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Sample records for acetonitrile-water mobile phase

  1. Effect of temperature on the chromatographic retention of ionizable compounds. II. Acetonitrile-water mobile phases.

    PubMed

    Gagliardi, Leonardo G; Castells, Cecilia B; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth

    2005-06-10

    The retentive behavior of weak acids and bases in reversed-phase liquid chromatography (RPLC) upon changes in column temperature has been theoretically and experimentally studied. The study focuses on examining the temperature dependence of the retention of various solutes at eluent pH close to their corresponding pKa values, and on the indirect role exerted by the buffer ionization equilibria on retention and selectivity. Retention factors of several ionizable compounds in a typical octadecylsilica column and using buffer solutions dissolved in 30% (v/v) acetonitrile as eluent at five temperatures in the range from 25 to 50 degrees C were carefully measured. Six buffer solutions were prepared from judiciously chosen conjugated pairs of different chemical nature. Their pKa values in this acetonitrile-water composition and within the range of 15-50 degrees C were determined potentiometrically. These compounds exhibit very different standard ionization enthalpies within this temperature range. Thus, whenever they are used to control mobile phase pH, the column temperature determines their final pH. Predictive equations of retention that take into account the temperature effect on both the transfer and the ionization processes are evaluated. This study demonstrates the significant role that the selected buffer would have on retention and selectivity in RPLC at temperatures higher than 25 degrees C, particularly for solutes that coelute. PMID:16001552

  2. Effect of temperature on the chromatographic retention of ionizable compounds. II. Acetonitrile-water mobile phases.

    PubMed

    Gagliardi, Leonardo G; Castells, Cecilia B; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth

    2005-06-10

    The retentive behavior of weak acids and bases in reversed-phase liquid chromatography (RPLC) upon changes in column temperature has been theoretically and experimentally studied. The study focuses on examining the temperature dependence of the retention of various solutes at eluent pH close to their corresponding pKa values, and on the indirect role exerted by the buffer ionization equilibria on retention and selectivity. Retention factors of several ionizable compounds in a typical octadecylsilica column and using buffer solutions dissolved in 30% (v/v) acetonitrile as eluent at five temperatures in the range from 25 to 50 degrees C were carefully measured. Six buffer solutions were prepared from judiciously chosen conjugated pairs of different chemical nature. Their pKa values in this acetonitrile-water composition and within the range of 15-50 degrees C were determined potentiometrically. These compounds exhibit very different standard ionization enthalpies within this temperature range. Thus, whenever they are used to control mobile phase pH, the column temperature determines their final pH. Predictive equations of retention that take into account the temperature effect on both the transfer and the ionization processes are evaluated. This study demonstrates the significant role that the selected buffer would have on retention and selectivity in RPLC at temperatures higher than 25 degrees C, particularly for solutes that coelute.

  3. Retention of ionizable compounds on HPLC. 5. pH scales and the retention of acids and bases with acetonitrile-water mobile phases

    PubMed

    Espinosa; Bosch; Roses

    2000-11-01

    The pH calibration procedures that lead to the different pH scales in acetonitrile-water mixtures used as mobile phases in reversed-phase liquid chromatography are discussed. Appropriate buffers of known pH value in acetonitrile-water mixtures are selected and used to establish the relationship (delta values) between the two rigorous acetonitrile-water pH scales: sspH and wspH (pH measured in acetonitrile-water mixtures and referred to acetonitrile-water or water, respectively, as standard state). These delta values allow one to convert pH values measured in acetonitrile-water with electrode systems calibrated with aqueous buffers (wspH scale) to sspH values, which are directly related to the thermodynamic acid-base constants. This offers an easy way to measure the pH of acetonitrile-water mobile phases and to relate this pH to the chromatographic retention of acids and bases through the thermodynamic acid-base constants. The relationships are tested for the variation of the retention of acids and bases with the pH of the mobile phase at several mobile-phase compositions and favorably compared with the relationships obtained with the common wwpH scale (pH measured in the aqueous buffer before mixing it with the organic modifier). The use of the rigorous sspH and wspH scales allows one to explain the retention behavior of bases, which in many instances cannot be justified from the pH measurement in the ill-founded wwpH scale. PMID:11080863

  4. Retention of ionizable compounds on HPLC. 5. pH scales and the retention of acids and bases with acetonitrile-water mobile phases

    PubMed

    Espinosa; Bosch; Roses

    2000-11-01

    The pH calibration procedures that lead to the different pH scales in acetonitrile-water mixtures used as mobile phases in reversed-phase liquid chromatography are discussed. Appropriate buffers of known pH value in acetonitrile-water mixtures are selected and used to establish the relationship (delta values) between the two rigorous acetonitrile-water pH scales: sspH and wspH (pH measured in acetonitrile-water mixtures and referred to acetonitrile-water or water, respectively, as standard state). These delta values allow one to convert pH values measured in acetonitrile-water with electrode systems calibrated with aqueous buffers (wspH scale) to sspH values, which are directly related to the thermodynamic acid-base constants. This offers an easy way to measure the pH of acetonitrile-water mobile phases and to relate this pH to the chromatographic retention of acids and bases through the thermodynamic acid-base constants. The relationships are tested for the variation of the retention of acids and bases with the pH of the mobile phase at several mobile-phase compositions and favorably compared with the relationships obtained with the common wwpH scale (pH measured in the aqueous buffer before mixing it with the organic modifier). The use of the rigorous sspH and wspH scales allows one to explain the retention behavior of bases, which in many instances cannot be justified from the pH measurement in the ill-founded wwpH scale.

  5. Retention of ionizable compounds on HPLC. 12. The properties of liquid chromatography buffers in acetonitrile-water mobile phases that influence HPLC retention.

    PubMed

    Espinosa, Sonia; Bosch, Elisabeth; Rosés, Marti

    2002-08-01

    The addition of acetonitrile to aqueous buffers to prepare RP HPLC mobile phases changes the buffer properties (pH and buffer capacity). This variation is studied for ace tate, phosphate, phthalate, citrate, and ammonia buffers in acetonitrile-water mixtures up to 60% in acetonitrile (v/v). Equations are proposed to relate pH and buffer capacity change of these buffers to the initial aqueous pH value and to the volume fraction of acetonitrile added. It is demonstrated that the pH change of the buffer depends not only on the initial aqueous pH of the buffer and on the percentage of acetonitrile added but also on the particular buffer used. The proposed equations allow an accurate prediction of this ionization for the studied buffers. Since the retention of acid/base compounds shows a strong dependence of their degree of ionization, the equations are used to predict the change in this ionization with addition of acetonitrile when the RP HPLC mobile phase is prepared. This prediction allows estimation of the retention of an acid/base compound in a particular acetonitrile-water buffered mobile phase.

  6. Gradient retention prediction of acid-base analytes in reversed phase liquid chromatography: a simplified approach for acetonitrile-water mobile phases.

    PubMed

    Andrés, Axel; Rosés, Martí; Bosch, Elisabeth

    2014-11-28

    In previous work, a two-parameter model to predict chromatographic retention of ionizable analytes in gradient mode was proposed. However, the procedure required some previous experimental work to get a suitable description of the pKa change with the mobile phase composition. In the present study this previous experimental work has been simplified. The analyte pKa values have been calculated through equations whose coefficients vary depending on their functional group. Forced by this new approach, other simplifications regarding the retention of the totally neutral and totally ionized species also had to be performed. After the simplifications were applied, new prediction values were obtained and compared with the previously acquired experimental data. The simplified model gave pretty good predictions while saving a significant amount of time and resources.

  7. Determination of the solvent density profiles across mesopores of silica-C18 bonded phases in contact with acetonitrile/water mixtures: A semi-empirical approach.

    PubMed

    Gritti, Fabrice

    2015-09-01

    The local volume fractions of water, acetonitrile, and C18-bonded chains across the 96Åmesopores of 5μm Symmetry particles were determined semi-empirically. The semi-empirical approach was based on previous molecular dynamics studies, which provided relevant mathematical expressions for the density profiles of C18 chains and water molecules, and on minor disturbance experiments, which measured the excess amount of acetonitrile adsorbed in the pores of Symmetry-C18 particles. The pore walls of the Symmetry-C18 material were in thermodynamic equilibrium with a series of binary mixtures of water and acetonitrile. The results show that C18 chains are mostly solvated by acetonitrile molecules, water is excluded from the C18-bonded layer, and acetonitrile concentrates across a 15-25Åthick interface region between the C18 layer and the bulk phase. These actual density profiles are expected to have a direct impact on the retention behaviour of charged, polar, and neutral analytes in RPLC. They also provide clues to predict the local mobility of analytes inside the pores and a sound physico-chemical description of the phenomenon of surface diffusion observed in RPLC.

  8. Mixture design optimization of extraction and mobile phase media for fingerprint analysis of Bauhinia variegata L.

    PubMed

    Delaroza, Fernanda; Scarminio, Ieda Spacino

    2008-04-01

    Two statistical mixture designs were used to optimize the proportions of solvents used in both the extraction medium and the reversed liquid chromatographic mobile phase to improve the quality of chromatographic fingerprints of Bauhinia variegata L extracts. For modeling, the number of peaks was used as a measure of fingerprint information. Three mobile phases, each with a chromatographic strength of two, gave good results. A methanol/water (77:23 v/v) mixture resulted in 17 peaks in the chromatographic fingerprint whereas acetonitrile/water (64.5:35.5 v/v) and methanol/acetonitrile/water (35:35:30 v/v/v) mixtures resulted in 18 and 20 peaks, respectively. The corresponding optimum solvent compositions to extract chemical substances for these three mobile phases were ethanol/acetone (25:75 v/v/v) and dichloromethane/acetone (70:30 v/v) mixtures, and pure dichloromethane, respectively. The mixture designs are useful for understanding the influence of different solvents on the strengths of the extraction medium and the mobile phase.

  9. Enhanced extraction yields and mobile phase separations by solvent mixtures for the analysis of metabolites in Annona muricata L. leaves.

    PubMed

    Ribeiro de Souza, Eloana Benassi; da Silva, Renata Reis; Afonso, Sabrina; Scarminio, Ieda Spacino

    2009-12-01

    The effects of five extraction solvents and their mixtures on the yield of metabolites in crude and fractionated extracts of Annona muricata L. leaves were investigated by direct comparison. Extraction media were prepared using simplex centroid mixtures of ethanol, ethyl acetate, dichloromethane, acetone, and chloroform. The effects of the mobile phase solvent strength and the analysis wavelength on the chromatographic separation were also investigated. Solvent mixtures rather than pure solvents were found to be the most efficient extractors for the different fractions. The results indicated that the mobile phase composed of methanol/acetonitrile/water (26:27:47 v/v/v) was most suitable for the basic fraction analysis at 254 nm, whereas the mobile phase composed of methanol/acetonitrile/water (35:35:30 v/v/v) was the most adequate for the organic fraction analysis at 254 nm. The results indicated that the chromatographic profiles and number of peaks were affected by the mobile phase strength and analysis wavelength.

  10. Electrochemical detection of benzo(a)pyrene in acetonitrile-water binary medium.

    PubMed

    Du, Chunyan; Hu, Yaqi; Li, Yunchao; Fan, Louzhen; Li, Xiaohong

    2015-06-01

    Electrochemical oxidation of adsorbed benzo(a)pyrene (BaP) on the glassy carbon electrode (GCE) was explored in acetonitrile-water. When the GCE was incubated in 100 nM BaP acetonitrile-water (V(water):V(acetonitrile)=1:1) for 10 min at open circuit, and then transferred into blank acetonitrile-water (V(water):V(acetonitrile)=1:1, pH= 0.70) for differential pulse voltammetry measurement, a distinct oxidation peak at 0.98 V (vs. Ag/AgCl) was observed. The peak potential was about 180 mV lower than that in acetonitrile. Importantly, the peak current was more than 22 times greater. The effects of water on BaP preconcentration on the electrode and electrochemical oxidation were revealed, respectively. Based on the results, an electrochemical assay for BaP detection was developed. The GCE was respectively incubated in acetonitrile-water (V(water):V(acetonitrile)=1:1)with BaP concentration ranged from 0 nM to 1000 nM, and then transferred into the corresponding blank acetonitrile-water (pH= 0.70) for DPV measurements. When the BaP concentration was increased, an increased oxidative current at 0.98 V (vs. Ag/AgCl) was observed, and a detection limit of 0.67 nM was achieved. Because all other priority polycyclic aromatic hydrocarbons could not be electrochemically oxidized at 0.98 V, the electrochemical assay showed very high selectivity to BaP. Finally, the developed electrochemical assay was successfully applied to determination of BaP in a series of real world samples, such as drinking water, tap water, lake water and river water.

  11. Ionic liquids as mobile phase additives for feasible assay of naphazoline in pharmaceutical formulation by HPTLC-UV-densitometric method.

    PubMed

    Marszałł, Michał Piotr; Sroka, Wiktor Dariusz; Balinowska, Aleksandra; Mieszkowski, Dominik; Koba, Marcin; Kaliszan, Roman

    2013-07-01

    A specific and reliable high-performance thin layer chromatography method with densitometry detection has been developed for the determination of naphazoline nitrate in nasal drops. The best separation of the basic analyte, without spot tailing, was achieved by using a mobile phase composed of acetonitrile-water (60:40, v/v), adding 1.5 % (v/v) imidazolium-class ionic liquid and covering the plates with a stationary phase based on RP-18 with F254S (10 × 20 cm). The presented results confirm that imidazolium tetrafluoroborate ionic liquids are efficient suppressors of free silanols, which are considered to be responsible for troublesome and irreproducible chromatographic determinations of basic compounds. The developed chromatographic system was found to be convenient in use and to provide a repeatable assay of naphazoline nitrate in nasal drops, which could not be obtained with the use of standard silanol suppressing mobile phase additives such as triethylamine or dimethyloctylamine.

  12. Another glimpse over the salting-out assisted liquid-liquid extraction in acetonitrile/water mixtures.

    PubMed

    Valente, Inês Maria; Gonçalves, Luís Moreira; Rodrigues, José António

    2013-09-20

    The use of the salting-out effect in analytical chemistry is very diverse and can be applied to increase the volatility of the analytes in headspace extractions, to cause the precipitation of proteins in biological samples or to improve the recoveries in liquid-liquid extractions. In the latter, the salting-out process can be used to create a phase separation between water-miscible organic solvents and water. Salting-out assisted liquid-liquid extraction (SALLE) is an advantageous sample preparation technique aiming HPLC-UV analysis when developing analytical methodologies. In fact, some new extraction methodologies like QuEChERS include the SALLE concept. This manuscript discusses another point of view over SALLE with particular emphasis over acetonitrile-water mixtures for HPLC-UV analysis; the influence of the salting-out agents, their concentration and the water-acetonitrile volume ratios were the studied parameters. α-dicarbonyl compounds and beer were used as test analytes and test samples, respectively. The influence of the studied parameters was characterized by the obtained phase separation volume ratio and the fraction of α-dicarbonyls extracted to the acetonitrile phase. Results allowed the distribution of salts within three groups according to the phase separation and their extractability: (1) chlorides and acetates, (2) carbonates and sulfates and (3) magnesium sulfate; of all tested salts, sodium chloride had the highest influence on the α-dicarbonyls fraction extracted.

  13. Potentiometric titrations in acetonitrile-water mixtures: evaluation of aqueous ionisation constant of ketoprofen.

    PubMed

    Herrador, M Angeles; González, A Gustavo

    2002-03-11

    Non ideality of acetonitrile-water mixtures was studied from data on the excess of molar volumes and viscosities. pH and autoprotolisis constants were evaluated at the standard state of the mixed solvent from titrations of a strong acid with a strong base. In order to illustrate the evaluation of the aqueous ionisation constant of water insoluble compounds from pH titrations in ACN-water mixtures, a typical insoluble arylpropionic acid, ketoprofen, was chosen. Ketoprofen was titrated in mixtures from 10 to 70% w/w of acetonitrile against a strong base. From the titration data, the ionisation constant of ketoprofen was evaluated at the standard state of the solvent mixture (pK(a)(*)). Aqueous pK(a) was determined by extrapolation, as the intercept of the plot of pK(a)(*) versus ACN mole fraction.

  14. Formation of iron complexs from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis

    SciTech Connect

    Shukla, Anil K.; Zhang, Rui; Orton, Daniel J.; Zhao, Rui; Clauss, Therese RW; Moore, Ronald J.; Smith, Richard D.

    2011-05-30

    Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are not due to any contamination from solvents and chemicals used for mobile and stationary phases or from the laboratory atmospheric environment. Instead these ions are clusters of trifluoroacetic acid formed in association with acetonitrile, water and iron from the stainless steel union used to connect the column with the electrospray tip and to apply high voltage; the molecular formulae are Fe+((OH)(H2O)2)9(CF3COOH)5 and Fe+((OH)(H2O)2)6 (CF3COOH)5.

  15. Separation and characterization of phenolic compounds and triterpenoid saponins in licorice (Glycyrrhiza uralensis) using mobile phase-dependent reversed-phase×reversed-phase comprehensive two-dimensional liquid chromatography coupled with mass spectrometry.

    PubMed

    Qiao, Xue; Song, Wei; Ji, Shuai; Wang, Qi; Guo, De-an; Ye, Min

    2015-07-10

    Licorice is one of the most popular herbal medicines worldwide. It contains a big array of phenolic compounds (flavonoids, coumarins, and diphenylethanones). Due to high structural diversity, low abundance, and co-elution with licorice saponins, these phenolic compounds are difficult to be separated by conventional chromatography. In this study, a mobile phase-dependent reversed-phase×reversed phase comprehensive two-dimensional liquid chromatography (RP×RP 2DLC) method was established to separate phenolic compounds in licorice (the roots of Glycyrrhiza uralensis). Organic solvents in the mobile phase were optimized to improve orthogonality of the first and second dimensions, and a synchronized gradient mode was used to improve chromatographic resolution. Finally, licorice extracts were eluted with methanol/water/formic acid in the first dimension (Acquity CSH C18 column), and acetonitrile/water/formic acid in the second dimension (Poroshell Phenyl-Hexyl column). By using this 2DLC system, a total of 311 compounds were detected within 40min. The practical and effective peak capacity was 1329 and 524, respectively, and the orthogonality was 79.8%. The structures of 21 selected unknown compounds were tentatively characterized by mass spectrometry, and 8 of them were discovered from G. uralensis for the first time. The mobile phase-dependent 2DLC/MS system could benefit the separation and characterization of natural products in complicated herbal extracts.

  16. Retention of ionisable compounds on high-performance liquid chromatography XVIII: pH variation in mobile phases containing formic acid, piperazine, tris, boric acid or carbonate as buffering systems and acetonitrile as organic modifier.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2009-03-20

    In the present work dissociation constants of commonly used buffering species, formic acid, piperazine, tris(hydroxymethyl)-aminomethane, boric acid and carbonate, have been determined for several acetonitrile-water mixtures. From these pK(a) values a previous model has been successfully evaluated to estimate pH values in acetonitrile-aqueous buffer mobile phases from the aqueous pH and concentration of the above mentioned buffers up to 60% of acetonitrile, and aqueous buffer concentrations between 0.005 (0.001 mol L(-1) for formic acid-formate) and 0.1 mol L(-1). The relationships derived for the presently studied buffers, together with those established for previously considered buffering systems, allow a general prediction of the pH variation of the most commonly used HPLC buffers when the composition of the acetonitrile-water mobile phase changes during the chromatographic process, such as in gradient elution. Thus, they are an interesting tool that can be easily implemented in general retention models to predict retention of acid-base analytes and optimize chromatographic separations.

  17. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning... compliance with all requirements for receipt of Mobility Fund Phase I support at the time that it...

  18. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning... compliance with all requirements for receipt of Mobility Fund Phase I support at the time that it...

  19. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 3 2014-10-01 2014-10-01 false Mobility Fund Phase I disbursements. 54.1008 Section 54.1008 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning bidder for Mobility Fund Phase I...

  20. Photophysics of Diphenylbutadiynes in Water, Acetonitrile-Water, and Acetonitrile Solvent Systems: Application to Single Component White Light Emission.

    PubMed

    Pati, Avik Kumar; Jana, Rounak; Gharpure, Santosh J; Mishra, Ashok K

    2016-07-28

    Diacetylenes have been the subject of current research because of their interesting optoelectronic properties. Herein, we report that substituted diphenylbutadiynes exhibit locally excited (LE) and excimer emissions in water and multiple emissions from the LE, excimer, and intramolecular charge transfer (ICT) states in acetonitrile-water solvent systems. The LE, excimer, and ICT emissions are clearly distinguishable for a diphenylbutadiynyl derivative with push (-NMe2)-pull (-CN) substituents and those are closely overlapped for non-push-pull analogues. In neat acetonitrile, the excimer emission disappears and the LE and ICT emissions predominate. In the case of the push (-NMe2)-pull (-CN) diphenylbutadiyne, the intensity of the ICT emission increases with increasing the fluorophore concentration. This suggests that the ICT emission accompanies with intermolecular CT emission which is of exciplex type. As the LE and exciplex emissions of the push-pull diphenylbutadiyne together cover the visible region (400-700 nm) in acetonitrile, a control of the fluorophore concentration makes the relative intensities of the LE and exciplex emissions such that pure white light emission is achieved. The white light emission is not observed in those diphenylbutadiynyl analogues in which the peripheral substituents of the phenyl rings do not possess strong push-pull character. PMID:27379734

  1. An automated mobile phase preparation workstation.

    PubMed

    Swinney, Kelly; Young, Benjamin; Jakubik, Matthew E; Clark, Hinton; Troisi, John; Fermier, Adam M

    2007-02-01

    An automated solvent dispensing workstation capable of delivering volumes ranging from 10 mL to 4.5 L for the preparation of solutions/mobile phases was developed and implemented into the industrial R&D laboratory. The workstation was designed to address business, safety, and compliance needs while meeting or exceeding the precision and accuracy of current manual methods of preparation. The system's performance was optimized with respect to liquid transfer tubing inner diameter, pumping pressure, flow characteristics of the valve, and computer control logic. The automated solvent dispensing workstation was shown to exceed the specifications set by the ASTM for Class A graduated cylinders for all dispense volumes (10 mL-4.5 L).

  2. Retention of ionisable compounds on high-performance liquid chromatography. XV. Estimation of the pH variation of aqueous buffers with the change of the acetonitrile fraction of the mobile phase.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2004-12-01

    The most commonly used mobile phases in reversed-phase high-performance liquid chromatography (RP-HPLC) are hydro-organic mixtures of an aqueous buffer and an organic modifier. The addition of this organic solvent to buffered aqueous solutions involves a variation of the buffer properties (pH and buffer capacity). In this paper, the pH variation is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-citrate, and ammonium-ammonia buffers. The proposed equations allow pH estimation of acetonitrile-water buffered mobile phases up to 60% (v/v) of organic modifier and initial aqueous buffer concentrations between 0.001 and 0.1 mol L(-1), from the initial aqueous pH. The estimated pH variation of the mobile phase and the pKa variation of the analytes allow us to predict the degree of ionisation of the analytes and from this and analyte hydrophobicities, to interpret the relative retention and separation of analyte mixtures.

  3. Impact of the nature and composition of the mobile phase on the mass transfer mechanism in chiral reversed phase liquid chromatography. Application to the minimization of the solvent cost in chiral separations.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2014-01-31

    The mechanism of mass transfer was studied on a cellulose-based chiral stationary phase (CSP, Lux Cellulose-1) using aqueous mixtures of acetonitrile (50/50-90/10, v/v) or methanol (90/10 and 100/0, v/v) as the mobile phase. An experimental protocol validated in RPLC and HILIC chromatography and recently extended to chiral RPLC was applied. The five mass-transfer contributions (longitudinal diffusion, short-range and long-range eddy dispersion, solid-liquid mass transfer resistances due to finite intra-particle diffusivity and slow adsorption-desorption) to the reduced height equivalent to a theoretical plate (HETP) were measured. The experimental results show that the adsorption rate constants kads of trans-stilbene enantiomers onto the CSP are three times larger with acetonitrile than with methanol as the organic modifier. This is correlated to the decrease of enantioselectivity from 1.4 (in methanol) to only 1.1 (in acetonitrile). The amount of solvent needed to achieve a separation factor of exactly 2.0 was determined. This showed that analysis cost could be reduced seven times by selecting pure methanol as the eluent for a 5cm long column rather than an acetonitrile-water mixture for a longer (20-45cm) column.

  4. MSAT mobile electronically steered phased array antenna development

    NASA Technical Reports Server (NTRS)

    Schmidt, Fred

    1988-01-01

    The Mobile Satellite Experiment (MSAT-X) breadboard antenna design demonstrates the feasibility of using a phased array in a mobile satellite application. An electronically steerable phased array capable of tracking geosynchronous satellites from anywhere in the Continental United States has been developed. The design is reviewed along with the test data. Cost analysis are presented which indicate that this design can be produced at a cost of $1620 per antenna.

  5. Unified pH values of liquid chromatography mobile phases.

    PubMed

    Suu, Agnes; Jalukse, Lauri; Liigand, Jaanus; Kruve, Anneli; Himmel, Daniel; Krossing, Ingo; Rosés, Martí; Leito, Ivo

    2015-03-01

    This work introduces a conceptually new approach of measuring pH of mixed-solvent liquid chromatography (LC) mobile phases. Mobile phase pH is very important in LC, but its correct measurement is not straightforward, and all commonly used approaches have deficiencies. The new approach is based on the recently introduced unified pH (pH(abs)) scale, which enables direct comparison of acidities of solutions made in different solvents based on chemical potential of the proton in the solutions. This work represents the first experimental realization of the pH(abs) concept using differential potentiometric measurement for comparison of the chemical potentials of the proton in different solutions (connected by a salt bridge), together with earlier published reference points for obtaining the pH(abs) values (referenced to the gas phase) or pH(abs)(H₂O) values (referenced to the aqueous solution). The liquid junction potentials were estimated in the framework of Izutsu's three-component method. pH(abs) values for a number of common LC and LC-MS mobile phases have been determined. The pH(abs) scale enables for the first time direct comparison of acidities of any LC mobile phases, with different organic additives, different buffer components, etc. A possible experimental protocol of putting this new approach into chromatographic practice has been envisaged and its applicability tested. It has been demonstrated that the ionization behavior of bases (cationic acids) in the mobile phases can be better predicted by using the pH(abs)(H₂O) values and aqueous pKa values than by using the alternative means of expressing mobile phase acidity. Description of the ionization behavior of acids on the basis of pH(abs)(H₂O) values is possible if the change of their pKa values with solvent composition change is taken into account. PMID:25664372

  6. Determination of the pH of binary mobile phases for reversed-phase liquid chromatography.

    PubMed

    Rosés, Martí

    2004-05-28

    The measurement of pH in chromatographic mobile phases has been a constant subject of discussion during many years. The pH of the mobile phase is an important parameter that determines the chromatographic retention of many analytes with acid-base properties. In many instances a proper pH measurement is needed to assure the accuracy of retention-pH relationships or the reproducibility of chromatographic procedures. Three different methods are common in pH measurement of mobile phases: measurement of pH in the aqueous buffer before addition of the organic modifier, measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with standard solutions prepared in the same mobile phase solvent, and measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with aqueous standard solutions. This review discusses the different pH measurement and calibration procedures in terms of the theoretical and operational definitions of the different pH scales that can be applied to water-organic solvent mixtures. The advantages and disadvantages of each procedure are also presented through chromatographic examples. Finally, practical recommendations to select the most appropriate pH measurement procedure for particular chromatographic problems are given.

  7. Phase transitions in contagion processes mediated by recurrent mobility patterns

    NASA Astrophysics Data System (ADS)

    Balcan, Duygu; Vespignani, Alessandro

    2011-07-01

    Human mobility and activity patterns mediate contagion on many levels, including the spatial spread of infectious diseases, diffusion of rumours, and emergence of consensus. These patterns however are often dominated by specific locations and recurrent flows and poorly modelled by the random diffusive dynamics generally used to study them. Here we develop a theoretical framework to analyse contagion within a network of locations where individuals recall their geographic origins. We find a phase transition between a regime in which the contagion affects a large fraction of the system and one in which only a small fraction is affected. This transition cannot be uncovered by continuous deterministic models because of the stochastic features of the contagion process and defines an invasion threshold that depends on mobility parameters, providing guidance for controlling contagion spread by constraining mobility processes. We recover the threshold behaviour by analysing diffusion processes mediated by real human commuting data.

  8. Isopropylammonium Formate as a Mobile Phase Modifier for Liquid Chromatography

    PubMed Central

    Collins, Matthew P.; Zhou, Ling; Camp, Suzanne E.; Danielson, Neil D.

    2012-01-01

    Isopropylammonium formate (IPAF), a new alkylammonium formate (AAF) room temperature ionic liquid, has been synthesized from isopropylamine and formic acid and characterized as an organic solvent mobile phase replacement for reversed-phase liquid chromatography (LC). Characterization of IPAF solvent properties in water such as pH, conductivity, and viscosity, as well as its synthesis, is described. The LC polarity (P′) and the solvent strength (S) parameters are determined to be 6.0 and 2.4, respectively, similar to those same parameters for methanol and acetonitrile. Application of this RTIL is demonstrated as an organic solvent replacement for reversed-phase LC to separate a test mixture of niacinamide, acetophenone and p-nitroaniline. The van Deemter plot profile for several columns of different dimensions, particle size, pore size and stationary phase are compared using an IPAF–water mobile phase. At flow rates above 2 mL/min, on-line mixing of the viscous IPAF with water appears not to be uniform. A flattening of the van Deemter profile is noted for particularly short (50 mm) wide bore (4.6 mm) columns packed with larger particles (10 µm). Small particle longer columns likely facilitated mixing at the beginning of the column generating typical linearly increasing van Deemeter curves. IPAF has been further shown as a function of temperature to be a non-denaturing modifier solvent for the separation of the protein cytochrome c from tryptophan compared to methanol. This is important to show, because the semi-preparative separation of native proteins using AAF mobile phases is the long-term goal of this research program. PMID:22718743

  9. Phase transition and surface sublimation of a mobile Potts model.

    PubMed

    Bailly-Reyre, A; Diep, H T; Kaufman, M

    2015-10-01

    We study in this paper the phase transition in a mobile Potts model by the use of Monte Carlo simulation. The mobile Potts model is related to a diluted Potts model, which is also studied here by a mean-field approximation. We consider a lattice where each site is either vacant or occupied by a q-state Potts spin. The Potts spin can move from one site to a nearby vacant site. In order to study the surface sublimation, we consider a system of Potts spins contained in a recipient with a concentration c defined as the ratio of the number of Potts spins N(s) to the total number of lattice sites N(L)=N(x)×N(y)×N(z). Taking into account the attractive interaction between the nearest-neighboring Potts spins, we study the phase transitions as functions of various physical parameters such as the temperature, the shape of the recipient, and the spin concentration. We show that as the temperature increases, surface spins are detached from the solid phase to form a gas in the empty space. Surface order parameters indicate different behaviors depending on the distance to the surface. At high temperatures, if the concentration is high enough, the interior spins undergo a first-order phase transition to an orientationally disordered phase. The mean-field results are shown as functions of temperature, pressure, and chemical potential, which confirm in particular the first-order character of the transition. PMID:26565221

  10. 77 FR 14012 - Eligible Telecommunications Carrier Designation for Participation in Mobility Fund Phase I

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-08

    ... Telecommunications Carrier Designation for Participation in Mobility Fund Phase I AGENCY: Federal Communications... Telecommunications Carrier (ETC) Designation from the Commission for participation in Mobility Fund Phase I Auction...) Mobility Fund Phase I support must be designated as an eligible telecommunications carrier in...

  11. Considerations of digital phase modulation for narrowband satellite mobile communication

    NASA Technical Reports Server (NTRS)

    Grythe, Knut

    1990-01-01

    The Inmarsat-M system for mobile satellite communication is specified as a frequency division multiple access (FDMA) system, applying Offset Quadrature Phase Shift Keying (QPSK) for transmitting 8 kbit/sec in 10 kHz user channel bandwidth. We consider Digital Phase Modulation (DPM) as an alternative modulation format for INMARSAT-M. DPM is similar to Continuous Phase Modulation (CPM) except that DPM has a finite memory in the premodular filter with a continuous varying modulation index. It is shown that DPM with 64 states in the VA obtains a lower bit error rate (BER). Results for a 5 kHz system, with the same 8 kbit/sec transmitted bitstream, is also presented.

  12. Properties of subcritical water as an eluent for reversed-phase liquid chromatography--disruption of the hydrogen-bond network at elevated temperature and its consequences.

    PubMed

    Allmon, Steven D; Dorsey, John G

    2010-09-10

    The use of subcritical water as an eluent for reversed-phase liquid chromatography is further explored. Shape selectivity as well as thermodynamic values for solute transfer were measured and compared to those seen with traditional ambient methanol/water and acetonitrile/water mobile phases. Linear solvation energy analysis was also used to analyze extrapolated values of the retention factor in pure water at ambient temperatures (k'w) for subcritical water and ambient hydroorganic mobile phases. Results indicate that it is likely that a large disruption in the hydrogen-bonding network of water at high temperatures causes unique chromatographic selectivity, as well as prohibits accurate extrapolation from high temperature to ambient conditions using pure water. Additionally, subcritical water was not found to be a suitable mobile phase for determining k'w for use in estimating octanol/water partition coefficients.

  13. Methylammonium formate as a mobile phase modifier for reversed-phase liquid chromatography

    PubMed Central

    Grossman, Shau; Danielson, Neil D.

    2009-01-01

    Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have been used as mobile phase “solvents” for liquid chromatography (LC), we have shown that methylammonium formate (MAF), in part because of its lower viscosity, can be an effective replacement for methanol (MeOH) in reversed-phase LC. Plots of log retention factor versus the fraction of MeOH and MAF in the mobile phase indicate quite comparable solvent strength slope values of 2.50 and 2.05, respectively. Using a polar endcapped C18 column, furazolidone and nitrofurantoin using 20% MAF-80% water could be separated in 22 min but no baseline separation was possible using MeOH as the modifier, even down to 10%. Suppression of silanol peak broadening effects by MAF is important permitting a baseline separation of pyridoxine, thiamine, and nicotinamide using 5% MAF-95% water at 0.7 mL/min. Using 5% MeOH-95% water, severe peak broadening for thiamine is evident. The compatibility of MAF as a mobile phase modifer for LC with mass spectrometry detection of water soluble vitamins is also shown. PMID:18849044

  14. Adsorbed solution model for prediction of normal-phase chromatography process with varying composition of the mobile phase.

    PubMed

    Piatkowski, Wojciech; Petrushka, Igor; Antos, Dorota

    2005-10-21

    The adsorbed solution model has been used to predict competitive adsorption equilibria of the solute and the active component of mobile phase in a normal-phase liquid chromatography system. The inputs to the calculations were the single adsorption isotherms accounting for energetic heterogeneity of the adsorbent surface and non-ideality of the mobile phase solution. The competitive adsorption model has been coupled with a model of the column dynamics and used for simulating of chromatography process at different mobile phase composition. The predictions have been verified by comparing the simulated and experimental chromatograms. The model allowed quantitative prediction of chromatography process on the basis of the pure-species adsorption isotherms.

  15. Simultaneous determination of four anti-dandruff agents including octopirox in shampoo products by reversed-phase liquid chromatography.

    PubMed

    Chao, L

    2001-06-01

    A method based on reversed-phase liquid chromatography (HPLC) has been developed for the simultaneous identification and quantitative determination of four anti-dandruff agents such as salicylic acid, ketoconazole, climbazole, octopirox in commercial anti-dandruff shampoo products. A symmetry C18 column (5 microm, 250 mm x 4.6 mm i.d.) was used at temperature of 35 degrees C, mobile phase with flow rate of 0.8 mL min(-1) was acetonitrile: water (containing 10 mm potassium dihydrogen phosphate, pH 4.0, adjusted with orthophosphoric acid) = 60 : 40 (V/V) and UV detection at 224 nm and 305 nm. Samples were extracted with mobile phase by stirring and ultrasonic method. The average recoveries of four anti-dandruff agents were 98.0-104.1%. The relative standard deviations for samples were 0.11-0.90%. The method is simple, rapid and reproducible. PMID:18498472

  16. High resolution ion mobility measurements for gas phase proteins: correlation between solution phase and gas phase conformations

    NASA Astrophysics Data System (ADS)

    Hudgins, Robert R.; Woenckhaus, Jürgen; Jarrold, Martin F.

    1997-11-01

    Our high resolution ion mobility apparatus has been modified by attaching an electrospray source to perform measurements for biological molecules. While the greater resolving power permits the resolution of more conformations for BPTI and cytochrome c, the resolved features are generally much broader than expected for a single rigid conformation. A major advantage of the new experimental configuration is the much gentler introduction of ions into the drift tube, so that the observed gas phase conformations appear to more closely reflect those present in solution. For example, it is possible to distinguish between the native state of cytochrome c and the methanol-denatured form on the basis of the ion mobility measurements; the mass spectra alone are not sensitive enough to detect this change. Thus this approach may provide a quick and sensitive tool for probing the solution phase conformations of biological molecules.

  17. Polarons and Mobile Impurities Near a Quantum Phase Transition

    NASA Astrophysics Data System (ADS)

    Shadkhoo, Shahriar

    This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which

  18. Effect of Mobile Phase on Electrospray Ionization Efficiency

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Kruve, Anneli; Leito, Ivo; Girod, Marion; Antoine, Rodolphe

    2014-08-01

    Electrospray (ESI) ionization efficiencies (IE) of a set of 10 compounds differing by chemical nature, extent of ionization in solution (basicity), and by hydrophobicity (tetrapropylammonium and tetraethylammonium ion, triethylamine, 1-naphthylamine, N,N-dimethylaniline, diphenylphthalate, dimethylphtahalate, piperidine, pyrrolidine, pyridine) have been measured in seven mobile phases (three acetonitrile percentages 20%, 50%, and 80%, and three different pH-adjusting additives, 0.1% formic acid, 1 mM ammonia, pH 5.0 buffer combination) using the relative measurement method. MS parameters were optimized separately for each ion. The resulting relative IE data were converted into comparable logIE values by anchoring them to the logIE of tetrapropylammonium ion taking into account the differences of ionization in different solvents and thereby making the logIE values of the compounds comparable across solvents. The following conclusions were made from analysis of the data. The compounds with pK a values in the range of the solution pH values displayed higher IE at lower pH. The sensitivity of IE towards pH depends on hydrophobicity being very strong with pyridine, weaker with N,N-dimethylaniline, and weakest with 1-naphthylamine. IEs of tetraalkylammonium ions and triethylamine were expectedly insensitive towards solution pH. Surprisingly high IEs of phthalate esters were observed. The differences in solutions with different acetonitrile content and similar pH were smaller compared with the pH effects. These results highlight the importance of hydrophobicity in electrospray and demonstrate that high hydrophobicity can sometimes successfully compensate for low basicity.

  19. Polarons and Mobile Impurities Near a Quantum Phase Transition

    NASA Astrophysics Data System (ADS)

    Shadkhoo, Shahriar

    This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which

  20. 77 FR 38803 - Mobility Fund Phase I Auction Updated Data For Auction 901

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-29

    ... Public Notice, 77 FR 32092, May 31, 2012, the Bureaus described how they identified census blocks... COMMISSION Mobility Fund Phase I Auction Updated Data For Auction 901 AGENCY: Federal Communications... Competition Bureaus (Bureaus) announce updated data files of census blocks eligible for the Mobility...

  1. 77 FR 38061 - Mobility Fund Phase I Auction Supplemental Short-Form Instructions and Other Information

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-26

    ... Notice, 77 FR 32092, May 31, 2012, the Bureaus provided general instructions for completing FCC Form 180... COMMISSION Mobility Fund Phase I Auction Supplemental Short-Form Instructions and Other Information AGENCY... Telecommunications and Wireline ] Competition Bureaus provide supplemental filing instructions for the Mobility...

  2. Determination of oxfendazole in cow milk by reversed-phase high-performance liquid chromatography.

    PubMed

    Tsina, I W; Matin, S B

    1981-08-01

    A specific and sensitive high-performance liquid chromatographic method for the analysis of oxfendazole in cow milk is described. Oxfendazole was extracted from milk using a mixture of acetone and chloroform under alkaline conditions. The solvents were evaporated, and the oily residue was purified by hexane-acetonitrile partition and acid-base extraction. The residue obtained after cleanup was redissolved in methanol for chromatographic analysis. Chromatography was performed on a reversed-phase column with acetonitrile-water as the mobile phase. As low as 0.005 microgram of oxfendazole/g can be measured by this method using 50 g of milk. The method was applied to measure oxfendazole in the milk of a cow given an oral 5-mg/kg dose.

  3. [Determination of main degradation products of lignin using reversed-phase high performance liquid chromatography].

    PubMed

    Jiang, Zhijing; Zhu, Junjun; Li, Xin; Lian, Zhina; Yu, Shiyuan; Yong, Qiang

    2011-01-01

    An analytical method using reversed-phase high performance liquid chromatography (RP-HPLC) was developed for the separation and quantitative determination of main degradation products of lignin (4-hydroxybenzoic acid, vanillic acid, syringic acid, 4-hydroxybenzaldehyde, vanillin and syringaldehyde) during the steam exploded pretreatment for corn stovers. The separation was carried out on a C18 column with the mobile phase of acetonitrile-water (containing 1.5% acetic acid) at 30 degrees C at a flow rate of 0.8 mL/min and the detection wavelengths of 254 and 280 nm. Under the optimized conditions, the correlation coefficients of the 6 compounds were between 0.999 9 and 1.000 0. The recoveries of the 6 compounds were all above 96% and the relative standard deviations (n = 6) were less than 2.5%. This method is suitable for the determination of the main degradation products of lignin during the steam exploded pretreatment of lignocellulosics.

  4. Effect of temperature in reversed phase liquid chromatography.

    PubMed

    Guillarme, D; Heinisch, S; Rocca, J L

    2004-10-15

    The high temperature liquid chromatography (HTLC) reveals interesting chromatographic properties but even now, it misses some theoretical aspects concerning the influence of high temperature on thermodynamic and kinetic aspects of chromatography: such a knowledge is very essential for method development. In this work, the effect of temperature on solute behavior has been studied using various stationary phases which are representative of the available thermally stable materials present on the market. The thermodynamic properties were evaluated by using different mobile phases: acetonitrile-water, methanol-water and pure water. The obtained results were discussed on the basis of both type of mobile phases and type of stationary phases. Type of mobile phase was found to play an important role on the retention of solutes. The kinetic aspect was studied at various temperatures ranging from ambient temperature to high temperature (typically from about 30 to 200 degrees C) by fitting the experimental data with the Knox equation and it was shown that the efficiency is improved significantly when the temperature is increased. In this paper, we also discussed the problem of temperature control for thermostating columns which may represent a significant source of peak broadening: by taking into account the three main parameters such as heat transfer, pressure drop and band broadening resulting from the preheating tube, suitable rules are set up for a judicious choice of the column internal diameter. PMID:15527119

  5. Retention characteristics of polybutadiene-coated zirconia and comparison to conventional bonded phases.

    PubMed

    Li, J; Carr, P W

    1996-09-01

    This paper presents a detailed study of retention on a reversed-phase material made by coating polybutadiene (PBD) on porous zirconia. PBD-coated zirconia particles with six different carbon loads (0.25-5.6% carbon by weight) were prepared by evaporatively depositing and cross-linking PBD on microparticulate porous zirconia. Retention data of a homologous series of alkylbenzenes were obtained on the six PBD phases as a function of mobile phase composition in methanol-water and acetonitrile-water mixtures from 20 to 50% (v/v). The results obtained for the phase were compared to those for conventional octadecylsilane (ODS) bonded phases, and the effect of the amount of PBD on retention was studied in detail. We find that, per amount of bonded phase, the PBD phase is less retentive than is the ODS phase, but it has comparable hydrophobic selectivity. Furthermore, the PBD phase has about the same sensitivity toward changes in mobile phase composition as does the ODS phase, and its solute shape selectivity is similar to that of a monomeric ODS phase. Finally, we conclude that retention arises primarily from a partition-like process. PMID:8794923

  6. Highly stereoselective, uniformly sized molecularly imprinted polymers for cinchona alkaloids in hydro-organic mobile phases.

    PubMed

    Haginaka, Jun; Kagawa, Chino

    2003-01-01

    Highly stereoselective, uniformly sized molecularly imprinted polymers (MIPs) for cinchona alkaloids, cinchonine (CN) and cinchonidine (CD), were prepared using methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The MIPs were evaluated using a mixture of phosphate buffer and acetonitrile as the mobile phase. The CN- and CD-imprinted MAA-co-EDMA polymers can recognize the respective template molecule more than the other diastereomer, and afford an excellent diastereomer separation of CN and CD. In addition, the MIPs gave diastereomer separations of structurally related compounds, quinidine and quinine. The retentive and stereoselective properties of those compounds on the MIPs suggest that electrostatic and hydrophobic interactions can work to recognize these compounds. Furthermore, thermodynamic studies reveal that the entropy-driven effect is significant at mobile-phase pH 5.4, while the enthalpy-driven interactions seem to be dominant at mobile-phase pH 9.6.

  7. Mobile phase additives for enhancing the chromatographic performance of astaxanthin on nonendcapped polymeric C30-bonded stationary phases.

    PubMed

    Kaiser, Philipp; Surmann, Peter; Fuhrmann, Herbert

    2009-01-01

    Astaxanthin shows peak deformation and reduced peak area response when eluted with methanol and methyl tert-butyl ether on nonendcapped polymeric C30-bonded HPLC phases. The present study tested different column manufacturers, column batches, and ten mobile phase additives including acids, bases, buffers, complexing and antioxidant agents for improvement of peak shape and peak area response. Concerning chromatographic benefits and feasibility, ammonium acetate was found to be the best additive followed by triethylamine for all columns tested. Variation of the mobile phase pH equivalent and the column temperature showed no synergistic effects on peak shape and peak area response. Results indicate that peak tailing and variation of peak area response are due to different on-column effects. Possible mechanisms of the observed phenomenon will be discussed. PMID:19051191

  8. Retention mechanism for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography with monomeric stationary phases.

    PubMed

    Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

    2011-12-23

    Reversed-phase liquid chromatography (RPLC) is the foremost technique for the separation of analytes that have very similar chemical functionalities, but differ only in their molecular shape. This ability is crucial in the analysis of various mixtures with environmental and biological importance including polycyclic aromatic hydrocarbons (PAHs) and steroids. A large amount of effort has been devoted to studying this phenomenon experimentally, but a detailed molecular-level description remains lacking. To provide some insight on the mechanism of shape selectivity in RPLC, particle-based simulations were carried out for stationary phases and chromatographic parameters that closely mimic those in an experimental study by Sentell and Dorsey [J. Chromatogr. 461 (1989) 193]. The retention of aromatic hydrocarbons ranging in size from benzene to the isomeric PAHs of the formula C(18)H(12) was examined for model RPLC systems consisting of monomeric dimethyl octadecylsilane (ODS) stationary phases with surface coverages ranging from 1.6 to 4.2 μmol/m(2) (i.e., stationary phases yielding low to intermediate shape selectivity) in contact with a 67/33 mol% acetonitrile/water mobile phase. The simulations show that the stationary phase acts as a very heterogeneous environment where analytes with different shapes prefer different spatial regions with specific local bonding environments of the ODS chains. However, these favorable retentive regions cannot be described as pre-existing cavities because the chain conformation in these local stationary phase regions adapts to accommodate the analytes.

  9. Change of mobile phase pH during gradient reversed-phase chromatography with 2,2,2-trifluoroethanol-water as mobile phase and its effect on the chromatographic hydrophobicity index determination.

    PubMed

    Espinosa, Sonia; Bosch, Elisabeth; Rosés, Martí; Valkó, Klára

    2002-04-19

    We have shown previously that using a trifluoroethanol containing mobile phase provides a unique chromatographic selectivity. This is essential to derive molecular descriptors by HPLC which requires retention data from several systems. It also requires that the ionisation is suppressed so that retention times reflect the properties of the neutral molecules. Therefore the pH change of the mobile phase during gradient elution and its effect on the solute ionisation have been studied. During gradient elution of mixtures of ammonium acetate and butylammonium formate with trifluoroethanol as an organic modifier it was found that the pH was almost constant when the gradient started with a low pH. However, when the starting mobile phase pH was above 8 the pH dropped very quickly as the trifluoroethanol concentration increased in the mobile phase. The CHI descriptor (a retention index derived directly from gradient retention times) of several basic compounds as a function of starting mobile phase pH has been measured using trifluoroethanol gradient. The effect of the trifluoroethanol on the pKa change of the compounds has been investigated. The experimental data fit closely to a previously derived equation that describes gradient retention times as a function of mobile phase pH and analyte ionisation constant (pKa). This equation makes it possible to predict the CHI descriptor for ionisable compounds at various pH values. We have used butylamine for high pH mobile phase preparation as is more basic than ammonia and for many basic drugs the retention of the neutral form could be obtained directly (without extrapolation).

  10. 77 FR 9655 - Mobility Fund Phase I Auction Updated List of Potentially Eligible Census Blocks

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-17

    ..., 77 FR 7152, February 10, 2012, comments are due on or before February 24, 2012. Reply comments are... Public Notice, 77 FR 7152, February 10, 2012, all filings in response to the notice must refer to AU... program requirements in the Auction 901 (Mobility Fund Phase I) Comment Public Notice, 77 FR...

  11. 78 FR 21355 - Tribal Mobility Fund Phase I Auction Scheduled for October 24, 2013; Comment Sought on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-10

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  12. 78 FR 61350 - Tribal Mobility Fund Phase I Auction (Auction 902); Short-Form Application Filing Window...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-03

    .... In the list of bidding areas released with the Auction 902 Procedures Public Notice, 78 FR 56875... COMMISSION Tribal Mobility Fund Phase I Auction (Auction 902); Short-Form Application Filing Window... Bureau, Auctions and Spectrum Access Division: For Tribal Mobility Fund Phase I questions:...

  13. The Role of Fluorinated Alcohols as Mobile Phase Modifiers for LC-MS Analysis of Oligonucleotides

    NASA Astrophysics Data System (ADS)

    Basiri, Babak; van Hattum, Hilde; van Dongen, William D.; Murph, Mandi M.; Bartlett, Michael G.

    2016-09-01

    Hexafluoroisopropanol (HFIP) has been widely used as an acidic modifier for mobile phases for liquid chromatography-mass spectrometry (LC-MS) analysis of oligonucleotides ever since the first report of its use for this purpose. This is not surprising, considering the exceptional performance of HFIP compared with carboxylic acids, which cause significant MS signal suppression in electrospray ionization. However, we have found that other fluorinated alcohols can also be utilized for mobile phase preparation and the choice of optimal fluorinated alcohol is determined by the ion-pairing (IP) agent. Although HFIP is a very good choice to be used alongside less hydrophobic IP agents, other fluorinated alcohols such as 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (HFMIP) can significantly outperform HFIP when used with more hydrophobic IP agents. We also found that more acidic fluorinated alcohols assist with the transfer of oligonucleotides with secondary structure (e.g., folded strands and hairpins) into the gas phase.

  14. The mobile phase in coals: Its nature and modes of release: Part 2, Efforts to better define the nature and magnitude of the mobile phase: Final report

    SciTech Connect

    Given, P.H.

    1987-04-01

    Several liquefaction conditions and many extracting solvents were used in attempts to set up conditions such that, as the conditions became more severe, progressively more hexane-solubles, analyzable by GC/MS, would be released. It was hoped to identify a threshold beyond which trapped mobile phase molecules would become evident. A set of 10 hexane-soluble fractions, all obtained under various conditions from the same coal (a sample of Herrin No. 6 seam, Illinois), were subjected to analysis by tandem mass spectrometry (MS/MS). Yields ranged from 0.6 to 16% of the organic matter in the coal. Prominent constituents of all of the fractions were homologous series of alkyl aromatic hydrocarbons, phenols and heterocycles, notably alkylacenaphthenes. Alkyl chains were either unbranched or lightly branched. There was a similarity in the spectra of all of the fractions irrespective of yield. The ease with which a certain homologous series can be released from a coal is highly variable. Thus the data are consistent with the concept of a mobile phase some components of which are trapped in cavities with entrances and exits of restricted size. Release of the various physically held species and the fragments from thermal breakdown of the structure will certainly present a very complex system for kinetic modeling. 30 refs., 10 tabs.

  15. Effect of mobile phase on resolution of the isomers and homologues of tocopherols on a triacontyl stationary phase.

    PubMed

    Saha, Supradip; Walia, Suresh; Kundu, Aditi; Pathak, Niti

    2013-11-01

    Reversed-phase liquid chromatographic (RPLC) separation of isomers and homologues of similar polarity is challenging. Tocopherol isomers and homologues are one such example. α, β, γ, and δ-tocopherols have been successfully separated by RPLC on triacontyl (C30) stationary phase. System suitability was tested by using four mobile phases, and observed chromatographic separations of β and γ-tocopherols were compared. Comparison indicated that methanol-tert-butyl methyl ether (TBME) 95:5 (v/v) at a flow rate of 0.75 mL min(-1) was the best mobile phase. Detection systems were also evaluated on the basis of limit of quantification; it was concluded that fluorescence detection was best. The method was validated by analysis of two homologues and two isomers of tocopherol in sesame, maize, and soybean samples. MS coupled with an ESI interface in negative-ion mode [M - H](-) was used for identification of individual components. It was concluded that addition of TBME to methanol was required to enhance the separation of β and γ-tocopherols, although methanol alone provided similar results. The applicability of the method to cereal, pulse, and oilseed samples was confirmed. The reproducibility of the procedure was good, with relative standard deviations in the range 1.7-3.9%. Recovery of tocopherols added to sesame samples ranged from 91 to 99%.

  16. A two-phase approach to Fourier transform ion mobility time-of-flight mass spectrometry.

    PubMed

    Clowers, Brian H; Siems, William F; Yu, Zhihao; Davis, Austen L

    2015-10-21

    It is well known that the duty cycle of common drift-tube ion mobility experiments is often below 1%. However, multiplexing approaches such as Fourier and Hadamard pulsing schemes have been shown to independently enhance the throughput of ion mobility spectrometry (IMS) experiments to levels that approach 50%. While challenges remain to their broad scale implementation we describe a new Fourier transform (FT) IMS experiment that is directly compatible with standard drift tube ion mobility mass spectrometers (DT-IMMS). Compared to previous FT-IMS experiments, our new approach requires only a single gate and circumvents the need for signal apodization by combining data from two frequency pulsing sequences 180° out of phase. Assessment of our initial results highlights an increase in signal-to-noise (SNR) relative to both previous implementations FT-IMS experiments and signal averaged (SA) experiments. For select tetraalkylammonium salts SNR improvements of more than one order of magnitude are routinely possible. To explore the performance metrics associated with the technique a number of experimental variables were systematically altered including frequency sweep range, sweep time, and data acquisition time. Using this experimental design we present the key aspects, considerations, and minimum resources necessary for other IMS researchers to incorporate this operational mode into their research. The two-phase FT-IMMS technique offers a tractable mechanism to enhance sensitivity for IMMS measurements and its broad-scale adoption by IMMS researchers promises to enhance the acquisition speed for mobility measurements using hybrid instrumentation.

  17. Fundamental studies of gas phase ionic reactions by ion mobility spectrometry

    NASA Technical Reports Server (NTRS)

    Giles, K.; Knighton, W. B.; Sahlstrom, K. E.; Grimsrud, E. P.

    1995-01-01

    Ion mobility spectrometry (IMS) provides a promising approach to the study of gas phase ionic reactions in buffer gases at unusually high pressures. This point is illustrated here by studies of the Sn2 nucleophilic displacement reaction, Cl(-) + CH3Br yields Br + CH3Br, using IMS at atmospheric pressure. The equilibrium clustering reaction, Cl(-)(CHCI3)(n - 1) + CHCI3 yields Cl(-)(CHCI3)(n), where n = 1 and 2, and the effect of clustering on the Sn2 reaction with CH3Br have also been characterized by this IMS-based kinetic method. Present problems and anticipated improvements in the application of ion mobility spectrometry to studies of other gas phase ionic processes are discussed.

  18. 78 FR 45071 - Annual Report for Mobility Fund Phase I Support and Record Retention

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    .... 54.1008(d) and (e), 54.1009(a) through (c) and 54.1010, published at 76 FR 73830, November 29, 2011.... 10-208; FCC 11-161, 76 FR 73830 and FCC 12-52, 77 FR 30904, May 24, 2012. If you have any comments on.... 01-92, 96-45; WT Docket No. 10-208; FCC 11-161; FCC 12-52] Annual Report for Mobility Fund Phase...

  19. Mobile phone imaging module with extended depth of focus based on axial irradiance equalization phase coding

    NASA Astrophysics Data System (ADS)

    Sung, Hsin-Yueh; Chen, Po-Chang; Chang, Chuan-Chung; Chang, Chir-Weei; Yang, Sidney S.; Chang, Horng

    2011-01-01

    This paper presents a mobile phone imaging module with extended depth of focus (EDoF) by using axial irradiance equalization (AIE) phase coding. From radiation energy transfer along optical axis with constant irradiance, the focal depth enhancement solution is acquired. We introduce the axial irradiance equalization phase coding to design a two-element 2-megapixel mobile phone lens for trade off focus-like aberrations such as field curvature, astigmatism and longitudinal chromatic defocus. The design results produce modulation transfer functions (MTF) and phase transfer functions (PTF) with substantially similar characteristics at different field and defocus positions within Nyquist pass band. Besides, the measurement results are shown. Simultaneously, the design results and measurement results are compared. Next, for the EDoF mobile phone camera imaging system, we present a digital decoding design method and calculate a minimum mean square error (MMSE) filter. Then, the filter is applied to correct the substantially similar blur image. Last, the blur and de-blur images are demonstrated.

  20. Modulation of phase behaviors and charge carrier mobilities by linkage length in discotic liquid crystal dimers.

    PubMed

    Wang, Yi-Fei; Zhang, Chun-Xiu; Wu, Hao; Zhang, Ao; Wang, Jian-Chuang; Zhang, Shuai-Feng; Pu, Jia-Ling

    2015-01-28

    A clear structure-property relationship was revealed in a series of triphenylene-based dimers, which contained two triphenylene nuclei each bearing five β-OC4H9 substituents and are linked through a flexible O(CH2)nO polymethylene chain (n=6-12). Dimers with the linkage close to twice the length of the free side chains (n=8, 9) exhibited a single Colhp phase, while others with the linkage shorter (n=6, 7) or longer (n=10, 11, 12) showed multiphase behaviors with a transition from the Colhp phase to Colh phase; hole mobilities of Colhp phases reached 1.4×10(-2) cm2 V(-1) s(-1) in the dimer for which the linkage is exactly twice the length of the free side chains (n=8), and decreased regularly both with linkage length becoming shorter or longer. This modulation of phase behaviors and charge carrier mobilities was demonstrated to be generated by various steric perturbations introduced by linkages with different lengths, which result in different degrees of lateral fluctuations of discotic moieties in the columns. PMID:25467212

  1. Degenerate mobilities in phase field models are insufficient to capture surface diffusion

    NASA Astrophysics Data System (ADS)

    Lee, Alpha A.; Münch, Andreas; Süli, Endre

    2015-08-01

    Phase field models frequently provide insight into phase transitions and are robust numerical tools to solve free boundary problems corresponding to the motion of interfaces. A body of prior literature suggests that interface motion via surface diffusion is the long-time, sharp interface limit of microscopic phase field models such as the Cahn-Hilliard equation with a degenerate mobility function. Contrary to this conventional wisdom, we show that the long-time behaviour of degenerate Cahn-Hilliard equation with a polynomial free energy undergoes coarsening, reflecting the presence of bulk diffusion, rather than pure surface diffusion. This reveals an important limitation of phase field models that are frequently used to model surface diffusion.

  2. STTR Phase 1 Final Technical Report for Project Entitled "Developing a Mobile Torrefaction Machine"

    SciTech Connect

    James, Joseph J.

    2014-03-11

    The goal of this project, sponsored by Agri-Tech Producers, LLC (ATP), the small business grantee, was to determine if the torrefaction technology, developed by North Carolina State University (NCSU), which ATP has licensed, could be feasibly deployed in a mobile unit. The study adds to the area investigated, by having ATP’s STTR Phase I team give thoughtful consideration to how to use NCSU’s technology in a mobile unit. The findings by ATP’s team were that NCSU’s technology would best perform in units 30’ by 80’ (See Spec Sheet for the Torre-Tech 5.0 Unit in the Appendix) and the technical effectiveness and economic feasibility investigation suggested that such units were not easily, efficiently or safely utilized in a forest or farm setting. (Note rendering of possible mobile system in the Appendix) Therefore, the findings by ATP’s team were that NCSU’s technology could not feasibly be deployed as a mobile unit.

  3. 77 FR 7152 - Mobility Fund Phase I Auction Scheduled for September 27, 2012; Comment Sought on Competitive...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-10

    ... the Commission in the USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562... COMMISSION Mobility Fund Phase I Auction Scheduled for September 27, 2012; Comment Sought on Competitive... Wireline Competition Bureaus announce a reverse auction to award $300 million in one-time Mobility...

  4. The mobility of the amorphous phase in polyethylene as a determining factor for slow crack growth.

    PubMed

    Men, Y F; Rieger, J; Enderle, H-F; Lilge, D

    2004-12-01

    Polyethylene (PE) pipes generally exhibit a limited lifetime, which is considerably shorter than their chemical degradation period. Slow crack growth failure occurs when pipes are used in long-distance water or gas distribution though being exposed to a pressure lower than the corresponding yield stress. This slow crack growth failure is characterized by localized craze growth and craze fibril rupture. In the literature, the lifetime of PE pipes is often considered as being determined by the density of tie chains connecting adjacent crystalline lamellae. But this consideration cannot explain the excellent durability of the recent bimodal grade PE for pipe application. We show in this paper the importance of the craze fibril length as the determining factor for the pipe lifetime. The conclusions are drawn from stress analysis. It is found that longer craze fibrils sustain lower stress and are deformed to a lesser degree. The mobility of the amorphous phase is found to control the amount of material that can be "sucked" in by the craze fibrils and thus the length of the craze fibrils. The mobility of the amorphous phase can be monitored by dynamic mechanical analysis measurements. Excellent agreement between the mobility thus derived and lifetimes of PE materials as derived from FNCT (full notch creep test) is given, thus providing an effective means to estimate the lifetime of PE pipes by considering well-defined physical properties.

  5. Effect of trace amounts of water in the mobile phase of normal-phase enantioselective high-performance liquid chromatography on selectivity and resolution of optical isomers.

    PubMed

    Lu, Jun; Rustum, Abu M

    2009-04-01

    The irreproducibility of normal-phase enantioselective high-performance liquid chromatography (HPLC) could be attributed to the presence or absence of trace amounts of water in one or more components of the mobile phase. The effect of trace amounts of water on chromatographic characteristics in normal-phase enantioselective HPLC was investigated by deliberate addition of controlled, trace amounts of water into the mobile phase for the separation of T-3811ME and its undesired enantiomer. Commercial 2-propanol was pre-mixed with 2% (v/v) water and then used for preparation of the mobile phase in combination with such organic modifiers as ethanol and methanol at different ratios. The results showed up to 30% improvement in the resolution (Rs), 4% in selectivity (alpha), and 39% in efficiency (plate number N) compared to using a mobile phase prepared from neat commercial 2-propanol. Thus, the effect of trace amounts of water in the mobile phase of normal-phase enantioselective HPLC was demonstrated. PMID:19406020

  6. Direct chiral resolution of metalaxyl and metabolite metalaxyl acid in aged mobile phases: the role of trace water.

    PubMed

    Zhang, Xiaoxiang; Xia, Tingting; Chen, Jingwen; Huang, Liping; Cai, Xiyun

    2010-04-28

    The separation of chiral transformation products greatly complements the understanding of the stereochemistry of chiral pollutants. In this study, direct enantiomeric resolution of metalaxyl and its main degradation product metalaxyl acid, often co-occurring in the environment, was carried out in normal-phase high-performance liquid chromatography with a Chiralcel OJ-H column. (R)-Metalaxyl acid and (S)-metalaxyl, which were almost parallel bonding to the chiral stationary phase, tended to separate, started to overlap, coeluted, and separated again with subtle changes of the mobile phase consisting of n-hexane, 2-propanol, acetic acid, and trace water. Their competition above hampered an acceptable direct separation in fresh mobile phases. Aged mobile phases with a storage period of 3-5 days, however, significantly improved their separation, in which trace water from moisture air diffusion was found to play a major role. Trace water differentially affected peak width and retention times and then induced enhanced peak separation, confirmed by deliberate addition of water to fresh mobile phases. Furthermore, none of the studied factors, involving temperature, concomitant analytes, and trace water, could cause changes of the configuration of the chiral stationary phase. Simultaneous enantiomeric separation of both compounds was achieved in aged or fresh mobile phases with adventitious or added water and gave satisfactory peak separation, all with Rs values of more than 1.20 in environmental samples.

  7. Use of vancomycin silica stationary phase in packed capillary electrochromatography: III. enantiomeric separation of basic compounds with the polar organic mobile phase.

