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Sample records for stationary phase metabolism

  1. Study of Stationary Phase Metabolism Via Isotopomer Analysis of Amino Acids from an Isolated Protein

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, AfshanS.; Tang, YinjieJ.; Mukhopadhyay, Aindrila; Martin, Hector Garcia; Gin, Jennifer; Benke, Peter; Keasling, Jay D.

    2009-09-14

    Microbial production of many commercially important secondary metabolites occurs during stationary phase, and methods to measure metabolic flux during this growth phase would be valuable. Metabolic flux analysis is often based on isotopomer information from proteinogenic amino acids. As such, flux analysis primarily reflects the metabolism pertinent to the growth phase during which most proteins are synthesized. To investigate central metabolism and amino acids synthesis activity during stationary phase, addition of fully 13C-labeled glucose followed by induction of green fluorescent protein (GFP) expression during stationary phase was used. Our results indicate that Escherichia coli was able to produce new proteins (i.e., GFP) in the stationary phase, and the amino acids in GFP were mostly from degraded proteins synthesized during the exponential growth phase. Among amino acid biosynthetic pathways, only those for serine, alanine, glutamate/glutamine, and aspartate/asparagine had significant activity during the stationary phase.

  2. Enhanced dipicolinic acid production during the stationary phase in Bacillus subtilis by blocking acetoin synthesis.

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    Toya, Yoshihiro; Hirasawa, Takashi; Ishikawa, Shu; Chumsakul, Onuma; Morimoto, Takuya; Liu, Shenghao; Masuda, Kenta; Kageyama, Yasushi; Ozaki, Katsuya; Ogasawara, Naotake; Shimizu, Hiroshi

    2015-01-01

    Bacterial bio-production during the stationary phase is expected to lead to a high target yield because the cells do not consume the substrate for growth. Bacillus subtilis is widely used for bio-production, but little is known about the metabolism during the stationary phase. In this study, we focused on the dipicolinic acid (DPA) production by B. subtilis and investigated the metabolism. We found that DPA production competes with acetoin synthesis and that acetoin synthesis genes (alsSD) deletion increases DPA productivity by 1.4-fold. The mutant showed interesting features where the glucose uptake was inhibited, whereas the cell density increased by approximately 50%, resulting in similar volumetric glucose consumption to that of the parental strain. The metabolic profiles revealed accumulation of pyruvate, acetyl-CoA, and the TCA cycle intermediates in the alsSD mutant. Our results indicate that alsSD-deleted B. subtilis has potential as an effective host for stationary-phase production of compounds synthesized from these intermediates.

  3. Temporal transcriptomic analysis of Desulfovibrio vulgaris Hildenborough transition into stationary phase growth during electrondonor depletion

    Energy Technology Data Exchange (ETDEWEB)

    Clark, M.E.; He, Q.; He, Z.; Huang, K.H.; Alm, E.J.; Wan, X.-F.; Hazen, T.C.; Arkin, A.P.; Wall, J.D.; Zhou, J.-Z.; Fields, M.W.

    2006-08-01

    Desulfovibrio vulgaris was cultivated in a defined medium, and biomass was sampled for approximately 70 h to characterize the shifts in gene expression as cells transitioned from the exponential to the stationary phase during electron donor depletion. In addition to temporal transcriptomics, total protein, carbohydrate, lactate, acetate, and sulfate levels were measured. The microarray data were examined for statistically significant expression changes, hierarchical cluster analysis, and promoter element prediction and were validated by quantitative PCR. As the cells transitioned from the exponential phase to the stationary phase, a majority of the down-expressed genes were involved in translation and transcription, and this trend continued at the remaining times. There were general increases in relative expression for intracellular trafficking and secretion, ion transport, and coenzyme metabolism as the cells entered the stationary phase. As expected, the DNA replication machinery was down-expressed, and the expression of genes involved in DNA repair increased during the stationary phase. Genes involved in amino acid acquisition, carbohydrate metabolism, energy production, and cell envelope biogenesis did not exhibit uniform transcriptional responses. Interestingly, most phage-related genes were up-expressed at the onset of the stationary phase. This result suggested that nutrient depletion may affect community dynamics and DNA transfer mechanisms of sulfate-reducing bacteria via the phage cycle. The putative feoAB system (in addition to other presumptive iron metabolism genes) was significantly up-expressed, and this suggested the possible importance of Fe{sup 2+} acquisition under metal-reducing conditions. The expression of a large subset of carbohydrate-related genes was altered, and the total cellular carbohydrate levels declined during the growth phase transition. Interestingly, the D. vulgaris genome does not contain a putative rpoS gene, a common attribute

  4. Non-stationary (13)C-metabolic flux ratio analysis.

    Science.gov (United States)

    Hörl, Manuel; Schnidder, Julian; Sauer, Uwe; Zamboni, Nicola

    2013-12-01

    (13)C-metabolic flux analysis ((13)C-MFA) has become a key method for metabolic engineering and systems biology. In the most common methodology, fluxes are calculated by global isotopomer balancing and iterative fitting to stationary (13)C-labeling data. This approach requires a closed carbon balance, long-lasting metabolic steady state, and the detection of (13)C-patterns in a large number of metabolites. These restrictions mostly reduced the application of (13)C-MFA to the central carbon metabolism of well-studied model organisms grown in minimal media with a single carbon source. Here we introduce non-stationary (13)C-metabolic flux ratio analysis as a novel method for (13)C-MFA to allow estimating local, relative fluxes from ultra-short (13)C-labeling experiments and without the need for global isotopomer balancing. The approach relies on the acquisition of non-stationary (13)C-labeling data exclusively for metabolites in the proximity of a node of converging fluxes and a local parameter estimation with a system of ordinary differential equations. We developed a generalized workflow that takes into account reaction types and the availability of mass spectrometric data on molecular ions or fragments for data processing, modeling, parameter and error estimation. We demonstrated the approach by analyzing three key nodes of converging fluxes in central metabolism of Bacillus subtilis. We obtained flux estimates that are in agreement with published results obtained from steady state experiments, but reduced the duration of the necessary (13)C-labeling experiment to less than a minute. These results show that our strategy enables to formally estimate relative pathway fluxes on extremely short time scale, neglecting cellular carbon balancing. Hence this approach paves the road to targeted (13)C-MFA in dynamic systems with multiple carbon sources and towards rich media. © 2013 Wiley Periodicals, Inc.

  5. Effect of benzalkonium chloride on viability and energy metabolism in exponential- and stationary-growth-phase cells of Listeria monocytogenes.

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    Luppens, S B; Abee, T; Oosterom, J

    2001-04-01

    The difference in killing exponential- and stationary-phase cells of Listeria monocytogenes by benzalkonium chloride (BAC) was investigated by plate counting and linked to relevant bioenergetic parameters. At a low concentration of BAC (8 mg liter(-1)), a similar reduction in viable cell numbers was observed for stationary-phase cells and exponential-phase cells (an approximately 0.22-log unit reduction), although their membrane potential and pH gradient were dissipated. However, at higher concentrations of BAC, exponential-phase cells were more susceptible than stationary-phase cells. At 25 mg liter(-1), the difference in survival on plates was more than 3 log units. For both types of cells, killing, i.e., more than 1-log unit reduction in survival on plates, coincided with complete inhibition of acidification and respiration and total depletion of ATP pools. Killing efficiency was not influenced by the presence of glucose, brain heart infusion medium, or oxygen. Our results suggest that growth phase is one of the major factors that determine the susceptibility of L. monocytogenes to BAC.

  6. Modelling of Hydrophilic Interaction Liquid Chromatography Stationary Phases Using Chemometric Approaches

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    Ortiz-Villanueva, Elena; Tauler, Romà

    2017-01-01

    Metabolomics is a powerful and widely used approach that aims to screen endogenous small molecules (metabolites) of different families present in biological samples. The large variety of compounds to be determined and their wide diversity of physical and chemical properties have promoted the development of different types of hydrophilic interaction liquid chromatography (HILIC) stationary phases. However, the selection of the most suitable HILIC stationary phase is not straightforward. In this work, four different HILIC stationary phases have been compared to evaluate their potential application for the analysis of a complex mixture of metabolites, a situation similar to that found in non-targeted metabolomics studies. The obtained chromatographic data were analyzed by different chemometric methods to explore the behavior of the considered stationary phases. ANOVA-simultaneous component analysis (ASCA), principal component analysis (PCA) and partial least squares regression (PLS) were used to explore the experimental factors affecting the stationary phase performance, the main similarities and differences among chromatographic conditions used (stationary phase and pH) and the molecular descriptors most useful to understand the behavior of each stationary phase. PMID:29064436

  7. Sinorhizobium meliloti sigma factors RpoE1 and RpoE4 are activated in stationary phase in response to sulfite.

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    Bénédicte Bastiat

    Full Text Available Rhizobia are soil bacteria able to establish a nitrogen-fixing symbiosis with legume plants. Both in soil and in planta, rhizobia spend non-growing periods resembling the stationary phase of in vitro-cultured bacteria. The primary objective of this work was to better characterize gene regulation in this biologically relevant growth stage in Sinorhizobium meliloti. By a tap-tag/mass spectrometry approach, we identified five sigma factors co-purifying with the RNA polymerase in stationary phase: the general stress response regulator RpoE2, the heat shock sigma factor RpoH2, and three extra-cytoplasmic function sigma factors (RpoE1, RpoE3 and RpoE4 belonging to the poorly characterized ECF26 subgroup. We then showed that RpoE1 and RpoE4 i are activated upon metabolism of sulfite-generating compounds (thiosulfate and taurine, ii display overlapping regulatory activities, iii govern a dedicated sulfite response by controlling expression of the sulfite dehydrogenase SorT, iv are activated in stationary phase, likely as a result of endogenous sulfite generation during bacterial growth. We showed that SorT is required for optimal growth of S. meliloti in the presence of sulfite, suggesting that the response governed by RpoE1 and RpoE4 may be advantageous for bacteria in stationary phase either by providing a sulfite detoxification function or by contributing to energy production through sulfite respiration. This paper therefore reports the first characterization of ECF26 sigma factors, the first description of sigma factors involved in control of sulphur metabolism, and the first indication that endogenous sulfite may act as a signal for regulation of gene expression upon entry of bacteria in stationary phase.

  8. The Proteome and Lipidome of Thermococcus kodakarensis across the Stationary Phase

    OpenAIRE

    Gagen, Emma J.; Yoshinaga, Marcos Y.; Garcia Prado, Franka; Hinrichs, Kai-Uwe; Thomm, Michael

    2016-01-01

    The majority of cells in nature probably exist in a stationary-phase-like state, due to nutrient limitation in most environments. Studies on bacteria and yeast reveal morphological and physiological changes throughout the stationary phase, which lead to an increased ability to survive prolonged nutrient limitation. However, there is little information on archaeal stationary phase responses. We investigated protein- and lipid-level changes in Thermococcus kodakarensis with extended time in the...

  9. A comparison of the radiosensitivity of stationary, exponential and G1 phase wild type and repair deficient yeast cultures: supporting evidence for stationary phase yeast cells being in G0

    International Nuclear Information System (INIS)

    Tippins, R.S.; Parry, J.M.

    1982-01-01

    The main points to emerge from this comparison of the radiosensitivity of stationary, exponential and G 1 phase yeast cultures were: (1) In wild type yeast cultures, G 1 cells were the most sensitive to the lethal effects of X-rays, exponential phase cells were the most resistant and stationary phase cells were intermediate in sensitivity. (2) With the excision-repair-defective strain D61-3 (rad 3) stationary phase cells were more resistant than exponential cells with G 1 cells again being most sensitive. (3) The rad 50 gene present in JD50 had a marked effect on the X-ray inactivation response of this strain. In the presence of the defective rad 50 allele, exponential phase cells were as sensitive as G 1 phase cells, with stationary phase cells being more resistant than either. (4) There were marked differences in sensitivity between stationary phase and G 1 phase cells. These differences, along with other physiological differences reported by other workers, lead the authors to suggest that stationary phase cells can be better described as being in G 0 phase, i.e. a stage which is outside the normal mitotic cell cycle of an exponential culture. (author)

  10. Selectivity of some basic solutes on a poly(methyltetradecylsiloxane)-silica stationary phase.

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    Borges, Endler M; Collins, Carol H

    2011-11-01

    Complex analyses of polar compounds, especially basic ones, require more selective stationary phases. The present paper describes a stationary phase prepared by thermal immobilization of poly(methyltetradecylsiloxane) onto chromatographic silica (PMTDS-SiO(2)). This stationary phase presents hydrophobic and ion-exchange interactions that confer both high retention and unique selectivities for basic solutes. The influence of ion-exchange interactions is confirmed by the increase in retention factors of basic solutes when the mobile-phase pH changes from acidic to neutral and by the decrease in retention factors when the mobile-phase pH changes from neutral to alkaline. The ion-exchange properties of the stationary phase are enriched in neutral mobile phase (pH 7-7.5) using soft Lewis bases such as tricine and tris as buffers but are suppressed in both acidic (pH 2.5-6) and highly alkaline mobile phases (pH≤10). Increasing both temperature and flow rate permits more rapid separations while maintaining the selectivity. The stability of the stationary phase is evaluated with acid, neutral and alkaline mobile phases. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Enantioselective potential of polysaccharide-based chiral stationary phases in supercritical fluid chromatography.

