, Benjamin J.; Rawlins, David S.; Weiss, Jeffrey A.

2016-01-01

Although it is easier to generate finite element discretizations with tetrahedral elements, trilinear hexahedral (HEX8) elements are more often used in simulations of articular contact mechanics. This is due to numerical shortcomings of linear tetrahedral (TET4) elements, limited availability of quadratic tetrahedron elements in combination with effective contact algorithms, and the perceived increased computational expense of quadratic finite elements. In this study we implemented both ten-node (TET10) and fifteen-node (TET15) quadratic tetrahedral elements in FEBio (www.febio.org) and compared their accuracy, robustness in terms of convergence behavior and computational cost for simulations relevant to articular contact mechanics. Suitable volume integration and surface integration rules were determined by comparing the results of several benchmark contact problems. The results demonstrated that the surface integration rule used to evaluate the contact integrals for quadratic elements affected both convergence behavior and accuracy of predicted stresses. The computational expense and robustness of both quadratic tetrahedral formulations compared favorably to the HEX8 models. Of note, the TET15 element demonstrated superior convergence behavior and lower computational cost than both the TET10 and HEX8 elements for meshes with similar numbers of degrees of freedom in the contact problems that we examined. Finally, the excellent accuracy and relative efficiency of these quadratic tetrahedral elements was illustrated by comparing their predictions with those for a HEX8 mesh for simulation of articular contact in a fully validated model of the hip. These results demonstrate that TET10 and TET15 elements provide viable alternatives to HEX8 elements for simulation of articular contact mechanics. PMID:26900037

Finite element simulation of articular contact mechanics with quadratic tetrahedral elements.

PubMed

Maas, Steve A; Ellis, Benjamin J; Rawlins, David S; Weiss, Jeffrey A

2016-03-21

Although it is easier to generate finite element discretizations with tetrahedral elements, trilinear hexahedral (HEX8) elements are more often used in simulations of articular contact mechanics. This is due to numerical shortcomings of linear tetrahedral (TET4) elements, limited availability of quadratic tetrahedron elements in combination with effective contact algorithms, and the perceived increased computational expense of quadratic finite elements. In this study we implemented both ten-node (TET10) and fifteen-node (TET15) quadratic tetrahedral elements in FEBio (www.febio.org) and compared their accuracy, robustness in terms of convergence behavior and computational cost for simulations relevant to articular contact mechanics. Suitable volume integration and surface integration rules were determined by comparing the results of several benchmark contact problems. The results demonstrated that the surface integration rule used to evaluate the contact integrals for quadratic elements affected both convergence behavior and accuracy of predicted stresses. The computational expense and robustness of both quadratic tetrahedral formulations compared favorably to the HEX8 models. Of note, the TET15 element demonstrated superior convergence behavior and lower computational cost than both the TET10 and HEX8 elements for meshes with similar numbers of degrees of freedom in the contact problems that we examined. Finally, the excellent accuracy and relative efficiency of these quadratic tetrahedral elements was illustrated by comparing their predictions with those for a HEX8 mesh for simulation of articular contact in a fully validated model of the hip. These results demonstrate that TET10 and TET15 elements provide viable alternatives to HEX8 elements for simulation of articular contact mechanics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tetrahedral 4 α and 12C+α cluster structures in 16O

NASA Astrophysics Data System (ADS)

Kanada-En'yo, Yoshiko

2017-09-01

I have investigated structures of the ground and excited states of 16O with the method of variation after spin-parity projection in the antisymmetrized molecular dynamics model combined with the generator coordinate method of 12C+α cluster. The calculation reasonably reproduces the experimental energy spectra; E 2 , E 3 , E 4 , and I S 1 transitions; and α -decay properties. The formation of 4 α clusters has been confirmed from nucleon degrees of freedom in the AMD model without assuming the existence of any clusters. They form "tetrahedral" 4 α - and 12C+α cluster structures. The 12C+α structure constructs the Kπ=0+ band consisting of the 02+, 21+, and 41+ states and the Kπ=0- band of the 12-, 32-, and 51- states. The 01+, 31-, and 42+ states are assigned to the ground band constructed from the tetrahedral 4 α structure. The 01+ and 31- are approximately interpreted as Td band members with the ideal tetrahedral configuration. The ground-state 4 α correlation plays an important role in the enhancement of the E 3 transition strength to the 31-. The 42+ state is not the ideal Td member but constructed from a distorted tetrahedral 4 α structure. Moreover, significant state mixing of the tetrahedral 4 α and 12C+α cluster structures occurs between 41+ and 42+ states, indicating that the Td configuration of 4 α is rather fragile at Jπ=4+ .

Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Komuro, Yoshitaka; Yamamoto, Hiroki; Kobayashi, Kazuo; Ohomori, Katsumi; Kozawa, Takahiro

2015-03-01

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub 10nm. An anion-bound polymer(ABP), in which at the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using γ and EUV radiolysis. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The protons of acids are considered to be mainly generated through the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through the hole transfer to the decomposition products of onium salts.

Effects of Hofmeister salt series on gluten network formation: Part II. Anion series.

PubMed

Tuhumury, H C D; Small, D M; Day, L

2016-12-01

Different anion salts from the Hofmeister series were used to investigate their effects on gluten network formation. The effects of these anion salts on the mixing properties of the dough and the rheological and chemical properties of gluten samples extracted from the dough with these respective salts were compared. The aim of this work was to determine how different anion salts influence the formation of the gluten structure during dough mixing. It was found that the Hofmeister anion salts affected the gluten network formation by interacting directly with specific amino acid residues that resulted in changes in gluten protein composition, specifically the percentage of the unextractable polymeric protein fractions (%UPP). These changes consequently led to remarkable differences in the mixing profiles and microstructural features of the dough, small deformation rheological properties of the gluten and a strain hardening behaviour of both dough and gluten samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Electronic structures of filled tetrahedral semiconductors LiMgN and LiZnN: conduction band distortion

NASA Astrophysics Data System (ADS)

Yu, L. H.; Yao, K. L.; Liu, Z. L.

2004-12-01

The band structures of the filled tetrahedral semiconductors LiMgN and LiZnN, viewed as the zinc-blende (MgN) - and (ZnN) - lattices partially filled with He-like Li + ion interstitials, were studied using the full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory. The conduction band distortions of LiMgN and LiZnN, compared to their “parent” zinc-blende analog AlN and GaN, are discussed. It was found that the insertion of Li + ions at the interstitial sites near the cation or anion pushes the conduction band minimum of the X point in the Brillouin zone upward, relative to that of the Γ point, for both (MgN) - and (ZnN) - lattices (the valence band maximum is at Γ for AlN, GaN, LiMgN, and LiZnN), which provides a method to convert a zinc-blende indirect gap semiconductor into a direct gap material, but the conduction band distortion of the β phase (Li + near the cation) is quite stronger than that of the α phase (Li + near the anion). The total energy calculations show the α phase to be more stable than the β phase for both LiMgN and LiZnN. The Li-N and Mg-N bonds exhibit a strong ionic character, whereas the Zn-N bond has a strong covalent character in LiMgN and LiZnN.

Solid polymeric electrolytes for lithium batteries

DOEpatents

Angell, Charles A.; Xu, Wu; Sun, Xiaoguang

2006-03-14

Novel conductive polyanionic polymers and methods for their preparion are provided. The polyanionic polymers comprise repeating units of weakly-coordinating anionic groups chemically linked to polymer chains. The polymer chains in turn comprise repeating spacer groups. Spacer groups can be chosen to be of length and structure to impart desired electrochemical and physical properties to the polymers. Preferred embodiments are prepared from precursor polymers comprising the Lewis acid borate tri-coordinated to a selected ligand and repeating spacer groups to form repeating polymer chain units. These precursor polymers are reacted with a chosen Lewis base to form a polyanionic polymer comprising weakly coordinating anionic groups spaced at chosen intervals along the polymer chain. The polyanionic polymers exhibit high conductivity and physical properties which make them suitable as solid polymeric electrolytes in lithium batteries, especially secondary lithium batteries.

Single-laser, one beam, tetrahedral magneto-optical trap.

PubMed

Vangeleyn, Matthieu; Griffin, Paul F; Riis, Erling; Arnold, Aidan S

2009-08-03

We have realized a 4-beam pyramidal magneto-optical trap ideally suited for future microfabrication. Three mirrors split and steer a single incoming beam into a tripod of reflected beams, allowing trapping in the four-beam overlap volume. We discuss the influence of mirror angle on cooling and trapping, finding optimum efficiency in a tetrahedral configuration. We demonstrate the technique using an ex-vacuo mirror system to illustrate the previously inaccessible supra-plane pyramid MOT configuration. Unlike standard pyramidal MOTs both the pyramid apex and its mirror angle are non-critical and our MOT offers improved molasses free from atomic shadows in the laser beams. The MOT scheme naturally extends to a 2-beam refractive version with high optical access. For quantum gas experiments, the mirror system could also be used for a stable 3D tetrahedral optical lattice.

Why Is the Tetrahedral Bond Angle 109 Degrees? The Tetrahedron-in-a-Cube

ERIC Educational Resources Information Center

Lim, Kieran F.

2012-01-01

The common question of why the tetrahedral angle is 109.471 degrees can be answered using a tetrahedron-in-a-cube, along with some Year 10 level mathematics. The tetrahedron-in-a-cube can also be used to demonstrate the non-polarity of tetrahedral molecules, the relationship between different types of lattice structures, and to demonstrate that…

The Kontsevich tetrahedral flow revisited

NASA Astrophysics Data System (ADS)

Bouisaghouane, A.; Buring, R.; Kiselev, A.

2017-09-01

We prove that the Kontsevich tetrahedral flow P ˙ =Qa:b(P) , the right-hand side of which is a linear combination of two differential monomials of degree four in a bi-vector P on an affine real Poisson manifold Nn, does infinitesimally preserve the space of Poisson bi-vectors on Nn if and only if the two monomials in Qa:b(P) are balanced by the ratio a : b = 1 : 6. The proof is explicit; it is written in the language of Kontsevich graphs.

Anion mediated polytype selectivity among the basic salts of Co(II)

NASA Astrophysics Data System (ADS)

Ramesh, T. N.; Rajamathi, Michael; Vishnu Kamath, P.

2006-08-01

Basic salts of Co(II) crystallize in the rhombohedral structure. Two different polytypes, 3R 1 and 3R 2, with distinct stacking sequences of the metal hydroxide slabs, are possible within the rhombohedral structure. These polytypes are generated by simple translation of successive layers by (2/3, 1/3, z) or (1/3, 2/3, z). The symmetry of the anion and the mode of coordination influences polytype selection. Cobalt hydroxynitrate crystallizes in the structure of the 3R 2 polytype while the hydroxytartarate, hydroxychloride and α-cobalt hydroxide crystallize in the structure of the 3R 1 polytype. Cobalt hydroxysulfate is turbostratically disordered. The turbostratic disorder is a direct consequence of the mismatch between the crystallographically defined interlayer sites generated within the crystal and the tetrahedral symmetry of the SO 42- ions.

Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Komuro, Yoshitaka; Yamamoto, Hiroki; Kobayashi, Kazuo; Utsumi, Yoshiyuki; Ohomori, Katsumi; Kozawa, Takahiro

2014-11-01

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub-10 nm. An anion-bound polymer (ABP), in which the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using electron (pulse), γ, and EUV radiolyses. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The major path for proton generation in the absence of effective proton sources is considered to be the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through hole transfer to the decomposition products of onium salts.

Quality Tetrahedral Mesh Smoothing via Boundary-Optimized Delaunay Triangulation

PubMed Central

Gao, Zhanheng; Yu, Zeyun; Holst, Michael

2012-01-01

Despite its great success in improving the quality of a tetrahedral mesh, the original optimal Delaunay triangulation (ODT) is designed to move only inner vertices and thus cannot handle input meshes containing “bad” triangles on boundaries. In the current work, we present an integrated approach called boundary-optimized Delaunay triangulation (B-ODT) to smooth (improve) a tetrahedral mesh. In our method, both inner and boundary vertices are repositioned by analytically minimizing the error between a paraboloid function and its piecewise linear interpolation over the neighborhood of each vertex. In addition to the guaranteed volume-preserving property, the proposed algorithm can be readily adapted to preserve sharp features in the original mesh. A number of experiments are included to demonstrate the performance of our method. PMID:23144522

Elucidating the correlation between morphology and ion dynamics in polymerized ionic liquids.

NASA Astrophysics Data System (ADS)

Heres, Maximilian; Cosby, Tyler; Iacob, Ciprian; Runt, James; Benson, Roberto; Liu, Hongjun; Paddison, Stephen; Sangoro, Joshua

Charge transport and dynamics are investigated for a series of poly-ammonium and poly-imidazolium-based polymerized ionic liquids (polyIL) with a common bis(trifluoromethylsulfonyl)imide anion using broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry. A significant enhancement of the Tg independent ionic conductivity is observed for ammonium based polyIL with shorter pendant groups, in comparison to imidazolium based systems. These results emphasize the importance of polymer backbone spacing as well as counter-ion size on ionic conductivity in polymerized ionic liquids. NSF DMR 1508394.

DNA tetrahedral scaffolds-based platform for the construction of electrochemiluminescence biosensor.

PubMed

Feng, Qiu-Mei; Zhou, Zhen; Li, Mei-Xing; Zhao, Wei; Xu, Jing-Juan; Chen, Hong-Yuan

2017-04-15

Proximal metallic nanoparticles (NPs) could quench the electrochemiluminescence (ECL) emission of semiconductor quantum dots (QDs) due to Förster energy transfer (FRET), but at a certain distance, the coupling of light-emission with surface plasmon resonance (SPR) result in enhanced ECL. Thus, the modification strategies and distances control between QDs and metallic NPs are critical for the ECL intensity of QDs. In this strategy, a SPR enhanced ECL sensor based on DNA tetrahedral scaffolds modified platform was reported for the detection of telomerase activity. Due to the rigid three-dimensional structure, DNA tetrahedral scaffolds grafting on the electrode surface could accurately modulate the distance between CdS QDs and luminol labelled gold nanoparticles (L-Au NPs), meanwhile provide an enhanced spatial dimension and accessibility for the assembly of multiple L-Au NPs. The ECL intensities of both CdS QDs (-1.25V vs. SCE) and luminol (+0.33V vs. SCE) gradually increased along with the formation of multiple L-Au NPs at the vertex of DNA tetrahedral scaffolds induced by telomerase, bringing in a dual-potential ECL analysis. The proposed method showed high sensitivity for the identification of telomerase and was successfully applied for the differentiation of cancer cells from normal cells. This work suggests that DNA tetrahedral scaffolds could serve as an excellent choice for the construction of SPR-ECL system. Copyright © 2016 Elsevier B.V. All rights reserved.

K4[Fe(CN)6] immobilized anion sensitive protonated amine functionalized polysilsesquioxane films for ultra-low electrochemical detection of dsDNA.

PubMed

Silambarasan, Krishnamoorthy; Narendra Kumar, Alam Venugopal; Joseph, James

2016-03-14

Charge transport in polymeric films bound by redox reagents is a topic of current interest. The dynamics of electroinactive ions across the interface is studied by immobilizing ferrocyanide anion in a polysilsesquioxanes (PSQs) modified electrode. Redox reagents can stay in the polymeric film by either physical forces or electrostatic binding. The present work describes the immobilization of ferro/ferricyanide redox couples in PSQ films possessing protonated amine functional groups by electrostatic interactions. Charge transport in [Fe(CN)6](4-)-PSQs film was found to be anion dependent, and its formal potential value varied with the relative hydrophilic or hydrophobic nature of the anion used in the supporting electrolyte, unlike the observed dependence on solution cation for electrodes modified with metal hexacyanoferrates (Prussian Blue analogues). The [Fe(CN)6](4-) bound PSQs films were extensively characterized by varying different supporting electrolytes anions using cyclic voltammetry. The redox peak currents were linearly proportional to the square root of the scan rate, implying that the transport of charge carriers is accompanied with redox ion diffusion and electron hopping in a confined space. dsDNA molecules were found to interact with this polymer matrix through anionic phosphate groups. Both voltammetry and A.C. impedance spectroscopy studies revealed that these interactions could be exploited for the determination of ultra-low level (0.5 attomolar) of dsDNA present in aqueous solution.

Ion Transport via Structural Relaxations in Polymerized Ionic Liquids

NASA Astrophysics Data System (ADS)

Ganesan, Venkat; Mogurampelly, Santosh

We study the mechanisms underlying ion transport in poly(1-butyl-3-vinylimidazolium-hexafluorophosphate) polymer electrolytes. We consider polymer electrolytes of varying polymerized ionic liquid to ionic liquid (polyIL:IL) ratios and use atomistic molecular dynamics (MD) simulations to probe the dynamical and structural characteristics of the electrolyte. Our results reveal that anion diffusion along polymer backbone occurs primarily viathe formation and breaking of ion-pairs involving threepolymerized cationic monomers of twodifferent polymer chains. Moreover, we observe that the ionic diffusivities exhibit a direct correlation with the structural relaxation times of the ion-pairs and hydrogen bonds (H-bonds). These results provide new insights into the mechanisms underlying ion transport in polymerized ionic liquid electrolytes.

Tetrahedrally Coordinated Fe3+ in Silicate Glasses: A Mossbauer, Iron K-edge XANES and Raman Spectroscopies Study

NASA Astrophysics Data System (ADS)

Cochain, B.; Neuville, D. R.; McCammon, C.; Henderson, G. S.; de Ligny, D.; Pinet, O.; Richet, P.

2009-05-01

In natural or industrial glasses, iron is the most abundant transition metal. A good knowledge of its redox equilibrium is important to better understand the chemical and structural evolution of magmas (crystallization, viscosity), and also to optimize vitrification processes and properties of iron-bearing glasses. To study the role of iron in silicate glasses and melts, we have used in a consistent manner the Mössbauer, iron K-edge XANES and Raman spectroscopies to investigate several series of silicate glasses as a function of redox state. The samples were selected to cover a wide composition range and to investigate the interactions of iron with two network forming cations, namely, Al3+ and B3+. The glasses investigated were synthesized at high temperature under various conditions of oxygen fugacity to achieve different redox ratios for each composition. Therefore, the iron redox state was varied from the most oxidized to the most reduced. Iron redox ratios were first determined by wet chemical analysis and in some cases by room temperature Mossbauer spectroscopy. This experimental method was also used to determine the local structure of iron of some of the investigated glasses. These results where compared to iron K-edge XANES/EXAFS spectroscopy results, which lead to the iron redox state and indicate that Fe2+ is in octahedral coordination whereas Fe3+ is in tetrahedral coordination. In addition, Raman spectroscopy gave us information on the network polymerization of glasses. Clearly changes in Raman spectra are visible with the evolution of iron redox ratio. For a given composition, we observed systematically, in the 800-1200 cm-1 envelope, which is sensitive to the environment of tetrahedrally coordinated cations, the growth of a band with the iron content and the oxidation state of the sample. The peak area of this band, which we attribute to vibrational modes involving tetrahedrally coordinated Fe3+, increases with the oxidation of the sample. This

A new method based on the Butler-Volmer formalism to evaluate voltammetric cation and anion sensors.

PubMed

Cano, Manuel; Rodríguez-Amaro, Rafael; Fernández Romero, Antonio J

2008-12-11

A new method based on the Butler-Volmer formalism is applied to assess the capability of two voltammetric ion sensors based on polypyrrole films: PPy/DBS and PPy/ClO4 modified electrodes were studied as voltammetric cation and anion sensors, respectively. The reversible potential versus electrolyte concentrations semilogarithm plots provided positive calibration slopes for PPy/DBS and negative ones for PPy/ClO4, as was expected from the proposed method and that based on the Nernst equation. The slope expressions deduced from Butler-Volmer include the electron-transfer coefficient, which allows slope values different from the ideal Nernstian value to be explained. Both polymeric films exhibited a degree of ion-selectivity when they were immersed in mixed-analyte solutions. Selectivity coefficients for the two proposed voltammetric cation and anion sensors were obtained by several experimental methods, including the separated solution method (SSM) and matched potential method (MPM). The K values acquired by the different methods were very close for both polymeric sensors.

Living olefin polymerization processes

DOEpatents

Schrock, Richard R.; Baumann, Robert

1999-01-01

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Living olefin polymerization processes

DOEpatents

Schrock, R.R.; Baumann, R.

1999-03-30

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Living olefin polymerization processes

DOEpatents

Schrock, Richard R.; Baumann, Robert

2003-08-26

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Living olefin polymerization processes

DOEpatents

Schrock, Richard R.; Bauman, Robert

2006-11-14

Processes for the living polymerization of olefin monomers with terminal carbon-carbon double bonds are disclosed. The processes employ initiators that include a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. The ligand is bonded to the metal atom through two anionic or covalent bonds and a dative bond. The initiators are particularly stable under reaction conditions in the absence of olefin monomer. The processes provide polymers having low polydispersities, especially block copolymers having low polydispersities. It is an additional advantage of these processes that, during block copolymer synthesis, a relatively small amount of homopolymer is formed.

Sol-gel chemistry by ring-opening polymerization

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

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.

2000-02-07

Sol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. The authors have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits them to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solventmore » is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenation. Anionic polymerization of these materials, either neat or with 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane as a copolymer, affords thermally stable transparent gels with no visible shrinkage. These materials provide an easy route to the introduction of sol-gel type materials in encapsulation of microelectronics, which they have successfully demonstrated.« less

Updates to Multi-Dimensional Flux Reconstruction for Hypersonic Simulations on Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2010-01-01

The quality of simulated hypersonic stagnation region heating with tetrahedral meshes is investigated by using an updated three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. An earlier implementation of this algorithm provided improved symmetry characteristics on tetrahedral grids compared to conventional reconstruction methods. The original formulation however displayed quantitative differences in heating and shear that were as large as 25% compared to a benchmark, structured-grid solution. The primary cause of this discrepancy is found to be an inherent inconsistency in the formulation of the flux limiter. The inconsistency is removed by employing a Green-Gauss formulation of primitive gradients at nodes to replace the previous Gram-Schmidt algorithm. Current results are now in good agreement with benchmark solutions for two challenge problems: (1) hypersonic flow over a three-dimensional cylindrical section with special attention to the uniformity of the solution in the spanwise direction and (2) hypersonic flow over a three-dimensional sphere. The tetrahedral cells used in the simulation are derived from a structured grid where cell faces are bisected across the diagonal resulting in a consistent pattern of diagonals running in a biased direction across the otherwise symmetric domain. This grid is known to accentuate problems in both shock capturing and stagnation region heating encountered with conventional, quasi-one-dimensional inviscid flux reconstruction algorithms. Therefore the test problems provide a sensitive indicator for algorithmic effects on heating. Additional simulations on a sharp, double cone and the shuttle orbiter are then presented to demonstrate the capabilities of the new algorithm on more geometrically complex flows with tetrahedral grids. These results provide the first indication that pure tetrahedral elements utilizing the updated, three-dimensional, upwind reconstruction algorithm may be used for the

Coarse-grained theory of a realistic tetrahedral liquid model

NASA Astrophysics Data System (ADS)

Procaccia, I.; Regev, I.

2012-02-01

Tetrahedral liquids such as water and silica-melt show unusual thermodynamic behavior such as a density maximum and an increase in specific heat when cooled to low temperatures. Previous work had shown that Monte Carlo and mean-field solutions of a lattice model can exhibit these anomalous properties with or without a phase transition, depending on the values of the different terms in the Hamiltonian. Here we use a somewhat different approach, where we start from a very popular empirical model of tetrahedral liquids —the Stillinger-Weber model— and construct a coarse-grained theory which directly quantifies the local structure of the liquid as a function of volume and temperature. We compare the theory to molecular-dynamics simulations and show that the theory can rationalize the simulation results and the anomalous behavior.

Simulation of Stagnation Region Heating in Hypersonic Flow on Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2007-01-01

Hypersonic flow simulations using the node based, unstructured grid code FUN3D are presented. Applications include simple (cylinder) and complex (towed ballute) configurations. Emphasis throughout is on computation of stagnation region heating in hypersonic flow on tetrahedral grids. Hypersonic flow over a cylinder provides a simple test problem for exposing any flaws in a simulation algorithm with regard to its ability to compute accurate heating on such grids. Such flaws predominantly derive from the quality of the captured shock. The importance of pure tetrahedral formulations are discussed. Algorithm adjustments for the baseline Roe / Symmetric, Total-Variation-Diminishing (STVD) formulation to deal with simulation accuracy are presented. Formulations of surface normal gradients to compute heating and diffusion to the surface as needed for a radiative equilibrium wall boundary condition and finite catalytic wall boundary in the node-based unstructured environment are developed. A satisfactory resolution of the heating problem on tetrahedral grids is not realized here; however, a definition of a test problem, and discussion of observed algorithm behaviors to date are presented in order to promote further research on this important problem.

The Effect of Titanium Tetrahedral Coordination of Silica-Titania Catalyst on the Physical Properties of Biodiesel

NASA Astrophysics Data System (ADS)

Nizar, U. K.; Hidayatul, J.; Sundari, R.; Bahrizal, B.; Amran, A.; Putra, A.; Latisma DJ, L.; Dewata, I.

2018-04-01

This study investigates the correlation of the number of titanium tetrahedral coordination and biodiesel production. The solid-state method has been used to synthesis of silica-titania catalyst for biodiesel production, which the precursors, i.e. silica and titania commercials were heated in the temperature range of 450 - 550°C. The characterization of the prepared silica-titania has been studied by FTIR and DR UV-Vis in order to identify and calculate the presence of titanium tetrahedral coordination in silica-titania catalyst. A very small peak at around 950 cm-1 indicated the presence of titanium tetrahedral coordination through Si–O–Ti bonds. Deconvolution of DR UV-Vis spectra showed the coordination of titanium in silica-titania is more octahedral. However, the number of titanium tetrahedral coordination of the prepared silica-titania is found higher than that of TiO2 commercial. The increasing of titanium tetrahedral fraction in silica-titania affects the physical properties of biodiesel in terms of boiling point, viscosity and density, which is produced by the reaction of methanol and palm oil.

Palladium (Ii) Catalyzed Polymerization Of Norbornene And Acrylates

DOEpatents

Sen, Ayusman; Kacker, Smita; Hennis, April; Polley, Jennifer D.

2001-10-09

Homopolymers or copolymers of acrylates, homopolymers or copolymers of norbornenes, and copolymers of acrylates with norbornenes, may be prepared by contacting acrylate and/or norbornene monomer reactant under polymerization conditions and in the presence of a solvent with a catalyst system consisting essentially of a Pd(II) dimer component having the formula: where L is a monodentate phosphorus or nitrogen ligand, X is an anionic group, and R is an alkyl or aryl group.

Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material

NASA Astrophysics Data System (ADS)

Ciezak, Jennifer

2007-06-01

High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions.

Comparison of hexahedral and tetrahedral elements in finite element analysis of the foot and footwear.

PubMed

Tadepalli, Srinivas C; Erdemir, Ahmet; Cavanagh, Peter R

2011-08-11

Finite element analysis has been widely used in the field of foot and footwear biomechanics to determine plantar pressures as well as stresses and strains within soft tissue and footwear materials. When dealing with anatomical structures such as the foot, hexahedral mesh generation accounts for most of the model development time due to geometric complexities imposed by branching and embedded structures. Tetrahedral meshing, which can be more easily automated, has been the approach of choice to date in foot and footwear biomechanics. Here we use the nonlinear finite element program Abaqus (Simulia, Providence, RI) to examine the advantages and disadvantages of tetrahedral and hexahedral elements under compression and shear loading, material incompressibility, and frictional contact conditions, which are commonly seen in foot and footwear biomechanics. This study demonstrated that for a range of simulation conditions, hybrid hexahedral elements (Abaqus C3D8H) consistently performed well while hybrid linear tetrahedral elements (Abaqus C3D4H) performed poorly. On the other hand, enhanced quadratic tetrahedral elements with improved stress visualization (Abaqus C3D10I) performed as well as the hybrid hexahedral elements in terms of contact pressure and contact shear stress predictions. Although the enhanced quadratic tetrahedral element simulations were computationally expensive compared to hexahedral element simulations in both barefoot and footwear conditions, the enhanced quadratic tetrahedral element formulation seems to be very promising for foot and footwear applications as a result of decreased labor and expedited model development, all related to facilitated mesh generation. Copyright © 2011. Published by Elsevier Ltd.

Acrylate intercalation and in situ polymerization in iron-, cobalt-, or manganese-substituted nickel hydroxides.

PubMed

Vaysse, C; Guerlou-Demourgues, L; Duguet, E; Delmas, C

2003-07-28

A chimie douce route based on successive redox and exchange reactions has allowed us to prepare new hybrid organic-inorganic materials, composed of polyacrylate macromolecules intercalated into layered double hydroxides (LDHs), deriving from Ni(OH)(2). Monomer intercalation and in situ polymerization mechanisms have appeared to be strongly dependent upon the nature of the substituting cation in the slabs. In the case of iron-based LDHs, a phase containing acrylate monomeric intercalates has been isolated and identified by X-ray diffraction and infrared spectroscopy. Second, interslab free-radical polymerization of acrylate anions has been successfully initiated using potassium persulfate. In cobalt- or manganese-based LDHs, one-step polymerization has been observed, leading directly to a material containing polyacrylate intercalate.

Hinge specification for a square-faceted tetrahedral truss

NASA Technical Reports Server (NTRS)

Adams, L. R.

1984-01-01

A square-faceted tetrahedral truss is geometrically analyzed. Expressions are developed for single degree of freedom hinges which allow packaging of the structure into a configuration in which all members are parallel and closely packed in a square pattern. Deployment is sequential, thus providing control over the structure during deployment.

New approach based on tetrahedral-mesh geometry for accurate 4D Monte Carlo patient-dose calculation

NASA Astrophysics Data System (ADS)

Han, Min Cheol; Yeom, Yeon Soo; Kim, Chan Hyeong; Kim, Seonghoon; Sohn, Jason W.

2015-02-01

In the present study, to achieve accurate 4D Monte Carlo dose calculation in radiation therapy, we devised a new approach that combines (1) modeling of the patient body using tetrahedral-mesh geometry based on the patient’s 4D CT data, (2) continuous movement/deformation of the tetrahedral patient model by interpolation of deformation vector fields acquired through deformable image registration, and (3) direct transportation of radiation particles during the movement and deformation of the tetrahedral patient model. The results of our feasibility study show that it is certainly possible to construct 4D patient models (= phantoms) with sufficient accuracy using the tetrahedral-mesh geometry and to directly transport radiation particles during continuous movement and deformation of the tetrahedral patient model. This new approach not only produces more accurate dose distribution in the patient but also replaces the current practice of using multiple 3D voxel phantoms and combining multiple dose distributions after Monte Carlo simulations. For routine clinical application of our new approach, the use of fast automatic segmentation algorithms is a must. In order to achieve, simultaneously, both dose accuracy and computation speed, the number of tetrahedrons for the lungs should be optimized. Although the current computation speed of our new 4D Monte Carlo simulation approach is slow (i.e. ~40 times slower than that of the conventional dose accumulation approach), this problem is resolvable by developing, in Geant4, a dedicated navigation class optimized for particle transportation in tetrahedral-mesh geometry.

Synthesis and Characterization of Comb and Centipede Multigraft Copolymers P nBA- g-PS with High Molecular Weight Using Miniemulsion Polymerization

DOE PAGES

Wang, Wenwen; Wang, Weiyu; Lu, Xinyi; ...

2014-10-23

For this study, comb and centipede multigraft copolymers, poly(n-butyl acrylate)-g-polystyrene (PnBA-g-PS) with PnBA backbones and PS side chains, were synthesized via high-vacuum anionic polymerization and miniemulsion polymerization. Single-tailed and double-tailed PS macromonomers were synthesized by anionic polymerization and Steglich esterification. Subsequently, the copolymerization of each macromonomer and nBA was carried out in miniemulsion, and multigraft copolymers were obtained. The latex particles of multigraft copolymers were characterized using dynamic light scattering. The molecular weights of macromonomers and multigraft copolymers were analyzed by size exclusion chromatography. Moreover, the molecular weights and structures of macromonomers were investigated by matrix-assisted laser desorption/ionization time-of-flight massmore » spectrometry and 1H nuclear magnetic resonance spectroscopy. The weight contents of PS in comb and centipede multigraft copolymers were calculated by 1H nuclear magnetic resonance spectroscopy. The thermal properties of multigraft copolymers were characterized by thermogravimetric analysis and differential scanning calorimetry. The microphase separation of multigraft copolymers was observed by atomic force microscopy and transmission electronic microscopy. Rheological measurements showed that comb and centipede multigraft copolymers have elastic properties when the weight content of PS side chains is 26–32 wt %. Centipede multigraft copolymers possess better elastic properties than comb multigraft copolymers with the similar weight content of PS. In conclusion, these findings are similar to previous results on poly(isoprene-g-polystyrene) comb and centipede copolymers made by anionic polymerization.« less

Occlusion of Sulfate-Based Diblock Copolymer Nanoparticles within Calcite: Effect of Varying the Surface Density of Anionic Stabilizer Chains.

PubMed

Ning, Yin; Fielding, Lee A; Ratcliffe, Liam P D; Wang, Yun-Wei; Meldrum, Fiona C; Armes, Steven P

2016-09-14

Polymerization-induced self-assembly (PISA) offers a highly versatile and efficient route to a wide range of organic nanoparticles. In this article, we demonstrate for the first time that poly(ammonium 2-sulfatoethyl methacrylate)-poly(benzyl methacrylate) [PSEM-PBzMA] diblock copolymer nanoparticles can be prepared with either a high or low PSEM stabilizer surface density using either RAFT dispersion polymerization in a 2:1 v/v ethanol/water mixture or RAFT aqueous emulsion polymerization, respectively. We then use these model nanoparticles to gain new insight into a key topic in materials chemistry: the occlusion of organic additives into inorganic crystals. Substantial differences are observed for the extent of occlusion of these two types of anionic nanoparticles into calcite (CaCO3), which serves as a suitable model host crystal. A low PSEM stabilizer surface density leads to uniform nanoparticle occlusion within calcite at up to 7.5% w/w (16% v/v), while minimal occlusion occurs when using nanoparticles with a high PSEM stabilizer surface density. This counter-intuitive observation suggests that an optimum anionic surface density is required for efficient occlusion, which provides a hitherto unexpected design rule for the incorporation of nanoparticles within crystals.

Kinetic Analysis for Macrocyclizations Involving Anionic Template at the Transition State

PubMed Central

Martí-Centelles, Vicente; Burguete, M. Isabel; Luis, Santiago V.

2012-01-01

Several kinetic models for the macrocyclization of a C2 pseudopeptide with a dihalide through a SN2 reaction have been developed. These models not only focus on the kinetic analysis of the main macrocyclization reaction, but also consider the competitive oligomerization/polymerization processes yielding undesired oligomeric/polymeric byproducts. The effect of anions has also been included in the kinetic models, as they can act as catalytic templates in the transition state reducing and stabilizing the transition state. The corresponding differential equation systems for each kinetic model can be solved numerically. Through a comprehensive analysis of these results, it is possible to obtain a better understanding of the different parameters that are involved in the macrocyclization reaction mechanism and to develop strategies for the optimization of the desired processes. PMID:22666148

Achieving Continuous Anion Transport Domains Using Block Copolymers Containing Phosphonium Cations

DOE PAGES

Zhang, Wenxu; Liu, Ye; Jackson, Aaron C.; ...

2016-06-22

Triblock and diblock copolymers based on isoprene (Ip) and chloromethylstyrene (CMS) were synthesized in this paper by sequential polymerization using reversible addition–fragmentation chain transfer radical polymerization (RAFT). The block copolymers were quaternized with tris(2,4,6-trimethoxyphenyl)phosphine (Ar 3P) to prepare soluble ionomers. The ionomers were cast from chloroform to form anion exchange membranes (AEMs) with highly ordered morphologies. At low volume fractions of ionic blocks, the ionomers formed lamellar morphologies, while at moderate volume fractions (≥30% for triblock and ≥22% for diblock copolymers) hexagonal phases with an ionic matrix were observed. Ion conductivities were higher through the hexagonal phase matrix than inmore » the lamellar phases. Finally, promising chloride conductivities (20 mS/cm) were achieved at elevated temperatures and humidified conditions.« less

Tetrahedral Models of Learning: Application to College Reading.

ERIC Educational Resources Information Center

Nist, Sherrie L.

J. D. Bransford's tetrahedral model of learning considers four variables: (1) learning activities, (2) characteristics of the learner, (3) criterial tasks, and (4) the nature of the materials. Bransford's model provides a research-based theoretical framework that can be used to teach, model, and have students apply a variety of study strategies to…

Self-assembled DNA tetrahedral optofluidic lasers with precise and tunable gain control.

PubMed

Chen, Qiushu; Liu, Huajie; Lee, Wonsuk; Sun, Yuze; Zhu, Dan; Pei, Hao; Fan, Chunhai; Fan, Xudong

2013-09-07

We have applied self-assembled DNA tetrahedral nanostructures for the precise and tunable control of the gain in an optofluidic fluorescence resonance energy transfer (FRET) laser. By adjusting the ratio of the donor and the acceptor attached to the tetrahedral vertices, 3.8 times reduction in the lasing threshold and 28-fold enhancement in the lasing efficiency were demonstrated. This work takes advantage of the self-recognition and self-assembly capabilities of biomolecules with well-defined structures and addressability, enabling nano-engineering of the laser down to the molecular level.

Practical implementation of tetrahedral mesh reconstruction in emission tomography

PubMed Central

Boutchko, R.; Sitek, A.; Gullberg, G. T.

2014-01-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

Practical implementation of tetrahedral mesh reconstruction in emission tomography

NASA Astrophysics Data System (ADS)

Boutchko, R.; Sitek, A.; Gullberg, G. T.

2013-05-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

Surfactant-controlled polymerization of semiconductor clusters to quantum dots through competing step-growth and living chain-growth mechanisms.

PubMed

Evans, Christopher M; Love, Alyssa M; Weiss, Emily A

2012-10-17

This article reports control of the competition between step-growth and living chain-growth polymerization mechanisms in the formation of cadmium chalcogenide colloidal quantum dots (QDs) from CdSe(S) clusters by varying the concentration of anionic surfactant in the synthetic reaction mixture. The growth of the particles proceeds by step-addition from initially nucleated clusters in the absence of excess phosphinic or carboxylic acids, which adsorb as their anionic conjugate bases, and proceeds indirectly by dissolution of clusters, and subsequent chain-addition of monomers to stable clusters (Ostwald ripening) in the presence of excess phosphinic or carboxylic acid. Fusion of clusters by step-growth polymerization is an explanation for the consistent observation of so-called "magic-sized" clusters in QD growth reactions. Living chain-addition (chain addition with no explicit termination step) produces QDs over a larger range of sizes with better size dispersity than step-addition. Tuning the molar ratio of surfactant to Se(2-)(S(2-)), the limiting ionic reagent, within the living chain-addition polymerization allows for stoichiometric control of QD radius without relying on reaction time.

Tetrahedral hydrocarbon nanoparticles in space: X-ray spectra

NASA Astrophysics Data System (ADS)

Bilalbegović, G.; Maksimović, A.; Valencic, L. A.

2018-06-01

It has been proposed, or confirmed, that diamond nanoparticles exist in various environments in space: close to active galactic nuclei, in the vicinity of supernovae and pulsars, in the interior of several planets in the Solar system, in carbon planets, and other exoplanets, carbon-rich stars, meteorites, in X-ray active Herbig Ae/Be stars, and in the interstellar medium. Using density functional theory methods, we calculate the carbon K-edge X-ray absorption spectrum of two large tetrahedral nanodiamonds: C26H32 and C51H52. We also study and test our methods on the astrophysical molecule CH4, the smallest C-H tetrahedral structure. A possible detection of nanodiamonds from X-ray spectra by future telescopes, such as the project Arcus, is proposed. Simulated spectra of the diffuse interstellar medium using Cyg X-2 as a source show that nanodiamonds studied in this work can be detected by Arcus, a high-resolution X-ray spectrometer mission selected by NASA for a Phase A concept study.

Transport of phase space densities through tetrahedral meshes using discrete flow mapping

NASA Astrophysics Data System (ADS)

Bajars, Janis; Chappell, David J.; Søndergaard, Niels; Tanner, Gregor

2017-01-01

Discrete flow mapping was recently introduced as an efficient ray based method determining wave energy distributions in complex built up structures. Wave energy densities are transported along ray trajectories through polygonal mesh elements using a finite dimensional approximation of a ray transfer operator. In this way the method can be viewed as a smoothed ray tracing method defined over meshed surfaces. Many applications require the resolution of wave energy distributions in three-dimensional domains, such as in room acoustics, underwater acoustics and for electromagnetic cavity problems. In this work we extend discrete flow mapping to three-dimensional domains by propagating wave energy densities through tetrahedral meshes. The geometric simplicity of the tetrahedral mesh elements is utilised to efficiently compute the ray transfer operator using a mixture of analytic and spectrally accurate numerical integration. The important issue of how to choose a suitable basis approximation in phase space whilst maintaining a reasonable computational cost is addressed via low order local approximations on tetrahedral faces in the position coordinate and high order orthogonal polynomial expansions in momentum space.

Tetrahedral Finite-Volume Solutions to the Navier-Stokes Equations on Complex Configurations

NASA Technical Reports Server (NTRS)

Frink, Neal T.; Pirzadeh, Shahyar Z.

1998-01-01

A review of the algorithmic features and capabilities of the unstructured-grid flow solver USM3Dns is presented. This code, along with the tetrahedral grid generator, VGRIDns, is being extensively used throughout the U.S. for solving the Euler and Navier-Stokes equations on complex aerodynamic problems. Spatial discretization is accomplished by a tetrahedral cell-centered finite-volume formulation using Roe's upwind flux difference splitting. The fluxes are limited by either a Superbee or MinMod limiter. Solution reconstruction within the tetrahedral cells is accomplished with a simple, but novel, multidimensional analytical formula. Time is advanced by an implicit backward-Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the near-wall region of the boundary layer. The issues of accuracy and robustness of USM3Dns Navier-Stokes capabilities are addressed for a flat-plate boundary layer, and a full F-16 aircraft with external stores at transonic speed.

Multi-Dimensional, Inviscid Flux Reconstruction for Simulation of Hypersonic Heating on Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Gnoffo, Peter A.

2009-01-01

The quality of simulated hypersonic stagnation region heating on tetrahedral meshes is investigated by using a three-dimensional, upwind reconstruction algorithm for the inviscid flux vector. Two test problems are investigated: hypersonic flow over a three-dimensional cylinder with special attention to the uniformity of the solution in the spanwise direction and hypersonic flow over a three-dimensional sphere. The tetrahedral cells used in the simulation are derived from a structured grid where cell faces are bisected across the diagonal resulting in a consistent pattern of diagonals running in a biased direction across the otherwise symmetric domain. This grid is known to accentuate problems in both shock capturing and stagnation region heating encountered with conventional, quasi-one-dimensional inviscid flux reconstruction algorithms. Therefore the test problem provides a sensitive test for algorithmic effects on heating. This investigation is believed to be unique in its focus on three-dimensional, rotated upwind schemes for the simulation of hypersonic heating on tetrahedral grids. This study attempts to fill the void left by the inability of conventional (quasi-one-dimensional) approaches to accurately simulate heating in a tetrahedral grid system. Results show significant improvement in spanwise uniformity of heating with some penalty of ringing at the captured shock. Issues with accuracy near the peak shear location are identified and require further study.

A finite element boundary integral formulation for radiation and scattering by cavity antennas using tetrahedral elements

NASA Technical Reports Server (NTRS)

Gong, J.; Volakis, J. L.; Chatterjee, A.; Jin, J. M.

1992-01-01

A hybrid finite element boundary integral formulation is developed using tetrahedral and/or triangular elements for discretizing the cavity and/or aperture of microstrip antenna arrays. The tetrahedral elements with edge based linear expansion functions are chosen for modeling the volume region and triangular elements are used for discretizing the aperture. The edge based expansion functions are divergenceless thus removing the requirement to introduce a penalty term and the tetrahedral elements permit greater geometrical adaptability than the rectangular bricks. The underlying theory and resulting expressions are discussed in detail together with some numerical scattering examples for comparison and demonstration.

In situ AFM investigation of electrochemically induced surface-initiated atom-transfer radical polymerization.

PubMed

Li, Bin; Yu, Bo; Zhou, Feng

2013-02-12

Electrochemically induced surface-initiated atom-transfer radical polymerization is traced by in situ AFM technology for the first time, which allows visualization of the polymer growth process. It affords a fundamental insight into the surface morphology and growth mechanism simultaneously. Using this technique, the polymerization kinetics of two model monomers were studied, namely the anionic 3-sulfopropyl methacrylate potassium salt (SPMA) and the cationic 2-(metharyloyloxy)ethyltrimethylammonium chloride (METAC). The growth of METAC is significantly improved by screening the ammonium cations by the addition of ionic liquid electrolyte in aqueous solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Palladium (II) catalyized polymerization of norbornene and acrylates

DOEpatents

Sen, Ayusman; Kacker, Smita; Hennis, April; Polley, Jennifer D.

2000-08-29

Homopolymers or copolymers of acrylates, homopolymers or copolymers of norbornenes, and copolymers of acrylates with norbornenes, may be prepared by contacting acrylate and/or norbornene monomer reactant under polymerization conditions and in the presence of a solvent with a catalyst system consisting essentially of a Pd(II) dimer component having the formula: [(L)Pd(R)(X)].sub.2, where L is a monodentate phosphorus or nitrogen ligand, X is an anionic group, and R is an alkyl or aryl group.

Polymerization and photochromism of ammonium molybdate in porous glass

NASA Astrophysics Data System (ADS)

Pak, V. N.; Borisov, A. N.

2016-08-01

Modification of porous glass (PG) plates is carried out by impregnation with aqueous solutions of ammonium molybdate (NH4)2MoO4 with subsequent removal of water at 120°C. A long-wavelength shift of absorption spectra upon accumulation of the salt in PG indicates polymerization of MoO 4 2- anions at low concentrations of the encapsulated salt. Photochromism manifests itself as the anionic forms in PG become larger. UV irradiation of the modified plates causes enhancement of continuous absorption in the visible range. The proposed mechanism of photoreduction of the polianions in PG involves the removal of oxygen atoms from the bridging-Mo-O-Mo-bonds and stabilization of the colored forms by means of conjugation of the electrons released from the 4 d-levels of pentavalent molybdenum.

Adsorption of Anionic, Cationic and Nonionic Surfactants on Carbonate Rock in Presence of ZrO 2 Nanoparticles

NASA Astrophysics Data System (ADS)

Esmaeilzadeh, Pouriya; Bahramian, Alireza; Fakhroueian, Zahra

The adsorption of surfactants at the solid-water interface is important for the control of wetting, lubrication, detergency and in mineral flotation.We have studied the adsorptions of different types of surfactants, cationic (Dodecyl trimethylammonium bromide, DTAB), anionic (sodium dodecyl sulfate, SDS) and non-anionic (lauryl alcohol-7 mole ethoxylate, LA7) on carbonate rock in presence of zirconium oxide spherical nanoparticles (17-19 nm). ZrO2 nanoparticles with tetrahedral structure have significant effect on adsorption of surfactants on the carbonate rock. We have used the measured conductivities to determine the rate of adsorption of surfactants at rock-water interfaces. The conductivity of DTAB in aqueous solutions containing calcite powder decreases more than the other surfactants in contact with ZrO2 nanoparticles. We have also investigated the adsorption of surfactants at the air-water interface. The presence of nanoparticles, as demonstrated by our experiments, enhances the surface activity and surface adsorption of the surfactants through electrostatic forces or formation of nanostructures. Dynamic light structuring data shows similar aggregation number of nanoparticles in presence of nanoparticles.

Methods development for separation of inorganic anions, organic acids and bases, and neutral organic compounds by ion chromatography and capillary electrophoresis

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

Li, Jie

1999-04-01

A novel anion-exchange resin containing three amine groups was prepared by reaction of a chloromethylated polystyrene-divinylbenzene (PS-DVB) resin with diethylenetriamine. After being protonated by contact with an aqueous acid, this resin can be used for ion chromatographic separation of anions. The charge on the resins can be varied from +1 to +3 by changing the mobile phase pH. The selectivity of the new ion exchangers for various inorganic anions was quite different from that of conventional anion exchangers. The performance of this new anion exchanger was studied by changing the pH and the concentration of the eluent, and several differentmore » eluents were used with some common anions as testing analytes. Conductivity detection and UV-visible detection were applied to detect the anions after separation. The new resin can also be used for HPLC separation of neutral organic compounds. Alkylphenols and alkylbenzenes were separated with this new polymeric resin, and excellent separations were obtained under simple conditions. This report contains Chapter 1: General introduction and Chapter 6: General conclusions.« less

A new third order finite volume weighted essentially non-oscillatory scheme on tetrahedral meshes

NASA Astrophysics Data System (ADS)

Zhu, Jun; Qiu, Jianxian

2017-11-01

In this paper a third order finite volume weighted essentially non-oscillatory scheme is designed for solving hyperbolic conservation laws on tetrahedral meshes. Comparing with other finite volume WENO schemes designed on tetrahedral meshes, the crucial advantages of such new WENO scheme are its simplicity and compactness with the application of only six unequal size spatial stencils for reconstructing unequal degree polynomials in the WENO type spatial procedures, and easy choice of the positive linear weights without considering the topology of the meshes. The original innovation of such scheme is to use a quadratic polynomial defined on a big central spatial stencil for obtaining third order numerical approximation at any points inside the target tetrahedral cell in smooth region and switch to at least one of five linear polynomials defined on small biased/central spatial stencils for sustaining sharp shock transitions and keeping essentially non-oscillatory property simultaneously. By performing such new procedures in spatial reconstructions and adopting a third order TVD Runge-Kutta time discretization method for solving the ordinary differential equation (ODE), the new scheme's memory occupancy is decreased and the computing efficiency is increased. So it is suitable for large scale engineering requirements on tetrahedral meshes. Some numerical results are provided to illustrate the good performance of such scheme.

Ring-opening polymerization of 19-electron [2]cobaltocenophanes: a route to high-molecular-weight, water-soluble polycobaltocenium polyelectrolytes.

PubMed

Mayer, Ulrich F J; Gilroy, Joe B; O'Hare, Dermot; Manners, Ian

2009-08-05

Water-soluble, high-molecular-weight polycobaltocenium polyelectrolytes have been prepared by ring-opening polymerization (ROP) techniques. Anionic polymerization of a strained 19-electron dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium chloride resulted in the formation of oligomers with up to nine repeat units. Thermal ROP of dicarba[2]cobaltocenophane followed by oxidation in the presence of ammonium nitrate resulted in the formation of high-molecular-weight polycobaltocenium nitrate, a redox-active cobalt-containing polyelectrolyte.

Parallel Anisotropic Tetrahedral Adaptation

NASA Technical Reports Server (NTRS)

Park, Michael A.; Darmofal, David L.

2008-01-01

An adaptive method that robustly produces high aspect ratio tetrahedra to a general 3D metric specification without introducing hybrid semi-structured regions is presented. The elemental operators and higher-level logic is described with their respective domain-decomposed parallelizations. An anisotropic tetrahedral grid adaptation scheme is demonstrated for 1000-1 stretching for a simple cube geometry. This form of adaptation is applicable to more complex domain boundaries via a cut-cell approach as demonstrated by a parallel 3D supersonic simulation of a complex fighter aircraft. To avoid the assumptions and approximations required to form a metric to specify adaptation, an approach is introduced that directly evaluates interpolation error. The grid is adapted to reduce and equidistribute this interpolation error calculation without the use of an intervening anisotropic metric. Direct interpolation error adaptation is illustrated for 1D and 3D domains.

On the influence of tetrahedral covalent-hybridization on electronic band structure of topological insulators from first principles

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

Zhang, X. M.; Xu, G. Z.; Liu, E. K.

Based on first-principles calculations, we investigate the influence of tetrahedral covalent-hybridization between main-group and transition-metal atoms on the topological band structures of binary HgTe and ternary half-Heusler compounds, respectively. Results show that, for the binary HgTe, when its zinc-blend structure is artificially changed to rock-salt one, the tetrahedral covalent-hybridization will be removed and correspondingly the topologically insulating band character lost. While for the ternary half-Heusler system, the strength of covalent-hybridization can be tuned by varying both chemical compositions and atomic arrangements, and the competition between tetrahedral and octahedral covalent-hybridization has been discussed in details. As a result, we found thatmore » a proper strength of tetrahedral covalent-hybridization is probably in favor to realizing the topologically insulating state with band inversion occurring at the Γ point of the Brillouin zone.« less

Molecular anions.

