Quantitative Characterization of Non-Classic Polarization of Cations on Clay Aggregate Stability

PubMed Central

Hu, Feinan; Li, Hang; Liu, Xinmin; Li, Song; Ding, Wuquan; Xu, Chenyang; Li, Yue; Zhu, Longhui

2015-01-01

Soil particle interactions are strongly influenced by the concentration, valence and ion species and the pH of the bulk solution, which will also affect aggregate stability and particle transport. In this study, we investigated clay aggregate stability in the presence of different alkali ions (Li+, Na+, K+, and Cs+) at concentrations from10−5 to 10−1 mol L−1. Strong specific ion effects on clay aggregate stability were observed, and showed the order Cs+>K+>Na+>Li+. We found that it was not the effects of ion size, hydration, and dispersion forces in the cation–surface interactions but strong non-classic polarization of adsorbed cations that resulted in these specific effects. In this study, the non-classic dipole moments of each cation species resulting from the non-classic polarization were estimated. By comparing non-classic dipole moments with classic values, the observed dipole moments of adsorbed cations were up to 104 times larger than the classic values for the same cation. The observed non-classic dipole moments sharply increased with decreasing electrolyte concentration. We conclude that strong non-classic polarization could significantly suppress the thickness of the diffuse layer, thereby weakening the electric field near the clay surface and resulting in improved clay aggregate stability. Even though we only demonstrated specific ion effects on aggregate stability with several alkali ions, our results indicate that these effects could be universally important in soil aggregate stability. PMID:25874864

Programmable Payload Release from Transient Polymer Microcapsules Triggered by a Specific Ion Coactivation Effect.

PubMed

Tang, Shijia; Tang, Liuyan; Lu, Xiaocun; Liu, Huiying; Moore, Jeffrey S

2018-01-10

Stimuli-responsive materials activated by a pair of molecular or ionic species are of interest in the design of chemical logic gates and signal amplification schemes. There are relatively few materials whose coactivated response has been well-characterized. Here, we demonstrate a specific ion coactivation (SICA) effect at the interfaces of transient polymer solids and liquid solutions. We found that depolymerization of the transient polymer, cyclic poly(phthalaldehyde) (cPPA), exhibited a SICA effect when the cPPA core-shell microcapsules were suspended in ion-containing acidic methanol solutions. Significant acceleration in cPPA depolymerization rate is triggered by the combination of acid and ion coactivators. Intriguingly, the SICA effect is related to the Hofmeister behavior. The SICA effect is primarily determined by anions, and cations exhibit a secondary effect that modulates the coactivation strength. Based on these observations, we developed cPPA programmable microcapsules whose payload release rates depend on the composition and concentration of the salt/acidic-methanol solutions.

Tracking ion irradiation effects using buried interface devices

NASA Astrophysics Data System (ADS)

Cutshall, D. B.; Kulkarni, D. D.; Miller, A. J.; Harriss, J. E.; Harrell, W. R.; Sosolik, C. E.

2018-05-01

We discuss how a buried interface device, specifically a metal-oxide-semiconductor (MOS) capacitor, can be utilized to track effects of ion irradiation on insulators. We show that the exposure of oxides within unfinished capacitor devices to ions can lead to significant changes in the capacitance of the finished devices. For multicharged ions, these capacitive effects can be traced to defect production within the oxide and ultimately point to a role for charge-dependent energy loss. In particular, we attribute the stretchout of the capacitance-voltage curves of MOS devices that include an irradiated oxide to the ion irradiation. The stretchout shows a power law dependence on the multicharged ion charge state (Q) that is similar to that observed for multicharged ion energy loss in other systems.

EXPERIMENTAL EFFECTS OF CONDUCTIVITY AND MAJOR IONS ON STREAM PERIPHYTON - abstract

EPA Science Inventory

Our study examined if specific conductivities comprised of different ions associated with resource extraction affected stream periphyton assemblages, which are important sources of primary production. Sixteen artificial streams were dosed with two ion recipes intended to mimic so...

Extraordinary effects of specific monovalent cations on activation of reovirus transcriptase by chymotrypsin in vitro.

PubMed

Borsa, J; Sargent, M D; Long, D G; Chapman, J D

1973-02-01

Activation of reovirus transcriptase activity, latent in intact virions, by digestion of purified virions with chymotrypsin (CHT) in vitro shows a stringent requirement for specific monovalent cations. Cs(+), Rb(+), or K(+) ions are capable of facilitating activation by chymotryptic digestion. Na(+), Li(+), or NH(4) (+) ions are not capable of facilitating the CHT activation of polymerase activity and are antagonistic towards the effects of the facilitating ions. The data indicate that the effect of the cations is exerted on activation of the polymerase activity by CHT as opposed to an effect on polymerization per se. This effect may be important biologically in that it provides a mechanism whereby the virion can sense whether it is in an intracellular or an extracellular environment and thereby can avoid premature uncoating.

Tuning ice nucleation with counterions on polyelectrolyte brush surfaces.

PubMed

He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

2016-06-01

Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN.

Tuning ice nucleation with counterions on polyelectrolyte brush surfaces

PubMed Central

He, Zhiyuan; Xie, Wen Jun; Liu, Zhenqi; Liu, Guangming; Wang, Zuowei; Gao, Yi Qin; Wang, Jianjun

2016-01-01

Heterogeneous ice nucleation (HIN) on ionic surfaces is ubiquitous in a wide range of atmospheric aerosols and at biological interfaces. Despite its great importance in cirrus cloud formation and cryopreservation of cells, organs, and tissues, it remains unclear whether the ion-specific effect on ice nucleation exists. Benefiting from the fact that ions at the polyelectrolyte brush (PB)/water interface can be reversibly exchanged, we report the effect of ions on HIN on the PB surface, and we discover that the distinct efficiency of ions in tuning HIN follows the Hofmeister series. Moreover, a large HIN temperature window of up to 7.8°C is demonstrated. By establishing a correlation between the fraction of ice-like water molecules and the kinetics of structural transformation from liquid- to ice-like water molecules at the PB/water interface with different counterions, we show that our molecular dynamics simulation analysis is consistent with the experimental observation of the ion-specific effect on HIN. PMID:27386581

Microbial Growth in the Magnesium- Chloride - Sodium- Sulphate Ion System: Implications for Habitability in Terrestrial and Extraterrestrial Salts

NASA Astrophysics Data System (ADS)

Loudon, C. M.; Aka, S.; Cockell, C. S.

2017-12-01

Icy moons in the outer solar system are key targets in the search for extra-terrestrial life as there is evidence that they harbour subsurface oceans. Observational evidence of icy moons such as Europa suggest that these likely brine oceans should be composed of chloride and sulphate salts. The effects of the ions that compose these salts on biology and how the interactions between them can create geochemical and geophysical barriers to life are poorly understood. Here we present an in depth study of four microorganisms grown in solutions with varying combinations of the magnesium- chloride- sodium- sulphate ions. We find that the ion composition of the brine solution can have a large effect on growth. Whilst the water activity must be permissible for growth we found that this alone could not predict the effects of the ions on growth, chaotropic effects and ion specific effects influenced by the specific physiology of organisms are also evident. For this reason we conclude that simply knowing which salts are present on icy moons is not sufficient information to determine their potential habitibility. A full sample of any brine ocean would need to be studied to fully determine the potential for biology on these outer solar system satellites.

Hofmeister effect on the interfacial free energy of aliphatic and aromatic surfaces studied by chemical force microscopy.

PubMed

Patete, Jonathan; Petrofsky, John M; Stepan, Jeffery; Waheed, Abdul; Serafin, Joseph M

2009-01-15

This work describes chemical force microscopy (CFM) studies of specific-ion effects on the aqueous interfacial free energy of hydrophobic monolayers. CFM measurements allow for the characterization of interfacial properties on length scales below 100 nm. The ions chosen span the range of the Hofmeister series, from the kosmotropic Na(2)SO(4) to the chaotropic NaSCN. The salt concentrations used are typical of many laboratory processes such as protein crystallization, 2-3 M. Both aliphatic (terminal methyl) and aromatic (terminal phenyl) monolayers were examined, and rather pronounced differences were observed between the two cases. The specific-ion dependence of the aliphatic monolayer closely follows the Hofmeister series, namely the chaotropic ions lowered the interfacial free energy and the kosmotropic ions increased the interfacial free energy. However, the aromatic monolayer had significant deviations from the Hofmeister series. Possible origins for this difference are discussed.

An unconventional origin of metal-ion rescue and inhibition in the Tetrahymena group I ribozyme reaction.

PubMed Central

Shan, S O; Herschlag, D

2000-01-01

The presence of catalytic metal ions in RNA active sites has often been inferred from metal-ion rescue of modified substrates and sometimes from inhibitory effects of alternative metal ions. Herein we report that, in the Tetrahymena group I ribozyme reaction, the deleterious effect of a thio substitution at the pro-Sp position of the reactive phosphoryl group is rescued by Mn2+. However, analysis of the reaction of this thio substrate and of substrates with other modifications strongly suggest that this rescue does not stem from a direct Mn2+ interaction with the Sp sulfur. Instead, the apparent rescue arises from a Mn2+ ion interacting with the residue immediately 3' of the cleavage site, A(+1), that stabilizes the tertiary interactions between the oligonucleotide substrate (S) and the active site. This metal site is referred to as site D herein. We also present evidence that a previously observed Ca2+ ion that inhibits the chemical step binds to metal site D. These and other observations suggest that, whereas the interactions of Mn2+ at site D are favorable for the chemical reaction, the Ca2+ at site D exerts its inhibitory effect by disrupting the alignment of the substrates within the active site. These results emphasize the vigilance necessary in the design and interpretation of metal-ion rescue and inhibition experiments. Conversely, in-depth mechanistic analysis of the effects of site-specific substrate modifications can allow the effects of specific metal ion-RNA interactions to be revealed and the properties of individual metal-ion sites to be probed, even within the sea of metal ions bound to RNA. PMID:10864040

Effects of ionic compositions of the medium on monosodium glutamate binding to taste epithelial cells.

PubMed

Hayashi, Y; Tsunenari, T; Mori, T

1999-03-01

Monosodium glutamate and nucleotides are umami taste substances in animals and have a synergistic effect on each other. We studied the ligand-binding properties of the glutamate receptors in taste epithelial cells isolated from bovine tongue. Specific glutamate binding was observed in an enriched suspension of taste receptor cells in Hanks' balanced salt solution, while no specific glutamate binding was apparent in the absence of divalent ions or when the cells had been depolarized by a high content of potassium in Hanks' balanced salt solution. There was no significant difference between the release of glutamate under depolarized or divalent ion-free conditions and under normal conditions. However, glutamate was easily released from the depolarized cells in the absence of divalent ions. These data suggest that the binding of glutamate to receptors depends on divalent ions, which also have an effect on maintaining binding between glutamate and receptors.

Crystal nucleation initiated by transient ion-surface interactions at aerosol interfaces

PubMed Central

Davis, Ryan D.; Tolbert, Margaret A.

2017-01-01

Particle collisions are a common occurrence in the atmosphere, but no empirical observations exist to fully predict the potential effects of these collisions on air quality and climate projections. The current consensus of heterogeneous crystal nucleation pathways relevant to the atmosphere dictates that collisions with amorphous particles have no effect on the crystallization relative humidity (RH) of aqueous inorganic aerosols because there is no stabilizing ion-surface interaction to facilitate the formation of crystal nuclei. In contrast to this view of heterogeneous nucleation, we report laboratory observations demonstrating that collisions with hydrophobic amorphous organic aerosols induced crystallization of aqueous inorganic microdroplets at high RH, the effect of which was correlated with destabilizing water-mediated ion-specific surface interactions. These same organic aerosols did not induce crystallization once internally mixed in the droplet, pointing toward a previously unconsidered transient ion-specific crystal nucleation pathway that can promote aerosol crystallization via particle collisions. PMID:28776032

Crystal nucleation initiated by transient ion-surface interactions at aerosol interfaces.

PubMed

Davis, Ryan D; Tolbert, Margaret A

2017-07-01

Particle collisions are a common occurrence in the atmosphere, but no empirical observations exist to fully predict the potential effects of these collisions on air quality and climate projections. The current consensus of heterogeneous crystal nucleation pathways relevant to the atmosphere dictates that collisions with amorphous particles have no effect on the crystallization relative humidity (RH) of aqueous inorganic aerosols because there is no stabilizing ion-surface interaction to facilitate the formation of crystal nuclei. In contrast to this view of heterogeneous nucleation, we report laboratory observations demonstrating that collisions with hydrophobic amorphous organic aerosols induced crystallization of aqueous inorganic microdroplets at high RH, the effect of which was correlated with destabilizing water-mediated ion-specific surface interactions. These same organic aerosols did not induce crystallization once internally mixed in the droplet, pointing toward a previously unconsidered transient ion-specific crystal nucleation pathway that can promote aerosol crystallization via particle collisions.

Cluster model studies of anion and molecular specificities via electrospray ionization photoelectron spectroscopy

DOE PAGES

Wang, Xue -Bin

2017-01-06

Ion specificity, a widely observed macroscopic phenomenon in condensed phases and at interfaces, is essentially a fundamental chemical physical issue. We have been investigating such effects using cluster models in an “atom-by-atom” and “molecule-by-molecule” fashion not possible with condensed-phase methods. We use electrospray ionization (ESI) to generate molecular and ionic clusters to simulate key molecular entities involved in local binding regions, and characterize them employing negative ion photoelectron spectroscopy (NIPES). Inter- and intramolecular interactions and binding configurations are directly obtained as functions of cluster size and composition, providing insightful molecular-level description and characterization over the local active sites that playmore » crucial roles in determining solution chemistry and condensed phase phenomena. Finally, the topics covered in this article are relevant to a wide scope of research fields ranging from ion specific effects in electrolyte solutions, ion selectivity/recognition in normal functioning of life, to molecular specificity in aerosol particle formation, as well as in rational material design and synthesis.« less

Extraordinary Effects of Specific Monovalent Cations on Activation of Reovirus Transcriptase by Chymotrypsin In Vitro

PubMed Central

Borsa, J.; Sargent, M. D.; Long, D. G.; Chapman, J. D.

1973-01-01

Activation of reovirus transcriptase activity, latent in intact virions, by digestion of purified virions with chymotrypsin (CHT) in vitro shows a stringent requirement for specific monovalent cations. Cs+, Rb+, or K+ ions are capable of facilitating activation by chymotryptic digestion. Na+, Li+, or NH4+ ions are not capable of facilitating the CHT activation of polymerase activity and are antagonistic towards the effects of the facilitating ions. The data indicate that the effect of the cations is exerted on activation of the polymerase activity by CHT as opposed to an effect on polymerization per se. This effect may be important biologically in that it provides a mechanism whereby the virion can sense whether it is in an intracellular or an extracellular environment and thereby can avoid premature uncoating. PMID:4347424

Lithium Ion Battery Design and Safety

NASA Technical Reports Server (NTRS)

Au, George; Locke, Laura

2001-01-01

This viewgraph presentation makes several recommendations to ensure the safe and effective design of Lithium ion cell batteries. Large lithium ion cells require pressure switches and small cells require pressure disconnects and other safety devices with the ability to instantly interrupt flow. Other suggestions include specifications for batteries and battery chargers.

Novel Separation of Actinides

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

Mariella, R

The separation of actinides and other elements of interest for nuclear forensics and threat reduction is currently performed using decades-old chemistries and ion-exchange columns. We propose to determine the technical feasibility of a novel method for separating actinide ions in solution. This method is based upon isotachophoresis (ITP), which has been applied in the purification of pharmaceuticals and other biochemical applications. This technique has the potential to separate inorganic ions more effectively than existing methods, which is key to analyzing very small samples. We will perform a quantitative assessment of the effectiveness of specific isotachophoretic approaches including predicting the physicalmore » and chemical properties, such as ion mobility, of inorganic ions under specific solvent conditions using a combination of ab initio calculations and semi-empirical methods. We expect to obtain a thorough understanding of the analytical systems parameters under which ITP is most effective for the separation of inorganic samples, including the influence of the double layer surrounding actinide ions, the Debye length for different ions and ion complexes, and Debye-Hueckel limits. Inorganic separations are key to nuclear forensics for countering terrorism and nuclear proliferation. If found to be feasible and potentially superior to currently used separation approaches, ITP could provide the conceptual basis for an improved means to separate samples of nuclear explosion debris for nuclear forensic analysis, in support of the Laboratory's missions in homeland and national security.« less

Comparison between Free and Immobilized Ion Effects on Hydrophobic Interactions: A Molecular Dynamics Study.

PubMed

Huang, Kai; Gast, Sebastian; Ma, C Derek; Abbott, Nicholas L; Szlufarska, Izabela

2015-10-15

Fundamental studies of the effect of specific ions on hydrophobic interactions are driven by the need to understand phenomena such as hydrophobically driven self-assembly or protein folding. Using β-peptide-inspired nanorods, we investigate the effects of both free ions (dissolved salts) and proximally immobilized ions on hydrophobic interactions. We find that the free ion effect is correlated with the water density fluctuation near a nonpolar molecular surface, showing that such fluctuation can be an indicator of hydrophobic interactions in the case of solution additives. In the case of immobilized ion, our results demonstrate that hydrophobic interactions can be switched on and off by choosing different spatial arrangements of proximal ions on a nanorod. For globally amphiphilic nanorods, we find that the magnitude of the interaction can be further tuned using proximal ions with varying ionic sizes. In general, univalent proximal anions are found to weaken hydrophobic interactions. This is in contrast to the effect of free ions, which according to our simulations strengthen hydrophobic interactions. In addition, immobilized anions of increasing ionic size do not follow the same ordering (Hofmeister-like ranking) as free ions when it comes to their impact on hydrophobic interactions. The immobilized ion effect is not simply correlated with the water density fluctuation near the nonpolar side of the amphiphilic nanorod. We propose a molecular picture that explains the contrasting effects of immobilized versus free ions.

Similarities and differences in acute response to major ions among several aquatic species: Implications for guideline development

EPA Science Inventory

Adverse effects from increased concentrations of major geochemical ions (Na, K, Ca, Mg, Cl, SO4, HCO3) to aquatic organisms have been demonstrated or implied in many settings. However, experimental work has shown that the toxicity of ion mixtures is dependent on the specific mix...

The neglected nano-specific toxicity of ZnO nanoparticles in the yeast Saccharomyces cerevisiae

PubMed Central

Zhang, Weicheng; Bao, Shaopan; Fang, Tao

2016-01-01

Nanoparticles (NPs) with unique physicochemical properties induce nano-specific (excess) toxicity in organisms compared with their bulk counterparts. Evaluation and consideration of nano-specific toxicity are meaningful for the safe design and environmental risk assessment of NPs. However, ZnO NPs have been reported to lack excess toxicity for diverse organisms. In the present study, the nano-specific toxicity of ZnO NPs was evaluated in the yeast Saccharomyces cerevisiae. Nano-specific toxicity of ZnO NPs was not observed in the wild type yeast. However, the ZnO NPs induced very similar nano-specific toxicities in the three mutants with comparable log Te (particle) values (0.64 vs 0.65 vs 0.62), suggesting that the mutants were more sensitive and specific for the NPs’ nano-specific toxicity. The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles. Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles. The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants. The log Te (particle) was a useful parameter for evaluation of NPs nano-specific toxicity, whereas log Te (ion) efficiently determined the NPs toxicity associated with released ions. PMID:27094203

The neglected nano-specific toxicity of ZnO nanoparticles in the yeast Saccharomyces cerevisiae

NASA Astrophysics Data System (ADS)

Zhang, Weicheng; Bao, Shaopan; Fang, Tao

2016-04-01

Nanoparticles (NPs) with unique physicochemical properties induce nano-specific (excess) toxicity in organisms compared with their bulk counterparts. Evaluation and consideration of nano-specific toxicity are meaningful for the safe design and environmental risk assessment of NPs. However, ZnO NPs have been reported to lack excess toxicity for diverse organisms. In the present study, the nano-specific toxicity of ZnO NPs was evaluated in the yeast Saccharomyces cerevisiae. Nano-specific toxicity of ZnO NPs was not observed in the wild type yeast. However, the ZnO NPs induced very similar nano-specific toxicities in the three mutants with comparable log Te (particle) values (0.64 vs 0.65 vs 0.62), suggesting that the mutants were more sensitive and specific for the NPs’ nano-specific toxicity. The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles. Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles. The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants. The log Te (particle) was a useful parameter for evaluation of NPs nano-specific toxicity, whereas log Te (ion) efficiently determined the NPs toxicity associated with released ions.

The neglected nano-specific toxicity of ZnO nanoparticles in the yeast Saccharomyces cerevisiae.

PubMed

Zhang, Weicheng; Bao, Shaopan; Fang, Tao

2016-04-20

Nanoparticles (NPs) with unique physicochemical properties induce nano-specific (excess) toxicity in organisms compared with their bulk counterparts. Evaluation and consideration of nano-specific toxicity are meaningful for the safe design and environmental risk assessment of NPs. However, ZnO NPs have been reported to lack excess toxicity for diverse organisms. In the present study, the nano-specific toxicity of ZnO NPs was evaluated in the yeast Saccharomyces cerevisiae. Nano-specific toxicity of ZnO NPs was not observed in the wild type yeast. However, the ZnO NPs induced very similar nano-specific toxicities in the three mutants with comparable log Te ((particle)) values (0.64 vs 0.65 vs 0.62), suggesting that the mutants were more sensitive and specific for the NPs' nano-specific toxicity. The toxic effects in the yeast were slightly attributable to dissolved zinc ions from the ZnO (nano or bulk) particles. Oxidative damage and mechanical damage contributed to the toxic effect of the ZnO particles. The mechanism of mechanical damage is proposed to be an inherent characteristic underlying the nano-specific toxicity in the mutants. The log Te ((particle)) was a useful parameter for evaluation of NPs nano-specific toxicity, whereas log Te ((ion)) efficiently determined the NPs toxicity associated with released ions.

Ion-specific weak adsorption of salts and water/octanol transfer free energy of a model amphiphilic hexapeptide.

PubMed

Déjugnat, Christophe; Dufrêche, Jean-François; Zemb, Thomas

2011-04-21

An amphiphilic hexapeptide has been used as a model to quantify how specific ion effects induced by addition of four salts tune the hydrophilic/hydrophobic balance and induce temperature-dependant coacervate formation from aqueous solution. The hexapeptide chosen is present as a dimer with low transfer energy from water to octanol. Taking sodium chloride as the reference state in the Hofmeister scale, we identify water activity effects and therefore measure the free energy of transfer from water to octanol and separately the free energy associated to the adsorption of chaotropic ions or the desorption of kosmotropic ions for the same amphiphilic peptide. These effects have the same order of magnitude: therefore, both energies of solvation as well as transfer into octanol strongly depend on the nature of the electrolytes used to formulate any buffer. Model peptides could be used on separation processes based on criteria linked to "Hofmeister" but different from volume and valency.

Metal Ion Binding at the Catalytic Site Induces Widely Distributed Changes in a Sequence Specific Protein–DNA Complex

PubMed Central

2016-01-01

Metal ion cofactors can alter the energetics and specificity of sequence specific protein–DNA interactions, but it is unknown if the underlying effects on structure and dynamics are local or dispersed throughout the protein–DNA complex. This work uses EcoRV endonuclease as a model, and catalytically inactive lanthanide ions, which replace the Mg2+ cofactor. Nuclear magnetic resonance (NMR) titrations indicate that four Lu3+ or two La3+ cations bind, and two new crystal structures confirm that Lu3+ binding is confined to the active sites. NMR spectra show that the metal-free EcoRV complex with cognate (GATATC) DNA is structurally distinct from the nonspecific complex, and that metal ion binding sites are not assembled in the nonspecific complex. NMR chemical shift perturbations were determined for 1H–15N amide resonances, for 1H–13C Ile-δ-CH3 resonances, and for stereospecifically assigned Leu-δ-CH3 and Val-γ-CH3 resonances. Many chemical shifts throughout the cognate complex are unperturbed, so metal binding does not induce major conformational changes. However, some large perturbations of amide and side chain methyl resonances occur as far as 34 Å from the metal ions. Concerted changes in specific residues imply that local effects of metal binding are propagated via a β-sheet and an α-helix. Both amide and methyl resonance perturbations indicate changes in the interface between subunits of the EcoRV homodimer. Bound metal ions also affect amide hydrogen exchange rates for distant residues, including a distant subdomain that contacts DNA phosphates and promotes DNA bending, showing that metal ions in the active sites, which relieve electrostatic repulsion between protein and DNA, cause changes in slow dynamics throughout the complex. PMID:27786446

Surface Passivation and Junction Formation Using Low Energy Hydrogen Implants

NASA Technical Reports Server (NTRS)

Fonash, S. J.

1985-01-01

New applications for high current, low energy hydrogen ion implants on single crystal and polycrystal silicon grain boundaries are discussed. The effects of low energy hydrogen ion beams on crystalline Si surfaces are considered. The effect of these beams on bulk defects in crystalline Si is addressed. Specific applications of H+ implants to crystalline Si processing are discussed. In all of the situations reported on, the hydrogen beams were produced using a high current Kaufman ion source.

Impact of ionizing radiation exposure on in vitro differentiation of preosteoblastic cell lines

NASA Astrophysics Data System (ADS)

Hu, Yueyuan; Lau, Patrick; Hellweg, Christine; Baumstark-Khan, Christa; Reitz, Guenther

Bone demineralization of astronauts during residence in microgravity is a well known phe-nomenon during space travel. Besides altered gravity conditions, radiation risk is considered to be one of the major health hazards for astronauts in both orbital and interplanetary space. Un-til know, little is known about the effects of space radiation on the skeletal system especially on the bone forming osteoblasts. Accelerator facilities are used to simulate parts of the radiation environment in space. We examined the effects of heavy ion exposure on osteoblastic differ-entiation of murine preosteoblastic cell lines to gain insight into potential cellular mechanisms involved in bone cellular response after exposure to heavy ions. Therefore, we examined gene expression modulation of bone specific transcription factors, osteoblast specific marker genes as well as genes function as coupling factors that link bone resorption to bone formation. mRNA levels were determined using quantitative real time reverse transcriptase PCR (qRT-PCR). Expression of a target gene was standardized to unregulated reference genes. We investigated the transcriptional regulation of Osteocalcin (OCN) as well as TGF-β1, p21(CDKN1A) and the bone specific transcription factor Runx2 (cbfa1). We investigated gene expression modula-tions after exposure to energetic carbon ions (35 MeV/u, 73 keV/µm), iron ions (1000 MeV/u, 150 keV/µm) and lead ions (29 MeV/u, 9600 keV/µm) versus low LET X-rays. X-irradiation dose-dependently increased the mRNA levels of p21(CDKN1A) and Runx2 (cbfa1) whereas expression of OCN and TGF-β1 were elevated at later time points. Exposure to heavy ions provoked a more pronounced effect on osteoblastic specific gene expression within the dif-ferentiation process. Collectively, our results indicate that heavy ions facilitate osteoblastic differentiation more effectively than X-ray. Using the proposed in vitro model we confirmed that exposure to ionizing radiation significantly modulates gene expression levels of marker genes involved in the differentiation of osteoblasts. The data presented allow us to suggest that exposure to ionizing radiation interferes with bone formation at the level of cell differentiation.

Effects of magnesium ions on the stabilization of RNA oligomers of defined structures.

PubMed Central

Serra, Martin J; Baird, John D; Dale, Taraka; Fey, Bridget L; Retatagos, Kimberly; Westhof, Eric

2002-01-01

Optical melting was used to determine the stabilities of 11 small RNA oligomers of defined secondary structure as a function of magnesium ion concentration. The oligomers included helices composed of Watson-Crick base pairs, GA tandem base pairs, GU tandem base pairs, and loop E motifs (both eubacterial and eukaryotic). The effect of magnesium ion concentration on stability was interpreted in terms of two simple models. The first assumes an uptake of metal ion upon duplex formation. The second assumes nonspecific electrostatic attraction of metal ions to the RNA oligomer. For all oligomers, except the eubacterial loop E, the data could best be interpreted as nonspecific binding of metal ions to the RNAs. The effect of magnesium ions on the stability of the eubacterial loop E was distinct from that seen with the other oligomers in two ways. First, the extent of stabilization by magnesium ions (as measured by either change in melting temperature or free energy) was three times greater than that observed for the other helical oligomers. Second, the presence of magnesium ions produces a doubling of the enthalpy for the melting transition. These results indicate that magnesium ion stabilizes the eubacterial loop E sequence by chelating the RNA specifically. Further, these results on a rather small system shed light on the large enthalpy changes observed upon thermal unfolding of large RNAs like group I introns. It is suggested that parts of those large enthalpy changes observed in the folding of RNAs may be assigned to variations in the hydration states and types of coordinating atoms in some specifically bound magnesium ions and to an increase in the observed cooperativity of the folding transition due to the binding of those magnesium ions coupling the two stems together. Brownian dynamic simulations, carried out to visualize the metal ion binding sites, reveal rather delocalized ionic densities in all oligomers, except for the eubacterial loop E, in which precisely located ion densities were previously calculated. PMID:12003491

Hierarchically porous Li3VO4/C nanocomposite as an advanced anode material for high-performance lithium-ion capacitors

NASA Astrophysics Data System (ADS)

Xu, Xuena; Niu, Feier; Zhang, Dapeng; Chu, Chenxiao; Wang, Chunsheng; Yang, Jian; Qian, Yitai

2018-04-01

Lithium-ion capacitors, as a hybrid electrochemical energy storage device, realize high specific energy and power density within one device, thus attracting extensive attention. Here, hierarchically porous Li3VO4/C nanocomposite is prepared by a solvo-thermal reaction, followed with a post-annealing process. This composite has macropores at the center and mesopores in the wall, thus effectively promoting electrolyte penetration and structure stability upon cycling simultaneously. Compared to mesoporous Li3VO4, the enhanced rate capability and specific capacity of hierarchically porous Li3VO4/C indicate the synergistic effect of mesopores and macropores. Inspired by these results, this composite is coupled with mesoporous carbon (CMK-3) for lithium-ion capacitors, generating a specific energy density of 105 Wh kg-1 at a power density of 188 W kg-1. Even if the power density increases to 9.3 kW kg-1, the energy density still remains 62 Wh kg-1. All these results demonstrate the promising potential of hierarchically porous Li3VO4 in lithium ion capacitors.

PREDICTING THE TOXICITY OF MAJOR IONS IN SEAWATER TO MYSID SHRIMP (MYSIDOPSIS BAHIA), SHEEPSHEAD MINNOW (CYPRINODON VARIEGATUS), AND INLAND SILVERSIDE MINNOW (MENIDIA BERYLLINA)

EPA Science Inventory

Although marine organisms are naturally adapted to salinities well above those of freshwater, elevated concentrations of specific ions have been shown to cause adverse effects on some saltwater species. Because some ions are also physiologically essential, a deficiency of these i...

Importance in catalysis of a magnesium ion with very low affinity for a hammerhead ribozyme

PubMed Central

Inoue, Atsushi; Takagi, Yasuomi; Taira, Kazunari

2004-01-01

Available evidence suggests that Mg2+ ions are involved in reactions catalyzed by hammerhead ribozymes. However, the activity in the presence of exclusively monovalent ions led us to question whether divalent metal ions really function as catalysts when they are present. We investigated ribozyme activity in the presence of high levels of Mg2+ ions and the effects of Li+ ions in promoting ribozyme activity. We found that catalytic activity increased linearly with increasing concentrations of Mg2+ ions and did not reach a plateau value even at 1 M Mg2+ ions. Furthermore, this dependence on Mg2+ ions was observed in the presence of a high concentration of Li+ ions. These results indicate that the Mg2+ ion is a very effective cofactor but that the affinity of the ribozyme for a specific Mg2+ ion is very low. Moreover, cleavage by the ribozyme in the presence of both Li+ and Mg2+ ions was more effective than expected, suggesting the existence of a new reaction pathway—a cooperative pathway—in the presence of these multiple ions, and the possibility that a Mg2+ ion with weak affinity for the ribozyme is likely to function in structural support and/or act as a catalyst. PMID:15302920

Understanding the Role of Metal Ions in RNA Folding and Function: Lessons from RNase P, a Ribonucleoprotein Enzyme

NASA Astrophysics Data System (ADS)

Harris, Michael E.; Christian, Eric L.

There is a large and rapidly growing literature relating RNA function to metal ion identity and concentration; however, due to the complexity and large number of interactions it remains a significant experimental challenge to tie the interactions of individual ions to specific aspects of RNA function. Investigation of the ribonculeopro-tein enzyme RNase P function has assisted in defining characteristics of RNA—metal ion interactions and provided a useful model system for understanding RNA catalysis and ribonucleoprotein assembly. The goal of this chapter is to review progress in understanding the physical basis of functional metal ion interactions with P RNA and relate this progress to the development of our understanding of RNA metal ion interactions in general. The research results reviewed here encompass: (1) Determination of the contribution of divalent metal ion binding to specific aspects of enzyme function, (2) Identification of individual metal ion binding sites in P RNA and their contribution to function, and (3) The effect of protein binding on RNA—metal ion affinity.

Imbalance of plasma membrane ion leak and pump relationship as a new aetiological basis of certain disease states.

PubMed

Ronquist, G; Waldenström, A

2003-12-01

The basis for life is the ability of the cell to maintain ion gradients across biological membranes. Such gradients are created by specific membrane-bound ion pumps [adenosine triphosphatases (ATPases)]. According to physicochemical rules passive forces equilibrate (dissipate) ion gradients. The cholesterol/phospholipid ratio of the membrane and the degree of saturation of phospholipid fatty acids are important factors for membrane molecular order and herewith a determinant of the degree of non-specific membrane leakiness. Other operative principles, i.e. specific ion channels can be opened and closed according to mechanisms that are specific to the cell. Certain compounds called ionophores can be integrated in the plasma membrane and permit specific inorganic ions to pass. Irrespective of which mechanism ions leak across the plasma membrane the homeostasis may be kept by increasing ion pumping (ATPase activity) in an attempt to restore the physiological ion gradient. The energy source for this work seems to be glycolytically derived ATP formation. Thus an increase in ion pumping is reflected by increased ATP hydrolysis and rate of glycolysis. This can be measured as an accumulation of breakdown products of ATP and end-products of anaerobic glycolysis (lactate). In certain disease entities, the balance between ATP formation and ion pumping may be disordered resulting in a decrease in inter alia (i.a.) cellular energy charge, and an increase in lactate formation and catabolites of adenylates. Cardiac syndrome X is proposed to be due to an excessive leakage of potassium ions, leading to electrocardiographic (ECG) changes, abnormal Tl-scintigraphy of the heart and anginal pain (induced by adenosine). Cocksackie B3 infections, a common agent in myocarditis might also induce an ionophore-like effect. Moreover, Alzheimer's disease is characterized by the formation of extracellular amyloid deposits in the brain of patients. Perturbation of cellular membranes by the amyloid peptide during the development of Alzheimer's disease is one of several mechanisms proposed to account for the toxicity of this peptide on neuronal membranes. We have studied the effects of the peptide and fragments thereof on 45Ca2+-uptake in human erythrocytes and the energetic consequences. Treatment of erythrocytes with the beta 1-40 peptide, results in qualitatively similar nucleotide pattern and decrease of energy charge as the treatment with Ca2+-ionophore A23187. Finally, in recent studies we have revealed and published in this journal that a rare condition, Tarui's disease or glycogenosis type VII, primarily associated with a defect M-subunit of phosphofructokinase, demonstrates as a cophenomenon an increased leak of Ca2+ into erythrocytes.

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

PubMed

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.

Interaction analysis of chimeric metal-binding green fluorescent protein and artificial solid-supported lipid membrane by quartz crystal microbalance and atomic force microscopy.

PubMed

Prachayasittikul, Virapong; Isarankura Na Ayudhya, Chartchalerm; Hilterhaus, Lutz; Hinz, Andreas; Tantimongcolwat, Tanawut; Galla, Hans-Joachim

2005-02-04

Non-specific adsorption and specific interaction between a chimeric green fluorescent protein (GFP) carrying metal-binding region and the immobilized zinc ions on artificial solid-supported lipid membranes was investigated using the quartz crystal microbalance technique and the atomic force microscopy (AFM). Supported lipid bilayer, composed of octanethiol and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-[N-(5-amino-1-carboxypentyl iminodiacetic acid)succinyl] (NTA-DOGS)-Zn2+, was formed on the gold electrode of quartz resonator (5 MHz). Binding of the chimeric GFP to zinc ions resulted in a rapid decrease of resonance frequency. Reversibility of the process was demonstrated via the removal of metal ions by EDTA. Nanoscale structural orientation of the chimeric GFP on the membrane was imaged by AFM. Association constant of the specific binding to metal ions was 2- to 3-fold higher than that of the non-specific adsorption, which was caused by the fluidization effect of the metal-chelating lipid molecules as well as the steric hindrance effect. This infers a possibility for a further development of biofunctionalized membrane. However, maximization is needed in order to attain closer advancement to a membrane-based sensor device.

Marine Toxins Targeting Ion Channels

PubMed Central

Arias, Hugo R.

2006-01-01

This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs), as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs), are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV), Ca2+ (CaV), and K+ (KV) channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR), and the ATP-activated (P2XnR) receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+), whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−). In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers) of ion channel functions to treat or to alleviate a specific ion channel-linked disease (e.g., channelopaties).

Long-range dipolar order and dispersion forces in polar liquids

NASA Astrophysics Data System (ADS)

Besford, Quinn Alexander; Christofferson, Andrew Joseph; Liu, Maoyuan; Yarovsky, Irene

2017-11-01

Complex solvation phenomena, such as specific ion effects, occur in polar liquids. Interpretation of these effects in terms of structure and dispersion forces will lead to a greater understanding of solvation. Herein, using molecular dynamics, we probe the structure of polar liquids through specific dipolar pair correlation functions that contribute to the potential of mean force that is "felt" between thermally rotating dipole moments. It is shown that unique dipolar order exists at separations at least up to 20 Å for all liquids studied. When the structural order is compared with a dipolar dispersion force that arises from local co-operative enhancement of dipole moments, a strong agreement is found. Lifshitz theory of dispersion forces was compared with the structural order, where the theory is validated for all liquids that do not have significant local dipole correlations. For liquids that do have significant local dipole correlations, specifically liquid water, Lifshitz theory underestimates the dispersion force by a factor of 5-10, demonstrating that the force that leads to the increased structure in liquid water is missed by Lifshitz theory of van der Waals forces. We apply similar correlation functions to an ionic aqueous system, where long-range order between water's dipole moment and a single chloride ion is found to exist at 20 Å of separation, revealing a long-range perturbation of water's structure by an ion. Furthermore, we found that waters within the 1st, 2nd, and 3rd solvation shells of a chloride ion exhibit significantly enhanced dipolar interactions, particularly with waters at larger distances of separation. Our results provide a link between structures, dispersion forces, and specific ion effects, which may lead to a more robust understanding of solvation.

Lifetime Assessment of the NEXT Ion Thruster

NASA Technical Reports Server (NTRS)

VanNoord, Jonathan L.

2010-01-01

Ion thrusters are low thrust, high specific impulse devices with required operational lifetimes on the order of 10,000 to 100,000 hr. The NEXT ion thruster is the latest generation of ion thrusters under development. The NEXT ion thruster currently has a qualification level propellant throughput requirement of 450 kg of xenon, which corresponds to roughly 22,000 hr of operation at the highest throttling point. Currently, a NEXT engineering model ion thruster with prototype model ion optics is undergoing a long duration test to determine wear characteristics and establish propellant throughput capability. The NEXT thruster includes many improvements over previous generations of ion thrusters, but two of its component improvements have a larger effect on thruster lifetime. These include the ion optics with tighter tolerances, a masked region and better gap control, and the discharge cathode keeper material change to graphite. Data from the NEXT 2000 hr wear test, the NEXT long duration test, and further analysis is used to determine the expected lifetime of the NEXT ion thruster. This paper will review the predictions for all of the anticipated failure mechanisms. The mechanisms will include wear of the ion optics and cathode s orifice plate and keeper from the plasma, depletion of low work function material in each cathode s insert, and spalling of material in the discharge chamber leading to arcing. Based on the analysis of the NEXT ion thruster, the first failure mode for operation above a specific impulse of 2000 sec is expected to be the structural failure of the ion optics at 750 kg of propellant throughput, 1.7 times the qualification requirement. An assessment based on mission analyses for operation below a specific impulse of 2000 sec indicates that the NEXT thruster is capable of double the propellant throughput required by these missions.

Effect of space relevant radiation exposure on differentiation and mineralization of murine osteoprogenitor cells

NASA Astrophysics Data System (ADS)

Lau, Patrick; Hu, Yueyuan; Hellweg, Christine; Baumstark-Khan, Christa; Reitz, Guenther

Extended exposure to altered gravity conditions like during long-term space flight results in significant bone loss. Exposure to ionizing radiation for cancer therapy causes bone damage and may increase the risk of fractures. Similarly, besides altered gravity conditions, astronauts on exploratory missions beyond low-Earth orbit will be exposed to high-energy heavy ions in addition to proton and photon radiation, although for prolonged periods and at lower doses and dose rates compared with therapy. Space conditions may place astronauts at a greater risk for mission-critical fractures. Until now, little is known about the effects of space radiation on the skeletal system especially on osteoprogenitor cells. Accelerator facilities are used to simulate parts of the radiation environment in space. Heavy ion accelerators therefore could be used to assess radiation risks for astronauts who will be exposed to higher radiation doses e.g. on a Mars mission. The aim of the present study was to determine the biological effects of spaceflight-relevant radiation exposure on the cellular level using murine osteoprogenitor cell lines compared to nonirradiated controls. To gain a deeper understanding of bone cell differenti-ation and mineralization after exposure to heavy ions, we examined gene expression modulation of bone specific transcription factors, osteoblast specific marker genes as well as genes function as coupling factors that link bone resorption to bone formation. We investigated the transcrip-tional modulation of type I collagen (Col I), osteocalcin (Ocn), Transforming growth factor-β1 (TGF-β1), interleukin-6 (IL-6) and the bone specific transcription factor Runx2 (Cbfa1). To gain deeper insight into potential cellular mechanisms involved in cellular response after ex-posure to heavy ions, we investigated gene expression modulations after exposure to energetic carbon ions (35 MeV/u, 73.2 keV/µm), iron ions (1000 MeV/u, 150 keV/µm) and lead ions (29 MeV/u, 9600 keV/µm) versus low LET X-rays. Exposure to X-irradiation dose-dependently increased the mRNA levels of Runx2 (cbfa1) whereas expression values of OCN and TGF-β1 were elevated at later time points. Exposure to heavy ions provoked a more marked effect on bone specific gene expression within the differentiation process. Collectively, our results indi-cate that heavy ions facilitate differentiation more effectively than X-rays as a major response in the progeny of irradiated osteoprogenitor cells. The data presented allow us to suggest that exposure to ionizing radiation interferes with bone formation at the level of cellular differenti-ation. In this regard, further experiments are needed to investigate gene expression patterns in mammalian cells that respond to differentiation after exposure to ionizing radiation.

Vibrational stark effects to identify ion pairing and determine reduction potentials in electrolyte-free environments

DOE PAGES

Mani, Tomoyasu; Grills, David C.; Miller, John R.

2015-01-02

A recently-developed instrument for time-resolved infrared detection following pulse radiolysis has been used to measure the ν(C≡N) IR band of the radical anion of a CN-substituted fluorene in tetrahydrofuran. Specific vibrational frequencies can exhibit distinct frequency shifts due to ion-pairing, which can be explained in the framework of the vibrational Stark effect. Measurements of the ratio of free ions and ion-pairs in different electrolyte concentrations allowed us to obtain an association constant and free energy change for ion-pairing. As a result, this new method has the potential to probe the geometry of ion-pairing and allows the reduction potentials of moleculesmore » to be determined in the absence of electrolyte in an environment of low dielectric constant.« less

Effects of nitrogen ion implantation time on tungsten films deposited by DC magnetron sputtering on AISI 410 martensitic stainless steel

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

Malau, Viktor, E-mail: malau@ugm.ac.id; Ilman, Mochammad Noer, E-mail: noer-ilman@yahoo.com; Iswanto, Priyo Tri, E-mail: priyatri@yahoo.com

Nitrogen ion implantation time on tungsten thin film deposited on surface of AISI 410 steel has been performed. Tungsten thin film produced by dc magnetron sputtering method was deposited on AISI 410 martensitic stainless steel substrates, and then the nitrogen ions were implanted on tungsten thin film. The objective of this research is to investigate the effects of implantation deposition time on surface roughness, microhardness, specific wear and corrosion rate of nitrogen implanted on tungsten film. Magnetron sputtering process was performed by using plasma gas of argon (Ar) to bombardier tungsten target (W) in a vacuum chamber with a pressuremore » of 7.6 x 10{sup −2} torr, a voltage of 300 V, a sputter current of 80 mA for sputtered time of 10 minutes. Nitrogen implantation on tungsten film was done with an initial pressure of 3x10{sup −6} mbar, a fluence of 2 x 10{sup 17} ions/cm{sup 2}, an energy of 100 keV and implantation deposition times of 0, 20, 30 and 40 minutes. The surface roughness, microhardness, specific wear and corrosion rate of the films were evaluated by surfcorder test, Vickers microhardness test, wear test and potentiostat (galvanostat) test respectively. The results show that the nitrogen ions implanted deposition time on tungsten film can modify the surface roughness, microhardness, specific wear and corrosion rate. The minimum surface roughness, specific wear and corrosion rate can be obtained for implantation time of 20 minutes and the maximum microhardness of the film is 329 VHN (Vickers Hardness Number) for implantation time of 30 minutes. The specific wear and corrosion rate of the film depend directly on the surface roughness.« less

Effect of multiply charged ions on the performance and beam characteristics in annular and cylindrical type Hall thruster plasmas

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

Kim, Holak; Lim, Youbong; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2014-10-06

Plasma plume and thruster performance characteristics associated with multiply charged ions in a cylindrical type Hall thruster (CHT) and an annular type Hall thruster are compared under identical conditions such as channel diameter, channel depth, propellant mass flow rate. A high propellant utilization in a CHT is caused by a high ionization rate, which brings about large multiply charged ions. Ion currents and utilizations are much different due to the presence of multiply charged ions. A high multiply charged ion fraction and a high ionization rate in the CHT result in a higher specific impulse, thrust, and discharge current.

Towards a Unified Understanding of Lithium Action in Basic Biology and its Significance for Applied Biology.

PubMed

Jakobsson, Eric; Argüello-Miranda, Orlando; Chiu, See-Wing; Fazal, Zeeshan; Kruczek, James; Nunez-Corrales, Santiago; Pandit, Sagar; Pritchet, Laura

2017-12-01

Lithium has literally been everywhere forever, since it is one of the three elements created in the Big Bang. Lithium concentration in rocks, soil, and fresh water is highly variable from place to place, and has varied widely in specific regions over evolutionary and geologic time. The biological effects of lithium are many and varied. Based on experiments in which animals are deprived of lithium, lithium is an essential nutrient. At the other extreme, at lithium ingestion sufficient to raise blood concentration significantly over 1 mM/, lithium is acutely toxic. There is no consensus regarding optimum levels of lithium intake for populations or individuals-with the single exception that lithium is a generally accepted first-line therapy for bipolar disorder, and specific dosage guidelines for sufferers of that condition are generally agreed on. Epidemiological evidence correlating various markers of social dysfunction and disease vs. lithium level in drinking water suggest benefits of moderately elevated lithium compared to average levels of lithium intake. In contrast to other biologically significant ions, lithium is unusual in not having its concentration in fluids of multicellular animals closely regulated. For hydrogen ions, sodium ions, potassium ions, calcium ions, chloride ions, and magnesium ions, blood and extracellular fluid concentrations are closely and necessarily regulated by systems of highly selective channels, and primary and secondary active transporters. Lithium, while having strong biological activity, is tolerated over body fluid concentrations ranging over many orders of magnitude. The lack of biological regulation of lithium appears due to lack of lithium-specific binding sites and selectivity filters. Rather lithium exerts its myriad physiological and biochemical effects by competing for macromolecular sites that are relatively specific for other cations, most especially for sodium and magnesium. This review will consider what is known about the nature of this competition and suggest using and extending this knowledge towards the goal of a unified understanding of lithium in biology and the application of that understanding in medicine and nutrition.

Polyamine replacement by magnesium ions in BHK-21/C13 cells

PubMed Central

Melvin, Maureen A. L.; Keir, Hamish M.

1979-01-01

Cultures of BHK-21/C13 cells, whose growth was inhibited by deprivation of serum, were stimulated to grow by addition of serum to the culture medium. Addition of MgCl2 to the medium, to increase the concentration of Mg2+ ions by 15mm, 30min before addition of serum, had no effect on the stimulation of cell growth, but inhibited the accumulation of cellular spermidine, so that the spermidine/spermine molar ratio was lower in these cultures than in cultures that had received no additional cations. The increase in the activity of ornithine decarboxylase that occurs 4–5h after serum `step-up' was substantially diminished by increasing the concentration of Mg2+ ions, but not of Na+ or K+ ions, in the medium by 30mm, 30min before addition of serum, and this inhibition was maintained for at least 24h. Methylglyoxal bis(guanylhydrazone), added to serum-deprived cultures to a concentration of 20μm, 30min before addition of serum, severely inhibited the increase in cell growth. The inhibitory effects of the drug were prevented by simultaneous addition of spermidine to the medium (to 100μm), and were partly prevented by the simultaneous addition of Mg2+ ions (to 30mm). Mg2+ ions were particularly effective in overcoming the inhibitory effect of methylglyoxal bis(guanylhydrazone) on the synthesis of DNA. Thus although a certain lack of specificity for cations exists in BHK-21/C13 cells, in that Mg2+ ions can be substituted for polyamines, particularly spermidine, to some extent, there are cellular processes for which the requirement for polyamines as cations is specific. PMID:444220

Carbon Ion Radiotherapy at the Gunma University Heavy Ion Medical Center: New Facility Set-up.

PubMed

Ohno, Tatsuya; Kanai, Tatsuaki; Yamada, Satoru; Yusa, Ken; Tashiro, Mutsumi; Shimada, Hirofumi; Torikai, Kota; Yoshida, Yukari; Kitada, Yoko; Katoh, Hiroyuki; Ishii, Takayoshi; Nakano, Takashi

2011-10-26

Carbon ion radiotherapy (C-ion RT) offers superior dose conformity in the treatment of deep-seated tumors compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. C-ion RT for the first patient at Gunma University Heavy Ion Medical Center (GHMC) was initiated in March of 2010. The major specifications of the facility were determined based on the experience of clinical treatments at the National Institute of Radiological Sciences (NIRS), with the size and cost being reduced to one-third of those at NIRS. The currently indicated sites of cancer treatment at GHMC are lung, prostate, head and neck, liver, rectum, bone and soft tissue. Between March 2010 and July 2011, a total of 177 patients were treated at GHMC although a total of 100 patients was the design specification during the period in considering the optimal machine performance. In the present article, we introduce the facility set-up of GHMC, including the facility design, treatment planning systems, and clinical preparations.

Carbon Ion Radiotherapy at the Gunma University Heavy Ion Medical Center: New Facility Set-up

PubMed Central

Ohno, Tatsuya; Kanai, Tatsuaki; Yamada, Satoru; Yusa, Ken; Tashiro, Mutsumi; Shimada, Hirofumi; Torikai, Kota; Yoshida, Yukari; Kitada, Yoko; Katoh, Hiroyuki; Ishii, Takayoshi; Nakano, Takashi

2011-01-01

Carbon ion radiotherapy (C-ion RT) offers superior dose conformity in the treatment of deep-seated tumors compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. C-ion RT for the first patient at Gunma University Heavy Ion Medical Center (GHMC) was initiated in March of 2010. The major specifications of the facility were determined based on the experience of clinical treatments at the National Institute of Radiological Sciences (NIRS), with the size and cost being reduced to one-third of those at NIRS. The currently indicated sites of cancer treatment at GHMC are lung, prostate, head and neck, liver, rectum, bone and soft tissue. Between March 2010 and July 2011, a total of 177 patients were treated at GHMC although a total of 100 patients was the design specification during the period in considering the optimal machine performance. In the present article, we introduce the facility set-up of GHMC, including the facility design, treatment planning systems, and clinical preparations. PMID:24213124

Ion propulsion

NASA Technical Reports Server (NTRS)

Meserole, J. S.; Keefer, Dennis; Ruyten, Wilhelmus; Peng, Xiaohang

1995-01-01

An ion engine is a plasma thruster which produces thrust by extracting ions from the plasma and accelerating them to high velocity with an electrostatic field. The ions are then neutralized and leave the engine as high velocity neutral particles. The advantages of ion engines are high specific impulse and efficiency and their ability to operate over a wide range of input powers. In comparison with other electric thrusters, the ion engine has higher efficiency and specific impulse than thermal electric devices such as the arcjet, microwave, radiofrequency and laser heated thrusters and can operate at much lower current levels than the MPD thruster. However, the thrust level for an ion engine may be lower than a thermal electric thruster of the same operating power, consistent with its higher specific impulse, and therefore ion engines are best suited for missions which can tolerate longer duration propulsive phases. The critical issue for the ion engine is lifetime, since the prospective missions may require operation for several thousands of hours. The critical components of the ion engine, with respect to engine lifetime, are the screen and accelerating grid structures. Typically, these are large metal screens that must support a large voltage difference and maintain a small gap between them. Metallic whisker growth, distortion and vibration can lead to arcing, and over a long period of time ion sputtering will erode the grid structures and change their geometry. In order to study the effects of long time operation of the grid structure, we are developing computer codes based on the Particle-In-Cell (PIC) technique and Laser Induced Fluorescence (LIF) diagnostic techniques to study the physical processes which control the performance and lifetime of the grid structures.

Ion aggregation in high salt solutions. VII. The effect of cations on the structures of ion aggregates and water hydrogen-bonding network

NASA Astrophysics Data System (ADS)

Choi, Jun-Ho; Choi, Hyung Ran; Jeon, Jonggu; Cho, Minhaeng

2017-10-01

Ions in high salt solutions have a strong propensity to form polydisperse ion aggregates with broad size and shape distributions. In a series of previous comparative investigations using femtosecond IR pump-probe spectroscopy, molecular dynamics simulation, and graph theoretical analysis, we have shown that there exists a morphological difference in the structures of ion aggregates formed in various salt solutions. As salt concentration increases, the ions in high salt solutions form either cluster-like structures excluding water molecules or network-like structures entwined with water hydrogen-bonding networks. Interestingly, such morphological characteristics of the ion aggregates have been found to be in correlation with the solubility limits of salts. An important question that still remains unexplored is why certain salts with different cations have notably different solubility limits in water. Here, carrying out a series of molecular dynamics simulations of aqueous salt solutions and analyzing the distributions and connectivity patterns of ion aggregates with a spectral graph analysis method, we establish the relationship between the salt solubility and the ion aggregate morphology with a special emphasis on the cationic effects on water structures and ion aggregation. We anticipate that the understanding of large scale ion aggregate structures revealed in this study will be critical for elucidating the specific ion effects on the solubility and conformational stability of co-solute molecules such as proteins in water.

Investigation of the heavy-ion mode in the FAIR High Energy Storage Ring

NASA Astrophysics Data System (ADS)

Kovalenko, O.; Dolinskii, O.; Litvinov, Yu A.; Maier, R.; Prasuhn, D.; Stöhlker, T.

2015-11-01

High energy storage ring (HESR) as a part of the future accelerator facility FAIR (Facility for Antiproton and Ion Research) will serve for a variety of internal target experiments with high-energy stored heavy ions (SPARC collaboration). Bare uranium is planned to be used as a primary beam. Since a storage time in some cases may be significant—up to half an hour—it is important to examine the high-order effects in the long-term beam dynamics. A new ion optics specifically for the heavy ion mode of the HESR is developed and is discussed in this paper. The subjects of an optics design, tune working point and a dynamic aperture are addressed. For that purpose nonlinear beam dynamics simulations are carried out. Also a flexibility of the HESR ion optical lattice is verified with regard to various experimental setups. Specifically, due to charge exchange reactions in the internal target, secondary beams, such as hydrogen-like and helium-like uranium ions, will be produced. Thus the possibility of separation of these secondary ions and the primary {{{U}}}92+ beam is presented with different internal target locations.

Label-free liquid crystal biosensor based on specific oligonucleotide probes for heavy metal ions.

PubMed

Yang, Shengyuan; Wu, Chao; Tan, Hui; Wu, Yan; Liao, Shuzhen; Wu, Zhaoyang; Shen, Guoli; Yu, Ruqin

2013-01-02

In this study, to enhance the capability of metal ions disturbing the orientation of liquid crystals (LCs), we designed a new label-free LC biosensor for the highly selective and sensitive detection of heavy metal ions. This strategy makes use of the target-induced DNA conformational change to enhance the disruption of target molecules for the orientation of LC leading to an amplified optical signal. The Hg(2+) ion, which possesses a unique property to bind specifically to two DNA thymine (T) bases, is used as a model heavy metal ion. In the presence of Hg(2+), the specific oligonucleotide probes form a conformational reorganization of the oligonucleotide probes from hairpin structure to duplex-like complexes. The duplex-like complexes are then bound on the triethoxysilylbutyraldehyde/N,N-dimethyl-N-octadecyl (3-aminopropyl) trimethoxysilyl chloride (TEA/DMOAP)-coated substrate modified with capture probes, which can greatly distort the orientational profile of LC, making the optical image of LC cell birefringent as a result. The optical signal of LC sensor has a visible change at the Hg(2+) concentration of low to 0.1 nM, showing good detection sensitivity. The cost-effective LC sensing method can translate the concentration signal of heavy metal ions in solution into the presence of DNA duplexes and is expected to be a sensitive detection platform for heavy metal ions and other small molecule monitors.

Free Energy Wells and Barriers to Ion Transport Across Membranes

NASA Astrophysics Data System (ADS)

Rempe, Susan

2014-03-01

The flow of ions across cellular membranes is essential to many biological processes. Ion transport is also important in synthetic materials used as battery electrolytes. Transport often involves specific ions and fast conduction. To achieve those properties, ion conduction pathways must solvate specific ions by just the ``right amount.'' The right amount of solvation avoids ion traps due to deep free energy wells, and avoids ion block due to high free energy barriers. Ion channel proteins in cellular membranes demonstrate this subtle balance in solvation of specific ions. Using ab initio molecular simulations, we have interrogated the link between binding site structure and ion solvation free energies in biological ion binding sites. Our results emphasize the surprisingly important role of the environment that surrounds ion-binding sites for fast transport of specific ions. We acknowledge support from Sandia's LDRD program. Sandia National Labs is a multi-program laboratory operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corp., for the US DOE's NNSA under contract DE-AC04-94AL85000.

EFFECTS OF CHLORAMINATION AND SITE SPECIFIC ISSUES ON NANOFILTRATION FLUX LOSS AND FOULANT CHARACTERISTICS

EPA Science Inventory

The presence of chloramines or free ammonium ion was found to have little effect on the final specific flux and fouling cake-layer characteristics of nanofiltration membrances fed pretreated Little Miami Aquifer water. The system fed chloraminated water had the greatest amount o...

Interchange mode excited by trapped energetic ions

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

Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp

2015-07-15

The kinetic energy principle describing the interaction between ideal magnetohydrodynamic (MHD) modes with trapped energetic ions is revised. A model is proposed on the basis of the reduced ideal MHD equations for background plasmas and the bounce-averaged drift-kinetic equation for trapped energetic ions. The model is applicable to large-aspect-ratio toroidal devices. Specifically, the effect of trapped energetic ions on the interchange mode in helical systems is analyzed. Results show that the interchange mode is excited by trapped energetic ions, even if the equilibrium states are stable to the ideal interchange mode. The energetic-ion-induced branch of the interchange mode might bemore » associated with the fishbone mode in helical systems.« less

Oligopeptidase B from Serratia proteamaculans. III. Inhibition analysis. Specific interactions with metalloproteinase inhibitors.

PubMed

Mikhailova, A G; Khairullin, R F; Kolomijtseva, G Ya; Rumsh, L D

2012-03-01

Inhibition of the novel oligopeptidase B from Serratia proteamaculans (PSP) by basic pancreatic trypsin inhibitor, Zn2+ ions, and o- and m-phenanthroline was investigated. A pronounced effect of calcium ions on the interaction of PSP with inhibitors was demonstrated. Inversion voltamperometry and atomic absorption spectrometry revealed no zinc ions in the PSP molecule. Hydrophobic nature of the enzyme inhibition by o- and m-phenanthroline was established.

Effects of pipette modulation and imaging distances on ion currents measured with scanning ion conductance microscopy (SICM).

PubMed

Chen, Chiao-Chen; Baker, Lane A

2011-01-07

Local conductance variations can be estimated by measuring ion current magnitudes with scanning ion conductance microscopy (SICM). Factors which influence image quality and quantitation of ion currents measured with SICM have been evaluated. Specifically, effects of probe-sample separation and pipette modulation have been systematically studied for the case of imaging conductance variations at pores in a polymer membrane under transmembrane concentration gradients. The influence of probe-sample separation on ion current images was evaluated using distance-modulated (ac) feedback. Approach curves obtained using non-modulated (dc) feedback were also recorded to determine the relative influence of pipette-generated convection by comparison of ion currents measured with both ac and dc feedback modes. To better interpret results obtained, comparison to a model based on a disk-shaped geometry for nanopores in the membrane, as well as relevant position-dependent parameters of the experiment is described. These results advance our current understanding of conductance measurements with SICM.

Ion energy/momentum effects during ion assisted growth of niobium nitride films

NASA Astrophysics Data System (ADS)

Klingenberg, Melissa L.

The research described herein was performed to better understand and discern ion energy vs. ion momentum effects during ion beam assisted (IBAD) film growth and their effects on residual stress, crystalline structure, morphology, and composition, which influence film tribological properties. NbxN y was chosen for this research because it is a refractory material that can possess a large number of crystalline structures, and it has been found to have good tribological properties. To separate the effects of momentum transfer per arriving atom (p/a), which considers bombarding species mass, energy, and ion-to-atom transport ratio, from those of energy deposition per arriving atom (E/a), a mass independent parameter, different inert ion beams (krypton, argon, and neon) were used to create a matrix of coatings formed using similar energy deposition, but different momentum transfer and vice versa. Deposition was conducted in a research-scale IBAD system using electron beam evaporation, a radio frequency ion source, and a neutral nitrogen gas backfill. Films were characterized using x-ray diffraction, atomic force microscopy, Rutherford backscattering spectrometry, and residual stress analysis. Direct and quantifiable effects of bombardment were observed; however, energy deposition and momentum transfer effects could not be completely separated, confirming that thin film processes are complex. Complexities arose from ion-specific interactions (ion size, recoil energy, per cent reflected neutrals, Penning ionization, etc.) and chemistry effects that are not considered by the simple models. Overall, it can be stated that bombardment promoted nitride formation, nanocrystallinity, and compressive stress formation; influenced morphology (which influenced post-deposition oxygen uptake) and stress evolution; increased lattice parameter; modified crystalline phase and texture; and led to inert gas incorporation. High stress levels correlated strongly with material disorder and closed-structured morphologies.

Aggregation and charging of sulfate and amidine latex particles in the presence of oxyanions.

PubMed

Sugimoto, Takuya; Cao, Tianchi; Szilagyi, Istvan; Borkovec, Michal; Trefalt, Gregor

2018-08-15

Electrophoretic mobility and time resolved light scattering are used to measure the effect on charging and aggregation of amidine and sulfate latex particles of different oxyanions namely, phosphate, arsenate, sulfate, and selenate. In the case of negatively charged sulfate latex particles oxyanions represent the coions, while they represent counterions in the case of the positively charged amidine latex. Repulsive interaction between the sulfate latex surface and the coions results in weak ion specific effects on the charging and aggregation. On the other hand the interaction of oxyanions with the amidine latex surface is highly specific. The monovalent dihydrogen phosphate ion strongly adsorbs to the positively charged surface and reverses the charge of the particle. This charge reversal leads also to the restabilization of the amidine latex suspension at the intermediate phosphate concentrations. In the case of dihydrogen arsenate the adsorption to amidine latex surface is weaker and no charge reversal and restabilization occurs. Similar differences are seen between the sulfate and selenate analogues, where selenate adsorbs more strongly to the surface as compared to the sulfate ion and invokes charge reversal. The present results indicate that ion specificity is much more pronounced in the case of counterions. Copyright © 2018 Elsevier Inc. All rights reserved.

Effects of Stopping Ions and LET Fluctuations on Soft Error Rate Prediction.

DOE PAGES

Weeden-Wright, S. L.; King, Michael Patrick; Hooten, N. C.; ...

2015-02-01

Variability in energy deposition from stopping ions and LET fluctuations is quantified for specific radiation environments. When compared to predictions using average LET via CREME96, LET fluctuations lead to an order-of-magnitude difference in effective flux and a nearly 4x decrease in predicted soft error rate (SER) in an example calculation performed on a commercial 65 nm SRAM. The large LET fluctuations reported here will be even greater for the smaller sensitive volumes that are characteristic of highly scaled technologies. End-of-range effects of stopping ions do not lead to significant inaccuracies in radiation environments with low solar activity unless the sensitivevolumemore » thickness is 100 μm or greater. In contrast, end-of-range effects for stopping ions lead to significant inaccuracies for sensitive- volume thicknesses less than 10 μm in radiation environments with high solar activity.« less

Effect of Zn2+ binding and enzyme active site on the transition state for RNA 2′-O-transphosphorylation interpreted through kinetic isotope effects

PubMed Central

Chen, Haoyuan; Piccirilli, Joseph A.; Harris, Michael E.; York, Darrin M.

2016-01-01

Divalent metal ions, due to their ability to stabilize high concentrations of negative charge, are important for RNA folding and catalysis. Detailed models derived from the structures and kinetics of enzymes and from computational simulations have been developed. However, in most cases the specific catalytic modes involving metal ions and their mechanistic roles and effects on transition state structures remains controversial. Valuable information about the nature of the transition state is provided by measurement of kinetic isotope effects (KIEs). However, KIEs reflect changes in all bond vibrational modes that differ between the ground state and transition state. QM calculations are therefore essential for developing structural models of the transition state and evaluating mechanistic alternatives. Herein, we present computational models for Zn2+ binding to RNA 2′O-transphosphorylation reaction models that aid in the interpretation of KIE experiments. Different Zn2+ binding modes produce distinct KIE signatures, and one binding mode involving two zinc ions is in close agreement with KIEs measured for non-enzymatic catalysis by Zn2+ aquo ions alone. Interestingly, the KIE signatures in this specific model are also very close to those in RNase A catalysis. These results allow a quantitative connection to be made between experimental KIE measurements and transition state structure and bonding, and provide insight into RNA 2′O-transphosphorylation reactions catalyzed by metal ions and enzymes. PMID:25812974

Coarse-graining, Electrostatics and pH effects in phospholipid systems

NASA Astrophysics Data System (ADS)

Travesset, Alex; Vangaveti, Sweta

2010-03-01

We introduce a minimal free energy describing the interaction of charged groups and counterions including both classical electrostatic and specific interactions. The predictions of the model are compared against the standard model for describing ions next to charged interfaces, consisting of Poisson-Boltzmann theory with additional constants describing ion binding, which are specific to the counterion and the interfacial charge (``chemical binding''). It is shown that the ``chemical'' model can be appropriately described by an underlying ``physical'' model over several decades in concentration, but the extracted binding constants are not uniquely defined, as they differ depending on the particular observable quantity being studied. It is also shown that electrostatic correlations for divalent (or higher valence) ions enhance the surface charge by increasing deprotonation, an effect not properly accounted within chemical models. The model is applied to the charged phospholipids phosphatidylserine, Phosphatidc acid and Phosphoinositides and implications for different biological processes are discussed.

Sodium effect on self-organization of amphiphilic carboxylates: formation of structured micelles and superlattices.

PubMed

Rosenlehner, Karin; Schade, Boris; Böttcher, Christoph; Jäger, Christof M; Clark, Timothy; Heinemann, Frank W; Hirsch, Andreas

2010-08-16

Not only the self-aggregation of dendritic polycarboxylates into structurally persistent micelles, but also that of the micelles themselves into superlattices is controlled by alkali-metal counterions and shows a pronounced sodium effect. Our combined experimental and computational work has revealed the formation of superlattices for the first time. The behavior of a variety of amphiphilic carboxylates and the different effects of the alkali cations Li(+), Na(+), and K(+) have been investigated by conductivity measurements, cryogenic transmission electron microscopy (cryo-TEM), and molecular-dynamics (MD) simulations. Together, these show that sodium salts of the amphiphiles give the most stable micelles, followed by lithium and potassium. Our results suggest that ion multiplets in bridging positions, rather than contact ion pairs, are responsible for the enhanced stability and the formation of hexagonally ordered superlattices with sodium counterions. Potassium ions do not form such ion multiplets and cannot therefore induce aggregation of the micelles. This sodium effect has far-reaching consequences for a large number of biological and technical systems and sheds new light on the origin of specific-ion effects.

An electrostatic potassium channel opener targeting the final voltage sensor transition

PubMed Central

Börjesson, Sara I.

2011-01-01

Free polyunsaturated fatty acids (PUFAs) modulate the voltage dependence of voltage-gated ion channels. As an important consequence thereof, PUFAs can suppress epileptic seizures and cardiac arrhythmia. However, molecular details for the interaction between PUFA and ion channels are not well understood. In this study, we have localized the site of action for PUFAs on the voltage-gated Shaker K channel by introducing positive charges on the channel surface, which potentiated the PUFA effect. Furthermore, we found that PUFA mainly affects the final voltage sensor movement, which is closely linked to channel opening, and that specific charges at the extracellular end of the voltage sensor are critical for the PUFA effect. Because different voltage-gated K channels have different charge profiles, this implies channel-specific PUFA effects. The identified site and the pharmacological mechanism will potentially be very useful in future drug design of small-molecule compounds specifically targeting neuronal and cardiac excitability. PMID:21624947

Ion specific correlations in bulk and at biointerfaces.

PubMed

Kalcher, I; Horinek, D; Netz, R R; Dzubiella, J

2009-10-21

Ion specific effects are ubiquitous in any complex colloidal or biological fluid in bulk or at interfaces. The molecular origins of these 'Hofmeister effects' are not well understood and their theoretical description poses a formidable challenge to the modeling and simulation community. On the basis of the combination of atomistically resolved molecular dynamics (MD) computer simulations and statistical mechanics approaches, we present a few selected examples of specific electrolyte effects in bulk, at simple neutral and charged interfaces, and on a short α-helical peptide. The structural complexity in these strongly Coulomb-correlated systems is highlighted and analyzed in the light of available experimental data. While in general the comparison of MD simulations to experiments often lacks quantitative agreement, mostly because molecular force fields and coarse-graining procedures remain to be optimized, the consensus as regards trends provides important insights into microscopic hydration and binding mechanisms.

Molecular simulation study on Hofmeister cations and the aqueous solubility of benzene.

PubMed

Ganguly, Pritam; Hajari, Timir; van der Vegt, Nico F A

2014-05-22

We study the ion-specific salting-out process of benzene in aqueous alkali chloride solutions using Kirkwood-Buff (KB) theory of solutions and molecular dynamics simulations with different empirical force field models for the ions and benzene. Despite inaccuracies in the force fields, the simulations indicate that the decrease of the Setchenow salting-out coefficient for the series NaCl > KCl > RbCl > CsCl is determined by direct benzene-cation correlations, with the larger cations showing weak interactions with benzene. Although ion-specific aqueous solubilities of benzene may be affected by indirect ion-ion, ion-water, and water-water correlations, too, these correlations are found to be unimportant, with little to no effect on the Setchenow salting-out coefficients of the various salts. We further considered LiCl, which is experimentally known to be a weaker salting-out agent than NaCl and KCl and, therefore, ranks at an unusual position within the Hofmeister cation series. The simulations indicate that hydrated Li(+) ions can take part of the benzene hydration shell while the other cations are repelled by it. This causes weaker Li(+) exclusion around the solute and a resulting, weaker salting-out propensity of LiCl compared to that of the other salts. Removing benzene-water and benzene-salt electrostatic interactions in the simulations does not affect this mechanism, which may therefore also explain the smaller effect of LiCl, as compared to that of NaCl or KCl, on aqueous solvation and hydrophobic interaction of nonpolar molecules.