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    Kucerova, Gabriela; Kalikova, Kveta; Tesarova, Eva

    2017-06-01

    The enantioselective potential of two polysaccharide-based chiral stationary phases for analysis of chiral structurally diverse biologically active compounds was evaluated in supercritical fluid chromatography using a set of 52 analytes. The chiral selectors immobilized on 2.5 μm silica particles were tris-(3,5-dimethylphenylcarmabate) derivatives of cellulose or amylose. The influence of the polysaccharide backbone, different organic modifiers, and different mobile phase additives on retention and enantioseparation was monitored. Conditions for fast baseline enantioseparation were found for the majority of the compounds. The success rate of baseline and partial enantioseparation with cellulose-based chiral stationary phase was 51.9% and 15.4%, respectively. Using amylose-based chiral stationary phase we obtained 76.9% of baseline enantioseparations and 9.6% of partial enantioseparations of the tested compounds. The best results on cellulose-based chiral stationary phase were achieved particularly with propane-2-ol and a mixture of isopropylamine and trifluoroacetic acid as organic modifier and additive to CO 2 , respectively. Methanol and basic additive isopropylamine were preferred on amylose-based chiral stationary phase. The complementary enantioselectivity of the cellulose- and amylose-based chiral stationary phases allows separation of the majority of the tested structurally different compounds. Separation systems were found to be directly applicable for analyses of biologically active compounds of interest. © 2017 Wiley Periodicals, Inc.

  12. Evaluation of ODS-AQ stationary phase for use in capillary electrochromatography.

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    Djordjevic, N M; Fitzpatrick, F; Houdiere, F

    2001-04-01

    The aim of this study was to evaluate the applicability of ODS-AQ packing material as a stationary phase in capillary electrochromatography (CEC). The electroosmotic flow created on an ODS-AQ stationary phase was measured at different mobile phase compositions and at different column temperatures. It was observed that the electroosmotic flow generated in the column increased by 50% when the temperature of the system was raised from 20 degrees C to 60 degrees C, while all other conditions were kept constant. The electroosmotic flow produced by the ODS-AQ stationary phase was found to be comparable to the flow generated in a column packed with Nucleosil bare-silica material. In addition, a set of polar compounds (D-lysergic acid diethylamide derivatives) was utilized to determine the influence of temperature and mobile phase composition on their chromatographic behavior on an ODS-AQ stationary phase in a CEC mode. A linear relationship between the solute retention factor and column temperatures was seen over the temperature range studied (20 degrees C to 60 degrees C). A quadratic function was used to describe the changes in the solute retention factors with variation of acetonitrile concentration in the mobile phase.

  13. The Proteome and Lipidome of Thermococcus kodakarensis across the Stationary Phase.

    Science.gov (United States)

    Gagen, Emma J; Yoshinaga, Marcos Y; Garcia Prado, Franka; Hinrichs, Kai-Uwe; Thomm, Michael

    2016-01-01

    The majority of cells in nature probably exist in a stationary-phase-like state, due to nutrient limitation in most environments. Studies on bacteria and yeast reveal morphological and physiological changes throughout the stationary phase, which lead to an increased ability to survive prolonged nutrient limitation. However, there is little information on archaeal stationary phase responses. We investigated protein- and lipid-level changes in Thermococcus kodakarensis with extended time in the stationary phase. Adaptations to time in stationary phase included increased proportion of membrane lipids with a tetraether backbone, synthesis of proteins that ensure translational fidelity, specific regulation of ABC transporters (upregulation of some, downregulation of others), and upregulation of proteins involved in coenzyme production. Given that the biological mechanism of tetraether synthesis is unknown, we also considered whether any of the protein-level changes in T. kodakarensis might shed light on the production of tetraether lipids across the same period. A putative carbon-nitrogen hydrolase, a TldE (a protease in Escherichia coli) homologue, and a membrane bound hydrogenase complex subunit were candidates for possible involvement in tetraether-related reactions, while upregulation of adenosylcobalamin synthesis proteins might lend support to a possible radical mechanism as a trigger for tetraether synthesis.

  14. The Proteome and Lipidome of Thermococcus kodakarensis across the Stationary Phase

    Directory of Open Access Journals (Sweden)

    Emma J. Gagen

    2016-01-01

    Full Text Available The majority of cells in nature probably exist in a stationary-phase-like state, due to nutrient limitation in most environments. Studies on bacteria and yeast reveal morphological and physiological changes throughout the stationary phase, which lead to an increased ability to survive prolonged nutrient limitation. However, there is little information on archaeal stationary phase responses. We investigated protein- and lipid-level changes in Thermococcus kodakarensis with extended time in the stationary phase. Adaptations to time in stationary phase included increased proportion of membrane lipids with a tetraether backbone, synthesis of proteins that ensure translational fidelity, specific regulation of ABC transporters (upregulation of some, downregulation of others, and upregulation of proteins involved in coenzyme production. Given that the biological mechanism of tetraether synthesis is unknown, we also considered whether any of the protein-level changes in T. kodakarensis might shed light on the production of tetraether lipids across the same period. A putative carbon-nitrogen hydrolase, a TldE (a protease in Escherichia coli homologue, and a membrane bound hydrogenase complex subunit were candidates for possible involvement in tetraether-related reactions, while upregulation of adenosylcobalamin synthesis proteins might lend support to a possible radical mechanism as a trigger for tetraether synthesis.

  15. Recent development of ionic liquid stationary phases for liquid chromatography.

    Science.gov (United States)

    Shi, Xianzhe; Qiao, Lizhen; Xu, Guowang

    2015-11-13

    Based on their particular physicochemical characteristics, ionic liquids have been widely applied in many fields of analytical chemistry. Many types of ionic liquids were immobilized on a support like silica or monolith as stationary phases for liquid chromatography. Moreover, different approaches were developed to bond covalently ionic liquids onto the supporting materials. The obtained ionic liquid stationary phases show multi-mode mechanism including hydrophobic, hydrophilic, hydrogen bond, anion exchange, π-π, and dipole-dipole interactions. Therefore, they could be used in different chromatographic modes including ion-exchange, RPLC, NPLC and HILIC to separate various classes of compounds. This review mainly summarizes the immobilized patterns and types of ionic liquid stationary phases, their retention mechanisms and applications in the recent five years. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Retention of Halogenated Solutes on Stationary Phases Containing Heavy Atoms

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    Toshio Miwa

    2013-05-01

    Full Text Available To examine the effects of weak intermolecular interactions on solid-phase extraction (SPE and chromatographic separation, we synthesized some novel stationary phases with a heavy atom effect layer by immobilizing halogenated aromatic rings and hydroxyl groups onto the surface of a hydrophilic base polymer. Using SPE cartridges packed with the functionalized materials, we found that the heavy atom stationary phases could selectively retain halophenols in organic solvents, such as 1-propanol which blocks the hydrogen bonding, or acetonitrile which blocks the p-p interaction. The extraction efficiency of the materials toward the halophenols depended on the dipole moments of phenoxy groups present as functional groups. On the other hand, the extraction efficiency of solutes toward the functional group depended on their molar refractions, i.e., induced dipole moments. The retention of the solutes to the stationary phase ultimately depended on not only strong intermolecular interactions, but also the effects of weak interactions such as the dispersion force.

  17. Evaluation of hydrophilic interaction liquid chromatography stationary phases for analysis of opium alkaloids.

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    Bagheri, Mohsen; Taheri, Mohammadreza; Farhadpour, Mohsen; Rezadoost, Hassan; Ghassempour, Alireza; Aboul-Enein, Hassan Y

    2017-08-18

    The separation of a mixture containing five major opium alkaloids, namely morphine, codeine, thebaine, noscapine and papaverine has been investigated in hydrophilic interaction liquid chromatography (HILIC) mode using five different stationary phases: bare silica, zwitterion, aminopropyl, diol and cyanopropyl. In order to propose the appropriate column for separation and purification, retention behaviors of the five natural opioids have been studied on mentioned HILIC stationary phases. The mechanism of separation in diverse HILIC media, based on the formation of water-rich layer on surface of the HILIC stationary phases and the physicochemical properties of opium alkaloids, such as pKa (acidic pK) and the octanol-water distribution coefficient (log Do/w) are discussed. Chromatographic responses including modified limit of detection LOD m , signal to noise ratio (S/N) m , and defined modified R Sm have considered for suggestion of the suitable column for quantitative/qualitative and preparative purposes. According to the obtained results, diol stationary phase is best suited for analytical chromatography, whereas bare silica and zwitterionic stationary phases are appropriate for preparative applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Haemophilus ducreyi Hfq contributes to virulence gene regulation as cells enter stationary phase.

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    Gangaiah, Dharanesh; Labandeira-Rey, Maria; Zhang, Xinjun; Fortney, Kate R; Ellinger, Sheila; Zwickl, Beth; Baker, Beth; Liu, Yunlong; Janowicz, Diane M; Katz, Barry P; Brautigam, Chad A; Munson, Robert S; Hansen, Eric J; Spinola, Stanley M

    2014-02-11

    To adapt to stresses encountered in stationary phase, Gram-negative bacteria utilize the alternative sigma factor RpoS. However, some species lack RpoS; thus, it is unclear how stationary-phase adaptation is regulated in these organisms. Here we defined the growth-phase-dependent transcriptomes of Haemophilus ducreyi, which lacks an RpoS homolog. Compared to mid-log-phase organisms, cells harvested from the stationary phase upregulated genes encoding several virulence determinants and a homolog of hfq. Insertional inactivation of hfq altered the expression of ~16% of the H. ducreyi genes. Importantly, there were a significant overlap and an inverse correlation in the transcript levels of genes differentially expressed in the hfq inactivation mutant relative to its parent and the genes differentially expressed in stationary phase relative to mid-log phase in the parent. Inactivation of hfq downregulated genes in the flp-tad and lspB-lspA2 operons, which encode several virulence determinants. To comply with FDA guidelines for human inoculation experiments, an unmarked hfq deletion mutant was constructed and was fully attenuated for virulence in humans. Inactivation or deletion of hfq downregulated Flp1 and impaired the ability of H. ducreyi to form microcolonies, downregulated DsrA and rendered H. ducreyi serum susceptible, and downregulated LspB and LspA2, which allow H. ducreyi to resist phagocytosis. We propose that, in the absence of an RpoS homolog, Hfq serves as a major contributor of H. ducreyi stationary-phase and virulence gene regulation. The contribution of Hfq to stationary-phase gene regulation may have broad implications for other organisms that lack an RpoS homolog. Pathogenic bacteria encounter a wide range of stresses in their hosts, including nutrient limitation; the ability to sense and respond to such stresses is crucial for bacterial pathogens to successfully establish an infection. Gram-negative bacteria frequently utilize the alternative sigma

  19. Assessment of the chromatographic lipophilicity of eight cephalosporins on different stationary phases.

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    Dąbrowska, Monika; Starek, Małgorzata; Komsta, Łukasz; Szafrański, Przemysław; Stasiewicz-Urban, Anna; Opoka, Włodzimierz

    2017-04-01

    The retention behaviors were investigated for a series of eight cephalosporins in thin-layer chromatography (TLC) using stationary phases of RP-2, RP-8, RP-18, NH 2 , DIOL, and CN chemically bonded silica gel. Additionally, various binary mobile phases (water/methanol and water/acetone) were used in different volume proportions. The retention behavior of the analyzed molecules was defined by R M0 constant. In addition, reversed phase high performance liquid chromatography (RP-HPLC) was performed in lipophilicity studies by using immobilized artificial membrane (IAM) stationary phase. Obtained chromatographic data (R M0 and logk' IAM ) were correlated with the lipophilicity, expressed as values of the log calculated (logP calc ) and experimental (logP exp(shake-flask) ) partition coefficient. Principal component analysis (PCA) was applied in order to obtain an overview of similarity or dissimilarity among the analyzed compounds. Hierarchical cluster analysis (HCA) was performed to compare the separation characteristics of the applied stationary phases. This study was undertaken to identify the best chromatographic system and chromatographic data processing method to enable the prediction of logP values. A comprehensive chromatographic investigation into the retention of the analyzed cephalosporins revealed a similar behavior on RP-18, RP-8 and CN stationary phases. The weak correlations obtained between experimental and certain computed lipophilicity indices revealed that R M0 and PC1/RM are relevant lipophilicity parameters and the RP-8, CN and RP-18 plates are appropriate stationary phases for lipophilicity investigation, whereas computational approaches still cannot fully replace experimentation. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Ionic liquid stationary phases for gas chromatography.

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    Poole, Colin F; Poole, Salwa K

    2011-04-01

    This article provides a summary of the development of ionic liquids as stationary phases for gas chromatography beginning with early work on packed columns that established details of the retention mechanism and established working methods to characterize selectivity differences compared with molecular stationary phases through the modern development of multi-centered cation and cross-linked ionic liquids for high-temperature applications in capillary gas chromatography. Since there are many reviews on ionic liquids dealing with all aspects of their chemical and physical properties, the emphasis in this article is placed on the role of gas chromatography played in the design of ionic liquids of low melting point, high thermal stability, high viscosity, and variable selectivity for separations. Ionic liquids provide unprecedented opportunities for extending the selectivity range and temperature-operating range of columns for gas chromatography, an area of separation science that has otherwise been almost stagnant for over a decade. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Surface-bonded ionic liquid stationary phases in high-performance liquid chromatography--a review.

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    Pino, Verónica; Afonso, Ana M

    2012-02-10

    Ionic liquids (ILs) are a class of ionic, nonmolecular solvents which remain in liquid state at temperatures below 100°C. ILs possess a variety of properties including low to negligible vapor pressure, high thermal stability, miscibility with water or a variety of organic solvents, and variable viscosity. IL-modified silica as novel high-performance liquid chromatography (HPLC) stationary phases have attracted considerable attention for their differential behavior and low free-silanol activity. Indeed, around 21 surface-confined ionic liquids (SCIL) stationary phases have been developed in the last six years. Their chromatographic behavior has been studied, and, despite the presence of a positive charge on the stationary phase, they showed considerable promise for the separation of neutral solutes (not only basic analytes), when operated in reversed phase mode. This aspect points to the potential for truly multimodal stationary phases. This review attempts to summarize the state-of-the-art about SCIL phases including their preparation, chromatographic behavior, and analytical performance. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Evaluation of gamma radiation effects on stationary phases using gas chromatografy

    International Nuclear Information System (INIS)

    Basso, M.A.; Collins, K.E.; Collins, C.H.

