Ion pairing in ionic liquids

International Nuclear Information System (INIS)

Kirchner, Barbara; Malberg, Friedrich; Firaha, Dzmitry S; Hollóczki, Oldamur

2015-01-01

In the present article we briefly review the extensive discussion in literature about the presence or absence of ion pair-like aggregates in ionic liquids. While some experimental studies point towards the presence of neutral subunits in ionic liquids, many other experiments cannot confirm or even contradict their existence. Ion pairs can be detected directly in the gas phase, but no direct method is available to observe such association behavior in the liquid, and the corresponding indirect experimental proofs are based on such assumptions as unity charges at the ions. However, we have shown by calculating ionic liquid clusters of different sizes that assuming unity charges for ILs is erroneous, because a substantial charge transfer is taking place between the ionic liquid ions that reduce their total charge. Considering these effects might establish a bridge between the contradicting experimental results on this matter. Beside these results, according to molecular dynamics simulations the lifetimes of ion–ion contacts and their joint motions are far too short to verify the existence of neutral units in these materials. (topical review)

Solvent-shared pairs of densely charged ions induce intense but short-range supra-additive slowdown of water rotation.

Science.gov (United States)

Vila Verde, Ana; Santer, Mark; Lipowsky, Reinhard

2016-01-21

The question "Can ions exert supra-additive effects on water dynamics?" has had several opposing answers from both simulation and experiment. We address this ongoing controversy by investigating water reorientation in aqueous solutions of two salts with large (magnesium sulfate) and small (cesium chloride) effects on water dynamics using molecular dynamics simulations and classical, polarizable models. The salt models are reparameterized to reproduce properties of both dilute and concentrated solutions. We demonstrate that water rotation in concentrated MgSO4 solutions is unexpectedly slow, in agreement with experiment, and that the slowdown is supra-additive: the observed slowdown is larger than that predicted by assuming that the resultant of the extra forces induced by the ions on the rotating water molecules tilts the free energy landscape associated with water rotation. Supra-additive slow down is very intense but short-range, and is strongly ion-specific: in contrast to the long-range picture initially proposed based on experiment, we find that intense supra-additivity is limited to water molecules directly bridging two ions in solvent-shared ion pair configuration; in contrast to a non-ion-specific origin to supra-additive effects proposed from simulations, we find that the magnitude of supra-additive slowdown strongly depends on the identity of the cations and anions. Supra-additive slowdown of water dynamics requires long-lived solvent-shared ion pairs; long-lived ion pairs should be typical for salts of multivalent ions. We discuss the origin of the apparent disagreement between the various studies on this topic and show that the short-range cooperative slowdown scenario proposed here resolves the existing controversy.

Usefulness of measurement of circulation time using MgSO4 : correlation with time-density curve using electron beam computed tomography

International Nuclear Information System (INIS)

Kim, Byung Ki; Lee, Hui Joong; Lee, Jong Min; Kim, Yong Joo; Kang, Duck Sik

1999-01-01

To determine the usefulness of MgSO 4 for measuring the systemic circulation time. Systemic circulation time, defined as elapsed time from the injection of MgSO 4 solution to the point of pharyngeal burning sensation, was measured in 63 volunteers. MgSO 4 was injected into a superficial vein of an upper extremity. Using dynamic electron beam computed tomography at the level of the abdominal aorta and celiac axis, a time-intensity curve was plotted, and for these two locations, maximal enhancement time was compared. For 60 of the 63 subjects, both systemic circulation time and maximal enhancement time were determined. Average systemic circulation time was 17.4 (SD:3.6) secs. and average maximal enhancement times at the level of the abdominal aorta and celiac axis were 17.5 (SD:3.0) secs. and 18.5 (SD:3.2) secs., respectively. Correlation coefficients between systemic circulation time and maximal enhancement time for the abdominal aorta and celiac axis were 0.73 (p 4 injection and maximal enhancement time for the abdominal aorta showed significant correlation. Thus, to determine the appropriate scanning time in contrast-enhanced radiological studies, MgSO 4 can be used instead of a test bolus study

Ion pairing of radical ions of aromatic alkenes and alkynes studied by pulse radiolysis

International Nuclear Information System (INIS)

Yamamoto, Satoshi; Yamamoto, Yukio; Hayashi, Koichiro

1991-01-01

Pulse radiolysis of 1,2-dichloroethane solutions of trans,trans-1,4-bis(2-phenylethenyl)benzene and 1,4-bis(2-phenylethynyl)benzene was undertaken in the presence of Bu 4 NPF 6 (Bu=butyl) to investigate the effect of ion pairing of the solute radical cations with PF 6 - . It was also undertaken for the tetrahydrofuran solutions of the above compounds in the presence of Bu 4 NPF 6 and NaBPh 4 , where the solute radical anions are generated and form ion pairs with Bu 4 N + and Na + . The decay of the radical ions, which is due to neutralization, is retarded by the ion pairing. The rate constants for the neutralization reactions in the free-ion and ion-paired states were determined. Also presented are the data for the radical ions of trans-stilbene, diphenylacetylene, trans,trans-1,4-diphenyl-1,3-butadiene, and diphenylbutadiene. The radical ions of the aromatic alkynes are less stabilized by the ion pairing than those of the aromatic alkenes having the same carbon skeletons probably because of more extensive charge delocalization of the former radical ions. Spectral shifts to shorter wavelengths caused by the ion pairing are appreciable for the radical anions. Dependence of the spectral shifts on the size of the radical anions is described. (author)

Anomalous surface behavior of hydrated guanidinium ions due to ion pairing

Science.gov (United States)

Ekholm, Victor; Vazdar, Mario; Mason, Philip E.; Bialik, Erik; Walz, Marie-Madeleine; Öhrwall, Gunnar; Werner, Josephina; Rubensson, Jan-Erik; Jungwirth, Pavel; Björneholm, Olle

2018-04-01

Surface affinity of aqueous guanidinium chloride (GdmCl) is compared to that of aqueous tetrapropylammonium chloride (TPACl) upon addition of sodium chloride (NaCl) or disodium sulfate (Na2SO4). The experimental results have been acquired using the surface sensitive technique X-ray photoelectron spectroscopy on a liquid jet. Molecular dynamics simulations have been used to produce radial distribution functions and surface density plots. The surface affinities of both TPA+ and Gdm+ increase upon adding NaCl to the solution. With the addition of Na2SO4, the surface affinity of TPA+ increases, while that of Gdm+ decreases. From the results of MD simulations it is seen that Gdm+ and SO4 2 - ions form pairs. This finding can be used to explain the decreased surface affinity of Gdm+ when co-dissolved with SO4 2 - ions. Since SO4 2 - ions avoid the surface due to the double charge and strong water interaction, the Gdm+-SO4 2 - ion pair resides deeper in the solutions' bulk than the Gdm+ ions. Since TPA+ does not form ion pairs with SO4 2 -, the TPA+ ions are instead enriched at the surface.

Interactions in ion pairs of protic ionic liquids: Comparison with aprotic ionic liquids

International Nuclear Information System (INIS)

Tsuzuki, Seiji; Shinoda, Wataru; Miran, Md. Shah; Kinoshita, Hiroshi; Yasuda, Tomohiro; Watanabe, Masayoshi

2013-01-01

The stabilization energies for the formation (E form ) of 11 ion pairs of protic and aprotic ionic liquids were studied by MP2/6-311G ** level ab initio calculations to elucidate the difference between the interactions of ions in protic ionic liquids and those in aprotic ionic liquids. The interactions in the ion pairs of protic ionic liquids (diethylmethylammonium [dema] and dimethylpropylammonium [dmpa] based ionic liquids) are stronger than those of aprotic ionic liquids (ethyltrimethylammonium [etma] based ionic liquids). The E form for the [dema][CF 3 SO 3 ] and [dmpa][CF 3 SO 3 ] complexes (−95.6 and −96.4 kcal/mol, respectively) are significantly larger (more negative) than that for the [etma][CF 3 SO 3 ] complex (−81.0 kcal/mol). The same trend was observed for the calculations of ion pairs of the three cations with the Cl − , BF 4 − , TFSA − anions. The anion has contact with the N–H bond of the dema + or dmpa + cations in the most stable geometries of the dema + and dmpa + complexes. The optimized geometries, in which the anions locate on the counter side of the cations, are 11.0–18.0 kcal/mol less stable, which shows that the interactions in the ions pairs of protic ionic liquids have strong directionality. The E form for the less stable geometries for the dema + and dmpa + complexes are close to those for the most stable etma + complexes. The electrostatic interaction, which is the major source of the attraction in the ion pairs, is responsible for the directionality of the interactions and determining the magnitude of the interaction energy. Molecular dynamic simulations of the [dema][TFSA] and [dmpa][TFSA] ionic liquids show that the N–H bonds of the cations have contact with the negatively charged (oxygen and nitrogen) atoms of TFSA − anion, while the strong directionality of the interactions was not suggested from the simulation of the [etma][CF 3 SO 3 ] ionic liquid

3-(Dicyanomethylidene)indan-1-one-Functionalized Calix[4]arene-Calix[4]pyrrole Hybrid: An Ion-Pair Sensor for Cesium Salts.

Science.gov (United States)

Yeon, Yerim; Leem, Soojung; Wagen, Corin; Lynch, Vincent M; Kim, Sung Kuk; Sessler, Jonathan L

2016-09-02

A chromogenic calix[4]arene-calix[4]pyrrole hybrid ion pair receptor bearing an indane substituent at a β-pyrrolic position has been prepared. On the basis of solution-phase UV-vis spectroscopic analysis and (1)H NMR spectroscopic studies carried out in 10% methanol in chloroform, receptor 1 is able to bind only cesium ion pairs (e.g., CsF, CsCl, and CsNO3) but not the constituent cesium cation (as its perchlorate salt) or the F(-), Cl(-), or NO3(-) anions (as the tetrabutylammonium salts). It thus displays rudimentary AND logic gate behavior. Receptor 1 shows a colorimetric response to cesium ion pairs under conditions of solid-liquid (nitrobenzene) and liquid-liquid (D2O-nitrobenzene-d5) extraction.

Rate theory of solvent exchange and kinetics of Li(+) - BF4 (-)/PF6 (-) ion pairs in acetonitrile.

Science.gov (United States)

Dang, Liem X; Chang, Tsun-Mei

2016-09-07

In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li(+) and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li(+) in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li(+)-[BF4] and Li(+)-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li(+). We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li(+)-[BF4] and Li(+)-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

Science.gov (United States)

Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei

2018-04-01

Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

Thermoluminescence characteristics in MgSO sub 4 : Tm, P phosphors

CERN Document Server

Tang Qiang; Li Hua; Luo Da Ling

2002-01-01

The TL glow curves and three dimensional spectrum of co-doped MgSO sub 4 : Tm, P powder sample were measured after exposed it to gamma radiation ( sup 6 sup 0 Co and sup 1 sup 3 sup 7 Cs gamma) from 10 sup - sup 4 - 2 x 10 sup 4 Gy. Some peaks parameters and trap parameters of TL peaks were calculated. The main dose peak is about at 289.3 degree C, and the dose response is super-linear. From the three dimensional TL spectrum, it shows that the main glow wavelengths is at about 365 nm, 460 nm and 660 nm. By comparison of some other TL materials, this phosphor has some good performances, such as high sensitivity, good stability and a wide span of dose response. It may be a good TL material that can be applied widely in dosimetry

Preferential solvation, ion pairing, and dynamics of concentrated aqueous solutions of divalent metal nitrate salts

Science.gov (United States)

Yadav, Sushma; Chandra, Amalendu

2017-12-01

We have investigated the characteristics of preferential solvation of ions, structure of solvation shells, ion pairing, and dynamics of aqueous solutions of divalent alkaline-earth metal nitrate salts at varying concentration by means of molecular dynamics simulations. Hydration shell structures and the extent of preferential solvation of the metal and nitrate ions in the solutions are investigated through calculations of radial distribution functions, tetrahedral ordering, and also spatial distribution functions. The Mg2+ ions are found to form solvent separated ion-pairs while the Ca2+ and Sr2+ ions form contact ion pairs with the nitrate ions. These findings are further corroborated by excess coordination numbers calculated through Kirkwood-Buff G factors for different ion-ion and ion-water pairs. The ion-pairing propensity is found to be in the order of Mg(NO3) 2 lead to the presence of substantial dynamical heterogeneity in these solutions of strongly interacting ions. The current study helps us to understand the molecular details of hydration structure, ion pairing, and dynamics of water in the solvation shells and also of ion diffusion in aqueous solutions of divalent metal nitrate salts.

Infrared and Raman spectroscopic study of ion pairing of strontium(II ...

African Journals Online (AJOL)

ABSTRACT. Infrared and Raman spectroscopy techniques have been used to study the ionic interactions of strontium(II) and barium(II) with thiocyanate ion in liquid ammonia. A number of bands were observed in both ν(CN) and ν(CS) regions of infrared and Raman spectra and these were assigned to 1:1 contact ion pair, ...

Heteroditopic receptors for ion-pair recognition.

Science.gov (United States)

McConnell, Anna J; Beer, Paul D

2012-05-21

Ion-pair recognition is a new field of research emerging from cation and anion coordination chemistry. Specific types of heteroditopic receptor designs for ion pairs and the complexity of ion-pair binding are discussed to illustrate key concepts such as cooperativity. The importance of this area of research is reflected by the wide variety of potential applications of ion-pair receptors, including applications as membrane transport and salt solubilization agents and sensors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rate theory of solvent exchange and kinetics of Li+ − BF4−/PF6− ion pairs in acetonitrile

International Nuclear Information System (INIS)

Dang, Liem X.; Chang, Tsun-Mei

2016-01-01

In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li + and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li + in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li + -[BF 4 ] and Li + -[PF 6 ] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li + . We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li + -[BF 4 ] and Li + -[PF 6 ] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems.

Contact isotopic- and contact ion-exchange between two adsorbents

International Nuclear Information System (INIS)

Bunzl, K.; Mohan, R.; Haimerl, M.

1975-01-01

The kinetics of contact ion exchange processes between an ion exchange membrane and resin ion exchange beads, stirred in pure water, was investigated. A general criterion was derived, which indicates whether diffusion of the ions between the intermingling electric double layers or the collision frequency between the two adsorbents is the rate dermining step. Since the latter process proved to be rate controlling under our experimental conditions, the corresponding rate equations were derived under various initial and boundary conditions. Experimentally, the kinetics of contact isotopic exchange of Cs + - and Na + -ions as well as of the reverse contact ion exchange process of Cs + -versus Na + -ions were investigated by using Na 22 and Cs 137 radioisotopes. The experiments reveal in quantitative accord with the theory that the rate of collision controlled contact ion exchange processes depends mainly on the 'exchange coefficient', the separation factor and the collision frequency. While the latter two quantities were determined independently by separate experiments, the 'exchange coefficient' was evaluated from a contact isotopic exchange experiment. (orig.) [de

Drift wave in pair-ion plasma

Indian Academy of Sciences (India)

ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.

Photoluminescence and thermoluminescence of K2 Mg(SO4 )2 :Eu and evaluation of its kinetic parameters.

Science.gov (United States)

Deshpande, Archana; Dhoble, N S; Gedam, S C; Dhoble, S J

2017-08-01

The K 2 Mg(SO 4 ) 2 :Eu phosphor, synthesized by a solid-state diffusion method, was studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. The X-ray diffraction (XRD) pattern of the material was matched with the standard JCPDF No. 36-1499. For PL characteristics, K 2 Mg(SO 4 ) 2 :Eu 2 + showed an emission peak at 474 nm when excited at 340 nm, while it showed Eu 3 + emission at 580 nm, and 594 nm splitting at 613 nm and 618 nm for an excitation of 396 nm wavelength due to radiative transitions from 5 D 0 to 7 F j (j = 0, 1, 2, 3). The Commission International de I' Eclairage (CIE) chromaticity coordinates were also calculated for the K 2 Mg(SO 4 ) 2 :Eu phosphor, and were close to the NTSC standard values. For the TL study, the prepared sample was irradiated using a 60 Co source of γ-irradiation at the dose rate of 0.322 kGy/h for 2 min. The formation of traps in K 2 Mg (SO 4 ) 2 :Eu and the effects of γ-radiation dose on the glow curve are discussed. Well defined broad glow peaks were obtained at 186°C. With increasing γ-ray dose, the sample showed linearity in intensity. The presence of a single glow peak indicated that there was only one set of traps being activated within the particular temperature range. The presented phosphors were also studied for their fading, reusability and trapping parameters. There was just 2% fading during a period of 30 days, indicating no serious fading problem. Kinetic parameters were calculated using the initial rise method and Chen's half-width method. Activation energy and frequency factor were found to be 0.77 eV and 1.41 × 10 6  sec -1 . Copyright © 2016 John Wiley & Sons, Ltd.

Ion acoustic waves in pair-ion plasma: Linear and nonlinear analyses

International Nuclear Information System (INIS)

Saeed, R.; Mushtaq, A.

2009-01-01

Linear and nonlinear properties of low frequency ion acoustic wave (IAW) in pair-ion plasma in the presence of electrons are investigated. The dispersion relation and Kadomtsev-Petviashvili equation for linear/nonlinear IAW are derived from sets of hydrodynamic equations where the ion pairs are inertial while electrons are Boltzmannian. The dispersion curves for various concentrations of electrons are discussed and compared with experimental results. The predicted linear IAW propagates at the same frequencies as those of the experimentally observed IAW if n e0 ∼10 4 cm -3 . It is found that nonlinear profile of the ion acoustic solitary waves is significantly affected by the percentage ratio of electron number density and temperature. It is also determined that rarefactive solitary waves can propagate in this system. It is hoped that the results presented in this study would be helpful in understanding the salient features of the finite amplitude localized ion acoustic solitary pulses in a laboratory fullerene plasma.

Nuclear Magnetic Resonance Structures of GCN4p Are Largely Conserved When Ion Pairs Are Disrupted at Acidic pH but Show a Relaxation of the Coiled Coil Superhelix.

Science.gov (United States)

Kaplan, Anne R; Brady, Megan R; Maciejewski, Mark W; Kammerer, Richard A; Alexandrescu, Andrei T

2017-03-21

To understand the roles ion pairs play in stabilizing coiled coils, we determined nuclear magnetic resonance structures of GCN4p at three pH values. At pH 6.6, all acidic residues are fully charged; at pH 4.4, they are half-charged, and at pH 1.5, they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with a decrease in pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix caused by the loss of interchain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of the knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH. Chemical shifts (HN, N, C', Cα, and Cβ) of GCN4p display a seven-residue periodicity that is consistent with α-helical structure and is invariant with pH. By contrast, periodicity in hydrogen exchange rates at neutral pH is lost at acidic pH as the exchange mechanism moves into the EX1 regime. On the basis of 1 H- 15 N nuclear Overhauser effect relaxation measurements, the α-helix monomers experience only small increases in picosecond to nanosecond backbone dynamics at acidic pH. By contrast, 13 C rotating frame T 1 relaxation (T 1ρ ) data evince an increase in picosecond to nanosecond side-chain dynamics at lower pH, particularly for residues that stabilize the coiled coil dimerization interface through ion pairs. The results on the structure and dynamics of GCNp4 over a range of pH values help rationalize why a single structure at neutral pH poorly predicts the pH dependence of the unfolding stability of the coiled coil.

Ageing without detailed balance in the bosonic contact and pair-contact processes: exact results

International Nuclear Information System (INIS)

Baumann, Florian; Henkel, Malte; Pleimling, Michel; Richert, Jean

2005-01-01

Ageing in systems without detailed balance is studied in the exactly solvable bosonic contact process and the critical bosonic pair-contact process. The two-time correlation function and the two-time response function are explicitly found. In the ageing regime, the dynamical scaling of these is analysed and exact results for the ageing exponents and the scaling functions are derived. For the critical bosonic pair-contact process, the autocorrelation and autoresponse exponents agree but the ageing exponents a and b are shown to be distinct

Beyond Chloride Brines: Variable Metabolomic Responses in the Anaerobic Organism Yersinia intermedia MASE-LG-1 to NaCl and MgSO4 at Identical Water Activity

Science.gov (United States)

Schwendner, Petra; Bohmeier, Maria; Rettberg, Petra; Beblo-Vranesevic, Kristina; Gaboyer, Frédéric; Moissl-Eichinger, Christine; Perras, Alexandra K.; Vannier, Pauline; Marteinsson, Viggó T.; Garcia-Descalzo, Laura; Gómez, Felipe; Malki, Moustafa; Amils, Ricardo; Westall, Frances; Riedo, Andreas; Monaghan, Euan P.; Ehrenfreund, Pascale; Cabezas, Patricia; Walter, Nicolas; Cockell, Charles

2018-01-01

Growth in sodium chloride (NaCl) is known to induce stress in non-halophilic microorganisms leading to effects on the microbial metabolism and cell structure. Microorganisms have evolved a number of adaptations, both structural and metabolic, to counteract osmotic stress. These strategies are well-understood for organisms in NaCl-rich brines such as the accumulation of certain organic solutes (known as either compatible solutes or osmolytes). Less well studied are responses to ionic environments such as sulfate-rich brines which are prevalent on Earth but can also be found on Mars. In this paper, we investigated the global metabolic response of the anaerobic bacterium Yersinia intermedia MASE-LG-1 to osmotic salt stress induced by either magnesium sulfate (MgSO4) or NaCl at the same water activity (0.975). Using a non-targeted mass spectrometry approach, the intensity of hundreds of metabolites was measured. The compatible solutes L-asparagine and sucrose were found to be increased in both MgSO4 and NaCl compared to the control sample, suggesting a similar osmotic response to different ionic environments. We were able to demonstrate that Yersinia intermedia MASE-LG-1 accumulated a range of other compatible solutes. However, we also found the global metabolic responses, especially with regard to amino acid metabolism and carbohydrate metabolism, to be salt-specific, thus, suggesting ion-specific regulation of specific metabolic pathways. PMID:29535699

Beyond Chloride Brines: Variable Metabolomic Responses in the Anaerobic Organism Yersinia intermedia MASE-LG-1 to NaCl and MgSO4 at Identical Water Activity

Directory of Open Access Journals (Sweden)

Petra Schwendner

2018-02-01

Full Text Available Growth in sodium chloride (NaCl is known to induce stress in non-halophilic microorganisms leading to effects on the microbial metabolism and cell structure. Microorganisms have evolved a number of adaptations, both structural and metabolic, to counteract osmotic stress. These strategies are well-understood for organisms in NaCl-rich brines such as the accumulation of certain organic solutes (known as either compatible solutes or osmolytes. Less well studied are responses to ionic environments such as sulfate-rich brines which are prevalent on Earth but can also be found on Mars. In this paper, we investigated the global metabolic response of the anaerobic bacterium Yersinia intermedia MASE-LG-1 to osmotic salt stress induced by either magnesium sulfate (MgSO4 or NaCl at the same water activity (0.975. Using a non-targeted mass spectrometry approach, the intensity of hundreds of metabolites was measured. The compatible solutes L-asparagine and sucrose were found to be increased in both MgSO4 and NaCl compared to the control sample, suggesting a similar osmotic response to different ionic environments. We were able to demonstrate that Yersinia intermedia MASE-LG-1 accumulated a range of other compatible solutes. However, we also found the global metabolic responses, especially with regard to amino acid metabolism and carbohydrate metabolism, to be salt-specific, thus, suggesting ion-specific regulation of specific metabolic pathways.

Mechanical strengths of modified PET mortar composites in aggressive MgSO4 medium: ACI & B.S predictions

OpenAIRE

Kazi Tani N; Benosman A.S.; Senhadji Y.; Taïbi H.; Mouli M.

2018-01-01

Composites mortars based on plastic aggregates are often considered as an innovative materials of the future because of their potential and the advantages they present. In this paper, a comparative study was carried out on the effect of magnesium sulfate MgSO4 (5%) attack on the durability of composite mortars modified by recycled polyethylene terephthalate (PET). Laboratory tests were accomplished on limestone sand and cement mortars where the blended Portland cement was partially replaced b...

Magnesium sulphate’s influence on calcium carbonate minerals

DEFF Research Database (Denmark)

Nielsen, Mia Rohde

The purpose of this PhD thesis was to explore the influence of magnesium sulphate (MgSO4 (aq)) on calcium carbonate (CaCO3) minerals and what role the MgSO40 ion pair had. CaCO3 minerals are abundant and widespread on Earth, particularly in marine environments, and have been so throughout Earth...

Pair housing for female longtailed and rhesus macaques in the laboratory: behavior in protected contact versus full contact.

Science.gov (United States)

Baker, Kate C; Crockett, Carolyn M; Lee, Grace H; Oettinger, Brooke C; Schoof, Valérie; Thom, Jinhee P

2012-01-01

Pair housing for caged macaques in the laboratory generally allows unrestricted tactile contact but, less commonly, may involve limited contact via grooming-contact bars or perforated panels. The purpose of using this protected contact housing, which prevents entry into pair-mates' cages, typically is to accommodate research and management requirements. The study used behavioral data collected on 12 pairs of female longtailed macaques (Macaca fascicularis) at the Washington National Primate Research Center and 7 pairs of female rhesus macaques (Macaca mulatta) housed at the Tulane National Primate Research Center to assess the relative benefits of protected versus full protected contact. The study collected data in stable pairs housed first in protected contact followed by full contact. Species combined, the study found the presence of the panel was associated with lower levels of social grooming and higher levels of self-grooming, abnormal behavior, and tension-related behavior. Within species, only the protected- versus full-contact contrasts for abnormal and tension were statistically significant-and only for rhesus macaques. Results suggest that for female rhesus macaques, potential disadvantages or inconveniences of full contact should be balanced against the improved behavioral profile in comparison to protected contact. The use of protected contact among female longtailed macaques does not appear to require the same cost-benefit analysis. Copyright © Taylor & Francis Group, LLC

Micropatterning of poly(4-hydroxystyrene) by ion beam contact lithography for the control of cell adhesion

International Nuclear Information System (INIS)

Hwang, In Tae; Jung, Chan Hee; Choi, Jae Hak; Nho, Young Chang; Lee, Byoung Min; Hong, Sung Kwon

2009-01-01

In this study, we report on a simple method of micropatterning of cells by using ion beam contact lithography. Thin poly(4-hydroxystyrene) (Phds) films spin-coated on a silicon wafer were irradiated through a pattern mask in a contact mode with proton ions and then developed to generate the patterns of the Phds. Well-defined 50 μm line (pitch 150 μm) patterns were obtained without using any additives. The remaining thickness after development was increased with an increasing fluence up to 3 x 10 14 ions cm -2 after which it leveled off. The in-vitro cell culture test revealed that the cells were preferentially adhered to and proliferated only on the space regions between the Phds line patterns. Inhibition of cell adhesion on the Phds patterns could be due to antifouling property of the irradiated PHS

Li+ solvation and kinetics of Li+-BF4-/PF6- ion pairs in ethylene carbonate. A molecular dynamics study with classical rate theories

Science.gov (United States)

Chang, Tsun-Mei; Dang, Liem X.

2017-10-01

Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ethylene carbonate (EC) exchange process between the first and second solvation shells around Li+ and the dissociation kinetics of ion pairs Li+-[BF4] and Li+-[PF6] in this solvent. We calculate the exchange rates using transition state theory and correct them with transmission coefficients computed by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found that the residence times of EC around Li+ ions varied from 60 to 450 ps, depending on the correction method used. We found that the relaxation times changed significantly from Li+-[BF4] to Li+-[PF6] ion pairs in EC. Our results also show that, in addition to affecting the free energy of dissociation in EC, the anion type also significantly influences the dissociation kinetics of ion pairing.

Secondary partitioning isotope effects on solvolytic ion pair intermediates

International Nuclear Information System (INIS)

Abbey, K.J.

1976-01-01

The thermal decomposition of N-benzhydryl N-nitrosobenzamide (BNB) has been shown to produce an ion pair which either forms ester or reacts with the solvent. In ethanol, the fraction of ester produced, R, was much smaller than R values obtained from solvolysis or from the diphenyldiazomethane (DDM)-benzoic acid reaction, which was suggested to yield the same ion pair as solvolysis. This difference led to the conclusion that the ionic species for the nitrosamide decomposition is a nitrogen-separated ion pair. This study was initiated on the assumption that BNB led to solvolytic ion pairs, but that both the intimate and solvent-separated ion pairs were produced directly from the nitrosamide. The use of α-tritiated BNB for the study of partitioning isotope effects (PIE's) in this system led to activity ratios much lower than expected from other reported work. Results of studies of ''special'' salt effect were not consistent for all situations, but the results do suggest that the assumption that BNB leads to solvolytic ion pairs is probably valid. The investigation of the more stable p-methoxybenzhydryl benzoate system proved to be highly productive. The ester fraction produced, R, responded dramatically to the addition of common-ion as well as ''special'' salts. The functional relationship of R on salt concentration could be explained in terms of Winstein's solvolytic scheme where the intimate ion pair, the solvent-separated ion pair, and the dissociated ion were important. Tritium-labelled compounds were used for PIE studies on 3 different compounds, and three different methods of reaction are proposed

Solvation and Ion Pair Association in Aqueous Metal Sulfates: Interpretation of NDIS raw data by isobaric-isothermal molecular dynamics simulation

International Nuclear Information System (INIS)

Chialvo, Ariel A.; Simonson, J. Michael

2010-01-01

We analyzed the solvation behavior of aqueous lithium, nickel, and ytterbium sulfates at ambient conditions in terms of the relevant radial distributions functions and the corresponding first-order difference of the sulfur-site neutron weighted distribution functions generated by isothermal-isobaric molecular dynamics simulation. We determined of the partial contributions to the neutron weighted distribution functions, to identify the main peaks, and the effect of the contact ion-pair configuration on the resulting H-S coordination number. Finally, we assessed the extent of the ion-pair formation according to Poirier-DeLap formalism and highlighted the significant increase of the ion-pair association exhibited by these salts with cation charge.

Solid-liquid stable phase equilibria of the ternary systems MgCl2 + MgB6O10+ H2O AND MgSO4 + MgB6O10 + H2O at 308.15 K

Directory of Open Access Journals (Sweden)

Lingzong Meng

2014-03-01

Full Text Available The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β(0, β(1, β(2 and CØ for MgCl2, MgSO4, and Mg(B6O7(OH6, the mixed ion-interaction parameters θCl,B6O10, θSO4,B6O10, ΨMg,Cl,B6O10, ΨMg,SO4,B6O10 of the systems at 308.15 K were fitted, In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.

Nonlinear electrostatic structures in homogeneous and inhomogeneous pair-ion plasmas

International Nuclear Information System (INIS)

Mahmood, S.; Ur-Rehman, H.; Shah, A.; Haque, Q.

2012-01-01

The nonlinear electrostatic structures such as solitons, shocks were studied in homogeneous, unmagnetized pair-ion plasma. The dissipation in the system was taken through kinematic viscosities of both pair-ion species. The one dimensional (Korteweg-de Vries-Burgers) KdVB equation was derived using reductive perturbation method. The analytical solution of KdVB equation was obtained using tanh method. It was found that solitons and monotonic shocks structures were formed in such type of plasmas depending on the value of dissipation in the system. Both compressive and refractive structures of solitons and monotonic shocks were obtained depending on the temperatures of negative and positive ions. The oscillatory shock structures in pair-ion plasmas were also obtained and its necessary conditions of formation were discussed. The acoustic solitons were also investigated in inhomogeneous unmagnetized pair-ion plasmas. The Korteweg-de Vries (KdV) like equation with an additional term due to density gradients was obtained by employing the reductive perturbation technique. It was found that amplitude of both compressive and refractive solitons was found to be enhanced as the density gradient parameter was increased. The Landau damping rates of electrostatic ion waves were studied for non-Maxwellian or Lorentzian pair-ion plasmas. The Val sov equation was solved analytically for weak damping effects in pair-ion plasma. It was found that Landau damping rate of ion plasma wave was increased in Lorentzian case in comparison with Maxwellian pair-ion plasmas. The numerical results were obtained by taking into account the parameters of pair-ion plasmas produced in laboratory experiments in Japan. (orig./A.B.)

Influence of the cylindrical gear pairs parameters to the transverse contact ratio

Directory of Open Access Journals (Sweden)

Predrag S. Dobratić

2014-06-01

Full Text Available In the field of transmission and power transformation from the power engine to the working machine, gear pairs, are mostly used in mechanical engineering due to their compactness of the structure, high reliability and capacity. One way of improving the performance characteristics of gear pairs, and thus the gear transmitters, is to increase the number of simultaneously meshed pairs of teeth, or increasing the transverse contact ratio. To this end, this paper analyzes in detail the partial and simultaneous influence of the number of teeth and tooth profile shapes, moving through shifting coefficient and pressure angle, to the number of simultaneously meshed pairs of teeth. The obtained results allow us to define the optimum parameters of cylindrical gear pairs, in terms of the size of the transverse contact ratio. Introduction The kinematic indicator of the existence of the transmitting continuity of a rotary movement is the total contact ratio. In order to achieve the transmitting continuity of a rotary movement, the total contact ratio must be higher than one. Based on the total contact ratio, the information on the number of simultaneously meshed pairs of the teeth which rotate during the contact period is obtained. For example, if the  – one and two pairs of teeth alternately take turn, and if the  – two and three pairs of teeth alternately take turn, etc. It should be noted that the  is a necessary but not sufficient condition for achieving multiple meshes. The next condition to meet is the compatibility between the accuracy of teeth production, the teeth rigidity and the intensity of the total load of the teeth pair. The influence of the addendum coefficient on the transverse contact ratio is shown in the paper (Li, 2008. It is shown that changes in the addendum coefficient in conjunction with the corresponding values of the shifting coefficient and gear ratio can achieve the transverse contact ratio value higher than four. The paper

Na Cl ion pair association in water-DMSO mixtures: Effect of ion pair ...

Indian Academy of Sciences (India)

The 12-6-1 potential model predicts running coordination numbers closest to experimental data. Keywords. ... value of interaction energy minimum between the Na. + and Cl. − ..... ion pair mostly remains as a CIP, a fair amount of SAIP is also ...

Adiabatic pair creation in heavy-ion and laser fields

International Nuclear Information System (INIS)

Pickl, P.; Durr, D.

2008-01-01

The planned generation of lasers and heavy-ion colliders renews the hope to see electron-positron pair creation in strong classical fields. This old prediction is usually referred to as spontaneous pair creation. We observe that both heavy-ion collisions and pair creation in strong laser fields, are instances of the theory of adiabatic pair creation. We shall present the theory, thereby correcting earlier results. We give the momentum distribution of created pairs in overcritical fields. We discuss carefully the proposed experimental verifications and conclude that pure laser-based experiments are highly questionable. We propose a new experiment, joining laser fields and heavy ions, which may be feasible with present-day technology and which may indeed verify the theoretical prediction of adiabatic pair creation. Our presentation relies on recent rigorous works in mathematical physics. (authors)

A simple and highly selective 2,2-diferrocenylpropane-based multi-channel ion pair receptor for Pb(2+) and HSO4(-).

Science.gov (United States)

Wan, Qian; Zhuo, Ji-Bin; Wang, Xiao-Xue; Lin, Cai-Xia; Yuan, Yao-Feng

2015-03-28

A structurally simple, 2,2-diferrocenylpropane-based ion pair receptor 1 was synthesized and characterized by (1)H NMR, (13)C NMR, HRMS, elemental analyses, and single-crystal X-ray diffraction. The ion pair receptor 1 showed excellent selectivity and sensitivity towards Pb(2+) with multi-channel responses: a fluorescence enhancement (more than 42-fold), a notable color change from yellow to red, redox anodic shift (ΔE1/2 = 151 mV), while HSO4(-) promoted fluorescence enhancement when Pb(2+) or Zn(2+) was bonded to the cation binding-site. (1)H NMR titration and density functional theory were performed to reveal the sensing mechanism based on photo-induced electron transfer (PET).

Ion-pair chromatography of nucleic acid derivatives

International Nuclear Information System (INIS)

Perrone, P.A.; Brown, P.R.

1985-01-01

Little work has been done on the ion-pair chromatography of nucleic acid constituents, although there is a great potential for the use of this technique in the field. Since the classic work in 1949, nucleotides, as well as nucleosides and bases, have been separated by ion-exchange chromatography. However, ion exchange is a difficult mode and most researchers prefer the use of reversed-phase whenever possible. Although reversed-phase is now the method of choice, ionic compounds like nucleotides and some of the more polar bases are not adequately retained by many systems of this type. In addition, it is difficult to analyze simultaneously members of all three classes of nucleic acid compounds (bases, nucleosides, and nucleotides) using a reversed-phase system, even with gradient elution. Ion pairing can be a useful technique because, theoretically, the separation of nonionic bases and nucleosides along with the ionic nucleotides can be achieved. Additionally, each group of compounds may be separated isocratically. In this chapter, they will discuss ion-pair chromatography as applied to nucleic acid constituents. The current theories, advantages and disadvantages, a limited number of applications, and potential for future work are presented

New Signal Readout Principle for Solid-Contact Ion-Selective Electrodes.

Science.gov (United States)

Vanamo, Ulriika; Hupa, Elisa; Yrjänä, Ville; Bobacka, Johan

2016-04-19

A novel approach to signal transduction concerning solid-contact ion-selective electrodes (SC-ISE) with a conducting polymer (CP) as the solid contact is investigated. The method presented here is based on constant potential coulometry, where the potential of the SC-ISE vs the reference electrode is kept constant using a potentiostat. The change in the potential at the interface between the ion-selective membrane (ISM) and the sample solution, due to the change in the activity of the primary ion, is compensated with a corresponding but opposite change in the potential of the CP solid contact. This enforced change in the potential of the solid contact results in a transient reducing/oxidizing current flow through the SC-ISE. By measuring and integrating the current needed to transfer the CP to a new state of equilibrium, the total cumulated charge that is linearly proportional to the change of the logarithm of the primary ion activity is obtained. In this work, different thicknesses of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) were used as solid contact. Also, coated wire electrodes (CWEs) were included in the study to show the general validity of the new approach. The ISM employed was selective for K(+) ions, and the selectivity of the membrane under implementation of the presented transduction mechanism was confirmed by measurements performed with a constant background concentration of Na(+) ions. A unique feature of this signal readout principle is that it allows amplification of the analytical signal by increasing the capacitance (film thickness) of the solid contact of the SC-ISE.

Effect of MgSO4 on expression of NSE and S-100 in rats brain tissue irradiated by 6 MeV electron beam

International Nuclear Information System (INIS)

Zhou Juying; Wang Lili; Yu Zhiying; Qin Songbing; Xu Xiaoting; Li Li; Tu Yu

2007-01-01

Objective: To explore the protection of magnesium sulfate (MgSO 4 ) on radiation-induced acute brain injuries. Methods: Thirty six mature Sprague-Dawley rats were randomly divided into 3 groups: blank control group, experimental control group and experimental administered group. The whole brain of SD rats of experimental control group and experimental-therapeutic group were irradiated with a dose of 20 Gy using 6 MeV electron beam. Magnesium sulfate was injected intraperitoneally into the rats of experimental-therapeutic group before and after irradiation for five times. The brain tissue were taken on days 1, 7, 14 and 30 after irradiation. Immunohistochemical method was used to detect the expressions of NSE and S-100 in brain tissue. All data were processed statistically with One-ANOVA analysis. Results: The expressions of NSE and S-100 after whole brain irradiation were time-dependent. Compared with blank control group, the expression of NSE in brains of experimental control group decreased significantly (P 4 can inhibit the expression of S-100, but induce the expression of NSE on radiation-induced acute brain injury. MgSO 4 has a protective effect on radiation-induced acute brain injury. (authors)

Separation of seven arsenic species by ion-pair and ion-exchange high performance liquid chromatography

DEFF Research Database (Denmark)

Larsen, Erik Huusfeldt; Hansen, Sven Hedegaard

1992-01-01

Arsenite, arsenate, monomethylarsonate, dimethylarsinate, arsenobetaine, arsenocholine and the tetramethylarsonium ion were subjected to ion-exchange and ion-pair reversed phase HPLC. The ion exchange method was superior in selectivity and time of analysis for the arsenic anions. The ammonium ions...... used for the ion-pair method only resulted in separation of some of the anionic arsenic compounds. Flame atomic absorption spectrometry was used for on-line arsenic-specific detection....

Study of the processes of ion pairs formation by the method of ion-ion coincidence: I2 and chlorine-containing hydrocarbons

International Nuclear Information System (INIS)

Golovin, A.V.

1991-01-01

A method of ion-ion coincidences was suggested to study the process of ion pairs formation during molecule photoionization. The principle of action of ion-ion coincidence method is based on recording of only the negative and positive ions that formed as a result of a molecule decomposition. The flowsheet of the facility of ion-ion coincidences was presented. The processes of ion pairs formation in iodine, chloroform, propyl-, n-propenyl-, tert.butyl- and benzyl-chlorides were studied. A simple model permitting to evaluate the dependence of quantum yield of ion pair formation on excitation energy was suggested

Potential of mean force for ion pairs in non-aqueous solvents. Comparison of polarizable and non-polarizable MD simulations

Science.gov (United States)

Odinokov, A. V.; Leontyev, I. V.; Basilevsky, M. V.; Petrov, N. Ch.

2011-01-01

Potentials of mean force (PMF) are calculated for two model ion pairs in two non-aqueous solvents. Standard non-polarizable molecular dynamics simulation (NPMD) and approximate polarizable simulation (PMD) are implemented and compared as tools for monitoring PMF profiles. For the polar solvent (dimethylsulfoxide, DMSO) the PMF generated in terms of the NPMD reproduces fairly well the refined PMD-PMF profile. For the non-polar solvent (benzene) the conventional NPMD computation proves to be deficient. The validity of the correction found in terms of the approximate PMD approach is verified by its comparison with the result of the explicit PMD computation in benzene. The shapes of the PMF profiles in DMSO and in benzene are quite different. In DMSO, owing to dielectric screening, the PMF presents a flat plot with a shallow minimum positioned in the vicinity of the van der Waals contact of the ion pair. For the benzene case, the observed minimum proves to be unexpectedly deep, which manifests the formation of a tightly-binded contact ion pair. This remarkable effect arises owing to the strong electrostatic interaction that is incompletely screened by a non-polar medium. The PMFs for the binary benzene/DMSO mixtures display intermediate behaviour depending on the DMSO content.

Ion pair formation in the vacuum ultraviolet region of NO studied by negative ion imaging spectroscopy

International Nuclear Information System (INIS)

Hikosaka, Y.; Kaneyasu, T.; Shigemasa, E.

2007-01-01

The pair formation of positive and negative fragment ions has been studied in the vacuum ultraviolet region of NO, with negative ion imaging spectroscopy. The negative ion yield curve obtained in the photon energy region of 19-25 eV exhibits many structures which are absent from the photoabsorption spectrum in the same region. The partial yields and asymmetry parameters associated with the dissociations into individual ion pair limits have been extracted from the negative ion images observed. On the basis of these quantities, the assignments for the structures exhibited on the negative ion yield curve are given and the dynamical properties on the ion pair dissociation are discussed

Probing subsistence of ion-pair and triple-ion of an ionic salt in liquid environments by means of conductometric contrivance

International Nuclear Information System (INIS)

Banik, Ishani; Roy, Mahendra Nath

2013-01-01

Highlights: • Study of ion-solvation of [Bu 4 NBF 4 ] in CH 3 CN, CH 3 OH, DMSO, and 1,3-DO. • Triple-ion formation in 1,3-Dioxolane. • Ion–solvent interaction is stronger in DMSO. • Ion–solvent interaction dominates over ion–ion interaction in the studied solutions. -- Abstract: Qualitative and quantitative analyses of molecular interaction prevailing in ionic salt-organic solvent media, probed by electrical conductances have been reported. Tetrabutylammonium tetrafluoroborate [Bu 4 NBF 4 ] in acetonitrile (CH 3 CN), methanol (CH 3 OH), dimethylsulfoxide (DMSO) and 1,3-dioxolane (1,3-DO) have been studied at 298.15 K. The extent of interaction is expressed in terms of the association constant (K A ) and shows the interaction to be a function of viscosity. Limiting molar conductances (Λ o ), association constants (K A ), and the association diameter (R) for ion-pair formation have been analyzed using the Fuoss conductance-concentration equation (1978). The observed molar conductivities were explained by the formation of ion-pairs (M + +X − ↔ MX, K P ) and triple-ions (2M + + X − ↔ M 2 X + ; M + + 2X − ↔ MX 2 − , K T ). The Walden product is obtained and discussed. The deviation of the conductometric curves (Λ vs c 1/2 ) from linearity for the electrolyte in 1,3-dioxolane indicates triple-ion formation, and therefore the corresponding conductance data have been analyzed by using the Fuoss–Kraus theory of triple-ions. The limiting ionic conductances (λ o ± ) have been calculated from the appropriate division of the limiting molar conductivity value of tetrabutylammonium tetraphenylborate [Bu 4 NBPh 4 ] as the “reference electrolyte” method along with a numerical evaluation of ion-pair and triple-ion formation constants (K P ≈ K A and K T ). The results have been interpreted in terms of solvent properties and configurational theory

Direct Detection of the Ion Pair to Free Ions Transformation upon Complexation with an Ion Receptor in Non-Polar Solvents by using Conductometry.

Science.gov (United States)

Iseda, Kazuya; Kokado, Kenta; Sada, Kazuki

2018-03-01

In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride ( TBACl ) ion-pair salt to the free ions through complexation with meso -octamethylcalix[4]pyrrole ( CP ), which is a well-known receptor for chloride anions. In the presence of CP , the conductivity of TBACl increases in various non-polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non-polar solvents. In other words, CP recognizes chloride as an ion-paired salt as well as a free anion in non-polar solvents. Additionally, the TBA(CP - Cl ) complex exhibited a considerably lower ion-pairing constant ( K ip ) than TBACl in non-polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli-responsive soft materials in organic solvents using coulombic forces.

Influence of ion pairing in ionic liquids on electrical double layer structures and surface force using classical density functional approach.

Science.gov (United States)

Ma, Ke; Forsman, Jan; Woodward, Clifford E

2015-05-07

We explore the influence of ion pairing in room temperature ionic liquids confined by planar electrode surfaces. Using a coarse-grained model for the aromatic ionic liquid [C4MIM(+)][BF4 (-)], we account for an ion pairing component as an equilibrium associating species within a classical density functional theory. We investigated the resulting structure of the electrical double layer as well as the ensuing surface forces and differential capacitance, as a function of the degree of ion association. We found that the short-range structure adjacent to surfaces was remarkably unaffected by the degree of ion pairing, up to several molecular diameters. This was even the case for 100% of ions being paired. The physical implications of ion pairing only become apparent in equilibrium properties that depend upon the long-range screening of charges, such as the asymptotic behaviour of surface forces and the differential capacitance, especially at low surface potential. The effect of ion pairing on capacitance is consistent with their invocation as a source of the anomalous temperature dependence of the latter. This work shows that ion pairing effects on equilibrium properties are subtle and may be difficult to extract directly from simulations.

Does an electronic continuum correction improve effective short-range ion-ion interactions in aqueous solution?

Science.gov (United States)

Bruce, Ellen E.; van der Vegt, Nico F. A.

2018-06-01

Non-polarizable force fields for hydrated ions not always accurately describe short-range ion-ion interactions, frequently leading to artificial ion clustering in bulk aqueous solutions. This can be avoided by adjusting the nonbonded anion-cation or cation-water Lennard-Jones parameters. This approach has been successfully applied to different systems, but the parameterization is demanding owing to the necessity of separate investigations of each ion pair. Alternatively, polarization effects may effectively be accounted for using the electronic continuum correction (ECC) of Leontyev et al. [J. Chem. Phys. 119, 8024 (2003)], which involves scaling the ionic charges with the inverse square-root of the water high-frequency dielectric permittivity. ECC has proven to perform well for monovalent salts as well as for divalent salts in water. Its performance, however, for multivalent salts with higher valency remains unexplored. The present work illustrates the applicability of the ECC model to trivalent K3PO4 and divalent K2HPO4 in water. We demonstrate that the ECC models, without additional tuning of force field parameters, provide an accurate description of water-mediated interactions between salt ions. This results in predictions of the osmotic coefficients of aqueous K3PO4 and K2HPO4 solutions in good agreement with experimental data. Analysis of ion pairing thermodynamics in terms of contact ion pair (CIP), solvent-separated ion pair, and double solvent-separated ion pair contributions shows that potassium-phosphate CIP formation is stronger with trivalent than with divalent phosphate ions.

Drift waves and counter rotating vortices in pair-ion plasmas

Energy Technology Data Exchange (ETDEWEB)

Haque, Q., E-mail: qamar_haque@hotmail.co [Theoretical Plasma Physics Division, PINSTECH P.O. Nilore, Islamabad (Pakistan)

2010-07-19

Linear dispersion relation has been found for drift and acoustic waves in pair-ion-electron plasmas. The stationary solution in the form of counter rotating vortices has been obtained in the presence of equilibrium potential profile. It is noticed that the speed of nonlinear structures is reduced with the increase of electrons concentration in pair-ion plasmas. Linear instability condition has also been found in the presence of shear flow. It is pointed out that the present results can be useful for future pair-ion plasma experiments.

The effect of magnesium ion concentration on the fibrocartilage regeneration potential of goat costal chondrocytes.

Science.gov (United States)

Hagandora, Catherine K; Tudares, Mauro A; Almarza, Alejandro J

2012-03-01

Magnesium has recently been explored as a potential biomaterial for degradable orthopedic implants but its effect on fibrocartilage remains unknown. The objective of this study was to assess the effect of high concentrations of magnesium ions on the matrix production of goat costal fibrochondrocytes in vitro. Cells were cultured using a scaffoldless approach with media containing magnesium chloride (MgCl(2)) or magnesium sulfate (MgSO(4)) at concentrations of 20, 50, and 100 mM in addition to the baseline magnesium concentration of 0.8 mM MgSO(4). At 4 weeks, there were no significant differences in compressive tangent modulus and total matrix production between constructs cultured in 20 mM Mg(2+) and the 0.8 mM Mg(2+) control (435 ± 47 kPa). There was a significant decrease in compressive tangent modulus compared to the 0.8 mM Mg(2+) constructs in the 50 mM MgCl(2) and MgSO(4) groups, while the 100 mM groups were not mechanically testable (p < 0.05). The collagen and glycosaminoglycan (GAG) content of the 50 and 100 mM MgCl(2) and MgSO(4) constructs was significantly lower than the control (6.9 ± 0.5% and 16.5 ± 1.3% per dry weight, respectively) (p < 0.05). The results show that goat costal fibrochondrocytes exhibit a high degree of resiliency to magnesium ion concentrations up to 20 mM in vitro.

Tailoring the Crystal Structure of Nanoclusters Unveiled High Photoluminescence via Ion Pairing

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2018-03-26

The lack of structurally distinct nanoclusters (NCs) of identical size and composition prevented the mechanistic understanding of their structural effects on ion pairing and concomitant optical properties. To produce such highly sought NCs, we designed a new monothiolate-for-dithiolate exchange strategy that enabled the selective transformation of the structure of a NC without affecting its metal atomicity or composition. Through this method, a bimetallic [PtAg28(BDT)12(PPh3)4]4– NC (1) was successfully synthesized from [PtAg28(S-Adm)18(PPh3)4]2+ NC (2) (S-Adm, 1-adamantanethiolate; BDT, 1,3-benzenedithiolate; PPh3, triphenylphosphine). The determined X-ray crystal structure of 1 showed a PtAg12 icosahedron core and a partially exposed surface, which are distinct from a face-centered cubic PtAg12 core and a fully covered surface of 2. We reveal through mass spectrometry (MS) that 1 forms ion pairs with counterions attracted by the core charge of the cluster, which is in line with density functional simulations. The MS data for 1, 2, and other NCs suggested that such attraction is facilitated by the exposed surface of 1. The formation of ion pairs increases the photoluminescence (PL) quantum yield of 1 up to 17.6% depending on the bulkiness of the counterion. Unlike small counterions, larger ones are calculated to occupy ≤90% of the volume near the exposed cluster surface and to make the ligand shell of 1 more rigid, which is observed to increase the PL. Thus, the developed synthesis strategy for structurally different NCs of the same size and composition allows us to probe the structure–property relationship for ion pairing and concomitant PL enhancement.

Interesting features of nonlinear shock equations in dissipative pair-ion-electron plasmas

International Nuclear Information System (INIS)

Masood, W.; Rizvi, H.

