Exploration of pH-dependent behavior of the anion receptor pocket of subdomain IIA of HSA: determination of effective pocket charge using the Debye-Hückel limiting law.

Science.gov (United States)

Bolel, Priyanka; Datta, Shubhashis; Mahapatra, Niharendu; Halder, Mintu

2014-01-09

Protein-ligand electrostatic interaction can be looked upon as ion receptor-ligand interaction, and the binding cavity of protein can be either an anion or cation receptor depending on the charge of the guest. Here we focus on the exploration of pH-modulated binding of a number of anionic ligands, specific to the subdomain IIA cavity of HSA, such as carmoisine, tartrazine, cochineal red, and warfarin. The logarithm of the binding constant is found to vary linearly with the square-root of ionic strength, indicating applicability of the Debye-Hückel limiting law to protein-ligand electrostatic binding equilibrium, and concludes that the subdomain IIA cavity is an anion receptor. The present approach is very unique that one can calculate the effective charge of the protein-based anion receptor pocket, and the calculated charge has been found to vary between +1 and +3 depending on the pH and ligand itself. The study also indicates that in such cases of specific ligand binding the pocket charge rather than the overall or surface charge of the macromolecule seems to have a paramount role in determining the strength of interaction. For the first time, it is demonstrated that the Debye-Hückel interionic interaction model can be successfully applied to understand the protein-based receptor-ligand electrostatic interaction in general.

Metal-Oxide Film Conversions Involving Large Anions

Energy Technology Data Exchange (ETDEWEB)

Pretty, S.; Zhang, X.; Shoesmith, D.W.; Wren, J.C. [The University of Western Ontario, Chemistry Department, 1151 Richmond St., N6A 5B7, London, Ontario (Canada)

2008-07-01

The main objective of my research is to establish the mechanism and kinetics of metal-oxide film conversions involving large anions (I{sup -}, Br{sup -}, S{sup 2-}). Within a given group, the anions will provide insight on the effect of anion size on the film conversion, while comparison of Group 6 and Group 7 anions will provide insight on the effect of anion charge. This research has a range of industrial applications, for example, hazardous radioiodine can be immobilized by reaction with Ag to yield AgI. From the perspective of public safety, radioiodine is one of the most important fission products from the uranium fuel because of its large fuel inventory, high volatility, and radiological hazard. Additionally, because of its mobility, the gaseous iodine concentration is a critical parameter for safety assessment and post-accident management. A full kinetic analysis using electrochemical techniques has been performed on the conversion of Ag{sub 2}O to (1) AgI and (2) AgBr. (authors)

Metal-Oxide Film Conversions Involving Large Anions

International Nuclear Information System (INIS)

Pretty, S.; Zhang, X.; Shoesmith, D.W.; Wren, J.C.

2008-01-01

The main objective of my research is to establish the mechanism and kinetics of metal-oxide film conversions involving large anions (I - , Br - , S 2- ). Within a given group, the anions will provide insight on the effect of anion size on the film conversion, while comparison of Group 6 and Group 7 anions will provide insight on the effect of anion charge. This research has a range of industrial applications, for example, hazardous radioiodine can be immobilized by reaction with Ag to yield AgI. From the perspective of public safety, radioiodine is one of the most important fission products from the uranium fuel because of its large fuel inventory, high volatility, and radiological hazard. Additionally, because of its mobility, the gaseous iodine concentration is a critical parameter for safety assessment and post-accident management. A full kinetic analysis using electrochemical techniques has been performed on the conversion of Ag 2 O to (1) AgI and (2) AgBr. (authors)

High Vacuum Techniques for Anionic Polymerization

KAUST Repository

Ratkanthwar, Kedar; Hadjichristidis, Nikolaos; Mays, Jimmy

2015-01-01

Anionic polymerization high vacuum techniques (HVTs) are the most suitable for the preparation of polymer samples with well-defined complex macromolecular architectures. Though HVTs require glassblowing skill for designing and making polymerization

High Vacuum Techniques for Anionic Polymerization

KAUST Repository

Ratkanthwar, Kedar

2015-09-01

Anionic polymerization high vacuum techniques (HVTs) are the most suitable for the preparation of polymer samples with well-defined complex macromolecular architectures. Though HVTs require glassblowing skill for designing and making polymerization reactor, it is the best way to avoid any termination of living polymers during the number of steps for the synthesis of polymers with complex structure. In this chapter, we describe the different polymerization reactors and HVTs for the purification of monomers, solvents, and other reagents for anionic polymerization as well as few model reactions for the synthesis of polymers with simple to complex structure.

Simultaneous anion and cation mobility in polypyrrole

DEFF Research Database (Denmark)

Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.

2003-01-01

and the expulsion of anions; a broad anodic peak centered at ca. - 0.5 V representing the expulsion of cations; and a second broad peak at +0.2 to +0.5 V corresponding to anions being inserted. Although the motion of cations is the most important, as expected, there is a significant anion contribution, thereby...... complicating reproducibility when employing PPy(DBS) polymers as actuators. When the cation is doubly charged, it enters the film less readily, and anions dominate the mobility. Using a large and bulky cation switches the mechanism to apparently total anion motion. The changes in area of the three peaks...

Charge-scaling effect in ionic liquids from the charge-density analysis of N,N'-dimethylimidazolium methylsulfate.

Science.gov (United States)

Beichel, Witali; Trapp, Nils; Hauf, Christoph; Kohler, Oliver; Eickerling, Georg; Scherer, Wolfgang; Krossing, Ingo

2014-03-17

The charge scaling effect in ionic liquids was explored on the basis of experimental and theoretical chargedensity analyses of [C1MIM][C1SO4] employing the quantum theory of atoms in molecules (QTAIM) approach. Integrated QTAIM charges of the experimental (calculated) charge density of the cation and anion resulted in non-integer values of ±0.90 (±0.87) e. Efficient charge transfer along the bond paths of the hydrogen bonds between the imidazolium ring and the anion was considered as the origin of these reduced charges. In addition, a detailed QTAIM analysis of the bonding situation in the [C1SO4]- anion revealed the presence of negative πO→σ*S-O hyperconjugation.

Highly Sensitive Electrochemical Sensor for the Detection of Anions in Water Based on a Redox-Active Monolayer Incorporating an Anion Receptor.

Science.gov (United States)

Kaur, Balwinder; Erdmann, Cristiane Andreia; Daniëls, Mathias; Dehaen, Wim; Rafiński, Zbigniew; Radecka, Hanna; Radecki, Jerzy

2017-12-05

In the present work, gold electrodes were modified using a redox-active layer based on dipyrromethene complexes with Cu(II) or Co(II) and a dipodal anion receptor functionalized with dipyrromethene. These modified gold electrodes were then applied for the electrochemical detection of anions (Cl - , SO 4 2- , and Br - ) in a highly diluted water solution (in the picomolar range). The results showed that both systems, incorporating Cu(II) as well as Co(II) redox centers, exhibited highest sensitivity toward Cl - . The selectivity sequence found for both systems was Cl - > SO 4 2- > Br - . The high selectivity of Cl - anions can be attributed to the higher binding constant of Cl - with the anion receptor and the stronger electronic effect between the central metal and anion in the complex. The detection limit for the determination of Cl - was found at the 1.0 pM level for both sensing systems. The electrodes based on Co(II) redox centers displayed better selectivity toward Cl - anion detection than those based on Cu(II) centers which can be attributed to the stronger electronic interaction between the receptor-target anion complex and the Co(II)/Co(III) redox centers in comparison to the Cu(II)/Cu(I) system. Applicability of gold electrodes modified with DPM-Co(II)-DPM-AR for the electrochemical determination of Cl - anions was demonstrated using the artificial matrix mimicking human serum.

Probing the early stages of salt nucleation—Experimental and theoretical investigations of sodium/potassium thiocyanate cluster anions

Science.gov (United States)

Deng, S. H. M.; Kong, Xiang-Yu; Wang, Xue-Bin

2015-01-01

Due to the fast solvent evaporation in electrospray ionization (ESI), the concentration of initially dilute electrolyte solutions rapidly increases to afford the formation of supersaturated droplets and generation of various pristine anhydrous salt clusters in the gas phase. The size, composition, and charge distributions of these clusters, in principle, witness the nucleation evolution in solutions. Herein, we report a microscopic study on the initial stage of nucleation and crystallization of sodium/potassium thiocyanate salt solutions simulated in the ESI process. Singly charged M x (SCN)x + 1 - , doubly charged M y (SCN)y + 2 2 - (M = Na, K), and triply charged K z (SCN)z + 3 3 - anion clusters (x, y, and z stand for the number of alkali atoms in the singly, doubly, and triply charged clusters, respectively) were produced via electrospray of the corresponding salt solutions and were characterized by negative ion photoelectron spectroscopy (NIPES). The vertical detachment energies (VDEs) of these sodium/potassium thiocyanate cluster anions were obtained, and theoretical calculations were carried out for the sodium thiocyanate clusters in assisting spectral identification. The measured VDEs of singly charged anions M x (SCN)x + 1 - (M = Na and K) demonstrate that they are superhalogen anions. The existence of doubly charged anions M y (SCN)y + 2 2 - (y = 2x, x ≥ 4 and 3 for M = Na and K, respectively) and triply charged anions K z (SCN)z + 3 3 - (z = 3x, x ≥ 6) was initially discovered from the photoelectron spectra for those singly charged anions of M x (SCN)x + 1 - with the same mass-to-charge ratio (m/z), and later independently confirmed by the observation of their distinct mass spectral distributions and by taking their NIPE spectra for those pure multiply charged anions with their m/z different from the singly charged species. For large clusters, multiply charged clusters were found to become preferred, but at higher temperatures, those multiply charged

Preparation of anionic clay–birnessite manganese oxide composites by interlayer oxidation of oxalate ions by permanganate

International Nuclear Information System (INIS)

Arulraj, James; Rajamathi, Michael

2013-01-01

Oxalate intercalated anionic clay-like nickel zinc hydroxysalt was obtained starting from nickel zinc hydroxyacetate, Ni 3 Zn 2 (OH) 8 (OAc) 2 ·2H 2 O, by anion exchange. The intercalated oxalate species was reacted with potassium permanganate in such a way that the layered manganese oxide formed was within the interlayer region of the anionic clay resulting in a layered composite in which the negative charges on the birnessite type manganese oxide layers compensate the positive charges on the anionic clay layers. Birnessite to anionic clay ratio could be varied by varying the reaction time or the amount of potassium permanganate used. - Graphical abstract: Nickel zinc hydroxyoxalate was reacted with potassium permanganate to get nickel zinc hydroxide birnessite composites in which the positive charges on the hydroxide layers are neutralized by the negative charges on birnessite layers. Highlights: ► Anionic and cationic layered solid composites prepared. ► Ni–Zn hydroxyoxalate reacted with KMnO 4 to deposit MnO 2 in the interlayer. ► Birnessite layers coexist with anionic clay layers in the composites. ► Birnessite/anionic clay ratio controlled by amount of KMnO 4 used and reaction time

Photodetachment of free hexahalogenometallate doubly charged anions in the gas phase: [ML6]2-, (M=Re, Os, Ir, Pt; L=Cl and Br)

International Nuclear Information System (INIS)

Wang, X.; Wang, L.

1999-01-01

We report the first observation and photodetachment photoelectron spectroscopic study of a series of hexahalogenometallates dianions MCl 6 2- (M=Re, Os, Ir, and Pt) and MBr 6 2- (M=Re, Ir, and Pt) in the gas phase. All of these species were found to be stable as free gaseous doubly charged anions. Photoelectron spectra of all the dianions were obtained at several detachment photon energies. The photon-energy-dependent spectra clearly revealed the dianion nature of these species and allowed the repulsive Coulomb barriers to be estimated. The binding energies of the second excess electron in MCl 6 2- (M=Re, Os, Ir, Pt) were determined to be 0.46 (5), 0.46 (5), 0.82 (5), and 1.58 (5) eV, respectively, and those in MBr 6 2- (M=Re, Ir, Pt) to be 0.76 (6), 0.96 (6), and 1.52 (6) eV, respectively. A wealth of electronic structure information about these metal complexes were obtained and low-lying and highly-excited electronic states of the corresponding singly charged anions were observed. Detachment from metal d orbitals or ligand orbitals were observed and could be clearly distinguished; detachments from the metal d-orbitals all occur at low binding energies whereas those from the ligand-dominated orbitals all take place at rather high binding energies. We also found a remarkable correlation between electron affinities measured in vacuo and the redox potentials obtained in the solution phase of these species. copyright 1999 American Institute of Physics

Preparation of Acrylamide-based Anionic Polyelectrolytes for Soil Establishment

Directory of Open Access Journals (Sweden)

Ahmad Rabiee

2012-12-01

Full Text Available Synthetic water soluble acrylamide-based polymers have wide range of ap-plications  in  the  feld  of  soil  establishment  and  non-desertifcation.  In  this research, the acrylamide-based anionic polyelectrolytes were prepared by  solution polymerization. The polymerization was carried out using AIBN as a radical initiator and at different degrees of anionic charges ranging between 10% and 30% using sodium hydroxide as hydrolyzing agents. The chemical structure of the  synthetic polymers was studied and confrmed by FTIR technique. The charge density on polymer backbone was determined by titration method. The rheological behavior of polymer solutions was evaluated by Brookfeld viscometer. The results show that the viscosity decreases with increasing the shear rate of solutions. Molecular weights of samples were measured by laser light scattering analyzer. The morphology of the polymer was studied by SEM and the EDX was used for elemental analysis determination. The anionic polymers with 10-30% negative charges were mixed with clay in order to evaluate the soil establishment. The results show that an anionic polyelectro-lyte can make soil particles more cohesive and improve soil physical properties.

Bactericidal and Hemocompatible Coating via the Mixed-Charged Copolymer.

Science.gov (United States)

Fan, Xiao-Li; Hu, Mi; Qin, Zhi-Hui; Wang, Jing; Chen, Xia-Chao; Lei, Wen-Xi; Ye, Wan-Ying; Jin, Qiao; Ren, Ke-Feng; Ji, Jian

2018-03-28

Cationic antibacterial coating based on quaternary ammonium compounds, with an efficient and broad spectrum bactericidal property, has been widely used in various fields. However, the high density of positive charges tends to induce weak hemocompatibility, which hinders the application of the cationic antibacterial coating in blood-contacting devices and implants. It has been reported that a negatively charged surface can reduce blood coagulation, showing improved hemocompatibility. Here, we describe a strategy to combine the cationic and anionic groups by using mixed-charged copolymers. The copolymers of poly (quaternized vinyl pyridine- co- n-butyl methacrylate- co-methacrylate acid) [P(QVP- co- nBMA- co-MAA)] were synthesized through free radical copolymerization. The cationic group of QVP, the anionic group of MAA, and the hydrophobic group of nBMA were designed to provide bactericidal capability, hemocompatibility, and coating stability, respectively. Our findings show that the hydrophilicity of the copolymer coating increased, and its zeta potential decreased from positive charge to negative charge with the increase of the anionic/cationic ratio. Meanwhile, the bactericidal property of the copolymer coating was kept around a similar level compared with the pure quaternary ammonium copolymer coating. Furthermore, the coagulation time, platelet adhesion, and hemolysis tests revealed that the hemocompatibility of the copolymer coating improved with the addition of the anionic group. The mixed-charged copolymer combined both bactericidal property and hemocompatibility and has a promising potential in blood-contacting antibacterial devices and implants.

Preparation of anionic clay-birnessite manganese oxide composites by interlayer oxidation of oxalate ions by permanganate

Energy Technology Data Exchange (ETDEWEB)

Arulraj, James [Materials Research Group, Department of Chemistry, St. Joseph' s College, 36 Langford Road, Bangalore 560 027 (India); Rajamathi, Michael, E-mail: mikerajamathi@rediffmail.com [Materials Research Group, Department of Chemistry, St. Joseph' s College, 36 Langford Road, Bangalore 560 027 (India)

2013-02-15

Oxalate intercalated anionic clay-like nickel zinc hydroxysalt was obtained starting from nickel zinc hydroxyacetate, Ni{sub 3}Zn{sub 2}(OH){sub 8}(OAc){sub 2}{center_dot}2H{sub 2}O, by anion exchange. The intercalated oxalate species was reacted with potassium permanganate in such a way that the layered manganese oxide formed was within the interlayer region of the anionic clay resulting in a layered composite in which the negative charges on the birnessite type manganese oxide layers compensate the positive charges on the anionic clay layers. Birnessite to anionic clay ratio could be varied by varying the reaction time or the amount of potassium permanganate used. - Graphical abstract: Nickel zinc hydroxyoxalate was reacted with potassium permanganate to get nickel zinc hydroxide birnessite composites in which the positive charges on the hydroxide layers are neutralized by the negative charges on birnessite layers. Highlights: Black-Right-Pointing-Pointer Anionic and cationic layered solid composites prepared. Black-Right-Pointing-Pointer Ni-Zn hydroxyoxalate reacted with KMnO{sub 4} to deposit MnO{sub 2} in the interlayer. Black-Right-Pointing-Pointer Birnessite layers coexist with anionic clay layers in the composites. Black-Right-Pointing-Pointer Birnessite/anionic clay ratio controlled by amount of KMnO{sub 4} used and reaction time.

Probing Intermolecular Electron Delocalization in Dimer Radical Anions by Vibrational Spectroscopy

International Nuclear Information System (INIS)

Mani, Tomoyasu; Brookhaven National Laboratory; Grills, David C.

2017-01-01

Delocalization of charges is one of the factors controlling charge transport in conjugated molecules. It is considered to play an important role in the performance of a wide range of molecular technologies, including organic solar cells and organic electronics. Dimerization reactions are well-suited as a model to investigate intermolecular spatial delocalization of charges. And while dimerization reactions of radical cations are well investigated, studies on radical anions are still scarce. Upon dimerization of radical anions with neutral counterparts, an electron is considered to delocalize over the two molecules. By using time-resolved infrared (TRIR) detection coupled with pulse radiolysis, we show that radical anions of 4-n-hexyl-4'-cyanobiphenyl (6CB) undergo such dimerization reactions, with an electron equally delocalized over the two molecules. We have recently demonstrated that nitrile ν(C≡N) vibrations respond to the degree of electron localization of nitrile-substituted anions: we can quantify the changes in the electronic charges from the neutral to the anion states in the nitriles by monitoring the ν(C≡N) IR shifts. In the first part of this article, we show that the sensitivity of the ν(C≡N) IR shifts does not depend on solvent polarity. In the second part, we describe how probing the shifts of the nitrile IR vibrational band unambiguously confirms the formation of dimer radical anions, with K dim = 3 × 10 4 M –1 . IR findings are corroborated by electronic absorption spectroscopy and electronic structure calculations. We find that the presence of a hexyl chain and the formation of π–π interactions are both crucial for dimerization of radical anions of 6CB with neutral 6CB. Our study provides clear evidence of spatial delocalization of electrons over two molecular fragments.

Sensing mechanism for a fluorescent off–on chemosensor for cyanide anion

International Nuclear Information System (INIS)

Li, Yang; Chen, Junsheng; Chu, Tian-Shu

2016-01-01

In this article, the sensing mechanism of cyanide anion chemosensor 2-((2-phenyl-2H-1,2,3-triazol-4-yl)methylene)malononitrile (M1) has been investigated through the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The theoretical results demonstrate that the reaction barrier of 13.02 kcal/mol means a favorable response speed of the chemosensor M1 for cyanide anion. Cyanide anion attacks C=C double bond and hinders the ICT process from the malononitrile moiety to the fluorophore phenyl ring. The high viscosity of DMSO restrains the twisting of the group, inhibits the formation of the ICT state in the first excited state. Due to weak ICT character, the nucleophilic addition product shows the dramatic “off–on” fluorescence enhancement. Meanwhile, intramolecular charge transfer (ICT) mechanism accounts for how different solvents influence the fluorescence spectra. That is, more obvious ICT character of product in EtOH causes fluorescence quenching. The “reaction-based” recognition mode and large bond energy between M1 and cyanide anion minimize the interference by other anions, such as F − , AcO − . Thus, the chemosensor M1 has a high selectivity for cyanide.

Sorption of vanillin on highly basic anion exchanger under static conditions

Science.gov (United States)

Sholokhova, A. Yu.; Eliseeva, T. V.; Voronyuk, I. V.

2017-11-01

The kinetics of the sorption of vanillin by a granulated anion exchanger is studied under static conditions. A comparison of the kinetic curves of the uptake of hydroxybenzaldehyde by gel and macroporous anion exchanger shows that macroporous sorbent has better kinetic characteristics. The effect temperature has on the capacity of an anion exchanger and the time needed to establish sorption equilibrium is found, and the activation energy of vanillin uptake is determined. Studying the effect experimental factors have on the rate of sorption and using the formal kinetics approach, it is established that in the investigated range of concentrations, the limiting stage of the uptake of vanillin by an anion exchanger with the functional groups of a quaternary ammonium base is that of external diffusion. Vanillin sorption by a highly basic anion exchanger in hydroxyl form is characterized by polymolecular uptake best described by a BET isotherm; at the same time, the uptake of sorbate by a chloride form is of a monomolecular character and can be described by a Freindlich isotherm. Structural changes in the anion exchanger sorbed hydroxybenzaldehyde are identified via FTIR spectroscopy.

Sensing mechanism for a fluorescent off–on chemosensor for cyanide anion

Energy Technology Data Exchange (ETDEWEB)

Li, Yang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Junsheng [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Chu, Tian-Shu, E-mail: tschu@dicp.ac.cn [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber, Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao 266071 (China)

2016-11-15

In this article, the sensing mechanism of cyanide anion chemosensor 2-((2-phenyl-2H-1,2,3-triazol-4-yl)methylene)malononitrile (M1) has been investigated through the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The theoretical results demonstrate that the reaction barrier of 13.02 kcal/mol means a favorable response speed of the chemosensor M1 for cyanide anion. Cyanide anion attacks C=C double bond and hinders the ICT process from the malononitrile moiety to the fluorophore phenyl ring. The high viscosity of DMSO restrains the twisting of the group, inhibits the formation of the ICT state in the first excited state. Due to weak ICT character, the nucleophilic addition product shows the dramatic “off–on” fluorescence enhancement. Meanwhile, intramolecular charge transfer (ICT) mechanism accounts for how different solvents influence the fluorescence spectra. That is, more obvious ICT character of product in EtOH causes fluorescence quenching. The “reaction-based” recognition mode and large bond energy between M1 and cyanide anion minimize the interference by other anions, such as F{sup −}, AcO{sup −}. Thus, the chemosensor M1 has a high selectivity for cyanide.

Schlenk Techniques for Anionic Polymerization

KAUST Repository

Ratkanthwar, Kedar

2015-09-01

Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands for time and skilled technical personnel, HVTs are currently used in only a few research laboratories worldwide. Instead, most researchers in this filed are attracted to more facile Schlenk techniques. The basic principle of this technique followed in all laboratories is substantially the same, i.e. the use of alternate vacuum and inert gas atmosphere in glass apparatus for the purification/charging of monomer, solvents, additives, and for the manipulation of air-sensitive compounds such as alkyl metal initiators, organometallic or organic catalysts. However, it is executed quite differently in each research group in terms of the structure of Schlenk apparatus (manifolds, connections, purification/storage flasks, reactors, etc.), the use of small supplementary devices (soft tubing, cannulas, stopcocks, etc.) and experimental procedures. The operational methods are partly purpose-oriented while also featured by a high flexibility, which makes it impossible to describe in detail each specific one. In this chapter we will briefly exemplify the application of Schlenk techniques for anionic polymerization by describing the performance of a few experiments from our own work.

Extracellular determinants of anion discrimination of the Cl-/H+ antiporter protein CLC-5.

Science.gov (United States)

De Stefano, Silvia; Pusch, Michael; Zifarelli, Giovanni

2011-12-23

Mammalian CLC proteins comprise both Cl- channels and Cl-/H+ antiporters that carry out fundamental physiological tasks by transporting Cl- across plasma membrane and intracellular compartments. The NO3- over Cl- preference of a plant CLC transporter has been pinpointed to a conserved serine residue located at Scen and it is generally assumed that the other two binding sites of CLCs, Sext and Sin, do not substantially contribute to anion selectivity. Here we show for the Cl-/H+ antiporter CLC-5 that the conserved and extracellularly exposed Lys210 residue is critical to determine the anion specificity for transport activity. In particular, mutations that neutralize or invert the charge at this position reverse the NO3- over Cl- preference of WT CLC-5 at a concentration of 100 mm, but do not modify the coupling stoichiometry with H+. The importance of the electrical charge is shown by chemical modification of K210C with positively charged cysteine-reactive compounds that reintroduce the WT preference for Cl-. At saturating extracellular anion concentrations, neutralization of Lys210 is of little impact on the anion preference, suggesting an important role of Lys210 on the association rate of extracellular anions to Sext.

Derivatives of Dodecahalo-Closo-Dodecaborate Di-Anion

OpenAIRE

Avelar, Amy Cindy

2009-01-01

ABSTRACT OF THE DISSERTATIONDerivatives of the Dodecahalo-Closo-Dodecaborate Di-AnionbyAmy AvelarDoctor of Philosophy, Graduate Program in ChemistryUniversity of California, Riverside, December 2009Dr. Christopher A. Reed, ChairpersonThe di-anion, dodecahalo-closo-dodecaborate, B12X122-, where the X = Cl or Br, has been determined to be a useful weakly coordinating anion, WCA. Despite the di- negative charge, several elusive and reactive cationic species were stabilized with B12X122- as the c...

Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere

Science.gov (United States)

Desai, R. T.; Coates, A. J.; Wellbrock, A.; Vuitton, V.; Crary, F. J.; González-Caniulef, D.; Shebanits, O.; Jones, G. H.; Lewis, G. R.; Waite, J. H.; Cordiner, M.; Taylor, S. A.; Kataria, D. O.; Wahlund, J.-E.; Edberg, N. J. T.; Sittler, E. C.

2017-08-01

Cassini discovered a plethora of neutral and ionized molecules in Titan’s ionosphere including, surprisingly, anions and negatively charged molecules extending up to 13,800 u q-1. In this Letter, we forward model the Cassini electron spectrometer response function to this unexpected ionospheric component to achieve an increased mass resolving capability for negatively charged species observed at Titan altitudes of 950-1300 km. We report on detections consistently centered between 25.8 and 26.0 u q-1 and between 49.0-50.1 u q-1 which are identified as belonging to the carbon chain anions, CN-/C3N- and/or C2H-/C4H-, in agreement with chemical model predictions. At higher ionospheric altitudes, detections at 73-74 u q-1 could be attributed to the further carbon chain anions C5N-/C6H- but at lower altitudes and during further encounters extend over a higher mass/charge range. This, as well as further intermediary anions detected at >100 u, provide the first evidence for efficient anion chemistry in space involving structures other than linear chains. Furthermore, at altitudes below environments where chain anions have been observed and shows that anion chemistry plays a role in the formation of complex organics within a planetary atmosphere as well as in the interstellar medium.

The chemistry of molecular anions in circumstellar sources

Energy Technology Data Exchange (ETDEWEB)

Agúndez, Marcelino [LUTH, Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92190 Meudon (France); Cernicharo, José [Departamento de Astrofísica, CAB, CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, 28850 Madrid (Spain); Guélin, Michel [Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d' Héres (France)

2015-01-22

The detection of negatively charged molecules in the interstellar and circumstellar medium in the past four years has been one of the most impacting surprises in the area of molecular astrophysics. It has motivated the interest of astronomers, physicists, and chemists on the study of the spectroscopy, chemical kinetics, and prevalence of molecular anions in the different astronomical regions. Up to six different molecular anions have been discovered in space to date, the last one being the small ion CN{sup −}, which has been observed in the envelope of the carbon star IRC +10216 and which contrary to the other larger anions is not formed by electron attachment to CN, but through reactions of large carbon anions with nitrogen atoms. Here we briefly review the current status of our knowledge of the chemistry of molecular anions in space, with particular emphasis on the circumstellar source IRC +10216, which to date is the astronomical source harboring the largest variety of anions.

Charge ordered insulating phases of DODHT salts with octahedral anions and a new radical salt, β''-(DODHT)2TaF6

Science.gov (United States)

Nishikawa, H.; Oshio, H.; Higa, M.; Kondo, R.; Kagoshima, S.; Nakao, A.; Sawa, H.; Yasuzuka, S.; Murata, K.

2008-10-01

Physical properties of isostructural β''-(DODHT)2X [DODHT = (l,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene; X = PF6, AsF6, and SbF6] at ambient pressure have been compared. The insulating phase of β''-(DODHT)2PF6 salt has already been revealed to be a charge ordering (CO) state by X-ray diffraction study and magnetic behavior. CO in this salt was also confirmed by the observation of satellite reflections in oscillation photograph using synchrotron radiation. Transport property of β''-(DODHT)2SbF6 salt was reinvestigated up to the pressure of 3.7 GPa applied by a cubic anvil apparatus. Although the SbF6 salt turned to be metallic above 2.0 GPa, no superconductivity was observed. In order to examine the anion size dependence of DODHT salts with octahedral anions, we prepared a new DODHT salt, β''-(DODHT)2TaF6, which has the larger counter anion compared with the previous salts. Crystal structure of this salt was isostructural to the other DODHT salts. The electrical and magnetic properties of this salt were similar to those of β''-(DODHT)2SbF6 salt.

In situ NMR spectroscopy of supercapacitors: insight into the charge storage mechanism.

Science.gov (United States)

Wang, Hao; Forse, Alexander C; Griffin, John M; Trease, Nicole M; Trognko, Lorie; Taberna, Pierre-Louis; Simon, Patrice; Grey, Clare P

2013-12-18

Electrochemical capacitors, commonly known as supercapacitors, are important energy storage devices with high power capabilities and long cycle lives. Here we report the development and application of in situ nuclear magnetic resonance (NMR) methodologies to study changes at the electrode-electrolyte interface in working devices as they charge and discharge. For a supercapacitor comprising activated carbon electrodes and an organic electrolyte, NMR experiments carried out at different charge states allow quantification of the number of charge storing species and show that there are at least two distinct charge storage regimes. At cell voltages below 0.75 V, electrolyte anions are increasingly desorbed from the carbon micropores at the negative electrode, while at the positive electrode there is little change in the number of anions that are adsorbed as the voltage is increased. However, above a cell voltage of 0.75 V, dramatic increases in the amount of adsorbed anions in the positive electrode are observed while anions continue to be desorbed at the negative electrode. NMR experiments with simultaneous cyclic voltammetry show that supercapacitor charging causes marked changes to the local environments of charge storing species, with periodic changes of their chemical shift observed. NMR calculations on a model carbon fragment show that the addition and removal of electrons from a delocalized system should lead to considerable increases in the nucleus-independent chemical shift of nearby species, in agreement with our experimental observations.

Extracellular Determinants of Anion Discrimination of the Cl−/H+ Antiporter Protein CLC-5*

Science.gov (United States)

De Stefano, Silvia; Pusch, Michael; Zifarelli, Giovanni

2011-01-01

Mammalian CLC proteins comprise both Cl− channels and Cl−/H+ antiporters that carry out fundamental physiological tasks by transporting Cl− across plasma membrane and intracellular compartments. The NO3− over Cl− preference of a plant CLC transporter has been pinpointed to a conserved serine residue located at Scen and it is generally assumed that the other two binding sites of CLCs, Sext and Sin, do not substantially contribute to anion selectivity. Here we show for the Cl−/H+ antiporter CLC-5 that the conserved and extracellularly exposed Lys210 residue is critical to determine the anion specificity for transport activity. In particular, mutations that neutralize or invert the charge at this position reverse the NO3− over Cl− preference of WT CLC-5 at a concentration of 100 mm, but do not modify the coupling stoichiometry with H+. The importance of the electrical charge is shown by chemical modification of K210C with positively charged cysteine-reactive compounds that reintroduce the WT preference for Cl−. At saturating extracellular anion concentrations, neutralization of Lys210 is of little impact on the anion preference, suggesting an important role of Lys210 on the association rate of extracellular anions to Sext. PMID:21921031

Mechanism of action of anions on the electron transport chain in thylakoid membranes of higher plants.

Science.gov (United States)

Singh-Rawal, Pooja; Zsiros, Ottó; Bharti, Sudhakar; Garab, Gyozo; Jajoo, Anjana

2011-04-01

With an aim to improve our understanding of the mechanisms behind specific anion effects in biological membranes, we have studied the effects of sodium salts of anions of varying valency in thylakoid membranes. Rates of electron transport of PS II and PS I, 77K fluorescence emission and excitation spectra, cyclic electron flow around PS I and circular dichroism (CD) spectra were measured in thylakoid membranes in order to elucidate a general mechanism of action of inorganic anions on photosynthetic electron transport chain. Re-distribution of absorbed excitation energy has been observed as a signature effect of inorganic anions. In the presence of anions, such as nitrite, sulphate and phosphate, distribution of absorbed excitation energy was found to be more in favor of Photosystem I (PS I). The amount of energy distributed towards PS I depended on the valency of the anion. In this paper, we propose for the first time that energy re-distribution and its valence dependence may not be the effect of anions per se. The entry of negative charge (anion) is accompanied by influx of positive charge (protons) to maintain a balance of charge across the thylakoid membranes. As reflected by the CD spectra, the observed energy re-distribution could be a result of structural rearrangements of the protein complexes of PS II caused by changes in the ionic environment of the thylakoid lumen.

Quantum mechanics of toroidal anions

International Nuclear Information System (INIS)

Afanas'ev, G.N.

1990-01-01

We consider a toroidal solenoid with an electric charge attached to it. It turns out that statistical properties of the wave function describing interacting toroidal anions depend on both their relative position and orientation. The influence of the particular gauge choice on the exchange properties of the wave function is studied. 30 refs.; 6 figs

Anion concurrence and anion selectivity in the sorption of radionuclides by organotones

International Nuclear Information System (INIS)

Behnsen, Julia G.

2007-01-01

Some long-lived and radiologically important nuclear fission products, such as I-129 (half-life t 1/2 = 1,6 . 10 7 a), Tc-99 (t 1/2 = 2,1 . 10 5 a), and Se-79 (t 1/2 = 6,5 . 10 4 a) are anionic in aqueous environments. This study focuses on the adsorption of such anions to organoclays and the understanding of the selectivity of the process. The organoclays used in this study were prepared from a bentonite (MX-80) and a vermiculite clay, and the cationic surfactants hexadcylpyridium, hexadecyltrimethylammonium, and benzethonium. Surfactant adsorption to the bentonite exceeds the cation exchange capacity of the clay, with the surplus positive charge being balanced by the co-adsorption of chloride. The interlayer distance of the bentonites is increased sufficiently to contain bi- and pseudotrimolecular structures of the surfactants. Adsorption experiments were carried out using the batch technique. Anion adsorption of iodide, perrhenate, selenite, nitrate, and sulphate is mainly due to ion exchange with chloride. As an additional adsorption mechanism, the incorporation of inorganic ion pairs into the interlayer space of the clay is proposed as a result of experiments showing differences in the adsorption levels of sodium and potassium iodide. Anion adsorption results show a clear selectivity of the organoclays, with the affinity sequence being: ReO - 4 > I - > NO - 3 > Cl - > SO 2- 4 > SeO 2- 3 . This sequence corresponds to the sequence of increasing hydration energies of the anions, thus selectivity could be due to the process of minimization of free energy of the system. (orig.)

Anion effect on the retention of recoil atom of coordination crystalline compounds

International Nuclear Information System (INIS)

Dimotakis, P.N.; Papadopoulos, B.P.

1980-01-01

The anion effect of various cobaltic crystalline compounds - having the same cation and differing in anion -on the retention of neutron activated central cobalt atom has been studied. The cation was trans-dichloro(bis)ethylenediamine cobalt(III) and the anions were simple spherical anions (Cl - , Br - , I - ), planar anions (NO 3 - ), trigonal pyramidal anions (ClO 3 - , BrO 3 - ), tetrahedral anions (SO 4 2- , CrO 4 2- , MnO 4 - ) and linear anions (SCN - ). The cobalt-60 activity after reactor irradiation either in simple Co 2+ cation or in cobaltic complex cation determined the retention values. In all irradiations at ordinary temperature and at liquid nitrogen temperature the results showed an effect of the different anions, depending on the geometry, volume and charge, on the recombination of the recoil cobalt with the ligands in the coordination sphere. (author)

Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere

Energy Technology Data Exchange (ETDEWEB)

Desai, R. T.; Coates, A. J.; Wellbrock, A.; González-Caniulef, D.; Jones, G. H.; Lewis, G. R.; Taylor, S. A.; Kataria, D. O. [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey RH5 6NT (United Kingdom); Vuitton, V. [Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble (France); Crary, F. J. [Laboratory for Atmospheric and Space Physics, University of Colorado, Innovation Drive, Boulder, CO 80303 (United States); Shebanits, O.; Wahlund, J.-E. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala (Sweden); Waite, J. H. [Space Science and Engineering Division, Southwest Research Institute (SWRI), 6220 Culebra Road, San Antonio, TX 78238 (United States); Cordiner, M.; Sittler, E. C. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Edberg, N. J. T., E-mail: r.t.desai@ucl.ac.uk [Swedish Institute of Space Physics, Box 537, SE-751 21 Uppsala (Sweden)

2017-08-01

Cassini discovered a plethora of neutral and ionized molecules in Titan’s ionosphere including, surprisingly, anions and negatively charged molecules extending up to 13,800 u q{sup −1}. In this Letter, we forward model the Cassini electron spectrometer response function to this unexpected ionospheric component to achieve an increased mass resolving capability for negatively charged species observed at Titan altitudes of 950–1300 km. We report on detections consistently centered between 25.8 and 26.0 u q{sup −1} and between 49.0–50.1 u q{sup −1} which are identified as belonging to the carbon chain anions, CN{sup −}/C{sub 3}N{sup −} and/or C{sub 2}H{sup −}/C{sub 4}H{sup −}, in agreement with chemical model predictions. At higher ionospheric altitudes, detections at 73–74 u q{sup −1} could be attributed to the further carbon chain anions C{sub 5}N{sup −}/C{sub 6}H{sup −} but at lower altitudes and during further encounters extend over a higher mass/charge range. This, as well as further intermediary anions detected at >100 u, provide the first evidence for efficient anion chemistry in space involving structures other than linear chains. Furthermore, at altitudes below <1100 km, the low-mass anions (<150 u q{sup −1}) were found to deplete at a rate proportional to the growth of the larger molecules, a correlation that indicates the anions are tightly coupled to the growth process. This study adds Titan to an increasing list of astrophysical environments where chain anions have been observed and shows that anion chemistry plays a role in the formation of complex organics within a planetary atmosphere as well as in the interstellar medium.

Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere

International Nuclear Information System (INIS)

Desai, R. T.; Coates, A. J.; Wellbrock, A.; González-Caniulef, D.; Jones, G. H.; Lewis, G. R.; Taylor, S. A.; Kataria, D. O.; Vuitton, V.; Crary, F. J.; Shebanits, O.; Wahlund, J.-E.; Waite, J. H.; Cordiner, M.; Sittler, E. C.; Edberg, N. J. T.

2017-01-01

Cassini discovered a plethora of neutral and ionized molecules in Titan’s ionosphere including, surprisingly, anions and negatively charged molecules extending up to 13,800 u q"−"1. In this Letter, we forward model the Cassini electron spectrometer response function to this unexpected ionospheric component to achieve an increased mass resolving capability for negatively charged species observed at Titan altitudes of 950–1300 km. We report on detections consistently centered between 25.8 and 26.0 u q"−"1 and between 49.0–50.1 u q"−"1 which are identified as belonging to the carbon chain anions, CN"−/C_3N"− and/or C_2H"−/C_4H"−, in agreement with chemical model predictions. At higher ionospheric altitudes, detections at 73–74 u q"−"1 could be attributed to the further carbon chain anions C_5N"−/C_6H"− but at lower altitudes and during further encounters extend over a higher mass/charge range. This, as well as further intermediary anions detected at >100 u, provide the first evidence for efficient anion chemistry in space involving structures other than linear chains. Furthermore, at altitudes below <1100 km, the low-mass anions (<150 u q"−"1) were found to deplete at a rate proportional to the growth of the larger molecules, a correlation that indicates the anions are tightly coupled to the growth process. This study adds Titan to an increasing list of astrophysical environments where chain anions have been observed and shows that anion chemistry plays a role in the formation of complex organics within a planetary atmosphere as well as in the interstellar medium.

Five Stereoactive Orbitals on Silicon: Charge and Spin Localization in the n-Si4Me10(-•) Radical Anion by Trigonal Bipyramidalization.

Science.gov (United States)

MacLeod, Matthew K; Michl, Josef

2013-05-16

RIUMP2/def2-TZVPPD calculations show that in addition to its usual conformation with charge and spin delocalized over the Si backbone, the isolated Si4Me10(-•) radical anion also has isomeric conformations with localized charge and spin. A structure with localization on a terminal Si atom has been examined in detail. In vacuum, it is calculated to lie 11.5 kcal/mol higher in energy than the charge-and-spin delocalized conformation, and in water the difference is as little as 1.6 kcal/mol. According to natural orbital and localized orbital analyses, the charge-and-spin-carrying terminal Si atom uses five stereoactive hybrid orbitals in a trigonal bipyramidal geometry. Four are built mostly from 3s and 3p atomic orbitals (AOs) and are used to attach a Si3(CH3)7 and three CH3 groups, whereas the larger equatorial fifth orbital is constructed from 4s and 4p AOs and acts as a nonbonding (radical) hybrid orbital with an occupancy of about 0.65 e.

High Guanidinium Permeability Reveals Dehydration-Dependent Ion Selectivity in the Plasmodial Surface Anion Channel

Directory of Open Access Journals (Sweden)

Abdullah A. B. Bokhari

2014-01-01

Full Text Available Malaria parasites grow within vertebrate erythrocytes and increase host cell permeability to access nutrients from plasma. This increase is mediated by the plasmodial surface anion channel (PSAC, an unusual ion channel linked to the conserved clag gene family. Although PSAC recognizes and transports a broad range of uncharged and charged solutes, it must efficiently exclude the small Na+ ion to maintain infected cell osmotic stability. Here, we examine possible mechanisms for this remarkable solute selectivity. We identify guanidinium as an organic cation with high permeability into human erythrocytes infected with Plasmodium falciparum, but negligible uptake by uninfected cells. Transport characteristics and pharmacology indicate that this uptake is specifically mediated by PSAC. The rank order of organic and inorganic cation permeabilities suggests cation dehydration as the rate-limiting step in transport through the channel. The high guanidinium permeability of infected cells also allows rapid and stringent synchronization of parasite cultures, as required for molecular and cellular studies of this pathogen. These studies provide important insights into how nutrients and ions are transported via PSAC, an established target for antimalarial drug development.

Design and synthesis of a water-stable anionic uranium-based metal-organic framework (MOF) with ultra large pores

Energy Technology Data Exchange (ETDEWEB)

Li, Peng; Vermeulen, Nicolaas A.; Gong, Xirui; Malliakas, Christos D.; Stoddart, J. Fraser; Hupp, Joseph T. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; Farha, Omar K. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; King Abdulaziz Univ., Jeddah (Saudi Arabia). Dept. of Chemistry

2016-08-22

Ionic metal-organic frameworks (MOFs) are a subclass of porous materials that have the ability to incorporate different charged species in confined nanospace by ion-exchange. To date, however, very few examples combining mesoporosity and water stability have been realized in ionic MOF chemistry. Herein, we report the rational design and synthesis of a water-stable anionic mesoporous MOF based on uranium and featuring tbo-type topology. The resulting tbo MOF exhibits exceptionally large open cavities (3.9 nm) exceeding those of all known anionic MOFs. By supercritical CO{sub 2} activation, a record-high Brunauer-Emmett-Teller (BET) surface area (2100 m{sup 2} g{sup -1}) for actinide-based MOFs has been obtained. Most importantly, however, this new uranium-based MOF is water-stable and able to absorb positively charged ions selectively over negatively charged ones, enabling the efficient separation of organic dyes and biomolecules.

Daylight-driven photocatalytic degradation of ionic dyes with negatively surface-charged In{sub 2}S{sub 3} nanoflowers: dye charge-dependent roles of reactive species

Energy Technology Data Exchange (ETDEWEB)

Ge, Suxiang [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China); Cai, Lejuan, E-mail: 494169965@qq.com [Central China Normal University, Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry (China); Li, Dapeng, E-mail: lidapengabc@126.com; Fa, Wenjun; Zhang, Yange; Zheng, Zhi [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China)

2015-12-15

Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In{sub 2}S{sub 3} nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In{sub 2}S{sub 3} nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

An ab initio study on BeX 3- superhalogen anions (X = F, Cl, Br)

Science.gov (United States)

Anusiewicz, Iwona; Skurski, Piotr

2002-06-01

The vertical electron detachment energies (VDE) of 10 BeX 3- (X = F, Cl, Br) anions were calculated at the outer valence Green function (OVGF) level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for BeF 3- system (7.63 eV). All negatively charged species possess the vertical electron detachment energies that are larger than 5.5 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the BeX 3- species on the ligand-central atom (Be-X) distance and on the partial atomic charge localized on Be was observed and discussed, as well as the other factors that may influence the electronic stability of such anions. In addition, the usefulness of the various theoretical treatments for estimating the VDEs of superhalogen anions was tested and analyzed.

Ultrathin nanofibrous films prepared from cadmium hydroxide nanostrands and anionic surfactants.

Science.gov (United States)

Peng, Xinsheng; Karan, Santanu; Ichinose, Izumi

2009-08-04

We developed a simple fabrication method of ultrathin nanofibrous films from the dispersion of cadmium hydroxide nanostrands and anionic surfactants. The nanostrands were prepared in a dilute aqueous solution of cadmium chloride by using 2-aminoethanol. They were highly positively charged and gave bundlelike fibers upon mixing an aqueous solution of anionic surfactant. The nanostrand/surfactant composite fibers were filtered on an inorganic membrane filter. The resultant nanofibrous film was very uniform in the area of a few centimeters square when the thickness was not less than 60 nm. The films obtained with sodium tetradecyl sulfate (STS) had a composition close to the electroneutral complex, [Cd37(OH)68(H2O)n] x 6(STS), as confirmed by energy dispersive X-ray analysis. They were water-repellent with a contact angle of 117 degrees, and the value slightly decreased with the alkyl chain length of anionic surfactants. Ultrathin nanofibrous films were stable enough to be used for ultrafiltration at pressure difference of 90 kPa. We could effectively separate Au nanoparticles of 40 nm at an extremely high filtration rate of 14000 L/(h m2 bar).

Patchy proteins, anions and the Hofmeister series

Energy Technology Data Exchange (ETDEWEB)

Lund, Mikael; Jungwirth, Pavel [Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo namesti 2, 16610 Prague 6 (Czech Republic); Center for Complex Molecular Systems and Biomolecules, Flemingovo namesti 2, 16610 Prague 6 (Czech Republic)], E-mail: mikael.lund@uochb.cas.cz

2008-12-10

We investigate specific anion binding to a range of patchy protein models and use our results to probe protein-protein interactions for aqueous lysozyme solutions. Our molecular simulation studies show that the ion-protein interaction mechanism and strength largely depend on the nature of the interfacial amino acid residues. Via direct ion pairing, small anions interact with charged side-chains while larger anions are attracted to non-polar residues due to several solvent assisted mechanisms. Incorporating ion and surface specificity into a mesoscopic model for protein-protein interactions we calculate the free energy of interaction between lysozyme molecules in aqueous solutions of sodium chloride and sodium iodide. In agreement with experiment, our finding is that 'salting out' follows the reverse Hofmeister series for pH below the iso-electric point and the direct series for pH above pI.

Production, transport and charge capture measurements of highly charged recoil ions

International Nuclear Information System (INIS)

Trebus, U.E.

1989-01-01

An experiment is described to study highly charged recoil ions on-line to the heavy accelerator UNILAC at GSI. The highly charged recoil ions are produced by heavy-ion bombardment of a gas target. Subsequently the slow highly charged recoil ions are extracted from the ionization volume, and guided through a beam transport line to a Wien filter for charge state selection and to a collision region to study charge transfer processes. Several experiments were carried out to show the efficient charge state separation. Charge states up to q = 15 were observed. When using a retarding field analyzer cross sections for single electron capture were determined for different charge states of Xe q+ for q = 4 to 11 and He gas. The experiments demonstrated increasing charge transfer cross sections with increasing charge state q and indicated the effect of near resonant charge capture for q = 6. The flexible data acquisition system used, is described and other future experiments, such as for instance in flight ion-trapping are indicated in the appendix

Production, transport and charge capture measurements of highly charged recoil ions

International Nuclear Information System (INIS)

Trebus, U.E.

1989-05-01

An experiment is described to study highly charged recoil ions on-line to the heavy ion accelerator UNILAC at GSI. The highly charged recoil ions are produced by heavy ion bombardment of a gas target. Subsequently the slow highly charged recoil ions are extracted from the ionization volume, and guided through a beam transport line to a Wien filter for charge state selection and to a collision region to study charge transfer processes. Several experiments were carried out to show the efficient charge state separation. Charge states up to q=15 were observed. When using a retarding field analyzer cross sections for single electron capture were determined for different charge states of Xe q+ for q=4 to 11 and He gas. The experiments demonstrated increasing charge transfer cross sections with increasing charge state q and indicated the effect of near resonant charge capture for q=6. The flexible data acquisition system used, is described and other future experiments, such as for instance in flight ion-trapping are indicated in the appendix. (orig.)

Separation and determination of alditols and sugars by high-pH anion-exchange chromatography with pulsed amperometric detection

DEFF Research Database (Denmark)

Andersen, Rikke; Sørensen, A.

2000-01-01

Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic-pulsed a......Carbohydrates such as alditols (polyols or sugar alcohols), monosaccharides and disaccharides are separated as anions by anion-exchange chromatography with a sodium hydroxide eluent, MA1 CarboPac column and pulsed amperometric detection. We report a high-pH anion-exchange chromatographic......-pulsed amperometric detection (HPAEC-PAD) method that determines all the polyols used as food additives in food products and the most commonly found mono- and disaccharides on a routine basis. The linearity, repeatability, internal reproducibility and accuracy are described. The applicability of the method has been...

Ab initio investigation of sulfur monofluoride and its singly charged cation and anion in their ground electronic state

International Nuclear Information System (INIS)

Li Song; Chen Shan-Jun; Chen Yan; Chen Peng

2016-01-01

The SF radical and its singly charged cation and anion, SF + and SF − , have been investigated on the MRCI/aug-cc-pVXZ (X = Q, 5, 6) levels of theory with Davidson correction. Both the core–valence correlation and the relativistic effect are considered. The extrapolating to the complete basis set (CBS) limit is adopted to remove the basis set truncation error. Geometrical parameters, potential energy curves (PECs), vibrational energy levels, spectroscopic constants, ionization potentials, and electron affinities of the ground electronic state for all these species are obtained. The information with respect to molecular characteristics of the SF n (n = −1, 0, +1) systems derived in this work will help to extend our knowledge and to guide further experimental or theoretical researches. (paper)

Anion retention in soil: Possible application to reduce migration of buried technetium and iodine

International Nuclear Information System (INIS)

Gu, B.; Schulz, R.K.

1991-10-01

This report summarizes a literature review of our present knowledge of the anion exchange properties of a number of soils and minerals, which may potentially be used as anion exchangers to retard migration of such anions as iodide (I - ), iodate (IO 3 - ) and pertechnetate (TcO 4 - ) away from disposal site. The amorphous clays allophane and imogolite, are found to be among the most important soil components capable of developing appreciable amounts of positive charge for anion exchange even at about neutral pH. Decreases in the SiO 2 /Al 2 O 3 ratio and soil pH result in an increase in soil AEC. Allophane and imogolite rich soils have an AEC ranging from 1 to 18 meq/100g at pH about 6. Highly weathered soils dominated by Fe and Al oxides and kaolinite may develop a significant amount of AEC as soil pH falls. The retention of iodine (I) and technetium (T c ), by soils is associated with both soil organic matter, and Fe and Al oxides, whereas sorption on layer silicate minerals in negligible. Fe and Al oxides become more important in the retention of anionic I - , IO 3 - , and TcO 4 - as pH falls, since more positive charge is developed on the oxide surfaces. Although few studies, if any, have been conducted on I and T c sorption by soil allophane and imogolite, it is estimated that a surface plough soil (2 million pounds soil per acre) with 5 meq/100g AEC, as is commonly found in andisols, shall retain approximately 5900 kg I and 4500 kg T c . It is conceivable that an anion exchanger such as an andisol could be used to modify the near field environment of a radioactive waste disposal facility. This whole disposal system would then offer similar migration resistance to anions as is normally afforded to cations by usual and normal soils. 93 refs., 10 figs., 7 tabs

Anion retention in soil: Possible application to reduce migration of buried technetium and iodine

Energy Technology Data Exchange (ETDEWEB)

Gu, B.; Schulz, R.K. (California Univ., Berkeley, CA (United States). Dept. of Soil Science)

1991-10-01

This report summarizes a literature review of our present knowledge of the anion exchange properties of a number of soils and minerals, which may potentially be used as anion exchangers to retard migration of such anions as iodide (I{sup {minus}}), iodate (IO{sub 3}{sup {minus}}) and pertechnetate (TcO{sub 4}{sup {minus}}) away from disposal site. The amorphous clays allophane and imogolite, are found to be among the most important soil components capable of developing appreciable amounts of positive charge for anion exchange even at about neutral pH. Decreases in the SiO{sub 2}/Al{sub 2}O{sub 3} ratio and soil pH result in an increase in soil AEC. Allophane and imogolite rich soils have an AEC ranging from 1 to 18 meq/100g at pH about 6. Highly weathered soils dominated by Fe and Al oxides and kaolinite may develop a significant amount of AEC as soil pH falls. The retention of iodine (I) and technetium ({Tc}), by soils is associated with both soil organic matter, and Fe and Al oxides, whereas sorption on layer silicate minerals in negligible. Fe and Al oxides become more important in the retention of anionic I{sup {minus}}, IO{sub 3}{sup {minus}}, and TcO{sub 4}{sup {minus}} as pH falls, since more positive charge is developed on the oxide surfaces. Although few studies, if any, have been conducted on I and {Tc} sorption by soil allophane and imogolite, it is estimated that a surface plough soil (2 million pounds soil per acre) with 5 meq/100g AEC, as is commonly found in andisols, shall retain approximately 5900 kg I and 4500 kg {Tc}. It is conceivable that an anion exchanger such as an andisol could be used to modify the near field environment of a radioactive waste disposal facility. This whole disposal system would then offer similar migration resistance to anions as is normally afforded to cations by usual and normal soils. 93 refs., 10 figs., 7 tabs.

