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Sample records for aggregates ions precipitants

  1. Precipitation Aggregation and the Local Environment

    NASA Astrophysics Data System (ADS)

    Smalley, Mark

    The details of large-scale spatial structures of precipitation have only recently become apparent with the advent of high-resolution near-global observations from space-borne radars. As such, the relationships between these structures and the local environment and global climate are just beginning to emerge in the scientific community. Precipitation aggregates on a wide variety of scales, from individual boundary layer instabilities to extra-tropical cyclones. Separate aggregation states have been associated with widely varying precipitation rates and atmospheric states, motivating the inclusion of spatial information in hydrologic and climate models. This work adds to the body of knowledge surrounding large-scale precipitation aggregation and its driving factors by describing and demonstrating a new method of defining the spatial characteristics of precipitation events. The analysis relies on the high sensitivity and high resolution of the CloudSat Cloud Profiling Radar for the identification of precipitation with near-global coverage. The method is based on the dependence of the probability of precipitation on search area, or spatial resolution. Variations in this relationship are caused by variations in the principal characteristics of event spatial patterns: the relative spacing between events, the number density of events, and the overall fraction of precipitating scenes at high resolution. Here, this relationship is modeled by a stretched exponential containing two coefficients, that are shown to depict seasonal general circulation patterns as well as local weather. NASA's Modern-Era Retrospective analysis for Research and Applications is then used to place those spatial characteristics in the context of the local and large-scale environment. At regional scale, precipitation event density during the Amazon wet season is shown to be dependent on zonal wind speed. On a global scale, the relative spacing of shallow oceanic precipitation depends on the

  2. Ion-specific aggregation of hydrophobic particles.

    PubMed

    López-León, Teresa; Ortega-Vinuesa, Juan Luis; Bastos-González, Delfina

    2012-06-18

    This work shows that colloidal stability and aggregation kinetics of hydrophobic polystyrene (PS) nanospheres are extremely sensitive to the nature of the salt used to coagulate them. Three PS latices and four aggregating electrolytes, which all share the same cation (Na(+)) but have various anions located at different positions in the classical Hofmeister series depending on their kosmotropic or chaotropic character, are used. The present study focuses on analyzing different aggregating parameters, such as critical coagulation concentrations (CCC), cluster size distributions (CSD), initial kinetic constants K(11), and fractal dimensions of the aggregates d(f). While aggregation induced by SO(4)(2-) and Cl(-) behaved according to the predictions of the classical Derjaguin-Landau-Verwey-Overbeek theory, important discrepancies are found with NO(3)(-), which become dramatic when using SCN(-). These discrepancies among the anions were far more significant when they acted as counterions rather than as co-ions. While SO(4)(2-) and Cl(-) trigger fast diffusion-limited aggregation, SCN(-) gives rise to a stationary cluster size distribution in a few aggregation times when working with cationic PS particles. Clear differences are found among all analyzed parameters (CCC, CSD, K(11), and d(f)), and the experimental findings show that particles aggregate in potential wells whose depth is controlled by the chaotropic character of the anion. This paper presents new experimental evidence that may help to understand the microscopic origin of Hofmeister effects, as the observations are consistent with appealing theoretical models developed in the last few years. PMID:22556130

  3. The Jovian aurora: Electron or ion precipitation

    NASA Technical Reports Server (NTRS)

    Waite, J. H., Jr.; Clarke, J. T.; Cravens, T. E.

    1986-01-01

    High signal-to-noise spectra of the Jovian aurora at UV wavelengths obtained using the International Ultraviolet Explorer Observatory (including the brightest Jovian aurora observed to date) set strigent upper limits for sulfur and oxygen emissions, which would be associated with the precipitation of energetic heavy ions in the upper Jovian atmosphere if they were solely responsible for Jovian auroral processes. Model calculations of heavy ion precipitation and corresponding estimates of the associated sulfur and oxygen UV emissions previously carried out suggest emission values for 1304 A OI emission that are at least 30 times larger than the upper limit values set by the IUE observations reported. On the other hand the observed (feature of SII at 1256 A of 2 kR) is quite comparable to the theoretically predicted emission intensity. Taken together these observations and calculations suggest that electron as well as ion precipitation play a role in Jovian auroral processes. In light of earlier X-ray observations and in-situ plasma observations that suggest energetic heavy ion precipitation in the Jovian auroral zone, a scenario is suggested where heavy ion auroral energy deposition is concentrated at altitudes below the homopause. Electrons with energies of 10 to 30 keV are responsible for the bulk of the observable UV and EUV emissions since they deposit their energy above the methane absorbing layer defined by the homopause.

  4. Ion aggregation in high salt solutions: Ion network versus ion cluster

    SciTech Connect

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-28

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O–D stretch mode of HDO in highly concentrated salt solutions and {sup 13}C-NMR chemical shift of S{sup 13}CN{sup −} in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  5. Ion aggregation in high salt solutions: Ion network versus ion cluster

    NASA Astrophysics Data System (ADS)

    Kim, Seongheun; Kim, Heejae; Choi, Jun-Ho; Cho, Minhaeng

    2014-09-01

    The critical aggregation phenomena are ubiquitous in many self-assembling systems. Ions in high salt solutions could also spontaneously form larger ion aggregates, but their effects on hydrogen-bond structures in water have long been controversial. Here, carrying out molecular dynamics (MD) simulation studies of high salt solutions and comparing the MD simulation results with infrared absorption and pump-probe spectroscopy of O-D stretch mode of HDO in highly concentrated salt solutions and 13C-NMR chemical shift of S13CN- in KSCN solutions, we find evidence on the onset of ion aggregate and large-scale ion-ion network formation that concomitantly breaks water hydrogen-bond structure in certain salt solutions. Despite that these experimental results cannot provide direct evidence on the three-dimensional morphological structures of ion aggregates, they serve as reference data for verifying MD simulation methods. The MD results suggest that disrupted water hydrogen-bond network is intricately intertwined with ion-ion network. This further shows morphological variation of ion aggregate structures from ion cluster to ion network in high salt solutions that are interrelated to the onset of macroscopic aggregate formation and the water hydrogen-bond structure making and breaking processes induced by Hofmeister ions.

  6. Ion aggregation in high salt solutions. V. Graph entropy analyses of ion aggregate structure and water hydrogen bonding network.

    PubMed

    Choi, Jun-Ho; Cho, Minhaeng

    2016-05-28

    Dissolved ions in water tend to form polydisperse ion aggregates such as ion pairs, relatively compact ion clusters, and even spatially extended ion networks with increasing salt concentration. Combining molecular dynamics simulation and graph theoretical analysis methods, we recently studied morphological structures of ion aggregates with distinctively different characteristics. They can be distinguished from each other by calculating various spectral graph theoretical properties such as eigenvalues and eigenvectors of adjacency matrices of ion aggregates and water hydrogen-bonding networks, minimum path lengths, clustering coefficients, and degree distributions. Here, we focus on percolation and graph entropic properties of ion aggregates and water hydrogen-bonding networks in high salt solutions. Ion network-forming K(+) and SCN(-) ions at high concentrations show a percolating behavior in their aqueous solutions, but ion cluster-forming ions in NaCl solutions do not show such a transition from isolated ion aggregates to percolating ion-water mixture morphology. Despite that the ion aggregate structures are strikingly different for either cluster- or network-forming ions in high salt solutions, it is interesting that the water structures remain insensitive to the electrostatic properties, such as charge densities and polydentate properties, of dissolved ions, and morphological structures of water H-bonding networks appear to be highly robust regardless of the nature and concentration of salt. We anticipate that the present graph entropy analysis results would be of use in understanding a variety of anomalous behaviors of interfacial water around biomolecules as well as electric conductivities of high electrolyte solutions. PMID:27250298

  7. Ion aggregation in high salt solutions. V. Graph entropy analyses of ion aggregate structure and water hydrogen bonding network

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Ho; Cho, Minhaeng

    2016-05-01

    Dissolved ions in water tend to form polydisperse ion aggregates such as ion pairs, relatively compact ion clusters, and even spatially extended ion networks with increasing salt concentration. Combining molecular dynamics simulation and graph theoretical analysis methods, we recently studied morphological structures of ion aggregates with distinctively different characteristics. They can be distinguished from each other by calculating various spectral graph theoretical properties such as eigenvalues and eigenvectors of adjacency matrices of ion aggregates and water hydrogen-bonding networks, minimum path lengths, clustering coefficients, and degree distributions. Here, we focus on percolation and graph entropic properties of ion aggregates and water hydrogen-bonding networks in high salt solutions. Ion network-forming K+ and SCN- ions at high concentrations show a percolating behavior in their aqueous solutions, but ion cluster-forming ions in NaCl solutions do not show such a transition from isolated ion aggregates to percolating ion-water mixture morphology. Despite that the ion aggregate structures are strikingly different for either cluster- or network-forming ions in high salt solutions, it is interesting that the water structures remain insensitive to the electrostatic properties, such as charge densities and polydentate properties, of dissolved ions, and morphological structures of water H-bonding networks appear to be highly robust regardless of the nature and concentration of salt. We anticipate that the present graph entropy analysis results would be of use in understanding a variety of anomalous behaviors of interfacial water around biomolecules as well as electric conductivities of high electrolyte solutions.

  8. Nucleoside-5'-phosphorothioate analogues are biocompatible antioxidants dissolving efficiently amyloid beta-metal ion aggregates.

    PubMed

    Amir, Aviran; Shmuel, Eran; Zagalsky, Rostislav; Sayer, Alon H; Nadel, Yael; Fischer, Bilha

    2012-07-28

    Amyloid beta (Aβ) peptide is known to precipitate and form aggregates with zinc and copper ions in vitro and, in vivo in Alzheimer's disease (AD) patients. Metal-ion-chelation was suggested as therapy for the metal-ion-induced Aβ aggregation, metal-ion overload, and oxidative stress. In a quest for biocompatible metal-ion chelators potentially useful for AD therapy, we tested a series of nucleoside 5'-phosphorothioate derivatives as re-solubilization agents of Cu(+)/Cu(2+)/Zn(2+)-induced Aβ-aggregates, and inhibitors of Fenton reaction in Cu(+) or Fe(2+)/H(2)O(2) system. The most promising chelator in this series was found to be APCPP-γ-S. This nucleotide was found to be more efficient than EDTA in re-solubilization of Aβ(40)-Cu(2+) aggregates as observed by the lower diameter, d(H), (86 vs. 64 nm, respectively) obtained in dynamic light scattering measurements. Likewise, APCPP-γ-S dissolved Aβ(40)-Cu(+) and Aβ(42)-Cu(2+)/Zn(2+) aggregates, as monitored by (1)H-NMR and turbidity assays, respectively. Furthermore, addition of APCPP-γ-S to nine-day old Aβ(40)-Cu(2+)/Zn(2+) aggregates, resulted in size reduction as observed by transition electron microscopy (diameter reduction from 2.5 to 0.1 μm for Aβ(40)-Cu(2+) aggregates). APCPP-γ-S proved to be more efficient than ascorbic acid and GSH in reducing OH radical production in Fe(2+)/H(2)O(2) system (IC(50) values 85, 216 and, 92 μM, respectively). Therefore, we propose APCPP-γ-S as a potential AD therapy capable of both reducing OH radical production and re-solubilization of Aβ(40/42)-M(n+) aggregates. PMID:22652964

  9. Ion aggregation in high salt solutions. IV. Graph-theoretical analyses of ion aggregate structure and water hydrogen bonding network.

    PubMed

    Choi, Jun-Ho; Cho, Minhaeng

    2015-09-14

    Ions in high salt solutions form a variety of ion aggregates, from ion pairs to clusters and networks. Their influences on water hydrogen bonding (H-bonding) network structures have long been of great interest. Recently, we have shown that the morphological structures of ion aggregates can be analyzed by using a spectral graph analysis theory, where each ion cluster or ion network is represented by a properly defined graph with edges and vertices. Here, to further examine the network properties of ion aggregates and water H-bonding networks in high salt solutions, we consider a few representative graph-theoretical descriptors: clustering coefficient, minimum path length, global efficiency, and degree distribution of ion aggregates. From the molecular dynamics trajectories, these graph theoretical properties of ion aggregates and water structures in NaCl and kosmotropic solutions are calculated and shown to be strongly dependent on the two types of ion aggregate structures, i.e., ion cluster and ion network. Ion clusters in high NaCl solutions exhibit typical behaviors of scale free network. The corresponding graph theoretical properties of ion networks in high KSCN solutions are notably different from those of NaCl ion clusters and furthermore they are very similar to those of water hydrogen-bonding network. The present graph-theoretical analysis results indicate that the high solubility limits of KSCN and other ion-network-forming salts might originate from their ability to form a large scale morphological network that can be intertwined with co-existing water H-bonding network. Furthermore, it is shown that the graph-theoretical properties of water H-bonding network structures do not strongly depend on the nature of dissolved ions nor on the morphological structures of ion aggregates, indicating that water's H-bonding interaction and network-forming capability are highly robust. We anticipate that the present graph-theoretical analysis results of high salt

  10. Ion aggregation in high salt solutions. IV. Graph-theoretical analyses of ion aggregate structure and water hydrogen bonding network

    NASA Astrophysics Data System (ADS)

    Choi, Jun-Ho; Cho, Minhaeng

    2015-09-01

    Ions in high salt solutions form a variety of ion aggregates, from ion pairs to clusters and networks. Their influences on water hydrogen bonding (H-bonding) network structures have long been of great interest. Recently, we have shown that the morphological structures of ion aggregates can be analyzed by using a spectral graph analysis theory, where each ion cluster or ion network is represented by a properly defined graph with edges and vertices. Here, to further examine the network properties of ion aggregates and water H-bonding networks in high salt solutions, we consider a few representative graph-theoretical descriptors: clustering coefficient, minimum path length, global efficiency, and degree distribution of ion aggregates. From the molecular dynamics trajectories, these graph theoretical properties of ion aggregates and water structures in NaCl and kosmotropic solutions are calculated and shown to be strongly dependent on the two types of ion aggregate structures, i.e., ion cluster and ion network. Ion clusters in high NaCl solutions exhibit typical behaviors of scale free network. The corresponding graph theoretical properties of ion networks in high KSCN solutions are notably different from those of NaCl ion clusters and furthermore they are very similar to those of water hydrogen-bonding network. The present graph-theoretical analysis results indicate that the high solubility limits of KSCN and other ion-network-forming salts might originate from their ability to form a large scale morphological network that can be intertwined with co-existing water H-bonding network. Furthermore, it is shown that the graph-theoretical properties of water H-bonding network structures do not strongly depend on the nature of dissolved ions nor on the morphological structures of ion aggregates, indicating that water's H-bonding interaction and network-forming capability are highly robust. We anticipate that the present graph-theoretical analysis results of high salt

  11. Secondary Ion Mass Spectrometry Imaging of Dictyostelium discoideum Aggregation Streams

    SciTech Connect

    Debord, J. Daniel; Smith, Donald F.; Anderton, Christopher R.; Heeren, Ronald M.; Pasa-Tolic, Ljiljana; Gomer, Richard H.; Fernandez-Lima, Francisco A.

    2014-06-09

    High resolution imaging mass spectrometry could become a valuable tool for cell and developmental biology, but both, high spatial and mass spectral resolution are needed to enable this. In this report, we employed Bi3 bombardment time-of-flight (Bi3 ToF-SIMS) and C60 bombardment Fourier transform ion cyclotron resonance secondary ion mass spectrometry (C60 FTICR-SIMS) to image Dictyostelium discoideum aggregation streams. Nearly 300 lipid species were identified from the aggregation streams. High resolution mass spectrometry imaging (FTICR-SIMS) enabled the generation of multiple molecular ion maps at the nominal mass level and provided good coverage for fatty acyls, prenol lipids, and sterol lipids. The comparison of Bi3 ToF-SIMS and C60 FTICR-SIMS suggested that while the first provides fast, high spatial resolution molecular ion images, the chemical complexity of biological samples warrants the use of high resolution analyzers for accurate ion identification.

  12. PRECIPITATION OF ZIRCONIUM AND FLUORIDE IONS FROM SOLUTIONS

    DOEpatents

    Newby, B.J.

    1963-06-11

    A process is given for removing zirconium and fluorine ions from aqueous solutions also containing uranium(VI). The precipitation is carried out with sodium formate, and the uranium remains in solution. (AEC)

  13. Contribution of Eu ions on the precipitation of silver nanoparticles in Ag-Eu co-doped borate glasses

    SciTech Connect

    Jiao, Qing; Qiu, Jianbei; Zhou, Dacheng; Xu, Xuhui

    2014-03-01

    Graphical abstract: - Highlights: • Silver nanoparticles are precipitated from the borate glasses during the melting process without any further heat treatment. • The reduction of Eu{sup 3+} ions to Eu{sup 2+} ions is presented in this material. • The intensity of Ag{sup +} luminescence. • The introduction of Eu ions accelerated the reaction between Eu{sup 2+} ions and silver ions inducing the silver clusters formation. - Abstract: Ag{sup +} doped sodium borate glasses with different Eu ions concentration were prepared by the melt-quenching method. The absorption at about 410 nm which was caused by the surface plasmon resonance (SPR) of Ag nanoparticles (NPs) is promoted with increasing of Eu ions concentration. Meanwhile, the luminescent spectra showed that the emission intensity of Ag{sup +} decreased while that of the Ag aggregates increased simultaneously. The results indicated that the Ag ions intend to form the high-polymeric state such as Ag aggregates and nanoparticles with increasing of europium ions. Owing to the self-reduction of Eu{sup 3+} to Eu{sup 2+} in our glass system, it revealed that Ag{sup +} has been reduced by the neighboring Eu{sup 2+} which leads to the formation of Ag aggregates and the precipitation of Ag NPs in the matrix. In addition, energy transfer (ET) process from Ag{sup +}/Ag aggregates to the Eu{sup 3+} was investigated for the enhancement of Eu{sup 3+} luminescence.

  14. Simulation of Ionic Aggregation and Ion Dynamics in Model Ionomers

    NASA Astrophysics Data System (ADS)

    Frischknecht, Amalie L.

    2012-02-01

    Ionomers, polymers containing a small fraction of covalently bound ionic groups, are of interest as possible electrolytes in batteries. A single-ion conducting polymer electrolyte would be safer and have higher efficiency than the currently-used liquid electrolytes. However, to date ionomeric materials do not have sufficiently high conductivities for practical application. This is most likely because the ions tend to form aggregates, leading to slow ion transport. A key question is therefore how molecular structure affects the ionic aggregation and ion dynamics. To probe these structure-property relationships, we have performed molecular simulations of a set of recently synthesized poly(ethylene-co-acrylic acid) copolymers and ionomers, with a focus on the morphology of the ionic aggregates. The ionomers have a precise, constant spacing of charged groups, making them ideal for direct comparisons with simulations. Ab initio calculations give insight into the expected coordination of cations with fragments of the ionomers. All-atom molecular dynamics (MD) simulations of the ionomer melt show aggregation of the ionic groups into extended string-like clusters. An extensive set of coarse-grained molecular dynamics simulations extend the results to longer times and larger length scales. The structure factors calculated from the MD simulations compare favorably with x-ray scattering data. Furthermore, the simulations give a detailed picture of the sizes, shapes, and composition of the ionic aggregates, and how they depend on polymer architecture. Implications for ion transport will be discussed. [Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. [Effect of Eu ions on the Ag nanoparticles precipitation and their optical properties in borate glasses].

    PubMed

    Liu, Zhi-liang; Jiao, Qing; Qiu, Jian-bei

    2014-08-01

    Eu-Ag co-doped borate glasses were prepared by the high temperature solid method in the present work. Absorption and emission spectra were employed to investigate the precipitation of Ag nanoparticles, which is influenced by the network form B2O3 and the co-doped Eu ions. It was found in the absorption spectra of Eu-Ag co-doped sample that a broad band centered at about 410 nm emerged and their intensity decreased with the increase in the BZ 03 concentration. Meanwhile, under the excitation of 340 nm, a broad emission band was observed in the wavelength range of 350-600 nm, which belongs to the blue-green light of Ag aggregates. The intensity of the Ag aggregates presented an increasing tendency with the increase in the B2O3 contents. The weak characteristic emission of Ag aggregates and Eu3+ was observed respectively in their singly doped samples. It is concluded that both their emissions get significant enhancement when Eu ions and Ag ions are used for co-doping the sample. In addition, the increased absorption of Ag nanoparticles was detected with the increase in the Eu ions concentration. Herein, the mechanism behind Eu3+ contribution to the precipitation of Ag nanoparticles is discussed in detail. The luminescence properties of borate glasses can be controlled by the microstructure of the borate glasses. Therefore, the white emission can be realized by the adjustment of glass structure and Eu ions concentration, owing to the red light from Eu3+ : (5)D0-->(7)Fj electronic transition and the blue-green light form the broad emission of Ag aggregates. The borate glasses are expected to be the candidates for the light-emission diode (LED) luminescent materials. PMID:25508714

  16. [Effect of Eu ions on the Ag nanoparticles precipitation and their optical properties in borate glasses].

    PubMed

    Liu, Zhi-liang; Jiao, Qing; Qiu, Jian-bei

    2014-08-01

    Eu-Ag co-doped borate glasses were prepared by the high temperature solid method in the present work. Absorption and emission spectra were employed to investigate the precipitation of Ag nanoparticles, which is influenced by the network form B2O3 and the co-doped Eu ions. It was found in the absorption spectra of Eu-Ag co-doped sample that a broad band centered at about 410 nm emerged and their intensity decreased with the increase in the BZ 03 concentration. Meanwhile, under the excitation of 340 nm, a broad emission band was observed in the wavelength range of 350-600 nm, which belongs to the blue-green light of Ag aggregates. The intensity of the Ag aggregates presented an increasing tendency with the increase in the B2O3 contents. The weak characteristic emission of Ag aggregates and Eu3+ was observed respectively in their singly doped samples. It is concluded that both their emissions get significant enhancement when Eu ions and Ag ions are used for co-doping the sample. In addition, the increased absorption of Ag nanoparticles was detected with the increase in the Eu ions concentration. Herein, the mechanism behind Eu3+ contribution to the precipitation of Ag nanoparticles is discussed in detail. The luminescence properties of borate glasses can be controlled by the microstructure of the borate glasses. Therefore, the white emission can be realized by the adjustment of glass structure and Eu ions concentration, owing to the red light from Eu3+ : (5)D0-->(7)Fj electronic transition and the blue-green light form the broad emission of Ag aggregates. The borate glasses are expected to be the candidates for the light-emission diode (LED) luminescent materials. PMID:25474935

  17. On The Choce of The Temporal Aggregation Level For Statistical Downscaling For Precipitation

    NASA Astrophysics Data System (ADS)

    Shabalova, M. V.; Buishand, T. A.

    Statistical downscaling methods are used in hydrological applications to translate cli- mate change scenarios generated by GCMs to the finer spatial grids. In these meth- ods the present-day statistical relationships between the local precipitation and atmo- spheric predictor variables are used to predict the change in precipitation given the changes in predictors. The predictors thus should be realistically modelled by GCMs and should fully represent the climate change signal. The proper choice of the tem- poral aggregation level of the data in statistical relationships is crucial. An inadequate choice may exclude vital for climate change predictors as statistically not significant. The chosen aggregation level also affects the sensitivity of the downscaling model to changes in predictors, as well as the model's efficiency. The results from various downscaling models for daily and monthly rainfall occurrence and amount developed in the class of generalised linear models for a number of stations in the River Rhine basin are discussed.

  18. Scaling behavior and local structure of ion aggregates in single-ion conductors.

    PubMed

    Lu, Keran; Rudzinski, Joseph F; Noid, W G; Milner, Scott T; Maranas, Janna K

    2014-02-21

    Single-ion conductors are attractive electrolyte materials because of their inherent safety and ease of processing. Most ions in a sodium-neutralized PEO sulfonated-isophthalate ionomer electrolyte exist as one dimensional chains, restricted in dimensionality by the steric hindrance of the attached polymer. Because the ions are slow to reconfigure, atomistic MD simulations of this material are unable to adequately sample equilibrium ion structures. We apply a novel coarse-graining scheme using a generalized-YBG procedure in which the polymer backbone is completely removed and implicitly represented by the effective potentials of the remaining ions. The ion-only coarse-grained simulation allows for substantial sampling of equilibrium aggregate configurations. We extend the wormlike micelle theory to model ion chain equilibrium. Our aggregates are random walks which become more positively charged with increasing size. Defects occur on the string-like structure in the form of “dust” and “knots,” which form due to cation coordination with open sites along the string. The presence of these defects suggest that cation hopping along open third-coordination sites could be an important mechanism of charge transport using ion aggregates. PMID:24983107

  19. Inhibition of precipitation and aggregation of metacinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    USGS Publications Warehouse

    Ravichandran, M.; Aiken, G.R.; Ryan, J.N.; Reddy, M.M.

    1999-01-01

    Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations (???3 mg C/L) of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations (??? x 10-8 M), DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations (5 x 10-5 M), DOM inhibited the aggregation of colloidal metacinnabar (Hg passed through a 0.1 ??m filter but was removed by centrifugation). At Hg concentrations greater than 5 x 10-4 M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 ??m filter. Organic matter rich in aromatic moleties was preferentially removed with the solid. Hydrophobic organic acids (humic and fulvic acids) inhibited aggregation better than hydrophilic organic acids. The presence of chloride, acetate, salicylate, EDTA, and cysteine did not inhibit the precipitation or aggregation of metacinnabar. Calcium enhanced metacinnabar aggregation even in the presence of DOM, but the magnitude of the effect was dependent on the concentrations of DOM, Hg, and Ca. Inhibition of metacinnabar precipitation appears to be a result of strong DOM-Hg binding. Prevention of aggregation of colloidal particles appears to be caused by adsorption of DOM and electrostatic repulsion.Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations (???3 mg C/L) of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations (???5??10-8 M), DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations (5??10-5 M), DOM inhibited the aggregation of colloidal metacinnabar (Hg passed through a 0.1 ??m filter but was removed by centrifugation). At Hg concentrations greater than 5??10-4 M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 ??m filter. Organic matter rich in aromatic moieties was preferentially

  20. Changes in soil aggregate dynamics following 18 years of experimentally increased precipitation in a cold desert ecosystem

    NASA Astrophysics Data System (ADS)

    De Graaff, M.; vanderVeen, J.; Germino, M. J.

    2011-12-01

    Climate change is expected to alter the amount and timing of precipitation in semiarid ecosystems of the intermountain west, which can alter soil carbon dynamics. Specifically, an increase in precipitation in arid ecosystems promotes microbial activity, which can increase soil aggregate formation and enhance sequestration of soil organic carbon within stable aggregates. This study was conducted to assess: (1) how precipitation shifts affect soil aggregate formation and associated soil organic carbon contents in semi arid ecosystems, and (2) how plants mediate precipitation impacts on soil aggregate dynamics. Soil samples were collected from a long-term ecohydrology study located in the cold desert of the Idaho National Lab, USA. Precipitation treatments delivered during the previous 18 years consist of three regimes: (1) a control (ambient precipitation), (2) 200 mm irrigation added during the growing season, and (3) 200 mm irrigation added during the cold dormant season. Experimental plots were planted with a diverse native mix of big sagebrush (Artemisia tridentate) and associated shrubs, grasses, and forbs, but had also become invaded by crested wheatgrass (Agropyron cristatum). Soils were collected in February (2011) with a 4.8 cm diameter soil corer to a depth of 15 cm. Across all precipitation treatments we sampled both directly beneath sagebrush and crested wheatgrass and from relatively bare plant-interspaces. Subsamples (100 g) were sieved (4.75 mm) and air dried. Then, the soils were fractionated into (1) macro aggregates (> 250 μm), (2) free micro aggregates (53-250 μm) and (3) free silt and clay fractions (<53 μm), using a wet sieving protocol. Further, macro aggregates were separated into particulate organic matter (POM), micro aggregates and silt and clay fractions using a micro aggregate isolator. Soil fractions were analyzed for soil organic carbon contents after removal of soil carbonates using sulfurous acid. Our preliminary results indicate

  1. Morphological and chemical analysis of different precipitates on mineral trioxide aggregate immersed in different fluids.

    PubMed

    Han, Linlin; Okiji, Takashi; Okawa, Seigo

    2010-10-01

    The purpose of this study was to analyze the ultrastructures and chemical compositions of precipitates formed on mineral trioxide aggregate (MTA; White ProRoot MTA) immersed in distilled water (DW) or phosphate buffered saline (PBS), based on the attribution that MTA's bioactivity and sealing ability are influenced by its interaction with the external fluid environment. After 1 and 14 days of immersion, precipitates formed on MTA disks were analyzed using wavelength-dispersive X-ray spectroscopy electron probe microanalyzer with image observation function (SEM-EPMA; EPMA1601, Shimadzu, Kyoto, Japan), and Fourier transform-infrared (FT-IR) spectroscopy. On DW specimens, cubic-like crystals containing Ca, O, and C (17, 66, and 17 at% respectively) were produced. State analysis of calcium k(β)spectrum also revealed calcium hydroxide. On PBS specimens, acicular-spherical and lath-like crystals with Ca/P molar ratios of 1.42 and 1.58 respectively were produced. In conclusion, the precipitates formed on DW specimens were identified as calcium carbonate and calcium hydroxide primarily, whereas the precipitates on PBS specimens were inferred to be amorphous calcium phosphate. PMID:20823620

  2. Extreme Precipitation Strengthening in Ion-Implanted Nickel

    SciTech Connect

    Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Petersen, G.A.

    1999-05-03

    Precipitation strengthening of nickel was investigated using ion-implantation alloying and nanoindentation testing for particle separations in the nanometer range and volume fractions extending above 10O/O. Ion implantation of either oxygen alone or oxygen plus aluminum at room temperature was shown to produce substantial strengthening in the ion-treated layer, with yield strengths near 5 GPa in both cases. After annealing to 550"C the oxygen-alone layer loses much of the benefit, with its yield strength reduced to 1.2 GP~ but the dual ion-implanted layer retains a substantially enhanced yield strength of over 4 GPa. Examination by transmission electron f microscopy showed very fine dispersions of 1-5 nm diameter NiO and y-A1203 precipitates in the implanted layers before annealing. The heat treatment at 550"C induced ripening of the NiO particles to sizes ranging from 7 to 20 nm, whereas the more stable ~-A1203 precipitates were little changed. The extreme strengthening we observe is in semiquantitative agreement with predictions based on the application of dispersion-hardening theory to these microstructure.

  3. Auroral ion precipitation at Jupiter: Predictions for Juno

    NASA Astrophysics Data System (ADS)

    Ozak, N.; Cravens, T. E.; Schultz, D. R.

    2013-08-01

    The spatially localized and highly variable polar cap emissions at Jupiter are part of a poorly understood current system linking the ionosphere and the magnetopause region. Strong X-ray emission has been observed from the polar caps and has been explained by the precipitation of oxygen and sulfur ions of several MeV energy. The present paper presents results of an extended model of the ion precipitation process at Jupiter. Specifically, we add to a previous model a more complete treatment of ionization of the atmosphere, generation of secondary electron fluxes and their escape from the atmosphere, and generation of downward field-aligned currents. Predictions relevant to observations by the upcoming NASA Juno mission are made, namely the existence of escaping electrons with energies from a few eV up to 10 keV, auroral H2 band emission rates of 80 kR, and downward field-aligned currents of at least 2 MA.

  4. Inhibition of precipitation and aggregation of metacinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

    SciTech Connect

    Ravichandran, M.; Ryan, J.N.; Aiken, G.R.; Reddy, M.M.

    1999-05-01

    Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations, DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations, DOM inhibited the aggregation of colloidal metacinnabar At Hg concentrations greater than 5 {times} 10{sup {minus}4} M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 {micro}m filter. Organic matter rich in aromatic moieties was preferentially removed with the solid. Hydrophobic organic acids inhibited aggregation better than hydrophilic organic acids. The presence of chloride, acetate, salicylate, EDTA, and cysteine did not inhibit the precipitation or aggregation of metacinnabar. Calcium enhanced metacinnabar aggregation even in the presence of DOM,m but the magnitude of the effect was dependent on the concentrations of DOM, Hg, and Ca. Inhibition of metacinnabar precipitation appears to be a result of strong DOM-Hg binding. Prevention of aggregation of colloidal particles appears to be caused by adsorption of DOM and electrostatic repulsion.

  5. Modelling overland flow during extreme precipitation events: influence of precipitation aggregation level, soil development and climate change

    NASA Astrophysics Data System (ADS)

    Leterme, B.; Beerten, K.

    2012-04-01

    In this study, the sensitivity of overland flow modelling to selected parameters in a small (several km2) recharge area in the Campine region, northern Belgium, is investigated. In first instance, the amount of overland flow is estimated according to the temporal resolution of rainfall data. In a second step, the effect of soil development and climate change is incorporated in the model as well. The study focuses on the extreme event of 23 August 2011, when ~40 mm of rain fell in ~25 minutes in the investigation area. Precipitation was recorded with a one-minute temporal resolution. The generation of saturation overland flow during this event is simulated with the van Genuchten-Mualem model (using HYDRUS-1D) for a Haplic Podzol typical of the area. The hydraulic barrier eventually causing overland flow is the Bh horizon at shallow depth, characterised by a saturated hydraulic conductivity (Ksat) of 4.5×10-6 m/s. The sensitivity of overland flow to the temporal resolution used in the model is investigated for daily, hourly, 20-minute and 10-minute time steps. Results show that the aggregation level has a critical influence on the amount of saturation overland flow, ranging from 0 to 4.0 mm. Landscape and soil evolution studies in the vicinity of the site indicate that cemented podzols may develop in several thousands of years, thus decreasing the Ksat of the Bh horizon by several orders of magnitude. On this time scale, global climate evolution is also expected to have an impact on the precipitation regime, possibly resulting in more severe extreme events for a given return period. These two processes are simulated respectively by decreasing Ksat by one or two orders of magnitude and by increasing rainfall rate by 4 and 16% (and potential evapotranspiration by 13 and 25%, based on the scenarios for the period 2071-2100 of the CCI-HYDR project; Baguis et al., 2009). Results show that in the most defavourable case, overland flow during the extreme event simulated

  6. Dextrose-mediated aggregation of therapeutic monoclonal antibodies in human plasma: Implication of isoelectric precipitation of complement proteins

    PubMed Central

    Luo, Shen; Zhang, Baolin

    2015-01-01

    Many therapeutic monoclonal antibodies (mAbs) are clinically administered through intravenous infusion after mixing with a diluent, e.g., saline, 5% dextrose. Such a clinical setting increases the likelihood of interactions among mAb molecules, diluent, and plasma components, which may adversely affect product safety and efficacy. Avastin® (bevacizumab) and Herceptin® (trastuzumab), but not Remicade® (infliximab), were shown to undergo rapid aggregation upon dilution into 5% dextrose when mixed with human plasma in vitro; however, the biochemical pathways leading to the aggregation were not clearly defined. Here, we show that dextrose-mediated aggregation of Avastin or Herceptin in plasma involves isoelectric precipitation of complement proteins. Using mass spectrometry, we found that dextrose-induced insoluble aggregates were composed of mAb itself and multiple abundant plasma proteins, namely complement proteins C3, C4, factor H, fibronectin, and apolipoprotein. These plasma proteins, which are characterized by an isoelectronic point of 5.5–6.7, lost solubility at the resulting pH in the mixture with formulated Avastin (pH 6.2) and Herceptin (pH 6.0). Notably, switching formulation buffers for Avastin (pH 6.2) and Remicade (pH 7.2) reversed their aggregation profiles. Avastin formed little, if any, insoluble aggregates in dextrose-plasma upon raising the buffer pH to 7.2 or above. Furthermore, dextrose induced pH-dependent precipitation of plasma proteins, with massive insoluble aggregates being detected at pH 6.5–6.8. These data show that isoelectric precipitation of complement proteins is a prerequisite of dextrose-induced aggregation of mAb in human plasma. This finding highlights the importance of assessing the compatibility of a therapeutic mAb with diluent and human plasma during product development. PMID:26338058

  7. On an energy-latitude dispersion pattern of ion precipitation potentially associated with magnetospheric EMIC waves

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Donovan, E.; Ni, B.; Yue, C.; Jiang, F.; Angelopoulos, V.

    2014-10-01

    Ion precipitation mechanisms are usually energy dependent and contingent upon magnetospheric/ionospheric locations. Therefore, the pattern of energy-latitude dependence of ion precipitation boundaries seen by low Earth orbit satellites can be implicative of the mechanism(s) underlying the precipitation. The pitch angle scattering of ions led by the field line curvature, a well-recognized mechanism of ion precipitation in the central plasma sheet (CPS), leads to one common pattern of energy-latitude dispersion, in that the ion precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. In this study, we introduce one other systematically existing pattern of energy-latitude dispersion of ion precipitation, in that the lower energy ion precipitation extends to lower latitude than the higher-energy ion precipitation. Via investigating such a "reversed" energy-latitude dispersion pattern, we explore possible mechanisms of ion precipitation other than the field line curvature scattering. We demonstrate via theories and simulations that the H-band electromagnetic ion cyclotron (EMIC) wave is capable of preferentially scattering keV protons in the CPS and potentially leads to the reversed energy-latitude dispersion of proton precipitation. We then present detailed event analyses and provide support to a linkage between the EMIC waves in the equatorial CPS and ion precipitation events with reversed energy-latitude dispersion. We also discuss the role of ion acceleration in the topside ionosphere which, together with the CPS ion population, may result in a variety of energy-latitude distributions of the overall ion precipitation.

  8. Using multiple equilibria in precipitation to understand self-aggregation of deep tropical convection in a warming climate

    NASA Astrophysics Data System (ADS)

    Sessions, Sharon; Sentic, Stipo; Raymond, David

    2013-03-01

    Understanding mechanisms of convective organization is currently an important problem in tropical meteorology. Recent numerical simulations show that the tendency for deep tropical convection to self-aggregate increases as sea surface temperatures (SSTs) increase. This has significant implications for hurricane genesis in a warming climate. Investigating the conditions over which convection self-aggregates requires large domains and is therefore computationally expensive. An alternative approach utilizes the analogy between multiple equilibria in limited domain simulations, and the dry and precipitating regions in a large domain with self-aggregated convection. Multiple equilibria refers to a steady state which either exhibits a completely dry troposphere or persistent precipitating deep convection under identical forcing conditions. The large scale circulation is parameterized based on the assumption that horizontal gradients in temperature are small in the tropics. Understanding the mechanisms which permit multiple equilibria on small domains is a computationally economic approach to understanding self-aggregation. We show how multiple equilibria depend on SSTs, and thus provide insight to self-aggregation in a warming climate. This work supported by NSF grant number AGS-1056254

  9. Features of the planetary distribution of ion precipitation at different levels of magnetic activity

    NASA Astrophysics Data System (ADS)

    Vorobjev, V. G.; Yagodkina, O. I.; Antonova, E. E.

    2015-09-01

    Observations from DMSP F6 and F7 spacecraft were used to examine the features of the planetary distribution of ion precipitation. Ion characteristics were defined within the boundaries of different types of auroral electron precipitation, which in accordance with the conclusions from (Starkov et al., 2002) were divided into a structured precipitation of an auroral oval (AOP) and zones of diffuse precipitation DAZ and SDP located equatorward and poleward of AOP, respectively. Analogous to electron precipitation, ion precipitation did not demonstrate dependences of the average energy and the average energy flux of precipitating particles on the Dst index value. In the diffuse precipitation zone (DAZ) equatorward of the auroral oval, ion energies clearly peaked in the sector of 1500-1800 MLT. The average energy value grows as magnetic activity increases from ~12 keV at AL =-1000 nT to ~18 keV at AL =-1000 nT. In the region of structured precipitation (AOP), the minimum of the average ion energy is observed in the dawn sector of 0600-0900 MLT. Ion energy fluxes ( F i ) are maximal in the nighttime MLT sectors. In the zone of soft diffuse precipitation (SDP) poleward of AOP, the highest ion energy fluxes are observed in the daytime sector, while the nightside F i values are insignificant. Ion energy fluxes in the SDP zone show an anticorrelation with the average ion energy in the same MLT sector. An ion precipitation model was created which yields a global distribution of both the average ion energies and the ion energy fluxes depending on the magnetic activity expressed by AL and Dst indices. Comparison of this model with the model of electron precipitation shows that the planetary power of ion precipitation at low magnetic activity (| AL| = 100 nT) is ~12% of the electron precipitation power and exponentially decreases to ~4% at | AL| > 1000 nT. The ion precipitation model was used to calculate the plasma pressure at the ionospheric altitudes. The planetary

  10. MAGNESIUM PRECIPITATION AND DIFUSSION IN Mg+ ION IMPLANTED SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-02

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. Calculations by Sawan et al. predict that at a dose of ~100 dpa (displacements per atom), there is ~0.5 at.% Mg generated in SiC. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <100> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4E-19 m2/s.

  11. Spontaneous aggregation of lithium ion coordination polymers in fluorinated electrolytes for high-voltage batteries

    DOE PAGESBeta

    Malliakas, Christos D.; Leung, Kevin; Pupek, Krzysztof Z.; Shkrob, Ilya A.; Abraham, Daniel P.

    2016-03-31

    Fluorinated carbonate solvents are pursued as liquid electrolytes for high-voltage Li-ion batteries. We report aggregation of [Li+(FEC)3]n polymer species from fluoroethylene carbonate containing electrolytes and scrutinized the causes for this behavior.

  12. The Aggregate Description of Semi-Arid Vegetation with Precipitation-Generated Soil Moisture Heterogeneity

    NASA Technical Reports Server (NTRS)

    White, Cary B.; Houser, Paul R.; Arain, Altaf M.; Yang, Zong-Liang; Syed, Kamran; Shuttleworth, W. James

    1997-01-01

    Meteorological measurements in the Walnut Gulch catchment in Arizona were used to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area with a grid resolution of 480 m for a continuous 18-month period which included two seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the acceptability (for modelling purposes) of assuming uniformity in all meteorological variables other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain gauges. These meteorological data were used as forcing variables for an equivalent array of stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the evolution of soil moisture and surface energy fluxes in response to the prevalent, heterogeneous pattern of convective precipitation. The calculated area-average behaviour was compared with that given by a single aggregate BATS simulation forced with area-average meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating differences in the transpiration and the intercepted rainfall components of total evaporation during rain storms. However, the calculated area-average surface energy fluxes given by the two simulations in rain-free conditions with strong heterogeneity in soil moisture were always close to identical, a result which is independent of whether default or site-specific vegetation and soil parameters were used. Because the spatial variability in soil moisture throughout the catchment has the same order of magnitude as the amount of rain failing in a typical convective storm (commonly 10% of the vegetation's root zone saturation) in a semi-arid environment, non-linearitv in the relationship between transpiration and the soil moisture available to the vegetation has limited influence on area-average surface fluxes.

  13. Calcium Binding to Beta-2-Microglobulin at Physiological Ph Drives the Occurrence of Conformational Changes Which Cause the Protein to Precipitate into Amorphous Forms That Subsequently Transform into Amyloid Aggregates

    PubMed Central

    Kumar, Sukhdeep; Sharma, Prerna; Arora, Kanika; Raje, Manoj; Guptasarma, Purnananda

    2014-01-01

    Using spectroscopic, calorimetric and microscopic methods, we demonstrate that calcium binds to beta-2-microglobulin (β2m) under physiological conditions of pH and ionic strength, in biological buffers, causing a conformational change associated with the binding of up to four calcium atoms per β2m molecule, with a marked transformation of some random coil structure into beta sheet structure, and culminating in the aggregation of the protein at physiological (serum) concentrations of calcium and β2m. We draw attention to the fact that the sequence of β2m contains several potential calcium-binding motifs of the DXD and DXDXD (or DXEXD) varieties. We establish (a) that the microscopic aggregation seen at physiological concentrations of β2m and calcium turns into actual turbidity and visible precipitation at higher concentrations of protein and β2m, (b) that this initial aggregation/precipitation leads to the formation of amorphous aggregates, (c) that the formation of the amorphous aggregates can be partially reversed through the addition of the divalent ion chelating agent, EDTA, and (d) that upon incubation for a few weeks, the amorphous aggregates appear to support the formation of amyloid aggregates that bind to the dye, thioflavin T (ThT), resulting in increase in the dye's fluorescence. We speculate that β2m exists in the form of microscopic aggregates in vivo and that these don't progress to form larger amyloid aggregates because protein concentrations remain low under normal conditions of kidney function and β2m degradation. However, when kidney function is compromised and especially when dialysis is performed, β2m concentrations probably transiently rise to yield large aggregates that deposit in bone joints and transform into amyloids during dialysis related amyloidosis. PMID:24755626

  14. Electrospray ion mobility mass spectrometry of positively charged sodium bis[2-ethythexyl)sulfosuccinate aggregates.

    PubMed

    Bongiorno, David; Indelicato, Serena; Giorgi, Gianluca; Scarpella, Simona; Liveri, Vincenzo Turco; Ceraulo, Leopoldo

    2014-01-01

    Collision cross-sections (CCS) of positively singly and multiply charged aggregates of the surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) in the gas phase have been measured by quadrupole ion mobility time-of-flight mass spectrometry. Calibration of the observed drift times to the CCS of the AOTNa non-covalent aggregates was achieved by collecting, under the same experimental conditions, the drift times of a range of singly and multiply charged polyalanine peptides whose CCS had been obtained by conventional ion mobility spectrometry. Together with an obvious increase of the aggregate cross-section with the aggregation number, it was found that the aggregate cross-section increases with the charge state due to the sodium counterions steric effect and the augmented electrostatic repulsion. This finding is consistent with the result of a previous molecular dynamics study on positively charged AOTNa aggregates in the gas phase showing that, by increasing the charge state, the aggregates become progressively more oblate; implying a rise of their CCS. Moreover, the occurrence at each aggregation number and extra charge of a unique value of cross section points toward aggregates whose conformations do not show discernible shape change in the experiment time scale. PMID:24895777

  15. Controlled aggregation of magnetic ions in a semiconductor: an experimental demonstration.

    PubMed

    Bonanni, A; Navarro-Quezada, A; Li, Tian; Wegscheider, M; Matĕj, Z; Holý, V; Lechner, R T; Bauer, G; Rovezzi, M; D'Acapito, F; Kiecana, M; Sawicki, M; Dietl, T

    2008-09-26

    The control on the distribution of magnetic ions into a semiconducting host is crucial for the functionality of magnetically doped semiconductors. Through a structural analysis at the nanoscale, we give experimental evidence that the aggregation of Fe ions in (Ga,Fe)N and consequently the magnetic response of the material are affected by the growth rate and doping with shallow impurities. PMID:18851460

  16. Dependence of ion concentration in simulated body fluid on apatite precipitation on titania surface

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Akira; Nakano, Masayuki; Hieda, Junko; Ohtake, Naoto; Akasaka, Hiroki

    2015-08-01

    Titanium and its alloys are used as biomaterials, because of their high biocompatibility. Apatite precipitates on a titania surface in vivo, and living bone and titanium alloy are coupled through the thin apatite layer. The initial precipitation behavior of apatite on titania in simulated body fluid (SBF) solutions was evaluated and the effect of inorganic ions in the SBF was investigated. Measurement using the SPR phenomenon was used to evaluate the initial apatite precipitation. An SBF containing approximately equal ion concentrations to those in blood plasma was added to a titania surface and the SPR profile was obtained, from which the initial apatite precipitation rate was found to be 1.14 nm/h. Furthermore, the relationship between the inorganic concentration and the precipitation rate was determined for SBFs with different Na+ and Ca2+ concentrations. Apatite precipitation did not occur in the SBF with a low Na+ concentration, whereas the initial apatite precipitation rate in the SBF that did not contain Ca2+ was 0.32 nm/h. According to these results, Ca2+ has little effect on the initial apatite precipitation. In the initial reaction of apatite precipitation, sodium titanate is formed by the absorption of Na+. Next, calcium titanate precipitates upon the substitution of Na+ with Ca2+. Finally, Na+, phosphate ions and hydroxyl ions are attracted to the surface and apatite is formed. Thus, the rate-limiting factor in the initial nucleation of apatite is the Na+ concentration.

  17. Self-consistent ion-by-ion growth model for kinetic isotopic fractionation during calcite precipitation

    NASA Astrophysics Data System (ADS)

    Nielsen, Laura C.; DePaolo, Donald J.; De Yoreo, James J.

    2012-06-01

    Microscopic mechanisms operating at the mineral-aqueous interface control rates of growth and dissolution, isotope fractionation and trace element partitioning during crystal growth. Despite the importance of characterizing surface kinetic controls on isotopic partitioning, no self-consistent microscopic theory has yet been presented which can simultaneously model both mineral growth rate and isotopic composition. Using a kinetic theory for AB or di-ionic crystal growth, we derive a model to predict precipitation rate and isotope fractionation as a function of growth solution oversaturation and solution stoichiometry and apply the theory to calcium isotope fractionation during calcite precipitation. Our model assimilates the current understanding of surface controlled isotope fractionation with kinetic theories of ion-by-ion mineral growth to predict isotopic partitioning during the growth of ionic crystals. This approach accounts for the effect of solution composition on microscopic mineral surface structure and composition, providing numerous testable hypotheses for growth of sparingly soluble AB crystals such as calcite, namely: Both oversaturation and solution stoichiometry control growth rate and partitioning of isotopes during precipitation; for growth driven primarily by step propagation, distinct expressions describe dislocation- and 2D nucleation-driven growth rates, while the expression for isotope fractionation is the same for both mechanisms; mineral precipitation occurring via the formation of an amorphous precursor will generate isotope effects that are not compatible with ion-by-ion growth theory and may therefore be excluded from comparison; and, the absolute kinetic limit of isotope fractionation may not be accessible at high oversaturation due to the formation of amorphous precursors. Using calcite as a model system, we derive expressions for growth rate and isotopic fractionation as a function of oversaturation and Ca:CO32- in solution

  18. Aggregation-induced emission active tetraphenylethene-based sensor for uranyl ion detection.

    PubMed

    Wen, Jun; Huang, Zeng; Hu, Sheng; Li, Shuo; Li, Weiyi; Wang, Xiaolin

    2016-11-15

    A novel tetraphenylethene-based fluorescent sensor, TPE-T, was developed for the detection of uranyl ions. The selective binding of TPE-T to uranyl ions resulted in a detectable signal owing to the quenching of its aggregation-induced emission. The developed sensor could be used to visually distinguish UO2(2+) from lanthanides, transition metals, and alkali metals under UV light; the presence of other metal ions did not interfere with the detection of uranyl ions. In addition, TPE-T was successfully used for the detection of uranyl ions in river water, illustrating its potential applications in environmental systems. PMID:27439180

  19. The precipitation of energetic heavy ions into the upper atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Horanyi, M.; Cravens, T. E.; Waite, J. H., Jr.

    1987-01-01

    Evidence for auroral particle precipitation at Jupiter was provided by the ultraviolet spectrometers onboard the Voyagers 1 and 2 spacecraft and by the International Ultraviolet Explorer (IUE). Magnetospheric measurements made by instruments onboard the Voyager spacecraft show that energetic sulfur and oxygen ions are precipitating into the upper atmosphere of Jupiter. A theoretical model has been constructed describing the interaction of precipitating oxygen with the Jovian atmosphere. The auroral energy is deposited in the atmosphere by means of ionization, excitation, and dissociation and heating of the atmospheric gas. Energetic ion and electron precipitation are shown to have similar effects on the atmosphere and ionosphere of Jupiter.

  20. Gas phase charged aggregates of bis(2-ethylhexyl)sulfosuccinate (AOT) and divalent metal ions: first evidence of AOT solvated aggregates.

    PubMed

    Giorgi, Gianluca; Pini, Ivana; Ceraulo, Leopoldo; Liveri, Vincenzo Turco

    2011-09-01

    Assembling and chelating properties of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) towards divalent metal ions have been investigated in the gas phase by electrospray ionization mass spectrometry. A variety of positively charged monometallated and mixed metal aggregates are formed. Interestingly, several ions contain solvent (MeOH, H(2)O) molecules and constitute the most abundant AOT cationic aggregates not containing sodium. These species are the first example of solvated AOT-metal ion aggregates in the gas phase. By increasing the surfactant aggregation number, the abundance of solvated species becomes lower than that of unsolvated ones. Decompositions of ionic species have been studied by tandem mass spectrometry, and their stability has been determined through energy resolved mass spectrometry. In contrast with positively charged AOT-alkaline metal ion aggregates, whose decompositions are dominated by the loss of individual surfactant molecules, AOTNa-divalent ion aggregates mainly dissociate through the cleavage of the AOT H(2)C-O bond followed by further intramolecular fragmentations. This finding, that is consistent with an enhanced chelation of divalent ions with AOT(-) head groups, has been taken as an indication that such aggregates are characterized by a reverse micelle-like organization with a ionic core formed by the metal cations interacting with the negatively charged surfactant polar heads, whereas the surfactant alkyl chains point outside. PMID:21915957

  1. Solution structure of copper ion-induced molecular aggregates of tyrosine melanin.

    PubMed

    Gallas, J M; Littrell, K C; Seifert, S; Zajac, G W; Thiyagarajan, P

    1999-08-01

    Melanin, the ubiquitous biological pigment, provides photoprotection by efficient filtration of light and also by its antioxidant behavior. In solutions of synthetic melanin, both optical and antioxidant behavior are affected by the aggregation states of melanin. We have utilized small-angle x-ray and neutron scattering to determine the molecular dimensions of synthetic tyrosine melanin in its unaggregated state in D(2)O and H(2)O to study the structure of melanin aggregates formed in the presence of copper ions at various copper-to-melanin molar ratios. In the absence of copper ions, or at low copper ion concentrations, tyrosine melanin is present in solution as a sheet-like particle with a mean thickness of 12.5 A and a lateral extent of approximately 54 A. At a copper-to-melanin molar ratio of 0.6, melanin aggregates to form long, rod-like structures with a radius of 32 A. At a higher copper ion concentration, with a copper-to-melanin ratio of 1.0, these rod-like structures further aggregate, forming sheet-like structures with a mean thickness of 51 A. A change in the charge of the ionizable groups induced by the addition of copper ions is proposed to account for part of the aggregation. The data also support a model for the copper-induced aggregation of melanin driven by pi stacking assisted by peripheral Cu(2+) complexation. The relationship between our results and a previous hypothesis for reduced cellular damage from bound-to-melanin redox metal ions is also discussed. PMID:10423458

  2. Precipitate evolution in ion-irradiated HCM12A

    NASA Astrophysics Data System (ADS)

    Jiao, Z.; Was, G. S.

    2012-06-01

    Precipitate evolution in HCM12A following proton irradiations to 3, 7 and 10 dpa at 400 °C, or following Fe++ irradiations to 100 and 500 dpa at 500 °C was studied. Ni/Si/Mn-rich precipitates were irradiation-induced and their nucleation was closely related to the local enrichment of Ni, Si and Mn at sinks such as dislocations due to radiation induced segregation. The composition of Ni/Si/Mn-rich precipitates evolved with irradiation dose and was different from that of the G-phase reported in irradiated ferritic-martensitic alloys. Nucleation of Cu-rich precipitates saturated after 3 dpa at 400 °C and coarsened at higher dose. Irradiation enhanced the precipitation of Cu-rich precipitates at 400 °C but suppressed the nucleation at 500 °C. Partial dissolution of Cu-rich precipitates must have occurred at 500 dpa at 500 °C as the volume fraction was smaller at 500 dpa than that at 100 dpa. Cr-rich precipitates were irradiation enhanced and were observed under irradiation at 400 °C but not observed at 500 °C due to the increase in Cr solubility with temperature. The evolution of Cr-rich precipitates with irradiation dose was likely related to the complex redistribution of Cr among chromium carbides, grain boundaries and matrix under irradiation. Radiation-induced Cr-rich carbides were observed following Fe++ irradiation to 500 dpa at 500 °C.

  3. Statistical properties of planetary heavy ion precipitations toward the Martian ionosphere based on Mars Express observations

    NASA Astrophysics Data System (ADS)

    Hara, T.; Seki, K.; Futaana, Y.; Yamauchi, M.; Barabash, S.; Fedorov, A. O.; Yagi, M.; Delcourt, D. C.

    2013-09-01

    Picked-up ion precipitations are a potential mechanism to increase an atmospheric escape from the unmagnetized planet of Mars. The interplanetary magnetic field (IMF) embedded in the supersonic solar wind is one of the crucial parameters to control the behavior of the Martian planetary heavy ions. We statistically investigated the effects of the IMF orientation on planetary heavy ions precipitating toward the Martian ionosphere by using data obtained from the Ion Mass Analyzer (IMA) onboard the Mars Express (MEX). To compensate for the absence of a magnetometer onboard MEX, we estimated the IMF orientation from the velocity distribution function of exospheric protons observed in the solar wind. The statistical analysis shows that the precipitations of planetary heavy ions tend to be observed in the direction or the anti-parallel direction of the solar wind electric field inferred from the estimated IMF orientation. We defined the IMF polarity for one event via comparisons of the ion velocity distribution function obtained from MEX/IMA observations and a statistical trajectory tracing of test particles. The estimated polarity corresponds to the anti-parallel direction to the solar wind electric field and is consistent with the asymmetrical distribution of planetary heavy ion precipitation in terms of the solar wind electric field derived from the previous numerical simulations. The observed precipitating planetary heavy ions are accelerated only up to a few keV. This feature may reflect the short distance from the picked-up region in the magnetosheath.

  4. Effects of humic substances on precipitation and aggregation of zinc sulfide nanoparticles

    USGS Publications Warehouse

    Deonarine, A.; Lau, B.L.T.; Aiken, G.R.; Ryan, J.N.; Hsu-Kim, H.

    2011-01-01

    Nanoparticulate metal sulfides such as ZnS can influence the transport and bioavailability of pollutant metals in anaerobic environments. The aim of this work was to investigate how the composition of dissolved natural organic matter (NOM) influences the stability of zinc sulfide nanoparticles as they nucleate and aggregate in water with dissolved NOM. We compared NOM fractions that were isolated from several surface waters and represented a range of characteristics including molecular weight, type of carbon, and ligand density. Dynamic light scattering was employed to monitor the growth and aggregation of Zn-S-NOM nanoparticles in supersaturated solutions containing dissolved aquatic humic substances. The NOM was observed to reduce particle growth rates, depending on solution variables such as type and concentration of NOM, monovalent electrolyte concentration, and pH. The rates of growth increased with increasing ionic strength, indicating that observed growth rates primarily represented aggregation of charged Zn-S-NOM particles. Furthermore, the observed rates decreased with increasing molecular weight and aromatic content of the NOM fractions, while carboxylate and reduced sulfur content had little effect. Differences between NOM were likely due to properties that increased electrosteric hindrances for aggregation. Overall, results of this study suggest that the composition and source of NOM are key factors that contribute to the stabilization and persistence of zinc sulfide nanoparticles in the aquatic environment. ?? 2011 American Chemical Society.

  5. Effects of humic substance on precipitation and aggregation of zinc sulfide nanoparticles

    USGS Publications Warehouse

    Deonarine, Amrika; Lau, Boris L.T.; Aiken, George R.; Ryan, Joseph N.; Hsu-Kim, Heileen

    2011-01-01

    Nanoparticulate metal sulfides such as ZnS can influence the transport and bioavailability of pollutant metals in anaerobic environments. The aim of this work was to investigate how the composition of dissolved natural organic matter (NOM) influences the stability of zinc sulfide nanoparticles as they nucleate and aggregate in water with dissolved NOM. We compared NOM fractions that were isolated from several surface waters and represented a range of characteristics including molecular weight, type of carbon, and ligand density. Dynamic light scattering was employed to monitor the growth and aggregation of Zn-S-NOM nanoparticles in supersaturated solutions containing dissolved aquatic humic substances. The NOM was observed to reduce particle growth rates, depending on solution variables such as type and concentration of NOM, monovalent electrolyte concentration, and pH. The rates of growth increased with increasing ionic strength, indicating that observed growth rates primarily represented aggregation of charged Zn-S-NOM particles. Furthermore, the observed rates decreased with increasing molecular weight and aromatic content of the NOM fractions, while carboxylate and reduced sulfur content had little effect. Differences between NOM were likely due to properties that increased electrosteric hindrances for aggregation. Overall, results of this study suggest that the composition and source of NOM are key factors that contribute to the stabilization and persistence of zinc sulfide nanoparticles in the aquatic environment.

  6. Dynamics and aggregation of the peptide ion channel alamethicin. Measurements using spin-labeled peptides.

    PubMed Central

    Archer, S J; Ellena, J F; Cafiso, D S

    1991-01-01

    Two spin-labeled derivatives of the ion conductive peptide alamethicin were synthesized and used to examine its binding and state of aggregation. One derivative was spin labeled at the C-terminus and the other, a leucine analogue, was spin labeled at the N-terminus. In methanol, both the C and N terminal labeled peptides were monomeric. In aqueous solution, the C-terminal derivative was monomeric at low concentrations, but aggregated at higher concentrations with a critical concentration of 23 microM. In the membrane, the C-terminal label was localized to the membrane-aqueous interface using 13C-NMR, and could assume more than one orientation. The membrane binding of the C-terminal derivative was examined using EPR, and it exhibited a cooperativity seen previously for native alamethicin. However, this cooperativity was not the result of an aggregation of the peptide in the membrane. When the spectra of either the C or N-terminal labeled peptide were examined over a wide range of membrane lipid to peptide ratios, no evidence for aggregation could be found and the peptides remained monomeric under all conditions examined. Because electrical measurements on this peptide provide strong evidence for an ion-conductive aggregate, the ion-conductive form of alamethicin likely represents a minor fraction of the total membrane bound peptide. PMID:1717016

  7. Activation energies of colloidal particle aggregation: towards a quantitative characterization of specific ion effects.

    PubMed

    Tian, Rui; Yang, Gang; Li, Hang; Gao, Xiaodan; Liu, Xinmin; Zhu, Hualing; Tang, Ying

    2014-05-21

    A quantitative description of specific ion effects is an essential and focused topic in colloidal and biological science. In this work, the dynamic light scattering technique was employed to study the aggregation kinetics of colloidal particles in the various alkali ion solutions with a wide range of concentrations. It indicated that the activation energies could be used to quantitatively characterize specific ion effects, which was supported by the results of effective hydrodynamic diameters, aggregation rates and critical coagulation concentrations. At a given concentration of 25 mmol L(-1), the activation energies for Li(+) are 1.2, 5.7, 28, and 126 times as much for Na(+), K(+), Rb(+), and Cs(+), respectively. Most importantly, the activation energy differences between two alkali cation species increase sharply with decrease of electrolyte concentrations, implying the more pronounced specific ion effects at lower concentrations. The dominant role of electrolyte cations during the aggregation of negatively charged colloidal particles was confirmed by alternative anions. Among the various theories, only the polarization effect can give a rational interpretation of the above specific ion effects, and this is substantially supported by the presence of strong electric fields from montmorillonite surfaces and its association mainly with electrolyte cations and montmorillonite particles. The classical induction theory, although with inclusion of electric field, requires significant corrections because it predicts an opposite trend to the experimentally observed specific ion effects. PMID:24603654

  8. Influence of Inorganic Ions on Aggregation and Adsorption Behaviors of Human Adenovirus

    EPA Science Inventory

    In this study, we investigated the influence of inorganic ions on the aggregation and deposition (adsorption) behavior of human adenovirus (HAdV). Experiments were conducted to determine the surface charge and size of HAdV and viral adsorption capacity of sand in different salt c...

  9. Spontaneous aggregation of lithium ion coordination polymers in fluorinated electrolytes for high-voltage batteries.

    PubMed

    Malliakas, Christos D; Leung, Kevin; Pupek, Krzysztof Z; Shkrob, Ilya A; Abraham, Daniel P

    2016-04-28

    Fluorinated carbonates are pursued as liquid electrolyte solvents for high-voltage Li-ion batteries. Here we report aggregation of [Li(+)(FEC)3]n polymer species in fluoroethylene carbonate containing electrolytes and scrutinize the causes for this behavior. PMID:27040896

  10. Selective nucleation induced by defect nanostructures: A way to control cobalt disilicide precipitation during ion implantation

    SciTech Connect

    Fortuna, F.; Nguyen, M.-A.; Ruault, M.-O.; Kirk, M. A.; Borodin, V. A.; Ganchenkova, M. G.

    2012-12-15

    In this paper, we show a way to control cobalt disilicide precipitation during Co ion implantation at high temperatures (650 Degree-Sign C) by affecting radiation defects involved in precipitate nucleation and growth. We demonstrate that the relative shares of different precipitate types nucleated by implantation are strongly affected by defect microstructures deliberately created in investigated samples prior to cobalt implantation. Especially interesting is the effect of a dense ensemble of extremely small (1-3 nm) cavities, which promotes the formation of a relatively uniform layer of coherent cobalt disilicide precipitates with a narrow size distribution. In order to better understand the mechanism of the microstructural influence on the precipitate nucleation modes during Co implantation, we investigate the disilicide precipitation using different implantation setups and compare the results with those for cavity-free Si specimens implanted in similar conditions.

  11. Selective nucleation induced by defect nanostructures: A way to control cobalt disilicide precipitation during ion implantation

    NASA Astrophysics Data System (ADS)

    Fortuna, F.; Nguyen, M.-A.; Ruault, M.-O.; Kirk, M. A.; Borodin, V. A.; Ganchenkova, M. G.

    2012-12-01

    In this paper, we show a way to control cobalt disilicide precipitation during Co ion implantation at high temperatures (650 °C) by affecting radiation defects involved in precipitate nucleation and growth. We demonstrate that the relative shares of different precipitate types nucleated by implantation are strongly affected by defect microstructures deliberately created in investigated samples prior to cobalt implantation. Especially interesting is the effect of a dense ensemble of extremely small (1-3 nm) cavities, which promotes the formation of a relatively uniform layer of coherent cobalt disilicide precipitates with a narrow size distribution. In order to better understand the mechanism of the microstructural influence on the precipitate nucleation modes during Co implantation, we investigate the disilicide precipitation using different implantation setups and compare the results with those for cavity-free Si specimens implanted in similar conditions.

  12. Insights into riming and aggregation processes as revealed by aircraft, radar, and disdrometer observations for a 27 April 2011 widespread precipitation event: Insights into Riming and Aggregation

    DOE PAGESBeta

    Giangrande, Scott E.; Toto, Tami; Bansemer, Aaron; Kumjian, Matthew R.; Mishra, Subhashree; Ryzhkov, Alexander V.

    2016-05-19

    Our study presents aircraft spiral ascent and descent observations intercepting a transition to riming processes during widespread stratiform precipitation. The sequence is documented using collocated scanning and profiling radar, including longer-wavelength dual polarization measurements and shorter-wavelength Doppler spectra. Riming regions are supported using aircraft measurements recording elevated liquid water concentrations, spherical particle shapes, and saturation with respect to water. Profiling cloud radar observations indicate riming regions during the event as having increasing particle fall speeds, rapid time-height changes, and bimodalities in Doppler spectra. These particular riming signatures are coupled to scanning dual polarization radar observations of higher differential reflectivity (ZDR)more » aloft. Moreover, reduced melting layer enhancements and delayed radar bright-band signatures in the column are also observed during riming periods, most notably with the profiling radar observations. The bimodal cloud radar Doppler spectra captured near riming zones indicate two time-height spectral ice peaks, one rimed particle peak, and one peak associated with pristine ice needle generation and/or growth between -4°C and -7°C also sampled by aircraft probes. We observe this pristine needle population near the rimed particle region which gives a partial explanation for the enhanced ZDR. The riming signatures aloft and radar measurements within the melting level are weakly lag correlated (r~0.6) with smaller median drop sizes at the surface, as compared with later times when aggregation of larger particle sizes was believed dominant.« less

  13. High latitude proton precipitation and light-ion density profiles during the magnetic storm initial phase

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Measurements of precipitating protons and light ion densities by experiments on OGO-4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause , up to Lambda 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3 kev and 23.8 kev protons is approximately 1 deg, compared with a 3.6 deg separation which has been computed using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons ase injected in predawn hours, with widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than approximately 7 kev drift eastward, while the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

  14. General association between discrete auroras and ion precipitation from the tail

    SciTech Connect

    Lyons, L.R.; Fennell, J.F.; Vampola, A.L.

    1988-11-01

    Using two-dimensional observations from the spinning, polar-orbiting S3-3 satellite, we have compared the locations of regions that we identify as discrete auroral arcs with regions of isotropic ion precipitation. Regions of discrete auroral arcs are defined to be regions containing particle distributions consistent with field-aligned potential drops approx. >0.5 kV. Polar cap arcs and local times near noon (0900--1500 MLT) are excluded from this study. Our most important result is that the inferred locations of discrete auroral arcs are almost exclusively confined to the region of isotropic ion precipitation at all local times studied. In the rare exceptions, the ion pitch angle distributions approach isotropy. This association is what is expected if magnetic field lines containing discrete auroal arcs thread the tail current sheet at distances where ion motion violates the guiding center approximations. We have also found that discrete arc regions are generally associated with spatial structure and boundaries in the precipitating ions. Additionally, we occasionally observe upward going, return-current electrons, and these are also associated with the structured, isotropic ion precipitation. copyright American Geophysical Union 1988

  15. Multiple Timescale Comparison of the Aggregate Drought Index (ADI), the Standardized Precipitation Index (SPI), and Tree Rings in Southern California

    NASA Astrophysics Data System (ADS)

    Keyantash, J.; Sakata, C.