    1988-01-01

    The overall objetive of this project is a thorough study of the effect of gamma radiation on supported stationary phases used in packed-column gas chromatography. The phases studied were SP-2100 on Supelcoport and SE-30 on Chromsorb W. The fases were irradiated with cobalt-60 gamma rays to various doses and subsequently subjected to tests of extractability, termal stability and efficiency as a chromatographic column packing. Extraction tests indicate that low doses of radiation are sufficient to produce significant immobilization of these polymethylsilicones; that is, to produce chemical bonds between different polymer chains or between the stationary phase and the support. Thermal stability is also increased. The values calculated for the number of theoretical plates (n) and resolution (Rsub (s)) after analysis of four synthetic mixtures of organic compounds also increase, in most cases, indicating that the gamma irradiation has positively altered the behavior of these stationary phases. (author) [pt

  3. Effect of benzalkonium chloride on viability and energy metabolism in exponential- and stationary-growth-phase cells of Listeria monocytogenes

    NARCIS (Netherlands)

    Luppens, S.B.I.; Abee, T.; Oosterom, J.

    2001-01-01

    The difference in killing exponential- and stationary-phase cells of Listeria monocytogenes by benzalkonium chloride (BAC) was investigated by plate counting and linked to relevant bioenergetic parameters. At a low concentration of BAC (8 mg liter-1), a similar reduction in viable cell numbers was

  4. Evaluation of an amide-based stationary phase for supercritical fluid chromatography

    Science.gov (United States)

    Borges-Muñoz, Amaris C.; Colón, Luis A.

    2017-01-01

    A relatively new stationary phase containing a polar group embedded in a hydrophobic backbone (i.e., ACE® C18-amide) was evaluated for use in supercritical fluid chromatography. The amide-based column was compared with columns packed with bare silica, C18 silica, and a terminal-amide silica phase. The system was held at supercritical pressure and temperature with a mobile phase composition of CO2 and methanol as cosolvent. The linear solvation energy relationship model was used to evaluate the behavior of these stationary phases, relating the retention factor of selected probes to specific chromatographic interactions. A five-component test mixture, consisting of a group of drug-like molecules was separated isocratically. The results show that the C18-amide stationary phase provided a combination of interactions contributing to the retention of the probe compounds. The hydrophobic interactions are favorable; however, the electron donating ability of the embedded amide group shows a large positive interaction. Under the chromatographic conditions used, the C18-amide column was able to provide baseline resolution of all the drug-like probe compounds in a text mixture, while the other columns tested did not. PMID:27396487

  5. Hierarchical CaCO3 chromatography: a stationary phase based on biominerals.

    Science.gov (United States)

    Sato, Kosuke; Oaki, Yuya; Takahashi, Daisuke; Toshima, Kazunobu; Imai, Hiroaki

    2015-03-23

    In biomineralization, acidic macromolecules play important roles for the growth control of crystals through a specific interaction. Inspired by this interaction, we report on an application of the hierarchical structures in CaCO3 biominerals to a stationary phase of chromatography. The separation and purification of acidic small organic molecules are achieved by thin-layer chromatography and flash chromatography using the powder of biominerals as the stationary phase. The unit nanocrystals and their oriented assembly, the hierarchical structure, are suitable for the adsorption site of the target organic molecules and the flow path of the elution solvents, respectively. The separation mode is ascribed to the specific adsorption of the acidic molecules on the crystal face and the coordination of the functional groups to the calcium ions. The results imply that a new family of stationary phase of chromatography can be developed by the fine tuning of hierarchical structures in CaCO3 materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Versatile ligands for high-performance liquid chromatography: An overview of ionic liquid-functionalized stationary phases.

    Science.gov (United States)

    Zhang, Mingliang; Mallik, Abul K; Takafuji, Makoto; Ihara, Hirotaka; Qiu, Hongdeng

    2015-08-05

    Ionic liquids (ILs), a class of unique substances composed purely by cation and anions, are renowned for their fascinating physical and chemical properties, such as negligible volatility, high dissolution power, high thermal stability, tunable structure and miscibility. They are enjoying ever-growing applications in a great diversity of disciplines. IL-modified silica, transforming the merits of ILs into chromatographic advantages, has endowed the development of high-performance liquid chromatography (HPLC) stationary phase with considerable vitality. In the last decade, IL-functionalized silica stationary phases have evolved into a series of branches to accommodate to different HPLC modes. An up-to-date overview of IL-immobilized stationary phases is presented in this review, and divided into five parts according to application mode, i.e., ion-exchange, normal-phase, reversed-phase, hydrophilic interaction and chiral recognition. Specific attention is channeled to synthetic strategies, chromatographic behavior and separation performance of IL-functionalized silica stationary phases. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Recent progress of chiral stationary phases for separation of enantiomers in gas chromatography.

    Science.gov (United States)

    Xie, Sheng-Ming; Yuan, Li-Ming

    2017-01-01

    Chromatography techniques based on chiral stationary phases are widely used for the separation of enantiomers. In particular, gas chromatography has developed rapidly in recent years due to its merits such as fast analysis speed, lower consumption of stationary phases and analytes, higher column efficiency, making it a better choice for chiral separation in diverse industries. This article summarizes recent progress of novel chiral stationary phases based on cyclofructan derivatives and chiral porous materials including chiral metal-organic frameworks, chiral porous organic frameworks, chiral inorganic mesoporous materials, and chiral porous organic cages in gas chromatography, covering original research papers published since 2010. The chiral recognition properties and mechanisms of separation toward enantiomers are also introduced. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Polar silica-based stationary phases. Part II- Neutral silica stationary phases with surface bound maltose and sorbitol for hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Rathnasekara, Renuka; El Rassi, Ziad

    2017-07-28

    Two neutral polyhydroxylated silica bonded stationary phases, namely maltose-silica (MALT-silica) and sorbitol-silica (SOR-silica), have been introduced and chromatographically characterized in hydrophilic interaction liquid chromatography (HILIC) for a wide range of polar compounds. The bonding of the maltose and sorbitol to the silica surface was brought about by first converting bare silica to an epoxy-activated silica surface via reaction with γ-glycidoxypropyltrimethoxysilane (GPTMS) followed by attaching maltose and sorbitol to the epoxy surface in the presence of the Lewis acid catalyst BF 3 .ethereate. Both silica based columns offered the expected retention characteristics usually encountered for neutral polar surface. The retention mechanism is majorly based on solute' differential partitioning between an organic rich hydro-organic mobile phase (e.g., ACN rich mobile phase) and an adsorbed water layer on the surface of the stationary phase although additional hydrogen bonding was also responsible in some cases for solute retention. The MALT-silica column proved to be more hydrophilic and offered higher retention, separation efficiency and resolution than the SOR-silica column among the tested polar solutes such as derivatized mono- and oligosaccharides, weak phenolic acids, cyclic nucleotide monophosphate and nucleotide-5'-monophosphates, and weak bases, e.g., nucleobases and nucleosides. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Exploitation of a microporous organic polymer as a stationary phase for capillary gas chromatography

    International Nuclear Information System (INIS)

    Lu, Cuiming; Liu, Shuqin; Xu, Jianqiao; Ding, Yajuan; Ouyang, Gangfeng

    2016-01-01

    Microporous organic polymers (MOPs) have emerged as a new class of functional porous materials with unique characteristics and potential uses in diverse areas. However, the field of MOPs for gas chromatographic (GC) separations has not been well explored. Herein, a MOP namely KAPs-1 was dynamic coated onto a capillary column for the first time. The fabricated column exhibited a nonpolar nature and the column efficiency for n-dodecane was up to 7769 plates m"−"1. The KAPs-1 coated column showed high GC separation performance for a series of volatile organic compounds (VOCs) including the challenging ethylbenzene and xylene isomers, which could not be resolved at baseline on the commercial 5% phenyl polysiloxane stationary phase. Moreover, the relative standard deviations for five replicate determinations of the studied analytes were 0.0–0.6%, 0.9–3.2%, 1.1–5.9%, 0.8–3.7% for retention time, peak area, peak height and peak width, respectively. To investigate the interaction between some analytes and the stationary phase, thermodynamic and kinetic parameters were also evaluated. The results of this study show it is very promising to utilize MOPs as stationary phases for capillary GC. - Highlights: • A microporous organic polymer was explored as a novel stationary phase for capillary GC. • The column showed high separation performance for VOCs including the challenging ethylbenzene and xylene isomers. • Thermodynamic and kinetic parameters for BTEXs were determined to study the analyte-stationary phase interaction.

  10. Stationary two-phase flow evaluation by the dynamic slip model

    International Nuclear Information System (INIS)

    Stevanovic, D.

    1986-01-01

    The equations which describe a dynamic slip model for stationary conditions are given in the paper. The basic solving procedure by the code DVOF4 is briefly described. The results are verified on the experiment FRIGG 313014. besides the void fraction and the vapor and liquid phase temperatures, the following parameters are plotted and explained: vapor phase generation rate, vapor and liquid phase velocities, slip between the phases, interfacial surface, friction drag between each phase and the wall, two-phase flow friction multiplier and pressure drop along the channel. (author)

  11. Modifying effect of caffeine on cell radiosensitivity in stationary and logarithmic phases of growth

    International Nuclear Information System (INIS)

    Plotnikova, E.D.; Kostenko, G.A.

    1978-01-01

    Studied was reproductive killing of cultivated fibroblasts of a Chinese hamster in stationary and exponential growth phases after gamma irradiation. After cell irradiation in a stationary phase at 1200 rad dose rate and postirradiation incubation in conditioned medium before resowing for 5 hrs the survival rate increased almost 5 times due to the reparation of potential-lethal injuries. Under sodium caffein-benzoate (4 mg/ml) effect on cells in a stationary growth phase for 5 hrs before irradiation the survival rate increased; protection level was almost the same as in case of reduction in a conditioned media. Modification factor of dose curve incline was 1.3. Caffein protective effect may be conjectured to relate to the inhibition of potentially-lethal injury fraction realization

  12. Proteomic analysis of lactose-starved Lactobacillus casei during stationary growth phase.

    Science.gov (United States)

    Hussain, M A; Knight, M I; Britz, M L

    2009-03-01

    Starvation stress is a condition that nonstarter lactic acid bacteria (NSLAB) normally encounter. This study was aimed to investigate starvation-induced proteins in Lactobacillus casei during stationary growth phase. The impact of carbohydrate starvation on L. casei GCRL163 was investigated using two different media (a modified de Man, Rogosa and Sharpe broth and a semi-defined medium). Cells were grown in the presence of excess lactose (1%) or starvation (0%) and differences in the patterns of one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and two-dimensional electrophoresis of the cytosolic protein fractions were investigated. Differentially regulated proteins were identified by MALDI-TOF/TOF mass spectrometry. Many differentially regulated proteins were enzymes of various metabolic pathways involved in carbohydrate metabolism to yield energy. Differences in protein expression were also observed in the two culture conditions tested in this experiment. Numerous glycolytic enzymes were differentially regulated under lactose starvation. The differential expression of these glycolytic enzymes suggests a potential survival strategy under harsh growth conditions (i.e. lactose starvation). This paper reports improved understanding of stress responses and survival mechanism of NSLAB under lactose-depleted cheese-ripening condition. This knowledge of how NSLAB bacteria adapt to lactose starvation could be applied to predict the performances of bacteria in other industrial applications.

  13. Tubing modifications for countercurrent chromatography (CCC): Stationary phase retention and separation efficiency.

    Science.gov (United States)

    Englert, Michael; Vetter, Walter

    2015-07-16

    Countercurrent chromatography (CCC) is a separation technique in which two immiscible liquid phases are used for the preparative purification of synthetic and natural products. In CCC the number of repetitive mixing and de-mixing processes, the retention of the stationary phase and the mass transfer between the liquid phases are significant parameters that influence the resolution and separation efficiency. Limited mass transfer is the main reason for peak broadening and a low number of theoretical plates along with impaired peak resolution in CCC. Hence, technical improvements with regard to column design and tubing modifications is an important aspect to enhance mixing and mass transfer. In this study we constructed a crimping tool which allowed us to make reproducible, semi-automated modifications of conventional round-shaped tubing. Six crimped tubing modifications were prepared, mounted onto multilayer coils which were subsequently installed in the CCC system. The stationary phase retention of the tubing modifications were compared to the conventional system with unmodified tubing in a hydrophobic, an intermediate and a hydrophilic two-phase solvent system. Generally, the tubing modifications provided higher capabilities to retain the stationary phase depending on the solvent system and flow rates. In the intermediate solvent system the separation efficiency was evaluated with a mixture of six alkyl p-hydroxybenzoates. The peak resolution could be increased up to 50% with one of the tubing modifications compared to the unmodified tubing. Using the most convincing tubing modification at fixed values for the stationary phase retention, a reasonable comparison to the unmodified tubing was achieved. The peak width could be reduced up to 49% and a strong positive impact at increased flow rates regarding peak resolution and theoretical plate number was observed compared to unmodified tubing. It could be concluded that the tubing modification enhanced the interphase

  14. Exploitation of a microporous organic polymer as a stationary phase for capillary gas chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Cuiming; Liu, Shuqin; Xu, Jianqiao; Ding, Yajuan; Ouyang, Gangfeng, E-mail: cesoygf@mail.sysu.edu.cn

    2016-01-01

    Microporous organic polymers (MOPs) have emerged as a new class of functional porous materials with unique characteristics and potential uses in diverse areas. However, the field of MOPs for gas chromatographic (GC) separations has not been well explored. Herein, a MOP namely KAPs-1 was dynamic coated onto a capillary column for the first time. The fabricated column exhibited a nonpolar nature and the column efficiency for n-dodecane was up to 7769 plates m{sup −1}. The KAPs-1 coated column showed high GC separation performance for a series of volatile organic compounds (VOCs) including the challenging ethylbenzene and xylene isomers, which could not be resolved at baseline on the commercial 5% phenyl polysiloxane stationary phase. Moreover, the relative standard deviations for five replicate determinations of the studied analytes were 0.0–0.6%, 0.9–3.2%, 1.1–5.9%, 0.8–3.7% for retention time, peak area, peak height and peak width, respectively. To investigate the interaction between some analytes and the stationary phase, thermodynamic and kinetic parameters were also evaluated. The results of this study show it is very promising to utilize MOPs as stationary phases for capillary GC. - Highlights: • A microporous organic polymer was explored as a novel stationary phase for capillary GC. • The column showed high separation performance for VOCs including the challenging ethylbenzene and xylene isomers. • Thermodynamic and kinetic parameters for BTEXs were determined to study the analyte-stationary phase interaction.