    PubMed

    Fanali, Salvatore; Catarcini, Paolo; Quaglia, Maria Giovanna

    2002-02-01

    The separation of basic compounds into their enantiomers was achieved using capillary electrochromatography in 50 or 75 microm inner diameter (ID) fused-silica capillaries packed with silica a stationary phase derivatized with vancomycin and mobile phases composed of mixtures of polar organic solvents containing 13 mM ammonium acetate. Enantiomer resolution, electroosmotic flow, and the number of theoretical plates were strongly influenced by the type and concentration of the organic solvent. Mobile phases composed of 13 mM ammonium acetate dissolved in mixtures of acetonitrile/methanol, ethanol, n-propanol, or isopropanol were tested and the highest enantioresolutions were achieved using the first mobile phase, allowing the separation of almost all investigated enantiomers (9 from 11 basic compounds). The use of capillaries with different ID (50 and 75 microm ID) packed with the same chiral stationary phase revealed that a higher number of theoretical plates and higher enantioresolution was achieved with the tube with lowest ID.

  8. Mobile terminal equipment design utilising split-loop phase-lock techniques

    NASA Technical Reports Server (NTRS)

    Kenington, P. B.; Mcgeehan, J. P.; Edwards, D. J.

    1990-01-01

    The design and resultant performance of the terminal equipment in a mobile satellite system is vitally important in respect to the overall cost/performance compromise of the whole system. Improvements in system performance which also result in a reduction of the equipment cost are rare. However, this paper details a significant advance in terminal design, utilizing a novel form of 'split-loop' phase locked receiver/downconverter system to enable an accurate, stable and wide coverage terminal to be realized at a reduced cost. The system has the capability of automatically locking onto any carrier within a complete transponder, and can cope with severe amplitude modulation and fading effects.

  9. Gas-phase metalloprotein complexes interrogated by ion mobility-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Faull, Peter A.; Korkeila, Karoliina E.; Kalapothakis, Jason M.; Gray, Andrew; McCullough, Bryan J.; Barran, Perdita E.

    2009-06-01

    Gas-phase biomolecular structure may be explored through a number of analytical techniques. Ion mobility-mass spectrometry (IM-MS) continues to prove itself as a sensitive and reliable bioanalytical tool for gas-phase structure determination due to intense study and development over the past 15 years. A vast amount of research interest, especially in protein and peptide conformational studies has generated a wealth of structural information for biological systems from small peptides to megadalton-sized biomolecules. In this work, linear low field IM-MS has been used to study gas-phase conformations and determine rotationally averaged collision cross-sections of three metalloproteins--cytochrome c, haemoglobin and calmodulin. Measurements have been performed on the MoQToF, a modified QToF 1 instrument (Micromass UK Ltd., Manchester, UK) modified in house. Gas-phase conformations and cross-sections of multimeric cytochrome c ions of the form [xM + nH+]n+ for x = 1-3 (monomer to trimer) have been successfully characterised and measured. We believe these to be the first reported collision cross-sections of higher order multimeric cytochrome c. Haemoglobin is investigated to obtain structural information on the associative mechanism of tetramer formation. Haemoglobin molecules, comprising apo- and holo-monomer chains, dimer and tetramer are transferred to the gas phase under a range of solution conditions. Structural information on the proposed critical intermediate, semi-haemoglobin, is reported. Cross-sections of the calcium binding protein calmodulin have been obtained under a range of calcium-bound conditions. Metalloprotein collision cross-sections from ion mobility measurements are compared with computationally derived values from published NMR and X-ray crystallography structural data. Finally we consider the change in the density of the experimentally measured rotationally averaged collision cross-section for compact geometries of the electrosprayed proteins.

  10. Influence of preferential adsorption of mobile phase on retention behavior of amino acids on the teicoplanin chiral selector.

    PubMed

    Poplewskaa, Izabela; Kramarz, Renata; Piatkowski, Wojciech; Seidel-Morgenstern, Andreas; Antos, Dorota

    2007-11-30

    The adsorption behavior of two amino acids, i.e., l,d-threonine and l,d-methionine has been investigated on the chiral stationary phase (CSP)column packed with teicoplanin bonded to a silica support. The study has been performed under non-linear conditions of adsorption isotherm for various types of organic modifiers (methanol, ethanol, propan-2-ol and acetonitrile) in the reversed-phase mode. A heterogeneous adsorption mechanism of amino acids has been identified that was strongly affected by the nature of organic modifier. Generally, isotherm non-linearity and retention decreased with decrease of the modifier content in the mobile phase exhibiting a minimum at water-rich mobile phases. These trends were suggested to result from a combined effect of the mobile as well as the adsorbed phase composition. To determine the composition of the adsorbed phase the excess adsorption of modifiers in aqueous solutions has been measured and their binary adsorption equilibria have been quantified and compared. Strongly non-ideal behavior of solvents in the mobile phase and the adsorbed phase has been accounted for by activity coefficients. The fraction of the modifiers in the adsorbed phase decreased in the sequence: methanol, ethanol, propan-2-ol and acetonitrile.

  11. Trying to detect gas-phase ions? Understanding Ion Mobility Spectrometry

    PubMed Central

    Cumeras, R.; Figueras, E.; Davis, C.E.; Baumbach, J.I.; Gràcia, I.

    2014-01-01

    Ion Mobility Spectrometry (IMS) is a widely used and ‘well-known’ technique of ion separation in gaseous phase based on the differences of ion mobilities under an electric field. This technique has received increased interest over the last several decades as evidenced by the pace and advances of new IMS devices available. In this review we explore the hyphenated techniques that are used with IMS, especially mass spectrometry as identification approach and multi-capillary column as pre-separation approach. Also, we will pay special attention to the key figures of merit of the ion mobility spectrum and how data is treated, and the influences of the experimental parameters in both a conventional drift time IMS (DTIMS) and a miniaturized IMS also known as high Field Asymmetric IMS (FAIMS) in the planar configuration. The current review article is preceded by a companion review article which details the current instrumentation and to the sections that configures both a conventional DTIMS and FAIMS devices. Those reviews will give the reader an insightful view of the main characteristics and aspects of the IMS technique. PMID:25465248

  12. Evaluation of the phase ratio for three C18 high performance liquid chromatographic columns.

    PubMed

    Caiali, Edvin; David, Victor; Aboul-Enein, Hassan Y; Moldoveanu, Serban C

    2016-02-26

    For a chromatographic column, phase ratio Φ is defined as the ratio between the volume of the stationary phase Vst and the void volume of the column V0, and it is an important parameter characterizing the HPLC process. Although apparently simple, the evaluation of Φ presents difficulties because there is no sharp boundary between the mobile phase and the stationary phase. In addition, the boundary depends not only on the nature of the stationary phase, but also on the composition of the mobile phase. In spite of its importance, phase ratio is seldom reported for commercially available HPLC columns and the data typically provided by the vendors about the columns do not provide key information that would allow the calculation of Φ based on Vst and V0 values. A different procedure for the evaluation of Φ is based on the following formula: log k'j=a log Kow,j+log Φ, where k'j is the retention factor for a compound j that must be a hydrocarbon, Kow,j is the octanol/water partition coefficient, and a is a proportionality constant. Present study describes the experimental evaluation of Φ based on the measurement of k'j for the compounds in the homologous series between benzene and butylbenzene for three C18 columns: Gemini C18, Luna C18 both with 5 μm particles, and a Chromolith Performance RP-18. The evaluation was performed for two mobile phase systems at different proportions of methanol/water and acetonitrile/water. The octanol/water partition coefficients were obtained from the literature. The results obtained in the study provide further support for the new procedure for the evaluation of phase ratio.

  13. Cryogenic Ion Mobility-Mass Spectrometry: Tracking Ion Structure from Solution to the Gas Phase.

    PubMed

    Servage, Kelly A; Silveira, Joshua A; Fort, Kyle L; Russell, David H

    2016-07-19

    Electrospray ionization (ESI) combined with ion mobility-mass spectrometry (IM-MS) is adding new dimensions, that is, structure and dynamics, to the field of biological mass spectrometry. There is increasing evidence that gas-phase ions produced by ESI can closely resemble their solution-phase structures, but correlating these structures can be complicated owing to the number of competing effects contributing to structural preferences, including both inter- and intramolecular interactions. Ions encounter unique hydration environments during the transition from solution to the gas phase that will likely affect their structure(s), but many of these structural changes will go undetected because ESI-IM-MS analysis is typically performed on solvent-free ions. Cryogenic ion mobility-mass spectrometry (cryo-IM-MS) takes advantage of the freeze-drying capabilities of ESI and a cryogenically cooled IM drift cell (80 K) to preserve extensively solvated ions of the type [M + xH](x+)(H2O)n, where n can vary from zero to several hundred. This affords an experimental approach for tracking the structural evolution of hydrated biomolecules en route to forming solvent-free gas-phase ions. The studies highlighted in this Account illustrate the varying extent to which dehydration can alter ion structure and the overall impact of cryo-IM-MS on structural studies of hydrated biomolecules. Studies of small ions, including protonated water clusters and alkyl diammonium cations, reveal structural transitions associated with the development of the H-bond network of water molecules surrounding the charge carrier(s). For peptide ions, results show that water networks are highly dependent on the charge-carrying species within the cluster. Specifically, hydrated peptide ions containing lysine display specific hydration behavior around the ammonium ion, that is, magic number clusters with enhanced stability, whereas peptides containing arginine do not display specific hydration around the

  14. Effects of twin boundary mobility on domain microstructure evolution in magnetic shape memory alloys: Phase field simulation

    SciTech Connect

    Jin, Yongmei M.

    2009-02-09

    Effects of twin boundary mobility on domain microstructure evolution during magnetic field-induced deformation in magnetic shape memory alloys are studied by phase field micromagnetic microelastic modeling. The simulations show that different twin boundary mobilities lead to drastically different domain microstructures and evolution pathways, yielding very different magnetization and strain responses, even with opposite signs. The study also reveals complex domain phenomena in magnetic shape memory alloys.

  15. Effect of the water content on the retention and enantioselectivity of albendazole and fenbendazole sulfoxides using amylose-based chiral stationary phases in organic-aqueous conditions.

    PubMed

    Materazzo, Sabrina; Carradori, Simone; Ferretti, Rosella; Gallinella, Bruno; Secci, Daniela; Cirilli, Roberto

    2014-01-31

    Four commercially available immobilized amylose-derived CSPs (Chiralpak IA-3, Chiralpak ID-3, Chiralpak IE-3 and Chiralpak IF-3) were used in the HPLC analysis of the chiral sulfoxides albendazole (ABZ-SO) and fenbendazole (FBZ-SO) and their in vivo sulfide precursor (ABZ and FBZ) and sulfone metabolite (ABZ-SO2 and FBZ-SO2) under organic-aqueous mode. U-shape retention maps, established by varying the water content in the acetonitrile- and ethanol-water mobile phases, were indicative of two retention mechanisms operating on the same CSP. The dual retention behavior of polysaccharide-based CSPs was exploited to design greener enantioselective and chemoselective separations in a short time frame. The enantiomers of ABZ-SO and FBZ-SO were baseline resolved with water-rich mobile phases (with the main component usually being 50-65% water in acetonitrile) on the IF-3 CSP and ethanol-water 100:5 mixture on the IA-3 and IE-3 CSPs. A simultaneous separation of ABZ (or FBZ), enantiomers of the corresponding sulfoxide and sulfone was achieved on the IA-3 using ethanol-water 100:60 (acetonitrile-water 100:100 for FBZ) as a mobile phase.

  16. Computational studies of coarsening rates for the Cahn-Hilliard equation with phase-dependent diffusion mobility

    NASA Astrophysics Data System (ADS)

    Dai, Shibin; Du, Qiang

    2016-04-01

    We study computationally coarsening rates of the Cahn-Hilliard equation with a smooth double-well potential, and with phase-dependent diffusion mobilities. The latter is a feature of many materials systems and makes accurate numerical simulations challenging. Our numerical simulations confirm earlier theoretical predictions on the coarsening dynamics based on asymptotic analysis. We demonstrate that the numerical solutions are consistent with the physical Gibbs-Thomson effect, even if the mobility is degenerate in one or both phases. For the two-sided degenerate mobility, we report computational results showing that the coarsening rate is on the order of l ∼ ct 1 / 4, independent of the volume fraction of each phase. For the one-sided degenerate mobility, that is non-degenerate in the positive phase but degenerate in the negative phase, we illustrate that the coarsening rate depends on the volume fraction of the positive phase. For large positive volume fractions, the coarsening rate is on the order of l ∼ ct 1 / 3 and for small positive volume fractions, the coarsening rate becomes l ∼ ct 1 / 4.

  17. [Research on the separation of limonoid glucosides by reversed-phase preparative high performance liquid chromatography].

    PubMed

    Tian, Q G; Dai, J; Ding, X L

    2000-03-01

    Obacunone-17-beta-D-glucopyranoside (OG) was isolated from the seeds of Citrus Sinensis Osbeck by using solvent extraction, classical polymer adsorption column separation and weak base anion ion-exchange separation, OG was finally purified by C18 reversed-phase preparative high performance liquid chromatography and was identified by thin-layer chromatography. The purity of OG was analyzed by analytical reversed-phase HPLC. At last the structure of OG was determined by 1H and 13C nuclear magnetic resonance spectrometry (NMR). In this work, the conditions of the reversed-phase preparative HPLC technique to purify limonoid glucosides was optimized. The reversed-phase preparative HPLC on a C18 column with a mobile phase of acidic acetonitrile-water (about 0.2% TFA, V/V) at pH 3 enabled the baseline separation of limonoid glucosides in the extract. The results show that OG is the predominant limonoid glucoside in the seeds of Citrus Sinensis Osbeck and nomilin glucoside is the second one. The results also show that the classical polymer adsorption column separation and weak base anion ion-exchange separation are effective for purifying limonoid glucosides.

  18. Explosive ordnance detection in land and water environments with solid phase extraction/ion mobility spectrometry

    NASA Astrophysics Data System (ADS)

    Chambers, William B.; Phelan, James M.; Rodacy, Philip J.; Reber, Steven; Woodfin, Ronald L.

    1999-08-01

    The qualitative and quantitative determination of nitroaromatic compounds such as trinitrotoluene (TNT) and dinitrotoluene (DNT) in water and soil has applications to environmental remediation and the detection of buried military ordnance. Recent results of laboratory and field test have shown that trace level concentrations of these compounds can be detected in water, soil, and solid gas samples taken from the vicinity of submerged or buried ordnance using specialized sampling and signal enhancement techniques. Solid phase micro-extraction methods have been combined with Ion Mobility Spectroscopy to provide rapid, sub-parts-per-billion analysis of these compounds. In this paper, we will describe the gas. These sampling systems, when combined with field-portable IMS, are being developed as a means of classifying buried or submerged objects as explosive ordnance.

  19. Simultaneous effect of pH, temperature and mobile phase composition in the chromatographic retention of ionizable compounds.

    PubMed

    Agrafiotou, Panagiota; Ràfols, Clara; Castells, Cecilia; Bosch, Elisabeth; Rosés, Martí

    2011-07-29

    The retention of 22 monoprotic acid-base solutes in 12 buffers (pH from 2 to 12) at 3 temperatures (25, 40 and 55°C) and in 3 mobile phase compositions (20, 40 and 60% acetonitrile) was measured. The retention data for each solute, temperature and mobile phase compositions was fitted to pH by means of the common sigmoidal equation and the retention and acid-base parameters were obtained (logk(HA), logk(A) and pK(a)). The dependence of these parameters on temperature (van't Hoff plots), mobile phase composition (ϕ, volume fraction of acetonitrile) and mobile phase polarity (P(m)(N) parameter) was investigated. Linear plots of the parameter values against the reverse of the absolute temperature, on one hand, and ϕ or P(m)(N), in the other hand, were generally obtained. From this analysis we propose 6-parameter equations to relate retention to pH and T at constant mobile phase composition, and to pH and ϕ or P(m)(N) at constant temperature. A general 12 parameter equation is also proposed to relate retention simultaneously to pH, T and ϕ or P(m)(N). The general constancy of some terms of the equations allow to simplify the 12 parameter equation to a 8 parameter equation able to predict retention of the studied solutes. The accuracy of the proposed method provided excellent results with the advantage of modeling the effects of various optimization variables (modifier concentration, mobile phase pH and temperature) using a single equation, based on only eight fitting parameters.

  20. Mineral phases and mobility of trace metals in white aluminum precipitates found in acid mine drainage.

    PubMed

    Kim, Yeongkyoo

    2015-01-01

    The white aluminum precipitates (S1,S2,S4-1,S4-2) collected at three different locations affected by acid mine and rock drainage were studied to characterize the mineral phases and mobility of trace metals. Chemical analysis, XRD, SEM, NMR, and sequential extraction method were mainly used. XRD data showed that most white aluminum precipitates are amorphous with small amount of gypsum, which was also confirmed by SEM. The (27)Al MAS NMR spectra provide more detailed information on the local environments of aluminum in those samples. The samples collected at two locations (S3, and S4-1 and S4-2) contain 4-coordinated aluminum, suggesting that the samples contain a significant amount of amorphous phase from Al13-tridecamer. Chemical data of calcium and sulfur with (27)Al MAS NMR spectra suggest that the relative amounts of amorphous phase from Al13-tridecamer, hydrobasaluminite, aluminum hydroxide, and gypsum are different for each sample. Different amount of amorphous phase from Al13-tridecamer in those samples are probably caused by the different geochemical conditions and hydrolysis by aging in water. Sequential extraction results show that water soluble fraction and sorbed and exchangeable fraction of trace metals in sample collected as suspended particles (S1) are higher than other samples, and can affect the ecological system in waters by releasing aluminum and trace metals. These results suggest that careful characterization of white aluminum precipitates is needed to estimate the environmental effects of those precipitates in acid mine drainage. PMID:25213794

  1. Performance of different C18 columns in reversed-phase liquid chromatography with hydro-organic and micellar-organic mobile phases.

    PubMed

    Ruiz-Angel, M J; Pous-Torres, S; Carda-Broch, S; García-Alvarez-Coque, M C

    2014-05-30

    Column selection in reversed-phase liquid chromatography (RPLC) can become a challenge if the target compounds interact with the silica-based packing. One of such interactions is the attraction of cationic solutes to the free silanols in silica-based columns, which is a slow sorption-desorption interaction process that gives rise to tailed and broad peaks. The effect of silanols is minimised by the addition of a competing agent in the mobile phase, such as the anionic surfactant sodium dodecyl sulphate (SDS). In micellar-organic RPLC, the adsorption of an approximately fixed amount of SDS monomers gives rise to a stable modified stationary phase, with properties remarkably different from those of the underlying bonded phase. The chromatographic behaviour (in terms of selectivity, analysis time and peak shape) of eight C18 columns in the analysis of weakly acidic phenols and basic β-blockers was examined with hydro-organic and micellar-organic mobile phases. The behaviour of the columns differed significantly when the cationic basic drugs were eluted with hydro-organic mobile phases. With micellar-organic mobile phases, the adsorption of surfactant, instead of making the columns similar, gave rise to a greater diversity of behaviours (especially in terms of selectivity and analysis time), for both groups of phenols and β-blockers, which should be explained by the residual effect of the underlying bonded stationary phase and the different amount of surfactant covering the packing. Therefore, the implementation of a micellar-organic procedure in RPLC will depend significantly on the selected type of C18 column.

  2. Ratchet Effects, Negative Mobility, and Phase Locking for Skyrmions on Periodic Substrates

    NASA Astrophysics Data System (ADS)

    Reichhardt, Charles; Ray, Dipanjan; Olson Reichhardt, Cynthia

    We examine the dynamics of skyrmions interacting with 1D and 2D periodic substrates in the presence of dc and ac drives. We find that the Magnus term strongly affects the skyrmion dynamics and that new kinds of phenomena can occur which are absent for overdamped ac and dc driven particles interacting with similar substrates. We show that it is possible to realize a Magnus induced ratchet for skyrmions interacting with an asymmetric potential, where the application of an ac drive can produce quantized dc motion of the skyrmions even when the ac force is perpendicular to the substrate asymmetry direction. For symmetric substrates it is also possible to achieve a negative mobility effect where the net skyrmion motion runs counter to an applied dc drive. Here, as a function of increasing dc drive, the velocity-force curves show a series of locking phases that have different features from the classic Shapiro steps found in overdamped systems. In the phase locking and ratcheting states, the skyrmions undergo intricate 2D orbits induced by the Magnus term.

  3. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  4. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage...

  5. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage...

  6. 77 FR 57085 - Mobility Fund Phase I Auction; Release of Files with Recalculated Road Miles for Auction 901...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-17

    .../ecfs/ . 1. In the Auction 901 Procedures Public Notice, 77 FR 32092, May 31, 2012, the Bureaus... Notice, 77 FR 7152, February 10, 2012, in calculating the number of road miles associated with each... COMMISSION Mobility Fund Phase I Auction; Release of Files with Recalculated Road Miles for Auction 901;...

  7. 77 FR 11115 - Mobility Fund Phase I Auction Limited Extension of Deadlines for Comments and Reply Comments on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-24

    ... released the Auction 901 Comment Public Notice, 77 FR 7152, February 10, 2012, which seeks comment on... Commission in the USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562, December 28... COMMISSION Mobility Fund Phase I Auction Limited Extension of Deadlines for Comments and Reply Comments...

  8. Understanding gas phase modifier interactions in rapid analysis by Differential Mobility-Tandem Mass Spectrometry

    PubMed Central

    Kafle, Amol; Coy, Stephen L.; Wong, Bryan M.; Fornace, Albert J.; Glick, James J.; Vouros, Paul

    2014-01-01

    A systematic study involving the use and optimization of gas phase modifiers in quantitative differential mobility- mass spectrometry (DMS-MS) analysis is presented using mucleoside-adduct biomarkers of DNA damage as an important reference point for analysis in complex matrices. Commonly used polar protic and polar aprotic modifiers have been screened for use against two deoxyguanosine adducts of DNA: N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP) and N-(deoxyguanosin-8-y1)-2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (dG-C8-PhIP). Particular attention was paid to compensation voltage (CoV) shifts, peak shapes and product ion signal intensities while optimizing the DMS-MS conditions. The optimized parameters were then applied to rapid quantitation of the DNA adducts in calf thymus DNA. After a protein precipitation step, adduct levels corresponding to less than one modification in 106 normal DNA bases were detected using the DMS-MS platform. Based on DMS fundamentals and ab-initio thermochemical results we interpret the complexity of DMS modifier responses in terms of thermal activation and the development of solvent shells. At very high bulk gas temperature, modifier dipole moment may be the most important factor in cluster formation and cluster geometry in mobility differences, but at lower temperatures multi-neutral clusters are important and less predictable. This work provides a useful protocol for targeted DNA adduct quantitation and a basis for future work on DMS modifier effects. PMID:24452298

  9. Quinine-Based Zwitterionic Chiral Stationary Phase as a Complementary Tool for Peptide Analysis: Mobile Phase Effects on Enantio- and Stereoselectivity of Underivatized Oligopeptides.

    PubMed

    Ianni, Federica; Sardella, Roccaldo; Carotti, Andrea; Natalini, Benedetto; Lindner, Wolfgang; Lämmerhofer, Michael

    2016-01-01

    Peptide stereoisomer analysis is of importance for quality control of therapeutic peptides, the analysis of stereochemical integrity of bioactive peptides in food, and the elucidation of the stereochemistry of peptides from a natural chiral pool which often contains one or more D-amino acid residues. In this work, a series of model peptide stereoisomers (enantiomers and diastereomers) were analyzed on a zwitterionic ion-exchanger chiral stationary phase (Chiralpak ZWIX(+) 5 µm), in order to investigate the retention and separation performance for such compounds on this chiral stationary phase and elucidate its utility for this purpose. The goal of the study focused on 1) investigations of the effects of the sample matrix used to dissolve the peptide samples; 2) optimization of the mobile phase (enabling deriving information on factors of relevance for retention and separation); and 3) derivation of structure-selectivity relationships. It turned out that small di- and tripeptides can be well resolved under optimized conditions, typically with resolutions larger than 1.5. The optimized mobile phase often consisted of methanol-tetrahydrofuran-water (49:49:2; v/v/v) with 25 mM formic acid and 12.5 mM diethylamine. This work proposes some guidance on which mobile phases can be most efficiently used for peptide stereoisomer separations on Chiralpak ZWIX. Chirality 28:5-16, 2016. © 2015 Wiley Periodicals, Inc.

  10. Influence of mobile phase composition on electroosmotic flow velocity, solute retention and column efficiency in open-tubular reversed-phase capillary electrochromatography.

    PubMed

    Crego, A L; Martínez, J; Marina, M L

    2000-02-11

    The effects of some experimental parameters, such as the volume fraction and type of organic modifier in the mobile phase, and the concentration, type and pH of the buffer on the electroosmotic flow velocity, the retention behavior of test solutes, and the column efficiency have been investigated in capillary electrochromatography (CEC) using an open-tubular column of 9.60 microm I.D. with a porous silica layer chemically modified with C18 as stationary phase. The retention of a group of polycyclic aromatic hydrocarbons (PAHs) used as a test mixture varied significantly by changing the organic modifier content in the hydroorganic mobile phase according to the reversed-phase-like selectivity of the stationary phase. In addition, an increase in the percentage of organic modifier resulted in a slight increase in the linear velocity of the EOF. On the other hand, when the phosphate buffer concentration was increased over the range 1-50 mM, the electroosmotic mobility fell dramatically, the retention of the solutes decreased steadily, and the plate height showed a significant increase. The results obtained with phosphate, trishydroxymethylaminomethane or 2-morpholinoethanesulfonic acid as buffers were similar when pH remained constant. Optimization in CEC was essential to achieve further enhancement of separation performance, because the analysis time and separation resolution are essentially affected when varying operating parameters. Separations of seven PAHs with more than 100000 plates are presented within 4 min analysis time.

  11. Utilization of deep eutectic solvents as novel mobile phase additives for improving the separation of bioactive quaternary alkaloids.

    PubMed

    Tan, Ting; Zhang, Mingliang; Wan, Yiqun; Qiu, Hongdeng

    2016-01-01

    Deep eutectic solvents (DESs) were used as novel mobile phase additives to improve chromatographic separation of four quaternary alkaloids including coptisine chloride, sanguinarine, berberine chloride and chelerythrine on a C18 column. DESs as a new class of ionic liquids are renewably sourced, environmentally benign, low cost and easy to prepare. Seven DESs were obtained by mixing different hydrogen acceptors and hydrogen-bond donors. The effects of organic solvents, the concentration of DESs, the types of DESs and the pH values of the buffer solution on the separation of the analytes were investigated. The composition of acetonitrile and 1.0% deep eutectic solvents aqueous solution (pH 3.3, adjusted with hydrochloric acid) in a 32:68 (v/v) ratio was used as optimized mobile phase, with which four quaternary alkaloids were well separated. When a small amount of DESs was added in the mobile phase for the separation of alkaloids on the C18 column, noticeable improvements were distinctly observed such as decreasing peak tailing and improving resolution. The separation mechanism mediated by DESs as mobile phase additives can be attributed to combined effect of both hydrogen acceptors and hydrogen-bond donors. For example, choline chloride can effectively cover the residual silanols on silica surface and ethylene glycol can reduce the retention time of analytes. The proposed method has been applied to determine BerbC in Lanqin Chinese herbal oral solution and BerbC tablet. Utilization of DESs in mobile phase can efficiently improve separation and selectivity of analytes from complex samples.

  12. Utilization of deep eutectic solvents as novel mobile phase additives for improving the separation of bioactive quaternary alkaloids.

    PubMed

    Tan, Ting; Zhang, Mingliang; Wan, Yiqun; Qiu, Hongdeng

    2016-03-01

    Deep eutectic solvents (DESs) were used as novel mobile phase additives to improve chromatographic separation of four quaternary alkaloids including coptisine chloride, sanguinarine, berberine chloride and chelerythrine on a C18 column. DESs as a new class of ionic liquids are renewably sourced, environmentally benign, low cost and easy to prepare. Seven DESs were obtained by mixing different hydrogen acceptors and hydrogen-bond donors. The effects of organic solvents, the concentration of DESs, the types of DESs and the pH values of the buffer solution on the separation of the analytes were investigated. The composition of acetonitrile and 1.0% deep eutectic solvents aqueous solution (pH 3.3, adjusted with hydrochloric acid) in a 32:68 (v/v) ratio was used as optimized mobile phase, with which four quaternary alkaloids were well separated. When a small amount of DESs was added in the mobile phase for the separation of alkaloids on the C18 column, noticeable improvements were distinctly observed such as decreasing peak tailing and improving resolution. The separation mechanism mediated by DESs as mobile phase additives can be attributed to combined effect of both hydrogen acceptors and hydrogen-bond donors. For example, choline chloride can effectively cover the residual silanols on silica surface and ethylene glycol can reduce the retention time of analytes. The proposed method has been applied to determine BerbC in Lanqin Chinese herbal oral solution and BerbC tablet. Utilization of DESs in mobile phase can efficiently improve separation and selectivity of analytes from complex samples. PMID:26717817

  13. Collection of ethanolamines in air and determination by mobile phase ion chromatography

    SciTech Connect

    Bouyoucos, S.A.; Melcher, R.G.

    1986-03-01

    A method is described for the collection and determination of monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) in air. Samples were collected by pulling air through a glass tube containing alumina, cleaned especially to remove interfering inorganic ions. The ethanolamines were desorbed with water and determined by Mobile Phase Ion Chromatography (MPIC). The recovery and total relative precision for MEA, DEA, and TEA - all collected from air at a flow rate of 100 mL/min for 7 hr - was 93.1 +/- 17%, 92.7 +/- 15% and 89.4 +/- 21%, respectively (95% confidence level). The method was validated for all three compounds from approximately the limit of detection (3 x noise) to ten times the limit of detection. Based on a sample size of 42 L, MEA was validated over the range from 0.12 to 3.0 ppm v/v (TLV=3), DEA over the range from 0.25 to 3.3 ppm v/v (TLV=3) and TEA from 0.31 to 3.7 ppm v/v (no TLV assigned). No effect on recovery was observed when sampling at high humidity or on storage of the samples for up to 31 days.

  14. Development and validation of a new stability indicating reversed phase liquid chromatographic method for the determination of prednisolone acetate and impurities in an ophthalmic suspension.

    PubMed

    Marley, Adrian; Stalcup, Apryll M; Connolly, Damian

    2015-01-01

    A new stability indicating reversed phase high performance liquid chromatography (RP-HPLC) method was developed and validated under current International Conference of Harmonisation (ICH) guidance for the determination of prednisolone acetate (PAC) and impurities in an ophthalmic suspension. The developed method is presented as an alternative to a modified version of the current RP-HPLC method described in the USP monograph for the assay of PAC in an ophthalmic suspension. Along with the assay of PAC, the new method is also capable of identifying and quantifying eight selected PAC impurities and degradation products in an ophthalmic suspension. Using an Agilent Poroshell 120 EC-C18 100 mm × 4.6mm (dp: 2.7 μm) column set to 60°C with step gradient elution generated using mobile phase A: acetonitrile/water (10:90) (v/v) and mobile phase B: acetonitrile delivered at 1.2 mL min(-1), all peaks of interest are eluted in 33 min with resolution of 1.5 between the critical pairs. The developed method was validated for PAC and impurities to ICH recommendations for accuracy, linearity, precision (repeatability), limit of detection, limit of quantitation, robustness and specificity.

  15. Greener liquid chromatography using a guard column with micellar mobile phase for separation of some pharmaceuticals and determination of parabens.

    PubMed

    Youngvises, Napaporn; Chaida, Thanatcha; Khonyoung, Supada; Kuppithayanant, Nattawan; Tiyapongpattana, Warawut; Itharat, Arunporn; Jakmunee, Jaroon

    2013-03-15

    In this research, a greener chromatography employing a short column, Zorbax SB C18 cartridge (12.5 × 4.6 mm, 5 μm) commonly used as a guard column in a reverse phase high performance liquid chromatography (RP-HPLC), was utilized as the analytical column in conjunction with a more eco-friendly micellar mobile phase of sodium dodecyl sulfate (SDS) for separation tertiary mixtures of local anesthetics and antihistamines; and binary mixture of colds drugs; and quaternary mixture of some parabens with different separation conditions. The chromatographic behavior of these analytes was studied to demonstrate separation efficiency of this guard column in a micellar mobile phase. Moreover, this column and SDS mobile phase was exploited for determination of parabens in 64 samples of cosmetic product, both those that were produced locally in the community and those that were commercially manufactured. Linear calibration graphs of the parabens as detected at 254 nm were obtained in the range of 1-100 μmol L(-1) with R(2)>0.9990. Percentage recoveries were 92.4-109.2 with %RSD<3, and the limit of detection and quantitation were 0.04-0.10 and 0.20-0.80 μmol L(-1), respectively. This analytical system is not only greener but also faster and employing simpler sample preparation than a conventional liquid chromatographic system. PMID:23598137

  16. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive

    PubMed Central

    Peng, Yangfeng; He, Quan Sophia; Cai, Jiang

    2016-01-01

    Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT). PMID:26880921

  17. Greener liquid chromatography using a guard column with micellar mobile phase for separation of some pharmaceuticals and determination of parabens.

    PubMed

    Youngvises, Napaporn; Chaida, Thanatcha; Khonyoung, Supada; Kuppithayanant, Nattawan; Tiyapongpattana, Warawut; Itharat, Arunporn; Jakmunee, Jaroon

    2013-03-15

    In this research, a greener chromatography employing a short column, Zorbax SB C18 cartridge (12.5 × 4.6 mm, 5 μm) commonly used as a guard column in a reverse phase high performance liquid chromatography (RP-HPLC), was utilized as the analytical column in conjunction with a more eco-friendly micellar mobile phase of sodium dodecyl sulfate (SDS) for separation tertiary mixtures of local anesthetics and antihistamines; and binary mixture of colds drugs; and quaternary mixture of some parabens with different separation conditions. The chromatographic behavior of these analytes was studied to demonstrate separation efficiency of this guard column in a micellar mobile phase. Moreover, this column and SDS mobile phase was exploited for determination of parabens in 64 samples of cosmetic product, both those that were produced locally in the community and those that were commercially manufactured. Linear calibration graphs of the parabens as detected at 254 nm were obtained in the range of 1-100 μmol L(-1) with R(2)>0.9990. Percentage recoveries were 92.4-109.2 with %RSD<3, and the limit of detection and quantitation were 0.04-0.10 and 0.20-0.80 μmol L(-1), respectively. This analytical system is not only greener but also faster and employing simpler sample preparation than a conventional liquid chromatographic system.

  18. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive.

    PubMed

    Peng, Yangfeng; He, Quan Sophia; Cai, Jiang

    2016-01-01

    Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT). PMID:26880921

  19. Impact of the intermixed phase and the channel network on the carrier mobility of nanostructured solar cells.

    PubMed

    Woellner, Cristiano F; Freire, José A

    2016-02-28

    We analyzed the impact of the complex channel network of donor and acceptor domains in nanostructured solar cells on the mobility of the charge carriers moving by thermally activated hopping. Particular attention was given to the so called intermixed phase, or interface roughness, that has recently been shown to promote an increase in the cell efficiency. The domains were obtained from a Monte Carlo simulation of a two-species lattice gas. We generated domain morphologies with controllable channel size and interface roughness. The field and density dependence of the carrier hopping mobility in different morphologies was obtained by solving a master equation. Our results show that the mobility decreases with roughness and increases with typical channel sizes. The deleterious effect of the roughness on the mobility is quite dramatic at low carrier densities and high fields. The complex channel network is shown to be directly responsible for two potentially harmful effects to the cell performance: a remarkable decrease of the mobility with increasing field and the accumulation of charge at the domains interface, which leads to recombination losses.

  20. Understanding Gas Phase Modifier Interactions in Rapid Analysis by Differential Mobility-Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Kafle, Amol; Coy, Stephen L.; Wong, Bryan M.; Fornace, Albert J.; Glick, James J.; Vouros, Paul

    2014-07-01

    A systematic study involving the use and optimization of gas-phase modifiers in quantitative differential mobility-mass spectrometry (DMS-MS) analysis is presented using nucleoside-adduct biomarkers of DNA damage as an important reference point for analysis in complex matrices. Commonly used polar protic and polar aprotic modifiers have been screened for use against two deoxyguanosine adducts of DNA: N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP) and N-(deoxyguanosin-8-y1)-2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (dG-C8-PhIP). Particular attention was paid to compensation voltage (CoV) shifts, peak shapes, and product ion signal intensities while optimizing the DMS-MS conditions. The optimized parameters were then applied to rapid quantitation of the DNA adducts in calf thymus DNA. After a protein precipitation step, adduct levels corresponding to less than one modification in 106 normal DNA bases were detected using the DMS-MS platform. Based on DMS fundamentals and ab initio thermochemical results, we interpret the complexity of DMS modifier responses in terms of thermal activation and the development of solvent shells. At very high bulk gas temperature, modifier dipole moment may be the most important factor in cluster formation and cluster geometry, but at lower temperatures, multi-neutral clusters are important and less predictable. This work provides a useful protocol for targeted DNA adduct quantitation and a basis for future work on DMS modifier effects.

  1. Understanding gas phase modifier interactions in rapid analysis by differential mobility-tandem mass spectrometry.

    PubMed

    Kafle, Amol; Coy, Stephen L; Wong, Bryan M; Fornace, Albert J; Glick, James J; Vouros, Paul

    2014-07-01

    A systematic study involving the use and optimization of gas-phase modifiers in quantitative differential mobility-mass spectrometry (DMS-MS) analysis is presented using nucleoside-adduct biomarkers of DNA damage as an important reference point for analysis in complex matrices. Commonly used polar protic and polar aprotic modifiers have been screened for use against two deoxyguanosine adducts of DNA: N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP) and N-(deoxyguanosin-8-y1)-2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (dG-C8-PhIP). Particular attention was paid to compensation voltage (CoV) shifts, peak shapes, and product ion signal intensities while optimizing the DMS-MS conditions. The optimized parameters were then applied to rapid quantitation of the DNA adducts in calf thymus DNA. After a protein precipitation step, adduct levels corresponding to less than one modification in 10(6) normal DNA bases were detected using the DMS-MS platform. Based on DMS fundamentals and ab initio thermochemical results, we interpret the complexity of DMS modifier responses in terms of thermal activation and the development of solvent shells. At very high bulk gas temperature, modifier dipole moment may be the most important factor in cluster formation and cluster geometry, but at lower temperatures, multi-neutral clusters are important and less predictable. This work provides a useful protocol for targeted DNA adduct quantitation and a basis for future work on DMS modifier effects.

  2. Use of micellar mobile phases and microbore column switching for the assay of drugs in physiological fluids.

    PubMed

    Koenigbauer, M J; Curtis, M A

    1988-06-01

    The feasibility of directly assaying drugs in physiological fluids using on-line preconcentration and microbore high-performance liquid chromatography has been demonstrated. The untreated sample is injected onto a hydrophobic pre-column, using micellar sodium dodecyl sulfate (SDS) in the case of serum or phosphate buffer in the case of urine, as the load mobile phase. This traps the components of interest which are then backflushed onto a microbore analytical column using a stronger mobile phase. This procedure was then applied to diazepam in serum and phenobarbital in urine. Recovery was linear and quantitative over the range 30-3000 ng/ml for diazepam in serum and 2-200 micrograms/ml for phenobarbital in urine. The diazepam method was specific against caffeine and the three major metabolites of diazepam: oxazepam, temazepam, and nordiazepam. The effects of varying pre-column dimensions, pre-column loading time, and SDS concentration volume were evaluated. PMID:3410911

  3. Retention of ionizable compounds on HPLC. 4. Mobile-phase pH measurement in methanol/water

    PubMed

    Canals; Portal; Bosch; Roses

    2000-04-15

    The different procedures used in HPLC to measure the pH of a mobile phase are evaluated in terms of the rigorous IUPAC definition of pH. The three procedures evaluated are as follows: measurement of the pH of the aqueous HPLC buffer before mixing it with the organic modifier, measurement of the pH of the HPLC buffer after mixing it with the organic modifier using a pH electrode system calibrated with aqueous buffers, and measurement of the pH of the HPLC buffer after mixing it with the organic modifier but calibrating the electrode system with reference buffers prepared in the same mixed solvent used as mobile phase. Following IUPAC definitions and recommendations, the three pH values can be related with the pH scales: w(w)pH, s(w)pH, and s(s)pH, respectively. The relationships between these three pH scales are also presented. The retention of several compounds with acid/base behavior in a C-18 and a polymeric column with buffered methanol/water as mobile phase is related to the mobile phase pH value measured in the three pH scales. It is demonstrated that the s(w)pH and s(s)pH scales give better relationships than the w(w)pH scale (pH measured in the aqueous buffer before mixing it with the organic modifier), commonly used on HPLC. The s(w)pH scale is specially recommended because of its simplicity of measurement: the pH is measured after mixing the aqueous buffer with the organic modifier, but the pH calibration is performed with the common aqueous reference buffers.

  4. Mechanisms for trapping and mobilization of residual fluids during capillary-dominated three-phase flow in porous rock

    NASA Astrophysics Data System (ADS)

    Helland, J. O.; Jettestuen, E.

    2016-07-01

    We use a multiphase level set approach to simulate capillary-controlled motions of isolated fluid ganglia surrounded by two other continuous fluids (i.e., double displacements) during three-phase flow on 3-D porous rock geometries. Double displacements and three-phase snap-off mechanisms are closely related. Water snap-off on gas/oil interfaces can initiate double displacements that mobilize isolated oil ganglia in water-wet rock, but it can also terminate ongoing double displacements and trap oil in water. The multiphase level set approach allows for calculating the evolution of disconnected-phase pressure during the motion. In the events of pore filling by double displacement of oil ganglia, and water snap-off on gas/oil interfaces, we find that the local gas/oil capillary pressure drops, while local oil/water capillary pressure increases, by a similar magnitude as observed for the capillary pressure drops during single-pore filling events in dynamic pore-scale experiments of two-phase drainage. We also find that oil ganglia decrease their surface area, and achieve a more compact shape, when the gas/oil interfacial area decreases at the expense of increased oil/water interfacial area during double displacement. By comparison with similar two-phase gas/water simulations, we find that the level of the gas/water capillary pressure curves, including hysteresis loops, are smaller when a mobile, disconnected oil is present, which suggests double displacement of oil is more favorable than direct gas/water displacement. We also present cases in which phase trapping occurred in the three-phase simulations, but not in the corresponding two-phase simulations, supporting the view that more trapping is possible in three-phase flow.

  5. Pulsed field gradient MAS-NMR studies of the mobility of carboplatin in cubic liquid-crystalline phases

    NASA Astrophysics Data System (ADS)

    Pampel, André; Michel, Dieter; Reszka, Regina

    2002-05-01

    A drug delivery system with cubic liquid-crystalline phase structure (cubic phase) containing the anti-cancer drug Carboplatin is studied. It is demonstrated that the combination of pulsed field gradient (PFG) NMR and MAS-NMR is a useful tool to study the biophysical properties of a cubic phase. The linewidth in 1H-NMR spectra is narrowed by MAS, which can be exploited to perform PFG diffusion NMR experiments under high-resolution conditions. Measurement of self-diffusion coefficients of all components of the cubic phase becomes possible. The influence of polyethylene glycol chains on the drug mobility is discussed. It is shown that polyethylene glycol chains interact with Carboplatin.

  6. [Determination of residual sulfonamides in meat by high performance liquid chromatography with solid-phase extraction].

    PubMed

    Zhang, Yan; Wu, Yinliang

    2005-11-01

    A method was developed for determining residual sulfonamides (SAs) such as sulfamethazine (SM2), sulfamonomethoxine (SMM), sulfamethiazole (SMZ), sulfadimethoxine (SDM) and sulfaquinoxaline (SQ) in pork and chicken using solid-phase extraction (SPE) and high performance liquid chromatography (HPLC) with a photodiode array detector. The samples were extracted with ethyl acetate. An NH2 column was used for clean up. For the HPLC determination, an Intersil ODS-2 column was used with a mixture of methanol-acetonitrile-water-acetic acid (2: 2: 9: 0.2, v/v) as the mobile phase. The detection limits (S/N = 3) were 3 microg/kg for SM2, SMM and SMZ, and 7 microg/kg for SDM and SQ. The quantitation limits (S/N = 10) were 10 microg/kg for SM2, SMM and SMZ, and 25 microg/kg for SDM and SQ. The linear ranges were 30 - 5 000 microg/L for SM2, SMM and SMZ, and 60 - 5 000 microg/L for SDM and SQ. The recoveries were between 73.2% and 97.3% with the relative standard deviations between 2.5% and 11.6% originated from the spiked level of 50 microg/kg. PMID:16498995

  7. Rapid and sensitive analysis of phthalate metabolites, bisphenol A, and endogenous steroid hormones in human urine by mixed-mode solid-phase extraction, dansylation, and ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry.

    PubMed

    Wang, He-xing; Wang, Bin; Zhou, Ying; Jiang, Qing-wu

    2013-05-01

    Steroid hormone levels in human urine are convenient and sensitive indicators for the impact of phthalates and/or bisphenol A (BPA) exposure on the human steroid hormone endocrine system. In this study, a rapid and sensitive method for determination of 14 phthalate metabolites, BPA, and ten endogenous steroid hormones in urine was developed and validated on the basis of ultra-performance liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry. The optimized mixed-mode solid phase-extraction separated the weakly acidic or neutral BPA and steroid hormones from acidic phthalate metabolites in urine: the former were determined in positive ion mode with a methanol/water mobile phase containing 10 mM ammonium formate; the latter were determined in negative ion mode with a acetonitrile/water mobile phase containing 0.1 % acetic acid, which significantly alleviated matrix effects for the analysis of BPA and steroid hormones. Dansylation of estrogens and BPA realized simultaneous and sensitive analysis of the endogenous steroid hormones and BPA in a single chromatographic run. The limits of detection were less than 0.84 ng/mL for phthalate metabolites and less than 0.22 ng/mL for endogenous steroid hormones and BPA. This proposed method had satisfactory precision and accuracy, and was successfully applied to the analyses of human urine samples. This method could be valuable when investigating the associations among endocrine-disrupting chemicals, endogenous steroid hormones, and relevant adverse outcomes in epidemiological studies.

  8. Green chromatography separation of analytes of greatly differing properties using a polyethylene glycol stationary phase and a low-toxic water-based mobile phase.

    PubMed

    Šatínský, Dalibor; Brabcová, Ivana; Maroušková, Alena; Chocholouš, Petr; Solich, Petr

    2013-07-01

    A simple, rapid, and environmentally friendly HPLC method was developed and validated for the separation of four compounds (4-aminophenol, caffeine, paracetamol, and propyphenazone) with different chemical properties. A "green" mobile phase, employing water as the major eluent, was proposed and applied to the separation of analytes with different polarity on polyethylene glycol (PEG) stationary phase. The chromatography separation of all compounds and internal standard benzoic acid was performed using isocratic elution with a low-toxicity mobile phase consisting of 0.04% (v/v) triethylamine and water. HPLC separation was carried out using a PEG reversed-phase stationary phase Supelco Discovery HS PEG column (15 × 4 mm; particle size 3 μm) at a temperature of 30 °C and flow rate at 1.0 mL min(-1). The UV detector was set at 210 nm. In this study, a PEG stationary phase was shown to be suitable for the efficient isocratic separation of compounds that differ widely in hydrophobicity and acid-base properties, particularly 4-aminophenol (log P, 0.30), caffeine (log P, -0.25), and propyphenazone (log P, 2.27). A polar PEG stationary phase provided specific selectivity which allowed traditional chromatographic problems related to the separation of analytes with different polarities to be solved. The retention properties of the group of structurally similar substances (aromatic amines, phenolic compounds, and xanthine derivatives) were tested with different mobile phases. The proposed green chromatography method was successfully applied to the analysis of active substances and one degradation impurity (4-aminophenol) in commercial preparation. Under the optimum chromatographic conditions, standard calibration was carried out with good linearity correlation coefficients for all compounds in the range (0.99914-0.99997, n = 6) between the peak areas and concentration of compounds. Recovery of the sample preparation was in the range 100 ± 5% for all compounds

  9. Electron Transport in a High Mobility Free-Standing GaN Substrate Grown by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Farina, L.; Kurdak, C.; Yun, F.; Morkoc, H.; Rode, D. L.; Tsen, K. T.; Park, S. S.; Lee, K. Y.

    2001-03-01

    We studied electron transport properties in a high quality free-standing GaN grown by hydride vapor phase epitaxy. The GaN, with a thickness of more than 200 μm, was lifted off the sapphire substrate and mechanically polished. At room temperature the carrier density is 1.3x10^16cm-3 and the Hall mobility is 1200 cm^2/V-s, which is the highest reported electron mobility for GaN with a wurtzite structure. Transport properties are studied using a van der Pauw geometry in a temperature range of 20 to 300 K and in magnetic fields up to 8 Tesla. Electron mobility is found to increase at lower temperatures with a peak mobility of 7400 cm^2/V-s at 48 K. The carrier density decreases exponentially at temperatures below 80 K with an activation energy of 28 meV. The electron transport measurements were used to examine the contributions of different scattering mechanisms. Numerical solution of the Boltzmann transport equation was carried out, including non-parabolic conduction bands and wavefunction admixture, along with lattice scattering and ionized-impurity scattering. LO and TO phonon energies were determined by Raman spectroscopy.

  10. [Chiral separation of five beta-blockers using di-n-hexyl L-tartrate-boric acid complex as mobile phase additive by reversed-phase liquid chromatography].

    PubMed

    Yang, Juan; Wang, Lijuan; Guo, Qiaoling; Yang, Gengliang

    2012-03-01

    A reversed-phase high performance liquid chromatographic (HPLC) method using the di-n-hexyl L-tartrate-boric acid complex as a chiral mobile phase additive was developed for the enantioseparation of five beta-blockers including propranolol, esmolol, metoprolol, bisoprolol and sotalol. In order to obtain a better enantioseparation, the influences of concentrations of di-n-butyl L-tartrate and boric acid, the type, concentration and pH of the buffer, methanol content as well as the molecular structure of analytes were extensively investigated. The separation of the analytes was performed on a Venusil MP-C18 column (250 mm x 4.6 mm, 5 microm). The mobile phase was 15 mmol/L ammonium acetate-methanol containing 60 mmol/L boric acid, 70 mmol/L di-n-hexyl L-tartrate (pH 6.00). The volume ratios of 15 mmol/L ammonium acetate to methanol were 20: 80 for propranolol, esmolol, metoprolol, bisoprolol and 30: 70 for sotalol. The flow rate was 0.5 mL/min and the detection wavelength was set at 214 nm. Under the optimized conditions, baseline enantioseparation was obtained separately for the five pairs of analytes.

  11. ENHANCED MOBILITY OF DENSE NONAQUEOUS-PHASE LIQUIDS (DNAPLs) USING DISSOLVED HUMIC ACIDS

    SciTech Connect

    EDWIN S. OLSON; JOHN R. GALLAGHER; MARC D. KURZ

    1998-10-01

    The specific objectives of this subtask are as follows: � Evaluate the suitability of using humic acids to enhance the solubility and mobility of DNAPL contaminants sorbed to soils. � Evaluate the toxicity and bioavailablity of the DNAPLs to biodegrading microorganisms. To meet the first objective, the Energy & Environmental Research Center (EERC) evaluated a set of humic acids (two) with different chemical compositions and polarities for the following: � Ability of the humates to mobilize/solubilize selected (three) DNAPLs � Mobilization/solubilization in batch soil�water experiments (one soil) � Removal rate via biotreatment with a well-established active microbial culture. The second objective was met by evaluating the inhibiting effects of a leonardite-derived humic acid on active microbial populations.

  12. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: a thermodynamic interpretation.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-01-01

    We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C(18)-bonded packing materials: XTerra-C(18), Gemini-C(18), Luna-C(18)(2), and Halo-C(18), using buffered methanol-water mobile phases. The pHWS of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention and the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at pHsWS that are well above or well below the pKWS(a) of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound pKWS(a)) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at pHsWS that are close to their pKWS(a). They also reveal the role of the buffer capacity on the resulting peak shape. With increasing pHWS, the overloaded profiles are first langmuirian (isotherm type I) at low pHsWS, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate pHsWS, and finally return to a langmuirian shape at high pHsWS. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An excellent agreement was achieved between experimental profiles and those calculated with a two-sites adsorption isotherm model at all pHsWS. The neutral

  13. Reversed-phase high-performance liquid chromatography of the stereoisomers of some sweetener peptides with a helical nickel(II) chelate in the mobile phase.

    PubMed

    Bazylak, G

    1994-05-13

    The use of a chiral mobile phase additive in the form of the helically distorted, square-planar, chiral nickel(II) chelate dl-[4,4'-(1-methyl-2-propylethane-1,2-diyldiimino)bis(pent-3 -en-2- onato)]nickel(II) was investigated for the resolution of optical isomers of dipeptide-type sweeteners, viz., aspartame, alitame and antiaspartame, and some of their decomposition products, e.g., diketopiperazines. The chiral discrimination mechanism for the solutes was elucidated. The proposed chiral RP-HPLC system was applied to the stereoselective determination of aspartame impurities in samples of its commercial dietetic and pharmaceutical formulations.

  14. Advanced heat pump for recovery of volatile organic compounds, Phase III - demonstration of BCSRHP mobile regenerator. Final report

    SciTech Connect

    Not Available

    1994-11-01

    Under Phase I of the subject contract, feasibility studies and basic engineering studies were performed for a Brayton Cycle Solvent Recovery Heat Pump (BCSRBP) system to prevent pollution from small source emitters. It was determined that the cost of a complete system, including adsorbers and regeneration process, would be far too much for the small emission source in most cases. This {open_quotes}integrated{close_quotes} approach was therefore not feasible. However, it was concluded that the expensive portion of the Brayton cycle process, the regenerator, could be shared by mounting it on a trailer that could be transported to different sites to regenerate an adsorber. Under Phase II of the project a mobile regenerator (BCSRI-IP) was designed and built to serve a large number of sites. Adsorbers were designed to control emissions for a week or more between regenerations. The purpose of phase III was to demonstrate the cost effectiveness and efficiency of the shared (decoupled) BRAYSORB{reg_sign} solvent recovery system in energy use and emission control compared to other control technologies through a performance testing program at representative industrial and commercial host sites in Southern California. NUCON was the prime contractor for the demonstration portion of this project. Support and funding were received from Southern California Edison Company, South Coast Air Quality Management District, and the U.S. Department of Energy in addition to the contribution by NUCON. Contractual arrangements were completed with each of the host sites and permits for both the stationary and mobile equipment were acquired. The adsorbers were installed at each host site and the appropriate interface connections were made. The mobile regenerator was transported to Southern California for the demonstration.

  15. [Simultaneous determination of captan and folpet pesticide residues in apples by solid-phase extraction and high performance liquid chromatography].

    PubMed

    Wang, Shuju; Yu, Yanbin; Tan, Peigong; Miao, Zaijing; Wei, Yishan

    2007-03-01

    A method for the simultaneous determination of captan and folpet pesticide residues in apples was developed by solid-phase extraction and high performance liquid chromatography. The sample was extracted with acetonitrile and cleaned-up by a mixture of homemade sorbent and silica gel with hexane-dichloromethane-acetonitrile (50:49: 1, v/v) as the eluent. The cleaned effects by using Florisil column, amino column, the mixed sorbent were compared, and the effect of the mixed sorbent was the best. The optimal analytical conditions were follow as: an methanol-acetonitrile-water (50: 5:45, v/v) containing 0. 1 mmol/L acetic-acetate buffer (pH 3. 80) as the mobile phase, detection at 210 nm. The method had a good linear relationship in the range of 0. 40 - 8. 00 mg/kg for captan and folpet (r > 0. 999 9). The detection limits of captan and folpet were 0. 27 mg/kg and 0. 20 mg/kg, respectively. The relative standard deviations (RSDs) of retention time were no more than 0. 60%. The average recoveries of captan and folpet from the apples spiked at three levels ranged from 69. 3% - 106% and 101% - 108%, with RSD of 3. 7% - 4. 7% and 1. 3% - 5. 4%, respectively.

  16. [Determination of deoxynivalenol in grain and its products by solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Huang, Juan; Chen, Guosong; Zhang, Xiaoyan; Shen, Chongyu; Lü, Chen; Wu, Bin; Liu, Yan; Chen, Huilan; Ding, Tao

    2012-11-01

    A method was established for the determination of deoxynivalenol (vomitoxin) in grain and its products based on solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was firstly extracted by acetonitrile-water (84:16, v/v). The extract was then cleaned-up by an HLB solid phase extraction cartridge. The separation was carried out on a Phenomenex Kinetex C18 column (100 mm x4. 6 mm, 2.6 microm) with a gradient elution using 0.3% per hundred ammonia solution-acetonitrile as mobile phases. The analysis of deoxynivalenol was performed under electrospray negative ionization mode. The limit of detection (LOD, S/N= 3) and the limit of quantification (LOQ, S/N = 10) were 20 microg/kg and 50 microg/kg, respectively. A good linearity (r > 0.99) was achieved for the target compound over the range of 20-1000 pg/L. The recoveries at the three spiked levels (50, 100, 500 microg/kg) in the blank matrices such as flour, barley, soybean, rice, cornmeal, cassava and wheat, were varied from 75.6% to 111.0% with the relative standard deviations no more than 13. 0%. The method is accurate, efficient, sensitive and practical. The cost of pretreatment is obviously reduced by replacing immunoaffinity columns and Mycosep columns with HLB columns which have the same purification effect. PMID:23451526

  17. [Determination of deoxynivalenol in grain and its products by solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Huang, Juan; Chen, Guosong; Zhang, Xiaoyan; Shen, Chongyu; Lü, Chen; Wu, Bin; Liu, Yan; Chen, Huilan; Ding, Tao

    2012-11-01

    A method was established for the determination of deoxynivalenol (vomitoxin) in grain and its products based on solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The sample was firstly extracted by acetonitrile-water (84:16, v/v). The extract was then cleaned-up by an HLB solid phase extraction cartridge. The separation was carried out on a Phenomenex Kinetex C18 column (100 mm x4. 6 mm, 2.6 microm) with a gradient elution using 0.3% per hundred ammonia solution-acetonitrile as mobile phases. The analysis of deoxynivalenol was performed under electrospray negative ionization mode. The limit of detection (LOD, S/N= 3) and the limit of quantification (LOQ, S/N = 10) were 20 microg/kg and 50 microg/kg, respectively. A good linearity (r > 0.99) was achieved for the target compound over the range of 20-1000 pg/L. The recoveries at the three spiked levels (50, 100, 500 microg/kg) in the blank matrices such as flour, barley, soybean, rice, cornmeal, cassava and wheat, were varied from 75.6% to 111.0% with the relative standard deviations no more than 13. 0%. The method is accurate, efficient, sensitive and practical. The cost of pretreatment is obviously reduced by replacing immunoaffinity columns and Mycosep columns with HLB columns which have the same purification effect.

  18. Chain Mobility in Polymer Systems: On the Borderline between Solid and Melt. 2. Crystal Size Influence in Phase Transition and Sintering of Ultrahigh Molecular Weight Polyethylene via the Mobile Hexagonal Phase.

    PubMed

    Rastogi; Kurelec; Lemstra

    1998-07-28

    Polymorphism is a well-established phenomenon in crystalline materials and is important for pharmaceutical and polymeric materials. In our study concerning the processability of polymers, we came across an unusual observation related to polymorphism induced by pressure. The experimental observation is that polyethylene crystals transform from the stable orthorhombic crystal into a transient hexagonal phase. The occurrence of a transient hexagonal phase is shown to be dependent on the polymer crystal size; smaller crystals transform into the transient hexagonal phase at temperatures and pressures much below the thermodynamic critical point Qo, which is located at P = 3.6 kbar and T = 230 degreesC. The crystal size dependence in the phase transition was investigated by in situ X-ray studies in the unirradiated and irradiated solution-crystallized films. Since the chain mobility is rather high in the hexagonal phase, sintering has been attempted via this transient phase using ultrahigh molecular weight polyethylene (UHMW-PE) as a model system. UHMW-PE is an intractable polymer due to its high molar mass but possesses excellent abrasion resistance properties. For this reason it is used as an inlay in demanding applications such as artificial hip and knee joints. The service life of UHMW-PE in these artificial joints, however, is limited due to the poor processing characteristics notably during sintering, and often a second operation is needed to replace the UHMW-PE interface. Sintering via the transient hexagonal phase could provide a solution for this important problem which concerns an increasing number of people. PMID:9680442

  19. Trellis coding with Continuous Phase Modulation (CPM) for satellite-based land-mobile communications

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This volume of the final report summarizes the results of our studies on the satellite-based mobile communications project. It includes: a detailed analysis, design, and simulations of trellis coded, full/partial response CPM signals with/without interleaving over various Rician fading channels; analysis and simulation of computational cutoff rates for coherent, noncoherent, and differential detection of CPM signals; optimization of the complete transmission system; analysis and simulation of power spectrum of the CPM signals; design and development of a class of Doppler frequency shift estimators; design and development of a symbol timing recovery circuit; and breadboard implementation of the transmission system. Studies prove the suitability of the CPM system for mobile communications.

  20. Direct, preparative enantioselective chromatography of propranolol hydrochloride and thioridazine hydrochloride using carbon dioxide-based mobile phases.

    PubMed

    Geiser, F; Schultz, M; Betz, L; Shaimi, M; Lee, J; Champion, W

    1999-12-31

    In this paper, we describe the direct, preparative enantioselective chromatography of racemic (rac)-propranolol hydrochloride (HCI) and rac-thioridazine.HCl using Chiralpak AD chiral stationary phase and mobile phase systems containing carbon dioxide and methanol without the use of basic or acidic additives. Isolated fractions of propranolol.HCl were positively identified by mass spectrometry, Beilstein flame test, melting point, and chemical analysis to be HCI enantiomers of propranolol-HCl salts exhibited characteristic mass spectra peaks at 36 and 38 mass-to-charge ratio in the expected 3:1 isotopic ratio for the solute that were absent in the mass spectra for the free-base forms. To our knowledge, the direct, preparative enantioselective isolation of HCI enantiomeric salts of rac-propranolol and of rac-thioridazine have not been previously demonstrated and published. PMID:10674944

  1. Direct, preparative enantioselective chromatography of propranolol hydrochloride and thioridazine hydrochloride using carbon dioxide-based mobile phases.

    PubMed

    Geiser, F; Schultz, M; Betz, L; Shaimi, M; Lee, J; Champion, W

    1999-12-31

    In this paper, we describe the direct, preparative enantioselective chromatography of racemic (rac)-propranolol hydrochloride (HCI) and rac-thioridazine.HCl using Chiralpak AD chiral stationary phase and mobile phase systems containing carbon dioxide and methanol without the use of basic or acidic additives. Isolated fractions of propranolol.HCl were positively identified by mass spectrometry, Beilstein flame test, melting point, and chemical analysis to be HCI enantiomers of propranolol-HCl salts exhibited characteristic mass spectra peaks at 36 and 38 mass-to-charge ratio in the expected 3:1 isotopic ratio for the solute that were absent in the mass spectra for the free-base forms. To our knowledge, the direct, preparative enantioselective isolation of HCI enantiomeric salts of rac-propranolol and of rac-thioridazine have not been previously demonstrated and published.

  2. Effects of temperature and mobile-phase composition on retentions in column liquid chromatography. [Hydroxyl-terminated polybutadiene

    SciTech Connect

    Hsu, A.

    1982-08-01

    Binary-additive mobile phase systems were investigated for a more exact control over chromatography. If the mobile phase was nonpolar binary solvents (e.g., n-hexane and dichloromethane), trace amounts of THF and/or ACN could be added to control solute retentions as a function of solvent composition. Temperature also plays an important role in the coverage of modifier molecules on the surface of the adsorbent. Higher efficiencies were obtained at lower temperatures. For chromatographic systems having large extra-column volumes, higher column temperature will also reduce column efficiency. Solvophobic effects and polar-group selectivity control the chromatographic behavior of phenols in reversed-phase liquid chromatography (RPLC). The former effect predominates with the THF system, and the latter with the MeOH system. Substituent groups decrease the hydrophobic effect of phenols in aqueous media. However, owing to steric effects, ortho-substituted phenols usually eluted later. Separation of the phenols was also found with 35% MeOH/H/sub 2/O eluent. Application of window diagrams led to baseline separation with 22% THF/H/sub 2/O. Optimum column temperature was 42/sup 0/C with a Zorbax C8 microbore column. The enthalpy-entropy compensation principle was applied to the retention data observed with reversed-phase systems. Relative retention data were found to provide a more consistent compensation temperature. RPLC was shown to be useful in the separation of high molecular-weight compounds such as hydroxyl-terminated polybutadiene (HTPB). HMDS-treated HTPB eluted without difficulty from silical gel. Sample overload can provide unique separations in GPC. (DLC)

  3. Combined effects of potassium chloride and ethanol as mobile phase modulators on hydrophobic interaction and reversed-phase chromatography of three insulin variants.