    2012-12-01

    The Aggregate Drought Index (ADI) [Keyantash and Dracup, 2004] is a drought index computed using the principal components of selected hydrological variables such as precipitation, evaporation, streamflow, reservoir storage, soil moisture, and alpine snowpack. Like the widely-used Standardized Precipitation Index (SPI), the ADI possesses the ability to simultaneously assess the shortage/abundance of water over a variety of desired timescales (e.g., 1 month, 12 month, 24 month, etc.). In this paper, the ADI is compared against the SPI, over multiple timescales, in the San Jacinto and Santa Ana River basins of Southern California. The comparisons occur between water years 1962 and 2011, an interval which spans three historic Southern California droughts (1976-77, 1987-1992, and 2007-2009). In both river basins, the drought indices are also compared against tree ring reconstructions of Big Cone Douglas Fir (Pseudotsuga macrocarpa), during a common crossover period in the latter 20th century. For historical perspective, the oldest tree ring reconstruction extends back to the year 1375.

  16. A general association between discrete auroras and ion precipitation from the tail

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.; Fennell, J. F.; Vampola, A. L.

    1988-01-01

    Observations from the spinning polar-orbiting S3-3 satellite were used to compare the locations of discrete auroral arcs (defined to be regions containing particle distributions consistent with field-aligned potential drops of not less than 0.5 kV) with regions of isotropic ion precipitation. It was found that the regions of discrete aurora are almost exclusively confined to the region of isotropic ion precipitation at all local times studied (polar cap arcs and local times near noon were not considered). It was also found that, throughout the local time interval studied, the discrete aurora was generally associated with spatial structure and boundaries in the precipitating ions, indicating that arc generation may be associated with structure in the particle population within the tail current sheet.

  17. Precipitation of nanoscale mercuric sulfides in the presence of natural organic matter: Structural properties, aggregation, and biotransformation

    NASA Astrophysics Data System (ADS)

    Pham, Anh Le-Tuan; Morris, Amanda; Zhang, Tong; Ticknor, Jonathan; Levard, Clément; Hsu-Kim, Heileen

    2014-05-01

    Mercuric sulfide species are likely the predominant forms of mercury (Hg) in anoxic environments where the bioavailability of Hg is a key factor for the production of methylmercury (MeHg) by microorganisms. Dissolved organic matter (DOM) is known to affect the formation, aggregation, and dissolution of HgS particles; however the connection of these processes to Hg bioavailability is not well understood. The objectives of this study were to gain insights into the molecular structure and aggregation properties of nanoscale HgS particles that were formed and aged in the presence of DOM and to link this information to bioavailability for methylating bacteria. Characterization of nanoscale HgS was performed with a series of techniques including transmission electron microscopy, photon scattering, X-ray diffraction, and X-ray absorption spectroscopy. The characterization results indicated that the HgS precipitates formed were metacinnabar-like spherical nanoparticles that were 3-5 nm in diameter. Over the course of the aging process, HgS nanoparticles (nano-HgS) agglomerated to form mass-fractal aggregates, although the size of each primary particle within the aggregates remained unchanged. Furthermore, the crystallinity of nano-HgS increased as the particles aged. The methylation potential of nano-HgS by sulfate-reducing bacteria decreased during the aging process. No clear correlation was observed between the net productions of MeHg and the concentrations of dissolved Hg(II) in the culture media, suggesting that the decrease in the methylation potential of aged nano-HgS was not simply because of the slower supply of dissolved Hg(II) by nano-HgS. While the link between the aging of nano-HgS and decrease of methylation potential is not fully understood, the results of our study indicate that freshly formed HgS particles in DOM-rich water will include a variety of nanoscale structures that have a wide range of methylation potentials. This knowledge provides a basis for

  18. Compressive strength and resistance to chloride ion penetration and carbonation of recycled aggregate concrete with varying amount of fly ash and fine recycled aggregate.

    PubMed

    Sim, Jongsung; Park, Cheolwoo

    2011-11-01

    Construction and demolition waste has been dramatically increased in the last decade, and social and environmental concerns on the recycling have consequently been increased. Recent technology has greatly improved the recycling process for waste concrete. This study investigates the fundamental characteristics of concrete using recycled concrete aggregate (RCA) for its application to structural concrete members. The specimens used 100% coarse RCA, various replacement levels of natural aggregate with fine RCA, and several levels of fly ash addition. Compressive strength of mortar and concrete which used RCA gradually decreased as the amount of the recycled materials increased. Regardless of curing conditions and fly ash addition, the 28 days strength of the recycled aggregate concrete was greater than the design strength, 40 MPa, with a complete replacement of coarse aggregate and a replacement level of natural fine aggregate by fine RCA up to 60%. The recycled aggregate concrete achieved sufficient resistance to the chloride ion penetration. The measured carbonation depth did not indicate a clear relationship to the fine RCA replacement ratio but the recycled aggregate concrete could also attain adequate carbonation resistance. Based on the results from the experimental investigations, it is believed that the recycled aggregate concrete can be successfully applied to structural concrete members. PMID:21784626

  19. 2-D Three Fluid Simulation of Upstreaming Ions Above Auroral Precipitation

    NASA Astrophysics Data System (ADS)

    Danielides, M. A.; Lummerzheim, D.; Otto, A.; Stevens, R. J.

    2006-12-01

    The ionosphere is a rich reservoir of charged particles from which a variable fraction is transported to the magnetosphere. An important transport phenomena is the formation of upward ion flow above auroral structure. A primary region of the outflow is not known, but contributions come from polar cap, dayside cusp/cleft region, auroral oval, or even from mid-latitudes. In the past global magnetospheric models and fluid codes were used to simulate large scale ion outflow above, e.g., the polar-cap aurora. However, satellites orbiting at low- altitudes have repeatingly detected localized ion outflow above the auroral oval. Ionosphere-magnetosphere coupling simulations gave first insides into the small-scale dynamics of aurora. The aim of this study is the investigation of coupled plasma and neutral dynamics in smaller scale aurora to explain the generation, structure, and dynamics of vertical ion upstream. We consider auroral electron precipitation at ionospheric heights in a 2-D three fluid ionospheric-magnetospheric coupling code (Otto and Zhu, 2003). Specially we examine the effects of the electron precipitation, heat conduction and heating in field- aligned current through coulomb collisions or turbulence causing: i) electron heating, ii) electron pressure gradients, and iii) upstreaming of ions through a resulting ambipolar electric field. Our first case studies are performed for different boundary conditions and for different auroral electron precipitation parameters (variation in characteristic auroral energy, auroral energy flux and horizontal scale). The results shall clarify how auroral precipitation can drive ions upwards. Finally we discuss the effect of ion drag and the interaction of the upstreaming ions with a stable neutral constituent. Otto, O. and H. Zhu, Fluid plasma simulation of coupled systems: Ionosphere and magnetosphere, Space Plasma Simulation. Edited by J. Buechner, C. Dum, and M. Scholer., Lecture Notes in Physics, vol. 615, p.193

  20. Traumatic Brain Injury Precipitates Cognitive Impairment and Extracellular Aβ Aggregation in Alzheimer's Disease Transgenic Mice

    PubMed Central

    Shimizu, Toru; Arendash, Gary W.; Borlongan, Cesar V.

    2013-01-01

    Traumatic brain injury (TBI) has become a signature wound of the wars in Iraq and Afghanistan. Many American soldiers, even those undiagnosed but likely suffering from mild TBI, display Alzheimer's disease (AD)-like cognitive impairments, suggesting a pathological overlap between TBI and AD. This study examined the cognitive and neurohistological effects of TBI in presymptomatic APP/PS1 AD-transgenic mice. AD mice and non-transgenic (NT) mice received an experimental TBI on the right parietal cortex using the controlled cortical impact model. Animals were trained in a water maze task for spatial memory before TBI, and then reevaluated in the same task at two and six weeks post-TBI. The results showed that AD mice with TBI made significantly more errors in the task than AD mice without TBI and NT mice regardless of TBI. A separate group of AD mice and NT mice were evaluated neurohistologically at six weeks after TBI. The number of extracellular beta-amyloid (Aβ)-deposits significantly increased by at least one fold in the cortex of AD mice that received TBI compared to the NT mice that received TBI or the AD and NT mice that underwent sham surgery. A significant decrease in MAP2 positive cells, indicating neuronal loss, was observed in the cortex of both the AD and NT mice that received TBI compared to the AD and NT mice subjected to sham surgery. Similar changes in extracellular Aβ deposits and MAP2 positive cells were also seen in the hippocampus. These results demonstrate for the first time that TBI precipitates cognitive impairment in presymptomatic AD mice, while also confirming extracellular Aβ deposits following TBI. The recognition of this pathological link between TBI and AD should aid in developing novel treatments directed at abrogating cellular injury and extracellular Aβ deposition in the brain. PMID:24223856

  1. Traumatic brain injury precipitates cognitive impairment and extracellular Aβ aggregation in Alzheimer's disease transgenic mice.

    PubMed

    Tajiri, Naoki; Kellogg, S Leilani; Shimizu, Toru; Arendash, Gary W; Borlongan, Cesar V

    2013-01-01

    Traumatic brain injury (TBI) has become a signature wound of the wars in Iraq and Afghanistan. Many American soldiers, even those undiagnosed but likely suffering from mild TBI, display Alzheimer's disease (AD)-like cognitive impairments, suggesting a pathological overlap between TBI and AD. This study examined the cognitive and neurohistological effects of TBI in presymptomatic APP/PS1 AD-transgenic mice. AD mice and non-transgenic (NT) mice received an experimental TBI on the right parietal cortex using the controlled cortical impact model. Animals were trained in a water maze task for spatial memory before TBI, and then reevaluated in the same task at two and six weeks post-TBI. The results showed that AD mice with TBI made significantly more errors in the task than AD mice without TBI and NT mice regardless of TBI. A separate group of AD mice and NT mice were evaluated neurohistologically at six weeks after TBI. The number of extracellular beta-amyloid (Aβ)-deposits significantly increased by at least one fold in the cortex of AD mice that received TBI compared to the NT mice that received TBI or the AD and NT mice that underwent sham surgery. A significant decrease in MAP2 positive cells, indicating neuronal loss, was observed in the cortex of both the AD and NT mice that received TBI compared to the AD and NT mice subjected to sham surgery. Similar changes in extracellular Aβ deposits and MAP2 positive cells were also seen in the hippocampus. These results demonstrate for the first time that TBI precipitates cognitive impairment in presymptomatic AD mice, while also confirming extracellular Aβ deposits following TBI. The recognition of this pathological link between TBI and AD should aid in developing novel treatments directed at abrogating cellular injury and extracellular Aβ deposition in the brain. PMID:24223856

  2. Mars heavy ion precipitating flux as measured by Mars Atmosphere and Volatile EvolutioN

    NASA Astrophysics Data System (ADS)

    Leblanc, F.; Modolo, R.; Curry, S.; Luhmann, J.; Lillis, R.; Chaufray, J. Y.; Hara, T.; McFadden, J.; Halekas, J.; Eparvier, F.; Larson, D.; Connerney, J.; Jakosky, B.

    2015-11-01

    In the absence of an intrinsic dipole magnetic field, Mars' O+ planetary ions are accelerated by the solar wind. Because of their large gyroradius, a population of these planetary ions can precipitate back into Mars' upper atmosphere with enough energy to eject neutrals into space via collision. This process, referred to as sputtering, may have been a dominant atmospheric loss process during earlier stages of our Sun. Yet until now, a limited number of observations have been possible; Analyzer of Space Plasmas and Energetic Atoms-3/Mars Express observed such a precipitation only during extreme conditions, suggesting that sputtering might be not as intense as theoretically predicted. Here we describe one example of precipitation of heavy ions during quiet solar conditions. Between November 2014 and April 2015, the average precipitating flux is significant and in agreement with predictions. From these measured precipitating fluxes, we estimate that a maximum of 1.0 × 1024 O/s could have been lost due to sputtering.

  3. An Improved Process for Precipitating Cyanide Ions from the Barren Solution at Different pHs

    NASA Astrophysics Data System (ADS)

    Figueroa, Gabriela V.; Parga, José R.; Valenzuela, Jesus L.; Vázquez, Victor; Valenzuela, Alejandro; Rodriguez, Mario

    2016-02-01

    In recent decades, the use of metal sulfides instead of hydroxide precipitation in hydrometallurgical processes has gained prominence. Some arguments for its preferential use are as follows: a high degree of metal removal at relatively low pH values, the sparingly soluble nature of sulfide precipitates, favorable dewatering characteristics, and the stability of the formed metal sulfides. The Merrill-Crowe zinc-precipitation process has been applied worldwide in a large number of operations for the recovery of gold and silver from cyanide solutions. However, in some larger plants, the quality of this precious precipitate is low because copper, zinc and especially lead are precipitated along with gold and silver. This results in higher consumption of zinc dust and flux during the smelting of the precipitate, the formation of the matte, and a shorter crucible life. The results show that pH has a significant effect on the removal efficiency of zinc and copper cyanide ions. The optimal pH range was determined to be 3-4, and the removal efficiency of zinc and copper cyanide ions was up to 99%.

  4. Ion precipitation in planetary upper atmospheres: test particle simulations and implications for escape

    NASA Astrophysics Data System (ADS)

    Parkinson, Christopher; Liemohn; Fang, Xiaohua

    A 3-D Monte Carlo energetic particle transport model has been developed and successfully applied to ion precipitation into planetary upper atmospheres in our solar system (viz., Earth, Mars, Jupiter, and Saturn), and can be readily be extended using a full Lorentz motion formu-lation in the absence of strong dipole planetary magnetic fields. This model can be used with a variety of other models to assess the influence of hot ion precipitation on the thermosphere and exosphere of planetary atmospheres and the subsequent sputtering and escape. For instance in the case of Mars, a pick-up ion transport model already exists to allow for particle acceleration exerted by the convection electric field used in conjunction with existing model results from the Mars Thermosphere General Circulation Model (MTGCM) and the BATS-R-US global MHD model. The loss of exospheric neutrals through ionization, in which they become pick-up ions in the solar wind, can be calculated to examine the relative contribution of the various ionization processes. Solar wind protons as well as pick-up ions from a planetary exosphere routinely enter and alter their upper atmosphere. A study of the pick-up ion escape, sputtering, ion-ization, excitation, and energy deposition will be reviewed and discussed, resulting in a robust examination of the influence of energetic ion transport on planetary upper atmospheres.

  5. Reversed energy-latitude dependence of ion precipitation boundary: observations and possible mechanisms

    NASA Astrophysics Data System (ADS)

    Liang, J.; Donovan, E.; Ni, B.; Angelopoulos, V.

    2013-12-01

    A previous survey by Donovan et al. [2003] revealed that there exist two typical patterns in terms of the energy-latitude dependence of the ion precipitation boundary. In one common pattern, the precipitation flux diminishes at higher (lower) latitudes for protons with lower (higher) energies. Correspondently, at a fixed latitude, the isotropic ratio, defined as the ratio between the precipitation flux and the trapped flux, tends to be higher (lower) for protons with higher (lower) energies. This pattern conforms to the scenario of the pitch-angle scattering of protons led by the field line curvature in the equatorial magnetosphere, which is well recognized as a major mechanism leading to the precipitation of plasma sheet protons. The second pattern, albeit less common than the first one, features distinctly 'reversed' energy-latitude dependences of the ion precipitation boundary, namely that, (a) the isotropic ratio diminishes at higher (lower) latitudes for protons with higher (lower) energies; (b) at a fixed latitude the isotropic ratio tends to be lower (higher) for protons with higher (lower) energies. Donovan et al. [2003] further noted that latter "reversed-type" events predominantly occur in midnight-morning MLT sectors, while their underlying mechanisms remain to be explored. In this study, we present detailed analyses of a few events with this 'reversed' energy-latitude dependence of the ion precipitation boundary, based upon joint observations from low-Earth-orbit satellites and THEMIS in-situ probes. We explore two potential mechanisms: the ion acceleration led by downward parallel electric field in the topside ionosphere, and the pitch-angle scattering of plasma sheet protons by electromagnetic ion cyclotron (EMIC) waves in the equatorial tail. Both mechanisms may act to enhance the precipitation fluxes of protons in energy range mainly between a few hundred eV and several keV; when they are operative in a region southward/earthward of the b2i boundary

  6. The chemical precipitation of nickel on ion exchangers and active carbons

    NASA Astrophysics Data System (ADS)

    Khorol'Skaya, S. V.; Zolotukhina, E. V.; Polyanskii, L. N.; Peshkov, S. V.; Kravchenko, T. A.; Krysanov, V. A.

    2010-12-01

    The chemical precipitation of nickel in the form of poorly soluble precipitates in ion exchanger matrices and on active carbons from solutions of nickel chloride and chemical nickel plating electrolytes was studied. The sorption of nickel ions from a solution of nickel chloride occurs most effectively on Purolite D24002 macroporous chelate forming ion exchanger, KU-23-15/100 sulfo cation exchanger, and KU-2-8 gel sulfo cation exchanger. Nickel enters sulfo cation exchangers in the form of counterions, and is adsorbed on Purolite D24002 largely because of complex formation. The subsequent precipitation of nickel in the solid state in matrix pores liberates ionogenic centers, which allows repeated sorption cycles to be performed. After three chemical precipitation cycles under static conditions, the amount of nickel is higher by 170-250% than the ion exchange capacity of the sorbents. The electrolyte of chemical nickel plating contains nickel predominantly in the form of negatively charged and neutral complexes with glycine, which cannot form bonds with the matrices under study. It is therefore reasonable to perform sorption at decreased solution pH values.

  7. IMPROVEMENT UPON THE CARRIER PRECIPITATION OF PLUTONIUM IONS FROM NITRIC ACID SOLUTIONS

    DOEpatents

    James, R.A.; Thompson, S.G.

    1958-12-23

    A process is reported for improving the removal of plutonlum by carrier precipitation by the addition of nitrite ions to a nitrlc acid solutlon of neutronirradiated unanium so as to destroy any hydrazine that may be present in the solution since the hydrazine tends to complex the tetravalent plutonium and prevents removal by the carrier precipltate, such as bismuth phospbate.

  8. AUREOL-3 observations of new boundaries in the auroral ion precipitation

    NASA Technical Reports Server (NTRS)

    Bosqued, Jean M.; Ashour-Abdalla, Maha; El Alaoui, Mostafa; Zelenyj, Lev M.; Berthlier, Annick

    1993-01-01

    Interesting and well-separated structures in the 1-20 keV ion precipitation pattern have been revealed by an analysis of more than 50 crossings of the nightside (21-03 MLT) auroral zone by the AUREOL-3 satellite. First, velocity-dispersed ion structures (VDIS) are crossed near the poleward edge of the oval, and are the best ionospheric signature of ion beams flowing along the plasma sheet boundary layer. Proceeding equatorward, a large majority of VDIS events are bounded by a new and interesting narrow band of strongly reduced precipitation, or a gap, which delineates VDIS from the diffuse precipitation region connected to the CPS. A statistical analysis shows that the gap has an extent of about 1-2 deg, which is almost independent of magnetic activity; its location, about 70 deg ILAT, shifts significantly equatorward with higher magnetic activity levels. Intense electron arcs are observed near the equatorward edge of the gap. An important result is that the overall sequence of VDIS-gap-CPS can be explained in terms of orbital dynamics in the tail. The gap in precipitation appears as the counterpart of the 'wall' regime in the equatorial plane, in which a cross-tail current carried by energetic ions is strongly enhanced between 8 and 12 R(E). This region has important consequences for the development of substorms.

  9. Particle precipitation due to ion-cyclotron instability in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Yahnin, Alexander

    Electromagnetic ion-cyclotron (EMIC) waves in the near-Earth equatorial magnetosphere effectively scatter energetic ions into the loss cone. As consequence, localized precipitation of energetic protons (LPEP) within the anisotropy zone is observed by low-orbiting satellites, like NOAA POES. Strong LPEP produces sub-oval proton auroras, which provide a two-dimensional image of the source region on the ionospheric screen. Here, we present some multipoint conjugate measurements confirming the relationship between LPEP and EMIC waves. Also, a conjugacy of LPEP and plasmapause structures is proved. In addition to LPEP, a wide (both in latitude and longitude) area of proton precipitation is often observed outside the plasmapause at sub-oval latitudes on the dayside. Both the case and statistical studies confirm that this dayside proton precipitation correlates with EMIC waves. Development of the ion-cyclotron instability on the dayside is evidently due to the enhanced transverse anisotropy of proton fluxes, which, in turn, is the result of the drift shell splitting. The anisotropy is “modulated” by the solar wind dynamic pressure. During magnetosphere compressions the precipitating proton flux increases, and flashes of the sub-oval proton aurora can be observed the dayside. It is suggested that EMIC waves also scatter relativistic electrons. Using the proton precipitation within the anisotropy zone as an indicator of the ion-cyclotron instability we performed a search of simultaneous relativistic electron precipitation (REP). We found that only 10 percent of REP events could be considered as potentially related to EMIC waves. These “EMIC wave related REP events” are observed only in the evening sector in connection with the plasmaspheric plume.

  10. Use of ion chromatography for analysis of MAP3S precipitation samples

    SciTech Connect

    Rothert, J.

    1980-07-01

    The Multistate Atmospheric Power Production Pollution Study/Regional Acidity of Industrial Emissions, MAP3S/RAINE program includes measurement and modeling of fossil-fuel effluent concentrations in precipitation and air in the northeastern United States. To determine precipitation concentrations of sulfur and nitrogen oxides as well as PO/sub 4//sup 3 -/, Cl/sup -/, Na/sup +/, K/sup +/, NH/sub 4//sup +/, Ca/sup 2 +/, Mg/sup 2 +/, pH, and conductivity, an eight-1 site precipitation network in rural eastern United States has been established. Two Dionex Model 10 ion chromatographs are being used to analyze the precipitation samples. This paper describes the use and operation of these instruments. (ACR)

  11. Quantification of alginate by aggregation induced by calcium ions and fluorescent polycations.

    PubMed

    Zheng, Hewen; Korendovych, Ivan V; Luk, Yan-Yeung

    2016-01-01

    For quantification of polysaccharides, including heparins and alginates, the commonly used carbazole assay involves hydrolysis of the polysaccharide to form a mixture of UV-active dye conjugate products. Here, we describe two efficient detection and quantification methods that make use of the negative charges of the alginate polymer and do not involve degradation of the targeted polysaccharide. The first method utilizes calcium ions to induce formation of hydrogel-like aggregates with alginate polymer; the aggregates can be quantified readily by staining with a crystal violet dye. This method does not require purification of alginate from the culture medium and can measure the large amount of alginate that is produced by a mucoid Pseudomonas aeruginosa culture. The second method employs polycations tethering a fluorescent dye to form suspension aggregates with the alginate polyanion. Encasing the fluorescent dye in the aggregates provides an increased scattering intensity with a sensitivity comparable to that of the conventional carbazole assay. Both approaches provide efficient methods for monitoring alginate production by mucoid P. aeruginosa. PMID:26408812

  12. Geochemical mass-balance relationships for selected ions in precipitation and stream water, Catoctin Mountains, Maryland.

    USGS Publications Warehouse

    Katz, B.G.; Bricker, O.P.; Kennedy, M.M.

    1985-01-01

    Results of a study of input/output mass balances for major ions based on the chemical composition of precipitation and stream-water, geochemical reactions with different loading rates of hydrogen ion, and watershed processes influencing the chemical character of stream-waters in two small watershed areas are reported with a view to predicting the effect of additions of acidic rain to the watershed systems. Geochemical weathering processes account for the observed changes in the chemistry of stream flow. Although present in bedrock in extremely small quantities, calcite plays an important role in neutralization of the total hydrogen-ion input.-M.S.

  13. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation.

    PubMed

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  14. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

    PubMed Central

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  15. Dayside pickup oxygen ion precipitation at Venus and Mars - Spatial distributions, energy deposition and consequences

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Kozyra, J. U.

    1991-04-01

    The fluxes and energy spectra of picked-up planetary O(+) ions incident on the dayside atmospheres of Venus and Mars are calculated. Maps of precipitating ion number flux and energy flux are presented which show the asymmetrical distribution of dayside energy deposition expected from this source. Although the associated heating of the atmosphere and ionosphere is found to be negligible compared to that from the usual sources, backscattered or sputtered neutral oxygen atoms are produced at energies which exceed that needed for escape from the gravitational fields of both planets. These neutral 'winds', driven by pickup ion precipitation, represent a possibly significant loss of atmospheric constituents over the age of the solar system.

  16. Precipitation-Induced Voltage-Dependent Ion Current Fluctuations in Conical Nanopores

    SciTech Connect

    Vlassiouk, Ivan V

    2010-01-01

    Single conically shaped nanopores produce stable ion current fluctuations when in contact with weakly soluble salts, such as calcium hydrogen phosphate (CaHPO{sub 4}) and cobalt hydrogen phosphate (CoHPO{sub 4}). The pore spontaneously switches between high and low conductance states, called open and closed states, respectively. Pore opening and closing are linked to the dynamic formation of the calcium and cobalt precipitates at the small opening of the pore. The probabilities of pore opening and closing are voltage-dependent, and this characteristic of ion current signal is known for biological voltage-gated channels. We show that new types of ion current fluctuations are obtained in conditions at which precipitates of CaHPO{sub 4} and CoHPO{sub 4} can form in the pore at the same time.

  17. Deuterium ion irradiation induced precipitation in Fe-Cr alloy: Characterization and effects on irradiation behavior

    NASA Astrophysics Data System (ADS)

    Liu, P. P.; Yu, R.; Zhu, Y. M.; Zhao, M. Z.; Bai, J. W.; Wan, F. R.; Zhan, Q.

    2015-04-01

    A new phase was found to precipitate in a Fe-Cr model alloy after 58 keV deuterium ion irradiation at 773 K. The nanoscale radiation-induced precipitate was studied systematically using high resolution transmission electron microscopy (HRTEM), image simulation and in-situ ultrahigh voltage transmission electron microscopy (HVEM). B2 structure is proposed for the new Cr-rich phase, which adopts a cube-on-cube orientation relationship with regard to the Fe matrix. Geometric phase analysis (GPA) was employed to measure the strain fields around the precipitate and this was used to explain its characteristic 1-dimensional elongation along the <1 0 0> Fe direction. The precipitate was stable under subsequent electron irradiation at different temperatures. We suggest that the precipitate with a high interface-to-volume ratio enhances the radiation resistance of the material. The reason for this is the presence of a large number of interfaces between the precipitate and the matrix, which may greatly reduce the concentration of point defects around the dislocation loops. This leads to a significant decrease in the growth rate.

  18. Na+, Ca2+, and Mg2+ in brines affect supercritical CO2-brine-biotite interactions: ion exchange, biotite dissolution, and illite precipitation.

    PubMed

    Hu, Yandi; Ray, Jessica R; Jun, Young-Shin

    2013-01-01

    For sustainable geologic CO(2) sequestration (GCS), a better understanding of the effects of brine cation compositions on mica dissolution, surface morphological change, and secondary mineral precipitation under saline hydrothermal conditions is needed. Batch dissolution experiments were conducted with biotite under conditions relevant to GCS sites (55-95 °C and 102 atm CO(2)). One molar NaCl, 0.4 M MgCl(2), or 0.4 M CaCl(2) solutions were used to mimic different brine compositions, and deionized water was used for comparison. Faster ion exchange reactions (Na(+)-K(+), Mg(2+)-K(+), and Ca(2+)-K(+)) occurred in these salt solutions than in water (H(+)-K(+)). The ion exchange reactions affected bump, bulge, and crack formation on the biotite basal plane, as well as the release of biotite framework ions. In these salt solutions, numerous illite fibers precipitated after reaction for only 3 h at 95 °C. Interestingly, in slow illite precipitation processes, oriented aggregation of hexagonal nanoparticles forming the fibrous illite was observed. These results provide new information for understanding scCO(2)-brine-mica interactions in saline aquifers with different brine cation compositions, which can be useful for GCS as well as other subsurface projects. PMID:22607371

  19. What is the Relationship Between Heavy Ion Outflow and High-Latitude Energetic Precipitation?

    NASA Technical Reports Server (NTRS)

    Wilson, Gordon R.

    2001-01-01

    Second quarter progress report for year 3 on contract NASW-99002 "What is the Relationship between heavy ion outflow and high latitude energetic particle precipitation". In this Project we are studying the relationship between the fluxes, mean energies, and field-aligned flow speeds of escaping suprathermal H+ and 0+ measured by the TEAMS instrument on FAST and the energy flux of precipitating electrons obtained from the LBHL images taken by the UVI camera on POLAR. In this portion of the project we are using UVI images to tell us when substorm onsets occur and how the auroral zone changes during the course of a substorm. We are correlating this information with TEAMS flux measurements made over the auroral zone at times close to these substorms. The goal is to understand how the flux of suprathermal ion outflow varies with substorm phase.

  20. Composite alginate hydrogel microparticulate delivery system of zidovudine hydrochloride based on counter ion induced aggregation

    PubMed Central

    Roy, Harekrishna; Rao, P. Venkateswar; Panda, Sanjay Kumar; Biswal, Asim Kumar; Parida, Kirti Ranjan; Dash, Jharana

    2014-01-01

    Aim: The present study deals with preparation of zidovudine loaded microparticle by counter ion induced aggregation method. During this study effect of polyacrylates and hypromellose polymers on release study were investigated. Materials and Methods: The ion induced aggregated alginate based microparticles were characterized for surface morphology, particle size analysis, drug entrapment study, in-vitro study, Fourier-transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC) study. Results and Discussion: The result showed Eudragit RL-100 (ERL) based formulations had smoother surface as well as their mean particle sizes were found greater compared with Eudragit RS-100 (ERS) microparticles. Furthermore, drug entrapments were found to be more in ERL formulae as compared with ERS. RL3 released 101.05% drug over a period of 8th h and followed Higuchi profile and Fickian diffusion. Moreover, data obtained illustrated that, higher amount of quaternary ammonium group, alkali value, and glass transition temperature may be possible reason for improving permeability of ERL based formulations. It was also noticed, hyroxypropyl methylcellulose (HPMC) K4M premium grade polymer sustained drug release more than HPMC K15M. In addition, drug-excipient interaction study was carried out by FTIR and DSC study. PMID:25298940

  1. High-latitude proton precipitation and light ion density profiles during the magnetic storm initial phase.

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1973-01-01

    Measurements of precipitating protons and light ion densities by experiments on Ogo 4 indicate that widespread proton precipitation occurs in predawn hours during the magnetic storm initial phase from the latitude of the high-latitude ion trough, or plasmapause, up to latitudes greater than 75 deg. A softening of the proton spectrum is apparent as the plasmapause is approached. The separation of the low-latitude precipitation boundaries for 7.3-keV and 23.8-keV protons is less than about 1 deg, compared with a 3.6-deg separation that has been computed by using the formulas of Gendrin and Eather and Carovillano. Consideration of probable proton drift morphology leads to the conclusion that protons are injected in predawn hours, widespread precipitation occurring in the region outside the plasmapause. Protons less energetic than 7 keV drift eastward, whereas the more energetic protons drift westward, producing the observed dawn-dusk asymmetry for the lower-energy protons.

  2. Specific ion effects induced by mono-valent salts in like charged aggregates in water.

    PubMed

    Huang, Ningdong; Tao, Jiaojiao; Liu, Jun; Wei, Shenghui; Li, Liangbin; Wu, Ziyu

    2014-06-28

    While salt mediated association between similarly charged poly-electrolytes occurs in a broad range of biological and colloidal systems, the effects of mono-valent salts remains little known experimentally. In this communication we systematically study influences of assorted mono-valent salts on structures of and interactions in two dimensional ordered bundles of charged fibrils assembled in water using Small Angle X-ray Scattering (SAXS). By quantitatively analyzing the scattering peak features, we discern two competing effects with opposite influences due to partitioning of salts in the aqueous complex. While electrostatic effects from salts residing between the fibrils suppress attraction between fibrils and expand the bundles, it is compensated by external osmotic pressure from peripheral salts in the aqueous media. The balance between the two effects varies for different salts and gives rise to ion-specific equilibrium behavior as well as structure of ordered bundles in salty water. The specific ions effects in like charged aggregates can be attributed to preferential distribution of ions inside or outside the bundles, correlated to the ranking of ions in Hofmeister series for macromolecules. Unlike conventional studies on Hofmeister effects by thermodynamic measurements relying on modeling for data interpretation, our study is based directly on structural analysis and is model-insensitive. PMID:24828119

  3. Aggregation induced emission enhancement from Bathophenanthroline microstructures and its potential use as sensor of mercury ions in water.

    PubMed

    Mazumdar, Prativa; Das, Debasish; Sahoo, Gobinda Prasad; Salgado-Morán, Guillermo; Misra, Ajay

    2014-04-01

    Bathophenanthroline (BA) microstructures of various morphologies have been synthesized using a reprecipitation method. The morphologies of the particles are characterized using optical and scanning electron microscopy (SEM) methods. An aqueous dispersion of BA microstructures shows aggregation induced emission enhancement (AIEE) compared to BA in a good solvent, THF. This luminescent property of aggregated BA hydrosol is used for the selective detection of trace amounts of mercury ion (Hg(2+)) in water. It is observed that Hg(2+) ions can quench the photoluminescence (PL) intensity of BA aggregates even at very low concentrations, compared to other heavy metal ions e.g. nickel (Ni(2+)), manganese (Mn(2+)), cadmium (Cd(2+)), cobalt (Co(2+)), copper (Cu(2+)), ferrous (Fe(2+)) and zinc (Zn(2+)). This strong fluorescence quenching of aggregated BA in the presence of Hg(2+) ions has been explained as a complex interplay between the ground state complexation between BA and Hg(2+) ions and external heavy atom induced perturbation by Hg(2+) ions on the excited states of the fluorophore BA. PMID:24569390

  4. Desalination and hydrogen, chlorine, and sodium hydroxide production via electrophoretic ion exchange and precipitation.

    PubMed

    Shkolnikov, Viktor; Bahga, Supreet S; Santiago, Juan G

    2012-08-28

    We demonstrate and analyze a novel desalination method which works by electrophoretically replacing sodium and chloride in feed salt water with a pair of ions, calcium and carbonate, that react and precipitate out. The resulting calcium carbonate precipitate is benign to health, and can be filtered or settled out, yielding low ionic strength product water. The ion exchange and precipitation employs self-sharpening interfaces induced by movement of multiple ions in an electric field to prevent contamination of the product water. Simultaneously, the electrolysis associated with the electromigration produces hydrogen gas, chlorine gas, and sodium hydroxide. We conducted an experimental study of this method's basic efficacy to desalinate salt water from 100 to 600 mol m(-3) sodium chloride. We also present physicochemical models of the process, and analyze replacement reagents consumption, permeate recovery ratio, and energy consumption. We hypothesize that the precipitate can be recycled back to replacement reagents using the well-known, commercially implemented Solvay process. We show that the method's permeate recovery ratio is 58% to 46%, which is on par with that of reverse osmosis. We show that the method's energy consumption requirement over and above that necessary to generate electrolysis is 3 to 10 W h l(-1), which is on par with the energy consumed by state-of-the-art desalination methods. Furthermore, the method operates at ambient temperature and pressure, and uses no specialized membranes. The process may be feasible as a part of a desalination-co-generation facility: generating fresh water, hydrogen and chlorine gas, and sodium hydroxide. PMID:22806549

  5. Insights into the crystal and aggregate structure of Fe[superscript 3+] oxide/silica co-precipitates

    SciTech Connect

    Dyer, Laurence G.; Chapman, Karena W.; English, Phillip; Saunders, Martin; Richmond, William R.

    2012-03-15

    Structural characteristics of Fe{sup 3+} oxide/silica co-precipitates were investigated. The association between these materials is relevant to practically all natural aqueous systems due to the prevalence of iron and silicon in the Earth's crust. Crystallographic information is very difficult to obtain from these precipitates due to the nanocrystalline nature of ferrihydrite and the amorphous structure of precipitated silica. Several previously undetermined key insights were gained into the structure of iron oxide/silica co-precipitates through this examination. The distribution of iron and silicon throughout co-precipitate particles is illustrated along with the influence of their association. Evidence to the governing factor behind differences in apparent crystallinity is also presented. This information culminates in the formulation of a precipitation pathway, displaying the formation of the co-precipitates.

  6. The Effect of the CO32- to Ca2+ Ion activity ratio on calcite precipitation kinetics and Sr2+ partitioning

    PubMed Central

    2012-01-01

    Background A proposed strategy for immobilizing trace metals in the subsurface is to stimulate calcium carbonate precipitation and incorporate contaminants by co-precipitation. Such an approach will require injecting chemical amendments into the subsurface to generate supersaturated conditions that promote mineral precipitation. However, the formation of reactant mixing zones will create gradients in both the saturation state and ion activity ratios (i.e., aCO32-/aCa2+). To better understand the effect of ion activity ratios on CaCO3 precipitation kinetics and Sr2+ co-precipitation, experiments were conducted under constant composition conditions where the supersaturation state (Ω) for calcite was held constant at 9.4, but the ion activity ratio (r=aCO32-/aCa2+) was varied between 0.0032 and 4.15. Results Calcite was the only phase observed, by XRD, at the end of the experiments. Precipitation rates increased from 41.3 ± 3.4 μmol m-2 min-1 at r = 0.0315 to a maximum rate of 74.5 ± 4.8 μmol m-2 min-1 at r = 0.306 followed by a decrease to 46.3 ± 9.6 μmol m-2 min-1 at r = 1.822. The trend was simulated using a simple mass transfer model for solute uptake at the calcite surface. However, precipitation rates at fixed saturation states also evolved with time. Precipitation rates accelerated for low r values but slowed for high r values. These trends may be related to changes in effective reactive surface area. The aCO32-/aCa2+ ratios did not affect the distribution coefficient for Sr in calcite (DPSr2+), apart from the indirect effect associated with the established positive correlation between DPSr2+ and calcite precipitation rate. Conclusion At a constant supersaturation state (Ω = 9.4), varying the ion activity ratio affects the calcite precipitation rate. This behavior is not predicted by affinity-based rate models. Furthermore, at the highest ion ratio tested, no precipitation was observed, while at the lowest ion ratio precipitation occurred immediately

  7. Investigation of metal ion extraction and aggregate formation combining acidic and neutral organophosphorous reagents

    SciTech Connect

    Braatz, A.D.; Nilsson, M.; Ellis, R.; Antonio, M.

    2013-07-01

    In the present study, we investigate how varying mixtures of tri-n-butyl phosphate (TBP) and dibutyl phosphate (HDBP) results in enhanced extraction of lanthanum(III), La{sup 3+}, and dysprosium(III), Dy{sup 3+}. Water and metal ion extraction were carefully monitored as a function of TBP:HDBP mole ratio.In addition to these techniques, EXAFS was used to determine the coordination environment of the metal ion in this system. To produce the necessary signal, a concentration of 1.25*10{sup -3} M La{sup 3+} and Dy{sup 3+} was used. Although previous studies of synergistic extraction of metal cations using combinations of neutral and acidic reagents explain the enhanced extraction by increased dehydration of the metal ion and the formation of mixed extractant complexes, our evidence for the increased water extraction coupled with the aggregate formation suggests a reverse micellar aspect to synergism in the system containing TBP and HDBP. It is quite possible that both of these phenomena contribute to our system behavior. The EXAFS data shows that, based on coordination numbers alone, several possible structures may exist. From this study, we cannot provide a definitive answer as to the nature of extraction in this system or the exact complex formed during extraction.

  8. Changes in precipitation isotope-climate relationships from temporal grouping and aggregation of weekly-resolved USNIP data: impacts on paleoclimate and environmental applications

    NASA Astrophysics Data System (ADS)

    Akers, P. D.; Welker, J. M.

    2015-12-01

    Spatial variations in precipitation isotopes have been the focus of much recent research, but relatively less work has explored changes at various temporal scales. This is partly because most spatially-diverse and long-term isotope databases are offered at a monthly resolution, while daily or event-level records are spatially and temporally limited by cost and logistics. A subset of 25 United States Network for Isotopes in Precipitation (USNIP) sites with weekly-resolution in the east-central United States was analyzed for site-specific relationships between δ18O and δD (the local meteoric water line/LMWL), δ18O and surface temperature, and δ18O and precipitation amount. Weekly data were then aggregated into monthly and seasonal data to examine the effect of aggregation on correlation and slope values for each of the relationships. Generally, increasing aggregation improved correlations (>25% for some sites) due to a reduced effect of extreme values, but estimates on regression variable error increased (>100%) because of reduced sample sizes. Aggregation resulted in small, but significant drops (5-25%) in relationship slope values for some sites. Weekly data were also grouped by month and season to explore changes in relationships throughout the year. Significant subannual variability exists in slope values and correlations even for sites with very strong overall correlations. LMWL slopes are highest in winter and lowest in summer, while the δ18O-surface temperature relationship is strongest in spring. Despite these overall trends, a high level of month-to-month and season-to-season variability is the norm for these sites. Researchers blindly applying overall relationships drawn from monthly-resolved databases to paleoclimate or environmental research risk assuming these relationships apply at all temporal resolutions. When possible, researchers should match the temporal resolution used to calculate an isotopic relationship with the temporal resolution of

  9. Structural phase transition of merocyanine J-aggregate induced by ion-recombination in the aqueous sub-phase

    NASA Astrophysics Data System (ADS)

    Kato, Noritaka; Saito, Kentaro; Uesu, Yoshiaki

    2000-08-01

    By using the sub-phase, which contains two different kinds of counter-ions, we found a reversible thermochromic transition between different J-aggregate states of amphiphilic merocyanine dye (MD) molecules in the monolayer at the air-water interface. This chromatic change is attributed to the structural phase transition of MD J-aggregate crystallites induced by the mutual recombination of different counter-ions to MD molecules. The drastic morphological change of the MD monolayer during the transition is revealed by the in-situ observation using a multipurpose non-linear optical microscope.

  10. An observational study of the relationship between precipitating ions and ENAs emerging from the ion/atmosphere interaction region

    NASA Astrophysics Data System (ADS)

    Mackler, David A.

    Plasmasheet particles transported Earthward during times of active magnetospheric convection can interact with thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low altitude (300--800 km) ion precipitation in the high latitude atmosphere/ionosphere are termed Low Altitude Emissions (LAEs). Remotely observed LAEs are highly non-isotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90 degrees. The Geomagnetic Emission Cone (GEC) of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity as well as comparisons of LAE signatures with in situ ion precipitation. The LAE data is from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000--2005). The SYM-H, AE, and Kp indices are used to describe geomagnetic activity. The in situ data is from the Defense Meteorological Satellite Program (DMSP). The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM-H showing the greatest non-linearity. The MLT distribution of LAEs are centered about midnight and spread with increasing activity. The Invariant Latitude for all indices has a slightly negative correlation. The combined results indicate that both LAE and DMSP data behave similarly to geomagnetic activity. LAEs are more spread out in latitude, possibly due to multiple charge exchange interactions, while the in situ data changes to lower latitudes dramatically with increasing flux. The bulk of the data indicates that the

  11. Hybrid surfactants decorated with copper ions: aggregation behavior, antimicrobial activity and anti-proliferative effect.

    PubMed

    Kaur, Gurpreet; Kumar, Sandeep; Dilbaghi, Neeraj; Bhanjana, Gaurav; Guru, Santosh Kumar; Bhushan, Shashi; Jaglan, Sundeep; Hassan, P A; Aswal, V K

    2016-09-14

    In the present study, the emphasis is laid on the self aggregation behavior of copper based inorganic-organic hybrids in aqueous media. The two complexes, cationic hexadecyl pyridinium trichloro cuprate (1 : 1), [Cp](+)[CuCl3](-), and bishexadecylpyridinium tetrachloro cuprate (2 : 1), [Cp2](2+)[CuCl4](2-), were synthesized using the ligand insertion method. The complexes were characterized using elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and thermogravimetric analysis. The copper complexes were found to be thermally stable, and in the solid state, they possessed the perovskite arrangement with [Cp2](2+)[CuCl4](2-) exhibiting superior stability and crystallinity. The self aggregation behavior of the prepared complexes was analyzed in solution phase (in aqueous medium) using surface tension, conductivity, XRD and small angle neutron scattering (SANS). The results show that the presence of copper as a co-ion in both the stoichiometries results in lower critical micellization concentrations than their precursor. Micellization was thermodynamically spontaneous and micelles formed were ellipsoidal in shape and underwent a prolate ellipsoidal growth with an increase in the concentration of metallosurfactant, as estimated from the SANS. Furthermore, these metallosurfactants were investigated for biocompatibility (using hemolytic assay), antimicrobial activity (fungus and bacteria) and cytotoxicity using human cancerous cells. The hemolysis activity was found to depend on the aggregated state of the metallosurfactants, displaying the highest activity in the monomeric state, and the minimum for post micellar concentrations. The surfactants were found to enhance the antibacterial activity by twofold or more, with the addition of metal in both the stoichiometries. On the contrary, for anticancer and antifungal activities, barely any regular trend or generalization could be obtained

  12. Formation of stable nanocarriers by in situ ion pairing during block-copolymer-directed rapid precipitation.

    PubMed

    Pinkerton, Nathalie M; Grandeury, Arnaud; Fisch, Andreas; Brozio, Jörg; Riebesehl, Bernd U; Prud'homme, Robert K

    2013-01-01

    We present an in situ hydrophobic salt forming technique for the encapsulation of weakly hydrophobic, ionizable active pharmaceutical ingredients (API) into stable nanocarriers (NCs) formed via a rapid precipitation process. Traditionally, NC formation via rapid precipitation has been difficult with APIs in this class because their intermediate solubility makes achieving high supersaturation difficult during the precipitation process and the intermediate solubility causes rapid Ostwald ripening or recrystallization after precipitation. By forming a hydrophobic salt in situ, the API solubility and crystallinity can be tuned to allow for NC formation. Unlike covalent API modification, the hydrophobic salt formation modifies properties via ionic interactions, thus circumventing the need for full FDA reapproval. This technique greatly expands the types of APIs that can be successfully encapsulated in NC form. Three model APIs were investigated and successfully incorporated into NCs by forming salts with hydrophobic counterions: cinnarizine, an antihistamine, clozapine, an antipsychotic, and α-lipoic acid, a common food supplement. We focus on cinnarizine to develop the rules for the in situ nanoprecipitation of salt NCs. These rules include the pK(a)s and solubilities of the API and counterion, the effect of the salt former-to-API ratio on particle stability and encapsulation efficiency, and the control of NC size. Finally, we present results on the release rates of these ion pair APIs from the NCs. PMID:23259920

  13. Effect of humic substances aggregation on the determination of fluoride in water using an ion selective electrode.

    PubMed

    Shen, Junjie; Gagliardi, Simona; McCoustra, Martin R S; Arrighi, Valeria

    2016-09-01

    The control of drinking water quality is critical in preventing fluorosis. In this study humic substances (HS) are considered as representative of natural organic matter (NOM) in water. We show that when HS aggregate the response of fluoride ion selective electrodes (ISE) may be perturbed. Dynamic light scattering (DLS) results of both synthetic solutions and natural water sample suggest that low pH and high ionic strength induce HS aggregation. In the presence of HS aggregates, fluoride concentration measured by ISE has a reduction up to 19%. A new "open cage" concept has been developed to explain this reversible phenomenon. The interference of HS aggregation on fluoride measurement can be effectively removed by centrifugation pretreatment. PMID:27276164

  14. The Effect of the CO32- to Ca2+ Ion activity ratio on calcite precipitation kinetics and Sr2+ partitioning

    SciTech Connect

    Tsigabu Gebrehiwet; Mikala S. Beig; George Redden; Yoshiko Fujita; Robert W. Smith

    2012-01-01

    Engineering the precipitation of calcium carbonate, which can co-precipitate trace metal contaminants, is a proposed strategy for remediating toxic or radioactive metals in subsurface environments. Engineering precipitation of multi-component minerals will involve injection of chemical amendments that must be mixed at a molecular level to supersaturated conditions that are sufficient to promote rapid mineral precipitation relative to natural systems. In subsurface systems this often means reactant mixing zones will be formed that are characterized by gradients in solute concentrations, saturation state, and solute activity ratios. To better understand the effect of ion activity ratios on CaCO{sub 3} precipitation kinetics and Sr{sup 2+} co-precipitation we experiments were conducted under constant composition conditions where the supersaturation state ({Omega}) with respect to calcite was held constant at 9.4, but the ion activity ratio (r = a{sub co{sub 3}{sup 2-}}/a{sub Ca{sup 2+}}) ranged from 0.003 to 4.15. Results: Under the chosen experimental conditions the CaCO{sub 3} phase formed was calcite and initial precipitation rates varied from a maximum rate of 84.7 {mu}mol/ m{sup 2}/min for a carbonate to calcium activity ratio of (0.21). However, precipitation rates were found to vary with time which could be indicative of variations in precipitation mechanisms that are related to the ion activity ratio. The observed trends in the distribution coefficients for co-precipitated Sr2+ (D{sup P}{sub Sr}{sup 2+}) relative to the calcite precipitation rate (i.e. a positive correlation) indicate that increasing calcite precipitation rates increase the incorporation of Sr{sup 2+}. Conclusion: The observed variation between the rate maxima and minima based on the ion activity ratio could have great deal of implication for sequestering radionuclides (e.g. {sup 90}Sr) and other toxic metals in engineered systems at contaminated sites. Extending our data plot range allowed us

  15. Diffuse, Monoenergetic, Broadband (wave) and Ion Aurora: Results from a New Generation Precipitation Model

    NASA Astrophysics Data System (ADS)

    Newell, Patrick; Sotirelis, Thomas; Wing, Simon

    We introduce an auroral precipitation model which separately categorizes the discrete aurora and both the electron and ion diffuse aurora. The discrete aurora includes acceleration by two distinct physical mechanisms, namely quasi-static electric fields, producing monoenergetic peaks, and dispersive Alfvén waves, producing broadband electron acceleration. The new model is parameterized by functional fits to solar wind driving, with each MLAT and MLT bin sepa-rately fitted, permitting the first comprehensive comparison of the hemispheric contribution by auroral type. The diffuse aurora is surprisingly dominant, constituting 84 pct of the energy flux into the ionosphere during conditions of low solar wind driving (63 pct e-, 21 pct ions). The diffuse aurora is not quiescent, tripling in power from low to high solar wind driving conditions. Even under the latter condition, the diffuse aurora contains 71 pct of the hemispheric energy flux (57 pct e-, 14 pct ions). Monoenergetic aurora contributes more energy flux than does broadband acceleration signatures. However the broadband aurora rises fastest with activity, increasing by a factor of 8.0 from low to high driving. Seasonal dependence is investigated. Dayside and nightside variations are separately considered, as are conditions of low and high solar wind driving. Several clear patterns emerge. One is that the dayside tends to maximize precipitation in the summer, and much more so for low solar wind driving. Nightside precipita-tion is higher in the winter, and much more so for high solar wind driving. Dayside effects are strongest in number flux, and stronger in diffuse aurora than accelerated aurora. The ease of ion entry through the summer cusp, along with the constraints of charge quasi-neutrality, and the rise in dayside currents in the summer hemisphere adequately explains much (perhaps all) of the dayside behavior. Nightside effects are more apparent in energy flux, with the winter/summer ratio of

  16. Precipitation, dissolution, and ion exchange processes coupled with a lattice Boltzmann advection diffusion solver

    NASA Astrophysics Data System (ADS)

    Hiorth, A.; Jettestuen, E.; Cathles, L. M.; Madland, M. V.

    2013-03-01

    Pore water chemistry can dramatically affect the mechanical strength of chalk cores and the recovery of oil from them, but despite a great many core experiments, the mechanisms responsible remain unclear. This is in part because no single model is presently available that can address the changes in surface complexes and potential and mineral dissolution and precipitation that occur when fluids of different chemistry are injected. We report here the construction of a lattice Boltzmann model that includes non-linear dissolution-precipitation kinetics, surface complexation, and ion exchange. A link-based boundary condition which allows mineral boundaries to move and porosity to change is shown to converge to a correct representation of the macroscopic pore surface area. We show the chemical LB model developed predicts mineral dissolution and ion exchange similar to those predicted by PHREEQC for similar parameters, and we show how the methods developed can be applied to chalk core experiments where synthetic seawater is flooded through the core at 130 °C.

  17. Counter-ion specificity explored in abnormal expansion of supra-molecular aggregates in aqueous solution of alkaline metal salts.

    PubMed

    Huang, Ningdong; Tao, Jiaojiao; Wei, Shenghui; Chen, Mingming; Wei, Chengsha; Li, Liangbin

    2015-09-21

    Ionic effects in aqueous solution of macro-ions showing specificity and unconventional characters, respectively, receive a lot of interests recently; however, the complexity of specific ion effects in unconventional phenomena remains ambiguous. In this study, the effects of univalent ions on aggregation of supra-molecular nano-fibrils with charged carboxylate groups on the surface as a prototype of macro-ions are investigated by Small Angle X-ray Scattering (SAXS) in aqueous solutions of alkaline metal chlorides. It is found that the columnar bundles of charged fibrils are expanded in certain salt concentration range contradicting the conventional screening effects of salts. The degree of expansion is dominated by cations as Na(+) induces drastic effects in comparison to rather gentle changes from K(+) and Cs(+). The specific cations effects observed by SAXS correlate with the pH behavior of the solutions, an indicator of surface charge, or number of carboxylate groups along the supra-molecular fibrils. It is postulated that while Na(+) with stronger affinity to carboxylates apparently reduces the surface charge, K(+) and Cs(+) only weakly interact with carboxylates and induce minor changes, accounting for the cation-sensitive aggregation behavior of fibrils observed by SAXS. By probing the bundling aggregation of charged supra-molecular nano-fibrils in salty water, we provide direct evidence of specific counter-ion effects in unusual expansion caused by univalent salts. PMID:26395732

  18. Influence of precipitating energetic ions caused by EMIC waves on the subauroral ionospheric E region during a geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Yuan, Zhigang; Xiong, Ying; Li, Haimeng; Huang, Shiyong; Qiao, Zheng; Wang, Zhenzhen; Zhou, Meng; Wang, Dedong; Deng, Xiaohua; Raita, Tero; Wang, Jingfang

    2014-10-01

    In this paper, we have presented the influence of precipitating energetic ions caused by electromagnetic ion cyclotron (EMIC) waves on the subauroral ionospheric E region during a geomagnetic storm on 8 March 2008 with observations of the Meteorological Operational (METOP-02) of the Polar Orbiting Environmental Satellites (POES), a GPS receiver in Vaasa of Finland and Finnish network of search coil magnetometers. Conjugate observations of the POES METOP-02 satellite and Finnish network of search coil magnetometers have demonstrated that enhancements of the precipitating energetic ion flux within the proton anisotropic zone are attributed to the interaction between ring current (RC) ions and EMIC waves. With enhancements of the intensity of Pc1 waves observed by search coil magnetometers, the total electron content observed by the GPS receiver accordingly increased, meaning that the enhancement of the ionospheric electron density is attributed to the precipitation of RC ions caused by EMIC waves. The electron density profiles derived by the International Reference Ionosphere (IRI-2007) model and with precipitating energetic protons observed by the POES METOP-02 satellite show that the energetic proton precipitation can cause the E layer peak electron density to increase from 1.62 × 109 m-3 to 5.05 × 1011 m-3 by 2.49 orders of magnitude. In comparison with the height-integrated conductivities derived by the IRI-2007 model, the height-integrated Pedersen and Hall conductivities derived with precipitating energetic protons increase by 2.4 and 2.34 orders of magnitude, respectively. Our result suggests that precipitating energetic ions caused by EMIC waves can lead to an obvious enhancement of the electron density and conductivities in the subauroral ionospheric E region during geomagnetic storms.

  19. Asymmetrical response of dayside ion precipitation to a large rotation of the IMF

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Richard, R. L.; Escoubet, C. P.; Wing, S.; Pitout, F.

    2016-01-01

    We have carried out global magnetohydrodynamics (MHD) simulations together with large-scale kinetic simulations to investigate the response of the dayside magnetospheric ion precipitation to a large rotation (135°) of the interplanetary magnetic field (IMF). The study uses simplified global MHD model (no dipole tilt and constant ionospheric conductance) and idealized solar wind conditions where the IMF rotates smoothly from a southward toward a northward direction (BX = 0) to clearly identify the effects of the impact of the discontinuity on the magnetopause. Results of the global simulations reveal that a strong north-south asymmetry develops in the pattern of precipitating ions during the interaction of the IMF rotation with the magnetopause. For a counterclockwise IMF rotation from its original southward direction (BY < 0), a spot of high-energy particle injections occurs in the Northern Hemisphere but not in the Southern Hemisphere. The spot moves poleward and dawnward as the interacting field rotates. In that case, reconnection is found close to the poleward edge of the northern cusp, while it occurs farther tailward in the Southern Hemisphere. Tracing magnetic field lines shows an asymmetry in the tilt of the cusps and indicates that the draping and subsequent double reconnection of newly opened field lines from the Southern Hemisphere over the dayside magnetosphere cause the symmetry breaking. The reverse north-south asymmetry is found for a clockwise IMF rotation from its original southward direction (BY > 0). Trends observed in the ion dispersions predicted from the simulations are in good agreement with Cluster observations of the midaltitude northern cusp, which motivated the study.

  20. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions.

    PubMed

    Choi, Jun-Ho; Kim, Heejae; Kim, Seongheun; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O-D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O-D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O-D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O-D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O-D stretch mode is shown to be important and the asymmetric line shapes of the O-D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We anticipate that this

  1. Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions

    SciTech Connect

    Choi, Jun-Ho; Lim, Sohee; Chon, Bonghwan; Cho, Minhaeng; Kim, Heejae; Kim, Seongheun

    2015-05-28

    The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O—D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O—D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O—D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O—D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O—D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O—D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O—D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O—D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O—D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O—D stretch mode is shown to be important and the asymmetric line shapes of the O—D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We

  2. Transport of gold nanoparticles through plasmodesmata and precipitation of gold ions in woody poplar.

    PubMed

    Zhai, Guangshu; Walters, Katherine S; Peate, David W; Alvarez, Pedro J J; Schnoor, Jerald L

    2014-02-11

    Poplar plants (Populus deltoides × nigra, DN-34) were used as a model to explore vegetative uptake of commercially available gold nanoparticles (AuNPs) and their subsequent translocation and transport into plant cells. AuNPs were directly taken up and translocated from hydroponic solution to poplar roots, stems and leaves. Total gold concentrations in leaves of plants treated with 15, 25 and 50 nm AuNPs at exposure concentrations of 498±50.5, 247±94.5 and 263±157 ng/mL in solutions were: 0.023±0.006, 0.0218±0.004 and 0.005±0.0003 µg/g dry weight, respectively, which accounted for 0.05, 0.10 and 0.03%, respectively, of the total gold mass added. The presence of total gold in plant tissues was measured by inductively coupled plasma mass spectrometry, while AuNPs were observed by transmission electron microscopy in plant tissues. In solution, AuNPs were distinguished from Au(III) ions by membrane separation and centrifugation. AuNPs behaved conservatively inside the plants and were not dissolved into gold ions. On the other hand, Au(III) ions were taken up and reduced into AuNPs inside whole plants. AuNPs were observed in the cytoplasm and various organelles of root and leaf cells. A distinct change in color from yellow to pink was observed as Au(III) ions were reduced and precipitated in hydroponic solution. The accumulation of AuNPs in the plasmodesma of the phloem complex in root cells clearly suggests ease of transport between cells and translocation throughout the whole plant, inferring the potential for entry and transfer in food webs. PMID:25386566

  3. What is the Relationship Between Heavy Ion Outflow and High-Latitude Energetic Particle Precipitation?

    NASA Technical Reports Server (NTRS)

    Wilson, Gordon R.

    2001-01-01

    This document is the fourth quarter progress report for year two on contract NAW-99002 'What is the relationship between heavy ion outflow and high latitude energetic particle precipitation'. In this project we are studying the relationship between the fluxes, mean energies, and field-aligned flow speeds of escaping suprathermal H+ and O+ measured by the TEAMS instrument on FAST and the energy flux of precipitating electrons obtained form the LBHL images taken by the Ultraviolet Imagery (UVI) camera on the Polar spacecraft. We have analyzed data from three time intervals, 7-11 Feb, 25-31 Jan, and 1-6 Feb 1997. We find that there indeed is a relationship between the O+ escape fluxes and the intensity of the aurora at the foot point of the field line. The time delay between an auroral intensification and the corresponding increase in escape flux is very short, only a few minutes. At low auroral luminosity the relationship between escape flux and luminosity appears to break down due possibly to the lack of sensitivity of the auroral emissions to large fluxes of low energy electrons.

  4. Wet precipitation of major ions, polonium-210, and organic carbon in a metropolitan city, Seoul, Korea

    NASA Astrophysics Data System (ADS)

    Yan, G.; Kim, G.

    2011-12-01

    An extensive survey of chemical constituents in precipitation including dissolved organic carbon, dissolved nitrogen, major ions, trace elements, and radionuclides was conducted in a representative urban environment of Seoul over one-year period from 2009 to 2010. The sources for these chemical species were apportioned by applying principal component analysis (PCA) in association with commonly acknowledged key tracers, such as Na, K, Ca, and V. The fossil fuel combustion (especially coal) was shown to be the dominant source for most constituents being investigated, with biomass burning being recognized as another significant source. With the aid of air mass backward trajectory analyses, we concluded that the primary fraction of the chemical species in our precipitation samples originated locally in Korea, albeit the frequent long-range transport from the eastern and northeastern China might contribute substantially. Overall, our study suggests the significant role of human activities in altering the atmospheric environment of Seoul and presumably most urban areas around the world, highlighting its profound environmental implications, such as health risks posed by excessive polonium-210, enhanced rainwater acidity from organic acids, and radiative forcing by organic aerosols.

  5. Multi-Element Preconcentration/Separation of Some Metal Ions in Environmental Samples by Using Co-precipitation.

    PubMed

    Soylak, Mustafa; Aydin, Ayse; Kizil, Nebiye

    2016-01-01

    A preconcentration/separation system for cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions has been established prior to their atomic absorption spectrometric determinations. The procedure is based on the co-precipitation of these ions by the aid of a praseodymium hydroxide (Pr(OH)3) precipitate. The precipitate was dissolved in 0.5 mL of concentrated HNO3, and made up to 10.0 mL with water. The analytes were determined by a flame atomic absorption spectrometer. The effects of analytical parameters including pH, amounts of praseodymium as carrier element, sample volume, etc. on the recoveries of heavy metals were investigated. The effects of matrix ions were also examined. The limits of detection for analyte ions were found in the range between 0.7-5.2 μg/L. The validation of this present procedure was verified by the analysis of certified reference materials, TMDA-54.4 (fortified water) and NIST 1570a (spinach leaves). The proposed co-precipitation procedure was applied for the determination of cadmium(II), nickel(II), copper(II), lead(II), iron(II), cobalt(II), and manganese(II) ions in various environmental water samples. PMID:27053469

  6. A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitating Fluxes

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Jordanova, V. K.; Krivorutsky, E. N.

    2002-01-01

    Initial results from a newly developed model of the interacting ring current ions and ion cyclotron waves are presented. The model is based on the system of two kinetic equations: one equation describes the ring current ion dynamics, and another equation describes wave evolution. The system gives a self-consistent description of the ring current ions and ion cyclotron waves in a quasilinear approach. These equations for the ion phase space distribution function and for the wave power spectral density were solved on aglobal magnetospheric scale undernonsteady state conditions during the 2-5 May 1998 storm. The structure and dynamics of the ring current proton precipitating flux regions and the ion cyclotron wave-active zones during extreme geomagnetic disturbances on 4 May 1998 are presented and discussed in detail.

  7. Dawn-dusk asymmetry in dayside ion precipitation for southward IMF: results from large-scale simulations

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Richard, R. L.; Escoubet, C.; Wing, S.; Pitout, F.

    2013-12-01

    We present the results of numerical studies of the interaction of solar wind ions with the dayside magnetospheric boundary for a southward interplanetary magnetic field (IMF). These studies use the time-dependent electric and magnetic fields predicted by three-dimensional global magnetohydrodynamic (MHD) simulations to compute the trajectories of large samples of solar wind ions launched upstream of the bow shock. Energy-latitude spectra computed from the large scale kinetic (LSK) simulations show that a strong dawn-dusk asymmetry develops in the precipitation of low to middle energy ions over the high-latitude dayside magnetosphere. These results are consistent with statistical studies of DMSP data showing that ion precipitation from the mantle is predominantly seen over the morning and pre-noon sector.

  8. Waste treatment by ion-exchange and precipitation methods after LOMI decontamination

    SciTech Connect

    Gokhale, A.S.; Venkateswaran, G.; Moorthy, P.N.

    1994-12-31

    Conventional polystyrene-based strong acid cation and strong base anion exchangers have been evaluated for the retention of {sup 60}Co from vanadium based low oxidation-state metal ion (LOMI) decontamination formulation. Cation exchange treatment results in decontamination factors (DFs) of 8--40 with respect to {sup 60}Co if the LOMI solution is treated immediately after decontamination but yields lower DFs of 3--4 if it is stored for >24 h under ambient conditions. In both cases, anionic treatment of the cation column effluent gives DFs in the range 45--400. These results point to the differential speciation of {sup 60}Co in fresh and stored LOMI solutions and hence the necessity of having both cation and anion exchange treatments for the near complete removal of {sup 60}Co. Coprecipitation with MnO{sub 2} obtained by mixing the used LOMI solution with the required amounts of alkaline KMnO{sub 4} employed for pretreating the oxide surfaces was also found to be an effective method for {sup 60}Co removal. From the point of view of total activity removal, the precipitation method was less efficient than ion-exchange method.

  9. Dawn-dusk asymmetry in solar wind ion entry and dayside precipitation: Results from large-scale simulations

    NASA Astrophysics Data System (ADS)

    Berchem, J.; Richard, R.; Escoubet, P.; Wing, S.; Pitout, F.

    2014-03-01

    We present the results of numerical studies of the interaction of solar wind ions with the dayside magnetospheric boundary for a southward interplanetary magnetic field and two solar wind speeds (250 and 500 km/s) using the results of global magnetohydrodynamics simulations in conjunction with large-scale kinetic calculations. Results of these studies show that a dawn-dusk asymmetry is found in the precipitation of low- to middle-energy ions over the high-latitude dayside magnetosphere. This asymmetry is consistent with statistical studies of DMSP data showing that ion precipitation from the mantle is predominantly seen over the morning and prenoon sector. Analysis of energy-latitude spectra and study of individual particle trajectories from the simulations revealed that low-energy ions can enter the magnetopause at high latitudes in regions where the parallel electric field associated with the magnetopause current is positive and strong enough for the ions to gain energies of the order of the parallel potential drop across the magnetopause. Because the parallel electric field in the Northern Hemisphere is positive in the prenoon sector and negative in the afternoon-evening sector, solar wind ions reaching the magnetopause in these regions are accelerated toward the ionosphere on the dawnside and outward on the duskside, creating the asymmetry in precipitation. The same dawn-dusk asymmetry is found in the Southern Hemisphere because both parallel electric field and magnetic field are reversed in direction.

  10. Analytical electron microscopy of precipitates in ion-implanted MgAl{sub 2}O{sub 4} spinel

    SciTech Connect

    Evans, N.D.; Zinkle, S.J.; Bentley, J.

    1994-12-31

    Magnesium aluminate spinel (MgAl{sub 2}O{sub 4}) is being considered as an insulator material within proposed fusion reactors where considerable radiation fields are anticipated. Analytical electron microscopy (AEM) has been used to investigate precipitates within MgAl{sub 2}O{sub 4} spinel following implantation of Al{sup +}, Mg{sup +}, or Fe{sup 2+} ions. Combined diffraction experiments, energy dispersive X-ray spectrometry (EDS), electron energy-loss spectrometry (EELS), and energy-filtered imaging were employed to identify and characterize precipitates observed in the implanted ion region. Diffraction studies suggested these are metallic aluminum colloids, although EELS and energy-filtered images revealed this to be the case only for the Al{sup +} and Mg{sup +} implantations, and not for Fe{sup 2+} ion implantations. Multiple-least-squares (MLS) fitting of EELS spectra was employed to quantify the volume fraction of metallic aluminum when present in the implanted ion region. Energy-filtered images of the implanted ion region clearly show the colloid distribution in the Al{sup +} and Mg{sup +} implanted spinel. Energy-filtered images from the Fe {sup 2+} ion implanted spinel indicate that the features visible in diffraction contrast cannot be associated with either metallic aluminum or iron-rich precipitates.