  15. Methylgroup interaction of hydrocarbon stationary phases and hydrocarbon solutes

    NARCIS (Netherlands)

    Kemenade, van A.W.C.; Groenendijk, H.

    1969-01-01

    The temperature dependency of the retention behaviour of some alkanes with squalane as stationary phase has been measured at a very high precision level, at temperatures from 30 to 90°C. Besides the retention index itself [1], its temperature dependency appears to be a source of information about

  16. Metal-Organic Framework Thin Films as Stationary Phases in Microfabricated Gas-Chromatography Columns.

    Energy Technology Data Exchange (ETDEWEB)

    Read, Douglas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sillerud, Colin Halliday [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    The overarching goal of this project is to integrate Sandia's microfabricated gas-chromatography ( GC) columns with a stationary phase material that is capable of retaining high-volatility chemicals and permanent gases. The successful integration of such a material with GCs would dramatically expand the repertoire of detectable compounds for Sandia's various microanalysis systems. One such promising class of candidate materials is metal-organic frameworks (MOFs). In this report we detail our methods for controlled deposition of HKUST-1 MOF stationary phases within GC columns. We demonstrate: the chromatographic separation of natural gas; a method for determining MOF film thickness from chromatography alone; and the first-reported GC x GC separation of natural gas -- in general -- let alone for two disparate MOF stationary phases. In addition we determine the fundamental thermodynamic constant for mass sorption, the partition coefficient, for HKUST-1 and several light hydrocarbons and select toxic industrial chemicals.

  17. Argentation gas chromatography revisited: Separation of light olefin/paraffin mixtures using silver-based ionic liquid stationary phases.

    Science.gov (United States)

    Nan, He; Zhang, Cheng; Venkatesh, Amrit; Rossini, Aaron J; Anderson, Jared L

    2017-11-10

    Silver ion or argentation chromatography utilizes stationary phases containing silver ions for the separation of unsaturated compounds. In this study, a mixed-ligand silver-based ionic liquid (IL) was evaluated for the first time as a gas chromatographic (GC) stationary phase for the separation of light olefin/paraffin mixtures. The selectivity of the stationary phase toward olefins can be tuned by adjusting the ratio of silver ion and the mixed ligands. The maximum allowable operating temperature of these stationary phases was determined to be between 125°C and 150°C. Nuclear magnetic resonance (NMR) spectroscopy was used to characterize the coordination behavior of the silver-based IL as well as provide an understanding into the retention mechanism of light olefins. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. A polyacrylamide-based silica stationary phase for the separation of carbohydrates using alcohols as the weak eluent in hydrophilic interaction liquid chromatography.

    Science.gov (United States)

    Cai, Jianfeng; Cheng, Lingping; Zhao, Jianchao; Fu, Qing; Jin, Yu; Ke, Yanxiong; Liang, Xinmiao

    2017-11-17

    A hydrophilic interaction liquid chromatography (HILIC) stationary phase was prepared by a two-step synthesis method, immobilizing polyacrylamide on silica sphere particles. The stationary phase (named PA, 5μm dia) was evaluated using a mixture of carbohydrates in HILIC mode and the column efficiency reached 121,000Nm -1 . The retention behavior of carbohydrates on PA stationary phase was investigated with three different organic solvents (acetonitrile, ethanol and methanol) employed as the weak eluent. The strongest hydrophilicity of PA stationary phase was observed in both acetonitrile and methanol as the weak eluent, when compared with another two amide stationary phases. Attributing to its high hydrophilicity, three oligosaccharides (xylooligosaccharide, fructooligosaccharide and chitooligosaccharides) presented good retention on PA stationary phase using alcohols/water as mobile phase. Finally, PA stationary phase was successfully applied for the purification of galactooligosaccharides and saponins of Paris polyphylla. It is feasible to use safer and cheaper alcohols to replace acetonitrile as the weak eluent for green analysis and purification of polar compounds on PA stationary phase. Copyright © 2017. Published by Elsevier B.V.

  19. Fundamental and practical studies on high-performance liquid affinity chromatography of biopolymers with novel stationary phases

    Energy Technology Data Exchange (ETDEWEB)

    Bacolod, M.D.

    1992-01-01

    Rigid microparticulate stationary phases having surface-bound metal chelating functions were developed and evaluated in high performance metal chelate affinity chromatography of proteins. Silica- and polystyrene-divinylbenzene-based metal chelate sorbents were produced in wide pore and in non-porous type of column packings. A major effort has been placed on development of non-porous highly crosslinked polystyrene-divinylbenzene (PSDVB). These PSDVB microparticles were produced by a two-step swelling polymerization, and exhibited excellent mechanical strength over a wide range of flow-rates and composition used in high performance liquid chromatography (HPLC). Simple and reproducible hydrophilic coatings were developed for the surface modification of hydrophobic PSDVB supports. A tetradentate metal chelating ligand, ethylenediamine-N, N[prime]-diacetic acid (EDDA), was covalently bound to the surface of the various supports. Sorbents having iminodiacetic acid (IDA) metal chelating functions were also evaluated. The hydrophilic character and surface coverage of various stationary phases were assessed chromatographically. Studies concerning the effects of eluent pH as well as the nature and concentration of salts on retention and selectivity with different metal chelate stationary phases having various immobilized metal ions were carried out. Elution schemes were developed for rapid separation of proteins in metal chelate affinity chromatography. EDDA stationary phases in metal forms can be viewed as complementary to IDA stationary phases since they afforded different selectivity and retentivity toward proteins. Hydrophilic PSDVB could be functionalized with IDA or EDDA metal chelating ligands or lectins. The non-porous metal chelate stationary phases afforded rapid separation of proteins by the development of multiple gradient systems, which permitted higher column peak capacity, enabling the separation of a greater number of proteins in a single chromatographic run.

  20. Peptidoglycan Recycling in Gram-Positive Bacteria Is Crucial for Survival in Stationary Phase

    Science.gov (United States)

    Borisova, Marina; Gaupp, Rosmarie; Duckworth, Amanda; Schneider, Alexander; Dalügge, Désirée; Mühleck, Maraike; Deubel, Denise; Unsleber, Sandra; Yu, Wenqi; Muth, Günther; Bischoff, Markus; Götz, Friedrich

    2016-01-01

    ABSTRACT Peptidoglycan recycling is a metabolic process by which Gram-negative bacteria reutilize up to half of their cell wall within one generation during vegetative growth. Whether peptidoglycan recycling also occurs in Gram-positive bacteria has so far remained unclear. We show here that three Gram-positive model organisms, Staphylococcus aureus, Bacillus subtilis, and Streptomyces coelicolor, all recycle the sugar N-acetylmuramic acid (MurNAc) of their peptidoglycan during growth in rich medium. They possess MurNAc-6-phosphate (MurNAc-6P) etherase (MurQ in E. coli) enzymes, which are responsible for the intracellular conversion of MurNAc-6P to N-acetylglucosamine-6-phosphate and d-lactate. By applying mass spectrometry, we observed accumulation of MurNAc-6P in MurNAc-6P etherase deletion mutants but not in either the isogenic parental strains or complemented strains, suggesting that MurQ orthologs are required for the recycling of cell wall-derived MurNAc in these bacteria. Quantification of MurNAc-6P in ΔmurQ cells of S. aureus and B. subtilis revealed small amounts during exponential growth phase (0.19 nmol and 0.03 nmol, respectively, per ml of cells at an optical density at 600 nm [OD600] of 1) but large amounts during transition (0.56 nmol and 0.52 nmol) and stationary (0.53 nmol and 1.36 nmol) phases. The addition of MurNAc to ΔmurQ cultures greatly increased the levels of intracellular MurNAc-6P in all growth phases. The ΔmurQ mutants of S. aureus and B. subtilis showed no growth deficiency in rich medium compared to the growth of the respective parental strains, but intriguingly, they had a severe survival disadvantage in late stationary phase. Thus, although peptidoglycan recycling is apparently not essential for the growth of Gram-positive bacteria, it provides a benefit for long-term survival. PMID:27729505

  1. Separation of U and Pu be the method of liquid chromatography with free stationary phase in TBP - white spirit - nitric acid system

    International Nuclear Information System (INIS)

    Litvina, M.N.; Malikov, D.A.; Maryutina, T.A.; Kulyako, Yu.M.; Myasoedov, B.F.

    2006-01-01

    Possibility is studied of the use of liquid chromatography with free stationary phase for U and Pu separation from organic extract obtained by direct dissolution of MOX-fuel in supercritical CO 2 containing TBP·nHNO 3 complex. As stationary phase solutions of TBP in white-spirit of different concentrations are used. Effect of composition of stationary and mobile phases on separation efficiency is investigated. It is shown that use of liquid chromatography with free stationary phase permits to separate U and Pu in conditions of TBP concentration gradient in stationary phase and HNO 3 concentration gradient in mobile one [ru

  2. Separation of piracetam derivatives on polysaccharide-based chiral stationary phases.

    Science.gov (United States)

    Kažoka, H; Koliškina, O; Veinberg, G; Vorona, M

    2013-03-15

    High-performance liquid chromatography was used for the enantiomeric separation of two chiral piracetam derivatives. The suitability of six commercially available polysaccharide-based chiral stationary phases (CSPs) under normal phase mode for direct enantioseparation has been investigated. The influence of the CSPs as well the nature and content of an alcoholic modifier in the mobile phase on separation and elution order was studied. It was established that CSP Lux Amylose-2 shows high chiral recognition ability towards 4-phenylsubstituted piracetam derivatives. Copyright © 2013 Elsevier B.V. All rights reserved.

  3. The extracellular proteome of Rhizobium etli CE3 in exponential and stationary growth phase

    Directory of Open Access Journals (Sweden)

    Mendoza-Hernández Guillermo

    2010-10-01

    Full Text Available Abstract Background The extracellular proteome or secretome of symbiotic bacteria like Rhizobium etli is presumed to be a key element of their infection strategy and survival. Rhizobia infect the roots of leguminous plants and establish a mutually beneficial symbiosis. To find out the possible role of secreted proteins we analyzed the extracellular proteome of R. etli CE3 in the exponential and stationary growth phases in minimal medium, supplemented with succinate-ammonium. Results The extracellular proteins were obtained by phenol extraction and identified by LC-ESI MS/MS. We identified 192 and 191 proteins for the exponential and stationary phases respectively. Using the software Signal P, we predicted signal peptides for 12.95% and 35.60% of the proteins identified in the exponential and stationary phases, respectively, which could therefore be secreted by the Sec pathway. For the exponential growth phase, we found in abundance proteins like the ribosomal proteins, toxins and proteins belonging to the group "defence mechanisms". For the stationary growth phase, we found that the most abundant proteins were those with unknown function, and in many of these we identified characteristic domains of proteases and peptidases. Conclusions Our study provided the first dataset of the secretome of R. etli and its modifications, which may lead to novel insights into the adaptive response of different stages of growth. In addition, we found a high number of proteins with unknown function; these proteins could be analyzed in future research to elucidate their role in the extracellular proteome of R. etli.

  4. Selectivity differences of water-soluble vitamins separated on hydrophilic interaction stationary phases.

    Science.gov (United States)

    Yang, Yuanzhong; Boysen, Reinhard I; Hearn, Milton T W

    2013-06-01

    In this study, the retention behavior and selectivity differences of water-soluble vitamins were evaluated with three types of polar stationary phases (i.e. an underivatized silica phase, an amide phase, and an amino phase) operated in the hydrophilic interaction chromatographic mode with ESI mass spectrometric detection. The effects of mobile phase composition, including buffer pH and concentration, on the retention and selectivity of the vitamins were investigated. In all stationary phases, the neutral or weakly charged vitamins exhibited very weak retention under each of the pH conditions, while the acidic and more basic vitamins showed diverse retention behaviors. With the underivatized silica phase, increasing the salt concentration of the mobile phase resulted in enhanced retention of the acidic vitamins, but decreased retention of the basic vitamins. These observations thus signify the involvement of secondary mechanisms, such as electrostatic interaction in the retention of these analytes. Under optimized conditions, a baseline separation of all vitamins was achieved with excellent peak efficiency. In addition, the effects of water content in the sample on retention and peak efficiency were examined, with sample stacking effects observed when the injected sample contained a high amount of water. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Schizosaccharomyces pombe Homologs of Human DJ-1 Are Stationary Phase-Associated Proteins That Are Involved in Autophagy and Oxidative Stress Resistance.