2011-01-01

Two dimensional nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion-electron plasmas in the presence of weak transverse perturbation. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions. In the linear case, a biquadratic dispersion relation is obtained, which yields the fast and slow modes in a pair-ion-electron plasma. It is shown that the limiting cases of electron-ion and pair-ion can be retrieved from the general biquadratic dispersion relation, and the differences in the characters of the waves propagating in both the cases are also highlighted. Using the small amplitude approximation method, the nonlinear Kadomtsev Petviashvili Burgers as well as Burgers-Kadomtsev Petviashvili equations are derived and their applicability for pair-ion-electron plasma is explained in detail. The present study may have relevance to understand the formation of two dimensional electrostatic shocks in laboratory produced pair-ion-electron plasmas.

Ion pair and solvation dynamics of [Bmim][BF4 ] + water system.

Science.gov (United States)

Cascão, João; Silva, Wagner; Ferreira, Ana S D; Cabrita, Eurico J

2018-02-01

In this work, 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures were analysed over the whole water composition (x w ) in order to study the rotational and translational behaviour of the ions. We employed a multinuclear NMR approach to determine anion/cation/water diffusion coefficients and longitudinal relaxation rates at different water content. In neat ionic liquids (IL), the cation diffuses faster than the anion, and at low x w , anions and cations share almost the same diffusion coefficient, but above a critical water concentration, the anion begins to diffuse faster than the cation. We identified this composition as approximately 10% x w where the ions share the same diffusion coefficient. We found that the water at this composition seems to have a much more dramatic effect in the rotational diffusion of the anion that decreases substantially and approaches that of the anion in the diluted IL. Translational and rotational dynamics of the ions suggest that water is first incorporated in pockets in the nanostructure of the IL allowing the ions to maintain most of the cation/anion interactions present in neat IL but already disrupting some anion/cation interactions due to preferential interaction with the anion. HOESY and NOESY data show that water displays contacts both with the cation and the anion in a positive NOE regime in contrary to the negative regime found for the cation/anion and cation/cation cross-relaxation. This is in accordance with the high relative diffusion coefficient of water and suggests that water molecules can exchange between preferential location sites that allow water to maintain contacts both with the anion and cation. Copyright © 2017 John Wiley & Sons, Ltd.

Quasi-equilibrium analysis of the ion-pair mediated membrane transport of low-permeability drugs.

Science.gov (United States)

Miller, Jonathan M; Dahan, Arik; Gupta, Deepak; Varghese, Sheeba; Amidon, Gordon L

2009-07-01

The aim of this research was to gain a mechanistic understanding of ion-pair mediated membrane transport of low-permeability drugs. Quasi-equilibrium mass transport analyses were developed to describe the ion-pair mediated octanol-buffer partitioning and hydrophobic membrane permeation of the model basic drug phenformin. Three lipophilic counterions were employed: p-toluenesulfonic acid, 2-naphthalenesulfonic acid, and 1-hydroxy-2-naphthoic acid (HNAP). Association constants and intrinsic octanol-buffer partition coefficients (Log P(AB)) of the ion-pairs were obtained by fitting a transport model to double reciprocal plots of apparent octanol-buffer distribution coefficients versus counterion concentration. All three counterions enhanced the lipophilicity of phenformin, with HNAP providing the greatest increase in Log P(AB), 3.7 units over phenformin alone. HNAP also enhanced the apparent membrane permeability of phenformin, 27-fold in the PAMPA model, and 4.9-fold across Caco-2 cell monolayers. As predicted from a quasi-equilibrium analysis of ion-pair mediated membrane transport, an order of magnitude increase in phenformin flux was observed per log increase in counterion concentration, such that log-log plots of phenformin flux versus HNAP concentration gave linear relationships. These results provide increased understanding of the underlying mechanisms of ion-pair mediated membrane transport, emphasizing the potential of this approach to enable oral delivery of low-permeability drugs.

Ion pair reinforced semi-interpenetrating polymer network for direct methanol fuel cell applications.

Science.gov (United States)

Fang, Chunliu; Julius, David; Tay, Siok Wei; Hong, Liang; Lee, Jim Yang

2012-06-07

This paper describes the synthesis of ion-pair-reinforced semi-interpenetrating polymer networks (SIPNs) as proton exchange membranes (PEMs) for the direct methanol fuel cells (DMFCs). Specifically, sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO), a linear polymer proton source, was immobilized in a brominated PPO (BPPO) network covalently cross-linked by ethylenediamine (EDA). The immobilization of SPPO in the SIPN network was accomplished not only by the usual means of mechanical interlocking but also by ion pair formation between the sulfonic acid groups of SPPO and the amine moieties formed during the cross-linking reaction of BPPO with EDA. Through the ion pair interactions, the immobilization of SPPO polymer in the BPPO network was made more effective, resulting in a greater uniformity of sulfonic acid cluster distribution in the membrane. The hydrophilic amine-containing cross-links also compensated for some of the decrease in proton conductivity caused by ion pair formation. The SIPN membranes prepared as such showed good proton conductivity, low methanol permeability, good mechanical properties, and dimensional stability. Consequently, the PPO based SIPN membranes were able to deliver a higher maximum power density than Nafion, demonstrating the potential of the SIPN structure for PEM designs.

The initial stages of NaCl dissolution: Ion or ion pair solvation?

Science.gov (United States)

Klimes, Jiri; Michaelides, Angelos

2009-03-01

The interaction of water with rock salt (NaCl) is important in a wide variety of natural processes and human activities. A lot is known about NaCl dissolution at the macroscopic level but we do not yet have a detailed atomic scale picture of how salt crystals dissolve. Here we report an extensive series of density functional theory, forcefield and molecular dynamics studies of water clusters at flat and defective NaCl surfaces and NaCl clusters. The focus is on answering seemingly elementary questions such as how many water molecules are needed before it becomes favorable to extract an ion or a pair of ions from the crystal or the cluster. It turns out, however, that the answers to these questions are not so straightforward: below a certain number of water molecules (˜ 12) solvation of individual ions is less costly and above this number solvation of ion pairs is favored. These results reveal a hitherto unknown complexity in the NaCl dissolution process born out of a subtle interplay between water-water and water-ion interactions.

Time-Resolved Magnetic Field Effects Distinguish Loose Ion Pairs from Exciplexes

Science.gov (United States)

2013-01-01

We describe the experimental investigation of time-resolved magnetic field effects in exciplex-forming organic donor–acceptor systems. In these systems, the photoexcited acceptor state is predominantly deactivated by bimolecular electron transfer reactions (yielding radical ion pairs) or by direct exciplex formation. The delayed fluorescence emitted by the exciplex is magnetosensitive if the reaction pathway involves loose radical ion pair states. This magnetic field effect results from the coherent interconversion between the electronic singlet and triplet radical ion pair states as described by the radical pair mechanism. By monitoring the changes in the exciplex luminescence intensity when applying external magnetic fields, details of the reaction mechanism can be elucidated. In this work we present results obtained with the fluorophore-quencher pair 9,10-dimethylanthracene/N,N-dimethylaniline (DMA) in solvents of systematically varied permittivity. A simple theoretical model is introduced that allows discriminating the initial state of quenching, viz., the loose ion pair and the exciplex, based on the time-resolved magnetic field effect. The approach is validated by applying it to the isotopologous fluorophore-quencher pairs pyrene/DMA and pyrene-d10/DMA. We detect that both the exciplex and the radical ion pair are formed during the initial quenching stage. Upon increasing the solvent polarity, the relative importance of the distant electron transfer quenching increases. However, even in comparably polar media, the exciplex pathway remains remarkably significant. We discuss our results in relation to recent findings on the involvement of exciplexes in photoinduced electron transfer reactions. PMID:24041160

Acoustic nonlinear periodic waves in pair-ion plasmas

Science.gov (United States)

Mahmood, Shahzad; Kaladze, Tamaz; Ur-Rehman, Hafeez

2013-09-01

Electrostatic acoustic nonlinear periodic (cnoidal) waves and solitons are investigated in unmagnetized pair-ion plasmas consisting of same mass and oppositely charged ion species with different temperatures. Using reductive perturbation method and appropriate boundary conditions, the Korteweg-de Vries (KdV) equation is derived. The analytical solutions of both cnoidal wave and soliton solutions are discussed in detail. The phase plane plots of cnoidal and soliton structures are shown. It is found that both compressive and rarefactive cnoidal wave and soliton structures are formed depending on the temperature ratio of positive and negative ions in pair-ion plasmas. In the special case, it is revealed that the amplitude of soliton may become larger than it is allowed by the nonlinear stationary wave theory which is equal to the quantum tunneling by particle through a potential barrier effect. The serious flaws in the earlier published results by Yadav et al., [PRE 52, 3045 (1995)] and Chawla and Misra [Phys. Plasmas 17, 102315 (2010)] of studying ion acoustic nonlinear periodic waves are also pointed out.

Preparation and Microbiological Evaluation of Amphiphilic Kanamycin-Lipoamino Acid Ion-Pairs

Directory of Open Access Journals (Sweden)

Rosario Pignatello

2014-05-01

Full Text Available Amphiphilic ion-pairs of kanamycin (KAN were prepared by evaporation of a water-ethanol co-solution of KAN base and a lipoamino acid bearing a 12-carbon atoms alkyl side chain (LAA12, at different molar ratios. Infrared spectroscopy confirmed the structure of ion-pairs, while differential scanning calorimetry (DSC and powder X-ray diffractometry (PXRD studies supported the formation of new saline species with a different crystalline structure than the starting components. The solubility pattern shown in a range of both aqueous and organic solvents confirmed that the ion-pairs possess an amphiphilic character. The LAA12 counter-ion showed not to improve the antibacterial activity of KAN, suggesting that such chemical strategy is not able to favor the penetration of this drug inside the bacteria cells. Nevertheless, a slight improving, i.e., a one-fold dilution, was observed in E. coli. The present study can also serve as the basis for a further evaluation of LAA ion-pairing of antibiotics, as a means to improve the loading of hydrophilic drugs into lipid-based nanocarriers.

Probing ion-specific effects on aqueous acetate solutions: Ion pairing versus water structure modifications.

Science.gov (United States)

Petit, Tristan; Lange, Kathrin M; Conrad, Gerrit; Yamamoto, Kenji; Schwanke, Christoph; Hodeck, Kai F; Dantz, Marcus; Brandenburg, Tim; Suljoti, Edlira; Aziz, Emad F

2014-05-01

The effect of monovalent cations (Li(+), K(+), NH4 (+), Na(+)) on the water structure in aqueous chloride and acetate solutions was characterized by oxygen K-edge X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy, and resonant inelastic X-ray scattering (RIXS) of a liquid microjet. We show ion- and counterion dependent effects on the emission spectra of the oxygen K-edge, which we attribute to modifications of the hydrogen bond network of water. For acetates, ion pairing with carboxylates was also probed selectively by XAS and RIXS. We correlate our experimental results to speciation data and to the salting-out properties of the cations.

Probing ion-specific effects on aqueous acetate solutions: Ion pairing versus water structure modifications

Directory of Open Access Journals (Sweden)

Tristan Petit

2014-05-01

Full Text Available The effect of monovalent cations (Li+, K+, NH4+, Na+ on the water structure in aqueous chloride and acetate solutions was characterized by oxygen K-edge X-ray absorption spectroscopy (XAS, X-ray emission spectroscopy, and resonant inelastic X-ray scattering (RIXS of a liquid microjet. We show ion- and counterion dependent effects on the emission spectra of the oxygen K-edge, which we attribute to modifications of the hydrogen bond network of water. For acetates, ion pairing with carboxylates was also probed selectively by XAS and RIXS. We correlate our experimental results to speciation data and to the salting-out properties of the cations.

Observation of water separated ion-pairs between cations and phospholipid headgroups.

Science.gov (United States)

van der Post, Sietse T; Hunger, Johannes; Bonn, Mischa; Bakker, Huib J

2014-04-24

In this work, we present evidence for ion pair formation of cations with a high surface charge density (Na(+) and Ca(2+)) and phosphate groups of phospholipids. We used femto-second infrared pump-probe and dielectric spectroscopy to probe the dynamics of water molecules in solutions of phosphorylethanolamine and different types of cations. We find that sodium and calcium cooperatively retard the dynamics of water in solutions of phosphorylethanolamine, implying the formation of solvent separated ion pairs. This ion-specific interaction is absent for potassium, cesium and ammonium. We compare our results to dielectric spectroscopy experiments, which probes the rotation of all dipolar molecules and ions in solution. The rotation of the dipolar phosphorylethanolamine ion shows that long-lived ion-pairs are only formed with calcium and not with ammonium, cesium, potassium, and sodium. This finding implies that the association between calcium and the phosphate is strong with lifetimes exceeding 200 ps, while the interaction with sodium is relatively short-lived (∼20-100 ps).

Effect of implanted doses of N+-ions on the contact resistance of copper contacts

International Nuclear Information System (INIS)

Dubravec, B.; Kovac, P.; Lipka, F.; Padysak, M.

1997-01-01

The paper deals with the effect of implanted doses of N + ions on the contact resistance. Dependencies of the contact resistance versus contact force R c =f(F c ) and microhardness of implanted surfaces were measured for three implanted profiles. The influence of the aggressive environs on the contact resistance of implanted contact is given too

High-performance liquid ion-pair chromatography in inorganic analysis

International Nuclear Information System (INIS)

Alimarin, I.P.; Basova, E.M.; Bol'shova, T.A.; Ivanov, V.M.

1990-01-01

In literature review for the recent 15 years theoretical foundations, regularities and mechanisms of ionized compound retention in reverse-phase ion-pair chromatography are considered, possibilities and prospects of its application in inorganic analysis being demonstrated. Analytic characteristics of the methods for the determination of inorganic anions (I - , IO 3 - , MoO 4 2- , etc.), as well as metals (Zr, Hf, V, Nb, Mo, W, Ru, lanthanides, etc.) in the form of chelates, are given

Contact hyperfine field of the 4p and 4f series elements (rare-earths)

International Nuclear Information System (INIS)

Doi, I.

1973-01-01

The Coulomb correlation effect in the description of the contact hyperfine magnetic structure was analysed. The hyperfine magnetic structure was calculated from the spin polarized Hartree-Fock formalism, using the free electron gas approximation to the exchange-correlation energy of the 4p series atoms and some atoms and ions of the 4f series. No one of the analysed approximations to the exchange-correlation energy describes satisfactorily the contact hyperfine magnetic structure of the 4p and 4f series elements, which were studied [pt

Effect of MgSO4 on the contents of Ca2+ in brain cell and NO in brain tissue of rats with radiation-induced acute brain injury

International Nuclear Information System (INIS)

Yuan Wenjia; Cui Fengmei; Liu Ping; He Chao; Tu Yu; Wang Lili

2009-01-01

The work is to explore the protection of magnesium sulfate(MgSO 4 ) on radiation-induced acute brain injury. Thirty six mature Sprague-Dawley(SD) rats were randomly divided into 3 groups of control, experimental control and experimental therapy group. The whole brains of SD rats of experimental control and experimental therapy group were irradiated with a dose of 20 Gy using 6 MeV electron beam. MgSO 4 was injected into the abdomen of experimental therapy rats group 1 day before, immediately and continue for 5 days after irradiation respectively. The brain tissues were taken on 3, 10, 17 and 24 d after irradiation. Ca 2+ content in brain cell was measured by laser scanning confocal microscopy, and the NO content in brain tissue was detected by the method of nitric acid reductase. Compared with the blank control group, the contents of Ca 2+ in brain cell and NO in brain tissue of the experimental control group increase (P 4 used in early stage can inhibit the contents of Ca 2+ in brain cell and NO in brain tissue after radiation-induced acute brain injury. It means that MgSO 4 has a protective effect on radiation-induced acute brain injury. (authors)

Drift wave in pair-ion plasma

Indian Academy of Sciences (India)

of charged particles in electromagnetic fields. The linear and nonlinear collective modes in electron-positron plasma have been investigated theoretically [3–6]. Recently, Oohara and Hatakeyama [7] have developed a novel method for generating a pair plasma con- sisting of only negative and positive ions with equal mass ...

Impedance study of the ion-to-electron transduction process for carbon cloth as solid-contact material in potentiometric ion sensors

International Nuclear Information System (INIS)

Mattinen, Ulriika; Rabiej, Sylwia; Lewenstam, Andrzej; Bobacka, Johan

2011-01-01

Carbon cloth was studied as solid-contact material in potentiometric ion sensors by using electrochemical impedance spectroscopy and potentiometry. The ion-to-electron transduction process was studied by electrochemical impedance spectroscopy by using a two-electrode symmetrical cell where a liquid electrolyte was sandwiched between two solid electrodes, including bare glassy carbon (GC), GC/carbon cloth and GC/poly(3,4-ethylenedioxythiophene). Impedance data for different electrode/electrolyte combinations were evaluated and compared. Solid-contact K + -selective electrodes were fabricated by coating the carbon cloth with a conventional plasticized PVC-based K + -selective membrane via drop casting. These K + -sensors showed proper analytical performance and acceptable long-term potential stability (potential drift ≈ 1 mV/day). Solid contact reference electrodes were fabricated in an analogous manner by coating the carbon cloth with a plasticized PVC membrane containing a moderately lipophilic salt. The results indicate that carbon cloth can be used as a solid-contact material in potentiometric ion sensors and pseudo-reference electrodes.

Communication: Potentials of mean force study of ionic liquid ion pair aggregation in polar covalent molecule solvents

Science.gov (United States)

Bandlamudi, Santosh Rathan Paul; Benjamin, Kenneth M.

2018-05-01

Molecular dynamics (MD) simulations were conducted for 1-ethyl-3-methylimidazolium methylsulfate [EMIM][MeSO4] dissolved in six polar covalent molecules [acetic acid, acetone, chloroform, dimethyl sulfoxide (DMSO), isopropyl alcohol, and methanol] to understand the free energies of ionic liquid (IL) ion pairing/aggregation in the limit of infinite dilution. Free energy landscapes or potentials of mean force (PMF) were computed using umbrella sampling and the weighted histogram analysis method. The PMF studies showed the strongest IL ion pairing in chloroform, and the strength of IL ion pairing decreases in the order of chloroform, acetone, propanol, acetic acid, DMSO, and methanol. In the limit of infinite dilution, the free energy curves for IL ion aggregation in co-solvents were characterized by two distinct minima [global (˜3.6 Å) and local (˜5.7 Å)], while free energy values at these minima differed significantly for IL in each co-solvent. The PMF studies were extended for determining the free energy of IL ion aggregation as a function of concentration of methanol. Studies showed that as the concentration of methanol increased, the free energy of ion aggregation decreased, suggesting greater ion pair stability, in agreement with previously reported MD clustering and radial distribution function data.

μ- and tau-pair production from relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Bottcher, C.; Strayer, M.R.

1986-01-01

The question is addressed of μ- and tau-pair production from the motional Coulomb fields available at the new relativistic heavy-ion accelerators. A semiclassical field theory is developed which is appropriate for families of leptons which are coupled electromagnetically. The field equations are mapped on to a lattice of collocation points using basis spline methods, and techniques for solving the resulting lattice equations are outlined. The properties of the transverse electromagnetic field near the heavy-ion beam are examined and physical arguments are given as to the feasibility of pair creation under a variety of circumstances. Using the Dirac-Hartree equations developed in part one, we shall dynamically evolve the vacuum, using the appropriate fields, and compute μ-pair and tau-pair production cross sections. 16 refs., 10 figs

Simultaneous Determination of Chelating Agents by Ion-Suppression and Ion-Pair Chromatography in Wastewater

International Nuclear Information System (INIS)

Dodi, Alain; Bouscarel, Maelle

2008-01-01

This article describes two methods for analysing chelating agents found in nuclear waste. First, ion-suppression chromatography using an anion exchange stationary phase and mobile phase consisting of a nitric acid solution and pure water gradient. UV detection was performed at 330 nm after the reaction with a post-column reagent composed of iron nitrate in perchloric acid. Secondly, ion-pair chromatography with a mobile phase consisting of a mixture of nitric acid, tetra-butyl-ammonium hydrogeno-sulphate, tetra-butyl-ammonium hydroxide and iron chloride. A reversed-phase material was used as a stationary phase and detection was performed by direct measurement of the UV absorption at 260 nm. The quantification limits were lower for ion-pair chromatography than for ion-suppression chromatography. Both methods were easy to implement and allow a multi-element separation in less than 30 min with low detection limits. (authors)

Simultaneous Determination of Chelating Agents by Ion-Suppression and Ion-Pair Chromatography in Wastewater

Energy Technology Data Exchange (ETDEWEB)

Dodi, Alain; Bouscarel, Maelle [Commissariat a l' energie atomique - C.E.A, Centre d' Etude de Cadarache, Laboratoire d' Analyses Radiochimiques et Chimiques, St Paul lez Durance (France)

2008-07-01

This article describes two methods for analysing chelating agents found in nuclear waste. First, ion-suppression chromatography using an anion exchange stationary phase and mobile phase consisting of a nitric acid solution and pure water gradient. UV detection was performed at 330 nm after the reaction with a post-column reagent composed of iron nitrate in perchloric acid. Secondly, ion-pair chromatography with a mobile phase consisting of a mixture of nitric acid, tetra-butyl-ammonium hydrogeno-sulphate, tetra-butyl-ammonium hydroxide and iron chloride. A reversed-phase material was used as a stationary phase and detection was performed by direct measurement of the UV absorption at 260 nm. The quantification limits were lower for ion-pair chromatography than for ion-suppression chromatography. Both methods were easy to implement and allow a multi-element separation in less than 30 min with low detection limits. (authors)

Thermochemical seasonal solar heat storage in salt hydrates for residential applications - Influence of the water vapor pressure on the desorption kinetics of MgSO4.7H2O

NARCIS (Netherlands)

Ferchaud, C.; Scherpenborg, R.A.A.; Zondag, H.A.; Boer, de R.

2013-01-01

An interesting thermochemical material for compact seasonal heat storage is magnesium sulfate heptahydrate MgSO4.7H2O. Previous studies in the field showed that this material presents a storage energy density of 1 GJ/m3 when the material is built in a TC storage system with a 50% porosity packed bed

Effects of Ion Beam Irradiation on Nanoscale InOx Cooper-Pair Insulators

Directory of Open Access Journals (Sweden)

Srdjan Milosavljević

2013-01-01

Full Text Available This paper examines the effects of irradiating indium oxide films of nanoscale thickness by ion beams, when these films are in the Cooper-pair insulator state. Radiation effects are predicted on the basis of Monte Carlo simulations of ion transport. Results of numerical experiments are interpreted within the theoretical model of a Cooper-pair insulator. The study suggests that radiation-induced changes in InOx films exposed to ion beams could significantly alter their current-voltage characteristics and that a transition to a metallic state is possible, due to radiation-induced perturbation of the fine-tuned granular structure. Furthermore, incident and displaced ions can break up enough Cooper pairs in InOx films to cause dissolution of this specific insulating state.

Tunnel oxide passivated contacts formed by ion implantation for applications in silicon solar cells

International Nuclear Information System (INIS)

Reichel, Christian; Feldmann, Frank; Müller, Ralph; Hermle, Martin; Glunz, Stefan W.; Reedy, Robert C.; Lee, Benjamin G.; Young, David L.; Stradins, Paul

2015-01-01

Passivated contacts (poly-Si/SiO x /c-Si) doped by shallow ion implantation are an appealing technology for high efficiency silicon solar cells, especially for interdigitated back contact (IBC) solar cells where a masked ion implantation facilitates their fabrication. This paper presents a study on tunnel oxide passivated contacts formed by low-energy ion implantation into amorphous silicon (a-Si) layers and examines the influence of the ion species (P, B, or BF 2 ), the ion implantation dose (5 × 10 14  cm −2 to 1 × 10 16  cm −2 ), and the subsequent high-temperature anneal (800 °C or 900 °C) on the passivation quality and junction characteristics using double-sided contacted silicon solar cells. Excellent passivation quality is achieved for n-type passivated contacts by P implantations into either intrinsic (undoped) or in-situ B-doped a-Si layers with implied open-circuit voltages (iV oc ) of 725 and 720 mV, respectively. For p-type passivated contacts, BF 2 implantations into intrinsic a-Si yield well passivated contacts and allow for iV oc of 690 mV, whereas implanted B gives poor passivation with iV oc of only 640 mV. While solar cells featuring in-situ B-doped selective hole contacts and selective electron contacts with P implanted into intrinsic a-Si layers achieved V oc of 690 mV and fill factor (FF) of 79.1%, selective hole contacts realized by BF 2 implantation into intrinsic a-Si suffer from drastically reduced FF which is caused by a non-Ohmic Schottky contact. Finally, implanting P into in-situ B-doped a-Si layers for the purpose of overcompensation (counterdoping) allowed for solar cells with V oc of 680 mV and FF of 80.4%, providing a simplified and promising fabrication process for IBC solar cells featuring passivated contacts

Modulation instability of ion thermal waves in a pair-ion plasma containing charged dust impurities

International Nuclear Information System (INIS)

Sabry, R.

2008-01-01

Modulation instability of ion thermal waves (ITWs) is investigated in a plasma composed of positive and negative ions as well as a fraction of stationary charged (positive or negative) dust impurities. For this purpose, a linear dispersion relation and a nonlinear Schroedinger equation are derived. The latter admits localized envelope solitary wave solutions of bright (pulses) and dark (holes, voids) type. The envelope soliton depends on the intrinsic plasma parameters. It is found that modulation instability of ITWs is significantly affected by the presence of positively/negatively charged dust grains. The findings of this investigation should be useful in understanding the stable electrostatic wave packet acceleration mechanisms in pair-ion plasma, and also enhances our knowledge on the occurrence of instability associated to the existence of charged dust impurities in pair-ion plasmas. Our results should be of relevance for laboratory plasmas.

Ion-pair cloud-point extraction: a new method for the determination of water-soluble vitamins in plasma and urine.

Science.gov (United States)

Heydari, Rouhollah; Elyasi, Najmeh S

2014-10-01

A novel, simple, and effective ion-pair cloud-point extraction coupled with a gradient high-performance liquid chromatography method was developed for determination of thiamine (vitamin B1 ), niacinamide (vitamin B3 ), pyridoxine (vitamin B6 ), and riboflavin (vitamin B2 ) in plasma and urine samples. The extraction and separation of vitamins were achieved based on an ion-pair formation approach between these ionizable analytes and 1-heptanesulfonic acid sodium salt as an ion-pairing agent. Influential variables on the ion-pair cloud-point extraction efficiency, such as the ion-pairing agent concentration, ionic strength, pH, volume of Triton X-100, extraction temperature, and incubation time have been fully evaluated and optimized. Water-soluble vitamins were successfully extracted by 1-heptanesulfonic acid sodium salt (0.2% w/v) as ion-pairing agent with Triton X-100 (4% w/v) as surfactant phase at 50°C for 10 min. The calibration curves showed good linearity (r(2) > 0.9916) and precision in the concentration ranges of 1-50 μg/mL for thiamine and niacinamide, 5-100 μg/mL for pyridoxine, and 0.5-20 μg/mL for riboflavin. The recoveries were in the range of 78.0-88.0% with relative standard deviations ranging from 6.2 to 8.2%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant Ion Pair Formation in Electron Collisions with Ground State Molecular Ions

International Nuclear Information System (INIS)

Zong, W.; Dunn, G.H.; Djuric, N.; Greene, C.H.; Neau, A.; Zong, W.; Larsson, M.; Al-Khalili, A.; Neau, A.; Derkatch, A.M.; Vikor, L.; Shi, W.; Rosen, S.; Le Padellec, A.; Danared, H.; Ugglas, M. af

1999-01-01

Resonant ion pair formation from collisions of electrons with ground state diatomic molecular ions has been observed and absolute cross sections measured. The cross section for HD + is characterized by an abrupt threshold at 1.9thinspthinspeV and 14 resolved peaks in the range of energies 0≤E≤14 eV . The dominant mechanism responsible for the structures appears to be resonant capture and stabilization, modified by two-channel quantum interference. Data on HF + show structure correlated with photoionization of HF and with dissociative recombination of electrons with this ion. copyright 1999 The American Physical Society

Ion pairs in non-redundant protein structures

Indian Academy of Sciences (India)

Ion pairs contribute to several functions including the activity of catalytic triads, fusion of viral membranes, stability in thermophilic proteins and solvent–protein interactions. Furthermore, they have the ability to affect the stability of protein structures and are also a part of the forces that act to hold monomers together.

Inhibitory effect of MgSO4 on calcium overload after radiation-induced brain injuries

International Nuclear Information System (INIS)

Tu Yu; Zhou Yuying; Wang Lili

2005-01-01

Objective: To explore the neuroprotective effect of magnesium sulfate (MgSO 4 ) on radiation-induced acute brain injuries. Methods: A total of 60 mature Sprague-Dawley rats were randomly divided into 3 groups: blank control group, experimental control group and experimental therapy group. The whole brain of SD rats of experimental control group and experimental therapy group was irradiated to a dose of 20 Gy using 6 MeV electrons. Magnesium sulfate was injected intraperitoneally into the rats of experimental therapy group before and after irradiation for five times. At different time points (24 h, 7 days, 14 days, 30 days after irradiation), the brain tissue was taken. Plasma direct reading spectrography was used to measure the contents of Ca 2+ , Mg 2+ in brain tissue, and the percentage of brain water content was calculated with the wet-dry weight formula. Results: Compared with the blank control group, the percentage of brain water and content of Ca 2+ in brain of the experimental control group increased markedly (P 2+ decreased significantly (P 2+ in brain of the experimental therapy group were significantly lower than those of the experimental control group (P<0.05). Conclusion: Magnesium sulfate used in the early stage after irradiation can inhibit the calcium overload in rat brain , and attenuate brain edema and injuries. (authors)

Feasibility of ion-pair/supercritical fluid extraction of an ionic compound--pseudoephedrine hydrochloride.

Science.gov (United States)

Eckard, P R; Taylor, L T

1997-02-01

The supercritical fluid extraction (SFE) of an ionic compound, pseudoephedrine hydrochloride, from a spiked-sand surface was successfully demonstrated. The effect of carbon dioxide density (CO2), supercritical fluid composition (pure vs. methanol modified), and the addition of a commonly used reversed-phase liquid chromatographic ion-pairing reagent, 1-heptanesulfonic acid, sodium salt, on extraction efficiency was examined. The extraction recoveries of pseudoephedrine hydrochloride with the addition of the ion-pairing reagent from a spiked-sand surface were shown to be statistically greater than the extraction recoveries without the ion-pairing reagent with both pure and methanol-modified carbon dioxide.

Electron-positron pair creation in heavy ion collisions

International Nuclear Information System (INIS)

Kienle, P.

1987-08-01

We review here the status of experiments to study the electron positron pair creation in heavy ion atom collisions at bombarding energies close to the Coulomb barrier. The disentanglement and characterisation of various sources of positrons observed in such collisions are described with a focus on the monoenergetic electron positron pairs observed. They seem to originate from the two-body decay of a family of neutral particles with masses of about 3 m e and life times in the range of 6x10 -14 s -10 s, produced by high Coulomb fields. First attempts were made to create these particles by resonant Bhabha scattering. First we present some experimental methods for high efficiency positron spectroscopy in heavy ion collisions. Then we describe the discovery of positron creation induced by strong time changing Coulomb fields. (orig./HSI)

Investigating the role of ion-pair strategy in regulating nicotine release from patch: Mechanistic insights based on intermolecular interaction and mobility of pressure sensitive adhesive.

Science.gov (United States)

Li, Qiaoyun; Wan, Xiaocao; Liu, Chao; Fang, Liang

2018-07-01

The aim of this study was to prepare a drug-in-adhesive patch of nicotine (NIC) and use ion-pair strategy to regulate drug delivery rate. Moreover, the mechanism of how ion-pair strategy regulated drug release was elucidated at molecular level. Formulation factors including pressure sensitive adhesives (PSAs), drug loading and counter ions (C 4 , C 6 , C 8 , C 10 , and C 12 ) were screened. In vitro release experiment and in vitro transdermal experiment were conducted to determine the rate-limiting step in drug delivery process. FT-IR and molecular modeling were used to characterize the interaction between drug and PSA. Thermal analysis and rheology study were conducted to investigate the mobility variation of PSA. The optimized patch prepared with NIC-C 8 had the transdermal profile fairly close to that of the commercial product (p > 0.05). The release rate constants (k) of NIC, NIC-C 4 and NIC-C 10 were 21.1, 14.4 and 32.4, respectively. Different release rates of NIC ion-pair complexes were attributed to the dual effect of ion-pair strategy on drug release. On one hand, ion-pair strategy enhanced the interaction between drug and PSA, which inhibited drug release. On the other hand, using ion-pair strategy improved the mobility of PSA, which facilitated drug release. Drug release behavior was determined by combined effect of two aspects above. These conclusions provided a new idea for us to regulate drug release behavior from patch. Copyright © 2018 Elsevier B.V. All rights reserved.

Nonlinear structure formation in ion-temperature-gradient driven drift waves in pair-ion plasma with nonthermal electron distribution

Science.gov (United States)

Razzaq, Javaria; Haque, Q.; Khan, Majid; Bhatti, Adnan Mehmood; Kamran, M.; Mirza, Arshad M.

2018-02-01

Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.

Recent progress in nonperturbative electromagnetic lepton-pair production with capture in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Wells, J.C.; Oberacker, V.E.; Umar, A.S.

1993-01-01

The prospect of new colliding-beam accelerators capable of producing collisions of highly stripped high-Z ions, at fixed-target energies per nucleon up to 20 TeV or more, has motivated much interest in lepton-pair production from the QED vacuum. The time-dependent and essentially classical electromagnetic fields involved in such collisions contain larger Fourier components which give rise to sizable lepton-pair production in addition to many other exotic particles. The process of electron-positron production with electron capture is a principal beam-loss mechanism for highly charged ions in a storage ring. In this process, the electron is created in a bound state of one of the participant heavy ions (most likely the 1s state), thus changing the ion's charge state and causing it to be deflected out of the beam. There is a long and sometimes controversial history concerning the use of perturbative methods in studying electromagnetic lepton-pair production; however, reliable perturbative calculations have been used as input into design models for the Relativistic Heavy-Ion Collider (RHIC). Applying perturbation theory to these processes at high energies and small impact parameters results in probabilities which violate unitarity, and cross sections which violate the Froissart bound. This evidence, along with the initial nonperturbative studies, suggests that higher-order QED effects will be important for extreme relativistic collisions. Clearly, large nonperturbative effects in electron-pair production with capture would have important implications for RHIC. In this paper, the authors briefly discuss recent progress in nonperturbative studies of the capture problem. In Section 2, they state the Dirac equation for a lepton in the time-dependent external field of a heavy ion which must be solved to compute lepton-capture probabilities. Section 4 surveys results from recent applications of coupled-channel and lattice techniques to the lepton-capture problem

Ion-pair and triple-ion formation of some tetraalkylammonium iodides in n-hexanol and its binary mixtures with o-toluidine

International Nuclear Information System (INIS)

Roy, Mahendra Nath; Sarkar, Lovely; Dewan, Rajani

2011-01-01

The electrolytic conductivity of the tetraalkylammonium iodides, R 4 NI (R = butyl to heptyl), has been studied in (0.00, 0.25, 0.50 and 0.75) mass fraction of o-toluidine (C 7 H 9 N) in n-hexanol (C 6 H 14 O) at T = 298.15 K. The limiting molar conductance Λ 0 , association constants K A and the co-sphere diameter R for ion-pair formation in 0.00 and 0.25 mass fraction of solvent mixture have been evaluated using the Fuoss-equation. However, the deviation of the conductometric curves (Λversusc 1/2 ) from linearity for the electrolytes at 0.50 and 0.75 mass fraction of o-toluidine (C 7 H 9 N) in n-hexanol (C 6 H 14 O) indicates triple ion formation, and therefore the corresponding conductance data have been analyzed by the Fuoss-Kraus theory of triple ions. The observed values of the molar conductivity are explained by the ion-pairs (M + + X - ↔ MX) and triple-ions (2M + +X - ↔M 2 X + ,M + +2X - ↔MX 2 - ) formation. From the investigations, the following trend in conductance of the solvated salts has been observed: Display Omitted

Spectrophotometric Determination of Gemifloxacin Mesylate in Pharmaceutical Formulations Through Ion-Pair Complex Formation

Directory of Open Access Journals (Sweden)

Marothu Vamsi Krishna

2008-01-01

Full Text Available Four simple and sensitive ion-pairing spectrophotometric methods have been described for the assay of gemifloxacin mesylate (GFX either in pure form or in pharmaceutical formulations. The developed methods involve formation of colored chloroform extractable ion-pair complexes of the drug with safranin O (SFN O and methylene blue (MB in basic medium; Napthol blue 12BR (NB 12BR and azocaramine G (AG in acidic medium. The extracted complexes showed absorbance maxima at 525, 650, 620 and 540 nm for SFN O, MB, NB 12BR and AG, respectively.Beer's law is obeyed in the concentration ranges 3-15, 4-20, 2-10 and 2-10 μg/mL with molar absorptivity of 2.81 × 104, 2.20 x 104, 4.02 × 104 and 4.15 × 104 L mole−1 cm−1 and relative standard deviation of 0.077, 0.104, 0.080 and 0.103% for SFN O, MB, NB 12BR and AG, respectively. These methods have been successfully applied for the assay of drug in pharmaceutical formulations. No interference was observed from common pharmaceutical adjuvants. Results of analysis were validated statistically and through recovery studies.

A quantum theoretical study of reactions of methyldiazonium ion with DNA base pairs

International Nuclear Information System (INIS)

Shukla, P.K.; Ganapathy, Vinay; Mishra, P.C.

2011-01-01

Graphical abstract: Reactions of methyldiazonium ion at the different sites of the DNA bases in the Watson-Crick GC and AT base pairs were investigated employing density functional and second order Moller-Plesset (MP2) perturbation theories. Display Omitted Highlights: → Methylation of the DNA bases is important as it can cause mutation and cancer. → Methylation reactions of the GC and AT base pairs with CH 3 N 2 + were not studied earlier theoretically. → Experimental observations have been explained using theoretical methods. - Abstract: Methylation of the DNA bases in the Watson-Crick GC and AT base pairs by the methyldiazonium ion was investigated employing density functional and second order Moller-Plesset (MP2) perturbation theories. Methylation at the N3, N7 and O6 sites of guanine, N1, N3 and N7 sites of adenine, O2 and N3 sites of cytosine and the O2 and O4 sites of thymine were considered. The computed reactivities for methylation follow the order N7(guanine) > N3(adenine) > O6(guanine) which is in agreement with experiment. The base pairing in DNA is found to play a significant role with regard to reactivities of the different sites.

Thermodynamic and structural properties of the specific binding between Ag⁺ ion and C:C mismatched base pair in duplex DNA to form C-Ag-C metal-mediated base pair.

Science.gov (United States)

Torigoe, Hidetaka; Okamoto, Itaru; Dairaku, Takenori; Tanaka, Yoshiyuki; Ono, Akira; Kozasa, Tetsuo

2012-11-01

Metal ion-nucleic acid interactions have attracted considerable interest for their involvement in structure formation and catalytic activity of nucleic acids. Although interactions between metal ion and mismatched base pair duplex are important to understand mechanism of gene mutations related to heavy metal ions, they have not been well-characterized. We recently found that the Ag(+) ion stabilized a C:C mismatched base pair duplex DNA. A C-Ag-C metal-mediated base pair was supposed to be formed by the binding between the Ag(+) ion and the C:C mismatched base pair to stabilize the duplex. Here, we examined specificity, thermodynamics and structure of possible C-Ag-C metal-mediated base pair. UV melting indicated that only the duplex with the C:C mismatched base pair, and not of the duplexes with the perfectly matched and other mismatched base pairs, was specifically stabilized on adding the Ag(+) ion. Isothermal titration calorimetry demonstrated that the Ag(+) ion specifically bound with the C:C base pair at 1:1 molar ratio with a binding constant of 10(6) M(-1), which was significantly larger than those for nonspecific metal ion-DNA interactions. Electrospray ionization mass spectrometry also supported the specific 1:1 binding between the Ag(+) ion and the C:C base pair. Circular dichroism spectroscopy and NMR revealed that the Ag(+) ion may bind with the N3 positions of the C:C base pair without distorting the higher-order structure of the duplex. We conclude that the specific formation of C-Ag-C base pair with large binding affinity would provide a binding mode of metal ion-DNA interactions, similar to that of the previously reported T-Hg-T base pair. The C-Ag-C base pair may be useful not only for understanding of molecular mechanism of gene mutations related to heavy metal ions but also for wide variety of potential applications of metal-mediated base pairs in various fields, such as material, life and environmental sciences. Copyright © 2012 Elsevier

Ab initio molecular dynamics approach to a quantitative description of ion pairing in water

Czech Academy of Sciences Publication Activity Database

Pluhařová, Eva; Maršálek, Ondřej; Schmidt, B.; Jungwirth, Pavel

2013-01-01

Roč. 4, č. 23 (2013), s. 4177-4181 ISSN 1948-7185 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : ion pairing * charge transfer * water * ab initio molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 6.687, year: 2013

Predissociation of high-lying Rydberg states of molecular iodine via ion-pair states

Energy Technology Data Exchange (ETDEWEB)

Bogomolov, Alexandr S. [Institute of Chemical Kinetics and Combustion, Institutskaya Str. 3, Novosibirsk 630090 (Russian Federation); Grüner, Barbara; Mudrich, Marcel [Physikalisches Institut, Universität Freiburg, D-79104 Freiburg (Germany); Kochubei, Sergei A. [Institute of Semiconductor Physics, ac. Lavrent' yev ave., 13, Novosibirsk 630090 (Russian Federation); Baklanov, Alexey V. [Institute of Chemical Kinetics and Combustion, Institutskaya Str. 3, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogova Str. 2, Novosibirsk 630090 (Russian Federation)

2014-03-28

Velocity map imaging of the photofragments arising from two-photon photoexcitation of molecular iodine in the energy range 73 500–74 500 cm{sup −1} covering the bands of high-lying gerade Rydberg states [{sup 2}Π{sub 1/2}]{sub c}6d;0{sub g}{sup +} and [{sup 2}Π{sub 1/2}]{sub c}6d;2{sub g} has been applied. The ion signal was dominated by the atomic fragment ion I{sup +}. Up to 5 dissociation channels yielding I{sup +} ions with different kinetic energies were observed when the I{sub 2} molecule was excited within discrete peaks of Rydberg states and their satellites in this region. One of these channels gives rise to images of I{sup +} and I{sup −} ions with equal kinetic energy indicating predissociation of I{sub 2} via ion-pair states. The contribution of this channel was up to about 50% of the total I{sup +} signal. The four other channels correspond to predissociation via lower lying Rydberg states giving rise to excited iodine atoms providing I{sup +} ions by subsequent one-photon ionization by the same laser pulse. The ratio of these channels varied from peak to peak in the spectrum but their total ionic signal was always much higher than the signal of (2 + 1) resonance enhanced multi-photon ionization of I{sub 2}, which was previously considered to be the origin of ionic signal in this spectral range. The first-tier E0{sub g}{sup +} and D{sup ′}2{sub g} ion-pair states are concluded to be responsible for predissociation of Rydberg states [{sup 2}Π{sub 1/2}]{sub c}6d;0{sub g}{sup +} and [{sup 2}Π{sub 1/2}]{sub c}6d;2{sub g}, respectively. Further predissociation of these ion-pair states via lower lying Rydberg states gives rise to excited I(5s{sup 2}5p{sup 4}6s{sup 1}) atoms responsible for major part of ion signal. The isotropic angular distribution of the photofragment recoil directions observed for all channels indicates that the studied Rydberg states are long-lived compared with the rotational period of the I{sub 2} molecule.

Variation in yield ratios of fragment ions and of ion-pairs from CF2Cl2 following monochromatic soft X-ray absorption

International Nuclear Information System (INIS)

Suzuki, I.H.; Saito, N.; Bozek, J.D.

1995-01-01

Fragment ions produced from CF 2 Cl 2 have been measured from 44 to 1200eV using a time-of-flight mass spectrometer and monochromatized synchrotron radiation. Positively charged ion pairs from this molecule were observed in the inner-shell excitation regions using a Selected photoion-photoion coincidence technique. Obtained yield ratios of fragment ions indicate that the atomic chlorine ion, Cl + , has the greatest intensity at all photon energies above 60eV and exhibits a steep increase at the Cl L 2,3 -edges. Some fragment ions, in particular CF 2 + , have a clear intensity increase at the transitions of inner-shell electrons to unoccupied molecular orbitals. The ion pair F + - Cl + exhibits the highest yield at most photon energies, and some of the branching ratios for ion-pair production changed significantly near the Cl L 2,3 -edges. (author)

Descriptors for ions and ion-pairs for use in linear free energy relationships.

Science.gov (United States)

Abraham, Michael H; Acree, William E

2016-01-22

The determination of Abraham descriptors for single ions is reviewed, and equations are given for the partition of single ions from water to a number of solvents. These ions include permanent anions and cations and ionic species such as carboxylic acid anions, phenoxide anions and protonated base cations. Descriptors for a large number of ions and ionic species are listed, and equations for the prediction of Abraham descriptors for ionic species are given. The application of descriptors for ions and ionic species to physicochemical processes is given; these are to water-solvent partitions, HPLC retention data, immobilised artificial membranes, the Finkelstein reaction and diffusion in water. Applications to biological processes include brain permeation, microsomal degradation of drugs, skin permeation and human intestinal absorption. The review concludes with a section on the determination of descriptors for ion-pairs. Copyright © 2015 Elsevier B.V. All rights reserved.

Lepton-pair production by bremsstrahlung in central relativistic heavy ion collisions

International Nuclear Information System (INIS)

Lippert, T.; Becker, U.; Gruen, N.; Scheid, W.; Soff, G.

1988-03-01

We study the production of lepton-pairs by classical bremsstrahlung in central relativistic heavy-ion collisions. For the stopping of the nuclei we assume a simple model of point charges and a deceleration time. Pair creation probabilities are calculated in first order perturbation theory. (orig.)

Conjugation of silica nanoparticles with cellulose acetate/polyethylene glycol 300 membrane for reverse osmosis using MgSO4 solution.

Science.gov (United States)

Sabir, Aneela; Shafiq, Muhammad; Islam, Atif; Jabeen, Faiza; Shafeeq, Amir; Ahmad, Adnan; Zahid Butt, Muhammad Taqi; Jacob, Karl I; Jamil, Tahir

2016-01-20

Thermally-induced phase separation (TIPS) method was used to synthesize polymer matrix (PM) membranes for reverse osmosis from cellulose acetate/polyethylene glycol (CA/PEG300) conjugated with silica nanoparticles (SNPs). Experimental data showed that the conjugation of SNPs changed the surface properties as dense and asymmetric composite structure. The results were explicitly determined by the permeability flux and salt rejection efficiency of the PM-SNPs membranes. The effect of SNPs conjugation on MgSO4 salt rejection was more significant in magnitude than on permeation flux i.e. 2.38 L/m(2)h. FTIR verified that SNPs were successfully conjugated on the surface of PM membrane. DSC of PM-SNPs shows an improved Tg from 76.2 to 101.8 °C for PM and PM-S4 respectively. Thermal stability of the PM-SNPs membranes was observed by TGA which was significantly enhanced with the conjugation of SNPs. The micrographs of SEM and AFM showed the morphological changes and increase in the valley and ridges on membrane surface. Experimental data showed that the PM-S4 (0.4 wt% SNPs) membrane has maximum salt rejection capacity and was selected as an optimal membrane. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optimization of polymeric triiodide membrane electrode based on clozapine-triiodide ion-pair using experimental design.

Science.gov (United States)

Farhadi, Khalil; Bahram, Morteza; Shokatynia, Donya; Salehiyan, Floria

2008-07-15

Central composite design (CCD) and response surface methodology (RSM) were developed as experimental strategies for modeling and optimization of the influence of some variables on the performance of a new PVC membrane triiodide ion-selective electrode. This triiodide sensor is based on triiodide-clozapine ion-pair complexation. PVC, plasticizers, ion-pair amounts and pH were investigated as four variables to build a model to achieve the best Nernstian slope (59.9 mV) as response. The electrode is prepared by incorporating the ion-exchanger in PVC matrix plasticized with 2-nitrophenyl octal ether, which is directly coated on the surface of a graphite electrode. The influence of foreign ions on the electrode performance was also investigated. The optimized membranes demonstrate Nernstian response for triiodide ions over a wide linear range from 5.0 x 10(-6) to 1.0 x 10(-2)mol L(-1) with a limit of detection 2.0 x 10(-6) mol L(-1) at 25 degrees C. The electrodes could be used over a wide pH range 4-8, and have the advantages of easy to prepare, good selectivity and fast response time, long lifetime (over 3 months) and small interferences from hydrogen ion. The proposed electrode was successfully used as indicator electrode in potentiometric titration of triiodide ions and ascorbic acid.

Electron-positron pair creation in heavy ion collisions

International Nuclear Information System (INIS)

Kienle, P.

1987-01-01

The authors review the status of experiments to study the electron positron pair creation in heavy ion atom collisions at bombarding energies close to the Coulomb barrier. The disentanglement and characterization of various sources of positrons observed in such collisions are described with a focus on the monoenergetic electron positron pairs observed. They seem to originate from the two-body decay of a family of neutral particles with masses of about 3m and lifetimes in the range of 6 x 10 - 14 s, produced by high Coulomb fields. First attempts were made to create these particles by resonant Bhabha scattering

Contact ionization ion source

International Nuclear Information System (INIS)

Hashmi, N.; Van Der Houven Van Oordt, A.J.

1975-01-01

An ion source in which an apertured or foraminous electrode having a multiplicity of openings is spaced from one or more active surfaces of an ionisation electrode, the active surfaces comprising a material capable of ionising by contact ionization a substance to be ionized supplied during operation to the active surface or surfaces comprises means for producing during operation a magnetic field which enables a stable plasma to be formed in the space between the active surface or surfaces and the apertured electrode, the field strength of the magnetic field being preferably in the range between 2 and 8 kilogauss. (U.S.)

Study of the reversible water vapour sorption process of MgSO4.7H2O and MgCl2.6H2O under the conditions of seasonal solar heat storage

NARCIS (Netherlands)

Ferchaud, C.; Zondag, H.A.; Veldhuis, J.B.J.; Boer, de R.

2012-01-01

The characterization of the structural, compositional and thermodynamic properties of MgSO4.7H2O and MgCl2.6H2O has been done using in-situ X-ray Diffraction and thermal analyses (TG/DSC) under practical conditions for seasonal heat storage (Tmax=150°C, p(H2O)=13 mbar). This study showed that these

Extractive liquid-liquid spectrophotometric procedure for the determination of thiocyanate ions employing the ion pair reagent amiloride monohydrochloride

International Nuclear Information System (INIS)

Bashammakh, A.S.; Bahaffi, S.O.; Al-Sibaai, A.A.; Al-Wael, H.O.; El-Shahawi, M.S.

2007-01-01

An accurate, inexpensive and less laborious liquid-liquid extractive spectrophotometric procedure for the determination of thiocyanate ions in aqueous media has been developed. The method has been based upon the formation of a yellow colored complex ion associate of the ion-pairing reagent 1-(3, 5-diamino-6-chloropyrazinecarboxyl) guanidine hydrochloride monohydrate, namely amiloride hydrochloride, DPG + .Cl - and the thiocyanate ions in aqueous media containing HNO 3 (0.5 mol L -1 ) and subsequent extraction with 4-methyl-2-pentanone. The absorption electronic spectrum of the ion associate showed one well-defined peak at λ max 366 nm. The stoichiometric mole ratio of DPG + .Cl - to the thiocyanate ions is 1:1.The effective molar absorptivity (ε) of the ion associate at λ max 366 nm is 1.1 ± 0.1 x 10 4 L mol -1 cm -1 . The extraction constants (K d , K ex , and β) enabled a simple and convenient use of the developed binary ion associate for the extractive spectrophotometric determination of traces of thiocyanate ions in the aqueous media. Beer's law and Ringbom's plots are obeyed in the concentration range 0.05-10 and 0.1-7 μg mL -1 of the thiocyanate ions, respectively with a relative standard deviation of ±2.3%. The calculated lower limits of detection (LOD) and quantitation (LOQ) of the developed procedure for the thiocyanate ions were found equal to 0.02 and 0.066 μg mL -1 , respectively. The developed method has been applied for the determination of trace amounts of thicyanate ions in tap-, waste- and natural water samples and compared successfully with the reported methods at the 95% confidence level. The proposed method was also applied successfully for the determination of thiocyanate ions in saliva samples

Rate theory of ion pairing at the water liquid-vapor interface: A case of sodium iodide

Science.gov (United States)

Dang, Liem X.; Schenter, Gregory K.