  11. Ion Specificity in Protein Aggregation Predicted from Diffusivity Measurements in Stable Protein Solutions

    NASA Astrophysics Data System (ADS)

    Rubin, Jonathan; San Miguel, Adriana; Bommarius, Andreas; Behrens, Sven

    2011-03-01

    The aggregation of therapeutic proteins in solution represents a major challenge in pharmaceutical development, as the mid- and long-term stability of these proteins is crucial for their efficacy and for compliance with FDA requirements. Monitoring slow aggregation experimentally is notoriously time-consuming, yet often unavoidable, since no theory with predictive power is currently available. In the present work, diffusion and aggregation kinetics of the globular model proteins lysozyme and BSA were studied in sodium-salt solutions of different composition and ionic strength using dynamic light scattering. We find a strong correlation between the concentration dependent protein diffusivity in stable solutions and the kinetics of protein aggregation in unstable solutions of similar composition but higher salt content. Our findings suggest a fast and convenient new way to assess a protein's specific tendency to aggregate in different types of electrolytes and buffer solutions.

  12. Precipitation of C, Si and metals nanoparticles in silicon-based gels induced by swift heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Pivin, J. C.; Avasthi, D. K.; Singh, F.; Kumar, A.; Pippel, E.; Sagon, G.

    2005-07-01

    Studies of irradiation effects in inorganic polymers and gels performed at CSNSM during the last ten years are summarized, and new results concerning the effect of the density of transferred energy on the precipitation kinetics of C, Si and metal clusters are presented. The precipitation yield as a function of the fluence of ions with different masses and energies was investigated by means of various spectroscopies, depending on the particles nature. The rates of gel to ceramics conversion and of C, Si and metal precipitation are determined by the density of electronic excitations and nuclear collisions have little effect. Particles formed by ion irradiation show a narrower size distribution and, consequently, more interesting characteristics for magnetic or optical applications than those formed in heat treated gels.

  13. End-to-End Study of the Transfer of Energy from Magnetosheath Ion Precipitation to the Cusp

    NASA Technical Reports Server (NTRS)

    Coffey, V. N.; Chandler, M. O.; Singh, Nagendra; Avanov, Levon

    2005-01-01

    This paper describes a study of the effects of unstable magnetosheath distributions on the cusp ionosphere. An end-to-end numerical model was used to study, first, the evolved distributions from precipitation due to reconnection and, secondly, the energy transfer into the high latitude ionosphere based on these solar wind/magnetosheath inputs. Using inputs of several representative examples of magnetosheath injections, waves were generated at the lower hybrid frequency and energy transferred to the ionospheric electrons and ions. The resulting wave spectra and ion and electron particle heating was analyzed. Keywords: Ion heating: Magnetosheath/Ionosphere coupling: Particle/Wave Interactions. Simulations

  14. Effects of calcium and ferric ions on struvite precipitation: A new assessment based on quantitative X-ray diffraction analysis.

    PubMed

    Yan, Hanlu; Shih, Kaimin

    2016-05-15

    The precipitation of struvite (MgNH4PO4·6H2O) from waste streams has attracted considerable attention due to its potential for recovering phosphorus for fertilization. As struvite is primarily acquired by means of precipitation and crystallization from aqueous solutions, it is important to evaluate the roles of common metal ions, particularly those that are commonly found in wastewater, in the struvite crystallization process. This study was performed to quantitatively evaluate the effects of calcium and ferric ions on struvite crystallization using the Rietveld refinement method, which is based on the analysis of X-ray diffraction data. The results indicate that both calcium and ferric ions significantly inhibit the formation of struvite crystals, and the effects vary under different pH conditions. There was a negative linear correlation between the struvite weight content in the precipitates and the Ca/Mg molar ratio in the initial solution. However, ferric ions were confirmed to be a more efficient inhibitor of struvite crystallization. Ca(2+) and Fe(3+) further modified the needle-like struvite into irregular shapes. An unambiguous and quantitative understanding of the effects of foreign ions on struvite crystallization will help to reliably improve the quality of struvite products recovered from wastewater and the control of struvite deposits in water and sludge piping systems. PMID:27016641

  15. Correlating DMSP and NOAA Ion Precipitation Observations with Low Altitude ENA Emissions During the Declining Phase of Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Mackler, D. A.; Jahn, J. M.; Perez, J. D.; Pollock, C. J.

    2014-12-01

    Plasma sheet particles with sufficiently low mirror points will interact with thermospheric neutrals through charge exchange. The resulting ENAs are no longer magnetically bound and can therefore be detected by remote platforms outside the ionosphere/lower atmosphere. These ENAs closely associated with ion precipitation are termed Low Altitude Emissions (LAEs). They are non-isotropic in velocity space and mimic the corresponding ion pitch angle distribution. In this study we present a statistical correlation between remote observations of the LAE emission characteristics and ion precipitation maps determined in situ over the declining phase of solar cycle 23 (2000-2005). We discuss the strength and derived location (MLT, iMLAT) of LAEs as a function of geomagnetic activity levels in relation to the simultaneously measured strength, location, and spectral characteristics of in situ ion precipitation. These comparisons may allow us to use ENA images to assess where and how much energy is deposited during any type of enhanced geomagnetic activity. The precipitating ion differential directional flux maps are built up from combining NOAA-14/15/16 TED and DMSP-13/14/15 SSJ4 data. Low altitude ENA source locations are identified algorithmically using IMAGE/MENA images. ENA flux maps are derived by computing the LAE source locations assuming an ENA emission altitude (h) of 650 km, then projecting each image pixel onto a sphere with radius Re+h to determine the local time and latitude extent of the ENA source. The IGRF magnetic field model is used in combination with the Solar Magnetic coordinates of LAE pixels to compute the pitch angle of the escaping neutrals (previously ion before charge exchanging). Pitch angles larger than 90° will have a mirror point further into the atmosphere than the assumed emission altitude.

  16. Ion Exchange Technology Development in Support of the Urine Processor Assembly Precipitation Prevention Project for the International Space Station

    NASA Technical Reports Server (NTRS)

    Mitchell, Julie L.; Broyan, James L.; Pickering, Karen D.; Adam, Niklas; Casteel, Michael; Callahan, Michael; Carrier, Chris

    2012-01-01

    In support of the Urine Processor Assembly Precipitation Prevention Project (UPA PPP), multiple technologies were explored to prevent CaSO4 2H2O (gypsum) precipitation during the on-orbit distillation process. Gypsum precipitation currently limits the water recovery rate onboard the International Space Station (ISS) to 70% versus the planned 85% target water recovery rate. Due to its ability to remove calcium cations in pretreated augmented urine (PTAU), ion exchange was selected as one of the technologies for further development by the PPP team. A total of 13 ion exchange resins were evaluated in various equilibrium and dynamic column tests with solutions of dissolved gypsum, urine ersatz, PTAU, and PTAU brine at 85% water recovery. While initial evaluations indicated that the Purolite SST60 resin had the highest calcium capacity in PTAU (0.30 meq/mL average), later tests showed that the Dowex G26 and Amberlite FPC12H resins had the highest capacity (0.5 meq/mL average). Testing at the Marshall Spaceflight Center (MSFC) integrates the ion exchange technology with a UPA ground article under flight-like pulsed flow conditions with PTAU. To date, no gypsum precipitation has taken place in any of the initial evaluations.

  17. Ion Exchange Technology Development in Support of the Urine Processor Assembly Precipitation Prevention Project for the International Space Station

    NASA Technical Reports Server (NTRS)

    Mitchell, Julie L.; Broyan, James L.; Pickering, Karen D.; Adam, Niklas; Casteel, Michael; Callaham, Michael; Carrier, Chris

    2011-01-01

    In support of the Urine Processor Assembly Precipitation Prevention Project (UPA PPP), multiple technologies were explored to prevent CaSO4 dot 2H2O (gypsum) precipitation during the on-orbit distillation process. Gypsum precipitation currently limits the water recovery rate onboard the International Space Station (ISS) to 70% versus the planned 85% target water recovery rate. Due to its advanced performance in removing calcium cations in pretreated augmented urine (PTAU), ion exchange was selected as one of the technologies for further development by the PPP team. A total of 12 ion exchange resins were evaluated in various equilibrium and dynamic column tests with solutions of dissolved gypsum, urine ersatz, PTAU, and PTAU brine at 85% water recovery. While initial evaluations indicated that the Purolite SST60 resin had the highest calcium capacity in PTAU (0.30 meq/mL average), later tests showed that the Dowex G26 and Amberlite FPC12H resins had the highest capacity (0.5 meq/mL average). Further dynamic column testing proved that G26 performance is +/- 10% of that value at flow rates of 0.45 and 0.79 Lph under continuous flow, and 10.45 Lph under pulsed flow. Testing at the Marshall Spaceflight Center (MSFC) integrates the ion exchange technology with a UPA ground article under flight-like pulsed flow conditions with PTAU. To date, no gypsum precipitation has taken place in any of the initial evaluations.

  18. Low-energy ion precipitation structures associated with pulsating auroral patches

    NASA Astrophysics Data System (ADS)

    Liang, Jun; Donovan, E.; Nishimura, Y.; Yang, B.; Spanswick, E.; Asamura, K.; Sakanoi, T.; Evans, D.; Redmon, R.

    2015-07-01

    Pulsating auroras often appear in forms of geo-stable or slowly convecting "patches." These patches can maintain their rough shape and size over many sequences of luminosity pulsations, yet they slowly drift with ionospheric E × B convection. Because of these characteristics, there has long been a speculation that the pulsating auroral patch (PAP) is connected to flux tubes filled with enhanced cold plasma. In this study, we perform a survey on pulsating auroral events when the footprints of low-Earth-orbit satellites traversed the PAPs, with a focus on the low-energy particle signatures associated with the PAPs. As a result, we identified, in a majority (~2/3) of events, the existence of a low-energy ion precipitation structure that is collocated with the PAP, with core energies ranging from several tens of eV up to a few hundred eV. This result supports the hypothesis that a PAP connects to flux tubes filled with enhanced cold plasma. We further propose that the plasma outflows from the ionosphere are the origin of such cold plasma flux tubes. We suggest that the PAP is formed by a combination of high-energy electrons of a magnetospheric origin, the low-energy plasma structure of an ionospheric origin, and certain ELF/VLF waves that are intensified and modulated in interactions with both the hot and cold plasma populations.

  19. A highly selective fluorescent probe for sulfide ions based on aggregation of Cu nanocluster induced emission enhancement.

    PubMed

    Li, Zenghe; Guo, Song; Lu, Chao

    2015-04-21

    In this study, S(2-) ions were found to enhance the fluorescence of cysteine-capped Cu nanoclusters (Cu NCs). High resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy-energy dispersive X-ray (SEM-EDX) measurements, zeta potential and X-ray photoelectron spectroscopy (XPS) measurements demonstrated that the S(2-) ion-induced aggregation of the Cu NCs contributed to the fluorescence enhancement of the dispersed Cu NCs. Based on these findings, a highly selective fluorescent probe was developed for the determination of H2S using the S(2-) ion-enhanced fluorescence of the as-prepared Cu NCs. The relative fluorescence intensity was proportional to the concentration of S(2-) in the range from 0.2 to 50 μM. The detection limit (S/N = 3) was 42 nM. The proposed method has been successfully applied to determine H2S produced from toys called "Fart Bomb" with recoveries of 97.6-101.8%. The results of the proposed method were in good agreement with those determined by a standard methylene blue method. This work is not only of importance for a better understanding of the aggregation induced emission (AIE) properties of the Cu NCs but also of great potential to find extensive biological applications for H2S. PMID:25697240

  20. Calcium carbonate precipitation rate as a function of ion ratio in the presence & absence of Sr2+

    NASA Astrophysics Data System (ADS)

    Gebrehiwet, T.; Beig, M. S.; Fujita, Y.; Redden, G. D.; Smith, R. W.

    2010-12-01

    Tsigabu Gebrehiwet 1*, Mikala Beig 2, Yoshiko Fujita 3, George Redden 3 and Robert W. Smith 1 1University of Idaho, 1776 Science Center Dr, Idaho Falls,ID, 83402 (*tgebrehiwet@uidaho.edu; smithbob@uidaho.edu ) 27963 Grasmere Dr.Boulder, CO 80301(mbeig@alumni.rice.edu) 3Idaho National Laboratory, MS 2208, Idaho Falls, ID 83415 (Yoshiko.Fujita@inl.gov; George.Redden@inl.gov) Engineered in situ precipitation of calcium carbonate is a proposed strategy for remediating toxic or radioactive metals (e.g., Sr2+)in subsurface environments as well as for modifying the physical properties (e.g., stiffness, permeability) of geomedia. Inducing the precipitation reaction will likely involve manipulating the geochemical conditions by adding calcium, (bi)carbonate, or both, and relying on mixing of the two reactants. Under these conditions, the ratio of Ca2+ to CO32- will vary with distance from the mixing interface, and for most or all of the porous medium, a 1:1 stoichiometry between calcium and carbonate is unlikely to be achieved. Indeed, in engineered systems where rapid treatment is an important objective, very steep ion concentration gradients may be generated, which would result in local reactant ratios varying from very small to very large over short distances, depending on the mixing geometry and particular chemical composition of the mixing fluids. This in turn has an impact on the rate of mineral precipitation. Typically, the rate of calcium carbonate precipitation is expressed with an affinity-based rate law of the type: Rate = k(Ω-1)n, where k is a rate constant, Ω is the saturation state for the mineral (e.g., calcite), and n is an empirical reaction order. The saturation state Ω is defined as the ratio of the ion activity product to the mineral solubility product. In this expression, the rate is simply dependent on the value of Ω; the actual activities of the individual ions (Ca2+ and CO32-) do not appear in the expression. In support of the development of

  1. Comprehensive Study of the Solubility, Thermochemistry, Ion Exchange, and Precipitation Kinetics of NO3 Cancrinite and NO33 Sodalite

    SciTech Connect

    Navrotsky, Alexandra; Liu, Qinyuan

    2004-12-01

    The precipitation of aluminosilicate phases from caustic nuclear wastes has proven to be problematic in a number of processes including radionuclide separations (cementation of columns by aluminosilicate phases), tank emptying (aluminosilicate tank heels), and condensation of wastes in evaporators (aluminosilicate precipitates in the evaporators, providing nucleation sites for growth of critical masses of radioactive actinide salts). In a collaboration between SNL and UCD, we have investigated why and how these phases form, and which conditions favor the formation of which phases. These studies have involved synthesis and characterization of aluminosilicate phases formed using a variety of synthesis techniques, kinetics of precipitation, structural investigations of aluminosilicate phases, thermodynamic calculations of aluminosilicate solubility, calorimetric studies of aluminosilicate precipitation, and a limited investigation of radionuclide partitioning and ion exchange processes (involving typical tank fluid chemistries and these materials). The predominant phases that are observed in the aluminosilicate precipitates from basic tanks wastes (i.e. Hanford, Savannah River Site ''SRS'' wastes) are the salt enclathrated zeolites: sodium nitrate, sodium carbonate and sodium hydroxide sodalite and cancrinite. These phases precipitate readily from the high ionic strength, highly basic solutions at ambient temperatures as well as at elevated temperatures, with or without the presence of an external Al and Si source (both are contained in the waste solutions), and upon interactions with reactive soil components such as clays.

  2. Aggregation of dialkyl-substituted diphosphonic acids and its effect on metal ion extraction.

    SciTech Connect

    Chiarizia, R.; Barrans, R. E., Jr.; Ferraro, J. R. Herlinger, A. W.; McAlister, D. R.

    1999-10-22

    Solvent extraction reagents containing the diphosphonic acid group exhibit an extraordinary affinity for tri-, tetra- and hexavalent actinides. Their use has been considered for actinide separation and pre-concentration procedures. Solvent extraction data obtained with P,P{prime}-di(2-ethylhexyl) methane-, ethane- and butanediphosphonic acids exhibit features that are difficult to explain without Knowledge of the aggregation state of the extractants. Information about the aggregation of the dialkyl-substituted diphosphonic acids in aromatic diluents has been obtained using the complementary techniques of vapor pressure osmometry (VPO), small angle neutron scattering (SANS), infrared spectroscopy and molecular mechanics. The results from these techniques provide an understanding of the aggregation behavior of these extractants that is fully compatible with the solvent extraction data. The most important results and their relevance to solvent extraction are reviewed in this paper.

  3. Impact of precipitation on the treatment of real ion-exchange brine using the H(2)-based membrane biofilm reactor.

    PubMed

    Van Ginkel, Steven W; Tang, Youneng; Rittmann, Bruce E

    2011-01-01

    The H(2)-based membrane biofilm reactor (MBfR) was used to remove nitrate and perchlorate from real ion-exchange brine at two different salinities (30- and 50-g/L NaCl). Base production from nitrate reduction to N(2) gas caused the pH to increase, and this exacerbated precipitation of calcium and magnesium carbonates onto the MBfR fibers. The precipitates lowered the H(2) flux to the biofilm and caused a deterioration of denitrification performance that could be reversed by mild citric-acid washing. The addition of acid seems to be the only mechanism to avoid serious precipitation, membrane fouling, and non-optimal pH for denitrification. PMID:21508550

  4. Nucleation, growth and Ostwald ripening of CoSi{sub 2} precipitates during Co ion implantation in Si

    SciTech Connect

    Reiss, S.; Heinig, K.H.; Ruault, M.O.; Clayton, J.; Kaitasov, O.; Bernas, H.

    1995-12-31

    The experimental conditions during the implantation step of Ion Beam Synthesis influence crucially the formation of a buried structure in subsequent annealing steps. Due to the complexity of the in-beam nucleation and evolution of precipitates of new phases there is still a low level of understanding. In this paper the authors present results of direct experimental investigations as well as results of computer simulations of in-beam nucleation and growth. The evolution of an ensemble of CoSi{sub 2} precipitates is mainly controlled by nucleation and diffusion. The observed decrease of the nucleation rate at high fluences can be explained by the decrease of the supersaturation of implanted atoms due to diffusion towards earlier nucleated precipitates.

  5. Rapid assessment of human amylin aggregation and its inhibition by copper(II) ions by laser ablation electrospray ionization mass spectrometry with ion mobility separation.

    PubMed

    Li, Hang; Ha, Emmeline; Donaldson, Robert P; Jeremic, Aleksandar M; Vertes, Akos

    2015-10-01

    Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. Here, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin-copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the -HSSNN- residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin-copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of amylin

  6. Rapid Assessment of Human Amylin Aggregation and Its Inhibition by Copper(II) Ions by Laser Ablation Electrospray Ionization Mass Spectrometry with Ion Mobility Separation

    PubMed Central

    Donaldson, Robert P.; Jeremic, Aleksandar M.; Vertes, Akos

    2015-01-01

    Native electrospray ionization (ESI) mass spectrometry (MS) is often used to monitor noncovalent complex formation between peptides and ligands. The relatively low throughput of this technique, however, is not compatible with extensive screening. Laser ablation electrospray ionization (LAESI) MS combined with ion mobility separation (IMS) can analyze complex formation and provide conformation information within a matter of seconds. Islet amyloid polypeptide (IAPP) or amylin, a 37-amino acid residue peptide, is produced in pancreatic beta-cells through proteolytic cleavage of its prohormone. Both amylin and its precursor can aggregate and produce toxic oligomers and fibrils leading to cell death in the pancreas that can eventually contribute to the development of type 2 diabetes mellitus. The inhibitory effect of the copper(II) ion on amylin aggregation has been recently discovered, but details of the interaction remain unknown. Finding other more physiologically tolerated approaches requires large scale screening of potential inhibitors. Here, we demonstrate that LAESI-IMS-MS can reveal the binding stoichiometry, copper oxidation state, and the dissociation constant of human amylin–copper(II) complex. The conformations of hIAPP in the presence of copper(II) ions were also analyzed by IMS, and preferential association between the β-hairpin amylin monomer and the metal ion was found. The copper(II) ion exhibited strong association with the –HSSNN– residues of the amylin. In the absence of copper(II), amylin dimers were detected with collision cross sections consistent with monomers of β-hairpin conformation. When copper(II) was present in the solution, no dimers were detected. Thus, the copper(II) ions disrupt the association pathway to the formation of β-sheet rich amylin fibrils. Using LAESI-IMS-MS for the assessment of amylin–copper(II) interactions demonstrates the utility of this technique for the high-throughput screening of potential inhibitors of

  7. Influence of Inorganic Ions and Aggregation and Adsorption Behaviors of Human Adenovirus

    EPA Science Inventory

    In this study, influence of solution chemistries to the transport properties (aggregation and attachment behavior) of human adenovirus (HAdV) was investigated. Results showed isoelectric point (IEP) of HAdV in different salt conditions varied minimally, and it ranged from pH 3.5 ...

  8. Complex polyion-surfactant ion salts in equilibrium with water: changing aggregate shape and size by adding oil.

    PubMed

    Bernardes, Juliana S; Norrman, Jens; Piculell, Lennart; Loh, Watson

    2006-11-23

    The phase behavior of ternary mixtures containing an alkyltrimethylammonium polyacrylate complex salt, water, and a nonpolar "oil" (n-decanol, p-xylene or cyclohexane) is investigated. The complex salts were prepared with short or long polyacrylates (30 or 6000 repeating units) and with hexadecyltrimethylammonium or dodecyltrimethylammonium surfactant ions. Phase diagrams and structures were determined by visual inspection and small-angle X-ray scattering analyses. Systems containing decanol display a predominance of lamellar phases, while hexagonal phases prevail in systems containing p-xylene or cyclohexane. The difference is interpreted as a result of the different locations of the oils within the surfactant aggregates. Decanol is incorporated at the aggregate interface, leading to a decrease in its curvature, which favors the appearance of lamellar structures. p-Xylene and cyclohexane, on the other hand, are mostly incorporated in the interior of the cylindrical aggregate, as reflected by its swelling as the oil content increases. The comparison of these results with those reported for similar systems with monovalent (bromide) counterions indicates a much more limited swelling of the lamellar phases with polymeric counterions by water. This limited swelling behavior is predominantly ascribed to bridging due to the polyions. PMID:17107195

  9. Role of imf orientation in the precipitation of solar wind ions into the upper atmosphere of venus.

    NASA Astrophysics Data System (ADS)

    Talha, Madeeha; Stenberg, Gabriella

    2016-07-01

    Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) is used to study the precipitation of solar wind ions (H+ and He2+) into the upper atmosphere of Venus for the period of April 2006 to December 2007 as representative of solar minimum. Precipitation cases are selected and analyzed for the orbits having extreme Interplanetary Magnetic Field (IMF) orientations: IMF perpendicular to the solar wind direction (IMFperp) and IMF aligned with the solar wind direction (IMFpll ). Large number of precipitation behind terminator (nightside) is observed for IMFpll as compared to IMFperp while the reverse trend is noted for the precipitation into the dayside. This is turn favour the presence and absence of magnetic barrier (MB) for IMFperp and IMFpll respectively, as less transport to the nightside and more ions escape from dayside ionosphere during IMFperp contribute for the formation of MB. Contribution in the proton flux by both orientations in the ionosphere and in the transition region is same i.e., 104cm

  10. A novel method for study of the aggregation of protein induced by metal ion aluminum(III) using resonance Rayleigh scattering technique

    NASA Astrophysics Data System (ADS)

    Long, Xiufen; Zhang, Caihua; Cheng, Jiongjia; Bi, Shuping

    2008-01-01

    We present a novel method for the study of the aggregation of protein induced by metal ion aluminum(III) using resonance Rayleigh scattering (RRS) technique. In neutral Tris-HCl medium, the effect of this aggregation of protein results in the enhancement of RRS intensity and the relationship between the enhancement of the RRS signal and the Al concentration is nonlinear. On this basis, we established a new method for the determination of the critical induced-aggregation concentrations ( CCIAC) of metal ion Al(III) inducing the protein aggregation. Our results show that many factors, such as, pH value, anions, salts, temperature and solvents have obvious effects. We also studied the extent of aggregation and structural changes using ultra-violet spectrometry, protein intrinsic fluorescence and circular dichroism to further understand the exact mechanisms of the aggregation characteristics of proteins induced by metal ion Al(III) at the molecular level, to help us to develop effective methods to investigate the toxicity of metal ion Al, and to provide theoretical and quantitative evidences for the development of appropriate treatments for neurodementia such as Parkinson's disease, Alzheimer's disease and dementia related to dialysis.

  11. End-to-End Study of the Transfer of Energy from Magnetosheath Ion Precipitation to the Ionospheric Cusp and Resulting Ion Outflow to the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Coffey, Victoria; Chandler, Michael; Singh, Nagendra; Avanov, Levon

    2003-01-01

    We will show results from an end-to-end study of the energy transfer from injected magnetosheath plasmas to the near-Earth magnetospheric and ionospheric plasmas and the resulting ion outflow to the magnetosphere. This study includes modeling of the evolution of the magnetosheath precipitation in the cusp using a kinetic code with a realistic magnetic field configuration. These evolved, highly non-Maxwellian distributions are used as input to a 2D PIC code to analyze the resulting wave generation. The wave analysis is used in the kinetic code as input to the cold ionospheric ions to study the transfer of energy to these ions and their outflow to the magnetosphere. Observations from the Thermal Ion Dynamics Experiment (TIDE) and other instruments on the Polar Spacecraft will be compared to the modeling.

  12. Uneven distribution of metallic ions in deposits precipitated in the Koshijihara DGA CO{sub 2} removal units

    SciTech Connect

    Tomoe, Y.; Sato, K.

    1997-08-01

    304 stainless steel has been suffering from general corrosion in CO{sub 2} removal units using a high concentration DGA solution in a natural gas processing plant. Deposits precipitated in the DGA units were sampled during annual inspections and analyzed for metallic ions and their compounds. It was found that Fe and Cr were rich in the deposits along the lean DGA lines and Ni was rich along the rich DGA lines. Fe and Cr precipitated as oxides and Ni precipitated as sulfides. This uneven distribution of metallic ions in the units was due to the differences in metal chelate stability with DGA and/or DGA carbamate and also due to the trace amount of H{sub 2}S in the raw natural gas. There has not been a direct proof of carbamates playing some roles in an actual amine unit, this uneven distribution of metallic ions is one evidence that DGA carbamate really plays some roles in actual DGA units.

  13. Photochemical precipitation of thorium and cerium and their separation from other ions in aqueous solution.

    PubMed

    Das, M; Heyn, A H; Hoffman, M Z; Agarwal, R P

    1970-10-01

    Thorium was precipitated from homogeneous solution by exposing solutions of thorium and periodate in dilute perchloric acid to 253.7 nm radiation from a low-pressure mercury lamp. Periodate is reduced photochemically to iodate which causes the formation of a dense precipitate of the basic iodate of thorium(IV). The precipitate was redissolved, the iodate reduced, the thorium precipitated first as the hydroxide, then as the oxalate and ignited to the dioxide for weighing. Thorium(IV) solutions containing 8-200 mg of ThO(2) gave quantitative results with a standard deviation (s) of 0.2 mg. Separations from 25 mg each of iron, calcium, magnesium, 50 mg of yttrium and up to 500 mg of uranium(VI) were quantitative (s = 0.25 mg). Separations from rare earths, except cerium, were accomplished by using hexamethylenetetramine rather than ammonia for the precipitation of the hydroxide. Cerium(III) was similarly precipitated and converted into CeO(2) for weighing. Quantitative results were obtained for 13-150 mg of CeO(2) with a standard deviation of 0.2 mg. Separations from 200 mg of uranium were quantitative. Other rare earths and yttrium interfered seriously. The precipitates of the basic cerium(IV) and thorium iodates obtained are more compact than those obtained by direct precipitation and can be handled easily. Attempts to duplicate Suzuki's method for separating cerium from neodymium and yttrium were not successful. PMID:18960820

  14. Bivalent Copper Ions Promote Fibrillar Aggregation of KCTD1 and Induce Cytotoxicity

    PubMed Central

    Liu, Zhepeng; Song, Feifei; Ma, Zhi-li; Xiong, Qiushuang; Wang, Jingwen; Guo, Deyin; Sun, Guihong

    2016-01-01

    Potassium channel tetramerization domain containing 1 (KCTD1) family members have a BTB/POZ domain, which can facilitate protein-protein interactions involved in the regulation of different signaling pathways. KCTD proteins have potential Zn2+/Cu2+ binding sites with currently unknown structural and functional roles. We investigated potential Cu2+-specific effects on KCTD1 using circular dichroism, turbidity measurement, fluorescent dye binding, proteinase K (PK) digestion, cell proliferation and apoptosis assays. These experiments indicate that the KCTD1 secondary structure assumes greater β-sheet content and the proteins aggregate into a PK-resistant form under 20 μM Cu2+, and this β-sheet-rich aggregation with Cu2+ promotes fibril formation, which results in increased cell toxicity by apoptosis. Our results reveal a novel role for Cu2+ in determining the structure and function of KCTD1. PMID:27596723

  15. Bivalent Copper Ions Promote Fibrillar Aggregation of KCTD1 and Induce Cytotoxicity.

    PubMed

    Liu, Zhepeng; Song, Feifei; Ma, Zhi-Li; Xiong, Qiushuang; Wang, Jingwen; Guo, Deyin; Sun, Guihong

    2016-01-01

    Potassium channel tetramerization domain containing 1 (KCTD1) family members have a BTB/POZ domain, which can facilitate protein-protein interactions involved in the regulation of different signaling pathways. KCTD proteins have potential Zn(2+)/Cu(2+) binding sites with currently unknown structural and functional roles. We investigated potential Cu(2+)-specific effects on KCTD1 using circular dichroism, turbidity measurement, fluorescent dye binding, proteinase K (PK) digestion, cell proliferation and apoptosis assays. These experiments indicate that the KCTD1 secondary structure assumes greater β-sheet content and the proteins aggregate into a PK-resistant form under 20 μM Cu(2+), and this β-sheet-rich aggregation with Cu(2+) promotes fibril formation, which results in increased cell toxicity by apoptosis. Our results reveal a novel role for Cu(2+) in determining the structure and function of KCTD1. PMID:27596723

  16. Carboxylate Ion Pairing with Alkali-Metal Ions for β-Lactoglobulin and Its Role on Aggregation and Interfacial Adsorption.

    PubMed

    Beierlein, Frank R; Clark, Timothy; Braunschweig, Björn; Engelhardt, Kathrin; Glas, Lena; Peukert, Wolfgang

    2015-04-30

    We report a combined experimental and computational study of the whey protein β-lactoglobulin (BLG) in different electrolyte solutions. Vibrational sum-frequency generation (SFG) and ellipsometry were used to investigate the molecular structure of BLG modified air-water interfaces as a function of LiCl, NaCl, and KCl concentrations. Molecular dynamics (MD) simulations and thermodynamic integration provided details of the ion pairing of protein surface residues with alkali-metal cations. Our results at pH 6.2 indicate that BLG at the air-water interface forms mono- and bilayers preferably at low and high ionic strength, respectively. Results from SFG spectroscopy and ellipsometry are consistent with intimate ion pairing of alkali-metal cations with aspartate and glutamate carboxylates, which is shown to be more effective for smaller cations (Li(+) and Na(+)). MD simulations show not only carboxylate-alkali-metal ion pairs but also ion multiplets with the alkali-metal ion in a bridging position between two or more carboxylates. Consequently, alkali-metal cations can bridge carboxylates not only within a monomer but also between monomers, thus providing an important dimerization mechanism between hydrophilic surface patches. PMID:25825918

  17. Organic oxalate as leachant and precipitant for the recovery of valuable metals from spent lithium-ion batteries

    SciTech Connect

    Sun Liang; Qiu Keqiang

    2012-08-15

    Graphical abstract: Display Omitted Highlights: Black-Right-Pointing-Pointer Vacuum pyrolysis as a pretreatment was used to separate cathode material from aluminum foils. Black-Right-Pointing-Pointer Cobalt and lithium can be leached using oxalate while cobalt can be directly precipitated as cobalt oxalate. Black-Right-Pointing-Pointer Cobalt and lithium can be separated efficiently from each other only in the oxalate leaching process. Black-Right-Pointing-Pointer High reaction efficiency of LiCoO{sub 2} was obtained with oxalate. - Abstract: Spent lithium-ion batteries containing lots of strategic resources such as cobalt and lithium are considered as an attractive secondary resource. In this work, an environmentally compatible process based on vacuum pyrolysis, oxalate leaching and precipitation is applied to recover cobalt and lithium from spent lithium-ion batteries. Oxalate is introduced as leaching reagent meanwhile as precipitant which leaches and precipitates cobalt from LiCoO{sub 2} and CoO directly as CoC{sub 2}O{sub 4}{center_dot}2H{sub 2}O with 1.0 M oxalate solution at 80 Degree-Sign C and solid/liquid ratio of 50 g L{sup -1} for 120 min. The reaction efficiency of more than 98% of LiCoO{sub 2} can be achieved and cobalt and lithium can also be separated efficiently during the hydrometallurgical process. The combined process is simple and adequate for the recovery of valuable metals from spent lithium-ion batteries.

  18. Relativistic electron precipitation events driven by electromagnetic ion-cyclotron waves

    SciTech Connect

    Khazanov, G. Sibeck, D.; Tel'nikhin, A.; Kronberg, T.

    2014-08-15

    We adopt a canonical approach to describe the stochastic motion of relativistic belt electrons and their scattering into the loss cone by nonlinear EMIC waves. The estimated rate of scattering is sufficient to account for the rate and intensity of bursty electron precipitation. This interaction is shown to result in particle scattering into the loss cone, forming ∼10 s microbursts of precipitating electrons. These dynamics can account for the statistical correlations between processes of energization, pitch angle scattering, and relativistic electron precipitation events, that are manifested on large temporal scales of the order of the diffusion time ∼tens of minutes.

  19. Hofmeister Ion-Induced Changes in Water Structure Correlate with Changes in Solvation of an Aggregated Protein Complex.

    PubMed

    Light, Taylor P; Corbett, Karen M; Metrick, Michael A; MacDonald, Gina

    2016-02-01

    RecA is a naturally aggregating Escherichia coli protein that catalyzes the strand exchange reaction utilized in DNA repair. Previous studies have shown that the presence of salts influence RecA activity, aggregation, and stability and that salts stabilize RecA in an inverse-anionic Hofmeister series. Here we utilized attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and circular dichroism (CD) to investigate how various Hofmeister salts alter the water structure and RecA solvation and aggregation. Spectroscopic studies performed in water and deuterium oxide suggest that salts alter water O-(1)H and O-(2)H stretch and bend vibrations as well as protein amide I (or I') and amide II (or II') vibrations. Anions have a much larger influence on water vibrations than cations. Water studies also show increased water-water and/or water-ion interactions in the presence of strongly hydrated SO4(2-) salts and evidence for decreased interactions with weakly hydrated Cl(-) and ClO4(-) salts. Salt-water difference infrared spectra show that kosmotropic salts are more hydrated than chaotropic salts. Interestingly, this is the opposite trend to the changes in protein solvation. Infrared spectra of RecA show that vibrations associated with protein desolvation were observed in the presence of SO4(2-) salts. Conversely, vibrations associated with protein solvation were observed in the presence of Cl(-) and ClO4(-) salts. Difference infrared studies on the dehydration of model proteins aided in identifying changes in RecA-solvent interactions. This study provides evidence that salt-induced changes in water vibrations correlate to changes in protein solvent interactions and thermal stability. PMID:26760222

  20. A Simple Fluorescence Probe Based on Aggregation-Induced Emission (AIE) Property for the Detection of Mg(2+) Ions.

    PubMed

    Bian, Yan-Jiang; Wang, Lu-Qiong; Cao, Fu-Xiang; Tang, Li-Jun

    2016-01-01

    A simple aggregation-induced emission-based fluorescence probe (1) for Mg(2+) was synthesized by condensation of benzene-1, 2-diamine with 5-bromo-2-hydroxybenzaldehyde, This compound shows favourable character of the AIE-active molecules. More importantly, after addition of Mg(2+) to probe (1) in acetonitrile, the solution changed from colorless to yellow colour solution under ultraviolet (UV) radiation obtained from hand-held UV lamp, this finding suggested that probe (1) can be used to detect Mg(2+) by colorimetric detection. Detection limit can reach 2.31 × 10(-5) M(-1). The practical value of the selective and sensitive fluorescence indicators was confirmed by its application to detection of magnesium ion in acetonitrile. PMID:26547420

  1. A stepwise recovery of metals from hybrid cathodes of spent Li-ion batteries with leaching-flotation-precipitation process

    NASA Astrophysics Data System (ADS)

    Huang, Yanfang; Han, Guihong; Liu, Jiongtian; Chai, Wencui; Wang, Wenjuan; Yang, Shuzhen; Su, Shengpeng

    2016-09-01

    The recovering of valuable metals in spent lithium-ion battery cathodes brings about economic and environmental benefits. A stepwise leaching-flotation-precipitation process is adopted to separate and recover Li/Fe/Mn from the mixed types of cathode materials (hybrid wastes of LiFePO4 and LiMn2O4). The optimal operating conditions for the stepwise recovery process are determined and analyzed by factorial design, thermodynamics calculation, XRD and SEM characterization in this study. First, Li/Fe/Mn ions are released from the cathode using HCl assisted with H2O2 in the acid leaching step. The leachability of metals follows the series Li > Fe > Mn in the acidic environment. Then Fe3+ ions are selectively floated and recovered as FeCl3 from the leachate in the flotation step. Finally, Mn2+/Mn3+ and Li+ ions are sequentially precipitated and separated as MnO2/Mn2O3 and Li3PO4 using saturated KMnO4 solution and hot saturated Na3PO4 solution, respectively. Under the optimized and advisable conditions, the total recovery of Li, Fe and Mn is respectively 80.93 ± 0.16%, 85.40 ± 0.12% and 81.02 ± 0.08%. The purity for lithium, ferrum and manganese compounds is respectively 99.32 ± 0.07%, 97.91 ± 0.05% and 98.73 ± 0.05%. This stepwise process could provide an alternative way for the effective separation and recovery of metal values from spent Li-ion battery cathodes in industry.

  2. Precipitate behavior in self-ion irradiated stainless steels at high doses

    NASA Astrophysics Data System (ADS)

    Jiao, Z.; Was, G. S.

    2014-06-01

    To study radiation-induced precipitation at high doses, solution annealed 304L SS and cold worked 316 SS were irradiated to 46 and 260 dpa at 380 °C using 5 MeV Fe++ and the radiation-induced precipitates were examined using atom probe tomography. Ni/Si-rich clusters were observed in all examined conditions. G-phase precipitates were observed in 316 SS at 46 dpa but only appeared in 304L SS at 260 dpa. Using the neutron irradiation to 46 dpa at 320 °C as a reference, the temperature shift for cold worked 316 SS appeared to be smaller than that of solution annealed 304L SS, probably due to the high density of dislocations, which served as defect sinks and mitigated the effect of high dose rate.

  3. Design of an anti-aggregated SERS sensing platform for metal ion detection based on bovine serum albumin-mediated metal nanoparticles.

    PubMed

    Ji, Wei; Chen, Lei; Xue, Xiangxin; Guo, Zhinan; Yu, Zhi; Zhao, Bing; Ozaki, Yukihiro

    2013-08-25

    Based on bovine serum albumin (BSA)-modified Au NPs, a simple and cost-effective approach was proposed to fabricate an anti-aggregated Au NP sensing platform for the detection of metal ions. It exhibits excellent stability even under highly ionic conditions due to its electrostatic stabilization, as well as the steric stabilization. PMID:23851712

  4. Design and synthesis of micron-sized spherical aggregates composed of hollow Fe2O3 nanospheres for use in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Cho, Jung Sang; Hong, Young Jun; Lee, Jong-Heun; Kang, Yun Chan

    2015-04-01

    A novel structure denoted a ``hollow nanosphere aggregate'' is synthesized by introducing nanoscale Kirkendall diffusion to the spray pyrolysis process. The hollow Fe2O3 nanosphere aggregates with spherical shape and micron size are synthesized as the first target material. A solid iron oxide-carbon composite powder that is prepared by a one-pot spray pyrolysis process is transformed into the hollow Fe2O3 nanosphere aggregates by sequential post-pyrolysis treatments under reducing and oxidizing atmospheres. The nanoscale Kirkendall diffusion plays a key role in the formation of the hollow Fe2O3 nanosphere aggregates with spherical shape and micron size. The unique structure of the hollow Fe2O3 nanosphere aggregates results in their superior electrochemical properties as an anode material for lithium ion batteries by improving the structural stability during cycling. The hollow metal oxide nanosphere aggregates with various compositions for wide applications including energy storage can be prepared by the simple fabrication method introduced in this study.A novel structure denoted a ``hollow nanosphere aggregate'' is synthesized by introducing nanoscale Kirkendall diffusion to the spray pyrolysis process. The hollow Fe2O3 nanosphere aggregates with spherical shape and micron size are synthesized as the first target material. A solid iron oxide-carbon composite powder that is prepared by a one-pot spray pyrolysis process is transformed into the hollow Fe2O3 nanosphere aggregates by sequential post-pyrolysis treatments under reducing and oxidizing atmospheres. The nanoscale Kirkendall diffusion plays a key role in the formation of the hollow Fe2O3 nanosphere aggregates with spherical shape and micron size. The unique structure of the hollow Fe2O3 nanosphere aggregates results in their superior electrochemical properties as an anode material for lithium ion batteries by improving the structural stability during cycling. The hollow metal oxide nanosphere aggregates with

  5. Ion-specific colloidal aggregation: population balance equations and potential of mean force.

    PubMed

    Odriozola, Gerardo

    2011-10-01

    Recently reported colloidal aggregation data obtained for different monovalent salts (NaCl, NaNO(3), and NaSCN) and at high electrolyte concentrations are matched with the stochastic solutions of the master equation to obtain bond average lifetimes and bond formation probabilities. This was done for a cationic and an anionic system of similar particle size and absolute charge. Following the series Cl(-), NO(3)(-), SCN(-), the parameters obtained from the fitting procedure to the kinetic data suggest: (i) The existence of a potential of mean force (PMF) barrier and an increasing trend for it for both lattices. (ii) An increasing trend for the PMF at contact, for the cationic system, and a practically constant value for the anionic system. (iii) A decreasing trend for the depth of the secondary minimum. This complex behavior is in general supported by Monte Carlo simulations, which are implemented to obtain the PMF of a pair of colloidal particles immersed in the corresponding electrolyte solution. All these findings contrast the Derjaguin, Landau, Verwey, and Overbeek theory predictions. PMID:21992332

  6. Low-Altitude Emission of Energetic Neutral Atoms from Precipitating Magnetospheric Ions: IMAGE/HENA Mission-Long Survey

    NASA Astrophysics Data System (ADS)

    Vievering, J. T.; Roelof, E. C.; Nair, H.; Sotirelis, T.

    2012-12-01

    Remote sensing of ring current losses should be of considerable utility to the RBSP mission. Low-altitude emission (LAE) of energetic neutral atoms (ENAs) yields a sensitive measurement of the precipitation of magnetospheric energetic ions into the dense monatomic oxygen (O) exosphere at altitudes ˜350 km. LAE is the brightest source of ENAs with energies 1ion population directly by charge exchange with the neutral hydrogen atom (H) geocorona. LAE has been detected by many spacecraft (including the NASA TWINS spacecraft now in orbit), but the HENA imager on the IMAGE spacecraft (operating during 2000-2005) had the highest angular resolution (6o×6opixels) and sensitivity (G=1.6 cm2 sr) over the energy range of the bulk of the ring current (20ions were precipitating on auroral-zone field lines. However, some case studies comparing LAE imaged by the TWINS imagers with DMSP in situ measurements

  7. Effect of dielectric interface on charge aggregation in the voltage-gated K+ ion channel

    PubMed Central

    Adhya, Lipika; Mapder, Tarunendu; Adhya, Samit

    2015-01-01

    Background: There is experimental evidence of many cases of stable macromolecular conformations with charged amino-acids facing lipid, an arrangement thought to be energetically unfavourable. Methods and Objectives: Employing classical electrostatics, we show that, this is not necessarily the case and studied the physical basis of the specific role of proximity of charges to the dielectric interface between two different environments. We illustrate how self and induced energies due to the dielectric medium polarization, on either side of the interface, contribute differentially to the stability of a pair of charges and hence the mutual conformation of the S3b-S4 α-helix pair of the voltage-gated K+ channel. Results and Conclusion: We show that (1) a pair of opposite charges on either side of lipid-protein interface confers significant stability; (2) hydrophobic media has an important role in holding together two similar repelling charges; (3) dielectric interface has stabilizing effect on a pair of charges, when an ion is closer to its interface than its neighboring charge; (4) in spite of the presence of dielectric interface, there is a nonexistence of any dielectric effect, when an ion is equidistant from its image and neighboring charge. We also demonstrate that, variation in dielectric media of the surrounding environment confers new mutual conformations to S3b-S4 α-helices of voltage sensor domain at zero potential, especially lipid environment on the helix side, which improved stability to the configuration by lowering the potential energy. Our results provide an answer to the long standing question of why charges face hydrophobic lipid membranes in the stable conformation of a protein. PMID:25810659

  8. Effect of calcium oxide on the efficiency of ferrous ion oxidation and total iron precipitation during ferrous ion oxidation in simulated acid mine drainage treatment with inoculation of Acidithiobacillus ferrooxidans.

    PubMed

    Liu, Fenwu; Zhou, Jun; Jin, Tongjun; Zhang, Shasha; Liu, Lanlan

    2016-01-01

    Calcium oxide was added into ferrous ion oxidation system in the presence of Acidithiobacillus ferrooxidans at concentrations of 0-4.00 g/L. The pH, ferrous ion oxidation efficiency, total iron precipitation efficiency, and phase of the solid minerals harvested from different treatments were investigated during the ferrous ion oxidation process. In control check (CK) system, pH of the solution decreased from 2.81 to 2.25 when ferrous ions achieved complete oxidation after 72 h of Acidithiobacillus ferrooxidans incubation without the addition of calcium oxide, and total iron precipitation efficiency reached 20.2%. Efficiency of ferrous ion oxidation and total iron precipitation was significantly improved when the amount of calcium oxide added was ≤1.33 g/L, and the minerals harvested from systems were mainly a mixture of jarosite and schwertmannite. For example, the ferrous ion oxidation efficiency reached 100% at 60 h and total iron precipitation efficiency was increased to 32.1% at 72 h when 1.33 g/L of calcium oxide was added. However, ferrous ion oxidation and total iron precipitation for jarosite and schwertmannite formation were inhibited if the amount of calcium oxide added was above 2.67 g/L, and large amounts of calcium sulfate dihydrate were generated in systems. PMID:27003087

  9. Structure of Fe(III) precipitates generated by Fe(0) electrocoagulation in the presence of groundwater ions

    NASA Astrophysics Data System (ADS)

    van Genuchten, C. M.; Pena, J.; Addy, S. E.; Gadgil, A. J.

    2012-12-01

    Electrocoagulation (EC) using Fe(0) electrodes is an inexpensive and efficient technology capable of removing a variety of contaminants from water supplies. Because of its ease of use and modest electricity and Fe(0) requirements, EC has potential as an arsenic-removal technology for rural South Asia, where millions drink groundwater contaminated by arsenic. In EC, a small external voltage applied to a sacrificial Fe(0) anode in contact with an electrolyte (e.g. pumped groundwater containing arsenic) promotes the oxidative dissolution of Fe ions, which polymerize and create reactive hydrous ferric oxides (HFO) in-situ with a high affinity for binding contaminants. The chemical composition of the electrolyte influences EC performance. For example, major inorganic ions present in groundwater (e.g. Ca, Mg, P, As(V), Si) alter the pathway by which FeO6 oligomers polymerize to form crystalline Fe (oxyhydr)oxide minerals. Because the precipitate structure largely determines properties that govern the efficiency of EC systems (e.g. precipitate reactivity and colloidal stability), it is essential to understand the individual and interdependent structural effects of common groundwater ions. In this work, we integrate Fe K-edge EXAFS spectroscopy with the Pair Distribution Function (PDF) technique to create a detailed description of EC precipitate structure as a function of electrolyte chemistry. EC precipitate samples were generated in a range of individual and combined concentrations of Ca, Mg, P, As(V), and Si, encompassing most of the typical levels found in natural groundwater. Combining complementary EXAFS and PDF techniques with batch uptake experiments and general chemical reasoning, we obtain structural representations of EC precipitates that are inaccessible with any single characterization technique. Our results indicate that the presence of As(V), P, and Si oxyanions promote the formation of nanoscale material bearing similar, but not identical, intermediate

  10. Design and synthesis of micron-sized spherical aggregates composed of hollow Fe2O3 nanospheres for use in lithium-ion batteries.

    PubMed

    Cho, Jung Sang; Hong, Young Jun; Lee, Jong-Heun; Kang, Yun Chan

    2015-05-14

    A novel structure denoted a "hollow nanosphere aggregate" is synthesized by introducing nanoscale Kirkendall diffusion to the spray pyrolysis process. The hollow Fe2O3 nanosphere aggregates with spherical shape and micron size are synthesized as the first target material. A solid iron oxide-carbon composite powder that is prepared by a one-pot spray pyrolysis process is transformed into the hollow Fe2O3 nanosphere aggregates by sequential post-pyrolysis treatments under reducing and oxidizing atmospheres. The nanoscale Kirkendall diffusion plays a key role in the formation of the hollow Fe2O3 nanosphere aggregates with spherical shape and micron size. The unique structure of the hollow Fe2O3 nanosphere aggregates results in their superior electrochemical properties as an anode material for lithium ion batteries by improving the structural stability during cycling. The hollow metal oxide nanosphere aggregates with various compositions for wide applications including energy storage can be prepared by the simple fabrication method introduced in this study. PMID:25899089

  11. Self-Consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 2; Waves, Precipitating Ring Current Ions, and Thermal Electron Heating

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.

    2006-01-01

    This paper is dedicated to further presentations and discussions of the results from our new global self-consistent theoretical model of interacting ring current ions and electromagnetic ion cyclotron waves [Khazanov et al., 2006; here referred to as Paper 1]. In order to adequately take into account the wave propagation and refraction in a multi-ion plasmasphere, we explicitly include the ray tracing equations in our previous self-consistent model and use the general form of the wave kinetic equation [for details see Paper 1]. To demonstrate the effects of the EMIC wave propagation and refraction on the RC proton precipitations and heating of the thermal plasmaspheric electrons we simulate the May 1998 storm. The main findings of our simulation can be summarized as follows. Firstly, the wave induced precipitations have a quite fine structure, and are highly organized by location of the plasmapause gradient. The strongest fluxes of about 4 (raised dot) 10(exp 6) [(cm (raised dot) s (raised dot) sr)(sup -l)] are observed during the main and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not simply connected to the most intense EMIC waves. The character of the EMIC wave power spectral density distribution over the equatorial wave normal angle is an extremely crucial for the effectiveness of the RC ion scattering. Secondly, comparison of the global proton precipitating patterns with the results from other ring current model [Kozyra et al., 1997] reveals that although we observe a qualitative agreement between localizations of the wave induced fluxes in the models, there is no quantitative agreement between the magnitudes of these fluxes. These differences are mainly due to a qualitative difference between the characters of the EMIC wave power spectral density distributions over the equatorial wave normal angle. Finally, the two energy sources to the

  12. Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission.

    PubMed

    Neupane, Lok Nath; Oh, Eun-Taex; Park, Heon Joo; Lee, Keun-Hyeung

    2016-03-15

    A fluorescent peptidyl chemosensor for the detection of heavy metal ions in aqueous solution as well as in cells was synthesized on the basis of the peptide receptor for the metal ions using an aggregation-induced emission fluorophore. The peptidyl chemosensor (1) bearing tetraphenylethylene fluorophore showed an exclusively selective turn-on response to Hg(2+) among 16 metal ions in aqueous buffered solution containing NaCl. The peptidyl chemosensor complexed Hg(2+) ions and then aggregated in aqueous buffered solution, resulting in the significant enhancement (OFF-On) of emissions at around 470 nm. The fluorescent sensor showed a highly sensitive response to Hg(2+), and about 1.0 equiv of Hg(2+) was enough for the saturation of the emission intensity change. The detection limit (5.3 nM, R(2) = 0.99) of 1 for Hg(2+) ions was lower than the maximum allowable level of Hg(2+) in drinking water by EPA. Moreover, the peptidyl chemosensor penetrated live cells and detected intracellular Hg(2+) ions by the turn-on response. PMID:26872241

  13. The variation of reconnection rate at the dayside magnetopause and cusp ion precipitation

    NASA Technical Reports Server (NTRS)

    Lockwood, M.; Smith, M. F.

    1992-01-01

    A method is presented which allows estimation of the variation of the rate of magnetic reconnection at the dayside magnetopause. This is achieved using observations of the cusp particle precipitation made by low-altitude polar-orbiting spacecraft. In this paper we apply the technique to a previously published example of a cusp intersection by the DMSP F7 satellite. It is shown that the cusp signature in this case was produced by three separate bursts of reconnection which were of the order of 10 min apart, each lasting roughly 1 min. This is similar to the variation of reconnection rate which is required to explain typical flux transfer event signatures at the magnetopause.

  14. Alfvénic field-aligned currents, ion upflow and electron precipitation during large geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Hatch, Spencer; LaBelle, James; Chaston, Christopher

    2016-04-01

    We present four years of FAST observations of Alfvénic field-aligned currents (FACs) in the Northern Hemisphere coincident with 40 moderate (Dst < -50 nT) to very large geomagnetic storms. Superposed epoch analysis of Alfvénic activity of storm periods demonstrate a sharp increase in the probability of AlfvÉn wave occurrence just after storm commencement, and analysis based on storm phase shows that the probability of Alfvén wave occurrence increases by more than a factor of 5 on both dayside and nightside. Additionally, recently reported Van Allen Probes measurements in the magnetosphere imply a region (˜60-68 degrees invariant latitude) in the nightside ionosphere where Alfvén waves are statistically likely to be observed during storm main phase; we report statistical observations during main phase showing that this region instead corresponds to both intense electron precipitation (>10 mW m-2) and strong upflowing ion number flux (> 108 cm^{-2 s-1), while observed Alfvénic FAC occurrence rates are diminished relative to Van Allen Probes measurements. FAST observations also indicate that the most intense electron precipitation associated with Alfvénic FACs occurs pre-midnight during storm recovery phase.

  15. Ion Upwelling and Height-Resolved Electrodynamic Response of the Ionosphere to ULF Waves and Precipitation: Comparison Between Simulation and EISCAT Observations

    NASA Astrophysics Data System (ADS)

    Sydorenko, D.; Rankin, R.

    2013-12-01

    We have developed a comprehensive two-dimensional (meridional) model of coupling between the magnetosphere and ionosphere that covers an altitude range from ~100 km to few thousand km at high latitudes [Sydorenko and Rankin, 2013]. The model describes propagation of inertial scale Alfven waves, including ponderomotive forces, and has a parametric model of energetic electron precipitation; it includes vertical ion flows and chemical reactions between ions and neutrals. Model results are presented that reproduce EISCAT radar observations of electron and ion temperatures, height integrated conductivity, ion densities, and ion flows during a period of ULF activity described in [Lester, Davies, and Yeoman, 2000]. We performed simulations where the precipitation and the Alfven wave perturb the ionosphere simultaneously. By adjusting parameters of the wave and the precipitation we have achieved qualitative, and sometimes even reasonable quantitative agreement between the observations and the simulation. The model results are discussed in the context of new results anticipated from the Canadian small satellite mission ePOP "Enhanced Polar Outflow Probe", scheduled for launch on September 9, 2013. Sydorenko D. and R. Rankin, 'Simulation of O+ upflows created by electron precipitation and Alfvén waves in the ionosphere' submitted to Journal of Geophysical Research, 2013. Lester M., J. A. Davies, and T. K. Yeoman, 'The ionospheric response during an interval of PC5 ULF wave activity', Ann. Geophysicae, v.18, p.257-261 (2000).

  16. Effects of DPPC/Cholesterol liposomes on the properties of freshly precipitated calcium carbonate.

    PubMed

    Szcześ, A

    2013-01-01

    DPPC/Cholesterol liposomes of average diameter below 100nm were used as a matrix for calcium carbonate precipitation. Adsorption of calcium ions on the vesicles was determined via zeta potential measurement. It was found that with increasing calcium ions concentration the electrokinetic potential of the vesicles varied toward more positive values. The changes became smaller with the cholesterol content increase. Accumulation of calcium ions close to the vesicles membranes lead to attraction of CO(3)(2-) ions and enhances nucleation and growth of small calcium carbonate crystals that aggregates within lipid vesicles forming porous balls aggregates. However, dipalmitoylphosphatidylcholine (DPPC) does not change the CaCO(3) crystal forms and calcite is the only form obtained during precipitation. Moreover, the influence of the phospholipid on the calcium carbonate precipitation is enhanced by the induction of cholesterol to the lipid membranes. PMID:22796770

  17. The impact of calcium ion on structure and aggregation propensity of peroxynitrite-modified lens crystallins: new insights into the pathogenesis of cataract disorders.

    PubMed

    Ghahramani, Maryam; Yousefi, Reza; Khoshaman, Kazem; Alavianmehr, Mohammad-Mehdi

    2015-01-01

    As a highly potent reactive oxygen and nitrogen species, peroxynitrite (PON) has been indicated in the pathogenesis of various ocular disorders. The PON induces mobilization of intra cellular calcium which plays an important function in structure and activity of lens proteins. Moreover, the amount of calcium increases to the pathogenic level in the cataractous lenses. The aim of this study was to assess the impact of calcium ion on structure and aggregation of PON-modified lens crystallins, using spectroscopic techniques and gel mobility shift assay. The PON modification of lens proteins was confirmed with detection of the significantly increased quantity of carbonyl group, dityrosine, nitrotyrosine and nitrotryptophan. Moreover, the modified proteins indicated high levels of solvent exposed hydrophobic surfaces and markedly elevated proteolytic instability which can be explained with their structural alteration upon this type of modification. The results of UV-vis absorption studies suggest that PON-modified lens crystallins are highly sensitive to aggregation in the presence of both physiological and pathological ranges of calcium ion. Also, the results of thioflavin T fluorescence study indicated absence of any ordered aggregate entity in the calcium-induced aggregate samples. The results of gel mobility shift assay demonstrated the importance of calcium ion in the induction of disulfide and dityrosine covalent cross-linking and formation of the oligomeric structure with relatively larger sizes in the PON-modified crystallins compared to the non-modified protein counterparts. Overall, this study may suggest that a simultaneous raise of calcium ion and PON in the eye ball is an important risk factor for development of cataract diseases. PMID:25486325

  18. Temperature-dependent toxicities of nano zinc oxide to marine diatom, amphipod and fish in relation to its aggregation size and ion dissolution.

    PubMed

    Wong, Stella W Y; Leung, Kenneth M Y

    2014-08-01

    This study, for the first time, concurrently investigated the influence of seawater temperature, exposure concentration and time on the aggregation size and ion dissolution of nano zinc oxides (nZnO) in seawater, and the interacting effect of temperature and waterborne exposure of nZnO to the marine diatom Skeletonema costatum, amphipod Melita longidactyla and fish Oryzias melastigma, respectively. Our results showed that aggregate size was jointly affected by seawater temperature, nZnO concentration and exposure time. Among the three factors, the concentration of nZnO was the most important and followed by exposure time, whereas temperature was less important as reflected by their F values in the three-way analysis of variance (concentration: F3, 300 = 247.305; time: F2, 300 = 20.923 and temperature: F4, 300 = 4.107; All p values <0.001). The aggregate size generally increased with increasing nZnO concentration and exposure time. The release of Zn ions from nZnO was significantly influenced by seawater temperature and exposure time; the ion dissolution rate generally increased with decreasing temperature and increasing exposure time. Growth inhibition of diatoms increased with increasing temperature, while temperature and nZnO had an interactional effect on their photosynthesis. For the amphipod, mortality was positively correlated with temperature. Fish larvae growth rate was only affected by temperature but not nZnO, while the two factors interactively modulated the expression of heat shock and metallothionein proteins. Evidently, temperature can influence aggregate size and ion dissolution and thus toxicity of nZnO to the marine organisms in a species-specific manner. PMID:24219175

  19. Pulsed Laser-Driven Molecular Self-assembly of Cephalexin: Aggregation-Induced Fluorescence and Its Utility as a Mercury Ion Sensor.

    PubMed

    Singh, Pradeep Kumar; Prabhune, Asmita; Ogale, Satishchandra

    2015-11-01

    A fluorescent self-assembly of cephalexin is obtained by pulsed laser irradiation process. An intense fluorescence emission is found in the self-assembled form due to occurrence of a typical aggregation-induced emission in cephalexin molecules. It is observed that fluorescence quenching of the self-assembled fluorescent nanostructures occurs in the presence of extremely low Hg(++) ions concentrations (10(-7) m) as compared to other heavy metal ions e.g. Ferrous (Fe(++) ), Manganese (Mn(++) ), Magnesium (Mg(++) ), Cobalt (Co(++) ), Nickel (Ni(++) ) and Zinc (Zn(++) ) at the same concentrations. PMID:26333412

  20. Preconcentration of some metal ions with lanthanum-8-hydroxyquinoline co-precipitation system.

    PubMed

    Feist, Barbara; Mikula, Barbara

    2014-03-15

    A method of separation and preconcentration of cadmium, copper, nickel, lead and zinc at trace level using 8-hydroxyquinoline as a chelating agent and lanthanum(III) as a carrier element is proposed. The heavy metals were determined after preconcentration by inductively coupled plasma optical emission spectrometry (ICP-OES). The results were compared with those obtained using flame atomic absorption spectrometry (F-AAS). The influence of several parameters such as pH, amount of lanthanum(III) as a carrier element, amount of 8-hydroxyquinoline, duration of co-precipitation was examined. Moreover, effects of inorganic matrix on recovery of the determined elements were studied. The detection limits (DL) for ICP-OES were 0.31, 2.9, 1.4, 3.2 and 1.2 μg L(-1) for Cd, Cu, Ni, Pb and Zn, respectively, whereas for F-AAS DL were 0.63, 1.1, 3.2, 2.7 and 0.74 μg L(-1). The recovery of the method for the determined elements was better than 94% with relative standard deviation between 0.63% and 2.9%. The preconcentration factor was 60. The proposed method was successfully applied for determination of Cd, Cu, Ni, Pb, and Zn in plant materials. Accuracy of the proposed method was verified using certified reference material (NCS ZC85006 Tomato). PMID:24206710

  1. A subauroral polarization stream driven by field-aligned currents associated with precipitating energetic ions caused by EMIC waves: A case study

    NASA Astrophysics Data System (ADS)

    Yuan, Zhigang; Xiong, Ying; Qiao, Zheng; Li, Haimeng; Huang, Shiyong; Wang, Dedong; Deng, Xiaohua; Raita, Tero; Wang, Jingfang

    2016-02-01

    During the energetic ion injection event observed by the Los Alamos National Laboratory geosynchronous spacecraft, observations of the NOAA 15 satellite and Finnish network of search coil magnetometers have shown that a sharp enhancement of precipitating ring current (RC) ion flux is contributed to the pitch angle scattering caused by electromagnetic ion cyclotron (EMIC) waves. At subauroral latitudes, lower than the equatorward edge of precipitating electrons from the plasma sheet, the DMSP F13 satellite observed a subauroral polarization stream (SAPS) with a peak velocity of 688 m/s. When passing the region of EMIC waves derived by the Finnish network of search coil magnetometers and NOAA 15 satellite, the DMSP F13 satellite simultaneously observed field-aligned currents (FACs) flowing into the ionosphere and precipitating RC ions in the region of the SAPS. The peak of the SAPS accords to the minimum of the ion density in the region of the SAPS. Our result suggests that loss of RC ions caused by EMIC waves would possibly lead to FACs flowing into the ionosphere and drive the SAPS in the evening sector.

  2. Effects of ion aggregation on the intervalence transfer band of the mixed-valence biferrocenium cation in solution

    SciTech Connect

    Lowery, M.D.; Hammack, W.S.; Drickamer, H.G.; Hendrickson, D.N.

    1987-12-23

    The concentration dependence of the energy (E/sup op/) of the intervalence transfer (IT) electronic absorption band of mixed-valence biferrocenium triiodide dissolved in either nitrobenzene or dichloromethane is examined. In nitrobenzene, E/sup op/ increases rapidly from approx. 5.57 to approx. 6.05 x 10/sup 3/ cm/sup -1/ in the 0.24-0.4 mM range, whereupon further increases in the concentration of biferrocenium triiodide lead to E/sup op/ increasing more gradually to a value approx. 6.3 x 10/sup 3/ cm/sup -1/ at 24 mM. On the other hand, the full width at half maximum (..delta.. anti v/sub 1/2) and the transition moment of the IT band decrease with increasing concentration for biferrocenium triiodide in nitrobenzene. E/sup op/ increases, ..delta.. anti v/sub 1/2 remains constant, and the transition moment of the IT band increases with increasing concentration for biferrocenium triiodide in dichloromethane in the more limited range of 0.30-0.95 mM. These concentration dependencies of the IT band for biferrocenium triiodide are attributable to variable degrees of ion aggregation in solution. The concentration dependencies of the electrical conductivity of solutions of biferrocenium triiodide in either nitrobenzene or dichloromethane substantiate this proposal. IT band contours obtained at different concentrations are fit to the PKS vibronic model to yield parameters that characterize the electronic and vibronic coupling within the mixed-valence biferrocenium cation.

  3. Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitations, Plasma Waves, and Convection Observed by POLAR

    NASA Technical Reports Server (NTRS)

    Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Pollock, C. J.; Gurnett, D. A.; Persoon, A. M.; Scudder, J. D.; Maynard, N. C.; Mozer, F. S.; Brittnacher, M. J.; Nagai, T.

    1997-01-01

    The POLAR satellite often observes upflowing ionospheric ions (UFls) in and near the auroral oval on southern perigee (approximately 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass-angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with auroral forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the dusk side after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawn side during the recovery phase. The UFls showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approximately 10 kHz, while no significant auroral activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped auroral kilometric radiation (AKR) signatures observed above approximately 200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument (EFI) were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating electrons and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs. the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.

  4. Relationship of Topside Ionospheric Ion Outflows to Auroral Forms and Precipitation, Plasma Waves, and Convection Observed by Polar

    NASA Technical Reports Server (NTRS)

    Hirahara, M.; Horwitz, J. L.; Moore, T. E.; Germany, G. A.; Spann, J. F.; Peterson, W. K.; Shelley, E. G.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Pollock, C. J.; Gurnett, D. A.; Pickett, J. S.; Persoon, A. M.; Scudder, J. D.; Maynard, N. C.; Mozer, F. S.; Brittnacher, M. J.; Nagai, T.

    1998-01-01

    The POLAR satellite often observes upflowing ionospheric ions (UFIs) in and near the aurora] oval on southern perigee (approx. 5000 km altitude) passes. We present the UFI features observed by the thermal ion dynamics experiment (TIDE) and the toroidal imaging mass angle spectrograph (TIMAS) in the dusk-dawn sector under two different geomagnetic activity conditions in order to elicit their relationships with auroral forms, wave emissions, and convection pattern from additional POLAR instruments. During the active interval, the ultraviolet imager (UVI) observed a bright discrete aurora on the duskside after the substorm onset and then observed a small isolated aurora form and diffuse auroras on the dawnside during the recovery phase. The UFIs showed clear conic distributions when the plasma wave instrument (PWI) detected strong broadband wave emissions below approx. 10 kHz, while no significant auroral activities were observed by UVI. At higher latitudes, the low-energy UFI conics gradually changed to the polar wind component with decreasing intensity of the broadband emissions. V-shaped auroral kilometric radiation (AKR) signatures observed above -200 kHz by PWI coincided with the region where the discrete aurora and the UFI beams were detected. The latitude of these features was lower than that of the UFI conics. During the observations of the UFI beams and conics, the lower-frequency fluctuations observed by the electric field instrument were also enhanced, and the convection directions exhibited large fluctuations. It is evident that large electrostatic potential drops produced the precipitating electrons and discrete auroras, the UFI beams, and the AKR, which is also supported by the energetic plasma data from HYDRA. Since the intense broadband emissions were also observed with the UFIs, the ionospheric ions could be energized transversely before or during the parallel acceleration due to the potential drops.

  5. Estimates of average major ion concentrations in bulk precipitation at two high-altitude sites near the continental divide in Southwestern Colorado

    USGS Publications Warehouse

    Reddy, M.M.; Claassen, H.C.

    1985-01-01

    The composition of bulk precipitation from two high-altitude sites, established in 1971 near the Continental Divide in southwestern Colorado, has been monitored by season during the past decade. Calcium ions are the predominant cationic species; sulfate is the major anionic constituent. Bulk precipitation major ion concentrations exhibit log-normal distributions. Representative mean and standard deviation values for the major inorganic ionic species present in bulk precipitation have been calculated for three years of consecutive seasons. Standard deviations for all species, except nitrate, are similar. For two years of data grouped into quarters, deviations from mean values fall well within the plus or minus two standard deviation limit. There does not seem to be a systematic deviation from the mean concentration values, with respect to either ionic component or season.