PubMed

Simons, Jack

2008-07-24

The experimental and theoretical study of molecular anions has undergone explosive growth over the past 40 years. Advances in techniques used to generate anions in appreciable numbers as well as new ion-storage, ion-optics, and laser spectroscopic tools have been key on the experimental front. Theoretical developments on the electronic structure and molecular dynamics fronts now allow one to achieve higher accuracy and to study electronically metastable states, thus bringing theory in close collaboration with experiment in this field. In this article, many of the experimental and theoretical challenges specific to studying molecular anions are discussed. Results from many research groups on several classes of molecular anions are overviewed, and both literature citations and active (in online html and pdf versions) links to numerous contributing scientists' Web sites are provided. Specific focus is made on the following families of anions: dipole-bound, zwitterion-bound, double-Rydberg, multiply charged, metastable, cluster-based, and biological anions. In discussing each kind of anion, emphasis is placed on the structural, energetic, spectroscopic, and chemical-reactivity characteristics that make these anions novel, interesting, and important.

Marine magnetotelluric inversion with an unstructured tetrahedral mesh

NASA Astrophysics Data System (ADS)

Usui, Yoshiya; Kasaya, Takafumi; Ogawa, Yasuo; Iwamoto, Hisanori

2018-05-01

The finite element method using an unstructured tetrahedral mesh is one of the most effective methods for the three-dimensional modelling of marine magnetotelluric data which are strongly affected by bathymetry, because it enables us to incorporate both small-scale and regional-scale bathymetry into a computational mesh with a practical number of elements. The authors applied a three-dimensional inversion scheme using mesh of this type to marine magnetotelluric problems for the first time and verified its applicability. Forward calculations for two bathymetry models demonstrated that the results obtained with an unstructured tetrahedral mesh are close to the reference solutions. To evaluate the forward calculation results, we developed a general TM-mode analytical formulation for a two-dimensional sinusoidal topography. Moreover, synthetic inversion test results confirmed that a three-dimensional inversion scheme with an unstructured tetrahedral mesh enables us to recover subseafloor resistivity structure properly even for a model including a land-sea boundary as well as seafloor undulations. The verified inversion scheme was subsequently applied to a set of marine magnetotelluric data observed around the Iheya North Knoll, the middle Okinawa Trough. Three-dimensional modelling using a mesh with precise bathymetry demonstrated that the data observed around the Iheya North Knoll are strongly affected by bathymetry, especially by the sea-depth differences between the depression of the trough and the shallow East China Sea. The estimated resistivity structure under the knoll is characterized by a conductive surface layer underlain by a resistive layer. The conductive layer implies permeable pelagic/hemi-pelagic sediments, which are consistent with a previous seismological study. Furthermore, the conductive layer has a resistive part immediately below the knoll, which is regarded as the consolidated magma intrusion that formed the knoll. Furthermore, at depth of 10 km

Anions coordinating anions: analysis of the interaction between anionic Keplerate nanocapsules and their anionic ligands.

PubMed

Melgar, Dolores; Bandeira, Nuno A G; Bonet Avalos, Josep; Bo, Carles

2017-02-15

Keplerates are a family of anionic metal oxide spherical capsules containing up to 132 metal atoms and some hundreds of oxygen atoms. These capsules holding a high negative charge of -12 coordinate both mono-anionic and di-anionic ligands thus increasing their charge up to -42, even up to -72, which is compensated by the corresponding counter-cations in the X-ray structures. We present an analysis of the relative importance of several energy terms of the coordinate bond between the capsule and ligands like carbonate, sulphate, sulphite, phosphinate, selenate, and a variety of carboxylates, of which the overriding component is contributed by solvation/de-solvation effects.

Reactive phosphorus removal from aquaculture and poultry productions systems using polymeric hydrogels.

PubMed

Kofinas, Peter; Kioussis, Dimitri R

2003-01-15

This work reports on the features of a sorption processes for the ultimate removal and recovery of reactive phosphorus from aquaculture and poultry production wastewater effluents. The sorbent used was a cross-linked polyamine (PAA-HCl) polymeric hydrogel. The PAA-HCl hydrogels were prepared by chemically cross-linking aqueous solutions of linear PAA-HCl chains with epichlorohydrin (EPI). The phosphorus binding capacity of the gels was measured in standard aqueous solutions as a function of ionic strength. Equilibrium PO4(3-), loadings of 100 mg anion/g gel were obtained. The regeneration ability of the gels was demonstrated by release of the bound phosphorus anions upon washing with 1-2 M NaOH solution, providing opportunities to recover and reuse the gel over multiple cycles. The ionic polyamine gels have been demonstrated to be appropriate materials for treating poultry and aquaculture wastewater effluents. Upon treatment phosphorus anion concentrations were reduced to levels suitable for discharge into natural surface waters.

Preparation of anionic polyurethane nanoparticles and blood compatible behaviors.

PubMed

Zhu, Qinshu; Wang, Yan; Zhou, Min; Mao, Chun; Huang, Xiaohua; Bao, Jianchun; Shen, Jian

2012-05-01

The anionic polyurethane nanoparticles (APU-NPs) were obtained by an emulsion polymerization method. It was found that the average size of the prepared APU-NPs is about 84 nm, and the APU-NPs have zeta-potential of -38.9 mV. The bulk characterization of synthesized APU-NPs was investigated by FTIR. The blood compatibility of APU-NPs was characterized by in vitro for coagulation tests, complement activation, platelet activation, cytotoxicity experiments, and hemolysis assay. The results showed that the APU-NPs synthesized in this paper are blood compatible with low level of cell cytotoxicity, and the results were significant for their potential use in vivo.

Mesh quality control for multiply-refined tetrahedral grids

NASA Technical Reports Server (NTRS)

Biswas, Rupak; Strawn, Roger

1994-01-01

A new algorithm for controlling the quality of multiply-refined tetrahedral meshes is presented in this paper. The basic dynamic mesh adaption procedure allows localized grid refinement and coarsening to efficiently capture aerodynamic flow features in computational fluid dynamics problems; however, repeated application of the procedure may significantly deteriorate the quality of the mesh. Results presented show the effectiveness of this mesh quality algorithm and its potential in the area of helicopter aerodynamics and acoustics.

Ultrahigh-resolution γ-ray spectroscopy of 156Gd: a test of tetrahedral symmetry.

PubMed

Jentschel, M; Urban, W; Krempel, J; Tonev, D; Dudek, J; Curien, D; Lauss, B; de Angelis, G; Petkov, P

2010-06-04

Tetrahedral symmetry in strongly interacting systems would establish a new class of quantum effects at subatomic scale. Excited states in 156Gd that could carry the information about the tetrahedral symmetry were populated in the 155Gd(n,γ)156Gd reaction and studied using the GAMS4/5 Bragg spectrometers at the Institut Laue-Langevin. We have identified the 5(1)- → 3(1)- transition of 131.983(12) keV in 156Gd and determined its intensity to be 1.9(3)x10(-6) per neutron capture. The lifetime τ=220(-30)(+180) fs of the 5(1)- state in 156Gd has been measured using the GRID technique. The resulting B(E2)=293(-134)(+6) Weisskopf unit rate of the 131.983 keV transition provides the intrinsic quadrupole moment of the 5(1)- state in 156Gd to be Q0=7.1(-1.6)(+0.7) b. This large value, comparable to the quadrupole moment of the ground state in 156Gd, gives strong evidence against tetrahedral symmetry in the lowest odd-spin, negative-parity band of 156Gd.

A tetrapyridine ligand with a rigid tetrahedral core forms metal-organic frameworks with PtS type architecture.

PubMed

Caputo, Christopher B; Vukotic, V Nicholas; Sirizzotti, Natalie M; Loeb, Stephen J

2011-08-14

A new tetradentate, pyridine ligand with a rigid tetrahedral core can be prepared in good yield by a cross-coupling methodology. Two metal organic framework structures of Cu(II) with PtS-type topology having a carbon atom as the tetrahedral node have been characterized utilising this ligand. This journal is © The Royal Society of Chemistry 2011

Determination of Inorganic Cations and Anions in Chitooligosaccharides by Ion Chromatography with Conductivity Detection.

PubMed

Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang

2017-02-22

Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na⁺, NH₄⁺, K⁺, Mg 2+ , Ca 2+ , and chloride, acetate and lactate anions was developed. Detection limits were 0.01-0.05 μM for cations and 0.5-0.6 μM for anions. The linear range was 0.001-0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate.

Determination of Inorganic Cations and Anions in Chitooligosaccharides by Ion Chromatography with Conductivity Detection

PubMed Central

Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang

2017-01-01

Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na+, NH4+, K+, Mg2+, Ca2+, and chloride, acetate and lactate anions was developed. Detection limits were 0.01–0.05 μM for cations and 0.5–0.6 μM for anions. The linear range was 0.001–0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate. PMID:28241416

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

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

Bowman-James, Kristen

2004-12-01

This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical andmore » structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.« less

Preliminary design of a large tetrahedral truss/hexagonal heatshield panel aerobrake

NASA Technical Reports Server (NTRS)

Dorsey, John T.; Mikulas, Martin M., Jr.

1989-01-01

An aerobrake structural concept is introduced which consists of two primary components: (1) a lightweight erectable tetrahedral support truss; and (2) sandwich hexagonal heatshield panels which, when attached to the truss, form a continuous impermeable aerobraking surface. Generic finite element models and a general analysis procedure to design tetrahedral truss/hexagonal heatshield panel aerobrakes is developed, and values of the aerobrake design parameters which minimize mass and packaging volume for a 120-foot-diameter aerobrake are determined. Sensitivity of the aerobrake design to variations in design parameters is also assessed. The results show that a 120-foot-diameter aerobrake is viable using the concept presented (i.e., the aerobrake mass is less than or equal to 15 percent of the payload spacecraft mass). Minimizing the aerobrake mass (by increasing the number of rings in the support truss) however, leads to aerobrakes with the highest part count.

A multifunctional azobenzene-based polymeric adsorbent for effective water remediation

PubMed Central

Wan, Decheng; Chen, Feng; Geng, Qingrui; Lu, Hang; Willcock, Helen; Liu, Qiuming; Wang, Fangyingkai; Zou, Kaidian; Jin, Ming; Pu, Hongting; Du, Jianzhong

2014-01-01

The efficient removal of trace carcinogenic organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and ionic dyes, from water is an important technical challenge. We report a highly effective recyclable multifunctional azobenzene (AZ)-based silica-supported polymeric adsorbent which can simultaneously remove both PAHs and anionic dyes from water to below parts per billion (ppb) level based on multiple interactions such as the hydrophobic effect, π–π stacking and electrostatic interactions, thus providing a new strategy for designer water remediation materials. PMID:25465671

Anion exchange membrane

DOEpatents

Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

2013-05-07

An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

Extended orientational correlation study for molecular liquids containing distorted tetrahedral molecules: Application to methylene halides

NASA Astrophysics Data System (ADS)

Pothoczki, Szilvia; Temleitner, László; Pusztai, László

2010-04-01

The method of Rey [Rey, J. Chem. Phys. 126, 164506 (2007)] for describing how molecules orient toward each other in systems with perfect tetrahedral molecules is extended to the case of distorted tetrahedral molecules of c2v symmetry by means of introducing 28 subgroups. Additionally, the original analysis developed for perfect tetrahedral molecules, based on six groups, is adapted for molecules with imperfect tetrahedral shape. Deriving orientational correlation functions have been complemented with detailed analyses of dipole-dipole correlations. This way, (up to now) the most complete structure determination can be carried out for such molecular systems. In the present work, these calculations have been applied for particle configurations resulting from reverse Monte Carlo computer modeling. These particle arrangements are fully consistent with structure factors from neutron and x-ray diffraction measurements. Here we present a complex structural study for methylene halide (chloride, bromide, and iodide) molecular liquids, as possibly the best representative examples. It has been found that the most frequent orientations of molecules are of the 2:2 type over the entire distance range in these liquids. Focusing on the short range orientation, neighboring molecules turn toward each other with there "H,Y"-"H,Y" (Y: Cl, Br, I) edges, apart from CH2Cl2 where the H,H-H,Cl arrangement is the most frequent. In general, the structure of methylene chloride appears to be different from the structure of the other two liquids.

Ion Transport and Structural Properties of Polymeric Electrolytes and Ionic Liquids from Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Borodin, Oleg

2010-03-01

Molecular dynamics simulations are well suited for exploring electrolyte structure and ion transport mechanisms on the nanometer length scale and the nanosecond time scales. In this presentation we will describe how MD simulations assist in answering fundamental questions about the lithium transport mechanisms in polymeric electrolytes and ionic liquids. In particular, in the first part of the presentation the extent of ion aggregation, the structure of ion aggregates and the lithium cation diffusion in binary polymeric electrolytes will be compared with that of single-ion conducting polymers. In the second part of the talk, the lithium transport in polymeric electrolytes will be compared with that of three ionic liquids ( [emim][FSI] doped with LiFSI , [pyr13][FSI] doped with LiFSI, [emim][BF4] doped with LiBF4). The relation between ionic liquid self-diffusion, conductivity and thermodynamic properties will be discussed in details. A number of correlations between heat of vaporization Hvap, cation-anion binding energy (E+/-), molar volume (Vm), self-diffusion coefficient (D) and ionic conductivity for 29 ionic liquids have been investigated using MD simulations. A significant correlation between D and Hvap has been found, while best correlation was found for -log((D Vm)) vs. Hvap+0.28E+/-. A combination of enthalpy of vaporization and a fraction of the cation-anion binding energy was suggested as a measure of the effective cohesive energy for ionic liquids.

Facile and Reliable in Situ Polymerization of Poly(Ethyl Cyanoacrylate)-Based Polymer Electrolytes toward Flexible Lithium Batteries.

PubMed

Cui, Yanyan; Chai, Jingchao; Du, Huiping; Duan, Yulong; Xie, Guangwen; Liu, Zhihong; Cui, Guanglei

2017-03-15

Polycyanoacrylate is a very promising matrix for polymer electrolyte, which possesses advantages of strong binding and high electrochemical stability owing to the functional nitrile groups. Herein, a facile and reliable in situ polymerization strategy of poly(ethyl cyanoacrylate) (PECA) based gel polymer electrolytes (GPE) via a high efficient anionic polymerization was introduced consisting of PECA and 4 M LiClO 4 in carbonate solvents. The in situ polymerized PECA gel polymer electrolyte achieved an excellent ionic conductivity (2.7 × 10 -3 S cm -1 ) at room temperature, and exhibited a considerable electrochemical stability window up to 4.8 V vs Li/Li + . The LiFePO 4 /PECA-GPE/Li and LiNi 1.5 Mn 0.5 O 4 /PECA-GPE/Li batteries using this in-situ-polymerized GPE delivered stable charge/discharge profiles, considerable rate capability, and excellent cycling performance. These results demonstrated this reliable in situ polymerization process is a very promising strategy to prepare high performance polymer electrolytes for flexible thin-film batteries, micropower lithium batteries, and deformable lithium batteries for special purpose.

Anion binding in the C3v-symmetric cavity of a protonated tripodal amine receptor: potentiometric and single crystal X-ray studies.

PubMed

Bose, Purnandhu; Ravikumar, I; Ghosh, Pradyut

2011-11-07

Tris(2-aminoethyl)amine (tren) based pentafluorophenyl-substituted tripodal L, tris[[(2,3,4,5,6-pentafluorobenzyl)amino]ethyl]amine receptor is synthesized in good yield and characterized by single crystal X-ray diffraction analysis. Detailed structural aspects of binding of different anionic guests toward L in its triprotonated form are examined thoroughly. Crystallographic results show binding of fluoride in the C(3v)-symmetric cavity of [H(3)L](3+) where spherical anion fluoride is in tricoordinated geometry via (N-H)(+)···F interaction in the complex [H(3)L(F)]·[F](2)·2H(2)O, (3). In the case of complexes [H(3)L(OTs)]·[OTs](2), (4) and [H(3)L(OTs)]·[NO(3)]·[OTs], (5), tetrahedral p-toluenesulphonate ion is engulfed in the cavity of [H(3)L](3+) via (N-H)(+)···O interactions. Interestingly, complex [(H(3)L)(2)(SiF(6))]·[BF(4)](4)·CH(3)OH·H(2)O, (6) shows encapsulation of octahedral hexafluorosilicate in the dimeric capsular assembly of two [H(3)L](3+) units, via a number of (N-H)(+)···F interactions. The kinetic parameters of L upon binding with different anions are evaluated using a potentiometric study in solution state. The potentiometric titration experiments in a polar protic methanol/water (1:1 v/v) binary solvent system show high affinity of the receptor toward more basic fluoride and acetate anions, with a lesser affinity for other inorganic anions (e.g., chloride, bromide, nitrate, sulfate, dihydrogenphosphate, and p-toluenesulphonate). © 2011 American Chemical Society

Preparation of a reversed-phase/anion-exchange mixed-mode spherical sorbent by Pickering emulsion polymerization for highly selective solid-phase extraction of acidic pharmaceuticals from wastewater.

PubMed

Huang, Chaonan; Li, Yun; Yang, Jiajia; Peng, Junyu; Jin, Jing; Dhanjai; Wang, Jincheng; Chen, Jiping

2017-10-27

The present work represents a simple and effective preparation of a novel mixed-mode anion-exchange (MAX) sorbent based on porous poly[2-(diethylamino)ethyl methacrylate-divinylbenzene] (poly(DEAEMA-DVB)) spherical particles synthesized by one-step Pickering emulsion polymerization. The poly(DEAEMA-DVB) particles were quaternized with 1,4-butanediol diglycidyl ether (BDDE) followed by triethylamine (TEA) via epoxy-amine reaction to offer strong anion exchange properties. The synthesized MAX sorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, nitrogen adsorption-desorption measurements and elemental analysis. The MAX sorbent possessed regular spherical shape and narrow diameter distribution (15-35μm), a high IEC of 0.54meq/g, with carbon and nitrogen contents of 80.3% and 1.62%, respectively. Compared to poly(DEAEMA-DVB), the MAX sorbent exhibited decreased S BET (390.5 vs. 515.3m 2 g -1 ), pore volume (0.74 vs. 0.85cm 3 g -1 ) and pore size (16.8 vs. 17.3nm). Moreover, changes of N content for producing the MAX sorbent reveal a successful two-step quaternization, which can be highly related to such a high IEC. Finally, the MAX sorbent was successfully evaluated for selective isolation and purification of some selected acidic pharmaceuticals (ketoprofen, KEP; naproxen, NAP; and ibuprofen, IBP) from neutral (hydrocortisone, HYC), basic (carbamazepine, CAZ; amitriptyline, AMT) pharmaceuticals and other interferences in water samples using solid phase extraction (SPE). An efficient analytical method based on the MAX-based mixed-mode SPE coupled with HPLC-UV was developed for highly selective extraction and cleanup of acidic KEP, NAP and IBP in spiked wastewater samples. The developed method exhibited good sensitivity (0.009-0.085μgL -1 limit of detection), satisfactory recoveries (82.1%-105.5%) and repeatabilities (relative standard deviation < 7.9%, n=3). Copyright © 2017 Elsevier B.V. All rights reserved.

A FAST ITERATIVE METHOD FOR SOLVING THE EIKONAL EQUATION ON TETRAHEDRAL DOMAINS

PubMed Central

Fu, Zhisong; Kirby, Robert M.; Whitaker, Ross T.

2014-01-01

Generating numerical solutions to the eikonal equation and its many variations has a broad range of applications in both the natural and computational sciences. Efficient solvers on cutting-edge, parallel architectures require new algorithms that may not be theoretically optimal, but that are designed to allow asynchronous solution updates and have limited memory access patterns. This paper presents a parallel algorithm for solving the eikonal equation on fully unstructured tetrahedral meshes. The method is appropriate for the type of fine-grained parallelism found on modern massively-SIMD architectures such as graphics processors and takes into account the particular constraints and capabilities of these computing platforms. This work builds on previous work for solving these equations on triangle meshes; in this paper we adapt and extend previous two-dimensional strategies to accommodate three-dimensional, unstructured, tetrahedralized domains. These new developments include a local update strategy with data compaction for tetrahedral meshes that provides solutions on both serial and parallel architectures, with a generalization to inhomogeneous, anisotropic speed functions. We also propose two new update schemes, specialized to mitigate the natural data increase observed when moving to three dimensions, and the data structures necessary for efficiently mapping data to parallel SIMD processors in a way that maintains computational density. Finally, we present descriptions of the implementations for a single CPU, as well as multicore CPUs with shared memory and SIMD architectures, with comparative results against state-of-the-art eikonal solvers. PMID:25221418

Exploration of tetrahedral structures in silicate cathodes using a motif-network scheme

PubMed Central

Zhao, Xin; Wu, Shunqing; Lv, Xiaobao; Nguyen, Manh Cuong; Wang, Cai-Zhuang; Lin, Zijing; Zhu, Zi-Zhong; Ho, Kai-Ming

2015-01-01

Using a motif-network search scheme, we studied the tetrahedral structures of the dilithium/disodium transition metal orthosilicates A2MSiO4 with A = Li or Na and M = Mn, Fe or Co. In addition to finding all previously reported structures, we discovered many other different tetrahedral-network-based crystal structures which are highly degenerate in energy. These structures can be classified into structures with 1D, 2D and 3D M-Si-O frameworks. A clear trend of the structural preference in different systems was revealed and possible indicators that affect the structure stabilities were introduced. For the case of Na systems which have been much less investigated in the literature relative to the Li systems, we predicted their ground state structures and found evidence for the existence of new structural motifs. PMID:26497381

Exploration of tetrahedral structures in silicate cathodes using a motif-network scheme

DOE PAGES

Zhao, Xin; Wu, Shunqing; Lv, Xiaobao; ...

2015-10-26

Using a motif-network search scheme, we studied the tetrahedral structures of the dilithium/disodium transition metal orthosilicates A 2MSiO 4 with A = Li or Na and M = Mn, Fe or Co. In addition to finding all previously reported structures, we discovered many other different tetrahedral-network-based crystal structures which are highly degenerate in energy. In addition, these structures can be classified into structures with 1D, 2D and 3D M-Si-O frameworks. A clear trend of the structural preference in different systems was revealed and possible indicators that affect the structure stabilities were introduced. For the case of Na systems which havemore » been much less investigated in the literature relative to the Li systems, we predicted their ground state structures and found evidence for the existence of new structural motifs.« less

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2018-05-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Simultaneous travel time tomography for updating both velocity and reflector geometry in triangular/tetrahedral cell model

NASA Astrophysics Data System (ADS)

Bai, Chao-ying; He, Lei-yu; Li, Xing-wang; Sun, Jia-yu

2017-12-01

To conduct forward and simultaneous inversion in a complex geological model, including an irregular topography (or irregular reflector or velocity anomaly), we in this paper combined our previous multiphase arrival tracking method (referred as triangular shortest-path method, TSPM) in triangular (2D) or tetrahedral (3D) cell model and a linearized inversion solver (referred to as damped minimum norms and constrained least squares problem solved using the conjugate gradient method, DMNCLS-CG) to formulate a simultaneous travel time inversion method for updating both velocity and reflector geometry by using multiphase arrival times. In the triangular/tetrahedral cells, we deduced the partial derivative of velocity variation with respective to the depth change of reflector. The numerical simulation results show that the computational accuracy can be tuned to a high precision in forward modeling and the irregular velocity anomaly and reflector geometry can be accurately captured in the simultaneous inversion, because the triangular/tetrahedral cell can be easily used to stitch the irregular topography or subsurface interface.

Improved Structural Design and CO 2 Capture of Porous Hydroxy-Rich Polymeric Organic Frameworks

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

Kidder, Michelle K.; Earl, Lyndsey D.; de Almeida, Valmor F.

2016-04-16

Polymeric organic frameworks (POFs) are tunable and robust porous materials with potential applications for gas capture, catalysis, and separations technologies. A series of new porous POFs have been synthesized from the reaction of phloroglucinol or resorcinol derivatives with aryl aldehyde precursors. The monomers have various molecular shapes including linear, bent, trigonal, and tetrahedral geometries. Depending on the size and geometric matching of the monomers, the polymers are dominantly microporous with some mesoporous character or they are non-porous. In addition to standard spectroscopic and surface characterization, the materials were screened as adsorbents for carbon dioxide capture at low pressure (0-1 bar).more » The best performing material (POF 1D) has a CO 2 capture capacity of 9.0 wt. % (2.04 mmol g -1) at 298 K and 1 bar which is comparable to other polymeric organic frameworks. Isosteric heats of adsorption for POF 1A, POF 2A, and POF 2B were found to be dependent on the weight percent of CO 2 adsorbed: this suggests there are both chemisorptive and physisorptive components of CO 2 capture by the POFs.« less

A new heterometallic hybrid based on polymeric iodoplumbate and lanthanide metal-carboxylic coordination polycation

NASA Astrophysics Data System (ADS)

Gong, An-Weng; Wu, Hong-Yan; Lian, Zhao-Xun; Dong, Hai-Jun; Li, Hao-Hong; Chen, Zhi-Rong

2013-03-01

A 3-D supramolecular hybrid {[La(EPC)3(H2O)3]2(Pb6I18)}n (EPC+ = N-ethyl-pyridium-4-carboxylate) (1) has been structurally determined, which assume significance for its incorporating lanthanide metal-carboxylic coordination polycation into polymeric iodoplumbate to get heterometallics. 1 consists of 1-D (PbI)n6n- zigzag-like anion chains with lanthanide metalcarboxylic [La(EPC)3(HO)3]n3n+ polycations, which arrange in a criss-cross configuration. C-H⋯I and C-H⋯O hydrogen bonds among inorganic anions and polycations contribute to the formation of a 3-D supramolecular framework. Moreover, the framework displays an absorption edge at 2.46 eV which is comparable to PbI2's absorption edge.

Methods for prismatic/tetrahedral grid generation and adaptation

NASA Technical Reports Server (NTRS)

Kallinderis, Y.

1995-01-01

The present work involves generation of hybrid prismatic/tetrahedral grids for complex 3-D geometries including multi-body domains. The prisms cover the region close to each body's surface, while tetrahedra are created elsewhere. Two developments are presented for hybrid grid generation around complex 3-D geometries. The first is a new octree/advancing front type of method for generation of the tetrahedra of the hybrid mesh. The main feature of the present advancing front tetrahedra generator that is different from previous such methods is that it does not require the creation of a background mesh by the user for the determination of the grid-spacing and stretching parameters. These are determined via an automatically generated octree. The second development is a method for treating the narrow gaps in between different bodies in a multiply-connected domain. This method is applied to a two-element wing case. A High Speed Civil Transport (HSCT) type of aircraft geometry is considered. The generated hybrid grid required only 170 K tetrahedra instead of an estimated two million had a tetrahedral mesh been used in the prisms region as well. A solution adaptive scheme for viscous computations on hybrid grids is also presented. A hybrid grid adaptation scheme that employs both h-refinement and redistribution strategies is developed to provide optimum meshes for viscous flow computations. Grid refinement is a dual adaptation scheme that couples 3-D, isotropic division of tetrahedra and 2-D, directional division of prisms.

Effect of inorganic regenerant properties on pharmaceutical adsorption and desorption performance on polymer anion exchange resin.

PubMed

Zheng, Shaokui; Li, Xiaofeng; Zhang, Xueyu; Wang, Wei; Yuan, Shengliu

2017-09-01

This study investigated the potential effect of four frequently used inorganic regenerant properties (i.e., ionic strength, cation type, anion type, and regeneration solution volume) on the desorption and adsorption performance of 14 pharmaceuticals, belonging to 12 therapeutic classes with different predominant chemical forms and hydrophobicities, using polymeric anion exchange resin (AER)-packed fixed-bed column tests. After preconditioning with NaCl, NaOH, or saline-alkaline (SA) solutions, all resulting mobile counterion types of AERs effectively adsorbed all 14 pharmaceuticals, where the preferential magnitude of OH - -type = Cl -  + OH - -type > Cl - -type. During regeneration, ionic strength (1 M versus 3 M NaCl) had no significant influence on desorption performance for any of the 14 pharmaceuticals, while no regenerant cation (HCl versus NaCl) or anion type (NaCl versus NaOH and SA) achieved higher desorption efficiencies for all pharmaceuticals. A volumetric increase in 1 M or 3 M NaCl solutions significantly improved the desorption efficiencies of most pharmaceuticals, irrespective of ionic strength. The results indicate that regeneration protocols, including regenerant cation type, anion type and volume, should be optimized to improve pharmaceutical removal by AERs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tetrahedral-Mesh Simulation of Turbulent Flows with the Space-Time Conservative Schemes

NASA Technical Reports Server (NTRS)

Chang, Chau-Lyan; Venkatachari, Balaji; Cheng, Gary C.

2015-01-01

Direct numerical simulations of turbulent flows are predominantly carried out using structured, hexahedral meshes despite decades of development in unstructured mesh methods. Tetrahedral meshes offer ease of mesh generation around complex geometries and the potential of an orientation free grid that would provide un-biased small-scale dissipation and more accurate intermediate scale solutions. However, due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for triangular and tetrahedral meshes at the cell interfaces, numerical issues exist when flow discontinuities or stagnation regions are present. The space-time conservative conservation element solution element (CESE) method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to more accurately simulate turbulent flows using unstructured tetrahedral meshes. To pave the way towards accurate simulation of shock/turbulent boundary-layer interaction, a series of wave and shock interaction benchmark problems that increase in complexity, are computed in this paper with triangular/tetrahedral meshes. Preliminary computations for the normal shock/turbulence interactions are carried out with a relatively coarse mesh, by direct numerical simulations standards, in order to assess other effects such as boundary conditions and the necessity of a buffer domain. The results indicate that qualitative agreement with previous studies can be obtained for flows where, strong shocks co-exist along with unsteady waves that display a broad range of scales, with a relatively compact computational domain and less stringent requirements for grid clustering near the shock. With the space-time conservation properties, stable solutions without any spurious wave reflections can be obtained without a need for buffer domains near the outflow/farfield boundaries. Computational results for the

A series of poly(butylimidazolium) ionic liquid functionalized copolymers for anion exchange membranes

NASA Astrophysics Data System (ADS)

Ouadah, Amina; Xu, Hulin; Luo, Tianwei; Gao, Shuitao; Wang, Xing; Fang, Zhou; Jing, Chaojun; Zhu, Changjin

2017-12-01

A new series of ionic liquid functionalized copolymers for anion exchange membranes (AEM) is prepared. Poly(butylvinylimidazolium)(b-VIB) is copolymerized with para-methyl styrene (p-MS) by the radical polymerization formed block copolymers b-VIB/p-MS, which is crosslinked with poly(diphenylether bibenzimidazole) (DPEBI) providing the desired materials b-VIB/p-MS/DPEBI. Structures are characterized via H1NMR, FTIR spectra and elemental analysis. The b-VIB blocks offer the anion conduction function while DPEBI moieties contribute to enhancing other properties. The prepared membranes display chloride conductivity as high as 19.5 mS/cm at 25 °C and 69.2 mS/cm at 100 °C-higher than that of the commercial membrane tokuyuama A201-. Their hydroxide conductivity reaches 35.7 Scm-1 at 25 °C and 73.1 Scm-1 at 100 °C. The membranes showed a linear Arrhenius behavior in the anion conduction, low activation energies and distinguished nanophase separation of hydrophilic/hydrophobic regions by the transmission electron microscopy (TEM) studies. Thermal investigations using TGA and DSC confirm that the membranes are stable up to 250 °C. Particularly, drastically alkaline stability due to no decrease in the hydroxide conductivity after 168 h of treatment with 2M KOH.

Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

DOEpatents

Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

2006-10-10

A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising {Cp*MRR'.sub.n}.sup.+{A}.sup.- wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 C.sub.20 hydrocarbyl, SiR''.sub.3, NR''.sub.2, OR'', SR'', GeR''.sub.3, SnR''.sub.3, and C.dbd.C-containing groups (R''=C.sub.1 C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

DOEpatents

Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

2003-04-08

A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising {Cp*MRR'.sub.n }.sup.+ {A}.sup.- wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 -C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 -C.sub.20 hydrocarbyl, SiR".sub.3, NR".sub.2, OR", SR", GeR".sub.3, and SnR".sub.3 containing groups (R"=C.sub.1 -C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

DOEpatents

Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

2007-01-09

A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising {Cp*MRR'.sub.n}.sup.+{A}.sup.- wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 C.sub.20 hydrocarbyl, SiR''.sub.3, NR''.sub.2, OR'', SR'', GeR''.sub.3, SnR''.sub.3, and C.dbd.C-containing groups (R''=C.sub.1 C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

Cyclopentadienyl-Containing Low-Valent Early Transition Metal Olefin Polymerization Catalysts

DOEpatents

Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

2004-06-08

A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising {Cp*MRR'.sub.n }.sup.+ {A}.sup.- wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 -C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 -C.sub.20 hydrocarbyl, SiR".sub.3, NR".sub.2, OR", SR", GeR".sub.3, SnR".sub.3, and C.dbd.C-containing groups (R"=C.sub.1 -C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

DOEpatents

Marks, Tobin J.; Luo, Lubin; Yoon, Sung Cheol

2003-12-30

A catalyst system useful to polymerize and co-polymerize polar and non-polar olefin monomers is formed by in situ reduction with a reducing agent of a catalyst precursor comprising wherein Cp* is a cyclopentadienyl or substituted cyclopentadienyl moiety; M is an early transition metal; R is a C.sub.1 -C.sub.20 hydrocarbyl; R' are independently selected from hydride, C.sub.1 -C.sub.20 hydrocarbyl, SiR".sub.3, NR".sub.2, OR", SR", GeR".sub.3, SnR".sub.3, and C.dbd.C containing groups (R".dbd.C.sub.1 -C.sub.10 hydrocarbyl); n is an integer selected to balance the oxidation state of M; and A is a suitable non-coordinating anionic cocatalyst or precursor. This catalyst system may form stereoregular olefin polymers including syndiotactic polymers of styrene and methylmethacrylate and isotactic copolymers of polar and nonpolar olefin monomers such as methylmethacrylate and styrene.

Nucleation and growth kinetics of electrodeposited sulfate-doped polypyrrole: determination of the diffusion coefficient of SO(4)(2-) in the polymeric membrane.

PubMed

Licona-Sánchez, T de J; Alvarez-Romero, G A; Mendoza-Huizar, L H; Galán-Vidal, C A; Palomar-Pardavé, M; Romero-Romo, M; Herrera-Hernández, H; Uruchurtu, J; Juárez-García, J M

2010-08-05

A kinetic study for the electrosynthesis of polypyrrole (Ppy) doped with SO(4)(2-) ions is presented. Ppy films were electrochemically polymerized onto a graphite-epoxy resin electrode. Experimental current density transients (j-t) were obtained for three different potentiometric behaviors: anionic, cationic, and a combination. Theoretical models were used to fit the experimental j-t data to determine the nucleation and growth processes controlling the polymer synthesis. It was encountered that, in all cases, pyrrole electropolimerization involves two concomitant processes, namely, a Ppy diffusion limited multiple 3D nucleation and growth and pyrrole electro-oxidation on the growing surface of the Ppy nuclei. SEM analysis of the electrodes surfaces reveals that Ppy deposition occurred over most of the electrode surface by multiple nucleation of hemispheres, as the theoretical model used for the analysis of the current transients required. Hemispherical particles formed the polymeric film displaying different sizes. The order for the particle size was as follows: anionic > anionic-cationic > cationic. These results are congruent with those obtained by theoretical analysis of the corresponding current transients. Analysis of the impedance measurements recorded on the anionic Ppy film, immersed in an aqueous solution with different sulfate ion concentrations evidenced that SO(4)(2-) ions diffuse through the Ppy film provoking a decrease of its electrical resistance and an increase of its dielectric constant. From the Warburg impedance coefficient, the sulfate coefficient of diffusion in the Ppy film was 1.38 x 10(-9) cm(2) s(-1).

Two-fold interpenetrating btc based cobaltous coordination polymer: A promising catalyst for solvent free oxidation of 1-hexene

NASA Astrophysics Data System (ADS)

Bora, Sanchay J.; Paul, Rima; Nandi, Mithun; Bhattacharyya, Pradip K.

2017-12-01

This work describes the synthesis of a new 2-D coordination polymer (CP), [Co3(btc)2(dmp)8]n (btc = 1,3,5-benzenetricarboxylate and dmp = 3,5-dimethylpyrazole) and its catalytic activity towards the oxidation reaction of 1-hexene to form oxygenated compounds under solvent free condition. Structural analysis reveals that Co(II) cations in this polymeric compound are linked by btc3- anions with alternate tetrahedral/octahedral coordination forming a two-fold interpenetrated 3-connected hcb underlying net. Electronic spectrum of the cobaltous polymer has been calculated using TDDFT/B3LYP method for making the appropriate assignments of electronic transitions. Catalytic results show good conversions of the starting material to oxygenated products with high selectivities for 1,2-epoxyhexane and 1-hexanal.

Computing Normal Shock-Isotropic Turbulence Interaction With Tetrahedral Meshes and the Space-Time CESE Method

NASA Astrophysics Data System (ADS)

Venkatachari, Balaji Shankar; Chang, Chau-Lyan

2016-11-01

The focus of this study is scale-resolving simulations of the canonical normal shock- isotropic turbulence interaction using unstructured tetrahedral meshes and the space-time conservation element solution element (CESE) method. Despite decades of development in unstructured mesh methods and its potential benefits of ease of mesh generation around complex geometries and mesh adaptation, direct numerical or large-eddy simulations of turbulent flows are predominantly carried out using structured hexahedral meshes. This is due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for unstructured meshes that can resolve multiple physical scales and flow discontinuities simultaneously. The CESE method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to accurately simulate turbulent flows using tetrahedral meshes. As part of the study, various regimes of the shock-turbulence interaction (wrinkled and broken shock regimes) will be investigated along with a study on how adaptive refinement of tetrahedral meshes benefits this problem. The research funding for this paper has been provided by Revolutionary Computational Aerosciences (RCA) subproject under the NASA Transformative Aeronautics Concepts Program (TACP).

Correlating morphology to dc conductivity in polymerized ionic liquids

NASA Astrophysics Data System (ADS)

Iacob, Ciprian; Matusmoto, Atsushi; Inoue, Tadashi; Runt, James

Polymerized ionic liquids (PILs) combine the attractive mechanical characteristics of polymers and unique physico-chemical properties of low molecular weight ionic liquids in the same material. PILs have shown remarkable advantages when employed in electrochemical devices such as dye-sensitized solar cells and lithium batteries, among others. Understanding their ionic transport mechanism is the key for designing highly conductive PILs. In the current study, the correlation between morphology and charge transport in two homologous series of PILs with systematic variation of the alkyl chain length and anions is investigated using broadband dielectric spectroscopy, rheology, differential scanning calorimetry and X-ray scattering. As the alkyl chain length increases, the backbone-to-backbone separation increases, and dc-conductivity consequently decreases. The cations dominate structural dynamics since they are attached to the polymer chains, while the anions are smaller and more mobile ionic species thereby controlling the ionic conductivity. Further interpretation of decoupling of dc conductivity from the segmental relaxation enabled the correlation between polymer morphology and dc conductivity. Supported by the National Science Foundation, Polymers Program.

Ultraslow Phase Transitions in an Anion-Anion Hydrogen-Bonded Ionic Liquid.

PubMed

Faria, Luiz F O; Lima, Thamires A; Ferreira, Fabio F; Ribeiro, Mauro C C

2018-02-15

A Raman spectroscopy study of 1-ethyl-3-methylimidazolium hydrogen sulfate, [C 2 C 1 im][HSO 4 ], as a function of temperature, has been performed to reveal the role played by anion-anion hydrogen bond on the phase transitions of this ionic liquid. Anion-anion hydrogen bonding implies high viscosity, good glass-forming ability, and also moderate fragility of [C 2 C 1 im][HSO 4 ] in comparison with other ionic liquids. Heating [C 2 C 1 im][HSO 4 ] from the glassy phase results in cold crystallization at ∼245 K. A solid-solid transition (crystal I → crystal II) is barely discernible in calorimetric measurements at typical heating rates, but it is clearly revealed by Raman spectroscopy and X-ray diffraction. Raman spectroscopy indicates that crystal I has extended ([HSO 4 ] - ) n chains of hydrogen-bonded anions but crystal II has not. Raman spectra recorded at isothermal condition show the ultraslow dynamics of cold crystallization, solid-solid transition, and continuous melting of [C 2 C 1 im][HSO 4 ]. A brief comparison is also provided between [C 2 C 1 im][HSO 4 ] and [C 4 C 1 im][HSO 4 ], as Raman spectroscopy shows that the latter does not form the crystalline phase with extended anion-anion chains.

Four-Coordinate Iron(II) Diaryl Compounds with Monodentate N-Heterocyclic Carbene Ligation: Synthesis, Characterization, and Their Tetrahedral-Square Planar Isomerization in Solution.

PubMed

Liu, Yuesheng; Luo, Lun; Xiao, Jie; Wang, Lei; Song, You; Qu, Jingping; Luo, Yi; Deng, Liang

2015-05-18

The salt elimination reactions of (IPr2Me2)2FeCl2 (IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with the corresponding aryl Grignard reagents afford [(IPr2Me2)2FeAr2] (Ar = Ph, 3; C6H4-p-Me, 4; C6H4-p-(t)Bu, 5; C6H3-3,5-(CF3)2, 6) in good yields. X-ray crystallographic studies revealed the presence of both tetrahedral and trans square planar isomers for 3 and 6 and the tetrahedral structures for 4 and 5. Magnetic susceptibility and (57)Fe Mössbauer spectrum measurements on the solid samples indicated the high-spin (S = 2) and intermediate-spin (S = 1) nature of the tetrahedral and square planar structures, respectively. Solution property studies, including solution magnetic susceptibility measurement, variable-temperature (1)H and (19)F NMR, and absorption spectroscopy, on 3-6, as well as an (57)Fe Mössbauer spectrum study on a frozen tetrahydrofuran solution of tetrahedral [(IPr2Me2)2(57)FePh2] suggest the coexistence of tetrahedral and trans square planar structures in solution phase. Density functional theory calculations on (IPr2Me2)2FePh2 disclosed that the tetrahedral and trans square planar isomers are close in energy and that the geometry isomerization can occur by spin-change-coupled geometric transformation on four-coordinate iron(II) center.

Platelet adhesion on phosphorus-incorporated tetrahedral amorphous carbon films

NASA Astrophysics Data System (ADS)

Liu, Aiping; Zhu, Jiaqi; Liu, Meng; Dai, Zhifei; Han, Xiao; Han, Jiecai

2008-11-01

The haemocompatibility of phosphorus-incorporated tetrahedral amorphous carbon (ta-C:P) films, synthesized by filtered cathodic vacuum arc technique with PH 3 as the dopant source, was assessed by in vitro platelet adhesion tests. Results based on scanning electron microscopy and contact angle measurements reveal that phosphorus incorporation improves the wettability and blood compatibility of ta-C film. Our studies may provide a novel approach for the design and synthesis of doped ta-C films to repel platelet adhesion and reduce thrombosis risk.

Influence of the type of oxidant on anion exchange properties of fibrous Cladophora cellulose/polypyrrole composites.

PubMed

Razaq, Aamir; Mihranyan, Albert; Welch, Ken; Nyholm, Leif; Strømme, Maria

2009-01-15

The electrochemically controlled anion absorption properties of a novel large surface area composite paper material composed of polypyrrole (PPy) and cellulose derived from Cladophora sp. algae, synthesized with two oxidizing agents, iron(III) chloride and phosphomolybdic acid (PMo), were analyzed in four different electrolytes containing anions (i.e., chloride, aspartate, glutamate, and p-toluenesulfonate) of varying size.The composites were characterized with scanning and transmission electron microscopy, N2 gas adsorption,and conductivity measurements. The potential-controlled ion exchange properties of the materials were studied by cyclic voltammetry and chronoamperometry at varying potentials. The surface area and conductivity of the iron(III) chloride synthesized sample were 58.8 m2/g and 0.65 S/cm, respectively, while the corresponding values for the PMo synthesized sample were 31.3 m2/g and 0.12 S/cm. The number of absorbed ions per sample mass was found to be larger for the iron(III) chloride synthesized sample than for the PMo synthesized one in all four electrolytes. Although the largest extraction yields were obtained in the presence of the smallest anion (i.e., chloride) for both samples, the relative degree of extraction for the largest ions (i.e., glutamate and p-toluenesulfonate) was higher for the PMo sample. This clearly shows that it is possible to increase the extraction yield of large anions by carrying out the PPy polymerization in the presence of large anions. The results likewise show that high ion exchange capacities, as well as extraction and desorption rates, can be obtained for large anions with high surface area composites coated with relatively thin layers of PPy.

Methods for the synthesis and polymerization of .alpha.,.alpha.'-dihalo-p-xylenes

DOEpatents

Ferraris, John P.; Neef, Charles J.

2002-07-30

The present invention describes an improved method for the polymerization of .alpha.,.alpha.-dihalo-p-xylene's such as the .alpha.,.alpha.'-dihalo-2-methoxy-5-(2-ethylhexyloxy)-xylene's. The procedure for synthesis is based on the specific order of addition of reagents and the use of an anionic initiator that allows control of the molecular weight of the polymer. The molecular weight control allows processability of the polymer which is important for its utility in applications including in light-emitting-diodes, field effect transistors and photovoltaic devices.

Anion-Anion Bonding and Topology in Ternary Iridium Seleno-Stannides.

PubMed

Trump, Benjamin A; Tutmaher, Jake A; McQueen, Tyrel M

2015-12-21

The synthesis and physical properties of two new and one known Ir-Sn-Se compound are reported. Their crystal structures are elucidated with transmission electron microscopy and powder X-ray diffraction. IrSn0.45Se1.55 is a pyrite phase which consists of tilted corner-sharing IrX6 octahedra with randomly distributed (Sn-Se)(4-) and (Se-Se)(2-) dimers. Ir2Sn3Se3 is a known trigonally distorted skutterudite that consists of cooperatively tilted corner-sharing IrSn3Se3 octahedra with ordered (Sn-Se)2(4-) tetramers. Ir2SnSe5 is a layered, distorted β-MnO2 (pyrolusite) structure consisting of a double IrSe6 octrahedral row, corner sharing in the a direction and edge sharing in the b direction. This distorted pyrolusite contains (Se-Se)(2-) dimers and Se(2-) anions, and each double row is "capped" with a (Sn-Se)n polymeric chain. Resistivity, specific heat, and magnetization measurements show that all three have insulating and diamagnetic behavior, indicative of low-spin 5d(6) Ir(3+). Electronic structure calculations on Ir2Sn3Se3 show a single, spherical, nonspin-orbit split valence band and suggest that Ir2Sn3Se3 is topologically nontrivial under tensile strain due to inversion of Ir-d and Se-p states.

Anions in Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven B.

2011-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2016-05-01

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

Simultaneous Enhancements of Conductivity and Stability for Anion Exchange Membranes (AEMs) through Precise Structure Design

PubMed Central

Ran, Jin; Wu, Liang; Wei, Bing; Chen, Yaoyao; Xu, Tongwen

2014-01-01

Polymeric materials as anion exchange membranes (AEMs) play an essential role in the field of energy and environment. The achievement of high performance AEMs by the precise manipulation of macromolecular architecture remains a daunting challenge. Herein, we firstly report a novel rod-coil graft copolymer AEM, possessing rigid hydrophobic main chains and soft hydrophilic graft chains. The low graft density, which can alleviate the adverse influences of ioinc graft chains on the main chains, was obtained by using the living polymerization technique. Consequently, the grafted ionic groups which result in the degradation of polymer backbone was decreased to a small degree. Moreover, the relatively long graft chains induced the nanophase separation between the hydrophobic polymer chains and hydrophilic graft chains, which creates a convinient pathway for high hydroxide ion mobility. Such an accurate molecular design simultaneously improves the hydroxide ion conductivity and alkaline stability as well as dimensional stability. PMID:25255843

Simultaneous Enhancements of Conductivity and Stability for Anion Exchange Membranes (AEMs) through Precise Structure Design

NASA Astrophysics Data System (ADS)

Ran, Jin; Wu, Liang; Wei, Bing; Chen, Yaoyao; Xu, Tongwen

2014-09-01

Polymeric materials as anion exchange membranes (AEMs) play an essential role in the field of energy and environment. The achievement of high performance AEMs by the precise manipulation of macromolecular architecture remains a daunting challenge. Herein, we firstly report a novel rod-coil graft copolymer AEM, possessing rigid hydrophobic main chains and soft hydrophilic graft chains. The low graft density, which can alleviate the adverse influences of ioinc graft chains on the main chains, was obtained by using the living polymerization technique. Consequently, the grafted ionic groups which result in the degradation of polymer backbone was decreased to a small degree. Moreover, the relatively long graft chains induced the nanophase separation between the hydrophobic polymer chains and hydrophilic graft chains, which creates a convinient pathway for high hydroxide ion mobility. Such an accurate molecular design simultaneously improves the hydroxide ion conductivity and alkaline stability as well as dimensional stability.

Isatinphenylsemicarbazones as efficient colorimetric sensors for fluoride and acetate anions - anions induce tautomerism.

PubMed

Jakusová, Klaudia; Donovalová, Jana; Cigáň, Marek; Gáplovský, Martin; Garaj, Vladimír; Gáplovský, Anton

2014-04-05

The anion induced tautomerism of isatin-3-4-phenyl(semicarbazone) derivatives is studied herein. The interaction of F(-), AcO(-), H2PO4(-), Br(-) or HSO4(-) anions with E and Z isomers of isatin-3-4-phenyl(semicarbazone) and N-methylisatin-3-4-phenyl(semicarbazone) as sensors influences the tautomeric equilibrium of these sensors in the liquid phase. This tautomeric equilibrium is affected by (1) the inter- and intra-molecular interactions' modulation of isatinphenylsemicarbazone molecules due to the anion induced change in the solvation shell of receptor molecules and (2) the sensor-anion interaction with the urea hydrogens. The acid-base properties of anions and the difference in sensor structure influence the equilibrium ratio of the individual tautomeric forms. Here, the tautomeric equilibrium changes were indicated by "naked-eye" experiment, UV-VIS spectral and (1)H NMR titration, resulting in confirmation that appropriate selection of experimental conditions leads to a high degree of sensor selectivity for some investigated anions. Sensors' E and Z isomers differ in sensitivity, selectivity and sensing mechanism. Detection of F(-) or CH3COO(-) anions at high weakly basic anions' excess is possible. Copyright © 2014 Elsevier B.V. All rights reserved.

Automated Tetrahedral Mesh Generation for CFD Analysis of Aircraft in Conceptual Design

NASA Technical Reports Server (NTRS)

Ordaz, Irian; Li, Wu; Campbell, Richard L.

2014-01-01

The paper introduces an automation process of generating a tetrahedral mesh for computational fluid dynamics (CFD) analysis of aircraft configurations in early conceptual design. The method was developed for CFD-based sonic boom analysis of supersonic configurations, but can be applied to aerodynamic analysis of aircraft configurations in any flight regime.

Fostering Teacher Development to a Tetrahedral Orientation in the Teaching of Chemistry

ERIC Educational Resources Information Center

Lewthwaite, Brian; Wiebe, Rick

2011-01-01

This paper reports on the initial outcomes from the end of the fourth year of a 5 year research and professional development project to improve chemistry teaching among three cohorts of chemistry teachers in Manitoba, Canada. The project responds to a new curriculum introduction advocating a tetrahedral orientation (Mahaffy, "Journal of…

Ionically fixed polymeric nanoparticles as a novel drug carrier.

PubMed

Lee, Sa-Won; Chang, Dong-Hoon; Shim, Myung-Seop; Kim, Bong-Oh; Kim, Sun-Ok; Seo, Min-Hyo

2007-08-01

In this study, we have prepared a novel polymeric drug delivery system comprised of ionically fixed polymeric nanoparticles (IFPN) and investigated their potential as a drug carrier for the passive targeting of water-insoluble anticancer drugs. For this purpose, the physicochemical characteristics of the IFPN were investigated by comparing them with conventional polymeric micelles. IFPN containing paclitaxel were prepared and evaluated for in vitro stability and in vivo pharmacokinetics. The IFPN were successfully fabricated using a monomethoxypolyethylene glycol-polylactide (mPEG-PLA) diblock copolymer and a sodium salt of D,L-poly(lactic acid) (D,L-PLACOONa) upon the addition of CaCl2. The transmittance of the IFPN solution was much lower than that of a polymeric micelle solution at the same polymer concentration implicating an increase in the number of appreciable particles. The particle size of the IFPN was approximately 20 approximately 30 nm which is in the range of particle sizes that facilitate sterile filtration using a membrane filter. The IFPN also have a regular spherical shape with a narrow size distribution. The zeta potential of the IFPN was almost neutral, similar to that of the polymeric micelles. In contrast, mixed micelles with a combination of mPEG-PLA and D,L-PLACOONa prior to the addition of Ca2+ showed a negative charge (-17 mV), possibly due to the carboxyl anion of polylactic acid exposed on the surface of the micelles. The IFPN formulation was highly kinetically stable in aqueous medium compared to the polymeric micelle formulation. The molecular weight of D,L-PLACOONa in the IFPN and the mPEG-PLA/D,L-PLACOONa molar ratio had a great influence upon the kinetic stability of the IFPN. Pharmacokinetic studies showed that the area under the concentration vs time curve (AUC) of IFPN in blood was statistically higher (about two times) when compared with that of Cremophor EL-based formulation (Taxol equivalent) or polymeric micelle formulation

A bicontinuous tetrahedral structure in a liquid-crystalline lipid

NASA Astrophysics Data System (ADS)

Longley, William; McIntosh, Thomas J.