    Directory of Open Access Journals (Sweden)

    Yang Su

    Full Text Available The Parkinson's disease protein DJ-1 is involved in various cellular functions including detoxification of dicarbonyl compounds, autophagy and oxidative stress response. DJ-1 homologs are widely found in both prokaryotes and eukaryotes, constituting a superfamily of proteins that appear to be involved in stress response. Schizosaccharomyces pombe contains six DJ-1 homologs, designated Hsp3101-Hsp3105 and Sdj1 (previously named SpDJ-1. Here we show that deletion of any one of these six genes somehow affects autophagy during prolonged stationary phase. Furthermore, deletions of each of these DJ-1 homologs result in reduced stationary phase survival. Deletion of sdj1 also increases the sensitivity of stationary-phase cells to oxidative stress induced by hydrogen peroxide (H2O2 whereas overexpression of sdj1 has the opposite effect. Consistent with their role in stationary phase, expression of hsp3101, hsp3102, hsp3105 and sdj1, and to a lesser extent hsp3103 and hsp3104, is increased in stationary phase. The induction of hsp3101, hsp3102, hsp3105 and sdj1 involves the Sty1-regulated transcription factor Atf1 but not the transcription factor Pap1. Our results firmly establish that S. pombe homologs of DJ-1 are stationary-phase associated proteins and are likely involved in autophagy and antioxidant defense in stationary phase of S. pombe cells.

  6. Preparation, characterization and application of a reversed phase liquid chromatography/hydrophilic interaction chromatography mixed-mode C18-DTT stationary phase.

    Science.gov (United States)

    Wang, Qing; Long, Yao; Yao, Lin; Xu, Li; Shi, Zhi-Guo; Xu, Lanying

    2016-01-01

    A mixed-mode chromatographic stationary phase, C18-DTT (dithiothreitol) silica (SiO2) was prepared through "thiol-ene" click chemistry. The obtained material was characterized by fourier transform infrared spectroscope, nitrogen adsorption analysis and contact angle analysis. Chromatographic performance of the C18-DTT was systemically evaluated by studying the effect of acetonitrile content, pH, buffer concentration of the mobile phase and column temperature. It was demonstrated that the novel stationary phase possessed reversed phase liquid chromatography (RPLC)/hydrophilic interaction liquid chromatography (HILIC) mixed-mode property. The stop-flow test revealed that C18-DTT exhibited excellent compatibility with 100% aqueous mobile phase. Additionally, the stability and column-to-column reproducibility of the C18-DTT material were satisfactory, with relative standard deviations of retention factor of the tested analytes (verapamil, fenbufen, guanine, tetrandrine and nicotinic acid) in the range of 1.82-3.72% and 0.85-1.93%, respectively. Finally, the application of C18-DTT column was demonstrated in the separation of non-steroidal anti-inflammatory drugs, aromatic carboxylic acids, alkaloids, nucleo-analytes and polycyclic aromatic hydrocarbons. It had great resolving power in the analysis of various compounds in HILIC and RPLC chromatographic conditions and was a promising RPLC/HILIC mixed-mode stationary phase. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Synthesis of a mixed-model stationary phase derived from glutamine for HPLC separation of structurally different biologically active compounds: HILIC and reversed-phase applications.

    Science.gov (United States)

    Aral, Tarık; Aral, Hayriye; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

    2015-01-01

    A novel mixed-mode stationary phase was synthesised starting from N-Boc-glutamine, aniline and spherical silica gel (4 µm, 60 Å). The prepared stationary phase was characterized by IR and elemental analysis. The new stationary phase bears an embedded amide group into phenyl ring, highly polar a terminal amide group and non-polar groups (phenyl and alkyl groups). At first, this new mixed-mode stationary phase was used for HILIC separation of four nucleotides and five nucleosides. The effects of different separation conditions, such as pH value, mobile phase and temperature, on the separation process were investigated. The optimum separation for nucleotides was achieved using HILIC isocratic elution with aqueous mobile phase and acetonitrile with 20°C column temperature. Under these conditions, the four nucleotides could be separated and detected at 265 nm within 14 min. Five nucleosides were separated under HILIC isocratic elution with aqueous mobile phase containing pH=3.25 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 265 nm within 14 min. Chromatographic parameters as retention factor, selectivity, theoretical plate number and peak asymmetry factor were calculated for the effect of temperature and water content in mobile phase on the separation process. The new column was also tested for nucleotides and nucleosides mixture and six analytes were separated in 10min. The chromatographic behaviours of these polar analytes on the new mixed-model stationary phase were compared with those of HILIC columns under similar conditions. Further, phytohormones and phenolic compounds were separated in order to see influence of the new stationary phase in reverse phase conditions. Eleven plant phytohormones were separated within 13 min using RP-HPLC gradient elution with aqueous mobile phase containing pH=2.5 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 230 or 278 nm. The best separation

  8. Comparison of GC stationary phases for the separation of fatty acid methyl esters in biodiesel fuels.

    Science.gov (United States)

    Goding, Julian C; Ragon, Dorisanne Y; O'Connor, Jack B; Boehm, Sarah J; Hupp, Amber M

    2013-07-01

    The fatty acid methyl ester (FAME) content of biodiesel fuels has traditionally been determined using gas chromatography with a polar stationary phase. In this study, a direct comparison of the separation of FAMEs present in various biodiesel samples on three polar stationary phases and one moderately polar stationary phase (with comparable column dimensions) was performed. Retention on each column was based on solubility in and polarity of the phase. Quantitative metrics describing the resolution of important FAME pairs indicate high resolution on all polar columns, yet the best resolution, particularly of geometric isomers, is achieved on the cyanopropyl column. In addition, the separation of four C18 monounsaturated isomers was optimized and the elution order determined on each column. FAME composition of various biodiesel fuel types was determined on each column to illustrate (1) chemical differences in biodiesels produced from different feedstocks and (2) chemical similarities in biodiesels of the same feedstock type produced in different locations and harvest seasons.

  9. Experimental comparison of chiral metal-organic framework used as stationary phase in chromatography.

    Science.gov (United States)

    Xie, Sheng-Ming; Zhang, Mei; Fei, Zhi-Xin; Yuan, Li-Ming

    2014-10-10

    Chiral metal-organic frameworks (MOFs) are a new class of multifunctional material, which possess diverse structures and unusual properties such as high surface area, uniform and permanent cavities, as well as good chemical and thermal stability. Their chiral functionality makes them attractive as novel enantioselective adsorbents and stationary phases in separation science. In this paper, the experimental comparison of a chiral MOF [In₃O(obb)₃(HCO₂)(H₂O)] solvent used as a stationary phase was investigated in gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The potential relationship between the structure and components of chiral MOFs with their chiral recognition ability and selectivity are presented. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Localization and stationary phase approximation on supermanifolds

    Science.gov (United States)

    Zakharevich, Valentin

    2017-08-01

    Given an odd vector field Q on a supermanifold M and a Q-invariant density μ on M, under certain compactness conditions on Q, the value of the integral ∫Mμ is determined by the value of μ on any neighborhood of the vanishing locus N of Q. We present a formula for the integral in the case where N is a subsupermanifold which is appropriately non-degenerate with respect to Q. In the process, we discuss the linear algebra necessary to express our result in a coordinate independent way. We also extend the stationary phase approximation and the Morse-Bott lemma to supermanifolds.

  11. An immobilized graphene oxide stationary phase for open-tubular capillary electrochromatography.

    Science.gov (United States)

    Wang, Chun; de Rooy, Sergio; Lu, Cheng-Fei; Fernand, Vivian; Moore, Leonard; Berton, Paula; Warner, Isiah M

    2013-04-01

    The research literature currently abounds with studies of graphene-related materials as a result of the extraordinary properties of such materials. On the basis of these citations, it is clear that the range of applications for such materials is substantial. In this manuscript, we report the immobilization of graphene oxide (GO) onto a fused-silica capillary to form a potential stationary phase for use in open-tubular CEC. We successfully incorporated GO through an in situ condensation reaction with (3-aminopropyl)triethoxysilane after silanization with (3-aminopropyl)triethoxysilane on the inner surface of the capillary. This GO-incorporated capillary was then characterized by use of SEM, infrared spectroscopy, and measurements of EOF. The electrochromatographic features of this stationary phase have also been investigated. Evaluation of acquired data indicates high electrochromatographic resolution and good capillary efficiency. Highly reproducible results between runs, days, and capillaries were also obtained. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. The Stationary-Phase Cells of Saccharomyces cerevisiae Display Dynamic Actin Filaments Required for Processes Extending Chronological Life Span.

    Science.gov (United States)

    Vasicova, Pavla; Lejskova, Renata; Malcova, Ivana; Hasek, Jiri

    2015-11-01

    Stationary-growth-phase Saccharomyces cerevisiae yeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. In S. cerevisiae stationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Our in vivo analyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficient cox4Δ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  13. Benznidazole induces in vitro anaerobic metabolism in Trypanosoma cruzi epimastigotes

    Directory of Open Access Journals (Sweden)

    Marina Clare Vinaud

    2017-11-01

    Full Text Available Objective: To determine the biochemical alterations of the energetic metabolism of Trypanosoma cruzi epimastigotes in vitro exposed to different concentrations of benzinidazole. Methods: Biochemical analyses were performed at 3, 6 (log phase, 9 and 12 (stationary phase days of culture. Parasites were exposed to five concentrations of benzinidazole. Glycolysis, tricarboxilic acid cycle and fatty acids oxidation pathways were quantified through chromatography. Glucose, urea and creatinine were quantified through spectrophotometric analysis. Results: Anaerobic fermentation and fatty acids oxidation were increased in the stationary phase of the culture. Benzinidazole at high concentrations induced anaerobic metabolism in the log phase of the culture while the parasites exposed to the lower concentrations preferred the citric acid cycle as energy production pathway. Benzinidazole did not influence on the proteins catabolism. Conclusions: It is possible to conclude that there are metabolic differences between evolutive forms of Trypanosoma cruzi and the main drug used for its treatment induces the anaerobic metabolism in the parasite, possibly impairing the mitochondrial pathways.

  14. Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

    Science.gov (United States)

    Boultwood, Tom; Affron, Dominic P.; Bull, James A.

    2014-01-01

    The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 °Cin the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 °C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control. Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to

  15. Strengthening of the DNA-protein complex during stationary phase aging of cell cultures

    International Nuclear Information System (INIS)

    Khokhlov, A.N.; Chirkova, E.Yu.; Gorin, A.I.

    1986-01-01

    The possibility of accumulation of cross-linkages in the DNA-protein complex was studied during stationary phase aging of cells in culture. Chinese hamster cells were used in the experiments, along with human fibroblasts. 3 H-thymidine, 14 C-valine, and 14 C-leucine were added to the medium. The quantity of protein firmly bound with DNA was judged from the value of the coefficient 14 C/ 3 H determined with allowance for penetration of counting from the 14 C-channel into the 3 H-channel. The authors maintain that the results presented in this paper provide further evidence of the value of stationary phase cell cultures for the study of the mechanisms of aging and also of some of the general principles underlying hereditary pathology

  16. Amino-modified diamond as a durable stationary phase for solid-phase extraction.

    Science.gov (United States)

    Saini, Gaurav; Yang, Li; Lee, Milton L; Dadson, Andrew; Vail, Michael A; Linford, Matthew R

    2008-08-15

    We report the formation of a highly stable amino stationary phase on diamond and demonstrate its use in solid-phase extraction (SPE). This process consists of spontaneous and self-limiting adsorption of polyallylamine (PAAm) from aqueous solution onto oxidized diamond. Thermal curing under reduced pressure or chemical cross-linking with a diepoxide was shown to fix the polymer to the particles. The resulting adsorbents are stable under even extreme pH conditions (from at least pH 0-14) and significantly more stable than a commercially available amino SPE adsorbent. Coated diamond particles were characterized by X-ray photoelectron spectroscopy (XPS) and diffuse reflectance Fourier transform-infrared spectroscopy (DRIFT). Model silicon surfaces were characterized by spectroscopic ellipsometry and wetting. Solid-phase extraction was demonstrated using cholesterol, hexadecanedioic acid, and palmitoyloleoylphosphatidylcholine as analytes, and these results were compared to those obtained with commercially available materials. Breakthrough curves indicate that, as expected, porous diamond particles have higher analyte capacity than nonporous solid particles.

  17. Convergence to stationary solutions for a parabolic-hyperbolic phase-field system

    Czech Academy of Sciences Publication Activity Database

    Grasselli, M.; Petzeltová, Hana; Schimperna, G.

    2006-01-01

    Roč. 5, č. 4 (2006), s. 827-838 ISSN 1534-0392 R&D Projects: GA AV ČR(CZ) IAA1019302 Institutional research plan: CEZ:AV0Z10190503 Keywords : phase-field models * convergence to stationary solutions * Łojasiewicz-Simon inequality Subject RIV: BA - General Mathematics Impact factor: 0.857, year: 2006

  18. Nutrient control for stationary phase cellulase production in Trichoderma reesei Rut C-30.

    Science.gov (United States)

    Callow, Nicholas V; Ray, Christopher S; Kelbly, Matthew A; Ju, Lu-Kwang

    2016-01-01

    This work describes the use of nutrient limitations with Trichoderma reesei Rut C-30 to obtain a prolonged stationary phase cellulase production. This period of non-growth may allow for dependable cellulase production, extended fermentation periods, and the possibility to use pellet morphology for easy product separation. Phosphorus limitation was successful in halting growth and had a corresponding specific cellulase production of 5±2 FPU/g-h. Combined with the addition of Triton X-100 for fungal pellet formation and low shear conditions, a stationary phase cellulase production period in excess of 300 h was achieved, with a constant enzyme production rate of 7±1 FPU/g-h. While nitrogen limitation was also effective as a growth limiter, it, however, also prevented cellulase production. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Ionic liquids as stationary phases for fatty acid analysis by gas chromatography.