  6. Episodic carbonate precipitation in the CM chondrite ALH 84049: An ion microprobe analysis of O and C isotopes

    NASA Astrophysics Data System (ADS)

    Tyra, Mark; Brearley, Adrian; Guan, Yunbin

    2016-02-01

    We have determined the O and C isotope compositions of dolomite grains and the C isotope compositions of calcite grains in the highly altered CM1 chondrite, ALH 84049, using Secondary Ion Mass Spectrometry (SIMS). Chemically-zoned dolomite constitutes 0.8 volume percent (vol%) of the sample and calcite 0.9 vol%. Thirteen separate dolomite grains have δ13C values that range from 37 to 60 (±2) ‰, δ18O values from 25 to 32 (±3) ‰, and δ17O values from 10 to 16 (±3) ‰ (VSMOW). Intragrain δ13C values in dolomite vary up to 10‰. The δ13C values of three calcite grains are distinct from those of dolomite and range from 10 to 13 (±2) ‰ (PDB). Calcite and dolomite appear to record different precipitation episodes. Carbon isotope values of both dolomite and calcite in this single sample encompass much of the reported range for CM chondrites; our results imply that bulk carbonate C and O isotope analyses may oversimplify the history of carbonate precipitation. Multiple generations of carbonates with variable isotope compositions exist in ALH 84049 and, perhaps, in many CM chondrites. This work shows that one should exercise caution when using a clumped isotope approach to determine the original temperature and the isotopic compositions of water for CM chondrite carbonates. Less altered CM meteorites with more-homogeneous C isotope compositions, however, may be suitable for bulk-carbonate analyses, but detailed carbonate petrologic and isotopic characterization of individual samples is advised.

  7. Application of linear pH gradients for the modeling of ion exchange chromatography: Separation of monoclonal antibody monomer from aggregates.

    PubMed

    Kluters, Simon; Wittkopp, Felix; Jöhnck, Matthias; Frech, Christian

    2016-02-01

    The mobile phase pH is a key parameter of every ion exchange chromatography process. However, mechanistic insights into the pH influence on the ion exchange chromatography equilibrium are rare. This work describes a mechanistic model capturing salt and pH influence in ion exchange chromatography. The pH dependence of the characteristic protein charge and the equilibrium constant is introduced to the steric mass action model based on a protein net charge model considering the number of amino acids interacting with the stationary phase. This allows the description of the adsorption equilibrium of the chromatographed proteins as a function of pH. The model parameters were determined for a monoclonal antibody monomer, dimer, and a higher aggregated species based on a manageable set of pH gradient experiments. Without further modification of the model parameters the transfer to salt gradient elution at fixed pH is demonstrated. A lumped rate model was used to predict the separation of the monoclonal antibody monomer/aggregate mixture in pH gradient elution and for a pH step elution procedure-also at increased protein loadings up to 48 g/L packed resin. The presented model combines both salt and pH influence and may be useful for the development and deeper understanding of an ion exchange chromatography separation. PMID:26549715

  8. Ratiometric fluorescent ion detection in water with high sensitivity via aggregation-mediated fluorescence resonance energy transfer using a conjugated polyelectrolyte as an optical platform.

    PubMed

    Le, Van Sang; Kim, Boram; Lee, Wonho; Jeong, Ji-Eun; Yang, Renqiang; Woo, Han Young

    2013-05-14

    A cationic conjugated polyelectrolyte was designed and synthesized based on poly(fluorene-co-phenylene) containing 5 mol% benzothiadiazole (BT) as a low energy trap and 15-crown-5 as a recognizing group for potassium ions. A potassium ion can form a sandwich-type 2:1 Lewis acid-based complex with 15-crown-5, to cause the intermolecular aggregation of polymers. This facilitates inter-chain fluorescence resonance energy transfer (FRET) to a low-energy BT segment, resulting in fluorescent signal amplification, even at dilute analyte concentrations. Highly sensitive and selective detection of K(+) ions was demonstrated in water. The linear response of ratiometric fluorescent signal as a function of [K(+) ] allows K(+) quantification in a range of nanomolar concentrations with a detection limit of ≈0.7 × 10(-9) M. PMID:23417971

  9. Effect of curcumin and Cu 2+/Zn 2+ ions on the fibrillar aggregates formed by the amyloid peptide and other peptides at the organic-aqueous interface

    NASA Astrophysics Data System (ADS)

    Sanghamitra, Nusrat J. M.; Varghese, Neenu; Rao, C. N. R.

    2010-08-01

    Characteristic features of a perilous neuro-degenerative disease such as the Alzhiemer's disease is fibrillar plaque formation by the amyloid (Aβ) peptide. We have modelled the formation and disintegration of fibrils by studying the aggregate structures formed by Aβ structural motif diphenylalanine as well as insulin and bovine serum albumin at the organic-aqueous interface. Even small concentrations of curcumin in the organic medium or Cu 2+ and Zn 2+ ions in the aqueous medium are found to break down the fibrillar structures.

  10. Synthesis of high capacity cathodes for lithium-ion batteries by morphology-tailored hydroxide co-precipitation

    NASA Astrophysics Data System (ADS)

    Wang, Dapeng; Belharouak, Ilias; Ortega, Luis H.; Zhang, Xiaofeng; Xu, Rui; Zhou, Dehua; Zhou, Guangwen; Amine, Khalil

    2015-01-01

    Nickel manganese hydroxide co-precipitation inside a continuous stirred tank reactor was studied with sodium hydroxide and ammonium hydroxide as the precipitation agents. The ammonium hydroxide concentration had an effect on the primary and secondary particle evolution. The two-step precipitation mechanism proposed earlier was experimentally confirmed. In cell tests, Li- and Mn-rich composite cathode materials based on the hydroxide precursors demonstrated good electrochemical performance in terms of cycle life over a wide range of lithium content.

  11. A kinetic model of the formation of the hot oxygen geocorona 2. Influence of O{sup +} ion precipitation

    SciTech Connect

    Bisikalo, D.V.; Shematovich, V.I.; Gerard, J.C.

    1995-03-01

    The authors model oxygen precipitation in the upper atmosphere by a Monte Carlo treatment of the Boltzman equation, during geomagnetically unstable times. They attempt to simulate the O precipitation for the storm conditions on September 17, 1971. They find that O precipitation greatly modifies the electron velocity distribution for the bulk oxygen population in the upper atmosphere, resulting in an enhanced hot O tail density.

  12. Multi-layer electrode with nano-Li4Ti5O12 aggregates sandwiched between carbon nanotube and graphene networks for high power Li-ion batteries

    PubMed Central

    Choi, Jin-Hoon; Ryu, Won-Hee; Park, Kyusung; Jo, Jeong-Dai; Jo, Sung-Moo; Lim, Dae-Soon; Kim, Il-Doo

    2014-01-01

    Self-aggregated Li4Ti5O12 particles sandwiched between graphene nanosheets (GNSs) and single-walled carbon nanotubes (SWCNTs) network are reported as new hybrid electrodes for high power Li-ion batteries. The multi-layer electrodes are fabricated by sequential process comprising air-spray coating of GNSs layer and the following electrostatic spray (E-spray) coating of well-dispersed colloidal Li4Ti5O12 nanoparticles, and subsequent air-spray coating of SWCNTs layer once again. In multi-stacked electrodes of GNSs/nanoporous Li4Ti5O12 aggregates/SWCNTs networks, GNSs and SWCNTs serve as conducting bridges, effectively interweaving the nanoporous Li4Ti5O12 aggregates, and help achieve superior rate capability as well as improved mechanical stability of the composite electrode by holding Li4Ti5O12 tightly without a binder. The multi-stacked electrodes deliver a specific capacity that maintains an impressively high capacity of 100 mA h g−1 at a high rate of 100C even after 1000 cycles. PMID:25476980

  13. Multi-layer electrode with nano-Li4Ti5O12 aggregates sandwiched between carbon nanotube and graphene networks for high power Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Choi, Jin-Hoon; Ryu, Won-Hee; Park, Kyusung; Jo, Jeong-Dai; Jo, Sung-Moo; Lim, Dae-Soon; Kim, Il-Doo

    2014-12-01

    Self-aggregated Li4Ti5O12 particles sandwiched between graphene nanosheets (GNSs) and single-walled carbon nanotubes (SWCNTs) network are reported as new hybrid electrodes for high power Li-ion batteries. The multi-layer electrodes are fabricated by sequential process comprising air-spray coating of GNSs layer and the following electrostatic spray (E-spray) coating of well-dispersed colloidal Li4Ti5O12 nanoparticles, and subsequent air-spray coating of SWCNTs layer once again. In multi-stacked electrodes of GNSs/nanoporous Li4Ti5O12 aggregates/SWCNTs networks, GNSs and SWCNTs serve as conducting bridges, effectively interweaving the nanoporous Li4Ti5O12 aggregates, and help achieve superior rate capability as well as improved mechanical stability of the composite electrode by holding Li4Ti5O12 tightly without a binder. The multi-stacked electrodes deliver a specific capacity that maintains an impressively high capacity of 100 mA h g-1 at a high rate of 100C even after 1000 cycles.

  14. Spatial distribution of Ion Precipitation into the High Latitude Inner Magnetosphere using Energetic Neutral Atom (ENA) images over the Declining Phase of Solar Cycle 23

    NASA Astrophysics Data System (ADS)

    Mackler, D. A.; Jahn, J.; Pollock, C. J.

    2013-12-01

    Plamasheet particles transported Earthward during times of active magnetic convection can interact with thermospheric neutrals through charge exchange. The resulting ENAs are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low altitude (300-800 km) ion precipitation in the high latitude inner mangetosphere are termed Low Altitude Emissions (LAEs). LAEs are highly non-isotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90 degrees. The observed Geomagnetic Emission Cone (GEC) of LAEs can be mapped spatially, showing where energy is deposited during storm/sub-storm times. In this study we present a statistical look at the particulate albedo of LAEs over the declining phase of solar cycle 23. The particulate albedo is defined as the ratio of the emitting energetic neutrals to the precipitating ions. The precipitating ion differential directional flux maps are built up from combining NOAA 14/15/16 TED and DMSP 13/14/15 SSJ4 data. Low altitude ENA signatures are identified manually using IMAGE/MENA images and selected out. The geomagnetic location of each pixel representing a LAE source region in the neutral images is computed assuming an altitude of 650 km. Before taking the ratio of the resulting flux of neutrals and ions, the Magnetic Local Time (MLT) and Invariant Latitude (IL) bin sizes are changed such that each has less than 20% error in counting statistics. The particulate albedo maps are then evaluated over changes in geomagnetic storm activity.

  15. Dependence of salt precipitation temperature in NaI PPG on MW

    SciTech Connect

    McLin, M.G.; Wintersgill, M.C.; Fontanella, J.J.; Brown, S.; Greenbaum, S.G.

    1993-12-31

    At present ion aggregation in polymer electrolytes is though to be due to either dielectric or entropic effects. This paper will discuss the results for a systematic study of the molecular weight, MW, dependence of salt precipitation temperature, dielectric properties, and {sup 23}Na T{sub 1} measurements in 1:8 NaI PPG electrolytes in terms of the validity of the dielectric vs entropic perspectives on ion aggregation. Also, the efficacy of using low MW liquid polymer electrolytes as model systems for phenomena in solid polymer electrolytes will be considered.

  16. Binding of heavy metal ions in aggregates of microbial cells, EPS and biogenic iron minerals measured in-situ using metal- and glycoconjugates-specific fluorophores

    NASA Astrophysics Data System (ADS)

    Hao, Likai; Guo, Yuan; Byrne, James M.; Zeitvogel, Fabian; Schmid, Gregor; Ingino, Pablo; Li, Jianli; Neu, Thomas R.; Swanner, Elizabeth D.; Kappler, Andreas; Obst, Martin

    2016-05-01

    Aggregates consisting of bacterial cells, extracellular polymeric substances (EPS) and Fe(III) minerals formed by Fe(II)-oxidizing bacteria are common at bulk or microscale chemical interfaces where Fe cycling occurs. The high sorption capacity and binding capacity of cells, EPS, and minerals controls the mobility and fate of heavy metals. However, it remains unclear to which of these component(s) the metals will bind in complex aggregates. To clarify this question, the present study focuses on 3D mapping of heavy metals sorbed to cells, glycoconjugates that comprise the majority of EPS constituents, and Fe(III) mineral aggregates formed by the phototrophic Fe(II)-oxidizing bacteria Rhodobacter ferrooxidans SW2 using confocal laser scanning microscopy (CLSM) in combination with metal- and glycoconjugates-specific fluorophores. The present study evaluated the influence of glycoconjugates, microbial cell surfaces, and (biogenic) Fe(III) minerals, and the availability of ferrous and ferric iron on heavy metal sorption. Analyses in this study provide detailed knowledge on the spatial distribution of metal ions in the aggregates at the sub-μm scale, which is essential to understand the underlying mechanisms of microbe-mineral-metal interactions. The heavy metals (Au3+, Cd2+, Cr3+, CrO42-, Cu2+, Hg2+, Ni2+, Pd2+, tributyltin (TBT) and Zn2+) were found mainly sorbed to cell surfaces, present within the glycoconjugates matrix, and bound to the mineral surfaces, but not incorporated into the biogenic Fe(III) minerals. Statistical analysis revealed that all ten heavy metals tested showed relatively similar sorption behavior that was affected by the presence of sorbed ferrous and ferric iron. Results in this study showed that in addition to the mineral surfaces, both bacterial cell surfaces and the glycoconjugates provided most of sorption sites for heavy metals. Simultaneously, ferrous and ferric iron ions competed with the heavy metals for sorption sites on the organic

  17. Homogeneous Precipitation of Nickel Hydroxide Powders

    SciTech Connect

    Bora Mavis

    2003-12-12

    Precipitation and characterization of nickel hydroxide powders were investigated. A comprehensive precipitation model incorporating the metal ion hydrolysis, complexation and precipitation reactions was developed for the production of the powders with urea precipitation method. Model predictions on Ni{sup 2+} precipitation rate were confirmed with precipitation experiments carried out at 90 C. Experimental data and model predictions were in remarkable agreement. Uncertainty in the solubility product data of nickel hydroxides was found to be the large contributor to the error. There were demonstrable compositional variations across the particle cross-sections and the growth mechanism was determined to be the aggregation of primary crystallites. This implied that there is a change in the intercalate chemistry of the primary crystallites with digestion time. Predicted changes in the concentrations of simple and complex ions in the solution support the proposed mechanism. The comprehensive set of hydrolysis reactions used in the model described above allows the investigation of other systems provided that accurate reaction constants are available. the fact that transition metal ions like Ni{sup 2+} form strong complexes with ammonia presents a challenge in the full recovery of the Ni{sup 2+}. On the other hand, presence of Al{sup 3+} facilitates the complete precipitation of Ni{sup 2+} in about 3 hours of digestion. A challenge in their predictive modeling studies had been the fact that simultaneous incorporation of more than one metal ion necessitates a different approach than just using the equilibrium constants of hydrolysis, complexation and precipitation reactions. Another limitation of using equilibrium constants is that the nucleation stage of digestion, which is controlled mainly by kinetics, is not fully justified. A new program released by IBM Almaden Research Center (Chemical Kinetics Simulator{trademark}, Version 1.01) lets the user change the order of

  18. Structure of Fe(III) precipitates generated by the electrolytic dissolution of Fe(0) in the presence of groundwater ions

    NASA Astrophysics Data System (ADS)

    van Genuchten, Case M.; Peña, Jasquelin; Amrose, Susan E.; Gadgil, Ashok J.

    2014-02-01

    We apply Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and pair distribution function (PDF) analysis of high-energy X-ray scattering to investigate the effects of bivalent cation-oxyanion pairs on the structure of Fe(III) precipitates formed from the oxidation of Fe(II) generated by the electrolytic dissolution of Fe(0) electrodes. We found that Fe(II) oxidation in the presence of weakly adsorbing electrolytes (NaCl, CaCl2, MgCl2) leads to pseudo-lepidocrocite (Lp; γ-FeOOH), a poorly crystalline version of Lp with low sheet-stacking coherence. In the absence of bivalent cations, P and As(V) have similar uptake behavior, but different effects on the average Fe(III) precipitate structure: pseudo-Lp dominates in the presence of P, whereas a disordered ferrihydrite-like precipitate akin to hydrous ferric oxide (HFO) is the dominant phase that forms in the presence of As(V). Despite its lower affinity for Fe(III) precipitates, Si leads to Si-HFO in all conditions tested. The presence of 1 mM Ca2+ or Mg2+ enhances oxyanion uptake, destabilizes the colloidally stable oxyanion-bearing particle suspensions and, in some P and As(V) electrolytes, results in more crystalline precipitates. The trends in oxyanion uptake and Fe(III) precipitate structure in the presence of Ca2+/Mg2+ suggest a systematic decrease in the strength of bivalent cation:oxyanion interaction in the order of Ca2+ > Mg2+ and P > As(V) ≫ Si. Using the PDF technique, we identify the polyhedral linkages that contribute to the intermediate structures (>6 Å) of disordered, nanoscale oxyanion-bearing Fe(III) precipitate samples. Our results suggest that oxyanions present during Fe(III) polymerization bind to corner-sharing Fe surface sites leading to a precipitate surface deficient in corner-sharing Fe, whereas the edge- and corner-sharing Fe sites in the precipitate core likely remain intact.

  19. Ion Precipitation: Loss Cone State and Low-Altitude Emission Response Time to Solar Wind Pressure Pulse-Driven Magnetospheric Compression

    NASA Astrophysics Data System (ADS)

    Llera, K.; Goldstein, J.; Valek, P. W.; McComas, D. J.

    2013-12-01

    We analyze low-altitude Energetic Neutral Atom (ENA) emissions triggered by solar wind pressure pulse-driven magnetospheric compression during a mild disturbance which occurred between 30 June through 3 July 2011. The dual-spacecraft Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) captures ENA images of Low-Altitude Emissions (LAEs) produced by ions precipitating into the ionosphere from the ring current. The National Oceanographic and Atmospheric Administration (NOAA) Polar-orbiting Operational Environmental Satellites (POES) system captures low-altitude energetic charged particle intensities. With different look directions, the NOAA/POES low-altitude ion data provides two or three-point sampling of ion pitch-angle distributions (PADs), from which we produce an interpolated fit to describe the loss-cone state; i.e., whether or not there is significant ion flux in the loss cone. Following earlier work, we compare low-altitude NOAA ion flux and pitch angle information with TWINS-observed LAEs during times of conjunction, when NOAA obtained data inside the global LAE region. We examine the degree to which response time for LAE intensification following a solar wind pressure pulse depends on the loss cone state. When there are no LAEs observed by TWINS, the NOAA-derived PAD will indicate whether the loss cone is empty.

  20. Mapping of Heavy Metal Ion Sorption to Cell-Extracellular Polymeric Substance-Mineral Aggregates by Using Metal-Selective Fluorescent Probes and Confocal Laser Scanning Microscopy

    PubMed Central

    Li, Jianli; Kappler, Andreas; Obst, Martin

    2013-01-01

    Biofilms, organic matter, iron/aluminum oxides, and clay minerals bind toxic heavy metal ions and control their fate and bioavailability in the environment. The spatial relationship of metal ions to biomacromolecules such as extracellular polymeric substances (EPS) in biofilms with microbial cells and biogenic minerals is complex and occurs at the micro- and submicrometer scale. Here, we review the application of highly selective and sensitive metal fluorescent probes for confocal laser scanning microscopy (CLSM) that were originally developed for use in life sciences and propose their suitability as a powerful tool for mapping heavy metals in environmental biofilms and cell-EPS-mineral aggregates (CEMAs). The benefit of using metal fluorescent dyes in combination with CLSM imaging over other techniques such as electron microscopy is that environmental samples can be analyzed in their natural hydrated state, avoiding artifacts such as aggregation from drying that is necessary for analytical electron microscopy. In this minireview, we present data for a group of sensitive fluorescent probes highly specific for Fe3+, Cu2+, Zn2+, and Hg2+, illustrating the potential of their application in environmental science. We evaluate their application in combination with other fluorescent probes that label constituents of CEMAs such as DNA or polysaccharides and provide selection guidelines for potential combinations of fluorescent probes. Correlation analysis of spatially resolved heavy metal distributions with EPS and biogenic minerals in their natural, hydrated state will further our understanding of the behavior of metals in environmental systems since it allows for identifying bonding sites in complex, heterogeneous systems. PMID:23974141

  1. Aggregation and Charge Behavior of Metallic and Nonmetallic Nanoparticles in the Presence of Competing Similarly-Charged Inorganic Ions

    EPA Science Inventory

    The influence of competing, similarly charged, inorganic ions on the size and charge behavior of suspended titanium-dioxide (nTiO2), silver (nAg) and fullerene (nC60) nanoparticles (NPs) was investigated. Under pH and ionic conditions similar to natural water bodies, Ca2+ induced...

  2. Formation and Structure of Calcium Carbonate Thin Films and Nanofibers Precipitated in the Presence of Poly(Allylamine Hydrochloride) and Magnesium Ions

    PubMed Central

    2013-01-01

    That the cationic polyelectrolyte poly(allylamine hydrochloride) (PAH) exerts a significant influence on CaCO3 precipitation challenges the idea that only anionic additives have this effect. Here, we show that in common with anionic polyelectrolytes such as poly(aspartic acid), PAH supports the growth of calcite thin films and abundant nanofibers. While investigating the formation of these structures, we also perform the first detailed structural analysis of the nanofibers by transmission electron microscopy (TEM) and selected area electron diffraction. The nanofibers are shown to be principally single crystal, with isolated domains of polycrystallinity, and the single crystal structure is even preserved in regions where the nanofibers dramatically change direction. The formation mechanism of the fibers, which are often hundreds of micrometers long, has been the subject of intense speculation. Our results suggest that they form by aggregation of amorphous particles, which are incorporated into the fibers uniquely at their tips, before crystallizing. Extrusion of polymer during crystallization may inhibit particle addition at the fiber walls and result in local variations in the fiber nanostructure. Finally, we investigate the influence of Mg2+ on CaCO3 precipitation in the presence of PAH, which gives thinner and smoother films, together with fibers with more polycrystalline, granular structures. PMID:24489438

  3. Some aspects of stratospheric chemical response to solar particle precipitations. I - Potential roles of N2/A3Sigma/ and ion-chemistry

    NASA Technical Reports Server (NTRS)

    Prasad, S. S.

    1979-01-01

    Large amounts of long lived N2(A3Sigma) are created by the energy degradation of precipitating solar particles. Laboratory data suggest that in the stratosphere N2(A3Sigma) are efficiently converted into N2O. Through reactions with O(1D), N2O may gradually release NO and thereby influence the long term aspects of stratospheric chemical response. During the daytime, negative ions may transform an active NO(x) into an inactive HNO3. At night both negative and positive ion chemistry generate HO(x). Omission of ionic chemistry results in considerable underestimation of O3 depletion during the initial phases of solar particle events, and thereby introduces significant error in the estimation of the nature of the prompt response.

  4. Self-consistent Model of Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves. 2. Wave Induced Ring Current Precipitation and Thermal Electron Heating

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. U.; Liemohn, M. W.

    2007-01-01

    This paper continues presentation and discussion of the results from our new global self-consistent theoretical model of interacting ring current ions and propagating electromagnetic ion cyclotron waves [Khazanov et al., 2006]. To study the effects of electromagnetic ion cyclotron wave propagation and refraction on the wave induced ring current precipitation and heating of the thermal plasmaspheric electrons, we simulate the May 1998 storm. The main findings after a simulation can be summarized as follows. Firstly, the wave induced ring current precipitation exhibits quite a lot of fine structure, and is highly organized by location of the plasmapause gradient. The strongest fluxes of about 4 x 10(exp 6) (cm(raised dot) s(raised dot) sr(raised dot) (sup -1)) are observed during the maill and early recovery phases of the storm. The very interesting and probably more important finding is that in a number of cases the most intense precipitating fluxes are not connected to the most intense waves in simple manner. The characteristics of the wave power spectral density distribution over the wave normal angle are extremely crucial for the effectiveness of the ring current ion scattering. Secondly, comparison of the global proton precipitating patterns with the results from RAM [Kozyra et al., 1997a] reveals that although we observe a qualitative agreement between the localizations of the wave induced precipitations in the models, there is no quantitative agreement between the magnitudes of the fluxes. The quantitative differences are mainly due to a qualitative difference between the characteristics of the wave power spectral density distributions over the wave normal angle in RAM and in our model. Thirdly, the heat fluxes to plasmaspheric electrons caused by Landau resonate energy absorption from electromagnetic ion cyclotron waves are observed in the postnoon-premidnight MLT sector, and can reach the magnitude of 10(exp 11) eV/(cm(sup 2)(raised dot)s). The Coulomb

  5. Hydrogen bond-assisted aggregation-induced emission and application in the detection of the Zn(ii) ion.

    PubMed

    Wang, Dan; Li, Shu-Mu; Li, Yu-Fei; Zheng, Xiang-Jun; Jin, Lin-Pei

    2016-05-28

    The compounds of 3-aminopyridine-2-carboxylic acid with K(+) (1) and Zn(2+) (2) were found to be AIE-active. The AIE behaviours could be attributed to the restriction of intramolecular rotation (RIR) and vibration (RIV) via hydrogen bonds, resulting in rigidity enhancement of the molecules. An AIE-based fluorescence turn on chemosensor for the Zn(ii) ion has been developed in aqueous media with high selectivity and sensitivity. PMID:27126357

  6. FORMATION OF URANIUM PRECIPITATES

    DOEpatents

    Googin, J.M. Jr.

    1959-03-17

    A method is described for precipitation of uranium peroxide from uranium- containing solutions so as to obtain larger aggregates which facilitates washings decantations filtrations centrifugations and the like. The desired larger aggregate form is obtained by maintaining the pH of the solution in the approximate range of 1 to 3 and the temperature at about 25 deg C or below while carrytng out the precipitation. Then prior to removal of the precipitate a surface active sulfonated bicarboxyacids such as di-octyl sodium sulfo-succinates is incorporated in an anount of the order of 0.01 to 0.05 percent by weights and the slurry is allowed to ripen for about one-half hour at a temperatare below 10 deg C.

  7. Microstrip structures of ZnO nanoparticle aggregates of millimetric length formed by selected-area ion implantation and thermal oxidation.

    PubMed

    Amekura, H; Wang, H-S; Hishita, S; Pan, J; Kishimoto, N; Buchal, Ch; Mantl, S

    2009-02-11

    Regularly arrayed microstrip regions of width approximately 1.4 microm and length extending up to approximately 5 mm, consisting of ZnO nanoparticles (NPs) of diameter approximately 50 nm, were fabricated on silica substrates by a two-step process: i.e., selected-area ion implantation and thermal oxidation. The implantation of 60 keV Zn ions in periodic microstrip regions via a resist mask generated periodic grooves with large wings on the surface of silica glass, which can be ascribed to the radiation-induced plastic deformation of silica and sputtering loss. This is the lowest record of the electronic energy loss (S(e)) value to induce the radiation-induced plastic deformation of silica, while no or very low threshold energy has been predicted from a recent study. After thermal oxidation at 700 degrees C for 1 h, the groove structures with the wings disappeared, and periodic microstrips of ZnO nanoparticle aggregates up to 5 mm long appeared on the surface of the substrate. A clear free-exciton peak due to ZnO NPs is observed from these microstrip structures both in optical absorption and photoluminescence spectra. PMID:19417379

  8. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  9. Synthesis of aqueous suspensions of magnetic nanoparticles with the co-precipitation of iron ions in the presence of aspartic acid

    NASA Astrophysics Data System (ADS)

    Pušnik, Klementina; Goršak, Tanja; Drofenik, Miha; Makovec, Darko

    2016-09-01

    There is increasing demand for the production of large quantities of aqueous suspensions of magnetic iron-oxide nanoparticles. Amino acids are one possible type of inexpensive, nontoxic, and biocompatible molecules that can be used as the surfactants for the preparation of stable suspensions. This preparation can be conducted in a simple, one-step process based on the co-precipitation of Fe3+/Fe2+ ions in the presence of the amino acid. However, the presence of this amino acid changes the mechanism of the magnetic nanoparticles' formation. In this investigation we analyzed the influence of aspartic amino acid (Asp) on the formation of magnetic iron-oxide nanoparticles during the co-precipitation. The process of the nanoparticles' formation was followed using a combination of TEM, x-ray diffractometry, magnetic measurements, in-situ FT-IR spectroscopy, and chemical analysis, and compared with the formation of nanoparticles without the Asp. The Asp forms a coordination complex with the Fe3+ ions, which impedes the formation of the intermediate iron oxyhydroxide phase and suppresses the growth of the final magnetic iron-oxide nanoparticles. Slower reaction kinetics can lead to the formation of nonmagnetic secondary phases. The aspartic-acid-absorbed nanoparticles can be dispersed to form relatively concentrated aqueous suspensions displaying a good colloidal stability at an increased pH.

  10. Ion beam induced dissolution and precipitation of in situ formed Si-nanostructures in a-SiNx:H matrix

    NASA Astrophysics Data System (ADS)

    Singh, Sarab Preet; Ghosh, Santanu; Vijaya Prakash, G.; Khan, Saif A.; Kanjilal, D.; Srivastava, A. K.; Srivastava, Himanshu; Srivastava, P.

    2012-04-01

    We report here the response of in situ formed Si-nanostructures embedded in Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation under normal incidence at room temperature. Prior to irradiation, Si-nanostructures are amorphous in nature having partial crystallinity. Irradiation with a fluence of 5 × 1012 ions/cm2 leads to dissolution of Si-nanostructures. Nevertheless, irradiation with a relatively higher fluence of 1 × 1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures. The results are understood on the basis of intense electronic energy loss induced hydrogen desorption and consequent rearrangement of the amorphous network under thermal spike formalism of ion-material interaction.

  11. Multi-instrument observations from Svalbard of a traveling convection vortex, electromagnetic ion cyclotron wave burst, and proton precipitation associated with a bow shock instability

    NASA Astrophysics Data System (ADS)

    Engebretson, M. J.; Yeoman, T. K.; Oksavik, K.; SøRaas, F.; Sigernes, F.; Moen, J. I.; Johnsen, M. G.; Pilipenko, V. A.; Posch, J. L.; Lessard, M. R.; Lavraud, B.; Hartinger, M. D.; Clausen, L. B. N.; Raita, T.; Stolle, C.

    2013-06-01

    An isolated burst of 0.35 Hz electromagnetic ion cyclotron (EMIC) waves was observed at four sites on Svalbard from 0947 to 0954 UT 2 January 2011, roughly 1 h after local noon. This burst was associated with one of a series of ~50 nT magnetic impulses observed at the northernmost stations of the IMAGE magnetometer array. Hankasalmi SuperDARN radar data showed a west-to-east (antisunward) propagating vortical ionospheric flow in a region of high spectral width ~ 1-2° north of Svalbard, confirming that this magnetic impulse was the signature of a traveling convection vortex. Ground-based observations of the Hα line at Longyearbyen indicated proton precipitation at the same time as the EMIC wave burst, and NOAA-19, which passed over the west coast of Svalbard between 0951 and 0952, observed a clear enhancement of ring current protons at the same latitude. Electron precipitation from this same satellite indicated that the EMIC burst was located on closed field lines, but near to the polar cap boundary. We believe these are the first simultaneous observations of EMIC waves and precipitating energetic protons so near to the boundary of the dayside magnetosphere. Although several spacecraft upstream of Earth observed a steady solar wind and predominantly radial interplanetary magnetic field orientation before and during this event, data from Geotail (near the morning bow shock) showed large reorientations of the interplanetary magnetic field and substantial decreases in ion density several minutes before it, and data from Cluster (near the afternoon bow shock) showed an outward excursion of the bow shock simultaneous with it. These upstream perturbations suggest that a spontaneous hot flow anomaly, a bow shock related instability, may have been responsible for triggering this event, but do not provide enough information to fully characterize that instability.

  12. Calculated ionization rates, ion densities, and airglow emission rates due to precipitating electrons in the nightside ionosphere of Mars

    NASA Technical Reports Server (NTRS)

    Haider, S. A.; Kim, J.; Nagy, A. F.; Keller, C. N.; Verigin, M. I.; Gringauz, K. I.; Shutte, N. M.; Szego, K.; Kiraly, P.

    1992-01-01

    The calculations presented in this paper clearly establish that the electron fluxes measured by the HARP instrument, carried on board Phobos 2, could cause significant electron impact ionization and excitation in the nightside atmosphere of Mars, if these electrons actually do precipitate. The calculated peak electron densities were found to be about a factor of 2 larger than the mean observed nightside densities, indicating that if a significant fraction of the measured electrons actually precipitate, they could be the dominant mechanism responsible for maintaining the nightside ionosphere. The calculated zenith column emission rates of the O I 5577-A and 6300-A and CO Cameron band emissions, due to electron impact and dissociative recombination mechanisms, were found to be significant.

  13. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  14. Precipitating and trapped ions and electrons observed at 840 km during the great magnetic storm of February 1986

    SciTech Connect

    Swider, W.

    1990-07-01

    A detailed picture is presented of the equatorward boundaries of the auroral ovals at dawn, morning, dusk, and evening for the three most disturbed days of February 1986. North-south symmetry for the boundaries of keV particles was good, and the differences between the ion and electron boundaries agreed with statistics which show the ion edge slightly equatorward of the electron edge at dusk, with the reverse for dawn. The electron boundary was most equatorward of the ion boundary for morning. Best symmetry and least difference were for evening, the sector nearest the central plasma sheet. Ions with energies from thermal to several hundred electron volts penetrated inward to L = 1.2. Initial penetration was confined mainly, if not exclusively, to the dawn sector. The sudden appearance of low-energy ions deep in the plasmasphere at dusk and evening after storm maximum suggests corotation from a plasmapause as low as L = 1.7 at dawn. Low-energy electrons rarely advanced equatorward of the deV electrons. On the other hand, keV electrons occasionally were detected about the equator, apparently in relation to the inward convection of the radiation belt. Very energetic, MeV, particles occurred near 52 deg MLAT, mainly after storm maximum and often unsymmetrically, which may reflect a characteristic akin to the South Atlantic Anomaly.

  15. NOx production due to energetic particle precipitation in the MLT region - results from an ion-chemistry model

    NASA Astrophysics Data System (ADS)

    Nieder, Holger; Sinnhuber, Miriam

    2013-04-01

    The chemistry in the mesosphere/lower thermosphere (MLT) region is driven by forcing from solar radiation and energetic particles. The resulting ionisation, dissociation and excitation of the constituents lead to production of neutral reactive species such as NOx (N, NO, NO2) and HOx (H, OH, HO2), both directly from dissociation of neutrals and indirectly from subsequent ion-neutral reactions. As NOx is long-lived during polar winter, it can be transported down to the stratosphere and contribute to catalytic ozone depletion. To study the effective NOx production rates during an ionisation event, runs with a one-dimensional state-of-the-art ion chemistry model (UBIC) are carried out and analysed. The model starts with a neutral atmosphere and uses direct ion and neutral production rates from Porter et al. (1976) and Rusch et al. (1981), adapted for the MLT region. Including raw ionisation rates from external sources such as AIMOS is possible. The ion-neutral reactions in the charged atmosphere are computed until equilibrium is reached, resulting in an effective production rate including impact of ion-neutral reactions. The indirect NOx production rate is found to depend on atmospheric parameters such as pressure, temperature and the abundance of NOx, atomic oxygen and H2O. For the MLT region, this leads to an increasing amount of NOx per ionpair created with increasing altitude due to an increasing atomic oxygen VMR. Values of >1.8 NOx per ionpair can be obtained. The results are made available to a 3D Chemistry Transport Model using a database-approach and multilinear interpolation for readout. Efficiency of this approach and first results from a 3D CTM using the ion-chemistry results are discussed.

  16. Weighted aggregation

    NASA Technical Reports Server (NTRS)

    Feiveson, A. H. (Principal Investigator)

    1979-01-01

    The use of a weighted aggregation technique to improve the precision of the overall LACIE estimate is considered. The manner in which a weighted aggregation technique is implemented given a set of weights is described. The problem of variance estimation is discussed and the question of how to obtain the weights in an operational environment is addressed.

  17. Multi-instrument Observations from Svalbard of a Traveling Convection Vortex, Electromagnetic Ion Cyclotron Wave Burst, and Proton Precipitation Associated with a Bow Shock Instability

    NASA Astrophysics Data System (ADS)

    Engebretson, M. J.; Posch, J. L.; Lessard, M.; Pilipenko, V.; Oksavik, K.; Soraas, F.; Sigernes, F.; Yeoman, T. K.; Wright, D. M.; Lavraud, B.; Clausen, L.

    2012-12-01

    An isolated burst of electromagnetic ion cyclotron (EMIC) waves with center frequency near 0.35 Hz and peak-to-peak amplitude ~ 1 nT was observed at all four stations in the Augsburg College - University of New Hampshire search coil magnetometer array on Svalbard from 0947 to 0954 UT January 2, 2011, roughly one hour after local noon. The wave burst was associated with one of a series of modest (~ 50 nT) magnetic impulses evident in data from the northernmost stations of the IMAGE magnetometer array. Hankasalmi SuperDARN radar data showed a west-to-east (antisunward) propagating vortical ionospheric flow in a region of high spectral width, confirming that this magnetic impulse was the signature of a traveling convection vortex (TCV). Ground-based observations of the Hα line from a magnetic zenith-pointing optical spectrometer at Longyearbyen indicated proton precipitation beginning at 0947 UT, the same time as the start of the EMIC wave burst. NOAA-19 passed over the west coast of Svalbard between 0951 and 0952, and observed a clear enhancement of protons in the 30-80 and 80-250 keV channels. Electron precipitation from this same satellite indicated that the burst was located on closed field lines, but near to the open/closed polar cap boundary. DMSP F17, which passed westward through the cusp just north of Svalbard near 0955 UT, at the same latitude as the region of high spectral width detected by the SuperDARN radar, detected cusp-energy precipitation (electrons with energies less than 300 eV, ions with energies <1 keV). We believe this is the first report of combined observations of Pc 1 waves and associated precipitating protons so near the outer boundary of the dayside magnetosphere. Although several spacecraft in the solar wind upstream from Earth reported a steady solar wind and predominantly radial IMF orientation, data from Geotail and Cluster, located near the morning and afternoon sector bow shock, respectively, showed large variations that suggest a

  18. Value of the Debris of Reduction Sculpture: Thiol Etching of Au Nanoclusters for Preparing Water-Soluble and Aggregation-Induced Emission-Active Au(I) Complexes as Phosphorescent Copper Ion Sensor.

    PubMed

    Shu, Tong; Su, Lei; Wang, Jianxing; Lu, Xin; Liang, Feng; Li, Chenzhong; Zhang, Xueji

    2016-06-01

    Chemical etching of gold by thiols has been known to be capable of generating nonluminescent gold(I) complexes, e.g., in size-focusing synthesis of atomically precise gold nanoclusters (GNCs). These nonluminescent gold(I) complexes have usually been considered as useless or worthless byproducts. This study shows a promising potential of thiol etching of GNCs to prepare novel water-soluble and phosphorescent gold(I) materials for sensing application. First, cysteamine-induced etching of GNCs is used to produce nonluminescent oligomeric gold(I)-thiolate complexes. Then, cadmium ion induces the aggregation of these oligomeric complexes to produce highly water-soluble ultrasmall intra-aggregates. These intra-aggregates can phosphoresce both in dilute aqueous solutions and in the solid phase. Studies on the effect of pH on their phosphorescent emission reveal the importance of the interaction between the amino groups of the ligands and cadmium ion for their phosphorescent emission property. Furthermore, Cu(2+) ion is found to quickly quench the phosphorescent emission of the intra-aggregates and simultaneously cause a Cu(2+)-concentration-dependent peak wavelength shift, enabling the establishment of a novel colorimetric sensor for sensitive and selective visual sensing of Cu(2+). PMID:27175974

  19. A single electrochemical biosensor for detecting the activity and inhibition of both protein kinase and alkaline phosphatase based on phosphate ions induced deposition of redox precipitates.

    PubMed

    Shen, Congcong; Li, Xiangzhi; Rasooly, Avraham; Guo, Linyan; Zhang, Kaina; Yang, Minghui

    2016-11-15

    Protein kinase (PKA) and alkaline phosphatase (ALP) are clinically relevant enzymes for a number of diseases. In this work, we developed a new simple electrochemical biosensor for the detection of the activity and inhibition of both PKA and ALP. One common feature of the PKA and ALP catalyzing process is that PKA can hydrolysis adenosine-5'-triphosphate (ATP) and ALP can hydrolysis pyrophosphate, both reactions produce phosphate ions, and the amount of phosphate ion produced is proportional to enzyme activity. Our assay is based on the principle that phosphate ions react with molybdate to form redox molybdophosphate precipitates on the electrode surface, thus generating electrochemical current. The detection limit for PKA and ALP were much lower than existing assays. The biosensor has good specificity and was used to measure drug-stimulated PKA from lysates of HeLa cells. We also evaluated the use of the biosensor as a screening tool for enzyme inhibitors. To the best of our knowledge, this is the first report of a biosensor capable of detecting the activity of both PKA and ALP. This tool has the potential to simplify PKA and ALP clinical measurement, thereby improving diagnostics of relevant diseases. It also may serve as the basis for a simple screening method for new enzyme inhibitors for disease treatment. PMID:27179562

  20. Aggregation-induced emission from gold nanoclusters for use as a luminescence-enhanced nanosensor to detect trace amounts of silver ions.

    PubMed

    Li, Bingzhi; Wang, Xi; Shen, Xin; Zhu, Wanying; Xu, Lei; Zhou, Xuemin

    2016-04-01

    Several research have reported that silver ions (Ag(+)) could enhance the photoluminescence of some kinds of gold nanoclusters (AuNCs), and redox reaction involved mechanisms were recognized as the main reason to cause such phenomenon. However, in this work, we found that Ag(+) could enhance the luminescence of aggregation-induced emission gold nanoclusters (AIE-AuNCs) without valence state change. Upon addition of Ag(+), the luminescence of AIE-AuNCs enhanced instantly by 7.2 times with a red-shift of emission peak and a complete restoration of luminescence features was observed when Ag(+) was removed. A cost-effective, rapid-response, highly sensitive and selective method to detect trace amount of Ag(+) has thereby been established using AIE-AuNCs as a nanosensor. This analytical method exhibited a linear range of 0.5nM-20μM with a limit of detection of 0.2nM and it showed great promise for Ag(+) monitoring in environmental water. PMID:26773614

  1. Hemin/G-quadruplex-based DNAzyme concatamers for in situ amplified impedimetric sensing of copper(II) ion coupling with DNAzyme-catalyzed precipitation strategy.

    PubMed

    Xu, Mingdi; Gao, Zhuangqiang; Wei, Qiaohua; Chen, Guonan; Tang, Dianping

    2015-12-15

    A new signal-amplification strategy based on copper(II) (Cu(2+))-dependent DNAzyme was developed for sensitive impedimetric biosensing of Cu(2+) in aqueous solution by coupling with target-induced formation of hemin/G-quadruplex-based DNAzyme and enzymatic catalytic precipitation technique. Initially, the target analyte cleaved the Cu(2+)-specific DNAzyme to generate an initiator strand on the sensor. Thereafter, the initiator strand underwent an unbiased strand-displacement reaction between hairpin probes in turn to construct a nicked double-helix, accompanying the formation of hemin/G-quadruplex DNAzyme on the long duplex DNA. The newly formed DNAzyme could oxidize the 4-chloro-1-naphthol (4-CN) to produce an insoluble precipitation on the sensor, thus resulting in a local alteration of the conductivity. Under the optimal conditions, the resistance increased with the increasing Cu(2+) in the sample, and exhibited a wide dynamic working range from 0.1 pM to 5.0 nM with a detection limit of 60 fM. The methodology also displayed a high selectivity for Cu(2+) relative to other potentially interfering ions owing to the highly specific Cu(2+)-dependent DNAzyme, and was applicable for monitoring Cu(2+) in real river samples. Thus, our strategy has a good potential in the environment surveys. PMID:26093122

  2. Theoretical and experimental study of the incorporation of tobramycin and strontium-ions into hydroxyapatite by means of co-precipitation

    NASA Astrophysics Data System (ADS)

    Wang, Baochang; Lilja, Mirjam; Ma, Taoran; Sörensen, Jan; Steckel, Hartwig; Ahuja, Rajeev; Strømme, Maria

    2014-09-01

    Antibiotic incorporation into hydroxyapatite (HA) coatings by co-precipitation and the impact of bone relevant doping elements on the adsorption kinetics are investigated from both theoretical and experimental points of view. Tobramycin interactions with bioactive TiO2 and HA surfaces are analyzed using density functional theory. According to the calculations, the drug molecule has larger adsorption energy than the Ca+ ion on both surfaces under study in Phosphate Buffered Saline (PBS). The results support the experimental observations that HA nucleation and growth are strongly limited on TiO2 surfaces in the presence of clinically relevant antibiotic concentrations in PBS. The drug molecule is more likely to adopt parallel arrangement onto the HA surface, as the adsorption energy of such arrangement is higher compared to a perpendicular one. Strontium substitution of the HA surface is found to results in a weaker drug-surface interaction, and leads also to a decrease in coating thickness. However, the presence of strontium gives rise to a coating morphology with enhanced drug incorporation capacity and slower antibiotic release compared to non-substituted, co-precipitated counterparts. Our theoretical calculation results were found to be in excellent agreement with experimental data and provide a powerful tool to understand the interaction mechanism between drug and different surface chemistries necessary for development of future versatile orthopedic and dental implant surfaces.

  3. Construction aggregates

    USGS Publications Warehouse

    Langer, W.H.; Tepordei, V.V.; Bolen, W.P.

    2000-01-01

    Construction aggregates consist primarily of crushed stone and construction sand and gravel. Total estimated production of construction aggregates increased in 1999 by about 2% to 2.39 Gt (2.64 billion st) compared with 1998. This record production level continued an expansion that began in 1992. By commodities, crushed stone production increased 3.3%, while sand and gravel production increased by about 0.5%.

  4. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1994-01-01

    Part of a special section on industrial minerals in 1993. The 1993 production of construction aggregates increased 6.3 percent over the 1992 figure, to reach 2.01 Gt. This represents the highest estimated annual production of combined crushed stone and construction sand and gravel ever recorded in the U.S. The outlook for construction aggregates and the issues facing the industry are discussed.

  5. Morphology controls of GeO 2 particles precipitated by a facile acid-induced decomposition of germanate ions in aqueous medium

    NASA Astrophysics Data System (ADS)

    Jing, Chengbin; Hou, Jinxia; Zhang, Yongheng

    2008-01-01

    GeO 2 single crystals with various morphologies were synthesized at room temperature by an acid-induced homogenous liquid phase precipitation technique without using any surfactants as studied previously. With addition of aqueous ammonia, the solubility of hexagonal GeO 2 in water was significantly increased by formation of soluble germanate ions as confirmed by IR spectra analyses. Supersaturated GeO 2 solution could be produced by adding acid into the GeO 2-ammonia solution through the acid-induced transformation of germinate ions into GeO 2. GeO 2 spheres were obtained with phosphoric acid addition. Truncated cubic-like and cubic-like GeO 2 single crystals could be produced in the solutions with hydrochloric acid and ascorbic acid (vitamin C) additions, respectively. The morphology developments of the GeO 2 particles induced by various acids were discussed and the growth mechanism conforms to BFDH and HP crystal growth models.

  6. Understanding of copper precipitation under electron or ion irradiations in FeCu0.1 wt% ferritic alloy by combination of experiments and modelling

    NASA Astrophysics Data System (ADS)

    Radiguet, B.; Barbu, A.; Pareige, P.

    2007-02-01

    This work is dedicated to the understanding of the basic processes involved in the formation of copper enriched clusters in low alloyed FeCu binary system (FeCu0.1 wt%) under irradiation at temperature close to 300 °C. Such an alloy was irradiated with electrons or with ions (Fe+ or He+) in order to deconvolute the effect of displacement cascades and the associated generation of point defect clusters (ion irradiations), and the super-saturation of mono-vacancies and self-interstitial atoms (electron irradiation). The microstructure of this alloy was characterised by tomographic atom probe. Experimental results were compared with results obtained with cluster dynamic model giving an estimation of the evolution of point defects (free or agglomerated) under irradiation on the one hand and describing homogeneous enhanced precipitation of copper on the other hand. The comparison between the results obtained on the different irradiation conditions and the model suggests that the point defect clusters (dislocation loops and/or nano-voids) created in displacement cascades play a major role in copper clustering in low copper alloy irradiated at 573 K.

  7. PbTe and SnTe quantum dot precipitates in a CdTe matrix fabricated by ion implantation

    SciTech Connect

    Kaufmann, E.; Schwarzl, T.; Groiss, H.; Hesser, G.; Schaeffler, F.; Palmetshofer, L.; Springholz, G.; Heiss, W.

    2009-08-15

    We present rock-salt IV-VI semiconductor quantum dots fabricated by implantation of Pb{sup +}, Te{sup +}, or Sn{sup +} ions into epitaxial zinc-blende CdTe layers. PbTe and SnTe nanoprecipitates of high structural quality are formed after implantation by thermal annealing due to the immiscibility of dot and matrix materials. For samples implanted only with Pb{sup +}, intense continuous-wave photoluminescence peaked at 1.6 mum at 300 K is found. In contrast, for PbTe quantum dots fabricated by coimplantation of Pb{sup +} and Te{sup +}, the 300 K emission peak is observed at 2.9 mum, indicating luminescence from much larger dots.

  8. A competitive aggregation model for flash nanoprecipitation.

    PubMed

    Cheng, Janine Chungyin; Vigil, R D; Fox, R O

    2010-11-15

    Flash NanoPrecipitation (FNP) is a novel approach for producing functional nanoparticles stabilized by amphiphilic block copolymers. FNP involves the rapid mixing of a hydrophobic active (organic) and an amphiphilic di-block copolymer with a non-solvent (water) and subsequent co-precipitation of nanoparticles composed of both the organic and copolymer. During this process, the particle size distribution (PSD) is frozen and stabilized by the hydrophilic portion of the amphiphilic di-block copolymer residing on the particle surface. That is, the particle growth is kinetically arrested and thus a narrow PSD can be attained. To model the co-precipitation process, a bivariate population balance equation (PBE) has been formulated to account for the competitive aggregation of the organic and copolymer versus pure organic-organic or copolymer-copolymer aggregation. Aggregation rate kernels have been derived to account for the major aggregation events: free coupling, unimer insertion, and aggregate fusion. The resulting PBE is solved both by direct integration and by using the conditional quadrature method of moments (CQMOM). By solving the competitive aggregation model under well-mixed conditions, it is demonstrated that the PSD is controlled primarily by the copolymer-copolymer aggregation process and that the energy barrier to aggregate fusion plays a key role in determining the PSD. It is also shown that the characteristic aggregation times are smaller than the turbulent mixing time so that the FNP process is always mixing limited. PMID:20800847

  9. Loss of Metal Ions, Disulfide Reduction and Mutations Related to Familial ALS Promote Formation of Amyloid-Like Aggregates from Superoxide Dismutase

    PubMed Central

    Oztug Durer, Zeynep A.; Cohlberg, Jeffrey A.; Dinh, Phong; Padua, Shelby; Ehrenclou, Krista; Downes, Sean; Tan, James K.; Nakano, Yoko; Bowman, Christopher J.; Hoskins, Jessica L.; Kwon, Chuhee; Mason, Andrew Z.; Rodriguez, Jorge A.; Doucette, Peter A.; Shaw, Bryan F.; Valentine, Joan Selverstone

    2009-01-01

    Mutations in the gene encoding Cu-Zn superoxide dismutase (SOD1) are one of the causes of familial amyotrophic lateral sclerosis (FALS). Fibrillar inclusions containing SOD1 and SOD1 inclusions that bind the amyloid-specific dye thioflavin S have been found in neurons of transgenic mice expressing mutant SOD1. Therefore, the formation of amyloid fibrils from human SOD1 was investigated. When agitated at acidic pH in the presence of low concentrations of guanidine or acetonitrile, metalated SOD1 formed fibrillar material which bound both thioflavin T and Congo red and had circular dichroism and infrared spectra characteristic of amyloid. While metalated SOD1 did not form amyloid-like aggregates at neutral pH, either removing metals from SOD1 with its intramolecular disulfide bond intact or reducing the intramolecular disulfide bond of metalated SOD1 was sufficient to promote formation of these aggregates. SOD1 formed amyloid-like aggregates both with and without intermolecular disulfide bonds, depending on the incubation conditions, and a mutant SOD1 lacking free sulfhydryl groups (AS-SOD1) formed amyloid-like aggregates at neutral pH under reducing conditions. ALS mutations enhanced the ability of disulfide-reduced SOD1 to form amyloid-like aggregates, and apo-AS-SOD1 formed amyloid-like aggregates at pH 7 only when an ALS mutation was also present. These results indicate that some mutations related to ALS promote formation of amyloid-like aggregates by facilitating the loss of metals and/or by making the intramolecular disulfide bond more susceptible to reduction, thus allowing the conversion of SOD1 to a form that aggregates to form resembling amyloid. Furthermore, the occurrence of amyloid-like aggregates per se does not depend on forming intermolecular disulfide bonds, and multiple forms of such aggregates can be produced from SOD1. PMID:19325915

  10. Drug delivery system for an anticancer agent, chlorogenate-Zn/Al-layered double hydroxide nanohybrid synthesised using direct co-precipitation and ion exchange methods

    NASA Astrophysics Data System (ADS)

    Barahuie, Farahnaz; Hussein, Mohd Zobir; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

    2014-09-01

    A nano-structured drug-inorganic clay hybrid involving an active anticancer compound, which is chlorogenic acid (CA) intercalated into Zn/Al-layered double hydroxide, has been assembled via ion-exchange and co-precipitation methods to form a nanohybrid CZAE (a chlorogenic acid-Zn/Al nanohybrid synthesised using an ion-exchange method) and CZAC (a chlorogenic acid-Zn/Al nanohybrid synthesised using a direct method), respectively. The X-ray diffraction (XRD) results confirmed that the CA-LDH had a hybrid structure in which the anionic chlorogenate is arranged between the interlayers as a horizontal monolayer at 90 and 20° angles from the x axis for CZAE and CZAC, respectively. Both nanohybrids have the properties of mesoporous materials. The high loading percentage of chlorogenic acid (approximately 43.2% for CZAE and 45.3% for CZAC) with basal spacings of 11.7 and 12.6 Å for CZAE and CZAC, respectively, corroborates the successful intercalation of chlorogenic acid into the interlayer gallery of layered double hydroxides. Free chlorogenic acid and the synthesised nanocomposites (CZAE, CZAC) were assessed for their cytotoxicity against various cancer cells. The Fourier transform infrared data supported the formation of both nanohybrids, and a thermal analysis showed that the nanohybrids are more thermally stable than their counterparts. The chlorogenate shows a sustained release, and the release rate of chlorogenate from CZAE and CZAC nanohybrids at pH 7.4 is remarkably lower than that at pH 4.8 due to their different release mechanisms. The release rate of chlorogenate from both nanohybrids can be described as pseudo-second order. The present investigation revealed the potential of the nanohybrids to enhance the in vitro anti-tumour effect of chlorogenic acid in liver and lung cancer cells in vitro.

  11. URANIUM PRECIPITATION PROCESS

    DOEpatents

    Thunaes, A.; Brown, E.A.; Smith, H.W.; Simard, R.

    1957-12-01

    A method for the recovery of uranium from sulfuric acid solutions is described. In the present process, sulfuric acid is added to the uranium bearing solution to bring the pH to between 1 and 1.8, preferably to about 1.4, and aluminum metal is then used as a reducing agent to convert hexavalent uranium to the tetravalent state. As the reaction proceeds, the pH rises amd a selective precipitation of uranium occurs resulting in a high grade precipitate. This process is an improvement over the process using metallic iron, in that metallic aluminum reacts less readily than metallic iron with sulfuric acid, thus avoiding consumption of the reducing agent and a raising of the pH without accomplishing the desired reduction of the hexavalent uranium in the solution. Another disadvantage to the use of iron is that positive ferric ions will precipitate with negative phosphate and arsenate ions at the pH range employed.

  12. The magnetic and oxidation behavior of bare and silica-coated iron oxide nanoparticles synthesized by reverse co-precipitation of ferrous ion (Fe2+) in ambient atmosphere

    NASA Astrophysics Data System (ADS)

    Mahmed, N.; Heczko, O.; Lancok, A.; Hannula, S.-P.

    2014-03-01

    The synthesis of iron oxide nanoparticles, i.e., magnetite was attempted by using only ferrous ion (Fe2+) as a magnetite precursor, under an ambient atmosphere. The room temperature reverse co-precipitation method was used, by applying two synthesis protocols. The freshly prepared iron oxide was also immediately coated with Stöber silica (SiO2) layer, forming the coreshell structure. The phase, stoichiometry, crystallite and the particle size of the synthesized powders were determined by using X-ray diffraction (XRD) and transmission electron microscope (TEM), while the magnetic and oxidation behaviors were studied by using the vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. Based on the results, the bare iron oxide nanoparticles are in the stoichiometry between the magnetite and the maghemite stoichiometry, i.e., oxidation occurs. This oxidation is depending on the synthesis protocols used. With the silica coating, the oxidation can be prevented, as suggested by the fits of Mössbauer spectra and low temperature magnetic measurement.

  13. Drug delivery system for an anticancer agent, chlorogenate-Zn/Al-layered double hydroxide nanohybrid synthesised using direct co-precipitation and ion exchange methods

    SciTech Connect

    Barahuie, Farahnaz; Hussein, Mohd Zobir; Arulselvan, Palanisamy; Fakurazi, Sharida; Zainal, Zulkarnain

    2014-09-15

    A nano-structured drug-inorganic clay hybrid involving an active anticancer compound, which is chlorogenic acid (CA) intercalated into Zn/Al-layered double hydroxide, has been assembled via ion-exchange and co-precipitation methods to form a nanohybrid CZAE (a chlorogenic acid-Zn/Al nanohybrid synthesised using an ion-exchange method) and CZAC (a chlorogenic acid-Zn/Al nanohybrid synthesised using a direct method), respectively. The X-ray diffraction (XRD) results confirmed that the CA-LDH had a hybrid structure in which the anionic chlorogenate is arranged between the interlayers as a horizontal monolayer at 90 and 20° angles from the x axis for CZAE and CZAC, respectively. Both nanohybrids have the properties of mesoporous materials. The high loading percentage of chlorogenic acid (approximately 43.2% for CZAE and 45.3% for CZAC) with basal spacings of 11.7 and 12.6 Å for CZAE and CZAC, respectively, corroborates the successful intercalation of chlorogenic acid into the interlayer gallery of layered double hydroxides. Free chlorogenic acid and the synthesised nanocomposites (CZAE, CZAC) were assessed for their cytotoxicity against various cancer cells. The Fourier transform infrared data supported the formation of both nanohybrids, and a thermal analysis showed that the nanohybrids are more thermally stable than their counterparts. The chlorogenate shows a sustained release, and the release rate of chlorogenate from CZAE and CZAC nanohybrids at pH 7.4 is remarkably lower than that at pH 4.8 due to their different release mechanisms. The release rate of chlorogenate from both nanohybrids can be described as pseudo-second order. The present investigation revealed the potential of the nanohybrids to enhance the in vitro anti-tumour effect of chlorogenic acid in liver and lung cancer cells in vitro. - Highlights: • We intercalated chlorogenic into Zn/Al-layered double hydroxide by ion-exchange and coprecipitation methods. • The two methods gave nanocomposites

  14. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1993-01-01

    Part of a special section on the market performance of industrial minerals in 1992. Production of construction aggregates increased by 4.6 percent in 1992. This increase was due, in part, to the increased funding for transportation and infrastructure projects. The U.S. produced about 1.05 Gt of crushed stone and an estimated 734 Mt of construction sand and gravel in 1992. Demand is expected to increase by about 5 percent in 1993.

  15. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  16. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  17. BOTANICAL ASPECTS OF ACIDIC PRECIPITATION

    EPA Science Inventory

    Acidic precipitation can be characterized as wet or frozen atmospheric deposition with a hydrogen ion concentration greater than 2.5 microequivalents liter-1. Acidic precipitation is perceived as a significant air pollution problem derived chiefly from combustion of fossil fuels,...

  18. Improvement in separation characteristics of protein precipitates by acoustic conditioning.

    PubMed

    Hoare, M; Titchener, N J; Foster, P R

    1987-01-01

    The effect of acoustic conditioning on the particle size distribution of isoelectric and calcium-ion-precipitated soya protein has been examined in low-residence-time chambers. In a previous study a beat frequency of 5 Hz obtained using a dual-source system of opposing vibrators was determined as giving optimal improvement in particle-settling characteristics for isoelectric soya protein precipitate. In this study the effect of amplitude of vibration, a measure of acoustic power input, and residence time of acoustic conditioning has been examined. Acoustic power input changed the flow pattern in the conditioning chamber from laminar streamline flow to a well-mixed, turbulent pattern. Such a mixing effect promoted the rapid aggregation of fine particles, a process that was modeled on the basis of orthokinetically controlled collisions. The rate of removal of fine particles due to acoustic conditioning was shown to be proportional to a mixing effect that was related to the acoustic power dissipated per unit volume. The consequences of fine-particle aggregation on the centrifugal recovery of the precipitate are discussed. PMID:18561125

  19. Construction aggregates

    USGS Publications Warehouse

    Bolen, W.P.; Tepordei, V.V.

    2001-01-01

    The estimated production during 2000 of construction aggregates, crushed stone, and construction sand and gravel increased by about 2.6% to 2.7 Gt (3 billion st), compared with 1999. The expansion that started in 1992 continued with record production levels for the ninth consecutive year. By commodity, construction sand and gravel production increased by 4.5% to 1.16 Gt (1.28 billion st), while crushed stone production increased by 1.3% to 1.56 Gt (1.72 billion st).

  20. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  1. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  2. Structure, Chaperone Activity, and Aggregation of Wild-Type and R12C Mutant αB-Crystallins in the Presence of Thermal Stress and Calcium Ion - Implications for Role of Calcium in Cataract Pathogenesis.

    PubMed

    Kashani, M Ragerdi; Yousefi, R; Akbarian, M; Alavianmehr, M M; Ghasemi, Y

    2016-02-01

    The current study was performed with the aim to evaluate the chaperoning ability, structural features, and aggregation propensity of wild-type and R12C mutant αB-crystallins (αB-Cry) under thermal stress and in the presence of calcium ion. The results of different spectroscopic analyses suggest that wild-type and mutant αB-Cry have dissimilar secondary and tertiary structures. Moreover, αB-Cry indicates slightly improved chaperone activity upon the R12C mutation. Thermal stress and calcium, respectively, enhance and reduce the extent of solvent-exposed hydrophobic surfaces accompanying formation of ordered and non-ordered aggregate entities in both proteins. Compared to the wild-type protein, the R12C mutant counterpart shows significant resistance against thermal and calcium-induced aggregation. In addition, in the presence of calcium, significant structural variation was accompanied by reduction in the solvent-exposed hydrophobic patches and attenuation of chaperone activity in both proteins. Additionally, gel mobility shift assay indicates the intrinsic propensity of R12C mutant αB-Cry for disulfide bridge-mediated protein dimerization. Overall, the results of this study are of high significance for understanding the molecular details of different factors that are involved in the pathomechanism of cataract disorders. PMID:27260392

  3. Precipitation Recycling

    NASA Technical Reports Server (NTRS)

    Eltahir, Elfatih A. B.; Bras, Rafael L.

    1996-01-01

    The water cycle regulates and reflects natural variability in climate at the regional and global scales. Large-scale human activities that involve changes in land cover, such as tropical deforestation, are likely to modify climate through changes in the water cycle. In order to understand, and hopefully be able to predict, the extent of these potential global and regional changes, we need first to understand how the water cycle works. In the past, most of the research in hydrology focused on the land branch of the water cycle, with little attention given to the atmospheric branch. The study of precipitation recycling which is defined as the contribution of local evaporation to local precipitation, aims at understanding hydrologic processes in the atmospheric branch of the water cycle. Simply stated, any study on precipitation recycling is about how the atmospheric branch of the water cycle works, namely, what happens to water vapor molecules after they evaporate from the surface, and where will they precipitate?

  4. STRONTIUM PRECIPITATION

    DOEpatents

    McKenzie, T.R.

    1960-09-13

    A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

  5. The fractal aggregation of asphaltenes.

    PubMed

    Hoepfner, Michael P; Fávero, Cláudio Vilas Bôas; Haji-Akbari, Nasim; Fogler, H Scott

    2013-07-16

    This paper discusses time-resolved small-angle neutron scattering results that were used to investigate asphaltene structure and stability with and without a precipitant added in both crude oil and model oil. A novel approach was used to isolate the scattering from asphaltenes that are insoluble and in the process of aggregating from those that are soluble. It was found that both soluble and insoluble asphaltenes form fractal clusters in crude oil and the fractal dimension of the insoluble asphaltene clusters is higher than that of the soluble clusters. Adding heptane also increases the size of soluble asphaltene clusters without modifying the fractal dimension. Understanding the process of insoluble asphaltenes forming fractals with higher fractal dimensions will potentially reveal the microscopic asphaltene destabilization mechanism (i.e., how a precipitant modifies asphaltene-asphaltene interactions). It was concluded that because of the polydisperse nature of asphaltenes, no well-defined asphaltene phase stability envelope exists and small amounts of asphaltenes precipitated even at dilute precipitant concentrations. Asphaltenes that are stable in a crude oil-precipitant mixture are dispersed on the nanometer length scale. An asphaltene precipitation mechanism is proposed that is consistent with the experimental findings. Additionally, it was found that the heptane-insoluble asphaltene fraction is the dominant source of small-angle scattering in crude oil and the previously unobtainable asphaltene solubility at low heptane concentrations was measured. PMID:23808932

  6. A Comparative High-Resolution Electron Microscope Study of Ag Clusters Produced by a Sputter-Gas Aggregation and Ion Cluster Beam Technique

    NASA Astrophysics Data System (ADS)

    Hohl, Georg-Friedrich; Hihara, Takehiko; Sakurai, Masaki; Oishi, Takashi; Wakoh, Kimio; Sumiyama, Kenji; Suzuki, Kenji

    1994-03-01

    Ag clusters were formed by a sputter-gas-aggregation process [H. Haberland et al..: J. Vac. Sci. Technol. A 10 (1992) 3266] and the ionized cluster beam (ICB) [T. Takagi: Ionized-Cluster Beam Deposition and Epitaxy (Noyes, Park Ridge, 1988)] technique. The Ag clusters deposited on collodion-coated microgrids were investigated by high-resolution transmission electron microscopy. The diameter of those clusters, d, ranges from 1 nm up to about 10 nm for specimens produced by the sputter-gas aggregation technique, depending on the sputter condition and the deposition time. Comparable times of the ICB deposition lead to a broader distribution up to d≈20 nm, suggesting the formation of islands with extremely flat shapes. High percentages of crystalline particles obtained by both techniques are either single crystals or multiple twins with clear lattice images.

  7. New insights into side effect of solvents on the aggregation of human islet amyloid polypeptide 11-20.

    PubMed

    Mao, Yexuan; Yu, Lanlan; Yang, Ran; Ma, Chuanguo; Qu, Ling-bo; Harrington, Peter de B

    2016-02-01

    The formation of highly ordered fibrils for the human islet amyloid polypeptide (hIAPP) is considered as one of the precipitating factors of type 2 diabetes mellitus. In this study, an emerging new approach microscale thermophoresis and conventional ThT fluorescence assay were utilized to investigate the aggregation behavior of hIAPP(11-20), giving a new insight of the solvent effect on the aggregation of hIAPP(11-20). hIAPP(11-20) displayed different aggregation behaviors in various buffers, revealing that hIAPP(11-20) not only self-aggregates but also binds to solvent components. hIAPP(11-20) had a higher binding affinity for Tris than other selected buffers because multiple hydrogen bonds form, resulting in weaker self-aggregation of hIAPP(11-20) at the early stage of aggregation and prolonging the fibril formation process. hIAPP(11-20) displayed similar self-aggregation in both HEPES and pure water. Negatively charged phosphate ions in the PBS solution 'neutralize' the charges carried by hIAPP(11-20) itself to some extent, causing rapid aggregation of hIAPP(11-20), and leading to a shorter fibrillation process of hIAPP(11-20). These results revealed that solvents contribute to the aggregation of hIAPP(11-20) and demonstrated the affect of solvents on the activity of biomolecules. Additionally, as a new technique, microscale thermophoresis offers a powerful and promising approach to study the early stages of aggregation of peptides or proteins. PMID:26653463

  8. Controlled synthesis of crystalline calcium carbonate aggregates with unusual morphologies involving the phase transformation from amorphous calcium carbonate

    SciTech Connect

    Tang Hua; Yu Jiaguo Zhao Xiufeng

    2009-04-02

    Peanut-shaped CaCO{sub 3} aggregates, featured of two dandelion-like heads built up from rod-like subunits, have been synthesized via a facile precipitation reaction between Na{sub 2}CO{sub 3} and CaCl{sub 2} at ambient temperature in the presence of magnesium ions and ethanol solvent. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a high magnesium concentration and ethanol solvent are necessary for the formation of the unusual peanut-like aggregates. In addition, a multistep phase transformation process from amorphous calcium carbonate (ACC) to a mixture of ACC and calcite and ultimately to calcite and aragonite was observed in the formation process of the unusual structures. A possible mechanism for the formation of the unusual peanut-shape aggregates has been proposed and discussed.