    PubMed

    Johansson, Karolina; Frederiksen, Søren S; Degerman, Marcus; Breil, Martin P; Mollerup, Jørgen M; Nilsson, Bernt

    2015-02-13

    The two main chromatographic modes based on hydrophobicity, hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC), are widely used for both analytical and preparative chromatography of proteins in the pharmaceutical industry. Despite the extensive application of these separation methods, and the vast amount of studies performed on HIC and RPC over the decades, the underlying phenomena remain elusive. As part of a systematic study of the influence of mobile phase modulators in hydrophobicity-based chromatography, we have investigated the effects of both KCl and ethanol on the retention of three insulin variants on two HIC adsorbents and two RPC adsorbents. The focus was on the linear adsorption range, separating the modulator effects from the capacity effects, but some complementary experiments at higher load were included to further investigate observed phenomena. The results show that the modulators have the same effect on the two RPC adsorbents in the linear range, indicating that the modulator concentration only affects the activity of the solute in the mobile phase, and not that of the solute-ligand complex, or that of the ligand. Unfortunately, the HIC adsorbents did not show the same behavior. However, the insulin variants displayed a strong tendency toward self-association on both HIC adsorbents; on one in particular. Since this causes peak fronting, the retention is affected, and this could probably explain the lack of congruity. This conclusion was supported by the results from the non-linear range experiments which were indicative of double-layer adsorption on the HIC adsorbents, while the RPC adsorbents gave the anticipated increased tailing at higher load.

  4. Prediction of the zeta potentials and ionic descriptors of a silica hydride stationary phase with mobile phases of different pH and ionic strength.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2015-02-15

    In this study, the zeta potentials of a silica hydride stationary phase (Diamond Hydride™) in the presence of different water-acetonitrile mixtures (from 0-80% (v/v) acetonitrile) of different ionic strengths (from 0-40mM) and pH values (from pH 3.0-7.0) have been investigated. Debye-Hückel theory was applied to explain the effect of changes in the pH and ionic strength of these aqueous media on the negative zeta potential of this stationary phase. The experimental zeta potentials of the Diamond Hydride™ particles as a function of acetonitrile content up to 50% (v/v) correlated (R(2)=0.998) with the predicted zeta potential values based on this established theory, when the values of the dissociation constant of all related species, as well as viscosity, dielectric constant and refractive index of the aqueous medium were taken into consideration. Further, the retention behavior of basic, acidic and neutral analytes was investigated under mobile phase conditions of higher pH and lower ionic strength. Under these conditions, the Diamond Hydride™ stationary phase surface became more negative, as assessed from the increasingly more negative zeta potentials, resulting in the ion exchange characteristics becoming more dominant and the basic analytes showing increasing retention. Ionic descriptors were derived from these chromatographic experiments based on the assumption that linear solvation energy relationships prevail. The results were compared with predicted ionic descriptors based on the different calculated zeta potential values resulting in an overall correlation of R(2)=0.888. These studies provide fundamental insights into the impact on the separation performance of changes in the zeta potential of the Diamond Hydride™ surface with the results relevant to other silica hydride and, potentially, to other types of stationary phase materials. PMID:25622609

  5. Prediction of the zeta potentials and ionic descriptors of a silica hydride stationary phase with mobile phases of different pH and ionic strength.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2015-02-15

    In this study, the zeta potentials of a silica hydride stationary phase (Diamond Hydride™) in the presence of different water-acetonitrile mixtures (from 0-80% (v/v) acetonitrile) of different ionic strengths (from 0-40mM) and pH values (from pH 3.0-7.0) have been investigated. Debye-Hückel theory was applied to explain the effect of changes in the pH and ionic strength of these aqueous media on the negative zeta potential of this stationary phase. The experimental zeta potentials of the Diamond Hydride™ particles as a function of acetonitrile content up to 50% (v/v) correlated (R(2)=0.998) with the predicted zeta potential values based on this established theory, when the values of the dissociation constant of all related species, as well as viscosity, dielectric constant and refractive index of the aqueous medium were taken into consideration. Further, the retention behavior of basic, acidic and neutral analytes was investigated under mobile phase conditions of higher pH and lower ionic strength. Under these conditions, the Diamond Hydride™ stationary phase surface became more negative, as assessed from the increasingly more negative zeta potentials, resulting in the ion exchange characteristics becoming more dominant and the basic analytes showing increasing retention. Ionic descriptors were derived from these chromatographic experiments based on the assumption that linear solvation energy relationships prevail. The results were compared with predicted ionic descriptors based on the different calculated zeta potential values resulting in an overall correlation of R(2)=0.888. These studies provide fundamental insights into the impact on the separation performance of changes in the zeta potential of the Diamond Hydride™ surface with the results relevant to other silica hydride and, potentially, to other types of stationary phase materials.

  6. Direct separation of the enantiomers of oxaliplatin on a cellulose-based chiral stationary phase in hydrophilic interaction liquid chromatography mode.

    PubMed

    Gallinella, Bruno; Bucciarelli, Lucia; Zanitti, Leo; Ferretti, Rosella; Cirilli, Roberto

    2014-04-25

    (R,R)-oxaliplatin is an anticancer enantiopure active pharmaceutical ingredient. Little attention has been devoted to the analysis of its enantiomeric composition. The enantioselective HPLC method reported in the current Pharmacopoeias shows clear disadvantages with regard to the low resolution and long elution times. In this work, it has been proven the applicability of a last generation polysaccharide-based chiral stationary phase (CSP), i.e. the Chiralpak IC-3, in the enantioseparation of oxaliplatin. Experimental results demonstrated the benefits arising from the development of enantioselective hydrophilic interaction liquid chromatography (HILIC) based strategies. A baseline separation with resolution factor of 5.8 was achieved using a 100mm×4.6mm I.D. IC-3 column set at the temperature of 40°C and a mobile phase consisting of acetonitrile-water 100:5 mixture. At a flow rate of 1mLmin(-1) the separation was completed within 8min. The optimized method was proven to be sensitive with LOD and LOQ of the enantiomeric impurity of 0.07 and 0.21μgmL(-1), respectively.

  7. Novel dispersive micro-solid-phase extraction combined with ultrahigh-performance liquid chromatography-high-resolution mass spectrometry to determine morpholine residues in citrus and apples.

    PubMed

    Chen, Dawei; Miao, Hong; Zou, Jianhong; Cao, Pei; Ma, Ning; Zhao, Yunfeng; Wu, Yongning

    2015-01-21

    This paper presents a new analytical method for the determination of morpholine residues in citrus and apples using a novel dispersive micro-solid-phase extraction (DMSPE), followed by ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS). Samples were extracted with 1% formic acid in acetonitrile/water (1:1, v/v) and then cleaned up using the DMSPE procedure. Morpholine from the extract was adsorbed to a polymer cation exchange sorbent and eluted with ammonium hydroxide/acetonitrile (3:97, v/v) through a 1 mL syringe with a 0.22 μm nylon syringe filter. All of the samples were analyzed by UHPLC-HRMS/MS on a Waters Acquity BEH hydrophilic interaction chromatography column using 0.1% formic acid and 4 mM ammonium formate in water/acetonitrile as the mobile phase with gradient elution. The method showed good linearity (R(2) > 0.999) in the range of 1-100 μg/L for the analyte. The limit of detection and limit of quantitation values of morpholine were 2 and 5 μg/kg, respectively. The average recoveries of morpholine from the citrus and apple samples spiked at three different concentrations (5, 20, and 100 μg/kg) were in a range from 78.4 to 102.7%.

  8. Sensitive determination of alkoxyethanols by pre-column derivatization with 1-anthroylnitrile and reversed-phase high-performance liquid chromatography.

    PubMed

    Yoshikawa, Masahiro; Tani, Chisato

    2003-07-11

    A new method for simultaneous determination of alkoxyethanols (2-methoxyethanol, 2-ethoxyethanol, 2-isopropoxyethanol, and 2-butoxyethanol) by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed. The alkoxyethanols and an internal standard (2-phenoxyethanol) were derivatized by treatment with 1-anthroylnitrile to give the anthroyl esters. The esterification was completed in 30 min in the presence of quinuclidine as base catalyst at room temperature. After stopping the reaction, an aliquot of the final solution was injected into the HPLC. The resulting anthroyl esters of the alkoxyethanols and the internal standard were separated on a C18 reversed-phase column with acetonitrile-water-acetic acid (65:35:0.1, v/v) as the mobile phase and detected fluorimetrically at excitation and emission wavelengths of 360 nm and 460 nm, respectively. The detection limits of the derivatives as alkoxyethanols at a signal-to-noise ratio of 3 were in the range of 1-3 pg per injection. The minimal amounts of alkoxyethanols derivatized in the reaction mixture for derivatization to determine the limits of detection were approximately 0.5 ng. This HPLC method was applied to the determination of some of alkoxyethanols in the air of the workplace where the thinner containing alkoxyethanols was used for painting.

  9. Liquid chromatography/tandem mass spectrometric bioanalysis using normal-phase columns with aqueous/organic mobile phases - a novel approach of eliminating evaporation and reconstitution steps in 96-well SPE.

    PubMed

    Naidong, Weng; Shou, Wilson Z; Addison, Thomas; Maleki, Saber; Jiang, Xiangyu

    2002-01-01

    Bioanalytical methods using automated 96-well solid-phase extraction (SPE) and liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS) are widely used in the pharmaceutical industry. SPE methods typically require manual steps of drying of the eluates and reconstituting of the analytes with a suitable injection solvent possessing elution strength weaker than the mobile phase. In this study, we demonstrated a novel approach of eliminating these two steps in 96-well SPE by using normal-phase LC/MS/MS methods with low aqueous/high organic mobile phases, which consisted of 70-95% organic solvent, 5-30% water, and small amount of volatile acid or buffer. While the commonly used SPE elution solvents (i.e. acetonitrile and methanol) have stronger elution strength than a mobile phase on reversed-phase chromatography, they are weaker elution solvents than a mobile phase for normal-phase LC/MS/MS and therefore can be injected directly. Analytical methods for a range of polar pharmaceutical compounds, namely, omeprazole, metoprolol, fexofenadine, pseudoephedrine as well as rifampin and its metabolite 25-desacetyl-rifampin, in biological fluids, were developed and optimized based on the foregoing principles. As a result of the time saving, a batch of 96 samples could be processed in one hour. These bioanalytical LC/MS/MS methods were validated according to "Guidance for Industry - Bioanalytical Method Validation" recommended by the Food and Drug Administration (FDA) of the United States.

  10. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: A thermodynamic interpretation

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C{sub 18}-bonded packing materials: XTerra-C{sub 18}, Gemini-C{sub 18}, Luna-C{sub 18}(2), and Halo-C{sub 18}, using buffered methanol-water mobile phases. The {sub W}{sup S}pH of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention and the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at {sub W}{sup S}pHs that are well above or well below the {sub W}{sup S}pK{sub a} of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound {sub W}{sup S}pK{sub a}) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at {sub W}{sup S}pHs that are close to their {sub W}{sup S}pK{sub a}. They also reveal the role of the buffer capacity on the resulting peak shape. With increasing {sub W}{sup S}pH, the overloaded profiles are first langmuirian (isotherm type I) at low {sub W}{sup S}pHs, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate {sub W}{sup S}pHs, and finally return to a langmuirian shape at high {sub W}{sup S}pHs. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An

  11. Towards the Development of a Mobile Phonopneumogram: Automatic Breath-Phase Classification Using Smartphones.

    PubMed

    Reyes, Bersain A; Reljin, Natasa; Kong, Youngsun; Nam, Yunyoung; Ha, Sangho; Chon, Ki H

    2016-09-01

    Correct labeling of breath phases is useful in the automatic analysis of respiratory sounds, where airflow or volume signals are commonly used as temporal reference. However, such signals are not always available. The development of a smartphone-based respiratory sound analysis system has received increased attention. In this study, we propose an optical approach that takes advantage of a smartphone's camera and provides a chest movement signal useful for classification of the breath phases when simultaneously recording tracheal sounds. Spirometer and smartphone-based signals were acquired from N = 13 healthy volunteers breathing at different frequencies, airflow and volume levels. We found that the smartphone-acquired chest movement signal was highly correlated with reference volume (ρ = 0.960 ± 0.025, mean ± SD). A simple linear regression on the chest signal was used to label the breath phases according to the slope between consecutive onsets. 100% accuracy was found for the classification of the analyzed breath phases. We found that the proposed classification scheme can be used to correctly classify breath phases in more challenging breathing patterns, such as those that include non-breath events like swallowing, talking, and coughing, and alternating or irregular breathing. These results show the feasibility of developing a portable and inexpensive phonopneumogram for the analysis of respiratory sounds based on smartphones.

  12. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-03-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 microL samples of a 50 mM probe solution were injected into C(18)-bonded columns using a series of five buffered mobile phases at (SW)pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C(18)-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C(18)-bonded layer and the bulk phase. PMID:18976999

  13. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-03-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 microL samples of a 50 mM probe solution were injected into C(18)-bonded columns using a series of five buffered mobile phases at (SW)pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C(18)-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C(18)-bonded layer and the bulk phase.

  14. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 {micro}L samples of a 50 mM probe solution were injected into C{sub 18}-bonded columns using a series of five buffered mobile phases at {sub W}{sup S}pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1 g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C{sub 18}-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C{sub 18}-bonded layer and the bulk

  15. Effect of basic and acidic additives on the separation of some basic drug enantiomers on polysaccharide-based chiral columns with acetonitrile as mobile phase.

    PubMed

    Gogaladze, Khatuna; Chankvetadze, Lali; Tsintsadze, Maia; Farkas, Tivadar; Chankvetadze, Bezhan

    2015-03-01

    The separation of enantiomers of 16 basic drugs was studied using polysaccharide-based chiral selectors and acetonitrile as mobile phase with emphasis on the role of basic and acidic additives on the separation and elution order of enantiomers. Out of the studied chiral selectors, amylose phenylcarbamate-based ones more often showed a chiral recognition ability compared to cellulose phenylcarbamate derivatives. An interesting effect was observed with formic acid as additive on enantiomer resolution and enantiomer elution order for some basic drugs. Thus, for instance, the enantioseparation of several β-blockers (atenolol, sotalol, toliprolol) improved not only by the addition of a more conventional basic additive to the mobile phase, but also by the addition of an acidic additive. Moreover, an opposite elution order of enantiomers was observed depending on the nature of the additive (basic or acidic) in the mobile phase.

  16. Prediction of the chromatographic retention of acid-base compounds in pH buffered methanol-water mobile phases in gradient mode by a simplified model.

    PubMed

    Andrés, Axel; Rosés, Martí; Bosch, Elisabeth

    2015-03-13

    Retention of ionizable analytes under gradient elution depends on the pH of the mobile phase, the pKa of the analyte and their evolution along the programmed gradient. In previous work, a model depending on two fitting parameters was recommended because of its very favorable relationship between accuracy and required experimental work. It was developed using acetonitrile as the organic modifier and involves pKa modeling by means of equations that take into account the acidic functional group of the compound (carboxylic acid, protonated amine, etc.). In this work, the two-parameter predicting model is tested and validated using methanol as the organic modifier of the mobile phase and several compounds of higher pharmaceutical relevance and structural complexity as testing analytes. The results have been quite good overall, showing that the predicting model is applicable to a wide variety of acid-base compounds using mobile phases prepared with acetonitrile or methanol.

  17. Chemical systems for improved oil recovery: Phase behavior, oil recovery, and mobility control studies

    SciTech Connect

    Llave, F.; Gall, B.; Gao, H., Scott, L., Cook, I.

    1995-09-01

    Selected surfactant systems containing a series of ethoxylated nonionic surfactants in combination with an anionic surfactant system have been studied to evaluate phase behavior as well as oil recovery potential. These experiments were conducted to evaluate possible improved phase behavior and overall oil recovery potential of mixed surfactant systems over a broad range of conditions. Both polyacrylamide polymers and Xanthan biopolymers were evaluated. Studies were initiated to use a chemical flooding simulation program, UTCHEM, to simulate oil recovery for laboratory and field applications and evaluate its use to simulate oil saturation distributions obtained in CT-monitoring of oil recovery experiments. The phase behavior studies focused on evaluating the effect of anionic-nonionic surfactant proportion on overall phase behavior. Two distinct transition behaviors were observed, depending on the dominant surfactant in the overall system. The first type of transition corresponded to more conventional behavior attributed to nonionic-dominant surfactant systems. This behavior is manifested by an oil-water-surfactant system that inverts from a water-external (highly conducting) microemulsion to an oil-external (nonconducting) one, as a function of temperature. The latter type which inverts in an opposite manner can be attributed to the separation of the anionic-nonionic mixtures into water- and oil-soluble surfactants. Both types of transition behavior can still be used to identify relative proximity to optimal areas. Determining these transition ranges provided more insight on how the behavior of these surfactant mixtures was affected by altering component proportions. Efforts to optimize the chemical system for oil displacement experiments were also undertaken. Phase behavior studies with systems formulated with biopolymer in solution were conducted.

  18. Boric acid as a mobile phase additive for high performance liquid chromatography separation of ribose, arabinose and ribulose.

    PubMed

    De Muynck, Cassandra; Beauprez, Joeri; Soetaert, Wim; Vandamme, Erick J

    2006-01-01

    A new high performance liquid chromatographic (HPLC) method is described for the analysis of ribose, arabinose and ribulose mixtures obtained from (bio)chemical isomerization processes. These processes gain importance since the molecules can be used for the synthesis of antiviral therapeutics. The HPLC method uses boric acid as a mobile phase additive to enhance the separation on an Aminex HPX-87K column. By complexing with boric acid, the carbohydrates become negatively charged, thus elute faster from the column by means of ion exlusion and are separated because the complexation capacity with boric acid differs from one carbohydrate to another. Excellent separation between ribose, ribulose and arabinose was achieved with concentrations between 0.1 and 10 gL(-1) of discrete sugar.

  19. Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2

    NASA Astrophysics Data System (ADS)

    Neupane, M.; Xu, S.-Y.; Sankar, R.; Alidoust, N.; Bian, G.; Liu, Chang; Belopolski, I.; Chang, T.-R.; Jeng, H.-T.; Lin, H.; Bansil, A.; Chou, Fangcheng; Hasan, M. Z.

    2014-03-01

    Experimental identification of three-dimensional (3D) Dirac semimetals in solid state systems is critical for realizing exotic topological phenomena and quantum transport. Using high-resolution angle-resolved photoemission spectroscopy, we performed systematic electronic structure studies on well-known compound Cd3As2. For the first time, we observe a highly linear bulk Dirac cone located at the Brillouin zone center projected onto the (001) surface, which is consistent with a 3D Dirac semimetal phase in Cd3As2. Remarkably, an unusually high Dirac Fermion velocity is seen in samples where the mobility far exceeds 20,000 cm2/V.s suggesting that Cd3As2 can be a promising candidate as a hypercone analog of graphene in many device-applications, which can also incorporate topological quantum phenomena in a large gap setting. This work is primarily supported by U.S. DOE and Princeton University.

  20. Carrier concentration and mobility in two-phase eutectic A/sup III/B/sup V/-Ge(Si) alloys

    SciTech Connect

    Leonov, V.V.

    1988-06-01

    The authors proposes a technique of determining the carrier concentration and mobility in the separate phases of two-phase alloys in which oriented rod-like inclusions have carrier concentrations similar to the host material. The calculations are then used to determine the carrier concentration and mobility in each alloy phase, and to discuss the doping processes and mechanisms of impurity incorporation in two-phase semiconductors. He studied the Hall constant R in two-phase, oriented eutectic alloys of InSb-Ge, InAs-Ge, GaAs-Ge, and GaAs-Si. He established that R depends on the relative orientations of the current flow, magnetic field, and elongated inclusions. Furthermore, the particular impurity concentration in the alloy also has an effect on R.

  1. The Use of Mobile, Electrochemical Sensor Nodes for the Measurement of Personal Exposure to Gas-Phase Air Pollutants

    NASA Astrophysics Data System (ADS)

    Stewart, G.; Popoola, O. A.; Mead, M. I.; McKeating, S. J.; Calleja, M.; Hayes, M.; Baron, R. P.; Saffell, J.; Jones, R.

    2012-12-01

    , and thus also the potential insufficiency at quantifying the risks to health in the surrounding area. Recent campaigns with mobile sensor nodes have included attempts to probe the differences in personal exposure to gas-phase air pollutants at different heights of breathing zone and between different methods of transport.

  2. Gas phase ion chemistry of an ion mobility spectrometry based explosive trace detector elucidated by tandem mass spectrometry.

    PubMed

    Kozole, Joseph; Levine, Lauren A; Tomlinson-Phillips, Jill; Stairs, Jason R

    2015-08-01

    The gas phase ion chemistry for an ion mobility spectrometer (IMS) based explosive detector has been elucidated using tandem mass spectrometry. The IMS system, which is operated with hexachloroethane and isobutyramide reagent gases and an ion shutter type gating scheme, is connected to the atmospheric pressure interface of a triple quadrupole mass spectrometer (MS/MS). Product ion masses, daughter ion masses, and reduced mobility values for a collection of nitro, nitrate, and peroxide explosives measured with the IMS/MS/MS instrument are reported. The mass and mobility data together with targeted isotopic labeling experiments and information about sample composition and reaction environment are leveraged to propose molecular formulas, structures, and ionization pathways for the various product ions. The major product ions are identified as [DNT-H](-) for DNT, [TNT-H](-) for TNT, [RDX+Cl](-) and [RDX+NO2](-) for RDX, [HMX+Cl](-) and [HMX+NO2](-) for HMX, [NO3](-) for EGDN, [NG+Cl](-) and [NG+NO3](-) for NG, [PETN+Cl](-) and [PETN+NO3](-) for PETN, [HNO3+NO3](-) for NH4NO3, [NO2](-) for DMNB, [HMTD-NC3H6O3+H+Cl](-) and [HMTD+H-CH2O-H2O2](+) for HMTD, and [(CH3)3CO2](+) for TATP. In general, the product ions identified for the IMS system studied here are consistent with the product ions reported previously for an ion trap mobility spectrometer (ITMS) based explosive trace detector, which is operated with dichloromethane and ammonia reagent gases and an ion trap type gating scheme. Differences between the explosive trace detectors include the [NG+Cl](-) and [PETN+Cl](-) product ions being major ions in the IMS system compared to minor ions in the ITMS system as well as the major product ion for TATP being [(CH3)3CO2](+) for the IMS system and [(CH3)2CNH2](+) for the ITMS system. PMID:26048817

  3. Gas phase ion chemistry of an ion mobility spectrometry based explosive trace detector elucidated by tandem mass spectrometry.

    PubMed

    Kozole, Joseph; Levine, Lauren A; Tomlinson-Phillips, Jill; Stairs, Jason R

    2015-08-01

    The gas phase ion chemistry for an ion mobility spectrometer (IMS) based explosive detector has been elucidated using tandem mass spectrometry. The IMS system, which is operated with hexachloroethane and isobutyramide reagent gases and an ion shutter type gating scheme, is connected to the atmospheric pressure interface of a triple quadrupole mass spectrometer (MS/MS). Product ion masses, daughter ion masses, and reduced mobility values for a collection of nitro, nitrate, and peroxide explosives measured with the IMS/MS/MS instrument are reported. The mass and mobility data together with targeted isotopic labeling experiments and information about sample composition and reaction environment are leveraged to propose molecular formulas, structures, and ionization pathways for the various product ions. The major product ions are identified as [DNT-H](-) for DNT, [TNT-H](-) for TNT, [RDX+Cl](-) and [RDX+NO2](-) for RDX, [HMX+Cl](-) and [HMX+NO2](-) for HMX, [NO3](-) for EGDN, [NG+Cl](-) and [NG+NO3](-) for NG, [PETN+Cl](-) and [PETN+NO3](-) for PETN, [HNO3+NO3](-) for NH4NO3, [NO2](-) for DMNB, [HMTD-NC3H6O3+H+Cl](-) and [HMTD+H-CH2O-H2O2](+) for HMTD, and [(CH3)3CO2](+) for TATP. In general, the product ions identified for the IMS system studied here are consistent with the product ions reported previously for an ion trap mobility spectrometer (ITMS) based explosive trace detector, which is operated with dichloromethane and ammonia reagent gases and an ion trap type gating scheme. Differences between the explosive trace detectors include the [NG+Cl](-) and [PETN+Cl](-) product ions being major ions in the IMS system compared to minor ions in the ITMS system as well as the major product ion for TATP being [(CH3)3CO2](+) for the IMS system and [(CH3)2CNH2](+) for the ITMS system.

  4. Wireless Roadside Inspection Phase II Tennessee Commercial Mobile Radio Services Pilot Test Final Report

    SciTech Connect

    Franzese, Oscar; Lascurain, Mary Beth; Capps, Gary J; Siekmann, Adam

    2011-05-01

    The Federal Motor Carrier Safety Administration (FMCSA) Wireless Roadside Inspection (WRI) Program is researching the feasibility and value of electronically assessing truck and bus driver and vehicle safety at least 25 times more often than is possible using only roadside physical inspections. The WRI program is evaluating the potential benefits to both the motor carrier industry and to government. These potential benefits include reduction in accidents, fatalities and injuries on our highways and keeping safe and legal drivers and vehicles moving on the highways. WRI Pilot tests were conducted to prototype, test and demonstrate the feasibility and benefits of electronically collecting safety data message sets from in-service commercial vehicles and performing wireless roadside inspections using three different communication methods. This report summarizes the design, conduct and results of the Tennessee CMRS WRI Pilot Test. The purpose of this Pilot test was to demonstrate the implementation of commercial mobile radio services to electronically request and collect safety data message sets from a limited number of commercial vehicles operating in Tennessee. The results of this test have been used in conjunction with the results of the complimentary pilot tests to support an overall assessment of the feasibility and benefits of WRI in enhancing motor carrier safety (reduction in accidents) due to increased compliance (change in motor carrier and driver behavior) caused by conducting frequent safety inspections electronically, at highway speeds, without delay or need to divert into a weigh station

  5. The stereochemical resolution of the enantiomers of aspartame on an immobilized alpha-chymotrypsin HPLC chiral stationary phase: the effect of mobile-phase composition and enzyme activity.

    PubMed

    Jadaud, P; Wainer, I W

    1990-01-01

    The enantioselective and diastereoselective resolutions of the stereoisomers of N alpha-aspartyl-phenylalanine 1-methyl ester (APME) have been accomplished on an HPLC chiral stationary phase based upon alpha-chymotrypsin (the ACHT-CSP) with observed enantioselectivities (alpha 1) for the DL-/LD-enantiomer of as high as 29.17 and for the DD-/LL-enantiomers of as high as 28.97. In addition, the effect on the chromatographic retention of the APME stereoisomers of the activity of the ACHT and the composition of the mobile phase--structure of the anionic component, molarity, and pH--have been studied. The results of this study suggest that the aspartyl moiety and/or the aspartyl-phenylalanine amide linkage play key roles in the observed enantioselectivity; the APME stereoisomers containing L-phenylalanine, i.e., DL- and LL-APME, bind at a different site in the ACHT molecule (the L-Phe site) than the APME stereoisomers containing D-phenylalanine (the D-Phe site); and the observed enantioselectivity is a measure of the difference in the binding affinities at the two sites rather than the consequence of differential affinities at a single site.

  6. Enantioseparation of mandelic acid derivatives by high performance liquid chromatography with substituted β-cyclodextrin as chiral mobile phase additive and evaluation of inclusion complex formation

    PubMed Central

    Tong, Shengqiang; Zhang, Hu; Shen, Mangmang

    2014-01-01

    The enantioseparation of ten mandelic acid derivatives was performed by reverse phase high performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) or sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as chiral mobile phase additives, in which inclusion complex formations between cyclodextrins and enantiomers were evaluated. The effects of various factors such as the composition of mobile phase, concentration of cyclodextrins and column temperature on retention and enantioselectivity were studied. The peak resolutions and retention time of the enantiomers were strongly affected by the pH, the organic modifier and the type of β-cyclodextrin in the mobile phase, while the concentration of buffer solution and temperature had a relatively low effect on resolutions. Enantioseparations were successfully achieved on a Shimpack CLC-ODS column (150×4.6 mm i.d., 5 μm). The mobile phase was a mixture of acetonitrile and 0.10 mol L-1 of phosphate buffer at pH 2.68 containing 20 mmol L-1 of HP-β-CD or SBE-β-CD. Semi-preparative enantioseparation of about 10 mg of α-cyclohexylmandelic acid and α-cyclopentylmandelic acid were established individually. Cyclodextrin-enantiomer complex stoichiometries as well as binding constants were investigated. Results showed that stoichiomertries for all the inclusion complex of cyclodextrin-enantiomers were 1:1. PMID:24893270

  7. Comparison of the performance of non-ionic and anionic surfactants as mobile phase additives in the RPLC analysis of basic drugs.

    PubMed

    Ruiz-Ángel, María J; García-Álvarez-Coque, María C

    2011-03-01

    Surfactants added to the mobile phases in reversed-phase liquid chromatography (RPLC) give rise to a modified stationary phase, due to the adsorption of surfactant monomers. Depending on the surfactant nature (ionic or non-ionic), the coated stationary phase can exhibit a positive net charge, or just change its polarity remaining neutral. Also, micelles in the mobile phase introduce new sites for solute interaction. This affects the chromatographic behavior, especially in the case of basic compounds. Two surfactants of different nature, the non-ionic Brij-35 and the anionic sodium dodecyl sulfate (SDS) added to water or aqueous-organic mixtures, are here compared in the separation of basic compounds (β-blockers and tricyclic antidepressants). The reversible/irreversible adsorption of the monomers of both surfactants on the stationary phase was examined. The changes in the nature of the chromatographic system using different columns and chromatographic conditions were followed based on the changes in retention and peak shape. The study revealed that Brij-35 is suitable for analyzing basic compounds of intermediate polarity, using "green chemistry", since the addition of an organic solvent is not needed and Brij-35 is a biodegradable surfactant. In contrast, RPLC with hydro-organic mixtures or mobile phases containing SDS required high concentrations of organic solvents. PMID:21328695

  8. Tensor-based classification of an auditory mobile BCI without a subject-specific calibration phase

    NASA Astrophysics Data System (ADS)

    Zink, Rob; Hunyadi, Borbála; Van Huffel, Sabine; De Vos, Maarten

    2016-04-01

    Objective. One of the major drawbacks in EEG brain-computer interfaces (BCI) is the need for subject-specific training of the classifier. By removing the need for a supervised calibration phase, new users could potentially explore a BCI faster. In this work we aim to remove this subject-specific calibration phase and allow direct classification. Approach. We explore canonical polyadic decompositions and block term decompositions of the EEG. These methods exploit structure in higher dimensional data arrays called tensors. The BCI tensors are constructed by concatenating ERP templates from other subjects to a target and non-target trial and the inherent structure guides a decomposition that allows accurate classification. We illustrate the new method on data from a three-class auditory oddball paradigm. Main results. The presented approach leads to a fast and intuitive classification with accuracies competitive with a supervised and cross-validated LDA approach. Significance. The described methods are a promising new way of classifying BCI data with a forthright link to the original P300 ERP signal over the conventional and widely used supervised approaches.

  9. Combined column-mobile phase mixture statistical design optimization of high-performance liquid chromatographic analysis of multicomponent systems.

    PubMed

    Breitkreitz, Márcia C; Jardim, Isabel C S F; Bruns, Roy E

    2009-02-27

    A statistical approach for the simultaneous optimization of the mobile and stationary phases used in reversed-phase liquid chromatography is presented. Mixture designs using aqueous mixtures of acetonitrile (ACN), methanol (MeOH) and tetrahydrofuran (THF) organic modifiers were performed simultaneously with column type optimization, according to a split-plot design, to achieve the best separation of compounds in two sample sets: one containing 10 neutral compounds with similar retention factors and another containing 11 pesticides. Combined models were obtained by multiplying a linear model for column type, C8 or C18, by quadratic or special cubic mixture models. Instead of using an objective response function, combined models were built for elementary chromatographic criteria (retention factors, resolution and relative retention) of each solute or pair of solutes and, after their validation, the global separation was accomplished by means of Derringer's desirability functions. For neutral compounds a 37:12:8:43 (v/v/v/v) percentage mixture of ACN:MeOH:THF:H2O with the C18 column and for pesticides a 15:15:70 (v/v/v) ACN:THF:H2O mixture with the C8 column provide excellent resolution of all peaks.

  10. Effect of the mobile phase on antibody-based enantiomer separations of amino acids in high-performance liquid chromatography.

    PubMed

    Hofstetter, Oliver; Lindstrom, Heather; Hofstetter, Heike

    2004-09-17

    The effect of the mobile phase parameters flow rate, temperature, pH and ionic strength, as well as the addition of various organic modifiers on the enantiomer separation of various aromatic alpha-amino acids was investigated using two antibody-based chiral stationary phases that have opposing stereoselectivity. On both columns, a decrease in flow rate or temperature resulted in increased interaction with the retained enantiomer. It was found that the retention factor k2 depends on the affinity between the analyte and the immobilized antibody and is not independent of the flow rate. Optimum separations of all amino acids investigated were obtained at pH 7.4 on both columns. While increased k2 values were obtained at low ionic strength on the anti-D-amino acid antibody column, no such effect was observed on the anti-L-amino acid antibody column. The addition of organic modifiers did not improve separations. In all studies, the unretained enantiomer eluted with the void volume.

  11. Chromatographic behavior of small organic compounds in low-temperature high-performance liquid chromatography using liquid carbon dioxide as the mobile phase.

    PubMed

    Motono, Tomohiro; Nagai, Takashi; Kitagawa, Shinya; Ohtani, Hajime

    2015-07-01

    Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns.

  12. Use of basic mobile phase to improve chromatography and boost sensitivity for quantifying tetrahydrocurcumin in human plasma by LC-MS/MS.

    PubMed

    Tan, Aimin; Wu, Yanxin; Wong, Molly; Licollari, Albert; Bolger, Gordon; Fanaras, John C; Shopp, George; Helson, Lawrence

    2016-08-15

    Tetrahydrocurcumin (THC), a major metabolite of curcumin, is often quantified by LC-MS or LC-MS/MS using acidic mobile phases due to the concern of its instability in a basic medium. However, acidic mobile phases often lead to poor chromatography (e.g. split or double peaks) and reduced detection sensitivity in the commonly used negative ionization mode. To overcome these shortcomings, a basic mobile phase was used for the first time in the LC-MS/MS quantification of THC. In comparison with the acidic mobile phases, a single symmetrical chromatographic peak was obtained and the sensitivity increased by 7-fold or more under the equivalent conditions. The new LC-MS/MS method using the basic mobile phase has been successfully validated for the quantification of THC in human EDTA plasma over the concentration range of 5-2500ng/ml. The within-batch accuracy (% nominal concentration) was between 88.7 and 104.9 and the between-batch accuracy ranged from 96.7 to 108.6. The CVs for within- and between-batch precisions were equal to or less than 5.5% and 9.1%, respectively. No significant matrix interference or matrix effect was observed from normal or lipemic and hemolytic plasma matrices. In addition, the common stabilities with adequate durations were established, including up to 5days of post-preparative stability. Furthermore, when the validated method was applied to a clinical study, the passing rate of ISR samples was 83%, indicating the good reproducibility of the method. The success of the unconventional approach presented in this article demonstrates that a mobile phase could be selected based mainly on its merits to facilitate LC separation and/or MS detection. There is no need for excessive concern about the stability of the compound(s) of interest in the selected mobile phase because the run time of modern LC-MS or LC-MS/MS methods is typically only a few minutes. PMID:27327398

  13. Use of basic mobile phase to improve chromatography and boost sensitivity for quantifying tetrahydrocurcumin in human plasma by LC-MS/MS.

    PubMed

    Tan, Aimin; Wu, Yanxin; Wong, Molly; Licollari, Albert; Bolger, Gordon; Fanaras, John C; Shopp, George; Helson, Lawrence

    2016-08-15

    Tetrahydrocurcumin (THC), a major metabolite of curcumin, is often quantified by LC-MS or LC-MS/MS using acidic mobile phases due to the concern of its instability in a basic medium. However, acidic mobile phases often lead to poor chromatography (e.g. split or double peaks) and reduced detection sensitivity in the commonly used negative ionization mode. To overcome these shortcomings, a basic mobile phase was used for the first time in the LC-MS/MS quantification of THC. In comparison with the acidic mobile phases, a single symmetrical chromatographic peak was obtained and the sensitivity increased by 7-fold or more under the equivalent conditions. The new LC-MS/MS method using the basic mobile phase has been successfully validated for the quantification of THC in human EDTA plasma over the concentration range of 5-2500ng/ml. The within-batch accuracy (% nominal concentration) was between 88.7 and 104.9 and the between-batch accuracy ranged from 96.7 to 108.6. The CVs for within- and between-batch precisions were equal to or less than 5.5% and 9.1%, respectively. No significant matrix interference or matrix effect was observed from normal or lipemic and hemolytic plasma matrices. In addition, the common stabilities with adequate durations were established, including up to 5days of post-preparative stability. Furthermore, when the validated method was applied to a clinical study, the passing rate of ISR samples was 83%, indicating the good reproducibility of the method. The success of the unconventional approach presented in this article demonstrates that a mobile phase could be selected based mainly on its merits to facilitate LC separation and/or MS detection. There is no need for excessive concern about the stability of the compound(s) of interest in the selected mobile phase because the run time of modern LC-MS or LC-MS/MS methods is typically only a few minutes.

  14. Ten- to 15-year results of the Oxford Phase III mobile unicompartmental knee arthroplasty

    PubMed Central

    Lisowski, L. A.; Meijer, L. I.; van den Bekerom, M. P. J.; Pilot, P.; Lisowski, A. E.

    2016-01-01

    Aims The interest in unicompartmental knee arthroplasty (UKA) for medial osteoarthritis has increased rapidly but the long-term follow-up of the Oxford UKAs has yet to be analysed in non-designer centres. We have examined our ten- to 15-year clinical and radiological follow-up data for the Oxford Phase III UKAs. Patients and Methods Between January 1999 and January 2005 a total of 138 consecutive Oxford Phase III arthroplasties were performed by a single surgeon in 129 patients for medial compartment osteoarthritis (71 right and 67 left knees, mean age 72.0 years (47 to 91), mean body mass index 28.2 (20.7 to 52.2)). Both clinical data and radiographs were prospectively recorded and obtained at intervals. Of the 129 patients, 32 patients (32 knees) died, ten patients (12 knees) were not able to take part in the final clinical and radiological assessment due to physical and mental conditions, but via telephone interview it was confirmed that none of these ten patients (12 knees) had a revision of the knee arthroplasty. One patient (two knees) was lost to follow-up. Results The mean follow-up was 11.7 years (10 to 15). A total of 11 knees (8%) were revised. The survival at 15 years with revision for any reason as the endpoint was 90.6% (95% confidence interval (CI) 85.2 to 96.0) and revision related to the prosthesis was 99.3% (95% CI 97.9 to 100). The mean total Knee Society Score was 47 (0 to 80) pre-operatively and 81 (30 to 100) at latest follow-up. The mean Oxford Knee Score was 19 (12 to 40) pre-operatively and 42 (28 to 55) at final follow-up. Radiolucency beneath the tibial component occurred in 22 of 81 prostheses (27.2%) without evidence of loosening. Conclusion This study supports the use of UKA in medial compartment osteoarthritis with excellent long-term functional and radiological outcomes with an excellent 15-year survival rate. Cite this article: Bone Joint J 2016;98-B(10 Suppl B):41–7. PMID:27694515

  15. [Determination of zearalanol and related mycotoxins in pork by solid-phase extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Li, Liping; Fan, Sai; Zhao, Rong; Li, Bing; Liu, Wei; Wu, Guohua

    2013-07-01

    A method was established for the determination of six compounds of zearalanol and related mycotoxins in pork and its products. After hydrolysis of the target compounds in the pork by beta-glucosidase/sulfatase, they were extracted with methanol aqueous solution and further purified by an HLB column. The separation was performed on a BEH C18 column with gradient elution using acetonitrile-water as mobile phases. The analytes were determined by mass spectrometry using electrospray ionization (ESI) in negative scan mode and multiple reaction monitoring (MRM) mode. alpha-Zearalenol-D7 and beta-zearalenol-D7 were used as internal standards. The good linearities (r > 0. 999) were achieved for the six compounds over the range of 1. 0 - 100 microg/L based on the internal standard calibration. The detection limits of the method were 0.03 -0.09 microg/kg. The mean recoveries of the six target compounds spiked at three levels from 1. 0 - 10. 0 microg/kg ranged from 76. 7% to 100. 5% with the relative standard deviations (RSDs) less than 20%. The proposed method is simple, sensitive, reproducible, and complies with the regulations for the determination of trace contaminant residues in food matrice. PMID:24164042

  16. [Determination of zearalanol and related mycotoxins in pork by solid-phase extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Li, Liping; Fan, Sai; Zhao, Rong; Li, Bing; Liu, Wei; Wu, Guohua

    2013-07-01

    A method was established for the determination of six compounds of zearalanol and related mycotoxins in pork and its products. After hydrolysis of the target compounds in the pork by beta-glucosidase/sulfatase, they were extracted with methanol aqueous solution and further purified by an HLB column. The separation was performed on a BEH C18 column with gradient elution using acetonitrile-water as mobile phases. The analytes were determined by mass spectrometry using electrospray ionization (ESI) in negative scan mode and multiple reaction monitoring (MRM) mode. alpha-Zearalenol-D7 and beta-zearalenol-D7 were used as internal standards. The good linearities (r > 0. 999) were achieved for the six compounds over the range of 1. 0 - 100 microg/L based on the internal standard calibration. The detection limits of the method were 0.03 -0.09 microg/kg. The mean recoveries of the six target compounds spiked at three levels from 1. 0 - 10. 0 microg/kg ranged from 76. 7% to 100. 5% with the relative standard deviations (RSDs) less than 20%. The proposed method is simple, sensitive, reproducible, and complies with the regulations for the determination of trace contaminant residues in food matrice.

  17. Sensitive determination of parabens in human urine and serum using methacrylate monoliths and reversed-phase capillary liquid chromatography-mass spectrometry.

    PubMed

    Carrasco-Correa, Enrique Javier; Vela-Soria, Fernando; Ballesteros, Oscar; Ramis-Ramos, Guillermo; Herrero-Martínez, José Manuel

    2015-01-30

    A method for the determination of parabens in human urine and serum by capillary liquid chromatography (cLC) with UV-Vis and mass spectrometry (MS) detection using methacrylate ester-based monolithic columns has been developed. The influence of composition of polymerization mixture was studied. The optimum monolith was obtained with butyl methacrylate monomer at 60/40% (wt/wt) butyl methacrylate/ethylene dimethacrylate ratio and 50wt% porogens (composed of 36wt% of 1,4-butanediol, 54wt% 1-propanol and 10wt% water). Baseline resolution of analytes was achieved through a mobile phase of acetonitrile/water in gradient elution mode. Additionally, dispersive liquid-liquid microextraction (DLLME) was combined with both cLC-UV-Vis and cLC-MS to achieve the determination of parabens in human urine and serum samples with very low limits of detection. Satisfactory intra- and inter-day repeatabilities were obtained in UV-Vis and MS detection, although the latter provided lower detection limits (up to 300-fold) than the UV-Vis detection. Recoveries for the target analytes from spiked biological samples ranged from 95.2% to 106.7%. The proposed methodology for the ultra-low determination of parabens in human urine and serum samples is simple and fast, the consumption of reagents is very low, and very small samples can be analyzed.

  18. Effect of temperature on the chromatographic retention of ionizable compounds. I. Methanol-water mobile phases.

    PubMed

    Castells, Cecilia B; Gagliardi, Leonardo G; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth

    2004-07-01

    The retention mechanism of acids and bases in reversed-phase liquid chromatography (RPLC) has been experimentally studied by examining the temperature dependence of retention, with emphasis on the role of the buffer ionization equilibria in the retention and selectivity. Retention factors of several ionizable compounds in a typical octadecylsilica column and using buffers dissolved in 50% (w/w) methanol as eluents at three temperatures in the range of 25-50 degrees C were measured. Two pairs of buffer solutions were prepared by a close adjusting of their pH at 25 degrees C; differences in their ionization enthalpies determined a different degree of ionization when temperature was raised and, as a consequence, a different shift in the eluent pH. Predictive equations of retention that take into account the temperature effect on both the transfer and the ionization processes are proposed. This study demonstrates the significant role that the selected buffer would have in retention and selectivity in RPLC at temperatures higher than 25 degrees C, particularly for co-eluted solutes. PMID:15296385

  19. Effect of temperature on the chromatographic retention of ionizable compounds. I. Methanol-water mobile phases.

    PubMed

    Castells, Cecilia B; Gagliardi, Leonardo G; Ràfols, Clara; Rosés, Martí; Bosch, Elisabeth

    2004-07-01

    The retention mechanism of acids and bases in reversed-phase liquid chromatography (RPLC) has been experimentally studied by examining the temperature dependence of retention, with emphasis on the role of the buffer ionization equilibria in the retention and selectivity. Retention factors of several ionizable compounds in a typical octadecylsilica column and using buffers dissolved in 50% (w/w) methanol as eluents at three temperatures in the range of 25-50 degrees C were measured. Two pairs of buffer solutions were prepared by a close adjusting of their pH at 25 degrees C; differences in their ionization enthalpies determined a different degree of ionization when temperature was raised and, as a consequence, a different shift in the eluent pH. Predictive equations of retention that take into account the temperature effect on both the transfer and the ionization processes are proposed. This study demonstrates the significant role that the selected buffer would have in retention and selectivity in RPLC at temperatures higher than 25 degrees C, particularly for co-eluted solutes.

  20. Evaluation of new mixed-mode UHPLC stationary phases and the importance of stationary phase choice when using low ionic-strength mobile phase additives.

    PubMed

    Nováková, Lucie; Vlčková, Hana; Petr, Solich

    2012-05-15

    In this study, the selectivity, retention properties, peak shape and loading capacity for bases were practically evaluated using two UHPLC mixed-mode hybrid CSH stationary phases modified by C18 or Phenyl group. The data were compared with the data obtained on other UHPLC hybrid stationary phases (BEH C18, BEH C8, BEH Phenyl and BEH Shield RP18) at both basic and acidic conditions using conventional HPLC buffers (50mM ammonium formate/acetate) as well as low ionic-strength additives such as, e.g. 0.1-0.01% formic/acetic acid and 1mM solution of ammonium formate/acetate, which are widely used in LC-MS applications. Ten pharmaceutically important compounds encompassing acids, bases and neutral were included into the study. Due to properties of CSH sorbent (which possess positively charged surface besides RP group), much improved peak shapes and weaker retention was obtained for bases even at very low concentration of acidic additives. Such conditions are ideally suited for LC-MS analysis of bases, where typical RP chromatographic separation (retention and good selectivity at basic pH) and LS-MS conditions (efficient ionization at acidic pH) are not in agreement. On the other hand, acids were more strongly retained and for some compounds the peak shape was influenced negatively due to ion-exchange mechanism. Further, the behavior of acidic, basic and neutral solutes is discussed using various additives at both basic and acidic pH for all above stated columns. The robustness of retention times after pH change from basic to acidic was also evaluated. The new CSH stationary phases represent an interesting selectivity tool preferably for separation of basic compounds. PMID:22483883

  1. Greening pharmaceutical applications of liquid chromatography through using propylene carbonate-ethanol mixtures instead of acetonitrile as organic modifier in the mobile phases.

    PubMed

    Tache, Florentin; Udrescu, Stefan; Albu, Florin; Micăle, Florina; Medvedovici, Andrei

    2013-03-01

    Substitution of acetonitrile (ACN) as organic modifier in mobile phases for liquid chromatography by mixtures of propylene carbonate (PC) and ethanol (EtOH) may be considered a greener approach for pharmaceutical applications. Such a replacement is achievable without any major compromise in terms of elution order, chromatographic retention, efficiency and peak symmetry. This has been equally demonstrated for reverse phase (RP), ion pair formation (IP) and hydrophilic interaction liquid chromatography (HILIC) separation modes. The impact on the sensitivity induced by the replacement between these organic solvents is discussed for UV-vis and mass spectrometric detection. A comparison between Van Deemter plots obtained under elution conditions based on ACN and PC/EtOH is presented. The alternative elution modes were also compared in terms of thermodynamic parameters, such as standard enthalpy (ΔH⁰) and entropic contributions to the partition between the mobile and the stationary phases, for some model compounds. Van't Hoff plots demonstrated that differences between the thermodynamic parameters are minor when shifting from ACN/water to PC/EtOH/water elution on an octadecyl chemically modified silicagel stationary phase. As long as large volume injection (LVI) of diluents non-miscible with the mobile phase is a recently developed topic having a high potential of greening the sample preparation procedures through elimination of the solvent evaporation stage, this feature was also assessed in the case of ACN replacement by PC/EtOH. PMID:23277155

  2. Applicability of the Remote Mobile Emplacement Package (RMEP) design as a mobility aid for proposed post-84 Mars missions, phase O

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The results of study to determine the applicability of the Remote Mobile Emplacement Package (RMEP) design concept as a mobility aid for the proposed post-'84 Mars missions are presented. The RMEP wheel and mobility subsystem parameters: wheel tire size, weight, stowed volume, and environmental effects; obstacle negotiation; reliability and wear; motor and drive train; and electrical power demand were reviewed. Results indicated that: (1) the basic RMEP wheel design would be satisfactory, with additional attention to heating, side loading, tread wear and ultraviolet radiation protection; (2) motor and drive train power requirements on Mars would be less than on Earth; and (3) the mobility electrical power requirements would be small enough to offer the option of operating the Mars mini rover untethered. Payload power required for certain sampling functions would preclude the use of battery power for these missions. Hazard avoidance and reverse direction maneuvers are discussed. Limited examination of vehicle payload integration and thermal design was made, pending establishment of a baseline vehicle/payload design.

  3. Stability-indicating reversed-phase liquid chromatographic method for simultaneous determination of atorvastatin and ezetimibe from their combination drug products.

    PubMed

    Chaudhari, Bharat G; Patel, Natvarlal M; Shah, Paresh B; Patel, Laxman J; Patel, Vipul P

    2007-01-01

    A simple, precise, and rapid stability-indicating reversed-phase column liquid chromatographic (RP-LC) method has been developed and subsequently validated for simultaneous estimation of atorvastatin (ATV) and ezetimibe (EZE) from their combination drug product. The proposed RP-LC method utilizes a LiChrospher 100 C18, 5 microm, 250 x 4.0 mm id column at ambient temperature; the optimum mobile phase consists of acetonitrile-water-methanol (45 + 40 + 15, v/v/v) with apparent pH adjusted to 4.0 +/- 0.1; mobile phase flow rate of 1.0 mL/min; and UV detection at 250 nm. ATV, EZE, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analyzed by the proposed method. There were no other coeluting, interfering peaks from excipients, impurities, or degradation products due to variable stress conditions, and the method is specific for the estimation of ATV and EZE in the presence of degradation products. The response was linear over the concentration range of 1-80 microg/mL for ATV and EZE. The mean recoveries were 99.27 and 98.5% for ATV and EZE, respectively. The intermediate precision data were obtained under different experimental conditions, and the calculated value of the coefficient of variation was found to be less than the critical value. The proposed method can be useful in the quality control of bulk manufacturing and pharmaceutical dosage forms.

  4. Solvent viscosity mismatch between the solute plug and the mobile phase: Considerations in the applications of two-dimensional HPLC

    SciTech Connect

    Shalliker, R. Andrew; Guiochon, Georges A

    2010-01-01

    Understanding the nature of viscosity contrast induced flow instabilities is an important aspect in the design of two-dimensional HPLC separations. When the viscosity contrast between the sample plug and the mobile phase is sufficiently large, the phenomenon known as viscous fingering can be induced. Viscous fingering is a flow instability phenomenon that occurs at the interface between two fluids with different viscosities. In liquid chromatography, viscous fingering results in the solute band undergoing a change in form as it enters into the chromatography column. Moreover, even in the absence of viscous fingering, band shapes change shape at low viscosity contrasts. These changes can result in a noticeable change in separation performance, with the result depending on whether the solvent pushing the solute plug has a higher or lower viscosity than the solute plug. These viscosity induced changes become more important as the solute injection volume increases and hence understanding the process becomes critical in the implementation of multidimensional HPLC techniques, since in these techniques the sample injection plug into the second dimension is an order of magnitude greater than in one-dimensional HPLC. This review article assesses the current understanding of the viscosity contrast induced processes as they relate to liquid chromatographic separation behaviour.

  5. Detection of cocaine and its metabolites in urine using solid phase extraction-ion mobility spectrometry with alternating least squares.

    PubMed

    Lu, Yao; O'Donnell, Ryan M; Harrington, Peter B

    2009-08-10

    A reliable, alternative screening method for detection of cocaine and its metabolites, benzoylecgonine and cocaethylene in urine is demonstrated using solid phase extraction (SPE) coupled with ion mobility spectrometry (IMS). Data analysis with alternating least squares (ALS) is used to model IMS spectral datasets and separate the reactant ion peak from the product ion peaks. IMS has been used as a screening device for drug and explosive detection for many years. It has the advantages of atmospheric pressure operation, simple sample preparation, portability, fast analysis, and high sensitivity when compared to similar methods. Coupling SPE with IMS decreases the detection limits of drug metabolites in urine while removing salts and other polar compounds that suppress ionization during the measurement. The IMS analysis time in this experiment is 20s, much shorter than traditional chromatographic analysis. The application of ALS further increases the sensitivity and selectivity of this method. The detection limits of benzoylecgonine and cocaethylene are 10 ng/mL and 4 ng/mL, respectively. Commercial adulteration of urine specimens does not influence the ability to detect cocaine metabolites after sampling the urine with SPE. This method provides forensic chemists a viable approach for fast and simple drug screening. PMID:19457629

  6. Simultaneous Determination of Diosmin and Hesperidin in Pharmaceuticals by RPLC using Ionic Liquids as Mobile Phase Modifiers

    PubMed Central

    Szymański, Marcin; Młynarek, Daria; Szymański, Arkadiusz; Matławska, Irena

    2016-01-01

    Diosmin and hesperidin are natural flavonoid glycosides found in various plant materials, mainly in citrus fruits in different concentrations. Diosmin for pharmaceutical use is obtained mainly semi-synthetically from hesperidin. Hesperidin often accompanies diosmin as a natural impurity in different pharmaceutical formulations; therefore, a simple, fast and precise method for the simultaneous assay of diosmin and hesperidin in pharmaceutical formulations has been developed to control their contents. Chromatographic resolution was performed using a column with C-18 packing and the following mobile phase: methanol/water (45:55, v/v) with 0.025% added didecyldimethylammonium lactate, which significantly affects retention, shortening analysis time and having a positive impact on the symmetry of resulting chromatographic peaks. The method shows linearity between 2.5 and 100 μg/mL, high repeatability (0.39 and 0.42% for diosmin and hesperidin, respectively) and accuracy of 96 to 102% for both the assayed compounds. Intraday and interday precision of the new method were less than RSD% 1, 2. The limit of detection of the assayed compounds is 2.5 and 1.2 μg/mL for diosmin and hesperidin, respectively. The method was tested on several pharmaceutical products available in Poland. PMID:27610154

  7. Proton-driven amide bond-cleavage pathways of gas-phase peptide ions lacking mobile protons.

    PubMed

    Bythell, Benjamin J; Suhai, Sándor; Somogyi, Arpád; Paizs, Béla

    2009-10-01

    The mobile proton model (Dongre, A. R., Jones, J. L., Somogyi, A. and Wysocki, V. H. J. Am. Chem. Soc. 1996, 118 , 8365-8374) of peptide fragmentation states that the ionizing protons play a critical role in the gas-phase fragmentation of protonated peptides upon collision-induced dissociation (CID). The model distinguishes two classes of peptide ions, those with or without easily mobilizable protons. For the former class mild excitation leads to proton transfer reactions which populate amide nitrogen protonation sites. This enables facile amide bond cleavage and thus the formation of b and y sequence ions. In contrast, the latter class of peptide ions contains strongly basic functionalities which sequester the ionizing protons, thereby often hindering formation of sequence ions. Here we describe the proton-driven amide bond cleavages necessary to produce b and y ions from peptide ions lacking easily mobilizable protons. We show that this important class of peptide ions fragments by different means from those with easily mobilizable protons. We present three new amide bond cleavage mechanisms which involve salt-bridge, anhydride, and imine enol intermediates, respectively. All three new mechanisms are less energetically demanding than the classical oxazolone b(n)-y(m) pathway. These mechanisms offer an explanation for the formation of b and y ions from peptide ions with sequestered ionizing protons which are routinely fragmented in large-scale proteomics experiments.

  8. Fast detection of methyl tert-butyl ether from water using solid phase microextraction and ion mobility spectrometry.

    PubMed

    Nousiainen, Marjaana; Holopainen, Sanna; Puton, Jaroslaw; Sillanpää, Mika

    2011-05-15

    Methyl tert-butyl ether (MTBE) is commonly used as chemical additive to increase oxygen content and octane rating of reformulated gasoline. Despite its impact on enhancing cleaner combustion of gasoline, MTBE poses a threat to surface and ground water when gasoline is released into the environment. Methods for onsite analysis of MTBE in water samples are also needed. A less common technique for MTBE detection from water is ion mobility spectrometry (IMS). We describe a method for fast sampling and screening of MTBE from water by solid phase microextraction (SPME) and IMS. MTBE is adsorbed from the head space of a sample to the coating of SPME fiber. The interface containing a heated sample chamber, which couples SPME and IMS, was constructed and the SPME fiber was introduced into the sample chamber for thermal desorption and IMS detection of MTBE vapors. The demonstrated SPME-IMS method proved to be a straightforward method for the detection of trace quantities of MTBE from waters including surface and ground water. We determined the relative standard deviation of 8.3% and detection limit of 5 mg L(-1) for MTBE. Because of short sampling, desorption, and detection times, the described configuration of combined SPME and IMS is a feasible method for the detection of hazardous substances from environmental matrices.

  9. Gas-phase microsolvation of ubiquitin: investigation of crown ether complexation sites using ion mobility-mass spectrometry.

    PubMed

    Göth, Melanie; Lermyte, Frederik; Schmitt, Xiao Jakob; Warnke, Stephan; von Helden, Gert; Sobott, Frank; Pagel, Kevin

    2016-10-01

    In this study the gas-phase structure of ubiquitin and its lysine-to-arginine mutants was investigated using ion mobility-mass spectrometry (IM-MS) and electron transfer dissociation-mass spectrometry (ETD-MS). Crown ether molecules were attached to positive charge sites of the proteins and the resulting non-covalent complexes were analysed. Collision induced dissociation (CID) experiments revealed relative energy differences between the wild type and the mutant crown-ether complexes. ETD-MS experiments were performed to identify the crown ether binding sites. Although not all of the binding sites could be revealed, the data confirm that the first crown ether is able to bind to the N-terminus. IM-MS experiments show a more compact structure for specific charge states of wild type ubiquitin when crown ethers are attached. However, data on ubiquitin mutants reveal that only specific lysine residues contribute to the effect of charge microsolvation. A compaction is only observed for one of the investigated mutants, in which the lysine has no proximate interaction partner. On the other hand when the lysine residues are involved in salt bridges, attachment of crown ethers has little effect on the structure. PMID:27494002

  10. A closure-independent Generalized Roe solver for free-surface, two-phase flows over mobile bed

    NASA Astrophysics Data System (ADS)

    Rosatti, Giorgio; Begnudelli, Lorenzo

    2013-12-01

    Several different natural phenomena can be studied in the framework of free-surface, two-phase flows over mobile bed. Mathematically, they can be described by the same set of highly nonlinear, hyperbolic nonconservative PDEs but they differ in the possible algebraic closure relations. These affect significantly the relevant eigenvalues and consequently, all finite-volume numerical methods based on upwind Godunov-type fluxes. In this work the Generalized Roe solver, introduced in [29] for the case of a specific closure, is reformulated in a complete closure-independent way. This gives the solver a quite general applicability to the class of problems previously mentioned. Moreover, the new method maintains all the desirable features shown by the original one: full two-dimensionality and exact well-balanceness. This result is made possible thanks to the development of a novel Multiple Averages (MAs) approach that allows a straightforward determination of the matrices required by the solver. Several tests show the capabilities of the proposed numerical strategy.

  11. Simultaneous Determination of Diosmin and Hesperidin in Pharmaceuticals by RPLC using Ionic Liquids as Mobile Phase Modifiers.

    PubMed

    Szymański, Marcin; Młynarek, Daria; Szymański, Arkadiusz; Matławska, Irena

    2016-01-01

    Diosmin and hesperidin are natural flavonoid glycosides found in various plant materials, mainly in citrus fruits in different concentrations. Diosmin for pharmaceutical use is obtained mainly semi-synthetically from hesperidin. Hesperidin often accompanies diosmin as a natural impurity in different pharmaceutical formulations; therefore, a simple, fast and precise method for the simultaneous assay of diosmin and hesperidin in pharmaceutical formulations has been developed to control their contents. Chromatographic resolution was performed using a column with C-18 packing and the following mobile phase: methanol/water (45:55, v/v) with 0.025% added didecyldimethylammonium lactate, which significantly affects retention, shortening analysis time and having a positive impact on the symmetry of resulting chromatographic peaks. The method shows linearity between 2.5 and 100 μg/mL, high repeatability (0.39 and 0.42% for diosmin and hesperidin, respectively) and accuracy of 96 to 102% for both the assayed compounds. Intraday and interday precision of the new method were less than RSD% 1, 2. The limit of detection of the assayed compounds is 2.5 and 1.2 μg/mL for diosmin and hesperidin, respectively. The method was tested on several pharmaceutical products available in Poland. PMID:27610154

  12. Selection of two reliable parameters to evaluate the impact of the mobile-phase composition on capillary electrochromatography performance with monolithic and particle-packed capillary columns.

    PubMed

    Progent, Frédéric; Augustin, Violaine; Tran, N Thuy; Descroix, Stéphanie; Taverna, Myriam

    2006-02-01

    Different models have been described in the literature to evaluate the total porosity of CEC columns: gravimetric, flow as well as conductivity-based methods. In this study, these models have been compared for two kinds of CEC columns: two mixed-mode silica particle stationary phases and different monolithic columns (acrylate or polystyrene divinylbenzene-based). The total porosities measured from the conductivity-based methods were lower than the total column porosities obtained by gravimetric or flow methods for all the investigated columns while the wide distribution of observed values shows that conductivity-based methods discriminate columns more efficiently with very different properties. We propose a conductivity-based method taking into account the actual length proposed by Horvath, to evaluate what we call an "actual electrokinetic" porosity (AEP). This parameter, based on electrokinetic theory only, affords the most consistent evaluation of porosity under experimental CEC conditions for the packed- and acrylate-based monolithic columns. To illustrate the potential of AEP and actual EOF for the estimation of the performances of a CEC system (stationary and mobile phases) we studied the influence of the mobile-phase composition on these parameters for CEC separations with an ammonium embedded packed stationary phase. The AEP and the actual electroosmotic mobility should allow a better understanding of the perfusive EOF and stationary-phase wettability. For neutral compounds (substituted phenols), AEP evaluation allowed us to predict the mobile-phase conditions able to enhance the efficiency while both AEP and actual EOF had to be considered in the case of peptide analysis.

  13. Study of the electroosmotic flow as a means to propel the mobile phase in capillary electrochromatography in view of further miniaturization of capillary electrochromatography systems.

    PubMed

    Szekely, Laszlo; Freitag, Ruth

    2005-05-01

    In this paper, we investigate the phenomenon of electroosmosis as a means to propel a mobile phase, in particular in view of an application in microfluidic systems, which are characterized by significantly smaller volumes of the reservoirs and the separation channels compared to conventional instrumentation. In the microfluidic chip, pH changes due to water electrolysis quickly showed an effect on the electroosmotic flow (EOF), which could be counteracted by either regularly exchanging or buffering the mobile phase. Surface treatment was of no effect in regard to EOF stabilization in empty channels but may have an influence in channels filled with a charged monolith. In fused-silica capillaries the EOF was generally found to decrease from 'naked' to surface-treated to monolith-filled capillaries. The EOF tended to be higher when an organic solvent (acetonitrile) was added to the mobile phase and could be further increased by substituting the water with equal amounts of methanol. In addition, the hydrostatic pressure exerted by the EOF was investigated. In a microfluidic chip with empty (cross-)channels such an effect could be responsible for a redirection of the flow. In capillaries partially filled with a noncharged (non-EOF-generating) monolith, a linear relationship could be established between the EOF created in the empty section of the capillary (apparent mobility) and the length of the monolith (backpressure). In capillaries partially filled with a charged (EOF-producing) monolith, flow inhomogeneities must be expected as a consequence of a superimposition of hydrodynamic pressure and EOF as mobile phase driving force.

  14. [Preparation and chromatographic performance of a eugenol-bonded silica gel stationary phase for high performance liquid chromatography].