2018-06-01

Studies on ion pairing at interfaces have been intensified recently because of their importance in many chemical reactive phenomena, such as ion-ion interactions that are affected by interfaces and their influence on kinetic processes. In this study, we performed simulations to examine the thermodynamics and kinetics of small polarizable sodium iodide ions in the bulk and near the water liquid-vapor interface. Using classical transition state theory, we calculated the dissociation rates and corrected them with transmission coefficients obtained from the reactive flux formalism and Grote-Hynes theory. Our results show that in addition to affecting the free energy of ions in solution, the interfacial environments significantly influence the kinetics of ion pairing. The results on the relaxation time obtained using the reactive flux formalism and Grote-Hynes theory present an unequivocal picture that the interface suppresses ion dissociation. The effects of the use of molecular models on the ion interactions as well as the ion-pair configurations at the interface are also quantified and discussed.

Multiple electromagnetic electron-positron pair production in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Alscher, A.; Hencken, K.; Trautmann, D.; Baur, G.

1997-01-01

We calculate the cross sections for the production of one and more electron-positron pairs due to the strong electromagnetic fields in relativistic heavy-ion collisions. We derive the N-pair amplitude using the generating functional of fermions in an external field and the path-integral formalism. The N-pair production probability is found to be an approximate Poisson distribution. We calculate total cross sections for the production of one pair in lowest order, including corrections from the Poisson distribution up to third order. Furthermore, we calculate cross sections for the production of up to five pairs including corrections from the Poisson distribution. copyright 1997 The American Physical Society

Resonant ion-pair formation in the recombination of NO+ with electrons: Cross-section determination

International Nuclear Information System (INIS)

Le Padellec, A.; Djuric, N.; Al-Khalili, A.; Danared, H.; Derkatch, A. M.; Neau, A.; Popovic, D. B.; Rosen, S.; Semaniak, J.; Thomas, R.

2001-01-01

Resonant ion-pair formation from the collisions of NO + ions with electrons was studied using the heavy-ion storage ring CRYRING at the Manne Siegbahn Laboratory of Stockholm University. The total cross section is measured for the formation of N + +O - for electron energies 8--18 eV, and the results are compared with ion-pair formation in photoionization work. A peak in the cross section is observed at 12.5 eV, with a magnitude of 8.5 x 10 -19 cm 2 . An attempt to extract the cross section for the reverse process of associative ionization is made

Identification of residue pairing in interacting β-strands from a predicted residue contact map.

Science.gov (United States)

Mao, Wenzhi; Wang, Tong; Zhang, Wenxuan; Gong, Haipeng

2018-04-19

Despite the rapid progress of protein residue contact prediction, predicted residue contact maps frequently contain many errors. However, information of residue pairing in β strands could be extracted from a noisy contact map, due to the presence of characteristic contact patterns in β-β interactions. This information may benefit the tertiary structure prediction of mainly β proteins. In this work, we propose a novel ridge-detection-based β-β contact predictor to identify residue pairing in β strands from any predicted residue contact map. Our algorithm RDb 2 C adopts ridge detection, a well-developed technique in computer image processing, to capture consecutive residue contacts, and then utilizes a novel multi-stage random forest framework to integrate the ridge information and additional features for prediction. Starting from the predicted contact map of CCMpred, RDb 2 C remarkably outperforms all state-of-the-art methods on two conventional test sets of β proteins (BetaSheet916 and BetaSheet1452), and achieves F1-scores of ~ 62% and ~ 76% at the residue level and strand level, respectively. Taking the prediction of the more advanced RaptorX-Contact as input, RDb 2 C achieves impressively higher performance, with F1-scores reaching ~ 76% and ~ 86% at the residue level and strand level, respectively. In a test of structural modeling using the top 1 L predicted contacts as constraints, for 61 mainly β proteins, the average TM-score achieves 0.442 when using the raw RaptorX-Contact prediction, but increases to 0.506 when using the improved prediction by RDb 2 C. Our method can significantly improve the prediction of β-β contacts from any predicted residue contact maps. Prediction results of our algorithm could be directly applied to effectively facilitate the practical structure prediction of mainly β proteins. All source data and codes are available at http://166.111.152.91/Downloads.html or the GitHub address of https://github.com/wzmao/RDb2C .

Capture from pair production as a beam loss mechanism for heavy ions at RHIC

International Nuclear Information System (INIS)

Feinberg, B.; Belkacem, A.; Claytor, N.; Dinneen, T.; Gould, H.

1997-05-01

Electron capture from electron-positron pair production is predicted to be a major source of beam loss for the heaviest ions at RHIC. Achieving the highest luminosity thus requires an understanding of the capture process. The authors report measurements of this process at Brookhaven National Laboratory's AGS using 10.8 GeV/nucleon Au 79+ projectiles on Au targets. Capture from pair production is a process in which the very high electromagnetic field involved in the collision of two relativistic heavy ions results in the production of an electron-positron pair with the capture of the electron by one of the ions. There are many theoretical papers published on capture from pair production with discrepancies between predicted cross sections. The experimental results are compared to theory and to previous experiments at 1 GeV/nucleon. The implications of extrapolations to RHIC energies are presented

Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

Science.gov (United States)

Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

2015-12-01

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons

Energy Technology Data Exchange (ETDEWEB)

Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)

2015-12-15

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)

Ion-pairing reversed-phased chromatography/mass spectrometry of heparin

DEFF Research Database (Denmark)

Henriksen, Jens; Roepstorff, Peter; Ringborg, Lene H.

2006-01-01

not well characterised. In order to further characterise such mixtures, two on-line ion-pairing reverse-phased chromatography electrospray ionisation (ESI) mass spectrometry methods have been developed. One of the systems allows the determination of more than 200 components in a medium molecular weight...

Ion-Induced Surface Modification of Magnetically Operated Contacts

Directory of Open Access Journals (Sweden)

Karen Arushanov

2012-02-01

Full Text Available A study has been made of permalloy (iron-nickel contacts of reed switches before and after ion-induced surface modification using atomic force and optical microscopy, Auger electron and X-ray photoelectron spectroscopy. It has been found that the formation of surface nitride layers enhances corrosion and erosion resistance of contacts. We proposed to produce such layers directly into sealed reed switches by means of pulsing glow-discharge nitrogen plasma.

Electromagnetic heavy-lepton pair production in relativistic heavy-ion collisions

Energy Technology Data Exchange (ETDEWEB)

Senguel, M.Y. [Atakent Mahallesi, 3. Etap, Halkali-Kuecuekcekmece, Istanbul (Turkey); Gueclue, M.C.; Mercan, Oe.; Karakus, N.G. [istanbul Technical University, Faculty of Science and Letters, Istanbul (Turkey)

2016-08-15

We calculate the cross sections of electromagnetic productions of muon- and tauon-pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement (Abrahamyan et al., Phys Rev Lett 108:112502, 2012) indicates that the neutrons are differently distributed from the protons; therefore this affects the cross section of the heavy-lepton pair production. In order to see the effects of the neutron distributions in the nucleus, we used analytical expression of the Fourier transforms of the Wood-Saxon distribution. Cross section calculations show that the Wood-Saxon distribution function is more sensitive to the parameter R compared to the parameter a. (orig.)

Quantitative Analysis of Tenofovir by Titrimetric, Extractive Ion-pair ...

African Journals Online (AJOL)

Methods: Tenofovir disoproxil forms a complex of 1:1 molar ratio with fumaric acid that was employed in its aqueous titration with sodium hydroxide. Non-aqueous titration was also employed for its determination. Extractive ion-pair spectrophotometric technique using methyl orange was similarly employed to evaluate ...

Assembling Metal Ions Induced Cyanide-Bridged Heterometallic 1D and Ion-Pair Complexes: Synthesis, Crystal Structures and Magnetic Properties

International Nuclear Information System (INIS)

Kong, Lingqian; Zhao, Zengdian; Chen, Kexun; Wang, Ping; Zhang, Daopeng

2013-01-01

We obtained a heterobimetallic one-dimensional cyanide-bridged Mn(II)-Ni(II) complex and an Co(III)-Ni(II) ion-pair complex with [Ni(CN) 4 ] 2- as building block and M(II)-phenanthroline (M = Mn, Co) compounds as assembling segment. The different structural types of complexes 1 and 2 indicate that the property of the metal ions the assembling segment contained have obvious influence on the structure of the cyanide-bridged complex. Investigation over the magnetic properties of complex 1 reveals an overall weak antiferromagnetic coupling between the adjacent Mn(II) ions bridged by the antiferromagnetic [-NC-Ni-CN-] unit. Among of all the molecular magnetism systems, for the well known reasons, cyanide-containing complexes have been widely employed as bridges to assemble homo/hetero-metallic molecular magnetic materials by using the cyanide bridge transferring magnetic coupling between the neighboring paramagnetic ions, in whichsome showed interesting magnetic properties, such as high-Tc magnets, spin crossover materials, single-molecule magnets (SMMs) and single-chain magnets (SCMs)

Carbon monoxide activation via O-bound CO using decamethylscandocinium-hydridoborate ion pairs.

Science.gov (United States)

Berkefeld, Andreas; Piers, Warren E; Parvez, Masood; Castro, Ludovic; Maron, Laurent; Eisenstein, Odile

2012-07-04

Ion pairs [Cp*(2)Sc](+)[HB(p-C(6)F(4)R)(3)](-) (R = F, 1-F; R = H, 1-H) were prepared and shown to be unreactive toward D(2) and α-olefins, leading to the conclusion that no back-transfer of hydride from boron to scandium occurs. Nevertheless, reaction with CO is observed to yield two products, both ion pairs of the [Cp*(2)Sc](+) cation with formylborate (2-R) and borataepoxide (3-R) counteranions. DFT calculations show that these products arise from the carbonyl adduct of the [Cp*(2)Sc](+) in which the CO is bonded to scandium through the oxygen atom, not the carbon atom. The formylborate 2-R is formed in a two-step process initiated by an abstraction of the hydride by the carbon end of an O-bound CO, which forms an η(2)-formyl intermediate that adds, in a second step, the borane at the carbon. The borataepoxide 3-R is suggested to result from an isomerization of 2-R. This unprecedented reaction represents a new way to activate CO via a reaction channel emanating from the ephemeral isocarbonyl isomer of the CO adduct.

Li ⁺ solvation and kinetics of Li⁺–BF₄^-/PF ₆ ^- ion pairs in ethylene carbonate. A molecular dynamics study with classical rate theories

Energy Technology Data Exchange (ETDEWEB)

Chang, Tsun-Mei [Department of Chemistry, University of Wisconsin–Parkside, Kenosha, Wisconsin 53141, USA; Dang, Liem X. [Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 93352, USA

2017-10-28

Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ethylene carbonate (EC) exchange process between the first and second solvation shells around Li+ and the dissociation kinetics of ion pairs Li+-[BF4] and Li+-[PF6] in this solvent. We calculate the exchange rates using transition state theory and correct them with transmission coefficients computed by the reactive flux; Impey, Madden, and McDonald approaches; and Grote-Hynes theory. We found the residence times of EC around Li+ ions varied from 70 to 450 ps, depending on the correction method used. We found the relaxation times changed significantly from Li+-[BF4] to Li+-[PF6] ion pairs in EC. Our results also show that, in addition to affecting the free energy of dissociation in EC, the anion type also significantly influence the dissociation kinetics of ion pairing. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.

Ion-pair high performance liquid chromatographic retention behavior of salicylic acid and its derivatives

Energy Technology Data Exchange (ETDEWEB)

Lee, K.W.; Chung, Y.S. [Chungbuk National University, Cheongju (Korea); Oh, S.K. [Handok Pharmaceuticals Co. Ltd., Chungbuk (Korea)

1999-06-01

The ion-pair high performance liquid chromatographic elution behavior of salicylic acid and its derivatives was studied with measuring capacity factor, k', changing the concentration of ion-pairing reagent (tetrabutylammonium chloride, TBACl) in mobile phase. As a result, it was found that k' of the samples increase at pH 7.2 as the TBACl concentration increase. The derivatives of salicylic acid were separated each other at an optimum mobile phase condition which was found from the observation of the retention behavior. The optimum mobile phase condition was methanol solution(MeOH:H{sub 2}O 30:70) containing 20 mM TBACl for the determination of salicylic acid and methanol solution (MeOH:H{sub 2}O 20:80) containing 40 mM TBACl for p-aminosalicylic acid at pH 7.2. The method has been applied for the analysis of the contents of salicylic acid derivatives in an aspirin tablet and a tuberculosis curing agent. 8 refs., 4 figs., 2 tabs.

Ion-selective electrode reviews

CERN Document Server

Thomas, J D R

1985-01-01

Ion-Selective Electrode Reviews, Volume 7 is a collection of papers that covers the applications of electrochemical sensors, along with the versatility of ion-selective electrodes. The coverage of the text includes solid contact in membrane ion-selective electrodes; immobilized enzyme probes for determining inhibitors; potentiometric titrations based on ion-pair formation; and application of ion-selective electrodes in soil science, kinetics, and kinetic analysis. The text will be of great use to chemists and chemical engineers.

Effects of ion pairs on the dynamics of erbium doped fiber laser in the inhomogeneous model

International Nuclear Information System (INIS)

Keyvaninia, Sh.; Karvar, M.; Bahrampour, A.

2006-01-01

In a high concentration erbium doped fiber, the erbium ions are so closed together that the ion pairs and clusters are formed. In such fiber amplifiers, the ion pairs and clusters acting as a saturable absorber are distributed along the fiber laser. The inhomogeneous rate equations for the laser modes in a high-concentration EDFA are written. The governing equations are an uncountable system of partial differential equations. For the first time we introduced an approximation method that the system of partial differential equations is converted to a finite system of ordinary differential equations. The effects of ion pairs concentration on erbium doped fiber are analyzed that is in good agreement whit the experimental result.

Improved drug loading and antibacterial activity of minocycline-loaded PLGA nanoparticles prepared by solid/oil/water ion pairing method

Science.gov (United States)

Kashi, Tahereh Sadat Jafarzadeh; Eskandarion, Solmaz; Esfandyari-Manesh, Mehdi; Marashi, Seyyed Mahmoud Amin; Samadi, Nasrin; Fatemi, Seyyed Mostafa; Atyabi, Fatemeh; Eshraghi, Saeed; Dinarvand, Rassoul

2012-01-01

Background Low drug entrapment efficiency of hydrophilic drugs into poly(lactic-co-glycolic acid) (PLGA) nanoparticles is a major drawback. The objective of this work was to investigate different methods of producing PLGA nanoparticles containing minocycline, a drug suitable for periodontal infections. Methods Different methods, such as single and double solvent evaporation emulsion, ion pairing, and nanoprecipitation were used to prepare both PLGA and PEGylated PLGA nanoparticles. The resulting nanoparticles were analyzed for their morphology, particle size and size distribution, drug loading and entrapment efficiency, thermal properties, and antibacterial activity. Results The nanoparticles prepared in this study were spherical, with an average particle size of 85–424 nm. The entrapment efficiency of the nanoparticles prepared using different methods was as follows: solid/oil/water ion pairing (29.9%) > oil/oil (5.5%) > water/oil/water (4.7%) > modified oil/water (4.1%) > nano precipitation (0.8%). Addition of dextran sulfate as an ion pairing agent, acting as an ionic spacer between PEGylated PLGA and minocycline, decreased the water solubility of minocycline, hence increasing the drug entrapment efficiency. Entrapment efficiency was also increased when low molecular weight PLGA and high molecular weight dextran sulfate was used. Drug release studies performed in phosphate buffer at pH 7.4 indicated slow release of minocycline from 3 days to several weeks. On antibacterial analysis, the minimum inhibitory concentration and minimum bactericidal concentration of nanoparticles was at least two times lower than that of the free drug. Conclusion Novel minocycline-PEGylated PLGA nanoparticles prepared by the ion pairing method had the best drug loading and entrapment efficiency compared with other prepared nanoparticles. They also showed higher in vitro antibacterial activity than the free drug. PMID:22275837

Direct Detection of the Ion Pair to Free Ions Transformation upon Complexation with an Ion Receptor in Non‐Polar Solvents by using Conductometry

Science.gov (United States)

Iseda, Kazuya

2018-01-01

Abstract In this study, we performed conductometry in various organic solvents to directly detect the transformation from tetrabutylammonium chloride (TBACl) ion‐pair salt to the free ions through complexation with meso‐octamethylcalix[4]pyrrole (CP), which is a well‐known receptor for chloride anions. In the presence of CP, the conductivity of TBACl increases in various non‐polar solvents, indicating that complexation with CP enhances the ionic dissociation of TBACl in such non‐polar solvents. In other words, CP recognizes chloride as an ion‐paired salt as well as a free anion in non‐polar solvents. Additionally, the TBA(CP–Cl) complex exhibited a considerably lower ion‐pairing constant (K ip) than TBACl in non‐polar solvents, resulting in enhanced conductivity. Based on these findings, we can conclude that complexation of an anion with a hydrophobic anion receptor will be useful for creating functional and stimuli‐responsive soft materials in organic solvents using coulombic forces. PMID:29610717

High-Energy-Density Aqueous Magnesium-Ion Battery Based on a Carbon-Coated FeVO4 Anode and a Mg-OMS-1 Cathode.

Science.gov (United States)

Zhang, Hongyu; Ye, Ke; Zhu, Kai; Cang, Ruibai; Yan, Jun; Cheng, Kui; Wang, Guiling; Cao, Dianxue

2017-12-01

Porous FeVO 4 is prepared by hydrothermal method and further modified by coating with carbon to obtain FeVO 4 /C with a hierarchical pore structure. FeVO 4 /C is used as an anodic electrode in aqueous rechargeable magnesium-ion batteries. The FeVO 4 /C material not only has improved electrical conductivity as a result of the carbon coating layer, but also has an increased specific surface area as a result of the hierarchical pore structure, which is beneficial for magnesium-ion insertion/deinsertion. Therefore, an aqueous rechargeable magnesium-ion full battery is successfully constructed with FeVO 4 /C as the anode, Mg-OMS-1 (OMS=octahedral molecular sieves) as the cathode, and 1.0 mol L -1 MgSO 4 as the electrolyte. The discharge capacity of the Mg-OMS-1//FeVO 4 /C aqueous battery is 58.9 mAh g -1 at a current density of 100 mA g -1 ; this value is obtained by calculating the total mass of two electrodes and the capacity retention rate of this device is 97.7 % after 100 cycles, with almost 100 % coulombic efficiency, which indicates that the system has a good electrochemical reversibility. Additionally, this system can achieve a high energy density of 70.4 Wh kg -1 , which provides powerful evidence that an aqueous magnesium-ion battery is possible. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells

International Nuclear Information System (INIS)

Yang, Guangtao; Ingenito, Andrea; Hameren, Nienke van; Isabella, Olindo; Zeman, Miro

2016-01-01

Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySi was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (R sh n-type  = 95 Ω/□ and R sh p-type  = 120 Ω/□). An efficiency of 19.2% (V oc  = 673 mV, J sc  = 38.0 mA/cm 2 , FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a V OC of 696 mV was also measured

An argon ion beam milling process for native AlOx layers enabling coherent superconducting contacts

Science.gov (United States)

Grünhaupt, Lukas; von Lüpke, Uwe; Gusenkova, Daria; Skacel, Sebastian T.; Maleeva, Nataliya; Schlör, Steffen; Bilmes, Alexander; Rotzinger, Hannes; Ustinov, Alexey V.; Weides, Martin; Pop, Ioan M.

2017-08-01

We present an argon ion beam milling process to remove the native oxide layer forming on aluminum thin films due to their exposure to atmosphere in between lithographic steps. Our cleaning process is readily integrable with conventional fabrication of Josephson junction quantum circuits. From measurements of the internal quality factors of superconducting microwave resonators with and without contacts, we place an upper bound on the residual resistance of an ion beam milled contact of 50 mΩ μm2 at a frequency of 4.5 GHz. Resonators for which only 6% of the total foot-print was exposed to the ion beam milling, in areas of low electric and high magnetic fields, showed quality factors above 106 in the single photon regime, and no degradation compared to single layer samples. We believe these results will enable the development of increasingly complex superconducting circuits for quantum information processing.

Observation of pH Value in Electrokinetic Remediation using various electrolyte (MgSO4, KH2PO4 and Na(NO3)) for Barren Acidic Soil at Ayer Hitam, Johor, Malaysia

Science.gov (United States)

Norashira, J.; Zaidi, E.; Aziman, M.; Saiful Azhar, A. T.

2016-07-01

Barren acidic soil collected at Ayer Hitam, Johor Malaysia was recorded at pH value of 2.36 with relative humidity of 86%. This pH value is not suitable for the growth of any plants especially for the soil stabilization purposes. Gradation weathering within the range of 4 to 6 indicates an incomplete/partial weathering process. The soil grade in this range is known as a black shale mudstone. Beside, this also influences to a factor of the high surface water runoff at this particular soil species. As the acidic pH become a major problem for soil fertilizing hence an appropriate technique was implemented known as using ‘Electrokinetic Remediation’, EKR. This technique has a great potential in changing the soil pH value from acidic to less acidic and also kept maintain the pH at the saturated rate of electrochemical process. This research study presents the monitoring data of pH value due to the effect of various electrolyte consist of 0.5M of MgSO4, KH2PO4, and Na(NO3). Here, the distilled water (DW) was used as reference solution. The electric field was provided by dipping two pieces of identical rectangular aluminum foil as anode and cathode. The EKR was conducted under a constant voltage gradient of 50 V/m across the sample bulk at 0.14 m length measured between both electrodes. The data collection was conducted during the total period of 7 days surveillance. The variation of pH values at the remediation area between anode and cathode for various type of electrolyte indicates that there are a significant saturated value as it reaches 7 days of treatment. During the analysis, it is found that the highest pH value at the remediation area after 7 days treatment using Na(NO3), KH2PO4 and MgSO4 was 3.93, 3.33 and 3.39 respectively. Hence from the last stage of pH value observation, it can be conclude that the best electrolyte for barren soil treatment is Na(NO3) whereby it contribute to highest pH value and turn the soil to be less acidic.

Separation of amaranthine-type betacyanins by ion-pair high-speed countercurrent chromatography.

Science.gov (United States)

Jerz, Gerold; Gebers, Nadine; Szot, Dominika; Szaleniec, Maciej; Winterhalter, Peter; Wybraniec, Slawomir

2014-05-30

Betacyanins, red-violet plant pigments, were fractionated by ion-pair high-speed countercurrent chromatography (IP-HSCCC) from leaves extract of Iresine lindenii Van Houtte, an ornamental plant of the family Amaranthaceae. An HSCCC solvent system consisting of TBME-1-BuOH-ACN-H2O (1:3:1:5, v/v/v/v) was applied using ion-pair forming heptafluorobutyric acid (HFBA). Significantly different elution profiles of betacyanin diastereomeric pairs (derivatives based on betanidin and isobetanidin) observed in the HSCCC in comparison to HPLC systems indicate a complementarity of both techniques' fractionation capabilities. The numerous diastereomeric pairs can be selectively separated from each other using the HSCCC system simplifying the pigment purification process. Apart from the three well known highly abundant pigments (amaranthine, betanin and iresinin I) together with their isoforms, three new acylated (feruloylated and sinapoylated) betacyanins as well as known pigment hylocerenin (previously isolated from cacti fruits) were characterized in the plant for the first time and they are new for the whole Amaranthaceae family. Copyright © 2014 Elsevier B.V. All rights reserved.

1/f Fluctuations in ion implanted metal semiconductor contacts

International Nuclear Information System (INIS)

Stojanovic, M.; Marjanovic, N.; Radojevic, B.

1998-01-01

Ion implanted Metal-Semiconductor contacts is the most widely used structures in electrical devices. Weather complete devices or some parts are of interest, properties of metal-semiconductor junction strongly influence the quality and external characteristic of electronic devices. That is the reason why special attention is paid to the investigation of factor (noise for example) that could influence given junction. Low frequency 1/f fluctuations (noise) are constantly present in metal-semiconductor junction, so measurement of their level as well as the dependence on factors such as temperature must be taken into account in detailed analysis of electrical characteristics of devices such as contact, nuclear detector with surface barrier etc. In this paper we present the results of low frequency noise level measurements on TiN-Ti-Si structures produced by As + ion implantation. (author)

Assembling Metal Ions Induced Cyanide-Bridged Heterometallic 1D and Ion-Pair Complexes: Synthesis, Crystal Structures and Magnetic Properties

Energy Technology Data Exchange (ETDEWEB)

Kong, Lingqian [Liaocheng Univ., Liaocheng (China); Zhao, Zengdian; Chen, Kexun; Wang, Ping; Zhang, Daopeng [Shandong Univ. of Technology, Zibo (China)

2013-07-15

We obtained a heterobimetallic one-dimensional cyanide-bridged Mn(II)-Ni(II) complex and an Co(III)-Ni(II) ion-pair complex with [Ni(CN){sub 4}]{sup 2-} as building block and M(II)-phenanthroline (M = Mn, Co) compounds as assembling segment. The different structural types of complexes 1 and 2 indicate that the property of the metal ions the assembling segment contained have obvious influence on the structure of the cyanide-bridged complex. Investigation over the magnetic properties of complex 1 reveals an overall weak antiferromagnetic coupling between the adjacent Mn(II) ions bridged by the antiferromagnetic [-NC-Ni-CN-] unit. Among of all the molecular magnetism systems, for the well known reasons, cyanide-containing complexes have been widely employed as bridges to assemble homo/hetero-metallic molecular magnetic materials by using the cyanide bridge transferring magnetic coupling between the neighboring paramagnetic ions, in whichsome showed interesting magnetic properties, such as high-Tc magnets, spin crossover materials, single-molecule magnets (SMMs) and single-chain magnets (SCMs)

Comparison of electrochemical performances of olivine NaFePO4 in sodium-ion batteries and olivine LiFePO4 in lithium-ion batteries.

Science.gov (United States)

Zhu, Yujie; Xu, Yunhua; Liu, Yihang; Luo, Chao; Wang, Chunsheng

2013-01-21

Carbon-coated olivine NaFePO(4) (C-NaFePO(4)) spherical particles with a uniform diameter of ∼80 nm are obtained by chemical delithiation and subsequent electrochemical sodiation of carbon-coated olivine LiFePO(4) (C-LiFePO(4)), which is synthesized by a solvothermal method. The C-NaFePO(4) electrodes are identical (particle size, particle size distribution, surface coating, and active material loading, etc.) to C-LiFePO(4) except that Li ions in C-LiFePO(4) are replaced by Na ions, making them ideal for comparison of thermodynamics and kinetics between C-NaFePO(4) cathode in sodium-ion (Na-ion) batteries and C-LiFePO(4) in lithium-ion (Li-ion) batteries. In this paper, the equilibrium potentials, reaction resistances, and diffusion coefficient of Na in C-NaFePO(4) are systematically investigated by using the galvanostatic intermittent titration technique (GITT), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and compared to those of the well-known LiFePO(4) cathodes in Li-ion batteries. Due to the lower diffusion coefficient of Na-ion and higher contact and charge transfer resistances in NaFePO(4) cathodes, the rate performance of C-NaFePO(4) in Na-ion batteries is much worse than that of C-LiFePO(4) in Li-ion batteries. However, the cycling stability of C-NaFePO(4) is almost comparable to C-LiFePO(4) by retaining 90% of its capacity even after 100 charge-discharge cycles at a charge-discharge rate of 0.1 C.

Solvent extraction of anionic chelate complexes of lanthanum(III), europium(III), lutetium(III), scandium(III), and indium(III) with 2-thenoyltrifluoroacetone as ion-pairs with tetrabutylammonium ions

International Nuclear Information System (INIS)

Noro, Junji; Sekine, Tatsuya.

1992-01-01

The solvent extraction of lanthanum(III), europium(III), lutetium(III), scandium(III), and indium(III) in 0.1 mol dm -3 sodium nitrate solutions with 2-thenoyltrifluoroacetone (Htta) in the absence and presence of tetrabutylammonium ions (tba + ) into carbon tetrachloride was measured. The extraction of lanthanum(III), europium(III), and lutetium(III) was greatly enhanced by the addition of tba + ; this could be explained in terms of the extraction of a ternary complex, M(tta) 4 - tba + . However, the extractions of scandium(III) and indium(III) were nearly the same when tba + was added. The data were treated on the basis of the formation equilibrium of the ternary complex from the neutral chelate, M(tta) 3 , with the extracted ion-pairs of the reagents, tta - tba + , in the organic phase. It was concluded that the degree of association of M(tta) 3 with the ion-pair, tta - tba + , is greater in the order La(tta) 3 ≅ Eu(tta) 3 > Lu(tta) 3 , or that the stability of the ternary complex in the organic phase is higher in the order La(tta) 4 - tba + ≅ Eu(tta) 4 - tba + > Lu(tta) 4 - tba + . This is similar to those of adduct metal chelates of Htta with tributylphosphate (TBP) in synergistic extraction systems. (author)

Automated Potentiometric Titrations in KCl/Water-Saturated Octanol: Method for Quantifying Factors Influencing Ion-Pair Partitioning

Science.gov (United States)

2009-01-01

The knowledge base of factors influencing ion pair partitioning is very sparse, primarily because of the difficulty in determining accurate log PI values of desirable low molecular weight (MW) reference compounds. We have developed a potentiometric titration procedure in KCl/water-saturated octanol that provides a link to log PI through the thermodynamic cycle of ionization and partitioning. These titrations have the advantage of being independent of the magnitude of log P, while maintaining a reproducibility of a few hundredths of a log P in the calculated difference between log P neutral and log P ion pair (diff (log PN − I)). Simple model compounds can be used. The titration procedure is described in detail, along with a program for calculating pKa′′ values incorporating the ionization of water in octanol. Hydrogen bonding and steric factors have a greater influence on ion pairs than they do on neutral species, yet these factors are missing from current programs used to calculate log PI and log D. In contrast to the common assumption that diff (log PN − I) is the same for all amines, they can actually vary more than 3 log units, as in our examples. A major factor affecting log PI is the ability of water and the counterion to approach the charge center. Bulky substituents near the charge center have a negative influence on log PI. On the other hand, hydrogen bonding groups near the charge center have the opposite effect by lowering the free energy of the ion pair. The use of this titration method to determine substituent ion pair stabilization values (IPS) should bring about more accurate log D calculations and encourage species-specific QSAR involving log DN and log DI. This work also brings attention to the fascinating world of nature’s highly stabilized ion pairs. PMID:19265385

Automated potentiometric titrations in KCl/water-saturated octanol: method for quantifying factors influencing ion-pair partitioning.

Science.gov (United States)

Scherrer, Robert A; Donovan, Stephen F

2009-04-01

The knowledge base of factors influencing ion pair partitioning is very sparse, primarily because of the difficulty in determining accurate log P(I) values of desirable low molecular weight (MW) reference compounds. We have developed a potentiometric titration procedure in KCl/water-saturated octanol that provides a link to log P(I) through the thermodynamic cycle of ionization and partitioning. These titrations have the advantage of being independent of the magnitude of log P, while maintaining a reproducibility of a few hundredths of a log P in the calculated difference between log P neutral and log P ion pair (diff (log P(N - I))). Simple model compounds can be used. The titration procedure is described in detail, along with a program for calculating pK(a)'' values incorporating the ionization of water in octanol. Hydrogen bonding and steric factors have a greater influence on ion pairs than they do on neutral species, yet these factors are missing from current programs used to calculate log P(I) and log D. In contrast to the common assumption that diff (log P(N - I)) is the same for all amines, they can actually vary more than 3 log units, as in our examples. A major factor affecting log P(I) is the ability of water and the counterion to approach the charge center. Bulky substituents near the charge center have a negative influence on log P(I). On the other hand, hydrogen bonding groups near the charge center have the opposite effect by lowering the free energy of the ion pair. The use of this titration method to determine substituent ion pair stabilization values (IPS) should bring about more accurate log D calculations and encourage species-specific QSAR involving log D(N) and log D(I). This work also brings attention to the fascinating world of nature's highly stabilized ion pairs.

Electron-positron pair production in ultrarelativistic atomic collisions: 6.4 TeV S16+ with Au, Pd and Al

International Nuclear Information System (INIS)

Datz, S.; Vane, C.R.; Dittner, P.F.; Krause, H.F.; Schuch, R.; Gao, H.; Hutton, R.

1994-01-01

Angular and momentum distributions have been measured for electron-positron pairs created in peripheral collisions of 6.4 TeV bare sulfur ions with thin targets of Al, Pd, and Au. Singly- and doubly-differential cross sections are presented for 1--17 MeV/c electrons and positrons detected independently and in coincidence as pairs. Various physical parameters are deduced from the coincident electron and positron data, including probability distributions for the pair transverse momentum, the pair total energy, and the positron fraction of the pair energy

Ion implantation into amorphous Si layers to form carrier-selective contacts for Si solar cells

International Nuclear Information System (INIS)

Feldmann, Frank; Mueller, Ralph; Reichel, Christian; Hermle, Martin

2014-01-01

This paper reports our findings on the boron and phosphorus doping of very thin amorphous silicon layers by low energy ion implantation. These doped layers are implemented into a so-called tunnel oxide passivated contact structure for Si solar cells. They act as carrier-selective contacts and, thereby, lead to a significant reduction of the cell's recombination current. In this paper we address the influence of ion energy and ion dose in conjunction with the obligatory high-temperature anneal needed for the realization of the passivation quality of the carrier-selective contacts. The good results on the phosphorus-doped (implied V oc = 725 mV) and boron-doped passivated contacts (iV oc = 694 mV) open a promising route to a simplified interdigitated back contact (IBC) solar cell featuring passivated contacts. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Linear and nonlinear low-frequency electrostatic waves in a nonuniform pair-ion-dust magnetoplasma

International Nuclear Information System (INIS)

Saleem, H; Shukla, P K; Eliasson, B

2008-01-01

Linear and nonlinear properties of the low-frequency (in comparison with the ion gyrofrequency) electrostatic oscillations in pair-ion-dust magnetoplasma are presented. In the linear limit, the Shukla-Varma mode is coupled with the ion oscillations while the nonlinearly coupled modes appear in the form of a dipolar or a monopolar vortex

Analysis of catecholamines in urine by unique LC/MS suitable ion-pairing chromatography.

Science.gov (United States)

Bergmann, Marianne L; Sadjadi, Seyed; Schmedes, Anne

2017-07-01

The catecholamines, epinephrine (E) and norepinephrine (NE) are small polar, hydrophilic molecules, posing significant challenges to liquid chromatography - tandem mass spectrometry (LC-MS/MS) method development. Specifically, these compounds show little retention on conventional reversed-phase liquid chromatography columns. This work presents development and validation of an LC-MS/MS method for determining catecholamines in urine, based on a new approach to ion-pairing chromatography (IPC), in which the ion-pairing reagent (IPR), 1-Heptane Sulfonic Acid (HSA), is added to the extracted samples instead of the mobile phases. A Hamilton STARlet workstation carried out the solid phase extraction of urine samples. The extracted samples were diluted with 60mmol/L HSA and injected on a Kinetex core-shell biphenyl column with conventional LC-MS/MS suitable mobile phases. Chromatographic separation of E and NE was achieved successfully with very stable retention times (RT). In 484 injections, the RTs were steady with a CV of less than ±4%. Furthermore, HSA was separated from E and NE, allowing HSA to be diverted to waste instead of entering the mass spectrometer ion chamber. The method was validated with good analytical performance, and even though the analysis for urinary catecholamines is increasingly being replaced by plasma free metanephrines in diagnosing pheochromocytomas, this work represents the application of a new analytical technique that can be transferred to other small polar molecules, that are difficult to chromatograph on traditional reversed phase columns. Copyright © 2017 Elsevier B.V. All rights reserved.

An investigation on the physicochemical properties of the nanostructured [(4-X)PMAT][N(CN)2] ion pairs as energetic and tunable aryl alkyl amino tetrazolium based ionic liquids

Science.gov (United States)

Khalili, Behzad; Rimaz, Mehdi

2017-06-01

In this study the different class of tunable and high nitrogen content ionic liquids termed TAMATILs (Tunable Aryl Methyl Amino Tetrazolium based Ionic Liquids) were designed. The physicochemical properties of the nanostructured TAMATILs composed of para substituted phenyl methyl amino tetrazolium cations [(4-X)PMAT]+ (X = H, Me, OCH3, OH, NH2, NO2, F, CN, CHO, CF3, COMe and CO2Me) and dicyanimide anion [N(CN)2]- were fully investigated using M06-2X functional in conjunction with the 6-311++G(2d,2p) basis set. For all of the studied nanostructured ILs the structural parameters, interaction energy, cation's enthalpy of formation, natural charges, charge transfer values and topological properties were calculated and discussed. The substituent effect on the interaction energy and physicochemical properties also is taking into account. The results showed that the strength of interaction has a linear correlation with electron content of the phenyl ring in a way the substituents with electron withdrawing effects lead to make more stable ion pairs with higher interaction energies. Some of the main physical properties of ILs such as surface tension, melting point, critical-point temperature, electrochemical stability and conductivity are discussed and estimated for studying ion pairs using quantum chemical computationally obtained thermochemical data. Finally the enthalpy and Gibbs free energy of formation for twelve nanostructured individual cations with the general formula of [(4-X)PMAT]+ (X = 4-H, 4-Me, 4-OMe, 4-OH, 4-NH2, 4-NO2, 4-F, 4-CN, 4-CHO, 4-CF3, 4-COMe and 4-CO2Me) are calculated.

Simple fabrication of back contact heterojunction solar cells by plasma ion implantation

Science.gov (United States)

Koyama, Koichi; Yamaguchi, Noboru; Hironiwa, Daisuke; Suzuki, Hideo; Ohdaira, Keisuke; Matsumura, Hideki

2017-08-01

A back-contact amorphous-silicon (a-Si)/crystalline silicon (c-Si) heterojunction is one of the most promising structures for high-efficiency solar cells. However, the patterning of back-contact electrodes causes the increase in fabrication cost. Thus, to simplify the fabrication of back-contact cells, we attempted to form p-a-Si/i-a-Si/c-Si and n-a-Si/i-a-Si/c-Si regions by the conversion of a patterned area of p-a-Si/i-a-Si/c-Si to n-a-Si/i-a-Si/c-Si by plasma ion implantation. It is revealed that the conversion of the conduction type can be realized by the plasma ion implantation of phosphorus (P) atoms into p-a-Si/i-a-Si/c-Si regions, and also that the quality of passivation can be kept sufficiently high, the same as that before ion implantation, when the samples are annealed at around 250 °C and also when the energy and dose of ion implantation are appropriately chosen for fitting to a-Si layer thickness and bulk c-Si carrier density.

IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts

NARCIS (Netherlands)

Yang, G.; Ingenito, A.; Isabella, O.; Zeman, M.

2016-01-01

Ion-implanted poly-crystalline silicon (poly-Si), in combination with a tunnel oxide layer, is investigated as a carrier-selective passivating contact in c-Si solar cells based on an interdigitated back contact (IBC) architecture. The optimized poly-Si passivating contacts enable low interface

Theoretical Probing of Weak Anion-Cation Interactions in Certain Pyridinium-Based Ionic Liquid Ion Pairs and the Application of Molecular Electrostatic Potential in Their Ionic Crystal Density Determination: A Comparative Study Using Density Functional Approach.

Science.gov (United States)

Joseph, Aswathy; Thomas, Vibin Ipe; Żyła, Gaweł; Padmanabhan, A S; Mathew, Suresh

2018-01-11

A comprehensive study on the structure, nature of interaction, and properties of six ionic pairs of 1-butylpyridinium and 1-butyl-4-methylpyridinium cations in combination with tetrafluoroborate (BF 4 - ), chloride (Cl - ), and bromide (Br - ) anions have been carried out using density functional theory (DFT). The anion-cation interaction energy (ΔE int ), thermochemistry values, theoretical band gap, molecular orbital energy order, DFT-based chemical activity descriptors [chemical potential (μ), chemical hardness (η), and electrophilicity index (ω)], and distribution of density of states (DOS) of these ion pairs were investigated. The ascendancy of the -CH 3 substituent at the fourth position of the 1-butylpyridinium cation ring on the values of ΔE int , theoretical band gap and chemical activity descriptors was evaluated. The ΔE int values were negative for all six ion pairs and were highest for Cl - containing ion pairs. The theoretical band gap value after -CH 3 substitution increased from 3.78 to 3.96 eV (for Cl - ) and from 2.74 to 2.88 eV (for Br - ) and decreased from 4.9 to 4.89 eV (for BF 4 - ). Ion pairs of BF 4 - were more susceptible to charge transfer processes as inferred from their significantly high η values and comparatively small difference in ω value after -CH 3 substitution. The change in η and μ values due to the -CH 3 substituent is negligibly small in all cases except for the ion pairs of Cl - . Critical-point (CP) analyses were carried out to investigate the AIM topological parameters at the interionic bond critical points (BCPs). The RDG isosurface analysis indicated that the anion-cation interaction was dominated by strong H cat ···X ani and C cat ···X ani interactions in ion pairs of Cl - and Br - whereas a weak van der Waal's effect dominated in ion pairs of BF 4 - . The molecular electrostatic potential (MESP)-based parameter ΔΔV min measuring the anion-cation interaction strength showed a good linear correlation with

Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis.

Science.gov (United States)

Yang, Haiming; An, Baigang; Wang, Shaoyan; Li, Lixiang; Jin, Wenjie; Li, Lihua

2013-06-01

Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4-PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.

Rapid determination of trace level copper in tea infusion samples by solid contact ion selective electrode

Directory of Open Access Journals (Sweden)

Aysenur Birinci

2016-07-01

Full Text Available A new solid contact copper selective electrode with a poly (vinyl chloride (PVC membrane consisting of o-xylylenebis(N,N-diisobutyldithiocarbamate as ionophore has been prepared. The main novelties of constructed ion selective electrode concept are the enhanced robustness, cheapness, and fastness due to the use of solid contacts. The electrode exhibits a rapid (< 10 seconds and near-Nernstian response to Cu2+ activity from 10−1 to 10−6 mol/L at the pH range of 4.0–6.0. No serious interference from common ions was found. The electrode characterizes by high potential stability, reproducibility, and full repeatability. The electrode was used as an indicator electrode in potentiometric titration of Cu(II ions with EDTA and for the direct assay of tea infusion samples by means of the calibration graph technique. The results compared favorably with those obtained by the atomic absorption spectroscopy (AAS.

Utilize the spectral line pair of the same ionized state ion to measure the ion temperature of tokamak plasma

International Nuclear Information System (INIS)

Lin Xiaodong

2000-01-01

Making use of a Fabry-Perot interferometer driven by a piezoelectric crystal and selecting the suitable separation of plates, the ion temperature is defined by measuring the superimposed profile of the spectral line pair of the same ionized state ions in Tokamak. The advantage of this method is to higher spectral resolution and wider spectral range select

Vinylimidazole-Based Asymmetric Ion Pair Comonomers: Synthesis, Polymerization Studies and Formation of Ionically Crosslinked PMMA

NARCIS (Netherlands)

Jana, S.; Vasantha, V.A.; Stubbs, L.P.; Parthiban, A.; Vancso, Gyula J.

2013-01-01

Vinylimidazole-based asymmetric ion pair comonomers (IPCs) which are free from nonpolymerizable counter ions have been synthesized, characterized and polymerized by free radical polymerization (FRP), atom transfer radical polymerization (ATRP), and reversible addition-fragmentation chain transfer

4.4 V lithium-ion polymer batteries with a chemical stable gel electrolyte

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Takeru; Hara, Tomitaro; Akashi, Hiroyuki [Sony Corporation, Energy Business Group, R and D Division, 1-1 Aza, Shimosugishita, Takakura, Hiwada-machi, Koriyama-shi, Fukushima 963-0531 (Japan); Segawa, Ken; Honda, Kazuo [Sony Energy Device Corporation, PB Technology Center, 1-1 Aza, Shimosugishita, Takakura, Hiwada-machi, Koriyama-shi, Fukushima 963-0531 (Japan)

2007-12-06

We tested 4.2 V Li-ion polymer batteries (LIPB) with physical gel electrolyte, poly(vinylidene fluoride) (PVDF), 4.4 V LIPB and 4.4 V Li-ion batteries (LIB) with a liquid electrolyte. The discharge capacity of the 4.4 V LIPB reached 520 Wh l{sup -1} which was 9% higher than that of the 4.2 V LIPB. The 4.4 V LIPB had a high capacity retention ratio of 91.4% at 3 C because of the excellent ion conductivity of the PVDF gel. The capacity retention ratio of the 4.4 V LIPB was 82% after 500 cycles, which is comparable to those of some commercial LIBs. The 4.4 V LIPB retained its original thickness even after many cycles and after being stored at 90 C, whereas the 4.4 V LIB swelled by over 20%. Peaks in the FT-IR spectrum of the discolored separator in the 4.4 V LIB after storage were assigned to C=C double bonds, suggesting that the separator in direct contact with the 4.4 V cathode had been oxidized. The PVDF gel electrolyte not only had a high ionic conductivity but also completely suppressed oxidation. The 4.4 V LIPB with PVDF gel electrolyte has properties suitable for practical cells, namely, high energy density, high permanence and it is safe to use. (author)

Soft-contact conductive carbon enabling depolarization of LiFePO4 cathodes to enhance both capacity and rate performances of lithium ion batteries

Science.gov (United States)

Ren, Wenju; Wang, Kai; Yang, Jinlong; Tan, Rui; Hu, Jiangtao; Guo, Hua; Duan, Yandong; Zheng, Jiaxin; Lin, Yuan; Pan, Feng

2016-11-01

Conductive nanocarbons generally are used as the electronic conductive additives to contact with active materials to generate conductive network for electrodes of commercial Li-ion batteries (LIBs). A typical of LiFePO4 (LFP), which has been widely used as cathode material for LIBs with low electronic conductivity, needs higher quantity of conductive nanocarbons to enhance the performance for cathode electrodes. In this work, we systematically studied three types of conductive nanocarbons and related performances in the LFP electrodes, and classify them as hard/soft-contact conductive carbon (named as H/SCC), respectively, according to their crystallite size, surface graphite-defect, specific surface area and porous structure, in which SCC can generate much larger contact area with active nano-particles of cathode materials than that of HCC. It is found that LFP nanocrystals wrapped in SCC networks perform significantly enhanced both capacity and rate performance than that in HCC. Combined experiments with multiphysics simulation, the mechanism is that LFP nanoparticles embedded in SCC with large contact area enable to generate higher depolarized effects with a relatively uniform current density vector (is) and lithium flux vector (NLi) than that in HCC. This discovery will guide us to how to design LIBs by selective using conductive carbon for high-performance LIBs.

Coupled channel calculations for electron-positron pair production in collisions of heavy ions

CERN Document Server

Gail, M; Scheid, W

2003-01-01

Coupled channel calculations are performed for electron-positron pair production in relativistic collisions of heavy ions. For this purpose the wavefunction is expanded into different types of basis sets consisting of atomic wavefunctions centred around the projectile ion only and around both of the colliding nuclei. The results are compared with experimental data from Belkacem et al (1997 Phys. Rev. A 56 2807).

Adsorption of ion pairs onto graphene flakes and impacts of counterions during the adsorption processes

Science.gov (United States)

Zhu, Chang; Yun, Jiena; Wang, Qian; Yang, Gang

2018-03-01

Although cations and anions are two integral constituents for all electrolytes, adsorption of ion pairs onto carbonaceous materials gains obviously less attention than adsorption of only cations or anions. Here DFT calculations are employed finding that four adsorption configurations emerge for KI onto graphene flakes (GF) instead of three for the other ion pairs. Reservation of ionic bonds is critical to their stabilities, and the bilateral configurations, where GFs couple with both cations and anions, are disfavored due to rupture of ionic bonds. Relative stabilities of two vertical configurations can be regulated and even reversed through edge-functionalization. Surprisingly, the horizontal adsorption configurations, which are global energy minima as long as present, are non-existent for a majority of ion pairs, and their existence or not is determined by the adsorption differences between halide ions and alkali ions (△Ead). Counterions effects for both cations and anions increase with the atomic electronegativities and cations correspond to stronger counterion effects; e.g., Li+ added on the other side of GFs promotes the adsorption of F- more pronouncedly than edge-functionalization. Mechanisms of electron transfers are also discussed, and three alteration patterns by counterions are observed for each type of adsorption configurations. Furthermore, addition of counterions causes band gaps to vary within a wider range that may be useful to design electronic devices.

Large aperture contact ionized Cs+1 ion source for an induction linac

International Nuclear Information System (INIS)

Abbott, S.; Chupp, W.; Faltens, A.; Herrmannsfeldt, W.; Hoyer, E.; Keefe, D.; Kim, C.H.; Rosenblum, S.; Shiloh, J.

1979-03-01

A 500 KeV one-ampere Cs +1 ion beam has been generated by contact ionization with a 30 cm dia. iridium hot plate. Reproducibility of space charge limited ion current wave forms at repetition rates up to 1 Hz has been verified. The beam is characterized to be very bright and suitable as an ion source for the induction linac based heavy ion fusion scheme. The hot anode plate was found to be reliable and self-cleaning during the operation

INFRARED AND RAMAN SPECTROSCOPIC STUDY OF ION ...

African Journals Online (AJOL)

Infrared and Raman spectroscopy techniques have been used to study the ionic interactions of strontium(II) and barium(II) with thiocyanate ion in liquid ammonia. A number of bands were observed in both n (CN) and n (CS) regions of infrared and Raman spectra and these were assigned to 1:1 contact ion pair, ...

Carbonic acid ionization and the stability of sodium bicarbonate and carbonate ion pairs to 200 °C - A potentiometric and spectrophotometric study

Science.gov (United States)

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2013-11-01

Carbonic acid ionization and sodium bicarbonate and carbonate ion pair formation constants have been experimentally determined in dilute hydrothermal solutions to 200 °C. Two experimental approaches were applied, potentiometric acid-base titrations at 10-60 °C and spectrophotometric pH measurements using the pH indicators, 2-napthol and 4-nitrophenol, at 25-200 °C. At a given temperature, the first and second ionization constants of carbonic acid (K1, K2) and the ion pair formation constants for NaHCO(aq)(K) and NaCO3-(aq)(K) were simultaneously fitted to the data. Results of this study compare well with previously determined values of K1 and K2. The NaHCO(aq) and NaCO3-(aq) ion pair formation constants vary between 25 and 200 °C having values of logK=-0.18 to 0.58 and logK=1.01 to 2.21, respectively. These ion pairs are weak at low-temperatures but become increasingly important with increasing temperature under neutral to alkaline conditions in moderately dilute to concentrated NaCl solutions, with NaCO3-(aq) predominating over CO32-(aq) in ⩾0.1 M NaCl solution at temperatures above 100 °C. The results demonstrate that NaCl cannot be considered as an inert (non-complexing) electrolyte in aqueous carbon dioxide containing solutions at elevated temperatures.

1/4-pinched contact sphere theorem

DEFF Research Database (Denmark)

Ge, Jian; Huang, Yang

2016-01-01

Given a closed contact 3-manifold with a compatible Riemannian metric, we show that if the sectional curvature is 1/4-pinched, then the contact structure is universally tight. This result improves the Contact Sphere Theorem in [EKM12], where a 4/9-pinching constant was imposed. Some tightness...

Investigation on the ion pair amphiphiles and their in vitro release of amantadine drug based on PLGA–PEG–PLGA gel

International Nuclear Information System (INIS)

Yang, Xiaoxia; Ji, Xiaoqing; Shi, Chunhuan; Liu, Jing; Wang, Haiyang; Luan, Yuxia

2014-01-01

The amantadine drug and oleic acid surfactant are used to form amantadine-based ion pair amphiphiles based on proton transfer reaction between the drug and the surfactant molecules. The ion pair amphiphiles are characterized by 1 H-nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray diffraction. Self-assembly properties of amantadine-based ion pair amphiphiles are studied by surface tension determination, transmission electron microscopy, zeta potential, and dynamic light scattering. The aggregation behavior studies indicate that the as-prepared ion pair amphiphiles can self-assemble into vesicles with the size of 200–300 nm in aqueous solution. The drug release results show that the amantadine release rate could be well controlled by incorporating the amantadine-based ion pair vesicles in poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA–PEG–PLGA) copolymer hydrogel. The drug release from the AT–OA vesicle-loaded PLGA–PEG–PLGA hydrogel is significantly inhibited in comparison with the AT-loaded PLGA–PEG–PLGA hydrogel. The present work thus demonstrates that the vesicle-loaded hydrogel is a good candidate for the drug delivery system with long-term controlled drug release behavior

Assessment of effect of Yb3+ ion pairs on a highly Yb-doped double-clad fibre laser

Science.gov (United States)

Vallés, J. A.; Martín, J. C.; Berdejo, V.; Cases, R.; Álvarez, J. M.; Rebolledo, M. Á.

2018-03-01

Using a previously validated characterization method based on the careful measurement of the characteristic parameters and fluorescence emission spectra of a highly Yb-doped double-clad fibre, we evaluate the contribution of ion pair induced processes to the output power of a double-clad Yb-doped fibre ring laser. This contribution is proved to be insignificant, contrary to analysis by other authors, who overestimate the role of ion pairs.