1983-06-01

The structure of most lipid-water phases can be visualized as an ordered distribution of two liquid media, water and hydrocarbons, separated by a continuous surface covered by the polar groups of the lipid molecules1. In the cubic phases in particular, rod-like elements are linked into three-dimensional networks1,2. Two of these phases (space groups Ia3d and Pn3m) contain two such three-dimensional networks mutually inter-woven and unconnected. Under the constraints of energy minimization3, the interface between the components in certain of these `porous fluids' may well resemble one of the periodic minimal surface structures of the type described mathematically by Schwarz4,5. A structure of this sort has been proposed for the viscous isotropic (cubic) form of glycerol monooleate (GMO) by Larsson et al.6 who suggested that the X-ray diagrams of Lindblom et al.7 indicated a body-centred crystal structure in which lipid bilayers might be arranged as in Schwarz's octahedral surface4. We have now found that at high water contents, a primitive cubic lattice better fits the X-ray evidence with the material in the crystal arranged in a tetrahedral way. The lipid appears to form a single bilayer, continuous in three dimensions, separating two continuous interlinked networks of water. Each of the water networks has the symmetry of the diamond crystal structure and the bilayer lies in the space between them following a surface resembling Schwarz's tetrahedral surface4.

Tetrahedral and polyhedral mesh evaluation for cerebral hemodynamic simulation--a comparison.

PubMed

Spiegel, Martin; Redel, Thomas; Zhang, Y; Struffert, Tobias; Hornegger, Joachim; Grossman, Robert G; Doerfler, Arnd; Karmonik, Christof

2009-01-01

Computational fluid dynamic (CFD) based on patient-specific medical imaging data has found widespread use for visualizing and quantifying hemodynamics in cerebrovascular disease such as cerebral aneurysms or stenotic vessels. This paper focuses on optimizing mesh parameters for CFD simulation of cerebral aneurysms. Valid blood flow simulations strongly depend on the mesh quality. Meshes with a coarse spatial resolution may lead to an inaccurate flow pattern. Meshes with a large number of elements will result in unnecessarily high computation time which is undesirable should CFD be used for planning in the interventional setting. Most CFD simulations reported for these vascular pathologies have used tetrahedral meshes. We illustrate the use of polyhedral volume elements in comparison to tetrahedral meshing on two different geometries, a sidewall aneurysm of the internal carotid artery and a basilar bifurcation aneurysm. The spatial mesh resolution ranges between 5,119 and 228,118 volume elements. The evaluation of the different meshes was based on the wall shear stress previously identified as a one possible parameter for assessing aneurysm growth. Polyhedral meshes showed better accuracy, lower memory demand, shorter computational speed and faster convergence behavior (on average 369 iterations less).

Ionic Liquids as a Medium for Ionic Chain Polymerizations: An Environmentally Responsible Approach to Macromolecular Synthesis with Controlled Architecture

DTIC Science & Technology

2004-09-16

published in non peer-reviewed journals: 1. Gross, SM, Hamilton JL. "Polymer Gels for Use in Lithium Polymer Batteries", Nebraska Academy of Science...a process for the anionic polymerization of styrene and methyl methacrylate in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ...Current polymer electrolyte composites used for these applications typically comprise polyethers with ethylene carbonate solvents containing lithium

Chemically Realistic Tetrahedral Lattice Models for Polymer Chains: Application to Polyethylene Oxide.

PubMed

Dietschreit, Johannes C B; Diestler, Dennis J; Knapp, Ernst W

2016-05-10

To speed up the generation of an ensemble of poly(ethylene oxide) (PEO) polymer chains in solution, a tetrahedral lattice model possessing the appropriate bond angles is used. The distance between noncovalently bonded atoms is maintained at realistic values by generating chains with an enhanced degree of self-avoidance by a very efficient Monte Carlo (MC) algorithm. Potential energy parameters characterizing this lattice model are adjusted so as to mimic realistic PEO polymer chains in water simulated by molecular dynamics (MD), which serves as a benchmark. The MD data show that PEO chains have a fractal dimension of about two, in contrast to self-avoiding walk lattice models, which exhibit the fractal dimension of 1.7. The potential energy accounts for a mild hydrophobic effect (HYEF) of PEO and for a proper setting of the distribution between trans and gauche conformers. The potential energy parameters are determined by matching the Flory radius, the radius of gyration, and the fraction of trans torsion angles in the chain. A gratifying result is the excellent agreement of the pair distribution function and the angular correlation for the lattice model with the benchmark distribution. The lattice model allows for the precise computation of the torsional entropy of the chain. The generation of polymer conformations of the adjusted lattice model is at least 2 orders of magnitude more efficient than MD simulations of the PEO chain in explicit water. This method of generating chain conformations on a tetrahedral lattice can also be applied to other types of polymers with appropriate adjustment of the potential energy function. The efficient MC algorithm for generating chain conformations on a tetrahedral lattice is available for download at https://github.com/Roulattice/Roulattice .

3D level set methods for evolving fronts on tetrahedral meshes with adaptive mesh refinement

DOE PAGES

Morgan, Nathaniel Ray; Waltz, Jacob I.

2017-03-02

The level set method is commonly used to model dynamically evolving fronts and interfaces. In this work, we present new methods for evolving fronts with a specified velocity field or in the surface normal direction on 3D unstructured tetrahedral meshes with adaptive mesh refinement (AMR). The level set field is located at the nodes of the tetrahedral cells and is evolved using new upwind discretizations of Hamilton–Jacobi equations combined with a Runge–Kutta method for temporal integration. The level set field is periodically reinitialized to a signed distance function using an iterative approach with a new upwind gradient. We discuss themore » details of these level set and reinitialization methods. Results from a range of numerical test problems are presented.« less

The important role of tetrahedral Ti{sup 4+} sites in the phase transformation and photocatalytic activity of TiO{sub 2} nanocomposites.

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

Li, G.; Dimitrijevic, N. M.; Chen, L.

Highly photoactive, tetrahedral Ti{sup 4+} sites can be created, other than in zeolite cavities and on silica substrate, in mixed-phase TiO{sub 2} nanocomposites. The tetrahedral Ti{sup 4+} species was shown to be an intermediate formed during the thermally driven phase transformation from anatase to rutile.

Evolution of stacking fault tetrahedral and work hardening effect in copper single crystals

NASA Astrophysics Data System (ADS)

Liu, Hai Tao; Zhu, Xiu Fu; Sun, Ya Zhou; Xie, Wen Kun

2017-11-01

Stacking fault tetrahedral (SFT), generated in machining of copper single crystal as one type of subsurface defects, has significant influence on the performance of workpiece. In this study, molecular dynamics (MD) simulation is used to investigate the evolution of stacking fault tetrahedral in nano-cutting of copper single crystal. The result shows that SFT is nucleated at the intersection of differently oriented stacking fault (SF) planes and SFT evolves from the preform only containing incomplete surfaces into a solid defect. The evolution of SFT contains several stress fluctuations until the complete formation. Nano-indentation simulation is then employed on the machined workpiece from nano-cutting, through which the interaction between SFT and later-formed dislocations in subsurface is studied. In the meanwhile, force-depth curves obtained from nano-indentation on pristine and machined workpieces are compared to analyze the mechanical properties. By simulation of nano-cutting and nano-indentation, it is verified that SFT is a reason of the work hardening effect.

Investigation of negative-parity states in Dy 156 : Search for evidence of tetrahedral symmetry

DOE PAGES

Hartley, D. J.; Riedinger, L. L.; Janssens, R. V. F.; ...

2017-01-01

An experiment populating low/medium-spin states in 156Dy was performed to investigate the possibility of tetrahedral symmetry in this nucleus. In particular, focus was placed on the low-spin, negative-parity states since recent theoretical studies suggest that these may be good candidates for this high-rank symmetry. The states were produced in the 148Nd( 12C,4 n) reaction and the Gammasphere array was utilized to detect the emitted rays. B(E 2) /B(E1) ratios of transition probabilities from the low-spin, negative-parity bands were determined and used to interpret whether these structures are best associated with tetrahedral symmetry or, as previously assigned, to octupole vibrations. Additionally,more » several other negative-parity structures were observed to higher spin and two new sequences were established« less

Investigation of negative-parity states in Dy 156 : Search for evidence of tetrahedral symmetry

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

Hartley, D. J.; Riedinger, L. L.; Janssens, R. V. F.

2017-01-01

An experiment populating low/medium-spin states in 156 Dy was performed to investigate the possibility of tetrahedral symmetry in this nucleus. In particular, focus was placed on the low-spin, negative-parity states since recent theoretical studies suggest that these may be good candidates for this high-rank symmetry. The states were produced in the 148 Nd ( 12 C , 4 n ) reaction and the Gammasphere array was utilized to detect the emitted γ rays. B ( E 2 ) / B ( E 1 ) ratios of transition probabilities from the low-spin, negative-parity bands were determined and used to interpret whethermore » these structures are best associated with tetrahedral symmetry or, as previously assigned, to octupole vibrations. In addition, several other negative-parity structures were observed to higher spin and two new sequences were established.« less

Cause and Cure - Deterioration in Accuracy of CFD Simulations With Use of High-Aspect-Ratio Triangular Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Chang, Sin-Chung; Chang, Chau-Lyan; Venkatachari, Balaji Shankar

2017-01-01

Traditionally high-aspect ratio triangular/tetrahedral meshes are avoided by CFD re-searchers in the vicinity of a solid wall, as it is known to reduce the accuracy of gradient computations in those regions and also cause numerical instability. Although for certain complex geometries, the use of high-aspect ratio triangular/tetrahedral elements in the vicinity of a solid wall can be replaced by quadrilateral/prismatic elements, ability to use triangular/tetrahedral elements in such regions without any degradation in accuracy can be beneficial from a mesh generation point of view. The benefits also carry over to numerical frameworks such as the space-time conservation element and solution element (CESE), where triangular/tetrahedral elements are the mandatory building blocks. With the requirement of the CESE method in mind, a rigorous mathematical framework that clearly identities the reason behind the difficulties in use of such high-aspect ratio triangular/tetrahedral elements is presented here. As will be shown, it turns out that the degree of accuracy deterioration of gradient computation involving a triangular element is hinged on the value of its shape factor Gamma def = sq sin Alpha1 + sq sin Alpha2 + sq sin Alpha3, where Alpha1; Alpha2 and Alpha3 are the internal angles of the element. In fact, it is shown that the degree of accuracy deterioration increases monotonically as the value of Gamma decreases monotonically from its maximal value 9/4 (attained by an equilateral triangle only) to a value much less than 1 (associated with a highly obtuse triangle). By taking advantage of the fact that a high-aspect ratio triangle is not necessarily highly obtuse, and in fact it can have a shape factor whose value is close to the maximal value 9/4, a potential solution to avoid accuracy deterioration of gradient computation associated with a high-aspect ratio triangular grid is given. Also a brief discussion on the extension of the current mathematical framework to the

Click polymerization for the synthesis of reduction-responsive polymeric prodrug

NASA Astrophysics Data System (ADS)

Zhang, Xiaojin; Wang, Hongquan; Dai, Yu

2018-05-01

Click polymerization is a powerful polymerization technique for the construction of new macromolecules with well-defined structures and multifaceted functionalities. Here, we synthesize reduction-responsive polymeric prodrug PEG- b-(PSS- g-MTX)- b-PEG containing disulfide bonds and pendant methotrexate (MTX) via two-step click polymerization followed by conjugating MTX to pendant hydroxyl. MTX content in polymeric prodrug is 13.5%. Polymeric prodrug is able to form polymeric micelles by self-assembly in aqueous solution. Polymeric micelles are spherical nanoparticles with tens of nanometers in size. Of note, polymeric micelles are reduction-responsive due to disulfide bonds in the backbone of PEG- b-(PSS- g-MTX)- b-PEG and could release pendant drugs in the presence of the reducing agents such as dl-dithiothreitol (DTT).

Photochemical removal of aniline in aqueous solutions: switching from photocatalytic degradation to photo-enhanced polymerization recovery.

PubMed

Tang, Heqing; Li, Jing; Bie, Yeqiang; Zhu, Lihua; Zou, Jing

2010-03-15

Organic pollutants may be treated by either a degradation process or a recovery process in the view point of sustainable chemistry. Photocatalytic removal of aniline was investigated in aqueous solutions. It was found that the photocatalytic oxidation of aniline resulted in its degradation or polymerization, depending on its concentration. Hence a new treatment strategy was proposed in combination of photocatalytic degradation and polymerization, where the polymerization was in fact a recovery process. When aniline concentration was as low as 0.1 mmol L(-1), it was possible to photocatalytically degrade aniline, which could be further enhanced by increasing solution pH, modifying TiO(2) surface with the addition of anions, or coupling with the photoreduction of added oxidants. When aniline concentration was increased to about 1 mmol L(-1), the photocatalytic oxidation was observed to yield the polymerization of aniline, leading to nanocomposites of polyaniline (PAN) and TiO(2). Alternatively, the photo-enhanced chemical polymerization of aniline at higher concentrations (>or=50 mmol L(-1)) in the presence of chemical oxidants produced PAN nanostructures. The conversion of pollutant aniline to valuable PAN nanostructures or nano-PAN/TiO(2) composites is suggestive for possible applications in the treatment of aniline wastewaters as a sustainable environmental protection measure. (c) 2009 Elsevier B.V. All rights reserved.

Tetrahedral Hohlraum Visualization and Pointings

NASA Astrophysics Data System (ADS)

Klare, K. A.; Wallace, J. M.; Drake, D.

1997-11-01

In designing experiments for Omega, the tetrahedral hohlraum (a sphere with four holes) can make full use of all 60 beams. There are some complications: the beams must clear the laser entrance hole (LEH), must miss a central capsule, absolutely must not go out the other LEHs, and should distribute in the interior of the hohlraum to maximize the uniformity of irradiation on the capsule while keeping reasonable laser spot sizes. We created a 15-offset coordinate system with which an IDL program computes clearances, writes a file for QuickDraw 3D (QD3D) visualization, and writes input for the viewfactor code RAYNA IV. Visualizing and adjusting the parameters by eye gave more reliable results than computer optimization. QD3D images permitted quick live rotations to determine offsets. The clearances obtained insured safe operation and good physics. The viewfactor code computes the initial irradiation of the hohlraum and capsule or of a uniform hohlraum source with the loss through the four LEHs and shows a high degree of uniformity with both, better for lasers because this deposits more energy near the LEHs to compensate for the holes.

Tetra-butyl-ammonium tetra-kis-(trimethyl-silanolato-κO)ferrate(III).

PubMed

Hay, Michael; Staples, Richard; Lee, Andre

2012-09-01

In the title salt, (C(16)H(36)N)[Fe(C(3)H(9)OSi)(4)], the cation contains a central N atom bonded to four n-butyl alkyl groups in a tetra-hedral arrangement, while the anion contains a central Fe(III) atom tetra-hedrally coordinated by four trimethyl-silanolate ligands.

Anion transport and supramolecular medicinal chemistry

DOE PAGES

Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto

2017-04-05

New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.

Anion transport and supramolecular medicinal chemistry

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

Gale, Philip A.; Davis, Jeffery T.; Quesada, Roberto

New approaches to the transmembrane transport of anions are discussed in this review. Advances in the design of small molecule anion carriers are reviewed in addition to advances in the design of synthetic anion channels. The application of anion transporters to the potential future treatment of disease is discussed in the context of recent findings on the selectivity of anion transporters.

MurD ligase from E. coli: Tetrahedral intermediate formation study by hybrid quantum mechanical/molecular mechanical replica path method.

PubMed

Perdih, Andrej; Hodoscek, Milan; Solmajer, Tom

2009-02-15

MurD (UDP-N-acetylmuramoyl-L-alanine:D-glutamate ligase), a three-domain bacterial protein, catalyses a highly specific incorporation of D-glutamate to the cytoplasmic intermediate UDP-N-acetyl-muramoyl-L-alanine (UMA) utilizing ATP hydrolysis to ADP and P(i). This reaction is part of a biosynthetic path yielding bacterial peptidoglycan. On the basis of structural studies of MurD complexes, a stepwise catalytic mechanism was proposed that commences with a formation of the acyl-phosphate intermediate, followed by a nucleophilic attack of D-glutamate that, through the formation of a tetrahedral reaction intermediate and subsequent phosphate dissociation, affords the final product, UDP-N-acetyl-muramoyl-L-alanine-D-glutamate (UMAG). A hybrid quantum mechanical/molecular mechanical (QM/MM) molecular modeling approach was utilized, combining the B3LYP QM level of theory with empirical force field simulations to evaluate three possible reaction pathways leading to tetrahedral intermediate formation. Geometries of the starting structures based on crystallographic experimental data and tetrahedral intermediates were carefully examined together with a role of crucial amino acids and water molecules. The replica path method was used to generate the reaction pathways between the starting structures and the corresponding tetrahedral reaction intermediates, offering direct comparisons with a sequential kinetic mechanism and the available structural data for this enzyme. The acquired knowledge represents new and valuable information to assist in the ongoing efforts leading toward novel inhibitors of MurD as potential antibacterial drugs. (c) 2008 Wiley-Liss, Inc.

Encapsulation of curcumin in polymeric nanoparticles for antimicrobial Photodynamic Therapy

PubMed Central

Trigo Gutierrez, Jeffersson Krishan; Zanatta, Gabriela Cristina; Ortega, Ana Laura Mira; Balastegui, Maria Isabella Cuba; Sanitá, Paula Volpato; Pavarina, Ana Cláudia; Barbugli, Paula Aboud

2017-01-01

Curcumin (CUR) has been used as photosensitizer in antimicrobial Photodynamic Therapy (aPDT). However its poor water solubility, instability, and scarce bioavalibility hinder its in vivo application. The aim of this study was to synthesize curcumin in polymeric nanoparticles (NP) and to evaluate their antimicrobial photodynamic effect and cytoxicity. CUR in anionic and cationic NP was synthesized using polylactic acid and dextran sulfate by the nanoprecipitation method. For cationic NP, cetyltrimethylammonium bromide was added. CUR-NP were characterized by physicochemical properties, photodegradation, encapsulation efficiency and release of curcumin from nanoparticles. CUR-NP was compared with free CUR in 10% dimethyl sulfoxide (DMSO) as a photosensitizer for aPDT against planktonic and biofilms (mono-, dual- and triple-species) cultures of Streptococcus mutans, Candida albicans and Methicillin-Resistant Staphylococcus aureus. The cytotoxicity effect of formulations was evaluated on keratinocytes. Data were analysed by parametric (ANOVA) and non-parametric (Kruskal-Wallis) tests (α = 0.05). CUR-NP showed alteration in the physicochemical properties along time, photodegradation similar to free curcumin, encapsulation efficiency up to 67%, and 96% of release after 48h. After aPDT planktonic cultures showed reductions from 0.78 log10 to complete eradication, while biofilms showed no antimicrobial effect or reductions up to 4.44 log10. Anionic CUR-NP showed reduced photoinactivation of biofilms. Cationic CUR-NP showed microbicidal effect even in absence of light. Anionic formulations showed no cytotoxic effect compared with free CUR and cationic CUR-NP and NP. The synthesized formulations improved the water solubility of CUR, showed higher antimicrobial photodynamic effect for planktonic cultures than for biofilms, and the encapsulation of CUR in anionic NP reduced the cytotoxicity of 10% DMSO used for free CUR. PMID:29107978

Artificial intelligence approach to planning the robotic assembly of large tetrahedral truss structures

NASA Technical Reports Server (NTRS)

Homemdemello, Luiz S.

1992-01-01

An assembly planner for tetrahedral truss structures is presented. To overcome the difficulties due to the large number of parts, the planner exploits the simplicity and uniformity of the shapes of the parts and the regularity of their interconnection. The planning automation is based on the computational formalism known as production system. The global data base consists of a hexagonal grid representation of the truss structure. This representation captures the regularity of tetrahedral truss structures and their multiple hierarchies. It maps into quadratic grids and can be implemented in a computer by using a two-dimensional array data structure. By maintaining the multiple hierarchies explicitly in the model, the choice of a particular hierarchy is only made when needed, thus allowing a more informed decision. Furthermore, testing the preconditions of the production rules is simple because the patterned way in which the struts are interconnected is incorporated into the topology of the hexagonal grid. A directed graph representation of assembly sequences allows the use of both graph search and backtracking control strategies.

Polyoxometal cations within polyoxometalate anions. Seven-coordinate uranium and zirconium heteroatom groups in [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14-

NASA Astrophysics Data System (ADS)

Gaunt, Andrew J.; May, Iain; Collison, David; Travis Holman, K.; Pope, Michael T.

2003-08-01

Two new composite polyoxotungstate anions with unprecedented structural features, [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- (1) and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14- (2) contain polyoxo-uranium and -zirconium clusters as bridging units. The anions are synthesized by reaction of Na12[P2W15O56] with solutions of UO2(NO3)2 and ZrCl4. The structure of 1 in the sodium salt contains four [P2W15O56]12- anions assembled into an overall tetrahedral cluster by means of trigonal bridging groups formed by three equatorial-edge-shared UO7 pentagonal bipyramids. The structure of anion 2 consists of a centrosymmetric assembly of two [P2W16O59]12- anions linked by a {Zr4O2(OH)2(H2O)4}10+ cluster. Both complexes in solution yield the expected two-line 31P-NMR spectra with chemical shifts of -2.95, -13.58 and -6.45, -13.69 ppm, respectively.

High-pressure NaCl-phase of tetrahedral compounds

NASA Astrophysics Data System (ADS)

Soma, T.; -Matsuo Kagaya, H.

1984-04-01

The phase transition of tetrahedral compounds such as GaP, InP, ZnS, ZnSe, ZnTe and CdTe under pressure is investigated from the electronic theory of solids by using our recently presented binding force, which includes mainly covalent interactions in the pseudopotential formalism and partially ionic interactions. The partially ionic forces give the important contributions to the high-pressure phase and stabilize the NaCl-type structure for the high-pressure phase of these compounds, although not reported for GaP experimentally. Then, the numerical results such as the transition pressure, the volume-discontinuity, the transition heat with respect to the pressure-induced phase transition from the zinc-blende-to the NaCl-type lattice are obtained theoretically.

Lymphatic trafficking kinetics and near-infrared imaging using star polymer architectures with controlled anionic character

PubMed Central

Bagby, Taryn R.; Cai, Shuang; Duan, Shaofeng; Yang, Qiuhong; Thati, Sharadvi; Berkland, Cory; Aires, Daniel J.; Forrest, M. Laird

2015-01-01

Targeted lymphatic delivery of nanoparticles for drug delivery and imaging is primarily dependent on size and charge. Prior studies have observed increased lymphatic uptake and retentions of over 48 hrs for negatively charged particles compared to neutral and positively charged particles. We have developed new polymeric materials that extend retention over a more pharmaceutically relevant 7-day period. We used whole body fluorescence imaging to observe in mice the lymphatic trafficking of a series of anionic star poly-(6-O-methacryloyl-D-galactose) polymer-NIR dye (IR820) conjugates. The anionic charge of polymers was increased by modifying galactose moieties in the star polymers with succinic anhydride. Increasing anionic nature was associated with enhanced lymphatic uptake up to a zeta potential of ca. -40 mV; further negative charge did not affect lymphatic uptake. Compared to the 20% acid-conjugate, the 40 to 90% acid-star-polymer conjugates exhibited a 2.5- to 3.5-fold increase in lymphatic uptake in both the popliteal and iliac nodes. The polymer conjugates exhibited node half-lives of 2 to 20 hrs in the popliteal nodes and 19 to 114 hrs in the deeper iliac nodes. These polymer conjugates can deliver drugs or imaging agents with rapid lymphatic uptake and prolonged deep-nodal retention; thus they may provide a useful vehicle for sustained intralymphatic drug delivery with low toxicity. PMID:22546180

Polymeric micellar pH-sensitive drug delivery system for doxorubicin.

PubMed

Hrubý, Martin; Konák, Cestmír; Ulbrich, Karel

2005-03-02

A novel polymeric micellar pH-sensitive system for delivery of doxorubicin (DOX) is described. Polymeric micelles were prepared by self-assembly of amphiphilic diblock copolymers in aqueous solutions. The copolymers consist of a biocompatible hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic block containing covalently bound anthracycline antibiotic DOX. The starting block copolymers poly(ethylene oxide)-block-poly(allyl glycidyl ether) (PEO-PAGE) with a very narrow molecular weight distribution (Mw/Mn ca. 1.05) were prepared by anionic ring opening polymerization using sodium salt of poly(ethylene oxide) monomethyl ether as macroinitiator and allyl glycidyl ether as functional monomer. The copolymers were covalently modified via reactive double bonds by the addition of methyl sulfanylacetate. The resulting ester subsequently reacted with hydrazine hydrate yielding polymer hydrazide. The hydrazide was coupled with DOX yielding pH-sensitive hydrazone bonds between the drug and carrier. The resulting conjugate containing ca. 3 wt.% DOX forms micelles with Rh(a)=104 nm in phosphate-buffered saline. After incubation in buffers at 37 degrees C DOX was released faster at pH 5.0 (close to pH in endosomes; 43% DOX released within 24 h) than at pH 7.4 (pH of blood plasma; 16% DOX released within 24 h). Cleavage of hydrazone bonds between DOX and carrier continues even after plateau in the DOX release from micelles incubated in aqueous solutions is reached.

Nuclear tetrahedral symmetry: possibly present throughout the periodic table.

PubMed

Dudek, J; Goźdź, A; Schunck, N; Miśkiewicz, M

2002-06-24

More than half a century after the fundamental, spherical shell structure in nuclei had been established, theoretical predictions indicated that the shell gaps comparable or even stronger than those at spherical shapes may exist. Group-theoretical analysis supported by realistic mean-field calculations indicate that the corresponding nuclei are characterized by the TD(d) ("double-tetrahedral") symmetry group. Strong shell-gap structure is enhanced by the existence of the four-dimensional irreducible representations of TD(d); it can be seen as a geometrical effect that does not depend on a particular realization of the mean field. Possibilities of discovering the TD(d) symmetry in experiment are discussed.

Effects of Cationic Pendant Groups on Ionic Conductivity for Anion Exchange Membranes: Structure Conductivity Relationships

NASA Astrophysics Data System (ADS)

Kim, Sojeong; Choi, Soo-Hyung; Lee, Won Bo

Anion exchange membranes(AEMs) have been widely studied due to their various applications, especially for Fuel cells. Previous proton exchange membranes(PEMs), such as Nafions® have better conductivity than AEMs so far. However, technical limitations such as slow electrode kinetics, carbon monoxide (CO) poisoning of metal catalysts, high methanol crossover and high cost of Pt-based catalyst detered further usages. AEMs have advantages to supplement its drawbacks. AEMs are environmentally friendly and cost-efficient. Based on the well-defined block copolymer, self-assembled morphology is expected to have some relationship with its ionic conductivity. Recently AEMs based on various cations, including ammonium, phosphonium, guanidinium, imidazolium, metal cation, and benzimidazolium cations have been developed and extensively studied with the aim to prepare high- performance AEMs. But more fundamental approach, such as relationships between nanostructure and conductivity is needed. We use well-defined block copolymer Poly(styrene-block-isoprene) as a backbone which is synthesized by anionic polymerization. Then we graft various cationic functional groups and analysis the relation between morphology and conductivity. Theoretical and computational soft matter lab.

Bipyrrole-Strapped Calix[4]pyrroles: Strong Anion Receptors That Extract the Sulfate Anion

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

Kim, Sung Kuk; Lee, Juhoon; Williams, Neil J

Cage-type calix[4]pyrroles 2 and 3 bearing two additional pyrrole groups on the strap have been synthesized. Compared with the parent calix[4]pyrrole (1), they were found to exhibit remarkably enhanced affinities for anions, including the sulfate anion (TBA+ salts), in organic media (CD2Cl2). This increase is ascribed to participation of the bipyrrole units in anion binding. Receptors 2 and 3 extract the hydrophilic sulfate anion (as the methyltrialkyl(C8-10)ammonium (A336+) salt)) from aqueous media into a chloroform phase with significantly improved efficiency (>10-fold relative to calix[4]pyrrole 1). These two receptors also solubilize into chloroform the otherwise insoluble sulfate salt, (TMA)2SO4 (tetramethylammonium sulfate).

Cause and Cure-Deterioration in Accuracy of CFD Simulations with Use of High-Aspect-Ratio Triangular/Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Chang, Sin-Chung; Chang, Chau-Lyan; Venkatachari, Balaji

2017-01-01

In the multi-dimensional space-time conservation element and solution element16 (CESE) method, triangles and tetrahedral mesh elements turn out to be the most natural building blocks for 2D and 3D spatial grids, respectively. As such, the CESE method is naturally compatible with the simplest 2D and 3D unstructured grids and thus can be easily applied to solve problems with complex geometries. However, because (a) accurate solution of a high-Reynolds number flow field near a solid wall requires that the grid intervals along the direction normal to the wall be much finer than those in a direction parallel to the wall and, as such, the use of grid cells with extremely high aspect ratio (103 to 106) may become mandatory, and (b) unlike quadrilateral hexahedral grids, it is well-known that accuracy of gradient computations involving triangular tetrahedral grids tends to deteriorate rapidly as cell aspect ratio increases. As a result, the use of triangular tetrahedral grid cells near a solid wall has long been deemed impractical by CFD researchers. In view of (a) the critical role played by triangular tetrahedral grids in the CESE development, and (b) the importance of accurate resolution of high-Reynolds number flow field near a solid wall, as will be presented in the main paper, a comprehensive and rigorous mathematical framework that clearly identifies the reasons behind the accuracy deterioration as described above has been developed for the 2D case involving triangular cells. By avoiding the pitfalls identified by the 2D framework, and its 3D extension, it has been shown numerically.

ADMET Polymerization Activities of Electrochemically Reduced W-Based Active Species for Ge- and Sn-Containing Dienes

NASA Astrophysics Data System (ADS)

Imamoglu, Yavuz; Aydogdu, Cemil; Karabulut, Solmaz; Düz, Bülent

In the last 20 years metal atom-containing polymers have become important classes of polymers [1]. Properties like high thermic stability, electric, and photo conductometry make them very interesting for producing films, fibers, and coating [2]. Many of these compounds can be synthesized by conventional methods [3]. For producing metal-containing polymers anionic, cationic, and radicalic polymerizations were used [4-6]. Metal-containing polymers were also synthesized via acyclic diene metathesis (ADMET) polymerization that is facilitated by Schrock’s molybdenum alkylidene, or Grubbs’ ruthenium carbene catalyst [7-9]. In 1979, Gilet and coworkers succeeded in synthesizing metathetically active species from electrochemical reduction of WCl6 and MoCl5 [10,11]. In the light of these works, we have showed that electrochemically generated tungsten-based active species (WCl6-e--Al-CH2Cl2) catalyzes various metathesis-related reactions [12-16].

Gallium based low-interaction anions

DOEpatents

King, Wayne A.; Kubas, Gregory J.

2000-01-01

The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

Nanoscale Origin of the Dichotimous Viscosity-Pressure Behavior in Silicate Melts

NASA Astrophysics Data System (ADS)

Wang, Y.; Sakamaki, T.; Skiner, L.; Jing, Z.; Yu, T.; Kono, Y.; Park, C.; Shen, G.; Rivers, M. L.; Sutton, S. R.

2013-12-01

A defining characteristic of silicate melts is the degree of polymerization (tetrahedral connectivity), which dictates physical properties such as viscosity and density. While viscosity of depolymerized silicate melts increases with pressure consistent with free volume theory, isothermal viscosity of polymerized melts decreases with pressure up to ~3 - 5 GPa, above which it turns over to normal (positive) pressure dependence. We conducted high-pressure melt structure studies along the jadeite (Jd) - diopside (Di) join, using a Paris-Edinburgh Press at the HPCAT beamline 16-BM-B and measured Jd melt density using a DIA type apparatus based on x-ray absorption at GSECARS beamline 13-BM-D. Structures of polymerized (Jd and Jd50Di50) and depolymerized (Di) melts show distinct responses to pressure. For Jd melt, T-O, T-T bond lengths (where T denotes tetrahedrally coordinated Al and Si) and T-O-T angle all exhibit rapid, sometimes non-linear decrease with increasing pressure to ~3 GPa. For Di melt, these parameters vary linearly with pressure and change very little. Molecular dynamics calculations, constrained by the x-ray structural data, were employed to examine details of structural evolution in polymerized and depolymerized liquids. A structural model is developed to link structural evolution to changes in melt properties, such as density and viscosity, with pressure. We show that the pressure of the viscosity turnover corresponds to the tetrahedral packing limit, below which the structure is compressed through tightening of the inter-tetrahedral bond angle, resulting in continual breakup of tetrahedral connectivity and viscosity decrease. Above the turnover pressure, Si and Al coordination increases to allow further packing, with increasing viscosity. This structural response prescribes the distribution of melt viscosity and density with depth, and may be the main controlling factor for magma transport rates in terrestrial planetary interiors.

Electromagnetic forward modelling for realistic Earth models using unstructured tetrahedral meshes and a meshfree approach

NASA Astrophysics Data System (ADS)

Farquharson, C.; Long, J.; Lu, X.; Lelievre, P. G.

2017-12-01

Real-life geology is complex, and so, even when allowing for the diffusive, low resolution nature of geophysical electromagnetic methods, we need Earth models that can accurately represent this complexity when modelling and inverting electromagnetic data. This is particularly the case for the scales, detail and conductivity contrasts involved in mineral and hydrocarbon exploration and development, but also for the larger scale of lithospheric studies. Unstructured tetrahedral meshes provide a flexible means of discretizing a general, arbitrary Earth model. This is important when wanting to integrate a geophysical Earth model with a geological Earth model parameterized in terms of surfaces. Finite-element and finite-volume methods can be derived for computing the electric and magnetic fields in a model parameterized using an unstructured tetrahedral mesh. A number of such variants have been proposed and have proven successful. However, the efficiency and accuracy of these methods can be affected by the "quality" of the tetrahedral discretization, that is, how many of the tetrahedral cells in the mesh are long, narrow and pointy. This is particularly the case if one wants to use an iterative technique to solve the resulting linear system of equations. One approach to deal with this issue is to develop sophisticated model and mesh building and manipulation capabilities in order to ensure that any mesh built from geological information is of sufficient quality for the electromagnetic modelling. Another approach is to investigate other methods of synthesizing the electromagnetic fields. One such example is a "meshfree" approach in which the electromagnetic fields are synthesized using a mesh that is distinct from the mesh used to parameterized the Earth model. There are then two meshes, one describing the Earth model and one used for the numerical mathematics of computing the fields. This means that there are no longer any quality requirements on the model mesh, which

Quaternized polymeric microgels as metal free catalyst for H2 production from the methanolysis of sodium borohydride

NASA Astrophysics Data System (ADS)

Sahiner, Nurettin; Sengel, Sultan Butun

2016-12-01

Polymeric microgels derived from tris(2-amino ethyl)amine (TAEA) and glycerol diglycidyl ether as p(TAEA-co-GDE) via microemulsion polymerization techniques are protonated by 0.5 M HCl treatment as p(TAEA-co-GDE)-HCl). These microgels are then exposed to anion exchange reactions with differ ionic liquid forming salts, such as potassium thiocyanate (PTC), sodium dicyanamide (SDCA), ammonium hexafluorophosphate (AHFP), and sodium tetrafluoroborate (STFB) in aqueous medium for the preparation of p(TAEA-co-GDE) based ionic liquid colloidal microgels. These anions exchanged p(TAEA-co-GDE) ionic liquid colloids (ILCs) are directly used as catalyst for hydrogen (H2) generation from the methanol solution of sodium borohydride (NaBH4). Various parameters affecting the H2 production rate such as the catalyst types, NaBH4 amount, and the temperature are investigated. It is found that the methanolysis of NaBH4 catalyzed by p(TAEA-co-GDE)-HCl obeys the first order reaction kinetic. The activation energy, enthalpy and entropy of the protonated p(TAEA-co-GDE) microgels are calculated and found as the 30.37 kJ mol-1, 27.96 kJ mol-1, and -148.08 J mol-1 K-1, respectively. Furthermore, the hydrogen generation rate of 3018 mL min-1 g-1 catalyzed by p(TAEA-co-GDE)-HCl catalyst is attained.

Atomic Scale Picture of the Ion Conduction Mechanism in Tetrahedral Network of Lanthanum Barium Gallate

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

Jalarvo, Niina H; Gourdon, Olivier; Bi, Zhonghe

2013-01-01

Combined experimental study of impedance spectroscopy, neutron powder diffraction and quasielastic neutron scattering was performed to shed light into the atomic scale ion migration processes in proton and oxide ion conductor; La0.8Ba1.2GaO3.9 . This material consist of tetrahedral GaO4 units, which are rather flexible and rocking motion of these units promotes the ionic migration process. The oxide ion (vacancy) conduction takes place on channels along c axis, involving a single elementary step, which occurs between adjacent tetrahedron (inter-tetrahedron jump). The proton conduction mechanism consists of intra-tetrahedron and inter-tetrahedron elementary processes. The intra-tetrahedron proton transport is the rate-limiting process, with activationmore » energy of 0.44 eV. The rocking motion of the GaO4 tetrahedron aids the inter-tetrahedral proton transport, which has the activation energy of 0.068 eV.« less

Geometric multigrid to accelerate the solution of the quasi-static electric field problem by tetrahedral finite elements.

PubMed

Hollaus, K; Weiss, B; Magele, Ch; Hutten, H

2004-02-01

The acceleration of the solution of the quasi-static electric field problem considering anisotropic complex conductivity simulated by tetrahedral finite elements of first order is investigated by geometric multigrid.

Novel double-confined polymeric ionic liquids as sorbents for solid-phase microextraction with enhanced stability and durability in high-ionic-strength solution.

PubMed

Feng, Juanjuan; Sun, Min; Xu, Lili; Wang, Shuai; Liu, Xia; Jiang, Shengxiang

2012-12-14

Because of the occurrence of ion exchange between high-ionic-strength solution and anions of polymeric ionic liquids (PILs), PILs based solid-phase microextraction (SPME) fibers were rarely used in direct immersion mode to high-salt-added samples. In this work, a novel double-confined PIL sorbent was prepared by co-polymerization of cation and anion of 1-vinyl-3-octylimidzaolium p-styrenesulfonate (VOIm(+)SS(-)). The poly(VOIm(+)-SS(-)) was chemically bonded onto functionalized stainless steel wire via surface radical chain-transfer reaction. Stability of poly(VOIm(+)-SS(-)) in high-ionic-strength solution was investigated and compared with that of poly(1-vinyl-3-octylimidzaolium benzenesulfonate) (poly(VOIm(+)BS(-))) by elemental analysis of sulfur element, and results turned out that the poly(VOIm(+)-SS(-)) was more stable. Coupled to gas chromatography (GC), the poly(VOIm(+)-SS(-)) fiber was used to extract three sorts of compounds including anilines, phenols and phthalate esters in aqueous solution. The as-established method showed good linearity, low detection limits, and acceptable repeatability. The direct immersion SPME-GC method was applied to determine the model phthalate esters in bottled mineral water. The determination results were satisfactory. Copyright © 2012 Elsevier B.V. All rights reserved.

Highly Dynamic Anion-Quadrupole Networks in Proteins.

PubMed

Kapoor, Karan; Duff, Michael R; Upadhyay, Amit; Bucci, Joel C; Saxton, Arnold M; Hinde, Robert J; Howell, Elizabeth E; Baudry, Jerome

2016-11-01

The dynamics of anion-quadrupole (or anion-π) interactions formed between negatively charged (Asp/Glu) and aromatic (Phe) side chains are for the first time computationally characterized in RmlC (Protein Data Bank entry 1EP0 ), a homodimeric epimerase. Empirical force field-based molecular dynamics simulations predict anion-quadrupole pairs and triplets (anion-anion-π and anion-π-π) are formed by the protein during the simulated trajectory, which suggests that the anion-quadrupole interactions may provide a significant contribution to the overall stability of the protein, with an average of -1.6 kcal/mol per pair. Some anion-π interactions are predicted to form during the trajectory, extending the number of anion-quadrupole interactions beyond those predicted from crystal structure analysis. At the same time, some anion-π pairs observed in the crystal structure exhibit marginal stability. Overall, most anion-π interactions alternate between an "on" state, with significantly stabilizing energies, and an "off" state, with marginal or null stabilizing energies. The way proteins possibly compensate for transient loss of anion-quadrupole interactions is characterized in the RmlC aspartate 84-phenylalanine 112 anion-quadrupole pair observed in the crystal structure. A double-mutant cycle analysis of the thermal stability suggests a possible loss of anion-π interactions compensated by variations of hydration of the residues and formation of compensating electrostatic interactions. These results suggest that near-planar anion-quadrupole pairs can exist, sometimes transiently, which may play a role in maintaining the structural stability and function of the protein, in an otherwise very dynamic interplay of a nonbonded interaction network as well as solvent effects.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes.

PubMed

Akhmetshina, Alsu A; Davletbaeva, Ilsiya M; Grebenschikova, Ekaterina S; Sazanova, Tatyana S; Petukhov, Anton N; Atlaskin, Artem A; Razov, Evgeny N; Zaripov, Ilnaz I; Martins, Carla F; Neves, Luísa A; Vorotyntsev, Ilya V

2015-12-30

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf₂N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N₂, NH₃, H₂S, and CO₂ gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF₆] and [emim][Tf₂N]. The modification of SILMs by nanosize silica particles leads to an increase of NH₃ separation relatively to CO₂ or H₂S.

Malleability and optimization of tetrahedral metamorphic element for deployable truss antenna reflector

NASA Astrophysics Data System (ADS)

Hu, Fei; Song, Yanping; Huang, Zhirong; Liu, Wenlan; Li, Wan

2018-05-01

The tetrahedral elements that make up the large deployable reflector (LDR) are a kind of metamorphic element, which belongs to the multi-loop coupling mechanism. Firstly, the method of combining topology with screw theory is put forward. The parametric model and the constrained matrix are established to analyze the malleability of 3RR-3RRR tetrahedral element. Secondly, the kinematics expression of each motion pair is deduced by the relationship between the velocity and the motion spinor. Finally, the configuration of the metamorphic element is optimized to make the parabolic antenna fully folded, so that the antenna can meet the maximum folding ratio. The results show that the 3RR-3RRR element is a single-degree of freedom (DOF) mechanism. What's more, three new configurations 3RS-3RRR, 3SR-3RRR and 3UU-3RRR are obtained on the basis of optimization. In particular, it proves to be that the LDR which consists of the 3RS-3RRR metamorphic element can achieve the maximum folding ratio. This paper provides a theoretical basis for the computer-aided design of the truss antennas, which has an excellent applicability in the field of aerospace and other multi-loop coupling mechanism.

Hydration of a Large Anionic Charge Distribution - Naphthalene-Water Cluster Anions

NASA Astrophysics Data System (ADS)

Weber, J. Mathias; Adams, Christopher L.

2010-06-01

We report the infrared spectra of anionic clusters of naphthalene with up to three water molecules. Comparison of the experimental infrared spectra with theoretically predicted spectra from quantum chemistry calculations allow conclusions regarding the structures of the clusters under study. The first water molecule forms two hydrogen bonds with the π electron system of the naphthalene moiety. Subsequent water ligands interact with both the naphthalene and the other water ligands to form hydrogen bonded networks, similar to other hydrated anion clusters. Naphthalene-water anion clusters illustrate how water interacts with negative charge delocalized over a large π electron system. The clusters are interesting model systems that are discussed in the context of wetting of graphene surfaces and polyaromatic hydrocarbons.

Tetrahedral aminopeptidase: a novel large protease complex from archaea

PubMed Central

Franzetti, B.; Schoehn, G.; Hernandez, J.-F.; Jaquinod, M.; Ruigrok, R.W.H.; Zaccai, G.

2002-01-01

A dodecameric protease complex with a tetrahedral shape (TET) was isolated from Haloarcula marismortui, a salt-loving archaeon. The 42 kDa monomers in the complex are homologous to metal-binding, bacterial aminopeptidases. TET has a broad aminopeptidase activity and can process peptides of up to 30–35 amino acids in length. TET has a central cavity that is accessible through four narrow channels (<17 Å wide) and through four wider channels (21 Å wide). This architecture is different from that of all the proteolytic complexes described to date that are made up by rings or barrels with a single central channel and only two openings. PMID:11980710

Anionic pH-Sensitive Lipoplexes.

PubMed

Mignet, Nathalie; Scherman, Daniel

2017-01-01

To provide long circulating nanoparticles able to carry a gene to tumors, we have designed anionic pegylated lipoplexes which are pH sensitive. Anionic pegylated lipoplexes have been prepared from the combined formulation of cationic lipoplexes and pegylated anionic liposomes. The neutralization of the particle surface charge as a function of the pH was monitored by light scattering in order to determine the ratio between anionic and cationic lipids that would give pH sensitive complexes. This ratio has been optimized to form particles sensitive to pH change in the range 5.5-6.5. Compaction of DNA into these newly formed anionic complexes is checked by DNA accessibility to picogreen. The transfection efficiency and pH sensitive property of these formulations has been shown in vitro using bafilomycin, a vacuolar H + -ATPase inhibitor.

Anion-π Catalysis on Fullerenes.

PubMed

López-Andarias, Javier; Frontera, Antonio; Matile, Stefan

2017-09-27

Anion-π interactions on fullerenes are about as poorly explored as the use of fullerenes in catalysis. However, strong exchange-correlation contributions and the localized π holes on their surface promise unique selectivities. To elaborate on this promise, tertiary amines are attached nearby. Dependent on their positioning, the resulting stabilization of anionic transition states on fullerenes is shown to accelerate disfavored enolate addition and exo Diels-Alder reactions enantioselectively. The found selectivities are consistent with computational simulations, particularly concerning the discrimination of differently planarized and charge-delocalized enolate tautomers by anion-π interactions. Enolate-π interactions on fullerenes are much shorter than standard π-π interactions and anion-π interactions on planar surfaces, and alternative cation-π interactions are not observed. These findings open new perspectives with regard to anion-π interactions in general and the use of carbon allotropes in catalysis.

Radical-Mediated Enzymatic Polymerizations

PubMed Central

Zavada, Scott R.; Battsengel, Tsatsral; Scott, Timothy F.

2016-01-01

Polymerization reactions are commonly effected by exposing monomer formulations to some initiation stimulus such as elevated temperature, light, or a chemical reactant. Increasingly, these polymerization reactions are mediated by enzymes―catalytic proteins―owing to their reaction efficiency under mild conditions as well as their environmental friendliness. The utilization of enzymes, particularly oxidases and peroxidases, for generating radicals via reduction-oxidation mechanisms is especially common for initiating radical-mediated polymerization reactions, including vinyl chain-growth polymerization, atom transfer radical polymerization, thiol–ene step-growth polymerization, and polymerization via oxidative coupling. While enzyme-mediated polymerization is useful for the production of materials intended for subsequent use, it is especially well-suited for in situ polymerizations, where the polymer is formed in the place where it will be utilized. Such polymerizations are especially useful for biomedical adhesives and for sensing applications. PMID:26848652

The effect of varying linker length on ion-transport properties in polymeric ionic liquids

NASA Astrophysics Data System (ADS)

Keith, Jordan; Mogurampelly, Santosh; Wheatle, Bill; Ganesan, Venkat

We report results of atomistic molecular dynamics simulations on polymerized 1-butyl-3-(n-alkyl)imidazolium ionic liquids with PF6- counterions. Consistent with experimental observations, we observe that the mobility of the PF6- ions increases with increasing n-alkyl linker length. Analysis of our results suggests that the motion of PF6- ions is driven by intermolecular ion hopping between chains, which in turn is influenced by ion-pair coordination numbers and intermolecular ionic separation distances. With increasing linker length, we observe 1) the anions coordinating less closely with cations and 2) intermolecular hopping distances decreasing.

Synthesis and Catalytic Activity of Pt Monolayer on Pd Tetrahedral Nanocrystals with CO-adsorption-induced Removal of Surfactants

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

Gong K.; Vukmirovic M.B.; Ma C.

2011-11-01

We synthesized the Pt monolayer shell-Pd tetrahedral core electrocatalysts that are notable for their high activity and stable performance. A small number of low-coordination sites and defects, and high content of the (1 1 1)-oriented facets on Pd tetrahedron makes them a suitable support for a Pt monolayer to obtain an active O{sub 2} reduction reaction (ORR) electrocatalyst. The surfactants, used to control size and shape of Pd tetrahedral nanoparticles, are difficult to remove and cause adverse effects on the ORR. We describe a simple and noninvasive method to synthesize high-purity tetrahedral Pd nanocrystals (TH Pd) by combining a hydrothermalmore » route and CO adsorption-induced removal of surfactants. Poly(vinylpyrrolidone) (PVP), used as a protecting and reducing agent in hydrothermal reactions, is strongly bonded to the surface of the resulting nanocrystals. We demonstrate that PVP was displaced efficiently by adsorbed CO. A clean surface was achieved upon CO stripping at a high potential (1.0 V vs RHE). It played a decisive role in improving the activity of the Pt monolayer/TH Pd electrocatalyst for the ORR. Furthermore, the results demonstrate a versatile method for removal of surfactants from various nanoparticles that severely limited their applications.« less

Photo-responsive polymeric micelles.

PubMed

Huang, Yu; Dong, Ruijiao; Zhu, Xinyuan; Yan, Deyue

2014-09-07

Photo-responsive polymeric micelles have received increasing attention in both academic and industrial fields due to their efficient photo-sensitive nature and unique nanostructure. In view of the photo-reaction mechanism, photo-responsive polymeric micelles can be divided into five major types: (1) photoisomerization polymeric micelles, (2) photo-induced rearrangement polymeric micelles, (3) photocleavage polymeric micelles, (4) photo-induced crosslinkable polymeric micelles, and (5) photo-induced energy conversion polymeric micelles. This review highlights the recent advances of photo-responsive polymeric micelles, including the design, synthesis and applications in various biomedical fields. Especially, the influence of different photo-reaction mechanisms on the morphology, structure and properties of the polymeric micelles is emphasized. Finally, the possible future directions and perspectives in this emerging area are briefly discussed.

Toxicological assessment of Anionic Methacrylate Copolymer: I. Characterization, bioavailability and genotoxicity.

PubMed

Eisele, Johanna; Haynes, Geoff; Kreuzer, Knut; Hall, Caroline

2016-12-01

Anionic Methacrylate Copolymer (AMC) is a fully polymerized copolymer used in the pharmaceutical industry as an enteric/delayed-release coating to permit the pH-dependent release of active ingredients in the gastrointestinal tract from oral dosage forms. This function is of potential use for food supplements. Oral administration of radiolabeled copolymer to rats resulted in the detection of chemically unchanged copolymer in the feces, with negligible absorption (<0.1%). AMC is therefore determined not to be bioavailable. Within a genotoxicity test battery AMC did not show any evidence of genotoxicity in bacteria and mammalian cells. Furthermore, no genotoxic effects occurred in vivo within a micronucleus test. There would therefore appear to be no safety concerns under intended conditions of oral use for the discussed toxicological endpoints. Copyright © 2016 Elsevier Inc. All rights reserved.

Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films

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

Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon

Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which aremore » anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.« less

POLYMERIZATION OF /cap alpha/-METHYLSTYRENE BY ELECTRON IRRADIATION (in German)

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

Braun, D.; Heufer, G.; Seufert, W.