Proton surface charge determination in Spodosol horizons with organically bound aluminum

Science.gov (United States)

Skyllberg, Ulf; Borggaard, Ole K.

1998-05-01

Net proton surface charge densities were determined in O, E, Bh, and Bs horizons of a sandy till, Spodosol from Denmark, by means of acid-base titration combined with ion adsorption in 0.005 M Ca(NO 3) 2 and independent permanent charge determination. The release of organic anions exceeded the adsorption of NO 3-, resulting in a desorption of anions in all horizons. Data were found to obey the law of balance between surface charges and adsorbed ions only when charges pertaining to Al and organic anions released during the titration experiments were accounted for, in addition to charges pertaining the potential determining ions (PDI) H + and OH - and the index ions Ca 2+ and NO 3-. It was furthermore shown that the point of zero net proton charge (PZNPC) in soils highly depends on the concentration of organically bound Al. Approaches previously used in soils, in which adsorbed Al n+ has been ignored (i.e., considered equivalent to nH + as a PDI), resulted in a PZNPC of 4.1 in the Bs horizon. If instead organically bound Al was accounted for as a counter-ion similar to 3/2Ca 2+, a PZNPC of 2.9 was obtained for the same Bs horizon. Based on PZNPC values estimated by the latter approach, combined with a weak-acid analog, it was shown that organic proton surface charges buffered pH with a similar intensity in the O, E, Bh, and Bs horizons of this study. Because the acidity of Al adsorbed to conjugate bases of soil organic acids is substantially weaker than the acidity of the corresponding protonated form of the organic acids, the point of zero net proton charge (PZNPC) will increase if the concentration of organically adsorbed Al increases at the expense of adsorbed H. This means that PZNPC values determined for soils with unknown concentrations of organically adsorbed Al are highly operational and not very meaningful as references.

Design and synthesis of a water-stable anionic uranium-based metal-organic framework (MOF) with ultra large pores

Energy Technology Data Exchange (ETDEWEB)

Li, Peng; Vermeulen, Nicolaas A.; Gong, Xirui; Malliakas, Christos D.; Stoddart, J. Fraser; Hupp, Joseph T. [Department of Chemistry, Northwestern University, Evanston, IL (United States); Farha, Omar K. [Department of Chemistry, Northwestern University, Evanston, IL (United States); Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia)

2016-08-22

Ionic metal-organic frameworks (MOFs) are a subclass of porous materials that have the ability to incorporate different charged species in confined nanospace by ion-exchange. To date, however, very few examples combining mesoporosity and water stability have been realized in ionic MOF chemistry. Herein, we report the rational design and synthesis of a water-stable anionic mesoporous MOF based on uranium and featuring tbo-type topology. The resulting tbo MOF exhibits exceptionally large open cavities (3.9 nm) exceeding those of all known anionic MOFs. By supercritical CO{sub 2} activation, a record-high Brunauer-Emmett-Teller (BET) surface area (2100 m{sup 2} g{sup -1}) for actinide-based MOFs has been obtained. Most importantly, however, this new uranium-based MOF is water-stable and able to absorb positively charged ions selectively over negatively charged ones, enabling the efficient separation of organic dyes and biomolecules. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

The role of surface charge in cellular uptake and cytotoxicity of medical nanoparticles

Directory of Open Access Journals (Sweden)

Fröhlich E

2012-11-01

Full Text Available Eleonore FröhlichCenter for Medical Research, Medical University of Graz, Graz, AustriaAbstract: Many types of nanoparticles (NPs are tested for use in medical products, particularly in imaging and gene and drug delivery. For these applications, cellular uptake is usually a prerequisite and is governed in addition to size by surface characteristics such as hydrophobicity and charge. Although positive charge appears to improve the efficacy of imaging, gene transfer, and drug delivery, a higher cytotoxicity of such constructs has been reported. This review summarizes findings on the role of surface charge on cytotoxicity in general, action on specific cellular targets, modes of toxic action, cellular uptake, and intracellular localization of NPs. Effects of serum and intercell type differences are addressed. Cationic NPs cause more pronounced disruption of plasma-membrane integrity, stronger mitochondrial and lysosomal damage, and a higher number of autophagosomes than anionic NPs. In general, nonphagocytic cells ingest cationic NPs to a higher extent, but charge density and hydrophobicity are equally important; phagocytic cells preferentially take up anionic NPs. Cells do not use different uptake routes for cationic and anionic NPs, but high uptake rates are usually linked to greater biological effects. The different uptake preferences of phagocytic and nonphagocytic cells for cationic and anionic NPs may influence the efficacy and selectivity of NPs for drug delivery and imaging.Keywords: endocytosis, plasma membrane, lysosomes, polystyrene particles, quantum dots, dendrimers

Ultracold Anions for High-Precision Antihydrogen Experiments.

Science.gov (United States)

Cerchiari, G; Kellerbauer, A; Safronova, M S; Safronova, U I; Yzombard, P

2018-03-30

Experiments with antihydrogen (H[over ¯]) for a study of matter-antimatter symmetry and antimatter gravity require ultracold H[over ¯] to reach ultimate precision. A promising path towards antiatoms much colder than a few kelvin involves the precooling of antiprotons by laser-cooled anions. Because of the weak binding of the valence electron in anions-dominated by polarization and correlation effects-only few candidate systems with suitable transitions exist. We report on a combination of experimental and theoretical studies to fully determine the relevant binding energies, transition rates, and branching ratios of the most promising candidate La^{-}. Using combined transverse and collinear laser spectroscopy, we determined the resonant frequency of the laser cooling transition to be ν=96.592 713(91)  THz and its transition rate to be A=4.90(50)×10^{4}  s^{-1}. Using a novel high-precision theoretical treatment of La^{-} we calculated yet unmeasured energy levels, transition rates, branching ratios, and lifetimes to complement experimental information on the laser cooling cycle of La^{-}. The new data establish the suitability of La^{-} for laser cooling and show that the cooling transition is significantly stronger than suggested by a previous theoretical study.

Vertical detachment energies of anionic thymidine: Microhydration effects.

Science.gov (United States)

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)].

Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

Science.gov (United States)

Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

2016-03-01

Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H]2- ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H]3- ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H]2- ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H]3- ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

Formation of interstellar anions

Science.gov (United States)

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

Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

Directory of Open Access Journals (Sweden)

Siekierka Anna

2017-01-01

Full Text Available Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity and energy requirements in charge/discharge steps. We described a configuration with anion-exchange membrane characterized by adsorption capacity of 35 mg/g of Li+ with 0.08Wh/g and removal efficiency of 60 % of lithium ions, using novel selective desalination technique.

Hybrid capacitive deionization with anion-exchange membranes for lithium extraction

Science.gov (United States)

Siekierka, Anna; Bryjak, Marek

2017-11-01

Lithium is considered to be a critical material for various industrial fields. We present our studies on extraction lithium from diluted aqueous solution by novel hybrid system based on a membrane capacitive deionization and batteries desalination. Hybrid CDI is comprised by a lithium selective adsorbent, activated carbon electrode and anion-exchange membranes. Here, we demonstrated implication of various type of anion-exchange membranes and influence their properties on effective capacity and energy requirements in charge/discharge steps. We described a configuration with anion-exchange membrane characterized by adsorption capacity of 35 mg/g of Li+ with 0.08Wh/g and removal efficiency of 60 % of lithium ions, using novel selective desalination technique.

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Bowman-James, K.; Wilson, G.; Moyer, B. A.

2004-01-01

This project involves the design and synthesis of receptors for oxoanions of environmental importance, including emphasis on high level and low activity waste. Target anions have included primarily oxoanions and a study of the basic concepts behind selective binding of target anions. A primary target has been sulfate because of its deleterious influence on the vitrification of tank wastes

Adsorption of anionic surfactant on porous and nonporous polyethylene terephthalate films

International Nuclear Information System (INIS)

Yamauchi, Yu.; Apel, P.Yu.

2016-01-01

We study the adsorption of anionic surfactant, sodium dodecyl diphenyloxide disulfonate (SDDD) on three types of polyethylene terephthalate (PET) substrates from aqueous solutions of SDDD of different concentrations. Neutral electrolyte (KCl) was added to the solutions to vary the ionic strength. Three types of substrates were used: 1) original PET film; 2) etched nonporous film, obtained from pristine film by chemical etching and bearing negative charge on the surface; 3) etched porous membranes, fabricated from pristine film by ion irradiation and subsequent chemical etching. The membranes have negative charge on the flat surface and on the inner pore walls. The comparison shows that the negative charge on the flat surface has weak effect on adsorption of the anionic surfactant, and the SDDD adsorption on the inner walls of pores is much weaker than on flat surface, even if the pore radius is significantly larger than the Debye length. This «exclusion» effect strongly depends on ionic strength of solution. [ru

Infrared spectroscopic studies on the cluster size dependence of charge carrier structure in nitrous oxide cluster anions

International Nuclear Information System (INIS)

Thompson, Michael C.; Weber, J. Mathias

2016-01-01

We report infrared photodissociation spectra of nitrous oxide cluster anions of the form (N 2 O) n O − (n = 1–12) and (N 2 O) n − (n = 7–15) in the region 800–1600 cm −1 . The charge carriers in these ions are NNO 2 − and O − for (N 2 O) n O − clusters with a solvation induced core ion switch, and N 2 O − for (N 2 O) n − clusters. The N–N and N–O stretching vibrations of N 2 O − (solvated by N 2 O) are reported for the first time, and they are found at (1595 ± 3) cm −1 and (894 ± 5) cm −1 , respectively. We interpret our infrared spectra by comparison with the existing photoelectron spectroscopy data and with computational data in the framework of density functional theory.

Chloride Anions Regulate Kinetics but Not Voltage-Sensor Qmax of the Solute Carrier SLC26a5.

Science.gov (United States)

Santos-Sacchi, Joseph; Song, Lei

2016-06-07

In general, SLC26 solute carriers serve to transport a variety of anions across biological membranes. However, prestin (SLC26a5) has evolved, now serving as a motor protein in outer hair cells (OHCs) of the mammalian inner ear and is required for cochlear amplification, a mechanical feedback mechanism to boost auditory performance. The mechanical activity of the OHC imparted by prestin is driven by voltage and controlled by anions, chiefly intracellular chloride. Current opinion is that chloride anions control the Boltzmann characteristics of the voltage sensor responsible for prestin activity, including Qmax, the total sensor charge moved within the membrane, and Vh, a measure of prestin's operating voltage range. Here, we show that standard narrow-band, high-frequency admittance measures of nonlinear capacitance (NLC), an alternate representation of the sensor's charge-voltage (Q-V) relationship, is inadequate for assessment of Qmax, an estimate of the sum of unitary charges contributed by all voltage sensors within the membrane. Prestin's slow transition rates and chloride-binding kinetics adversely influence these estimates, contributing to the prevalent concept that intracellular chloride level controls the quantity of sensor charge moved. By monitoring charge movement across frequency, using measures of multifrequency admittance, expanded displacement current integration, and OHC electromotility, we find that chloride influences prestin kinetics, thereby controlling charge magnitude at any particular frequency of interrogation. Importantly, however, this chloride dependence vanishes as frequency decreases, with Qmax asymptoting at a level irrespective of the chloride level. These data indicate that prestin activity is significantly low-pass in the frequency domain, with important implications for cochlear amplification. We also note that the occurrence of voltage-dependent charge movements in other SLC26 family members may be hidden by inadequate

Evaluation of chitosan–anionic polymers based tablets for extended-release of highly water-soluble drugs

Directory of Open Access Journals (Sweden)

Yang Shao

2015-02-01

Full Text Available The objective of this study is to develop chitosan–anionic polymers based extended-release tablets and test the feasibility of using this system for the sustained release of highly water-soluble drugs with high drug loading. Here, the combination of sodium valproate (VPS and valproic acid (VPA were chosen as the model drugs. Anionic polymers studied include xanthan gum (XG, carrageenan (CG, sodium carboxymethyl cellulose (CMC-Na and sodium alginate (SA. The tablets were prepared by wet granulation method. In vitro drug release was carried out under simulated gastrointestinal condition. Drug release mechanism was studied. Compared with single polymers, chitosan–anionic polymers based system caused a further slowdown of drug release rate. Among them, CS–xanthan gum matrix system exhibited the best extended-release behavior and could extend drug release for up to 24 h. Differential scanning calorimetry (DSC and Fourier transform infrared spectroscopy (FTIR studies demonstrated that polyelectrolyte complexes (PECs were formed on the tablet surface, which played an important role on retarding erosion and swelling of the matrix in the later stage. In conclusion, this study demonstrated that it is possible to develop highly water-soluble drugs loaded extended-release tablets using chitosan–anionic polymers based system.

Distribution of anionic sites in Bruch's membrane of the rabbit eye.

Science.gov (United States)

Essner, E; Pino, R M

1982-06-01

The organization of anionic (negatively charged) sites in Bruch's membrane of the rabbit eye at various stages of postnatal development was studied using the cationic polymer, polyethyleneimine (PEI). PEI-positive sites were demonstrable as rows of particles (diameter ca. 18 nm) located at intervals along either side of the basal laminae of the retinal pigment epithelium and choriocapillary endothelium. In tangential sections through Bruch's membrane, stained particles appeared to be arranged in a semi-regular, lattice-like pattern in which the sites were separated from each other by an interval of approximately 50 nm. PEI-positive particles were also observed on collagen fibers where they were distributed at regular intervals along the length of the fiber. In tangential sections, collagen fibers formed a loosely packed meshwork in the central zone of Bruch's membrane. In addition, individual fibers were frequently oriented so that one end was located close to or within the substance of the basal laminae, a result suggesting that the anionic sites on these fibers might contribute to the network present in the basal laminae. The findings lend further support to the suggestion that anionic sites in Bruch's membrane may serve as a charge barrier which retards the movement of anionic molecules that are in transit from the choriocapillaris to the retinal pigment epithelium and outer neural retina.

Intramolecular, Exciplex-Mediated, Proton-Coupled, Charge-Transfer Processes in N,N-Dimethyl-3-(1-pyrenyl)propan-1-ammonium Cations: Influence of Anion, Solvent Polarity, and Temperature.

Science.gov (United States)

Safko, Trevor M; Faleiros, Marcelo M; Atvars, Teresa D Z; Weiss, Richard G

2016-06-16

An intramolecular exciplex-mediated, proton-coupled, charge-transfer (PCCT) process has been investigated for a series of N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium cations with different anions (PyS) in solvents of low to intermediate polarity over a wide temperature range. Solvent mediates both the equilibrium between conformations of the cation that place the pyrenyl and ammonium groups in proximity (conformation C) or far from each other (conformation O) and the ability of the ammonium group to transfer a proton adiabatically in the PyS excited singlet state. Thus, exciplex emission, concurrent with the PCCT process, was observed only in hydrogen-bond accepting solvents of relatively low polarity (tetrahydrofuran, ethyl acetate, and 1,4-dioxane) and not in dichloromethane. From the exciplex emission and other spectroscopic and thermodynamic data, the acidity of the ammonium group in conformation C of the excited singlet state of PyS (pKa*) has been estimated to be ca. -3.4 in tetrahydrofuran. The ratios between the intensities of emission from the exciplex and the locally excited state (IEx/ILE) appear to be much more dependent on the nature of the anion than are the rates of exciplex formation and decay, although the excited state data do not provide a quantitative measure of the anion effect on the C-O equilibrium. The activation energies associated with exciplex formation in THF are calculated to be 0.08 to 0.15 eV lower than for the neutral amine, N,N-dimethyl-3-(1-pyrenyl)propan-1-amine. Decay of the exciplexes formed from the deprotonation of PyS is hypothesized to occur through charge-recombination processes. To our knowledge, this is the first example in which photoacidity and intramolecular exciplex formation (i.e., a PCCT reaction) are coupled.

Production and application of cation/anion exchange membranes of high performance

International Nuclear Information System (INIS)

Xu Zhili; Tan Chunhong; Yang Xiangmin

1995-01-01

A third affiliated factory of our university has been established for the production in batches of cation/anion exchange membranes of high performance, trade marks of which are HF-1 and HF-2. Membrane products have been applied in various fields (including industries and research institutions) with great success

A density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic gold clusters

Science.gov (United States)

Wu, X.; Senapati, L.; Nayak, S. K.; Selloni, A.; Hajaligol, M.

2002-08-01

CO adsorption on small cationic, neutral, and anionic Aun (n=1-6) clusters has been investigated using density functional theory in the generalized gradient approximation. Among various possible CO adsorption sites, the on-top (one-fold coordinated) is found to be the most favorable one, irrespective of the charge state of the cluster. In addition, planar structures are preferred by both the bare and the CO-adsorbed clusters. The adsorption energies of CO on the cationic clusters are generally greater than those on the neutral and anionic complexes, and decrease with size. The adsorption energies on the anions, instead, increase with cluster size and reach a local maximum at Au5CO-, in agreement with recent experiment. The differences in adsorption energies for the different charge states decrease with increasing cluster size.

Improvement of calcium mineral separation contrast using anionic reagents: electrokinetics properties and flotation

Science.gov (United States)

Lafhaj, Z.; Filippov, L. O.; Filippova, I. V.

2017-07-01

The flotation separation of salt type calcium minerals is problematic, due to the similarities in their same active Ca2+ related site for interaction with anionic collectors and similar physicochemical characteristics such as solubility, zero-point charge, surface speciation and Ca-site density. The work was performed to achieve effective and selective separation of the calcium-minerals using pure minerals samples: orange calcite with Mg impurities, optic calcite with impurities level and an apatite. The pure samples surface was examined using techniques sensitive near-surface like infrared spectroscopy (FTIR) and chemical composition was obtained by ICPMS. The isoelectric point (IEP) and point of zero charge (PZC) in electrolyte were recorded using electrophoresis method at different ionic strengths of the solution. Mechanisms of charge development at the mineral-water interface are discussed. The time of contact as important parameter for the charge equilibrium was deduced from kinetics study and fixed to 30 minutes. The difference in the values obtained between IEP and PZSE can be explained by the presence of a specific adsorption of cations and anions on the surface. The effect of pure anionic collectors such as oleic and linoleic acid were studied. At low pH, both collectors lead to a good recovery for the calcites. The flotation recovery of optic calcite at pH 9 with sodium oleate is higher than with sodium linoleate. At alkaline pH, apatite showed a better recovery with sodium linoleate.

Novel use of positively charged nylon transfer membranes for trapping indoleacetic acid or other small anions during efflux from plant tissues

Science.gov (United States)

Evans, M. L.; Hangarter, R. P.

1993-01-01

Positively charged nylon blotting membranes were used as an anion binding medium to trap [14C]indoleactic acid (IAA) as it exited cells at the basal ends of Coleus blumei L. stem and Zea mays L. coleoptile segments. Autoradiography was used to visualize where the [14C] that moved out of the cut ends was localized on the nylon membrane. Diffusion of [14C]IAA from the initial point of contact with the nylon membrane was minimal. Comparison of the autoradiograms with anatomical tissue prints of the cut ends of the segments was used to determine what tissues participate in IAA movement. The results of these initial studies were consistent with other reports suggesting that [14C]IAA movement was primarily associated with vascular tissues in both C. blumei stems and corn coleoptiles, but the resolution was not sufficient to identify which vascular tissues were involved in IAA transport. With further refinements, this technique could also be used for studying the movement of other small charged molecules through plant tissues.

An Anthracene-Based Tripodal Chemosensor for Anion Sensing

Directory of Open Access Journals (Sweden)

Whitney A. Quinn

2010-05-01

Full Text Available An anthracene-based tripodal ligand was synthesized from the condensation of tren with 9-anthraldehyde, and the subsequent reduction with sodium borohydride. The neutral ligand was protonated from the reaction with p-toluenesulfonic acid to give a triply charged chemosensor that was examined for its anion binding ability toward fluoride, chloride, bromide, sulfate and nitrate by the fluorescence spectroscopy in DMSO. The addition of an anion to the ligand resulted in an enhancement in fluorescence intensity at the excitation of 310 nm. Analysis of the spectral changes suggested that the ligand formed a 1:1 complex with each of the anions, showing strong affinity for fluoride and sulfate in DMSO. The unsubstituted tren was reacted with sulfuric acid to form a sulfate complex and the structure was determined by the X-ray crystallography. Analysis of the complex revealed that three sulfates are held between two ligands by multiple hydrogen bonding interactions with protonated amines.

Benzonitrile: Electron affinity, excited states, and anion solvation

Science.gov (United States)

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.

Atomic force microscopy study of anion intercalation into highly oriented pyrolytic graphite

Energy Technology Data Exchange (ETDEWEB)

Alliata, D; Haering, P; Haas, O; Koetz, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H [University of Berne (Switzerland)

1999-08-01

In the context of ion transfer batteries, we studied highly oriented pyrolytic graphite (HOPG) in perchloric acid, as a model to elucidate the mechanism of electrochemical intercalation in graphite. Aim of the work is the local and time dependent investigation of dimensional changes of the host material during electrochemical intercalation processes on the nanometer scale. We used atomic force microscopy (AFM), combined with cyclic voltammetry, as in-situ tool of analysis during intercalation and expulsion of perchloric anions into the HOPG electrodes. According to the AFM measurements, the HOPG interlayer spacing increases by 32% when perchloric anions intercalate, in agreement with the formation of stage IV of graphite intercalation compounds. (author) 3 figs., 3 refs.

A Cation-containing Polymer Anion Exchange Membrane based on Poly(norbornene)

Science.gov (United States)

Beyer, Frederick; Price, Samuel; Ren, Xiaoming; Savage, Alice

Cation-containing polymers are being studied widely for use as anion exchange membranes (AEMs) in alkaline fuel cells (AFCs) because AEMs offer a number of potential benefits including allowing a solid state device and elimination of the carbonate poisoning problem. The successful AEM will combine high performance from several orthogonal properties, having robust mechanical strength even when wet, high hydroxide conductivity, and the high chemical stability required for long device lifetimes. In this study, we have synthesized a model cationic polymer that combines three of the key advantages of Nafion. The polymer backbone based on semicrystalline atactic poly(norbornene) offers good mechanical properties. A flexible, ether-based tether between the backbone and fixed cation charged species (quaternary ammonium) should provide the low-Tg, hydrophilic environment required to facilitate OH- transport. Finally, methyl groups have been added at the beta position relative to the quaternary ammonium cation to prevent Hoffman elimination, one mechanism by which AEMs are neutralized in a high pH environment. In this poster, we will present our findings on mechanical properties, morphology, charge transport, and chemical stability of this material.

Space-charge compensation of highly charged ion beam from laser ion source

International Nuclear Information System (INIS)

Kondrashev, S.A.; Collier, J.; Sherwood, T.R.

1996-01-01

The problem of matching an ion beam delivered by a high-intensity ion source with an accelerator is considered. The experimental results of highly charged ion beam transport with space-charge compensation by electrons are presented. A tungsten thermionic cathode is used as a source of electrons for beam compensation. An increase of ion beam current density by a factor of 25 is obtained as a result of space-charge compensation at a distance of 3 m from the extraction system. The process of ion beam space-charge compensation, requirements for a source of electrons, and the influence of recombination losses in a space-charge-compensated ion beam are discussed. (author)

Surface charge compensation for a highly charged ion emission microscope

International Nuclear Information System (INIS)

McDonald, J.W.; Hamza, A.V.; Newman, M.W.; Holder, J.P.; Schneider, D.H.G.; Schenkel, T.

2003-01-01

A surface charge compensation electron flood gun has been added to the Lawrence Livermore National Laboratory (LLNL) highly charged ion (HCI) emission microscope. HCI surface interaction results in a significant charge residue being left on the surface of insulators and semiconductors. This residual charge causes undesirable aberrations in the microscope images and a reduction of the Time-Of-Flight (TOF) mass resolution when studying the surfaces of insulators and semiconductors. The benefits and problems associated with HCI microscopy and recent results of the electron flood gun enhanced HCI microscope are discussed

Supramolecular Chemistry of Environmentally Relevant Anions

International Nuclear Information System (INIS)

Bowman-James, Kristin; Moyer, B.A.; Sessler, Jonathan L.

2003-01-01

The goal of this project is the development of highly selective extractants for anions targeting important and timely problems of critical interest to the EMSP mission. In particular, sulfate poses a special problem in cleaning up the Hanford waste tanks in that it interferes with vitrification, but available technologies for sulfate removal are limited. The basic chemical aspects of anion receptor design of functional pH independent systems as well as design of separations strategies for selective and efficient removal of targeted anions have been probed. Key findings include: (1) some of 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 from acidic, nitrate-containing aqueous media. Receptor design, structural influences on anion binding affinities, and findings from liquid-liquid extraction studies will be discussed

Graphene-coated polymeric anion exchangers for ion chromatography

Energy Technology Data Exchange (ETDEWEB)

Zhang, Kai; Cao, Minyi; Lou, Chaoyan [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Wu, Shuchao, E-mail: wushch2002@163.com [Zhejiang Institute of Geology and Mineral Resources, Hangzhou 310007 (China); Zhang, Peimin [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Zhi, Mingyu [Hangzhou Vocational & Technical College, Hangzhou, 310018 (China); Zhu, Yan, E-mail: zhuyan@zju.edu.cn [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China)

2017-06-01

Carbonaceous stationary phases have gained much attention for their peculiar selectivity and robustness. Herein we report the fabrication and application of a graphene-coated polymeric stationary phase for anion exchange chromatography. The graphene-coated particles were fabricated by a facile evaporation-reduction method. These hydrophilic particles were proven appropriate substrates for grafting of hyperbranched condensation polymers (HBCPs) to make pellicular anion exchangers. The new phase was characterized by zeta potentials, Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscope. Frontal displacement chromatography showed that the capacities of the anion exchangers were tuned by both graphene amount and HBCPs layer count. The chromatographic performance of graphene-coated anion exchangers was demonstrated with separation of inorganic anions, organic acids, carbohydrates and amino acids. Good reproducibility was obtained by consecutive injections, indicating high chemical stability of the coating. - Highlights: • Graphene-coated polymeric particles were fabricated by a facile method. • Hyperbranched condensation polymers (HBCPs) were grafted from graphene-coated particles to make anion exchangers. • Graphene amount and HBCPs layer count had significant effects on the anion exchange capacities. • Separation of diverse anionic analytes on the anion exchangers was demonstrated. • The prepared anion exchangers exhibited high stability.

Density functional study of carbon monoxide adsorption on small cationic, neutral, and anionic aluminum nitride clusters

Science.gov (United States)

Guo, Ling

CO adsorption on small cationic, neutral, and anionic (AlN)n (n = 1-6) clusters has been investigated using density functional theory in the generalized gradient approximation. Among various possible CO adsorption sites, an N on-top (onefold coordinated) site is found to be the most favorable one, irrespective of the charge state of the clusters. The adsorption energies of CO on the anionic (AlN)nCO (n = 2-4) clusters are greater than those on the neutral and cationic complexes. The adsorption energies on the cationic and neutral complexes reflect the odd-even oscillations, and the adsorption energies of CO on the cationic (AlN)nCO (n = 5, 6) clusters are greater than those on the neutral and anionic complexes. The adsorption energies for the different charge states decrease with increasing cluster size.

An ab initio study on MgX3- and CaX3- superhalogen anions (X=F, Cl, Br)

International Nuclear Information System (INIS)

Anusiewicz, Iwona; Sobczyk, Monika; Dabkowska, Iwona; Skurski, Piotr

2003-01-01

The vertical electron detachment energies (VDEs) of twenty MX 3 - (M=Mg, Ca; X=F, Cl, Br) anions were calculated at the OVGF level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for MgF 3 - system (8.793 eV). All negatively charged species possess the VDEs that are larger than 5.9 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the MX 3 - species on the ligand-central atom (M-X) distance and on the partial atomic charge localized on Mg or Ca was observed and discussed, as well as the other factors that may influence the electronic stability of such anions

An ab initio study on MgX 3- and CaX 3- superhalogen anions (X=F, Cl, Br)

Science.gov (United States)

Anusiewicz, Iwona; Sobczyk, Monika; Dąbkowska, Iwona; Skurski, Piotr

2003-06-01

The vertical electron detachment energies (VDEs) of twenty MX 3- (M=Mg, Ca; X=F, Cl, Br) anions were calculated at the OVGF level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for MgF 3- system (8.793 eV). All negatively charged species possess the VDEs that are larger than 5.9 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the MX 3- species on the ligand-central atom (M-X) distance and on the partial atomic charge localized on Mg or Ca was observed and discussed, as well as the other factors that may influence the electronic stability of such anions.

Analysis of quaternary ammonium and phosphonium ionic liquids by reversed-phase high-performance liquid chromatography with charged aerosol detection and unified calibration.

Science.gov (United States)

Stojanovic, Anja; Lämmerhofer, Michael; Kogelnig, Daniel; Schiesel, Simone; Sturm, Martin; Galanski, Markus; Krachler, Regina; Keppler, Bernhard K; Lindner, Wolfgang

2008-10-31

Several hydrophobic ionic liquids (ILs) based on long-chain aliphatic ammonium- and phosphonium cations and selected aromatic anions were analyzed by reversed-phase high-performance liquid chromatography (RP-HPLC) employing trifluoroacetic acid as ion-pairing additive to the acetonitrile-containing mobile phase and adopting a step-gradient elution mode. The coupling of charged aerosol detection (CAD) for the non-chromophoric aliphatic cations with diode array detection (DAD) for the aromatic anions allowed their simultaneous analysis in a set of new ILs derived from either tricaprylmethylammonium chloride (Aliquat 336) and trihexyltetradecylphosphonium chloride as precursors. Aliquat 336 is a mix of ammonium cations with distinct aliphatic chain lengths. In the course of the studies it turned out that CAD generates an identical detection response for all the distinct aliphatic cations. Due to lack of single component standards of the individual Aliquat 336 cation species, a unified calibration function was established for the quantitative analysis of the quaternary ammonium cations of the ILs. The developed method was validated according to ICH guidelines, which confirmed the validity of the unified calibration. The application of the method revealed molar ratios of cation to anion close to 1 indicating a quantitative exchange of the chloride ions of the precursors by the various aromatic anions in the course of the synthesis of new ILs. Anomalies of CAD observed for the detection of some aromatic anions (thiosalicylate and benzoate) are discussed.

The effect of interlayer anion on the reactivity of Mg-Al layered double hydroxides: improving and extending the customization capacity of anionic clays.

Science.gov (United States)

Rojas, Ricardo; Bruna, Felipe; de Pauli, Carlos P; Ulibarri, M Ángeles; Giacomelli, Carla E

2011-07-01

Layered double hydroxides (LDHs) reactivity and interfacial behavior are closely interconnected and control particle properties relevant to the wide range of these solids' applications. Despite their importance, their relationship has been hardly described. In this work, chloride and dodecylsulfate (DDS(-)) intercalated LDHs are studied combining experimental data (electrophoretic mobility and contact angle measurements, hydroxyl and organic compounds uptake) and a simple mathematical model that includes anion-binding and acid-base reactions. This approach evidences the anion effect on LDHs interfacial behavior, reflected in the opposite particle charge and the different surface hydrophobic/hydrophilic character. LDHs reactivity are also determined by the interlayer composition, as demonstrated by the cation uptake capability of the DDS(-) intercalated sample. Consequently, the interlayer anion modifies the LDHs interfacial properties and reactivity, which in turn extends the customization capacity of these solids. Copyright © 2011 Elsevier Inc. All rights reserved.

Charge ordered insulating phases of DODHT salts with octahedral anions and a new radical salt, {beta}''-(DODHT){sub 2}TaF{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Nishikawa, H; Oshio, H; Yasuzuka, S [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan); Higa, M; Kondo, R; Kagoshima, S [Department of Basic Science, University of Tokyo, Tokyo 153-8902 (Japan); Nakao, A; Sawa, H [Photon Factory, Institute of Material Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Murata, K [Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan)], E-mail: nishikaw@chem.tsukuba.ac.jp

2008-10-15

Physical properties of isostructural {beta}''-(DODHT){sub 2}X [DODHT = (l,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene; X = PF{sub 6}, AsF{sub 6}, and SbF{sub 6}] at ambient pressure have been compared. The insulating phase of {beta}''-(DODHT){sub 2}PF{sub 6} salt has already been revealed to be a charge ordering (CO) state by X-ray diffraction study and magnetic behavior. CO in this salt was also confirmed by the observation of satellite reflections in oscillation photograph using synchrotron radiation. Transport property of {beta}''-(DODHT){sub 2}SbF{sub 6} salt was reinvestigated up to the pressure of 3.7 GPa applied by a cubic anvil apparatus. Although the SbF{sub 6} salt turned to be metallic above 2.0 GPa, no superconductivity was observed. In order to examine the anion size dependence of DODHT salts with octahedral anions, we prepared a new DODHT salt, {beta}''-(DODHT){sub 2}TaF{sub 6}, which has the larger counter anion compared with the previous salts. Crystal structure of this salt was isostructural to the other DODHT salts. The electrical and magnetic properties of this salt were similar to those of {beta}''-(DODHT){sub 2}SbF{sub 6} salt.

Anionic chromogenic chemosensors highly selective for fluoride or cyanide based on 4-(4-Nitrobenzylideneamine)phenol

Energy Technology Data Exchange (ETDEWEB)

Nicoleti, Celso R; Marini, Vanderleia G; Zimmermann, Lizandra M; Machado, Vanderlei G., E-mail: vanderlei.machado@ufsc.br [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

2012-08-15

4-(4-Nitrobenzylideneamine)phenol was used in two strategies allowing the highly selective detection of F{sup -} and CN{sup -}. Firstly, the compound in acetonitrile acts as a chromogenic chemosensor based on the idea that more basic anions cause its deprotonation (colorless solution), generating a colored solution containing phenolate. The discrimination of CN{sup -} over F{sup -} was obtained by adding 1.4% water to acetonitrile: water preferentially solvates F{sup -}, leaving the CN{sup -} free to deprotonate the compound. Another strategy involved an assay comprised of the competition between phenolate dye and the analyte for calyx[4]pyrrole in acetonitrile, a receptor highly selective for F{sup -}. Phenolate and calyx[4]pyrrole form a hydrogen-bonded complex, which changes the color of the medium. On the addition of various anions, only F{sup -} was able to restore the original color corresponding to phenolate in solution due to the fact that the anion dislodges phenolate from the complexation site. (author)

Anionic chromogenic chemosensors highly selective for fluoride or cyanide based on 4-(4-Nitrobenzylideneamine)phenol

International Nuclear Information System (INIS)

Nicoleti, Celso R.; Marini, Vanderleia G.; Zimmermann, Lizandra M.; Machado, Vanderlei G.

2012-01-01

4-(4-Nitrobenzylideneamine)phenol was used in two strategies allowing the highly selective detection of F - and CN - . Firstly, the compound in acetonitrile acts as a chromogenic chemosensor based on the idea that more basic anions cause its deprotonation (colorless solution), generating a colored solution containing phenolate. The discrimination of CN - over F - was obtained by adding 1.4% water to acetonitrile: water preferentially solvates F - , leaving the CN - free to deprotonate the compound. Another strategy involved an assay comprised of the competition between phenolate dye and the analyte for calyx[4]pyrrole in acetonitrile, a receptor highly selective for F - . Phenolate and calyx[4]pyrrole form a hydrogen-bonded complex, which changes the color of the medium. On the addition of various anions, only F - was able to restore the original color corresponding to phenolate in solution due to the fact that the anion dislodges phenolate from the complexation site. (author)

Rational design of organic superconductors through the use of the large, discrete molecular anions M(CF3)4-(M = Cu, Ag, Au) and SO3CF2CH2SF5-

International Nuclear Information System (INIS)

Schlueter, J.A.; Geiser, U.; Williams, J.M.

1996-01-01

A new approach to synthesis of organic superconductors has recently been pioneered which involves the use of large discrete molecular anions as the charge-compensating entities in these charge transfer salts. The organic electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) has been electrocrystallized with the novel organometallic M(CF 3 ) 4 - (M=Cu, Ag, Au) anions in a variety of 1,1,2-trihaloethane solvents. Over 20 organic superconductors have been synthesized which can be described by (ET) 2 M(CF 3 ) 4 (1,1,2- trihaloethane). These solvated salts are shown to have highly anisotropic physical properties which can be tuned via modifications of each of their three molecular components: ET electron donor molecule, M(CF 3 ) 4 - anion, and neutral 1,1,2- trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF 5 CH 2 CF 2 SO 3 - anion with onset temperature near 5.2 K

Charged Porous Polymers using a Solid C-O Cross-Coupling Reaction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pengfei; Jiang, Xueguang; Wan, Shun; Dai, Sheng

2015-07-15

Here in this paper, we report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li+ cations were fabricated by solid grinding under solvent-free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60–90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO2 capture, and Li+-functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs.

Charged Porous Polymers using a Solid C-O Cross-Coupling Reaction

Energy Technology Data Exchange (ETDEWEB)

Zhang, Pengfei; Jiang, Xueguang; Wan, Shun; Dai, Sheng

2015-07-15

Herein, we report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li+ cations were fabricated by solid grinding under solvent-free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60–90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO2 capture, and Li+-functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs.

Tetrel Bonding as a Vehicle for Strong and Selective Anion Binding

Directory of Open Access Journals (Sweden)

Steve Scheiner

2018-05-01

Full Text Available Tetrel atoms T (T = Si, Ge, Sn, and Pb can engage in very strong noncovalent interactions with nucleophiles, which are commonly referred to as tetrel bonds. The ability of such bonds to bind various anions is assessed with a goal of designing an optimal receptor. The Sn atom seems to form the strongest bonds within the tetrel family. It is most effective in the context of a -SnF3 group and a further enhancement is observed when a positive charge is placed on the receptor. Connection of the -SnF3 group to either an imidazolium or triazolium provides a strong halide receptor, which can be improved if its point of attachment is changed from the C to an N atom of either ring. Aromaticity of the ring offers no advantage nor is a cyclic system superior to a simple alkyl amine of any chain length. Placing a pair of -SnF3 groups on a single molecule to form a bipodal dicationic receptor with two tetrel bonds enhances the binding, but falls short of a simple doubling. These two tetrel groups can be placed on opposite ends of an alkyl diamine chain of any length although SnF3+NH2(CH2nNH2SnF3+ with n between 2 and 4 seems to offer the strongest halide binding. Of the various anions tested, OH− binds most strongly: OH− > F− > Cl− > Br− > I−. The binding energy of the larger NO3− and HCO3− anions is more dependent upon the charge of the receptor. This pattern translates into very strong selectivity of binding one anion over another. The tetrel-bonding receptors bind far more strongly to each anion than an equivalent number of K+ counterions, which leads to equilibrium ratios in favor of the former of many orders of magnitude.

Simultaneous determination of 13 carbohydrates using high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry.

Science.gov (United States)

Zhao, Dan; Feng, Feng; Yuan, Fei; Su, Jin; Cheng, Yan; Wu, Hanqiu; Song, Kun; Nie, Bo; Yu, Lian; Zhang, Feng

2017-04-01

A simple, accurate, and highly sensitive method was developed for the determination of 13 carbohydrates in polysaccharide of Spirulina platensis based on high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry. Samples were extracted with deionized water using ultrasonic-assisted extraction, and the ultrasound-assisted extraction conditions were optimized by Box-Behnken design. Then the extracted polysaccharide was hydrolyzed by adding 1 mol/L trifluoroacetic acid before determination by high-performance anion-exchange chromatography coupled with pulsed amperometric detection and confirmed by high-performance anion-exchange chromatography coupled with mass spectrometry. The high-performance anion-exchange chromatography coupled with pulsed amperometric detection method was performed on a CarboPac PA20 column by gradient elution using deionized water, 0.1 mol/L sodium hydroxide solution, and 0.4 mol/L sodium acetate solution. Excellent linearity was observed in the range of 0.05-10 mg/L. The average recoveries ranged from 80.7 to 121.7%. The limits of detection and limits of quantification for 13 carbohydrates were 0.02-0.10 and 0.2-1.2  μg/kg, respectively. The developed method has been successfully applied to ambient samples, and the results indicated that high-performance anion-exchange chromatography coupled with pulsed amperometric detection and mass spectrometry could provide a rapid and accurate method for the simultaneous determination of carbohydrates. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy density functionals from the strong-coupling limit applied to the anions of the He isoelectronic series

International Nuclear Information System (INIS)

Mirtschink, André; Gori-Giorgi, Paola; Umrigar, C. J.; Morgan, John D.

2014-01-01

Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge Z − and to capture in general the physics of loosely bound anions, with a tendency to strongly overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which improve the results

Polyethylenimine-modified fungal biomass as a high-capacity biosorbent for Cr(VI) anions: sorption capacity and uptake mechanisms.

Science.gov (United States)

Deng, Shubo; Ting, Yen Peng

2005-11-01

Heavy metal pollution in the aqueous environment is a problem of global concern. Biosorption has been considered as a promising technology for the removal of low levels of toxic metals from industrial effluents and natural waters. A modified fungal biomass of Penicillium chrysogenum with positive surface charges was prepared by grafting polyethylenimine (PEI) onto the biomass surface in a two-step reaction. The presence of PEI on the biomass surface was verified by FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Due to the high density of amine groups in the long chains of PEI molecules on the surface, the modified biomass was found to possess positive zeta potential at pH below 10.4 as well as high sorption capacity for anionic Cr(VI). Using the Langmuir adsorption isotherm, the maximum sorption capacity for Cr(VI) at a pH range of 4.3-5.5 was 5.37 mmol/g of biomass dry weight, the highest sorption capacity for Cr(VI) compared to other sorbents reported in the literature. Scanning electronic microscopy (SEM) provided evidence of chromium aggregates formed on the biomass surface. XPS results verified the presence of Cr(III) on the biomass surface in the pH range 2.5-10.5, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption. The sorption kinetics indicated that redox reaction occurred on the biomass surface, and whether the converted Cr(III) ions were released to solution or adsorbed on the biomass depended on the solution pH. Sorption mechanisms including electrostatic interaction, chelation, and precipitation were found to be involved in the complex sorption of chromium on the PEI-modified biomass.

Ultrathin self-assembled anionic polymer membranes for superfast size-selective separation

Science.gov (United States)

Deng, Chao; Zhang, Qiu Gen; Han, Guang Lu; Gong, Yi; Zhu, Ai Mei; Liu, Qing Lin

2013-10-01

Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than commercial membranes, and can highly efficiently separate 5 and 15 nm gold nanoparticles from their mixtures. The newly developed nanoporous membranes have a wide application in separation and purification of biomacromolecules and nanoparticles.Nanoporous membranes with superior separation performance have become more crucial with increasing concerns in functional nanomaterials. Here novel ultrahigh permeable nanoporous membranes have been fabricated on macroporous supports by self-assembly of anionic polymer on copper hydroxide nanostrand templates in organic solution. This facile approach has a great potential for the fabrication of ultrathin anionic polymer membranes as a general method. The as-fabricated self-assembled membranes have a mean pore size of 5-12 nm and an adjustable thickness as low as 85 nm. They allow superfast permeation of water, and exhibit excellent size-selective separation properties and good fouling resistance for negatively-charged solutes during filtration. The 85 nm thick membrane has an ultrahigh water flux (3306 l m-2 h-1 bar-1) that is an order of magnitude larger than

Phospatidylserine or ganglioside--which of anionic lipids determines the effect of cationic dextran on lipid membrane?

Science.gov (United States)

Hąc-Wydro, Katarzyna; Wydro, Paweł; Cetnar, Andrzej; Włodarczyk, Grzegorz

2015-02-01

In this work the influence of cationic polymer, namely diethylaminoethyl DEAE-dextran on model lipid membranes was investigated. This polymer is of a wide application as a biomaterial and a drug carrier and its cytotoxicity toward various cancer cells was also confirmed. It was suggested that anticancer effect of cationic dextran is connected with the binding of the polymer to the negatively charged sialic acid residues overexpressed in cancer membrane. This fact encouraged us to perform the studies aimed at verifying whether the effect of cationic DEAE-dextran on membrane is determined only by the presence of the negatively charged lipid in the system or the kind of anionic lipid is also important. To reach this goal systematic investigations on the effect of dextran on various one-component lipid monolayers and multicomponent hepatoma cell model membranes differing in the level and the kind of anionic lipids (phosphatidylserine, sialic acid-containing ganglioside GM3 or their mixture) were done. As evidenced the results the effect of DEAE-dextran on the model system is determined by anionic lipid-polymer electrostatic interactions. However, the magnitude of the effect of cationic polymer is strongly dependent on the kind of anionic lipid in the model system. Namely, the packing and ordering of the mixtures containing ganglioside GM3 were more affected by DEAE-dextran than phosphatidylserine-containing monolayers. Although the experiments were done on model systems and therefore further studies are highly needed, the collected data may indicate that ganglioside may be important in the differentiation of the effect of cationic dextran on membranes. Copyright © 2014 Elsevier B.V. All rights reserved.

Highly charged ion trapping and cooling

International Nuclear Information System (INIS)

Beck, B. R.; Church, D. A.; Gruber, L.; Holder, J. P.; Schneider, D.; Steiger, J.

1998-01-01

In the past few years a cryogenic Penning trap (RETRAP) has been operational at the Electron Beam Ion Trap (EBIT) facility at Lawrence Livermore National Laboratory. The combination of RETRAP and EBIT provides a unique possibility of producing and re-trapping highly charged ions and cooling them to very low temperatures. Due to the high Coulomb potentials in such an ensemble of cold highly charged ions the Coulomb coupling parameter (the ratio of Coulomb potential to the thermal energy) can easily reach values of 172 and more. To study such systems is not only of interest in astrophysics to simulate White Dwarf star interiors but opens up new possibilities in a variety of areas (e.g. laser spectroscopy), cold highly charged ion beams

Photoabsorption of green and red fluorescent protein chromophore anions in vacuo.

Science.gov (United States)

Wan, Songbo; Liu, Shasha; Zhao, Guangjiu; Chen, Maodu; Han, Keli; Sun, Mengtao

2007-09-01

Photoabsorption properties of green and red fluorescent protein chromophore anions in vacuo were investigated theoretically, based on the experimental results in gas phase [Phys. Rev. Lett. 2001, 87, 228102; Phys. Rev. Lett. 2003, 90, 118103]. Their calculated transition energies in absorption with TD-DFT and ZINDO methods are directly compared to the experimental reports in gas phase, and the calculations with ZINDO method can correctly reproduce the absorption spectra. The orientation and strength of their transition dipole moments were revealed with transition density. We also showed the orientation and result of their intramolecular charge transfer with transition difference density. The calculated results show that with the increase of the extended conjugated system, the orientation of transition dipole moments and the orientation of charge transfer can be reversed. They are the linear responds with the external electric fields. These theoretical results reveal the insight understanding of the photoinduced dynamics of green and red fluorescent protein chromophore anions and cations in vacuo.

Multiply-negatively charged aluminium clusters and fullerenes

Energy Technology Data Exchange (ETDEWEB)

Walsh, Noelle

2008-07-15

Multiply negatively charged aluminium clusters and fullerenes were generated in a Penning trap using the 'electron-bath' technique. Aluminium monoanions were generated using a laser vaporisation source. After this, two-, three- and four-times negatively charged aluminium clusters were generated for the first time. This research marks the first observation of tetra-anionic metal clusters in the gas phase. Additionally, doubly-negatively charged fullerenes were generated. The smallest fullerene dianion observed contained 70 atoms. (orig.)

Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer.

Science.gov (United States)

Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

2016-06-09

A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L(-1) to 2 mg L(-1), the sensitivity and detection limit of the sensor is 3.191 μA/mg L(-1) and 1.97 μg L(-1), respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection.

Ab initio investigation of sulfur monofluoride and its singly charged cation and anion in their ground electronic state

Science.gov (United States)

Song, Li; Shan-Jun, Chen; Yan, Chen; Peng, Chen

2016-03-01

The SF radical and its singly charged cation and anion, SF+ and SF-, have been investigated on the MRCI/aug-cc-pVXZ (X = Q, 5, 6) levels of theory with Davidson correction. Both the core-valence correlation and the relativistic effect are considered. The extrapolating to the complete basis set (CBS) limit is adopted to remove the basis set truncation error. Geometrical parameters, potential energy curves (PECs), vibrational energy levels, spectroscopic constants, ionization potentials, and electron affinities of the ground electronic state for all these species are obtained. The information with respect to molecular characteristics of the SFn (n = -1, 0, +1) systems derived in this work will help to extend our knowledge and to guide further experimental or theoretical researches. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304023 and 11447172), the Young and Middle-Aged Talent of Education Burea of Hubei Province, China (Grant No. Q20151307), and the Yangtze Youth Talents Fund of Yangtze University, China (Grant No. 2015cqr21).

Pseudocapacitance of MnO{sub 2} originates from reversible insertion/desertion of thiocyanate anions studied using in situ X-ray absorption spectroscopy in ionic liquid electrolyte

Energy Technology Data Exchange (ETDEWEB)

Lee, Ming-Tsung; Tsai, Wen-Ta; Chang, Jeng-Kuei [Department of Materials Science and Engineering, National Cheng Kung University, 1 University Road, Tainan (China); Deng, Ming-Jay; Cheng, Hui-Fang; Sun, I-Wen [Department of Chemistry, National Cheng Kung University, 1 University Road, Tainan (China)

2010-02-01

Charge storage mechanisms of electrodeposited MnO{sub 2} in various aprotic ionic liquids (ILs) are studied using in situ X-ray absorption spectroscopy (XAS). The analytical results show that a unique thiocyanate (SCN{sup -}) anion can reversibly insert/desert into/from the tunnels between the [MnO{sub 6}] octahedral subunits depending on the applied potential. This process charge compensates the Mn{sup 3+}/Mn{sup 4+} redox transition upon charging-discharging and thus contributes to an ideal pseudocapacitive behavior of the MnO{sub 2} electrode. The present work would open up a route for developing a novel oxide-based supercapacitor, with high cell-voltage, high thermal stability, and high safety, incorporating IL electrolytes. (author)

Ab initio studies of O-2(-) (H2O)(n) and O-3(-) (H2O)(n) anionic molecular clusters, n

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurten, T.; Enghoff, Martin Andreas Bødker

2011-01-01

that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding....... Although clustering up to 12 H2O, we find that the O-2 and O-3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O-2(-) and O-3(-) speicies are thus accessible for further reactions. We consider the distributions of cluster sizes as function of altitude before...

Rotaxane and catenane host structures for sensing charged guest species.

Science.gov (United States)

Langton, Matthew J; Beer, Paul D

2014-07-15

CONSPECTUS: The promise of mechanically interlocked architectures, such as rotaxanes and catenanes, as prototypical molecular switches and shuttles for nanotechnological applications, has stimulated an ever increasing interest in their synthesis and function. The elaborate host cavities of interlocked structures, however, can also offer a novel approach toward molecular recognition: this Account describes the use of rotaxane and catenane host systems for binding charged guest species, and for providing sensing capability through an integrated optical or electrochemical reporter group. Particular attention is drawn to the exploitation of the unusual dynamic properties of interlocked molecules, such as guest-induced shuttling or conformational switching, as a sophisticated means of achieving a selective and functional sensor response. We initially survey interlocked host systems capable of sensing cationic guests, before focusing on our accomplishments in synthesizing rotaxanes and catenanes designed for the more challenging task of selective anion sensing. In our group, we have developed the use of discrete anionic templation to prepare mechanically interlocked structures for anion recognition applications. Removal of the anion template reveals an interlocked host system, possessing a unique three-dimensional geometrically restrained binding cavity formed between the interlocked components, which exhibits impressive selectivity toward complementary anionic guest species. By incorporating reporter groups within such systems, we have developed both electrochemical and optical anion sensors which can achieve highly selective sensing of anionic guests. Transition metals, lanthanides, and organic fluorophores integrated within the mechanically bonded structural framework of the receptor are perturbed by the binding of the guest, with a concomitant change in the emission profile. We have also exploited the unique dynamics of interlocked hosts by demonstrating that an

Charged vortices in high-Tc superconductors

International Nuclear Information System (INIS)

Matsuda, Y.; Kumagai, K.