Measurements of Coulomb Cross Section for Production of Direct Electron-pairs by High Energy Ions at the CERN SPS

CERN Multimedia

2002-01-01

QED predicts copious direct electron pair production by ultrarelativistic heavy nuclei in a high Z medium such as nuclear emulsion. First order QED calculations (combined screening and non-screening) for this process show that 1000@+32 electron pairs above 100~keV energy) should be emitted for a total |1|6O track length of 10.9~m in nuclear emulsion at 200~GeV/AMU. Emulsion exposures with oxygen (and other nuclei if available) at 60 and 200~GeV/AMU will be used to calibrate the energy dependent cross section @s~@j~(1n~E)|2|-|3, whose exponent depends on atomic screening. The oxygen tracks in the developed emulsions will be scanned with a microscope, and the number of direct electron pairs will be counted for individual tracks. The exposed stacks will contain sufficient emulsion (and CR39 plastic to check for possible interactions) that adequate path length will be available for exposures to @$>$~10|4~ions at each energy and ion species. \\\\ \\\\ If the absolute value of this cross section is confirmed as large a...

Preconcentration of ultra-trace amounts of iron and antimony using ion pair solid phase extraction with modified multi-walled carbon nanotubes

International Nuclear Information System (INIS)

Fazelirad, Hamid; Taher, Mohammad Ali

2014-01-01

Ion pair solid phase extraction was applied to the simultaneous preconcentration of iron and antimony. The ion pairs consisting of FeCl 4 − or SbCl 4 − anions and the benzyldimethyltetradecyl ammonium cation were formed on the surface of multi-walled carbon nanotubes, then eluted with nitric acid, and the elements finally quantified by ETAAS. The adsorption capacities of the impregnated MWCNTs are 9.2 mg g −1 for iron and 27.5 mg g −1 for antimony. The following analytical figures of merit were determined for iron and antimony, respectively: Enrichment factors of 210 and 230, assay precisions of ±5.3 % and ±4.8 %, linear calibration plots from 0.7 to 9.4 and 13.0 to 190 ng L −1 , and detection limits of 0.17 and 3.5 ng L −1 . The method was applied to the determination of iron and antimony in human hair, synthetic sample, and to the certified reference materials gold ore (MA-1b) and trace elements in water (SRM 1643d). (author)

Ionic pairing in binary liquids of charged hard spheres with non-additive diameters

International Nuclear Information System (INIS)

Pastore, G.; Giaquinta, P.V.; Thakur, J.S.; Tosi, M.P.

1985-07-01

We examine types of short range order that arise in binary liquids from a combination of Coulombic interactions and non-additivity of excluded volumes, the initial motivation being observations of complex formation by hydrated ions in concentrated aqueous solutions. The model is a fluid of charged hard spheres with contact distances σsub(+-)not=1/2(σsub(++)+σsub(--)), its structural functions being evaluated in the mean spherical approximation and in the hypernetted chain approximation. Cation-anion pairing is clearly seen in the calculated structural functions for negative deviations from additivity (σsub(+-) σsub(++)=σsub(--)) favour long-wavelength concentration fluctuations and demixing in a neutral mixture: these are suppressed by Coulombic interactions in favour of microscopic intermixing of the two species in the local liquid structure, up to like-ion pairing. Contact is made with diffraction from concentrated aqueous solutions of cadmium sulphate and other instances of possible applicability of the model are pointed out. (author)

Role of ion-pair states in the predissociation dynamics of Rydberg states of molecular iodine.

Science.gov (United States)

von Vangerow, J; Bogomolov, A S; Dozmorov, N V; Schomas, D; Stienkemeier, F; Baklanov, A V; Mudrich, M

2016-07-28

Using femtosecond pump-probe ion imaging spectroscopy, we establish the key role of I(+) + I(-) ion-pair (IP) states in the predissociation dynamics of molecular iodine I2 excited to Rydberg states. Two-photon excitation of Rydberg states lying above the lowest IP state dissociation threshold (1st tier) is found to be followed by direct parallel transitions into IP states of the 1st tier asymptotically correlating to a pair of I ions in their lowest states I(+)((3)P2) + I(-)((1)S0), of the 2nd tier correlating to I(+)((3)P0) + I(-)((1)S0), and of the 3rd tier correlating to I(+)((1)D2) + I(-)((1)S0). Predissociation via the 1st tier proceeds presumably with a delay of 1.6-1.7 ps which is close to the vibrational period in the 3rd tier state (3rd tier-mediated process). The 2nd tier IP state is concluded to be the main precursor for predissociation via lower lying Rydberg states proceeding with a characteristic time of 7-8 ps and giving rise to Rydberg atoms I(5s(2)5p(4)6s(1)). The channel generating I((2)P3/2) + I((2)P1/2) atoms with total kinetic energy corresponding to one-photon excitation is found to proceed via a pump - dump mechanism with dramatic change of angular anisotropy of this channel as compared with earlier nanosecond experiments.

Multiple electromagnetic pair production in ultrarelativistic heavy ion collisions

International Nuclear Information System (INIS)

Best, C.

1992-04-01

The problem of the unitary violation in the pair production in ultrarelativistic heavy ion collisions was studied by a consideration of the field-theoretical foundations. The quantum electrodynamics in an external field were thereby reduced to a Dirac-sea model, the equivalence of which to the non-radiative QED resulted from the equality of the generating functionals. The latter can both be expressed explicitely by means of the complet set of the solutions of the Dirac equation in an external field. This method is based solely on the path-integral approach, which makes it possible to discriminate clearly between the physically given correlation functions and their generating functional at the one hand and at the other hand between the models constructed to their interpretation. From the model expression for the pair production amplitudes and multiplicities could be calculated, for which only the knowledge of the one-particle S matrix is necessary. For the calculation of the multiplicities different forms of the perturbation theory were discussed. Finally an impact-parameter dependent Weizsaecker-Williams approximation for the calculation of arbitrary two-photon graphs was constructed and applied to the given problem. The results indicate that at small distances very high pair multiplicities are to be expected. Finally a new approach to the pair production in an external field was discussed, which is not based on the canonical field theory, but on the formalism of the Wigner functions. (orig./HSI) [de

Synthesis of guanidinium–sulfonimide ion pairs: towards novel ionic liquid crystals

Directory of Open Access Journals (Sweden)

Martin Butschies

2013-06-01

Full Text Available The recently introduced concept of ionic liquid crystals (ILCs with complementary ion pairs, consisting of both, mesogenic cation and anion, was extended from guanidinium sulfonates to guanidinium sulfonimides. In this preliminary study, the synthesis and mesomorphic properties of selected derivatives were described, which provide the first example of an ILC with the sulfonimide anion directly attached to the mesogenic unit.

Analysis of a variety of inorganic and organic additives in food products by ion-pairing liquid chromatography coupled to high-resolution mass spectrometry.

Science.gov (United States)

Kaufmann, Anton; Widmer, Mirjam; Maden, Kathryn; Butcher, Patrick; Walker, Stephan

2018-03-05

A reversed-phase ion-pairing chromatographic method was developed for the detection and quantification of inorganic and organic anionic food additives. A single-stage high-resolution mass spectrometer (orbitrap ion trap, Orbitrap) was used to detect the accurate masses of the unfragmented analyte ions. The developed ion-pairing chromatography method was based on a dibutylamine/hexafluoro-2-propanol buffer. Dibutylamine can be charged to serve as a chromatographic ion-pairing agent. This ensures sufficient retention of inorganic and organic anions. Yet, unlike quaternary amines, it can be de-charged in the electrospray to prevent the formation of neutral analyte ion-pairing agent adducts. This process is significantly facilitated by the added hexafluoro-2-propanol. This approach permits the sensitive detection and quantification of additives like nitrate and mono-, di-, and triphosphate as well as citric acid, a number of artificial sweeteners like cyclamate and aspartame, flavor enhancers like glutamate, and preservatives like sorbic acid. This is a major advantage, since the currently used analytical methods as utilized in food safety laboratories are only capable in monitoring a few compounds or a particular category of food additives. Graphical abstract Deptotonation of ion pair agent in the electrospray interface.

Investigation of Uranyl Nitrate Ion Pairs Complexed with Amide Ligands using Electrospray Ionization Ion Trap Mass Spectrometry and Density Functional Theory

International Nuclear Information System (INIS)

Groenewold, Gary S.; Dinescu, Adriana; Benson, Michael T.; Gresham, Garold L.; van Stipdonk, Michael J.

2011-01-01

Ion populations formed from electrospray of uranyl nitrate solutions containing different amides vary depending on ligand nucleophilicity and steric crowding at the metal center. The most abundant species were ion pair complexes having the general formula (UO2(NO3)(amide)n=2,3)+, and complexes containing the amide conjugate base, reduced uranyl UO2+, and a 2+ charge were also formed. The formamide experiment produced the greatest diversity of species that stems from weaker amide binding leading to dissociation and subsequent solvent coordination or metal reduction. Experiments using methyl formamide, dimethyl formamide, acetamide, and methyl acetamide produced ion pair and doubly charged complexes that were more abundant, and less abundant complexes containing solvent or reduced uranyl. This pattern is reversed in the dimethylacetamide experiment, which displayed reduced doubly charged complexes and augmented reduced uranyl complexes. DFT investigations of the tris-amide ion pair complexes showed that inter-ligand repulsion distorts the amide ligands out of the uranyl equatorial plane, and that complex stabilities do not increase with increasing amide nucleophilicity. Elimination of an amide ligand largely relieves the interligand repulsion, and the remaining amide ligands become closely aligned with the equatorial plane in the structures of the bis-amide ligands. The studies show that the phenomenological distribution of coordination complexes in a metal-ligand electrospray experiment is a function of both ligand nucleophilicity and interligand repulsion, and that the latter factor begins exerting influence even in the case of relatively small ligands like the substituted methyl-formamide and methyl-acetamide ligands.

Ex-reactor determination of thermal gap and contact conductance between uranium dioxide: zircaloy-4 interfaces. Stage I: low gas pressure

International Nuclear Information System (INIS)

Garnier, J.E.; Begej, S.

1979-04-01

A study of thermal gap and contact conductance between depleted uranium dioxide (UO 2 ) and Zircaloy-4 (Zr4) has been made utilizing two measurement apparatuses developed as part of this program. The Modified Pulse Design (MPD) apparatus is a transient technique employing a heat pulse (laser) and a signal detector to monitor the thermal energy transmitted through a UO 2 /Zr4 sample pair which are either physically separated or in contact. The Modified Longitudinal Design (MLD) apparatus is a steady-state technique based on a modified cylindrical column design with a self-guarding sample geometry. Description of the MPD and MLD apparatus, data acquisition, reduction and error analysis is presented along with information on specimen preparation, thermal property and surface characterization. A technique using an optical height gauge to determine the average mean-plane of separation between the simple pairs is also presented

A newly developed highly selective Zn2+-AcO- ion-pair sensor through partner preference: equal efficiency under solitary and colonial situation.

Science.gov (United States)

Karar, Monaj; Paul, Suvendu; Biswas, Bhaskar; Majumdar, Tapas; Mallick, Arabinda

2018-05-10

Unusual self-sorting of an ion-pair under highly crowded conditions driven by a synthesized intelligent molecule 2-((E)-(3-((E)-2-hydroxy-3-methoxybenzylideneamino)-2-hydroxypropyl imino)methyl)-6-methoxyphenol, hereafter HBP, is described. When a mixture of various metal salts was allowed to react with HBP, only a specific ion-pair ZnII/AcO- in the solution simultaneously reacted, resulting in high-fidelity ion-pair recognition of HBP. This phenomenon was evidenced by significant changes in the absorption spectra and huge enhancement in emission intensity of HBP. The property that one molecule preferring one particular cation-anion pair over others is a rare but interesting phenomenon. Thus, the potential to interact selectively with the targeted ion-pair resulting in the formation of a specific complex recognized HBP as a new class of molecule that might find future applications in real time and on-site monitoring and separation of new molecules.

Effects of ion strength and ion pairing on (plant-wide) modelling of anaerobic digestion processes

DEFF Research Database (Denmark)

Flores-Alsina, Xavier; Mbamba, Christian Kazadi; Solon, Kimberly

2014-01-01

the effects that an improved physico-chemical description will have on the predicted effluent quality (EQI) and operational cost (OCI) indices. The acid-base equilibria implemented in the Anaerobic Digestion Model No.1 (ADM1) are modified to account for non-ideal aqueous-phase chemistry. The model corrects......The objective of this study is to show the influence of ionic strength (as activity corrections) andion pairing on (plant-wide) modelling of anaerobic digestion processes in wastewater treatment plants(WWTPs). Using the Benchmark Simulation Model No. 2 (BSM2) as a case study, this paper presents...... for ionic strength via the Davies approach to consider chemical activities instead of molar concentrations. Also, a speciation sub-routine based on a multi-dimensional Newton-Raphson iteration method accounts for the formation of some of the ion pairs playing an important role in wastewater treatment...

Resonant ion-pair formation in electron collisions with HD+ and OH+

International Nuclear Information System (INIS)

Larson, Aa.; Djuric, N.; Zong, W.; Greene, C. H.; Orel, A. E.; Al-Khalili, A.; Derkatch, A. M.; Le Padellec, A.; Neau, A.; Rosen, S.

2000-01-01

Resonant ion-pair formation from collisions of electrons with electronic and vibronic ground-state diatomic molecular ions has been studied in the present work for HD + and OH + . The cross section for HD + has a magnitude of the order of 3x10 -19 cm 2 and is characterized by an energy threshold and 14 resolved peaks in the energy range up to 16 eV. A theoretical study confirms that the structures derive primarily from quantum interference of the multiple dissociation pathways. Measurements for OH + reveal that the cross section for H + and O - formation is lower than 10 -21 cm 2 at energies of 6 and 12 eV. (c) 2000 The American Physical Society

ComplexContact: a web server for inter-protein contact prediction using deep learning

KAUST Repository

Zeng, Hong; Wang, Sheng; Zhou, Tianming; Zhao, Feifeng; Li, Xiufeng; Wu, Qing; Xu, Jinbo

2018-01-01

ComplexContact (http://raptorx2.uchicago.edu/ComplexContact/) is a web server for sequence-based interfacial residue-residue contact prediction of a putative protein complex. Interfacial residue-residue contacts are critical for understanding how proteins form complex and interact at residue level. When receiving a pair of protein sequences, ComplexContact first searches for their sequence homologs and builds two paired multiple sequence alignments (MSA), then it applies co-evolution analysis and a CASP-winning deep learning (DL) method to predict interfacial contacts from paired MSAs and visualizes the prediction as an image. The DL method was originally developed for intra-protein contact prediction and performed the best in CASP12. Our large-scale experimental test further shows that ComplexContact greatly outperforms pure co-evolution methods for inter-protein contact prediction, regardless of the species.

ComplexContact: a web server for inter-protein contact prediction using deep learning

KAUST Repository

Zeng, Hong

2018-05-20

ComplexContact (http://raptorx2.uchicago.edu/ComplexContact/) is a web server for sequence-based interfacial residue-residue contact prediction of a putative protein complex. Interfacial residue-residue contacts are critical for understanding how proteins form complex and interact at residue level. When receiving a pair of protein sequences, ComplexContact first searches for their sequence homologs and builds two paired multiple sequence alignments (MSA), then it applies co-evolution analysis and a CASP-winning deep learning (DL) method to predict interfacial contacts from paired MSAs and visualizes the prediction as an image. The DL method was originally developed for intra-protein contact prediction and performed the best in CASP12. Our large-scale experimental test further shows that ComplexContact greatly outperforms pure co-evolution methods for inter-protein contact prediction, regardless of the species.

ComplexContact: a web server for inter-protein contact prediction using deep learning.

Science.gov (United States)

Zeng, Hong; Wang, Sheng; Zhou, Tianming; Zhao, Feifeng; Li, Xiufeng; Wu, Qing; Xu, Jinbo

2018-05-22

ComplexContact (http://raptorx2.uchicago.edu/ComplexContact/) is a web server for sequence-based interfacial residue-residue contact prediction of a putative protein complex. Interfacial residue-residue contacts are critical for understanding how proteins form complex and interact at residue level. When receiving a pair of protein sequences, ComplexContact first searches for their sequence homologs and builds two paired multiple sequence alignments (MSA), then it applies co-evolution analysis and a CASP-winning deep learning (DL) method to predict interfacial contacts from paired MSAs and visualizes the prediction as an image. The DL method was originally developed for intra-protein contact prediction and performed the best in CASP12. Our large-scale experimental test further shows that ComplexContact greatly outperforms pure co-evolution methods for inter-protein contact prediction, regardless of the species.

Ligandless, ion pair-based and ultrasound assisted emulsification solidified floating organic drop microextraction for simultaneous preconcentration of ultra-trace amounts of gold and thallium and determination by GFAAS.

Science.gov (United States)

Fazelirad, Hamid; Taher, Mohammad Ali

2013-01-15

In the present work, a new, simple and efficient method for simultaneous preconcentration of ultra-trace amounts of gold and thallium is developed using an ion pair based-ultrasound assisted emulsification-solidified floating organic drop microextraction procedure before graphite furnace atomic absorption spectrometry determination. This methodology was used to preconcentrate the ion pairs formed between AuCl(4)(-) and TlCl(4)(-) and [C(23)H(42)]N(+) in a microliter-range volume of 1-undecanol. Several factors affecting the microextraction efficiency, such as HCl volume, type and volume of extraction solvent, sonication time, sample volume, temperature, ionic strength and [C(23)H(42)]NCl volume were investigated and optimized. Under the optimized conditions, the enrichment factor of 441 and 443 and calibration graphs of 2.2-89 and 22.2-667 ng L(-1) for gold and thallium were obtained, respectively. The intra- and inter-day precision of ± 4.4 and ± 4.9% for Au and ± 4.8 and ± 5.4% for Tl were obtained. The detection limit was 0.66 ng L(-1) for Au and 4.67 ng L(-1) for Tl. The results show that the liquid-liquid pretreatment using ion pair forming, is sensitive, rapid, simple and safe method for the simultaneous preconcentration of gold and thallium. The method was successfully applied for determination of gold and thallium in natural water and hair samples. Copyright © 2012 Elsevier B.V. All rights reserved.

[Separation of p-aminobenzenearsonic acid and its oxide by ion-pair reversed-phase high performance liquid chromatography].

Science.gov (United States)

Kang, J; Ma, X; Meng, L; Ma, D

1999-05-01

To study the separation of p-aminobenzenearsonic acid (PABAA) and its oxide, p-aminophenylarsine oxide (PAPAO), both the absorption spectra were scanned at the wavelengths from 200 nm to 380 nm. PABAA had absorption maximum at 254 nm and PAPAO 258 nm. The effects of salt concentration, column temperature, methanol and ion-pair agent concentrations on the capacity factor were investigated. Compounds of high polarity showed almost no retention on reversed-phase column; as the volume fraction of the methanol decreased from 90% to 10%, the retention time of PABAA gradually increased with broad peak, and partially eluted when methanol volume fraction being below 20%. With temperature rising, the retention time of PABAA was decreased. But PABAA capacity factor can be increased by selecting an appropriate salt concentration for the mobile phase. The cetyltrimethyl and tetrabutyl ammonium ions were separately added as ion-pair agents to the mobile phase containing methanol in phosphate buffer of 10 mmol/L, the changes of retention time were observed. The mechanism of retention based on reversed phase ion-pair model is proposed. Besides, the retention behaviour is also influenced by size exclusion in stationary phase as well as polar interactions with residual silanol group on the silica surface.

Determination of adrenaline, noradrenaline and corticosterone in rodent blood by ion pair reversed phase UHPLC-MS/MS.

Science.gov (United States)

Bergh, Marianne Skov-Skov; Bogen, Inger Lise; Andersen, Jannike Mørch; Øiestad, Åse Marit Leere; Berg, Thomas

2018-01-01

A novel ion pair reversed phase ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous determination of the stress hormones adrenaline, noradrenaline and corticosterone in rodent blood was developed and fully validated. Separations were performed on an Acquity HSS T3 column (2.1mm i.d.×100mm, 1.8μm) with gradient elution and a runtime of 5.5min. The retention of adrenaline and noradrenaline was substantially increased by employing the ion pair reagent heptafluorobutyric acid (HFBA). Ion pair reagents are usually added to the mobile phase only, but we demonstrate for the first time that including HFBA to the sample reconstitution solvent as well, has a major impact on the chromatography of these compounds. The stability of adrenaline and corticosterone in rodent blood was investigated using the surrogate analytes adrenaline-d 3 and corticosterone-d 8 . The applicability of the described method was demonstrated by measuring the concentration of stress hormones in rodent blood samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Development of a new all solid contact Cs"+ ion selective electrode

International Nuclear Information System (INIS)

Ramanjaneyulu, P.S.; Abha Naveen Kumar; Sharma, M.K.

2017-01-01

Studies were carried out to develop all solid contact cesium ion selective electrode with 25,27-bis(1-octyloxy)calix[4]arene-crown-6 as an ionophore. Polyaniline (PANI), deposited on Pt electrode by electrochemical method, was used as a transducer. Three different types of electrodes were made with variation in thickness of PANI film and gold nanoparticles doped PANI as transducers. The best response was observed with ISE having Au nanoparticles doped PANI as a transducer. The optimised ISE gave Nernstian response in the range 10"-"7 to 10"-"2 M with the slope of 55.0 ± 0.6 mV/decade of Cs"+. The response of ISE for Cs"+ is fairly constant above the pH 4. The developed ISE was successfully employed to determine Cs"+ in simulated high level nuclear waste solutions and CsCl spiked tap water samples. (author)

Optical and electronic properties of polyvinyl alcohol doped with pairs of mixed valence metal ions

International Nuclear Information System (INIS)

Bulinski, Mircea; Kuncser, Victor; Plapcianu, Carmen; Krautwald, Stefan; Franke, Hilmar; Rotaru, P; Filoti, George

2004-01-01

The electronic mechanisms induced by the UV exposure of thin films of polyvinyl alcohol doped with pairs of mixed valence metal ions were studied in relation to their optical behaviour by Moessbauer spectroscopy and optical absorption. The results obtained definitely point to the role of each element from the pair in the electronic mechanism involved, with influence on the optical properties regarding applications in real-time holography and integrated optics

Simultaneous quantitative analysis of metabolites using ion-pair liquid chromatography-electrospray ionization mass spectrometry

NARCIS (Netherlands)

Coulier, L.; Bas, R.; Jespersen, S.; Verheij, E.; Werf, M.J. van der; Hankemeier, T.

2006-01-01

We have developed an analytical method, consisting of ion-pair liquid chromatography coupled to electrospray ionization mass spectrometry (IP-LC-ESI-MS), for the simultaneous quantitative analysis of several key classes of polar metabolites, like nucleotides, coenzyme A esters, sugar nucleotides,

Ni-Ni ion pair excitation transfer in D sub(3h) symmetry

International Nuclear Information System (INIS)

Terrile, M.C.

1990-01-01

The mechanisms contributing to excitation transfer are examined for Ni-Ni ion pairs in order to explain the delocalized character of electronic excitations observed in CsNiF sub(3). Using both first-and second-order perturbation theory and from symmetry arguments, the kind of interactions giving matrix elements between states connecting different sites for the position of the excitation are discussed. (author)

Assessing the Interplay between the Physicochemical Parameters of Ion-Pairing Reagents and the Analyte Sequence on the Electrospray Desorption Process for Oligonucleotides

Science.gov (United States)

Basiri, Babak; Murph, Mandi M.; Bartlett, Michael G.

2017-08-01

Alkylamines are widely used as ion-pairing agents during LC-MS of oligonucleotides. In addition to a better chromatographic separation, they also assist with the desorption of oligonucleotide ions into the gas phase, cause charge state reduction, and decrease cation adduction. However, the choice of such ion-pairing agents has considerable influence on the MS signal intensity of oligonucleotides as they can also cause significant ion suppression. Interestingly, optimal ion-pairing agents should be selected on a case by case basis as their choice is strongly influenced by the sequence of the oligonucleotide under investigation. Despite imposing major practical difficulties to analytical method development, such a highly variable system that responds very strongly to the nuances of the electrospray composition provides an excellent opportunity for a fundamental study of the electrospray ionization process. Our investigations using this system quantitatively revealed the major factors that influenced the ESI ionization efficiency of oligonucleotides. Parameters such as boiling point, proton affinity, partition coefficient, water solubility, and Henry's law constants for the ion-pairing reagents and the hydrophobic thymine content of the oligonucleotides were found to be the most significant contributors. Identification of these parameters also allowed for the development of a statistical predictive algorithm that can assist with the choice of an optimum IP agent for each particular oligonucleotide sequence. We believe that research in the field of oligonucleotide bioanalysis will significantly benefit from this algorithm (included in Supplementary Material) as it advocates for the use of lesser-known but more suitable ion-pair alternatives to TEA for many oligonucleotide sequences.

On the rogue wave propagation in ion pair superthermal plasma

Energy Technology Data Exchange (ETDEWEB)

Abdelwahed, H. G., E-mail: hgomaa-eg@yahoo.com, E-mail: hgomaa-eg@mans.edu.eg; Zahran, M. A. [Physics Department, College of Sciences and Humanities Studies Al-Kharj, Prince Sattam Bin Abdulaziz University, Al-Kharj (Saudi Arabia); Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt); El-Shewy, E. K., E-mail: emadshewy@yahoo.com; Elwakil, S. A. [Theoretical Physics Group, Physics Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

2016-02-15

Effects of superthermal electron on the features of nonlinear acoustic waves in unmagnetized collisionless ion pair plasma with superthermal electrons have been examined. The system equations are reduced in the form of the nonlinear Schrodinger equation. The rogue wave characteristics dependences on the ionic density ratio (ν = n{sub –0}/n{sub +0}), ionic mass ratio (Q = m{sub +}/m{sub −}), and superthermality index (κ) are investigated. It is worth mentioning that the results present in this work could be applicable in the Earth's ionosphere plasmas.

Ex-reactor determination of thermal gap and contact conductance between uranium dioxide: zircaloy-4 interfaces. Stage I: low gas pressure. [PWR; BWR

Energy Technology Data Exchange (ETDEWEB)

Garnier, J.E.; Begej, S.

1979-04-01

A study of thermal gap and contact conductance between depleted uranium dioxide (UO/sub 2/) and Zircaloy-4 (Zr4) has been made utilizing two measurement apparatuses developed as part of this program. The Modified Pulse Design (MPD) apparatus is a transient technique employing a heat pulse (laser) and a signal detector to monitor the thermal energy transmitted through a UO/sub 2//Zr4 sample pair which are either physically separated or in contact. The Modified Longitudinal Design (MLD) apparatus is a steady-state technique based on a modified cylindrical column design with a self-guarding sample geometry. Description of the MPD and MLD apparatus, data acquisition, reduction and error analysis is presented along with information on specimen preparation, thermal property and surface characterization. A technique using an optical height gauge to determine the average mean-plane of separation between the simple pairs is also presented.

Pseudoclassical approach to electron and ion density correlations in simple liquid metals

International Nuclear Information System (INIS)

Vericat, F.; Tosi, M.P.; Pastore, G.

1986-04-01

Electron-electron and electron-ion structural correlations in simple liquid metals are treated by using effective pair potentials to incorporate quantal effects into a pseudoclassical description of the electron fluid. An effective pair potential between simultaneous electron density fluctuations is first constructed from known properties of the degenerate jellium model, which are the plasmon sum rule, the Kimball-Niklasson relation and Yasuhara's values of the electron pair distribution function at contact. An analytic expression is thereby obtained in the Debye-Hueckel approximation for the electronic structure factor in jellium over a range of density appropriate to metals, with results which compare favourably with those of fully quantal evaluations. A simple pseudoclassical model is then set up for a liquid metal: this involves a model of charged hard spheres for the ion-ion potential and an empty core model for the electron-ion potential, the Coulombic tails being scaled as required by the relation between the long-wavelength partial structure factors and the isothermal compressibility of the metal. The model is solved analytically by a pseudoclassical linear response treatment of the electron-ion coupling and numerical results are reported for partial structure factors in liquid sodium and liquid beryllium. Contact is made for the latter system with data on the electron-electron structure factor in the crystal from inelastic X-ray scattering experiments of Eisenberger, Marra and Brown. (author)

Kinetics of uncatalyzed thermochemical sulfate reduction by sulfur-free paraffin

Science.gov (United States)

Zhang, Tongwei; Ellis, Geoffrey S.; Ma, Qisheng; Amrani, Alon; Tang, Yongchun

2012-01-01

published experimental TSR data yield kinetic parameters that are consistent with our values. Assuming MgSO4 contact-ion-pair ([MgSO4]CIP) as the reactive form of sulfate in petroleum reservoir formation waters, a simple extrapolation of our experimentally derived HSO4− reduction kinetics as a proxy for [MgSO4]CIP to geologically reasonable conditions predicts onset temperatures (130–140 °C) that are comparable to those observed in nature.

Comprehensive Analysis of Umami Compounds by Ion-Pair Liquid Chromatography Coupled to Mass Spectrometry

NARCIS (Netherlands)

Coulier, L.; Bas, R.; Hekman, M.; Werff, B.J.C. van der; Burgering, M.; Thissen, U.

2011-01-01

An ion-pair LC-ESI-MS method was developed capable of analyzing various reported umami or umami-enhancing compounds, including glutamic acid and 5'-ribonucleotides. The method was validated using tomato and potato samples and showed overall good analytical performance with respect to selectivity,

The separation of [32P]inositol phosphates by ion-pair chromatography: Optimization of the method and biological applications

International Nuclear Information System (INIS)

Sulpice, J.C.; Gascard, P.; Journet, E.; Rendu, F.; Renard, D.; Poggioli, J.; Giraud, F.

1989-01-01

We have developed an ion-pair reverse-phase HPLC method to measure inositol phosphates in 32 P-labeled cells. The different chromatographic parameters were analyzed to optimize the resolution of the 32 P-labeled metabolites. Analysis of inositol phosphates in biological samples was improved by a single charcoal pretreatment which eliminated interfering nucleotides without removing inositol phosphates. The kinetics of production of inositol phosphates in calcium-activated erythrocytes, vasopressin-stimulated hepatocytes, and thrombin-activated platelets were analyzed. Original data on the activation of phosphoinositide phospholipase C were obtained in intact erythrocytes by direct measurement of inositol (1,4,5)P3. Data from agonist-stimulated hepatocytes and platelets were consistent with those from previous studies. In conclusion, this technique offers many advantages over the methodologies currently employed involving anion-exchange chromatography and [ 3 H]inositol labeling: (i) 32 P labeling is less expensive and more efficient than 3 H labeling and can be used with all types of cells without permeabilization treatments and (ii) ion-pair HPLC gives good resolution of inositol phosphates from nucleotides with shorter retention times, and long reequilibration periods are not required

Gyro-viscosity and linear dispersion relations in pair-ion magnetized plasmas

Energy Technology Data Exchange (ETDEWEB)

Kono, M. [Faculty of Policy Studies, Chuo University, Tokyo 192-0393 (Japan); Vranjes, J. [Instituto de Astrofisica de Canarias, Tenerife E38205 (Spain); Departamento de Astrofisica, Universidad de La Laguna, Tenerife E38205 (Spain)

2015-11-15

A fluid theory has been developed by taking account of gyro-viscosity to study wave propagation characteristics in a homogeneous pair-ion magnetized plasma with a cylindrical symmetry. The exact dispersion relations derived by the Hankel-Fourier transformation are shown comparable with those observed in the experiment by Oohara and co-workers. The gyro-viscosity is responsible for the change in propagation characteristics of the ion cyclotron wave from forward to backward by suppressing the effect of the thermal pressure which normally causes the forward nature of dispersion. Although the experiment has been already explained by a kinetic theory by the present authors, the kinetic derivations are so involved because of exact particle orbits in phase space, finite Lamor radius effects, and higher order ion cyclotron resonances. The present fluid theory provides a simple and transparent structure to the dispersion relations since the gyro-viscosity is renormalized into the ion cyclotron frequency which itself indicates the backward nature of dispersion. The usual disadvantage of a fluid theory, which treats only fundamental modes of eigen-waves excited in a system and is not able to describe higher harmonics that a kinetic theory does, is compensated by simple derivations and clear picture based on the renormalization of the gyro-viscosity.

Impact-parameter dependence of the total probability for electromagnetic electron-positron pair production in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Hencken, K.; Trautmann, D.; Baur, G.

1995-01-01

We calculate the impact-parameter-dependent total probability P total (b) for the electromagnetic production of electron-positron pairs in relativistic heavy-ion collisions in lowest order. We study expecially impact parameters smaller than the Compton wavelength of the electron, where the equivalent-photon approximation cannot be used. Calculations with and without a form factor for the heavy ions are done; the influence is found to be small. The lowest-order results are found to violate unitarity and are used for the calculation of multiple-pair production probabilities with the help of the approximate Poisson distribution already found in earlier publications

Modified Extraction-Free Ion-Pair Methods for the Determination of Flunarizine Dihydrochloride in Bulk Drug, Tablets, and Human Urine

Science.gov (United States)

Prashanth, K. N.; Basavaiah, K.

2018-01-01

Two simple and sensitive extraction-free spectrophotometric methods are described for the determination of flunarizine dihydrochloride. The methods are based on the ion-pair complex formation between the nitrogenous compound flunarizine (FNZ), converted from flunarizine dihydrochloride (FNH), and the acidic dye phenol red (PR), in which experimental variables were circumvented. The first method (method A) is based on the formation of a yellow-colored ion-pair complex (1:1 drug:dye) between FNZ and PR in chloroform, which is measured at 415 nm. In the second method (method B), the formed drug-dye ion-pair complex is treated with ethanolic potassium hydroxide in an ethanolic medium, and the resulting base form of the dye is measured at 580 nm. The stoichiometry of the formed ion-pair complex between the drug and dye (1:1) is determined by Job's continuous variations method, and the stability constant of the complex is also calculated. These methods quantify FNZ over the concentration ranges 5.0-70.0 in method A and 0.5-7.0 μg/mL in method B. The calculated molar absorptivities are 6.17 × 103 and 5.5 × 104 L/mol·cm-1 for method A and method B, respectively, with corresponding Sandell sensitivity values of 0.0655 and 0.0074 μg/cm2. The methods are applied to the determination of FNZ in pure drug and human urine.

Di-ureasil hybrids doped with LiBF{sub 4}: Spectroscopic study of the ionic interactions and hydrogen bonding

Energy Technology Data Exchange (ETDEWEB)

Fernandes, Mariana [Departamento de Quimica/CQ-VR, Universidade de Tras-os-Montes e Alto Douro, 5001-801 Vila Real (Portugal); Barbosa, Paula C.; Manuela Silva, M.; Smith, Michael J. [Departamento de Quimica/Centro de Quimica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga (Portugal); Zea Bermudez, Veronica de, E-mail: vbermude@utad.pt [Departamento de Quimica/CQ-VR, Universidade de Tras-os-Montes e Alto Douro, 5001-801 Vila Real (Portugal)

2011-09-15

Highlights: {yields} FT-IR and FT-Raman spectroscopy were used to characterize cation interactions in two LiBF{sub 4}-doped di-ureasil networks incorporating POE chains with different length. {yields} Over the range of salt content analyzed the cations bond to amorphous POE chains and form ion contact pairs with BF{sub 4}{sup -}. {yields} A crystalline POE/LiBF{sub 4} complex of unknown stoichiometry emerges at high salt concentration. - Abstract: In the present work Fourier transform infrared and Raman spectroscopy were used to characterize the cation/polymer, cation/cross-link, cation/anion and hydrogen bonding interactions in hybrid electrolytes composed of lithium tetrafluoroborate (LiBF{sub 4}) and di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks (di-ureasils) designated as d-U(2000) and d-U(600) and incorporating polyether chains with ca. 40.5 and 8.5 oxyethylene repeat units, respectively. Samples with {infinity} > n {>=} 2.5 (where n, composition, is the molar ratio of CH{sub 2}CH{sub 2}O units per Li{sup +} ion) were analyzed. In both di-ureasil systems over the whole range of salt content examined the Li{sup +} ions bond to the ether oxygen atoms of amorphous POE chains and to BF{sub 4}{sup -} ions forming ion contact pairs. Spectroscopic evidences and SEM images confirm the presence of a crystalline POE/LiBF{sub 4} complex of unknown stoichiometry at n < 20 and 25, respectively. Ionic association is particularly important in the case of the d-U(600)-based materials, as a result of the presence of strong hydrogen-bonded aggregates that prevent the establishment of Li{sup +}/urea carbonyl oxygen atom interactions.

A chemical approach for site-specific identification of NMR signals from protein side-chain NH3+ groups forming intermolecular ion pairs in protein–nucleic acid complexes

International Nuclear Information System (INIS)

Anderson, Kurtis M.; Nguyen, Dan; Esadze, Alexandre; Zandrashvili, Levani; Gorenstein, David G.; Iwahara, Junji

2015-01-01

Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH 3 + groups forming the intermolecular ion pairs. A characteristic change in their 1 H and 15 N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain 15 N and DNA phosphorodithiaote 31 P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well

Elasticity and electrical resistivity of chalk and greensand during water flooding with selective ions

DEFF Research Database (Denmark)

Katika, Konstantina; Alam, Mohammad Monzurul; Alexeev, Artem

2018-01-01

is water-wet after flooding. Greensand remained mixed wet throughout the experiments. Electrical resistivity data are in agreement with this interpretation. The electrical resistivity data during flooding revealed that the formation brine is not fully replaced by the injected water in both chalk......Water flooding with selective ions has in some cases lead to increased oil recovery. We investigate the physical processes on a pore scale that are responsible for changes in petrophysical and mechanical properties of four oil-bearing chalk and four oil-bearing greensand samples caused by flooding...... with brines containing varying amounts of dissolved NaCl, Na2SO4, MgCl2 and MgSO4. Ultrasonic P-wave velocity and AC resistivity measurements were performed prior to, during and after flow through experiments in order to identify and quantify the processes related to water flooding with selective ions. Low...

Nitrate and nitrite content in bottled beverages by ion-pair high-performance liquid chromatography.

Science.gov (United States)

Song, Yang; Deng, Gui-Fang; Xu, Xiang-Rong; Chen, Yong-Hong; Chen, Feng; Li, Hua-Bin

2013-01-01

Nitrate and nitrite levels in six types of beverages--total of 292 individual samples from 73 brands (four bottles each)--from Guangzhou city in China were evaluated by ion-pair high-performance liquid chromatography. All samples contained nitrate. Nitrate and nitrite ranges were 0.43-46.08 and safety of Chinese bottled beverages.

Ion-ion interaction and energy transfer of 4+ transuranium ions in cerium tetrafluoride

International Nuclear Information System (INIS)

Liu, G.K.; Beitz, J.V.

1990-01-01

Dynamics of excited 5f electron states of the transuranium ions Cm 4+ and Bk 4+ in CeF 4 are compared. Based on time- and wavelength-resolved laser-induced fluorescence, excitation energy transfer processes have been probed. Depending on concentration and electronic energy level structure of the studied 4+ transuranium ion, the dominant energy transfer mechanisms were identified as cross relaxation, exciton-exciton annihilation, and trapping. Energy transfer rates derived from the fitting of the observed fluorescence decays to theoretical models, based on electric multipolar ion-ion interactions, are contrasted with prior studies of 4f states of 3+ lanthanide and 3d states of transition metal ions. 16 refs., 1 tab

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

Science.gov (United States)

Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.

2015-11-01

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants.

Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials

International Nuclear Information System (INIS)

Hofmann, F.; Mason, D. R.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Dudarev, S. L.

2015-01-01

Knowledge of mechanical and physical property evolution due to irradiation damage is essential for the development of future fission and fusion reactors. Ion-irradiation provides an excellent proxy for studying irradiation damage, allowing high damage doses without sample activation. Limited ion-penetration-depth means that only few-micron-thick damaged layers are produced. Substantial effort has been devoted to probing the mechanical properties of these thin implanted layers. Yet, whilst key to reactor design, their thermal transport properties remain largely unexplored due to a lack of suitable measurement techniques. Here we demonstrate non-contact thermal diffusivity measurements in ion-implanted tungsten for nuclear fusion armour. Alloying with transmutation elements and the interaction of retained gas with implantation-induced defects both lead to dramatic reductions in thermal diffusivity. These changes are well captured by our modelling approaches. Our observations have important implications for the design of future fusion power plants

Uptake of CrO{sub 4}{sup 2-} ions by Fe-treated tri-calcium phosphate

Energy Technology Data Exchange (ETDEWEB)

Serrano G, J.; Ramirez S, J. L.; Bonifacio M, J.; Granados C, F.; Badillo A, V. E., E-mail: juan.serrano@inin.gob.m [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2010-07-01

CrO{sub 4}{sup 2-} ion adsorption of Fe-treated tri-calcium phosphate was studied by batch experiments as a function of contact time, initial concentration of metal ion and temperature. Adsorption results showed that at ph 5.5 and 1.0 x 10{sup -4} M chromium concentration the adsorption capacity of Fe-treated tri-calcium phosphate for CrO{sub 4}{sup 2-} ions was 7.10 x 10{sup -3} mmol/g. Chromium adsorption data on Fe-treated tri-calcium phosphate at various initial concentration fitted the Freundlich isotherm. By temperature studies the thermodynamic parameters {Delta}H{sup 0}, {Delta}G{sup 0} and {Delta}S{sup 0} were estimated and the obtained results showed that the adsorption reaction was endothermic and spontaneous. (Author)

Pair production with electron capture in peripheral collisions of relativistic heavy ions

Energy Technology Data Exchange (ETDEWEB)

Bertulani, C.A.C.A. E-mail: bertu@if.ufrj.br; Dolci, D.D. E-mail: dolci@if.ufrj.br

2001-02-26

The production of electron-positron pairs with the capture of the electron in an atomic orbital is investigated for the conditions of the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). Dirac wave functions for the leptons are used, taking corrections to orders of Z{alpha} into account. The dependence on the transverse momentum transfer is studied and the accuracy of the equivalent photon approximation is discussed as a function of the nuclear charge.

Solvent, isotope, and magnetic field effects in the geminate recombination of radical ion pairs

International Nuclear Information System (INIS)

Werner, H.; Staerk, H.; Weller, A.

1978-01-01

The magnetic field dependence of the geminate recombination triplet yield of radical ion pairs generated via photoinduced electron transfer in polar solvents is investigated for the systems pyrene/N,N-dimethylaniline (Py/DMA), pyrene/3,5-dimethoxy-N,N-dimethylaniline (Py/DMDMA), and the perdeuterated system Py-d 10 /DMA-d 11 . The magnetic field dependence characterized through its B/sub 1/2/ value is found to be dependent on the sum of the hyperfine coupling constants in the radical pair in agreement with previous theoretical predictions. A drastic reduction of the B/sub 1/2/ value is observed with the perdeuterated system. By means of measurements of the radical ion and triplet absorption signals with nanosecond time resolution, the influence of the solvent on the geminate singlet and triplet recombination yields is investigated. Complementary measurements of exciplex lifetimes and quantum yields are carried out in a series of solvents with different polarities in order to determine the rate constants of fluorescence emission and intersystem crossing in the exciplexes

Dependence of the Rate of LiF Ion-Pairing on the Description of Molecular Interaction

Czech Academy of Sciences Publication Activity Database

Pluhařová, Eva; Baer, M. D.; Schenter, G. K.; Jungwirth, Pavel; Mundy, C. J.

2016-01-01

Roč. 120, č. 8 (2016), s. 1749-1758 ISSN 1520-6106 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : molecular dynamics * ion pairing kinetics * lithium fluoride Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.177, year: 2016

Importance of the ion-pair interactions in the OPEP coarse-grained force field: parametrization and validation.

Science.gov (United States)

Sterpone, Fabio; Nguyen, Phuong H; Kalimeri, Maria; Derreumaux, Philippe

2013-10-08

We have derived new effective interactions that improve the description of ion-pairs in the OPEP coarse-grained force field without introducing explicit electrostatic terms. The iterative Boltzmann inversion method was used to extract these potentials from all atom simulations by targeting the radial distribution function of the distance between the center of mass of the side-chains. The new potentials have been tested on several systems that differ in structural properties, thermodynamic stabilities and number of ion-pairs. Our modeling, by refining the packing of the charged amino-acids, impacts the stability of secondary structure motifs and the population of intermediate states during temperature folding/unfolding; it also improves the aggregation propensity of peptides. The new version of the OPEP force field has the potentiality to describe more realistically a large spectrum of situations where salt-bridges are key interactions.

Positive cooperativity of the specific binding between Hg2+ ion and T:T mismatched base pairs in duplex DNA

International Nuclear Information System (INIS)

Torigoe, Hidetaka; Miyakawa, Yukako; Ono, Akira; Kozasa, Tetsuo

2012-01-01

Highlights: ► Hg 2+ specifically bound with the T:T mismatched base pair at 1:1 molar ratio. ► The binding constant between Hg 2+ and the T:T mismatched base pair was 10 6 M −1 . ► The binding constant was larger than those for nonspecific metal–DNA interactions. ► The binding constant for the second Hg 2+ was larger than that for the first Hg 2+ . ► The positive cooperative binding was observed between Hg 2+ and multiple T:T. - Abstract: Metal-mediated base pairs by the interaction between metal ions and artificial bases in oligonucleotides have been developed for their potential applications in nanotechnology. We recently found that a natural T:T mismatched base pair bound with Hg 2+ ion to form a novel T–Hg–T base pair. Here, we examined the thermodynamic properties of the binding between Hg 2+ and each of the single and double T:T mismatched base pair duplex DNAs by isothermal titration calorimetry. Hg 2+ specifically bound with the T:T mismatched base pair at 1:1 molar ratio with 10 6 M −1 binding constant, which was significantly larger than those for nonspecific metal ion–DNA interactions. In the Hg 2+ –double T:T mismatched base pair interaction, the affinity for the second Hg 2+ binding was significantly larger than that for the first Hg 2+ binding. The positively cooperative binding may be favorable to align multiple Hg 2+ in duplex DNA for the application of the metal-mediated base pairs in nanotechnology.

T/sub 4/ radioimmunoassay with ion-exchange resin separation

Energy Technology Data Exchange (ETDEWEB)

Michael, J D; Modha, K [Hoechst Pharmaceuticals Research Ltd., Milton Keynes (UK)

1977-05-28

An explanation is provided for the reports of falsely low values of serum-thyroxine (T/sub 4/) measured by radioimmunoassay (RIA), particularly in sera containing raised concentrations of thyroxine-binding globulin (TBG) (Burr, W.A., Evans, S.E., Hogan, T.C., 1977, Lancet, April 2, 757). A re-examination of the assay technique used in commercial RIA kits ('RIA-gnost T/sub 3/' and 'RIA-gnost T/sub 4/', Behring Diagnostics) showed that blocking of binding proteins by 8-anilino-1-naphthalene sulphonic acid (ANS) was incomplete in sera with raised TBG levels. Spectroscopic determination of the blocker concentration during the time the solution was in contact with the ion exchange resin showed that 98% of the ANS was removed from solution by 10 min contact with the resin, yet 60 min was required to absorb the free T/sub 4/. There was therefore ample time for unblocked TBG to recombine with free T/sub 4/ which was then misclassified as antibody-bound T/sub 4/. The assay technique used in the kits was therefore modified. The less polar TBG blocking agent, ethylmercurithiosalicylate (merthiolate), replaced ANS and it was demonstrated that accurate T/sub 3/ and T/sub 4/ measurements in high TBG sera could be made by resin-separation RIA without resorting to prior denaturation or alcohol extraction.

Effects of C+ ion implantation on electrical properties of NiSiGe/SiGe contacts

International Nuclear Information System (INIS)

Zhang, B.; Yu, W.; Zhao, Q.T.; Buca, D.; Breuer, U.; Hartmann, J.-M.; Holländer, B.; Mantl, S.; Zhang, M.; Wang, X.

2013-01-01

We have investigated the morphology and electrical properties of NiSiGe/SiGe contact by C + ions pre-implanted into relaxed Si 0.8 Ge 0.2 layers. Cross-section transmission electron microscopy revealed that both the surface and interface of NiSiGe were improved by C + ions implantation. In addition, the effective hole Schottky barrier heights (Φ Bp ) of NiSiGe/SiGe were extracted. Φ Bp was observed to decrease substantially with an increase in C + ion implantation dose

Quantum mechanical theory of positron production in heavy ion collisions with nuclear contact

International Nuclear Information System (INIS)

Heinz, U.

1986-01-01

The interplay between atomic and nuclear interactions in heavy ion collisions with nuclear contact is studied. The general theoretical description is outlined and analyzed in a number of different limits (semiclassical approximation, DWBA, fully quantal description). The two most important physical mechanisms for generating atomic-nuclear interference, i.e., energy conservation and the introduction of additional phase shifts by nuclear reactions, are extracted. The resulting typical coupling matrix elements are analyzed for their relative importance in atomic and nuclear excitations. The description of nuclear influence on atomic excitations in terms of a classical time delay caused by nuclear reactions is reviewed, and its relationship to the underlying quantal character of the nuclear reaction is discussed. The theory is applied to spontaneous positron emission in supercritical heavy-ion collisions (Z/sub tot/ ≥ 173). It is shown that nuclear contact can lead to line structures in the positron energy spectra if the probability distribution for nuclear delay times caused by the contact has contributions for T ≥ 10 -19 sec. We explicitly evaluate a model where a pocket in the internuclear potential near the touching configuration leads to formation of nuclear molecules, and predict a resonance-like excitation function for the positron peak. 25 refs., 7 figs

Temperature and ion-mass dependence of amorphization dose for ion beam irradiated zircon (ZrSiO4)

International Nuclear Information System (INIS)

Wang, L.M.; Ewing, R.C.; Eby, R.K.

1992-12-01

The temperature dependence of amorphization dose for zircon under 1.5 MeV Kr ion irradiation has been investigated using the ANL HVEM-Tandem Facility. Three regimes were observed in the amorphization dose-temperature curve. In the first regime (15 to 300 K), the critical amorphization dose increased from 3.06 to 4.5 ions/nm 2 . In the second regime (300 to 473 K), there is little change in the amorphizationdose. In the third regime (> 473 K), the amorphization dose increased exponentially to 8.3 ions/nm 2 at 913 K. This temperature dependence of amorphization dose can be described by two processes with different activation energies (0.018 and 0.31 eV respectively) which are attributed to close pair recombination in the cascades at low temperatures and radiation-enhanced epitaxial recrystallization at higher temperatures. The upper temperature limit for amorphization of zircon is estimated to be 1100 K. The ion-mass dependence of the amorphization dose (in dpa) has also been discussed in terms of the energy to recoils based on data obtained from He, Ne, Ar, Kr, Xe irradiations and a 238 Pu-doped sample

Universality-class crossover by a nonorder field introduced to the pair contact process with diffusion

Science.gov (United States)

Park, Su-Chan

2017-09-01

The one-dimensional pair contact process with diffusion (PCPD), an interacting particle system with diffusion, pair annihilation, and creation by pairs, has defied consensus about the universality class to which it belongs. An argument by Hinrichsen [Physica A 361, 457 (2006), 10.1016/j.physa.2005.06.101] claims that freely diffusing particles in the PCPD should play the same role as frozen particles when it comes to the critical behavior. Therefore, the PCPD is claimed to have the same critical phenomena as a model with infinitely many absorbing states that belongs to the directed percolation (DP) universality class. To investigate if diffusing particles are really indistinguishable from frozen particles in the sense of the renormalization group, we study numerically a variation of the PCPD by introducing a nonorder field associated with infinitely many absorbing states. We find that a crossover from the PCPD to DP occurs due to the nonorder field. By studying a similar model, we exclude the possibility that the mere introduction of a nonorder field to one model can entail a nontrivial crossover to another model in the same universality class, thus we attribute the observed crossover to the difference of the universality class of the PCPD from the DP class.

SO4--SO3- radical pair formation in Ce doped and Ce, U co-doped K3Na(SO4)2: EPR evidence and its role in TSL

International Nuclear Information System (INIS)

Natarajan, V.; Seshagiri, T.K.; Kadam, R.M.; Sastry, M.D.