1964-01-01

Ampoules of alpha -methylstyrene sealed under vacuum were irradiated with 1-Mev electrons in a type JS Van de Graaff generator; comparative experiments with gamma rays were carried out with a /sup 60/Co source of 3000 deg C. High doses of electrons (ca. 10/sup 8/ rad) are necessary for polymerization. The conversion is graphed as a function of dose at 0 deg C; it reaches a maximum plateau of 65% at 4 x 10/sup 8/ rad; this may point to radiolysis of the polymer at doses above this. Polymerization conversion increases with decreasing dose rate, when dose and temperature are heldmore » constant; and conversion increases with decreasing temperature (22% at --22 deg C; 10% at 15 deg C; <1% at 60 deg C), as has been found with gamma rays. In the solid state between --40 deg C and --80 deg C the maximum yield is only about 5%. The molecular weights of all poly- alpha -methylstyrenes thus formed lie between 3000 and 12,000, independently of dose rate and temperature. All polymethylstyrenes formed in the liquid state have approximately the same tacticity independent of temperature (isotactic about 20%; syndiotactic about 80%). This corresponds to the tacticity of polymers formed cationically with Lewis acids. In the solid state the tacticity is: isotactic 38%, syndiotactic, 62%, comparable with the tacticity of anionic polymerization. In the liquid state the tacticity and the sensitivity towards water indicate a cationic mechanism for the reaction. NMR studies also indicate a cationic mechanism. (BBB)« less

Unraveling the Voltage-Fade Mechanism in High-Energy-Density Lithium-Ion Batteries: Origin of the Tetrahedral Cations for Spinel Conversion

DOE PAGES

Mohanty, Debasish; Li, Jianlin; Abraham, Daniel P.; ...

2014-09-30

Discovery of high-voltage layered lithium-and manganese-rich (LMR) composite oxide electrode has dramatically enhanced the energy density of current Li-ion energy storage systems. However, practical usage of these materials is currently not viable because of their inability to maintain a consistent voltage profile (voltage fading) during subsequent charge-discharge cycles. This report rationalizes the cause of this voltage fade by providing the evidence of layer to spinel-like (LSL) structural evolution pathways in the host Li 1.2Mn 0.55Ni 0.15Co 0.1O 2 LMR composite oxide. By employing neutron powder diffraction, and temperature dependent magnetic susceptibility, we show that LSL structural rearrangement in LMR oxidemore » occurs through a tetrahedral cation intermediate via: i) diffusion of lithium atoms from octahedral to tetrahedral sites of the lithium layer [(Li Lioct →Li Litet] which is followed by the dispersal of the lithium ions from the adjacent octahedral site of the metal layer to the tetrahedral sites of lithium layer [Li TM oct → Li Litet]; and ii) migration of Mn from the octahedral sites of the transition metal layer to the permanent octahedral site of lithium layer via tetrahedral site of lithium layer [Mn TMoct Mn Litet Mn Lioct)]. The findings opens the door to the potential routes to mitigate this atomic restructuring in the high-voltage LMR composite oxide cathodes by manipulating the composition/structure for practical use in high-energy-density lithium-ion batteries.« less

Genetic training of network using chaos concept: application to QSAR studies of vibration modes of tetrahedral halides.

PubMed

Lu, Qingzhang; Shen, Guoli; Yu, Ruqin

2002-11-15

The chaotic dynamical system is introduced in genetic algorithm to train ANN to formulate the CGANN algorithm. Logistic mapping as one of the most important chaotic dynamic mappings provides each new generation a high chance to hold GA's population diversity. This enhances the ability to overcome overfitting in training an ANN. The proposed CGANN has been used for QSAR studies to predict the tetrahedral modes (nu(1)(A1) and nu(2)(E)) of halides [MX(4)](epsilon). The frequencies predicted by QSAR were compared with those calculated by quantum chemistry methods including PM3, AM1, and MNDO/d. The possibility of improving the predictive ability of QSAR by including quantum chemistry parameters as feature variables has been investigated using tetrahedral tetrahalide examples. Copyright 2002 Wiley Periodicals, Inc.

Aza-Bambusurils En Route to Anion Transporters.

PubMed

Singh, Mandeep; Solel, Ephrath; Keinan, Ehud; Reany, Ofer

2016-06-20

Previous calculations of anion binding with various bambusuril analogs predicted that the replacement of oxygen by nitrogen atoms to produce semiaza-bambus[6]urils would award these new cavitands with multiple anion binding properties. This study validates the hypothesis by efficient synthesis, crystallography, thermogravimetric analysis and calorimetry. These unique host molecules are easily accessible from the corresponding semithio-bambusurils in a one-pot reaction, which converts a single anion receptor into a potential anion channel. Solid-state structures exhibit simultaneous accommodation of three anions, linearly positioned within the cavity along the main symmetry axis. The ability to hold anions at a short distance of about 4 Å is reminiscent of natural chloride channels in E. coli, which exhibit similar distances between their adjacent anion binding sites. The calculated transition-state energy for double-anion movement through the channel suggests that although these host-guest complexes are thermodynamically stable they enjoy high kinetic flexibility to render them efficient anion channels. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A fabrication strategy for nanosized zero valent iron (nZVI)-polymeric anion exchanger composites with tunable structure for nitrate reduction.

PubMed

Jiang, Zhenmao; Zhang, Shujuan; Pan, Bingcai; Wang, Wenfeng; Wang, Xiaoshu; Lv, Lu; Zhang, Weiming; Zhang, Quanxing

2012-09-30

To reveal how the distribution of nanoscale zero-valent iron (nZVI) affect their reduction efficiency of its polymer-based composites and to further develop a simple strategy to tune the structure of the composites, we prepared four nZVI-polymerstyrene anion exchanger composites with similar nZVI loadings (13.5-14.4 Fe % in mass) but different distributions just through varying the concentration of NaBH(4) (0.9, 1.8, 3.6, and 7.2% in mass) solution during reduction of nZVI precursor (FeCl(4)(-) anions). As observed by SEM-EDX images, increasing the NaBH(4) concentration resulted in a more uniform nZVI distribution within the polymer, and thereto higher NH(4)(+)N production, faster reaction rate and more gaseous products during its reduction of nitrate and nitrite. nZVI distribution of the composites was suggested to greatly depend upon two processes, the hydrolyzation of anionic FeCl(4)(-) into cationic Fe(3+) and the reduction of both Fe(III) species by NaBH(4). Higher NaBH(4) concentration favored its faster diffusion into the inside polymer and in situ reduction of Fe(III) species into nZVI, causing a more uniform nZVI distribution. The results reported herein suggest that adjusting the NaBH(4) concentration was a simple and effective method to control the nZVI distribution in the supporting polymers, and indirectly tune the reactivity of the resultant nZVI hybrids. Copyright © 2012 Elsevier B.V. All rights reserved.

Binding of anions in triply interlocked coordination catenanes and dynamic allostery for dehalogenation reactions† †Electronic supplementary information (ESI) available: Characterization data and additional tables and figures. CCDC 1515722 and 1515723. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7sc04070a

PubMed Central

Yang, Linlin; Jing, Xu; An, Bowen; Yang, Yang

2017-01-01

By synergistic combination of multicomponent self-assembly and template-directed approaches, triply interlocked metal organic catenanes that consist of two isolated chirally identical tetrahedrons were constructed and stabilized as thermodynamic minima. In the presence of suitable template anions, the structural conversion from the isolated tetrahedral conformers into locked catenanes occurred via the cleavage of an intrinsically reversible coordination bond in each of the tetrahedrons, followed by the reengineering and interlocking of two fragments with the regeneration of the broken coordination bonds. The presence of several kinds of individual pocket that were attributed to the triply interlocked patterns enabled the possibility of encapsulating different anions, allowing the dynamic allostery between the unlocked/locked conformers to promote the dehalogenation reaction of 3-bromo-cyclohexene efficiently, as with the use of dehalogenase enzymes. The interlocked structures could be unlocked into two individual tetrahedrons through removal of the well-matched anion templates. The stability and reversibility of the locked/unlocked structures were further confirmed by the catching/releasing process that accompanied emission switching, providing opportunities for the system to be a dynamic molecular logic system. PMID:29675152

Poly(terphenylene) Anion Exchange Membranes: The Effect of Backbone Structure on Morphology and Membrane Property

DOE PAGES

Lee, Woo-Hyung; Park, Eun Joo; Han, Junyoung; ...

2017-05-05

A new design concept for ion-conducting polymers in anion exchange membranes (AEMs) fuel cells is proposed based on structural studies and conformational analysis of polymers and their effect on the properties of AEMs. Thermally, chemically, and mechanically stable terphenyl-based polymers with pendant quaternary ammonium alkyl groups were synthesized to investigate the effect of varying the arrangement of the polymer backbone and cation-tethered alkyl chains. The results demonstrate that the microstructure and morphology of these polymeric membranes significantly influence ion conductivity and fuel cell performance. Finally, the results of this study provide new insights that will guide the molecular design ofmore » polymer electrolyte materials to improve fuel cell performance.« less

Anion-π Catalysts with Axial Chirality.

PubMed

Wang, Chao; Matile, Stefan

2017-09-04

The idea of anion-π catalysis is to stabilize anionic transition states by anion-π interactions on aromatic surfaces. For asymmetric anion-π catalysis, π-acidic surfaces have been surrounded with stereogenic centers. This manuscript introduces the first anion-π catalysts that operate with axial chirality. Bifunctional catalysts with tertiary amine bases next to π-acidic naphthalenediimide planes are equipped with a bulky aromatic substituent in the imide position to produce separable atropisomers. The addition of malonic acid half thioesters to enolate acceptors is used for evaluation. In the presence of a chiral axis, the selective acceleration of the disfavored but relevant enolate addition was much better than with point chirality, and enantioselectivity could be observed for the first time for this reaction with small-molecule anion-π catalysts. Enantioselectivity increased with the π acidity of the π surface, whereas the addition of stereogenic centers around the aromatic plane did not cause further improvements. These results identify axial chirality of the active aromatic plane generated by atropisomerism as an attractive strategy for asymmetric anion-π catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of high-capacity polyelectrolyte brush-grafted porous AAO-silica composite membrane via RAFT polymerization.

PubMed

Song, Cunfeng; Wang, Meijie; Liu, Xin; Wang, He; Chen, Xiaoling; Dai, Lizong

2017-09-01

Surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization has been utilized to fabricate high-capacity strong anion-exchange (AEX) membrane for the separation of protein. By means of RAFT polymerization, quaternized poly(3-(methacrylamidomethyl)-pyridine) brushes formed 3-dimensional nanolayers on the surface of porous anodic aluminum oxide (AAO)-silica composite membrane. The surface properties of the membranes were analyzed by SEM, water contact angle, ATR-FTIR, XPS and TGA. To investigate the adsorption performance, the new AEX membranes were applied to recover a model protein, ovalbumin (OVA). High adsorption capacities of 95.8mg/g membranes (static) and 65.3mg/g membranes (dynamic) were obtained at ambient temperature. In the further studies, up to 90% of the adsorbed OVA was efficiently eluted by using phosphate buffer-1M NaCl as elution medium. The successful separation of OVA with high purity from a mixture protein solution was also achieved by using the AEX membranes. The present study demonstrated that under mild reaction condition, RAFT polymerization can be used to fabricate ion-exchange membrane which has many remarkable features, such as high capacity and selectivity, easy elution and so on. Copyright © 2017. Published by Elsevier B.V.

Mesoporous titanium phosphate molecular sieves with ion-exchange capacity.

PubMed

Bhaumik, A; Inagaki, S

2001-01-31

Novel open framework molecular sieves, titanium(IV) phosphates named, i.e., TCM-7 and -8 (Toyota Composite Materials, numbers 7 and 8), with new mesoporous cationic framework topologies obtained by using both cationic and anionic surfactants are reported. The (31)P MAS NMR, UV-visible absorption, and XANES data suggest the tetrahedral state of P and Ti, and stabilization of the tetrahedral state of Ti in TCM-7/8 is due to the incorporation of phosphorus (at Ti/P = 1:1) vis-à-vis the most stable octahedral state of Ti in the pure mesoporous TiO(2). Mesoporous TCM-7 and -8 show anion exchange capacity due to the framework phosphonium cation and cation exchange capacity due to defective P-OH groups. The high catalytic activity in the liquid-phase partial oxidation of cyclohexene with a dilute H(2)O(2) oxidant supports the tetrahedral coordination of Ti in these materials.

Cause and Cure - Deterioration in Accuracy of CFD Simulations with Use of High-Aspect-Ratio Triangular/Tetrahedral Grids

NASA Technical Reports Server (NTRS)

Chang, Sin-Chung; Chang, Chau-Lyan; Venkatachari, Balaji Shankar

2017-01-01

Traditionally high-aspect ratio triangular/tetrahedral meshes are avoided by CFD researchers in the vicinity of a solid wall, as it is known to reduce the accuracy of gradient computations in those regions. Although for certain complex geometries, the use of high-aspect ratio triangular/tetrahedral elements in the vicinity of a solid wall can be replaced by quadrilateral/prismatic elements, ability to use triangular/tetrahedral elements in such regions without any degradation in accuracy can be beneficial from a mesh generation point of view. The benefits also carry over to numerical frameworks such as the space-time conservation element and solution element (CESE), where simplex elements are the mandatory building blocks. With the requirement of the CESE method in mind, a rigorous mathematical framework that clearly identifies the reason behind the difficulties in use of such high-aspect ratio simplex elements is formulated using two different approaches and presented here. Drawing insights from the analysis, a potential solution to avoid that pitfall is also provided as part of this work. Furthermore, through the use of numerical simulations of practical viscous problems involving high-Reynolds number flows, how the gradient evaluation procedures of the CESE framework can be effectively used to produce accurate and stable results on such high-aspect ratio simplex meshes is also showcased.

Electron-deficient triarylborane block copolymers: synthesis by controlled free radical polymerization and application in the detection of fluoride ions.

PubMed

Cheng, Fei; Bonder, Edward M; Jäkle, Frieder

2013-11-20

Luminescent triarylborane homo and block copolymers with well-defined chain architectures were synthesized via reversible addition-fragmentation chain transfer polymerization of a vinyl-functionalized borane monomer. The Lewis acid properties of the polymers were exploited in the luminescent detection of fluoride ions. A dual-responsive fluoride sensor was developed by taking advantage of the reversible self-assembly of a PNIPAM-based amphiphilic block copolymer. Anion detection in aqueous solution was realized by introducing positively charged pyridinium moieties along the polymer chain.

Ion exchange polymers for anion separations

DOEpatents

Jarvinen, Gordon D.; Marsh, S. Fredric; Bartsch, Richard A.

1997-01-01

Anion exchange resins including at least two positively charged sites and a ell-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

Ion exchange polymers for anion separations

DOEpatents

Jarvinen, G.D.; Marsh, S.F.; Bartsch, R.A.

1997-09-23

Anion exchange resins including at least two positively charged sites and a well-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

Finite-element design and optimization of a three-dimensional tetrahedral porous titanium scaffold for the reconstruction of mandibular defects.

PubMed

Luo, Danmei; Rong, Qiguo; Chen, Quan

2017-09-01

Reconstruction of segmental defects in the mandible remains a challenge for maxillofacial surgery. The use of porous scaffolds is a potential method for repairing these defects. Now, additive manufacturing techniques provide a solution for the fabrication of porous scaffolds with specific geometrical shapes and complex structures. The goal of this study was to design and optimize a three-dimensional tetrahedral titanium scaffold for the reconstruction of mandibular defects. With a fixed strut diameter of 0.45mm and a mean cell size of 2.2mm, a tetrahedral structural porous scaffold was designed for a simulated anatomical defect derived from computed tomography (CT) data of a human mandible. An optimization method based on the concept of uniform stress was performed on the initial scaffold to realize a minimal-weight design. Geometric and mechanical comparisons between the initial and optimized scaffold show that the optimized scaffold exhibits a larger porosity, 81.90%, as well as a more homogeneous stress distribution. These results demonstrate that tetrahedral structural titanium scaffolds are feasible structures for repairing mandibular defects, and that the proposed optimization scheme has the ability to produce superior scaffolds for mandibular reconstruction with better stability, higher porosity, and less weight. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Polymeric microspheres

DOEpatents

Walt, David R.; Mandal, Tarun K.; Fleming, Michael S.

2004-04-13

The invention features core-shell microsphere compositions, hollow polymeric microspheres, and methods for making the microspheres. The microspheres are characterized as having a polymeric shell with consistent shell thickness.

Determination of arsenate and organic arsenic via potentiometric titration of its heteropoly anions.

PubMed

Metelka, R; Slavíková, S; Vytras, K

2002-08-16

Determination of arsenate based on its conversion to molybdoarsenate heteropoly anions followed by potentiometric titration is described. The titration is realized on the ion-pairing principle using cetylpyridinium chloride (or an analogous titrant containing a lipophilic cation), and is monitored by a carbon paste electrode, although other liquid-polymeric membrane-based electrodes can also be used. Calibration plots of the titrant end-point consumption versus concentration of arsenic were constructed and used to evaluate the content of arsenic in aqueous samples. The method could be applied in the analyses of samples with quite low arsenic content (amounts approximately 10 mug As in 50 cm(3) could be titrated). Organic arsenic was determined analogously after the Schöniger combustion of the sample and conversion of its arsenic to arsenate.

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated "Click-Radical" Concurrent Polymerization.

PubMed

Xue, Wentao; Wang, Jie; Wen, Ming; Chen, Gaojian; Zhang, Weidong

2017-03-01

The successful chain-growth copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel-permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition, the electron transfer mediated "click-radical" concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well-defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boundary Recovery For Delaunay Tetrahedral Meshes Using Local Topological Transformations

PubMed Central

Ghadyani, Hamid; Sullivan, John; Wu, Ziji

2009-01-01

Numerous high-quality, volume mesh-generation systems exist. However, no strategy can address all geometry situations without some element qualities being compromised. Many 3D mesh generation algorithms are based on Delaunay tetrahedralization which frequently fails to preserve the input boundary surface topology. For biomedical applications, this surface preservation can be critical as they usually contain multiple material regions of interest coherently connected. In this paper we present an algorithm as a post-processing method that optimizes local regions of compromised element quality and recovers the original boundary surface facets (triangles) regardless of the original mesh generation strategy. The algorithm carves out a small sub-volume in the vicinity of the missing boundary facet or compromised element, creating a cavity. If the task is to recover a surface boundary facet, a natural exit hole in the cavity will be present. This hole is patched with the missing boundary surface face first followed by other patches to seal the cavity. If the task was to improve a compromised region, then the cavity is already sealed. Every triangular facet of the cavity shell is classified as an active face and can be connected to another shell node creating a tetrahedron. In the process the base of the tetrahedron is removed from the active face list and potentially 3 new active faces are created. This methodology is the underpinnings of our last resort method. Each active face can be viewed as the trunk of a tree. An exhaustive breath and depth search will identify all possible tetrahedral combinations to uniquely fill the cavity. We have streamlined this recursive process reducing the time complexity by orders of magnitude. The original surfaces boundaries (internal and external) are fully restored and the quality of compromised regions improved. PMID:20305743

Polymerization Reactor Engineering.

ERIC Educational Resources Information Center

Skaates, J. Michael

1987-01-01

Describes a polymerization reactor engineering course offered at Michigan Technological University which focuses on the design and operation of industrial polymerization reactors to achieve a desired degree of polymerization and molecular weight distribution. Provides a list of the course topics and assigned readings. (TW)

A study of pH-dependence of shrink and stretch of tetrahedral DNA nanostructures.

PubMed

Wang, Ping; Xia, Zhiwei; Yan, Juan; Liu, Xunwei; Yao, Guangbao; Pei, Hao; Zuo, Xiaolei; Sun, Gang; He, Dannong

2015-04-21

We monitored the shrink and stretch of the tetrahedral DNA nanostructure (TDN) and the i-motif connected TDN structure at pH 8.5 and pH 4.5, and we found that not only the i-motif can change its structure when the pH changes, but also the TDN and the DNA double helix change their structures when the pH changes.

Tetraarylborate polymer networks as single-ion conducting solid electrolytes

DOE PAGES

Van Humbeck, Jeffrey F.; Aubrey, Michael L.; Alsbaiee, Alaaeddin; ...

2015-06-23

A new family of solid polymer electrolytes based upon anionic tetrakis(phenyl)borate tetrahedral nodes and linear bis-alkyne linkers is reported. Sonogashira polymerizations using tetrakis(4-iodophenyl)borate, tetrakis(4-iodo-2,3,5,6-tetrafluorophenyl)borate and tetrakis(4-bromo-2,3,5,6-tetrafluorophenyl)borate delivered highly cross-linked polymer networks with both 1,4-diethynylbeznene and a tri(ethylene glycol) substituted derivative. Promising initial conductivity metrics have been observed, including high room temperature conductivities (up to 2.7 × 10 -4 S cm -1), moderate activation energies (0.25–0.28 eV), and high lithium ion transport numbers (up to t Li+ = 0.93). Initial investigations into the effects of important materials parameters such as bulk morphology, porosity, fluorination, and other chemical modification, provide starting designmore » parameters for further development of this new class of solid electrolytes.« less

Photonuclear sum rules and the tetrahedral configuration of He4

NASA Astrophysics Data System (ADS)

Gazit, Doron; Barnea, Nir; Bacca, Sonia; Leidemann, Winfried; Orlandini, Giuseppina

2006-12-01

Three well-known photonuclear sum rules (SR), i.e., the Thomas-Reiche-Kuhn, the bremsstrahlungs and the polarizability SR are calculated for He4 with the realistic nucleon-nucleon potential Argonne V18 and the three-nucleon force Urbana IX. The relation between these sum rules and the corresponding energy weighted integrals of the cross section is discussed. Two additional equivalences for the bremsstrahlungs SR are given, which connect it to the proton-neutron and neutron-neutron distances. Using them, together with our result for the bremsstrahlungs SR, we find a deviation from the tetrahedral symmetry of the spatial configuration of He4. The possibility to access this deviation experimentally is discussed.

Lattice vibrational contribution to equation of state for tetrahedral compounds

NASA Astrophysics Data System (ADS)

Kagaya, H.-Matsuo; Kotoku, H.; Soma, T.

1989-02-01

The lattice vibrational contributions to the Helmholtz free energy and the thermal pressure of tetrahedral compounds such as GaP, InP, ZnS, ZnSe, ZnTe and CdTe are investigated from the electronic theory of solids in the dynamical treatment based on our presented binding force. The temperature dependence of Helmholtz free energy and thermal pressure from lattice vibrational term are quantitatively obtained, and vibrational contributions to free energy are small compared with the static crystal energy. The influence of the thermal pressure is important to the equation of state in high temperatures, and the reformulation of the volume scale for the pressure-volume relation is given by considering the thermal pressure.

ADAPTIVE TETRAHEDRAL GRID REFINEMENT AND COARSENING IN MESSAGE-PASSING ENVIRONMENTS

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

Hallberg, J.; Stagg, A.

2000-10-01

A grid refinement and coarsening scheme has been developed for tetrahedral and triangular grid-based calculations in message-passing environments. The element adaption scheme is based on an edge bisection of elements marked for refinement by an appropriate error indicator. Hash-table/linked-list data structures are used to store nodal and element formation. The grid along inter-processor boundaries is refined and coarsened consistently with the update of these data structures via MPI calls. The parallel adaption scheme has been applied to the solution of a transient, three-dimensional, nonlinear, groundwater flow problem. Timings indicate efficiency of the grid refinement process relative to the flow solvermore » calculations.« less

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes

PubMed Central

Akhmetshina, Alsu A.; Davletbaeva, Ilsiya M.; Grebenschikova, Ekaterina S.; Sazanova, Tatyana S.; Petukhov, Anton N.; Atlaskin, Artem A.; Razov, Evgeny N.; Zaripov, Ilnaz I.; Martins, Carla F.; Neves, Luísa A.; Vorotyntsev, Ilya V.

2015-01-01

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S. PMID:26729177

Evidence of Multiple Sorption Modes in Layered Double Hydroxides Using Mo As Structural Probe.

PubMed

Ma, Bin; Fernandez-Martinez, Alejandro; Grangeon, Sylvain; Tournassat, Christophe; Findling, Nathaniel; Claret, Francis; Koishi, Ayumi; Marty, Nicolas C M; Tisserand, Delphine; Bureau, Sarah; Salas-Colera, Eduardo; Elkaïm, Erik; Marini, Carlo; Charlet, Laurent

2017-05-16

Layered double hydroxides (LDHs) have been considered as effective phases for the remediation of aquatic environments, to remove anionic contaminants mainly through anion exchange mechanisms. Here, a combination of batch isotherm experiments and X-ray techniques was used to examine molybdate (MoO 4 2- ) sorption mechanisms on CaAl LDHs with increasing loadings of molybdate. Advanced modeling of aqueous data shows that the sorption isotherm can be interpreted by three retention mechanisms, including two types of edge sites complexes, interlayer anion exchange, and CaMoO 4 precipitation. Meanwhile, Mo geometry evolves from tetrahedral to octahedral on the edge, and back to tetrahedral coordination at higher Mo loadings, indicated by Mo K-edge X-ray absorption spectra. Moreover, an anion exchange process on both CaAl LDHs was followed by in situ time-resolved synchrotron-based X-ray diffraction, remarkably agreeing with the sorption isotherm. This detailed molecular view shows that different uptake mechanisms-edge sorption, interfacial dissolution-reprecipitation-are at play and control anion uptake under environmentally relevant conditions, which is contrast to the classical view of anion exchange as the primary retention mechanism. This work puts all these mechanisms in perspective, offering a new insight into the complex interplay of anion uptake mechanisms by LDH phases, by using changes in Mo geometry as powerful molecular-scale probe.

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method

PubMed Central

Pereira, N F; Sitek, A

2011-01-01

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated. PMID:20736496

Evaluation of a 3D point cloud tetrahedral tomographic reconstruction method

NASA Astrophysics Data System (ADS)

Pereira, N. F.; Sitek, A.

2010-09-01

Tomographic reconstruction on an irregular grid may be superior to reconstruction on a regular grid. This is achieved through an appropriate choice of the image space model, the selection of an optimal set of points and the use of any available prior information during the reconstruction process. Accordingly, a number of reconstruction-related parameters must be optimized for best performance. In this work, a 3D point cloud tetrahedral mesh reconstruction method is evaluated for quantitative tasks. A linear image model is employed to obtain the reconstruction system matrix and five point generation strategies are studied. The evaluation is performed using the recovery coefficient, as well as voxel- and template-based estimates of bias and variance measures, computed over specific regions in the reconstructed image. A similar analysis is performed for regular grid reconstructions that use voxel basis functions. The maximum likelihood expectation maximization reconstruction algorithm is used. For the tetrahedral reconstructions, of the five point generation methods that are evaluated, three use image priors. For evaluation purposes, an object consisting of overlapping spheres with varying activity is simulated. The exact parallel projection data of this object are obtained analytically using a parallel projector, and multiple Poisson noise realizations of these exact data are generated and reconstructed using the different point generation strategies. The unconstrained nature of point placement in some of the irregular mesh-based reconstruction strategies has superior activity recovery for small, low-contrast image regions. The results show that, with an appropriately generated set of mesh points, the irregular grid reconstruction methods can out-perform reconstructions on a regular grid for mathematical phantoms, in terms of the performance measures evaluated.

Influence of 300°C thermal conversion of Fe-Ce hydrous oxides prepared by hydrothermal precipitation on the adsorptive performance of five anions: Insights from EXAFS/XANES, XRD and FTIR (companion paper).

PubMed

Chubar, Natalia; Gerda, Vasyl; Banerjee, Dipanjan

2017-04-01

In this work, we report atomic-scale reconstruction processes in Fe-Ce oxide-based composites (hydrothermally precipitated at Fe-to-Ce dosage ratios of 1:0, 2:1, 1:1, 1:2, and 0:1), upon treatment at 300°C. The structural changes are correlated with the adsorptive removal of arsenate, phosphate, fluoride, bromide, and bromate. The presence of the carbonate-based Ce-component and surface sulfate in precursor samples creates favorable conditions for phase transformation, resulting in the formation of novel (unknown) layered compounds of Fe and Ce. These compounds are of the layered double hydroxide type, with sulfate in the interlayer space. In spite of general awareness of the importance of surface area in adsorptive removal, the increase in surface area upon thermal treatment did not increase adsorption of the studied anions. However, EXAFS simulations and the adsorption tests provided evidence of regularities between local structures of Fe in composites obtained at 80 and 300°C and adsorption performance of most studied anions. The best adsorption of tetrahedral anions was demonstrated by samples whose simulated outer Fe shells resulted from oscillations from both O and Fe atoms. In contrast, the loss of extended x-ray absorption fine structure was correlated with the decrease of adsorptive removal. Both Fe K-edge and Ce L 3 -edge EXAFS suggested the formation of solid solutions. For the first time, the utilization of extended x-ray absorption fine structure is suggested as a methodological approach (first expressed in the companion paper) to estimate the surface reactivity of inorganic materials intended for use as anion exchange adsorbents. Copyright © 2016 Elsevier Inc. All rights reserved.

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

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

Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu

2015-07-28

Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent developmentmore » in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.« less

Bis(1,3-di-tert-butylimidazolin-2-iminato) titanium complexes as effective catalysts for the monodisperse polymerization of propylene.

PubMed

Sharma, Manab; Yameen, Haneen Simaan; Tumanskii, Boris; Filimon, Sabina-Alexandra; Tamm, Matthias; Eisen, Moris S

2012-10-17

The use of bis(1,3-di-tert-butylimidazolin-2-iminato) titanium dichloride (1) and dimethyl (2) complexes in the polymerization of propylene is presented. The complexes were activated using different amounts of methylalumoxane (MAO), giving in each case a very active catalytic mixture and producing polymers with a narrow molecular weight distribution (polydispersity = 1.10). The use of the cocatalyst triphenylcarbenium (trityl) tetra(pentafluorophenyl)borate totally inhibits the reaction, producing the corresponding bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(III) methyl complex, the trityl radical ((•)CPh(3)), the anionic MeB(C(6)F(5))(4)(-), B(C(6)F(5))(3), and the bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(IV) dimethyl·B(C(6)F(5))(3) complex. The use of a combination of physical methods such as NMR, ESR-C(60), and MALDI-TOF analyses enabled us to propose a plausible mechanism for the polymerization of propylene, presenting that the polymerization is mainly carried out in a living fashion. In addition, we present a slow equilibrium toward a small amount of a dormant species responsible for 2,1-misinsertions and chain transfer processes.

Chiral transcription in self-assembled tetrahedral Eu 4L 6 chiral cages displaying sizable circularly polarized luminescence

DOE PAGES

Yeung, Chi -Tung; Yim, King -Him; Wong, Ho -Yin; ...

2017-10-24

Predictable stereoselective formation of supramolecular assembly is generally believed to be an important but complicated process. Here, we show that point chirality of a ligand decisively influences its supramolecular assembly behavior. We designed three closely related chiral ligands with different point chiralities, and observe their self-assembly into europium (Eu) tetrametallic tetrahedral cages. One ligand exhibits a highly diastereoselective assembly into homochiral (either ΔΔΔΔ or ΛΛΛΛ) Eu tetrahedral cages whereas the two other ligands, with two different approaches of loosened point chirality, lead to a significant breakdown of the diastereoselectivity to generate a mixture of (ΔΔΔΔ and ΛΛΛΛ) isomers. The cagesmore » are highly emissive (luminescence quantum yields of 16(1) to 18(1)%) and exhibit impressive circularly polarized luminescence properties (|g lum |: up to 0.16). With in-depth studies, we present an example that correlates the nonlinear enhancement of the chiroptical response to the nonlinearity dependence on point chirality.« less

Thermally Cross-Linked Anion Exchange Membranes from Solvent Processable Isoprene Containing Ionomers

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

Tsai, Tsung-Han; Ertem, S. Piril; Maes, Ashley M.

2015-01-28

Random copolymers of isoprene and 4-vinylbenzyl chloride (VBCl) with varying compositions were synthesized via nitroxide-mediated polymerization. Subsequent quaternization afforded solvent processable and cross-linkable ionomers with a wide range of ion exchange capacities (IECs). Solution cast membranes were thermally cross-linked to form anion exchange membranes. Cross-linking was achieved by taking advantage of the unsaturations on the polyisoprene backbone, without added cross-linkers. A strong correlation was found between water uptake and ion conductivity of the membranes: conductivities of the membranes with IECs beyond a critical value were found to be constant related to their high water absorption. Environmentally controlled small-angle X-ray scatteringmore » experiments revealed a correlation between the average distance between ionic clusters and the ion conductivity, indicating that a well-connected network of ion clusters is necessary for efficient ion conduction and high ion conductivity.« less

Densely quaternized poly(arylene ether)s with distinct phase separation for highly anion-conductive membranes

NASA Astrophysics Data System (ADS)

Hu, Yuanfang; Wang, Bingxi; Li, Xiao; Chen, Dongyang; Zhang, Weiying

2018-05-01

To develop high performance anion exchange membranes (AEMs), a novel bisphenol monomer bearing eight benzylmethyl groups at the outer edge of the molecule was synthesized, which after condensation polymerization with various amounts of 4,4‧-dihydroxydiphenylsulfone and 4,4‧-difluorobenzophenone yielded novel poly(arylene ether)s with densely located benzylmethyl groups. These benzylmethyl groups were then converted to quaternary ammonium groups by radical-initiated bromination and quaternization in tandem, leading to the emergence of densely quaternized poly(arylene ether sulfone)s (QA-PAEs) with controlled ion exchange capacities (IECs) ranging from 1.61 to 2.32 mmol g-1. Both small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) studies revealed distinct phase separation in the QA-PAEs. The QA-PAE-40 with an IEC of 2.32 mmol g-1 exhibited a Br- conductivity of 9.2 mS cm-1 and a SO42- conductivity of 14.0 mS cm-1 at room temperature, much higher than those of a control membrane with a similar IEC but without obvious phase separation. Therefore, phase separation of AEMs was validated to be advantageous for the efficient conducting of anions. The experimental results also showed that the QA-PAEs were promising AEM materials, especially for non-alkaline applications.

Arsenate removal from water by a weak-base anion exchange fibrous adsorbent.

PubMed

Awual, Md Rabiul; Urata, Shinya; Jyo, Akinori; Tamada, Masao; Katakai, Akio

2008-02-01

A weak-base anion exchange fiber named FVA with primary amino groups for selective and rapid removal of arsenate species was prepared by means of electron irradiation induced liquid phase graft polymerization of N-vinylformamide onto polyethylene coated polypropylene fibers and by the subsequent alkaline hydrolysis of amide group on the grafted polymer chains. Two types of FVA were prepared. One was a non-woven cloth type named FVA-c for the batch-mode study, which clarified that uptake of arsenate species decreases with an increase in pH, and chloride and sulfate do not strongly interfere with uptake of arsenate species different from conventional anion exchange resins based on crosslinked polystyrene matrices. The other was a filamentary type one named FVA-f used in the column-mode study, which clarified that arsenate species were successfully removed from neutral pH arsenate solutions containing 1.0-99 mg of As/L at feed flow rates of 100-1050 h(-1) in space velocity (SV). The most important findings are that the 1% breakthrough point in uptake from the arsenate solution containing 1.0mg of As/L at the high feed flow rate of 1050h(-1) in SV was as large as 4670 bed volumes, giving the 1% breakthrough capacity of 0.298 mmol/g of FVA-f. Adsorbed arsenate was able to be quantitatively eluted with 1M hydrochloric acid and FVA-f was simultaneously regenerated. Then, the repeated use of FVA-f was possible.

Process for removing sulfate anions from waste water

DOEpatents

Nilsen, David N.; Galvan, Gloria J.; Hundley, Gary L.; Wright, John B.

1997-01-01

A liquid emulsion membrane process for removing sulfate anions from waste water is disclosed. The liquid emulsion membrane process includes the steps of: (a) providing a liquid emulsion formed from an aqueous strip solution and an organic phase that contains an extractant capable of removing sulfate anions from waste water; (b) dispersing the liquid emulsion in globule form into a quantity of waste water containing sulfate anions to allow the organic phase in each globule of the emulsion to extract and absorb sulfate anions from the waste water and (c) separating the emulsion including its organic phase and absorbed sulfate anions from the waste water to provide waste water containing substantially no sulfate anions.

Organic solvent and temperature-enhanced ion chromatography-high resolution mass spectrometry for the determination of low molecular weight organic and inorganic anions.

PubMed

Gilchrist, Elizabeth S; Nesterenko, Pavel N; Smith, Norman W; Barron, Leon P

2015-03-20

There has recently been increased interest in coupling ion chromatography (IC) to high resolution mass spectrometry (HRMS) to enable highly sensitive and selective analysis. Herein, the first comprehensive study focusing on the direct coupling of suppressed IC to HRMS without the need for post-suppressor organic solvent modification is presented. Chromatographic selectivity and added HRMS sensitivity offered by organic solvent-modified IC eluents on a modern hyper-crosslinked polymeric anion-exchange resin (IonPac AS18) are shown using isocratic eluents containing 5-50 mM hydroxide with 0-80% methanol or acetonitrile for a range of low molecular weight anions (<165 Da). Comprehensive experiments on IC thermodynamics over a temperature range between 20-45 °C with the eluent containing up to 60% of acetonitrile or methanol revealed markedly different retention behaviour and selectivity for the selected analytes on the same polymer based ion-exchange resin. Optimised sensitivity with HRMS was achieved with as low as 30-40% organic eluent content. Analytical performance characteristics are presented and compared with other IC-MS based works. This study also presents the first application of IC-HRMS to forensic detection of trace low-order anionic explosive residues in latent human fingermarks. Copyright © 2015 Elsevier B.V. All rights reserved.

Structure characterization, photoluminescence and dielectric properties of a new hybrid compound containing chlorate anions of zincate (II)

NASA Astrophysics Data System (ADS)

Lassoued, Mohamed Saber; Abdelbaky, Mohammed S. M.; Ben Soltan, Wissem; Lassoued, Abdelmajid; Ammar, Salah; Gadri, Abdellatif; Ben Salah, Abdelhamid; García-Granda, Santiago

2018-04-01

A new hybrid compound, bis (2-aminophenylenamonium) tetrachlorozincate (II), was synthesized and formulated as (C6H9N2)2ZnCl4. Its crystal structure was solved by single crystal X-ray diffraction reveling that compound crystallizes in the monoclinic system, space group C2/c (N°: 15) with cell parameters a = 7.4957(4) Å, b = 25.6837(15) Å, c = 9.4041(5) Å, β = 94.35(0)°, V = 1805.23(45) Å3. Their atomic arrangement can be described as an alternation of inorganic and organic layers, [ZnCl4]2- tetrahedral anions and 2-aminophenylenamonium cations. The cohesion of the atomic arrangement is ensured by hydrogen bonds (strong Nsbnd H⋯N and weak Nsbnd H⋯Cl) and π-π stacking interactions between identical antiparallel organic moieties. In optical transmission and photoluminescence measurements, this material exhibit two absorption bands (253 and 316 nm) and a strong emission line (390 nm), while the thermal analysis disclosed a phase transition at 420-445 K previously to the sample decomposition at 476 K. Finally, electrical measurements were performed to discuss the phase-transition mechanism.

Polymeric nanoparticulate system augmented the anticancer therapeutic efficacy of gemcitabine.

PubMed

Arias, José L; Reddy, L Harivardhan; Couvreur, Patrick

2009-09-01

Gemcitabine hydrochloride is an anticancer nucleoside analogue indicated in clinic for the treatment of various solid tumors. Although this drug has been demonstrated to display anticancer activity against a wide variety of tumors, it is needed to be administered at high doses to elicit the required therapeutic response, simultaneously leading to severe adverse effects. We hypothesized that the efficient delivery of gemcitabine to tumors using a biodegradable carrier system could reduce the dose required to elicit sufficient therapeutic response. Thus, we have developed a nanoparticle formulation of gemcitabine suitable for parenteral administration based on the biodegradable polymer poly(octylcyanoacrylate) (POCA). The nanoparticles were synthesized by anionic polymerization of the corresponding monomer. Two drug loading methods were analyzed: the first one based on gemcitabine surface adsorption onto the preformed nanoparticles, and the second method being gemcitabine addition before the polymerization process leading to drug entrapment in the polymeric network. A detailed investigation of the capabilities of the polymer particles to load this drug is described. Gemcitabine entrapment into the polymer matrix yielded a higher drug loading and a slower drug release profile as compared with drug adsorption procedure. The main factors determining the gemcitabine incorporation to the polymer network were the nanoparticles preparation procedure, the monomer concentration, the surfactant concentration, the pH, and the drug concentration. The release kinetic of gemcitabine was found to be controlled by the pH and the type of drug incorporation. The cytotoxicity studies performed on L1210 tumor cells revealed a similar anticancer activity of the gemcitabine-loaded POCA (GPOCA) nanoparticle as free gemcitabine. Following intravenous administration into the mice bearing L1210 wt subcutaneous tumor, the GPOCA nanoparticles displayed significantly greater anticancer activity

Capillary electrophoresis of inorganic anions.

PubMed

Kaniansky, D; Masár, M; Marák, J; Bodor, R

1999-02-26

This review deals with the separation mechanisms applied to the separation of inorganic anions by capillary electrophoresis (CE) techniques. It covers various CE techniques that are suitable for the separation and/or determination of inorganic anions in various matrices, including capillary zone electrophoresis, micellar electrokinetic chromatography, electrochromatography and capillary isotachophoresis. Detection and sample preparation techniques used in CE separations are also reviewed. An extensive part of this review deals with applications of CE techniques in various fields (environmental, food and plant materials, biological and biomedical, technical materials and industrial processes). Attention is paid to speciations of anions of arsenic, selenium, chromium, phosphorus, sulfur and halogen elements by CE.

Semithiobambus[6]uril is a transmembrane anion transporter.

PubMed

Lang, Chao; Mohite, Amar; Deng, Xiaoli; Yang, Feihu; Dong, Zeyuan; Xu, Jiayun; Liu, Junqiu; Keinan, Ehud; Reany, Ofer

2017-07-04

Semithiobambus[6]uril is shown to be an efficient transmembrane anion transporter. Although all bambusuril analogs (having either O, S or N atoms in their portals) are excellent anion binders, only the sulfur analog is also an effective anion transporter capable of polarizing lipid membranes through selective anion uniport. This notable divergence reflects significant differences in the lipophilic character of the bambusuril analogs.

Anion channels: master switches of stress responses.

PubMed

Roelfsema, M Rob G; Hedrich, Rainer; Geiger, Dietmar

2012-04-01

During stress, plant cells activate anion channels and trigger the release of anions across the plasma membrane. Recently, two new gene families have been identified that encode major groups of anion channels. The SLAC/SLAH channels are characterized by slow voltage-dependent activation (S-type), whereas ALMT genes encode rapid-activating channels (R-type). Both S- and R-type channels are stimulated in guard cells by the stress hormone ABA, which leads to stomatal closure. Besides their role in ABA-dependent stomatal movement, anion channels are also activated by biotic stress factors such as microbe-associated molecular patterns (MAMPs). Given that anion channels occur throughout the plant kingdom, they are likely to serve a general function as master switches of stress responses. Copyright © 2012 Elsevier Ltd. All rights reserved.

Radiation-induced polymerization of glass-forming systems. IV. Effect of the homogeneity of polymerization phase and polymer concentration on temperature dependence of initial polymerization rate

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

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-06-01

The effect of homogeneity of polymerization phase and monomer concentration on the temperature dependence of initial polymerization rate was studied in the radiation-induced radical polymerization of binary systems consisting of glass-forming monomer and solvent. In the polymerization of a completely homogeneous system such as HEMA-propylene glycol, a maximum and a minimum in polymerization rates as a function of temperature, characteristic of the polymerization in glass-forming systems, were observed for all monomer concentrations. However, in the heterogeneous polymerization systems such as HEMA-triacetin and HEMAisoamyl acetate, maximum and minimum rates were observed in monomer-rich compositions but not at low monomer concentrations. Furthermore,more » in the HEMA-dioctyl phthalate polymerization system, which is extremely heterogeneous, no maximum and minimum rates were observed at any monomer concentration. The effect of conversion on the temperature dependence of polymerization rate in homogeneous bulk polymerization of HEMA and GMA was investigated. Maximum and minimum rates were observed clearly in conversions less than 10% in the case of HEMA and less than 50% in the case of GMA, but the maximum and minimum changed to a mere inflection in the curve at higher conversions. A similar effect of polymer concentration on the temperature dependence of polymerization rate in the GMA-poly(methyl methacrylate) system was also observed. It is deduced that the change in temperature dependence of polymerization rate is attributed to the decrease in contribution of mutual termination reaction of growing chain radicals to the polymerization rate. (auth)« less

Dynamics and Regulation of RecA Polymerization and De-Polymerization on Double-Stranded DNA

PubMed Central

Muniyappa, Kalappa; Yan, Jie

2013-01-01

The RecA filament formed on double-stranded (ds) DNA is proposed to be a functional state analogous to that generated during the process of DNA strand exchange. RecA polymerization and de-polymerization on dsDNA is governed by multiple physiological factors. However, a comprehensive understanding of how these factors regulate the processes of polymerization and de-polymerization of RecA filament on dsDNA is still evolving. Here, we investigate the effects of temperature, pH, tensile force, and DNA ends (in particular ssDNA overhang) on the polymerization and de-polymerization dynamics of the E. coli RecA filament at a single-molecule level. Our results identified the optimal conditions that permitted spontaneous RecA nucleation and polymerization, as well as conditions that could maintain the stability of a preformed RecA filament. Further examination at a nano-meter spatial resolution, by stretching short DNA constructs, revealed a striking dynamic RecA polymerization and de-polymerization induced saw-tooth pattern in DNA extension fluctuation. In addition, we show that RecA does not polymerize on S-DNA, a recently identified novel base-paired elongated DNA structure that was previously proposed to be a possible binding substrate for RecA. Overall, our studies have helped to resolve several previous single-molecule studies that reported contradictory and inconsistent results on RecA nucleation, polymerization and stability. Furthermore, our findings also provide insights into the regulatory mechanisms of RecA filament formation and stability in vivo. PMID:23825559

Optimization of Time-Dependent Particle Tracing Using Tetrahedral Decomposition

NASA Technical Reports Server (NTRS)

Kenwright, David; Lane, David

1995-01-01

An efficient algorithm is presented for computing particle paths, streak lines and time lines in time-dependent flows with moving curvilinear grids. The integration, velocity interpolation and step-size control are all performed in physical space which avoids the need to transform the velocity field into computational space. This leads to higher accuracy because there are no Jacobian matrix approximations or expensive matrix inversions. Integration accuracy is maintained using an adaptive step-size control scheme which is regulated by the path line curvature. The problem of cell-searching, point location and interpolation in physical space is simplified by decomposing hexahedral cells into tetrahedral cells. This enables the point location to be done analytically and substantially faster than with a Newton-Raphson iterative method. Results presented show this algorithm is up to six times faster than particle tracers which operate on hexahedral cells yet produces almost identical particle trajectories.

Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis

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

Beletskiy, Evgeny V.; Hou, Xianliang; Shen, Zhongliang

2016-03-17

Mild calcination in ozone of a (POSS)-Sn- (POSS) complex grafted on silica generated a heterogenized catalyst that mostly retained the tetrahedral coordination of its homogeneous precursor, as evidenced by spectroscopic characterizations using EXAFS, NMR, UV-vis, and DRIFT. The Sn centers are accessible and uniform and can be quantified by stoichiometric pyridine poisoning. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. However, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn-O-Si bond. The resulting acidic silanol is activemore » in epoxide ring opening and acetalization reactions.« less

Pressure-volume relations and bulk modulus under pressure of tetrahedral compounds

NASA Astrophysics Data System (ADS)

Soma, T.; Takahashi, Y.; Kagaya, H.-M.

1985-03-01

The pressure-volume relation and the compression effect on the bulk modulus of tetrahedral compounds such as GaP, InP, ZnS, ZnSe, ZnTe and CdTe are investigated from the electronic theory of solids by using a recently presented binding force, which includes mainly covalent interactions in the pseudopotential formalism and partially ionic interactions. The calculated results of the pressure-volume relations involving the pressure-induced phase transition are useful when comparing with the experimental data under high pressure. The calculated bulk modulus of these compounds increases as the crystal volume decreases. Further, the pressure derivative of bulk modulus is not constant and decreases with the reduction of the crystal volume.

N-acetylglyoxylic amide bearing a nitrophenyl group as anion receptors: NMR and X-ray investigations on anion binding and selectivity

NASA Astrophysics Data System (ADS)

Suryanti, Venty; Bhadbhade, Mohan; Black, David StC; Kumar, Naresh

2017-10-01

N-Nitrophenylglyoxylic amides 1 and 2 in presence of tetrabutylammonium cation (TBA) act as receptors for anions HSO4-, Cl-, Br- and NO3- as investigated by NMR studies. The receptors formed 1:1 host-guest complexes in solution. X-ray structure of 1 along with TBA that bind a chloride anion is reported. Molecule 1 showed the highest selectivity for HSO4- anion over others measured. X-ray structure of the bound Cl- revealed a pocket containing the anion making strong (Nsbnd H⋯Cl) and weak hydrogen bonds (Csbnd H⋯Cl) that contribute to the recognition of the chloride anion. Nsbnd H and Csbnd H hydrogen bonds resulted in a relatively strong binding for chloride ions.

In situ X-ray polymerization: from swollen lamellae to polymer-surfactant complexes.

PubMed

Agzenai, Yahya; Lindman, Björn; Alfredsson, Viveka; Topgaard, Daniel; Renamayor, Carmen S; Pacios, Isabel E

2014-01-30

The influence of the monomer diallyldimethylammonium chloride (D) on the lamellar liquid crystal formed by the anionic surfactant aerosol OT (AOT) and water is investigated, determining the lamellar spacings by SAXS and the quadrupolar splittings by deuterium NMR, as a function of the D or AOT concentrations. The cationic monomer D induces a destabilization of the AOT lamellar structure such that, at a critical concentration higher than 5 wt %, macroscopic phase separation takes place. When the monomer, which is dissolved in the AOT lamellae, is polymerized in situ by X-ray initiation, a new collapsed lamellar phase appears, corresponding to the complexation of the surfactant with the resulting polymer. A theoretical model is employed to analyze the variation of the interactions between the AOT bilayers and the stability of the lamellar structure.

A preference for edgewise interactions between aromatic rings and carboxylate anions: the biological relevance of anion-quadrupole interactions.

PubMed

Jackson, Michael R; Beahm, Robert; Duvvuru, Suman; Narasimhan, Chandrasegara; Wu, Jun; Wang, Hsin-Neng; Philip, Vivek M; Hinde, Robert J; Howell, Elizabeth E

2007-07-19

Noncovalent interactions are quite important in biological structure-function relationships. To study the pairwise interaction of aromatic amino acids (phenylalanine, tyrosine, tryptophan) with anionic amino acids (aspartic and glutamic acids), small molecule mimics (benzene, phenol or indole interacting with formate) were used at the MP2 level of theory. The overall energy associated with an anion-quadrupole interaction is substantial (-9.5 kcal/mol for a benzene-formate planar dimer at van der Waals contact distance), indicating the electropositive ring edge of an aromatic group can interact with an anion. Deconvolution of the long-range coplanar interaction energy into fractional contributions from charge-quadrupole interactions, higher-order electrostatic interactions, and polarization terms was achieved. The charge-quadrupole term contributes between 30 to 45% of the total MP2 benzene-formate interaction; most of the rest of the interaction arises from polarization contributions. Additional studies of the Protein Data Bank (PDB Select) show that nearly planar aromatic-anionic amino acid pairs occur more often than expected from a random angular distribution, while axial aromatic-anionic pairs occur less often than expected; this demonstrates the biological relevance of the anion-quadrupole interaction. While water may mitigate the strength of these interactions, they may be numerous in a typical protein structure, so their cumulative effect could be substantial.

Gas-Grain Models for Interstellar Anion Chemistry

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Charnely, S. B.

2012-01-01

Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

Photoelectron spectroscopy of nitromethane anion clusters

NASA Astrophysics Data System (ADS)

Pruitt, Carrie Jo M.; Albury, Rachael M.; Goebbert, Daniel J.

2016-08-01

Nitromethane anion and nitromethane dimer, trimer, and hydrated cluster anions were studied by photoelectron spectroscopy. Vertical detachment energies, estimated electron affinities, and solvation energies were obtained from the photoelectron spectra. Cluster structures were investigated using theoretical calculations. Predicted detachment energies agreed with experiment. Calculations show water binds to nitromethane anion through two hydrogen bonds. The dimer has a non-linear structure with a single ionic Csbnd H⋯O hydrogen bond. The trimer has two different solvent interactions, but both involve the weak Csbnd H⋯O hydrogen bond.

A versatile tripodal amide receptor for the encapsulation of anions or hydrated anions via formation of dimeric capsules.