    Science.gov (United States)

    Fanali, C; Micalizzi, G; Dugo, P; Mondello, L

    2017-12-04

    The present paper provides an overview of the application of ionic liquid (IL) columns for GC analysis of fatty acid methyl esters (FAMEs). Although their separation can be carried out utilizing GC columns containing polar stationary phases, some ILs have been employed as stationary phases, either commercial or laboratory made, in GC analysis. Monodimensional and bidimensional GC methods have been optimized in order to achieve the best separation especially considering the geometric and positional isomers of unsaturated fatty acids. Several methods for the analysis of trans-fatty acids have also been reported. The use of GC-GC, using either the same IL columns or different columns in the first and second dimensions, allowed the separation of a large number of FAMEs. The application of the IL columns for GC analysis of FAMEs in different types of real samples is described, e.g., oil of different nature (fish, flaxseed, and olive), margarine and butter, biodiesel, milk, bacteria etc.

  20. Proteomic Analysis of Stationary Phase in the Marine Bacterium "Candidatus Pelagibacter ubique"

    Energy Technology Data Exchange (ETDEWEB)

    Sowell, S. M.; Norbeck, A. D.; Lipton, M. S.; Nicora, C. D.; Callister, S. J.; Smith, R. D.; Barofsky, D. F.; Giovannoni, S. J.

    2008-05-09

    The α-proteobacterium ‘Candidatus Pelagibacter ubique’ str. HTCC1062, and most other members of the SAR11 clade, lack genes for assimilatory sulfate reduction, making them dependent on organosulfur compounds that occur naturally in seawater. To investigate how these cells adapt to sulfur limitation, batch cultures were grown in defined media containing either limiting or non-limiting amounts of dimethylsulfoniopropionate (DMSP) as the sole sulfur source. Protein and mRNA expression were measured during exponential growth, immediately prior to stationary phase, and in late stationary phase. Two distinct responses were observed: one as DMSP became exhausted, and another as cells acclimated to a sulfur-limited environment. The first response was characterized by increased transcription and translation of all Ca. P. ubique genes downstream of previously confirmed S-adenosyl methionine (SAM) riboswitches: bhmT, mmuM, and metY. Proteins encoded by these genes were up to 33 times more abundant as DMSP became limiting. Their predicted function is to shunt all available sulfur to methionine. The secondary response, observed during sulfur-depleted stationary phase, was a 6-10 fold increase in transcription of the heme c shuttle ccmC and two small genes of unknown function (SAR11_1163 and SAR11_1164). This bacterium's strategy for coping with sulfur stress appears to be intracellular redistribution to support methionine biosynthesis, rather than increasing organosulfur import. Many of the genes and SAM riboswitches involved in this response are located in a hypervariable genome region (HVR). One of these HVR genes, ordL, is located downstream of a conserved motif that evidence suggests is a novel riboswitch.

  1. Micro-fabricated semi-packed column for gas chromatography by using functionalized parylene as a stationary phase

    International Nuclear Information System (INIS)

    Nakai, T; Nishiyama, S; Shuzo, M; Delaunay, J-J; Yamada, I

    2009-01-01

    The conformal coating of effective stationary phases onto micro-fabricated columns having complex geometries such as semi-packed columns poses a real challenge. Here, we report for the first time the conformal coating of a semi-packed column with amino-functionalized parylene diX-AM (poly-aminomethyl-[2,2]-paracyclophane), which was found to be an effective stationary-phase material for the chromatography of short-retention-time compounds. A semi-packed column (consisting of a zigzag array of 30 µm square micro-pillars in a 1.0 m long, 180 µm wide and 230 µm deep channel) and an open tubular column (1.0 m long, 160 µm wide and 230 µm deep channel) used for comparison purposes were micro-fabricated on silicon that was subsequently coated with diX-AM parylene and thermally bonded. The chromatograms recorded on a commercial gas chromatograph demonstrated the usefulness of the conformal diX-AM coating as a stationary phase for semi-packed columns. The separation efficiency of the semi-packed column was found to be more than ten times that of the open tubular column

  2. Synthesis and characterization of mesoporous silica modified with chiral auxiliaries for their potential application as chiral stationary phase.

    Science.gov (United States)

    Mayani, Vishal J; Abdi, S H R; Kureshy, R I; Khan, N H; Agrawal, Santosh; Jasra, R V

    2008-05-16

    Novel chiral stationary phase (CSP) based on chiral aminoalcohol immobilized on ordered mesoporous silica SBA-15 1a and standard silica 1b and their copper complexes 1a' and 1b', respectively, was synthesized as potential material for chiral ligand exchange chromatography (CLEC). Microanalysis, inductively coupled plasma spectroscopy (ICP), thermo-gravimetric analysis (TGA), cross polarized magic angle spinning (CP-MAS) (13)C NMR, Powder X-ray diffraction (PXRD), FTIR, N(2) adsorption isotherm, scanning electron microscopy (SEM), transmitted electron microscope (TEM) and solid reflectance UV-vis spectroscopy were used to characterize these materials. All the chiral stationary phases thus synthesized were used for the separation of different racemic compounds such as mandelic acid, 2,2'-dihydroxy-1,1'-binaphthalene BINOL) and diethyl tartrate by simple medium-pressure column chromatography. Successful enantio-separation of racemic mandelic acid was achieved with all the stationary phases but 1a and 1b gave slightly better resolution than their copper complexes 1a' and 1b'. Remarkably these materials are stable under the given experimental conditions and can be used repeatedly for several cycles of enantioresolution. It was observed that the porosity and surface area of the stationary phase play an important role in the chiral separation.

  3. A stationary phase solution for mountain waves with application to mesospheric mountain waves generated by Auckland Island

    Science.gov (United States)

    Broutman, Dave; Eckermann, Stephen D.; Knight, Harold; Ma, Jun

    2017-01-01

    A relatively general stationary phase solution is derived for mountain waves from localized topography. It applies to hydrostatic, nonhydrostatic, or anelastic dispersion relations, to arbitrary localized topography, and to arbitrary smooth vertically varying background temperature and vector wind profiles. A simple method is introduced to compute the ray Jacobian that quantifies the effects of horizontal geometrical spreading in the stationary phase solution. The stationary phase solution is applied to mesospheric mountain waves generated by Auckland Island during the Deep Propagating Gravity Wave Experiment. The results are compared to a Fourier solution. The emphasis is on interpretations involving horizontal geometrical spreading. The results show larger horizontal geometrical spreading for nonhydrostatic waves than for hydrostatic waves in the region directly above the island; the dominant effect of horizontal geometrical spreading in the lower ˜30 km of the atmosphere, compared to the effects of refraction and background density variation; and the enhanced geometrical spreading due to directional wind in the approach to a critical layer in the mesosphere.

  4. Escherichia coli adhesive coating as a chiral stationary phase for open tubular capillary electrochromatography enantioseparation

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Qifeng, E-mail: fuqifeng1990@163.com [Department of Medicinal Chemistry, Southwest Medical University, Luzhou 646000 (China); Zhang, Kailian; Gao, Die; Wang, Lujun [Department of Medicinal Chemistry, Southwest Medical University, Luzhou 646000 (China); Yang, Fengqing; Liu, Yao [School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China); Xia, Zhining, E-mail: tcm_anal_cqu@163.com [Innovative Drug Research Centre and School of Pharmaceutical Sciences, Chongqing University, Chongqing 400030 (China); School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030 (China)

    2017-05-29

    Bacteria, the microorganism with intrinsic chirality, have numerous fascinating chiral phenomena such as various chirality-triggered biological processes and behaviors. Herein, bacteria were firstly explored as novel chiral stationary phases in open-tubular capillary electrochromatography (OT-CEC) for enantioseparation of fluoroquinolone enantiomers and simultaneous separation of six fluoroquinolone antibiotics. The model strain, i.e. non-pathogenic Escherichia coli (E. coli) DH5α, was adhered onto the inner surface of positively charged polyethyleneimine (PEI) modified capillaries based on the bacterial adhesion characteristics and strong electrostatic interaction. The morphology and thickness of the bacteria adhesive coatings in the capillary were characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Baseline separation of ofloxacin and partial separation of lomefloxacin enantiomers could be achieved by the E. coli coated columns. The preparation parameters including the coating time and concentration of bacteria that affecting the chiral resolution were intensively investigated. The electrophoretic parameters, including pH, buffer concentration and applied voltage, were also optimized. The developed method was validated (linearity, LOD, LOQ, intra-day, inter-day and column-to-column repeatability and recovery) and successfully utilized for the quantitative analysis of ofloxacin enantiomers in the ofloxacin tablets. Moreover, only a slight decrease in the separation efficiency was observed after 90 consecutive runs on the E. coli@capillary. These results demonstrated that bacteria are promising stationary phases for chiral separation in CEC. - Highlights: • Bacteria were firstly introduced in OT-CEC as a chiral stationary phase for chiral separation. • Enantioseparation of ofloxacin enantiomers was achieved on E. coli coated open tubular capillary column. • Bacterial stationary phases may be used to

  5. Escherichia coli adhesive coating as a chiral stationary phase for open tubular capillary electrochromatography enantioseparation

    International Nuclear Information System (INIS)

    Fu, Qifeng; Zhang, Kailian; Gao, Die; Wang, Lujun; Yang, Fengqing; Liu, Yao; Xia, Zhining

    2017-01-01

    Bacteria, the microorganism with intrinsic chirality, have numerous fascinating chiral phenomena such as various chirality-triggered biological processes and behaviors. Herein, bacteria were firstly explored as novel chiral stationary phases in open-tubular capillary electrochromatography (OT-CEC) for enantioseparation of fluoroquinolone enantiomers and simultaneous separation of six fluoroquinolone antibiotics. The model strain, i.e. non-pathogenic Escherichia coli (E. coli) DH5α, was adhered onto the inner surface of positively charged polyethyleneimine (PEI) modified capillaries based on the bacterial adhesion characteristics and strong electrostatic interaction. The morphology and thickness of the bacteria adhesive coatings in the capillary were characterized by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Baseline separation of ofloxacin and partial separation of lomefloxacin enantiomers could be achieved by the E. coli coated columns. The preparation parameters including the coating time and concentration of bacteria that affecting the chiral resolution were intensively investigated. The electrophoretic parameters, including pH, buffer concentration and applied voltage, were also optimized. The developed method was validated (linearity, LOD, LOQ, intra-day, inter-day and column-to-column repeatability and recovery) and successfully utilized for the quantitative analysis of ofloxacin enantiomers in the ofloxacin tablets. Moreover, only a slight decrease in the separation efficiency was observed after 90 consecutive runs on the E. coli@capillary. These results demonstrated that bacteria are promising stationary phases for chiral separation in CEC. - Highlights: • Bacteria were firstly introduced in OT-CEC as a chiral stationary phase for chiral separation. • Enantioseparation of ofloxacin enantiomers was achieved on E. coli coated open tubular capillary column. • Bacterial stationary phases may be used to

  6. Molecular theory of chromatography for blocklike solutes in anisotropic stationary phases and its application

    International Nuclear Information System (INIS)

    Yan, Chao; Martire, D.E.

    1992-01-01

    DiMarzio's lattice model is successfully applied to describe the equilibrium partitioning of blocklike molecules between an isotropic mobile phase and an anisotropic stationary phase in various types of fluid chromatography to obtain a retention equation. A linear relationship between the logarithm of the solute distribution coefficient and minimum area is predicted. 44 refs., 8 figs., 2 tabs

  7. Preparation and characterization of a new microwave immobilized poly(2-phenylpropyl)methylsiloxane stationary phase for reversed phase high-performance liquid chromatography.

    Science.gov (United States)

    Begnini, Fernanda R; Jardim, Isabel C S F

    2013-07-05

    A new reversed phase high-performance liquid chromatography (RP-HPLC) stationary phase was prepared and its chromatographic and physical-chemical properties were evaluated. The new stationary phase was prepared with a silica support and poly(2-phenylpropyl)methylsiloxane (PPPMS), a phenyl type polysiloxane copolymer. Since this is a new copolymer and there is little information in the literature, it was submitted to physical-chemical characterization by infrared spectroscopy and thermogravimetry. The chromatographic phase was prepared through sorption and microwave immobilization of the copolymer onto a silica support. The chromatographic performance was evaluated by employing test procedures suggested by Engelhardt and Jungheim, Tanaka and co-workers, Neue, and Szabó and Csató. These test mixtures provide information about the hydrophobic selectivity, silanophilic activity, ion-exchange capacity, shape selectivity and interaction with polar analytes of the new Si-PPPMS reversed phase. Stability tests were developed using accelerated aging tests under both basic and acidic conditions to provide information about the lifetime of the packed columns. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Nanostructured pillars based on vertically aligned carbon nanotubes as the stationary phase in micro-CEC.

    Science.gov (United States)

    Wu, Ren-Guei; Yang, Chung-Shi; Wang, Pen-Cheng; Tseng, Fan-Gang

    2009-06-01

    We present a micro-CEC chip carrying out a highly efficient separation of dsDNA fragments through vertically aligned multi-wall carbon nanotubes (MWCNTs) in a microchannel. The vertically aligned MWCNTs were grown directly in the microchannel to form straight nanopillar arrays as ordered and directional chromatographic supports. 1-Pyrenedodecanoic acid was employed for the surface modification of the MWCNTs' stationary phase to adsorb analytes by hydrophobic interactions. This device was used for separating dsDNA fragments of three different lengths (254, 360, and 572 bp), and fluorescence detection was employed to verify the electrokinetic transport in the MWCNT array. The micro-CEC separation of the three compounds was achieved in less than 300 s at a field strength of 66 V/cm due to superior laminar flow patterns and a lower flow resistance resulting from the vertically aligned MWCNTs being used as the stationary phase medium. In addition, a fivefold reduction of band broadening was obtained when the analyte was separated by the chromatographic MWCNT array channel instead of the CE channel. From all of the results, we suggest that an in situ grown and directional MWCNT array can potentially be useful for preparing more diversified forms of stationary phases for vertically efficient chip-based electrochromatography.