Plasma sheath effects on ion collection by a pinhole

NASA Technical Reports Server (NTRS)

Herr, Joel L.; Snyder, David B.

1993-01-01

This work presents tables to assist in the evaluation of pinhole collection effects on spacecraft. These tables summarize results of a computer model which tracks particle trajectories through a simplified electric field in the plasma sheath. A technique is proposed to account for plasma sheath effects in the application of these results and scaling rules are proposed to apply the calculations to specific situations. This model is compared to ion current measurements obtained by another worker, and the agreement is very good.

Heavy ion action on yeast cells: Inhibition of ribosomal-RNA synthesis, loss of colony forming ability and induction of mutants

NASA Astrophysics Data System (ADS)

Kiefer, J.; Rase, S.; Schöpfer, F.; Schneider, E.; Weber, K.; Kraft, G.

The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic δ-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range δ-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains.

Protein destabilisation in ionic liquids: the role of preferential interactions in denaturation.

PubMed

Figueiredo, Angelo Miguel; Sardinha, Joao; Moore, Geoffrey R; Cabrita, Eurico J

2013-12-07

The preferential binding of anions and cations in aqueous solutions of the ionic liquids (ILs) 1-butyl-3-methylimidazolium ([C4mim](+)) and 1-ethyl-3-methylimidazolium ([C2mim](+)) chloride and dicyanamide (dca(-)) with the small alpha-helical protein Im7 was investigated using a combination of differential scanning calorimetry, NMR spectroscopy and molecular dynamics (MD) simulations. Our results show that direct ion interactions are crucial to understand the effects of ILs on the stability of proteins and that an anion effect is dominant. We show that the binding of weakly hydrated anions to positively charged or polar residues leads to the partial dehydration of the backbone groups, and is critical to control stability, explaining why dca(-) is more denaturing than Cl(-). Direct cation-protein interactions also mediate stability; cation size and hydrophobicity are relevant to account for destabilisation as shown by the effect of [C4mim](+) compared to [C2mim](+). The specificity in the interaction of IL ions with protein residues established by weak favourable interactions is confirmed by NMR chemical shift perturbation, amide hydrogen exchange data and MD simulations. Differences in specificity are due to the balance of interaction established between ion pairs and ion-solvent that determine the type of residues affected. When the interaction of both cation and anion with the protein is strong the net result is similar to a non-specific interaction, leading ultimately to unfolding. Since the nature of the ions is a determinant of the level of interaction with the protein towards denaturation or stabilisation, ILs offer a unique possibility to modulate protein stabilisation or even folding events.

Amine-modified magnetic iron oxide nanoparticle as a promising carrier for application in bio self-healing concrete.

PubMed

Seifan, Mostafa; Ebrahiminezhad, Alireza; Ghasemi, Younes; Samani, Ali Khajeh; Berenjian, Aydin

2018-01-01

Self-healing mechanisms are a promising solution to address the concrete cracking issue. Among the investigated self-healing strategies, the biotechnological approach is distinguished itself by inducing the most compatible material with concrete composition. In this method, the potent bacteria and nutrients are incorporated into the concrete matrix. Once cracking occurs, the bacteria will be activated, and the induced CaCO 3 crystals will seal the concrete cracks. However, the effectiveness of a bio self-healing concrete strictly depends on the viability of bacteria. Therefore, it is required to protect the bacteria from the resulted shear forces caused by mixing and drying shrinkage of concrete. Due to the positive effects on mechanical properties and the high compatibility of metallic nanoparticles with concrete composition, for the first time, we propose 3-aminopropyltriethoxy silane-coated iron oxide nanoparticles (APTES-coated IONs) as a biocompatible carrier for Bacillus species. This study was aimed to investigate the effect of APTES-coated IONs on the bacterial viability and CaCO 3 yield for future application in the concrete structures. The APTES-coated IONs were successfully synthesized and characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that the presence of 100 μg/mL APTES-coated IONs could increase the bacterial viability. It was also found that the CaCO 3 -specific yield was significantly affected in the presence of APTES-coated IONs. The highest CaCO 3 -specific yield was achieved when the cells were decorated with 50 μg/mL of APTES-coated IONs. This study provides new insights for the application of APTES-coated IONs in designing bio self-healing strategies.

Light ion production for a future radiobiological facility at CERN: Preliminary studies

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

Stafford-Haworth, Joshua, E-mail: Joshua.Stafford-Haworth@cern.ch; John Adams Institute at Royal Holloway, University of London, Egham, Surrey TW20 0EX; Bellodi, Giulia

2014-02-15

Recent medical applications of ions such as carbon and helium have proved extremely effective for the treatment of human patients. However, before now a comprehensive study of the effects of different light ions on organic targets has not been completed. There is a strong desire for a dedicated facility which can produce ions in the range of protons to neon in order to perform this study. This paper will present the proposal and preliminary investigations into the production of light ions, and the development of a radiobiological research facility at CERN. The aims of this project will be presented alongmore » with the modifications required to the existing linear accelerator (Linac3), and the foreseen facility, including the requirements for an ion source in terms of some of the specification parameters and the flexibility of operation for different ion types. Preliminary results from beam transport simulations will be presented, in addition to some planned tests required to produce some of the required light ions (lithium, boron) to be conducted in collaboration with the Helmholtz-Zentrum für Materialien und Energie, Berlin.« less

Light ion production for a future radiobiological facility at CERN: preliminary studies.

PubMed

Stafford-Haworth, Joshua; Bellodi, Giulia; Küchler, Detlef; Lombardi, Alessandra; Röhrich, Jörg; Scrivens, Richard

2014-02-01

Recent medical applications of ions such as carbon and helium have proved extremely effective for the treatment of human patients. However, before now a comprehensive study of the effects of different light ions on organic targets has not been completed. There is a strong desire for a dedicated facility which can produce ions in the range of protons to neon in order to perform this study. This paper will present the proposal and preliminary investigations into the production of light ions, and the development of a radiobiological research facility at CERN. The aims of this project will be presented along with the modifications required to the existing linear accelerator (Linac3), and the foreseen facility, including the requirements for an ion source in terms of some of the specification parameters and the flexibility of operation for different ion types. Preliminary results from beam transport simulations will be presented, in addition to some planned tests required to produce some of the required light ions (lithium, boron) to be conducted in collaboration with the Helmholtz-Zentrum für Materialien und Energie, Berlin.

A versatile MOF-based trap for heavy metal ion capture and dispersion.

PubMed

Peng, Yaguang; Huang, Hongliang; Zhang, Yuxi; Kang, Chufan; Chen, Shuangming; Song, Li; Liu, Dahuan; Zhong, Chongli

2018-01-15

Current technologies for removing heavy metal ions are typically metal ion specific. Herein we report the development of a broad-spectrum heavy metal ion trap by incorporation of ethylenediaminetetraacetic acid into a robust metal-organic framework. The capture experiments for a total of 22 heavy metal ions, covering hard, soft, and borderline Lewis metal ions, show that the trap is very effective, with removal efficiencies of >99% for single-component adsorption, multi-component adsorption, or in breakthrough processes. The material can also serve as a host for metal ion loading with arbitrary selections of metal ion amounts/types with a controllable uptake ratio to prepare well-dispersed single or multiple metal catalysts. This is supported by the excellent performance of the prepared Pd 2+ -loaded composite toward the Suzuki coupling reaction. This work proposes a versatile heavy metal ion trap that may find applications in the fields of separation and catalysis.

Predicting ion specific capacitances of supercapacitors due to quantum ionic interactions.

PubMed

Parsons, Drew F

2014-08-01

A new theoretical framework is now available to help explain ion specific (Hofmeister) effects. All measurements in physical chemistry show ion specificity, inexplicable by classical electrostatic theories. These ignore ionic dispersion forces that change ionic adsorption. We explored ion specificity in supercapacitors using a modified Poisson-Boltzmann approach that includes ionic dispersion energies. We have applied ab initio quantum chemical methods to determine required ion sizes and ion polarisabilities. Our model represents graphite electrodes through their optical dielectric spectra. The electrolyte was 1.2 M Li salt in propylene carbonate, using the common battery anions, PF6(-), BF4(-) and ClO4(-). We also investigated the perhalate series with BrO4(-) and IO4(-). The capacitance C=dσ/dψ was calculated from the predicted electrode surface charge σ of each electrode with potential ψ between electrodes. Compared to the purely electrostatic calculation, the capacitance of a positively charged graphite electrode was enhanced by more than 15%, with PF6(-) showing >50% increase in capacitance. IO4(-) provided minimal enhancement. The enhancement is due to adsorption of both anions and cations, driven by ionic dispersion forces. The Hofmeister series in the single-electrode capacitance was PF6(-)>BF4(-)>ClO4(-)>BrO4(-)>IO4(-) . When the graphite electrode was negatively charged, the perhalates provided almost no enhancement of capacitance, while PF6(-) and BF4(-) decreased capacitance by about 15%. Due to the asymmetric impact of nonelectrostatic ion interactions, the capacitances of positive and negative electrodes are not equal. The capacitance of a supercapacitor should therefore be reported as two values rather than one, similar to the matrix of mutual capacitances used in multielectrode devices. Copyright © 2014 Elsevier Inc. All rights reserved.

Effect of Monovalent Ion Parameters on Molecular Dynamics Simulations of G-Quadruplexes.

PubMed

Havrila, Marek; Stadlbauer, Petr; Islam, Barira; Otyepka, Michal; Šponer, Jiří

2017-08-08

G-quadruplexes (GQs) are key noncanonical DNA and RNA architectures stabilized by desolvated monovalent cations present in their central channels. We analyze extended atomistic molecular dynamics simulations (∼580 μs in total) of GQs with 11 monovalent cation parametrizations, assessing GQ overall structural stability, dynamics of internal cations, and distortions of the G-tetrad geometries. Majority of simulations were executed with the SPC/E water model; however, test simulations with TIP3P and OPC water models are also reported. The identity and parametrization of ions strongly affect behavior of a tetramolecular d[GGG] 4 GQ, which is unstable with several ion parametrizations. The remaining studied RNA and DNA GQs are structurally stable, though the G-tetrad geometries are always deformed by bifurcated H-bonding in a parametrization-specific manner. Thus, basic 10-μs-scale simulations of fully folded GQs can be safely done with a number of cation parametrizations. However, there are parametrization-specific differences and basic force-field errors affecting the quantitative description of ion-tetrad interactions, which may significantly affect studies of the ion-binding processes and description of the GQ folding landscape. Our d[GGG] 4 simulations indirectly suggest that such studies will also be sensitive to the water models. During exchanges with bulk water, the Na + ions move inside the GQs in a concerted manner, while larger relocations of the K + ions are typically separated. We suggest that the Joung-Cheatham SPC/E K + parameters represent a safe choice in simulation studies of GQs, though variation of ion parameters can be used for specific simulation goals.

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1.

PubMed

Li, Wenbo; Lacey, Randy F; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Wen, Chi-Kuang; Binder, Brad M; Zhao, Yang

2017-04-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human.

Nuclear recoil effect on g-factor of heavy ions: prospects for tests of quantum electrodynamics in a new region

NASA Astrophysics Data System (ADS)

Malyshev, A. V.; Shabaev, V. M.; Glazov, D. A.; Tupitsyn, I. I.

2017-12-01

The nuclear recoil effect on the g-factor of H- and Li-like heavy ions is evaluated to all orders in αZ. The calculations include an approximate treatment of the nuclear size and the electron-electron interaction corrections to the recoil effect. As the result, the second largest contribution to the theoretical uncertainty of the g-factor values of 208Pb79+ and 238U89+ is strongly reduced. Special attention is paid to tests of the QED recoil effect on the g-factor in experiments with heavy ions. It is found that, while the QED recoil effect on the g-factor value is masked by the uncertainties of the nuclear size and nuclear polarization contributions, it can be probed on a few-percent level in the specific difference of the g-factors of H- and Li-like heavy ions. This provides a unique opportunity to test QED in a new region-strong-coupling regime beyond the Furry picture.

Nuclear Recoil Effect on the g-Factor of Heavy Ions: Prospects for Tests of Quantum Electrodynamics in a New Region

NASA Astrophysics Data System (ADS)

Malyshev, A. V.; Shabaev, V. M.; Glazov, D. A.; Tupitsyn, I. I.

2017-12-01

The nuclear recoil effect on the g-factor of H- and Li-like heavy ions is evaluated to all orders in αZ. The calculations include an approximate treatment of the nuclear size and the electron-electron interaction corrections to the recoil effect. As the result, the second largest contribution to the theoretical uncertainty of the g-factor values of 208Pb79+ and 238U89+ is strongly reduced. Special attention is paid to tests of the QED recoil effect on the g-factor in experiments with heavy ions. It is found that, while the QED recoil effect on the gfactor value is masked by the uncertainties of the nuclear size and nuclear polarization contributions, it can be probed on a few-percent level in the specific difference of the g-factors of H- and Li-like heavy ions. This provides a unique opportunity to test QED in a new region of the strong-coupling regime beyond the Furry picture.

Cobalt silicate hierarchical hollow spheres for lithium-ion batteries.

PubMed

Yang, Jun; Guo, Yuanyuan; Zhang, Yufei; Sun, Chencheng; Yan, Qingyu; Dong, Xiaochen

2016-09-09

In this paper, the synthesis of cobalt silicate novel hierarchical hollow spheres via a facile hydrothermal method is presented. With a unique hollow structure, the Co2SiO4 provides a large surface area, which can shorten the lithium ions diffusion length and effectively accommodate the volumetic variation during the lithiation/de-lithiation process. Serving as an anode material in lithium-ion battery application, the Co2SiO4 electrode demonstrates a high reversible specific capacity (first-cycle charge capacity of 948.6 mAh g(-1) at 100 mA g(-1)), a cycling durability (specific capacity of 791.4 mAh g(-1) after 100 cycles at 100 mA g(-1)), and a good rate capability (specific capacity of 349.4 mAh g(-1) at 10 A g(-1)). The results indicate that the cobalt silicate hierarchical hollow sphere holds the potential applications in energy storage electrodes.

Thermodynamics and kinetics of Na+/K+-formate ion pairs association in polarizable water: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Nguyen, Phuong T. M.; Nguyen, Van T.; Annapureddy, Harsha V. R.; Dang, Liem X.; Do, D. D.

2012-12-01

To enhance our understanding of ion specific activity in biological systems, the potential of mean force approach was utilized to study solvent effects on the interactions between two alkali cations (Na+ and K+) with a formate anion in water. A very complex free energy landscape was observed, much more so than alkali-halide ion pairs. Furthermore, a stronger binding between the Na+-formate pair was found in comparison to the K+-formate pair in water, which is in agreement with experimental and theoretical studies [1-4]. The kinetics of ion-pair inter-conversions was studied using the transition rate theory, along with a number of theoretical approaches such as the Kramers and Grote-Hynes theories. These kinetic results were used to predict solvent effects on dynamical features of ion-pair association, in which we have found that the dynamics of K+-formate pairs is faster than Na+-formate pairs.

Ion optics for high power 50-cm-diam ion thrusters

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.; Millis, Marc G.

1989-01-01

The process used at the NASA-Lewis to fabricate 30 and 50-cm-diameter ion optics is described. The ion extraction capabilities of the 30 and 50-cm diameter ion optics were evaluated on divergent field and ring-cusp discharge chambers and compared. Perveance was found to be sensitive to the effects of the type and power of the discharge chamber and to the accelerator electrode hole diameter. Levels of up to 0.64 N and 20 kW for thrust and input power, respectively, were demonstrated with the divergent-field discharge chamber. Thruster efficiencies and specific impulse values up to 79 percent and 5000 sec., respectively, were achieved with the ring-cusp discharge chamber.

Quenching the firefly bioluminescence by various ions.

PubMed

Zhang, Huateng; Bai, Haixiu; Jiang, Tianyu; Ma, Zhao; Cheng, Yanna; Zhou, Yubin; Du, Lupei; Li, Minyong

2016-02-01

The luciferase reporter gene assay system is broadly applied in various biomedical aspects, including signaling pathway dissection, transcriptional activity analysis, and genetic toxicity testing. It significantly improves the experimental accuracy and reduces the experimental error by the addition of an internal control. In the current research, we discovered some specific ions that could selectively inhibit firefly luciferase while having a negligible effect on renilla luciferase in vitro in the dual-reporter gene assay. We showed that these ionic compounds had a high potential of being utilized as quench-and-activate reagents in the dual-reporter assay. Furthermore, results from kinetic studies on ion-mediated quenching effects indicated that different ions have distinct inhibition modes. Our study is anticipated to guide a more affordable design of quench-and-activate reagents in biomedicine and pharmaceutical analysis.

In vitro cytotoxicity of superparamagnetic iron oxide nanoparticles on neuronal and glial cells. Evaluation of nanoparticle interference with viability tests.

PubMed

Costa, Carla; Brandão, Fátima; Bessa, Maria João; Costa, Solange; Valdiglesias, Vanessa; Kiliç, Gözde; Fernández-Bertólez, Natalia; Quaresma, Pedro; Pereira, Eulália; Pásaro, Eduardo; Laffon, Blanca; Teixeira, João Paulo

2016-03-01

Superparamagnetic iron oxide nanoparticles (ION) have attracted great interest for use in several biomedical fields. In general, they are considered biocompatible, but little is known of their effects on the human nervous system. The main objective of this work was to evaluate the cytotoxicity of two ION (magnetite), coated with silica and oleic acid, previously determining the possible interference of the ION with the methodological procedures to assure the reliability of the results obtained. Human neuroblastoma SHSY5Y and glioblastoma A172 cells were exposed to different concentrations of ION (5-300 µg ml(-1)), prepared in complete and serum-free cell culture medium for three exposure times (3, 6 and 24 h). Cytotoxicity was evaluated by means of the MTT, neutral red uptake and alamar blue assays. Characterization of the main physical-chemical properties of the ION tested was also performed. Results demonstrated that both ION could significantly alter absorbance readings. To reduce these interferences, protocols were modified by introducing additional washing steps and cell-free systems. Significant decreases in cell viability were observed for both cell lines in specific conditions by all assays. In general, oleic acid-coated ION were less cytotoxic than silica-coated ION; besides, a serum-protective effect was observed for both ION studied and cell lines. These results contribute to increase the knowledge of the potential harmful effects of ION on the human nervous system. Understanding these effects is essential to establish satisfactory regulatory policies on the safe use of magnetite nanoparticles in biomedical applications. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of Zn2+ binding and enzyme active site on the transition state for RNA 2'-O-transphosphorylation interpreted through kinetic isotope effects.

PubMed

Chen, Haoyuan; Piccirilli, Joseph A; Harris, Michael E; York, Darrin M

2015-11-01

Divalent metal ions, due to their ability to stabilize high concentrations of negative charge, are important for RNA folding and catalysis. Detailed models derived from the structures and kinetics of enzymes and from computational simulations have been developed. However, in most cases the specific catalytic modes involving metal ions and their mechanistic roles and effects on transition state structures remain controversial. Valuable information about the nature of the transition state is provided by measurement of kinetic isotope effects (KIEs). However, KIEs reflect changes in all bond vibrational modes that differ between the ground state and transition state. QM calculations are therefore essential for developing structural models of the transition state and evaluating mechanistic alternatives. Herein, we present computational models for Zn2+ binding to RNA 2'O-transphosphorylation reaction models that aid in the interpretation of KIE experiments. Different Zn2+ binding modes produce distinct KIE signatures, and one binding mode involving two zinc ions is in close agreement with KIEs measured for non-enzymatic catalysis by Zn2+ aquo ions alone. Interestingly, the KIE signatures in this specific model are also very close to those in RNase A catalysis. These results allow a quantitative connection to be made between experimental KIE measurements and transition state structure and bonding, and provide insight into RNA 2'O-ransphosphorylation reactions catalyzed by metal ions and enzymes. This article is part of a Special Issue entitled: Enzyme Transition States from Theory and Experiment. Copyright © 2015. Published by Elsevier B.V.

Establishing Ion Ratio Thresholds Based on Absolute Peak Area for Absolute Protein Quantification using Protein Cleavage Isotope Dilution Mass Spectrometry

PubMed Central

Loziuk, Philip L.; Sederoff, Ronald R.; Chiang, Vincent L.; Muddiman, David C.

2014-01-01

Quantitative mass spectrometry has become central to the field of proteomics and metabolomics. Selected reaction monitoring is a widely used method for the absolute quantification of proteins and metabolites. This method renders high specificity using several product ions measured simultaneously. With growing interest in quantification of molecular species in complex biological samples, confident identification and quantitation has been of particular concern. A method to confirm purity or contamination of product ion spectra has become necessary for achieving accurate and precise quantification. Ion abundance ratio assessments were introduced to alleviate some of these issues. Ion abundance ratios are based on the consistent relative abundance (RA) of specific product ions with respect to the total abundance of all product ions. To date, no standardized method of implementing ion abundance ratios has been established. Thresholds by which product ion contamination is confirmed vary widely and are often arbitrary. This study sought to establish criteria by which the relative abundance of product ions can be evaluated in an absolute quantification experiment. These findings suggest that evaluation of the absolute ion abundance for any given transition is necessary in order to effectively implement RA thresholds. Overall, the variation of the RA value was observed to be relatively constant beyond an absolute threshold ion abundance. Finally, these RA values were observed to fluctuate significantly over a 3 year period, suggesting that these values should be assessed as close as possible to the time at which data is collected for quantification. PMID:25154770

Hydration patterns and salting effects in sodium chloride solution.

PubMed

Li, Weifeng; Mu, Yuguang

2011-10-07

The salting effects of 2M sodium chloride electrolyte are studied based on a series of model solutes with properties ranging from hydrophobic to hydrophilic. Generally, hydrophobic solutes will be salted out and hydrophilic solutes will be salted in by NaCl solution. The solvation free energy changes are highly correlated with Kirkwood-Buff integrals. The underlying mechanism resorts to the preferential binding of ions and water to solutes. Our results demonstrate that the salting effect not only depends on the salt's position in Hofmeister series, but also on the solutes' specifics. Taking the hydration free energies of solutes and ions as independent variables, a schematic diagram of salting effects is suggested. The resolved multifaceted salting effects rely on the sensitive balance of the tripartite interaction among solutes, ions, and water. © 2011 American Institute of Physics

Photoluminescent carbon dots based on a rare 3D inorganic-organic hybrid cadmium borate crystal.

PubMed

Zhou, Kang; Zhang, Wen-Jin; Luo, Yuan-Zhang; Pan, Chun-Yang

2018-05-17

A 3D inorganic-organic hybridized skeleton cadmium borate [Cden][B5O8(OH)] (1) (en = ethylenediamine) has been solvothermally synthesized. By calcining it, specific shape carbon dots (C-dots) with abundant free radicals were observed. In addition, C-dots in the ethanol phase exhibited variable photoluminescence and showed rare turn on or off effects to Cr3+ ions and CdSe/ZnS quantum dots, but only a turn on effect to Cs+ ions and a turn off effect to CsPbBr3 quantum dots.

Salt exclusion in silane-laced epoxy coatings.

PubMed

Wang, Peng; Schaefer, Dale W

2010-01-05

The corrosion protection mechanism of a one-step silane-laced epoxy coating system was investigated using neutron reflectivity. Pure epoxy and silane-laced epoxy films were examined at equilibrium with saturated NaCl water solution. The results demonstrate that the addition of silane introduces a salt-exclusion effect to epoxy coating. Specifically, the addition of silane densifies the epoxy network, which leads to exclusion of hydrated salt ions by a size effect. The effect is particularly significant at the metal-coating interface. Exclusion of ions improves the corrosion resistance, particularly for metals susceptible to pitting.

A rapid total reflection X-ray fluorescence protocol for micro analyses of ion profiles in Arabidopsis thaliana

NASA Astrophysics Data System (ADS)

Höhner, Ricarda; Tabatabaei, Samaneh; Kunz, Hans-Henning; Fittschen, Ursula

2016-11-01

The ion homeostasis of macro and micronutrients in plant cells and tissues is a fundamental requirement for vital biochemical pathways including photosynthesis. In nature, ion homeostasis is affected mainly by three processes: 1. Environmental stress factors, 2. Developmental effects, and 3. Loss or gain-of-function mutations in the plant genome. Here we present a rapid total reflection X-ray fluorescence (TXRF) protocol that allows for simultaneous quantification of several elements such as potassium (K), calcium (Ca), sulfur (S), manganese (Mn) and strontium (Sr) in Arabidopsis thaliana leaf specimens. Our procedure is cost-efficient and enables precise, robust and highly reproducible measurements on tissue samples as small as 0.3 mg dry weight. As shown here, we apply the TXRF procedure to detect accurately the early replacement of K by Na ions in leaves of plants exposed to soil salinity, a globally increasing abiotic stress factor. Furthermore, we were able to prove the existence of a leaf development-dependent ion gradient for K, Ca, and other divalent ions in A. thaliana; i.e. old leaves contain significantly lower K but higher Ca than young leaves. Lastly, we show that our procedure can be readily applied to reveal subtle differences in tissue-specific ion contents of plant mutants. We employed independent A. thaliana kea1kea2 loss-of-function mutants that lack KEA1 and KEA2, two highly active chloroplast K exchange proteins. We found significantly increased K levels specifically in kea1kea2 mutants, i.e. 55 mg ∗ g- 1 dry weight, compared to 40 mg ∗ g- 1 dry weight in wild type plants. The TXRF procedure can be supplemented with Flame atomic absorption (FAAS) and emission spectrometry (FAES) to expand the detection range to sodium (Na) and magnesium (Mg). Because of the small sample amounts required, this method is especially suited to probe individual leaves in single plants or even specific leaf areas. Therefore, TXRF represents a powerful method to gain detailed quantitative insights into I) the effect of environmental stress on plant ion homeostasis, II) ion gradients between plant tissues, and III) ion levels in plant mutants with compromised growth or heterogeneous phenotypes.

SU-C-204-04: Irradiation of Human Cell Lines Using Various Ions

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

Lin, Y; McMahon, S; Kaminuma, T

2016-06-15

Purpose: The purpose of this study is to investigate and quantify the biological effects of ion radiation using several human cell lines. We aim to answer the question of whether carbon ion the most ideal ion species for heavy ion radiotherapy. Methods: The cells were irradiated at different positions along the pristine Bragg peak of several ions with different atomic number. The biological effectiveness was evaluated using the clonogenic cell survival assay. Irradiation of three human lung cancer cell lines and a fibroblast cell line were undertaken using the charged particle beam at the NASA Space Radiation Laboratory at Brookhavenmore » National Lab. Four mono-energetic ion beams (carbon, oxygen, helium and lithium) were used to irradiate the cells. Water or media-filled T25 flasks were lined up along the beam line so that the cell-containing surfaces of the flasks were placed at a specific depth along the pristine Bragg curve. Four depths along the curve, representing entrance point, rising peak, peak and distal fall off, were selected to determine biological effectiveness. Gaf-chromic films were placed between the flasks to monitor the irradiation as soon as it was finished. Results: For all ion radiations, the maximum cell killing effect occurs at either peak or distal fall off, depending on the cell lines. For instance, for the fibroblast cell line AGO1522, RBEs of 1.4, 1.2, 1.4 and 1.9 were observed at the Bragg peak for Helium, Lithium, Carbon and Oxygen ions. Comparing positions, RBEs of 0.9, 1.2, 1.4 and 1.8 were observed for carbon irradiation of AGO-1522 cells positions corresponding to entrance, rising peak, peak and distal fall off. Conclusion: RBE values differ with position in the Bragg peak, ion species and cell line. Ions other than carbon may prove more effective in certain irradiation conditions and may contribute to optimized heavy ion therapy.« less

Nanobodies that block gating of the P2X7 ion channel ameliorate inflammation.

PubMed

Danquah, Welbeck; Meyer-Schwesinger, Catherine; Rissiek, Björn; Pinto, Carolina; Serracant-Prat, Arnau; Amadi, Miriam; Iacenda, Domenica; Knop, Jan-Hendrik; Hammel, Anna; Bergmann, Philine; Schwarz, Nicole; Assunção, Joana; Rotthier, Wendy; Haag, Friedrich; Tolosa, Eva; Bannas, Peter; Boué-Grabot, Eric; Magnus, Tim; Laeremans, Toon; Stortelers, Catelijne; Koch-Nolte, Friedrich

2016-11-23

Ion channels are desirable therapeutic targets, yet ion channel-directed drugs with high selectivity and few side effects are still needed. Unlike small-molecule inhibitors, antibodies are highly selective for target antigens but mostly fail to antagonize ion channel functions. Nanobodies-small, single-domain antibody fragments-may overcome these problems. P2X7 is a ligand-gated ion channel that, upon sensing adenosine 5'-triphosphate released by damaged cells, initiates a proinflammatory signaling cascade, including release of cytokines, such as interleukin-1β (IL-1β). To further explore its function, we generated and characterized nanobodies against mouse P2X7 that effectively blocked (13A7) or potentiated (14D5) gating of the channel. Systemic injection of nanobody 13A7 in mice blocked P2X7 on T cells and macrophages in vivo and ameliorated experimental glomerulonephritis and allergic contact dermatitis. We also generated nanobody Dano1, which specifically inhibited human P2X7. In endotoxin-treated human blood, Dano1 was 1000 times more potent in preventing IL-1β release than small-molecule P2X7 antagonists currently in clinical development. Our results show that nanobody technology can generate potent, specific therapeutics against ion channels, confirm P2X7 as a therapeutic target for inflammatory disorders, and characterize a potent new drug candidate that targets P2X7. Copyright © 2016, American Association for the Advancement of Science.

Triplin, a small molecule, reveals copper ion transport in ethylene signaling from ATX1 to RAN1

PubMed Central

Li, Wenbo; Ye, Yajin; Lu, Juan; Yeh, Kuo-Chen; Xiao, Youli; Li, Laigeng; Binder, Brad M.

2017-01-01

Copper ions play an important role in ethylene receptor biogenesis and proper function. The copper transporter RESPONSIVE-TO-ANTAGONIST1 (RAN1) is essential for copper ion transport in Arabidopsis thaliana. However it is still unclear how copper ions are delivered to RAN1 and how copper ions affect ethylene receptors. There is not a specific copper chelator which could be used to explore these questions. Here, by chemical genetics, we identified a novel small molecule, triplin, which could cause a triple response phenotype on dark-grown Arabidopsis seedlings through ethylene signaling pathway. ran1-1 and ran1-2 are hypersensitive to triplin. Adding copper ions in growth medium could partially restore the phenotype on plant caused by triplin. Mass spectrometry analysis showed that triplin could bind copper ion. Compared to the known chelators, triplin acts more specifically to copper ion and it suppresses the toxic effects of excess copper ions on plant root growth. We further showed that mutants of ANTIOXIDANT PROTEIN1 (ATX1) are hypersensitive to tiplin, but with less sensitivity comparing with the ones of ran1-1 and ran1-2. Our study provided genetic evidence for the first time that, copper ions necessary for ethylene receptor biogenesis and signaling are transported from ATX1 to RAN1. Considering that triplin could chelate copper ions in Arabidopsis, and copper ions are essential for plant and animal, we believe that, triplin not only could be useful for studying copper ion transport of plants, but also could be useful for copper metabolism study in animal and human. PMID:28388654

Low voltage 30cm ion thruster

NASA Technical Reports Server (NTRS)

1972-01-01

The construction of an ion thruster module (including thruster, power conditioning, and control system) capable of operating for 10,000 hours over a five to one range at an effective specific impulse of approximately 2800 seconds is discussed. The several interrelated tasks involved in the construction of the engine are described. Performance tests of the engine and the effects of various modifications are reported. It was demonstrated that thruster performance and stability were not materially affected by reasonable changes from the nominal operating point.

Silicon oxide based high capacity anode materials for lithium ion batteries

DOEpatents

Deng, Haixia; Han, Yongbong; Masarapu, Charan; Anguchamy, Yogesh Kumar; Lopez, Herman A.; Kumar, Sujeet

2017-03-21

Silicon oxide based materials, including composites with various electrical conductive compositions, are formulated into desirable anodes. The anodes can be effectively combined into lithium ion batteries with high capacity cathode materials. In some formulations, supplemental lithium can be used to stabilize cycling as well as to reduce effects of first cycle irreversible capacity loss. Batteries are described with surprisingly good cycling properties with good specific capacities with respect to both cathode active weights and anode active weights.

Air ions and respiratory function outcomes: a comprehensive review

PubMed Central

2013-01-01

Background From a mechanistic or physical perspective there is no basis to suspect that electric charges on clusters of air molecules (air ions) would have beneficial or deleterious effects on respiratory function. Yet, there is a large lay and scientific literature spanning 80 years that asserts exposure to air ions affects the respiratory system and has other biological effects. Aims This review evaluates the scientific evidence in published human experimental studies regarding the effects of exposure to air ions on respiratory performance and symptoms. Methods We identified 23 studies (published 1933–1993) that met our inclusion criteria. Relevant data pertaining to study population characteristics, study design, experimental methods, statistical techniques, and study results were assessed. Where relevant, random effects meta-analysis models were utilized to quantify similar exposure and outcome groupings. Results The included studies examined the therapeutic benefits of exposure to negative air ions on respiratory outcomes, such as ventilatory function and asthmatic symptoms. Study specific sample sizes ranged between 7 and 23, and studies varied considerably by subject characteristics (e.g., infants with asthma, adults with emphysema), experimental method, outcomes measured (e.g., subjective symptoms, sensitivity, clinical pulmonary function), analytical design, and statistical reporting. Conclusions Despite numerous experimental and analytical differences across studies, the literature does not clearly support a beneficial role in exposure to negative air ions and respiratory function or asthmatic symptom alleviation. Further, collectively, the human experimental studies do not indicate a significant detrimental effect of exposure to positive air ions on respiratory measures. Exposure to negative or positive air ions does not appear to play an appreciable role in respiratory function. PMID:24016271

The effects of electron cyclotron heating and current drive on toroidal Alfvén eigenmodes in tokamak plasmas

NASA Astrophysics Data System (ADS)

Sharapov, S. E.; Garcia-Munoz, M.; Van Zeeland, M. A.; Bobkov, B.; Classen, I. G. J.; Ferreira, J.; Figueiredo, A.; Fitzgerald, M.; Galdon-Quiroga, J.; Gallart, D.; Geiger, B.; Gonzalez-Martin, J.; Johnson, T.; Lauber, P.; Mantsinen, M.; Nabais, F.; Nikolaeva, V.; Rodriguez-Ramos, M.; Sanchis-Sanchez, L.; Schneider, P. A.; Snicker, A.; Vallejos, P.; the AUG Team; the EUROfusion MST1 Team

2018-01-01

Dedicated studies performed for toroidal Alfvén eigenmodes (TAEs) in ASDEX-Upgrade (AUG) discharges with monotonic q-profiles have shown that electron cyclotron resonance heating (ECRH) can make TAEs more unstable. In these AUG discharges, energetic ions driving TAEs were obtained by ion cyclotron resonance heating (ICRH). It was found that off-axis ECRH facilitated TAE instability, with TAEs appearing and disappearing on timescales of a few milliseconds when the ECRH power was switched on and off. On-axis ECRH had a much weaker effect on TAEs, and in AUG discharges performed with co- and counter-current electron cyclotron current drive (ECCD), the effects of ECCD were found to be similar to those of ECRH. Fast ion distributions produced by ICRH were computed with the PION and SELFO codes. A significant increase in T e caused by ECRH applied off-axis is found to increase the fast ion slowing-down time and fast ion pressure causing a significant increase in the TAE drive by ICRH-accelerated ions. TAE stability calculations show that the rise in T e causes also an increase in TAE radiative damping and thermal ion Landau damping, but to a lesser extent than the fast ion drive. As a result of the competition between larger drive and damping effects caused by ECRH, TAEs become more unstable. It is concluded, that although ECRH effects on AE stability in present-day experiments may be quite significant, they are determined by the changes in the plasma profiles and are not particularly ECRH specific.

Method and apparatus for removing ions from soil

DOEpatents

Bibler, J.P.

1993-03-02

A method and apparatus are presented for selectively removing species of ions from an area of soil. Permeable membranes 14 and 18 impregnated with an ion exchange resin that is specific to one or more species of chemical ions are inserted into ground 12 in close proximity to, and on opposing sides of, a soil area of interest 22. An electric potential is applied across electrodes 26 and 28 to cause the migration of ions out of soil area 22 toward the membranes 14 and 18. Preferably, the resin exchanges ions of sodium or hydrogen for ions of mercury that it captures from soil area 22. Once membranes 14 and 18 become substantially saturated with mercury ions, the potential applied across electrodes 26 and 28 is discontinued and membranes 14 and 18 are preferably removed from soil 12 for storage or recovery of the ions. The membranes are also preferably impregnated with a buffer to inhibit the effect of the hydrolysis of water by current from the electrodes.

Method and apparatus for removing ions from soil

DOEpatents

Bibler, Jane P.

1993-01-01

A method and apparatus for selectively removing species of ions from an area of soil. Permeable membranes 14 and 18 impregnated with an ion exchange resin that is specific to one or more species of chemical ions are inserted into ground 12 in close proximity to, and on opposing sides of, a soil area of interest 22. An electric potential is applied across electrodes 26 and 28 to cause the migration of ions out of soil area 22 toward the membranes 14 and 18. Preferably, the resin exchanges ions of sodium or hydrogen for ions of mercury that it captures from soil area 22. Once membranes 14 and 18 become substantially saturated with mercury ions, the potential applied across electrodes 26 and 28 is discontinued and membranes 14 and 18 are preferably removed from soil 12 for storage or recovery of the ions. The membranes are also preferably impregnated with a buffer to inhibit the effect of the hydrolysis of water by current from the electrodes.

Ion-plasma protective coatings for gas-turbine engine blades

NASA Astrophysics Data System (ADS)

Kablov, E. N.; Muboyadzhyan, S. A.; Budinovskii, S. A.; Lutsenko, A. N.

2007-10-01

Evaporated, diffusion, and evaporation—diffusion protective and hardening multicomponent ionplasma coatings for turbine and compressor blades and other gas-turbine engine parts are considered. The processes of ion surface treatment (ion etching and ion saturation of a surface in the metallic plasma of a vacuum arc) and commercial equipment for the deposition of coatings and ion surface treatment are analyzed. The specific features of the ion-plasma coatings deposited from the metallic plasma of a vacuum arc are described, and the effect of the ion energy on the phase composition of the coatings and the processes occurring in the surface layer of an article to be treated are discussed. Some properties of ion-plasma coatings designed for various purposes are presented. The ion surface saturation of articles made from structural materials is shown to change the structural and phase states of their surfaces and, correspondingly, the related properties of these materials (i.e., their heat resistance, corrosion resistance, fatigue strength, and so on).

Modeling electrokinetics in ionic liquids: General

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

Wang, Chao; Bao, Jie; Pan, Wenxiao

2017-04-07

Using direct numerical simulations we provide a thorough study on the electrokinetics of ionic liquids. In particular, the modfied Poisson-Nernst-Planck (MPNP) equations are solved to capture the crowding and overscreening effects that are the characteristics of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the MPNP equations are coupled with the Navier-Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel plates, charging dynamics in a 2D straight-walled pore, electro-osmotic ow in a nano-channel, electroconvective instability on a plane ion-selective surface, and electroconvective ow onmore » a curved ion-selective surface. We discuss how the crowding and overscreening effects and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less

Sensitive and comprehensive detection of chemical warfare agents in air by atmospheric pressure chemical ionization ion trap tandem mass spectrometry with counterflow introduction.

PubMed

Seto, Yasuo; Sekiguchi, Hiroshi; Maruko, Hisashi; Yamashiro, Shigeharu; Sano, Yasuhiro; Takayama, Yasuo; Sekioka, Ryoji; Yamaguchi, Shintaro; Kishi, Shintaro; Satoh, Takafumi; Sekiguchi, Hiroyuki; Iura, Kazumitsu; Nagashima, Hisayuki; Nagoya, Tomoki; Tsuge, Kouichiro; Ohsawa, Isaac; Okumura, Akihiko; Takada, Yasuaki; Ezawa, Naoya; Watanabe, Susumu; Hashimoto, Hiroaki

2014-05-06

A highly sensitive and specific real-time field-deployable detection technology, based on counterflow air introduction atmospheric pressure chemical ionization, has been developed for a wide range of chemical warfare agents (CWAs) comprising gaseous (two blood agents, three choking agents), volatile (six nerve gases and one precursor agent, five blister agents), and nonvolatile (three lachrymators, three vomiting agents) agents in air. The approach can afford effective chemical ionization, in both positive and negative ion modes, for ion trap multiple-stage mass spectrometry (MS(n)). The volatile and nonvolatile CWAs tested provided characteristic ions, which were fragmented into MS(3) product ions in positive and negative ion modes. Portions of the fragment ions were assigned by laboratory hybrid mass spectrometry (MS) composed of linear ion trap and high-resolution mass spectrometers. Gaseous agents were detected by MS or MS(2) in negative ion mode. The limits of detection for a 1 s measurement were typically at or below the microgram per cubic meter level except for chloropicrin (submilligram per cubic meter). Matrix effects by gasoline vapor resulted in minimal false-positive signals for all the CWAs and some signal suppression in the case of mustard gas. The moisture level did influence the measurement of the CWAs.

Effects of Replacement of External Sodium Chloride with Sucrose on Membrane Currents of the Squid Giant Axon

PubMed Central

Adelman, William J.; Taylor, Robert E.

1964-01-01

It was observed that a reduction of the sodium chloride concentration in the external solution bathing a squid giant axon by replacement with sucrose resulted in marked decreases in the peak inward and steady-state outward currents through the axon membrane following a step decrease in membrane potential. These effects are quantitatively acounted for by the increase in series resistance resulting from the decreased conductivity of the sea water and the assumption that the sodium current obeys a relation of the form I = k1C1 - k2C2 where C1, C2 are internal and external ion activities and k1, k2 are independent of concentration. It is concluded that the potassium ion current is independent of the sodium concentration. That the inward current is carried by sodium ions has been confirmed. The electrical potential (or barrier height) profile in the membrane which drives sodium ions appears to be independent of sodium ion concentration or current. A specific effect of the sucrose on hyperpolarizing currents was observed and noted but not investigated in detail. PMID:14232131

UREA/ammonium ion removal system for the orbiting frog otolith experiment. [ion exchange resins for water treatment during space missions

NASA Technical Reports Server (NTRS)

Schulz, J. R.; Anselmi, R. T.

1976-01-01

The feasibility of using free urease enzyme and ANGC-101 ion exchange resin to remove urea and ammonium ion for space system waste water applications was studied. Specifically examined is the prevention of urea and ammonia toxicity in a 30-day Orbiting Frog Otolith (OFO) flight experiment. It is shown that free urease enzyme used in conjunction with ANGC-101 ion-exchange resin and pH control can control urea and amonium ion concentration in unbuffered recirculating water. In addition, the resin does not adversely effect the bullfrogs by lowering the concentration of cations below critical minimum levels. Further investigations on bioburden control, frog waste excretion on an OFO diet, a trade-off analysis of methods of automating the urea/ammonium ion removal system and fabrication and test of a semiautomated breadboard were recommended as continuing efforts. Photographs of test equipment and test animals are shown.

Energetic heavy ion dominance in the outer magnetosphere

NASA Astrophysics Data System (ADS)

Cohen, Ian; Mitchell, Don; Mauk, Barry; Anderson, Brian; Ohtani, Shin; Kistler, Lynn; Hamilton, Doug; Turner, Drew; Blake, Bern; Fennell, Joe; Jaynes, Allison; Leonard, Trevor; Gerrard, Andy; Lanzerotti, Lou; Burch, Jim

2017-04-01

Despite the extensive study of ring current ion composition, little exists in the literature regarding the nature of energetic ions with energies >200 keV, especially in the outer magnetosphere (r > 9 RE). In particular, information on the relative fluxes and spectral shapes of the different ion species over these energy ranges is lacking. However, new observations from the Energetic Ion Spectrometer (EIS) instruments on the Magnetospheric Multiscale (MMS) spacecraft have revealed the dominance of heavy ion species (specifically oxygen and helium) at these energies in the outer magnetosphere. This result is supported by prior but previously unreported observations obtained by the Geotail spacecraft, which also show that these heavy ion species are primarily dominated by multiply-charged populations from the solar wind. Using additional observations from the inner magnetosphere obtained by the RBSPICE instrument on the Van Allen Probes suggest, we will investigate whether this effect is due to a preferential loss of protons in the outer magnetosphere.

Electroviscous Effects in Ceramic Nanofiltration Membranes.

PubMed

Farsi, Ali; Boffa, Vittorio; Christensen, Morten Lykkegaard

2015-11-16

Membrane permeability and salt rejection of a γ-alumina nanofiltration membrane were studied and modeled for different salt solutions. Salt rejection was predicted by using the Donnan-steric pore model, in which the extended Nernst-Planck equation was applied to predict ion transport through the pores. The solvent flux was modeled by using the Hagen-Poiseuille equation by introducing electroviscosity instead of bulk viscosity. γ-Alumina particles were used for ζ-potential measurements. The ζ-potential measurements show that monovalent ions did not adsorb on the γ-alumina surface, whereas divalent ions were highly adsorbed. Thus, for divalent ions, the model was modified, owing to pore shrinkage caused by ion adsorption. The ζ-potential lowered the membrane permeability, especially for membranes with a pore radius lower than 3 nm, a ζ-potential higher than 20 mV, and an ionic strength lower than 0.01 m. The rejection model showed that, for a pore radius lower than 3 nm and for solutions with ionic strengths lower than 0.01 m, there is an optimum ζ-potential for rejection, because of the concurrent effects of electromigration and convection. Hence, the model can be used as a prediction tool to optimize membrane perm-selectivity by designing a specific pore size and surface charge for application at specific ionic strengths and pH levels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery

PubMed Central

Imbrici, Paola; Liantonio, Antonella; Camerino, Giulia M.; De Bellis, Michela; Camerino, Claudia; Mele, Antonietta; Giustino, Arcangela; Pierno, Sabata; De Luca, Annamaria; Tricarico, Domenico; Desaphy, Jean-Francois; Conte, Diana

2016-01-01

In the human genome more than 400 genes encode ion channels, which are transmembrane proteins mediating ion fluxes across membranes. Being expressed in all cell types, they are involved in almost all physiological processes, including sense perception, neurotransmission, muscle contraction, secretion, immune response, cell proliferation, and differentiation. Due to the widespread tissue distribution of ion channels and their physiological functions, mutations in genes encoding ion channel subunits, or their interacting proteins, are responsible for inherited ion channelopathies. These diseases can range from common to very rare disorders and their severity can be mild, disabling, or life-threatening. In spite of this, ion channels are the primary target of only about 5% of the marketed drugs suggesting their potential in drug discovery. The current review summarizes the therapeutic management of the principal ion channelopathies of central and peripheral nervous system, heart, kidney, bone, skeletal muscle and pancreas, resulting from mutations in calcium, sodium, potassium, and chloride ion channels. For most channelopathies the therapy is mainly empirical and symptomatic, often limited by lack of efficacy and tolerability for a significant number of patients. Other channelopathies can exploit ion channel targeted drugs, such as marketed sodium channel blockers. Developing new and more specific therapeutic approaches is therefore required. To this aim, a major advancement in the pharmacotherapy of channelopathies has been the discovery that ion channel mutations lead to change in biophysics that can in turn specifically modify the sensitivity to drugs: this opens the way to a pharmacogenetics strategy, allowing the development of a personalized therapy with increased efficacy and reduced side effects. In addition, the identification of disease modifiers in ion channelopathies appears an alternative strategy to discover novel druggable targets. PMID:27242528

Therapeutic Approaches to Genetic Ion Channelopathies and Perspectives in Drug Discovery.

PubMed

Imbrici, Paola; Liantonio, Antonella; Camerino, Giulia M; De Bellis, Michela; Camerino, Claudia; Mele, Antonietta; Giustino, Arcangela; Pierno, Sabata; De Luca, Annamaria; Tricarico, Domenico; Desaphy, Jean-Francois; Conte, Diana

2016-01-01

In the human genome more than 400 genes encode ion channels, which are transmembrane proteins mediating ion fluxes across membranes. Being expressed in all cell types, they are involved in almost all physiological processes, including sense perception, neurotransmission, muscle contraction, secretion, immune response, cell proliferation, and differentiation. Due to the widespread tissue distribution of ion channels and their physiological functions, mutations in genes encoding ion channel subunits, or their interacting proteins, are responsible for inherited ion channelopathies. These diseases can range from common to very rare disorders and their severity can be mild, disabling, or life-threatening. In spite of this, ion channels are the primary target of only about 5% of the marketed drugs suggesting their potential in drug discovery. The current review summarizes the therapeutic management of the principal ion channelopathies of central and peripheral nervous system, heart, kidney, bone, skeletal muscle and pancreas, resulting from mutations in calcium, sodium, potassium, and chloride ion channels. For most channelopathies the therapy is mainly empirical and symptomatic, often limited by lack of efficacy and tolerability for a significant number of patients. Other channelopathies can exploit ion channel targeted drugs, such as marketed sodium channel blockers. Developing new and more specific therapeutic approaches is therefore required. To this aim, a major advancement in the pharmacotherapy of channelopathies has been the discovery that ion channel mutations lead to change in biophysics that can in turn specifically modify the sensitivity to drugs: this opens the way to a pharmacogenetics strategy, allowing the development of a personalized therapy with increased efficacy and reduced side effects. In addition, the identification of disease modifiers in ion channelopathies appears an alternative strategy to discover novel druggable targets.

IONIC EFFECTS ON LIGNIFICATION AND PEROXIDASE IN TISSUE CULTURES

PubMed Central

Lipetz, Jacques; Garro, Anthony J.

1965-01-01

Crown-gall tumor tissue cultures release peroxidase into the medium in response to the concentration of specific ions in the medium. This release is not due to diffusion from cut surfaces or injured cells. Calcium, magnesium, and ammonium were, in that order, most effective in increasing peroxidase release. The enzyme was demonstrated cytochemically on the cell walls and in the cytoplasm. Cell wall fractions, exhaustively washed in buffer, still contained bound peroxidase. This bound peroxidase could be released by treating the wall fractions with certain divalent cations or ammonium. The order of effectiveness for removing the enzyme from the washed cell walls is: Ca++ ≈ Sr++ > Ba++ > Mg++ > NH4 +. These data support the thesis presented that specific ions can control the deposition of lignin on cell walls by affecting the peroxidase levels on these walls. PMID:19866650

Electrostatic effects on clustering and ion dynamics in ionomer melts

NASA Astrophysics Data System (ADS)

Ma, Boran; Nguyen, Trung; Pryamitsyn, Victor; Olvera de La Cruz, Monica

An understanding of the relationships between ionomer chain morphology, dynamics and counter-ion mobility is a key factor in the design of ion conducting membranes for battery applications. In this study, we investigate the influence of electrostatic coupling between randomly charged copolymers (ionomers) and counter ions on the structural and dynamic features of a model system of ionomer melts. Using coarse-grained molecular dynamics (CGMD) simulations, we found that variations in electrostatic coupling strength (Γ) remarkably affect the formation of ion-counter ion clusters, ion mobility, and polymer dynamics for a range of charged monomer fractions. Specifically, an increase in Γ leads to larger ionic cluster sizes and reduced polymer and ion mobility. Analysis of the distribution of the radius of gyration of the clusters further reveals that the fractal dimension of the ion clusters is nearly independent from Γ for all the cases studied. Finally, at sufficiently high values of Γ, we observed arrested heterogeneous ions mobility, which is correlated with an increase in ion cluster size. These findings provide insight into the role of electrostatics in governing the nanostructures formed by ionomers.

Multifunctional mesoporous bioactive glasses for effective delivery of therapeutic ions and drug/growth factors.

PubMed

Wu, Chengtie; Chang, Jiang

2014-11-10

Regeneration of large-size bone defects represents a significant challenge clinically, which requires the use of scaffolds with multifunction, such as anti-bacterial activity, and stimulation of osteogenesis and angiogenesis. It is known that functional ions or drug/growth factors play an important role to stimulate tissue regeneration. Mesoporous bioactive glasses (MBG) possess excellent bioactivity and drug-delivery ability as well as effective ionic release in the body fluids microenvironment due to its specific mesoporous structure and large surface area. For these reasons, functional ions (e.g. lithium (Li), strontium (Sr), Copper (Cu) and Boron (B)) and drug/growth factors (e.g. dexamethasone, vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)) have been incorporated into MBG, which shows high loading efficiency and effective release. The release of therapeutic ions and drug/growth factors from MBG offers it multifunctional properties, such as improved osteogenesis, angiogenesis, anti-bacterial/cancer activity. However, there is no a systematic review about delivery of therapeutic ions and drugs/growth factors from MBG for the functional effect on the tissue regeneration despite that significant progress has been achieved in the past five years. Therefore, in this review, we mainly focused on the new advances for the functional effect of delivering therapeutic ions and drugs/growth factors on the ostegeogenesis, angiogenesis and antibacterial activity. It is expected that the review will offer new concept to develop multifunctional biomaterials for bone regeneration by the synergistic effect of therapeutic ions and drug/growth factors. Copyright © 2014 Elsevier B.V. All rights reserved.

Aminoglycoside antibiotics as a tool for the study of the biological role of calcium ions. Historical overview.

PubMed

Corrado, A P; de Morais, I P; Prado, W A

1989-01-01

Beginning with the pioneering work of Vital-Brazil and Corrado (1957), which suggested a possible interaction between aminoglycoside antibiotics (AGA) and calcium ions at the neuromuscular junction, the authors review the studies that demonstrated the existence of a competitive antagonism between AGA and calcium ions. In view of the low liposolubility of AGA and their inability to cross biological membranes, this antagonism seems to occur exclusively at calcium-binding sites at the level of the outer opening of calcium channels of the N-subtype, which are also the sites of interaction of omega-conotoxin. Being highly water soluble, AGA are easily removed from their binding sites with a consequent rapid reversal of their effects, a factor of primary importance to explain their wide use as tools in the pharmacological analysis of the study of the biological role of calcium ion on the membrane's outer surface. This use has advantages over the use of inorganic di- and trivalent cations such as Mg2+, Mn2+, Cd2+, Ni2+, La3+, etc., since the latter, though they are considered to be the most specific competitive antagonists of calcium ions, may induce biphasic effects due to their ability to cross the membranes and replace calcium and/or increase intracellular calcium concentration. The performance of AGA is also superior when compared with the so-called "specific" organic calcium antagonists--verapamil and nifedipine derivatives--since the latter, in addition to inducing possible biphasic effects, antagonize calcium in a non-competitive manner. Finally, the authors remark that AGA-Ca2+ antagonism relevance is not limited only to basic aspects and that it may have therapeutic implications since it provides alternatives for reducing the toxic adverse effects of this important group of antibiotics.

A small electron beam ion trap/source facility for electron/neutral–ion collisional spectroscopy in astrophysical plasmas

NASA Astrophysics Data System (ADS)

Liang, Gui-Yun; Wei, Hui-Gang; Yuan, Da-Wei; Wang, Fei-Lu; Peng, Ji-Min; Zhong, Jia-Yong; Zhu, Xiao-Long; Schmidt, Mike; Zschornack, Günter; Ma, Xin-Wen; Zhao, Gang

2018-01-01

Spectra are fundamental observation data used for astronomical research, but understanding them strongly depends on theoretical models with many fundamental parameters from theoretical calculations. Different models give different insights for understanding a specific object. Hence, laboratory benchmarks for these theoretical models become necessary. An electron beam ion trap is an ideal facility for spectroscopic benchmarks due to its similar conditions of electron density and temperature compared to astrophysical plasmas in stellar coronae, supernova remnants and so on. In this paper, we will describe the performance of a small electron beam ion trap/source facility installed at National Astronomical Observatories, Chinese Academy of Sciences.We present some preliminary experimental results on X-ray emission, ion production, the ionization process of trapped ions as well as the effects of charge exchange on the ionization.

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials

NASA Astrophysics Data System (ADS)

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S.; Zeng, Xiao Cheng; Wang, Jianjun

2017-05-01

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4+/-4.1 to 277.5+/-30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering.

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials

PubMed Central

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S.; Zeng, Xiao Cheng; Wang, Jianjun

2017-01-01

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4±4.1 to 277.5±30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering. PMID:28462937

Ion-specific ice recrystallization provides a facile approach for the fabrication of porous materials.

PubMed

Wu, Shuwang; Zhu, Chongqin; He, Zhiyuan; Xue, Han; Fan, Qingrui; Song, Yanlin; Francisco, Joseph S; Zeng, Xiao Cheng; Wang, Jianjun

2017-05-02

Ice recrystallization is of great importance to both fundamental research and practical applications, however understanding and controlling ice recrystallization processes remains challenging. Here, we report the discovery of an ion-specific effect on ice recrystallization. By simply changing the initial type and concentration of ions in an aqueous solution, the size of ice grains after recrystallization can be tuned from 27.4±4.1 to 277.5±30.9 μm. Molecular dynamics simulations show that the ability of the ion to be incorporated into the ice phase plays a key role in the ultimate size of the ice grains after recrystallization. Moreover, by using recrystallized ice crystals as templates, 2D and 3D porous networks with tuneable pore sizes could be prepared from various materials, for example, NaBr, collagen, quantum dots, silver and polystyrene colloids. These porous materials are suitable for a wide range of applications, for example, in organic electronics, catalysis and bioengineering.

A conserved residue, PomB-F22, in the transmembrane segment of the flagellar stator complex, has a critical role in conducting ions and generating torque.

PubMed

Terauchi, Takashi; Terashima, Hiroyuki; Kojima, Seiji; Homma, Michio

2011-08-01

Bacterial flagellar motors exploit the electrochemical potential gradient of a coupling ion (H(+) or Na(+)) as their energy source, and are composed of stator and rotor proteins. Sodium-driven and proton-driven motors have the stator proteins PomA and PomB or MotA and MotB, respectively, which interact with each other in their transmembrane (TM) regions to form an ion channel. The single TM region of PomB or MotB, which forms the ion-conduction pathway together with TM3 and TM4 of PomA or MotA, respectively, has a highly conserved aspartate residue that is the ion binding site and is essential for rotation. To investigate the ion conductivity and selectivity of the Na(+)-driven PomA/PomB stator complex, we replaced conserved residues predicted to be near the conserved aspartate with H(+)-type residues, PomA-N194Y, PomB-F22Y and/or PomB-S27T. Motility analysis revealed that the ion specificity was not changed by either of the PomB mutations. PomB-F22Y required a higher concentration of Na(+) to exhibit swimming, but this effect was suppressed by additional mutations, PomA-N194Y or PomB-S27T. Moreover, the motility of the PomB-F22Y mutant was resistant to phenamil, a specific inhibitor for the Na(+) channel. When PomB-F22 was changed to other amino acids and the effects on swimming ability were investigated, replacement with a hydrophilic residue decreased the maximum swimming speed and conferred strong resistance to phenamil. From these results, we speculate that the Na(+) flux is reduced by the PomB-F22Y mutation, and that PomB-F22 is important for the effective release of Na(+) from PomB-D24.

Unidirectional Flux Balance of Monovalent Ions in Cells with Na/Na and Li/Na Exchange: Experimental and Computational Studies on Lymphoid U937 Cells

PubMed Central

Vereninov, Igor A.; Yurinskaya, Valentina E.; Model, Michael A.; Vereninov, Alexey A.

2016-01-01

Monovalent ion traffic across the cell membrane occurs via various pathways. Evaluation of individual fluxes in whole cell is hampered by their strong interdependence. This difficulty can be overcome by computational analysis of the whole cell flux balance. However, the previous computational studies disregarded ion movement of the self-exchange type. We have taken this exchange into account. The developed software allows determination of unidirectional fluxes of all monovalent ions via the major pathways both under the balanced state and during transient processes. We show how the problem of finding the rate coefficients can be solved by measurement of monovalent ion concentrations and some of the fluxes. Interdependence of fluxes due to the mandatory conditions of electroneutrality and osmotic balance and due to specific effects can be discriminated, enabling one to identify specific changes in ion transfer machinery under varied conditions. To test the effectiveness of the developed approach we made use of the fact that Li/Na exchange is known to be an analogue of the coupled Na/Na exchange. Thus, we compared the predicted and experimental data obtained on U937 cells under varied Li+ concentrations and following inhibition of the sodium pump with ouabain. We found that the coupled Na/Na exchange in U937 cells comprises a significant portion of the entire Na+ turnover. The data showed that the loading of the sodium pump by Li/Na exchange involved in the secondary active Li+ transport at 1–10 mM external Li+ is small. This result may be extrapolated to similar Li+ and Na+ flux relationships in erythrocytes and other cells in patients treated with Li+ in therapeutic doses. The developed computational approach is applicable for studying various cells and can be useful in education for demonstrating the effects of individual transporters and channels on ion gradients, cell water content and membrane potential. PMID:27159324

Swift heavy ion-induced radiation damage in isotropic graphite studied by micro-indentation and in-situ electrical resistivity

NASA Astrophysics Data System (ADS)

Hubert, Christian; Voss, Kay Obbe; Bender, Markus; Kupka, Katharina; Romanenko, Anton; Severin, Daniel; Trautmann, Christina; Tomut, Marilena

2015-12-01

Due to its excellent thermo-physical properties and radiation hardness, isotropic graphite is presently the most promising material candidate for new high-power ion accelerators which will provide highest beam intensities and energies. Under these extreme conditions, specific accelerator components including production targets and beam protection modules are facing the risk of degradation due to radiation damage. Ion-beam induced damage effects were tested by irradiating polycrystalline, isotropic graphite samples at the UNILAC (GSI, Darmstadt) with 4.8 MeV per nucleon 132Xe, 150Sm, 197Au, and 238U ions applying fluences between 1 × 1011 and 1 × 1014 ions/cm2. The overall damage accumulation and its dependence on energy loss of the ions were studied by in situ 4-point resistivity measurements. With increasing fluence, the electric resistivity increases due to disordering of the graphitic structure. Irradiated samples were also analyzed off-line by means of micro-indentation in order to characterize mesoscale effects such as beam-induced hardening and stress fields within the specimen. With increasing fluence and energy loss, hardening becomes more pronounced.

Amperometric biosensors for the determination of heavy metals

NASA Astrophysics Data System (ADS)

Compagnone, Dario; Palleschi, Giuseppe; Varallo, Giuseppe; Imperiali, PierLuigi

1995-10-01

A bioelectrochemical method for the determination of heavy metal ions has been developed. This method is based on the inhibition effect of metal ions on the enzymatic activity of oxidase enzymes. The enzymatic activity was determined with an amperometric hydrogen peroxide probe. The inhibition effect on enzymes in solution and covalently immobilized on polymeric supports has been evaluated. Hg(II) was the metal ion that inhibited almost all the enzymes, particularly glycerol-3-P oxidase. Hg(II) was detected in the 0.05/0.5 ppm range with the enzyme in solution. Calibration curves for Hg(II) were also obtained with the other oxidase enzymes in the 0.5/10 ppm range. The other metal ions tested inhibited the enzymes more specifically. The metal ion/enzyme systems which gave the best inhibition were Se(IV)/glutathione oxidase, Ni(II)/sarcosine oxidase, V(V)/glutathione oxidase, Cu(II)/alcohol oxidase from Pichia Pastoris and Cd(II)/D-aminoacid oxidase. All these metal ions were detected in the 0.1/10 ppm range using the enzymes in solution or covalently immobilized.

A novel approach to TEM preparation with a (7-axis stage) triple-beam FIB-SEM system

NASA Astrophysics Data System (ADS)

Clarke, Jamil J.

2015-10-01

Preparation of lamellae from bulk to grid for Cs-corrected Transmission Electron Microscope (TEM) observation has mostly become routine work on the latest FIB-SEM systems, with standardized techniques that often are left to automation for the initial steps. The finalization of lamellae however, has mostly become, non-routine, non-repeatable and often driven by user experience level in most cases to produce high quality damage-less cross section. Materials processing of the latest technologies, with ever-shrinking Nano-sized structures pose challenges to modern FIB-SEM systems. This can often lead to specialized techniques and hyper-specific functions for producing ultra-thin high quality lamellae that often are lab specific, preventing practical use of such techniques across multiple materials and applications. Several factors that should be incorporated in processing fine structured materials successfully include how the use of electron and ion scan conditions can affect a thin section during ion milling, the type of ion species applied for material processing during the finalization of lamellae with gallium ions or of a smaller ion species type such as Ar/Xe, sample orientation of the lamella during the thinning process which is linked to ion beam incident angle as a direct relationship in the creation of waterfall effects or curtain effects, and how software can be employed to aid in the reduction of these artifacts with reproducible results regardless of FIB-SEM experience for site-specific lift outs. A traditional TEM preparation was performed of a fine structure specimen in pursuit of a process technique to produce a high quality TEM lamella which would address all of the factors mentioned. These new capabilities have been refined and improved upon during the FIB-SEM design and development stages with an end result of a new approach that yields an improvement in quality by the reduction of common ion milling artifacts such as curtain effects, amorphous material, and better pin pointing of the area of interest while reducing overall processing time for the TEM sample preparation process and enhancing repeatability through ease of use via software controls. The development of these new technologies, incorporating a third Ar/Xe ion beam column in conjunction with the electron and gallium ion beam column, a 7-axis stage for enhanced sample orientation with tilt functions in two axes and automated swing control along with a host of additional functions which address the factors aforementioned such as electron and ion scan techniques and curtain effect removal by the use of hardware and software components that are key to reduce typical FIB related artifacts, all of which are called "ACE [Anti Curtaining Effect] Technologies" are explained. The overall developments of these technologies are to address a significant point that productivity, throughput and repeatability are comprised by synergy between the user, application, software and hardware within a FIB-SEM system. The latest Hitachi FIB-SEM platform offers these innovations for reliability, repeatability and high quality lamella preparation for Cs-corrected (S)TEMs.

Wave Effects Related to Altitude Variations in the Ion Composition of the Ionosphere

NASA Astrophysics Data System (ADS)

Vavilov, D. I.; Shklyar, D. R.

2016-12-01

Properties of the waves, which can propagate in a magnetized plasma in the frequency range below the proton gyrofrequency, depend strongly on the ion composition of the plasma. Addition of a new sort of ions leads to the appearance of a new resonance frequency, at which the refractive index becomes infinite, and a new cutoff frequency, at which the refractive index becomes zero. In this case, the topology of frequency dependence of the squared refractive index changes. Specifically, a new oscillation branch appears, which is located above the cutoff frequency. A question arises whether these oscillations are excited if radiation with the corresponding frequency, which propagates in a different mode, is present in the plasma. A linear transformation of the waves is another important effect, which is related to variations in the ion plasma composition. These two issues, which are directly related to the theory of formation of proton whistlers in the ionosphere, where the ion composition varies with altitude, are considered in this work.

Theoretical studies of the solar atmosphere and interstellar pickup ions

NASA Technical Reports Server (NTRS)

1994-01-01

Solar atmosphere research activities are summarized. Specific topics addressed include: (1) coronal mass ejections and related phenomena; (2) parametric instabilities of Alfven waves; (3) pickup ions in the solar wind; and (4) cosmic rays in the outer heliosphere. Also included is a list of publications covering the following topics: catastrophic evolution of a force-free flux rope; maximum energy release in flux-rope models of eruptive flares; sheet approximations in models of eruptive flares; material ejection, motions of loops and ribbons of two-ribbon flares; dispersion relations for parametric instabilities of parallel-propagating; parametric instabilities of parallel-propagating Alfven waves; beat, modulation, and decay instabilities of a circularly-polarized Alfven wave; effects of time-dependent photoionization on interstellar pickup helium; observation of waves generated by the solar wind pickup of interstellar hydrogen ions; ion thermalization and wave excitation downstream of the quasi-perpendicular bowshock; ion cyclotron instability and the inverse correlation between proton anisotrophy and proton beta; and effects of cosmic rays and interstellar gas on the dynamics of a wind.

Porous Silicon as Anode Material for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Thakur, Madhuri; Pernites, Roderick; Sinsabaugh, Steve L.; Wong, Michael S.; Biswal, Sibani L.

Lithium-ion batteries are ubiquitous in our modern society, powering everything from cell phones, laptops, and power tools.They are also powering emerging applications such as electric vehicles and used for on-grid power stabilization. Lithium-ion batteries are a significant and growing part of this market due to their high specific energy. The worldwide market for lithium-ion batteries is projected to reach more than USD 9 billion by 2015. While lithium-ion batteries are often selected for their high specific energy, the market is demanding yet higher performance, usually in terms of energy stored per unit mass of battery. Many groups have recently turned their attention toward developing a silicon-based anode material to increase lithium-ion battery density. Silicon continues to draw great interest as an anode for lithium-ion batteries due to its large specific capacity as compared to the conventional graphite. Despite this exciting property, its practical use has been limited due to a large volume change associated with the insertion and extraction of lithium, which oftentimes leads to cracking and pulverization of the anode, limiting its cycle life. To overcome this problem, significant research has been focused toward developing various silicon nanostructures to accommodate the severe volume expansion and contraction. The structuring of the silicon often involves costly processing steps, limiting its application in price sensitive commercial lithium-ion batteries. To achieve commercial viability, work is being pursued on silicon battery anode structures and processes with a special emphasis on the cost and environment. In this review book chapter, we will summarize recent development of a cost-effective electrochemically etched porous silicon as an anode material for lithium-ion batteries. Briefly, the new approach involves creating hierarchical micron-and nanometer-sized pores on the surface of micron-sized silicon particulates, which are combined with an excellent conductor binder.

Efficiency Analysis of a High-Specific Impulse Hall Thruster

NASA Technical Reports Server (NTRS)

Jacobson, David (Technical Monitor); Hofer, Richard R.; Gallimore, Alec D.

2004-01-01

Performance and plasma measurements of the high-specific impulse NASA-173Mv2 Hall thruster were analyzed using a phenomenological performance model that accounts for a partially-ionized plasma containing multiply-charged ions. Between discharge voltages of 300 to 900 V, the results showed that although the net decrease of efficiency due to multiply-charged ions was only 1.5 to 3.0 percent, the effects of multiply-charged ions on the ion and electron currents could not be neglected. Between 300 to 900 V, the increase of the discharge current was attributed to the increasing fraction of multiply-charged ions, while the maximum deviation of the electron current from its average value was only +5/-14 percent. These findings revealed how efficient operation at high-specific impulse was enabled through the regulation of the electron current with the applied magnetic field. Between 300 to 900 V, the voltage utilization ranged from 89 to 97 percent, the mass utilization from 86 to 90 percent, and the current utilization from 77 to 81 percent. Therefore, the anode efficiency was largely determined by the current utilization. The electron Hall parameter was nearly constant with voltage, decreasing from an average of 210 at 300 V to an average of 160 between 400 to 900 V. These results confirmed our claim that efficient operation can be achieved only over a limited range of Hall parameters.

Effect of ion concentration, solution and membrane permittivity on electric energy storage and capacitance.

PubMed

Tajparast, Mohammad; Glavinović, Mladen I

2018-06-06

Bio-membranes as capacitors store electric energy, but their permittivity is low whereas the permittivity of surrounding solution is high. To evaluate the effective capacitance of the membrane/solution system and determine the electric energy stored within the membrane and in the solution, we estimated their electric variables using Poisson-Nernst-Planck simulations. We calculated membrane and solution capacitances from stored electric energy. The effective capacitance was calculated by fitting a six-capacitance model to charges (fixed and ion) and associated potentials, because it cannot be considered as a result of membrane and solution capacitance in series. The electric energy stored within the membrane (typically much smaller than that in the solution), depends on the membrane permittivity, but also on the external electric field, surface charge density, water permittivity and ion concentration. The effect on capacitances is more specific. Solution capacitance rises with greater solution permittivity or ion concentration, but the membrane capacitance (much smaller than solution capacitance) is only influenced by its permittivity. Interestingly, the effective capacitance is independent of membrane or solution permittivity, but rises as the ion concentration increases and surface charge becomes positive. Experimental estimates of membrane capacitance are thus not necessarily a reliable index of its surface area. Copyright © 2018. Published by Elsevier B.V.