2002-01-01

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on cerium doped and cerium-uranium co-doped K 3 Na(SO 4 ) 2 samples after γ-irradiation. Three glow peaks around 352, 415 and 475 K were observed and their spectral characteristics have shown that Ce 3+ and UO 2 2+ act as the emission centres in K 3 Na(SO 4 ) 2 :Ce and K 3 Na(SO 4 ) 2 :Ce, U, respectively. In Ce-U co-doped sample, energy transfer from cerium to uranium takes place. The commonly occurring radiation-induced centres in sulphates, viz SO 3 - and SO 4 - were observed by EPR and SO 4 - radical ion was found to take part in the TSL emission at 415 K. The hitherto unknown information, however, is the formation of SO 4 - -SO 3 - radical pair creating deep traps in these lattices, apparently assisted by the dopants. This is the first observation of such radical pair formation leading to the identification of deep traps in this lattice. The radical pair, (SO 3 - -SO 4 - ) which is stable up to 970 K, decreases the intensity of the peak at 415 K due to the depletion of SO 4 - centres

Ion-Pair Extractive Spectrophotometric Assay of Terbinafine Hydrochloride in Pharmaceuticals and Spiked Urine Using Bromocresol Purple

Science.gov (United States)

Salem Qarah, N. A.; Basavaiah, K.; Swamy, N.

2016-09-01

Two simple, rapid, selective, and sensitive methods were developed and validated for the determination of terbinafi ne hydrochloride (TBH) in pharmaceuticals and urine. The fi rst method (method A) is based on the formation of a yellow ion-pair complex of TBH and bromocresol purple (BCP), a sulfonephthalein dye, in Walpole buffer of pH 3.61, which was extracted into chloroform and investigated at 420 nm. For the second method (method B) the drug-dye ion-pair was broken in alkaline KOH medium, and the resulting free dye color was measured at 610 nm. All variables were studied to optimize the reaction conditions. The regression analysis of Beer's law plots showed good correlation in the concentration ranges of 1-10 and 0.1-2.0 μg/mL for method A and method B, respectively. Molar absorptivity values were 2.99 × 104, and 1.51×105 L/(mol × cm) for measurements by these methods. The methods were also validated for limits of detection (LOD) and quantifi cation (LOQ), intra-day and inter-day accuracy and precision, selectivity, robustness and ruggedness. The composition of the ion-pair (drug-dye) used in the method A was found to be 1:1 by both mole-ratio and Job's methods. The developed methods were applied to tablets, and the results were in good agreement with the label claim and those of the reference method. Because of its high sensitivity, method A was applied to spiked human urine with percent recoveries in the range 96.58-107.3 and a standard deviation <2%.

Effect of thermal contact resistances on fast charging of large format lithium ion batteries

International Nuclear Information System (INIS)

Ye, Yonghuang; Saw, Lip Huat; Shi, Yixiang; Somasundaram, Karthik; Tay, Andrew A.O.

2014-01-01

Highlights: • The effect of thermal contact resistance on thermal performance of large format lithium ion batteries. • The effect of temperature gradient on electrochemical performance of large format batteries during fast charging. • The thermal performance of lithium ion battery utilizing pulse charging protocol. • Suggestions on battery geometry design optimization to improve thermal performance. - Abstract: A two dimensional electrochemical thermal model is developed on the cross-plane of a laminate stack plate pouch lithium ion battery to study the thermal performance of large format batteries. The effect of thermal contact resistance is taken into consideration, and is found to greatly increase the maximum temperature and temperature gradient of the battery. The resulting large temperature gradient would induce in-cell non-uniformity of charging-discharging current and state of health. Simply increasing the cooling intensity is inadequate to reduce the maximum temperature and narrow down the temperature difference due to the poor cross-plane thermal conductivity. Pulse charging protocol does not help to mitigate the temperature difference on the bias of same total charging time, because of larger time-averaged heat generation rate than constant current charging. Suggestions on battery geometry optimizations for both prismatic/pouch battery and cylindrical battery are proposed to reduce the maximum temperature and mitigate the temperature gradient within the lithium ion battery

A chemical approach for site-specific identification of NMR signals from protein side-chain NH{sub 3}{sup +} groups forming intermolecular ion pairs in protein–nucleic acid complexes

Energy Technology Data Exchange (ETDEWEB)

Anderson, Kurtis M. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Nguyen, Dan; Esadze, Alexandre; Zandrashvili, Levani [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States); Gorenstein, David G. [University of Texas Health Science Center at Houston, Department of NanoMedicine and Biomedical Engineering and Institute of Molecular Medicine (United States); Iwahara, Junji, E-mail: juiwahar@utmb.edu, E-mail: j.iwahara@utmb.edu [University of Texas Medical Branch, Department of Biochemistry and Molecular Biology, Sealy Center for Structural Biology and Molecular Biophysics (United States)

2015-05-15

Protein–nucleic acid interactions involve intermolecular ion pairs of protein side-chain and DNA or RNA phosphate groups. Using three protein–DNA complexes, we demonstrate that site-specific oxygen-to-sulfur substitution in phosphate groups allows for identification of NMR signals from the protein side-chain NH{sub 3}{sup +} groups forming the intermolecular ion pairs. A characteristic change in their {sup 1}H and {sup 15}N resonances upon this modification (i.e., substitution of phosphate to phosphorodithioate) can represent a signature of an intermolecular ion pair. Hydrogen-bond scalar coupling between protein side-chain {sup 15}N and DNA phosphorodithiaote {sup 31}P nuclei provides direct confirmation of the intermolecular ion pair. The same approach is likely applicable to protein–RNA complexes as well.

Fermion pair physics at LEP2

International Nuclear Information System (INIS)

Georgios, Anagnostou

2004-01-01

Combined measurements of the 4 LEP collaborations for the fermion pair processes e + e - →f anti f are presented. The results show no significant deviations when compared with the Standard Model predictions and are used to set limits on contact interactions, Z' gauge bosons and low scale gravity models with large extra dimensions. (orig.)

Ion-pair extraction of [3]histobadine from biological fluids

International Nuclear Information System (INIS)

Scasnar, V.

1997-01-01

A simple and specific radiometric assay was developed for determination of stobadine, a cardio protective drug, in the serum of experimental animals. It is based on a single extraction step of the radioactively labeled drug from serum into the benzene solution of dicarbolide of cobalt followed by the quantitation of the extracted radioactivity by using liquid scintillation counting. The extraction mechanism involves the ion-pair formation between the protonized molecule of stobadine and the hydrophobic, negatively charged molecule of dicarbollide of cobalt. The extraction of yield of stobadine from 1 ml of serum was 95% in the concentration range from 1 to 6000 ng/ml. The co extraction of metabolites was less than 5%. The assay was applied to determination of stobadine in serum of dogs and the data obtained were in good agreement with those obtained by high performance liquid chromatography. (author)

NMR studies of echinomycin bisintercalation complexes with d(A1-C2-G3-T4) and d(T1-C2-G3-A4) duplexes in aqueous solution: sequence-dependent formation of Hoogsteen A1 x T4 and Watson-Crick T1 x A4 base pairs flanking the bisintercalation site

International Nuclear Information System (INIS)

Gao, X.; Patel, D.J.

1988-01-01

The authors report on two-dimensional proton NMR studies of echinomycin complexes with the self-complementary d(A1-C2-G3-Tr) and d(T1-C2-G3-A4) duplexes in aqueous solution. The exchangeable and nonexchangeable antibiotic and nucleic acid protons in the 1 echinomycin per tetranucleotide duplex complexes have been assigned from analyses of scalar coupling and distance connectivities in two-dimensional data sets records in H 2 O and D 2 O solution. An analysis of the intermolecular NOE patterns for both complexes combined with large upfield imino proton and large downfield phosphorus complexation chemical shift changes demonstrates that the two quinoxaline chromophores of echinomycin bisintercalate into the minor groove surrounding the dC-dG step of each tetranucleotide duplex. Further, the quinoxaline rings selectively stack between A1 and C2 bases in the d(ACGT) complex and between T1 and C2 bases in the d(TCGA) complex. The intermolecular NOE patterns and the base and sugar proton chemical shifts for residues C2 and G3 are virtually identical for the d(ACGT) and d(TCGA) complexes. A large set of intermolecular contacts established from nuclear Overhauser effects (NOEs) between antibiotic and nucleic acid protons in the echinomycin-tetranucleotide complexes in solution are consistent with corresponding contacts reported for echinomycin-oligonucleotide complexes in the crystalline state. The authors demonstrate that the G x G base pairs adopt Watson-Crick pairing in both d(ACGT) and d(TCGA) complexes in solution. By contrast, the A1 x T4 base pairs adopt Hoogsteen pairing for the echinomycin-d(A1-C2-G3-Tr) complex while the T1 x A4 base pairs adopt Watson-Crick pairing for the echinomycin-d(T1-C2-G3-A4) complex in aqueous solution. These results emphasize the role of sequence in discriminating between Watson-Crick and Hoogsteen pairs at base pairs flanking the echinomycin bisintercalation site in solution

Selenium speciation in urine by ion-pairing chromatography with perfluorinated carboxylic acids and ICP-MS detection

DEFF Research Database (Denmark)

Gammelgaard, Bente; Bendahl, L.; Sidenius, U.

2002-01-01

Five aqueous standards, selenomethionine (SeMet), methylselenomethionine (MeSeMet), methylselenocysteine (MeSeCys), selenogammaaminobutyric acid (SeGaba) and the trimethylselenonium ion (TMSe), were separated in ion-pairing chromatographic systems based on perfluorinated carboxylic acids in metha...... were major compounds in urine samples-even after massive consumption of selenium-containing supplements. The selenium species in the urine samples showed a limited stability, as they changed during storage at +4 degreesC as well as -18 degreesC...... of between 2.3 and 5.1 pg. Urine samples from different individuals before and during supplementation with selenomethionine were analysed. Several species were separated in the different urine samples. A major component eluting at the beginning of the chromatogram was predominant in many samples, especially...... after selenium consumption. This species was not identified and solid phase extraction experiments suggested that it was neutral. When different urine samples were spiked with the available standards, co-elution of species with TMSe, MeSeMet or SeMet was observed in some samples. None of these species...

Simultaneous quantification of porcine myocardial adenine nucleotides and creatine phosphate by ion-pair reverse-phase high-performance liquid chromatography

International Nuclear Information System (INIS)

Cordis, G.A.; Das, D.K.

1987-01-01

In order to follow the energy metabolism and the levels of high-energy phosphate compounds in porcine myocardium subjected to ischemic insult, it was necessary to develop a high-performance liquid chromatography (HPLC) method where creatine phosphate (CP) and the adenine nucleotides could be measured simultaneously in a single run. Currently available ion-pair reverse-phase HPLC methods require a separate injection with a change in wavelength and mobile phase in order to measure the creatine phosphate, while baseline separation of AMP is lacking. The ion-exchange HPLC method includes a simultaneous determination, but the baseline drifts due to the gradient and baseline separation of AMP is not achieved. In the following ion-pair reverse-phase HPLC method, simultaneous measurements of porcine myocardial adenine nucleotides and creatine phosphate were achieved along with a stable baseline and homogeneous baseline separation of each measured compound, allowing accurate quantification

A new method of making ohmic contacts to p-GaN

Energy Technology Data Exchange (ETDEWEB)

Hernández-Gutierrez, C.A., E-mail: chernandez@fis.cinvestav.mx [DNyN, Cinvestav-IPN, México, DF, 07360 (Mexico); Kudriavtsev, Yu. [Departamento Ingeniería Eléctrica – SEES, Cinvestav-IPN, México, DF, 07360 (Mexico); Mota, Esteban [ESIME, Instituto Politécnico Nacional, México, DF, 07738 (Mexico); Hernández, A.G.; Escobosa-Echavarría, A.; Sánchez-Resendiz, V. [Departamento Ingeniería Eléctrica – SEES, Cinvestav-IPN, México, DF, 07360 (Mexico); Casallas-Moreno, Y.L.; López-López, M. [Departamento Física, Cinvestav-IPN, México, DF, 07360 (Mexico)

2016-12-01

Highlights: • Low resistance Ohmic contacts preparation is based on low energy high dose In{sup +} ion implantation into Metal/p-GaN to achieve a thin layer of In{sub x}Ga{sub 1-x}N just at the interface. • The specific ohmic contact was reduced from 10{sup −2} Ωcm{sup 2} to 2.5 × 10{sup −4} Ωcm{sup 2}. - Abstract: The structural, chemical, and electrical characteristics of In{sup +} ion-implanted Au/Ni, Au/Nb and Au/W ohmic contacts to p-GaN were investigated. After the preparation of Ni, Nb and W electrode on the surface of p-GaN, the metal/p-GaN contact interface was implanted by 30 keV In{sup +} ions with an implantation dose of 5 × 10{sup 15} ions/cm{sup 2} at room temperature to form a thin layer of In{sub x}Ga{sub 1-x}N located at the metal-semiconductor interface, achieved to reduce the specific contact resistance due to the improving quantum tunneling transport trough to the structure. The characterization was carried out by high-resolution X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and secondary ion mass spectrometry to investigate the formation of ternary alloy, re-crystallization by rapid thermal annealing process after In{sup +} implantation, and the redistribution of elements. The specific contact resistance was extracted by current-voltage (I-V) curves using transmission line method; the lowest specific contact resistance of 2.5 × 10{sup −4} Ωcm{sup 2} was achieved for Au/Ni/p-In{sub x}Ga{sub 1-x}N/p-GaN ohmic contacts.

Dual-directional regulation of drug permeating amount by combining the technique of ion-pair complexation with chemical enhancers for the synchronous permeation of indapamide and bisoprolol in their compound patch through rabbit skin.

Science.gov (United States)

Song, Wenting; Cun, Dongmei; Quan, Peng; Liu, Nannan; Chen, Yang; Cui, Hongxia; Xiang, Rongwu; Fang, Liang

2015-04-01

To achieve the synchronous skin permeation of indapamide (IND) and bisoprolol (BSP) in their compound patch, the techniques of ion-pair complexation and chemical enhancers were combined to dual-directionally regulate drug permeating amounts. Ion-pair complexes of BSP and various organic acids were formed by the technique of ion-pair complexation. Among the complexes formed, bisoprolol tartrate (BSP.T) down-regulated the permeating amount of BSP to the same extent as that of IND. Then, to simultaneously up-regulate the amounts of the two drugs, an enhancer combination of 15.8% Span80 (SP), 6.0% Azone (AZ) and 2.2% N-methyl pyrrolidone (NMP) was obtained by central composite design and exhibited an outstanding and simultaneous enhancement on IND and BSP with enhancing ratio (ER) of 4.52 and 3.49, respectively. The effect of the dual-directional regulation was evaluated by in vitro permeation experiments and in vivo pharmacokinetic studies. For IND and BSP, their observed permeation profiles were comparable and their MAT (mean absorption time) showed no significant difference, which both demonstrated these two drugs achieved the synchronous skin permeation in their compound patch by the dual-directional regulation strategy of combining the technique of ion-pair complexation with chemical enhancers. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb(II) ion-selective electrode

DEFF Research Database (Denmark)

Joon, Narender Kumar; He, Ning; Wagner, Michal

2017-01-01

In this work, the influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb2+-selective electrode (Pb2+-ISE) was studied. The effects of bovine serum albumin (BSA) adsorption at the surface of the ion-selective membrane combined...... ions studied (Cu2+, Cd2+). Conditioning of the Pb2+-ISE in 0.01 mol dm–3 PBS resulted in a super-Nernstian response which was related to fixation/extraction of Pb2+ in the ion-selective membrane via precipitation of Pb3(PO4)2 by PO43– anions present in PBS. By conditioning of the Pb2+-ISE in 0.01 mol...

Separation of polar betalain pigments from cacti fruits of Hylocereus polyrhizus by ion-pair high-speed countercurrent chromatography.

Science.gov (United States)

Wybraniec, Sławomir; Stalica, Paweł; Jerz, Gerold; Klose, Bettina; Gebers, Nadine; Winterhalter, Peter; Spórna, Aneta; Szaleniec, Maciej; Mizrahi, Yosef

2009-10-09

Polar betacyanin pigments together with betaxanthins from ripe cactus fruits of Hylocereus polyrhizus (Cactaceae) were fractionated by means of preparative ion-pair high-speed countercurrent chromatography (IP-HSCCC) also using the elution-extrusion (EE) approach for a complete pigment recovery. HSCCC separations were operated in the classical 'head-to-tail' mode with an aqueous mobile phase. Different CCC solvent systems were evaluated in respect of influence and effectiveness of fractionation capabilities to separate the occurring pigment profile of H. polyrhizus. For that reason, the additions of two different volatile ion-pair forming perfluorinated carboxylic acids (PFCA) were investigated. For a direct comparison, five samples of Hylocereus pigment extract were run on preparative scale (900 mg) in 1-butanol-acetonitrile-aqueous TFA 0.7% (5:1:6, v/v/v) and the modified systems tert.-butyl methyl ether-1-butanol-acetonitrile-aqueous PFCA (2:2:1:5, v/v/v/v) using 0.7% and 1.0% trifluoroacetic acid (TFA) or heptafluorobutyric acid (HFBA) in the aqueous phase, respectively. The chemical affinity to the organic stationary CCC solvent phases and in consequence the retention of these highly polar betalain pigments was significantly increased by the use of the more lipophilic fluorinated ion-pair reagent HFBA instead of TFA. The HFBA additions separated more effectively the typical cacti pigments phyllocactin and hylocerenin from betanin as well as their iso-forms. Unfortunately, similar K(D) ratios and selectivity factors alpha around 1.0-1.1 in all tested solvent systems proved that the corresponding diastereomers, 15S-type pigments cannot be resolved from the 15R-epimers (iso-forms). Surprisingly, additions of the stronger ion-pair reagent (HFBA) resulted in a partial separation of hylocerenin from phyllocactin which were not resolved in the other solvent systems. The pigments were detected by means of HPLC-DAD and HPLC-electrospray ionization-MS using also

Structure of 2,4-Diaminopyrimidine - Theobromine Alternate Base Pairs

Science.gov (United States)

Gengeliczki, Zsolt; Callahan, Michael P.; Kabelac, Martin; Rijs, Anouk M.; deVries, Mattanjah S.

2011-01-01

We report the structure of clusters of 2,4-diaminopyrimidine with 3,7-dimethylxanthine (theobromine) in the gas phase determined by IR-UV double resonance spectroscopy in both the near-IR and mid-IR regions in combination with ab initio computations. These clusters represent potential alternate nucleobase pairs, geometrically equivalent to guanine-cytosine. We have found the four lowest energy structures, which include the Watson-Crick base pairing motif. This Watson-Crick structure has not been observed by resonant two-photon ionization (R2PI) in the gas phase for the canonical DNA base pairs.

Restoring the consistency with the contact density theorem of a classical density functional theory of ions at a planar electrical double layer.

Science.gov (United States)

Gillespie, Dirk

2014-11-01

Classical density functional theory (DFT) of fluids is a fast and efficient theory to compute the structure of the electrical double layer in the primitive model of ions where ions are modeled as charged, hard spheres in a background dielectric. While the hard-core repulsive component of this ion-ion interaction can be accurately computed using well-established DFTs, the electrostatic component is less accurate. Moreover, many electrostatic functionals fail to satisfy a basic theorem, the contact density theorem, that relates the bulk pressure, surface charge, and ion densities at their distances of closest approach for ions in equilibrium at a smooth, hard, planar wall. One popular electrostatic functional that fails to satisfy the contact density theorem is a perturbation approach developed by Kierlik and Rosinberg [Phys. Rev. A 44, 5025 (1991)PLRAAN1050-294710.1103/PhysRevA.44.5025] and Rosenfeld [J. Chem. Phys. 98, 8126 (1993)JCPSA60021-960610.1063/1.464569], where the full free-energy functional is Taylor-expanded around a bulk (homogeneous) reference fluid. Here, it is shown that this functional fails to satisfy the contact density theorem because it also fails to satisfy the known low-density limit. When the functional is corrected to satisfy this limit, a corrected bulk pressure is derived and it is shown that with this pressure both the contact density theorem and the Gibbs adsorption theorem are satisfied.

CoSix contact resistance after etching and ashing plasma exposure

International Nuclear Information System (INIS)

Katahira, Ken; Fukasawa, Masanaga; Kobayashi, Shoji; Takizawa, Toshifumi; Isobe, Michio; Hamaguchi, Satoshi; Nagahata, Kazunori; Tatsumi, Tetsuya

2009-01-01

The authors investigated the contact resistance fluctuation caused by CoSi x damage in plasma etching and ashing processes. They found that CoSi x layers damaged by plasma process exposure are readily oxidized when exposed to air resulting in increased resistance. They also found that the contact resistance increases more when CH 3 F is used instead of CF 4 during etching process. The lower the mass number of dominant ions becomes, the deeper the ions penetrate. Molecular dynamics simulation revealed that dissociated species from lighter ions penetrate deeper and that this stimulates deeper oxidation. They also found that contact resistance further increased by using postetch ashing plasma even in an H 2 /N 2 ashing process in which O 2 was not used. Here, too, the reason for this is that the ion penetration causes deep oxidation. They observed that the contact resistance has a linear relationship with the oxide concentration in CoSi x . This leads to the conclusion that it is essential to precisely control the ion energy as well as to properly select the ion species in the plasma process in the fabrication of next-generation semiconductor devices.

Improvement of Thermal Stability via Outer-Loop Ion Pair Interaction of Mutated T1 Lipase from Geobacillus zalihae Strain T1

Directory of Open Access Journals (Sweden)

Mahiran Basri

2012-01-01

Full Text Available Mutant D311E and K344R were constructed using site-directed mutagenesis to introduce an additional ion pair at the inter-loop and the intra-loop, respectively, to determine the effect of ion pairs on the stability of T1 lipase isolated from Geobacillus zalihae. A series of purification steps was applied, and the pure lipases of T1, D311E and K344R were obtained. The wild-type and mutant lipases were analyzed using circular dichroism. The Tm for T1 lipase, D311E lipase and K344R lipase were approximately 68.52 °C, 70.59 °C and 68.54 °C, respectively. Mutation at D311 increases the stability of T1 lipase and exhibited higher Tm as compared to the wild-type and K344R. Based on the above, D311E lipase was chosen for further study. D311E lipase was successfully crystallized using the sitting drop vapor diffusion method. The crystal was diffracted at 2.1 Å using an in-house X-ray beam and belonged to the monoclinic space group C2 with the unit cell parameters a = 117.32 Å, b = 81.16 Å and c = 100.14 Å. Structural analysis showed the existence of an additional ion pair around E311 in the structure of D311E. The additional ion pair in D311E may regulate the stability of this mutant lipase at high temperatures as predicted in silico and spectroscopically.

Fabrication of surfaces with extremely high contact angle hysteresis from polyelectrolyte multilayer.

Science.gov (United States)

Wang, Liming; Wei, Jingjing; Su, Zhaohui

2011-12-20

High contact angle hysteresis on polyelectrolyte multilayers (PEMs) ion-paired with hydrophobic perfluorooctanoate anions is reported. Both the bilayer number of PEMs and the ionic strength of deposition solutions have significant influence on contact angle hysteresis: higher ionic strength and greater bilayer number cause increased contact angle hysteresis values. The hysteresis values of ~100° were observed on smooth PEMs and pinning of the receding contact line on hydrophilic defects is implicated as the cause of hysteresis. Surface roughness can be used to further tune the contact angle hysteresis on the PEMs. A surface with extremely high contact angle hysteresis of 156° was fabricated when a PEM was deposited on a rough substrate coated with submicrometer scale silica spheres. It was demonstrated that this extremely high value of contact angle hysteresis resulted from the penetration of water into the rough asperities on the substrate. The same substrate hydrophobized by chemical vapor deposition of 1H,1H,2H,2H-perfluorooctyltriethoxysilane exhibits high advancing contact angle and low hysteresis. © 2011 American Chemical Society

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices.

Science.gov (United States)

Batra, Nitin M; Patole, Shashikant P; Abdelkader, Ahmed; Anjum, Dalaver H; Deepak, Francis L; Costa, Pedro M F J

2015-11-06

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode-interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode-nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices

KAUST Repository

Batra, Nitin M; Patole, Shashikant P.; Abdelkader, Ahmed; Anjum, Dalaver H.; Deepak, Francis L; Da Costa, Pedro M. F. J.

2015-01-01

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode–interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode–nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Structural changes of electron and ion beam-deposited contacts in annealed carbon-based electrical devices

KAUST Repository

Batra, Nitin M

2015-10-09

The use of electron and ion beam deposition to make devices containing discrete nanostructures as interconnectors is a well-known nanofabrication process. Classically, one-dimensional materials such as carbon nanotubes (CNTs) have been electrically characterized by resorting to these beam deposition methods. While much attention has been given to the interconnectors, less is known about the contacting electrodes (or leads). In particular, the structure and chemistry of the electrode–interconnector interface is a topic that deserves more attention, as it is critical to understand the device behavior. Here, the structure and chemistry of Pt electrodes, deposited either with electron or ion beams and contacted to a CNT, are analyzed before and after thermally annealing the device in a vacuum. Free-standing Pt nanorods, acting as beam-deposited electrode models, are also characterized pre- and post-annealing. Overall, the as-deposited leads contain a non-negligible amount of amorphous carbon that is consolidated, upon heating, as a partially graphitized outer shell enveloping a Pt core. This observation raises pertinent questions regarding the definition of electrode–nanostructure interfaces in electrical devices, in particular long-standing assumptions of metal-CNT contacts fabricated by direct beam deposition methods.

Surface tension alteration on calcite, induced by ion substitution

DEFF Research Database (Denmark)

Sakuma, Hiroshi; Andersson, Martin Peter; Bechgaard, Klaus

2014-01-01

The interaction of water and organic molecules with mineral surfaces controls many processes in nature and industry. The thermodynamic property, surface tension, is usually determined from the contact angle between phases, but how does one understand the concept of surface tension at the nanoscale...... preferentially as ion pairs at solution-calcite interfaces. Mg2+ incorporation weakens organic molecule adhesion while strengthening water adsorption so Mg2+ substitution renders calcite more water wet. When Mg2+ replaces 10% of surface Ca2+, the contact angle changes dramatically, by 40 to 70, converting...

Energetics and dynamics of the non-natural fluorescent 4AP:DAP base pair

KAUST Repository

Chawla, Mohit

2018-01-02

The fluorescent non-natural 4-aminophthalimide (4AP) base, when paired to the complementary 2,4-diaminopyrimidine (DAP) nucleobase, is accommodated in a B-DNA duplex being efficiently recognized and incorporated by DNA polymerases. To complement the experimental studies and rationalize the impact of the above non-natural bases on the structure, stability and dynamics of nucleic acid structures, we performed quantum mechanics (QM) calculations along with classical molecular dynamics (MD) simulations. QM calculations were initially focused on the geometry and energetics of the 4AP:DAP non-natural pair and of H-bonded base pairs between 4AP and all the natural bases in their classical Watson-Crick geometries. The QM calculations indicate that the 4AP:DAP pair, despite the fact that it can form 3 H-bonds in a classic Watson-Crick geometry, has a stability comparable to the A:T pair. Then, we extended the study to reverse Watson-Crick geometries, characteristic of parallel strands. MD simulations were carried out on two 13-mer DNA duplexes, featuring a central 4AP:DAP or A:T pair, respectively. No major structural deformation of the duplex was observed during the MD simulation. Snapshots from the MD simulations were subjected to QM calculations to investigate the 4AP:DAP interaction energy when embedded into a duplex structure, and to investigate the impact of the two non-natural bases on the stacking interactions with adjacent bases in the DNA duplex. We found a slight increase in stacking interactions involving the 4AP:DAP pair, counterbalanced by a moderate decrease in H-bonding interactions of the 4AP:DAP and of the adjacent base pairs in the duplex. The results of our study are in agreement with experimental data and complement them by providing an insight into which factors contribute positively and which factors contribute negatively to the structural compatibility of the fluorescent 4AP:DAP pair with a B-DNA structure.

Anisotropic exchange interaction for magnetic ion pairs in insulators

International Nuclear Information System (INIS)

Passeggi, M.C.G.

1975-12-01

The sources of possible contributions to the magnetic anisotropy for a pair of orbitally non degenerate magnetic ions are investigated. The problem being formulated with the help of the operator form of perturbation theory and irreducible tensor operators. Apart from the usual dipole-dipole effective interaction, mainly induced by the electronic spin-spin dipole coupling corrected by covalency, other mechanisms mediated by the spin-orbit coupling appear. These are a consequence of an appropriate description of the spin-orbit operators for a system which allows for delocalization of the magnetic electrons. A process similar to that known as pseudodipolar appears from contributions in which spin orbit combined with the Coulomb repulsion and with one-electron interactions (acting analogously as for the ''kinetic exchange'') produce compensating effects in third and fourth order, respectively. However, this effect does not appear to be describable in terms of the phenomenological exchange, as is usually assumed. (Passeggi, M.C.G.)

Magnetic field effect in fluorescence of excited fluorophore equilibrated with exciplex that reversibly dissociates into radical-ion pair undergoing the spin conversion.

Science.gov (United States)

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2012-07-14

The fluorescence of the photoexcited electron acceptor, (1)A∗, and the exciplex, (1)[D(+δ)A(-δ)] formed at contact of (1)A∗ with an electron donor (1)D, is known to be very sensitive to a magnetic field, assisting the spin conversion in the resulting geminate radical ion pair (RIP), (1, 3)[D(+)...A(-)]. The relative increase of the fluorescence in the highest magnetic field compared to the lowest one, known as the magnetic field effect, crucially depends on the dielectric constant of the solvent, ɛ. This phenomenon first studied experimentally is at first reproduced here theoretically by means of the so called integral encounter theory. It was shown to be very sensitive to the position of the exciplex energy level relative to the levels of exciplex precursors and the charged products of its dissociation. The results obtained strongly depend on the dielectric properties of the solvents as well as on the exciplex and RIP formation rates.

Electron-positron pair production in Coulomb collisions at ultrarelativistic energies

International Nuclear Information System (INIS)

Vane, C.R.; Datz, S.; Dittner, P.F.; Krause, H.F.; Bottcher, C.; Strayer, M.; Schuch, R.; Gao, H.; Hutton, R.

1993-01-01

We have measured angular and momentum distributions for electrons and positrons created as pairs in peripheral collisions of 6.4 TeV bare sulfur ions with fixed targets of Al, Pd, and Au. Singly- and doubly-differential cross sections have been determined for 1--17 MeV/c electrons and positrons detected independently and in coincidence as pairs. Integrated yields for pair production are found to vary as the square of the target nuclear charge. Relative angular and momentum differential cross sections are effectively target independent. Probability distributions for the pair total momentum, the positron fraction of the pair momentum, and the pair traverse momentum have been derived from the coincident electron-positron data

All-Solid-State Sodium-Selective Electrode with a Solid Contact of Chitosan/Prussian Blue Nanocomposite

Directory of Open Access Journals (Sweden)

Tanushree Ghosh

2017-11-01

Full Text Available Conventional ion-selective electrodes with a liquid junction have the disadvantage of potential drift. All-solid-state ion-selective electrodes with solid contact in between the metal electrode and the ion-selective membrane offer high capacitance or conductance to enhance potential stability. Solution-casted chitosan/Prussian blue nanocomposite (ChPBN was employed as the solid contact layer for an all-solid-state sodium ion-selective electrode in a potentiometric sodium ion sensor. Morphological and chemical analyses confirmed that the ChPBN is a macroporous network of chitosan that contains abundant Prussian blue nanoparticles. Situated between a screen-printed carbon electrode and a sodium-ionophore-filled polyvinylchloride ion-selective membrane, the ChPBN layer exhibited high redox capacitance and fast charge transfer capability, which significantly enhanced the performance of the sodium ion-selective electrode. A good Nernstian response with a slope of 52.4 mV/decade in the linear range from 10−4–1 M of NaCl was observed. The stability of the electrical potential of the new solid contact was tested by chronopotentiometry, and the capacitance of the electrode was 154 ± 4 µF. The response stability in terms of potential drift was excellent (1.3 µV/h for 20 h of continuous measurement. The ChPBN proved to be an efficient solid contact to enhance the potential stability of the all-solid-state ion-selective electrode.

Heavy Rydberg behaviour in high vibrational levels of some ion-pair states of the halogens and inter-halogens

International Nuclear Information System (INIS)

Donovan, Robert J.; Lawley, Kenneth P.; Ridley, Trevor

2015-01-01

We report the identification of heavy Rydberg resonances in the ion-pair spectra of I 2 , Cl 2 , ICl, and IBr. Extensive vibrational progressions are analysed in terms of the energy dependence of the quantum defect δ(E b ) rather than as Dunham expansions. This is shown to define the heavy Rydberg region, providing a more revealing fit to the data with fewer coefficients and leads just as easily to numbering data sets separated by gaps in the observed vibrational progressions. Interaction of heavy Rydberg states with electronic Rydberg states at avoided crossings on the inner wall of the ion-pair potential is shown to produce distinctive changes in the energy dependence of δ(E b ), with weak and strong interactions readily distinguished. Heavy Rydberg behaviour is found to extend well below near-dissociation states, down to vibrational levels ∼18 000-20 000 cm −1 below dissociation. The rapid semi-classical calculation of δ(E b ) for heavy Rydberg states is emphasised and shows their absolute magnitude to be essentially the volume of phase space excluded from the vibrational motion by avoiding core-core penetration of the ions

Origin of Enhanced Reactivity of a Microsolvated Nucleophile in Ion Pair SN2 Reactions: The Cases of Sodium p-Nitrophenoxide with Halomethanes in Acetone.

Science.gov (United States)

Li, Qiang-Gen; Xu, Ke; Ren, Yi

2015-04-30

In a kinetic experiment on the SN2 reaction of sodium p-nitrophenoxide with iodomethane in acetone-water mixed solvent, Humeres et al. (J. Org. Chem. 2001, 66, 1163) found that the reaction depends strongly on the medium, and the fastest rate constant was observed in pure acetone. The present work tries to explore why acetone can enhance the reactivity of the title reactions. Accordingly, we make a mechanistic study on the reactions of sodium p-nitrophenoxide with halomethanes (CH3X, X = Cl, Br, I) in acetone by using a supramolecular/continuum model at the PCM-MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) level, in which the ion pair nucleophile is microsolvated by one to three acetone molecules. We compared the reactivity of the microsolvated ion pair nucleophiles with solvent-free ion pair and anionic ones. Our results clearly reveal that the microsolvated ion pair nucleophile is favorable for the SN2 reactions; meanwhile, the origin of the enhanced reactivity induced by microsolvation of the nucleophile is discussed in terms of the geometries of transition state (TS) structures and activation strain model, suggesting that lower deformation energies and stronger interaction energies between the deformed reactants in the TS lead to the lower overall reaction barriers for the SN2 reaction of microsolvated sodium p-nitrophenoxide toward halomethanes in acetone.

Diffusion, Ion Pairing and Aggregation in 1-Ethyl-3-Methylimidazolium-Based Ionic Liquids Studied by 1 H and 19 F PFG NMR: Effect of Temperature, Anion and Glucose Dissolution.

Science.gov (United States)

D'Agostino, Carmine; Mantle, Mick D; Mullan, Claire L; Hardacre, Christopher; Gladden, Lynn F

2018-01-31

In this work, using 1 H and 19 F PFG NMR, we probe the effect of temperature, ion size/type and glucose dissolution on the rate of transport in 1-ethyl-3-methylimidazolium ([EMIM] + )-based ionic liquids by measuring self-diffusion coefficients. Using such data, we are able to establish the degree of ion pairing and quantify the extent of ionic aggregation during diffusion. For the neat 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) a strong degree of ion pairing is observed. The substitution of the [OAc] - anion with the bis{(trifluoromethyl)sulfonyl}imide ([TFSI] - ) anion reduces the pairing between the ions, which is attributed to a lower electric charge density on the [TFSI] - anion, hence a weaker electric interaction with the [EMIM] + cation. The effect of glucose, important for applications of ionic liquids as extracting media, on the strongly paired [EMIM][OAc] sample was also investigated and it is observed that the carbohydrate decreases the degree of ion pairing, which is attributed to the ability of glucose to disrupt inter-ionic interactions by forming hydrogen bonding, particularly with the [OAc] - anion. Calculations of aggregation number from diffusion data show that the [OAc] - anion diffuses as a part of larger aggregates compared to the [EMIM] + cation. The results and analysis presented here show the usefulness of PFG NMR in studies of ionic liquids, giving new insights into ion pairing and aggregation and the factors affecting these parameters. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrasound-assisted leaching of rare earths from the weathered crust elution-deposited ore using magnesium sulfate without ammonia-nitrogen pollution.

Science.gov (United States)

Yin, Shaohua; Pei, Jiannan; Jiang, Feng; Li, Shiwei; Peng, Jinhui; Zhang, Libo; Ju, Shaohua; Srinivasakannan, Chandrasekar

2018-03-01

The in situ leaching process of China's unique ion-adsorption rare earth ores has caused severe environmental damages due to the use of (NH 4 ) 2 SO 4 solution. This study reports that magnesium sulfate (MgSO 4 ) as a leaching agent would replace (NH 4 ) 2 SO 4 by ultrasonically assisted leaching to deal with the ammonia-nitrogen pollution problem and enhance leaching process. At leaching conditions of 3wt% MgSO 4 concentration, 3:1L/S ratio and 30min, the total rare earth leaching efficiency reaches 75.5%. Ultrasound-assisted leaching experiments show that the leaching efficiency of rare earths is substantially increased by introducing ultrasound, and nearly completely leached out after two stage leaching process. Thus, ultrasonic-assisted leaching process with MgSO 4 is not only effective but also environmentally friendly, and beneficial to leach rare earths at laboratory scale. Copyright © 2017 Elsevier B.V. All rights reserved.

Enabling the intestinal absorption of highly polar antiviral agents: ion-pair facilitated membrane permeation of zanamivir heptyl ester and guanidino oseltamivir.

Science.gov (United States)

Miller, Jonathan M; Dahan, Arik; Gupta, Deepak; Varghese, Sheeba; Amidon, Gordon L

2010-08-02

Antiviral drugs often suffer from poor intestinal permeability, preventing their delivery via the oral route. The goal of this work was to enhance the intestinal absorption of the low-permeability antiviral agents zanamivir heptyl ester (ZHE) and guanidino oseltamivir (GO) utilizing an ion-pairing approach, as a critical step toward making them oral drugs. The counterion 1-hydroxy-2-naphthoic acid (HNAP) was utilized to enhance the lipophilicity and permeability of the highly polar drugs. HNAP substantially increased the log P of the drugs by up to 3.7 log units. Binding constants (K(11(aq))) of 388 M(-1) for ZHE-HNAP and 2.91 M(-1) for GO-HNAP were obtained by applying a quasi-equilibrium transport model to double-reciprocal plots of apparent octanol-buffer distribution coefficients versus HNAP concentration. HNAP enhanced the apparent permeability (P(app)) of both compounds across Caco-2 cell monolayers in a concentration-dependent manner, as substantial P(app) (0.8-3.0 x 10(-6) cm/s) was observed in the presence of 6-24 mM HNAP, whereas no detectable transport was observed without counterion. Consistent with a quasi-equilibrium transport model, a linear relationship with slope near 1 was obtained from a log-log plot of Caco-2 P(app) versus HNAP concentration, supporting the ion-pair mechanism behind the permeability enhancement. In the rat jejunal perfusion assay, the addition of HNAP failed to increase the effective permeability (P(eff)) of GO. However, the rat jejunal permeability of ZHE was significantly enhanced by the addition of HNAP in a concentration-dependent manner, from essentially zero without HNAP to 4.0 x 10(-5) cm/s with 10 mM HNAP, matching the P(eff) of the high-permeability standard metoprolol. The success of ZHE-HNAP was explained by its >100-fold stronger K(11(aq)) versus GO-HNAP, making ZHE-HNAP less prone to dissociation and ion-exchange with competing endogenous anions and able to remain intact during membrane permeation. Overall, this

Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

KAUST Repository

Alsam, Amani Abdu; Aly, Shawkat Mohammede; Usman, Anwar; Parida, Manas R.; Del Gobbo, Silvano; Alarousu, Erkki; Mohammed, Omar F.

2015-01-01

We explored the excited-state interactions of bimolecular, non-covalent systems consisting of cationic poly[(9,9-di(3,3’-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and 1,4-dicyanobenzene (DCB) using steady-state and time-resolved techniques, including femto- and nanosecond transient absorption and femtosecond infrared spectroscopies with broadband capabilities. The experimental results demonstrated that photo-induced electron transfer from PFN to DCB occurs on the picosecond time scale, leading to the formation of PFN+• and DCB-• radical ions. Interestingly, real-time observations of the vibrational marker modes on the acceptor side provided direct evidence and insight into the electron transfer process indirectly inferred from UV-Vis experiments. The band narrowing on the picosecond time scale observed on the antisymmetric C-N stretching vibration of the DCB radical anion provides clear experimental evidence that a substantial part of the excess energy is channeled into vibrational modes of the electron transfer product and that the geminate ion pairs dissociate. More importantly, our nanosecond time-resolved data indicate that the charge-separated state is very long lived ( 30 ns) due to the dissociation of the contact radical ion pair into free ions. Finally, the fast electron transfer and slow charge recombination anticipate the current donor−acceptor system with potential applications in organic solar cells.

Bimolecular Excited-State Electron Transfer with Surprisingly Long-Lived Radical Ions

KAUST Repository

Alsam, Amani Abdu

2015-09-02

We explored the excited-state interactions of bimolecular, non-covalent systems consisting of cationic poly[(9,9-di(3,3’-N,N’-trimethyl-ammonium) propyl fluorenyl-2,7-diyl)-alt-co-(9,9-dioctyl-fluorenyl-2,7-diyl)] diiodide salt (PFN) and 1,4-dicyanobenzene (DCB) using steady-state and time-resolved techniques, including femto- and nanosecond transient absorption and femtosecond infrared spectroscopies with broadband capabilities. The experimental results demonstrated that photo-induced electron transfer from PFN to DCB occurs on the picosecond time scale, leading to the formation of PFN+• and DCB-• radical ions. Interestingly, real-time observations of the vibrational marker modes on the acceptor side provided direct evidence and insight into the electron transfer process indirectly inferred from UV-Vis experiments. The band narrowing on the picosecond time scale observed on the antisymmetric C-N stretching vibration of the DCB radical anion provides clear experimental evidence that a substantial part of the excess energy is channeled into vibrational modes of the electron transfer product and that the geminate ion pairs dissociate. More importantly, our nanosecond time-resolved data indicate that the charge-separated state is very long lived ( 30 ns) due to the dissociation of the contact radical ion pair into free ions. Finally, the fast electron transfer and slow charge recombination anticipate the current donor−acceptor system with potential applications in organic solar cells.

Effect of the presence of inorganic salts on the photocatalytic inactivation of E. Coli in water Efecto de la presencia de sales inorgánicas sobre la inactivación fotocatalítica de E. Coli en agua

Directory of Open Access Journals (Sweden)

Edwing Velasco

2013-03-01

Full Text Available This article presents the effect of inorganic salts MgSO4, NaCl and CaCO3 on the photocatalytic water disinfection. TiO2-P25 was used as a photocatalyst, and E. Coli was used as a contaminant. Disinfection tests were performed by controlling lighting of batch reactors loaded with contaminated water, salts and TiO2. The results of these tests were used to determine the kinetic parameters of a type Langmuir-Hinshelwood model. It was found that the salts have a strong influence on the photocatalytic inactivation of E. Coli and that each salt and its concentration affect disinfection differently in the following order: NaCl>CaCO3>>MgSO4. Additionally, the value of the calculated parameters was different for each salt, showing that the salts affect the process by several mechanisms related to the ion-bacteria interactions, ion-oxidizing species and ion-TiO2.En este artículo se presenta el efecto de las sales inorgánicas MgSO4, NaCl y CaCO3 en la desinfección fotocatalítica del agua. Se usó TiO2-P25 como fotocatalizador y E. Coli como microorganismo contaminante. Las pruebas de desinfección se realizaron mediante la iluminación controlada de reactores batch cargados con agua contaminada, sales y TiO2. Los resultados de estas pruebas fueron usados para determinar los parámetros cinéticos de un modelo tipo Langmuir-Hinshelwood. Se encontró que las sales tienen una fuerte influencia sobre la inactivación fotocatalítica de E. Coli, y que cada sal y su concentración afectan la desinfección de forma diferente y en el siguiente orden: NaCl>CaCO3>>MgSO4. Adicionalmente, el valor de los parámetros calculados fue diferente para cada sal, evidenciando que las sales afectan el proceso por varios mecanismos relacionados con las interacciones ion-bacteria, ion-especie oxidante e ion-TiO2.

Adsorption and ion-pairing interactions of phospholipids in the system of two immiscible electrolyte solutions. Part II: ...

Czech Academy of Sciences Publication Activity Database

Jänchenová, Hana; Štulík, K.; Mareček, Vladimír

2007-01-01

Roč. 604, č. 2 (2007), s. 109-114 ISSN 0022-0728 R&D Projects: GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : liquid/liquid interfaces * adsorption of phosphodolipids * DPPC * surface-active amines * ion pairing Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.580, year: 2007

Ion-pair extraction of [3H]stobadine from biological fluids

International Nuclear Information System (INIS)

Scasnar, V.

1998-01-01

A simple and specific radiometric assay was developed for the determination of stobadine, a cardioprotective drug, in the serum of experimental animals. The assay is based on a single extraction step of the radioactively labeled drug from serum into the benzene solution of dicarbolide of cobalt followed by quantitation of the extracted radioactivity by using liquid scintillation counting. The extraction mechanism involves the ion-pair formation between the protonized molecule of stobadine and the hydrophobic, negatively charged molecule of dicarbolide of cobalt. The extraction yield of stobadine from 1 ml of serum was 95% in the concentration range from 1 to 6000 ng/ml. The co-extraction of metabolites was less than 5%. The method was applied to the determination of stobadine in serum of dogs and the data obtained were in a good agreement with those obtained by high performance liquid chromatography. (author)

Nonperturbative electromagnetic muon-pair production with capture in peripheral relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Wells, J.C.

1991-01-01

We discuss preliminary calculations of impact-parameter-dependent probabilities and cross sections for muon-pair production with capture of the negative muon into the K-shell of the target caused by the time-dependent electromagnetic fields generated in peripheral relativistic heavy-ion collisions. Our approach is nonperturbative in that we calculate probabilities by solving the time-dependent Dirac equation on a three-dimensional Cartesian lattice using the basis-spline collocation method. Use of the axial gauge for the electromagnetic potentials produces an interaction easier to implement on the lattice than the Lorentz gauge. 19 refs., 5 figs

Retention modeling under organic modifier gradient conditions in ion-pair reversed-phase chromatography. Application to the separation of a set of underivatized amino acids.

Science.gov (United States)

Pappa-Louisi, A; Agrafiotou, P; Papachristos, K

2010-07-01

The combined effect of the ion-pairing reagent concentration, C(ipr), and organic modifier content, phi, on the retention under phi-gradient conditions at different constant C(ipr) was treated in this study by using two approaches. In the first approach, the prediction of the retention time of a sample solute is based on a direct fitting procedure of a proper retention model to 3-D phi-gradient retention data obtained under the same phi-linear variation but with different slope and time duration of the initial isocratic part and in the presence of various constant C(ipr) values in the eluent. The second approach is based on a retention model describing the combined effect of C(ipr) and phi on the retention of solutes in isocratic mode and consequently analyzes isocratic data obtained in mobile phases containing different C(ipr) values. The effectiveness of the above approaches was tested in the retention prediction of a mixture of 16 underivatized amino acids using mobile phases containing acetonitrile as organic modifier and sodium dodecyl sulfate as ion-pairing reagent. From these approaches, only the first one gives satisfactory predictions and can be successfully used in optimization of ion-pair chromatographic separations under gradient conditions. The failure of the second approach to predict the retention of solutes in the gradient elution mode in the presence of different C(ipr) values was attributed to slow changes in the distribution equilibrium of ion-pairing reagents caused by phi-variation.

An automated method for the analysis of phenolic acids in plasma based on ion-pairing micro-extraction coupled on-line to gas chromatography/mass spectrometry with in-liner derivatisation

NARCIS (Netherlands)

Peters, S.; Kaal, E.; Horsting, I.; Janssen, H.-G.

2012-01-01

A new method is presented for the analysis of phenolic acids in plasma based on ion-pairing ‘Micro-extraction in packed sorbent’ (MEPS) coupled on-line to in-liner derivatisation-gas chromatography-mass spectrometry (GC-MS). The ion-pairing reagent served a dual purpose. It was used both to improve

ANALYSIS OF SULFONATES IN AQUEOUS SAMPLES BY ION-PAIR LC/ESI-MS/MS WITH IN-SOURCE CID FOR ADDUCT PEAK ELIMINATION

Energy Technology Data Exchange (ETDEWEB)

OUYANG,S.; VAIRAVAMURTHY,M.A.

1999-06-13

Determination of low-molecular-weight organic sulfonates (e.g. taurine and cysteic acid) in aqueous solutions is important in many applications of biological, environmental and pharmaceutical sciences. These compounds are difficult to be determined by commonly used reversed-phase liquid chromatographic separation combined with UV-Visible detection because of their high solubility and the lack chromophoric moieties. Here the authors report a method combining ion-pair liquid chromatography and electrospray ionization tandem mass spectrometry (IPLC/ESI-MS/MS)for determining sulfonates. The ability of low-molecular-weight sulfonates to form ion-pairs with quaternary ammonium cations in aqueous solutions allowed LC separation with a C{sub 18} column. Detection of the sulfonates was accomplished with ESI-MS that lends a universal mode of mass detection for polar, water soluble compounds. An in-source collision induced dissociation (CID) was applied to eliminate the adduct peaks in mass spectra. Characteristic marker ions showed in the second stage mass spectra lent a method for identifying sulfonates.

Charge Inversion and Ion-Ion Correlation Effects at the Mercury/Aqueous MgSO4 Interface: Toward the Solution of a Long-Standing Issue

Czech Academy of Sciences Publication Activity Database

Wernersson, Erik; Kjellander, R.; Lyklema, J.

2010-01-01

Roč. 114, č. 4 (2010), s. 1849-1866 ISSN 1932-7447 Institutional research plan: CEZ:AV0Z40550506 Keywords : charge inversion * colloid * aqueous interface Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.520, year: 2010

Ion-pair vortex assisted liquid-liquid microextraction with back extraction coupled with high performance liquid chromatography-UV for the determination of metformin in plasma.

Science.gov (United States)

Alshishani, Anas; Makahleh, Ahmad; Yap, Hui Fang; Gubartallah, Elbaleeq Adam; Salhimi, Salizawati Muhamad; Saad, Bahruddin

2016-12-01

A new sample preparation method, ion-pair vortex assisted liquid-liquid microextraction (VALLME-BE), for the determination of a highly polar anti-diabetic drug (metformin) in plasma sample was developed. The VALLME-BE was performed by diluting the plasma in borate buffer and extracted to 150µL 1-octanol containing 0.2M di-(2-ethylhexyl)phosphoric acid as intermediate phase. The drug was next back-extracted into 20µL of 0.075M HCl solution. The effects of pH, ion-pair concentration, type of organic solvent, volume of extraction phases, ionic strength, vortexing and centrifugation times on the extraction efficiency were investigated. The optimum conditions were at pH 9.3, 60s vortexing and 2min centrifugation. The microextract, contained metformin and buformin (internal standard), was directly injected into a HPLC unit using C1 column (250mm×4.6mm×10µm) and detected at 235nm. The method was validated and calibration curve was linear with r 2 >0.99 over the range of 20-2000µgL -1 . The limits of detection and quantitation were 1.4 and 4.1µgL -1 , respectively. The accuracy was within 94.8-108% of the nominal concentration. The relative standard deviation for inter- and intra-day precision was less than 10.8%. The method was conveniently applied for the determination of metformin in plasma samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemistry and safety of Li 4Ti 5O 12 and graphite anodes paired with LiMn 2O 4 for hybrid electric vehicle Li-ion battery applications

Science.gov (United States)

Belharouak, Ilias; Koenig, Gary M.; Amine, K.

A promising anode material for hybrid electric vehicles (HEVs) is Li 4Ti 5O 12 (LTO). LTO intercalates lithium at a voltage of ∼1.5 V relative to lithium metal, and thus this material has a lower energy compared to a graphite anode for a given cathode material. However, LTO has promising safety and cycle life characteristics relative to graphite anodes. Herein, we describe electrochemical and safety characterizations of LTO and graphite anodes paired with LiMn 2O 4 cathodes in pouch cells. The LTO anode outperformed graphite with regards to capacity retention on extended cycling, pulsing impedance, and calendar life and was found to be more stable to thermal abuse from analysis of gases generated at elevated temperatures and calorimetric data. The safety, calendar life, and pulsing performance of LTO make it an attractive alternative to graphite for high power automotive applications, in particular when paired with LiMn 2O 4 cathode materials.

Iodide Ion Pairing with Highly Charged Ruthenium Polypyridyl Cations in CH3CN.