    PubMed

    Xu, Lili; Zhong, Minghua; Chen, Xiaojing

    2015-05-01

    A eugenol-bonded silica gel stationary phase (EGSP) for high performance liquid chromatography ( HPLC) has been synthesized by the solid-liquid successive reaction method. The preparation process included two steps: firstly, γ-glycidoxypropyltrimethoxy-silane (KH-560) was covalently attached to the surface of spherical silica gel. Then the bonded silica gel continued to react with eugenol ligand, which was a plant active component, and obtained EGSP. The structure of EGSP was characterized by elemental analysis, thermogravimetric analysis and Fourier transform infrared spectroscopy. Using naphthalene as a probe, the column efficiency was tested under the mobile phase of acetonitrile-water (35:65, v/v) at a flow rate of 0.8 mL/min. The chromatographic properties and the retention mechanism of EGSP were evaluated by using neutral, basic and acidic analytes as solute probes. Meanwhile, the comparative study with C18 column and phenyl column was also carried out under the same chromatographic conditions. The result showed that the eugenol ligand was successfully bonded to the surface of silica gel with a 0.28 mmol/g of bonded amount, and the theoretical plate number of EGSP column was about 24 707 N/m. The EGSP appeared to be a kind of excellent reversed-phase stationary phase with suitable hydrophobicity and various synergistic sites. The eugenol ligand bonded on silica gel could first provide π-π interaction sites for different analytes because of its benzene ring and alkenyl. In addition, the methoxy groups of eugenol were responsible for dipole-dipole and hydrogen-bonding interactions between the ligand and solutes in the effective separation process. Comparing with traditional C18 column and phenyl column, EGSP has an advantage in the fast separation of polar compounds under simple experimental conditions. PMID:26387202

  15. [Preparation and chromatographic performance of a eugenol-bonded silica gel stationary phase for high performance liquid chromatography].

    PubMed

    Xu, Lili; Zhong, Minghua; Chen, Xiaojing

    2015-05-01

    A eugenol-bonded silica gel stationary phase (EGSP) for high performance liquid chromatography ( HPLC) has been synthesized by the solid-liquid successive reaction method. The preparation process included two steps: firstly, γ-glycidoxypropyltrimethoxy-silane (KH-560) was covalently attached to the surface of spherical silica gel. Then the bonded silica gel continued to react with eugenol ligand, which was a plant active component, and obtained EGSP. The structure of EGSP was characterized by elemental analysis, thermogravimetric analysis and Fourier transform infrared spectroscopy. Using naphthalene as a probe, the column efficiency was tested under the mobile phase of acetonitrile-water (35:65, v/v) at a flow rate of 0.8 mL/min. The chromatographic properties and the retention mechanism of EGSP were evaluated by using neutral, basic and acidic analytes as solute probes. Meanwhile, the comparative study with C18 column and phenyl column was also carried out under the same chromatographic conditions. The result showed that the eugenol ligand was successfully bonded to the surface of silica gel with a 0.28 mmol/g of bonded amount, and the theoretical plate number of EGSP column was about 24 707 N/m. The EGSP appeared to be a kind of excellent reversed-phase stationary phase with suitable hydrophobicity and various synergistic sites. The eugenol ligand bonded on silica gel could first provide π-π interaction sites for different analytes because of its benzene ring and alkenyl. In addition, the methoxy groups of eugenol were responsible for dipole-dipole and hydrogen-bonding interactions between the ligand and solutes in the effective separation process. Comparing with traditional C18 column and phenyl column, EGSP has an advantage in the fast separation of polar compounds under simple experimental conditions.

  16. Defect-mediated relaxation in the random tiling phase of a binary mixture: Birth, death and mobility of an atomic zipper

    SciTech Connect

    Tondl, Elisabeth; Ramsay, Malcolm; Harrowell, Peter; Widmer-Cooper, Asaph

    2014-03-14

    This paper describes the mechanism of defect-mediated relaxation in a dodecagonal square-triangle random tiling phase exhibited by a simulated binary mixture of soft discs in 2D. We examine the internal transitions within the elementary mobile defect (christened the “zipper”) that allow it to move, as well as the mechanisms by which the zipper is created and annihilated. The structural relaxation of the random tiling phase is quantified and we show that this relaxation is well described by a model based on the distribution of waiting times for each atom to be visited by the diffusing zipper. This system, representing one of the few instances where a well defined mobile defect is capable of structural relaxation, can provide a valuable test case for general theories of relaxation in complex and disordered materials.

  17. Defect-mediated relaxation in the random tiling phase of a binary mixture: Birth, death and mobility of an atomic zipper

    NASA Astrophysics Data System (ADS)

    Tondl, Elisabeth; Ramsay, Malcolm; Harrowell, Peter; Widmer-Cooper, Asaph

    2014-03-01

    This paper describes the mechanism of defect-mediated relaxation in a dodecagonal square-triangle random tiling phase exhibited by a simulated binary mixture of soft discs in 2D. We examine the internal transitions within the elementary mobile defect (christened the "zipper") that allow it to move, as well as the mechanisms by which the zipper is created and annihilated. The structural relaxation of the random tiling phase is quantified and we show that this relaxation is well described by a model based on the distribution of waiting times for each atom to be visited by the diffusing zipper. This system, representing one of the few instances where a well defined mobile defect is capable of structural relaxation, can provide a valuable test case for general theories of relaxation in complex and disordered materials.

  18. [The resolution of racemic sec-phenethyl alcohol on cellulose tribenzoate-based CSP: influence of different alcohols in the mobile phase].

    PubMed

    Wang, L; Lü, S; Gao, P; Li, S

    1999-07-01

    Several primary and secondary alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol) were used as the mobile phase components separately, to investigate their effects on the capacity factor and stereoselectivity of sec-phenethyl alcohol enantiomers on cellulose tribenzoate-based CSP. The chiral recognition mechanism for the enantiomeric aromatic alcohols studied may involve: (1) the aromatic portion of the solute may insert into a chiral cavity of the CSP through a hydrogen bonding interaction between the solute's alcoholic hydrogen and the ester carbonyl group on the CSP; (2) the mobile phase modifiers (various alcohols) compete with the solutes for chiral, as well as achiral, binding sites on the CSP; (3) the structure of the modifier has some effect on stereoselectivity through an alteration of the steric environment of the chiral cavity.

  19. The effect of pressure and mobile phase velocity on the retention properties of small analytes and large biomolecules in ultra-high pressure liquid chromatography.

    PubMed

    Fekete, Szabolcs; Veuthey, Jean-Luc; McCalley, David V; Guillarme, Davy

    2012-12-28

    A possible complication of ultra-high pressure liquid chromatography (UHPLC) is related to the effect of pressure and mobile phase velocity on the retention properties of the analytes. In the present work, numerous model compounds have been selected including small molecules, peptides, and proteins (such as monoclonal antibodies). Two instrumental setups were considered to attain elevated pressure drops, firstly the use of a post-column restrictor capillary at low mobile phase flow rate (pure effect of pressure) and secondly the increase of mobile phase flow rate without restrictor (i.e. a combined effect of pressure and frictional heating). In both conditions, the goal was to assess differences in retention behaviour, depending on the type or character of the analyte. An important conclusion is that the effect of pressure and mobile phase velocity on retention varied in proportion with the size of the molecule and in some cases showed very different behaviour. In isocratic mode, the pure effect of pressure (experiments with a post-column restrictor capillary) induces an increase in retention by 25-100% on small molecules (MW<300 g/mol), 150% for peptides (~1.3 kDa), 800% for insulin (~6 kDa) and up to >3000% for myoglobin (~17 kDa) for an increase in pressure from 100 bar up to 1100 bar. The important effect observed for the isocratic elution of proteins is probably related to conformational changes of the protein in addition to the effect of molecular size. Working in gradient elution mode, the pressure related effects on retention were found to be less pronounced but still present (an increase of apparent retention factor between 0.2 and 2.5 was observed).

  20. Pressure, temperature and density drops along supercritical fluid chromatography columns in different thermal environments. III. Mixtures of carbon dioxide and methanol as the mobile phase.

    PubMed

    Poe, Donald P; Veit, Devon; Ranger, Megan; Kaczmarski, Krzysztof; Tarafder, Abhijit; Guiochon, Georges

    2014-01-01

    The pressure, temperature and density drops along SFC columns eluted with a CO2/methanol mobile phase were measured and compared with theoretical values. For columns packed with 3- and 5-μm particles the pressure and temperature drops were measured using a mobile phase of 95% CO2 and 5% methanol at a flow rate of 5mL/min, at temperatures from 20 to 100°C, and outlet pressures from 80 to 300bar. The density drop was calculated based on the temperature and pressure at the column inlet and outlet. The columns were suspended in a circulating air bath, either bare or covered with foam insulation. The experimental measurements were compared to theoretical results obtained by numerical simulation. For the convective air condition at outlet pressures above 100bar the average difference between the experimental and calculated temperature drops and pressure drops were 0.1°C and 0.7% for the bare 3-μm column, respectively, and were 0.6°C and 4.1% for the insulated column. The observed temperature drops for the insulated columns are consistent with those predicted by the Joule-Thomson coefficients for isenthalpic expansion. The dependence of the temperature and the pressure drops on the Joule-Thomson coefficient and kinematic viscosity are described for carbon dioxide mobile phases containing up to 20% methanol.

  1. [Intersection point rule for the retention value with mobile phase composition and boiling point of the homologues and chlorobenzenes in soil leaching column chromatography].

    PubMed

    Xu, F; Liang, X; Lin, B; Su, F

    1999-03-01

    Based on the linear retention equation of the logarithm of the capacity factor (logk') vs. the methanol volume fraction (psi) of aqueous binary mobile phase in soil leaching column chromatography, the intersection point rule for the logk' of homologues and weak polar chlorobenzenes, with psi, as well as with boiling point, has been derived due to existence of the similar interactions among solutes of the same series, stationary phase (soil) and eluent (methanol-water). These rules were testified by experimental data of homologues (n-alkylbenzenes, methylbenzenes) and weak polar chlorobenzenes.

  2. Simultaneous determination of fangchinoline and tetrandrine in Stephania tetrandra S. Moore by using 1-alkyl-3-methylimidazolium-based ionic liquids as the RP-HPLC mobile phase additives.

    PubMed

    Tang, Yan; Sun, Ailing; Liu, Renmin; Zhang, Yongqing

    2013-03-12

    A reversed phase high performance liquid chromatography (RP-HPLC) method for simultaneous determination of fangchinoline (FAN) and tetrandrine (TET) in Stephania tetrandra S. Moore was established by using 1-hexyl-3-methylimidazolium tetrafluoroborate as the mobile phase additives in this paper. Four types of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) were used as additives of the mobile phase to separate FAN and TET by RP-HPLC. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of IL and the pH of the mobile phase, which influenced the chromatographic behaviors of FAN and TET, were investigated in detail. The linearity, sensitivity, accuracy and repeatability of the proposed method were also investigated. The probable mechanism of the separation with ILs as the mobile phase additives was explored and discussed. PMID:23452799

  3. Effect of (+) or (-) camphorsulfonic acid additives to the mobile phase on enantioseparations of some basic drugs on a Chiralcel OD column.

    PubMed

    Bielejewska, A; Duszczyk, K; Zukowski, J

    2005-08-12

    This paper describes the modification of Chiralcel OD column properties by adsorption of (+) or (-) camphorsulfonic acids (CSAs) used as additives to the mobile phase. The effects on retention, selectivity and efficiency, of adsorption of (+) and (-) CSAs on a Chiralcel OD column were examined. Racemic anti-histamines, anti-malarial and anti-fungal drugs, namely doxylamine, miconazole, sulconazole, hydroxyzine, homochlorcyclizine, methoxypheniramine, cyclopentolate and ephedrine were investigated as chiral tested compounds. All the studied drugs have an amino nitrogen atom in their structure. Only the enantioseparation of ephedrine enantiomers with CSAs alone was studied on the Nucleosil stationary phase, and these results were compared with the results obtained on the Chiralcel OD phase. A new dynamically generated stationary phase, with very good enantioseparation ability towards the studied compounds, was obtained by the adsorption of (-) CSA on the Chiralcel OD column. PMID:16078699

  4. A diffuse interface model for two-phase incompressible flows with non-local interactions and non-constant mobility

    NASA Astrophysics Data System (ADS)

    Frigeri, Sergio; Grasselli, Maurizio; Rocca, Elisabetta

    2015-05-01

    We consider a diffuse interface model for incompressible isothermal mixtures of two immiscible fluids with matched constant densities. This model consists of the Navier-Stokes system coupled with a convective non-local Cahn-Hilliard equation with non-constant mobility. We first prove the existence of a global weak solution in the case of non-degenerate mobilities and regular potentials of polynomial growth. Then we extend the result to degenerate mobilities and singular (e.g. logarithmic) potentials. In the latter case we also establish the existence of a global attractor in dimension two. Using a similar technique, we show that there is a global attractor for the convective non-local Cahn-Hilliard equation with degenerate mobility and singular potential in dimension three.

  5. Thermodynamic studies of the solvent effects in chromatography on molecularly imprinted polymers. 3. Nature of the organic mobile phase

    SciTech Connect

    Kim, Hyunjung; Guiochon, Georges A

    2005-04-01

    Experimental isotherm data of the Fmoc-tryptophan (Fmoc-Trp) enantiomers were measured by frontal analysis on a Fmoc-L-Trp imprinted polymer, using different organic mobile phases, in a wide concentration range. The nonlinear regression of the data and the independent calculation of the affinity energy distributions of the two enantiomers allowed the selection of the isotherm model and the determination of the isotherm parameters. The organic solvents studied were acetonitrile (MeCN), methylene chloride, chloroform, and tetrahydrofuran (THF), all in the presence of the same concentration of acetic acid, used as an organic modifier. It was found that the highest overall affinity and enantiomeric selectivity were obtained in MeCN, which is also the solvent used in the polymerization. In the other solvents, the overall affinity decreases with increasing hydrogen-bonding ability of the solvents but not the enantiomer selectivity. In MeCN, three types of adsorption sites coexist for the two enantiomers on the MIP. The highest energy sites for Fmoc-L-Trp in MeCN are inactive in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF, and only two types of sites were identified in these solvents. Increasing the acetic acid concentration from 0.2 to 0.9 M causes a large decrease in the association constant of the highest energy sites in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF but not in MeCN. The overall affinity of Fmoc-L-trp in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF is dominated by adsorption on the lowest energy sites, the most abundant ones. In contrast, in MeCN, the overall affinity of Fmoc-L-Trp is dominated by adsorption on the highest energy sites, the least abundant sites. In CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF, the number of each type of sites increases with decreasing hydrogen-bonding ability of the solvents while the association constant of the corresponding sites does not change significantly.

  6. Liquid phase separation of proteins based on electrophoretic effects in an electrospray setup during sample introduction into a gas-phase electrophoretic mobility molecular analyzer (CE–GEMMA/CE–ES–DMA)

    PubMed Central

    Weiss, Victor U.; Kerul, Lukas; Kallinger, Peter; Szymanski, Wladyslaw W.; Marchetti-Deschmann, Martina; Allmaier, Günter

    2014-01-01

    Nanoparticle characterization is gaining importance in food technology, biotechnology, medicine, and pharmaceutical industry. An instrument to determine particle electrophoretic mobility (EM) diameters in the single-digit to double-digit nanometer range receiving increased attention is the gas-phase electrophoretic mobility molecular analyzer (GEMMA) separating electrophoretically single charged analytes in the gas-phase at ambient pressure. A fused-silica capillary is used for analyte transfer to the gas-phase by means of a nano electrospray (ES) unit. The potential of this capillary to separate analytes electrophoretically in the liquid phase due to different mobilities is, at measurement conditions recommended by the manufacturer, eliminated due to elevated pressure applied for sample introduction. Measurements are carried out upon constant feeding of analytes to the system. Under these conditions, aggregate formation is observed for samples including high amounts of non-volatile components or complex samples. This makes the EM determination of individual species sometimes difficult, if not impossible. With the current study we demonstrate that liquid phase electrophoretic separation of proteins (as exemplary analytes) occurs in the capillary (capillary zone electrophoresis, CE) of the nano ES unit of the GEMMA. This finding was consecutively applied for on-line desalting allowing EM diameter determination of analytes despite a high salt concentration within samples. The present study is to our knowledge the first report on the use of the GEMMA to determine EM diameters of analytes solubilized in the ES incompatible electrolyte solutions by the intended use of electrophoresis (in the liquid phase) during sample delivery. Results demonstrate the proof of concept of such an approach and additionally illustrate the high potential of a future on-line coupling of a capillary electrophoresis to a GEMMA instrument. PMID:25109866

  7. Effects of lipid-analog detergent solubilization on the functionality and lipidic cubic phase mobility of the Torpedo californica nicotinic acetylcholine receptor.

    PubMed

    Padilla-Morales, Luis F; Morales-Pérez, Claudio L; De La Cruz-Rivera, Pamela C; Asmar-Rovira, Guillermo; Báez-Pagán, Carlos A; Quesada, Orestes; Lasalde-Dominicci, José A

    2011-10-01

    Over the past three decades, the Torpedo californica nicotinic acetylcholine receptor (nAChR) has been one of the most extensively studied membrane protein systems. However, the effects of detergent solubilization on nAChR stability and function are poorly understood. The use of lipid-analog detergents for nAChR solubilization has been shown to preserve receptor stability and functionality. The present study used lipid-analog detergents from phospholipid-analog and cholesterol-analog detergent families for solubilization and affinity purification of the receptor and probed nAChR ion channel function using planar lipid bilayers (PLBs) and stability using analytical size exclusion chromatography (A-SEC) in the detergent-solubilized state. We also examined receptor mobility on the lipidic cubic phase (LCP) by measuring the nAChR mobile fraction and diffusion coefficient through fluorescence recovery after photobleaching (FRAP) experiments using lipid-analog and non-lipid-analog detergents. Our results show that it is possible to isolate stable and functional nAChRs using lipid-analog detergents, with characteristic ion channel currents in PLBs and minimal aggregation as observed in A-SEC. Furthermore, fractional mobility and diffusion coefficient values observed in FRAP experiments were similar to the values observed for these parameters in the recently LCP-crystallized β(2)-adrenergic receptor. The overall results show that phospholipid-analog detergents with 16 carbon acyl-chains support nAChR stability, functionality and LCP mobility.

  8. Advantages of the AlGaN spacer in InAlN high-electron-mobility transistors grown using metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yamada, Atsushi; Ishiguro, Tetsuro; Kotani, Junji; Tomabechi, Shuichi; Nakamura, Norikazu; Watanabe, Keiji

    2016-05-01

    We demonstrate the advantages of an AlGaN spacer layer in an InAlN high-electron-mobility transistor (HEMT). We investigated the effects of the growth parameters of the spacer layer on electron mobility in InAlN HEMTs grown by metalorganic vapor phase epitaxy, focusing on the surface roughness of the spacer layer and sharpness of the interface with the GaN channel layer. The electron mobility degraded, as evidenced by the formation of a graded AlGaN layer at the top of the GaN channel layer and the surface roughness of the AlN spacer layer. We believe that the short migration length of aluminum atoms is responsible for the observed degradation. An AlGaN spacer layer was employed to suppress the formation of the graded AlGaN layer and improve surface morphology. A high electron mobility of 1550 cm2 V-1 s-1 and a low sheet resistance of 211 Ω/sq were achieved for an InAlN HEMT with an AlGaN spacer layer.

  9. Practical method development for the separation of monoclonal antibodies and antibody-drug-conjugate species in hydrophobic interaction chromatography, part 1: optimization of the mobile phase.

    PubMed

    Rodriguez-Aller, Marta; Guillarme, Davy; Beck, Alain; Fekete, Szabolcs

    2016-01-25

    The goal of this work is to provide some recommendations for method development in HIC using monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) as model drug candidates. The effects of gradient steepness, mobile phase pH, salt concentration and type, as well as organic modifier were evaluated for tuning selectivity and retention in HIC. Except the nature of the stationary phase, which was not discussed in this study, the most important parameter for modifying selectivity was the gradient steepness. The addition of organic solvent (up to 15% isopropanol) in the mobile phase was also found to be useful for mAbs analysis, since it could provide some changes in elution order, in some cases. On the contrary, isopropanol was not beneficial with ADCs, since the most hydrophobic DAR species (DAR6 and DAR8) cannot be eluted from the stationary phase under these conditions. This study also illustrates the possibility to perform HIC method development using optimization software, such as Drylab. The optimum conditions suggested by the software were tested using therapeutic mAbs and commercial cysteine linked ADC (brentuximab-vedotin) and the average retention time errors between predicted and experimental retention times were ∼ 1%.

  10. The hydrophilicity vs. ion interaction selectivity plot revisited: The effect of mobile phase pH and buffer concentration on hydrophilic interaction liquid chromatography selectivity behavior.

    PubMed

    Iverson, Chad D; Gu, Xinyun; Lucy, Charles A

    2016-08-01

    This work systematically investigates the selectivity changes on many HILIC phases from w(w)pH 3.7-6.8, at 5 and 25mM buffer concentrations. Hydrophilicity (kcytosine/kuracil) vs. ion interaction (kBTMA/kuracil) selectivity plots developed by Ibrahim et al. (J. Chromatogr. A 1260 (2012) 126-131) are used to investigate the effect of mobile phase changes on the selectivity of 18 HILIC columns from various classes. "Selectivity change plots" focus on the change in hydrophilicity and ion interaction that the columns exhibit upon changing mobile phase conditions. In general, the selectivity behavior of most HILIC columns is dominated by silanol activity. Minimal changes in selectivity are observed upon changing pH between w(w)pH 5 and 6.8. However, a reduction in ionic interaction is observed when the buffer concentration is increased at w(w)pH≥5.0 due to ionic shielding. Reduction of the w(w)pH to<5.0 results in decreasing cation exchange activity due to silanol protonation. Under all eluent conditions, the majority of phases show little change in their hydrophilicity.

  11. Understanding the importance of the viscosity contrast between the sample solvent plug and the mobile phase and its potential consequences in two-dimensional high-performance liquid chromatography

    SciTech Connect

    Shalliker, R. Andrew; Guiochon, Georges A

    2009-01-01

    The effect of solvent viscosity mismatch on elution performance in reversed-phase HPLC was studied using moment analysis. Two conditions were tested: (1) the mobile phase viscosity was less than the injection plug viscosity, and (2) the mobile phase viscosity was greater than the injection plug viscosity. Under the first condition, retention time and elution performance decreased as the viscosity contrast between the mobile phase and injection plug increased. The effect on performance was more marked as the injection volume increased. A decrease in performance of 12% for compounds with retention factors up to 2.8 was apparent even when the viscosity contrast was only 0.165 cP. In the second set of conditions, elution performance was actually observed to increase, by as much as 25% for a 40 {micro}L injection, as the viscosity contrast between the mobile phase and the solute plug increased. No change in the retention factor was observed. This behaviour was attributed to the shape of an injection plug as it enters into the column, whereby a low viscosity plug permeates away from the wall when the column contains a higher viscosity mobile phase, and vice a versa for a high viscosity plug entering a low viscosity mobile phase. At no stage was either a band splitting or shoulders observed with viscosity contrasts up to 1.283 cP, as could have been expected.

  12. pH effect on the mechanical performance and phase mobility of thermally processed wheat gluten-based natural polymer materials.

    PubMed

    Zhang, Xiaoqing; Hoobin, Pam; Burgar, Iko; Do, My Dieu

    2006-12-01

    The mechanical properties, phase composition, and molecular motions of thermally processed wheat gluten- (WG-) based natural polymer materials were studied by mechanical testing, dynamic mechanical analysis (DMA), and solid-state NMR spectroscopy. The performance of the materials was mainly determined by the denaturization and cross-linking occurring in the thermal processing and the nature or amount of plasticizers used. The pH effect also played an important role in the materials when water was used as the only plasticizer (WG-w). Alkaline conditions modified the chemical structure of WG, possibly via deamidation; enhanced the thermal cross-linking of WG macromolecules to form a more stable aggregation structure; and promoted intermolecular interactions between water and all components in WG (proteins, starch, and lipid), resulting in a strong adhesion among different components and phases. The saponification of lipid under alkaline conditions also enhanced the hydrophilicity of lipid and the miscibility among lipid, water, and WG components. However, when glycerol was used with water as a plasticizer (WG-wg), the phase mobility and composition of the materials mainly depended on the content of glycerol when the water content was constant. During thermal processing under either acidic or alkaline conditions, glycerol was unlikely to thermally cross-link with WG as suggested previously. The advanced mechanical performance of the WG-wg materials was attributed to the nature of hydrogen-bonding interactions between glycerol and WG components in the materials. This caused the whole material to behave like a strengthened "cross-linked" structure at room temperature due to the low mobility of glycerol. The pH effect on phase mobility and compositions of WG-wg systems was not as significant as that for WG-w materials.

  13. Portable solid phase micro-extraction coupled with ion mobility spectrometry system for on-site analysis of chemical warfare agents and simulants in water samples.

    PubMed

    Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

    2014-01-01

    On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples.

  14. Portable Solid Phase Micro-Extraction Coupled with Ion Mobility Spectrometry System for On-Site Analysis of Chemical Warfare Agents and Simulants in Water Samples

    PubMed Central

    Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

    2014-01-01

    On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples. PMID:25384006

  15. Portable solid phase micro-extraction coupled with ion mobility spectrometry system for on-site analysis of chemical warfare agents and simulants in water samples.

    PubMed

    Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

    2014-01-01

    On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples. PMID:25384006

  16. Electronic structure calculations of mercury mobilization from mineral phases and photocatalytic removal from water and the atmosphere.

    PubMed

    Da Pieve, Fabiana; Stankowski, Martin; Hogan, Conor

    2014-09-15

    Mercury is a hazardous environmental pollutant mobilized from natural sources, and anthropogenically contaminated and disturbed areas. Current methods to assess mobility and environmental impact are mainly based on field measurements, soil monitoring, and kinetic modelling. In order to understand in detail the extent to which different mineral sources can give rise to mercury release it is necessary to investigate the complexity at the microscopic level and the possible degradation/dissolution processes. In this work, we investigated the potential for mobilization of mercury structurally trapped in three relevant minerals occurring in hot spring environments and mining areas, namely, cinnabar (α-HgS), corderoite (α-Hg3S2Cl2), and mercuric chloride (HgCl2). Quantum chemical methods based on density functional theory as well as more sophisticated approaches are used to assess the possibility of a) direct photoreduction and formation of elemental Hg at the surface of the minerals, providing a path for ready release in the environment; and b) reductive dissolution of the minerals in the presence of solutions containing halogens. Furthermore, we study the use of TiO2 as a potential photocatalyst for decontamination of polluted waters (mainly Hg(2+)-containing species) and air (atmospheric Hg(0)). Our results partially explain the observed pathways of Hg mobilization from relevant minerals and the microscopic mechanisms behind photocatalytic removal of Hg-based pollutants. Possible sources of disagreement with observations are discussed and further improvements to our approach are suggested.

  17. Socio-Technical Dimensions of an Outdoor Mobile Learning Environment: A Three-Phase Design-Based Research Investigation

    ERIC Educational Resources Information Center

    Land, Susan M.; Zimmerman, Heather Toomey

    2015-01-01

    This design-based research project examines three iterations of Tree Investigators, a learning environment designed to support science learning outdoors at an arboretum and nature center using mobile devices (iPads). Researchers coded videorecords and artifacts created by children and parents (n = 53) to understand how both social and…

  18. 78 FR 56875 - Tribal Mobility Fund Phase I Auction Rescheduled for December 19, 2013; Notice and Filing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-16

    ... service support through reverse competitive bidding. The USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562, December 28, 2011, established the Mobility Fund as a universal service... program details. On March 29, 2013, the Bureaus released the Auction 902 Comment Public Notice, 78...

  19. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties.

    PubMed

    Stoumpos, Constantinos C; Malliakas, Christos D; Kanatzidis, Mercouri G

    2013-08-01

    A broad organic-inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3(+)) or formamidinium (HC(NH2)2(+)) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1-4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25-1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn(1-x)Pb(x)I3 (5). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as p- or n-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n-type; p

  20. Development and application of a specially designed heating system for temperature-programmed high-performance liquid chromatography using subcritical water as the mobile phase.

    PubMed

    Teutenberg, T; Goetze, H-J; Tuerk, J; Ploeger, J; Kiffmeyer, T K; Schmidt, K G; Kohorst, W gr; Rohe, T; Jansen, H-D; Weber, H

    2006-05-01

    A specially designed heating system for temperature-programmed HPLC was developed based on experimental measurements of eluent temperature inside a stainless steel capillary using a very thin thermocouple. The heating system can be operated at temperatures up to 225 degrees C and consists of a preheating, a column heating and a cooling unit. Fast cycle times after a temperature gradient can be realized by an internal silicone oil bath which cools down the preheating and column heating unit. Long-term thermal stability of a polybutadiene-coated zirconium dioxide column has been evaluated using a tubular oven in which the column was placed. The packing material was stable after 50h of operation at 185 degrees C. A mixture containing four steroids was separated at ambient conditions using a mobile phase of 25% acetonitrile:75% deionized water and a mobile phase of pure deionized water at 185 degrees C using the specially designed heating system and the PBD column. Analysis time could be drastically reduced from 17 min at ambient conditions and a flow rate of 1 mL/min to only 1.2 min at 185 degrees C and a flow rate of 5 mL/min. At these extreme conditions, no thermal mismatch was observed and peaks were not distorted, thus underlining the performance of the developed heating system. Temperature programming was performed by separating cytostatic and antibiotic drugs with a temperature gradient using only water as the mobile phase. In contrast to an isocratic elution of this mixture at room temperature, overall analysis time could be reduced two-fold from 20 to 10 min. PMID:16530210

  1. Fast vaporization solid phase microextraction and ion mobility spectrometry: A new approach for determination of creatinine in biological fluids.

    PubMed

    Jafari, Mostafa; Ebrahimzadeh, Homeira; Banitaba, Mohamma Hossein

    2015-11-01

    In this work a rapid and simple method for creatinine determination in urine and plasma samples based on aqueous derivatization of creatinine and complete vaporization of sample (as low as 10 µL), followed by ion mobility spectrometry analysis has been proposed. The effect of four important parameters (extraction temperature, total volume of solution, desorption temperature and extraction time) on ion mobility signal has been studied. Under the optimized conditions, the quantitative response of ion mobility spectrometry for creatinine was linear in the range of 0-500 mg L(-1) with a detection limit of 0.6 mg L(-1) in urine and 0-250 mg L(-1) with a detection limit of 2.6 mg L(-1) in plasma sample. The limit of quantitation of creatinine was 2.1 mg L(-1) and 8.7 mg L(-1) in urine and plasma samples, respectively. The relative standard deviation of the method was found to be 13%. The method was successfully applied to the analysis of creatinine in biological samples, showing recoveries from 92% to 104% in urine and 101-110% in plasma samples. PMID:26452850

  2. Insights into chiral recognition mechanisms in supercritical fluid chromatography V. Effect of the nature and proportion of alcohol mobile phase modifier with amylose and cellulose tris-(3,5-dimethylphenylcarbamate) stationary phases.

    PubMed

    Khater, Syame; West, Caroline

    2014-12-19

    In enantioselective supercritical fluid chromatography (SFC) with chiral stationary phases (CSP), the elution strength of carbon dioxide is usually modulated by the use of polar organic solvents, also called modifiers. Alcohols like methanol, ethanol and isopropanol are the most commonly used co-solvents. While most applications of chiral SFC are optimized through a process of varying the co-solvent nature and proportion, only a limited number of thorough investigations have been carried out to unravel the effects of the co-solvent on the enantioseparation process. In an attempt to clarify the effect of the mobile phase co-solvent on enantioselective SFC separations, a wide range of compounds (achiral and chiral) were analyzed on an amylosic (Chiralpak AD-H) and a cellulosic (Lux cellulose-1) CSP. The influence of the modifier polarity and steric hindrance must be considered thus several different alcoholic solvents were evaluated: methanol, ethanol, 1-propanol, 2-propanol and 1-butanol, with a proportion of 10% in carbon dioxide. A selected group of racemates was further analyzed with varying proportions of each alcohol ranging from 5 to 25%. Besides, because mixtures of solvents were sometimes reported to produce unexpected results, a 50:50 mixture of methanol and ethanol was also evaluated. Chemometric methods provide some insight into the enantio-separation process and help identifying the differences between the mobile phase conditions.

  3. Chiral separation of cathinone and amphetamine derivatives by HPLC/UV using sulfated ß-cyclodextrin as chiral mobile phase additive.

    PubMed

    Taschwer, Magdalena; Seidl, Yvonne; Mohr, Stefan; Schmid, Martin G

    2014-08-01

    In the last years the identification of new legal and illegal highs has become a huge challenge for the police and prosecution authorities. In an analytical context, only a few analytical methods are available to identify these new substances. Moreover, many of these recreational drugs are chiral and it is supposed that the enantiomers differ in their pharmacological potency. Since nonenantioselective synthesis is easier and cheaper, they are mainly sold as racemic mixtures. The goal of this research work was to develop an inexpensive method for the chiral separation of cathinones and amphetamines. This should help to discover if the substances are sold as racemic mixtures and give further information about their quality as well as their origin. Chiral separation of a set of 6 amphetamine and 25 cathinone derivatives, mainly purchased from various Internet shops, is presented. A LiChrospher 100 RP-18e, 250 x 4 mm, 5 µm served as the stationary phase. The chiral mobile phase consisted of methanol, water, and sulfated ß-cyclodextrin. Measurements were performed under isocratic conditions in reversed phase mode using UV detection. Four model compounds of the two substance classes were used to optimize the mobile phase. Under final conditions (methanol:water 2.5:97.5 + 2% sulfated ß-cyclodextrin) enantiomers of amphetamine and five derivatives were baseline separated within 23 min. In all, 17 cathinones were completely or partially chirally separated. However, as only 3 of 25 cathinones were baseline resolved, the application of this method is limited for cathinone analogs. Additionally, the results were compared with an RP-8e column.

  4. Industrial application of green chromatography--I. Separation and analysis of niacinamide in skincare creams using pure water as the mobile phase.

    PubMed

    Yang, Yu; Strickland, Zackary; Kapalavavi, Brahmam; Marple, Ronita; Gamsky, Chris

    2011-03-15

    In this work, chromatographic separation of niacin and niacinamide using pure water as the sole component in the mobile phase has been investigated. The separation and analysis of niacinamide have been optimized using three columns at different temperatures and various flow rates. Our results clearly demonstrate that separation and analysis of niacinamide from skincare products can be achieved using pure water as the eluent at 60°C on a Waters XTerra MS C18 column, a Waters XBridge C18 column, or at 80°C on a Hamilton PRP-1 column. The separation efficiency, quantification quality, and analysis time of this new method are at least comparable with those of the traditional HPLC methods. Compared with traditional HPLC, the major advantage of this newly developed green chromatography technique is the elimination of organic solvents required in the HPLC mobile phase. In addition, the pure water chromatography separations described in this work can be directly applied in industrial plant settings without further modification of the existing HPLC equipment.

  5. Conformational ordering of biomolecules in the gas phase: nitrogen collision cross sections measured on a prototype high resolution drift tube ion mobility-mass spectrometer.

    PubMed

    May, Jody C; Goodwin, Cody R; Lareau, Nichole M; Leaptrot, Katrina L; Morris, Caleb B; Kurulugama, Ruwan T; Mordehai, Alex; Klein, Christian; Barry, William; Darland, Ed; Overney, Gregor; Imatani, Kenneth; Stafford, George C; Fjeldsted, John C; McLean, John A

    2014-02-18

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid "omni-omic" characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field.

  6. Injury Risk Assessment of Extravehicular Mobility Unit (EMU) Phase VI and Series 4000 Gloves During Extravehicular Activity (EVA) Hand Manipulation Tasks

    NASA Technical Reports Server (NTRS)

    Kilby, Melissa

    2015-01-01

    Functional Extravehicular Mobility Units (EMUs) with high precision gloves are essential for the success of Extravehicular Activity (EVA). Previous research done at NASA has shown that total strength capabilities and performance are reduced when wearing a pressurized EMU. The goal of this project was to characterize the human-space suit glove interaction and assess the risk of injury during common EVA hand manipulation tasks, including pushing, pinching and gripping objects. A custom third generation sensor garment was designed to incorporate a combination of sensors, including force sensitive resistors, strain gauge sensors, and shear force sensors. The combination of sensors was used to measure the forces acting on the finger nails, finger pads, finger tips, as well as the knuckle joints. In addition to measuring the forces, data was collected on the temperature, humidity, skin conductance, and blood perfusion of the hands. Testing compared both the Phase VI and Series 4000 glove against an ungloved condition. The ungloved test was performed wearing the sensor garment only. The project outcomes identified critical landmarks that experienced higher workloads and are more likely to suffer injuries. These critical landmarks varied as a function of space suit glove and task performed. The results showed that less forces were acting on the hands while wearing the Phase VI glove as compared to wearing the Series 4000 glove. Based on our findings, the engineering division can utilize these methods for optimizing the current space suit glove and designing next generation gloves to prevent injuries and optimize hand mobility and comfort.

  7. Relative quantification of multi-components in Panax notoginseng (Sanqi) by high-performance liquid chromatography with mass spectrometry using mobile phase compensation.

    PubMed

    Lai, Chang-jiang-sheng; Tan, Ting; Zeng, Su-ling; Dong, Xin; Liu, E-Hu; Li, Ping

    2015-01-01

    Relative quantification of multi-components in complex mixture is significantly affected by the ionization variance caused by mobile phase composition in high-performance liquid chromatography with electrospray ionization mass spectrometry (HPLC-ESI-MS) analyses. The normalization methods for eliminating the variance are still less investigated. Herein, the mobile-phase compensation (MPC) method was applied to overcome the above problem. The developed method was firstly used for convenient evaluation of the coeluent interference and subsequently applied for relative quantification of the identified multi-components in Panax notoginseng (Sanqi) samples. The good linearity, precision and low limit of quantification of targeted analytes confirmed that the MPC-HPLC-ESI-MS method in gradient elution could achieve the isocratic test results compared with classical HPLC-ESI-MS. The established method was used for relative quantification of the minor Sanqi saponins by their detected peak areas divided by that of ginsenoside Rd. The results demonstrated the potential of the newly developed method for obtaining the normalized data shared in different laboratories.

  8. Ultra high performance supercritical fluid chromatography coupled with tandem mass spectrometry for screening of doping agents. I: Investigation of mobile phase and MS conditions.

    PubMed

    Nováková, Lucie; Grand-Guillaume Perrenoud, Alexandre; Nicoli, Raul; Saugy, Martial; Veuthey, Jean-Luc; Guillarme, Davy

    2015-01-01

    The conditions for the analysis of selected doping substances by UHPSFC-MS/MS were optimized to ensure suitable peak shapes and maximized MS responses. A representative mixture of 31 acidic and basic doping agents was analyzed, in both ESI+ and ESI- modes. The best compromise for all compounds in terms of MS sensitivity and chromatographic performance was obtained when adding 2% water and 10mM ammonium formate in the CO2/MeOH mobile phase. Beside mobile phase, the nature of the make-up solvent added for interfacing UHPSFC with MS was also evaluated. Ethanol was found to be the best candidate as it was able to compensate for the negative effect of 2% water addition in ESI- mode and provided a suitable MS response for all doping agents. Sensitivity of the optimized UHPSFC-MS/MS method was finally assessed and compared to the results obtained in conventional UHPLC-MS/MS. Sensitivity was improved by 5-100-fold in UHPSFC-MS/MS vs. UHPLC-MS/MS for 56% of compounds, while only one compound (bumetanide) offered a significantly higher MS response (4-fold) under UHPLC-MS/MS conditions. In the second paper of this series, the optimal conditions for UHPSFC-MS/MS analysis will be employed to screen >100 doping agents in urine matrix and results will be compared to those obtained by conventional UHPLC-MS/MS.

  9. Direct determination of theophylline in human serum by high-performance liquid chromatography using zwitterionic micellar mobile phase. Comparison with an enzyme multiplied immunoassay technique.

    PubMed

    Habel, D; Guermouche, S; Guermouche, M H

    1993-12-01

    A liquid chromatographic procedure is reported for the direct determination of theophylline in human serum. It includes the use of a micellar zwitterionic mobile phase [10(-3) mol l-1 3-(dimethyldodecylammonio) propanesulfonate (also known as C12 DAPS)-propanol (97 + 3, v/v) and a muBondapak phenyl column. Detection is based on ultraviolet absorption at a wavelength of 273 nm. After dilution with the mobile phase, the serum is injected into the chromatography; no solvent extraction or deproteinization is performed. The linearity of the method described was excellent over the range 0.5-20 mg l-1. The within-run precision was better than 2%, and the recovery of the theophylline approached 98%. Two hundred direct injections of serum samples did not affect the column life. The total analysis time, including chromatography, was approximately 15 min. As little as 0.5 mg l-1 of theophylline could be detected, and the results were in good agreement with those of an enzyme multiplied immunoassay technique.

  10. Characterizing the gas phase ion chemistry of an ion trap mobility spectrometry based explosive trace detector using a tandem mass spectrometer.

    PubMed

    Kozole, Joseph; Tomlinson-Phillips, Jill; Stairs, Jason R; Harper, Jason D; Lukow, Stefan R; Lareau, Richard T; Boudries, Hacene; Lai, Hanh; Brauer, Carolyn S

    2012-09-15

    A commercial-off-the-shelf (COTS) ion trap mobility spectrometry (ITMS) based explosive trace detector (ETD) has been interfaced to a triple quadrupole mass spectrometer (MS/MS) for the purpose of characterizing the gas phase ion chemistry intrinsic to the ITMS instrument. The overall objective of the research is to develop a fundamental understanding of the gas phase ionization processes in the ITMS based ETD to facilitate the advancement of its operational effectiveness as well as guide the development of next generation ETDs. Product ion masses, daughter ion masses, and reduced mobility values measured by the ITMS/MS/MS configuration for a suite of nitro, nitrate, and peroxide containing explosives are reported. Molecular formulas, molecular structures, and ionization pathways for the various product ions are inferred using the mass and mobility data in conjunction with density functional theory. The predominant product ions are identified as follows: [TNT-H](-) for trinitrotoluene (TNT), [RDX+Cl](-) for cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), [NO(3)](-) for ethylene glycol dinitrate (EGDN), [NG+NO(3)](-) for nitroglycerine (NG), [PETN+NO(3)](-) for pentaerythritol tetranitrate (PETN), [HNO(3)+NO(3)](-) for ammonium nitrate (NH(4)NO(3)), [HMTD-NC(3)H(6)O(3)+H+Cl](-) for hexamethylene triperoxide diamine (HMTD), and [(CH(3))(2)CNH(2)](+) for triacetone triperoxide (TATP). The predominant ionization pathways for the formation of the various product ions are determined to include proton abstraction, ion-molecule attachment, autoionization, first-order and multi-order thermolysis, and nucleophilic substitution. The ion trapping scheme in the reaction region of the ITMS instrument is shown to increase predominant ion intensities relative to the secondary ion intensities when compared to non-ion trap operation. PMID:22967626

  11. Enhanced lipid isomer separation in human plasma using reversed-phase UPLC with ion-mobility/high-resolution MS detection[S

    PubMed Central

    Damen, Carola W. N.; Isaac, Giorgis; Langridge, James; Hankemeier, Thomas; Vreeken, Rob J.

    2014-01-01

    An ultraperformance LC (UPLC) method for the separation of different lipid molecular species and lipid isomers using a stationary phase incorporating charged surface hybrid (CSH) technology is described. The resulting enhanced separation possibilities of the method are demonstrated using standards and human plasma extracts. Lipids were extracted from human plasma samples with the Bligh and Dyer method. Separation of lipids was achieved on a 100 × 2.1 mm inner diameter CSH C18 column using gradient elution with aqueous-acetonitrile-isopropanol mobile phases containing 10 mM ammonium formate/0.1% formic acid buffers at a flow rate of 0.4 ml/min. A UPLC run time of 20 min was routinely used, and a shorter method with a 10 min run time is also described. The method shows extremely stable retention times when human plasma extracts and a variety of biofluids or tissues are analyzed [intra-assay relative standard deviation (RSD) <0.385% and <0.451% for 20 and 10 min gradients, respectively (n = 5); interassay RSD <0.673% and <0.763% for 20 and 10 min gradients, respectively (n = 30)]. The UPLC system was coupled to a hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer, equipped with a traveling wave ion-mobility cell. Besides demonstrating the separation for different lipids using the chromatographic method, we demonstrate the use of the ion-mobility MS platform for the structural elucidation of lipids. The method can now be used to elucidate structures of a wide variety of lipids in biological samples of different matrices. PMID:24891331

  12. Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2007-01-01

    The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

  13. [Influences of the mobile phase constitution, salt concentration and pH value on retention characters of proteins on the metal chelate column].

    PubMed

    Li, R; Di, Z M; Chen, G L

    2001-09-01

    The effects of the nature and concentration of salts, pH value and competitive eluent in the mobile phase on the protein retention have been systematically investigated. A mathematical expression describing the protein retention in metal chelate chromatography has been derived. It is proposed that the eluting power of the salt solution can be expressed by the eluent strength exponent epsilon. According to the retention characters of protein under different chromatographic conditions, the interaction between the various metal chelate ligands and proteins is discussed. The protein retention on the metal chelate column is a cooperative interactions of coordination, electrostatic and hydrophobic interaction. For the strong combined metal column with proteins such as IDA-Cu, the coordination is the most important, and the electrostatic interaction is secondary in chromatographic process. However, for the weak combined metal columns with proteins such as IDA-Ni, IDA-Co and IDA-Zn, the electrostatic interaction between the metal chelate ligands and proteins is the chief one, while the coordination is the next in importance. When the mobile phase contains high concentration of salt which can't form complex with the immobilized metal, the hydrophobic interaction between the protein and stationary phase will be increased. As the interaction between the metal chelate ligand and proteins relates to chromatographic operating conditions closely, different elution processes may be selected for different metal chelate columns. The gradient elution is generally performed by the low concentration of salt or different pH for weakly combined columns with proteins, however the competitive elution procedure is commonly utilized for strongly combined column. The experiment showed that NH3 is an excellent competitive eluent. It isn't only give the efficient separation of proteins, but also has the advantages of cheapness, less bleeding of the immobilized metals and ease of controlling NH3

  14. Analysis of a common cold virus and its subviral particles by gas-phase electrophoretic mobility molecular analysis and native mass spectrometry.

    PubMed

    Weiss, Victor U; Bereszcazk, Jessica Z; Havlik, Marlene; Kallinger, Peter; Gösler, Irene; Kumar, Mohit; Blaas, Dieter; Marchetti-Deschmann, Martina; Heck, Albert J R; Szymanski, Wladyslaw W; Allmaier, Günter

    2015-09-01

    Gas-phase electrophoretic mobility molecular analysis (GEMMA) separates nanometer-sized, single-charged particles according to their electrophoretic mobility (EM) diameter after transition to the gas-phase via a nano electrospray process. Electrospraying as a soft desorption/ionization technique preserves noncovalent biospecific interactions. GEMMA is therefore well suited for the analysis of intact viruses and subviral particles targeting questions related to particle size, bioaffinity, and purity of preparations. By correlating the EM diameter to the molecular mass (Mr) of standards, the Mr of analytes can be determined. Here, we demonstrate (i) the use of GEMMA in purity assessment of a preparation of a common cold virus (human rhinovirus serotype 2, HRV-A2) and (ii) the analysis of subviral HRV-A2 particles derived from such a preparation. (iii) Likewise, native mass spectrometry was employed to obtain spectra of intact HRV-A2 virions and empty viral capsids (B-particles). Charge state resolution for the latter allowed its Mr determination. (iv) Cumulatively, the data measured and published earlier were used to establish a correlation between the Mr and EM diameter for a range of globular proteins and the intact virions. Although a good correlation resulted from this analysis, we noticed a discrepancy especially for the empty and subviral particles. This demonstrates the influence of genome encapsulation (preventing analytes from shrinking upon transition into the gas-phase) on the measured analyte EM diameter. To conclude, GEMMA is useful for the determination of the Mr of intact viruses but needs to be employed with caution when subviral particles or even empty viral capsids are targeted. The latter could be analyzed by native MS.

  15. CsSnI3: Semiconductor or metal? High electrical conductivity and strong near-infrared photoluminescence from a single material. High hole mobility and phase-transitions.

    PubMed

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D; Li, Hao; Freeman, Arthur J; Kenney, John T; Kanatzidis, Mercouri G

    2012-05-23

    CsSnI(3) is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI(3) have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI(3), coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI(3). The black orthorhombic form of CsSnI(3) demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI(3) indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of ∼ 10(17) cm(-3) and a hole mobility of ∼585 cm(2) V(-1) s(-1). The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise

  16. CsSnI3: Semiconductor or metal? High electrical conductivity and strong near-infrared photoluminescence from a single material. High hole mobility and phase-transitions.

    PubMed

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D; Li, Hao; Freeman, Arthur J; Kenney, John T; Kanatzidis, Mercouri G

    2012-05-23

    CsSnI(3) is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI(3) have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI(3), coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI(3). The black orthorhombic form of CsSnI(3) demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI(3) indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of ∼ 10(17) cm(-3) and a hole mobility of ∼585 cm(2) V(-1) s(-1). The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise

  17. Development of an achiral supercritical fluid chromatography method with ultraviolet absorbance and mass spectrometric detection for impurity profiling of drug candidates. Part I: Optimization of mobile phase composition.

    PubMed

    Lemasson, Elise; Bertin, Sophie; Hennig, Philippe; Boiteux, Hélène; Lesellier, Eric; West, Caroline

    2015-08-21

    Supercritical fluid chromatography (SFC) is a very useful tool in the purpose of impurity profiling of drug candidates, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. The purpose of the present work is to develop a method for chemical purity assessment. The first part, presented here, focuses on mobile phase selection to ensure adequate elution and detection of drug-like molecules, while the second part focuses on stationary phase selection for optimal separation and orthogonality. The use of additives in the carbon dioxide - solvent mobile phase in SFC is now commonplace, and enables in particular to increase the number of eluted compounds and to improve peak shapes. The objective of this first part was to test different additives (acids, bases, salts and water) for their chromatographic performance assessed in gradient elution with a diode-array detector, but also for the mass responses obtained with a single-quadrupole mass detector, equipped with an electrospray ionization source (Waters ACQUITY QDa). In this project, we used a selection of one hundred and sixty compounds issued from Servier Research Laboratories to screen a set of columns and additives in SFC with a Waters ACQUITY UPC(2) system. The selected columns were all high-performance columns (1.7-1.8μm with totally porous particles or 2.6-2.7μm with superficially porous particles) with a variety of stationary phase chemistries. Initially, eight additives dissolved in the methanol co-solvent were tested on a UPC(2) ACQUITY UPC(2) HSS C18 SB column. A Derringer desirability function was used to classify the additives according to selected criteria: elution capability, peak shapes, UV baseline drift, and UV and mass responses (signal-to-noise ratios). Following these tests, the two best additives (ammonium acetate and ammonium hydroxide) were tested on a larger number of columns (10) where the two additives appeared

  18. Ion mobility, conductivity, structure, and phase transitions in K0.7M0.3SbF4 compounds with M=Rb, NH4

    NASA Astrophysics Data System (ADS)

    Kavun, V. Ya.; Gerasimenko, A. V.; Uvarov, N. F.; Polyantsev, M. M.; Zemnukhova, L. A.

    2016-09-01

    Ion mobility, phase transitions, structure, and conductivity in the K0.7M0.3SbF4 (M=Rb, NH4) compounds were studied by NMR spectroscopy, DSC, X-ray, and conductivity measurements. The predominant form in the ion motions resulting from the phase transition of high modification was diffusion of fluoride and ammonium ions above 450 K. The high-temperature phases of K0.7M0.3SbF4 (M=Rb, NH4) are superionic, while their conductivity attains the values of ~10-2-10-4 S/cm at 450-500 K. The structures of α- and β-modifications of the K0.7Rb0.3SbF4 are monoclinic (space group P21/m). The main structural units in them are statistically substituting each other K+ and Rb+ cations and complex ∞1[ SbF4]- anions linked into zigzag-like chains by bridge fluorine atoms. The nearest surrounding of each antimony atom contains five fluorine atoms, so that the antimony coordination polyhedron can be described, taking into account the lone electron pair, as a distorted SbF5E octahedron (ψ-octahedron).

  19. Ion mobility, conductivity, structure, and phase transitions in K0.7M0.3SbF4 compounds with M=Rb, NH4

    NASA Astrophysics Data System (ADS)

    Kavun, V. Ya.; Gerasimenko, A. V.; Uvarov, N. F.; Polyantsev, M. M.; Zemnukhova, L. A.

    2016-09-01

    Ion mobility, phase transitions, structure, and conductivity in the K0.7M0.3SbF4 (M=Rb, NH4) compounds were studied by NMR spectroscopy, DSC, X-ray, and conductivity measurements. The predominant form in the ion motions resulting from the phase transition of high modification was diffusion of fluoride and ammonium ions above 450 K. The high-temperature phases of K0.7M0.3SbF4 (M=Rb, NH4) are superionic, while their conductivity attains the values of ~10-2-10-4 S/cm at 450-500 K. The structures of α- and β-modifications of the K0.7Rb0.3SbF4 are monoclinic (space group P21/m). The main structural units in them are statistically substituting each other K+ and Rb+ cations and complex 1[ SbF4 ]- ∞ anions linked into zigzag-like chains by bridge fluorine atoms. The nearest surrounding of each antimony atom contains five fluorine atoms, so that the antimony coordination polyhedron can be described, taking into account the lone electron pair, as a distorted SbF5E octahedron (ψ-octahedron).

  20. On-site quantitation of arsenic in drinking water by disk solid-phase extraction/mobile X-ray fluorescence spectrometry.

    PubMed

    Hagiwara, Kenta; Koike, Yuya; Aizawa, Mamoru; Nakamura, Toshihiro

    2015-11-01

    A rapid and simple method was developed for As determination in drinking water by solid-phase extraction (SPE)/mobile X-ray fluorescence (XRF) spectrometry. A 50 mL aqueous sample was adjusted to pH 3 with dilute hydrochloric acid, and then passed through a Ti and Zr-loaded carbon disk (TiZr-CD) to pre-concentrate the As. The SPE disk was adhered to an acrylic plate with cellophane tape, and then examined by mobile XRF spectrometry. The TiZr-CD adsorbed inorganic As (as As(III) and As(V)) and organic As (as methyl, phenyl and aromatic arsenic compounds) from water. The As calibration curve had good linearity over the range of 0.5-5 μg, and the limit of detection was 0.10 μg (2.0 μgL(-1) in As concentration). The concentrations of As in well water samples were determined using the proposed method were similar to results obtained from atomic absorption spectrometry. The proposed method did not require a power supply or a toxic solution and/or gas in any analytical step, therefore it is suitable for the on-site determination of As in drinking water. PMID:26452891

  1. Energetics and structural characterization of isomers using ion mobility and gas-phase H/D exchange: Learning from lasso peptides.

    PubMed

    Hanozin, Emeline; Morsa, Denis; De Pauw, Edwin

    2015-08-01

    State-of-the-art characterization of proteins using MS namely relies on fragmentation methods that allow exploring featured dissociative reaction pathways. These pathways are often initiated by a series of potentially informative mass-constant conformational changes that are nonetheless frequently overlooked by lack of adequate investigation techniques. In the present study, we propose a methodology to readily address both structural and energetic aspects of stereoisomerization reactions using ion mobility coupled with MS. To this end, a commercial spectrometer was used as a reactor comprising an energy resolved collisional activation step intended at promoting controlled conformational changes and a structural assignment step dedicated to the identification of the generated isomers. This identification relies on ion mobility and other on-line coupled techniques, namely an originally designed gas-phase H/D exchange experiment. We here apply this methodology to characterize the isomerization kinetics of capistruin, a 19-residue long lasso-folded peptide. We expect this approach to bring insights into the physical origin of global dissociation thresholds monitored in MS/MS experiments and to set a promising basis for quantitative investigations of the stability of different molecular folds.

  2. On-site quantitation of arsenic in drinking water by disk solid-phase extraction/mobile X-ray fluorescence spectrometry.

    PubMed

    Hagiwara, Kenta; Koike, Yuya; Aizawa, Mamoru; Nakamura, Toshihiro

    2015-11-01

    A rapid and simple method was developed for As determination in drinking water by solid-phase extraction (SPE)/mobile X-ray fluorescence (XRF) spectrometry. A 50 mL aqueous sample was adjusted to pH 3 with dilute hydrochloric acid, and then passed through a Ti and Zr-loaded carbon disk (TiZr-CD) to pre-concentrate the As. The SPE disk was adhered to an acrylic plate with cellophane tape, and then examined by mobile XRF spectrometry. The TiZr-CD adsorbed inorganic As (as As(III) and As(V)) and organic As (as methyl, phenyl and aromatic arsenic compounds) from water. The As calibration curve had good linearity over the range of 0.5-5 μg, and the limit of detection was 0.10 μg (2.0 μgL(-1) in As concentration). The concentrations of As in well water samples were determined using the proposed method were similar to results obtained from atomic absorption spectrometry. The proposed method did not require a power supply or a toxic solution and/or gas in any analytical step, therefore it is suitable for the on-site determination of As in drinking water.

  3. The origin of halide melt phases in layered intrusions, and their significance to platinum-group element mobility

    NASA Astrophysics Data System (ADS)

    Hanley, J. J.

    2007-12-01

    Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles became increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids, and the partitioning behavior of Cl in fluid-melt systems. Previously unreported, the latest stage volatiles in the layered intrusions were halide melts (slightly hydrous molten salts) of relatively simply composition (NaCl with minor KCl or CaCl2) with salinities in excess of 90 wt% eq. NaCl or CaCl2. These volatiles were trapped at minimum temperatures of 760-800°C, near the eutectic temperature for water-saturated granitic liquid at moderate crustal pressures. Trace element analysis of the salt melt inclusions by laser ablation ICP-MS (ETH Zürich) show that they contain no detectable concentrations of ore and accessory metals. This is in contrast to the earlier, lower salinity volatiles which contain ppm-concentrations of Pt, Pd, As, Bi, Sb as well as abundant S and base metals. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic or felsic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H2O ratios for the parental silicate liquid (> 9 for a granitic residue). Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show

  4. Intelligent mobile sensor system for drum inspection and monitoring: Phase 1. Topical report, October 1, 1992--June 8, 1993

    SciTech Connect

    Not Available

    1993-06-01

    The objective of this project was to develop an operational system for monitoring and inspection activities for waste storage facility operations at several DOE sites. Specifically, the product of this effort is a robotic device with enhanced intelligence and maneuverability capable of conducting routine inspection of stored waste drums. The device is capable of operating in narrow aisles and interpolating the free aisle space between rows of stacked drums. The system has an integrated sensor suite for leak detection, and is interfaced with a site database both for inspection planning and for data correlation, updating, and report generation. The system is capable of departing on an assigned mission, collecting required data, recording which positions of its mission had to be aborted or modified due to environmental constraints, and reporting back when the mission is complete. Successful identification of more than 90% of all drum defects has been demonstrated in a high fidelity waste storage facility mockup. Identified anomalies included rust spots, rust streaks, areas of corrosion, dents, and tilted drums. All drums were positively identified and correlated with the site database. This development effort is separated into three phases of which phase one is now complete. The first phase has demonstrated an integrated system for monitoring and inspection activities for waste storage facility operations. This demonstration system was quickly fielded and evaluated by leveraging technologies developed from previous NASA and DARPA contracts and internal research. The second phase will demonstrate a prototype system appropriate for operational use in an actual storage facility. The prototype provides an integrated design that considers operational requirements, hardware costs, maintenance, safety, and robustness. The final phase will demonstrate commercial viability using the prototype vehicle in a pilot waste operations and inspection project.

  5. Analysis of Phenacylester Derivatives of Fatty Acids from Human Skin Surface Sebum by Reversed-Phase HPLC: Chromatographic Mobility as a Function of Physico-Chemical Properties

    PubMed Central

    Bodoprost, Juliana; Rosemeyer, Helmut

    2007-01-01

    A set of 13 fatty acids was transformed into their phenacyl esters by reaction with phenacyl bromide in acetonitrile using 18-crown-6 as phase-transfer catalyst. Conditions for the RP-18 HPL chromatographic separation of most of the esters has been worked out. Using this standard the fatty acid spectra from skin surface sebum lipids of 17 test persons was taken after microwave-assisted hydrolysis, neutralization and extraction with n-hexane. Quantitative evaluation of the chromatograms exhibits that oleic acid predominates in the sebum of all test persons. In the second part of the work the chromatographic mobility (RE values) of fatty acid phenacyl esters is correlated with calculated physico-chemical parameters of the corresponding acids. The best linear correlation was found between the RE and the logP values. This is helpful for the structural elucidation of un-identified fatty acids in a chromatogram.

  6. Comprehensive Size-Determination of Whole Virus Vaccine Particles Using Gas-Phase Electrophoretic Mobility Macromolecular Analyzer, Atomic Force Microscopy, and Transmission Electron Microscopy

    PubMed Central

    Havlik, Marlene; Marchetti-Deschmann, Martina; Friedbacher, Gernot; Winkler, Wolfgang; Messner, Paul; Perez-Burgos, Laura; Tauer, Christa; Allmaier, Günter

    2015-01-01

    Biophysical properties including particle size distribution, integrity, and shape of whole virus vaccine particles at different stages in tick-borne encephalitis (TBE) vaccines formulation were analyzed by a new set of methods. Size-exclusion chromatography (SEC) was used as a conservative sample preparation for vaccine particle fractionation and gas-phase electrophoretic mobility macromolecular analyzer (GEMMA) for analyzing electrophoretic mobility diameters of isolated TBE virions. The derived particle diameter was then correlated with molecular weight. The diameter of the TBE virions determined after SEC by GEMMA instrumentation was 46.8 ± 1.1 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were implemented for comparison purposes and to gain morphological information on the virion particle. Western blotting (Dot Blot) as an immunological method confirmed biological activity of the particles at various stages of the developed analytical strategy. AFM and TEM measurements revealed higher diameters with much higher SD for a limited number of virions, 60.4 ± 8.5 and 53.5 ± 5.3 nm, respectively. GEMMA instrumentation was also used for fractionation of virions with specifically selected diameters in the gas-phase, which were finally collected by means of an electrostatic sampler. At that point (i.e., after particle collection), AFM and TEM showed that the sampled virions were still intact, exhibiting a narrow size distribution (i.e., 59.8 ± 7.8 nm for AFM and 47.5 ± 5.2 nm for TEM images), and most importantly, dot blotting confirmed immunological activity of the collected samples. Furthermore dimers and virion artifacts were detected, too. PMID:26266988

  7. Dependence of negative-mode electrospray ionization response factors on mobile phase composition and molecular structure for newly-authenticated neutral acylsucrose metabolites.

    PubMed

    Ghosh, Banibrata; Jones, A Daniel

    2015-10-01

    Authentic standards of known concentrations serve as references for accurate absolute quantification of plant metabolites using liquid chromatography/mass spectrometry (LC/MS). However, often such standards are not commercially available or not amenable for custom syntheses. Despite the widespread use of electrospray ionization for metabolite analyses, the fundamentals needed for reliable prediction of molecular response factors have yet to be explored in detail for analytes that lack ionized functional groups. In order to lay a foundation for quantifying unknown neutral plant metabolites in absence of authentic standards, sub-milligram quantities of purified homologous acylsucrose metabolites were authenticated by subjecting each to basic hydrolysis and quantifying the sucrose product using stable-isotope dilution ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with multiple reaction monitoring (MRM). Once authenticated, molar response factors of [M + formate](-) ions for the acylsucrose metabolites were determined at different mobile phase compositions ranging from 40%-80% acetonitrile, and demonstrated relationships of response factors with mobile phase composition and metabolite structural features including nonpolar surface areas, the length of the longest acyl chain, and the number of hydroxyl groups. This approach was employed to calculate predicted response factors for three authenticated acylsucroses based on mean values for all isomers with a common number of total acyl carbon atoms. Absolute UHPLC-MS quantification was performed on these three metabolites in an extract from leaves of the wild tomato Solanum habrochaites LA1777, yielding deviations of 26%, 6.7%, and 7.3% from values established using compound-specific response factors. PMID:26331907

  8. A novel dispersive micro solid phase extraction using PCX as the sorbent for the determination of melamine and cyromazine in milk and milk powder by UHPLC-HRMS/MS.

    PubMed

    Chen, Dawei; Zhao, Yunfeng; Miao, Hong; Wu, Yongning

    2015-03-01

    A novel dispersive micro solid phase extraction (DMSPE) cleanup method based on the PCX sorbent (a kind of cation exchange polymer material) was applied to the analysis of melamine and cyromazine residues in milk and milk powder, and ultra high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) was used as instrument detection. Milk powder samples were first extracted with 1% formic acid in acetonitrile/water (1:1 v/v), and milk samples were cleaned up directly without any pre-extraction. Then, melamine and cyromazine in the extracts or milk were adsorbed to the PCX powder. Subsequently, the analytes in PCX sorbent were eluted with ammonium hydroxide/acetonitrile (2.5:97.5 v/v) through a simple unit device equipped with 1 mL syringe and 0.22 μm nylon syringe filter. All the samples were analyzed by UHPLC-HRMS/MS on a Waters Acquity BEH HILIC column with 0.1% formic acid and 4mM ammonium formate in water/acetonitrile as the mobile phase with gradient elution. The matrix effect, recovery, and repeatability, within laboratory reproducibility, CCα and CCβ of the DMSPE cleanup method were investigated. The proposed method provided a significant improvement for the determination of melamine and cyromazine in milk and milk powder in terms of efficient, rapid, economical, and miniaturized sample preparation methods, which yielded fewer matrix effects compared with SPE method. The established cleanup method is expected to be widely applied for the sample preparation of alkaline contaminants at trace levels in the future. PMID:25618651

  9. A radial differential mobility analyzer for the size-classification of gas-phase synthesized nanoparticles at low pressures

    NASA Astrophysics Data System (ADS)

    Nanda, K. K.; Kruis, F. E.