2002-01-01

It is well known that a vortex in type II superconductors traps a magnetic flux. Recently the possibility that a vortex can accumulate a finite electric charge as well has come to be realized. The sign and magnitude of the vortex charge not only is closely related to the microscopic electronic structure of the vortex, but also strongly affects the dynamical properties of the vortex. In this chapter we demonstrate that a vortex in high-T c superconductors (HTSC) indeed traps a finite electronic charge, using the high resolution measurements of the nuclear quadrupole frequencies. We then discuss the vortex Hall anomaly whose relation with the vortex charging effect has recently received considerable attention. We show that the sign of the trapped charge is opposite to the sign predicted by the conventional BCS theory and deviation of the magnitude of the charge from the theory is also significant. We also show that the electronic structure of underlying system is responsible for the Hall sign in the vortex state and again the Hall sign is opposite to the sign predicted by the BCS theory. It appears that these unexpected features observed in both electrostatics and dynamics of the vortex may be attributed to the novel electronic structure of the vortex in HTSC. (orig.)

Effect of anionic surfactant concentration on the variable range hopping conduction in polypyrrole nanoparticles

International Nuclear Information System (INIS)

Rawal, Ishpal; Kaur, Amarjeet

2014-01-01

The mechanism of charge transport in polypyrrole (PPy) nanoparticles prepared with different concentrations (5 to 30 mM) of anionic surfactant (sodium dodecyl sulfate) is reported. Transmission electron microscopy technique confirms the formation of PPy nanoparticles of sizes ∼52 to 28 nm under surfactant directed approach. The room temperature electrical conductivity of the prepared nanoparticles found to increase from 3 to 22 S/cm with surfactant concentration. The temperature dependent activation energy rules out the possibility of band conduction mechanism in the prepared PPy nanoparticles and thus the synthesized nanoparticles are analyzed under variable range hopping (VRH) model for conduction mechanism. The PPy nanoparticles, reduced with liquid ammonia, hold 3D VRH conduction mechanism for the charge transport. However, in the doped samples, some deviation from 3D VRH conduction behavior at higher temperatures (>150 K) has been observed. This may be attributed to the presence of anionic surfactant in these samples. The doping of anionic surfactant causes rise in conducting islands, which may lead to the change in the shape/distribution of density of states governed by Gaussian or exponential type near Fermi level

Effect of anionic surfactant concentration on the variable range hopping conduction in polypyrrole nanoparticles

Science.gov (United States)

Rawal, Ishpal; Kaur, Amarjeet

2014-01-01

The mechanism of charge transport in polypyrrole (PPy) nanoparticles prepared with different concentrations (5 to 30 mM) of anionic surfactant (sodium dodecyl sulfate) is reported. Transmission electron microscopy technique confirms the formation of PPy nanoparticles of sizes ˜52 to 28 nm under surfactant directed approach. The room temperature electrical conductivity of the prepared nanoparticles found to increase from 3 to 22 S/cm with surfactant concentration. The temperature dependent activation energy rules out the possibility of band conduction mechanism in the prepared PPy nanoparticles and thus the synthesized nanoparticles are analyzed under variable range hopping (VRH) model for conduction mechanism. The PPy nanoparticles, reduced with liquid ammonia, hold 3D VRH conduction mechanism for the charge transport. However, in the doped samples, some deviation from 3D VRH conduction behavior at higher temperatures (>150 K) has been observed. This may be attributed to the presence of anionic surfactant in these samples. The doping of anionic surfactant causes rise in conducting islands, which may lead to the change in the shape/distribution of density of states governed by Gaussian or exponential type near Fermi level.

The 79,81Br and 127I NQR spectra of some halogenated anions of nido-7,8-dicarbaundecaborates

International Nuclear Information System (INIS)

Semin, G.K.; Zakharkin, L.I.; Kuznetsov, S.I.; Zhigareva, G.G.; Bryukhova, E.V.

1998-01-01

Spectra of nuclear quadrupole resonance of bromine and iodine atoms in the series of halogenated anions of cesium nido-7,8-dicarbaundecaborates have been studied. Considerable shift of the spectrum in the low-frequency range compared to closo-carborane derivatives can be explained by negative charge localization in anion of nido-7,8-dicarbaundecaborates with its certain prevalence in the pentagonal plane [ru

Using AFM to probe the complexation of DNA with anionic lipids mediated by Ca(2+): the role of surface pressure.

Science.gov (United States)

Luque-Caballero, Germán; Martín-Molina, Alberto; Sánchez-Treviño, Alda Yadira; Rodríguez-Valverde, Miguel A; Cabrerizo-Vílchez, Miguel A; Maldonado-Valderrama, Julia

2014-04-28

Complexation of DNA with lipids is currently being developed as an alternative to classical vectors based on viruses. Most of the research to date focuses on cationic lipids owing to their spontaneous complexation with DNA. Nonetheless, recent investigations have revealed that cationic lipids induce a large number of adverse effects on DNA delivery. Precisely, the lower cytotoxicity of anionic lipids accounts for their use as a promising alternative. However, the complexation of DNA with anionic lipids (mediated by cations) is still in early stages and is not yet well understood. In order to explore the molecular mechanisms underlying the complexation of anionic lipids and DNA we proposed a combined methodology based on the surface pressure-area isotherms, Gibbs elasticity and Atomic Force Microscopy (AFM). These techniques allow elucidation of the role of the surface pressure in the complexation and visualization of the interfacial aggregates for the first time. We demonstrate that the DNA complexes with negatively charged model monolayers (DPPC/DPPS 4 : 1) only in the presence of Ca(2+), but is expelled at very high surface pressures. Also, according to the Gibbs elasticity plot, the complexation of lipids and DNA implies a whole fluidisation of the monolayer and a completely different phase transition map in the presence of DNA and Ca(2+). AFM imaging allows identification for the first time of specific morphologies associated with different packing densities. At low surface coverage, a branched net like structure is observed whereas at high surface pressure fibers formed of interfacial aggregates appear. In summary, Ca(2+) mediates the interaction between DNA and negatively charged lipids and also the conformation of the ternary system depends on the surface pressure. Such observations are important new generic features of the interaction between DNA and anionic lipids.

Production of High-Intensity, Highly Charged Ions

CERN Document Server

Gammino, S.

2013-12-16

In the past three decades, the development of nuclear physics facilities for fundamental and applied science purposes has required an increasing current of multicharged ion beams. Multiple ionization implies the formation of dense and energetic plasmas, which, in turn, requires specific plasma trapping configurations. Two types of ion source have been able to produce very high charge states in a reliable and reproducible way: electron beam ion sources (EBIS) and electron cyclotron resonance ion sources (ECRIS). Multiple ionization is also obtained in laser-generated plasmas (laser ion sources (LIS)), where the high-energy electrons and the extremely high electron density allow step-by-step ionization, but the reproducibility is poor. This chapter discusses the atomic physics background at the basis of the production of highly charged ions and describes the scientific and technological features of the most advanced ion sources. Particular attention is paid to ECRIS and the latest developments, since they now r...

A Survey of Aspartate Phenylalanine and Glutamate Phenylalanine Interactions in the Protein Data Bank: Searching for Anion Pairs

Energy Technology Data Exchange (ETDEWEB)

Philip, Vivek M [ORNL; Harris, Jason B [ORNL; Adams, Rachel M [ORNL; Nguyen, Don [University of Tennessee, Knoxville (UTK); Spires, Jeremy [University of Tennessee, Knoxville (UTK); Howell, Elizabeth E. [University of Tennessee, Knoxville (UTK); Hinde, Robert J [ORNL

2011-01-01

Protein structures are stabilized using noncovalent interactions. In addition to the traditional noncovalent interactions, newer types of interactions are thought to be present in proteins. One such interaction, an anion pair, in which the positively charged edge of an aromatic ring interacts with an anion, forming a favorable anion quadrupole interaction, has been previously proposed [Jackson, M. R., et al. (2007) J. Phys. Chem. B111, 8242 8249]. To study the role of anion interactions in stabilizing protein structure, we analyzed pairwise interactions between phenylalanine (Phe) and the anionic amino acids, aspartate (Asp) and glutamate (Glu). Particular emphasis was focused on identification of Phe Asp or Glu pairs separated by less than 7 in the high-resolution, nonredundant Protein Data Bank. Simplifying Phe to benzene and Asp or Glu to formate molecules facilitated in silico analysis of the pairs. Kitaura Morokuma energy calculations were performed on roughly 19000 benzene formate pairs and the resulting energies analyzed as a function of distance and angle. Edgewise interactions typically produced strongly stabilizing interaction energies (2 to 7.3 kcal/mol), while interactions involving the ring face resulted in weakly stabilizing to repulsive interaction energies. The strongest, most stabilizing interactions were identified as preferentially occurring in buried residues. Anion pairs are found throughout protein structures, in helices as well as strands. Numerous pairs also had nearby cation interactions as well as potential stacking. While more than 1000 structures did not contain an anion pair, the 3134 remaining structures contained approximately 2.6 anion pairs per protein, suggesting it is a reasonably common motif that could contribute to the overall structural stability of a protein.

Beta decay of highly charged ions

International Nuclear Information System (INIS)

Litvinov, Yuri A; Bosch, Fritz

2011-01-01

Beta decay of highly charged ions has attracted much attention in recent years. An obvious motivation for this research is that stellar nucleosynthesis proceeds at high temperatures where the involved atoms are highly ionized. Another important reason is addressing decays of well-defined quantum-mechanical systems, such as one-electron ions where all interactions with other electrons are excluded. The largest modifications of nuclear half-lives with respect to neutral atoms have been observed in beta decay of highly charged ions. These studies can be performed solely at ion storage rings and ion traps, because there high atomic charge states can be preserved for extended periods of time (up to several hours). Currently, all experimental results available in this field originate from experiments at the heavy-ion complex GSI in Darmstadt. There, the fragment separator facility FRS allows the production and separation of exotic, highly charged nuclides, which can then be stored and investigated in the storage ring facility ESR. In this review, we present and discuss in particular two-body beta decays, namely bound-state beta decay and orbital electron capture. Although we focus on experiments conducted at GSI, we will also attempt to provide general requirements common to any other experiment in this context. Finally, we address challenging but not yet performed experiments and we give prospects for the new radioactive beam facilities, such as FAIR in Darmstadt, IMP in Lanzhou and RIKEN in Wako.

High speed auto-charging system for condenser bank

International Nuclear Information System (INIS)

Mizuno, Yasunori; Bito, Fumio; Fujita, Kazuhiko; Sometani, Taro

1987-01-01

A current-control type high-speed charging system, which is intended for auto-charging of the condenser bank, is developed. Moreover, the system can also serve to compensate the current leakage from the condenser bank so that the charged voltage can be kept constant. The system consists of a sequence circuit, a charging current control circuit (or auto-charging circuit) and a charging circuit. The auto-charging circuit is characterized by the use of a triac to control the current. The current, controlled by the circuit, is supplied to the condenser bank through a step-up transformer and voltage doubler rectifier circuit. It is demonstrated that the use of the high-speed auto-charging circuit can largely decrease the required charging time, compared to constant voltage charging. In addition, the compensation function is shown to serve effectively for maintaining a constant voltage after the completion of charging. The required charging time is decreases as the charging current increases. The maximum charging current is decided by the rating of the traic and the current rating of the rectifier diode in the secondary circuit. Major components of these circuits have decreased impedances to minimize the effect of noise, so that the possibility of an accident can be eliminated. Other various improvements are made in the grounding circuit and the charging protection circuit in order to ensure safety. (Nogami, K.)

Perchlorate adsorption and desorption on activated carbon and anion exchange resin.

Science.gov (United States)

Yoon, In-Ho; Meng, Xiaoguang; Wang, Chao; Kim, Kyoung-Woong; Bang, Sunbaek; Choe, Eunyoung; Lippincott, Lee

2009-05-15

The mechanisms of perchlorate adsorption on activated carbon (AC) and anion exchange resin (SR-7 resin) were investigated using Raman, FTIR, and zeta potential analyses. Batch adsorption and desorption results demonstrated that the adsorption of perchlorate by AC and SR-7 resin was reversible. The reversibility of perchlorate adsorption by the resin was also proved by column regeneration test. Solution pH significantly affected perchlorate adsorption and the zeta potential of AC, while it did not influence perchlorate adsorption and the zeta potential of resin. Zeta potential measurements showed that perchlorate was adsorbed on the negatively charged AC surface. Raman spectra indicated the adsorption resulted in an obvious position shift of the perchlorate peak, suggesting that perchlorate was associated with functional groups on AC at neutral pH through interactions stronger than electrostatic interaction. The adsorbed perchlorate on the resin exhibited a Raman peak at similar position as the aqueous perchlorate, indicating that perchlorate was adsorbed on the resin through electrostatic attraction between the anion and positively charged surface sites.

Ab initio studies of O2-(H2O)n and O3-(H2O)n anionic molecular clusters, n≤12

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurtén, T.; Enghoff, Martin Andreas Bødker

2011-01-01

that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although...... clustering up to 12 H2O, we find that the O2 and O3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O2− and O3− speicies are thus accessible for further reactions. Finally, the thermodynamics of a few relevant cluster reactions are considered....

Gas-Grain Models for Interstellar Anion Chemistry

Science.gov (United States)

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

Anionic solid lipid nanoparticles supported on protamine/DNA complexes

International Nuclear Information System (INIS)

Ye Jiesheng; Liu Chunxi; Chen Zhijin; Zhang Na; Wang Aihua

2008-01-01

The objective of this study was to design novel anionic ternary nanoparticles for gene delivery. These ternary nanoparticles were equipped with protamine/DNA binary complexes (150-200 nm) as the support, and the anionic formation was achieved by absorption of anionic solid lipid nanoparticles (≤20 nm) onto the surface of the binary complexes. The small solid lipid nanoparticles (SLNs) were prepared by a modified film dispersion-ultrasonication method, and adsorption of the anionic SLNs onto the binary complexes was typically carried out in water via electrostatic interaction. The formulated ternary nanoparticles were found to be relatively uniform in size (257.7 ± 10.6 nm) with a 'bumpy' surface, and the surface charge inversion from 19.28 ± 1.14 mV to -17.16 ± 1.92 mV could be considered as evidence of the formation of the ternary nanoparticles. The fluorescence intensity measurements from three batches of the ternary nanoparticles gave a mean adsorption efficiency of 96.75 ± 1.13%. Circular dichroism spectra analysis showed that the protamine/DNA complexes had been coated by small SLNs, and that the anionic ternary nanoparticles formed did not disturb the construction of the binary complexes. SYBR Green I analysis suggested that the ternary nanoparticles could protect the DNA from nuclease degradation, and cell viability assay results showed that they exhibit lower cytotoxicity to A549 cells compared with the binary complexes and lipofectamine. The transfection efficiency of the ternary nanoparticles was better than that of naked DNA and the binary complexes, and almost equal to that of lipofectamine/DNA complexes, as revealed by inversion fluorescence microscope observation. These results indicated that the anionic ternary nanoparticles could facilitate gene transfer in cultured cells, and might alleviate the drawbacks of the conventional cationic vector/DNA complexes for gene delivery in vivo

ECRIS sources for highly charged ions

International Nuclear Information System (INIS)

Geller, R.

1991-01-01

The so-called Philips ionization gauge ion sources (PIGIS) were used until quite recently in heavy ion accelerators so multiply charged ions could only be obtained by incorporating a stripper to remove electrons. Electron cyclotron resonance ion sources (ECRIS) now dominate as they produce more highly charged ions. (orig.)

Quantum chemical study of the interaction of elemental Hg with small neutral, anionic and cationic Aun (n = 1–6) clusters

International Nuclear Information System (INIS)

Siddiqui, Shamoon Ahmad; Bouarissa, Nadir; Rasheed, Tabish; Al-Assiri, M.S.

2013-01-01

Graphical abstract: Binding energies as a function of cluster size for Au n Hg, Au n Hg + and Au n Hg − complexes. Highlights: ► Hg adsorption of neutral and charged Au n (n = 1–6) clusters has been discussed. ► Size and charged state of cluster significantly affect the Hg adsorption. ► Transfer of electron mainly found from s orbital of Hg to s orbital of Au. - Abstract: Adsorption of elemental mercury (Hg) on small neutral, cationic and anionic gold clusters (Au n , n = 1–6) has been studied by using the density functional theory (DFT). Results of this investigation show that frontier molecular orbital theory is a useful tool to predict the selectivity of Hg adsorption. It is found that adsorption of Hg on neutral, cationic and anionic Au n (n = 1–6) clusters are thermodynamically favorable. The binding energies of Hg on the cationic Au n clusters are greater than those on the neutral and anionic clusters. Natural bond orbital (NBO) analysis indicates that the flow of electrons in the neutral and charged clusters is mainly due to the s orbitals of Hg and Au. Results of NBO analysis also indicate that the binding energy of Hg with Au n clusters is directly proportional to the charge transfer, i.e. greater is the charge transfer, higher is the binding energy

Effects of anion size and concentration on electrolyte invasion into molecular-sized nanopores

International Nuclear Information System (INIS)

Liu Ling; Chen Xi; Kim, Taewan; Han Aijie; Qiao Yu

2010-01-01

When an electrolyte solution is pressurized into a molecular-sized nanopore, oppositely charged ions are strongly inclined to aggregate, which effectively reduces the ion solubility to zero. Inside the restrictive confinement, a unique quasi-periodic structure is formed where the paired ion couples are periodically separated by a number of water molecules. As the anion size or ion concentration varies, the geometrical characteristics of the confined ion structure would change considerably, leading to a significant variation in the transport pressure. Both experimental and simulation results indicate that, contradictory to the prediction of conventional theory, infiltration pressure decreases as the anions become larger.

Highly stable pyridinium-functionalized cross-linked anion exchange membranes for all vanadium redox flow batteries

Science.gov (United States)

Zeng, L.; Zhao, T. S.; Wei, L.; Zeng, Y. K.; Zhang, Z. H.

2016-11-01

It has recently been demonstrated that the use of anion exchange membranes (AEMs) in vanadium redox flow batteries (VRFBs) can reduce the migration of vanadium ions through the membrane due to the Donnan exclusion effect among the positively charged functional groups and vanadium ions. However, AEMs are plagued by low chemical stability in harsh chemical environments. Here we propose and fabricate a pyridinium-functionalized cross-linked AEM for VRFBs. The pyridinium-functionalized bromomethylated poly (2,6-dimethyl-1,4-phenylene oxide) exhibits a superior chemical stability as a result of the strengthened internal cross-linking networks and the chemical inertness of the polymer backbone. Therefore, the membrane exhibits littler decay in a harsh environment for 20 days during the course of an ex situ immersion test. A cycling test also demonstrates that the VRFB assembled with the membrane enable to retain 80% of the initial discharge capacity over 537 cycles with a capacity decay rate of 0.037% cycle-1. Meanwhile, the membrane also shows a low vanadium permeability and a reasonably high conductivity in supporting electrolytes. Hence, all the measurements and performance tests reported in this work suggest that the membrane is a promising AEM for redox flow batteries to achieve excellent cycling stability and superior cell performance.

Atomic structure of highly-charged ions. Final report

International Nuclear Information System (INIS)

Livingston, A. Eugene

2002-01-01

Atomic properties of multiply charged ions have been investigated using excitation of energetic heavy ion beams. Spectroscopy of excited atomic transitions has been applied from the visible to the extreme ultraviolet wavelength regions to provide accurate atomic structure and transition rate data in selected highly ionized atoms. High-resolution position-sensitive photon detection has been introduced for measurements in the ultraviolet region. The detailed structures of Rydberg states in highly charged beryllium-like ions have been measured as a test of long-range electron-ion interactions. The measurements are supported by multiconfiguration Dirac-Fock calculations and by many-body perturbation theory. The high-angular-momentum Rydberg transitions may be used to establish reference wavelengths and improve the accuracy of ionization energies in highly charged systems. Precision wavelength measurements in highly charged few-electron ions have been performed to test the most accurate relativistic atomic structure calculations for prominent low-lying excited states. Lifetime measurements for allowed and forbidden transitions in highly charged few-electron ions have been made to test theoretical transition matrix elements for simple atomic systems. Precision lifetime measurements in laser-excited alkali atoms have been initiated to establish the accuracy of relativistic atomic many-body theory in many-electron systems

Preparation and characterisation of high-density ionic liquids incorporating halobismuthate anions.

Science.gov (United States)

Cousens, Nico E A; Taylor Kearney, Leah J; Clough, Matthew T; Lovelock, Kevin R J; Palgrave, Robert G; Perkin, Susan

2014-07-28

A range of ionic liquids containing dialkylimidazolium cations and halobismuthate anions ([BiBr(x)Cl(y)I(z)](-) and [Bi2Br(x)Cl(y)I(z)](-)) were synthesised by combining dialkylimidazolium halide ionic liquids with bismuth(III) halide salts. The majority were room temperature liquids, all with very high densities. The neat ionic liquids and their mixtures with 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide were characterised using Densitometry, Viscometry, NMR Spectroscopy, Electrospray Ionisation Mass Spectrometry (ESI), Liquid Secondary Ion Mass Spectrometry (LSIMS), Matrix-assisted Laser Desorption/Ionization Mass Spectrometry (MALDI), X-Ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA), to establish their speciation and suitability for high-temperature applications.

A highly sensitive and selective fluorescent sensor for detection of sulfide anion based on the steric hindrance effect

Science.gov (United States)

Chen, Guanfan; Tang, Mengzhuo; Fu, Xiufang; Cheng, Fenmin; Zou, Xianghua; Wang, Jingpei; Zeng, Rongjin

2018-01-01

Sulfide anions are not only generated as a byproduct from industrial processes but also as a crucial kind of element in biological systems. Therefore, fluorescent probes for detecting sulfide anion with sensitive and selective characters are highly popular. In this study, we report a highly sensitive and selective fluorescent sensor M1 for detection of sulfide anion based on the steric hindrance effect, where the recognition unit, dinitrobenzenesulfonate ester group is linked to aromatic ortho-position in the porphyrin, and correspondingly the fluorescence of fluorescein is efficiently quenched. Compared with the sensors with recognition unit linked to the other aromatic positions, the fluorescent sensor M1 has a lower fluorescence background. Furthermore, the corresponding fluorescence responses (F/F0) of M1 for mercapto amino-acid GSH, Hcy and Cys, were all far lower than the relative fluorescence ratio F/F0 values for S2-. It means that M1 is sensitive and selective to detection of S2-, and has an anti-disturbance ability to the biologically-relevant thiols, GSH, Hcy and Cys, and has the prospect of application in the exact detection of sulfide anions in living organisms. This approach offers some useful insights for realizing sensitive and selective fluorescent turn-on sensing in the detection assays for other analytes.

Schlenk Techniques for Anionic Polymerization

KAUST Repository

Ratkanthwar, Kedar; Zhao, Junpeng; Zhang, Hefeng; Hadjichristidis, Nikolaos; Mays, Jimmy

2015-01-01

Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands

Understanding weakly coordinating anions: tetrakis(pentafluorophenyl)borate paired with inorganic and organic cations.

Science.gov (United States)

Andreeva, Nadezhda A; Chaban, Vitaly V

2017-03-01

Efficient design of ionic compounds requires a systematic understanding of cation-anion interactions. Weakening of electrostatic attraction is essential to increase the liquid range of the ionic compound and decrease its melting point. Here, we report simulations of the closest-approach cation-anion distances in a variety of ion pairs containing the tetrakis(pentafluorophenyl)borate (TFPB - ) anion. Small alkali cations (Li + , Na + ) penetrate the TFPB - core, whereas K + and larger organic cations do not. In the latter case, the shortest possible distance from the cations to the boron atom of TFPB - ranges from 0.50 nm to 0.63 nm. TFPB - was shown to be substantially rigid, providing a steric hindrance to thermodynamically efficient cation-anion coordination. Our results prove that TFPB - is more efficient for electrostatic charge confinement than the tetraoctylammonium cation, whereas the perfluorophenyl group is more efficient than linear alkyl chains. These simulations will motivate development of TFPB - -based ionic liquids with low phase transition points. Graphical Abstract Ionic configuration of the equilibrated "TFPB + K"system.

Enabling the high capacity of lithium-rich anti-fluorite lithium iron oxide by simultaneous anionic and cationic redox

Science.gov (United States)

Zhan, Chun; Yao, Zhenpeng; Lu, Jun; Ma, Lu; Maroni, Victor A.; Li, Liang; Lee, Eungje; Alp, Esen E.; Wu, Tianpin; Wen, Jianguo; Ren, Yang; Johnson, Christopher; Thackeray, Michael M.; Chan, Maria K. Y.; Wolverton, Chris; Amine, Khalil

2017-12-01

Anionic redox reactions in cathodes of lithium-ion batteries are allowing opportunities to double or even triple the energy density. However, it is still challenging to develop a cathode, especially with Earth-abundant elements, that enables anionic redox activity for real-world applications, primarily due to limited strategies to intercept the oxygenates from further irreversible oxidation to O2 gas. Here we report simultaneous iron and oxygen redox activity in a Li-rich anti-fluorite Li5FeO4 electrode. During the removal of the first two Li ions, the oxidation potential of O2- is lowered to approximately 3.5 V versus Li+/Li0, at which potential the cationic oxidation occurs concurrently. These anionic and cationic redox reactions show high reversibility without any obvious O2 gas release. Moreover, this study provides an insightful guide to designing high-capacity cathodes with reversible oxygen redox activity by simply introducing oxygen ions that are exclusively coordinated by Li+.

Charge collection and charge pulse formation in highly irradiated silicon planar detectors

International Nuclear Information System (INIS)

Dezillie, B.; Li, Z.; Eremin, V.

1998-06-01

The interpretation of experimental data and predictions for future experiments for high-energy physics have been based on conventional methods like capacitance versus voltage (C-V) measurements. Experiments carried out on highly irradiated detectors show that the kinetics of the charge collection and the dependence of the charge pulse amplitude on the applied bias are deviated too far from those predicted by the conventional methods. The described results show that in highly irradiated detectors, at a bias lower than the real full depletion voltage (V fd ), the kinetics of the charge collection (Q) contains a fast and a slow component. At V = V fd *, which is the full depletion voltage traditionally determined by the extrapolation of the fast component amplitude of q versus bias to the maximum value or from the standard C-V measurements, the pulse has a slow component with significant amplitude. This slow component can only be eliminated by applying additional bias that amounts to the real full depletion voltage (V fd ) or more. The above mentioned regularities are explained in this paper in terms of a model of an irradiated detector with multiple regions. This model allows one to use C-V, in a modified way, as well as TChT (transient charge technique) measurements to determine the V fd for highly irradiated detectors

Adsorção e dessorção aniônicas individuais por gibbsita pedogenética Individual anionic adsorption and desorption by pedogenic gibbsite

Directory of Open Access Journals (Sweden)

Adélia A. A. Pozza

2009-01-01

Full Text Available Anion adsorption/desorption dynamics was studied as individual processes on surface of particles of a gibbsitic clay. The data suggest a remarkable gibbsite role as nitrate leaching retardant in soil. The opposite behavior of gibbsite towards adsorption/desorption of silicate and phosphate suggests the need of an adequate compromise solution regarding interval and rate applications of anions in cultivated gibbsitic soils. The high P adsorption verified in pH values lower than that reported for the point of zero charge of synthetic Al-hydroxides implies that this process takes place in pedogenic gibbsites through inner sphere complexation.

Evidence for F-/SiO- anion exchange in the framework of As-synthesized all-silica zeolites

KAUST Repository

Liu, Xiaolong; Ravon, Ugo; Tuel, Alain

2011-01-01

Not everything changes: Charge-compensating anions can be exchanged in as-synthesized zeolite frameworks with changes in both the density of defect sites and of the hydrophobic character of the zeolite. The reversible transformation occurs without

The anionic biosurfactant rhamnolipid does not denature industrial enzymes

Directory of Open Access Journals (Sweden)

Jens Kvist Madsen

2015-04-01

Full Text Available Biosurfactants (BS are surface-active molecules produced by microorganisms. Their combination of useful properties and sustainable production make them promising industrial alternatives to petrochemical and oleochemical surfactants. Here we compare the impact of the anionic BS rhamnolipid (RL and the conventional/synthetic anionic surfactant sodium dodecyl sulfate (SDS on the structure and stability of three different commercially used enzymes, namely the cellulase Carezyme® (CZ, the phospholipase Lecitase Ultra® (LT and the α-amylase Stainzyme® (SZ. Our data reveal a fundamental difference in their mode of interaction. SDS shows great diversity of interaction towards the different enzymes. It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the protein well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT. SDS binds with even lower stoichiometry to SZ and leads to an increase in thermal stability. In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries to SZ. Furthermore all enzymes maintain activity at both monomeric and micellar concentrations of RL. We conclude that RL, despite its anionic charge, is a surfactant that does not compromise the structural integrity of industrially relevant proteins. This makes RL a promising alternative to current synthetic anionic surfactants in a wide range of commercial applications.

Capturing the effect of [PF3(C2F5)3]-vs. [PF6]-, flexible anion vs. rigid, and scaled charge vs. unit on the transport properties of [bmim]+-based ionic liquids: a comparative MD study.

Science.gov (United States)

Kowsari, Mohammad H; Ebrahimi, Soraya

2018-05-16

Comprehensive molecular dynamics simulations are performed to study the average single-particle dynamics and the transport properties of 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP], ionic liquids (ILs) at 400 K. We applied one of the most widely used nonpolarizable all-atom force fields for ILs, both with the original unit (±1) charges on each ion and with the partial charges uniformly scaled to 80-85%, taking into account the average polarizability and tracing the experimentally compatible transport properties. In all simulations, [bmim]+ was considered to be flexible, while the effect of a flexible vs. rigid structure of the anions and the effect of two applied charge sets on the calculated properties were separately investigated in detail. The simulation results showed that replacing [PF6]- with [FAP]-, considering anion flexibility, and applying the charge-scaled model significantly enhanced the ionic self-diffusion, ionic conductivity, inverse viscosity, and hyper anion preference (HAP). Both of the calculated self-diffusion coefficients from the long-time linear slope of the mean-square displacement (MSD) and from the integration of the velocity autocorrelation function (VACF) for the centers of mass of the ions were used for evaluation of the ionic transference number, HAP, ideal Nernst-Einstein ionic conductivity (σNE), and the Stokes-Einstein viscosity. In addition, for quantification of the degree of complicated ionic association (known as the Nernst-Einstein deviation parameter, Δ) and ionicity phenomena in the two studied ILs, the ionic conductivity was determined more rigorously by the Green-Kubo integral of the electric-current autocorrelation function (ECACF), and then the σGK/σNE ratio was evaluated. It was found that the correlated motion of the (cationanion) neighbors in [bmim][FAP] is smaller than in [bmim][PF6]. The relaxation times of

Effects of Anion Mobility on Electrochemical Behaviors of Lithium–Sulfur Batteries

Energy Technology Data Exchange (ETDEWEB)

Han, Kee Sung; Chen, Junzheng; Cao, Ruiguo; Rajput, Nav Nidhi; Murugesan, Vijayakumar; Shi, Lili; Pan, Huilin; Zhang, Jiguang; Liu, Jun; Persson, Kristin A.; Mueller, Karl T.

2017-10-27

The electrolyte is a crucial component of lithium-sulfur (Li-S) batteries, as it controls polysulfide dissolution, charge shuttling processes, and solid-electrolyte interphase (SEI) layer formation. Experimentally, the overall performance of Li-S batteries varies with choice of solvent system and Li-salt used in the electrolyte, and a lack of predictive understanding about the effects of individual electrolyte components inhibits the rational design of electrolytes for Li-S batteries. Here we analyze the role of the counter anions of common Li salts (such as TfO-, FSI-, TFSI-, and TDI-) when dissolved in DOL/DME (1:1 vol.) for use in Li-S batteries. The evolution of ion-ion and ion-solvent interactions due to vari-ous anions was analyzed using 17O NMR and pulsed-field gradient (PFG) NMR and then correlated with electrochemi-cal performance in Li-S cells. These data reveal that the for-mation of the passivation layer on the anode and the loss of active materials from the cathode (evidenced by polysulfide dissolution) are related to anion mobility and affinity with lithium polysulfide, respectively. For future electrolyte de-sign, anions with lower mobility and weaker interactions with lithium polysulfides may be superior candidates for increasing the long-term stability of Li-S batteries.

The study towards high intensity high charge state laser ion sources.

Science.gov (United States)

Zhao, H Y; Jin, Q Y; Sha, S; Zhang, J J; Li, Z M; Liu, W; Sun, L T; Zhang, X Z; Zhao, H W

2014-02-01

As one of the candidate ion sources for a planned project, the High Intensity heavy-ion Accelerator Facility, a laser ion source has been being intensively studied at the Institute of Modern Physics in the past two years. The charge state distributions of ions produced by irradiating a pulsed 3 J/8 ns Nd:YAG laser on solid targets of a wide range of elements (C, Al, Ti, Ni, Ag, Ta, and Pb) were measured with an electrostatic ion analyzer spectrometer, which indicates that highly charged ions could be generated from low-to-medium mass elements with the present laser system, while the charge state distributions for high mass elements were relatively low. The shot-to-shot stability of ion pulses was monitored with a Faraday cup for carbon target. The fluctuations within ±2.5% for the peak current and total charge and ±6% for pulse duration were demonstrated with the present setup of the laser ion source, the suppression of which is still possible.

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Moyer, Bruce a.; Bostick, Debra A.; Fowler, Christopher J.; Kang, Hyun-Ah; Ruas, Alexandre; Delmau, Laetitia H.; Haverlock, Tamara J.; Llinares, Jose M.; Hossain, Alamgir; Kang, S. O.; Bowman-James, Kristin; Shriver, James A.; Marquez, Manuel; Sessler, Jonathan L.

2005-01-01

The major thrust of this project led by the University of Kansas (Prof. Kristin Bowman-Jones) entails the exploration of the principles of recognition and separation of sulfate by the design, synthesis, and testing of novel sulfate extractants. A key science need for the cleanup of tank wastes at Hanford has been identified in developing methods to separate those bulk waste components that have low solubilities in borosilicate glass. Sulfate has been identified as a particularly difficult and expensive problem in that its concentration in the waste is relatively high, its solubility in glass is especially low, and it interferes with the performance of both vitrification equipment and the glass waste form. The new extractants will be synthesized by the University of Kansas and the University of Texas, Austin. Oak Ridge National Laboratory (ORNL) is subjecting the new extractants to experiments that will determine their properties and effectiveness in separating sulfate from the major competing anions in the waste, especially nitrate. Such experiments will entail primarily liquid-liquid extraction. Current efforts focus on exciting new systems in which the anion receptors act as synergists for anion exchange

A survey of aspartate-phenylalanine and glutamate-phenylalanine interactions in the protein data bank: searching for anion-π pairs.

Science.gov (United States)

Philip, Vivek; Harris, Jason; Adams, Rachel; Nguyen, Don; Spiers, Jeremy; Baudry, Jerome; Howell, Elizabeth E; Hinde, Robert J

2011-04-12

Protein structures are stabilized using noncovalent interactions. In addition to the traditional noncovalent interactions, newer types of interactions are thought to be present in proteins. One such interaction, an anion-π pair, in which the positively charged edge of an aromatic ring interacts with an anion, forming a favorable anion-quadrupole interaction, has been previously proposed [Jackson, M. R., et al. (2007) J. Phys. Chem. B111, 8242-8249]. To study the role of anion-π interactions in stabilizing protein structure, we analyzed pairwise interactions between phenylalanine (Phe) and the anionic amino acids, aspartate (Asp) and glutamate (Glu). Particular emphasis was focused on identification of Phe-Asp or -Glu pairs separated by less than 7 Å in the high-resolution, nonredundant Protein Data Bank. Simplifying Phe to benzene and Asp or Glu to formate molecules facilitated in silico analysis of the pairs. Kitaura-Morokuma energy calculations were performed on roughly 19000 benzene-formate pairs and the resulting energies analyzed as a function of distance and angle. Edgewise interactions typically produced strongly stabilizing interaction energies (-2 to -7.3 kcal/mol), while interactions involving the ring face resulted in weakly stabilizing to repulsive interaction energies. The strongest, most stabilizing interactions were identified as preferentially occurring in buried residues. Anion-π pairs are found throughout protein structures, in helices as well as β strands. Numerous pairs also had nearby cation-π interactions as well as potential π-π stacking. While more than 1000 structures did not contain an anion-π pair, the 3134 remaining structures contained approximately 2.6 anion-π pairs per protein, suggesting it is a reasonably common motif that could contribute to the overall structural stability of a protein.

A Survey of Aspartate-Phenylalanine and Glutamate-Phenylalanine Interactions in the Protein Data Bank: Searching for Anion-pi Pairs

Energy Technology Data Exchange (ETDEWEB)

Philip, Vivek M [ORNL; Harris, Jason B [ORNL; Adams, Rachel M [ORNL; Nguyen, Don [University of Tennessee; Spiers, Jeremy D [ORNL; Baudry, Jerome Y [ORNL; Howell, Elizabeth E [ORNL; Hinde, Robert J [ORNL

2011-01-01

Protein structures are stabilized using noncovalent interactions. In addition to the traditional noncovalent interactions, newer types of interactions are thought to be present in proteins. One such interaction, an anion-{pi} pair, in which the positively charged edge of an aromatic ring interacts with an anion, forming a favorable anion-quadrupole interaction, has been previously proposed [Jackson, M. R., et al. (2007) J. Phys. Chem. B111, 8242-8249]. To study the role of anion-{pi} interactions in stabilizing protein structure, we analyzed pairwise interactions between phenylalanine (Phe) and the anionic amino acids, aspartate (Asp) and glutamate (Glu). Particular emphasis was focused on identification of Phe-Asp or -Glu pairs separated by less than 7 {angstrom} in the high-resolution, nonredundant Protein Data Bank. Simplifying Phe to benzene and Asp or Glu to formate molecules facilitated in silico analysis of the pairs. Kitaura-Morokuma energy calculations were performed on roughly 19000 benzene-formate pairs and the resulting energies analyzed as a function of distance and angle. Edgewise interactions typically produced strongly stabilizing interaction energies (-2 to -7.3 kcal/mol), while interactions involving the ring face resulted in weakly stabilizing to repulsive interaction energies. The strongest, most stabilizing interactions were identified as preferentially occurring in buried residues. Anion-{pi} pairs are found throughout protein structures, in helices as well as {beta} strands. Numerous pairs also had nearby cation-{pi} interactions as well as potential {pi}-{pi} stacking. While more than 1000 structures did not contain an anion-{pi} pair, the 3134 remaining structures contained approximately 2.6 anion-{pi} pairs per protein, suggesting it is a reasonably common motif that could contribute to the overall structural stability of a protein.

Fluoride Anion Recognition by a Multifunctional Urea Derivative: An Experimental and Theoretical Study

Directory of Open Access Journals (Sweden)

Jana Schiller

2016-05-01

Full Text Available In this work we demonstrate the ability of a multifaceted N,N′-disubstituted urea to selectively recognize fluoride anion (F− among other halides. This additional function is now added to its already reported organocatalytic and organogelator properties. The signaling mechanism relies on the formation of a charge-transfer (CT complex between the urea-based sensor and F¯ in the ground state with a high association constant as demonstrated by absorption and fluorescence spectroscopy. The nature of the hydrogen bonding interaction between the sensor and F¯ was established by 1H-NMR studies and theoretical calculations. Moreover, the recovery of the sensor was achieved by addition of methanol.

Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zanni, Martin Thomas [Univ. of California, Berkeley, CA (United States)

1999-12-01

This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents.

Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

International Nuclear Information System (INIS)

Zanni, Martin T.

1999-01-01

This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have developed a new technique, anion femtosecond photoelectron spectroscopy, and applied it to gas phase photodissociation and charge transfer processes. Studies are presented that (1) characterize the ground and excited states of isolated and clustered anions, (2) monitor the photodissociation dynamics of isolated and clustered anions, and (3) explore the charge-transfer-to-solvent states of atomic iodide clustered with polar and non-polar solvents

Salt effects on hydrophobic interaction and charge screening in the folding of a negatively charged peptide to a coiled coil (leucine zipper).

Science.gov (United States)

Jelesarov, I; Dürr, E; Thomas, R M; Bosshard, H R

1998-05-19

The stability of a coiled coil or leucine zipper is controlled by hydrophobic interactions and electrostatic forces between the constituent helices. We have designed a 30-residue peptide with the repeating seven-residue pattern of a coiled coil, (abcdefg)n, and with Glu in positions e and g of each heptad. The glutamate side chains prevented folding at pH values above 6 because of electrostatic repulsion across the helix dimer interface as well as within the individual helices. Protonation of the carboxylates changed the conformation from a random coil monomer to a coiled coil dimer. Folding at alkaline pH where the peptide had a net charge of -7e was promoted by the addition of salts. The nature of the charge screening cation was less important than that of the anion. The high salt concentrations (>1 M) necessary to induce folding indicated that the salt-induced folding resulted from alterations in the protein-water interaction. Folding was promoted by the kosmotropic anions sulfate and fluoride and to a lesser extent by the weak kosmotrope formate, whereas chloride and the strong chaotrope perchlorate were ineffective. Kosmotropes are excluded from the protein surface, which is preferentially hydrated, and this promotes folding by strengthening hydrophobic interactions at the coiled coil interface. Although charge neutralization also contributed to folding, it was effective only when the screening cation was partnered by a good kosmotropic anion. Folding conformed to a two-state transition from random coil monomer to coiled coil dimer and was enthalpy driven and characterized by a change in the heat capacity of unfolding of 3.9 +/- 1.2 kJ mol-1 K-1. The rate of folding was analyzed by fluorescence stopped-flow measurements. Folding occurred in a biphasic reaction in which the rapid formation of an initial dimer (kf = 2 x 10(7) M-1 s-1) was followed by an equally rapid concentration-independent rearrangement to the folded dimer (k > 100 s-1).

High Voltage Charge Pump

KAUST Repository

Emira, Ahmed A.; Abdelghany, Mohamed A.; Elsayed, Mohannad Yomn; Elshurafa, Amro M; Salama, Khaled N.

2014-01-01

Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

High Voltage Charge Pump

KAUST Repository

Emira, Ahmed A.

2014-10-09

Various embodiments of a high voltage charge pump are described. One embodiment is a charge pump circuit that comprises a plurality of switching stages each including a clock input, a clock input inverse, a clock output, and a clock output inverse. The circuit further comprises a plurality of pumping capacitors, wherein one or more pumping capacitors are coupled to a corresponding switching stage. The circuit also comprises a maximum selection circuit coupled to a last switching stage among the plurality of switching stages, the maximum selection circuit configured to filter noise on the output clock and the output clock inverse of the last switching stage, the maximum selection circuit further configured to generate a DC output voltage based on the output clock and the output clock inverse of the last switching stage.

Diffuse neutron scattering from anion-excess strontium chloride

DEFF Research Database (Denmark)

Goff, J.P.; Clausen, K.N.; Fåk, B.

1992-01-01

The defect structure and diffusional processes have been studied in the anion-excess fluorite (Sr, Y)Cl2.03 by diffuse neutron scattering techniques. Static cuboctahedral clusters found at ambient temperature break up at temperatures below 1050 K, where the anion disorder is highly dynamic. The a...

Gas phase structures and charge localization in small aluminum oxide anions: Infrared photodissociation spectroscopy and electronic structure calculations

Energy Technology Data Exchange (ETDEWEB)

Song, Xiaowei; Fagiani, Matias R. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstrasse 2, D-04103 Leipzig (Germany); Gewinner, Sandy; Schöllkopf, Wieland [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Asmis, Knut R., E-mail: knut.asmis@uni-leipzig.de, E-mail: js@chemie.hu-berlin.de [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstrasse 2, D-04103 Leipzig (Germany); Bischoff, Florian A.; Berger, Fabian; Sauer, Joachim, E-mail: knut.asmis@uni-leipzig.de, E-mail: js@chemie.hu-berlin.de [Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, D-10099 Berlin (Germany)

2016-06-28

We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D{sub 2}-tagged AlO{sub 1-4}{sup −} and Al{sub 2}O{sub 3-6}{sup −} are measured in the region from 400 to 1200 cm{sup −1}. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al{sub 2}O{sub 3-6}{sup −} anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO{sub 3}{sup −}. Terminal Al–O stretching modes are found between 1140 and 960 cm{sup −1}. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm{sup −1}) and lower energies (850-570 cm{sup −1}), respectively. Four modes in-between 910 and 530 cm{sup −1} represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al–(O){sub 2}–Al ring.

Thermal spike analysis of highly charged ion tracks

International Nuclear Information System (INIS)

Karlušić, M.; Jakšić, M.

2012-01-01

The irradiation of material using swift heavy ion or highly charged ion causes excitation of the electron subsystem at nanometer scale along the ion trajectory. According to the thermal spike model, energy deposited into the electron subsystem leads to temperature increase due to electron–phonon coupling. If ion-induced excitation is sufficiently intensive, then melting of the material can occur, and permanent damage (i.e., ion track) can be formed upon rapid cooling. We present an extension of the analytical thermal spike model of Szenes for the analysis of surface ion track produced after the impact of highly charged ion. By applying the model to existing experimental data, more than 60% of the potential energy of the highly charged ion was shown to be retained in the material during the impact and transformed into the energy of the thermal spike. This value is much higher than 20–40% of the transferred energy into the thermal spike by swift heavy ion. Thresholds for formation of highly charged ion track in different materials show uniform behavior depending only on few material parameters.

Green sample preparation for liquid chromatography and capillary electrophoresis of anionic and cationic analytes.

Science.gov (United States)

Wuethrich, Alain; Haddad, Paul R; Quirino, Joselito P

2015-04-21

A sample preparation device for the simultaneous enrichment and separation of cationic and anionic analytes was designed and implemented in an eight-channel configuration. The device is based on the use of an electric field to transfer the analytes from a large volume of sample into small volumes of electrolyte that was suspended into two glass micropipettes using a conductive hydrogel. This simple, economical, fast, and green (no organic solvent required) sample preparation scheme was evaluated using cationic and anionic herbicides as test analytes in water. The analytical figures of merit and ecological aspects were evaluated against the state-of-the-art sample preparation, solid-phase extraction. A drastic reduction in both sample preparation time (94% faster) and resources (99% less consumables used) was observed. Finally, the technique in combination with high-performance liquid chromatography and capillary electrophoresis was applied to analysis of quaternary ammonium and phenoxypropionic acid herbicides in fortified river water as well as drinking water (at levels relevant to Australian guidelines). The presented sustainable sample preparation approach could easily be applied to other charged analytes or adopted by other laboratories.

Photoconversion and dynamic hole recycling process in anion vacancies in neutron-irradiated MgO crystals

International Nuclear Information System (INIS)

Monge, M.A.; Gonzalez, R.; Munoz Santiuste, J.E.; Pareja, R.; Chen, Y.; Kotomin, E.A.; Popov, A.I.

1999-01-01

Optical spectroscopy and theory demonstrate that photon excitation of the positively charged anion vacancies (F + centers) at 5.0 eV in neutron-irradiated MgO crystals releases holes that are subsequently trapped at V-type centers, which are cation vacancies charge compensated by impurities, such as Al 3+ , F - , and OH - ions. The concentration of trapped-hole centers was found to exceed that of available anion vacancies. The disproportionately large amount of holes produced is attributed to a dynamic recycling process, by which the F + center serves to release a hole to the V-type centers and subsequently trap a hole from an Fe 3+ ion. The net effect was the increase of V-type centers mostly at the expense of Fe 3+ ions. It was also shown that concurrently there was a component which distributed holes directly from Fe 3+ to the V-type centers. copyright 1999 The American Physical Society

Photoelectron spectroscopy and density functional theory studies of (FeS)mH- (m = 2-4) cluster anions: effects of the single hydrogen.

Science.gov (United States)

Yin, Shi; Bernstein, Elliot R

2017-12-20

Single hydrogen containing iron hydrosulfide cluster anions (FeS) m H - (m = 2-4) are studied by photoelectron spectroscopy (PES) at 3.492 eV (355 nm) and 4.661 eV (266 nm) photon energies, and by Density Functional Theory (DFT) calculations. The structural properties, relative energies of different spin states and isomers, and the first calculated vertical detachment energies (VDEs) of different spin states for these (FeS) m H - (m = 2-4) cluster anions are investigated at various reasonable theory levels. Two types of structural isomers are found for these (FeS) m H - (m = 2-4) clusters: (1) the single hydrogen atom bonds to a sulfur site (SH-type); and (2) the single hydrogen atom bonds to an iron site (FeH-type). Experimental and theoretical results suggest such available different SH- and FeH-type structural isomers should be considered when evaluating the properties and behavior of these single hydrogen containing iron sulfide clusters in real chemical and biological systems. Compared to their related, respective pure iron sulfur (FeS) m - clusters, the first VDE trend of the diverse type (FeS) m H 0,1 - (m = 1-4) clusters can be understood through (1) the different electron distribution properties of their highest singly occupied molecular orbital employing natural bond orbital analysis (NBO/HSOMO), and (2) the partial charge distribution on the NBO/HSOMO localized sites of each cluster anion. Generally, the properties of the NBO/HSOMOs play the principal role with regard to the physical and chemical properties of all the anions. The change of cluster VDE from low to high is associated with the change in nature of their NBO/HSOMO from a dipole bound and valence electron mixed character, to a valence p orbital on S, to a valence d orbital on Fe, and to a valence p orbital on Fe or an Fe-Fe delocalized valence bonding orbital. For clusters having the same properties for NBO/HSOMOs, the partial charge distributions at the NBO/HSOMO localized sites additionally

Band-gap-confinement and image-state-recapture effects in the survival of anions scattered from metal surfaces

International Nuclear Information System (INIS)

Schmitz, Andrew; Shaw, John; Chakraborty, Himadri S.; Thumm, Uwe

2010-01-01

The resonant charge transfer process in the collision of hydrogen anions with metal surfaces is described within a single-active-electron wave-packet propagation method. The ion-survival probability is found to be strongly enhanced at two different surface-specific perpendicular velocities of the ion. It is shown that, while the low-velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, the high-velocity enhancement is due to electron recapture from transiently populated image states. Results are presented for Li(110), Cu(111), and Pd(111) surfaces.

Carbon dioxide is tightly bound in the [Co(Pyridine)(CO2)](-) anionic complex.

Science.gov (United States)

Graham, Jacob D; Buytendyk, Allyson M; Zhang, Xinxing; Kim, Seong K; Bowen, Kit H

2015-11-14

The [Co(Pyridine)(CO2)](-) anionic complex was studied through the combination of photoelectron spectroscopy and density functional theory calculations. This complex was envisioned as a primitive model system for studying CO2 binding to negatively charged sites in metal organic frameworks. The vertical detachment energy (VDE) measured via the photoelectron spectrum is 2.7 eV. Our calculations imply a structure for [Co(Pyridine)(CO2)](-) in which a central cobalt atom is bound to pyridine and CO2 moieties on either sides. This structure was validated by acceptable agreement between the calculated and measured VDE values. Based on our calculations, we found CO2 to be bound within the anionic complex by 1.4 eV.

Carbon dioxide is tightly bound in the [Co(Pyridine)(CO2)]- anionic complex

Science.gov (United States)

Graham, Jacob D.; Buytendyk, Allyson M.; Zhang, Xinxing; Kim, Seong K.; Bowen, Kit H.

2015-11-01

The [Co(Pyridine)(CO2)]- anionic complex was studied through the combination of photoelectron spectroscopy and density functional theory calculations. This complex was envisioned as a primitive model system for studying CO2 binding to negatively charged sites in metal organic frameworks. The vertical detachment energy (VDE) measured via the photoelectron spectrum is 2.7 eV. Our calculations imply a structure for [Co(Pyridine)(CO2)]- in which a central cobalt atom is bound to pyridine and CO2 moieties on either sides. This structure was validated by acceptable agreement between the calculated and measured VDE values. Based on our calculations, we found CO2 to be bound within the anionic complex by 1.4 eV.

The Role of Coulomb Interactions for Spin Crossover Behaviors and Crystal Structural Transformation in Novel Anionic Fe(III Complexes from a π-Extended ONO Ligand

Directory of Open Access Journals (Sweden)

Suguru Murata

2016-05-01

Full Text Available To investigate the π-extension effect on an unusual negative-charged spin crossover (SCO FeIII complex with a weak N2O4 first coordination sphere, we designed and synthesized a series of anionic FeIII complexes from a π-extended naphthalene derivative ligand. Acetonitrile-solvate tetramethylammonium (TMA salt 1 exhibited an SCO conversion, while acetone-solvate TMA salt 2 was in a high-spin state. The crystal structural analysis for 2 revealed that two-leg ladder-like cation-anion arrays derived from π-stacking interactions between π-ligands of the FeIII complex anion and Coulomb interactions were found and the solvated acetone molecules were in one-dimensional channels between the cation-anion arrays. A desolvation-induced single-crystal-to-single-crystal transformation to desolvate compound 2’ may be driven by Coulomb energy gain. Furthermore, the structural comparison between quasi-polymorphic compounds 1 and 2 revealed that the synergy between Coulomb and π-stacking interactions induces a significant distortion of coordination structure of 2.

Precision laser spectroscopy of highly charged ions

International Nuclear Information System (INIS)

Kuehl, T.; Borneis, S.; Becker, S.; Dax, A.; Engel, T.; Grieser, R.; Huber, G.; Klaft, I.; Klepper, O.; Kohl, A.; Marx, D.; Meier, K.; Neumann, R.; Schmitt, F.; Seelig, P.; Voelker, L.

1996-01-01

Recently, intense beams of highly charged ions have become available at heavy ion cooler rings. The obstacle for producing these highly interesting candidates is the large binding energy of K-shell electrons in heavy systems in excess of 100 keV. One way to remove these electrons is to strip them off by passing the ion through material. In the cooler ring, the ions are cooled to a well defined velocity. At the SIS/ESR complex it is possible to produce, store, and cool highly charged ions up to bare uranium with intensities exceeding 10 8 atoms in the ring. This opens the door for precision laser spectroscopy of hydrogenlike-heavy ions, e.g. 209 Bi 82+ , and allows to examine the interaction of the single electron with the large fields of the heavy nucleus, exceeding any artificially produced electric and magnetic fields by orders of magnitude. In the electron cooler the interaction of electrons and highly charged ions otherwise only present in the hottest plasmas can be studied. (orig.)