Comparison of single-ion molecular dynamics in common solvents

NASA Astrophysics Data System (ADS)

Muralidharan, A.; Pratt, L. R.; Chaudhari, M. I.; Rempe, S. B.

2018-06-01

Laying a basis for molecularly specific theory for the mobilities of ions in solutions of practical interest, we report a broad survey of velocity autocorrelation functions (VACFs) of Li+ and PF6- ions in water, ethylene carbonate, propylene carbonate, and acetonitrile solutions. We extract the memory function, γ(t), which characterizes the random forces governing the mobilities of ions. We provide comparisons controlling for the effects of electrolyte concentration and ion-pairing, van der Waals attractive interactions, and solvent molecular characteristics. For the heavier ion (PF6-), velocity relaxations are all similar: negative tail relaxations for the VACF and a clear second relaxation for γ (t ), observed previously also for other molecular ions and with n-pentanol as the solvent. For the light Li+ ion, short time-scale oscillatory behavior masks simple, longer time-scale relaxation of γ (t ). But the corresponding analysis of the solventberg Li+(H2O)4 does conform to the standard picture set by all the PF6- results.

Microsecond Simulations of DNA and Ion Transport in Nanopores with Novel Ion-Ion and Ion-Nucleotides Effective Potentials

PubMed Central

De Biase, Pablo M.; Markosyan, Suren; Noskov, Sergei

2014-01-01

We developed a novel scheme based on the Grand-Canonical Monte-Carlo/Brownian Dynamics (GCMC/BD) simulations and have extended it to studies of ion currents across three nanopores with the potential for ssDNA sequencing: solid-state nanopore Si3N4, α-hemolysin, and E111N/M113Y/K147N mutant. To describe nucleotide-specific ion dynamics compatible with ssDNA coarse-grained model, we used the Inverse Monte-Carlo protocol, which maps the relevant ion-nucleotide distribution functions from an all-atom MD simulations. Combined with the previously developed simulation platform for Brownian Dynamic (BD) simulations of ion transport, it allows for microsecond- and millisecond-long simulations of ssDNA dynamics in nanopore with a conductance computation accuracy that equals or exceeds that of all-atom MD simulations. In spite of the simplifications, the protocol produces results that agree with the results of previous studies on ion conductance across open channels and provide direct correlations with experimentally measured blockade currents and ion conductances that have been estimated from all-atom MD simulations. PMID:24738152

Timeframe Dependent Fragment Ions Observed in In-Source Decay Experiments with β-Casein Using MALDI MS.

PubMed

Sekiya, Sadanori; Nagoshi, Keishiro; Iwamoto, Shinichi; Tanaka, Koichi; Takayama, Mitsuo

2015-09-01

The fragment ions observed with time-of-flight (TOF) and quadrupole ion trap (QIT) TOF mass spectrometers (MS) combined with matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) experiments of phosphorylated analytes β-casein and its model peptide were compared from the standpoint of the residence timeframe of analyte and fragment ions in the MALDI ion source and QIT cell. The QIT-TOF MS gave fragment c-, z'-, z-ANL, y-, and b-ions, and further degraded fragments originating from the loss of neutrals such as H(2)O, NH(3), CH(2)O (from serine), C2H4O (from threonine), and H(3)PO(4), whereas the TOF MS merely showed MALDI source-generated fragment c-, z'-, z-ANL, y-, and w-ions. The fragment ions observed in the QIT-TOF MS could be explained by the injection of the source-generated ions into the QIT cell or a cooperative effect of a little internal energy deposition, a long residence timeframe (140 ms) in the QIT cell, and specific amino acid effects on low-energy CID, whereas the source-generated fragments (c-, z'-, z-ANL, y-, and w-ions) could be a result of prompt radical-initiated fragmentation of hydrogen-abundant radical ions [M + H + H](+) and [M + H - H](-) within the 53 ns timeframe, which corresponds to the delayed extraction time. The further degraded fragment b/y-ions produced in the QIT cell were confirmed by positive- and negative-ion low-energy CID experiments performed on the source-generated ions (c-, z'-, and y-ions). The loss of phosphoric acid (98 u) from analyte and fragment ions can be explained by a slow ergodic fragmentation independent of positive and negative charges.

Timeframe Dependent Fragment Ions Observed in In-Source Decay Experiments with β-Casein Using MALDI MS

NASA Astrophysics Data System (ADS)

Sekiya, Sadanori; Nagoshi, Keishiro; Iwamoto, Shinichi; Tanaka, Koichi; Takayama, Mitsuo

2015-09-01

The fragment ions observed with time-of-flight (TOF) and quadrupole ion trap (QIT) TOF mass spectrometers (MS) combined with matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) experiments of phosphorylated analytes β-casein and its model peptide were compared from the standpoint of the residence timeframe of analyte and fragment ions in the MALDI ion source and QIT cell. The QIT-TOF MS gave fragment c-, z'-, z-ANL, y-, and b-ions, and further degraded fragments originating from the loss of neutrals such as H2O, NH3, CH2O (from serine), C2H4O (from threonine), and H3PO4, whereas the TOF MS merely showed MALDI source-generated fragment c-, z'-, z-ANL, y-, and w-ions. The fragment ions observed in the QIT-TOF MS could be explained by the injection of the source-generated ions into the QIT cell or a cooperative effect of a little internal energy deposition, a long residence timeframe (140 ms) in the QIT cell, and specific amino acid effects on low-energy CID, whereas the source-generated fragments (c-, z'-, z-ANL, y-, and w-ions) could be a result of prompt radical-initiated fragmentation of hydrogen-abundant radical ions [M + H + H]+ and [M + H - H]- within the 53 ns timeframe, which corresponds to the delayed extraction time. The further degraded fragment b/y-ions produced in the QIT cell were confirmed by positive- and negative-ion low-energy CID experiments performed on the source-generated ions (c-, z'-, and y-ions). The loss of phosphoric acid (98 u) from analyte and fragment ions can be explained by a slow ergodic fragmentation independent of positive and negative charges.

Specification For ST-5 Li Ion Battery

NASA Technical Reports Server (NTRS)

Castell, Karen D.; Day, John H. (Technical Monitor)

2000-01-01

This Specification defines the general requirements for rechargeable Space Flight batteries intended for use in the ST-5 program. The battery chemistry chosen for this mission is lithium ion (Li-Ion).

Effect of salt solutions on radiosensitivity of mammalian cells. I. Specific ion effects.

PubMed

Raaphorst, G P; Kruuv, J

1977-07-01

The radiation isodose survival curve of cells subjected to a wide concentration range of sucrose solutions has two maxima separated by a minimum. Both cations and anions can alter the cellular radiosensitivity above and beyond the osmotic effect observed for cells treated with sucrose solutions. The basic shape of the isodose curve can also be modulated by changes in temperature and solution exposure times. Some of these alterations in radiosensitivity may be related to changes in the amount and structure of cellular water or macromolecular conformation or to the direct effect of the ions, expecially at high solute concentrations.

pH- and ion-sensitive polymers for drug delivery

PubMed Central

Yoshida, Takayuki; Lai, Tsz Chung; Kwon, Glen S; Sako, Kazuhiro

2013-01-01

Introduction Drug delivery systems (DDSs) are important for effective, safe, and convenient administration of drugs. pH- and ion-responsive polymers have been widely employed in DDS for site-specific drug release due to their abilities to exploit specific pH- or ion-gradients in the human body. Areas covered Having pH-sensitivity, cationic polymers can mask the taste of drugs and release drugs in the stomach by responding to gastric low pH. Anionic polymers responsive to intestinal high pH are used for preventing gastric degradation of drug, colon drug delivery and achieving high bioavailability of weak basic drugs. Tumor-targeted DDSs have been developed based on polymers with imidazole groups or poly(β-amino ester) responsive to tumoral low pH. Polymers with pH-sensitive chemical linkages, such as hydrazone, acetal, ortho ester and vinyl ester, pH-sensitive cell-penetrating peptides and cationic polymers undergoing pH-dependent protonation have been studied to utilize the pH gradient along the endocytic pathway for intracellular drug delivery. As ion-sensitive polymers, ion-exchange resins are frequently used for taste-masking, counterion-responsive drug release and sustained drug release. Polymers responding to ions in the saliva and gastrointestinal fluids are also used for controlled drug release in oral drug formulations. Expert opinion Stimuli-responsive DDSs are important for achieving site-specific and controlled drug release; however, intraindividual, interindividual and intercellular variations of pH should be considered when designing DDSs or drug products. Combination of polymers and other components, and deeper understanding of human physiology are important for development of pH- and ion-sensitive polymeric DDS products for patients. PMID:23930949

Effects of multiscale phase-mixing and interior conductance in the lunar-like pickup ion plasma wake. First results from 3-D hybrid kinetic modeling

NASA Astrophysics Data System (ADS)

Lipatov, A. S.; Sarantos, M.; Farrell, W. M.; Cooper, J. F.

2018-07-01

The study of multiscale pickup ion phase-mixing in the lunar plasma wake with a hybrid model is the main subject of our investigation in this paper. Photoionization and charge exchange of protons with the lunar exosphere are the ionization processes included in our model. The computational model includes the self-consistent dynamics of the light (H+ or H2+ and He+), and heavy (Na+) pickup ions. The electrons are considered as a fluid. The lunar interior is considered as a weakly conducting body. In this paper we considered for the first time the cumulative effect of heavy neutrals in the lunar exosphere (e.g., Al, Ar), an effect which was simulated with one species of Na+ but with a tenfold increase in total production rates. We find that various species produce various types of plasma tail in the lunar plasma wake. Specifically, Na+ and He+ pickup ions form a cycloid-like tail, whereas the H+ or H2+ pickup ions form a tail with a high density core and saw-like periodic structures in the flank region. The length of these structures varies from 1.5RM to 3.3RM depending on the value of gyroradius for H+ or H2+ pickup ions. The light pickup ions produce more symmetrical jump in the density and magnetic field at the Mach cone which is mainly controlled by the conductivity of the interior, an effect previously unappreciated. Although other pickup ion species had little effect on the nature of the interaction of the Moon with the solar wind, the global structure of the lunar tail in these simulations appeared quite different when the H2+ production rate was high.

Metal Ion-Loaded Nanofibre Matrices for Calcification Inhibition in Polyurethane Implants

PubMed Central

Singh, Charanpreet; Wang, Xungai

2017-01-01

Pathologic calcification leads to structural deterioration of implant materials via stiffening, stress cracking, and other structural disintegration mechanisms, and the effect can be critical for implants intended for long-term or permanent implantation. This study demonstrates the potential of using specific metal ions (MI)s for inhibiting pathological calcification in polyurethane (PU) implants. The hypothesis of using MIs as anti-calcification agents was based on the natural calcium-antagonist role of Mg2+ ions in human body, and the anti-calcification effect of Fe3+ ions in bio-prosthetic heart valves has previously been confirmed. In vitro calcification results indicated that a protective covering mesh of MI-doped PU can prevent calcification by preventing hydroxyapatite crystal growth. However, microstructure and mechanical characterisation revealed oxidative degradation effects from Fe3+ ions on the mechanical properties of the PU matrix. Therefore, from both a mechanical and anti-calcification effects point of view, Mg2+ ions are more promising candidates than Fe3+ ions. The in vitro MI release experiments demonstrated that PU microphase separation and the structural design of PU-MI matrices were important determinants of release kinetics. Increased phase separation in doped PU assisted in consistent long-term release of dissolved MIs from both hard and soft segments of the PU. The use of a composite-sandwich mesh design prevented an initial burst release which improved the late (>20 days) release rate of MIs from the matrix. PMID:28644382

Solar wind pickup of ionized Venus exosphere atoms

NASA Technical Reports Server (NTRS)

Curtis, S. A.

1981-01-01

Previous calculations of electrostatic and electromagnetic growth rates for plasma instabilities have neglected the thermal spread of the distribution function of the planetary ions. We consider the effects of finite temperatures for exospheric ions borne in the solar wind. Specifically, growth rates are calculated for electromagnetic instabilities in the low-frequency case for Alfven waves and the intermediate frequency case for whistlers. Also, electrostatic growth rates are calculated for the intermediate frequency regime. From these growth rates, estimates are derived for the pickup times of the planetary ions. The electromagnetic instabilities are shown to produce the most rapid pickup. In the situation where the angle between the local Venus magnetic field and the plasma flow direction is small, the pickup times for both electromagnetic and electrostatic instabilities become very long. A possible consequence of this effect is to produce regions of enhanced planetary ion density in favorable Venus magnetic field-solar wind flow geometries.

One-pot hydrothermal synthesis of ZnS quantum dots/graphene hybrids as a dual anode for sodium ion and lithium ion batteries

NASA Astrophysics Data System (ADS)

Zhang, Rupeng; Wang, Yu; Jia, Mengqiu; Xu, Junjie; Pan, Erzhuang

2018-04-01

Committed to research high-performance sodium-ion batteries(SIBs) and lithium-ion batteries(LIBs) anode materials is attractive but challenging. Among the many promising anode materials, sulfides are considered as promising available anode material. In this paper, we successfully synthesized uniformly dispersed ZnS quantum dots (QDs) with sub-10-nm-scale on graphene nanosheets via a facile hydrothermal method. The prepared ZnS/graphene composites was studied as a dual anode for sodium-ion and lithium-ion batteries. Tested against SIBs, the nanocomposites exhibits an impressive specific capacity of 491 mAh/g at 100 mA/g after 100 cycles. Tested against LIBs, the nanocomposites delivers a superior specific capacity of 759 mAh/g at 100 mA/g after 100 cycles. This excellent performance is mainly due to the fact that graphene can improve the conductivity of the composites and effectively prevent the agglomeration and pulverization of ZnS quantum dots during cycling. Meanwhile, ZnS quantum dots with sub-10-nm-scale may also shorten diffuse path and reduce migration barrier, which is in favor of the full utilization of the active material and the improvement of the stability of the structure

Pseudomonas fluorescens' view of the periodic table.

PubMed

Workentine, Matthew L; Harrison, Joe J; Stenroos, Pernilla U; Ceri, Howard; Turner, Raymond J

2008-01-01

Growth in a biofilm modulates microbial metal susceptibility, sometimes increasing the ability of microorganisms to withstand toxic metal species by several orders of magnitude. In this study, a high-throughput metal toxicity screen was initiated with the aim of correlating biological toxicity data in planktonic and biofilm cells to the physiochemical properties of metal ions. To this end, Pseudomonas fluorescens ATCC 13525 was grown in the Calgary Biofilm Device (CBD) and biofilms and planktonic cells of this microorganism were exposed to gradient arrays of different metal ions. These arrays included 44 different metals with representative compounds that spanned every group of the periodic table (except for the halogens and noble gases). The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentration (MBEC) values were obtained after exposing the biofilms to metal ions for 4 h. Using these values, metal ion toxicity was correlated to the following ion-specific physicochemical parameters: standard reduction-oxidation potential, electronegativity, the solubility product of the corresponding metal-sulfide complex, the Pearson softness index, electron density and the covalent index. When the ions were grouped according to outer shell electron structure, we found that heavy metal ions gave the strongest correlations to these parameters and were more toxic on average than the other classes of the ions. Correlations were different for biofilms than for planktonic cells, indicating that chemical mechanisms of metal ion toxicity differ between the two modes of growth. We suggest that biofilms can specifically counter the toxic effects of certain physicochemical parameters, which may contribute to the increased ability of biofilms to withstand metal toxicity.

Drug insight: If inhibitors as specific heart-rate-reducing agents.

PubMed

Borer, Jeffrey S

2004-12-01

Heart rate is determined primarily by spontaneously repeating net inward current carried by sodium ions and potassium ions through hyperpolarization-activated cyclic-nucleotide-gated channels. Within the heart, these channels are found most abundantly in sinoatrial cardiomyocytes. The channels open in response to membrane hyperpolarization, modulated by local cAMP concentrations. They permit activation of the I(f) current, which can be blocked specifically by molecules characterized by linked benzazepinone and benzocyclobutane rings, and which are devoid of effects on cardiac conduction, inotropy or peripheral vascular tone. The resulting heart-rate reduction has been effective in angina prevention in clinical trials involving 4,000 patients, using the prototype I(f) inhibitor, ivabradine. No serious adverse events have been attributed to the treatment; the most prominent side-effect is dose-related, always reversible and often transient visual symptoms that seldom result in voluntary drug discontinuation.

Dipole Excitation With A Paul Ion Trap Mass Spectrometer

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

MacAskill, J. A.; Madzunkov, S. M.; Chutjian, A.

Preliminary results are presented for the use of an auxiliary radiofrequency (rf) excitation voltage in combination with a high purity, high voltage rf generator to perform dipole excitation within a high precision Paul ion trap. These results show the effects of the excitation frequency over a continuous frequency range on the resultant mass spectra from the Paul trap with particular emphasis on ion ejection times, ion signal intensity, and peak shapes. Ion ejection times are found to decrease continuously with variations in dipole frequency about several resonant values and show remarkable symmetries. Signal intensities vary in a complex fashion withmore » numerous resonant features and are driven to zero at specific frequency values. Observed intensity variations depict dipole excitations that target ions of all masses as well as individual masses. Substantial increases in mass resolution are obtained with resolving powers for nitrogen increasing from 114 to 325.« less

Measurement of acetates in air using differential ion mobility spectrometer

NASA Astrophysics Data System (ADS)

Szczurek, Andrzej; Maciejewska, Monika; Zajiczek, Żaneta; Maziejuk, Mirosław

2017-11-01

Volatile organic compounds are one of the most important group of air pollutants. Potential health and environmental problems resulting from their emission prompted the requirement for monitoring these species. It motivates development of new measurement techniques which are fast, cost effective, reliable and field deployable. One of novel approaches is ion mobility spectrometry. It dwells on ion separation in electric field, based on differences in ion mobility. Many variants of this method are developed. In this wok, differential ion mobility spectrometry (DMS) was considered in respect of acetate measurements in air. It was demonstrated that DMS offers linear response to methyl, ethyl, propyl and butyl acetate in concentration range from 0.3 ppm to 7 ppm. Positive ions spectrum has to be utilised for this purpose. We showed that fragments of DMS spectrum which secure linearity are compound-specific. The obtained results are promising from the application point of view.

The matrix effect in secondary ion mass spectrometry

NASA Astrophysics Data System (ADS)

Seah, M. P.; Shard, A. G.

2018-05-01

Matrix effects in the secondary ion mass spectrometry (SIMS) of selected elemental systems have been analyzed to investigate the applicability of a mathematical description of the matrix effect, called here the charge transfer (CT) model. This model was originally derived for proton exchange and organic positive secondary ions, to characterise the enhancement or suppression of intensities in organic binary systems. In the systems considered in this paper protons are specifically excluded, which enables an assessment of whether the model applies for electrons as well. The present importance is in organic systems but, here we analyse simpler inorganic systems. Matrix effects in elemental systems cannot involve proton transfer if there are no protons present but may be caused by electron transfer and so electron transfer may also be involved in the matrix effects for organic systems. There are general similarities in both the magnitudes of the ion intensities as well as the matrix effects for both positive and negative secondary ions in both systems and so the CT model may be more widely applicable. Published SIMS analyses of binary elemental mixtures are analyzed. The data of Kim et al., for the Pt/Co system, provide, with good precision, data for such a system. This gives evidence for the applicability of the CT model, where electron, rather than proton, transfer is the matrix enhancing and suppressing mechanism. The published data of Prudon et al., for the important Si/Ge system, provides further evidence for the effects for both positive and negative secondary ions and allows rudimentary rules to be developed for the enhancing and suppressing species.

Copper Complexation Screen Reveals Compounds with Potent Antibiotic Properties against Methicillin-Resistant Staphylococcus aureus

PubMed Central

Haeili, Mehri; Moore, Casey; Davis, Christopher J. C.; Cochran, James B.; Shah, Santosh; Shrestha, Tej B.; Zhang, Yaofang; Bossmann, Stefan H.; Benjamin, William H.

2014-01-01

Macrophages take advantage of the antibacterial properties of copper ions in the killing of bacterial intruders. However, despite the importance of copper for innate immune functions, coordinated efforts to exploit copper ions for therapeutic interventions against bacterial infections are not yet in place. Here we report a novel high-throughput screening platform specifically developed for the discovery and characterization of compounds with copper-dependent antibacterial properties toward methicillin-resistant Staphylococcus aureus (MRSA). We detail how one of the identified compounds, glyoxal-bis(N4-methylthiosemicarbazone) (GTSM), exerts its potent strictly copper-dependent antibacterial properties on MRSA. Our data indicate that the activity of the GTSM-copper complex goes beyond the general antibacterial effects of accumulated copper ions and suggest that, in contrast to prevailing opinion, copper complexes can indeed exhibit species- and target-specific activities. Based on experimental evidence, we propose that copper ions impose structural changes upon binding to the otherwise inactive GTSM ligand and transfer antibacterial properties to the chelate. In turn, GTSM determines target specificity and utilizes a redox-sensitive release mechanism through which copper ions are deployed at or in close proximity to a putative target. According to our proof-of-concept screen, copper activation is not a rare event and even extends to already established drugs. Thus, copper-activated compounds could define a novel class of anti-MRSA agents that amplify copper-dependent innate immune functions of the host. To this end, we provide a blueprint for a high-throughput drug screening campaign which considers the antibacterial properties of copper ions at the host-pathogen interface. PMID:24752262

Dose- and time-dependent gene expression alterations in prostate and colon cancer cells after in vitro exposure to carbon ion and X-irradiation

PubMed Central

Suetens, Annelies; Moreels, Marjan; Quintens, Roel; Soors, Els; Buset, Jasmine; Chiriotti, Sabina; Tabury, Kevin; Gregoire, Vincent; Baatout, Sarah

2015-01-01

Hadrontherapy is an advanced form of radiotherapy that uses beams of charged particles (such as protons and carbon ions). Compared with conventional radiotherapy, the main advantages of carbon ion therapy are the precise absorbed dose localization, along with an increased relative biological effectiveness (RBE). This high ballistic accuracy of particle beams deposits the maximal dose to the tumor, while damage to the surrounding healthy tissue is limited. Currently, hadrontherapy is being used for the treatment of specific types of cancer. Previous in vitro studies have shown that, under certain circumstances, exposure to charged particles may inhibit cell motility and migration. In the present study, we investigated the expression of four motility-related genes in prostate (PC3) and colon (Caco-2) cancer cell lines after exposure to different radiation types. Cells were irradiated with various absorbed doses (0, 0.5 and 2 Gy) of accelerated 13C-ions at the GANIL facility (Caen, France) or with X-rays. Clonogenic assays were performed to determine the RBE. RT-qPCR analysis showed dose- and time-dependent changes in the expression of CCDC88A, FN1, MYH9 and ROCK1 in both cell lines. However, whereas in PC3 cells the response to carbon ion irradiation was enhanced compared with X-irradiation, the effect was the opposite in Caco-2 cells, indicating cell-type–specific responses to the different radiation types. PMID:25190155

Predicting the toxicity of major ions in seawater to mysid shrimp (Mysidopsis bahia), sheepshead minnow (Cyprinodon variegatus), and inland silverside minnow (Menidia beryllina)

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

Pillard, D.A.; DuFresne, D.L.; Caudle, D.D.

2000-01-01

Although marine organisms are naturally adapted to salinities well above those of freshwater, elevated concentrations of specific ions have been shown to cause adverse effects on some saltwater species. Because some ions are also physiologically essential, a deficiency of these ions can also cause significant effects. To provide a predictive tool to assess toxicity associated with major ions, mysid shrimp (Mysidopsis bahia), sheepshead minnows (Cyprinodon variegatus), and inland silverside minnows (Menidia beryllina) were exposed to saline solutions containing calcium, magnesium, potassium, strontium, bicarbonate, borate, bromide, and sulfate at concentrations above and below what would be found in seawater. Solution salinitymore » was maintained at approximately 31% by increasing or decreasing sodium and chloride concentrations. Logistic regression models were developed with both the ion molar concentrations and ion activity. Toxicity to all three species was observed when either a deficiency or an excess of potassium and calcium occurred. Significant mortality occurred in all species when exposed to excess concentrations of magnesium, bicarbonate, and borate. The response to the remaining ions varied with species. Sheepshead minnows were the most tolerant of both deficient and elevated levels of the different ions. Mysid shrimp and inland silverside minnows demonstrated similar sensitivities to several ions, but silverside minnow response was more variable. As a result, the logistic models that predict inland silverside minnow survival generally were less robust than for the other two species.« less

Hormonal control of euryhalinity

USGS Publications Warehouse

Takei, Yoshio; McCormick, Stephen D.; McCormick, Stephen D.; Farrell, Anthony Peter; Brauner, Colin J.

2013-01-01

Hormones play a critical role in maintaining body fluid balance in euryhaline fishes during changes in environmental salinity. The neuroendocrine axis senses osmotic and ionic changes, then signals and coordinates tissue-specific responses to regulate water and ion fluxes. Rapid-acting hormones, e.g. angiotensins, cope with immediate challenges by controlling drinking rate and the activity of ion transporters in the gill, gut, and kidney. Slow-acting hormones, e.g. prolactin and growth hormone/insulin-like growth factor-1, reorganize the body for long-term acclimation by altering the abundance of ion transporters and through cell proliferation and differentiation of ionocytes and other osmoregulatory cells. Euryhaline species exist in all groups of fish, including cyclostomes, and cartilaginous and teleost fishes. The diverse strategies for responding to changes in salinity have led to differential regulation and tissue-specific effects of hormones. Combining traditional physiological approaches with genomic, transcriptomic, and proteomic analyses will elucidate the patterns and diversity of the endocrine control of euryhalinity.

Smolt physiology and endocrinology

USGS Publications Warehouse

McCormick, Stephen D.; McCormick, Stephen D.; Farrell, Anthony Peter; Brauner, Colin J.

2013-01-01

Hormones play a critical role in maintaining body fluid balance in euryhaline fishes during changes in environmental salinity. The neuroendocrine axis senses osmotic and ionic changes, then signals and coordinates tissue-specific responses to regulate water and ion fluxes. Rapid-acting hormones, e.g. angiotensins, cope with immediate challenges by controlling drinking rate and the activity of ion transporters in the gill, gut, and kidney. Slow-acting hormones, e.g. prolactin and growth hormone/insulin-like growth factor-1, reorganize the body for long-term acclimation by altering the abundance of ion transporters and through cell proliferation and differentiation of ionocytes and other osmoregulatory cells. Euryhaline species exist in all groups of fish, including cyclostomes, and cartilaginous and teleost fishes. The diverse strategies for responding to changes in salinity have led to differential regulation and tissue-specific effects of hormones. Combining traditional physiological approaches with genomic, transcriptomic, and proteomic analyses will elucidate the patterns and diversity of the endocrine control of euryhalinity.

Species-specific toxicity of major ion salts 1: Fathead minnows and pond snails

EPA Science Inventory

Elevated major ion concentrations (Na, K, Ca, Mg, Cl, SO4, HCO3) have been recognized as a cause of surface water impairment and the toxicity of these major ions has been shown to be dependent on the specific ion composition of the water. A long-term research project was initiate...

Species-specific toxicity of major ion salts 2: Hyalella azteca, Lumbriculus variegatus, and Chironomus tentans

EPA Science Inventory

Elevated major ion concentrations (Na, K, Ca, Mg, Cl, SO4, HCO3) have been recognized as a cause of surface water impairment and the toxicity of these major ions has been shown to be dependent on the specific ion composition of the water. A long-term research project was initiate...

Strain-specific variations in cation content and transport in mouse erythrocytes

PubMed Central

Rivera, Alicia; Zee, Robert Y. L.; Alper, Seth L.; Peters, Luanne L.

2013-01-01

Studies of ion transport pathophysiology in hematological disorders and tests of possible new therapeutic agents for these disorders have been carried out in various mouse models because of close functional similarities between mouse and human red cells. We have explored strain-specific differences in erythrocyte membrane physiology in 10 inbred mouse strains by determining erythrocyte contents of Na+, K+, and Mg2+, and erythrocyte transport of ions via the ouabain-sensitive Na-K pump, the amiloride-sensitive Na-H exchanger (NHE1), the volume and chloride-dependent K-Cl cotransporter (KCC), and the charybdotoxin-sensitive Gardos channel (KCNN4). Our data reveal substantial strain-specific and sex-specific differences in both ion content and trans-membrane ion transport in mouse erythrocytes. These differences demonstrate the feasibility of identifying specific quantitative trait loci for erythroid ion transport and content in genetically standardized inbred mouse strains. PMID:23482811

Strain-specific variations in cation content and transport in mouse erythrocytes.

PubMed

Rivera, Alicia; Zee, Robert Y L; Alper, Seth L; Peters, Luanne L; Brugnara, Carlo

2013-05-01

Studies of ion transport pathophysiology in hematological disorders and tests of possible new therapeutic agents for these disorders have been carried out in various mouse models because of close functional similarities between mouse and human red cells. We have explored strain-specific differences in erythrocyte membrane physiology in 10 inbred mouse strains by determining erythrocyte contents of Na(+), K(+), and Mg(2+), and erythrocyte transport of ions via the ouabain-sensitive Na-K pump, the amiloride-sensitive Na-H exchanger (NHE1), the volume and chloride-dependent K-Cl cotransporter (KCC), and the charybdotoxin-sensitive Gardos channel (KCNN4). Our data reveal substantial strain-specific and sex-specific differences in both ion content and trans-membrane ion transport in mouse erythrocytes. These differences demonstrate the feasibility of identifying specific quantitative trait loci for erythroid ion transport and content in genetically standardized inbred mouse strains.

Terbium(III) Modified Fluorescent Carbon Dots for Highly Selective and Sensitive Ratiometry of Stringent.

PubMed

Chen, Bin Bin; Liu, Meng Li; Zhan, Lei; Li, Chun Mei; Huang, Cheng Zhi

2018-03-20

Highly selective and sensitive detection of guanosine 3'-diphosphate-5'-diphosphate (ppGpp), namely, the stringent in plants or microorganisms responding to strict or extreme environmental conditions such as stress and starvation, which plays an important role in gene expression, rRNA and antibiotics production, regulations of virulence of bacteria, and growth of plants, faces a great challenge owing to its extreme similarity to normal nucleotides. By modifying the surface groups of a facile two-step hydrothermal route prepared carbon dots (CDs) with terbium ions (Tb 3+ ) in this contribution, a novel fluorescent probe with excellent properties such as highly physical and chemical stability, narrow emission and excitation wavelength-independent emission was prepared. The Tb 3+ ions on the surface of CDs cannot only preserve the intrinsic fluorescence (FL) of CDs but also keep its own coordination capacity with rare earth complex, and thus the clamp structure (four phosphate groups) of ppGpp can specific binding with Tb 3+ ions on the surface of CDs to produce antenna effect. Therefore, a highly selective and sensitive fluorescent ratiometry of ppGpp was developed by terbium-modified carbon dots (CDs-Tb) with the limit of detection as low as 50 nM based on the synergistic effect of antenna effect of Tb 3+ ions and specific recognition capacity of CDs. The applicability of this assay was demonstrated by CDs-Tb-based paper sensor for high distinguishing ppGpp from other nucleotides with similar structure.

Mechanism of Prophylaxis by Silver Compounds against Infection of Burns

PubMed Central

Ricketts, C. R.; Lowbury, E. J. L.; Lawrence, J. C.; Hall, M.; Wilkins, M. D.

1970-01-01

To clarify tthe mechanism by which local application of silver compounds protects burns against infection, an ion-specific electrode was used to measùre the concentration of silver ions in solutions. By this method it was shown that in burn dressings silver ions were reduced to a very low level by precipitation as silver chloride. The antibacterial effect was found to depend on the availability of silver ions from solution in contact with precipitate. Between 10-5 and 10-6 molar silver nitrate solution in water was rapidly bactericidal. The minimal amount of silver nitrate causing inhibition of respiration of skin in tissue culture was about 25 times the minimal concentration of silver nitrate that inhibited growth of Pseudomonas aeruginosa. PMID:4986877

Effects of the Discharge Parameters on the Efficiency and Stability of Ambient Metastable-Induced Desorption Ionization

NASA Astrophysics Data System (ADS)

Zhang, Xiaotian; Chen, Chilai; Liu, Youjiang; Wang, Hongwei; Zhang, Lehua; Kong, Deyi; Mario, Chavarria

2015-12-01

Ionization efficiency is an important factor for ion sources in mass spectrometry and ion mobility spectrometry. Using helium as the discharge gas, acetone as the sample, and high-field asymmetric ion mobility spectrometry (FAIMS) as the ion detection method, this work investigates in detail the effects of discharge parameters on the efficiency of ambient metastable-induced desorption ionization (AMDI) at atmospheric pressure. The results indicate that the discharge power and gas flow rate are both significantly correlated with the ionization efficiency. Specifically, an increase in the applied discharge power leads to a rapid increase in the ionization efficiency, which gradually reaches equilibrium due to ion saturation. Moreover, when the discharge voltage is fixed at 2.1 kV, a maximum efficiency can be achieved at the flow rate of 9.0 m/s. This study provides a foundation for the design and application of AMDI for on-line detection with mass spectrometry and ion mobility spectrometry. supported by National Natural Science Foundation of China (No. 61374016), the Changzhou Science and Technology Support Program, China (No. CE20120081) and the External Cooperation Program of Chinese Academy of Sciences (No. GJHZ1218)

A Stabilized Finite Element Method for Modified Poisson-Nernst-Planck Equations to Determine Ion Flow Through a Nanopore

PubMed Central

Chaudhry, Jehanzeb Hameed; Comer, Jeffrey; Aksimentiev, Aleksei; Olson, Luke N.

2013-01-01

The conventional Poisson-Nernst-Planck equations do not account for the finite size of ions explicitly. This leads to solutions featuring unrealistically high ionic concentrations in the regions subject to external potentials, in particular, near highly charged surfaces. A modified form of the Poisson-Nernst-Planck equations accounts for steric effects and results in solutions with finite ion concentrations. Here, we evaluate numerical methods for solving the modified Poisson-Nernst-Planck equations by modeling electric field-driven transport of ions through a nanopore. We describe a novel, robust finite element solver that combines the applications of the Newton's method to the nonlinear Galerkin form of the equations, augmented with stabilization terms to appropriately handle the drift-diffusion processes. To make direct comparison with particle-based simulations possible, our method is specifically designed to produce solutions under periodic boundary conditions and to conserve the number of ions in the solution domain. We test our finite element solver on a set of challenging numerical experiments that include calculations of the ion distribution in a volume confined between two charged plates, calculations of the ionic current though a nanopore subject to an external electric field, and modeling the effect of a DNA molecule on the ion concentration and nanopore current. PMID:24363784

A novel algorithm for the calculation of physical and biological irradiation quantities in scanned ion beam therapy: the beamlet superposition approach

NASA Astrophysics Data System (ADS)

Russo, G.; Attili, A.; Battistoni, G.; Bertrand, D.; Bourhaleb, F.; Cappucci, F.; Ciocca, M.; Mairani, A.; Milian, F. M.; Molinelli, S.; Morone, M. C.; Muraro, S.; Orts, T.; Patera, V.; Sala, P.; Schmitt, E.; Vivaldo, G.; Marchetto, F.

2016-01-01

The calculation algorithm of a modern treatment planning system for ion-beam radiotherapy should ideally be able to deal with different ion species (e.g. protons and carbon ions), to provide relative biological effectiveness (RBE) evaluations and to describe different beam lines. In this work we propose a new approach for ion irradiation outcomes computations, the beamlet superposition (BS) model, which satisfies these requirements. This model applies and extends the concepts of previous fluence-weighted pencil-beam algorithms to quantities of radiobiological interest other than dose, i.e. RBE- and LET-related quantities. It describes an ion beam through a beam-line specific, weighted superposition of universal beamlets. The universal physical and radiobiological irradiation effect of the beamlets on a representative set of water-like tissues is evaluated once, coupling the per-track information derived from FLUKA Monte Carlo simulations with the radiobiological effectiveness provided by the microdosimetric kinetic model and the local effect model. Thanks to an extension of the superposition concept, the beamlet irradiation action superposition is applicable for the evaluation of dose, RBE and LET distributions. The weight function for the beamlets superposition is derived from the beam phase space density at the patient entrance. A general beam model commissioning procedure is proposed, which has successfully been tested on the CNAO beam line. The BS model provides the evaluation of different irradiation quantities for different ions, the adaptability permitted by weight functions and the evaluation speed of analitical approaches. Benchmarking plans in simple geometries and clinical plans are shown to demonstrate the model capabilities.

Specific effects of background electrolytes on the kinetics of step propagation during calcite growth

NASA Astrophysics Data System (ADS)

Ruiz-Agudo, Encarnación; Putnis, Christine V.; Wang, Lijun; Putnis, Andrew

2011-07-01

The mechanisms by which background electrolytes modify the kinetics of non-equivalent step propagation during calcite growth were investigated using Atomic Force Microscopy (AFM), at constant driving force and solution stoichiometry. Our results suggest that the acute step spreading rate is controlled by kink-site nucleation and, ultimately, by the dehydration of surface sites, while the velocity of obtuse step advancement is mainly determined by hydration of calcium ions in solution. According to our results, kink nucleation at acute steps could be promoted by carbonate-assisted calcium attachment. The different sensitivity of obtuse and acute step propagation kinetics to cation and surface hydration could be the origin of the reversed geometries of calcite growth hillocks (i.e., rate of obtuse step spreading < rate of acute step spreading) observed in concentrated (ionic strength, IS = 0.1) KCl and CsCl solutions. At low IS (0.02), ion-specific effects seem to be mainly associated with changes in the solvation environment of calcium ions in solution. With increasing electrolyte concentration, the stabilization of surface water by weakly paired salts appears to become increasingly important in determining step spreading rate. At high ionic strength (IS = 0.1), overall calcite growth rates increased with increasing hydration of calcium in solution (i.e., decreasing ion pairing of background electrolytes for sodium-bearing salts) and with decreasing hydration of the carbonate surface site (i.e., increasing ion pairing for chloride-bearing salts). Changes in growth hillock morphology were observed in the presence of Li +, F - and SO42-, and can be interpreted as the result of the stabilization of polar surfaces due to increased ion hydration. These results increase our ability to predict crystal reactivity in natural fluids which contain significant amounts of solutes.

Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces

PubMed Central

Dalui, Malay; Wang, W.-M.; Trivikram, T. Madhu; Sarkar, Subhrangshu; Tata, Sheroy; Jha, J.; Ayyub, P.; Sheng, Z. M.; Krishnamurthy, M.

2015-01-01

High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈0.25 μm) layer of 25–30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2×1018  W/cm2. However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration. PMID:26153048

Differentiation of isomeric 2-aryldimethyltetrahydro-5-quinolinones by electron ionization and electrospray ionization mass spectrometry.

PubMed

Kumar, Ch Dinesh; Chary, V Naresh; Dinesh, A; Reddy, P S; Srinivas, K; Gayatri, G; Sastry, G N; Prabhakar, S

2011-10-15

A series of isomeric 2-aryl-6,6-dimethyltetrahydro-5-quinolinones (set I) and 2-aryl-7,7-dimethyltetrahydro-5-quinolinones (set II) were studied under positive ion electron ionization (EI) and electrospray ionization (ESI) techniques. Under EI conditions, the molecular ions were found to be less stable in set I isomers, and they resulted in abundant fragment ions, i.e., [M-CH(3)](+), [M-CO](+.), [M-HCO](+), [M-(CH(3),CO)](+), and [M-(CH(3),CH(2)O)](+), when compared with set II isomers. In addition, the set I isomers showed specific fragment ions corresponding to [M-OH](+) and [M-OCH(3)](+). The retro-Diels-Alder (RDA) product ion was always higher in set II isomers. The ESI mass spectra produced [M + H](+) ions, and their decomposition showed favorable loss of CH(3) radical, CH(4) and C(2)H(6) molecules in set I isomers. The set II isomers, however, showed predominant RDA product ions, and specific loss of H(2)O. The selectivity in EI and ESI was attributed to the instability of set I isomers by the presence of a gem-dimethyl group at the α-position, and it was supported by the data from model compounds without a gem-dimethyl group. Density functional theory (DFT) calculations successfully corroborated the fragmentation pathways for diagnostic ions. This study revealed the effect of a gem-dimethyl group located at the α-position to the carbonyl having aromatic/unsaturated carbon on the other side of the carbonyl group. Copyright © 2011 John Wiley & Sons, Ltd.

Effect of Iron Redox Equilibrium on the Foaming Behavior of MgO-Saturated Slags

NASA Astrophysics Data System (ADS)

Park, Youngjoo; Min, Dong Joon

2018-04-01

In this study, the foaming index of CaO-SiO2-FetO and CaO-SiO2-FetO-Al2O3 slags saturated with MgO was measured to understand the relationship between their foaming behavior and physical properties. The foaming index of MgO-saturated slags increases with the FetO content due to the redox equilibrium of FetO. Experimental results indicated that MgO-saturated slag has relatively high ferric ion concentration, and the foaming index increases due to the effect of ferric ion. Therefore, the foaming behavior of MgO-saturated slag is more reasonably explained by considering the effect of ferric ion on the estimation of slag properties such as viscosity, surface tension, and density. Specifically, the estimation of slag viscosity was additionally verified by NBO/T, and this is experimentally obtained through Raman spectroscopy.

High Power Ion Cyclotron Heating in the VASIMR

NASA Astrophysics Data System (ADS)

Longmier, B. W.; Brukardt, M. S.; Bering, E. A.; Chang Diaz, F.; Squire, J.

2009-12-01

The Variable Specific Impulse Magnetoplasma Rocket (VASIMR®) is an electric propulsion system under development at Ad Astra Rocket Company that utilizes several processes of ion acceleration and heating that occur in the Birkeland currents of an auroral arc system. Among these processes are parallel electric field acceleration, lower hybrid resonance heating, and ion cyclotron resonance heating. The VASIMR® is capable of laboratory simulation of electromagnetic ion cyclotron wave heating during a single pass of ions through the resonance region. The plasma is generated by a helicon discharge of 35 kW then passes through a 176 kW RF booster stage that couples left hand polarized slow mode waves from the high field side of the resonance. VX-200 auroral simulation results from the past year are discussed. Ambipolar acceleration has been shown to produce 35eV argon ions in the helicon exhaust. The effects on the ion exhaust with an addition of 150-200 kW of ion cyclotron heating are presented. The changes to the VASIMR® experiment at Ad Astra Rocket Company's new facility in Webster, Texas will also be discussed, including the possibility of collaborative experiments.

Dynamics of nanoparticle morphology under low energy ion irradiation.

PubMed

Holland-Moritz, Henry; Graupner, Julia; Möller, Wolfhard; Pacholski, Claudia; Ronning, Carsten

2018-08-03

If nanostructures are irradiated with energetic ions, the mechanism of sputtering becomes important when the ion range matches about the size of the nanoparticle. Gold nanoparticles with diameters of ∼50 nm on top of silicon substrates with a native oxide layer were irradiated by gallium ions with energies ranging from 1 to 30 keV in a focused ion beam system. High resolution in situ scanning electron microscopy imaging permits detailed insights in the dynamics of the morphology change and sputter yield. Compared to bulk-like structures or thin films, a pronounced shaping and enhanced sputtering in the nanostructures occurs, which enables a specific shaping of these structures using ion beams. This effect depends on the ratio of nanoparticle size and ion energy. In the investigated energy regime, the sputter yield increases at increasing ion energy and shows a distinct dependence on the nanoparticle size. The experimental findings are directly compared to Monte Carlo simulations obtained from iradina and TRI3DYN, where the latter takes into account dynamic morphological and compositional changes of the target.

Iron oxide nanoparticles in modern microbiology and biotechnology.

PubMed

Dinali, Ranmadugala; Ebrahiminezhad, Alireza; Manley-Harris, Merilyn; Ghasemi, Younes; Berenjian, Aydin

2017-08-01

Iron oxide nanoparticles (IONs) are one of the most developed and used nanomaterials in biotechnology and microbiology. These particles have unique physicochemical properties, which make them unique among nanomaterials. Therefore, many experiments have been conducted to develop facile synthesis methods for these particles and to make them biocompatible. Various effects of IONs on microorganisms have been reported. Depending on the microbial strain and nanoparticle (NP) concentration, IONs can stimulate or inhibit microbial growth. Due to the superparamagnetic properties of IONs, these NPs have used as nano sources of heat for hyperthermia in infected tissues. Antibiotic-loaded IONs are used for targeted delivery of chemical therapy direct to the infected organ and IONs have been used as a dirigible carrier for more potent antimicrobial nanomaterials such as silver nanoparticles. Magnetic NPs have been used for specific separation of pathogen and non-pathogen bacterial strains. Very recently, IONs were used as a novel tool for magnetic immobilization of microbial cells and process intensification in a biotechnological process. This review provides an overview of application of IONs in different microbial processes. Recommendations are also given for areas of future research.

Epigenetic Analysis of Heavy-ion Radiation Induced Bystander Effects in Mice

NASA Astrophysics Data System (ADS)

Zhang, Meng; Sun, Yeqing; Cui, Changna; Xue, Bei

Abstract: Radiation-induced bystander effect was defined as the induction of damage in neighboring non-hit cells by signals released from directly-irradiated cells. Recently, low dose of high LET radiation induced bystander effects in vivo have been reported more and more. It has been indicated that radiation induced bystander effect was localized not only in bystander tissues but also in distant organs. Genomic, epigenetic and proteomics plays significant roles in regulating heavy-ion radiation stress responses in mice. To identify the molecular mechanism that underlies bystander effects of heavy-ion radiation, the male Balb/c and C57BL mice were exposed head-only to 40, 200, 2000mGy dose of (12) C heavy-ion radiation, while the rest of the animal body was shielded. Directly radiation organ ear and the distant organ liver were detected on 1h, 6h, 12h and 24h after radiation, respectively. Methylation-sensitive amplification polymorphism (MSAP) was used to monitor the level of polymorphic genomic DNA methylation changed with dose and time effects. The results show that heavy-ion irradiated mouse head could induce genomic DNA methylation changes significantly in both the directly radiation organ ear and the distant organ liver. The percent of DNA methylation changes were time-dependent and tissue-specific. Demethylation polymorphism rate was highest separately at 1 h in 200 mGy and 6 h in 2000 mGy after irradiation. The global DNA methylation changes tended to occur in the CG sites. The results illustrated that genomic methylation changes of heavy ion radiation-induced bystander effect in liver could be obvious 1 h after radiation and achieved the maximum at 6 h, while the changes could recover gradually at 12 h. The results suggest that mice head exposed to heavy-ion radiation can induce damage and methylation pattern changed in both directly radiation organ ear and distant organ liver. Moreover, our findings are important to understand the molecular mechanism of radiation induced bystander effects in vivo.

Impact of water chemistry on the particle-specific toxicity of copper nanoparticles to Daphnia magna.

PubMed

Xiao, Yinlong; Peijnenburg, Willie J G M; Chen, Guangchao; Vijver, Martina G

2018-01-01

Toxicity of metallic nanoparticle suspensions (NP (total) ) is generally assumed to result from the combined effect of the particles present in suspensions (NP (particle) ) and their released ions (NP (ion) ). Evaluation and consideration of how water chemistry affects the particle-specific toxicity of NP (total) are critical for environmental risk assessment of nanoparticles. In this study, it was found that the toxicity of Cu NP (particle) to Daphnia magna, in line with the trends in toxicity for Cu NP (ion) , decreased with increasing pH and with increasing concentrations of divalent cations and dissolved organic carbon (DOC). Without the addition of DOC, the toxicity of Cu NP (total) to D. magna at the LC50 was driven mainly by Cu NP (ion) (accounting for ≥53% of the observed toxicity). However, toxicity of Cu NP (total) in the presence of DOC at a concentration ranging from 5 to 50mg C/L largely resulted from the NP (particle) (57%-85%), which could be attributable to the large reduction of the concentration of Cu NP (ion) and the enhancement of the stability of Cu NP (particle) when DOC was added. Our results indicate that water chemistry needs to be explicitly taken into consideration when evaluating the role of NP (particle) and NP (ion) in the observed toxicity of NP (total) . Copyright © 2017 Elsevier B.V. All rights reserved.

Nitrogen-Doped Porous Carbon Nanosheets from Eco-Friendly Eucalyptus Leaves as High Performance Electrode Materials for Supercapacitors and Lithium Ion Batteries.

PubMed

Mondal, Anjon Kumar; Kretschmer, Katja; Zhao, Yufei; Liu, Hao; Wang, Chengyin; Sun, Bing; Wang, Guoxiu

2017-03-13

Nitrogen-doped porous carbon nanosheets were prepared from eucalyptus tree leaves by simply mixing the leaf powders with KHCO 3 and subsequent carbonisation. Porous carbon nanosheets with a high specific surface area of 2133 m 2  g -1 were obtained and applied as electrode materials for supercapacitors and lithium ion batteries. For supercapacitor applications, the porous carbon nanosheet electrode exhibited a supercapacitance of 372 F g -1 at a current density of 500 mA g -1 in 1 m H 2 SO 4 aqueous electrolyte and excellent cycling stability over 15 000 cycles. In organic electrolyte, the nanosheet electrode showed a specific capacitance of 71 F g -1 at a current density of 2 Ag -1 and stable cycling performance. When applied as the anode material for lithium ion batteries, the as-prepared porous carbon nanosheets also demonstrated a high specific capacity of 819 mA h g -1 at a current density of 100 mA g -1 , good rate capability, and stable cycling performance. The outstanding electrochemical performances for both supercapacitors and lithium ion batteries are derived from the large specific surface area, porous nanosheet structure and nitrogen doping effects. The strategy developed in this paper provides a novel route to utilise biomass-derived materials for low-cost energy storage systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A multiple-cathode, high-power, rectangular ion thruster discharge chamber of increasing thruster lifetime

NASA Astrophysics Data System (ADS)

Rovey, Joshua Lucas

Ion thrusters are high-efficiency, high-specific impulse space propulsion systems proposed for deep space missions requiring thruster operational lifetimes of 7--14 years. One of the primary ion thruster components is the discharge cathode assembly (DCA). The DCA initiates and sustains ion thruster operation. Contemporary ion thrusters utilize one molybdenum keeper DCA that lasts only ˜30,000 hours (˜3 years), so single-DCA ion thrusters are incapable of satisfying the mission requirements. The aim of this work is to develop an ion thruster that sequentially operates multiple DCAs to increase thruster lifetime. If a single-DCA ion thruster can operate 3 years, then perhaps a triple-DCA thruster can operate 9 years. Initially, a multiple-cathode discharge chamber (MCDC) is designed and fabricated. Performance curves and grid-plane current uniformity indicate operation similar to other thrusters. Specifically, the configuration that balances both performance and uniformity provides a production cost of 194 W/A at 89% propellant efficiency with a flatness parameter of 0.55. One of the primary MCDC concerns is the effect an operating DCA has on the two dormant cathodes. Multiple experiments are conducted to determine plasma properties throughout the MCDC and near the dormant cathodes, including using "dummy" cathodes outfitted with plasma diagnostics and internal plasma property mapping. Results are utilized in an erosion analysis that suggests dormant cathodes suffer a maximum pre-operation erosion rate of 5--15 mum/khr (active DCA maximum erosion is 70 mum/khr). Lifetime predictions indicate that triple-DCA MCDC lifetime is approximately 2.5 times longer than a single-DCA thruster. Also, utilization of new keeper materials, such as carbon graphite, may significantly decrease both active and dormant cathode erosion, leading to a further increase in thruster lifetime. Finally, a theory based on the near-DCA plasma potential structure and propellant flow rate effects is developed to explain active DCA erosion. The near-DCA electric field pulls ions into the DCA such that they bombard and erode the keeper. Charge-exchange collisions between bombarding ions and DCA-expelled neutral atoms reduce erosion. The theory explains ion thruster long-duration wear-test results and suggests increasing propellant flow rate may eliminate or reduce DCA erosion.

Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors.

PubMed

Ozdemir, Orhan; Du, Hao; Karakashev, Stoyan I; Nguyen, Anh V; Celik, M S; Miller, Jan D

2011-03-15

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions using alkylammonium and alkylsulfate collectors such as dodecylamine hydrochloride and sodium dodecylsulfate. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modeling techniques for determining solution viscosity, surface tension, bubble-particle attachment time, contact angle, and molecular dynamics simulation have been used to provide further information on air-solution and solid-solution interfacial phenomena, especially with respect to the interfacial water structure due to the presence of dissolved ions. In addition atomic force microscopy, and sum frequency generation vibrational spectroscopy have been used to provide further information on surface states. These studies indicate that the ion specificity effect is the most significant factor influencing flotation in brine solutions. Copyright © 2011 Elsevier B.V. All rights reserved.

Specific interaction between negative atmospheric ions and organic compounds in atmospheric pressure corona discharge ionization mass spectrometry.

PubMed

Sekimoto, Kanako; Sakai, Mami; Takayama, Mitsuo

2012-06-01

The interaction between negative atmospheric ions and various types of organic compounds were investigated using atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. Atmospheric negative ions such as O(2)(-), HCO(3)(-), COO(-)(COOH), NO(2)(-), NO(3)(-), and NO(3)(-)(HNO(3)) having different proton affinities served as the reactant ions for analyte ionization in APCDI in negative-ion mode. The individual atmospheric ions specifically ionized aliphatic and aromatic compounds with various functional groups as atmospheric ion adducts and deprotonated analytes. The formation of the atmospheric ion adducts under certain discharge conditions is most likely attributable to the affinity between the analyte and atmospheric ion and the concentration of the atmospheric ion produced under these conditions. The deprotonated analytes, in contrast, were generated from the adducts of the atmospheric ions with higher proton affinity attributable to efficient proton abstraction from the analyte by the atmospheric ion.

Copper complexation screen reveals compounds with potent antibiotic properties against methicillin-resistant Staphylococcus aureus.

PubMed

Haeili, Mehri; Moore, Casey; Davis, Christopher J C; Cochran, James B; Shah, Santosh; Shrestha, Tej B; Zhang, Yaofang; Bossmann, Stefan H; Benjamin, William H; Kutsch, Olaf; Wolschendorf, Frank

2014-07-01

Macrophages take advantage of the antibacterial properties of copper ions in the killing of bacterial intruders. However, despite the importance of copper for innate immune functions, coordinated efforts to exploit copper ions for therapeutic interventions against bacterial infections are not yet in place. Here we report a novel high-throughput screening platform specifically developed for the discovery and characterization of compounds with copper-dependent antibacterial properties toward methicillin-resistant Staphylococcus aureus (MRSA). We detail how one of the identified compounds, glyoxal-bis(N4-methylthiosemicarbazone) (GTSM), exerts its potent strictly copper-dependent antibacterial properties on MRSA. Our data indicate that the activity of the GTSM-copper complex goes beyond the general antibacterial effects of accumulated copper ions and suggest that, in contrast to prevailing opinion, copper complexes can indeed exhibit species- and target-specific activities. Based on experimental evidence, we propose that copper ions impose structural changes upon binding to the otherwise inactive GTSM ligand and transfer antibacterial properties to the chelate. In turn, GTSM determines target specificity and utilizes a redox-sensitive release mechanism through which copper ions are deployed at or in close proximity to a putative target. According to our proof-of-concept screen, copper activation is not a rare event and even extends to already established drugs. Thus, copper-activated compounds could define a novel class of anti-MRSA agents that amplify copper-dependent innate immune functions of the host. To this end, we provide a blueprint for a high-throughput drug screening campaign which considers the antibacterial properties of copper ions at the host-pathogen interface. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Movement of Potassium Ions inside KcsA in the High Concentration Regime using a Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Kim, Myojeong; Jo, Byeong Chul; Yoon, Hyun Jung; Wu, Sangwook; Thangappan, Jayaraman; Eun, Changsun

2018-05-01

The selectivity and conduction specificity of the KcsA channel toward potassium ions is crucial to the activity of this protein and this channel is intricately associated with several osmotic regulation and neuronal signaling processes. Despite multi-ion characteristics, the selective conduction behavior of KcsA is controlled by the size and distance specific electrostatic interaction between the selected residues and the potassium ions. The mechanism describing the movement of potassium ions in the channel and the conformational changes to KcsA that facilitate ion movement were investigated by a molecular dynamics (MD) simulation. In this study, we analyze the movement of potassium ions and water molecules at various time intervals during a 90 ns molecular dynamics simulation in the high potassium ion concentration regime and in the absence of the voltage. Examination of specific (3.6, 17.3, 43.38 and 43.44 ns) simulation periods revealed that key residues in the selectivity filter of KcsA influence the movement of potassium ions in the channel.

Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions

PubMed Central

Gokarn, Yatin R; Fesinmeyer, R Matthew; Saluja, Atul; Razinkov, Vladimir; Chase, Susan F; Laue, Thomas M; Brems, David N

2011-01-01

Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3M) salt concentrations, in dilute (<0.1M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li+, Na+, K+, Rb+, Cs+, GdnH+, and Ca2+), identity. The Q* decreased in the order F− > Cl− > Br− > NO3− ∼ I− > SCN− > ClO4− ≫ SO42−, demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO42− anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface. PMID:21432935

Induction of apoptosis by accelerated heavy-ion beams in cultured fetal rat testes and its modification

NASA Astrophysics Data System (ADS)

Wang, Bing; Tanaka, Kaoru; Shang, Yi; Fujita, Kazuko; Ninomiya, Yasuharu; Moreno, Stephanie G.; Coffigny, Herve; Hayata, Isamu; Murakami, Masahiro; Eguchi-Kasai, Kiyomi; Nenoi, Mitsuru

The increasing human activities in space missions make the study on effects from high-LET ionizing radiation an important issue to be addressed. We reported previously that prenatal irradiations with heavy-ion beams on gestation day 15 generally induced markedly detrimental effects on prenatal gonads, postnatal testicular development and male breeding activity in rats. To explore the mechanisms involved in radiation-induced gonocyte apoptosis in fetal gonads, which played a critical role in the fate of postnatal testis development, accelerated heavy-ion irradiations and organotypic culture of Wistar fetal rat testes were applied to investigations focused on cellular and molecular events after irradiations with or without chemical addition. Results showed that, in addition to the clustered distribution, both the time course and the percentage of apoptosis in gonocytes on gestation day 15 equivalent in vitro appeared similar to that in utero after exposure to either carbon-ion beams with a LET value of about 13 keV/µm or neon-ion beams with a LET value of about 30 keV/µm. Irradiations induced increased p53 expression in a dose dependent manner and decreased expressions of p21 and Bcl- 2 by Western Blot examination. Administration of pan-caspase inhibitor prior to irradiations effectively inhibited apoptosis occurrence and reduced the extent of clustered apoptosis, while such effects were not observed with the presence of p53 inhibitor, gap junction inhibitor, or nitric oxide specific scavenger. These findings indicated that irradiations of cultured fetal rat testes manifested pathologically similar apoptosis induction in gonocytes to that in utero. P53 expression was possibly responsible for the response to radiation damage rather than induction of apoptosis. The syncytial organization of gonocytes played a key role in formation of the clustered apoptosis, an event that both gap junction inhibitor and nitric oxide specific scavenger were incapable of preventing.

Spiers Memorial Lecture. Ions at aqueous interfaces.

PubMed

Jungwirth, Pavel

2009-01-01

Studies of aqueous interfaces and of the behavior of ions therein have been profiting from a recent remarkable progress in surface selective spectroscopies, as well as from developments in molecular simulations. Here, we summarize and place in context our investigations of ions at aqueous interfaces employing molecular dynamics simulations and electronic structure methods, performed in close contact with experiment. For the simplest of these interfaces, i.e. the open water surface, we demonstrate that the traditional picture of an ion-free surface is not valid for large, soft (polarizable) ions such as the heavier halides. Both simulations and spectroscopic measurements indicate that these ions can be present and even enhanced at surface of water. In addition we show that the ionic product of water exhibits a peculiar surface behavior with hydronium but not hydroxide accumulating at the air/water and alkane/water interfaces. This result is supported by surface-selective spectroscopic experiments and surface tension measurements. However, it contradicts the interpretation of electrophoretic and titration experiments in terms of strong surface adsorption of hydroxide; an issue which is further discussed here. The applicability of the observed behavior of ions at the water surface to investigations of their affinity for the interface between proteins and aqueous solutions is explored. Simulations show that for alkali cations the dominant mechanism of specific interactions with the surface of hydrated proteins is via ion pairing with negatively charged amino acid residues and with the backbone amide groups. As far as halide anions are concerned, the lighter ones tend to pair with positively charged amino acid residues, while heavier halides exhibit affinity to the amide group and to non-polar protein patches, the latter resembling their behavior at the air/water interface. These findings, together with results for more complex molecular ions, allow us to formulate a local model of interactions of ions with proteins with the aim to rationalize at the molecular level ion-specific Hofmeister effects, e.g. the salting out of proteins.

Higher Initial DNA Damage and Persistent Cell Cycle Arrest after Carbon Ion Irradiation Compared to X-irradiation in Prostate and Colon Cancer Cells

PubMed Central

Suetens, Annelies; Konings, Katrien; Moreels, Marjan; Quintens, Roel; Verslegers, Mieke; Soors, Els; Tabury, Kevin; Grégoire, Vincent; Baatout, Sarah

2016-01-01

The use of charged-particle beams, such as carbon ions, is becoming a more and more attractive treatment option for cancer therapy. Given the precise absorbed dose-localization and an increased biological effectiveness, this form of therapy is much more advantageous compared to conventional radiotherapy, and is currently being used for treatment of specific cancer types. The high ballistic accuracy of particle beams deposits the maximal dose to the tumor, while damage to the surrounding healthy tissue is limited. In order to better understand the underlying mechanisms responsible for the increased biological effectiveness, we investigated the DNA damage and repair kinetics and cell cycle progression in two p53 mutant cell lines, more specifically a prostate (PC3) and colon (Caco-2) cancer cell line, after exposure to different radiation qualities. Cells were irradiated with various absorbed doses (0, 0.5, and 2 Gy) of accelerated 13C-ions at the Grand Accélérateur National d’Ions Lourds facility (Caen, France) or with X-rays (0, 0.1, 0.5, 1, 2, and 5 Gy). Microscopic analysis of DNA double-strand breaks showed dose-dependent increases in γ-H2AX foci numbers and foci occupancy after exposure to both types of irradiation, in both cell lines. However, 24 h after exposure, residual damage was more pronounced after lower doses of carbon ion irradiation compared to X-irradiation. Flow cytometric analysis showed that carbon ion irradiation induced a permanent G2/M arrest in PC3 cells at lower doses (2 Gy) compared to X-rays (5 Gy), while in Caco-2 cells the G2/M arrest was transient after irradiation with X-rays (2 and 5 Gy) but persistent after exposure to carbon ions (2 Gy). PMID:27148479

Preparation of chitosan/amine modified diatomite composites and adsorption properties of Hg(II) ions.

PubMed

Fu, Yong; Huang, Yue; Hu, Jianshe; Zhang, Zhengjie

2018-03-01

A green functional adsorbent (CAD) was prepared by Schiff base reaction of chitosan and amino-modified diatomite. The morphology, structure and adsorption properties of the CAD were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and Brunauer Emmett Teller measurements. The effect of pH value, contact time and temperature on the adsorption of Hg(II) ions for the CAD is discussed in detail. The experimental results showed that the CAD had a large specific surface area and multifunctional groups such as amino, hydroxyl and Schiff base. The optimum adsorption effect was obtained when the pH value, temperature and contact time were 4, 25 °C and 120 min, respectively, and the corresponding maximum adsorption capacity of Hg(II) ions reached 102 mg/g. Moreover, the adsorption behavior of Hg(II) ions for the CAD followed the pseudo-second-order kinetic model and Langmuir model. The negative ΔG 0 and ΔH 0 suggested that the adsorption was a spontaneous exothermic process.

MeV per Nucleon Ion Irradiation of Nuclear Materials with High Energy Synchrotron X-ray Characterization

DOE PAGES

Pellin, M. J.; Yacout, Abdellatif M.; Mo, Kun; ...

2016-01-14

The combination of MeV/Nucleon ion irradiation (e.g. 133 MeV Xe) and high energy synchrotron x-ray characterization (e.g. at the Argonne Advanced Photon Source, APS) provides a powerful characterization method to understand radiation effects and to rapidly screen materials for the nuclear reactor environment. Ions in this energy range penetrate ~10 μm into materials. Over this range, the physical interactions vary (electronic stopping, nuclear stopping and added interstitials). Spatially specific x-ray (and TEM and nanoindentation) analysis allow individual quantification of these various effects. Hard x-rays provide the penetration depth needed to analyze even nuclear fuels. Here, this combination of synchrotron x-raymore » and MeV/Nucleon ion irradiation is demonstrated on U-Mo fuels. A preliminary look at HT-9 steels is also presented. We suggest that a hard x-ray facility with in situ MeV/nucleon irradiation capability would substantially accelerate the rate of discovery for extreme materials.« less

Numerical experiments on charging of a spherical body in a plasma with Maxwellian distributions of charged particles

NASA Astrophysics Data System (ADS)

Krasovsky, Victor L.; Kiselyov, Alexander A.

2017-12-01

New results of numerical simulation of collisionless plasma perturbation caused by a sphere absorbing electrons and ions are presented. Consideration is given to nonstationary phenomena accompanying the process of charging as well as to plasma steady state reached at long times. Corresponding asymptotic values of charges of the sphere and trapped-ion cloud around it have been found along with self-consistent electric field pattern depending on parameters of the unperturbed plasma. It is established that contribution of the trapped ions to screening of the charged sphere can be quite significant, so that the screening becomes essentially nonlinear in nature. A simple interconnection between the sphere radius, electron and ion Debye lengths has been revealed as the condition for maximum trapped-ion effect. Kinetic structure of the space charge induced in the plasma is discussed with relation to the specific form of the unperturbed charged particle distribution functions.

First prototypes of hybrid potassium-ion capacitor (KIC): An innovative, cost-effective energy storage technology for transportation applications

NASA Astrophysics Data System (ADS)

Le Comte, Annaïg; Reynier, Yvan; Vincens, Christophe; Leys, Côme; Azaïs, Philippe

2017-09-01

Hybrid supercapacitors, combining capacitive carbon-based positive electrode with a Li-ion battery-type negative electrode have been developed in the pursuit of increasing the energy density of conventional supercapacitor without impacting the power density. However, lithium-ion capacitors yet hardly meet the specifications of automotive sector. Herein we report for the first time the development of new hybrid potassium-ion capacitor (KIC) technology. Compared to lithium-ion capacitor (LIC) all strategic materials (lithium and copper) have been replaced. Excellent electrochemical performance have been achieved at a pouch cell scale, with cyclability superior to 55 000 cycles at high charge/discharge regime. For the same cell scale, the energy density is doubled compared to conventional supercapacitor up to high power regime (>1.5 kW kg-1). Finally, the technology was successfully scaled up to 18650 format leading to very promising prospects for transportation applications.

Inhibition of Monometalated Methionine Aminopeptidase: Inhibitor Discovery and Crystallographic Analysis†

PubMed Central

Huang, Min; Xie, Sheng-Xue; Ma, Ze-Qiang; Huang, Qing-Qing; Nan, Fa-Jun; Ye, Qi-Zhuang

2008-01-01

Two divalent metal ions are commonly seen in the active site cavity of methionine aminopeptidase, and at least one of the metal ions is directly involved in catalysis. Although ample structural and functional information is available for dimetalated enzyme, methionine aminopeptidase likely functions as a monometalated enzyme under physiological conditions. Information on structure, as well as catalysis and inhibition, of the monometalated enzyme is lacking. By improving conditions of high throughput screening, we identified a unique inhibitor with specificity toward the monometalated enzyme. Kinetic characterization indicates a mutual exclusivity in binding between the inhibitor and the second metal ion at the active site. This is confirmed by X-ray structure, and this inhibitor coordinates with the first metal ion and occupies the space normally occupied by the second metal ion. Kinetic and structural analyses of the inhibition by this and other inhibitors provide insight in designing effective inhibitors of methionine aminopeptidase. PMID:17948983

A HiPIMS plasma source with a magnetic nozzle that accelerates ions: application in a thruster

NASA Astrophysics Data System (ADS)

Bathgate, Stephen N.; Ganesan, Rajesh; Bilek, Marcela M. M.; McKenzie, David R.

2017-01-01

We demonstrate a solid fuel electrodeless ion thruster that uses a magnetic nozzle to collimate and accelerate copper ions produced by a high power impulse magnetron sputtering discharge (HiPIMS). The discharge is initiated using argon gas but in a practical device the consumption of argon could be minimised by exploiting the self-sputtering of copper. The ion fluence produced by the HiPIMS discharge was measured with a retarding field energy analyzer (RFEA) as a function of the magnetic field strength of the nozzle. The ion fraction of the copper was determined from the deposition rate of copper as a function of substrate bias and was found to exceed 87%. The ion fluence and ion energy increased in proportion with the magnetic field of the nozzle and the energy of the ions was found to follow a Maxwell-Boltzmann distribution with a directed velocity. The effectiveness of the magnetic nozzle in converting the randomized thermal motion of the ions into a jet was demonstrated from the energy distribution of the ions. The maximum ion exhaust velocity of at least 15.1 km/s, equivalent to a specific impulse of 1543 s was measured which is comparable to existing Hall thrusters and exceeds that of Teflon pulsed plasma thrusters.

Water-mediated ion-ion interactions are enhanced at the water vapor-liquid interface.

PubMed

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-06-17

There is overwhelming evidence that ions are present near the vapor-liquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ion-ion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vapor-liquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. "Sticky" electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from α-helical to a hairpin-turn-like one in response to charging of its ends.

Measurements of ion concentration in gasoline and diesel engine exhaust

NASA Astrophysics Data System (ADS)

Yu, Fangqun; Lanni, Thomas; Frank, Brian P.

The nanoparticles formed in motor vehicle exhaust have received increasing attention due to their potential adverse health effects. It has been recently proposed that combustion-generated ions may play a critical role in the formation of these volatile nanoparticles. In this paper, we design an experiment to measure the total ion concentration in motor vehicle engine exhaust, and report some preliminary measurements in the exhaust of a gasoline engine (K-car) and a diesel engine (diesel generator). Under the experimental set-up reported in this study and for the specific engines used, the total ion concentration is ca. 3.3×10 6 cm -3 with almost all of the ions smaller than 3 nm in the gasoline engine exhaust, and is above 2.7×10 8 cm -3 with most of the ions larger than 3 nm in the diesel engine exhaust. This difference in the measured ion properties is interpreted as a result of the different residence times of exhaust inside the tailpipe/connecting pipe and the different concentrations of soot particles in the exhaust. The measured ion concentrations appear to be within the ranges predicted by a theoretical model describing the evolution of ions inside a pipe.

Metal-assisted SIMS and cluster ion bombardment for ion yield enhancement

NASA Astrophysics Data System (ADS)

Heile, A.; Lipinsky, D.; Wehbe, N.; Delcorte, A.; Bertrand, P.; Felten, A.; Houssiau, L.; Pireaux, J.-J.; De Mondt, R.; Van Vaeck, L.; Arlinghaus, H. F.

2008-12-01

In addition to structural information, a detailed knowledge of the local chemical environment proves to be of ever greater importance, for example for the development of new types of materials as well as for specific modifications of surfaces and interfaces in multiple fields of materials science or various biomedical and chemical applications. But the ongoing miniaturization and therefore reduction of the amount of material available for analysis constitute a challenge to the detection limits of analytical methods. In the case of time-of-flight secondary ion mass spectrometry (TOF-SIMS), several methods of secondary ion yield enhancement have been proposed. This paper focuses on the investigation of the effects of two of these methods, metal-assisted SIMS and polyatomic primary ion bombardment. For this purpose, thicker layers of polystyrene (PS), both pristine and metallized with different amounts of gold, were analyzed using monoatomic (Ar +, Ga +, Xe +, Bi +) and polyatomic (SF 5+, Bi 3+, C 60+) primary ions. It was found that polyatomic ions generally induce a significant increase of the secondary ion yield. On the other hand, with gold deposition, a yield enhancement can only be detected for monoatomic ion bombardment.