  9. The Effect of Nanoparticle Aggregation Processes on Aggregate Structure and Metal Uptake

    NASA Astrophysics Data System (ADS)

    Gilbert, B.; Ching, K. A.; Ono, R. K.; Kim, C. S.

    2007-12-01

    Nanoscale oxide and oxyhydroxide minerals are commonly found in the natural environment, and play important roles in adsorbing and sequestering aqueous ions including nutrients such as phosphates and contaminants such as heavy metals. After formation, these materials are typically subjected to natural flocculation events that reduce the nanoparticle surface area that is accessible by aqueous ions. However, no studies have addressed the impact of different aggregation processes on the capacity of the nanoparticles to sorb aqueous metal ions. We synthesized a suspension of ~6 nm iron oxyhydroxide nanoparticles and subjected portions of this suspension to analogues of natural aggregation processes. These included: pH variation around the point of zero surface charge (simulating the neutralization of acid mine drainage); ionic strength elevation (simulating mixing of aquifer and saline water); drying; and freezing. The effect of aggregation on metal ion uptake was then studied by exposing batches of aggregated and control samples to 0.5 mM Cu(NO3)2 at pH 6.0 for 24 hours. In addition, we used in situ small-angle x-ray scattering to quantify and visualize the aggregate morphology. We found that the aggregates produced by the different mechanisms varied considerably in their interior porosity and their ability to sequester aqueous ions. In particular, the results demonstrate the important role of water in preserving hydrated channels among aggregated nanoparticles that are permeable to aqueous metal ions.

  10. Precipitation Matters

    ERIC Educational Resources Information Center

    McDuffie, Thomas

    2007-01-01

    Although weather, including its role in the water cycle, is included in most elementary science programs, any further examination of raindrops and snowflakes is rare. Together rain and snow make up most of the precipitation that replenishes Earth's life-sustaining fresh water supply. When viewed individually, raindrops and snowflakes are quite…

  11. Chemical characteristics of mineral trioxide aggregate and its hydration reaction

    PubMed Central

    2012-01-01

    Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyapatite (CDHA). These mineral precipitate were reported to form the MTA-dentin interfacial layer which enhances the sealing ability of MTA. Clinically, the use of zinc oxide euginol (ZOE) based materials may retard the setting of MTA. Also, the use of acids or contact with excessive blood should be avoided before complete set of MTA, because these conditions could adversely affect the hydration reaction of MTA. Further studies on the chemical nature of MTA hydration reaction are needed. PMID:23429542

  12. Chemical characteristics of mineral trioxide aggregate and its hydration reaction.

    PubMed

    Chang, Seok-Woo

    2012-11-01

    Mineral trioxide aggregate (MTA) was developed in early 1990s and has been successfully used for root perforation repair, root end filling, and one-visit apexification. MTA is composed mainly of tricalcium silicate and dicalcium silicate. When MTA is hydrated, calcium silicate hydrate (CSH) and calcium hydroxide is formed. Formed calcium hydroxide interacts with the phosphate ion in body fluid and form amorphous calcium phosphate (ACP) which finally transforms into calcium deficient hydroxyapatite (CDHA). These mineral precipitate were reported to form the MTA-dentin interfacial layer which enhances the sealing ability of MTA. Clinically, the use of zinc oxide euginol (ZOE) based materials may retard the setting of MTA. Also, the use of acids or contact with excessive blood should be avoided before complete set of MTA, because these conditions could adversely affect the hydration reaction of MTA. Further studies on the chemical nature of MTA hydration reaction are needed. PMID:23429542

  13. Aggregate breakdown of nanoparticulate titania

    NASA Astrophysics Data System (ADS)

    Venugopal, Navin

    Six nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales. Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime. A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from

  14. Acidic precipitation

    SciTech Connect

    Martin, H.C.

    1987-01-01

    At the International Symposium on Acidic Precipitation, over 400 papers were presented, and nearly 200 of them are included here. They provide an overview of the present state of the art of acid rain research. The Conference focused on atmospheric science (monitoring, source-receptor relationships), aquatic effects (marine eutrophication, lake acidification, impacts on plant and fish populations), and terrestrial effects (forest decline, soil acidification, etc.).

  15. The interaction between oxytetracycline and divalent metal ions in aqueous and mixed solvent systems.

    PubMed

    Tongaree, S; Flanagan, D R; Poust, R I

    1999-01-01

    The effects of pH, mixed solvent systems, and divalent metal ions on oxytetracycline (OTC) solubility and the interactions between OTC and metal ions in aqueous and mixed solvent systems were investigated. OTC solubility profiles were obtained for pH 4-9. The cosolvents studied were glycerin, propylene glycol, PEG 400, and 2-pyrrolidone with the following metal ions: magnesium, calcium, and zinc. OTC and its interactions with these metal ions were evaluated by solubility, NMR, circular dichroism (CD), and electron diffraction (ED) methods. At pH 5.6, no complexation occurred with these metal ions, but OTC zwitterion formed aggregates in aqueous solutions as shown by NMR spectra. The hydration of the metal ions was observed to affect OTC aggregation, with Mg+2 causing the greatest OTC aggregation. At pH 7.5, OTC aggregation and metal-OTC complexation were observed in solutions with Ca+2 and Mg+2. Zinc ion was found to decrease OTC solubility because of zincate formation, which caused anionic OTC to precipitate. Electron diffraction revealed a relationship between OTC and metal-OTC complex crystallinity and solubility behavior. The zinc-OTC complex exhibited the highest crystallinity and lowest solubility at pH 8.0. Various cosolvents generally enhanced OTC solubility, with 2-pyrrolidone having the best solubility power. In OTC-metal-2-pyrrolidone and OTC-Zn(+2)-PEG 400 systems, circular dichroism provided evidence for the formation of soluble ternary complexes. PMID:10578513

  16. PRECIPITATION METHOD OF SEPARATION OF NEPTUNIUM

    DOEpatents

    Magnusson, L.B.

    1958-07-01

    A process is described for the separation of neptunium from plutonium in an aqueous solution containing neptunium ions in a valence state not greater than +4, plutonium ioms in a valence state not greater than +4, and sulfate ions. The Process consists of adding hypochlorite ions to said solution in order to preferentially oxidize the neptunium and then adding lanthanum ions and fluoride ions to form a precipitate of LaF/sub 3/ carrying the plutonium, and thereafter separating the supernatant solution from the precipitate.

  17. Mesoscale Simulation of Asphaltene Aggregation.

    PubMed

    Wang, Jiang; Ferguson, Andrew L

    2016-08-18

    Asphaltenes constitute a heavy aromatic crude oil fraction with a propensity to aggregate and precipitate out of solution during petroleum processing. Aggregation is thought to proceed according to the Yen-Mullins hierarchy, but the molecular mechanisms underlying mesoscopic assembly remain poorly understood. By combining coarse-grained molecular models parametrized using all-atom data with high-performance GPU hardware, we have performed molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microsecond time scales. Our simulations reveal a hierarchical self-assembly mechanism consistent with the Yen-Mullins model, but the details are sensitive and depend on asphaltene chemistry and environment. At low concentrations asphaltenes exist predominantly as dispersed monomers. Upon increasing concentration, we first observe parallel stacking into 1D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates associated by offset, T-shaped, and edge-edge stacking. Asphaltenes possessing long aliphatic side chains cannot form nanoaggregate clusters due to steric repulsions between their aliphatic coronae. At very high concentrations, we observe a porous percolating network of rod-like nanoaggregates suspended in a sea of interpenetrating aliphatic side chains with a fractal dimension of ∼2. The lifetime of the rod-like aggregates is described by an exponential distribution reflecting a dynamic equilibrium between coagulation and fragmentation. PMID:27455391

  18. Aggregate-mediated charge transport in ionomeric electrolytes

    NASA Astrophysics Data System (ADS)

    Lu, Keran; Maranas, Janna; Milner, Scott

    Polymers such PEO can conduct ions, and have been studied as possible replacements for organic liquid electrolytes in rechargeable metal-ion batteries. More generally, fast room-temperature ionic conduction has been reported for a variety of materials, from liquids to crystalline solids. Unfortunately, polymer electrolytes generally have limited conductivity; these polymers are too viscous to have fast ion diffusion like liquids, and too unstructured to promote cooperative transport like crystalline solids. Ionomers are polymer electrolytes in which ionic groups are covalently bound to the polymer backbone, neutralized by free counterions. These materials also conduct ions, and can exhibit strong ionic aggregation. Using coarse-grained molecular dynamics, we explore the forces driving ionic aggregation, and describe the role ion aggregates have in mediating charge transport. The aggregates are string-like such that ions typically have two neighbors. We find ion aggregates self-assemble like worm-like micelles. Excess charge, or free ions, occasionally coordinate with aggregates and are transported along the chain in a Grotthuss-like mechanism. We propose that controlling ionomer aggregate structure through materials design can enhance cooperative ion transport.

  19. Making Graphene Resist Aggregation

    NASA Astrophysics Data System (ADS)

    Luo, Jiayan

    lose surface area. So their capacitive performance tends to decrease with increased loading level. But the crumpled balls can resist aggregation and retain high capacitance at high loading level. The crumpled graphene balls can be also used as expandable shells for wrapping lithium ion battery anode materials such as Si nanoparticles, which can accommodate their expansion/contraction without facture, and thus greatly improve the coulombic efficiency of the anode.

  20. Asphaltene Aggregation and Fouling Behavior

    NASA Astrophysics Data System (ADS)

    Derakhshesh, Marzie

    . Analysis of the spectra of the whole asphaltene samples in toluene indicates that the absorbance of visible light with wavelengths > 600 nm follows a lambda--4 dependence. This functional dependence is consistent with Rayleigh scattering. Rayleigh scattering provides strong evidence that the apparent absorption of visible light by asphaltenes from 600-800 nm is not a molecular absorption phenomenon but rather a scattering mechanism. Rayleigh scattering equations were combined with experimental visible spectra to estimate the average nanoaggregate sizes, which were in a very good agreement with the sizes reported in the literature. The occlusion of two polynuclear aromatic hydrocarbons (PAHs) (pyrene and phenanthrene) in asphaltene precipitates was tested by adding PAHs to the asphaltene in toluene solutions, precipitating by n-pentane and determining the amount of PAHs in precipitates using simulated distillation instrument. Pyrene and phenanthrene, which are normally soluble in the toluene-n-pentane solutions, were detected in the asphaltene precipitates at up to 6 wt% concentration. Trapping of PAHs outside of the nanoaggregates during precipitation gave 7-14 times less of the PAHs in the solid precipitate. This study shows that asphaltene aggregates can interact significantly with PAHs. The results are consistent with the presence open porous asphaltene nanoaggregates in solutions such as toluene.

  1. Iron Oxidation and Precipitation of Ferric Hydroxysulfates by Resting Thiobacillus ferrooxidans Cells

    PubMed Central

    Lazaroff, Norman; Sigal, Warren; Wasserman, Andrew

    1982-01-01

    The oxidation of ferrous ions, in acid solution, by resting suspensions of Thiobacillus ferrooxidans produced sediments consisting of crystalline jarosites, amorphous ferric hydroxysulfates, or both. These products differed conspicuously in chemical composition and infrared spectra from precipitates formed by abiotic oxidation under similar conditions. The amorphous sediments, produced by bacterial oxidation, exhibited a distinctive fibroporous microstructure when examined by scanning electron microscopy. Infrared spectra indicated outer-sphere coordination of Fe(III) by sulfate ions, as well as inner-sphere coordination by water molecules and bridging hydroxo groups. In the presence of excess sulfate and appropriate monovalent cations, jarosites, instead of amorphous ferric hydroxysulfates, precipitated from bacterially oxidized iron solutions. It is proposed that the jarositic precipitates result from the conversion of outer-sphere (Td) sulfate, present in a soluble polymeric Fe(III) complex, to inner-sphere (C3v) bridging sulfate. The amorphous precipitates result from the further polymerization of hydroxo-linked iron octahedra and charge stabilized aggregation of the resulting iron complexes in solution. This view was supported by observations that bacterially oxidized iron solutions gave rise to either amorphous or jarositic sediments in response to ionic environments imposed after oxidation had been completed and the bacteria had been removed by filtration. Images PMID:16345996

  2. Modeling Protein Aggregate Assembly and Structure

    NASA Astrophysics Data System (ADS)

    Guo, Jun-tao; Hall, Carol K.; Xu, Ying; Wetzel, Ronald

    One might say that "protein science" got its start in the domestic arts, built around the abilities of proteins to aggregate in response to environmental stresses such as heating (boiled eggs), heating and cooling (gelatin), and pH (cheese). Characterization of proteins in the late nineteenth century likewise focused on the ability of proteins to precipitate in response to certain salts and to aggregate in response to heating. Investigations by Chick and Martin (Chick and Martin, 1910) showed that the inactivating response of proteins to heat or solvent treatment is a two-step process involving separate denaturation and precipitation steps. Monitoring the coagulation and flocculation responses of proteins to heat and other stresses remained a major approach to understanding protein structure for decades, with solubility, or susceptibility to aggregation, serving as a kind of benchmark against which results of other methods, such as viscosity, chemical susceptibility, immune activity, crystallizability, and susceptibility to proteolysis, were compared (Mirsky and Pauling, 1936;Wu, 1931). Toward the middle of the last century, protein aggregation studies were largely left behind, as improved methods allowed elucidation of the primary sequence of proteins, reversible unfolding studies, and ultimately high-resolution structures. Curiously, the field of protein science, and in particular protein folding, is now gravitating back to a closer look at protein aggregation and protein aggregates. Unfortunately, the means developed during the second half of the twentieth century for studying native, globular proteins have not proved immediately amenable to the study of aggregate structures. Great progress is being made, however, to modify classical methods, including NMR and X-ray diffraction, as well as to develop newer techniques, that together should continue to expand our picture of aggregate structure (Kheterpal and Wetzel, 2006; Wetzel, 1999).

  3. Spatial and temporal distribution of 13C labelled plant residues in soil aggregates and Lumbricus terrestris surface casts: A combination of Transmission Electron Microscopy and Nanoscale Secondary Ion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Vidal, Alix; Remusat, Laurent; Watteau, Françoise; Derenne, Sylvie; Quenea, Katell

    2016-04-01

    Earthworms play a central role in litter decomposition, soil structuration and carbon cycling. They ingest both organic and mineral compounds which are mixed, complexed with mucus and dejected in form of casts at the soil surface and along burrows. Bulk isotopic or biochemical technics have often been used to study the incorporation of litter in soil and casts, but they could not reflect the complex interaction between soil, plant and microorganisms at the microscale. However, the heterogeneous distribution of organic carbon in soil structures induces contrasted microbial activity areas. Nano-scale secondary ion mass spectrometry (NanoSIMS), which is a high spatial resolution method providing elemental and isotopic maps of organic and mineral materials, has recently been applied in soil science (Herrmann et al., 2007; Vogel et al., 2014). The combination of Nano-scale secondary ion mass spectrometry (NanoSIMS) and Transmission Electron Microscopy (TEM) has proven its potential to investigate labelled residues incorporation in earthworm casts (Vidal et al., 2016). In line of this work, we studied the spatial and temporal distribution of plant residues in soil aggregates and earthworm surface casts. This study aimed to (1) identify the decomposition states of labelled plant residues incorporated at different time steps, in casts and soil, (2) identify the microorganisms implied in this decomposition (3) relate the organic matter states of decomposition with their 13C signature. A one year mesocosm experiment was set up to follow the incorporation of 13C labelled Ryegrass (Lolium multiflorum) litter in a soil in the presence of anecic earthworms (Lumbricus terrestris). Soil and surface cast samples were collected after 8 and 54 weeks, embedded in epoxy resin and cut into ultra-thin sections. Soil was fractionated and all and analyzed with TEM and NanoSIMS, obtaining secondary ion images of 12C, 16O, 12C14N, 13C14N and 28Si. The δ13C maps were obtained using the 13C14

  4. LiMn0.8Fe0.2PO4/C cathode material synthesized via co-precipitation method with superior high-rate and low-temperature performances for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Yang, Wenchao; Bi, Yujing; Qin, Yinping; Liu, Yang; Zhang, Xianhui; Yang, Bangcheng; Wu, Qu; Wang, Deyu; Shi, Siqi

    2015-02-01

    Developing rechargeable lithium ion batteries with fast charge/discharge rate, high capacity and power, long lifespan, and broad temperature adaptability is still a significant challenge. In order to realize the fast and efficient transport of ions and electrons during the charging/discharging process, a pure and well-crystallized LiMn0.8Fe0.2PO4 cathode material is directly synthesized via co-precipitation method at ambient pressure and 130 °C. Nano-LiMn0.8Fe0.2PO4/C with 5.7 wt% conductive carbon delivers a discharge capacity of 160.6 mAh g-1 at 0.05 C, close to the theoretical value (170 mAh g-1). Even at 10 C, 20 C and 50 C, stable capacities of 113 mAh g-1, 102 mAh g-1 and 83 mAh g-1 are obtained, respectively. The discharge capacity at -15 °C is as high as 97 mAh g-1 at 0.1 C. The excellent high-rate and low-temperature performances of nano-LiMn0.8Fe0.2PO4/C effectively promote its practical usage in lithium-ion batteries.

  5. Platelet aggregation test

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003669.htm Platelet aggregation test To use the sharing features on this page, please enable JavaScript. The platelet aggregation blood test checks how well platelets , a ...

  6. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  7. Platelet aggregation test

    MedlinePlus

    The platelet aggregation blood test checks how well platelets , a part of blood, clump together and cause blood to clot. ... Decreased platelet aggregation may be due to: Autoimmune ... Fibrin degradation products Inherited platelet function defects ...

  8. SEPARATION OF PLUTONYL IONS

    DOEpatents

    Connick, R.E.; McVey, Wm.H.

    1958-07-15

    A process is described for separating plutonyl ions from the acetate ions with which they are associated in certaln carrier precipitation methods of concentrating plutonium. The method consists in adding alkaline earth metal ions and subsequently alkalizing the solution, causing formation of an alkaltne earth plutonate precipitate. Barium hydroxide is used in a preferred embodiment since it provides alkaline earth metal ion and alkalizes the solution in one step forming insoluble barium platonate.

  9. Fractal dimension and mechanism of aggregation of apple juice particles.

    PubMed

    Benítez, E I; Lozano, J E; Genovese, D B

    2010-04-01

    Turbidity of freshly squeezed apple juice is produced by a polydisperse suspension of particles coming from the cellular tissue. After precipitation of coarse particles by gravity, only fine-colloidal particles remain in suspension. Aggregation of colloidal particles leads to the formation of fractal structures. The fractal dimension is a measure of the internal density of these aggregates and depends on their mechanism of aggregation. Digitized images of primary particles and aggregates of depectinized, diafiltered cloudy apple juice were obtained by scanning electron microscopy (SEM). Average radius of the primary particles was found to be a = 40 ± 11 nm. Maximum radius of the aggregates, R(L), ranged between 250 and 7750 nm. Fractal dimension of the aggregates was determined by analyzing SEM images with the variogram method, obtaining an average value of D(f) = 2.3 ± 0.1. This value is typical of aggregates formed by rapid flocculation or diffusion limited aggregation. Diafiltration process was found to reduce the average size and polydispersity of the aggregates, determined by photon correlation spectroscopy. Average gyration radius of the aggregates before juice diafiltration was found to be R(g) = 629 ± 87 nm. Average number of primary particles per aggregate was calculated to be N = 1174. PMID:21339133

  10. Impact of Particle Aggregation on Nanoparticle Reactivity

    NASA Astrophysics Data System (ADS)

    Jassby, David

    2011-12-01

    decline in hydroxyl radical generation could be attributed to two key parameters. First, increased aggregate size was associated with increased particle shadowing, as determined from the observed decrease in the rate of optically induced transitions. Secondly, aggregate structure was associated both with increased shadowing (denser aggregates exhibited more shadowing than similarly sized loose aggregates), and with an increase in radical quenching on neighboring particle surfaces in an aggregate. Aggregation had a positive impact on hydroxylated fullerene membrane separation, increasing removal efficiency to around 80%, regardless of transmembrane pressure. However, the type of electrolyte used determined whether aggregation was successful at increasing removal. Divalent ions, capable of forming strong covalent bonds with surface oxygen groups, increased removal efficiency and made it pressure insensitive. In contrast, monovalent ions increased removal efficiency slightly, but maintained the pressure dependence of the removal efficiency. Evidence is presented to support the hypothesis that divalently aggregated hydroxylated fullerenes deform under increased pressure and partially penetrate the membrane. Finally, nanoparticle reactive properties depend on the primary particle aggregation state. Both size and structure are key factors when evaluating nanomaterial reactivity under aggregation-inducing conditions. However, the impact of aggregation is not easily predicted. Some materials exhibit a decreased reactivity while others experience an increase. Therefore, the impact of aggregation on nanoparticle reactive properties must be evaluated on a material-by-material basis, while considering all of the particle and aggregate characteristics as well as environmental ones.

  11. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia) shell calcite precipitated at constant temperature

    NASA Astrophysics Data System (ADS)

    Freitas, P. S.; Clarke, L. J.; Kennedy, H.; Richardson, C. A.

    2009-01-01

    Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS) profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves P. maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as shell Mg content influencing Sr and Mn heterogeneity, the influence of shell organic content and/or conditions at the shell crystal-solution interface. Invariant Mg/Ca ratios observed in the mid and innermost regions of the P. maximus shell suggests a potential application as a palaeotemperature proxy.

  12. Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia) shell calcite precipitated at constant temperature

    NASA Astrophysics Data System (ADS)

    Freitas, P. S.; Clarke, L. J.; Kennedy, H.; Richardson, C. A.

    2009-07-01

    Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS) profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

  13. Investigation of the Role of Ce3+ Substituted Ions on Dielectric Properties of Co-Cr Ferrites Prepared by Co-precipitation Method

    NASA Astrophysics Data System (ADS)

    Mustafa, Ghulam; Islam, M. U.; Zhang, Wenli; Arshad, M. I.; Jamil, Yasir; Anwar, Hafeez; Murtaza, G.; Hussain, Mudassar; Ahmad, Mukhtar

    2016-07-01

    A series of a CoCr0.04Ce x Fe1.96-x O4 spinel ferrite system with 0 ≤ x ≤ 0.1 (in steps of 0.02) has been synthesized by the co-precipitation technique. The synthesized samples were characterized using a Fourier transform infrared spectroscope (FT-IR), Raman spectroscopy, a scanning electron microscope (SEM), and dielectric measurements. The typical FT-IR spectrum of the samples annealed at 850°C exhibited two frequency bands due to the formation of octahedral (B-site) and tetrahedral (A-site) clusters of metal oxide, respectively. The SEM images showed the spherical morphology of synthesized material and confirmed the grain size in the range of (0.33-0.44) μm. The decrease of permittivity with the increase of frequency in the range of 1 MHz to 3 GHz follows the Maxwell-Wagner model. Moreover, the Ce3+substituted materials have smaller values of loss tangent and dielectric constant especially for x = 0.10, which is favorable for the applications where low losses are desired. The value of ac (alternating current) conductivity increases with an increase in the frequency and decreases with Ce3+ substitution, which reflects the hopping mechanism at respective sites. Such characteristics of these materials may be suitable␣for potential applications such as electromagnetic attenuation materials, switching applications, and microwave devices.

  14. Controlling and engineering precipitation patterns.

    PubMed

    Lagzi, István

    2012-02-21

    Controlling and engineering chemical structures are the most important scientific challenges in material science. Precipitation patterns from ions or nanoparticles are promising candidates for designing bulk structure for catalysis, energy production, storage, and electronics. There are only a few procedures and techniques to control precipitation (Liesegang) patterns in gel media (e.g., using an electric field, varying the initial concentration of the electrolytes). However, those methods provide just a limited degree of freedom. Here, we provide a robust and transparent way to control and engineer Liesegang patterns by varying gel concentration and inducing impurity by addition of gelatin to agarose gel. Using this experimental method, different precipitation structures can be obtained with different width and spatial distribution of the formed bands. A new variant of a sol-coagulation model was developed to describe and understand the effect of the gel concentration and impurities on Liesegang pattern formation. PMID:22283626

  15. Asphaltene aggregation and impact of alkylphenols.

    PubMed

    Goual, Lamia; Sedghi, Mohammad; Wang, Xiaoxiao; Zhu, Ziming

    2014-05-20

    The main objective of this study was to provide novel insights into the mechanism of asphaltene aggregation in toluene/heptane (Heptol) solutions and the effect of alkylphenols on asphaltene dispersion through the integration of advanced experimental and modeling methods. High-resolution transmission electron microscope (HRTEM) images revealed that the onset of asphaltene flocculation occurs near a toluene/heptane volume ratio of 70:30 and that flocculates are well below 1 μm in size. To assess the impact of alkylphenols on asphaltene aggregation, octylphenol (OP) and dodecylphenol (DP) were evaluated by impedance analysis based on their ability to delay the precipitation onset and to reduce the size of nonflocculated asphaltene aggregates in 80:20 toluene/heptane solutions. Although a longer dispersant chain length did not affect the precipitation onset, it reduced the size of the aggregates. Molecular dynamics simulations were then performed to understand the mechanism of interaction between a model asphaltene and OP in heptane. OP molecules saturated the H-bonding sites of asphaltenes and prevented them from interacting laterally between themselves. This explained why OP favored the formation of flocculates with filamentary rather than globular structures, which were clearly observed by HRTEM. Although OP proved to be an effective dispersant, its effectiveness was hindered by its self-association and the fact that it interacted at the periphery of asphaltenes, leaving their aromatic cores uncovered. PMID:24784502

  16. THE INFLUENCE OF ELECTROLYTES ON THE SOLUTION AND PRECIPITATION OF CASEIN AND GELATIN.

    PubMed

    Loeb, J; Loeb, R F

    1921-11-20

    1. Colloids have been divided into two groups according to the ease with which their solutions or suspensions are precipitated by electrolytes. One group (hydrophilic colloids), e.g., solutions of gelatin or crystalline egg albumin in water, requires high concentrations of electrolytes for this purpose, while the other group (hydrophobic colloids) requires low concentrations. In the latter group the precipitating ion of the salt has the opposite sign of charge as the colloidal particle (Hardy's rule), while no such relation exists in the precipitation of colloids of the first group. 2. The influence of electrolytes on the solubility of solid Na caseinate, which belongs to the first group (hydrophilic colloids), and of solid casein chloride which belongs to the second group (hydrophobic colloids), was investigated and it was found that the forces determining the solution are entirely different in the two cases. The forces which cause the hydrophobic casein chloride to go into solution are forces regulated by the Donnan equilibrium; namely, the swelling of particles. As soon as the swelling of a solid particle of casein chloride exceeds a certain limit it is dissolved. The forces which cause the hydrophilic Na caseinate to go into solution are of a different character and may be those of residual valency. Swelling plays no rôle in this case, and the solubility of Na caseinate is not regulated by the Donnan equilibrium. 3. The stability of solutions of casein chloride (requiring low concentrations of electrolytes for precipitation) is due, first, to the osmotic pressure generated through the Donnan equilibrium between the casein ions tending to form an aggregate, whereby the protein ions of the nascent micellum are forced apart again; and second, to the potential difference between the surface of a micellum and the surrounding solution (also regulated by the Donnan equilibrium) which prevents the further coalescence of micella already formed. This latter consequence

  17. Light-Scattering Study of Petroleum Asphaltene Aggregation

    NASA Astrophysics Data System (ADS)

    Burya, Yevgeniy G.; Yudin, Igor K.; Dechabo, Victor A.; Kosov, Victor I.; Anisimov, Mikhail A.

    2001-08-01

    Dynamic light scattering with an original optical scheme has been used for the investigation of opaque (strongly light-absorbing) asphaltene colloids in crude oils and hydrocarbon mixtures. Diffusion-limited aggregation and reaction-limited aggregation as well as a crossover between these two regimes have been observed. A simple interpolation for the crossover kinetics is proposed. Asphaltene colloidal structures, originally persisting in crude oils, have been detected. Addition of a precipitant above a threshold induces asphaltene aggregation. Depending on the nature of the precipitant, different crude oils respond differently on its addition: (a) exponential-in-time growth of aggregates to huge flocks or (b) fast formation of stable-in-size particles.

  18. Mechanisms of carbon nanotube aggregation and the reversion of carbon nanotube aggregates in aqueous medium.

    PubMed

    Koh, Byumseok; Cheng, Wei

    2014-09-16

    Single-walled carbon nanotubes (SWCNTs) dispersed in aqueous medium have many potential applications in chemistry, biology, and medicine. Reversible aggregation of SWCNTs dispersed in water has been frequently reported, but the mechanisms behind are not well understood. Here we show that SWCNTs dispersed into aqueous medium assisted by various charged molecules can be reversibly aggregated by a variety of electrolytes with two distinct mechanisms. Direct binding of counterions to SWCNTs leads to aggregation when the surface charge is neutralized from 74 to 86%. This aggregation is driven by electrostatic instead of van der Waals interactions, thus showing similarity to that of DNA condensation induced by multivalent cations. Sequestration of counterions by chelating reagents leads to the redispersion of SWCNT aggregates. In contrast to various metal ions, polyelectrolytes have the unique ability to induce SWCNT aggregation by bridging between individual SWCNTs. Aggregation through the latter mechanism can be engineered to be reversible by exploiting various mechanisms of chain breaking, including reduction of disulfide bond in the polymer chain, and the cleavage action of proteolytic enzymes. These findings clarify the mechanisms of SWCNT aggregation, and have broad implications in various applications of SWCNTs in water. PMID:25144606

  19. Mesoscale simulation of asphaltene aggregation

    NASA Astrophysics Data System (ADS)

    Wang, Jiang; Ferguson, Andrew

    Asphaltenes constitute a heavy aromatic crude oil fraction that can aggregate and precipitate out of solution. Association is thought to proceed hierarchically according to the Yen-Mullins model, but the molecular mechanisms and pathways remain poorly understood. In this study, we perform molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microseconds using the coarse-grained Martini force field. We identified a hierarchical self-assembly mechanism consistent with Yen-Mullins model, but the details of which are strongly dependent on asphaltene molecular structure. Monomeric asphaltenes first self-assemble into 1-D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates. At high concentrations, asphaltenes with short aliphatic side chains assemble into a percolating network with the binding of 1-D rods. Conversely, molecules with more and longer side chains cannot efficiently stack, producing a fractal network of 1-D rods suspended in a sea of interpenetrating aliphatic side chains. Our results provide the first molecularly-detailed validation of the full Yen-Mullins hierarchy, and are in good agreement with recent computational and experimental studies. ACS Petroleum Research Fund.

  20. Factors affecting crystallization, dispersion, and aggregation of calcium oxalate monohydrate in various urinary environments

    NASA Astrophysics Data System (ADS)

    Christmas, Kimberly Gail

    The mechanisms for the formation of kidney stones are not well understood. One possible mechanism is the formation of aggregates in the nephron tubules of the kidneys. However, altering the urinary environment may be a method to help prevent the recurrence of the formation of kidney stones. The primary inorganic constituent found in kidney stones of North American patients is calcium oxalate monohydrate (COM). In this research, studies on the effect of mixing rate on COM precipitation showed that rapid mixing compared to slow mixing produced smaller particle sizes and a narrower particle size distribution due to the more uniform supersaturation level. The findings are consistent with the general contention that mixing directly influences nucleation rate while mixing rate has relatively little influence over rate of growth in precipitation processes. Screening and central composite experimental designs are used to determine the effect of various factors on the aggregation and dispersion characteristics of previously grown calcium oxalate monohydrate (COM) crystals in artificial urinary environments of controlled variables. The variables examined are pH, calcium, oxalate, pyrophosphate, citrate, and protein concentrations in ultrapure water and artificial urine. Optical density measurements, zeta potential analysis, particle size analyzer, optical microscopy, AFM force measurements, protein adsorption, and ions and small molecule adsorption have been used to assess the state of aggregation and dispersion of the COM crystals and to elucidate the mechanisms involved in such a complex system. The data indicate that our model protein, mucin, acts as a dispersant. This is attributed to steric hindrance resulting from the adsorbed mucoprotein. Oxalate, however, promotes aggregation. Interesting interactions between protein and oxalate along with protein and citrate are observed. Such interactions (synergistic or antagonistic) are found to depend on the concentrations of

  1. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  2. Scaling Linguistic Characterization of Precipitation Variability

    NASA Astrophysics Data System (ADS)

    Primo, C.; Gutierrez, J. M.

    2003-04-01

    Rainfall variability is influenced by changes in the aggregation of daily rainfall. This problem is of great importance for hydrological, agricultural and ecological applications. Rainfall averages, or accumulations, are widely used as standard climatic parameters. However different aggregation schemes may lead to the same average or accumulated values. In this paper we present a fractal method to characterize different aggregation schemes. The method provides scaling exponents characterizing weekly or monthly rainfall patterns for a given station. To this aim, we establish an analogy with linguistic analysis, considering precipitation as a discrete variable (e.g., rain, no rain). Each weekly, or monthly, symbolic precipitation sequence of observed precipitation is then considered as a "word" (in this case, a binary word) which defines a specific weekly rainfall pattern. Thus, each site defines a "language" characterized by the words observed in that site during a period representative of the climatology. Then, the more variable the observed weekly precipitation sequences, the more complex the obtained language. To characterize these languages, we first applied the Zipf's method obtaining scaling histograms of rank ordered frequencies. However, to obtain significant exponents, the scaling must be maintained some orders of magnitude, requiring long sequences of daily precipitation which are not available at particular stations. Thus this analysis is not suitable for applications involving particular stations (such as regionalization). Then, we introduce an alternative fractal method applicable to data from local stations. The so-called Chaos-Game method uses Iterated Function Systems (IFS) for graphically representing rainfall languages, in a way that complex languages define complex graphical patterns. The box-counting dimension and the entropy of the resulting patterns are used as linguistic parameters to quantitatively characterize the complexity of the patterns

  3. PRECIPITATION OF PLUTONOUS PEROXIDE

    DOEpatents

    Barrick, J.G.; Manion, J.P.

    1961-08-15

    A precipitation process for recovering plutonium values contained in an aqueous solution is described. In the process for precipitating plutonium as plutonous peroxide, hydroxylamine or hydrazine is added to the plutoniumcontaining solution prior to the addition of peroxide to precipitate plutonium. The addition of hydroxylamine or hydrazine increases the amount of plutonium precipitated as plutonous peroxide. (AEC)

  4. Aggregation kinetics and structure of cryoimmunoglobulins clusters

    NASA Astrophysics Data System (ADS)

    Spirito, M. De; Chiappini, R.; Bassi, F. Andreasi; Stasio, E. Di; Giardina, B.; Arcovito, G.

    2002-02-01

    Cryoimmunoglobulins are pathological antibodies characterized by a temperature-dependent reversible insolubility. Rheumatoid factors (RF) are immunoglobulins possessing anti-immunoglobulin activity and usually consist of an IgM antibody that recognizes IgG as antigen. These proteins are present in sera of patients affected by a large variety of different pathologies, such as HCV infection, neoplastic and autoimmune diseases. Aggregation and precipitation of cryoimmunoglobulins, leading to vasculiti, are physical phenomena behind such pathologies. A deep knowledge of the physico-chemical mechanisms regulating such phenomena plays a fundamental role in biological and clinical applications. In this work, a preliminary investigation of the aggregation kinetics and of the final macromolecular structure of the aggregates is presented. Through static light scattering techniques, the gyration radius Rg and the fractal dimension Dm of the growing clusters have been determined. However, while the initial aggregation mechanism could be described using the universal reaction-limited cluster-cluster aggregation (RLCCA) theory, at longest times from the beginning of the process, the RLCCA theory fails and a restructuring of clusters is observed together with an increase of the cluster fractal dimension Dm up to a value Dm∼3. The time tn, at which the restructuring takes place, and the final cluster size can be modulated by varying the quenching temperature.

  5. IMPROVED PROCESS OF PLUTONIUM CARRIER PRECIPITATION

    DOEpatents

    Faris, B.F.

    1959-06-30

    This patent relates to an improvement in the bismuth phosphate process for separating and recovering plutonium from neutron irradiated uranium, resulting in improved decontamination even without the use of scavenging precipitates in the by-product precipitation step and subsequently more complete recovery of the plutonium in the product precipitation step. This improvement is achieved by addition of fluomolybdic acid, or a water soluble fluomolybdate, such as the ammonium, sodium, or potassium salt thereof, to the aqueous nitric acid solution containing tetravalent plutonium ions and contaminating fission products, so as to establish a fluomolybdate ion concentration of about 0.05 M. The solution is then treated to form the bismuth phosphate plutonium carrying precipitate.

  6. Interactions of Divalent and Trivalent Metal Counterions with Anionic Sulfonate Gemini Surfactant and Induced Aggregate Transitions in Aqueous Solution.

    PubMed

    Liu, Zhang; Cao, Meiwen; Chen, Yao; Fan, Yaxun; Wang, Dong; Xu, Hai; Wang, Yilin

    2016-05-01

    Interactions of multivalent metal counterions with anionic sulfonate gemini surfactant 1,3-bis(N-dodecyl-N-propanesulfonate sodium)-propane (C12C3C12(SO3)2) and the induced aggregate transitions in aqueous solution have been studied. Divalent metal ions Ca(2+), Mg(2+), Cu(2+), Zn(2+), Mn(2+), Co(2+), and Ni(2+) and trivalent metal ions Al(3+), Fe(3+), and Cr(3+) were chosen. The results indicate that the critical micelle concentration (CMC) of C12C3C12(SO3)2 is greatly reduced by the ions, and the aggregate morphologies of C12C3C12(SO3)2 are adjusted by changing the nature and molar ratio of the metal ions. These metal ions can be classified into four groups because the ions in each group have very similar interaction mechanisms with C12C3C12(SO3)2: (I) Cu(2+) and Zn(2+); (II) Ca(2+), Mn(2+) and Mg(2+); (III) Ni(2+) and Co(2+); and (IV) Cr(3+), Al(3+) and Fe(3+). Cu(2+), Mg(2+), Ni(2+), and Al(3+) then were selected as representatives for each group to further study their interaction with C12C3C12(SO3)2. C12C3C12(SO3)2 interacts with the multivalent metal ions by electrostatic interaction and coordination interaction. C12C3C12(SO3)2 forms prolate micelles and plate-like micelles with Cu(2+), vesicles and wormlike micelles with Al(3+) or Ni(2+), and viscous three-dimensional network structure with Mg(2+). Moreover, precipitation does not take place in aqueous solution even at a high ion/surfactant ratio. The related mechanisms have been discussed. The present work provides guidance on how to apply the anionic surfactant into the solutions containing the multivalent metal ions, and those aggregates may have potential usage in separating heavy metal ions from aqueous solutions. PMID:27096262

  7. Role of peach proteins in juice precipitation induced by high pressure CO2.

    PubMed

    Zhao, Feng; Zhou, Linyan; Wang, Yongtao; Liao, Xiaojun

    2016-10-15

    To better understand the role of peach proteins in juice precipitation induced by high pressure CO2 (HPCD), proteins extracted from peach juice were subjected to HPCD and heat, and changes in particle size distribution (PSD) and structure were investigated. PSD analysis showed aggregations of proteins were both induced by HPCD and heat, but HPCD induced a stronger aggregation. The endotherm of HPCD- and heat-treated proteins moved to lower temperature, indicating that higher-order structures were altered after treatments. Furthermore, proteins related to HPCD- and heat-induced precipitation were analyzed by proteomics and bioinformatics. It was found that proteins with low content of α-helix and hydrogen bonds were more inclined to precipitate under HPCD, and HPCD precipitated proteins with more compact structures than heat, which might cause the stronger aggregation of proteins by HPCD. In conclusion, HPCD could induce the aggregation of peach proteins by destroying higher-order structures, which contributes to juice precipitation. PMID:27173537

  8. Synthesis of high-performance MnOx/carbon composite as lithium-ion battery anode by a facile co-precipitation method: Effects of oxygen stoichiometry and carbon morphology

    NASA Astrophysics Data System (ADS)

    Lee, Rung-Chuan; Lin, Yen-Po; Weng, Yu-Ting; Pan, Hsiao-An; Lee, Jyh-Fu; Wu, Nae-Lih

    2014-05-01

    Manganese oxide/carbon (MnOx/C) composite powders showing high performance as lithium-ion battery anode are synthesized by a facile co-precipitation process followed by thermal calcination between 400 °C and 700 °C in N2, where the as-deposited MnO2 is reduced progressively to Mn3O4 and then to MnO. The role of conductive additive is investigated by adopting two carbon (C) materials of different dimensionalities, including carbon black (CB) nanoparticles and micron-sized graphitic flakes (GFs). For MnOx/CB composite, the cycling stability is remarkably enhanced with increasing calcination temperature, and this is due to increasing content of MnO, which exhibits superior redox reversibility than the oxides having higher Mn valences. Attempt to achieve single-phase MnO at higher temperature (700 °C), nevertheless, leads to deteriorated cycle performance because of the formation of large oxide particles having poor contact with CB. The use of the two-dimensional GFs creates the "balls-on-plate" oxide-C configuration. This configuration facilitates MnO formation at lower temperature and simultaneously enables retention of good oxide-C contact, leading to significantly enhanced cycling stability and rate performance. The MnOx/GF composites obtained by calcination at 500-600 °C show specific capacities of 550-600 mAh g-1-(oxide + C) with no capacity fading after 150 cycles.

  9. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  10. [The formation of the influenza virus aggregates, enriched with hemagglutinin].

    PubMed

    Prokudina, E N; Semenova, N P; Chumakov, V M; Rudneva, I A; Iamnikova, S S

    2002-01-01

    The formation of electrostatic aggregates was studied by analysis of two types of virus-containing liquids: initial warm liquid collected at temperature 37 degrees and the same liquid stored over the night at temperature 4 degrees C. The formation of virus aggregates was revealed at 4 degrees C. The aggregates formed at temperature 4 degrees C had a relatively high HA/NP ratio in comparison with unassociated virus analyzed at 37 degrees. HA-enriched aggregates were found in the precipitate formed under short-term high-speed centrifugation as well as in "heavy arm" of the virus profile in the saccharose gradient. Aggregates formed at 4 degrees C dissociated at 37 degrees. The ability to form aggregates is reversible and correlates with the virus concentration. It is shown also that virus containing liquid contains heterogenic structures with molecular weight under 2000 kD having HA involved in the forming aggregates enriching HA. Possible nature of low-molecular HA-containing structures involved in the aggregates and nature of relations stabilizing aggregates are discussed. PMID:12271719

  11. Control of binder viscosity and hygroscopicity on particle aggregation efficiency

    NASA Astrophysics Data System (ADS)

    Mueller, Sebastian B.; Kueppers, Ulrich; Ayris, Paul M.; Jacob, Michael; Delmelle, Pierre; Dingwell, Donald B.

    2016-04-01

    In the course of explosive volcanic eruptions, large amounts of ash are released into the atmosphere and may subsequently pose a threat to infrastructure, such as aviation industry. Ash plume forecasting is therefore a crucial tool for volcanic hazard mitigation but may be significantly affected by aggregation, altering the aerodynamic properties of particles. Models struggle with the implementation of aggregation since external conditions promoting aggregation have not been completely understood; in a previous study we have shown the rapid generation of ash aggregates through liquid bonding via the use of fluidization bed technology and further defined humidity and temperature ranges necessary to trigger aggregation. Salt (NaCl) was required for the recovery of stable aggregates, acting as a cementation agent and granting aggregate cohesion. A numerical model was used to explain the physics behind particle aggregation mechanisms and further predicted a dependency of aggregation efficiency on liquid binder viscosity. In this study we proof the effect of viscosity on particle aggregation. HCl and H2SO4 solutions were diluted to various concentrations resulting in viscosities between 1 and 2 mPas. Phonolitic and rhyolitic ash samples as well as soda-lime glass beads (serving as analogue material) were fluidized in the ProCell Lab® of Glatt Ingenieurtechnik GmbH and treated with the acids via a bottom-spray technique. Chemically driven interaction between acid liquids and surfaces of the three used materials led to crystal precipitation. Salt crystals (e.g. NaCl) have been confirmed through scanning electron microscopy (SEM) and leachate analysis. Both volcanic ash samples as well as the glass beads showed a clear dependency of aggregation efficiency on viscosity of the sprayed HCl solution. Spraying H2SO4 provoked a collapse of the fluidized bed and no aggregation has been observed. This is accounted by the high hygroscopicity of H2SO4. Dissolving CaCl2 (known to be

  12. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  13. Precipitation Climate Data Records

    NASA Astrophysics Data System (ADS)

    Nelson, B. R.; Prat, O.; Vasquez, L.

    2015-12-01

    Five precipitation CDRs are now or soon will be transitioned to NOAA's CDR program. These include the PERSIANN data set, which is a 30-year record of daily adjusted global precipitation based on retrievals from satellite microwave data using artificial neural networks. The AMSU-A/B/Hydrobundle is an 11-year record of precipitable water, cloud water, ice water, and other variables. CMORPH (the NOAA Climate Prediction Center Morphing Technique) is a 17-year record of daily and sub-daily adjusted global precipitation measured from passive microwave and infrared data at high spatial and temporal resolution. GPCP (the Global Precipitation Climatology Project) is an approximately 30-year record of monthly and pentad adjusted global precipitation and a 17-year record of daily adjusted global precipitation. The NEXRAD Reanalysis is a 10-year record of high resolution NEXRAD radar based adjusted CONUS-wide hourly and daily precipitation. This study provides an assessment of the existing and transitioned long term precipitation CDRs and includes the verification of the five precipitation CDRs using various methods including comparison with in-situ data sets and trend analysis. As all of the precipitation related CDRs are transitioned, long term analyses can be performed. Comparisons at varying scales (hourly, daily and longer) of the precipitation CDRs with in-situ data sets are provided as well as a first look at what could be an ensemble long term precipitation data record.

  14. Metal ion implantation in inert polymers for strain gauge applications

    NASA Astrophysics Data System (ADS)

    Di Girolamo, Giovanni; Massaro, Marcello; Piscopiello, Emanuela; Tapfer, Leander

    2010-10-01

    Metal ion implantation in inert polymers may produce ultra-thin conducting films below the polymer surface. These subsurface films are promising structures for strain gauge applications. To this purpose, polycarbonate substrates were irradiated at room temperature with low-energy metal ions (Cu + and Ni +) and with fluences in the range between 1 × 10 16 and 1 × 10 17 ions/cm 2, in order to promote the precipitation of dispersed metal nanoparticles or the formation of a continuous thin film. The nanoparticle morphology and the microstructural properties of polymer nanocomposites were investigated by glancing-incidence X-ray diffraction and transmission electron microscopy (TEM) measurements. At lower fluences (<5 × 10 16 ions/cm 2) a spontaneous precipitation of spherical-shaped metal nanoparticles occurred below the polymer top-surface (˜50 nm), whereas at higher fluences the aggregation of metal nanoparticles produced the formation of a continuous polycrystalline nanofilm. Furthermore, a characteristic surface plasmon resonance peak was observed for nanocomposites produced at lower ion fluences, due to the presence of Cu nanoparticles. A reduced electrical resistance of the near-surface metal-polymer nanocomposite was measured. The variation of electrical conductivity as a function of the applied surface load was measured: we found a linear relationship and a very small hysteresis.

  15. Some characteristics of the precipitation formed within winter storms over eastern Newfoundland

    NASA Astrophysics Data System (ADS)

    Stewart, R. E.; Crawford, R. W.

    During the second Canadian Atlantic Storms Program (CASP 11) field experiment, detailed measurements and photographs were made of the surface precipitation. Observed precipitation characteristics include aggregates of ice pellets, needles coexisting with ice pellets, very large snowflakes, very rough ice pellets, sharp-edged crystals and mixed phase particles. The nature and formation of such precipitation characteristics are discussed and conceptual models of the development of these forms of winter precipitation are developed.

  16. Precipitation climate maps of Belgium

    NASA Astrophysics Data System (ADS)

    Journée, M.; Delvaux, C.; Bertrand, C.

    2015-04-01

    Investigations are conducted to best estimate precipitation climate maps over Belgium from daily observations available for the period 1981-2010. Several mapping approaches are compared in a cross-validation exercise. These approaches differ by several aspects and in particular by the order in which the temporal aggregation (i.e. computation of climate mean values from daily data) and spatial interpolation steps are performed, and by the integration of ancillary information in the spatial interpolation method. The selected approach is used to derive a large panel of climate maps. In particular, the main spatio-temporal features of the annual cycle of rainfall in Belgium are extracted by principal component analysis (PCA).

  17. Microbial Reduction and Precipitation of Vanadium by Shewanella oneidensis

    PubMed Central

    Carpentier, W.; Sandra, K.; De Smet, I.; Brigé, A.; De Smet, L.; Van Beeumen, J.

    2003-01-01

    Shewanella oneidensis couples anaerobic oxidation of lactate, formate, and pyruvate to the reduction of vanadium pentoxide (VV). The bacterium reduces VV (vanadate ion) to VIV (vanadyl ion) in an anaerobic atmosphere. The resulting vanadyl ion precipitates as a VIV-containing solid. PMID:12788772

  18. Aggregation of MBP in chronic demyelination

    PubMed Central

    Frid, Kati; Einstein, Ofira; Friedman-Levi, Yael; Binyamin, Orli; Ben-Hur, Tamir; Gabizon, Ruth

    2015-01-01

    Objectives Misfolding of key disease proteins to an insoluble state is associated with most neurodegenerative conditions, such as prion, Parkinson, and Alzheimer’s diseases. In this work, and by studying animal models of multiple sclerosis, we asked whether this is also the case for myelin basic protein (MBP) in the late and neurodegenerative phases of demyelinating diseases. Methods To this effect, we tested whether MBP, an essential myelin component, present prion-like properties in animal models of MS, as is the case for Cuprizone-induced chronic demyelination or chronic phases of Experimental Autoimmune Encephalomyelitis (EAE). Results We show here that while total levels of MBP were not reduced following extensive demyelination, part of these molecules accumulated thereafter as aggregates inside oligodendrocytes or around neuronal cells. In chronic EAE, MBP precipitated concomitantly with Tau, a marker of diverse neurodegenerative conditions, including MS. Most important, analysis of fractions from Triton X-100 floatation gradients suggest that the lipid composition of brain membranes in chronic EAE differs significantly from that of naïve mice, an effect which may relate to oxidative insults and subsequently prevent the appropriate insertion and compaction of new MBP in the myelin sheath, thereby causing its misfolding and aggregation. Interpretation Prion-like aggregation of MBP following chronic demyelination may result from an aberrant lipid composition accompanying this pathological status. Such aggregation of MBP may contribute to neuronal damage that occurs in the progressive phase of MS. PMID:26273684

  19. Salt-induced aggregation of lysozyme: Implications for crystal growth

    NASA Technical Reports Server (NTRS)

    Wilson, Lori J.

    1994-01-01

    Crystallization of proteins is a prerequisite for structural analysis by x-ray crystallography. While improvements in protein crystals have been obtained in microgravity onboard the U.S. Space Shuttle, attempts to improve the crystal growth process both on the ground and in space have been limited by our lack of understanding of the mechanisms involved. Almost all proteins are crystallized with the aid of a precipitating agent. Many of the common precipitating agents are inorganic salts. An understanding of the role of salts on the aggregation of protein monomers is the key to the elucidation of the mechanisms involved in protein crystallization. In order for crystallization to occur individual molecules must self-associate into aggregates. Detection and characterization of aggregates in supersaturated protein solutions is the first step in understanding salt-induced crystallization.

  20. Salt-induced aggregation of lysozyme: Implications for crystal growth

    NASA Astrophysics Data System (ADS)

    Wilson, Lori J.

    1994-10-01

    Crystallization of proteins is a prerequisite for structural analysis by x-ray crystallography. While improvements in protein crystals have been obtained in microgravity onboard the U.S. Space Shuttle, attempts to improve the crystal growth process both on the ground and in space have been limited by our lack of understanding of the mechanisms involved. Almost all proteins are crystallized with the aid of a precipitating agent. Many of the common precipitating agents are inorganic salts. An understanding of the role of salts on the aggregation of protein monomers is the key to the elucidation of the mechanisms involved in protein crystallization. In order for crystallization to occur individual molecules must self-associate into aggregates. Detection and characterization of aggregates in supersaturated protein solutions is the first step in understanding salt-induced crystallization.

  1. Precipitated silica as flow regulator.

    PubMed

    Müller, Anne-Kathrin; Ruppel, Joanna; Drexel, Claus-Peter; Zimmermann, Ingfried

    2008-08-01

    Flow regulators are added to solid pharmaceutical formulations to improve the flow properties of the powder mixtures. The primary particles of the flow regulators exist in the form of huge agglomerates which are broken down into smaller aggregates during the blending process. These smaller aggregates adsorb at the surface of the solid's grains and thus diminish attractive Van-der-Waals-forces by increasing the roughness of the host's surface. In most cases amorphous silica is used as flow additive but material properties like particle size or bond strength influence the desagglomeration tendency of the agglomerates and thus the flow regulating potency of each silica. For some silica types we will show that the differences in their flow regulating potency are due to the rate and extent by which they are able to cover the surface of the host particles. Binary powder mixtures consisting of a pharmaceutical excipient and an added flow regulator were blended in a Turbula mixer for a defined period of time. As pharmaceutical excipient corn starch was used. The flow regulators were represented by a selection of amorphous silicon dioxide types like a commercial fumed silica and various types of SIPERNAT precipitated silica provided by Evonik-Degussa GmbH, Hanau, Germany. Flowability parameters of the mixtures were characterized by means of a tensile strength tester. The reduction of tensile strength with the blending time can be correlated with an increase in fragmentation of the flow regulator. PMID:18595668

  2. Self-aggregation and its dependence on domain size

    NASA Astrophysics Data System (ADS)

    Jeevanjee, N.; Romps, D. M.

    2012-12-01

    When evaluating a single-column model against a cloud-resolving model (CRM), the choice of CRM domain size can exert a substantial influence on the results. In particular, recent studies have shown that self-aggregation of convection in numerical models occurs only beyond a certain threshold domain size of about 200-300 km. We present evidence that, in the absence of cold pools, self-aggregation can actually occur in any size domain, implying that self-aggregation is a more universal tendency than previously thought. At small (~ 50 km) domains, however, the degree of aggregation (as measured by the precipitable water in the dry region) is quite small. As the domain size increases, though, the degree of aggregation increases as well, peaking in the same 200-300 km regime in which the transition from un-aggregated to self-aggregated convection (with cold pools) has been seen to occur. We will discuss some of the factors responsible for setting this scale. 2D horizontal plots of boundary-layer specific humidity for different domain sizes. The different degrees of aggregation are evident

  3. Validation of a Rapid and Sensitive UPLC-MS-MS Method Coupled with Protein Precipitation for the Simultaneous Determination of Seven Pyrethroids in 100 µL of Rat Plasma by Using Ammonium Adduct as Precursor Ion.

    PubMed

    Singh, Sheelendra Pratap; Dwivedi, Nistha; Raju, Kanumuri Siva Rama; Taneja, Isha; Wahajuddin, Mohammad

    2016-04-01

    United States Environmental Protection Agency has recommended estimating pyrethroids' risk using cumulative exposure. For cumulative risk assessment, it would be useful to have a bioanalytical method for quantification of one or several pyrethroids simultaneously in a small sample volume to support toxicokinetic studies. Therefore, in the present study, a simple, sensitive and high-throughput ultraperformance liquid chromatography-tandem mass spectrometry method was developed and validated for simultaneous analysis of seven pyrethroids (fenvalerate, fenpropathrin, bifenthrin, lambda-cyhalothrin, cyfluthrin, cypermethrin and deltamethrin) in 100 µL of rat plasma. A simple single-step protein precipitation method was used for the extraction of target compounds. The total chromatographic run time of the method was 5 min. The chromatographic system used a Supelco C18 column and isocratic elution with a mobile phase consisting of methanol and 5 mM ammonium formate in the ratio of 90 : 10 (v/v). Mass spectrometer (API 4000) was operated in multiple reaction monitoring positive-ion mode using the electrospray ionization technique. The calibration curves were linear in the range of 7.8-2,000 ng/mL with correlation coefficients of ≥0.99. All validation parameters such as precision, accuracy, recovery, matrix effect and stability met the acceptance criteria according to the regulatory guidelines. The method was successfully applied to the toxicokinetic study of cypermethrin in rats. To the best of our knowledge, this is the first LC-MS-MS method for the simultaneous analysis of pyrethroids in rat plasma. This validated method with minimal modification can also be utilized for forensic and clinical toxicological applications due to its simplicity, sensitivity and rapidity. PMID:26801239

  4. Phase-field modeling of two-dimensional solute precipitation/dissolution: Solid fingers and diffusion-limited precipitation

    SciTech Connect

    Xu, Zhijie; Meakin, Paul

    2011-01-28

    Two-dimensional dendritic growth due to solute precipitation was simulated using a phase-field model reported earlier [Z. Xu and P. Meakin, J. Chem. Phys. 129, 014705 (2008)]. It was shown that diffusion-limited precipitation due to the chemical reaction at the solid-liquid interface posses similarities with diffusion-limited aggregation (DLA). The diffusion-limited precipitation is attained by setting the chemical reaction rate much larger compared to the solute diffusion to eliminate the effect of the interface growth kinetics. The phase-field simulation results were in reasonable agreement with the analytical solutions. The fractal solid fingers can be formed in the diffusion-limited precipitation and have a fractal dimension measured , close to 1.64, the fractal dimensionality of large square lattice diffusion-limited aggregation (DLA) clusters.

  5. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  6. Superconductor precursor mixtures made by precipitation method

    DOEpatents

    Bunker, Bruce C.; Lamppa, Diana L.; Voigt, James A.

    1989-01-01

    Method and apparatus for preparing highly pure homogeneous precursor powder mixtures for metal oxide superconductive ceramics. The mixes are prepared by instantaneous precipitation from stoichiometric solutions of metal salts such as nitrates at controlled pH's within the 9 to 12 range, by addition of solutions of non-complexing pyrolyzable cations, such as alkyammonium and carbonate ions.

  7. Dialysis: a characterization method of aggregation tendency.

    PubMed

    Pesarrodona, Mireia; Unzueta, Ugutz; Vázquez, Esther

    2015-01-01

    All researchers immersed in the world of recombinant protein production are in agreement that often the production and purification process of a protein can become a nightmare due to an unexpected behavior of the protein at different protocol stages. Once the protein is purified, scientists know that they still cannot relax. There is a decisive last step missing: performing a protein dialysis in a suitable buffer for subsequent experimental trials. Here is when we can find proteins that precipitate during dialysis by buffer-related factors (ionic strength, pH, etc.), which are intrinsic to each protein and are difficult to predict. How can we find the buffer in which a protein is more stable and with less tendency to precipitate? In this chapter we go over possible factors affecting the protein precipitation tendency during the dialysis process and describe a general dialysis protocol with tricks to reduce protein aggregation. Furthermore, we propose a fast method to detect the most appropriate buffer for the stability of a particular protein, performing microdialysis on a battery of different buffers to measure afterwards precipitation by a colorimetric method, and thus being able to choose the most suitable buffer for the dialysis of a given protein. PMID:25447873

  8. Reply to "Comment on 'A Self-Consistent Model of the Interacting Ring Current Ions and Electromagnetic Ion Cyclotron Waves, Initial Results: Waves and Precipitation Fluxes' and 'Self-Consistent Model of the Magnetospheric Ring Current and Propagating Electromagnetic Ion Cyclotron Waves: Waves in Multi-Ion Magnetosphere' by Khazanov et al. et al."

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Gamayunov, K. V.; Gallagher, D. L.; Kozyra, J. W.

    2007-01-01

    It is well-known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wavenormal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and[ particles. Such a self-consistent model is being progressively developed by Khazanov et al. [2002, 2006, 2007]. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. Thome and Home [2007] (hereafter referred to as TH2007) call the Khazanov et al. [2002, 2006] results into question in their Comment. The points in contention can be summarized as follows. TH2007 claim that: (1) "the important damping of waves by thermal heavy ions is completely ignored", and Landau damping during resonant interaction with thermal electrons is not included in our model; (2) EMIC wave damping due to RC O + is not included in our simulation; (3) non-linear processes limiting EMIC wave amplitude are not included in our model; (4) growth of the background fluctuations to a physically significantamplitude"must occur during a single transit of the unstable region" with subsequent damping below bi-ion latitudes,and consequently"the bounce averaged wave kinetic equation employed in the code contains a physically erroneous 'assumption". Our reply will address each of these points as well as other criticisms mentioned in the Comment. TH2007 are focused on two of our papers that are separated by four years. Significant progress in the self-consistent treatment of the RC-EMIC wave system has been achieved during those years. The paper by Khazanov et al. [2006] presents the latest version of our model, and in

  9. Aggregates, broccoli and cauliflower

    NASA Astrophysics Data System (ADS)

    Grey, Francois; Kjems, Jørgen K.

    1989-09-01

    Naturally grown structures with fractal characters like broccoli and cauliflower are discussed and compared with DLA-type aggregates. It is suggested that the branching density can be used to characterize the growth process and an experimental method to determine this parameter is proposed.

  10. On the complex conductivity signatures of calcite precipitation

    SciTech Connect

    Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan

    2009-11-01

    Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl{sub 2} and Na{sub 2}CO{sub 3} solutions. The experiment continued for 12 days with a constant precipitation rate of {approx}0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

  11. Technical bases for precipitate hydrolysis process operating parameters

    SciTech Connect

    Bannochie, C.J.; Lambert, D.P.

    1992-11-09

    This report provides the experimental data and rationale in support of the operating parameters for tetraphenylborate precipitate hydrolysis specified in WSRC-RP-92-737. The report is divided into two sections, the first dealing with lab-scale precipitate hydrolysis experimentation while the second part addresses large-scale runs conducted to demonstrate the revised operating parameters in the Precipitate Hydrolysis Experimental Facility (PHEF). The program was in conjunction with reducing the nitrite ion level in DWPF feed.

  12. Technical bases for precipitate hydrolysis process operating parameters. Revision 1

    SciTech Connect

    Bannochie, C.J.; Lambert, D.P.

    1992-11-09

    This report provides the experimental data and rationale in support of the operating parameters for tetraphenylborate precipitate hydrolysis specified in WSRC-RP-92-737. The report is divided into two sections, the first dealing with lab-scale precipitate hydrolysis experimentation while the second part addresses large-scale runs conducted to demonstrate the revised operating parameters in the Precipitate Hydrolysis Experimental Facility (PHEF). The program was in conjunction with reducing the nitrite ion level in DWPF feed.

  13. Selective Precipitation of Proteins.

    PubMed

    Matulis, Daumantas

    2016-01-01

    Selective precipitation of proteins can be used as a bulk method to recover the majority of proteins from a crude lysate, as a selective method to fractionate a subset of proteins from a protein solution, or as a very specific method to recover a single protein of interest from a purification step. This unit describes a number of methods suitable for selective precipitation. In each of the protocols that are outlined, the physical or chemical basis of the precipitation process, the parameters that can be varied for optimization, and the basic steps for developing an optimized precipitation are described. PMID:26836410

  14. Global Precipitation Measurement

    NASA Technical Reports Server (NTRS)

    Hou, Arthur Y.; Skofronick-Jackson, Gail; Kummerow, Christian D.; Shepherd, James Marshall

    2008-01-01

    This chapter begins with a brief history and background of microwave precipitation sensors, with a discussion of the sensitivity of both passive and active instruments, to trace the evolution of satellite-based rainfall techniques from an era of inference to an era of physical measurement. Next, the highly successful Tropical Rainfall Measuring Mission will be described, followed by the goals and plans for the Global Precipitation Measurement (GPM) Mission and the status of precipitation retrieval algorithm development. The chapter concludes with a summary of the need for space-based precipitation measurement, current technological capabilities, near-term algorithm advancements and anticipated new sciences and societal benefits in the GPM era.

  15. Effect of antiscalants on precipitation of an RO concentrate: metals precipitated and particle characteristics for several water compositions.

    PubMed

    Greenlee, Lauren F; Testa, Fabrice; Lawler, Desmond F; Freeman, Benny D; Moulin, Philippe

    2010-04-01

    Inland brackish water reverse osmosis (RO) is economically and technically limited by the large volume of salty waste (concentrate) produced. The use of a controlled precipitation step, followed by solid/liquid separation (filtration), has emerged as a promising side-stream treatment process to treat reverse osmosis concentrate and increase overall system recovery. The addition of antiscalants to the RO feed prevents precipitation within the membrane system but might have a deleterious effect on a concentrate treatment process that uses precipitation to remove problematic precipitates. The effects of antiscalant type and concentration on salt precipitation and precipitate particle morphology were evaluated for several water compositions. The primary precipitate for the synthetic brackish waters tested was calcium carbonate; the presence of magnesium, sulfate, minor ions, and antiscalant compounds affected the amount of calcium precipitated, as well as the phases of calcium carbonate formed during precipitation. Addition of antiscalant decreased calcium precipitation but increased incorporation of magnesium and sulfate into precipitating calcium carbonate. Antiscalants prevented the growth of nucleated precipitates, resulting in the formation of small (100-200 nm diameter) particles, as well as larger (6-10 microm) particles. Elemental analysis revealed changes in composition and calcium carbonate polymorph with antiscalant addition and antiscalant type. Results indicate that the presence of antiscalants does reduce the extent of calcium precipitation and can worsen subsequent filtration performance. PMID:20172582

  16. Measuring and modeling hemoglobin aggregation below the freezing temperature.

    PubMed

    Rosa, Mónica; Lopes, Carlos; Melo, Eduardo P; Singh, Satish K; Geraldes, Vitor; Rodrigues, Miguel A

    2013-08-01

    Freezing of protein solutions is required for many applications such as storage, transport, or lyophilization; however, freezing has inherent risks for protein integrity. It is difficult to study protein stability below the freezing temperature because phase separation constrains solute concentration in solution. In this work, we developed an isochoric method to study protein aggregation in solutions at -5, -10, -15, and -20 °C. Lowering the temperature below the freezing point in a fixed volume prevents the aqueous solution from freezing, as pressure rises until equilibrium (P,T) is reached. Aggregation rates of bovine hemoglobin (BHb) increased at lower temperature (-20 °C) and higher BHb concentration. However, the addition of sucrose substantially decreased the aggregation rate and prevented aggregation when the concentration reached 300 g/L. The unfolding thermodynamics of BHb was studied using fluorescence, and the fraction of unfolded protein as a function of temperature was determined. A mathematical model was applied to describe BHb aggregation below the freezing temperature. This model was able to predict the aggregation curves for various storage temperatures and initial concentrations of BHb. The aggregation mechanism was revealed to be mediated by an unfolded state, followed by a fast growth of aggregates that readily precipitate. The aggregation kinetics increased for lower temperature because of the higher fraction of unfolded BHb closer to the cold denaturation temperature. Overall, the results obtained herein suggest that the isochoric method could provide a relatively simple approach to obtain fundamental thermodynamic information about the protein and the aggregation mechanism, thus providing a new approach to developing accelerated formulation studies below the freezing temperature. PMID:23808610

  17. Precipitation Structure in the Sierra Nevada of California During Winter

    NASA Technical Reports Server (NTRS)

    Pandey, Ganesh R.; Cayan, Daniel R.; Georgakakos, Kostantine P.

    1998-01-01

    The influences of upper air characteristics along the coast of California upon the winter time precipitation in the Sierra Nevada region were investigated. Most precipitation episodes in the Sierra are associated with moist southwesterly winds and also tend to occur when the 700-mb temperature is close to -2 C. This favored wind direction and temperature signifies the equal importance of moisture transport and orographic lifting for maximum precipitation frequency. Making use of this observation, simple linear models were formulated to quantify the precipitation totals observed at different sites as a function of moisture transport. The skill of the model is least for daily precipitation and increases with time scale of aggregation. In terms of incremental gain, the skill of the model is optimal for an aggregation period of 5-7 days, which is also the duration of the most frequent precipitation events in the Sierra. This indicates that upper air moisture transport at can be used to make reasonable estimates of the precipitation totals for most frequent events in the Sierra region.

  18. Photophoretic force on aggregate grains

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin S.; Kimery, Jesse B.; Wurm, Gerhard; de Beule, Caroline; Kuepper, Markus; Hyde, Truell W.

    2016-01-01

    The photophoretic force may impact planetary formation by selectively moving solid particles based on their composition and structure. This generates collision velocities between grains of different sizes and sorts the dust in protoplanetary discs by composition. This numerical simulation studied the photophoretic force acting on fractal dust aggregates of μm-scale radii. Results show that aggregates tend to have greater photophoretic drift velocities than spheres of similar mass or radii, though with a greater spread in the velocity. While the drift velocities of compact aggregates continue to increase as the aggregates grow larger in size, fluffy aggregates have drift velocities which are relatively constant with size. Aggregates formed from an initially polydisperse size distribution of dust grains behave differently from aggregates formed from a monodisperse population, having smaller drift velocities with directions which deviate substantially from the direction of illumination. Results agree with microgravity experiments which show the difference of photophoretic forces with aggregation state.