Pu Anion Exchange Process Intensification

International Nuclear Information System (INIS)

Taylor-Pashow, Kathryn M. L.

2017-01-01

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 the 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.

Pu Anion Exchange Process Intensification

Energy Technology Data Exchange (ETDEWEB)

Taylor-Pashow, Kathryn M. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2017-10-06

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 the 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.

Cytotoxic mechanisms of hydrosulfide anion and cyanide anion in primary rat hepatocyte cultures

International Nuclear Information System (INIS)

Thompson, Rodney W.; Valentine, Holly L.; Valentine, William M.

2003-01-01

Hydrogen sulfide and hydrogen cyanide are known to compromise mitochondrial respiration through inhibition of cytochrome c oxidase and this is generally considered to be their primary mechanism of toxicity. Experimental studies and the efficiency of current treatment protocols suggest that H 2 S may exert adverse physiological effects through additional mechanisms. To evaluate the role of alternative mechanisms in H 2 S toxicity, the relative contributions of electron transport inhibition, uncoupling of mitochondrial respiration, and opening of the mitochondrial permeability transition pore (MPTP) to hydrosulfide and cyanide anion cytotoxicity in primary hepatocyte cultures were examined. Supplementation of hepatocytes with the glycolytic substrate, fructose, rescued hepatocytes from cyanide anion induced toxicity, whereas fructose supplementation increased hydrosulfide anion toxicity suggesting that hydrosulfide anion may compromise glycolysis in hepatocytes. Although inhibitors of the MPTP opening were protective for hydrosulfide anion, they had no effect on cyanide anion toxicity, consistent with an involvement of the permeability transition pore in hydrosulfide anion toxicity but not cyanide anion toxicity. Exposure of isolated rat liver mitochondria to hydrosulfide did not result in large amplitude swelling suggesting that if H 2 S induces the permeability transition it does so indirectly through a mechanism requiring other cellular components. Hydrosulfide anion did not appear to be an uncoupler of mitochondrial respiration in hepatocytes based upon the inability of oligomycin and fructose to protect hepatocytes from hydrosulfide anion toxicity. These findings support mechanisms additional to inhibition of cytochrome c oxidase in hydrogen sulfide toxicity. Further investigations are required to assess the role of the permeability transition in H 2 S toxicity, determine whether similar affects occur in other cell types or in vivo and evaluate whether this may

Cassini CAPS-ELS observations of carbon-based anions and aerosol growth in Titan's ionosphere

Science.gov (United States)

Desai, Ravindra; Coates, Andrew; Wellbrock, Anne; Kataria, Dhiren; Jones, Geraint; Lewis, Gethyn; Waite, J.

2016-06-01

Cassini observations of Titans ionosphere revealed an atmosphere rich in positively charged ions with masses up to > 350 amu and negatively charged ions and aerosols with mass over charge ratios as high as 13,800 amu/q. The detection of negatively charged molecules by the Cassini CAPS Electron Spectrometer (CAPS-ELS) was particularly surprising and showed how the synthesis of large aerosol-size particles takes place at altitudes much greater than previously thought. Here, we present further analysis into this CAPS-ELS dataset, through an enhanced understanding of the instrument's response function. In previous studies the intrinsic E/E energy resolution of the instrument did not allow specific species to be identified and the detections were classified into broad mass ranges. In this study we use an updated fitting procedure to show how the ELS mass spectrum can be resolved into specific peaks at multiples of carbon-based anions up to > 100 amu/q. The negatively charged ions and aerosols in Titans ionosphere increase in mass with decreasing altitude, the lightest species being observed close to Titan's exobase of ˜1,450km and heaviest species observed at altitudes < 950km. We identify key stages in this apparent growth process and report on key intermediaries which appear to trigger the rapid growth of the larger aerosol-size particles.

Comparing Positively and Negatively Charged Distonic Radical Ions in Phenylperoxyl Forming Reactions.

Science.gov (United States)

Williams, Peggy E; Marshall, David L; Poad, Berwyck L J; Narreddula, Venkateswara R; Kirk, Benjamin B; Trevitt, Adam J; Blanksby, Stephen J

2018-06-04

In the gas phase, arylperoxyl forming reactions play a significant role in low-temperature combustion and atmospheric processing of volatile organic compounds. We have previously demonstrated the application of charge-tagged phenyl radicals to explore the outcomes of these reactions using ion trap mass spectrometry. Here, we present a side-by-side comparison of rates and product distributions from the reaction of positively and negatively charge tagged phenyl radicals with dioxygen. The negatively charged distonic radical ions are found to react with significantly greater efficiency than their positively charged analogues. The product distributions of the anion reactions favor products of phenylperoxyl radical decomposition (e.g., phenoxyl radicals and cyclopentadienone), while the comparable fixed-charge cations yield the stabilized phenylperoxyl radical. Electronic structure calculations rationalize these differences as arising from the influence of the charged moiety on the energetics of rate-determining transition states and reaction intermediates within the phenylperoxyl reaction manifold and predict that this influence could extend to intra-molecular charge-radical separations of up to 14.5 Å. Experimental observations of reactions of the novel 4-(1-carboxylatoadamantyl)phenyl radical anion confirm that the influence of the charge on both rate and product distribution can be modulated by increasing the rigidly imposed separation between charge and radical sites. These findings provide a generalizable framework for predicting the influence of charged groups on polarizable radicals in gas phase distonic radical ions. Graphical Abstract.

Structural Arrangement of Water Molecules around Highly Charged Nanoparticles: Molecular Dynamics Simulation

International Nuclear Information System (INIS)

Kim, Eunae; Yeom, Min Sun

2014-01-01

Molecular dynamics simulations were performed to understand the structural arrangement of water molecules around highly charged nanoparticles under aqueous conditions. The effect of two highly charged nanoparticles on the solvation charge asymmetry has been examined. We calculated the radial distribution functions of the components of water molecules around nanoparticles which have four charge types at two different salt concentrations. Even though the distributions of water molecules surrounding a sodium ion and a chloride ion are hardly affected by the charges of nanoparticles and the salt concentrations, those around highly charged nanoparticles are strongly influenced by the charges of nanoparticles, but hardly by the charges of nanoparticles and salt concentrations. We find that the distributions of hydrogen atoms in water molecules around one highly charged nanoparticle are dependent on the magnitude of the nanoparticle charge

High-LET charged particle radiotherapy

International Nuclear Information System (INIS)

Castro, J.R.; California Univ., San Francisco, CA

1991-07-01

The Department of Radiation Oncology at UCSF Medical Center and the Radiation Oncology Department at UC Lawrence Berkeley Laboratory have been evaluating the use of high LET charged particle radiotherapy in a Phase 1--2 research trial ongoing since 1979. In this clinical trail, 239 patients have received at least 10 Gy (physical) minimum tumor dose with neon ions, meaning that at least one-half of their total treatment was given with high-LET charged particle therapy. Ninety-one patients received all of their therapy with neon ions. Of the 239 patients irradiated, target sites included lesions in the skin, subcutaneous tissues, head and neck such as paranasal sinuses, nasopharynx and salivary glands (major and minor), skull base and juxtaspinal area, GI tract including esophagus, pancreas and biliary tract, prostate, lung, soft tissue and bone. Analysis of these patients has been carried out with a minimum followup period of 2 years

Modelling the transport of carbonic acid anions through anion-exchange membranes

International Nuclear Information System (INIS)

Nikonenko, V.; Lebedev, K.; Manzanares, J.A.; Pourcelly, G.

2003-01-01

Electrodiffusion of carbonate and bicarbonate anions through anion-exchange membranes (AEM) is described on the basis of the Nernst-Planck equations taking into account coupled hydrolysis reactions in the external diffusion boundary layers (DBLs) and internal pore solution. The model supposes local electroneutrality as well as chemical and thermodynamic equilibrium. The transport is considered in three layers being an anion exchange membrane and two adjoining diffusion layers. A mechanism of competitive transport of HCO 3 - and CO 3 2- anions through the membrane which takes into account Donnan exclusion of H + ions is proposed. It is predicted that the pH of the depleting solution decreases and that of the concentrating solution increases during electrodialysis (ED). Eventual deviations from local electroneutrality and local chemical equilibrium are discussed

[Co(NH3)6]3[Cu4(OH)(CO3)8].2H2O--a new carbonato-copper(II) anion stabilized by extensive hydrogen bonding.

Science.gov (United States)

Abrahams, Brendan F; Haywood, Marissa G; Robson, Richard

2004-04-21

Addition of Co(NH3)6(3+) to aqueous solutions of Cu(II) in excess carbonate promotes the assembly of a new highly charged carbonato-copper(II) anion, [Cu4(OH)(CO3)8](9-), which contains an unusual mu4 hydroxo-bridged square Cu4 arrangement, stabilised in the crystal by no less than forty hydrogen bonds (< 3 Angstrom) to hexammine cations.

Charge-state correlated cross sections for the production of low-velocity highly charged Ne ions by heavy-ion bombardment

International Nuclear Information System (INIS)

Gray, T.J.; Cocke, C.L.; Justiniano, E.

1980-01-01

We report measured cross sections for the collisional production of highly charged low-velocity Ne recoil ions resulting from the bombardment of a thin Ne gas target by highly charged 1-MeV/amu C, N, O, and F projectiles. The measurements were made using time-of-flight techniques which allowed the simultaneous identification of the final charge state of both the low-velocity recoil ion and the high-velocity projectile for each collision event. For a given incident-projectile charge state, the recoil charge-state distribution is very dependent upon the final charge state of the projectile. Single- and double-electron capture events by incident bare nuclei and projectile K-shell ionization during the collision cause large shifts in the recoil charge-state distributions toward higher charge states. A previously proposed energy-deposition model is modified to include the effects of projectile charge-changing collisions during the collision for bare and hydrogenlike projectiles and is used to discuss the present experimental results

Theoretical study on effects of curvature of graphene in conjunction with simultaneous anion- and - stacking interactions

Directory of Open Access Journals (Sweden)

Pouya Karimi

2015-12-01

Full Text Available A graphene sheet (C102H30 has been rolled up by computational quantum chemistry methods to construct single-walled carbon nanotube fragments (SWCNTFs. The anion-π interactions of F- anion together with π-π stacking interactions of benzene on inner face and outer face of the central rings of SWCNTFs have been concurrently investigated. Structural parameters and energy data of the ternary benzene-SWCNTF-F- complexes were considered. Also, effects of charge transfer and aromaticity were estimated to determine how curvature of graphene influences on simultaneous anion-π and π-π stacking interactions.  Results indicate that curvature of graphene leads to structural changes in SWCNTFs which effects on simultaneous interactions of F- anion and benzene with SWCNTFs. Also, results show that although p-p stacking is a weak interaction, but it can impact on order of binding energies in complexes involved both p-p stacking and anion-p interactions. 

Charged dust in planetary magnetospheres: Hamiltonian dynamics and numerical simulations for highly charged grains

Science.gov (United States)

Schaffer, L.; Burns, J. A.

1994-01-01

We use a combination of analytical and numerical methods to investigate the dynamics of charged dust grains in planetary magnetospheres. Our emphasis is on obtaining results valid for particles that are not necessarily dominated either by gravitational or electromagnetic forces. A Hamiltonian formulation of the problem yields exact results, for all values of charge-to-mass ratio, when we introduce two constraints: particles remain in the equatorial plane and the magnetic field is taken as axially symmetric. In particular, we obtain locations of equilibrium points, the frequencies of stable periodic orbits, the topology of separatrices in phase space, and the rate of longitudinal drift. These results are significant for specific applications: motion in the nearly aligned dipolar field of Saturn, and the trajectories of arbitrarily charged particles in complex magnetic fields for limited periods of time after ejection from parent bodies. Since the model is restrictive, we also use numerical integrations of the full three-dimensional equations of motion and illustrate under what conditions the constrained problem yields reasonable results. We show that a large fraction of the intermediately charged and highly charged (gyrating) particles will always be lost to a planet's atmosphere within a few hundred hours, for motion through tilted-dipole magnetic fields. We find that grains must have a very high charge-to-mass ratio in order to be mirrored back to the ring plane. Thus, except perhaps at Saturn where the dipole tilt is very small, the likely inhabitants of the dusty ring systems are those particles that are either nearly Keplerian (weakly charged) grains or grains whose charges place them in the lower end of the intermediate charge zone. Fianlly, we demonstrate the effect of plasma drag on the orbits of gyrating particles to be a rapid decrease in gyroradius followed by a slow radial evolution of the guiding center.

Inhibition of nuclear waste solutions containing multiple aggressive anions

International Nuclear Information System (INIS)

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. 10 refs., 5 figs., 2 tabs

Beamline for low-energy transport of highly charged ions at HITRAP

International Nuclear Information System (INIS)

Andelkovic, Z.; Herfurth, F.; Kotovskiy, N.; König, K.; Maaß, B.; Murböck, T.; Neidherr, D.; Schmidt, S.; Steinmann, J.; Vogel, M.; Vorobjev, G.

2015-01-01

A beamline for transport of highly charged ions with energies as low as a few keV/charge has been constructed and commissioned at GSI. Complementary to the existing infrastructure of the HITRAP facility for deceleration of highly charged ions from the GSI accelerator, the new beamline connects the HITRAP ion decelerator and an EBIT with the associated experimental setups. Therefore, the facility can now transport the decelerated heavy highly charged ions to the experiments or supply them offline with medium-heavy highly charged ions from the EBIT, both at energies as low as a few keV/charge. Here we present the design of the 20 m long beamline with the corresponding beam instrumentation, as well as its performance in terms of energy and transport efficiency

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

Energy Technology Data Exchange (ETDEWEB)

Li, Jie [Iowa State Univ., Ames, IA (United States)

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 different 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.

Intermolecular proton transfer in anionic complexes of uracil with alcohols

International Nuclear Information System (INIS)

Haranczyk, Maciej; Rak, Janusz; Gutowski, Maciej S.; Radisic, Dunja; Stokes, Sarah T.; Bowen, Kit H.

2005-01-01

A series of eighteen alcohols (ROH) has been designed with an enthalpy of deprotonation (H DP ) in a range of 13.8-16.3 eV. The effects of excess electron attachment to the binary alcohol-uracil (ROH...U) complexes have been studied at the density functional level with a B3LYP exchange-correlation functional and at the second order Moeller-Plesset perturbation theory level. The photoelectron spectra of anionic complexes of uracil with three alcohols (ethanol, 2,2,3,3,3-pentafluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol) have been measured with 2.54 eV photons. For ROHs with deprotonation enthalpies larger than 14.8 eV only the ROH...U - minimum exists on the potential energy surface of the anionic complex. For alcohols with deprotonation enthalpies in a range of 14.3-14.8 eV two minima might exist on the anionic potential energy surface, which correspond to the RO - ...HU . and ROH...U - structures. For ROHs with deprotonation enthalpies smaller than 14.3 eV, the excess electron attachment to the ROH...U complex always induces a barrier-free proton transfer from the hydroxyl group of ROH to the O8 atom of U, with the product being RO - ...HU . . A driving force for the intermolecular proton transfer is to stabilize the excess negative charge localized on a orbital of uracil. Therefore, these complexes with proton transferred to the anionic uracil are characterized by larger values of electron vertical detachment energy (VDE). The values of VDE for anionic complexes span a range from 1.0 to 2.3 eV and roughly correlate with the acidity of alcohols. However, there is a gap of ∼0.5 eV in the values of VDE, which separates the two families, ROH...U - and RO - ...HU . , of anionic complexes. The energy of stabilization for the anionic complexes spans a range from 0.6 to 1.7 eV and roughly correlates with the acidity of alcohols. The measured photoelectron spectra are in good agreement with the theoretical predictions

Calculating potential of mean force between like-charged nanoparticles: A comprehensive study on salt effects

International Nuclear Information System (INIS)

Wu, Yuan-Yan; Wang, Feng-Hua; Tan, Zhi-Jie

2013-01-01

Ions are critical to the structure and stability of polyelectrolytes such as nucleic acids. In this work, we systematically calculated the potentials of mean force between two like-charged nanoparticles in salt solutions by Monte Carlo simulations. The pseudo-spring method is employed to calculate the potential of mean force and compared systematically with the inversed-Boltzmann method. An effective attraction is predicted between two like-charged nanoparticles in divalent/trivalent salt solution and such attraction becomes weakened at very high salt concentration. Our analysis reveals that for the system, the configuration of ion-bridging nanoparticles is responsible for the attraction, and the invasion of anions into the inter-nanoparticles region at high salt concentration would induce attraction weakening rather than the charge inversion effect. The present method would be useful for calculating effective interactions during nucleic acid folding.

Production of highly charged ion beams with SECRAL

International Nuclear Information System (INIS)

Sun, L. T.; Zhao, H. W.; Zhang, X. Z.; Feng, Y. C.; Li, J. Y.; Guo, X. H.; Ma, H. Y.; Zhao, H. Y.; Ma, B. H.; Wang, H.; Li, X. X.; Jin, T.; Xie, D. Z.; Lu, W.; Cao, Y.; Shang, Y.

2010-01-01

Superconducting electron cyclotron resonance ion source with advanced design in Lanzhou (SECRAL) is an all-superconducting-magnet electron cyclotron resonance ion source (ECRIS) for the production of intense highly charged ion beams to meet the requirements of the Heavy Ion Research Facility in Lanzhou (HIRFL). To further enhance the performance of SECRAL, an aluminum chamber has been installed inside a 1.5 mm thick Ta liner used for the reduction of x-ray irradiation at the high voltage insulator. With double-frequency (18+14.5 GHz) heating and at maximum total microwave power of 2.0 kW, SECRAL has successfully produced quite a few very highly charged Xe ion beams, such as 10 e μA of Xe 37+ , 1 e μA of Xe 43+ , and 0.16 e μA of Ne-like Xe 44+ . To further explore the capability of the SECRAL in the production of highly charged heavy metal ion beams, a first test run on bismuth has been carried out recently. The main goal is to produce an intense Bi 31+ beam for HIRFL accelerator and to have a feel how well the SECRAL can do in the production of very highly charged Bi beams. During the test, though at microwave power less than 3 kW, more than 150 e μA of Bi 31+ , 22 e μA of Bi 41+ , and 1.5 e μA of Bi 50+ have been produced. All of these results have again demonstrated the great capability of the SECRAL source. This article will present the detailed results and brief discussions to the production of highly charged ion beams with SECRAL.

Electrolyte effects in a model of proton discharge on charged electrodes

Science.gov (United States)

Wiebe, Johannes; Kravchenko, Kateryna; Spohr, Eckhard

2015-01-01

We report results on the influence of NaCl electrolyte dissolved in water on proton discharge reactions from aqueous solution to charged platinum electrodes. We have extended a recently developed combined proton transfer/proton discharge model on the basis of empirical valence bond theory to include NaCl solutions with several different concentrations of cations and anions, both stoichiometric (1:1) compositions and non-stoichiometric ones with an excess of cations. The latter solutions partially screen the electrostatic potential from the surface charge of the negatively charged electrode. 500-1000 trajectories of a discharging proton were integrated by molecular dynamics simulations until discharge occurred, or for at most 1.5 ns. The results show a strong dependence on ionic strength, but only a weak dependence on the screening behavior, when comparing stoichiometric and non-stoichiometric solutions. Overall, the Na+ cations exert a more dominant effect on the discharge reaction, which we argue is likely due to the very rigid arrangements of the cations on the negatively polarized electrode surface. Thus, our model predicts, for the given and very high negative surface charge densities, the fastest discharge reaction for pure water, but obviously cannot take into account the fact that such high charge densities are even more out of reach experimentally than for higher electrolyte concentrations.

Charged current weak interactions at high energy

International Nuclear Information System (INIS)

Cline, D.

1977-01-01

We review high energy neutrino and antineutrino charged current interactions. An overview of the experimental data is given, including a discussion of the experimental status of the y anomaly. Locality tests, μ-e universality and charge symmetry invariance tests are discussed. Charm production is discussed. The experimental status of trimuon events and possible phenomenological models for these events are presented. (orig.) [de

Recognition of anions using urea and thiourea substituted calixarenes: A density functional theory study of non-covalent interactions

Science.gov (United States)

Athar, Mohd; Lone, Mohsin Y.; Jha, Prakash C.

2018-02-01

Designing of new calixarene receptors for the selective binding of anions is an age-old concept; even though expected outcomes from this field are at premature stage. Herein, we have performed quantum chemical calculations to provide structural basis of anion binding with urea and thiourea substituted calixarenes (1, 2, and 3). In particular, spherical halides (F-, Cl-, Br-) and linear anions (CN-, N3-, SCN-) were modelled for calculating binding energies with receptor 1, 2 and 3 followed by their marked IR vibrations; taking the available experimental information into account. We found that the thiourea substitutions have better capability to stabilize the anions. Results have suggested that the structural behaviour of macrocyclic motifs were responsible for displaying the anion binding potentials. Moreover, second order "charge transfer" interactions of n-σ∗NH and n-σ∗OH type along the H-bond axis played critical role in developing hydrogen bonds. The present work also examines the role of non-covalent interactions (NCI) and their effects on thermodynamic and chemical-reactivity descriptors.

Dansyl-labeled anionic amphiphile with a hexadecanoic carbon chain: Synthesis and detection for shape transitions in organized molecular assemblies

Science.gov (United States)

Gao, Lining; Xia, Huiyun; Wang, Xiaoman; Li, Li; Chen, Huaxin

2015-03-01

The probing properties of a new fluorophore-labeled anionic surfactant, sodium 16-(N-dansyl)aminocetylate (16-DAN-ACA) were investigated systematically in molecular assemblies, especially in the transitions between micelles and vesicles. 16-DAN-ACA can efficiently differentiate the two different aggregate types in mixed cationic and anionic surfactant systems. The fluorescence anisotropy of 16-DAN-ACA was found to be sensitive for directly detecting the micellar growth in micelles containing oppositely charged surfactants; both cationic cetyltrimethylammonium bromide (CTAB) systems and anionic sodium dodecyl sulfate (SDS) systems were studied. The results indicated that the 16-DAN-ACA is a good fluorescent probe for differentiating the different aggregates, and even more can be used to detect the micellar growth.

A high charge state heavy ion beam source for HIF

International Nuclear Information System (INIS)

Eylon, S.; Henestroza, E.

1995-04-01

A high current low emittance high charge state heavy ion beam source is being developed. This is designed to deliver HIF (heavy ion fusion) driver accelerator scale beam. Using high-charge-state beam in a driver accelerator for HIF may increase the acceleration efficiency, leading to a reduction in the driver accelerator size and cost. The proposed source system which consists of the gas beam electron stripper followed by a high charge state beam separator, can be added to existing single charge state, low emittance, high brightness ion sources and injectors. We shall report on the source physics design using 2D beam envelope simulations and experimental feasibility studies' results using a neutral gas stripper and a beam separator at the exit of the LBL 2 MV injector

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

International Nuclear Information System (INIS)

Sessler, Jonathan L.

2007-01-01

The major thrust of this project, led by the University of Kansas (Prof. Kristin Bowman-James), entails an exploration of the basic determinants of anion recognition and their application to the design, synthesis, and testing of novel sulfate extractants. A key scientific inspiration for the work comes from the need, codified in simple-to-appreciate terms by the Oak Ridge National Laboratory component of the team (viz. Dr. Bruce Moyer), for chemical entities that can help in the extractive removal of species that have low solubilities in borosilicate glass. Among such species, sulfate anion, has been identified as particularly insidious. Its presence interferes with the vitrification process, thus rendering the remediation of tank waste from, e.g., the Hanford site far more difficult and expensive. The availability of effective extractants, that would allow for the separation of separating sulfate from the major competing anions in the waste, especially nitrate, could allow for pre-vitrification removal of sulfate via liquid-liquid extraction. The efforts at The University of Texas, the subject of this report, have thus concentrated on the development of new sulfate receptors. These systems are designed to increase our basic understanding of anion recognition events and set the stage for the development of viable sulfate anion extractants. In conjunction with the Oak Ridge National Laboratory (ORNL) members of the research team, several of these new receptors were studied as putative extractants, with two of the systems being shown to act as promising synergists for anion exchange.

Tandem mass spectrometry characteristics of polyester anions and cations formed by electrospray ionization.

Science.gov (United States)

Arnould, Mark A; Buehner, Rita W; Wesdemiotis, Chrys; Vargas, Rafael

2005-01-01

Electrospray ionization of polyesters composed of isophthalic acid and neopentyl glycol produces carboxylate anions in negative mode and mainly sodium ion adducts in positive mode. A tandem mass spectrometry (MS/MS) study of these ions in a quadrupole ion trap shows that the collisionally activated dissociation pathways of the anions are simpler than those of the corresponding cations. Charge-remote fragmentations predominate in both cases, but the spectra obtained in negative mode are devoid of the complicating cation exchange observed in positive mode. MS/MS of the Na(+) adducts gives rise to a greater number of fragments but not necessarily more structural information. In either positive or negative mode, polyester oligomers with different end groups fragment by similar mechanisms. The observed fragments are consistent with rearrangements initiated by the end groups. Single-stage ESI mass spectra also are more complex in positive mode because of extensive H/Na substitutions; this is also true for matrix-assisted laser desorption ionization (MALDI) mass spectra. Hence, formation and analysis of anions might be the method of choice for determining block length, end group structure and copolymer sequence, provided the polyester contains at least one carboxylic acid end group that is ionizable to anions.

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

KAUST Repository

Han, Yang

2018-03-13

Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices. Compared to p-type dopants, the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions. In this article, we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2) in organic thin film transistor devices by soluble anion dopants. The addition of the dopants resulted in the formation of stable radical anions in thin films, as confirmed by EPR spectroscopy. By tuning the dopant concentration via simple solution mixing, the transistor parameters could be readily controlled. Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced, which resulted in the transistor behaviour approaching the desirable gate voltage-independent model. Reduced hysteresis was also observed, thanks to the trap filling by the dopant. Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude. Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

KAUST Repository

Han, Yang; Fei, Zhuping; Lin, Yen-Hung; Martin, Jaime; Tuna, Floriana; Anthopoulos, Thomas D.; Heeney, Martin

2018-01-01

Molecular doping is an important strategy to improve the charge transport properties of organic semiconductors in various electronic devices. Compared to p-type dopants, the development of n-type dopants is especially challenging due to poor dopant stability against atmospheric conditions. In this article, we report the n-doping of the milestone naphthalenediimide-based conjugated polymer P(NDI2OD-T2) in organic thin film transistor devices by soluble anion dopants. The addition of the dopants resulted in the formation of stable radical anions in thin films, as confirmed by EPR spectroscopy. By tuning the dopant concentration via simple solution mixing, the transistor parameters could be readily controlled. Hence the contact resistance between the electrodes and the semiconducting polymer could be significantly reduced, which resulted in the transistor behaviour approaching the desirable gate voltage-independent model. Reduced hysteresis was also observed, thanks to the trap filling by the dopant. Under optimal doping concentrations the channel on-current was increased several fold whilst the on/off ratio was simultaneously increased by around one order of magnitude. Hence doping with soluble organic salts appears to be a promising route to improve the charge transport properties of n-type organic semiconductors.

DNA release from lipoplexes by anionic lipids: correlation with lipid mesomorphism, interfacial curvature, and membrane fusion

Energy Technology Data Exchange (ETDEWEB)

Tarahovsky, Yury S.; Koynova, Rumiana; MacDonald, Robert C. (Northwestern)

2010-01-18

DNA release from lipoplexes is an essential step during lipofection and is probably a result of charge neutralization by cellular anionic lipids. As a model system to test this possibility, fluorescence resonance energy transfer between DNA and lipid covalently labeled with Cy3 and BODIPY, respectively, was used to monitor the release of DNA from lipid surfaces induced by anionic liposomes. The separation of DNA from lipid measured this way was considerably slower and less complete than that estimated with noncovalently labeled DNA, and depends on the lipid composition of both lipoplexes and anionic liposomes. This result was confirmed by centrifugal separation of released DNA and lipid. X-ray diffraction revealed a clear correlation of the DNA release capacity of the anionic lipids with the interfacial curvature of the mesomorphic structures developed when the anionic and cationic liposomes were mixed. DNA release also correlated with the rate of fusion of anionic liposomes with lipoplexes. It is concluded that the tendency to fuse and the phase preference of the mixed lipid membranes are key factors for the rate and extent of DNA release. The approach presented emphasizes the importance of the lipid composition of both lipoplexes and target membranes and suggests optimal transfection may be obtained by tailoring lipoplex composition to the lipid composition of target cells.

Retention of metal and sulphate ions from acidic mining water by anionic nanofibrillated cellulose.

Science.gov (United States)

Venäläinen, Salla H; Hartikainen, Helinä

2017-12-01

We carried out an adsorption experiment to investigate the ability of anionic nanofibrillated cellulose (NFC) to retain metal and SO 4 2- ions from authentic highly acidic (pH3.2) mining water. Anionic NFC gels of different consistencies (1.1-%, 1.4-% and 1.8-% w/w) were allowed to react for 10min with mining water, after which NFC-induced changes in the metal and SO 4 2- concentrations of the mining water were determined. The sorption capacities of the NFC gels were calculated as the difference between the element concentrations in the untreated and NFC-treated mining water samples. All the NFCs efficiently co-adsorbed both metals and SO 4 2- . The retention of metals was concluded to take place through formation of metal-ligand complexes. The reaction between the NFC ligand and the polyvalent cations renders the cellulose nanofibrils positively charged and, thus, able to retain SO 4 2- electrostatically. Adsorption capacity of the NFC gels substantially increased upon decreasing DM content as a result of the dilution-induced weakening of the mutual interactions between individual cellulose nanofibrils. This outcome reveals that the dilution of the NFC gel not only increases its purification capacity but also reduces the demand for cellulosic raw material. These results suggest that anionic NFC made of renewable materials serves as an environmentally sound and multifunctional purification agent for acidic multimetal mining waters or AMDs of high ionic strength. Unlike industrial minerals traditionally used to precipitate valuable metals from acidic mining effluents before their permanent disposal from the material cycle, NFC neither requires mining of unrenewable raw materials nor produces inorganic sludges. Copyright © 2017 Elsevier B.V. All rights reserved.

Anionic lipids and the maintenance of membrane electrostatics in eukaryotes.

Science.gov (United States)

Platre, Matthieu Pierre; Jaillais, Yvon

2017-02-01

A wide range of signaling processes occurs at the cell surface through the reversible association of proteins from the cytosol to the plasma membrane. Some low abundant lipids are enriched at the membrane of specific compartments and thereby contribute to the identity of cell organelles by acting as biochemical landmarks. Lipids also influence membrane biophysical properties, which emerge as an important feature in specifying cellular territories. Such parameters are crucial for signal transduction and include lipid packing, membrane curvature and electrostatics. In particular, membrane electrostatics specifies the identity of the plasma membrane inner leaflet. Membrane surface charges are carried by anionic phospholipids, however the exact nature of the lipid(s) that powers the plasma membrane electrostatic field varies among eukaryotes and has been hotly debated during the last decade. Herein, we discuss the role of anionic lipids in setting up plasma membrane electrostatics and we compare similarities and differences that were found in different eukaryotic cells.

Anionic silicate organic frameworks constructed from hexacoordinate silicon centres

Science.gov (United States)

Roeser, Jérôme; Prill, Dragica; Bojdys, Michael J.; Fayon, Pierre; Trewin, Abbie; Fitch, Andrew N.; Schmidt, Martin U.; Thomas, Arne

2017-10-01

Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by 29Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks—M2[Si(C16H10O4)1.5], where M = Li, Na, K and C16H10O4 is 9,10-dimethylanthracene-2,3,6,7-tetraolate—crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1,276 m2 g-1) was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.

Multistage charged particle accelerator, with high-vacuum insulation

International Nuclear Information System (INIS)

Holl, P.

1976-01-01

A multistage charged-particle accelerator for operating with accelerating voltages higher than 150 kV is described. The device consists essentially of a high-voltage insulator, a source for producing charged particles, a Wehnelt cylinder, an anode, and a post-accelerating tube containing stack-wise positioned post-accelerating electrodes. A high vacuum is used for insulating the parts carrying the high voltages, and at least one cylindrical screen surrounding these parts is interposed between them and the vacuum vessel, which can itself also function as a cylindrical screen

Anion exchange behavior of Ti, Zr, Hf, Nb and Ta as homologues of Rf and Db in mixed HF-acetone solutions

International Nuclear Information System (INIS)

Aksenov, N.V.; Bozhikov, G.A.; Starodub, G.Ya.; Dmitriev, S.N.; Filosofov, D.V.; Jon Sun Jin; Radchenko, V.I.; Lebedev, N.A.; Novgorodov, A.F.

2009-01-01

We studied in detail the sorption behavior of Ti, Zr, Hf, Nb and Ta on AG 1 anion exchange resin in HF-acetone mixed solutions as a function of organic cosolvent and acid concentrations. Anion exchange behavior was found to be strongly acetone concentration dependent. The distribution coefficients of Ti, Zr, Hf and Nb increased and those of Ta decreased with increasing content of acetone in HF solutions. With increasing HF concentration, anion exchange equilibrium analysis indicated the formation of fluoride complexes of group-4 elements with charge -3 and Ta with charge -2. For Nb the slope of -2 increased up to -5. Optimal conditions for separation of the elements using AIX chromatography were found. Group-4 elements formed MF 7 3- (M = Ti, Zr, Hf) complexes whose sorption decreased Ti > Hf > Zr in reverse order of complex stability. This fact is of particular interest for studying ion exchange behavior of Rf compared to Ti. The advantages of studying chemical properties of Rf and Db in aqueous HF solutions mixed with organic solvents are briefly discussed

Determination of carbohydrates by high performance anion chromatography-pulsed amperometric detection in mushrooms.

Science.gov (United States)

Zhou, Shuai; Tang, Qingjiu; Luo, Xi; Xue, Jun-Jie; Liu, Yanfang; Yang, Yan; Zhang, Jingsong; Feng, Na

2012-01-01

A method of detecting carbohydrates (fucose, trehalose, mannitol, arabitol, mannose, glucose, galactose, fructose, and ribose) by high-performance anion chromatography-pulsed amperometric detection (HAPEC-PAD) was established. The conditions are: CarboPac MA1 column, NaOH as the eluent, temperature 30°C, Au working electrode, Ag/AgCl reference electrode, and flow rate 0.4 mL/min. These nine analytes, which yielded high resolution by this method, could be detected in 40 minutes. Mushrooms were tested and good precision, stability, and reproducibility were achieved. This method is suitable for mushroom samples and could support research and development on sugar and sugar alcohol, which contains special effects.

Double layer for hard spheres with an off-center charge

Directory of Open Access Journals (Sweden)

W. Silvestre-Alcantara

2016-02-01

Full Text Available Simulations for the density and potential profiles of the ions in the planar electrical double layer of a model electrolyte or an ionic liquid are reported. The ions of a real electrolyte or an ionic liquid are usually not spheres; in ionic liquids, the cations are molecular ions. In the past, this asymmetry has been modelled by considering spheres that are asymmetric in size and/or valence (viz., the primitive model or by dimer cations that are formed by tangentially touching spheres. In this paper we consider spherical ions that are asymmetric in size and mimic the asymmetrical shape through an off-center charge that is located away from the center of the cation spheres, while the anion charge is at the center of anion spheres. The various singlet density and potential profiles are compared to (i the dimer situation, that is, the constituent spheres of the dimer cation are tangentially tethered, and (ii the standard primitive model. The results reveal the double layer structure to be substantially impacted especially when the cation is the counterion. As well as being of intrinsic interest, this off-center charge model may be useful for theories that consider spherical models and introduce the off-center charge as a perturbation.

Photophysical study of a charge transfer oxazole dye in micelles: Role of surfactant headgroups

Energy Technology Data Exchange (ETDEWEB)

Maiti, Jyotirmay [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Sarkar, Yeasmin; Parui, Partha Pratim [Department of Chemistry, Jadavpur University, Kolkata 700032 (India); Chakraborty, Sandipan [Department of Microbiology, University of Calcutta, Kolkata 700019 (India); Biswas, Suman [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India); Das, Ranjan, E-mail: ranjan.das68@gmail.com [Department of Chemistry, West Bengal State University, Barasat, Kolkata 700126 (India)

2015-07-15

Photophysics of 5-(4′′-dimethylaminophenyl)-2-(4′-sulfophenyl)oxazole, sodium salt (DMO) which undergoes intramolecular charge transfer in the excited state was studied in micelles. In the cationic and the nonionic micelles, significantly higher fluorescence quantum yield is observed in comparison to the anionic micelles, due to much lower accessibility of DMO to the water molecules in the former micelles than the latter. Time-resolved fluorescence decays were characterized by a fast (τ{sub 1}) and a slow (τ{sub 2}) component of decay in all the micelles. The fast decay component (τ{sub 1}) increases significantly in going from the anionic micelles to the cationic micelles, because of the poorly hydrated headgroup region of the latter micelles compared to the former. Furthermore, much higher value of the slow component of decay (τ{sub 2}) is observed for the cationic and the neutral micelles than the anionic micelles. This is attributed to the increased penetration of water molecules into the micellar core of the anionic micelles compared to the cationic and the neutral micelles. - Highlights: • Photophysics of the fluorophore are remarkably different in the cationic and the anionic micelles. • Differential hydration of the surfactant headgroups gives rise to significantly different fluorescence quantum yield and lifetime in oppositely charged micelles. • Electrostatic interactions fine tune location of the fluorophore in the micelle–water interface of ionic micelles.

Structures and properties of anionic clay minerals

International Nuclear Information System (INIS)

Koch, Chr. Bender

1998-01-01

The Moessbauer spectra of pyroaurite-sjoegrenite-type compounds (PTC) (layered anion exchangers) are discussed with reference to the crystal structure, cation order, and crystallite morphology. It is shown that cation-ordered layers are produced in the synthesis of carbonate and sulphate types of green rust. In contrast, synthetic and natural pyroaurite only occurs as disordered types. The redox chemistry of Fe(III) within the metal hydroxide layer is illustrated with examples of electrochemical oxidation and reversible reduction by boiling glycerol. The chemistry of iron in the interlayer is exemplified by the intercalation of Fe-cyanide complexes in hydrotalcite. This reaction may be used as a probe for the charge distribution in the interlayer

Signal amplification in electrochemical detection of buckwheat allergenic protein using field effect transistor biosensor by introduction of anionic surfactant

Directory of Open Access Journals (Sweden)

Sho Hideshima

2016-03-01

Full Text Available Food allergens, especially buckwheat proteins, sometimes induce anaphylactic shock in patients after ingestion. Development of a simple and rapid screening method based on a field effect transistor (FET biosensor for food allergens in food facilities or products is in demand. In this study, we achieved the FET detection of a buckwheat allergenic protein (BWp16, which is not charged enough to be electrically detected by FET biosensors, by introducing additional negative charges from anionic surfactants to the target proteins. A change in the FET characteristics reflecting surface potential caused by the adsorption of target charged proteins was observed when the target sample was coupled with the anionic surfactant (sodium dodecyl sulfate; SDS, while no significant response was detected without any surfactant treatment. It was suggested that the surfactant conjugated with the protein could be useful for the charge amplification of the target proteins. The surface plasmon resonance analysis revealed that the SDS-coupled proteins were successfully captured by the receptors immobilized on the sensing surface. Additionally, we obtained the FET responses at various concentrations of BWp16 ranging from 1 ng/mL to 10 μg/mL. These results suggest that a signal amplification method for FET biosensing is useful for allergen detection in the food industry. Keywords: Field effect transistor biosensor, Food allergen, Signal amplification, Ionic surfactant, Intrinsic charge

HITRAP: A Facility for Experiments with Trapped Highly Charged Ions

International Nuclear Information System (INIS)

Quint, W.; Dilling, J.; Djekic, S.; Haeffner, H.; Hermanspahn, N.; Kluge, H.-J.; Marx, G.; Moore, R.; Rodriguez, D.; Schoenfelder, J.; Sikler, G.; Valenzuela, T.; Verdu, J.; Weber, C.; Werth, G.

2001-01-01

HITRAP is a planned ion trap facility for capturing and cooling of highly charged ions produced at GSI in the heavy-ion complex of the UNILAC-SIS accelerators and the ESR storage ring. In this facility heavy highly charged ions up to uranium will be available as bare nuclei, hydrogen-like ions or few-electron systems at low temperatures. The trap for receiving and studying these ions is designed for operation at extremely high vacuum by cooling to cryogenic temperatures. The stored highly charged ions can be investigated in the trap itself or can be extracted from the trap at energies up to about 10 keV/q. The proposed physics experiments are collision studies with highly charged ions at well-defined low energies (eV/u), high-accuracy measurements to determine the g-factor of the electron bound in a hydrogen-like heavy ion and the atomic binding energies of few-electron systems, laser spectroscopy of HFS transitions and X-ray spectroscopy

Experimental investigation on the use of highly charged nanoparticles to improve the stability of weakly charged colloidal system.

Science.gov (United States)

Zubir, Mohd Nashrul Mohd; Badarudin, A; Kazi, S N; Misran, Misni; Amiri, Ahmad; Sadri, Rad; Khalid, Solangi

2015-09-15

The present work highlighted on the implementation of a unique concept for stabilizing colloids at their incipiently low charge potential. A highly charged nanoparticle was introduced within a coagulated prone colloidal system, serving as stabilizer to resist otherwise rapid flocculation and sedimentation process. A low size asymmetry of nanoparticle/colloid serves as the new topic of investigation in addition to the well-established large size ratio nanoparticle/microparticle study. Highly charged Al2O3 nanoparticles were used within the present research context to stabilize TiO2 and Fe3O4 based colloids via the formation of composite structures. It was believed, based on the experimental evidence, that Al2O3 nanoparticle interact with the weakly charged TiO2 and Fe3O4 colloids within the binary system via absorption and/or haloing modes to increase the overall charge potential of the respective colloids, thus preventing further surface contact via van der Waal's attraction. Series of experimental results strongly suggest the presence of weakly charged colloids in the studied bimodal system where, in the absence of highly charged nanoparticle, experience rapid instability. Absorbance measurement indicated that the colloidal stability drops in accordance to the highly charged nanoparticle sedimentation rate, suggesting the dominant influence of nanoparticles to attain a well-dispersed binary system. Further, it was found that the level of colloidal stability was enhanced with increasing nanoparticle fraction within the mixture. Rheological observation revealed that each hybrid complexes demonstrated behavior reminiscence to water with negligible increase in viscosity which serves as highly favorable condition particularly in thermal transport applications. Copyright © 2015 Elsevier Inc. All rights reserved.

A study of sorption of pertechnetate anion on chitosan

International Nuclear Information System (INIS)

Pivarciova, L.; Rosskopfova, O.; Rajec, P.; Galambos, M.

2015-01-01

Chitosan is one of the natural materials of biological origin. The sorption of pertechnetate anions from aqueous solutions on chitosan was studied in a batch system. This work was aimed to study influence of the contact time, effect of pH and effect of different ions on sorption of pertechnetate anions on chitosan. This sorbent was characterized by BET-surface area and potentiometric titration. The point of zero charge (pH pzc ) was at pH=7.15. The highest percentage of technetium sorption on chitosan was near pH 3. The adsorption capacity of chitosan decreased with increase in pH value above 3. In the initial pH range of 4-10, final pHs are the same. The selectivity of chitosan for these cations with concentration above 1·10 -3 mol·dm -3 was in the order Na + > Ca 2+ > Fe 3+ > Fe 2+ . The competition effect of (SO 4 ) 2- towards TcO 4 - sorption was stronger than the competition effect (ClO 4 ) - of ions. (authors)

High-resolution x-ray scattering studies of charge ordering in highly correlated electron systems

International Nuclear Information System (INIS)

Ghazi, M.E.

2002-01-01

Many important properties of transition metal oxides such as, copper oxide high-temperature superconductivity and colossal magnetoresistance (CMR) in manganites are due to strong electron-electron interactions, and hence these systems are called highly correlated systems. These materials are characterised by the coexistence of different kinds of order, including charge, orbital, and magnetic moment. This thesis contains high-resolution X-ray scattering studies of charge ordering in such systems namely the high-T C copper oxides isostructural system, La 2-x Sr x NiO 4 with various Sr concentrations (x = 0.33 - 0.2), and the CMR manganite system, Nd 1/2 Sr 1/2 MnO 3 . It also includes a review of charge ordering in a large variety of transition metal oxides, such as ferrates, vanadates, cobaltates, nickelates, manganites, and cuprates systems, which have been reported to date in the scientific literature. Using high-resolution synchrotron X-ray scattering, it has been demonstrated that the charge stripes exist in a series of single crystals of La 2-x Sr x NiO 4 with Sr concentrations (x = 0.33 - 0.2) at low temperatures. Satellite reflections due to the charge ordering were found with the wavevector (2ε, 0, 1) below the charge ordering transition temperature, T CO , where 2ε is the amount of separation from the corresponding Bragg peak. The charge stripes are shown to be two-dimensional in nature both by measurements of their correlation lengths and by measurement of the critical exponents of the charge stripe melting transition with an anomaly at x = 0.25. The results show by decreasing the hole concentration from the x = 0.33 to 0.2, the well-correlated charge stripes change to a glassy state at x = 0.25. The electronic transition into the charge stripe phase is second-order without any corresponding structural transition. Above the second-order transition critical scattering was observed due to fluctuations into the charge stripe phase. In a single-crystal of Nd

Binding of chloroquine to ionic micelles: Effect of pH and micellar surface charge

Energy Technology Data Exchange (ETDEWEB)

Souza Santos, Marcela de, E-mail: marcelafarmausp77@gmail.com [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Perpétua Freire de Morais Del Lama, Maria, E-mail: mpemdel@fcfrp.usp.br [Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Avenida do Café, s/n, Ribeirão Preto, São Paulo 14040-903 (Brazil); Instituto Nacional de Ciência e Tecnologia de Bioanalítica, Departamento de Química Analítica, Universidade Estadual de Campinas, Cidade Universitária Zeferino Vaz, s/n, Campinas, São Paulo 13083-970 (Brazil); Siuiti Ito, Amando, E-mail: amandosi@ffclrp.usp.br [Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes, 3900, Ribeirão Preto, São Paulo 14040-901 (Brazil); and others

2014-03-15

The pharmacological action of chloroquine relies on its ability to cross biological membranes in order to accumulate inside lysosomes. The present work aimed at understanding the basis for the interaction between different chloroquine species and ionic micelles of opposite charges, the latter used as a simple membrane model. The sensitivity of absorbance and fluorescence of chloroquine to changes in its local environment was used to probe its interaction with cetyltrimethylammonium micelles presenting bromide (CTAB) and sulfate (CTAS) as counterions, in addition to dodecyl sulfate micelles bearing sodium (SDS) and tetramethylammonium (TMADS) counterions. Counterion exchange was shown to have little effect on drug–micelle interaction. Chloroquine first dissociation constant (pKa{sub 1}) shifted to opposite directions when anionic and cationic micelles were compared. Chloroquine binding constants (K{sub b}) revealed that electrostatic forces mediate charged drug–micelle association, whereas hydrophobic interactions allowed neutral chloroquine to associate with anionic and cationic micelles. Fluorescence quenching studies indicated that monoprotonated chloroquine is inserted deeper into the micelle surface of anionic micelles than its neutral form, the latter being less exposed to the aqueous phase when associated with cationic over anionic assemblies. The findings provide further evidence that chloroquine–micelle interaction is driven by a tight interplay between the drug form and the micellar surface charge, which can have a major effect on the drug biological activity. -- Highlights: • Chloroquine (CQ) pKa{sub 1} increased for SDS micelles and decreased for CTAB micelles. • CQ is solubilized to the surface of both CTAB and SDS micelles. • Monoprotonated CQ is buried deeper into SDS micelles than neutral CQ. • Neutral CQ is less exposed to aqueous phase in CTAB over SDS micelles. • Local pH and micellar surface charge mediate interaction of CQ with

High Lithium Transference Number Electrolytes via Creation of 3-Dimensional, Charged, Nanoporous Networks from Dense Functionalized Nanoparticle Composites

KAUST Repository

Schaefer, Jennifer L.

2013-03-26

High lithium transference number, tLi+, electrolytes are desired for use in both lithium-ion and lithium metal rechargeable battery technologies. Historically, low tLi+ electrolytes have hindered device performance by allowing ion concentration gradients within the cell, leading to high internal resistances that ultimately limit cell lifetime, charging rates, and energy density. Herein, we report on the synthesis and electrochemical features of electrolytes based on nanoparticle salts designed to provide high tLi+. The salts are created by cofunctionalization of metal oxide nanoparticles with neutral organic ligands and tethered lithium salts. When dispersed in a conducting fluid such as tetraglyme, they spontaneously form a charged, nanoporous network of particles at moderate nanoparticle loadings. Modification of the tethered anion chemistry from -SO3 - to -SO3BF3 - is shown to enhance ionic conductivity of the electrolytes by facilitating ion pair dissociation. At a particle volume fraction of 0.15, the electrolyte exists as a self-supported, nanoporous gel with an optimum ionic conductivity of 10 -4 S/cm at room temperature. Galvanostatic polarization measurements on symmetric lithium metal cells containing the electrolyte show that the cell short circuit time, tSC, is inversely proportional to the square of the applied current density tSC ∼ J-2, consistent with previously predicted results for traditional polymer-in-salt electrolytes with low tLi+. Our findings suggest that electrolytes with tLi+ ≈ 1 and good ion-pair dissociation delay lithium dendrite nucleation and may lead to improved lithium plating in rechargeable batteries with metallic lithium anodes. © 2013 American Chemical Society.

ICR studies of some anionic gas phase reactions and FTICR software design

International Nuclear Information System (INIS)

Noest, A.J.

1983-01-01

This thesis consists of two parts. Part one (Chs. 1-5) reports experimental results from mostly drift-cell ICR studies of negative ion-molecule reactions; part two (Chs. 6-11) concerns the design of software for an FTICR instrument. The author discusses successively: 1. ion cyclotron resonance spectrometry; 2. the gas phase allyl anion; 3. the (M-H) and (M-H2) anions from acetone; 4. negative ion-molecule reactions of aliphatic nitrites studied by cyclotron resonance; 5. homoconjugation versus charge-dipole interaction effects in the stabilization of carbanions in the gas phase; 6. the Fourier Transform ICR method; 7. the FTICR-software; 8. an efficient adaptive matcher filter for fast transient signals; 9. reduction of spectral peak height errors by time-domain weighing; 10. Chirp excitation; 11. Compact data storage. The book concludes with a Dutch and English summary (G.J.P.)

Concept for high-charge-state ion induction accelerators

International Nuclear Information System (INIS)

Logan, B.G.; Perry, M.D.; Caporaso, G.J.

1996-01-01

This work describes a particular concept for ion induction linac accelerators using high-charge-state ions produced by an intense, short pulse laser, and compares the costs of a modular driver system producing 6.5 MJ for a variety of ion masses and charge states using a simple but consistent cost model

Seasonal variations in Na, K, Mg and Ca charge balance in marine brown algae from Saurashtra Coast (NW coast of India)

Digital Repository Service at National Institute of Oceanography (India)

Rao, Ch.K.; Singbal, S.Y.S.

) strongly correlated with Cl content suggesting that these cations were balanced by chloride ions. Divalent cations (Ca + Mg) seem to be balanced by the anion sulphate. Ash content of the algae was accounted by these major cations and anions. Charge...

Electron capture by highly charged low-velocity ions

International Nuclear Information System (INIS)

Cocke, C.L.; Dubois, R.; Justiniano, E.; Gray, T.J.; Can, C.

1982-01-01

This paper describes the use of a fast heavy ion beam to produce, by bombardment of gaseous targets, highly-charged low-velocity recoil ions, and the use of these secondary ions in turn as projectiles in studies of electron capture and ionization in low-energy collision systems. The interest in collisions involving low-energy highly-charged projectiles comes both from the somewhat simplifying aspects of the physics which attend the long-range capture and from applications to fusion plasmas, astrophysics and more speculative technology such as the production of X-ray lasers. The ions of interest in such applications should have both electronic excitation and center-of-mass energies in the keV range and cannot be produced by simply stripping fast heavy ion beams. Several novel types of ion source have been developed to produce low-energy highly-charged ions, of which the secondary ion recoil source discussed in this paper is one. (Auth.)

(100) faceted anion voids in electron irradiated fluorite

International Nuclear Information System (INIS)

Johnson, E.

1979-01-01

High fluence electron irradiation of fluorite crystals in the temperature range 150 to 320 K results in formation of a simple cubic anion void superlattice. Above 320 K the damage structure changes to a random distribution of large [001] faceted anion voids. This voidage behaviour, similar to that observed in a range of irradiated metals, is discussed in terms points defect rather than conventional colour centre terminology. (Auth.)

Photophysical Properties of SrTaO2N Thin Films and Influence of Anion Ordering: A Joint Theoretical and Experimental Investigation

KAUST Repository

Ziani, Ahmed

2017-04-10

Converting photon energy into chemical energy using inorganic materials requires the successful capture of photons, exciton dissociation, and the charge carrier diffusion. This study reports a thorough analysis of the optoelectronic properties of visible-light-responsive SrTaON perovskites to quantify their absorption coefficient and the generated charge carriers\\' effective masses, dielectric constants, and electronic structures. The measurements on such intrinsic properties were attempted using both epitaxial and polycrystalline SrTaON films deposited by radiofrequency magnetron sputtering under N reactive plasma. Density functional theory calculations using the HSE06 functional provided reliable values of these optoelectronic properties. Such quantities obtained by both measurements and calculations gave excellent correspondence and provide possible variations that account for the small discrepancies observed. One of the significant factors determining the optical properties was found to be the anion ordering in the perovskite structure imposed by the cations. As a result, the different anion ordering has a noticeable influence on the optical properties and high sensitivity of the hole effective mass. Determination of relative band positions with respect to the water redox properties was also attempted by Mott-Schottky analysis. All these results offer the opportunity to understand why SrTaON possesses intrinsically all the ingredients needed for an efficient water splitting device.