  9. Hilbert and Blaschke phases in the temporal coherence function of stationary broadband light.

    Science.gov (United States)

    Fernández-Pousa, Carlos R; Maestre, Haroldo; Torregrosa, Adrián J; Capmany, Juan

    2008-10-27

    We show that the minimal phase of the temporal coherence function gamma (tau) of stationary light having a partially-coherent symmetric spectral peak can be computed as a relative logarithmic Hilbert transform of its amplitude with respect to its asymptotic behavior. The procedure is applied to experimental data from amplified spontaneous emission broadband sources in the 1.55 microm band with subpicosecond coherence times, providing examples of degrees of coherence with both minimal and non-minimal phase. In the latter case, the Blaschke phase is retrieved and the position of the Blaschke zeros determined.

  10. Antimicrobial efficacy of chlorine dioxide against Candida albicans in stationary and starvation phases in human root canal: An in-vitro study

    Directory of Open Access Journals (Sweden)

    Shirur Krishnaraj Somayaji

    2014-01-01

    Full Text Available Introduction: Candida albicans (C. albicans is the most commonly isolated fungal pathogen from dental root canal. C. albicans forms biofilm and develops resistance against root canal irrigants . This study determines the fungicidal efficacy of 13.8% chlorine dioxide in extracted human teeth at stationary and starvation phases of C. albicans. Materials and Methods: Teeth were decoronated and coronal portion of the roots were prepared into blocks, which were incubated at 37°C with C. albicans for five days. The samples were treated with chlorine dioxide for 12 and 20 minutes. Total of fifty blocks were taken in the study. Colony-forming units were counted in Sabourauds dextrose agar and scanning electron microscopic observation was done. Data were analyzed by one-way ANOVA and Bonferoni′s post hoc test. Results: Teeth at stationary phase (12 min showed mean colony count of 28,000 ± 1814 which is significantly (P < 0.001 less than control group. Teeth at starvation phase (12 min showed colony count of 65,600 ± 1912 which is also significantly (P < 0.001 less than control group. Teeth irrigated at stationary phase (20 min showed mean colony count of 23,400 ± 1776 (P < 0.001. Teeth irrigated at starvation phase (20 min showed mean colony count of 48,100 ± 1663 which is also significantly (P < 0.001 less than that of control group. Conclusion: Treatment of chlorine dioxide reduces the C. albicans count in root canals of extracted human teeth at stationary and starvation phases. Efficacy of chlorine dioxide against C. albicans is relatively higher in stationary phase than that of starvation phase.

  11. Stationary phase expression of the arginine biosynthetic operon argCBH in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Sun Yuan

    2006-02-01

    Full Text Available Abstract Background Arginine biosynthesis in Escherichia coli is elevated in response to nutrient limitation, stress or arginine restriction. Though control of the pathway in response to arginine limitation is largely modulated by the ArgR repressor, other factors may be involved in increased stationary phase and stress expression. Results In this study, we report that expression of the argCBH operon is induced in stationary phase cultures and is reduced in strains possessing a mutation in rpoS, which encodes an alternative sigma factor. Using strains carrying defined argR, and rpoS mutations, we evaluated the relative contributions of these two regulators to the expression of argH using operon-lacZ fusions. While ArgR was the main factor responsible for modulating expression of argCBH, RpoS was also required for full expression of this biosynthetic operon at low arginine concentrations (below 60 μM L-arginine, a level at which growth of an arginine auxotroph was limited by arginine. When the argCBH operon was fully de-repressed (arginine limited, levels of expression were only one third of those observed in ΔargR mutants, indicating that the argCBH operon is partially repressed by ArgR even in the absence of arginine. In addition, argCBH expression was 30-fold higher in ΔargR mutants relative to levels found in wild type, fully-repressed strains, and this expression was independent of RpoS. Conclusion The results of this study indicate that both derepression and positive control by RpoS are required for full control of arginine biosynthesis in stationary phase cultures of E. coli.

  12. Iptycene-based stationary phase with three-dimensional aromatic structure for highly selective separation of H-bonding analytes and aromatic isomers.

    Science.gov (United States)

    Yang, Xiaohong; Han, Ying; Qi, Meiling; Chen, Chuanfeng

    2016-05-06

    Unique structures and molecular recognition ability endow iptycene derivatives with great potential as stationary phases in chromatography, which, however, has not been explored yet. Herein, we report the first example of utilizing a pentiptycene quinone (PQ) for gas chromatographic (GC) separations. Remarkably, the statically coated capillary column with the stationary phase achieved extremely high column efficiency of 4800 plates/m. It exhibited preferential retention and high resolving capability for H-bonding and aromatic analytes and positional isomers, showing advantages over the ordinary polysiloxane phase. Moreover, the fabricated iptycene column showed excellent separation repeatability with RSD values of 0.02-0.06% for intra-day, 0.20-0.35% for inter-day and 3.1-5.5% for between-column, respectively. In conclusion, iptycene derivatives as a new class of stationary phases show promising future for their use in GC separations. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Chiral chromatography studies of chemical behavior of cinacalcet on polysaccharide chiral reversed-phase HPLC stationary phases.

    Science.gov (United States)

    Dousa, Michal; Brichác, Jirí

    2012-01-01

    A rapid HPLC method for the analytical resolution of cinacalcet enantiomers was developed. Four chiral columns (two amylose and two cellulose type) were evaluated in RP systems. Excellent enantioseparation with a resolution of more than 6 was achieved on Chiralpak AY (amylose 5-chloro-2-methylphenylcarbamate chiral stationary phase) using 10 mM triethylamine (pH 8.0)-acetonitrile (40 + 60, v/v) mobile phase. Validation of the HPLC method, including linearity, LOD, LOQ, precision, accuracy, and selectivity, was performed according to the International Conference on Harmonization guidelines. The method was successfully applied for the determination of (S)-cinacalcet in enantiopure active pharmaceutical ingredient (R)-cinacalcet.

  14. Stationary phases for superheated water chromatography

    International Nuclear Information System (INIS)

    Saha, Shikha

    2002-01-01

    This project focused on the comparison of conventional liquid chromatography and superheated water chromatography. It examined the differences in efficiency and retention of a range of different stationary phases. Alkyl aryl ketones and eight aromatic compounds were separated on PBD-zirconia, Xterra RP 18, Luna C 18 (2) and Oasis HLB columns using conventional LC and superheated water chromatography system. The retention indices were determined in the different eluents. On changing the organic component of the eluent from methanol to acetonitrile to superheated water considerable improvements were found in the peak shapes and column efficiencies on the PBD-zirconia and Oasis HLB columns. PS-DVB, PBD-zirconia and Xterra RP 18 columns have been used in efficiency studies. It was found that simply elevating the column temperature did not increase the efficiency of a separation in superheated water chromatography. The efficiency depended on flow rate, injection volume and also mobile phase preheating system. Although high efficiencies were not achieved with superheated water on PS-DVB and Xterra RP 18 columns, a higher efficiency was achieved on a PBD-zirconia column with superheated water than with 25-35% ACN at room temperature. The proposed theoretical increases in u opt were measured on three columns using superheated water as the mobile phase. The application of the superheated water chromatographic method to the separation of the pungent constituents of ginger by superheated water chromatography-NMR coupling system was studied. The coupling of superheated water chromatography using deuterium oxide to NMR spectroscopy for the separation of dry ginger extract was successful, although the NMR sensitivity in on-line mode coupling system was low. However, four compounds were identified in the ginger extract by stop-flow mode on superheated water chromatography-UV-NMR detection system. (author)

  15. Role of nutrient limitation and stationary-phase existence in Klebsiella pneumoniae biofilm resistance to ampicillin and ciprofloxacin.

    Science.gov (United States)

    Anderl, Jeff N; Zahller, Jeff; Roe, Frank; Stewart, Philip S

    2003-04-01

    Biofilms formed by Klebsiella pneumoniae resisted killing during prolonged exposure to ampicillin or ciprofloxacin even though these agents have been shown to penetrate bacterial aggregates. Bacteria dispersed from biofilms into medium quickly regained most of their susceptibility. Experiments with free-floating bacteria showed that stationary-phase bacteria were protected from killing by either antibiotic, especially when the test was performed in medium lacking carbon and nitrogen sources. These results suggested that the antibiotic tolerance of biofilm bacteria could be explained by nutrient limitation in the biofilm leading to stationary-phase existence of at least some of the cells in the biofilm. This mechanism was supported by experimental characterization of nutrient availability and growth status in biofilms. The average specific growth rate of bacteria in biofilms was only 0.032 h(-1) compared to the specific growth rate of planktonic bacteria of 0.59 h(-1) measured in the same medium. Glucose did not penetrate all the way through the biofilm, and oxygen was shown to penetrate only into the upper 100 micro m. The specific catalase activity was elevated in biofilm bacteria to a level similar to that of stationary-phase planktonic cells. Transmission electron microscopy revealed that bacteria were affected by ampicillin near the periphery of the biofilm but were not affected in the interior. Taken together, these results indicate that K. pneumoniae in this system experience nutrient limitation locally within the biofilm, leading to zones in which the bacteria enter stationary phase and are growing slowly or not at all. In these inactive regions, bacteria are less susceptible to killing by antibiotics.

  16. Growth potential of exponential- and stationary-phase Salmonella Typhimurium during sausage fermentation

    DEFF Research Database (Denmark)

    Birk, Tina; Henriksen, Sidsel; Müller, K.

    2016-01-01

    - and stationary-phase Salmonella Typhimurium (DT12 and DTU292) during freezing at − 18 °C and their subsequent growth potential during 72 h sausage fermentation at 25 °C. After 0, 7 and > 35 d of frozen storage, sausage batters were prepared with NaCl (3%) and NaNO2 (0, 100 ppm) and fermented with and without...

  17. Prolonged Stationary-Phase Incubation Selects for lrp Mutations in Escherichia coli K-12

    Science.gov (United States)

    Zinser, Erik R.; Kolter, Roberto

    2000-01-01

    Evolution by natural selection occurs in cultures of Escherichia coli maintained under carbon starvation stress. Mutants of increased fitness express a growth advantage in stationary phase (GASP) phenotype, enabling them to grow and displace the parent as the majority population. The first GASP mutation was identified as a loss-of-function allele of rpoS, encoding the stationary-phase global regulator, ςS (M. M. Zambrano, D. A. Siegele, M. A. Almirón, A. Tormo, and R. Kolter, Science 259:1757–1760, 1993). We now report that a second global regulator, Lrp, can also play a role in stationary-phase competition. We found that a mutant that took over an aged culture of an rpoS strain had acquired a GASP mutation in lrp. This GASP allele, lrp-1141, encodes a mutant protein lacking the critical glycine in the turn of the helix-turn-helix DNA-binding domain. The lrp-1141 allele behaves as a null mutation when in single copy and is dominant negative when overexpressed. Hence, the mutant protein appears to retain stability and the ability to dimerize but lacks DNA-binding activity. We also demonstrated that a lrp null allele generated by a transposon insertion has a fitness gain identical to that of the lrp-1141 allele, verifying that cells lacking Lrp activity have a competitive advantage during prolonged starvation. Finally, we tested by genetic analysis the hypothesis that the lrp-1141 GASP mutation confers a fitness gain by enhancing amino acid catabolism during carbon starvation. We found that while amino acid catabolism may play a role, it is not necessary for the lrp GASP phenotype, and hence the lrp GASP phenotype is due to more global physiological changes. PMID:10894750

  18. Kinetic modeling of sporulation and product formation in stationary phase by Bacillus coagulans RK-02 vis-à-vis other Bacilli.

    Science.gov (United States)

    Das, Subhasish; Sen, Ramkrishna

    2011-10-01

    A logistic kinetic model was derived and validated to characterize the dynamics of a sporogenous bacterium in stationary phase with respect to sporulation and product formation. The kinetic constants as determined using this model are particularly important for describing intrinsic properties of a sporogenous bacterial culture in stationary phase. Non-linear curve fitting of the experimental data into the mathematical model showed very good correlation with the predicted values for sporulation and lipase production by Bacillus coagulans RK-02 culture in minimal media. Model fitting of literature data of sporulation and product (protease and amylase) formation in the stationary phase by some other Bacilli and comparison of the results of model fitting with those of Bacillus coagulans helped validate the significance and robustness of the developed kinetic model. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Immunoassay of paralytic shellfish toxins by moving magnetic particles in a stationary liquid-phase lab-on-a-chip.

    Science.gov (United States)

    Kim, Myoung-Ho; Choi, Suk-Jung

    2015-04-15

    In this study, we devised a stationary liquid-phase lab-on-a-chip (SLP LOC), which was operated by moving solid-phase magnetic particles in the stationary liquid phase. The SLP LOC consisted of a sample chamber to which a sample and reactants were added, a detection chamber containing enzyme substrate solution, and a narrow channel connecting the two chambers and filled with buffer. As a model system, competitive immunoassays of saxitoxin (STX), a paralytic shellfish toxin, were conducted in the SLP LOC using protein G-coupled magnetic particles (G-MPs) as the solid phase. Anti-STX antibodies, STX-horseradish peroxidase conjugate, G-MPs, and a STX sample were added to the sample chamber and reacted by shaking. While liquids were in the stationary state, G-MPs were transported from the sample chamber to the detection chamber by moving a magnet below the LOC. After incubation to allow the enzymatic reaction to occur, the absorbance of the detection chamber solution was found to be reciprocally related to the STX concentration of the sample. Thus, the SLP LOC may represent a novel, simple format for point-of-care testing applications of enzyme-linked immunosorbent assays by eliminating complicated liquid handling steps. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Reversed phase liquid chromatography with UV absorbance and flame ionization detection using a water mobile phase and a cyano propyl stationary phase Analysis of alcohols and chlorinated hydrocarbons.