Aqueous ionic liquids and their effects on protein structures: an overview on recent theoretical and experimental results

NASA Astrophysics Data System (ADS)

Smiatek, Jens

2017-06-01

Ionic liquids (ILs) are used in a variety of technological and biological applications. Recent experimental and simulation results reveal the influence of aqueous ionic liquids on the stability of protein and enzyme structures. Depending on different parameters like the concentration and the ion composition, one can observe distinct stabilization or denaturation mechanisms for various ILs. In this review, we summarize the main findings and discuss the implications with regard to molecular theories of solutions and specific ion effects. A preferential binding model is introduced in order to discuss protein-IL effects from a statistical mechanics perspective. The value of the preferential binding coefficient determines the strength of the ion influence and indicates a shift of the chemical equilibrium either to the native or the denatured state of the protein. We highlight the role of water in order to explain the self-association behavior of the IL species and discuss recent experimental and simulation results in the light of the observed binding effects.

Conformational Specific Infrared and Ultraviolet Spectroscopy of Cold YA(D-Pro)AA\\cdotH+ Ions: a Sterochemical "twist" on the Proline Effect

NASA Astrophysics Data System (ADS)

Harrilal, Christopher P.; DeBlase, Andrew F.; Burke, Nicole L.; McLuckey, Scott A.; Zwier, Timothy S.

2016-06-01

The "proline effect" is a well-known fragmentation phenomenon in mass spectrometry, in which y-fragments are produced preferentially over b-fragments during the collision induced dissociation of protonated L-proline containing peptide ions. This specific fragmentation channel is favored because of the high basicity of the secondary amine intermediate and the ring instability in alternative bn+ products [ASMS 2014, 25, 1705]. In contrast, peptides containing the D-Pro stereoisomer have been shown to largely favor the production of b4+ ions over y3+ ions. This strongly suggests that differences in the conformational preferences between the D-Pro and L-Pro diastereomers are likely to be responsible but structural evidence has been lacking to date. Using tandem mass spectrometry and IR-UV double resonant action spectroscopy we are able to compare the 3D structures of cold [YA(D-Pro)AA+H]+ to [YA(L-Pro)AA+H]+ ions. The UV action spectra reveals two major conformers in [YA(D-Pro)AA+H]+ and one major conformer in [YA(L-Pro)AA+H]+. Clear differences in the hydrogen bonding patterns are apparent between the two conformers observed in the D-Pro specie which are both distinct from the L-Pro diastereomer. Furthermore, conformer and diastereomer specific photofragmentation patterns are observed. It is also noted that a ten-fold photofragment enhancement unique to one of the D-Pro conformers is observed upon absorption of a resonant IR photon after UV excitation. Differences in the excited state photophysics between the two D-Pro conformers suggest that vibrational excitation of S1 turns on coupling to the dissociative -Tyr channel in one conformer, while this coupling is already present in the vibronic ground state of the other. Calculated harmonic spectra (M052X/6-31+G*) of conformers obtained from Monte Carlo searches to the experimental spectra.

BioMEMS for mitochondria medicine

NASA Astrophysics Data System (ADS)

Padmaraj, Divya

A BioMEMS device to study cell-mitochondrial physiological functionalities was developed. The pathogenesis of many diseases including obesity, diabetes and heart failure as well as aging has been linked to functional defects of mitochondria. The synthesis of Adenosine Tri Phosphate (ATP) is determined by the electrical potential across the inner mitochondrial membrane and by the pH difference due to proton flux across it. Therefore, electrical characterization by E-fields with complementary chemical testing was used here. The BioMEMS device was fabricated as an SU-8 based microfluidic system with gold electrodes on SiO2/Si wafers for electromagnetic interrogation. Ion Sensitive Field Effect Transistors (ISFETs) were incorporated for proton studies important in the electron transport chain, together with monitoring Na+, K+ and Ca++ ions for ion channel studies. ISFETs are chemically sensitive Metal Oxide Semiconductor Field Effect Transistor (MOSFET) devices and their threshold voltage is directly proportional to the electrolytic H+ ion variation. These ISFETs (sensitivity ˜55 mV/pH for H+) were further realized as specific ion sensitive Chemical Field Effect Transistors (CHEMFETs) by depositing a specific ion sensitive membrane on the gate. Electrodes for dielectric spectroscopy studies of mitochondria were designed as 2- and 4-probe structures for optimized operation over a wide frequency range. In addition, to limit polarization effects, a 4-electrode set-up with unique meshed pickup electrodes (7.5x7.5 mum2 loops with 4 mum wires) was fabricated. Sensitivity of impedance spectroscopy to membrane potential changes was confirmed by studying the influence of uncouplers and glucose on mitochondria. An electrical model was developed for the mitochondrial sample, and its frequency response correlated with impedance spectroscopy experiments of sarcolemmal mitochondria. Using the mesh electrode structure, we obtained a reduction of 83.28% in impedance at 200 Hz. COMSOL simulations of selected electrical structures in this sensor were compared with experimental results to better understand the physical system. A broadband permittivity analysis tool consisting of lumped and distributed structures was also developed. The frequency range of this device is from 100 Hz to 40 GHz and utilizes an interdigitated capacitor and coplanar waveguide. The simultaneous measurement of membrane potential, ion concentrations and pH would enhance diagnostics and studies of mitochondrial diseases.

Microstructure of room temperature ionic liquids at stepped graphite electrodes

DOE PAGES

Feng, Guang; Li, Song; Zhao, Wei; ...

2015-07-14

Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two-dimensional microstructure of ionmore » layers exhibits different patterns and alignments of counter-ion/co-ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL-electrode interfaces in supercapacitors.« less

Investigation into accurate mass capability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, with respect to radical ion species.

PubMed

Wyatt, Mark F; Stein, Bridget K; Brenton, A Gareth

2006-05-01

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) has been shown to be an effective technique for the characterization of organometallic, coordination, and highly conjugated compounds. The preferred matrix is 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), with radical ions observed. However, MALDI-TOFMS is generally not favored for accurate mass measurement. A specific method had to be developed for such compounds to assure the quality of our accurate mass results. Therefore, in this preliminary study, two methods of data acquisition, and both even-electron (EE+) ion and odd-electron (OE+.) radical ion mass calibration standards, have been investigated to establish the basic measurement technique. The benefit of this technique is demonstrated for a copper compound for which ions were observed by MALDI, but not by electrospray (ESI) or liquid secondary ion mass spectrometry (LSIMS); a mean mass accuracy error of -1.2 ppm was obtained.

Mercury ion thruster research, 1977. [plasma acceleration

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1977-01-01

The measured ion beam divergence characteristics of two and three-grid, multiaperture accelerator systems are presented. The effects of perveance, geometry, net-to-total accelerating voltage, discharge voltage and propellant are examined. The applicability of a model describing doubly-charged ion densities in mercury thrusters is demonstrated for an 8-cm diameter thruster. The results of detailed Langmuir probing of the interior of an operating cathode are given and used to determine the ionization fraction as a function of position upstream of the cathode orifice. A mathematical model of discharge chamber electron diffusion and collection processes is presented along with scaling laws useful in estimating performance of large diameter and/or high specific impluse thrusters. A model describing the production of ionized molecular nitrogen in ion thrusters is included.

Synthesis and Characterization of Templated Ion Exchange Resins for the Selective Complexion of Actinide Ions

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

Murrray, George M.; Uy, O. Manuel

The purpose of this research is to develop polymeric extractants for the selective complexation of uranyl ions (and subsequently other actinyl and actinide ions) from aqueous solutions. Selectivity for a specific actinide ion is obtained by providing the polymers with cavities lined with complexing ligands so arranged as to match the charge, coordination number, coordination geometry, and size of the actinide ion. These cavity-containing polymers are produced by using a specific actinide ion (or surrogate) as a template around which monomeric complexing ligands are polymerized. The polymers provide useful sequestering agents for removing actinide ions from wastes and will formmore » the basis for a variety of analytical techniques for actinide determination.« less

An electrodynamic ion funnel for electrospray ionization source based time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

Bhushan, K. G.; Rao, K. C.; Sule, U.; Reddy, P.; Rodrigues, S. M.; Gaikwad, D. T.; Mukundhan, R.; Gupta, S. K.

2016-04-01

An electrodynamic ion funnel has been developed for improving the sensitivity of electrospray ionization sources widely used in the mass spectrometric study of proteins and other biological macromolecules. The ion funnel consists of 52 electrodes and works under the combined influence of RF and DC voltages in the pressure range of 0.1 to 5 mbar. A novel feature of this ion funnel is the specific shape of the exit electrode that improves transmission of lower mass ions by reducing the depth of effective trapping potentials. In this paper, we report on the optimization of the ion funnel design using ion trajectory simulation software SIMION 8.0 especially in the mass range 500-5000 amu, followed by experimental observations of the ion transmission from the electrospray interface. It is seen that the electrospray-ion funnel combination greatly enhances the transmission when compared with an electrospray-skimmer interface. Ion currents > 1 nA could be obtained at the exit of the ion funnel for dilute Streptomycin Sulphate (~ 1500 amu) solution with the ion funnel operating in the 500-900 kHz frequency range, amplitude of 70 Vp-p, under a DC gradient of about 20 Volts/cm at a background pressure of 0.3 mbar. Details of the construction of the ion funnel along with the experimental results are presented.

Bacterially Induced Dolomite Formation in the Presence of Sulfate Ions under Aerobic Conditions

NASA Astrophysics Data System (ADS)

Sanchez-Roman, M.; McKenzie, J. A.; Vasconcelos, C.; Rivadeneyra, M.

2005-12-01

The origin of dolomite remains a long-standing enigma in sedimentary geology because, although thermodynamically favorable, precipitation of dolomite from modern seawater does not occur. Experiments conducted at elevated temperatures (200 oC) indicated that the presence of small concentrations of sulfate ions inhibits the transformation of calcite to dolomite [1]. Indeed, sulfate ions appeared to inhibit dolomite formation above 2 mM concentration (versus 28 mM in modern seawater). Recently, culture experiments have demonstrated that sulfate-reducing bacteria mediate the precipitation of dolomite at Earth surface conditions in the presence of sustained sulfate ion concentrations [2,3]. Additionally, in a number of modern hypersaline environments, dolomite forms from solutions with high sulfate ion concentrations (2 to 70 times seawater). These observations suggest that the experimentally observed sulfate-ion inhibition [1] may not apply to all ancient dolomite formation. Here, we report aerobic culture experiments conducted at low temperatures (25 and 35 oC) and variable sulfate ion concentrations (0, 0.5, 1 and 2 x seawater values) using moderately halophilic bacteria, Halomonas meridiana. After an incubation period of 15 days, experiments at 35 oC with variable sulfate ion concentrations (0, 0.5 x and seawater values) contained crystals of Ca-dolomite and stochiometric dolomite. The experiment at 35 oC with 2 x seawater sulfate ion concentration produced dolomite crystals after 20 days of incubation. In a parallel set of experiments at 25 oC, precipitation of dolomite was observed after 25 days of incubation in cultures with variable sulfate ion concentrations (0, 0.5 x and seawater values). In the culture with 2 x seawater sulfate ion concentration, dolomite crystals were observed after 30 days. Our study demonstrates that halophilic bacteria (or heterotrophic microorganisms), which do not require sulfate ions for metabolism, can mediate dolomite precipitation in the presence of sulfate ions. Apparently, microbial dolomite precipitation is not intrinsically linked to any particular group of organisms or specific metabolic processes or even specific environment. Furthermore, because heterotrophic microorganisms appear to be able to mediate microbial dolomite precipitation with or without sulfate ions in the media, our results indicate that the kinetic inhibition effect of sulfate ions can be overcome under specific sedimentary conditions. The present study adds a new insight to the dolomite problem, which could lead to a better clarification of the mechanism(s) involved in the massive dolomite formation observed in the geological record. References: [1] Baker, P.A., and Kastner, M., (1981), Science, 213, 214-216. [2] Vasconcelos, C., McKenzie, J.A., Bernasconi, S., Grujic, D. and Tien, A.J., (1995), Nature 377, 220-222.. [3] Warthmann R., van Lith Y., Vasconcelos C., McKenzie J.A. and Karpoff A.M., (2000), Geology 28, 1091-1094.

Theoretical level energies and transition data for 4p64d4, 4p64d34f and 4p54d5 configurations of W34+ ion

NASA Astrophysics Data System (ADS)

Karpuškienė, R.; Bogdanovich, P.; Kisielius, R.

2017-05-01

The ab initio quasirelativistic approach developed specifically for the calculation of spectral parameters of highly charged ions was used to derive transition data for the tungsten ion W34+. The configuration interaction method was applied to include electron correlation effects. The relativistic effects were taken into account in the Breit-Pauli approximation. The level energies, radiative lifetimes τ, Landé g-factors are determined for the ground configuration 4p64d4 and two excited configurations 4p64d34f and 4p54d5. The radiative transition wavelengths λ and emission transition probabilities A for the electric dipole, electric quadrupole, electric octupole, magnetic dipole, and magnetic quadrupole transitions among the levels of these configurations are produced.

Stretching magnetism with an electric field in a nitride semiconductor

PubMed Central

Sztenkiel, D.; Foltyn, M.; Mazur, G. P.; Adhikari, R.; Kosiel, K.; Gas, K.; Zgirski, M.; Kruszka, R.; Jakiela, R.; Li, Tian; Piotrowska, A.; Bonanni, A.; Sawicki, M.; Dietl, T.

2016-01-01

The significant inversion symmetry breaking specific to wurtzite semiconductors, and the associated spontaneous electrical polarization, lead to outstanding features such as high density of carriers at the GaN/(Al,Ga)N interface—exploited in high-power/high-frequency electronics—and piezoelectric capabilities serving for nanodrives, sensors and energy harvesting devices. Here we show that the multifunctionality of nitride semiconductors encompasses also a magnetoelectric effect allowing to control the magnetization by an electric field. We first demonstrate that doping of GaN by Mn results in a semi-insulating material apt to sustain electric fields as high as 5 MV cm−1. Having such a material we find experimentally that the inverse piezoelectric effect controls the magnitude of the single-ion magnetic anisotropy specific to Mn3+ ions in GaN. The corresponding changes in the magnetization can be quantitatively described by a theory developed here. PMID:27782126

Interconnected V2O5 nanoporous network for high-performance supercapacitors.

PubMed

Saravanakumar, B; Purushothaman, Kamatchi K; Muralidharan, G

2012-09-26

Vanadium pentoxide (V(2)O(5)) has attracted attention for supercapcitor applications because of its extensive multifunctional properties. In the present study, V(2)O(5) nanoporous network was synthesized via simple capping-agent-assisted precipitation technique and it is further annealed at different temperatures. The effect of annealing temperature on the morphology, electrochemical and structural properties, and stability upon oxidation-reduction cycling has been analyzed for supercapacitor application. We achieved highest specific capacitance of 316 F g(-1) for interconnected V(2)O(5) nanoporous network. This interconnected nanoporous network creates facile nanochannels for ion diffusion and facilitates the easy accessibility of ions. Moreover, after six hundred consecutive cycling processes the specific capacitance has changed only by 24%. A simple cost-effective preparation technique of V(2)O(5) nanoporous network with excellent capacitive behavior, energy density, and stability encourages its possible commercial exploitation for the development of high-performance supercapacitors.

Dielectric Self-Energy in Poisson-Boltzmann and Poisson-Nernst-Planck Models of Ion Channels

PubMed Central

Corry, Ben; Kuyucak, Serdar; Chung, Shin-Ho

2003-01-01

We demonstrated previously that the two continuum theories widely used in modeling biological ion channels give unreliable results when the radius of the conduit is less than two Debye lengths. The reason for this failure is the neglect of surface charges on the protein wall induced by permeating ions. Here we attempt to improve the accuracy of the Poisson-Boltzmann and Poisson-Nernst-Planck theories, when applied to channel-like environments, by including a specific dielectric self-energy term to overcome spurious shielding effects inherent in these theories. By comparing results with Brownian dynamics simulations, we show that the inclusion of an additional term in the equations yields significant qualitative improvements. The modified theories perform well in very wide and very narrow channels, but are less successful at intermediate sizes. The situation is worse in multi-ion channels because of the inability of the continuum theories to handle the ion-to-ion interactions correctly. Thus, further work is required if these continuum theories are to be reliably salvaged for quantitative studies of biological ion channels in all situations. PMID:12770869

Atomic-scale thermocapillary flow in focused ion beam milling

NASA Astrophysics Data System (ADS)

Das, Kallol; Johnson, Harley; Freund, Jonathan

2016-11-01

Focused ion beams (FIB) offer an attractive tool for nanometer-scale manufacturing and material processing, particularly because they can be focused to a few nanometer diameter spot. This motivates their use for many applications, such as sample preparation for transmission electron microscopy (TEM), forming nanometer scale pores in thin films for DNA sequencing. Despite its widespread use, the specific mechanisms of FIB milling, especially at high ion fluxes for which significant phase change might occur, remains incompletely understood. Here we investigate the process of nanopore fabrication in thin Si films using molecular dynamics simulation where Ga+ ions are used as the focused ions. For a range of ion intensities in a realistic configuration, a recirculating melt region develops, which is seen to flow with a symmetrical pattern, counter to how it would flow were it is driven by the ion momentum flux. Such flow is potentially important for the shape and composition of the formed structures. Relevant stress scales and estimated physical properties of silicon under these extreme conditions support the importance thermocapillary effects. A continuum flow model with Marangoni forcing reproduces the flow.

HPRT mutations in V79 Chinese hamster cells induced by accelerated Ni, Au and Pb ions.

PubMed

Stoll, U; Barth, B; Scheerer, N; Schneider, E; Kiefer, J

1996-07-01

Mutation induction by accelerated heavy ions to 6-TG resistance (HPRT system) in V79 Chinese hamster cells was investigated with Ni (6-630 Me V/u), Au (2.2, 8.7 Me V/u) and Pb ions (11.6-980 Me V/u) corresponding to a LET range between 180 and 12895 ke V/microns. Most experiments could only be performed once due to technical limitations using accelerator beam times. Survival curves were exponential, mutation induction curves linear with fluence. From their slopes inactivation- and mutation-induction cross-sections were derived. If they are plotted versus LET, single, ion-specific curves are obtained. It is shown that other parameters like ion energy and effective charge play an important role. In the case of Au and Pb ions the cross-sections follow a common line, since these ions have nearly the same atomic weight, so that they should have similar spatial ionization patterns in matter at the same energies. Calculated RBEs were higher for mutation induction than for killing for all LETs.

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

NASA Astrophysics Data System (ADS)

Nguyen, Mary; Rick, Steven W.

2018-06-01

The diffusion rates for water molecules in salt solutions depend on the identity of the ions, as well as their concentration. Among the alkali metal ions, cesium and potassium increase and sodium strongly decreases the diffusion constant of water. The origin of the difference can be understood by examining the simulation results using different potential models. In this work, aqueous solutions of salts are simulated with a variety of models. Commonly used non-polarizable models, which otherwise reproduce many experimental properties, do not capture the trend in the diffusion constant, while models which include polarization and/or charge transfer interactions do. For the non-polarizable models, the diffusion constant decreases too strongly with salt concentration. The changes in the water diffusion constant with increasing salt concentration match the diffusion constant of the ion. The ion diffusion constant is dependent on the residence time for water in the ion solvation shell. The non-polarizable models over-estimate the residence time, relative to the translational diffusion constant and so tend to under-estimate the ion and water diffusion constants.

Structural Feature Ions for Distinguishing N- and O-Linked Glycan Isomers by LC-ESI-IT MS/MS

NASA Astrophysics Data System (ADS)

Everest-Dass, Arun V.; Abrahams, Jodie L.; Kolarich, Daniel; Packer, Nicolle H.; Campbell, Matthew P.

2013-06-01

Glycomics is the comprehensive study of glycan expression in an organism, cell, or tissue that relies on effective analytical technologies to understand glycan structure-function relationships. Owing to the macro- and micro-heterogeneity of oligosaccharides, detailed structure characterization has required an orthogonal approach, such as a combination of specific exoglycosidase digestions, LC-MS/MS, and the development of bioinformatic resources to comprehensively profile a complex biological sample. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS) has emerged as a key tool in the structural analysis of oligosaccharides because of its high sensitivity, resolution, and robustness. Here, we present a strategy that uses LC-ESI-MS/MS to characterize over 200 N- and O-glycans from human saliva glycoproteins, complemented by sequential exoglycosidase treatment, to further verify the annotated glycan structures. Fragment-specific substructure diagnostic ions were collated from an extensive screen of the literature available on the detailed structural characterization of oligosaccharides and, together with other specific glycan structure feature ions derived from cross-ring and glycosidic-linkage fragmentation, were used to characterize the glycans and differentiate isomers. The availability of such annotated mass spectrometric fragmentation spectral libraries of glycan structures, together with such substructure diagnostic ions, will be key inputs for the future development of the automated elucidation of oligosaccharide structures from MS/MS data.

Heavy ion action on single cells: Cellular inactivation capability of single accelerated heavy ions

NASA Technical Reports Server (NTRS)

Kost, M.; Pross, H.-D.; Russmann, C.; Schneider, E.; Kiefer, J.; Kraft, G.; Lenz, G.; Becher, W.

1994-01-01

Heavy ions (HZE-particles) constitute an important part of radiation in space. Although their number is small the high amount of energy transferred by individual particles may cause severe biological effects. Their investigation requires special techniques which were tested by experiments performed at the UNILAC at the GSI (Darmstadt). Diploid yeast was used which is a suitable eucaryotic test system because of its resistance to extreme conditions like dryness and vacuum. Cells were placed on nuclear track detector foils and exposed to ions of different atomic number and energy. To assess the action of one single ion on an individual cell, track parameters and the respective colony forming abilities (CFA) were determined with the help of computer aided image analysis. There is mounting evidence that not only the amount of energy deposited along the particle path, commonly given by the LET, is of importance but also the spatial problem of energy deposition at a submicroscopical scale. It is virtually impossible to investigate track structure effects in detail with whole cell populations and (globally applied) high particle fluences. It is, therefore, necessary to detect the action of simple ions in individual cells. The results show that the biological action depends on atomic number and specific energy of the impinging ions, which can be compared with model calculations of recent track structure models.

Higher sensitivity secondary ion mass spectrometry of biological molecules for high resolution, chemically specific imaging.

PubMed

McDonnell, Liam A; Heeren, Ron M A; de Lange, Robert P J; Fletcher, Ian W

2006-09-01

To expand the role of high spatial resolution secondary ion mass spectrometry (SIMS) in biological studies, numerous developments have been reported in recent years for enhancing the molecular ion yield of high mass molecules. These include both surface modification, including matrix-enhanced SIMS and metal-assisted SIMS, and polyatomic primary ions. Using rat brain tissue sections and a bismuth primary ion gun able to produce atomic and polyatomic primary ions, we report here how the sensitivity enhancements provided by these developments are additive. Combined surface modification and polyatomic primary ions provided approximately 15.8 times more signal than using atomic primary ions on the raw sample, whereas surface modification and polyatomic primary ions yield approximately 3.8 and approximately 8.4 times more signal. This higher sensitivity is used to generate chemically specific images of higher mass biomolecules using a single molecular ion peak.

How Closely Related Are Conformations of Protein Ions Sampled by IM-MS to Native Solution Structures?

NASA Astrophysics Data System (ADS)

Chen, Shu-Hua; Russell, David H.

2015-09-01

Here, we critically evaluate the effects of changes in the ion internal energy (Eint) on ion-neutral collision cross sections (CCS) of ions of two structurally diverse proteins, specifically the [M + 6H]6+ ion of ubiquitin (ubq6+), the [M + 5H]5+ ion of the intrinsically disordered protein (IDP) apo-metallothionein-2A (MT), and its partially- and fully-metalated isoform, the [CdiMT]5+ ion. The ion-neutral CCS for ions formed by "native-state" ESI show a strong dependence on Eint. Collisional activation is used to increase Eint prior to the ions entering and within the traveling wave (TW) ion mobility analyzer. Comparisons of experimental CCSs with those generated by molecular dynamics (MD) simulation for solution-phase ions and solvent-free ions as a function of temperature provide new insights about conformational preferences and retention of solution conformations. The Eint-dependent CCSs, which reveal increased conformational diversity of the ion population, are discussed in terms of folding/unfolding of solvent-free ions. For example, ubiquitin ions that have low internal energies retain native-like conformations, whereas ions that are heated by collisional activation possess higher internal energies and yield a broader range of CCS owing to increased conformational diversity due to losses of secondary and tertiary structures. In contrast, the CCS profile for the IDP apoMT is consistent with kinetic trapping of an ion population composed of a wide range of conformers, and as the Eint is increased, these structurally labile conformers unfold to an elongated conformation.

Confirming the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials by PECVD

NASA Astrophysics Data System (ADS)

Liu, Yulin; Lin, Jinghuang; Jia, Henan; Chen, Shulin; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Feng, Jicai; Fei, Weidong

2017-11-01

In order to confirm the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials (NCMs), here we report a novel strategy to create different Ar+ ion states in situ in plasma enhanced chemical vapor deposition (PECVD) by separating catalyst film from the substrate. Different bombardment environments on either side of the catalyst film were created simultaneously to achieve multi-layered structural NCMs. Results showed that Ar+ ion bombardment is crucial and complex for the growth of NCMs. Firstly, Ar+ ion bombardment has both positive and negative effects on carbon nanotubes (CNTs). On one hand, Ar+ ions can break up the graphic structure of CNTs and suppress thin CNT nucleation and growth. On the other hand, Ar+ ion bombardment can remove redundant carbon layers on the surface of large catalyst particles which is essential for thick CNTs. As a result, the diameter of the CNTs depends on the Ar+ ion state. As for vertically oriented few-layer graphene (VFG), Ar+ ions are essential and can even convert the CNTs into VFG. Therefore, by combining with the catalyst separation method, specific or multi-layered structural NCMs can be obtained by PECVD only by changing the intensity of Ar+ ion bombardment, and these special NCMs are promising in many fields.

Confirming the key role of Ar+ ion bombardment in the growth feature of nanostructured carbon materials by PECVD.

PubMed

Liu, Yulin; Lin, Jinghuang; Jia, Henan; Chen, Shulin; Qi, Junlei; Qu, Chaoqun; Cao, Jian; Feng, Jicai; Fei, Weidong

2017-11-24

In order to confirm the key role of Ar + ion bombardment in the growth feature of nanostructured carbon materials (NCMs), here we report a novel strategy to create different Ar + ion states in situ in plasma enhanced chemical vapor deposition (PECVD) by separating catalyst film from the substrate. Different bombardment environments on either side of the catalyst film were created simultaneously to achieve multi-layered structural NCMs. Results showed that Ar + ion bombardment is crucial and complex for the growth of NCMs. Firstly, Ar + ion bombardment has both positive and negative effects on carbon nanotubes (CNTs). On one hand, Ar + ions can break up the graphic structure of CNTs and suppress thin CNT nucleation and growth. On the other hand, Ar + ion bombardment can remove redundant carbon layers on the surface of large catalyst particles which is essential for thick CNTs. As a result, the diameter of the CNTs depends on the Ar + ion state. As for vertically oriented few-layer graphene (VFG), Ar + ions are essential and can even convert the CNTs into VFG. Therefore, by combining with the catalyst separation method, specific or multi-layered structural NCMs can be obtained by PECVD only by changing the intensity of Ar + ion bombardment, and these special NCMs are promising in many fields.

Influence of nanoparticle-ion and nanoparticle-polymer interactions on ion transport and viscoelastic properties of polymer electrolytes

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

Mogurampelly, Santosh; Sethuraman, Vaidyanathan; Pryamitsyn, Victor

We use atomistic simulations to probe the ion conductivities and mechanical properties of polyethylene oxide electrolytes containing Al{sub 2}O{sub 3} nanoparticles. We specifically study the influence of repulsive polymer-nanoparticle and ion-nanoparticle interactions and compare the results with those reported for electrolytes containing the polymorph β-Al{sub 2}O{sub 3} nanoparticles. We observe that incorporating repulsive nanoparticle interactions generally results in increased ionic mobilities and decreased elastic moduli for the electrolyte. Our results indicate that both ion transport and mechanical properties are influenced by the polymer segmental dynamics in the interfacial zones of the nanoparticle in the ion-doped systems. Such effects were seenmore » to be determined by an interplay between the nanoparticle-polymer, nanoparticle-ion, and ion-polymer interactions. In addition, such interactions were also observed to influence the number of dissociated ions and the resulting conductivities. Within the perspective of the influence of nanoparticles on the polymer relaxation times in ion-doped systems, our results in the context of viscoelastic properties were consistent with the ionic mobilities. Overall, our results serve to highlight some issues that confront the efforts to use nanoparticle dispersions to simultaneously enhance the conductivity and the mechanical strength of polymer electrolyte.« less

A detailed examination of laser-ion acceleration mechanisms in the relativistic transparency regime using tracers

NASA Astrophysics Data System (ADS)

Stark, David J.; Yin, Lin; Albright, Brian J.; Nystrom, William; Bird, Robert

2018-04-01

We present a particle-in-cell study of linearly polarized laser-ion acceleration systems, in which we use both two-dimensional (2D) and three-dimensional (3D) simulations to characterize the ion acceleration mechanisms in targets which become transparent to the laser pulse during irradiation. First, we perform a target length scan to optimize the peak ion energies in both 2D and 3D, and the predictive capabilities of 2D simulations are discussed. Tracer analysis allows us to isolate the acceleration into stages of target normal sheath acceleration (TNSA), hole boring (HB), and break-out afterburner (BOA) acceleration, which vary in effectiveness based on the simulation parameters. The thinnest targets reveal that enhanced TNSA is responsible for accelerating the most energetic ions, whereas the thickest targets have ions undergoing successive phases of HB and TNSA (in 2D) or BOA and TNSA (in 3D); HB is not observed to be a dominant acceleration mechanism in the 3D simulations. It is in the intermediate optimal regime, both when the laser breaks through the target with appreciable amplitude and when there is enough plasma to form a sustained high density flow, that BOA is most effective and is responsible for the most energetic ions. Eliminating the transverse laser spot size effects by performing a plane wave simulation, we can isolate with greater confidence the underlying physics behind the ion dynamics we observe. Specifically, supplemented by wavelet and FFT analyses, we match the post-transparency BOA acceleration with a wave-particle resonance with a high-amplitude low-frequency electrostatic wave of increasing phase velocity, consistent with that predicted by the Buneman instability.

[Application of precursor ion scanning method in rapid screening of illegally added phosphodiesterase-5 inhibitors and their unknown derivatives in Chinese traditional patent medicines and health foods].

PubMed

Sun, Jing; Cao, Ling; Feng, Youlong; Tan, Li

2014-11-01

The compounds with similar structure often have similar pharmacological activities. So it is a trend for illegal addition that new derivatives of effective drugs are synthesized to avoid the statutory test. This bring challenges to crack down on illegal addition behavior, however, modified derivatives usually have similar product ions, which allow for precursor ion scanning. In this work, precursor ion scanning mode of a triple quadrupole mass spectrometer was first applied to screen illegally added drugs in complex matrix such as Chinese traditional patent medicines and healthy foods. Phosphodiesterase-5 inhibitors were used as experimental examples. Through the analysis of the structure and mass spectrum characteristics of the compounds, phosphodiesterase-5 inhibitors were classified, and their common product ions were screened by full scan of product ions of typical compounds. Then high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method with precursor ion scanning mode was established based on the optimization of MS parameters. The effect of mass parameters and the choice of fragment ions were also studied. The method was applied to determine actual samples and further refined. The results demonstrated that this method can meet the need of rapid screening of unknown derivatives of phosphodiesterase-5 inhibitors in complex matrix, and prevent unknown derivatives undetected. This method shows advantages in sensitivity, specificity and efficiency, and is worth to be further investigated.

Sequence-specific binding of counterions to B-DNA

PubMed Central

Denisov, Vladimir P.; Halle, Bertil

2000-01-01

Recent studies by x-ray crystallography, NMR, and molecular simulations have suggested that monovalent counterions can penetrate deeply into the minor groove of B form DNA. Such groove-bound ions potentially could play an important role in AT-tract bending and groove narrowing, thereby modulating DNA function in vivo. To address this issue, we report here 23Na magnetic relaxation dispersion measurements on oligonucleotides, including difference experiments with the groove-binding drug netropsin. The exquisite sensitivity of this method to ions in long-lived and intimate association with DNA allows us to detect sequence-specific sodium ion binding in the minor groove AT tract of three B-DNA dodecamers. The sodium ion occupancy is only a few percent, however, and therefore is not likely to contribute importantly to the ensemble of B-DNA structures. We also report results of ion competition experiments, indicating that potassium, rubidium, and cesium ions bind to the minor groove with similarly weak affinity as sodium ions, whereas ammonium ion binding is somewhat stronger. The present findings are discussed in the light of previous NMR and diffraction studies of sequence-specific counterion binding to DNA. PMID:10639130

Mitochondrial calcium ion and membrane potential transients follow the pattern of epileptiform discharges in hippocampal slice cultures.

PubMed

Kovács, Richard; Kardos, Julianna; Heinemann, Uwe; Kann, Oliver

2005-04-27

Emerging evidence suggests that mitochondrial dysfunction contributes to the pathophysiology of epilepsy. Recurrent mitochondrial Ca2+ ion load during seizures might act on mitochondrial membrane potential (DeltaPsim) and proton motive force. By using electrophysiology and confocal laser-scanning microscopy, we investigated the effects of epileptiform activity, as induced by low-Mg2+ ion perfusion in hippocampal slice cultures, on changes in DeltaPsim and in mitochondrial Ca2+ ion concentration ([Ca2+]m). The mitochondrial compartment was identified by monitoring DeltaPsim in the soma and dendrites of patched CA3 pyramidal cells using the mitochondria-specific voltage-sensitive dye rhodamine-123 (Rh-123). Interictal activity was accompanied by localized mitochondrial depolarization that was restricted to a few mitochondria in small dendrites. In contrast, robust Rh-123 release into the cytosol was observed during seizure-like events (SLEs), indicating simultaneous depolarization of mitochondria. This was critically dependent on Ca2+ ion uptake and extrusion, because inhibition of the mitochondrial Ca2+ ion uniporter by Ru360 and the mitochondrial Na+/Ca2+ ion exchanger by 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one but not the inhibitor of mitochondrial permeability transition pore, cyclosporin A, decreased the SLE-associated mitochondrial depolarization. The Ca2+ ion dependence of simultaneous mitochondrial depolarization suggested enhanced Ca2+ ion cycling across mitochondrial membranes during epileptiform activity. Indeed, [Ca2+]m fluctuated during interictal activity in single dendrites, and these fluctuations spread over the entire mitochondrial compartment during SLEs, as revealed using mitochondria-specific dyes (rhod-2 and rhod-ff) and spatial frequency-based image analysis. These findings strengthen the hypothesis that epileptic activity results in Ca2+ ion-dependent changes in mitochondrial function that might contribute to the neuronal injury during epilepsy.

High voltage and high specific capacity dual intercalating electrode Li-ion batteries

NASA Technical Reports Server (NTRS)

Blanco, Mario (Inventor); West, William C. (Inventor)

2010-01-01

The present invention provides high capacity and high voltage Li-ion batteries that have a carbonaceous cathode and a nonaqueous electrolyte solution comprising LiF salt and an anion receptor that binds the fluoride ion. The batteries can comprise dual intercalating electrode Li ion batteries. Methods of the present invention use a cathode and electrode pair, wherein each of the electrodes reversibly intercalate ions provided by a LiF salt to make a high voltage and high specific capacity dual intercalating electrode Li-ion battery. The present methods and systems provide high-capacity batteries particularly useful in powering devices where minimizing battery mass is important.

Comparative Toxicities of Salts on Microbial Processes in Soil

PubMed Central

Maheshwari, Arpita; Bengtson, Per; Rousk, Johannes

2016-01-01

Soil salinization is a growing threat to global agriculture and carbon sequestration, but to date it remains unclear how microbial processes will respond. We studied the acute response to salt exposure of a range of anabolic and catabolic microbial processes, including bacterial (leucine incorporation) and fungal (acetate incorporation into ergosterol) growth rates, respiration, and gross N mineralization and nitrification rates. To distinguish effects of specific ions from those of overall ionic strength, we compared the addition of four salts frequently associated with soil salinization (NaCl, KCl, Na2SO4, and K2SO4) to a nonsaline soil. To compare the tolerance of different microbial processes to salt and to interrelate the toxicity of different salts, concentration-response relationships were established. Growth-based measurements revealed that fungi were more resistant to salt exposure than bacteria. Effects by salt on C and N mineralization were indistinguishable, and in contrast to previous studies, nitrification was not found to be more sensitive to salt exposure than other microbial processes. The ion-specific toxicity of certain salts could be observed only for respiration, which was less inhibited by salts containing SO42− than Cl− salts, in contrast to the microbial growth assessments. This suggested that the inhibition of microbial growth was explained solely by total ionic strength, while ion-specific toxicity also should be considered for effects on microbial decomposition. This difference resulted in an apparent reduction of microbial growth efficiency in response to exposure to SO42− salts but not to Cl− salts; no evidence was found to distinguish K+ and Na+ salts. PMID:26801570

Effects of halide ions on photodegradation of sulfonamide antibiotics: Formation of halogenated intermediates.

PubMed

Li, Yingjie; Qiao, Xianliang; Zhang, Ya-Nan; Zhou, Chengzhi; Xie, Huaijun; Chen, Jingwen

2016-10-01

The occurrence of sulfonamide antibiotics (SAs) in estuarine waters urges insights into their environmental fate for ecological risk assessment. Although many studies focused on the photochemical behavior of SAs, yet the effects of halide ions relevant to estuarine and marine environments on their photodegradation have been poorly understood. Here, we investigated the effects of halide ions on the photodegradation of SAs with sulfapyridine, sulfamethazine, and sulfamethoxazole as representative compounds. Results showed that halide ions did not significantly impact the photodegradation of sulfapyridine and sulfamethoxazole, while they significantly promoted the photodegradation of sulfamethazine. Further experiments found that ionic strength applied with NaClO4 significantly enhanced the photodegradation of the SAs, which was attributed to the decreased quenching rate constant of the triplet-excited SAs ((3)SA(∗)). Compared with ionic strength, specific Cl(-) effects retarded the photodegradation of the SAs. Our study found that triplet-excited sulfamethazine can oxidize halide ions to produce halogen radicals, subsequently leading to the halogenation of sulfamethazine, which was confirmed by the identification of both chlorinated and brominated intermediates. These results indicate that halide ions play an important role in the photochemical behavior of some SAs in estuarine waters and seawater. The occurrence of halogenation for certain organic pollutants can be predicted by comparing the oxidation potentials of triplet-excited contaminants with those of halogen radicals. Our findings are helpful in understanding the photochemical behavior and assessing the ecological risks of SAs and other organic pollutants in estuarine and marine environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Magnesium/Lithium-Ion Hybrid Battery with High Reversibility by Employing NaV3O8·1.69H2O Nanobelts as a Positive Electrode.

PubMed

Rashad, Muhammad; Li, Xianfeng; Zhang, Huamin

2018-06-27

Recently, magnesium-ion batteries (MIBs) have been under remarkable research focus owing to their appealingly high energy density and natural abundance of magnesium. Nevertheless, MIBs exhibit a very limited performance because of sluggish solid-state Mg 2+ ion diffusion and high polarizability, which hinder their progress toward commercialization. Herein, we report a Mg 2+ /Li + hybrid-ion battery (MLIB) with NaV 3 O 8 ·1.69H 2 O (NVO) nanobelts synthesized at room temperature working as the positive electrode. In the hybrid-ion system, Li + intercalates/deintercalates along with a small amount of Mg 2+ adsorption at the NVO cathode, whereas the anode side of the cell is dominated by Mg 2+ deposition/dissolution. As a result, the MLIB exhibits a much higher rate capability (i.e., 446 mA h g -1 at 20 mA g -1 ) than the previously reported MLIBs. MLIB maintains a high specific capacity of 200 mA h g -1 at 80 mA g -1 for 150 cycles, showing excellent stability. Moreover, the effect of different Li-ion concentrations (i.e., 0.5-2.0 M) in the electrolyte and cutoff voltage (ranging from 2 to 2.6 V) on the specific capacities are investigated. The current study highlights a strategy to exploit the Mg 2+ /Li + hybrid electrolyte system with various electrode materials for high-performance MIBs.

Polyhydric polymer-functionalized fluorescent probe with enhanced aqueous solubility and specific ion recognition: A test strips-based fluorimetric strategy for the rapid and visual detection of Fe3+ ions.

PubMed

Duan, Zhiqiang; Zhang, Chunxian; Qiao, Yuchun; Liu, Fengjuan; Wang, Deyan; Wu, Mengfan; Wang, Ke; Lv, Xiaoxia; Kong, Xiangmu; Wang, Hua

2017-08-01

A polyhydric polymer-functionalized probe with enhanced aqueous solubility was designed initially by coupling 1-pyrenecarboxyaldehyde (Pyr) onto poly(vinyl alcohol) (PVA) via the one-step condensation reaction. Polyhydric PVA polymer chains could facilitate the Pyr fluorophore with largely improved aqueous solubility and especially strong cyan fluorescence. Importantly, the fluorescence of the PVA-Pyr probes could thereby be quenched specifically by Fe 3+ ions through the strong PVA-Fe 3+ interaction triggering the polymeric probe aggregation. Furthermore, a test strips-based fluorimetric method was developed with the stable and uniform probe distribution by taking advantage of the unique film-forming ability and the depression capacity of "coffee-stain" effects of PVA matrix. The as-developed test strips could allow for the rapid and visual detections of Fe 3+ ions simply by a dipping way, showing a linear concentration range of 5.00-300μM, with the detection limit of 0.73μM. Moreover, the proposed method was applied to the evaluation of Fe 3+ ions in natural water samples, showing the analysis performances better or comparable to those of current detection techniques. This test strips-based fluorimetric strategy promises the extensive applications for the rapid on-site monitoring of Fe 3+ ions in environmental water and the outdoor finding of the potential iron mines. Copyright © 2017 Elsevier B.V. All rights reserved.

Taking SiC Power Devices to the Final Frontier: Addressing Challenges of the Space Radiation Environment

NASA Technical Reports Server (NTRS)

Lauenstein, Jean-Marie; Casey, Megan

2017-01-01

Silicon carbide power device technology has the potential to enable a new generation of aerospace power systems that demand high efficiency, rapid switching, and reduced mass and volume in order to expand space-based capabilities. For this potential to be realized, SiC devices must be capable of withstanding the harsh space radiation environment. Commercial SiC components exhibit high tolerance to total ionizing dose but to date, have not performed well under exposure to heavy ion radiation representative of the on-orbit galactic cosmic rays. Insertion of SiC power device technology into space applications to achieve breakthrough performance gains will require intentional development of components hardened to the effects of these highly-energetic heavy ions. This work presents heavy-ion test data obtained by the authors over the past several years for discrete SiC power MOSFETs, JFETs, and diodes in order to increase the body of knowledge and understanding that will facilitate hardening of this technology to space radiation effects. Specifically, heavy-ion irradiation data taken under different bias, temperature, and ion beam conditions is presented for devices from different manufacturers, and the emerging patterns discussed.

Thermodynamics and Kinetics of Na+/K+-Formate Ion Pairs Association in Polarizable Water: A Molecular Dynamics Study

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

Nguyen, Phuong T.; Nguyen, Van T.; Annapureddy, Harsha V.

2012-12-03

To elevate our understanding of ion specific activity in biological systems, the potential of mean force approach was utilized to study solvent effects on interactions between two alkali cations (Na+ and K+) with a formate anion in water. A very complex free energy landscape was observed, much more so than alkali-halide ion pairs. Furthermore, stronger binding between the Na+-formate pair was found in comparison to the K+-formate pair in water, a finding that agrees with experimental and theoretical studies of these systems. The kinetics of ion-pair interconversions were studied using transition rate theory, along with a variety of theoretical approachesmore » such as the Kramers and Grote Hynes theories. These rate results were used to predict solvent effects on dynamical features of contact ion-pair association, in which faster dynamics were found for K+-formate pairs than for Na+-formate pairs. This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory is a multiprogram national laboratory operated for DOE by Battelle.« less

Cobalt doping of the MOF-5 framework and its effect on gas-adsorption properties.

PubMed

Botas, Juan A; Calleja, Guillermo; Sánchez-Sánchez, Manuel; Orcajo, M Gisela

2010-04-20

Partial isomorphic substitution of Zn in IRMOF metal clusters by cobalt ions is described for the first time. Specifically, different numbers of Co(2+) ions have been incorporated during solvothermal crystallization into the Zn-based MOF-5 (IRMOF-1) framework, which is one of the most studied MOF materials. The amount of Zn that can be substituted seems to be limited, being no more than 25% of total metal content, that is, no more than one Co atom inside every metal cluster formed by four transition-metal ions, on average. Several characterization techniques, including X-ray diffraction, DR UV-visible spectroscopy, N(2) adsorption isotherms, and thermogravimetrical analysis, strongly support the effective incorporation of Co into the material framework. As-synthesized CoMOF-5 has cobalt ions in octahedral coordination, changing to tetrahedral by simple evacuation, presumably by the removal of two diethylformamide molecules per Co ion. Moreover, the H(2), CH(4), and CO(2) uptake of MOF-5 materials systematically increases with the Co content, particularly at high pressure. Such an increase is moderate anyway, considering that Co is incorporated into unexposed metal sites that are less accessible to gas molecules.

Doping effect of polyaniline/MWCNT composites on capacitance and cyclic stability of supercapacitors.

PubMed

Karthikeyan, G; Sahoo, S; Nayak, G C; Das, C K

2012-03-01

Polyaniline doped by Zn2+ ions was synthesized as nanocomposites with multiwalled carbon nanotubes (MWCNT) by in-situ oxidative polymerization and investigated as electrode material for supercapacitors. The uniform coating of polyaniline on MWCNT was characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effect of Zn2+ ions on nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances were investigated by cyclic voltammetry (CV), constant current charging/discharging cyclic test (CC) and electrochemical impedance spectroscopy (EIS) using a three-electrode system. The doped polyaniline composites show higher specific capacitance and better cyclic stability.

Microwave-Assisted Preparation and Characterization of a Polyoxometalate-Based Inorganic 2D Framework Anode for Enhancing Lithium-Ion Battery Performance.

PubMed

Nie, Yan-Mei; Liang, Shuang; Yu, Wei-Dong; Yuan, Hao; Yan, Jun

2018-05-04

A pure inorganic 2D network molybdophosphate, [Mn 3 Mo 12 O 24 (OH) 6 (HPO 3 ) 8 (H 2 O) 6 ] 4- (1 a), synthesized through microwave irradiation with the existence of Mn 2+ and organic cations and isolated as [(CH 3 ) 2 NH 2 ] 3 Na[Mn 3 Mo 12 O 24 (OH) 6 (HPO 3 ) 8 (H 2 O) 6 ]⋅12 H 2 O (1), is found to possess highly enhanced performance in lithium-ion batteries' anode materials. The molecule shows multielectron redox properties suitable for producing anode materials with a specific capacity of 602 mA h g -1 at 100 mA g -1 after 50 cycles in lithium-ion batteries, although its specific capacity is the highest among all the reported pure inorganic 2D polyoxometalates to date, the cyclic stability is not that satisfactory. A hybrid nanocomposite of this 2D network and polypyrrole cations effectively reduces the capacity fading in initial cycles, and increases the stability and improves the electrochemical performance of lithium-ion batteries as well. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphene-modified nanostructured vanadium pentoxide hybrids with extraordinary electrochemical performance for Li-ion batteries

DOE PAGES

Liu, Qi; Li, Zhe-Fei; Liu, Yadong; ...

2015-01-20

The long-standing issues of low intrinsic electronic conductivity, slow lithium-ion diffusion and irreversible phase transitions on deep discharge prevent the high specific capacity/energy (443 mAh g -1 and 1,550 Wh kg -1) vanadium pentoxide from being used as the cathode material in practical battery applications. Here we develop a method to incorporate graphene sheets into vanadium pentoxide nanoribbons via the sol–gel process. The resulting graphene-modified nanostructured vanadium pentoxide hybrids contain only 2 wt. % graphene, yet exhibits extraordinary electrochemical performance: a specific capacity of 438 mAh g -1, approaching the theoretical value (443 mAh g -1), a long cyclability andmore » significantly enhanced rate capability. Such performance is the result of the combined effects of the graphene on structural stability, electronic conduction, vanadium redox reaction and lithium-ion diffusion supported by various experimental studies. Finally, this method provides a new avenue to create nanostructured metal oxide/graphene materials for advanced battery applications.« less

New frontiers of atomic layer etching

NASA Astrophysics Data System (ADS)

Sherpa, Sonam D.; Ranjan, Alok

2018-03-01

Interest in atomic layer etching (ALE) has surged recently because it offers several advantages over continuous or quasicontinuous plasma etching. These benefits include (1) independent control of ion energy, ion flux, and radical flux, (2) flux-independent etch rate that mitigates the iso-dense loading effects, and (3) ability to control the etch rate with atomic or nanoscale precision. In addition to these benefits, we demonstrate an area-selective etching for maskless lithography as a new frontier of ALE. In this paper, area-selective etching refers to the confinement of etching into the specific areas of the substrate. The concept of area-selective etching originated during our studies on quasi-ALE of silicon nitride which consists of sequential exposure of silicon nitride to hydrogen and fluorinated plasma. The findings of our studies reported in this paper suggest that it may be possible to confine the etching into specific areas of silicon nitride without using any mask by replacing conventional hydrogen plasma with a localized source of hydrogen ions.

Thermal expansion and specific heat of La1-xTexCoO3

NASA Astrophysics Data System (ADS)

Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.

2018-05-01

We present the specific heat and thermal expansion of La1-xTexCoO3 family using Modified Rigid Ion Model (MRIM). The effect of Te doping on the thermal and cohesive properties have been studied by an atomistic approach. The Debye temperature of these perovskite materials is also predicted. The effect of Tellurium doping on lattice specific heat (C), thermal expansion (α) of La1-xTexCoO3 (x= 0.05-0.25) as a function of temperature (1K≤T≤1000K) is reported probably for the first time.

Dissecting blue light signal transduction pathway in leaf epidermis using a pharmacological approach.

PubMed

Živanović, Branka D; Shabala, Lana I; Elzenga, Theo J M; Shabala, Sergey N

2015-10-01

Blue light signalling pathway in broad bean leaf epidermal cells includes key membrane transporters: plasma- and endomembrane channels and pumps of H (+) , Ca (2+) and K (+) ions, and plasma membrane redox system. Blue light signalling pathway in epidermal tissue isolated from the abaxial side of fully developed Vicia faba leaves was dissected by measuring the effect of inhibitors of second messengers on net K(+), Ca(2+) and H(+) fluxes using non-invasive ion-selective microelectrodes (the MIFE system). Switching the blue light on-off caused transient changes of the ion fluxes. The effects of seven groups of inhibitors were tested in this study: CaM antagonists, ATPase inhibitors, Ca(2+) anatagonists or chelators, agents affecting IP3 formation, redox system inhibitors, inhibitors of endomembrane Ca(2+) transport systems and an inhibitor of plasma membrane Ca(2+)-permeable channels. Most of the inhibitors had a significant effect on steady-state (basal) net fluxes, as well as on the magnitude of the transient ion flux responses to blue light fluctuations. The data presented in this study suggest that redox signalling and, specifically, plasma membrane NADPH oxidase and coupled Ca(2+) and K(+) fluxes play an essential role in blue light signal transduction.

NASA Electronic Parts and Packaging Field Programmable Gate Array Single Event Effects Test Guideline Update

NASA Technical Reports Server (NTRS)

Berg, Melanie D.; LaBel, Kenneth A.

2018-01-01

The following are updated or new subjects added to the FPGA SEE Test Guidelines manual: academic versus mission specific device evaluation, single event latch-up (SEL) test and analysis, SEE response visibility enhancement during radiation testing, mitigation evaluation (embedded and user-implemented), unreliable design and its affects to SEE Data, testing flushable architectures versus non-flushable architectures, intellectual property core (IP Core) test and evaluation (addresses embedded and user-inserted), heavy-ion energy and linear energy transfer (LET) selection, proton versus heavy-ion testing, fault injection, mean fluence to failure analysis, and mission specific system-level single event upset (SEU) response prediction. Most sections within the guidelines manual provide information regarding best practices for test structure and test system development. The scope of this manual addresses academic versus mission specific device evaluation and visibility enhancement in IP Core testing.

NASA Electronic Parts and Packaging (NEPP) Field Programmable Gate Array (FPGA) Single Event Effects (SEE) Test Guideline Update

NASA Technical Reports Server (NTRS)

Berg, Melanie D.; LaBel, Kenneth A.

2018-01-01

The following are updated or new subjects added to the FPGA SEE Test Guidelines manual: academic versus mission specific device evaluation, single event latch-up (SEL) test and analysis, SEE response visibility enhancement during radiation testing, mitigation evaluation (embedded and user-implemented), unreliable design and its affects to SEE Data, testing flushable architectures versus non-flushable architectures, intellectual property core (IP Core) test and evaluation (addresses embedded and user-inserted), heavy-ion energy and linear energy transfer (LET) selection, proton versus heavy-ion testing, fault injection, mean fluence to failure analysis, and mission specific system-level single event upset (SEU) response prediction. Most sections within the guidelines manual provide information regarding best practices for test structure and test system development. The scope of this manual addresses academic versus mission specific device evaluation and visibility enhancement in IP Core testing.

Water-mediated ion–ion interactions are enhanced at the water vapor–liquid interface

PubMed Central

Venkateshwaran, Vasudevan; Vembanur, Srivathsan; Garde, Shekhar

2014-01-01

There is overwhelming evidence that ions are present near the vapor–liquid interface of aqueous salt solutions. Charged groups can also be driven to interfaces by attaching them to hydrophobic moieties. Despite their importance in many self-assembly phenomena, how ion–ion interactions are affected by interfaces is not understood. We use molecular simulations to show that the effective forces between small ions change character dramatically near the water vapor–liquid interface. Specifically, the water-mediated attraction between oppositely charged ions is enhanced relative to that in bulk water. Further, the repulsion between like-charged ions is weaker than that expected from a continuum dielectric description and can even become attractive as the ions are drawn to the vapor side. We show that thermodynamics of ion association are governed by a delicate balance of ion hydration, interfacial tension, and restriction of capillary fluctuations at the interface, leading to nonintuitive phenomena, such as water-mediated like charge attraction. “Sticky” electrostatic interactions may have important consequences on biomolecular structure, assembly, and aggregation at soft liquid interfaces. We demonstrate this by studying an interfacially active model peptide that changes its structure from α-helical to a hairpin-turn–like one in response to charging of its ends. PMID:24889634

Trends in Effective Diffusion Coefficients for Ion-exchange Strengthening of Soda Lime Silicate Glasses

NASA Astrophysics Data System (ADS)

Karlsson, Stefan; Wondraczek, Lothar; Ali, Sharafat; Jonson, Bo

2017-04-01

Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.

Effect of Multivalent Ions on Electroosmotic Flow in Micro- and Nano-channels

NASA Astrophysics Data System (ADS)

Zheng, Zhi; Conlisk, A. Terrence

2002-11-01

In this work, the effect of multivalent ions on electroosmotic flow is investigated. Applications in biomedical engineering are numerous, including design of drug delivery systems, rapid molecular analysis and lab-on-a-chip. We specifically consider incorporating Ca^2+ and HPO4^2- and other monovalent ions, such as K^+ and H2PO4^-, into an aqueous NaCl solution. All previous work has been for the case where the mixture contains a pair of ionic species of equal valence. Electrochemical equilibrium considerations are used in determining the boundary conditions. The results can be applied to rectangular channels for which the height is on the nanometer scale up to the micrometer scale. The classical electroosmotic velocity profile is obtained at larger channel heights for fixed electrolyte concentration where an analytic solution for the velocity, potential and mole fractions may be obtained. The theory is valid for an arbitrary number of ionic species.

ISFET pH Sensitivity: Counter-Ions Play a Key Role.

PubMed

Parizi, Kokab B; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H S Philip

2017-02-02

The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor.

Management of extravasation of oxaliplatin by mimicking its biotransformation.

PubMed

Bahadori, F; Demiray, M

2018-04-27

Although oxaliplatin (Oxali) plays a key role in the treatment of many types of cancer and has been reported to be an irritant, there is no specific and effective method for its extravasation and failure in Oxali extravasation management results in the need for plastic surgery. In the body, Oxali bio-transforms upon dilution in chloride-containing buffer salts to its di-chloro derivative and loses an oxalate molecule. Consequently, the chloride ions exchange with water molecules in the intracellular environment to produce the di-aqua derivative, which is the most active biotransformation product of Oxali in terms of forming the DNA adducts. Thus, inhibiting transformation of di-chloro to di-aqua derivatives by accumulating chloride ions at the site of extravasation and saturating the Oxali molecule with these ions is a strategy that could help manage extravasation. Injecting normal saline at this site is a simple yet effective way to achieve this goal.

ISFET pH Sensitivity: Counter-Ions Play a Key Role

PubMed Central

Parizi, Kokab B.; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H. S. Philip

2017-01-01

The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor. PMID:28150700

Ion-Specific Nutrient Management in Closed Systems: The Necessity for Ion-Selective Sensors in Terrestrial and Space-Based Agriculture and Water Management Systems

PubMed Central

Bamsey, Matthew; Graham, Thomas; Thompson, Cody; Berinstain, Alain; Scott, Alan; Dixon, Michael

2012-01-01

The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution. The greenhouse sector has invested in research examining the potential of a number of these technologies to meet the industry's demanding requirements, and although no ideal solution yet exists for on-line measurement, growers do utilize technologies such as high-performance liquid chromatography to provide off-line measurements. An analogous situation exists on the International Space Station where, technological solutions are sought, but currently on-orbit water quality monitoring is considerably restricted. This paper examines the specific advantages that on-line ion-selective sensors could provide to plant production systems both terrestrially and when utilized in space-based biological life support systems and how similar technologies could be applied to nominal on-orbit water quality monitoring. A historical development and technical review of the various ion-selective monitoring technologies is provided. PMID:23201999

Ion-specific nutrient management in closed systems: the necessity for ion-selective sensors in terrestrial and space-based agriculture and water management systems.

PubMed

Bamsey, Matthew; Graham, Thomas; Thompson, Cody; Berinstain, Alain; Scott, Alan; Dixon, Michael

2012-10-01

The ability to monitor and control plant nutrient ions in fertigation solutions, on an ion-specific basis, is critical to the future of controlled environment agriculture crop production, be it in traditional terrestrial settings (e.g., greenhouse crop production) or as a component of bioregenerative life support systems for long duration space exploration. Several technologies are currently available that can provide the required measurement of ion-specific activities in solution. The greenhouse sector has invested in research examining the potential of a number of these technologies to meet the industry's demanding requirements, and although no ideal solution yet exists for on-line measurement, growers do utilize technologies such as high-performance liquid chromatography to provide off-line measurements. An analogous situation exists on the International Space Station where, technological solutions are sought, but currently on-orbit water quality monitoring is considerably restricted. This paper examines the specific advantages that on-line ion-selective sensors could provide to plant production systems both terrestrially and when utilized in space-based biological life support systems and how similar technologies could be applied to nominal on-orbit water quality monitoring. A historical development and technical review of the various ion-selective monitoring technologies is provided.

Excess Li-Ion Storage on Reconstructed Surfaces of Nanocrystals To Boost Battery Performance

DOE PAGES

Duan, Yandong; Zhang, Bingkai; Zheng, Jiaxin; ...

2017-08-03

Because of their enhanced kinetic properties, nanocrystallites have received much attention as potential electrode materials for energy storage. However, because of the large specific surface areas of nanocrystallites, they usually suffer from decreased energy density, cycling stability, and effective electrode capacity. Here, in this work, we report a size-dependent excess capacity beyond theoretical value (170 mA h g -1) by introducing extra lithium storage at the reconstructed surface in nanosized LiFePO 4 (LFP) cathode materials (186 and 207 mA h g -1 in samples with mean particle sizes of 83 and 42 nm, respectively). Moreover, this LFP composite also showsmore » excellent cycling stability and high rate performance. Our multimodal experimental characterizations and ab initio calculations reveal that the surface extra lithium storage is mainly attributed to the charge passivation of Fe by the surface C–O–Fe bonds, which can enhance binding energy for surface lithium by compensating surface Fe truncated symmetry to create two types of extra positions for Li-ion storage at the reconstructed surfaces. Such surface reconstruction nanotechnology for excess Li-ion storage makes full use of the large specific surface area of the nanocrystallites, which can maintain the fast Li-ion transport and greatly enhance the capacity. Finally, this discovery and nanotechnology can be used for the design of high-capacity and efficient lithium ion batteries.« less

Excess Li-Ion Storage on Reconstructed Surfaces of Nanocrystals To Boost Battery Performance

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

Duan, Yandong; Zhang, Bingkai; Zheng, Jiaxin

Because of their enhanced kinetic properties, nanocrystallites have received much attention as potential electrode materials for energy storage. However, because of the large specific surface areas of nanocrystallites, they usually suffer from decreased energy density, cycling stability, and effective electrode capacity. Here, in this work, we report a size-dependent excess capacity beyond theoretical value (170 mA h g -1) by introducing extra lithium storage at the reconstructed surface in nanosized LiFePO 4 (LFP) cathode materials (186 and 207 mA h g -1 in samples with mean particle sizes of 83 and 42 nm, respectively). Moreover, this LFP composite also showsmore » excellent cycling stability and high rate performance. Our multimodal experimental characterizations and ab initio calculations reveal that the surface extra lithium storage is mainly attributed to the charge passivation of Fe by the surface C–O–Fe bonds, which can enhance binding energy for surface lithium by compensating surface Fe truncated symmetry to create two types of extra positions for Li-ion storage at the reconstructed surfaces. Such surface reconstruction nanotechnology for excess Li-ion storage makes full use of the large specific surface area of the nanocrystallites, which can maintain the fast Li-ion transport and greatly enhance the capacity. Finally, this discovery and nanotechnology can be used for the design of high-capacity and efficient lithium ion batteries.« less

Nonlinear Ion Harmonics in the Paul Trap with Added Octopole Field: Theoretical Characterization and New Insight into Nonlinear Resonance Effect.

PubMed

Xiong, Caiqiao; Zhou, Xiaoyu; Zhang, Ning; Zhan, Lingpeng; Chen, Yongtai; Nie, Zongxiu

2016-02-01

The nonlinear harmonics within the ion motion are the fingerprint of the nonlinear fields. They are exclusively introduced by these nonlinear fields and are responsible to some specific nonlinear effects such as nonlinear resonance effect. In this article, the ion motion in the quadrupole field with a weak superimposed octopole component, described by the nonlinear Mathieu equation (NME), was studied by using the analytical harmonic balance (HB) method. Good accuracy of the HB method, which was comparable with that of the numerical fourth-order Runge-Kutta (4th RK), was achieved in the entire first stability region, except for the points at the stability boundary (i.e., β = 1) and at the nonlinear resonance condition (i.e., β = 0.5). Using the HB method, the nonlinear 3β harmonic series introduced by the octopole component and the resultant nonlinear resonance effect were characterized. At nonlinear resonance, obvious resonant peaks were observed in the nonlinear 3β series of ion motion, but were not found in the natural harmonics. In addition, both resonant excitation and absorption peaks could be observed, simultaneously. These are two unique features of the nonlinear resonance, distinguishing it from the normal resonance. Finally, an approximation equation was given to describe the corresponding working parameter, q nr , at nonlinear resonance. This equation can help avoid the sensitivity degradation due to the operation of ion traps at the nonlinear resonance condition.

Comparative investigation of the energetic ion spectra comprising the magnetospheric ring currents of the solar system

PubMed Central

Mauk, B H

2014-01-01

Investigated here are factors that control the intensities and shapes of energetic ion spectra that make up the ring current populations of the strongly magnetized planets of the solar system, specifically those of Earth, Jupiter, Saturn, Uranus, and Neptune. Following a previous and similar comparative investigation of radiation belt electrons, we here turn our attention to ions. Specifically, we examine the possible role of the differential ion Kennel-Petschek limit, as moderated by Electromagnetic Ion Cyclotron (EMIC) waves, as a standard for comparing the most intense ion spectra within the strongly magnetized planetary magnetospheres. In carrying out this investigation, the substantial complexities engendered by the very different ion composition distributions of these diverse magnetospheres must be addressed, given that the dispersion properties of the EMIC waves are strongly determined by the ion composition of the plasmas within which the waves propagate. Chosen for comparison are the ion spectra within these systems that are the most intense observed, specifically at 100 keV and 1 MeV. We find that Earth and Jupiter are unique in having their most intense ion spectra likely limited and sculpted by the Kennel-Petschek process. The ion spectra of Saturn, Uranus, and Neptune reside far below their respective limits and are likely limited by interactions with gas and dust (Saturn) and by the absence of robust ion acceleration processes (Uranus and Neptune). Suggestions are provided for further testing the efficacy of the differential Kennel-Petschek limit for ions using the Van Allen Probes. PMID:26167438

Antiradiation vaccine: Technology and development of prophylaxis, prevention and treatment of biological consequences from Heavy Ion irradiation.

NASA Astrophysics Data System (ADS)

Popov, Dmitri; Maliev, Vecheslav

Introduction: An anti-radiation vaccine could be an important part of a countermeasures reg-imen for effective radioprotection, immunoprophylaxis and immunotherapy of the acute radi-ation syndromes (ARS) after gamma-irradiation, neutron irradiation or heavy ion irradiation. Reliable protection of non-neoplastic regions of patients with different forms of cancer which undergo to heavy ion therapy ( e.g. Hadron-therapy) can significantly extend the efficiency of the therapeutic course. The protection of cosmonauts astronauts from the heavy ion ra-diation component of space radiation with specific immunoprophylaxis by the anti-radiation vaccine may be an important part of medical management for long term space missions. Meth-ods and experiments: 1. The Antiradiation Vaccine preparation -standard (mixture of toxoid form of Radiation Toxins -SRD-group) which include Cerebrovascular RT Neurotoxin, Car-diovascular RT Neurotoxin, Gastrointestinal RT Neurotoxin, Hematopoietic RT Hematotoxin. Radiation Toxins Specific Radiation Determinant Group were isolated from a central lymph of gamma-irradiated animals with Cerebrovascular, Cardiovascular, Gastrointestiinal, Hematopoi-etic forms of ARS. Devices for γ-radiation are "Panorama", "Puma". 2. Heavy ion exposure was accomplished at Department of Scientific Research Institute of Nuclear Physics, Dubna, Russia. The heavy ions irradiation was generated in heavy ion (Fe56) accelerator -UTI. Heavy Ion linear transfer energy -2000-2600 KeV mkm, 600 MeV U. Absorbed Dose -3820 Rad. 3. Experimental Design: Rabbits from all groups were irradiated by heavy ion accelerator. Group A -control -10 rabbits; Group B -placebo -5 rabbits; Group C -radioprotectant Cystamine (50 mg kg)-5 rabbits, 15 minutes before irradiation -5 rabbits; Group D -radioprotectant Gammafos (Amifostine -400mg kg ), -5 rabbits; Group E -Antiradiation Vaccine: subcuta-neus administration or IM -2 ml of active substance, 14 days before irradiation -5 rabbits. 4. Results: Group A -100% mortality within two hours after heavy ion irradiation with clinical symptoms of the acute cerebrovascular and cardiovascular syndromes. Group B -100% mortal-ity within 15 hours following irradiation. Group C -100% mortality within 14-15 hours after irradiation. Group D -100% mortality within 15-16 hours after irradiation. In groups A-D, development of the acute radiation cerebrovascular and cardiovascular syndromes as well as ex-tensive burns of skin caused rapid death. Group E -100% mortality in 280-290 hours (12 days) following heavy ion irradiation while animals were exhibiting a combination or individual forms of the acute cerebrovascular, cardiovascular, and gastrointestinal forms and focal skin burns. Discussion: The Antiradiation Vaccine (ARV) and specific immune-prophylaxis are an effective method of neutralization of Radiation Toxins. Vaccination with the ARV significantly extended the survival time after irradiation with heavy ions from two hours up to 300 hours. Clinical signs, clinical features, symptoms were somewhat attenuated. Degree of clinical forms of the Acute Radiation Syndromes were diminished in their severity. Groups A-D demonstrated an extremely severe degree (Degree 4) of Cerebrovascular and Cardiovascular forms of the Acute Radiation Syndromes and lethality 100% was registered in a short time after irradiation. Radi-ation induced burns in this groups (with Cutaneous sub-syndrome of ARS -Degree 4) that were deep with extensive and total dysfunction and possible muscle involvement developed. Animals from group E -Radioprotectant -anti-radiation vaccine had demonstrated later development of the severe Degree 3 or even Degree 2-3 forms of Cerebrovascular and Cardiovascular forms of the ARS and a survival time of irradiated animals was significantly prolonged. Cutaneous sub-syndrome developed in Degree 3 or Degree 2-3. Our results have demonstrated the potential radioprotection efficacy of specific immune-prophylaxis with the Antiradiation vaccine against heavy ion irradiation.

Novel graphene-like electrodes for capacitive deionization.

PubMed

Li, Haibo; Zou, Linda; Pan, Likun; Sun, Zhuo

2010-11-15

Capacitive deionization (CDI) is a novel technology that has been developed for removal of charged ionic species from salty water, such as salt ions. The basic concept of CDI, as well as electrosorption, is to force charged ions toward oppositely polarized electrodes through imposing a direct electric field to form a strong electrical double layer and hold the ions. Once the electric field disappears, the ions are instantly released back to the bulk solution. CDI is an alternative low-energy consumption desalination technology. Graphene-like nanoflakes (GNFs) with relatively high specific surface area have been prepared and used as electrodes for capacitive deionization. The GNFs were synthesized by a modified Hummers' method using hydrazine for reduction. They were characterized by atomic force microscopy, N2 adsorption at 77 K and electrochemical workstation. It was found that the ratio of nitric acid and sulfuric acid plays a vital role in determining the specific surface area of GNFs. Its electrosorption performance was much better than commercial activated carbon (AC), suggesting a great potential in capacitive deionisation application. Further, the electrosorptive performance of GNFs electrodes with different bias potentials, flow rates and ionic strengths were measured and the electrosorption isotherm and kinetics were investigated. The results showed that GNFs prepared by this process had the specific surface area of 222.01 m²/g. The specific electrosorptive capacity of the GNFs was 23.18 µmol/g for sodium ions (Na+) when the initial concentration was at 25 mg/L, which was higher than that of previously reported data using graphene and AC under the same experimental condition. In addition, the equilibrium electrosorption capacity was determined as 73.47 µmol/g at 2.0 V by fitting data through the Langmuir isotherm, and the rate constant was found to be 1.01 min⁻¹ by fitting data through pseudo first-order adsorption. The results suggested that the chemically synthesized GNFs can be used as effective electrode materials in CDI process for brackish water desalination.

Method and apparatus for ion mobility spectrometry with alignment of dipole direction (IMS-ADD)

DOEpatents

Shvartsburg, Alexandre A [Richland, WA; Tang, Keqi [Richland, WA; Smith, Richard D [Richland, WA

2007-01-30

Techniques and instrumentation are described for analyses of substances, including complex samples/mixtures that require separation prior to characterization of individual components. A method is disclosed for separation of ion mixtures and identification of ions, including protein and other macromolecular ions and their different structural isomers. Analyte ions are not free to rotate during the separation, but are substantially oriented with respect to the drift direction. Alignment is achieved by applying, at a particular angle to the drift field, a much stronger alternating electric field that "locks" the ion dipoles with moments exceeding a certain value. That value depends on the buffer gas composition, pressure, and temperature, but may be as low as .about.3 Debye under certain conditions. The presently disclosed method measures the direction-specific cross-sections that provide the structural information complementing that obtained from known methods, and, when coupled to those methods, increases the total peak capacity and specificity of gas-phase separations. Simultaneous 2-D separations by direction-specific cross sections along and orthogonally to the ion dipole direction are also possible.