Photophysical Properties of SrTaO2N Thin Films and Influence of Anion Ordering: A Joint Theoretical and Experimental Investigation

KAUST Repository

Ziani, Ahmed; Le Paven, Claire; Le Gendre, Laurent; Marlec, Florent; Benzerga, Ratiba; Tessier, Franck; Cheviré , Franç ois; Hedhili, Mohamed N.; Garcia-Esparza, Angel T.; Melissen, Sigismund; Sautet, Philippe; Le Bahers, Tangui; Takanabe, Kazuhiro

2017-01-01

Converting photon energy into chemical energy using inorganic materials requires the successful capture of photons, exciton dissociation, and the charge carrier diffusion. This study reports a thorough analysis of the optoelectronic properties of visible-light-responsive SrTaON perovskites to quantify their absorption coefficient and the generated charge carriers' effective masses, dielectric constants, and electronic structures. The measurements on such intrinsic properties were attempted using both epitaxial and polycrystalline SrTaON films deposited by radiofrequency magnetron sputtering under N reactive plasma. Density functional theory calculations using the HSE06 functional provided reliable values of these optoelectronic properties. Such quantities obtained by both measurements and calculations gave excellent correspondence and provide possible variations that account for the small discrepancies observed. One of the significant factors determining the optical properties was found to be the anion ordering in the perovskite structure imposed by the cations. As a result, the different anion ordering has a noticeable influence on the optical properties and high sensitivity of the hole effective mass. Determination of relative band positions with respect to the water redox properties was also attempted by Mott-Schottky analysis. All these results offer the opportunity to understand why SrTaON possesses intrinsically all the ingredients needed for an efficient water splitting device.

Influence of Charge State on the Reaction of FeO3^+/- with Carbon Monoxide

Science.gov (United States)

Reveles, J. U.; Khanna, S. N.; Reilly, N. M.; Johnson, G. E.; Castleman, A. W., Jr.

2007-03-01

A synergistic study combining experiments in molecular beams and first principles electronic structure calculations within a gradient corrected density functional approach is used to investigate the reactivity of charged FeO3 clusters with CO. It is shown that highly oxidized iron clusters are able to readily effect the oxidation of CO to CO2 at ambient temperature. Calculated energy profiles of the reaction demonstrate that the oxidation efficiency is governed by the strength of oxygen binding to the iron atom. Results for FeO3^+/- are presented and reveal that cation clusters are more efficient than the corresponding anion clusters at effecting the oxidation reaction due to different bond energies resulting from charge distribution.

Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance. Final Report

International Nuclear Information System (INIS)

Bowman-James, Kristin

2008-01-01

This project focused on identifying selective binding agents for the removal of negative ions that hamper vitrification efforts. The project was led by Professor Kristin Bowman-James at the University of Kansas (KU) and consisted of a collaborative effort between the KU group, the group of Professor Jonathan Sessler at the University of Texas Austin (UT), and Dr. Bruce Moyer at Oak Ridge National Laboratory (ORNL). Research efforts during this funding period have focused on a particularly difficult target species, sulfate ion, which is highly insoluble in borosilicate glass. The project is unique in that it combines the synthetic expertise of the Bowman-James and Sessler groups with the analytical/extraction expertise of the Moyer group at ORNL, with a synergy that can bridge disciplines. Sulfate ion is a relatively small ionic species that, because of its solubility characteristics as well as its caustic nature, are a hindrance to the vitrification process. Not only is it relatively insoluble in the medium that has been chosen to store the wastes, but it also has the potential for accelerating the corrosion of the furnaces used to vitrify the borosilicate in a liquid to allow for waste incorporation. The goal of the Bowman-James group has been to design sequestering agents for sulfate that are selective for that ion over nitrate, for example, to allow for a liquid-liquid extraction step that can remove most of the sulfate prior to vitrification. The collaborative design efforts between the Bowman-James and Sessler groups helped to accelerate progress in the design process. In particular the Bowman-James group has been probing the influence of dimensionality and charge on sulfate binding, i.e., progressing from circular to spherical extractants, while at the same time adding positive charges to the agents so that when sulfate is bound, the resulting species is neutral. Not only does this project serve to benefit the remediation process, but it also provides an

Electrodialytic Transport Properties of Anion-Exchange Membranes Prepared from Poly(vinyl alcohol) and Poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride).

Science.gov (United States)

Jikihara, Atsushi; Ohashi, Reina; Kakihana, Yuriko; Higa, Mitsuru; Kobayashi, Kenichi

2013-01-02

Random-type anion-exchange membranes (AEMs) have been prepared by blending poly(vinyl alcohol) (PVA) and the random copolymer-type polycation, poly(vinyl alcohol-co-methacryloyl aminopropyl trimethyl ammonium chloride) at various molar percentages of anion-exchange groups to vinyl alcohol groups, Cpc, and by cross-linking the PVA chains with glutaraldehyde (GA) solution at various GA concentrations, CGA. The characteristics of the random-type AEMs were compared with blend-type AEMs prepared in our previous study. At equal molar percentages of the anion exchange groups, the water content of the random-type AEMs was lower than that of the blend-type AEMs. The effective charge density of the random-type AEMs increased with increasing Cpc and reached a maximum value. Further, the maximum value of the effective charge density increased with increasing CGA. The maximum value of the effective charge density, 0.42 mol/dm3, was obtained for the random-type AEM with Cpc = 4.2 mol % and CGA = 0.15 vol %. A comparison of the random-type and blend-type AEMs with almost the same Cpc showed that the random-type AEMs had lower membrane resistance than the blend-type ones. The membrane resistance and dynamic transport number of the random-type AEM with Cpc = 6.0 mol % and CGA = 0.15 vol % were 4.8 Ω cm2 and 0.83, respectively.

Highly charged atomic physics at HIRFL-CSR

International Nuclear Information System (INIS)

Ma Xinwen; Wang Youde; Hou Mingdong; Jin Gengmin

1996-01-01

HIRFL-CSR is a proposed electron cooling storage ring optimized to accelerate and store beams of highly charged heavy ions. Several possibilities for advanced atomic physics studies are discussed, such as studies of electron-ion, ion-atoms, photon-ion-electron interactions and high resolution spectroscopy

High-frequency acoustic charge transport in GaAs nanowires

NARCIS (Netherlands)

Büyükköse, S.; Hernandez-Minguez, A.; Vratzov, B.; Somaschini, C.; Geelhaar, L.; Riechert, H.; van der Wiel, Wilfred Gerard; Santos, P.V.

2014-01-01

The oscillating piezoelectric fields accompanying surface acoustic waves are able to transport charge carriers in semiconductor heterostructures. Here, we demonstrate high-frequency (above 1 GHz) acoustic charge transport in GaAs-based nanowires deposited on a piezoelectric substrate. The short

Electrostatic solvation free energies of charged hard spheres using molecular dynamics with density functional theory interactions

Science.gov (United States)

Duignan, Timothy T.; Baer, Marcel D.; Schenter, Gregory K.; Mundy, Chistopher J.

2017-10-01

Determining the solvation free energies of single ions in water is one of the most fundamental problems in physical chemistry and yet many unresolved questions remain. In particular, the ability to decompose the solvation free energy into simple and intuitive contributions will have important implications for models of electrolyte solution. Here, we provide definitions of the various types of single ion solvation free energies based on different simulation protocols. We calculate solvation free energies of charged hard spheres using density functional theory interaction potentials with molecular dynamics simulation and isolate the effects of charge and cavitation, comparing to the Born (linear response) model. We show that using uncorrected Ewald summation leads to unphysical values for the single ion solvation free energy and that charging free energies for cations are approximately linear as a function of charge but that there is a small non-linearity for small anions. The charge hydration asymmetry for hard spheres, determined with quantum mechanics, is much larger than for the analogous real ions. This suggests that real ions, particularly anions, are significantly more complex than simple charged hard spheres, a commonly employed representation.

Effects of arginine on multimodal anion exchange chromatography.

Science.gov (United States)

Hirano, Atsushi; Arakawa, Tsutomu; Kameda, Tomoshi

2015-12-01

The effects of arginine on binding and elution properties of a multimodal anion exchanger, Capto adhere, were examined using bovine serum albumin (BSA) and a monoclonal antibody against interleukin-8 (mAb-IL8). Negatively charged BSA was bound to the positively charged Capto adhere and was readily eluted from the column with a stepwise or gradient elution using 1M NaCl at pH 7.0. For heat-treated BSA, small oligomers and remaining monomers were also eluted using a NaCl gradient, whereas larger oligomers required arginine for effective elution. The positively charged mAb-IL8 was bound to Capto adhere at pH 7.0. Arginine was also more effective for elution of the bound mAb-IL8 than was NaCl. The results imply that arginine interacts with the positively charged Capto adhere. The mechanism underlying the interactions of arginine with Capto adhere was examined by calculating the binding free energy between an arginine molecule and a Capto adhere ligand in water through molecular dynamics simulations. The overall affinity of arginine for Capto adhere is attributed to the hydrophobic and π-π interactions between an arginine side chain and the aromatic moiety of the ligand as well as hydrogen bonding between arginine and the ligand hydroxyl group, which may account for the characteristics of protein elution using arginine. Copyright © 2015 Elsevier Inc. All rights reserved.

Charged-particle mutagenesis II. Mutagenic effects of high energy charged particles in normal human fibroblasts

Science.gov (United States)

Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

1994-01-01

The biological effects of high LET charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 micrometer2 and 0.09 to 5.56 x 10(-3) micrometer2, respectively. The maximum values were obtained by 56Fe with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(-5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

Formation and stabilization of anionic metal complexes in concentrated aqueous quaternary ammonium salt solutions

International Nuclear Information System (INIS)

Aronson, F.L.; Hwang, L.L.Y.; Ronca, N.; Solomon, N.A.; Steigman, J.

1985-01-01

Anionic complexes of transition metals were stabilized in aqueous solutions containing high concentrations of various short-chain quaternary ammonium salts. Compounds with longer paraffin chains were effective in much less concentrated solution. Complex ions were detected spectrophotometrically. FeCl 4 - , which is usually formed in concentrated HCl, was the predominant Fe(III) complex in 30 m choline chloride containing only 0.12 M HCl. A yellow transitory Tc(VII) chloro-addition intermediate, formed in the reduction of TcO 4 - by concentrated HCl, was stabilized when the solution also contained 25 m choline chloride. Its spectrum, as well as the isolation of an already known Tc(VII) bipyridyl complex, is reported. Concentrated organic electrolytes also stabilized Tc(V) oxide halides against disproportionation and Tc(IV) hexahalides against hydrolysis. Halochromates of Cr(VI) were formed and stabilized in dilute acid containing quaternary ammonium salts. Their UV spectra showed the well-resolved vibronic fine structure associated with the symmetric chromium-to-oxygen charge-transfer band. It is known that these progressions are resolved in aprotic solvents, but not in aqueous acidic solution alone, and that the loss of fine structure in aqueous media is due to hydrogen bonding. The stabilization of anionic metal complexes and the resolution of vibronic structure in halochromates are probably consequences of water-structure-enforced ion paring. The present work suggests that the water molecules in immediate contact with the complex anions are more strongly hydrogen bonded to each other than to the complex. 21 references, 4 figures

Measurements of the Properties of Highly-charged high-Z ions

International Nuclear Information System (INIS)

Augustine J. Smith, Ph.D.

2007-01-01

We had proposed carrying out a systematic experimental investigation of the atomic physics of highly charged, high-Z ions, produced in the Lawrence Livermore National Laboratory LLNL electron beam ion trap (EBIT-I) in its high energy mode, superEBIT. In particular we were going to accurately measure line positions for Δn=0 transitions in few electron high-Z ions; this was meant to enable us to investigate relativistic and quantum electrodynamics QED contributions to the energy levels as well as the nuclear properties of heavy ions. We were also going to measure cross sections for various electron-ion interactions, the degree of polarization of emitted x-rays, and radiation cooling rates of various ionization stages of highly charged, high-Z ions. This would enable us to study fundamental atomic physics of high-Z ions at relativistic electron impact energies and in the intense nuclear fields of highly ionized, high-Z ions. This would extend previous measurements we have carried out to a regime where there is a paucity of good data. These measurements were expected to generate increased theoretical interest and activity in this area. The project will extend a very successful collaboration between Morehouse College (MC) and a national laboratory LLNL, Minority student training and development are major components of the proposal

Charging of Dust Grains in a Nuclear-Induced Plasma at High Pressures

International Nuclear Information System (INIS)

Pal’, A. F.; Starostin, A. N.; Filippov, A. V.

2001-01-01

The process of dust-grain charging in plasmas produced by radioactive decay products or spontaneous fission fragments in air and xenon at high pressures is studied numerically in the hydrodynamic approximation. It is shown that, at sufficiently high rates of gas ionization, the dust grains in air are charged by electrons rather than ions, so that the grain charge in air is comparable to that in electropositive gases. The results of numerical calculations based on a complete model agree well with the experimental data. The time evolution of the grain charge is investigated, and the characteristic time scales on which the grains acquire an electric charge are established. The validity of approximate theories of dust-grain charging in electropositive and electronegative gases at high pressures is examined

Charge identification of highly ionizing particles in desensitized nuclear emulsion using high speed read-out system

International Nuclear Information System (INIS)

Toshito, T.; Kodama, K.; Yusa, K.; Ozaki, M.; Amako, K.; Kameoka, S.; Murakami, K.; Sasaki, T.; Aoki, S.; Ban, T.; Fukuda, T.; Naganawa, N.; Nakamura, T.; Natsume, M.; Niwa, K.; Takahashi, S.; Kanazawa, M.; Kanematsu, N.; Komori, M.; Sato, S.; Asai, M.; Koi, T.; Fukushima, C.; Ogawa, S.; Shibasaki, M.; Shibuya, H.

2006-01-01

We performed an experimental study of charge identification of heavy ions from helium to carbon having energy of about 290MeV/u using an emulsion chamber. Emulsion was desensitized by means of forced fading (refreshing) to expand a dynamic range of response to highly charged particles. For the track reconstruction and charge identification, the fully automated high speed emulsion read-out system, which was originally developed for identifying minimum ionizing particles, was used without any modification. Clear track by track charge identification up to Z=6 was demonstrated. The refreshing technique has proved to be a powerful technique to expand response of emulsion film to highly ionizing particles

Anion induced conformational preference of Cα NN motif residues in functional proteins.

Science.gov (United States)

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.

Improvement of highly charged ion output from an ECR source

International Nuclear Information System (INIS)

Shirkov, G.D.

1995-01-01

The physical limitations of the highly charged ion production in the ECR source is analyzed in this report. General methods to increase the output ion current and the attainable charged states of heavy ions are discussed. Some new ways to improve the output of highly charged ions from the ECR source for heavy ions are proposed. A new library of computer codes for the mathematical simulation of heavy ion production in the ECR ion source is used for numerical experiments to test these ways for improving the operation of the ECR source. (orig.)

Anionic chromogenic chemosensors highly selective for fluoride or cyanide based on 4-(4-Nitrobenzylideneamine)phenol

OpenAIRE

Nicoleti,Celso R.; Marini,Vanderléia G.; Zimmermann,Lizandra M.; Machado,Vanderlei G.

2012-01-01

4-(4-Nitrobenzylideneamine)phenol was used in two strategies allowing the highly selective detection of F- and CN-. Firstly, the compound in acetonitrile acts as a chromogenic chemosensor based on the idea that more basic anions cause its deprotonation (colorless solution), generating a colored solution containing phenolate. The discrimination of CN- over F- was obtained by adding 1.4% water to acetonitrile: water preferentially solvates F-, leaving the CN- free to deprotonate the compound. A...

Photoproduction of charged particle with high transverse momentum

International Nuclear Information System (INIS)

Campos Costa Ramos, S.E. de.

1986-09-01

Inclusive cross sections of high transverse moment charged pions induced by a high energy photon beam have been measured. These results do not account, neither in slope nor in normalisation, for the VDM component of the photon, evaluated with pion induced data taken in the same experimental conditions after VDM subtraction, excellent agreement is found with QCD calculations up to second order in α s , in an extended cinematic region, different choices of the gluon fragmentation function do not alter this conclusion. Our measures of the inclusive final state charge asymmetries also confirm QCD expectations. 42 refs [fr

Charged-particle mutagenesis 2. Mutagenic effects of high energy charged particles in normal human fibroblasts

Science.gov (United States)

Chen, D. J.; Tsuboi, K.; Nguyen, T.; Yang, T. C.

1994-01-01

The biological effects of high Linear Energy Transfer (LET) charged particles are a subject of great concern with regard to the prediction of radiation risk in space. In this report, mutagenic effects of high LET charged particles are quantitatively measured using primary cultures of human skin fibroblasts, and the spectrum of induced mutations are analyzed. The LET of the charged particles ranged from 25 KeV/micrometer to 975 KeV/micrometer with particle energy (on the cells) between 94-603 MeV/u. The X-chromosome linked hypoxanthine guanine phosphoribosyl transferase (hprt) locus was used as the target gene. Exposure to these high LET charged particles resulted in exponential survival curves; whereas, mutation induction was fitted by a linear model. The Relative Biological Effect (RBE) for cell-killing ranged from 3.73 to 1.25, while that for mutant induction ranged from 5.74 to 0.48. Maximum RBE values were obtained at the LET of 150 keV/micrometer. The inactivation cross-section (alpha i) and the action cross-section for mutant induction (alpha m) ranged from 2.2 to 92.0 sq micrometer and 0.09 to 5.56 x 10(exp -3) sq micrometer respectively. The maximum values were obtained by Fe-56 with an LET of 200 keV/micrometer. The mutagenicity (alpha m/alpha i) ranged from 2.05 to 7.99 x 10(exp -5) with the maximum value at 150 keV/micrometer. Furthermore, molecular analysis of mutants induced by charged particles indicates that higher LET beams are more likely to cause larger deletions in the hprt locus.

Methods and systems for measuring anions

KAUST Repository

Masih, Dilshad; Mohammed, Omar F.; Aly, Shawkat M.; Alarousu, Erkki

2016-01-01

Embodiments of the present disclosure provide for methods for detecting the presence and/or concentration of anions in a solution, systems for detecting the presence and/or concentration of anions in a solution, anion sensor systems, and the like.

Methods and systems for measuring anions

KAUST Repository

Masih, Dilshad

2016-08-18

Embodiments of the present disclosure provide for methods for detecting the presence and/or concentration of anions in a solution, systems for detecting the presence and/or concentration of anions in a solution, anion sensor systems, and the like.

Single-Crystal-to-Single-Crystal Anion Exchange in a Gadolinium MOF: Incorporation of POMs and [AuCl4]−

Directory of Open Access Journals (Sweden)

Javier López-Cabrelles

2016-04-01

Full Text Available The encapsulation of functional molecules inside porous coordination polymers (also known as metal-organic frameworks, MOFs has become of great interest in recent years at the field of multifunctional materials. In this article, we present a study of the effects of size and charge in the anion exchange process of a Gd based MOF, involving molecular species like polyoxometalates (POMs, and [AuCl4]−. This post-synthetic modification has been characterized by IR, EDAX, and single crystal diffraction, which have provided unequivocal evidence of the location of the anion molecules in the framework.

Detection of cyanide anion by zinc porphyrin-spiropyran dyad

Energy Technology Data Exchange (ETDEWEB)

Kho, Young Min; Hur, Dae Young; Shin, Eun Ju [Dept. of Chemistry, Sunchon National University, Suncheon (Korea, Republic of)

2016-10-15

Versatile methods of the sensitive and selective detection for cyanide anion to monitor toxic cyanide have been developed. These include colorimetric, colorimetric, chromatographic, and electrochemical analyses. Among those methods for cyanide detection, optical methods based on absorption and fluorescence spectroscopy are relatively simple, inexpensive, and sensitive. A number of organic sensors for cyanide anion have been designed and synthesized. Absorption and/or fluorescence spectra of these sensors are changed by forming coordination complex or bonding covalently with cyanide. Compared with other anions, cyanide anion has some characteristic properties, such as its strong nucleophilicity and high binding affinity toward metal ions, and is superior and useful for the development of the sensors. Both covalent bond-based sensors and coordination complex-based sensors have been developed for cyanide detection. The results indicate that ZnP-SP plays a role as a CN{sup -} selective, colorimetric sensor either without or with UV irradiation.

Detection of cyanide anion by zinc porphyrin-spiropyran dyad

International Nuclear Information System (INIS)

Kho, Young Min; Hur, Dae Young; Shin, Eun Ju

2016-01-01

Versatile methods of the sensitive and selective detection for cyanide anion to monitor toxic cyanide have been developed. These include colorimetric, colorimetric, chromatographic, and electrochemical analyses. Among those methods for cyanide detection, optical methods based on absorption and fluorescence spectroscopy are relatively simple, inexpensive, and sensitive. A number of organic sensors for cyanide anion have been designed and synthesized. Absorption and/or fluorescence spectra of these sensors are changed by forming coordination complex or bonding covalently with cyanide. Compared with other anions, cyanide anion has some characteristic properties, such as its strong nucleophilicity and high binding affinity toward metal ions, and is superior and useful for the development of the sensors. Both covalent bond-based sensors and coordination complex-based sensors have been developed for cyanide detection. The results indicate that ZnP-SP plays a role as a CN"- selective, colorimetric sensor either without or with UV irradiation

Phosphazene-promoted anionic polymerization

KAUST Repository

Zhao, Junpeng

2014-01-01

In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

Interaction of slow highly-charged ions with metals and insulators

International Nuclear Information System (INIS)

Yamazaki, Y.

2007-01-01

Interaction of slow highly charged ions with insulator as well as metallic surfaces is discussed. In addition to the usual flat surface targets, studies with thin foils having a multitude of straight holes of ∼100 nm in diameter (micro-capillary foil) are introduced, which provide various unique information on the above surface interaction. In the case of an insulator micro-capillary foil, a so-called guiding effect was observed, where slow highly charged ions can transmit through the capillary tunnel keeping their initial charge state even when the capillary axis is tilted against the incident beam. A similar guiding effect has recently been found for slow highly-charged ions transmitted through a single tapered glass capillary. In both cases, the guiding effects are expected to be governed by a self-organized charging and discharging of the inner-wall of the insulator capillary. One of the prominent features of this guiding effect with the tapered capillary is the formation of a nano-size beam, which can be applied in various fields of science including surface nano-modification/analysis, nano-surgery of living cells, etc

Mapping of Residues Forming the Voltage Sensor of the Voltage-Dependent Anion-Selective Channel

Science.gov (United States)

Thomas, Lorie; Blachly-Dyson, Elizabeth; Colombini, Marco; Forte, Michael

1993-06-01

Voltage-gated ion-channel proteins contain "voltage-sensing" domains that drive the conformational transitions between open and closed states in response to changes in transmembrane voltage. We have used site-directed mutagenesis to identify residues affecting the voltage sensitivity of a mitochondrial channel, the voltage-dependent anion-selective channel (VDAC). Although charge changes at many sites had no effect, at other sites substitutions that increased positive charge also increased the steepness of voltage dependance and substitutions that decreased positive charge decreased voltage dependance by an appropriate amount. In contrast to the plasma membrane K^+ and Na^+ channels, these residues are distributed over large parts of the VDAC protein. These results have been used to define the conformational transitions that accompany voltage gating of an ion channel. This gating mechanism requires the movement of large portions of the VDAC protein through the membrane.

A combined experimental and computational study of the molecular interactions between anionic ibuprofen and water

International Nuclear Information System (INIS)

Zapata-Escobar, Andy; Manrique-Moreno, Marcela; Guerra, Doris; Hadad, C. Z.; Restrepo, Albeiro

2014-01-01

In this work, we report a detailed study of the microsolvation of anionic ibuprofen, Ibu − . Stochastic explorations of the configurational spaces for the interactions of Ibu − with up to three water molecules at the DFT level lead to very rich and complex potential energy surfaces. Our results suggest that instead of only one preponderant structure, a collection of isomers with very similar energies would have significant contributions to the properties of the solvated drug. One of these properties is the shift on the vibrational frequencies of the asymmetric stretching band of the carboxylate group in hydrated Ibu − with respect to the anhydrous drug, whose experimental values are nicely reproduced using the weighted contribution of the structures. We found at least three types of stabilizing interactions, including conventional CO 2 − ⋯H 2 O, H 2 O⋯H 2 O charge assisted hydrogen bonds (HBs), and less common H 2 O⋯H–C and H 2 O⋯π interactions. Biological water molecules, those in direct contact with Ibu − , prefer to cluster around the carboxylate oxygen atoms via cyclic or bridged charge assisted hydrogen bonds. Many of those interactions are strongly affected by the formal carboxylate charge, resulting in “enhanced” HBs with increased strengths and degree of covalency. We found striking similarities between this case and the microsolvation of dymethylphosphate, which lead us to hypothesize that since microsolvation of phosphatidylcholine depends mainly on the formal charge of its ionic PO 2 − group in the polar head, then microsolvation of anionic ibuprofen and interactions of water molecules with eukaryotic cell membranes are governed by the same types of physical interactions

Are polynuclear superhalogens without halogen atoms probable? A high-level ab initio case study on triple-bridged binuclear anions with cyanide ligands

Science.gov (United States)

Yin, Bing; Li, Teng; Li, Jin-Feng; Yu, Yang; Li, Jian-Li; Wen, Zhen-Yi; Jiang, Zhen-Yi

2014-03-01

The first theoretical exploration of superhalogen properties of polynuclear structures based on pseudohalogen ligand is reported here via a case study on eight triply-bridged [Mg2(CN)5]- clusters. From our high-level ab initio results, all these clusters are superhalogens due to their high vertical electron detachment energies (VDE), of which the largest value is 8.67 eV at coupled-cluster single double triple (CCSD(T)) level. Although outer valence Green's function results are consistent with CCSD(T) in most cases, it overestimates the VDEs of three anions dramatically by more than 1 eV. Therefore, the combined usage of several theoretical methods is important for the accuracy of purely theoretical prediction of superhalogen properties of new structures. Spatial distribution of the extra electron of high-VDE anions here indicates two features: remarkable aggregation on bridging CN units and non-negligible distribution on every CN unit. These two features lower the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to detachment of CN-1 were also investigated for these anions. The collection of these results indicates that polynuclear structures based on pseudohalogen ligand are promising candidates for new superhalogens with enhanced properties.

Spectroscopy with trapped highly charged ions

International Nuclear Information System (INIS)

Beiersdorfer, Peter

2009-01-01

We give an overview of atomic spectroscopy performed on electron beam ion traps at various locations throughout the world. Spectroscopy at these facilities contributes to various areas of science and engineering, including but not limited to basic atomic physics, astrophysics, extreme ultraviolet lithography, and the development of density and temperature diagnostics of fusion plasmas. These contributions are accomplished by generating, for example, spectral surveys, making precise radiative lifetime measurements, accounting for radiative power emitted in a given wavelength band, illucidating isotopic effects, and testing collisional-radiative models. While spectroscopy with electron beam ion traps had originally focused on the x-ray emission from highly charged ions interacting with the electron beam, the operating modes of such devices have expanded to study radiation in almost all wavelength bands from the visible to the hard x-ray region; and at several facilities the ions can be studied even in the absence of an electron beam. Photon emission after charge exchange or laser excitation has been observed; and the work is no longer restricted to highly charged ions. Much of the experimental capabilities are unique to electron beam ion traps, and the work performed with these devices cannot be undertaken elsewhere. However, in other areas the work on electron beam ion traps rivals the spectroscopy performed with conventional ion traps or heavy-ion storage rings. The examples we present highlight many of the capabilities of the existing electron beam ion traps and their contributions to physics.

High charge state heavy ion production from a PIG source

International Nuclear Information System (INIS)

Bex, L.; Clark, D.J.; Ellsworth, C.E.; Flood, W.S.; Gough, R.A.; Holley, W.R.; Meriwether, J.R.; Morris, D.

1975-03-01

The comparison of pulsed vs. dc arc operation for nitrogen and argon shows a shift in charge distribution toward the higher charge states for the pulsed case. Tests with various magnetic field shapes along the arc column show a significant increase in high charge state output for a uniform field compared to the case with a field low at the cathodes. (U.S.)

Adsorption of a cationic dye molecule on polystyrene microspheres in colloids: effect of surface charge and composition probed by second harmonic generation.

Science.gov (United States)

Eckenrode, Heather M; Jen, Shih-Hui; Han, Jun; Yeh, An-Gong; Dai, Hai-Lung

2005-03-17

Nonlinear optical probe, second harmonic generation (SHG), of the adsorption of the dye molecule malachite green (MG), in cationic form at pH polystyrene microspheres in aqueous solution is used to study the effect of surface charge and composition on molecular adsorption. Three types of polystyrene microspheres with different surface composition are investigated: (1) a sulfate terminated, anionic surface, (2) a neutral surface without any functional group termination, and (3) an amine terminated, cationic surface. The cationic dye was found to adsorb at all three surfaces, regardless of surface charge. The adsorption free energies, DeltaG's, measured for the three surfaces are -12.67, -12.39, and -10.46 kcal/mol, respectively, with the trend as expected from the charge interactions. The adsorption density on the anionic surface, where attractive charge-charge interaction dominates, is determined by the surface negative charge density. The adsorption densities on the neutral and cationic surfaces are on the other hand higher, perhaps as a result of a balance between minimizing repulsive charge interaction and maximizing attractive molecule-substrate and intermolecular interactions. The relative strength of the SH intensity per molecule, in combination of a model calculation, reveals that the C(2) axis of the MG molecule is nearly perpendicular to the surface on the anionic surface and tilts away from the surface norm when the surface is neutral and further away when cationic. Changing the pH of the solution may alter the surface charge and subsequently affect the adsorption configuration and SH intensity.

PEGylated carboxymethyl chitosan/calcium phosphate hybrid anionic nanoparticles mediated hTERT siRNA delivery for anticancer therapy.

Science.gov (United States)

Xie, Ying; Qiao, Hongzhi; Su, Zhigui; Chen, Minglei; Ping, Qineng; Sun, Minjie

2014-09-01

Lack of safe and effective delivery vehicle is the main obstacle for siRNA mediated cancer therapy. In this study, we synthesized a pH-sensitive polymer of PEG grafted carboxymethyl chitosan (PEG-CMCS) and developed anionic-charged hybrid nanoparticles of PEG-CMCS and calcium phosphate (CaP) for siRNA delivery through a single-step self-assembly method in aqueous condition. The formed nanoparticles with charge of around -8.25 mv and average diameter of 102.1 nm exhibited efficient siRNA encapsulation and enhanced colloidal and serum stability. The test in vitro indicated that the nanoparticles entered into HepG2 cells by endocytosis, and achieved endosomal escape of siRNA effectively due to the pH-responsive disassembly of nanoparticles and dissolution of CaP in the endosome. Reporter gene silencing assay showed that luciferase siRNA delivered by the anionic nanoparticles could achieve gene silencing efficacy comparable to that of conventional Lipofectamine 2000. Additionally, dramatic hTERT knockdown mediated by the anionic nanoparticles transfection induced significant apoptosis of HepG2 cells in vitro. After intravenous injection in tumor-bearing BALB/c nude mice, the nanoparticles specifically accumulated into tumor regions by EPR effect, leading to efficient and specific gene silencing sequentially. Most importantly, the nanoparticles carrying hTERT siRNA inhibited tumor growth significantly via silencing hTERT expression and inducing cells apoptosis in HepG2 tumor xenograft. Moreover, comprehensive safety studies of the nanoparticles confirmed their superior safety both in vitro and in vivo. We concluded that the PEG-CMCS/CaP hybrid anionic nanoparticles possessed potential as a safe and effective siRNA delivery system for anticancer therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

REACTIVITY OF ANIONS IN INTERSTELLAR MEDIA: DETECTABILITY AND APPLICATIONS

Energy Technology Data Exchange (ETDEWEB)

Senent, M. L. [Departamento de Quimica y Fisica Teoricas, Instituto de Estructura de la Materia, IEM-C.S.I.C., Serrano 121, Madrid E-28006 (Spain); Hochlaf, M., E-mail: senent@iem.cfmac.csic.es, E-mail: hochlaf@univ-mlv.fr [Laboratoire de Modelisation et Simulation Multi Echelle, Universite Paris-Est, MSME UMR 8208 CNRS, 5 boulevard Descartes, F-77454 Marne-la-Vallee (France)

2013-05-01

We propose a general rule to distinguish between detectable and undetectable astronomical anions. We believe that only few anions live long enough in the interstellar medium and thus can be detected. Our method is based on quantum mechanical calculations capable of describing accurately the evolution of electronic states during chemical processes. The still not fully understood reactivity at low temperatures is discussed considering non-adiabatic effects. The role of excited states has usually been neglected in previous works which basically focused on the ground electronic state for interpretations of experimental observations. Here, we deal with unsaturated carbon chains (e.g., C{sub n} H{sup -}), which show a high density of electronic states close to their corresponding ground electronic states, complex molecular dynamics, and non-adiabatic phenomena. Our general rule shows that it is not sufficient that anions exist in the gas phase (in the laboratory) to be present in media such as astrophysical media, since formation and decomposition reactions of these anions may allow the population of anionic electronic states to autodetach, forming neutrals. For C{sub n} H, reactivity depends strongly on n, where long and short chains behave differently. Formation of linear chains is relevant.

Electron impact ionization of highly charged lithiumlike ions

International Nuclear Information System (INIS)

Wong, K.L.

1992-10-01

Electron impact ionization cross sections can provide valuable information about the charge-state and power balance of highly charged ions in laboratory and astrophysical plasmas. In the present work, a novel technique based on x-ray measurements has been used to infer the ionization cross section of highly charged lithiumlike ions on the Livermore electron beam ion trap. In particular, a correspondence is established between an observed x ray and an ionization event. The measurements are made at one energy corresponding to approximately 2.3 times the threshold energy for ionization of lithiumlike ions. The technique is applied to the transition metals between Z=22 (titanium, Ti 19+ ) and Z=26 (iron, Fe 23+ ) and to Z=56 (barium, Ba 53+ ). The results for the transition metals, which have an estimated 17-33% uncertainty, are in good overall agreement with a relativistic distorted-wave calculation. However, less good agreement is found for barium, which has a larger uncertainty. Methods for properly accounting for the polarization in the x-ray intensities and for inferring the charge-state abundances from x-ray observations, which were developed for the ionization measurements, as well as an x-ray model that assists in the proper interpretation of the data are also presented

Anion-π Catalysts with Axial Chirality.

Science.gov (United States)

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.

Adsorption of the Inflammatory Mediator High-Mobility Group Box 1 by Polymers with Different Charge and Porosity

Directory of Open Access Journals (Sweden)

Carla Tripisciano

2014-01-01

Full Text Available High-mobility group box 1 protein (HMGB1 is a conserved protein with a variety of biological functions inside as well as outside the cell. When released by activated immune cells, it acts as a proinflammatory cytokine. Its delayed release has sparked the interest in HMGB1 as a potential therapeutic target. Here, we studied the adsorption of HMGB1 to anionic methacrylate-based polymers as well as to neutral polystyrene-divinylbenzene copolymers. Both groups of adsorbents exhibited efficient binding of recombinant HMGB1 and of HMGB1 derived from lipopolysaccharide-stimulated peripheral blood mononuclear cells. The adsorption characteristics depended on particle size, porosity, accessibility of the pores, and charge of the polymers. In addition to these physicochemical parameters of the adsorbents, modifications of the molecule itself (e.g., acetylation, phosphorylation, and oxidation, interaction with other plasma proteins or anticoagulants (e.g., heparin, or association with extracellular microvesicles may influence the binding of HMGB1 to adsorbents and lead to preferential depletion of HMGB1 subsets with different biological activity.

Turn-on fluorescence probes based on pyranine/viologen charge-transfer complexes for the determination of nucleotides

Energy Technology Data Exchange (ETDEWEB)

Schäferling, Michael, E-mail: Michael.schaeferling@utu.fi; Lang, Thomas; Schnettelker, Annette

2014-10-15

The formation of ground state charge-transfer complexes between pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid) and viologen (paraquat) derivatives is utilized for the design of novel fluoroionophores for the determination of phosphate species, particularly of nucleotides. The strong quenching of the pyranine fluorescence by viologen-type charge transfer acceptors can be countermanded if these are functionalized with triethylammonium groups that serve as recognition elements for phosphate anions. We report on the fluorogenic responses of these water-soluble molecular probes in presence of different phosphates. Absorbance measurements give additional information on the charge transfer complex formation and the interaction with nucleotides. The experimental data show that these aggregates form attractive, simple and versatile fluorescence turn-on probes for nucleoside triphosphates. The reversibility of the fluorescence response is demonstrated by means of an enzymatic model assay using ATPase for the decomposition of adenosine triphosphate. - Highlights: • Pyranine/viologen charge-transfer complexes as molecular probe for ATP recognition. • Fluorescence turn on mechanism. • Selective compared to other nucleotides and phosphate anions. • Fast and reversible response applicable to monitor enzymatic reactions.

Importance of poly(ethylene oxide)-modification and chloride anion for the electron transfer reaction of cytochrome c in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide

International Nuclear Information System (INIS)

Ohno, Hiroyuki; Suzuki, Chiiko; Fujita, Kyoko

2006-01-01

Horse heart cytochrome c (cyt c) was chemically modified with poly(ethylene oxide) (PEO) to dissolve it in room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([emim][TFSI]). The redox response of the modified cyt c, hereafter PEO-cyt c, was analyzed in [emim][TFSI]. PEO modification to the surface of cyt c, which exceeded 60% of the total mass of the PEO-cyt c, was an effective method to solubilize the cyt c. In spite of the high ion density and sufficient ionic conductivity of [emim][TFSI], no redox response of pure PEO-cyt c was detected. However, a reversible redox response of PEO-cyt c was observed after adding a simple electrolyte such as KCl to [emim][TFSI]. The redox response of PEO-cyt c was sensitive to the anion radius of the added salt, and the chloride anion was found to be the best anion species to produce a redox response of PEO-cyt c in [emim][TFSI]. However, above a certain salt concentration, the resulting increase in solution viscosity would suppress the redox reaction. The results strongly indicate that the chloride anions, because of their mobility in the polypeptide matrix, compensate the charge change of heme during the electron transfer reaction. Larger anions did not show such an effect due to sterical restrictions on the migration through the protein shell to the heme pocket of cyt c

Highly charged ions: a miniature laboratory for new fundamental science

International Nuclear Information System (INIS)

Gillaspy, J.D.

2002-01-01

Full text: Highly charged ions are 10-100 times smaller than ordinary atoms, yet they present within themselves a remarkably rich arena for testing fundamental aspects of physics. These tests are based on a precise analysis of the energy distribution of the photons that are emitted as electrons hop between energy levels within the highly charged ions. With sufficiently precise analysis, it may be possible to obtain new information about the structure of the vacuum, the effect of special relativity on many-body correlation, physics beyond the Standard Model, and the fundamental nature of quantum measurements. This talk will review the current state-of-the-art in the spectroscopy of highly charged ions, and give a look towards the future

Temperature Dependence of Charge Localization in High-Mobility, Solution-Crystallized Small Molecule Semiconductors Studied by Charge Modulation Spectroscopy

DEFF Research Database (Denmark)

Meneau, Aurélie Y. B.; Olivier, Yoann; Backlund, Tomas

2016-01-01

In solution-processable small molecule semiconductors, the extent of charge carrier wavefunction localization induced by dynamic disorder can be probed spectroscopically as a function of temperature using charge modulation spectroscopy (CMS). Here, it is shown based on combined fi eld-effect tran......In solution-processable small molecule semiconductors, the extent of charge carrier wavefunction localization induced by dynamic disorder can be probed spectroscopically as a function of temperature using charge modulation spectroscopy (CMS). Here, it is shown based on combined fi eld......-effect transistor and CMS measurements as a function of temperature that in certain molecular semiconductors, such as solution-processible pentacene, charge carriers become trapped at low temperatures in environments in which the charges become highly localized on individual molecules, while in some other molecules...

Influence of charge state on the reaction of FeO3+/- with carbon monoxide

Science.gov (United States)

Reilly, Nelly M.; Ulises Reveles, J.; Johnson, Grant E.; Khanna and, Shiv N., Jr.; Castleman, A. W.

2007-02-01

A combined experimental and theoretical study shows that highly oxidized iron clusters are able to readily effect the oxidation of CO to CO 2 at ambient temperature. Calculated energy profiles of the reaction demonstrate that the oxidation efficiency is governed by the strength of oxygen binding to the iron atom. Results for FeO3+/- are presented and reveal that cation clusters are more efficient than the corresponding anion clusters at effecting the oxidation reaction due to different oxygen bond energies resulting from charge distribution.

Creating molecular macrocycles for anion recognition

Directory of Open Access Journals (Sweden)

Amar H. Flood

2016-03-01

Full Text Available The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures.

High density thermite mixture for shaped charge ordnance disposal

Directory of Open Access Journals (Sweden)

Tamer Elshenawy

2017-10-01

Full Text Available The effect of thermite mixture based on aluminum and ferric oxides for ammunition neutralization has been studied and tested. Thermochemical calculations have been carried out for different percentage of Al using Chemical Equilibrium Code to expect the highest performance thermite mixture used for shaped charge ordnance disposal. Densities and enthalpy of different formulations have been calculated and demonstrated. The optimized thermite formulation has been prepared experimentally using cold iso-static pressing technique, which exhibited relatively high density and high burning rate thermite mixture. The produced green product compacted powder mixture was tested against small caliber shaped charge bomblet for neutralization. Theoretical and experimental results showed that the prepared thermite mixture containing 33% of aluminum as a fuel with ferric oxide can be successfully used for shaped charge ordnance disposal.

Electronic properties of the charge carriers on oligofluorene backbone

International Nuclear Information System (INIS)

Koizumi, Yoshiko; Seki, Shu; Saeki, Akinori; Tagawa, Seiichi

2007-01-01

The transient absorption of radical anions and cations of 9,9'-di-n-hexyl-oligofluorene was measured using pulse radiolysis and low-temperature γ-radiolysis techniques. The infrared absorption maxima of both radical anions and cations exhibit red-shift continuously upon elongation of the chain length. The absorption bands are blue-shifted by 0.04-0.07 eV with increasing the temperature from 80 to 106 K. The extinction coefficients were determined by scavenging technique, demonstrating an increase with the elongation of the chain length. The optimized geometry of fluorene trimers, calculated using density functional theory, shows that the oligofluorene molecules are more planar in its charged state than in its neutral state

Influence of the substitution of β-cyclodextrins by cationic groups on the complexation of organic anions

International Nuclear Information System (INIS)

Hbaieb, S.; Kalfat, R.; Chevalier, Y.; Amdouni, N.; Parrot-Lopez, H.

2008-01-01

The inclusion complexation of the organic anion, dansyl-acid, by cationic derivatives of β-cyclodextrin has been investigated. A series of cationic β-cyclodextrins with various positive charge has been synthesized by selective functionalization of the primary face of β-cyclodextrin with amino groups. The complexes were of the 1:1 stoichiometry; the stability constants (K 11 ) have been evaluated from UV-Vis measurements by application of the Benesi-Hildebrand equation. The presence of amino groups increased the complexation ability. β-cyclodextrin fully substituted at the primary face with amino groups showed the strongest inclusion binding ability towards the dansyl-acid guest. The enhanced complexation for anions was ascribed to the cationic amino groups. A simple thermodynamic model of the electrostatic contribution to the complexation is presented

Carbon dioxide is tightly bound in the [Co(Pyridine)(CO{sub 2})]{sup −} anionic complex

Energy Technology Data Exchange (ETDEWEB)

Graham, Jacob D.; Buytendyk, Allyson M.; Zhang, Xinxing; Bowen, Kit H., E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Kim, Seong K. [Department of Chemistry, Seoul National University, Seoul 151-747 (Korea, Republic of)

2015-11-14

The [Co(Pyridine)(CO{sub 2})]{sup −} anionic complex was studied through the combination of photoelectron spectroscopy and density functional theory calculations. This complex was envisioned as a primitive model system for studying CO{sub 2} binding to negatively charged sites in metal organic frameworks. The vertical detachment energy (VDE) measured via the photoelectron spectrum is 2.7 eV. Our calculations imply a structure for [Co(Pyridine)(CO{sub 2})]{sup −} in which a central cobalt atom is bound to pyridine and CO{sub 2} moieties on either sides. This structure was validated by acceptable agreement between the calculated and measured VDE values. Based on our calculations, we found CO{sub 2} to be bound within the anionic complex by 1.4 eV.

A high charge state heavy ion beam source for heavy ion fusion

International Nuclear Information System (INIS)

Eylon, S.; Henestroza, E.

1996-01-01

A high current, low emittance, high charge state heavy ion beam source is being developed. This is designed to deliver a heavy ion fusion (HIF) driver accelerator scale beam. Using a high charge state beam in a driver accelerator for HIF may increase the acceleration efficiency, leading to a reduction in the driver accelerator size and cost. The proposed source system, which consists of a gas beam electron stripper followed by a high charge state beam separator, can be added to existing single charge state, low emittance, high brightness ion sources and injectors. We shall report on the source physics design using 3D beam simulations and experimental feasibility study results using a neutral gas stripper and a beam separator at the exit of the LBL 2 MV injector. (orig.)

Nitrate Anion Exchange in Pu-238 Aqueous Scrap Recovery Operations

International Nuclear Information System (INIS)

Pansoy-Hjelvik, M.E.; Silver, G.L.; Reimus, M.A.H.; Ramsey, K.B.

1999-01-01

Strong base, nitrate anion exchange (IX) is crucial to the purification of 238 Pu solution feedstocks with gross levels of impurities. This paper discusses the work involved in bench scale experiments to optimize the nitrate anion exchange process. In particular, results are presented of experiments conducted to (a) demonstrate that high levels of impurities can be separated from 238 Pu solutions via nitrate anion exchange and, (b) work out chemical pretreatment methodology to adjust and maintain 238 Pu in the IV oxidation state to optimize the Pu(IV)-hexanitrato anionic complex sorption to Reillex-HPQ resin. Additional experiments performed to determine the best chemical treatment methodology to enhance recovery of sorbed Pu from the resin, and VIS-NIR absorption studies to determine the steady state equilibrium of Pu(IV), Pu(III), and Pu(VI) in nitric acid are discussed

Reducing nitrogen crossover in microbial reverse-electrodialysis cells by using adjacent anion exchange membranes and anion exchange resin

KAUST Repository

Wallack, Maxwell J.; Geise, Geoffrey M.; Hatzell, Marta C.; Hickner, Michael A.; Logan, Bruce E.

2015-01-01

Microbial reverse electrodialysis cells (MRECs) combine power generation from salinity gradient energy using reverse electrodialysis (RED), with power generation from organic matter using a microbial fuel cell. Waste heat can be used to distill ammonium bicarbonate into high (HC) and low salt concentration (LC) solutions for use in the RED stack, but nitrogen crossover into the anode chamber must be minimized to avoid ammonia loses, and foster a healthy microbial community. To reduce nitrogen crossover, an additional low concentration (LC) chamber was inserted before the anode using an additional anion exchange membrane (AEM) next to another AEM, and filled with different amounts of anion or cation ion exchange resins. Addition of the extra AEM increased the ohmic resistance of the test RED stack from 103 Ω cm2 (1 AEM) to 295 Ω cm2 (2 AEMs). However, the use of the anion exchange resin decreased the solution resistance of the LC chamber by 74% (637 Ω cm2, no resin; 166 Ω cm2 with resin). Nitrogen crossover into the anode chamber was reduced by up to 97% using 50% of the chamber filled with an anion exchange resin compared to the control (no additional chamber). The added resistance contributed by the use of the additional LC chamber could be compensated for by using additional LC and HC membrane pairs in the RED stack.

The interactions of high-energy, highly charged Xe ions with buckyballs

International Nuclear Information System (INIS)

Ali, R.; Berry, H.G.; Cheng, S.

1994-01-01

Ionization and fragmentation have been measured for C 60 molecules bombarded by highly charged (up to 35+) xenon ions with energies ranging up to 625 MeV. The observed mass distribution of positively charged fragments is explained in terms of a theoretical model indicating that the total interaction cross section contains roughly equal contributions from (a) excitation of the giant plasmon resonance, and (b) large-energy-transfer processes that lead to multiple fragmentation of the molecule. Preliminary results of measurements on VUV photons emitted in these interactions are also presented

Reversible anionic redox chemistry in high-capacity layered-oxide electrodes

Science.gov (United States)

Sathiya, M.; Rousse, G.; Ramesha, K.; Laisa, C. P.; Vezin, H.; Sougrati, M. T.; Doublet, M.-L.; Foix, D.; Gonbeau, D.; Walker, W.; Prakash, A. S.; Ben Hassine, M.; Dupont, L.; Tarascon, J.-M.

2013-09-01

Li-ion batteries have contributed to the commercial success of portable electronics and may soon dominate the electric transportation market provided that major scientific advances including new materials and concepts are developed. Classical positive electrodes for Li-ion technology operate mainly through an insertion-deinsertion redox process involving cationic species. However, this mechanism is insufficient to account for the high capacities exhibited by the new generation of Li-rich (Li1+xNiyCozMn(1-x-y-z)O2) layered oxides that present unusual Li reactivity. In an attempt to overcome both the inherent composition and the structural complexity of this class of oxides, we have designed structurally related Li2Ru1-ySnyO3 materials that have a single redox cation and exhibit sustainable reversible capacities as high as 230 mA h g-1. Moreover, they present good cycling behaviour with no signs of voltage decay and a small irreversible capacity. We also unambiguously show, on the basis of an arsenal of characterization techniques, that the reactivity of these high-capacity materials towards Li entails cumulative cationic (Mn+→M(n+1)+) and anionic (O2-→O22-) reversible redox processes, owing to the d-sp hybridization associated with a reductive coupling mechanism. Because Li2MO3 is a large family of compounds, this study opens the door to the exploration of a vast number of high-capacity materials.

Effect of chemical retention on anionic species diffusion in compacted clays

International Nuclear Information System (INIS)

Bazer-Bachi, Frederic

2005-01-01

Anionic radioisotopes are of particular importance within the framework of the calculated health risk associated with high-level and long-lived intermediate-level underground radioactive waste disposal. Therefore, the objective of this work is the construction of a transport model coupled with chemistry in order to quantify the behaviour of anionic solutes in the Callovo-Oxfordian (CO_x) argillite, the argillaceous host rock of the ANDRA Meuse/Haute-Marne underground laboratory. An experimental methodology was defined to characterize this migration, several experimental methods being implemented: batch experiments, laboratory columns and through-diffusion cells. The study of the diffusion of the non-sorbing anionic tracer "3"6Cl"- highlighted the fact that, due to anionic exclusion, anions only had access to a part of the porosity. The retention of "3"5SO_4"2"- and "1"2"5I- on CO_x argillite was then characterized, quantified by batch experiments and confirmed by other experimental methods. Nevertheless, their migration was less retarded than expected by a model based on batch experiments and on "3"6Cl"- diffusive data. This difference was explained by anion exclusion which reduced sorption site accessibility. Thus, the intensity of this phenomenon has to be considered to model anion migration in compacted clays. (author) [fr

Interstellar Chemistry Gets More Complex With New Charged-Molecule Discovery

Science.gov (United States)

2007-07-01

Astronomers using data from the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) have found the largest negatively-charged molecule yet seen in space. The discovery of the third negatively-charged molecule, called an anion, in less than a year and the size of the latest anion will force a drastic revision of theoretical models of interstellar chemistry, the astronomers say. Molecule formation Formation Process of Large, Negatively-Charged Molecule in Interstellar Space CREDIT: Bill Saxton, NRAO/AUI/NSF Click on image for page of graphics and detailed information "This discovery continues to add to the diversity and complexity that is already seen in the chemistry of interstellar space," said Anthony J. Remijan of the National Radio Astronomy Observatory (NRAO). "It also adds to the number of paths available for making the complex organic molecules and other large molecular species that may be precursors to life in the giant clouds from which stars and planets are formed," he added. Two teams of scientists found negatively-charged octatetraynyl, a chain of eight carbon atoms and one hydrogen atom, in the envelope of gas around an old, evolved star and in a cold, dark cloud of molecular gas. In both cases, the molecule had an extra electron, giving it a negative charge. About 130 neutral and about a dozen positively-charged molecules have been discovered in space, but the first negatively-charged molecule was not discovered until late last year. The largest previously-discovered negative ion found in space has six carbon atoms and one hydrogen atom. "Until recently, many theoretical models of how chemical reactions evolve in interstellar space have largely neglected the presence of anions. This can no longer be the case, and this means that there are many more ways to build large organic molecules in cosmic environments than have been explored," said Jan M. Hollis of NASA's Goddard Space Flight Center (GSFC). Ultraviolet light from stars can

Are polynuclear superhalogens without halogen atoms probable? A high-level ab initio case study on triple-bridged binuclear anions with cyanide ligands

International Nuclear Information System (INIS)

Yin, Bing; Wen, Zhen-Yi; Li, Teng; Li, Jin-Feng; Yu, Yang; Li, Jian-Li; Jiang, Zhen-Yi

2014-01-01

The first theoretical exploration of superhalogen properties of polynuclear structures based on pseudohalogen ligand is reported here via a case study on eight triply-bridged [Mg 2 (CN) 5 ] − clusters. From our high-level ab initio results, all these clusters are superhalogens due to their high vertical electron detachment energies (VDE), of which the largest value is 8.67 eV at coupled-cluster single double triple (CCSD(T)) level. Although outer valence Green's function results are consistent with CCSD(T) in most cases, it overestimates the VDEs of three anions dramatically by more than 1 eV. Therefore, the combined usage of several theoretical methods is important for the accuracy of purely theoretical prediction of superhalogen properties of new structures. Spatial distribution of the extra electron of high-VDE anions here indicates two features: remarkable aggregation on bridging CN units and non-negligible distribution on every CN unit. These two features lower the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to detachment of CN −1 were also investigated for these anions. The collection of these results indicates that polynuclear structures based on pseudohalogen ligand are promising candidates for new superhalogens with enhanced properties

Are polynuclear superhalogens without halogen atoms probable? A high-level ab initio case study on triple-bridged binuclear anions with cyanide ligands

Energy Technology Data Exchange (ETDEWEB)

Yin, Bing, E-mail: rayinyin@gmail.com; Wen, Zhen-Yi [MOE Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Institute of Modern Physics, Northwest University, Xi' an 710069 (China); Li, Teng; Li, Jin-Feng; Yu, Yang; Li, Jian-Li [MOE Key Laboratory of Synthetic and Natural Functional Molecule Chemistry, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry and Materials Science, Northwest University, Xi' an 710069 (China); Jiang, Zhen-Yi [Institute of Modern Physics, Northwest University, Xi' an 710069 (China)

2014-03-07

The first theoretical exploration of superhalogen properties of polynuclear structures based on pseudohalogen ligand is reported here via a case study on eight triply-bridged [Mg{sub 2}(CN){sub 5}]{sup −} clusters. From our high-level ab initio results, all these clusters are superhalogens due to their high vertical electron detachment energies (VDE), of which the largest value is 8.67 eV at coupled-cluster single double triple (CCSD(T)) level. Although outer valence Green's function results are consistent with CCSD(T) in most cases, it overestimates the VDEs of three anions dramatically by more than 1 eV. Therefore, the combined usage of several theoretical methods is important for the accuracy of purely theoretical prediction of superhalogen properties of new structures. Spatial distribution of the extra electron of high-VDE anions here indicates two features: remarkable aggregation on bridging CN units and non-negligible distribution on every CN unit. These two features lower the potential and kinetic energies of the extra electron respectively and thus lead to high VDE. Besides superhalogen properties, the structures, relative stabilities and thermodynamic stabilities with respect to detachment of CN{sup −1} were also investigated for these anions. The collection of these results indicates that polynuclear structures based on pseudohalogen ligand are promising candidates for new superhalogens with enhanced properties.