PubMed

Arunachalam, M; Ghosh, Pradyut

2010-02-01

A bowl-shaped tripodal receptor with an appropriately positioned amide functionality on the benzene platform and electron-withdrawing p-nitrophenyl terminals (L(1)) has been designed, synthesized, and studied for the anion binding properties. The single-crystal X-ray crystallographic analysis on crystals of L(1) with tetrabutylammonium salts of nitrate (1), acetate (2), fluoride (3), and chloride (4) obtained in moist dioxane medium showed encapsulation of two NO(3)(-), [(AcO)(2)(H(2)O)(4)](2-), [F(2)(H(2)O)(6)](2-), and [Cl(2)(H(2)O)(4)](2-) respectively as the anionic guests inside the staggered dimeric capsular assembly of L(1). The p-nitro substitution in the aryl terminals assisted the formation of dimeric capsular assembly of L(1) exclusively upon binding/encapsulating above different guests. Though L(1) demonstrates capsule formation upon anion or hydrated anion complexation for all of the anions studied here, its positional isomer with the o-nitro-substituted tripodal triamide receptor L(2) selectively formed the dimeric capsular assembly upon encapsulation of [F(2)(H(2)O)(6)](2-) and noncapsular aggregates in the cases of other anions such as Cl(-), NO(3)(-), and AcO(-). Interestingly, structural investigations upon anion exchange of the complexes revealed that both isomers have selectivity toward the formation of a [F(2)(H(2)O)(6)](2-) encapsulated dimeric capsule. In contrast, solution-state (1)H NMR titration studies of L(1) and L(2) in DMSO-d(6) with AcO(-) indicated 1:3 (host:guest) binding.

Spectroscopic criteria for identification of nuclear tetrahedral and octahedral symmetries: Illustration on a rare earth nucleus

NASA Astrophysics Data System (ADS)

Dudek, J.; Curien, D.; Dedes, I.; Mazurek, K.; Tagami, S.; Shimizu, Y. R.; Bhattacharjee, T.

2018-02-01

We formulate criteria for identification of the nuclear tetrahedral and octahedral symmetries and illustrate for the first time their possible realization in a rare earth nucleus 152Sm. We use realistic nuclear mean-field theory calculations with the phenomenological macroscopic-microscopic method, the Gogny-Hartree-Fock-Bogoliubov approach, and general point-group theory considerations to guide the experimental identification method as illustrated on published experimental data. Following group theory the examined symmetries imply the existence of exotic rotational bands on whose properties the spectroscopic identification criteria are based. These bands may contain simultaneously states of even and odd spins, of both parities and parity doublets at well-defined spins. In the exact-symmetry limit those bands involve no E 2 transitions. We show that coexistence of tetrahedral and octahedral deformations is essential when calculating the corresponding energy minima and surrounding barriers, and that it has a characteristic impact on the rotational bands. The symmetries in question imply the existence of long-lived shape isomers and, possibly, new waiting point nuclei—impacting the nucleosynthesis processes in astrophysics—and an existence of 16-fold degenerate particle-hole excitations. Specifically designed experiments which aim at strengthening the identification arguments are briefly discussed.

Ab initio theoretical study of dipole-bound anions of molecular complexes: (HF)3- and (HF)4- anions

NASA Astrophysics Data System (ADS)

Ramaekers, Riet; Smith, Dayle M. A.; Smets, Johan; Adamowicz, Ludwik

1997-12-01

Ab initio calculations have been performed to determine structures and vertical electron detachment energy (VDE) of the hydrogen fluoride trimer and tetramer anions, (HF)3- and (HF)4-. In these systems the excess electron is bound by the dipole field of the complex. It was determined that, unlike the neutral complexes which prefer the cyclic structures, the equilibrium geometries of the anions have "zig-zag" shapes. For both complexes the predicted VDEs are positive [210 meV and 363 meV for (HF)3- and (HF)4-, respectively], indicating that the anions are stable systems with respect to the vertical electron detachment. These results were obtained at the coupled-cluster level of theory with single, double and triple excitations [CCSD(T) method; the triple-excitation contribution in this method is calculated approximately using the perturbation approach] with the anion geometries obtained using the second-order Møller-Plesset perturbation theory (MP2) method. The same approach was also used to determine the adiabatic electron affinities (AEA) of (HF)3 and (HF)4. In addition to the electronic contribution, we also calculated the contributions (using the harmonic approximation) resulting from different zero-point vibration energies of the neutral and anionic clusters. The calculations predicted that while the AEA of (HF)3 is positive (44 meV), the AEA for (HF)4 is marginally negative (-16 meV). This suggests that the (HF)3- anion should be a stable system, while the (HF)4- is probably metastable.

Pyromellitamide aggregates and their response to anion stimuli.

PubMed

Webb, James E A; Crossley, Maxwell J; Turner, Peter; Thordarson, Pall

2007-06-06

The N,N',N'',N'''-1,2,4,5-tetra(ethylhexanoate) pyromellitamide is found to be capable of both intermolecular aggregation and binding to small anions. It is synthesized by aminolysis of pyromellitic anhydride with ethanolamine, followed by a reaction with hexanoyl chloride. The single-crystal X-ray structure of the pyromellitamide shows that it forms one-dimensional columnar stacks through an intermolecular hydrogen-bonding network. It also forms self-assembled gels in nonpolar solvents, presumably by a hydrogen-bonding network similar to the solid-state structure as shown by IR and XRD studies. Aggregation by intermolecular hydrogen bonding of the pyromellitamide is also observed by NMR and IR in solution. Fitting of NMR dilution data for pyromellitamide in d6-acetone to a cooperative aggregation model gave KE=232 M-1 and positive cooperativity of aggregation (rho=0.22). The pyromellitamide binds to a range of small anions with the binding strength decreasing in the order chloride>acetate>bromide>nitrate approximately iodide. The data indicate that the pyromellitamide binds two anions and that it displays negative cooperativity. The intermolecular aggregation of the pyromellitamide can also be altered using small anion stimuli; anion addition to preformed self-assembled pyromellitamide gels causes their collapse. The kinetics of anion-induced gel collapse are qualitatively correlated to the binding affinities of the same anions in solution. The cooperative anion binding properties and the sensitivity of the self-assembled gels formed by pyromellitamide toward anions could be useful in the development of sensors and switching/releasing devices.

Polymerization of perfluorobutadiene

NASA Technical Reports Server (NTRS)

Newman, J.; Toy, M. S.

1970-01-01

Diisopropyl peroxydicarbonate dissolved in liquid perfluorobutadiene is conducted in a sealed vessel at the autogenous pressure of polymerization. Reaction temperature, ratio of catalyst to monomer, and amount of agitation determine degree of polymerization and product yield.

Self-organizing layers from complex molecular anions

DOE PAGES

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.; ...

2018-05-14

The formation of traditional ionic materials occurs principally via joint accumulation of both anions and cations. Here in this paper, we describe a previously unreported phenomenon by which macroscopic liquid-like thin layers with tunable self-organization properties form through accumulation of stable complex ions of one polarity on surfaces. Using a series of highly stable molecular anions we demonstrate a strong influence of the internal charge distribution of the molecular ions, which is usually shielded by counterions, on the properties of the layers. Detailed characterization reveals that the intrinsically unstable layers of anions on surfaces are stabilized by simultaneous accumulation ofmore » neutral molecules from the background environment. Different phases, self-organization mechanisms and optical properties are observed depending on the molecular properties of the deposited anions, the underlying surface and the coadsorbed neutral molecules. This demonstrates rational control of the macroscopic properties (morphology and size of the formed structures) of the newly discovered anion-based layers.« less

Self-organizing layers from complex molecular anions

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

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.

The formation of traditional ionic materials occurs principally via joint accumulation of both anions and cations. Here in this paper, we describe a previously unreported phenomenon by which macroscopic liquid-like thin layers with tunable self-organization properties form through accumulation of stable complex ions of one polarity on surfaces. Using a series of highly stable molecular anions we demonstrate a strong influence of the internal charge distribution of the molecular ions, which is usually shielded by counterions, on the properties of the layers. Detailed characterization reveals that the intrinsically unstable layers of anions on surfaces are stabilized by simultaneous accumulation ofmore » neutral molecules from the background environment. Different phases, self-organization mechanisms and optical properties are observed depending on the molecular properties of the deposited anions, the underlying surface and the coadsorbed neutral molecules. This demonstrates rational control of the macroscopic properties (morphology and size of the formed structures) of the newly discovered anion-based layers.« less

Zero-point energy effects in anion solvation shells.

PubMed

Habershon, Scott

2014-05-21

By comparing classical and quantum-mechanical (path-integral-based) molecular simulations of solvated halide anions X(-) [X = F, Cl, Br and I], we identify an ion-specific quantum contribution to anion-water hydrogen-bond dynamics; this effect has not been identified in previous simulation studies. For anions such as fluoride, which strongly bind water molecules in the first solvation shell, quantum simulations exhibit hydrogen-bond dynamics nearly 40% faster than the corresponding classical results, whereas those anions which form a weakly bound solvation shell, such as iodide, exhibit a quantum effect of around 10%. This observation can be rationalized by considering the different zero-point energy (ZPE) of the water vibrational modes in the first solvation shell; for strongly binding anions, the ZPE of bound water molecules is larger, giving rise to faster dynamics in quantum simulations. These results are consistent with experimental investigations of anion-bound water vibrational and reorientational motion.

Relative Positioning Evaluation of a Tetrahedral Flight Formation’s Satellites

NASA Astrophysics Data System (ADS)

Mahler, W. F. C.; Rocco, E. M.; Santos, D. P. S.

2017-10-01

This paper presents a study about the tetrahedral layout of four satellites in a way that every half-orbital period this set groups together while flying in formation. The formation is calculated analyzing the problem from a geometrical perspective and disposed by precisely adjusting the orbital parameters of each satellite. The dynamic modelling considers the orbital motion equations. The results are analyzed, compared and discussed. A detection algorithm is used as flag to signal the regular tetrahedron’s exact moments of occurrence. To do so, the volume calculated during the simulation is compared to the real volume, based on the initial conditions of the exact moment of formation and respecting a tolerance. This tolerance value is stablished arbitrarily depending on the mission and the formation’s geometrical parameters. The simulations will run on a computational environment.

Strong spin-orbit effects in transition metal oxides with tetrahedral coordination

NASA Astrophysics Data System (ADS)

Forte, Filomena; Guerra, Delia; Autieri, Carmine; Romano, Alfonso; Noce, Canio; Avella, Adolfo

2018-05-01

To prove that spin-orbit coupling can play a relevant role in determining the magnetic structure of transition metal oxides with tetrahedral coordination, we investigate the d1 Mott insulator KOsO4, combining density functional theory calculations and the exact diagonalization approach. We find that the interplay between crystal field, strong spin-orbit coupling, electronic correlations and structural distortions brings the system towards an antiferromagnetic phase, characterized by a non-vanishing orbital angular momentum and anisotropy among the in-plane and the out-of-plane antiferromagnetic correlations. We also show that, due to the peculiar interplay between spin-orbit coupling, Hund's coupling and hopping connectivity the system is on the verge of developing short range ferromagnetic correlations marked by strong directionality.

Thio-amide functionalized polymers via polymerization or post-polymerization modification

NASA Astrophysics Data System (ADS)

Ozcam, Ali; Henke, Adam; Stibingerova, Iva; Srogl, Jiri; Genzer, Jan

2011-03-01

Decreasing supplies of fresh water and increasing population necessitates development of advanced water cleaning technologies, which would facilitate the removal of water pollutants. Amongst the worst of such contaminants are heavy metals and cyanides, infamous for their high toxicity. To assist the water purification processes, we aim to synthesize functionalized macromolecules that would contribute in the decontamination processes by scavenging detrimental chemicals. Epitomizing this role thio-amide unit features remarkable chemical flexibility that facilitates reversible catch-release of the ions, where the behavior controlled by subtle red-ox changes in the environment. Chemical tunability of the thio-amide moiety enables synthesis of thio-amide based monomers and post-polymerization modification agents. Two distinct synthetic pathways, polymerization and post-polymerization modification, have been exploited, leading to functional thioamide-based macromolecules: thioamide-monomers were copolymerized with N-isopropylacrylamide and post-polymerization modifications of poly(dimethylaminoethyl methacrylate) and poly(propargyl methacrylate) were accomplished via quarternization and ``click'' reactions, respectively.

Anion photoelectron imaging spectroscopy of glyoxal

NASA Astrophysics Data System (ADS)

Xue, Tian; Dixon, Andrew R.; Sanov, Andrei

2016-09-01

We report a photoelectron imaging study of the radical-anion of glyoxal. The 532 nm photoelectron spectrum provides the first direct spectroscopic determination of the adiabatic electron affinity of glyoxal, EA = 1.10 ± 0.02 eV. This assignment is supported by a Franck-Condon simulation of the experimental spectrum that successfully reproduces the observed spectral features. The vertical detachment energy of the radical-anion is determined as VDE = 1.30 ± 0.04 eV. The reported EA and VDE values are attributed to the most stable (C2h symmetry) isomers of the neutral and the anion.

Purification Or Organic Acids Using Anion Exchange Chromatography.

DOEpatents

Ponnampalam; Elankovan

2001-09-04

Disclosed is a cost-effective method for purifying and acidifying carboxylic acids, including organic acids and amino acids. The method involves removing impurities by allowing the anionic form of the carboxylic acid to bind to an anion exchange column and washing the column. The carboxylic anion is displaced as carboxylic acid by washing the resin with a strong inorganic anion. This method is effective in removing organic carboxylic acids and amino acids from a variety of industrial sources, including fermentation broths, hydrolysates, and waste streams.

Functional anion concept: effect of fluorine anion on hydrogen storage of sodium alanate.

PubMed

Yin, Li-Chang; Wang, Ping; Kang, Xiang-Dong; Sun, Cheng-Hua; Cheng, Hui-Ming

2007-03-28

Doping NaAlH(4) with Ti-catalyst has produced a promising hydrogen storage system that can be reversibly operated at moderate temperature conditions. Of the various dopant precursors, TiCl(3) was well recognized due to its pronounced catalytic effect on the reversible dehydrogenation processes of sodium aluminium hydrides. Quite recently we experimentally found that TiF(3) was even better than TiCl(3) in terms of the critical hydrogen storage properties of the doped hydrides, in particular the dehydriding performance at Na(3)AlH(6)/NaH + Al step at moderate temperature. We present here the DFT calculation results of the TiF(3) or TiCl(3) doped Na(3)AlH(6). Our computational studies have demonstrated that F(-) and Cl(-) anions differ substantially from each other with regard to the state and function in the doped sodium aluminium hydride. In great contrast to the case of chloride doping where Cl(-) anion constitutes the "dead weight" NaCl, the fluoride doping results in a substitution of H(-) by F(-) anion in the hydride lattice and accordingly, a favorable thermodynamics adjustment. These results well explain the observed dehydriding performance associated with TiF(3)/TiCl(3)-doping. More significantly, the coupled computational and experimental efforts allow us to put forward a "functional anion" concept. This renews the current mechanism understanding in the catalytically enhanced sodium alanate.

Studies of anions sorption on natural zeolites.

PubMed

Barczyk, K; Mozgawa, W; Król, M

2014-12-10

This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. Copyright © 2014 Elsevier B.V. All rights reserved.

Interstellar dehydrogenated PAH anions: vibrational spectra

NASA Astrophysics Data System (ADS)

Buragohain, Mridusmita; Pathak, Amit; Sarre, Peter; Gour, Nand Kishor

2018-03-01

Interstellar polycyclic aromatic hydrocarbon (PAH) molecules exist in diverse forms depending on the local physical environment. Formation of ionized PAHs (anions and cations) is favourable in the extreme conditions of the interstellar medium (ISM). Besides in their pure form, PAHs are also likely to exist in substituted forms; for example, PAHs with functional groups, dehydrogenated PAHs etc. A dehydrogenated PAH molecule might subsequently form fullerenes in the ISM as a result of ongoing chemical processes. This work presents a density functional theory (DFT) calculation on dehydrogenated PAH anions to explore the infrared emission spectra of these molecules and discuss any possible contribution towards observed IR features in the ISM. The results suggest that dehydrogenated PAH anions might be significantly contributing to the 3.3 μm region. Spectroscopic features unique to dehydrogenated PAH anions are highlighted that may be used for their possible identification in the ISM. A comparison has also been made to see the size effect on spectra of these PAHs.

Photoinitiated polymerization of 1-vinylimidazole

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

Joshi, M.G.; Rodriguez, F.

1984-04-01

The photoinitiated polymerization of 1-vinylimidazole (VI) does not follow the classical kinetic scheme for free radical polymerization. Kinetic results for VI suggest a degradative addition reaction between the macroradical and the monomer to produce a relatively stable, unreactive radical, which does not reinitiate polymerization, is low, 1.5 kcal/mol. Among the 3 photoinitiators used, the highest quantum efficiency was demonstrated by 2,2'-diethoxyacetophenone followed by bezoin methyl ether and benzoin isopropyl ether. Under the experimental conditions used, the polymerization of VI does not proceed to complete conversion, and the phenomenon of dead-end polymerization is observed.

Fluorescence anisotropy of tyrosinate anion using one-, two- and three-photon excitation: tyrosinate anion fluorescence.

PubMed

Kierdaszuk, Borys

2013-03-01

We examined the emission spectra and steady-state anisotropy of tyrosinate anion fluorescence with one-photon (250-310 nm), two-photon (570-620 nm) and three-photon (750-930 nm) excitation. Similar emission spectra of the neutral (pH 7.2) and anionic (pH 13) forms of N-acetyl-L-tyrosinamide (NATyrA) (pKa 10.6) were observed for all modes of excitation, with the maxima at 302 and 352 nm, respectively. Two-photon excitation (2PE) and three-photon excitation (3PE) spectra of the anionic form were the same as that for one-photon excitation (1PE). In contrast, 2PE spectrum from the neutral form showed ~30-nm shift to shorter wavelengths relative to 1PE spectrum (λmax 275 nm) at two-photon energy (550 nm), the latter being overlapped with 3PE spectrum, both at two-photon energy (550 nm). Two-photon cross-sections for NATyrA anion at 565-580 nm were 10 % of that for N-acetyl-L-tryptophanamide (NATrpA), and increased to 90 % at 610 nm, while for the neutral form of NATyrA decreased from 2 % of that for NATrpA at 570 nm to near zero at 585 nm. Surprisingly, the fundamental anisotropy of NATyrA anion in vitrified solution at -60 °C was ~0.05 for 2PE at 610 nm as compared to near 0.3 for 1PE at 305 nm, and wavelength-dependence appears to be a basic feature of its anisotropy. In contrast, the 3PE anisotropy at 900 nm was about 0.5, and 3PE and 1PE anisotropy values appear to be related by the cos(6) θ to cos(2) θ photoselection factor (approx. 10/6) independently of excitation wavelength. Attention is drawn to the possible effect of tyrosinate anions in proteins on their multi-photon induced fluorescence emission and excitation spectra as well as excitation anisotropy spectra.

A computational study of anion-modulated cation-π interactions.

PubMed

Carrazana-García, Jorge A; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

2012-05-24

The interaction of anions with cation-π complexes formed by the guanidinium cation and benzene was thoroughly studied by means of computational methods. Potential energy surface scans were performed in order to evaluate the effect of the anion coming closer to the cation-π pair. Several structures of guanidinium-benzene complexes and anion approaching directions were examined. Supermolecule calculations were performed on ternary complexes formed by guanidinium, benzene, and one anion and the interaction energy was decomposed into its different two- and three-body contributions. The interaction energies were further dissected into their electrostatic, exchange, repulsion, polarization and dispersion contributions by means of local molecular orbital energy decomposition analysis. The results confirm that, besides the electrostatic cation-anion attraction, the effect of the anion over the cation-π interaction is mainly due to polarization and can be rationalized following the changes in the anion-π and the nonadditive (three-body) terms of the interaction. When the cation and the anion are on the same side of the π system, the three-body interaction is anticooperative, but when the anion and the cation are on opposite sides of the π system, the three-body interaction is cooperative. As far as we know, this is the first study where this kind of analysis is carried out with a structured cation as guanidinium with a significant biological interest.

Grain boundary mobility in anion doped MgO

NASA Technical Reports Server (NTRS)

Kapadia, C. M.; Leipold, M. H.

1973-01-01

Certain anions OH(-), F(-) and Gl(-) are shown to enhance grain growth in MgO. The magnitude of their effect decreases in the order in which the anions are listed and depends on their location (solid-solution, second phase) in the MgO lattice. As most anions exhibit relatively high vapor pressures at sintering temperatures, they retard densification and invariably promote residual porosity. The role of anions on grain growth rates was studied in relation to their effect on pore mobility and pore removal; the atomic process controlling the actual rates was determined from observed kinetics in conjunction with the microstructural features. With respect to controlling mechanisms, the effects of all anions are not the same. OH(-) and F(-) control behavior through creation of a defect structure and a grain boundary liquid phase while Cl(-) promotes matter transport within pores by evaporation-condensation. Studies on an additional anion, S to the minus 2nd power gave results which were no different from undoped MgO, possibly because of evaporative losses during hot pressing. Hence, the effect of sulphur is negligible or undetermined.

Step-Growth Polymerization.

ERIC Educational Resources Information Center

Stille, J. K.

1981-01-01

Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

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

Kan, Ze; Chen, Peng; Liu, Zhengying

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, andmore » the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.« less

Reactive processing of textile-natural fiber reinforced anionic polyamide-6 composites

NASA Astrophysics Data System (ADS)

Kan, Ze; Chen, Peng; Liu, Zhengying; Feng, Jianmin; Yang, Mingbo

2015-05-01

Nowadays natural fiber, used in reinforced composites, is widely concerned. However, no natural fiber reinforced reactive thermoplastic polymer grades had been prepared so far. Through our studies, it was demonstrated that there was a severe retardation and discoloration occurred in the reactive processing between anionic polyamide-6 (APA-6) and natural fiber, which result in incomplete polymerization when put together. In order to solve the problem, two methods were adopted in this paper, which are fiber pretreatment and usage of a new-style initiator called caprolactam magnesium bromide. The former is to remove sizing agent and impurities on the surface of fiber, and the latter is to weaken the side reactions between APA-6 and natural fiber by the nature of its lower reactivity and weaker alkaline. In cooperation with both methods, the severe retardation and discoloration had been improved significantly, so that the polymerization of APA-6 in natural fiber was occurred smoothly. Following textile-natural fiber reinforced APA-6 composites with an average thickness of 2.5 mm and a fiber volume content of 50% was prepared by vacuum assisted resin transfer molding (VARTM). The soxhlet extraction, dilute solution viscometry and differential scanning calorimeter (DSC) measurements respectively suggested the degree of conversion, viscosity-average molar mass and crystallization of composites was up to 94%, 11.3×104 and 50%. Remarkable improvement of mechanical properties were achieved through dynamic mechanical analysis (DMA), tensile and three-point bending test. Favorable interfacial adhesion and wettability were revealed by scanning electron microscopy (SEM) observation. Therefore, all of the above good performance make this new-style and environmentally friendly composites have broad application prospects.

Anion Gap Blood Test: MedlinePlus Lab Test Information

MedlinePlus

... medlineplus.gov/labtests/aniongapbloodtest.html Anion Gap Blood Test To use the sharing features on this page, ... enable JavaScript. What is an Anion Gap Blood Test? An anion gap blood test is a way ...

Photoelectron spectroscopy of the 6-azauracil anion.

PubMed

Chen, Jing; Buonaugurio, Angela; Dolgounitcheva, Olga; Zakrzewski, V G; Bowen, Kit H; Ortiz, J V

2013-02-14

We report the photoelectron spectrum of the 6-azauracil anion. The spectrum is dominated by a broad band exhibiting a maximum at an electron binding energy (EBE) of 1.2 eV. This spectral pattern is indicative of a valence anion. Our calculations were carried out using ab initio electron propagator and other many-body methods. Comparison of the anion and corresponding neutral of 6-azauracil with those of uracil shows that substituting a nitrogen atom for C-H at the C6 position of uracil gives rise to significant changes in the electronic structure of 6-azauracil versus that of uracil. The adiabatic electron affinity (AEA) of the canonical 6-azauracil tautomer is substantially larger than that of canonical uracil. Among the five tautomeric, 6-azauracil anions studied computationally, the canonical structure was found to be the most stable. The vertical detachment energies (VDE) of the canonical, valence-bound anion of 6-azauracil and its closest "very-rare" tautomer have been calculated. Electron propagator calculations on the canonical anion yield a VDE value that is in close agreement with the experimentally determined VDE value of 1.2 eV. The AEA value of 6-azauracil, assessed at the CCSD(T) level of theory to be 0.5 eV, corresponds with the EBE value of the onset of the experimental spectrum.

Changes in chroma of two indirect composite materials polymerized with different polymerization systems.

PubMed

Ayano, Michiya

2012-01-01

This study evaluated chroma change in two composite materials (Sinfony and Pearleste) polymerized with two different systems. Disk specimens were prepared using a metal halide unit (Hyper LII) and an exposure time of 60 to 180 s. The proprietary polymerization systems (Visio and Pearlcure systems) were used as the reference polymerization modes. After storage at 37°C for 24 h, CIE 1976 L*a*b* values were measured by using a dental chroma meter (ShadeEye NCC) with a gray background. The specimens were then immersed in water or tea. Color change from baseline to 4 weeks was evaluated by measuring ΔL*, Δa*, and Δb*, after which ΔE*(ab) values were calculated. The brightness of Sinfony specimens was reduced by tea immersion. The color of both materials shifted to yellow after tea immersion, although color change in Sinfony specimens was greater than that in Pearleste specimens. For both materials, color change was less after polymerization with the metal halide unit. In conclusion, Sinfony polymerized with the Hyper LII unit, and Pearleste polymerized with either system, were stable against discoloration due to tea immersion.

Mixed-mode high-power impulse magnetron sputter deposition of tetrahedral amorphous carbon with pulse-length control of ionization

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

Tucker, M. D.; Marks, N. A.; Ganesan, R.

2016-04-21

High-power impulse magnetron sputtering (HiPIMS) is used to deposit amorphous carbon thin films with sp{sup 3} fractions of 13% to 82%. Increasing the pulse length results in a transition from conventional HiPIMS deposition to a “mixed-mode” in which an arc triggers on the target surface, resulting in a large flux of carbon ions. The films are characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, ellipsometry, nanoindentation, elastic recoil detection analysis, and measurements of stress and contact angle. All properties vary in a consistent manner, showing a high tetrahedral character only for long pulses, demonstrating that mixed-mode deposition is the source ofmore » the high carbon ion flux. Varying the substrate bias reveals an “energy window” effect, where the sp{sup 3} fraction of the films is greatest for a substrate bias around −100 V and decreases for higher or lower bias values. In the absence of bias, the films' properties show little dependence on the pulse length, showing that energetic ions are the origin of the highly tetrahedral character.« less

Making Polymeric Microspheres

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Anion-π interactions in active centers of superoxide dismutases.

PubMed

Ribić, Vesna R; Stojanović, Srđan Đ; Zlatović, Mario V

2018-01-01

We investigated 1060 possible anion-π interactions in a data set of 41 superoxide dismutase active centers. Our observations indicate that majority of the aromatic residues are capable to form anion-π interactions, mainly by long-range contacts, and that there is preference of Trp over other aromatic residues in these interactions. Furthermore, 68% of total predicted interactions in the dataset are multiple anion-π interactions. Anion-π interactions are distance and orientation dependent. We analyzed the energy contribution resulting from anion-π interactions using ab initio calculations. The results showed that, while most of their interaction energies lay in the range from -0 to -4kcalmol -1 , those energies can be up to -9kcalmol -1 and about 34% of interactions were found to be repulsive. Majority of the suggested anion-π interacting residues in ternary complexes are metal-assisted. Stabilization centers for these proteins showed that all the six residues found in predicted anion-π interactions are important in locating one or more of such centers. The anion-π interacting residues in these proteins were found to be highly conserved. We hope that these studies might contribute useful information regarding structural stability and its interaction in future designs of novel metalloproteins. Copyright © 2017 Elsevier B.V. All rights reserved.

Self-assembly of a tetrahedral 58-nuclear barium vanadium oxide cluster.

PubMed

Kastner, Katharina; Puscher, Bianka; Streb, Carsten

2013-01-07

We report the synthesis and characterization of a molecular barium vanadium oxide cluster featuring high nuclearity and high symmetry. The tetrameric, 2.3 nm cluster H(5)[Ba(10)(NMP)(14)(H(2)O)(8)[V(12)O(33)](4)Br] is based on a bromide-centred, octahedral barium scaffold which is capped by four previously unknown [V(12)O(33)](6-) clusters in a tetrahedral fashion. The compound represents the largest polyoxovanadate-based heterometallic cluster known to date. The cluster is formed in organic solution and it is suggested that the bulky N-methyl-2-pyrrolidone (NMP) solvent ligands allow the isolation of this giant molecule and prevent further condensation to a solid-state metal oxide. The cluster is fully characterized using single-crystal XRD, elemental analysis, ESI mass spectrometry and other spectroscopic techniques.

Extraction of acidic degradation products of organophosphorus chemical warfare agents. Comparison between silica and mixed-mode strong anion-exchange cartridges.

PubMed

Kanaujia, Pankaj K; Pardasani, Deepak; Gupta, A K; Kumar, Rajesh; Srivastava, R K; Dubey, D K

2007-08-17

The analysis of alkyl alkylphosphonic acids (AAPAs) and alkylphosphonic acids (APAs), the hydrolyzed products of nerve agents, constitutes an important aspect for verifying the compliance to the Chemical weapons convention (CWC). This work devotes on the development of solid-phase extraction method using polymeric mixed-mode strong anion-exchange (Oasis MAX) cartridges for extraction of AAPAs and APAs from water. The extracted analytes were analyzed by GC-MS under full scan and selected ion monitoring mode. The extraction efficiencies of MAX and silica-based anion-exchange cartridges were compared, and results revealed that MAX sorbents yielded better recoveries. Extraction parameters, such as loading capacity, extraction solvent, its volume, and washing solvent were optimized. Best recoveries were obtained using 1 mL of acidic methanol (0.1 M), and limits of detection could be achieved up to 5 x 10(-4) microg mL(-1) (in SIM) and 0.05 microg mL(-1) in full scan mode. The method was successfully employed for the detection and identification of alkylphosphonic acids present in soil sample sent by the Organization for Prohibition of Chemical Weapons (OPCW) in the official proficiency tests.

Matrix elements of vibration kinetic energy operator of tetrahedral molecules in non-orthogonal-dependent coordinates

NASA Astrophysics Data System (ADS)

Protasevich, Alexander E.; Nikitin, Andrei V.

2018-01-01

In this work, we propose an algorithm for calculating the matrix elements of the kinetic energy operator for tetrahedral molecules. This algorithm uses the dependent six-angle coordinates (6A) and takes into account the full symmetry of molecules. Unlike A.V. Nikitin, M. Rey, and Vl. G. Tyuterev who operate with the kinetic energy operator only in Radau orthogonal coordinates, we consider a general case. The matrix elements are shown to be a sum of products of one-dimensional integrals.

A Deep Penetration Problem Calculation Using AETIUS:An Easy Modeling Discrete Ordinates Transport Code UsIng Unstructured Tetrahedral Mesh, Shared Memory Parallel

NASA Astrophysics Data System (ADS)

KIM, Jong Woon; LEE, Young-Ouk

2017-09-01

As computing power gets better and better, computer codes that use a deterministic method seem to be less useful than those using the Monte Carlo method. In addition, users do not like to think about space, angles, and energy discretization for deterministic codes. However, a deterministic method is still powerful in that we can obtain a solution of the flux throughout the problem, particularly as when particles can barely penetrate, such as in a deep penetration problem with small detection volumes. Recently, a new state-of-the-art discrete-ordinates code, ATTILA, was developed and has been widely used in several applications. ATTILA provides the capabilities to solve geometrically complex 3-D transport problems by using an unstructured tetrahedral mesh. Since 2009, we have been developing our own code by benchmarking ATTILA. AETIUS is a discrete ordinates code that uses an unstructured tetrahedral mesh such as ATTILA. For pre- and post- processing, Gmsh is used to generate an unstructured tetrahedral mesh by importing a CAD file (*.step) and visualizing the calculation results of AETIUS. Using a CAD tool, the geometry can be modeled very easily. In this paper, we describe a brief overview of AETIUS and provide numerical results from both AETIUS and a Monte Carlo code, MCNP5, in a deep penetration problem with small detection volumes. The results demonstrate the effectiveness and efficiency of AETIUS for such calculations.

Syntheses, crystal structures, and properties of six new lanthanide(III) transition metal tellurium(IV) oxyhalides with three types of structures.

PubMed

Shen, Yue-Ling; Mao, Jiang-Gao

2005-07-25

Solid-state reactions of lanthanide(III) oxide (and lanthanide(III) oxyhalide), transition metal halide (and transition metal oxide), and TeO(2) at high temperature lead to six new lanthanide transition metal tellurium(IV) oxyhalides with three different types of structures, namely, DyCuTe(2)O(6)Cl, ErCuTe(2)O(6)Cl, ErCuTe(2)O(6)Br, Sm(2)Mn(Te(5)O(13))Cl(2), Dy(2)Cu(Te(5)O(13))Br(2), and Nd(4)Cu(TeO(3))(5)Cl(3). Compounds DyCuTe(2)O(6)Cl, ErCuTe(2)O(6)Cl, and ErCuTe(2)O(6)Br are isostructural. The lanthanide(III) ion is eight-coordinated by eight oxygen atoms, and the copper(II) ion is five-coordinated by four oxygens and a halide anion in a distorted square pyramidal geometry. The interconnection of Ln(III) and Cu(II) ions by bridging tellurite anions results in a three-dimensional (3D) network with tunnels along the a-axis; the halide anion and the lone-pair electrons of the tellurium(IV) ions are oriented toward the cavities of the tunnels. Compounds Sm(2)Mn(Te(5)O(13))Cl(2) and Dy(2)Cu(Te(5)O(13))Br(2) are isostructural. The lanthanide(III) ions are eight-coordinated by eight oxygens, and the divalent transition metal ion is octahedrally coordinated by six oxygens. Two types of polymeric tellurium(IV) oxide anions are formed: Te(3)O(8)(4)(-) and Te(4)O(10)(4)(-). The interconnection of the lanthanide(III) and divalent transition metal ions by the above two types of polymeric tellurium(IV) oxide anions leads to a 3D network with long, narrow-shaped tunnels along the b-axis. The halide anions remain isolated and are located at the above tunnels. Nd(4)Cu(TeO(3))(5)Cl(3) features a different structure. All five of the Nd(III) ions are eight-coordinated (NdO(8) for Nd(1), Nd(2), Nd(4), and Nd(5) and NdO(7)Cl for Nd(3)), and the copper(I) ion is tetrahedrally coordinated by four chloride anions. The interconnection of Nd(III) ions by bridging tellurite anions resulted in a 3D network with large tunnels along the b-axis. The CuCl(4) tetrahedra are interconnected into

Anion complexation and the Hofmeister effect.

PubMed

Carnegie, Ryan S; Gibb, Corinne L D; Gibb, Bruce C

2014-10-20

The (1)H NMR spectroscopic analysis of the binding of the ClO4(-) anion to the hydrophobic, concave binding site of a deep-cavity cavitand is presented. The strength of association between the host and the ClO4(-) anion is controlled by both the nature and concentration of co-salts in a manner that follows the Hofmeister series. A model that partitions this trend into the competitive binding of the co-salt anion to the hydrophobic pocket of the host and counterion binding to its external carboxylate groups successfully accounts for the observed changes in ClO4(-) affinity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Filters, microporous polymeric. 177.2250 Section... Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in... liquid food. (a) Microporous polymeric filters consist of a suitably permeable, continuous, polymeric...

Anion channels in the sea urchin sperm plasma membrane.

PubMed

Morales, E; de la Torre, L; Moy, G W; Vacquier, V D; Darszon, A

1993-10-01

Ionic fluxes in sea urchin sperm plasma membrane regulate cell motility and the acrosome reaction (AR). Although cationic channels mediate some of the ionic movements, little is known about anion channels in these cells. The fusion of sperm plasma membranes into lipid bilayers allowed identification of a 150 pS anion channel. This anion channel was enriched from detergent-solubilized sperm plasma membranes using a wheat germ agglutinin Sepharose column. Vesicles formed from this preparation were fused into black lipid membranes (BLM), yielding single channel anion-selective activity with the properties of those found in the sperm membranes. The following anion selectivity sequence was found: NO3- > CNS- > Br- > Cl-. This anion channel has a high open probability at the holding potentials tested, it is partially blocked by 4,4'-diisothiocyano-2,2'-stilbendisulfonic acid (DIDS), and it often displays substates. The sperm AR was also inhibited by DIDS.

Anion binding in biological systems

NASA Astrophysics Data System (ADS)

Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

2009-11-01

We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

Experimentally quantifying anion polarizability at the air/water interface.

PubMed

Tong, Yujin; Zhang, Igor Ying; Campen, R Kramer

2018-04-03

The adsorption of large, polarizable anions from aqueous solution on the air/water interface controls important atmospheric chemistry and is thought to resemble anion adsorption at hydrophobic interfaces generally. While the favourability of adsorption of such ions is clear, quantifying adsorption thermodynamics has proven challenging because it requires accurate description of the structure of the anion and its solvation shell at the interface. In principle anion polarizability offers a structural window, but to the best of our knowledge there has so far been no experimental technique that allowed its characterization with interfacial specificity. Here, we meet this challenge using interface-specific vibrational spectroscopy of Cl-O vibrations of the [Formula: see text] anion at the air/water interface and report that the interface breaks the symmetry of the anion, the anisotropy of [Formula: see text]'s polarizability tensor is more than two times larger than in bulk water and concentration dependent, and concentration-dependent polarizability changes are consistent with correlated changes in surface tension.

The Thermodynamics of Anion Complexation to Nonpolar Pockets.

PubMed

Sullivan, Matthew R; Yao, Wei; Tang, Du; Ashbaugh, Henry S; Gibb, Bruce C

2018-02-08

The interactions between nonpolar surfaces and polarizable anions lie in a gray area between the hydrophobic and Hofmeister effects. To assess the affinity of these interactions, NMR and ITC were used to probe the thermodynamics of eight anions binding to four different hosts whose pockets each consist primarily of hydrocarbon. Two classes of host were examined: cavitands and cyclodextrins. For all hosts, anion affinity was found to follow the Hofmeister series, with associations ranging from 1.6-5.7 kcal mol -1 . Despite the fact that cavitand hosts 1 and 2 possess intrinsic negative electrostatic fields, it was determined that these more enveloping hosts generally bound anions more strongly. The observation that the four hosts each possess specific anion affinities that cannot be readily explained by their structures, points to the importance of counter cations and the solvation of the "empty" hosts, free guests, and host-guest complexes, in defining the affinity.

Highly conductive side chain block copolymer anion exchange membranes.

PubMed

Wang, Lizhu; Hickner, Michael A

2016-06-28

Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days.

Radiation-induced polymerization of glass-forming systems. V. Initial polymerization rate in binary glass-forming systems

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

Kaetsu, Isao; Okubo, Hiroshi; Ito, Akihiko

1973-06-01

The radiation-induced polymerization of binary systems consisting of glass-forming monomer and glass-forming solvent in supercooled phase was studied. The initial polymerization rates were markedly affected by T/sub g/ (glass transition temperature) and T/sub v/ of the system (30-50 deg C higher than T/sub g/), which are functions of the composition. The composition and temperature dependence of initial polymerization rate in binary glass-forming systems were much affected by homogeneity of the polymerization system and the T of the glass- forming solvent. The composition and temperature dependences in the glycidyl methacrylate --triacetin system as a typical homogeneous polymerization system were studied inmore » detail, and the polymerizations of hydroxyethyl methacrylate triacetln and hydroxyethyl methacrylate --isoamyl acetate systems were studied for the heterogeneous polymerization systems; the former illustrates the combination of lower T/sub g/ monomer and higher T/sub g/ solvent and the latter typifies a system consisting of higher T/sub g/ monomer and lower T/sub g/ solvent. All experimental results for the composition and temperature dependence of initial polymerization rate in binary glass-forming systems could be explained by considering the product of the effect of the physical effect relating to T/sub v/ and T/sub g/ of the system and the effect of composition in normal solution polymerization at higher temperature, which was also the product of a dilution effect and a chemical or physical acceleration effect. (auth)« less

Polymeric nanoparticles

PubMed Central

Bolhassani, Azam; Javanzad, Shabnam; Saleh, Tayebeh; Hashemi, Mehrdad; Aghasadeghi, Mohammad Reza; Sadat, Seyed Mehdi

2014-01-01

Nanocarriers with various compositions and biological properties have been extensively applied for in vitro/in vivo drug and gene delivery. The family of nanocarriers includes polymeric nanoparticles, lipid-based carriers (liposomes/micelles), dendrimers, carbon nanotubes, and gold nanoparticles (nanoshells/nanocages). Among different delivery systems, polymeric carriers have several properties such as: easy to synthesize, inexpensive, biocompatible, biodegradable, non-immunogenic, non-toxic, and water soluble. In addition, cationic polymers seem to produce more stable complexes led to a more protection during cellular trafficking than cationic lipids. Nanoparticles often show significant adjuvant effects in vaccine delivery since they may be easily taken up by antigen presenting cells (APCs). Natural polymers such as polysaccharides and synthetic polymers have demonstrated great potential to form vaccine nanoparticles. The development of new adjuvants or delivery systems for DNA and protein immunization is an expanding research field. This review describes polymeric carriers especially PLGA, chitosan, and PEI as vaccine delivery systems. PMID:24128651

Epitaxially stabilized iridium spinel oxide without cations in the tetrahedral site

NASA Astrophysics Data System (ADS)

Kuriyama, Hiromichi; Matsuno, Jobu; Niitaka, Seiji; Uchida, Masaya; Hashizume, Daisuke; Nakao, Aiko; Sugimoto, Kunihisa; Ohsumi, Hiroyuki; Takata, Masaki; Takagi, Hidenori

2010-05-01

Single-crystalline thin film of an iridium dioxide polymorph Ir2O4 has been fabricated by the pulsed laser deposition of LixIr2O4 precursor and the subsequent Li-deintercalation using soft chemistry. Ir2O4 crystallizes in a spinel (AB2O4) without A cations in the tetrahedral site, which is isostructural to λ-MnO2. Ir ions form a pyrochlore sublattice, which is known to give rise to a strong geometrical frustration. This Ir spinel was found to be a narrow gap insulator, in remarkable contrast to the metallic ground state of rutile-type IrO2. We argue that an interplay of a strong spin-orbit coupling and a Coulomb repulsion gives rise to an insulating ground state as in a layered perovskite Sr2IrO4.

Oxygen anion (O- ) and hydroxide anion (HO- ) reactivity with a series of old and new refrigerants.

PubMed

Le Vot, Clotilde; Lemaire, Joël; Pernot, Pascal; Heninger, Michel; Mestdagh, Hélène; Louarn, Essyllt

2018-04-01

The reactivity of a series of commonly used halogenated compounds (trihalomethanes, chlorofluorocarbon, hydrochlorofluorocarbon, fluorocarbons, and hydrofluoroolefin) with hydroxide and oxygen anion is studied in a compact Fourier transform ion cyclotron resonance. O - is formed by dissociative electron attachment to N 2 O and HO - by a further ion-molecule reaction with ammonia. Kinetic experiments are performed by increasing duration of introduction of the studied molecule at a constant pressure. Hydroxide anion reactions mainly proceed by proton transfer for all the acidic compounds. However, nucleophilic substitution is observed for chlorinated and brominated compounds. For fluorinated compounds, a specific elimination of a neutral fluorinated alkene is observed in our results in parallel with the proton transfer reaction. Oxygen anion reacts rapidly and extensively with all compounds. Main reaction channels result from nucleophilic substitution, proton transfer, and formal H 2 + transfer. We highlight the importance of transfer processes (atom or ion) in the intermediate ion-neutral complex, explaining part of the observed reactivity and formed ions. In this paper, we present the first reactivity study of anions with HFO 1234yf. Finally, the potential of O - and HO - as chemical ionization reagents for trace analysis is discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Supramolecular "Step Polymerization" of Preassembled Micelles: A Study of "Polymerization" Kinetics.

PubMed

Yang, Chaoying; Ma, Xiaodong; Lin, Jiaping; Wang, Liquan; Lu, Yingqing; Zhang, Liangshun; Cai, Chunhua; Gao, Liang

2018-03-01

In nature, sophisticated functional materials are created through hierarchical self-assembly of nanoscale motifs, which has inspired the fabrication of man-made materials with complex architectures for a variety of applications. Herein, a kinetic study on the self-assembly of spindle-like micelles preassembled from polypeptide graft copolymers is reported. The addition of dimethylformamide and, subsequently, a selective solvent (water) can generate a "reactive point" at both ends of the spindles as a result of the existence of structural defects, which induces the "polymerization" of the spindles into nanowires. Experimental results combined with dissipative particle dynamics simulations show that the polymerization of the micellar subunits follows a step-growth polymerization mechanism with a second-order reaction characteristic. The assembly rate of the micelles is dependent on the subunit concentration and on the activity of the reactive points. The present work reveals a law governing the self-assembly kinetics of micelles with structural defects and opens the door for the construction of hierarchical structures with a controllable size through supramolecular step polymerization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The crystal and magnetic structures of Sr 2LaFe 3O 8

NASA Astrophysics Data System (ADS)

Battle, P. D.; Gibb, T. C.; Lightfoot, P.

1990-02-01

The crystal and magnetic structures of the anion-deficient perovskite Sr 2LaFe 3O 8 (space group Pmma, a = 5.5095(1), b = 11.8845(5), c = 5.6028(1)AÅ) have been refined from X-ray and neutron powder diffraction data collected at room temperature. The crystal structure consists of layers of octahedral (O) and tetrahedral (T) iron-oxygen polyhedra arranged in the stacking sequence … OOTOOT … perpendicular to theyˆaxis of the unit cell. The magnetic structure is that of a G-type antiferromagnet with ordered magnetic moments of 3.77(5) and 3.15(11) μ B at the octahedral and tetrahedral sites, respectively. The low moment at the tetrahedral site is consistent with the observed disorder and magnetic anisotropy.

Synthesis and anion exchange properties of a Zn/Ni double hydroxide salt with a guarinoite structure

NASA Astrophysics Data System (ADS)

Delorme, F.; Seron, A.; Licheron, M.; Veron, E.; Giovannelli, F.; Beny, C.; Jean-Prost, V.; Martineau, D.

2009-09-01

In this study, the first route to synthesize a compound with the guarinoite structure (Zn,Co,Ni) 6(SO 4)(OH,Cl) 10·5H 2O is reported. Zn/Ni guarinoite is obtained from the reaction of NiSO 4·7H 2O with solid ZnO in aqueous solution. The resulting green Zn/Ni guarinoite ((Zn 3.52Ni 1.63)(SO 4) 1.33(OH 7.64)·4.67H 2O) was characterized by X-ray diffraction, infrared spectrometry, UV-Visible spectrometry and thermal analysis. It is shown that its structure is similar to the one described for the layered Zn sulfate hydroxide hydrate, i.e. brucite layers with {1}/{4} empty octahedra presenting tetrahedrally coordinated divalent atoms above and below the empty octahedra. Ni atoms are located in the octahedra and zinc atoms in tetrahedra and octahedra. In this structure the exchangeable anions are located at the apex of tetrahedra. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the Zn/Ni guarinoite is composed of aggregates of hexagonal plates of several hundreds of nanometers. Due to its interest for industrial or environmental applications, the exchange of sulfate groups by carbonates has been investigated. Results show a limited exchange and a higher affinity of the Zn/Ni guarinoite for sulfates compared to carbonates.

Anion-free bambus[6]uril and its supramolecular properties.

PubMed

Svec, Jan; Dusek, Michal; Fejfarova, Karla; Stacko, Peter; Klán, Petr; Kaifer, Angel E; Li, Wei; Hudeckova, Edita; Sindelar, Vladimir

2011-05-09

Methods for the preparation of anion-free bambus[6]uril (BU6) are presented. They are based on the oxidation of iodide anion, which is bound inside the macrocycle, utilizing dark oxidation by hydrogen peroxide or photooxidation in the presence of titanium dioxide. Anion-free BU6 was found to be insoluble in any of the investigated solvents; however, it dissolves in methanol/chloroform (1:1) or acetonitrile/water (1:1) mixtures in the presence of the tetrabutylammonium salt of a suitable anion. The association constants with halide ions, BF(4)(-), NO(3)(-), and CN(-), were measured by (1)H NMR spectroscopy. The highest association constant (8.9×10(5) M(-1)) was found for the 1:1 complex of BU6 with I(-) in acetonitrile/water mixture. A number of crystal structures of BU6 complexes with various anions were obtained. The influence of the anion size on the macrocycle diameter is discussed together with an unusual arrangement of the macrocycles into separate layers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonlinear optical and conductive polymeric material

DOEpatents

Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

1992-05-19

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Nonlinear optical and conductive polymeric material

DOEpatents

Barton, T.J.; Ijadi-Maghsooodi, S; Yi Pang.

1993-10-19

A polymeric material is described which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6].

Nonlinear optical and conductive polymeric material

DOEpatents

Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

1992-05-19

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl[sub 5] or W(CO)[sub 6]/hv.

Nonlinear optical and conductive polymeric material

DOEpatents

Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

1993-10-19

A polymeric material which exhibits nonlinear optical properties if undoped and conductive properties if doped. The polymer is prepared by polymerizing diethynylsilane compositions, the resulting polymeric material having a weight average molecular weight between about 20,000 and about 200,000 grams per mole. The polymer is prepared and catalytically polymerized by exposure to a catalyst, such as MoCl.sub.5 or W(CO).sub.6 /hv.

Part I. Student success in intensive versus traditional introductory chemistry courses. Part II. Synthesis of salts of the weakly coordinating trisphat anion

NASA Astrophysics Data System (ADS)

Hall, Mildred V.

Part I. Intensive courses have been shown to be associated with equal or greater student success than traditional-length courses in a wide variety of disciplines and education levels. Student records from intensive and traditional-length introductory general chemistry courses were analyzed to determine the effects, of the course format, the level of academic experience, life experience (age), GPA, academic major and gender on student success in the course. Pretest scores, GPA and ACT composite scores were used as measures of academic ability and prior knowledge; t-tests comparing the means of these variables were used to establish that the populations were comparable prior to the course. Final exam scores, total course points and pretest-posttest differences were used as measures of student success; t-tests were used to determine if differences existed between the populations. ANCOVA analyses revealed that student GPA, pretest scores and course format were the only variables tested that were significant in accounting for the variance of the academic success measures. In general, the results indicate that students achieved greater academic success in the intensive-format course, regardless of the level of academic experience, life experience, academic major or gender. Part II. Weakly coordinating anions have many important applications, one of which is to function as co-catalysts in the polymerization of olefins by zirconocene. The structure of tris(tetrachlorobenzenedialato) phosphate(V) or "trisphat" anion suggests that it might be an outstanding example of a weakly coordinating anion. Trisphat acid was synthesized and immediately used to prepare the stable tributylammonium trisphat, which was further reacted to produce trisphat salts of Group I metal cations in high yields. Results of the 35Cl NQR analysis of these trisphat salts indicate only very weak coordination between the metal cations and the chlorine atoms of the trisphat anion.

Kinetics of Corrosion Inhibition of Aluminum in Acidic Media by Water-Soluble Natural Polymeric Pectates as Anionic Polyelectrolyte Inhibitors.

PubMed

Hassan, Refat M; Zaafarany, Ishaq A

2013-06-17

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyeletrolyte pectates (PEC) as a water-soluble natural polymer polysaccharide has been studied using both gasometric and weight loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing inhibitor concentration and decrease with increasing temperature. The inhibition action of PEC on Al metal surface was found to obey the Freundlich isotherm. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the kinetic results is discussed in the paper.

Inhibition of nuclear waste solutions containing multiple aggressive anions

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

Congdon, J.W.

1988-01-01

The inhibition of localized corrosion of carbon steel in caustic, high-level radioactive waste solutions was studied using cyclic potentiodynamic polarization scans, supplemented by partially immersed coupon tests. The electrochemical tests provided a rapid and accurate means of determining the relationship between the minimum inhibitor requirements and the concentration of the aggressive anions in this system. Nitrate, sulfate, chloride, and fluoride were identified as aggressive anions, however, no synergistic effects were observed between these anions. This observation may have important theoretical implications because it tends to contradict the behavior of aggressive anions as predicted by existing theories for localized corrosion.

Inhibition of nuclear waste solutions containing multiple aggressive anions

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

Congdon, J.W.