Structural basis for stabilization of Z-DNA by cobalt hexaammine and magnesium cations

NASA Technical Reports Server (NTRS)

Gessner, R. V.; Quigley, G. J.; Wang, A. H.; van der Marel, G. A.; van Boom, J. H.; Rich, A.

1985-01-01

In the equilibrium between B-DNA and Z-DNA in poly(dC-dG), the [Co(NH3)6]3+ ion stabilizes the Z form 4 orders of magnitude more effectively than the Mg2+ ion. The structural basis of this difference is revealed in Z-DNA crystal structures of d(CpGpCpGpCpG) stabilized by either Na+/Mg2+ or Na+/Mg2+ plus [Co(NH3)6]3+. The crystals diffract X-rays to high resolution, and the structures were refined at 1.25 A. The [Co(NH3)6]3+ ion forms five hydrogen bonds onto the surface of Z-DNA, bonding to a guanine O6 and N7 as well as to a phosphate group in the ZII conformation. The Mg2+ ion binds through its hydration shell with up to three hydrogen bonds to guanine N7 and O6. Higher charge, specific fitting of more hydrogen bonds, and a more stable complex all contribute to the great effectiveness of [Co(NH3)6]3+ in stabilizing Z-DNA.

Research for the design of visual fatigue based on the computer visual communication

NASA Astrophysics Data System (ADS)

Deng, Hu-Bin; Ding, Bao-min

2013-03-01

With the era of rapid development of computer networks. The role of network communication in the social, economic, political, become more and more important and suggested their special role. The computer network communicat ion through the modern media and byway of the visual communication effect the public of the emotional, spiritual, career and other aspects of the life. While its rapid growth also brought some problems, It is that their message across to the public, its design did not pass a relat ively perfect manifestation to express the informat ion. So this not only leads to convey the error message, but also to cause the physical and psychological fatigue for the audiences. It is said that the visual fatigue. In order to reduce the fatigue when people obtain the useful information in using computer. Let the audience in a short time to obtain the most useful informat ion, this article gave a detailed account of its causes, and propose effective solutions and, through the specific examples to explain it, also in the future computer design visual communicat ion applications development prospect.

Chemoprevention of Radiation Induced Rat Mammary Neoplasms

NASA Technical Reports Server (NTRS)

Huso, David L.

1999-01-01

Radiations encountered in space include protons and heavy ions such as iron as well as their secondaries. The relative biological effect (RBE) of these ions is not known, particularly at the doses and dose-rates expected for planetary missions. Neutrons, are not particularly relevant to space travel, but have been found experimentally to have an increase in their RBE with decreasing dose. If a similar trend of increasing RBE with decreasing dose is present for heavy ions and protons during irradiation in space, the small doses received during space travel could potentially have substantial carcinogenic risk. Clearly more investigation of the effects of heavy ions and protons is needed before accurate risk assessment for prolonged travel in space can be done. One means to mitigate the increased risk of cancer due to radiation exposure in space is by developing effective countermeasures that can reduce the incidence of tumor development. Tamoxifen has recently been shown to be an effective chemopreventive agent in both animal models and humans for the prevention of mammary tumors. Tamoxifen is a unique drug, with a highly specific mechanism of action affecting a specific radiation-sensitive population of epithelial cells in the mammary gland. In human studies, the annual incidence of a primary tumor in the contralateral breast of women with previous breast cancer is about 8 per 1000, making them an exceedingly high-risk group for the development of breast cancer. In this high risk group, treated with tamoxifen, daily, for 2 years, the incidence of a new primary tumor in the contralateral breast was approximately one third of that noted in the non-tamoxifen treatment group. Tamoxifen antagonizes the action of estrogen by competing for the nuclear receptor complex thereby altering the association of the receptor complex and nuclear binding sites. Its effects in reducing the development of breast cancer could be accomplished by controlling clinically undetectable microcancers, arresting preneoplastic lesions, or correcting abnormal environments which predispose to high risk of malignant transformation.

Ammonia stress on nitrogen metabolism in tolerant aquatic plant-Myriophyllum aquaticum.

PubMed

Zhou, Qingyang; Gao, Jingqing; Zhang, Ruimin; Zhang, Ruiqin

2017-09-01

Ammonia has been a major reason of macrophyte decline in the water environment, and ammonium ion toxicity should be seen as universal, even in species frequently labeled as "NH 4 + specialists". To study the effects of high NH 4 + -N stress of ammonium ion nitrogen on tolerant submerged macrophytes and investigate the pathways of nitrogen assimilation in different organisms, Myriophyllum aquaticum was selected and treated with various concentrations of ammonium ions at different times. Increasing of ammonium concentration leads to an overall increase in incipient ammonia content in leaves and stems of plants. In middle and later stages, high concentrations of NH 4 + ion nitrogen taken up by M. aquaticum decreased, whereas the content of NO 3 - ion nitrogen increased. Moreover, in M. aquaticum, the activities of the enzymes nitrate reductase, glutamine synthetase and asparagine synthetase changed remarkably in the process of alleviating NH 4 + toxicity and deficiency. The results of the present study may support the studies on detoxification of high ammonium ion content in NH 4 + -tolerant submerged macrophytes and exploration of tissue-specific expression systems. Copyright © 2017. Published by Elsevier Inc.

On the effectiveness of ion range determination from in-beam PET data

NASA Astrophysics Data System (ADS)

Fiedler, Fine; Shakirin, Georgy; Skowron, Judith; Braess, Henning; Crespo, Paulo; Kunath, Daniela; Pawelke, Jörg; Pönisch, Falk; Enghardt, Wolfgang

2010-04-01

At present, in-beam positron emission tomography (PET) is the only method for in vivo and in situ range verification in ion therapy. At the GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI) Darmstadt, Germany, a unique in-beam PET installation has been operated from 1997 until the shut down of the carbon ion therapy facility in 2008. Therapeutic irradiation by means of 12C ion beams of more than 400 patients have been monitored. In this paper a first quantitative study on the accuracy of the in-beam PET method to detect range deviations between planned and applied treatment in clinically relevant situations using simulations based on clinical data is presented. Patient treatment plans were used for performing simulations of positron emitter distributions. For each patient a range difference of ± 6 mm in water was applied and compared to simulations without any changes. The comparisons were performed manually by six experienced evaluators for data of 81 patients. The number of patients required for the study was calculated using the outcome of a pilot study. The results indicate a sensitivity of (91 ± 3)% and a specificity of (96 ± 2)% for detecting an overrange, a reduced range is recognized with a sensitivity of (92 ± 3)% and a specificity of (96 ± 2)%. The positive and the negative predictive value of this method are 94% and 87%, respectively. The interobserver coefficient of variation is between 3 and 8%. The in-beam PET method demonstrated a high sensitivity and specificity for the detection of range deviations. As the range is a most indicative factor of deviations in the dose delivery, the promising results shown in this paper confirm the in-beam PET method as an appropriate tool for monitoring ion therapy.

Ion engine auxiliary propulsion applications and integration study

NASA Technical Reports Server (NTRS)

Zafran, S. (Editor)

1977-01-01

The benefits derived from application of the 8-cm mercury electron bombardment ion thruster were assessed. Two specific spacecraft missions were studied. A thruster was tested to provide additional needed information on its efflux characteristics and interactive effects. A Users Manual was then prepared describing how to integrate the thruster for auxiliary propulsion on geosynchronous satellites. By incorporating ion engines on an advanced communications mission, the weight available for added payload increases by about 82 kg (181 lb) for a 100 kg (2200 lb) satellite which otherwise uses electrothermal hydrazine. Ion engines can be integrated into a high performance propulsion module that is compatible with the multimission modular spacecraft and can be used for both geosynchronous and low earth orbit applications. The low disturbance torques introduced by the ion engines permit accurate spacecraft pointing with the payload in operation during thrusting periods. The feasibility of using the thruster's neutralizer assembly for neutralization of differentially charged spacecraft surfaces at geosynchronous altitude was demonstrated during the testing program.

Simulation of the effect of a magnetically insulated anode on a low-power cylindrical Hall thruster

NASA Astrophysics Data System (ADS)

Yongjie, DING; Hong, LI; Boyang, JIA; Peng, LI; Liqiu, WEI; Yu, XU; Wuji, PENG; Hezhi, SUN; Yong, CAO; Daren, YU

2018-03-01

The intersection point of the characteristic magnetic field line (CMFL) crossing the anode boundary with the discharge channel wall, and its influence on thruster performance and the energy and flux of ions bombarding the channel wall, have been studied numerically. The simulation results demonstrate that with the increase in distance from the crossover point of the CMFL with the channel wall to the bottom of the thruster channel, the ionization rate in the discharge channel gradually increases; meanwhile, the ion energy and ion current density bombarding the channel wall decreases. When the point of the CMFL with the channel wall is at the channel outlet, the thrust, specific impulse, and efficiency are at a maximum, while the ion energy and ion current density bombarding the channel wall are at a minimum. Therefore, to improve the performance and lifetime of the thruster, it is important to control the point of intersection of the CMFL with the channel wall.

Dissociation of biomolecules in liquid environments during fast heavy-ion irradiation

NASA Astrophysics Data System (ADS)

Nomura, Shinji; Tsuchida, Hidetsugu; Kajiwara, Akihiro; Yoshida, Shintaro; Majima, Takuya; Saito, Manabu

2017-12-01

The effect of aqueous environment on fast heavy-ion radiation damage of biomolecules was studied by comparative experiments using liquid- and gas-phase amino acid targets. Three types of amino acids with different chemical structures were used: glycine, proline, and hydroxyproline. Ion-induced reaction products were analyzed by time-of-flight secondary-ion mass spectrometry. The results showed that fragments from the amino acids resulting from the C—Cα bond cleavage were the major products for both types of targets. For liquid-phase targets, specific products originating from chemical reactions in solutions were observed. Interestingly, multiple dissociated atomic fragments were negligible for the liquid-phase targets. We found that the ratio of multifragment to total fragment ion yields was approximately half of that for gas-phase targets. This finding agreed with the results of other studies on biomolecular cluster targets. It is concluded that the suppression of molecular multifragmentation is caused by the energy dispersion to numerous water molecules surrounding the biomolecular solutes.

Physical response of gold nanoparticles to single self-ion bombardment

DOE PAGES

Bufford, Daniel C.; Hattar, Khalid

2014-09-23

The reliability of nanomaterials depends on maintaining their specific sizes and structures. However, the stability of many nanomaterials in radiation environments remains uncertain due to the lack of a fully developed fundamental understanding of the radiation response on the nanoscale. To provide an insight into the dynamic aspects of single ion effects in nanomaterials, gold nanoparticles (NPs) with nominal diameters of 5, 20, and 60 nm were subjected to self-ion irradiation at energies of 46 keV, 2.8 MeV, and 10 MeV in situ inside of a transmission electron microscope. Ion interactions created a variety of far-from-equilibrium structures including small (~1more » nm) sputtered nanoclusters from the parent NPs of all sizes. Single ions created surface bumps and elongated nanofilaments in the 60 nm NPs. As a result, similar shape changes were observed in the 20 nm nanoparticles, while the 5 nm nanoparticles were transiently melted or explosively broken apart.« less

Implication of the solvent effect, metal ions and topology in the electronic structure and hydrogen bonding of human telomeric G-quadruplex DNA.

PubMed

Poudel, Lokendra; Steinmetz, Nicole F; French, Roger H; Parsegian, V Adrian; Podgornik, Rudolf; Ching, Wai-Yim

2016-08-03

We present a first-principles density functional study elucidating the effects of solvent, metal ions and topology on the electronic structure and hydrogen bonding of 12 well-designed three dimensional G-quadruplex (G4-DNA) models in different environments. Our study shows that the parallel strand structures are more stable in dry environments and aqueous solutions containing K(+) ions within the tetrad of guanine but conversely, that the anti-parallel structure is more stable in solutions containing the Na(+) ions within the tetrad of guanine. The presence of metal ions within the tetrad of the guanine channel always enhances the stability of the G4-DNA models. The parallel strand structures have larger HOMO-LUMO gaps than antiparallel structures, which are in the range of 0.98 eV to 3.11 eV. Partial charge calculations show that sugar and alkali ions are positively charged whereas nucleobases, PO4 groups and water molecules are all negatively charged. Partial charges on each functional group with different signs and magnitudes contribute differently to the electrostatic interactions involving G4-DNA and favor the parallel structure. A comparative study between specific pairs of different G4-DNA models shows that the Hoogsteen OH and NH hydrogen bonds in the guanine tetrad are significantly influenced by the presence of metal ions and water molecules, collectively affecting the structure and the stability of G4-DNA.

Interferon-γ alters downstream signaling originating from epidermal growth factor receptor in intestinal epithelial cells: functional consequences for ion transport.

PubMed

Paul, Gisela; Marchelletta, Ronald R; McCole, Declan F; Barrett, Kim E

2012-01-13

The epidermal growth factor receptor (EGFr) regulates many cellular functions, such as proliferation, apoptosis, and ion transport. Our aim was to investigate whether long term treatment with interferon-γ (IFN-γ) modulates EGF activation of downstream signaling pathways in intestinal epithelial cells and if this contributes to dysregulation of epithelial ion transport in inflammation. Polarized monolayers of T(84) and HT29/cl.19A colonocytes were preincubated with IFN-γ prior to stimulation with EGF. Basolateral potassium transport was studied in Ussing chambers. We also studied inflamed colonic mucosae from C57BL/6 mice treated with dextran sulfate sodium or mdr1a knock-out mice and controls. IFN-γ increased intestinal epithelial EGFr expression without increasing its phosphorylation. Conversely, IFN-γ caused a significant decrease in EGF-stimulated phosphorylation of specific EGFr tyrosine residues and activation of ERK but not Akt-1. In IFNγ-pretreated cells, the inhibitory effect of EGF on carbachol-stimulated K(+) channel activity was lost. In inflamed colonic tissues, EGFr expression was significantly increased, whereas ERK phosphorylation was reduced. Thus, although it up-regulates EGFr expression, IFN-γ causes defective EGFr activation in colonic epithelial cells via reduced phosphorylation of specific EGFr tyrosine residues. This probably accounts for altered downstream signaling consequences. These observations were corroborated in the setting of colitis. IFN-γ also abrogates the ability of EGF to inhibit carbachol-stimulated basolateral K(+) currents. Our data suggest that, in the setting of inflammation, the biological effect of EGF, including the inhibitory effect of EGF on Ca(2+)-dependent ion transport, is altered, perhaps contributing to diarrheal and other symptoms in vivo.

Ammonium Ion Binding to DNA G-Quadruplexes: Do Electrospray Mass Spectra Faithfully Reflect the Solution-Phase Species?

NASA Astrophysics Data System (ADS)

Balthasart, Françoise; Plavec, Janez; Gabelica, Valérie

2013-01-01

G-quadruplex nucleic acids can bind ammonium ions in solution, and these complexes can be detected by electrospray mass spectrometry (ESI-MS). However, because ammonium ions are volatile, the extent to which ESI-MS quantitatively could provide an accurate reflection of such solution-phase equilibria is unclear. Here we studied five G-quadruplexes having known solution-phase structure and ammonium ion binding constants: the bimolecular G-quadruplexes (dG4T4G4)2, (dG4T3G4)2, and (dG3T4G4)2, and the intramolecular G-quadruplexes dG4(T4G4)3 and dG2T2G2TGTG2T2G2 (thrombin binding aptamer). We found that not all mass spectrometers are equally suited to reflect the solution phase species. Ion activation can occur in the electrospray source, or in a high-pressure traveling wave ion mobility cell. When the softest instrumental conditions are used, ammonium ions bound between G-quartets, but also additional ammonium ions bound at specific sites outside the external G-quartets, can be observed. However, even specifically bound ammonium ions are in some instances too labile to be fully retained in the gas phase structures, and although the ammonium ion distribution observed by ESI-MS shows biases at specific stoichiometries, the relative abundances in solution are not always faithfully reflected. Ion mobility spectrometry results show that all inter-quartet ammonium ions are necessary to preserve the G-quadruplex fold in the gas phase. Ion mobility experiments, therefore, help assign the number of inner ammonium ions in the solution phase structure.[Figure not available: see fulltext.

Parts-Per-Billion Mass Measurement Accuracy Achieved through the Combination of Multiple Linear Regression and Automatic Gain Control in a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

PubMed Central

Williams, D. Keith; Muddiman, David C.

2008-01-01

Fourier transform ion cyclotron resonance mass spectrometry has the ability to achieve unprecedented mass measurement accuracy (MMA); MMA is one of the most significant attributes of mass spectrometric measurements as it affords extraordinary molecular specificity. However, due to space-charge effects, the achievable MMA significantly depends on the total number of ions trapped in the ICR cell for a particular measurement. Even through the use of automatic gain control (AGC), the total ion population is not constant between spectra. Multiple linear regression calibration in conjunction with AGC is utilized in these experiments to formally account for the differences in total ion population in the ICR cell between the external calibration spectra and experimental spectra. This ability allows for the extension of dynamic range of the instrument while allowing mean MMA values to remain less than 1 ppm. In addition, multiple linear regression calibration is used to account for both differences in total ion population in the ICR cell as well as relative ion abundance of a given species, which also affords mean MMA values at the parts-per-billion level. PMID:17539605

Local Electric Field Facilitates High-Performance Li-Ion Batteries.

PubMed

Liu, Youwen; Zhou, Tengfei; Zheng, Yang; He, Zhihai; Xiao, Chong; Pang, Wei Kong; Tong, Wei; Zou, Youming; Pan, Bicai; Guo, Zaiping; Xie, Yi

2017-08-22

By scrutinizing the energy storage process in Li-ion batteries, tuning Li-ion migration behavior by atomic level tailoring will unlock great potential for pursuing higher electrochemical performance. Vacancy, which can effectively modulate the electrical ordering on the nanoscale, even in tiny concentrations, will provide tempting opportunities for manipulating Li-ion migratory behavior. Herein, taking CuGeO 3 as a model, oxygen vacancies obtained by reducing the thickness dimension down to the atomic scale are introduced in this work. As the Li-ion storage progresses, the imbalanced charge distribution emerging around the oxygen vacancies could induce a local built-in electric field, which will accelerate the ions' migration rate by Coulomb forces and thus have benefits for high-rate performance. Furthermore, the thus-obtained CuGeO 3 ultrathin nanosheets (CGOUNs)/graphene van der Waals heterojunctions are used as anodes in Li-ion batteries, which deliver a reversible specific capacity of 1295 mAh g -1 at 100 mA g -1 , with improved rate capability and cycling performance compared to their bulk counterpart. Our findings build a clear connection between the atomic/defect/electronic structure and intrinsic properties for designing high-efficiency electrode materials.

A laboratory study on the dissociative recombination of vibrationally excited O2/+/ions

NASA Technical Reports Server (NTRS)

Zipf, E. C.

1980-01-01

The dissociative recombination of vibrationally excited O2(+) ions is studied in light of the possible importance of this reaction in upper atmospheric chemistry. A plasma spectroscopy experiment was performed in a microwave cavity filled by an argon-oxygen mixture, with O(1S) production monitored by measurements of the 5577-A afterglow, the O2(+) density and the electron concentration. Plasma and optical data reveal the predominant afterglow ions to be Ar2(+) and O2(+), with an effective O(1S) dissociative recombination coefficient of 2.1 x 10 to the -8th cu cm/sec, corresponding to a quantum yield of 10%. Experiments with an argon-krypton-oxygen mixture reveal that vibrationally excited O2(+) ions are the chief source of the O(1S) atoms, with a specific recombination coefficient for the dissociation of O2(+)(2 pi g) into O(1S) and O(1D) of 4.2 x 10 to the -9th cu cm/sec. A comparison of the laboratory results with Atmospheric Explorer data on the 5577-A airglow implies that O2(+) ions in the sunlit ionosphere are vibrationally excited to the same degree as in the laboratory, with the vibrational relaxation of these ions much slower than dissociative recombination. Results also predict a dawn-twilight asymmetry in the effective O(1S) yield due to the normal variation of electron content.

Amorphous Zn₂GeO₄ Nanoparticles as Anodes with High Reversible Capacity and Long Cycling Life for Li-ion Batteries

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

Yi, Ran; Feng, Jinkui; Lv, Dongping

2013-07-30

Amorphous and crystalline Zn₂GeO₄ nanoparticles were prepared and characterized as anode materials for Li-ion batteries. A higher reversible specific capacity of 1250 mAh/g after 500 cycles and excellent rate capability were obtained for amorphous Zn₂GeO₄ nanoparticles, compared to that of crystalline Zn₂GeO₄ nanoparticles. Small particle size, amorphous phase and incorporation of zinc and oxygen contribute synergetically to the improved performance by effectively mitigating the huge volume variations during lithiation and delithiation process.

J1-J2 square lattice antiferromagnetism in the orbitally quenched insulator MoOPO4

NASA Astrophysics Data System (ADS)

Yang, L.; Jeong, M.; Babkevich, P.; Katukuri, V. M.; Náfrádi, B.; Shaik, N. E.; Magrez, A.; Berger, H.; Schefer, J.; Ressouche, E.; Kriener, M.; Živković, I.; Yazyev, O. V.; Forró, L.; Rønnow, H. M.

2017-07-01

We report magnetic and thermodynamic properties of a 4 d1 (Mo5 +) magnetic insulator MoOPO4 single crystal, which realizes a J1-J2 Heisenberg spin-1 /2 model on a stacked square lattice. The specific-heat measurements show a magnetic transition at 16 K which is also confirmed by magnetic susceptibility, ESR, and neutron diffraction measurements. Magnetic entropy deduced from the specific heat corresponds to a two-level degree of freedom per Mo5 + ion, and the effective moment from the susceptibility corresponds to the spin-only value. Using ab initio quantum chemistry calculations, we demonstrate that the Mo5 + ion hosts a purely spin-1 /2 magnetic moment, indicating negligible effects of spin-orbit interaction. The quenched orbital moments originate from the large displacement of Mo ions inside the MoO6 octahedra along the apical direction. The ground state is shown by neutron diffraction to support a collinear Néel-type magnetic order, and a spin-flop transition is observed around an applied magnetic field of 3.5 T. The magnetic phase diagram is reproduced by a mean-field calculation assuming a small easy-axis anisotropy in the exchange interactions. Our results suggest 4 d molybdates as an alternative playground to search for model quantum magnets.

Fabrication of a Biomass-Based Hydrous Zirconium Oxide Nanocomposite for Preferable Phosphate Removal and Recovery.

PubMed

Qiu, Hui; Liang, Chen; Zhang, Xiaolin; Chen, Mindong; Zhao, Yunxia; Tao, Tao; Xu, Zhengwen; Liu, Gang

2015-09-23

Advanced removal of phosphate by low-cost adsorbents from municipal wastewater or industrial effluents is an effective and economic way to prevent the occurrence of eutrophication. Here, we proposed a novel method to immobilize hydrous zirconium oxide nanoparticle within quaternary-aminated wheat straw, and obtained an inexpensive, eco-friendly nanocomposite Ws-N-Zr. The biomass-based Ws-N-Zr exhibited higher preference toward phosphate than commercial anion exchanger IRA-900 when competing sulfate ions coexisted at relatively high levels. Such excellent performance of Ws-N-Zr resulted from its specific hybrid structure, the quaternary ammonium groups bonded on the host favor the preconcentration of phosphate ions inside the wheat straw based on Donnan effect, and the encapsulated HZO nanoparticle exhibits preferable sequestration of phosphate ions through specific interaction, as further demonstrated by FTIR and X-ray photoelectron spectroscopy. Cycle adsorption and regeneration experiments demonstrated that Ws-N-Zr could be employed for repeated use without significant capacity loss, when the binary NaOH-NaCl solution was employed as the regenerant. The influence of solution pH and contact time was also examined. The results suggested that Ws-N-Zr has a great potential in efficient removal of phosphate in contaminated waters.

The coupling between stability and ion pair formation in magnesium electrolytes from first-principles quantum mechanics and classical molecular dynamics

DOE PAGES

Rajput, Nav Nidhi; Qu, Xiaohuui; Sa, Niya; ...

2015-02-10

Here in this work we uncover a novel effect between concentration dependent ion pair formation and anion stability at reducing potentials, e.g., at the metal anode. Through comprehensive calculations using both first-principles as well as well-benchmarked classical molecular dynamics over a matrix of electrolytes, covering solvents and salt anions with a broad range in chemistry, we elucidate systematic correlations between molecular level interactions and composite electrolyte properties, such as electrochemical stability, solvation structure, and dynamics. We find that Mg electrolytes are highly prone to ion pair formation, even at modest concentrations, for a wide range of solvents with different dielectricmore » constants, which have implications for dynamics as well as charge transfer. Specifically, we observe that, at Mg metal potentials, the ion pair undergoes partial reduction at the Mg cation center (Mg 2+ -> Mg +), which competes with the charge transfer mechanism and can activate the anion to render it susceptible to decomposition. Specifically, TFSI exhibits a significant bond weakening while paired with the transient, partially reduced Mg +. In contrast, BH 4 $-$ and BF 4 $-$ are shown to be chemically stable in a reduced ion pair configuration. Furthermore, we observe that higher order glymes as well as DMSO improve the solubility of Mg salts, but only the longer glyme chains reduce the dynamics of the ions in solution. This information provides critical design metrics for future electrolytes as it elucidates a close connection between bulk solvation and cathodic stability as well as the dynamics of the salt.« less

Cometary particulate analyzer. [mass spectrometry of laser plasmas

NASA Technical Reports Server (NTRS)

Friichtenicht, J. F.; Miller, D. J.; Utterback, N. G.

1979-01-01

A concept for determining the relative abundance of elements contained in cometary particulates was evaluated. The technique utilizes a short, high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. Critical aspects of the development of this system are determining the ionization efficiencies for various atomic species and achieving adequate mass resolution. A technique called energy-time focus, which utilizes static electric fields to alter the length of the ion flight path in proportion to the ion initial energy, was used which results in a corresponding compression to the range of ion flight times which effectively improves the inherent resolution. Sufficient data were acquired to develop preliminary specifications for a flight experiment.

Seeking structural specificity: direct modulation of pentameric ligand-gated ion channels by alcohols and general anesthetics.

PubMed

Howard, Rebecca J; Trudell, James R; Harris, R Adron

2014-01-01

Alcohols and other anesthetic agents dramatically alter neurologic function in a wide range of organisms, yet their molecular sites of action remain poorly characterized. Pentameric ligand-gated ion channels, long implicated in important direct effects of alcohol and anesthetic binding, have recently been illuminated in renewed detail thanks to the determination of atomic-resolution structures of several family members from lower organisms. These structures provide valuable models for understanding and developing anesthetic agents and for allosteric modulation in general. This review surveys progress in this field from function to structure and back again, outlining early evidence for relevant modulation of pentameric ligand-gated ion channels and the development of early structural models for ion channel function and modulation. We highlight insights and challenges provided by recent crystal structures and resulting simulations, as well as opportunities for translation of these newly detailed models back to behavior and therapy.

Alkyl Pyrocarbonate Electrolyte Additives for Performance Enhancement of Li Ion Cells

NASA Technical Reports Server (NTRS)

Smart, M. C.; Ratnakumar, B. V.; Surampudi, S.

2000-01-01

Lithium ion rechargeable batteries are being developed for various aerospace applications under a NASA-DoD Interagency program. These applications require further improvements in several areas, specifically in the cycle life for LEO and GEO satellites and in the low temperature performance for the Mars Lander and Rover missions. Accordingly, we have been pursuing research studies to achieve improvement in the low temperature performance, long cycle life and active life of Li ion cells. The studies are mainly focused on electrolytes, to identify newer formulations of new electrolyte additives to enhance Li permeability (at low temperatures) and stability towards the electrode. The latter approach is particularly aimed at the formation suitable SEI (solid electrolyte interphase) on carbon electrodes. In this paper, we report the beneficial effect of using alkyl pyrocarbonates as electrolyte additives to improve the low temperature performance of Li ion cells.

Seeking Structural Specificity: Direct Modulation of Pentameric Ligand-Gated Ion Channels by Alcohols and General Anesthetics

PubMed Central

Trudell, James R.; Harris, R. Adron

2014-01-01

Alcohols and other anesthetic agents dramatically alter neurologic function in a wide range of organisms, yet their molecular sites of action remain poorly characterized. Pentameric ligand-gated ion channels, long implicated in important direct effects of alcohol and anesthetic binding, have recently been illuminated in renewed detail thanks to the determination of atomic-resolution structures of several family members from lower organisms. These structures provide valuable models for understanding and developing anesthetic agents and for allosteric modulation in general. This review surveys progress in this field from function to structure and back again, outlining early evidence for relevant modulation of pentameric ligand-gated ion channels and the development of early structural models for ion channel function and modulation. We highlight insights and challenges provided by recent crystal structures and resulting simulations, as well as opportunities for translation of these newly detailed models back to behavior and therapy. PMID:24515646

Electro-synthesis of novel nanostructured PEDOT films and their application as catalyst support

PubMed Central

2011-01-01

Poly(3,4-ethylenedioxythiophene) (PEDOT) films doped with nitric and chlorine ions have been electrochemically deposited simply by a one-step electrochemical method in an aqueous media in the absence of any surfactant. The fabricated PEDOT films were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results indicate that the hierarchical structured PEDOT film doped with nitric ions displays a 'lunar craters' porous morphology consisting of PEDOT nano-sheets with a thickness of less than 2 nm. The effect of counter ions on the electro-polymerization, the electrochemistry, and the morphology of the polymer film was studied. Compared with PEDOT film doped with nitric acid, PEDOT film deposited in the presence of chlorine ions shows irregular morphology and less electrochemical activity. The specific nanostructure of the polymer was further studied as catalyst support for platinum nanoparticles to methanol electro-oxidation. PMID:21711871

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries.

PubMed

Zhang, Jin; Wang, Beibei; Zhou, Jiachen; Xia, Ruoyu; Chu, Yingli; Huang, Jia

2017-01-17

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group "-(CH₂)₅COOH", and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g -1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes.

Fluorescence enhancement of photoswitchable metal ion sensors

NASA Astrophysics Data System (ADS)

Sylvia, Georgina; Heng, Sabrina; Abell, Andrew D.

2016-12-01

Spiropyran-based fluorescence sensors are an ideal target for intracellular metal ion sensing, due to their biocompatibility, red emission frequency and photo-controlled reversible analyte binding for continuous signal monitoring. However, increasing the brightness of spiropyran-based sensors would extend their sensing capability for live-cell imaging. In this work we look to enhance the fluorescence of spiropyran-based sensors, by incorporating an additional fluorophore into the sensor design. We report a 5-membered monoazacrown bearing spiropyran with metal ion specificity, modified to incorporate the pyrene fluorophore. The effect of N-indole pyrene modification on the behavior of the spiropyran molecule is explored, with absorbance and fluorescence emission characterization. This first generation sensor provides an insight into fluorescence-enhancement of spiropyran molecules.

In situ formed Si nanoparticle network with micron-sized Si particles for lithium-ion battery anodes.

PubMed

Wu, Mingyan; Sabisch, Julian E C; Song, Xiangyun; Minor, Andrew M; Battaglia, Vincent S; Liu, Gao

2013-01-01

To address the significant challenges associated with large volume change of micrometer-sized Si particles as high-capacity anode materials for lithium-ion batteries, we demonstrated a simple but effective strategy: using Si nanoparticles as a structural and conductive additive, with micrometer-sized Si as the main lithium-ion storage material. The Si nanoparticles connected into the network structure in situ during the charge process, to provide electronic connectivity and structure stability for the electrode. The resulting electrode showed a high specific capacity of 2500 mAh/g after 30 cycles with high initial Coulombic efficiency (73%) and good rate performance during electrochemical lithiation and delithiation: between 0.01 and 1 V vs Li/Li(+).

Biologische Wirkungen der Bestrahlung mit schweren Ionen

NASA Astrophysics Data System (ADS)

Kiefer, Jürgen

1982-06-01

Experiments with accelerated heavy ions may contribute to the understanding of biological radiation action. After outlining the theoretical background experiments are described which were carried out at the UNILAC-machine (Gesellschaft für Schwerionenforschung, Darmstadt, Germany) where ions up to uranium can be accelerated to maximal specific energies of 10 MeV/u. Yeast cells served as biological test systems with the synthesis of ribosomal RNA (r-RNA), colony-forming ability and mutation induction as experimental endpoints. A relationship between action and energy deposition by individual particles can be demonstrated for the inhibition of r-RNA synthesis, in other cases the ion energy plays also an important role indicating that the interaction of δ-electrons from different particles contributes significantly to the biological effect.

Effect of Ion Binding in Palmitoyl-Oleoyl Phosphatidylserine Monolayers

NASA Astrophysics Data System (ADS)

Eckler, Matthew; Matysiak, Silvina

2013-03-01

Molecular dynamics simulations of palmitoyl-oleoyl phosphatidylserine (POPS) monolayers at the air-water interface were performed with different ionic strengths with the aim of determining the specific organization and dynamics of counterion binding events. Na + ions penetrated the monolayers into both the ester carbonyl and carboxylate regions of the phospholipids. The binding events increase with the addition of salt. Differences in lipid order parameter, headgroup orientation, and prevalence of inter- and intramolecular hydrogen bonding events between the amine group of the lipid and oxygen groups are observed depending on whether the Na + is binding near the carboxylate or ester region of the lipid. The observed changes are explained in terms of the salting-out effect.

NICA project management information system

NASA Astrophysics Data System (ADS)

Bashashin, M. V.; Kekelidze, D. V.; Kostromin, S. A.; Korenkov, V. V.; Kuniaev, S. V.; Morozov, V. V.; Potrebenikov, Yu. K.; Trubnikov, G. V.; Philippov, A. V.

2016-09-01

The science projects growth, changing of the efficiency criteria during the project implementation require not only increasing of the management specialization level but also pose the problem of selecting the effective planning methods, monitoring of deadlines and interaction of participants involved in research projects. This paper is devoted to choosing the project management information system for the new heavy-ion collider NICA (Nuclotron based Ion Collider fAcility). We formulate the requirements for the project management information system with taking into account the specifics of the Joint Institute for Nuclear Research (JINR, Dubna, Russia) as an international intergovernmental research organization, which is developed on the basis of a flexible and effective information system for the NICA project management.

Nanostructuring superconductors by ion beams: A path towards materials engineering

NASA Astrophysics Data System (ADS)

Gerbaldo, Roberto; Ghigo, Gianluca; Gozzelino, Laura; Laviano, Francesco; Amato, Antonino; Rovelli, Alberto; Cherubini, Roberto

2013-07-01

The paper deals with nanostructuring of superconducting materials by means of swift heavy ion beams. The aim is to modify their structural, optical and electromagnetic properties in a controlled way, to provide possibility of making them functional for specific applications. Results are presented concerning flux pinning effects (implantation of columnar defects with nanosize cross section to enhance critical currents and irreversibility fields), confined flux-flow and vortex guidance, design of devices by locally tailoring the superconducting material properties, analysis of disorder-induced effects in multi-band superconductors. These studies were carried out on different kinds of superconducting samples, from single crystals to thin films, from superconducting oxides to magnesium diboride, to recently discovered iron-based superconductors.

Boric-Acid-Functional Lanthanide Metal-Organic Frameworks for Selective Ratiometric Fluorescence Detection of Fluoride Ions.

PubMed

Yang, Zhong-Rui; Wang, Man-Man; Wang, Xue-Sheng; Yin, Xue-Bo

2017-02-07

Here, we report that boric acid is used to tune the optical properties of lanthanide metal-organic frameworks (LMOFs) for dual-fluorescence emission and improves the selectivity of LMOFs for the determination of F - ions. The LMOFs are prepared with 5-boronoisophthalic acid (5-bop) and Eu 3+ ions as the precursors. Emission mechanism study indicates that 5-bop is excited with UV photons to produce its triplet state, which then excites Eu 3+ ions for their red emission. This is the general story of the antenna effect, but electron-deficient boric acid decreases the energy transfer efficiency from the triplet state of 5-bop to Eu 3+ ions, so dual emission from both 5-bop and Eu 3+ ions is efficiently excited at the single excitation of 275 nm. Moreover, boric acid is used to identify fluoride specifically as a free accessible site. The ratiometric fluorescent detection of F - ions is validated with the dual emission at single excitation. The LMOFs are very monodisperse, so the determination of aqueous F - ions is easily achieved with high selectivity and a low detection limit (2 μM). For the first time, we reveal that rational selection of functional ligands can improve the sensing efficiency of LMOFs through tuning their optical property and enhancing the selectivity toward targets.

Search for selective ion diffusion through membranes

NASA Technical Reports Server (NTRS)

May, C. E.; Philipp, W. H.

1983-01-01

The diffusion rates of several ions through some membranes developed as battery separators were measured. The ions investigated were Li(+), Rb(+), Cl(-), and So4. The members were crosslinked polyvinyl alcohol, crosslinked polyacrylic acid, a copolymer of the two, crosslinked calcium polyacrylate, cellulose, and several microporous polyphenylene oxide based films. No true specificity for diffusion of any of these ions was found for any of the membranes. But the calcium polyacrylate membrane was found to exhibit ion exchange with the diffusing ions giving rise to the leaching of the calcium ion and low reproducibility. These findings contrast earlier work where the calcium polyacrylate membrane did show specificity to the diffusion of the copper ion. In general, Fick's law appeared to be obeyed. Except for the microporous membranes, the coefficients for ion diffusion through the membranes were comparable with their values in water. For the microporous membranes, the values found for the coefficients were much less, due to the tortuosity of the micropores.

Electrolytes and thermoregulation

NASA Technical Reports Server (NTRS)

Nielsen, B.; Greenleaf, J. E.

1977-01-01

The influence of ions on temperature is studied for cases where the changes in ionic concentrations are induced by direct infusion or injection of electrolyte solutions into the cerebral ventricles or into specific areas of brain tissue; intravenous infusion or injection; eating food or drinking solutions of different ionic composition; and heat or exercise dehydration. It is shown that introduction of Na(+) and Ca(++) into the cerebral ventricles or into the venous system affects temperature regulation. It appears that the specific action of these ions is different from their osmotic effects. It is unlikely that their action is localized to the thermoregulatory centers in the brain. The infusion experiments demonstrate that the changes in sodium balance occurring during exercise and heat stress are large enough to affect sweat gland function and vasomotor activity.

Stimulation of TRPC5 cationic channels by low micromolar concentrations of lead ions (Pb{sup 2+})

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

Sukumar, Piruthivi; Beech, David J., E-mail: d.j.beech@leeds.ac.uk

2010-02-26

Lead toxicity is long-recognised but continues to be a major public health problem. Its effects are wide-ranging and include induction of hyper-anxiety states. In general it is thought to act by interfering with Ca{sup 2+} signalling but specific targets are not clearly identified. Transient receptor potential canonical 5 (TRPC5) is a Ca{sup 2+}-permeable ion channel that is linked positively to innate fear responses and unusual amongst ion channels in being stimulated by trivalent lanthanides, which include gadolinium. Here we show investigation of the effect of lead, which is a divalent ion (Pb{sup 2+}). Intracellular Ca{sup 2+} and whole-cell patch-clamp recordingsmore » were performed on HEK 293 cells conditionally over-expressing TRPC5 or other TRP channels. Extracellular application of Pb{sup 2+} stimulated TRPC5 at concentrations greater than 1 {mu}M. Control cells without TRPC5 showed little or no response to Pb{sup 2+} and expression of other TRP channels (TRPM2 or TRPM3) revealed partial inhibition by 10 {mu}M Pb{sup 2+}. The stimulatory effect on TRPC5 depended on an extracellular residue (E543) near the ion pore: similar to gadolinium action, E543Q TRPC5 was resistant to Pb{sup 2+} but showed normal stimulation by the receptor agonist sphingosine-1-phosphate. The study shows that Pb{sup 2+} is a relatively potent stimulator of the TRPC5 channel, generating the hypothesis that a function of the channel is to sense metal ion poisoning.« less

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries.

PubMed

Badi, Nacer; Erra, Abhinay Reddy; Hernandez, Francisco C Robles; Okonkwo, Anderson O; Hobosyan, Mkhitar; Martirosyan, Karen S

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization.

Low-cost carbon-silicon nanocomposite anodes for lithium ion batteries

PubMed Central

2014-01-01

The specific energy of the existing lithium ion battery cells is limited because intercalation electrodes made of activated carbon (AC) materials have limited lithium ion storage capacities. Carbon nanotubes, graphene, and carbon nanofibers are the most sought alternatives to replace AC materials but their synthesis cost makes them highly prohibitive. Silicon has recently emerged as a strong candidate to replace existing graphite anodes due to its inherently large specific capacity and low working potential. However, pure silicon electrodes have shown poor mechanical integrity due to the dramatic expansion of the material during battery operation. This results in high irreversible capacity and short cycle life. We report on the synthesis and use of carbon and hybrid carbon-silicon nanostructures made by a simplified thermo-mechanical milling process to produce low-cost high-energy lithium ion battery anodes. Our work is based on an abundant, cost-effective, and easy-to-launch source of carbon soot having amorphous nature in combination with scrap silicon with crystalline nature. The carbon soot is transformed in situ into graphene and graphitic carbon during mechanical milling leading to superior elastic properties. Micro-Raman mapping shows a well-dispersed microstructure for both carbon and silicon. The fabricated composites are used for battery anodes, and the results are compared with commercial anodes from MTI Corporation. The anodes are integrated in batteries and tested; the results are compared to those seen in commercial batteries. For quick laboratory assessment, all electrochemical cells were fabricated under available environment conditions and they were tested at room temperature. Initial electrochemical analysis results on specific capacity, efficiency, and cyclability in comparison to currently available AC counterpart are promising to advance cost-effective commercial lithium ion battery technology. The electrochemical performance observed for carbon soot material is very interesting given the fact that its production cost is away cheaper than activated carbon. The cost of activated carbon is about $15/kg whereas the cost to manufacture carbon soot as a by-product from large-scale milling of abundant graphite is about $1/kg. Additionally, here, we propose a method that is environmentally friendly with strong potential for industrialization. PMID:25114651

Glyoxal in aqueous ammonium sulfate solutions: products, kinetics and hydration effects.

PubMed

Yu, Ge; Bayer, Amanda R; Galloway, Melissa M; Korshavn, Kyle J; Fry, Charles G; Keutsch, Frank N

2011-08-01

Reactions and interactions between glyoxal and salts in aqueous solution were studied. Glyoxal was found to react with ammonium to form imidazole, imidazole-2-carboxaldehyde, formic acid, N-glyoxal substituted imidazole, and minor products at very low concentrations. Overall reaction orders and rates for each major product were measured. Sulfate ions have a strong and specific interaction with glyoxal in aqueous solution, which shifts the hydration equilibria of glyoxal from the unhydrated carbonyl form to the hydrated form. This ion-specific effect contributes to the observed enhancement of the effective Henry's law coefficient for glyoxal in sulfate-containing solutions. The results of UV-vis absorption and NMR spectroscopy studies of solutions of glyoxal with ammonium, methylamine, and dimethylamine salts reveal that light absorbing compounds require the formation of nitrogen containing molecules. These findings have implications on the role of glyoxal in the atmosphere, both in models of the contribution of glyoxal to form secondary organic aerosol (SOA), the role of nitrogen containing species for aerosol optical properties and in predictions of the behavior of other carbonyls or dicarbonyls in the atmosphere.

Ion sensing method

DOEpatents

Smith, Richard Harding; Martin, Glenn Brian

2004-05-18

The present invention allows the determination of trace levels of ionic substances in a sample solution (ions, metal ions, and other electrically charged molecules) by coupling a separation method, such as liquid chromatography, with ion selective electrodes (ISE) prepared so as to allow detection at activities below 10.sup.-6 M. The separation method distributes constituent molecules into fractions due to unique chemical and physical properties, such as charge, hydrophobicity, specific binding interactions, or movement in an electrical field. The separated fractions are detected by means of the ISE(s). These ISEs can be used singly or in an array. Accordingly, modifications in the ISEs are used to permit detection of low activities, specifically, below 10.sup.-6 M, by using low activities of the primary analyte (the molecular species which is specifically detected) in the inner filling solution of the ISE. Arrays constructed in various ways allow flow-through sensing for multiple ions.

Integrating a DNA Strand Displacement Reaction with a Whispering Gallery Mode Sensor for Label-Free Mercury (II) Ion Detection.

PubMed

Wu, Fengchi; Wu, Yuqiang; Niu, Zhongwei; Vollmer, Frank

2016-07-29

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world's attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg(2+) ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species.

Integrating a DNA Strand Displacement Reaction with a Whispering Gallery Mode Sensor for Label-Free Mercury (II) Ion Detection

PubMed Central

Wu, Fengchi; Wu, Yuqiang; Niu, Zhongwei; Vollmer, Frank

2016-01-01

Mercury is an extremely toxic chemical pollutant of our environment. It has attracted the world’s attention due to its high mobility and the ease with which it accumulates in organisms. Sensitive devices and methods specific for detecting mercury ions are, hence, in great need. Here, we have integrated a DNA strand displacement reaction with a whispering gallery mode (WGM) sensor for demonstrating the detection of Hg2+ ions. Our approach relies on the displacement of a DNA hairpin structure, which forms after the binding of mercury ions to an aptamer DNA sequence. The strand displacement reaction of the DNA aptamer provides highly specific and quantitative means for determining the mercury ion concentration on a label-free WGM sensor platform. Our approach also shows the possibility for manipulating the kinetics of a strand displacement reaction with specific ionic species. PMID:27483277

Novel multi-layered 1-D nanostructure exhibiting the theoretical capacity of silicon for a super-enhanced lithium-ion battery

NASA Astrophysics Data System (ADS)

Lee, Byoung-Sun; Yang, Ho-Sung; Jung, Heechul; Jeon, Seung-Yeol; Jung, Changhoon; Kim, Sang-Won; Bae, Jihyun; Choong, Chwee-Lin; Im, Jungkyun; Chung, U.-In; Park, Jong-Jin; Yu, Woong-Ryeol

2014-05-01

Silicon/carbon (Si/C) nanocomposites have recently received much attention as Li-ion battery negative electrodes due to their mutual synergetic effects in capacity and mechanical integrity. The contribution of Si to the total capacity of the Si/C nanocomposites determines their structural efficiency. Herein, we report on a multi-layered, one-dimensional nanostructure that exhibits the theoretical specific capacity of Si in the nanocomposite. Concentrically tri-layered, compartmentalized, C-core/Si-medium/C-shell nanofibers were fabricated by triple coaxial electrospinning. The pulverization of Si was accommodated inside the C-shell, whereas the conductive pathway of the Li-ions and electrons was provided by the C-core, which was proven by ex situ Raman spectroscopy. The compartmentalized Si in between the C-core and C-shell led to excellent specific capacity at a high current rate (>820 mA h g-1 at 12000 mA g-1) and the realization of the theoretical specific capacity of the Li15Si4 phase of Si nanoparticles (3627 mA h g-1). The electrochemical characterization and inductively coupled plasma-atomic emission spectrometry provided direct evidence of full participation of Si in the electrochemical reactions.Silicon/carbon (Si/C) nanocomposites have recently received much attention as Li-ion battery negative electrodes due to their mutual synergetic effects in capacity and mechanical integrity. The contribution of Si to the total capacity of the Si/C nanocomposites determines their structural efficiency. Herein, we report on a multi-layered, one-dimensional nanostructure that exhibits the theoretical specific capacity of Si in the nanocomposite. Concentrically tri-layered, compartmentalized, C-core/Si-medium/C-shell nanofibers were fabricated by triple coaxial electrospinning. The pulverization of Si was accommodated inside the C-shell, whereas the conductive pathway of the Li-ions and electrons was provided by the C-core, which was proven by ex situ Raman spectroscopy. The compartmentalized Si in between the C-core and C-shell led to excellent specific capacity at a high current rate (>820 mA h g-1 at 12000 mA g-1) and the realization of the theoretical specific capacity of the Li15Si4 phase of Si nanoparticles (3627 mA h g-1). The electrochemical characterization and inductively coupled plasma-atomic emission spectrometry provided direct evidence of full participation of Si in the electrochemical reactions. Electronic supplementary information (ESI) available: Simulation details, quantitative measurement of Si content in the nanofibers and ex situ Raman characterization sample preparation procedures are demonstrated. See DOI: 10.1039/c4nr00318g

Core top confirmation of the carbonate ion effect in multiple species of planktic foraminifera and a reassessment of the upper water column equatorial Pacific δ13CFORAM records.

NASA Astrophysics Data System (ADS)

Fehrenbacher, J. S.; Spero, H. J.

2017-12-01

Planktic foraminifera carbon (δ13CFORAM) and oxygen (δ18OFORAM) isotope records play a vital role in paleoceanographic reconstructions. The δ18OFORAM values are typically minimally offset from equilibrium δ18O-calcite and are widely applied in oceanographic reconstructions of upper water column hydrography. In contrast, δ13CFORAM are underutilized in paleoceanographic reconstructions. δ13CFORAM are more difficult to interpret due to species-specific δ13CFORAM offsets from the δ13C of the dissolved inorganic carbon of seawater (δ13CDIC). In this study, we analyzed the δ18OFORAM and δ13CFORAM of individual foraminifera shells from a suite of planktic foraminifer species obtained from core top (Holocene) intervals from Eastern Equatorial Pacific (TR163-19), Western Caribbean (ODP 999A), and Equatorial Indian Ocean (ODP 714A) cores. We also include published records from the Western Equatorial Pacific (MW91-9 15GGC). We find the δ13CFORAM offsets from the local water column δ13CDIC are large, variable, region specific, and are correlated to the ambient carbonate ion concentration ([CO32-]) of seawater. We show that the regional offsets from δ13CDIC are due to the carbonate ion effect (CIE) on δ13CFORAM (Spero et al., 1997; Bijma et al., 1999) and variations in water column [CO32-]. More importantly, our results demonstrate that regional and/or culture based δ13CFORAM offsets from δ13CDIC are not applicable globally. Rather, owing to regional differences in water column [CO32-] and species-specific relationships between [CO32-] and δ13CFORAM, δ13CFORAM must be corrected for the regional CIE in order to infer vertical δ13CDIC gradients or to compare δ13CFORAM records from one region to another. Laboratory culture suggests the carbonate ion effect on δ18OFORAM is 1/3 that of δ13CFORAM (Spero et al., 1997). Thus, in order to obtain correct δ18OFORAM temperatures or δ18OSW (when used in conjunction with Mg/Ca) the δ18OFORAM offsets from δ18OCALCITE-EQ must also be corrected for offsets due to the carbonate ion effect. Finally, we use the regional d13CFORAM offsets from d13CDIC to correct for the CIE and reassess the δ13CFORAM and δ18OFORAM gradients from previously published down core records in the EEP (TR163-19; Spero et al., 2003).

Effects of MHD instabilities on neutral beam current drive

NASA Astrophysics Data System (ADS)

Podestà, M.; Gorelenkova, M.; Darrow, D. S.; Fredrickson, E. D.; Gerhardt, S. P.; White, R. B.

2015-05-01

Neutral beam injection (NBI) is one of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility. However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CD efficiency are investigated. A new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ∼50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.

Active Radiation Detectors for Use in Space Beyond Low Earth Orbit: Spatial and Energy Resolution Requirements and Methods for Heavy Ion Charge Classification

NASA Astrophysics Data System (ADS)

McBeth, Rafe A.

Space radiation exposure to astronauts will need to be carefully monitored on future missions beyond low earth orbit. NASA has proposed an updated radiation risk framework that takes into account a significant amount of radiobiological and heavy ion track structure information. These models require active radiation detection systems to measure the energy and ion charge Z. However, current radiation detection systems cannot meet these demands. The aim of this study was to investigate several topics that will help next generation detection systems meet the NASA objectives. Specifically, this work investigates the required spatial resolution to avoid coincident events in a detector, the effects of energy straggling and conversion of dose from silicon to water, and methods for ion identification (Z) using machine learning. The main results of this dissertation are as follows: 1. Spatial resolution on the order of 0.1 cm is required for active space radiation detectors to have high confidence in identifying individual particles, i.e., to eliminate coincident events. 2. Energy resolution of a detector system will be limited by energy straggling effects and the conversion of dose in silicon to dose in biological tissue (water). 3. Machine learning methods show strong promise for identification of ion charge (Z) with simple detector designs.

Effects of MHD instabilities on neutral beam current drive

DOE PAGES

Podestà, M.; Gorelenkova, M.; Darrow, D. S.; ...

2015-04-17

One of the primary tools foreseen for heating, current drive (CD) and q-profile control in future fusion reactors such as ITER and a Fusion Nuclear Science Facility is the neutral beam injection (NBI). However, fast ions from NBI may also provide the drive for energetic particle-driven instabilities (e.g. Alfvénic modes (AEs)), which in turn redistribute fast ions in both space and energy, thus hampering the control capabilities and overall efficiency of NB-driven current. Based on experiments on the NSTX tokamak (M. Ono et al 2000 Nucl. Fusion 40 557), the effects of AEs and other low-frequency magneto-hydrodynamic instabilities on NB-CDmore » efficiency are investigated. When looking at the new fast ion transport model, which accounts for particle transport in phase space as required for resonant AE perturbations, is utilized to obtain consistent simulations of NB-CD through the tokamak transport code TRANSP. It is found that instabilities do indeed reduce the NB-driven current density over most of the plasma radius by up to ~50%. Moreover, the details of the current profile evolution are sensitive to the specific model used to mimic the interaction between NB ions and instabilities. Finally, implications for fast ion transport modeling in integrated tokamak simulations are briefly discussed.« less

Mesh-structured N-doped graphene@Sb2Se3 hybrids as an anode for large capacity sodium-ion batteries.

PubMed

Zhao, Wenxi; Li, Chang Ming

2017-02-15

A mesh-structured N-doped graphene@Sb 2 Se 3 (NGS) hybrid was one-pot prepared to realize N-doping, nanostructuring and hybridization for a sodium-ion battery anode to deliver much larger reversible specific capacity, faster interfacial electron transfer rate, better ionic and electronic transport, higher rate performance and longer cycle life stability in comparison to the plain Sb 2 Se 3 one. The better performance is ascribed to the unique intertwined porous mash-like structure associated with a strong synergistic effect of N-doped graphene for dramatic improvement of electronic and ionic conductivity by the unique porous structure, the specific capacity of graphene from N doping and fast interfacial electron transfer rate by N-doping induced surface effect and the structure-shortening insertion/desertion pathway of Na + . The detail electrochemical process on the NGS electrode is proposed and analyzed in terms of the experimental results. Copyright © 2016 Elsevier Inc. All rights reserved.

Radiation biophysical aspects of charged particles: From the nanoscale to therapy

NASA Astrophysics Data System (ADS)

Scifoni, Emanuele

2015-06-01

Charged particle applications for radiotherapy are motivated by their specific advantages in terms of dose delivery and biological effect. These advantages have to a large extent originated from the peculiarities of ion beam energy deposition patterns in the medium on a microscopic, down to a nanoscopic scale. A large amount of research was conducted in this direction, especially in the last two decades, profiting also from the parallel investigations going on in radiation protection for space exploration. The main biophysical aspects of charged particles, which are relevant to hadrontherapy are shortly reviewed in the present contribution, namely focusing on relative biological effectiveness (RBE), oxygen enhancement ratio (OER) and combination with radiosensitizers. A summary of present major research direction on both microscopic and macroscopic assessment of the specific mechanism of radiation damage will be given, as well as several open challenges for a better understanding of the whole process, which still limit the full exploitation of ion beams for radiotherapy.

Mass spectrometry of analytical derivatives. 2. "Ortho" and "Para" effects in electron ionization mass spectra of derivatives of hydroxy, mercapto and amino benzoic acids.

PubMed

Todua, Nino G; Mikaia, Anzor I

2016-01-01

Derivatives requiring either anhydrous or aqueous reaction conditions were prepared for robust and reliable gas chromatography/mass spectrometry (GC/MS) characterization of hydroxyl, mercapto, and amino benzoic acids Methylation and trialkylsilytation are employed for blocking the acidic function. Alkyl, trimethylsilyl, acetyl, perfluoroacyl and alkoxycarbonyl derivatization groups are introduced to hydroxyl, mercapto and amino functions. The electron ionization induced fragmentation characteristics of corresponding derivatives are explained by comparing the MS 1 spectra of unlabeled compounds to their 2 H and 13 C labeled analogs, and analysis of collision-induced dissociation data from MS 2 spectra. Competing fragmentation alternatives are identified and specific decomposition processes are detailed that characterize (a) ortho isomers due to interaction or vicinal functional substituents and (b) para isomers prone to forming para quinoid type structures. Skeletal and hydrogen rearrangements typical for methyl benzoates and the blocking groups are considered when discussing diagnostically important ions. Characteristic ions produced as a result of rearrangements in ortho isomers are classified, and skeletal rearrangements required to produce para quinoid type ions specific for para isomers are noted. Key ions for structure elucidation and differentiation of isomers for derivatives of substituted benzoic acids by GC/MS are suggested.

Mass spectrometry of analytical derivatives. 2. “Ortho” and “Para” effects in electron ionization mass spectra of derivatives of hydroxy, mercapto and amino benzoic acids1

PubMed Central

Todua, Nino G.; Mikaia, Anzor I.

2016-01-01

Derivatives requiring either anhydrous or aqueous reaction conditions were prepared for robust and reliable gas chromatography/mass spectrometry (GC/MS) characterization of hydroxyl, mercapto, and amino benzoic acids Methylation and trialkylsilytation are employed for blocking the acidic function. Alkyl, trimethylsilyl, acetyl, perfluoroacyl and alkoxycarbonyl derivatization groups are introduced to hydroxyl, mercapto and amino functions. The electron ionization induced fragmentation characteristics of corresponding derivatives are explained by comparing the MS1 spectra of unlabeled compounds to their 2H and 13C labeled analogs, and analysis of collision-induced dissociation data from MS2 spectra. Competing fragmentation alternatives are identified and specific decomposition processes are detailed that characterize (a) ortho isomers due to interaction or vicinal functional substituents and (b) para isomers prone to forming para quinoid type structures. Skeletal and hydrogen rearrangements typical for methyl benzoates and the blocking groups are considered when discussing diagnostically important ions. Characteristic ions produced as a result of rearrangements in ortho isomers are classified, and skeletal rearrangements required to produce para quinoid type ions specific for para isomers are noted. Key ions for structure elucidation and differentiation of isomers for derivatives of substituted benzoic acids by GC/MS are suggested. PMID:27891187

The Use of OXYGEN-18 in the Development of Methods for Controlled Sputter Deposition of High Critical Transition Temperature Material Thin Films of Predicted Composition and Good Uniformity

NASA Astrophysics Data System (ADS)

Tidrow, Steven Clay

Two primary concerns, in the sputter deposition of high T_{c} material films, are the prevention of oxygen deficiency in the films and the elimination of the negative ion effect. "Oxygen deficiency" occurs when the amount of oxygen incorporated into the film is less than the amount of oxygen required to form the superconducting material lattice. Oxygen deficiency is due to the volatile nature of oxygen. The negative ion effect occurs when an atom or molecule (typically oxygen) gains an extra electron, is accelerated away from the target and impinges upon a film being grown directly in front of the sputtering target. The impinging particle has enough energy to cause resputtering of the deposited film. The presence of Sr and to a greater extent Ba, may enhance the negative ion effect in these materials. However, it is oxygen which readily forms negative ions that is primarily responsible for the negative ion effect. Thus, oxygen must be given special attention in the sputter deposition of high T_{c} material films. A specially designed sputtering system is used to demonstrate that the negative ion effect can be reduced such that large uniform high T_{c} material films possessing predicted and repeated composition can be grown in an on-axis arrangement. Utilizing this same sputtering system and the volatile nature of oxygen, it is demonstrated that oxygen processes occurring in the chamber during growth of high T_ {c} material films can be investigated using the tracer ^{18}O. In particular, it is shown that ^{18}O can be utilized as a tool for (1) investigating the negative ion effect, (2) investigating oxygen incorporation into high T_{c} material films, (3) investigating oxygen incorporation into the target, (4) tailoring films for oxygen migration and interface investigations and (5) tailoring films for the other specific oxygen investigations. Such sputtering systems that utilize the tracer ^{18}O are necessary for systematic growth of high T_ {c} material films for systematic investigations into the nature of these materials.

Ion beam applications research. A summary of Lewis Research Center Programs

NASA Technical Reports Server (NTRS)

Banks, B. A.

1981-01-01

A summary of the ion beam applications research (IBAR) program organized to enable the development of materials, products, and processes through the nonpropulsive application of ion thruster technology is given. Specific application efforts utilizing ion beam sputter etching, deposition, and texturing are discussed as well as ion source and component technology applications.

Hyperthermal (1-100 eV) nitrogen ion scattering damage to D-ribose and 2-deoxy-D-ribose films.

PubMed

Deng, Zongwu; Bald, Ilko; Illenberger, Eugen; Huels, Michael A

2007-10-14

Highly charged heavy ion traversal of a biological medium can produce energetic secondary fragment ions. These fragment ions can in turn cause collisional and reactive scattering damage to DNA. Here we report hyperthermal (1-100 eV) scattering of one such fragment ion (N(+)) from biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose condensed on polycrystalline Pt substrate. The results indicate that N(+) ion scattering at kinetic energies down to 10 eV induces effective decomposition of both sugar molecules and leads to the desorption of abundant cation and anion fragments. Use of isotope-labeled molecules (5-(13)C D-ribose and 1-D D-ribose) partly reveals some site specificity of the fragment origin. Several scattering reactions are also observed. Both ionic and neutral nitrogen atoms abstract carbon from the molecules to form CN(-) anion at energies down to approximately 5 eV. N(+) ions also abstract hydrogen from hydroxyl groups of the molecules to form NH(-) and NH(2) (-) anions. A fraction of OO(-) fragments abstract hydrogen to form OH(-). The formation of H(3)O(+) ions also involves hydrogen abstraction as well as intramolecular proton transfer. These findings suggest a variety of severe damaging pathways to DNA molecules which occur on the picosecond time scale following heavy ion irradiation of a cell, and prior to the late diffusion-limited homogeneous chemical processes.

Apparatus for reduction of selected ion intensities in confined ion beams

DOEpatents

Eiden, Gregory C.; Barinaga, Charles J.; Koppenaal, David W.

2001-01-01

An apparatus for producing an ion beam having an increased proportion of analyte ions compared to carrier gas ions is disclosed. Specifically, the apparatus has an ion trap or a collision cell containing a reagent gas wherein the reagent gas accepts charge from the analyte ions thereby selectively neutralizing the carrier gas ions. Also disclosed is the collision cell as employed in various locations within analytical instruments including an inductively coupled plasma mass spectrometer.

Retrograde degeneration of neurite membrane structural integrity of nerve growth cones following in vitro exposure to mercury.

PubMed

Leong, C C; Syed, N I; Lorscheider, F L

2001-03-26

Inhalation of mercury vapor (Hg0) inhibits binding of GTP to rat brain tubulin, thereby inhibiting tubulin polymerization into microtubules. A similar molecular lesion has also been observed in 80% of brains from patients with Alzheimer disease (AD) compared to age-matched controls. However the precise site and mode of action of Hg ions remain illusive. Therefore, the present study examined whether Hg ions could affect membrane dynamics of neurite growth cone morphology and behavior. Since tubulin is a highly conserved cytoskeletal protein in both vertebrates and invertebrates, we hypothesized that growth cones from animal species could be highly susceptible to Hg ions. To test this possibility, the identified, large Pedal A (PeA) neurons from the central ring ganglia of the snail Lymnoea stagnalis were cultured for 48 h in 2 ml brain conditioned medium (CM). Following neurite outgrowth, metal chloride solution (2 microl) of Hg, Al, Pb, Cd, or Mn (10(-7) M) was pressure applied directly onto individual growth cones. Time-lapse images with inverted microscopy were acquired prior to, during, and after the metal ion exposure. We demonstrate that Hg ions markedly disrupted membrane structure and linear growth rates of imaged neurites in 77% of all nerve growth cones. When growth cones were stained with antibodies specific for both tubulin and actin, it was the tubulin/microtubule structure that disintegrated following Hg exposure. Moreover, some denuded neurites were also observed to form neurofibrillary aggregates. In contrast, growth cone exposure to other metal ions did not effect growth cone morphology, nor was their motility rate compromised. To determine the growth suppressive effects of Hg ions on neuronal sprouting, cells were cultured either in the presence or absence of Hg ions. We found that in the presence of Hg ions, neuronal somata failed to sprout, whereas other metalic ions did not effect growth patterns of cultured PeA cells. We conclude that this visual evidence and previous biochemical data strongly implicate Hg as a potential etiological factor in neurodegeneration.

[Effect of calcium and magnesium ions on the interaction of corticosterone with the cytosol receptor(s) in the rat brain].

PubMed

Ueda, M

1981-01-01

The effects of calcium and magnesium ions on the corticosterone binding to rat brain cytosol receptor protein(s) were investigated. The increasing amounts of CaCl2 or MgCl2 up to 5.0 mM were added, the specific [3H] corticosterone binding increased 1.3-fold and 1.5 respectively. The addition of MnCl2 and KCl did not affect this binding. The binding of corticosterone with rat brain cytosol receptor(s) were decreased by increasing amounts of EDTA and complete inhibition was observed at concentration equal to and greater than 2.5 mM. Inhibition of this binding by EDTA was less than by EGTA. Either theophylline or dibutyryl cyclic AMP had no effect on this binding.

The Role of DNA Methylation Changes in Radiation-Induced Bystander Effects in cranial irradiated Mice

NASA Astrophysics Data System (ADS)

Zhang, Meng; Sun, Yeqing; Xue, Bei; Wang, Xinwen; Wang, Jiawen

2016-07-01

Heavy-ion radiation could lead to bystander effect in neighboring non-hit cells by signals released from directly-irradiated cells. The exact mechanisms of radiation-induced bystander effect in distant organ remain obscure, yet accumulating evidence points to the role of DNA methylation changes in bystander effect. To identify the molecular mechanism that underlies bystander effects of heavy-ion radiation, the male Balb/c and C57BL mice were cranial exposed to 40, 200, 2000mGy dose of carbon heavy-ion radiation, while the rest of the animal body was shielded. The γH2AX foci as the DNA damage biomarker in directly irradiation organ ear and the distant organ liver were detected on 0, 1, 2, 6, 12 and 24h after radiation, respectively. Methylation-sensitive amplifcation polymorphism (MSAP) was used to monitor the level of polymorphic genomic DNA methylation changed with dose and time effects. The results show that cranial irradiated mice could induce the γH2AX foci and genomic DNA methylation changes significantly in both the directly irradiation organ ear and the distant organ liver. The percent of DNA methylation changes were time-dependent and tissue-specific. Demethylation polymorphism rate were highest separately at 1 h in 200 mGy and 6 h in 2000 mGy after irradiation in ear. The global DNA methylation changes tended to occur in the CG sites. We also found that the numbers of γH2AX foci and the genomic methylation changes of heavy-ion radiation-induced bystander effect in liver could be obvious 1 h after radiation and achieved the maximum at 6 h, while the changes could recover gradually at 12 h. The results suggest that mice head exposed to heavy-ion radiation can induce damage and methylation pattern changed in both directly radiation organ ear and distant organ liver. Moreover, our findings are important to understand the molecular mechanism of radiation induced bystander effects in vivo. Keywords: Heavy-ion radiation; Bystander effect; DNA methylation; γH2AX; Mice.

Non-specific binding of Na+ and Mg2+ to RNA determined by force spectroscopy methods

PubMed Central

Bizarro, C. V.; Alemany, A.; Ritort, F.

2012-01-01

RNA duplex stability depends strongly on ionic conditions, and inside cells RNAs are exposed to both monovalent and multivalent ions. Despite recent advances, we do not have general methods to quantitatively account for the effects of monovalent and multivalent ions on RNA stability, and the thermodynamic parameters for secondary structure prediction have only been derived at 1M [Na+]. Here, by mechanically unfolding and folding a 20 bp RNA hairpin using optical tweezers, we study the RNA thermodynamics and kinetics at different monovalent and mixed monovalent/Mg2+ salt conditions. We measure the unfolding and folding rupture forces and apply Kramers theory to extract accurate information about the hairpin free energy landscape under tension at a wide range of ionic conditions. We obtain non-specific corrections for the free energy of formation of the RNA hairpin and measure how the distance of the transition state to the folded state changes with force and ionic strength. We experimentally validate the Tightly Bound Ion model and obtain values for the persistence length of ssRNA. Finally, we test the approximate rule by which the non-specific binding affinity of divalent cations at a given concentration is equivalent to that of monovalent cations taken at 100-fold concentration for small molecular constructs. PMID:22492710

Ion-Specific Modulation of Interfacial Interaction Potentials between Solid Substrates and Cell-Sized Particles Mediated via Zwitterionic, Super-Hydrophilic Poly(sulfobetaine) Brushes.

PubMed

Higaki, Yuji; Fröhlich, Benjamin; Yamamoto, Akihisa; Murakami, Ryo; Kaneko, Makoto; Takahara, Atsushi; Tanaka, Motomu

2017-02-16

Zwitterionic polymer brushes draw increasing attention not only because of their superhydrophilic, self-cleaning capability but also due to their excellent antifouling capacity. We investigated the ion-specific modulation of the interfacial interaction potential via densely packed, uniform poly(sulfobetaine) brushes. The vertical Brownian motion of a cell-sized latex particle was monitored by microinterferometry, yielding the effective interfacial interaction potentials V(Δh) and the autocorrelation function of height fluctuation. The potential curvature V″(Δh) exhibited a monotonic increase according to the increase in monovalent salt concentrations, implying the sharpening of the potential confinement. An opposite tendency was observed in CaCl 2 solutions, suggesting that the ion specific modulation cannot be explained by the classical Hofmeister series. When the particle fluctuation was monitored in the presence of free sulfobetaine molecules, the increase in [sulfobetaine] resulted in a distinct increase in hydrodynamic friction. This was never observed in all the other salt solutions, suggesting the interference of zwitterionic pairing of sulfobetaine side chains by the intercalation of sulfobetaine molecules into the brush layer. Furthermore, poly(sulfobetaine) brushes exhibited a very low V″(Δh) and hydrodynamic friction to human erythrocytes, which seems to explain the excellent blood repellency of zwitterionic polymer materials.

Calixarene cleansing formulation for uranium skin contamination.

PubMed

Phan, Guillaume; Semili, Naïma; Bouvier-Capely, Céline; Landon, Géraldine; Mekhloufi, Ghozlene; Huang, Nicolas; Rebière, François; Agarande, Michelle; Fattal, Elias

2013-10-01

An oil-in-water cleansing emulsion containing calixarene molecule, an actinide specific chelating agent, was formulated in order to improve the decontamination of uranium from the skin. Commonly commercialized cosmetic ingredients such as surfactants, mineral oil, or viscosifying agents were used in preparing the calixarene emulsion. The formulation was characterized in terms of size and apparent viscosity measurements and then was tested for its ability to limit uranyl ion permeation through excoriated pig-ear skin explants in 24-h penetration studies. Calixarene emulsion effectiveness was compared with two other reference treatments consisting of DTPA and EHBP solutions. Application of calixarene emulsion induced the highest decontamination effect with an 87% decrease in uranium diffusion flux. By contrast, EHBP and DTPA solutions only allowed a 50% and 55% reduction of uranium permeation, respectively, and had the same effect as a simple dilution of the contamination by pure water. Uranium diffusion decrease was attributed to uranyl ion-specific chelation by calixarene within the formulation, since no significant effect was obtained after application of the same emulsion without calixarene. Thus, calixarene cleansing emulsion could be considered as a promising treatment in case of accidental contamination of the skin by highly diffusible uranium compounds.

Comparative effectiveness of metal ions in inducing curvature of primary roots of Zea mays

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Evans, M. L.; Stinemetz, C. L.; Moore, R.; Fondren, W. M.; Koon, E. C.; Higby, M. A.; Smucker, A. J.