  19. Characterization of nanoparticle formation and aggregation on mineral surfaces

    SciTech Connect

    Glenn Waychunas; Young-Shin Jun

    2007-04-19

    The research effort in the Waychunas group is focused on the characterization and measurement of processes at the mineral-water interfaces specifically related to the onset of precipitation. This effort maps into one of the main project groups with the Penn State University EMSI (CEKA) known as PIG (Precipitation Interest Group), and involves collaborations with several members of that group. Both synchrotron experimentation and technique development are objectives, with the goals of allowing precipitation from single molecule attachment to sub-monolayer coverage to be detected and analyzed. The problem being addressed is the change in reactivity of mineral interfaces due to passivation or activation by precipitates or sorbates. In the case of passivation, fewer active sites may be involved in reactions with environmental fluids, while in the activated case the precipitate may be much more reactive than the substrate, or result in the creation of a higher density of active sites. We approach this problem by making direct measurements of several types of precipitation reactions: iron-aluminum oxide formation on quartz and other substrates from both homogeneous (in solution) nucleation, and heterogeneous (on the surface) nucleation; precipitation and sorption of silicate monomers and polymers on Fe oxide surfaces; and development of grazing-incidence small angle x-ray scattering (GISAXS) as a tool for in-situ measurement of precipitate growth, morphology and aggregation. We expect that these projects will produce new fundamental information on reactive interface growth, passivation and activation, and be applicable to a wide range of environmental interfaces.

  20. Global Precipitation Measurement Poster

    NASA Technical Reports Server (NTRS)

    Azarbarzin, Art

    2010-01-01

    This poster presents an overview of the Global Precipitation Measurement (GPM) constellation of satellites which are designed to measure the Earth's precipitation. It includes the schedule of launches for the various satellites in the constellation, and the coverage of the constellation, It also reviews the mission capabilities, and the mission science objectives.

  1. PRECIPITATION OF PROTACTINIUM

    DOEpatents

    Moore, R.L.

    1958-07-15

    An lmprovement in the separation of protactinium from aqueous nitric acid solutions is described. 1t covers the use of lead dioxide and tin dioxide as carrier precipitates for the protactinium. In carrying out the process, divalent lead or divalent tin is addcd to the solution and oxidized, causing formation of a carrier precipitate of lead dioxide or stannic oxide, respectively.

  2. The Thorbex precipitation experiment

    NASA Astrophysics Data System (ADS)

    Nína Petersen, Guðrún; Ágústsson, Hálfdán; Ólafsson, Haraldur; Arason, Þórður

    2016-04-01

    During the autumn of 2014, precipitation was observed by a dense network of automatic raingauges covering a 243 m high and steep mountain, Þorbjörn, in the Reykjanes peninsula in SW-Iceland. The experiment is backed by continuous radar observations of winds and precipitation, radiosondes every 12 hours at the nearby Keflavik airport and a number of automatic weather stations. Some of the key results are: -The observations indicate that the average maximum rain over or close to the mountain maybe ~1.7 times the background rain. -Although the precipitation is only liquid, there seems to be great observation errors, likely due to strong winds. This calls for revision of the climatology of precipitation in Iceland and in other windy places. -The maximum wind loss and the spatial variability are of a similar magnitude. This complicates mapping of true precipitation.

  3. Precipitation and floodiness

    NASA Astrophysics Data System (ADS)

    Stephens, E.; Day, J. J.; Pappenberger, F.; Cloke, H.

    2015-12-01

    There are a number of factors that lead to nonlinearity between precipitation anomalies and flood hazard; this nonlinearity is a pertinent issue for applications that use a precipitation forecast as a proxy for imminent flood hazard. We assessed the degree of this nonlinearity for the first time using a recently developed global-scale hydrological model driven by the ERA-Interim/Land precipitation reanalysis (1980-2010). We introduced new indices to assess large-scale flood hazard, or floodiness, and quantified the link between monthly precipitation, river discharge, and floodiness anomalies at the global and regional scales. The results show that monthly floodiness is not well correlated with precipitation, therefore demonstrating the value of hydrometeorological systems for providing floodiness forecasts for decision-makers. A method is described for forecasting floodiness using the Global Flood Awareness System, building a climatology of regional floodiness from which to forecast floodiness anomalies out to 2 weeks.

  4. Proteins aggregation and human diseases

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2015-04-01

    Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

  5. COSMIC DUST AGGREGATION WITH STOCHASTIC CHARGING

    SciTech Connect

    Matthews, Lorin S.; Hyde, Truell W.; Shotorban, Babak

    2013-10-20

    The coagulation of cosmic dust grains is a fundamental process which takes place in astrophysical environments, such as presolar nebulae and circumstellar and protoplanetary disks. Cosmic dust grains can become charged through interaction with their plasma environment or other processes, and the resultant electrostatic force between dust grains can strongly affect their coagulation rate. Since ions and electrons are collected on the surface of the dust grain at random time intervals, the electrical charge of a dust grain experiences stochastic fluctuations. In this study, a set of stochastic differential equations is developed to model these fluctuations over the surface of an irregularly shaped aggregate. Then, employing the data produced, the influence of the charge fluctuations on the coagulation process and the physical characteristics of the aggregates formed is examined. It is shown that dust with small charges (due to the small size of the dust grains or a tenuous plasma environment) is affected most strongly.

  6. Origins of the Earth's Diffuse Auroral Precipitation

    NASA Astrophysics Data System (ADS)

    Ni, Binbin; Thorne, Richard M.; Zhang, Xiaojia; Bortnik, Jacob; Pu, Zuyin; Xie, Lun; Hu, Ze-jun; Han, Desheng; Shi, Run; Zhou, Chen; Gu, Xudong

    2016-04-01

    The Earth's diffuse auroral precipitation provides the major source of energy input into the nightside upper atmosphere and acts as an essential linkage of the magnetosphere-ionosphere coupling. Resonant wave-particle interactions play a dominant role in the scattering of injected plasma sheet electrons, leading to the diffuse auroral precipitation. We review the recent advances in understanding the origin of the diffuse aurora and in quantifying the exact roles of various magnetospheric waves in producing the global distribution of diffuse auroral precipitation and its variability with the geomagnetic activity. Combined scattering by upper-and lower-band chorus accounts for the most intense inner magnetospheric electron diffuse auroral precipitation on the nightside. Dayside chorus can be responsible for the weaker dayside electron diffuse auroral precipitation. Pulsating auroras, the dynamic auroral structures embedded in the diffuse aurora, can be mainly caused by modulation of the excitation of lower band chorus due to macroscopic density variations in the magnetosphere. Electrostatic electron cyclotron harmonic waves are an important or even dominant cause for the nightside electron diffuse auroral precipitation beyond {˜}8Re and can also contribute to the occurrence of the pulsating aurora at high L-shells. Scattering by electromagnetic ion cyclotron waves could quite possibly be the leading candidate responsible for the ion precipitation (especially the reversed-type events of the energy-latitude dispersion) in the regions of the central plasma sheet and ring current. We conclude the review with a summary of current understanding, outstanding questions, and a number of suggestions for future research.

  7. Confirmation of EMIC wave-driven relativistic electron precipitation

    NASA Astrophysics Data System (ADS)

    Hendry, Aaron T.; Rodger, Craig J.; Clilverd, Mark A.; Engebretson, Mark J.; Mann, Ian R.; Lessard, Marc R.; Raita, Tero; Milling, David K.

    2016-06-01

    Electromagnetic ion cyclotron (EMIC) waves are believed to be an important source of pitch angle scattering driven relativistic electron loss from the radiation belts. To date, investigations of this precipitation have been largely theoretical in nature, limited to calculations of precipitation characteristics based on wave observations and small-scale studies. Large-scale investigation of EMIC wave-driven electron precipitation has been hindered by a lack of combined wave and precipitation measurements. Analysis of electron flux data from the POES (Polar Orbiting Environmental Satellites) spacecraft has been suggested as a means of investigating EMIC wave-driven electron precipitation characteristics, using a precipitation signature particular to EMIC waves. Until now the lack of supporting wave measurements for these POES-detected precipitation events has resulted in uncertainty regarding the driver of the precipitation. In this paper we complete a statistical study comparing POES precipitation measurements with wave data from several ground-based search coil magnetometers; we further present a case study examining the global nature of this precipitation. We show that a significant proportion of the precipitation events correspond with EMIC wave detections on the ground; for precipitation events that occur directly over the magnetometers, this detection rate can be as high as 90%. Our results demonstrate that the precipitation region is often stationary in magnetic local time, narrow in L, and close to the expected plasmapause position. Predominantly, the precipitation is associated with helium band rising tone Pc1 waves on the ground. The success of this study proves the viability of POES precipitation data for investigating EMIC wave-driven electron precipitation.

  8. Dynamics of fire ant aggregations

    NASA Astrophysics Data System (ADS)

    Tennenbaum, Michael; Hu, David; Fernandez-Nieves, Alberto

    Fire ant aggregations are an inherently active system. Each ant harvests its own energy and can convert it into motion. The motion of individual ants contributes non-trivially to the bulk material properties of the aggregation. We have measured some of these properties using plate-plate rheology, where the response to an applied external force or deformation is measured. In this talk, we will present data pertaining to the aggregation behavior in the absence of any external force. We quantify the aggregation dynamics by monitoring the rotation of the top plate and by measuring the normal force. We then compare the results with visualizations of 2D aggregations.

  9. Activation of Alpha Chymotrypsin by Three Phase Partitioning Is Accompanied by Aggregation

    PubMed Central

    Rather, Gulam Mohmad; Mukherjee, Joyeeta; Halling, Peter James; Gupta, Munishwar Nath

    2012-01-01

    Precipitation of alpha chymotrypsin in the simultaneous presence of ammonium sulphate and t-butanol (three phase partitioning) resulted in preparations which showed self aggregation of the enzyme molecules. Precipitation with increasing amounts of ammonium sulphate led to increasing size of aggregates. While light scattering estimated the hydrodynamic diameter of these aggregates in the range of 242–1124 nm; Nanoparticle tracking analysis (NTA) gave the value as 130–462 nm. Scanning electron microscopy and gel filtration on Sephadex G-200 showed extensive aggregation in these preparations. Transmission electron microscopy showed that the aggregates had irregular shapes. All the aggregates had about 3× higher catalytic activity than the native enzyme. These aggregates did not differ in λmax of fluorescence emission which was around 340 nm. However, all the aggregates showed higher fluorescence emission intensity. Far-UV and near-UV circular dichroism also showed no significant structural changes as compared to the native molecule. Interestingly, HPLC gel filtration (on a hydroxylated silica column) gave 14 nm as the diameter for all preparations. Light scattering of preparations in the presence of 10% ethylene glycol also dissociated the aggregates to monomers of 14 nm. Both these results indicated that hydrophobic interactions were the driving force behind this aggregation. These results indicate: (1) Even without any major structural change, three phase partitioning led to protein molecules becoming highly prone to aggregation. (2) Different methods gave widely different estimates of sizes of aggregates. It was however possible to reconcile the data obtained with various approaches. (3) The nature of the gel filtration column is crucial and use of this technique for refolding and studying aggregation needs a rethink. PMID:23239966

  10. Cloud and Precipitation Radar

    NASA Astrophysics Data System (ADS)

    Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

    Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

  11. Characterisation of Suspension Precipitated Nanocrystalline Hydroxyapatite Powders

    NASA Astrophysics Data System (ADS)

    Mallik, P. K.; Swain, P. K.; Patnaik, S. C.

    2016-02-01

    Hydroxyapatite (HA) is a well-known biomaterial for coating on femoral implants, filling of dental cavity and scaffold for tissue replacement. Hydroxyapatite possess limited load bearing capacity due to their brittleness. In this paper, the synthesis of nanocrystalline hydroxyapatite powders was prepared by dissolving calcium oxide in phosphoric acid, followed by addition of ammonia liquor in a beaker. The prepared solution was stirred by using magnetic stirrer operated at temperature of 80°C for an hour. This leads to the formation of hydroxyapatite precipitate. The precipitate was dried in oven for overnight at 100°C. The dried agglomerated precipitate was calcined at 800°C in conventional furnace for an hour. The influence of calcium oxide concentration and pH on the resulting precipitates was studied using BET, XRD and SEM. As result, a well-defined sub-rounded morphology of powders size of ∼41 nm was obtained with a salt concentration of 0.02 M. Finally, it can be concluded that small changes in the reaction conditions led to large changes in final size, shape and degree of aggregation of the hydroxyapatite particles.

  12. MINERAL-SURFACTANT INTERACTIONS FOR MINIMUM REAGENTS PRECIPITATION AND ADSORPTION FOR IMPROVED OIL RECOVERY

    SciTech Connect

    P. Somasundaran

    2005-04-30

    The aim of this project is to delineate the role of mineralogy of reservoir rocks in determining interactions between reservoir minerals and externally added reagents (surfactants/polymers) and its effect on critical solid-liquid and liquid-liquid interfacial properties such as adsorption, wettability and interfacial tension in systems relevant to reservoir conditions. Previous studies have suggested that significant surfactant loss by precipitation or adsorption on reservoir minerals can cause chemical schemes to be less than satisfactory for enhanced oil recovery. Both macroscopic adsorption, wettability and microscopic orientation and conformation studies for various surfactant/polymer mixtures/reservoir rocks systems were conducted to explore the cause of chemical loss by means of precipitation or adsorption, and the effect of rock mineralogy on the chemical loss. During this period, the adsorption of mixed system of n-dodecyl-{beta}-D-maltoside (DM) and dodecyl sulfonate (C{sub 12}SO{sub 3}Na) has been studied. The effects of solution pH, surfactant mixing ratio and different salts on surfactant adsorption on alumina have been investigated in detail. Along with these adsorption studies, changes in mineral wettability due to the adsorption of the mixtures were determined under relevant conditions to identify the nano-structure of the adsorbed layers. Solution properties of C{sub 12}SO{sub 3}Na/DM mixtures were also studied to identify surfactant interactions that affect the mixed aggregate formation in solution. Adsorption of SDS on gypsum and limestone suggested stronger surfactant/mineral interaction than on alumina, due to the precipitation of surfactant by dissolved calcium ions. The effects of different salts such as sodium nitrate, sodium sulfite and sodium chloride on DM adsorption on alumina have also been determined. As surfactant hemimicelles at interface and micelles in solution have drastic effects on oil recovery processes, their microstructures in

  13. Chemisorption And Precipitation Reactions

    EPA Science Inventory

    The transport and bioavailability of chemical components within soils is, in part, controlled by partitioning between solids and solution. General terms used to describe these partitioning reactions include chemisorption and precipitation. Chemisorption is inclusive of the suit...

  14. Precipitation Estimates for Hydroelectricity

    NASA Technical Reports Server (NTRS)

    Tapiador, Francisco J.; Hou, Arthur Y.; de Castro, Manuel; Checa, Ramiro; Cuartero, Fernando; Barros, Ana P.

    2011-01-01

    Hydroelectric plants require precise and timely estimates of rain, snow and other hydrometeors for operations. However, it is far from being a trivial task to measure and predict precipitation. This paper presents the linkages between precipitation science and hydroelectricity, and in doing so it provides insight into current research directions that are relevant for this renewable energy. Methods described include radars, disdrometers, satellites and numerical models. Two recent advances that have the potential of being highly beneficial for hydropower operations are featured: the Global Precipitation Measuring (GPM) mission, which represents an important leap forward in precipitation observations from space, and high performance computing (HPC) and grid technology, that allows building ensembles of numerical weather and climate models.

  15. My NASA Data Precipitation

    NASA Video Gallery

    This lesson has two activities that help students develop a basic understanding of the relationship between cloud type and the form of precipitation and the relationship between the amount of water...

  16. IMERG Global Precipitation Rates

    NASA Video Gallery

    NASA's Global Precipitation Measurement mission has produced its first global map of rainfall and snowfall. The GPM Core Observatory launched one year ago on Feb. 27, 2014 as a collaboration betwee...

  17. Hydride precipitation in titanium

    SciTech Connect

    Numakura, H.; Kowia, M.

    1984-10-01

    The crystal structure and morphology of hydride (deuteride) precipitates are investigated on ..cap alpha..-titanium specimens containing 1-3 at.% H or D by transmission electron microscopy. The hydride is found to have a face-centered tetragonal structure (c/a = 1.09) with an ordered arrangement of hydrogen, being isomorphous to ..gamma..-zirconium hydride. Two types of precipitation mode are observed with the habit planes (0110) and near (0225).

  18. Aluminosilicate Precipitation Impact on Uranium

    SciTech Connect

    WILMARTH, WILLIAM

    2006-03-10

    Experiments have been conducted to examine the fate of uranium during the formation of sodium aluminosilicate (NAS) when wastes containing high aluminate concentrations are mixed with wastes of high silicate concentration. Testing was conducted at varying degrees of uranium saturation. Testing examined typical tank conditions, e.g., stagnant, slightly elevated temperature (50 C). The results showed that under sub-saturated conditions uranium is not removed from solution to any large extent in both simulant testing and actual tank waste testing. This aspect was not thoroughly understood prior to this work and was necessary to avoid criticality issues when actual tank wastes were aggregated. There are data supporting a small removal due to sorption of uranium on sites in the NAS. Above the solubility limit the data are clear that a reduction in uranium concentration occurs concomitant with the formation of aluminosilicate. This uranium precipitation is fairly rapid and ceases when uranium reaches its solubility limit. At the solubility limit, it appears that uranium is not affected, but further testing might be warranted.

  19. Taurine and platelet aggregation

    SciTech Connect

    Nauss-Karol, C.; VanderWende, C.; Gaut, Z.N.

    1986-03-01

    Taurine is a putative neurotransmitter or neuromodulator. The endogenous taurine concentration in human platelets, determined by amino acid analysis, is 15 ..mu..M/g. In spite of this high level, taurine is actively accumulated. Uptake is saturable, Na/sup +/ and temperature dependent, and suppressed by metabolic inhibitors, structural analogues, and several classes of centrally active substances. High, medium and low affinity transport processes have been characterized, and the platelet may represent a model system for taurine transport in the CNS. When platelets were incubated with /sup 14/C-taurine for 30 minutes, then resuspended in fresh medium and reincubated for one hour, essentially all of the taurine was retained within the cells. Taurine, at concentrations ranging from 10-1000 ..mu..M, had no effect on platelet aggregation induced by ADP or epinephrine. However, taurine may have a role in platelet aggregation since 35-39% of the taurine taken up by human platelets appears to be secreted during the release reaction induced by low concentrations of either epinephrine or ADP, respectively. This release phenomenon would imply that part of the taurine taken up is stored directly in the dense bodies of the platelet.

  20. PRECIPITATION OF URANIUM PEROXIDE OF LOW FLUORIDE CONTENT FROM SOLUTIONS CONTAINING FLUORIDES

    DOEpatents

    King, E.J.; Clark, H.M.

    1958-08-12

    S>A method is described for the preparation of fluoride free uraniunn peroxide precipitates, even though the solution from which the precipitation is made is contaminated with fluorides. This is accomplished by add ing aluminum ions to the solution, where they complex any fluoride present and prevent its precipitation with the uramum peroxide.

  1. Evaluation of precipitates used in strainer head loss testing : Part I. chemically generated precipitates.

    SciTech Connect

    Bahn, C. B.; Kasza, K. E.; Shack, W. J.; Natesan, K.; Klein, P.; Nuclear Engineering Division

    2009-12-01

    The purpose of the current program was to evaluate the properties of chemical precipitates proposed by industry that have been used in sump strainer head loss testing. Specific precipitates that were evaluated included aluminum oxyhydroxide (AlOOH) and sodium aluminum silicate (SAS) prepared according to the procedures in WCAP-16530-NP, along with precipitates formed from injecting chemicals into the test loop according to the procedure used by one sump strainer test vendor for U.S. pressurized water reactors. The settling rates of the surrogate precipitates are strongly dependent on their particle size and are reasonably consistent with those expected from Stokes Law or colloid aggregation models. Head loss tests showed that AlOOH and SAS surrogates are quite effective in increasing the head loss across a perforated pump inlet strainer that has an accumulated fibrous debris bed. The characteristics of aluminum hydroxide precipitate using sodium aluminate were dependent on whether it was formed in high-purity or ordinary tap water and whether excess silicate was present or not.

  2. Aqueous formation and manipulation of the iron-oxo Keggin ion

    NASA Astrophysics Data System (ADS)

    Sadeghi, Omid; Zakharov, Lev N.; Nyman, May

    2015-03-01

    There is emerging evidence that growth of synthetic and natural phases occurs by the aggregation of prenucleation clusters, rather than classical atom-by-atom growth. Ferrihydrite, an iron oxyhydroxide mineral, is the common form of Fe3+ in soils and is also in the ferritin protein. We isolated a 10 angstrom discrete iron-oxo cluster (known as the Keggin ion, Fe13) that has the same structural features as ferrihydrite. The stabilization and manipulation of this highly reactive polyanion in water is controlled exclusively by its counterions. Upon dissolution of Fe13 in water with precipitation of its protecting Bi3+-counterions, it rapidly aggregates to ~22 angstrom spherical ferrihydrite nanoparticles. Fe13 may therefore also be a prenucleation cluster for ferrihydrite formation in natural systems, including by microbial and cellular processes.

  3. The Sensitivity of Orographic Precipitation to Flow Direction

    NASA Astrophysics Data System (ADS)

    Mass, C.; Picard, L.

    2015-12-01

    An area of substantial interest is the sensitivity of orographic precipitation to the characteristics of the incoming flow and to the surrounding environment. Some studies have suggested substantial sensitivity of precipitation within individual river drainages for relatively small directional or stability variations of incoming flow. A characterization of such flow sensitivity would be of great value for hydrometeorological prediction, the determination of Probable Maximum Precipitation statistics, and for quantifying the uncertainty in precipitation and hydrological forecasts. To gain insight into this problem, an idealized version of the Weather Research and Forecasting (WRF) modeling system was created in which simulations are driven by a single vertical sounding, with the assumption of thermal wind balance. The actual terrain is used and the full physics complement of the modeling system. The presentation will show how precipitation over the Olympic Mountains of Washington State varies as flow direction changes. This analysis will include both the aggregate precipitation over the barrier and the precipitation within individual drainages or areas. The role of surrounding terrain and the nearby coastline are also examined by removing these features from simulations. Finally, the impact of varying flow stability and speed on the precipitation over this orographic feature will be described.

  4. Bioactivity of Mg-ion-implanted zirconia and titanium

    NASA Astrophysics Data System (ADS)

    Liang, H.; Wan, Y. Z.; He, F.; Huang, Y.; Xu, J. D.; Li, J. M.; Wang, Y. L.; Zhao, Z. G.

    2007-01-01

    Titanium and zirconia are bioinert materials lacking bioactivity. In this work, surface modification of the two typical biomaterials is conducted by Mg-ion-implantation using a MEVVA ion source in an attempt to increase their bioactivity. Mg ions were implanted into zirconia and titanium with fluences ranging from 1 × 10 17 to 3 × 10 17 ions/cm 2 at 40 keV. The Mg-implanted samples, as well as control (unimplanted) samples, were immersed in SBF for 7 days and then removed to identify the presence of calcium and phosphate (Ca-P) coatings and to characterize their morphology and structure by SEM, XRD, and FT-IR. SEM observations confirm that globular aggregates are formed on the surfaces of the Mg-implanted zirconia and titanium while no precipitates are observed on the control samples. XRD and FT-IR analyses reveal that the deposits are carbonated hydroxyapatite (HAp). Our experimental results demonstrate that Mg-implantation improves the bioactivity of zirconia and titanium. Further, it is found that the degree of bioactivity is adjustable by the ion dose. Mechanisms are proposed to interpret the improvement of bioactivity as a result of Mg implantation and the difference in bioactivity between zirconia and titanium.

  5. Precipitation titration of perchlorate using new titrants

    SciTech Connect

    Selig, W.

    1980-05-01

    We have evaluated the following new titrants for the potentiometric precipitation titration of perchlorate: cetyltrimethylammonium chloride (CETAC), cetyltrimethylammonium bromide (CETAB), cetylpyridinium chloride (CPC), and benzyldimethyltetradecylammonium chloride (BDTAC). Titrations were monitored with a fluoroborate ion-selective electrode (ISE) and a double-junction reference electrode. The titration system was controlled by a Tektronix 4051 graphics system. The perchlorate, nitrate, and calcium ISE may also be used to monitor emf's. 7 tables, 2 figures.

  6. Holographic characterization of protein aggregates

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhong, Xiao; Ruffner, David; Stutt, Alexandra; Philips, Laura; Ward, Michael; Grier, David

    Holographic characterization directly measures the size distribution of subvisible protein aggregates in suspension and offers insights into their morphology. Based on holographic video microscopy, this analytical technique records and interprets holograms of individual aggregates in protein solutions as they flow down a microfluidic channel, without requiring labeling or other exceptional sample preparation. The hologram of an individual protein aggregate is analyzed in real time with the Lorenz-Mie theory of light scattering to measure that aggregate's size and optical properties. Detecting, counting and characterizing subvisible aggregates proceeds fast enough for time-resolved studies, and lends itself to tracking trends in protein aggregation arising from changing environmental factors. No other analytical technique provides such a wealth of particle-resolved characterization data in situ. Holographic characterization promises accelerated development of therapeutic protein formulations, improved process control during manufacturing, and streamlined quality assurance during storage and at the point of use. Mrsec and MRI program of the NSF, Spheryx Inc.

  7. Dye-sensitized solar cell employing zinc oxide aggregates grown in the presence of lithium

    DOEpatents

    Zhang, Qifeng; Cao, Guozhong

    2013-10-15

    Provided are a novel ZnO dye-sensitized solar cell and method of fabricating the same. In one embodiment, deliberately added lithium ions are used to mediate the growth of ZnO aggregates. The use of lithium provides ZnO aggregates that have advantageous microstructure, morphology, crystallinity, and operational characteristics. Employing lithium during aggregate synthesis results in a polydisperse collection of ZnO aggregates favorable for porosity and light scattering. The resulting nanocrystallites forming the aggregates have improved crystallinity and more favorable facets for dye molecule absorption. The lithium synthesis improves the surface stability of ZnO in acidic dyes. The procedures developed and disclosed herein also help ensure the formation of an aggregate film that has a high homogeneity of thickness, a high packing density, a high specific surface area, and good electrical contact between the film and the fluorine-doped tin oxide electrode and among the aggregate particles.

  8. Anodic Stripping Voltammetry of Silver Nanoparticles: Aggregation Leads to Incomplete Stripping

    PubMed Central

    Cloake, Samantha J; Toh, Her Shuang; Lee, Patricia T; Salter, Chris; Johnston, Colin; Compton, Richard G

    2015-01-01

    The influence of nanoparticle aggregation on anodic stripping voltammetry is reported. Dopamine-capped silver nanoparticles were chosen as a model system, and melamine was used to induce aggregation in the nanoparticles. Through the anodic stripping of the silver nanoparticles that were aggregated to different extents, it was found that the peak area of the oxidative signal corresponding to the stripping of silver to silver(I) ions decreases with increasing aggregation. Aggregation causes incomplete stripping of the silver nanoparticles. Two possible mechanisms of ‘partial oxidation’ and ‘inactivation’ of the nanoparticles are proposed to account for this finding. Aggregation effects must be considered when anodic stripping voltammetry is used for nanoparticle detection and quantification. Hence, drop casting, which is known to lead to aggregation, is not encouraged for preparing electrodes for analytical purposes. PMID:25861566

  9. Aggregation kinetics and dissolution of coated silver nanoparticles.

    PubMed

    Li, Xuan; Lenhart, John J; Walker, Harold W

    2012-01-17

    Determining the fate of manufactured nanomaterials in the environment is contingent upon understanding how stabilizing agents influence the stability of nanoparticles in aqueous systems. In this study, the aggregation and dissolution tendencies of uncoated silver nanoparticles and the same particles coated with three common coating agents, trisodium citrate, sodium dodecyl sulfate (SDS), and Tween 80 (Tween), were evaluated. Early stage aggregation kinetics of the uncoated and coated silver nanoparticles were assessed by dynamic light scattering over a range of electrolyte types (NaCl, NaNO(3), and CaCl(2)) and concentrations that span those observed in natural waters. Although particle dissolution was observed, aggregation of all particle types was still consistent with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The aggregation of citrate-coated particles and SDS-coated particles were very similar to that for the uncoated particles, as the critical coagulation concentrations (CCC) of the particles in different electrolytes were all approximately the same (40 mM NaCl, 30 mM NaNO(3), and 2 mM CaCl(2)). The Tween-stabilized particles were significantly more stable than the other particles, however, and in NaNO(3) aggregation was not observed up to an electrolyte concentration of 1 M. Differences in the rate of aggregation under diffusion-limited aggregation conditions at high electrolyte concentrations for the SDS and Tween-coated particles, in combination with the moderation of their electrophoretic mobilities, suggest SDS and Tween imparted steric interactions to the particles. The dissolution of the silver nanoparticles was inhibited by the SDS and Tween coatings, but not by the citrate coating, and in chloride-containing electrolytes a secondary precipitate of AgCl was observed bridging the individual particles. These results indicate that coating agents could significant influence the fate of silver nanoparticles in aquatic systems, and in some

  10. Precipitation of heterogeneous nanostructures: Metal nanoparticles and dielectric nanocrystallites

    SciTech Connect

    Masai, Hirokazu; Takahashi, Yoshihiro; Fujiwara, Takumi; Tokuda, Yomei; Yoko, Toshinobu

    2010-07-15

    Heterogeneous precipitation of nanocrystallites of metallic Bi and anatase was observed in CaO-Bi{sub 2}O{sub 3}-B{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-TiO{sub 2} glass-ceramics. Addition of AlN reduced the Bi{sub 2}O{sub 3} to Bi metal nanoparticles, which were uniformly dispersed in the glass. After heat-treatment of the Bi-precipitated glass around the glass transition temperature, nanocrystalline anatase precipitated out without aggregation of the Bi metal particles. It was found that the anatase nanocrystal size was affected by the distance between a nanocrystal and a precipitated Bi nanoparticle. The glass-ceramic produced is a functional material containing a random dispersion of different types of nanoparticles with different dielectric constants.

  11. Influence of temperature and solvent on the precipitation of asphaltenes

    SciTech Connect

    Andersen, S.I.; Birdi, K.S. )

    1990-01-01

    Asphaltenes has been precipitated from a Kuwait flash residue using different n-alkanes (n-C5 to n-C8) at various temperatures ranging from 4{degrees}C to reflux temperatures of the used precipitants. Structures in the asphaltenes fractions has been revealed using U.V. fluorescence spectroscopy, elemental analysis and to some extent 1H-nmr. The analysis shows that asphaltenes precipitated in the same amount but at different temperature and with different solvents have merely the same composition. For all n-alkanes the curves of precipitated amount versus temperature show maxima at about 25{degrees}C, implying a shift in the solubility of the asphaltenes. The impact of alkane chain length on the aggregation of asphaltenes through hydrogen bonds is discussed using the alkane-alcohol system as a model. The asphaltene solubility is discussed with the help of the Scatchard--Hildebrand equation.

  12. Aggregation dynamics of rigid polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Tom, Anvy Moly; Rajesh, R.; Vemparala, Satyavani

    2016-01-01

    Similarly charged polyelectrolytes are known to attract each other and aggregate into bundles when the charge density of the polymers exceeds a critical value that depends on the valency of the counterions. The dynamics of aggregation of such rigid polyelectrolytes are studied using large scale molecular dynamics simulations. We find that the morphology of the aggregates depends on the value of the charge density of the polymers. For values close to the critical value, the shape of the aggregates is cylindrical with height equal to the length of a single polyelectrolyte chain. However, for larger values of charge, the linear extent of the aggregates increases as more and more polymers aggregate. In both the cases, we show that the number of aggregates decrease with time as power laws with exponents that are not numerically distinguishable from each other and are independent of charge density of the polymers, valency of the counterions, density, and length of the polyelectrolyte chain. We model the aggregation dynamics using the Smoluchowski coagulation equation with kernels determined from the molecular dynamics simulations and justify the numerically obtained value of the exponent. Our results suggest that once counterions condense, effective interactions between polyelectrolyte chains short-ranged and the aggregation of polyelectrolytes are diffusion-limited.

  13. Precipitating factors of insomnia.

    PubMed

    Bastien, Célyne H; Vallières, Annie; Morin, Charles M

    2004-01-01

    Insomnia is a prevalent health complaint whose onset is precipitated by a variety of factors. There is an important need to identify and describe these factors to improve our understanding of risk factors and the natural history of insomnia. This article is aimed at identifying and describing the types of precipitating factors related to the onset of insomnia. A total of 345 patients evaluated for insomnia at a sleep-disorders clinic completed a sleep survey and underwent a semistructured clinical interview. As part of the evaluation, the specific precipitating events related to the onset of insomnia were identified. Subsequently, these factors were categorized (work-school, family, physical or psychological health, or indeterminate), and their affective valence (negative, positive, or indeterminate) was coded. The most common precipitating factors of insomnia were related to family, health, and work-school events. Sixty-five percent of precipitating events had a negative valence. These events differed with the age of onset of insomnia but not with the gender of participants. These findings are useful to identify potential risk factors for insomnia and improve our understanding of the natural history of insomnia. PMID:15600224

  14. Copper Oxide Precipitates in NBS Standard Reference Material 482

    PubMed Central

    Windsor, Eric S.; Carlton, Robert A.; Gillen, Greg; Wight, Scott A.; Bright, David S.

    2002-01-01

    Copper oxide has been detected in the copper containing alloys of NBS Standard Reference Material (SRM) 482. This occurrence is significant because it represents heterogeneity within a standard reference material that was certified to be homogeneous on a micrometer scale. Oxide occurs as elliptically to spherically shaped precipitates whose size differs with alloy composition. The largest precipitates occur in the Au20-Cu80 alloy and range in size from submicrometer up to 2 μm in diameter. Precipitates are observed using light microscopy, electron microscopy, and secondary ion mass spectrometry (SIMS). SIMS has demonstrated that the precipitates are present within all the SRM 482 wires that contain copper. Only the pure gold wire is precipitate free. Initial results from the analysis of the Au20-Cu80 alloy indicate that the percentage of precipitates is less than 1 % by area. Electron probe microanalysis (EPMA) of large (2 μm) precipitates in this same alloy indicates that precipitates are detectable by EPMA and that their composition differs significantly from the certified alloy composition. The small size and low percentage of these oxide precipitates minimizes the impact that they have upon the intended use of this standard for electron probe microanalysis. Heterogeneity caused by these oxide precipitates may however preclude the use of this standard for automated EPMA analyses and other microanalysis techniques. PMID:27446759

  15. Copper Oxide Precipitates in NBS Standard Reference Material 482.

    PubMed

    Windsor, Eric S; Carlton, Robert A; Gillen, Greg; Wight, Scott A; Bright, David S

    2002-01-01

    Copper oxide has been detected in the copper containing alloys of NBS Standard Reference Material (SRM) 482. This occurrence is significant because it represents heterogeneity within a standard reference material that was certified to be homogeneous on a micrometer scale. Oxide occurs as elliptically to spherically shaped precipitates whose size differs with alloy composition. The largest precipitates occur in the Au20-Cu80 alloy and range in size from submicrometer up to 2 μm in diameter. Precipitates are observed using light microscopy, electron microscopy, and secondary ion mass spectrometry (SIMS). SIMS has demonstrated that the precipitates are present within all the SRM 482 wires that contain copper. Only the pure gold wire is precipitate free. Initial results from the analysis of the Au20-Cu80 alloy indicate that the percentage of precipitates is less than 1 % by area. Electron probe microanalysis (EPMA) of large (2 μm) precipitates in this same alloy indicates that precipitates are detectable by EPMA and that their composition differs significantly from the certified alloy composition. The small size and low percentage of these oxide precipitates minimizes the impact that they have upon the intended use of this standard for electron probe microanalysis. Heterogeneity caused by these oxide precipitates may however preclude the use of this standard for automated EPMA analyses and other microanalysis techniques. PMID:27446759

  16. A cluster-optimizing regression-based approach for precipitation spatial downscaling in mountainous terrain

    NASA Astrophysics Data System (ADS)

    Guan, Huade; Wilson, John L.; Xie, Hongjie

    2009-09-01

    SummaryPrecipitation temporal and spatial variability often controls terrestrial hydrological processes and states. Common remote-sensing and modeling precipitation products have a spatial resolution that is often too coarse to reveal hydrologically important spatial variability. A statistical algorithm was developed for downscaling low-resolution spatial precipitation fields. This algorithm auto-searches precipitation spatial structures (rain-pixel clusters), and orographic effects on precipitation distribution without prior knowledge of atmospheric setting. It is composed of three components: rain-pixel clustering, multivariate regression, and random cascade. The only required input data for the downscaling algorithm are coarse-pixel precipitation map and a topographic map. The algorithm was demonstrated with 4 km × 4 km Next Generation Radar (NEXRAD) precipitation fields, and tested by downscaling NEXRAD-aggregated 16 km × 16 km precipitation fields to 4 km × 4 km pixel precipitation, which was then compared to the original NEXRAD data. The demonstration and testing were performed at both daily and hourly temporal resolutions for the northern New Mexico mountainous terrain and the central Texas Hill Country. The algorithm downscaled daily precipitation fields are in good agreement with the original 4 km × 4 km NEXRAD precipitation, as measured by precipitation spatial structures and the statistics between the downscaling and the original NEXRAD precipitation maps. For three daily precipitation events, downscaled precipitation map reproduces precipitation variance of the disaggregation field, and with Pearson correlation coefficients between the downscaled map and the NEXRAD map of 0.65, 0.71, and 0.80. The algorithm does not perform as well on downscaling hourly precipitation fields at the examined scale range (from 16 km to 4 km), which underestimates precipitation variance of the disaggregation field. For a scale range from 4 km to 1 km, the algorithm has

  17. Phase-field modeling of two-dimensional solute precipitation/dissolution: Solid fingers and diffusion-limited precipitation

    SciTech Connect

    Zhijie Xu; Paul Meakin

    2011-01-01

    Two-dimensional dendritic growth due to solute precipitation was simulated using a phase-field model reported earlier [Z. Xu and P. Meakin, J. Chem. Phys. 129, 014705 (2008)]. It was shown that diffusion-limited precipitation due to the chemical reaction at the solid–liquid interface has similarities with diffusion-limited aggregation (DLA). The diffusion-limited precipitation is attained by setting the chemical reaction rate much larger compared to the solute diffusion to eliminate the effect of the interface growth kinetics. The phase-field simulation results were in reasonable agreement with the analytical solutions. The fractal solid fingers can be formed in the diffusion-limited precipitation and have a fractal dimension measured df = 1.68, close to 1.64, the fractal dimensionality of large square lattice DLA clusters.

  18. Phase-field modeling of two-dimensional solute precipitation/dissolution: Solid fingers and diffusion-limited precipitation

    NASA Astrophysics Data System (ADS)

    Xu, Zhijie; Meakin, Paul

    2011-01-01

    Two-dimensional dendritic growth due to solute precipitation was simulated using a phase-field model reported earlier [Z. Xu and P. Meakin, J. Chem. Phys. 129, 014705 (2008)]. It was shown that diffusion-limited precipitation due to the chemical reaction at the solid-liquid interface has similarities with diffusion-limited aggregation (DLA). The diffusion-limited precipitation is attained by setting the chemical reaction rate much larger compared to the solute diffusion to eliminate the effect of the interface growth kinetics. The phase-field simulation results were in reasonable agreement with the analytical solutions. The fractal solid fingers can be formed in the diffusion-limited precipitation and have a fractal dimension measured d_f = 1.68, close to 1.64, the fractal dimensionality of large square lattice DLA clusters.

  19. Precipitation-Regulated Feedback

    NASA Astrophysics Data System (ADS)

    Voit, Mark

    2016-07-01

    Star formation in the central galaxies of galaxy clusters appears to be fueled by precipitation of cold clouds out of hot circumgalactic gas via thermal instability. I will present both observational and theoretical support for the precipitation mode in large galaxies and discuss how it can be implemented in cosmological simulations of galaxy evolution. Galaxy cluster cores are unique laboratories for studying the astrophysics of thermal instability and may be teaching us valuable lessons about how feedback works in galaxies spanning the entire mass spectrum.

  20. Quantitative characterization of non-classic polarization of cations on clay aggregate stability.

    PubMed

    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

  1. 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

  2. Supramolecular aggregates in vacuum: positively monocharged sodium alkanesulfonate clusters.

    PubMed

    Bongiorno, David; Ceraulo, Leopoldo; Giorgi, Gianluca; Indelicato, Serena; Ruggirello, Angela; Turco Liveri, Vincenzo

    2010-01-01

    The formation and structural features of positively monocharged aggregates of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium methane--(MetS), butane--(ButS) and octane--(OctS) sulfonate molecules in gas phase have been investigated by electrospray ionization mass spectrometry, energy resolved mass spectrometry and density functional theory (DFT) calculations. The experimental results show that the center-of-mass collision energy required to dissociate 50% of these monocharged aggregates scantly depends on the length of the alkyl chain as well as on the aggregation number. This, together with the large predominance of monocharged species in the mass spectra, was rationalized in terms of an aggregation pattern mainly driven by the counter ions and head groups electrostatic interactions while minor effects were attributed to the steric hindrance caused by the size of the surfactant head group and alkyl chain. DFT calculations show that the most favoured structural arrangement of these aggregates is always characterized by an internal polar core constituted by the sodium counter ions and surfactant head groups surrounded by an external layer composed by the surfactant alkyl chains. PMID:20065519

  3. Peptide aggregation in neurodegenerative disease.

    PubMed

    Murphy, Regina M

    2002-01-01

    In the not-so-distant past, insoluble aggregated protein was considered as uninteresting and bothersome as yesterday's trash. More recently, protein aggregates have enjoyed considerable scientific interest, as it has become clear that these aggregates play key roles in many diseases. In this review, we focus attention on three polypeptides: beta-amyloid, prion, and huntingtin, which are linked to three feared neurodegenerative diseases: Alzheimer's, "mad cow," and Huntington's disease, respectively. These proteins lack any significant primary sequence homology, yet their aggregates possess very similar features, specifically, high beta-sheet content, fibrillar morphology, relative insolubility, and protease resistance. Because the aggregates are noncrystalline, secrets of their structure at nanometer resolution are only slowly yielding to X-ray diffraction, solid-state NMR, and other techniques. Besides structure, the aggregates may possess similar pathways of assembly. Two alternative assembly pathways have been proposed: the nucleation-elongation and the template-assisted mode. These two modes may be complementary, not mutually exclusive. Strategies for interfering with aggregation, which may provide novel therapeutic approaches, are under development. The structural similarities between protein aggregates of dissimilar origin suggest that therapeutic strategies successful against one disease may have broad utility in others. PMID:12117755

  4. Topics in Probabilistic Judgment Aggregation

    ERIC Educational Resources Information Center

    Wang, Guanchun

    2011-01-01

    This dissertation is a compilation of several studies that are united by their relevance to probabilistic judgment aggregation. In the face of complex and uncertain events, panels of judges are frequently consulted to provide probabilistic forecasts, and aggregation of such estimates in groups often yield better results than could have been made…

  5. Mineral of the month: aggregates

    USGS Publications Warehouse

    Tepordei, Valentin V.

    2005-01-01

    Natural aggregates, consisting of crushed stone, and sand and gravel, are a major contributor to economic health, and have an amazing variety of uses. Aggregates are among the most abundant mineral resources and are major basic raw materials used by construction, agriculture and other industries that employ complex chemical and metallurgical processes.

  6. Mechanics of fire ant aggregations

    NASA Astrophysics Data System (ADS)

    Tennenbaum, Michael; Liu, Zhongyang; Hu, David; Fernandez-Nieves, Alberto

    2016-01-01

    Fire ants link their bodies to form aggregations; these can adopt a variety of structures, they can drip and spread, or withstand applied loads. Here, by using oscillatory rheology, we show that fire ant aggregations are viscoelastic. We find that, at the lowest ant densities probed and in the linear regime, the elastic and viscous moduli are essentially identical over the spanned frequency range, which highlights the absence of a dominant mode of structural relaxation. As ant density increases, the elastic modulus rises, which we interpret by alluding to ant crowding and subsequent jamming. When deformed beyond the linear regime, the aggregation flows, exhibiting shear-thinning behaviour with a stress load that is comparable to the maximum load the aggregation can withstand before individual ants are torn apart. Our findings illustrate the rich, collective mechanical behaviour that can arise in aggregations of active, interacting building blocks.

  7. Mechanics of fire ant aggregations.

    PubMed

    Tennenbaum, Michael; Liu, Zhongyang; Hu, David; Fernandez-Nieves, Alberto

    2016-01-01

    Fire ants link their bodies to form aggregations; these can adopt a variety of structures, they can drip and spread, or withstand applied loads. Here, by using oscillatory rheology, we show that fire ant aggregations are viscoelastic. We find that, at the lowest ant densities probed and in the linear regime, the elastic and viscous moduli are essentially identical over the spanned frequency range, which highlights the absence of a dominant mode of structural relaxation. As ant density increases, the elastic modulus rises, which we interpret by alluding to ant crowding and subsequent jamming. When deformed beyond the linear regime, the aggregation flows, exhibiting shear-thinning behaviour with a stress load that is comparable to the maximum load the aggregation can withstand before individual ants are torn apart. Our findings illustrate the rich, collective mechanical behaviour that can arise in aggregations of active, interacting building blocks. PMID:26501413

  8. Molecular aggregation of humic substances

    USGS Publications Warehouse

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  9. Imbibition kinetics of spherical aggregates

    NASA Astrophysics Data System (ADS)

    Hébraud, Pascal; Lootens, Didier; Debacker, Alban

    The imbibition kinetics of a millimeter-sized aggregate of 300 nm diameter colloidal particles by a wetting pure solvent is studied. Three successive regimes are observed : in the first one, the imbibition proceeds by compressing the air inside the aggregate. Then, the solvent stops when the pressure of the compressed air is equal to the Laplace pressure at the meniscus of the wetting solvent in the porous aggregate. The interface is pinned and the aggregate slowly degases, up to a point where the pressure of the entrapped air stops decreasing and is controlled by the Laplace pressure of small bubbles. Depending on the curvature of the bubble, the system may then be in an unstable state. The imbibition then starts again, but with an inner pressure in equilibrium with these bubbles. This last stage leads to the complete infiltration of the aggregate.

  10. Immunogenicity of Therapeutic Protein Aggregates.

    PubMed

    Moussa, Ehab M; Panchal, Jainik P; Moorthy, Balakrishnan S; Blum, Janice S; Joubert, Marisa K; Narhi, Linda O; Topp, Elizabeth M

    2016-02-01

    Therapeutic proteins have a propensity for aggregation during manufacturing, shipping, and storage. The presence of aggregates in protein drug products can induce adverse immune responses in patients that may affect safety and efficacy, and so it is of concern to both manufacturers and regulatory agencies. In this vein, there is a lack of understanding of the physicochemical determinants of immunological responses and a lack of standardized analytical methods to survey the molecular properties of aggregates associated with immune activation. In this review, we provide an overview of the basic immune mechanisms in the context of interactions with protein aggregates. We then critically examine the literature with emphasis on the underlying immune mechanisms as they relate to aggregate properties. Finally, we highlight the gaps in our current understanding of this issue and offer recommendations for future research. PMID:26869409

  11. Pulsed electric field (PEF)-induced aggregation between lysozyme, ovalbumin and ovotransferrin in multi-protein system.

    PubMed

    Wu, Li; Zhao, Wei; Yang, Ruijin; Yan, Wenxu

    2015-05-15

    The aggregation of multi-proteins is of great interest in food processing and a good understanding of the formation of aggregates during PEF processing is needed for the application of the process to pasteurize protein-based foods. The aggregates formation of a multi-protein system (containing ovalbumin, ovotransferrin and lysozyme) was studied through turbidity, size exclusion chromatography and SDS-PAGE patterns for interaction studies and binding forces. Results from size exclusion chromatography indicated that there was no soluble aggregates formed during PEF processing. The existence of lysozyme was important to form insoluble aggregates in the chosen ovalbumin solution. The results of SDS-PAGE patterns indicated that lysozyme was prone to precipitate, and was relatively the higher component of aggregates. Citric acid could be effective in inhibiting lysozyme from interacting with other proteins during PEF processing. Blocking the free sulphydryl by N-ethylmaleimide (NEM) did not affect aggregation inhibition. PMID:25577059

  12. EFFECTS OF ACID PRECIPITATION

    EPA Science Inventory

    Recent reviews of available data indicate that precipitation in a large region of North America is highly acidic when its pH is compared with the expected pH value of 5.65 for pure rain water in equilibrium with CO2. A growing body of evidence suggests that acid rain is responsib...

  13. Global precipitation measurement (GPM)

    NASA Astrophysics Data System (ADS)

    Neeck, Steven P.; Flaming, Gilbert M.; Adams, W. James; Smith, Eric A.

    2001-12-01

    The National Aeronautics and Space Administration (NASA) is studying options for future space-based missions for the EOS Follow-on Era (post 2003), building upon the measurements made by Pre-EOS and EOS First Series Missions. One mission under consideration is the Global Precipitation Measurement (GPM), a cooperative venture of NASA, Japan, and other international partners. GPM will capitalize on the experience of the highly successful Tropical Rainfall Measurement Mission (TRMM). Its goal is to extend the measurement of rainfall to high latitudes with high temporal frequency, providing a global data set every three hours. A reference concept has been developed consisting of an improved TRMM-like primary satellite with precipitation radar and microwave radiometer to make detailed and accurate estimates of the precipitation structure and a constellation of small satellites flying compact microwave radiometers to provide the required temporal sampling of highly variable precipitation systems. Considering that DMSP spacecraft equipped with SSMIS microwave radiometers, successor NPOESS spacecraft equipped with CMIS microwave radiometers, and other relevant international systems are expected to be in operation during the timeframe of the reference concept, the total number of small satellites required to complete the constellation will be reduced. A nominal plan is to begin implementation in FY'03 with launches in 2007. NASA is presently engaged in advanced mission studies and advanced instrument technology development related to the mission.

  14. The Global Precipitation Mission

    NASA Technical Reports Server (NTRS)

    Braun, Scott; Kummerow, Christian

    2000-01-01

    The Global Precipitation Mission (GPM), expected to begin around 2006, is a follow-up to the Tropical Rainfall Measuring Mission (TRMM). Unlike TRMM, which primarily samples the tropics, GPM will sample both the tropics and mid-latitudes. The primary, or core, satellite will be a single, enhanced TRMM satellite that can quantify the 3-D spatial distributions of precipitation and its associated latent heat release. The core satellite will be complemented by a constellation of very small and inexpensive drones with passive microwave instruments that will sample the rainfall with sufficient frequency to be not only of climate interest, but also have local, short-term impacts by providing global rainfall coverage at approx. 3 h intervals. The data is expected to have substantial impact upon quantitative precipitation estimation/forecasting and data assimilation into global and mesoscale numerical models. Based upon previous studies of rainfall data assimilation, GPM is expected to lead to significant improvements in forecasts of extratropical and tropical cyclones. For example, GPM rainfall data can provide improved initialization of frontal systems over the Pacific and Atlantic Oceans. The purpose of this talk is to provide information about GPM to the USWRP (U.S. Weather Research Program) community and to discuss impacts on quantitative precipitation estimation/forecasting and data assimilation.

  15. Total Precipitable Water

    SciTech Connect

    2012-01-01

    The simulation was performed on 64K cores of Intrepid, running at 0.25 simulated-years-per-day and taking 25 million core-hours. This is the first simulation using both the CAM5 physics and the highly scalable spectral element dynamical core. The animation of Total Precipitable Water clearly shows hurricanes developing in the Atlantic and Pacific.

  16. [pi]-Stacking and aggregation of pyridinium-substituted indolizines

    SciTech Connect

    Carter, P.W.; DiMagno, S.G. ); Porter, J.D.; Streitwieser, A. )

    1993-02-04

    The tendency for pyridinium-substituted indolizines to aggregate in aqueous and acetonitrile solution is dominated by solute-solvent interactions and by the amphiphilic nature of the cations. In solution, these compounds exhibit an unusual sequence of discrete, red-shifted fluorescence bands whose intensities are a function of concentration over the range 10[sup [minus]5]--10[sup [minus]3] M. It is proposed that [pi]-stacking of the indolizine residues results in weak electronic interactions ([beta] [approximately]0.13 eV) which are sufficient to result in the delocalization of bound excitonic states over the aggregate. Fluorescence from the aggregate occurs by radiative annihilation of the delocalized exciton. Stepwise dimerization (K[sub 2]) and trimerization (K[sub 3]) equilibrium constants for the cations calculated from the emission spectra range from about 400 to 65,000. Solution conductivity measurements indicate that cation aggregation does not require ion pairing. However, where significant ion-pairing does occur, K[sub 2] and K[sub 3] are increased by at least an order of magnitude. X-ray crystallography was used to determine the structures of cation dimers which form in the solid state, and these structures were used as working models for the geometry of the solution aggregates. Electrostatic and dispersion interactions calculated on the basis of those geometries account for some of the free energy of aggregate formation, but solvent entropic effects are believed to provide the strongest driving force for indolizine aggregation in solution. 58 refs., 8 figs., 4 tabs.

  17. Daily spatiotemporal precipitation simulation using latent and transformed Gaussian processes

    NASA Astrophysics Data System (ADS)

    Kleiber, William; Katz, Richard W.; Rajagopalan, Balaji

    2012-01-01

    A daily stochastic spatiotemporal precipitation generator that yields spatially consistent gridded quantitative precipitation realizations is described. The methodology relies on a latent Gaussian process to drive precipitation occurrence and a probability integral transformed Gaussian process for intensity. At individual locations, the model reduces to a Markov chain for precipitation occurrence and a gamma distribution for precipitation intensity, allowing statistical parameters to be included in a generalized linear model framework. Statistical parameters are modeled as spatial Gaussian processes, which allows for interpolation to locations where there are no direct observations via kriging. One advantage of such a model for the statistical parameters is that stochastic generator parameters are immediately available at any location, with the ability to adapt to spatially varying precipitation characteristics. A second advantage is that parameter uncertainty, generally unavailable with deterministic interpolators, can be immediately quantified at all locations. The methodology is illustrated on two data sets, the first in Iowa and the second over the Pampas region of Argentina. In both examples, the method is able to capture the local and domain aggregated precipitation behavior fairly well at a wide range of time scales, including daily, monthly, and annually.

  18. [Responses of spatial distribution pattern of Artemisia ordosica population to the precipitation gradient on Ordos Plateau].

    PubMed

    Li, Qiu-shuang; Zhang, Chao; Wang, Fei; Lai, Li-ming; Zhang, Li; Li, Wen-ting; Bai, Hua; Zheng, Yuan-run

    2009-09-01

    Five sites along the precipitation gradient (336-249 mm x a(-1)) from east to west in Ordos Plateau were selected to study the spatial distribution pattern of Artemisia ordosica population and its responses to the precipitation gradient by the methods of variance mean ratio, aggregative index, and point pattern analysis. The reduction of precipitation affected the spatial distribution pattern of A. ordosica population significantly. With decreasing precipitation gradient, the spatial pattern of A. ordosica population changed from uniform to random in small scale, and from random to clumpy in large scale, suggesting that in the ecological restoration of Ordos Plateau, a rational arrangement of A. ordosica should be made. PMID:20030129

  19. Tau Aggregation Propensity Engrained in Its Solution State.

    PubMed

    Eschmann, Neil A; Do, Thanh D; LaPointe, Nichole E; Shea, Joan-Emma; Feinstein, Stuart C; Bowers, Michael T; Han, Songi

    2015-11-12

    A peptide fragment of the human tau protein which stacks to form neat cross β-sheet fibrils, resembling that found in pathological aggregation, (273)GKVQIINKKLDL(284) (here "R2/WT"), was modified with a spin-label at the N-terminus. With the resulting peptide, R2/G273C-SL, we probed events at time scales spanning seconds to hours after aggregation is initiated using transmission electron microscopy (TEM), thioflavin T (THT) fluorescence, ion mobility mass spectrometry (IMMS), electron paramagnetic resonance (EPR), and Overhauser dynamic nuclear polarization (ODNP) to determine if deliberate changes to its conformational states and population in solution influence downstream propensity to form fibrillar aggregates. We find varying solution conditions by adding the osmolyte urea or TMAO, or simply using different buffers (acetate buffer, phosphate buffer, or water), produces significant differences in early monomer/dimer populations and conformations. Crucially, these characteristics of the peptide in solution state before aggregation is initiated dictate the fibril formation propensity after aggregation. We conclude the driving forces that accelerate aggregation, when heparin is added, do not override the subtle intra- or interprotein interactions induced by the initial solvent conditions. In other words, the balance of protein-protein vs protein-solvent interactions present in the initial solution conditions is a critical driving force for fibril formation. PMID:26484390

  20. Mechanism of algal aggregation by Bacillus sp. strain RP1137.

    PubMed

    Powell, Ryan J; Hill, Russell T

    2014-07-01

    Alga-derived biofuels are one of the best alternatives for economically replacing liquid fossil fuels with a fungible renewable energy source. Production of fuel from algae is technically feasible but not yet economically viable. Harvest of dilute algal biomass from the surrounding water remains one of the largest barriers to economic production of algal biofuel. We identified Bacillus sp. strain RP1137 in a previous study and showed that this strain can rapidly aggregate several biofuel-producing algae in a pH- and divalent-cation-dependent manner. In this study, we further characterized the mechanism of algal aggregation by RP1137. We show that aggregation of both algae and bacteria is optimal in the exponential phase of growth and that the density of ionizable residues on the RP1137 cell surface changes with growth stage. Aggregation likely occurs via charge neutralization with calcium ions at the cell surface of both algae and bacteria. We show that charge neutralization occurs at least in part through binding of calcium to negatively charged teichoic acid residues. The addition of calcium also renders both algae and bacteria more able to bind to hydrophobic beads, suggesting that aggregation may occur through hydrophobic interactions. Knowledge of the aggregation mechanism may enable engineering of RP1137 to obtain more efficient algal harvesting. PMID:24771029

  1. Mechanism of Algal Aggregation by Bacillus sp. Strain RP1137

    PubMed Central

    Powell, Ryan J.

    2014-01-01

    Alga-derived biofuels are one of the best alternatives for economically replacing liquid fossil fuels with a fungible renewable energy source. Production of fuel from algae is technically feasible but not yet economically viable. Harvest of dilute algal biomass from the surrounding water remains one of the largest barriers to economic production of algal biofuel. We identified Bacillus sp. strain RP1137 in a previous study and showed that this strain can rapidly aggregate several biofuel-producing algae in a pH- and divalent-cation-dependent manner. In this study, we further characterized the mechanism of algal aggregation by RP1137. We show that aggregation of both algae and bacteria is optimal in the exponential phase of growth and that the density of ionizable residues on the RP1137 cell surface changes with growth stage. Aggregation likely occurs via charge neutralization with calcium ions at the cell surface of both algae and bacteria. We show that charge neutralization occurs at least in part through binding of calcium to negatively charged teichoic acid residues. The addition of calcium also renders both algae and bacteria more able to bind to hydrophobic beads, suggesting that aggregation may occur through hydrophobic interactions. Knowledge of the aggregation mechanism may enable engineering of RP1137 to obtain more efficient algal harvesting. PMID:24771029

  2. Perspectives on Preference Aggregation.

    PubMed

    Regenwetter, Michel

    2009-07-01

    For centuries, the mathematical aggregation of preferences by groups, organizations, or society itself has received keen interdisciplinary attention. Extensive theoretical work in economics and political science throughout the second half of the 20th century has highlighted the idea that competing notions of rational social choice intrinsically contradict each other. This has led some researchers to consider coherent democratic decision making to be a mathematical impossibility. Recent empirical work in psychology qualifies that view. This nontechnical review sketches a quantitative research paradigm for the behavioral investigation of mathematical social choice rules on real ballots, experimental choices, or attitudinal survey data. The article poses a series of open questions. Some classical work sometimes makes assumptions about voter preferences that are descriptively invalid. Do such technical assumptions lead the theory astray? How can empirical work inform the formulation of meaningful theoretical primitives? Classical "impossibility results" leverage the fact that certain desirable mathematical properties logically cannot hold in all conceivable electorates. Do these properties nonetheless hold true in empirical distributions of preferences? Will future behavioral analyses continue to contradict the expectations of established theory? Under what conditions do competing consensus methods yield identical outcomes and why do they do so? PMID:26158988

  3. The Earliest Ion Channels

    NASA Astrophysics Data System (ADS)

    Pohorille, A.; Wilson, M. A.; Wei, C.

    2009-12-01

    Supplying protocells with ions required assistance from channels spanning their membrane walls. The earliest channels were most likely short proteins that formed transmembrane helical bundles surrounding a water-filled pore. These simple aggregates were capable of transporting ions with efficiencies comparable to those of complex, contemporary ion channels. Channels with wide pores exhibited little ion selectivity but also imposed only modest constraints on amino acid sequences of channel-forming proteins. Channels with small pores could have been selective but also might have required a more precisely defined sequence of amino acids. In contrast to modern channels, their protocellular ancestors had only limited capabilities to regulate ion flux. It is postulated that subsequent evolution of ion channels progressed primarily to acquire precise regulation, and not high efficiency or selectivity. It is further proposed that channels and the surrounding membranes co-evolved.

  4. Precipitation Indices Low Countries

    NASA Astrophysics Data System (ADS)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  5. The Global Precipitation Measurement (GPM) Project

    NASA Technical Reports Server (NTRS)

    Azarbarazin, Ardeshir Art; Carlisle, Candace C.

    2008-01-01

    The GIobd Precipitation hleasurement (GPM) mission is an international cooperatiee ffort to advance weather, climate, and hydrological predictions through space-based precipitation measurements. The Core Observatory will be a reference standard to uniform11 calibrate data from a constellatism of spacecraft with passive microuave sensors. GP3l mission data will be used for scientific research as well as societal applications. GPM is being developed under a partnership between the United States (US) National .Aeronautics and Space Administration (XASA) and the Japanese Aerospace and Exploration Agency (JAYA). NASA is developing the Core Observatory, a Low-Inclination Constellation Observatory, two GPM Rlicrowave Imager (GXII) instruments. Ground Validation System and Precipitation Processing System for the GPRl mission. JAXA will provide a Dual-frequency Precipitation Radar (DPR) for installation on the Core satellite and launch services for the Core Observatory. Other US agencies and international partners contribute to the GPkf mission by providing precipitation measurements obtained from their own spacecraft and,'or providing ground-based precipitation measurements to support ground validation activities. The GPM Core Observatory will be placed in a low earth orbit (-400 krn) with 65-degree inclination, in order to calibrate partner instruments in a variety of orbits. The Core Observatory accommodates 3 instruments. The GkfI instrument provides measurements of precipitation intensity and distribution. The DPR consists of Ka and Ku band instruments, and provides threedimensional measurements of cloud structure, precipitation particle size distribution and precipitation intensitj and distribution. The instruments are key drivers for GPM Core Observatory overall size (1 1.6m x 6.5m x 5.0m) and mass (3500kg), as well as the significant (-1 950U.3 power requirement. The Core Spacecraft is being built in-house at Goddard Space Flight Center. The spacecraft structure

  6. in situ Calcite Precipitation for Contaminant Immobilization

    SciTech Connect

    Yoshiko Fujita; Robert W. Smith

    2009-08-01

    in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita (Yoshiko.fujita@inl.gov) (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at

  7. Petrography study on altered flint aggregate by alkali-silica reaction

    SciTech Connect

    Bulteel, D. . E-mail: bulteel@ensm-douai.fr; Rafai, N.; Degrugilliers, P.; Garcia-Diaz, E.

    2004-11-15

    The aim of our study is to improve our understanding of an alkali-silica reaction (ASR) via petrography. We used a chemical concrete subsystem: flint aggregate, portlandite and KOH. The altered flint aggregate is followed by optical microscopy and scanning electron microscopy (SEM) before and after acid treatment at different intervals. After acid treatment, the observations showed an increase in aggregate porosity and revealed internal degradation of the aggregate. This degradation created amorphous zones. Before acid treatment, the analyses on polished sections by scanning electron microscopy coupled with energy dispersive spectroscopy (EDS) enabled visualization of K{sup +} and Ca{sup 2+} penetration into the aggregate. The appearance of amorphous zones and penetration of positive ions into the aggregate are correlated with the increase in the molar fraction of silanol sites. This degradation is specific to the alkali-silica reaction.

  8. Precipitation hardening austenitic superalloys

    DOEpatents

    Korenko, Michael K.

    1985-01-01

    Precipitation hardening, austenitic type superalloys are described. These alloys contain 0.5 to 1.5 weight percent silicon in combination with about 0.05 to 0.5 weight percent of a post irradiation ductility enhancing agent selected from the group of hafnium, yttrium, lanthanum and scandium, alone or in combination with each other. In addition, when hafnium or yttrium are selected, reductions in irradiation induced swelling have been noted.

  9. Filler modification for papermaking with starch/oleic acid complexes with the aid of calcium ions.

    PubMed

    Huang, Xiujie; Shen, Jing; Qian, Xueren

    2013-10-15

    To mitigate the negative effect of filler addition on paper strength and improve filler retention, filler modification with hydrogen bonding polymers (e.g., starch) or their composites is an interesting research topic. Differing from previous reports, the concept related to the deposition of starch/oleic acid complexes on precipitated calcium carbonate (PCC) with the aid of calcium ions was demonstrated. The introduction of calcium ions resulted in effective starch deposition. As a result of filler modification, filler retention and the tensile strength of the filled paper were simultaneously improved essentially due to the aggregation of PCC particles in filler modification process as well as improved filler bondability. The concept demonstrated in this brief study may provide an alternative approach to filler bondability enhancement for improved papermaking performances. PMID:23987430

  10. Monosized aggregates -- A new model

    SciTech Connect

    Gopal, M.

    1997-08-01

    For applications requiring colloidal particles, it is desirable that they be monosized to better control the structure and the properties. In a number of systems, the monosized particles come together to form aggregates that are also monosized. A model is presented here to explain the formation of these monosized aggregates. This is of particular importance in the fields of ceramics, catalysis, pigments, pharmacy, photographic emulsions, etc.

  11. Glycation precedes lens crystallin aggregation

    SciTech Connect

    Swamy, M.S.; Perry, R.E.; Abraham, E.C.

    1987-05-01

    Non-enzymatic glycosylation (glycation) seems to have the potential to alter the structure of crystallins and make them susceptible to thiol oxidation leading to disulfide-linked high molecular weight (HMW) aggregate formation. They used streptozotocin diabetic rats during precataract and cataract stages and long-term cell-free glycation of bovine lens crystallins to study the relationship between glycation and lens crystallin aggregation. HMW aggregates and other protein components of the water-soluble (WS) and urea-soluble (US) fractions were separated by molecular sieve high performance liquid chromatography. Glycation was estimated by both (/sup 3/H)NaBH/sub 4/ reduction and phenylboronate agarose affinity chromatography. Levels of total glycated protein (GP) in the US fractions were about 2-fold higher than in the WS fractions and there was a linear increase in GP in both WS and US fractions. This increase was parallelled by a corresponding increase in HMW aggregates. Total GP extracted by the affinity method from the US fraction showed a predominance of HMW aggregates and vice versa. Cell-free glycation studies with bovine crystallins confirmed the results of the animals studies. Increasing glycation caused a corresponding increase in protein insolubilization and the insoluble fraction thus formed also contained more glycated protein. It appears that lens protein glycation, HMW aggregate formation, and protein insolubilization are interrelated.

  12. Modifiers of mutant huntingtin aggregation

    PubMed Central

    Teuling, Eva; Bourgonje, Annika; Veenje, Sven; Thijssen, Karen; de Boer, Jelle; van der Velde, Joeri; Swertz, Morris; Nollen, Ellen

    2011-01-01

    Protein aggregation is a common hallmark of a number of age-related neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and polyglutamine-expansion disorders such as Huntington’s disease, but how aggregation-prone proteins lead to pathology is not known. Using a genome-wide RNAi screen in a C. elegans-model for polyglutamine aggregation, we previously identified 186 genes that suppress aggregation. Using an RNAi screen for human orthologs of these genes, we here present 26 human genes that suppress aggregation of mutant huntingtin in a human cell line. Among these are genes that have not been previously linked to mutant huntingtin aggregation. They include those encoding eukaryotic translation initiation, elongation and translation factors, and genes that have been previously associated with other neurodegenerative diseases, like the ATP-ase family gene 3-like 2 (AFG3L2) and ubiquitin-like modifier activating enzyme 1 (UBA1). Unravelling the role of these genes will broaden our understanding of the pathogenesis of Huntington’s disease. PMID:21915392

  13. Kinetic model for erythrocyte aggregation.

    PubMed

    Bertoluzzo, S M; Bollini, A; Rasia, M; Raynal, A

    1999-01-01

    It is well known that light transmission through blood is the most widely utilized method for the study of erythrocyte aggregation. The curves obtained had been considered empirically as exponential functions. In consequence, the process becomes characterized by an only parameter that varies with all the process factors without discrimination. In the present paper a mathematical model for RBC aggregation process is deduced in accordance with von Smoluchowski's theory about the kinetics of colloidal particles agglomeration. The equation fitted the experimental pattern of the RBC suspension optical transmittance closely and contained two parameters that estimate the most important characteristics of the aggregation process separately, i.e., (1) average size of rouleaux at equilibrium and (2) aggregation rate. The evaluation of the method was assessed by some factors affecting erythrocyte aggregation, such as temperature, plasma dilutions, Dextran 500, Dextran 70 and PVP 360, at different media concentrations, cellular membrane alteration by the alkylating agent TCEA, and decrease of medium osmolarity. Results were interpreted considering the process characteristics estimated by the parameters, and there were also compared with similar studies carried out by other authors with other methods. This analysis allowed us to conclude that the equation proposed is reliable and useful to study erythrocyte aggregation. PMID:10660481

  14. Precipitation chemistry: its behavior and its calculation

    SciTech Connect

    Hales, J.M.