Science.gov (United States)

Swords, Wesley B; Li, Guocan; Meyer, Gerald J

2015-05-04

A series of three highly charged cationic ruthenium(II) polypyridyl complexes of the general formula [Ru(deeb)3-x(tmam)x](PF6)2x+2, where deeb is 4,4'-diethyl ester-2,2'-bipyridine and tmam is 4,4'-bis[(trimethylamino)methyl]-2,2'-bipyridine, were synthesized and characterized and are referred to as 1, 2, or 3 based on the number of tmam ligands. Crystals suitable for X-ray crystallography were obtained for the homoleptic complex 3, which was found to possess D3 symmetry over the entire ruthenium complex. The complexes displayed visible absorption spectra typical of metal-to-ligand charge-transfer (MLCT) transitions. In acetonitrile, quasi-reversible waves were assigned to Ru(III/II) electron transfer, with formal reduction potentials that shifted negative as the number of tmam ligands was increased. Room temperature photoluminescence was observed in acetonitrile with quantum yields of ϕ ∼ 0.1 and lifetimes of τ ∼ 2 μs. The spectroscopic and electrochemical data were most consistent with excited-state localization on the deeb ligand for 1 and 2 and on the tmam ligand for 3. The addition of tetrabutylammonium iodide to the complexes dissolved in a CH3CN solution led to changes in the UV-vis absorption spectra consistent with ion pairing. A Benesi-Hildebrand-type analysis of these data revealed equilibrium constants that increased with the cationic charge 1 10(8) s(-1). The possible relevance of this work to solar energy conversion and dye-sensitized solar cells is discussed.

Analysis of phosphorus herbicides by ion-pairing reversed-phase liquid chromatography coupled to inductively coupled plasma mass spectrometry with octapole reaction cell.

Science.gov (United States)

Sadi, Baki B M; Vonderheide, Anne P; Caruso, Joseph A

2004-09-24

A reversed phase ion-pairing high performance liquid chromatographic (RPIP-HPLC) method is developed for the separation of two phosphorus herbicides, Glufosinate and Glyphosate as well as Aminomethylphosphonic acid (AMPA), the major metabolite of Glyphosate. Tetrabutylammonium hydroxide is used as the ion-pairing reagent in conjunction with an ammonium acetate/acetic acid buffering system at pH 4.7. An inductively coupled plasma mass spectrometer (ICP-MS) is coupled to the chromatographic system to detect the herbicides at m/z = 31P. Historically, phosphorus has been recognized as one of the elements difficult to analyze in argon plasma. This is due to its relatively high ionization potential (10.5 eV) as well as the inherent presence of the polyatomic interferences 14N16O1H+ and 15N16O+ overlapping its only isotope at m/z = 31. An octapole reaction cell is utilized to minimize the isobaric polyatomic interferences and to obtain the highest signal-to-background ratio. Detection limits were found to be in the low ppt range (25-32 ng/l). The developed method is successfully applied to the analysis of water samples collected from the Ohio River and spiked with a standard compounds at a level of 20 microg/l.

Raman spectroscopic studies on single supersaturated droplets of sodium and magnesium acetate.

Science.gov (United States)

Wang, Liang-Yu; Zhang, Yun-Hong; Zhao, Li-Jun

2005-02-03

Raman spectroscopy was used to study structural changes, in particular, the formation of contact-ion pairs in supersaturated aqueous NaCH(3)COO and Mg(CH(3)COO)(2) droplets at ambient temperatures. The single droplets levitated in an electrodynamic balance (EDB), lost water, and became supersaturated when the relative humidity (RH) decreased. For NaCH(3)COO droplet the water-to-solute molar ratio (WSR) was 3.87 without solidification when water molecules were not enough to fill in the first hydration layer of Na(+), in favor of the formation of contact-ion pairs. However, the symmetric stretching vibration band (nu(3) mode) of free -COO(-) constantly appeared at 1416 cm(-1), and no spectroscopic information related to monodentate, bidentate, or bridge bidentate contact-ion pairs was observed due to the weak interactions between the Na(+) and acetate ion. On the other hand, the band of methyl deformation blue shifted from 1352 to 1370 cm(-1) (at RH = 34.2%, WSR = 2.43), corresponding to the solidification process of a novel metastable phase in the highly supersaturated solutions. With further decreasing RH, a small amount of supersaturated solution still existed and was proposed to be hermetically covered by the metastable phase of the particle. In contrast, the interaction between Mg(2+) and acetate ion is much stronger. When WSR decreased from 21.67 to 2.58 for the Mg(CH(3)COO)(2) droplet, the band of C-C-symmetric stretching (nu(4) mode) had a blue shift from 936 to 947 cm(-1). The intensity of the two new shoulders (approximately 1456 and approximately 1443 cm(-1)) of the nu(3) band of free -COO(-) at 1420 cm(-1) increased with the decrease of WSR. These changes were attributed to the formation of contact-ion pairs with bidentate structures. In particular, the small frequency difference between the shoulder at approximately 1443 cm(-1) and the nu(3) band of the free -COO(-) group (approximately 1420 cm(-1)) was proposed to be related to the formation of a chain

Evaluation of Spur Gear Pair on Tooth Root Bending Stress in Radial Misalignment Contact Condition

Directory of Open Access Journals (Sweden)

Lias M.R.

2014-07-01

Full Text Available This paper evaluates the effects of radial misalignment contact on the tooth root bending stress values of spur gear pair during the gear meshing cycle. Radial misalignment (H is denoted as the deviation of the pinion nominal position with respect to the gear tooth along the pinion axis to the gear which happened from manufacturing assembly errors (AE. A model based on involute 3D parametric CAD geometry, of spur gear design ISO 6336:2006 is analysed with allowable AE values from minimum 10μm to maximum 40μm with Finite-Element Method (FEM model based methodology using a dynamics module from ANSYS. Main parameters of interest are the Tooth root bending stress (TRBS in H condition with AE along the critical region with respect to face width of pinion-gear section. A comparison between standard High point single tooth contact models (HPSTC to this model showed a good agreement that H with AE had great influence on TRBS as the values’ increase. Radial misalignment influence factor (RMIF was introduced as indication of TRBS values in consideration of H due to AE shows and inverted patterns higher for pinion, give a good justification that the pinion is weaker compared to the gear.

Simultaneous determination of 11 fluorescent whitening agents in food-contact paper and board by ion-pairing high-performance liquid chromatography with fluorescence detection.

Science.gov (United States)

Jiang, Dingguo; Chen, Lisong; Fu, Wusheng; Qiu, Hanquan

2015-02-01

4,4'-Diaminostilbene-2,2'-disulfonic acid based fluorescent whitening agents (DSD-FWAs) are prohibited in food-contact paper and board in many countries. In this work, a reliable high-performance liquid chromatography method was developed for the simultaneous determination of 11 common DSD-FWAs in paper material. Sample preparation and extraction as well as chromatographic separation of multicomponent DSD-FWAs were successfully optimized. DSD-FWAs in prepared samples were ultrasonically extracted with acetonitrile/water/triethylamine (40:60:1, v/v/v), separated on the C(18) column with the mobile phase containing tetrabutylammonium bromide, and then detected by a fluorescence detector. The limits of detection were 0.12-0.24 mg/kg, and the calibration curves showed the linear correlation (R(2) ≥ 0.9994) within the range of 8.0-100 ng/mL, which was equivalent to the range of 0.80-10 mg/kg in the sample. The average recoveries and the RSDs were 81-106% and 2-9% at two fortification levels (1.0 and 5.0 mg/kg) in paper bowls, respectively. The successful determination of 11 DSD-FWAs in food-contact paper and board obtained from local markets indicated that the newly developed method was rapid, accurate, and highly selective. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complementary b/y fragment ion pairs from post-source decay of metastable YahO for calibration of MALDI-TOF-TOF-MS/MS

Science.gov (United States)

Complementary b/y fragment ion pairs from post-source decay (PSD) of metastable YahO protein ion were evaluated for use in the calibration of MALDI-TOF-TOF for tandem mass spectrometry (MS/MS). The yahO gene from pathogenic Escherichia coli O157:H7 strain EDL933 was cloned into a pBAD18 plasmid vect...

Evidence for pair correlation effects in heavy ion reactions

CERN Document Server

Auditore, L; D'Amico, V; De Pasquale, D; Trifiró, A; Trimarchi, M; Italiano, A

2003-01-01

The study of the sup 1 sup 2 C( sup 1 sup 4 N, sup 1 sup 4 N) sup 1 sup 2 C reaction was performed at 28 and 35 MeV beam energies. The results were analyzed in the frame of the EFRDWBA (Exact-Finite-Range Distorted Wave Born Approximation) assuming the simultaneous and sequential transfer of a np pair. The angular distributions, fairly reproduced in the first case, confirm the validity of the generalized BCS (Bardeen-Cooper-Schrieffer) theory to explain this behaviour. Moreover, this process could be regarded as a possible Nuclear Josephson Effect. (author)

Extractive spectrophotometric determination of five selected drugs by ion-pair complex formation with bromothymol blue in pure form and pharmaceutical preparations

Directory of Open Access Journals (Sweden)

Sneha G. Nair

2015-12-01

Full Text Available Simple, precise, selective, and expeditious spectrophotometric methods have been developed for the determination of itopride (ITO, midodrine (MID, diclofenac (DIC, mesalamine (MES, and sumatriptan (SUM in their pure form as well as in pharmaceutical preparations. The method was based on ion-pair complex formation between the drugs and anionic dye, bromothymol blue in an acidic medium (pH 2.0–4.0. The yellow colored complexes formed were quantitatively extracted into chloroform and measured at 411, 410, 413, 412, and 414 nm wavelength for ITO, MID, DIC, MES, and SUM, respectively. Beer’s law was obeyed in the concentration range of 3.0–30 µg/mL for ITO, 1.0–20 µg/mL for MID, 1.5–40 µg/mL for DIC, 1.2–12 µg/mL for MES, and 0.5–15 µg/mL for SUM. The stoichiometry of the complexes formed between the drugs and the dye was 1:1 as determined by Job’s method of continuous variation. The association constant (KIP of the ion-pair complexes formed was evaluated using Benesi–Hildebrand equation. Limit of detection, limit of quantification, and Sandell’s sensitivity of the methods were also estimated. The proposed methods were successfully employed for the determination of these drugs in their pharmaceutical dosage forms.

Rigid supersymmetry on 5-dimensional Riemannian manifolds and contact geometry

International Nuclear Information System (INIS)

Pan, Yiwen

2014-01-01

In this note we generalize the methods of http://dx.doi.org/10.1007/JHEP08(2012)141, http://dx.doi.org/10.1007/JHEP01(2013)072 and http://dx.doi.org/10.1007/JHEP05(2013)017 to 5-dimensional Riemannian manifolds M. We study the relations between the geometry of M and the number of solutions to a generalized Killing spinor equation obtained from a 5-dimensional supergravity. The existence of 1 pair of solutions is related to almost contact metric structures. We also discuss special cases related to M=S 1 ×M 4 , which leads to M being foliated by submanifolds with special properties, such as Quaternion-Kähler. When there are 2 pairs of solutions, the closure of the isometry sub-algebra generated by the solutions requires M to be S 3 or T 3 -fibration over a Riemann surface. 4 pairs of solutions pin down the geometry of M to very few possibilities. Finally, we propose a new supersymmetric theory for N=1 vector multiplet on K-contact manifold admitting solutions to the Killing spinor equation

The Mathematical and Computer Aided Analysis of the Contact Stress of the Surface With 4th Order

Science.gov (United States)

Huran, Liu

Inspired from some gears with heavy power transmission in practical usage after serious plastic deformation in metallurgical industry, we believe that there must existed some kind of gear profile which is most suitable in both the contact and bending fatigue strength. From careful analysis and deep going investigation, we think that it is the profile of equal conjugate curvature with high order of contact, and analyzed the forming principle of this kind of profile. Based on the second curve and comparative analysis of fourth order curves, combined with Chebyshev polynomial terms of higher order contact with tooth contact stress formula derived. Note high exposure in the case of two extreme points of stress and extreme positions and the derived extreme contact stress formula. Finally, a pair of conjugate gear tooth profile curvature provides specific contact stress calculation.

Use of magnesium-aluminium and zinc-aluminium hydroxycompounds as adsorbents of uranium ions in aqueous solutions

International Nuclear Information System (INIS)

Maki, Toshio

1981-01-01

It was found that precipitates formed by adding NaOH solution to the mixed solutions of MgSO 4 and Al 2 (SO 4 ) 3 with Mg/Al molar ratios of 2 to 4 and to the mixed solution of ZnSO 4 and Al 2 (SO 4 ) 3 with Zn/Al molar ratio of 2, respectively, can be used as efficient adsorbents of [UO 2 (CO 3 ) 3 ] 4- ions in aqueous alkaline carbonate solutions. The ideal structural formulas of the precipitates formed from the mixed Mg-Al solution with Mg/Al ratio of 2.0 and the mixed Zn-Al solution with Zn/Al ratio of 2.0 were estimated to be [Mg 4 Al 2 (OH) 12 ] 2+ [SO 4 .3H 2 O] 2- and [Zn 4 Al 2 (OH) 12 ] 2+ [SO 4 .3H 2 O] 2- , respectively. It has been shown that 0.1 g of the Mg-Al and Zn-Al double hydroxysulphate powders (particle size 70 - 170 μ uptake >97% of the U(VI) ions from 50 ml of an aqueous alkaline carbonate solution containing 100 ppm of U(VI) within 2 h at room temperature. The rates of adsorption of [UO 2 (CO 3 ) 3 ] 4- ions for the Mg-Al and Zn-Al double hydroxysulphate powders were both about 2 times that for the hydrous Ti(IV) oxide powders. Five weight percent sodium bicarbonate solution was found to be effective for the desorption of [UO 2 (CO 3 ) 3 ] 4- ions from the double hydroxysulphate powders. Adsorption capacity of the double hydroxysulphates was discussed in relation to their structure. (author)

CoSi{sub x} contact resistance after etching and ashing plasma exposure

Energy Technology Data Exchange (ETDEWEB)

Katahira, Ken; Fukasawa, Masanaga; Kobayashi, Shoji; Takizawa, Toshifumi; Isobe, Michio; Hamaguchi, Satoshi; Nagahata, Kazunori; Tatsumi, Tetsuya [Nagasaki Production Division 1, Sony Semiconductor Kyushu Corporation, 1883-43 Tsukuba-machi, Isahaya-shi, Nagasaki 854-0065 (Japan); Semiconductor Technology Development Division, Semiconductor Business Group, Sony Corporation, 4-14-1 Asahi-cho, Atsugi-shi, Kanagawa 243-0014 (Japan); Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Semiconductor Technology Development Division, Semiconductor Business Group, Sony Corporation, 4-14-1 Asahi-cho, Atsugi-shi, Kanagawa 243-0014 (Japan)

2009-07-15

The authors investigated the contact resistance fluctuation caused by CoSi{sub x} damage in plasma etching and ashing processes. They found that CoSi{sub x} layers damaged by plasma process exposure are readily oxidized when exposed to air resulting in increased resistance. They also found that the contact resistance increases more when CH{sub 3}F is used instead of CF{sub 4} during etching process. The lower the mass number of dominant ions becomes, the deeper the ions penetrate. Molecular dynamics simulation revealed that dissociated species from lighter ions penetrate deeper and that this stimulates deeper oxidation. They also found that contact resistance further increased by using postetch ashing plasma even in an H{sub 2}/N{sub 2} ashing process in which O{sub 2} was not used. Here, too, the reason for this is that the ion penetration causes deep oxidation. They observed that the contact resistance has a linear relationship with the oxide concentration in CoSi{sub x}. This leads to the conclusion that it is essential to precisely control the ion energy as well as to properly select the ion species in the plasma process in the fabrication of next-generation semiconductor devices.

Supercritical fluid chromatographic resolution of water soluble isomeric carboxyl/amine terminated peptides facilitated via mobile phase water and ion pair formation.

Science.gov (United States)

Patel, M A; Riley, F; Ashraf-Khorassani, M; Taylor, L T

2012-04-13

Both analytical scale and preparative scale packed column supercritical fluid chromatography (SFC) have found widespread applicability for chiral separations of multiple polar pharmaceutical candidates. However, SFC is rapidly becoming an achiral technique. More specifically, ion pair SFC is finding greater utility for separation of ionic analytes such as amine salts and organic sulfonates. The key to this success is, in part, the incorporation of additives such as trifluoroacetic acid and ammonium acetate into the mobile phase in association with a wide variety of both bonded silica stationary phases and high purity bare silica. Ion pairing SFC coupled with evaporative light scattering detection and mass spectrometric detection is presented here for the separation of water soluble, uncapped, isomeric peptide pairs that differ in amino acid arrangement. The separation is best achieved on either diol-bonded silica or bare silica with 1-5% (w/w) water as a significant ingredient in the mobile phase. Nitrogenous stationary phases such as 2-ethylpyridine, which had been very successful for the separation of capped peptides failed to yield the desired separation regardless of the mobile phase composition. A HILIC type retention mechanism is postulated for the separation of both isomeric uncapped peptide pairs. Copyright © 2012 Elsevier B.V. All rights reserved.

Surface negative ion production in ion sources

International Nuclear Information System (INIS)

Belchenko, Y.

1993-01-01

Negative ion sources and the mechanisms for negative ion production are reviewed. Several classes of sources with surface origin of negative ions are examined in detail: surface-plasma sources where ion production occurs on the electrode in contact with the plasma, and ''pure surface'' sources where ion production occurs due to conversion or desorption processes. Negative ion production by backscattering, impact desorption, and electron- and photo-stimulated desorption are discussed. The experimental efficiencies of intense surface negative ion production realized on electrodes contacted with hydrogen-cesium or pure hydrogen gas-discharge plasma are compared. Recent modifications of surface-plasma sources developed for accelerator and fusion applications are reviewed in detail

Improvement of Vitamin K2 Production by Escherichia sp. with Nitrogen Ion Beam Implantation Induction

International Nuclear Information System (INIS)

Liu Yan; Wang Li; Zheng Zhiming; Wang Peng; Zhao Genhai; Liu Hui; Gong Guohong; Wu Hefang; Liu Hongxia; Tan Mu; Li Zhemin

2015-01-01

Low-energy ion implantation as a novel mutagen has been increasingly applied in the microbial mutagenesis for its higher mutation frequency and wider mutation spectra. In this work, N + ion beam implantation was used to enhance Escherichia sp. in vitamin K 2 yield. Optimization of process parameters under submerged fermentation was carried out to improve the vitamin K 2 yield of mutant FM5-632. The results indicate that an excellent mutant FM5-632 with a yield of 123.2±1.6 μg/L, that is four times that of the original strain, was achieved by eight successive implantations under the conditions of 15 keV and 60×2.6×10 13 ions/cm 2 . A further optimization increased the yield of the mutant by 39.7%, i.e. 172.1±1.2 μg/L which occurred in the mutant cultivated in the optimal fermentation culture medium composed of (per liter): 15.31 g glycerol, 10 g peptone, 2.89 g yeast extract, 5 g K 2 HPO 4 , 1 g NaCl, 0.5 g MgSO 4 ·7H 2 O and 0.04 g cedar wood oil, incubated at 33 °C, pH 7.0 and 180 rpm for 120 h. (plasma technology)

Improvement of Vitamin K2 Production by Escherichia sp. with Nitrogen Ion Beam Implantation Induction

Science.gov (United States)

Liu, Yan; Wang, Li; Zheng, Zhiming; Wang, Peng; Zhao, Genhai; Liu, Hui; Gong, Guohong; Wu, Hefang; Liu, Hongxia; Tan, Mu; Li, Zhemin

2015-02-01

Low-energy ion implantation as a novel mutagen has been increasingly applied in the microbial mutagenesis for its higher mutation frequency and wider mutation spectra. In this work, N+ ion beam implantation was used to enhance Escherichia sp. in vitamin K2 yield. Optimization of process parameters under submerged fermentation was carried out to improve the vitamin K2 yield of mutant FM5-632. The results indicate that an excellent mutant FM5-632 with a yield of 123.2±1.6 μg/L, that is four times that of the original strain, was achieved by eight successive implantations under the conditions of 15 keV and 60×2.6×1013 ions/cm2. A further optimization increased the yield of the mutant by 39.7%, i.e. 172.1±1.2 μg/L which occurred in the mutant cultivated in the optimal fermentation culture medium composed of (per liter): 15.31 g glycerol, 10 g peptone, 2.89 g yeast extract, 5 g K2HPO4, 1 g NaCl, 0.5 g MgSO4·7H2O and 0.04 g cedar wood oil, incubated at 33 °C, pH 7.0 and 180 rpm for 120 h.

Perfluorinated acids as ion-pairing agents in the determination of monoamine transmitters and some prominent metabolites in rat brain by high-performance liquid chromatography with amperometric detection.

Science.gov (United States)

Patthy, M; Gyenge, R

1988-09-30

The behaviour of trifluoroacetate and heptafluorobutyrate as pairing ions for the reversed-phase ion-pair separation of monoamine transmitters and related metabolites was studied. The performance of systems with the perfluorinated acids was compared with that of systems containing sodium octyl sulphonate and was found to be better in terms of peak resolution combined with total analysis time, day-to-day reproducibility and the time required for attaining initial chromatographic equilibrium. Rat brain samples were deproteinized in the acidified mobile phase, injected directly on to a high-performance liquid chromatographic column and quantitated using an amperometric detector. Sample run times were 6-8 min, at a relatively low flow-rate. The detection limits achieved are fairly uncommon with conventional bore columns. The two perfluorinated acids studied differ in the dominant mechanisms of ion-pair formation and show selectivity differences as a result.

Modelación del contacto entre dos pares de dientes en las coronas de molinos de caña//Modeling of contact between two pairs of teeth in the sugar cane mills gears

Directory of Open Access Journals (Sweden)

Abdel Mendoza‐Fernández

2013-09-01

Full Text Available En el trabajo se propone un mecanismo equivalente para la modelación del funcionamiento de las coronas de molino de caña de azúcar cuando teóricamente hay dos pares de dientes en contacto. A través del análisis de movilidad del mecanismo se demuestra que no es posible el contacto simultaneo entre dos pares de dientes y que el coeficiente de recubrimiento en estos engranes es igual o menor que la unidad. A partir de los resultados del análisis cinemático del contacto entre un par de dientes, y combinándolo con la modelación del contacto entre dos pares de dientes se demuestra que el coeficiente de recubrimiento real en estos engranajes es menor que la unidad y se producen impactos entre los dientes al inicio del contacto.Palabras claves: molinos de caña, coronas de molinos, coeficiente de recubrimiento, engranajes._________________________________________________________________________________AbstractThe paper proposes an equivalent mechanism for modeling the functioning of the crowns of sugar cane mill when theoretically there are two pairs of teeth in contact. Through mobility analysis of the mechanism is demonstrated that is not possible the simultaneous contact between two pairs of teeth and that the coating coefficient of these gears is equal or less than unity. Combining kinematic analysis results for the contact between a pair of teeth with the modeling the contact between two pairs of teeth, it is demonstrated that gear ratio of these gears is less than unity and impacts occur between the teeth at the start of contact.Key words: sugar cane mills, sugar cane mills gears, contact ratio, gears.

Determination of anionic surfactants during wastewater recycling process by ion pair chromatography with suppressed conductivity detection

Science.gov (United States)

Levine, L. H.; Judkins, J. E.; Garland, J. L.; Sager, J. C. (Principal Investigator)

2000-01-01

A direct approach utilizing ion pairing reversed-phase chromatography coupled with suppressed conductivity detection was developed to monitor biodegradation of anionic surfactants during wastewater recycling through hydroponic plant growth systems and fixed-film bioreactors. Samples of hydroponic nutrient solution and bioreactor effluent with high concentrations (up to 120 mS electrical conductance) of inorganic ions can be analyzed without pretreatment or interference. The presence of non-ionic surfactants did not significantly affect the analysis. Dynamic linear ranges for tested surfactants [Igepon TC-42, ammonium lauryl sulfate, sodium laureth sulfate and sodium alkyl (C10-C16) ether sulfate] were 2 to approximately 500, 1 to approximately 500, 2.5 to approximately 550 and 3.0 to approximately 630 microg/ml, respectively.

[Application of reversed-phase ion-pair chromatography for universal estimation of octanol-water partition coefficients of acid, basic and amphoteric drugs].

Science.gov (United States)

Zhu, Hui; Yang, Ri-Fang; Yun, Liu-Hong; Jiang, Yu; Li, Jin

2009-09-01

This paper is to establish a reversed-phase ion-pair chromatography (RP-IPC) method for universal estimation of the octanol/water partition coefficients (logP) of a wide range of structurally diverse compounds including acidic, basic, neutral and amphoteric species. The retention factors corresponding to 100% water (logk(w)) were derived from the linear part of the logk'/phi relationship, using at least four isocratic logk' values containing different organic compositions. The logk(w) parameters obtained were close to the corresponding logP values obtained with the standard "shake flask" methods. The mean deviation for test drugs is 0.31. RP-IPC with trifluoroacetic acid as non classic ion-pair agents can be applicable to determine the logP values for a variety of drug-like molecules with increased accuracy.

Ionic association and interspecies interactions of 1-1 electrolytes in ethyl acetate solutions at 5-45 deg C

International Nuclear Information System (INIS)

Kalugin, O. N.; Panchenko, V. G.; V'yunnik, I. N.

2005-01-01

The data of conductometric studies of LiClO 4 , NaClO 4 , NaBPh 4 , and Bu 4 NClO 4 solutions in ethylacetate in the temperature range 5 to 45 deg C are reported. The constants of ionic association resulting in formation of ion pairs and triple ions, as well as limiting molar electric conductivities of the ions and triple ions are determined. It is found that the formation of contact triple ions having mutually interpenetrated structural elements in cavities of each others is characteristic of electrolytes with bulky organic ions. Anomalous temperature dependence of dynamic sizes of the [Na 2 BPh 4 ] + and [Na(BPh 4 ) 2 ] - ions and substantial differences in energy characteristics of inter-ion interactions are revealed during formation of ion pairs and triple ions in ethylacetate solutions of NaBPh 4 [ru

Separation of deuteriated isotopomers of dopamine by ion-pair reversed-phase high-performance liquid chromatography

International Nuclear Information System (INIS)

Masters, C.F.; Markey, S.P.; Mefford, I.N.; Duncan, M.W.

1988-01-01

The ion-pair reversed-phase separation of dopamine and deuterium-substituted dopamine isotopomers is described. Chromatographic parameters and deuterium isotope effects governing the resolution are examined and compared to the factors regulating the resolution are examined and compared to the factors regulating the resolution of the chemically distinct entities dopamine, norepinephrine, and epinephrine. The potential utility of the [ 2 H 7 ]dopamine, isotopomer as an internal standard for the high-performance liquid chromatography analysis of dopamine is demonstrated by using aluminum oxide extraction prior to chromatographic separation

Coherent and noncoherent double diffractive production of QQ-bar pairs in heavy-ion collisions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Chatrchyan, S.A.; Galoyan, A.S.; Malakhov, A.I.; Melkumov, G.L.; Zarubin, P.I.; Jenkovszky, L.L.

1999-01-01

The coherent and noncoherent double diffractive production of heavy quark-antiquark pairs in ion scattering at the LHC energies has been considered. The total and differential cross sections for such processes featuring the production of cc-bar and bb-bar quark pairs in pp, CaCa, and PbPb collisions have been estimated. It has been shown that the fraction of heavy quark-antiquark pairs produced in double diffractive scattering amounts to a few percent of the number of QQ-bar pairs produced in hard QCD scattering; therefore, it is necessary to take into account such processes in detecting heavy quarks, in seeking Higgs bosons of intermediate mass, in investigating the suppression of heavy quarkonia in quark-gluon plasma, and so on. It has been demonstrated that the cross section for coherent scattering is so large that this process can be used to study collective effects in nuclei at high energies. Large values of the quark-antiquark invariant mass, M QQ-bar > or approx. 100 GeV, in association with a large rapidity gap between diffractive jets, Δη>5, exemplify manifestations of such nuclear interactions

Primary amine/CSA ion pair: A powerful catalytic system for the asymmetric enamine catalysis

KAUST Repository

Liu, Chen; Zhu, Qiang; Huang, Kuo-Wei; Lu, Yixin

2011-01-01

A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated. © 2011 American Chemical Society.

Primary amine/CSA ion pair: A powerful catalytic system for the asymmetric enamine catalysis

KAUST Repository

Liu, Chen

2011-05-20

A novel ion pair catalyst containing a chiral counteranion can be readily derived by simply mixing cinchona alkaloid-derived diamine with chiral camphorsulfonic acid (CSA). A mixture of 9-amino(9-deoxy)epi-quinine 8 and (-)-CSA was found to be the best catalyst with matching chirality, enabling the direct amination of α-branched aldehydes to proceed in quantitative yields and with nearly perfect enantioselectivities. A 0.5 mol % catalyst loading was sufficient to catalyze the reaction, and a gram scale enantioselective synthesis of biologically important α-methyl phenylglycine has been successfully demonstrated. © 2011 American Chemical Society.

Deformed model Sp(4) model for studying pairing correlations in atomic nuclei

CERN Document Server

Georgieva, A I; Sviratcheva, K

2002-01-01

A fermion representation of the compact symplectic sp(4) algebra introduces a theoretical framework for describing pairing correlations in atomic nuclei. The important non-deformed and deformed subalgebras of sp sub ( sub q sub ) (4) and the corresponding reduction chains are explored for the multiple orbit problem. One realization of the u sub ( sub q sub ) (2) subalgebra is associated with the valence isospin, other reductions describe coupling between identical nucleons or proton-neutron pairs. Microscopic non-deformed and deformed Hamiltonians are expressed in terms of the generators of the sp(4) and sp sub q (4) algebras. In both cases eigenvalues of the isospin breaking Hamiltonian are fit to experimental ground state energies. The theory can be used to investigate the origin of the deformation and predict binding energies of nuclei in proton-rich regions. The q-deformation parameter changes the pairing strength and in so doing introduces a non-linear coupling into the collective degree of freedom

Metal-free reduction of the greenhouse gas sulfur hexafluoride, formation of SF5 containing ion pairs and the application in fluorinations

KAUST Repository

Rueping, Magnus; Nikolaienko, Pavlo; Lebedev, Yury; Adams, Alina

2017-01-01

A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (SF6) by organic electron donors at ambient temperature has been developed. The reaction yields solid ion pairs consisting of donor

Spectroscopic Observation of Water-Mediated Deformation of the CARBOXYLATE-M2+ (M= Mg, Ca) Contact Ion Pair

Science.gov (United States)

Kelleher, Patrick J.; DePalma, Joseph W.; Johnson, Mark

2016-06-01

The binding of alkaline earth dications to the biologically relevant carboxylate ligand has previously been studied using vibrational sum frequency generation (VSFG) spectroscopy of the air-water interface, infrared multiple photon dissociation (IRMPD) spectroscopy of clusters, and DFT methods. These results suggest the presence of both monodentate and bidentate binding motifs of the M2+ ions to the cayboxyl head groups depending on the extent of solvation. We revisit these systems using vibrational predissociation spectroscopy to measure the gas-phase vibrational spectra of the D2-tagged microhydrated [MgOAc(H2O)n=1-5]+ and [CaOAc(H2O)n=1-6]+ clusters. The spectra show that [MgOAc(H2O)n]+ switches from bidentate to monodentate binding promptly at n = 5, while [CaOAc(H2O)n]+ retains its bidentate attachment such that the sixth water molecule initiates the second solvation shell. The difference in binding behavior between these two divalent metal ions is analyzed in the context of the local acidity of the solvent water molecules and the strength of the metal-carboxylate and metal-water interactions. This cluster study provides insight into the chemical physics underlying the unique and surprising impacts of Mg2+ and Ca2+ on the chemistry mediated by sea spray aerosols. Funding for this work was provided by the NSF's Center for Aerosol Impacts on Climate and the Environment.

Pyrrolo-dC Metal-Mediated Base Pairs in the Reverse Watson-Crick Double Helix: Enhanced Stability of Parallel DNA and Impact of 6-Pyridinyl Residues on Fluorescence and Silver-Ion Binding.

Science.gov (United States)

Yang, Haozhe; Mei, Hui; Seela, Frank

2015-07-06

Reverse Watson-Crick DNA with parallel-strand orientation (ps DNA) has been constructed. Pyrrolo-dC (PyrdC) nucleosides with phenyl and pyridinyl residues linked to the 6 position of the pyrrolo[2,3-d]pyrimidine base have been incorporated in 12- and 25-mer oligonucleotide duplexes and utilized as silver-ion binding sites. Thermal-stability studies on the parallel DNA strands demonstrated extremely strong silver-ion binding and strongly enhanced duplex stability. Stoichiometric UV and fluorescence titration experiments verified that a single (2py) PyrdC-(2py) PyrdC pair captures two silver ions in ps DNA. A structure for the PyrdC silver-ion base pair that aligns 7-deazapurine bases head-to-tail instead of head-to-head, as suggested for canonical DNA, is proposed. The silver DNA double helix represents the first example of a ps DNA structure built up of bidentate and tridentate reverse Watson-Crick base pairs stabilized by a dinuclear silver-mediated PyrdC pair. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Measurement of line overlap for resonant photopumping of transitions in neonlike ions by nickel-like ions

International Nuclear Information System (INIS)

Elliott, S.; Beiersdorfer, P.; Nilsen, J.

1993-01-01

A measurement is made of the 3d-4f transition energies in the Ni-like ions Re 47+ , Ir 49+ , Pt 50+ , Au 51+ , and Bi 55+ and the 2p-4d transition energies in the Ne-like ions Br 25+ , Kr 26+ , Rb 27+ , and Y 29+ using the Livermore electron-beam ion trap. The ions studied are candidates for an x-ray laser scheme based on resonant photopumping which predicts lasing among the 3p-3s transitions in a Ne-like ion. The results of the measurements are compared to multiconfiguration Dirac-Fock calculations and systematic differences are found. The best resonance is found for the Pt-Rb pair at 2512 eV, whose energies differ by 0.4±0.1 eV, that is, by only 160 ppm

H- ion sources for CERN's Linac4

Science.gov (United States)

Lettry, J.; Aguglia, D.; Coutron, Y.; Chaudet, E.; Dallocchio, A.; Gil Flores, J.; Hansen, J.; Mahner, E.; Mathot, S.; Mattei, S.; Midttun, O.; Moyret, P.; Nisbet, D.; O'Neil, M.; Paoluzzi, M.; Pasquino, C.; Pereira, H.; Arias, J. Sanchez; Schmitzer, C.; Scrivens, R.; Steyaert, D.

2013-02-01

The specifications set to the Linac4 ion source are: H- ion pulses of 0.5 ms duration, 80 mA intensity and 45 keV energy within a normalized emittance of 0.25 mmmrad RMS at a repetition rate of 2 Hz. In 2010, during the commissioning of a prototype based on H- production from the plasma volume, it was observed that the powerful co-extracted electron beam inherent to this type of ion source could destroy its electron beam dump well before reaching nominal parameters. However, the same source was able to provide 80 mA of protons mixed with a small fraction of H2+ and H3+ molecular ions. The commissioning of the radio frequency quadrupole accelerator (RFQ), beam chopper and H- beam diagnostics of the Linac4 are scheduled for 2012 and its final installation in the underground building is to start in 2013. Therefore, a crash program was launched in 2010 and reviewed in 2011 aiming at keeping the original Linac4 schedule with the following deliverables: Design and production of a volume ion source prototype suitable for 20-30 mA H- and 80 mA proton pulses at 45 keV by mid-2012. This first prototype will be dedicated to the commissioning of the low energy components of the Linac4. Design and production of a second prototype suitable for 40-50 mA H- based on an external RF solenoid plasma heating and cesiated-surface production mechanism in 2013 and a third prototype based on BNL's Magnetron aiming at reliable 2 Hz and 80 mA H- operations in 2014. In order to ease the future maintenance and allow operation with Ion sources based on three different production principles, an ion source "front end" providing alignment features, pulsed gas injection, pumping units, beam tuning capabilities and pulsed bipolar high voltage acceleration was designed and is being produced. This paper describes the progress of the Linac4 ion source program, the design of the Front end and first ion source prototype. Preliminary results of the summer 2012 commissioning are presented. The outlook on

Recombination Proteins Mediate Meiotic Spatial Chromosome Organization and Pairing

Science.gov (United States)

Storlazzi, Aurora; Gargano, Silvana; Ruprich-Robert, Gwenael; Falque, Matthieu; David, Michelle; Kleckner, Nancy; Zickler, Denise

2010-01-01

SUMMARY Meiotic chromosome pairing involves not only recognition of homology but also juxtaposition of entire chromosomes in a topologically regular way. Analysis of filamentous fungus Sordaria macrospora reveals that recombination proteins Mer3, Msh4 and Mlh1 play direct roles in all of these aspects, in advance of their known roles in recombination. Absence of Mer3 helicase results in interwoven chromosomes, thereby revealing the existence of features that specifically ensure “entanglement avoidance”. Entanglements that remain at zygotene, i.e. “interlockings”, require Mlh1 for resolution, likely to eliminate constraining recombinational connections. Patterns of Mer3 and Msh4 foci along aligned chromosomes show that the double-strand breaks mediating homologous alignment have spatially separated ends, one localized to each partner axis, and that pairing involves interference among developing interhomolog interactions. We propose that Mer3, Msh4 and Mlh1 execute all of these roles during pairing by modulating the state of nascent double-strand break/partner DNA contacts within axis-associated recombination complexes. PMID:20371348

Ionomers for Ion-Conducting Energy Materials

Science.gov (United States)

Colby, Ralph

For ionic actuators and battery separators, it is vital to utilize single-ion conducting ionomers that avoid the detrimental polarization of other ions. Single-ion conducting ionomers are synthesized based on DFT calculations, with low glass transition temperatures (facile dynamics) to prepare ion-conducting membranes for battery separators that conduct Li+ or Na+. Characterization by X-ray scattering, dielectric spectroscopy, FTIR, NMR and linear viscoelasticity collectively develop a coherent picture of ionic aggregation and both counterion and polymer dynamics. 7Li NMR diffusion measurements find that diffusion is faster than expected by conductivity using the Nernst-Einstein equation, which means that the majority of Li diffusion occurs by ion pairs moving with the polymer segmental motion. Segmental motion only contributes to ionic conduction in the rare event that one of these ion pairs has an extra Li (a positive triple ion). This leads us to a new metric for ion-conducting soft materials, the product of the cation number density p0 and their diffusion coefficient D; p0D is the diffusive flux of lithium ions. This new metric has a maximum at intermediate ion content that corresponds to the overlap of ion pair polarizability volumes. At higher ion contents, the ion pairs interact strongly and form larger aggregation states that retard segmental motion of both mobile ion pairs and triple ions.

Separation of transition-metal and 8-hydroxyquinoline-5-sulfonic acid complexes using ion-pair liquid chromatography

International Nuclear Information System (INIS)

Basova, E.M.; Demurov, L.M.; Shpigun, O.A.; Van Iyuchun'

1994-01-01

The retention of chelates of Fe(3), Cu(2), Co(2), Ni(2), Zn(2), Cd(2), Hg(2), and Pb)(2) with 8-hydroxyquinoline-5-sulfonic acid depending on the concentration of cetyltrimethylammonium bromide, acetonitrile, and pH of the mobile phase was investigated using the ion-pair reversed-phase high-performance liquid chromatography on separon C 18 . Under the optimum conditions, the separation of mixtures of Fe(3), Co(2) and Ni(2) is performed within 8 to 12 min

Simultaneous determination of chloroquine and its three metabolites in human plasma, whole blood and urine by ion-pair high-performance liquid chromatography.

Science.gov (United States)

Houzé, P; de Reynies, A; Baud, F J; Benatar, M F; Pays, M

1992-02-14

A method was developed for the separation and measurement of chloroquine and three metabolites (desethylchloroquine, bisdesethylchloroquine and 4-amino-7-chloroquinoline) in biological samples by ion-pair high-performance liquid chromatography with UV detection. The method uses 2,3-diaminoaphthalene as an internal standard and provides a limit of detection between 1 and 2 ng/ml for chloroquine and its metabolites. The assay was linear in the range 12.5-250 ng/ml and the analytical recovery and reproducibility were sufficient. The assay was applied to the analysis of biological samples from a patient undergoing chloroquine chemoprophylaxis and a patient who had ingested chloroquine in a suicide attempt.

Effects of level of social contact on dairy calf behavior and health

DEFF Research Database (Denmark)

Jensen, Margit Bak; Larsen, Lars Erik

2014-01-01

Housing preweaned dairy calves in pairs rather than individually has been found to positively affect behavioral responses in novel social and environmental situations, but concerns have been raised that close contact among very young animals may impair their health. In previous studies, the level...... of social contact permitted in individual housing has been auditory, visual, or physical contact. It is unclear how these various levels of social contact compare with each other and to pair housing, when their effects on behavior and health are considered, and whether the timing of pair housing has...

[2- (2, 4-dimethylphenylthio) phenyl] aniline and it

Indian Academy of Sciences (India)

Sambhaji

MgSO4, 0.5 g aspargine and 2 ml glycerol in distilled water (100 ml) followed by pH ..... aniline and its derivatives with the crystal structure of. Page 13. 13. Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA) (PDB ID: 4TZK).

Experimental ion mobility measurements in Xe-CH4

Science.gov (United States)

Perdigoto, J. M. C.; Cortez, A. F. V.; Veenhof, R.; Neves, P. N. B.; Santos, F. P.; Borges, F. I. G. M.; Conde, C. A. N.

2017-09-01

Data on ion mobility is important to improve the performance of large volume gaseous detectors. In the present work, the method, experimental setup and results for the ion mobility measurements in Xe-CH4 mixtures are presented. The results for this mixture show the presence of two distinct groups of ions. The nature of the ions depend on the mixture ratio since they are originated by both Xe and CH4. The results here presented were obtained for low reduced electric fields, E/N, 10-25 Td (2.4-6.1 kV ṡ cm-1 ṡ bar-1), at low pressure (8 Torr) (10.6 mbar), and at room temperature.

Ion-pairing reversed-phase chromatography coupled to inductively coupled plasma mass spectrometry as a tool to determine mercurial species in freshwater fish.

Science.gov (United States)

Cheng, Heyong; Chen, Xiaopan; Shen, Lihuan; Wang, Yuanchao; Xu, Zigang; Liu, Jinhua

2018-01-05

Most of analytical community is focused on reversed phase high performance liquid chromatography (RP-HPLC) for mercury speciation by employing mobile phases comprising of high salts and moderate amounts of organic solvents. This study aims at rapid mercury speciation analysis by ion-pairing RP-HPLC with inductively coupled plasma mass spectrometry (ICP-MS) detection only using low salts for the sake of green analytical chemistry. Two ion-pairing HPLC methods were developed on individual usage of positively and negatively charged ion-pairing reagents (tetrabutylammonium hydroxide -TBAH and sodium dodecylbenzene sulfonate -SDBS), where sodium 3-mercapto-1-propysulfonate (MPS) and l-cysteine (Cys) were individually added in mobile phases to transform mercury species into negative and positive Hg-complexes for good resolution. Addition of phenylalanine was also utilized for rapid baseline separation in combination of short C 18 guard columns. Optimum mobile phases of 2.0mM SDBS+2.0mM Cys+1.0mM Phe (pH 3.0) and 4.0mM TBAH+2.0mM MPS+2.0mM Phe (pH 6.0) both achieved baseline separation of inorganic mercury (Hg 2+ ), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) on two consecutive 12.5-mm C 18 columns. The former mobile phase was selected for mercury speciation in freshwater fish because of short separation time (3.0min). Detection limits of 0.015 for Hg 2+ , 0.014 for MeHg, 0.028 for EtHg and 0.042μgL -1 for PhHg were obtained along with satisfactory precisions of peak height and area (1.0-2.8% for 5.0μgL -1 Hg-mixture standard). Good accordance of determined values of MeHg and total mercury in certified reference materials of fish tissue (GBW 10029) and tuna fish (BCR-463) with certified values as well as good recoveries (91-106%) proved good accuracy of the proposed method. An example application to freshwater fish indicated its potential in routine analysis, where MeHg was presented at 3.7-20.3μgkg -1 as the dominate species. Copyright © 2017

Theoretical Treatment of Degenerate Electron Exchange and Dimerization in Spin Dynamics of Radical Ion Pairs as Observed by Magnetic Field Effects

NARCIS (Netherlands)

Ivanov, K.L.; Stass, D.V.; Kalneus, E.V.; Kaptein, R.; Lukzen, N.K.

2013-01-01

In this work we have compared manifestations of degenerate electron exchange (DEE) and dimerization reactions in MARY (magnetically affected reaction yield) spectroscopy and time-resolved magnetic field effects (TR-MFE) of radical ion pairs (RIPs). It is shown that dimerization results in phase and

4-(3-Chlorophenyl-1-(3-chloropropylpiperazin-1-ium chloride redetermined at 100 K

Directory of Open Access Journals (Sweden)

Muzzaffar Ahmad Bhat

2016-02-01

Full Text Available The crystal structure of the title salt, C13H19Cl2N2+·Cl−, has been reported previously [Homrighausen & Krause Bauer (2002. Acta Cryst. E58, o1395–o1396] based on room-temperature data, where it was found to contain a disordered chloropropyl group. We now present the structure at 100 K in which the chloropropyl group is ordered. The piperazine ring adopts a chair conformation with the exocyclic N—C bonds in equatorial orientations. The dihedral angle between the piperazine ring (all atoms and the benzene ring is 28.47 (5°. The chloropropyl group has an extended conformation [N—C—C—C = −177.25 (8 ° and C—C—C—Cl = 174.23 (7°]. In the crystal, charge-assisted N—H...Cl hydrogen bonds link the cation and anion into ion pairs. Numerous weak C—H...Cl interactions link the ion pairs into a three-dimensional network. Short Cl...Cl contacts [3.2419 (4 Å] are also observed.

Effects of the spaces available for cations in strongly acidic cation-exchange resins on the exchange equilibria by quaternary ammonium ions and on the hydration states of metal ions.

Science.gov (United States)

Watanabe, Yuuya; Ohnaka, Kenji; Fujita, Saki; Kishi, Midori; Yuchi, Akio

2011-10-01

The spaces (voids) available for cations in the five exchange resins with varying exchange capacities and cross-linking degrees were estimated, on the basis of the additivity of molar volumes of the constituents. Tetraalkylammonium ions (NR(4)(+); R: Me, Et, Pr) may completely exchange potassium ion on the resin having a larger void radius. In contrast, the ratio of saturated adsorption capacity to exchange capacity of the resin having a smaller void radius decreased with an increase in size of NR(4)(+) ions, due to the interionic contacts. Alkali metal ions could be exchanged quantitatively. While the hydration numbers of K(+), Rb(+), and Cs(+) were independent of the void radius, those of Li(+) and Na(+), especially Na(+), decreased with a decrease in void radius. Interionic contacts between the hydrated ions enhance the dehydration. Multivalent metal ions have the hydration numbers, comparable to or rather greater than those in water. A greater void volume available due to exchange stoichiometry released the interionic contacts and occasionally promoted the involvement of water molecules other than directly bound molecules. The close proximity between ions in the conventional ion-exchange resins having higher exchange capacities may induce varying interactions.

Improving methodological aspects of the analysis of five regulated haloacetic acids in water samples by solid-phase extraction, ion-pair liquid chromatography and electrospray tandem mass spectrometry.

Science.gov (United States)

Prieto-Blanco, M C; Alpendurada, M F; López-Mahía, P; Muniategui-Lorenzo, S; Prada-Rodríguez, D; Machado, S; Gonçalves, C

2012-05-30

Haloacetic acids (HAAs) are organic pollutants originated from the drinking water disinfection process, which ought to be controlled and minimized. In this work a method for monitoring haloacetic acids (HAAs) in water samples is proposed, which can be used in quality control laboratories using the techniques most frequently available. Among its main advantages we may highlight its automated character, including minimal steps of sample preparation, and above all, its improved selectivity and sensitivity in the analysis of real samples. Five haloacetic acids (HAA5) were analyzed using solid-phase extraction (SPE) combined with ion-pair liquid chromatography and tandem mass spectrometry. For the optimization of the chromatographic separation, two amines (triethylamine, TEA and dibutylamine, DBA) as ion pair reagents were compared, and a better selectivity and sensitivity was obtained using DBA, especially for monohaloacetic acids. SPE conditions were optimized using different polymeric adsorbents. The electrospray source parameters were studied for maximum precursor ion accumulation, while the collision cell energy of the triple quadrupole mass spectrometer was adjusted for optimum fragmentation. Precursor ions detected were deprotonated, dimeric and decarboxylated ions. The major product ions formed were: ionized halogen atom (chloride and bromide) and decarboxylated ions. After enrichment of the HAAs in Lichrolut EN adsorbent, the limits of detection obtained by LC-MS/MS analysis (between 0.04 and 0.3 ng mL(-1)) were comparable to those obtained by GC-MS after derivatization. Linearity with good correlation coefficients was obtained over two orders of magnitude irrespective of the compound. Adequate recoveries were achieved (60-102%), and the repeatability and intermediate precision were in the range of 2.4-6.6% and 3.8-14.8%, respectively. In order to demonstrate the usefulness of the method for routine HAAs monitoring, different types of water samples were

Crystal structures of 1,4-diazabicyclo[2.2.2]octan-1-ium 4-nitrobenzoate dihydrate and 1,4-diazabicyclo[2.2.2]octane-1,4-diium bis(4-nitrobenzoate: the influence of solvent upon the stoichiometry of the formed salt

Directory of Open Access Journals (Sweden)

Aina Mardia Akhmad Aznan

2014-07-01

Full Text Available The 1:1 co-crystallization of 1,4-diazabicyclo[2.2.2]octane (DABCO with 4-nitrobenzoic acid in ethanol–water (3/1 gave the salt dihydrate C6H13N2+·C7H4NO4−·2H2O, (1, whereas from methanol, the salt C6H14N22+·2C7H4NO4−, (2, was isolated. In (1, the cation and anion are linked by a strong N—H...O hydrogen bond, and the carboxylate anion is close to planar [dihedral angle between terminal residues = 6.83 (9°]. In (2, a three-ion aggregate is assembled by two N—H...O hydrogen bonds, and the carboxylate anions are again close to planar [dihedral angles between terminal residues = 1.7 (3 and 5.9 (3°]. Through the intervention of solvent water molecules, which self-assemble into helical supramolecular chains along the b axis, the three-dimensional architecture in (1 is stabilized by water–DABCO O—H...N and water–carboxylate O—H...O hydrogen bonds, with additional stability afforded by C—H...O interactions. The global crystal structure comprises alternating layers of water molecules and ion pairs stacked along the c axis. In the crystal of (2, the three-ion aggregates are assembled into a three-dimensional architecture by a large number of methylene–carboxylate/nitro C—H...O interactions as well as π–π contacts between inversion-related benzene rings [inter-centroid distances = 3.5644 (16 and 3.6527 (16 Å]. The cations and anions assemble into alternating layers along the c axis.

Helium Nanodroplet Isolation and Infrared Spectroscopy of the Isolated Ion-Pair 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Science.gov (United States)

2013-09-01

Isolated Ion- Pair 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide   Emmanuel I. Obi†, Christopher M. Leavitt†, Paul L. Raston... Christopher P. Moradi†, Steven D.   Flynn†, Jerry A. Boatz§,*, Steven D. Chambreau‡,* and Gary E. Douberly†,*     †Department of Chemistry, University of...Windus, T. L.; Dupuis , M.; Montgomery, J. A. General Atomic and Molecular Electronic-Structure System. J. Comput. Chem. 1993, 14, 1347-1363

Inflation of the screening length induced by Bjerrum pairs.

Science.gov (United States)

Zwanikken, Jos; van Roij, René

2009-10-21

Within a modified Poisson-Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale [Formula: see text] over which electric fields are screened in electrolyte solutions, taking into account a simple association-dissociation equilibrium between free ions and Bjerrum pairs. At low densities of Bjerrum pairs, this length scale is well approximated by the Debye length [Formula: see text], with ρ(s) the free-ion density. At high densities of Bjerrum pairs, however, we find [Formula: see text], which is significantly larger than 1/κ due to the enhanced effective permittivity of the electrolyte, caused by the polarization of Bjerrum pairs. We argue that this mechanism may explain the recently observed anomalously large colloid-free zones between an oil-dispersed colloidal crystal and a colloidal monolayer at the oil-water interface.

Pair potentials in liquid metals

International Nuclear Information System (INIS)

Faber, T.E.