1988-01-01

We used five cultivars of Zea mays (Bear Hybrid WF9 * 38MS, B73 * Missouri 17, Yellow Dent, Merit, and Great Lakes Hybrid 422) to reinvestigate the specificity of metal ions for inducing root curvature. Of 17 cations tested, 6 (Al3+, Ba2+, Ca2+, Cd2+, Cu2+, Zn2+) induced curvature. Roots curved away from Al3+, Ba2+, and Cd2+. Roots curved away from low (0.1 millimolar) concentrations of Cu2+ but toward higher (1-5 millimolar) concentrations. Roots initially curved away from Zn2+ but the direction of the subsequent curvature was unpredictable. In most cases, roots of all cultivars curved towards calcium. However, in some tests there was no response to calcium or even (especially in the cultivars Merit and B73 * Missouri 17) substantial curvature away from calcium. The results indicate that the induction of root curvature is not specific for calcium. The results are discussed relative to the possible role of calmodulin as a mediator of ion-induced root curvature.

Electrostatic correlations at the Stern layer: Physics or chemistry?

NASA Astrophysics Data System (ADS)

Travesset, A.; Vangaveti, S.

2009-11-01

We introduce a minimal free energy describing the interaction of charged groups and counterions including both classical electrostatic and specific interactions. The predictions of the model are compared against the standard model for describing ions next to charged interfaces, consisting of Poisson-Boltzmann theory with additional constants describing ion binding, which are specific to the counterion and the interfacial charge ("chemical binding"). It is shown that the "chemical" model can be appropriately described by an underlying "physical" model over several decades in concentration, but the extracted binding constants are not uniquely defined, as they differ depending on the particular observable quantity being studied. It is also shown that electrostatic correlations for divalent (or higher valence) ions enhance the surface charge by increasing deprotonation, an effect not properly accounted within chemical models. The charged phospholipid phosphatidylserine is analyzed as a concrete example with good agreement with experimental results. We conclude with a detailed discussion on the limitations of chemical or physical models for describing the rich phenomenology of charged interfaces in aqueous media and its relevance to different systems with a particular emphasis on phospholipids.

Method of detecting luminescent target ions with modified magnetic microspheres

DOEpatents

Shkrob, Ilya A; Kaminski, Michael D

2014-05-13

This invention provides methods of using modified magnetic microspheres to extract target ions from a sample in order to detect their presence in a microfluidic environment. In one or more embodiments, the microspheres are modified with molecules on the surface that allow the target ions in the sample to form complexes with specific ligand molecules on the microsphere surface. In one or more embodiments, the microspheres are modified with molecules that sequester the target ions from the sample, but specific ligand molecules in solution subsequently re-extract the target ions from the microspheres into the solution, where the complexes form independent of the microsphere surface. Once the complexes form, they are exposed to an excitation wavelength light source suitable for exciting the target ion to emit a luminescent signal pattern. Detection of the luminescent signal pattern allows for determination of the presence of the target ions in the sample.

The Generation of Dehydroalanine Residues in Protonated Polypeptides: Ion/Ion Reactions for Introducing Selective Cleavages

NASA Astrophysics Data System (ADS)

Peng, Zhou; Bu, Jiexun; McLuckey, Scott A.

2017-09-01

We examine a gas-phase approach for converting a subset of amino acid residues in polypeptide cations to dehydroalanine (Dha). Subsequent activation of the modified polypeptide ions gives rise to specific cleavage N-terminal to the Dha residue. This process allows for the incorporation of selective cleavages in the structural characterization of polypeptide ions. An ion/ion reaction within the mass spectrometer between a multiply protonated polypeptide and the sulfate radical anion introduces a radical site into the multiply protonated polypeptide reactant. Subsequent collisional activation of the polypeptide radical cation gives rise to radical side chain loss from one of several particular amino acid side chains (e.g., leucine, asparagine, lysine, glutamine, and glutamic acid) to yield a Dha residue. The Dha residues facilitate preferential backbone cleavages to produce signature c- and z-ions, demonstrated with cations derived from melittin, mechano growth factor (MGF), and ubiquitin. The efficiencies for radical side chain loss and for subsequent generation of specific c- and z-ions have been examined as functions of precursor ion charge state and activation conditions using cations of ubiquitin as a model for a small protein. It is noted that these efficiencies are not strongly dependent on ion trap collisional activation conditions but are sensitive to precursor ion charge state. Moderate to low charge states show the greatest overall yields for the specific Dha cleavages, whereas small molecule losses (e.g., water/ammonia) dominate at the lowest charge states and proton catalyzed amide bond cleavages that give rise to b- and y-ions tend to dominate at high charge states. [Figure not available: see fulltext.

Utilization of Methacrylates and Polymer Matrices for the Synthesis of Ion Specific Resins

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

Czerwinski, Kenneth

2013-10-29

Disposal, storage, and/or transmutation of actinides such as americium (Am) will require the development of specific separation schemes. Existing efforts focus on solvent extraction systems for achieving suitable separation of actinide from lanthanides. However, previous work has shown the feasibility of ion-imprinting polymer-based resins for use in ion-exchange-type separations with metal ion recognition. Phenolic-based resins have been shown to function well for Am-Eu separations, but these resins exhibited slow kinetics and difficulties in the imprinting process. This project addresses the need for new and innovative methods for the selective separation of actinides through novel ion-imprinted resins. The project team willmore » explore incorporation of metals into extended frameworks, including the possibility of 3D polymerized matrices that can serve as a solid-state template for specific resin preparation. For example, an anhydrous trivalent f-element chain can be formed directly from a metal carbonate, and methacrylic acid from water. From these simple coordination complexes, molecules of discrete size or shape can be formed via the utilization of coordinating ligands or by use of an anionic multi-ligand system incorporating methacrylate. Additionally, alkyl methyl methacrylates have been used successfully to create template nanospaces, which underscores their potential utility as 3D polymerized matrices. This evidence provides a unique route for the preparation of a specific metal ion template for the basis of ion-exchange separations. Such separations may prove to be excellent discriminators of metal ions, even between f-elements. Resins were prepared and evaluated for sorption behavior, column properties, and proton exchange capacity.« less

Well-ordered mesoporous Fe2O3/C composites as high performance anode materials for sodium-ion batteries.

PubMed

Li, Mei; Ma, Chao; Zhu, Qian-Cheng; Xu, Shu-Mao; Wei, Xiao; Wu, Yong-Min; Tang, Wei-Ping; Wang, Kai-Xue; Chen, Jie-Sheng

2017-04-11

Sodium-ion batteries have attracted considerable attention in recent years. In order to promote the practical application of sodium-ion batteries, the electrochemical performances, such as specific capacity, reversibility, and rate capability of the anode materials, should be further improved. In this work, a Fe 2 O 3 /C composite with a well-ordered mesoporous structure is prepared via a facile co-impregnation method by using mesoporous silica SBA-15 as a hard template. When used as an anode material for sodium-ion batteries, the well-ordered mesoporous structure ensures fast mass transport kinetics. The presence of nano-sized Fe 2 O 3 particles confined within the carbon walls significantly enhances the specific capacity of the composite. The carbon walls in the composite act not only as an active material contributing to the specific capacity, but also as a conductive matrix improving the cycling stability of Fe 2 O 3 nanoparticles. As a result, the well-ordered mesoporous Fe 2 O 3 /C composite exhibits high specific capacity, excellent cycleability, and high rate capability. It is proposed that this simple co-impregnation method is applicable for the preparation of well-ordered mesoporous transition oxide/carbon composite electrode materials for high performance sodium-ion and lithium-ion batteries.

Detection of trace heavy metal ions in water by nanostructured porous Si biosensors.

PubMed

Shtenberg, Giorgi; Massad-Ivanir, Naama; Segal, Ester

2015-07-07

A generic biosensing platform, based on nanostructured porous Si (PSi), Fabry-Pérot thin films, for label-free monitoring of heavy metal ions in aqueous solutions by enzymatic activity inhibition, is described. First, we show a general detection assay by immobilizing horseradish peroxidase (HRP) within the oxidized PSi nanostructure and monitor its catalytic activity in real time by reflective interferometric Fourier transform spectroscopy. Optical studies reveal the high specificity and sensitivity of the HRP-immobilized PSi towards three metal ions (Ag(+) > Pb(2+) > Cu(2+)), with a detection limit range of 60-120 ppb. Next, we demonstrate the concept of specific detection of Cu(2+) ions (as a model heavy metal) by immobilizing Laccase, a multi-copper oxidase, within the oxidized PSi. The resulting biosensor allows for specific detection and quantification of copper ions in real water samples by monitoring the Laccase relative activity. The optical biosensing results are found to be in excellent agreement with those obtained by the gold standard analytical technique (ICP-AES) for all water samples. The main advantage of the presented biosensing concept is the ability to detect heavy metal ions at environmentally relevant concentrations using a simple and portable experimental setup, while the specific biosensor design can be tailored by varying the enzyme type.

Novel Colloidal and Dynamic Interfacial Phenomena in Liquid Crystalline Systems

DTIC Science & Technology

2014-09-13

Pablo. Effects of anchoring strength on the diffusivity of nanoparticles in model liquid-crystalline fluids, Soft Matter, (03 2011): 6828. doi...10.1021/la103975s Santanu Kumar Pal, Claribel Acevedo-Ve?lez, Jacob T. Hunter, Nicholas L. Abbott. Effects of Divalent Ligand Interactions on Surface...peer-reviewed journals: (c) Presentations 7 Presentation #1 (a) Electrical double layer and specific ion effects at interfaces between thermotropic

Manufacturing of 57cm carbon-carbon composite ion optics for the NEXIS ion engine

NASA Technical Reports Server (NTRS)

Beatty, John S.; Snyder, John Steven; Shih, Wei

2005-01-01

Exploration of the outer planets can be taxing on the ion optics of ion propulsion systems because of the higher power and propellant throughout than the present state-of-the art. Carbon-carbon composite ion optics are an enabling technology extending the life of ion optics operated at high specific impulse, power, and propellant throughout because of their low erosion rates compared to molybdenum ion optics.

Ceramic Electrolyte Membrane Technology: Enabling Revolutionary Electrochemical Energy Storage

DTIC Science & Technology

2015-10-05

ion batteries . Solid-state Li- ion batteries could significantly improve safety and eliminate the need for complex...advancing ceramic electrolyte technology for use in solid-state Li- ion batteries . Solid-state Li- ion batteries could significantly improve safety and...technology for use in solid-state Li- ion batteries and high specific energy Li-S and Li- air batteries . Solid-state Li- ion batteries could

Graph Theory and Ion and Molecular Aggregation in Aqueous Solutions.

PubMed

Choi, Jun-Ho; Lee, Hochan; Choi, Hyung Ran; Cho, Minhaeng

2018-04-20

In molecular and cellular biology, dissolved ions and molecules have decisive effects on chemical and biological reactions, conformational stabilities, and functions of small to large biomolecules. Despite major efforts, the current state of understanding of the effects of specific ions, osmolytes, and bioprotecting sugars on the structure and dynamics of water H-bonding networks and proteins is not yet satisfactory. Recently, to gain deeper insight into this subject, we studied various aggregation processes of ions and molecules in high-concentration salt, osmolyte, and sugar solutions with time-resolved vibrational spectroscopy and molecular dynamics simulation methods. It turns out that ions (or solute molecules) have a strong propensity to self-assemble into large and polydisperse aggregates that affect both local and long-range water H-bonding structures. In particular, we have shown that graph-theoretical approaches can be used to elucidate morphological characteristics of large aggregates in various aqueous salt, osmolyte, and sugar solutions. When ion and molecular aggregates in such aqueous solutions are treated as graphs, a variety of graph-theoretical properties, such as graph spectrum, degree distribution, clustering coefficient, minimum path length, and graph entropy, can be directly calculated by considering an ensemble of configurations taken from molecular dynamics trajectories. Here we show percolating behavior exhibited by ion and molecular aggregates upon increase in solute concentration in high solute concentrations and discuss compelling evidence of the isomorphic relation between percolation transitions of ion and molecular aggregates and water H-bonding networks. We anticipate that the combination of graph theory and molecular dynamics simulation methods will be of exceptional use in achieving a deeper understanding of the fundamental physical chemistry of dissolution and in describing the interplay between the self-aggregation of solute molecules and the structure and dynamics of water.

Graph Theory and Ion and Molecular Aggregation in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Choi, Jun-Ho; Lee, Hochan; Choi, Hyung Ran; Cho, Minhaeng

2018-04-01

In molecular and cellular biology, dissolved ions and molecules have decisive effects on chemical and biological reactions, conformational stabilities, and functions of small to large biomolecules. Despite major efforts, the current state of understanding of the effects of specific ions, osmolytes, and bioprotecting sugars on the structure and dynamics of water H-bonding networks and proteins is not yet satisfactory. Recently, to gain deeper insight into this subject, we studied various aggregation processes of ions and molecules in high-concentration salt, osmolyte, and sugar solutions with time-resolved vibrational spectroscopy and molecular dynamics simulation methods. It turns out that ions (or solute molecules) have a strong propensity to self-assemble into large and polydisperse aggregates that affect both local and long-range water H-bonding structures. In particular, we have shown that graph-theoretical approaches can be used to elucidate morphological characteristics of large aggregates in various aqueous salt, osmolyte, and sugar solutions. When ion and molecular aggregates in such aqueous solutions are treated as graphs, a variety of graph-theoretical properties, such as graph spectrum, degree distribution, clustering coefficient, minimum path length, and graph entropy, can be directly calculated by considering an ensemble of configurations taken from molecular dynamics trajectories. Here we show percolating behavior exhibited by ion and molecular aggregates upon increase in solute concentration in high solute concentrations and discuss compelling evidence of the isomorphic relation between percolation transitions of ion and molecular aggregates and water H-bonding networks. We anticipate that the combination of graph theory and molecular dynamics simulation methods will be of exceptional use in achieving a deeper understanding of the fundamental physical chemistry of dissolution and in describing the interplay between the self-aggregation of solute molecules and the structure and dynamics of water.

Protecting Water While Developing Energy and Mineral Resources

EPA Science Inventory

This project will provide the basis for informed decision making to evaluate the impacts of wastewater discharges on aquatic life for specific regions of the US and determine how acute and chronic effects from ion mixtures can be modeled and/or addressed. It will contribute to ne...

Differentiation of vasoactive renal sympathetic nerve fibres.

PubMed

Dibona, G F

2000-01-01

Activation of renal sympathetic nerves produces marked changes in renal haemodynamics, tubular ion and water transport and renin secretion. This review examines information indicating that these effects are mediated by functionally specific groups of renal sympathetic nerve fibres separately innervating the renal vessels, tubules and juxtaglomerular granular cells.

Red mud carbonation using carbon dioxide: Effects of carbonate and calcium ions on goethite surface properties and settling.

PubMed

Liang, Gaojie; Chen, Wenmi; Nguyen, Anh V; Nguyen, Tuan A H

2018-05-01

Carbonation using CO 2 appears as an attractive solution for disposing of red mud suspensions, an aluminum industry hazardous waste since it also offers an option for CO 2 sequestration. Here we report the novel findings that CO 3 2- together with Ca 2+ can significantly affect the surface properties and settling of goethite, a major component of red mud. Specifically, their effects on the goethite surface chemistry, colloidal interaction forces and settling in alkaline solutions are investigated. The surface potential becomes more negative by the formation of carbonate inner-sphere complexes on goethite surface. It is consistent with the strong repulsion, decreased particle size and settling velocity with increased carbonate concentrations as measured by atomic force microscopy, particle size analysis, and particle settling. Adding Ca 2+ that forms outer-sphere complexes with pre-adsorbed carbonate changes goethite surface charge negligibly. Changing repulsion to the attraction between goethite surfaces by increasing calcium dosage indicates the surface bridging, in accordance with the increased settling velocity. The adverse effect of carbonate on goethite flocculation is probably due to its specific chemisorption and competition with flocculants. By forming outer-sphere complexes together with the flocculant-calcium bridging effect, calcium ions can eliminate the negative influence of carbonate and improve the flocculation of goethite particles. These findings contribute to a better understanding of goethite particle interaction with salt ions and flocculants in controlling the particle behavior in the handling processes, including the red mud carbonation. Copyright © 2018 Elsevier Inc. All rights reserved.

Do preclinical seizure models preselect certain adverse effects of antiepileptic drugs.

PubMed

Meldrum, Brian

2002-06-01

Classical screening tests (maximal electroshock, MES, and threshold pentylenetetrazol, PTZ) employ non-epileptic rodents and identify antiepileptic drugs (AEDs) with mechanisms of action associated with significant CNS side effects. Thus MES identifies drugs acting on Na+ channels that produce cerebellar toxicity. It may be possible to produce novel AEDs more selectively targeted at voltage-sensitive (VS) ion channels. There is little specific evidence for the likely success of this strategy with subunit selective agents targeted at the different VS Na+ channels. Drugs targeted at specific VS Ca++ channels (T, N, P/Q types) may be useful in generalised seizures. There are many as yet unexplored possibilities relating to K+ channels. GABA related drugs acting on PTZ clonic seizures tend to induce sedation and muscle hypotonia. Studies in mice, particularly with knock-in mutations, but also with subunit selective agents acting via the GABA(A) benzodiazepine site, suggest that it is possible to produce agents which do or do not induce particular side effects (sedative, hypnotic, anxiolytic, muscle relaxant, amnesia, anaesthesia). Whether these findings transfer to man has yet to be established. Acquired epilepsy in rodents (e.g. kindling or spontaneous seizures following chemically- or electrically-induced status epilepticus) or acquired epilepsy in man (following prolonged febrile seizures or traumatic brain injury) is associated with multiple changes in the function and subunit composition of ion channels and receptor molecules. Optimal screening of novel AEDs, both for efficacy and side effects, requires models with receptor and ion channel changes similar to those in the target human syndrome.

Method for reduction of selected ion intensities in confined ion beams

DOEpatents

Eiden, Gregory C.; Barinaga, Charles J.; Koppenaal, David W.

1998-01-01

A method for producing an ion beam having an increased proportion of analyte ions compared to carrier gas ions is disclosed. Specifically, the method has the step of addition of a charge transfer gas to the carrier analyte combination that accepts charge from the carrier gas ions yet minimally accepts charge from the analyte ions thereby selectively neutralizing the carrier gas ions. Also disclosed is the method as employed in various analytical instruments including an inductively coupled plasma mass spectrometer.

Method for reduction of selected ion intensities in confined ion beams

DOEpatents

Eiden, G.C.; Barinaga, C.J.; Koppenaal, D.W.

1998-06-16

A method for producing an ion beam having an increased proportion of analyte ions compared to carrier gas ions is disclosed. Specifically, the method has the step of addition of a charge transfer gas to the carrier analyte combination that accepts charge from the carrier gas ions yet minimally accepts charge from the analyte ions thereby selectively neutralizing the carrier gas ions. Also disclosed is the method as employed in various analytical instruments including an inductively coupled plasma mass spectrometer. 7 figs.

Three-dimensional Model of Tissue and Heavy Ions Effects

NASA Technical Reports Server (NTRS)

Ponomarev, Artem L.; Sundaresan, Alamelu; Huff, Janice L.; Cucinotta, Francis A.

2007-01-01

A three-dimensional tissue model was incorporated into a new Monte Carlo algorithm that simulates passage of heavy ions in a tissue box . The tissue box was given as a realistic model of tissue based on confocal microscopy images. The action of heavy ions on the cellular matrix for 2- or 3-dimensional cases was simulated. Cells were modeled as a cell culture monolayer in one example, where the data were taken directly from microscopy (2-d cell matrix), and as a multi-layer obtained from confocal microscopy (3-d case). Image segmentation was used to identify cells with precise areas/volumes in an irradiated cell culture monolayer, and slices of tissue with many cell layers. The cells were then inserted into the model box of the simulated physical space pixel by pixel. In the case of modeled tissues (3-d), the tissue box had periodic boundary conditions imposed, which extrapolates the technique to macroscopic volumes of tissue. For the real tissue (3-d), specific spatial patterns for cell apoptosis and necrosis are expected. The cell patterns were modeled based on action cross sections for apoptosis and necrosis estimated from current experimental data. A spatial correlation function indicating a higher spatial concentration of damaged cells from heavy ions relative to the low-LET radiation cell damage pattern is presented. The spatial correlation effects among necrotic cells can help studying microlesions in organs, and probable effects of directionality of heavy ion radiation on epithelium and endothelium.

Development of portable mass spectrometer with electron cyclotron resonance ion source for detection of chemical warfare agents in air.

PubMed

Urabe, Tatsuya; Takahashi, Kazuya; Kitagawa, Michiko; Sato, Takafumi; Kondo, Tomohide; Enomoto, Shuichi; Kidera, Masanori; Seto, Yasuo

2014-01-01

A portable mass spectrometer with an electron cyclotron resonance ion source (miniECRIS-MS) was developed. It was used for in situ monitoring of trace amounts of chemical warfare agents (CWAs) in atmospheric air. Instrumental construction and parameters were optimized to realize a fast response, high sensitivity, and a small body size. Three types of CWAs, i.e., phosgene, mustard gas, and hydrogen cyanide were examined to check if the mass spectrometer was able to detect characteristic elements and atomic groups. From the results, it was found that CWAs were effectively ionized in the miniECRIS-MS, and their specific signals could be discerned over the background signals of air. In phosgene, the signals of the 35Cl+ and 37Cl+ ions were clearly observed with high dose-response relationships in the parts-per-billion level, which could lead to the quantitative on-site analysis of CWAs. A parts-per-million level of mustard gas, which was far lower than its lethal dosage (LCt50), was successfully detected with a high signal-stability of the plasma ion source. It was also found that the chemical forms of CWAs ionized in the plasma, i.e., monoatomic ions, fragment ions, and molecular ions, could be detected, thereby enabling the effective identification of the target CWAs. Despite the disadvantages associated with miniaturization, the overall performance (sensitivity and response time) of the miniECRIS-MS in detecting CWAs exceeded those of sector-type ECRIS-MS, showing its potential for on-site detection in the future. Copyright © 2013 Elsevier B.V. All rights reserved.

Biological and Clinical Aspects of Lanthanide Coordination Compounds

PubMed Central

Misra, Sudhindra N.; M., Indira Devi; Shukla, Ram S.

2004-01-01

The coordinating chemistry of lanthanides, relevant to the biological, biochemical and medical aspects, makes a significant contribution to understanding the basis of application of lanthanides, particularly in biological and medical systems. The importance of the applications of lanthanides, as an excellent diagnostic and prognostic probe in clinical diagnostics, and an anticancer material, is remarkably increasing. Lanthanide complexes based X-ray contrast imaging and lanthanide chelates based contrast enhancing agents for magnetic resonance imaging (MRI) are being excessively used in radiological analysis in our body systems. The most important property of the chelating agents, in lanthanide chelate complex, is its ability to alter the behaviour of lanthanide ion with which it binds in biological systems, and the chelation markedly modifies the biodistribution and excretion profile of the lanthanide ions. The chelating agents, especially aminopoly carboxylic acids, being hydrophilic, increase the proportion of their complex excreted from complexed lanthanide ion form biological systems. Lanthanide polyamino carboxylate-chelate complexes are used as contrast enhancing agents for Magnetic Resonance Imaging. Conjugation of antibodies and other tissue specific molecules to lanthanide chelates has led to a new type of specific MRI contrast agents and their conjugated MRI contrast agents with improved relaxivity, functioning in the body similar to drugs. Many specific features of contrast agent assisted MRI make it particularly effective for musculoskeletal and cerebrospinal imaging. Lanthanide-chelate contrast agents are effectively used in clinical diagnostic investigations involving cerebrospinal diseases and in evaluation of central nervous system. Chelated lanthanide complexes shift reagent aided 23Na NMR spectroscopic analysis is used in cellular, tissue and whole organ systems. PMID:18365075

Different roles of glutathione in copper and zinc chelation in Brassica napus roots.

PubMed

Zlobin, Ilya E; Kartashov, Alexander V; Shpakovski, George V

2017-09-01

We investigated the specific features of copper and zinc excess action on the roots of canola (Brassica napus L.) plants. Copper rapidly accumulated in canola root cells and reached saturation during several hours of treatment, whereas the root zinc content increased relatively slowly. Excessive copper and zinc entry inside the cell resulted in significant cell damage, as evidenced by alterations in plasmalemma permeability and decreases in cellular enzymatic activity. Zinc excess specifically damaged root hair cells, which correlated with a pronounced elevation of their labile zinc level. In vitro, we showed that reduced glutathione (GSH) readily reacted with copper ions to form complexes with blocked sulfhydryl groups. In contrast, zinc ions were ineffective as glutathione blockers, and glutathione molecules did not lose their specific chemical activity in the presence of Zn 2+ ions. The effect of copper and zinc excess on the glutathione pool in canola root cells was analysed by a combination of biochemical determination of total and oxidized glutathione contents and fluorescent staining of free reduced glutathione with monochlorobimane dye. Excess copper led to dose-dependent diminution of free reduced glutathione contents in the root cells, which could not be explained by the loss of total cellular glutathione or its oxidation. In contrast, we observed little effect of much higher intracellular zinc concentrations on the free reduced glutathione content. We concluded that GSH plays an important role in copper excess, but not zinc excess chelation, in canola root cells. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Interaction of colloidal nanoparticles with their local environment: the (ionic) nanoenvironment around nanoparticles is different from bulk and determines the physico-chemical properties of the nanoparticles

PubMed Central

Pfeiffer, Christian; Rehbock, Christoph; Hühn, Dominik; Carrillo-Carrion, Carolina; de Aberasturi, Dorleta Jimenez; Merk, Vivian; Barcikowski, Stephan; Parak, Wolfgang J.

2014-01-01

The physico-chemical properties of colloidal nanoparticles (NPs) are influenced by their local environment, as, in turn, the local environment influences the physico-chemical properties of the NPs. In other words, the local environment around NPs has a profound impact on the NPs, and it is different from bulk due to interaction with the NP surface. So far, this important effect has not been addressed in a comprehensive way in the literature. The vicinity of NPs can be sensitively influenced by local ions and ligands, with effects already occurring at extremely low concentrations. NPs in the Hückel regime are more sensitive to fluctuations in the ionic environment, because of a larger Debye length. The local ion concentration hereby affects the colloidal stability of the NPs, as it is different from bulk owing to Debye Hückel screening caused by the charge of the NPs. This can have subtle effects, now caused by the environment to the performance of the NP, such as for example a buffering effect caused by surface reaction on ultrapure ligand-free nanogold, a size quenching effect in the presence of specific ions and a significant impact on fluorophore-labelled NPs acting as ion sensors. Thus, the aim of this review is to clarify and give an unifying view of the complex interplay between the NP's surface with their nanoenvironment. PMID:24759541

Electrostatic Plasma Accelerator (EPA)

NASA Technical Reports Server (NTRS)

Brophy, John R.; Aston, Graeme

1989-01-01

The Electrostatic Plasma Accelerator (EPA) is a thruster concept which promises specific impulse levels between low power arcjets and those of the ion engine while retaining the relative simplicity of the arcjet. The EPA thruster produces thrust through the electrostatic acceleration of a moderately dense plasma. No accelerating electrodes are used and the specific impulse is a direct function of the applied discharge voltage and the propellant atomic mass. The goal of the present program is to demonstrate feasibility of the EPA thruster concept through experimental and theoretical investigations of the EPA acceleration mechanism and discharge chamber performance. Experimental investigations will include operating the test bed ion (TBI) engine as an EPA thruster and parametrically varying the thruster geometry and operating conditions to quantify the electrostatic plasma acceleration effect. The theoretical investigations will include the development of a discharge chamber model which describes the relationships between the engine size, plasma properties, and overall performance. For the EPA thruster to be a viable propulsion concept, overall thruster efficiencies approaching 30% with specific impulses approaching 1000 s must be achieved.

Charge-transfer-based terbium MOF nanoparticles as fluorescent pH sensor for extreme acidity.

PubMed

Qi, Zewan; Chen, Yang

2017-01-15

Newly emerged metal organic frameworks (MOFs) have aroused the great interest in designing functional materials by means of its flexible structure and component. In this study, we used lanthanide Tb 3+ ions and small molecular ligands to design and assemble a kind of pH-sensitive MOF nanoparticle based on intramolecular-charge-transfer effect. This kind of made-to-order MOF nanoparticle for H + is highly specific and sensitive and could be used to fluorescently indicate pH value of strong acidic solution via preset mechanism through luminescence of Tb 3+ . The long luminescence lifetime of Tb 3+ allows eliminating concomitant non-specific fluorescence by time-revised fluorescence techniques, processing an advantage in sensing H + in biological media with strong autofluorescence. Our method showed a great potential of MOF structures in designing and constructing sensitive sensing materials for specific analytes directly via the assembly of functional ions/ligands. Copyright © 2016 Elsevier B.V. All rights reserved.

Structural Studies of Fucosylated N-Glycans by Ion Mobility Mass Spectrometry and Collision-Induced Fragmentation of Negative Ions

NASA Astrophysics Data System (ADS)

Harvey, David J.; Struwe, Weston B.

2018-05-01

There is considerable potential for the use of ion mobility mass spectrometry in structural glycobiology due in large part to the gas-phase separation attributes not typically observed by orthogonal methods. Here, we evaluate the capability of traveling wave ion mobility combined with negative ion collision-induced dissociation to provide structural information on N-linked glycans containing multiple fucose residues forming the Lewisx and Lewisy epitopes. These epitopes are involved in processes such as cell-cell recognition and are important as cancer biomarkers. Specific information that could be obtained from the intact N-glycans by negative ion CID included the general topology of the glycan such as the presence or absence of a bisecting GlcNAc residue and the branching pattern of the triantennary glycans. Information on the location of the fucose residues was also readily obtainable from ions specific to each antenna. Some isobaric fragment ions produced prior to ion mobility could subsequently be separated and, in some cases, provided additional valuable structural information that was missing from the CID spectra alone.

Concurrent Automated Sequencing of the Glycan and Peptide Portions of O-Linked Glycopeptide Anions by Ultraviolet Photodissociation Mass Spectrometry

PubMed Central

Madsen, James A.; Ko, Byoung Joon; Xu, Hua; Iwashkiw, Jeremy A.; Robotham, Scott A.; Shaw, Jared B.; Feldman, Mario F.; Brodbelt, Jennifer S.

2013-01-01

O -glycopeptides are often acidic owing to the frequent occurrence of acidic saccharides in the glycan, rendering traditional proteomic workflows that rely on positive mode tandem mass spectrometry (MS/MS) less effective. In this report, we demonstrate the utility of negative mode ultraviolet photodissociation (UVPD) MS for the characterization of acidic O-linked glycopeptide anions. This method was evaluated for a series of singly- and multiply-deprotonated glycopeptides from the model glycoprotein kappa casein, resulting in production of both peptide and glycan product ions that afforded 100% sequence coverage of the peptide and glycan moieties from a single MS/MS event. The most abundant and frequent peptide sequence ions were a/x-type products, which, importantly, were found to retain the labile glycan modifications. The glycan-specific ions mainly arose from glycosidic bond cleavages (B, Y, C, and Z ions) in addition to some less common cross-ring cleavages. Based on the UVPD fragmentation patterns, an automated database searching strategy (based on the MassMatrix algorithm) was designed that is specific for the analysis of glycopeptide anions by UVPD. This algorithm was used to identify glycopeptides from mixtures of glycosylated and non-glycosylated peptides, sequence both glycan and peptide moieties simultaneously, and pinpoint the correct site(s) of glycosylation. This methodology was applied to uncover novel site-specificity of the O-linked glycosylated OmpA/MotB from the “superbug” A. baumannii to help aid in the elucidation of the functional role that protein glycosylation plays in pathogenesis. PMID:24006841

Pharmaceutical Applications of Ion-Exchange Resins

ERIC Educational Resources Information Center

Elder, David

2005-01-01

The historical uses of ion-exchanged resins and a summary of the basic chemical principles involved in the ion-exchanged process are discussed. Specific applications of ion-exchange are provided that include drug stabilization, pharmaceutical excipients, taste-masking agents, oral sustained-release products, topical products for local application…

A review of thermal performance improving methods of lithium ion battery: Electrode modification and thermal management system

NASA Astrophysics Data System (ADS)

Zhao, Rui; Zhang, Sijie; Liu, Jie; Gu, Junjie

2015-12-01

Lithium ion (Li-ion) battery has emerged as an important power source for portable devices and electric vehicles due to its superiority over other energy storage technologies. A mild temperature variation as well as a proper operating temperature range are essential for a Li-ion battery to perform soundly and have a long service life. In this review paper, the heat generation and dissipation of Li-ion battery are firstly analyzed based on the energy conservation equations, followed by an examination of the hazardous effects of an above normal operating temperature. Then, advanced techniques in respect of electrode modification and systematic battery thermal management are inspected in detail as solutions in terms of reducing internal heat production and accelerating external heat dissipation, respectively. Specifically, variable parameters like electrode thickness and particle size of active material, along with optimization methods such as coating, doping, and adding conductive media are discussed in the electrode modification section, while the current development in air cooling, liquid cooling, heat pipe cooling, and phase change material cooling systems are reviewed in the thermal management part as different ways to improve the thermal performance of Li-ion batteries.

Nanodosimetry of Low Energy (0.1 - 100 eV) Cation Damage to DNA

NASA Astrophysics Data System (ADS)

Sellami, L.; Martin, F.; Hunting, D.; Lacombe, S.; Huels, M. A.

2004-03-01

The importance of heavy ions in radiobiology is twofold: (1) they represent the most efficient and volume selective mode of radiotherapy of deep-seated and non-operable tumors, (2) in space environments, or at supersonic altitudes, the most lethal radiation consists of cosmic rays which have a high efficiency to induce clustered DNA lesions, mutations, and cancer. Thus, the study of their effects on DNA is essential for radiation risk assessment, dosimetry, and efficient use of hadrontherapy. Here, we investigate damage to DNA and its components, induced by heavy ion impact, via a novel ion-plasma method, which allows us to probe ion energy depositions in the 0.1-100 eV/nm range in nanoscopic biomolecular films. Cations are generated by electron impact in ultra pure gases (Ar, N2, CO, etc.), and are uniformly accelerated by grids towards the inside surface of a cylinder where an organic film was deposited. After ion irradiation at a specific energy and ion dose, the film is recovered and analyzed. For DNA, gel electrophoresis is used to quantify yields of single, double, and multiple strand breaks. For DNA components (mononucleotides), fragmentation and new products are measured by HPLC and MS.

Swift heavy ion track formation in Gd2Zr2-xTixO7 pyrochlore: Effect of electronic energy loss

NASA Astrophysics Data System (ADS)

Lang, Maik; Toulemonde, Marcel; Zhang, Jiaming; Zhang, Fuxiang; Tracy, Cameron L.; Lian, Jie; Wang, Zhongwu; Weber, William J.; Severin, Daniel; Bender, Markus; Trautmann, Christina; Ewing, Rodney C.

2014-10-01

The morphology of swift heavy ion tracks in the Gd2Zr2-xTixO7 pyrochlore system has been investigated as a function of the variation in chemical composition and electronic energy loss, dE/dx, over a range of energetic ions: 58Ni, 101Ru, 129Xe, 181Ta, 197Au, 208Pb, and 238U of 11.1 MeV/u specific energy. Bright-field transmission electron microscopy, synchrotron X-ray diffraction, and Raman spectroscopy reveal an increasing degree of amorphization with increasing Ti-content and dE/dx. The size and morphology of individual ion tracks in Gd2Ti2O7 were characterized by high-resolution transmission electron microscopy revealing a core-shell structure with an outer defect-fluorite dominated shell at low dE/dx to predominantly amorphous tracks at high dE/dx. Inelastic thermal-spike calculations have been used together with atomic-scale characterization of ion tracks in Gd2Ti2O7 by high resolution transmission electron microscopy to deduce critical energy densities for the complex core-shell morphologies induced by ions of different dE/dx.

Voltage sweep ion mobility spectrometry.

PubMed

Davis, Eric J; Williams, Michael D; Siems, William F; Hill, Herbert H

2011-02-15

Ion mobility spectrometry (IMS) is a rapid, gas-phase separation technique that exhibits excellent separation of ions as a standalone instrument. However, IMS cannot achieve optimal separation power with both small and large ions simultaneously. Similar to the general elution problem in chromatography, fast ions are well resolved using a low electric field (50-150 V/cm), whereas slow drifting molecules are best separated using a higher electric field (250-500 V/cm). While using a low electric field, IMS systems tend to suffer from low ion transmission and low signal-to-noise ratios. Through the use a novel voltage algorithm, some of these effects can be alleviated. The electric field was swept from low to high while monitoring a specific drift time, and the resulting data were processed to create a 'voltage-sweep' spectrum. If an optimal drift time is calculated for each voltage and scanned simultaneously, a spectrum may be obtained with optimal separation throughout the mobility range. This increased the resolving power up to the theoretical maximum for every peak in the spectrum and extended the peak capacity of the IMS system, while maintaining accurate drift time measurements. These advantages may be extended to any IMS, requiring only a change in software.

Depth profile of halide anions under highly charged biological membrane

NASA Astrophysics Data System (ADS)

Sung, Woongmo; Wang, Wenjie; Lee, Jonggwan; Vaknin, David; Kim, Doseok

2015-03-01

Halide ion (Cl- and I-) distribution under a cationic Langmuir monolayer consisting of 1,2-dipalmitoyl-3 trimethylammonium-propane (DPTAP) molecules was investigated by vibrational sum-frequency generation (VSFG) and X-ray spectroscopy. From VSFG spectra, it was observed that large halide anions (I-) screen surface charge more efficiently so that interfacial water alignment becomes more randomized. On the other hand, number density of ions directly measured by X-ray fluorescence spectroscopy at grazing incidence angle reveals that the ion densities within 6 ~ 8 nm are the same for both I- and Cl-. Since the observed ion densities in both cases are almost equal to the charge density of the DPTAP monolayer, we propose that larger halide anions are attracted closer to the surface making direct binding with the charged headgroups of the molecules in the monolayer, accomplishing charge neutrality in short distance. This direct adsorption of anions also disturbs the monolayer structure both in terms of the conformation of alkyl chains and the vertical configuration of the monolayer, with iodine having the stronger effect. Our study shows that the length scale that ions neutralize a charged interface varies significantly and specifically even between monovalent ions.

Quantum tunneling recombination in a system of randomly distributed trapped electrons and positive ions.

PubMed

Pagonis, Vasilis; Kulp, Christopher; Chaney, Charity-Grace; Tachiya, M

2017-09-13

During the past 10 years, quantum tunneling has been established as one of the dominant mechanisms for recombination in random distributions of electrons and positive ions, and in many dosimetric materials. Specifically quantum tunneling has been shown to be closely associated with two important effects in luminescence materials, namely long term afterglow luminescence and anomalous fading. Two of the common assumptions of quantum tunneling models based on random distributions of electrons and positive ions are: (a) An electron tunnels from a donor to the nearest acceptor, and (b) the concentration of electrons is much lower than that of positive ions at all times during the tunneling process. This paper presents theoretical studies for arbitrary relative concentrations of electrons and positive ions in the solid. Two new differential equations are derived which describe the loss of charge in the solid by tunneling, and they are solved analytically. The analytical solution compares well with the results of Monte Carlo simulations carried out in a random distribution of electrons and positive ions. Possible experimental implications of the model are discussed for tunneling phenomena in long term afterglow signals, and also for anomalous fading studies in feldspars and apatite samples.

Modeling electrokinetics in ionic liquids: General

DOE PAGES

Wang, Chao; Bao, Jie; Pan, Wenxiao; ...

2017-04-01

Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson–Nernst–Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier–Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on amore » curved ionselective surface. Lastly, we also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.« less

Laser-driven Ion Acceleration using Nanodiamonds

NASA Astrophysics Data System (ADS)

D'Hauthuille, Luc; Nguyen, Tam; Dollar, Franklin

2016-10-01

Interactions of high-intensity lasers with mass-limited nanoparticles enable the generation of extremely high electric fields. These fields accelerate ions, which has applications in nuclear medicine, high brightness radiography, as well as fast ignition for inertial confinement fusion. Previous studies have been performed with ensembles of nanoparticles, but this obscures the physics of the interaction due to the wide array of variables in the interaction. The work presented here looks instead at the interactions of a high intensity short pulse laser with an isolated nanodiamond. Specifically, we studied the effect of nanoparticle size and intensity of the laser on the interaction. A novel target scheme was developed to isolate the nanodiamond. Particle-in-cell simulations were performed using the EPOCH framework to show the sheath fields and resulting energetic ion beams.

Understanding materials challenges for rechargeable ion batteries with in situ transmission electron microscopy

NASA Astrophysics Data System (ADS)

Yuan, Yifei; Amine, Khalil; Lu, Jun; Shahbazian-Yassar, Reza

2017-08-01

An in-depth understanding of material behaviours under complex electrochemical environment is critical for the development of advanced materials for the next-generation rechargeable ion batteries. The dynamic conditions inside a working battery had not been intensively explored until the advent of various in situ characterization techniques. Real-time transmission electron microscopy of electrochemical reactions is one of the most significant breakthroughs poised to enable radical shift in our knowledge on how materials behave in the electrochemical environment. This review, therefore, summarizes the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasizes the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces. New electrochemical systems such as lithium-oxygen, lithium-sulfur and sodium ion batteries are included, considering the rapidly increasing application of in situ transmission electron microscopy in these areas. A systematic comparison between lithium ion-based electrochemistry and sodium ion-based electrochemistry is also given in terms of their thermodynamic and kinetic differences. The effect of the electron beam on the validity of in situ observation is also covered. This review concludes by providing a renewed perspective for the future directions of in situ transmission electron microscopy in rechargeable ion batteries.

In-situ luminescence monitoring of ion-induced damage evolution in SiO 2 and Al 2O 3

DOE PAGES

Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; ...

2015-12-17

Real-time, in-situ ionoluminescence measurements provide information of evolution of emission bands with ion fluence, and thereby establish a correlation between point defect kinetics and phase stability. Using fast light ions (2 MeV H and 3.5 He MeV) and medium mass-high energy ions (8 MeV O, E=0.5 MeV/amu), scintillation materials of a-SiO 2, crystalline quartz, and Al 2O 3 are comparatively investigated at room temperature with the aim of obtaining a further insight on the structural defects induced by ion irradiation and understand the role of electronic energy loss on the damage processes. For more energetic heavy ions, the electronic energymore » deposition pattern offers higher rates of excitation deeper into the material and allows to evaluate the competing mechanisms between the radiative and non-radiative de-excitation processes. Irradiations with 8 MeV O ions have been selected corresponding to the electronic stopping regime, where the electronic stopping power is dominant, and above the critical amorphization threshold for quartz. Lastly, the usefulness of IBIL and its specific capabilities as a sensitive tool to investigate the material characterization and evaluation of radiation effects are demonstrated.« less

Effects of Thermal and Pressure Histories on the Chemical Strengthening of Sodium Aluminosilicate Glass

NASA Astrophysics Data System (ADS)

Svenson, Mouritz; Thirion, Lynn; Youngman, Randall; Mauro, John; Bauchy, Mathieu; Rzoska, Sylwester; Bockowski, Michal; Smedskjaer, Morten

2016-03-01

Glasses can be chemically strengthened through the ion exchange process, wherein smaller ions in the glass (e.g., Na+) are replaced by larger ions from a salt bath (e.g., K+). This develops a compressive stress (CS) on the glass surface, which, in turn, improves the damage resistance of the glass. The magnitude and depth of the generated CS depends on the thermal and pressure histories of the glass prior to ion exchange. In this study, we investigate the ion exchange-related properties (mutual diffusivity, CS, and hardness) of a sodium aluminosilicate glass, which has been densified through annealing below the initial fictive temperature of the glass or through pressure-quenching from the glass transition temperature at 1 GPa prior to ion exchange. We show that the rate of alkali interdiffusivity depends only on the density of the glass, rather than on the applied densification method. However, we also demonstrate that for a given density, the increase in CS and increase in hardness induced by ion exchange strongly depends on the densification method. Specifically, at constant density, the CS and hardness values achieved through thermal annealing are larger than those achieved through pressure-quenching. These results are discussed in relation to the structural changes in the environment of the network-modifier and the overall network densification.

Ion-Responsive Drug Delivery Systems.

PubMed

Yoshida, Takayuki; Shakushiro, Kohsuke; Sako, Kazuhiro

2018-02-08

Some kinds of cations and anions are contained in body fluids such as blood, interstitial fluid, gastrointestinal juice, and tears at relatively high concentration. Ionresponsive drug delivery is available to design the unique dosage formulations which provide optimized drug therapy with effective, safe and convenient dosing of drugs. The objective of the present review was to collect, summarize, and categorize recent research findings on ion-responsive drug delivery systems. Ions in body fluid/formulations caused structural changes of polymers/molecules contained in the formulations, allow formulations exhibit functions. The polymers/molecules responding to ions were ion-exchange resins/fibers, anionic or cationic polymers, polymers exhibiting transition at lower critical solution temperature, self-assemble supramolecular systems, peptides, and metalorganic frameworks. The functions of ion-responsive drug delivery systems were categorized to controlled drug release, site-specific drug release, in situ gelation, prolonged retention at the target sites, and enhancement of drug permeation. Administration of the formulations via oral, ophthalmic, transdermal, and nasal routes has showed significant advantages in the recent literatures. Many kinds of drug delivery systems responding to ions have been reported recently for several administration routes. Improvement and advancement of these systems can maximize drugs potential and contribute to patients in the world. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Understanding materials challenges for rechargeable ion batteries with in situ transmission electron microscopy

PubMed Central

Yuan, Yifei; Amine, Khalil; Lu, Jun; Shahbazian-Yassar, Reza

2017-01-01

An in-depth understanding of material behaviours under complex electrochemical environment is critical for the development of advanced materials for the next-generation rechargeable ion batteries. The dynamic conditions inside a working battery had not been intensively explored until the advent of various in situ characterization techniques. Real-time transmission electron microscopy of electrochemical reactions is one of the most significant breakthroughs poised to enable radical shift in our knowledge on how materials behave in the electrochemical environment. This review, therefore, summarizes the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasizes the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces. New electrochemical systems such as lithium–oxygen, lithium–sulfur and sodium ion batteries are included, considering the rapidly increasing application of in situ transmission electron microscopy in these areas. A systematic comparison between lithium ion-based electrochemistry and sodium ion-based electrochemistry is also given in terms of their thermodynamic and kinetic differences. The effect of the electron beam on the validity of in situ observation is also covered. This review concludes by providing a renewed perspective for the future directions of in situ transmission electron microscopy in rechargeable ion batteries.

Ion-Specific Interfacial Crystallization of Polymer-Grafted Nanoparticles

DOE PAGES

Zhang, Honghu; Wang, Wenjie; Mallapragada, Surya; ...

2017-06-27

In this study, ion-specific effects on the assembly and crystallization of polyethylene-glycol-grafted Au nanoparticles (PEG-AuNPs) at the vapor–liquid interface are examined by surface sensitive synchrotron X-ray scattering methods. We show that monovalent salts, such as KCl and NaCl, that do not advance phase separation of pure PEG at room temperature induce two-dimensional (2D) self-assembly and crystallization of PEG-AuNPs with some distinctions. Whereas for KCl the 2D hexagonal coherence length of the PEG-AuNP superlattices is remarkably large compared to other salts (over micron-sized crystalline grains), NaCl induces coexistence of two hexagonal structures. Using various salts, we find that the value ofmore » the lattice constant is correlated to the ionic hydration entropy consistent with the Hofmeister series.« less

Biological Impact of Bioactive Glasses and Their Dissolution Products.

PubMed

Hoppe, Alexander; Boccaccini, Aldo R

2015-01-01

For many years, bioactive glasses (BGs) have been widely considered for bone tissue engineering applications due to their ability to bond to hard as well as soft tissue (a property termed bioactivity) and for their stimulating effects on bone formation. Ionic dissolution products released during the degradation of the BG matrix induce osteogenic gene expression leading to enhanced bone regeneration. Recently, adding bioactive metallic ions (e.g. boron, copper, cobalt, silver, zinc and strontium) to silicate (or phosphate and borate) glasses has emerged as a promising route for developing novel BG formulations with specific therapeutic functionalities, including antibacterial, angiogenic and osteogenic properties. The degradation behaviour of BGs can be tailored by adjusting the glass chemistry making these glass matrices potential carrier systems for controlled therapeutic ion release. This book chapter summarises the fundamental aspects of the effect of ionic dissolution products from BGs on osteogenesis and angiogenesis, whilst discussing novel BG compositions with controlled therapeutic ion release. © 2015 S. Karger AG, Basel.

Automation of experiments at Dubna Gas-Filled Recoil Separator

NASA Astrophysics Data System (ADS)

Tsyganov, Yu. S.

2016-01-01

Approaches to solving the problems of automation of basic processes in long-term experiments in heavy ion beams of the Dubna Gas-Filled Recoil Separator (DGFRS) facility are considered. Approaches in the field of spectrometry, both of rare α decays of superheavy nuclei and those for constructing monitoring systems to provide accident-free experiment running with highly radioactive targets and recording basic parameters of experiment, are described. The specific features of Double Side Silicon Strip Detectors (DSSSDs) are considered, special attention is paid to the role of boundary effects of neighboring p-n transitions in the "active correlations" method. An example of an off-beam experiment attempting to observe Zeno effect is briefly considered. Basic examples for nuclear reactions of complete fusion at 48Ca ion beams of U-400 cyclotron (LNR, JINR) are given. A scenario of development of the "active correlations" method for the case of very high intensity beams of heavy ions at promising accelerators of LNR, JINR, is presented.

Controllable construction of flower-like FeS/Fe2O3 composite for lithium storage

NASA Astrophysics Data System (ADS)

Wang, Jie; He, Huan; Wu, Zexing; Liang, Jianing; Han, Lili; Xin, Huolin L.; Guo, Xuyun; Zhu, Ye; Wang, Deli

2018-07-01

Transitions metal sulfides/oxides have been considered as promising anode candidates for next generation lithium-ion batteries (LIBs) due to high theoretical capacities. However, the large volume change during lithiation/delithiation process and poor electronic conductivity often result in a poor charging/discharging performance. Herein, we design a flower-like FeS/Fe2O3 composite via a simple "solvothermal-oxidation" method, in which the Fe2O3 is most distributed on the surface of the flower. The unique porous structure and synergistic effect between FeS and Fe2O3 not only accommodate the large volume expansion, but also facilitate Li ion and electron transport. The Fe2O3 shell effectively reduce the dissolution of Li2Sx during discharge/charge process. When serving as the anode material in lithium ion battery, FeS/Fe2O3 exhibits superior specific capacity, rate capacity and cycling stability compared with pure FeS and Fe2O3.

Effect of Acetylene Black Content to Half Cells Li-ion Battery Performance Based on Li4Ti5O12 using Li2CO3 as Lithium Ion Source with Hydrothermal Mechanochemical Process

NASA Astrophysics Data System (ADS)

Priyono, B.; Faizah; Syahrial, A. Z.; Subhan, A.

2017-07-01

Lithium titanate (Li4Ti5O12)/LTO is a promising candidate to be used as anode electrode in Li-ion battery, to replace graphite in Li-ion battery application. Crystal structure of lithium titanate/LTO is more stable or undergoes less strain than graphite during intercalation and de-intercalation process Li+ ions. However, although lithium titanate has good stability, the material has low electrical conductivity and lithium ion diffusion. The purpose of this research is to synthesis the spinel LTO using combinated hydrothermal and mechanochemical processes from xerogel TiO2. Then, to increase the conductivity, in the half-cell battery assembly process it was added acetylene black conductive (AB) additive with various from 10%, to 15% in wt. The LTO obtained were characterized using scanning electron microscope (SEM), X-Ray Diffraction (XRD) and Brunauer-Emmett-Teller (BET). The XRD showed a rutile as minor phase, while SEM showed homogeneous distribution of particle with an average particle size of 0.35 μm. The BET showed that the surface area of LTO formed is 2.26 m2/g. The assembled coin half cells used this Li4Ti5O12 as a cathode and lithium metal foil as the anode were tested using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge discharge (CD). The conductivity value obtained from EIS corresponds to the contents of AB. Meanwhile, the CV and CD testing showed that higher percentage of AB causing the decrease of battery specific capacity. The highest specific capacity at the rate of 10C is obtained at the mixture of 10wt% AB with the value of 40.91 mAh/g.

Effects of the single-ion anisotropy on magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) cylindrical Ising nanowire

NASA Astrophysics Data System (ADS)

Wang, Wei; Bi, Jiang-lin; Liu, Rui-jia; Chen, Xu; Liu, Jin-ping

2016-10-01

Monte Carlo simulation has been performed in detail to study magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) cylindrical Ising nanowire with core-shell structure. The ground phase diagrams are obtained for different single-ion anisotropies. The system can display rich phase transitions such as the second- and first-order phase transitions, the tricritical points and the compensation points. Especially, emphasis has been given to the effects of the single-ion anisotropy and the temperate on the magnetization, the internal energy, the specific heat, the compensation points and hysteresis loops of the system as well as two sublattices. A number of characteristic phenomena such as such as various types of magnetization curves and triple, duadruple as well as quintuple hysteresis loops behaviors have been observed for certain physical parameters, originating from the competitions among the anisotropies, temperature and the longitudinal magnetic field. It is found that the single-ion anisotropy and the temperature strongly affect the coercivity and the remanence of the system. A satisfactory agreement can be achieved from comparisons between our results and previous theoretical and experimental works.

Physicochemical hydrodynamics of porous structures in vascular plants

NASA Astrophysics Data System (ADS)

Ryu, Jeongeun; Ahn, Sungsook; Kim, Seung-Gon; Kim, Taejoo; Lee, Sang Joon

2013-11-01

Transport of sap flow through xylem conduits of vascular plants has been considered as a passive process, because the xylem conduits are regarded as inert, dead wood. However, plants can actively regulate water transport using ion-mediated response for adapting to environmental changes. In order to understand the active regulation mechanism of physicochemical hydrodynamics of porous structures in vascular plants, the effects of specific ion types and their ionic ratios on the water transport were experimentally investigated under in vivocondition. Based on the experimental results, the principle of ionic effects will be explained through in-vitro comparative experiments and theoretical considerations. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government (MSIP) (No. 2008-0061991).

Dislocation loop formation by swift heavy ion irradiation of metals.

PubMed

Khara, Galvin S; Murphy, Samuel T; Duffy, Dorothy M

2017-07-19

A coupled two-temperature, molecular dynamics methodology is used to simulate the structural evolution of bcc metals (Fe and W) and fcc metals (Cu and Ni) following irradiation by swift heavy ions. Electronic temperature dependent electronic specific heat capacities and electron-phonon coupling strengths are used to capture the full effects of the variation in the electronic density of states. Tungsten is found to be significantly more resistant to damage than iron, due both to the higher melting temperature and the higher thermal conductivity. Very interesting defect structures, quite different from defects formed in cascades, are found to be created by swift heavy ion irradiation in the bcc metals. Isolated vacancies form a halo around elongated interstitial dislocation loops that are oriented along the ion path. Such configurations are formed by rapid recrystallization of the molten cylindrical region that is created by the energetic ion. Vacancies are created at the recrystallization front, resulting in excess atoms at the core which form interstitial dislocation loops on completion of crystallization. These unique defect structures could, potentially, be used to create metal films with superior mechanical properties and interesting nanostructures.

Dislocation loop formation by swift heavy ion irradiation of metals

NASA Astrophysics Data System (ADS)

Khara, Galvin S.; Murphy, Samuel T.; Duffy, Dorothy M.

2017-07-01

A coupled two-temperature, molecular dynamics methodology is used to simulate the structural evolution of bcc metals (Fe and W) and fcc metals (Cu and Ni) following irradiation by swift heavy ions. Electronic temperature dependent electronic specific heat capacities and electron-phonon coupling strengths are used to capture the full effects of the variation in the electronic density of states. Tungsten is found to be significantly more resistant to damage than iron, due both to the higher melting temperature and the higher thermal conductivity. Very interesting defect structures, quite different from defects formed in cascades, are found to be created by swift heavy ion irradiation in the bcc metals. Isolated vacancies form a halo around elongated interstitial dislocation loops that are oriented along the ion path. Such configurations are formed by rapid recrystallization of the molten cylindrical region that is created by the energetic ion. Vacancies are created at the recrystallization front, resulting in excess atoms at the core which form interstitial dislocation loops on completion of crystallization. These unique defect structures could, potentially, be used to create metal films with superior mechanical properties and interesting nanostructures.

Impact of Lactic Acid and Hydrogen Ion on the Simultaneous Fermentation of Glucose and Xylose by the Carbon Catabolite Derepressed Lactobacillus brevis ATCC 14869.

PubMed

Jeong, Kyung Hun; Israr, Beenish; Shoemaker, Sharon P; Mills, David A; Kim, Jaehan

2016-07-28

Lactobacillus brevis ATCC 14869 exhibited a carbon catabolite de-repressed (CCR) phenotype which has ability to consume fermentable sugar simultaneously with glucose. To evaluate this unusual phenotype under harsh conditions during fermentation, the effect of lactic acid and hydrogen ion concentrations on L. brevis ATCC 14869 were examined. Kinetic equations describing the relationship between specific cell growth rate and lactic acid or hydrogen ion concentration has been reduced. The change of substrate utilization and product formation according to lactic acid and hydrogen ion concentration in the media were quantitatively described. Moreover; utilization of other compounds were also observed along with hydrogen ion and lactic acid concentration simultaneously. It has been found that substrate preference changes significantly regarding to utilization of compounds in media. That could result into formation of two-carbon products. In particular, acetic acid present in the media as sodium acetate were consumed by L. brevis ATCC 14869 under extreme pH of both acid and alkaline conditions.

Potential therapeutic targets for ATP-gated P2X receptor ion channels.

PubMed

Li, Zhiyuan; Liang, Dong; Chen, Ling

2008-04-01

P2X receptors make up a novel family of ligand-gated ion channels that are activated by binding of extracellular ATP. These receptors can form a number of homomeric and heteromeric ion channels, which are widely distributed throughout the human body. They are thought to play an important role in many cellular processes, including synaptic transmission and thrombocyte aggregation. These ion channels are also involved in the pathology of several disease states, including chronic inflammation and neuropathic pain, and thus are the potential targets for drug development. The recent discovery of potent and highly selective antagonists for P2X(7) receptors, through the use of high-throughput screening, has helped to further understand the P2X receptor pharmacology and provided new evidence that P2X(7) receptors play a specific role in chronic pain states. In this review, we discuss how the P2X family of ion channels has distinguished itself as a potential new drug target. We are optimistic that safe and effective candidate drugs will be suitable for progression into clinical development.

Proton and Ion Acceleration using Multi-kJ Lasers

NASA Astrophysics Data System (ADS)

Wilks, S. C.; Ma, T.; Kemp, A. J.; Tabak, M.; Link, A. J.; Haefner, C.; Hermann, M. R.; Mariscal, D. A.; Rubenchik, S.; Sterne, P.; Kim, J.; McGuffey, C.; Bhutwala, K.; Beg, F.; Wei, M.; Kerr, S. M.; Sentoku, Y.; Iwata, N.; Norreys, P.; Sevin, A.

2017-10-01

Short (<50 ps) laser pulses are capable of accelerating protons and ions from solid (or dense gas jet) targets as demonstrated by a number of laser facilities around the world in the past 20 years accelerating protons to between 1 and 100 MeV, depending on specific laser parameters. Over this time, a distinct scaling with energy has emerged that shows a trend towards increasing maximum accelerated proton (ion) energy with increasing laser energy. We consider the physical basis underlying this scaling, and use this to estimate future results when multi-kJ laser systems begin operating in this new high energy regime. In particular, we consider the effects of laser prepulse, intensity, energy, and pulse length on the number and energy of the ions, as well as target size and composition. We also discuss potential uses of these ion beams in High Energy Density Physics Experiments. This work was performed under the auspices of the U.S. Department of Energy (DOE) by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LLNL LDRD program under tracking code 17-ERD-039.

Swift heavy ion irradiation of interstellar dust analogues. Small carbonaceous species released by cosmic rays

NASA Astrophysics Data System (ADS)

Dartois, E.; Chabot, M.; Pino, T.; Béroff, K.; Godard, M.; Severin, D.; Bender, M.; Trautmann, C.

2017-03-01

Context. Interstellar dust grain particles are immersed in vacuum ultraviolet (VUV) and cosmic ray radiation environments influencing their physicochemical composition. Owing to the energetic ionizing interactions, carbonaceous dust particles release fragments that have direct impact on the gas phase chemistry. Aims: The exposure of carbonaceous dust analogues to cosmic rays is simulated in the laboratory by irradiating films of hydrogenated amorphous carbon interstellar analogues with energetic ions. New species formed and released into the gas phase are explored. Methods: Thin carbonaceous interstellar dust analogues were irradiated with gold (950 MeV), xenon (630 MeV), and carbon (43 MeV) ions at the GSI UNILAC accelerator. The evolution of the dust analogues is monitored in situ as a function of fluence at 40, 100, and 300 K. Effects on the solid phase are studied by means of infrared spectroscopy complemented by simultaneously recording mass spectrometry of species released into the gas phase. Results: Specific species produced and released under the ion beam are analyzed. Cross sections derived from ion-solid interaction processes are implemented in an astrophysical context.

The Effects of Magnetic Exposure on the Nervous System: A study on the effects of low-strength low-frequency magnetic fields on neurotransmitter exocytosis and cell viability through ionic cyclotron resonance frequency

NASA Astrophysics Data System (ADS)

Saveriades, George

This PhD dissertation focuses on the study of the effects of magnetic exposure on biological systems using amperometry techniques and viability assays. In our prior work based on the cyclotron resonance model, chromaffin cells in physiological saline and Ca2+-free media were exposed for 5 minutes to a 2.7 muT magnetic field, with frequency sweeps going from 30-60 Hz (targeting several ions involved in exocytosis) and 44-48 Hz (targeting specifically Ca2+ ions), with noticeable effects on exocytosis. The present study extended the work on chromaffin cells by covering frequency sweeps for different ions, manipulating the time of exposure and the strength of the magnetic field. Furthermore, amperometry was conducted on acute coronal brain slices, to demonstrate that the recorded effects could be measured on neuronal tissue. The viability of chromaffin cells and primary neuronal cultures exposed to magnetic fields was also addressed. The results demonstrate that cellular exocytosis is sensitive to the frequency of the magnetic field it is exposed to, the strength of the magnetic field and the duration of exposure. No significant effects were established with regards to the viability of the cells exposed to magnetic fields.

[Effect of plasma membrane ion permeability modulators on respiration and heat output of wheat roots].

PubMed

Alekseeva, V A; Gordon, L Kh; Loseva, N L; Rakhimova, G G; Tsentsevitskiĭ, A N

2006-01-01

A study was made of changes in the rates of respiration, heat production, and membrane characteristics in cells of excised roots of wheat seedlings under the modulation of plasma membrane ion permeability by two membrane active compounds: valinomycin (20 microM (V50)) and chlorpromazine (50 microM (CP50) and 100 microM (CP100)). Both compounds increased the loss of potassium ions, which correlated with the lowering of membrane potential, rate of respiration, and heat production after a 2 h exposure. The differences in alteration of these parameters were due to specific action of either compound on the membrane and to the extent of ion homeostasis disturbance. V20 had a weak effect on the studied parameters. V50 caused an increase of the rate of respiration and heat production, which enhanced following a prolonged action (5 h) and were associated with ion homeostatis restoration. The extent of alteration of membrane characteristics (an increase of potassium loss by roots, and lowering of cell membrane potential) as well as energy expense under the action of CP50 during the first period were more pronounced than in the presence of V50. During a prolonged action of CP50, the increase of respiration intensity and heat production correlated with partial recovery of ion homeostatis in cells. Essential lowering of membrane potential and substantial loss of potassium by cells, starting from the early stages of their response reaction, were followed by inhibition of respiration rate and heat production. Alterations of the structure and functional characteristics of excised root cells indicate the intensification of the membrane-tropic effect of a prolonged action of CP100, and the lack of cell energy resources.

Large fraction of crystal directions leads to ion channeling

NASA Astrophysics Data System (ADS)

Nordlund, K.; Djurabekova, F.; Hobler, G.

2016-12-01

It is well established that when energetic ions are moving in crystals, they may penetrate much deeper if they happen to be directed in some specific crystal directions. This `channeling' effect is utilized for instance in certain ion beam analysis methods and has been described by analytical theories and atomistic computer simulations. However, there have been very few systematic studies of channeling in directions other than the principal low-index ones. We present here a molecular dynamics-based approach to calculate ion channeling systematically over all crystal directions, providing ion `channeling maps' that easily show in which directions channeling is expected. The results show that channeling effects can be quite significant even at energies below 1 keV, and that in many cases, significant planar channeling occurs also in a wide range of crystal directions between the low-index principal ones. In all of the cases studied, a large fraction (˜20 -60 % ) of all crystal directions show channeling. A practical implication of this is that modern experiments on randomly oriented nanostructures will have a large probability of channeling. It also means that when ion irradiations are carried out on polycrystalline samples, channeling effects on the results cannot a priori be assumed to be negligible. The maps allow for easy selection of good `nonchanneling' directions in experiments or alternatively finding wide channels for beneficial uses of channeling. We implement channeling theory to also give the fraction of channeling directions in a manner directly comparable to the simulations. The comparison shows good qualitative agreement. In particular, channeling theory is very good at predicting which channels are active at a given energy. This is true down to sub-keV energies, provided the penetration depth is not too small.

Bio-Sensing of Cadmium(II) Ions Using Staphylococcus aureus†

PubMed Central

Sochor, Jiri; Zitka, Ondrej; Hynek, David; Jilkova, Eva; Krejcova, Ludmila; Trnkova, Libuse; Adam, Vojtech; Hubalek, Jaromir; Kynicky, Jindrich; Vrba, Radimir; Kizek, Rene

2011-01-01

Cadmium, as a hazardous pollutant commonly present in the living environment, represents an important risk to human health due to its undesirable effects (oxidative stress, changes in activities of many enzymes, interactions with biomolecules including DNA and RNA) and consequent potential risk, making its detection very important. New and unique technological and biotechnological approaches for solving this problems are intensely sought. In this study, we used the commonly occurring potential pathogenic microorganism Staphylococcus aureus for the determination of markers which could be used for sensing of cadmium(II) ions. We were focused on monitoring the effects of different cadmium(II) ion concentrations (0, 1.25, 2.5, 5, 10, 15, 25 and 50 μg mL−1) on the growth and energetic metabolism of Staphylococcus aureus. Highly significant changes have been detected in the metabolism of thiol compounds—specifically the protein metallothionein (0.79–26.82 mmol/mg of protein), the enzyme glutathione S-transferase (190–5,827 μmol/min/mg of protein), and sulfhydryl groups (9.6–274.3 μmol cysteine/mg of protein). The ratio of reduced and oxidized glutathione indicated marked oxidative stress. In addition, dramatic changes in urease activity, which is connected with resistance of bacteria, were determined. Further, the effects of cadmium(II) ions on the metabolic pathways of arginine, β-glucosidase, phosphatase, N-acetyl β-d-glucosamine, sucrose, trehalose, mannitol, maltose, lactose, fructose and total proteins were demonstrated. A metabolomic profile of Staphylococcus aureus under cadmium(II) ion treatment conditions was completed seeking data about the possibility of cadmium(II) ion accumulation in cells. The results demonstrate potential in the application of microorganisms as modern biosensor systems based on biological components. PMID:22346664

Chloride analysis of concrete by ion-specific potentiometry : its implementation in Virginia.

DOT National Transportation Integrated Search

1974-01-01

In response to an urgent request from the Materials Division, a literature search was conducted to find a suitable analytical method for the determination of chloride in hardened concrete. It was found that an ion-specific potentiometric method emplo...

Environmental Technology Verification Report for Instrumentation Northwest, Inc., Aquistar® TempHion Smart Sensor and Datalogger Nitrate-specific Ion-selective Electrode for Groundwater Remediation Monitoring

EPA Science Inventory

Environmental Technology Verification Report for Instrumentation Northwest, Inc., Aquistar® TempHion Smart Sensor and Datalogger Nitrate-specific Ion-selective Electrode for Groundwater Remediation Monitoring

New generation ion-imprinted nanocarrier for removal of Cr(VI) from wastewater

NASA Astrophysics Data System (ADS)

Uygun, Murat; Feyzioğlu, Esra; Özçalışkan, Emir; Caka, Müşerref; Ergen, Aygen; Akgöl, Sinan; Denizli, Adil

2013-08-01

The purpose of this study was to prepare a novel ion-imprinted nanoparticle to remove Cr(VI) ions from waste water. For this, Cr(VI) ions were complexed with 2-methacryloylamido histidine (MAH) and then Cr(VI)-imprinted poly(HEMAH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique. The templates, Cr(VI) ions, were removed from the nanoparticles using 0.1 M of HNO3 solution. The specific surface area of the Cr(VI)-imprinted poly(HEMAH) nanoparticles was found to be 1,397.85 m2/g, and the particle size was calculated as 155.3 nm. These Cr(VI)-imprinted nanoparticles were used for the adsorption/desorption of Cr(VI) ions from its aqueous solutions. The effects of initial Cr(VI) concentration and medium pH on the Cr(VI) adsorption capacity were also studied. The maximum adsorbed amount of Cr(VI) on the imprinted nanoparticles was found to be 3,830.58 mg/g nanoparticle in pH 4.0. In order to investigate the selectivity of the imprinted nanoparticle, adsorption studies were repeated using Cr(III) ions. The selectivity results demonstrated that Cr(VI)-imprinted poly(HEMAH) nanoparticles showed high affinity for the Cr(VI) ions than Cr(III). The Cr(VI)-imprinted nanoparticles were used several times without decreasing their Cr(VI) adsorption capacities.

A High-Performance Lithium-Ion Capacitor Based on 2D Nanosheet Materials.

PubMed

Li, Shaohui; Chen, Jingwei; Cui, Mengqi; Cai, Guofa; Wang, Jiangxin; Cui, Peng; Gong, Xuefei; Lee, Pooi See

2017-02-01

Lithium-ion capacitors (LICs) are promising electrical energy storage systems for mid-to-large-scale applications due to the high energy and large power output without sacrificing long cycle stability. However, due to the different energy storage mechanisms between anode and cathode, the energy densities of LICs often degrade noticeably at high power density, because of the sluggish kinetics limitation at the battery-type anode side. Herein, a high-performance LIC by well-defined ZnMn 2 O 4 -graphene hybrid nanosheets anode and N-doped carbon nanosheets cathode is presented. The 2D nanomaterials offer high specific surface areas in favor of a fast ion transport and storage with shortened ion diffusion length, enabling fast charge and discharge. The fabricated LIC delivers a high specific energy of 202.8 Wh kg -1 at specific power of 180 W kg -1 , and the specific energy remains 98 Wh kg -1 even when the specific power achieves as high as 21 kW kg -1 . © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Capabilities of laser ablation mass spectrometry in the differentiation of natural and artificial opal gemstones.

PubMed

Erel, Eric; Aubriet, Frédéric; Finqueneisel, Gisèle; Muller, Jean-François

2003-12-01

The potentialities of laser ablation coupled to ion cyclotron resonance Fourier transform mass spectrometry are evaluated to distinguish natural and artificial opals. The detection of specific species in both ion detection modes leads us to obtain relevant criteria of differentiation. In positive ions, species including hafnium and large amounts of zirconium atoms are found to be specific for artificial opal. In contrast, aluminum, titanium, iron, and rubidium are systematically detected in the study of natural opals. Moreover, some ions allow us to distinguish between natural opal from Australia and from Mexico. Australian gemstone includes specifically strontium, cesium, and barium. Moreover, it is also found that the yield of (H2O)0-1(SiO2)nX- (X- = O-, OH-, KO-, NaO-, SiO2-, AlO1-2-, FeO2-, ZrO2-, and ZrO3-) and (Al2O3)(SiO2)nAlO2- ions depends on the composition of the sample when opals are laser ablated. Ions, which include zirconium oxide species, are characteristics of artificial gem. In contrast, natural opals lead us, after laser ablation, to the production of ions including H2O, Al2O3 motifs and AlO-, KO-, NaO-, and FeO2- species.