1988-05-01

The inhibition of localized corrosion of carbon steel in caustic, high-level radioactive waste solutions was studied using cyclic potentiodynamic polarization scans supplemented by partially immersed coupon tests. The electrochemical tests provided a rapid and accurate means of determining the relationship between the minimum inhibitor requirements and the concentration of the aggressive anions in this system. Nitrate, sulfate, chloride, and fluoride were identified as aggressive anions; however, no synergistic effects were observed between these anions. This observation may have important theoretical implications because it tends to contradict the behavior of aggressive anions as predicted by existing theories for localized corrosion.

Thermally Stable, Piezoelectric and Pyroelectric Polymeric Substrates

NASA Technical Reports Server (NTRS)

Simpson, Joycely O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers. acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors, in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors. weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 1000 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium; applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Benzonitrile: Electron affinity, excited states, and anion solvation

NASA Astrophysics Data System (ADS)

Dixon, Andrew R.; Khuseynov, Dmitry; Sanov, Andrei

2015-10-01

We report a negative-ion photoelectron imaging study of benzonitrile and several of its hydrated, oxygenated, and homo-molecularly solvated cluster anions. The photodetachment from the unsolvated benzonitrile anion to the X ˜ 1 A 1 state of the neutral peaks at 58 ± 5 meV. This value is assigned as the vertical detachment energy (VDE) of the valence anion and the upper bound of adiabatic electron affinity (EA) of benzonitrile. The EA of the lowest excited electronic state of benzonitrile, a ˜ 3 A 1 , is determined as 3.41 ± 0.01 eV, corresponding to a 3.35 eV lower bound for the singlet-triplet splitting. The next excited state, the open-shell singlet A ˜ 1 A 1 , is found about an electron-volt above the triplet, with a VDE of 4.45 ± 0.01 eV. These results are in good agreement with ab initio calculations for neutral benzonitrile and its valence anion but do not preclude the existence of a dipole-bound state of similar energy and geometry. The step-wise and cumulative solvation energies of benzonitrile anions by several types of species were determined, including homo-molecular solvation by benzonitrile, hydration by 1-3 waters, oxygenation by 1-3 oxygen molecules, and mixed solvation by various combinations of O2, H2O, and benzonitrile. The plausible structures of the dimer anion of benzonitrile were examined using density functional theory and compared to the experimental observations. It is predicted that the dimer anion favors a stacked geometry capitalizing on the π-π interactions between the two partially charged benzonitrile moieties.

Prebiotic potential of Agave angustifolia Haw fructans with different degrees of polymerization.

PubMed

Velázquez-Martínez, José Rodolfo; González-Cervantes, Rina M; Hernández-Gallegos, Minerva Aurora; Mendiola, Roberto Campos; Aparicio, Antonio R Jiménez; Ocampo, Martha L Arenas

2014-08-19

Inulin-type fructans are the most studied prebiotic compounds because of their broad range of health benefits. In particular, plants of the Agave genus are rich in fructans. Agave-derived fructans have a branched structure with both β-(2→1) and β-(2→6) linked fructosyl chains attached to the sucrose start unit with a degree of polymerization (DP) of up to 80 fructose units. The objective of this work was to assess the prebiotic potential of three Agave angustifolia Haw fructan fractions (AFF) with different degrees of polymerization. The three fructan fractions were extracted from the agave stem by lixiviation and then purified by ultrafiltration and ion exchange chromatography: AFF1, AFF2 and AFF3 with high (3-60 fructose units), medium (2-40) and low (2-22) DP, respectively. The fructan profile was determined with high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), which confirmed a branched fructan structure. Structural elucidation was performed by Fourier Transform Infra-Red Spectroscopy. The AFF spectrum shows characteristic fructan bands. The prebiotic effect of these fractions was assessed in vitro through fermentation by Bifidobacterium and Lactobacillus strains. Four growth patterns were observed. Some bacteria did not grow with any of the AFF, while other strains grew with only AFF3. Some bacteria grew according to the molecular weight of the AFF and some grew indistinctly with the three fructan fractions.

The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

PubMed

Černý, Radovan; Schouwink, Pascal

2015-12-01

The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

Mesostructured Metal Germanium Sulfide and Selenide Materials Based on the Tetrahedral [Ge 4S 10] 4- and [Ge 4Se 10] 4- Units: Surfactant Templated Three-Dimensional Disordered Frameworks Perforated with Worm Holes

NASA Astrophysics Data System (ADS)

Wachhold, Michael; Kasthuri Rangan, K.; Lei, Ming; Thorpe, M. F.; Billinge, Simon J. L.; Petkov, Valeri; Heising, Joy; Kanatzidis, Mercouri G.

2000-06-01

The polymerization of [Ge4S10]4- and [Ge4Se10]4- unit clusters with the divalent metal ions Zn2+, Cd2+, Hg2+, Ni2+, and Co2+ in the presence of various surfactant cations leads to novel mesostructured phases. The surfactants are the quaternary ammonium salts C12H25NMe3Br, C14H29NMe3Br, C16H33NMe3Br, and C18H37NMe3Br, which play the role of templates, helping to assemble a three-dimensional mesostructured metal-germanium chalcogenide framework. These materials are stoichiometric in nature and have the formula of (R-NMe3)2[MGe4Q10] (Q=S, Se). The local atomic structure was probed by X-ray diffuse scattering and pair distribution function analysis methods and indicates that the adamantane clusters stay intact while the linking metal atoms possess a tetrahedral coordination environment. A model can be derived, from the comparison of measured and simulated X-ray powder diffraction patterns, describing the structure as an amorphous three-dimensional framework consisting of adamantane [Ge4Q10]4- units that are bridged by tetrahedral coordinated M2+ cations. The network structures used in the simulations were derived from corresponding disordered structures developed for amorphous silicon. The frameworks in (R-NMe3)2[MGe4Q10] are perforated with worm hole-like tunnels, occupied by the surfactant cations, which show no long-range order. This motif is supported by transmission electron microscopy images of these materials. The pore sizes of these channels were estimated to lie in the range of 20-30 Å, depending on the appointed surfactant cation length. The framework wall thickness of ca. 10 Å is thereby independent from the surfactant molecules used. Up to 80% of the surfactant molecules can be removed by thermal degradation under vacuum without loss of mesostructural integrity. Physical, chemical, and spectroscopic properties of these materials are discussed.

Polyamorphism in tetrahedral substances: Similarities between silicon and ice

NASA Astrophysics Data System (ADS)

Garcez, K. M. S.; Antonelli, A.

2015-07-01

Tetrahedral substances, such as silicon, water, germanium, and silica, share various unusual phase behaviors. Among them, the so-called polyamorphism, i.e., the existence of more than one amorphous form, has been intensively investigated in the last three decades. In this work, we study the metastable relations between amorphous states of silicon in a wide range of pressures, using Monte Carlo simulations. Our results indicate that the two amorphous forms of silicon at high pressures, the high density amorphous (HDA) and the very high density amorphous (VHDA), can be decompressed from high pressure (˜20 GPa) down to the tensile regime, where both convert into the same low density amorphous. Such behavior is also observed in ice. While at high pressure (˜20 GPa), HDA is less stable than VHDA, at the pressure of 10 GPa both forms exhibit similar stability. On the other hand, at much lower pressure (˜5 GPa), HDA and VHDA are no longer the most stable forms, and, upon isobaric annealing, an even less dense form of amorphous silicon emerges, the expanded high density amorphous, again in close similarity to what occurs in ice.

4-[2-(4-cyanophenyl)ethenyl]-N-methylpyridinium tetraphenylborate.

PubMed

Jin, Dan; Zhang, De Chun

2005-11-01

In the title compound, C(15)H(13)N(2)(+).C(24)H(20)B(-), the pyridyl ring of the cation makes a dihedral angle of 1.6 degrees with the benzene ring. Each is rotated in the same direction with respect to the central -C-CH=CH-C- linkage, by 3.8 and 5.3 degrees, respectively. The anions have a slightly distorted tetrahedral geometry. Molecular packing analysis was carried out using the packing energy portioning scheme in the program OPEC. Around each anion in the crystal structure there are eight anions, which interact with the central anion through C-H...pi interactions. The cations are hydrogen bonded in a head-to-tail fashion, forming chains along [101].

Acrylic esters in radiation polymerization

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

Fomina, N.V.; Khoromskaya, V.A.; Shiryaeva, G.V.

1988-03-01

The radiation behavior of (meth)acrylic esters of varying structure was studied. It was shown that in radiation polymerization, in contrast to thermal polymerization, the structure of the ester part can significantly affect the reaction rate and capacity for polymerization in the presence of oxygen. The experimental data are explained from the point of view of consideration of nonvalence effects of the substitutent on the reactivity of the double bond.

Equilibrium polymerization on the equivalent-neighbor lattice

NASA Technical Reports Server (NTRS)

Kaufman, Miron

1989-01-01

The equilibrium polymerization problem is solved exactly on the equivalent-neighbor lattice. The Flory-Huggins (Flory, 1986) entropy of mixing is exact for this lattice. The discrete version of the n-vector model is verified when n approaches 0 is equivalent to the equal reactivity polymerization process in the whole parameter space, including the polymerized phase. The polymerization processes for polymers satisfying the Schulz (1939) distribution exhibit nonuniversal critical behavior. A close analogy is found between the polymerization problem of index the Schulz r and the Bose-Einstein ideal gas in d = -2r dimensions, with the critical polymerization corresponding to the Bose-Einstein condensation.

Phosphoniums as catalysts for metal-free polymerization: Synthesis of well-defined poly(propylene oxide)

NASA Astrophysics Data System (ADS)

Zhang, Jie; Liu, Quan; Ren, Haojun; Zhang, Nanjie; Li, Pengfei; Yang, Kang

2017-11-01

The anionic ring-opening polymerization of propylene oxide (PO) was initiated with glycerol and catalyzed by three new synthetic phosphonium salts, tetrakis (pyrrolidino) phosphonium (Py4P1+), tetrakis (piperidino) phosphonium (Pi4P1+), tetrakis (morpholino) phosphonium (Mo4P1+), and the known tetrakis [cyclohexyl (methyl) amino] phosphonium (Cy4P1+) and tetrakis [tris (dimethylamino) phosphonoamino] phosphazene (P5+). The effects of substituents on the polymerization behavior, especially the molecular weight and its distribution, degree of unsaturation, and the sequential structures of poly (propylene oxide) (PPO) were investigated. The structures of these catalysts and PPOs were characterized by FT-IR, 1H and 13C NMR, and GPC. The results indicate that Cy4P1+, Py4P1+, and Pi4P1+ have lower optimum reaction temperatures at 90, 70, and 70 °C, respectively, and are better than traditional catalysts KOH and double metal cyanide. PPO samples with high molecular weight, narrow polydispersity, and high functionality were accessible when catalyzed with Cy4P1+, Pi4P1+, and P5+ at the optimum temperature. Notably, Pi4P1+ formed unimodal distribution PPO with 9000 g/mol, 2.93 of functionality, and 0.008 mmol/g degree of unsaturation. Majority segments of PPO from five catalysts adopted the stereoregular head-to-tail structure, exhibiting excellent regularity.

Photoelectron spectroscopic studies of 5-halouracil anions

PubMed Central

Radisic, Dunja; Ko, Yeon Jae; Nilles, John M.; Stokes, Sarah T.; Sevilla, Michael D.; Rak, Janusz; Bowen, Kit H.

2011-01-01

The parent negative ions of 5-chlorouracil, UCl− and 5-fluorouracil, UF− have been studied using anion photoelectron spectroscopy in order to investigate the electrophilic properties of their corresponding neutral halouracils. The vertical detachment energies (VDE) of these anions and the adiabatic electron affinities (EA) of their neutral molecular counterparts are reported. These results are in good agreement with the results of previously published theoretical calculations. The VDE values for both UCl− and UF− and the EA values for their neutral molecular counterparts are much greater than the corresponding values for both anionic and neutral forms of canonical uracil and thymine. These results are consistent with the observation that DNA is more sensitive to radiation damage when thymine is replaced by halouracil. While we also attempted to prepare the parent anion of 5-bromouracil, UBr−, we did not observe it, the mass spectrum exhibiting only Br− fragments, i.e., 5-bromouracil apparently underwent dissociative electron attachment. This observation is consistent with a previous assessment, suggesting that 5-bromouracil is the best radio-sensitizer among these three halo-nucleobases. PMID:21219027

Self-organizing layers from complex molecular anions

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

Warneke, Jonas; McBriarty, Martin E.; Riechers, Shawn L.

Ions are promising building blocks for tunable self-organizing materials with advanced technological applications. However, because of strong Coulomb attraction with counterions, the intrinsic properties of ions are difficult to exploit for preparation of bulk materials. Here, we report the precisely-controlled preparation of macroscopic surface layers by soft landing of mass selected complex anions which determine the self organization of the layers with their molecular properties. The family of halogenated dodecaborates [B12X12]2- (X = F, Cl, Br, I), in which the internal charge distribution between core and shell regions of the molecular ions systematically vary, was deposited on different self assembledmore » monolayer surfaces (SAMs) on gold at high coverage. Layers of anions were found to be stabilized by accumulation of neutral molecules. Different phases, self-organization mechanisms and optical properties were observed to depend upon the internal charge distribution of the deposited anions, the underlying surface and the coadsorbed molecules. This demonstrates rational control of the properties of anion based layers.« less

Syntheses, crystal structures and Raman spectra of Ba(BF{sub 4})(PF{sub 6}), Ba(BF{sub 4})(AsF{sub 6}) and Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}); the first examples of metal salts containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} anions

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

Lozinsek, Matic; Bunic, Tina; Goreshnik, Evgeny, E-mail: evgeny.goreshnik@ijs.s

2009-10-15

In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen fluoride (aHF) a compound Ba(BF{sub 4})(PF{sub 6}) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF{sub 4})(PF{sub 6}) crystallizes in a hexagonal P6-bar2m space group with a=10.2251(4) A, c=6.1535(4) A, V=557.17(5) A{sup 3} at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF{sub 4}{sup -} and PF{sub 6}{sup -} anions. In the analogous system with AsF{sub 5} instead of PF{sub 5} the compound Ba(BF{sub 4})(AsF{sub 6}) was isolated and characterized.more » It crystallizes in an orthorhombic Pnma space group with a=10.415(2) A, b=6.325(3) A, c=11.8297(17) A, V=779.3(4) A{sup 3} at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF{sub 6}{sup -} and four F atoms from BF{sub 4}{sup -} anions. When the system BaF{sub 2}/BF{sub 3}/AsF{sub 5}/aHF is made basic with an extra addition of BaF{sub 2}, the compound Ba{sub 2}(BF{sub 4}){sub 2}(AsF{sub 6})(H{sub 3}F{sub 4}) was obtained. It crystallizes in a hexagonal P6{sub 3}/mmc space group with a=6.8709(9) A, c=17.327(8) A, V=708.4(4) A{sup 3} at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF{sub 4}{sup -}, three AsF{sub 6}{sup -} and three H{sub 3}F{sub 4}{sup -} anions. All F atoms, except the central atom in H{sub 3}F{sub 4} moiety, act as mu{sub 2}-bridges yielding a complex 3-D structural network. - Graphical abstract: The first three compounds, containing simultaneously tetrahedral BF{sub 4}{sup -} and octahedral AF{sub 6}{sup -} (A=P, As) anions have been synthesized and characterized by Raman spectroscopy and X-ray single crystal diffraction. In the system BaF{sub 2}/BF{sub 3}/PF{sub 5}/anhydrous hydrogen

Vertical detachment energies of anionic thymidine: Microhydration effects.

PubMed

Kim, Sunghwan; Schaefer, Henry F

2010-10-14

Density functional theory has been employed to investigate microhydration effects on the vertical detachment energy (VDE) of the thymidine anion by considering the various structures of its monohydrates. Structures were located using a random searching procedure. Among 14 distinct structures of the anionic thymidine monohydrate, the low-energy structures, in general, have the water molecule bound to the thymine base unit. The negative charge developed on the thymine moiety increases the strength of the intermolecular hydrogen bonding between the water and base units. The computed VDE values of the thymidine monohydrate anions are predicted to range from 0.67 to 1.60 eV and the lowest-energy structure has a VDE of 1.32 eV. The VDEs of the monohydrates of the thymidine anion, where the N(1)[Single Bond]H hydrogen of thymine has been replaced by a 2(')-deoxyribose ring, are greater by ∼0.30 eV, compared to those of the monohydrates of the thymine anion. The results of the present study are in excellent agreement with the accompanying experimental results of Bowen and co-workers [J. Chem. Phys. 133, 144304 (2010)].

Temporary anion states of selected amino acids

NASA Astrophysics Data System (ADS)

Aflatooni, K.; Hitt, B.; Gallup, G. A.; Burrow, P. D.

2001-10-01

Vertical attachment energies for the formation of low-lying temporary anion states of glycine, alanine, phenylalanine, tryptophan, and proline in the gas phase are reported using electron transmission spectroscopy. Electron attachment into the empty π* orbital of the -COOH group was observed in all the compounds. Temporary anion states associated with the side groups in phenylalanine and tryptophan are found to be stabilized with respect to those in the reference compounds toluene and indole, respectively, by approximately 0.2 eV. We attribute this to electrostatic effects and explore, using simple theoretical models, the extent to which such anion states could be further stabilized if these amino acids were in zwitterionic form.

Kinetics of Corrosion Inhibition of Aluminum in Acidic Media by Water-Soluble Natural Polymeric Pectates as Anionic Polyelectrolyte Inhibitors

PubMed Central

Hassan, Refat M.; Zaafarany, Ishaq A.

2013-01-01

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyeletrolyte pectates (PEC) as a water-soluble natural polymer polysaccharide has been studied using both gasometric and weight loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing inhibitor concentration and decrease with increasing temperature. The inhibition action of PEC on Al metal surface was found to obey the Freundlich isotherm. Factors such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and temperature affecting the corrosion rates were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the kinetic results is discussed in the paper. PMID:28809282

Unusual structures of MgF5- superhalogen anion

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Skurski, Piotr

2007-05-01

The vertical electron detachment energies (VDE) of three MgF5- anions were calculated at the outer valence Green function level with the 6-311 + G(3df) basis sets. This species was found to form unusual geometrical structures each of which corresponds to an anionic state exhibiting superhalogen nature. The global minimum structure was described as a system in which two central magnesium atoms are linked via symmetrical triangle formed by three fluorine atoms. Extremely large electron binding energies of these anions (exceeding 8.5 eV in all cases) were predicted and discussed.

Anion exchange polymer electrolytes

DOEpatents

Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

2013-07-23

Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

Conductive polymeric compositions for lithium batteries

DOEpatents

Angell, Charles A [Mesa, AZ; Xu, Wu [Tempe, AZ

2009-03-17

Novel chain polymers comprising weakly basic anionic moieties chemically bound into a polyether backbone at controllable anionic separations are presented. Preferred polymers comprise orthoborate anions capped with dibasic acid residues, preferably oxalato or malonato acid residues. The conductivity of these polymers is found to be high relative to that of most conventional salt-in-polymer electrolytes. The conductivity at high temperatures and wide electrochemical window make these materials especially suitable as electrolytes for rechargeable lithium batteries.

Comprehensive understanding of mole concept subject matter according to the tetrahedral chemistry education (empirical study on the first-year chemistry students of Technische Universität Dresden)

NASA Astrophysics Data System (ADS)

Prabowo, D. W.; Mulyani, S.; van Pée, K.-H.; Indriyanti, N. Y.

2018-05-01

This research aims to apprehend: (1) the shape of tetrahedral chemistry education which is called the future of chemistry education, (2) comprehensive understanding of chemistry first-year students of Technische Universität Dresden according to the chemistry education’s tetrahedral shape on mole concept subject matter. This research used quantitative and qualitative; paper and pencil test and interview. The former was conducted in the form of test containing objective test instrument. The results of this study are (1) learning based on tetrahedral shape of chemistry education put the chemical substance (macroscopic), symbolic representation (symbol), and its process (molecular) in the context of human beings (human element) by integrating content and context, without emphasis on one thing and weaken another, (2) first-year chemistry students of Technische Universität Dresden have comprehensively understood the mole concept associated with the context of everyday life, whereby students are able to find out macroscopic information from statements that are contextual to human life and then by using symbols and formulas are able to comprehend the molecular components as well as to interpret and analyse problems effectively.

Output-Adaptive Tetrahedral Cut-Cell Validation for Sonic Boom Prediction

NASA Technical Reports Server (NTRS)

Park, Michael A.; Darmofal, David L.

2008-01-01

A cut-cell approach to Computational Fluid Dynamics (CFD) that utilizes the median dual of a tetrahedral background grid is described. The discrete adjoint is also calculated, which permits adaptation based on improving the calculation of a specified output (off-body pressure signature) in supersonic inviscid flow. These predicted signatures are compared to wind tunnel measurements on and off the configuration centerline 10 body lengths below the model to validate the method for sonic boom prediction. Accurate mid-field sonic boom pressure signatures are calculated with the Euler equations without the use of hybrid grid or signature propagation methods. Highly-refined, shock-aligned anisotropic grids were produced by this method from coarse isotropic grids created without prior knowledge of shock locations. A heuristic reconstruction limiter provided stable flow and adjoint solution schemes while producing similar signatures to Barth-Jespersen and Venkatakrishnan limiters. The use of cut-cells with an output-based adaptive scheme completely automated this accurate prediction capability after a triangular mesh is generated for the cut surface. This automation drastically reduces the manual intervention required by existing methods.

Versatile Tandem Ring-Opening/Ring-Closing Metathesis Polymerization: Strategies for Successful Polymerization of Challenging Monomers and Their Mechanistic Studies.

PubMed

Park, Hyeon; Kang, Eun-Hye; Müller, Laura; Choi, Tae-Lim

2016-02-24

Tandem ring-opening/ring-closing metathesis (RO/RCM) results in extremely fast living polymerization; however, according to previous reports, only monomers containing certain combinations of cycloalkenes, terminal alkynes, and nitrogen linkers successfully underwent tandem polymerization. After examining the polymerization pathways, we proposed that the relatively slow intramolecular cyclization might lead to competing side reactions such as intermolecular cross metathesis reactions to form inactive propagating species. Thus, we developed two strategies to enhance tandem polymerization efficiency. First, we modified monomer structures to accelerate tandem RO/RCM cyclization by enhancing the Thorpe-Ingold effect. This strategy increased the polymerization rate and suppressed the chain transfer reaction to achieve controlled polymerization, even for challenging syntheses of dendronized polymers. Alternatively, reducing the reaction concentration facilitated tandem polymerization, suggesting that the slow tandem RO/RCM cyclization step was the main reason for the previous failure. To broaden the monomer scope, we used monomers containing internal alkynes and observed that two different polymer units with different ring sizes were produced as a result of nonselective α-addition and β-addition on the internal alkynes. Thorough experiments with various monomers with internal alkynes suggested that steric and electronic effects of the alkyne substituents influenced alkyne addition selectivity and the polymerization reactivity. Further polymerization kinetics studies revealed that the rate-determining step of monomers containing certain internal alkynes was the six-membered cyclization step via β-addition, whereas that for other monomers was the conventional intermolecular propagation step, as observed in other chain-growth polymerizations. This conclusion agrees well with all those polymerization results and thus validates our strategies.

Inhibition of nuclear waste solutions containing multiple aggressive anions

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

Congdon, J.W.

1987-01-01

The inhibition of localized corrosion of carbon steel in caustic, high-level radioactive waste solutions was studied using cyclic potentiodynamic polarization scans, supplemented by partially immersed coupon tests. The electrochemical tests provided a rapid and accurate means of determining the relationship between the minimum inhibitor requirements and the concentration of the aggressive anions in this system. Nitrate, sulfate, chloride, and fluoride were identified as aggressive anions, however, no synergistic effects were observed between these anions. This observation may have important theoretical implications because it tends to contradict the behavior of aggressive anions as predicted by existing theories for localized corrosion. 10more » refs., 5 figs., 2 tabs.« less

An assessment of the adaptive unstructured tetrahedral grid, Euler Flow Solver Code FELISA

NASA Technical Reports Server (NTRS)

Djomehri, M. Jahed; Erickson, Larry L.

1994-01-01

A three-dimensional solution-adaptive Euler flow solver for unstructured tetrahedral meshes is assessed, and the accuracy and efficiency of the method for predicting sonic boom pressure signatures about simple generic models are demonstrated. Comparison of computational and wind tunnel data and enhancement of numerical solutions by means of grid adaptivity are discussed. The mesh generation is based on the advancing front technique. The FELISA code consists of two solvers, the Taylor-Galerkin and the Runge-Kutta-Galerkin schemes, both of which are spacially discretized by the usual Galerkin weighted residual finite-element methods but with different explicit time-marching schemes to steady state. The solution-adaptive grid procedure is based on either remeshing or mesh refinement techniques. An alternative geometry adaptive procedure is also incorporated.

Detecting Levels of Polyquaternium-10 (PQ-10) via Potentiometric Titration with Dextran Sulphate and Monitoring the Equivalence Point with a Polymeric Membrane-Based Polyion Sensor.

PubMed

Ferguson, Stephen A; Wang, Xuewei; Meyerhoff, Mark E

2016-08-07

Polymeric quaternary ammonium salts (polyquaterniums) have found increasing use in industrial and cosmetic applications in recent years. More specifically, polyquaternium-10 (PQ-10) is routinely used in cosmetic applications as a conditioner in personal care product formulations. Herein, we demonstrate the use of potentiometric polyion-sensitive polymeric membrane-based electrodes to quantify PQ-10 levels. Mixtures containing both PQ-10 and sodium lauryl sulfate (SLS) are used as model samples to illustrate this new method. SLS is often present in cosmetic samples that contain PQ-10 (e.g., shampoos, etc.) and this surfactant species interferes with the polyion sensor detection chemistry. However, it is shown here that SLS can be readily separated from the PQ-10/SLS mixture by use of an anion-exchange resin and that the PQ-10 can then be titrated with dextran sulphate (DS). This titration is monitored by potentiometric polyanion sensors to provide equivalence points that are directly proportional to PQ-10 concentrations.

Design of Semiconducting Tetrahedral Mn 1-xZn xO Alloys and Their Application to Solar Water Splitting

DOE PAGES

Peng, Haowei; Ndione, Paul F.; Ginley, David S.; ...

2015-03-18

Transition metal oxides play important roles as contact and electrode materials, but their use as active layers in solar energy conversion requires achieving semiconducting properties akin to those of conventional semiconductors like Si or GaAs. In particular, efficient bipolar carrier transport is a challenge in these materials. Based on the prediction that a tetrahedral polymorph of MnO should have such desirable semiconducting properties, and the possibility to overcome thermodynamic solubility limits by nonequilibrium thin-film growth, we exploit both structure-property and composition-structure relationships to design and realize novel wurtzite-structure Mn 1₋xZn xO alloys. At Zn compositions above x≈0.3, thin films ofmore » these alloys assume the tetrahedral wurtzite structure instead of the octahedral rocksalt structure of MnO, thereby enabling semiconductor properties that are unique among transition metal oxides, i.e., a band gap within the visible spectrum, a band-transport mechanism for both electron and hole carriers, electron doping, and a band lineup suitable for solar hydrogen generation. In conclusion, a proof of principle is provided by initial photo-electrocatalytic device measurements, corroborating, in particular, the predicted favorable hole-transport properties of these alloys.« less

Structural stiffness, strength and dynamic characteristics of large tetrahedral space truss structures

NASA Technical Reports Server (NTRS)

Mikulas, M. M., Jr.; Bush, H. G.; Card, M. F.

1977-01-01

Physical characteristics of large skeletal frameworks for space applications are investigated by analyzing one concept: the tetrahedral truss, which is idealized as a sandwich plate with isotropic faces. Appropriate analytical relations are presented in terms of the truss column element properties which for calculations were taken as slender graphite/epoxy tubes. Column loads, resulting from gravity gradient control and orbital transfer, are found to be small for the class structure investigated. Fundamental frequencies of large truss structures are shown to be an order of magnitude lower than large earth based structures. Permissible loads are shown to result in small lateral deflections of the truss due to low-strain at Euler buckling of the slender graphite/epoxy truss column elements. Lateral thermal deflections are found to be a fraction of the truss depth using graphite/epoxy columns.

Signal amplification strategies for DNA and protein detection based on polymeric nanocomposites and polymerization: A review.

PubMed

Zhou, Shaohong; Yuan, Liang; Hua, Xin; Xu, Lingling; Liu, Songqin

2015-06-02

Demand is increasing for ultrasensitive bioassays for disease diagnosis, environmental monitoring and other research areas. This requires novel signal amplification strategies to maximize the signal output. In this review, we focus on a series of significant signal amplification strategies based on polymeric nanocomposites and polymerization. Some common polymers are used as carriers to increase the local concentration of signal probes and/or biomolecules on their surfaces or in their interiors. Some polymers with special fluorescence and optical properties can efficiently transfer the excitation energy from a single site to the whole polymer backbone. This results in superior fluorescence signal amplification due to the resulting collective effort (integration of signal). Recent polymerization-based signal amplification strategies that employ atom transfer radical polymerization (ATRP) and photo-initiated polymerization are also summarized. Several distinctive applications of polymers in ultrasensitive bioanalysis are highlighted. Copyright © 2015 Elsevier B.V. All rights reserved.

Configuration and energy landscape of the benzonitrile anion

NASA Astrophysics Data System (ADS)

Kirnosov, Nikita; Adamowicz, Ludwik

2017-05-01

Quantum chemical calculations are employed to study the configurational isomers of the anion formed by benzene substituted with a cyano group. It is found that an excess electron can form dipole-bound (DB) states with benzonitrile and phenyl-isocyanide isomers. It can also attach to the cyano group, if this group is separated from the benzene ring by some distance, forming a covalent CN- anion. There are four positions at peripherals of the benzene ring where this anion can localize and form stable complexes with the benzene radical. In these complexes CN- is connected to the benzene radical via non-covalent interactions.

Novel fragmentation pathways of anionic adducts of steroids formed by electrospray anion attachment involving regioselective attachment, regiospecific decompositions, charge-induced pathways, and ion-dipole complex intermediates.

PubMed

Rannulu, Nalaka S; Cole, Richard B

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion](-) adducts of these steroids revealed that fluoride adduct [M + F](-) precursors first lose HF to produce [M - H](-) and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d(4)-pregnenolone, are also discussed.

Novel Fragmentation Pathways of Anionic Adducts of Steroids Formed by Electrospray Anion Attachment Involving Regioselective Attachment, Regiospecific Decompositions, Charge-Induced Pathways, and Ion-Dipole Complex Intermediates

NASA Astrophysics Data System (ADS)

Rannulu, Nalaka S.; Cole, Richard B.

2012-09-01

The analysis of several bifunctional neutral steroids, 5-α-pregnane diol (5-α-pregnane-3α-20βdiol), estradiol (3,17α-dihydroxy-1,3,5(10)-estratriene), progesterone (4-pregnene-3,20-dione), lupeol (3β-hydroxy-20(29)-lupene), pregnenolone (5-pregnen-3β-ol-20-one), and pregnenolone acetate (5-pregnen-3β-ol-20-one acetate) was accomplished by negative ion electrospray mass spectrometry (ESI-MS) employing adduct formation with various anions: fluoride, bicarbonate, acetate, and chloride. Fluoride yielded higher abundances of anionic adducts and more substantial abundances of deprotonated molecules compared with other investigated anions. Collision-induced dissociation (CID) of precursor [M + anion]- adducts of these steroids revealed that fluoride adduct [M + F]- precursors first lose HF to produce [M - H]- and then undergo consecutive decompositions to yield higher abundances of structurally-informative product ions than the other tested anions. In addition to charge-remote fragmentations, the majority of CID pathways of estradiol are deduced to occur via charge-induced fragmentation. Most interestingly, certain anions exhibit preferential attachment to a specific site on these bifunctional steroid molecules, which we are calling "regioselective anion attachment." Regioselective anion attachment is evidenced by subsequent regiospecific decomposition. Regioselective attachment of fluoride (and acetate) anions to low (and moderate) acidity functional groups of pregnenolone, respectively, is demonstrated using deuterated compounds. Moreover, the formation of unique intermediate ion-dipole complexes leading to novel fragmentation pathways of fluoride adducts of pregnenolone acetate, and bicarbonate adducts of d4-pregnenolone, are also discussed.

Colorimetric sensing of anions in water using ratiometric indicator-displacement assay.

PubMed

Feng, Liang; Li, Hui; Li, Xiao; Chen, Liang; Shen, Zheng; Guan, Yafeng

2012-09-19

The analysis of anions in water presents a difficult challenge due to their low charge-to-radius ratio, and the ability to discriminate among similar anions often remains problematic. The use of a 3×6 ratiometric indicator-displacement assay (RIDA) array for the colorimetric detection and identification of ten anions in water is reported. The sensor array consists of different combinations of colorimetric indicators and metal cations. The colorimetric indicators chelate with metal cations, forming the color changes. Upon the addition of anions, anions compete with the indicator ligands according to solubility product constants (K(sp)). The indicator-metal chelate compound changes color back dramatically when the competition of anions wins. The color changes of the RIDA array were used as a digital representation of the array response and analyzed with standard statistical methods, including principal component analysis and hierarchical clustering analysis. No confusion or errors in classification by hierarchical clustering analysis were observed in 44 trials. The limit of detection was calculated approximately, and most limits of detections of anions are well below μM level using our RIDA array. The pH effect, temperature influence, interfering anions were also investigated, and the RIDA array shows the feasibility of real sample testing. Copyright © 2012 Elsevier B.V. All rights reserved.

Role of Anions Associated with the Formation and Properties of Silver Clusters.

PubMed

Wang, Quan-Ming; Lin, Yu-Mei; Liu, Kuan-Guan

2015-06-16

Metal clusters have been very attractive due to their aesthetic structures and fascinating properties. Different from nanoparticles, each cluster of a macroscopic sample has a well-defined structure with identical composition, size, and shape. As the disadvantages of polydispersity are ruled out, informative structure-property relationships of metal clusters can be established. The formation of a high-nuclearity metal cluster involves the organization of metal ions into a complex entity in an ordered way. To achieve controllable preparation of metal clusters, it is helpful to introduce a directing agent in the formation process of a cluster. To this end, anion templates have been used to direct the formation of high nuclearity clusters. In this Account, the role of anions played in the formation of a variety of silver clusters has been reviewed. Silver ions are positively charged, so anionic species could be utilized to control the formation of silver clusters on the basis of electrostatic interactions, and the size and shape of the resulted clusters can be dictated by the templating anions. In addition, since the anion is an integral component in the silver clusters described, the physical properties of the clusters can be modulated by functional anions. The templating effects of simple inorganic anions and polyoxometales are shown in silver alkynyl clusters and silver thiolate clusters. Intercluster compounds are also described regarding the importance of anions in determining the packing of the ion pairs and making contribution to electron communications between the positive and negative counterparts. The role of the anions is threefold: (a) an anion is advantageous in stabilizing a cluster via balancing local positive charges of the metal cations; (b) an anion template could help control the size and shape of a cluster product; (c) an anion can be a key factor in influencing the function of a cluster through bringing in its intrinsic properties. Properties

Indirect photometric detection of boron cluster anions electrophoretically separated in methanol.

PubMed

Vítová, Lada; Fojt, Lukáš; Vespalec, Radim

2014-04-18

3,5-Dinitrobenzoate and picrate are light absorbing anions pertinent to indirect photometric detection of boron cluster anions in buffered methanolic background electrolytes (BGEs). Tris(hydroxymethyl)aminomethane and morpholine have been used as buffering bases, which eliminated baseline steps, and minimized the baseline noise. In methanolic BGEs, mobilities of boron cluster anions depend on both ionic constituents of the BGE buffer. This dependence can be explained by ion pair interaction of detected anions with BGE cations, which are not bonded into ion pairs with the BGE anions. The former ion pair interaction decreases sensitivity of the indirect photometric detection. Copyright © 2014 Elsevier B.V. All rights reserved.

Polymeric membrane materials for artificial organs.

PubMed

Kawakami, Hiroyoshi

2008-01-01

Many polymeric materials have already been used in the field of artificial organs. However, the materials used in artificial organs are not necessarily created with the best material selectivity and materials design; therefore, the development of synthesized polymeric membrane materials for artificial organs based on well-defined designs is required. The approaches to the development of biocompatible polymeric materials fall into three categories: (1) control of physicochemical characteristics on material surfaces, (2) modification of material surfaces using biomolecules, and (3) construction of biomimetic membrane surfaces. This review will describe current issues regarding polymeric membrane materials for use in artificial organs.

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

NASA Technical Reports Server (NTRS)

West, William C.; Whitacre, Jay F.; Leifer, Nicole; Greenbaum, Steve; Smart, Marshall; Bugga, Ratnakumar; Blanco, Mario; Narayanan, S. R.

2007-01-01

We have demonstrated a route to reversibly intercalate fluoride-anion receptor complexes in graphite via a nonaqueous electrochemical process. This approach may find application for a rechargeable lithium-fluoride dual-ion intercalating battery with high specific energy. The cell chemistry presented here uses graphite cathodes with LiF dissolved in a nonaqueous solvent through the aid of anion receptors. Cells have been demonstrated with reversible cathode specific capacity of approximately 80 mAh/g at discharge plateaus of upward of 4.8 V, with graphite staging of the intercalant observed via in situ synchrotron X-ray diffraction during charging. Electrochemical impedance spectroscopy and B-11 nuclear magnetic resonance studies suggest that cointercalation of the anion receptor with the fluoride occurs during charging, which likely limits the cathode specific capacity. The anion receptor type dictates the extent of graphite fluorination, and must be further optimized to realize high theoretical fluorination levels. To find these optimal anion receptors, we have designed an ab initio calculations-based scheme aimed at identifying receptors with favorable fluoride binding and release properties.

Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

PubMed

Weiber, E Annika; Jannasch, Patric

2014-09-01

A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biochemical indicators of nephrotoxicity in blood serum of rats treated with novel 4-thiazolidinone derivatives or their complexes with polyethylene glycol-containing nanoscale polymeric carrier

PubMed

Kоbyli nska, L I; Havrylyuk, D Ya; Mitina, N E; Zaichenko, A S; Lesyk, R B; Zіme nkovsky, B S; Stoika, R S

2016-01-01

The aim of this study was to compare the effect of new synthetic 4-thiazolidinone derivatives (potential anticancer compounds denoted as 3882, 3288 and 3833) and doxorubicin (positive control) in free form and in their complexes with synthetic polyethylene glycol-containing nanoscale polymeric carrier on the biochemical indicators of nephrotoxicity in blood serum of rats. The concentration of total protein, urea, creatinine, glucose, ions of sodium, potassium, calcium, iron and chloride was measured. It was found that after injection of the investigated compounds, the concentration of sodium cations and chloride anions in blood serum was increased compared with control (untreated animals). Doxorubicin’s injection was accompanied by a decrease in the concentration of iron cations. The concentration of total protein, urea and creatinine decreased under the influence of the studied compounds. Complexation of these аntineoplastic substances with a synthetic polymeric nanocarrier lowered the concentration of the investigated metabolites substantially compared to the effect of these compounds in free form. The normalization of concentration of total protein, urea and creatinine in blood serum of rats treated with complexes of the studied compounds with the polymeric carrier comparing with increased concentration of these indicators at the introduction of such compounds in free form was found.

Polymeric Beads for Organic Coatings

DTIC Science & Technology

1982-10-31

Clear Solid Polymeric Beads A solid polymeric bead is comprised of a sol id mass of polymerized unsaturated polyester/styrene resin mixture . 2. lear...than the current unsaturated polyester resin . For example, a bead male from acrylic resin could be more trans- - parent, more durable and provide more...0.44 Isopropyl Alcohol I 11.26 I 1 .73 60% Wt. Alkyd Resin - Volume I 251.26 i 30.52 " Sol ids 51% 1 I Anti.-Skinning Agent I 0.90 I 0.12 Mineral

Process for separating and recovering an anionic dye from an aqueous solution

DOEpatents

Rogers, Robin; Horwitz, E. Philip; Bond, Andrew H.

1998-01-01

A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution.

Process for separating and recovering an anionic dye from an aqueous solution

DOEpatents

Rogers, R.; Horwitz, E.P.; Bond, A.H.

1998-01-13

A solid/liquid phase process for the separation and recovery of an anionic dye from an aqueous solution is disclosed. The solid phase comprises separation particles having surface-bonded poly(ethylene glycol) groups, whereas the aqueous solution from which the anionic dye molecules are separated contains a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt. After contact between the aqueous solution and separation particles, the anionic dye is bound to the particles. The bound anionic dye molecules are freed from the separation particles by contacting the anionic dye-bound particles with an aqueous solution that does not contain a poly(ethylene glycol) liquid/liquid biphase-forming amount of a dissolved lyotropic salt to form an aqueous anionic dye solution whose anionic dye concentration is preferably higher than that of the initial dye-containing solution. 7 figs.

Metabolomic profiling of anionic metabolites by capillary electrophoresis mass spectrometry.

PubMed

Soga, Tomoyoshi; Igarashi, Kaori; Ito, Chiharu; Mizobuchi, Katsuo; Zimmermann, Hans-Peter; Tomita, Masaru

2009-08-01

We describe a sheath flow capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) method in the negative mode using a platinum electrospray ionization (ESI) spray needle, which allows the comprehensive analysis of anionic metabolites. The material of the spray needle had significant effect on the measurement of anions. A stainless steel spray needle was oxidized and corroded at the anodic electrode due to electrolysis. The precipitation of iron oxides (rust) plugged the capillary outlet, resulting in shortened capillary lifetime. Many anionic metabolites also formed complexes with the iron oxides or migrating nickel ion, which was also generated by electrolysis and moved toward the cathode (the capillary inlet). The metal-anion complex formation significantly reduced detection sensitivity of the anionic compounds. The use of a platinum ESI needle prevented both oxidation of the metals and needle corrosion. Sensitivity using the platinum needle increased from several- to 63-fold, with the largest improvements for anions exhibiting high metal chelating properties such as carboxylic acids, nucleotides, and coenzyme A compounds. The detection limits for most anions were between 0.03 and 0.87 micromol/L (0.8 and 24 fmol) at a signal-to-noise ratio of 3. This method is quantitative, sensitive, and robust, and its utility was demonstrated by the analysis of the metabolites in the central metabolic pathways extracted from mouse liver.

Synthesis and applications of MANs/poly(MMA-co-BA) nanocomposite latex by miniemulsion polymerization

PubMed Central

Chen, Huayao; Zhou, Xinhua; Gunasekaran, Sundaram

2017-01-01

We have synthesized core-shell structured 3-methacryloxypropyltrimethoxysilane (MPS) functionalized antimony-doped tin oxide nanoparticles (MANs)–poly(methyl methacrylate-co-butyl acrylate) (PMMA-co-BA, PMB) nanocomposite latex particles via miniemulsion polymerization method. Polymerizable anionic surfactant DNS-86 (allyloxy polyoxyethylene(10) nonyl ammonium sulfate) was first introduced to synthesize core-shell nanocomposite. The morphologies of synthesized MANs and MANs/PMB latex nanocomposite particles were studied with transmission electron microscopy, which revealed particles, on average 70 nm in size, with a core-shell structure. Owing to the uniformity and hydrophobicity of MANs, the MANs-embedded PMB latex nanocomposite can be tailored more precisely than other nanoparticles-embedded nanocomposites. Films incorporating 10 wt% of MANs in the MAN/PMB latex nanocomposite exhibit good transmittance in the visible region, and excellent opacity in the near infrared region. The MANs/PMB nanocomposite film also appears suitable for heat insulation applications. PMID:29291076

Multi-Criterion Preliminary Design of a Tetrahedral Truss Platform

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey

1995-01-01

An efficient method is presented for multi-criterion preliminary design and demonstrated for a tetrahedral truss platform. The present method requires minimal analysis effort and permits rapid estimation of optimized truss behavior for preliminary design. A 14-m-diameter, 3-ring truss platform represents a candidate reflector support structure for space-based science spacecraft. The truss members are divided into 9 groups by truss ring and position. Design variables are the cross-sectional area of all members in a group, and are either 1, 3 or 5 times the minimum member area. Non-structural mass represents the node and joint hardware used to assemble the truss structure. Taguchi methods are used to efficiently identify key points in the set of Pareto-optimal truss designs. Key points identified using Taguchi methods are the maximum frequency, minimum mass, and maximum frequency-to-mass ratio truss designs. Low-order polynomial curve fits through these points are used to approximate the behavior of the full set of Pareto-optimal designs. The resulting Pareto-optimal design curve is used to predict frequency and mass for optimized trusses. Performance improvements are plotted in frequency-mass (criterion) space and compared to results for uniform trusses. Application of constraints to frequency and mass and sensitivity to constraint variation are demonstrated.

Effects of organic solvents on drug incorporation into polymeric carriers and morphological analyses of drug-incorporated polymeric micelles.

PubMed

Harada, Yoshiko; Yamamoto, Tatsuhiro; Sakai, Masaru; Saiki, Toshiharu; Kawano, Kumi; Maitani, Yoshie; Yokoyama, Masayuki

2011-02-14

We incorporated an anticancer agent, camptothecin (CPT), into polymeric micelle carriers by using two different solvents (TFE and chloroform) in the solvent-evaporation drug incorporation process. We observed significant differences in the drug-incorporation behaviors, in the morphologies of the incorporated drug and the polymeric micelles, and in the pharmacokinetic behaviors between the two solvents' cases. In particular, the CPT-incorporated polymeric micelles prepared with TFE as the incorporation solvent exhibited more stable circulation in blood than those prepared with chloroform. This contrast indicates a novel technological perspective regarding the drug incorporation into polymeric micelle carriers. Morphological analyses of the inner core have revealed the presence of the directed alignment of the CPT molecules and CPT crystals in the micelle inner core. This is the first report of the morphologies of the drug incorporated into the polymeric micelle inner cores. We believe these analyses are very important for further pharmaceutical developments of polymeric micelle drug-carrier systems. Copyright © 2010 Elsevier B.V. All rights reserved.

Electron transfer from alpha-keggin anions to dioxygen

Treesearch

Yurii V. Geletii; Rajai H. Atalla; Craig L. Hill; Ira A. Weinstock

2004-01-01

Polyoxometalates (POMs), of which alpha-Keggin anions are representative, are a diverse and rapidly growing class of water-soluble cluster-anion structures with applications ranging from molecular catalysis to materials. [1] POMs are inexpensive, minimally or non-toxic, negatively charged clusters comprised of early transition-metals, usually in their do electronic...

Laser cooling of molecular anions.

PubMed

Yzombard, Pauline; Hamamda, Mehdi; Gerber, Sebastian; Doser, Michael; Comparat, Daniel

2015-05-29

We propose a scheme for laser cooling of negatively charged molecules. We briefly summarize the requirements for such laser cooling and we identify a number of potential candidates. A detailed computation study with C_{2}^{-}, the most studied molecular anion, is carried out. Simulations of 3D laser cooling in a gas phase show that this molecule could be cooled down to below 1 mK in only a few tens of milliseconds, using standard lasers. Sisyphus cooling, where no photodetachment process is present, as well as Doppler laser cooling of trapped C_{2}^{-}, are also simulated. This cooling scheme has an impact on the study of cold molecules, molecular anions, charged particle sources, and antimatter physics.

Melting line of polymeric nitrogen

NASA Astrophysics Data System (ADS)

Yakub, L. N.

2013-05-01

We made an attempt to predict location of the melting line of polymeric nitrogen using two equations for Helmholtz free energy: proposed earlier for cubic gauche-structure and developed recently for liquid polymerized nitrogen. The P-T relation, orthobaric densities and latent heat of melting were determined using a standard double tangent construction. The estimated melting temperature decreases with increasing pressure, alike the temperature of molecular-nonmolecular transition in solid. We discuss the possibility of a triple point (solid-molecular fluid-polymeric fluid) at ˜80 GPa and observed maximum of melting temperature of nitrogen.

Theoretical vibrational spectra of diformates: Diformate anion

NASA Astrophysics Data System (ADS)

Dobrowolski, Jan Cz.; Jamróz, Michał H.; Kazimirski, Jan K.; Bajdor, Krzysztof; Borowiak, Marek A.; Larsson, Ragnar

1999-05-01

The IR spectrum of the most stable diformate anion was calculated at the MP2/6-311++G(3df, 3pd), RHF/6-311++G **, and B3PW91/6-311++G ** levels. The internal coordinates were defined for the diformate anion and used in potential energy distribution (PED) analysis. The PED analysis of the theoretical spectra form the basis for elucidation of the future matrix isolation IR spectra.

Density functional theory and conductivity studies of boron-based anion receptors

DOE PAGES

Leung, Kevin; Chaudhari, Mangesh I.; Rempe, Susan B.; ...

2015-07-10

Anion receptors that bind strongly to fluoride anions in organic solvents can help dissolve the lithium fluoride discharge products of primary carbon monofluoride (CFx) batteries, thereby preventing the clogging of cathode surfaces and improving ion conductivity. The receptors are also potentially beneficial to rechargeable lithium ion and lithium air batteries. We apply Density Functional Theory (DFT) to show that an oxalate-based pentafluorophenyl-boron anion receptor binds as strongly, or more strongly, to fluoride anions than many phenyl-boron anion receptors proposed in the literature. Experimental data shows marked improvement in electrolyte conductivity when this oxalate anion receptor is present. The receptor ismore » sufficiently electrophilic that organic solvent molecules compete with F – for boron-site binding, and specific solvent effects must be considered when predicting its F – affinity. To further illustrate the last point, we also perform computational studies on a geometrically constrained boron ester that exhibits much stronger gas-phase affinity for both F – and organic solvent molecules. After accounting for specific solvent effects, however, its net F – affinity is about the same as the simple oxalate-based anion receptor. Lastly, we propose that LiF dissolution in cyclic carbonate organic solvents, in the absence of anion receptors, is due mostly to the formation of ionic aggregates, not isolated F – ions.« less

Determination of the dissolved anion composition of ancient lakes from fossil ostracodes.

USGS Publications Warehouse

Forester, R.M.

1986-01-01

The mineralogy of evaporite and other precipitated minerals has provided traditional sources of information about the major dissolved ion composition of ancient lakes. The paleocompositional resolving power of these methods is generally greatest in high-salinity lakes. Ostracodes live in dilute saline lakes where a species occurrence is determined by the relative proportions of the lake's major dissolved anions, so that each species describes specific areas on an anion trilinear diagram. The upper salinity tolerance of each species depends upon the types of major anions in solution and is therefore anion-specific. Knowledge about both anion and anion-salinity tolerances of an ostracode may ultimately provide a means of estimating absolute anion concentrations in paleolakes. Because ostracodes are common fossils in lake sediments, they provide an important new source of original paleocompositional information suitable for many geologic, climatic, geochemical, and paleontologic studies. -from Author

Free Energy Defect Model for the Cu-In-Ga-Se Tetrahedral Lattice

NASA Astrophysics Data System (ADS)

Stanbery, B. J.

2003-03-01

The most efficient thin-film photovoltaic converters of solar insolation to electrical power have recently achieved conversion efficiencies exceeding 19%, and are based on light absorbing layers containing the binary alloy (CuInSe_2)_1-X(CuGaSe_2)X of the α phases of these ternary chalcopyrite compounds. A statistical quantum mechanical model of the thermodynamic equilibrium defect structure of the tetrahedral lattice of copper, indium, and selenium with composition in the domain between that of the stoichiometric CuIn_1-XGa_XSe2 alloy and the β phase Cu(In_1-XGa_X)_3Se5 composition is presented. Compositions more copper-deficient than the latter have been reported experimentally to result in a breakdown of the tetrahedral coordination characteristic of the chalcopyrite lattice. These computations are based on a cluster expansion algorithm that minimizes the total free energy of the system using the Gibbs-Duhem equation to compute quasichemical reaction equilibria between the neutral clusters, and explicitly incorporates Fermi-Dirac statistics to determine their ionization equilibria and consequent carrier concentrations in the conduction and valence bands. The results are consistent with recent experimental evidence that the stoichiometric CuIn_1-XGa_XSe2 composition segregates in equilibrium into a two-phase mixture of a copper-deficient quaternary Cu_1-γIn_1-XGa_XSe2 composition and the binary Cu_2-δSe compound. The model predicts that the hole majority carrier (p-type) can only be achieved in the equilibrium single-phase chalcopyrite lattice with compositions that correspond to Cu_1-γIn_1-XGa_XSe_2+ɛ with γ and ɛ >0. This predicted requirement for selenium enrichment compared to the stoichiometric CuIn_1-XGa_XSe2 alloy composition for the dominance of holes over electrons as the majority carrier type is consistent with experimental evidence, and is explained in terms of a transition of the dominant lattice defect from the selenium vacancy in the

Polymeric microchip for the simultaneous determination of anions and cations by hydrodynamic injection using a dual-channel sequential injection microchip electrophoresis system.