    2014-07-01

    Differential mobility analyzers (DMAs) are commonly used to generate monodisperse nanoparticle aerosols. Commercial DMAs operate at quasi-atmospheric pressures and are therefore not designed to be vacuum-tight. In certain particle synthesis methods, the use of a vacuum-compatible DMA is a requirement as a process step for producing high-purity metallic particles. A vacuum-tight radial DMA (RDMA) has been developed and tested at low pressures. Its performance has been evaluated by using a commercial NANO-DMA as the reference. The performance of this low-pressure RDMA (LP-RDMA) in terms of the width of its transfer function is found to be comparable with that of other NANO-DMAs at atmospheric pressure and is almost independent of the pressure down to 30 mbar. It is shown that LP-RDMA can be used for the classification of nanometer-sized particles (5-20 nm) under low pressure condition (30 mbar) and has been successfully applied to nanoparticles produced by ablating FeNi at low pressures.

  10. Performance of the Extravehicular Mobility Unit (EMU): Airlock Coolant Loop Recovery (A/L CLR) Hardware - Phase II

    NASA Technical Reports Server (NTRS)

    Steele, John; Rector, tony; Gazda, Daniel; Lewis, John

    2009-01-01

    An EMU water processing kit (Airlock Coolant Loop Recovery A/L CLR) was developed as a corrective action to Extravehicular Mobility Unit (EMU) coolant flow disruptions experienced on the International Space Station (ISS) in May of 2004 and thereafter. Conservative schedules for A/L CLR use and component life were initially developed and implemented based on prior analysis results and analytical modeling. The examination of postflight samples and EMU hardware in November of 2006 indicated that the A/L CLR kits were functioning well and had excess capacity that would allow a relaxation of the initially conservative schedules of use and component life. A relaxed use schedule and list of component lives was implemented thereafter. Since the adoption of the relaxed A/L CLR schedules of use and component lives, several A/L CLR kit components, transport loop water samples and sensitive EMU transport loop components have been examined to gage the impact of the relaxed requirements. The intent of this paper is to summarize the findings of that evaluation, and to outline updated schedules for A/L CLR use and component life.

  11. Supercritical fluid chromatography and two-dimensional supercritical fluid chromatography of polar car lubricant additives with neat CO(2) as mobile phase.

    PubMed

    Lavison, Gwenaelle; Bertoncini, Fabrice; Thiébaut, Didier; Beziau, Jean-François; Carrazé, Bernadette; Valette, Pascale; Duteurtre, Xavier

    2007-08-17

    Car lubricant additives are added to mineral or synthetic base stocks to improve viscosity and resistance to oxidation of the lubricant and to limit wear of engines. Their total amount in the commercial lubricant varies from a few percents to 20-25%. As they belong to various chemical classes and are added to a very complex medium, the base stock, their detailed chromatographic analysis is very difficult and time consuming as it should involve sample treatment and preparative scale separations in order to simplify the sample. The aim of this work is to determine the feasibility of the separation of low molecular weight lubricant additives using various packed columns with pure CO(2) as a mobile phase to enable implementation of flame ionisation detection as universal detector. This is part of a hypernated system including more sophisticated specific detectors, such as AED, FTIR or MS to obtain detailed structural information of compounds. This paper is devoted to the comparison of some stationary phases supposed to provide hydrocarbon group type separation (silica and normal phase) or separations on alkyl-bonded silica in non-aqueous mode of some selected classes of additives in test mixtures or in base stocks. Adsorption chromatography allows partial separation of additives from the base stocks while the direct elution of test additives can only be obtained on reversed phase supports having a very efficient silanol group protection so the interaction of the more polar compounds is much reduced. A two-dimensional scheme of analysis is also described. It combines adsorption chromatography to separate most of the polar additives from the base stock and alkyl-bonded silica for more detailed separation of the additives. However, overlapping between groups of compounds and the lack of resolution between some additives and the base stock should be addressed by the implementing of selective detectors. PMID:17582427

  12. Alterations in oxidant/antioxidant balance, high-mobility group box 1 protein and acute phase response in cross-bred suckling piglets suffering from rotaviral enteritis.

    PubMed

    Kumar De, Ujjwal; Mukherjee, Reena; Nandi, Sukdeb; Patel, Bhimnere Hanumatnagouda Manjunatha; Dimri, Umesh; Ravishankar, Chintu; Verma, Ashok Kumar

    2014-10-01

    Rotaviral enteritis has emerged as a major cause of morbidity and mortality in piglets during their post-natal life. The present study was carried out to examine high-mobility group box 1 (HMGB1) protein, acute phase response and oxidative stress indices in the serum of suckling piglets suffering from enteritis with or without association of porcine group A rotavirus infection. The present investigation utilized 23 clinical cases with signs of acute enteritis and 12 more healthy piglets of a similar age group as control animals. Out of 23 enteritis cases, 12 cases were found to be positive for porcine group A rotavirus infection as confirmed by reverse transcription-polymerase chain reaction (RT-PCR) using specific primers for group A rotavirus, and the rest were found negative. The acute enteritis cases in piglets were associated with an elevated level of HMGB1 protein and serum haptoglobin and ceruloplasmin suggestive of an acute phase response. Among the oxidative stress indices, the concentrations of malondialdehyde (MDA) and nitric oxide (NO) in serum were significantly increased. A pronounced drop of total antioxidant capacity and the activity of antioxidant enzymes such as catalase and superoxide dismutase in the serum of piglets suffering from acute enteritis compared to healthy ones were also noticed. The alterations in HMGB1 protein, acute phase response and oxidative stress indices were more pronounced in cases with the involvement of porcine rotavirus as compared to rotavirus-negative cases. It is concluded that HMGB1 protein, markers of oxidative stress and acute phase proteins might play an important role in the aetiopathogenesis of porcine diarrhoea caused by rotavirus and might be true markers in diagnosing the conditions leading to the extension of the prompt and effective therapeutic care.

  13. Universal model based on the mobile order and disorder theory for predicting lipophilicity and partition coefficients in all mutually immiscible two-phase liquid systems

    PubMed

    Ruelle

    2000-05-01

    The quantitative thermodynamic development of the mobile order and disorder theory in H-bonded liquids has been extended in order to predict partition coefficients. The model enables "a priori" estimation of the partition coefficient (log P) of neutral solutes, not only in the conventional 1-octanol/water reference but also in all mutually saturated two-phase systems made up of largely immiscible solvents. The model is obtained from the thermodynamic treatment of the various physicochemical free energy processes encoded in the overall distribution process and accordingly provides a useful tool for better understanding both the origin and the factors, such as the solute molar volume, that determine the partition coefficient of nonelectrolytes in a given system. From the comparison of the relative magnitude of the processes contributing to the log P value, a lot of information can also be gained regarding the variation in log P of the same substance partitioned between different solvent systems. As a demonstration, the model has been successfully applied to predict the log P of a great number of chemicals of varying structure, size, and chemical nature partitioned in a large set of essentially immiscible solvent pairs, differing either by their nonpolar or by their polar phase. In the systems involving water as the polar phase, the hydrophobic effect is always the driving force that governs the distribution process irrespective of the interacting or noninteracting nature of the substances studied. In the other two-phase systems, the partitioning of complexing solutes in particular appears to be ruled rather by their hydrogen-bonding capabilities than by their hydrophobicities.

  14. Mobile satellite service for Canada

    NASA Technical Reports Server (NTRS)

    Sward, David

    1988-01-01

    The Mobile Satellite (MSAT) system and a special program designed to provide interim mobile satellite services (IMSS) during the construction phase of MSAT are described. A mobile satellite system is a key element in extending voice and and data telecommunications to all Canadians.

  15. A solid-state NMR study of phase structure, molecular interactions, and mobility in blends of citric acid and paracetamol.

    PubMed

    Schantz, S; Hoppu, P; Juppo, A M

    2009-05-01

    Citric acid anhydrate (CAA) and paracetamol (PARA), prepared as crystalline physical mixtures and as amorphous blends, were studied using (13)C solid-state cross polarization magic angle spinning (CPMAS) NMR. Amorphous blends showed significant line broadening from the conformational distribution as compared to the crystalline samples. Also, chemical shift variations were observed between crystalline and amorphous blends, which were attributed to differences in intermolecular interactions. Averaging of proton rotating-frame spin-lattice relaxation times (T(1rho)) probed via different (13)C sites in the amorphous blends confirmed molecular level mixing. For some, initially amorphous, sample compositions the onset of crystallization was evident directly from spectra and from the significantly longer T(1rho) relaxations. Thus, crystallization caused phase separation with properties of the two phases resembling those of pure CAA and PARA, respectively. (13)C spectra of amorphous 50/50 (w/w, %) CAA/PARA recorded from above the glass transition temperature broadened as the temperature increased to a maximum at T approximately T(g) + 33 K. This was the result of a dynamic interference between the line narrowing techniques being applied and the time scale of molecular reorientation in the miscible melt. The derived average correlation time was found to correspond well with previous results from melt rheology. We conclude that the underlying reasons for physical instability (i.e., crystallization from the miscible melt, including molecular interactions and dynamics) of this class of amorphous binary mixtures can be effectively evaluated using NMR spectroscopy.

  16. Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS].

    PubMed

    Steiner, Wes E; Harden, Charles S; Hong, Feng; Klopsch, Steve J; Hill, Herbert H; McHugh, Vincent M

    2006-02-01

    The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined. Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified reference materials (CRM) of CWA degradation products for the detection of Schedule 1, 2, or 3 toxic chemicals or their precursors as defined by the chemical warfare convention (CWC) treaty verification were used in this study. A mixture of six G-series nerve related CWA degradation products (EMPA, IMPA, EHEP, IHEP, CHMPA, and PMPA) and their related collision induced dissociation (CID) fragment ions (MPA and EPA) were found in each case to be clearly resolved and detected using the IM(tof)MS instrument in negative ion monitoring mode. Corresponding ions, masses, drift times, K(o) values, and signal intensities for each of the CWA degradation products are reported. PMID:16413205

  17. The estimation of melting points and fusion enthalpies using experimental solubilities, estimated total phase change entropies, and mobile order and disorder theory.

    PubMed

    Chickos, James S; Nichols, Gary; Ruelle, Paul

    2002-01-01

    Melting points and fusion enthalpies are predicted for a series of 81 compounds by combining experimental solubilities in a variety of solvents and analyzed according to the theory of mobile order and disorder (MOD) and using the total phase change entropy estimated by a group additivity method. The error associated in predicting melting points is dependent on the magnitude of the temperature predicted. An error of +/- 12 K (+/- 1 sigma) was obtained for compounds melting between ambient temperature and 350 K (24 entries). This error increased to +/- 23 K when the temperature range was expanded to 400 K (46 entries) and +/- 39 K for the temperature range 298-555 K (79 entries). Fusion enthalpies were predicted within +/- 2sigma of the experimental values (+/- 6.4 kJ mol(-1)) for 79 entries. The uncertainty in the fusion enthalpy did not appear dependent on the magnitude of the melting point. Two outliers, adamantane and camphor, have significant phase transitions that occur below room temperature. Estimates of melting temperature and fusion enthalpy for these compounds were characterized by significantly larger errors.

  18. Nano electrospray gas-phase electrophoretic mobility molecular analysis (nES GEMMA) of liposomes: applicability of the technique for nano vesicle batch control

    PubMed Central

    Weiss, Victor U.; Urey, Carlos; Gondikas, Andreas; Golesne, Monika; Friedbacher, Gernot; von der Kammer, Frank; Hofmann, Thilo; Andersson, Roland; Marko-Varga, György; Marchetti-Deschmann, Martina

    2016-01-01

    Liposomes are biodegradable nanoparticle vesicles consisting of a lipid bilayer encapsulating an aqueous core. Entrapped cargo material is shielded from the extra-vesicular medium and sustained release of encapsulated material can be achieved. However, application of liposomes as nano-carriers demands their characterization concerning size and size distribution, particle-number concentration, occurrence of vesicle building blocks in solution and determination of the resulting vesicle encapsulation capacity. These questions can be targeted via gas-phase electrophoretic mobility molecular analysis (GEMMA) based on a nano electrospray (nES) charge-reduction source. This instrument separates single-charged nanoparticles in the gas-phase according to size in a high-laminar sheath-flow by means of an orthogonal, tunable electric field. nES GEMMA analysis enables to confirm liposome integrity after passage through the instrument (in combination with atomic force microscopy) as well as to exclude vesicle aggregation. Additionally, nanoparticle diameters at peak apexes and size distribution data are obtained. Differences of hydrodynamic and dry particle diameter values, as well as the effect of number- and mass-based concentration data analysis on obtained liposome diameters are shown. Furthermore, the repeatability of liposome preparation is studied, especially upon incorporation of PEGylated lipids in the bilayer. Finally, the instruments applicability to monitor mechanical stress applied to vesicles is demonstrated. PMID:27549027

  19. Extraction of toxic compounds from saliva by magnetic-stirring-assisted micro-solid-phase extraction step followed by headspace-gas chromatography-ion mobility spectrometry.

    PubMed

    Criado-García, Laura; Arce, Lourdes

    2016-09-01

    A new sample extraction procedure based on micro-solid-phase extraction (μSPE) using a mixture of sorbents of different polarities (polymeric reversed-phase sorbent HLB, silica-based sorbent C18, and multiwalled carbon nanotubes) was applied to extract benzene, toluene, butyraldehyde, benzaldehyde, and tolualdehyde present in saliva to avoid interference from moisture and matrix components and enhance sensitivity and selectivity of the ion mobility spectrometry (IMS) methodology proposed. The extraction of target analytes from saliva samples by using μSPE were followed by the desorption step carried out in the headspace vials placed in the autosampler of the IMS device. Then, 200 μL of headspace was injected into the GC column coupled to the IMS for its analysis. The method was fully validated in terms of sensitivity, precision, and recovery. The LODs and LOQs obtained, when analytes were dissolved in saliva samples to consider the matrix effect, were within the range of 0.38-0.49 and 1.26-1.66 μg mL(-1), respectively. The relative standard deviations were <3.5 % for retention time and drift time values, which indicate that the method proposed can be applied to determine toxic compounds in saliva samples. Graphical abstract Summary of steps followed in the experimental set up of this work. PMID:27481168

  20. Rapid analysis of tile industry gaseous emissions by ion mobility spectrometry and comparison with solid phase micro-extraction/gas chromatography/mass spectrometry.

    PubMed

    Pozzi, R; Bocchini, P; Pinelli, F; Galletti, G C

    2006-12-01

    The present paper reports on a rapid method for the analysis of gaseous emissions from ceramic industry, based on ion mobility spectrometry (IMS) as a means for on-site monitoring of volatile organic compounds (VOCs) produced during tile baking. IMS was calibrated with a set of reference compounds (i.e. ethyl acetate, ethanol, ethylene glycol, diethylene glycol, acetaldehyde, formaldehyde, 2-methyl-1,3-dioxolane, 2,2-dimethyl-1,3-dioxolane, 1,3-dioxolane, 1,4-dioxane, benzene, toluene, cyclohexane, acetone, acetic acid) via air-flow permeation. The technique was tested on a laboratory-scale kiln and tiles prepared with selected glycol- and resin-based additives. Finally, the analytical method was applied to emissions from two industries in the Modena (Italy) ceramic area. The results of all experimental phases were compared to those obtained by solid phase micro-extraction/gas chromatography/mass spectrometry (SPME/GC/MS). IMS showed potential as a real-time monitoring device for quality assessment in ceramic industry emissions. IMS spectra, SPME/GC/MS data, relationship between additives/baking conditions and produced VOCs and advantages and limitations of both techniques will be discussed.

  1. Effect of solvent strength and temperature on retention for a polar-endcapped, octadecylsiloxane-bonded silica stationary phase with methanol-water mobile phases.

    PubMed

    Kiridena, Waruna; Poole, Colin F; Koziol, Wladyslaw W

    2004-12-10

    Synergi Hydro-RP is a new type of polar-endcapped, octadecylsiloxane-bonded silica packing for reversed-phase liquid chromatography. Its retention properties as a function of solvent strength and temperature are evaluated from the change in retention factors over the composition range (0-70% v/v methanol) and temperature range (25-65 degrees C) using the solvation parameter model and response surface methodologies. The main factors that affect retention are solute size and hydrogen-bond basicity, with minor contributions from solute hydrogen-bond acidity, dipole-type and electron lone pair interactions. Within the easily accessible range for both temperature and solvent strength, the ability to change selectivity is much greater for solvent strength than temperature. Also, a significant portion of the effect of increasing temperature is to reduce retention without changing selectivity. Response surfaces for the system constants are smooth and non-linear, except for cavity formation and dispersion interactions (v system constant), which is linear. Modeling of the response surfaces suggests that solvent strength and temperature are not independent factors for the b, s and e system constants and for the model intercept (c term). PMID:15628160

  2. Mobile Learning Using Mobile Phones

    ERIC Educational Resources Information Center

    Vicente, Paula

    2013-01-01

    The participation in mobile learning programs is conditioned by having/using mobile communication technology. Those who do not have or use such technology cannot participate in mobile learning programs. This study evaluates who are the most likely participants of mobile learning programs by examining the demographic profile and mobile phone usage…

  3. Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use.

    PubMed

    Yu, Changxun; Peltola, Pasi; Nystrand, Miriam I; Virtasalo, Joonas J; Österholm, Peter; Ojala, Antti E K; Hogmalm, Johan K; Åström, Mats E

    2016-01-15

    This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Rönnskär smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter.

  4. Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use.

    PubMed

    Yu, Changxun; Peltola, Pasi; Nystrand, Miriam I; Virtasalo, Joonas J; Österholm, Peter; Ojala, Antti E K; Hogmalm, Johan K; Åström, Mats E

    2016-01-15

    This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Rönnskär smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter. PMID:26558848

  5. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization

    NASA Astrophysics Data System (ADS)

    Pepin, Robert; Laszlo, Kenneth J.; Marek, Aleš; Peng, Bo; Bush, Matthew F.; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-10-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions.

  6. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization

    NASA Astrophysics Data System (ADS)

    Pepin, Robert; Laszlo, Kenneth J.; Marek, Aleš; Peng, Bo; Bush, Matthew F.; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-07-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions.

  7. Elastic Properties, Defect Thermodynamics, Electrochemical Window, Phase Stability, and Li(+) Mobility of Li3PS4: Insights from First-Principles Calculations.

    PubMed

    Yang, Yanhan; Wu, Qu; Cui, Yanhua; Chen, Yongchang; Shi, Siqi; Wang, Ru-Zhi; Yan, Hui

    2016-09-28

    The improved ionic conductivity (1.64 × 10(-4) S cm(-1) at room temperature) and excellent electrochemical stability of nanoporous β-Li3PS4 make it one of the promising candidates for rechargeable all-solid-state lithium-ion battery electrolytes. Here, elastic properties, defect thermodynamics, phase diagram, and Li(+) migration mechanism of Li3PS4 (both γ and β phases) are examined via the first-principles calculations. Results indicate that both γ- and β-Li3PS4 phases are ductile while γ-Li3PS4 is harder under volume change and shear stress than β-Li3PS4. The electrochemical window of Li3PS4 ranges from 0.6 to 3.7 V, and thus the experimentally excellent stability (>5 V) is proposed due to the passivation phenomenon. The dominant diffusion carrier type in Li3PS4 is identified over its electrochemical window. In γ-Li3PS4 the direct-hopping of Lii(+) along the [001] is energetically more favorable than other diffusion processes, whereas in β-Li3PS4 the knock-off diffusion of Lii(+) along the [010] has the lowest migration barrier. The ionic conductivity is evaluated from the concentration and the mobility calculations using the Nernst-Einstein relationship and compared with the available experimental results. According to our calculated results, the Li(+) prefers to transport along the [010] direction. It is suggested that the enhanced ionic conductivity in nanostructured β-Li3PS4 is due to the larger possibility of contiguous (010) planes provided by larger nanoporous β-Li3PS4 particles. By a series of motivated and closely linked calculations, we try to provide a portable method, by which researchers could gain insights into the physicochemical properties of solid electrolyte. PMID:27588896

  8. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization.

    PubMed

    Pepin, Robert; Laszlo, Kenneth J; Marek, Aleš; Peng, Bo; Bush, Matthew F; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-10-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions. Graphical Abstract ᅟ.

  9. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization.

    PubMed

    Pepin, Robert; Laszlo, Kenneth J; Marek, Aleš; Peng, Bo; Bush, Matthew F; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-10-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions. Graphical Abstract ᅟ. PMID:27400696

  10. Elastic Properties, Defect Thermodynamics, Electrochemical Window, Phase Stability, and Li(+) Mobility of Li3PS4: Insights from First-Principles Calculations.

    PubMed

    Yang, Yanhan; Wu, Qu; Cui, Yanhua; Chen, Yongchang; Shi, Siqi; Wang, Ru-Zhi; Yan, Hui

    2016-09-28

    The improved ionic conductivity (1.64 × 10(-4) S cm(-1) at room temperature) and excellent electrochemical stability of nanoporous β-Li3PS4 make it one of the promising candidates for rechargeable all-solid-state lithium-ion battery electrolytes. Here, elastic properties, defect thermodynamics, phase diagram, and Li(+) migration mechanism of Li3PS4 (both γ and β phases) are examined via the first-principles calculations. Results indicate that both γ- and β-Li3PS4 phases are ductile while γ-Li3PS4 is harder under volume change and shear stress than β-Li3PS4. The electrochemical window of Li3PS4 ranges from 0.6 to 3.7 V, and thus the experimentally excellent stability (>5 V) is proposed due to the passivation phenomenon. The dominant diffusion carrier type in Li3PS4 is identified over its electrochemical window. In γ-Li3PS4 the direct-hopping of Lii(+) along the [001] is energetically more favorable than other diffusion processes, whereas in β-Li3PS4 the knock-off diffusion of Lii(+) along the [010] has the lowest migration barrier. The ionic conductivity is evaluated from the concentration and the mobility calculations using the Nernst-Einstein relationship and compared with the available experimental results. According to our calculated results, the Li(+) prefers to transport along the [010] direction. It is suggested that the enhanced ionic conductivity in nanostructured β-Li3PS4 is due to the larger possibility of contiguous (010) planes provided by larger nanoporous β-Li3PS4 particles. By a series of motivated and closely linked calculations, we try to provide a portable method, by which researchers could gain insights into the physicochemical properties of solid electrolyte.

  11. Gas-Phase Structure of Amyloid-β (12 - 28) Peptide Investigated by Infrared Spectroscopy, Electron Capture Dissociation and Ion Mobility Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Le, Thi Nga; Poully, Jean Christophe; Lecomte, Frédéric; Nieuwjaer, Nicolas; Manil, Bruno; Desfrançois, Charles; Chirot, Fabien; Lemoine, Jerome; Dugourd, Philippe; van der Rest, Guillaume; Grégoire, Gilles

    2013-12-01

    The gas-phase structures of doubly and triply protonated Amyloid-β12-28 peptides have been investigated through the combination of ion mobility (IM), electron capture dissociation (ECD) mass spectrometry, and infrared multi-photon dissociation (IRMPD) spectroscopy together with theoretical modeling. Replica-exchange molecular dynamics simulations were conducted to explore the conformational space of these protonated peptides, from which several classes of structures were found. Among the low-lying conformers, those with predicted diffusion cross-sections consistent with the ion mobility experiment were further selected and their IR spectra simulated using a hybrid quantum mechanical/semiempirical method at the ONIOM DFT/B3LYP/6-31 g(d)/AM1 level. In ECD mass spectrometry, the c/z product ion abundance (PIA) has been analyzed for the two charge states and revealed drastic differences. For the doubly protonated species, N - Cα bond cleavage occurs only on the N and C terminal parts, while a periodic distribution of PIA is clearly observed for the triply charged peptides. These PIA distributions have been rationalized by comparison with the inverse of the distances from the protonated sites to the carbonyl oxygens for the conformations suggested from IR and IM experiments. Structural assignment for the amyloid peptide is then made possible by the combination of these three experimental techniques that provide complementary information on the possible secondary structure adopted by peptides. Although globular conformations are favored for the doubly protonated peptide, incrementing the charge state leads to a conformational transition towards extended structures with 310- and α-helix motifs.

  12. Minimizing ultraviolet noise due to mis-matches between detector flow cell and post column mobile phase temperatures in supercritical fluid chromatography: effect of flow cell design.

    PubMed

    Berger, Terry A

    2014-10-17

    A mis-match between the post-column mobile phase temperature and the UV detector flow cell temperature can cause significant UV noise in supercritical fluid chromatography (SFC). Deviations as little as 5 °C can increase noise as much as 5 times, making the detector unsuited for trace analysis. Two approaches were used to minimize this noise. When a flow cell was in direct thermal contact (metal on metal) with the detector optical bench, the mobile phase temperature was actively controlled to the measured flow cell temperature, by using one of the heat exchangers (HX) in the column compartment. However, with some older, but still widely used flow cell designs, this required repeated, hourly monitoring of the flow cell temperature and repeated manual adjustment of the heat exchanger temperature, due to thermal drift. Flow cell design had a strong influence on susceptibility to this thermally induced noise. Thermally insulating the flow cell from the optical bench made some cells much less susceptible to such thermally induced noise. Five different flow cells, some insulated, some un-insulated, were evaluated. Most had a truncated conical flow path, but one had a cylindrical flow path. Using either approach, the ASTM noise, with a 10mm, 13 μL conical flow cell, could be optimized to ≈0.007 mAU at 2.5 Hz, in SFC, which is very near the 0.006 mAU manufacturer's specification for HPLC. The insulated version of this flow cell required far less optimization, compared to the un-insulated version. At 150 bar, an experimental 3mm, 2 μL flow cell, with only one side insulated, yielded noise slightly too high (≈0.16-0.18 mAU) for trace analysis, at 80 Hz. However, at 200 bar, noise at 80 Hz was <0.06 mAU, which should allow quantification of a 1 mAU tall trace component with a signal to noise ratio (S/N) >10. Even partially un-insulated, this flow cell design was much less susceptible to thermally induced noise. Further insulating this flow cell design failed to improve

  13. Minimizing ultraviolet noise due to mis-matches between detector flow cell and post column mobile phase temperatures in supercritical fluid chromatography: effect of flow cell design.

    PubMed

    Berger, Terry A

    2014-10-17

    A mis-match between the post-column mobile phase temperature and the UV detector flow cell temperature can cause significant UV noise in supercritical fluid chromatography (SFC). Deviations as little as 5 °C can increase noise as much as 5 times, making the detector unsuited for trace analysis. Two approaches were used to minimize this noise. When a flow cell was in direct thermal contact (metal on metal) with the detector optical bench, the mobile phase temperature was actively controlled to the measured flow cell temperature, by using one of the heat exchangers (HX) in the column compartment. However, with some older, but still widely used flow cell designs, this required repeated, hourly monitoring of the flow cell temperature and repeated manual adjustment of the heat exchanger temperature, due to thermal drift. Flow cell design had a strong influence on susceptibility to this thermally induced noise. Thermally insulating the flow cell from the optical bench made some cells much less susceptible to such thermally induced noise. Five different flow cells, some insulated, some un-insulated, were evaluated. Most had a truncated conical flow path, but one had a cylindrical flow path. Using either approach, the ASTM noise, with a 10mm, 13 μL conical flow cell, could be optimized to ≈0.007 mAU at 2.5 Hz, in SFC, which is very near the 0.006 mAU manufacturer's specification for HPLC. The insulated version of this flow cell required far less optimization, compared to the un-insulated version. At 150 bar, an experimental 3mm, 2 μL flow cell, with only one side insulated, yielded noise slightly too high (≈0.16-0.18 mAU) for trace analysis, at 80 Hz. However, at 200 bar, noise at 80 Hz was <0.06 mAU, which should allow quantification of a 1 mAU tall trace component with a signal to noise ratio (S/N) >10. Even partially un-insulated, this flow cell design was much less susceptible to thermally induced noise. Further insulating this flow cell design failed to improve

  14. Determination of hydrogen ion by ion chromatography (IC) with sulfonated cation-exchange resin as the stationary phase and aqueous EDTA (ethylenediamine-N,N,N',N'-tetraacetic acid) solution as the mobile phase.

    PubMed

    Hu, W; Iles, A; Hasebe, K; Matsukami, H; Cao, S; Tanaka, K

    2001-05-01

    An ion chromatographic (IC) method has been developed for determination of hydrogen ion (H+). It is based on the use of sulfonated cation-exchange resin as stationary phase, aqueous ethylenediamine-N,N,N',N'-tetraacetic acid (dipotassium salt, EDTA-2K, written as K2H2Y) solution as mobile phase, and conductivity for detection. H+ was separated mainly by cation-exchange, but its elution was accelerated by the presence of EDTA. The order of elution for the model cations was H+ > Li+ > Na+ > NH4+ > Ca2+ > > Mg2+. A sharp and highly symmetrical peak was obtained for H+ and this was attributed to the capacity of H2Y2(2-) to receive and bind H+. H+ was detected conductiometrically and detector response (reduction in conductivity as a result of H+ +H2Y2- --> H3Y-) was linearly proportional to the concentration of H+ in the sample. The detection limit for H+ with this IC system was better than 4.7 micromol L(-1). A significant advantage of this method was the ability to separate and determine, in one step, H+ and other cations. The successful determination of H+ and other cation species in real acid-rain samples demonstrated the usefulness of this method.

  15. Linear modeling of the soil-water partition coefficient normalized to organic carbon content by reversed-phase thin-layer chromatography.

    PubMed

    Andrić, Filip; Šegan, Sandra; Dramićanin, Aleksandra; Majstorović, Helena; Milojković-Opsenica, Dušanka

    2016-08-01

    Soil-water partition coefficient normalized to the organic carbon content (KOC) is one of the crucial properties influencing the fate of organic compounds in the environment. Chromatographic methods are well established alternative for direct sorption techniques used for KOC determination. The present work proposes reversed-phase thin-layer chromatography (RP-TLC) as a simpler, yet equally accurate method as officially recommended HPLC technique. Several TLC systems were studied including octadecyl-(RP18) and cyano-(CN) modified silica layers in combination with methanol-water and acetonitrile-water mixtures as mobile phases. In total 50 compounds of different molecular shape, size, and various ability to establish specific interactions were selected (phenols, beznodiazepines, triazine herbicides, and polyaromatic hydrocarbons). Calibration set of 29 compounds with known logKOC values determined by sorption experiments was used to build simple univariate calibrations, Principal Component Regression (PCR) and Partial Least Squares (PLS) models between logKOC and TLC retention parameters. Models exhibit good statistical performance, indicating that CN-layers contribute better to logKOC modeling than RP18-silica. The most promising TLC methods, officially recommended HPLC method, and four in silico estimation approaches have been compared by non-parametric Sum of Ranking Differences approach (SRD). The best estimations of logKOC values were achieved by simple univariate calibration of TLC retention data involving CN-silica layers and moderate content of methanol (40-50%v/v). They were ranked far well compared to the officially recommended HPLC method which was ranked in the middle. The worst estimates have been obtained from in silico computations based on octanol-water partition coefficient. Linear Solvation Energy Relationship study revealed that increased polarity of CN-layers over RP18 in combination with methanol-water mixtures is the key to better modeling of

  16. Soil phosphorus mobility and solid-to-solution phase resupply studied by diffusive gradients in thin films: background soil properties driving their variation

    NASA Astrophysics Data System (ADS)

    Menezes-Blackburn, Daniel; Zhang, Hao; Giles, Courtney; George, Timothy; Shand, Charlie; Lumsdon, David; Cooper, Patricia; Wendler, Renate; Brown, Lawrie; Stutter, Marc; Blackwell, Martin; Darch, Tegan; Wearing, Catherine; Philip, Haygarth

    2015-04-01

    The mobility and resupply of inorganic phosphorus (P) from the solid phase was studied in 32 representative soils from the UK. The objective was to identify the background soil properties driving the variation of soil inorganic P desorption kinetics across different soil types. Diffusive gradients in thin films (DGT), diffusive equilibration in thin films (DET) and the DGT-induced fluxes in sediments model (DIFS) were used as tools for exploring solid-to-solution desorption kinetics. Previously characterized physicochemical properties of the same soils were used for correlation analysis. On average and across soil types, the inorganic P maximum distance of depletion was 0.42±0.10 cm, the equilibration time (Tc) was 3.63 h, the desorption rate constant (k-1) was 0.0046 h-1, and the desorption rate was 4.71 nmol l-1 s-1. The correlation between P in Olsen extractcs (POlsen) with PDGT, PDET and phosphorus effective concentration (PE) was enhanced when similar soils were isolated and used in the comparison, clearly showing that these parameters are affected differently by soil types. The PE was better correlated to Ptot, POlsen, PFeO, and PNaOH/EDTA than PDGT. This may indicate that PE is a better representation of P availability across soil types than PDGT. While the relative DGT-induced inorganic P flux in the first hour is mainly a function of soil wetting properties and % Corg, at longer times it is a function of the resupply capacity (R-Rdiff) of the soil solid phase. In general, resupply of P from the solid phase was less than that for other chemical elements, as shown by high Tc and low k-1 values. Desorption rates and resupply from the solid phase were fundamentally influenced by P saturation status, as reflected by their strong correlation with P concentration in water, FeO strips, Olsen and NaOH-EDTA extracts. Soil pH and particle size distribution had little or no effect on the evaluated parameters. The DGT and DET techniques, along with the DIFS model

  17. Aqueous phase oligomerization of α,β-unsaturated carbonyls and acids investigated using ion mobility spectrometry coupled to mass spectrometry (IMS-MS)

    NASA Astrophysics Data System (ADS)

    Renard, Pascal; Tlili, Sabrine; Ravier, Sylvain; Quivet, Etienne; Monod, Anne

    2016-04-01

    One of the current essential issues to unravel our ability to forecast future climate change and air quality, implies a better understanding of natural processes leading to secondary organic aerosol (SOA) formation, and in particular the formation and fate of oligomers. The difficulty in characterizing macromolecules is to discern between large oxygenated molecules from series of oligomers containing repeated small monomers of diverse structures. In the present study, taking advantage from previously established radical vinyl oligomerization of methyl vinylketone (MVK) in the aqueous phase, where relatively simple oligomers containing up to 14 monomers were observed, we have investigated the same reactivity on several other unsaturated water soluble organic compounds (UWSOCs) and on a few mixtures of these precursor compounds. The technique used to characterize the formed oligomers was a traveling wave ion mobility spectrometry coupled to a hybrid quadrupole - time of flight mass spectrometer (IMS-MS) fitted with an electrospray source and ultra-high performance liquid chromatography (UPLC). The technique allows for an additional separation, especially for large ions, containing long carbon chains. We have shown the efficiency of the IMS-mass spectrometry technique to detect oligomers derived from MVK photooxidation in the aqueous phase. The results were then compared to other oligomers, derived from ten other individual biogenic UWSOCs. The technique allowed distinguishing between different oligomers arising from different precursors. It also clearly showed that compounds bearing a non-conjugated unsaturation did not provide oligomerization. Finally, it was shown that the IMS-mass spectrometry technique, applied to mixtures of unsaturated conjugated precursors, exhibited the ability of these precursors to co-oligomerize, i.e. forming only one complex oligomer system bearing monomers of different structures. The results are discussed in terms of atmospheric

  18. Comparison of large scale purification processes of naproxen enantiomers by chromatography using methanol-water and methanol-supercritical carbon dioxide mobile phases.

    PubMed

    Kamarei, Fahimeh; Vajda, Péter; Guiochon, Georges

    2013-09-20

    This paper compares two methods used for the preparative purification of a mixture of (S)-, and (R)-naproxen on a Whelk-O1 column, using either high performance liquid chromatography or supercritical fluid chromatography. The adsorption properties of both enantiomers were measured by frontal analysis, using methanol-water and methanol-supercritical carbon dioxide mixtures as the mobile phases. The measured adsorption data were modeled, providing the adsorption isotherms and their parameters, which were derived from the nonlinear fit of the isotherm models to the experimental data points. The model used was a Bi-Langmuir isotherm, similar to the model used in many enantiomeric separations. These isotherms were used to calculate the elution profiles of overloaded elution bands, assuming competitive Bi-Langmuir behavior of the two enantiomers. The analysis of these profiles provides the basis for a comparison between supercritical fluid chromatographic and high performance liquid chromatographic preparative scale separations. It permits an illustration of the advantages and disadvantages of these methods and a discussion of their potential performance.

  19. Detection of piperonal emitted from polymer controlled odor mimic permeation systems utilizing Canis familiaris and solid phase microextraction-ion mobility spectrometry.

    PubMed

    Macias, Michael S; Guerra-Diaz, Patricia; Almirall, José R; Furton, Kenneth G

    2010-02-25

    Currently, in the field of odor detection, there is generally a wider variation in limit of detections (LODs) for canines than instruments. The study presented in this paper introduces an improved protocol for the creation of controlled odor mimic permeation system (COMPS) devices for use as standards in canine training and discusses the canine detection thresholds of piperonal, a starting material for the illicit drug 3,4-methylenedioxymethamphetamine (MDMA), when exposed to these devices. Additionally, this paper describes the first-ever reported direct comparison of solid phase microextraction-ion mobility spectrometry (SPME-IMS) to canine detection for the MDMA odorant, piperonal. The research presented shows the reliability of COMPS devices as low cost field calibrants providing a wide range of odorant concentrations for biological and instrumental detectors. The canine LOD of piperonal emanating from the 100 ng s(-1) COMPS was found to be 1 ng as compared to the SPME-IMS LOD of piperonal in a static, closed system at 2 ng, with a linear dynamic range from 2 ng to 11 ng. The utilization of the COMPS devices would allow for training that will reduce the detection variability between canines and maintain improved consistency for training purposes. Since both SPME and IMS are field portable technologies, it is expected that this coupled method will be useful as a complement to canine detection for the field detection of MDMA. PMID:20044224

  20. High Sensitivity Method to Estimate Distribution of Hyaluronan Molecular Sizes in Small Biological Samples Using Gas-Phase Electrophoretic Mobility Molecular Analysis

    PubMed Central

    Do, Lan; Dahl, Christen P.; Kerje, Susanne; Hansell, Peter; Mörner, Stellan; Lindqvist, Ulla; Engström-Laurent, Anna; Larsson, Göran; Hellman, Urban

    2015-01-01

    Hyaluronan is a negatively charged polydisperse polysaccharide where both its size and tissue concentration play an important role in many physiological and pathological processes. The various functions of hyaluronan depend on its molecular size. Up to now, it has been difficult to study the role of hyaluronan in diseases with pathological changes in the extracellular matrix where availability is low or tissue samples are small. Difficulty to obtain large enough biopsies from human diseased tissue or tissue from animal models has also restricted the study of hyaluronan. In this paper, we demonstrate that gas-phase electrophoretic molecular mobility analyzer (GEMMA) can be used to estimate the distribution of hyaluronan molecular sizes in biological samples with a limited amount of hyaluronan. The low detection level of the GEMMA method allows for estimation of hyaluronan molecular sizes from different parts of small organs. Hence, the GEMMA method opens opportunity to attain a profile over the distribution of hyaluronan molecular sizes and estimate changes caused by disease or experimental conditions that has not been possible to obtain before. PMID:26448761

  1. Determination of furfural and hydroxymethylfurfural from baby formula using headspace solid phase microextraction based on nanostructured polypyrrole fiber coupled with ion mobility spectrometry.

    PubMed

    Kamalabadi, Mahdie; Ghaemi, Elham; Mohammadi, Abdorreza; Alizadeh, Naader

    2015-08-15

    Furfural (Fu) and hydroxymethylfurfural (HMFu) are extracted using a dodecylbenzenesulfonate-doped polypyrrole coating as a fiber for headspace solid phase microextraction (HS-SPME) method in baby formula samples and detected using ion mobility spectrometry (IMS). Sample pH, salt effect, extraction time and temperature were investigated and optimized as effective parameters in HS-SPME. The calibration curves were linear in the range of 20-300 ng g(-1) (R(2)>0.99). Limits of detection for Fu and HMFu were 6 ng g(-1) and 5 ng g(-1), respectively. The RSD% of Fu and HMFu for five analyses was 4.4 and 4.9, respectively. The proposed method was successfully applied to determine of Fu and HMFu in the different baby formula samples with satisfactory result. The results were in agreement with those obtained using HPLC analysis. The HS-SPME-IMS is precise, selective and sensitive analytical method for determination of Fu and HMFu in baby formula samples, without any derivatization process.

  2. Dependence on the mobile phase pH of the adsorption behavior of propranolol enantiomers on a cellulase protein used as the chiral selector

    SciTech Connect

    Fornstedt, T.; Goetmar, G.; Andersson, M.; Guiochon, G.

    1999-02-17

    The authors reported previously on the unusual thermodynamic characteristics of the enantioselective interactions between the enantiomers of the {beta}-blocker propranolol and the protein cellobiohydrolase I immobilized on silica. The adsorption of the more retained enantiomer, (S)-propranolol, is endothermic while that of the (R)-propranolol is exothermic. This causes a rapid increase of the selectivity factor with increasing temperature. In this work, the complex dependence of the selectivity factor on the pH of the solvent is studied. They determined the equilibrium isotherms of (R)- and (S)-propranolol in a wide concentration range (0.25 {micro}M to 1.1 mM) at six different mobile-phase pHs (4.7, 5.0, 5.2, 5.5, 5.7, and 6.0) and fitted the data obtained to the bi-Langmuir model. This gave the saturation capacity and the binding constant of the nonselective contribution for the two enantiomers. It also gave these parameters for the enantioselective contributions of each of them. The dependence of these parameters on the pH is discussed and interpreted in terms of the retention mechanism. Conclusions are in excellent agreement with recent, independent results on the structure of the protein obtained by X-ray crystallography.

  3. Carbon nanotubes@silicon dioxide nanohybrids coating for solid-phase microextraction of organophosphorus pesticides followed by gas chromatography-corona discharge ion mobility spectrometric detection.

    PubMed

    Saraji, Mohammad; Jafari, Mohammad Taghi; Mossaddegh, Mehdi

    2016-01-15

    A high efficiency solid-phase microextraction (SPME) fiber coated with porous carbon nanotubes-silicon dioxide (CNTs-SiO2) nanohybrids was synthesized and applied for the determination of some organophosphorus pesticides (OPPs) in vegetables, fruits and water samples. Gas chromatography-corona discharge ion mobility spectrometry was used as the detection system. Glucose, as a biocompatible compound, was used for connecting CNT and SiO2 during a hydrothermal process. The electrospinning technique was also applied for the fiber preparation. The parameters affecting the efficiency of extraction, including stirring rate, salt effect, extraction temperature, extraction time, desorption temperature and desorption time, were investigated and optimized. The developed CNTs@SiO2 fiber presented better extraction efficiency than the commercial SPME fibers (PA, PDMS, and PDMS-DVB). The intra- and inter-day relative standard deviations were found to be lower than 6.2 and 9.0%, respectively. For water samples, the limits of detection were in the range of 0.005-0.020 μg L(-1) and the limits of quantification were between 0.010 and 0.050 μg L(-1). The results showed a good linearity in the range of 0.01-3.0 μg L(-1) for the analytes. The spiking recoveries ranged from 79 (± 9) to 99 (± 8). The method was successfully applied for the determination of OPPs in real samples.

  4. HPLC/APCI Mass Spectrometry of Saturated and Unsaturated Hydrocarbons by Using Hydrocarbon Solvents as the APCI Reagent and HPLC Mobile Phase

    NASA Astrophysics Data System (ADS)

    Gao, Jinshan; Owen, Benjamin C.; Borton, David J.; Jin, Zhicheng; Kenttämaa, Hilkka I.

    2012-05-01

    Saturated and unsaturated, linear, branched, and cyclic hydrocarbons, as well as polyaromatic and heteroaromatic hydrocarbons, were successfully ionized by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a linear quadrupole ion trap (LQIT) mass spectrometer. Pentane was proved to be the best reagent among the hydrocarbon reagents studied. This ionization method generated different types of abundant ions (i.e., [M + H]+, M+•, [M - H]+ and [M - 2H]+ •), with little or no fragmentation. The radical cations can be differentiated from the even-electron ions by using dimethyl disulfide, thus facilitating molecular weight (MW) determination. While some steroids and lignin monomer model compounds, such as androsterone and 4-hydroxy-3-methoxybenzaldehyde, also formed abundant M+• and [M + H]+ ions, this was not true for all of them. Analysis of two known mixtures as well as a base oil sample demonstrated that each component of the known mixtures could be observed and that a correct MW distribution was obtained for the base oil. The feasibility of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography (HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis.

  5. Polypyrrole nanowire as an excellent solid phase microextraction fiber for bisphenol A analysis in food samples followed by ion mobility spectrometry.

    PubMed

    Kamalabadi, Mahdie; Mohammadi, Abdorreza; Alizadeh, Naader

    2016-08-15

    A polypyrrole nanowire coated fiber was prepared and used in head-space solid phase microextraction coupled with ion mobility spectrometry (HS-SPME-IMS) to the analysis of bisphenol A (BPA) in canned food samples, for the first time. This fiber was synthesized by electrochemical oxidation of the monomer in aqueous solution. The fiber characterization by scanning electron microscopy (SEM) revealed that the new fiber exhibited two-dimensional structures with a nanowire morphology. The effects of important extraction parameters on the efficiency of HS-SPME were investigated and optimized. Under the optimum conditions, the linearity of 10-150ngg(-1) and limit of detection (based on S/N=3) of 1ngg(-1) were obtained in BPA analysis. The repeatability (n=5) expressed as the relative standard deviation (RSD%) was 5.8%. At the end, the proposed method was successfully applied to determine BPA in various canned food samples (peas, corns, beans). Relative recoveries were obtained 93-96%. Method validation was conducted by comparing our results with those obtained through HPLC with fluorescence detection (FLD). Compatible results indicate that the proposed method can be successfully used in BPA analysis. This method is simple and cheaper than chromatographic methods, with no need of extra organic solvent consumption and derivatization prior to sample introduction. PMID:27260447

  6. Determining urea levels in dialysis human serum by means of headspace solid phase microextraction coupled with ion mobility spectrometry and on the basis of nanostructured polypyrrole film.

    PubMed

    Kalhor, Hamideh; Alizadeh, Naader

    2013-06-01

    A simple and sensitive headspace (HS) solid phase microextraction (SPME) coupled with ion mobility spectrometry (IMS) method is presented for analysis of urea in dialysis human serum samples. A dodecylbenzenesulfonate-doped polypyrrole coating was used as a fiber for SPME. The HS-SPME-IMS method exhibits good repeatability (relative standard deviation of 3% or less), simplicity, and good sensitivity. The influence of various analytical parameters such as pH, ionic strength, extraction time and temperature was investigated and the parameters were optimized. The calibration graph was linear in the range from 5 to 50 μg mL(-1), and the detection limit was 2 μg mL(-1). The method was applied successfully for determination of urea in human serum and with acceptable recovery (more than 98%). Finally, a standard addition calibration method was applied to the HS-SPME-IMS method for the analysis of human serum samples before and at the end of dialysis. The proposed method appears to be suitable for the analysis of urea in serum samples as it is not time-consuming and requires only small quantities of the sample without any derivatization process.

  7. A novel method for the determination of three volatile organic compounds in exhaled breath by solid-phase microextraction-ion mobility spectrometry.

    PubMed

    Allafchian, Ali Reza; Majidian, Zahra; Ielbeigi, Vahideh; Tabrizchi, Mahmoud

    2016-01-01

    A method was carried out for the quantitative determination of the concentrations of volatile organic compounds (VOCs) using solid-phase microextraction and ion mobility spectrometry (SPME-IMS). This method was optimized and evaluated. The best results were obtained at sorption temperature 70 °C, desorption temperature 200 °C, and extraction time 15 min. Under the optimized conditions, the linear dynamic range was found to be 0.01-4.0 ppb (R(2) > 0.995), 2.3-400 ppm (R(2) > 0.994), and 2.5-76 ppb (R(2) > 0.998) for acetone, acetaldehyde, and acetonitrile, respectively. The detection limits for acetone, acetaldehyde, and acetonitrile were 0.001 ppb, 0.18 ppm, and 0.22 ppb, respectively. As a practical application, the method was applied for the determination of acetone, acetaldehyde, and acetonitrile in human breath matrix. Therefore, the proposed method was found to be effective and simple enough to be strongly recommended for real sample analysis.

  8. Halloysite nanotubes-titanium dioxide as a solid-phase microextraction coating combined with negative corona discharge-ion mobility spectrometry for the determination of parathion.

    PubMed

    Saraji, Mohammad; Jafari, Mohammad Taghi; Mossaddegh, Mehdi

    2016-07-01

    Halloysite nanotubes-titanium dioxide (HNTs-TiO2) as a biocompatible environmentally friendly solid-phase microextraction (SPME) fiber coating was prepared. HNTs-TiO2 was chemically coated on the surface of a fused-silica fiber using a sol-gel process. Parathion as an organophosphorus pesticide was selected as a model compound to investigate the extraction efficiency of the fiber. The extracted analyte was detected by negative corona discharge-ion mobility spectrometer (NCD-IMS). The effective parameters on the extraction efficiency, such as salt effect, extraction temperature and extraction time were investigated and optimized. The extraction efficiency of HNTs-TiO2 fiber was compared with bare-silica (sol-gel based coating without HNTs-TiO2), HNTs, carbon nanotubes and commercial SPME fibers (PA, PDMS, and PDMS-DVB). The HNTs-TiO2 fiber showed highest extraction efficiency among the studied fibers. The intra- and inter-day relative standard deviations were found to be 4.3 and 6.3%, respectively. The limit of detection and limit of quantification values were 0.03 and 0.1 μg L(-1), respectively. The dynamic range of the method was in the range of 0.1-25 μg L(-1). The spiking recoveries were between 85 (±9) and 97 (±6). The SPME-HNTs-TiO2 combined with NCD-IMS was successfully applied for the determination of parathion in apple, strawberry, celery and water samples. PMID:27216393

  9. Rapid screening of methamphetamines in human serum by headspace solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry.

    PubMed

    Alizadeh, Naader; Mohammadi, Abdorreza; Tabrizchi, Mahmoud

    2008-03-01

    A simple, rapid and highly sensitive method for simultaneous analysis of methamphetamine (MA) and 3,4-methylenedioxy methamphetamine (MDMA) in human serum was developed using the solid-phase microextraction (SPME) combined with ion mobility spectrometry (IMS). A dodecylsulfate-doped polypyrrole (PPy-DS) was applied as a new fiber for SPME. Electrochemically polymerized PPy is formed on the surface of a platinum wire and will contain charge-compensating anion (dodecylsulfate) incorporated during synthesis using cyclic voltammetry (CV) technique. The extraction properties of the fiber to MA and MDMA were examined, using a headspace-SPME (HS-SPME) device and thermal desorption in injection port of IMS. The results show that PPy-DS as a SPME fiber coating is suitable for the successful extraction of these compounds. This method is suitable for the identification and determination of MAs, is not time-consuming, requires small quantities of sample and does not require any derivatization. Parameters like pH, extraction time, ionic strength, and temperature of the sample were studied and optimized to obtain the best extraction results. The HS-SPME-IMS method provided good repeatability (RSDs<7.8 %) for spiked serum samples. The calibration graphs were linear in the range of 20-4000 ng ml(-1) (R(2)>0.99) and detection limits for MDMA and MA were 5 and 8 ng ml(-1), respectively. HS-SPME-IMS of non-spiked serum sample provided a spectrum without any peak from the matrix, supporting an effective sample clean-up. Finally, the proposed method was applied for analysis one of the ecstasy tablet.

  10. N-MOSFETs Formed on Solid Phase Epitaxially Grown GeSn Film with Passivation by Oxygen Plasma Featuring High Mobility.

    PubMed

    Fang, Yung-Chin; Chen, Kuen-Yi; Hsieh, Ching-Heng; Su, Chang-Chia; Wu, Yung-Hsien

    2015-12-01

    Solid phase epitaxially grown GeSn was employed as the platform to assess the eligibility of direct O2 plasma treatment on GeSn surface for passivation of GeSn N-MOSFETs. It has been confirmed that O2 plasma treatment forms a GeSnO(x) film on the surface and the GeSnO(x) topped by in situ Al2O3 constitutes the gate stack of GeSn MOS devices. The capability of the surface passivation was evidenced by the low interface trap density (D(it)) of 1.62 × 10(11) cm(-2) eV(-1), which is primarily due to the formation of Ge-O and Sn-O bonds at the surface by high density/reactivity oxygen radicals that effectively suppress dangling bonds and decrease gap states. The good D(it) not only makes tiny frequency dispersion in the characterization of GeSn MOS capacitors, but results in GeSn N-MOSFETs with outstanding peak electron mobility as high as 518 cm(2)/(V s) which outperforms other devices reported in the literature due to reduced undesirable carrier scattering. In addition, the GeSn N-MOSFETs also exhibit promising characteristics in terms of acceptable subthreshold swing of 156 mV/dec and relatively large I(ON)/I(OFF) ratio more than 4 orders. Moreover, the robust reliability in terms small V(t) variation against high field stress attests the feasibility of using the O2 plasma-treated passivation to advanced GeSn technology.

  11. The effects of mobile ATM switches on PNNI peer group operation

    SciTech Connect

    Martinez, L.; Sholander, P.; Tolendino, L.

    1997-04-01

    This contribution discusses why, and how, mobile networks and mobile switches might be discussed during Phase 1 of the WATM standards process. Next, it reviews mobile routers within Mobile IP. That IP mobility architecture may not apply to the proposed mobile ATM switches. Finally, it discusses problems with PNNI peer group formation and operation when mobile ATM switches are present.

  12. Rapid analysis of pesticide residues in drinking water samples by dispersive solid-phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry.

    PubMed

    Zou, Nan; Gu, Kejia; Liu, Shaowen; Hou, Yanbing; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping

    2016-03-01

    An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77 μg/kg. The linear range was 0.005-0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site. PMID:27027594

  13. Rapid analysis of pesticide residues in drinking water samples by dispersive solid-phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry.

    PubMed

    Zou, Nan; Gu, Kejia; Liu, Shaowen; Hou, Yanbing; Zhang, Jialei; Xu, Xiang; Li, Xuesheng; Pan, Canping

    2016-03-01

    An analytical method based on dispersive solid-phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass-mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4- to 48.7-fold (theoretical enrichment factor was 50-fold). The detection limits of pesticides were 0.01∼0.77 μg/kg. The linear range was 0.005-0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high-performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.

  14. A novel cation exchange polymer as a reversed-dispersive solid phase extraction sorbent for the rapid determination of rhodamine B residue in chili powder and chili oil.

    PubMed

    Chen, Dawei; Zhao, Yunfeng; Miao, Hong; Wu, Yongning

    2014-12-29

    This paper presents a new analytical method for the determination of rhodamine B (RB) residue in chili powder and chili oil based on a novel reversed-dispersive solid phase extraction (r-dSPE) and ultra high performance liquid chromatography–high resolution mass spectrometry (UHPLC–HRMS). Chili powder and chili oil samples were first extracted with acetonitrile/water (1:1, v/v) and acetonitrile, respectively. Then, RB from the extract was adsorbed to the polymer cation exchange (PCX) sorbent with the characteristics of ion exchange and reversed-phase retention. Subsequently, the analyte in PCX sorbent was eluted with ammonium hydroxide/methanol (1:99, v/v) through a simple unit device equipped with 1 mL syringe and 0.22 μm nylon syringe filter. All of the samples were analyzed by UHPLC–HRMS/MS on a Waters Acquity BEH C18 column with 0.1% formic acid and 4 mM ammonium formate in water/acetonitrile as the mobile phase with gradient elution. The matrix effect, recovery, and repeatability, within laboratory reproducibility, and the LODs and LOQs of the r-dSPE cleanup method were investigated. The method showed a good linearity (R2 > 0.999) in the ranges of 0.01–1 μg/L and 1–100 μg/L for the analyte. The LODs of RB for chili powder and chili oil samples were 0.5 μg/kg. The average recoveries of RB from the samples spiked at four different concentrations (2, 20, 500 and 5000 μg/kg) were in a range from 76.7 to 104.9%. Results showed that the proposed method was simple, fast, economical and effective for the determination of RB in chili powder and chili oil. Considering the excellent sorptive performance of PCX for RB, further work should be done to evaluate the usefulness of the PCX in r-dSPE for the clean-up and analyses of other trace-level alkaline contaminants. PMID:25498558

  15. High-throughput biopolymer desalting by solid-phase extraction prior to mass spectrometric analysis.

    PubMed

    Gilar, M; Belenky, A; Wang, B H

    2001-06-29

    In the last 10 years mass spectrometry (MS) has become an important method for analysis of peptides, proteins and DNA. It was recently utilized for accurate high-throughput protein identification, sequencing and DNA genotyping. The presence of non-volatile buffers compromises sensitivity and accuracy of MS biopolymer analysis; it is essential to remove sample contaminants prior to analysis. We have developed a fast and efficient method for desalting of DNA oligonucleotides and peptides using 96-well solid-phase extraction plates packed with 5 mg of Waters Oasis HLB sorbent (Waters, Milford, MA, USA). This reversed-phase sorbent retains the biopolymer analytes, while non-retained inorganic ions are washed out with pure deionized water. DNA oligonucleotides or peptides are eluted using a small amount (20-100 microl) of acetonitrile-water (70:30, v/v) solution. The SPE desalting performance meets the requirements for MS applications such as protein digest analysis and DNA genotyping. PMID:11461010

  16. Simultaneous analysis of non-steroidal anti-inflammatory drugs using electrochemically controlled solid-phase microextraction based on nanostructure molecularly imprinted polypyrrole film coupled to ion mobility spectrometry.

    PubMed

    Ameli, Akram; Kalhor, Hamideh; Alizadeh, Naader

    2013-06-01

    A simple, rapid, and highly sensitive method for simultaneous analysis of anti-inflammatory drugs (naproxen, ibuprofen, and mefenamic acid) in diluted human serum was developed using the electrochemically controlled solid-phase microextraction coupled to ion mobility spectrometry. A conducting molecularly imprinted polymer film based on polypyrrole was synthesized for the selective uptake and release of drugs. The film was prepared by incorporation of a template molecule (naproxen) during the electropolymerization of pyrrole onto a platinum electrode using cyclic voltammetry method. The measured ion mobility spectrometry intensity was related to the concentration of analytes taken up into the films. The calibration graphs (naproxen, ibuprofen, and mefenamic acid) were linear in the range of 0.1-30 ng/mL and detection limits were 0.07-0.37 ng/mL and relative standard deviation was lower than 6%. On the basis of the results obtained in this work, the conducting molecularly imprinted polymer films as absorbent have been applied in the electrochemically controlled solid-phase microextraction and ion mobility spectrometry system for the selective clean-up and quantification of trace amounts of anti-inflammatory drugs in human serum samples. Scanning electron microscopy has confirmed the nano-structure morphology of the polypyrrole film.

  17. The clinical usefulness of ESR, CRP, and disease duration in ankylosing spondylitis: the product of these acute-phase reactants and disease duration is associated with patient's poor physical mobility.

    PubMed

    Chen, Chun-Hsiung; Chen, Hung-An; Liao, Hsien-Tzung; Liu, Chin-Hsiu; Tsai, Chang-Youh; Chou, Chung-Tei

    2015-07-01

    We evaluated the clinical usefulness of ESR, CRP, and disease duration in ankylosing spondylitis (AS) disease severity. There were 156 Chinese AS patients included in Taiwan. Patients completed the questionnaires, containing demographic data, disease activity (BASDAI), functional status (BASFI), and patient's global assessment (BASG). Meanwhile, patient's physical mobility (BASMI) and acute-phase reactants, including ESR and CRP levels were measured. Receiver operating characteristic (ROC) plot analysis was used to evaluate the performance of ESR, CRP, and disease duration in the AS patients. ESR mildly correlated with BASFI (r = 0.176, p = 0.028) and disease duration (r = 0.214, p = 0.008), and moderately correlated with BASMI (r = 0.427, p < 0.001). CRP moderately correlated with BASMI (r = 0.410, p < 0.001). By using ROC plot analysis, ESR, CRP, and disease duration showed the best and significant "area under the curve (AUC)", in distinguishing the AS patients with poor physical mobility (BASMI ≥ 3.6, the Median) (AUC = 0.748, 0.751 and 0.738, respectively, all p < 0.001), as compared to BASDAI, BASFI, and BASG. ESR × disease duration (AUC = 0.801, p < 0.001) and CRP × disease duration (AUC = 0.821, p < 0.001) showed higher AUC values than ESR or CRP alone in indicating poor physical mobility. For detecting poor physical mobility (BASMI ≥ 3.6) in the AS patients: ESR × disease duration (≥60.0 mm/h × year): sensitivity = 72.7 % and specificity = 72.8 %; CRP × disease duration (≥8.3 mg/dl × year): sensitivity = 72.7 % and specificity = 74.6 %. ESR, CRP, and disease duration are particularly related to AS patient's poor physical mobility. Combining the usefulness of acute-phase reactants and disease duration, the values of ESR × disease duration and CRP × disease duration demonstrate better association with poor physical mobility in AS patients.

  18. An integrated electrophoretic mobility control device with split design for signal improvement in liquid chromatography-electrospray ionization mass spectrometry analysis of aminoglycosides using a heptafluorobutyric acid containing mobile phase.

    PubMed

    Hung, Sih-Hua; Yu, Meng-Ju; Wang, Nan-Hsuan; Hsu, Ren-Yu; Wei, Guor-Jien; Her, Guor-Rong

    2016-08-24

    Electrophoretic mobility control (EMC) was used to alleviate the adverse effect of the ion-pairing agent heptafluorobutyric acid (HFBA) in the liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) analysis of aminoglycosides. Aminoglycosides separated by LC were directed to a connecting column before their detection via ESI. Applying an electric field across the connecting column caused the positively charged aminoglycosides to migrate toward the mass spectrometer whereas the HFBA anions remained in the junction reservoir, thus alleviating the ion suppression caused by HFBA. To accommodate the flow rate of a narrow-bore column, minimize the effect of electrophoretic mobility on separation, and facilitate the operation, an integrated EMC device with a split design was fabricated. With the proposed EMC device, the signals of aminoglycosides were enhanced by a factor of 5-85 without affecting the separation efficiency or elution order. For the analysis of aminoglycosides in bovine milk, the proposed approach demonstrates a sensitivity that is at least 10 times below the maximum residue limits set by most countries. PMID:27497008

  19. Satellite mobile data service for Canada

    NASA Technical Reports Server (NTRS)

    Egan, Glenn R.; Sward, David J.

    1990-01-01

    A commercial mobile satellite system which is to be constructed and operated in Canada is examined. This is done in two phases. First, mobile data services was introduced. Hub equipment and 3000 mobile data terminals were supplied. Over the satellite tests were performed. The mobile data service provides full two way digital messaging automatic vehicle location and fleet management services. The second phase is to construct, launch and make operational the MSAT satellite and associated network control facilities. The implementation is examined of the mobile data service in Canada, including the technical description. Marketing and applications are also examined.

  20. Acetonitrile-water hydrogen-bonded interaction: Matrix-isolation infrared and ab initio computation

    NASA Astrophysics Data System (ADS)

    Gopi, R.; Ramanathan, N.; Sundararajan, K.

    2015-08-01

    The 1:1 hydrogen-bonded complex of acetonitrile (CH3CN) and water (H2O) was trapped in Ar and N2 matrices and studied using infrared technique. Ab initio computations showed two types of complexes formed between CH3CN and H2O, a linear complex A with a Ctbnd N⋯H interaction between nitrogen of CH3CN and hydrogen of H2O and a cyclic complex B, in which the interactions are between the hydrogen of CH3CN with oxygen of H2O and hydrogen of H2O with π cloud of sbnd Ctbnd N of CH3CN. Vibrational wavenumber calculations revealed that both the complexes A and B were minima on the potential energy surface. Interaction energies computed at B3LYP/6-311++G(d,p) showed that linear complex A is more stable than cyclic complex B. Computations identified a blue shift of ∼11.5 cm-1 and a red shift of ∼6.5 cm-1 in the CN stretching mode for the complexes A and B, respectively. Experimentally, we observed a blue shift of ∼15.0 and ∼8.3 cm-1 in N2 and Ar matrices, respectively, in the CN stretching mode of CH3CN, which supports the formation of complex A. The Onsager Self Consistent Reaction Field (SCRF) model was used to explain the influence of matrices on the complexes A and B. To understand the nature of the interactions, Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analyses were carried out for the complexes A and B.