The effect of low-frequency electromagnetic field on human bone marrow stem/progenitor cell differentiation

PubMed Central

Ross, Christina L.; Siriwardane, Mevan; Almeida-Porada, Graça; Porada, Christopher D.; Brink, Peter; Christ, George J.; Harrison, Benjamin S.

2015-01-01

Human bone marrow stromal cells (hBMSCs, also known as bone marrow-derived mesenchymal stem cells) are a population of progenitor cells that contain a subset of skeletal stem cells (hSSCs), able to recreate cartilage, bone, stroma that supports hematopoiesis and marrow adipocytes. As such, they have become an important resource in developing strategies for regenerative medicine and tissue engineering due to their self-renewal and differentiation capabilities. The differentiation of SSCs/BMSCs is dependent on exposure to biophysical and biochemical stimuli that favor early and rapid activation of the in vivo tissue repair process. Exposure to exogenous stimuli such as an electromagnetic field (EMF) can promote differentiation of SSCs/BMSCs via ion dynamics and small signaling molecules. The plasma membrane is often considered to be the main target for EMF signals and most results point to an effect on the rate of ion or ligand binding due to a receptor site acting as a modulator of signaling cascades. Ion fluxes are closely involved in differentiation control as stem cells move and grow in specific directions to form tissues and organs. EMF affects numerous biological functions such as gene expression, cell fate, and cell differentiation, but will only induce these effects within a certain range of low frequencies as well as low amplitudes. EMF has been reported to be effective in the enhancement of osteogenesis and chondrogenesis of hSSCs/BMSCs with no documented negative effects. Studies show specific EMF frequencies enhance hSSC/BMSC adherence, proliferation, differentiation, and viability, all of which play a key role in the use of hSSCs/BMSCs for tissue engineering. While many EMF studies report significant enhancement of the differentiation process, results differ depending on the experimental and environmental conditions. Here we review how specific EMF parameters (frequency, intensity, and time of exposure) significantly regulate hSSC/BMSC differentiation in vitro. We discuss optimal conditions and parameters for effective hSSC/BMSC differentiation using EMF treatment in an in vivo setting, and how these can be translated to clinical trials. PMID:26042793

CALUTRON RECEIVERS

DOEpatents

Schmidt, F.H.; Stone, K.F.

1958-09-01

S>This patent relates to improvements in calutron devices and, more specifically, describes a receiver fer collecting the ion curreot after it is formed into a beam of non-homogeneous isotropic cross-section. The invention embodies a calutron receiver having an ion receiving pocket for separately collecting and retaining ions traveling in a selected portion of the ion beam and anelectrode for intercepting ions traveling in another selected pontion of the ion beam. The electrode is disposed so as to fix the limit of one side of the pontion of the ion beam admitted iato the ion receiving pocket.

Effect of lithium and sodium salt on the performance of Nb2O5/rGO nanocomposite based supercapacitor

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Rafat, M.

2018-03-01

The present work reports the synthesis of Nb2O5/rGO composite using hydrothermal method and thermal annealing process. The prepared composite was found to have suitable characteristics necessary to be used as electrode material in supercapacitors. These characteristics were ascertained employing the techniques of scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy and N2 adsorption-desorption isotherm. Further, the electrochemical performance of the prepared composite was compared in two different organic electrolytes, of lithium and sodium salt using the techniques of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge-discharge measurements. The organic electrolyte solutions were prepared by dispersing 1 M LiClO4/NaClO4 in a mixture of ethylene carbonate/propylene carbonate (1:1 by volume). The observed results indicate that the composite of Nb2O5/rGO offers higher value of specific capacitance in sodium salt electrolyte and higher cyclic stability in lithium salt electrolyte. This is probably due to ion properties of electrolyte. Specific capacitance is observed according to efficient ion/charge diffusion/exchange and relaxation time (Li+ < Na+), while the cyclic stability is observed according to cation size (Na+ > Li+). Thus, the present study reveals the significant effect of electrolyte ions on electrochemical performance of Nb2O5/rGO composite.

Sodium transport through the cerebral sodium-glucose transporter exacerbates neuron damage during cerebral ischaemia.

PubMed

Yamazaki, Yui; Harada, Shinichi; Wada, Tetsuyuki; Yoshida, Shigeru; Tokuyama, Shogo

2016-07-01

We recently demonstrated that the cerebral sodium-glucose transporter (SGLT) is involved in postischaemic hyperglycaemia-induced exacerbation of cerebral ischaemia. However, the associated SGLT-mediated mechanisms remain unclear. Thus, we examined the involvement of cerebral SGLT-induced excessive sodium ion influx in the development of cerebral ischaemic neuronal damage. [Na+]i was estimated according to sodium-binding benzofuran isophthalate fluorescence. In the in vitro study, primary cortical neurons were prepared from fetuses of ddY mice. Primary cortical neurons were cultured for 5 days before each treatment with reagents, and these survival rates were assessed using biochemical assays. In in vivo study, a mouse model of focal ischaemia was generated using middle cerebral artery occlusion (MCAO). In these experiments, treatment with high concentrations of glucose induced increment in [Na+]i, and this phenomenon was suppressed by the SGLT-specific inhibitor phlorizin. SGLT-specific sodium ion influx was induced using a-methyl-D-glucopyranoside (a-MG) treatments, which led to significant concentration-dependent declines in neuronal survival rates and exacerbated hydrogen peroxide-induced neuronal cell death. Moreover, phlorizin ameliorated these effects. Finally, intracerebroventricular administration of a-MG exacerbated the development of neuronal damage induced by MCAO, and these effects were ameliorated by the administration of phlorizin. Hence, excessive influx of sodium ions into neuronal cells through cerebral SGLT may exacerbate the development of cerebral ischaemic neuronal damage. © 2016 Royal Pharmaceutical Society.

Density functional theory and conductivity studies of boron-based anion receptors

DOE PAGES

Leung, Kevin; Chaudhari, Mangesh I.; Rempe, Susan B.; ...

2015-07-10

Anion receptors that bind strongly to fluoride anions in organic solvents can help dissolve the lithium fluoride discharge products of primary carbon monofluoride (CFx) batteries, thereby preventing the clogging of cathode surfaces and improving ion conductivity. The receptors are also potentially beneficial to rechargeable lithium ion and lithium air batteries. We apply Density Functional Theory (DFT) to show that an oxalate-based pentafluorophenyl-boron anion receptor binds as strongly, or more strongly, to fluoride anions than many phenyl-boron anion receptors proposed in the literature. Experimental data shows marked improvement in electrolyte conductivity when this oxalate anion receptor is present. The receptor ismore » sufficiently electrophilic that organic solvent molecules compete with F – for boron-site binding, and specific solvent effects must be considered when predicting its F – affinity. To further illustrate the last point, we also perform computational studies on a geometrically constrained boron ester that exhibits much stronger gas-phase affinity for both F – and organic solvent molecules. After accounting for specific solvent effects, however, its net F – affinity is about the same as the simple oxalate-based anion receptor. Lastly, we propose that LiF dissolution in cyclic carbonate organic solvents, in the absence of anion receptors, is due mostly to the formation of ionic aggregates, not isolated F – ions.« less

Nanoscale Seebeck effect at hot metal nanostructures

NASA Astrophysics Data System (ADS)

Ly, Aboubakry; Majee, Arghya; Würger, Alois

2018-02-01

We theoretically study the electrolyte Seebeck effect in the vicinity of a heated metal nanostructure, such as the cap of an active Janus colloid in an electrolyte, or gold-coated interfaces in optofluidic devices. The thermocharge accumulated at the surface varies with the local temperature, thus modulating the diffuse part of the electric double layer. On a conducting surface with non-uniform temperature, the isopotential condition imposes a significant polarization charge within the metal. Surprisingly, this does not affect the slip velocity, which takes the same value on insulating and conducting surfaces. Our results for specific-ion effects agree qualitatively with recent observations for Janus colloids in different electrolyte solutions. Comparing the thermal, hydrodynamic, and ion diffusion time scales, we expect a rich transient behavior at the onset of thermally powered swimming, extending to microseconds after switching on the heating.

PEROXOTITANATE- AND MONOSODIUM METAL-TITANATE COMPOUNDS AS INHIBITORS OF BACTERIAL GROWTH

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

Hobbs, D.

2011-01-19

Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), andmore » measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.« less

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

Allcorn, Eric

Lithium-ion battery safety is a critical issue in the adoption of the chemistry to larger scale applications such as transportation and stationary storage. One of the critical components impacting the safety of lithium-ion batteries is their use of highly flammable organic electrolytes. In this work, brominated flame retardants (BFR’s) – an existing class of flame retardant materials – are incorporated as additives to lithium-ion battery electrolytes with the intention to reduce the electrolyte flammability and thereby improve safety. There are a few critical needs for a successful electrolyte additive: solubility in the electrolyte, electrochemical stability over the range of batterymore » operation, and minimal detrimental effects on battery performance. Those detrimental effects can take the form of electrolyte specific impacts, such as a reduction in conductivity, or electrode impacts, such as SEI-layer modification or chemical instability to the active material. In addition to these needs, the electrolyte additive also needs to achieve its intended purpose, which in this case is to reduce the flammability of the electrolyte. For the work conducted as part of this SPP agreement three separate BFR materials were provided by Albemarle to be tested by Sandia as additives in a traditional lithium-ion battery electrolyte. The provided BFR materials were tribromo-neopentyl alcohol, tetrabromo bisphenol A, and tribromoethylene. These materials were incorporated as separate 4 wt.% additives into a traditional lithium-ion battery electrolyte and compared to said traditional electrolyte, designated Gen2.« less

Phase transition in lithium ammonium sulphate doped with cesium metal ions

NASA Astrophysics Data System (ADS)

Gaafar, M.; Kassem, M. E.; Kandil, S. H.

2000-07-01

Effects of doped cesium (C s+) metal ions (with different molar ratios n) on the phase transition of lithium ammonium sulphate LiNH 4SO 4 system have been studied by measuring the specific heat Cp( T) of the doped systems in the temperature range from 400 to 480 K. The study shows a peculiar phase transition of the pure system ( n=0) characterized by double distinct peaks, changed to a single sharp and narrow one as a result of the doping process. The measurements exhibit different effects of enhanced molar ratios of dopants on the phase transition behaviour of this system. At low dopant content ( n≤3%), the excess specific heat (Δ Cp) max at the transition temperature T1 decreases till a minimum value at n=0.8%, then it increases gradually. In this case, Δ Cp( T) behaviour is varied quantitatively and not modified. Enhanced dopant content ( n>3%) has a pronounced effect on the critical behaviour, which is significantly changed and considerably modified relative to the pure system. In addition, broadening of the critical temperature region, and decrease of (Δ Cp) max associated with changes of the Landau expansion coefficients are obtained and discussed. The study deals with the contribution of the thermally excited dipoles to the specific heat in the ferroelectric region and shows that their energy depends on doping.

Ion laser isotope enrichment by photo-predissociation of formaldehyde

DOEpatents

Marling, John B.

1977-06-17

Enrichment of carbon, hydrogen and/or oxygen isotopes by means of isotopically selective photo-predissociation of formaldehyde is achieved by irradiation with a fixed frequency ion laser, specifically, a neon, cadmium, or xenon ion laser.

Alpha particle effects in burning tokamak plasmas: overview and specific examples

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

Sigmar, D.J.

1986-07-01

Using the total power balance of an ignited tokamak plasma as a guideline, a range of alpha driven effects is surveyed regarding their impact on achieving and maintaining fusion burn. Specific examples of MHD and kinetic modes and multi species transport dynamics are discussed, including the possible interaction of these categories of effects. This power balance approach rather than a straightforward enumeration of possible effects serves to reveal their non-linear dependence and the ensuing fragility of our understanding of the approach to and maintenance of ignition. Specific examples are given of the interaction between ..cap alpha..-power driven sawtoothing and idealmore » MHD stability, and direct ..cap alpha..-effects on MHD modes including kinetic corrections. Anomalous ion heat transport and central impurity peaking mechanisms and anomalous and collisional ..cap alpha..-transport including the ambipolar electric field are discussed.« less

Peptide Fragmentation Induced by Radicals at Atmospheric Pressure

PubMed Central

Vilkov, Andrey N.; Laiko, Victor V.; Doroshenko, Vladimir M.

2009-01-01

A novel ion dissociation technique, which is capable of providing an efficient fragmentation of peptides at essentially atmospheric pressure conditions, is developed. The fragmentation patterns observed often contain c-type fragments that are specific to ECD/ETD, along with the y-/b- fragments that are specific to CAD. In the presented experimental setup, ion fragmentation takes place within a flow reactor located in the atmospheric pressure region between the ion source and the mass spectrometer. According to a proposed mechanism, the fragmentation results from the interaction of ESI-generated analyte ions with the gas-phase radical species produced by a corona discharge source. PMID:19034885

Low-Power Ion Thruster Development Status

NASA Technical Reports Server (NTRS)

Patterson, Michael J.

1999-01-01

An effort is on-going to examine scaling relationships and design criteria for ion propulsion systems, and to address the need for a light weight, low power, high specific impulse propulsion option for small spacecraft. An element of this activity is the development of a low-power (sub-0.5 kW) ion thruster. This development effort has led to the fabrication and preliminary performance assessment of an 8 cm prototype xenon ion thruster operating over an input power envelope of 0.1-0.3 kW. Efficiencies for the thruster vary from 0.31 at 1750 seconds specific impulse at 0.1 kW, to about 0.48 at 2700 seconds specific impulse and 0.3 kW input power. Discharge losses for the thruster over this power range varied from about 320-380 W/A down to about 220-250 W/A. Ion optics performance compare favorably to that obtained with 30 cm ion optics, when scaled for the difference in beam area. The neutralizer, fabricated using 3 mm hollow cathode technology, operated at keeper currents of about 0.2-0.3 A, at a xenon flow rate of about 0.06 mg/s, over the 0.1-0.3 kW thruster input power envelope.

Fragmentation of negative ions from N-linked carbohydrates, part 4. Fragmentation of complex glycans lacking substitution on the 6-antenna.

PubMed

Harvey, David J; Jaeken, Jaak; Butler, Mike; Armitage, Alison J; Rudd, Pauline M; Dwek, Raymond A

2010-05-01

Negative ion CID spectra of N-linked glycans released from glycoproteins contain many ions that are diagnostic for specific structural features such as the detailed arrangement of antennae and the location of fucose residues. Identification of such ions requires reference glycans that are often difficult to acquire in a pure state. The recent acquisition of a sample of N-glycans from a patient lacking the enzyme N-acetylglucosaminyltransferase-2 provided an opportunity to investigate fragmentation of glycans lacking a 6-antenna. These glycans contained one or two galactose-N-acetylglucosamine-chains attached to the 3-linked mannose residue of the trimannosyl-chitobiose core with and without fucose substitution. The spectra from the patient sample clearly defined the antenna distribution and showed striking differences from the spectra of isomeric compounds obtained from normal subjects. Furthermore, they provided additional information on previously identified antenna-specific fragment ions and indicated the presence of additional ions that were diagnostic of fucose substitution. Glycans obtained from such enzyme-deficient patients can, thus, be a valuable way of obtaining spectra of specific isomers in a relatively pure state for interpretation of mass spectra. 2010 John Wiley & Sons, Ltd.

Grafting: A Technique to Modify Ion Accumulation in Horticultural Crops

PubMed Central

Nawaz, Muhammad A.; Imtiaz, Muhammad; Kong, Qiusheng; Cheng, Fei; Ahmed, Waqar; Huang, Yuan; Bie, Zhilong

2016-01-01

Grafting is a centuries-old technique used in plants to obtain economic benefits. Grafting increases nutrient uptake and utilization efficiency in a number of plant species, including fruits, vegetables, and ornamentals. Selected rootstocks of the same species or close relatives are utilized in grafting. Rootstocks absorb more water and ions than self-rooted plants and transport these water and ions to the aboveground scion. Ion uptake is regulated by a complex communication mechanism between the scion and rootstock. Sugars, hormones, and miRNAs function as long-distance signaling molecules and regulate ion uptake and ion homeostasis by affecting the activity of ion transporters. This review summarizes available information on the effect of rootstock on nutrient uptake and utilization and the mechanisms involved. Information on specific nutrient-efficient rootstocks for different crops of commercial importance is also provided. Several other important approaches, such as interstocking (during double grafting), inarching, use of plant-growth-promoting rhizobacteria, use of arbuscular mycorrhizal fungi, use of plant growth substances (e.g., auxin and melatonin), and use of genetically engineered rootstocks and scions (transgrafting), are highlighted; these approaches can be combined with grafting to enhance nutrient uptake and utilization in commercially important plant species. Whether the rootstock and scion affect each other's soil microbiota and their effect on the nutrient absorption of rootstocks remain largely unknown. Similarly, the physiological and molecular bases of grafting, crease formation, and incompatibility are not fully identified and require investigation. Grafting in horticultural crops can help reveal the basic biology of grafting, the reasons for incompatibility, sensing, and signaling of nutrients, ion uptake and transport, and the mechanism of heavy metal accumulation and restriction in rootstocks. Ion transporter and miRNA-regulated nutrient studies have focused on model and non-grafted plants, and information on grafted plants is limited. Such information will improve the development of nutrient-efficient rootstocks. PMID:27818663

Explicit ions/implicit water generalized Born model for nucleic acids

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

Tolokh, Igor S.; Thomas, Dennis G.; Onufriev, Alexey V.

Ion atmosphere around highly charged nucleic acid molecules plays a significant role in their dynamics, structure and interactions. Here we utilized the implicit solvent framework to develop a model for the explicit treatment of ions interacting with nucleic acid molecules. The proposed explicit ions/implicit water model is based on a significantly modified generalized Born (GB) model, and utilizes a non-standard approach to defining the solute/solvent dielectric boundary. Specifically, the model includes modifications to the GB interaction terms for the case of multiple interacting solutes – disconnected dielectric boundary around the solute-ion or ion-ion pairs. Fully analytical description of all energymore » components for charge-charge interactions is provided. The effectiveness of the approach is demonstrated by calculating the potential of mean force (PMF) for Na+-Cl− ion pair and by carrying out a set of Monte Carlo (MC) simulations of mono- and trivalent ions interacting with DNA and RNA duplexes. The monovalent (Na+) and trivalent (CoHex3+) counterion distributions predicted by the model are in close quantitative agreement with all-atom explicit water molecular dynamics simulations used as reference. Expressed in the units of energy, the maximum deviations of local ion concentrations from the reference are within kBT. The proposed explicit ions/implicit water GB model is able to resolve subtle features and differences of CoHex distributions around DNA and RNA duplexes. These features include preferential CoHex binding inside the major groove of RNA duplex, in contrast to CoHex biding at the "external" surface of the sugar-phosphate backbone of DNA duplex; these differences in the counterion binding patters were shown earlier to be responsible for the observed drastic differences in condensation propensities between short DNA and RNA duplexes. MC simulations of CoHex ions interacting with homopolymeric poly(dA·dT) DNA duplex with modified (de-methylated) and native Thymine bases are used to explore the physics behind CoHex-Thymine interactions. The simulations suggest that the ion desolvation penalty due to proximity to the low dielectric volume of the methyl group can contribute significantly to CoHex-Thymine interactions. Compared to the steric repulsion between the ion and the methyl group, the desolvation penalty interaction has a longer range, and may be important to consider in the context of methylation effects on DNA condensation.« less

Explicit ions/implicit water generalized Born model for nucleic acids

NASA Astrophysics Data System (ADS)

Tolokh, Igor S.; Thomas, Dennis G.; Onufriev, Alexey V.

2018-05-01

The ion atmosphere around highly charged nucleic acid molecules plays a significant role in their dynamics, structure, and interactions. Here we utilized the implicit solvent framework to develop a model for the explicit treatment of ions interacting with nucleic acid molecules. The proposed explicit ions/implicit water model is based on a significantly modified generalized Born (GB) model and utilizes a non-standard approach to define the solute/solvent dielectric boundary. Specifically, the model includes modifications to the GB interaction terms for the case of multiple interacting solutes—disconnected dielectric boundary around the solute-ion or ion-ion pairs. A fully analytical description of all energy components for charge-charge interactions is provided. The effectiveness of the approach is demonstrated by calculating the potential of mean force for Na+-Cl- ion pair and by carrying out a set of Monte Carlo (MC) simulations of mono- and trivalent ions interacting with DNA and RNA duplexes. The monovalent (Na+) and trivalent (CoHex3+) counterion distributions predicted by the model are in close quantitative agreement with all-atom explicit water molecular dynamics simulations used as reference. Expressed in the units of energy, the maximum deviations of local ion concentrations from the reference are within kBT. The proposed explicit ions/implicit water GB model is able to resolve subtle features and differences of CoHex distributions around DNA and RNA duplexes. These features include preferential CoHex binding inside the major groove of the RNA duplex, in contrast to CoHex biding at the "external" surface of the sugar-phosphate backbone of the DNA duplex; these differences in the counterion binding patters were earlier shown to be responsible for the observed drastic differences in condensation propensities between short DNA and RNA duplexes. MC simulations of CoHex ions interacting with the homopolymeric poly(dA.dT) DNA duplex with modified (de-methylated) and native thymine bases are used to explore the physics behind CoHex-thymine interactions. The simulations suggest that the ion desolvation penalty due to proximity to the low dielectric volume of the methyl group can contribute significantly to CoHex-thymine interactions. Compared to the steric repulsion between the ion and the methyl group, the desolvation penalty interaction has a longer range and may be important to consider in the context of methylation effects on DNA condensation.

Serum albumin forms a lactoferrin-like soluble iron-binding complex in presence of hydrogen carbonate ions.

PubMed

Ueno, Hiroshi M; Urazono, Hiroshi; Kobayashi, Toshiya

2014-02-15

The iron-lactoferrin complex is a common food ingredient because of its iron-solubilizing capability in the presence of hydrogen carbonate ions. However, it is unclear whether the formation of a stable iron-binding complex is limited to lactoferrin. In this study, we investigated the effects of bovine serum albumin (BSA) on iron solubility and iron-catalyzed lipid oxidation in the presence of hydrogen carbonate ions. BSA could solubilize >100-fold molar equivalents of iron at neutral pH, exceeding the specific metal-binding property of BSA. This iron-solubilizing capability of BSA was impaired by thermally denaturing BSA at ≥ 70 °C for 10 min at pH 8.5. The resulting iron-BSA complex inhibited iron-catalyzed oxidation of soybean oil in a water-in-oil emulsion measured using the Rancimat test. Our study is the first to show that BSA, like lactoferrin, forms a soluble iron-binding complex in the presence of hydrogen carbonate ions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Silicon etch with chromium ions generated by a filtered or non-filtered cathodic arc discharge

PubMed Central

Scopece, Daniele; Döbeli, Max; Passerone, Daniele; Maeder, Xavier; Neels, Antonia; Widrig, Beno; Dommann, Alex; Müller, Ulrich; Ramm, Jürgen

2016-01-01

Abstract The pre-treatment of substrate surfaces prior to deposition is important for the adhesion of physical vapour deposition coatings. This work investigates Si surfaces after the bombardment by energetic Cr ions which are created in cathodic arc discharges. The effect of the pre-treatment is analysed by X-ray diffraction, Rutherford backscattering spectroscopy, scanning electron microscopy and in-depth X-ray photoemission spectroscopy and compared for Cr vapour produced from a filtered and non-filtered cathodic arc discharge. Cr coverage as a function of ion energy was also predicted by TRIDYN Monte Carlo calculations. Discrepancies between measured and simulated values in the transition regime between layer growth and surface removal can be explained by the chemical reactions between Cr ions and the Si substrate or between the substrate surface and the residual gases. Simulations help to find optimum and more stable parameters for specific film and substrate combinations faster than trial-and-error procedure. PMID:27877854

Graphene-Based Materials for Lithium-Ion Hybrid Supercapacitors.

PubMed

Ma, Yanfeng; Chang, Huicong; Zhang, Miao; Chen, Yongsheng

2015-09-23

Lithium-ion hybrid supercapacitors (LIHSs), also called Li-ion capacitors, have attracted much attention due to the combination of the rapid charge-discharge and long cycle life of supercapacitors and the high energy-storage capacity of lithium-ion batteries. Thus, LIHSs are expected to become the ultimate power source for hybrid and all-electric vehicles in the near future. As an electrode material, graphene has many advantages, including high surface area and porous structure, high electric conductivity, and high chemical and thermal stability, etc. Compared with other electrode materials, such as activated carbon, graphite, and metal oxides, graphene-based materials with 3D open frameworks show higher effective specific surface area, better control of channels, and higher conductivity, which make them better candidates for LIHS applications. Here, the latest advances in electrode materials for LIHSs are briefly summarized, with an emphasis on graphene-based electrode materials (including 3D graphene networks) for LIHS applications. An outlook is also presented to highlight some future directions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of Advanced CuO Nanowires/Functionalized Graphene Composite Anode Material for Lithium Ion Batteries

PubMed Central

Zhang, Jin; Wang, Beibei; Zhou, Jiachen; Xia, Ruoyu; Chu, Yingli; Huang, Jia

2017-01-01

The copper oxide (CuO) nanowires/functionalized graphene (f-graphene) composite material was successfully composed by a one-pot synthesis method. The f-graphene synthesized through the Birch reduction chemistry method was modified with functional group “–(CH2)5COOH”, and the CuO nanowires (NWs) were well dispersed in the f-graphene sheets. When used as anode materials in lithium-ion batteries, the composite exhibited good cyclic stability and decent specific capacity of 677 mA·h·g−1 after 50 cycles. CuO NWs can enhance the lithium-ion storage of the composites while the f-graphene effectively resists the volume expansion of the CuO NWs during the galvanostatic charge/discharge cyclic process, and provide a conductive paths for charge transportation. The good electrochemical performance of the synthesized CuO/f-graphene composite suggests great potential of the composite materials for lithium-ion batteries anodes. PMID:28772432

On the mechanism of aluminum ion-induced neurotoxicity: The effects of aluminum species on G-protein-mediated processes and on drug interactions with the N-methyl-D-aspartate modulated ionophore

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

Hubbard, C.M.

1989-01-01

To establish what effects Al{sup 3+} may have on G-protein mediate signal transduction, the effects of Al{sup 3+} on the signal-coupling G-protein from retinal rod outer segments (G{sub t} or transducin) have been investigated as a model for the effects of Al{sup 3+} on signal transduction by G-proteins in general. In this investigation, we have studied the effects of Al{sup 3+} on the isolated, light-dependent rhodopsin catalyzed GTP-GDP exchange on G{sub t}; the light-dependent GTPase activity of G{sub t}; the light-independent cGMP hydrolysis by PDE; and the light activated, rhodopsin catalyzed, cGMP hydrolysis by PDE in vitro. To determine themore » effects of two defined species of aluminum on N-methyl-D-aspartic acid (NMDA) receptor-channel modulation we utilized a specific radioligand binding assay. This allowed us to compare the effects of aluminum to other metal ions on specific ({sup 3}H)MK-801 binding to the NMDA receptor-channel complex. This complex is involved in long-term potentiation, which is currently being investigated as the mechanism by which learning and memory occur and has been implicated in the pathology of Alzheimer's disease. We have investigated the effects of two different species of aluminum, as well as Ca{sup 2+}, Zn{sup 2+}, Mg{sup 2+}, and Li{sup +} on the specific binding of ({sup 3}H)MK-801 to the NMDA receptor-channel complex under depolarized conditions.« less

ARS-Media: A spreadsheet tool for calculating media recipes based on ion-specific constraints

USDA-ARS?s Scientific Manuscript database

ARS-Media is an ion solution calculator that uses Microsoft Excel to generate recipes of salts for complex ion mixtures specified by the user. Generating salt combinations (recipes) that result in pre-specified target ion values is a linear programming problem. Thus, the recipes are generated using ...

Ion Mobility Separation of Isomeric Carbohydrate Precursor Ions and Acquisition of their Independent Tandem Mass Spectra

PubMed Central

Zhu, Maolei; Bendiak, Brad; Clowers, Brian; Hill, Herbert H.

2010-01-01

The rapid separation of isomeric precursor ions of oligosaccharides prior to their analysis by MSn was demonstrated using an ambient pressure ion mobility spectrometer (IMS) interfaced with a quadrupole ion trap. Separations were not limited to specific types of isomers; representative isomers differing solely in the stereochemistry of sugars, in their anomeric configurations, and in their overall branching patterns and linkage positions could be resolved in the millisecond time frame. Physical separation of precursor ions permitted independent mass spectra of individual oligosaccharide isomers to be acquired to at least MS3, the number of stages of dissociation limited only practically by the abundance of specific product ions. IMS-MSn analysis was particularly valuable in the evaluation of isomeric oligosaccharides that yielded identical sets of product ions in MS/MS experiments, revealing pairs of isomers that would otherwise not be known to be present in a mixture if evaluated solely by MS dissociation methods alone. A practical example of IMS-MSn analysis of a set of isomers included within a single HPLC fraction of oligosaccharides released from bovine submaxillary mucin is described. PMID:19562326

Investigation of Ion Transmission Effects on Intact Protein Quantification in a Triple Quadrupole Mass Spectrometer

NASA Astrophysics Data System (ADS)

Wang, Evelyn H.; Appulage, Dananjaya Kalu; McAllister, Erin A.; Schug, Kevin A.

2017-09-01

Recently, direct intact protein quantitation using triple quadrupole mass spectrometry (QqQ-MS) and multiple reaction monitoring (MRM) was demonstrated (J. Am. Soc. Mass Spectrom. 27, 886-896 (2016)). Even though QqQ-MS is known to provide extraordinary detection sensitivity for quantitative analysis, we found that intact proteins exhibited a less than 5% ion transmission from the first quadrupole to the third quadrupole mass analyzer in the presence of zero collision energy (ZCE). With the goal to enhance intact protein quantitation sensitivity, ion scattering effects, proton transfer effects, and mass filter resolution widths were examined for their contributions to the lost signal. Protein standards myoglobin and ubiquitin along with small molecules reserpine and vancomycin were analyzed together with various collision induced dissociation (CID) gases (N2, He, and Ar) at different gas pressures. Mass resolution settings played a significant role in reducing ion transmission signal. By narrowing the mass resolution window by 0.35 m/z on each side, roughly 75%-90% of the ion signal was lost. The multiply charged proteins experienced additional proton transfer effects, corresponding to 10-fold signal reduction. A study of increased sensitivity of the method was also conducted with various MRM summation techniques. Although the degree of enhancement was analyte-dependent, an up to 17-fold increase in sensitivity was observed for ubiquitin using a summation of multiple MRM transitions. Biological matrix, human urine, and equine plasma were spiked with proteins to demonstrate the specificity of the method. This study provides additional insight into optimizing the use and sensitivity of QqQ-MS for intact protein quantification. [Figure not available: see fulltext.

A 3D Monte Carlo model of radiation affecting cells, and its application to neuronal cells and GCR irradiation

NASA Astrophysics Data System (ADS)

Ponomarev, Artem; Sundaresan, Alamelu; Kim, Angela; Vazquez, Marcelo E.; Guida, Peter; Kim, Myung-Hee; Cucinotta, Francis A.

A 3D Monte Carlo model of radiation transport in matter is applied to study the effect of heavy ion radiation on human neuronal cells. Central nervous system effects, including cognitive impairment, are suspected from the heavy ion component of galactic cosmic radiation (GCR) during space missions. The model can count, for instance, the number of direct hits from ions, which will have the most affect on the cells. For comparison, the remote hits, which are received through δ-rays from the projectile traversing space outside the volume of the cell, are also simulated and their contribution is estimated. To simulate tissue effects from irradiation, cellular matrices of neuronal cells, which were derived from confocal microscopy, were simulated in our model. To produce this realistic model of the brain tissue, image segmentation was used to identify cells in the images of cells cultures. The segmented cells were inserted pixel by pixel into the modeled physical space, which represents a volume of interacting cells with periodic boundary conditions (PBCs). PBCs were used to extrapolate the model results to the macroscopic tissue structures. Specific spatial patterns for cell apoptosis are expected from GCR, as heavy ions produce concentrated damage along their trajectories. The apoptotic cell patterns were modeled based on the action cross sections for apoptosis, which were estimated from the available experimental data. The cell patterns were characterized with an autocorrelation function, which values are higher for non-random cell patterns, and the values of the autocorrelation function were compared for X rays and Fe ion irradiations. The autocorrelation function indicates the directionality effects present in apoptotic neuronal cells from GCR.

Microwave exfoliated graphene oxide/TiO{sub 2} nanowire hybrid for high performance lithium ion battery

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

Ishtiaque Shuvo, Mohammad Arif; Rodriguez, Gerardo; Karim, Hasanul

Lithium ion battery (LIB) is a key solution to the demand of ever-improving, high energy density, clean-alternative energy systems. In LIB, graphite is the most commonly used anode material; however, lithium-ion intercalation in graphite is limited, hindering the battery charge rate and capacity. To date, one of the approaches in LIB performance improvement is by using porous carbon (PC) to replace graphite as anode material. PC's pore structure facilitates ion transport and has been proven to be an excellent anode material candidate in high power density LIBs. In addition, to overcome the limited lithium-ion intercalation obstacle, nanostructured anode assembly hasmore » been extensively studied to increase the lithium-ion diffusion rate. Among these approaches, high specific surface area metal oxide nanowires connecting nanostructured carbon materials accumulation have shown promising results for enhanced lithium-ion intercalation. Herein, we demonstrate a hydrothermal approach of growing TiO{sub 2} nanowires (TON) on microwave exfoliated graphene oxide (MEGO) to further improve LIB performance over PC. This MEGO-TON hybrid not only uses the high surface area of MEGO but also increases the specific surface area for electrode–electrolyte interaction. Therefore, this new nanowire/MEGO hybrid anode material enhances both the specific capacity and charge–discharge rate. Scanning electron microscopy and X-ray diffraction were used for materials characterization. Battery analyzer was used for measuring the electrical performance of the battery. The testing results have shown that MEGO-TON hybrid provides up to 80% increment of specific capacity compared to PC anode.« less

Nanoporous Au-based chronocoulometric aptasensor for amplified detection of Pb(2+) using DNAzyme modified with Au nanoparticles.

PubMed

Zhang, Chen; Lai, Cui; Zeng, Guangming; Huang, Danlian; Tang, Lin; Yang, Chunping; Zhou, Yaoyu; Qin, Lei; Cheng, Min

2016-07-15

The authors herein described an amplified detection strategy employing nanoporous Au (NPG) and gold nanoparticles (AuNPs) to detect Pb(2+) ions in aqueous solution. The thiol modified Pb(2+)-specific DNAzyme was self-assembled onto the surface of the NPG modified electrode for hybridizing with the AuNPs labeled oligonucleotide and for forming the DNA double helix structure. Electrochemical signal, redox charge of hexaammineruthenium(III) chloride (RuHex), was measured by chronocoulometry. Taking advantage of amplification effects of the NPG electrode for increasing the reaction sites of capture probe and DNA-AuNPs complexes for bringing about the adsorption of large numbers of RuHex molecules, this electrochemical sensor could detect Pb(2+) quantitatively, in the range of 0.05-100nM, with a limit of detection as low as 0.012nM. Selectivity measurements revealed that the sensor was specific for Pb(2+) even with interference by high concentrations of other metal ions. This sensor was also used to detect Pb(2+) ions from samples of tap water, river water, and landfill leachate samples spiked with Pb(2+) ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. This simple aptasensor represented a promising potential for on-site detecting Pb(2+) in drinking water. Copyright © 2016 Elsevier B.V. All rights reserved.

Differentiating chondroitin sulfate glycosaminoglycans using collision-induced dissociation; uronic acid cross-ring diagnostic fragments in a single stage of tandem mass spectrometry.

PubMed

Kailemia, Muchena J; Patel, Anish B; Johnson, Dane T; Li, Lingyun; Linhardt, Robert J; Amster, I Jonathan

2015-01-01

The stereochemistry of the hexuronic acid residues of the structure of glycosaminoglycans (GAGs) is a key feature that affects their interactions with proteins and other biological functions. Electron based tandem mass spectrometry methods, in particular electron detachment dissociation (EDD), have been able to distinguish glucuronic acid (GlcA) from iduronic acid (IdoA) residues in some heparan sulfate tetrasaccharides by producing epimer-specific fragments. Similarly, the relative abundance of glycosidic fragment ions produced by collision-induced dissociation (CID) or EDD has been shown to correlate with the type of hexuronic acid present in chondroitin sulfate GAGs. The present work examines the effect of charge state and degree of sodium cationization on the CID fragmentation products that can be used to distinguish GlcA and IdoA containing chondroitin sulfate A and dermatan sulfate chains. The cross-ring fragments (2,4)A(n) and (0,2)X(n) formed within the hexuronic acid residues are highly preferential for chains containing GlcA, distinguishing it from IdoA. The diagnostic capability of the fragments requires the selection of a molecular ion and fragment ions with specific ionization characteristics, namely charge state and number of ionizable protons. The ions with the appropriate characteristics display diagnostic properties for all the chondroitin sulfate and dermatan sulfate chains (degree of polymerization of 4-10) studied.

First-principles study of mixed eldfellite compounds Nax(Fe1/2M1/2) (SO4)2 (x=0-2, M = Mn, Co, Ni): A new family of high electrode potential cathodes for the sodium-ion battery

NASA Astrophysics Data System (ADS)

Ri, Gum-Chol; Choe, Song-Hyok; Yu, Chol-Jun

2018-02-01

Natural abundance of sodium and its similar behavior to lithium triggered recent extensive studies of cost-effective sodium-ion batteries (SIBs) for large-scale energy storage systems. A challenge is to develop electrode materials with a high electrode potential, specific capacity and a good rate capability. In this work we propose mixed eldfellite compounds Nax(Fe1/2M1/2) (SO4)2 (x = 0-2, M = Mn, Co, Ni) as a new family of high electrode potential cathodes of SIBs and present their material properties predicted by first-principles calculations. The structural optimizations show that these materials have significantly small volume expansion rates below 5% upon Na insertion/desertion with negative Na binding energies. Through the electronic structure calculations, we find band insulating properties and hole (and/or electron) polaron hoping as a possible mechanism for the charge transfer. Especially we confirm the high electrode voltages over 4 V with reasonably high specific capacities. We also investigate the sodium ion mobility by estimating plausible diffusion pathways and calculating the corresponding activation barriers, demonstrating the reasonably fast migrations of sodium ions during the operation. Our calculation results indicate that these mixed eldfellite compounds can be suitable materials for high performance SIB cathodes.

Identification of heavy-ion radiation-induced microRNAs in rice

NASA Astrophysics Data System (ADS)

Zhang, Meng; Liang, Shujian; Hang, Xiaoming; Xiang, Yingxia; Cheng, Zhenlong; Li, Wenjian; Shi, Jinming; Huang, Lei; Sun, Yeqing

2011-03-01

MicroRNAs (miRNAs) are a family of small non-coding RNAs, which play significant roles in regulating development and stress responses in plant. As an excellent model organism for studying the effects of environmental stress, rice has been used to assess the damage of the space radiation environment for decades. Heavy-ions radiation show higher relative biological effectiveness compared to other cosmic-rays radiation. To identify the specific miRNAs that underlie biological effects of heavy-ion radiation, the germinated seeds of rice were exposed to 1 Gy, 10 Gy and 20 Gy dose of 12C heavy-ion radiation, respectively. Analysis of phenotype indicated that 20 Gy dose of heavy-ion radiation was the semi-lethal dose of rice seedling. The microarray of μparaflo™ chip was employed to monitor the expression profiles of miRNAs in rice (Oryza sativa) under 20 Gy dose of radiation stress. miR164a, miR164c, miR164d and miR156a-j were identified as heavy-ion radiation-induced miRNAs. miR164 and miR156 family were increased in all three exposed samples by using quantitative real-time PCR (qRT-RCP). As targets of miR156 and miR164, SQUAMOSA PROMOTER BINDING-LIKE (SPL) transcription factors and NAM/ATAF/CUC (NAC) transcription factors expression were down-regulated correlating with an up-regulated level of the regulated miRNAs. Since SPL transcription factors and NAC transcription factors regulated growth and development of plant, we used 2-dimension electrophoresis (2-DE) gel to analyze changes of functional proteins in 20 Gy exposed samples. It was evident that both the height and survival rates of seedlings were markedly decreased. The abundance of some developmentally regulated proteins was also changed. To our knowledge, this study is the first to report heavy-ion radiation stress responsive miRNAs in plant. Moreover, our findings are important to understand the molecular mechanism of space biology.

Mesocosm Community Response Sensitivities to Specific Conductivity Comprised of Different Major Ions

EPA Science Inventory

Traditional toxicity test assays have been used to evaluate the relative sensitivity to different major ion mixtures as a proxy for understanding what the response of aquatic species growing in their natural environment would be during exposure to specific conductivity stress ema...

Highly charged ion secondary ion mass spectroscopy

DOEpatents

Hamza, Alex V.; Schenkel, Thomas; Barnes, Alan V.; Schneider, Dieter H.

2001-01-01

A secondary ion mass spectrometer using slow, highly charged ions produced in an electron beam ion trap permits ultra-sensitive surface analysis and high spatial resolution simultaneously. The spectrometer comprises an ion source producing a primary ion beam of highly charged ions that are directed at a target surface, a mass analyzer, and a microchannel plate detector of secondary ions that are sputtered from the target surface after interaction with the primary beam. The unusually high secondary ion yield permits the use of coincidence counting, in which the secondary ion stops are detected in coincidence with a particular secondary ion. The association of specific molecular species can be correlated. The unique multiple secondary nature of the highly charged ion interaction enables this new analytical technique.

Atomistic Detailed Mechanism and Weak Cation-Conducting Activity of HIV-1 Vpu Revealed by Free Energy Calculations

PubMed Central

Padhi, Siladitya; Burri, Raghunadha Reddy; Jameel, Shahid; Priyakumar, U. Deva

2014-01-01

The viral protein U (Vpu) encoded by HIV-1 has been shown to assist in the detachment of virion particles from infected cells. Vpu forms cation-specific ion channels in host cells, and has been proposed as a potential drug target. An understanding of the mechanism of ion transport through Vpu is desirable, but remains limited because of the unavailability of an experimental structure of the channel. Using a structure of the pentameric form of Vpu – modeled and validated based on available experimental data – umbrella sampling molecular dynamics simulations (cumulative simulation time of more than 0.4 µs) were employed to elucidate the energetics and the molecular mechanism of ion transport in Vpu. Free energy profiles corresponding to the permeation of Na+ and K+ were found to be similar to each other indicating lack of ion selection, consistent with previous experimental studies. The Ser23 residue is shown to enhance ion transport via two mechanisms: creating a weak binding site, and increasing the effective hydrophilic length of the channel, both of which have previously been hypothesized in experiments. A two-dimensional free energy landscape has been computed to model multiple ion permeation, based on which a mechanism for ion conduction is proposed. It is shown that only one ion can pass through the channel at a time. This, along with a stretch of hydrophobic residues in the transmembrane domain of Vpu, explains the slow kinetics of ion conduction. The results are consistent with previous conductance studies that showed Vpu to be a weakly conducting ion channel. PMID:25392993

Preparation of PPy-Coated MnO2 Hybrid Micromaterials and Their Improved Cyclic Performance as Anode for Lithium-Ion Batteries

NASA Astrophysics Data System (ADS)

Feng, Lili; Zhang, Yinyin; Wang, Rui; Zhang, Yanli; Bai, Wei; Ji, Siping; Xuan, Zhewen; Yang, Jianhua; Zheng, Ziguang; Guan, Hongjin

2017-09-01

MnO2@PPy core-shell micromaterials are prepared by chemical polymerization of pyrrole on the MnO2 surface. The polypyrrole (PPy) is formed as a homogeneous organic shell on the MnO2 surface. The thickness of PPy shell can be adjusted by the usage of pyrrole. The analysis of SEM, FT-IR, X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and XRD are used to confirm the formation of PPy shell. Galvanostatic cell cycling and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical performance as anode for lithium-ion batteries. The results show that after formation of MnO2@PPy core-shell micromaterials, the cyclic performance as anode for lithium-ion batteries is improved. Fifty microliters of PPy-coated caddice-clew-like MnO2 has the best cyclic performances as has 620 mAh g-1 discharge specific capacities after 300 cycles. As a comparison, the discharge specific capacity of bare MnO2 materials falls to below 200 mAh g-1 after 10 cycles. The improved lithium-storage cyclic stability of the MnO2@PPy samples attributes to the core-shell hybrid structure which can buffer the structural expansion and contraction of MnO2 caused by the repeated embedding and disengagement of Li ions and can prevent the pulverization of MnO2. This experiment provides an effective way to mitigate the problem of capacity fading of the transition metal oxide materials as anode materials for (lithium-ion batteries) LIBs.

Preparation of PPy-Coated MnO2 Hybrid Micromaterials and Their Improved Cyclic Performance as Anode for Lithium-Ion Batteries.

PubMed

Feng, Lili; Zhang, Yinyin; Wang, Rui; Zhang, Yanli; Bai, Wei; Ji, Siping; Xuan, Zhewen; Yang, Jianhua; Zheng, Ziguang; Guan, Hongjin

2017-09-02

MnO 2 @PPy core-shell micromaterials are prepared by chemical polymerization of pyrrole on the MnO 2 surface. The polypyrrole (PPy) is formed as a homogeneous organic shell on the MnO 2 surface. The thickness of PPy shell can be adjusted by the usage of pyrrole. The analysis of SEM, FT-IR, X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA), and XRD are used to confirm the formation of PPy shell. Galvanostatic cell cycling and electrochemical impedance spectroscopy (EIS) are used to evaluate the electrochemical performance as anode for lithium-ion batteries. The results show that after formation of MnO 2 @PPy core-shell micromaterials, the cyclic performance as anode for lithium-ion batteries is improved. Fifty microliters of PPy-coated caddice-clew-like MnO 2 has the best cyclic performances as has 620 mAh g -1 discharge specific capacities after 300 cycles. As a comparison, the discharge specific capacity of bare MnO 2 materials falls to below 200 mAh g -1 after 10 cycles. The improved lithium-storage cyclic stability of the MnO 2 @PPy samples attributes to the core-shell hybrid structure which can buffer the structural expansion and contraction of MnO 2 caused by the repeated embedding and disengagement of Li ions and can prevent the pulverization of MnO 2 . This experiment provides an effective way to mitigate the problem of capacity fading of the transition metal oxide materials as anode materials for (lithium-ion batteries) LIBs.

A Multicusp Ion Source for Radioactive Ion Beams

NASA Astrophysics Data System (ADS)

Wutte, D.; Freedman, S.; Gough, R.; Lee, Y.; Leitner, M.; Leung, K. N.; Lyneis, C.; Picard, D. S.; Sun, L.; Williams, M. D.; Xie, Z. Q.

1997-05-01

In order to produce a radioactive ion beam of (14)O+, a 10-cm-diameter, 13.56 MHz radio frequency (rf) driven multicusp ion source is now being developed at Lawrence Berkeley National Laboratory. In this paper we describe the specific ion source design and the basic ion source characteristics using Ar, Xe and a 90types of measurements have been performed: extractable ion current, ion species distributions, gas efficiency, axial energy spread and ion beam emittance measurements. The source can generate ion current densities of approximately 60 mA/cm2 . In addition the design of the ion beam extraction/transport system for the actual experimental setup for the radioactive beam line will be presented.

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

Laskin, Julia; Johnson, Grant E.; Prabhakaran, Venkateshkumar

Immobilization of complex molecules and clusters on supports plays an important role in a variety of disciplines including materials science, catalysis and biochemistry. In particular, deposition of clusters on surfaces has attracted considerable attention due to their non-scalable, highly size-dependent properties. The ability to precisely control the composition and morphology of clusters and small nanoparticles on surfaces is crucial for the development of next generation materials with rationally tailored properties. Soft- and reactive landing of ions onto solid or liquid surfaces introduces unprecedented selectivity into surface modification by completely eliminating the effect of solvent and sample contamination on the qualitymore » of the film. The ability to select the mass-to-charge ratio of the precursor ion, its kinetic energy and charge state along with precise control of the size, shape and position of the ion beam on the deposition target makes soft-landing an attractive approach for surface modification. High-purity uniform thin films on surfaces generated using mass-selected ion deposition facilitate understanding of critical interfacial phenomena relevant to catalysis, energy generation and storage, and materials science. Our efforts have been directed toward understanding charge retention by soft-landed metal and metal-oxide cluster ions, which may affect both their structure and reactivity. Specifically, we have examined the effect of the surface on charge retention by both positively and negatively charged cluster ions. We found that the electronic properties of the surface play an important role in charge retention by cluster cations. Meanwhile, the electron binding energy is a key factor determining charge retention by cluster anions. These findings provide the scientific foundation for the rational design of interfaces for advanced catalysts and energy storage devices. Further optimization of electrode-electrolyte interfaces for applications in energy storage and electrocatalysis may be achieved by understanding and controlling the properties of soft-landed cluster ions.« less

Infrared thermography non-destructive evaluation of lithium-ion battery

NASA Astrophysics Data System (ADS)

Wang, Zi-jun; Li, Zhi-qiang; Liu, Qiang

2011-08-01

The power lithium-ion battery with its high specific energy, high theoretical capacity and good cycle-life is a prime candidate as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Safety is especially important for large-scale lithium-ion batteries, especially the thermal analysis is essential for their development and design. Thermal modeling is an effective way to understand the thermal behavior of the lithium-ion battery during charging and discharging. With the charging and discharging, the internal heat generation of the lithium-ion battery becomes large, and the temperature rises leading to an uneven temperature distribution induces partial degradation. Infrared (IR) Non-destructive Evaluation (NDE) has been well developed for decades years in materials, structures, and aircraft. Most thermographic methods need thermal excitation to the measurement structures. In NDE of battery, the thermal excitation is the heat generated from carbon and cobalt electrodes in electrolyte. A technique named "power function" has been developed to determine the heat by chemical reactions. In this paper, the simulations of the transient response of the temperature distribution in the lithium-ion battery are developed. The key to resolving the security problem lies in the thermal controlling, including the heat generation and the internal and external heat transfer. Therefore, three-dimensional modelling for capturing geometrical thermal effects on battery thermal abuse behaviour is required. The simulation model contains the heat generation during electrolyte decomposition and electrical resistance component. Oven tests are simulated by three-dimensional model and the discharge test preformed by test system. Infrared thermography of discharge is recorded in order to analyze the security of the lithium-ion power battery. Nondestructive detection is performed for thermal abuse analysis and discharge analysis.

A Monte Carlo approach to the microdosimetric kinetic model to account for dose rate time structure effects in ion beam therapy with application in treatment planning simulations.

PubMed

Manganaro, Lorenzo; Russo, Germano; Cirio, Roberto; Dalmasso, Federico; Giordanengo, Simona; Monaco, Vincenzo; Muraro, Silvia; Sacchi, Roberto; Vignati, Anna; Attili, Andrea

2017-04-01

Advanced ion beam therapeutic techniques, such as hypofractionation, respiratory gating, or laser-based pulsed beams, have dose rate time structures which are substantially different from those found in conventional approaches. The biological impact of the time structure is mediated through the β parameter in the linear quadratic (LQ) model. The aim of this study was to assess the impact of changes in the value of the β parameter on the treatment outcomes, also accounting for noninstantaneous intrafraction dose delivery or fractionation and comparing the effects of using different primary ions. An original formulation of the microdosimetric kinetic model (MKM) is used (named MCt-MKM), in which a Monte Carlo (MC) approach was introduced to account for the stochastic spatio-temporal correlations characteristic of the irradiations and the cellular repair kinetics. A modified version of the kinetic equations, validated on experimental cell survival in vitro data, was also introduced. The model, trained on the HSG cells, was used to evaluate the relative biological effectiveness (RBE) for treatments with acute and protracted fractions. Exemplary cases of prostate cancer irradiated with different ion beams were evaluated to assess the impact of the temporal effects. The LQ parameters for a range of cell lines (V79, HSG, and T1) and ion species (H, He, C, and Ne) were evaluated and compared with the experimental data available in the literature, with good results. Notably, in contrast to the original MKM formulation, the MCt-MKM explicitly predicts an ion and LET-dependent β compatible with observations. The data from a split-dose experiment were used to experimentally determine the value of the parameter related to the cellular repair kinetics. Concerning the clinical case considered, an RBE decrease was observed, depending on the dose, ion, and LET, exceeding up to 3% of the acute value in the case of a protraction in the delivery of 10 min. The intercomparison between different ions shows that the clinical optimality is strongly dependent on a complex interplay between the different physical and biological quantities considered. The present study provides a framework for exploiting the temporal effects of dose delivery. The results show the possibility of optimizing the treatment outcomes accounting for the correlation between the specific dose rate time structure and the spatial characteristic of the LET distribution, depending on the ion type used. © 2017 American Association of Physicists in Medicine.

High-molecular-weight glutenin subunit-deficient mutants induced by ion beam and the effects of Glu-1 loci deletion on wheat quality properties.

PubMed

Zhang, Lujun; Chen, Qiufang; Su, Mingjie; Yan, Biao; Zhang, Xiangqi; Jiao, Zhen

2016-03-15

High-molecular-weight glutenin subunits (HMW-GSs) play a critical role in determining the viscoelastic properties of wheat. Mutations induced by ion beam radiation have been applied to improve the yield and quality of crop. In this study, HMW-GS-deficient mutant lines were selected and the effects of Glu-1 loci deletion on wheat quality properties were illustrated according to the analysis of dry seeds of common wheat (Triticum aestivum L.) Xiaoyan 81 treated with a nitrogen ion beam. Three HMW-GS-deficient mutant lines were obtained and then detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Large-chromosome-fragment deletion resulted in specific deficiencies, and the deleted region sizes were determined using molecular markers. Agronomic characters, quantity and proportion of glutenins and dough microstructure of the deletion lines all proved to be quite different from those of wild-type Xiaoyan 81. Analysis of quality properties suggested that GluA1(-) had superior property parameters, while GluB1(-) and GluD1(-) both showed a significant decrease in quality properties compared with Xiaoyan 81. The effects of the three Glu-1 loci on flour and dough quality-related parameters should be Glu-D1 > Glu-B1 > Glu-A1. Ion beam radiation can be used as a mutagen to create new crop mutants. © 2015 Society of Chemical Industry.

Effect of polarization force on head-on collision between multi-solitons in dusty plasma

NASA Astrophysics Data System (ADS)

Singh, Kuldeep; Sethi, Papihra; Saini, N. S.

2018-03-01

Head-on collision among dust acoustic (DA) multi-solitons in a dusty plasma with ions featuring non-Maxwellian hybrid distribution under the effect of the polarization force is investigated. The presence of the non-Maxwellian ions leads to eloquent modifications in the polarization force. Specifically, an increase in the superthermality index of ions (via κi) and nonthermal parameter (via α) diminishes the polarization parameter. By employing the extended Poincaré-Lighthill-Kuo method, two sided KdV equations are derived. The Hirota direct method is used to obtain multi-soliton solutions for each KdV equation, and all of them move along the same direction where the fastest moving soliton eventually overtakes the others. The expressions for collisional phase shifts after head-on collision of two, four, and six-(DA) solitons are derived under the influence of polarization force. It is found that the effect of polarization force and the presence of non-Maxwellian ions have an emphatic influence on the phase shifts after the head-on collision of DA rarefactive multi-solitons. In a small amplitude limit, the impact of polarization force on time evolution of multi-solitons is also illustrated. It is intensified that the present theoretical pronouncements actually effectuate in laboratory experiments and in space/astrophysical environments, in particular in Saturn's magnetosphere and comet tails.

Radiation Effects in Advanced Multiple Gate and Silicon-on-Insulator Transistors

NASA Astrophysics Data System (ADS)

Simoen, Eddy; Gaillardin, Marc; Paillet, Philippe; Reed, Robert A.; Schrimpf, Ron D.; Alles, Michael L.; El-Mamouni, Farah; Fleetwood, Daniel M.; Griffoni, Alessio; Claeys, Cor

2013-06-01

The aim of this review paper is to describe in a comprehensive manner the current understanding of the radiation response of state-of-the-art Silicon-on-Insulator (SOI) and FinFET CMOS technologies. Total Ionizing Dose (TID) response, heavy-ion microdose effects and single-event effects (SEEs) will be discussed. It is shown that a very high TID tolerance can be achieved by narrow-fin SOI FinFET architectures, while bulk FinFETs may exhibit similar TID response to the planar devices. Due to the vertical nature of FinFETs, a specific heavy-ion response can be obtained, whereby the angle of incidence becomes highly important with respect to the vertical sidewall gates. With respect to SEE, the buried oxide in the SOI FinFETs suppresses the diffusion tails from the charge collection in the substrate compared to the planar bulk FinFET devices. Channel lengths and fin widths are now comparable to, or smaller than the dimensions of the region affected by the single ionizing ions or lasers used in testing. This gives rise to a high degree of sensitivity to individual device parameters and source-drain shunting during ion-beam or laser-beam SEE testing. Simulations are used to illuminate the mechanisms observed in radiation testing and the progress and needs for the numerical modeling/simulation of the radiation response of advanced SOI and FinFET transistors are highlighted.

Modulation of individual steps in group I intron catalysis by a peripheral metal ion.

PubMed

Forconi, Marcello; Piccirilli, Joseph A; Herschlag, Daniel

2007-10-01

Enzymes are complex macromolecules that catalyze chemical reactions at their active sites. Important information about catalytic interactions is commonly gathered by perturbation or mutation of active site residues that directly contact substrates. However, active sites are engaged in intricate networks of interactions within the overall structure of the macromolecule, and there is a growing body of evidence about the importance of peripheral interactions in the precise structural organization of the active site. Here, we use functional studies, in conjunction with published structural information, to determine the effect of perturbation of a peripheral metal ion binding site on catalysis in a well-characterized catalytic RNA, the Tetrahymena thermophila group I ribozyme. We perturbed the metal ion binding site by site-specifically introducing a phosphorothioate substitution in the ribozyme's backbone, replacing the native ligands (the pro-R (P) oxygen atoms at positions 307 and 308) with sulfur atoms. Our data reveal that these perturbations affect several reaction steps, including the chemical step, despite the absence of direct contacts of this metal ion with the atoms involved in the chemical transformation. As structural probing with hydroxyl radicals did not reveal significant change in the three-dimensional structure upon phosphorothioate substitution, the effects are likely transmitted through local, rather subtle conformational rearrangements. Addition of Cd(2+), a thiophilic metal ion, rescues some reaction steps but has deleterious effects on other steps. These results suggest that native interactions in the active site may have been aligned by the naturally occurring peripheral residues and interactions to optimize the overall catalytic cycle.

One and two fluid numerical investigations of solar wind gas releases

NASA Astrophysics Data System (ADS)

Harold, James Benedict

1993-01-01

The dynamics of gas releases into high Mach number flowing plasmas are investigated. Emphasis is placed on systems of intermediate magnetization for which the scale size of the release lies between the ion and electron Larmor radii. The study is motivated by the December 1984 AMPTE (Active Magnetospheric Particle Tracer Explorer) solar wind barium release in which, contrary to the predictions of MHD theory, the barium cloud shifted transverse to the solar wind (in the uwind x B0 direction) before eventually turning downstream. Particular emphasis is given to identifying mechanisms responsible for this lateral motion. A modified MHD cold fluid approach that takes advantage of the supersonic nature of the problem forms the basis of this work. Two specific models are developed which incorporate large effective ion Larmor radius effects. The first is for a single ion species, the second for two ion species. Two physical effects are identified which are not present in the conventional MHD system: the Hall effect, based on a Hall magnetic drift wave, and a hybrid electrostatic ion cyclotron mode. Linear analysis shows that the effect of the Hall term is to propagate the upwind magnetic field compression azimuthally to the downwind side of the cloud, leading to a quasi-steady state field compression on the -uwind x BO side of the cloud. The cyclotron mode can lead to a similar compression through deflection of the solar wind ions into the uwind x BO direction. In each case the resulting compression leads to a transverse acceleration of the cloud. The relative importance of these two mechanisms is shown to depend on deltac / rc, the ratio of the collisionless skin depth to the cloud size. Nonlinear, two-dimensional simulations are performed for each model. These simulations produce the expected field compressions and the resultant lateral acceleration, in general qualitative agreement with the AMPTE experiment. The dependence of these mechanisms on the ratio deltac / rc is demonstrated. While no simulations are performed that precisely duplicate the parameters of the AMPTE release, the results suggest that the Hall effect, and possibly deflection of the solar wind by the cyclotron mode, constitute plausible mechanisms for the AMPTE shift.

Controlling Ionic Transport for Device Design in Synthetic Nanopores

NASA Astrophysics Data System (ADS)

Kalman, Eric Boyd

Polymer nanopores present a number of behaviors not seen in microscale systems, such as ion current rectification, ionic selectivity, size exclusion and potential dependent ion concentrations in and near the pore. The existence of these effects stems from the small size of nanopores with respect to the characteristic length scales of surface interactions at the interface between the nanopore surface and the solution within it. The large surface-to-volume ratio due to the nanoscale geometry of a nanopore, as well as similarity in scale between geometry and interaction demands the solution interact with the nanopore walls. As surfaces in solution almost always carry residual charge, these surface forces are primarily the electrostatic interactions between the charge groups on the pore surface and the ions in solution. These interactions may be used by the experimentalist to control ionic transport through synthetic nanopores, and use them as a template for the construction of devices. In this research, we present our work on creating a number of ionic analogs to seminal electronic devices, specifically diodes, and transistors, by controlling ionic transport through the electrostatic interactions between a single synthetic nanopore and ions. Control is achieved by "doping" the effective charge carrier concentration in specific regions of the nanopore through manipulation of the pore's surface charge. This manipulation occurs through two mechanisms: chemical modification of the surface charge and electrostatic manipulation of the local internal nanopore potential using a gate electrode. Additionally, the innate selectivity of the charged nanopores walls allows for the separation of charges in solution. This well-known effect, which spawns measureable quantities, the streaming potential and current, has been used to create nanoscale water desalination membranes. We attempt to create a device using membranes with large nanopore densities for the desalination of water which should theoretically outperform currently available devices, as through our previous work we have developed techniques allowing for transport manipulation not current accessible in traditional membrane motifs.

Endowing CuTCNQ with a new role: a high-capacity cathode for K-ion batteries.

PubMed

Ma, Jing; Zhou, En; Fan, Cong; Wu, Bo; Li, Chao; Lu, Zheng-Hong; Li, Jingze

2018-05-29

Herein, copper-tetracyanoquinodimethane (CuTCNQ) with phase-I kinetics character has been proposed as an effective cathode for potassium-ion batteries. In a voltage range of 2-4.1 V (vs. K+/K), both cuprous cations (Cu+) and organic anions (TCNQ-) are electrochemically active, and they render a three-electron redox mechanism, thereby enabling CuTCNQ to yield a high specific discharge capacity of 244 mA h g-1. Even after 50 cycles, the discharge capacity of 170 mA h g-1 is retained at 50 mA g-1. In addition, when the current density is elevated to 1000 mA g-1, the discharge capacity is still maintained at 125 mA h g-1. These test data are among the best results reported for high-potential cathodes of potassium-ion batteries.

Biomass carbon composited FeS2 as cathode materials for high-rate rechargeable lithium-ion battery

NASA Astrophysics Data System (ADS)

Xu, Xin; Meng, Zhen; Zhu, Xueling; Zhang, Shunlong; Han, Wei-Qiang

2018-03-01

Pyrite FeS2 has long been used as commercial primary lithium batteries at room temperature. To achieve rechargeable FeS2 battery, biomass-carbon@FeS2 composites are prepared using green and renewable auricularia auricula as carbon source through the process of carbonization and sulfuration. The auricularia auricula has strong swelling characteristics to absorb aqueous solution which can effectively absorb Fe ions into its body. FeS2 homogeneously distributed in biomass carbon matrix performs high electronic and ionic conductivity. The specific capacity of biomass-carbon@FeS2 composites remains 850 mAh g-1 after 80 cycles at 0.5C and 700 mAh g-1 at the rate of 2C after 150 cycles. Biomass-carbon@FeS2 composites exhibit high-rate capacity in lithium-ion battery.

Interactive effects of pH, EC and nitrogen on yields and nutrient absorption of rice (Oryza sativa L.)

USDA-ARS?s Scientific Manuscript database

Soil salinity and sodicity can not only directly restrain crop growth by osmotic and specific ion stresses, it also may reduce grain yield indirectly by impacting plant absorption of essential nutrients. Ensuring adequate nitrogen is an important management aspect of rice production in saline-sodic ...

Electrolyte Solutions and Specific Ion Effects on Interfaces

ERIC Educational Resources Information Center

Friedman, Ran

2013-01-01

Introductory general and physical chemistry courses often deal with colligative properties of solutions and do not discuss nonideal solutions in detail. Yet, a growing body of evidence reveals that even at physiological concentrations electrolyte solutions cannot be treated as ideal when a charged or partially charged solute (such as a protein) is…

An Analysis of Heavy-Ion Single Event Effects for a Variety of Finite State-Machine Mitigation Strategies

NASA Technical Reports Server (NTRS)

Berg, Melanie D.; Label, Kenneth A.; Kim, Hak; Phan, Anthony; Seidleck, Christina

2014-01-01

Finite state-machines (FSMs) are used to control operational flow in application specific integrated circuits (ASICs) and field programmable gate array (FPGA) devices. Because of their ease of interpretation, FSMs simplify the design and verification process and consequently are significant components in a synchronous design.

Calibration and performance of synchronous SIM/scan mode for simultaneous targeted and discovery (non-targeted) analysis of exhaled breath samples from firefighters

EPA Science Inventory

Traditionally, gas chromatography – mass spectrometry (GC-MS) analysis has used a targeted approach called selected ion monitoring (SIM) to quantify specific compounds that may have adverse health effects. Due to method limitations and the constraints of preparing duplicat...

A top-down approach for fabricating free-standing bio-carbon supercapacitor electrodes with a hierarchical structure.

PubMed

Li, Yingzhi; Zhang, Qinghua; Zhang, Junxian; Jin, Lei; Zhao, Xin; Xu, Ting

2015-09-23

Biomass has delicate hierarchical structures, which inspired us to develop a cost-effective route to prepare electrode materials with rational nanostructures for use in high-performance storage devices. Here, we demonstrate a novel top-down approach for fabricating bio-carbon materials with stable structures and excellent diffusion pathways; this approach is based on carbonization with controlled chemical activation. The developed free-standing bio-carbon electrode exhibits a high specific capacitance of 204 F g(-1) at 1 A g(-1); good rate capability, as indicated by the residual initial capacitance of 85.5% at 10 A g(-1); and a long cycle life. These performance characteristics are attributed to the outstanding hierarchical structures of the electrode material. Appropriate carbonization conditions enable the bio-carbon materials to inherit the inherent hierarchical texture of the original biomass, thereby facilitating effective channels for fast ion transfer. The macropores and mesopores that result from chemical activation significantly increase the specific surface area and also play the role of temporary ion-buffering reservoirs, further shortening the ionic diffusion distance.

Inorganic biochemistry with short-lived radioisotopes as nuclear probes

NASA Astrophysics Data System (ADS)

Tröger, W.; Butz, T.

2000-12-01

Metal ions are ubiquitous in the biosphere. In living organisms metalloproteins with specifically designed metal cores perform vital chemical processes. On the other hand, several heavy metals are detrimental to living organisms and nature has developed effective enzymatic detoxification systems which convert toxic metal ions to less toxic species. The nuclear spectroscopy technique Time Differential Perturbed Angular Correlation (TDPAC) of γ-rays uses radioactive isotopes as nuclear probes in these metal cores to obtain a better understanding of the structural and functional significance of these metal cores by monitoring the nuclear quadrupole interaction of the TDPAC probe. Since this technique is based on the nuclear decay, it is also applicable under physiological conditions, i.e., especially at picomolar concentrations. For these studies an indispensable prerequisite is the production of the TDPAC probes with highest possible specific activity and purity as is done by the on-line mass separator ISOLDE at CERN in Geneva.

Selective removal of cesium by ammonium molybdophosphate - polyacrylonitrile bead and membrane.

PubMed

Ding, Dahu; Zhang, Zhenya; Chen, Rongzhi; Cai, Tianming

2017-02-15

The selective removal of radionuclides with extremely low concentrations from environmental medium remains a big challenge. Ammonium molybdophosphate possess considerable selectivity towards cesium ion (Cs + ) due to the specific ion exchange between Cs + and NH 4 + . Ammonium molybdophosphate - polyacrylonitrile (AMP-PAN) membrane was successfully prepared for the first time in this study. Efficient removal of Cs + (95.7%, 94.1% and 91.3% of 1mgL -1 ) from solutions with high ionic strength (400mgL -1 of Na + , Ca 2+ or K + ) was achieved by AMP-PAN composite. Multilayer chemical adsorption process was testified through kinetic and isotherm studies. The estimated maximum adsorption capacities even reached 138.9±21.3mgg -1 . Specifically, the liquid film diffusion was identified as the rate-limiting step throughout the removal process. Finally, AMP-PAN membrane could eliminate Cs + from water effectively through the filtration adsorption process. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrochemical performance of PVA stabilized nickel ferrite nanoparticles via microwave route

NASA Astrophysics Data System (ADS)

William, J. Johnson; Babu, I. Manohara; Muralidharan, G.

2017-05-01

Nanosized nickel ferrite nanoparticles were effectively synthesized through microwave route.PVA is used as a stabilizer. The cubic inverse spinel crystal structure was identified from the X-ray diffraction pattern. FTIR spectrum identified the octahedral site vibrations of the Ni2+ ions and tetrahedral sites vibrations of Fe3+ ions, which additionally confirms the existence of nickel ferrite nanoparticles. Nano-granular morphology was observed from scanning electron microscope. The tuning of morphology was clearly seen in SEM images. Electrochemical performance of nickel ferrite nanoparticles was studied using cyclic voltammetry and chronopotentiometry. Highest specific capacitance of 459 F g-1 was achieved through cyclic voltammetry at 2 mV s-1 for NF10. Also, non-linearity was observed in chronopotentiometry which confirms the pseudocapacitance nature of nickel ferrite nanoparticles. The estimated specific capacitance was 341 F g-1 at 2.5 A g-1.

Genetic defects disrupting glial ion and water homeostasis in the brain.

PubMed

Min, Rogier; van der Knaap, Marjo S

2018-05-01

Electrical activity of neurons in the brain, caused by the movement of ions between intracellular and extracellular compartments, is the basis of all our thoughts and actions. Maintaining the correct ionic concentration gradients is therefore crucial for brain functioning. Ion fluxes are accompanied by the displacement of osmotically obliged water. Since even minor brain swelling leads to severe brain damage and even death, brain ion and water movement has to be tightly regulated. Glial cells, in particular astrocytes, play a key role in ion and water homeostasis. They are endowed with specific channels, pumps and carriers to regulate ion and water flow. Glial cells form a large panglial syncytium to aid the uptake and dispersal of ions and water, and make extensive contacts with brain fluid barriers for disposal of excess ions and water. Genetic defects in glial proteins involved in ion and water homeostasis disrupt brain functioning, thereby leading to neurological diseases. Since white matter edema is often a hallmark disease feature, many of these diseases are characterized as leukodystrophies. In this review we summarize our current understanding of inherited glial diseases characterized by disturbed brain ion and water homeostasis by integrating findings from MRI, genetics, neuropathology and animal models for disease. We discuss how mutations in different glial proteins lead to disease, and highlight the similarities and differences between these diseases. To come to effective therapies for this group of diseases, a better mechanistic understanding of how glial cells shape ion and water movement in the brain is crucial. © 2018 The Authors. Brain Pathology published by John Wiley & Sons Ltd on behalf of International Society of Neuropathology.