PubMed

Gaudry, Adam J; Nai, Yi Heng; Guijt, Rosanne M; Breadmore, Michael C

2014-04-01

A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single sample. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the sample flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous sampling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with individual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in individual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

Formation of interstellar anions

NASA Astrophysics Data System (ADS)

Senent, Maria Luisa

2012-05-01

Formation of interstellar anions: M.L. Senent. The recent detection of negative charged species in the ISM1 has instigated enthusiasm for anions in the astrophysical community2. Many of these species are new and entail characterization. How they are formed in astrophysical sources is a question of major relevance. The anion presence in ISM was first predicted theoretically on the basis of electron affinities and on the negative linear chain molecular stabilities. Although very early, they were considered in astrochemical models3-4, their discovery is so recent because their abundances seem to be relatively low. These have to be understood in terms of molecular stabilities, reaction probabilities and radiative and collisional excitations. Then, we present our theoretical work on even carbon chains type Cn and CnH (n=2,4,6) focused to the understanding of anion abundances. We use highly correlated ab initio methods. We performed spectroscopic studies of various isomers that can play important roles as intermediates5-8. In previous papers9-10, we compared C2H and C2H- collisional rates responsible for observed line intensities. Actually, we study hydrogen attachment (Cn +H → CnH and Cn- +H → CnH-) and associative detachment processes (Cn- +H → CnH +e-) for 2, 4 and 6 carbon atom chains11. [1] M.C.McCarthy, C.A.Gottlieb, H.Gupta, P.Thaddeus, Astrophys.J, 652, L141 (2006) [2] V.M.Bierbaum, J.Cernicharo, R.Bachiller, eds., 2011, pp 383-389. [3] A. Dalgarno, R.A. Mc Cray, Astrophys.J,, 181, 95 (1973) [4] E. Herbst E., Nature, 289, 656 (1981); [5] H.Massó, M.L.Senent, P.Rosmus, M.Hochlaf, J.Chem.Phys., 124, 234304 (2006) [6] M.L.Senent, M.Hochlaf, Astrophys. J. , 708, 1452(2010) [7] H.Massó, M.L.Senent, J.Phys.Chem.A, 113, 12404 (2009) [8] D. Hammoutene, M.Hochlaf, M.L.Senent, submitted. [9] A. Spielfiedel, N. Feautrier, F. Najar, D. ben Abdallah, F. Dayou, M.L. Senent, F. Lique, Mon.Not.R.Astron.Soc., 421, 1891 (2012) [10] F.Dumouchel, A, Spielfieldel , M

Lithium cluster anions: photoelectron spectroscopy and ab initio calculations.

PubMed

Alexandrova, Anastassia N; Boldyrev, Alexander I; Li, Xiang; Sarkas, Harry W; Hendricks, Jay H; Arnold, Susan T; Bowen, Kit H

2011-01-28

Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Li(n)(-), n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found using the gradient embedded genetic algorithm program. Subsequently, state-of-the-art ab initio techniques, including time-dependent density functional theory, coupled cluster, and multireference configurational interactions methods, were employed to interpret the experimental spectra.

Soft Chemistry, Coloring and Polytypism in Filled Tetrahedral Semiconductors: Toward Enhanced Thermoelectric and Battery Materials.

PubMed

White, Miles A; Medina-Gonzalez, Alan M; Vela, Javier

2018-03-12

Filled tetrahedral semiconductors are a rich family of compounds with tunable electronic structure, making them ideal for applications in thermoelectrics, photovoltaics, and battery anodes. Furthermore, these materials crystallize in a plethora of related structures that are very close in energy, giving rise to polytypism through the manipulation of synthetic parameters. This Minireview highlights recent advances in the solution-phase synthesis and nanostructuring of these materials. These methods enable the synthesis of metastable phases and polytypes that were previously unobtainable. Additionally, samples synthesized in solution phase have enhanced thermoelectric performance due to their decreased grain size. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The triel bond: a potential force for tuning anion-π interactions

NASA Astrophysics Data System (ADS)

Esrafili, Mehdi D.; Mousavian, Parisasadat

2018-02-01

Using ab-initio calculations, the mutual influence between anion-π and B···N or B···C triel bond interactions is investigated in some model complexes. The properties of these complexes are studied by molecular electrostatic potential, noncovalent interaction index, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. According to the results, the formation of B···N or B···C triel bond interactions in the multi-component systems makes a significant shortening of anion-π distance. Such remarkable variation in the anion-π distances has not been reported previously. The strengthening of the anion-π bonding in the multi-component systems depend significantly on the nature of the anion, and it becomes larger in the order Br- > Cl- > F-. The parameters derived from the QTAIM and NBO methodologies are used to study the mechanism of the cooperativity between the anion-π and triel bond interactions in the multi-component complexes.

Efficient, non-toxic anion transport by synthetic carriers in cells and epithelia

NASA Astrophysics Data System (ADS)

Li, Hongyu; Valkenier, Hennie; Judd, Luke W.; Brotherhood, Peter R.; Hussain, Sabir; Cooper, James A.; Jurček, Ondřej; Sparkes, Hazel A.; Sheppard, David N.; Davis, Anthony P.

2016-01-01

Transmembrane anion transporters (anionophores) have potential for new modes of biological activity, including therapeutic applications. In particular they might replace the activity of defective anion channels in conditions such as cystic fibrosis. However, data on the biological effects of anionophores are scarce, and it remains uncertain whether such molecules are fundamentally toxic. Here, we report a biological study of an extensive series of powerful anion carriers. Fifteen anionophores were assayed in single cells by monitoring anion transport in real time through fluorescence emission from halide-sensitive yellow fluorescent protein. A bis-(p-nitrophenyl)ureidodecalin shows especially promising activity, including deliverability, potency and persistence. Electrophysiological tests show strong effects in epithelia, close to those of natural anion channels. Toxicity assays yield negative results in three cell lines, suggesting that promotion of anion transport may not be deleterious to cells. We therefore conclude that synthetic anion carriers are realistic candidates for further investigation as treatments for cystic fibrosis.

Anion induced conformational preference of Cα NN motif residues in functional proteins.

PubMed

Patra, Piya; Ghosh, Mahua; Banerjee, Raja; Chakrabarti, Jaydeb

2017-12-01

Among different ligand binding motifs, anion binding C α NN motif consisting of peptide backbone atoms of three consecutive residues are observed to be important for recognition of free anions, like sulphate or biphosphate and participate in different key functions. Here we study the interaction of sulphate and biphosphate with C α NN motif present in different proteins. Instead of total protein, a peptide fragment has been studied keeping C α NN motif flanked in between other residues. We use classical force field based molecular dynamics simulations to understand the stability of this motif. Our data indicate fluctuations in conformational preferences of the motif residues in absence of the anion. The anion gives stability to one of these conformations. However, the anion induced conformational preferences are highly sequence dependent and specific to the type of anion. In particular, the polar residues are more favourable compared to the other residues for recognising the anion. © 2017 Wiley Periodicals, Inc.

Electron localization of anions probed by nitrile vibrations

DOE PAGES

Mani, Tomoyasu; Grills, David C.; Newton, Marshall D.; ...

2015-08-02

Localization and delocalization of electrons is a key concept in chemistry, and is one of the important factors determining the efficiency of electron transport through organic conjugated molecules, which have potential to act as “molecular wires”. This, in turn, substantially influences the efficiencies of organic solar cells and other molecular electronic devices. It is also necessary to understand the electronic energy landscape and the dynamics of electrons through molecular chain that govern their transport capabilities in one-dimensional conjugated chains so that we can better define the design principles of conjugated molecules for their applications. We show that nitrile ν(C≡N) vibrationsmore » respond to the degree of electron localization in nitrile-substituted organic anions by utilizing time-resolved infrared (TRIR) detection combined with pulse radiolysis. Measurements of a series of aryl nitrile anions allow us to construct a semi-empirical calibration curve between the changes in the ν(C≡N) IR shifts and the changes in the electronic charges from the neutral to the anion states in the nitriles; more electron localization in the nitrile anion results in larger IR shifts. Furthermore, the IR linewidth in anions can report a structural change accompanying changes in the electronic density distribution. Probing the shift of the nitrile ν(C≡N) IR vibrational bands enables us to determine how the electron is localized in anions of nitrile-functionalized oligofluorenes, considered as organic mixed-valence compounds. We estimate the diabatic electron transfer distance, electronic coupling strengths, and energy barriers in these organic mixed-valence compounds. The analysis reveals a dynamic picture, showing that the electron is moving back and forth within the oligomers with a small activation energy of ≤ k BT, likely controlled by the movement of dihedral angles between monomer units. Thus, implications for the electron transport capability

Superoxide anion production by human neutrophils activated by Trichomonas vaginalis.

PubMed

Song, Hyun-Ouk; Ryu, Jae-Sook

2013-08-01

Neutrophils are the predominant inflammatory cells found in vaginal discharges of patients infected with Trichomonas vaginalis. In this study, we examined superoxide anion (O2 (.-)) production by neutrophils activated by T. vaginalis. Human neutrophils produced superoxide anions when stimulated with either a lysate of T. vaginalis, its membrane component (MC), or excretory-secretory product (ESP). To assess the role of trichomonad protease in production of superoxide anions by neutrophils, T. vaginalis lysate, ESP, and MC were each pretreated with a protease inhibitor cocktail before incubation with neutrophils. Superoxide anion production was significantly decreased by this treatment. Trichomonad growth was inhibited by preincubation with supernatants of neutrophils incubated for 3 hr with T. vaginalis lysate. Furthermore, myeloperoxidase (MPO) production by neutrophils was stimulated by live trichomonads. These results indicate that the production of superoxide anions and MPO by neutrophils stimulated with T. vaginalis may be a part of defense mechanisms of neutrophils in trichomoniasis.

Tetrahedral Arrangements of Perylene Bisimide Columns via Supramolecular Orientational Memory.

PubMed

Sahoo, Dipankar; Peterca, Mihai; Aqad, Emad; Partridge, Benjamin E; Heiney, Paul A; Graf, Robert; Spiess, Hans W; Zeng, Xiangbing; Percec, Virgil

2017-01-24

Chiral, shape, and liquid crystalline memory effects are well-known to produce commercial macroscopic materials with important applications as springs, sensors, displays, and memory devices. A supramolecular orientational memory effect that provides complex nanoscale arrangements was only recently reported. This supramolecular orientational memory was demonstrated to preserve the molecular orientation and packing within supramolecular units of a self-assembling cyclotriveratrylene crown at the nanoscale upon transition between its columnar hexagonal and Pm3̅n cubic periodic arrays. Here we report the discovery of supramolecular orientational memory in a dendronized perylene bisimide (G2-PBI) that self-assembles into tetrameric crowns and subsequently self-organizes into supramolecular columns and spheres. This supramolecular orientation memory upon transition between columnar hexagonal and body-centered cubic (BCC) mesophases preserves the 3-fold cubic [111] orientations rather than the 4-fold [100] axes, generating an unusual tetrahedral arrangement of supramolecular columns. These results indicate that the supramolecular orientational memory concept may be general for periodic arrays of self-assembling dendrons and dendrimers as well as for other periodic and quasiperiodic nanoscale organizations comprising supramolecular spheres, generated from other organized complex soft matter including block copolymers and surfactants.

Low-lying electronic structure of EuH, EuOH, and EuO neutrals and anions determined by anion photoelectron spectroscopy and DFT calculations

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

Kafader, Jared O.; Ray, Manisha; Jarrold, Caroline Chick, E-mail: cjarrold@indiana.edu

2015-07-21

The anion photoelectron (PE) spectra of EuH{sup −} and the PE spectrum of overlapping EuOH{sup −} and EuO{sup −} anions are presented and analyzed with supporting results from density functional theory calculations on the various anions and neutrals. Results point to ionically bound, high-spin species. EuH and EuOH anions and neutrals exhibit analogous electronic structures: Transitions from {sup 8}Σ{sup −} anion ground states arising from the 4f{sup 7}σ{sub 6s}{sup 2} superconfiguration to the close-lying neutral {sup 9}Σ{sup −} and {sup 7}Σ{sup −} states arising from the 4f{sup 7}σ{sub 6s} superconfiguration are observed spaced by an energy interval similar to themore » free Eu{sup +} [4f{sup 7}6s] {sup 9}S - {sup 7}S splitting. The electron affinities (EAs) of EuH and EuOH are determined to be 0.771 ± 0.009 eV and 0.700 ± 0.011 eV, respectively. Analysis of spectroscopic features attributed to EuO{sup −} photodetachment is complicated by the likely presence of two energetically competitive electronic states of EuO{sup −} populating the ion beam. However, based on the calculated relative energies of the close-lying anion states arising from the 4f{sup 7}σ{sub 6s} and 4f{sup 6}σ{sub 6s}{sup 2} configurations and the relative energies of the one-electron accessible 4f{sup 7} and 4f{sup 6}σ{sub 6s} neutral states based on ligand-field theory [M. Dulick, E. Murad, and R. F. Barrow, J. Chem. Phys. 85, 385 (1986)], the remaining features are consistent with the 4f{sup 6}σ{sub 6s}{sup 2}  {sup 7}Σ{sup −} and 4f{sup 7}σ{sub 6s}{sup 7}Σ{sup −} anion states lying very close in energy (the former was calculated to be 0.15 eV lower in energy than the latter), though the true anion ground state and neutral EA could not be established unambiguously. Calculations on the various EuO anion and neutral states suggest 4f-orbital overlap with 2p orbitals in species with 4f{sup 6} occupancy.« less

Production of monodisperse, polymeric microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chang, Manchium (Inventor)

1990-01-01

Very small, individual polymeric microspheres with very precise size and a wide variation in monomer type and properties are produced by deploying a precisely formed liquid monomer droplet, suitably an acrylic compound such as hydroxyethyl methacrylate into a containerless environment. The droplet which assumes a spheroid shape is subjected to polymerizing radiation such as ultraviolet or gamma radiation as it travels through the environment. Polymeric microspheres having precise diameters varying no more than plus or minus 5 percent from an average size are recovered. Many types of fillers including magnetic fillers may be dispersed in the liquid droplet.

Radiation-induced polymerization of glass forming systems. VI. Polymerization rate at higher conversion in binary systems

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

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-08-01

The effect of temperature and composition on the inflection point in the time-conversion curve and the saturated conversion was investigated in the gamma -radio-induced radical polymerization of binary systems consisting of a glass- forming monomer and a solvent. In the polymerization of completely homogeneous systems such as glycidyl methacrylate (GMA) -triacetin and hydroxyethyl methacrylate (HEMA) --propylene glycol systems, the time-conversion curve has an inflection point at polymerization temperatures between T/sub vm/(T/sub v/ of monomer system) and T/sub vp/ (T/sub v/ of polymer system). Such conversions at the inflection point changed monotonically between 0 and 100% in this temperature range. T/submore » v/ was found to be 30 to 50 deg C higher than T/sub g/ (glass transition temperature) and a monotonic function of composition (monomer -- polymer -- solvent). The acceleration effect continued to 100% conversion above T/sub vp/, and no acceleration effect was observed below T/sub vm/. The saturated conversion in homogeneous systems changed monotonically between 0 and 100% for polymerization temperatures between T/sub gm/ (T/sub g/ of monomer system) and T/sub gp/(T of polymer system). T/sub g/ was also a monotonic function of composition. No saturation in conversion was observed above T/sub gp/ , and no polymerization occurred below T/sub gm/. In the polymerization of completely heterogeneous systems such as HEMA-dioctyl phthalate, no acceleration effect was observed at any temperature and composition. The saturated conversion was 100% sbove T/sub g/ of pure HEMA, and no polymerization occurred below this temperature in this system. (auth)« less

Synthesis, Structure, and Pressure-Induced Polymerization of Li3Fe(CN)6 Accompanied with Enhanced Conductivity.

PubMed

Li, Kuo; Zheng, Haiyan; Hattori, Takanori; Sano-Furukawa, Asami; Tulk, Christopher A; Molaison, Jamie; Feygenson, Mikhail; Ivanov, Ilia N; Yang, Wenge; Mao, Ho-Kwang

2015-12-07

Pressure-induced polymerization of charged triple-bond monomers like acetylide and cyanide could lead to formation of a conductive metal-carbon network composite, thus providing a new route to synthesize inorganic/organic conductors with tunable composition and properties. The industry application of this promising synthetic method is mainly limited by the reaction pressure needed, which is often too high to be reached for gram amounts of sample. Here we successfully synthesized highly conductive Li3Fe(CN)6 at maximum pressure around 5 GPa and used in situ diagnostic tools to follow the structural and functional transformations of the sample, including in situ X-ray and neutron diffraction and Raman and impedance spectroscopy, along with the neutron pair distribution function measurement on the recovered sample. The cyanide anions start to react around 1 GPa and bond to each other irreversibly at around 5 GPa, which are the lowest reaction pressures in all known metal cyanides and within the technologically achievable pressure range for industrial production. The conductivity of the polymer is above 10(-3) S · cm(-1), which reaches the range of conductive polymers. This investigation suggests that the pressure-induced polymerization route is practicable for synthesizing some types of functional conductive materials for industrial use, and further research like doping and heating can hence be motivated to synthesize novel materials under lower pressure and with better performances.

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Filters, microporous polymeric. 177.2250 Section... as Components of Articles Intended for Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in paragraph (a) of this section may be safely used, subject to the...

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Filters, microporous polymeric. 177.2250 Section... as Components of Articles Intended for Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in paragraph (a) of this section may be safely used, subject to the...

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Filters, microporous polymeric. 177.2250 Section... as Components of Articles Intended for Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in paragraph (a) of this section may be safely used, subject to the...

21 CFR 177.2250 - Filters, microporous polymeric.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Filters, microporous polymeric. 177.2250 Section... as Components of Articles Intended for Repeated Use § 177.2250 Filters, microporous polymeric. Microporous polymeric filters identified in paragraph (a) of this section may be safely used, subject to the...

A versatile, pulsed anion source utilizing plasma-entrainment: Characterization and applications

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

Lu, Yu-Ju; Lehman, Julia H.; Lineberger, W. Carl, E-mail: wcl@jila.colorado.edu

2015-01-28

A novel pulsed anion source has been developed, using plasma entrainment into a supersonic expansion. A pulsed discharge source perpendicular to the main gas expansion greatly reduces unwanted “heating” of the main expansion, a major setback in many pulsed anion sources in use today. The design principles and construction information are described and several examples demonstrate the range of applicability of this anion source. Large OH{sup −}(Ar){sub n} clusters can be generated, with over 40 Ar solvating OH{sup −}. The solvation energy of OH{sup −}(Ar){sub n}, where n = 1-3, 7, 12, and 18, is derived from photoelectron spectroscopy andmore » shows that by n = 12-18, each Ar is bound by about 10 meV. In addition, cis– and trans– HOCO{sup −} are generated through rational anion synthesis (OH{sup −} + CO + M → HOCO{sup −} + M) and the photoelectron spectra compared with previous results. These results, along with several further proof-of-principle experiments on solvation and transient anion synthesis, demonstrate the ability of this source to efficiently produce cold anions. With modifications to two standard General Valve assemblies and very little maintenance, this anion source provides a versatile and straightforward addition to a wide array of experiments.« less

LiBSi2: a tetrahedral semiconductor framework from boron and silicon atoms bearing lithium atoms in the channels.

PubMed

Zeilinger, Michael; van Wüllen, Leo; Benson, Daryn; Kranak, Verina F; Konar, Sumit; Fässler, Thomas F; Häussermann, Ulrich

2013-06-03

Silicon swallows up boron: The novel open tetrahedral framework structure (OTF) of the Zintl phase LiBSi2 was made by applying high pressure to a mixture of LiB and elemental silicon. The compound represents a new topology in the B-Si net (called tum), which hosts Li atoms in the channels (see picture). LiBSi2 is the first example where B and Si atoms form an ordered common framework structure with B engaged exclusively in heteronuclear B-Si contacts.

Infrared spectroscopy of hydrated naphthalene cluster anions.

PubMed

Knurr, Benjamin J; Adams, Christopher L; Weber, J Mathias

2012-09-14

We present infrared spectra of mass-selected C(10)H(8)(-)·(H(2)O)(n)·Ar(m) cluster anions (n = 1-6) obtained by Ar predissociation spectroscopy. The experimental spectra are compared with predicted spectra from density functional theory calculations. The OH groups of the water ligands are involved in H-bonds to other water molecules or to the π system of the naphthalene anion, which accommodates the excess electron. The interactions in the water network are generally found to be more important than those between water molecules and the ion. For 2 ≤ n ≤ 4 the water molecules form single layer water networks on one side of the naphthalene anion, while for n = 5 and 6, cage and multilayer structures become more energetically favorable. For cluster sizes with more than 3 water molecules, multiple conformers are likely to be responsible for the experimental spectra.

Anion permselective membrane

NASA Technical Reports Server (NTRS)

Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

1984-01-01

Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

Probing adsorption of polyacrylamide-based polymers on anisotropic Basal planes of kaolinite using quartz crystal microbalance.

PubMed

Alagha, Lana; Wang, Shengqun; Yan, Lujie; Xu, Zhenghe; Masliyah, Jacob

2013-03-26

Quartz crystal microbalance with dissipation (QCM-D) was applied to investigate the adsorption characteristics of polyacrylamide-based polymers (PAMs) on anisotropic basal planes of kaolinite. Kaolinite basal planes were differentiated by depositing kaolinite nanoparticles (KNPs) on silica and alumina sensors in solutions of controlled pH values. Adsorption of an in-house synthesized organic-inorganic Al(OH)3-PAM (Al-PAM) as an example of cationic hybrid PAM and a commercially available partially hydrolyzed polyacrylamide (MF1011) as an example of anionic PAM was studied. Cationic Al-PAM was found to adsorb irreversibly and preferentially on tetrahedral silica basal planes of kaolinite. In contrast, anionic MF1011 adsorbed strongly on aluminum-hydroxy basal planes, while its adsorption on tetrahedral silica basal planes was weak and reversible. Adsorption study revealed that both electrostatic attraction and hydrogen-bonding mechanisms contribute to adsorption of PAMs on kaolinite. The adsorbed Al-PAM layer was able to release trapped water overtime and became more compact, while MF1011 film became more dissipative as backbones stretched out from kaolinite surface with minimal overlapping. Experimental results obtained from this study provide clear insights into the phenomenon that governs flocculation-based solid-liquid separation processes using multicomponent flocculants of anionic and cationic nature.

Intrinsic electrophilic properties of nucleosides: Photoelectron spectroscopy of their parent anions

NASA Astrophysics Data System (ADS)

Stokes, Sarah T.; Li, Xiang; Grubisic, Andrej; Ko, Yeon Jae; Bowen, Kit H.

2007-08-01

The nucleoside parent anions 2'-deoxythymidine-, 2'-deoxycytidine-, 2'-deoxyadenosine-, uridine-, cytidine-, adenosine-, and guanosine- were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG-, the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.

Intrinsic electrophilic properties of nucleosides: photoelectron spectroscopy of their parent anions.

PubMed

Stokes, Sarah T; Li, Xiang; Grubisic, Andrej; Ko, Yeon Jae; Bowen, Kit H

2007-08-28

The nucleoside parent anions 2(')-deoxythymidine(-), 2(')-deoxycytidine(-), 2(')-deoxyadenosine(-), uridine(-), cytidine(-), adenosine(-), and guanosine(-) were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al. [J. Am. Chem. Soc. 126, 4404 (2004)] and by Li et al. [Radiat. Res. 165, 721 (2006)]. Through the combination of our experimental results and their theoretical calculations, several implications emerge. (1) With the possible exception of dG(-), the parent anions of nucleosides exist, and they are stable. (2) These nucleoside anions are valence anions, and in most cases the negative charge is closely associated with the nucleobase moiety. (3) The nucleoside parent anions we have generated and studied are the negative ions of canonical, neutral nucleosides, similar to those found in DNA.

Thorium Copper Phosphides: More Diverse Metal-Phosphorus and Phosphorus-Phosphorus Interactions than U analogues

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

Jin, Geng Bang; Malliakas, Christos D.; Lin, Jian

To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP 2, beta-ThCu 2P 2, and ThCu 5P 3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP 2 can be described as a filled UTe 2-type with both dimeric P 2 4- and monomeric P 3- anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu 2P 2 contains only P 3- anions and is isostructural with BaCumore » 2S 2. In this structure, Th is coordinated by seven P atoms in monocapped trigonal prismatic geometry and Cu is tetrahedrally coordinated by four P atoms. ThCu 5P 3 adopts the YCo 5P 3-type structure consisting of P 3- anions. This structure contains Th atoms coordinated by six P atoms in a trigonal prismatic arrangement and Cu atoms that are either tetrahedrally coordinated by four P atoms or square pyramidally coordinated by five P atoms. Electric resistivity measurements and electronic structure calculations on β-ThCu 2P 2 indicate a metal. These new compounds may be charge-balanced and formulated as Th 4+Cu +(P 2 4-) 1/2P 3-, Th 4+(Cu +) 2(P 3-) 2, and Th 4+(Cu +) 5(P 3-) 3, respectively. The structural, bonding, and property relationships between these Th compounds and related actinide and rare-earth phases are discussed. In conclusion, titled compounds display more diverse ion-ion interactions and different electronic structures from those in UCuP 2 and UCu 2P 2 that were synthesized under similar experimental conditions, suggesting divergence of thorium-phosphide chemistry from uranium-phosphide chemistry.« less

Thorium Copper Phosphides: More Diverse Metal-Phosphorus and Phosphorus-Phosphorus Interactions than U analogues

DOE PAGES

Jin, Geng Bang; Malliakas, Christos D.; Lin, Jian

2017-09-28

To explore the chemical analogy between thorium and heavier actinides in soft anionic environments, three new thorium phosphides (ThCuP 2, beta-ThCu 2P 2, and ThCu 5P 3) have been prepared through solid-state reactions using CuI as a reaction promoter. The structure of ThCuP 2 can be described as a filled UTe 2-type with both dimeric P 2 4- and monomeric P 3- anions, in which Th is coordinated by eight P atoms in a bicapped trigonal prismatic arrangement and Cu is tetrahedrally coordinated by four P atoms. β-ThCu 2P 2 contains only P 3- anions and is isostructural with BaCumore » 2S 2. In this structure, Th is coordinated by seven P atoms in monocapped trigonal prismatic geometry and Cu is tetrahedrally coordinated by four P atoms. ThCu 5P 3 adopts the YCo 5P 3-type structure consisting of P 3- anions. This structure contains Th atoms coordinated by six P atoms in a trigonal prismatic arrangement and Cu atoms that are either tetrahedrally coordinated by four P atoms or square pyramidally coordinated by five P atoms. Electric resistivity measurements and electronic structure calculations on β-ThCu 2P 2 indicate a metal. These new compounds may be charge-balanced and formulated as Th 4+Cu +(P 2 4-) 1/2P 3-, Th 4+(Cu +) 2(P 3-) 2, and Th 4+(Cu +) 5(P 3-) 3, respectively. The structural, bonding, and property relationships between these Th compounds and related actinide and rare-earth phases are discussed. In conclusion, titled compounds display more diverse ion-ion interactions and different electronic structures from those in UCuP 2 and UCu 2P 2 that were synthesized under similar experimental conditions, suggesting divergence of thorium-phosphide chemistry from uranium-phosphide chemistry.« less

Octamethyl-octaundecylcyclo[8]pyrrole: A Promising Sulfate Anion Extractant

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

Eller, Leah R; Stepien, Marcin; Fowler, Christopher J

The diprotonated form of an organic-solubilized cyclo[8]pyrrole derivative, bearing eight undecyl chains on the {beta}-pyrrolic positions, was found to extract sulfate anion effectively from neutral aqueous media into a toluene organic phase. The kinetics of sulfate anion exchange between the two phases were found to be exceedingly slow in the absence of the phase-transfer catalyst, Aliquat 336-nitrate (A336N), but appreciable in its presence. The bisnitrate anion bound form of this cyclo[8]pyrrole could be generated in situ by subjecting the toluene phase containing initially 0.5 mM of the sulfate anion bound form and 0.1 mM trioctylamine (TOA) to successive equilibrations withmore » aqueous 0.1 M HNO{sub 3} until sulfate was no longer detected in the aqueous phase. This bisnitrate complex, when studied as a 0.5 mM solution in toluene in the presence of 0.1 mM (TOAH){sup +}(NO{sub 3}{sup -}), was also found to be an effective extractant for sulfate anion. D{sub SO4} values of 0.001 and 1000 were observed at 1 M NaNO{sub 3}(aq) and 0.3 mM NaNO{sub 3}(aq), respectively, and the logarithm of the conditional exchange constant, log(K{prime}{sub exch}), was calculated to be 4.9 {+-} 0.4. The present cyclo[8]pyrrole system is thus noteworthy as being the first synthetic receptor that displays a high selectivity for sulfate anion in the presence of excess nitrate under conditions of solvent extraction.« less

Direct Density Functional Energy Minimization using an Tetrahedral Finite Element Grid

NASA Astrophysics Data System (ADS)

Vaught, A.; Schmidt, K. E.; Chizmeshya, A. V. G.

1998-03-01

We describe an O(N) (N proportional to volume) technique for solving electronic structure problems using the finite element method (FEM). A real--space tetrahedral grid is used as a basis to represent the electronic density, of a free or periodic system and Poisson's equation is solved as a boundary value problem. Nuclear cusps are treated using a local grid consisting of radial elements. These features facilitate the implementation of complicated energy functionals and permit a direct (constrained) energy minimization with respect to the density. We demonstrate the usefulness of the scheme by calculating the binding trends and polarizabilities of a number of atoms and molecules using a number of recently proposed non--local, orbital--free kinetic energy functionals^1,2. Scaling behavior, computational efficiency and the generalization to band--structure will also be discussed. indent 0 pt øbeylines øbeyspaces skip 0 pt ^1 P. Garcia-Gonzalez, J.E. Alvarellos and E. Chacon, Phys. Rev. B 54, 1897 (1996). ^2 A. J. Thakkar, Phys.Rev.B 46, 6920 (1992).

AT base pair anions versus (9-methyl-A)(1-methyl-T) base pair anions.

PubMed

Radisic, Dunja; Bowen, Kit H; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej

2005-05-04

The anionic base pairs of adenine and thymine, (AT)(-), and 9-methyladenine and 1-methylthymine, (MAMT)(-), have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)(-) found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)(-) was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)(-) and a resulting (MAMT)(-) configuration that was either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)(-) occurred at a completely different electron binding energy than had (AT)(-). Moreover, the VDE value of (MAMT)(-) was in agreement with that predicted by theory. The configuration of (MAMT)(-) and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced DNA alterations, BFPT in the WC/HS configurations of (AT)(-) is not feasible.

Self-exchange reactions of radical anions in n-hexane.

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

Werst, D. W.; Chemistry

The formation and reactions of radical anions in n-hexane at 190 K were investigated by pulse radiolysis and time-resolved fluorescence-detected magnetic resonance (FDMR). Electron attachment was found to occur for compounds with gas-phase electron affinities (EA) more positive than -1.1 {+-} 0.1 eV. The FDMR concentration and time dependence are interpreted as evidence for self-exchange electron-transfer reactions, indicating that formation of dimer radical anions is not prevalent for the range of molecules studied. FDMR detection of radical anions is mainly restricted to electron acceptors with EA less than approximately 0.5 eV.

Structural basis of reverse nucleotide polymerization

PubMed Central

Nakamura, Akiyoshi; Nemoto, Taiki; Heinemann, Ilka U.; Yamashita, Keitaro; Sonoda, Tomoyo; Komoda, Keisuke; Tanaka, Isao; Söll, Dieter; Yao, Min

2013-01-01

Nucleotide polymerization proceeds in the forward (5′-3′) direction. This tenet of the central dogma of molecular biology is found in diverse processes including transcription, reverse transcription, DNA replication, and even in lagging strand synthesis where reverse polymerization (3′-5′) would present a “simpler” solution. Interestingly, reverse (3′-5′) nucleotide addition is catalyzed by the tRNA maturation enzyme tRNAHis guanylyltransferase, a structural homolog of canonical forward polymerases. We present a Candida albicans tRNAHis guanylyltransferase-tRNAHis complex structure that reveals the structural basis of reverse polymerization. The directionality of nucleotide polymerization is determined by the orientation of approach of the nucleotide substrate. The tRNA substrate enters the enzyme’s active site from the opposite direction (180° flip) compared with similar nucleotide substrates of canonical 5′-3′ polymerases, and the finger domains are on opposing sides of the core palm domain. Structural, biochemical, and phylogenetic data indicate that reverse polymerization appeared early in evolution and resembles a mirror image of the forward process. PMID:24324136

Regeneration of strong-base anion-exchange resins by sequential chemical displacement

DOEpatents

Brown, Gilbert M.; Gu, Baohua; Moyer, Bruce A.; Bonnesen, Peter V.

2002-01-01

A method for regenerating strong-base anion exchange resins utilizing a sequential chemical displacement technique with new regenerant formulation. The new first regenerant solution is composed of a mixture of ferric chloride, a water-miscible organic solvent, hydrochloric acid, and water in which tetrachloroferrate anion is formed and used to displace the target anions on the resin. The second regenerant is composed of a dilute hydrochloric acid and is used to decompose tetrachloroferrate and elute ferric ions, thereby regenerating the resin. Alternative chemical displacement methods include: (1) displacement of target anions with fluoroborate followed by nitrate or salicylate and (2) displacement of target anions with salicylate followed by dilute hydrochloric acid. The methodology offers an improved regeneration efficiency, recovery, and waste minimization over the conventional displacement technique using sodium chloride (or a brine) or alkali metal hydroxide.

Photoinduced Bimolecular Electron Transfer from Cyano Anions in Ionic Liquids

DOE PAGES

Wu, Boning; Liang, Min; Maroncelli, Mark; ...

2015-10-26

Ionic liquids with electron-donating anions are used to investigate rates and mechanisms of photoinduced bimolecular electron transfer to the photoexcited acceptor 9,10-dicyanoanthracene (9,10-DCNA). The set of five cyano anion ILs studied comprises the 1-ethyl-3-methylimidazolium cation paired with each of these five anions: selenocyanate, thiocyanate, dicyanamide, tricyanomethanide, and tetracyano-borate. Measurements with these anions dilute in acetonitrile and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-amide show that the selenocyanate and tricyanomethanide anions are strong quenchers of the 9,10-DCNA fluorescence, thiocyanate is a moderately strong quencher, dicyanamide is a weak quencher, and no quenching is observed for tetracyanoborate. Quenching rates are obtained from both time-resolved fluorescence transients andmore » time-integrated spectra. Finally, application of a Smoluchowski diffusion-and-reaction model showed that the complex kinetics observed can be fit using only two adjustable parameters, D and V 0, where D is the relative diffusion coefficient between donor and acceptor and V 0 is the value of the electronic coupling at donor-acceptor contact.« less

Measurement and Analysis of in vitro Actin Polymerization

PubMed Central

Doolittle, Lynda K.; Rosen, Michael K.; Padrick, Shae B.

2014-01-01

Summary The polymerization of actin underlies force generation in numerous cellular processes. While actin polymerization can occur spontaneously, cells maintain control over this important process by preventing actin filament nucleation and then allowing stimulated polymerization and elongation by several regulated factors. Actin polymerization, regulated nucleation and controlled elongation activities can be reconstituted in vitro, and used to probe the signaling cascades cells use to control when and where actin polymerization occurs. Introducing a pyrene fluorophore allows detection of filament formation by an increase in pyrene fluorescence. This method has been used for many years and continues to be broadly used, owing to its simplicity and flexibility. Here we describe how to perform and analyze these in vitro actin polymerization assays, with an emphasis on extracting useful descriptive parameters from kinetic data. PMID:23868594

A carbohydrate-anion recognition system in aprotic solvents.

PubMed

Ren, Bo; Dong, Hai; Ramström, Olof

2014-05-01

A carbohydrate-anion recognition system in nonpolar solvents is reported, in which complexes form at the B-faces of β-D-pyranosides with H1-, H3-, and H5-cis patterns similar to carbohydrate-π interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate-anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CH⋅⋅⋅A(-) hydrogen bonds between the binding partners and is related to electron-withdrawing groups of the carbohydrates as well as increased hydrogen-bond-accepting capability of the anions. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Molecular Anions in Protostars, Prestellar Cores and Dark Clouds

NASA Technical Reports Server (NTRS)

Cordiner, Martin; Charnley, Steven; Buckle, Jane; Wash, Catherine; Millar, Tom

2011-01-01

From our recent survey work using the Green Bank Telescope, microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H have been detected in six new sources. Using HC3N = 10(exp -9) emission maps, we targeted the most carbon-chain-rich sources for our anion survey, which included the low-mass Class 0 protostar L1251A-IRS3, the prestellar cores L1389-SMM1 and L1512, and the interstellar clouds Ll172A, TMC-1C and L1495B. Derived [C6H(-)]/[C6H] anion-to-neutral ratios are approximately 1-10. The greatest C6H(-) column densities are found in the quiescent clouds TMC-1C and L1495B, but the anion-to-neutral ratios are greatest in the prestellar cores and protostars. These results are interpreted in terms of the physical and chemical properties of the sources, and the implications for molecular cloud chemistry are discussed.

Escalation of polymerization in a thermal gradient

PubMed Central

Mast, Christof B.; Schink, Severin; Gerland, Ulrich; Braun, Dieter

2013-01-01

For the emergence of early life, the formation of biopolymers such as RNA is essential. However, the addition of nucleotide monomers to existing oligonucleotides requires millimolar concentrations. Even in such optimistic settings, no polymerization of RNA longer than about 20 bases could be demonstrated. How then could self-replicating ribozymes appear, for which recent experiments suggest a minimal length of 200 nt? Here, we demonstrate a mechanism to bridge this gap: the escalated polymerization of nucleotides by a spatially confined thermal gradient. The gradient accumulates monomers by thermophoresis and convection while retaining longer polymers exponentially better. Polymerization and accumulation become mutually self-enhancing and result in a hyperexponential escalation of polymer length. We describe this escalation theoretically under the conservative assumption of reversible polymerization. Taking into account the separately measured thermophoretic properties of RNA, we extrapolate the results for primordial RNA polymerization inside a temperature gradient in pores or fissures of rocks. With a dilute, nanomolar concentration of monomers the model predicts that a pore length of 5 cm and a temperature difference of 10 K suffice to polymerize 200-mers of RNA in micromolar concentrations. The probability to generate these long RNAs is raised by a factor of >10600 compared with polymerization in a physical equilibrium. We experimentally validate the theory with the reversible polymerization of DNA blocks in a laser-driven thermal trap. The results confirm that a thermal gradient can significantly enlarge the available sequence space for the emergence of catalytically active polymers. PMID:23630280

Nucleotide Selectivity in Abiotic RNA Polymerization Reactions.

PubMed

Coari, Kristin M; Martin, Rebecca C; Jain, Kopal; McGown, Linda B

2017-09-01

In order to establish an RNA world on early Earth, the nucleotides must form polymers through chemical rather than biochemical reactions. The polymerization products must be long enough to perform catalytic functions, including self-replication, and to preserve genetic information. These functions depend not only on the length of the polymers, but also on their sequences. To date, studies of abiotic RNA polymerization generally have focused on routes to polymerization of a single nucleotide and lengths of the homopolymer products. Less work has been done the selectivity of the reaction toward incorporation of some nucleotides over others in nucleotide mixtures. Such information is an essential step toward understanding the chemical evolution of RNA. To address this question, in the present work RNA polymerization reactions were performed in the presence of montmorillonite clay catalyst. The nucleotides included the monophosphates of adenosine, cytosine, guanosine, uridine and inosine. Experiments included reactions of mixtures of an imidazole-activated nucleotide (ImpX) with one or more unactivated nucleotides (XMP), of two or more ImpX, and of XMP that were activated in situ in the polymerization reaction itself. The reaction products were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify the lengths and nucleotide compositions of the polymerization products. The results show that the extent of polymerization, the degree of heteropolymerization vs. homopolymerization, and the composition of the polymeric products all vary among the different nucleotides and depend upon which nucleotides and how many different nucleotides are present in the mixture.

Nucleotide Selectivity in Abiotic RNA Polymerization Reactions

NASA Astrophysics Data System (ADS)

Coari, Kristin M.; Martin, Rebecca C.; Jain, Kopal; McGown, Linda B.

2017-09-01

In order to establish an RNA world on early Earth, the nucleotides must form polymers through chemical rather than biochemical reactions. The polymerization products must be long enough to perform catalytic functions, including self-replication, and to preserve genetic information. These functions depend not only on the length of the polymers, but also on their sequences. To date, studies of abiotic RNA polymerization generally have focused on routes to polymerization of a single nucleotide and lengths of the homopolymer products. Less work has been done the selectivity of the reaction toward incorporation of some nucleotides over others in nucleotide mixtures. Such information is an essential step toward understanding the chemical evolution of RNA. To address this question, in the present work RNA polymerization reactions were performed in the presence of montmorillonite clay catalyst. The nucleotides included the monophosphates of adenosine, cytosine, guanosine, uridine and inosine. Experiments included reactions of mixtures of an imidazole-activated nucleotide (ImpX) with one or more unactivated nucleotides (XMP), of two or more ImpX, and of XMP that were activated in situ in the polymerization reaction itself. The reaction products were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify the lengths and nucleotide compositions of the polymerization products. The results show that the extent of polymerization, the degree of heteropolymerization vs. homopolymerization, and the composition of the polymeric products all vary among the different nucleotides and depend upon which nucleotides and how many different nucleotides are present in the mixture.

Coating of plasma polymerized film

NASA Technical Reports Server (NTRS)

Morita, S.; Ishibashi, S.

1980-01-01

Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

Spring-loaded polymeric gel actuators

DOEpatents

Shahinpoor, Mohsen

1995-01-01

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

Investigation of Solution Polymerizations in Microgravity and 1 G

NASA Technical Reports Server (NTRS)

Kennedy, Alvin P.

1998-01-01

The in-situ dielectric spectra for the solution polymerization of polydiacetylene has been successfully measured. The results show a distinct difference between the response for the bulk solution and surface polymerization. It also shows a low frequency peak in the dissipation factor which is present in both the bulk and surface polymerizations. These features may prove to be significant indicators for important polymerization processes. Future studies will investigate the mechanisms responsible for these dielectric responses. This technique will eventually be used to monitor microgravity polymerizations and provide in-situ data on how microgravity affects solution polymerization.

Boric acid and boronic acids inhibition of pigeonpea urease.

PubMed

Reddy, K Ravi Charan; Kayastha, Arvind M

2006-08-01

Urease from the seeds of pigeonpea was competitively inhibited by boric acid, butylboronic acid, phenylboronic acid, and 4-bromophenylboronic acid; 4-bromophenylboronic acid being the strongest inhibitor, followed by boric acid > butylboronic acid > phenylboronic acid, respectively. Urease inhibition by boric acid is maximal at acidic pH (5.0) and minimal at alkaline pH (10.0), i.e., the trigonal planar B(OH)3 form is a more effective inhibitor than the tetrahedral B(OH)4 -anionic form. Similarly, the anionic form of phenylboronic acid was least inhibiting in nature.

Mixed mode HILIC/anion exchange separations on latex coated silica monoliths.

PubMed

Ibrahim, Mohammed E A; Lucy, Charles A

2012-10-15

Bare silica monoliths do not possess anion exchange sites hence they show low retention for anions. Moreover, bare silica monoliths show low retention in hydrophilic interaction liquid chromatography (HILIC). Coating the silica surface with cationic nanoparticles e.g. AS9-SC (latex A), AS12A (latex B) and DNApac (latex C) increases the thickness of the water layer on the Onyx silica monolith 8-10 times enabling HILIC retention when a high % acetonitrile (ACN) mobile phase is used. The formed water layer by itself is not sufficient to perform good separation of the studied anions (acetate, formate, nitrate, bromate, thiocyanate and iodide). On the other hand, the latex nanoparticles introduce positively charged sites, making anion exchange chromatography possible, with the anion exchange capacity varying with the latex adsorbed (44.1 ± 0.2, 4.4 ± 0.1 and 14.0 ± 0.7 μeq/column for latex A, B and C, respectively). Latex A nanoparticles which provided the highest ion exchange capacity separated all tested anions with reasonable resolution. Fast separation (2.5 min) of acetate, formate, nitrate, bromate, thiocyanate and iodide was performed using the latex A coated silica monolith. The obtained efficiencies are 13,000-50,000 plates/m at 3 mL/min with a minimum resolution of 0.85. Retention is mixed mode under HILIC conditions with HILIC dominating for the kosmotropic anions and ion exchange dominating for the chaotropic anions. The two different brands of silica monoliths (Merck Chromolith and Phenomenex Onyx) coated with the same latex A nanoparticles displayed similar water layer volumes, ion exchange capacity and selectivity. Copyright © 2012 Elsevier B.V. All rights reserved.

Spring-loaded polymeric gel actuators

DOEpatents

Shahinpoor, M.

1995-02-14

Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

Micro-fluidic partitioning between polymeric sheets for chemical amplification and processing

DOEpatents

Anderson, Brian L.

2017-01-24

A system for fluid partitioning for chemical amplification or other chemical processing or separations of a sample, comprising a first dispenser of a first polymeric sheet, wherein the first polymeric sheet contains chambers; a second dispenser of a second polymeric sheet wherein the first dispenser and the second dispenser are positioned so that the first polymeric sheet and the second polymeric sheet become parallel; a dispenser of the fluid positioned to dispense the fluid between the first polymeric sheet and the second polymeric sheet; and a seal unit that seals the first polymeric sheet and the second polymeric sheet together thereby sealing the sample between the first polymeric sheet and the second polymeric sheet and partitioning the fluid for chemical amplification or other chemical processing or separations.

Micro-fluidic partitioning between polymeric sheets for chemical amplification and processing

DOEpatents

Anderson, Brian L.

2015-05-26

A system for fluid partitioning for chemical amplification or other chemical processing or separations of a sample, comprising a first dispenser of a first polymeric sheet, wherein the first polymeric sheet contains chambers; a second dispenser of a second polymeric sheet wherein the first dispenser and the second dispenser are positioned so that the first polymeric sheet and the second polymeric sheet become parallel; a dispenser of the fluid positioned to dispense the fluid between the first polymeric sheet and the second polymeric sheet; and a seal unit that seals the first polymeric sheet and the second polymeric sheet together thereby sealing the sample between the first polymeric sheet and the second polymeric sheet and partitioning the fluid for chemical amplification or other chemical processing or separations.

Synthesis, characterization, adsorption, and interfacial rheological properties of four-arm anionic fluorosurfactants.

PubMed

Ertekin, Ayça; Kausch, Charles M; Kim, Yongsin; Thomas, Richard R

2008-03-18

Four-arm oligo(fluorooxetane) tetraols containing -CF3 and -C2F5 groups were prepared in reasonable yields by cationic, ring-opening polymerization of fluorinated oxetane monomers using a tetrafunctional, alkoxylated polyol as initiator and BF3.THF as catalyst. The tetraols were then converted to ammonium sulfate salts using oleum followed by neutralization with ammonium hydroxide in excellent yields. The four-arm oligo(fluorooxetane) sulfates (1=-CF3, 2=-C2F5) have an architecture characterized by a hydrophobic core of oligo(fluorooxetane) arms with a hydrophilic sulfate shell and initiator. The four-arm anionic oligo(fluorooxetane)s are surface active with critical micelle concentration values approximately 4.2x10(-6) and 2.4x10(-6) mol/L for 1 and 2, respectively. Surface tension isotherms in pH 8 buffered solution were measured and data fitted parametrically to the Davies surface tension isotherm equation. Molecular areas at saturation were estimated to be approximately 89 and approximately 85 A2 with DeltaGads=-12.7 and -13.2 kcal/mol for 1 and 2, respectively. The results are compared to two-arm, bolaamphiphilic analogues of 1 and 2 and a small molecule, long perfluoroalkyl-chain (-C8F17), anionic fluorosurfactant (Kausch, C. M.; Kim, Y.; Russell, V. M.; Medsker, R. E.; Thomas, R. R. Langmuir 2003, 19, 7182). Dynamic surface tension data for 1 and 2 were analyzed using the Ward-Tordai mass transport equation to yield concentration-dependent diffusion coefficients. In the concentration range approximately 10(-6) mol/L, diffusion coefficients were estimated to be approximately 1-3x10(-5) cm2/s. Dilational interfacial rheological parameters for 1 and 2 were measured. Values of |E| and E' were found to be larger than those of the two-arm analogues of the same perfluoroalkyl chain length while E' 'and phi were found to be smaller. The magnitude of these values reflects the difference in adsorption strength and mass transport and/or relaxation between the two

Highly parallel demagnetization field calculation using the fast multipole method on tetrahedral meshes with continuous sources

NASA Astrophysics Data System (ADS)

Palmesi, P.; Exl, L.; Bruckner, F.; Abert, C.; Suess, D.

2017-11-01

The long-range magnetic field is the most time-consuming part in micromagnetic simulations. Computational improvements can relieve problems related to this bottleneck. This work presents an efficient implementation of the Fast Multipole Method [FMM] for the magnetic scalar potential as used in micromagnetics. The novelty lies in extending FMM to linearly magnetized tetrahedral sources making it interesting also for other areas of computational physics. We treat the near field directly and in use (exact) numerical integration on the multipole expansion in the far field. This approach tackles important issues like the vectorial and continuous nature of the magnetic field. By using FMM the calculations scale linearly in time and memory.

Chaotropic Monovalent Anion-Induced Rectification Inversion at Nanopipettes Modified by Polyimidazolium Brushes.

PubMed

He, Xiulan; Zhang, Kailin; Liu, Yang; Wu, Fei; Yu, Ping; Mao, Lanqun

2018-04-16

A nonintuitive observation of monovalent anion-induced ion current rectification inversion at polyimidazolium brush (PimB)-modified nanopipettes is presented. The rectification inversion degree is strongly dependent on the concentration and species of monovalent anions. For chaotropic anions (for example, ClO 4 - ), the rectification inversion is easily observed at a low concentration (5 mm), while there is no rectification inversion observed for kosmotropic anions (Cl - ) even at a high concentration (1 m). Moreover, at the specific concentration (for example, 10 mm), the variation of rectification ratio on the type of anions is ranged by Hofmeister series (Cl - ≥NO 3 - >BF 4 - >ClO 4 - >PF 6 - >Tf 2 N - ). Estimation of the electrokinetic charge density (σ ek ) demonstrates that rectification inversion originates from the charge inversion owing to the over-adsorption of chaotropic monovalent anion. To qualitatively understand this phenomenon, a concentration-dependent adsorption mechanism is proposed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bambus[n]urils: a new family of macrocyclic anion receptors.

PubMed

Havel, Vaclav; Svec, Jan; Wimmerova, Michaela; Dusek, Michal; Pojarova, Michaela; Sindelar, Vladimir

2011-08-05

A recently discovered anion receptor is jointed by three related macrocycles differing in the number of glycoluril units and type of substitution. The synthesis is carried out in nonpolar solvents compared to aqueous media used in the case of the original macrocycle. The size of macrocycle is controlled by a template. A hexameric macrocycle with benzyl substitution binds halide anions with an affinity exceeding 10(9) M(-1) while a tetrameric analog does not bind any of the investigated anions. © 2011 American Chemical Society

Nonperturbative Renormalization Group Approach to Polymerized Membranes

NASA Astrophysics Data System (ADS)

Essafi, Karim; Kownacki, Jean-Philippe; Mouhanna, Dominique

2014-03-01

Membranes or membrane-like materials play an important role in many fields ranging from biology to physics. These systems form a very rich domain in statistical physics. The interplay between geometry and thermal fluctuations lead to exciting phases such flat, tubular and disordered flat phases. Roughly speaking, membranes can be divided into two group: fluid membranes in which the molecules are free to diffuse and thus no shear modulus. On the other hand, in polymerized membranes the connectivity is fixed which leads to elastic forces. This difference between fluid and polymerized membranes leads to a difference in their critical behaviour. For instance, fluid membranes are always crumpled, whereas polymerized membranes exhibit a phase transition between a crumpled phase and a flat phase. In this talk, I will focus only on polymerized phantom, i.e. non-self-avoiding, membranes. The critical behaviour of both isotropic and anisotropic polymerized membranes are studied using a nonperturbative renormalization group approach (NPRG). This allows for the investigation of the phase transitions and the low temperature flat phase in any internal dimension D and embedding d. Interestingly, graphene behaves just as a polymerized membrane in its flat phase.