    1980-02-01

    The purposes of this paper are twofold. The first of these is to present a rational basis for examining the aggregate set of scavenging-calculation techniques, and for guiding the reader in his course toward choosing the most appropriate technique for his particular application. The second purpose of this paper is to present a somewhat brief survey of our current understanding of scavenging and precipitation chemistry. Both objectives will be implemented by a flowchart approach, which attempts to draw the various facets of scavenging calculations together and present a generalized approach to the problem in total. The mathematical level of this paper is restricted to the presentation of the equations necessary to provide the reader with a basic appreciation of the fundamental concepts involved. References to more detailed mathematical treatments are cited at appropriate juncture points, for the reader interested in more detailed pursuit.

  15. Pulsed hydrogen–deuterium exchange mass spectrometry probes conformational changes in amyloid beta (Aβ) peptide aggregation

    PubMed Central

    Zhang, Ying; Rempel, Don L.; Zhang, Jun; Sharma, Anuj K.; Mirica, Liviu M.; Gross, Michael L.

    2013-01-01

    Probing the conformational changes of amyloid beta (Aβ) peptide aggregation is challenging owing to the vast heterogeneity of the resulting soluble aggregates. To investigate the formation of these aggregates in solution, we designed an MS-based biophysical approach and applied it to the formation of soluble aggregates of the Aβ42 peptide, the proposed causative agent in Alzheimer’s disease. The approach incorporates pulsed hydrogen–deuterium exchange coupled with MS analysis. The combined approach provides evidence for a self-catalyzed aggregation with a lag phase, as observed previously by fluorescence methods. Unlike those approaches, pulsed hydrogen–deuterium exchange does not require modified Aβ42 (e.g., labeling with a fluorophore). Furthermore, the approach reveals that the center region of Aβ42 is first to aggregate, followed by the C and N termini. We also found that the lag phase in the aggregation of soluble species is affected by temperature and Cu2+ ions. This MS approach has sufficient structural resolution to allow interrogation of Aβ aggregation in physiologically relevant environments. This platform should be generally useful for investigating the aggregation of other amyloid-forming proteins and neurotoxic soluble peptide aggregates. PMID:23959898

  16. Ash Aggregates in Proximal Settings

    NASA Astrophysics Data System (ADS)

    Porritt, L. A.; Russell, K.

    2012-12-01

    Ash aggregates are thought to have formed within and been deposited by the eruption column and plume and dilute density currents and their associated ash clouds. Moist, turbulent ash clouds are considered critical to ash aggregate formation by facilitating both collision and adhesion of particles. Consequently, they are most commonly found in distal deposits. Proximal deposits containing ash aggregates are less commonly observed but do occur. Here we describe two occurrences of vent proximal ash aggregate-rich deposits; the first within a kimberlite pipe where coated ash pellets and accretionary lapilli are found within the intra-vent sequence; and the second in a glaciovolcanic setting where cored pellets (armoured lapilli) occur within <1 km of the vent. The deposits within the A418 pipe, Diavik Diamond Mine, Canada, are the residual deposits within the conduit and vent of the volcano and are characterised by an abundance of ash aggregates. Coated ash pellets are dominant but are followed in abundance by ash pellets, accretionary lapilli and rare cored pellets. The coated ash pellets typically range from 1 - 5 mm in diameter and have core to rim ratios of approximately 10:1. The formation and preservation of these aggregates elucidates the style and nature of the explosive phase of kimberlite eruption at A418 (and other pipes?). First, these pyroclasts dictate the intensity of the kimberlite eruption; it must be energetic enough to cause intense fragmentation of the kimberlite to produce a substantial volume of very fine ash (<62 μm). Secondly, the ash aggregates indicate the involvement of moisture coupled with the presence of dilute expanded eruption clouds. The structure and distribution of these deposits throughout the kimberlite conduit demand that aggregation and deposition operate entirely within the confines of the vent; this indicates that aggregation is a rapid process. Ash aggregates within glaciovolcanic sequences are also rarely documented. The

  17. Precipitation Indices Low Countries

    NASA Astrophysics Data System (ADS)

    van Engelen, A. F. V.; Ynsen, F.; Buisman, J.; van der Schrier, G.

    2009-09-01

    Since 1995, KNMI published a series of books(1), presenting an annual reconstruction of weather and climate in the Low Countries, covering the period AD 763-present, or roughly, the last millennium. The reconstructions are based on the interpretation of documentary sources predominantly and comparison with other proxies and instrumental observations. The series also comprises a number of classifications. Amongst them annual classifications for winter and summer temperature and for winter and summer dryness-wetness. The classification of temperature have been reworked into peer reviewed (2) series (AD 1000-present) of seasonal temperatures and temperature indices, the so called LCT (Low Countries Temperature) series, now incorporated in the Millennium databases. Recently we started a study to convert the dryness-wetness classifications into a series of precipitation; the so called LCP (Low Countries Precipitation) series. A brief outline is given here of the applied methodology and preliminary results. The WMO definition for meteorological drought has been followed being that a period is called wet respectively dry when the amount of precipitation is considerable more respectively less than usual (normal). To gain a more quantitative insight for four locations, geographically spread over the Low Countries area (De Bilt, Vlissingen, Maastricht and Uccle), we analysed the statistics of daily precipitation series, covering the period 1900-present. This brought us to the following definition, valid for the Low Countries: A period is considered as (very) dry respectively (very) wet if over a continuous period of at least 60 days (~two months) cq 90 days (~three months) on at least two out of the four locations 50% less resp. 50% more than the normal amount for the location (based on the 1961-1990 normal period) has been measured. This results into the following classification into five drought classes hat could be applied to non instrumental observations: Very wet period

  18. By suppressing the expression of anterior pharynx-defective-1α and -1β and inhibiting the aggregation of β-amyloid protein, magnesium ions inhibit the cognitive decline of amyloid precursor protein/presenilin 1 transgenic mice.

    PubMed

    Yu, Xin; Guan, Pei-Pei; Guo, Jing-Wen; Wang, Yue; Cao, Long-Long; Xu, Guo-Biao; Konstantopoulos, Konstantinos; Wang, Zhan-You; Wang, Pu

    2015-12-01

    Alzheimer's disease (AD) is associated with a magnesium ion (Mg(2+)) deficit in the serum or brain. However, the mechanisms regulating the roles of Mg(2+) in the pathologic condition of AD remain unknown. We studied whether brain Mg(2+) can decrease β-amyloid (Aβ) deposition and ameliorate the cognitive decline in a model of AD, the APPswe/PS1DE9 transgenic (Tg) mouse. We used a recently developed compound, magnesium-L-threonate (MgT), for a treatment that resulted in enhanced clearance of Aβ in an anterior pharynx-defective (APH)-1α/-1β-dependent manner. To further explore how MgT treatment inhibits cognitive decline in APP/PS1 Tg mice, the critical molecules for amyloid precursor protein (APP) cleavage and signaling pathways were investigated. In neurons, ERK1/2 and PPARγ signaling pathways were activated by MgT treatment, which in turn suppressed (by >80%) the expression of APH-1α/-1β, which is responsible for the deposition of Aβ and potentially contributes to the memory deficit that occurs in AD. More important, Aβ oligomers in the cerebrospinal fluid (CSF) further promoted the expression of APH-1α/-1β (by >2.5-fold), which enhances the γ-cleavage of APP and Aβ deposition during AD progression. These findings provide new insights into the mechanisms of AD progression and are instrumental for developing better strategies to combat the disease. PMID:26293690

  19. Aggregation of sulfosuccinate surfactants in water

    SciTech Connect

    Magid, L.J.; Daus, K.A.; Butler, P.D.; Quincy, R.B.

    1983-12-22

    The aggregation of sodium di-n-alkyl sulfosuccinates in water (H/sub 2/O and D/sub 2/O at 45/sup 0/C) has been investigated. A self-consistent picture of the dependence of sodium ion binding on surfactant concentration is obtained from emf measurements, conductimetry, and small-angle neutron scattering (SANS) measurements. The concentration dependence of the micellar agregation number for the sulfosuccinates and related double-tailed surfactants depends markedly on surfactant solubility. A sphere-to-disk transition in micellar shape, which might have been expected as a precursor to formation of a lamellar mesophase, was not observed as the surfactant concentration was increased. 8 figures, 2 tables.

  20. Promotion and nucleation of carbonate precipitation during microbial iron reduction.

    PubMed

    Zeng, Z; Tice, M M

    2014-07-01

    Iron-bearing early diagenetic carbonate cements are common in sedimentary rocks, where they are thought to be associated with microbial iron reduction. However, little is yet known about how local environments around actively iron-reducing cells affect carbonate mineral precipitation rates and compositions. Precipitation experiments with the iron-reducing bacterium Shewanella oneidensis MR-1 were conducted to examine the potential role of cells in promoting precipitation and to explore the possible range of precipitate compositions generated in varying fluid compositions. Actively iron-reducing cells induced increased carbonate mineral saturation and nucleated precipitation on their poles. However, precipitation only occurred when calcium was present in solution, suggesting that cell surfaces lowered local ferrous iron concentrations by adsorption or intracellular iron oxide precipitation even as they locally raised pH. Resultant precipitates were a range of thermodynamically unstable calcium-rich siderites that would likely act as precursors to siderite, calcite, or even dolomite in nature. By modifying local pH, providing nucleation sites, and altering metal ion concentrations around cell surfaces, iron-reducing micro-organisms could produce a wide range of carbonate cements in natural sediments. PMID:24862734

  1. Nano-precipitation in hot-pressed silicon carbide

    SciTech Connect

    Zhang, Xiao Feng; Sixta, Mark E.; Chen, Da; De Jonghe, Lutgard C.

    2000-05-16

    Heat treatments at 1300 degrees C, 1400 degrees C, 1500 degrees C, and 1600 degrees C in Ar were found to produce nanoscale precipitates in hot-pressed silicon carbide containing aluminum, boron, and carbon sintering additives (ABC-SiC). The precipitates were studied by transmission electron microscopy (TEM) and nano-probe energy-dispersive X-ray spectroscopy (nEDS). The precipitates were plate-like in shape, with a thickness, length and separation of only a few nanometers, and their size coarsened with increasing annealing temperature, accompanied by reduced number density. The distribution of the precipitates was uniform inside the SiC grains, but depleted zones were observed in the vicinity of the SiC grain boundaries. A coherent orientation relationship between the precipitates and the SiC matrix was found. Combined high-resolution electron microscopy, computer simulation, and nEDS identified an Al4C3-based structure and composition for the nano-precipitates. Most Al ions in SiC lattice exsolved as precipitates during the annealing at 1400 to 1500 degrees C. Formation mechanism and possible influences of the nanoscale precipitates on mechanical properties are discussed.

  2. Crystal aggregation in kidney stones; a polymer aggregation problem?

    NASA Astrophysics Data System (ADS)

    Wesson, J.; Beshensky, A.; Viswanathan, P.; Zachowicz, W.; Kleinman, J.

    2008-03-01

    Kidney stones most frequently form as aggregates of calcium oxalate monohydrate (COM) crystals with organic layers between them, and the organic layers contain principally proteins. The pathway leading to the formation of these crystal aggregates in affected people has not been identified, but stone forming patients are thought to have a defect in the structure or distribution of urinary proteins, which normally protect against stone formation. We have developed two polyelectrolyte models that will induce COM crystal aggregation in vitro, and both are consistent with possible urinary protein compositions. The first model was based on mixing polyanionic and polycationic proteins, in portions such that the combined protein charge is near zero. The second model was based on reducing the charge density on partially charged polyanionic proteins, specifically Tamm-Horsfall protein, the second most abundant protein in urine. Both models demonstrated polymer phase separation at solution conditions where COM crystal aggregation was observed. Correlation with data from other bulk crystallization measurements suggest that the anionic side chains form critical binding interactions with COM surfaces that are necessary along with the phase separation process to induce COM crystal aggregation.

  3. Self-organization of convective clouds and extreme precipitation

    NASA Astrophysics Data System (ADS)

    Moseley, Christopher; Hohenegger, Cathy; Berg, Peter; Haerter, Jan

    2016-04-01

    The response of convective-type cloud and associated precipitation rates to temperature changes is far from clear. Observational studies have identified a strong sensitivity of convective precipitation extreme intensities to surface temperature --- even exceeding the thermodynamic constraint through the Clausius-Clapayron relationship (Berg et al., Nature Geoscience, 2013). It has been speculated that such strong changes may result from dynamical changes of the atmospheric flow, whereby thermodynamic constraints could be bypassed. Indeed, convective cloud has long been suspected to self-organize or even aggregate, but whether and how such structural transitions relate to modified precipitation rates is largely unexplored. Large-eddy simulations (LES) are a versatile tool suited for high-resolution numerical experiments of the convective cloud field. At horizontal resolutions on the scale of 100 m, they now allow 3d simulations of the moist atmospheric dynamics within domains of hundreds of kilometers laterally. Such simulations grant access to virtually all relevant observables. Using LES along with precipitation cell tracking, we isolate the effect of self-organization, quantify structural changes within the cloud field as a function of time and extract mechanisms that lead to increased convective precipitation intensities. We make contact to classical measures of large-scale convective potential, e.g. CAPE, CIN and moisture convergence, and contrast cloud-scale feedbacks to those previously implicated in quasi-equilibrium, large-scale, aggregation processes. Together, our results suggest that the build-up of extreme precipitation must ultimately be understood within a non-equilibrium framework. We relate our findings to current developments in global and regional climate modeling.

  4. Spatial Downscaling of TRMM Precipitation using MODIS product in the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Cho, H.; Choi, M.

    2013-12-01

    Precipitation is a major driving force in the water cycle. But, it is difficult to provide spatially distributed precipitation data from isolated individual in situ. The Tropical Rainfall Monitoring Mission (TRMM) satellite can provide precipitation data with relatively coarse spatial resolution (0.25° scale) at daily basis. In order to overcome the coarse spatial resolution of TRMM precipitation products, we conducted a downscaling technique using a scaling parameter from the Moderate Resolution Imaging Spectroradiometers (MODIS) sensor. In this study, statistical relations between precipitation estimates derived from the TRMM satellite and the normalized difference vegetation index (NDVI) which is obtained from the MODIS sensor in TERRA satellite are found for different spatial scales on the Korean peninsula in northeast Asia. We obtain the downscaled precipitation mapping by regression equation between yearly TRMM precipitations values and annual average NDVI aggregating 1km to 25 degree. The downscaled precipitation is validated using time series of the ground measurements precipitation dataset provided by Korea Meteorological Organization (KMO) from 2002 to 2005. To improve the spatial downscaling of precipitation, we will conduct a study about correlation between precipitation and land surface temperature, perceptible water and other hydrological parameters.

  5. Heat stability of aggregated particles of casein micelles and kappa-carrageenan.

    PubMed

    Flett, Kelly L; Corredig, Milena; Goff, H Douglas

    2010-06-01

    Aggregated particles of casein micelles and kappa-carrageenan were produced as a dried milk ingredient, then reconstituted and subjected to a heat treatment of 70 degrees C for 10 min. The reconstituted aggregates were found to be unstable when heated. Light scattering results showed that the aggregates dissociated partially into casein micelles. It was hypothesized that the removal of ions during ultrafiltration before spray-drying to produce the powdered ingredient significantly decreased stability upon reconstitution and heat treatment. When ions, either from whey permeate or calcium addition, were added to reconstituted aggregates, stability was greatly enhanced and the aggregates remained intact when subjected to heat. The effect of heat treatment on aggregates freshly produced with skim milk powder and kappa-carrageenan was also studied. These aggregates were found to be stable during heating due to the unchanged ionic environment. Therefore, incorporation of powdered aggregates of casein micelles and kappa-carrageenan into products would require the addition of whey permeate or calcium after reconstitution for stability during subsequent heating. PMID:20629864

  6. Developing precipitation modes for preventing the calcium-oxalate contamination of sugar beet pectins.

    PubMed

    Guo, Xiaoming; Meng, Hecheng; Zhu, Siming; Tang, Qiang; Pan, Runquan; Yu, Shujuan

    2015-09-01

    Effects of precipitation modes on the co-precipitation of insoluble oxalates particles during the purification of sugar beet pectins (SBP) from the extract were investigated. It was observed that soluble oxalate ions formed insoluble oxalate salts with calcium and precipitated with pectins during ethanol precipitation as pH of the medium increased and the solvent changed from water to ethanol-water mixture. Comparison among the employed precipitation methods revealed that both the dialysis-ethanol-precipitation and metal precipitation effectively prevented the calcium-oxalate contamination of SBP. Emulsifying properties of DEPP, EPP and MPP were also studied. It was observed that DEPP performed better than the remainder with respect to emulsifying ability. Based on these results, we concluded that the dialysis-ethanolic-precipitation can be a suitable method for improving the purity as well as emulsifying properties of the resulting pectins. PMID:25842309

  7. DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

    DOEpatents

    Fries, B.A.

    1959-11-10

    A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

  8. Fractal Aggregates in Tennis Ball Systems

    ERIC Educational Resources Information Center

    Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.

    2009-01-01

    We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…

  9. Strong aggregation and directional assembly of aromatic oligoamide macrocycles.

    SciTech Connect

    Yang, Y.; Feng, W.; Hu, J.; Zou, S.; Gao, R.; Yamato, K.; Kline, M.; Cai, Z.; Gao, Y.; Wang, Y.; Li, Y.; Yang, Y.; Yuan, L.; Zeng, X.; Gong, B.

    2011-10-01

    Aromatic oligoamide macrocycles exhibit strong preference for highly directional association. Aggregation happens in both nonpolar and polar solvents but is weakened as solvent polarity increases. The strong, directional assembly is rationalized by the cooperative action of dipole-dipole and {pi}-{pi} stacking interactions, leading to long nanotubular assemblies that are confirmed by SEM, TEM, AFM, and XRD. The persistent nanotubular assemblies contain non-collapsible hydrophilic internal pores that mediate highly efficient ion transport observed with these macrocycles and serve as cylindrical sites for accommodating guests such as metal ions.

  10. Silica Transport and Cementation in Quartz Aggregates

    NASA Astrophysics Data System (ADS)

    Pebble, C.; Farver, J.; Onasch, C.; Winslow, D.

    2008-12-01

    Silica transport and cementation in quartz aggregates have been experimentally investigated. Starting materials include a natural quartz arenite (Pocono sandstone), sized clasts of synthetic quartz, and sized grains of disaggregated natural sandstones. Experimental charges consisted of amorphous silica powder (~25 mg), AlCl3 powder (~3 mg), 25 wt% NaCl brine solution (~20 mg), and the starting material (~150 mg). The charges were weld-sealed in gold capsules and run in cold-seal pressure vessels at 300°C to 600°C at 150 MPa confining pressure for up to 4 weeks. Detailed calibrations of the furnaces indicate the maximum temperature variation across the length of the sample charges (3-7mm) was <5°C, and typically <3°C. After the experiments, samples were vacuum impregnated with epoxy containing a blue dye and sawn in half along the long axis of the sample charge. The nature and amount of silica transport and cementation in the samples was determined by a combination of Cathodoluminescence (CL), Light Microscopy (LM), and Scanning Electron Microscopy (SEM). Photomosaics of the samples were collected and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement was easily recognized from the quartz grains by the difference in luminescence. The experiments indicate that the presence of amorphous silica results in rapid silica cementation in quartz aggregates (e.g., up to 12% cement by volume in 4 weeks at 450°C). The amount of cementation is a function of substrate type, time, temperature, and ionic strength of the brine. The rate of silica transport through the length of the experimental charge appears to be limited by the silica solubility and its rapid depletion by cementation. Although most of the cement was derived from the amorphous silica, evidence for local dissolution-precipitation was observed. The experiments demonstrate that the mobility of silica, and consequent precipitation of cement, does not require a

  11. Aggregated Recommendation through Random Forests

    PubMed Central

    2014-01-01

    Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy. PMID:25180204

  12. Aggregated recommendation through random forests.

    PubMed

    Zhang, Heng-Ru; Min, Fan; He, Xu

    2014-01-01

    Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy. PMID:25180204

  13. Solvent modulation strategy for superior antibody monomer/aggregate separation in cation exchange chromatography.

    PubMed

    Kluters, Simon; Frech, Christian; von Hirschheydt, Thomas; Schaubmar, Andreas; Neumann, Sebastian

    2015-12-01

    Cation exchange chromatography (CEX) is an integral part of many downstream processes for monoclonal antibodies (mAbs). However, in some cases CEX methods with standard mobile phase conditions do not lead to a sufficient removal of soluble antibody aggregates. The addition of neutral polymers such as polyethylene glycol (PEG) to the mobile phase can improve the separation of proteins in IEC remarkably. The applicability of this solvent modulation technique is limited by protein precipitation at higher PEG concentrations. To overcome this limitation solubility enhancers like polyols and amino acids can be added to the mobile phase. These additives are known to inhibit PEG-induced protein precipitation in solution. This new solvent modulation strategy was tested with three different mAbs on two different CEX resins in the presence of PEG in combination with various solubility enhancers. In order to assess the general applicability of this method, mAbs were selected that show major differences with respect to their sensitivity to PEG-induced precipitation and monomer/aggregate resolution performance that is achieved by CEX under standard conditions. For all three mAbs precipitation could be prevented without elimination of the positive PEG-effect. The addition of solubility enhancers gives access to improved separation at elevated PEG concentrations and high protein loadings without running into precipitation issues. Our data indicate that this method is generically applicable and leads to a superior antibody monomer/aggregate separation. PMID:26520020

  14. On the dynamics of the TPPS4 aggregation in aqueous solutions: successive formation of H and J aggregates.

    PubMed

    Aggarwal, Lucimara P F; Borissevitch, Iouri E

    2006-01-01

    The dynamics of aggregation of meso-tetrakis (p-sulfonatofenyl) porphyrin (TPPS4) in function of its concentration, pH and ionic strength was studied by optical absorption, fluorescence and resonance light scattering (RLS) techniques. In the region of pH, where TPPS4 exists in biprotonated form, the addition of NaCl induces the TPPS4 aggregation due to the formation of the "cloud" of counter ions around the TPPS4 molecule thus reducing electrostatic repulsion between the porphyrin molecules. The formation of this "cloud" shifts the pKa value to acid region (from 5.0 in the absence of salt to 4.5 at [NaCl] = 0.4 M), reduces the TPPS4 absorption in all spectral range and quantum yield and lifetime of fluorescence (from 0.27 to 0.17 and from 4.00+/-0.04 to 3.00+/-0.03 ns in the absence of salt and in the presence of NaCl, respectively). The aggregation process involves two successive stages: initially H aggregates are formed, which in time are transformed in J ones. The existence of these two stages was confirmed by the fluorescence and RLS data. The kinetics of the formation of J aggregates is characterized by the induction time t1 and the average growth time t2, which depend on both TPPS4 and salt concentrations. The induction period t1 appears as a result of initial formation of H aggregates and their successive transformation in J ones. At very high TPPS4 concentrations, the J aggregates are united in more complex structures such as hollow cylinders or helixes. PMID:15955725

  15. Structural changes in precipitated silica induced by external forces

    NASA Astrophysics Data System (ADS)

    Schneider, Gerald Johannes; Göritz, Dietmar

    2010-04-01

    The morphology of pure precipitated silica, silica filled in polydimethylsiloxane rubber, and silica filled in styrene butadiene rubber was studied by means of small-angle X-ray scattering experiments. The silica at a length scale of a few nanometers consists of primary particles, which form aggregates, and clusters with aggregates as basic units. It is evidenced that the aggregate branching, represented by the mass fractal dimension, and the aggregate diameter are different if pure silica and silica in rubber are compared. Contrary, the size of the primary particles and their surface are not influenced. It is demonstrated that the change in the aggregate morphology is due to the external mechanical forces appearing during the mixing process. This is achieved by model experiments using a pistil and a mortar and a composite with different silica fractions. By that means, a systematic change in the morphology with grinding time is observed. Then, the experiments on the composite demonstrate that the major contributions to the mass fractal dimensions are due to the external mechanical forces. In order to test reproducibility and universal validity in the case of precipitated silicas, independent experiments on one silica and further silicas are performed. Several important conclusions are obtained from the study. First, it is shown that a comparison of different pure silica samples without knowing their history may be difficult or questionable. Second, it becomes evident that it is not sufficient to provide only a description of the materials, rather than the details of the sample treatment have to be reported. Therefore, solely the characterization of the morphology of the pure silica is not sufficient to be compared to the mechanical properties of the composites.

  16. Event based climatology of extreme precipitation in Europe

    NASA Astrophysics Data System (ADS)

    Nissen, Katrin M.; Becker, Nico; Ulbrich, Uwe

    2015-04-01

    An event based detection algorithm to identify extreme precipitation events in gridded data sets is introduced and applied to the observational E-OBS data set. The algorithm identifies all grid boxes in which the rainfall exceeds a threshold, which depends on the location and the aggregation period. The aggregation periods taken into account in this study range from a single time step up to 72 hours. The local 50-year return level is calculated for all aggregation periods and used as a threshold. All identified grid boxes which are located within the same continuous rain area (i.e. which are not separated by rain free grid boxes) are considered as belonging to the same event and form a cluster. The centre of mass is calculated for each cluster. The clusters are then tracked in time using a nearest neighbor approach. Thus, each detected event can consist of several grid boxes and can last for several time steps. A precipitation severity index (PSI) is assigned to the events. The severity index takes the affected area and the amount of precipitation accumulated over the duration of the event into account. It is normalized by the long-term mean annual precipitation sum expected for the grid box. The severity index can be used to compare the strength of the identified events. The detection algorithm also stores additional information for each event, such as the date, location, affected area, duration, severity and maximum precipitation. Comparing all events detected in the E-OBS data set, which exceeded the local 50-year return levels, the highest severity index was calculated for an event affecting Spain, which took place in November 1997. It had a severity index of 49.9 and was also described in the literature. In comparison, the average PSI for the extreme precipitation events over Europe is 2.4. Overall, the most active season for extreme precipitation in Europe is summer. The longest duration of an event in the data set was 11 days. It occurred over Estonia in

  17. Aggregation operations for multiaspect fuzzy soft sets

    NASA Astrophysics Data System (ADS)

    Sulaiman, Nor Hashimah; Mohamad, Daud

    2015-10-01

    Multiaspect fuzzy soft set (MAFSS) is one of the generalized forms of fuzzy soft sets. In this paper, we introduce two types of aggregation operations for MAFSSs, namely the weighted arithmetic mean (WAM)-based MAFSS aggregation, and the ordered weighted aggregation (OWA)-based MAFSS aggregation. The applicability of the two MAFSS-aggregation operations is illustrated with numerical examples in group decision making.

  18. The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset

    NASA Technical Reports Server (NTRS)

    Huffman, George J.; Adler, Robert F.; Arkin, Philip; Chang, Alfred; Ferraro, Ralph; Gruber, Arnold; Janowiak, John; McNab, Alan; Rudolf, Bruno; Schneider, Udo

    1997-01-01

    The Global Precipitation Climatology Project (GPCP) has released the GPCP Version 1 Combined Precipitation Data Set, a global, monthly precipitation dataset covering the period July 1987 through December 1995. The primary product in the dataset is a merged analysis incorporating precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit -satellite infrared data, and rain gauge observations. The dataset also contains the individual input fields, a combination of the microwave and infrared satellite estimates, and error estimates for each field. The data are provided on 2.5 deg x 2.5 deg latitude-longitude global grids. Preliminary analyses show general agreement with prior studies of global precipitation and extends prior studies of El Nino-Southern Oscillation precipitation patterns. At the regional scale there are systematic differences with standard climatologies.

  19. PRECIPITATION METHOD OF SEPARATING PLUTONIUM FROM CONTAMINATING ELEMENTS

    DOEpatents

    Duffield, R.B.

    1959-02-24

    S>A method is described for separating plutonium, in a valence state of less than five, from an aqueous solution in which it is dissolved. The niethod consists in adding potassium and sulfate ions to such a solution while maintaining the solution at a pH of less than 7.1, and isolating the precipitate of potassium plutonium sulfate thus formed.

  20. HIGH RESISTIVITY BEHAVIOR OF HOT-SIDE ELECTROSTATIC PRECIPITATORS

    EPA Science Inventory

    The report gives results of experiments to explain the high resistivity behavior of hot-side electrostatic precipitators (ESPs) collecting fly ash. The working hypothesis is that the behavior is the result of the buildup of a thin layer of sodium-ion-depleted fly ash which has a ...

  1. PARTICULATE CONTROL HIGHLIGHTS: ADVANCED CONCEPTS IN ELECTROSTATIC PRECIPITATORS: PARTICLE CHARGING

    EPA Science Inventory

    The report gives highlights of an EPA research program aimed at developing and verifying an accurate theory of particle charging for conditions that are typically found in industrial electrostatic precipitators. A new theory was developed, in which the thermal motion of ions is a...

  2. SPATIAL AND TEMPORAL PATTERNS OF ACID PRECIPITATION AND THEIR INTERPRETATION

    EPA Science Inventory

    Using data compiled from seven nationwide precipitation chemistry networks in the U.S. and Canada, the spatial distribution of hydrogen, sulfate, and nitrate ions in North America is discussed. Geographic patterns of concentration and deposition are characterized using isopleth m...

  3. Evaporation effects in elastocapillary aggregation

    NASA Astrophysics Data System (ADS)

    Vella, Dominic; Hadjittofis, Andreas; Singh, Kiran; Lister, John

    2015-11-01

    We consider the effect of evaporation on the aggregation of a number of elastic objects due to a liquid's surface tension. In particular, we consider an array of spring-block elements in which the gaps between blocks are filled by thin liquid films that evaporate during the course of an experiment. Using lubrication theory to account for the fluid flow within the gaps, we study the dynamics of aggregation. We find that a non-zero evaporation rate causes the elements to aggregate more quickly and, indeed, to contact within finite time. However, we also show that the number of elements within each cluster decreases as the evaporation rate increases. We explain these results quantitatively by comparison with the corresponding two-body problem and discuss their relevance for controlling pattern formation in carbon nanotube forests.

  4. Molecular Aggregation in Disodium Cromoglycate

    NASA Astrophysics Data System (ADS)

    Singh, Gautam; Agra-Kooijman, D.; Collings, P. J.; Kumar, Satyendra

    2012-02-01

    Details of molecular aggregation in the mesophases of the anti-asthmatic drug disodium cromoglycate (DSCG) have been studied using x-ray synchrotron scattering. The results show two reflections, one at wide angles corresponding to π-π stacking (3.32 å) of molecules, and the other at small angles which is perpendicular to the direction of molecular stacking and corresponds to the distance between the molecular aggregates. The latter varies from 35 - 41 å in the nematic (N) phase and 27 -- 32 å in the columnar (M) phase. The temperature evolution of the stack height, positional order correlations in the lateral direction, and orientation order parameter were determined in the N, M, and biphasic regions. The structure of the N and M phases and the nature of the molecular aggregation, together with their dependence on temperature and concentration, will be presented.

  5. Global kinetic analysis of seeded BSA aggregation.

    PubMed

    Sahin, Ziya; Demir, Yusuf Kemal; Kayser, Veysel

    2016-04-30

    Accelerated aggregation studies were conducted around the melting temperature (Tm) to elucidate the kinetics of seeded BSA aggregation. Aggregation was tracked by SEC-HPLC and intrinsic fluorescence spectroscopy. Time evolution of monomer, dimer and soluble aggregate concentrations were globally analysed to reliably deduce mechanistic details pertinent to the process. Results showed that BSA aggregated irreversibly through both sequential monomer addition and aggregate-aggregate interactions. Sequential monomer addition proceeded only via non-native monomers, starting to occur only by 1-2°C below the Tm. Aggregate-aggregate interactions were the dominant mechanism below the Tm due to an initial presence of small aggregates that acted as seeds. Aggregate-aggregate interactions were significant also above the Tm, particularly at later stages of aggregation when sequential monomer addition seemed to cease, leading in some cases to insoluble aggregate formation. The adherence (or non-thereof) of the mechanisms to Arrhenius kinetics were discussed alongside possible implications of seeding for biopharmaceutical shelf-life and spectroscopic data interpretation, the latter of which was found to often be overlooked in BSA aggregation studies. PMID:26970282

  6. Environmentalism and natural aggregate mining

    USGS Publications Warehouse

    Drew, L.J.; Langer, W.H.; Sachs, J.S.

    2002-01-01

    Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy-hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers-their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is "man must live more lightly on the land." The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for

  7. Aggregation work at polydisperse micellization: ideal solution and "dressed micelle" models comparing to molecular dynamics simulations.

    PubMed

    Burov, S V; Shchekin, A K

    2010-12-28

    General thermodynamic relations for the work of polydisperse micelle formation in the model of ideal solution of molecular aggregates in nonionic surfactant solution and the model of "dressed micelles" in ionic solution have been considered. In particular, the dependence of the aggregation work on the total concentration of nonionic surfactant has been analyzed. The analogous dependence for the work of formation of ionic aggregates has been examined with regard to existence of two variables of a state of an ionic aggregate, the aggregation numbers of surface active ions and counterions. To verify the thermodynamic models, the molecular dynamics simulations of micellization in nonionic and ionic surfactant solutions at two total surfactant concentrations have been performed. It was shown that for nonionic surfactants, even at relatively high total surfactant concentrations, the shape and behavior of the work of polydisperse micelle formation found within the model of the ideal solution at different total surfactant concentrations agrees fairly well with the numerical experiment. For ionic surfactant solutions, the numerical results indicate a strong screening of ionic aggregates by the bound counterions. This fact as well as independence of the coefficient in the law of mass action for ionic aggregates on total surfactant concentration and predictable behavior of the "waterfall" lines of surfaces of the aggregation work upholds the model of "dressed" ionic aggregates. PMID:21197978

  8. Unusual Cyclodextrin Derivatives as a New Avenue to Modulate Self- and Metal-Induced Aβ Aggregation.

    PubMed

    Oliveri, Valentina; Bellia, Francesco; Pietropaolo, Adriana; Vecchio, Graziella

    2015-09-28

    Mounting evidence suggests an important role of cyclodextrins in providing protection in neurodegenerative disorders. Metal dyshomeostasis is reported to be a pathogenic factor in neurodegeneration because it could be responsible for damage involving oxidative stress and protein aggregation. As such, metal ions represent an effective target. To improve the metal-binding ability of cyclodextrin, we synthesized three new 8-hydroxyquinoline-cyclodextrin conjugates with difunctionalized cyclodextrins. In particular, the 3-difunctionalized regioisomer represents the first example of cyclodextrin with two pendants at the secondary rim, resulting in a promising compound. The derivatives have significant antioxidant capacity and the powerful activity in inhibiting self-induced amyloid-β aggregation seems to be led by synergistic effects of both cyclodextrin and hydroxyquinoline. Moreover, the derivatives are also able to complex metal ions and to inhibit metal-induced protein aggregation. Therefore, these compounds could have potential as therapeutic agents in diseases related to protein aggregation and metal dyshomeostasis. PMID:26298549

  9. Glycation by Ascorbic Acid Oxidation Products Leads to the Aggregation of Lens Proteins

    PubMed Central

    Linetsky, Mikhail; Shipova, Ekaterina; Cheng, Rongzhu; Ortwerth, Beryl J.

    2008-01-01

    Previous studies from this laboratory have shown that there are striking similarities between the yellow chromophores, fluorophores and modified amino acids released by proteolytic digestion from calf lens proteins ascorbylated in vitro and their counterparts isolated from aged and cataractous lens proteins. The studies reported in this communication were conducted to further investigate whether ascorbic acid-mediated modification of lens proteins could lead to the formation of lens protein aggregates capable of scattering visible light, similar to the high molecular aggregates found in aged human lenses. Ascorbic acid, but not glucose, fructose, ribose or erythrulose, caused the aggregation of calf lens proteins to proteins ranging from 2.2 × 106 up to 3.0 × 108 Da. This compared to proteins ranging from 1.8 × 106 up to 3.6 × 108 Da for the water-soluble (WS) proteins isolated from aged human lenses. This aggregation was likely due to the glycation of lens crystallins because [U-14C] ascorbate was incorporated into the aggregate fraction and because CNBH3, which reduces the initial Schiff base, prevented any protein aggregation. Reactions of ascorbate with purified crystallin fractions showed little or no aggregation of α-crystallin, significant aggregation of βH-crystallin, but rapid precipitation of purified βL- and γ-crystallin. The aggregation of lens proteins can be prevented by the binding of damaged crystallins to alpha-crystallin due to its chaperone activity. Depending upon the ratios between the components of the incubation mixtures, α-crystallin prevented the precipitation of the purified βL- and γ-crystallin fractions during ascorbylation. The addition of at least 20% of alpha-crystallin by weight into glycation mixtures with βL-, or γ-crystallins completely inhibited protein precipitation, and increased the amount of the high molecular weight aggregates in solution. Static and dynamic light scattering measurements of the supernatants from

  10. [Chemical characteristics of precipitation in South China Sea].

    PubMed

    Xiao, Hong-Wei; Long, Ai-Min; Xie, Lu-Hua; Xiao, Hua-Yun; Liu, Cong-Qiang

    2014-02-01

    Rainwater samples were collected in the summer on "Shiyan 3" during the 2012 South China Sea Sectional Scientific Survey. The concentrations of anion and cation, and pH in precipitation were determined and backward trajectories of air mass were simulated to analyze the chemical characteristics of ions and examine the source of ions. The results indicated that the mean pH value of precipitation was 6.3, with 5.6 of minimal value in summer in South China Sea. The order of anion and cation abundance was Cl(-) > S04(2-) > NO3(-) and Na(+) > Mg(2+) > Ca(2+) > K(+). Cl(-) was the major anion and Na(+) was the major cation, with concentrations of 2 637.5 microeq x L(-1) and 2095.5 microeq x L(-1), respectively, showing that they were the characteristics of marine atmospheric precipitation. There was a good linear relationship between each pair of 7 ions, with correlation coefficient above 0.9, suggesting that they may have a common source. However, the correlation coefficients were lower between NO3(-) and other ions than the others, suggesting that NO3(-) had more complex sources. The concentrations of Ca(2+) and K(+) in precipitation may be related to coral environment in South China Sea. The backward trajectories in 6 stations showed that the air mass was from south and southwest of South China Sea, without passing through above the continent. These results suggested that precipitation affected by human ion source can be ignored in summer in South China Sea. PMID:24812936

  11. Precipitation of copper and chromium impurities in lanthanum magnesium aluminate crystals during thermochemical reduction

    SciTech Connect

    Ballesteros, C. ); Gonzalez, R. ); Chen, Y. ); Kokta, M.R. )

    1993-02-01

    Thermochemical reduction at high temperatures has been performed on chromium-doped lanthanum magnesium aluminate crystals. Analytical transmission-electron-microscopy and optical-absorption techniques were used to characterize the crystals. Copper impurities inherently present in the crystals began to aggregate and form Cu-rich particles at 1500 K near the surface region. Below 1870 K there was no evidence of chromium precipitates being formed. However, Cr-rich particles were formed at 2020 K. The distribution of the precipitates was very inhomogeneous and the precipitates were also concentrated near the surface region.

  12. Relation of precipitation quality to storm type, and deposition of dissolved chemical constituents from precipitation in Massachusetts, 1983-85

    USGS Publications Warehouse

    Gay, F.B.; Melching, C.S.

    1995-01-01

    Precipitation samples were collected for 83 storms at a rural inland site in Princeton, Mass., and 73 storms at a rural coastal site in Truro, Mass., to examine the quality of precipitation from storms and relate quality to three storm types (oceanic cyclone, continental cyclone, and cold front). At the inland site, Princeton, ranked-means of precipitation depth, storm duration, specific conductance, and concentrations and loads of hydrogen, sulfate, aluminum, bromide, and copper ions were affected by storm type. At the coastal site, Truro, ranked means of precipitation depth, storm duration, and concentrations and loads of calcium, chloride, magnesium, potassium, and sodium ions were affected by storm type. Precipitation chemistry at the coastal site was 85 percent oceanic in orgin, whereas precipitation 72 kilometers inland was 60 percent hydrogen, nitrate, and sulfate ions, reflecting fossil-fuel combustion. Concentrations and loads for specific conductance and 9 chemical constituents on an annual and seasonal basis were determined from National Atmospheric Deposition Program data for spring 1983 through winter 1985 at Quabbin (rural, inland), Waltham (suburban, inland) and Truro (rural, coastal), Massachusetts. Concentrations of magnesium, potassium, sodium, and chloride concentrations were highest at the coast and much lower inland, with very little difference between Waltham and Quabbin. Loads of ammonium, nitrate, sulfate, and hydrogen are highest at Quabbin and are about equal at Waltham and Truro. About twice as much nitrate and hydrogen and about 35 percent more sulfate is deposited at Quabbin than at Waltham or Truro; this pattern indicates that the interior of Massachusetts receives more acidic precipitation than do the eastern or the coastal areas of Massachusetts.

  13. Ten years trends (1984-1993) in the precipitation chemistry in central Austria

    NASA Astrophysics Data System (ADS)

    Puxbaum, H.; Simeonov, V.; Kalina, M. F.

    Since 1984, wet precipitation samples have been collected from five sampling sites in the eastern Alpine region of Austria. The chemical analysis performed included pH, NH 4+, Na +, K +, Ca 2+, Mg 2+, Cl -, NO 3- SO 42- and precipitation amount. These data were used to determine the 10 years (1984-1993) trends in precipitation chemistry and deposition for all major ions. The statistical data treatment by the use of least-squares linear regression revealed a significant decrease of sulfate and hydrogen ion concentrations and depositions at all sites in consideration (above 65% for hydrogen ion and over 33% for sulfate concentration and 40% for hydrogen and 36% for sulfate deposition). An effort is made to explain the acidity decrease not only by the parallel decrease of sulfate concentration but by the participation of the other constituents of the wet precipitation events. It has been found that when the hydrogen ion concentration decrease is stronger than that of sulfate ion concentrations a compensation mainly by ammonium ion concentration increase is achieved. On the contrary, when the hydrogen ion concentration decrease is weaker than sulfate concentration decrease, a calcium ion concentration decrease is present for the sites in consideration. The results obtained indicate that the precipitation chemistry in Central Austria follows the global trends of controlled reduction of atmospheric acidity.

  14. Label free and high specific detection of mercury ions based on silver nano-liposome.

    PubMed

    Priyadarshini, Eepsita; Pradhan, Nilotpala; Pradhan, Arun K; Pradhan, Pallavi

    2016-06-15

    Herein, we report an eco-friendly, mild and one-pot approach for synthesis of silver nanoparticles via a lipopeptide biosurfactant - CHBS. The biosurfactant forms liposome vesicles when dispersed in an aqueous medium. The amino acid groups of the biosurfactant assists in the reduction of Ag(+) ions leading to the production of homogeneous silver nanoparticles, encapsulated within the liposome vesicle, as confirmed from TEM analysis. Rate of synthesis and size of particle were greatly dependent on pH and reaction temperature. Kinetic analysis suggests the involvement of an autocatalytic reaction and the observed rate constant (kobs) was found to decrease with temperature, suggesting faster reaction with increasing temperature. Furthermore, the silver nanoparticles served as excellent probes for highly selective and sensitive recognition of Hg(2+) ions. Interaction with Hg(2+) ions results in an immediate change in colour of nanoparticle solution form brownish red to milky white. With increasing Hg(2+) ions concentration, a gradual disappearance of SPR peak was observed. A linear relationship (A420/660) with an R(2) value of 0.97 was observed in the range of 20 to 100ppm Hg(2+) concentration. Hg(2+) ions are reduced to their elemental forms which thereby interact with the vesicles, leading to aggregation and precipitation of particles. The detection method avoids the need of functionalizing ligands and favours Hg(2+) detection in aqueous samples by visible range spectrophotometry and hence can be used for simple and rapid analysis. PMID:27045785

  15. Label free and high specific detection of mercury ions based on silver nano-liposome

    NASA Astrophysics Data System (ADS)

    Priyadarshini, Eepsita; Pradhan, Nilotpala; Pradhan, Arun K.; Pradhan, Pallavi

    2016-06-01

    Herein, we report an eco-friendly, mild and one-pot approach for synthesis of silver nanoparticles via a lipopeptide biosurfactant - CHBS. The biosurfactant forms liposome vesicles when dispersed in an aqueous medium. The amino acid groups of the biosurfactant assists in the reduction of Ag+ ions leading to the production of homogeneous silver nanoparticles, encapsulated within the liposome vesicle, as confirmed from TEM analysis. Rate of synthesis and size of particle were greatly dependent on pH and reaction temperature. Kinetic analysis suggests the involvement of an autocatalytic reaction and the observed rate constant (kobs) was found to decrease with temperature, suggesting faster reaction with increasing temperature. Furthermore, the silver nanoparticles served as excellent probes for highly selective and sensitive recognition of Hg2 + ions. Interaction with Hg2 + ions results in an immediate change in colour of nanoparticle solution form brownish red to milky white. With increasing Hg2 + ions concentration, a gradual disappearance of SPR peak was observed. A linear relationship (A420/660) with an R2 value of 0.97 was observed in the range of 20 to 100 ppm Hg2 + concentration. Hg2 + ions are reduced to their elemental forms which thereby interact with the vesicles, leading to aggregation and precipitation of particles. The detection method avoids the need of functionalizing ligands and favours Hg2 + detection in aqueous samples by visible range spectrophotometry and hence can be used for simple and rapid analysis.

  16. Asphalt-aggregate interactions in hot recycling. Final report, April 1985-March 1987

    SciTech Connect

    Kiggundu, B.M.; Newman, J.K.

    1987-07-01

    This report summarizes results of an investigation of asphalt-aggregate interactions in hot recycled systems. Materials used in the research included a severe stripping aggregate and a nonstripping aggregate. Both were evaluated using the Lottman 70% retained tensile-strength criteria. Additional materials included a 40/60 RAP new aggregate system, one virgin asphalt, two RAP recovered binders, one modifier or recycling agent, and two blends. The modifier was selected using a recently developed specification involving physical, composition, and solubility properties. Aggregates were evaluated for surface area, bulk composition, water-soluble ions, cation exchange capacity, gradation, and specific gravities. Binders were tested for physical properties and composition properties using a modified Clay-Gel procedure, and compatibility properties using a modified Heithaus procedure.

  17. Aggregate expansivity due to sulfide oxidation. 2: Physico-chemical modeling of sulfate attack

    SciTech Connect

    Casanova, I.; Aguado, A.; Agullo, L.

    1997-11-01

    Weathering of sulfide-bearing aggregates in concrete causes the release of sulfate ions that can react with cement components to yield expansive products. The extent of the sulfate attack of the paste is controlled by the composition and size of the aggregate, the kinetics of sulfide oxidation, the composition of cement and mixing proportioning of concrete. The extent of sulfate attack has been successfully simulated using a combined kinetic-thermodynamic approach.

  18. Cu(II) Mediates Kinetically Distinct, Non-amyloidogenic Aggregation of Amyloid-β Peptides*

    PubMed Central

    Pedersen, Jeppe T.; Østergaard, Jesper; Rozlosnik, Noemi; Gammelgaard, Bente; Heegaard, Niels H. H.

    2011-01-01

    Cu(II) ions are implicated in the pathogenesis of Alzheimer disease by influencing the aggregation of the amyloid-β (Aβ) peptide. Elucidating the underlying Cu(II)-induced Aβ aggregation is paramount for understanding the role of Cu(II) in the pathology of Alzheimer disease. The aim of this study was to characterize the qualitative and quantitative influence of Cu(II) on the extracellular aggregation mechanism and aggregate morphology of Aβ1–40 using spectroscopic, microelectrophoretic, mass spectrometric, and ultrastructural techniques. We found that the Cu(II):Aβ ratio in solution has a major influence on (i) the aggregation kinetics/mechanism of Aβ, because three different kinetic scenarios were observed depending on the Cu(II):Aβ ratio, (ii) the metal:peptide stoichiometry in the aggregates, which increased to 1.4 at supra-equimolar Cu(II):Aβ ratio; and (iii) the morphology of the aggregates, which shifted from fibrillar to non-fibrillar at increasing Cu(II):Aβ ratios. We observed dynamic morphological changes of the aggregates, and that the formation of spherical aggregates appeared to be a common morphological end point independent on the Cu(II) concentration. Experiments with Aβ1–42 were compatible with the conclusions for Aβ1–40 even though the low solubility of Aβ1–42 precluded examination under the same conditions as for the Aβ1–40. Experiments with Aβ1–16 and Aβ1–28 showed that other parts than the Cu(II)-binding His residues were important for Cu(II)-induced Aβ aggregation. Based on this study we propose three mechanistic models for the Cu(II)-induced aggregation of Aβ1–40 depending on the Cu(II):Aβ ratio, and identify key reaction steps that may be feasible targets for preventing Cu(II)-associated aggregation or toxicity in Alzheimer disease. PMID:21642429

  19. RAGG - R EPISODIC AGGREGATION PACKAGE

    EPA Science Inventory

    The RAGG package is an R implementation of the CMAQ episodic model aggregation method developed by Constella Group and the Environmental Protection Agency. RAGG is a tool to provide climatological seasonal and annual deposition of sulphur and nitrogen for multimedia management. ...

  20. An Aggregation Advisor for Ligand Discovery.

    PubMed

    Irwin, John J; Duan, Da; Torosyan, Hayarpi; Doak, Allison K; Ziebart, Kristin T; Sterling, Teague; Tumanian, Gurgen; Shoichet, Brian K

    2015-09-10

    Colloidal aggregation of organic molecules is the dominant mechanism for artifactual inhibition of proteins, and controls against it are widely deployed. Notwithstanding an increasingly detailed understanding of this phenomenon, a method to reliably predict aggregation has remained elusive. Correspondingly, active molecules that act via aggregation continue to be found in early discovery campaigns and remain common in the literature. Over the past decade, over 12 thousand aggregating organic molecules have been identified, potentially enabling a precedent-based approach to match known aggregators with new molecules that may be expected to aggregate and lead to artifacts. We investigate an approach that uses lipophilicity, affinity, and similarity to known aggregators to advise on the likelihood that a candidate compound is an aggregator. In prospective experimental testing, five of seven new molecules with Tanimoto coefficients (Tc's) between 0.95 and 0.99 to known aggregators aggregated at relevant concentrations. Ten of 19 with Tc's between 0.94 and 0.90 and three of seven with Tc's between 0.89 and 0.85 also aggregated. Another three of the predicted compounds aggregated at higher concentrations. This method finds that 61 827 or 5.1% of the ligands acting in the 0.1 to 10 μM range in the medicinal chemistry literature are at least 85% similar to a known aggregator with these physical properties and may aggregate at relevant concentrations. Intriguingly, only 0.73% of all drug-like commercially available compounds resemble the known aggregators, suggesting that colloidal aggregators are enriched in the literature. As a percentage of the literature, aggregator-like compounds have increased 9-fold since 1995, partly reflecting the advent of high-throughput and virtual screens against molecular targets. Emerging from this study is an aggregator advisor database and tool ( http://advisor.bkslab.org ), free to the community, that may help distinguish between

  1. Development of a global historic monthly mean precipitation dataset

    NASA Astrophysics Data System (ADS)

    Yang, Su; Xu, Wenhui; Xu, Yan; Li, Qingxiang

    2016-04-01

    Global historic precipitation dataset is the base for climate and water cycle research. There have been several global historic land surface precipitation datasets developed by international data centers such as the US National Climatic Data Center (NCDC), European Climate Assessment & Dataset project team, Met Office, etc., but so far there are no such datasets developed by any research institute in China. In addition, each dataset has its own focus of study region, and the existing global precipitation datasets only contain sparse observational stations over China, which may result in uncertainties in East Asian precipitation studies. In order to take into account comprehensive historic information, users might need to employ two or more datasets. However, the non-uniform data formats, data units, station IDs, and so on add extra difficulties for users to exploit these datasets. For this reason, a complete historic precipitation dataset that takes advantages of various datasets has been developed and produced in the National Meteorological Information Center of China. Precipitation observations from 12 sources are aggregated, and the data formats, data units, and station IDs are unified. Duplicated stations with the same ID are identified, with duplicated observations removed. Consistency test, correlation coefficient test, significance t-test at the 95% confidence level, and significance F-test at the 95% confidence level are conducted first to ensure the data reliability. Only those datasets that satisfy all the above four criteria are integrated to produce the China Meteorological Administration global precipitation (CGP) historic precipitation dataset version 1.0. It contains observations at 31 thousand stations with 1.87 × 107 data records, among which 4152 time series of precipitation are longer than 100 yr. This dataset plays a critical role in climate research due to its advantages in large data volume and high density of station network, compared to

  2. Capturing a Reactive State of Amyloid Aggregates

    PubMed Central

    Parthasarathy, Sudhakar; Yoo, Brian; McElheny, Dan; Tay, William; Ishii, Yoshitaka

    2014-01-01

    The interaction of redox-active copper ions with misfolded amyloid β (Aβ) is linked to production of reactive oxygen species (ROS), which has been associated with oxidative stress and neuronal damages in Alzheimer disease. Despite intensive studies, it is still not conclusive how the interaction of Cu+/Cu2+ with Aβ aggregates leads to ROS production even at the in vitro level. In this study, we examined the interaction between Cu+/Cu2+ and Aβ fibrils by solid-state NMR (SSNMR) and other spectroscopic methods. Our photometric studies confirmed the production of ∼60 μm hydrogen peroxide (H2O2) from a solution of 20 μm Cu2+ ions in complex with Aβ(1–40) in fibrils ([Cu2+]/[Aβ] = 0.4) within 2 h of incubation after addition of biological reducing agent ascorbate at the physiological concentration (∼1 mm). Furthermore, SSNMR 1H T1 measurements demonstrated that during ROS production the conversion of paramagnetic Cu2+ into diamagnetic Cu+ occurs while the reactive Cu+ ions remain bound to the amyloid fibrils. The results also suggest that O2 is required for rapid recycling of Cu+ bound to Aβ back to Cu2+, which allows for continuous production of H2O2. Both 13C and 15N SSNMR results show that Cu+ coordinates to Aβ(1–40) fibrils primarily through the side chain Nδ of both His-13 and His-14, suggesting major rearrangements from the Cu2+ coordination via Nϵ in the redox cycle. 13C SSNMR chemical shift analysis suggests that the overall Aβ conformations are largely unaffected by Cu+ binding. These results present crucial site-specific evidence of how the full-length Aβ in amyloid fibrils offers catalytic Cu+ centers. PMID:24523414

  3. Mechanism of cellular response to nanoscale aggregates of small molecules

    NASA Astrophysics Data System (ADS)

    Kuang, Yi

    This dissertation research focused on the illustration of the molecular mechanism of cellular response to nanoscale aggregates formed by small molecules. There are five chapters in this dissertation. Chapter 1 summarizes the current research on the evaluation of cell response (i.e., biocompatibility/cytotoxicity) to small molecular hydrogelators. Chapter 2 describes an interesting phenomenon that supramolecular hydrogelators consisting of N-terminated dipeptides, which exhibit selective inhibitory effects against cancer cells. This study calls for the development of a new approach for identification of protein targets of the hydrogelators. Chapter 3 describes the evaluation of interactions between cytosol proteins of a mammalian cell line and morphologically different nanoscale molecular aggregates formed by small peptidic molecules. Chapter 4 describes the research on the mechanism of a type of molecular aggregates, which cluster short microtubules to prevent the growth of microtubule. This unprecedented mechanism of "self-assembly to interfere with self-organization " contributes to inhibiting growth of cancer cells in several mammalian cell based assays and a xenograft tumor mice model. At the end, Chapter 5 reports a novel supramolecular hydrogelator, which consists of fluorene and the pentapeptide epitope (TIGYG) of potassium ion (K+) channels, to self-assemble in water to form the tunable, hierarchical nanostructures dictated by the concentration of K+. In conclusion, this dissertation research demonstrates a new approach for investigating cellular target and molecular mechanism of self-assembled aggregates formed by small peptide derivatives based hydrogelators, which will make contribution to the development of supramolecular hydrogelators as biomaterials. Moreover, the differential cytotoxicity of molecular aggregates illustrated in this research promises a new direction for developing anti-cancer drug based on interactions between molecular aggregates and

  4. Endoplasmic reticulum stress activates transglutaminase 2 leading to protein aggregation

    PubMed Central

    LEE, JIN-HAENG; JEONG, JAEHO; JEONG, EUI MAN; CHO, SUNG-YUP; KANG, JEONG WOOK; LIM, JISUN; HEO, JINBEOM; KANG, HYUNSOOK; KIM, IN-GYU; SHIN, DONG-MYUNG

    2014-01-01

    Aberrant activation of transglutaminase 2 (TGase2) contributes to a variety of protein conformational disorders such as neurodegenerative diseases and age-related cataracts. The accumulation of improperly folded proteins in the endoplasmic reticulum (ER) triggers the unfolded protein response (UPR), which promotes either repair or degradation of the damaged proteins. Inadequate UPR results in protein aggregation that may contribute to the development of age-related degenerative diseases. TGase2 is a calcium-dependent enzyme that irreversibly modifies proteins by forming cross-linked protein aggregates. Intracellular TGase2 is activated by oxidative stress which generates large quantities of unfolded proteins. However, the relationship between TGase2 activity and UPR has not yet been established. In the present study, we demonstrated that ER stress activated TGase2 in various cell types. TGase2 activation was dependent on the ER stress-induced increase in the intracellular calcium ion concentration but not on the TGase2 protein expression level. Enzyme substrate analysis revealed that TGase2-mediated protein modification promoted protein aggregation concurrently with decreasing water solubility. Moreover, treatment with KCC009, a TGase2 inhibitor, abrogated ER stress-induced TGase2 activation and subsequent protein aggregation. However, TGase2 activation had no effect on ER stress-induced cell death. These results demonstrate that the accumulation of misfolded proteins activates TGase2, which further accelerates the formation of protein aggregates. Therefore, we suggest that inhibition of TGase2 may be a novel strategy by which to prevent the protein aggregation in age-related degenerative diseases. PMID:24481335

  5. Formation and Growth of Stacking Fault Tetrahedra in Ni via Vacancy Aggregation Mechanism

    SciTech Connect

    Aidhy, Dilpuneet S.; Lu, Chenyang; Jin, Ke; Bei, Hongbin; Zhang, Yanwen; Wang, Lumin; Weber, William J.

    2015-12-29

    Using molecular dynamics simulations, the formation and growth of stacking fault tetrahedra (SFT) are captured by vacancy cluster diffusion and aggregation mechanisms in Ni. The vacancytetrahedron acts as a nucleation point for SFT formation. Simulations show that perfect SFT can grow to the next size perfect SFT via a vacancy aggregation mechanism. The stopping and range of ions in matter (SRIM) calculations and transmission electron microscopy (TEM) observations reveal that SFT can form farther away from the initial cascade-event locations, indicating the operation of diffusion-based vacancy-aggregation mechanism.

  6. A novel approach to evaluate the spatial complexity of soil aggregates using NanoSIMS

    NASA Astrophysics Data System (ADS)

    Steffens, Markus; Rogge, Derek; Hoeschen, Carmen; Mueller, Carsten

    2015-04-01

    Soil aggregation is a key factor for a number of biogeochemical processes (e.g. soil organic matter stabilization and nutrient and pollutant sorption) in soils. Although there is a large number of studies on the factors controlling such soil processes, it is still challenging to study these processes in-situ. However it can be assumed that the spatial arrangement of biogenic and mineral soil constituents in soil aggregates and thus the aggregate structure determine the processes happening at the aggregate scale. We used the nano-scale secondary ion mass spectrometry (NanoSIMS) technology to study a cross section of a single large aggregate from the top-soil of an agricultural cropland with a regular grid of 45 measurements (each with a size of 30x30 µm). Using Cs+ as primary ion, the negatively charged ions 12C-, 12C14N-, 12C15N-, 27Al16O-, 56Fe16O- and 28Si- were collected with a lateral resolution of up to 100 nm. We applied pre-processing algorithms and unsupervised classifications to separate and identify organic and inorganic compartments in the NanoSIMS measurements. Our approach enabled us to explore the elemental and isotopic composition of organic and inorganic particles at a before unresolved lateral resolution for a complete soil aggregate and spatially explicitly map and quantify the different compartments.

  7. Sulfate anion delays the self-assembly of human insulin by modifying the aggregation pathway.

    PubMed

    Owczarz, Marta; Arosio, Paolo

    2014-07-01

    The understanding of the molecular mechanisms underlying protein self-assembly and of their dependence on solvent composition has implications in a large number of biological and biotechnological systems. In this work, we characterize the aggregation process of human insulin at acidic pH in the presence of sulfate ions using a combination of Thioflavin T fluorescence, dynamic light scattering, size exclusion chromatography, Fourier transform infrared spectroscopy, and transmission electron microscopy. It is found that the increase of sulfate concentration inhibits the conversion of insulin molecules into aggregates by modifying the aggregation pathway. At low sulfate concentrations (0-5 mM) insulin forms amyloid fibrils following the nucleated polymerization mechanism commonly observed under acidic conditions in the presence of monovalent anions. When the sulfate concentration is increased above 5 mM, the sulfate anion induces the salting-out of ∼18-20% of insulin molecules into reversible amorphous aggregates, which retain a large content of α-helix structures. During time these aggregates undergo structure rearrangements into β-sheet structures, which are able to recruit monomers and bind to the Thioflavin T dye. The alternative aggregation mechanism observed at large sulfate concentrations is characterized by a larger activation energy and leads to more polymorphic structures with respect to the self-assembly in the presence of chloride ions. The system shown in this work represents a case where amorphous aggregates on pathway to the formation of structures with amyloid features could be detected and analyzed. PMID:24988354

  8. Sulfate Anion Delays the Self-Assembly of Human Insulin by Modifying the Aggregation Pathway

    PubMed Central

    Owczarz, Marta; Arosio, Paolo

    2014-01-01

    The understanding of the molecular mechanisms underlying protein self-assembly and of their dependence on solvent composition has implications in a large number of biological and biotechnological systems. In this work, we characterize the aggregation process of human insulin at acidic pH in the presence of sulfate ions using a combination of Thioflavin T fluorescence, dynamic light scattering, size exclusion chromatography, Fourier transform infrared spectroscopy, and transmission electron microscopy. It is found that the increase of sulfate concentration inhibits the conversion of insulin molecules into aggregates by modifying the aggregation pathway. At low sulfate concentrations (0–5 mM) insulin forms amyloid fibrils following the nucleated polymerization mechanism commonly observed under acidic conditions in the presence of monovalent anions. When the sulfate concentration is increased above 5 mM, the sulfate anion induces the salting-out of ∼18–20% of insulin molecules into reversible amorphous aggregates, which retain a large content of α-helix structures. During time these aggregates undergo structure rearrangements into β-sheet structures, which are able to recruit monomers and bind to the Thioflavin T dye. The alternative aggregation mechanism observed at large sulfate concentrations is characterized by a larger activation energy and leads to more polymorphic structures with respect to the self-assembly in the presence of chloride ions. The system shown in this work represents a case where amorphous aggregates on pathway to the formation of structures with amyloid features could be detected and analyzed. PMID:24988354

  9. Examination of Ataxin-3 (atx-3) Aggregation by Structural Mass Spectrometry Techniques: A Rationale for Expedited Aggregation upon Polyglutamine (polyQ) Expansion*

    PubMed Central

    Scarff, Charlotte A.; Almeida, Bruno; Fraga, Joana; Macedo-Ribeiro, Sandra; Radford, Sheena E.; Ashcroft, Alison E.

    2015-01-01

    Expansion of polyglutamine stretches leads to the formation of polyglutamine-containing neuronal aggregates and neuronal death in nine diseases for which there currently are no treatments or cures. This is largely due to a lack in understanding of the mechanisms by which expanded polyglutamine regions contribute to aggregation and disease. To complicate matters further, several of the polyglutamine-disease related proteins, including ataxin-3, have a multistage aggregation mechanism in which flanking domain self-assembly precedes polyglutamine aggregation yet is influenced by polyglutamine expansion. How polyglutamine expansion influences flanking domain aggregation is poorly understood. Here, we use a combination of mass spectrometry and biophysical approaches to investigate this issue for ataxin-3. We show that the conformational dynamics of the flanking Josephin domain in ataxin-3 with an expanded polyglutamine tract are altered in comparison to those exhibited by its nonexpanded counterpart, specifically within the aggregation-prone region of the Josephin domain (amino acid residues 73–96). Expansion thus exposes this region more frequently in ataxin-3 containing an expanded polyglutamine tract, providing a molecular explanation of why aggregation is accelerated upon polyglutamine expansion. Here, harnessing the power of ion mobility spectrometry-mass spectrometry, oligomeric species formed during aggregation are characterized and a model for oligomer growth proposed. The results suggest that a conformational change occurs at the dimer level that initiates self-assembly. New insights into ataxin-3 fibril architecture are also described, revealing the region of the Josephin domain involved in protofibril formation and demonstrating that polyglutamine aggregation proceeds as a distinct second step after protofibril formation without requiring structural rearrangement of the protofibril core. Overall, the results enable the effect of polyglutamine expansion on

  10. Nano-Scale Analysis of Precipitates in Nitrogen-Doped Czochralski SIlicon

    SciTech Connect

    Rozgonyi, G. A.; Karoui, A.; Kvit, A.; Duscher, Gerd J M

    2003-01-01

    Nitrogen-doped Czochralski (CZ) silicon wafers were heat treated with Lo-Hi annealing in argon. Nanoscale defects were then examined by high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM) in the Z-contrast mode, and electron energy loss spectroscopy (EELS) analyses using a field emission JEOL 2010 with a resolution below 2 {angstrom}. The structures of precipitates, stacking faults and interstitial aggregates were found to depend on their location relative to the wafer surface. Precipitate composition, strain at the interface and interface roughness were obtained and are discussed in connection with the point defects generated during crystal growth and modified during wafer annealing. An excellent correlation was found between Z-contrast line scans across the precipitates and the N to O concentration ratio determined with EELS. In the precipitate central region that ratio is between 1 and 6%, whereas at precipitate boundaries it reaches 17%.

  11. Improved ethanol precipitation of DNA.

    PubMed

    Fregel, Rosa; González, Ana; Cabrera, Vicente M

    2010-04-01

    In this Short Communication, a shorter version of the standard DNA ethanol precipitation and purification protocol is described. It uses a mixture of 70% ethanol, 75 mM ammonium acetate and different concentrations of different carriers to perform DNA precipitation and washing in only one step. PMID:20336673

  12. Precipitation Process and Apparatus Therefor

    DOEpatents

    Stang, Jr, L C

    1950-12-05

    This invention concerns an apparatus for remotely-controlled precipitation and filtration operations. Liquid within a precipitation chamber is maintained above a porous member by introducing air beneath the member; pressure beneath the porous member is reduced to suck the liquid through the member and effect filtration.

  13. Acid precipitation in historical perspective

    SciTech Connect

    Cowling, E.B.

    1982-02-01

    The history of acid precipitation is traced from the first awareness of the problem in the mid-17th century to the present. An outline of the National Acid Precipitation Assessment program is also given, and the author makes recommendations for future research. (JMT)

  14. Precipitation in the Solar System

    ERIC Educational Resources Information Center

    McIntosh, Gordon

    2007-01-01

    As an astronomy instructor, I am always looking for commonly observed Earthly experiences to help my students and me understand and appreciate similar occurrences elsewhere in the solar system. Recently I wrote a short TPT article on frost. This paper is on the related phenomena of precipitation. Precipitation, so common on most of the Earth's…

  15. Resistivity Problems in Electrostatic Precipitation

    ERIC Educational Resources Information Center

    White, Harry J.