Synthesis and properties of highly dispersed ionic silica-poly(ethylene oxide) nanohybrids.

KAUST Repository

Fernandes, Nikhil J; Akbarzadeh, Johanna; Peterlik, Herwig; Giannelis, Emmanuel P

2013-01-01

We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent.

Synthesis and properties of highly dispersed ionic silica-poly(ethylene oxide) nanohybrids.

KAUST Repository

Fernandes, Nikhil J

2013-02-04

We report an ionic hybrid based on silica nanoparticles as the anion and amine-terminated poly(ethylene oxide) (PEO) as a cation. The charge on the nanoparticle anion is carried by the surface hydroxyls. SAXS and TEM reveal an exceptional degree of dispersion of the silica in the polymer and high degree of order in both thin film and bulk forms. In addition to better dispersion, the ionic hybrid shows improved flow characteristics compared to silica/PEO mixtures in which the ionic interactions are absent.

The interactions of high-energy, highly-charged ions with fullerenes

International Nuclear Information System (INIS)

Ali, R.; Berry, H.G.; Cheng, S.

1996-01-01

In 1985, Robert Curl and Richard Smalley discovered a new form of carbon, the fullerene, C 60 , which consists of 60 carbon atoms in a closed cage resembling a soccer ball. In 1990, Kritschmer et al. were able to make macroscopic quantities of fullerenes. This has generated intense activity to study the properties of fullerenes. One area of research involves collisions between fullerenes and atoms, ions or electrons. In this paper we describe experiments involving interactions between fullerenes and highly charged ions in which the center-of-mass energies exceed those used in other work by several orders of magnitude. The high values of projectile velocity and charge state result in excitation and decay processes differing significantly from those seen in studies 3 at lower energies. Our results are discussed in terms of theoretical models analogous to those used in nuclear physics and this provides an interesting demonstration of the unity of physics

Identification of inorganic anions by gas chromatography/mass spectrometry.

Science.gov (United States)

Sakayanagi, Masataka; Yamada, Yaeko; Sakabe, Chikako; Watanabe, Kunio; Harigaya, Yoshihiro

2006-03-10

Inorganic anions were identified by using gas chromatography/mass spectrometry (GC/MS). Derivatization of the anions was achieved with pentafluorobenzyl p-toluenesulphonate (PFB-Tos) as the reaction reagent and a crown ether as a phase transfer catalyst. When PFB-Br was used as the reaction reagent, the retention time of it was close to those of the derivatized inorganic anions and interfered with the analysis. In contrast, the retention time of PFB-Tos differed greatly from the PFB derivatives of the inorganic anions and the compounds of interest could be detected without interference. Although the PFB derivatives of SO4, S2O3, CO3, ClO4, and ClO3 could not be detected, the derivatives of F, Cl, Br, I, CN, OCN, SCN, N3, NO3, and NO2 were detected using PFB-Tos as the derivatizing reagent. The inorganic anions were detectable within 30 ng approximately, which is of sufficient sensitivity for use in forensic chemistry. Accurate mass number was measured for each PFB derivative by high-resolution mass spectrometry (HRMS) within a measurement error of 2 millimass units (mmu), which allowed determination of the compositional formula from the mass number. In addition, actual analysis was performed successively by our method using trial samples of matrix.

A combined experimental and computational study of the molecular interactions between anionic ibuprofen and water

Energy Technology Data Exchange (ETDEWEB)

Zapata-Escobar, Andy; Manrique-Moreno, Marcela; Guerra, Doris; Hadad, C. Z.; Restrepo, Albeiro, E-mail: albeiro@exactas.udea.edu.co [Instituto de Química, Universidad de Antioquia UdeA, Calle 70 No. 52–21, Medellín (Colombia)

2014-05-14

In this work, we report a detailed study of the microsolvation of anionic ibuprofen, Ibu{sup −}. Stochastic explorations of the configurational spaces for the interactions of Ibu{sup −} with up to three water molecules at the DFT level lead to very rich and complex potential energy surfaces. Our results suggest that instead of only one preponderant structure, a collection of isomers with very similar energies would have significant contributions to the properties of the solvated drug. One of these properties is the shift on the vibrational frequencies of the asymmetric stretching band of the carboxylate group in hydrated Ibu{sup −} with respect to the anhydrous drug, whose experimental values are nicely reproduced using the weighted contribution of the structures. We found at least three types of stabilizing interactions, including conventional CO {sub 2}{sup −}⋯H{sub 2}O, H{sub 2}O⋯H{sub 2}O charge assisted hydrogen bonds (HBs), and less common H{sub 2}O⋯H–C and H{sub 2}O⋯π interactions. Biological water molecules, those in direct contact with Ibu{sup −}, prefer to cluster around the carboxylate oxygen atoms via cyclic or bridged charge assisted hydrogen bonds. Many of those interactions are strongly affected by the formal carboxylate charge, resulting in “enhanced” HBs with increased strengths and degree of covalency. We found striking similarities between this case and the microsolvation of dymethylphosphate, which lead us to hypothesize that since microsolvation of phosphatidylcholine depends mainly on the formal charge of its ionic PO {sub 2}{sup −} group in the polar head, then microsolvation of anionic ibuprofen and interactions of water molecules with eukaryotic cell membranes are governed by the same types of physical interactions.

Vacuum improvements for ultra high charge state ion acceleration

International Nuclear Information System (INIS)

Xie, Z.Q.; Lyneis, C.M.; Clark, D.J.; Guy, A.; Lundgren, S.A

1998-06-01

The installation of a second cryo panel has significantly improved the vacuum in the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The neutral pressure in the extraction region decreased from 1.2 x 10 -6 down to about 7 x 10 -7 Torr. The vacuum improvement reduces beam loss from charge changing collisions and enhances the cyclotron beam transmission, especially for the high charge state heavy ions. Tests with improved vacuum show the cyclotron transmission increased more than 50% (from 5.7% to 9.0%) for a Xe 27+ at 603 MeV, more than doubled for a Bi 41+ beam (from 1.9% to 4.6%) at 904 MeV and tripled for a U 47+ beam (from 1.2% to 3.6%) at 1,115 MeV. At about 5 NeV/nucleon 92 enA (2.2 pnA) for Bi 41+ and 14 enA (0.3 pnA) for U 47+ were extracted ut of the 88-Inch Cyclotron Ion beams with charge states as high as U 64+ have been produced by the LBNL AECR-U ion source and accelerated through the cyclotron for the first time. The beam losses for a variety of ultra high charge state ions were measured as a function of cyclotron pressure and compared with the calculations from the existing models

Vacuum improvements for ultra high charge state ion acceleration

International Nuclear Information System (INIS)

Xie, Z.Q.; Lyneis, C.M.; Clark, D.J.; Guy, A.; Lundgren, S.A.

1999-01-01

The installation of a second cryo panel has significantly improved the vacuum in the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. The neutral pressure in the extraction region decreased from 1.2 x 10 -6 down to about 7 x 10 -7 Torr. The vacuum improvement reduces beam loss from charge changing collisions and enhances the cyclotron beam transmission, especially for the high charge state heavy ions. Tests with improved vacuum show the cyclotron transmission increased more than 50% (from 5.7% to 9.0%) for a Xe 27+ at 603 MeV, more than doubled for a Bi 41+ beam (from 1.9% % to 4.6%) at 904 MeV and tripled for a U 47+ beam (from 1.2% to 3.6%) at 1115 MeV. At about 5 MeV/nucleon 92 enA (2.2 pnA) for Bi 41+ and 14 enA (0.3 pnA) for U 47+ were extracted out of the 88-Inch Cyclotron Ion beams with charge states as high as U 64+ have been produced by the LBNL AECR-U ion source and accelerated through the cyclotron for the first time. The beam losses for a variety of ultra high charge state ions were measured as a function of cyclotron pressure and compared with the calculations from the existing models. (authors)

Sensitization of microorganisms and enzymes by radiation-induced selective inorganic radical anions

International Nuclear Information System (INIS)

Schubert, J.; Stegeman, H.

1981-01-01

Bacterial survival and enzymatic inactivation were examined following exposure to radiolytically-generated radical anions, X - 2 , where X=Cl, Br, I or CNS - . Depending on pH, radical anions react selectively or specifically with cysteine, tryptophan, tyrosine and histidine. Consequently, when one or more of these amino acids is crucial for enzymatic activity or bacterial survival and is attacked by a radical anion, a high degree or radiosensitization may be realized. Halide radical anions can form free chlorine, bromine or iodine. However, these bactericidal halogens are destroyed by reaction with the hydrated electron, e - sub(aq), or at pHs>9, as occurs, for example, when a medium saturated with nitrous oxide, N 2 O, and e - sub(aq) scavenger, is replaced by nitrogen or oxygen. Increasing concentration of other e - sub(aq) scavengers, such as phosphate buffer, promotes formation of halogen from halides. The conditions producing formation and elimination of halogens in irradiated media must be appreciated to avoid confusing radiosensitization by X 2 to X - 2 . Radiosensitization by radical anions of several microorganisms: S. faecalis, S. typhimurium, E. coli, and M. radiodurens is described. A crucial amino acid for survival of S. faecalis appears to be tyrosine, while both tyrosine and tryptophan seem essential for recovery of S. typhimurium from effects of ionizing radiation. It is postulated that the radiosensitizing action of radical anions involves inhibition of DNA repair of strand-breaks by depriving the cells of energy. In view of the high OH scavenging power of foods, it is concluded that the radiosensitization of bacteria and enzymes in foods by radical anions, except for special cases, is not practical. Rather, radical anions serve to identify crucial amino acids to radiosensitization mechanisms in model systems, and possibly in radiotherapy. (author)

Comparison of analytical charge-form and equilibrium thermodynamic speciation of certain radionuclides

International Nuclear Information System (INIS)

Jenne, E.A.; Cowan, C.E.; Robertson, D.E.

1984-01-01

Calculating trace element speciation with a thermodynamic model is often challenged on the basis that the existing thermodynamic data are not sufficiently reliable. Water quality data and corresponding analytical charge-form speciation analysis were available for radionuclides occurring in a low-level radioactive groundwater. This offered an opportunity for comparing the results of an equilibrium thermodynamic model with the results of analytical charge-form speciation. The charge-form speciation was determined using the Battelle Large Volume Water Sampler, which contains consecutive layers of cation resin, anion resin and activated aluminum oxide for retention of cationic, anionic and non-ionic dissolved chemical species, respectively. The thermodynamic speciation of Cs, Cr, Fe, I, Mn, Mo, Na, and Zn was calculated using the MINTEQ geochemical model. Ce, Co, Tc, Np, Pm, and Sb were speciated by hand calculation. Excellent agreement between the analytically determined charge-form and the thermodynamic speciation was observed for 54 Mn, 144 Ce, 131 I, 24 Na, 137 Cs, 99 Mo, 99 Tc, 151 Pm, 239 Np. Organic complexation by natural and/or synthetic organics in the waters may be important in the speciation of 65 An, 60 Co, 131 I, 59 Fe and possibly 51 Cr. Both 124 Sb and 125 Sb appeared to be in redox disequilibria with the groundwater. 29 references, 2 tables

Vibrational Spectroscopy of Cation and Anion Channelrhodopsins

Science.gov (United States)

Yi, Adrian S.

Optogenetics is a technique to control and monitor cell activity with light by expression of specific microbial rhodopsins. Cation channelrhodopsins (CCRs) and anion channelrhodopsins (ACRs) have been demonstrated to activate and silence cell activity, respectively. In this dissertation, the molecular mechanisms of two channelrhodopsins are studied: a CCR from Chlamydomonas augustae (CaChR1) and an ACR from Guillardia theta (GtACR1). The recently discovered GtACR1is especially interesting, as it achieves neural silencing with 1/1000th of the light intensity compared to previous microbial rhodopsin silencing ion pumps. Static and time-resolved resonance Raman, FTIR difference, and UV-visible spectroscopies were utilized in addition to various biochemical and genetic techniques to explore the molecular mechanisms of these channelrhodopsins. In CaChR1, Glu169 and Asp299 residues are located nearby the Schiff base (SB) similar to the homologous residues Asp85 and Asp212, which exist in an ionized state in unphotolyzed bacteriorhodopsin (BR) and play a key role in proton pumping. We observe significant changes in the protonation states of the SB, Glu169, and Asp299 of CaChR1 leading up to the open-channel P2 state, where all three groups exist in a charge neutral state. This unusual charge neutrality along with the position of these groups in the CaChR1 ion channel suggests that charge neutrality plays an important role in cation gating and selectivity in these low efficiency CCRs. Significant differences exist in the photocycle and protonation/hydrogen bonding states of key residues inGtACR1compared to BR and CaChR1. Resonance Raman studies reveal that in the unphotolyzed state of GtACR1, residues Glu68, Ser97 (BR Asp85 homolog), and Asp234 (BR Asp212 homolog) located near the SB exist in charge neutral states. Furthermore, upon K formation, these residues do not change their protonation states. At room temperature, a slow decay of the red-shifted K intermediate is

Production of highly charged ion beams from ECR ion sources

International Nuclear Information System (INIS)

Xie, Z.Q.

1997-09-01

Electron Cyclotron Resonance (ECR) ion source development has progressed with multiple-frequency plasma heating, higher mirror magnetic fields and better technique to provide extra cold electrons. Such techniques greatly enhance the production of highly charged ions from ECR ion sources. So far at cw mode operation, up to 300 eμA of O 7+ and 1.15 emA of O 6+ , more than 100 eμA of intermediate heavy ions for charge states up to Ar 13+ , Ca 13+ , Fe 13+ , Co 14+ and Kr 18+ , and tens of eμA of heavy ions with charge states to Kr 26+ , Xe 28+ , Au 35+ , Bi 34+ and U 34+ have been produced from ECR ion sources. At an intensity of at least 1 eμA, the maximum charge state available for the heavy ions are Xe 36+ , Au 46+ , Bi 47+ and U 48+ . An order of magnitude enhancement for fully stripped argon ions (I ≥ 60 enA) also has been achieved. This article will review the ECR ion source progress and discuss key requirement for ECR ion sources to produce the highly charged ion beams

Influence of the substitution of {beta}-cyclodextrins by cationic groups on the complexation of organic anions

Energy Technology Data Exchange (ETDEWEB)

Hbaieb, S. [U.R. Physico-Chimie des Materiaux Solides, Faculte des Sciences de Tunis, Manar II, 2092 Tunis (Tunisia)], E-mail: Souhairabouchaira@yahoo.fr; Kalfat, R. [U.R. Physico-Chimie des Materiaux Solides, Faculte des Sciences de Tunis, Manar II, 2092 Tunis (Tunisia); Chevalier, Y. [Laboratoire d' Automatique et de Genie des Procedes (LAGEP), UMR 5007 CNRS-Universite Claude Bernard Lyon 1, 69622 Villeurbanne (France)], E-mail: chevalier@lagep.univ-lyon1.fr; Amdouni, N. [U.R. Physico-Chimie des Materiaux Solides, Faculte des Sciences de Tunis, Manar II, 2092 Tunis (Tunisia); Parrot-Lopez, H. [Institut de Chimie et Biochimie Moleculaires et Supramoleculaires (ICBMS), UMR 5246 CNRS-Universite Claude Bernard Lyon 1, 69622 Villeurbanne (France)], E-mail: helene.parrot@univ-lyon1.fr

2008-07-01

The inclusion complexation of the organic anion, dansyl-acid, by cationic derivatives of {beta}-cyclodextrin has been investigated. A series of cationic {beta}-cyclodextrins with various positive charge has been synthesized by selective functionalization of the primary face of {beta}-cyclodextrin with amino groups. The complexes were of the 1:1 stoichiometry; the stability constants (K{sub 11}) have been evaluated from UV-Vis measurements by application of the Benesi-Hildebrand equation. The presence of amino groups increased the complexation ability. {beta}-cyclodextrin fully substituted at the primary face with amino groups showed the strongest inclusion binding ability towards the dansyl-acid guest. The enhanced complexation for anions was ascribed to the cationic amino groups. A simple thermodynamic model of the electrostatic contribution to the complexation is presented.

The assessment of pellicular anion-exchange resins for the determination of anions by ion chromatography

International Nuclear Information System (INIS)

Pohlandt, C.

1981-01-01

Because pellicular anion-exchange resins suitable for the determination, by ion chromatography, of anions with alkaline eluents were unavailable in South Africa at the inception of this work, an attempt was made to prepare such resins. In this study it is shown that the pellicular resins produced are more efficient than the surface-aminated resins used previously. The simultaneous separation and determination of five common anions is demonstrated. The method was applied to the analysis of uranium leach liquors, effluent samples, and a solid sample of ferric oxide (goethite)

On the law of interaction between charged defects in ionic crystals

International Nuclear Information System (INIS)

Varaksin, A.N.; Kolmogorov, Yu.N.

1990-01-01

Values of E int PC (R 12 ) interaction energy between dominant defects in NaCl- and CaF 2 -type crystals are calculated using Mott-Littleton method in harmonic approximation. It is shown, that interaction between cationic and anionic vacancies in NaCl type crystals is described using Coulomb law for charge interaction in dielectric up till R 12 smallest distances between vacancies. Good conformity of E int PC R 12 values with calculation made using Coulomb formula should be expected for Frenkel anionic pair in CaF 2 type crystals. Deviations from Coulomb law are possible for other defects at R 12 small distances; deviation degree depends on lattice type, defect type and on relative polarizability of crystal cationic and anionic sublattices. Calculations of E int PC (R 12 ) values using Mott-Littleton method are compared with calculations conducted by MOLSTAT program using molecular static method

Resonance charge exchange mechanism at high and moderate energies

International Nuclear Information System (INIS)

Bogdanov, A.V.; Gevorkyan, A.S.

1984-01-01

Charge exchange mechanisms at high and medium energies are investigated, ta king the resonance charge exchange of a proton by an hydrogen atom as an example . It is established that there are two classical charge exchange mechanisms rel ated to direct proton knockout from the bound state and one quantum-mechanical mechanism corresponding to the electron tunnelling from one bound state to anoth er. The classical cross-section diverges for two of these mechanisms, and the quasiclassical scattering amplitude must be calculated on the base of a complex classical trajectory. Physical grounds for the choice of such trajectories are discussed and calculations of the Van Vleck determinant for these mechanisms a re presented. Contributions from different mechanisms to the total charge excha nge cross-section are analyzed. A comparison with experimental data and results of other authors is made

High Intensity High Charge State ECR Ion Sources

CERN Document Server

Leitner, Daniela

2005-01-01

The next-generation heavy ion beam accelerators such as the proposed Rare Isotope Accelerator (RIA), the Radioactive Ion Beam Factory at RIKEN, the GSI upgrade project, the LHC-upgrade, and IMP in Lanzhou require a great variety of high charge state ion beams with a magnitude higher beam intensity than currently achievable. High performance Electron Cyclotron Resonance (ECR) ion sources can provide the flexibility since they can routinely produce beams from hydrogen to uranium. Over the last three decades, ECR ion sources have continued improving the available ion beam intensities by increasing the magnetic fields and ECR heating frequencies to enhance the confinement and the plasma density. With advances in superconducting magnet technology, a new generation of high field superconducting sources is now emerging, designed to meet the requirements of these next generation accelerator projects. The talk will briefly review the field of high performance ECR ion sources and the latest developments for high intens...

Synthetic high-charge organomica: effect of the layer charge and alkyl chain length on the structure of the adsorbed surfactants.

Science.gov (United States)

Pazos, M Carolina; Castro, Miguel A; Orta, M Mar; Pavón, Esperanza; Valencia Rios, Jesús S; Alba, María D

2012-05-15

A family of organomicas was synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg(6)F(4)O(20)·XH(2)O, where n = 2, 3, and 4) exchanged with dodecylammonium and octadecylammonium cations. The molecular arrangement of the surfactant was elucidated on the basis on XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas was investigated by (13)C, (27)Al, and (29)Si MAS NMR. The arrangement of alkylammonium ions in these high-charge synthetic micas depends on the combined effects of the layer charge of the mica and the chain length of the cation. In the organomicas with dodecylammonium, a transition from a parallel layer to a bilayer-paraffin arrangement is observed when the layer charge of the mica increases. However, when octadecylammonium is the interlayer cation, the molecular arrangement of the surfactant was found to follow the bilayer-paraffin model for all values of layer charge. The amount of ordered conformation all-trans is directly proportional of layer charge.

Production of Highly Charged Pharmaceutical Aerosols Using a New Aerosol Induction Charger.

Science.gov (United States)

Golshahi, Laleh; Longest, P Worth; Holbrook, Landon; Snead, Jessica; Hindle, Michael

2015-09-01

Properly charged particles can be used for effective lung targeting of pharmaceutical aerosols. The objective of this study was to characterize the performance of a new induction charger that operates with a mesh nebulizer for the production of highly charged submicrometer aerosols to bypass the mouth-throat and deliver clinically relevant doses of medications to the lungs. Variables of interest included combinations of model drug (albuterol sulfate) and charging excipient (NaCl) as well as strength of the charging field (1-5 kV/cm). Aerosol charge and size were measured using a modified electrical low pressure impactor system combined with high performance liquid chromatography. At the approximate mass median aerodynamic diameter (MMAD) of the aerosol (~0.4 μm), the induction charge on the particles was an order of magnitude above the field and diffusion charge limit. The nebulization rate was 439.3 ± 42.9 μl/min, which with a 0.1% w/v solution delivered 419.5 ± 34.2 μg of medication per minute. A new correlation was developed to predict particle charge produced by the induction charger. The combination of the aerosol induction charger and predictive correlations will allow for the practical generation and control of charged submicrometer aerosols for targeting deposition within the lungs.

High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

International Nuclear Information System (INIS)

Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

1996-01-01

Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several μs) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

High ion charge states in a high-current, short-pulse, vacuum arc ion source

International Nuclear Information System (INIS)

Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

1995-09-01

Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1--4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several micros) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution

Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

International Nuclear Information System (INIS)

Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

2013-01-01

Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

X-ray emission in slow highly charged ion-surface collisions

International Nuclear Information System (INIS)

Watanabe, H; Abe, T; Fujita, Y; Sun, J; Takahashi, S; Tona, M; Yoshiyasu, N; Nakamura, N; Sakurai, M; Yamada, C; Ohtani, S

2007-01-01

X-rays emitted in the collisions of highly charged ions with a surface have been measured to investigate dissipation schemes of their potential energies. While 8.1% of the potential energy was dissipated in the collisions of He-like I ions with a W surface, 29.1% has been dissipated in the case of He-like Bi ions. The x-ray emissions play significant roles in the dissipation of the potential energies in the interaction of highly charged heavy ions with the surface

Making the invisible visible: improved electrospray ion formation of metalloporphyrins/-phthalocyanines by attachment of the formate anion (HCOO(-)).

Science.gov (United States)

Hitzenberger, Jakob Felix; Dammann, Claudia; Lang, Nina; Lungerich, Dominik; García-Iglesias, Miguel; Bottari, Giovanni; Torres, Tomás; Jux, Norbert; Drewello, Thomas

2016-02-21

A protocol is developed for the coordination of the formate anion (HCOO(-)) to neutral metalloporphyrins (Pors) and -phthalocyanines (Pcs) containing divalent metals as a means to improve their ion formation in electrospray ionization (ESI). This method is particularly useful when the oxidation of the neutral metallomacrocycle fails. While focusing on Zn(II)Pors and Zn(II)Pcs, we show that formate is also readily attached to Mn(II), Mg(II) and Co(II)Pcs. However, for the Co(II)Pc secondary reactions can be observed. Upon collision-induced dissociation (CID), Zn(II)Por/Pc·formate supramolecular complexes can undergo the loss of CO2 in combination with transfer of a hydride anion (H(-)) to the zinc metal center. Further dissociation leads to electron transfer and hydrogen atom loss, generating a route to the radical anion of the Zn(II)Por/Pc without the need for electrochemical reduction, although the Zn(II)Por/Pc may have a too low electron affinity to allow electron transfer directly from the formate anion. In addition to single Por molecules, multi Por arrays were successfully analyzed by this method. In this case, multiple addition of formate occurs, giving rise to multiply charged species. In these multi Por arrays, complexation of the formate anion occurs by two surrounding Por units (sandwich). Therefore, the maximum attainment of formate anions in these arrays corresponds to the number of such sandwich complexes rather than the number of porphyrin moieties. The same bonding motif leads to dimers of the composition [(Zn(II)Por/Pc)2·HCOO](-). In these, the formate anion can act as a structural probe, allowing the distinction of isomeric ions with the formate bridging two macrocycles or being attached to a dimer of directly connected macrocycles.

Process for removing sulfate anions from waste water

Science.gov (United States)

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.

A photoelectron imaging and quantum chemistry study of the deprotonated indole anion.

Science.gov (United States)

Parkes, Michael A; Crellin, Jonathan; Henley, Alice; Fielding, Helen H

2018-05-29

Indole is an important molecular motif in many biological molecules and exists in its deprotonated anionic form in the cyan fluorescent protein, an analogue of green fluorescent protein. However, the electronic structure of the deprotonated indole anion has been relatively unexplored. Here, we use a combination of anion photoelectron velocity-map imaging measurements and quantum chemistry calculations to probe the electronic structure of the deprotonated indole anion. We report vertical detachment energies (VDEs) of 2.45 ± 0.05 eV and 3.20 ± 0.05 eV, respectively. The value for D0 is in agreement with recent high-resolution measurements whereas the value for D1 is a new measurement. We find that the first electronically excited singlet state of the anion, S1(ππ*), lies above the VDE and has shape resonance character with respect to the D0 detachment continuum and Feshbach resonance character with respect to the D1 continuum.

Photoinduced High-Frequency Charge Oscillations in Dimerized Systems

Science.gov (United States)

Yonemitsu, Kenji

2018-04-01

Photoinduced charge dynamics in dimerized systems is studied on the basis of the exact diagonalization method and the time-dependent Schrödinger equation for a one-dimensional spinless-fermion model at half filling and a two-dimensional model for κ-(bis[ethylenedithio]tetrathiafulvalene)2X [κ-(BEDT-TTF)2X] at three-quarter filling. After the application of a one-cycle pulse of a specifically polarized electric field, the charge densities at half of the sites of the system oscillate in the same phase and those at the other half oscillate in the opposite phase. For weak fields, the Fourier transform of the time profile of the charge density at any site after photoexcitation has peaks for finite-sized systems that correspond to those of the steady-state optical conductivity spectrum. For strong fields, these peaks are suppressed and a new peak appears on the high-energy side, that is, the charge densities mainly oscillate with a single frequency, although the oscillation is eventually damped. In the two-dimensional case without intersite repulsion and in the one-dimensional case, this frequency corresponds to charge-transfer processes by which all the bonds connecting the two classes of sites are exploited. Thus, this oscillation behaves as an electronic breathing mode. The relevance of the new peak to a recently found reflectivity peak in κ-(BEDT-TTF)2X after photoexcitation is discussed.

Experimental characterization of the Hitrap Cooler trap with highly charged ions.

OpenAIRE

Fedotova, Svetlana

2013-01-01

The HITRAP (Highly charged Ions TRAP)facility is being set up and commissioned at GSI, Darmstadt. It will provide heavy, highly charged ions at low velocities to high-precision atomic physics experiments. Within this work the Cooler trap- the key element of the HITRAP facility was tested. The Cooler trap was assembled, aligned, and commissioned in trapping experiments with ions from off-line sources.The work performed within the scope of this thesis provided the baseline for further operation...

High-order space charge effects using automatic differentiation

International Nuclear Information System (INIS)

Reusch, Michael F.; Bruhwiler, David L.

1997-01-01

The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach

Electron capture by highly charged ions from surfaces and gases

International Nuclear Information System (INIS)

Allen, F.

2008-01-01

In this study highly charged ions produced in Electron Beam Ion Traps are used to investigate electron capture from surfaces and gases. The experiments with gas targets focus on spectroscopic measurements of the K-shell x-rays emitted at the end of radiative cascades following electron capture into Rydberg states of Ar 17+ and Ar 18+ ions as a function of collision energy. The ions are extracted from an Electron Beam Ion Trap at an energy of 2 keVu -1 , charge-selected and then decelerated down to 5 eVu -1 for interaction with an argon gas target. For decreasing collision energies a shift to electron capture into low orbital angular momentum capture states is observed. Comparative measurements of the K-shell x-ray emission following electron capture by Ar 17+ and Ar 18+ ions from background gas in the trap are made and a discrepancy in the results compared with those from the extraction experiments is found. Possible explanations are discussed. For the investigation of electron capture from surfaces, highly charged ions are extracted from an Electron Beam Ion Trap at energies of 2 to 3 keVu -1 , charge-selected and directed onto targets comprising arrays of nanoscale apertures in silicon nitride membranes. The highly charged ions implemented are Ar 16+ and Xe 44+ and the aperture targets are formed by focused ion beam drilling in combination with ion beam assisted thin film deposition, achieving hole diameters of 50 to 300 nm and aspect ratios of 1:5 to 3:2. After transport through the nanoscale apertures the ions pass through an electrostatic charge state analyzer and are detected. The percentage of electron capture from the aperture walls is found to be much lower than model predictions and the results are discussed in terms of a capillary guiding mechanism. (orig.)

Effective electrostatic interactions among charged thermo-responsive microgels immersed in a simple electrolyte

Energy Technology Data Exchange (ETDEWEB)

González-Mozuelos, P. [Departamento de Física, Cinvestav del I. P. N., Av. Instituto Politécnico Nacional 2508, Mexico, Distrito Federal, C. P. 07360 (Mexico)

2016-02-07

This work explores the nature and thermodynamic behavior of the effective electrostatic interactions among charged microgels immersed in a simple electrolyte, taking special interest in the effects due to the thermally induced variation of the microgel size while the remaining parameters (microgel charge and concentration, plus the amount of added salt) are kept constant. To this end, the rigorous approach obtained from applying the precise methodology of the dressed ion theory to the proper definition of the effective direct correlation functions, which emerge from tracing-out the degrees of freedom of the microscopic ions, is employed to provide an exact description of the parameters characterizing such interactions: screening length, effective permittivity, and renormalized charges. A model solution with three components is assumed: large permeable anionic spheres for the microgels, plus small charged hard spheres of equal size for the monovalent cations and anions. The two-body correlations among the components of this model suspension, used as the input for the determination of the effective interaction parameters, are here calculated by using the hyper-netted chain approximation. It is then found that at finite microgel concentrations the values of these parameters change as the microgel size increases, even though the ionic strength of the supporting electrolyte and the bare charge of the microgels remain fixed during this process. The variation of the screening length, as well as that of the effective permittivity, is rather small, but still interesting in view of the fact that the corresponding Debye length stays constant. The renormalized charges, in contrast, increase markedly as the microgels swell. The ratio of the renormalized charge to the corresponding analytic result obtained in the context of an extended linear response theory allows us to introduce an effective charge that accounts for the non-linear effects induced by the short

Effect of reagent charge on the labeling of erythrocyte membrane proteins by photoactivated reagents

International Nuclear Information System (INIS)

Schaeffer, J.C.; Hakimian, R.; Shimer, M.L.

1986-01-01

Leaky erythrocyte ghosts were labeled with 3 H-[2-(4-azido-2-nitroanilino)ethyl]trimethylammonium iodide (cationic label) or 3 H-N-(4-azido-2-nitrophenyl)-β-alanine (anionic label). After the membranes were thoroughly washed, seven times as much cationic label was associated with the membranes as anionic label at 5 μM, whereas at 50 μM the cationic label was favored 15-fold. The distribution of label in the membrane proteins was ascertain by SDS-gel electrophoresis followed by autoradiography. At 50 μM cationic label, erythrocyte membrane protein bands 1,2,3,4.2, and 5 were intensely labeled, while band 6 was labeled weakly. At 5 μM cationic label, bands 1 and 4.2 were heavily labeled, while 2,3 and 5 were labeled less well. At both 50 μM and 5 μM anionic label, bands 1 and 6 were most prominently labeled. Bands 2,3,4.2 and 5 were labeled also at 50 μM, but they were labeled only very weakly at 5 μM. Band 4.1 was labeled very poorly if at all by either reagent. A mixture of the reagents gave an additive pattern. Thus, the charge and concentration of these reagents appear to play a major role in their ability to label membrane proteins indiscriminately. Because these reagents contain the same chromophore, 4-azido-2-nitroaniline, and differ mainly only in their charge, they may prove useful in assessing the location of charged sites on proteins in supramolecular complexes

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

Science.gov (United States)

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.

Effect of charge state and stoichiometry on the structure and reactivity of nickel oxide clusters with CO

Science.gov (United States)

Johnson, Grant E.; Reilly, Nelly M.; Castleman, A. W., Jr.

2009-02-01

The collision induced fragmentation and reactivity of cationic and anionic nickel oxide clusters with carbon monoxide were studied experimentally using guided-ion-beam mass spectrometry. Anionic clusters with a stoichiometry containing one more oxygen atom than nickel atom (NiO2-, Ni2O3-, Ni3O4- and Ni4O5-) were found to exhibit dominant products resulting from the transfer of a single oxygen atom to CO, suggesting the formation of CO2. Of these four species, Ni2O3- and Ni4O5- were observed to be the most reactive having oxygen transfer products accounting for approximately 5% and 10% of the total ion intensity at a maximum pressure of 15 mTorr of CO. Our findings, therefore, indicate that anionic nickel oxide clusters containing an even number of nickel atoms and an odd number of oxygen atoms are more reactive than those with an odd number of nickel atoms and an even number of oxygen atoms. The majority of cationic nickel oxides, in contrast to anionic species, reacted preferentially through the adsorption of CO onto the cluster accompanied by the loss of either molecular O2 or nickel oxide units. The adsorption of CO onto positively charged nickel oxides, therefore, is exothermic enough to break apart the gas-phase clusters. Collision induced dissociation experiments, employing inert xenon gas, were also conducted to gain insight into the structural properties of nickel oxide clusters. The fragmentation products were found to vary considerably with size and stoichiometry as well as ionic charge state. In general, cationic clusters favored the collisional loss of molecular O2 while anionic clusters fragmented through the loss of both atomic oxygen and nickel oxide units. Our results provide insight into the effect of ionic charge state on the structure of nickel oxide clusters. Furthermore, we establish how the size and stoichiometry of nickel oxide clusters influences their ability to oxidize CO, an important reaction for environmental pollution abatement.

Infrared spectroscopy of anionic hydrated fluorobenzenes

International Nuclear Information System (INIS)

Schneider, Holger; Vogelhuber, Kristen M.; Weber, J. Mathias

2007-01-01

We investigate the structural motifs of anionic hydrated fluorobenzenes by infrared photodissociation spectroscopy and density functional theory. Our calculations show that all fluorobenzene anions under investigation are strongly distorted from the neutral planar molecular geometries. In the anions, different F atoms are no longer equivalent, providing structurally different binding sites for water molecules and giving rise to a multitude of low-lying isomers. The absorption bands for hexa- and pentafluorobenzene show that only one isomer for the respective monohydrate complexes is populated in our experiment. For C 6 F 6 - ·H 2 O, we can assign these bands to an isomer where water forms a weak double ionic hydrogen bond with two F atoms in the ion, in accord with the results of Bowen et al. [J. Chem. Phys. 127, 014312 (2007), following paper.] The spectroscopic motif of the binary complexes changes slightly with decreasing fluorination of the aromatic anion. For dihydrated hexafluorobenzene anions, several isomers are populated in our experiments, some of which may be due to hydrogen bonding between water molecules

Anion channels: master switches of stress responses.

Science.gov (United States)

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.

The role of the anionic and cationic pt sites in the adsorption site preference of water and ethanol on defected Pt4/Pt(111) substrates: A density functional theory investigation within the D3 van der waals corrections

Science.gov (United States)

Seminovski, Yohanna; Amaral, Rafael C.; Tereshchuk, Polina; Da Silva, Juarez L. F.

2018-01-01

Platinum (Pt) atoms in the bulk face-centered cubic structure have neutral charge because they are equivalent by symmetry, however, in clean Pt surfaces, the effective charge on Pt atoms can turn slightly negative (anionic) or positive (cationic) while increasing substantially in magnitude for defected (low-coordinated) Pt sites. The effective charge affect the adsorption properties of molecular species on Pt surfaces and it can compete in importance with the coupling of the substrate-molecule electronic states. Although several studies have been reported due to the importance of Pt for catalysis, our understanding of the role played by low-coordinated sites is still limited. Here, we employ density functional theory within the Perdew-Burke-Ernzerhof exchange-correlation functional and the D3 van der Waals (vdW) correction to investigate the role of the cationic and anionic Pt sites on the adsorption properties of ethanol and water on defected Pt4/Pt(111) substrates. Four substrates were carefully selected, namely, two two-dimensional (2D) Pt4 configurations (2D-strand and 2D-island) and two tri-dimensional (3D) Pt4 (3D-fcc and 3D-hcp), to understand the role of coordination, effective charge, and coupling of the electronic states in the adsorption properties. From the Bader charge analysis, we identified the cationic and anionic sites among the Pt atoms exposed to the vacuum region in the Pt4/Pt(111) substrates. We found that ethanol and water bind via the anionic O atoms to the low-coordinated defected Pt sites of the substrates, where the angle PtOH is nearly 100° for most configurations. In the 3D-fcc or 3D-hcp defected configurations, the lowest-coordinated Pt atoms are anionic, hence, those Pt sites are not preferable for the adsorption of O atoms. The charge transfer from water and ethanol to the Pt substrates has similar magnitude for all cases, which implies similar Coulomb contribution to the adsorption energy. Moreover, we found a correlation of the

High-speed charge-to-time converter ASIC for the Super-Kamiokande detector

Energy Technology Data Exchange (ETDEWEB)

Nishino, H., E-mail: nishino@post.kek.j [Institute for Cosmic Ray Research, University of Tokyo, Chiba 277-8582 (Japan); Awai, K.; Hayato, Y.; Nakayama, S.; Okumura, K.; Shiozawa, M.; Takeda, A. [Institute for Cosmic Ray Research, University of Tokyo, Chiba 277-8582 (Japan); Ishikawa, K.; Minegishi, A. [Iwatsu Test Instruments Corporation, Tokyo 168-8511 (Japan); Arai, Y. [The Institute of Particle and Nuclear Studies, KEK, Ibaraki 305-0801 (Japan)

2009-11-11

A new application-specific integrated circuit (ASIC), the high-speed charge-to-time converter (QTC) IWATSU CLC101, provides three channels, each consisting of preamplifier, discriminator, low-pass filter, and charge integration circuitry, optimized for the waveform of a photomultiplier tube (PMT). This ASIC detects PMT signals using individual built-in discriminators and drives output timing signals whose width represents the integrated charge of the PMT signal. Combined with external input circuits composed of passive elements, the QTC provides full analog signal processing for the detector's PMTs, ready for further processing by time-to-digital converters (TDCs). High-rate (>1MHz) signal processing is achieved by short-charge-conversion-time and baseline-restoration circuits. Wide-range charge measurements are enabled by offering three gain ranges while maintaining a short cycle time. QTC chip test results show good analog performance, with efficient detection for a single photoelectron signal, four orders of magnitude dynamic range (0.3mVapprox3V; 0.2approx2500pC), 1% charge linearity, 0.2 pC charge resolution, and 0.1 ns timing resolution. Test results on ambient temperature dependence, channel isolation, and rate dependence also meet specifications.

High-speed charge-to-time converter ASIC for the Super-Kamiokande detector

International Nuclear Information System (INIS)

Nishino, H.; Awai, K.; Hayato, Y.; Nakayama, S.; Okumura, K.; Shiozawa, M.; Takeda, A.; Ishikawa, K.; Minegishi, A.; Arai, Y.

2009-01-01

A new application-specific integrated circuit (ASIC), the high-speed charge-to-time converter (QTC) IWATSU CLC101, provides three channels, each consisting of preamplifier, discriminator, low-pass filter, and charge integration circuitry, optimized for the waveform of a photomultiplier tube (PMT). This ASIC detects PMT signals using individual built-in discriminators and drives output timing signals whose width represents the integrated charge of the PMT signal. Combined with external input circuits composed of passive elements, the QTC provides full analog signal processing for the detector's PMTs, ready for further processing by time-to-digital converters (TDCs). High-rate (>1MHz) signal processing is achieved by short-charge-conversion-time and baseline-restoration circuits. Wide-range charge measurements are enabled by offering three gain ranges while maintaining a short cycle time. QTC chip test results show good analog performance, with efficient detection for a single photoelectron signal, four orders of magnitude dynamic range (0.3mV∼3V; 0.2∼2500pC), 1% charge linearity, 0.2 pC charge resolution, and 0.1 ns timing resolution. Test results on ambient temperature dependence, channel isolation, and rate dependence also meet specifications.

Effect of the pore water composition on the diffusive anion transport in argillaceous, low permeability sedimentary rocks.

Science.gov (United States)

Wigger, Cornelia; Van Loon, Luc R

2018-06-01

The effect of the pore water composition on the diffusive anion transport was studied for two different argillaceous, low permeability sedimentary rocks, Opalinus Clay (OPA) and Helvetic Marl (HM). The samples were saturated with different solutions with varying molar concentration and different main cations in the solution: NaCl based pore solutions and CaCl 2 based pore solutions. The total porosity was measured by through-diffusion experiments with the neutral tracer HTO. Experiments performed in NaCl solutions resulted in a porosity of 0.12 for OPA and 0.03 for HM, and are consistent with results of the experiments in CaCl 2 solutions. The total porosity was independent of the molar concentration, in contrast to the measured anion porosity, which increased with increasing molar concentration. It could further be observed that the pore solution based on the bivalent cation calcium shielded the negative surface charge stronger than the monovalent cation sodium, resulting in a larger measureable anion-accessible porosity in the case of CaCl 2 solutions. The data was modelled based on an adapted Donnan approach of Birgersson and Karnland (2009). The model had to be adjusted with a permanent free, uncharged porosity, as well as with structural information on the permanent anion exclusion because of so-called bottleneck pores. Both parameters can only be evaluated from experiments. Nevertheless, taking these two adaptions into account, the effect of varying pore water compositions on the anion-accessible porosity of the investigated argillaceous rocks could be satisfactorily described. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of the pore water composition on the diffusive anion transport in argillaceous, low permeability sedimentary rocks

Science.gov (United States)

Wigger, Cornelia; Van Loon, Luc R.

2018-06-01

The effect of the pore water composition on the diffusive anion transport was studied for two different argillaceous, low permeability sedimentary rocks, Opalinus Clay (OPA) and Helvetic Marl (HM). The samples were saturated with different solutions with varying molar concentration and different main cations in the solution: NaCl based pore solutions and CaCl2 based pore solutions. The total porosity was measured by through-diffusion experiments with the neutral tracer HTO. Experiments performed in NaCl solutions resulted in a porosity of 0.12 for OPA and 0.03 for HM, and are consistent with results of the experiments in CaCl2 solutions. The total porosity was independent of the molar concentration, in contrast to the measured anion porosity, which increased with increasing molar concentration. It could further be observed that the pore solution based on the bivalent cation calcium shielded the negative surface charge stronger than the monovalent cation sodium, resulting in a larger measureable anion-accessible porosity in the case of CaCl2 solutions. The data was modelled based on an adapted Donnan approach of Birgersson and Karnland (2009). The model had to be adjusted with a permanent free, uncharged porosity, as well as with structural information on the permanent anion exclusion because of so-called bottleneck pores. Both parameters can only be evaluated from experiments. Nevertheless, taking these two adaptions into account, the effect of varying pore water compositions on the anion-accessible porosity of the investigated argillaceous rocks could be satisfactorily described.

Charged particle beam scanning using deformed high gradient insulator

Science.gov (United States)

Chen, Yu -Jiuan

2015-10-06

Devices and methods are provided to allow rapid deflection of a charged particle beam. The disclosed devices can, for example, be used as part of a hadron therapy system to allow scanning of a target area within a patient's body. The disclosed charged particle beam deflectors include a dielectric wall accelerator (DWA) with a hollow center and a dielectric wall that is substantially parallel to a z-axis that runs through the hollow center. The dielectric wall includes one or more deformed high gradient insulators (HGIs) that are configured to produce an electric field with an component in a direction perpendicular to the z-axis. A control component is also provided to establish the electric field component in the direction perpendicular to the z-axis and to control deflection of a charged particle beam in the direction perpendicular to the z-axis as the charged particle beam travels through the hollow center of the DWA.

Generalized polymer effective charge measurement by capillary isotachophoresis.

Science.gov (United States)

Chamieh, Joseph; Koval, Dušan; Besson, Adeline; Kašička, Václav; Cottet, Hervé

2014-11-28

In this work, we have generalized the use of capillary isotachophoresis as a universal method for determination of effective charge of anionic and cationic (co)polymers on ordinary capillary electrophoresis instruments. This method is applicable to a broad range of strong or weak polyelectrolytes with good repeatability. Experimental parameters (components and concentrations of leading and terminating electrolytes, capillary diameters, constant electric current intensity) were optimized for implementation in 100 μm i.d. capillaries for both polyanions and polycations. Determined values of polymer effective charge were in a very good agreement with those obtained by capillary electrophoresis with indirect UV detection. Uncertainty of the effective charge measurement using isotachophoresis was addressed and estimated to be ∼5-10% for solutes with mobilities in the 20-50 × 10(-9)m(2)V(-1)s(-1) range. Copyright © 2014 Elsevier B.V. All rights reserved.

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

International Nuclear Information System (INIS)

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

2015-01-01

Highlights: • IC selectivity at high contents of organic solvent in eluent and elevated temperature is studied. • Solvent-enhanced IC coupled to high resolution MS is beneficial for sensitive detection of ions. • The first application of IC-HRMS to the detection of low explosives in fingermarks is shown. - Abstract: 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

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

Energy Technology Data Exchange (ETDEWEB)

Gilchrist, Elizabeth S. [Analytical & Environmental Science Division, Department of Forensic & Analytical Science, King’s College London, 150 Stamford Street, London, SE1 9NH (United Kingdom); Nesterenko, Pavel N. [Australian Centre for Research on Separation Science, School of Physical Sciences, University of Tasmania, Private Bag 75, Hobart 7001 (Australia); Smith, Norman W. [Analytical & Environmental Science Division, Department of Forensic & Analytical Science, King’s College London, 150 Stamford Street, London, SE1 9NH (United Kingdom); Barron, Leon P., E-mail: leon.barron@kcl.ac.uk [Analytical & Environmental Science Division, Department of Forensic & Analytical Science, King’s College London, 150 Stamford Street, London, SE1 9NH (United Kingdom)

2015-03-20

Highlights: • IC selectivity at high contents of organic solvent in eluent and elevated temperature is studied. • Solvent-enhanced IC coupled to high resolution MS is beneficial for sensitive detection of ions. • The first application of IC-HRMS to the detection of low explosives in fingermarks is shown. - Abstract: 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.

Stability of anionic polymers in presence of multivalent cations

International Nuclear Information System (INIS)

Sabbagh, Imad

1997-01-01

This research thesis aimed at studying the stability of poly-electrolytes in saline environments, and the interactions between ions and poly-electrolytes of different charge densities. For this purpose, the author more particularly studied specific interactions between anionic poly-electrolytes and multivalent cations. After a recall of properties of neutral polymers and poly-electrolytes in solution, the author evokes interactions between poly-electrolytes and counter-ions, and briefly presents two models of stability of poly-electrolytes in saline solutions. The next part presents various experimental spectroscopic and electrochemical techniques and results of the characterization of the used products. Spectroscopic techniques allow ion-polymer interactions at the atomic scale to be studied, and electrochemical techniques allow the behaviour of small ions to be studied. The author then discusses the main differences of solubility between poly-electrolytes containing sulphonate or sulphate groups and those containing carboxylate groups. A model is then developed to generalise phase diagrams of a poly-electrolyte with respect to the chemical affinity of its functional group with ions of opposite sign. The author then addresses the behaviour of a non charged polyacrylic acid in various saline solutions, and presents a phase diagram model [fr

EBIT spectroscopy of highly charged heavy ions relevant to hot plasmas

Science.gov (United States)

Nakamura, Nobuyuki

2013-05-01

An electron beam ion trap (EBIT) is a versatile device for studying highly charged ions. We have been using two types of EBITs for the spectroscopic studies of highly charged ions. One is a high-energy device called the Tokyo-EBIT, and another is a compact low-energy device called CoBIT. Complementary use of them enables us to obtain spectroscopic data for ions over a wide charge-state range interacting with electrons over a wide energy range. In this talk, we present EBIT spectra of highly charged ions for tungsten, iron, bismuth, etc., which are relevant to hot plasmas. Tungsten is considered to be the main impurity in the ITER (the next generation nuclear fusion reactor) plasma, and thus its emission lines are important for diagnosing and controlling the ITER plasma. We have observed many previously unreported lines to supply the lack of spectroscopic data of tungsten ions. Iron is one of the main components of the solar corona, and its spectra are used to diagnose temperature, density, etc. The diagnostics is usually done by comparing observed spectra with model calculations. An EBIT can provide spectra under a well-defined condition; they are thus useful to test the model calculations. Laser-produced bismuth plasma is one of the candidates for a soft x-ray source in the water window region. An EBIT has a narrow charge state distribution; it is thus useful to disentangle the spectra of laser-produced plasma containing ions with a wide charge-state range. Performed with the support and under the auspices of the NIFS Collaboration Research program (NIFS09KOAJ003) and JSPS KAKENHI Number 23246165, and partly supported by the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics.

Revisiting imidazolium based ionic liquids: Effect of the conformation bias of the [NTf2] anion studied by molecular dynamics simulations

Science.gov (United States)

Neumann, Jan; Golub, Benjamin; Odebrecht, Lisa-Marie; Ludwig, Ralf; Paschek, Dietmar

2018-05-01

We study ionic liquids composed of 1-alkyl-3-methylimidazolium cations and bis(trifluoromethyl-sulfonyl)imide anions ([CnMIm][NTf2]) with varying chain-length n = 2, 4, 6, 8 by using molecular dynamics simulations. We show that a reparametrization of the dihedral potentials as well as charges of the [NTf2] anion leads to an improvement of the force field model introduced by Köddermann, Paschek, and Ludwig [ChemPhysChem 8, 2464 (2007)] (KPL-force field). A crucial advantage of the new parameter set is that the minimum energy conformations of the anion (trans and gauche), as deduced from ab initio calculations and Raman experiments, are now both well represented by our model. In addition, the results for [CnMIm][NTf2] show that this modification leads to an even better agreement between experiment and molecular dynamics simulation as demonstrated for densities, diffusion coefficients, vaporization enthalpies, reorientational correlation times, and viscosities. Even though we focused on a better representation of the anion conformation, also the alkyl chain-length dependence of the cation behaves closer to the experiment. We strongly encourage to use the new NGOLP (Neumann, Golub, Odebrecht, Ludwig, Paschek) force field for the [NTf2] anion instead of the earlier KPL parameter set for computer simulations aiming to describe the thermodynamics, dynamics, and also structure of imidazolium-based ionic liquids.