Cholinergic regulation of epithelial ion transport in the mammalian intestine

PubMed Central

Hirota, C L; McKay, D M

2006-01-01

Acetylcholine (ACh) is critical in controlling epithelial ion transport and hence water movements for gut hydration. Here we review the mechanism of cholinergic control of epithelial ion transport across the mammalian intestine. The cholinergic nervous system affects basal ion flux and can evoke increased active ion transport events. Most studies rely on measuring increases in short-circuit current (ISC = active ion transport) evoked by adding ACh or cholinomimetics to intestinal tissue mounted in Ussing chambers. Despite subtle species and gut regional differences, most data indicate that, under normal circumstances, the effect of ACh on intestinal ion transport is mainly an increase in Cl- secretion due to interaction with epithelial M3 muscarinic ACh receptors (mAChRs) and, to a lesser extent, neuronal M1 mAChRs; however, AChR pharmacology has been plagued by a lack of good receptor subtype-selective compounds. Mice lacking M3 mAChRs display intact cholinergically-mediated intestinal ion transport, suggesting a possible compensatory mechanism. Inflamed tissues often display perturbations in the enteric cholinergic system and reduced intestinal ion transport responses to cholinomimetics. The mechanism(s) underlying this hyporesponsiveness are not fully defined. Inflammation-evoked loss of mAChR-mediated control of epithelial ion transport in the mouse reveals a role for neuronal nicotinic AChRs, representing a hitherto unappreciated braking system to limit ACh-evoked Cl- secretion. We suggest that: i) pharmacological analyses should be supported by the use of more selective compounds and supplemented with molecular biology techniques targeting specific ACh receptors and signalling molecules, and ii) assessment of ion transport in normal tissue must be complemented with investigations of tissues from patients or animals with intestinal disease to reveal control mechanisms that may go undetected by focusing on healthy tissue only. PMID:16981004

Stabilizing effect of citrate buffer on the photolysis of riboflavin in aqueous solution

PubMed Central

Ahmad, Iqbal; Sheraz, Muhammad Ali; Ahmed, Sofia; Kazi, Sadia Hafeez; Mirza, Tania; Aminuddin, Mohammad

2011-01-01

In the present investigation the photolysis of riboflavin (RF) in the presence of citrate species at pH 4.0–7.0 has been studied. A specific multicomponent spectrophotometric method has been used to assay RF in the presence of photoproducts during the reactions. The overall first-order rate constants (kobs) for the photolysis of RF range from 0.42 to 1.08×10–2 min−1 in the region. The values of kobs have been found to decrease with an increase in citrate concentration indicating an inhibitory effect of these species on the rate of reaction. The second-order rate constants for the interaction of RF with total citrate species causing inhibition range from 1.79 to 5.65×10–3 M−1 min−1 at pH 4.0–7.0. The log k–pH profiles for the reactions at 0.2–1.0 M citrate concentration show a gradual decrease in kobs and the value at 1.0 M is more than half compared to that of k0, i.e., in the absence of buffer, at pH 5.0. Divalent citrate ions cause a decrease in RF fluorescence due to the quenching of the excited singlet state resulting in a decrease in the rate of reaction and consequently leading to the stabilization of RF solutions. The greater quenching of fluorescence at pH 4.0 compared to that of 7.0 is in accordance with the greater concentration of divalent citrate ions (99.6%) at that pH. The trivalent citrate ions exert a greater inhibitory effect on the rate of RF photolysis compared to that of the divalent citrate ions probably as a result of excited triplet state quenching. The values of second-order rate constants for the interaction of divalent and trivalent citrate ions are 0.44×10–2 and 1.06×10–3 M–1 min–1, respectively, indicating that the trivalent ions exert a greater stabilizing effect, compared to the divalent ions, on RF solutions. PMID:25755977

Regulation of TRP channels by steroids: Implications in physiology and diseases.

PubMed

Kumar, Ashutosh; Kumari, Shikha; Majhi, Rakesh Kumar; Swain, Nirlipta; Yadav, Manoj; Goswami, Chandan

2015-09-01

While effects of different steroids on the gene expression and regulation are well established, it is proven that steroids can also exert rapid non-genomic actions in several tissues and cells. In most cases, these non-genomic rapid effects of steroids are actually due to intracellular mobilization of Ca(2+)- and other ions suggesting that Ca(2+) channels are involved in such effects. Transient Receptor Potential (TRP) ion channels or TRPs are the largest group of non-selective and polymodal ion channels which cause Ca(2+)-influx in response to different physical and chemical stimuli. While non-genomic actions of different steroids on different ion channels have been established to some extent, involvement of TRPs in such functions is largely unexplored. In this review, we critically analyze the literature and summarize how different steroids as well as their metabolic precursors and derivatives can exert non-genomic effects by acting on different TRPs qualitatively and/or quantitatively. Such effects have physiological repercussion on systems such as in sperm cells, immune cells, bone cells, neuronal cells and many others. Different TRPs are also endogenously expressed in diverse steroid-producing tissues and thus may have importance in steroid synthesis as well, a process which is tightly controlled by the intracellular Ca(2+) concentrations. Tissue and cell-specific expression of TRP channels are also regulated by different steroids. Understanding of the crosstalk between TRP channels and different steroids may have strong significance in physiological, endocrinological and pharmacological context and in future these compounds can also be used as potential biomedicine. Copyright © 2014 Elsevier Inc. All rights reserved.

Performance and Safety of Lithium Ion Cells

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Smart, M. C.; Whitcanack, L.; Surampudi, S.; Marsh, R.

2001-01-01

This report evaluates the performance and safety of Lithium Ion (Li-Ion) cells when used in batteries. Issues discussed include the cycle life, energy efficiency, tolerance to higher charge voltage, tolerance to extended tapered charge voltage, charge on cycling, specific energy, low temperature discharge, low temperature charge, various charge characteristics, storage characteristics, and more of Li-Ion cells.

Trapping, retention and laser cooling of Th3+ ions in a multisection linear quadrupole trap

NASA Astrophysics Data System (ADS)

Borisyuk, P. V.; Vasil'ev, O. S.; Derevyashkin, S. P.; Kolachevsky, N. N.; Lebedinskii, Yu. Yu.; Poteshin, S. S.; Sysoev, A. A.; Tkalya, E. V.; Tregubov, D. O.; Troyan, V. I.; Khabarova, K. Yu.; Yudin, V. I.; Yakovlev, V. P.

2017-06-01

A multisection linear quadrupole trap for Th3+ ions is described. Multiply charged ions are obtained by the laser ablation method. The possibility of trapping and retention of ˜103 ions is demonstrated in macroscopic time scales of ˜30 s. Specific features of cooling Th3+ ions on the electron transitions with wavelengths of 1088, 690 and 984 nm in Th3+ ion are discussed; a principal scheme of a setup for laser cooling is presented.

Mechanics of torque generation in the bacterial flagellar motor

PubMed Central

Mandadapu, Kranthi K.; Nirody, Jasmine A.; Berry, Richard M.; Oster, George

2015-01-01

The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual “power stroke.” Specifically, we propose that ion-induced conformational changes about a proline “hinge” residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque–speed and speed–ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator. PMID:26216959

Fully integrated graphene electronic biosensor for label-free detection of lead (II) ion based on G-quadruplex structure-switching.

PubMed

Li, Yijun; Wang, Cheng; Zhu, Yibo; Zhou, Xiaohong; Xiang, Yu; He, Miao; Zeng, Siyu

2017-03-15

This work presents a fully integrated graphene field-effect transistor (GFET) biosensor for the label-free detection of lead ions (Pb 2+ ) in aqueous-media, which first implements the G-quadruplex structure-switching biosensing principle in graphene nanoelectronics. We experimentally illustrate the biomolecular interplay that G-rich DNA single-strands with one-end confined on graphene surface can specifically interact with Pb 2+ ions and switch into G-quadruplex structures. Since the structure-switching of electrically charged DNA strands can disrupt the charge distribution in the vicinity of graphene surface, the carrier equilibrium in graphene sheet might be altered, and manifested by the conductivity variation of GFET. The experimental data and theoretical analysis show that our devices are capable of the label-free and specific quantification of Pb 2+ with a detection limit down to 163.7ng/L. These results first verify the signaling principle competency of G-quadruplex structure-switching in graphene electronic biosensors. Combining with the advantages of the compact device structure and convenient electrical signal, a label-free GFET biosensor for Pb 2+ monitoring is enabled with promising application potential. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanics of torque generation in the bacterial flagellar motor.

PubMed

Mandadapu, Kranthi K; Nirody, Jasmine A; Berry, Richard M; Oster, George

2015-08-11

The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual "power stroke." Specifically, we propose that ion-induced conformational changes about a proline "hinge" residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque-speed and speed-ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator.

Ion Counting from Explicit-Solvent Simulations and 3D-RISM

PubMed Central

Giambaşu, George M.; Luchko, Tyler; Herschlag, Daniel; York, Darrin M.; Case, David A.

2014-01-01

The ionic atmosphere around nucleic acids remains only partially understood at atomic-level detail. Ion counting (IC) experiments provide a quantitative measure of the ionic atmosphere around nucleic acids and, as such, are a natural route for testing quantitative theoretical approaches. In this article, we replicate IC experiments involving duplex DNA in NaCl(aq) using molecular dynamics (MD) simulation, the three-dimensional reference interaction site model (3D-RISM), and nonlinear Poisson-Boltzmann (NLPB) calculations and test against recent buffer-equilibration atomic emission spectroscopy measurements. Further, we outline the statistical mechanical basis for interpreting IC experiments and clarify the use of specific concentration scales. Near physiological concentrations, MD simulation and 3D-RISM estimates are close to experimental results, but at higher concentrations (>0.7 M), both methods underestimate the number of condensed cations and overestimate the number of excluded anions. The effect of DNA charge on ion and water atmosphere extends 20–25 Å from its surface, yielding layered density profiles. Overall, ion distributions from 3D-RISMs are relatively close to those from corresponding MD simulations, but with less Na+ binding in grooves and tighter binding to phosphates. NLPB calculations, on the other hand, systematically underestimate the number of condensed cations at almost all concentrations and yield nearly structureless ion distributions that are qualitatively distinct from those generated by both MD simulation and 3D-RISM. These results suggest that MD simulation and 3D-RISM may be further developed to provide quantitative insight into the characterization of the ion atmosphere around nucleic acids and their effect on structure and stability. PMID:24559991

High Voltage Magnesium-ion Battery Enabled by Nanocluster Mg3Bi2 Alloy Anode in Noncorrosive Electrolyte.

PubMed

Tan, Yi-Hong; Yao, Wei-Tang; Zhang, Tianwen; Ma, Tao; Lu, Lei-Lei; Zhou, Fei; Yao, Hong-Bin; Yu, Shu-Hong

2018-05-03

Currently, developing high voltage (beyond 2 V) rechargeable Mg-ion batteries still remains a great challenge owing to the limit of corrosive electrolyte and low compatibility of anode material. Here we report a facile one step solid state alloying route to synthesize nanoclustered Mg 3 Bi 2 alloy as a high-performance anode to build up a 2 V Mg-ion battery using noncorrosive electrolyte. The fabricated nanoclustered Mg 3 Bi 2 anode delivers a high reversible specific capacity (360 mAh g -1 ) with excellent stability (90.7% capacity retention over 200 cycles) and high Coulombic efficiency (average 98%) at 0.1 A g -1 . The good performance is attributed to the stable nanostructures, which effectively accommodate the reversible Mg 2+ ion insertion/deinsertion without losing electric contact among clusters. Significantly, the nanoclustered Mg 3 Bi 2 anode can be coupled with high voltage cathode Prussian Blue to assemble a full cell using noncorrosive electrolyte, showing a stable cycling (88% capacity retention over 200 cycles at 0.2 A g -1 ) and good rate capability (103 mAh g -1 at 0.1 A g -1 and 58 mAh g -1 at 2 A g -1 ). The energy and power density of the as-fabricated full cell can reach up to 81 Wh kg -1 and 2850 W kg -1 , respectively, which are both the highest values among the reported Mg-ion batteries using noncorrosive electrolytes. This study demonstrates a cost-effective route to fabricate stable and high voltage rechargeable Mg-ion battery potentially for grid-scale energy storage.

Novel hybrid isotope separation scheme and apparatus

DOEpatents

Maya, Jakob

1991-01-01

A method of yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which the specific isotope is to be isolated, radiating the gas with frequencies characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photoionization reaction of the desired isotope, and collecting the specific isotope ion by suitable ion collection means.

Ionic liquid/water mixtures: from hostility to conciliation.

PubMed

Kohno, Yuki; Ohno, Hiroyuki

2012-07-21

Water was originally inimical to ionic liquids (ILs) especially in the analysis of their detailed properties. Various data on the properties of ILs indicate that there are two ways to design functions of ionic liquids. The first is to change the structure of component ions, to provide "task-specific ILs". The second is to mix ILs with other components, such as other ILs, organic solvents or water. Mixing makes it easy to control the properties of the solution. In this strategy, water is now a very important partner. Below, we summarise our recent results on the properties of IL/water mixtures. Stable phase separation is an effective method in some separation processes. Conversely, a dynamic phase change between a homogeneous mixture and separation of phases is important in many fields. Analysis of the relation between phase behaviour and the hydration state of the component ions indicates that the pattern of phase separation is governed by the hydrophilicity of the ions. Sufficiently hydrophilic ions yielded ILs that are miscible with water, and hydrophobic ions gave stable phase separation with water. ILs composed of hydrophobic but hydrated ions undergo a dynamic phase change between a homogeneous mixture and separate phases according to temperature. ILs having more than seven water molecules per ion pair undergo this phase transition. These dynamic phase changes are considered, with some examples, and application is made to the separation of water-soluble proteins.

Focused helium-ion-beam-induced deposition

NASA Astrophysics Data System (ADS)

Alkemade, P. F. A.; Miro, H.

2014-12-01

The recent introduction of the helium ion microscope (HIM) offers new possibilities for materials modification and fabrication with spatial resolution below 10 nm. In particular, the specific interaction of He+ ions in the tens of keV energy range with materials—i.e., minimal deflection and mainly energy loss via electronic excitations—renders the HIM a special tool for ion-beam-induced deposition. In this work, an overview is given of all studies of helium-ion-beam-induced deposition (He-IBID) that appeared in the literature before summer 2014. Continuum models that describe the deposition processes are presented in detail, with emphasis on precursor depletion and replenishment. In addition, a Monte Carlo model is discussed. Basic experimental He-IBID studies are critically examined. They show deposition rates of up to 0.1 nm3/ion. Analysis by means of a continuum model yields the precursor diffusion constant and the cross sections for beam-induced precursor decomposition and beam-induced desorption. Moreover, it is shown that deposition takes place only in a small zone around the beam impact point. Furthermore, the characterization of deposited materials is discussed in terms of microstructure and resistivity. It is shown that He-IBID material resembles more electron-beam-induced-deposition (EBID) material than Ga-ion-beam-induced-deposition (Ga-IBID) material. Nevertheless, the spatial resolution for He-IBID is in general better than for EBID and Ga-IBID; in particular, proximity effects are minimal.

Insights into channel dysfunction from modelling and molecular dynamics simulations.

PubMed

Musgaard, Maria; Paramo, Teresa; Domicevica, Laura; Andersen, Ole Juul; Biggin, Philip C

2018-04-01

Developments in structural biology mean that the number of different ion channel structures has increased significantly in recent years. Structures of ion channels enable us to rationalize how mutations may lead to channelopathies. However, determining the structures of ion channels is still not trivial, especially as they necessarily exist in many distinct functional states. Therefore, the use of computational modelling can provide complementary information that can refine working hypotheses of both wild type and mutant ion channels. The simplest but still powerful tool is homology modelling. Many structures are available now that can provide suitable templates for many different types of ion channels, allowing a full three-dimensional interpretation of mutational effects. These structural models, and indeed the structures themselves obtained by X-ray crystallography, and more recently cryo-electron microscopy, can be subjected to molecular dynamics simulations, either as a tool to help explore the conformational dynamics in detail or simply as a means to refine the models further. Here we review how these approaches have been used to improve our understanding of how diseases might be linked to specific mutations in ion channel proteins. This article is part of the Special Issue entitled 'Channelopathies.' Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

An innovative approach for characteristic analysis and state-of-health diagnosis for a Li-ion cell based on the discrete wavelet transform

NASA Astrophysics Data System (ADS)

Kim, Jonghoon; Cho, B. H.

2014-08-01

This paper introduces an innovative approach to analyze electrochemical characteristics and state-of-health (SOH) diagnosis of a Li-ion cell based on the discrete wavelet transform (DWT). In this approach, the DWT has been applied as a powerful tool in the analysis of the discharging/charging voltage signal (DCVS) with non-stationary and transient phenomena for a Li-ion cell. Specifically, DWT-based multi-resolution analysis (MRA) is used for extracting information on the electrochemical characteristics in both time and frequency domain simultaneously. Through using the MRA with implementation of the wavelet decomposition, the information on the electrochemical characteristics of a Li-ion cell can be extracted from the DCVS over a wide frequency range. Wavelet decomposition based on the selection of the order 3 Daubechies wavelet (dB3) and scale 5 as the best wavelet function and the optimal decomposition scale is implemented. In particular, this present approach develops these investigations one step further by showing low and high frequency components (approximation component An and detail component Dn, respectively) extracted from variable Li-ion cells with different electrochemical characteristics caused by aging effect. Experimental results show the clearness of the DWT-based approach for the reliable diagnosis of the SOH for a Li-ion cell.

Calorimetric and counterion binding studies of the interactions between micelles and ions. The observation of lyotropic series

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

Larsen, J.W.; Magid, L.J.

1974-09-04

Heats of transfer of a variety of salts from water to solutions of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and sodium dodecyl sulfate (NaLS) were measured. Lyotropic series for both cations and anions were observed for all soaps, the series for the 2 cationic soaps being almost identical. The dependence of the observed heats of transfer for anions from H/sub 2/O to CTAB and DTAB solutions and for cations from H2O to NaLS solutions on the hydrated radii of the ions involved supports the contention that favorable binding of counterions depends on how closely they can approach the charged micellarmore » surfaces. It is clear that a lyotropic series similar to that existing for proteins exists for ion binding to micelles. The controlling factor in this binding seems to be the distance of closest approach of the ion to the micelle, although polarizable organic ions may be the exceptions. Chain length has little effect on binding. It is felt that the work discussed has established the usefulness of a calorimetric investigation and the use of ion-specific electrodes for characterizing surfactant systems containing more than one species of counterions. (37 refs.)« less

Isomer separation and effect of the degree of polymerization on the gas-phase structure of chondroitin sulfate oligosaccharides analyzed by ion mobility and tandem mass spectrometry.

PubMed

Poyer, Salomé; Lopin-Bon, Chrystel; Jacquinet, Jean-Claude; Salpin, Jean-Yves; Daniel, Régis

2017-12-15

Chondroitin sulfate (CS) glycosaminoglycans are bioactive sulfated polysaccharides comprising repeating units of uronic acid and N-acetyl galactose sulfated at various positions. The optimal length and sulfation pattern of the CS bioactive sequences remain elusive so that structure-activity relationships cannot be easily established. Development of efficient analytical methods allowing the differentiation of the various sulfation patterns of CS sequences is therefore of particular importance to correlate their biological functions to the sulfation pattern. Discrimination of different oligomers (dp2 to dp6) of synthetic chondroitin sulfate isomers was evaluated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) in the negative-ion mode from deprotonated and alkali adduct species. In addition, ion mobility mass spectrometry (IMS-MS) was used to study the influence of both the degree of polymerization and sulfate group location on the gas-phase conformation of CS oligomers. ESI-MS/MS spectra of chondroitin sulfate isomers show characteristic product ions exclusively from alkali adduct species (Li, Na, K and Cs). Whatever the alkali adducts studied, MS/MS of chondroitin oligosaccharides sulfated at position 6 yields a specific product ion at m/z 139 while CS oligosaccharides sulfated at position 4 show a specific product ion at m/z 154. Being observed for the different CS oligomers di-, tetra- and hexasaccharides, these fragment ions are considered as diagnostic ions for chondroitin 6-O-sulfate and chondroitin 4-O-sulfate, respectively. IMS-MS experiments reveal that collision cross-sections (CCS) of CS oligomers with low charge states evolved linearly with degrees of polymerization indicating a similar gas-phase conformation. This study allows the fast and unambiguous differentiation of CS isomers sulfated at position 6 or 4 for both saturated and unsaturated analogues from MS/MS experiments. In addition, the CCS linear evolution of CS oligomers in function of the degree of polymerization indicates that no folding occurs even for hexasaccharides. Copyright © 2017 John Wiley & Sons, Ltd.

TOFSIMS-P: a web-based platform for analysis of large-scale TOF-SIMS data.

PubMed

Yun, So Jeong; Park, Ji-Won; Choi, Il Ju; Kang, Byeongsoo; Kim, Hark Kyun; Moon, Dae Won; Lee, Tae Geol; Hwang, Daehee

2011-12-15

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been a useful tool to profile secondary ions from the near surface region of specimens with its high molecular specificity and submicrometer spatial resolution. However, the TOF-SIMS analysis of even a moderately large size of samples has been hampered due to the lack of tools for automatically analyzing the huge amount of TOF-SIMS data. Here, we present a computational platform to automatically identify and align peaks, find discriminatory ions, build a classifier, and construct networks describing differential metabolic pathways. To demonstrate the utility of the platform, we analyzed 43 data sets generated from seven gastric cancer and eight normal tissues using TOF-SIMS. A total of 87 138 ions were detected from the 43 data sets by TOF-SIMS. We selected and then aligned 1286 ions. Among them, we found the 66 ions discriminating gastric cancer tissues from normal ones. Using these 66 ions, we then built a partial least square-discriminant analysis (PLS-DA) model resulting in a misclassification error rate of 0.024. Finally, network analysis of the 66 ions showed disregulation of amino acid metabolism in the gastric cancer tissues. The results show that the proposed framework was effective in analyzing TOF-SIMS data from a moderately large size of samples, resulting in discrimination of gastric cancer tissues from normal tissues and identification of biomarker candidates associated with the amino acid metabolism.

Zinc-ion-dependent acid phosphatase exhibits magnesium-ion-dependent myo-inositol-1-phosphatase activity.

PubMed

Fujimoto, S; Okano, I; Tanaka, Y; Sumida, Y; Tsuda, J; Kawakami, N; Shimohama, S

1996-06-01

We have purified bovine brain Zn(2+)-dependent acid phosphatase (Zn(2+)-APase), which requires Zn2+ ions to hydrolyze the substrate p-nitrophenyl phosphate (pNPP) in an acidic environment. The substrate specificity and metal requirement of Zn(2+)-APase at a physiological pH was also studied. The enzyme exhibited hydrolytic activity on myo-inositol-1- and -2-monophosphates, 2'-adenosine monophosphate, 2'-guanosine monophosphate, and the alpha- and beta-glycerophosphates, glucose-1-phosphate, and fructose-6-phosphate in 50 mM Tris-HCl buffer (pH 7.4) in the presence of Mg2+ ions, but not on pNPP and phosphotyrosine. Zn2+, Mn2+ and Co2+ ions were less effective for activation. Among the above substrates, myo-inositol-1-phosphate was the most susceptible to hydrolysis by the enzyme in the presence of 3 mM Mg2+ ions. The enzyme exhibited an optimum pH at around 8 for myo-inositol-1-phosphate in the presence of 3 mM Mg2+ ions. The Mg(2+)-dependent myo-inositol-1-phosphatase activity of the enzyme was significantly inhibited by Li+ ions. The Zn(2+)-dependent p-nitrophenyl phosphatase activity and Mg(2+)-dependent myo-inositol-1-phosphatase activity of the purified enzyme fraction exhibited similar behavior on Sephadex G-100 and Mono Q colomns. These findings suggest that Zn(2+)-APase also exhibits Mg(2+)-dependent myo-inositol-1-phosphatase activity under physiological conditions.

The use of a diuretic agent as a probe to investigate site and mechanism of ion transport processes.

PubMed

Giebisch, G

1985-01-01

Several features emerge from consideration of a furosemide-sensitive cotransport mechanism in the various tissues surveyed. First discovered in epithelia, above all in the kidney because of its potent diuretic effect, furosemide inhibits a cotransport mechanism that tightly couples the movement of sodium, chloride and potassium. Its mode of operation is electrically neutral and in all tissues so far examined, the cotransport-mediated ion movement is driven by the electrochemical potential of the cotransported ion-species. The energy for this ion movement derives ultimately from the Na-K pump that establishes the Na gradient that drives the coupled ion movement. This type of carrier-mediated and ion-specific solute movement expands the traditional "pump-leak" model of cellular ion transport by providing dissipative "leak" pathways in addition to the well-established ion channels that allow solute movement by electrodiffusion. An important feature of the cotransport mechanism is its important role in both reabsorptive and secretory epithelial transport operations. This variability can be adequately explained by the location of the cotransport mechanism in either the apical or basolateral cell membrane of such epithelia as the renal tubule, the intestinal mucosa, the rectal gland or the trachea. In addition, the furosemide-sensitive transporter has also been shown to play a significant role in cell volume regulation, both in epithelia and in non-epithelia cells, and it appears to participate in the regulation of the cell chloride concentrations in excitable tissues.

A Unifying Mechanism for Cancer Cell Death through Ion Channel Activation by HAMLET

PubMed Central

Storm, Petter; Kjaer Klausen, Thomas; Trulsson, Maria; Ho CS, James; Dosnon, Marion; Westergren, Tomas; Chao, Yinxia; Rydström, Anna; Yang, Henry; Pedersen, Stine Falsig; Svanborg, Catharina

2013-01-01

Ion channels and ion fluxes control many aspects of tissue homeostasis. During oncogenic transformation, critical ion channel functions may be perturbed but conserved tumor specific ion fluxes remain to be defined. Here we used the tumoricidal protein-lipid complex HAMLET as a probe to identify ion fluxes involved in tumor cell death. We show that HAMLET activates a non-selective cation current, which reached a magnitude of 2.74±0.88 nA within 1.43±0.13 min from HAMLET application. Rapid ion fluxes were essential for HAMLET-induced carcinoma cell death as inhibitors (amiloride, BaCl2), preventing the changes in free cellular Na+ and K+ concentrations also prevented essential steps accompanying carcinoma cell death, including changes in morphology, uptake, global transcription, and MAP kinase activation. Through global transcriptional analysis and phosphorylation arrays, a strong ion flux dependent p38 MAPK response was detected and inhibition of p38 signaling delayed HAMLET-induced death. Healthy, differentiated cells were resistant to HAMLET challenge, which was accompanied by innate immunity rather than p38-activation. The results suggest, for the first time, a unifying mechanism for the initiation of HAMLET’s broad and rapid lethal effect on tumor cells. These findings are particularly significant in view of HAMLET’s documented therapeutic efficacy in human studies and animal models. The results also suggest that HAMLET offers a two-tiered therapeutic approach, killing cancer cells while stimulating an innate immune response in surrounding healthy tissues. PMID:23505537

A unifying mechanism for cancer cell death through ion channel activation by HAMLET.

PubMed

Storm, Petter; Klausen, Thomas Kjaer; Trulsson, Maria; Ho C S, James; Dosnon, Marion; Westergren, Tomas; Chao, Yinxia; Rydström, Anna; Yang, Henry; Pedersen, Stine Falsig; Svanborg, Catharina

2013-01-01

Ion channels and ion fluxes control many aspects of tissue homeostasis. During oncogenic transformation, critical ion channel functions may be perturbed but conserved tumor specific ion fluxes remain to be defined. Here we used the tumoricidal protein-lipid complex HAMLET as a probe to identify ion fluxes involved in tumor cell death. We show that HAMLET activates a non-selective cation current, which reached a magnitude of 2.74±0.88 nA within 1.43±0.13 min from HAMLET application. Rapid ion fluxes were essential for HAMLET-induced carcinoma cell death as inhibitors (amiloride, BaCl2), preventing the changes in free cellular Na(+) and K(+) concentrations also prevented essential steps accompanying carcinoma cell death, including changes in morphology, uptake, global transcription, and MAP kinase activation. Through global transcriptional analysis and phosphorylation arrays, a strong ion flux dependent p38 MAPK response was detected and inhibition of p38 signaling delayed HAMLET-induced death. Healthy, differentiated cells were resistant to HAMLET challenge, which was accompanied by innate immunity rather than p38-activation. The results suggest, for the first time, a unifying mechanism for the initiation of HAMLET's broad and rapid lethal effect on tumor cells. These findings are particularly significant in view of HAMLET's documented therapeutic efficacy in human studies and animal models. The results also suggest that HAMLET offers a two-tiered therapeutic approach, killing cancer cells while stimulating an innate immune response in surrounding healthy tissues.

A Molecular Determinant of Subtype-Specific Desensitization in Ionotropic Glutamate Receptors.

PubMed

Alsaloum, Matthew; Kazi, Rashek; Gan, Quan; Amin, Johansen; Wollmuth, Lonnie P

2016-03-02

AMPA and NMDA receptors are glutamate-gated ion channels that mediate fast excitatory synaptic transmission throughout the nervous system. In the continual presence of glutamate, AMPA and NMDA receptors containing the GluN2A or GluN2B subunit enter into a nonconducting, desensitized state that can impact synaptic responses and glutamate-mediated excitotoxicity. The process of desensitization is dramatically different between subtypes, but the basis for these differences is unknown. We generated an extensive sequence alignment of ionotropic glutamate receptors (iGluRs) from diverse animal phyla and identified a highly conserved motif, which we termed the "hydrophobic box," located at the extracellular interface of transmembrane helices. A single position in the hydrophobic box differed between mammalian AMPA and NMDA receptors. Surprisingly, we find that an NMDAR-to-AMPAR exchange mutation at this position in the rat GluN2A or GluN2B subunit had a dramatic and highly specific effect on NMDAR desensitization, making it AMPAR-like. In contrast, a reverse exchange mutation in AMPARs had minimal effects on desensitization. These experiments highlight differences in desensitization between iGluR subtypes and the highly specific contribution of the GluN2 subunit to this process. Rapid communication between cells in the nervous system depends on ion channels that are directly activated by neurotransmitter molecules. Here, we studied ionotropic glutamate receptors (iGluRs), which are ion channels activated by the neurotransmitter glutamate. By comparing the sequences of a vast number of iGluR proteins from diverse animal species, assisted by available structural information, we identified a highly conserved motif. We showed that a single amino acid difference in this motif between mammalian iGluR subtypes has dramatic effects on receptor function. These results have implications in both the evolution of synaptic function, as well as the role of iGluRs in health and disease. Copyright © 2016 the authors 0270-6474/16/362617-06$15.00/0.

ETD in a traveling wave ion guide at tuned Z-spray ion source conditions allows for site-specific hydrogen/deuterium exchange measurements.

PubMed

Rand, Kasper D; Pringle, Steven D; Morris, Michael; Engen, John R; Brown, Jeffery M

2011-10-01

The recent application of electron transfer dissociation (ETD) to measure the hydrogen exchange of proteins in solution at single-residue resolution (HX-ETD) paves the way for mass spectrometry-based analyses of biomolecular structure at an unprecedented level of detail. The approach requires that activation of polypeptide ions prior to ETD is minimal so as to prevent undesirable gas-phase randomization of the deuterium label from solution (i.e., hydrogen scrambling). Here we explore the use of ETD in a traveling wave ion guide of a quadrupole-time-of-flight (Q-TOF) mass spectrometer with a "Z-spray" type ion source, to measure the deuterium content of individual residues in peptides. We systematically identify key parameters of the Z-spray ion source that contribute to collisional activation and define conditions that allow ETD experiments to be performed in the traveling wave ion guide without gas-phase hydrogen scrambling. We show that ETD and supplemental collisional activation in a subsequent traveling wave ion guide allows for improved extraction of residue-specific deuterium contents in peptides with low charge. Our results demonstrate the feasibility, and illustrate the advantages of performing HX-ETD experiments on a high-resolution Q-TOF instrument equipped with traveling wave ion guides. Determination of parameters of the Z-spray ion source that contribute to ion heating are similarly pertinent to a growing number of MS applications that also rely on an energetically gentle transfer of ions into the gas-phase, such as the analysis of biomolecular structure by native mass spectrometry in combination with gas-phase ion-ion/ion-neutral reactions or ion mobility spectrometry. © American Society for Mass Spectrometry, 2011

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

Faraby, H.; DiBattista, M.; Bandaru, P. R., E-mail: pbandaru@ucsd.edu

The electrical impedance (both the resistive and capacitive aspects) of focused ion beam (FIB) deposited SiO{sub 2} has been correlated to the specific composition of the ion beam, in Ga- and Xe-based FIB systems. The presence of electrically percolating Ga in concert with carbon (inevitably found as the product of the hydrocarbon precursor decomposition) has been isolated as a major cause for the observed decrease in the resistivity of the deposited SiO{sub 2}. Concomitant with the decreased resistivity, an increased capacitance and effective dielectric constant was observed. Our study would be useful to understand the constraints to the deposition ofmore » high quality insulator films through FIB based methodologies.« less

An alternate approach to the production of radioisotopes for nuclear medicine applications

NASA Astrophysics Data System (ADS)

D'Auria, John M.; Keller, Roderich; Ladouceur, Keith; Lapi, Suzanne E.; Ruth, Thomas J.; Schmor, Paul

2013-03-01

There is a growing need for the production of radioisotopes for both diagnostic and therapeutic medical applications. Radioisotopes that are produced using the (n,γ) or (γ,n) reactions, however, typically result in samples with low specific activity (radioactivity/gram) due to the high abundance of target material of the same element. One method to effectively remove the isotopic impurity is electro-magnetic mass separation. An Ion Source Test Facility has been constructed at TRIUMF to develop high-intensity, high-efficiency, reliable ion sources for purification of radioactive isotopes, particularly those used in nuclear medicine. In progress studies are presented.

An alternate approach to the production of radioisotopes for nuclear medicine applications.

PubMed

D'Auria, John M; Keller, Roderich; Ladouceur, Keith; Lapi, Suzanne E; Ruth, Thomas J; Schmor, Paul

2013-03-01

There is a growing need for the production of radioisotopes for both diagnostic and therapeutic medical applications. Radioisotopes that are produced using the (n,γ) or (γ,n) reactions, however, typically result in samples with low specific activity (radioactivity∕gram) due to the high abundance of target material of the same element. One method to effectively remove the isotopic impurity is electro-magnetic mass separation. An Ion Source Test Facility has been constructed at TRIUMF to develop high-intensity, high-efficiency, reliable ion sources for purification of radioactive isotopes, particularly those used in nuclear medicine. In progress studies are presented.

Electrodeposition of high-density lithium vanadate nanowires for lithium-ion battery

NASA Astrophysics Data System (ADS)

Hua, Kang; Li, Xiujuan; Fang, Dong; Yi, Jianhong; Bao, Rui; Luo, Zhiping

2018-07-01

Lithium vanadate nanowires have been electrodeposited onto a titanium (Ti) foil by a direct current electrodeposition without template. The morphology, crystal structure, and the effects of deposition voltage, temperature and time on the prepared samples were tested and presented. The as-prepared lithium vanadate nanowires/Ti composite can be used as electrode for lithium-ion battery. Electrochemical measurements showed that the electrode displayed a specific discharge capacitance as high as 235.1 mAh g-1 after 100 cycles at a current density of 30 mA g-1. This research provides a new pathway to explore high tap density vanadates nanowires on metals with enhanced electrochemical performance.

Full color modulation of firefly luciferase through engineering with unified Stark effect.

PubMed

Cai, Duanjun; Marques, Miguel A L; Nogueira, Fernando

2013-11-07

The firefly luciferase has been a unique marking tool used in various bioimaging techniques. Extensive color modulation is strongly required to meet special marking demands; however, intentional and accurate wavelength tuning has yet to be achieved. Here, we demonstrate that the color shift of the firefly chromophore (OxyLH2-1) by internal and external fields can be described as a unified Stark shift. Electrostatic microenvironmental effects on fluorescent spectroscopy are modeled in vacuo through effective electric fields by using time-dependent density functional theory. A complete visible fluorescence spectrum of firefly chromophore is depicted, which enables one to control the emission in a specific color. As an application, the widely observed pH-correlated color shift is proved to be associated with the local Stark field generated by the trace water-ions (vicinal hydronium and hydroxide ions) at active sites close to the OxyLH2-1.

Virus-Inspired Nanogenes Free from Man-Made Materials for Host-Specific Transfection and Bio-Aided MR Imaging.

PubMed

Zhu, Jing-Yi; Zhang, Ming-Kang; Ding, Xian-Guang; Qiu, Wen-Xiu; Yu, Wu-Yang; Feng, Jun; Zhang, Xian-Zheng

2018-05-01

Many viruses have a lipid envelope derived from the host cell membrane that contributes much to the host specificity and the cellular invasion. This study puts forward a virus-inspired technology that allows targeted genetic delivery free from man-made materials. Genetic therapeutics, metal ions, and biologically derived cell membranes are nanointegrated. Vulnerable genetic therapeutics contained in the formed "nanogene" can be well protected from unwanted attacks by blood components and enzymes. The surface envelope composed of cancer cell membrane fragments enables host-specific targeting of the nanogene to the source cancer cells and homologous tumors while effectively inhibiting recognition by macrophages. High transfection efficiency highlights the potential of this technology for practical applications. Another unique merit of this technology arises from the facile combination of special biofunction of metal ions with genetic therapy. Typically, Gd(III)-involved nanogene generates a much higher T 1 relaxation rate than the clinically used Gd magnetic resonance imaging agent and harvests the enhanced MRI contrast at tumors. This virus-inspired technology points out a distinctive new avenue for the disease-specific transport of genetic therapeutics and other biomacromolecules. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biological effects of mixed-ion beams. Part 1: Effect of irradiation of the CHO-K1 cells with a mixed-ion beam containing the carbon and oxygen ions.

PubMed

Czub, Joanna; Banaś, Dariusz; Braziewicz, Janusz; Buraczewska, Iwona; Jaskóła, Marian; Kaźmierczak, Urszula; Korman, Andrzej; Lankoff, Anna; Lisowska, Halina; Szefliński, Zygmunt; Wojewódzka, Maria; Wójcik, Andrzej

2018-05-30

Carbon and oxygen ions were accelerated simultaneously to estimate the effect of irradiation of living cells with the two different ions. This mixed ion beam was used to irradiate the CHO-K1 cells, and a survival test was performed. The type of the effect of the mixed ion beam on the cells was determined with the isobologram method, whereby survival curves for irradiations with individual ion beams were also used. An additive effect of irradiation with the two ions was found. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sterol Regulation of Voltage-Gated K+ Channels.

PubMed

Balajthy, Andras; Hajdu, Peter; Panyi, Gyorgy; Varga, Zoltan

2017-01-01

Cholesterol is an essential lipid building block of the cellular plasma membrane. In addition to its structural role, it regulates the fluidity and raft structure of the membrane and influences the course of numerous membrane-linked signaling pathways and the function of transmembrane proteins, including ion channels. This is supported by a vast body of scientific data, which demonstrates the modulation of ion channels with a great variety of ion selectivity, gating, and tissue distribution by changes in membrane cholesterol. Here, we review what is currently known about the modulation of voltage-gated K + (Kv) channels by changes in membrane cholesterol content, considering raft association of the channels, the roles of cholesterol recognition sites, and those of adaptor proteins in cholesterol-Kv channel interactions. We specifically focus on Kv1.3, the dominant K + channel of human T cells. Effects of cholesterol depletion and enrichment and 7-dehydrocholesterol enrichment on Kv1.3 gating are discussed in the context of the immunological synapse and the comparison of the in vitro effects of sterol modifications on Kv1.3 function with ex vivo effects on cells from hypercholesterolemic and Smith-Lemli-Opitz patients. © 2017 Elsevier Inc. All rights reserved.

TBI server: a web server for predicting ion effects in RNA folding.

PubMed

Zhu, Yuhong; He, Zhaojian; Chen, Shi-Jie

2015-01-01

Metal ions play a critical role in the stabilization of RNA structures. Therefore, accurate prediction of the ion effects in RNA folding can have a far-reaching impact on our understanding of RNA structure and function. Multivalent ions, especially Mg²⁺, are essential for RNA tertiary structure formation. These ions can possibly become strongly correlated in the close vicinity of RNA surface. Most of the currently available software packages, which have widespread success in predicting ion effects in biomolecular systems, however, do not explicitly account for the ion correlation effect. Therefore, it is important to develop a software package/web server for the prediction of ion electrostatics in RNA folding by including ion correlation effects. The TBI web server http://rna.physics.missouri.edu/tbi_index.html provides predictions for the total electrostatic free energy, the different free energy components, and the mean number and the most probable distributions of the bound ions. A novel feature of the TBI server is its ability to account for ion correlation and ion distribution fluctuation effects. By accounting for the ion correlation and fluctuation effects, the TBI server is a unique online tool for computing ion-mediated electrostatic properties for given RNA structures. The results can provide important data for in-depth analysis for ion effects in RNA folding including the ion-dependence of folding stability, ion uptake in the folding process, and the interplay between the different energetic components.

Electrolytes with Improved Safety Characteristics for High Voltage, High Specific Energy Li-ion Cells

NASA Technical Reports Server (NTRS)

Smart, M. C.; Krause, F. C.; Hwang, C.; West, W. C.; Soler, J.; Whitcanack, L. W.; Prakash, G. K. S.; Ratnakumar, B. V.

2012-01-01

(1) NASA is actively pursuing the development of advanced electrochemical energy storage and conversion devices for future lunar and Mars missions; (2) The Exploration Technology Development Program, Energy Storage Project is sponsoring the development of advanced Li-ion batteries and PEM fuel cell and regenerative fuel cell systems for the Altair Lunar Lander, Extravehicular Activities (EVA), and rovers and as the primary energy storage system for Lunar Surface Systems; (3) At JPL, in collaboration with NASA-GRC, NASA-JSC and industry, we are actively developing advanced Li-ion batteries with improved specific energy, energy density and safety. One effort is focused upon developing Li-ion battery electrolyte with enhanced safety characteristics (i.e., low flammability); and (4) A number of commercial applications also require Li-ion batteries with enhanced safety, especially for automotive applications.

Ion thruster project

NASA Technical Reports Server (NTRS)

Perche, G. E.

1984-01-01

The mercury bombardment electrostatic ion thruster is the most successful electric thruster available today. A 5 cm diameter ion thruster with 3,000 specific impulse and 5mN thrust is described. The advantages of electric propulsion and the tests that will be performed are also presented.

Explanation by the double-metal-ion mechanism of catalysis for the differential metal ion effects on the cleavage rates of 5′-oxy and 5′-thio substrates by a hammerhead ribozyme

PubMed Central

Zhou, De-Min; Zhang, Li-He; Taira, Kazunari

1997-01-01

In a previous examination using natural all-RNA substrates that contained either a 5′-oxy or 5′-thio leaving group at the cleavage site, we demonstrated that (i) the attack by the 2′-oxygen at C17 on the phosphorus atom is the rate-limiting step only for the substrate that contains a 5′-thio group (R11S) and (ii) the departure of the 5′ leaving group is the rate-limiting step for the natural all-RNA substrate (R11O) in both nonenzymatic and hammerhead ribozyme-catalyzed reactions; the energy diagrams for these reactions were provided in our previous publication. In this report we found that the rate of cleavage of R11O by a hammerhead ribozyme was enhanced 14-fold when Mg2+ ions were replaced by Mn2+ ions, whereas the rate of cleavage of R11S was enhanced only 2.2-fold when Mg2+ ions were replaced by Mn2+ ions. This result appears to be exactly the opposite of that predicted from the direct coordination of the metal ion with the leaving 5′-oxygen, because a switch in metal ion specificity was not observed with the 5′-thio substrate. However, our quantitative analyses based on the previously provided energy diagram indicate that this result is in accord with the double-metal-ion mechanism of catalysis. PMID:9405614

Hyperthermal (1-100 eV) nitrogen ion scattering damage to D-ribose and 2-deoxy-D-ribose films

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

Deng Zongwu; Bald, Ilko; Illenberger, Eugen

2007-10-14

Highly charged heavy ion traversal of a biological medium can produce energetic secondary fragment ions. These fragment ions can in turn cause collisional and reactive scattering damage to DNA. Here we report hyperthermal (1-100 eV) scattering of one such fragment ion (N{sup +}) from biologically relevant sugar molecules D-ribose and 2-deoxy-D-ribose condensed on polycrystalline Pt substrate. The results indicate that N{sup +} ion scattering at kinetic energies down to 10 eV induces effective decomposition of both sugar molecules and leads to the desorption of abundant cation and anion fragments. Use of isotope-labeled molecules (5-{sup 13}C D-ribose and 1-D D-ribose) partlymore » reveals some site specificity of the fragment origin. Several scattering reactions are also observed. Both ionic and neutral nitrogen atoms abstract carbon from the molecules to form CN{sup -} anion at energies down to {approx}5 eV. N{sup +} ions also abstract hydrogen from hydroxyl groups of the molecules to form NH{sup -} and NH{sub 2}{sup -} anions. A fraction of O/O{sup -} fragments abstract hydrogen to form OH{sup -}. The formation of H{sub 3}O{sup +} ions also involves hydrogen abstraction as well as intramolecular proton transfer. These findings suggest a variety of severe damaging pathways to DNA molecules which occur on the picosecond time scale following heavy ion irradiation of a cell, and prior to the late diffusion-limited homogeneous chemical processes.« less

Influence of Ionization Source Conditions on the Gas-Phase Protomer Distribution of Anilinium and Related Cations

NASA Astrophysics Data System (ADS)

Attygalle, Athula B.; Xia, Hanxue; Pavlov, Julius

2017-08-01

The gas-phase-ion generation technique and specific ion-source settings of a mass spectrometer influence heavily the protonation processes of molecules and the abundance ratio of the generated protomers. Hitherto that has been attributed primarily to the nature of the solvent and the pH. By utilizing electrospray ionization and ion-mobility mass spectrometry (IM-MS), we demonstrate, even in the seemingly trivial case of protonated aniline, that the protomer ratio strongly depends on the source conditions. Under low in-source ion activation, nearly 100% of the N-protomer of aniline is produced, and it can be subsequently converted to the C-protomer by collisional activation effected by increasing the electrical potential difference between the entrance and exit orifices of the first vacuum region. This activation and transformation process takes place even before the ion is mass-selected and subjected to IM separation. Despite the apparent simplicity of the problem, the preferred protonation site of aniline in the gas phase—the amino group or the aromatic ring—has been a topic of controversy. Our results not only provide unambiguous evidence that ring- and nitrogen-protonated aniline can coexist and be interconverted in the gas phase, but also that the ratio of the protomers depends on the internal energy of the original ion. There are many dynamic ion-transformation and fragmentation processes that take place in the different physical compartments of a Synapt G2 HDMS instrument. Such processes can dramatically change the very identity even of small ions, and therefore should be taken into account when interpreting product-ion mass spectra.

A rhodamine-based 'turn-on' Al³⁺ ion-selective reporter and the resultant complex as a secondary sensor for F⁻ ion are applicable to living cell staining.

PubMed

Sen, Buddhadeb; Mukherjee, Manjira; Banerjee, Samya; Pal, Siddhartha; Chattopadhyay, Pabitra

2015-05-14

A newly designed fluorescent aluminum(III) complex (L'-Al; 2) of a structurally characterized non-fluorescent rhodamine Schiff base (L) has been isolated in pure form and characterized using spectroscopic and physico-chemical methods with theoretical density functional theory (DFT) support. On addition of Al(III) ions to a solution of L in HEPES buffer (1 mM, pH 7.4; EtOH-water, 1 : 3 v/v) at 25 °C, the systematic increase in chelation-enhanced fluorescence (CHEF) enables the detection of Al(III) ions as low as 60 nM with high selectivity, unaffected by the presence of competitive ions. Interestingly, the Al(III) complex (L'-Al; 2) is specifically able to detect fluoride ions by quenching the fluorescence in the presence of large amounts of other anions in the HEPES buffer (1 mM, pH 7.4) at 25 °C. On the basis of our experimental and theoretical findings, the addition of Al(3+) ions to a solution of L helps to generate a new fluorescence peak at 590 nm, due to the selective binding of Al(3+) ions with L in a 1 : 1 ratio with a binding constant (K) of 8.13 × 10(4) M(-1). The Schiff base L shows no cytotoxic effect, and it can therefore be employed for determining the intracellular concentration of Al(3+) and F(-) ions by 2 in living cells using fluorescence microscopy.

Selective complexation of K+ and Na+ in simple polarizable ion-ligating systems.

PubMed

Bostick, David L; Brooks, Charles L

2010-09-29

An influx of experimental and theoretical studies of ion transport protein structure has inspired efforts to understand underlying determinants of ionic selectivity. Design principles for selective ion binding can be effectively isolated and interrogated using simplified models composed of a single ion surrounded by a set of ion-ligating molecular species. While quantum mechanical treatments of such systems naturally incorporate electronic degrees of freedom, their computational overhead typically prohibits thorough dynamic sampling of configurational space and, thus, requires approximations when determining ion-selective free energy. As an alternative, we employ dynamical simulations with a polarizable force field to probe the structure and K(+)/Na(+) selectivity in simple models composed of one central K(+)/Na(+) ion surrounded by 0-8 identical model compounds: N-methylacetamide, formamide, or water. In the absence of external restraints, these models represent gas-phase clusters displaying relaxed coordination structures with low coordination number. Such systems display Na(+) selectivity when composed of more than ∼3 organic carbonyl-containing compounds and always display K(+) selectivity when composed of water molecules. Upon imposing restraints that solely enforce specific coordination numbers, we find all models are K(+)-selective when ∼7-8-fold ion coordination is achieved. However, when models composed of the organic compounds provide ∼4-6-fold coordination, they retain their Na(+) selectivity. From these trends, design principles emerge that are of basic importance in the behavior of K(+) channel selectivity filters and suggest a basis not only for K(+) selectivity but also for modulation of block and closure by smaller ions.

Elucidation of reaction mechanisms of Ni2SnP in Li-ion and Na-ion systems

NASA Astrophysics Data System (ADS)

Marino, C.; Dupré, N.; Villevieille, C.

2017-10-01

Electrochemical performance of Ni2SnP was assessed in Li-ion and Na-ion battery systems. When cycled versus Li, Ni2SnP exhibited a reversible specific charge of 700 mAh.g-1 (theoretical specific charge: 742 mAh.g-1). In the Na system, the specific observed charge was ca. 200 mAh.g-1 (theoretical specific charge: 676 mAh.g-1). X-ray diffraction, Ni K-edge X-ray absorption spectroscopy, and 31P and 7Li/23Na nuclear magnetic resonance spectroscopy were used to elucidate the electrochemical mechanisms in both systems. Versus Li, Ni2SnP undergoes a conversion reaction resulting in the extrusion of Ni and the alloying of Li-Sn and Li-P. On delithiation, the material partially recombines into a Sn- and Ni-deficient form. In the Na system, Ni2SnP reacts through the conversion of P into Na3P. These results indicate that the recombination of the pristine material (even partially) increases cycling stability.

Characterization of advanced electric propulsion systems

NASA Technical Reports Server (NTRS)

Ray, P. K.

1982-01-01

Characteristics of several advanced electric propulsion systems are evaluated and compared. The propulsion systems studied are mass driver, rail gun, MPD thruster, hydrogen free radical thruster and mercury electron bombardment ion engine. These are characterized by specific impulse, overall efficiency, input power, average thrust, power to average thrust ratio and average thrust to dry weight ratio. Several important physical characteristics such as dry system mass, accelerator length, bore size and current pulse requirement are also evaluated in appropriate cases. Only the ion engine can operate at a specific impulse beyond 2000 sec. Rail gun, MPD thruster and free radical thruster are currently characterized by low efficiencies. Mass drivers have the best performance characteristics in terms of overall efficiency, power to average thrust ratio and average thrust to dry weight ratio. But, they can only operate at low specific impulses due to large power requirements and are extremely long due to limitations of driving current. Mercury ion engines have the next best performance characteristics while operating at higher specific impulses. It is concluded that, overall, ion engines have somewhat better characteristics as compared to the other electric propulsion systems.

Destabilization of Titania Nanosheet Suspensions by Inorganic Salts: Hofmeister Series and Schulze-Hardy Rule.

PubMed

Rouster, Paul; Pavlovic, Marko; Szilagyi, Istvan

2017-07-13

Ion specific effects on colloidal stability of titania nanosheets (TNS) were investigated in aqueous suspensions. The charge of the particles was varied by the pH of the solutions, therefore, the influence of mono- and multivalent anions on the charging and aggregation behavior could be studied when they were present either as counter or co-ions in the systems. The aggregation processes in the presence of inorganic salts were mainly driven by interparticle forces of electrostatic origin, however, chemical interactions between more complex ions and the surface led to additional attractive forces. The adsorption of anions significantly changed the surface charge properties and hence, the resistance of the TNS against salt-induced aggregation. On the basis of their ability in destabilization of the dispersions, the monovalent ions could be ordered according to the Hofmeister series in acidic solutions, where they act as counterions. However, the behavior of the biphosphate anion was atypical and its adsorption induced charge reversal of the particles. The multivalent anions destabilized the oppositely charged TNS more effectively and the aggregation processes followed the Schulze-Hardy rule. Only weak or negligible interactions were observed between the anions and the particles in alkaline suspensions, where the TNS possessed negative charge.

Effect of Pore Clogging on Kinetics of Lead Uptake by Clinoptilolite.

PubMed

Inglezakis; Diamandis; Loizidou; Grigoropoulou

1999-07-01

The kinetics of lead-sodium ion exchange using pretreated natural clinoptilolite are investigated, more specifically the influence of agitation (0, 210, and 650 rpm) on the limiting step of the overall process, for particle sizes of 0.63-0.8 and 0.8-1 mm at ambient temperature and initial lead solutions of 500 mg l-1 without pH adjustment. The isotopic exchange model is found to fit the ion exchange process. Particle diffusion is shown to be the controlling step for both particle sizes under agitation, while in the absence of agitation film diffusion is shown to control. The ion exchange process effective diffusion coefficients are calculated and found to depend strongly on particle size in the case of agitation at 210 rpm and only slightly on particle size at 650 rpm. Lead uptake rates are higher for smaller particles only at rigorous agitation, while at mild agitation the results are reversed. These facts are due to partial clogging of the pores of the mineral during the grinding process. This is verified through comparison of lead uptake rates for two samples of the same particle size, one of which is rigorously washed for a certain time before being exposed to the ion exchange. Copyright 1999 Academic Press.

Tunicate-Inspired Gallic Acid/Metal Ion Complex for Instant and Efficient Treatment of Dentin Hypersensitivity.

PubMed

Prajatelistia, Ekavianty; Ju, Sung-Won; Sanandiya, Naresh D; Jun, Sang Ho; Ahn, Jin-Soo; Hwang, Dong Soo

2016-04-20

Dentin hypersensitivity is sharp and unpleasant pains caused by exposed dentinal tubules when enamel outside of the tooth wears away. The occlusion of dentinal tubules via in situ remineralization of hydroxyapatite is the best method to alleviate the symptoms caused by dentin hypersensitivity. Commercially available dental desensitizers are generally effective only on a specific area and are relatively toxic, and their performance usually depends on the skill of the clinician. Here, a facile and efficient dentin hypersensitivity treatment with remarkable aesthetic improvement inspired by the tunicate-self-healing process is reported. As pyrogallol groups in tunicate proteins conjugate with metal ions to heal the torn body armor of a tunicate, the ingenious mechanism by introducing gallic acid (GA) as a cheap, abundant, and edible alternative to the pyrogallol groups of the tunicate combined with a varied daily intake of metal ion sources is mimicked. In particular, the GA/Fe(3+) complex exhibits the most promising results, to the instant ≈52% blockage in tubules within 4 min and ≈87% after 7 d of immersion in artificial saliva. Overall, the GA/metal ion complex-mediated coating is facile, instant, and effective, and is suggested as an aesthetic solution for treating dentin hypersensitivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transition metal ion capture using functional mesoporous carbon made with 1,10-phenanthroline

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

Chouyyok, Wilaiwan; Yantasee, Wassana; Shin, Yongsoon

2009-11-01

Functional mesoporous carbon has been built using 1,10-phenanthroline as the fundamental building block, resulting in a nanoporous, high surface area sorbent capable of selectively binding transition metal ions. This material had a specific surface area of 870 m2/g, an average pore size of about 30Å, and contained as much as 8.2 weight percent N. Under acidic conditions, where the 1,10-phenanthroline ligand is protonated, this material was found to be an effective anion exchange material for transition metal anions like PdCl4-2 and H2VO4-1. 1,10-phenanthroline functionalized mesoporous carbon (“Phen-FMC”) was found to have a high affinity for Cu(II), even down to amore » pH of 1. At pHs above 5, Phen-FMC was found to bind a variety of transition metal cations (e.g. Co(II), Ni(II), Zn(II), etc.) from filtered ground water, river water and seawater. Phen-FMC displayed rapid sorption kinetics with Co(II) in filtered river water, reaching equilibrium in less than an hour, and easily lowering the [Co(II)] to sub-ppb levels. Phen-FMC was found to be more effective for transition metal ion capture than ion exchange resin or activated carbon.« less

Effect of charge on the conformation of highly basic peptides including the tail regions of histone proteins by ion mobility mass spectrometry.

PubMed

Akashi, Satoko; Downard, Kevin M

2016-09-01

The first systematic and comprehensive study of the charging behaviour and effect of charge on the conformation of specifically constructed arginine-rich peptides and its significance to the N- and C-terminal basic tail regions of histone proteins was conducted using ion mobility mass spectrometry (IM-MS). Among the basic amino acids, arginine has the greatest impact on the charging behaviour and structures of gas phase ions by virtue of its high proton affinity. A close linear correlation was found between either the maximum charge, or most abundant charge state, that the peptides support and their average collision cross section (CCS) values measured by ion mobility mass spectrometry. The calculated collision cross sections for the lowest energy solution state models predicted by the PEP-FOLD algorithm using a modified MOBCAL trajectory method were found to best correlate with the values measured by IM-MS. In the case of the histone peptides, more compact folded structures, supporting less than the maximum number of charges, were observed. These results are consistent with those previously reported for histone dimers where neutralization of the charge at the basic residues of the tail regions did not affect their CCS values.

Specific interactions versus counterion condensation. 2. Theoretical treatment within the counterion condensation theory.

PubMed

Donati, Ivan; Benegas, Julio C; Cesàro, Attilio; Paoletti, Sergio

2006-05-01

Polyuronates such as pectate and alginate are very well-known examples of biological polyelectrolytes undergoing, upon addition of divalent cations, an interchain association that acts as the junction of an eventually formed stable hydrogel. In the present paper, a thermodynamic model based on the counterion condensation theory has been developed to account for this cation-induced chain pairing of negatively charged polyelectrolytes. The strong interactions between cross-linking ions and uronate moieties in the specific binding site have been described in terms of chemical bonding, with complete charge annihilation between the two species. The chain-pairing process is depicted as progressively increasing with the concentration of cross-linking counterions and is thermodynamically defined by the fraction of each species. On these bases, the total Gibbs energy of the system has been expressed as the sum of the contributions of the Gibbs energy of the (single) chain stretches and of the (associated) dimers, weighted by their respective fractions 1 - theta and theta. In addition, the model assumes that the condensed divalent counterions exhibit an affinity free-energy for the chain, G(C)(aff,0), and the junction, G(D)(aff,0), respectively. Moreover, a specific Gibbs energy of chemical bonding, G(bond,0), has been introduced as the driving force for the formation of dimers. The model provides the mathematical formalism for calculating the fraction, theta, of chain dimers formed and the amount of ions condensed and bound onto the polyelectrolyte when two different types of counterions (of equal or different valence) are present. The effect of the parameter G(bond,0) has been investigated and, in particular, its difference from G(C,D)(aff,0) was found to be crucial in determining the distribution of the ions into territorial condensation and chemical bonding, respectively. Finally, the effect of the variation of the molar ratio between cross-linking ions and uronic groups in the specific binding sites, sigma0, was evaluated. In particular, a remarkable decrease in the amount of condensed counterions has been pointed out in the case of sigma0 = 1/3, with respect to the value of sigma0 = 1/4, characterizing the traditional "egg-box" structure, as a result of the drop of the charge density of the polyelectrolyte induced by complete charge annihilation.

Enhancing glycan isomer separations with metal ions and positive and negative polarity ion mobility spectrometry-mass spectrometry analyses

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

Zheng, Xueyun; Zhang, Xing; Schocker, Nathaniel S.

Glycomics has become an increasingly important field of research since glycans play critical roles in biology processes ranging from molecular recognition and signaling to cellular communication. Glycans often conjugate with other biomolecules such as proteins and lipids, and alter their properties and functions, so understanding the effect glycans have on cellular systems is essential. However the analysis of glycans is extremely difficult due to their complexity and structural diversity (i.e., the number and identity of monomer units, and configuration of their glycosidic linkages and connectivities). In this work, we coupled ion mobility spectrometry with mass spectrometry (IMS-MS) to characterize glycanmore » standards and biologically important isomers of synthetic αGal-containing O-glycans including glycotopes of the protozoan parasite Trypanosoma cruzi, which is the causative agent of Chagas disease. IMS-MS results showed significant differences for the glycan structural isomers when analyzed in positive and negative polarity and complexed with different metal cations. These results suggest specific metal ions or ion polarities could be used to target and baseline separate glycan isomers of interest with IMS-MS.« less

Radiative, nonradiative, and mixed-decay transitions of rare-earth ions in dielectric media

NASA Astrophysics Data System (ADS)

Burshtein, Zeev

2010-09-01

We present and discuss in a comprehensive, deductive, and simplified manner, issues of nonradiative transitions involvement in fluorescence of ions embedded in dielectric solid matrices. The semiclassical approach is favored over a full quantum description, and empiric quantities are introduced from the start. One issue is nonradiative single-phonon transitions when the energy gap between the adjacent electronic ion states is smaller than the cutoff matrix phonon energy. Another issue is transitions in a complex energy scheme, where some visible and near-visible transitions are radiative and others are nonradiative. A refined Füchtbauer-Ladenburg recipe for calculation of the stimulated emission spectrum on the basis of measurable absorption and fluorescence emission spectra is worked out. The last issue is multiphonon nonradiative transitions occurring when the energy gap between adjacent electronic ion states is larger than the cutoff matrix phonon energy. Transition probabilities were calculated on the basis of anharmonicity of the effective potential supporting the internal atomic basis vibrations. An expression in a closed form is obtained, similar to the empiric ``energy gap'' law, however, with parameters related to specific host material properties and the actual transition in the ion. Comparison to existing experimental evidence is presented and discussed in detail.

Chemistry of Marine Ligands and Siderophores

PubMed Central

Vraspir, Julia M.; Butler, Alison

2011-01-01

Marine microorganisms are presented with unique challenges to obtain essential metal ions required to survive and thrive in the ocean. The production of organic ligands to complex transition metal ions is one strategy to both facilitate uptake of specific metals, such as iron, and to mitigate the potential toxic effects of other metal ions, such as copper. A number of important trace metal ions are complexed by organic ligands in seawater, including iron, cobalt, nickel, copper, zinc, and cadmium, thus defining the speciation of these metal ions in the ocean. In the case of iron, siderophores have been identified and structurally characterized. Siderophores are low molecular weight iron-binding ligands produced by marine bacteria. Although progress has been made toward the identity of in situ iron-binding ligands, few compounds have been identified that coordinate the other trace metals. Deciphering the chemical structures and production stimuli of naturally produced organic ligands and the organisms they come from is fundamental to understanding metal speciation and bioavailability. The current evidence for marine ligands, with an emphasis on siderophores, and discussion of the importance and implications of metal-binding ligands in controlling metal speciation and cycling within the world’s oceans are presented. PMID:21141029

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

PubMed

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.

Space charge effect in spectrometers of ion mobility increment with planar drift chamber.

PubMed

Elistratov, A A; Sherbakov, L A

2007-01-01

The effect of space charge on the ion beam in a spectrometer of ion mobility increment with the planar drift chamber has been investigated. A model for the drift of ions under a non-uniform high-frequency electric field(1-3) has been developed recently. We have amplified this model by taking space charge effect into account. The ion peak shape taking into consideration the space charge effect is obtained. The output current saturation effect limiting the rise of the ion peak with increasing ion density at the input of the drift chamber of a spectrometer is observed. We show that the saturation effect is caused by the following phenomenon. The maximum possible output ion density exists, depending on the ion type (constant ion mobility, k(0)) and the time of the motion of ions through the drift chamber. At the same time, the ion density does not depend on the parameters of the drift chamber.

Development of ultralow energy (1–10 eV) ion scattering spectrometry coupled with reflection absorption infrared spectroscopy and temperature programmed desorption for the investigation of molecular solids

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

Bag, Soumabha; Bhuin, Radha Gobinda; Methikkalam, Rabin Rajan J.

2014-01-15

Extremely surface specific information, limited to the first atomic layer of molecular surfaces, is essential to understand the chemistry and physics in upper atmospheric and interstellar environments. Ultra low energy ion scattering in the 1–10 eV window with mass selected ions can reveal extremely surface specific information which when coupled with reflection absorption infrared (RAIR) and temperature programmed desorption (TPD) spectroscopies, diverse chemical and physical properties of molecular species at surfaces could be derived. These experiments have to be performed at cryogenic temperatures and at ultra high vacuum conditions without the possibility of collisions of neutrals and background deposition inmore » view of the poor ion intensities and consequent need for longer exposure times. Here we combine a highly optimized low energy ion optical system designed for such studies coupled with RAIR and TPD and its initial characterization. Despite the ultralow collision energies and long ion path lengths employed, the ion intensities at 1 eV have been significant to collect a scattered ion spectrum of 1000 counts/s for mass selected CH{sub 2}{sup +}.« less

Inner-shell photodetachment of transition metal negative ions

NASA Astrophysics Data System (ADS)

Dumitriu, Ileana

This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe- and Ru- . Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy. Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell. Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe- and Ru -. In the case of Fe-, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48--72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru- was measured over 30--90 eV photon energy range The absolute photodetachment cross sections of Ru - ([Kr] 4d75s 2) leading to Ru+, Ru2+, and Ru 3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4 p-electrons to the quasi-bound 4p54d85s 2 states and the 4d→epsilonf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru- than in Fe- photodetachment.

Novel hybrid isotope separation scheme and apparatus

DOEpatents

Maya, J.

1991-06-18

A method is described for yielding selectively a desired enrichment in a specific isotope including the steps of inputting into a spinning chamber a gas from which the specific isotope is to be isolated, radiating the gas with frequencies characteristic of the absorption of a particular isotope of the atomic or molecular gas, thereby inducing a photoionization reaction of the desired isotope, and collecting the specific isotope ion by suitable ion collection means. 3 figures.

Delay Tolerant Networking on NASA's Space Communication and Navigation Testbed

NASA Technical Reports Server (NTRS)

Johnson, Sandra; Eddy, Wesley

2016-01-01

This presentation covers the status of the implementation of an open source software that implements the specifications developed by the CCSDS Working Group. Interplanetary Overlay Network (ION) is open source software and it implements specifications that have been developed by two international working groups through IETF and CCSDS. ION was implemented on the SCaN Testbed, a testbed located on an external pallet on ISS, by the GRC team. The presentation will cover the architecture of the system, high level implementation details, and issues porting ION to VxWorks.

Method of isotope separation by chemi-ionization

DOEpatents

Wexler, Sol; Young, Charles E.

1977-05-17

A method for separating specific isotopes present in an isotopic mixture by aerodynamically accelerating a gaseous compound to form a jet of molecules, and passing the jet through a stream of electron donor atoms whereby an electron transfer takes place, thus forming negative ions of the molecules. The molecular ions are then passed through a radiofrequency quadrupole mass filter to separate the specific isotopes. This method may be used for any compounds having a sufficiently high electron affinity to permit negative ion formation, and is especially useful for the separation of plutonium and uranium isotopes.

An Air Breathing Lithium-Oxygen Battery

NASA Astrophysics Data System (ADS)

Sayahpour, Baharak Sayah

Given that the current Li-ion battery technology is approaching theoretical specific capacity and specific energy values that are still not enough for powering satisfactorily electric vehicles or providing enough grid level storage capacities, interest in other electrochemical energy conversion and storage devices have emerged. Although systems based on multi-valent cations (Mg 2+, Zn2+, etc.) are also been studied, metal air batteries have shown the highest theoretical capacity and energy densities of any other battery chemistries. However, some fundamental challenges have hampered the applications of this class of batteries as the alternative for metal-ion batteries. In brief, the major challenges holding the metal air system from large scale applications are: (i) absence of an effective air electrode which easily transfer oxygen to the heterogenous reaction interphase for oxygen reduction and evolution reactions. (ii) electrolyte instability in large voltage windows which usually occurs because of high charge overpotentials. (iii) anode poisoning and corrosion due to oxidation or reaction with air species such as CO 2 and moisture. Given such obstacles, development of novel materials is needed to overcome these challenges in metal air batteries. In this thesis, a system comprised of a protected anode based on lithium carbonate, molybdenum disulfide cathode, and ionic liquid/dimethyl sulfoxide electrolyte is studied that work together, in presence of air components, such as Nitrogen, Carbon dioxide, and humidity, as a real Li-air battery with high cyclability performance up to 700 cycles. The combination of experimental and computational studies are used to provide insight into how this system operates in air and revealed that the long-life performance of this system is due to (i) a suppression of side reactions on the cathode side, which prevent the formation of by-products such as Li2CO 3 and LiOH, and (ii) an effective protected anode covered with a Li 2CO3 coating that effectively blocks the diffusion of the actual air components e.g., N2, CO2, and H2O and allowing only for Li ion transport. The Li-air battery developed in this work, which for the first time successfully operates in a realistic atmosphere with high cycle-life, is a promising step toward engineering the next generation of Li batteries with much higher specific energy density than Li-ion batteries.

Preliminary Tests of a Paul ion Trap as an Ion Source

NASA Astrophysics Data System (ADS)

Sadat Kiai, S. M.; Zirak, A. R.; Elahi, M.; Adlparvar, S.; Mortazavi, B. N.; Safarien, A.; Farhangi, S.; Sheibani, S.; Alhooie, S.; Khalaj, M. M. A.; Dabirzadeh, A. A.; Ruzbehani, M.; Zahedi, F.

2010-10-01

The paper reports on the design and construction of a Paul ion trap as an ion source by using an impact electron ionization technique. Ions are produced in the trap and confined for the specific time which is then extracted and detected by a Faraday cup. Especial electronic configurations are employed between the end caps, ring electrodes, electron gun and a negative voltage for the detector. This configuration allows a constant low level of pure ion source between the pulsed confined ion sources. The present experimental results are based on the production and confinement of Argon ions with good stability and repeatability, but in principle, the technique can be used for various Argon like ions.

Reactive ion etched substrates and methods of making and using

DOEpatents

Rucker, Victor C [San Francisco, CA; Shediac, Rene [Oakland, CA; Simmons, Blake A [San Francisco, CA; Havenstrite, Karen L [New York, NY

2007-08-07

Disclosed herein are substrates comprising reactive ion etched surfaces and specific binding agents immobilized thereon. The substrates may be used in methods and devices for assaying or isolating analytes in a sample. Also disclosed are methods of making the reactive ion etched surfaces.

A 2.5 kW advanced technology ion thruster

NASA Technical Reports Server (NTRS)

Poeschel, R. L.

1974-01-01

A program has been conducted in order to improve the performance characteristics of 30 cm thrusters. This program was divided into three distinct, but related tasks: (1) the discharge chamber and component design modifications proposed for inclusion in the engineering model thruster were evaluated and engineering specifications were verified; (2) thrust losses which result from the contributions of double charged ions and nonaxial ion trajectories to the ion beam current were measured and (3) the specification and verification of power processor and control requirements of the engineering model thruster design were demonstrated. Proven design modifications which provide improved efficiencies are incorporated into the engineering model thruster during a structural re-design without introducing additional delay in schedule or new risks. In addition, a considerable amount of data is generated on the relation of double ion production and beam divergence to thruster parameters. Overall thruster efficiency is increased from 68% to 71% at full power, including corrections for double ion and beam divergence thrust losses.