    1974-01-01

    The process of electrostatic precipitation has ever-increasing application in more efficient collection of fine particles from industrial air emissions. This article details a large number of new developments in the field. The emphasis is on high resistivity particles which are a common cause of poor precipitator performance. (LS)

  16. Solar wind precipitation - a comparison between Mars and Venus

    NASA Astrophysics Data System (ADS)

    Stenberg Wieser, Gabriella; Nilsson, Hans; Futaana, Yoshifumi; Holmström, Mats; Barabash, Stas

    2015-04-01

    Mars and Venus both have atmospheres but both lack a substantial intrinsic magnetic field. Hence, their interaction with the solar wind is similar. Due to currents set up in the ionospheres the interplanetary magnetic field embedded in the solar wind drapes around the planets forming induced magnetospheres. The plasma instrument packages ASPERA-3 and ASPERA-4 on the two spacecraft Mars Express and Venus Express are very similar and invite to a comparison between the two plasma environments. In this study we used the Ion Mass Analyser (IMA) on both spacecraft to investigate the solar wind precipitation onto the upper atmospheres. We focus on the differences between the two planets. We conclude that on Mars we regularly observe precipitating solar wind ions (H+ and He2+) inside the induced magnetosphere boundary (IMB). The precipitation is clearly guided by the solar wind convection electric field and He2+ and H+ are seen independently of each other. On Venus precipitation of He2+ is only observed close to the IMB and always together with H+. The precipitation events on Venus have no clear correlation with the solar wind electric field.

  17. Comparing the relationship between precipitation and river geochemistry

    NASA Astrophysics Data System (ADS)

    Epp, A.; Luymes, R.; Bennett, M.; DaSilva, J.; Marsh, S. J.; Gillies, S. L.; Peucker-Ehrenbrink, B.; Voss, B.

    2013-12-01

    The geochemistry of precipitation affects the geochemistry of river water. Ideally, studies of river biogeochemistry should therefore include collection and analyses of dry and wet deposition. The Global Rivers Observatory has studied the Fraser River near Vancouver since the summer of 2009 at roughly bi-weekly resolution. The interpretation of this temporal record of river biogeochemistry, particularly the various sources of solutes, could be improved with a better understanding of atmospheric contributions. In this study precipitation and river water will be analysed from the Fraser River basin for nutrients as well as major and select trace ion concentrations. The nutrients analyzed will include ammonium (NH4), nitrate and nitrate (NO3-NO2), phosphate (PO4) and silicate (SiO4). Major ions include sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), and sulfate (SO4). Trace elements may include molybdenum, strontium, barium, uranium, rubidium, manganese and iron. Samples will be collected using the bulk method which collects both wet and dry deposition . Correlating precipitation chemistry with data on wind direction may help elucidate sources of nutrients and major ions. For instance, westerly sources may transport pollution from the City of Vancouver and agricultural lands in the Fraser delta. Such pollutants may increase the acidity of precipitation and imprint the water chemistry with a unique chemical signature . The results of this study will be helpful in correcting Fraser River water data for contributions from atmospheric deposition.

  18. Ion-specific effect on dynamics of polyelectrolyte chains.

    PubMed

    Luo, Zhenli; Wang, Xiaoyan; Zhang, Guangzhao

    2012-05-21

    The sedimentation of quaternized poly(4-vinyl pyridine) (QP4VP) or poly(N-methyl 4-vinyl pyridine iodide) in aqueous solution has been investigated by using an analytical ultracentrifuge (AUC) via sedimentation velocity (SV). When NaI is introduced, either the sedimentation coefficient (s) or apparent molar mass (Mw) of QP4VP increases with NaI concentration because the polyelectrolyte chains aggregate or even form precipitates due to hydrophobic interaction. Upon addition of NaCl, either s or Mw exhibits a maximum as NaCl concentration increases. The sedimentation in NaBr solution falls in between. Besides, the diffusion coefficient (D) shows a minimum as the added salt concentration increases when either of the salts is added. Isothermal titration calorimetry (ITC) measurements show that the enthalpy change increases from NaI over NaBr to NaCl when each of them is mixed with QP4VP, revealing that the order of the strength of the anion-pyridinium interaction is I(-) > Br(-) > Cl(-). When I(-) ions are added, they only screen the electrostatic interaction and no counterion competition happens. Upon addition of Cl(-) or Br(-) ions, the original counterions (I(-)) win the competition at low Cl(-) or Br(-) concentration, so that the added anions only screen the electrostatic interaction. When the concentration of Cl(-) or Br(-) ions is high enough, they replace I(-) ions to interact with the polyelectrolyte chains due to osmotic pressure. The present study demonstrates that the complex dynamics of the polyelectrolyte is greatly influenced by the ion-specific effect. PMID:22495384

  19. Aggregation of metallochlorophylls - Examination by spectroscopy

    NASA Technical Reports Server (NTRS)

    Boucher, L. J.; Katz, J. J.

    1969-01-01

    Nuclear magnetic resonance measurements determine which metallochlorophylls, besides magnesium-containing chlorophylls, possess coordination aggregation properties. Infrared spectroscopy reveals that only zinc pheophytin and zinc methyl pheophorbide showed significant coordination aggregation, whereas divalent nickel and copper did not.

  20. Oligomeric baroeffect and gas aggregation states

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1992-01-01

    The baroeffect is analyzed to include a gas that aggregates into higher-order polymers or oligomers. The resulting pressure change is found to vary independently of the molecular weight of the gas components and to depend only on the aggregation or oligomeric order of the gas. With increasing aggregation, diffusive slip velocities are found to increase. The calculations are extended to include general counterdiffusion of two distinct aggregation states (k-, j-mer) for the gas, and the pressure change is derived as a function that is independent of both molecular weight and the absolute aggregation. The only parameter that determines the baroeffect is the ratio of aggregated states, beta = k/j. For gases that reversibly aggregate, possible oscillatory behavior and complex dynamics for pressure are discussed. Gas aggregation may play a role for low-temperature crystal-growth conditions in which vapor concentrations of one (or more) species are high.

  1. Morphology and structure of photosensitive dye J-aggregates adsorbed on AgBr microcrystals grown in gelatin.

    PubMed

    Saijo, H; Shiojiri, M

    1998-07-15

    Though the cyanine dye J-aggregates carry the role to sense the exposing light in the silver halide photographic system, little research on the morphology of the aggregates in adsorption has been made with modern surface analytical methods. In this paper, we describe the size, epitaxy, multi-layered array formation, nucleation and preferential adsorption, and irregular distribution of population between particles and the segregation on a particle, of J-aggregates adsorbed on AgBr grown in gelatin. We employed cathodoluminescence microscopy, low energy high resolution scanning electron microscopy, and atomic force microscopy. Dye molecules aggregate together near the surface of AgBr and adsorb on the surface. The growth of adsorbed aggregates is controlled by the diffusion of dye molecules from the surrounding solution. The population of J-aggregates adsorbed on an AgBr particle varies from almost none to full coverage. Each aggregate is about (20-30) x (30-50) nm in size and is 2.1 nm thick for thiacarbocyanine with sodium ion, 1.04 nm for thiacarbocyanine with tosyl ion, and 0.5 nm for an oxacarbocyanine. The aggregates connect their longer edges to each other to form arrays, and the arrays build up multi-layered stacks. The arrays align parallel and segregate to form terraces. The longer edges of J-aggregates align along [210] on AgBr (100) or [632] on AgBr (111). PMID:9728883

  2. Stable, Metastable, and Kinetically Trapped Amyloid Aggregate Phases

    PubMed Central

    2015-01-01

    Self-assembly of proteins into amyloid fibrils plays a key role in a multitude of human disorders that range from Alzheimer’s disease to type II diabetes. Compact oligomeric species, observed early during amyloid formation, are reported as the molecular entities responsible for the toxic effects of amyloid self-assembly. However, the relation between early-stage oligomeric aggregates and late-stage rigid fibrils, which are the hallmark structure of amyloid plaques, has remained unclear. We show that these different structures occupy well-defined regions in a peculiar phase diagram. Lysozyme amyloid oligomers and their curvilinear fibrils only form after they cross a salt and protein concentration-dependent threshold. We also determine a boundary for the onset of amyloid oligomer precipitation. The oligomeric aggregates are structurally distinct from rigid fibrils and are metastable against nucleation and growth of rigid fibrils. These experimentally determined boundaries match well with colloidal model predictions that account for salt-modulated charge repulsion. The model also incorporates the metastable and kinetic character of oligomer phases. Similarities and differences of amyloid oligomer assembly to metastable liquid–liquid phase separation of proteins and to surfactant aggregation are discussed. PMID:25469942

  3. Protein aggregation in salt solutions

    PubMed Central

    Kastelic, Miha; Kalyuzhnyi, Yurij V.; Hribar-Lee, Barbara; Dill, Ken A.; Vlachy, Vojko

    2015-01-01

    Protein aggregation is broadly important in diseases and in formulations of biological drugs. Here, we develop a theoretical model for reversible protein–protein aggregation in salt solutions. We treat proteins as hard spheres having square-well-energy binding sites, using Wertheim’s thermodynamic perturbation theory. The necessary condition required for such modeling to be realistic is that proteins in solution during the experiment remain in their compact form. Within this limitation our model gives accurate liquid–liquid coexistence curves for lysozyme and γ IIIa-crystallin solutions in respective buffers. It provides good fits to the cloud-point curves of lysozyme in buffer–salt mixtures as a function of the type and concentration of salt. It than predicts full coexistence curves, osmotic compressibilities, and second virial coefficients under such conditions. This treatment may also be relevant to protein crystallization. PMID:25964322

  4. Purification of diverse hemoglobins by metal salt precipitation.

    PubMed

    Zimmerman, Devon; Dienes, Jack; Abdulmalik, Osheiza; Elmer, Jacob J

    2016-09-01

    Although donated blood is the preferred material for transfusion, its limited availability and stringent storage requirements have motivated the development of blood substitutes. The giant extracellular hemoglobin (aka erythrocruorin) of the earthworm Lumbricus terrestris (LtEc) has shown promise as a blood substitute, but an efficient purification method for LtEc must be developed to meet the potential large demand for blood substitutes. In this work, an optimized purification process that uses divalent and trivalent metal salts to selectively precipitate human, earthworm, and bloodworm hemoglobin (HbA, LtEc, and GdHb, respectively) from crude solutions was developed. Although several metal ions were able to selectively precipitate LtEc, Zn(2+) and Ni(2+) provided the lowest heme oxidation and highest overall yield of LtEc. In contrast, Zn(2+) was the only metal ion that completely precipitated HbA and GdHb. Polyacrylamide gel electrophoresis (PAGE) analysis shows that metal precipitation removes several impurities to provide highly pure hemoglobin samples. Heme oxidation levels were relatively low for Zn(2+)-purified HbA and LtEc (2.4±1.3% and 5.3±2.1%, respectively), but slightly higher for Ni(2+)-purified LtEc (8.4±1.2%). The oxygen affinity and cooperativity of the precipitated samples are also identical to samples purified with tangential flow filtration (TFF) alone, indicating the metal precipitation does not significantly affect the function of the hemoglobins. Overall, these results show that hemoglobins from several different species can be highly purified using a combination of metal (Zn(2+)) precipitation and tangential flow filtration. PMID:26363116

  5. De-aggregated hazard of freezing rain events

    NASA Astrophysics Data System (ADS)

    Erfani, R.; Chouinard, L.; Cloutier, L.

    2014-08-01

    The objective of the work presented here is to improve estimates of atmospheric icing hazards, specifically for radial ice accumulation on electrical transmission lines, by clustering freezing rainstorms into different groups and using de-aggregate statistical analysis. In this paper, freezing rain storms were clustered based on anomaly maps constructed using NCEP reanalysis data of 1000 hPa to 500 hPa geopotential heights or SLP. The procedure is demonstrated with data from Montreal, as well as a superstation of Montreal, Quebec City, and Ottawa together. The physical meaning of the different clusters was also analyzed and discussed in terms of wind speed, total precipitation or ice accumulation, air mass positions, and compared with Rauber's archetypical patterns. The results presented indicate that the clusters have statistical and physical significance. Clustering based on either SLP or 1000 hPa to 500 hPa height anomalies produces clusters with different precipitation characteristics which can be explained on a physical basis. Clustering Montreal storms based on 1000 hPa to 500 hPa height anomalies produced one cluster containing the five worst ice storms that occurred in Montreal during that time period. This cluster was characterized by an expansive zone of 1000 hPa to 500 hPa height positive anomalies over Montreal that extend far north. It also shows significant SLP anomalies and cold air damming. The de-aggregated hazard analysis is able to demonstrate that the relative contribution of each cluster changes for more extreme events. The de-aggregated analysis produces optimal statistical fits for clusters and introduces robustness in the estimation of the return period over a range threshold. Finally, a small bias is suggested in the single population analysis where the return periods are consistently lower over a range of quantiles and thresholds.

  6. Aggregation behavior of a gemini surfactant with a tripeptide spacer.

    PubMed

    Wang, Meina; Han, Yuchun; Qiao, Fulin; Wang, Yilin

    2015-02-28

    A peptide gemini surfactant, 12-G(NH2)LG(NH2)-12, has been constructed with two dodecyl chains separately attached to the two terminals of a glutamic acid-lysine-glutamic acid peptide and the aggregation behavior of the surfactant was studied in aqueous solution. The 12-G(NH2)LG(NH2)-12 molecules form fiber-like precipitates around pH 7.0, and the precipitation range is widened on increasing the concentration. At pHs 3.0 and 11.0, 12-G(NH2)LG(NH2)-12 forms soluble aggregates because each molecule carries two positively charged amino groups at the two ends of the peptide spacer at pH 3.0, while each molecule carries one negatively charged carboxyl group in the middle of the peptide spacer at pH 11.0. 12-G(NH2)LG(NH2)-12 displays a similar concentration-dependent process at these two pHs: forming small micelles above the critical micelle concentration and transferring to fibers at pH 3.0 or twisted ribbons at pH 11.0 above the second critical concentration. The fibers formed at pH 3.0 tend to aggregate into bundles with twisted structure. Both the twisted fibers at pH 3.0 and the twisted ribbons at pH 11.0 contain β-sheet structure formed by the peptide spacer. PMID:25588349

  7. Fractal structure and the dynamics of aggregation of synthetic melanin in low pH aqueous solutions

    SciTech Connect

    Huang, J.S.; Sung, J.; Eisner, M.; Moss, S.C.; Gallas, J.

    1989-01-01

    We have used static and dynamic light scattering to study the dynamics of aggregation of synthetic melanin, an amorphous biopolymeric substance, in low pH aqueous solution. We have found that, depending on the final pH value of the solutions, there existed two regimes of the aggregation kinetics, one corresponding to diffusion limited aggregation (DLA), and the other corresponding to reaction limited aggregation (RLA). The precipitates formed in these two regimes can be characterized by fractal structures. We have found fractal dimensions of d/sub f/ = 1.8 for the DLA clusters and d/sub f/ = 2.2 for the RLA clusters. These results agree well with the proposed limits of the fractal dimensions of the gold aggregates formed in aqueous solutions by Weitz et al.

  8. A perturbation approach for assessing trends in precipitation extremes across Iran

    NASA Astrophysics Data System (ADS)

    Tabari, Hossein; AghaKouchak, Amir; Willems, Patrick

    2014-11-01

    Extreme precipitation events have attracted a great deal of attention among the scientific community because of their devastating consequences on human livelihood and socio-economic development. To assess changes in precipitation extremes in a given region, it is essential to analyze decadal oscillations in precipitation extremes. This study examines temporal oscillations in precipitation data in several sub-regions of Iran using a novel quantile perturbation method during 1980-2010. Precipitation data from NASA's Modern-Era Retrospective Analysis for Research and Applications-Land (MERRA-Land) are used in this study. The results indicate significant anomalies in precipitation extremes in the northwest and southeast regions of Iran. Analysis of extreme precipitation perturbations reveals that perturbations for the monthly aggregation level are generally lower than the annual perturbations. Furthermore, high-oscillation and low-oscillation periods are found in extreme precipitation quantiles across different seasons. In all selected regions, a significant anomaly (i.e., extreme wet/dry conditions) in precipitation extremes is observed during spring.

  9. Precipitation of lamellar gold nanocrystals in molten polymers

    NASA Astrophysics Data System (ADS)

    Palomba, M.; Carotenuto, G.

    2016-05-01

    Non-aggregated lamellar gold crystals with regular shape (triangles, squares, pentagons, etc.) have been produced by thermal decomposition of gold chloride (AuCl) molecules in molten amorphous polymers (polystyrene and poly(methyl methacrylate)). Such covalent inorganic gold salt is high soluble into non-polar polymers and it thermally decomposes at temperatures compatible with the polymer thermal stability, producing gold atoms and chlorine radicals. At the end of the gold precipitation process, the polymer matrix resulted chemically modified because of the partial cross-linking process due to the gold atom formation reaction.

  10. Aggregated Authentication (AMAC) Using Universal Hash Functions

    NASA Astrophysics Data System (ADS)

    Znaidi, Wassim; Minier, Marine; Lauradoux, Cédric

    Aggregation is a very important issue to reduce the energy consumption in Wireless Sensors Networks (WSNs). There is currently a lack of cryptographic primitives for authentication of aggregated data. The theoretical background for Aggregated Message Authentication Codes (AMACs) has been proposed by Chan and Castelluccia at ISIT 08.

  11. Mineral resource of the month: aggregates

    USGS Publications Warehouse

    Willett, Jason C.

    2012-01-01

    Crushed stone and construction sand and gravel, the two major types of natural aggregates, are among the most abundant and accessible natural resources on the planet. The earliest civilizations used aggregates for various purposes, mainly construction. Today aggregates provide the basic raw materials for the foundation of modern society.

  12. 28 CFR 2.5 - Sentence aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 1 2010-07-01 2010-07-01 false Sentence aggregation. 2.5 Section 2.5 Judicial Administration DEPARTMENT OF JUSTICE PAROLE, RELEASE, SUPERVISION AND RECOMMITMENT OF PRISONERS... aggregation. When multiple sentences are aggregated by the Bureau of Prisons pursuant to 18 U.S.C. 4161...

  13. Molecular dynamics simulations of ionic aggregates in a coarse%3CU%2B2010%3Egrained ionomer melt.

    SciTech Connect

    Hall, Lisa Michelle; Frischknecht, Amalie Lucile; Stevens, Mark Jackson

    2010-11-01

    Ionomers--polymers containing a small fraction of covalently bound ionic groups--have potential application as solid electrolytes in batteries. Understanding ion transport in ionomers is essential for such applications. Due to strong electrostatic interactions in these materials, the ions form aggregates, tending to slow counterion diffusion. A key question is how ionomer properties affect ionic aggregation and counterion dynamics on a molecular level. Recent experimental advances have allowed synthesis and extensive characterization of ionomers with a precise, constant spacing of charged groups, making them ideal for controlled measurement and more direct comparison with molecular simulation. We have used coarse-grained molecular dynamics to simulate such ionomers with regularly spaced charged beads. The charged beads are placed either in the polymer backbone or as pendants on the backbone. The polymers, along with the counterions, are simulated at melt densities. The ionic aggregate structure was determined as a function of the dielectric constant, spacing of the charged beads on the polymer, and the sizes of the charged beads and counterions. The pendant ion architecture can yield qualitatively different aggregate structures from those of the linear polymers. For small pendant ions, roughly spherical aggregates have been found above the glass transition temperature. The implications of these aggregates for ion diffusion will be discussed.

  14. Cytotoxic effects of aggregated nanomaterials.

    PubMed

    Soto, Karla; Garza, K M; Murr, L E

    2007-05-01

    This study deals with cytotoxicity assays performed on an array of commercially manufactured inorganic nanoparticulate materials, including Ag, TiO(2), Fe(2)O(3), Al(2)O(3), ZrO(2), Si(3)N(4), naturally occurring mineral chrysotile asbestos and carbonaceous nanoparticulate materials such as multiwall carbon nanotube aggregates and black carbon aggregates. The nanomaterials were characterized by TEM, as the primary particles, aggregates or long fiber dimensions ranged from 2nm to 20microm. Cytotoxicological assays of these nanomaterials were performed utilizing a murine alveolar macrophage cell line and human macrophage and epithelial lung cell lines as comparators. The nanoparticulate materials exhibited varying degrees of cytoxicity for all cell lines and the general trends were similar for both the murine and human macrophage cell lines. These findings suggest that representative cytotoxic responses for humans might be obtained by nanoparticulate exposures to simple murine macrophage cell line assays. Moreover, these results illustrate the utility in performing rapid in vitro assays for cytotoxicity assessments of nanoparticulate materials as a general inquiry of potential respiratory health risks in humans. PMID:17275430

  15. Aggregation of Heterogeneously Charged Colloids.

    PubMed

    Dempster, Joshua M; Olvera de la Cruz, Monica

    2016-06-28

    Patchy colloids are attractive as programmable building blocks for metamaterials. Inverse patchy colloids, in which a charged surface is decorated with patches of the opposite charge, are additionally noteworthy as models for heterogeneously charged biological materials such as proteins. We study the phases and aggregation behavior of a single charged patch in an oppositely charged colloid with a single-site model. This single-patch inverse patchy colloid model shows a large number of phases when varying patch size. For large patch sizes we find ferroelectric crystals, while small patch sizes produce cross-linked gels. Intermediate values produce monodisperse clusters and unusual worm structures that preserve finite ratios of area to volume. The polarization observed at large patch sizes is robust under extreme disorder in patch size and shape. We examine phase-temperature dependence and coexistence curves and find that large patch sizes produce polarized liquids, in contrast to mean-field predictions. Finally, we introduce small numbers of unpatched charged colloids. These can either suppress or encourage aggregation depending on their concentration and the size of the patches on the patched colloids. These effects can be exploited to control aggregation and to measure effective patch size. PMID:27253725

  16. Estimation of continental precipitation recycling

    NASA Technical Reports Server (NTRS)

    Brubaker, Kaye L.; Entekhabi, Dara; Eagleson, P. S.

    1993-01-01

    The total amount of water that precipitates on large continental regions is supplied by two mechanisms: 1) advection from the surrounding areas external to the region and 2) evaporation and transpiration from the land surface within the region. The latter supply mechanism is tantamount to the recycling of precipitation over the continental area. The degree to which regional precipitation is supplied by recycled moisture is a potentially significant climate feedback mechanism and land surface-atmosphere interaction, which may contribute to the persistence and intensification of droughts. Gridded data on observed wind and humidity in the global atmosphere are used to determine the convergence of atmospheric water vapor over continental regions. A simplified model of the atmospheric moisture over continents and simultaneous estimates of regional precipitation are employed to estimate, for several large continental regions, the fraction of precipitation that is locally derived. The results indicate that the contribution of regional evaporation to regional precipitation varies substantially with location and season. For the regions studied, the ratio of locally contributed to total monthly precipitation generally lies between 0. 10 and 0.30 but is as high as 0.40 in several cases.

  17. Precipitation in 9Ni-12Cr-2Cu maraging steels

    SciTech Connect

    Stiller, K.; Haettestrand, M.; Danoix, F.

    1998-11-02

    Two maraging steels with the compositions 9Ni-12Cr-2Cu-4Mo (wt%) and 9Ni-12Cr-2Cu and with small additions of Al and Ti were investigated using atom probe field ion microscopy. Tomographic atom probe investigations were performed to clarify the spatial distribution of elements in and close to the precipitates. Materials heat treated at 475 C for 5, 25 min, 1, 2, 4 and 400 h were analyzed. Precipitates in the Mo-rich material were observed already after 5 min of aging, while in the material without MO, precipitation started later. In both materials precipitation begins with the formation of Cu-rich particles which work as nucleation sites for a Ni-rich phase of type Ni{sub 3}(Ti,Al). A Mo-rich phase was detected in the Mo-rich steel after 2 h of aging. The distribution of alloying elements in the precipitates, their role in the precipitation process, and the mechanism of hardening in the two materials are discussed.

  18. Direct cellular delivery of human proteasomes to delay tau aggregation.

    PubMed

    Han, Dong Hoon; Na, Hee-Kyung; Choi, Won Hoon; Lee, Jung Hoon; Kim, Yun Kyung; Won, Cheolhee; Lee, Seung-Han; Kim, Kwang Pyo; Kuret, Jeff; Min, Dal-Hee; Lee, Min Jae

    2014-01-01

    The 26S proteasome is the primary machinery that degrades ubiquitin (Ub)-conjugated proteins, including many proteotoxic proteins implicated in neurodegeneraton. It has been suggested that the elevation of proteasomal activity is tolerable to cells and may be beneficial to prevent the accumulation of protein aggregates. Here we show that purified proteasomes can be directly transported into cells through mesoporous silica nanoparticle-mediated endocytosis. Proteasomes that are loaded onto nanoparticles through non-covalent interactions between polyhistidine tags and nickel ions fully retain their proteolytic activity. Cells treated with exogenous proteasomes are more efficient in degrading overexpressed human tau than endogenous proteasomal substrates, resulting in decreased levels of tau aggregates. Moreover, exogenous proteasome delivery significantly promotes cell survival against proteotoxic stress caused by tau and reactive oxygen species. These data demonstrate that increasing cellular proteasome activity through the direct delivery of purified proteasomes may be an effective strategy for reducing cellular levels of proteotoxic proteins. PMID:25476420

  19. Reactivity, swelling and aggregation of mixed-size silicate nanoplatelets

    NASA Astrophysics Data System (ADS)

    Segad, M.; Cabane, B.; Jönsson, Bo

    2015-10-01

    Montmorillonite is a key ingredient in a number of technical applications. However, little is known regarding the microstructure and the forces between silicate platelets. The size of montmorillonite platelets from different natural sources can vary significantly. This has an influence on their swelling behavior in water as well as in salt solutions, particularly when tactoid formation occurs, that is when divalent counterions are present in the system. A tactoid consists of a limited number of platelets aggregated in a parallel arrangement with a constant separation. The tactoid size increases with platelet size and with very small nanoplatelets, ~30 nm, no tactoids are observed irrespectively of the platelet origin and concentration of divalent ions. The formation and dissociation of tactoids seem to be reversible processes. A large proportion of small nanoplatelets in a mixed-size system affects the tactoid formation, reduces the aggregation number and increases the extra-lamellar swelling in the system.

  20. Aggregation and Aggregate Carbon in a Forested Southeastern Coastal Plain Spodosol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil aggregation is influenced by the soil environment and is a factor in soil carbon sequestration. Sandy Coastal Plain soils often do not have the clay to promote aggregation nor have been considered soils with high levels of aggregation. This study was conducted to examine the aggregate morpholog...

  1. Precipitation Measurements from Space: The Global Precipitation Measurement Mission

    NASA Technical Reports Server (NTRS)

    Hou, Arthur Y.

    2007-01-01

    Water is fundamental to the life on Earth and its phase transition between the gaseous, liquid, and solid states dominates the behavior of the weather/climate/ecological system. Precipitation, which converts atmospheric water vapor into rain and snow, is central to the global water cycle. It regulates the global energy balance through interactions with clouds and water vapor (the primary greenhouse gas), and also shapes global winds and dynamic transport through latent heat release. Surface precipitation affects soil moisture, ocean salinity, and land hydrology, thus linking fast atmospheric processes to the slower components of the climate system. Precipitation is also the primary source of freshwater in the world, which is facing an emerging freshwater crisis in many regions. Accurate and timely knowledge of global precipitation is essential for understanding the behavior of the global water cycle, improving freshwater management, and advancing predictive capabilities of high-impact weather events such as hurricanes, floods, droughts, and landslides. With limited rainfall networks on land and the impracticality of making extensive rainfall measurements over oceans, a comprehensive description of the space and time variability of global precipitation can only be achieved from the vantage point of space. This presentation will examine current capabilities in space-borne rainfall measurements, highlight scientific and practical benefits derived from these observations to date, and provide an overview of the multi-national Global Precipitation Measurement (GPM) Mission scheduled to bc launched in the early next decade.

  2. [AGGREGATION OF METABOLICALLY DEPLETED HUMAN ERYTHROCYTES].

    PubMed

    Sheremet'ev, Yu A; Popovicheva, A N; Rogozin, M M; Levin, G Ya

    2016-01-01

    An aggregation of erythrocytes in autologous plasma after blood storage for 14 days at 4 °C was studied using photometry and light microscopy. The decrease of ATP content, the formation of echinocytes and spheroechinocytes, the decrease of rouleaux form of erythrocyte aggregation were observed during the storage. On the other hand the aggregates of echinocytes were formed in the stored blood. The addition of plasma from the fresh blood didn't restore the normal discocytic shape and aggregation of erythrocytes in the stored blood. The possible mechanisms of erythrocytes and echinocytes aggregation are discussed. PMID:27220249

  3. [Lysophosphatidic acid and human erythrocyte aggregation].

    PubMed

    Sheremet'ev, Iu A; Popovicheva, A N; Levin, G Ia

    2014-01-01

    The effects of lysophosphatidic acid on the morphology and aggregation of human erythrocytes has been studied. Morphology of erythrocytes and their aggregates were studied by light microscopy. It has been shown that lysophosphatidic acid changes the shape of red blood cells: diskocyte become echinocytes. Aggregation of red blood cells (rouleaux) was significantly reduced in autoplasma. At the same time there is a strong aggregation of echinocytes. This was accompanied by the formation of microvesicles. Adding normal plasma to echinocytes restores shape and aggregation of red blood cells consisting of "rouleaux". A possible mechanism of action of lysophosphatidic acid on erythrocytes is discussed. PMID:25509147

  4. TRMM .25 deg x .25 deg Gridded Precipitation Text Product

    NASA Technical Reports Server (NTRS)

    Stocker, Erich; Kelley, Owen

    2009-01-01

    Since the launch of the Tropical Rainfall Measuring Mission (TRMM), the Precipitation Measurement Missions science team has endeavored to provide TRMM precipitation retrievals in a variety of formats that are more easily usable by the broad science community than the standard Hierarchical Data Format (HDF) in which TRMM data is produced and archived. At the request of users, the Precipitation Processing System (PPS) has developed a .25 x .25 gridded product in an easily used ASCII text format. The entire TRMM mission data has been made available in this format. The paper provides the details of this new precipitation product that is designated with the TRMM designator 3G68.25. The format is packaged into daily files. It provides hourly precipitation information from the TRMM microwave imager (TMI), precipitation radar (PR), and TMI/PR combined rain retrievals. A major advantage of this approach is the inclusion only of rain data, compression when a particular grid has no rain from the PR or combined, and its direct ASCII text format. For those interested only in rain retrievals and whether rain is convection or stratiform, these products provide a huge reduction in the data volume inherent in the standard TRMM products. This paper provides examples of the 3G68 data products and their uses. It also provides information about C tools that can be used to aggregate daily files into larger time samples. In addition, it describes the possibilities inherent in the spatial sampling which allows resampling into coarser spatial sampling. The paper concludes with information about downloading the gridded text data products.

  5. Evidence for the spontaneous formation of disulfide crosslinked aggregates of tubulin during nondenaturing electrophoresis.

    PubMed

    Correia, J J; Welch, M K; Williams, R C

    1987-06-01

    Phosphocellulose-purified tubulin has been shown to form a characteristic "ladder" of nonmicrotubular aggregates during nondenaturing gel electrophoresis (J. J. Correia and R. C. Williams, Jr. (1985) Arch. Biochem. Biophys. 239, 120-129). In this paper we describe evidence that the intersubunit bonds responsible for formation of these oligomeric particles are disulfides. Two-dimensional nondenaturing-denaturing gel electrophoresis demonstrates that each aggregate zone is composed of alpha- and beta-subunits of tubulin. Omission of beta-mercaptoethanol during the sodium dodecyl sulfate (SDS)-electrophoresis step causes a pattern of aggregates to appear and implicates disulfide linkages in their stabilization. Molecular weights, estimated from mobilities in the second (SDS) dimension of two-dimensional gels, suggest that the aggregates are crosslinked in units of monomers, not heterodimers. Consistent with this conclusion, alpha- or beta-subunits alone (isolated by isoelectric focusing) will form the same ladder of aggregates. The disulfide crosslinking of tubulin is also achievable in solution. It is favored by high concentrations of alcohol, the presence of oxidizing agents, high pH, and high temperature, conditions that denature tubulin and cause rapid noncovalent aggregation or precipitation. When aggregate formation was monitored as a function of time by SDS-gel electrophoresis in the absence of beta-mercaptoethanol and by quantitative sulfhydryl and disulfide titrations, the most effective conditions for the crosslinking reaction included greater than 75% alcohol, excess H2O2, or excess iodine. These results suggest that proximity of a hydrophobic gel matrix, high pH, the presence of oxidizing agents, high protein concentration, tubulin's propensity to aggregate nonspecifically, and the availability of as many as 20 sulfhydryls in alpha beta-tubulin contribute, during nondenaturing gel electrophoresis, to the spontaneous formation of disulfide

  6. Examination of bioaffinity immobilization by precipitation of mannan and mannan-containing enzymes with legume lectins.

    PubMed

    Mislovicová, D; Gemeiner, P; Sandula, J; Masárová, J; Vikartovská, A; Docolomanský, P

    2000-04-01

    The interaction of four lectins from crops of the legume family with Saccharomyces cerevisiae alpha-mannan, and also with two glycoenzymes containing mainly alpha-mannan moieties, has been studied. The interaction was characterized by a quantitative precipitation assay. The results of precipitation differ with respect to both quality (the point of maximum precipitation) and of the quantity (the amount of aggregated lectin and saccharide). The lectin concanavalin A [Con A, from jack bean (Canavalia ensiformis)] was observed to form more extensive precipitates with Saccharomyces cerevisiae mannan and glycoenzymes than did lectins from Lens culinaris (lentil) and Pisum sativum (garden pea), while in the case of Vicia faba (broad or fava bean) no interaction was found with either the examined mannans or with glycosylated enzymes. The complete precipitation of invertase and glucoamylase with Con A (enzymes and also Con A; up to 100%) was achieved at a Con A glycoenzyme molar ratio of 20.2 and 2.3 respectively, whereby about 85% of precipitated and also of initial activities of glycoenzymes were determined in the aggregates. More valuable results were achieved by the technique of enzyme immobilization called 'multiple bioaffinity layering' which is based on the stepwise biospecific adsorption of the glycosylated enzymes and Con A on a matrix precoupled with Con A. A 3-fold repetition of the layering procedure afforded up to a 10-fold increase in catalytic activity of the immobilized invertase, in contrast with a 2.1-fold increase in catalytic activity of the immobilized glucoamylase. PMID:10744960

  7. Probing the conformation of protein (bFGF) precipitates by fluorescence spectroscopy.

    PubMed

    Shahrokh, Z; Eberlein, G; Wang, Y J

    1994-08-01

    Aggregation and precipitation are major events in the handling and aging of most protein pharmaceuticals. We demonstrate the utility of fluorescence spectroscopy in determining protein conformation in precipitates using basic fibroblast growth factor (bFGF) as an example. Conversion of the native to the soluble denatured from by chaotropes was accompanied by an increase in tryptophan emission. The emission spectra of resuspended precipitates were as reproducible as the spectra of the soluble form. The sum of emission spectra of native soluble bFGF and denatured precipitated bFGF was superimposable on the spectrum of the unfractionated suspension, suggesting that quantitative analysis of denatured aggregates in turbid protein formulations is possible. The ratio of tryptophan to tyrosine emissions increased with increasing extent of denaturation both in solution and in suspension. For example, salting out by ammonium sulphate increased the fluorescence index (indicative of denaturation) which was reversible upon dissolution. In addition, aging (35 degrees C) of bFGF in the presence of sulphated ligands produced precipitates with native-like fluorescence index, in contrast to denatured precipitates formed without ligands. PMID:7819377

  8. Microwave extinction characteristics of nanoparticle aggregates

    NASA Astrophysics Data System (ADS)

    Wu, Y. P.; Cheng, J. X.; Liu, X. X.; Wang, H. X.; Zhao, F. T.; Wen, W. W.

    2016-07-01

    Structure of nanoparticle aggregates plays an important role in microwave extinction capacity. The diffusion-limited aggregation model (DLA) for fractal growth is utilized to explore the possible structures of nanoparticle aggregates by computer simulation. Based on the discrete dipole approximation (DDA) method, the microwave extinction performance by different nano-carborundum aggregates is numerically analyzed. The effects of the particle quantity, original diameter, fractal structure, as well as orientation on microwave extinction are investigated, and also the extinction characteristics of aggregates are compared with the spherical nanoparticle in the same volume. Numerical results give out that proper aggregation of nanoparticle is beneficial to microwave extinction capacity, and the microwave extinction cross section by aggregated granules is better than that of the spherical solid one in the same volume.

  9. Simulation of J-aggregate microcavity photoluminescence

    NASA Astrophysics Data System (ADS)

    Michetti, Paolo; La Rocca, Giuseppe C.

    2008-05-01

    We have developed a model in order to account for the photoexcitation dynamics of J-aggregate films and strongly coupled J-aggregate microcavities. The J aggregates are described as a disordered Frenkel exciton system in which relaxation occurs due to the presence of a thermal bath of molecular vibrations. The correspondence between the photophysics in J-aggregate films and that in J-aggregate microcavities is obtained by introducing a model polariton wave function mixing cavity photon modes and J-aggregate super-radiant excitons. With the same description of the material properties, we have calculated both absorption and luminescence spectra for the J-aggregate film and the photoluminescence of strongly coupled organic microcavities. The model is able to account for the fast relaxation dynamics in organic microcavities following nonresonant pumping and explains the temperature dependence of the ratio between the upper polariton and the lower polariton luminescence.

  10. Silica Precipitation and Lithium Sorption

    SciTech Connect

    Jay Renew

    2015-09-20

    This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

  11. Electrical precipitation apparatus and method

    SciTech Connect

    Furlong, D.A.

    1984-11-06

    An electrostatic precipitator having improved collection efficiency for suspended particles having either high or low electrical resistivities is provided. The precipitator utilizes porous collecting surfaces which permit passage of gas while retaining suspended particles and means are provided to create an electrostatic field causing the particles to migrate toward the collecting surfaces. According to the invention, only a portion of the inlet gas flow to the precipitator, sufficient to provide aerodynamic forces to facilitate adherence of the particles to the collecting surface, is drawn through the porous collecting surfaces with the remainder of the gas flow being essentially parallel to such surfaces. The two gas streams are separately withdrawn and may be combined to provide a clean gas effluent. The invention also provides an improved method for removing suspended particles from gases by electrical precipitation.

  12. Evaluation of Coupled Precipitator Two

    SciTech Connect

    Stone, M.E.

    1999-11-08

    The offline testing of the Coupled Precipitator Two (CP-2) has been completed. The tests were conducted and are documented. The tests were conducted at an offline test rack near the Drain Tube Test Stand facility in 672-T.

  13. Identifying Anomality in Precipitation Processes

    NASA Astrophysics Data System (ADS)

    Jiang, P.; Zhang, Y.

    2014-12-01

    Safety, risk and economic analyses of engineering constructions such as storm sewer, street and urban drainage, and channel design are sensitive to precipitation storm properties. Whether the precipitation storm properties exhibit normal or anomalous characteristics remains obscure. In this study, we will decompose a precipitation time series as sequences of average storm intensity, storm duration and interstorm period to examine whether these sequences could be treated as a realization of a continuous time random walk with both "waiting times" (interstorm period) and "jump sizes" (average storm intensity and storm duration). Starting from this viewpoint, we will analyze the statistics of storm duration, interstorm period, and average storm intensity in four regions in southwestern United States. We will examine whether the probability distribution is temporal and spatial dependent. Finally, we will use fractional engine to capture the randomness in precipitation storms.

  14. Some Statistics of Instantaneous Precipitation.

    NASA Astrophysics Data System (ADS)

    Jones, Douglas M. A.; Wendland, Wayne M.

    1984-09-01

    Known sources of data from arrays of instantaneous precipitation intensity recorders in southern Germany, east-central Illinois, northeastern Illinois, central Florida, and Hilo, Hawaii are obtained. These data are analyzed for line averages of the percent frequency of occurrence of the exceedance of selected threshold precipitation intensities. The correlation coefficients of the precipitation intensity at sites at varying distances from a reference site are determined. The decay in correlation is found to be a function of climatic region and the type of precipitation: showery or continuous. Showery rains are found to be essentially uncorrelated about 12 km from the reference site while continuous rain exhibits no correlation beyond about 50 km.Single-station intensity data collected at Urbana, Illinois; Paris, France; Inyanga, Zimbabwe; Bogor, Indonesia; Reading, United Kingdom; Island Beach, New Jersey; Miami, Florida; Franklin, North Carolina; and Majuro, Marshall Islands, are compared.

  15. Heavy Precipitation Events in Lithuania

    NASA Astrophysics Data System (ADS)

    Bukantis, A.; Rimkus, E.; Kažys, J.

    2010-09-01

    Analysis of heavy precipitation events in Lithuania is presented in this work. Research was divided into two parts. Spatial distribution and dynamic of heavy precipitation events in Lithuania during observation period (1961-2008) is presented in the first part and climate predictions for XXI century according to outputs of CCLM model are in the second. Daily data from 17 meteorological stations were used for the analysis of heavy precipitation events in Lithuania. Research covers period from 1961 to 2008. Annual and seasonal heavy precipitation values and the recurrence of extreme daily and 3-day precipitation events were analyzed. Spatial distribution of heavy precipitation events in Lithuania was determined; the trends of such precipitation recurrence were identified. Also, daily and 3-day annual maxima probabilities were calculated using the Generalized Extreme Value (GEV) distribution. 10, 30 and 100 years return period was analyzed. Finally, atmospheric circulation processes during heavy precipitation events were described using the adapted Hess & Brezowski macrocirculation form classification Predictions of changes of heavy precipitation recurrence in Lithuania are also presented in this study. Output data of the regional climate model CCLM (COSMO - Climate Limited-area Model) for the period 1971-2100 were used. Predictions were based on A1B and B1 emission scenarios. Despite of relatively small area and quite negligible differences in altitude there are significant unevenness in spatial distribution of heavy precipitation events in Lithuania. The mean annual number of cases when daily precipitation amount exceeded 10 mm fluctuates from 12.4 to 21.9 and from 5.3 to 10.5 when 3-day precipitation exceeded 20 mm. The probability of maximum precipitation amount for 10 year return period appears very familiar to spatial distribution of heavy precipitation recurrence: the highest values can be expected in the western part (55-60 mm daily and 75-85 mm in 3-days

  16. Environmental Radioactivity, Temperature, and Precipitation.

    ERIC Educational Resources Information Center

    Riland, Carson A.

    1996-01-01

    Reports that environmental radioactivity levels vary with temperature and precipitation and these effects are due to radon. Discusses the measurement of this environmental radioactivity and the theory behind it. (JRH)

  17. The 2014 Silba Precipitation Extreme

    NASA Astrophysics Data System (ADS)

    Rasol, Dubravka; Ólafsson, Haraldur

    2015-04-01

    On 30 July 2014 a 24 h precipitation record of 218 mm was set at the island of Silba in the N-Adriatic Sea. The precipitation was of convective nature and significantly less precipitation was recorded only small distances away, at the coast of mainland Croatia. The event is reproduced numerically and discussed in terms of dynamics and predictability. On a large scale, the precipitation extreme was associated with a slow-moving upper tropospheric low that formed over the N-Atlantic several days earlier. At lower levels, there were humid mediterranean airmasses. On a smaller scale, there are indications that the extreme convection may have been triggered by an orographic disturbance.

  18. Application of an Object-Oriented Connectivity Algorithm to Remotely Sensed Precipitation Data

    NASA Astrophysics Data System (ADS)

    Sellars, S.; Nguyen, P.; Chu, W.; Gao, X.; Sorooshian, S.

    2012-12-01

    object must exist for at least 24 hours. The connectivity algorithm using these criteria returned 48,695 objects. Characteristics of each of the 48,695 segmented objects were aggregated into a separate database. The characteristics that will be demonstrated in this poster will be: 1) Max Intensity, 2) Duration, 3) Total Precipitation, 4) Average Speed, 5) Area and 6) Centroid ("center of mass"). A comparison study will be reported on using the three-hour accumulated precipitation version of this dataset, three-hourly Tropical Rainfall Measuring Mission (TRMM) 3B42 Version 7 and the three-hourly National Oceanic Atmospheric Administration's (NOAA) CPC Morphing (CMORPH) Technique precipitation datasets. Visual examples of individual precipitation objects and precipitation characteristic statistics from the three precipitation products will also be compared and displayed.

  19. Oceanic Precipitation Measurement - Surface Validation

    NASA Astrophysics Data System (ADS)

    Klepp, Christian

    2013-04-01

    State-of-the-art satellite derived and reanalysis based precipitation climatologies still show remarkably large differences in frequency, amount, intensity, variability and temporal behavior of precipitation over the oceans. Additionally so far appropriate in-situ validation instruments were not available for shipboard use. The uncertainties are largest for light precipitation within the ITCZ and subtropics and for cold season high-latitude precipitation including mix-phase and snowfall. Hence, a long-term issue on which IPWG and GPM-GV is urging more attention is the provision of high quality surface validation data in oceanic areas using innovative ship-based instruments. Precipitation studies would greatly benefit from systematic dataset collection and analysis as such data could also be used to constrain precipitation retrievals. To achieve this goal, the KlimaCampus and Max Planck Institute for Meteorology in Hamburg, Germany funded this project that uses automated shipboard optical disdrometers, called Eigenbrodt ODM470, that are capable of measuring liquid and solid precipitation using drop size distributions in minute intervals on moving ships with high accuracy even under high wind speeds and rough sea states. Since the project start in 2009 the statistical basis for a conclusive validation has significantly improved with comprehensive data collection of more than 3 million minutes of precipitation measurements onboard six ships. Currently, six ODM470 instrument systems are available of which three are long-term mounted onboard the German research icebreaker R/V Polarstern (Alfred Wegner Institut) since June 2010, on R/V Akademik Ioffe (P.P.Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia) since September 2010 and on R/V Maria S. Merian (Brise Research, University of Hamburg) since December 2011. Three instruments are used for additional short-term shipboard campaigns and intercomparison projects. The core regions for these

  20. Global Precipitation Measurement (GPM) implementation

    NASA Astrophysics Data System (ADS)

    Neeck, Steven P.; Kakar, Ramesh K.; Azarbarzin, Ardeshir A.; Hou, Arthur Y.

    2010-10-01

    The Global Precipitation Measurement (GPM) mission will provide enhanced space-based precipitation measurements with sufficient coverage, spatial resolution, temporal sampling, retrieval accuracy, and microphysical information to advance the understanding of Earth's water and energy cycle and to improve predictions of its climate, weather, and hydrometeorological processes. Such improvements will in turn improve decision support systems in broad societal applications (e.g. water resource management, agriculture, transportation, etc). GPM is a partnership between NASA and the Japan Aerospace Exploration Agency (JAXA), building upon their highly successful partnership on the Tropical Rainfall Measuring Mission (TRMM). The GPM architecture consists of NASA satellites operating in partnership with other earth-observing satellites and instruments to produce global precipitation science data. The current generation of multi-satellite global precipitation products based on microwave/infrared sensors from uncoordinated satellite missions has for its anchor the TRMM precipitation radar and the TRMM Microwave Imager measurements over the tropics and subtropics (+/- 35 degrees latitude), with a mean sampling time of approximately 17 hours. The GPM mission will deploy a spaceborne Core Observatory as a reference standard to unify a space constellation of research and operational microwave sensors aimed at providing uniformly calibrated precipitation measurements globally every 2-4 hours. The Core Observatory measurements will provide, for the first time, quantitative information on precipitation particle size distribution needed for improving the accuracy of precipitation estimates by microwave radiometers and radars. In addition, the GPM will also include a second microwave radiometer and a Tracking and Data Relay Satellite (TDRS) communications subsystem for near real time data relay for a future partner-provided constellation satellite. This second GPM Microwave Imager (GMI

  1. The new automatic precipitation phase distinction algorithm for OceanRAIN data over the global ocean

    NASA Astrophysics Data System (ADS)

    Burdanowitz, Jörg; Klepp, Christian; Bakan, Stephan

    2015-04-01

    The hitherto lack of surface precipitation data over the global ocean limits the capabilities to validate recent and future precipitation satellite retrievals. The first systematic ship-based surface precipitation data set OceanRAIN (Ocean Rain And Ice-phase precipitation measurement Network) aims at providing in-situ precipitation data through particle size distributions (PSDs) from optical disdrometers deployed on research vessels (RVs). From the RV Polarstern, OceanRAIN currently contains more than four years of 1-minute resolution precipitation data, which corresponds to more than 200,000 minutes of precipitation. The calculation of the precipitation rate requires to know the precipitation phase (PP) of the falling particles. We develop a novel algorithm to automatically retrieve the PP using OceanRAIN data and ancillary meteorological measurements from RVs. The main objective is to improve accuracy and efficiency of the current time-consuming manual method of discriminating liquid and solid precipitation particles. The new PP distinction algorithm is based on the relation of air temperature and relative humidity (T-rH) with respect to PP. For first-time usage over oceanic areas, the land-retrieved coefficients of this empirical relationship are adjusted to OceanRAIN data. The measured PSD supports determining the PP in certain cases where large snow aggregates exist at distinctly positive air temperatures. The classification, based on T-rH and PSD, is statistically exploited and weighed with respect to the current weather conditions to obtain an overall PP probability at 1-minute resolution. The new PP distinction algorithm agrees in more than 92% (94% excl. mixed-phase) of precipitating cases with the manually-determined PP in the RV Polarstern data. The PP distinction algorithm complements the valuable information of OceanRAIN surface precipitation over the ocean.

  2. Rapid thermal annealing of ion beam synthesized {beta}-FeSi{sub 2} nanoparticles in Si

    SciTech Connect

    Sun, C. M.; Tsang, H. K.; Wong, S. P.; Cheung, W. Y.; Ke, N.; Hark, S. K.

    2008-05-26

    High crystal-quality {beta}-FeSi{sub 2} nanoparticles in silicon, prepared by ion beam synthesis and subjected to rapid thermal annealing (RTA), are investigated. Completely amorphous Fe-Si layers are formed by Fe implantation at cryogenic temperature, with a dosage of 5x10{sup 15} cm{sup -2}, into float-zone silicon. After RTA at 900 deg. C for 60 s, {beta}-FeSi{sub 2} precipitates are aggregated in the Si matrix and give {approx}1.5 {mu}m photoluminescence. High-resolution plan-view transmission electron microscopy revealed that some strain is present in the RTA treated FeSi{sub 2} particles. Silicon dislocations, coming from the strain relaxation during the additional long-term annealing, are observed around {beta}-FeSi{sub 2} particles.

  3. Measurement of visible and UV emission from Energetic Neutral Atom Precipitation (ENAP), on Spacelab

    NASA Astrophysics Data System (ADS)

    Tinsley, B. A.

    1980-10-01

    The charge exchange of plasmaspheric ions and exospheric H and O and of solar wind ions with exospheric and interplanetary H are sources of precipitating neutrals whose faint emission may be observed by the imaging spectrometric observatory during dark periods of the SL-1 orbit. Measurements of the interactions of these precipitating atoms with the thermosphere are needed to evaluate the heating and ionization effects on the atmosphere as well as the selective loss of i energetic ions from the sources (predominantly the ring current).

  4. Measurement of visible and UV emission from Energetic Neutral Atom Precipitation (ENAP), on Spacelab

    NASA Technical Reports Server (NTRS)

    Tinsley, B. A.

    1980-01-01

    The charge exchange of plasmaspheric ions and exospheric H and O and of solar wind ions with exospheric and interplanetary H are sources of precipitating neutrals whose faint emission may be observed by the imaging spectrometric observatory during dark periods of the SL-1 orbit. Measurements of the interactions of these precipitating atoms with the thermosphere are needed to evaluate the heating and ionization effects on the atmosphere as well as the selective loss of i energetic ions from the sources (predominantly the ring current).

  5. Enrichment of phosphorylated peptides and proteins by selective precipitation methods.

    PubMed

    Rainer, Matthias; Bonn, Günther K

    2015-01-01

    Protein phosphorylation is one of the most prominent post-translational modifications involved in the regulation of cellular processes. Fundamental understanding of biological processes requires appropriate bioanalytical methods for selectively enriching phosphorylated peptides and proteins. Most of the commonly applied enrichment approaches include chromatographic materials including Fe(3+)-immobilized metal-ion affinity chromatography or metal oxides. In the last years, the introduction of several non-chromatographic isolation technologies has increasingly attracted the interest of many scientists. Such approaches are based on the selective precipitation of phosphorylated peptides and proteins by applying various metal cations. The excellent performance of precipitation-based enrichment methods can be explained by the absence of any stationary phase, resin or sorbent, which usually leads to unspecific binding. This review provides an overview of recently published methods for the selective precipitation of phosphorylated peptides and proteins. PMID:25587840

  6. Inhomogeneous diffusion-limited aggregation

    NASA Technical Reports Server (NTRS)

    Selinger, Robin Blumberg; Nittmann, Johann; Stanley, H. E.

    1989-01-01

    It is demonstrated here that inhomogeneous diffusion-limited aggregation (DLA) model can be used to simulate viscous fingering in a medium with inhomogeneous permeability and homogeneous porosity. The medium consists of a pipe-pore square-lattice network in which all pores have equal volume and the pipes have negligible volume. It is shown that fluctuations in a DLA-based growth process may be tuned by noise reduction, and that fluctuations in the velocity of the moving interface are multiplicative in form.

  7. Aggregate stability, surface-water runoff, and soil loss in wheat-sunflower and corn-soybean rotations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Developing improved management options that limit soil erosion requires a greater understanding of the interactions between crop rotation, residue management, and precipitation patterns. We conducted a six-year study to evaluate how seasonal variation in aggregate stability, ground cover, soil moist...

  8. Precipitation of radiation belt electrons by EMIC waves, observed from ground and space

    SciTech Connect

    Jordanova, Vania K; Miyoski, Y; Sakaguchi, K; Shiokawa, K; Evans, D S; Albert, Jay; Connors, M

    2008-01-01

    We show evidence that left-hand polarised electromagnetic ion cyclotron (EMIC) plasma waves can cause the loss of relativistic electrons into the atmosphere. Our unique set of ground and satellite observations shows coincident precipitation of ions with energies of tens of keY and of relativistic electrons into an isolated proton aurora. The coincident precipitation was produced by wave-particle interactions with EMIC waves near the plasmapause. The estimation of pitch angle diffusion coefficients supports that the observed EMIC waves caused coincident precipitation ofboth ions and relativistic electrons. This study clarifies that ions with energies of tens of ke V affect the evolution of relativistic electrons in the radiation belts via cyclotron resonance with EMIC waves, an effect that was first theoretically predicted in the early 1970's.

  9. NASA Dual Precipitation Radar Arrives at Goddard

    NASA Video Gallery

    The Dual-frequency Precipitation Radar (DPR) built by the Japan Aerospace Exploration Agency (JAXA) for the Global Precipitation Measurement (GPM) mission's Core Observatory arrived on Friday, Marc...

  10. Perspective: Interactive material property databases through aggregation of literature data

    NASA Astrophysics Data System (ADS)

    Seshadri, Ram; Sparks, Taylor D.

    2016-05-01

    Searchable, interactive, databases of material properties, particularly those relating to functional materials (magnetics, thermoelectrics, photovoltaics, etc.) are curiously missing from discussions of machine-learning and other data-driven methods for advancing new materials discovery. Here we discuss the manual aggregation of experimental data from the published literature for the creation of interactive databases that allow the original experimental data as well additional metadata to be visualized in an interactive manner. The databases described involve materials for thermoelectric energy conversion, and for the electrodes of Li-ion batteries. The data can be subject to machine-learning, accelerating the discovery of new materials.

  11. Advanced Microwave Precipitation Radiometer (AMPR) for remote observation of precipitation

    NASA Technical Reports Server (NTRS)

    Galliano, J. A.; Platt, R. H.

    1990-01-01

    The design, development, and tests of the Advanced Microwave Precipitation Radiometer (AMPR) operating in the 10 to 85 GHz range specifically for precipitation retrieval and mesoscale storm system studies from a high altitude aircraft platform (i.e., ER-2) are described. The primary goals of AMPR are the exploitation of the scattering signal of precipitation at frequencies near 10, 19, 37, and 85 GHz together to unambiguously retrieve precipitation and storm structure and intensity information in support of proposed and planned space sensors in geostationary and low earth orbit, as well as storm-related field experiments. The development of AMPR will have an important impact on the interpretation of microwave radiances for rain retrievals over both land and ocean for the following reasons: (1) A scanning instrument, such as AMPR, will allow the unambiguous detection and analysis of features in two dimensional space, allowing an improved interpretation of signals in terms of cloud features, and microphysical and radiative processes; (2) AMPR will offer more accurate comparisons with ground-based radar data by feature matching since the navigation of the ER-2 platform can be expected to drift 3 to 4 km per hour of flight time; and (3) AMPR will allow underflights of the SSM/I satellite instrument with enough spatial coverage at the same frequencies to make meaningful comparisons of the data for precipitation studies.

  12. Precipitation of filamentous bacteriophages for their selective recovery in primary purification.

    PubMed

    Branston, Steven; Stanley, Emma; Keshavarz-Moore, Eli; Ward, John

    2012-01-01

    Filamentous bacteriophages and their derivatives are showing great promise as a whole new class of industrial agents, such as biologically based nano-materials and viral vectors. This raises challenges for their large-scale manufacture, principally due to the lack of bioprocessing knowledge. This article addresses what will be a potentially important option in the primary purification of the bacteriophages. Polyethylene glycol (PEG)-salt dual precipitants, calcium ions, spermidine, and isoelectric precipitation were first examined for their potential suitability for bacteriophage concentration under both pure and broth conditions. Successful precipitants were further studied on the basis of their selective purification ability from DNA and protein contaminants in a clarified broth system. Both PEG-based and isoelectric precipitations resulted in bacteriophage purity improvements, and PEG-based precipitations offered the highest selectivities. This work shows that precipitation of bacteriophages can be an effective primary purification step in a large-scale bioprocess. PMID:21905275

  13. Microbially induced and microbially catalysed precipitation: two different carbonate factories

    NASA Astrophysics Data System (ADS)

    Meister, Patrick

    2016-04-01

    The landmark paper by Schlager (2003) has revealed three types of benthic carbonate production referred to as "carbonate factories", operative at different locations at different times in Earth history. The tropical or T-factory comprises the classical platforms and fringing reefs and is dominated by carbonate precipitation by autotrophic calcifying metazoans ("biotically controlled" precipitation). The cool or C-factory is also biotically controlled but via heterotrophic, calcifying metazoans in cold and deep waters at the continental margins. A further type is the mud-mound or M-factory, where carbonate precipitation is supported by microorganisms but not controlled by a specific enzymatic pathway ("biotically induced" precipitation). How exactly the microbes influence precipitation is still poorly understood. Based on recent experimental and field studies, the microbial influence on modern mud mound and microbialite growth includes two fundamentally different processes: (1) Metabolic activity of microbes may increase the saturation state with respect to a particular mineral phase, thereby indirectly driving the precipitation of the mineral phase: microbially induced precipitation. (2) In a situation, where a solution is already supersaturated but precipitation of the mineral is inhibited by a kinetic barrier, microbes may act as a catalyser, i.e. they lower the kinetic barrier: microbially catalysed precipitation. Such a catalytic effect can occur e.g. via secreted polymeric substances or specific chemical groups on the cell surface, at which the minerals nucleate or which facilitate mechanistically the bonding of new ions to the mineral surface. Based on these latest developments in microbialite formation, I propose to extend the scheme of benthic carbonate factories of Schlager et al. (2003) by introducing an additional branch distinguishing microbially induced from microbially catalysed precipitation. Although both mechanisms could be operative in a M

  14. Preparation of crosslinked enzyme aggregates (CLEAs) of acid urease with urethanase activity and their application.

    PubMed

    Zhang, Qian; Zha, Xiaohong; Zhou, Nandi; Tian, Yaping

    2016-04-01

    An acid urease from Providencia rettgeri JN-B815 was purified via ultrasonication, ethanol precipitation, and DEAE ion-exchange column chromatography. It was found that the enzyme exhibits not only urease activity, but also urethanase activity, which made it possible to reduce EC already existed or would produce and its precursor urea at the same time. Then, crosslinked enzyme aggregates of P. rettgeri urease (PRU-CLEAs) were prepared using genipin as crosslinking agent. The purification process of acid urease, the effects of genipin concentration, and crosslinking time on PRU-CLEAs activity were investigated. The crosslinking was performed at pH 4.5 for 2.5 h, using 0.3% genipin as crosslinking agent, and 0.3 g · L(-1) bovine serum albumin as protein feeder. Using the obtained PRU-CLEAs, the removal rate of urea was up to 9.31 mg · L(-1) · h(-1). The removal rate of urea was still up to 7.56 mg · L(-1) · h(-1) after PRU-CLEAs was re-used for 6 times. When PRU-CLEAs were applied in a batch stirred and membrane reactor, the removal rate of urea in rice wine reached 5.16 mg · L(-1) · h(-1) and the removal rate of EC was 9.21 μg · L(-1) · h(-1). Furthermore, the treatment with PRU-CLEAs revealed no significant change of volatile flavor substances in Chinese rice wine. Thus PRU-CLEAs have great potential in the elimination of EC in Chinese rice wine. PMID:26627914

  15. Modeling Snow Aggregates and their Single Scattering Properties: Implications to Snowfall Remote Sensing

    NASA Astrophysics Data System (ADS)

    Nowell, H.; Liu, G.

    2012-12-01

    With the advent of satellites, we can now observe areas of the globe that have sparse to no ground data coverage. Both active and passive satellite sensors aboard satellites including CloudSat's Cloud Profiling Radar (CPR), Aqua's Advanced Microwave Scanning Radiometer (AMSR-E) and the upcoming Global Precipitation Measurement's (GPM) Dual-Frequency Precipitation Radar (DPR) and GPM Microwave Imager (GMI) study ice and snow particles. A good retrieval algorithm for these satellite sensors can only be developed when the single scattering properties of the snowflakes are accurately calculated in radiative transfer models. This becomes crucial at frequencies at and above the W-band when aggregate ice crystals become detectable by satellite radiometers. Snowflakes are often modeled as spheres or oblate spheroids to ease the complexity of calculations, despite the fact that they are typically aggregates of crystals. For improved accuracy in satellite remote sensing, it is important to model snowflakes as close to nature as possible. Several recent studies model flakes as pristine crystal types [Liu, 2008], generate aggregate flakes as fractals [Ishimoto, 2008] or via the Monte Carlo method [Maruyama and Fujioshi, 2005]. Modeling snowflakes as pristine crystals, however, has the drawback of not accurately reflecting snowflakes as most tend to be aggregates of different crystal types. Other studies where aggregates are generated tend to overlook size-density relationships of aggregate flakes or other studied statistical parameters such as aspect ratio. In an effort to improve available single-scattering properties of aggregate flakes, we developed a new method of generating flakes. Starting out with a six-bullet rosette crystal of accurate size and density, aggregate flakes are generated with two different bullet rosette crystal sizes of 200 and/or 400 microns in maximum dimension. The flakes similarly follow size-density relationships of aggregate as determined from

  16. Effect of the slope and initial moisture content on soil loss, aggregate and particle size distribution

    NASA Astrophysics Data System (ADS)

    Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka

    2015-04-01

    Soil structure degradation has effect through the soil water balance and nutrient supply on the agricultural potential of an area. The soil erosion process comprises two phases: detachment and transport by water. To study the transport phase nozzle type laboratory-scale rainfall simulator was used with constant 80 mmhr-1 intensity on an arable haplic Cambisol. Measuring the aggregate and particle size distribution of the soil loss gives a good approach the erosion process. The primary objective of this study was to examine the sediment concentration, and detect the quality and quantity change of the soil loss during a single precipitation under six treatment combinations (recently tilled and crusty soil surface on two different slope steepness, inland inundation and drought soil conditions). Soil loss were collected continually, and separated per aggregate size fractions with sieves in three rounds during a rain to measure the weights. The particle size distribution was measured with Horiba LA-950 particle size analyzer. In general the ratio of the macro aggregates decreases and the ratio of the micro aggregates and clay fraction increases in the sediment with time during the precipitation due to the raindrop impact. Sediment concentration depends on the slope steepness, as from steeper slopes the runoff can transport bigger amount of sediment, but from the tilled surface bigger aggregates were washing down. Micro aggregate fraction is one of the indicators of good soil structure. The degradation of micro aggregates occurs in steeper slopes and the most erosive time period depends on the micromorphology of the surface. And while the aggregate size distribution of the soil loss of the treatments shows high variety of distribution and differs from the original soil, the particle size distribution of each aggregate size fraction shows similar trends except the 50-250 µm fraction where the fine sand fraction is dominating instead of the loam. This anomaly may be

  17. Investigating the mechanisms leading to protein aggregation

    NASA Astrophysics Data System (ADS)

    McNamara, Ruth; McManus, Jennifer J.

    2014-03-01

    The formation of protein aggregates is a feature of several diseases and is a problem during the manufacture of biopharmaceutical and protein based food products. During processing, stability may become compromised leading to the condensation of proteins to form non-native aggregates. The aim of this work is to induce aggregation on model proteins by the imposition of a particular stress to evaluate the extent of aggregation and to assess the degree of structural change to the protein. Aggregation of two proteins, lysozyme and bovine serum albumin has been induced by several mechanisms. Using various techniques (electrophoresis, HPLC, spectroscopic analysis, and microscopic techniques) both the level of aggregation extent of protein unfolding has been investigated for a range of solution conditions. Our results show that the amount of aggregation depends strongly on the mechanism by which non-native aggregation proceeds, and within each mechanism, solution conditions are an important factor. With the exception of aggregation by self-association (which is concentration dependent), the appearance of aggregation is driven by structural changes induced by the applied stress (heat, chemical denaturant, oxidation or contact with a surface). Author would like to acknowledge support from Science Foundation Ireland (SFI), National University of Maynooth John and Pat Hume Scholarship.

  18. Applications of aggregation theory to sustainability assessment

    DOE PAGESBeta

    Pollesch, N.; Dale, V. H.

    2015-04-01

    In order to aid in transition towards operations that promote sustainability goals, researchers and stakeholders use sustainability assessments. Although assessments take various forms, many utilize diverse sets of indicators that can number anywhere from two to over 2000. Indices, composite indicators, or aggregate values are used to simplify high dimensional and complex data sets and to clarify assessment results. Although the choice of aggregation function is a key component in the development of the assessment, there are few examples to be found in literature to guide appropriate aggregation function selection. This paper develops a connection between the mathematical study ofmore » aggregation functions and sustainability assessment in order to aid in providing criteria for aggregation function selection. Relevant mathematical properties of aggregation functions are presented and interpreted. Lastly, we provide cases of these properties and their relation to previous sustainability assessment research. Examples show that mathematical aggregation properties can be used to address the topics of compensatory behavior and weak versus strong sustainability, aggregation of data under varying units of measurements, multiple site multiple indicator aggregation, and the determination of error bounds in aggregate output for normalized and non-normalized indicator measures.« less

  19. Applications of aggregation theory to sustainability assessment

    SciTech Connect

    Pollesch, N.; Dale, V. H.

    2015-04-01

    In order to aid in transition towards operations that promote sustainability goals, researchers and stakeholders use sustainability assessments. Although assessments take various forms, many utilize diverse sets of indicators that can number anywhere from two to over 2000. Indices, composite indicators, or aggregate values are used to simplify high dimensional and complex data sets and to clarify assessment results. Although the choice of aggregation function is a key component in the development of the assessment, there are few examples to be found in literature to guide appropriate aggregation function selection. This paper develops a connection between the mathematical study of aggregation functions and sustainability assessment in order to aid in providing criteria for aggregation function selection. Relevant mathematical properties of aggregation functions are presented and interpreted. Lastly, we provide cases of these properties and their relation to previous sustainability assessment research. Examples show that mathematical aggregation properties can be used to address the topics of compensatory behavior and weak versus strong sustainability, aggregation of data under varying units of measurements, multiple site multiple indicator aggregation, and the determination of error bounds in aggregate output for normalized and non-normalized indicator measures.

  20. A review of volcanic ash aggregation

    NASA Astrophysics Data System (ADS)

    Brown, R. J.; Bonadonna, C.; Durant, A. J.

    2012-01-01

    Most volcanic ash particles with diameters <63 μm settle from eruption clouds as particle aggregates that cumulatively have larger sizes, lower densities, and higher terminal fall velocities than individual constituent particles. Particle aggregation reduces the atmospheric residence time of fine ash, which results in a proportional increase in fine ash fallout within 10-100 s km from the volcano and a reduction in airborne fine ash mass concentrations 1000 s km from the volcano. Aggregate characteristics vary with distance from the volcano: proximal aggregates are typically larger (up to cm size) with concentric structures, while distal aggregates are typically smaller (sub-millimetre size). Particles comprising ash aggregates are bound through hydro-bonds (liquid and ice water) and electrostatic forces, and the rate of particle aggregation correlates with cloud liquid water availability. Eruption source parameters (including initial particle size distribution, erupted mass, eruption column height, cloud water content and temperature) and the eruption plume temperature lapse rate, coupled with the environmental parameters, determines the type and spatiotemporal distribution of aggregates. Field studies, lab experiments and modelling investigations have already provided important insights on the process of particle aggregation. However, new integrated observations that combine remote sensing studies of ash clouds with field measurement and sampling, and lab experiments are required to fill current gaps in knowledge surrounding the theory of ash aggregate formation.