  1. Retention of ionisable compounds on high-performance liquid chromatography XIX. pH variation in mobile phases containing formic acid, piperazine and tris as buffering systems and methanol as organic modifier.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2009-07-10

    In previous works a model to estimate the pH of methanol-aqueous buffer mobile phases from the aqueous pH and concentration of the buffer and the fraction of organic modifier was developed. This model was successfully applied and validated for buffers prepared from ammonia, acetic, phosphoric and citric acids. In the present communication this model has been extended to formic acid, piperazine and tris(hydroxymethyl)aminomethane buffers. Prior to the modelling work, the pK(a) values of the studied buffers at several methanol-water compositions were determined.

  2. Modeling Mobility

    NASA Astrophysics Data System (ADS)

    Berl, Andras

    In wireless networks, communication can take place based on an infrastructure (e.g. WLAN access point or GPRS base station) or it can take place in adhoc mode, where mobile devices are connected directly to each other and care for the routing by themselves (mobile ad-hoc networks). When such wireless networks are investigated and simulations are performed, it is often necessary to consider the movement of entities within the simulated environment.

  3. Tailoring ultraresins based on the cross-linking of polyethylene imines. Comparative investigation of the chemical composition, the swelling, the mobility, the chemical accessibility, and the performance in solid-phase synthesis of very high loaded resins.

    PubMed

    Barth, Michael; Rademann, Jörg

    2004-01-01

    Ultraresins have been prepared from polyethyleneimines and cross-linking molecules and have been provided with various degrees of cross-linking. The total nitrogen loading and the loading with secondary and with tertiary amines have been determined in all products. Nitrogen loadings of the novel resins were up to 15 mmol/g, reactive secondary amines up to 13.8 mmol/g. In addition to the exceptionally high loading, the novel resins displayed efficient swelling volumes in polar and nonpolar solvents. The mobility of resin-bound species as determined by EPR-spectroscopy, depending on the amount of cross-linker, indicated good flexibility and reactivity of this resin type. The novel, high-loaded resins have been investigated subsequently in solid-phase synthesis. The Rink amide linker and two different hydroxy linkers (hydroxyacetamide, HMPB) have been attached to the resin. Despite the high loadings, the secondary amines were easily accessible and could be functionalized exhaustively. Reactivity of the linker-coupled resins was found to be closely related to the resin composition. Increased resin cross-linking led to reduced swelling, reduced mobility, and reduced reactivity in the synthesis of a medium-sized model peptide. As the result of the systematic investigation of structure-property relations in Ultraresins, a support material was identified that combined high reactivity and a mobility in the range of the extremely flexible Tentagel supports. In the optimized Ultraresin, >95% of all available secondary nitrogens could be coupled with Rink linker or with the small 2-hydroxyacetamide anchor, resulting in loadings from 2.7 to 6.8 mmol/g, respectively. A resin with an attached HMPB linker and spacer delivered analytically pure peptides in solid-phase synthesis, fully exploiting the exceptionally high loadings.

  4. Comprehensive separation of secondary metabolites in natural products by high-speed counter-current chromatography using a three-phase solvent system.

    PubMed

    Yanagida, Akio; Yamakawa, Yutaka; Noji, Ryoko; Oda, Ako; Shindo, Heisaburo; Ito, Yoichiro; Shibusawa, Yoichi

    2007-06-01

    High-speed counter-current chromatography (HSCCC) using the three-phase solvent system n-hexane-methyl acetate-acetonitrile-water at a volume ratio of 4:4:3:4 was applied to the comprehensive separation of secondary metabolites in several natural product extracts. A wide variety of secondary metabolites in each natural product was effectively extracted with the three-phase solvent system, and the filtered extract was directly submitted to the HSCCC separation using the same three-phase system. In the HSCCC profiles of crude natural drugs listed in the Japanese Pharmacopoeia, several physiologically active compounds were clearly separated from other components in the extracts. The HSCCC profiles of several tea products, each manufactured by a different process, clearly showed their compositional difference in main compounds such as catechins, caffeine, and pigments. These HSCCC profiles also provide useful information about hydrophobic diversity of whole components present in each natural product.

  5. Investigating changes in the gas-phase conformation of Antithrombin III upon binding of Arixtra using traveling wave ion mobility spectrometry (TWIMS)

    PubMed Central

    Zhao, Yuejie; Singh, Arunima; Li, Lingyun; Linhardt, Robert J.; Xu, Yongmei; Liu, Jian; Woods, Robert J.

    2015-01-01

    We validate the utility of ion mobility to measure protein conformational changes induced by the binding of glycosaminoglycan ligands, using the well characterized system of Antithrombin III (ATIII) and Arixtra, a pharmaceutical agent with heparin (Hp) activity. Heparin has been used as a therapeutic anticoagulant drug for several decades through its interaction with ATIII, a serine protease inhibitor that plays a central role in the blood coagulation cascade. This interaction induces conformational changes within ATIII that dramatically enhance the ATIII-mediated inhibition rate. Arixtra is the smallest synthetic Hp containing the specific pentasaccharide sequence required to bind with ATIII. Here we report the first travelling wave ion mobility mass spectrometry (TWIMS) investigation of the conformational changes in ATIII induced by its interaction with Arixtra. Native electrospray ionization mass spectrometry allowed the gentle transfer of the native topology of ATIII and ATIII–Arixtra complex. IM measurements of ATIII and ATIII–Arixtra complex showed a single structure, with well-defined collisional cross section (CCS) values. An average 3.6% increase in CCS of ATIII occurred as a result of its interaction with Arixtra, which agrees closely with the theoretical estimation of the change in CCS based on protein crystal structures. A comparison of the binding behavior of ATIII under both denaturing and non-denaturing conditions confirmed the significance of a folded tertiary structure of ATIII for its biological activity. A Hp oligosaccharide whose structure is similar to Arixtra but missing the 3-O sulfo group on the central glucosamine residue showed a dramatic decrease in binding affinity towards ATIII, but no change in the mobility behavior of the complex, consistent with prior studies that suggested that 3-O sulfation affects the equilibrium constant for binding to ATIII, but not the mode of interaction. In contrast, nonspecific binding by a Hp

  6. rhGM-CSF vs placebo following rhGM-CSF-mobilized PBPC transplantation: a phase III double-blind randomized trial.

    PubMed

    Legros, M; Fleury, J; Bay, J O; Choufi, B; Basile, M; Condat, P; Glenat, C; Communal, Y; Tavernier, F; Bons, J M; Chollet, P; Plagne, R; Chassagne, J

    1997-02-01

    In this placebo-controlled randomized trial we evaluated the hematological and clinical effects of r-Hu GM-CSF after high-dose chemotherapy (HDC) followed by GM-CSF-mobilized PBPC transplantation. Fifty patients with poor prognosis malignancies were randomized in a double-blind study to receive either GM-CSF or placebo after HDC followed by PBPC rescue. For all patients, PBPCs were recruited using a combination of VP-16 (300 mg/m2 on days 1 and 2), cytoxan (3 g/m2 on days 3 and 4) and GM-CSF (5 micrograms/kg from day 5). No differences were demonstrated between the two groups in median time to neutrophil or platelet recoveries. There was no significant difference between the GM-CSF group and the placebo group in the median duration of post-transplant hospitalization, in the number of days of antibiotic treatment, in the number of infections and in red blood cell or platelet transfusion requirements. There was a significant difference with an advantage for the placebo group in the mean duration of febrile days (P = 0.01). We conclude that the administration of GM-CSF in patients transplanted with GM-CSF-mobilized PBPC is not associated with a clinical benefit in term of tempo of engraftment, numbers of documented infections, transfusion requirements and mucositis grading.

  7. Simple setup for gas-phase H/D exchange mass spectrometry coupled to electron transfer dissociation and ion mobility for analysis of polypeptide structure on a liquid chromatographic time scale.

    PubMed

    Mistarz, Ulrik H; Brown, Jeffery M; Haselmann, Kim F; Rand, Kasper D

    2014-12-01

    Gas-phase hydrogen/deuterium exchange (HDX) is a fast and sensitive, yet unharnessed analytical approach for providing information on the structural properties of biomolecules, in a complementary manner to mass analysis. Here, we describe a simple setup for ND3-mediated millisecond gas-phase HDX inside a mass spectrometer immediately after ESI (gas-phase HDX-MS) and show utility for studying the primary and higher-order structure of peptides and proteins. HDX was achieved by passing N2-gas through a container filled with aqueous deuterated ammonia reagent (ND3/D2O) and admitting the saturated gas immediately upstream or downstream of the primary skimmer cone. The approach was implemented on three commercially available mass spectrometers and required no or minor fully reversible reconfiguration of gas-inlets of the ion source. Results from gas-phase HDX-MS of peptides using the aqueous ND3/D2O as HDX reagent indicate that labeling is facilitated exclusively through gaseous ND3, yielding similar results to the infusion of purified ND3-gas, while circumventing the complications associated with the use of hazardous purified gases. Comparison of the solution-phase- and gas-phase deuterium uptake of Leu-Enkephalin and Glu-Fibrinopeptide B, confirmed that this gas-phase HDX-MS approach allows for labeling of sites (heteroatom-bound non-amide hydrogens located on side-chains, N-terminus and C-terminus) not accessed by classical solution-phase HDX-MS. The simple setup is compatible with liquid chromatography and a chip-based automated nanoESI interface, allowing for online gas-phase HDX-MS analysis of peptides and proteins separated on a liquid chromatographic time scale at increased throughput. Furthermore, online gas-phase HDX-MS could be performed in tandem with ion mobility separation or electron transfer dissociation, thus enabling multiple orthogonal analyses of the structural properties of peptides and proteins in a single automated LC-MS workflow.

  8. Gas-Phase Analysis of the Complex of Fibroblast GrowthFactor 1 with Heparan Sulfate: A Traveling Wave Ion Mobility Spectrometry (TWIMS) and Molecular Modeling Study

    NASA Astrophysics Data System (ADS)

    Zhao, Yuejie; Singh, Arunima; Xu, Yongmei; Zong, Chengli; Zhang, Fuming; Boons, Geert-Jan; Liu, Jian; Linhardt, Robert J.; Woods, Robert J.; Amster, I. Jonathan

    2016-09-01

    Fibroblast growth factors (FGFs) regulate several cellular developmental processes by interacting with cell surface heparan proteoglycans and transmembrane cell surface receptors (FGFR). The interaction of FGF with heparan sulfate (HS) is known to induce protein oligomerization, increase the affinity of FGF towards its receptor FGFR, promoting the formation of the HS-FGF-FGFR signaling complex. Although the role of HS in the signaling pathways is well recognized, the details of FGF oligomerization and formation of the ternary signaling complex are still not clear, with several conflicting models proposed in literature. Here, we examine the effect of size and sulfation pattern of HS upon FGF1 oligomerization, binding stoichiometry and conformational stability, through a combination of ion mobility (IM) and theoretical modeling approaches. Ion mobility-mass spectrometry (IMMS) of FGF1 in the presence of several HS fragments ranging from tetrasaccharide (dp4) to dodecasaccharide (dp12) in length was performed. A comparison of the binding stoichiometry of variably sulfated dp4 HS to FGF1 confirmed the significance of the previously known high-affinity binding motif in FGF1 dimerization, and demonstrated that certain tetrasaccharide-length fragments are also capable of inducing dimerization of FGF1. The degree of oligomerization was found to increase in the presence of dp12 HS, and a general lack of specificity for longer HS was observed. Additionally, collision cross-sections (CCSs) of several FGF1-HS complexes were calculated, and were found to be in close agreement with experimental results. Based on the (CCSs) a number of plausible binding modes of 2:1 and 3:1 FGF1-HS are proposed.

  9. Volatile organic compound (VOC) emissions characterization during the flow-back phase of a hydraulically refractured well in the Uintah Basin, Utah using mobile PTR-MS measurements

    NASA Astrophysics Data System (ADS)

    Geiger, F.; Warneke, C.; Brown, S. S.; De Gouw, J. A.; Dube, W. P.; Edwards, P.; Gilman, J.; Graus, M.; Helleis, F.; Kofler, J.; Lerner, B. M.; Orphal, J.; Petron, G.; Roberts, J. M.; Zahn, A.

    2014-12-01

    Ongoing improvements in advanced technologies for crude oil and natural gas extraction from unconventional reserves, such as directional drilling and hydraulic fracturing, have greatly increased the production of fossil fuels within recent years. The latest forecasts even estimate an enhancement of 56% in total natural gas production due to increased development of shale gas, tight gas and offshore natural gas resources from 2012 to 2040 with the largest contribution from shale formations [US EIA: Annual Energy Outlook 2014]. During the field intensive 'Energy and Environment - Uintah Basin Winter Ozone Study (UBWOS)', measurements of volatile organic compounds (VOCs) were made using proton-transfer-reactions mass spectrometry (PTR-MS) at the ground site Horse Pool and using a mobile laboratory in the Uintah Basin, Utah, which is a region well known for intense fossil fuel production. A reworked gas well in the Red Wash fields was sampled regularly within two weeks performing mobile laboratory measurements downwind of the well site. The well had been recently hydraulically refractured at that time and waste water was collected into an open flow-back pond. Very high mixing ratios of aromatic hydrocarbons (C6-C13) up to the ppm range were observed coming from condensate and flow-back reservoirs. The measurements are used to determine sources of specific VOC emissions originating from the different parts of the well site and mass spectra are used to classify the air composition in contrast to samples taken at the Horse Pool field site and crude oil samples from South Louisiana. Enhancement ratios and time series of measured peak values for aromatics showed no clear trend, which indicates changes in emissions with operations at the site.

  10. Characterization of TATP gas phase product ion chemistry via isotope labeling experiments using ion mobility spectrometry interfaced with a triple quadrupole mass spectrometer.

    PubMed

    Tomlinson-Phillips, Jill; Wooten, Alfred; Kozole, Joseph; Deline, James; Beresford, Pamela; Stairs, Jason

    2014-09-01

    Identification of the fragment ion species associated with the ion reaction mechanism of triacetone triperoxide (TATP), a homemade peroxide-based explosive, is presented. Ion mobility spectrometry (IMS) has proven to be a key analytical technique in the detection of trace explosive material. Unfortunately, IMS alone does not provide chemical identification of the ions detected; therefore, it is unknown what ion species are actually formed and separated by the IMS. In IMS, ions are primarily characterized by their drift time, which is dependent on the ion׳s mass and molecular cross-section; thus, IMS as a standalone technique does not provide structural signatures, which is in sharp contrast to the chemical and molecular information that is generally obtained from other customary analytical techniques, such as NMR, Raman and IR spectroscopy and mass spectrometry. To help study the ion chemistry that gives rise to the peaks observed in IMS, the hardware of two different commercial IMS instruments has been directly coupled to triple quadrupole (QQQ) mass spectrometers, in order to ascertain each ion׳s corresponding mass/charge (m/z) ratios with different dopants at two temperatures. Isotope labeling was then used to help identify and confirm the molecular identity of the explosive fragment and adduct ions of TATP. The m/z values and isotope labeling experiments were used to help propose probable molecular formulas for the ion fragments. In this report, the fragment and adduct ions m/z 58 and 240 of TATP have been confirmed to be [C3H6NH·H](+) and [TATP·NH4](+), respectively; while the fragment ions m/z 73 and 89 of TATP are identified as having the molecular formulas [C4H9NH2](+) and [C4H9O2](+), respectively. It is anticipated that the work in this area will not only help to facilitate improvements in mobility-based detection (IMS and MS), but also aid in the development and optimization of MS-based detection algorithms for TATP.

  11. Characterization of TATP gas phase product ion chemistry via isotope labeling experiments using ion mobility spectrometry interfaced with a triple quadrupole mass spectrometer.

    PubMed

    Tomlinson-Phillips, Jill; Wooten, Alfred; Kozole, Joseph; Deline, James; Beresford, Pamela; Stairs, Jason

    2014-09-01

    Identification of the fragment ion species associated with the ion reaction mechanism of triacetone triperoxide (TATP), a homemade peroxide-based explosive, is presented. Ion mobility spectrometry (IMS) has proven to be a key analytical technique in the detection of trace explosive material. Unfortunately, IMS alone does not provide chemical identification of the ions detected; therefore, it is unknown what ion species are actually formed and separated by the IMS. In IMS, ions are primarily characterized by their drift time, which is dependent on the ion׳s mass and molecular cross-section; thus, IMS as a standalone technique does not provide structural signatures, which is in sharp contrast to the chemical and molecular information that is generally obtained from other customary analytical techniques, such as NMR, Raman and IR spectroscopy and mass spectrometry. To help study the ion chemistry that gives rise to the peaks observed in IMS, the hardware of two different commercial IMS instruments has been directly coupled to triple quadrupole (QQQ) mass spectrometers, in order to ascertain each ion׳s corresponding mass/charge (m/z) ratios with different dopants at two temperatures. Isotope labeling was then used to help identify and confirm the molecular identity of the explosive fragment and adduct ions of TATP. The m/z values and isotope labeling experiments were used to help propose probable molecular formulas for the ion fragments. In this report, the fragment and adduct ions m/z 58 and 240 of TATP have been confirmed to be [C3H6NH·H](+) and [TATP·NH4](+), respectively; while the fragment ions m/z 73 and 89 of TATP are identified as having the molecular formulas [C4H9NH2](+) and [C4H9O2](+), respectively. It is anticipated that the work in this area will not only help to facilitate improvements in mobility-based detection (IMS and MS), but also aid in the development and optimization of MS-based detection algorithms for TATP. PMID:24913870

  12. Phase Behavior, Solid Organic Precipitation, and Mobility Characterization Studies in Support of Enhanced Heavy Oil Recovery on the Alaska North Slope

    SciTech Connect

    Shirish Patil; Abhijit Dandekar; Santanu Khataniar

    2008-12-31

    The medium-heavy oil (viscous oil) resources in the Alaska North Slope are estimated at 20 to 25 billion barrels. These oils are viscous, flow sluggishly in the formations, and are difficult to recover. Recovery of this viscous oil requires carefully designed enhanced oil recovery processes. Success of these recovery processes is critically dependent on accurate knowledge of the phase behavior and fluid properties, especially viscosity, of these oils under variety of pressure and temperature conditions. This project focused on predicting phase behavior and viscosity of viscous oils using equations of state and semi-empirical correlations. An experimental study was conducted to quantify the phase behavior and physical properties of viscous oils from the Alaska North Slope oil field. The oil samples were compositionally characterized by the simulated distillation technique. Constant composition expansion and differential liberation tests were conducted on viscous oil samples. Experiment results for phase behavior and reservoir fluid properties were used to tune the Peng-Robinson equation of state and predict the phase behavior accurately. A comprehensive literature search was carried out to compile available compositional viscosity models and their modifications, for application to heavy or viscous oils. With the help of meticulously amassed new medium-heavy oil viscosity data from experiments, a comparative study was conducted to evaluate the potential of various models. The widely used corresponding state viscosity model predictions deteriorate when applied to heavy oil systems. Hence, a semi-empirical approach (the Lindeloff model) was adopted for modeling the viscosity behavior. Based on the analysis, appropriate adjustments have been suggested: the major one is the division of the pressure-viscosity profile into three distinct regions. New modifications have improved the overall fit, including the saturated viscosities at low pressures. However, with the limited

  13. Mobile Customer Relationship Management and Mobile Security

    NASA Astrophysics Data System (ADS)

    Sanayei, Ali; Mirzaei, Abas

    The purpose of this study is twofold. First, in order to guarantee a coherent discussion about mobile customer relationship management (mCRM), this paper presents a conceptualization of mCRM delineating its unique characteristics because of Among the variety of mobile services, considerable attention has been devoted to mobile marketing and in particular to mobile customer relationship management services. Second, the authors discusses the security risks in mobile computing in different level(user, mobile device, wireless network,...) and finally we focus on enterprise mobile security and it's subgroups with a series of suggestion and solution for improve mobile computing security.

  14. Are the Radical Centers in Peptide Radical Cations Mobile? The Generation, Tautomerism, and Dissociation of Isomeric α-Carbon-Centered Triglycine Radical Cations in the Gas Phase

    SciTech Connect

    Chu, Ivan K.; Zhao, Junfang; Xu, Minjie; Siu, Shiu On; Hopkinson, Alan C.; Siu , K W Michael

    2008-05-31

    The mobility of the radical center in three isomeric triglycine radical cationss[G•GG]+, [GG•G]+, and [GGG•]+shas been investigated theoretically via density functional theory (DFT) and experimentally via tandem mass spectrometry. These radical cations were generated by collision-induced dissociations (CIDs) of Cu(II)-containing ternary complexes that contain the tripeptides YGG, GYG, and GGY, respectively (G and Y are the glycine and tyrosine residues, respectively). Dissociative electron transfer within the complexes led to observation of [Y•GG]+, [GY•G]+, and [GGY•]+; CID resulted in cleavage of the tyrosine side chain as p-quinomethide, yielding [G•GG]+, [GG•G]+, and [GGG•]+, respectively. Interconversions between these isomeric triglycine radical cations have relatively high barriers (g44.7 kcal/mol), in support of the thesis that isomerically pure [G•GG]+, [GG•G]+, and [GGG•]+ can be experimentally produced. This is to be contrasted with barriers < 17 kcal/mol that were encountered in the tautomerism of protonated triglycine [Rodriquez C. F. et al. J. Am. Chem. Soc. 2001, 123, 3006-3012]. The CID spectra of [G•GG]+, [GG•G]+, and [GGG•]+ were substantially different, providing experimental proof that initially these ions have distinct structures. DFT calculations showed that direct dissociations are competitive with interconversions followed by dissociation.

  15. Investigations on the mobility of the glycosidic linkage in sucrose by study of the phase space structure of a two-degrees of freedom model.

    PubMed

    Longhi, G; Malandrino, M; Abbate, S

    2000-04-01

    Using the theoretical Ramachandran (phi, psi) maps reported in the literature for sucrose in vacuo and in aqueous solution, we constructed a two-degrees of freedom model in which the glucose and fructose units are substituted by pseudo-atoms. The complete dynamics of this model is studied numerically at fixed energies. Use is made of the graphic method of the Poincaré surfaces of section in phase space and of the Lissajous maps in configuration space. The reduction to just two degrees of freedom allows one to deal with all initial conditions in phase space, whereas the results of molecular dynamics calculations with all internal degrees of freedoms and with the explicit consideration of solvent molecules are taken into account via effective kinetic and potential energy terms. The conformational isomerization mechanism is investigated by singling out the most reactive trajectories in phase space that are associated with the so-called reactive islands and with the resonances found between the phi and psi motions. PMID:10994519

  16. Going mobile

    NASA Astrophysics Data System (ADS)

    Brus, Eric

    1987-12-01

    By 1990, all metropolitan areas in the U.S. and rural areas close to major cities or towns are expected to have cellular telephone service; 22 Canadian cities also feature cellular service. To supply mobile telecommunication services to sparsely-populated rural areas, a mobile satellite service (MSS) is now being developed. In this paper the projected possibilities of the MSS system are discussed, including a possibility that a piggyback-MSS payload be added to the GSTAR-4 satellite which is scheduled for a launch in 1988 or 1989; one in which some of the hardware from aborted direct-broadcast satellites would be used; and the possibility of building a new MSS satellite with large servicing capacity. Canada is planning to launch its own mobile satellite, MSAT, in the early 1990s. The MSS is expected to be 'generic', serving not only people on land but maritime and aeronautical users as well. It will also offer major benefits to truck and automobile drivers, making it possible for them to conduct business or to call for assistance from locations beyond the range of cellular systems.

  17. Mobile antennas for COMETS advanced mobile Satcom experiment

    NASA Technical Reports Server (NTRS)

    Hase, Yoshihiro; Tanaka, Masato; Saito, Haruo

    1995-01-01

    Advanced mobile satellite communication experiments in the Ka-band and the mm-wave will be carried out using the COMETS satellite, which is scheduled for launch in 1997. Mobile antennas will play a much more key role in high frequency systems such as COMETS than in conventional L-band mobile systems. This paper describes three types of antennas which are now being developed by the Communications Research Laboratory (CRL) for the COMETS mobile experiments. One is a mechanically steered waveguide slot array antenna, another is an electronically steered active phased array antenna, and the third is a mechanically steered torus reflector antenna. The first two antennas will be used in the Ka-band, while the latter will be used in the mm-wave.

  18. Electrospray ionization-ion mobility spectrometry as a detection system for three-phase hollow fiber microextraction technique and simultaneous determination of trimipramine and desipramine in urine and plasma samples.

    PubMed

    Jafari, M T; Saraji, M; Sherafatmand, H

    2011-04-01

    A novel method based on three-phase hollow fiber microextraction technique (HF-LPME) coupled with electrospray ionization-ion mobility spectrometry (ESI-IMS) was developed for the simultaneous determination of two antidepressant drugs (trimipramine and desipramine) in urine and plasma samples. The effects of various parameters such as type of organic solvent, composition of donor and acceptor phase, stirring rate, salt addition, extraction time, and temperature were investigated. Under the optimized conditions, the relative standard deviation was in the range of 5-6%, and the method quantitation limit (MQL) of utilizing HF-LPME/ESI-IMS was 5 μg/L for both drugs. The relative recoveries obtained by the proposed method from urine and plasma samples were in the range 94% to 97% for trimipramine and 92% to 96% for desipramine. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of trace amounts of trimipramine and desipramine in biological samples without any significant matrix effect.

  19. Carrier recovery techniques on satellite mobile channels

    NASA Technical Reports Server (NTRS)

    Vucetic, B.; Du, J.

    1990-01-01

    An analytical method and a stored channel model were used to evaluate error performance of uncoded quadrature phase shift keying (QPSK) and M-ary phase shift keying (MPSK) trellis coded modulation (TCM) over shadowed satellite mobile channels in the presence of phase jitter for various carrier recovery techniques.

  20. A Mobile Internet Service for Self-Management of Physical Activity in People With Rheumatoid Arthritis: Challenges in Advancing the Co-Design Process During the Requirements Specification Phase

    PubMed Central

    Martin, Cathrin; H. Opava, Christina; Brusewitz, Maria; Keller, Christina; Åsenlöf, Pernilla

    2015-01-01

    Background User involvement in the development of health care services is important for the viability, usability, and effectiveness of services. This study reports on the second step of the co-design process. Objective The aim was to explore the significant challenges in advancing the co-design process during the requirements specification phase of a mobile Internet service for the self-management of physical activity (PA) in rheumatoid arthritis (RA). Methods A participatory action research design was used to involve lead users and stakeholders as co-designers. Lead users (n=5), a clinical physiotherapist (n=1), researchers (n=2) with knowledge in PA in RA and behavioral learning theories, an eHealth strategist (n=1), and an officer from the patient organization (n=1) collaborated in 4 workshops. Data-collection methods included video recordings and naturalistic observations. Results The inductive qualitative video-based analysis resulted in 1 overarching theme, merging perspectives, and 2 subthemes reflecting different aspects of merging: (1) finding a common starting point and (2) deciding on design solutions. Seven categories illustrated the specific challenges: reaching shared understanding of goals, clarifying and handling the complexity of participants’ roles, clarifying terminology related to system development, establishing the rationale for features, negotiating features, transforming ideas into concrete features, and participants’ alignment with the agreed goal and task. Conclusions Co-designing the system requirements of a mobile Internet service including multiple stakeholders was a complex and extensive collaborative decision-making process. Considering, valuing, counterbalancing, and integrating different perspectives into agreements and solutions (ie, the merging of participants’ perspectives) were crucial for moving the process forward and were considered the core challenges of co-design. Further research is needed to replicate the results

  1. Mobile Transporter

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The Space Shuttle Atlantis, STS-110 mission, deployed this railcar, called the Mobile Transporter, and an initial 43-foot section of track, the S0 (S-zero) truss, preparing the International Space Station (ISS) for future spacewalks. The first railroad in space, the Mobile Transporter will allow the Station's robotic arm to travel up and down the finished truss for future assembly and maintenance. The 27,000-pound S0 truss is the first of 9 segments that will make up the Station's external framework that will eventually stretch 356 feet (109 meters), or approximately the length of a football field. The completed truss structure will hold solar arrays and radiators to provide power and cooling for additional international research laboratories from Japan and Europe that will be attached to the Station. The Space Shuttle Orbiter Atlantis, STS-110 mission, was launched April 8, 2002 and returned to Earth April 19, 2002. STS-110's Extravehicular Activity (EVA) marked the first use of the Station's robotic arm to maneuver spacewalkers around the Station.

  2. Modem for the land mobile satellite channel

    NASA Technical Reports Server (NTRS)

    Henely, Steven J.

    1988-01-01

    This paper describes a modem which has been developed and implemented using a digital signal processor (DSP) for a land mobile satellite demonstration system. The requirements of this digital modem were determined by the characteristics of the land mobile satellite channel. This paper discusses the algorithms which implement the differentiated phase shift keying (DPSK) demodulator. An algorithm is included which estimates symbol timing independent of carrier phase without the use of a square-law nonlinearity.

  3. Mobile shearography

    NASA Astrophysics Data System (ADS)

    Kalms, Michael; Jueptner, Werner

    2005-04-01

    By reason of their sensitivity, accuracy and non-contact as well as non-destructive characteristics, modern optical methods such as digital speckle shearography have found an increasing interest for NDT applications on the factory floor. With new carbon filter technologies and other lightweight constructions in aircraft and automotive manufacturing, adapted examination designs and especially developed testing methods are necessary. Shearography as a coherent optical method has been widely accepted as an useful NDT tool. It is a robust interferometric method to determine locations with maximum stress on various material structures. However, limitations of this technique can be found in the bulky equipment components, the interpretation of the complex sherographic result images and at the work with non-cooperative surfaces (dark absorber, bright shining reflectors). We report a mobile shearography system that was especially designed for investigations at aircraft and automotive constructions.

  4. Polypyrrole/montmorillonite nanocomposite as a new solid phase microextraction fiber combined with gas chromatography-corona discharge ion mobility spectrometry for the simultaneous determination of diazinon and fenthion organophosphorus pesticides.

    PubMed

    Jafari, Mohammad T; Saraji, Mohammad; Sherafatmand, Hossein

    2014-03-01

    A novel solid phase microextraction (SPME) fiber was prepared and coupled with gas chromatography corona discharge ion mobility spectrometry (GC-CD-IMS) based on polypyrrole/montmorillonite nanocomposites for the simultaneous determination of diazinon and fenthion. The nanocomposite polymer was coated using a three-electrode electrochemical system and directly deposited on a Ni-Cr wire by applying a constant potential. The scanning electron microscopy images revealed that the new fiber exhibited a rather porous and homogenous surface. The thermal stability of the fabricated fiber was investigated by thermogravimetric analysis. The effects of different parameters influencing the extraction efficiency such as extraction temperature and time, salt addition, stirring rate, the amount of nanoclay, and desorption temperature were investigated and optimized. The method was exhaustively evaluated in terms of sensitivity, recovery, and reproducibility. The linearity ranges of 0.05-10 and 0.08-10 μg L(-1), and the detection limits of 0.020 and 0.035 μg L(-1) were obtained for diazinon and fenthion, respectively. The relative standard deviation values were calculated to be lower than 5% and 8% for intra-day and inter-day, respectively. Finally, the developed method was applied to determine the diazinon and fenthion (as model compounds) in cucumber, lettuce, apple, tap and river water samples. The satisfactory recoveries revealed the capability of the two-dimensional separation technique (retention time in GC and drift time in IMS) for the analysis of complex matrices extracted by SPME. PMID:24528846

  5. Cooperating mobile robots

    DOEpatents

    Harrington, John J.; Eskridge, Steven E.; Hurtado, John E.; Byrne, Raymond H.

    2004-02-03

    A miniature mobile robot provides a relatively inexpensive mobile robot. A mobile robot for searching an area provides a way for multiple mobile robots in cooperating teams. A robotic system with a team of mobile robots communicating information among each other provides a way to locate a source in cooperation. A mobile robot with a sensor, a communication system, and a processor, provides a way to execute a strategy for searching an area.

  6. Mobile Schools for a Mobile World

    ERIC Educational Resources Information Center

    Booth, Susan

    2013-01-01

    Overwhelmingly, independent schools are embracing mobile devices--laptops, iPads or other tablets, and smartphones--to enhance teaching and learning. This article describes the results of the "NAIS 2012 Mobile Learning Survey." Among its findings were that 75 percent of NAIS-member schools currently use mobile learning devices in at…

  7. Design characteristics of the Sludge Mobilization System

    SciTech Connect

    McMahon, C.L.

    1990-09-30

    Radioactive waste stored in underground tanks at the West Valley Demonstration Project is being processed into low-level waste and solidified in cement. High-level waste also stored underground will be vitrified and solidified into canistered glass logs. To move the waste from where it resides at the Waste Tank Farm to the Vitrification Facility requires equipment to prepare the storage tanks for low-level and high-level waste processing, equipment to mobilize and mix the radioactive sludge into a homogeneous slurry, and equipment to transfer the slurry for vitrification. The design of the Sludge Mobilization System has incorporated the necessary components to effect the preparation and transfer of waste in five operational phases. The first phase of the Sludge Mobilization System, which began in 1987, prepared the waste tanks to process radioactive liquid for delivery to the Cement Solidification System and to support the mobilization equipment. The second phase, beginning in 1991, will wash the sludge that remains after the liquid supernatant is decanted to prepare it for mobilization operations. The third phase will combine the contents of various waste tanks into one tank. The fourth phase will resuspend and mix the contents of the high-level waste tank. The fifth and final phase of the Sludge Mobilization System will entail transferring the waste mixture to the Vitrification Facility for processing into glass logs. Provisions for recycling the waste streams or slurries within the tank farm or for returning process streams to the Waste Tank Farm from the Vitrification Facility are also included in the final phase. This document addresses the Sludge Mobilization System equipment design characteristics in terms of its use in each of the five operational phases listed above.

  8. Pravastatin Improves Function in Hibernating Myocardium by Mobilizing CD133+ and cKit+ Bone Marrow Progenitor Cells and Promoting Myocytes to Reenter the Growth Phase of the Cardiac Cell Cycle

    PubMed Central

    Suzuki, Gen; Iyer, Vijay; Cimato, Thomas; Canty, John M.

    2009-01-01

    HMG-CoA reductase inhibitors have been reported to increase circulating bone marrow progenitor cells (BMPCs) and variably improve global function in heart failure. The potential role of improved perfusion vs. direct effects of statins on cardiac myocytes has not been established. We chronically instrumented swine with an LAD stenosis to produce chronic hibernating myocardium with regional contractile dysfunction in the absence of heart failure. Hemodynamics, function, perfusion and histopathology were assessed in pigs treated for five-weeks with pravastatin (n=12) vs. untreated controls (n=10). Regional LAD wall thickening was depressed under baseline conditions (LAD 3.7±0.3 vs. 6.6 ±0.3 in remote regions, p<0.01). It remained unchanged in untreated animals but increased from 3.8±0.6 to 5.2±0.5 mm after pravastatin (p<0.01). There was no increase in myocardial perfusion at rest or during vasodilation. Pravastatin mobilized circulating CD133+/cKit+ BMPCs and increased myocardial tissue levels (LAD CD133+ cells from 140±33 to 884±167 cells/106myocyte nuclei and cKit+ cells from 223±49 to 953±123 cells/106myocyte nuclei). Pravastatin increased myocytes in mitosis (phospho-histone-H3; 9±5 to 43±7 nuclei/106myocyte nuclei, p<0.05) and the growth phase of the cell cycle (Ki67; 410±82 to 1261±235 nuclei/106myocyte nuclei, p<0.05) in diseased but not normal hearts. As a result, pravastatin increased LAD myocyte nuclear density from 830±41 to 1027±55 nuclei/mm2 (p<0.05). These data indicate that, in the absence of impaired endothelial function and heart failure, dysfunctional hibernating myocardium improves after pravastatin. This effect is independent of myocardial perfusion and related to mobilization of CD133+/cKit+ BMPCs which stimulate myocyte proliferation resulting in quantitative increases in myocyte nuclear density. PMID:19096024

  9. Mobility of University Staff.

    ERIC Educational Resources Information Center

    Council for Cultural Cooperation, Strasbourg (France).

    This study deals with interuniversity mobility. Part I examines the harmonization of action taken to encourage mobility, the removal of legislative and statutory obstacles to mobility, the simplification of university staff regulations and careers, and incentives to mobility. Part II describes the ideas and activities of UNESCO, the Council of…

  10. Water uptake on polar stationary phases under conditions for hydrophilic interaction chromatography and its relation to solute retention.

    PubMed

    Dinh, Ngoc Phuoc; Jonsson, Tobias; Irgum, Knut

    2013-12-13

    Since water associated with the stationary phase surface appears to be the essence of the retention mechanism in hydrophilic interaction chromatography (HILIC), we developed a method to characterize the water-absorbing capabilities of twelve different HILIC stationary phases. Adsorption isotherms for non-modified and monomerically functionalized silica phases adhered to a pattern of monolayer formation followed by multilayer adsorption, whereas water uptake on polymerically functionalized silica stationary phases showed the characteristics of formation and swelling of hydrogels. Water accumulation was affected by adding ammonium acetate as buffer electrolyte and by replacing 5% of the acetonitrile with tertiary solvents capable of hydrogen bonding such as methanol or tetrahydrofuran. The relationship between water uptake and retention mechanism was investigated by studying the correlations between retention factors of neutral analytes and the phase ratios of HILIC columns, calculated either from the surface area (adsorption) or the volume of the water layer enriched from the acetonitrile/water eluent (partitioning). These studies made it evident that adsorption and partitioning actually coexist as retention promoters for neutral solutes in the water concentration regime normally encountered in HILIC. Which factors that dominates is dependent on the nature of the solute, the stationary phase, and the eluting conditions. PMID:24200388

  11. Understanding the spreading patterns of mobile phone viruses.

    PubMed

    Wang, Pu; González, Marta C; Hidalgo, César A; Barabási, Albert-László

    2009-05-22

    We modeled the mobility of mobile phone users in order to study the fundamental spreading patterns that characterize a mobile virus outbreak. We find that although Bluetooth viruses can reach all susceptible handsets with time, they spread slowly because of human mobility, offering ample opportunities to deploy antiviral software. In contrast, viruses using multimedia messaging services could infect all users in hours, but currently a phase transition on the underlying call graph limits them to only a small fraction of the susceptible users. These results explain the lack of a major mobile virus breakout so far and predict that once a mobile operating system's market share reaches the phase transition point, viruses will pose a serious threat to mobile communications.

  12. Solid colloids with surface-mobile linkers.

    PubMed

    van der Meulen, Stef A J; Helms, Gesa; Dogterom, Marileen

    2015-06-17

    In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell-cell interactions and cell adhesion processes.

  13. SOFCo mobile planar solid oxide generator

    SciTech Connect

    Khandkar, A.C.; Privette, R.M.

    1995-08-01

    This paper presents results from the first phase of a three phase, four-year program with the objective of designing and demonstrating a 10 kW mobile electric power generator operating on logistic fuel. Objectives of the first phase include: the development of a preliminary system design, an assessment of technologies critical to system performance, and the fabrication of three multi-stack test units.

  14. Mobile Router Technology Development

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Stewart, David H.; Bell, Terry L.; Kachmar, Brian A.; Shell, Dan; Leung, Kent

    2002-01-01

    Cisco Systems and NASA have been performing joint research on mobile routing technology under a NASA Space Act Agreement. Cisco developed mobile router technology and provided that technology to NASA for applications to aeronautic and space-based missions. NASA has performed stringent performance testing of the mobile router, including the interaction of routing and transport-level protocols. This paper describes mobile routing, the mobile router, and some key configuration parameters. In addition, the paper describes the mobile routing test network and test results documenting the performance of transport protocols in dynamic routing environments.

  15. Ion mobility sensor system

    DOEpatents

    Xu, Jun; Watson, David B.; Whitten, William B.

    2013-01-22

    An ion mobility sensor system including an ion mobility spectrometer and a differential mobility spectrometer coupled to the ion mobility spectrometer. The ion mobility spectrometer has a first chamber having first end and a second end extending along a first direction, and a first electrode system that generates a constant electric field parallel to the first direction. The differential mobility spectrometer includes a second chamber having a third end and a fourth end configured such that a fluid may flow in a second direction from the third end to the fourth end, and a second electrode system that generates an asymmetric electric field within an interior of the second chamber. Additionally, the ion mobility spectrometer and the differential mobility spectrometer form an interface region. Also, the first end and the third end are positioned facing one another so that the constant electric field enters the third end and overlaps the fluid flowing in the second direction.

  16. Tandem mobile robot system

    DOEpatents

    Buttz, James H.; Shirey, David L.; Hayward, David R.

    2003-01-01

    A robotic vehicle system for terrain navigation mobility provides a way to climb stairs, cross crevices, and navigate across difficult terrain by coupling two or more mobile robots with a coupling device and controlling the robots cooperatively in tandem.

  17. Superintendent Vulnerability and Mobility.

    ERIC Educational Resources Information Center

    Parker, Phyllis

    1996-01-01

    Examined Callahan's vulnerability thesis to determine its ability to explain the mobility of superintendents in Texas between 1985 and 1990. Questionnaire and interview data indicated that, at least in Texas where superintendent mobility reached 50% in that time period, vulnerability did not appear to account for much of superintendent mobility.…

  18. Mobility and Young Children.

    ERIC Educational Resources Information Center

    Bernard van Leer Foundation Newsletter, 1994

    1994-01-01

    This newsletter theme issue deals with the phenomenon of mobility or transience in India, Kenya, Greece, Ireland, Malaysia, Thailand and Israel. The primary focus is on mobility's effect on young children, specifically their health and education; some of the broader concerns also addressed by the newsletter are the causes of mobility and its…

  19. Mobile Student Information System

    ERIC Educational Resources Information Center

    Asif, Muhammad; Krogstie, John

    2011-01-01

    Purpose: A mobile student information system (MSIS) based on mobile computing and context-aware application concepts can provide more user-centric information services to students. The purpose of this paper is to describe a system for providing relevant information to students on a mobile platform. Design/methodology/approach: The research…

  20. A secure network access system for mobile IPv6

    NASA Astrophysics Data System (ADS)

    Zhang, Hong; Yuan, Man; He, Rui; Jiang, Luliang; Ma, Jian; Qian, Hualin

    2004-03-01

    With the fast development of Internet and wireless and mobile communication technology, the Mobile Internet Age is upcoming. For those providing Mobile Internet services, especially from the view of ISP (Internet Service Provider), current mobile IP protocol is insufficient. Since the Mobile IPv6 protocol will be popular in near future, how to provide a secure mobile IPv6 service is important. A secure mobile IPv6 network access system is highly needed for mobile IPv6 deployment. Current methods and systems are still inadequate, including EAP, PANA, 802.1X, RADIUS, Diameter, etc. In this paper, we describe main security goals for a secure mobile IPv6 access system, and propose a secure network access system to achieve them. This access system consists of access router, attendant and authentication servers. The access procedure is divided into three phases, which are initial phase, authentication and registration phase and termination phase. This system has many advantages, including layer two independent, flexible and extensible, no need to modify current IPv6 address autoconfiguration protocols, binding update optimization, etc. Finally, the security of the protocol in this system is analyzed and proved with Extended BAN logic method, and a brief introduction of system implementation is given.

  1. Ion mobility sensor

    DOEpatents

    Koo, Jackson C.; Yu, Conrad M.

    2005-08-23

    An ion mobility sensor which can detect both ion and molecules simultaneously. Thus, one can measure the relative arrival times between various ions and molecules. Different ions have different mobility in air, and the ion sensor enables measurement of ion mobility, from which one can identify the various ions and molecules. The ion mobility sensor which utilizes a pair of glow discharge devices may be designed for coupling with an existing gas chromatograph, where various gas molecules are already separated, but numbers of each kind of molecules are relatively small, and in such cases a conventional ion mobility sensor cannot be utilized.

  2. Mobile Virtual Private Networking

    NASA Astrophysics Data System (ADS)

    Pulkkis, Göran; Grahn, Kaj; Mårtens, Mathias; Mattsson, Jonny

    Mobile Virtual Private Networking (VPN) solutions based on the Internet Security Protocol (IPSec), Transport Layer Security/Secure Socket Layer (SSL/TLS), Secure Shell (SSH), 3G/GPRS cellular networks, Mobile IP, and the presently experimental Host Identity Protocol (HIP) are described, compared and evaluated. Mobile VPN solutions based on HIP are recommended for future networking because of superior processing efficiency and network capacity demand features. Mobile VPN implementation issues associated with the IP protocol versions IPv4 and IPv6 are also evaluated. Mobile VPN implementation experiences are presented and discussed.

  3. 33 CFR 165.835 - Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL. 165.835 Section 165.835 Navigation and Navigable Waters COAST GUARD... § 165.835 Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL. (a) Definition. As used...

  4. 33 CFR 165.835 - Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL. 165.835 Section 165.835 Navigation and Navigable Waters COAST GUARD... § 165.835 Security Zone; Port of Mobile, Mobile Ship Channel, Mobile, AL. (a) Definition. As used...

  5. Modeling vapor uptake induced mobility shifts in peptide ions observed with transversal modulation ion mobility spectrometry-mass spectrometry.

    PubMed

    Rawat, Vivek K; Vidal-de-Miguel, Guillermo; Hogan, Christopher J

    2015-10-21

    Low field ion mobility spectrometry-mass spectrometry (IMS-MS) techniques exhibit low orthogonality, as inverse mobility often scales with mass to charge ratio. This inadequacy can be mitigated by adding vapor dopants, which may cluster with analyte ions and shift their mobilities by amounts independent of both mass and mobility of the ion. It is therefore important to understand the interactions of vapor dopants with ions, to better quantify the extent of dopant facilitated mobility shifts. Here, we develop predictive models of vapor dopant facilitated mobility shifts, and compare model calculations to measurements of mobility shifts for peptide ions exposed to variable gas phase concentrations of isopropanol. Mobility measurements were made at atmospheric pressure and room temperature using a recently developed transversal modulation ion mobility spectrometer (TMIMS). Results are compared to three separate models, wherein mobility shifts due to vapor dopants are attributed to changes in gas composition and (I) no vapor dopant uptake is assumed, (II) site-specific dopant uptake by the ion is assumed (approximated via a Langmuir adsorption model), and (III) site-unspecific dopant uptake by the ion is assumed (approximated via a classical nucleation model). We find that mobility shifts in peptide ions are in excellent agreement with model II, site-specific binding predictions. Conversely, mobility shifts of tetraalkylammonium ions from previous measurements were compared with these models and best agreement was found with model III predictions, i.e. site-unspecific dopant uptake.

  6. Mobile Bay turbidity plume study

    NASA Technical Reports Server (NTRS)

    Crozier, G. F.

    1976-01-01

    Laboratory and field transmissometer studies on the effect of suspended particulate material upon the appearance of water are reported. Quantitative correlations were developed between remotely sensed image density, optical sea truth data, and actual sediment load. Evaluation of satellite image sea truth data for an offshore plume projects contours of transmissivity for two different tidal phases. Data clearly demonstrate the speed of change and movement of the optical plume for water patterns associated with the mouth of Mobile bay in which relatively clear Gulf of Mexico water enters the bay on the eastern side. Data show that wind stress in excess of 15 knots has a marked impact in producing suspended sediment loads.

  7. Mobile workstation for decontamination and decommissioning operations

    SciTech Connect

    Whittaker, W.L.; Osborn, J.F.; Thompson, B.R.

    1993-10-01

    This project is an interdisciplinary effort to develop effective mobile worksystems for decontamination and decommissioning (D&D) of facilities within the DOE Nuclear Weapons Complex. These mobile worksystems will be configured to operate within the environmental and logistical constraints of such facilities and to perform a number of work tasks. Our program is designed to produce a mobile worksystem with capabilities and features that are matched to the particular needs of D&D work by evolving the design through a series of technological developments, performance tests and evaluations. The project has three phases. In this the first phase, an existing teleoperated worksystem, the Remote Work Vehicle (developed for use in the Three Mile Island Unit 2 Reactor Building basement), was enhanced for telerobotic performance of several D&D operations. Its ability to perform these operations was then assessed through a series of tests in a mockup facility that contained generic structures and equipment similar to those that D&D work machines will encounter in DOE facilities. Building upon the knowledge gained through those tests and evaluations, a next generation mobile worksystem, the RWV II, and a more advanced controller will be designed, integrated and tested in the second phase, which is scheduled for completion in January 1995. The third phase of the project will involve testing of the RWV II in the real DOE facility.

  8. ACTS mobile SATCOM experiments

    NASA Technical Reports Server (NTRS)

    Abbe, Brian S.; Frye, Robert E.; Jedrey, Thomas C.

    1993-01-01

    Over the last decade, the demand for reliable mobile satellite communications (satcom) for voice, data, and video applications has increased dramatically. As consumer demand grows, the current spectrum allocation at L-band could become saturated. For this reason, NASA and the Jet Propulsion Laboratory are developing the Advanced Communications Technology Satellites (ACTS) mobile terminal (AMT) and are evaluating the feasibility of K/Ka-band (20/30 GHz) mobile satcom to meet these growing needs. U.S. industry and government, acting as co-partners, will evaluate K/Ka-band mobile satcom and develop new technologies by conducting a series of applications-oriented experiments. The ACTS and the AMT testbed will be used to conduct these mobile satcom experiments. The goals of the ACTS Mobile Experiments Program and the individual experiment configurations and objectives are further presented.

  9. Mobile learning in medicine

    NASA Astrophysics Data System (ADS)

    Serkan Güllüoüǧlu, Sabri

    2013-03-01

    This paper outlines the main infrastructure for implicating mobile learning in medicine and present a sample mobile learning application for medical learning within the framework of mobile learning systems. Mobile technology is developing nowadays. In this case it will be useful to develop different learning environments using these innovations in internet based distance education. M-learning makes the most of being on location, providing immediate access, being connected, and acknowledges learning that occurs beyond formal learning settings, in places such as the workplace, home, and outdoors. Central to m-learning is the principle that it is the learner who is mobile rather than the device used to deliver m learning. The integration of mobile technologies into training has made learning more accessible and portable. Mobile technologies make it possible for a learner to have access to a computer and subsequently learning material and activities; at any time and in any place. Mobile devices can include: mobile phone, personal digital assistants (PDAs), personal digital media players (eg iPods, MP3 players), portable digital media players, portable digital multimedia players. Mobile learning (m-learning) is particularly important in medical education, and the major users of mobile devices are in the field of medicine. The contexts and environment in which learning occurs necessitates m-learning. Medical students are placed in hospital/clinical settings very early in training and require access to course information and to record and reflect on their experiences while on the move. As a result of this paper, this paper strives to compare and contrast mobile learning with normal learning in medicine from various perspectives and give insights and advises into the essential characteristics of both for sustaining medical education.

  10. Exploring the mobility of mobile phone users

    NASA Astrophysics Data System (ADS)

    Csáji, Balázs Cs.; Browet, Arnaud; Traag, V. A.; Delvenne, Jean-Charles; Huens, Etienne; Van Dooren, Paul; Smoreda, Zbigniew; Blondel, Vincent D.

    2013-03-01

    Mobile phone datasets allow for the analysis of human behavior on an unprecedented scale. The social network, temporal dynamics and mobile behavior of mobile phone users have often been analyzed independently from each other using mobile phone datasets. In this article, we explore the connections between various features of human behavior extracted from a large mobile phone dataset. Our observations are based on the analysis of communication data of 100,000 anonymized and randomly chosen individuals in a dataset of communications in Portugal. We show that clustering and principal component analysis allow for a significant dimension reduction with limited loss of information. The most important features are related to geographical location. In particular, we observe that most people spend most of their time at only a few locations. With the help of clustering methods, we then robustly identify home and office locations and compare the results with official census data. Finally, we analyze the geographic spread of users’ frequent locations and show that commuting distances can be reasonably well explained by a gravity model.

  11. Molecularly imprinted polymer solid-phase extraction for detection of zearalenone in cereal sample extracts.

    PubMed

    Lucci, Paolo; Derrien, Delphine; Alix, Florent; Pérollier, Céline; Bayoudh, Sami

    2010-07-01

    The aim of this work was to develop a method for the clean-up and preconcentration of zearalenone from corn and wheat samples employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE). Cereal samples were extracted with acetonitrile/water (75:25, v/v) and the extract was diluted with water and applied to an AFFINIMIP ZON MIP-SPE column. The column was then washed to eliminate the interferences and zearalenone was eluted with methanol and quantified using HPLC with fluorescence detection (lambda(exc)=275/lambda(em)=450 nm). The precision and accuracy of the method were satisfactory for both cereals at the different fortification levels tested and it gave recoveries between 82 and 87% (RSDr 2.5-6.2%, n=3) and 86 and 90% (RSDr 0.9-6.8%, n=3) for wheat and maize, respectively. MIP-SPE column capacity was determined to be not less than 6.6 microg of zearalenone and to be at least four times higher than that of immunoaffinity column (IAC). The application of AFFINIMIP ZON molecularly imprinted polymer as a selective sorbent material for detection of zearalenone fulfilled the method performance criteria required by the Commission Regulation (EC) No. 401/2006, demonstrating the suitability of the technique for the control of zearalenone in cereal samples.

  12. Mobility control agent

    SciTech Connect

    Argabright, P.A.; Phillips, B.L.; Rhudy, J.S.

    1983-05-17

    Polymer mobility control agents useful in supplemental oil recovery processes, which give improved reciprocal relative mobilities, are prepared by initiating the polymerization of a monomer containing a vinyl group with a catalyst comprising a persulfate and ferrous ammonium sulfate. The vinyl monomer is an acrylyl, a vinyl cyanide, a styryl and water soluble salts thereof.

  13. Mobile Apps for Librarians

    ERIC Educational Resources Information Center

    Power, June L.

    2013-01-01

    In an increasing mobile environment, library and reading-related activities often take place on a phone or tablet device. Not only does this mean that library Web sites must keep mobile navigability in mind, but also develop and utilize apps that allow patrons to interact with information and with libraries. While apps do not serve every purpose,…

  14. Mobile Learning Anytime, Anywhere

    ERIC Educational Resources Information Center

    Hlodan, Oksana

    2010-01-01

    Some educational institutions are taking the leap to mobile learning (m-learning) by giving out free iPods. For example, Abilene Christian University gave iPods or iPhones to freshman students and developed 15 Web applications specifically for the mobile devices. The iPod is not the only ubiquitous m-learning device. Any technology that connects…

  15. Mastering Mobile Security

    ERIC Educational Resources Information Center

    Panettieri, Joseph C.

    2007-01-01

    Without proper security, mobile devices are easy targets for worms, viruses, and so-called robot ("bot") networks. Hackers increasingly use bot networks to launch massive attacks against eCommerce websites--potentially targeting one's online tuition payment or fundraising/financial development systems. How can one defend his mobile systems against…

  16. Mobility and Reading Achievement.

    ERIC Educational Resources Information Center

    Waters, Theresa Z.

    A study examined the effect of geographic mobility on elementary school students' achievement. Although such mobility, which requires students to make multiple moves among schools, can have a negative impact on academic achievement, the hypothesis for the study was that it was not a determining factor in reading achievement test scores. Subjects…

  17. Mobile Goes Mainstream

    ERIC Educational Resources Information Center

    Eisele-Dyrli, Kurt

    2011-01-01

    Mobile learning--the use of mobile devices for educational purposes by students--is rapidly moving from an experimental initiative by a few innovative districts over the last five years to a broadly accepted concept in K12. The latest research and surveys, results of pilot programs, and analysis of trends in both public education and the broader…

  18. [Cognition and mobility].

    PubMed

    Bridenbaugh, Stephanie A

    2015-04-01

    Felix Platter Hospital, University Center for Medicine of Aging, Basel, Switzerland; There is a strong association between cognition and mobility. Older adults with gait deficits have an increased risk of developing cognitive deficits, even dementia. Cognitive deficits, on the other hand, are associated with worsening gait. Cognitive as well as mobility deficits are associated with an increased fall risk. Assessments of cognition, particularly the executive functions, and functional mobility should therefore be an integral part of every comprehensive geriatric assessment. Some quick screening tests for mobility disorders can be performed in a clinical praxis. If those assessments provide pathological results, then consider patient referral for an in-depth gait analysis. Gait analyses that utilize dual task paradigms (walking and simultaneously performing a second task) are particularly meaningful for early detection of mobility and cognitive deficits. Early detection permits timely implementation of targeted interventions to improve gait and brain function. PMID:25791044

  19. Skylab mobile laboratory

    NASA Technical Reports Server (NTRS)

    Primeaux, G. R.; Larue, M. A.

    1975-01-01

    The Skylab mobile laboratory was designed to provide the capability to obtain necessary data on the Skylab crewmen 30 days before lift-off, within 1 hour after recovery, and until preflight physiological baselines were reattained. The mobile laboratory complex consisted of six laboratories that supported cardiovascular, metabolic, nutrition and endocrinology, operational medicine, blood, and microbiology experiments; a utility package; and two shipping containers. The objectives and equipment requirements of the Skylab mobile laboratory and the data acquisition systems are discussed along with processes such as permanently mounting equipment in the individual laboratories and methods of testing and transporting the units. The operational performance, in terms of amounts of data collected, and the concept of mobile laboratories for medical and scientific experiments are evaluated. The Skylab mobile laboratory succeeded in facilitating the data collection and sample preservation associated with the three Skylab manned flights.

  20. Gone Mobile? (Mobile Libraries Survey 2010)

    ERIC Educational Resources Information Center

    Thomas, Lisa Carlucci

    2010-01-01

    Librarians, like patrons and researchers, are caught between traditional library service models and the promise of evolving information technologies. In recent years, professional conferences have strategically featured programs and presentations geared toward building a mobile agenda and adapting or adopting services to meet new demands of mobile…

  1. Mobility Modification Alleviates Environmental Influence on Incident Mobility Difficulty among Community-Dwelling Older People: A Two-Year Follow-Up Study

    PubMed Central

    Portegijs, Erja; Viljanen, Anne; Iwarsson, Susanne; Rantanen, Taina

    2016-01-01

    Background Environmental barriers increase risk for mobility difficulties in old age. Mobility difficulty is preceded by a phase where people try to postpone a difficulty through mobility modification. We studied whether perceived environmental mobility barriers outdoors correlate with mobility modification and mobility difficulty, predict development of mobility difficulty over a two-year follow-up, and whether mobility modification alleviates the risk for difficulty. Methods At baseline, 848 people aged 75–90 were interviewed face-to-face. Telephone follow-up interviews were conducted one (n = 816) and two years (n = 761) later. Environmental barriers to mobility were self-reported using a15-item structured questionnaire at baseline, summed and divided into tertiles (0, 1 and 2 or more barriers). Mobility difficulty was assessed as self-reported ability to walk 2 km at all assessment points and categorized into ‘no difficulty’, ‘no difficulty but mobility modifications’ (reducing frequency, stopping walking, using an aid, slowing down or resting during the performance) and ‘difficulty’. Results At baseline, 212 participants reported mobility modifications and 356 mobility difficulties. Those reporting one or multiple environmental barriers had twice the odds for mobility modifications and up to five times the odds for mobility difficulty compared to those reporting no environmental barriers. After multiple adjustments for health and functioning, reporting multiple environmental barriers outdoors continued to predict the development of incident mobility difficulty over the two-year follow-up. Mobility modifications attenuated the association. Conclusion For older people who successfully modify their performance, environmental influence on incident mobility difficulty can be diminished. Older people use mobility modification to alleviate environmental press on mobility. PMID:27104750

  2. Limits of social mobilization.

    PubMed

    Rutherford, Alex; Cebrian, Manuel; Dsouza, Sohan; Moro, Esteban; Pentland, Alex; Rahwan, Iyad

    2013-04-16

    The Internet and social media have enabled the mobilization of large crowds to achieve time-critical feats, ranging from mapping crises in real time, to organizing mass rallies, to conducting search-and-rescue operations over large geographies. Despite significant success, selection bias may lead to inflated expectations of the efficacy of social mobilization for these tasks. What are the limits of social mobilization, and how reliable is it in operating at these limits? We build on recent results on the spatiotemporal structure of social and information networks to elucidate the constraints they pose on social mobilization. We use the DARPA Network Challenge as our working scenario, in which social media were used to locate 10 balloons across the United States. We conduct high-resolution simulations for referral-based crowdsourcing and obtain a statistical characterization of the population recruited, geography covered, and time to completion. Our results demonstrate that the outcome is plausible without the presence of mass media but lies at the limit of what time-critical social mobilization can achieve. Success relies critically on highly connected individuals willing to mobilize people in distant locations, overcoming the local trapping of diffusion in highly dense areas. However, even under these highly favorable conditions, the risk of unsuccessful search remains significant. These findings have implications for the design of better incentive schemes for social mobilization. They also call for caution in estimating the reliability of this capability. PMID:23576719

  3. Limits of social mobilization.

    PubMed

    Rutherford, Alex; Cebrian, Manuel; Dsouza, Sohan; Moro, Esteban; Pentland, Alex; Rahwan, Iyad

    2013-04-16

    The Internet and social media have enabled the mobilization of large crowds to achieve time-critical feats, ranging from mapping crises in real time, to organizing mass rallies, to conducting search-and-rescue operations over large geographies. Despite significant success, selection bias may lead to inflated expectations of the efficacy of social mobilization for these tasks. What are the limits of social mobilization, and how reliable is it in operating at these limits? We build on recent results on the spatiotemporal structure of social and information networks to elucidate the constraints they pose on social mobilization. We use the DARPA Network Challenge as our working scenario, in which social media were used to locate 10 balloons across the United States. We conduct high-resolution simulations for referral-based crowdsourcing and obtain a statistical characterization of the population recruited, geography covered, and time to completion. Our results demonstrate that the outcome is plausible without the presence of mass media but lies at the limit of what time-critical social mobilization can achieve. Success relies critically on highly connected individuals willing to mobilize people in distant locations, overcoming the local trapping of diffusion in highly dense areas. However, even under these highly favorable conditions, the risk of unsuccessful search remains significant. These findings have implications for the design of better incentive schemes for social mobilization. They also call for caution in estimating the reliability of this capability.

  4. Mobile sensing systems.

    PubMed

    Macias, Elsa; Suarez, Alvaro; Lloret, Jaime

    2013-12-16

    Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high.

  5. Mobile Sensing Systems

    PubMed Central

    Macias, Elsa; Suarez, Alvaro; Lloret, Jaime

    2013-01-01

    Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high. PMID:24351637

  6. Limits of social mobilization

    PubMed Central

    Rutherford, Alex; Cebrian, Manuel; Dsouza, Sohan; Moro, Esteban; Pentland, Alex; Rahwan, Iyad

    2013-01-01

    The Internet and social media have enabled the mobilization of large crowds to achieve time-critical feats, ranging from mapping crises in real time, to organizing mass rallies, to conducting search-and-rescue operations over large geographies. Despite significant success, selection bias may lead to inflated expectations of the efficacy of social mobilization for these tasks. What are the limits of social mobilization, and how reliable is it in operating at these limits? We build on recent results on the spatiotemporal structure of social and information networks to elucidate the constraints they pose on social mobilization. We use the DARPA Network Challenge as our working scenario, in which social media were used to locate 10 balloons across the United States. We conduct high-resolution simulations for referral-based crowdsourcing and obtain a statistical characterization of the population recruited, geography covered, and time to completion. Our results demonstrate that the outcome is plausible without the presence of mass media but lies at the limit of what time-critical social mobilization can achieve. Success relies critically on highly connected individuals willing to mobilize people in distant locations, overcoming the local trapping of diffusion in highly dense areas. However, even under these highly favorable conditions, the risk of unsuccessful search remains significant. These findings have implications for the design of better incentive schemes for social mobilization. They also call for caution in estimating the reliability of this capability. PMID:23576719

  7. Mobile sensing systems.

    PubMed

    Macias, Elsa; Suarez, Alvaro; Lloret, Jaime

    2013-01-01

    Rich-sensor smart phones have made possible the recent birth of the mobile sensing research area as part of ubiquitous sensing which integrates other areas such as wireless sensor networks and web sensing. There are several types of mobile sensing: individual, participatory, opportunistic, crowd, social, etc. The object of sensing can be people-centered or environment-centered. The sensing domain can be home, urban, vehicular… Currently there are barriers that limit the social acceptance of mobile sensing systems. Examples of social barriers are privacy concerns, restrictive laws in some countries and the absence of economic incentives that might encourage people to participate in a sensing campaign. Several technical barriers are phone energy savings and the variety of sensors and software for their management. Some existing surveys partially tackle the topic of mobile sensing systems. Published papers theoretically or partially solve the above barriers. We complete the above surveys with new works, review the barriers of mobile sensing systems and propose some ideas for efficiently implementing sensing, fusion, learning, security, privacy and energy saving for any type of mobile sensing system, and propose several realistic research challenges. The main objective is to reduce the learning curve in mobile sensing systems where the complexity is very high. PMID:24351637

  8. Displays enabling mobile multimedia

    NASA Astrophysics Data System (ADS)

    Kimmel, Jyrki

    2007-02-01

    With the rapid advances in telecommunications networks, mobile multimedia delivery to handsets is now a reality. While a truly immersive multimedia experience is still far ahead in the mobile world, significant advances have been made in the constituent audio-visual technologies to make this become possible. One of the critical components in multimedia delivery is the mobile handset display. While such alternatives as headset-style near-to-eye displays, autostereoscopic displays, mini-projectors, and roll-out flexible displays can deliver either a larger virtual screen size than the pocketable dimensions of the mobile device can offer, or an added degree of immersion by adding the illusion of the third dimension in the viewing experience, there are still challenges in the full deployment of such displays in real-life mobile communication terminals. Meanwhile, direct-view display technologies have developed steadily, and can provide a development platform for an even better viewing experience for multimedia in the near future. The paper presents an overview of the mobile display technology space with an emphasis on the advances and potential in developing direct-view displays further to meet the goal of enabling multimedia in the mobile domain.