1980-01-01

The argument which justifies the use of a pair potential to describe the structure-dependent term in the energy of liquid metals is briefly reviewed. Because there is an additional term in the energy which depends upon volume rather than structure, and because the pair potential itself is volume-dependent, the relationship between pair potential and observable properties such as pressure, bulk modulus and pair distribution function is more complicated for liquid metals than it is for molecular liquids. Perhaps for this reason, the agreement between pair potentials inferred from observable properties and pair potentials calculated by means of pseudo-potential theory is still far from complete. The pair potential concept is applicable only to simple liquid metals, in which the electron-ion interaction is weak. No attempt is made to discuss liquid transition and rare-earth metals, which are not simple in this sense. (author)

Exciplexes versus Loose Ion Pairs: How Does the Driving Force Impact the Initial Product Ratio of Photoinduced Charge Separation Reactions?

Science.gov (United States)

2014-01-01

Many donor–acceptor systems can undergo a photoinduced charge separation reaction, yielding loose ion pairs (LIPs). LIPs can be formed either directly via (distant) electron transfer (ET) or indirectly via the dissociation of an initially formed exciplex or tight ion pair. Establishing the prevalence of one of the reaction pathways is challenging because differentiating initially formed exciplexes from LIPs is difficult due to similar spectroscopic footprints. Hence, no comprehensive reaction model has been established for moderately polar solvents. Here, we employ an approach based on the time-resolved magnetic field effect (MFE) of the delayed exciplex luminescence to distinguish the two reaction channels. We focus on the effects of the driving force of ET and the solvent permittivity. We show that, surprisingly, the exciplex channel is significant even for an exergonic ET system with a free energy of ET of −0.58 eV and for the most polar solutions studied (butyronitrile). Our findings demonstrate that exciplexes play a crucial role even in polar solvents and at moderate driving forces, contrary to what is usually assumed. PMID:25243054

Solvolysis of deuterium-labeled β-(syn-7-norbornenyl)ethyl p-bromobenzenesulfonates. Multiple cation automerizations in tight ion pairs

International Nuclear Information System (INIS)

Bly, R.S.; Bly, R.K.; Hamilton, J.B.; Jindal, S.P.

1977-01-01

The brosylates of α,α- 2 H 2 -, β,β- 2 H 2 -, and α,α,β,β- 2 H 4 -β-(syn-7-norbornenyl)ethanol have been prepared and solvolyzed at 25 0 C in buffered acetic acid, in buffered formic acid, and in buffered 90 percent acetone-water. The deuterated exo-2-brendyl and exo-4-brexyl derivatives produced in each case after a single hydrogen or deuterium shift have been converted to deuterated brendan-2-one and brexan-4-one mixtures and the position of the deuterium labels in each ketone determined mass spectrometrically. Comparison of the deuterium content of the brexan-4-one both before and after base-catalyzed exchange with protium permits analysis of the fractions of solvolysis product derived from each recognizably discrete rearranged cation. From these results it is clear that some hydrogen or deuterium migration occurs from each methylenic carbon of the starting brosylate and that 10 to 19 percent of those migrations are preceded by at least one Wagner--Meerwein automerization. It is suggested that the observed effect of the different solvents on the product distribution is due in part to ion pairing which affects the rate of transformations that change the net charge separation in the initial intermediate

Evaluation of residue-residue contact predictions in CASP9

KAUST Repository

Monastyrskyy, Bohdan

2011-01-01

This work presents the results of the assessment of the intramolecular residue-residue contact predictions submitted to CASP9. The methodology for the assessment does not differ from that used in previous CASPs, with two basic evaluation measures being the precision in recognizing contacts and the difference between the distribution of distances in the subset of predicted contact pairs versus all pairs of residues in the structure. The emphasis is placed on the prediction of long-range contacts (i.e., contacts between residues separated by at least 24 residues along sequence) in target proteins that cannot be easily modeled by homology. Although there is considerable activity in the field, the current analysis reports no discernable progress since CASP8.

Effect of MgSO4 on the expression of C-fos gene and the abilities of learning and memory in the rat brain with radiation induced injuries

International Nuclear Information System (INIS)

Zhang Wei; Wang Rui; Wang Lili; Zhou Juying; Tu Yu; Zou Rong; Zhou Weifang

2009-01-01

Objective: To investigate the effect of magnesium sulfate (MgSO 4 ) on the nerves function after hemisphere irradiation and explore possible mechanism of the effect. Methods: Mature Sprague-Dawley rats were randomly divided into 3 groups: blank control group (n = 26), experimental control group (n = 32) and experimental group (n = 32). To selecte rats randomly from the experimental control group and the experimental therapy group for 1/2 brain irradiation to a single-fraction maximal dose of 20 Gy using 5 MeV electrons. Magnesium sulfate was injected intraperitoneally into the rats that from the experimental group before and after irradiation for total seven times. The expression of c-fos gene was observed in the hippocampal formation of the rat brain with the immunofluorescence technique in 24 h after irradiation. The learning and memory results in Y-maze test were detected 8 weeks after irradiation respectively with the other rats and then had the pathomorphology observation. Results: Compared with the blank control group, the number of c-fos immunopositive cells in the hippocampal formation of experimental control group were increased markedly (P<0.01), and the learning and memory results of Y-maze test in the irradiation control group declined significantly (P<0.01). Compared with the irradiation control group, the experimental group's Fos immunopositive cells decreased significantly (P<0.05), and also the cognitive function of learning attempt times (at 4 and 8 weeks, P<0.01) and memory reappearance times (P<0.05) were significantly different from that in the irradiation control group. Conclusion: Magnesium sulfate can promote the recovery of the rats' cognitive impairment in the early stage after irradiation, and may play a role of protecting hippocampus neurons by the way of decreasing the expression of Fos protin in hippocampal formation. (authors)

Silver(I)-Mediated Base Pairs in DNA Sequences Containing 7-Deazaguanine/Cytosine: towards DNA with Entirely Metallated Watson-Crick Base Pairs.

Science.gov (United States)

Méndez-Arriaga, José M; Maldonado, Carmen R; Dobado, José A; Galindo, Miguel A

2018-03-26

DNA sequences comprising noncanonical 7-deazaguanine ( 7C G) and canonical cytosine (C) are capable of forming Watson-Crick base pairs via hydrogen bonds as well as silver(I)-mediated base pairs by coordination to central silver(I) ions. Duplexes I and II containing 7C G and C have been synthesized and characterized. The incorporation of silver(I) ions into these duplexes has been studied by means of temperature-dependent UV spectroscopy, circular dichroism, and DFT calculations. The results suggest the formation of DNA molecules comprising contiguous metallated 7C G-Ag I -C Watson-Crick base pairs that preserve the original B-type conformation. Furthermore, additional studies performed on duplex III indicated that, in the presence of Ag I ions, 7C G-C and 7C A-T Watson-Crick base pairs ( 7C A, 7-deazadenine; T, thymine) can be converted to metallated 7C G-Ag I -C and 7C A-Ag I -T base pairs inside the same DNA molecule whilst maintaining its initial double helix conformation. These findings are very important for the development of customized silver-DNA nanostructures based on a Watson-Crick complementarity pattern. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

VS4 Nanoparticles Anchored on Graphene Sheets as a High-Rate and Stable Electrode Material for Sodium Ion Batteries.

Science.gov (United States)

Pang, Qiang; Zhao, Yingying; Yu, Yanhao; Bian, Xiaofei; Wang, Xudong; Wei, Yingjin; Gao, Yu; Chen, Gang

2018-02-22

The size and conductivity of the electrode materials play a significant role in the kinetics of sodium-ion batteries. Various characterizations reveal that size-controllable VS 4 nanoparticles can be successfully anchored on the surface of graphene sheets (GSs) by a simple cationic-surfactant-assisted hydrothermal method. When used as an electrode material for sodium-ion batteries, these VS 4 @GS nanocomposites show large specific capacity (349.1 mAh g -1 after 100 cycles), excellent long-term stability (84 % capacity retention after 1200 cycles), and high rate capability (188.1 mAh g -1 at 4000 mA g -1 ). A large proportion of the capacity was contributed by capacitive processes. This remarkable electrochemical performance was attributed to synergistic interactions between nanosized VS 4 particles and a highly conductive graphene network, which provided short diffusion pathways for Na + ions and large contact areas between the electrolyte and electrode, resulting in considerably improved electrochemical kinetic properties. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The optimization of molybdenum back contact films for Cu(In,Ga)Se{sub 2} solar cells by the cathodic arc ion plating method

Energy Technology Data Exchange (ETDEWEB)

Cho, Yong Ki, E-mail: choyk@kitech.re.kr [Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Gang Sam; Song, Young Sik; Lim, Tae Hong [Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Jung, Donggeun [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

2013-12-02

Molybdenum back contact films for Cu(In,Ga)Se{sub 2} (CIGS) solar cells have been deposited using DC magnetron sputtering methods. The electronic pathway properties of the molybdenum film have been highly dependent on the working gas pressure in magnetron sputtering, which should be carefully controlled to obtain high conductivity and adhesion. A coating method, cathodic arc ion plating, was used for molybdenum back contact electrode fabrication. The aim of this work was to find a metallization method for CIGS solar cells, which has less sensitivity on the working pressure. The resistivity, grain size, growth structures, stress, and efficiency of the films in CIGS solar cells were investigated. The results reveal that the growth structures of the molybdenum films mainly affect the conductivity. The lowest electrical resistivity of the ion-plated molybdenum films was 6.9 μΩ-cm at a pressure of 0.7 Pa. The electrical resistivity variation showed a gently increasing slope with linearity under a working gas pressure of 13.3 Pa. However, a high value of the residual stress of over 1.3 GPa was measured. In order to reduce stress, titanium film was selected as the buffer layer material, and the back contact films were optimized by double-layer coating of two kinds of hetero-materials with arc ion plating. CIGS solar cells prepared molybdenum films to measure the efficiency and to examine the effects of the back contact electrode. The resistivity, grain size, and surface morphology of molybdenum films were measured by four-point probe, X-ray diffraction, and a scanning electron microscope. The residual stress of the films was calculated from differences in bending curvatures measured using a laser beam. - Highlights: • Molybdenum back contact films for Cu(In,Ga)Se{sub 2} solar cells were prepared by the cathodic arc ion plating. • The lowest electrical resistivity of molybdenum film was 6.9 μΩ-cm. • Titanium buffer layer reduced the compressive residual stress

Retention of nucleic acids in ion-pair reversed-phase high-performance liquid chromatography depends not only on base composition but also on base sequence.

Science.gov (United States)

Qiao, Jun-Qin; Liang, Chao; Wei, Lan-Chun; Cao, Zhao-Ming; Lian, Hong-Zhen

2016-12-01

The study on nucleic acid retention in ion-pair reversed-phase high-performance liquid chromatography mainly focuses on size-dependence, however, other factors influencing retention behaviors have not been comprehensively clarified up to date. In this present work, the retention behaviors of oligonucleotides and double-stranded DNAs were investigated on silica-based C 18 stationary phase by ion-pair reversed-phase high-performance liquid chromatography. It is found that the retention of oligonucleotides was influenced by base composition and base sequence as well as size, and oligonucleotides prone to self-dimerization have weaker retention than those not prone to self-dimerization but with the same base composition. However, homo-oligonucleotides are suitable for the size-dependent separation as a special case of oligonucleotides. For double-stranded DNAs, the retention is also influenced by base composition and base sequence, as well as size. This may be attributed to the interaction of exposed bases in major or minor grooves with the hydrophobic alky chains of stationary phase. In addition, no specific influence of guanine and cytosine content was confirmed on retention of double-stranded DNAs. Notably, the space effect resulted from the stereostructure of nucleic acids also influences the retention behavior in ion-pair reversed-phase high-performance liquid chromatography. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-free reduction of the greenhouse gas sulfur hexafluoride, formation of SF5 containing ion pairs and the application in fluorinations

KAUST Repository

Rueping, Magnus

2017-05-04

A protocol for the fast and selective two-electron reduction of the potent greenhouse gas sulfur hexafluoride (SF6) by organic electron donors at ambient temperature has been developed. The reaction yields solid ion pairs consisting of donor dications and SF5-anions which can be effectively used in fluorination reactions.

Coherent and non-coherent double diffractive production of QQ-bar-pairs in collisions of heavy ions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Galoyan, A.S.; Enkovskij, L.L.; Zarubin, P.I.; Malakhov, A.I.; Melkumov, G.L.; Chatrchyan, S.A.

1999-01-01

The double coherent and non-coherent diffractive production of heavy quark-antiquark pairs (QQ-bar) in heavy ion scattering at high energies (LHC) is considered. The total and differential cross sections of these processes with the formation of cc-bar and bb-bar pairs in pp, CaCa and PbPb collisions are evaluated. The contribution of the considered mechanisms is a few per cent of the number of heavy quark-antiquark pairs obtained in the processes of hard (QCD) scattering, and it will be taken into account in the registration of c, b quarks or, for instance, in the study of the heavy quarkonia suppression effect in Quark-Gluon Plasma, in the search got intermediate mass Higgs bosons and so on. It is shown that the cross section of the coherently scattering process is great enough. This makes it suitable for studying collective effects in nuclear interactions at high energies. An example of such effects is given: large values of the invariant mass of a QQ-bar pair, M QQ-bar ≥ 100 GeV, in association with a large rapidity gap between diffractive jets Δη >5 [ru

Coherent and non-coherent double diffractive production of QQ-bar - pairs in collisions of heavy ions at high energies

International Nuclear Information System (INIS)

Agababyan, N.M.; Chatrchyan, S.A.; Galoyan, A.S.; Malakhov, A.I.; Melkumov, G.L.; Zarubin, P.I.; Jenkovszky, L.L.

1998-01-01

The double coherent and non-coherent diffractive production of heavy quark-antiquark pair (QQ-bar) in heavy ion scattering at high energies (LHC) is considered. The total and differential cross sections of these processes with the formation of cc bar and bb bar pairs in pp, CaCa and PbPb collisions are evaluated. The contribution of the considered mechanisms is a few per cent of the number of heavy quark-antiquark pairs obtained in the processes of hard (QCD) scattering, and it will be taken into account in the registration of c, b quarks or, for instance, in the study of the heavy quarkonia suppression effects in quark-gluon plasma, in the search for intermediate mass Higgs bosons and so on. It is shown that the cross section of the coherent scattering process is great enough. This makes it suitable for studying collective effects in nuclear interactions at high energies. An example of such effects is given: large values of the invariant mass of a QQ- bar pair, M QQb ar ≥ 100 GeV, in association with a large rapidity gap between diffractive jets Δη>5

Ion Trapping, Storage, and Ejection in Structures for Lossless Ion Manipulations.

Science.gov (United States)

Zhang, Xinyu; Garimella, Sandilya V B; Prost, Spencer A; Webb, Ian K; Chen, Tsung-Chi; Tang, Keqi; Tolmachev, Aleksey V; Norheim, Randolph V; Baker, Erin S; Anderson, Gordon A; Ibrahim, Yehia M; Smith, Richard D

2015-06-16

A new Structures for Lossless Ion Manipulations (SLIM) module, having electrode arrays patterned on a pair of parallel printed circuit boards (PCB), was constructed and utilized to investigate capabilities for ion trapping at a pressure of 4 Torr. Positive ions were confined by application of RF voltages to a series of inner rung electrodes with alternating phase on adjacent electrodes, in conjunction with positive DC potentials on surrounding guard electrodes on each PCB. An axial DC field was also introduced by stepwise varying the DC potentials applied to the inner rung electrodes to control the ion transport and accumulation inside the ion trapping region. We show that ions can be trapped and accumulated with up to 100% efficiency, stored for at least 5 h with no significant losses, and then could be rapidly ejected from the SLIM trap. The present results provide a foundation for the development of much more complex SLIM devices that facilitate extended ion manipulations.

Towards highly stable storage of sodium ions: a porous Na(3)V(2)(PO(4))(3)/C cathode material for sodium-ion batteries.

Science.gov (United States)

Shen, Wei; Wang, Cong; Liu, Haimei; Yang, Wensheng

2013-10-18

A porous Na3 V2 (PO4 )3 cathode material coated uniformly with a layer of approximately 6 nm carbon has been synthesized by the sol-gel method combined with a freeze-drying process. The special porous morphology and structure significantly increases the specific surface area of the material, which greatly enlarges the contact area between the electrode and electrolyte, and consequently supplies more active sites for sodium ions. When employed as a cathode material of sodium-ion batteries, this porous Na3 V2 (PO4 )3 /C exhibits excellent rate performance and cycling stability; for instance, it shows quite a flat potential plateau at 3.4 V in the potential window of 2.7-4.0 V versus Na(+) /Na and delivers an initial capacity as high as 118.9 and 98.0 mA h g(-1) at current rates of 0.05 and 0.5 C, respectively, and after 50 cycles, a good capacity retention of 92.7 and 93.6 % are maintained. Moreover, even when the discharge current density is increased to 5 C (590 mA g(-1) ), an initial capacity of 97.6 mA h g(-1) can still be achieved, and an exciting capacity retention of 88.6 % is obtained after 100 cycles. The good cycle performance, excellent rate capability, and moreover, the low cost of Na3 V2 (PO4 )3 /C suggest that this material is a promising cathode for large-scale sodium-ion rechargeable batteries. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dispersive solid phase extraction combined with ion-pair ultra high-performance liquid chromatography tandem mass spectrometry for quantification of nucleotides in Lactococcus lactis

DEFF Research Database (Denmark)

Magdenoska, Olivera; Martinussen, Jan; Thykær, Jette

2013-01-01

solid phase extraction with charcoal and subsequent analysis with ion-pair liquid chromatography coupled with electrospray ionization tandem mass spectrometry was established for quantification of intracellular pools of the 28 most important nucleotides. The method can handle extracts where cells leak...

Coherent diffractive photoproduction of ρ0 mesons on gold nuclei at 200 GeV/nucleon-pair at the Relativistic Heavy Ion Collider

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, X.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Gupta, S.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, B.; Huang, X.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Klein, S. R.; Kochenda, L.; Kocmanek, M.; Kollegger, T.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, W.; Li, Y.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, H.; Liu, P.; Liu, Y.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, G. L.; Ma, L.; Ma, Y. G.; Ma, R.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Meehan, K.; Mei, J. C.; Miller, Z. W.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Ray, R. L.; Reed, R.; Rehbein, M. J.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Roth, J. D.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Saur, M.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Strikhanov, M.; Stringfellow, B.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, Y.; Sun, X. M.; Sun, X.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vasiliev, A. N.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, G.; Wang, Y.; Wang, F.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, J.; Xu, N.; Xu, Q. H.; Xu, Y. F.; Xu, Z.; Yang, Y.; Yang, Q.; Yang, C.; Yang, S.; Ye, Z.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, Z.; Zhang, X. P.; Zhang, J. B.; Zhang, S.; Zhang, J.; Zhang, Y.; Zhang, J.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, L.; Zhou, C.; Zhu, X.; Zhu, Z.; Zyzak, M.; STAR Collaboration

2017-11-01

The STAR Collaboration reports on the photoproduction of π+π- pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly real photon emitted by one ion scatters from the other ion. We fit the π+π- invariant-mass spectrum with a combination of ρ0 and ω resonances and a direct π+π- continuum. This is the first observation of the ω in ultraperipheral collisions, and the first measurement of ρ -ω interference at energies where photoproduction is dominated by Pomeron exchange. The ω amplitude is consistent with the measured γ p →ω p cross section, a classical Glauber calculation, and the ω →π+π- branching ratio. The ω phase angle is similar to that observed at much lower energies, showing that the ρ -ω phase difference does not depend significantly on photon energy. The ρ0 differential cross section d σ /d t exhibits a clear diffraction pattern, compatible with scattering from a gold nucleus, with two minima visible. The positions of the diffractive minima agree better with the predictions of a quantum Glauber calculation that does not include nuclear shadowing than with a calculation that does include shadowing.

Anomeric 2'-Deoxycytidines and Silver Ions: Hybrid Base Pairs with Greatly Enhanced Stability and Efficient DNA Mismatch Detection with α-dC.

Science.gov (United States)

Guo, Xiurong; Seela, Frank

2017-09-04

α-d-Nucleosides are rare in nature but can develop fascinating properties when incorporated into DNA. This work reports on the first silver-mediated base pair constructed from two anomeric nucleosides: α-dC and β-dC. The hybrid base pair was integrated into the DNA and DNA/RNA double helix. A 12-mer duplex with α-dC and β-dC pair exhibits a higher thermal stability (T m =43 °C) than that incorporating the β-dC-Ag + -β-dC homo pair (T m =34 °C). Furthermore, α-dC shows excellent mismatch discrimination for DNA single nucleotide polymorphism (SNP). All four SNPs were identified on the basis of large T m value differences measured in the presence of silver ions. High resolution melting was not required. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Positron-electron pairs produced in heavy-ion collisions

International Nuclear Information System (INIS)

Ahmad, I.; Austin, Sam. M.; Back, B. B.; Betts, R. R.; Calaprice, F. P.; Chan, K. C.; Chishti, A.; Conner, C. M.; Dunford, R. W.; Fox, J. D.

1999-01-01

The production of positron-electron pairs in collisions of 238 U+ 232 Th at 5.95 MeV/nucleon, and of 238 U+ 181 Ta at 5.95, 6.1, and 6.3 MeV/nucleon, has been studied with the APEX spectrometer at Argonne National Laboratory. Several analyses have been performed to search for sharp structures in sum-energy spectra for positron-electron pairs. Such features have been reported in previous experiments. No statistically convincing evidence for such behavior is observed in the present data. (c) 1999 The American Physical Society

H- Ion Sources For CERN’s Linac4

CERN Document Server

Lettry, J; Coutron, Y; Chaudeta, E; Dallocchio, A; Gil Flores, J; Hansen, J; Mahner, E; Mathot, S; Mattei, S; Midttun, O; Moyret, P; Nisbet, D; O’Neil, M; Paoluzzi, M; Pasquino, C; Pereira, H; Sanchez Arias, J; Schmitzer, C; Scrivens, R; Steyaert, D

2013-01-01

The specifications set to the Linac4 ion source are: H- ion pulses of 0.5 ms duration, 80 mA intensity and 45 keV energy within a normalized emittance of 0.25 mmmrad RMS at a repetition rate of 2 Hz. In 2010, during the commissioning of a prototype based on H- production from the plasma volume, it was observed that the powerful co-extracted electron beam inherent to this type of ion source could destroy its electron beam dump well before reaching nominal parameters. However, the same source was able to provide 80 mA of protons mixed with a small fraction of H2+ and H3+ molecular ions. The commissioning of the radio frequency quadrupole accelerator (RFQ), beam chopper and H- beam diagnostics of the Linac4 are scheduled for 2012 and its final installation in the underground building is to start in 2013. Therefore, a crash program was launched in 2010 and reviewed in 2011 aiming at keeping the original Linac4 schedule with the following deliverables: Design and production of a volume ion source prototype suitabl...

Molecular treatment of the ion-pair formation reaction in H(1s) + H(1s) collisions

Energy Technology Data Exchange (ETDEWEB)

Borondo, F.; Martin, F.; Yaez, M.

1987-01-01

All the available theoretical calculations of the cross section for the ion-pair formation reaction H(1s)+H(1s)..-->..H/sup +/H/sup -/(1s/sup 2/) have been performed using methods that are only valid at high collision energies. They get good agreement with the experiments for impact energies greater than 25 keV, but fail completely at smaller energies. In this work we report the cross section for this reaction at impact energies less than 10 keV, calculated in the framework of the impact-parameter approximation and using the molecular method with a common translation factor.

Molecular treatment of the ion-pair formation reaction in H(1s) + H(1s) collisions

International Nuclear Information System (INIS)

Borondo, F.; Martin, F.; Yaez, M.

1987-01-01

All the available theoretical calculations of the cross section for the ion-pair formation reaction H(1s)+H(1s)→H + H - (1s 2 ) have been performed using methods that are only valid at high collision energies. They get good agreement with the experiments for impact energies greater than 25 keV, but fail completely at smaller energies. In this work we report the cross section for this reaction at impact energies less than 10 keV, calculated in the framework of the impact-parameter approximation and using the molecular method with a common translation factor

Ion vs. ion pair receptor: NMR and DFT study of the interaction of Thallium and Cesium ions and ion pairs with meso-octamethylcalix[4]pyrrole

Czech Academy of Sciences Publication Activity Database

Kříž, Jaroslav; Dybal, Jiří; Makrlík, E.; Sedláková, Zdeňka

2012-01-01

Roč. 400, 25 May (2012), s. 19-28 ISSN 0301-0104 R&D Projects: GA ČR GA203/09/1478 Institutional research plan: CEZ:AV0Z40500505 Keywords : calix[4]pyrrole * cesium receptor * fluoride receptor Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.957, year: 2012

PAIR PRODUCTION IN LOW-LUMINOSITY GALACTIC NUCLEI

International Nuclear Information System (INIS)

Moscibrodzka, M.; Gammie, C. F.; Dolence, J. C.; Shiokawa, H.

2011-01-01

Electron-positron pairs may be produced near accreting black holes by a variety of physical processes, and the resulting pair plasma may be accelerated and collimated into a relativistic jet. Here, we use a self-consistent dynamical and radiative model to investigate pair production by γγ collisions in weakly radiative accretion flows around a black hole of mass M and accretion rate M-dot . Our flow model is drawn from general relativistic magnetohydrodynamic simulations, and our radiation field is computed by a Monte Carlo transport scheme assuming the electron distribution function is thermal. We argue that the pair production rate scales as r -6 M -1 M-dot 6 . We confirm this numerically and calibrate the scaling relation. This relation is self-consistent in a wedge in M, M-dot parameter space. If M-dot is too low the implied pair density over the poles of the black hole is below the Goldreich-Julian density and γγ pair production is relatively unimportant; if M-dot is too high the models are radiatively efficient. We also argue that for a power-law spectrum the pair production rate should scale with the observables L X ≡ X-ray luminosity and M as L 2 X M -4 . We confirm this numerically and argue that this relation likely holds even for radiatively efficient flows. The pair production rates are sensitive to black hole spin and to the ion-electron temperature ratio which are fixed in this exploratory calculation. We finish with a brief discussion of the implications for Sgr A* and M87.

Zinc terephthalates ZnC_8H_4O_4 as anodes for lithium ion batteries

International Nuclear Information System (INIS)

Wang, Liping; Zou, Jian; Chen, Shulin; Yang, Jingyi; Qing, Fangzhu; Gao, Peng; Li, Jingze

2017-01-01

Graphical abstract: Both of well-crystalline and amorphous zinc terephthalates ZnC_8H_4O_4 are synthesized and amorphous structure demonstrates a higher capacity and better cycling performance. - Highlights: • Crystalline and amorphous ZnC_8H_4O_4 are obtained. • Both crystalline and amorphous ZnC_8H_4O_4 have σ_e of 10"−"7 S m"−"1. • Lithium ion diffusion is the rate-determine process. • Amorphous has a high capacity and durable performance. • Amorphous ZnC_8H_4O_4 has a high apparent lithium ion diffusion coefficient. - Abstract: Organic materials offer the advantages of cost-effective, environmental benignity, and molecular structural diversity as applications of electrode materials for lithium ion batteries. In fact, their lithium storage behaviors in terms of dynamics and kinetics intrinsically lie in ion migration in solids. Thus the solid forms including crystalline and amorphous states are crucial for the properties. In this study, a conventional carbonyl type organic material, namely zinc terephthalate (ZnC_8H_4O_4), is obtained in both well-crystalline and amorphous forms and applied as anodes for lithium ion batteries. ZnC_8H_4O_4 with amorphous structure shows higher lithium storage capacity and better capacity retention compared with that of crystalline one. It is ascribed that the amorphous phase provides a higher lithium ion diffusion coefficient than the crystalline one under the conditions of similar electronic conductivity.

Contact spectroscopy on S/TI/N devices: Induced pairing on the surface of a topological insulator

Science.gov (United States)

Stehno, Martin P.; Ngabonziza, Prosper; Snelder, Marieke; Myoren, Hiroaki; Pan, Yu; de Visser, Anne; Huang, Y.; Golden, Mark S.; Brinkman, Alexander

Translating concepts of topological quantum computation into applications requires fine-tuning of parameters in the model Hamiltonians of candidate systems. Such level of control has proven difficult to achieve in devices where superconductors are used to induce pairing in topological insulator (TI) materials. While local probe experiments have indicated features of p-wave superconducting correlations in TIs (as suggested by theory), results on extended devices often remain ambiguous. We present contact spectroscopy data on superconductor/topological insulator/normal metal devices with bulk-insulating TI material and compare these with bulk conducting samples. We discuss the magnitude of the induced gap and unusual features in the conductance traces of the bulk-insulating samples that may suggest the presence of p-wave type correlations in the TI. This work is financially supported by the Dutch Foundation for Fundamental Research on Matter (FOM), the Netherlands Organization for Scientific Research (NWO), and by the European Research Council (ERC).

QED corrections to the 4p-4d transition energies of copperlike heavy ions

International Nuclear Information System (INIS)

Chen, M. H.; Cheng, K. T.; Johnson, W. R.; Sapirstein, J.

2006-01-01

Quantum electrodynamic (QED) corrections to 4p-4d transition energies of several copperlike ions with Z=70-92 are calculated nonperturbatively in strong external fields to all orders in binding corrections. Dirac-Kohn-Sham potentials are used to account for screening and core-relaxation effects. For the 4p 1/2 -4d 3/2 transition in copperlike bismuth, thorium, and uranium, results are in good agreement with empirical QED corrections deduced from differences between transition energies obtained from recent high-precision electron-beam ion-trap measurements and those calculated with the relativistic many-body perturbation theory (RMBPT). These comparisons provide sensitive tests of QED corrections for high-angular-momentum states in many-electron heavy ions and illustrate the importance of core-relaxation corrections. Comparisons are also made with other theories and with experiments on the 4s-4p transition energies of high-Z Cu-like ions as accuracy checks of the present RMBPT and QED calculations

Fragment profiling of low molecular weight heparins using reversed phase ion pair liquid chromatography-electrospray mass spectrometry.

Science.gov (United States)

Xu, Xiaohui; Li, Daoyuan; Chi, Lequan; Du, Xuzhao; Bai, Xue; Chi, Lianli

2015-04-30

Low molecular weight heparins (LMWHs) are linear and highly charged carbohydrate polymers prepared by chemical or enzymatic depolymerization of heparin. Compared to unfractionated heparin (UFH), LMWHs are prevalently used as clinical anticoagulant drugs due to their lower side effects and better bioavailability. The work presented herein provides a rapid and powerful fragment mapping method for structural characterization of LMWHs. The chain fragments of two types of LMWHs, enoxaparin and nadroparin, were generated by controlled enzymatic digestion with each of heparinase I (Hep I, Enzyme Commission (EC) # 4.2.2.7), heparinase II (Hep II, no EC # assigned) and heparinase III (Hep III, EC # 4.2.2.8). Reversed phase ion pair high performance liquid chromatography (RPIP-HPLC) coupled with electrospray ion trap time-of-flight mass spectrometry (ESI-IT-TOF-MS) was used to profile the oligosaccharide chains ranging from disaccharides to decasaccharides. A database containing all theoretical structural compositions was established to assist the mass spectra interpretation. The six digests derived by three enzymes from two types of LMWHs exhibited distinguishable fingerprinting patterns. And a total of 94 enoxaparin fragments and 109 nadroparin fragments were detected and identified. Besides the common LMWH oligosaccharides, many components containing characteristic LMWH structures such as saturated L-idopyranosuronic acid, 2,5-anhydro-D-mannitol, 1,6-anhydro-D-aminopyranose, as well as odd number oligosaccharides were also revealed. Quantitative comparison of major components derived from innovator and generic nadroparin products was presented. This approach to profile LMWHs' fragments offers a highly reproducible, high resolution and information-rich tool for evaluating the quality of this category of anticoagulant drugs or comparing structural similarities among samples from various sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

Role of copper oxides in contact killing of bacteria.

Science.gov (United States)

Hans, Michael; Erbe, Andreas; Mathews, Salima; Chen, Ying; Solioz, Marc; Mücklich, Frank

2013-12-31

The potential of metallic copper as an intrinsically antibacterial material is gaining increasing attention in the face of growing antibiotics resistance of bacteria. However, the mechanism of the so-called "contact killing" of bacteria by copper surfaces is poorly understood and requires further investigation. In particular, the influences of bacteria-metal interaction, media composition, and copper surface chemistry on contact killing are not fully understood. In this study, copper oxide formation on copper during standard antimicrobial testing was measured in situ by spectroscopic ellipsometry. In parallel, contact killing under these conditions was assessed with bacteria in phosphate buffered saline (PBS) or Tris-Cl. For comparison, defined Cu2O and CuO layers were thermally generated and characterized by grazing incidence X-ray diffraction. The antibacterial properties of these copper oxides were tested under the conditions used above. Finally, copper ion release was recorded for both buffer systems by inductively coupled plasma atomic absorption spectroscopy, and exposed copper samples were analyzed for topographical surface alterations. It was found that there was a fairly even growth of CuO under wet plating conditions, reaching 4-10 nm in 300 min, but no measurable Cu2O was formed during this time. CuO was found to significantly inhibit contact killing, compared to pure copper. In contrast, thermally generated Cu2O was essentially as effective in contact killing as pure copper. Copper ion release from the different surfaces roughly correlated with their antibacterial efficacy and was highest for pure copper, followed by Cu2O and CuO. Tris-Cl induced a 10-50-fold faster copper ion release compared to PBS. Since the Cu2O that primarily forms on copper under ambient conditions is as active in contact killing as pure copper, antimicrobial objects will retain their antimicrobial properties even after oxide formation.

Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography

Science.gov (United States)

Dumanli, Rukiye; Attar, Azade; Erci, Vildan; Isildak, Ibrahim

2016-01-01

A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na+), potassium (K+), ammonium (NH4+), chloride (Cl−) and nitrate (NO3−) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples. PMID:26786906

Cumulative approaches to track formation under swift heavy ion (SHI) irradiation: Phenomenological correlation with formation energies of Frenkel pairs

Energy Technology Data Exchange (ETDEWEB)

Crespillo, M.L., E-mail: mcrespil@utk.edu [Centro de Microanálisis de Materiales, CMAM-UAM, Cantoblanco, Madrid 28049 (Spain); Department of Materials Science & Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Agulló-López, F., E-mail: fal@uam.es [Centro de Microanálisis de Materiales, CMAM-UAM, Cantoblanco, Madrid 28049 (Spain); Zucchiatti, A. [Centro de Microanálisis de Materiales, CMAM-UAM, Cantoblanco, Madrid 28049 (Spain)

2017-03-01

Highlights: • Extensive survey formation energies Frenkel pairs and electronic stopping thresholds. • Correlation: track formation thresholds and the energies for Frenkel pair formation. • Formation energies Frenkel pairs discussed in relation to the cumulative mechanisms. • Amorphous track formation mechanisms: defect accumulation models versus melting. • Advantages cumulative models to deal with new hot topics: nuclear-electronic synergy. - Abstract: An extensive survey for the formation energies of Frenkel pairs, as representative candidates for radiation-induced point defects, is presented and discussed in relation to the cumulative mechanisms (CM) of track formation in dielectric materials under swift heavy ion (SHI) irradiation. These mechanisms rely on the generation and accumulation of point defects during irradiation followed by collapse of the lattice once a threshold defect concentration is reached. The physical basis of those approaches has been discussed by Fecht as a defect-assisted transition to an amorphous phase. Although a first quantitative analysis of the CM model was previously performed for LiNbO{sub 3} crystals, we have, here, adopted a broader phenomenological approach. It explores the correlation between track formation thresholds and the energies for Frenkel pair formation for a broad range of materials. It is concluded that the threshold stopping powers can be roughly scaled with the energies required to generate a critical Frenkel pair concentration in the order of a few percent of the total atomic content. Finally, a comparison with the predictions of the thermal spike model is discussed within the analytical Szenes approximation.

Dust ion-acoustic shock waves in magnetized pair-ion plasma with kappa distributed electrons

Science.gov (United States)

Kaur, B.; Singh, M.; Saini, N. S.

2018-01-01

We have performed a theoretical and numerical analysis of the three dimensional dynamics of nonlinear dust ion-acoustic shock waves (DIASWs) in a magnetized plasma, consisting of positive and negative ion fluids, kappa distributed electrons, immobile dust particulates along with positive and negative ion kinematic viscosity. By employing the reductive perturbation technique, we have derived the nonlinear Zakharov-Kuznetsov-Burgers (ZKB) equation, in which the nonlinear forces are balanced by dissipative forces (associated with kinematic viscosity). It is observed that the characteristics of DIASWs are significantly affected by superthermality of electrons, magnetic field strength, direction cosines, dust concentration, positive to negative ions mass ratio and viscosity of positive and negative ions.

Colored Contact Lens Dangers

Medline Plus

Full Text Available ... a souvenir shop, but 10 hours after she first put in a pair of colored contact lenses, ... APR 24, 2018 By Kate Rauch In a first, scientists in China have created artificial photoreceptors to ...

Acid-base properties of complexes of 3 group elements with tetra-4-tert. butylphthalocyanine. [Elements: Al, Ga, In, Sc

Energy Technology Data Exchange (ETDEWEB)

Borovkov, N Yu; Akopov, A S

1987-01-01

Step-like constants of pKn complex ionization of In and Sc with tetra-4-tert.butylphthalocyanine in CH/sub 3/COOH-H/sub 2/SO/sub 4/ and B-CH/sub 3/COOH-H/sub 2/SO/sub 4/, where B is antipyrine or urea are determined. They have the next values at n equalling 1, 2, 3, 4: +2.70+-0.30; -0.26+-0.09; -3.70+-0.20; -6.10+-0.20 for HOIn phthalocyanine substituted correspondingly. Effect of the methane atom nature on the basicity of phthalocyanine nitrogen mesonic atoms is considered. Using the conductometry method, it is established that phthalocyanines in concentrated H/sub 2/SO/sub 4/ form both completely protonated shapes and contact ion pairs.

Triplet formation in the ion recombination in irradiated liquids

International Nuclear Information System (INIS)

Bartczak, W.M.; Tachiya, M.; Hummel, A.

1990-01-01

The formation of singlet and triplet excited stages in the ion recombination in groups of oppositely charged ions (or positive ions and electrons) in nonpolar liquids, as occurs in the tracks of high energy electrons, is considered. Theoretical studies on triplet formation in groups of ion pairs have thus far concentrated on the case where recombination of the negative ions with any of the positive ions in the group is equally probable (random recombination). In this paper the probability for geminate recombination (electron and parent positive ion) vs cross-recombination (an electron with a positive ion other than its parent ion) in multiple ion pair groups is calculated by computer simulation and the effect of the initial spatial configuration of the charged species is investigated. It is also shown explicitly that the probability for singlet formation as a result of cross recombination is equal to 1/4, when spin relaxation by magnetic interaction with the medium and by exchange interaction can be neglected. The effect of the preferential recombination on the singlet formation probability is illustrated and recent experimental results on singlet to triplet ratios are discussed. (author)

Base pair mismatches and carcinogen-modified bases in DNA: an NMR study of G x T and G x O4meT pairing in dodecanucleotide duplexes

International Nuclear Information System (INIS)

Kalnik, M.W.; Kouchakdjian, M.; Li, B.F.L.; Swann, P.F.; Patel, D.J.

1988-01-01

High-resolution two-dimensional NMR studies have been completed on the self-complementary d(C-G-C-G-A-G-C-T-T-G-C-G) duplex (designated G x T 12-mer) and the self-complementary d(C-G-C-G-A-G-C-T-O 4 meT-G-C-G) duplex (designated G x O 4 meT 12-mer) containing G x T and G x O 4 meT pairs at identical positions four base pairs in from either end of the duplex. The exchangeable and nonexchangeable proton resonances have been assigned from an analysis of two-dimensional nuclear Overhauser enhancement (NOESY) spectra for the G x T 12-mer and G x O 4 meT 12-mer duplexes in H 2 O and D 2 O solution. The guanosine and thymidine imino protons in the G x T mismatch resonate at 10.57 and 11.98 ppm, respectively, and exhibit a strong NOE between themselves and to imino protons of flanking base pairs in the G x T 12-mer duplex. The large upfield chemical shift of this proton relative to that of the imino proton resonance of G in the G x T mismatch or in G x C base pairs indicates that hydrogen bonding to O 4 meT is either very weak or absent. This guanosine imino proton has an NOE to the OCH 3 group of O 4 meT across the pair and NOEs to the imino protons of flanking base pairs. Taken together with data from the NMR of nonexchangeable protons, this shows that both G and O 4 meT have anti-glycosidic torsion angles and are stacked into the duplex. Comparison of the intensity of the NOEs between the guanosine imino proton and the OCH 3 of O 4 meT as well as other protons in its vicinity demonstrates that the OCH 3 group of O 4 meT adopts the syn orientation with respect to N3 of the methylated thymidine. The authors propose an alternate base pairing mode stabilized by one short hydrogen bond between the 2-amino group of guanosine and the 2-carbonyl group of O 4 met

Method for the preparation of cellulose acetate flat sheet composite membranes for forward osmosis—Desalination using MgSO4 draw solution

KAUST Repository

Sairam, M.; Sereewatthanawut, E.; Li, K.; Bismarck, A.; Livingston, A.G.

2011-01-01

A lab scale method for the preparation of defect free flat sheet composite membranes for forward osmosis (FO) has been developed. Membranes containing a thin layer of cellulose acetate (CA) cast on a nylon fabric of 50μm thick were prepared by phase inversion in water. Cellulose acetate (CA) membranes with an overall thickness of 70-80μm have been prepared with lactic acid, maleic acid and zinc chloride as pore forming agents, at different annealing temperatures, for forward osmosis. These membranes have been tested in the desalination of saline feeds (35g·L-1 of NaCl) using magnesium sulphate solution (150g·L-1) as the draw solution. The water flux, and rejection of NaCl, were compared with those of commercially available membranes tested under the same FO conditions. The commercially available FO membrane from Hydration Technologies Inc, OR (M1) has a permeability of 0.13L·h-1·m-2·bar-1 with a NaCl rejection of 97% when tested with 150g·L-1 of MgSO4 in the draw solution. Another commercially available membrane for FO from Hydration Technologies Inc, OR, M2 has a water permeability of 0.014L·h-1·m-2·bar-1 with NaCl rejection of 100%. The flux and rejection of the CA membranes prepared in this work are found to be dependent on the nature of the pore forming agent, and annealing temperature. Impregnation of an inorganic filler, sodium montmorrillonite in CA membranes and coating of CA membranes with hydrophilic PVA did not enhance the flux of base CA membranes. Cellulose acetate membranes cast from dope solutions containing acetone/isopropanol and lactic acid, maleic acid and zinc chloride as pore forming agents have water permeabilities of 0.13, 0.09 and 0.68L·h-1·m-2·bar-1 respectively, with NaCl rejections of 97.7, 99.3 and 88% when annealed at 50°C. CA membranes prepared with zinc chloride as a pore forming agent have good permeability of 0.27L·h-1·m-2·bar-1 with a NaCl rejection of 95% when annealed at 70°C. © 2011.

Method for the preparation of cellulose acetate flat sheet composite membranes for forward osmosis—Desalination using MgSO4 draw solution

KAUST Repository

Sairam, M.

2011-06-01

A lab scale method for the preparation of defect free flat sheet composite membranes for forward osmosis (FO) has been developed. Membranes containing a thin layer of cellulose acetate (CA) cast on a nylon fabric of 50μm thick were prepared by phase inversion in water. Cellulose acetate (CA) membranes with an overall thickness of 70-80μm have been prepared with lactic acid, maleic acid and zinc chloride as pore forming agents, at different annealing temperatures, for forward osmosis. These membranes have been tested in the desalination of saline feeds (35g·L-1 of NaCl) using magnesium sulphate solution (150g·L-1) as the draw solution. The water flux, and rejection of NaCl, were compared with those of commercially available membranes tested under the same FO conditions. The commercially available FO membrane from Hydration Technologies Inc, OR (M1) has a permeability of 0.13L·h-1·m-2·bar-1 with a NaCl rejection of 97% when tested with 150g·L-1 of MgSO4 in the draw solution. Another commercially available membrane for FO from Hydration Technologies Inc, OR, M2 has a water permeability of 0.014L·h-1·m-2·bar-1 with NaCl rejection of 100%. The flux and rejection of the CA membranes prepared in this work are found to be dependent on the nature of the pore forming agent, and annealing temperature. Impregnation of an inorganic filler, sodium montmorrillonite in CA membranes and coating of CA membranes with hydrophilic PVA did not enhance the flux of base CA membranes. Cellulose acetate membranes cast from dope solutions containing acetone/isopropanol and lactic acid, maleic acid and zinc chloride as pore forming agents have water permeabilities of 0.13, 0.09 and 0.68L·h-1·m-2·bar-1 respectively, with NaCl rejections of 97.7, 99.3 and 88% when annealed at 50°C. CA membranes prepared with zinc chloride as a pore forming agent have good permeability of 0.27L·h-1·m-2·bar-1 with a NaCl rejection of 95% when annealed at 70°C. © 2011.

Ab initio study of ortho-meta-isomerism of Li4AB3+ ions of nitrite and phosphite oxo- and thiosalts (A=N, P; B=O, S)

International Nuclear Information System (INIS)

Charkin, O.D.; MakKi, M.L.; Charkin, O.P.

2000-01-01

In the framework of MP2(6-31*//HF/6-31G + ZPE(HF/6-31G*) and MP4SDTQ/6-31G*//MP2/6-31G* + ZPE(MP2/6-31G*) approximations ab initio calculations of surfaces of potential energy of Li 4 NO 3 + , Li 4 PO 3 + , Li 4 NS 3 + , LiPS 3 + ions and Li 3 NO 3 , Li 3 PO 3 , Li 3 NS 3 , Li 3 PS 3 molecules of lithium oxo-and thiosalts with 26 valent electrons. Several low-level energy local minimums are determined for each of these ions including (Li + ) 4 ·AB 3 3- ortho-structure of C 3V symmetry with pyramidal three-charge AB 3 3- anion and totality of meta-structures of L + ·AB 2 - ·BL 3 + ion type and AB 2 - ·BL 4 2+ ion pair of C 2V and C s symmetry with onium OLi 3 + , OLi 4 2+ cations or their thio-analogues. Equilibrium geometric parameters and relative energy of isomers, energy of different channels of decomposition, frequencies and IR-intensities of normal vibrations, characteristics of electron density distribution are determined [ru

Quantitative determination of acidic hydrolysis products of Chemical Weapons Convention related chemicals from aqueous and soil samples using ion-pair solid-phase extraction and in situ butylation.

Science.gov (United States)

Pal Anagoni, Suresh; Kauser, Asma; Maity, Gopal; Upadhyayula, Vijayasarathi V R

2018-02-01

Chemical warfare agents such as organophosphorus nerve agents, mustard agents, and psychotomimetic agent like 3-quinuclidinylbenzilate degrade in the environment and form acidic degradation products, the analysis of which is difficult under normal analytical conditions. In the present work, a simultaneous extraction and derivatization method in which the analytes are butylated followed by gas chromatography and mass spectrometric identification of the analytes from aqueous and soil samples was carried out. The extraction was carried out using ion-pair solid-phase extraction with tetrabutylammonium hydroxide followed by gas chromatography with mass spectrometry in the electron ionization mode. Various parameters such as optimum concentration of the ion-pair reagent, pH of the sample, extraction solvent, and type of ion-pair reagent were optimized. The method was validated for various parameters such as linearity, accuracy, precision, and limit of detection and quantification. The method was observed to be linear from 1 to 1000 ng/mL range in selected ion monitoring mode. The extraction recoveries were in the range of 85-110% from the matrixes with the limit of quantification for alkyl phosphonic acids at 1 ng/mL, thiodiglycolic acid at 20 ng/mL, and benzilic acid at 50 ng/mL with intra- and interday precisions below 15%. The developed method was applied for the samples prepared in the scenario of challenging inspection. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mesoporous Spinel Li4Ti5O12 Nanoparticles for High Rate Lithium-ion Battery Anodes

International Nuclear Information System (INIS)

Liu, Weijian; Shao, Dan; Luo, Guoen; Gao, Qiongzhi; Yan, Guangjie; He, Jiarong; Chen, Dongyang; Yu, Xiaoyuan; Fang, Yueping

2014-01-01

Graphical abstract: - Highlights: • Mesoporous Li 4 Ti 5 O 12 nanoparticles were prepared by a simple hydrothermal method. • The mesoporous Li 4 Ti 5 O 12 nanoparticles exhibited a diameter of 40 ± 5 nm and a pore-size distribution of 6 - 8 nm. • Cells with the mesoporous Li 4 Ti 5 O 12 anode showed excellent high rate electrochemical properties. - Abstract: Mesoporous spinel lithium titanate (Li 4 Ti 5 O 12 ) nanoparticles with the diameter of 40 ± 5 nm and the pore-size distribution of 6 - 8 nm were prepared by a simple hydrothermal method. As an anode material for lithium-ion batteries, these spinel Li 4 Ti 5 O 12 mesoporous nanoparticles exhibited desirable lithium storage properties with an initial discharge capacity of 176 mAh g −1 at 1 C rate and a capacity of approximately 145 mAh g −1 after 200 cycles at a high rate of 20 C. These excellent electrochemical properties at high charge/discharge rates are due to the mesoporous nano-scale structures with small size particles, uniform mesopores and larger electrode/electrolyte contact area, which shortens the diffusion path for both electrons and Li + ions, and offers more active sites for Li + insertion-extraction process

Diffusion of 99TcO4- in compacted bentonite: Effect of pH, concentration, density and contact time

International Nuclear Information System (INIS)

Xiangke Wang; Forschungszentrum Karlsruhe; Zuyi Tao

2004-01-01

In order to assess radionuclide diffusion and transport properties in compacted bentonite, the 'in-diffusion' method based on bentonite filled capillaries is used. The effect of 99 TcO 4 - concentration and pH value of the solution, the contact time and the dry density of compacted bentonite on the apparent diffusion coefficient (D a ) and on the distribution coefficient (K d ) values obtained from the capillary test was studied. The D a and K d values decrease with increasing of the bulk dry density of compacted bentonite. Ion exclusion influences the diffusion of 99 TcO 4 - 4 in the same substance. As compared to literature data, the K d values obtained from capillary tests are in most cases lower than those from batch tests, the difference between the two K d values is a strong function of dry density of the compacted bentonite. (author)

Effect of magnesium sulfate and thyroxine on inflammatory markers in a rat model of hypothyroidism.

Science.gov (United States)

Abbas, Amr M; Sakr, Hussein F

2016-04-01

Inflammation is a major risk factor for cardiovascular complications. Magnesium sulfate (MgSO4) has anti-inflammatory actions. Therefore we investigated the effects of levothyroxine and MgSO4 on inflammatory markers as C-reactive protein (CRP), interleukin-6, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in hypothyroid rats. Sixty male rats were divided into 6 groups; normal, normal + MgSO4, hypothyroidism, hypothyroidism + levothyroxine, hypothyroidism + MgSO4, and hypothyroidism + levothyroxine + MgSO4. Thyroxine, triiodothyronine, and thyroid-stimulating hormone (TSH), CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 were measured in all rats. Hypothyroidism significantly increased TSH, CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 and decreased triiodothronine and thyroxine. Treatment of hypothyroid rats with levothyroxine or MgSO4 significantly decreased CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1. Combined therapy of hypothyroid rats with levothyroxine and MgSO4 significantly decreased CRP, interleukin-6, TNF-α, ICAM-1, and VCAM-1 compared with hypothyroid rats either untreated or treated with levothyroxine or MgSO4. This study demonstrates that hypothyroid rats have chronic low grade inflammation, which may account for increased risk of cardiovascular diseases. Combined levothyroxine and MgSO4 is better than levothyroxine or MgSO4 alone in alleviating the chronic low grade inflammatory status and therefore reducing the risk of cardiovascular diseases in hypothyroid animals.

Complexation and extraction of series 4f, 5f and 4d ions by dialkyldithiophosphoric acids

International Nuclear Information System (INIS)

Fitoussi, Richard.

1982-04-01

A study was carried out on the complexing and extracting properties of various dialkyldithiophosphoric acids towards ions of the 4f, 5f and 4d series. Sulphurated donors complex and extract ions of the 4f and 5f series less strongly than their oxygenated homologues. However the affinity of trivalent actinide ions for dialkythiophosphate ions is shown to be greater than that of lanthanides. The conditions of ruthenium extraction from nitric acid are defined [fr

Visual colorimetry for trace antimony(V) by ion-pair solid-phase extraction with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) on a PTFE type membrane filter.