Targeted polymeric nanoparticles for cancer gene therapy

PubMed Central

Kim, Jayoung; Wilson, David R.; Zamboni, Camila G.; Green, Jordan J.

2015-01-01

In this article, advances in designing polymeric nanoparticles for targeted cancer gene therapy are reviewed. Characterization and evaluation of biomaterials, targeting ligands, and transcriptional elements are each discussed. Advances in biomaterials have driven improvements to nanoparticle stability and tissue targeting, conjugation of ligands to the surface of polymeric nanoparticles enable binding to specific cancer cells, and the design of transcriptional elements has enabled selective DNA expression specific to the cancer cells. Together, these features have improved the performance of polymeric nanoparticles as targeted non-viral gene delivery vectors to treat cancer. As polymeric nanoparticles can be designed to be biodegradable, non-toxic, and to have reduced immunogenicity and tumorigenicity compared to viral platforms, they have significant potential for clinical use. Results of polymeric gene therapy in clinical trials and future directions for the engineering of nanoparticle systems for targeted cancer gene therapy are also presented. PMID:26061296

Theoretical Studies of Routes to Synthesis of Tetrahedral N4

NASA Technical Reports Server (NTRS)

Lee, Timothy J.; Dateo, Christopher E.

2007-01-01

A paper [Chem. Phys. Lett. 345, 295 (2001)] describes theoretical studies of excited electronic states of nitrogen molecules, with a view toward utilizing those states in synthesizing tetrahedral N4, or Td N4 a metastable substance under consideration as a high-energy-density rocket fuel. Several ab initio theoretical approaches were followed in these studies, including complete active space self-consistent field (CASSCF), state-averaged CASSCF (SA-CASSCF), singles configuration interaction (CIS), CIS with second-order and third-order correlation corrections [CIS(D) and CIS(3)], and linear response singles and doubles coupled-cluster (LRCCSD). Standard double zeta polarized and triple zeta double polarized one-particle basis sets were used. The CASSCF calculations overestimated the excitation energies, while SACASSCF calculations partly corrected these overestimates. The accuracy of the CIS calculations varied, depending on the particular state, while the CIS(D), CIS(3), and LRCCSD results were in generally good agreement. The energies of the lowest six excited singlet states of Td N4 as calculated by the LRCCSD were compared with the energies of possible excited states of N2 + N2 fragments, leading to the conclusion that the most likely route for synthesis of Td N4 would involve a combination of two bound quintet states of N2.

The effects of cations and anions on hydrogen chemisorption at Pt

NASA Technical Reports Server (NTRS)

Huang, J. C.; Ogrady, W. E.; Yeager, E.

1977-01-01

Experimental evidence based on linear sweep voltammetry is presented to substantiate the view that ionic adsorption substantially shifts electrode potentials in addition to the relative heights of the hydrogen adsorption peaks. HClO4 and HF are chosen as better reference electrolytes for anion studies. The voltammetry curves for 0.1M HF and 0.1M HClO4 as well as the effect of adding successively increasing amounts of H2SO4 to these electrolytes are discussed. The measurements are also extended to alkaline solutions. Mechanisms whereby the addition of various cations and anions to electrolytes such as HF and HClO4 can induce changes in the structure of the hydrogen adsorption region in the voltammetry curves are identified: (1) blocking of sites by anion adsorption and coupling of hydrogen adsorption and anion desorption, (2) modification in the hydrogen adsorption energies for sites adjacent to adsorbed anions, (3) changes in the potential distribution across the interface, and (4) surface restructuring.

Increasing Photovoltaic Performance of an Organic Cationic Chromophore by Anion Exchange

PubMed Central

Gesevičius, Donatas; Neels, Antonia; Jenatsch, Sandra; Hack, Erwin; Viani, Lucas; Athanasopoulos, Stavros; Heier, Jakob

2017-01-01

Abstract A symmetrical cyanine dye chromophore is modified with different counteranions to study the effect on crystal packing, polarizability, thermal stability, optical properties, light absorbing layer morphology, and organic photovoltaic (OPV) device parameters. Four sulfonate‐based anions and the bulky bistriflylimide anion are introduced to the 2‐[5‐(1,3‐dihydro‐1,3,3‐trimethyl‐2H‐indol‐2‐ylidene)‐1,3‐pentadien‐1‐yl]‐1,3,3‐trimethyl‐3H‐indolium chromophore using an Amberlyst A26 (OH− form) anion exchanger. Anionic charge distribution clearly correlates with device performance, whereby an average efficiency of 2% was reached in a standard bilayer organic solar. Evidence is given that the negative charge of the anion distributed over a large number of atoms is significantly more important than the size of the organic moieties of the sulfonate charge carrying group. This provides a clear strategy for future design of more efficient cyanine dyes for OPV applications. PMID:29610723

Interactions between Hofmeister anions and the binding pocket of a protein.

PubMed

Fox, Jerome M; Kang, Kyungtae; Sherman, Woody; Héroux, Annie; Sastry, G Madhavi; Baghbanzadeh, Mostafa; Lockett, Matthew R; Whitesides, George M

2015-03-25

This paper uses the binding pocket of human carbonic anhydrase II (HCAII, EC 4.2.1.1) as a tool to examine the properties of Hofmeister anions that determine (i) where, and how strongly, they associate with concavities on the surfaces of proteins and (ii) how, upon binding, they alter the structure of water within those concavities. Results from X-ray crystallography and isothermal titration calorimetry show that most anions associate with the binding pocket of HCAII by forming inner-sphere ion pairs with the Zn(2+) cofactor. In these ion pairs, the free energy of anion-Zn(2+) association is inversely proportional to the free energetic cost of anion dehydration; this relationship is consistent with the mechanism of ion pair formation suggested by the "law of matching water affinities". Iodide and bromide anions also associate with a hydrophobic declivity in the wall of the binding pocket. Molecular dynamics simulations suggest that anions, upon associating with Zn(2+), trigger rearrangements of water that extend up to 8 Å away from their surfaces. These findings expand the range of interactions previously thought to occur between ions and proteins by suggesting that (i) weakly hydrated anions can bind complementarily shaped hydrophobic declivities, and that (ii) ion-induced rearrangements of water within protein concavities can (in contrast with similar rearrangements in bulk water) extend well beyond the first hydration shells of the ions that trigger them. This study paints a picture of Hofmeister anions as a set of structurally varied ligands that differ in size, shape, and affinity for water and, thus, in their ability to bind to—and to alter the charge and hydration structure of—polar, nonpolar, and topographically complex concavities on the surfaces of proteins.

Simultaneous anionic and cationic redox

NASA Astrophysics Data System (ADS)

Jung, Sung-Kyun; Kang, Kisuk

2017-12-01

It is challenging to unlock anionic redox activity, accompanied by full utilization of available cationic redox process, to boost capacity of battery cathodes. Now, material design by tuning the metal-oxygen interaction is shown to be a promising solution.

Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren-9-olato- Anions and Indium(III) Phthalocyanine Bromide Radical Anions.

PubMed

Konarev, Dmitri V; Khasanov, Salavat S; Ishikawa, Manabu; Nakano, Yoshiaki; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

2017-04-18

Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu 4 N + ) 2 [M III (HFl-O - )(Pc .3- )] .- (Br - )⋅1.5 C 6 H 4 Cl 2 [M=Al (1), Ga (2); HFl-O - =fluoren-9-olato - anion; Pc=phthalocyanine] and (Bu 4 N + ) [In III Br(Pc .3- )] .- ⋅0.875 C 6 H 4 Cl 2 ⋅0.125 C 6 H 14 (3). The salts were found to contain Pc .3- radical anions with negatively charged phthalocyanine macrocycles, as evidenced by the presence of intense bands of Pc .3- in the near-IR region and a noticeable blueshift in both the Q and Soret bands of phthalocyanine. The metal(III) atoms coordinate HFl-O - anions in 1 and 2 with short Al-O and Ga-O bond lengths of 1.749(2) and 1.836(6) Å, respectively. The C-O bonds [1.402(3) and 1.391(11) Å in 1 and 2, respectively] in the HFl-O - anions are longer than the same bond in the fluorenone ketyl (1.27-1.31 Å). Salts 1-3 show effective magnetic moments of 1.72, 1.66, and 1.79 μ B at 300 K, respectively, owing to the presence of unpaired S=1/2 spins on Pc .3- . These spins are coupled antiferromagnetically with Weiss temperatures of -22, -14, and -30 K for 1-3, respectively. Coupling can occur in the corrugated two-dimensional phthalocyanine layers of 1 and 2 with an exchange interaction of J/k B =-0.9 and -1.1 K, respectively, and in the π-stacking {[In III Br(Pc .3- )] .- } 2 dimers of 3 with an exchange interaction of J/k B =-10.8 K. The salts show intense electron paramagnetic resonance (EPR) signals attributed to Pc .3- . It was found that increasing the size of the central metal atom strongly broadened these EPR signals. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymeric Sulfated Amino Acid Surfactants: A New Class of Versatile Chiral Selectors for Micellar Electrokinetic Chromatography (MEKC) and MEKC-MS

PubMed Central

Ali Rizvi, Syed Asad; Zheng, Jie; Apkarian, Robert P.; Dublin, Steven N.; Shamsi, Shahab A.

2008-01-01

�-blockers, phenoxypropionic acid, benzoin derivatives, PTH-amino acids, and benzodiazepinones) studied also provided improved chiral separation at low pH compared to high pH conditions. Among the three polymeric sulfated surfactants, poly-L-SUCILS with two chiral centers on the polymer head group provided overall higher enantioresolution for the investigated acidic, basic and neutral compounds. This work clearly demonstrates for the first time the superiority of chiral separation and sensitive MS detection at low pH over conventional high pH chiral separation and detection employing anionic chiral polymeric surfactants in MEKC and MEKC-MS. PMID:17263313

Kinetics of corrosion inhibition of aluminum in acidic media by water-soluble natural polymeric chondroitin-4-sulfate as anionic polyelectrolyte inhibitor.

PubMed

Hassan, Refat M; Ibrahim, Samia M; Takagi, Hideo D; Sayed, Suzan A

2018-07-15

Corrosion inhibition of aluminum (Al) in hydrochloric acid by anionic polyelectrolyte chondroitin-4-sulfate (CS) polysaccharide has been studied using both gasometrical and weight-loss techniques. The results drawn from these two techniques are comparable and exhibit negligible differences. The inhibition efficiency was found to increase with increasing the inhibitor concentration and decreased with increasing temperature. The inhibition action of CS on Al metal surface was found to obey both of Langmuir and Freundlich isotherms. The factors affecting the corrosion rates such as the concentration and geometrical structure of the inhibitor, concentration of the corrosive medium, and the temperature were examined. The kinetic parameters were evaluated and a suitable corrosion mechanism consistent with the results obtained is discussed. Copyright © 2018. Published by Elsevier Ltd.

Anion Binding and Transport by Prodigiosin and Its Analogs

NASA Astrophysics Data System (ADS)

Davis, Jeffery T.

The red-colored prodiginines, exemplified by prodigiosin 1, are secondary metabolites produced by a number of microorganisms, including the bacterium Serratia marcescens. These tripyrrole natural products and their synthetic analogs have received renewed attention over the past deacade, primarily because of their promising immunosuppressive and anticancer activities. One of the hallmarks of prodiginin chemistry is the ability of the monoprotonated ligand to bind anions, including the essential chloride and bicarbonate ions. The resulting lipophilic ion pair is then able to diffuse across the hydrophobic barrier presented by phospholipid bilayers. Thus, prodiginines have been found to be potent transmembrane anion transporters and HCl cotransporters. In this chapter, the author reviews what is known about the solid-state structure of prodiginins and their anion complexes, the solution conformation of prodiginines, and the biochemcal evidence for the ability to bind anions and to transport HCl across cell membranes. Recent progress in making synthetic models of prodiginines and recent results on the ability of prodigiosin to transport HCO 3 - across lipid membranes are discussed.

21 CFR 872.6070 - Ultraviolet activator for polymerization.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ultraviolet activator for polymerization. 872.6070 Section 872.6070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... polymerization. (a) Identification. An ultraviolet activator for polymerization is a device that produces...

21 CFR 872.6070 - Ultraviolet activator for polymerization.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ultraviolet activator for polymerization. 872.6070 Section 872.6070 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... polymerization. (a) Identification. An ultraviolet activator for polymerization is a device that produces...

Structure of cyano-anion ionic liquids: X-ray scattering and simulations.

PubMed

Dhungana, Kamal B; Faria, Luiz F O; Wu, Boning; Liang, Min; Ribeiro, Mauro C C; Margulis, Claudio J; Castner, Edward W

2016-07-14

Ionic liquids with cyano anions have long been used because of their unique combination of low-melting temperatures, reduced viscosities, and increased conductivities. Recently we have shown that cyano anions in ionic liquids are particularly interesting for their potential use as electron donors to excited state photo-acceptors [B. Wu et al., J. Phys. Chem. B 119, 14790-14799 (2015)]. Here we report on bulk structural and quantum mechanical results for a series of ionic liquids based on the 1-ethyl-3-methylimidazolium cation, paired with the following five cyano anions: SeCN(-), SCN(-), N(CN)2 (-), C(CN)3 (-), and B(CN)4 (-). By combining molecular dynamics simulations, high-energy X-ray scattering measurements, and periodic boundary condition DFT calculations, we are able to obtain a comprehensive description of the liquid landscape as well as the nature of the HOMO-LUMO states for these ionic liquids in the condensed phase. Features in the structure functions for these ionic liquids are somewhat different than the commonly observed adjacency, charge-charge, and polarity peaks, especially for the bulkiest B(CN)4 (-) anion. While the other four cyano-anion ionic liquids present an anionic HOMO, the one for Im2,1 (+)/B(CN)4 (-) is cationic.

Tubulin polymerization-stimulating activity of Ganoderma triterpenoids.

PubMed

Kohno, Toshitaka; Hai-Bang, Tran; Zhu, Qinchang; Amen, Yhiya; Sakamoto, Seiichi; Tanaka, Hiroyuki; Morimoto, Satoshi; Shimizu, Kuniyoshi

2017-04-01

Tubulin polymerization is an important target for anticancer therapies. Even though the potential of Ganoderma triterpenoids against various cancer targets had been well documented, studies on their tubulin polymerization-stimulating activity are scarce. This study was conducted to evaluate the effect of Ganoderma triterpenoids on tubulin polymerization. A total of twenty-four compounds were investigated using an in vitro tubulin polymerization assay. Results showed that most of the studied triterpenoids exhibited microtuble-stabilizing activity to different degrees. Among the investigated compounds, ganoderic acid T-Q, ganoderiol F, ganoderic acid S, ganodermanontriol and ganoderic acid TR were found to have the highest activities. A structure-activity relationship (SAR) analysis was performed. Extensive investigation of the SAR suggests the favorable structural features for the tubulin polymerization-stimulating activity of lanostane triterpenes. These findings would be helpful for further studies on the potential mechanisms of the anticancer activity of Ganoderma triterpenoids and give some indications on the design of tubulin-targeting anticancer agents.

Spatial control of actin polymerization during neutrophil chemotaxis

PubMed Central

Weiner, Orion D.; Servant, Guy; Welch, Matthew D.; Mitchison, Timothy J.; Sedat, John W.; Bourne, Henry R.

2010-01-01

Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients. PMID:10559877

Spatial control of actin polymerization during neutrophil chemotaxis.

PubMed

Weiner, O D; Servant, G; Welch, M D; Mitchison, T J; Sedat, J W; Bourne, H R

1999-06-01

Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients.

Crystal structure of bis-[tetra-kis-(tetra-hydro-furan-κO)lithium] bis[μ-2,2',2''-methanetriyltris(4,6-di-tert-butylphenolato)-κ4O,O':O',O'']-dimagnesiate.

PubMed

Zhou, Hongyan; Wang, Lei

2017-07-01

The title ion-association metal complex, [Li(C 4 H 8 O) 4 ] 2 [Mg 2 (C 43 H 61 O 3 ) 2 ], has been synthesized from the tridentate phenolic ligand tris-(3,5-di- tert -butyl-2-hy-droxy-phen-yl)methane in tetra-hydro-furan (THF). The aryl-oxo magnesiate complex anion is binuclear with each Mg 2 O 4 complex unit inversion-related and bridged through the two tridentate chelating phenolate O-donors of the ligand. The complex centres have a distorted tetra-hedral stereochemistry [Mg-O range 1.8796 (17)-2.0005 (16) Å] and an Mg⋯Mg separation of 2.9430 (14) Å]. The LiO 4 coodination sphere of the cation comprises four THF O-donor atoms and has a slightly distorted tetra-hedral conformation [Li-O range 1.899 (5)- 1.953 (5) Å]. In the crystal, a number of stabilizing intra-anion C-H⋯O hydrogen-bonding inter-actions are present but no inter-species associations are found.

Recurrent high anion gap metabolic acidosis secondary to 5-oxoproline (pyroglutamic acid).

PubMed

Tailor, Prayus; Raman, Tuhina; Garganta, Cheryl L; Njalsson, Runa; Carlsson, Katarina; Ristoff, Ellinor; Carey, Hugh B

2005-07-01

High anion gap metabolic acidosis in adults is a severe metabolic disorder for which the primary organic acid usually is apparent by clinical history and standard laboratory testing. We report a case of recurrent high anion gap metabolic acidosis in a 48-year-old man who initially presented with anorexia and malaise. Physical examination was unrevealing. Arterial pH was 6.98, P co 2 was 5 mm Hg, and chemistry tests showed a bicarbonate level of 3 mEq/L (3 mmol/L), anion gap of 32 mEq/L (32 mmol/L), and a negative toxicology screen result, except for an acetaminophen (paracetamol) level of 7.5 mug/mL. Metabolic acidosis resolved with administration of intravenous fluids. Subsequently, he experienced 5 more episodes of high anion gap metabolic acidosis during an 8-month span. Methanol, ethylene glycol, acetone, ethanol, d -lactate, and hippuric acid screens were negative. Lactate levels were modestly elevated, and acetaminophen levels were elevated for 5 of 6 admissions. These episodes defied explanation until 3 urinary organic acid screens, obtained on separate admissions, showed striking elevations of 5-oxoproline levels. Inborn errors of metabolism in the gamma-glutamyl cycle causing recurrent 5-oxoprolinuria and high anion gap metabolic acidosis are rare, but well described in children. Recently, there have been several reports of apparent acquired 5-oxoprolinuria and high anion gap metabolic acidosis in adults in association with acetaminophen use. Acetaminophen may, in susceptible individuals, disrupt regulation of the gamma-glutamyl cycle and result in excessive 5-oxoproline production. Suspicion for 5-oxoproline-associated high anion gap metabolic acidosis should be entertained when the cause of high anion gap metabolic acidosis remains poorly defined, the anion gap cannot be explained reasonably by measured organic acids, and there is concomitant acetaminophen use.

Suppression of H-/O2- exchange by incorporated nitride anions in the perovskite lattice

NASA Astrophysics Data System (ADS)

Takeiri, Fumitaka; Yajima, Takeshi; Yamamoto, Takafumi; Kobayashi, Yoji; Matsui, Toshiaki; Hester, James; Kageyama, Hiroshi

2017-12-01

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH2 reduction of (Sr1-xLax)Ti(O3-xNx) (0anion exchange of hydride for oxide rather than nitride, yielding the oxyhydride-nitride (Sr1-xLax)Ti(O3-x-yHyNx). However, the exchange of hydride is drastically suppressed with increasing nitrogen content and is completely impeded when the nitride content reaches 10% of the anionic site. This implies that the N3- anions in the oxide lattice play a crucial role in lowering diffusion of O2- (and H-). The present study indicates the necessity to consider kinetic aspects when manipulating anion compositions, in particular in a mixed anion system with a small amount of anion vacancies.

21 CFR 870.3650 - Pacemaker polymeric mesh bag.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...

21 CFR 870.3650 - Pacemaker polymeric mesh bag.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...

21 CFR 870.3650 - Pacemaker polymeric mesh bag.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...

21 CFR 870.3650 - Pacemaker polymeric mesh bag.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...

Analytical and Photogrammetric Characterization of a Planar Tetrahedral Truss

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Adams, Richard R.; Rhodes, Marvin D.

1990-01-01

Future space science missions are likely to require near-optical quality reflectors which are supported by a stiff truss structure. This support truss should conform closely with its intended shape to minimize its contribution to the overall surface error of the reflector. The current investigation was conducted to evaluate the planar surface accuracy of a regular tetrahedral truss structure by comparing the results of predicted and measured node locations. The truss is a 2-ring hexagonal structure composed of 102 equal-length truss members. Each truss member is nominally 2 meters in length between node centers and is comprised of a graphite/epoxy tube with aluminum nodes and joints. The axial stiffness and the length variation of the truss components were determined experimentally and incorporated into a static finite element analysis of the truss. From this analysis, the root mean square (RMS) surface error of the truss was predicted to be 0.11 mm (0004 in). Photogrammetry tests were performed on the assembled truss to measure the normal displacements of the upper surface nodes and to determine if the truss would maintain its intended shape when subjected to repeated assembly. Considering the variation in the truss component lengths, the measures rms error of 0.14 mm (0.006 in) in the assembled truss is relatively small. The test results also indicate that a repeatable truss surface is achievable. Several potential sources of error were identified and discussed.

An anion channel in Arabidopsis hypocotyls activated by blue light

NASA Technical Reports Server (NTRS)

Cho, M. H.; Spalding, E. P.; Evans, M. L. (Principal Investigator)

1996-01-01

A rapid, transient depolarization of the plasma membrane in seedling stems is one of the earliest effects of blue light detected in plants. It appears to play a role in transducing blue light into inhibition of hypocotyl (stem) elongation, and perhaps other responses. The possibility that activation of a Cl- conductance is part of the depolarization mechanism was raised previously and addressed here. By patch clamping hypocotyl cells isolated from dark-grown (etiolated) Arabidopsis seedlings, blue light was found to activate an anion channel residing at the plasma membrane. An anion-channel blocker commonly known as NPPB 15-nitro-2-(3-phenylpropylamino)-benzoic acid] potently and reversibly blocked this anion channel. NPPB also blocked the blue-light-induced depolarization in vivo and decreased the inhibitory effect of blue light on hypocotyl elongation. These results indicate that activation of this anion channel plays a role in transducing blue light into growth inhibition.

Fast and Exact Fiber Surfaces for Tetrahedral Meshes.

PubMed

Klacansky, Pavol; Tierny, Julien; Carr, Hamish; Zhao Geng

2017-07-01

Isosurfaces are fundamental geometrical objects for the analysis and visualization of volumetric scalar fields. Recent work has generalized them to bivariate volumetric fields with fiber surfaces, the pre-image of polygons in range space. However, the existing algorithm for their computation is approximate, and is limited to closed polygons. Moreover, its runtime performance does not allow instantaneous updates of the fiber surfaces upon user edits of the polygons. Overall, these limitations prevent a reliable and interactive exploration of the space of fiber surfaces. This paper introduces the first algorithm for the exact computation of fiber surfaces in tetrahedral meshes. It assumes no restriction on the topology of the input polygon, handles degenerate cases and better captures sharp features induced by polygon bends. The algorithm also allows visualization of individual fibers on the output surface, better illustrating their relationship with data features in range space. To enable truly interactive exploration sessions, we further improve the runtime performance of this algorithm. In particular, we show that it is trivially parallelizable and that it scales nearly linearly with the number of cores. Further, we study acceleration data-structures both in geometrical domain and range space and we show how to generalize interval trees used in isosurface extraction to fiber surface extraction. Experiments demonstrate the superiority of our algorithm over previous work, both in terms of accuracy and running time, with up to two orders of magnitude speedups. This improvement enables interactive edits of range polygons with instantaneous updates of the fiber surface for exploration purpose. A VTK-based reference implementation is provided as additional material to reproduce our results.

A point-centered arbitrary Lagrangian Eulerian hydrodynamic approach for tetrahedral meshes

DOE PAGES

Morgan, Nathaniel R.; Waltz, Jacob I.; Burton, Donald E.; ...

2015-02-24

We present a three dimensional (3D) arbitrary Lagrangian Eulerian (ALE) hydrodynamic scheme suitable for modeling complex compressible flows on tetrahedral meshes. The new approach stores the conserved variables (mass, momentum, and total energy) at the nodes of the mesh and solves the conservation equations on a control volume surrounding the point. This type of an approach is termed a point-centered hydrodynamic (PCH) method. The conservation equations are discretized using an edge-based finite element (FE) approach with linear basis functions. All fluxes in the new approach are calculated at the center of each tetrahedron. A multidirectional Riemann-like problem is solved atmore » the center of the tetrahedron. The advective fluxes are calculated by solving a 1D Riemann problem on each face of the nodal control volume. A 2-stage Runge–Kutta method is used to evolve the solution forward in time, where the advective fluxes are part of the temporal integration. The mesh velocity is smoothed by solving a Laplacian equation. The details of the new ALE hydrodynamic scheme are discussed. Results from a range of numerical test problems are presented.« less

Synthesis, Structure, and Pressure-Induced Polymerization of Li 3 Fe(CN) 6 Accompanied with Enhanced Conductivity

DOE PAGES

Li, Kuo; Zheng, Haiyan; Hattori, Takanori; ...

2015-11-17

By providing a new route to synthesize inorganic/organic conductors with tunable composition and properties, pressure-induced polymerization of charged triple-bond monomers like acetylide and cyanide could lead to formation of a conductive metal–carbon network composite. The industry application of this promising synthetic method is mainly limited by the reaction pressure needed, which is often too high to be reached for gram amounts of sample. Here we successfully synthesized highly conductive Li 3Fe(CN) 6 at maximum pressure around 5 GPa and used in situ diagnostic tools to follow the structural and functional transformations of the sample, including in situ X-ray and neutronmore » diffraction and Raman and impedance spectroscopy, along with the neutron pair distribution function measurement on the recovered sample. The cyanide anions start to react around 1 GPa and bond to each other irreversibly at around 5 GPa, which are the lowest reaction pressures in all known metal cyanides and within the technologically achievable pressure range for industrial production. Moreover, the conductivity of the polymer is above 10 –3 S·cm –1, which reaches the range of conductive polymers. Our investigation suggests that the pressure-induced polymerization route is practicable for synthesizing some types of functional conductive materials for industrial use, and further research like doping and heating can hence be motivated to synthesize novel materials under lower pressure and with better performances.« less

Self-Assembled DNA Tetrahedral Scaffolds for the Construction of Electrochemiluminescence Biosensor with Programmable DNA Cyclic Amplification.

PubMed

Feng, Qiu-Mei; Guo, Yue-Hua; Xu, Jing-Juan; Chen, Hong-Yuan

2017-05-24

A novel DNA tetrahedron-structured electrochemiluminescence (ECL) platform for bioanalysis with programmable DNA cyclic amplification was developed. In this work, glucose oxidase (GOD) was labeled to a DNA sequence (S) as functional conjugation (GOD-S), which could hybridize with other DNA sequences (L and P) to form GOD-S:L:P probe. In the presence of target DNA and a help DNA (A), the programmable DNA cyclic amplification was activated and released GOD-S via toehold-mediated strand displacement. Then, the obtained GOD-S was further immobilized on the DNA tetrahedral scaffolds with a pendant capture DNA and Ru(bpy) 3 2+ -conjugated silica nanoparticles (RuSi NPs) decorated on the electrode surface. Thus, the amount of GOD-S assembled on the electrode surface depended on the concentration of target DNA and GOD could catalyze glucose to generate H 2 O 2 in situ. The ECL signal of Ru(bpy) 3 2+ -TPrA system was quenched by the presence of H 2 O 2 . By integrating the programmable DNA cyclic amplification and in situ generating H 2 O 2 as Ru(bpy) 3 2+ ECL quencher, a sensitive DNA tetrahedron-structured ECL sensing platform was proposed for DNA detection. Under optimized conditions, this biosensor showed a wide linear range from 100 aM to 10 pM with a detection limit of 40 aM, indicating a promising application in DNA analysis. Furthermore, by labeling GOD to different recognition elements, the proposed strategy could be used for the detection of various targets. Thus, this programmable cascade amplification strategy not only retains the high selectivity and good capturing efficiency of tetrahedral-decorated electrode surface but also provides potential applications in the construction of ECL biosensor.

Glycine Polymerization on Oxide Minerals.

PubMed

Kitadai, Norio; Oonishi, Hiroyuki; Umemoto, Koichiro; Usui, Tomohiro; Fukushi, Keisuke; Nakashima, Satoru

2017-06-01

It has long been suggested that mineral surfaces played an important role in peptide bond formation on the primitive Earth. However, it remains unclear which mineral species was key to the prebiotic processes. This is because great discrepancies exist among the reported catalytic efficiencies of minerals for amino acid polymerizations, owing to mutually different experimental conditions. This study examined polymerization of glycine (Gly) on nine oxide minerals (amorphous silica, quartz, α-alumina and γ-alumina, anatase, rutile, hematite, magnetite, and forsterite) using identical preparation, heating, and analytical procedures. Results showed that a rutile surface is the most effective site for Gly polymerization in terms of both amounts and lengths of Gly polymers synthesized. The catalytic efficiency decreased as rutile > anatase > γ-alumina > forsterite > α- alumina > magnetite > hematite > quartz > amorphous silica. Based on reported molecular-level information for adsorption of Gly on these minerals, polymerization activation was inferred to have arisen from deprotonation of the NH 3 + group of adsorbed Gly to the nucleophilic NH 2 group, and from withdrawal of electron density from the carboxyl carbon to the surface metal ions. The orientation of adsorbed Gly on minerals is also a factor influencing the Gly reactivity. The examination of Gly-mineral interactions under identical experimental conditions has enabled the direct comparison of various minerals' catalytic efficiencies and has made discussion of polymerization mechanisms and their relative influences possible Further systematic investigations using the approach reported herein (which are expected to be fruitful) combined with future microscopic surface analyses will elucidate the role of minerals in the process of abiotic peptide bond formation.

Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

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

Moyer, Bruce A; Sloop Jr, Frederick; Fowler, Christopher J

2010-01-01

When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1more » receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.« less

Urine Anion Gap to Predict Urine Ammonium and Related Outcomes in Kidney Disease.

PubMed

Raphael, Kalani L; Gilligan, Sarah; Ix, Joachim H

2018-02-07

Low urine ammonium excretion is associated with ESRD in CKD. Few laboratories measure urine ammonium, limiting clinical application. We determined correlations between urine ammonium, the standard urine anion gap, and a modified urine anion gap that includes sulfate and phosphate and compared risks of ESRD or death between these ammonium estimates and directly measured ammonium. We measured ammonium, sodium, potassium, chloride, phosphate, and sulfate from baseline 24-hour urine collections in 1044 African-American Study of Kidney Disease and Hypertension participants. We evaluated the cross-sectional correlations between urine ammonium, the standard urine anion gap (sodium + potassium - chloride), and a modified urine anion gap that includes urine phosphate and sulfate in the calculation. Multivariable-adjusted Cox models determined the associations of the standard urine anion gap and the modified urine anion gap with the composite end point of death or ESRD; these results were compared with results using urine ammonium as the predictor of interest. The standard urine anion gap had a weak and direct correlation with urine ammonium ( r =0.18), whereas the modified urine anion gap had a modest inverse relationship with urine ammonium ( r =-0.58). Compared with the highest tertile of urine ammonium, those in the lowest urine ammonium tertile had higher risk of ESRD or death (hazard ratio, 1.46; 95% confidence interval, 1.13 to 1.87) after adjusting for demographics, GFR, proteinuria, and other confounders. In comparison, participants in the corresponding standard urine anion gap tertile did not have higher risk of ESRD or death (hazard ratio, 0.82; 95% confidence interval, 0.64 to 1.07), whereas the risk for those in the corresponding modified urine anion gap tertile (hazard ratio, 1.32; 95% confidence interval, 1.03 to 1.68) approximated that of directly measured urine ammonium. Urine anion gap is a poor surrogate of urine ammonium in CKD unless phosphate and

Ultra-small and anionic starch nanospheres: formation and vitro thrombolytic behavior study.

PubMed

Huang, Yinjuan; Ding, Shenglong; Liu, Mingzhu; Gao, Chunmei; Yang, Jinlong; Zhang, Xinjie; Ding, Bin

2013-07-25

This paper is considered as the first report on the investigation of nattokinase (NK) release from anionic starch nanospheres. The ultra-small and anionic starch nanospheres were prepared by the method of reverse micro-emulsion crosslinking in this work. Starch nanospheres were characterized through Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and dynamic light scattering (DLS). Effects of preparation conditions on particle size were studied. The cytotoxicity, biodegradable and vitro thrombolytic behaviors of nattokinase (NK) loaded anionic starch nanospheres were also studied. The results showed that the anionic starch nanospheres are non-toxic, biocompatible and biodegradable. Moreover, the anionic starch nanospheres can protect NK from fast biodegradation hence prolongs the circulation in vivo and can reduce the risk of acute hemorrhage complication by decreasing the thrombolysis rate. Copyright © 2013 Elsevier Ltd. All rights reserved.

Anion–Anion Bonding and Topology in Ternary Iridium Seleno–Stannides

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

Trump, Benjamin A.; Tutmaher, Jake A.; McQueen, Tyrel M.

2015-12-21

The synthesis and physical properties of two new and one known Ir–Sn–Se compound are reported. Their crystal structures are elucidated with transmission electron microscopy and powder X-ray diffraction. IrSn0.45Se1.55 is a pyrite phase which consists of tilted corner-sharing IrX6 octahedra with randomly distributed (Sn–Se)4– and (Se–Se)2– dimers. Ir2Sn3Se3 is a known trigonally distorted skutterudite that consists of cooperatively tilted corner-sharing IrSn3Se3 octahedra with ordered (Sn–Se)24– tetramers. Ir2SnSe5 is a layered, distorted β-MnO2 (pyrolusite) structure consisting of a double IrSe6 octrahedral row, corner sharing in the a direction and edge sharing in the b direction. This distorted pyrolusite contains (Se–Se)2– dimersmore » and Se2– anions, and each double row is “capped” with a (Sn–Se)n polymeric chain. Resistivity, specific heat, and magnetization measurements show that all three have insulating and diamagnetic behavior, indicative of low-spin 5d6 Ir3+. Electronic structure calculations on Ir2Sn3Se3 show a single, spherical, nonspin–orbit split valence band and suggest that Ir2Sn3Se3 is topologically nontrivial under tensile strain due to inversion of Ir-d and Se-p states.« less

Selective removal of arsenate from drinking water using a polymeric ligand exchanger.

PubMed

An, Byungryul; Steinwinder, Thomas R; Zhao, Dongye

2005-12-01

The new maximum contaminant level (MCL) of 10 microg/L for arsenic in the US drinking water will take effect on January 22, 2006. The compliance cost is estimated to be approximately dollar 600 million per year using current treatment technologies. This research aims to develop an innovative ion exchange process that may help water utilities comply with the new MCL in a more cost-effective manner. A polymeric ligand exchanger (PLE) was prepared by loading Cu2+ to a commercially available chelating ion exchange resin. Results from batch and column experiments indicated that the PLE offered unusually high selectivity for arsenate over other ubiquitous anions such as sulfate, bicarbonate and chloride. The average binary arsenate/sulfate separation factor for the PLE was determined to be 12, which were over two orders of magnitude greater than that (0.1-0.2) for commercial strong-base anion (SBA) exchangers. Because of the enhanced arsenate selectivity, the PLE was able to treat approximately 10 times more bed volumes (BVs) of water than commonly used SBA resins. The PLE can operate optimally in the neutral pH range (6.0-8.0). The exhausted PLE can be regenerated highly efficiently. More than 95% arsenate capacity can be recovered using approximately 22 BVs of 4% (w/w) NaCl at pH 9.1, and the regenerated PLE can be reused without any capacity drop. Upon treatment using FeCl3, the spent brine was recovered and reused for regeneration, which may cut down the regenerant need and reduces the volume of process waste residuals. The PLE can be used as a highly selective and reusable sorbent for removal of arsenate from drinking water.

Electron anions and the glass transition temperature.

PubMed

Johnson, Lewis E; Sushko, Peter V; Tomota, Yudai; Hosono, Hideo

2016-09-06

Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32](2+) ⋅ (e(-))2, we demonstrate that electron anions in this system behave as glass modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. The concentration of such electron anions is a consequential control parameter: It invokes materials evolution pathways and properties not available in conventional glasses, which opens a unique avenue in rational materials design.

Electron anions and the glass transition temperature

DOE PAGES

Johnson, Lewis E.; Sushko, Peter V.; Tomota, Yudai; ...

2016-08-24

Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca 12Al 14O 32] 2+ ∙ (e –) 2, we demonstrate that electron anions in this system behave as glass-modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. Concentration of such electron anions is a consequential control parameter: it invokes materials evolution pathways and properties not available in conventional glasses, which opens a new avenue in rational materials design.

Photodissociation of nitromethane cluster anions.

PubMed

Goebbert, Daniel J; Khuseynov, Dmitry; Sanov, Andrei

2010-08-28

Three types of anionic fragments are observed in the photodissociation of nitromethane cluster anions, (CH(3)NO(2))(n)(-), n=1-6, at 355 nm: NO(2)(-)(CH(3)NO(2))(k), (CH(3)NO(2))(k)(-), and OH(-) (kanion core, CH(3)NO(2)(-), solvated by n-1 neutral nitromethane molecules. The NO(2)(-)(CH(3)NO(2))(k) and OH(-) fragments formed from these clusters are described as core-dissociation products, while the (CH(3)NO(2))(k)(-) fragments are attributed to energy transfer from excited CH(3)NO(2)(-) into the solvent network or a core-dissociation-recombination (caging) mechanism. As with other cluster families, the fraction of caged photofragments shows an overall increase with increasing cluster size. The low-lying A(2)A' and/or B(2)A' electronic states of CH(3)NO(2)(-) are believed responsible for photoabsorption leading to dissociation to NO(2)(-) based fragments, while the C(2)A" state is a candidate for the OH(-) pathway. Compared to neutral nitromethane, the photodissociation of CH(3)NO(2)(-) requires lower energy photons because the photochemically active electron occupies a high energy pi* orbital (which is vacant in the neutral). Although the electronic states in the photodissociation of CH(3)NO(2) and CH(3)NO(2)(-) are different, the major fragments, CH(3)+NO(2) and CH(3)+NO(2)(-), respectively, both form via C-N bond cleavage.

A protein with anion exchange properties found in the kidney proximal tubule.

PubMed

Soleimani, M; Bizal, G L; Anderson, C C

1993-09-01

One important mechanism for reabsorption of chloride in the kidney proximal tubule involves anion exchange of chloride for a base. Anion exchange transport systems in general demonstrate sensitivity to inhibition by disulfonic stilbenes, probenecid, furosemide, and the arginyl amino group modifier phenylglyoxal. Using disulfonic stilbene affinity chromatography, we have identified and partially purified a protein with anion exchanger properties in luminal membrane vesicles isolated from rabbit kidney cortex. This protein has a molecular weight of 162 kD. The binding of the 162 kD protein to the stilbene affinity matrix is inhibited by disulfonic stilbenes, probenecid, furosemide, and phenylglyoxal. Reconstitution of the proteins eluted from the affinity matrix into liposomes demonstrates anion exchange activity as assayed by radiolabeled chloride influx. Deletion of the 162 kD protein from the eluted mixture by probenecid diminishes the anion exchanger activity in the reconstituted liposomes. Further purification of the disulfonic stilbene column eluant by Econo-Pac Q ion exchange chromatography resulted in significant enrichment in 162 kD protein abundance and also anion exchange activity in reconstituted liposomes. The results of the above experiments strongly suggest that the 162 kD protein is an anion exchanger. Insight into the functional and molecular characteristics of this protein should provide important information about the mechanism(s) of chloride reabsorption in the kidney proximal tubule.

Preparation and characterization of novel anion phase change heat storage materials.

PubMed

Hong, Wei; Lil, Qingshan; Sun, Jing; Di, Youbo; Zhao, Zhou; Yu, Wei'an; Qu, Yuan; Jiao, TiFeng; Wang, Guowei; Xing, Guangzhong

2013-10-01

In this paper, polyurethane phase change material was successfully prepared with TDI with BDO for hard segments and PEG for soft segments. Moreover, based on this the solid-solid phase change material, A-PCM1030 which can release anions was prepared with the successful addition of anion additives A1030 for the first time. Then the test of the above material was conducted utilizing FT-IR, DSC, TEM, WAXD and Air Ion Detector. The Results indicated that the polyurethane phase change material possesses excellent thermal stability since there was no appearance of liquid leakage and phase separation after 50 times warming-cooling thermal cycles. It also presented reversibility on absorbing and releasing heat. In addition, adding a little A1030 can increase the thermal stability and reduce phase transition temperatures, as well as reduce the undercooling of the polyurethane phase change material. In addition, the anion test results suggested that the supreme amount of anion released by A-PCM1030 could reach 2510 anions/cm3 under dynamic conditions, which is beneficial for human health.

Gas-Phase Anionic σ-Adduct (Trans)formations in Heteroaromatic Systems1

NASA Astrophysics Data System (ADS)

Zimnicka, Magdalena; Danikiewicz, Witold

2015-07-01

Anions of nitroderivatives of thiophene and furan were subjected to the reactions with selected C-H acids in the gas phase. Various structures and reaction pathways were proposed for the observed ionic products. In general, the reactions of heteroaromatic anions with C-H acids may be divided into three groups, depending on the proton affinity difference between C-H acid's conjugate base and heteroaromatic anion (ΔPA). The proton transfer from C-H acid to heteroaromatic anion is a dominant process in the reactions for which ΔPA < 0 kcal mol-1, whereas the reactions with high ΔPA (ΔPA > 16 kcal mol-1) do not lead to any ionic products. The formation of σ-adducts and products of their further transformations according to the VNS, SNAr, cine, and tele substitution mechanisms have been proposed for reactions with moderate ΔPA. The other possible mechanisms as SN2 reaction, nucleophilic addition to the cyano group, ring-opening pathway, and halogenophilic reaction have also been discussed to contribute in the reactions between heteroaromatic anions and C-H acids.

Method of Making Thermally Stable, Piezoelectric and Proelectric Polymeric Substrates

NASA Technical Reports Server (NTRS)

Simpson, Joycelyn O. (Inventor); St.Clair, Terry L. (Inventor)

1999-01-01

A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors. in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100 C; depositing a metal electrode material onto the polymer film; attaching a plurality of electrical leads to the metal electrode coated polymeric substrate; heating the metal electrode coated polymeric substrate in a low dielectric medium: applying a voltage to the heated metal electrode coated polymeric substrate to induce polarization; and cooling the polarized metal electrode coated polymeric electrode while maintaining a constant voltage.

Guilty as charged: unmeasured urinary anions in a case of pyroglutamic acidosis.

PubMed

Rolleman, E J; Hoorn, E J; Didden, P; Zietse, R

2008-09-01

A patient developed an unexplained metabolic acidosis with the characteristics of renal tubular acidosis. By correcting the serum anion gap for hypoalbuminaemia and analysing the urinary anions and cations, the presence of unmeasured anions was revealed. The diagnosis of pyroglutamic acidosis, caused by a combination of flucloxacillin and acetaminophen, was established. Strategies for solving complex cases of metabolic acidosis are discussed.

Structure of cyano-anion ionic liquids: X-ray scattering and simulations

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

Dhungana, Kamal B.; Faria, Luiz F. O.; Wu, Boning

2016-07-14

Ionic liquids with cyano anions have long been used because of their unique combination of low-melting temperatures, reduced viscosities, and increased conductivities. Recently we have shown that cyano anions in ionic liquids are particularly interesting for their potential use as electron donors to excited state photo-acceptors [B. Wu et al., J. Phys. Chem. B 119, 14790–14799 (2015)]. Here we report on bulk structural and quantum mechanical results for a series of ionic liquids based on the 1-ethyl-3-methylimidazolium cation, paired with the following five cyano anions: SeCN-, SCN-, N(CN)-2N(CN)2-, C(CN)-3C(CN)3-, and B(CN)-4B(CN)4-. By combining molecular dynamics simulations, high-energy X-ray scattering measurements,more » and periodic boundary condition DFT calculations, we are able to obtain a comprehensive description of the liquid landscape as well as the nature of the HOMO-LUMO states for these ionic liquids in the condensed phase. Features in the structure functions for these ionic liquids are somewhat different than the commonly observed adjacency, charge-charge, and polarity peaks, especially for the bulkiest B(CN)-4B(CN)4- anion. While the other four cyano-anion ionic liquids present an anionic HOMO, the one for Im+2,1Im2,1+/B(CN)-4B(CN)4- is cationic.« less

Expanding frontiers in materials chemistry and physics with multiple anions.

PubMed

Kageyama, Hiroshi; Hayashi, Katsuro; Maeda, Kazuhiko; Attfield, J Paul; Hiroi, Zenji; Rondinelli, James M; Poeppelmeier, Kenneth R

2018-02-22

During the last century, inorganic oxide compounds laid foundations for materials synthesis, characterization, and technology translation by adding new functions into devices previously dominated by main-group element semiconductor compounds. Today, compounds with multiple anions beyond the single-oxide ion, such as oxyhalides and oxyhydrides, offer a new materials platform from which superior functionality may arise. Here we review the recent progress, status, and future prospects and challenges facing the development and deployment of mixed-anion compounds, focusing mainly on oxide-derived materials. We devote attention to the crucial roles that multiple anions play during synthesis, characterization, and in the physical properties of these materials. We discuss the opportunities enabled by recent advances in synthetic approaches for design of both local and overall structure, state-of-the-art characterization techniques to distinguish unique structural and chemical states, and chemical/physical properties emerging from the synergy of multiple anions for catalysis, energy conversion, and electronic materials.

Frontal Polymerization of Dicyclopentadiene: A Numerical Study.

PubMed

Goli, Elyas; Robertson, Ian D; Geubelle, Philippe H; Moore, Jeffrey S

2018-04-26

As frontal polymerization is being considered as a faster and more energy efficient manufacturing technique for polymer-matrix fiber-reinforced composites, we perform a finite-element-based numerical study of the initiation and propagation of a polymerization front in dicyclopentadiene (DCPD). The transient thermochemical simulations are complemented by an analytical study of the steady-state propagation of the polymerization front, allowing to draw a direct link between the cure kinetics model and the key characteristics of the front, i.e., front velocity and characteristic length scales. The second part of this study focuses on the prediction of the temperature spike associated with the merger of two polymerization fronts. The thermal peak, which might be detrimental to the properties of the polymerized material, is due to the inability of the heat associated with the highly exothermic reaction to be dissipated when the two fronts merge. The analysis investigates how the amplitude of the thermal spike is affected by the degree of cure at the time of the front merger.

Correcting the anion gap for hypoalbuminaemia does not improve detection of hyperlactataemia

PubMed Central

Dinh, C H; Ng, R; Grandinetti, A; Joffe, A; Chow, D C

2006-01-01

Background An elevated lactate level reflects impaired tissue oxygenation and is a predictor of mortality. Studies have shown that the anion gap is inadequate as a screen for hyperlactataemia, particularly in critically ill and trauma patients. A proposed explanation for the anion gap's poor sensitivity and specificity in detecting hyperlactataemia is that the serum albumin is frequently low. This study therefore, sought to compare the predictive values of the anion gap and the anion gap corrected for albumin (cAG) as an indicator of hyperlactataemia as defined by a lactate ⩾2.5 mmol/l. Methods A retrospective review of 639 sets of laboratory values from a tertiary care hospital. Patients' laboratory results were included in the study if serum chemistries and lactate were drawn consecutively. The sensitivity, specificity, and predictive values were obtained. A receiver operator characteristics curve (ROC) was drawn and the area under the curve (AUC) was calculated. Results An anion gap ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 39%, 89%, 79%, and 58%, respectively, and a cAG ⩾12 provided a sensitivity, specificity, positive predictive value, and negative predictive value of 75%, 59%, 66%, and 69%, respectively. The ROC curves between anion gap and cAG as a predictor of hyperlactataemia were almost identical. The AUC was 0.757 and 0.750, respectively. Conclusions The sensitivities, specificities, and predictive values of the anion gap and cAG were inadequate in predicting the presence of hyperlactataemia. The cAG provides no additional advantage over the anion gap in the detection of hyperlactataemia. PMID:16858097

Cation and anion sequences in dark-adapted Balanus photoreceptor

PubMed Central

1977-01-01

Anion and cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na+) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI greater than PSO4 greater than PBr greater than PCl greater than Pisethionate greater than Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than Cl-. The alkali-metal cation permeability sequence obtained was PK greater than PRb greater than PCx greater than PNa approximately PLi. This corresponds to Eisenman's IV which is the same sequencethat has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK greater than GRb greater than GCs greater than GNa greater than GLi. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K+ which was generally higher. PMID:199688

A bambusuril macrocycle that binds anions in water with high affinity and selectivity.

PubMed

Yawer, Mirza Arfan; Havel, Vaclav; Sindelar, Vladimir

2015-01-02

Synthetic receptors that function in water are important for the qualitative and quantitative detection of anions, which may act as pollutants in the environment or play important roles in biological processes. Neutral receptors are particularly appealing because they are often more selective than positively charged receptors; however, their affinity towards anions in pure water is only in range of 1-10(3)  L mol(-1) . The anion-templated synthesis of a water-soluble bambusuril derivative is shown to be an outstanding receptor for various inorganic anions in pure water, with association constants of up to 10(7)  L mol(-1) . Furthermore, the macrocycle discriminates between anions with unprecedented selectivity (up to 500 000-fold). We anticipate that the combination of remarkable affinity and selectivity of this macrocycle will enable the efficient detection and isolation of diverse anions in aqueous solutions, which is not possible with current supramolecular systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic Levitation To Characterize the Kinetics of Free-Radical Polymerization.

PubMed

Ge, Shencheng; Semenov, Sergey N; Nagarkar, Amit A; Milette, Jonathan; Christodouleas, Dionysios C; Yuan, Li; Whitesides, George M

2017-12-27

This work describes the development of magnetic levitation (MagLev) to characterize the kinetics of free-radical polymerization of water-insoluble, low-molecular-weight monomers that show a large change in density upon polymerization. Maglev measures density, and certain classes of monomers show a large change in density when monomers covalently join in polymer chains. MagLev characterized both the thermal polymerization of methacrylate-based monomers and the photopolymerization of methyl methacrylate and made it possible to determine the orders of reaction and the Arrhenius activation energy of polymerization. MagLev also made it possible to monitor polymerization in the presence of solids (aramid fibers, and carbon fibers, and glass fibers). MagLev offers a new analytical technique to materials and polymer scientists that complements other methods (even those based on density, such as dilatometry), and will be useful in investigating polymerizations, evaluating inhibition of polymerizations, and studying polymerization in the presence of included solid materials (e.g., for composite materials).

Method for forming polymerized microfluidic devices

DOEpatents

Sommer, Gregory J [Livermore, CA; Hatch, Anson V [Tracy, CA; Wang, Ying-Chih [Pleasanton, CA; Singh, Anup K [Danville, CA; Renzi, Ronald F [Tracy, CA; Claudnic, Mark R [Livermore, CA

2011-11-01

Methods for making a micofluidic device according to embodiments of the present invention include defining a cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

Method for forming polymerized microfluidic devices

DOEpatents

Sommer, Gregory J.; Hatch, Anson V.; Wang, Ying-Chih; Singh, Anup K.; Renzi, Ronald F.; Claudnic, Mark R.

2013-03-12

Methods for making a microfluidic device according to embodiments of the present invention include defining.about.cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

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

Zheng, Haiyan; Wang, Lijuan; Li, Kuo

Transformation between different types of carbon–carbon bonding in carbides often results in a dramatic change of physical and chemical properties. Under external pressure, unsaturated carbon atoms form new covalent bonds regardless of the electrostatic repulsion. It was predicted that calcium acetylide (also known as calcium carbide, CaC2) polymerizes to form calcium polyacetylide, calcium polyacenide and calcium graphenide under high pressure. In this work, the phase transitions of CaC2 under external pressure were systematically investigated, and the amorphous phase was studied in detail for the first time. Polycarbide anions like C 6 6- are identified with gas chromatography-mass spectrometry and severalmore » other techniques, which evidences the pressure induced polymerization of the acetylide anions and suggests the existence of the polyacenide fragment. Additionally, the process of polymerization is accompanied with a 107 fold enhancement of the electrical conductivity. The polymerization of acetylide anions demonstrates that high pressure compression is a viable route to synthesize novel metal polycarbides and materials with extended carbon networks, while shedding light on the synthesis of more complicated metal organics.« less

Separation of anionic oligosaccharides by high-performance liquid chromatography

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

Green, E.D.; Baenziger, J.U.

1986-10-01