Ionization of water clusters by fast Highly Charged Ions: Stability, fragmentation, energetics and charge mobility

International Nuclear Information System (INIS)

Legendre, S; Maisonny, R; Capron, M; Bernigaud, V; Cassimi, A; Gervais, B; Grandin, J-P; Huber, B A; Manil, B; Rousseau, P; Tarisien, M; Adoui, L; Lopez-Tarifa, P; AlcamI, M; MartIn, F; Politis, M-F; Penhoat, M A Herve du; Vuilleumier, R; Gaigeot, M-P; Tavernelli, I

2009-01-01

We study dissociative ionization of water clusters by impact of fast Ni ions. Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) is used to obtain information about stability, energetics and charge mobility of the ionized clusters. An unusual stability of the (H 2 O) 4 H ''+ ion is observed, which could be the signature of the so called ''Eigen'' structure in gas phase water clusters. High charge mobility, responsible for the formation of protonated water clusters that dominate the mass spectrum, is evidenced. These results are supported by CPMD and TDDFT simulations, which also reveal the mechanisms of such mobility.

Isotope effect study of κ-(BEDT-TTF)2Cu(NCS)2: Labeling in the anion

International Nuclear Information System (INIS)

Kini, A.M.; Wang, H.H.; Schlueter, J.A.

1995-01-01

Since the initial discovery of organic superconductivity in 1979, a large number of organic superconductors have now been synthesized. However, the mechanism of electron-pairing in these novel superconductors has remained largely unresolved. Isotope effect studies constitute an important experimental tool for the investigation of whether or not the electron-pairing mechanism in organic superconductors is phonon-mediated, as in conventional superconductors. Recent isotope effect studies in the authors' laboratory, involving seven different isotopically labeled BEDT-TTF (or ET) derivatives, have demonstrated the following: (1) intramolecular phonon modes involving C double-bond C and Csingle bondS stretching vibrations in the ET donor molecule are not the dominant mediators of electron-pairing, and (2) in κ-(ET) 2 Cu(NCS) 2 , there exist two competing isotope effects--a normal mass effect, i.e., lowering of T c upon isotopic labeling, when the ET molecular mass is increased by concurrent 13 C and 34 S labeling, in addition to an inverse isotope effect upon deuterium labeling in ET. It is of great interest to investigate if there is an isotope effect when the charge-compensating anions, which are also located within the non-conducting layer in the superconducting cation-radical salts, are isotopically labeled. The existence of an isotope effect when the anions are labeled would be indicative of electron-pairing with the mediation of vibrational frequencies associated with the anions. In this paper, the authors present the results of the first isotope effect study in which isotopic labeling in the anion portion of κ-(ET) 2 Cu(NCS) 2 is carried out. The authors find no isotope effect when the carbon and nitrogen atoms of the thiocyanate groups in the anion are replaced with 13 C and 15 N isotopes

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

Science.gov (United States)

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.

Natural minerals and synthetic materials for sorption of radioactive anions

Energy Technology Data Exchange (ETDEWEB)

Kang, Mun Ja; Chun, Kwan Sik; Kim, Seung Soo

1998-07-01

Technetium-99 and iodine-129 are fission products with long half-lives, and exist as highly soluble anionic species. Studies on natural and synthetic materials sorbing TcO{sub 4} and/or I have been performed by several researchers. The application of these materials as an additive in the high-level waste disposal has been considered. The iron- or sulfide-containing minerals such as metal iron, iron powder, stibnite and pyrrhotite show a high capacity for TcO{sub 4} sorption. And the small amounts of activated carbon are reported to have high distribution coefficients recently. In the iodine sorption studies, sulfide-, copper-, lead- or mercury-containing minerals can be a candidate. Pyrite, chalcopyrite, galena, Cu{sub 2}S and CuS reveal a high capacity for I sorption. The synthetic materials were found to have high sorption capacity and compensate the defects of natural minerals, which contain hydrous oxides such as zirconium oxide, aluminium oxide and mercarbide. The mercarbide has the high distribution coefficients for the sorption of TcO{sub 4} and I. Recently it was proposed that the synthetic clay, hydrotalcite, could be useful for the fixation of anion. However, to determine the applicability of those natural and synthetic materials as an additive to a buffer or backfill material for sorption of TcO{sub 4} and/or I, the sorption behavior of the anions on those materials under the repository conditions should be identified. (author). 32 refs., 21 tabs., 10 figs

A Cadmium Anionic 1-D Coordination Polymer {[Cd(H2O6][Cd2(atr2(μ2-btc2(H2O4] 2H2O}n within a 3-D Supramolecular Charge-Assisted Hydrogen-Bonded and π-Stacking Network

Directory of Open Access Journals (Sweden)

Anas Tahli

2016-03-01

Full Text Available The hydrothermal reaction of 4,4′-bis(1,2,4-triazol-4-yl (btr and benzene-1,3,5-tricarboxylic acid (H3btc with Cd(OAc2·2H2O at 125 °C in situ forms 4-amino-1,2,4-triazole (atr from btr, which crystallizes to a mixed-ligand, poly-anionic chain of [Cd2(atr2(µ2-btc2(H2O4]2–. Together with a hexaaquacadmium(II cation and water molecules the anionic coordination-polymeric forms a 3-D supramolecular network of hexaaquacadmium(II-catena-[bis(4-amino-1,2,4-triazoletetraaquabis(benzene-1,3,5-tricarboxylatodicadmate(II] dihydrate, 1-D-{[Cd(H2O6][Cd2(atr2(µ2-btc2(H2O4] 2H2O}n which is based on hydrogen bonds (in part charge-assisted and π–π interactions.

Extraction Compression and Acceleration of High Line Charge Density Ion Beams

CERN Document Server

Henestroza, Enrique; Grote, D P; Peters, Craig; Yu, Simon

2005-01-01

HEDP applications require high line charge density ion beams. An efficient method to obtain this type of beams is to extract a long pulse, high current beam from a gun at high energy, and let the beam pass through a decelerating field to compress it. The low energy beam bunch is loaded into a solenoid and matched to a Brillouin flow. The Brillouin equilibrium is independent of the energy if the relationship between the beam size (a), solenoid magnetic field strength (B) and line charge density is such that (Ba)2

Charge exchange processes of high energy heavy ions channeled in crystals

International Nuclear Information System (INIS)

Andriamonje, S.; Dural, J.; Toulemonde, M.; Groeneveld, K.O.; Maier, R.; Quere, Y.

1990-01-01

The interaction of moving ions with single crystals is very sensitive to the orientation of the incident beam with respect to the crystalline directions of the target. The experiments show that high energy heavy ion channeling deeply modifies the slowing down and charge exchange processes. In this review, we describe the opportunity offered by channeling conditions to study the charge exchange processes. Some aspects of the charge exchange processes with high energy channeled heavy ions are selected from the extensive literature published over the past few years on this subject. Special attention is given to the work performed at the GANIL facility on the study of Radiative Electron Capture (REG), Electron Impact Ionisation (EII), and convoy electron emission. Finally we emphasize the interest of studying resonant charge exchange processes such as Resonant Coherent Excitation (RCE), Resonant Transfer and Excitation (RTE) or Dielectronic Recombination (DR) and the recently proposed Nuclear Excitation by Electron Capture (NEEC)

Atomic physics with highly charged ions. Progress report

Energy Technology Data Exchange (ETDEWEB)

Richard, P.

1994-08-01

The study of inelastic collision phenomena with highly charged projectile ions and the interpretation of spectral features resulting from these collisions remain as the major focal points in the atomic physics research at the J.R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas. The title of the research project, ``Atomic Physics with Highly Charged Ions,`` speaks to these points. The experimental work in the past few years has divided into collisions at high velocity using the primary beams from the tandem and LINAC accelerators and collisions at low velocity using the CRYEBIS facility. Theoretical calculations have been performed to accurately describe inelastic scattering processes of the one-electron and many-electron type, and to accurately predict atomic transition energies and intensities for x rays and Auger electrons. Brief research summaries are given for the following: (1) electron production in ion-atom collisions; (2) role of electron-electron interactions in two-electron processes; (3) multi-electron processes; (4) collisions with excited, aligned, Rydberg targets; (5) ion-ion collisions; (6) ion-molecule collisions; (7) ion-atom collision theory; and (8) ion-surface interactions.

High-order space charge effects using automatic differentiation

International Nuclear Information System (INIS)

Reusch, M.F.; Bruhwiler, D.L.; Computer Accelerator Physics Conference Williamsburg, Virginia 1996)

1997-01-01

The Northrop Grumman Topkark code has been upgraded to Fortran 90, making use of operator overloading, so the same code can be used to either track an array of particles or construct a Taylor map representation of the accelerator lattice. We review beam optics and beam dynamics simulations conducted with TOPKARK in the past and we present a new method for modeling space charge forces to high-order with automatic differentiation. This method generates an accurate, high-order, 6-D Taylor map of the phase space variable trajectories for a bunched, high-current beam. The spatial distribution is modeled as the product of a Taylor Series times a Gaussian. The variables in the argument of the Gaussian are normalized to the respective second moments of the distribution. This form allows for accurate representation of a wide range of realistic distributions, including any asymmetries, and allows for rapid calculation of the space charge fields with free space boundary conditions. An example problem is presented to illustrate our approach. copyright 1997 American Institute of Physics

Occurrence of high-tonnage anionic surfactants into Spanish sewage sludge

Energy Technology Data Exchange (ETDEWEB)

Cantarero, S.; Prieto, C. A.; Lopez, I.; Berna, J. L.

2009-07-01

The sewage Sludge directive 86/278/EEc seeks to encourage the disposal of sewage sludge in agriculture applications and regulate its use to prevent harmful effects on the soil environment. currently, the sewage sludge Directive is under revision and a possible cut-off limit for some organic chemicals (including linear alkylbenzene sulphonates. LAS, the main synthetic anionic surfactant) is to be implemented. This legal limit is based on monitoring studies carried out in Scandinavian countries, being strongly rejected by most EU countries since the Nordic situations was regarded as not representative. (Author)

Occurrence of high-tonnage anionic surfactants into Spanish sewage sludge

International Nuclear Information System (INIS)

Cantarero, S.; Prieto, C. A.; Lopez, I.; Berna, J. L.

2009-01-01

The sewage Sludge directive 86/278/EEc seeks to encourage the disposal of sewage sludge in agriculture applications and regulate its use to prevent harmful effects on the soil environment. currently, the sewage sludge Directive is under revision and a possible cut-off limit for some organic chemicals (including linear alkylbenzene sulphonates. LAS, the main synthetic anionic surfactant) is to be implemented. This legal limit is based on monitoring studies carried out in Scandinavian countries, being strongly rejected by most EU countries since the Nordic situations was regarded as not representative. (Author)

Moment-Preserving Computational Approach for High Energy Charged Particle Transport

Science.gov (United States)

2016-05-16

posed, but with modified cross sections such that the resulting single-event Monte Carlo simulation is computationally efficient (minutes vs . days...configurations, which are all characteristics of real world applications. In other words , it is possible to simulate real, physical phenomena using charged...0 < 0.95) ~ 1 2() ≫ 1, (3) Demonstrating that scattering is highly forward peaked. Thus, the picture of charged particle interactions

Dissociative electron attachment and charge transfer in condensed matter

International Nuclear Information System (INIS)

Bass, A.D.; Sanche, L.

2003-01-01

Experiments using energy-selected beams of electrons incident from vacuum upon thin vapour deposited solids show that, as in the gas-phase, scattering cross sections at low energies are dominated by the formation of temporary negative ions (or resonances) and that molecular damage may be effected via dissociative electron attachment (DEA). Recent results also show that charge transfer between anionic states of target molecules and their environment is often crucial in determining cross sections for electron driven processes. Here, we review recent work from our laboratory, in which charge transfer is observed. For rare gas solids, electron exchange between the electron-exciton complex and either a metal substrate or co-adsorbed molecule enhances the desorption of metastable atoms and/or molecular dissociation. We discuss how transient electron capture by surface electron states of a substrate and subsequent electron transfer to a molecular adsorbate enhances the effective cross sections for DEA. We also consider the case of DEA to CF 2 Cl 2 condensed on water and ammonia ices, where electron exchange between pre-solvated electron states of ice and transient molecular anions can also increase DEA cross sections. Electron transfer from molecular resonances into pre-solvated electron states of ice is also discussed

Solar photovoltaic charging of high voltage nickel metal hydride batteries using DC power conversion

Science.gov (United States)

Kelly, Nelson A.; Gibson, Thomas L.

There are an increasing number of vehicle choices available that utilize batteries and electric motors to reduce tailpipe emissions and increase fuel economy. The eventual production of electricity and hydrogen in a renewable fashion, such as using solar energy, can achieve the long-term vision of having no tailpipe environmental impact, as well as eliminating the dependence of the transportation sector on dwindling supplies of petroleum for its energy. In this report we will demonstrate the solar-powered charging of the high-voltage nickel-metal hydride (NiMH) battery used in the GM 2-mode hybrid system. In previous studies we have used low-voltage solar modules to produce hydrogen via the electrolysis of water and to directly charge lithium-ion battery modules. Our strategy in the present work was to boost low-voltage PV voltage to over 300 V using DC-DC converters in order to charge the high-voltage NiMH battery, and to regulate the battery charging using software to program the electronic control unit supplied with the battery pack. A protocol for high-voltage battery charging was developed, and the solar to battery charging efficiency was measured under a variety of conditions. We believe this is the first time such high-voltage batteries have been charged using solar energy in order to prove the concept of efficient, solar-powered charging for battery-electric vehicles.

Electron capture by highly charged ions from surfaces and gases

Energy Technology Data Exchange (ETDEWEB)

Allen, F.

2008-01-11

In this study highly charged ions produced in Electron Beam Ion Traps are used to investigate electron capture from surfaces and gases. The experiments with gas targets focus on spectroscopic measurements of the K-shell x-rays emitted at the end of radiative cascades following electron capture into Rydberg states of Ar{sup 17+} and Ar{sup 18+} ions as a function of collision energy. The ions are extracted from an Electron Beam Ion Trap at an energy of 2 keVu{sup -1}, charge-selected and then decelerated down to 5 eVu{sup -1} for interaction with an argon gas target. For decreasing collision energies a shift to electron capture into low orbital angular momentum capture states is observed. Comparative measurements of the K-shell x-ray emission following electron capture by Ar{sup 17+} and Ar{sup 18+} ions from background gas in the trap are made and a discrepancy in the results compared with those from the extraction experiments is found. Possible explanations are discussed. For the investigation of electron capture from surfaces, highly charged ions are extracted from an Electron Beam Ion Trap at energies of 2 to 3 keVu{sup -1}, charge-selected and directed onto targets comprising arrays of nanoscale apertures in silicon nitride membranes. The highly charged ions implemented are Ar{sup 16+} and Xe{sup 44+} and the aperture targets are formed by focused ion beam drilling in combination with ion beam assisted thin film deposition, achieving hole diameters of 50 to 300 nm and aspect ratios of 1:5 to 3:2. After transport through the nanoscale apertures the ions pass through an electrostatic charge state analyzer and are detected. The percentage of electron capture from the aperture walls is found to be much lower than model predictions and the results are discussed in terms of a capillary guiding mechanism. (orig.)

Dissociative electron attachment to methyl chloride: A quasi-diatomic potential curve for the fragmentation of the metastable CH3Cl- anion

International Nuclear Information System (INIS)

Mach, P.; Urban, J.; Staemmler, V.

2009-01-01

Potential energy curves have been calculated for the dissociation of the neutral CH 3 Cl molecule and its negative ion into CH 3 + Cl and CH 3 +Cl - , respectively. The neutral molecule and the anion could be treated by means of standard wave function based quantum chemical ab initio methods for C-Cl distances larger than about 2.4 A, where CH 3 Cl - is a stable anion. In the present calculation MP3 and CCSD(T) were employed. At shorter C-Cl distances the CH 3 Cl - anion is only metastable and cannot be treated by such methods. We have applied a stabilization scheme, first proposed by Nestmann and Peyerimhoff, to stabilize the metastable anion by adding extra positive charges to the molecule. By this trick it was possible to generate the resonance energy E res and width Γ as functions of the C-Cl distance in the resonance regime between 1.5 and 2.5 A. The calculated values for the threshold energy E thresh and the exothermicity ΔE 0 of the DEA (dissociative electron attachment) process are in very good agreement with experiment; the vertical attachment energy (VAE) is smaller than its experimental counterpart

The Influence of Anion Shape on the Electrical Double Layer Microstructure and Capacitance of Ionic Liquids-Based Supercapacitors by Molecular Simulations

Directory of Open Access Journals (Sweden)

Ming Chen

2017-02-01

Full Text Available Room-temperature ionic liquids (RTILs are an emerging class of electrolytes for supercapacitors. In this work, we investigate the effects of different supercapacitor models and anion shape on the electrical double layers (EDLs of two different RTILs: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonylimide ([Emim][Tf2N] and 1-ethyl-3-methylimidazolium 2-(cyanopyrrolide ([Emim][CNPyr] by molecular dynamics (MD simulation. The EDL microstructure is represented by number densities of cations and anions, and the potential drop near neutral and charged electrodes reveal that the supercapacitor model with a single electrode has the same EDL structure as the model with two opposite electrodes. Nevertheless, the employment of the one-electrode model without tuning the bulk density of RTILs is more time-saving in contrast to the two-electrode one. With the one-electrode model, our simulation demonstrated that the shapes of anions significantly imposed effects on the microstructure of EDLs. The EDL differential capacitance vs. potential (C-V curves of [Emim][CNPyr] electrolyte exhibit higher differential capacitance at positive potentials. The modeling study provides microscopic insight into the EDLs structure of RTILs with different anion shapes.

Strong charge state dependence of H+ and H2+ sputtering induced by slow highly charged ions

International Nuclear Information System (INIS)

Kakutani, N.; Azuma, T.; Yamazaki, Y.; Komaki, K.; Kuroki, K.

1995-01-01

Secondary ion emission has been studied for very slow ( similar 0.01ν B ) highly charged Ar and N ions bombarding C 60 containing hydrogen as an impurity. It is found that the fragmentations of C 60 are very rare even for Ar 16+ bombardments. On the other hand, the sputtering of H + and H 2 + has been observed to increase drastically as a function of incident charge q like q γ (e.g., γ similar 4.6 for H + sputtering by 500 eV Ar q+ ). (orig.)

Effect of Anionic Salt and Highly Fermentable Carbohydrate Supplementations on Urine pH and on Experimentally Induced Hypocalcaemia in Cows

Directory of Open Access Journals (Sweden)

Enemark JMD

2004-09-01

Full Text Available The objective of this experiment was to determine the effect of dietary grain on calcium homeostasis. Six rumen-fistulated dairy cows with 3 or more previous lactations and no history of parturient paresis were randomly assigned to a sequence of diets in a crossover study with 4 periods of 10 days each. Dietary treatments were: A control ration consisting of wrap grass silage alone (1, the control ration supplemented with ammonium chloride and ammonium sulphate salt solution (2, control ration following a period with supplementation (3 and control ration supplemented with increasing amounts of barley from 4 to 10 kg/cow per day, expected to produce subclinical rumen acidosis (4. Daily intake of the diets was adjusted to 14 kg DM/cow per day. On day 11, the calcium-regulating mechanisms in cows were challenged until recumbency by a standardized intravenous EDTA infusion and cows were left to recover spontaneously. Anion supplementation and the feeding of highly fermentable carbohydrate lowered urine pH below 7.0 due to subclinical acidosis. During spontaneous recovery from EDTA induced hypocalcaemia, the cows more quickly regained a whole blood free calcium concentration of 1.00 mmol/L if they had most recently been supplemented with either anionic salts or with increasing amounts of barley, as compared to the basic ration. It is concluded that so-called slug-feeding or 'steaming up' with highly fermentable carbohydrates before parturition in milk fever susceptible cows enhanced calcium homeostasis similar to the effect seen in cows on anionic diets.

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

Science.gov (United States)

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.

Acceleration of high charge density electron beams in the SLAC linac

International Nuclear Information System (INIS)

Sheppard, J.C.; Clendenin, J.E.; Jobe, R.K.; Lueth, V.G.; Millich, A.; Ross, M.C.; Seeman, J.T.; Stiening, R.F.

1984-01-01

The SLAC Linear Collider (SLC) will require both electron and positron beams of very high charge density and low emittance to be accelerated to about 50 GeV in the SLAC 3-km linac. The linac is in the process of being improved to meet this requirement. The program to accelerate an electron beam of high charge density through the first third of the SLC linac is described and the experimental results are discussed. 7 references, 5 figures

Synthesis and photophysical properties of a novel terephthalic PH sensor based on internal charge transfer

International Nuclear Information System (INIS)

Miladinova, Polya M.

2016-01-01

A novel fluorescence sensing derivative of 2-aminodimethylterephthalate configured as a “fluorophore-receptor” system was synthesized and investigated. Due to the internal charge transfer, the designed fluorophore was able to act as a pH-probe via an “off-on” fluorescence sensing mechanism. The sensor activity toward protons as cations and hydroxide as anions in DMF was studied by monitoring the changes of the fluorescence intensity. Keywords: 2-aminoterephthalic derivative, ICT (internal charge transfer), pH sensor.

Charge transport and structure in semimetallic polymers

DEFF Research Database (Denmark)

Rudd, Sam; Franco-Gonzalez, Juan F.; Kumar Singh, Sandeep

2017-01-01

Owing to changes in their chemistry and structure, polymers can be fabricated to demonstrate vastly different electrical conductivities over many orders of magnitude. At the high end of conductivity is the class of conducting polymers, which are ideal candidates for many applications in low......-cost electronics. Here, we report the influence of the nature of the doping anion at high doping levels within the semi-metallic conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) on its electronic transport properties. Hall effect measurements on a variety of PEDOT samples show that the choice of doping...... that the chosen doping anion modifies the way PEDOT chains stack together. This link between structure and specific anion doping at high doping levels has ramifications for the fabrication of conducting polymer-based devices....

Initial observations of high-charge, low-emittance electron beams at HIBAF (High Brightness Accelerator FEL)

Energy Technology Data Exchange (ETDEWEB)

Lumpkin, A.H.; Feldman, R.B.; Carsten, B.E.; Feldman, D.W.; Sheffield, R.L.; Stein, W.E.; Johnson, W.J.; Thode, L.E.; Bender, S.C.; Busch, G.E.

1990-01-01

We report our initial measurements of bright (high-charge, low-emittance) electron beams generated at the Los Alamos High Brightness Accelerator FEL (HIBAF) Facility. Normalized emittance values of less than 50 {pi} mm-mrad for charges ranging from 0.7 to 8.7 nC were obtained for single micropulses at a y-waist and at an energy of 14.7 MeV. These measurements were part of the commissioning campaign on the HIBAF photoelectric injector. Macropulse measurements have also been performed and are compared with PARMELA simulations. 5 refs., 8 figs., 3 tabs.

Interaction of low-energy highly charged ions with matter

International Nuclear Information System (INIS)

Ginzel, Rainer

2010-01-01

The thesis presented herein deals with experimental studies of the interaction between highly charged ions and neutral matter at low collision energies. The energy range investigated is of great interest for the understanding of both charge exchange reactions between ions comprising the solar wind and various astrophysical gases, as well as the creation of near-surface nanostructures. Over the course of this thesis an experimental setup was constructed, capable of reducing the kinetic energy of incoming ions by two orders of magnitude and finally focussing the decelerated ion beam onto a solid or gaseous target. A coincidence method was employed for the simultaneous detection of photons emitted during the charge exchange process together with the corresponding projectile ions. In this manner, it was possible to separate reaction channels, whose superposition presumably propagated large uncertainties and systematic errors in previous measurements. This work has unveiled unexpectedly strong contributions of slow radiative decay channels and clear evidence of previously only postulated decay processes in charge exchange-induced X-ray spectra. (orig.)

Electrical Conductivity of Rocks and Dominant Charge Carriers. Part 1; Thermally Activated Positive Holes

Science.gov (United States)

Freund, Friedemann T.; Freund, Minoru M.

2012-01-01

The prevailing view in the geophysics community is that the electrical conductivity structure of the Earth's continental crust over the 5-35 km depth range can best be understood by assuming the presence of intergranular fluids and/or of intragranular carbon films. Based on single crystal studies of melt-grown MgO, magma-derived sanidine and anorthosite feldspars and upper mantle olivine, we present evidence for the presence of electronic charge carriers, which derive from peroxy defects that are introduced during cooling, under non-equilibrium conditions, through a redox conversion of pairs of solute hydroxyl arising from dissolution of H2O.The peroxy defects become thermally activated in a 2-step process, leading to the release of defect electrons in the oxygen anion sublattice. Known as positive holes and symbolized by h(dot), these electronic charge carriers are highly mobile. Chemically equivalent to O(-) in a matrix of O(2-) they are highly oxidizing. Being metastable they can exist in the matrix of minerals, which crystallized in highly reduced environments. The h(dot) are highly mobile. They appear to control the electrical conductivity of crustal rocks in much of the 5-35 km depth range.

Radiative recombination of highly charged ions: Enhanced rates at low energies

International Nuclear Information System (INIS)

Frank, A.; Mueller, A.; Haselbauer, J.; Schennach, S.; Spies, W.; Uwira, O.; Wagner, M.

1992-01-01

In a single-pass merged-beams experiment employing a dense cold electron target recombination of highly charged ions is studied. Unexpected high recombination rates are observed at low energies E cm in the electron-ion center-of-mass frame. In particular, theoretical estimates for radiative recombination are dramatically exceeded by the experimental recombination rates at E cm =0 eV for U 28+ and for Au 25+ ions. Considerable rate enhancement is also observed for Ar 15+ . This points to a general phenomenon which has to be interpreted as a consequence of high electron densities, low electron beam temperatures, high ion charge states and presence of strong magnetic fields. (orig.)

Transforming Anion Instability into Stability: Contrasting Photoionization of Three Protonation Forms of the Phosphate Ion upon Moving into Water

Czech Academy of Sciences Publication Activity Database

Pluhařová, Eva; Ončák, M.; Seidel, R.; Schroeder, C.; Schroeder, W.; Winter, B.; Bradforth, S. E.; Jungwirth, Pavel; Slavíček, P.

2012-01-01

Roč. 116, č. 44 (2012), s. 13254-13264 ISSN 1520-6106 R&D Projects: GA ČR(CZ) GAP208/10/1724; GA ČR GA203/08/0114 Institutional research plan: CEZ:AV0Z40550506 Keywords : multiply-charged anions * ab-initio calculations * aqueous-solution * photoelectron-spectroscopy * ionization energies * emission-spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.607, year: 2012

Charge transport in highly efficient iridium cored electrophosphorescent dendrimers

Science.gov (United States)

Markham, Jonathan P. J.; Samuel, Ifor D. W.; Lo, Shih-Chun; Burn, Paul L.; Weiter, Martin; Bässler, Heinz

2004-01-01

Electrophosphorescent dendrimers are promising materials for highly efficient light-emitting diodes. They consist of a phosphorescent core onto which dendritic groups are attached. Here, we present an investigation into the optical and electronic properties of highly efficient phosphorescent dendrimers. The effect of dendrimer structure on charge transport and optical properties is studied using temperature-dependent charge-generation-layer time-of-flight measurements and current voltage (I-V) analysis. A model is used to explain trends seen in the I-V characteristics. We demonstrate that fine tuning the mobility by chemical structure is possible in these dendrimers and show that this can lead to highly efficient bilayer dendrimer light-emitting diodes with neat emissive layers. Power efficiencies of 20 lm/W were measured for devices containing a second-generation (G2) Ir(ppy)3 dendrimer with a 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene electron transport layer.

Specificity of anion-binding in the substrate-pocket ofbacteriorhodopsin

Energy Technology Data Exchange (ETDEWEB)

Facciotti, Marc T.; Cheung, Vincent S.; Lunde, Christopher S.; Rouhani, Shahab; Baliga, Nitin S.; Glaeser, Robert M.

2003-08-30

The structure of the D85S mutant of bacteriorhodopsin with a nitrate anion bound in the Schiff-base binding site, and the structure of the anion-free protein have been obtained in the same crystal form. Together with the previously solved structures of this anion pump, in both the anion-free state and bromide-bound state, these new structures provide insight into how this mutant of bacteriorhodopsin is able to bind a variety of different anions in the same binding pocket. The structural analysis reveals that the main structural change that accommodates different anions is the repositioning of the polar side-chain of S85. On the basis of these x-ray crystal structures, the prediction is then made that the D85S/D212N double mutant might bind similar anions and do so over a broader pH range than does the single mutant. Experimental comparison of the dissociation constants, K{sub d}, for a variety of anions confirms this prediction and demonstrates, in addition, that the binding affinity is dramatically improved by the D212N substitution.

Novel charge sensitive preamplifier without high-value feedback resistor

International Nuclear Information System (INIS)

Xi Deming

1992-01-01

A novel charge sensitive preamplifier is introduced. The method of removing the high value feedback resistor, the circuit design and analysis are described. A practical circuit and its measured performances are provided

Solution and gas phase evidence of anion binding through the secondary bonding interactions of a bidentate bis-antimony(iii) anion receptor.

Science.gov (United States)

Qiu, J; Song, B; Li, X; Cozzolino, A F

2017-12-20

The solution and gas phase halide binding to a bis-antimony(iii) anion receptor was studied. This new class of anion receptors utilizes the strong Sb-centered secondary bonding interactions (SBIs) that are formed opposite to the polar Sb-O primary bond. 1 H NMR titration data were fitted statistically to binding models and solution-phase binding energetics were extracted, while the formation of anion-to-receptor complexes was observed using ESI-MS. Density functional theory calculations suggest that their affinity towards binding halide anions is mitigated by the strong explicit solvation effect in DMSO, which gives insights into future designs that circumvent direct solvent binding and are anticipated to yield tighter and perhaps more selectivity in anion binding.

Zero-point energy effects in anion solvation shells.

Science.gov (United States)

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.

Origin of negative resistance in anion migration controlled resistive memory

Science.gov (United States)

Banerjee, Writam; Wu, Facai; Hu, Yuan; Wu, Quantan; Wu, Zuheng; Liu, Qi; Liu, Ming

2018-03-01

Resistive random access memory (RRAM) is one of the most promising emerging nonvolatile technologies for the futuristic memory devices. Resistive switching behavior often shows negative resistance (NR), either voltage controlled or current controlled. In this work, the origin of a current compliance dependent voltage controlled NR effect during the resetting of anion migration based RRAM devices is discussed. The N-type voltage controlled NR is a high field driven phenomena. The current conduction within the range of a certain negative voltage is mostly dominated by space charge limited current. But with the higher negative voltage, a field induced tunneling effect is generated in the NR region. The voltage controlled NR is strongly dependent on the compliance current. The area independent behavior indicates the filamentary switching. The peak to valley ratio (PVR) is > 5. The variation of PVR as a function of the conduction band offset is achieved. Compared to other reported works, based on the PVR, it is possible to distinguish the RRAM types. Generally, due to the higher electric field effect on the metallic bridge during RESET, the electrochemical metallization type RRAM shows much higher PVR than the valance change type RRAM.

High Charge State Ions Extracted from Metal Plasmas in the Transition Regime from Vacuum Spark to High Current Vacuum Arc

International Nuclear Information System (INIS)

Yushkov, Georgy Yu.; Anders, A.

2008-01-01

Metal ions were extracted from pulsed discharge plasmas operating in the transition region between vacuum spark (transient high voltage of kV) and vacuum arc (arc voltage ∼ 20 V). At a peak current of about 4 kA, and with a pulse duration of 8 (micro)s, we observed mean ion charges states of about 6 for several cathode materials. In the case of platinum, the highest average charge state was 6.74 with ions of charge states as high as 10 present. For gold we found traces of charge state 11, with the highest average charge state of 7.25. At currents higher than 5 kA, non-metallic contaminations started to dominate the ion beam, preventing further enhancement of the metal charge states

Construction of a Nano Biosensor for Cyanide Anion Detection and Its Application in Environmental and Biological Systems.

Science.gov (United States)

Dong, Zhen-Zhen; Yang, Chao; Vellaisamy, Kasipandi; Li, Guodong; Leung, Chung-Hang; Ma, Dik-Lung

2017-10-27

We have developed a Ag@Au core-shell nanoparticle (NP)/iridium(III) complex-based sensing platform for the sensitive luminescence "turn-on" sensing of cyanide ions, an acutely toxic pollutant. The assay is based on the quenching effect of Ag@Au NPs on the emission of complex 1, but luminescence is restored after the addition of cyanide anions due to their ability to dissolve the Au shell. Our sensing platform exhibited a high sensitivity toward cyanide anions with a detection limit of 0.036 μM, and also showed high selectivity for cyanide over 10-fold excess amounts of other anions. The sensing platform was also successfully applied to monitor cyanide anions in drinking water and in living cells.

On the effect of image states on resonant neutralization of hydrogen anions near metal surfaces

International Nuclear Information System (INIS)

Chakraborty, Himadri S.; Niederhausen, Thomas; Thumm, Uwe

2005-01-01

We directly assess the role of image state electronic structures on the ion-survival by comparing the resonant charge transfer dynamics of hydrogen anions near Pd(1 1 1), Pd(1 0 0), and Ag(1 1 1) surfaces. Our simulations show that image states that are degenerate with the metal conduction band favor the recapture of electrons by outgoing ions. In sharp contrast, localized image states that occur inside the band gap hinder the recapture process and thus enhance the ion-neutralization probability

Laser focusing of high-energy charged-particle beams

International Nuclear Information System (INIS)

Channell, P.J.

1986-01-01

It is shown that laser focusing of high-energy charged-particle beams using the inverse Cherenkov effect is well suited for applications with large linear colliders. Very high gradient (>0.5 MG/cm) lenses result that can be added sequentially without AG cancellation. These lenses are swell understood, have small geometric aberrations, and offer the possibility of correlating phase and energy aberrations to produce an achromatic final focus

Nanometer-size surface modification produced by single, low energy, highly charged ions

International Nuclear Information System (INIS)

Stockli, M.P.

1994-01-01

Atomically flat surfaces of insulators have been bombarded with low energy, highly charged ions to search for nanometer-size surface modifications. It is expected that the high electron deficiency of highly charged ions will capture and/or remove many of the insulator's localized electrons when impacting on an insulating surface. The resulting local electron deficiency is expected to locally disintegrate the insulator through a open-quotes Coulomb explosionclose quotes forming nanometer-size craters. Xe ions with charge states between 10+ and 45+ and kinetic energies between 0 and 10 keV/q were obtained from the KSU-CRYEBIS, a CRYogenic Electron Beam Ion Source and directed onto various insulating materials. Mica was favored as target material as atomically flat surfaces can be obtained reliably through cleaving. However, the authors observations with an atomic force microscope have shown that mica tends to defoliate locally rather than disintegrate, most likely due to the small binding forces between adjacent layers. So far the authors measurements indicate that each ion produces one blister if the charge state is sufficiently high. The blistering does not seem to depend very much on the kinetic energy of the ions

Status of Charge Exchange Cross Section Measurements for Highly Charged Ions on Atomic Hydrogen

Science.gov (United States)

Draganic, I. N.; Havener, C. C.; Schultz, D. R.; Seely, D. G.; Schultz, P. C.

2011-05-01

Total cross sections of charge exchange (CX) for C5+, N6+, and O7+ ions on ground state atomic hydrogen are measured in an extended collision energy range of 1 - 20,000 eV/u. Absolute CX measurements are performed using an improved merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source mounted on a high voltage platform. In order to improve the problematic H+ signal collection for these exoergic CX collisions at low relative energies, a new double focusing electrostatic analyzer was installed. Experimental CX data are in good agreement with all previous H-oven relative measurements at higher collision energies. We compare our results with the most recent molecular orbital close-coupling (MOCC) and atomic orbital close-coupling (AOCC) theoretical calculations. Work supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, and the Office of Basic Energy Sciences of the U.S. DoE.

Energy of charged states in the acetanilide crystal: Trapping of charge-transfer states at vacancies as a possible mechanism for optical damage

Science.gov (United States)

Tsiaousis, D.; Munn, R. W.

2004-04-01

Calculations for the acetanilide crystal yield the effective polarizability (16.6 Å3), local electric field tensor, effective dipole moment (5.41 D), and dipole-dipole energy (-12.8 kJ/mol). Fourier-transform techniques are used to calculate the polarization energy P for a single charge in the perfect crystal (-1.16 eV); the charge-dipole energy WD is zero if the crystal carries no bulk dipole moment. Polarization energies for charge-transfer (CT) pairs combine with the Coulomb energy EC to give the screened Coulomb energy Escr; screening is nearly isotropic, with Escr≈EC/2.7. For CT pairs WD reduces to a term δWD arising from the interaction of the charge on each ion with the change in dipole moment on the other ion relative to the neutral molecule. The dipole moments calculated by density-functional theory methods with the B3LYP functional at the 6-311++G** level are 3.62 D for the neutral molecule, changing to 7.13 D and 4.38 D for the anion and cation, relative to the center of mass. Because of the large change in the anion, δWD reaches -0.9 eV and modifies the sequence of CT energies markedly from that of Escr, giving the lowest two CT pairs at -1.98 eV and -1.41 eV. The changes in P and WD near a vacancy are calculated; WD changes for the individual charges because the vacancy removes a dipole moment and modifies the crystal dielectric response, but δWD and EC do not change. A vacancy yields a positive change ΔP that scatters a charge or CT pair, but the change ΔWD can be negative and large enough to outweigh ΔP, yielding traps with depths that can exceed 150 meV for single charges and for CT pairs. Divacancies yield traps with depths nearly equal to the sum of those produced by the separate vacancies and so they can exceed 300 meV. These results are consistent with a mechanism of optical damage in which vacancies trap optically generated CT pairs that recombine and release energy; this can disrupt the lattice around the vacancy, thereby favoring

Highly charged cyanine fluorophores for trafficking scaffold degradation

International Nuclear Information System (INIS)

Owens, Eric A; Alyabyev, Sergey; Henary, Maged; Hyun, Hoon; Kim, Soon Hee; Lee, Jeong Heon; Park, GwangLi; Ashitate, Yoshitomo; Choi, Jungmun; Hong, Gloria H; Choi, Hak Soo; Lee, Sang Jin; Khang, Gilson

2013-01-01

Biodegradable scaffolds have been extensively used in the field of tissue engineering and regenerative medicine. However, noninvasive monitoring of in vivo scaffold degradation is still lacking. In order to develop a real-time trafficking technique, a series of meso-brominated near-infrared (NIR) fluorophores were synthesized and conjugated to biodegradable gelatin scaffolds. Since the pentamethine cyanine core is highly lipophilic, the side chain of each fluorophore was modified with either quaternary ammonium salts or sulfonate groups. The physicochemical properties such as lipophilicity and net charge of fluorophores played a key role in the fate of NIR-conjugated scaffolds in vivo after biodegradation. The positively charged fluorophore-conjugated scaffold fragments were found in salivary glands, lymph nodes, and most of the hepatobiliary excretion route. However, halogenated fluorophores intensively accumulated into lymph nodes and the liver. Interestingly, balanced-charged gelatin scaffolds were degraded into urine in a short period of time. These results demonstrate that the noninvasive optical imaging using NIR fluorophores can be useful for the translation of biodegradable scaffolds into the clinic. (paper)

Neutral anion receptors: design and application

NARCIS (Netherlands)

Antonisse, M.M.G.; Reinhoudt, David

1998-01-01

After the development of synthetic cation receptors in the late 1960s, only in the past decade has work started on the development of synthetic neutral anion receptors. Combination and preorganization of different anion binding groups, like amides, urea moieties, or Lewis acidic metal centers lead

The longitudinal space charge problem in the high current linear proton accelerators

International Nuclear Information System (INIS)

Lustfeld, H.

1984-01-01

In a linear proton accelerator peak currents of 200 mA lead to high space charge densities and the resultant space charge forces reduce the effective focussing considerably. In particular the longitudinal focussing is affected. A new concept based on linear theory is proposed that restricts the influence of the space charge forces on the longitudinal focussing by increasing a, the mean transverse bunch radius, as a proportional(βγ)sup(3/8). This concept is compared with other concepts for the Alvarez (1 MeV - 100 MeV) and for the high energy part (100 MeV - 1100 MeV) of the SNQ linear accelerator. (orig.)

A safety and tolerability study of differently-charged nanoparticles for local pulmonary drug delivery

International Nuclear Information System (INIS)

Harush-Frenkel, Oshrat; Bivas-Benita, Maytal; Nassar, Taher; Springer, Chaim; Sherman, Yoav; Avital, Avraham; Altschuler, Yoram; Borlak, Jurgen; Benita, Simon

2010-01-01

Nanoparticle (NP) based drug delivery systems provide promising opportunities in the treatment of lung diseases. Here we examined the safety and tolerability of pulmonary delivered NPs consisting of PEG-PLA as a function of particle surface charge. The rationale for such a comparison should be attributed to the differential pulmonary toxicity of positively and negatively charged PEG-PLA NP. Thus, the local and systemic effects of pulmonary administered NPs were investigated following 5 days of daily endotracheal instillation to BALB/c mice that were euthanized on the eighth or nineteenth day of the experiment. We collected bronchoalveolar lavages and studied hematological as well as histochemistry parameters. Notably, the cationic stearylamine based PEG-PLA NPs elicited increased local and systemic toxic effects both on the eighth and nineteenth day. In contrast, anionic NPs of similar size were much better tolerated with local inflammatory effects observed only on the eighth experimental day after pulmonary instillation. No systemic toxicity effect was observed although a moderate change was noted in the platelet count that was not considered to be of clinical significance. No pathological observations were detected in the internal organs following instillation of anionic NPs. Overall these observations suggest that anionic PEG-PLA NPs are useful pulmonary drug carriers that should be considered as a promising therapeutic drug delivery system.

Interstellar dehydrogenated PAH anions: vibrational spectra

Science.gov (United States)

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.

First observation of alkyne radical anions by electron spin resonance spectroscopy: Hexyne/n-hexane mixed crystals

International Nuclear Information System (INIS)

Matsuura, K.; Muto, H.

1991-01-01

The radical anions of alkynes have been first observed by electron spin resonance spectroscopy following alkene anions previously studied. Hexyne radical anions were formed in 1-, 2-, or 3-hexyne/n--hexane mixed crystals irradiated at 4.2 or 77 K. The characters of the anions were as follows; (a) the α-proton hyperfine coupling is very large (∼4.5 mT for the 1-hexyne anion), (b) the β-proton couplings are very small (∼1.0 mT for C--H β proton with the conformational angle of 0 degree), and (c) the radicals show a negative g shift (2.0014). From these observations, it was found that the anions have a nonlinear(bent) molecule structure in the anticonfiguration (trans C--C≡C--C) with the bend angle ∼60 degree, and that the unpaired electron orbital is approximately composed of the anticombination of the sp 2 hybrid orbitals of the C≡C carbon atoms. A discussion based on complete neglect of differential overlap (CNDO) molecular orbital (MO) calculations was given for the observed negative g shift, which was shown to be characteristic of the alkyne anions which have a high-lying unpaired electron orbital and an antibonding 2p--2p π carbon orbital just above it on the upper energy side

Anionic water pentamer and hexamer clusters: An extensive study of structures and energetics

Science.gov (United States)

Ünal, Aslı; Bozkaya, Uǧur

2018-03-01

An extensive study of structures and energetics for anionic pentamer and hexamer clusters is performed employing high level ab initio quantum chemical methods, such as the density-fitted orbital-optimized linearized coupled-cluster doubles (DF-OLCCD), coupled-cluster singles and doubles (CCSD), and coupled-cluster singles and doubles with perturbative triples [CCSD(T)] methods. In this study, sixteen anionic pentamer clusters and eighteen anionic hexamer clusters are reported. Relative, binding, and vertical detachment energies (VDE) are presented at the complete basis set limit (CBS), extrapolating energies of aug4-cc-pVTZ and aug4-cc-pVQZ custom basis sets. The largest VDE values obtained at the CCSD(T)/CBS level are 9.9 and 11.2 kcal mol-1 for pentamers and hexamers, respectively, which are in very good agreement with the experimental values of 9.5 and 11.1 kcal mol-1. Our binding energy results, at the CCSD(T)/CBS level, indicate strong bindings in anionic clusters due to hydrogen bond interactions. The average binding energy per water molecules is -5.0 and -5.3 kcal mol-1 for pentamers and hexamers, respectively. Furthermore, our results demonstrate that the DF-OLCCD method approaches to the CCSD(T) quality for anionic clusters. The inexpensive analytic gradients of DF-OLCCD compared to CCSD or CCSD(T) make it very attractive for high-accuracy studies.

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

Science.gov (United States)

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.

Development of a Sweetness Sensor for Aspartame, a Positively Charged High-Potency Sweetener

Directory of Open Access Journals (Sweden)

Masato Yasuura

2014-04-01

Full Text Available Taste evaluation technology has been developed by several methods, such as sensory tests, electronic tongues and a taste sensor based on lipid/polymer membranes. In particular, the taste sensor can individually quantify five basic tastes without multivariate analysis. However, it has proven difficult to develop a sweetness sensor, because sweeteners are classified into three types according to the electric charges in an aqueous solution; that is, no charge, negative charge and positive charge. Using membrane potential measurements, the taste-sensing system needs three types of sensor membrane for each electric charge type of sweetener. Since the commercially available sweetness sensor was only intended for uncharged sweeteners, a sweetness sensor for positively charged high-potency sweeteners such as aspartame was developed in this study. Using a lipid and plasticizers, we fabricated various lipid/polymer membranes for the sweetness sensor to identify the suitable components of the sensor membranes. As a result, one of the developed sensors showed responses of more than 20 mV to 10 mM aspartame and less than 5 mV to any other taste. The responses of the sensor depended on the concentration of aspartame. These results suggested that the developed sweetness sensor had high sensitivity to and high selectivity for aspartame.

Development of a sweetness sensor for aspartame, a positively charged high-potency sweetener.

Science.gov (United States)

Yasuura, Masato; Tahara, Yusuke; Ikezaki, Hidekazu; Toko, Kiyoshi

2014-04-23

Taste evaluation technology has been developed by several methods, such as sensory tests, electronic tongues and a taste sensor based on lipid/polymer membranes. In particular, the taste sensor can individually quantify five basic tastes without multivariate analysis. However, it has proven difficult to develop a sweetness sensor, because sweeteners are classified into three types according to the electric charges in an aqueous solution; that is, no charge, negative charge and positive charge. Using membrane potential measurements, the taste-sensing system needs three types of sensor membrane for each electric charge type of sweetener. Since the commercially available sweetness sensor was only intended for uncharged sweeteners, a sweetness sensor for positively charged high-potency sweeteners such as aspartame was developed in this study. Using a lipid and plasticizers, we fabricated various lipid/polymer membranes for the sweetness sensor to identify the suitable components of the sensor membranes. As a result, one of the developed sensors showed responses of more than 20 mV to 10 mM aspartame and less than 5 mV to any other taste. The responses of the sensor depended on the concentration of aspartame. These results suggested that the developed sweetness sensor had high sensitivity to and high selectivity for aspartame.

High gradient lens for charged particle beam

Science.gov (United States)

Chen, Yu-Jiuan

2014-04-29

Methods and devices enable shaping of a charged particle beam. A dynamically adjustable electric lens includes a series of alternating a series of alternating layers of insulators and conductors with a hollow center. The series of alternating layers when stacked together form a high gradient insulator (HGI) tube to allow propagation of the charged particle beam through the hollow center of the HGI tube. A plurality of transmission lines are connected to a plurality of sections of the HGI tube, and one or more voltage sources are provided to supply an adjustable voltage value to each transmission line of the plurality of transmission lines. By changing the voltage values supplied to each section of the HGI tube, any desired electric field can be established across the HGI tube. This way various functionalities including focusing, defocusing, acceleration, deceleration, intensity modulation and others can be effectuated on a time varying basis.

Anion size and isotope effects in (EDO-TTF)2XF6

International Nuclear Information System (INIS)

Nakano, Yoshiaki; Yamochi, Hideki; Saito, Gunzi; Uruichi, Mikio; Yakushi, Kyuya

2009-01-01

(EDO-TTF) 2 PF 6 is a quasi one-dimensional molecular conductor and undergoes a peculiar metal-insulator (MI) transition. The phase transition mechanism is cooperative among Peierls, charge ordering, and anion ordering transitions, which is accompanied with a distinct molecular deformation. (EDO-TTF) 2 XF 6 (X = P (1h), As (2h), Sb (3h)) showed that the transition temperature (T MI ) and the width of thermal hysteresis (ΔT MI ) were systematically changed depending on the anion size, i.e., the T MI decreased in order of 279.0 K (1h), 270.8 K (2h), and 242 K (3h) and the ΔT MI increased in order of 1.0 K (1h), 5.5 K (2h), and 14 K (3h). The deuterated salts, (EDO-TTF-d 2 ) 2 XF 6 (X = P (1d) and As (2d)), showed higher T MI of 282.0 (1d) and 274.0 K (2d) and narrower ΔT MI of 0.0 (1d) and 5.0 K (2d) than the undeuterated 1h and 2h, respectively. X-ray analysis revealed the anisotropic thermal expansion of unit cell. The linear relationship between ΔT MI and volume change at T MI was found.

New anion-exchange polymers for improved separations

International Nuclear Information System (INIS)

Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

1997-01-01

Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials

Use of new tandem cation/anion exchange system with clinical-scale generators provides high specific volume solutions of technetium-99m and rhenium-188

International Nuclear Information System (INIS)

Knapp, F.F. Jr.; Beets, A.L.; Mirzadeh, S.; Guhlke, S.

1998-01-01

In this paper we describe the first application of our simple and inexpensive post-elution tandem cation/anion exchange column system which is based on generator elution with salts of weak acids such as ammonium acetate instead of saline solution to provide very high specific volume solutions of technetium-99m and rhenium-188 from clinical-scale molybdenum-99/technetium-99m generator prepared from low specific activity (n,y) molybdenum-99, and tungsten-188/rhenium-188 generators, respectively. Initial passage of the bolus through a strong cation exchange cartridge converts the ammonium acetate to acetic acid which is essentially not ionized at the acidic pH, allowing specific subsequent amine-type (QMA SepPak TM ) anion exchange cartridge column trapping of the microscopic levels of the pertechnetate or perrhenate. Subsequent elution of the anion cartridge with a small volume ( 500 mCi/mL) from the alumina-based tungsten-188/rhenium-188 generator. (author)

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

Science.gov (United States)

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.

Experimental determination of net protein charge, [A]tot, and Ka of nonvolatile buffers in bird plasma.

Science.gov (United States)

Stämpfli, Henry; Taylor, Michael; McNicoll, Carl; Gancz, Ady Y; Constable, Peter D

2006-06-01

The quantitative mechanistic acid-base approach to clinical assessment of acid-base status requires species-specific values for [A]tot (the total concentration of nonvolatile buffers in plasma) and Ka (the effective dissociation constant for weak acids in plasma). The aim of this study was to determine [A]tot and Ka values for plasma in domestic pigeons. Plasma from 12 healthy commercial domestic pigeons was tonometered with 20% CO2 at 37 degrees C. Plasma pH, Pco2, and plasma concentrations of strong cations (Na, K, Ca), strong anions (Cl, L-lactate), and nonvolatile buffer ions (total protein, albumin, phosphate) were measured over a pH range of 6.8-7.7. Strong ion difference (SID) (SID5=Na+K+Ca-Cl-lactate) was used to calculate [A]tot and Ka from the measured pH and Pco2 and SID5. Mean (+/-SD) values for bird plasma were as follows: [A]tot=7.76+/-2.15 mmol/l (equivalent to 0.32 mmol/g of total protein, 0.51 mmol/g of albumin, 0.23 mmol/g of total solids); Ka=2.15+/-1.15x10(-7); and pKa=6.67. The net protein charge at normal pH (7.43) was estimated to be 6 meq/l; this value indicates that pigeon plasma has a much lower anion gap value than mammals after adjusting for high mean L-lactate concentrations induced by restraint during blood sampling. This finding indicates that plasma proteins in pigeons have a much lower net anion charge than mammalian plasma protein. An incidental finding was that total protein concentration measured by a multianalyzer system was consistently lower than the value for total solids measured by refractometer.

High-k shallow traps observed by charge pumping with varying discharging times

International Nuclear Information System (INIS)

Ho, Szu-Han; Chen, Ching-En; Tseng, Tseung-Yuen; Chang, Ting-Chang; Lu, Ying-Hsin; Lo, Wen-Hung; Tsai, Jyun-Yu; Liu, Kuan-Ju; Wang, Bin-Wei; Cao, Xi-Xin; Chen, Hua-Mao; Cheng, Osbert; Huang, Cheng-Tung; Chen, Tsai-Fu

2013-01-01

In this paper, we investigate the influence of falling time and base level time on high-k bulk shallow traps measured by charge pumping technique in n-channel metal-oxide-semiconductor field-effect transistors with HfO 2 /metal gate stacks. N T -V high level characteristic curves with different duty ratios indicate that the electron detrapping time dominates the value of N T for extra contribution of I cp traps. N T is the number of traps, and I cp is charge pumping current. By fitting discharge formula at different temperatures, the results show that extra contribution of I cp traps at high voltage are in fact high-k bulk shallow traps. This is also verified through a comparison of different interlayer thicknesses and different Ti x N 1−x metal gate concentrations. Next, N T -V high level characteristic curves with different falling times (t falling time ) and base level times (t base level ) show that extra contribution of I cp traps decrease with an increase in t falling time . By fitting discharge formula for different t falling time , the results show that electrons trapped in high-k bulk shallow traps first discharge to the channel and then to source and drain during t falling time . This current cannot be measured by the charge pumping technique. Subsequent measurements of N T by charge pumping technique at t base level reveal a remainder of electrons trapped in high-k bulk shallow traps

Acute and chronic influence of temperature on red blood cell anion exchange.