Science.gov (United States)

Mizuguchi, Hitoshi; Matsuda, Yuki; Mori, Takehito; Uehara, Atsushi; Ishikawa, Yuta; Endo, Masatoshi; Shida, Junichi

2008-02-01

A new visual colorimetry for trace antimony(V) based on ion-pair solid-phase extraction to a PTFE-type membrane filter with bis[2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) ion ([Co(5-Cl-PADAP)(2)](+)) has been developed. Experiments showed that hexachloroantimonate(V) ion (SbCl(6)(-)) was adsorbed with [Co(5-Cl-PADAP)(2)](+) to the front surface of the PTFE filter. The adsorption of antimony(V) ion was promoted by the addition of lithium chloride as a source of chloride ion. The excess reagent of [Co(5-Cl-PADAP)(2)](+) was eluted by rinsing with a 10 wt% methanol aqueous solution. In this case, the slow rate of the hydrolysis reaction of SbCl(6)(-) and the difference of the hydrophobicity of the ion pairs were important for adsorption and separation with a PTFE-type membrane filter. The antimony(V) concentration was determined through a visual comparison with a standard series. The visual detection limit was 0.10 microg. The calibration curve assessed with the reflection spectrometric responses at 580 nm was linear in the concentration range of 0.10 - 1.2 microg (r = 0.996). The proposed method has been applied to the determination of sub-microgram levels of antimony(V) ion in water samples.

On-line solid phase extraction using ion-pair microparticles combined with ICP-OES for the simultaneous preconcentration and determination of uranium and thorium

Energy Technology Data Exchange (ETDEWEB)

Yousefi, Seyed Reza; Zolfonoun, Ehsan [Nuclear Science and Technology Research Institute, Tehran (Iran, Islamic Republic of). NFCRS

2016-07-01

In this work, after on-line and in-situ solid phase extraction technique was used for the extraction and preconcentration of uranium and thorium from aqueous samples prior to inductively coupled plasma optical emission spectrometry (ICP-OES) determination. In this method, sodium hexafluorophosphate (as an ion-pairing agent) was added to the sample solution containing the cationic surfactant (dodecyltrimethylammonium bromide) and the complexing agent (dibenzoylmethane). A cloudy solution was formed as a result of formation of an ion pair between surfactant and hexafluorophosphate. The solid microparticles were passed through a microcolumn filter and the adsorbed microparticles were subsequently eluted with acid, which was directly introduced into the ICP-OES nebulizer. The main variables affecting the pre-concentration and determination steps of uranium and thorium were studied and optimized. Under the optimum conditions, the enhancement factors of 97 and 95 and the detection limits of 0.52 and 0.21 μg L{sup -1} were obtained for uranium and thorium, respectively.

Linac4 H− ion sources

International Nuclear Information System (INIS)

Lettry, J.; Aguglia, D.; Andersson, P.; Bertolo, S.; Butterworth, A.; Coutron, Y.; Dallocchio, A.; David, N.; Chaudet, E.; Fink, D. A.; Garlasche, M.; Grudiev, A.; Guida, R.; Hansen, J.; Haase, M.; Jones, A.; Koszar, I.; Lallement, J.-B.; Lombardi, A. M.; Machado, C.

2016-01-01

CERN’s 160 MeV H − linear accelerator (Linac4) is a key constituent of the injector chain upgrade of the Large Hadron Collider that is being installed and commissioned. A cesiated surface ion source prototype is being tested and has delivered a beam intensity of 45 mA within an emittance of 0.3 π ⋅ mm ⋅ mrad. The optimum ratio of the co-extracted electron- to ion-current is below 1 and the best production efficiency, defined as the ratio of the beam current to the 2 MHz RF-power transmitted to the plasma, reached 1.1 mA/kW. The H − source prototype and the first tests of the new ion source optics, electron-dump, and front end developed to minimize the beam emittance are presented. A temperature regulated magnetron H − source developed by the Brookhaven National Laboratory was built at CERN. The first tests of the magnetron operated at 0.8 Hz repetition rate are described

Are isotope pairs in inorganic electrolyte systems comparable with ion pairs

International Nuclear Information System (INIS)

Heumann, K.G.; Gindner, F.; Hoffmann, R.; Kloeppel, H.; Schwarz, A.

1977-03-01

Intensive studies on the causes of isotope effects in electrolyte studies have been carried out with the final target of making possible chemical pre-enrichment of stable isotopes which are of increasing importance for labelling purposes. The findings are also of general interest for the behaviour of ions in solutions. (orig.) [de

Time domain contact model for tyre/road interaction including nonlinear contact stiffness due to small-scale roughness

Science.gov (United States)

Andersson, P. B. U.; Kropp, W.

2008-11-01

Rolling resistance, traction, wear, excitation of vibrations, and noise generation are all attributes to consider in optimisation of the interaction between automotive tyres and wearing courses of roads. The key to understand and describe the interaction is to include a wide range of length scales in the description of the contact geometry. This means including scales on the order of micrometres that have been neglected in previous tyre/road interaction models. A time domain contact model for the tyre/road interaction that includes interfacial details is presented. The contact geometry is discretised into multiple elements forming pairs of matching points. The dynamic response of the tyre is calculated by convolving the contact forces with pre-calculated Green's functions. The smaller-length scales are included by using constitutive interfacial relations, i.e. by using nonlinear contact springs, for each pair of contact elements. The method is presented for normal (out-of-plane) contact and a method for assessing the stiffness of the nonlinear springs based on detailed geometry and elastic data of the tread is suggested. The governing equations of the nonlinear contact problem are solved with the Newton-Raphson iterative scheme. Relations between force, indentation, and contact stiffness are calculated for a single tread block in contact with a road surface. The calculated results have the same character as results from measurements found in literature. Comparison to traditional contact formulations shows that the effect of the small-scale roughness is large; the contact stiffness is only up to half of the stiffness that would result if contact is made over the whole element directly to the bulk of the tread. It is concluded that the suggested contact formulation is a suitable model to include more details of the contact interface. Further, the presented result for the tread block in contact with the road is a suitable input for a global tyre/road interaction model

A general way of analyzing EPR spectroscopy for a pair of magnetically equivalent lanthanide ions in crystal: A case study of BaY2F8:Yb3+ crystal

Science.gov (United States)

Liu, Honggang; Zheng, Wenchen

2018-01-01

Electron paramagnetic resonance (EPR) is an important tool to study the complex interactions (e.g., exchange and magnetic dipole-dipole interactions) for a pair of lanthanide (Ln) ions in crystals. How to analyze these EPR spectra and obtain the strength of each interaction is a challenge for experimentalists. In this work, a general way of calculating the EPR lines for two magnetically equivalent Ln ions is given by us to solve this problem. In order to explain their EPR spectra and obtain exchange interaction parameters Ji (i = x, y, z) between them, we deduce the analytic formulas for computing the angular dependent EPR lines for such Ln pairs under the condition of weak coupling (|Ji| ≪ hv, where v is the microwave frequency in the EPR experiment) and set up the spin-Hamiltonian energy matrix that should be diagonalized to obtain these lines if intermediate (|Ji| ˜ hv) and strong (|Ji| > hv) couplings are encountered. To verify our method, the experimental EPR spectra for the Yb3+ doped BaY2F8 crystal are considered by us and the EPR lines from the isolated Yb3+ ion and Yb3+-Yb3+ pair with distance R equal to 0.371 nm are identified clearly. Moreover, exchange interaction parameters (Jx ≈ -0.04 cm-1, Jy ≈ -0.24 cm-1, and Jz ≈ -0.1 cm-1) for such a pair are also determined by our calculations. This case study demonstrates that the theoretical method given in this work would be useful and could be applied to understand interactions between Ln ions in crystals.

Holographic EPR Pairs, Wormholes and Radiation

OpenAIRE

Chernicoff, Mariano; Güijosa, Alberto; Pedraza, Juan F.

2013-01-01

As evidence for the ER=EPR conjecture, it has recently been observed that the string that is holographically dual to an entangled quark-antiquark pair separating with (asymptotically) uniform acceleration has a wormhole on its worldsheet. We point out that a two-sided horizon and a wormhole actually appear for much more generic quark-antiquark trajectories, which is consistent with the fact that the members of an EPR pair need not be permanently out of causal contact. The feature that determi...

Utility of Charge Transfer and Ion-Pair Complexation for Spectrophotometric Determination of Eletriptan Hydrobromide in Pure and Dosage Forms

Directory of Open Access Journals (Sweden)

Ayman A. Gouda

2013-01-01

Full Text Available Three simple, sensitive, and accurate spectrophotometric methods have been developed for the determination of eletriptan hydrobromide (ELT in pure and dosage forms. The first two methods are based on charge transfer complex formation between ELT and chromogenic reagents quinalizarin (Quinz and alizarin red S (ARS producing charge transfer complexes which showed an absorption maximum at 569 and 533 nm for Quinz and ARS, respectively. The third method is based on the formation of ion-pair complex between ELT with molybdenum(V-thiocyanate inorganic complex in hydrochloric acid medium followed by extraction of the colored ion-pair with dichloromethane and measured at 470 nm. Different variables affecting the reactions were studied and optimized. Beer's law is obeyed in the concentration ranges 2.0–18, 1.0–8.0, and 2.0–32 μg mL−1 for Quinz, ARS, and Mo(V-thiocyanate, respectively. The molar absorptivity, Sandell sensitivity, detection, and quantification limits are also calculated. The correlation coefficients were ≥0.9994 with a relative standard deviation (R.S.D%. of ≤0.925. The proposed methods were successfully applied for simultaneous determination of ELT in tablets with good accuracy and precision and without interferences from common additives, and the validity is assessed by applying the standard addition technique, which is compared with those obtained using the reported method.

Spectroscopic and quantum-chemical investigation of association of ions in acetonitrile - LiX (X=I, ClO4, NCS) systems

International Nuclear Information System (INIS)

Semenov, S.G.; Solov'eva, L.A.; Akopyan, S.Kh.

1995-01-01

Data on association constants of ions in acetonitrile-salt binary systems, obtained from the data on intensity of IR absorption bands of acetonitrile (Acn) molecules contained in solvate shells of Li + cations, have been analyzed. Using the CCP MO LCAO semiempirical method in the PPDP approximation, electronic structure of acetonitrile molecule and Acn k Li + and Acn m Li + X - complexes has been studied. It is ascertained that relative stability of ionic pairs Acn 3 Li + X - , estimated by the squares of their dipole momenta (characterizing solvation energy) increases in the series X=I, ClO 4 , NCS in agreement with data of spectroscopic experiment, according to which the constant of ion association for LiNCS solution in acetonitrile is much higher than for the systems CH 3 CN-LiI and CH 3 CN-LiClO 4 . 13 refs.,2 figs., 2 tabs.64

Hydration and Ion Pairing in Aqueous Mg2+ and Zn2+ Solutions: Force-Field Description Aided by Neutron Scattering Experiments and Ab Initio Molecular Dynamics Simulations.

Science.gov (United States)

Duboué-Dijon, Elise; Mason, Philip E; Fischer, Henry E; Jungwirth, Pavel

2018-04-05

Magnesium and zinc dications possess the same charge and have an almost identical size, yet they behave very differently in aqueous solutions and play distinct biological roles. It is thus crucial to identify the origins of such different behaviors and to assess to what extent they can be captured by force-field molecular dynamics simulations. In this work, we combine neutron scattering experiments in a specific mixture of H 2 O and D 2 O (the so-called null water) with ab initio molecular dynamics simulations to probe the difference in the hydration structure and ion-pairing properties of chloride solutions of the two cations. The obtained data are used as a benchmark to develop a scaled-charge force field for Mg 2+ that includes electronic polarization in a mean field way. We show that using this electronic continuum correction we can describe aqueous magnesium chloride solutions well. However, in aqueous zinc chloride specific interaction terms between the ions need to be introduced to capture ion pairing quantitatively.

The reaction of 1,2-Dichloro-4,5-dinitrobenzene with hydroxide ion: roles of Meisenheimer complexes and radical pairs

Energy Technology Data Exchange (ETDEWEB)

Blasko, Andrei; Bunton, Clifford A.; Gillitt, Nichollas D.; Bacaloglu, Radu [Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA (United States); Yunes, Santiago F.; Zucco, Cesar, E-mail: c.zucco@ufsc.br, E-mail: santiago.yunes@ufsc.br [Departamento de Quimica, Universidade Federal de Santa Catarina, Florianopolis-SC (Brazil)

2013-07-15

The reaction of 1,2-dichloro-4,5-dinitrobenzene (DCDNB) with aqueous OH{sup -} produces (after acidification) 2-nitro-4,5-dichlorophenol with loss of NO{sub 2} . Nevertheless, with > 2 mol L{sup -1} OH{sup -}, only DCDNB was recovered due to the formation of the long-lived 3,6-dihydroxy Meisenheimer complex (M{sup 2-}), and that in acid, reverted to the starting material. Fast formation of monohydroxy Meisenheimer complex (M{sup 1-}) can be followed in DMSO:H{sub 2}O 7:3 v/v and rate constants for its interconversion with DCDNB and for formation and return with M{sup 2-} complex were estimated, with evidence for these reactions in DMSO:H{sub 2}O 1:1 v/v and H{sub 2}O. The rapid hydrogen exchange in OD{sup -}/D{sub 2}O limits the use of {sup 1}H nuclear magnetic resonance (NMR) spectroscopy in identifying intermediates. {sup 1}H and {sup 13}C NMR signals of M{sup 2-} complex were observed in DMSO-H{sub 2}O-KOH. There is evidence for the formation of free radicals in DMSO:H{sub 2} O 4:1 v/v, and overall kinetics in more aqueous medium were treated in terms of the transient existence of anionic radical pairs. (author)

Social isolation affects partner-directed social behavior and cortisol during pair formation in marmosets, Callithrix geoffroyi.

Science.gov (United States)

Smith, Adam S; Birnie, Andrew K; French, Jeffrey A

2011-10-24

Pair-bonded relationships form during periods of close spatial proximity and high sociosexual contact. Like other monogamous species, marmosets form new social pairs after emigration or ejection from their natal group resulting in periods of social isolation. Thus, pair formation often occurs following a period of social instability and a concomitant elevation in stress physiology. Research is needed to assess the effects that prolonged social isolation has on the behavioral and cortisol response to the formation of a new social pair. We examined the sociosexual behavior and cortisol during the first 90-days of cohabitation in male and female Geoffroy's tufted-ear marmosets (Callithrix geoffroyi) paired either directly from their natal group (Natal-P) or after a prolonged period of social isolation (ISO-P). Social isolation prior to pairing seemed to influence cortisol levels, social contact, and grooming behavior; however, sexual behavior was not affected. Cortisol levels were transiently elevated in all paired marmosets compared to natal-housed marmosets. However, ISO-P marmosets had higher cortisol levels throughout the observed pairing period compared to Natal-P marmoset. This suggests that the social instability of pair formation may lead to a transient increase in hypothalamic-pituitary-adrenal (HPA) axis activity while isolation results in a prolonged HPA axis dysregulation. In addition, female social contact behavior was associated with higher cortisol levels at the onset of pairing; however, this was not observed in males. Thus, isolation-induced social contact with a new social partner may be enhanced by HPA axis activation, or a moderating factor. Published by Elsevier Inc.

Analysis of the facilitatory effect of the ACTH-(4–9) analog ORG 2766 on active social contact in rats

NARCIS (Netherlands)

Ree, J.M. van; Niesink, R.J.M.

1984-01-01

Pairs of male rats were tested for active social interaction, either in a familiar test arena under low illumination or in an unfamiliar test arena under high illumination conditions. Rats tested in an unfamiliar environment and under high light, spent less time in active social contact than rats

Low work-function thermionic emission and orbital-motion-limited ion collection at bare-tether cathodic contact

Energy Technology Data Exchange (ETDEWEB)

Chen, Xin, E-mail: xin.chen@upm.es; Sanmartín, J. R., E-mail: juanr.sanmartin@upm.es [Departamento de Física Aplicada, Escuela Técnica Superior de Ingeniería Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Plaza Cardenal Cisneros, 3, 28040 Madrid (Spain)

2015-05-15

With a thin coating of low-work-function material, thermionic emission in the cathodic segment of bare tethers might be much greater than orbital-motion-limited (OML) ion collection current. The space charge of the emitted electrons decreases the electric field that accelerates them outwards, and could even reverse it for high enough emission, producing a potential hollow. In this work, at the conditions of high bias and relatively low emission that make the potential monotonic, an asymptotic analysis is carried out, extending the OML ion-collection analysis to investigate the probe response due to electrons emitted by the negatively biased cylindrical probe. At given emission, the space charge effect from emitted electrons increases with decreasing magnitude of negative probe bias. Although emitted electrons present negligible space charge far away from the probe, their effect cannot be neglected in the global analysis for the sheath structure and two thin layers in between sheath and the quasineutral region. The space-charge-limited condition is located. It is found that thermionic emission increases the range of probe radius for OML validity and is greatly more effective than ion collection for cathodic contact of tethers.

Improved Light Extraction Efficiency by Photonic Crystal Arrays on Transparent Contact Layer Using Focused Ion Beams

International Nuclear Information System (INIS)

Wu, G.M.; Tsai, B.H.; Kung, S.F.; Wu, C.F.

2011-01-01

Nitride-based thin-film materials have become increasingly important for the high brightness light-emitting diode applications. The improvements in light extraction and lower power consumption are highly desired. Although the internal quantum efficiency of GaN-based LED has been relatively high, only a small fraction of light can be extracted. In this study, a new design of two-dimensional photonic crystal array has been prepared on the top transparent contact layer of indium-tin oxide film to improve the light extraction efficiency using focused ion beam. The acceleration voltage of the Ga dual-beam nanotechnology system SMI 3050 was 30 kV and the ion beam current was 100 pA. The cylindrical air holes had the diameter of 150 nm and depth of 100 nm. The micro photoluminescence analysis results showed that the light output intensity could be 1.5 times of that of the non-patterned control sample. In addition, the structural damage from the focused ion beam drilling of GaN step could be eliminated. The excellent I-V characteristics have been maintained, and the external light extraction efficiency would be still improved for the LED devices. (author)

Refining intra-protein contact prediction by graph analysis

Directory of Open Access Journals (Sweden)

Eyal Eran

2007-05-01

Full Text Available Abstract Background Accurate prediction of intra-protein residue contacts from sequence information will allow the prediction of protein structures. Basic predictions of such specific contacts can be further refined by jointly analyzing predicted contacts, and by adding information on the relative positions of contacts in the protein primary sequence. Results We introduce a method for graph analysis refinement of intra-protein contacts, termed GARP. Our previously presented intra-contact prediction method by means of pair-to-pair substitution matrix (P2PConPred was used to test the GARP method. In our approach, the top contact predictions obtained by a basic prediction method were used as edges to create a weighted graph. The edges were scored by a mutual clustering coefficient that identifies highly connected graph regions, and by the density of edges between the sequence regions of the edge nodes. A test set of 57 proteins with known structures was used to determine contacts. GARP improves the accuracy of the P2PConPred basic prediction method in whole proteins from 12% to 18%. Conclusion Using a simple approach we increased the contact prediction accuracy of a basic method by 1.5 times. Our graph approach is simple to implement, can be used with various basic prediction methods, and can provide input for further downstream analyses.

Ion irradiation of CH4-containing icy mixtures

International Nuclear Information System (INIS)

Baratta, G.A.; Domingo, M.; Ferini, G.; Leto, G.; Palumbo, M.E.; Satorre, M.A.; Strazzulla, G.

2003-01-01

We have studied by infrared absorption spectroscopy the effects of ion irradiation with 60 keV Ar 2+ ions on pure methane (CH 4 ) ice at 12 K and mixtures with water (H 2 O) and nitrogen (N 2 ). Ion irradiation, among other effects, causes the rupture of original molecular bonds and the formation of molecular species not present in the initial ice. Here we present the experimental results and discuss their astrophysical relevance

Ohmic contacts to semiconducting diamond

Science.gov (United States)

Zeidler, James R.; Taylor, M. J.; Zeisse, Carl R.; Hewett, C. A.; Delahoussaye, Paul R.

1990-10-01

Work was carried out to improve the electron beam evaporation system in order to achieve better deposited films. The basic system is an ion pumped vacuum chamber, with a three-hearth, single-gun e-beam evaporator. Four improvements were made to the system. The system was thoroughly cleaned and new ion pump elements, an e-gun beam adjust unit, and a more accurate crystal monitor were installed. The system now has a base pressure of 3 X 10(exp -9) Torr, and can easily deposit high-melting-temperature metals such as Ta with an accurately controlled thickness. Improved shadow masks were also fabricated for better alignment and control of corner contacts for electrical transport measurements. Appendices include: A Thermally Activated Solid State Reaction Process for Fabricating Ohmic Contacts to Semiconducting Diamond; Tantalum Ohmic Contacts to Diamond by a Solid State Reaction Process; Metallization of Semiconducting Diamond: Mo, Mo/Au, and Mo/Ni/Au; Specific Contact Resistance Measurements of Ohmic Contracts to Diamond; and Electrical Activation of Boron Implanted into Diamond.

Inflation of the screening length induced by Bjerrum pairs

NARCIS (Netherlands)

Zwanikken, J.W.; van Roij, R.H.H.G.

2009-01-01

Within a modified Poisson–Boltzmann theory we study the effect of Bjerrum pairs on the typical length scale 1/¯κ over which electric fields are screened in electrolyte solutions, taking into account a simple association–dissociation equilibrium between free ions and Bjerrum pairs. At low densities

Strong Neutron Pairing in core+4n Nuclei.

Science.gov (United States)

Revel, A; Marqués, F M; Sorlin, O; Aumann, T; Caesar, C; Holl, M; Panin, V; Vandebrouck, M; Wamers, F; Alvarez-Pol, H; Atar, L; Avdeichikov, V; Beceiro-Novo, S; Bemmerer, D; Benlliure, J; Bertulani, C A; Boillos, J M; Boretzky, K; Borge, M J G; Caamaño, M; Casarejos, E; Catford, W N; Cederkäll, J; Chartier, M; Chulkov, L; Cortina-Gil, D; Cravo, E; Crespo, R; Datta Pramanik, U; Díaz Fernández, P; Dillmann, I; Elekes, Z; Enders, J; Ershova, O; Estradé, A; Farinon, F; Fraile, L M; Freer, M; Galaviz, D; Geissel, H; Gernhäuser, R; Golubev, P; Göbel, K; Hagdahl, J; Heftrich, T; Heil, M; Heine, M; Heinz, A; Henriques, A; Ignatov, A; Johansson, H T; Jonson, B; Kahlbow, J; Kalantar-Nayestanaki, N; Kanungo, R; Kelic-Heil, A; Knyazev, A; Kröll, T; Kurz, N; Labiche, M; Langer, C; Le Bleis, T; Lemmon, R; Lindberg, S; Machado, J; Marganiec, J; Movsesyan, A; Nacher, E; Najafi, M; Nilsson, T; Nociforo, C; Paschalis, S; Perea, A; Petri, M; Pietri, S; Plag, R; Reifarth, R; Ribeiro, G; Rigollet, C; Röder, M; Rossi, D; Savran, D; Scheit, H; Simon, H; Syndikus, I; Taylor, J T; Tengblad, O; Thies, R; Togano, Y; Velho, P; Volkov, V; Wagner, A; Weick, H; Wheldon, C; Wilson, G; Winfield, J S; Woods, P; Yakorev, D; Zhukov, M; Zilges, A; Zuber, K

2018-04-13

The emission of neutron pairs from the neutron-rich N=12 isotones ^{18}C and ^{20}O has been studied by high-energy nucleon knockout from ^{19}N and ^{21}O secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay ^{19}N(-1p)^{18}C^{*}→^{16}C+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a ^{14}C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay ^{21}O(-1n)^{20}O^{*}→^{18}O+n+n, attributed to its formation through the knockout of a deeply bound neutron that breaks the ^{16}O core and reduces the number of pairs.

Temperature Dependence of the Stability of Ion Pair Interactions ...

Indian Academy of Sciences (India)

The occurrence of bridging water molecules between the ions ensures that the ions are not ... The structural features that render this thermostability ..... dehydrogenase single site mutant T198I from Thermus thermophilus with PDB ID 1BDM.

Pair potentials and structure factors of liquid alkali metals

International Nuclear Information System (INIS)

Kumaravadivel, R.; Tosi, M.P.

1984-03-01

Measured structure factors of liquid alkali metals are examined in the framework of screened-pair-potentials theory. Information on the main attractive well in the effective pair potential is obtained from the structural data by an approximate method stemming from an optimized random phase treatment of the indirect ion-ion attraction. The results are compared with a variety of theoretical pair potentials in the cases of sodium and potassium, after a test of the method against computer simulation data on a model for rubidium. Results for the other alkali metals are also given and discussed. The small-angle scattering region is then examined in considerable detail, with special attention to the possibility of a linear term in a series expansion of the structure factor at very small momentum transfer. Although sensitivity to both the bare electron-ion coupling and the local field factor in the screening function is demonstrated and analyzed, no linear term of the magnitude reported in recent X-ray diffraction experiments is found in the present theoretical framework. (author)

Exotic pairing in 1D spin-3/2 atomic gases with SO(4 symmetry

Directory of Open Access Journals (Sweden)

Yuzhu Jiang

2015-06-01

Full Text Available Tuning interactions in the spin singlet and quintet channels of two colliding atoms could change the symmetry of the one-dimensional spin-3/2 fermionic systems of ultracold atoms while preserving the integrability. Here we find a novel SO(4 symmetry integrable point in the spin-3/2 Fermi gas and derive the exact solution of the model using the Bethe ansatz. In contrast to the model with SU(4 and SO(5 symmetries, the present model with SO(4 symmetry preserves spin singlet and quintet Cooper pairs in two sets of SU(2⊗SU(2 spin subspaces. We obtain full phase diagrams, including the Fulde–Ferrel–Larkin–Ovchinnikov like pair correlations, spin excitations and quantum criticality through the generalized Yang–Yang thermodynamic equations. In particular, various correlation functions are calculated by using finite-size corrections in the frame work of conformal field theory. Moreover, within the local density approximation, we further find that spin singlet and quintet pairs form subtle multiple shell structures in density profiles of the trapped gas.

Sulfonated Magnetic Nanocomposite Based on Reactive PGMA-MAn Copolymer@Fe3O4 Nanoparticles: Effective Removal of Cu(II Ions from Aqueous Solutions

Directory of Open Access Journals (Sweden)

Reza Hasanzadeh

2016-01-01

Full Text Available Chelating magnetic nanocomposites have been considered as suitable materials for removal of heavy metal ions for water treatment. In this work poly(glycidyl methacrylate-maleic anhydride copolymer (PGMA-MAn is modified with 4-aminobenzenesulfonic acid (ABSAc and subsequently the product reacted with modified Fe3O4 nanoparticles and 1,2-ethanedithiol (EDT in the presence of ultrasonic irradiation for preparation of tridimensional chelating magnetic nanocomposite. Synthesized magnetic nanocomposite was characterized by Fourier transform infrared spectroscopy (FT-IR, scanning electron microscopy (SEM, X-ray diffraction analysis (XRD, vibrating sample magnetometer (VSM, energy dispersive X-ray analysis (EDX, elemental mapping analysis (EMA, Brunauer-Emmett-Teller (BET, and thermal gravimetric analysis (TGA. The adsorption behavior of Cu(II ions was investigated by synthesized nanocomposite in various parameters such as pH, contact time, metal ion concentration, and adsorbent dosage. The equilibrium distribution coefficient (kd was determined and the findings prove that the kd value is approximately high in the case of all selected metal ions. The synthesized nanocomposite exhibited good tendency for removing Cu(II ions from aqueous solutions even at an acidic pH.

Molecular [(Fe3)–(Fe3)] and [(Fe4)–(Fe4)] coordination cluster pairs as single or composite arrays.

Science.gov (United States)

Sañudo, E Carolina; Uber, Jorge Salinas; Pons Balagué, Alba; Roubeau, Olivier; Aromí, Guillem

2012-08-06

The synthesis of molecular cluster pairs is a challenge for coordination chemists due to the potential applications of these species in molecular spintronics or quantum computing. The ligand H(4)L, 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-2-methoxybenzene, has been successfully used to obtain a series of such complexes using the basic Fe(III) trinuclear carboxylates as starting materials. Synthetic control has allowed the isolation of the two molecular cluster pairs that form the composite [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2)[Fe(3)O(PhCO(2))(5)(py)(H(2)L)](2) (1). The dimers of trinuclear units, [Fe(3)O(PhCO(2))(5)(H(2)O)(H(2)L)](2) (2) and [Fe(3)O(o-MePhCO(2))(5)(H(2)L)(py)](2) (3), and the dimers of tetranuclear units, [Fe(4)O(2)(PhCO(2))(6)(H(2)L)(pz)](2) (4) and [Fe(4)O(2)(o-MePhCO(2))(6)(H(2)L)(pz)](2) (5), are presented here. The magnetic properties of the reported aggregates show that they are pairs of semi-independent clusters weakly interacting magnetically as required for two-qubit quantum gates.

[Quantum-chemical investigation of tautomerization ways of Watson-Crick DNA base pair guanine-cytosine].

Science.gov (United States)

Brovarets', O O; Hovorun, D M

2010-01-01

A novel physico-chemical mechanism of the Watson-Crick DNA base pair Gua.Cyt tautomerization Gua.Cyt*Gua.CytGua*.Cyt (mutagenic tautomers of bases are marked by asterisks) have been revealed and realized in a pathway of single proton transfer through two mutual isoenergetic transition states with Gibbs free energy of activation 30.4 and 30.6 kcal/mol and they are ion pairs stabilized by three (N2H...N3, N1H...N4- and O6+H...N4-) and five (N2H...O2, N1H...O2, N1H...N3, O6+H...N4- and 06+H...N4-) H-bonds accordingly. Stable base pairs Gua-Cyt* and Gua*.Cyt which dissociate comparably easy into monomers have acceptable relative Gibbs energies--12.9 and 14.3 kcal/mol--for the explanation of the nature of the spontaneous transitions of DNA replication. Results are obtained at the MP2/6-311++G(2df,pd)//B3LYP/6-31 1++G(d,p) level of theory in vacuum approach.

Ion-ion and ion-solvent interactions in lithium imidazolide electrolytes studied by Raman spectroscopy and DFT models.

Science.gov (United States)

Scheers, Johan; Niedzicki, Leszek; Zukowska, Grażyna Z; Johansson, Patrik; Wieczorek, Władysław; Jacobsson, Per

2011-06-21

Molecular level interactions are of crucial importance for the transport properties and overall performance of ion conducting electrolytes. In this work we explore ion-ion and ion-solvent interactions in liquid and solid polymer electrolytes of lithium 4,5-dicyano-(2-trifluoromethyl)imidazolide (LiTDI)-a promising salt for lithium battery applications-using Raman spectroscopy and density functional theory calculations. High concentrations of ion associates are found in LiTDI:acetonitrile electrolytes, the vibrational signatures of which are transferable to PEO-based LiTDI electrolytes. The origins of the spectroscopic changes are interpreted by comparing experimental spectra with simulated Raman spectra of model structures. Simple ion pair models in vacuum identify the imidazole nitrogen atom of the TDI anion to be the most important coordination site for Li(+), however, including implicit or explicit solvent effects lead to qualitative changes in the coordination geometry and improved correlation of experimental and simulated Raman spectra. To model larger aggregates, solvent effects are found to be crucial, and we finally suggest possible triplet and dimer ionic structures in the investigated electrolytes. In addition, the effects of introducing water into the electrolytes-via a hydrate form of LiTDI-are discussed.

A plant-wide aqueous phase chemistry module describing pH variations and ion speciation/pairing in wastewater treatment process models.

Science.gov (United States)

Flores-Alsina, Xavier; Kazadi Mbamba, Christian; Solon, Kimberly; Vrecko, Darko; Tait, Stephan; Batstone, Damien J; Jeppsson, Ulf; Gernaey, Krist V

2015-11-15

There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico-chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton-Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependent of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some

Ion funnel device

Energy Technology Data Exchange (ETDEWEB)

Ibrahim, Yehia M.; Chen, Tsung-Chi; Harrer, Marques B.; Tang, Keqi; Smith, Richard D.

2017-11-21

An ion funnel device is disclosed. A first pair of electrodes is positioned in a first direction. A second pair of electrodes is positioned in a second direction. The device includes an RF voltage source and a DC voltage source. A RF voltage with a superimposed DC voltage gradient is applied to the first pair of electrodes, and a DC voltage gradient is applied to the second pair of electrodes.

The behavior of exciplex decay processes and interplay of radiationless transition and preliminary reorganization mechanisms of electron transfer in loose and tight pairs of reactants.

Science.gov (United States)

Kuzmin, Michael G; Soboleva, Irina V; Dolotova, Elena V

2007-01-18

Exciplex emission spectra and rate constants of their decay via internal conversion and intersystem crossing are studied and discussed in terms of conventional radiationless transition approach. Exciplexes of 9-cyanophenanthrene with 1,2,3-trimethoxybenzene and 1,3,5-trimethoxybenzene were studied in heptane, toluene, butyl acetate, dichloromethane, butyronitrile, and acetonitrile. A better description of spectra and rate constants is obtained using 0-0 transition energy and Gauss broadening of vibrational bands rather than the free energy of electron transfer and reorganization energy. The coincidence of parameters describing exciplex emission spectra and dependence of exciplex decay rate constants on energy gap gives the evidence of radiationless quantum transition mechanism rather than thermally activated medium reorganization mechanism of charge recombination in exciplexes and excited charge transfer complexes (contact radical ion pairs) as well as in solvent separated radical ion pairs. Radiationless quantum transition mechanism is shown to provide an appropriate description also for the main features of exergonic excited-state charge separation reactions if fast mutual transformations of loose and tight pairs of reactants are considered. In particular, very fast electron transfer (ET) in tight pairs of reactants with strong electronic coupling of locally excited and charge transfer states can prevent the observation of an inverted region in bimolecular excited-state charge separation even for highly exergonic reactions.

Relationship between the real contact area and contact force in pre-sliding regime

International Nuclear Information System (INIS)

Song Baojiang; Yan Shaoze

2017-01-01

The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To investigate the relationship between contact status and contact force in pre-sliding friction, an optical experimental method is presented in this paper. With this method, the real contact state at the interface of a transparent material can be observed based on the total reflection principle of light by using an image processing technique. A novel setup, which includes a pair of rectangular trapezoidal blocks, is proposed to solve the challenging issue of accurately applying different tangential and normal forces to the contact interface. The improved Otsu’s method is used for measurement. Through an experimental study performed on polymethyl methacrylate (PMMA), the quantity of contact asperities is proven to be the dominant factor that affects the real contact area. The relationship between the real contact area and the contact force in the pre-sliding regime is studied, and the distribution of static friction at the contact interface is qualitatively discussed. New phenomena in which the real contact area expands along with increasing static friction are identified. The aforementioned relationship is approximately linear at the contact interface under a constant normal pressure, and the distribution of friction stress decreases from the leading edge to the trailing edge. (paper)

Excited-state proton transfer of 4-hydroxyl-1, 8-naphthalimide derivatives: A combined experimental and theoretical investigation

Energy Technology Data Exchange (ETDEWEB)

Qu, Zongjin; Li, Peng; Zhang, Xuexiang; Wang, Endong; Wang, Yanni; Zhou, Panwang, E-mail: pwzhou@dicp.ac.cn

2016-09-15

The photophysical properties of N-butyl-4-hydroxyl-1, 8-naphthalimide (BOH) and N-(morpholinoethyl)−4-hydroxy-1, 8-naphthalimide (MOH) in various solvents are presented and the density functional theory (DFT)/time-dependent density functional theory (TDDFT) methods at the B3LYP/TZVP theoretical level are adopted to investigate the UV–visible absorption and emission data. An efficient intermolecular excited-state proton transfer (ESPT) reaction occurs for both compounds in DMSO, methanol and water. In aqueous solution, both BOH and MOH can be used as ratiometric pH probes and perform as strong photoacids with pKa*=−2.2, −2.4, respectively. Most interestingly, in the steady-state fluorescence spectra of BOH and MOH in concentrated HCl, an unexpected blue-shifted band is observed and assumed to originate from the contact ion pair (CIP) formed by hydronium ion and the anionic form of the photoacid resulted from ESPT. Theoretical calculations are used to simulate the CIP in the case of BOH, which afford reasonable results compared with the experimental data.

Period variation studies of six contact binaries in M4

Science.gov (United States)

Rukmini, Jagirdar; Shanti Priya, Devarapalli

2018-04-01

We present the first period study of six contact binaries in the closest globular cluster M4 the data collected from June 1995‑June 2009 and Oct 2012‑Sept 2013. New times of minima are determined for all the six variables and eclipse timing (O-C) diagrams along with the quadratic fit are presented. For all the variables, the study of (O-C) variations reveals changes in the periods. In addition, the fundamental parameters for four of the contact binaries obtained using the Wilson-Devinney code (v2003) are presented. Planned observations of these binaries using the 3.6-m Devasthal Optical Telescope (DOT) and the 4-m International Liquid Mirror Telescope (ILMT) operated by the Aryabhatta Research Institute of Observational Sciences (ARIES; Nainital) can throw light on their evolutionary status from long term period variation studies.

Coherent lepton pair production in hadronic heavy ion collisions

Science.gov (United States)

Zha, W.; Ruan, L.; Tang, Z.; Xu, Z.; Yang, S.

2018-06-01

Recently, significant enhancements of e+e- pair production at very low transverse momentum (pT < 0.15 GeV/c) were observed by the STAR collaboration in peripheral hadronic A+A collisions. This excesses can not be described by the QGP thermal radiation and ρ in-medium broadening calculations. This is a sign of coherent photon-photon interactions, which were conventionally studied only in ultra-peripheral collisions. In this article, we present calculations of lepton pair (e+e- and μ+μ-) production from coherent photon-photon interactions in hadronic A+A collisions at RHIC and LHC energies within the STAR and ALICE acceptance.

Angle-resolved ion TOF spectrometer with a position sensitive detector

Energy Technology Data Exchange (ETDEWEB)

Saito, Norio [Electrotechnical Lab., Tsukuba, Ibaraki (Japan); Heiser, F; Wieliczec, K; Becker, U

1996-07-01

A angle-resolved ion time-of-flight mass spectrometer with a position sensitive anode has been investigated. Performance of this spectrometer has been demonstrated by measuring an angular distribution of a fragment ion pair, C{sup +} + O{sup +}, from CO at the photon energy of 287.4 eV. The obtained angular distribution is very close to the theoretically expected one. (author)

Electroless Formation of Hybrid Lithium Anodes for Fast Interfacial Ion Transport

KAUST Repository

Choudhury, Snehashis; Tu, Zhengyuan; Stalin, Sanjuna; Vu, Duylinh; Fawole, Kristen; Gunceler, Deniz; Sundararaman, Ravishankar; Archer, Lynden A.

2017-01-01

Rechargeable batteries based on metallic anodes are of interest for fundamental and application-focused studies of chemical and physical kinetics of liquids at solid interfaces. Approaches that allow facile creation of uniform coatings on these metals to prevent physical contact with liquid electrolytes, while enabling fast ion transport, are essential to address chemical instability of the anodes. Here, we report a simple electroless ion-exchange chemistry for creating coatings of indium on lithium. By means of joint density functional theory and interfacial characterization experiments, we show that In coatings stabilize Li by multiple processes, including exceptionally fast surface diffusion of lithium ions and high chemical resistance to liquid electrolytes. Indium coatings also undergo reversible alloying reactions with lithium ions, facilitating design of high-capacity hybrid In-Li anodes that use both alloying and plating approaches for charge storage. By means of direct visualization, we further show that the coatings enable remarkably compact and uniform electrodeposition. The resultant In-Li anodes are shown to exhibit minimal capacity fade in extended galvanostatic cycling when paired with commercial-grade cathodes.

Electroless Formation of Hybrid Lithium Anodes for Fast Interfacial Ion Transport

KAUST Repository

Choudhury, Snehashis

2017-08-17

Rechargeable batteries based on metallic anodes are of interest for fundamental and application-focused studies of chemical and physical kinetics of liquids at solid interfaces. Approaches that allow facile creation of uniform coatings on these metals to prevent physical contact with liquid electrolytes, while enabling fast ion transport, are essential to address chemical instability of the anodes. Here, we report a simple electroless ion-exchange chemistry for creating coatings of indium on lithium. By means of joint density functional theory and interfacial characterization experiments, we show that In coatings stabilize Li by multiple processes, including exceptionally fast surface diffusion of lithium ions and high chemical resistance to liquid electrolytes. Indium coatings also undergo reversible alloying reactions with lithium ions, facilitating design of high-capacity hybrid In-Li anodes that use both alloying and plating approaches for charge storage. By means of direct visualization, we further show that the coatings enable remarkably compact and uniform electrodeposition. The resultant In-Li anodes are shown to exhibit minimal capacity fade in extended galvanostatic cycling when paired with commercial-grade cathodes.

Improved separation and antifouling properties of thin-film composite nanofiltration membrane by the incorporation of cGO

Science.gov (United States)

Li, Hongbin; Shi, Wenying; Du, Qiyun; Zhou, Rong; Zhang, Haixia; Qin, Xiaohong

2017-06-01

Poly(piperazine amide) composite nanofiltration (NF) membranes were modified through the incorporation of carboxylated graphene oxide (cGO) in the polyamide layer during the interfacial polymerization (IP) process on the polysulfone (PSF)/nonwoven fabric (NWF) ultrafiltration (UF) substrate membrane surface. The composition and morphology of the prepared NF membrane surface were determined by means of ATR-FTIR, SEM-EDX and AFM. The effects of cGO contents on membrane hydrophilicity, separation performance and antifouling properties were investigated through Water Contact Angle (WCA) analysis, the permeance and three-cycle fouling measurements. The growth model of cGO-incorporated polyamide thin-film was proposed. Compared to the original NF membranes, the surface hydrophilicity, water permeability, salt rejection and antifouling properties of the cGO-incorporated NF membrane had all improved. When cGO content was 100 ppm, the MgSO4 rejection of composite NF membrane reached a maximum value of 99.2% meanwhile membrane obtained an obvious enhanced water flux (81.6 L m-2 h-1, at 0.7 MPa) which was nearly three times compared to the virginal NF membrane. The cGO-incorporated NF membrane showed an excellent selectivity of MgSO4 and NaCl with the rejection ratio of MgSO4/NaCl of approximately 8.0.

Quantum electrodynamics effects in the 4s-4p transitions in Cu-like and Zn-like ions

International Nuclear Information System (INIS)

Cheng, K.; Wagner, R.A.

1987-01-01

Multiconfiguration Dirac-Fock energies are compared with experiment for the 4s-4p transitions in Cu-like ions and the 4s 2 1 S 0 --4s4p 1 P 1 transition in Zn-like ions for Au, Pb, Bi, Th, and U. The Coulomb, Breit, and QED contributions to these transitions are tabulated for selected ions in the range Z = 50--92. Results show that the agreement between theory and experiment is good enough to show the importance of QED corrections in the spectra of these highly stripped ions. Contrary to earlier findings by Seely et al. [Phys. Rev. Lett. 57, 2924 (1986)] we find no significant differences between the observed and calculated transition energies after finite-nuclear-size corrections are included

Solid-Contact pH Sensor without CO2 Interference with a Superhydrophobic PEDOT-C14 as Solid Contact: The Ultimate "Water Layer" Test.

Science.gov (United States)

Guzinski, Marcin; Jarvis, Jennifer M; D'Orazio, Paul; Izadyar, Anahita; Pendley, Bradford D; Lindner, Ernő

2017-08-15

The aim of this study was to find a conducting polymer-based solid contact (SC) for ion-selective electrodes (ISEs) that could become the ultimate, generally applicable SC, which in combination with all kinds of ion-selective membranes (ISMs) would match the performance characteristics of conventional ISEs. We present data collected with electrodes utilizing PEDOT-C 14 , a highly hydrophobic derivative of poly(3,4-ethylenedioxythiophene), PEDOT, as SC and compare its performance characteristics with PEDOT-based SC ISEs. PEDOT-C 14 has not been used in SC ISEs previously. The PEDOT-C 14 -based solid contact (SC) ion-selective electrodes (ISEs) (H + , K + , and Na + ) have outstanding performance characteristics (theoretical response slope, short equilibration time, excellent potential stability, etc.). Most importantly, PEDOT-C 14 -based SC pH sensors have no CO 2 interference, an essential pH sensors property when aimed for whole-blood analysis. The superhydrophobic properties (water contact angle: 136 ± 5°) of the PEDOT-C 14 SC prevent the detachment of the ion-selective membrane (ISM) from its SC and the accumulation of an aqueous film between the ISM and the SC. The accumulation of an aqueous film between the ISM and its SC has a detrimental effect on the sensor performance. Although there is a test for the presence of an undesirable water layer, if the conditions for this test are not selected properly, it does not provide an unambiguous answer. On the other hand, recording the potential drifts of SC electrodes with pH-sensitive membranes in samples with different CO 2 levels can effectively prove the presence or absence of a water layer in a short time period.

Alkylsulfonates as probes of uncoupling protein transport mechanism. Ion pair transport demonstrates that direct H(+) translocation by UCP1 is not necessary for uncoupling

Czech Academy of Sciences Publication Activity Database

Jabůrek, M.; Vařecha, M.; Ježek, Petr; Garlid, K. D.

2001-01-01

Roč. 276, č. 34 (2001), s. 31897-31905 ISSN 0021-9258 R&D Projects: GA AV ČR IAA5011106 Grant - others:NIH(US) DK56273 Institutional research plan: CEZ:AV0Z5011922 Keywords : mitochondrial uncoupling proteins * alkylsulfonates * ion pair transport Subject RIV: CE - Biochemistry Impact factor: 7.258, year: 2001

Social behavior of young dairy calves housed with limited or full social contact with a peer

DEFF Research Database (Denmark)

Duve, Linda Rosager; Jensen, Margit Bak

2012-01-01

grouping in duration of rest and rest with a neighbor. In conclusion, from the age of 3wk of life, calves housed with full social contact performed more social behaviors than calves housed individually with limited social contact, whereas only minor differences were found in the social behavior of calves......This study compared the effect of individual and pair housing and age at pair housing on the social behavior of young dairy calves. Twenty-seven pairs of calves were reared from birth until 6 wk either individually (limited social contact between bars; L calves), in pairs (full social contact; F...... sniffing and licking another calf more than were the L calves. No difference was found in duration of lying down in body contact with another calf between F and LF calves on d 22; however, on d 34, LF calves performed more of this behavior than did F calves. Continuous recordings of social behavior were...

Magnesium sulfate as an oral contrast medium in magnetic resonance imaging of the small intestine.

Science.gov (United States)

Shi, Hao; Liu, Cun; Ding, Hong Yu; Li, Chun Wei

2012-03-01

To explore the use of magnesium sulfate (MgSO4) as an oral contrast medium (CM) in MRI of the small intestine. By comparing MgSO4 SNRs at different concentrations, we determined that 2.5% MgSO4 is the ideal concentration for small bowel MRI. Twenty volunteers underwent MRI after drinking 2.5% MgSO4. Thirty-one patients with clinical suspicion of small intestinal pathology underwent both MRI and the air-barium contrast examination. The patient's tolerance, side effects and complications were noted. 2.5% MgSO4 can decrease the absorption of water and fully fill the enteric cavity, thereby increasing the contrast between the intestinal wall and lumen and facilitating radiographic examination of the small bowel. The mean diameter of the small intestine was 19.8±1.21 mm in the 20 volunteers consuming 2.5% MgSO4 and 12.7±0.84 mm in the 20 volunteers given water. There was a significant difference (P0.05) in side effects between MgSO4 and water groups. Small intestinal MRI was successfully performed in all 31 patients, who were also examined by the double contrast barium, which gave almost identical diagnoses to MRI in all cases except for 1 patient with small intestinal hemorrhage. MRI with 2.5% MgSO4 can demonstrate intestinal abnormalities. Therefore, 2.5% MgSO4 solution is an ideal oral CM for small bowel MRI. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Atom-Pair Kinetics with Strong Electric-Dipole Interactions.

Science.gov (United States)

Thaicharoen, N; Gonçalves, L F; Raithel, G

2016-05-27

Rydberg-atom ensembles are switched from a weakly to a strongly interacting regime via adiabatic transformation of the atoms from an approximately nonpolar into a highly dipolar quantum state. The resultant electric dipole-dipole forces are probed using a device akin to a field ion microscope. Ion imaging and pair-correlation analysis reveal the kinetics of the interacting atoms. Dumbbell-shaped pair-correlation images demonstrate the anisotropy of the binary dipolar force. The dipolar C_{3} coefficient, derived from the time dependence of the images, agrees with the value calculated from the permanent electric-dipole moment of the atoms. The results indicate many-body dynamics akin to disorder-induced heating in strongly coupled particle systems.

Calcium Ion Removal by KMnO4 Modified Pineapple Leaf Waste Carbon Prepared from Waste of Pineapple Leaf Fiber Production Processing

Directory of Open Access Journals (Sweden)

Sumrit Mopoung

2016-12-01

Full Text Available Pineapple leaf fiber waste carbon, modified with 3% KMnO4, was used for Ca2+ removal from aqueous solution. The effects of contact time, loading, water hardness, and isotherms on Ca2+ adsorption were studied. The results show that the Ca2+ ion removal by pineapple leaf fiber waste carbon could be improved by modification with KMnO4. The adsorption would reach equilibrium state at about 60 min for a water source with hardness values of 40-200 mg/dm3. Increases in total hardness (40 to 200 mg/dm3 lead to a decrease in Ca2+ ion removal efficiency (90.05% to 37.65% and an increase in Ca2+ ion adsorption capacity at equilibrium (4.37 mg/g to 8.95 mg/g. The Ca2+ removal efficiencies increase with increasing loading of modified waste carbon. The equilibrium data were fitted well by both the Langmuir isotherm and the Freundlich isotherm. For the Langmuir isotherm model, the values of the maximum Ca2+ adsorption capacity and Langmuir constant being 2.81 mg/g and 0.9262 dm3 /g, respectively. On the other hand for the Freundlich isotherm model, the KF and n values are 1.374 dm3 (1/n mg (1-1/n/g and 4.671, respectively. These results indicate that modified pineapple fiber waste carbon is a material with high Ca2+ ion adsorption capacity, heterogeneity, and high affinity.

Ag(I)-mediated homo and hetero pairs of guanosine and cytidine: monitoring by circular dichroism spectroscopy.

Science.gov (United States)

Goncharova, Iryna

2014-01-24

Ag(I)-containing compounds are attractive as antibacterial and antifungal agents. The renewed interest in the application of silver(I) compounds has led to the need for detailed knowledge of the mechanism of their action. One of the possible ways is the coordination of Ag(I) to G-C pairs of DNA, where Ag(+) ions form Ag(I)-mediated base pairs and inhibit the transcription. Herein, a systematic chiroptical study on silver(I)-mediated homo and mixed pairs of the C-G complementary-base derivatives cytidine(C) and 5'-guanosine monophosphate(G) in water is presented. Ag(I)-mediated homo and hetero pairs of G and C and their self-assembled species were studied under two pH levels (7.0 and 10.0) by vibrational (VCD) and electronic circular dichroism(ECD). VCD was used for the first time in this field and showed itself to be a powerful method for obtaining specific structural information in solution. Based on results of the VCD experiments, the different geometries of the homo pairs were proposed under pH 7.0 and 10.0. ECD was used as a diagnostic tool to characterize the studied systems and as a contact point between the previously defined structures of the metal or proton mediated pairs of nucleobases and the systems studied here. On the basis of the obtained data, the formation of the self-assembled species of cytidine with a structure similar to the i-motif structure in DNA was proposed at pH 10.0. Copyright © 2013 Elsevier B.V. All rights reserved.

An Ion-pair Dispersive Liquid-Liquid Microextraction for Simultaneous Determination of Synthetic Dyes in Ice Cream Samples by HPLC

Directory of Open Access Journals (Sweden)

Mohammad Faraji

2017-05-01

Full Text Available An efficient, sensitive and fast method was developed based on an ultrasound-assisted extraction followed by an ion-pair dispersive liquid-liquid microextraction (USAE-IP-DLLME for the simultaneous determination of five commonly used synthetic sulfonate dyes (tartarazine, quinoline yellow, sunset yellow, azorubine, and brilliant blue in ice cream samples using high performance liquid chromatography. First, important parameters on USAE and samples clean-up were investigated and optimized. Then, some effective parameters on DLLME were studied and optimized. Under the optimum conditions, good linearity (0.5–1000 µg L-1, > r2=0.99 were obtained for the dyes. Limits of detection and limits of quantization were in the range of 0.01–0.05 µg L-1 and 0.03–0.15 µg L-1, respectively. The recoveries of the five synthetic colorants ranged from 90.3 to 109.7%. Intra (1.4–6.4% and inter-day precision (3.9–9.7% expressed as relative standard deviation (RSD at 10 and 100 µg L-1 levels less than 10% were also achieved. Finally, this method has been applied successfully in the determination of the colorants in the ice cream samples.