  9. Mobile sociology. 2000.

    PubMed

    Urry, John

    2010-01-01

    This article seeks to develop a manifesto for a sociology concerned with the diverse mobilities of peoples, objects, images, information, and wastes; and of the complex interdependencies between, and social consequences of, such diverse mobilities. A number of key concepts relevant for such a sociology are elaborated: 'gamekeeping', networks, fluids, scapes, flows, complexity and iteration. The article concludes by suggesting that a 'global civil society' might constitute the social base of a sociology of mobilities as we move into the twenty-first century.

  10. Biomolecule Analysis by Ion Mobility Spectrometry

    PubMed Central

    Bohrer, Brian C.; Merenbloom, Samuel I.; Koeniger, Stormy L.; Hilderbrand, Amy E.; Clemmer, David E.

    2013-01-01

    Although nonnative protein conformations, including intermediates along the folding pathway and kinetically trapped misfolded species that disfavor the native state, are rarely isolated in the solution phase, they are often stable in the gas phase, where macromolecular ions from electrospray ionization can exist in varying charge states. Differences in the structures of nonnative conformations in the gas phase are often large enough to allow different shapes and charge states to be separated because of differences in their mobilities through a gas. Moreover, gentle collisional activation can be used to induce structural transformations. These new structures often have different mobilities. Thus, there is the possibility of developing a multidimensional separation that takes advantage of structural differences of multiple stable states. This review discusses how nonnative states differ in the gas phase compared with solution and presents an overview of early attempts to utilize and manipulate structures in order to develop ion mobility spectrometry as a rapid and sensitive technique for separating complex mixtures of biomolecules prior to mass spectrometry. PMID:20636082

  11. AUSSAT mobile satellite services

    NASA Technical Reports Server (NTRS)

    Nowland, Wayne L.; Wagg, Michael; Simpson, Daniel

    1988-01-01

    An overview of AUSSAT's planned mobile satellite system is given. The development program which is being undertaken to achieve the 1992 service date is described. Both business and technical aspects of the development program are addressed.

  12. Understanding Mobile Apps

    MedlinePlus

    ... a device, you’re committed to using the operating system and the type of apps that go with it. The Android, Apple, Microsoft and BlackBerry mobile operating systems have app stores online where you can look ...

  13. Persuasive Mobile Health Applications

    NASA Astrophysics Data System (ADS)

    Garcia Wylie, Carlos; Coulton, Paul

    With many industrialized societies bearing the cost of an increasingly sedentary lifestyle on the health of their populations there is a need to find new ways of encouraging physical activity to promote better health and well being. With the increasing power of mobile phones and the recent emergence of personal heart rate monitors, aimed at dedicated amateur runners, there is now a possibility to develop “Persuasive Mobile Health Applications” to promote well being through the use of real-time physiological data and persuade users to adopt a healthier lifestyle. In this paper we present a novel general health monitoring software for mobile phones called Heart Angel. This software is aimed at helping users monitor, record, as well as improve their fitness level through built-in cardio-respiratory tests, a location tracking application for analyzing heart rate exertion over time and location, and a fun mobile-exergame called Health Defender.

  14. Validation of a HPLC method for simultaneous determination of five sunscreens in lotion preparation.

    PubMed

    Kedor-Hackmann, E R M; De Lourdes Pérez González, M L; Singh, A K; Santoro, M I R M

    2006-06-01

    The aim of this research was to develop and validate a high-performance liquid chromatographic (HPLC) method for simultaneous determination of five sunscreens, namely benzophenone-3 (B-3), butyl methoxydibenzoylmethane (BM), octyl methoxycinnamate (OM), octyl salicylate (OS) and homosalate (HS). The separation and quantitative determination was made by HPLC at 40 +/-1 degrees C with a gradient elution from 10% to 100% mobile phase B in mobile phase A. The gradient liquid chromatographic system constituted of mobile phase A [acetonitrile : water (10 : 90 v/v)] and mobile phase B [acetonitrile : water (90 : 10 v/v)], at a flow rate of 1.0 mL min(-1) and ultraviolet detection at 310 nm. The separation was obtained with two Waters reversed phase columns: Novapack C-18 and Symmetry((R)) C-18 connected in series. All sunscreens were efficiently separated within 17 min. The coefficient of correlation and average recovery for B-3, BM, OM, OS and HS were 0.9798 and 98.5%, 0.9672 and 98.8%, 0.9922 and 99.1%, 0.9961 and 98.9% and 0.9909 and 99.4% respectively. The relative standard deviations obtained were between 1.07% and 2.44%. The excipients did not interfere in the analysis. The results showed that the proposed method could be used for rapid and simultaneous determination of B-3, BM, OM, OS and HS in sunscreen lotions with precision, accuracy and specificity.

  15. Mobile antenna development at JPL

    NASA Technical Reports Server (NTRS)

    Huang, J.; Jamnejad, V.; Densmore, A.; Tulintseff, A.; Thomas, R.; Woo, K.

    1993-01-01

    The Jet Propulsion Laboratory (JPL), under the sponsorship of NASA, has pioneered the development of land vehicle antennas for commercial mobile satellite communications. Several novel antennas have been developed at L-band frequencies for the Mobile Satellite (MSAT) program initiated about a decade ago. Currently, two types of antennas are being developed at K- and Ka-band frequencies for the ACTS (Advanced Communications Technology Satellite) Mobile Terminal (AMT) project. For the future, several hand-held antenna concepts are proposed for the small terminals of the Ka-band Personal Access Satellite System (PASS). For the L-band MSAT program, a number of omni-directional low-gain antennas, such as the crossed drooping-dipoles, the higher-order-mode circular microstrip patch, the quadrifilar helix, and the wrapped-around microstrip 'mast' array, have been developed for lower data rate communications. Several medium-gain satellite tracking antennas, such as the electronically scanned low-profile phased array, the mechanically steered tilted microstrip array, the mechanically steered low-profile microstrip Yagi array, and the hybrid electronically/mechanically steered low-profile array, have been developed for the MSAT's higher data rate and voice communications. To date, for the L-band vehicle application, JPL has developed the world's lowest-profile phased array (1.8 cm height), as well as the lowest-profile mechanically steered antenna (3.7 cm height). For the 20/30 GHz AMT project, a small mechanically steered elliptical reflector antenna with a gain of 23 dBi has recently been developed to transmit horizontal polarization at 30 GHz and receive vertical polarization at 20 GHz. Its hemispherical radome has a height of 10 cm and a base diameter of 23 cm. In addition to the reflector, a mechanically steered printed MMIC active array is currently being developed to achieve the same electrical requirements with a low profile capability. These AMT antenna developments

  16. Mobile multiple access study

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Multiple access techniques (FDMA, CDMA, TDMA) for the mobile user and attempts to identify the current best technique are discussed. Traffic loading is considered as well as voice and data modulation and spacecraft and system design. Emphasis is placed on developing mobile terminal cost estimates for the selected design. In addition, design examples are presented for the alternative techniques of multiple access in order to compare with the selected technique.

  17. Power and spectrally efficient M-ARY QAM schemes for future mobile satellite communications

    NASA Technical Reports Server (NTRS)

    Sreenath, K.; Feher, K.

    1990-01-01

    An effective method to compensate nonlinear phase distortion caused by the mobile amplifier is proposed. As a first step towards the future use of spectrally efficient modulation schemes for mobile satellite applications, we have investigated effects of nonlinearities and the phase compensation method on 16-QAM. The new method provides about 2 dB savings in power for 16-QAM operation with cost effective amplifiers near saturation and thereby promising use of spectrally efficient linear modulation schemes for future mobile satellite applications.

  18. Solid colloids with surface-mobile linkers.

    PubMed

    van der Meulen, Stef A J; Helms, Gesa; Dogterom, Marileen

    2015-06-17

    In this report we review the possibilities of using colloids with surface mobile linkers for the study of colloidal self-assembly processes. A promising route to create systems with mobile linkers is the use of lipid (bi-)layers. These lipid layers can be either used in the form of vesicles or as coatings for hard colloids and emulsion droplets. Inside the lipid bilayers molecules can be inserted via membrane anchors. Due to the fluidity of the lipid bilayer, the anchored molecules remain mobile. The use of different lipid mixtures even allows creating Janus-like particles that exhibit directional bonding if linkers are used which have a preference for a certain lipid phase. In nature mobile linkers can be found e.g. as receptors in cells. Therefore, towards the end of the review, we also briefly address the possibility of using colloids with surface mobile linkers as model systems to mimic cell-cell interactions and cell adhesion processes. PMID:25993272

  19. Libraries and the Mobile Web

    ERIC Educational Resources Information Center

    Hanson, Cody

    2011-01-01

    In 2011, cell phones and mobile devices are ubiquitous. The vast majority of Americans now own cell phones, and over half of them have mobile access to the Internet through a phone or other mobile device. For libraries to stay relevant, they must be able to offer content and services through the mobile web. In this issue of "Library Technology…

  20. Mobility. Snapshot Report, Fall 2011

    ERIC Educational Resources Information Center

    National Student Clearinghouse, 2011

    2011-01-01

    This paper presents information on student mobility for 2011. It offers data on the following: (1) Mobility Rates by Student Enrollment Status; (2) Mobile Student Enrollment at 2-/4-Year Institutions; and (3) Mobile Student Enrollment at Public/Private Institutions.

  1. The American mobile satellite system

    NASA Technical Reports Server (NTRS)

    Garner, William B.

    1990-01-01

    During 1989, the American Mobile Satellite Corporation (AMSC) was authorized to construct, launch, and operate satellites to provide mobile satellite services (MSS) to the U.S. and Puerto Rico. The AMSC has undertaken three major development programs to bring a full range of MSS services to the U.S. The first program is the space segment program that will result in the construction and launch of the satellites as well as the construction and installation of the supporting ground telemetry and command system. The second segment will result in the specification, design, development, construction, and installation of the Network Control System necessary for managing communications access to the satellites, and the specification and development of ground equipment for standard circuit switched and packet switched communications services. The third program is the Phase 1 program to provide low speed data services within the U.S. prior to availability of the AMSC satellites and ground segment. Described here are the present status and plans for these three programs as well as an update on related business arrangements and regulatory matters.

  2. Mobile Variable Depth Sampling System Design Study

    SciTech Connect

    BOGER, R.M.

    2000-08-25

    A design study is presented for a mobile, variable depth sampling system (MVDSS) that will support the treatment and immobilization of Hanford LAW and HLW. The sampler can be deployed in a 4-inch tank riser and has a design that is based on requirements identified in the Level 2 Specification (latest revision). The waste feed sequence for the MVDSS is based on Phase 1, Case 3S6 waste feed sequence. Technical information is also presented that supports the design study.

  3. Efficient Mobility Management Signalling in Network Mobility Supported PMIPV6

    PubMed Central

    Jebaseeli Samuelraj, Ananthi; Jayapal, Sundararajan

    2015-01-01

    Proxy Mobile IPV6 (PMIPV6) is a network based mobility management protocol which supports node's mobility without the contribution from the respective mobile node. PMIPV6 is initially designed to support individual node mobility and it should be enhanced to support mobile network movement. NEMO-BSP is an existing protocol to support network mobility (NEMO) in PMIPV6 network. Due to the underlying differences in basic protocols, NEMO-BSP cannot be directly applied to PMIPV6 network. Mobility management signaling and data structures used for individual node's mobility should be modified to support group nodes' mobility management efficiently. Though a lot of research work is in progress to implement mobile network movement in PMIPV6, it is not yet standardized and each suffers with different shortcomings. This research work proposes modifications in NEMO-BSP and PMIPV6 to achieve NEMO support in PMIPV6. It mainly concentrates on optimizing the number and size of mobility signaling exchanged while mobile network or mobile network node changes its access point. PMID:26366431

  4. Efficient Mobility Management Signalling in Network Mobility Supported PMIPV6.

    PubMed

    Samuelraj, Ananthi Jebaseeli; Jayapal, Sundararajan

    2015-01-01

    Proxy Mobile IPV6 (PMIPV6) is a network based mobility management protocol which supports node's mobility without the contribution from the respective mobile node. PMIPV6 is initially designed to support individual node mobility and it should be enhanced to support mobile network movement. NEMO-BSP is an existing protocol to support network mobility (NEMO) in PMIPV6 network. Due to the underlying differences in basic protocols, NEMO-BSP cannot be directly applied to PMIPV6 network. Mobility management signaling and data structures used for individual node's mobility should be modified to support group nodes' mobility management efficiently. Though a lot of research work is in progress to implement mobile network movement in PMIPV6, it is not yet standardized and each suffers with different shortcomings. This research work proposes modifications in NEMO-BSP and PMIPV6 to achieve NEMO support in PMIPV6. It mainly concentrates on optimizing the number and size of mobility signaling exchanged while mobile network or mobile network node changes its access point.

  5. Efficient Mobility Management Signalling in Network Mobility Supported PMIPV6.

    PubMed

    Samuelraj, Ananthi Jebaseeli; Jayapal, Sundararajan

    2015-01-01

    Proxy Mobile IPV6 (PMIPV6) is a network based mobility management protocol which supports node's mobility without the contribution from the respective mobile node. PMIPV6 is initially designed to support individual node mobility and it should be enhanced to support mobile network movement. NEMO-BSP is an existing protocol to support network mobility (NEMO) in PMIPV6 network. Due to the underlying differences in basic protocols, NEMO-BSP cannot be directly applied to PMIPV6 network. Mobility management signaling and data structures used for individual node's mobility should be modified to support group nodes' mobility management efficiently. Though a lot of research work is in progress to implement mobile network movement in PMIPV6, it is not yet standardized and each suffers with different shortcomings. This research work proposes modifications in NEMO-BSP and PMIPV6 to achieve NEMO support in PMIPV6. It mainly concentrates on optimizing the number and size of mobility signaling exchanged while mobile network or mobile network node changes its access point. PMID:26366431

  6. Mobile propeller dynamometer validation

    NASA Astrophysics Data System (ADS)

    Morris, Mason Wade

    With growing interest in UAVs and OSU's interest in propeller performance and manufacturing, evaluating UAV propeller and propulsion system performance has become essential. In attempts to evaluate these propellers a mobile propeller dynamometer has been designed, built, and tested. The mobile dyno has been designed to be cost effective through the ability to load it into the back of a test vehicle to create simulated forward flight characteristics. This allows much larger propellers to be dynamically tested without the use of large and expensive wind tunnels. While evaluating the accuracy of the dyno, several improvements had to be made to get accurate results. The decisions made to design and improve the mobile propeller dyno will be discussed along with attempts to validate the dyno by comparing its results against known sources. Another large part of assuring the accuracy of the mobile dyno is determining if the test vehicle will influence the flow going into the propellers being tested. The flow into the propeller needs to be as smooth and uniform as possible. This is determined by characterizing the boundary layer and accelerated flow over the vehicle. This evaluation was accomplished with extensive vehicle aerodynamic measurements with the use of full-scale tests using a pitot-rake and the actual test vehicle. Additional tests were conducted in Oklahoma State University's low speed wind tunnel with a 1/8-scale model using qualitative flow visualization with smoke. Continuing research on the mobile dyno will be discussed, along with other potential uses for the dyno.

  7. Autonomous mobile communication relays

    NASA Astrophysics Data System (ADS)

    Nguyen, Hoa G.; Everett, Hobart R.; Manouk, Narek; Verma, Ambrish

    2002-07-01

    Maintaining a solid radio communication link between a mobile robot entering a building and an external base station is a well-recognized problem. Modern digital radios, while affording high bandwidth and Internet-protocol-based automatic routing capabilities, tend to operate on line-of-sight links. The communication link degrades quickly as a robot penetrates deeper into the interior of a building. This project investigates the use of mobile autonomous communication relay nodes to extend the effective range of a mobile robot exploring a complex interior environment. Each relay node is a small mobile slave robot equipped with sonar, ladar, and 802.11b radio repeater. For demonstration purposes, four Pioneer 2-DX robots are used as autonomous mobile relays, with SSC-San Diego's ROBART III acting as the lead robot. The relay robots follow the lead robot into a building and are automatically deployed at various locations to maintain a networked communication link back to the remote operator. With their on-board external sensors, they also act as rearguards to secure areas already explored by the lead robot. As the lead robot advances and RF shortcuts are detected, relay nodes that become unnecessary will be reclaimed and reused, all transparent to the operator. This project takes advantage of recent research results from several DARPA-funded tasks at various institutions in the areas of robotic simulation, ad hoc wireless networking, route planning, and navigation. This paper describes the progress of the first six months of the project.

  8. Mobile systems capability plan

    SciTech Connect

    1996-09-01

    This plan was prepared to initiate contracting for and deployment of these mobile system services. 102,000 cubic meters of retrievable, contact-handled TRU waste are stored at many sites around the country. Also, an estimated 38,000 cubic meters of TRU waste will be generated in the course of waste inventory workoff and continuing DOE operations. All the defense TRU waste is destined for disposal in WIPP near Carlsbad NM. To ship TRU waste there, sites must first certify that the waste meets WIPP waste acceptance criteria. The waste must be characterized, and if not acceptable, subjected to additional processing, including repackaging. Most sites plan to use existing fixed facilities or open new ones between FY1997-2006 to perform these functions; small-quantity sites lack this capability. An alternative to fixed facilities is the use of mobile systems mounted in trailers or skids, and transported to sites. Mobile systems will be used for all characterization and certification at small sites; large sites can also use them. The Carlsbad Area Office plans to pursue a strategy of privatization of mobile system services, since this offers a number of advantages. To indicate the possible magnitude of the costs of deploying mobile systems, preliminary estimates of equipment, maintenance, and operating costs over a 10-year period were prepared and options for purchase, lease, and privatization through fixed-price contracts considered.

  9. C₁₈-bound porous silica monolith particles as a low-cost high-performance liquid chromatography stationary phase with an excellent chromatographic performance.

    PubMed

    Ali, Faiz; Cheong, Won Jo

    2014-12-01

    Ground porous silica monolith particles with an average particle size of 2.34 μm and large pores (363 Å) exhibiting excellent chromatographic performance have been synthesized on a relatively large scale by a sophisticated sol-gel procedure. The particle size distribution was rather broad, and the d(0.1)/d(0.9) ratio was 0.14. The resultant silica monolith particles were chemically modified with chlorodimethyloctadecylsilane and end-capped with a mixture of hexamethyldisilazane and chlorotrimethylsilane. Very good separation efficiency (185,000/m) and chromatographic resolution were achieved when the C18 -bound phase was evaluated for a test mixture of five benzene derivatives after packing in a stainless-steel column (1.0 mm × 150 mm). The optimized elution conditions were found to be 70:30 v/v acetonitrile/water with 0.1% trifluoroacetic acid at a flow rate of 25 μL/min. The column was also evaluated for fast analysis at a flow rate of 100 μL/min, and all the five analytes were eluted within 3.5 min with reasonable efficiency (ca. 60,000/m) and resolution. The strategy of using particles with reduced particle size and large pores (363 Å) combined with C18 modification in addition to partial-monolithic architecture has resulted in a useful stationary phase (C18 -bound silica monolith particles) of low production cost showing excellent chromatographic performance.

  10. Mobile Phone Terminal

    NASA Technical Reports Server (NTRS)

    1978-01-01

    In the photo, an employee of a real estate firm is contacting his office by means of HICOM, an advanced central terminal for mobile telephones. Developed by the Orlando Division of Martin Marietta Aerospace, Orlando, Florida, and manufactured by Harris Corporation's RF Division, Rochester, N.Y., HICOM upgrades service to users, provides better system management to telephone companies, and makes more efficient use of available mobile telephone channels through a computerized central control terminal. The real estate man, for example, was able to dial his office and he could also have direct-dialed a long distance number. Mobile phones in most areas not yet served by HICOM require an operator's assistance for both local and long distance calls. HICOM improves system management by automatically recording information on all calls for accurate billing, running continual performance checks on its own operation, and reporting any malfunctions to a central office.

  11. Mobility of Plasmids†

    PubMed Central

    Smillie, Chris; Garcillán-Barcia, M. Pilar; Francia, M. Victoria; Rocha, Eduardo P. C.; de la Cruz, Fernando

    2010-01-01

    Summary: Plasmids are key vectors of horizontal gene transfer and essential genetic engineering tools. They code for genes involved in many aspects of microbial biology, including detoxication, virulence, ecological interactions, and antibiotic resistance. While many studies have decorticated the mechanisms of mobility in model plasmids, the identification and characterization of plasmid mobility from genome data are unexplored. By reviewing the available data and literature, we established a computational protocol to identify and classify conjugation and mobilization genetic modules in 1,730 plasmids. This allowed the accurate classification of proteobacterial conjugative or mobilizable systems in a combination of four mating pair formation and six relaxase families. The available evidence suggests that half of the plasmids are nonmobilizable and that half of the remaining plasmids are conjugative. Some conjugative systems are much more abundant than others and preferably associated with some clades or plasmid sizes. Most very large plasmids are nonmobilizable, with evidence of ongoing domestication into secondary chromosomes. The evolution of conjugation elements shows ancient divergence between mobility systems, with relaxases and type IV coupling proteins (T4CPs) often following separate paths from type IV secretion systems. Phylogenetic patterns of mobility proteins are consistent with the phylogeny of the host prokaryotes, suggesting that plasmid mobility is in general circumscribed within large clades. Our survey suggests the existence of unsuspected new relaxases in archaea and new conjugation systems in cyanobacteria and actinobacteria. Few genes, e.g., T4CPs, relaxases, and VirB4, are at the core of plasmid conjugation, and together with accessory genes, they have evolved into specific systems adapted to specific physiological and ecological contexts. PMID:20805406

  12. Autonomous mobile robot teams

    NASA Technical Reports Server (NTRS)

    Agah, Arvin; Bekey, George A.

    1994-01-01

    This paper describes autonomous mobile robot teams performing tasks in unstructured environments. The behavior and the intelligence of the group is distributed, and the system does not include a central command base or leader. The novel concept of the Tropism-Based Cognitive Architecture is introduced, which is used by the robots in order to produce behavior transforming their sensory information to proper action. The results of a number of simulation experiments are presented. These experiments include worlds where the robot teams must locate, decompose, and gather objects, and defend themselves against hostile predators, while navigating around stationary and mobile obstacles.

  13. Correlation ion mobility spectroscopy

    DOEpatents

    Pfeifer, Kent B.; Rohde, Steven B.

    2008-08-26

    Correlation ion mobility spectrometry (CIMS) uses gating modulation and correlation signal processing to improve IMS instrument performance. Closely spaced ion peaks can be resolved by adding discriminating codes to the gate and matched filtering for the received ion current signal, thereby improving sensitivity and resolution of an ion mobility spectrometer. CIMS can be used to improve the signal-to-noise ratio even for transient chemical samples. CIMS is especially advantageous for small geometry IMS drift tubes that can otherwise have poor resolution due to their small size.

  14. Segway robotic mobility platform

    NASA Astrophysics Data System (ADS)

    Nguyen, Hoa G.; Morrell, John; Mullens, Katherine D.; Burmeister, Aaron B.; Miles, Susan; Farrington, Nathan; Thomas, Kari M.; Gage, Douglas W.

    2004-12-01

    The Segway Robotic Mobility Platform (RMP) is a new mobile robotic platform based on the self-balancing Segway Human Transporter (HT). The Segway RMP is faster, cheaper, and more agile than existing comparable platforms. It is also rugged, has a small footprint, a zero turning radius, and yet can carry a greater payload. The new geometry of the platform presents researchers with an opportunity to examine novel topics, including people-height sensing and actuation modalities. This paper describes the history and development of the platform, its characteristics, and a summary of current research projects involving the platform at various institutions across the United States.

  15. Mobile transporter path planning

    NASA Technical Reports Server (NTRS)

    Baffes, Paul; Wang, Lui

    1990-01-01

    The use of a genetic algorithm (GA) for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Elements of the genetic algorithm are explored in both a theoretical and experimental sense. Specifically, double crossover, greedy crossover, and tournament selection techniques are examined. Additionally, the use of local optimization techniques working in concert with the GA are also explored. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research.

  16. Hemopathologic consequences of protracted gamma irradiation: alterations in granulocyte reserves and granulocyte mobilization

    SciTech Connect

    Seed, T.M.; Cullen, S.M.; Kaspar, L.V.; Tolle, D.V.; Fritz, T.E.

    1980-07-01

    Aplastic anemia and myelogenous leukemia are prominent pathologic effects in beagles exposed to continuous, daily, low-dose gamma irradiation. In the present work, granulocyte reserves and related mobilization functions have been sequentially assessed by the endotoxin stress assay during the preclinical and clinical phases of these hemopoietic disorders. Characteristic patterns of granulocyte reserve mobilization are described that reflect given stages of pathologic progression. For radiation-induced leukemia, a five-stage pattern has been proposed. In contrast, a simple pattern of progressive, time-dependent contraction of granulocyte reserves and mobilization capacity was noted in the development of terminal aplastic anemia. Early preclinical phases of radiation-induced leukemia appear to involve an extensive depletion of the granulocyte reserves (phase I) during the first approx. 200 days of exposure followed by a partial renewal of the reserves and associated mobilization functions between approx. 200 and 400 days (phase II). Sustained, subnormal granulocyte mobilizations (phase III) following endotoxin stress typify the responses of dogs during the intermediate phase, whereas late preclinical, preleukemic stages (phase IV) are characterized by a further expansion of the reserves and in the mobilization capacities, particularly of the less mature granulocytes. Such late alterations in the pattern of granulocyte mobilization, together with other noted cellular aberrancies in the peripheral blood and marrow, appear to indicate leukemia (phase V) onset.

  17. Global Health Diplomacy, Monitoring & Evaluation, and the Importance of Quality Assurance & Control: Findings from NIMH Project Accept (HPTN 043): A Phase III Randomized Controlled Trial of Community Mobilization, Mobile Testing, Same-Day Results, and Post-Test Support for HIV in Sub-Saharan Africa and Thailand

    PubMed Central

    Kevany, Sebastian; Khumalo-Sakutukwa, Gertrude; Singh, Basant; Chingono, Alfred; Morin, Stephen

    2016-01-01

    Background Provision and scale-up of high quality, evidence-based services is essential for successful international HIV prevention interventions in order to generate and maintain intervention uptake, study integrity and participant trust, from both health service delivery and diplomatic perspectives. Methods We developed quality assurance (QAC) procedures to evaluate staff fidelity to a cluster-randomized trial of the NIMH Project Accept (HPTN 043) assessing the effectiveness of a community-based voluntary counseling and testing strategy. The intervention was comprised of three components—Mobile Voluntary Counseling and Testing (MVCT), Community Mobilization (CM) and Post-Test Support Services (PTSS). QAC procedures were based on standardized criteria, and were designed to assess both provider skills and adherence to the intervention protocol. Supervisors observed a random sample of 5% to 10% of sessions each month and evaluated staff against multiple criteria on scales of 1–5. A score of 5 indicated 100% adherence, 4 indicated 95% adherence, and 3 indicated 90% adherence. Scores below 3 were considered unsatisfactory, and protocol deviations were discussed with the respective staff. Results During the first year of the intervention, the mean scores of MVCT and CM staff across the 5 study sites were 4 (95% adherence) or greater and continued to improve over time. Mean QAC scores for the PTSS component were lower and displayed greater fluctuations. Challenges to PTSS staff were identified as coping with the wide range of activities in the PTSS component and the novelty of the PTSS process. QAC fluctuations for PTSS were also associated with new staff hires or changes in staff responsibilities. Through constant staff monitoring and support, by Year 2, QAC scores for PTSS activities had reached those of MVCT and CM. Conclusions The implementation of a large-sale, evidence based HIV intervention requires extensive QAC to ensure implementation effectiveness

  18. An aeronautical mobile satellite experiment

    NASA Technical Reports Server (NTRS)

    Jedrey, T. C.; Dessouky, K. I.; Lay, N. E.

    1990-01-01

    The various activities and findings of a NASA/FAA/COMSAT/INMARSAT collaborative aeronautical mobile satellite experiment are detailed. The primary objective of the experiment was to demonstrate and evaluate an advanced digital mobile satellite terminal developed at the Jet Propulsion Laboratory under the NASA Mobile Satellite Program. The experiment was a significant milestone for NASA/JPL, since it was the first test of the mobile terminal in a true mobile satellite environment. The results were also of interest to the general mobile satellite community because of the advanced nature of the technologies employed in the terminal.

  19. ATHLETE: A Mobility and Manipulation System for Mobile Lunar Habitats

    NASA Astrophysics Data System (ADS)

    Wilcox, B. H.

    2008-03-01

    ATHLETE is a mobility and manipulation system considered by recent Lunar Architecture Teams. This presentation will discuss the possible use of ATHLETE-based mobile habitats for global-scale scientific exploration of the moon.

  20. Developing Mobile Based Instruction

    ERIC Educational Resources Information Center

    Martin, Florence; Pastore, Raymond; Snider, Jean

    2012-01-01

    This paper describes an instructional design class's experience developing instruction for the mobile web. The class was taught at a southeastern university in the United States in a master's level computer based instruction course. Two example projects are showcased and student reflections on design issues are highlighted. Additionally,…

  1. Mobile Applications for Extension

    ERIC Educational Resources Information Center

    Drill, Sabrina L.

    2012-01-01

    Mobile computing devices (smart phones, tablets, etc.) are rapidly becoming the dominant means of communication worldwide and are increasingly being used for scientific investigation. This technology can further our Extension mission by increasing our power for data collection, information dissemination, and informed decision-making. Mobile…

  2. Mobile lighting apparatus

    DOEpatents

    Roe, George Michael; Klebanoff, Leonard Elliott; Rea, Gerald W; Drake, Robert A; Johnson, Terry A; Wingert, Steven John; Damberger, Thomas A; Skradski, Thomas J; Radley, Christopher James; Oros, James M; Schuttinger, Paul G; Grupp, David J; Prey, Stephen Carl

    2013-05-14

    A mobile lighting apparatus includes a portable frame such as a moveable trailer or skid having a light tower thereon. The light tower is moveable from a stowed position to a deployed position. A hydrogen-powered fuel cell is located on the portable frame to provide electrical power to an array of the energy efficient lights located on the light tower.

  3. Visions of Mobile Learning

    ERIC Educational Resources Information Center

    T.H.E. Journal, 2011

    2011-01-01

    It is almost a foregone conclusion that the mobile device will become an indispensable tool for learning in the future. That's why "T.H.E. Journal" asked a number of educators to let their imaginations go wild and conjure up visions of the future of the device in the classroom. This paper presents the views of educators who conjure up the mobile…

  4. Mobile Learning for All

    ERIC Educational Resources Information Center

    Bestwick, Angel; Campbell, John R.

    2010-01-01

    Parents and educational professionals are asking the question, "Are schools preparing students for their future lives?" Mobile technologies such as smart phones, iPods, GPS systems, iPads, and a constant stream of information drive much of people's world and work. The use of such technologies increases with each passing day. But how often do…

  5. ORION mobile unit design

    NASA Technical Reports Server (NTRS)

    Brunn, D. L.; Wu, S. C.; Thom, E. H.; Mclaughlin, F. D.; Sweetser, B. M.

    1980-01-01

    An overview of the design of the ORION mobile system is presented. System capability and performance characteristics are outlined. Functional requirements and key performance parameters are stated for each of the nine subsystems. A master design and implementation schedule is given.

  6. Mobile Equipment Expands Inventory.

    ERIC Educational Resources Information Center

    McGough, Robert L.; And Others

    1978-01-01

    Describes the Mobile Equipment Modules (MEM) system in Duluth, Minnesota. MEM is a way to hold down costs and increase learning opportunities by consolidating purchases of expensive shop equipment within the school district, grouping the equipment in modules, and scheduling and moving it from school to school as needed. (MF)

  7. Mobile Agents Applications.

    ERIC Educational Resources Information Center

    Martins, Rosane Maria; Chaves, Magali Ribeiro; Pirmez, Luci; Rust da Costa Carmo, Luiz Fernando

    2001-01-01

    Discussion of the need to filter and retrieval relevant information from the Internet focuses on the use of mobile agents, specific software components which are based on distributed artificial intelligence and integrated systems. Surveys agent technology and discusses the agent building package used to develop two applications using IBM's Aglet…

  8. Mathematics and Mobile Learning

    ERIC Educational Resources Information Center

    White, Tobin; Martin, Lee

    2014-01-01

    This paper argues for an approach to mobile learning that leverages students' informal digital practices as resources for designing mathematics classrooms activities. We briefly describe two exploratory designs along these lines, one featuring the use of photos taken by students outside class and the other centered on their recording and…

  9. Mobil lube dewaxing technologies

    SciTech Connect

    Baker, C.L.; McGuiness, M.P.

    1995-09-01

    Currently, the lube refining industry is in a period of transition, with both hydroprocessing and catalytic dewaxing gathering momentum as replacements for solvent extraction and solvent dewaxing. In addition, lube product quality requirements have been increasing, both in the US and abroad. Mobil has developed a broad array of dewaxing catalytic technologies which can serve refiners throughout the stages of this transition. In the future, lube feedstocks which vary in source and wax content will become increasingly important, requiring an optimized system for highest performance. The Mobil Lube Dewaxing (MLDW) process is the work-horse of the catalytic dewaxing technologies, being a robust, low cost technology suitable for both solvent extracted and hydrocracked feeds. The Mobil Selective Dewaxing (MSDW) process has been recently introduced in response to the growth of hydroprocessing. MSDW requires either severely hydrotreated or hydrocracked feeds and provides improved lube yields and VI. For refiners with hydrocrackers and solvent dewaxing units, Mobil Wax Isomerization (MWI) technology can make higher VI base stocks to meet the growing demand for very high quality lube products. A review of these three technologies is presented in this paper.

  10. Essays on Teacher Mobility

    ERIC Educational Resources Information Center

    Cook, Jeremy A.

    2012-01-01

    The allocation of quality teachers across schools is of interest because of both the importance and costliness of teachers as inputs in the education production process. Furthermore, because teachers have preferences over their workplace characteristics, this allocation across schools is nonrandom. This research examines teacher mobility within…

  11. Mathematics and Mobile Learning

    ERIC Educational Resources Information Center

    Sayed, Fayez

    2015-01-01

    The wide range of Mathematical Apps targeting different mathematical concepts and the various types of mobile devices available present a demanding and challenging problem to the teaching and learning in the field of mathematics. In an attempt to address this issue, a few Apps were selected, implemented and tested in this work. [For complete…

  12. Private Schools. Goin' Mobile.

    ERIC Educational Resources Information Center

    Miller, Laura

    1995-01-01

    To give children of migrant farm workers an academic boost, teachers at one Roman Catholic elementary school became mobile, following them to their destinations and offering a sense of stability to the Mexican and Mexican American students. The program integrates Mexican culture and Spanish language and provides outreach to families. (SM)

  13. Cohesin and the nucleolus constrain the mobility of spontaneous repair foci.

    PubMed

    Dion, Vincent; Kalck, Véronique; Seeber, Andrew; Schleker, Thomas; Gasser, Susan M

    2013-11-01

    The regulation of chromatin mobility in response to DNA damage is important for homologous recombination in yeast. Anchorage reduces rates of recombination, whereas increased chromatin mobility correlates with more efficient homology search. Here we tracked the mobility and localization of spontaneous S-phase lesions bound by Rad52, and find that these foci have reduced movement, unlike enzymatically induced double-strand breaks. Moreover, spontaneous repair foci are positioned in the nuclear core, abutting the nucleolus. We show that cohesin and nucleolar integrity constrain the mobility of these foci, consistent with the notion that spontaneous, S-phase damage is preferentially repaired from the sister chromatid.

  14. Asymmetric soliton mobility in competing linear-nonlinear parity-time-symmetric lattices.

    PubMed

    Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis

    2016-09-15

    We address the transverse mobility of spatial solitons in competing parity-time-symmetric linear and nonlinear lattices. The competition between out-of-phase linear and nonlinear lattices results in a drastic mobility enhancement within a range of soliton energies. We show that within such a range, the addition of even a small imaginary part in the linear potential makes soliton mobility strongly asymmetric. For a given initial phase tilt, the velocity of soliton motion grows with an increase of the balanced gain/losses. In this regime of enhanced mobility, tilted solitons can efficiently drag other solitons that were initially at rest to form moving soliton pairs. PMID:27628394

  15. Weak Solutions for the Cahn-Hilliard Equation with Degenerate Mobility

    NASA Astrophysics Data System (ADS)

    Dai, Shibin; Du, Qiang

    2016-03-01

    In this paper, we study the well-posedness of Cahn-Hilliard equations with degenerate phase-dependent diffusion mobility. We consider a popular form of the equations which has been used in phase field simulations of phase separation and microstructure evolution in binary systems. We define a notion of weak solutions for the nonlinear equation. The existence of such solutions is obtained by considering the limits of Cahn-Hilliard equations with non-degenerate mobilities.

  16. Mobility platform coupling device and method for coupling mobility platforms

    DOEpatents

    Shirey, David L.; Hayward, David R.; Buttz, James H.

    2002-01-01

    A coupling device for connecting a first mobility platform to a second mobility platform in tandem. An example mobility platform is a robot. The coupling device has a loose link mode for normal steering conditions and a locking position, tight link mode for navigation across difficult terrain and across obstacles, for traversing chasms, and for navigating with a reduced footprint in tight steering conditions.

  17. Social Mobility and Social Participation

    ERIC Educational Resources Information Center

    Sewell, William H.

    1978-01-01

    Examines data related to social mobility and social participation of Americans. Topics include educational and occupational mobility; voting; volunteer work; charitable giving; community participation; views on religion; and anomie. For journal availability, see SO 506 144. (Author/DB)

  18. Advanced extravehicular mobility unit study

    NASA Technical Reports Server (NTRS)

    Elkins, W.

    1982-01-01

    Components of the advanced extravehicular mobility unit (suit) are described. Design considerations for radiation protection, extravehicular operational pressure, mobility effects, tool/glove/effector, anthropometric definition, lighting, and equipment turnaround are addressed.

  19. Mobility, Fertility, and Residential Crowding

    ERIC Educational Resources Information Center

    Morris, Earl W.

    1977-01-01

    Regression analyses predicting fertility and mobility in a sample of a metropolitan county in New York State indicate that residential mobility serves to release the negative pressure that residential crowding might exert on fertility behavior. (Author)

  20. Charge carrier mobility in hybrid halide perovskites

    PubMed Central

    Motta, Carlo; El-Mellouhi, Fedwa; Sanvito, Stefano

    2015-01-01

    The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5–10 cm2V−1s−1 and that for holes within 1–5 cm2V−1s−1, where the variations depend on the crystal structure investigated and the level of doping. Such results, in good agreement with recent experiments, set the relaxation time to about 1 ps, which is the time-scale for the molecular rotation at room temperature. For the room temperature tetragonal phase we explore two possible orientations of the organic cations and find that the mobility has a significant asymmetry depending on the direction of the current with respect to the molecular axis. This is due mostly to the way the PbI3 octahedral symmetry is broken. Interestingly we find that substituting I with Cl has minor effects on the mobilities. Our analysis suggests that the carrier mobility is probably not a key factor in determining the high solar-harvesting efficiency of this class of materials. PMID:26235910

  1. Fade-Free Mobile Communication

    NASA Technical Reports Server (NTRS)

    Stevenson, C. R.

    1986-01-01

    Scheme for mobile communication reduces multipath fading and interference between adjacent channels. Proposed communication system lends itself to almost completely digital implementation, eliminating costly and bulky crystal filters. Scheme suitable for satellite-aided or terrestrial mobile communication, including cellular mobile telephony, at frequencies in 150-to-900-MHz range.

  2. Libraries and the Mobile Revolution

    ERIC Educational Resources Information Center

    Krishnan, Yvonne

    2011-01-01

    With the advent of mobile phones--and smartphones in particular--people are slowly moving away from the notion that mobile phones are just for making calls and texting. This coupled with the fact that the uptake of mobile phones hit the 5 billion mark in 2010 has spurred many libraries to offer services that can be used by their patrons on these…

  3. Mobile Technology in Educational Services

    ERIC Educational Resources Information Center

    Chen, Jueming; Kinshuk

    2005-01-01

    The use of computers and the Internet has successfully enabled educational institutions to provide their students and staff members with various online educational services. With the recent developments in mobile technology, further possibilities are emerging to provide such services through mobile devices such as mobile phones and PDAs. By…

  4. Long range hopping mobility platform.

    SciTech Connect

    Spletzer, Barry Louis; Fischer, Gary John

    2003-03-01

    Sandia National Laboratories has developed a mesoscale hopping mobility platform (Hopper) to overcome the longstanding problems of mobility and power in small scale unmanned vehicles. The system provides mobility in situations such as negotiating tall obstacles and rough terrain that are prohibitive for other small ground base vehicles. The Defense Advanced Research Projects Administration (DARPA) provided the funding for the hopper project.

  5. Mobile Learning in Higher Education

    ERIC Educational Resources Information Center

    Fraga, Lucretia M.

    2012-01-01

    This mixed method research study investigated the beliefs of university faculty regarding mobile learning. As well as to determine if providing technology professional development to university faculty supports the increase of mobile learning opportunities in higher education. This study used the Beliefs About Mobile Learning Inventory (BAMLI) to…

  6. Book Reporting with Book Mobiles.

    ERIC Educational Resources Information Center

    Bates, Ellie

    1984-01-01

    Students can be motivated to share their reading interests and their writing talents by creating book report mobiles. After students have read a book, they begin their mobile by attaching string to an empty box which has been covered with plain paper. Next, they decorate one side of the mobile with a drawing which illustrates the story or they…

  7. Mobile Multicast in Hierarchical Proxy Mobile IPV6

    NASA Astrophysics Data System (ADS)

    Hafizah Mohd Aman, Azana; Hashim, Aisha Hassan A.; Mustafa, Amin; Abdullah, Khaizuran

    2013-12-01

    Mobile Internet Protocol Version 6 (MIPv6) environments have been developing very rapidly. Many challenges arise with the fast progress of MIPv6 technologies and its environment. Therefore the importance of improving the existing architecture and operations increases. One of the many challenges which need to be addressed is the need for performance improvement to support mobile multicast. Numerous approaches have been proposed to improve mobile multicast performance. This includes Context Transfer Protocol (CXTP), Hierarchical Mobile IPv6 (HMIPv6), Fast Mobile IPv6 (FMIPv6) and Proxy Mobile IPv6 (PMIPv6). This document describes multicast context transfer in hierarchical proxy mobile IPv6 (H-PMIPv6) to provide better multicasting performance in PMIPv6 domain.

  8. Extractability and mobility of mercury from agricultural soils surrounding industrial and mining contaminated areas.

    PubMed

    Reis, Ana Teresa; Rodrigues, Sónia Morais; Davidson, Christine M; Pereira, Eduarda; Duarte, Armando C

    2010-12-01

    This study focussed on a comparison of the extractability of mercury in soils with two different contamination sources (a chlor-alkali plant and mining activities) and on the evaluation of the influence of specific soil properties on the behaviour of the contaminant. The method applied here did not target the identification of individual species, but instead provided information concerning the mobility of mercury species in soil. Mercury fractions were classified as mobile, semi-mobile and non-mobile. The fractionation study revealed that in all samples mercury was mainly present in the semi-mobile phase (between 63% and 97%). The highest mercury mobility (2.7 mg kg(-1)) was found in soils from the industrial area. Mining soils exhibited higher percentage of non-mobile mercury, up to 35%, due to their elevated sulfur content. Results of factor analysis indicate that the presence of mercury in the mobile phase could be related to manganese and aluminium soil contents. A positive relation between mercury in the semi-mobile fraction and the aluminium content was also observed. By contrary, organic matter and sulfur contents contributed to mercury retention in the soil matrix reducing the mobility of the metal. Despite known limitations of sequential extraction procedures, the methodology applied in this study for the fractionation of mercury in contaminated soil samples provided relevant information on mercury's relative mobility.

  9. Mobility-Based Mobile Relay Selection in MANETs

    NASA Astrophysics Data System (ADS)

    Kim, Gilnam; Lee, Hyoungjoo; Lee, Kwang Bok

    The future wireless mobile communication networks are expected to provide seamless wireless access and data exchange to mobile users. In particular, it is expected that the demand for ubiquitous data exchange between mobile users will increase with the widespread use of various wireless applications of the intelligent transportation system (ITS) and intelligent vehicles. Mobile ad hoc networks (MANETs) are one of the representative research areas pursuing the technology needed to satisfy the increasing mobile communication requirements. However, most of the works on MANET systems do not take into account the continuous and dynamic changes of nodal mobility to accommodate system design and performance evaluation. The mobility of nodes limits the reliability of communication between the source and the destination node since a link between two continuously moving nodes is established only when one node enters the transmission range of the other. To alleviate this problem, mobile relay has been studied. In particular, it is shown that relay selection is an efficient way to support nodal mobility in MANET systems. In this paper, we propose a mobility-based relay selection algorithm for the MANET environment. Firstly, we define the lifetime as the maximum link duration for which the link between two nodes remains active. Therefore, the lifetime indicates the reliability of the relay link which measures its capability to successfully support relayed communication when requested by the source node. Furthermore, we consider a series of realistic scenarios according to the randomness of nodal mobility. Thus, the proposed algorithm can be easily applied in practical MANET systems by choosing the appropriate node mobility behavior. The numerical results show that the improved reliability of the proposed algorithm's relayed communication is achieved with a proper number of mobile relay nodes rather than with the conventional selection algorithm. Lastly, we show that random

  10. Mobile extracorporeal shockwave lithotripsy.

    PubMed

    Rajagopal, V; Bailey, M J

    1991-01-01

    During the last 18 months, extracorporeal shockwave lithotripsy (ESWL) has been provided at Epsom District Hospital using a mobile unit containing a Dornier HM4 lithotriptor. Patients with upper ureteric and renal stones were selected for treatment, which was performed without anaesthesia or sedation as a day-case procedure; 83 patients were treated, 5 of them with bilateral stones. Seventy patients required 1 treatment session, 17 required 2 and 1 patient required 3. There were no serious complications but 3 patients needed ureteroscopy to remove obstructing stones. The overall success rate was 86%. The cost to treat each NHS patient was 253 pounds. Mobile lithotripsy as a day-case procedure is a safe and cost-effective means of treating urolithiasis and can be performed in a District General Hospital.

  11. Mobile Biomass Pelletizing System

    SciTech Connect

    Thomas Mason

    2009-04-16

    This grant project examines multiple aspects of the pelletizing process to determine the feasibility of pelletizing biomass using a mobile form factor system. These aspects are: the automatic adjustment of the die height in a rotary-style pellet mill, the construction of the die head to allow the use of ceramic materials for extreme wear, integrating a heat exchanger network into the entire process from drying to cooling, the use of superheated steam for adjusting the moisture content to optimum, the economics of using diesel power to operate the system; a break-even analysis of estimated fixed operating costs vs. tons per hour capacity. Initial development work has created a viable mechanical model. The overall analysis of this model suggests that pelletizing can be economically done using a mobile platform.

  12. Mobile Autonomous Humanoid Assistant

    NASA Technical Reports Server (NTRS)

    Diftler, M. A.; Ambrose, R. O.; Tyree, K. S.; Goza, S. M.; Huber, E. L.

    2004-01-01

    A mobile autonomous humanoid robot is assisting human co-workers at the Johnson Space Center with tool handling tasks. This robot combines the upper body of the National Aeronautics and Space Administration (NASA)/Defense Advanced Research Projects Agency (DARPA) Robonaut system with a Segway(TradeMark) Robotic Mobility Platform yielding a dexterous, maneuverable humanoid perfect for aiding human co-workers in a range of environments. This system uses stereo vision to locate human team mates and tools and a navigation system that uses laser range and vision data to follow humans while avoiding obstacles. Tactile sensors provide information to grasping algorithms for efficient tool exchanges. The autonomous architecture utilizes these pre-programmed skills to form human assistant behaviors. The initial behavior demonstrates a robust capability to assist a human by acquiring a tool from a remotely located individual and then following the human in a cluttered environment with the tool for future use.

  13. Miniaturized Ion Mobility Spectrometer

    NASA Technical Reports Server (NTRS)

    Kaye, William J. (Inventor); Stimac, Robert M. (Inventor)

    2015-01-01

    By utilizing the combination of a unique electronic ion injection control circuit in conjunction with a particularly designed drift cell construction, the instantly disclosed ion mobility spectrometer achieves increased levels of sensitivity, while achieving significant reductions in size and weight. The instant IMS is of a much simpler and easy to manufacture design, rugged and hermetically sealed, capable of operation at high temperatures to at least 250.degree. C., and is uniquely sensitive, particularly to explosive chemicals.

  14. Telemedicine by mobile communication.

    PubMed

    Shimizu, K

    1999-01-01

    A concept of mobile telemedicine has been proposed to provide emergency care in a moving vehicle. The practicality of this technique was investigated through technical considerations required to realize mobile telemedicine. Some problems with this technique were identified, and measures to resolve the problems were devised. Then, theoretical analysis verified the feasibility of the proposed technique. Different multiplexing techniques for the multiple medical data transmission by mobile communication were investigated. An experimental system that can simultaneously transmit color images, an audio signal, three-channel ECGs, and blood pressure from a moving vehicle to a fixed station was developed. Experiments on the transmission of multichannel medical data from a moving ambulance, a navigating ship, and a flying aircraft were conducted. The results of these experiments verified the practical feasibility of the proposed technique. In the practical application of this technique, there may be some legal problems: for example, whether medical treatment through a communication medium would be legally acceptable or not, and whether the transmission of medical data violates the protection of personal privacy. However, considering the emergency nature of this technique and the significance of the results, both problems seem to be either legally or technically solvable. This application of mobile communication to telemedicine is not confined to merely a proposal to use new techniques. It can also bring about a methodological change in the concept of conventional telemedicine by changing it from static to dynamic, and by enlarging its scope from a local area to a global or cosmic area. It may also have an impact on conventional emergency medicine in that it will open up a new field of application that applies to moving vehicles.

  15. Mobility implants: a review.

    PubMed

    Danz, W

    1990-01-01

    We present a brief review of mobility implants, their contribution, and the experiences derived after almost 40 years since the new concepts of full mobility implants were introduced. In early 1940, experiments with a new material for the making of plastic artificial eyes was also being considered for the making of orbital implants. Methyl-methacrylate (MMA) had proven inert and satisfactory for dental products. The Surgeon Generals office of the Armed Services encouraged further research and experimental work in the development of plastic eyes. The success of the new material sponsored the beginning of great expansion with new concepts for orbital implants. Through a period of more than a decade, the design and types of implants went through three stages. First, the buried implant was introduced, then the exposed integrated followed, and the buried integrated subsequently followed. The path of progress was not smooth. Theoretically correct designs and surgical procedures met unexpected practical difficulties for the ophthalmic surgeon, the patient, and the eye maker. Surgical and technical efforts were carefully reviewed to eliminate the problems encountered, only to have further unforeseen complications arise. Infections, extrusions, and migration of the implant were not uncommon. The exposed integrated implant was eventually abandoned. However, there were some extraordinary successes of mobility. A new era introduced fully buried mobility implants that were more successful. However, this procedure also produced some problems, causing infection (or allergy), extrusion, and migration. Tantalum mesh and gauze gave great promise with the inception of their use. Orbital tissue grew into the material in an astonishing way, making it possible to secure the extraocular muscles and tenons.(ABSTRACT TRUNCATED AT 250 WORDS)

  16. Integrated mobile robot control

    NASA Technical Reports Server (NTRS)

    Amidi, Omead; Thorpe, Charles

    1991-01-01

    This paper describes the structure, implementation, and operation of a real-time mobile robot controller which integrates capabilities such as: position estimation, path specification and tracking, human interfaces, fast communication, and multiple client support. The benefits of such high-level capabilities in a low-level controller was shown by its implementation for the Navlab autonomous vehicle. In addition, performance results from positioning and tracking systems are reported and analyzed.

  17. [Application of electroosmotic pump on micro column liquid chromatography].

    PubMed

    Chen, Ling-Xin; Guan, Ya-Feng

    2002-03-01

    An electroosmotic pump(EOP) was designed and evaluated, which could replace the mechanical pump. The EOP could generate 2.0 MPa-6.0 MPa output pressure and tens of nL/min-3 microL/min flow rate. A test mixture containing naphthalene, anthracene and phenanthrene was separated on a 14 cm x 320 microns i.d., 5 microns, C18 micro column with acetonitrile/water as a mobile phase, which demonstrated the applicability of the EOP.

  18. Determination of pindolol in human serum by HPLC.

    PubMed

    Chmielowiec, D; Schuster, D; Gengo, F

    1991-01-01

    A method for determining pindolol from human serum by high-performance liquid chromatography (HPLC) is presented. Pindolol is extracted into methylene chloride from 1 mL of alkalinized serum with a recovery of 87%. The organic layer is evaporated and the residue is reconstituted in mobile phase for injection into the column. Samples are eluted from a 5-micron C18 column (250 x 4.6 mm) with acetonitrile-water containing 0.1% triethylamine, pH adjusted to 3.5 with phosphoric acid (20:80 v/v). Samples as low as 2 ng/mL have been detected.

  19. High-mobility diamond

    NASA Astrophysics Data System (ADS)

    Landstrass, Maurice I.

    1994-04-01

    Recent improvements in the CVD diamond deposition process have made possible the fabrication of diamond photoconductive diodes with carrier mobility and lifetime exceeding the values typical of natural gemstones. One of the more surprising recent results is that the best room-temperature carrier properties have been measured on polycrystalline diamond films. The combined electron- hole mobility, as measured by transient photoconductivity at low carrier densities, is 4000 square centimeters per volt per second at electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond films. The collection distance within the diamond films, at the highest applied fields, is comparable to the average film grain size, indicative of little or no carrier scattering at grain boundaries. A comparison of SIMS measurements with electrical results suggest that impurity incorporation in the near grain boundary regions are responsible for controlling the carrier mobility.

  20. Mobile lunar base project

    NASA Astrophysics Data System (ADS)

    Kozlov, I. A.; Shevchenko, V. V.

    1995-01-01

    An explorer must possess maximal mobility on the Moon if he is to discover natural anomalies most interesting for investigation. The same problem arises in the case of utilization of lunar natural resources. Moreover, according to lunar ecology requirements we should not destroy lunar surface layers over a wide area. For mining processes, many small plots should be chosen far away from each other. The concept of a mobile lunar manned base is proposed. The base structure consists of three vertical cylindrical modules placed into triangular (top view) girder construction. Each module is 5 meters in diameter with a height of 7 meters. The space around the cylinders is filled by a one meter protective layer of lunar soil. The ends of three vertical tube-type supports are put on the separate chassis. Total volume of living and working space is about 350 cubic meters. These modules are sized for a crew of nine. The velocity of the mobile lunar base is about 8 km per hour on a horizontal surface.

  1. Integron associated mobile genes

    PubMed Central

    Labbate, Maurizio; Boucher, Yan; Luu, Ivan; Chowdhury, Piklu Roy; Stokes, H.W.

    2012-01-01

    Lateral gene transfer (LGT) impacts on the evolution of prokaryotes in both the short and long-term. The short-term impacts of mobilized genes are a concern to humans since LGT explains the global rise of multi drug resistant pathogens seen in the past 70 years. However, LGT has been a feature of prokaryotes from the earliest days of their existence and the concept of a bifurcating tree of life is not entirely applicable to prokaryotes since most genes in extant prokaryotic genomes have probably been acquired from other lineages. Successful transfer and maintenance of a gene in a new host is understandable if it acts independently of cell networks and confers an advantage. Antibiotic resistance provides an example of this whereby a gene can be advantageous in virtually any cell across broad species backgrounds. In a longer evolutionary context however laterally transferred genes can be assimilated into even essential cell networks. How this happens is not well understood and we discuss recent work that identifies a mobile gene, unique to a cell lineage, which is detrimental to the cell when lost. We also present some additional data and believe our emerging model will be helpful in understanding how mobile genes integrate into cell networks. PMID:22754748

  2. Magnetically assisted solid phase extraction using Fe3O4 nanoparticles combined with enhanced spectrofluorimetric detection for aflatoxin M1 determination in milk samples.

    PubMed

    Taherimaslak, Zohreh; Amoli-Diva, Mitra; Allahyary, Mehdi; Pourghazi, Kamyar

    2014-09-01

    A novel, facile and inexpensive solid phase extraction (SPE) method using ethylene glycol bis-mercaptoacetate modified 3-(trimethoxysilyl)-1-propanethiol grafted Fe(3)O(4) nanoparticles coupled with spectrofluorimetric detection was proposed for determination of aflatoxin M1 (AFM1) in liquid milk samples. The method uses the advantage fluorescence enhancement by β-cyclodexterin complexation of AFM1 in 12% (v/v) acetonitrile-water and the remarkable properties of Fe(3)O(4) nanoparticles namely high surface area and strong magnetization were utilized to achieve high enrichment factor (57) and satisfactory extraction recoveries (91-102%) using only 100 mg of magnetic adsorbent. Furthermore, fast separation time of about 15 min avoids many time-consuming column-passing procedures of conventional SPE. The main factors affecting extraction efficiency including pH value, desorption conditions, extraction/desorption time, sample volume, and adsorbent amount were evaluated and optimized. Under the optimal conditions, a wide linear range of 0.04-8 ng mL(-1) with a low detection limit of 0.015 ng mL(-1) was obtained. The developed method was applied for extraction and preconcentration of AFM1 in three commercially available milk samples and the results were compared with the official AOAC method.

  3. Surfactant-enhanced spectrofluorimetric determination of total aflatoxins from wheat samples after magnetic solid-phase extraction using modified Fe3O4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Manafi, Mohammad Hanif; Allahyari, Mehdi; Pourghazi, Kamyar; Amoli-Diva, Mitra; Taherimaslak, Zohreh

    2015-07-01

    The extraction and preconcentration of total aflatoxins (including aflatoxin B1, B2, G1, and G2) using magnetic nanoparticles based solid phase extraction (MSPE) followed by surfactant-enhanced spectrofluorimetric detection was proposed. Ethylene glycol bis-mercaptoacetate modified silica coated Fe3O4 nanoparticles as an efficient antibody-free adsorbent was successfully applied to extract aflatoxins from wheat samples. High surface area and strong magnetization properties of magnetic nanoparticles were utilized to achieve high enrichment factor (97), and satisfactory recoveries (92-105%) using only 100 mg of the adsorbent. Furthermore, the fast separation time (less than 10 min) avoids many time-consuming cartridge loading or column-passing procedures accompany with the conventional SPE. In determination step, signal enhancement was performed by formation of Triton X-100 micelles around the analytes in 15% (v/v) acetonitrile-water which dramatically increase the sensitivity of the method. Main factors affecting the extraction efficiency and signal enhancement of the analytes including pH of sample solution, desorption conditions, extraction time, sample volume, adsorbent amount, surfactant concentration and volume and time of micelle formation were evaluated and optimized. Under the optimum conditions, wide linear range of 0.1-50 ng mL-1 with low detection limit of 0.03 ng mL-1 were obtained. The developed method was successfully applied to the extraction and preconcentration of aflatoxins in three commercially available wheat samples and the results were compared with the official AOAC method.

  4. Surfactant-enhanced spectrofluorimetric determination of total aflatoxins from wheat samples after magnetic solid-phase extraction using modified Fe₃O₄ nanoparticles.

    PubMed

    Manafi, Mohammad Hanif; Allahyari, Mehdi; Pourghazi, Kamyar; Amoli-Diva, Mitra; Taherimaslak, Zohreh

    2015-07-01

    The extraction and preconcentration of total aflatoxins (including aflatoxin B1, B2, G1, and G2) using magnetic nanoparticles based solid phase extraction (MSPE) followed by surfactant-enhanced spectrofluorimetric detection was proposed. Ethylene glycol bis-mercaptoacetate modified silica coated Fe3O4 nanoparticles as an efficient antibody-free adsorbent was successfully applied to extract aflatoxins from wheat samples. High surface area and strong magnetization properties of magnetic nanoparticles were utilized to achieve high enrichment factor (97), and satisfactory recoveries (92-105%) using only 100mg of the adsorbent. Furthermore, the fast separation time (less than 10 min) avoids many time-consuming cartridge loading or column-passing procedures accompany with the conventional SPE. In determination step, signal enhancement was performed by formation of Triton X-100 micelles around the analytes in 15% (v/v) acetonitrile-water which dramatically increase the sensitivity of the method. Main factors affecting the extraction efficiency and signal enhancement of the analytes including pH of sample solution, desorption conditions, extraction time, sample volume, adsorbent amount, surfactant concentration and volume and time of micelle formation were evaluated and optimized. Under the optimum conditions, wide linear range of 0.1-50 ng mL(-1) with low detection limit of 0.03 ng mL(-1) were obtained. The developed method was successfully applied to the extraction and preconcentration of aflatoxins in three commercially available wheat samples and the results were compared with the official AOAC method.

  5. Multiresidue method for the determination of pharmacologically active substances in egg and honey using a continuous solid-phase extraction system and gas chromatography-mass spectrometry.

    PubMed

    Azzouz, Abdelmonaim; Ballesteros, Evaristo

    2015-07-01

    A sensitive, selective, efficient gas chromatography-mass spectrometry method for the simultaneous determination of 22 pharmacologically active substances (antibacterials, nonsteroidal antiinflammatories, antiseptics, antiepileptics, lipid regulators, β-blockers and hormones) in eggs and honey was developed. The sample pretreatment includes precipitation of proteins and lipids with acetonitrile:water (3:2, v/v), centrifugation and continuous solid-phase extraction for cleanup and preconcentration. The proposed method was validated with quite good analytical results including limits of detection of 0.4-3.3 ng/kg for 2g of sample and good linearity (r(2)>0.995) throughout the studied concentration ranges. The recoveries of analytes from real honey and egg samples spiked at concentrations of 15-2,000 ng/kg fell in the range 87-102%, with relative standard deviations from 2.6% to 7.0%. The method was successfully used to determine the target compounds in various types of eggs (hen, quail and duck) and honey samples (flower, forest, acacia, sunflower, clover and pine tree). Two samples of hen eggs bought at supermarkets and one of quail eggs were found to contain florfenicol, pyrimethamine, estrone and 17β-estradiol at levels from 0.095 to 2.7 μg/kg.

  6. [Determination of 28 organochlorine and pyrethroid pesticides in pine nuts using solid-phase extraction and on-line gel permeation chromatography-gas chromatography/mass spectrometry].

    PubMed

    Kang, Qinghe; Wu, Yan; Gao, Kaiyang; Li, Zhibin

    2009-03-01

    An analytical method has been developed for the determination of 28 organochlorine pesticides and pyrethroid pesticides in pine nuts. The sample was extracted With acetonitrile-water (4:1, v/v) as the extraction solution by means of high-speed homogenization. The crude extract was purified by an Aluminium-N solid phase extraction column to remove most of the fat and sterols in the sample, then on-line gel permeation chromatography-gas chromatography/ mass spectrometry (GPC-GC/MS) analysis was performed. The recoveries for the most of pesticides in the sample spiked with the standards of 0.05 mg/kg were 70%-120%, and the relative standard deviations were less than 15%. The limits of detection of 28 organochlorine pesti- and pyrethroid pesticides were 0.002-0.05 mg/kg. The linear relationship and the recovery results were satisfactory. The method is rapid, accurate, highly senstive, and can be used for the simultaneous determination of pesticide residues in pine nuts.

  7. An experimental design approach employing artificial neural networks for the determination of potential endocrine disruptors in food using matrix solid-phase dispersion.

    PubMed

    Boti, Vasiliki I; Sakkas, Vasilios A; Albanis, Triantafyllos A

    2009-02-27

    Matrix solid-phase dispersion (MSPD) as a sample preparation method for the determination of two potential endocrine disruptors, linuron and diuron and their common metabolites, 1-(3,4-dichlorophenyl)-3-methylurea (DCPMU), 1-(3,4-dichlorophenyl) urea (DCPU) and 3,4-dichloroaniline (3,4-DCA) in food commodities has been developed. The influence of the main factors on the extraction process yield was thoroughly evaluated. For that purpose, a 3 fractional factorial design in further combination with artificial neural networks (ANNs) was employed. The optimal networks found were afterwards used to identify the optimum region corresponding to the highest average recovery displaying at the same time the lowest standard deviation for all analytes. Under final optimal conditions, potato samples (0.5 g) were mixed and dispersed on the same amount of Florisil. The blend was transferred on a polypropylene cartridge and analytes were eluted using 10 ml of methanol. The extract was concentrated to 50 microl of acetonitrile/water (50:50) and injected in a high performance liquid chromatography coupled to UV-diode array detector system (HPLC/UV-DAD). Recoveries ranging from 55 to 96% and quantification limits between 5.3 and 15.2 ng/g were achieved. The method was also applied to other selected food commodities such as apple, carrot, cereals/wheat flour and orange juice demonstrating very good overall performance.