Science.gov (United States)

Jensen, F B; Wang, T; Brahm, J

2001-01-01

Unidirectional (36)Cl(-) efflux via the red blood cell anion exchanger was measured under Cl(-) self-exchange conditions (i.e. no net flow of anions) in rainbow trout Oncorhynchus mykiss and red-eared freshwater turtle Trachemys scripta to examine the effects of acute temperature changes and acclimation temperature on this process. We also evaluated the possible adaptation of anion exchange to different temperature regimes by including our previously published data on other animals. An acute temperature increase caused a significant increase in the rate constant (k) for unidirectional Cl(-) efflux in rainbow trout and freshwater turtle. After 3 weeks of temperature acclimation, 5 degrees C-acclimated rainbow trout showed only marginally higher Cl(-) transport rates than 15 degrees C-acclimated trout when compared at the same temperature. Apparent activation energies for red blood cell Cl(-) exchange in trout and turtle were lower than values reported in endothermic animals. The Q(10) for red blood cell anion exchange was 2.0 in trout and 2.3 in turtle, values close to those for CO(2) excretion, suggesting that, in ectothermic animals, the temperature sensitivity of band-3-mediated anion exchange matches the temperature sensitivity of CO(2) transport (where red blood cell Cl(-)/HCO(3)(-) exchange is a rate-limiting step). In endotherms, such as man and chicken, Q(10) values for red blood cell anion exchange are considerably higher but are no obstacle to CO(2) transport, because body temperature is normally kept constant at values at which anion exchange rates are high. When compared at constant temperature, red blood cell Cl(-) permeability shows large differences among species (trout, carp, eel, cod, turtle, alligator, chicken and man). Cl(-) permeabilities are, however, remarkable similar when compared at preferred body temperatures, suggesting an appropriate evolutionary adaptation of red blood cell anion exchange function to the different thermal niches occupied

A High-Level Functional Architecture for GNSS-Based Road Charging Systems

DEFF Research Database (Denmark)

Zabic, Martina

2011-01-01

, a short introduction is provided followed by a presentation of the system engineering methodology to illustrate how and why system architectures can be beneficial for GNSS-based road charging systems. Hereafter, a basic set of system functions is determined based on functional system requirements, which...... charging systems, it is important to highlight the overall system architecture which is the framework that defines the basic functions and important concepts of the system. This paper presents a functional architecture for GNSS-based road charging systems based on the concepts of system engineering. First...... defines the necessary tasks that these systems must accomplish. Finally, this paper defines the system functionalities; and provides a generic high-level functional architecture for GNSS-based road charging systems....

Probing electron density of H-bonding between cation-anion of imidazolium-based ionic liquids with different anions by vibrational spectroscopy.

Science.gov (United States)

Gao, Yan; Zhang, Liqun; Wang, Yong; Li, Haoran

2010-03-04

Attenuated total reflection infrared spectroscopy and density functional theory calculation have been employed to study the spectral properties of imidazolium-based ionic liquids (ILs) with different anions. ILs based on 1-butyl-3-methylimidazolium cation with different anions, OH(-), CF(3)CO(2)(-), HSO(4)(-), H(2)PO(4)(-), Cl(-), PF(6)(-), and BF(4)(-), are investigated in the present work. It has been shown that the C(2)-H stretching vibration of the imidazolium ring is closely related to the electron density of H-bonding between the two closest cations and anions for pure ILs. The electron density of H-bonding between cation and anion with different anions decreases in the order [OH](-) > [H(2)PO(4)](-) > [HSO(4)](-) > [CF(3)CO(2)](-) > [Cl](-) > [BF(4)](-) > [PF(6)](-). For aqueous ILs, with increasing water content, the aromatic C-H stretching vibration of the imidazolium cation showed systematic blue-shifts. Especially for BmimOH, the nu(C(2))(-H) undergoes a drastic blue-shift by 58 cm(-1), suggesting that the formation of the strong hydrogen bonds O-H...O may greatly weaken the electron density of H-bonding between the cation and anion of ILs.

The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces

Science.gov (United States)

Uematsu, Yuki; Netz, Roland R.; Bonthuis, Douwe Jan

2018-02-01

Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson-Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.

Hydration of excess electrons trapped in charge pockets on molecular surfaces

Science.gov (United States)

Jalbout, Abraham F.; Del Castillo, R.; Adamowicz, Ludwik

2007-01-01

In this work we strive to design a novel electron trap located on a molecular surface. The process of electron trapping involves hydration of the trapped electron. Previous calculations on surface electron trapping revealed that clusters of OH groups can form stable hydrogen-bonded networks on one side of a hydrocarbon surface (i.e. cyclohexane sheets), while the hydrogen atoms on the opposite side of the surface form pockets of positive charge that can attract extra negative charge. The excess electron density on such surfaces can be further stabilized by interactions with water molecules. Our calculations show that these anionic systems are stable with respect to vertical electron detachment (VDE).

Photoelectron spectroscopy of the 6-azauracil anion.

Science.gov (United States)

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.

Charge modification of the endothelial surface layer modulates the permeability barrier of isolated rat mesenteric small arteries

NARCIS (Netherlands)

van Haaren, Paul M. A.; VanBavel, Ed; Vink, Hans; Spaan, Jos A. E.

2005-01-01

We hypothesized that modulation of the effective charge density of the endothelial surface layer ( ESL) results in altered arterial barrier properties to transport of anionic solutes. Rat mesenteric small arteries ( diameter similar to 190 mu m) were isolated, cannulated, perfused, and superfused

The influence of channel anion identity on the high-pressure crystal structure, compressibility, and stability of apatite

Science.gov (United States)

Skelton, Richard; Walker, Andrew M.

2018-03-01

The material properties of the common phosphate mineral apatite are influenced by the identity of the channel anion, which is usually F-, Cl-, or (OH)-. Density functional theory calculations have been used to determine the effect of channel anion identity on the compressibility and structure of apatite. Hydroxyapatite and fluorapatite are found to have similar zero pressure bulk moduli, of 79.2 and 82.1 GPa, respectively, while chlorapatite is considerably more compressible, with K 0 = 55.0 GPa. While the space groups of hydroxyapatite and fluorapatite do not change between 0 and 25 GPa, symmetrization of the Cl- site in chlorapatite at 7.5 GPa causes the space group to change from P2 1 /b to P6 3 /m. Examination of the valence electron density distribution in chlorapatite reveals that this symmetry change is associated with a change in the coordination of the Cl- anion from threefold to sixfold coordinated by Ca. We also calculate the pressure at which apatite decomposes to form tuite, a calcium orthophosphate mineral, and find that the transition pressure is sensitive to the identity of the channel anion, being lowest for fluorapatite (13.8 GPa) and highest for chlorapatite (26.9 GPa). Calculations are also performed within the DFT-D2 framework to investigate the influence of dispersion forces on the compressibility of apatite minerals.

Anion Gap Blood Test: MedlinePlus Lab Test Information

Science.gov (United States)

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

Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

Science.gov (United States)

Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

2018-04-01

The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

Diffusion, sorption, and retardation processes of anions in bentonite and organo-bentonites for multibarrier systems

Science.gov (United States)

Schampera, Birgit; Dultz, Stefan

2013-04-01

experiments with NO3- will support the understanding of sorption behavior of the anions. All hydrophilic samples have a higher retardation capacity, indicated by diffusion coefficients of 2.44 x 10-11 m/s2 for original bentonite and ˜2.1 x 10-11m/s2 for hydrophilic organo-clays. For hydrophobic organo-clays the H2O diffusion can be higher and is increased at high bulk density (1-1.5 g/m3) up to 2.76 x 10-10m2/s. Experiments with NO3- at bulk density of 1.5 g/m3 reveal that the apparent diffusion coefficients of nitrate are with results up to 5.61 x 1012 m2/s distinctively lower than free diffusion of nitrate in pure water (6.46 x 1010 m2/s at experimental conditions) and nitrate diffusion in natural bentonite (2.63 x 1011 m2/s). The measurements allow the interpretation of the different sorption mechanisms, retardation capacity and diffusion behavior of the analyzed clays at different anion concentrations. Ongoing molecular dynamic simulations will contribute understanding of diffusion processes in organo-clays including the conditions at the interface of the clay minerals and in solution. References: [1] Shackelford, C.D., Moore S.M. (2013) Fickian diffusion of radionuclides for engineered containment barriers: Diffusion coefficients, porosities, and complicating issues. Engineering Geology, 152, 133-147. [2] Rytwo, G., Nir, S., Shuali, U. (2012) Clay and water treatment. Applied Clay Science, 67-68, 117-118. [3] Lorenzetti, R.L., Bartelt-Hunt, S.L., Burns, S.E., Smith, J.A. (2005) Hydraulic conductivities and effective diffusion coefficients of geosynthetic clay liners with organobentonite amendments. Geotextiles and Geomembranes, 23, 385-400. [4] Schampera, B., Dultz, S. (2011) H2O self-diffusion in compacted clays as influenced by surface charge and wettability - obstruction effects of bound H2O layers. Clay and Clay Minerals,59, 42-57.

Occurrence of high-tonnage anionic surfactants in Spanish sewage sludge.

Science.gov (United States)

Cantarero, Samuel; Prieto, Carlos A; López, Ignacio

2012-03-01

Agricultural application has become the most widespread method of sewage sludge disposal, being the most economical outlet for sludge and also recycling beneficial plant nutrients and organic matter to soil for crop production. As a matter of fact, the European Sewage Sludge Directive 86/278/EEC seeks to encourage the disposal of sewage sludge in agriculture applications and regulate its use to prevent harmful effects on the soil environment. At the present time, the sewage sludge Directive is under revision and a possible cut-off limit for some organic chemicals may be implemented. Linear alkylbenzene sulphonate (LAS), the main synthetic anionic surfactant, has been included in the draft list of chemicals to be limited. The present research work deals with the monitoring of LAS and soap in Spanish sewage sludge. The average concentration of LAS found in anaerobic sewage sludge samples was 8.06 g/kg, higher than the average values for European sludge. Besides, it has been also found that more than 55% of Spanish anaerobic sludge would not fulfil the limit proposed by the 3rd European Working paper on sludge. As a consequence, the implementation of the limit for LAS would make the disposal of most Spanish biosolids for agricultural applications almost impossible. Regarding the mechanisms why anionic surfactants are found in sludge, two surfactants are compared: LAS and soap, both readily biodegraded in aerobic conditions. Irrespective of the anaerobic biodegradability of soap, its concentration found in sludge is higher than LAS (only anaerobically biodegradable under particular conditions). The relevance of anaerobic biodegradation to assure environmental protection is discussed for this case. Copyright © 2011 Elsevier Ltd. All rights reserved.

Atomic physics of highly charged ions in an electron beam ion trap

International Nuclear Information System (INIS)

Marrs, R.E.

1990-07-01

Two electron beam ion traps are in use at LLNL for the purpose of studying the properties of very highly charged ions and their interactions with electrons. This paper reviews the operation of the traps and discusses recent experiments in three areas: precision transition energy measurements in the limit of very high ion charge, dielectronic recombination measurements for the He-like isoelectronic sequence, and measurements of x-ray polarization. 22 refs., 11 figs., 1 tab

Multi-frequency inversion-charge pumping for charge separation and mobility analysis in high-k/InGaAs metal-oxide-semiconductor field-effect transistors

Energy Technology Data Exchange (ETDEWEB)

Djara, V.; Cherkaoui, K.; Negara, M. A.; Hurley, P. K., E-mail: paul.hurley@tyndall.ie [Tyndall National Institute, University College Cork, Dyke Parade, Cork (Ireland)

2015-11-28

An alternative multi-frequency inversion-charge pumping (MFICP) technique was developed to directly separate the inversion charge density (N{sub inv}) from the trapped charge density in high-k/InGaAs metal-oxide-semiconductor field-effect transistors (MOSFETs). This approach relies on the fitting of the frequency response of border traps, obtained from inversion-charge pumping measurements performed over a wide range of frequencies at room temperature on a single MOSFET, using a modified charge trapping model. The obtained model yielded the capture time constant and density of border traps located at energy levels aligned with the InGaAs conduction band. Moreover, the combination of MFICP and pulsed I{sub d}-V{sub g} measurements enabled an accurate effective mobility vs N{sub inv} extraction and analysis. The data obtained using the MFICP approach are consistent with the most recent reports on high-k/InGaAs.

Recovery of nitric acid from simulated acidic high level radioactive waste using pore-filled anion exchange membranes

International Nuclear Information System (INIS)

Chavan, Vivek; Agarwal, Chhavi; Pandey, A.K.; Goswami, A.

2014-01-01

Acidic waste is generated at different stages of nuclear fuel cycle. The waste contains minor amounts of actinides ( 241 Am, Pu, Np) along with large number of long-lived radionuclides such as 137 Cs, 90 Sr, 106 Ru etc. Before disposal or storage, the overall activity of the waste needs to be reduced. Along with this, the high amount of acid present in the waste needs to be removed. In this study, DD has been used to recover nitric acid from acidic solutions with compositions similar to radioactive waste using pore-filled anion exchange membranes

Phase shift PWM with double two-switch bridge for high power capacitor charging

International Nuclear Information System (INIS)

Karandikar, U.S.; Singh, Yashpal; Thakurta, A.C.

2013-01-01

Pulse power supply systems working at higher voltage and high repetition rate demands for higher power from capacitor chargers. Capacitor charging requirement become more challenging in such cases. In pulse power circuits, energy storage capacitor should be charged to its desired voltage before the next switching occurs. It is discharged within a small time, delivering large pulse power. A capacitor charger has to work with wide load variation repeatedly. Many schemes are used for this purpose. The proposed scheme aims at reducing stresses on switches by reducing peak current and their evils. A high voltage power supply is designed for capacitor charging. The proposed scheme is based on a Phase-Shifted PWM without using any extra component to achieve soft switching. Indirect constant average current capacitor charging is achieved with a simple control scheme. A double two-switch bridge is proposed to enhance reliability. Power supply has been developed to charge a capacitor of 50 μF to 2.5 kV at 25 Hz. (author)

Mean charged hadron multiplicities in high-energy collisions

Energy Technology Data Exchange (ETDEWEB)

Albini, E [Istituto di Matematica dell' Universita Cattolica di Brescia (Italy); Capiluppi, P; Giacomelli, G; Rossi, A M [Bologna Univ. (Italy). Istituto di Fisica

1976-03-01

A collection of mean charged hadron multiplicities per inelastic collision in various high-energy processes is presented. An extensive list of fits of as a function of energy is presented and discussed. As the energy increases the multiplicities for different collisions tend to a unique curve, independent of the type of colliding particles.

Evidence for F-/SiO- anion exchange in the framework of As-synthesized all-silica zeolites

KAUST Repository

Liu, Xiaolong

2011-05-12

Not everything changes: Charge-compensating anions can be exchanged in as-synthesized zeolite frameworks with changes in both the density of defect sites and of the hydrophobic character of the zeolite. The reversible transformation occurs without dissolution/recrystallization of the zeolite and preserves the size and shape of the crystals (see picture). Fluoride removal is not possible in all-silica D4R units, for which fluoride ions play a structure-directing role. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results

Directory of Open Access Journals (Sweden)

Shirley Nakagaki

2016-02-01

Full Text Available Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic. These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs and Layered Hydroxide Salts (LHSs, published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1 and intercalated with different anions (CO32− or NO3−. The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

Science.gov (United States)

Nakagaki, Shirley; Mantovani, Karen Mary; Machado, Guilherme Sippel; Castro, Kelly Aparecida Dias de Freitas; Wypych, Fernando

2016-02-29

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO₃(2-) or NO₃(-)). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Tripodal receptors for cation and anion sensors

NARCIS (Netherlands)

Kuswandi, Bambang; Nuriman, [Unknown; Verboom, Willem; Reinhoudt, David

2006-01-01

This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing

Postglomerular capillary solute flux restricted by shape and charge in the dog

International Nuclear Information System (INIS)

Whiteside, C.; Silverman, M.

1987-01-01

The permselectivity characteristics of the postglomerular (PG) microcirculation in dog kidney were investigated employing 3 H-labeled cationic (DEAE) and anionic sulfated dextrans (dextran-SO 4 ) ranging from 19 to 29 angstrom Stokes-Einstein Radius. With the use of the multiple-indicator dilution (MID) technique, a bolus injection was made into the left renal artery and timed serial samples were obtained from renal venous and urine outflows. The injection solution contained 125 I-labeled albumin (plasma reference), [ 14 C]inulin and/or creatinine (glomerular and interstitial references), and a test [ 3 H]dextran probe. A control run was carried out with tracer, then charge interaction was analyzed by repeating the MID run with excess unlabeled compound or after protamine sulfate infusion. After loading, renal vein recovery and mean transit time (bar t) were unchanged relative to [ 14 C]inulin for [ 3 H]dextran-SO 4 . But excess DEAE resulted in reduced recovery and decreased bar t for [ 3 H]DEAE. After protamine sulfate, the renal vein and urine recoveries of [ 3 H]dextran-SO 4 decreased and the renal vein bar t increased. These findings demonstrate saturable anionic binding sites in the PG microcirculation. Under conditions where charge interaction was eliminated, the ratio of renal vein bar t for 125 I-albumin to cationic or anionic dextran was always less than its ratio to neutral dextran, implying a larger apparent volume of distribution. The authors concluded that PG capillaries also limit solute flux on the basis of shape

Techniques for enhancing the performance of high charge state ECR ion sources

International Nuclear Information System (INIS)

Xie, Z.Q.

1999-01-01

Electron Cyclotron Resonance ion source (ECRIS), which produces singly to highly charged ions, is widely used in heavy ion accelerators and is finding applications in industry. It has progressed significantly in recent years thanks to a few techniques, such as multiple-frequency plasma heating, higher mirror magnetic fields and a better cold electron donor. These techniques greatly enhance the production of highly charged ions. More than 1 emA of He 2+ and O 6+ , hundreds of eμA of O 7+ , Ne 8+ , Ar 12+ , more than 100 eμA of intermediate heavy ions with charge states up to Ne 9+ , Ar 13+ , Ca 13+ , Fe 13+ , Co 14+ and Kr 18+ , tens of eμA of heavy ions with charge states up to Xe 28+ , Au 35+ , Bi 34+ and U 34+ were produced at cw mode operation. At an intensity of about 1 eμA, the charge states for the heavy ions increased up to Xe 36+ , Au 46+ , Bi 47+ and U 48+ . More than an order of magnitude enhancement of fully stripped argon ions was achieved (I≥0.1 and h;eμA). Higher charge state ions up to Kr 35+ , Xe 46+ and U 64+ at low intensities were produced for the first time from an ECRIS. copyright 1999 American Institute of Physics

Rejuvenation processes applied to 'poisoned' anion exchangers in uranium processing

International Nuclear Information System (INIS)

Gilmore, A.J.

1979-11-01

The removal of 'poisons' from anion exchangers in uranium processing of Canadian radioactive ores is commonly called rejuvenation or regeneration. The cost of the ion exchange recovery of uranium is adversely affected by a decrease in the capacity and efficiency of the anion exchangers, due to their being 'poisoned' by silica, elemental sulphur, molybdenum and tetrathionates. These 'poisons' have a high affinity for the anion exchangers, are adsorbed in preference to the uranyl complex, and do not desorb with the reagents used normally in the uranyl desorption phase. The frequency of rejuvenation and the reagents required for rejuvenation are determined by the severity of the 'poisoning' accumulated by the exchanger in contact with the uranium leach liquor. Caustic soda (NaOH) at approximately equal to 18 cents/lb is commonly used to remove uranium anion exchangers of tetrathionate ((S 4 0 6 )/-/-) 'poisons'. A potential saving in operating cost would be of consequence if other reagents, e.g. sodium carbonate (Na 2 CO 3 ) at approximately equal to 3.6 cents/lb or calcium hydroxide (Ca(OH) 2 ) at approximately equal to 1.9 cents/lb, were effective in removing (S 4 0 6 )/-/-) from a 'poisoned' exchanger. A rejuvenation process for a test program was adopted after a perusal of the literature

The gecko visual pigment: the anion hypsochromic effect.

Science.gov (United States)

Crescitelli, F; Karvaly, B

1991-01-01

The 521-pigment in the retina of the Tokay gecko (Gekko gekko) readily responds to particular physical and chemical changes in its environment. When solubilized in chloride deficient state the addition of Class I anions (Cl-, Br-) induces a bathochromic shift of the absorption spectrum. Class II anions (NO3-, IO3-, N3-, OCN-, SCN-, SeCN-, N(CN)2-), which exhibit ambidental properties, cause an hypsochromic shift. Class III anions (F-, I-, NO2-, CN-, AsO3-, SO2(4-), S2O2(3-) have no spectral effect on the 521-pigment. Cations appear to have no influence on the pigment absorption and Class I anions prevent or reverse the hypsochromic shift caused by Class II anions. It is suggested that the spectral displacements reflect specific changes in the opsin conformation, which alter the immediate (dipolar) environment of the retinal chromophore. The protein conformation seems to promote excited-state processes most in the native 521-pigment state and least in the presence of Class II anions. This in turn suggests that the photosensitivity of the 521-pigment is controlled by the excited rather than by the ground-state properties of the pigment.

Organic anion transporter (Slc22a) family members as mediators of toxicity

International Nuclear Information System (INIS)

Sweet, Douglas H.

2005-01-01

Exposure of the body to toxic organic anions is unavoidable and occurs from both intentional and unintentional sources. Many hormones, neurotransmitters, and waste products of cellular metabolism, or their metabolites, are organic anions. The same is true for a wide variety of medications, herbicides, pesticides, plant and animal toxins, and industrial chemicals and solvents. Rapid and efficient elimination of these substances is often the body's best defense for limiting both systemic exposure and the duration of their pharmacological or toxicological effects. For organic anions, active transepithelial transport across the renal proximal tubule followed by elimination via the urine is a major pathway in this detoxification process. Accordingly, a large number of organic anion transport proteins belonging to several different gene families have been identified and found to be expressed in the proximal nephron. The function of these transporters, in combination with the high volume of renal blood flow, predisposes the kidney to increased toxic susceptibility. Understanding how the kidney mediates the transport of organic anions is integral to achieving desired therapeutic outcomes in response to drug interactions and chemical exposures, to understanding the progression of some disease states, and to predicting the influence of genetic variation upon these processes. This review will focus on the organic anion transporter (OAT) family and discuss the known members, their mechanisms of action, subcellular localization, and current evidence implicating their function as a determinant of the toxicity of certain endogenous and xenobiotic agents

Ion-exchange concentration of inorganic anions from aqueous solution

Directory of Open Access Journals (Sweden)

L. P. Bondareva

2016-01-01

Full Text Available Monitoring of natural waters in the present time - consuming process, the accuracy of which is influenced by many factors: the composition of water, the presence of impurities and "interfering" components. The water sample preparation process includes the step of concentration and separation of ions determined. The most versatile, efficient, and frequently used method is the concentration of inorganic anions from aqueous solutions by ion exchanger, which can optimize the composition of water to the optimal for identification and quantitative determination of anions. The characteristics of sorption chloride, nitrate and sulfate ions of basic anion exchange resin AВ-17 and Purolite A430 were compared in the article. The constants of protolysis of ion exchangers both AB 17 and Purolite A430 are the same and equal 0.037 ± 0,002. The value of total capacity (POE Purolite A430 was 4.3 mmol/g, AB 17 – 3.4 mmol/g. The studied ion exchangers have the same type of ionic groups – quaternary ammonium, but their number and denotes differ. The number of quaternary ammonium groups is higher in Purolite A430, respectively the number of absorbed anions of these ion exchanger is higher. The values of dynamic exchange capacity (DOE of ion exchanger Purolite A430 is higher than these values of AB-17 and equal to 1.48 ± 0.03 mmol / dm3 for chloride ion, 1.50 ± 0.03 mmol / dm3 for nitrate ion, 1.62 ± 0.03 mmol / dm3 for sulfate ion. The values of the POE and DOE of anion-exchange resins Purolite A430 and AV-17 and the characteristics of the individual sorption of chloride, nitrate, sulfate ions showed an advantage of the Purolite for the concentrationing of anions. It is found that times of anions sorption from triple-anion solutions by Purolite A430 are significantly different for different anions, and these times are close for anion-exchanger AV-17. It proves the possibility of quantitative separation and concentration by anion-exchanger Purolite A430.

Penning traps with unitary architecture for storage of highly charged ions.

Science.gov (United States)

Tan, Joseph N; Brewer, Samuel M; Guise, Nicholas D

2012-02-01

Penning traps are made extremely compact by embedding rare-earth permanent magnets in the electrode structure. Axially-oriented NdFeB magnets are used in unitary architectures that couple the electric and magnetic components into an integrated structure. We have constructed a two-magnet Penning trap with radial access to enable the use of laser or atomic beams, as well as the collection of light. An experimental apparatus equipped with ion optics is installed at the NIST electron beam ion trap (EBIT) facility, constrained to fit within 1 meter at the end of a horizontal beamline for transporting highly charged ions. Highly charged ions of neon and argon, extracted with initial energies up to 4000 eV per unit charge, are captured and stored to study the confinement properties of a one-magnet trap and a two-magnet trap. Design considerations and some test results are discussed.

Penning traps with unitary architecture for storage of highly charged ions

International Nuclear Information System (INIS)

Tan, Joseph N.; Guise, Nicholas D.; Brewer, Samuel M.

2012-01-01

Penning traps are made extremely compact by embedding rare-earth permanent magnets in the electrode structure. Axially-oriented NdFeB magnets are used in unitary architectures that couple the electric and magnetic components into an integrated structure. We have constructed a two-magnet Penning trap with radial access to enable the use of laser or atomic beams, as well as the collection of light. An experimental apparatus equipped with ion optics is installed at the NIST electron beam ion trap (EBIT) facility, constrained to fit within 1 meter at the end of a horizontal beamline for transporting highly charged ions. Highly charged ions of neon and argon, extracted with initial energies up to 4000 eV per unit charge, are captured and stored to study the confinement properties of a one-magnet trap and a two-magnet trap. Design considerations and some test results are discussed.

Dehydroabiethylamine acetate as metal-containing anion precipitant

International Nuclear Information System (INIS)

Skrylev, L.D.; Borisov, V.A.

1979-01-01

The precipitation is studied of vanadate, tungstate-, molybdate- and chromate-ions by dehydroabiethylamine acetate. The degree of precipitation of metal-bearing anions is a function of the anion and of pH of the treated solutions. There exists a predetermined value of pH for each anion, at which the content of metal-bearing anion in the ultra-filtrate is at a minimum. For vanadate-ions, this pH is 5.0; for tungstate-ions, 3.0; for molybdate-ions, 4.0; for chrommate-ions, 8.0. The heats of solution of methavanadate, paratungstate, paramolybdate and dehydroabiethylamine chromate, calculated in accordance with the Vant-Hoff equation, range between 3.5 and 8.3 kJ/mole; free energy varies between 45.8 and 137.5 kJ/mole; and entropy varies between 110 and 371 J/degree mole

Intramolecular anionic diels-alder reactions of 1-aryl-4-oxahepta-1,6-diyne systems in DMSO.

Science.gov (United States)

Kudoh, Takayuki; Mori, Tomoko; Shirahama, Mitsuhito; Yamada, Masashi; Ishikawa, Teruhiko; Saito, Seiki; Kobayashi, Hisayoshi

2007-04-25

Base-promoted cycloaddition reactions of 1-aryl- or 1-aryl-7-substituted-4-oxahepta-1,6-diyne systems in DMSO have proven to involve an anionic intramolecular Diels-Alder process taking place even at room temperature in spite of the reaction suffering from temporary disruption of aromaticity. Although initially formed alpha-arylallenide anion can be protonated by DMSO, it can be back to the allenide anion probably because of a small acidity difference between alpha-arylallene and DMSO. The alpha-arylallenide anion in combination with the alpha-aryl substituent can constitute an anionic diene structure that undergoes the intramolecular Diels-Alder reaction involving the C(6)-yne part, a very fast process probably because of the increased HOMO-1 level of the anionic diene, as shown by DFT calculations. Diversified substituted naphthalenes, benzofurans, phenanthrenes, and quinolines, including biaryl architectures, are available from 4-oxahepta-1,6-diynes in a highly expeditious way.

Anion binding in biological systems

Energy Technology Data Exchange (ETDEWEB)

Feiters, Martin C [Department of Organic Chemistry, Institute for Molecules and Materials, Faculty of Science, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Meyer-Klaucke, Wolfram [EMBL Hamburg Outstation at DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Kostenko, Alexander V; Soldatov, Alexander V [Faculty of Physics, Southern Federal University, Sorge 5, Rostov-na-Donu, 344090 (Russian Federation); Leblanc, Catherine; Michel, Gurvan; Potin, Philippe [Centre National de la Recherche Scientifique and Universite Pierre et Marie Curie Paris-VI, Station Biologique de Roscoff, Place Georges Teissier, BP 74, F-29682 Roscoff cedex, Bretagne (France); Kuepper, Frithjof C [Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, Scotland (United Kingdom); Hollenstein, Kaspar; Locher, Kaspar P [Institute of Molecular Biology and Biophysics, ETH Zuerich, Schafmattstrasse 20, Zuerich, 8093 (Switzerland); Bevers, Loes E; Hagedoorn, Peter-Leon; Hagen, Wilfred R, E-mail: m.feiters@science.ru.n [Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft (Netherlands)

2009-11-15

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 L{sub 3} (2p{sub 3/2}) 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.

Anion binding in biological systems

International Nuclear Information System (INIS)

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

2009-01-01

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 L 3 (2p 3/2 ) 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.

Anion binding in biological systems

Science.gov (United States)

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.

High Pressure Optical Studies of the Thallous Halides and of Charge-Transfer Complexes

Science.gov (United States)

Jurgensen, Charles Willard

High pressure was used to study the insulator -to-metal transition in sulfur and the thallous halides and to study the intermolecular interactions in charge -transfer complexes. The approach to the band overlap insulator -to-metal transition was studied in three thallous halides and sulfur by optical absorption measurements of the band gap as a function of pressure. The band gap of sulfur continuously decreases with pressure up to the insulator -to-metal transition which occurs between 450 and 485 kbars. The results on the thallous halides indicate that the indirect gap decreases more rapidly than the direct gap; the closing of the indirect gap is responsible for the observed insulator -to-metal transitions. High pressure electronic and vibrational spectroscopic measurements on the solid-state complexes of HMB-TCNE were used to study the intermolecular interactions of charge -transfer complexes. The vibrational frequency shifts indicate that the degree of charge transfer increases with pressure which is independently confirmed by an increase in the molar absorptivity of the electronic charge-transfer peak. Induction and dispersion forces contribute towards a red shift of the charge-transfer peak; however, charge-transfer resonance contributes toward a blue shift and this effect is dominant for the HMB-TCNE complexes. High pressure electronic spectra were used to study the effect of intermolecular interactions on the electronic states of TCNQ and its complexes. The red shifts with pressure of the electronic spectra of TCNQ and (TCNQ)(' -) in polymer media and of crystalline TCNQ can be understood in terms of Van der Waals interactions. None of the calculations which considered intradimer distance obtained the proper behavior for either the charge-transfer of the locally excited states of the complexes. The qualitative behavior of both states can be interpreted as the effect of increased mixing of the locally excited and charge transfer states.

A New Approach to Non-Coordinating Anions: Lewis Acid Enhancement of Porphyrin Metal Centers in a Zwitterionic Metal$-$Organic Framework

Energy Technology Data Exchange (ETDEWEB)

Johnson, Jacob A. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemistry; Petersen, Brenna M. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemistry; Kormos, Attila [Hungarian Academy of Sciences, Budapest (Hungary); Echeverría, Elena [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Physics and Astronomy; Chen, Yu-Sheng [Univ. of Chicago, Argonne, IL (United States). ChemMatCARS, Center for Advanced Radiation Sources; Zhang, Jian [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemistry

2017-02-28

Here, we describe a new strategy to generate non-coordinating anions using zwitterionic metal–organic frameworks (MOFs). By assembly of anionic inorganic secondary building blocks (SBUs) ([In(CO₂)₄]^$-$) with cationic metalloporphyrin-based organic linkers, we prepared zwitterionic MOFs in which the complete internal charge separation effectively prevents the potential binding of the counteranion to the cationic metal center. We demonstrate the enhanced Lewis acidity of Mn^III- and Fe^III-porphyrins in the zwitterionic MOFs in three representative electrocyclization reactions: [2 + 1] cycloisomerization of enynes, [3 + 2] cycloaddition of aziridines and alkenes, and [4 + 2] hetero-Diels–Alder cycloaddition of aldehydes with dienes. Lastly, this work paves a new way to design functional MOFs for tunable chemical catalysis.

Chemical Hydrogen Storage Using Polyhedral Borane Anions and Aluminum-Ammonia-Borane Complexes

Energy Technology Data Exchange (ETDEWEB)

Hawthorne, M. Frederick; Jalisatgi, Satish S.; Safronov, Alexander V.; Lee, Han Beak; Wu, Jianguo

2010-10-01

Phase 1. Hydrolysis of borohydride compounds offer the potential for significant hydrogen storage capacity, but most work to date has focused on one particular anion, BH4-, which requires high pH for stability. Other borohydride compounds, in particular polyhedral borane anions offer comparable hydrogen storage capacity without requiring high pH media and their long term thermal and hydrolytic stability coupled with non-toxic nature make them a very attractive alternative to NaBH4. The University of Missouri project provided the overall program focal point for the investigation of catalytic hydrolysis of polyhedral borane anions for hydrogen release. Due to their inherent stability, a transition metal catalyst was necessary for the hydrolysis of polyhedral borane anions. Transition metal ions such as cobalt, nickel, palladium and rhodium were investigated for their catalytic activity in the hydrolysis of nido-KB11H14, closo-K2B10H10, and closo-K2B12H12. The rate of hydrolysis follows first-order kinetics with respect to the concentration of the polyhedral borane anion and surface area of the rhodium catalyst. The rate of hydrolysis depends upon a) choice of polyhedral borane anion, c) concentration of polyhedral borane anion, d) surface area of the rhodium catalyst and e) temperature of the reaction. In all cases the yield of hydrogen was 100% which corresponds to ~7 wt% of hydrogen (based on material wt%). Phase 2. The phase 2 of program at the University of Missouri was focused upon developing aluminum ammonia-boranes (Al-AB) as chemical hydrogen storage materials, specifically their synthesis and studies of their dehydrogenation. The ammonia borane molecule (AB) is a demonstrated source of chemically stored hydrogen (19.6 wt%) which meets DOE performance parameters except for its regeneration from spent AB and elemental hydrogen. The presence of an aluminum center bonded to multiple AB residues might combine the efficiency of AB dehydrogenation with an aluminum

Charge redistribution and properties of high-temperature superconductors

International Nuclear Information System (INIS)

Khomskii, D.I.; Kusmartsev, F.V.

1992-01-01

We show that in high-T c superconductors (HTSC) with two groups of electrons (e.g., holes in CuO 2 planes and in a ''reservoir'') there should exist a charge redistribution with the temperature: the hole concentration N h in ''active'' superconducting CuO 2 planes increases below T c . This effect may explain structural changes such as the shift of the apical oxygen atom, anomalous thermal expansion, the shift of nuclear quadrupole resonance lines, the change of the positron lifetime, and the modification of the ion channeling below T c . Some other possible consequences of the charge redistribution (the modification of the temperature dependence of a gap Δ and of the ratio 2Δ 0 /T c , the phenomena at a contact of HTSC with normal metals and semiconductors) are discussed

Practical Approaches to Mitigation of Specimen Charging in High-Resolution Transmission Electron Microscopy

Directory of Open Access Journals (Sweden)

Young-Min Kim

2010-09-01

Full Text Available Specimen charging that is associated with the electron bombardment on the sample is a practical hindrance to high-resolution transmission electron microscopy (HRTEM analysis because it causes a severe loss of resolution in either diffraction or image data. Conductive thin film deposition on an insulating specimen has been proposed as an effective approach to the mitigation of the specimen charging; however, this method is generally not useful in HRTEM imaging of materials because the deposited film induces another artifact in the HRTEM image contrast. In this study, we propose practical methods to mitigate the specimen charging that takes place during the HRTEM of materials. For bulk-type specimens prepared by either an ion-thinning or focused-ion beam (FIB process, a plasma cleaning treatment is significantly effective in eliminating the charging phenomenon. In the case of low-dimensional nanomaterials such as nanowires and nanoparticles, the plasma cleaning is not feasible; however, the charging effect can be effectively eliminated by adjusting the electron illumination condition. The proposed methods facilitate a decrease in the buildup of specimen charging, thereby enhancing the quality of high-resolution images significantly.

High Br- Content CsPb(Cl yBr1- y)3 Perovskite Nanocrystals with Strong Mn2+ Emission through Diverse Cation/Anion Exchange Engineering.

Science.gov (United States)

Li, Fei; Xia, Zhiguo; Pan, Caofeng; Gong, Yue; Gu, Lin; Liu, Quanlin; Zhang, Jin Z

2018-04-11

The unification of tunable band edge (BE) emission and strong Mn 2+ doping luminescence in all-inorganic cesium lead halide perovskite nanocrystals (NCs) CsPbX 3 (X = Cl and Br) is of fundamental importance in fine tuning their optical properties. Herein, we demonstrate that benefiting from the differentiation of the cation/anion exchange rate, ZnBr 2 and preformed CsPb 1- x Cl 3 : xMn 2+ NCs can be used to obtain high Br - content Cs(Pb 1- x- z Zn z )(Cl y Br 1- y ) 3 : xMn 2+ perovskite NCs with strong Mn 2+ emission, and the Mn 2+ substitution ratio can reach about 22%. More specifically, the fast anion exchange could be realized by the soluble halide precursors, leading to anion exchange within a few seconds as observed from the strong BE emission evolution, whereas the cation exchange instead generally required at least a few hours; moreover, their exchange mechanism and dynamics process have been evaluated. The Mn 2+ emission intensity could be further varied by controlling the replacement of Mn 2+ by Zn 2+ with prolonged ion exchange reaction time. White light emission of the doped perovskite NCs via this cation/anion synergistic exchange strategy has been realized, which was also successfully demonstrated in a prototype white light-emitting diode (LED) device based on a commercially available 365 nm LED chip.

Modelling of prompt losses of high energy charged particles in Tokamaks

International Nuclear Information System (INIS)

Dillner, Oe.; Anderson, D.; Hamnen, H.; Lisak, M.

1990-01-01

A simple analytical expression for the total prompt loss fraction of high energy charged particles in an axisymmetric Tokamak is derived. The results are compared with predictions obtained from numerical simulations and show good agreement. An application is made to sawtooth induced changes in the losses of fusion generated high energy charged particles. Particular emphasis is given to the importance of sawtooth induced profile changes of the background ion densities and temperature as well as to redistribution of particles which have accumulated during the sawtooth rise but are being lost by redistribution at the sawtooth crash. (au)

Use of a new tandem cation/anion exchange system with clinical-scale generators provides high specific volume solutions of technetium-99m and rhenium-188

International Nuclear Information System (INIS)

Knapp, F.R. Jr.; Beets, A.L.; Mirzadeh, S.; Guhlke, S.; Univ. of Bonn

1998-03-01

In this paper the authors describe the first application of a simple and inexpensive post elution tandem cation-anion exchange column system which is based on generator elution with salts of weak acids such as ammonium acetate instead of saline solution to provide very high specific volume solutions of technetium-99m and rhenium-188 from clinical scale molybdenum-99/technetium-99m generator prepared from low specific activity (n,y) molybdenum-99, and tungsten-188/rhenium-188 generators, respectively. Initial passage of the bolus through a strong cation exchange cartridge converts the ammonium acetate to acetic acid which is essentially not ionized at the acidic pH, allowing specific subsequent amine type (QMA SepPak trademark) anion exchange cartridge column trapping of the microscopic levels of the pertechnetate or perrhenate. Subsequent elution of the anion cartridge with a small volume ( 500 mCi/mL) from the alumina-based tungsten-188/rhenium-188 generator

Increased anion channel activity is an unavoidable event in ozone-induced programmed cell death.

Directory of Open Access Journals (Sweden)

Takashi Kadono

Full Text Available BACKGROUND: Ozone is a major secondary air pollutant often reaching high concentrations in urban areas under strong daylight, high temperature and stagnant high-pressure systems. Ozone in the troposphere is a pollutant that is harmful to the plant. PRINCIPAL FINDINGS: By exposing cells to a strong pulse of ozonized air, an acute cell death was observed in suspension cells of Arabidopsis thaliana used as a model. We demonstrated that O(3 treatment induced the activation of a plasma membrane anion channel that is an early prerequisite of O(3-induced cell death in A. thaliana. Our data further suggest interplay of anion channel activation with well known plant responses to O(3, Ca(2+ influx and NADPH-oxidase generated reactive oxygen species (ROS in mediating the oxidative cell death. This interplay might be fuelled by several mechanisms in addition to the direct ROS generation by O(3; namely, H(2O(2 generation by salicylic and abscisic acids. Anion channel activation was also shown to promote the accumulation of transcripts encoding vacuolar processing enzymes, a family of proteases previously reported to contribute to the disruption of vacuole integrity observed during programmed cell death. SIGNIFICANCE: Collectively, our data indicate that anion efflux is an early key component of morphological and biochemical events leading to O(3-induced programmed cell death. Because ion channels and more specifically anion channels assume a crucial position in cells, an understanding about the underlying role(s for ion channels in the signalling pathway leading to programmed cell death is a subject that warrants future investigation.

The Effect of Voltage Charging on the Transport Properties of Gold Nanotube Membranes.

Science.gov (United States)

Experton, Juliette; Martin, Charles R

2018-05-01

Porous membranes are used in chemical separations and in many electrochemical processes and devices. Research on the transport properties of a unique class of porous membranes that contain monodisperse gold nanotubes traversing the entire membrane thickness is reviewed here. These gold nanotubes can act as conduits for ionic and molecular transports through the membrane. Because the tubes are electronically conductive, they can be electrochemically charged by applying a voltage to the membrane. How this "voltage charging" affects the transport properties of gold nanotube membranes is the subject of this Review. Experiments showing that voltage charging can be used to reversibly switch the membrane between ideally cation- and anion-transporting states are reviewed. Voltage charging can also be used to enhance the ionic conductivity of gold nanotube membranes. Finally, voltage charging to accomplish electroporation of living bacteria as they pass through gold nanotube membranes is reviewed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Thermodynamics of Anion Complexation to Nonpolar Pockets.

Science.gov (United States)

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.

Mechanisms for production of highly charged ions

International Nuclear Information System (INIS)

McGuire, J.H.

1987-01-01

Various experimental data at high collision velocity are interpreted in terms of direct (D) and rearrangement (R) mechanisms for production of multiply charged ions. We consider double ionization in helium by protons, electrons, heavy ions, antiprotons, positrons and photons. Qualitative differences are discussed in the context of the R and D mechanisms. Multiple ionization in many electron atoms is considered as is simultaneous capture and ionization and fragmentation of methane molecules. Some other theoretical methods are briefly discussed. (orig.)

A high-resolution photoelectron imaging and theoretical study of CP- and C2P.

Science.gov (United States)

Czekner, Joseph; Cheung, Ling Fung; Johnson, Eric L; Fortenberry, Ryan C; Wang, Lai-Sheng

2018-01-28

The discovery of interstellar anions has been a milestone in astrochemistry. In the search for new interstellar anions, CP - and C 2 P - are viable candidates since their corresponding neutrals have already been detected astronomically. However, scarce data exist for these negatively charged species. Here we report the electron affinities of CP and C 2 P along with the vibrational frequencies of their anions using high-resolution photoelectron imaging. These results along with previous spectroscopic data of the neutral species are used further to benchmark very accurate quartic force field quantum chemical methods that are applied to CP, CP - , C 2 P, and two electronic states of C 2 P - . The predicted electron affinities, vibrational frequencies, and rotational constants are in excellent agreement with the experimental data. The electron affinities of CP (2.8508 ± 0.0007 eV) and C 2 P (2.6328 ± 0.0006 eV) are measured accurately and found to be quite high, suggesting that the CP - and C 2 P - anions are thermodynamically stable and possibly observable. The current study suggests that the combination of high-resolution photoelectron imaging and quantum chemistry can be used to determine accurate molecular constants for exotic radical species of astronomical interest.

Test procedure for anion exchange chromatography

International Nuclear Information System (INIS)

Cooper, T.D.

1994-01-01

Plutonium from stored nitrate solutions will be sorbed onto anion exchange resins and converted to storable plutonium dioxide. Useful information will be simultaneously gained on the thermal stability and ion exchange capacity of four commercially available anion exchange resins over several years and under severe degradative conditions. This information will prove useful in predicting the safe and efficient lifetimes of these resins

Self-Assembling of Tetradecylammonium Chain on Swelling High Charge Micas (Na-Mica-3 and Na-Mica-2): Effect of Alkylammonium Concentration and Mica Layer Charge.

Science.gov (United States)

Pazos, M Carolina; Cota, Agustín; Osuna, Francisco J; Pavón, Esperanza; Alba, María D

2015-04-21

A family of tetradecylammonium micas is synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg6F4O20·XH2O, where n = 2 and 3) exchanged with tetradecylammonium cations. The molecular arrangement of the surfactant is elucidated on the basis of XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas is investigated by IR/FT, (13)C, (27)Al, and (29)Si MAS NMR. The structural arrangement of the tetradecylammonium cation in the interlayer space of high-charge micas is more sensitive to the effect of the mica layer charge at high concentration. The surfactant arrangement is found to follow the bilayer-paraffin model for all values of layer charge and surfactant concentration. However, at initial concentration below the mica CEC, a lateral monolayer is also observed. The amount of ordered conformation all-trans is directly proportional to the layer charge and surfactant concentration.

Understanding CO-stripping mechanism from Ni{sub UPD}/Pt(1 1 0) in view of the measured nickel formal partial charge number upon underpotential deposition on platinum surfaces in sulphate media

Energy Technology Data Exchange (ETDEWEB)

Chatenet, Marian [Laboratoire d' Electrochimie et de Physicochimie des Materiaux et des Interfaces, LEPMI, UMR 5631 CNRS-INPG-UJF, BP 75, 38402 Saint-Martin d' Heres Cedex (France)], E-mail: Marian.Chatenet@lepmi.inpg.fr; Soldo-Olivier, Yvonne; Chainet, Eric; Faure, Rene [Laboratoire d' Electrochimie et de Physicochimie des Materiaux et des Interfaces, LEPMI, UMR 5631 CNRS-INPG-UJF, BP 75, 38402 Saint-Martin d' Heres Cedex (France)

2007-12-01

We recently showed nickel-underpotential deposition (Ni-UPD) occurs on polycrystalline or single crystal platinum electrodes in acidic media. Whereas the decoupling of the nickel and hydrogen adsorption/desorption peaks is difficult for low pH, these processes can be better separated for higher pH values, typically pH > 3. However, even for platinum single crystals, high pH solutions do not enable to sufficiently separate nickel from hydrogen phenomena. As a result, electrochemistry alone cannot yield important information about Ni-UPD, such as the formal partial charge number (valency of electrosorption) and the role of the sulphate or hydrogen sulphate anions. So, we decided to couple cyclic voltammetry to electrochemical quartz crystal microbalance (EQCM). EQCM measurements enable to decorrelate the simultaneous hydrogen and nickel adsorption/desorption peaks, which we could not attempt solely with electrochemistry. The coupling between gravimetric and electrochemical measurements allows us to detect the contribution of the anions and thus to isolate that of nickel: nickel coverage can then be determined. Nearly 4/5 Ni{sub UPD} monolayer ({theta}{sub Ni} {approx} 0.8) over platinum is reached at nickel equilibrium potential for high pH solutions (5.5). The QCM and electrochemistry coupling further allows the determination of nickel formal partial charge number: {iota}{sub Ni,EQCM} = 1.3 {+-} 0.13. Direct electrochemistry measurements (Swathirajan and Bruckenstein method) yield: {iota}{sub Ni,Pt(poly)} = 1.5 {+-} 0.17. These two values are close, which validates the electrochemical method for the nickel/platinum system. In consequence, we used Swathirajan and Bruckenstein method for Pt(1 1 0)-(1 x 2) crystal and found: {iota}{sub Ni,Pt(110)} {approx} 1.4 {+-} 0.1. Whatever the system (Ni{sub UPD}/Pt(poly) or Ni{sub UPD}/Pt(1 1 0)-(1 x 2)) or the experimental technique, nickel formal partial charge number is lower than nickel cation charge: {iota}{sub Ni} < z

Spatial Rearrangement and Mobility Heterogeneity of an Anionic Lipid Monolayer Induced by the Anchoring of Cationic Semiflexible Polymer Chains

Directory of Open Access Journals (Sweden)

Xiaozheng Duan

2016-06-01

Full Text Available We use Monte Carlo simulations to investigate the interactions between cationic semiflexible polymer chains and a model fluid lipid monolayer composed of charge-neutral phosphatidyl-choline (PC, tetravalent anionic phosphatidylinositol 4,5-bisphosphate (PIP2, and univalent anionic phosphatidylserine (PS lipids. In particular, we explore how chain rigidity and polymer concentration influence the spatial rearrangement and mobility heterogeneity of the monolayer under the conditions where the cationic polymers anchor on the monolayer. We find that the anchored cationic polymers only sequester the tetravalent PIP2 lipids at low polymer concentrations, where the interaction strength between the polymers and the monolayer exhibits a non-monotonic dependence on the degree of chain rigidity. Specifically, maximal anchoring occurs at low polymer concentrations, when the polymer chains have an intermediate degree of rigidity, for which the PIP2 clustering becomes most enhanced and the mobility of the polymer/PIP2 complexes becomes most reduced. On the other hand, at sufficiently high polymer concentrations, the anchoring strength decreases monotonically as the chains stiffen—a result that arises from the pronounced competitions among polymer chains. In this case, the flexible polymers can confine all PIP2 lipids and further sequester the univalent PS lipids, whereas the stiffer polymers tend to partially dissociate from the monolayer and only sequester smaller PIP2 clusters with greater mobilities. We further illustrate that the mobility gradient of the single PIP2 lipids in the sequestered clusters is sensitively modulated by the cooperative effects between anchored segments of the polymers with different rigidities. Our work thus demonstrates that the rigidity and concentration of anchored polymers are both important parameters for tuning the regulation of anionic lipids.

Rendering high charge density of states in ionic liquid-gated MoS 2 transistors

NARCIS (Netherlands)

Lee, Y.; Lee, J.; Kim, S.; Park, H.S.

2014-01-01

We investigated high charge density of states (DOS) in the bandgap of MoS2 nanosheets with variable temperature measurements on ionic liquid-gated MoS2 transistors. The thermally activated charge transport indicates that the electrical current in the two-dimensional MoS 2 nanosheets under high

High-k shallow traps observed by charge pumping with varying discharging times

Energy Technology Data Exchange (ETDEWEB)

Ho, Szu-Han; Chen, Ching-En; Tseng, Tseung-Yuen [Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan (China); Chang, Ting-Chang, E-mail: tcchang@mail.phys.nsysu.edu.tw [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Advanced Optoelectronics Technology Center, National Cheng Kung University, Tainan, Taiwan (China); Lu, Ying-Hsin; Lo, Wen-Hung; Tsai, Jyun-Yu; Liu, Kuan-Ju [Department of Physics, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Wang, Bin-Wei; Cao, Xi-Xin [Department of Embedded System Engineering, Peking University, Beijing, P.R.China (China); Chen, Hua-Mao [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu, Taiwan (China); Cheng, Osbert; Huang, Cheng-Tung; Chen, Tsai-Fu [Device Department, United Microelectronics Corporation, Tainan Science Park, Taiwan (China)

2013-11-07

In this paper, we investigate the influence of falling time and base level time on high-k bulk shallow traps measured by charge pumping technique in n-channel metal-oxide-semiconductor field-effect transistors with HfO{sub 2}/metal gate stacks. N{sub T}-V{sub high} {sub level} characteristic curves with different duty ratios indicate that the electron detrapping time dominates the value of N{sub T} for extra contribution of I{sub cp} traps. N{sub T} is the number of traps, and I{sub cp} is charge pumping current. By fitting discharge formula at different temperatures, the results show that extra contribution of I{sub cp} traps at high voltage are in fact high-k bulk shallow traps. This is also verified through a comparison of different interlayer thicknesses and different Ti{sub x}N{sub 1−x} metal gate concentrations. Next, N{sub T}-V{sub high} {sub level} characteristic curves with different falling times (t{sub falling} {sub time}) and base level times (t{sub base} {sub level}) show that extra contribution of I{sub cp} traps decrease with an increase in t{sub falling} {sub time}. By fitting discharge formula for different t{sub falling} {sub time}, the results show that electrons trapped in high-k bulk shallow traps first discharge to the channel and then to source and drain during t{sub falling} {sub time}. This current cannot be measured by the charge pumping technique. Subsequent measurements of N{sub T} by charge pumping technique at t{sub base} {sub level} reveal a remainder of electrons trapped in high-k bulk shallow traps.

Determination of arsenate in water by anion selective membrane electrode using polyurethane–silica gel fibrous anion exchanger composite

Energy Technology Data Exchange (ETDEWEB)