  8. Ionic liquid molecularly imprinted polymers for application in pipette-tip solid-phase extraction coupled with gas chromatography for rapid screening of dicofol in celery.

    PubMed

    Yan, Hongyuan; Yang, Chen; Sun, Yunyun; Row, Kyung Ho

    2014-09-26

    A new type of ionic liquid molecularly imprinted polymers (IL-MIPs) synthesized by precipitation polymerization using 1-allyl-3-methylimidazolium bromide as an auxiliary solvent and α-chloro-dichlorodiphenyltrichloroethane (α-chloro-DDT) as the template was applied as a selective sorbent of minimized pipette tip-solid-phase extraction (PT-SPE) for rapid isolation and extraction of dicofol (DCF) from celery samples. The pretreatment procedure of celery samples involved only 2.0mg of IL-MIPs, 0.8 mL of acetonitrile-water (ACN-H2O; 1:1, v/v) (washing solvent), and 1.0 mL of acetone-10% acetic acid (HOAc) (elution solvent). Compared with molecularly imprinted polymers (MIPs), ionic liquid-non-imprinted polymers (IL-NIPs) and conventional sorbents such as C18, Si, NH2, and Al2O3-N, IL-MIPs showed higher adsorption and purification capacity to DCF in aqueous solution. Good linearity for DCF was observed in the range from 2.3 to 232.5 ng g(-1) (r(2)=0.9995). The average recoveries at three spiking levels ranged from 86.6% to 101.9% with relative standard deviations (RSDs) of ≤ 6.5% (n=3). The presented IL-MIPs-PT-SPE-GC/ECD method combines the advantages of MIPs, IL, and PT-SPE, and can be used in aqueous conditions with high affinity and selectivity to analytes of complex samples.

  9. Visualization of surfactant enhanced NAPL mobilization and solubilization in a two-dimensional micromodel

    SciTech Connect

    ZHONG,LIRONG; MAYER,ALEX; GLASS JR.,ROBERT J.

    2000-03-08

    Surfactant-enhanced aquifer remediation is an emerging technology for aquifers contaminated with nonaqueous phase liquids (NAPLs). A two-dimensional micromodel and image capture system were applied to observe NAPL mobilization and solubilization phenomena. In each experiment, a common residual NAPL field was established, followed by a series of mobilization and solubilization experiments. Mobilization floods included pure water floods with variable flow rates and surfactant floods with variations in surfactant formulations. At relatively low capillary numbers (N{sub ca}<10{sup {minus}3}), the surfactant mobilization floods resulted in higher NAPL saturations than for the pure water flood, for similar N{sub ca}.These differences in macroscopic saturations are explained by differences in micro-scale mobilization processes. Solubilization of the residual NAPL remaining after the mobilization stage was dominated by the formation of dissolution fingers, which produced nonequilibrium NAPL solubilization. A macroemulsion phase also as observed to form spontaneously and persist during the solubilization stage of the experiments.

  10. Studies on deaf mobile application

    NASA Astrophysics Data System (ADS)

    Nathan, Shelena Soosay; Hussain, Azham; Hashim, Nor Laily

    2016-08-01

    The deaf normally considered to be disabled that do not need any mobile technology due to the inabilities of hearing and talking. However, many deaf are using mobile phone in their daily life for various purposes such as communication and learning. Many studies have attempted to identify the need of deaf people in mobile application and level of usage of the applications. This study aims in studying the recent research conducted on deaf mobile application to understand the level of importance of mobile technology for this disabled community. This paper enable identification of studies conducted are limited and the need of more research done of this disabled people to ensure their privilege of using mobile technology and its application, which leads to the identification of deaf user requirement for mobile application as future study.

  11. Perceptions of Power Mobility Use and Safety within Residential Facilities

    PubMed Central

    Mortenson, William B; Miller, William C.; Boily, Jeanette; Steele, Barbara; Crawford, Erin M.; Desharnais, Guylaine

    2014-01-01

    Power wheelchairs enhance quality of life by enabling occupation, improving self-esteem and facilitating social interaction. Despite these benefits, there are risks associated with power mobility use; and accidents, which may occur, are a serious concern. As there is no gold standard to assess when a client is unsafe with power mobility, therapists generally rely on their clinical reasoning to make a decision. This paper presents the findings of the first phase of a two-part study to develop client-centred guidelines for power mobility. In the first phase of the study, 18 in-depth, qualitative interviews were conducted with a variety of stakeholders, including power mobility users, other residents, staff and family members. A thematic analysis of the interviews revealed four main themes: 1) “the meaning of power mobility,” 2) “learning the rules of the road,” 3) “red flags: concerns about safety,” and 4) “solutions.” The findings of this study have important implications for the safe use of power mobility. PMID:15988961

  12. Securing mobile code.

    SciTech Connect

    Link, Hamilton E.; Schroeppel, Richard Crabtree; Neumann, William Douglas; Campbell, Philip LaRoche; Beaver, Cheryl Lynn; Pierson, Lyndon George; Anderson, William Erik

    2004-10-01

    If software is designed so that the software can issue functions that will move that software from one computing platform to another, then the software is said to be 'mobile'. There are two general areas of security problems associated with mobile code. The 'secure host' problem involves protecting the host from malicious mobile code. The 'secure mobile code' problem, on the other hand, involves protecting the code from malicious hosts. This report focuses on the latter problem. We have found three distinct camps of opinions regarding how to secure mobile code. There are those who believe special distributed hardware is necessary, those who believe special distributed software is necessary, and those who believe neither is necessary. We examine all three camps, with a focus on the third. In the distributed software camp we examine some commonly proposed techniques including Java, D'Agents and Flask. For the specialized hardware camp, we propose a cryptographic technique for 'tamper-proofing' code over a large portion of the software/hardware life cycle by careful modification of current architectures. This method culminates by decrypting/authenticating each instruction within a physically protected CPU, thereby protecting against subversion by malicious code. Our main focus is on the camp that believes that neither specialized software nor hardware is necessary. We concentrate on methods of code obfuscation to render an entire program or a data segment on which a program depends incomprehensible. The hope is to prevent or at least slow down reverse engineering efforts and to prevent goal-oriented attacks on the software and execution. The field of obfuscation is still in a state of development with the central problem being the lack of a basis for evaluating the protection schemes. We give a brief introduction to some of the main ideas in the field, followed by an in depth analysis of a technique called 'white-boxing'. We put forth some new attacks and improvements

  13. Effect of weathering transformations of coal combustion residuals on trace element mobility in view of the environmental safety and sustainability of their disposal and use. I. Hydrogeochemical processes controlling pH and phase stability.

    PubMed

    Stefaniak, Sebastian; Miszczak, Ewa; Szczepańska-Plewa, Jadwiga; Twardowska, Irena

    2015-06-01

    Coal combustion residuals (CCRs) are one of the most abundant high-volume waste materials disposed in impoundments worldwide. Some methods of CCR recycling, e.g. their use as structural fill for low lying areas or as soil amendment, also expose this material to atmospheric conditions. Combustion processes result in concentration of trace elements in CCRs at about an order of magnitude compared to coal. In order to assess an effect of long-term weathering transformations of CCRs on trace element binding/release, a study has been carried out. It is based on the chemical composition of real pore solutions extracted from the most abundant primary alkaline Class F bituminous CCRs, 0 to >40 years old, sampled from the surface layer and vertical profiles at four different impoundments. In this part of the study, results of a hydrogeochemical simulation of the saturation state of real pore solutions with respect to mineral phases of CCRs with use of the PHREEQC program, related to actual pH values reflecting the full cycle of weathering transformations, have been discussed. This study is the first geochemical proof of the general trend towards a progressive acidification up to pH < 4 of primary alkaline CCRs due to release of protons during internal processes of formation of gibbsite and aluminosilicate minerals, buffered by carbonates at the alkaline - near-neutral stages, and followed by parallel dissolution and buffering by aluminosilicates at pH < 7 after carbonate depletion, to the level up to pH∼3.5-4.0. The intrinsic geochemical changes have resulted in the different susceptibility of trace elements to release and associated changes in risk to the environment at consecutive stages of weathering. PMID:25841194

  14. Effect of weathering transformations of coal combustion residuals on trace element mobility in view of the environmental safety and sustainability of their disposal and use. I. Hydrogeochemical processes controlling pH and phase stability.

    PubMed

    Stefaniak, Sebastian; Miszczak, Ewa; Szczepańska-Plewa, Jadwiga; Twardowska, Irena

    2015-06-01

    Coal combustion residuals (CCRs) are one of the most abundant high-volume waste materials disposed in impoundments worldwide. Some methods of CCR recycling, e.g. their use as structural fill for low lying areas or as soil amendment, also expose this material to atmospheric conditions. Combustion processes result in concentration of trace elements in CCRs at about an order of magnitude compared to coal. In order to assess an effect of long-term weathering transformations of CCRs on trace element binding/release, a study has been carried out. It is based on the chemical composition of real pore solutions extracted from the most abundant primary alkaline Class F bituminous CCRs, 0 to >40 years old, sampled from the surface layer and vertical profiles at four different impoundments. In this part of the study, results of a hydrogeochemical simulation of the saturation state of real pore solutions with respect to mineral phases of CCRs with use of the PHREEQC program, related to actual pH values reflecting the full cycle of weathering transformations, have been discussed. This study is the first geochemical proof of the general trend towards a progressive acidification up to pH < 4 of primary alkaline CCRs due to release of protons during internal processes of formation of gibbsite and aluminosilicate minerals, buffered by carbonates at the alkaline - near-neutral stages, and followed by parallel dissolution and buffering by aluminosilicates at pH < 7 after carbonate depletion, to the level up to pH∼3.5-4.0. The intrinsic geochemical changes have resulted in the different susceptibility of trace elements to release and associated changes in risk to the environment at consecutive stages of weathering.

  15. Quantitative analysis of olanzapine in rat brain microdialysates by HPLC-MS/MS coupled with column-switching technique.

    PubMed

    Zheng, Qiaoling; Wang, Feng; Li, Huande; Xu, Ping; Tang, Huaibo; Li, Lanfang; Cheng, Rihua

    2012-09-15

    A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method coupled with column-switching technique was developed for the determination of olanzapine in rat brain microdialysates. A C8 guard column was used to desalt the samples before analytical separation on a C18 column and detection with tandem mass spectrometry. The mobile phase consisted of methanol/acetonitrile/water (v/v/v, 22.5/22.2/55) was used for desalting and the mobile phase consisted of methanol/acetonitrile/water (v/v/v, 43/43/14) was for analytical separation, water in both mobile phases contained 0.1% ammonium acetate. The lower limit of quantification (LLOQ) for olanzapine was 0.085 ng/ml. The method was linear from LLOQ to 34 ng/ml with a coefficient of determination >0.998. Intra- and inter-day accuracy and precision were determined with variability less than 13.24% (R.S.D). This sensitive method was successfully applied to quantify the concentration of olanzapine in rat brain microdialysates. With this study, the effect of the alcohol extract of Schisandra sphenanthera Rehd. et Wils on the concentration of olanzapine in brain was investigated. PMID:22917592

  16. Active microrheology in active matter systems: Mobility, intermittency, and avalanches.

    PubMed

    Reichhardt, C; Reichhardt, C J Olson

    2015-03-01

    We examine the mobility and velocity fluctuations of a driven particle moving through an active matter bath of self-mobile disks for varied density or area coverage and varied activity. We show that the driven particle mobility can exhibit nonmonotonic behavior that is correlated with distinct changes in the spatiotemporal structures that arise in the active media. We demonstrate that the probe particle velocity distributions exhibit specific features in the different dynamic regimes and identify an activity-induced uniform crystallization that occurs for moderate activity levels and is distinct from the previously observed higher activity cluster phase. The velocity distribution in the cluster phase has telegraph noise characteristics produced when the probe particle moves alternately through high-mobility areas that are in the gas state and low-mobility areas that are in the dense phase. For higher densities and large activities, the system enters what we characterize as an active jamming regime. Here the probe particle moves in intermittent jumps or avalanches that have power-law-distributed sizes that are similar to the avalanche distributions observed for nonactive disk systems near the jamming transition.

  17. Active microrheology in active matter systems: Mobility, intermittency, and avalanches.

    PubMed

    Reichhardt, C; Reichhardt, C J Olson

    2015-03-01

    We examine the mobility and velocity fluctuations of a driven particle moving through an active matter bath of self-mobile disks for varied density or area coverage and varied activity. We show that the driven particle mobility can exhibit nonmonotonic behavior that is correlated with distinct changes in the spatiotemporal structures that arise in the active media. We demonstrate that the probe particle velocity distributions exhibit specific features in the different dynamic regimes and identify an activity-induced uniform crystallization that occurs for moderate activity levels and is distinct from the previously observed higher activity cluster phase. The velocity distribution in the cluster phase has telegraph noise characteristics produced when the probe particle moves alternately through high-mobility areas that are in the gas state and low-mobility areas that are in the dense phase. For higher densities and large activities, the system enters what we characterize as an active jamming regime. Here the probe particle moves in intermittent jumps or avalanches that have power-law-distributed sizes that are similar to the avalanche distributions observed for nonactive disk systems near the jamming transition. PMID:25871116

  18. Active microrheology in active matter systems: Mobility, intermittency, and avalanches

    NASA Astrophysics Data System (ADS)

    Reichhardt, C.; Reichhardt, C. J. Olson

    2015-03-01

    We examine the mobility and velocity fluctuations of a driven particle moving through an active matter bath of self-mobile disks for varied density or area coverage and varied activity. We show that the driven particle mobility can exhibit nonmonotonic behavior that is correlated with distinct changes in the spatiotemporal structures that arise in the active media. We demonstrate that the probe particle velocity distributions exhibit specific features in the different dynamic regimes and identify an activity-induced uniform crystallization that occurs for moderate activity levels and is distinct from the previously observed higher activity cluster phase. The velocity distribution in the cluster phase has telegraph noise characteristics produced when the probe particle moves alternately through high-mobility areas that are in the gas state and low-mobility areas that are in the dense phase. For higher densities and large activities, the system enters what we characterize as an active jamming regime. Here the probe particle moves in intermittent jumps or avalanches that have power-law-distributed sizes that are similar to the avalanche distributions observed for nonactive disk systems near the jamming transition.

  19. Multidirectional mobilities: Advanced measurement techniques and applications

    NASA Astrophysics Data System (ADS)

    Ivarsson, Lars Holger

    Today high noise-and-vibration comfort has become a quality sign of products in sectors such as the automotive industry, aircraft, components, households and manufacturing. Consequently, already in the design phase of products, tools are required to predict the final vibration and noise levels. These tools have to be applicable over a wide frequency range with sufficient accuracy. During recent decades a variety of tools have been developed such as transfer path analysis (TPA), input force estimation, substructuring, coupling by frequency response functions (FRF) and hybrid modelling. While these methods have a well-developed theoretical basis, their application combined with experimental data often suffers from a lack of information concerning rotational DOFs. In order to measure response in all 6 DOFs (including rotation), a sensor has been developed, whose special features are discussed in the thesis. This transducer simplifies the response measurements, although in practice the excitation of moments appears to be more difficult. Several excitation techniques have been developed to enable measurement of multidirectional mobilities. For rapid and simple measurement of the loaded mobility matrix, a MIMO (Multiple Input Multiple Output) technique is used. The technique has been tested and validated on several structures of different complexity. A second technique for measuring the loaded 6-by-6 mobility matrix has been developed. This technique employs a model of the excitation set-up, and with this model the mobility matrix is determined from sequential measurements. Measurements on ``real'' structures show that both techniques give results of similar quality, and both are recommended for practical use. As a further step, a technique for measuring the unloaded mobilities is presented. It employs the measured loaded mobility matrix in order to calculate compensation forces and moments, which are later applied in order to compensate for the loading of the

  20. A robust signalling system for land mobile satellite services

    NASA Technical Reports Server (NTRS)

    Irish, Dale; Shmith, Gary; Hart, Nick; Wines, Marie

    1989-01-01

    Presented here is a signalling system optimized to ensure expedient call set-up for satellite telephony services in a land mobile environment. In a land mobile environment, the satellite to mobile link is subject to impairments from multipath and shadowing phenomena, which result in signal amplitude and phase variations. Multipath, caused by signal scattering and reflections, results in sufficient link margin to compensate for these variations. Direct signal attenuation caused by shadowing due to buildings and vegetation may result in attenuation values in excess of 10 dB and commonly up to 20 dB. It is not practical to provide a link with sufficient margin to enable communication when the signal is blocked. When a moving vehicle passes these obstacles, the link will experience rapid changes in signal strength due to shadowing. Using statistical models of attenuation as a function of distance travelled, a communication strategy has been defined for the land mobile environment.

  1. [Determination of 61 organophosphorous pesticide residues in fruits, vegetables, milk, vegetable oils and animal muscles by dispersive solid-phase extraction and ultra performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Ye, Ruihong; Su, Jianfeng

    2011-07-01

    A dispersive solid-phase extraction coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 61 organophosphorous pesticide residues in fruits, vegetables, milk, vegetable oils and animal muscles. The fruit, vegetable and milk samples were extracted with acetonitrile and separated with salting out method; vegetable oil samples were dissolved by n-hexane, and extracted with acetonitrile; animal muscle samples were extracted with acetonitrile-water assisted by n-hexane and separated with salting out method. And then the supernatants were purified using dispersive solid-phase extraction (C18 and primary secondary amine powder) prior to the UPLC-MS/MS analysis. The analytes were indentified in positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) mode. The matrix-matched external standard calibration curves were used for quantitative analysis. Under the optimal conditions, the detection limits (S/N > or = 10) of the method were 0.01 mg/kg. The recoveries were 62.8%-107%, and the relative standard deviations (RSDs) were in the range of 4.2%-19%. The method has the advantages of easy, fast, and more sensitive, and can meet the requirement of the determination of organophosphorous pesticide residues in the foods.

  2. Gradient enhanced-fluidity liquid hydrophilic interaction chromatography of ribonucleic acid nucleosides and nucleotides: A "green" technique.

    PubMed

    Beilke, Michael C; Beres, Martin J; Olesik, Susan V

    2016-03-01

    A "green" hydrophilic interaction liquid chromatography (HILIC) technique for separating the components of mixtures with a broad range of polarities is illustrated using enhanced-fluidity liquid mobile phases. Enhanced-fluidity liquid chromatography (EFLC) involves the addition of liquid CO2 to conventional liquid mobile phases. Decreased mobile phase viscosity and increased analyte diffusivity results when a liquefied gas is dissolved in common liquid mobile phases. The impact of CO2 addition to a methanol:water (MeOH:H2O) mobile phase was studied to optimize HILIC gradient conditions. For the first time a fast separation of 16 ribonucleic acid (RNA) nucleosides/nucleotides was achieved (16min) with greater than 1.3 resolution for all analyte pairs. By using a gradient, the analysis time was reduced by over 100% compared to similar separations conducted under isocratic conditions. The optimal separation using MeOH:H2O:CO2 mobile phases was compared to MeOH:H2O and acetonitrile:water (ACN:H2O) mobile phases. Based on chromatographic performance parameters (efficiency, resolution and speed of analysis) and an assessment of the environmental impact of the mobile phase mixtures, MeOH:H2O:CO2 mixtures are preferred over ACN:H2O or MeOH:H2O mobile phases for the separation of mixtures of RNA nucleosides and nucleotides.

  3. Shuttle-run synchronization in mobile ad hoc networks

    NASA Astrophysics Data System (ADS)

    Ma, Sheng-Fei; Bi, Hong-Jie; Zou, Yong; Liu, Zong-Hua; Guan, Shu-Guang

    2015-06-01

    In this work, we study the collective dynamics of phase oscillators in a mobile ad hoc network whose topology changes dynamically. As the network size or the communication radius of individual oscillators increases, the topology of the ad hoc network first undergoes percolation, forming a giant cluster, and then gradually achieves global connectivity. It is shown that oscillator mobility generally enhances the coherence in such networks. Interestingly, we find a new type of phase synchronization/clustering, in which the phases of the oscillators are distributed in a certain narrow range, while the instantaneous frequencies change signs frequently, leading to shuttle-run-like motion of the oscillators in phase space. We conduct a theoretical analysis to explain the mechanism of this synchronization and obtain the critical transition point.

  4. First satellite mobile communication trials using BLQS-CDMA

    NASA Technical Reports Server (NTRS)

    Luzdemateo, Maria; Johns, Simon; Dothey, Michel; Vanhimbeeck, Carl; Deman, Ivan; Wery, Bruno

    1993-01-01

    In this paper, technical results obtained in the first MSBN Land mobile technical trial are reported. MSBN (Mobile Satellite Business Network) is a new program undertaken by the European Space Agency (ESA) to promote mobile satellite communication in Europe, in particular voice capability. The first phase of the MSBN system implementation plan is an experimental phase. Its purpose is to evaluate through field experiments the performance of the MSBN system prior to finalization of its specifications. Particularly, the objective is to verify in the field and possibly improve the performance of the novel satellite access technique BLQS-CDMA (Band Limited Quasi-Synchronous-Code Division Multiple Access), which is proposed as baseline for the MSBN.

  5. Spacesuit mobility knee joints

    NASA Technical Reports Server (NTRS)

    Vykukal, H. C. (Inventor)

    1979-01-01

    Pressure suit mobility joints are for use in interconnecting adjacent segments of an hermetically sealed spacesuit in which low torques, low leakage and a high degree of reliability are required. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics and includes linkages which restrain the joint from longitudinal distension and includes a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

  6. Mobile Bay turbidity study

    NASA Technical Reports Server (NTRS)

    Crozier, G. F.; Schroeder, W. W.

    1978-01-01

    The termination of studies carried on for almost three years in the Mobile Bay area and adjacent continental shelf are reported. The initial results concentrating on the shelf and lower bay were presented in the interim report. The continued scope of work was designed to attempt a refinement of the mathematical model, assess the effectiveness of optical measurement of suspended particulate material and disseminate the acquired information. The optical characteristics of particulate solutions are affected by density gradients within the medium, density of the suspended particles, particle size, particle shape, particle quality, albedo, and the angle of refracted light. Several of these are discussed in detail.

  7. Trauma and Mobile Radiography

    SciTech Connect

    Drafke, M.W.

    1989-01-01

    Trauma and Mobile Radiography focuses on the radiography of trauma patients and of patients confined to bed. This book offers students a foundation in the skills they need to produce quality radiograms without causing additional injury or pain to the patient. Features of this new book include: coverage of the basics of radiography and patient care, including monitoring of heavily sedated, immobile, and accident patients. Information on the injuries associated with certain types of accidents, and methods for dealing with these problems. Detailed explanation of the positioning of each anatomical area. A Quick Reference Card with information on evaluating, monitoring and radiographing trauma patients.

  8. Mobile health monitoring systems.

    PubMed

    Walker, William; Aroul, A L Praveen; Bhatia, Dinesh

    2009-01-01

    Advancements are being made towards a cheap and effective means for health monitoring. A mobile monitoring system is proposed for monitoring a bicycle rider using light weight, low power wireless sensors. Biometric and environmental information pertaining to the bicycle rider is captured, transmitted to, and stored in a remote database with little user interaction required. Remote users have real time access to the captured information through a web application. Possible applications for this system include the monitoring of a soldier in the battlefield and the monitoring of a patient during an ambulance ride. PMID:19965041

  9. Creating a Mobile Library Website

    ERIC Educational Resources Information Center

    Cutshall, Tom C.; Blake, Lindsay; Bandy, Sandra L.

    2011-01-01

    The overwhelming results were iPhones and Android devices. Since the library wasn't equipped technologically to develop an in-house application platform and because we wanted the content to work across all mobile platforms, we decided to focus on creating a mobile web-based platform. From the NLM page of mobile sites we chose the basic PubMed/…

  10. INFLUENCE OF VISCOUS AND BUOYANCY FORCES ON THE MOBILIZATION OF RESIDUAL TETRACHLOROETHYLENE DURING SURFACTANT FLUSHING

    EPA Science Inventory

    The potential for nonaqueous phase liquid (NAPL) mobilization is one of the most important considerations in the development and implementation of surfactant-based remediation technologies. Column experiments were performed to investigate the onset and extent of tetrachloroethyle...

  11. Asymmetric soliton mobility in competing linear–nonlinear parity-time-symmetric lattices

    NASA Astrophysics Data System (ADS)

    Kartashov, Yaroslav V.; Vysloukh, Victor A.; Torner, Lluis

    2016-09-01

    We address the transverse mobility of spatial solitons in competing parity-time-symmetric linear and nonlinear lattices. The competition between out-of-phase linear and nonlinear lattices results in a drastic mobility enhancement within a range of soliton energies. We show that within such range, the addition of even a small imaginary part in the linear potential makes soliton mobility strongly asymmetric. The minimal phase tilt required for setting solitons into radiationless motion across the lattice in the direction opposite to that of the internal current drops to nearly zero, while the minimal phase tilt required for motion in the opposite direction notably increases. For a given initial phase tilt, the velocity of soliton motion grows with an increase of the balanced gain/losses. In this regime of enhanced mobility, tilted solitons can efficiently drag other solitons that were initially at rest, to form moving soliton pairs.

  12. The Mobile Chamber

    NASA Technical Reports Server (NTRS)

    Scharfstein, Gregory; Cox, Russell

    2012-01-01

    A document discusses a simulation chamber that represents a shift from the thermal-vacuum chamber stereotype. This innovation, currently in development, combines the capabilities of space simulation chambers, the user-friendliness of modern-day electronics, and the modularity of plug-and-play computing. The Mobile Chamber is a customized test chamber that can be deployed with great ease, and is capable of bringing payloads at temperatures down to 20 K, in high vacuum, and with the desired metrology instruments integrated to the systems control. Flexure plans to lease Mobile Chambers, making them affordable for smaller budgets and available to a larger customer base. A key feature of this design will be an Apple iPad-like user interface that allows someone with minimal training to control the environment inside the chamber, and to simulate the required extreme environments. The feedback of thermal, pressure, and other measurements is delivered in a 3D CAD model of the chamber's payload and support hardware. This GUI will provide the user with a better understanding of the payload than any existing thermal-vacuum system.

  13. Space station mobile transporter

    NASA Technical Reports Server (NTRS)

    Renshall, James; Marks, Geoff W.; Young, Grant L.

    1988-01-01

    The first quarter of the next century will see an operational space station that will provide a permanently manned base for satellite servicing, multiple strategic scientific and commercial payload deployment, and Orbital Maneuvering Vehicle/Orbital Transfer Vehicle (OMV/OTV) retrieval replenishment and deployment. The space station, as conceived, is constructed in orbit and will be maintained in orbit. The construction, servicing, maintenance and deployment tasks, when coupled with the size of the station, dictate that some form of transportation and manipulation device be conceived. The Transporter described will work in conjunction with the Orbiter and an Assembly Work Platform (AWP) to construct the Work Station. The Transporter will also work in conjunction with the Mobile Remote Servicer to service and install payloads, retrieve, service and deploy satellites, and service and maintain the station itself. The Transporter involved in station construction when mounted on the AWP and later supporting a maintenance or inspection task with the Mobile Remote Servicer and the Flight Telerobotic Servicer is shown.

  14. Mobile access control vestibule

    NASA Astrophysics Data System (ADS)

    DePoy, Jennifer M.

    1998-12-01

    The mobile access control vestibule (MACV) is an adaptation of techniques developed for mobile military command centers. The overall configuration of modules acts as an entry control/screening facility or transportable command center. The system would provide the following capabilities: (1) A key element for force protection, rapid deployment units sent to areas having no prepositioned equipment or where there has been a degradation of that equipment as a result of natural disasters or civil unrest. (2) A rapidly deployable security control center to upgrade the security at nonmilitary sites (e.g., diplomatic or humanitarian organizations). (3) Personnel screening, package screening, badge/identification card production for authorized personnel, centralized monitoring of deployed perimeter sensors, and centralized communications for law enforcement personnel. (4) Self-contained screening and threat detection systems, including explosives detection using the system developed by Sandia National Laboratories for the FAA. When coupled with transportable electric generators, the system is self-sufficient. The communication system for the MACV would be a combination of physically wired and wireless communication units that supports by ad hoc networking.

  15. Ghana social mobilization analysis.

    PubMed

    Tweneboa-Kodua, A; Obeng-Quaidoo, I; Abu, K

    1991-01-01

    In order to increase communication channels for child survival and development, the government and UNICEF Ghana undertook a "social mobilization analysis." This analysis included three studies that aimed to identify individuals and existing organizations with the potential to serve as health communicators and to determine the type of assistance that they needed to maximize their effectiveness in this role. The first study surveyed governmental institutions, trade unions, revolutionary organizations, traditional leaders, and others and found a largely untapped reservoir of capacities to promote child health, with varying levels of current involvement. The primary need identified was for information and training materials. The second study focused on the mass media and revealed a low coverage of maternal and child health topics and the need for better cooperation between journalists and health professionals. The third study assessed sources of health information for parents and found several sources, such as religious organizations, women's groups, and school teachers that could be mobilized to promote child health. Recommendations are made for the use of the findings. PMID:2037495

  16. Wideband, mobile networking technologies

    NASA Astrophysics Data System (ADS)

    Hyer, Kevin L.; Bowen, Douglas G.; Pulsipher, Dennis C.

    2005-05-01

    Ubiquitous communications will be the next era in the evolving communications revolution. From the human perspective, access to information will be instantaneous and provide a revolution in services available to both the consumer and the warfighter. Services will be from the mundane - anytime, anywhere access to any movie ever made - to the vital - reliable and immediate access to the analyzed real-time video from the multi-spectral sensors scanning for snipers in the next block. In the former example, the services rely on a fixed infrastructure of networking devices housed in controlled environments and coupled to fixed terrestrial fiber backbones - in the latter, the services are derived from an agile and highly mobile ad-hoc backbone established in a matter of minutes by size, weight, and power-constrained platforms. This network must mitigate significant changes in the transmission media caused by millisecond-scale atmospheric temperature variations, the deployment of smoke, or the drifting of a cloud. It must mitigate against structural obscurations, jet wash, or incapacitation of a node. To maintain vital connectivity, the mobile backbone must be predictive and self-healing on both near-real-time and real-time time scales. The nodes of this network must be reconfigurable to mitigate intentional and environmental jammers, block attackers, and alleviate interoperability concerns caused by changing standards. The nodes must support multi-access of disparate waveform and protocols.

  17. Mobilization of Pollutant-Degrading Bacteria by Eukaryotic Zoospores.

    PubMed

    Sungthong, Rungroch; van West, Pieter; Heyman, Fredrik; Jensen, Dan Funck; Ortega-Calvo, Jose Julio

    2016-07-19

    The controlled mobilization of pollutant-degrading bacteria has been identified as a promising strategy for improving bioremediation performance. We tested the hypothesis whether the mobilization of bacterial degraders may be achieved by the action of eukaryotic zoospores. We evaluated zoospores that are produced by the soil oomycete Pythium aphanidermatum as a biological vector, and, respectively, the polycyclic aromatic hydrocarbon (PAH)-degrading bacteria Mycobacterium gilvum VM552 and Pseudomonas putida G7, acting as representative nonflagellated and flagellated species. The mobilization assay was performed with a chemical-in-capillary method, in which zoospores mobilized bacterial cells only when they were exposed to a zoospore homing inducer (5% (v/v) ethanol), which caused the tactic response and settlement of zoospores. The mobilization was strongly linked to a lack of bacterial motility, because the nonflagellated cells from strain M. gilvum VM552 and slightly motile, stationary-phase cells from P. putida G7 were mobilized effectively, but the actively motile, exponentially grown cells of P. putida G7 were not mobilized. The computer-assisted analysis of cell motility in mixed suspensions showed that the swimming rate was enhanced by zoospores in stationary, but not in exponentially grown, cells of P. putida G7. It is hypothesized that the directional swimming of zoospores caused bacterial mobilization through the thrust force of their flagellar propulsion. Our results suggest that, by mobilizing pollutant-degrading bacteria, zoospores can act as ecological amplifiers for fungal and oomycete mycelial networks in soils, extending their potential in bioremediation scenarios. PMID:27286642

  18. Moon Phases

    ERIC Educational Resources Information Center

    Riddle, Bob

    2010-01-01

    When teaching Moon phases, the focus seems to be on the sequence of Moon phases and, in some grade levels, how Moon phases occur. Either focus can sometimes be a challenge, especially without the use of models and observations of the Moon. In this month's column, the author describes some of the lessons that he uses to teach the phases of the Moon…

  19. Re-thinking residential mobility

    PubMed Central

    van Ham, Maarten; Findlay, Allan M.

    2015-01-01

    While researchers are increasingly re-conceptualizing international migration, far less attention has been devoted to re-thinking short-distance residential mobility and immobility. In this paper we harness the life course approach to propose a new conceptual framework for residential mobility research. We contend that residential mobility and immobility should be re-conceptualized as relational practices that link lives through time and space while connecting people to structural conditions. Re-thinking and re-assessing residential mobility by exploiting new developments in longitudinal analysis will allow geographers to understand, critique and address pressing societal challenges. PMID:27330243

  20. Webizing mobile augmented reality content

    NASA Astrophysics Data System (ADS)

    Ahn, Sangchul; Ko, Heedong; Yoo, Byounghyun

    2014-01-01

    This paper presents a content structure for building mobile augmented reality (AR) applications in HTML5 to achieve a clean separation of the mobile AR content and the application logic for scaling as on the Web. We propose that the content structure contains the physical world as well as virtual assets for mobile AR applications as document object model (DOM) elements and that their behaviour and user interactions are controlled through DOM events by representing objects and places with a uniform resource identifier. Our content structure enables mobile AR applications to be seamlessly developed as normal HTML documents under the current Web eco-system.

  1. Nuclear powerplants for mobile applications.

    NASA Technical Reports Server (NTRS)

    Anderson, J. L.

    1972-01-01

    Mobile nuclear powerplants for applications other than large ships and submarines will require compact, lightweight reactors with especially stringent impact-safety design. This paper examines the technical and economic feasibility that the broadening role of civilian nuclear power, in general, (land-based nuclear electric generating plants and nuclear ships) can extend to lightweight, safe mobile nuclear powerplants. The paper discusses technical experience, identifies potential sources of technology for advanced concepts, cites the results of economic studies of mobile nuclear powerplants, and surveys future technical capabilities needed by examining the current use and projected needs for vehicles, machines, and habitats that could effectively use mobile nuclear reactor powerplants.

  2. Ion Mobility Spectrometry (IMS) and Mass Spectrometry

    SciTech Connect

    Shvartsburg, Alexandre A.

    2010-04-20

    In a media of finite viscosity, the Coulomb force of external electric field moves ions with some terminal speed. This dynamics is controlled by “mobility” - a property of the interaction potential between ions and media molecules. This fact has been used to separate and characterize gas-phase ions in various modes of ion mobility spectrometry (IMS) developed since 1970. Commercial IMS devices were introduced in 1980-s for field detection of volatile traces such as explosives and chemical warfare agents. Coupling to soft-ionization sources, mass spectrometry (MS), and chromatographic methods in 1990-s had allowed IMS to handle complex samples, enabling new applications in biological and environmental analyses, nanoscience, and other areas. Since 2003, the introduction of commercial systems by major instrument vendors started bringing the IMS/MS capability to broad user community. The other major development of last decade has been the differential IMS or “field asymmetric waveform IMS” (FAIMS) that employs asymmetric time-dependent electric field to sort ions not by mobility itself, but by the difference between its values in strong and weak electric fields. Coupling of FAIMS to conventional IMS and stacking of conventional IMS stages have enabled two-dimensional separations that dramatically expand the power of ion mobility methods.

  3. Mobile Router Developed and Tested

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.

    2002-01-01

    The NASA Glenn Research Center, under a NASA Space Act Agreement with Cisco Systems, has been performing joint networking research to apply Internet-based technologies and protocols to space-based communications. As a result of this research, NASA performed stringent performance testing of the mobile router, including the interaction of routing and the transport-level protocol. In addition, Cisco Systems developed the mobile router for both commercial and Government markets. The code has become part of the Cisco Systems Internetworking Operating System (IOS) as of release 12.2 (4) T--which will make this capability available to the community at large. The mobile router is software code that resides in a network router and enables entire networks to roam while maintaining connectivity to the Internet. This router code is pertinent to a myriad of applications for both Government and commercial sectors, including the "wireless battlefield." NASA and the Department of Defense will utilize this technology for near-planetary observation and sensing spacecraft. It is also a key enabling technology for aviation-based information applications. Mobile routing will make it possible for information such as weather, air traffic control, voice, and video to be transmitted to aircraft using Internet-based protocols. This technology shows great promise in reducing congested airways and mitigating aviation disasters due to bad weather. The mobile router can also be incorporated into emergency vehicles (such as ambulances and life-flight aircraft) to provide real-time connectivity back to the hospital and health-care experts, enabling the timely application of emergency care. Commercial applications include entertainment services, Internet protocol (IP) telephone, and Internet connectivity for cruise ships, commercial shipping, tour buses, aircraft, and eventually cars. A mobile router, which is based on mobile IP, allows hosts (mobile nodes) to seamlessly "roam" among various IP

  4. Virtual Mobility in Reality: A Study of the Use of ICT in Finnish Leonardo da Vinci Mobility Projects.

    ERIC Educational Resources Information Center

    Valjus, Sonja

    An e-mail survey and interviews collected data on use of information and communications technology (ICT) in Finnish Leonardo da Vinci mobility projects from 2000-02. Findings showed that the most common ICT tools used were e-mail, digital tools, and the World Wide Web; ICT was used during all project phases; the most common problems concerned…

  5. Mobile Learning and Integration of Mobile Technologies in Education

    ERIC Educational Resources Information Center

    Keengwe, Jared; Bhargava, Malini

    2014-01-01

    Mobile technologies have a huge potential to transform education provided these technologies are designed and implemented in such a way that they are relevant to the social and cultural context of learning. Clearly, the application, implementation, and design of mobile technology in the global educational context pose technological and…

  6. Mobile Learning with a Mobile Game: Design and Motivational Effects

    ERIC Educational Resources Information Center

    Schwabe, Gerhard; Goth, Christoph

    2005-01-01

    Mobile technologies offer the opportunity to embed learning in a natural environment. This paper describes the design of the MobileGame prototype, exploring the opportunities to support learning through an orientation game in a university setting. The paper first introduces the scenario and then describes the general architecture of the prototype.…

  7. Mobile Perspectives: On Websites. Mobile Matters--Communication Trumps Technology

    ERIC Educational Resources Information Center

    Evans, Susan T.

    2011-01-01

    Mobile technology is a favorite discussion topic among senior IT leaders and higher education administrators. Mobile is the future for content delivery. Colleges and universities need to establish a strategy now and make the decisions necessary to take advantage of this communication opportunity. In this article, the author recommends making…

  8. A Mobile IPv6 based Distributed Mobility Management Mechanism of Mobile Internet

    NASA Astrophysics Data System (ADS)

    Yan, Shi; Jiayin, Cheng; Shanzhi, Chen

    A flatter architecture is one of the trends of mobile Internet. Traditional centralized mobility management mechanism faces the challenges such as scalability and UE reachability. A MIPv6 based distributed mobility management mechanism is proposed in this paper. Some important network entities and signaling procedures are defined. UE reachability is also considered in this paper through extension to DNS servers. Simulation results show that the proposed approach can overcome the scalability problem of the centralized scheme.

  9. Need for, and financial feasibility of, satellite-aided land mobile communications

    NASA Technical Reports Server (NTRS)

    Castruccio, P. A.; Marantz, C. S.; Freibaum, J.

    1982-01-01

    Questions regarding the role of a mobile-satellite system in augmenting the terrestrial communications system are considered, and a market assessment study is discussed. Aspects of an investment analysis are examined, taking into account a three phase financial study of four postulated land Mobile Satellite Service (LMSS) systems, project profitability evaluation methods, risk analysis methods, financial projections, potential investor acceptance standards, and a risk analysis. It is concluded that a satellite augmented terrestrial mobile service appears to be economically and technically superior to a service depending exclusively on terrestrial systems. The interest in the Mobile Satellite Service is found to be worldwide, and the ground equipment market is potentially large.

  10. Mobile electric power

    SciTech Connect

    Bloomfield, V.J.; Bloomfield, D.P.; Johnson, B.Q.

    1992-01-30

    Analytic Power has proven the feasibility of a mobile electric power unit in the form of a hydride fueled ion-exchange membrane (IEM) fuel cell stack. We have over 5 years experience building and testing IEM fuel cells. The power section of a 350 watt fuel cell stack weighs 4.65 pounds based on our five cell sub-stack component weights. The composite stack structure is fabricated from two components; a unitized flow field and catalyzed membrane. The lightweight unitized flow field concept was proven in the first three months of the contract. A single unit flow field weighs 0.155 pounds and can seal to 60 psi. The single cell catalyzed Nafion membrane exceeded our performance goal of 0.6 volts at 100 ASF. Stack performance points were 0.42 volts at 113 ASF and .75 volts at 96 asf.

  11. Phobos Mobility Simulation

    NASA Technical Reports Server (NTRS)

    Bielski, Paul

    2015-01-01

    Phobos, the larger of Mars' moons, provides a potential staging location for human exploration of the Martian surface. Its low gravity (about 1/200th of Earth) and lack of atmosphere makes it an attractive destination before a more complex human landing on Mars is attempted. While easier to approach and depart than Mars itself, Phobos provides unique challenges to visiting crews. It is irregularly shaped, so its local gravitational field does not always point straight down with respect to the visible horizon. It is very close to Mars and tidally locked, so the Martian gravity gradient and applied acceleration greatly affect the perceived surface gravity direction and magnitude. This simulation allows the assessment of unique mobility approaches on the surface of Phobos, including hopping in particular.

  12. Modelling an Institutional Mobile Learning Readiness Analyser

    ERIC Educational Resources Information Center

    Ireri, Bonface Ngari; Omwenga, Elijah I.

    2015-01-01

    Due to the affordability, ease of use and availability of mobile devices, many people in Africa and developing countries have acquired at least a mobile device. The penetration of mobile devices places many learning institution in a position to adopt mobile learning, however there are few tools for measuring mobile learning readiness for an…

  13. Carbon phosphide monolayers with superior carrier mobility.

    PubMed

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P

    2016-04-28

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics. PMID:27067002

  14. OPACs and the Mobile Revolution

    ERIC Educational Resources Information Center

    Liston, Samuel

    2009-01-01

    Since the turn of the century, one of the hottest topics in the IT world has been the coming mobile revolution. While there's been some arguing over the details, the fundamental tenet of the mobile revolution is that lots and lots of people will start accessing web content from handheld portable devices instead of using a traditional laptop or…

  15. Social Mobility and Educational Selection

    ERIC Educational Resources Information Center

    Dong, Zefang; Wang, Yanbin; Chen, Wenjiao

    2009-01-01

    There is a close interactive relationship between social mobility and educational selection. On one side, the character, direction, speed, level, methods and trends of social mobility affect the aims, goals, functions, scope, strategy, content and methods of choice in education. On the other side, the goals, basis and means of choosing education…

  16. Why Mobile Is a Must

    ERIC Educational Resources Information Center

    McCaffrey, Mary

    2011-01-01

    There is a need for a new educational model that makes learning personal and motivating, and helps secure students' future in the knowledge economy. Mobile technology opens the door to it. Mobile devices provide the platform and, as importantly, the incentive for students to take personal ownership of the learning experience. The lessons absorbed…

  17. The Sutton Trust: Mobility Manifesto

    ERIC Educational Resources Information Center

    Sutton Trust, 2014

    2014-01-01

    Ahead of the party conference season, the Sutton Trust is urging fairer admissions to comprehensives, grammar schools and independent schools as part of a 10-point Mobility Manifesto setting out ten practical policy steps designed to put social mobility at the heart of the 2015 election campaign. The manifesto urges greater use of ballots (random…

  18. Education & Mobility. CEE DP 100

    ERIC Educational Resources Information Center

    Machin, Stephen; Pelkonen, Panu; Salvanes, Kjell G.

    2008-01-01

    Regional labour mobility has long been viewed as a crucial component in the functioning of the labour markets of different countries. Indeed, the study of regional labour mobility has moved towards the top of the research agenda, especially in Europe, where regional unemployment differentials have been persistently larger than in the United…

  19. Transformations: Mobile Interaction & Language Learning

    ERIC Educational Resources Information Center

    Carroll, Fiona; Kop, Rita; Thomas, Nathan; Dunning, Rebecca

    2015-01-01

    Mobile devices and the interactions that these technologies afford have the potential to change the face and nature of education in our schools. Indeed, mobile technological advances are seen to offer better access to educational material and new interactive ways to learn. However, the question arises, as to whether these new technologies are…

  20. Exploring Mobile Learning Success Factors

    ERIC Educational Resources Information Center

    Cochrane, Thomas D.

    2010-01-01

    This paper is a comparative account and analysis of three mobile Web 2.0 projects instigated within a tertiary learning environment during 2008. Following the successful instigation of a mobile Web 2.0 project in the third year of a Bachelor of Product Design course during semester one, similar projects were initiated in semester two within the…

  1. Mobility. Snapshot™ Report, Spring 2014

    ERIC Educational Resources Information Center

    National Student Clearinghouse, 2014

    2014-01-01

    Just over 9% of all students attended more than one institution during the 2012-13 academic year. In each year studied, nearly three-fourths of all mobile students had at least one enrollment at a 2-year public institution. In each of the included years, students in the 20 and under age group had the highest mobility rates, followed by students in…

  2. Savannah: Mobile Gaming and Learning?

    ERIC Educational Resources Information Center

    Facer, K.; Joiner, R.; Stanton, D.; Reid, J.; Hull, R.; Kirk, D.

    2004-01-01

    This paper reports a study that attempts to explore how using mobile technologies in direct physical interaction with space and with other players can be combined with principles of engagement and self-motivation to create a powerful and engaging learning experience. We developed a mobile gaming experience designed to encourage the development of…

  3. Mobile Technology and Liberal Education

    ERIC Educational Resources Information Center

    Rossing, Jonathan P.

    2012-01-01

    In this article, the author offers reflections on the impact of mobile technology for liberal education. These reflections are based on his own experience of incorporating iPads in his communication courses during the 2010-2011 academic year. As a member of an interdisciplinary faculty learning community on the use of mobile tablets, he explored…

  4. Social Properties of Mobile Video

    NASA Astrophysics Data System (ADS)

    Mitchell, April Slayden; O'Hara, Kenton; Vorbau, Alex

    Mobile video is now an everyday possibility with a wide array of commercially available devices, services, and content. These new technologies have created dramatic shifts in the way video-based media can be produced, consumed, and delivered by people beyond the familiar behaviors associated with fixed TV and video technologies. Such technology revolutions change the way users behave and change their expectations in regards to their mobile video experiences. Building upon earlier studies of mobile video, this paper reports on a study using diary techniques and ethnographic interviews to better understand how people are using commercially available mobile video technologies in their everyday lives. Drawing on reported episodes of mobile video behavior, the study identifies the social motivations and values underpinning these behaviors that help characterize mobile video consumption beyond the simplistic notion of viewing video only to kill time. This paper also discusses the significance of user-generated content and the usage of video in social communities through the description of two mobile video technology services that allow users to create and share content. Implications for adoption and design of mobile video technologies and services are discussed as well.

  5. Joint Transmit Antenna Selection and Power Allocation for ISDF Relaying Mobile-to-Mobile Sensor Networks

    PubMed Central

    Xu, Lingwei; Zhang, Hao; Gulliver, T. Aaron

    2016-01-01

    The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation problem is formulated to determine the optimal division of transmit power between the broadcast and relay phases. The OP performance under different conditions is evaluated via numerical simulation to verify the analysis. These results show that the optimal TAS scheme has better OP performance than the suboptimal scheme. Further, the power allocation parameter has a significant influence on the OP performance. PMID:26907282

  6. Joint Transmit Antenna Selection and Power Allocation for ISDF Relaying Mobile-to-Mobile Sensor Networks.

    PubMed

    Xu, Lingwei; Zhang, Hao; Gulliver, T Aaron

    2016-02-19

    The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation problem is formulated to determine the optimal division of transmit power between the broadcast and relay phases. The OP performance under different conditions is evaluated via numerical simulation to verify the analysis. These results show that the optimal TAS scheme has better OP performance than the suboptimal scheme. Further, the power allocation parameter has a significant influence on the OP performance.

  7. Joint Transmit Antenna Selection and Power Allocation for ISDF Relaying Mobile-to-Mobile Sensor Networks.

    PubMed

    Xu, Lingwei; Zhang, Hao; Gulliver, T Aaron

    2016-01-01

    The outage probability (OP) performance of multiple-relay incremental-selective decode-and-forward (ISDF) relaying mobile-to-mobile (M2M) sensor networks with transmit antenna selection (TAS) over N-Nakagami fading channels is investigated. Exact closed-form OP expressions for both optimal and suboptimal TAS schemes are derived. The power allocation problem is formulated to determine the optimal division of transmit power between the broadcast and relay phases. The OP performance under different conditions is evaluated via numerical simulation to verify the analysis. These results show that the optimal TAS scheme has better OP performance than the suboptimal scheme. Further, the power allocation parameter has a significant influence on the OP performance. PMID:26907282

  8. Surfactant dissolution and mobilization of LNAPL contaminants in aquifers.

    PubMed

    Chevalier, Lizette R

    2003-05-01

    Improper disposal, accidental spills and leaks of non-aqueous phase liquids (NAPL) such as gasoline, fuel oil and creosote result in long-term persistent sources of groundwater pollution. Column and 2-D tanks experiments were conducted to evaluate the use of surfactant-enhanced recovery of light non-aqueous phase liquids (LNAPL) in groundwater aquifers. These experiments focused on the use of surfactants to promote dissolution and mobilization in addition to evaluating the increase of aqueous phase permeability as residual NAPL is recovered. Further experiments are presented that show the innovative use of surfactants during primary pumping to recover free product can potentially increase the amount of free product recovered, can potentially reduce the amount of residual NAPL remaining after primary pumping and performs better than the use of surfactants to mobilize trapped residual NAPL.

  9. Unravelling daily human mobility motifs.

    PubMed

    Schneider, Christian M; Belik, Vitaly; Couronné, Thomas; Smoreda, Zbigniew; González, Marta C

    2013-07-01

    Human mobility is differentiated by time scales. While the mechanism for long time scales has been studied, the underlying mechanism on the daily scale is still unrevealed. Here, we uncover the mechanism responsible for the daily mobility patterns by analysing the temporal and spatial trajectories of thousands of persons as individual networks. Using the concept of motifs from network theory, we find only 17 unique networks are present in daily mobility and they follow simple rules. These networks, called here motifs, are sufficient to capture up to 90 per cent of the population in surveys and mobile phone datasets for different countries. Each individual exhibits a characteristic motif, which seems to be stable over several months. Consequently, daily human mobility can be reproduced by an analytically tractable framework for Markov chains by modelling periods of high-frequency trips followed by periods of lower activity as the key ingredient.

  10. Performance measurement of mobile manipulators

    NASA Astrophysics Data System (ADS)

    Bostelman, Roger; Hong, Tsai; Marvel, Jeremy

    2015-05-01

    This paper describes a concept for measuring the reproducible performance of mobile manipulators to be used for assembly or other similar tasks. An automatic guided vehicle with an onboard robot arm was programmed to repeatedly move to and stop at a novel, reconfigurable mobile manipulator artifact (RMMA), sense the RMMA, and detect targets on the RMMA. The manipulator moved a laser retroreflective sensor to detect small reflectors that can be reconfigured to measure various manipulator positions and orientations (poses). This paper describes calibration of a multi-camera, motion capture system using a 6 degree-of-freedom metrology bar and then using the camera system as a ground truth measurement device for validation of the reproducible mobile manipulator's experiments and test method. Static performance measurement of a mobile manipulator using the RMMA has proved useful for relatively high tolerance pose estimation and other metrics that support standard test method development for indexed and dynamic mobile manipulator applications.

  11. The mobile Sousy-Doppler radar: Technical design and first results

    NASA Technical Reports Server (NTRS)

    Czechowsky, P.; Schmidt, G.; Ruster, R.

    1983-01-01

    A mobile VHF Doppler system was developed. The electronic part is installed in a 20 ft container and tested using a special log periodic aerial to illuminate the 300 m dish. The system was extended by designing a mobile phased antenna array with finally 576 Yagi elements. The grouping of the single Yagis, the system of transmission lines, the phase shifters, the power splitters and the T/R switch are described. Results from the first two campaigns and a survey of future programs demonstrating the flexibility of this mobile system are summarized.

  12. Determination of endocrine disrupting compounds using temperature-dependent inclusion chromatography: I. Optimization of separation protocol.

    PubMed

    Zarzycki, Paweł K; Włodarczyk, Elzbieta; Baran, Michał J

    2009-10-30

    In the present work we optimised the separation of battery of key UV non-transparent low-molecular-mass compounds having possible endocrine disrupting compounds (EDCs) activity or which may be used as the endocrine effect biomarkers. Simple optimization strategy was based on strong temperature effect that is driven by electrostatic interactions between macrocyclic mobile phase additives like cyclodextrins and eluted components of interest under C18 stationary phase and acetonitrile/water mobile phase conditions. Particularly, the effect of temperature involving native beta-cyclodextrin and its hydroxypropyl derivative to improve separation of number of natural (d-equilenin, equilin, estetrol, estriol, estrone, 17beta-estradiol, 17alpha-hydroxyprogesterone, 20alpha-hydroxyprogesterone, cortisol, cortisone, progesterone, testosterone, tetrahydrocortisol and tetrahydrocortisone) and artificial steroids (ethynylestradiol, norgestrel isomers, medroxyprogesterone, mestranol, methyltestosterone, norethindrone, 17alpha-estradiol) as well as non-steroidal compounds (diethylstilbesterol, bisphenol A, 4-tert-butylphenol, dimethyl phthalate, dibutyl phthalate and dioctyl phthalate) was investigated. It has been found that successful isocratic separation of 27 chemicals can be achieved using acetonitrile/water eluents modified with beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin at concentration of 10 mM and temperature of 47 degrees C. Separation protocol is simple, reliable, direct and non-radioactive and may be easily adapted for rapid separation and quantification of wide range of given steroids and related EDCs in environmental samples, particularly those that are characterised by unstable biological matrix and components of interest load. PMID:19362314

  13. iFringe: a fringe analysis application for mobile smart devices

    NASA Astrophysics Data System (ADS)

    Chan, Jacob; Teo, Josias Y. S.; Qian, Kemao

    2015-03-01

    This paper introduces iFringe, a mobile application that attempts to incorporate the resource heavy fringe analysis algorithms into the smart mobile devices platform. This first step taken towards mobility in the optical processing field aims to become a catalyst for modernization of various aspects of the field as well as to diversify developments to other applications. Predominantly, the motivation of this work stems from the vastly indifferent human interactive method of mobile devices, which enable images displayed on its touch screen to be manipulated in ways that could enhance the fringe analysis experience. Furthermore, given its hardware compatibility to the conventional fringe projection system, these mobile devices could potentially serve as a much more compact replacement. However, one imperative weakness that mobile devices pose is its limited computing ability. Therefore, to examine the feasibility of incorporating the fringe analysis algorithms into a mobile platform, we have implemented two fundamental fringe analysis techniques, namely the Fourier transform fringe analysis method and the phase-shifting technique. Formulas and processing procedures such as discrete Fourier transform (DFT) and quality-guided phase unwrapping, were included in accordance to their original algorithms to test their performance and usability on a smart mobile device. Details of the implementation and the performance results will also be presented in this paper to demonstrate the practicality of these algorithms on the smart mobile device platform.

  14. Mobile evaporator corrosion test results

    SciTech Connect

    Rozeveld, A.; Chamberlain, D.B.

    1997-05-01

    Laboratory corrosion tests were conducted on eight candidates to select a durable and cost-effective alloy for use in mobile evaporators to process radioactive waste solutions. Based on an extensive literature survey of corrosion data, three stainless steel alloys (304L, 316L, AL-6XN), four nickel-based alloys (825, 625, 690, G-30), and titanium were selected for testing. The corrosion tests included vapor phase, liquid junction (interface), liquid immersion, and crevice corrosion tests on plain and welded samples of candidate materials. Tests were conducted at 80{degrees}C for 45 days in two different test solutions: a nitric acid solution. to simulate evaporator conditions during the processing of the cesium ion-exchange eluant and a highly alkaline sodium hydroxide solution to simulate the composition of Tank 241-AW-101 during evaporation. All of the alloys exhibited excellent corrosion resistance in the alkaline test solution. Corrosion rates were very low and localized corrosion was not observed. Results from the nitric acid tests showed that only 316L stainless steel did not meet our performance criteria. The 316L welded interface and crevice specimens had rates of 22.2 mpy and 21.8 mpy, respectively, which exceeds the maximum corrosion rate of 20 mpy. The other welded samples had about the same corrosion resistance as the plain samples. None of the welded samples showed preferential weld or heat-affected zone (HAZ) attack. Vapor corrosion was negligible for all alloys. All of the alloys except 316L exhibited either {open_quotes}satisfactory{close_quotes} (2-20 mpy) or {open_quotes}excellent{close_quotes} (<2 mpy) corrosion resistance as defined by National Association of Corrosion Engineers. However, many of the alloys experienced intergranular corrosion in the nitric acid test solution, which could indicate a susceptibility to stress corrosion cracking (SCC) in this environment.

  15. Simultaneous determination of six resorcylic acid lactones in feed using liquid chromatography-tandem mass spectrometry and multi-walled carbon nanotubes as a dispersive solid phase extraction sorbent.

    PubMed

    Ying, Yong-Fei; Wu, Yin-Liang; Wen, Yi; Yang, Ting; Xu, Xiu-Qin; Wang, Yi-Zhen

    2013-09-13

    A simple and cost-effective pre-treatment procedure was developed for six resorcylic acid lactones (RALs) in feed using dispersive solid phase extraction (dSPE) with multi-walled carbon nanotubes (MWCNTs). The sample was analysed after purification by ultra-high performance liquid chromatography-negative electrospray ionisation tandem mass spectrometry (UHPLC-ESI-MS/MS). After extraction with acetonitrile/water (80:20, v/v) and dilution with water, a dSPE procedure was carried out with MWCNTs. The pH value of the extract, the extraction time for MWCNTs, the type and amount of MWCNTs and the type of eluent were optimised to increase the sample throughput and the sensitivity. The samples were quantified using the internal standard zearalenone-D6. The absolute recoveries of the target compounds from feed samples were most efficient when using 100mg of MWCNTs with an outer diameter of less than 8nm and a length of 10-30μm, and ethyl acetate was shown to be the most suitable solvent for desorbing the target compounds from the MWCNTs. The mean recoveries from fortified swine mixed feed samples ranged from 95.3% to 107.2% and had relative standard deviations lower than 10%; the limits of detection and quantification for RALs were in the ranges of 0.20-0.29μg/kg and 0.54-0.78μg/kg, respectively.

  16. Determination of cadmium, zinc, nickel and cobalt in tobacco by reversed-phase high-performance liquid chromatography with 2-(8-quinolylazo)-4,5-diphenylimidazole as a chelating reagent.

    PubMed

    Zhang, Chengjie; Miura, Jun'ichiro; Nagaosa, Yukio

    2005-09-01

    A sensitive and selective method has been developed for the simultaneous determination of cadmium, zinc, nickel and cobalt. The method is based on the chelation of metal ions with 2-(8-quinolylazo)-4,5-diphenylimidazole (QAI) and the subsequent reversed-phase (RP) high-performance liquid chromatographic separation and spectrophotometric detection of the metal chelates. The chelates were separated on an RP column with acetonitrile-water containing ethylenediamine tetraacetic acid and sodium acetate (pH 7.5). Though Zn(II) and Cd(II) chelates with azo compounds were generally labile in the RP column, these chelates with QAI were successfully detected. When analyses were carried out at 575 nm and at 0.001 absorbance unit full scale, the peak height calibration curves were linear up to 2.0 ng for Cd(II), 2.4 ng for Zn(II), 0.14 ng for Ni(II) and 0.72 ng for Co(II) in 100-microL injections, respectively; the detection limits (3sigma, three times of the standard deviation for the blank signal) for Cd(II), Zn(II), Ni(II) and Co(II) were 4.8, 24, 2.4 and 7.2 pg in 100 microL of injected solution, respectively. The proposed method was successfully applied to the analysis of tobacco without any preliminary concentration or separation.

  17. Ubiquitous Mobility with Mobile Phones: A Cultural Ecology for Mobile Learning

    ERIC Educational Resources Information Center

    Cook, John; Pachler, Norbert; Bachmair, Ben

    2011-01-01

    This article argues that mobile phones should be viewed as new cultural resources that operate within an individualized, mobile and convergent mass communication; such a recognition facilitates the options for a cultural ecology. A particular challenge here is to find adequate curricular functions in school where the inclusion of these new…

  18. Vehicle antenna for the mobile satellite experiment

    NASA Technical Reports Server (NTRS)

    Peng, Sheng Y.; Chung, H. H.; Leggiere, D.; Foy, W.; Schaffner, G.; Nelson, J.; Pagels, W.; Vayner, M.; Faller, H. L.; Messer, L.

    1988-01-01

    A low profile, low cost, printed circuit, electronically steered, right hand circularly polarized phase array antenna system has been developed for the Mobile Satellite Experiment (MSAT-X) Program. The success of this antenna is based upon the development of a crossed-slot element array and detailed trade-off analyses for both the phased array and pointing system design. The optimized system provides higher gain at low elevation angles (20 degrees above the horizon) and broader frequency coverage (approximately 8 1/2 percent bandwidth) than is possible with a patch array. Detailed analysis showed that optimum performance could be achieved with a 19 element array of a triangular lattice geometry of 3.9 inch element spacing. This configuration has the effect of minimizing grating lobes at large scan angles plus it improves the intersatellite isolation. The array has an aperture 20 inches in diameter and is 0.75 inch thick overall, exclusive of the RF and power connector. The pointing system employs a hybrid approach that operates with both an external rate sensor and an internal error signal as a means of fine tuning the beam acquisition and track. Steering the beam is done electronically via 18, 3-bit diode phase shifters. A nineteenth phase shifter is not required as the center element serves as a reference only. Measured patterns and gain show that the array meets the stipulated performance specifications everywhere except at some low elevation angles.

  19. Mobilization of intensive care patients: a multidisciplinary practical guide for clinicians

    PubMed Central

    Green, Margot; Marzano, Vince; Leditschke, I Anne; Mitchell, Imogen; Bissett, Bernie

    2016-01-01

    Objectives To describe our experience and the practical tools we have developed to facilitate early mobilization in the intensive care unit (ICU) as a multidisciplinary team. Background Despite the evidence supporting early mobilization for improving outcomes for ICU patients, recent international point-prevalence studies reveal that few patients are mobilized in the ICU. Existing guidelines rarely address the practical issues faced by multidisciplinary ICU teams attempting to translate evidence into practice. We present a comprehensive strategy for safe mobilization utilized in our ICU, incorporating the combined skills of medical, nursing, and physiotherapy staff to achieve safe outcomes and establish a culture which prioritizes this intervention. Methods A raft of tools and strategies are described to facilitate mobilization in ICU by the multidisciplinary team. Patients without safe unsupported sitting balance and without ≥3/5 (Oxford scale) strength in the lower limbs commence phase 1 mobilization, including training of sitting balance and use of the tilt table. Phase 2 mobilization involves supported or active weight-bearing, incorporating gait harnesses if necessary. The Plan B mnemonic guides safe multidisciplinary mobilization of invasively ventilated patients and emphasizes the importance of a clearly articulated plan in delivering this valuable treatment as a team. Discussion These tools have been used over the past 5 years in a tertiary ICU with a very low incidence of adverse outcomes (<2%). The tools and strategies described are useful not only to guide practical implementation of early mobilization, but also in the creation of a unit culture where ICU staff prioritize early mobilization and collaborate daily to provide the best possible care. Conclusion These practical tools allow ICU clinicians to safely and effectively implement early mobilization in critically ill patients. A genuinely multidisciplinary approach to safe mobilization in ICU is

  20. The mobile satellite system of Telesat Mobile Inc

    NASA Astrophysics Data System (ADS)

    Bertenyi, E.; Rahman, F.

    1992-08-01

    Telesat Mobile Inc. (TMI), the Canadian mobile satellite operator, is planning to introduce full two-way mobile voice and data communications services in 1994, using its large geostationary MSAT spacecraft which is currently under construction. MSAT will provide TMI with the capability to enable its customers, even in the most remote parts of the continent, to communicate from their mobile or transportable terminals with any other point within North America, and indeed with the whole world. This paper outlines TMI's currently planned MSAT services and the main features of the overall system. A brief summary of the space and ground segments is presented, and the key performance parameters and configuration of the MSAT spacecraft are reviewed.