    Science.gov (United States)

    Quigley, W W; Ecker, S T; Vahey, P G; Synovec, R E

    1999-10-01

    The development of liquid chromatography with a commercially available cyano propyl stationary phase and a 100% water mobile phase is reported. Separations were performed at ambient temperature, simplifying instrumental requirements. Excellent separation efficiency using a water mobile phase was achieved, for example N=18 800, or 75 200 m(-1), was obtained for resorcinol, at a retention factor of k'=4.88 (retention time of 9.55 min at 1 ml min(-1) for a 25 cmx4.6 mm i.d. column, packed with 5 mum diameter particles with the cyano propyl stationary phase). A separation via reversed phase liquid chromatography (RP-LC) with a 100% water mobile phase of six phenols and related compounds was compared to a separation of the same compounds by traditional RP-LC, using octadecylsilane (ODS), i.e. C18, bound to silica and an aqueous mobile phase modified with acetonitrile. Nearly identical analysis time was achieved for the separation of six phenols and related compounds using the cyano propyl stationary phase with a 100% water mobile phase, as compared to traditional RP-LC requiring a relatively large fraction of organic solvent modifier in the mobile phase (25% acetonitrile:75% water). Additional understanding of the retention mechanism with the 100% water mobile phase was obtained by relating measured retention factors of aliphatic alcohols, phenols and related compounds, and chlorinated hydrocarbons to their octanol:water partition coefficients. The retention mechanism is found to be consistent with a RP-LC mechanism coupled with an additional retention effect due to residual hydroxyl groups on the cyano propyl stationary phase. Advantages due to a 100% water mobile phase for the chemical analysis of alcohol mixtures and chlorinated hydrocarbons are reported. By placing an absorbance detector in-series and preceding a novel drop interface to a flame ionization detector (FID), selective detection of a separated mixture of phenols and related compounds and aliphatic

  1. Transcriptional Characterization of Salmonella TAl00 in Growth and Stationary Phase: Mutagenesis of MX in Both Types of Cells

    Science.gov (United States)

    The Salmonella (Ames) mutagenicity assay can be performed using cells that are in different growth phases. Thus, the plate-incorporation assay involves plating stationary-phase cells with the mutagen, after which the cells undergo a brief lag phase and, consequently, are exposed ...

  2. Mutations Enhancing Amino Acid Catabolism Confer a Growth Advantage in Stationary Phase

    Science.gov (United States)

    Zinser, Erik R.; Kolter, Roberto

    1999-01-01

    Starved cultures of Escherichia coli undergo successive rounds of population takeovers by mutants of increasing fitness. These mutants express the growth advantage in stationary phase (GASP) phenotype. Previous work identified the rpoS819 allele as a GASP mutation allowing cells to take over stationary-phase cultures after growth in rich media (M. M. Zambrano, D. A. Siegele, M. A. Almirón, A. Tormo, and R. Kolter, Science 259:1757–1760, 1993). Here we have identified three new GASP loci from an aged rpoS819 strain: sgaA, sgaB, and sgaC. Each locus is capable of conferring GASP on the rpoS819 parent, and they can provide successively higher fitnesses for the bacteria in the starved cultures. All four GASP mutations isolated thus far allow for faster growth on both individual and mixtures of amino acids. Each mutation confers a growth advantage on a different subset of amino acids, and these mutations act in concert to increase the overall catabolic capacity of the cell. We present a model whereby this enhanced ability to catabolize amino acids is responsible for the fitness gain during carbon starvation, as it may allow GASP mutants to outcompete the parental cells when growing on the amino acids released by dying cells. PMID:10482523

  3. Comparison of core-shell and totally porous ultra high performance liquid chromatographic stationary phases based on their selectivity towards alfuzosin compounds.

    Science.gov (United States)

    Szulfer, Jarosław; Plenis, Alina; Bączek, Tomasz

    2014-06-13

    This paper focuses on the application of a column classification system based on the Katholieke Universiteit Leuven for the characterization of physicochemical properties of core-shell and ultra-high performance liquid chromatographic stationary phases, followed by the verification of the reliability of the obtained column classification in pharmaceutical practice. In the study, 7 stationary phases produced in core-shell technology and 18 ultra-high performance liquid chromatographic columns were chromatographically tested, and ranking lists were built on the FKUL-values calculated against two selected reference columns. In the column performance test, an analysis of alfuzosin in the presence of related substances was carried out using the brands of the stationary phases with the highest ranking positions. Next, a system suitability test as described by the European Pharmacopoeia monograph was performed. Moreover, a study was also performed to achieve a purposeful shortening of the analysis time of the compounds of interest using the selected stationary phases. Finally, it was checked whether methods using core-shell and ultra-high performance liquid chromatographic columns can be an interesting alternative to the high-performance liquid chromatographic method for the analysis of alfuzosin in pharmaceutical practice. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Increments to chiral recognition facilitating enantiomer separations of chiral acids, bases, and ampholytes using Cinchona-based zwitterion exchanger chiral stationary phases.

    Science.gov (United States)

    Wernisch, Stefanie; Pell, Reinhard; Lindner, Wolfgang

    2012-07-01

    The intramolecular distances of anion and cation exchanger sites of zwitterionic chiral stationary phases represent potential tuning sites for enantiomer selectivity. In this contribution, we investigate the influence of alkanesulfonic acid chain length and flexibility on enantiomer separations of chiral acids, bases, and amphoteric molecules for six Cinchona alkaloid-based chiral stationary phases in comparison with structurally related anion and cation exchangers. Employing polar-organic elution conditions, we observed an intramolecular counterion effect for acidic analytes which led to reduced retention times but did not impair enantiomer selectivities. Retention of amphoteric analytes is based on simultaneous double ion pairing of their charged functional groups with the acidic and basic sites of the zwitterionic selectors. A chiral center in the vicinity of the strong cation exchanger site is vital for chiral separations of bases. Sterically demanding side chains are beneficial for separations of free amino acids. Enantioseparations of free (un-derivatized) peptides were particularly successful in stationary phases with straight-chain alkanesulfonic acid sites, pointing to a beneficial influence of more flexible moieties. In addition, we observed pseudo-enantiomeric behavior of quinine and quinidine-derived chiral stationary phases facilitating reversal of elution orders for all analytes. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A new imidazolium-embedded C{sub 18} stationary phase with enhanced performance in reversed-phase liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Qiu Hongdeng [Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Lanzhou Institute of Chemical Physics, Chinese Academy of Science, Lanzhou 730000 (China); Mallik, Abul K. [Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Takafuji, Makoto [Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kumamoto Institute for Photo-Electro Organics (Phoenics), Kumamoto 862-0901 (Japan); Liu Xia; Jiang Shengxiang [Lanzhou Institute of Chemical Physics, Chinese Academy of Science, Lanzhou 730000 (China); Ihara, Hirotaka, E-mail: ihara@kumamoto-u.ac.jp [Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555 (Japan); Kumamoto Institute for Photo-Electro Organics (Phoenics), Kumamoto 862-0901 (Japan)

    2012-08-13

    Highlights: Black-Right-Pointing-Pointer Imidazolium-embedded C{sub 18} stationary phase was prepared and characterized. Black-Right-Pointing-Pointer Enhanced chromatographic selectivity was observed in SiImC{sub 18} column. Black-Right-Pointing-Pointer Seven nucleosides and bases were separated using only water as eluent within 8 min. Black-Right-Pointing-Pointer Multiple-interactions induced by embedded polar imidazolium was investigated. - Abstract: In this paper, a new imidazolium-embedded C{sub 18} stationary phase (SiImC{sub 18}) for reversed-phase high-performance liquid chromatography is described. 1-Allyl-3-octadecylimidazolium bromide ionic liquid compound having a long alkyl chain and reactive groups was newly prepared and grafted onto 3-mercaptopropyltrimethoxysilane-modified silica via a surface-initiated radical-chain transfer addition reaction. The SiImC{sub 18} obtained was characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, diffuse reflectance infrared Fourier transform, and solid-state {sup 13}C and {sup 29}Si cross-polarization/magic angle spinning nuclear magnetic resonance spectroscopy. The selectivity toward polycyclic aromatic hydrocarbons relative to that toward alkylbenzenes exhibited by SiImC{sub 18} was higher than the corresponding selectivity exhibited by a conventional octadecyl silica (ODS) column, which could be explained by electrostatic {pi}-{pi} interaction cationic imidazolium and electron-rich aromatic rings. On the other hand, SiImC{sub 18} also showed high selectivity for polar compounds, which was based on the multiple interaction and retention mechanisms of this phase with different analytes. 1,6-Dinitropyrene and 1,8-dinitropyrene, which form a positional isomer pair of dipolar compounds, were separated successfully with the SiImC{sub 18} phase. Seven nucleosides and bases (i.e. cytidine, uracil, uridine, thymine, guanosine, xanthosine, and adenosine) were separated using only water as

  6. Quantitation of anticonvulsant drugs in serum by gas-chromatography on the stationary phase SP-2510.

    Science.gov (United States)

    Godolphin, W; Thoma, J

    1978-03-01

    A new column packing, SP-2510 DA (Supelco, Inc., Bellefonte, Pa. 16823), is an excellent stationary phase for the determination of a wide variety of anticonvulsant drugs by gas--liquid chromatography without derivatization. However, when uncomplicated extraction procedures are used, serum cholesterol interferes with the determination of primidone. By the simple expedient of adding a short "pre-column" containing another phase (SP-2250 DA) the problem is overcome.

  7. Multi-mode application of graphene quantum dots bonded silica stationary phase for high performance liquid chromatography.

    Science.gov (United States)

    Wu, Qi; Sun, Yaming; Zhang, Xiaoli; Zhang, Xia; Dong, Shuqing; Qiu, Hongdeng; Wang, Litao; Zhao, Liang

    2017-04-07

    Graphene quantum dots (GQDs), which possess hydrophobic, hydrophilic, π-π stacking and hydrogen bonding properties, have great prospect in HPLC. In this study, a novel GQDs bonded silica stationary phase was prepared and applied in multiple separation modes including normal phase, reversed phase and hydrophilic chromatography mode. Alkaloids, nucleosides and nucleobases were chosen as test compounds to evaluate the separation performance of this column in hydrophilic chromatographic mode. The tested polar compounds achieved baseline separation and the resolutions reached 2.32, 4.62, 7.79, 1.68 for thymidine, uridine, adenosine, cytidine and guanosine. This new column showed satisfactory chromatographic performance for anilines, phenols and polycyclic aromatic hydrocarbons in normal and reversed phase mode. Five anilines were completely separated within 10min under the condition of mobile phase containing only 10% methanol. The effect of water content, buffer concentration and pH on chromatographic separation was further investigated, founding that this new stationary phase showed a complex retention mechanism of partitioning, adsorption and electrostatic interaction in hydrophilic chromatography mode, and the multiple retention interactions such as π-π stacking and π-π electron-donor-acceptor interaction played an important role during the separation process. This GQDs bonded column, which allows us to adjust appropriate chromatography mode according to the properties of analytes, has possibility in actual application after further research. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Thin-layer chromatography with stationary phase gradient as a method for separation of water-soluble vitamins.

    Science.gov (United States)

    Cimpoiu, Claudia; Hosu, Anamaria; Puscas, Anitta

    2012-02-03

    The group of hydrophilic vitamins play an important role in human health, and their lack or excess produces specific diseases. Therefore, the analysis of these compounds is indispensable for monitoring their content in pharmaceuticals and food in order to prevent some human diseases. TLC was successfully applied in the analysis of hydrophilic vitamins, but the most difficult problem in the simultaneous analysis of all these compounds is to find an optimum stationary phase-mobile phase system due to different chemical characteristics of analytes. Unfortunately structural analogues are difficult to separate in one chromatographic run, and this is the case in hydrophilic vitamins investigations. TLC gives the possibility to perform two-dimensional separations by using stationary phase gradient achieving the highest resolution by combining two systems with different selectivity. The goal of this work was to develop a method of analysis enabling separation of hydrophilic vitamins using TLC with adsorbent gradient. The developed method was used for identifying the water-soluble vitamins in alcoholic extracts of Hippophae rhamnoides and of Ribes nigrum. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Copolymerization preparation of cationic cyclodextrin chiral stationary phases for drug enantioseparation in chromatography

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Ren-Qi Wang, Teng-Teng Ong, Ke Huang, Weihua Tang & Siu-Choon Ng ### Abstract We described a facile and effective protocol wherein radical copolymerization is employed to covalently bond cationic β-cyclodextrin (β-CD) onto silica particles with extended linkage, resulting in a chiral stationary phase (IMPCSP) that can be used for the enantioseparation of racemic drugs in both high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). Starting ...

  10. Bacteriophage T4 Infection of Stationary Phase E. coli: Life after Log from a Phage Perspective

    Directory of Open Access Journals (Sweden)

    Elizabeth Martin Kutter

    2016-09-01

    Full Text Available Virtually all studies of phage infections investigate bacteria growing exponentially in rich media. In nature, however, phages largely encounter non-growing cells. Bacteria entering stationary phase often activate well-studied stress defense mechanisms that drastically alter the cell, facilitating its long-term survival. An understanding of phage-host interactions in such conditions is of major importance from both an ecological and therapeutic standpoint. Here, we show that bacteriophage T4 can efficiently bind to, infect and kill E. coli in stationary phase, both in the presence and absence of a functional stationary-phase sigma factor, and explore the response of T4-infected stationary phase cells to the addition of fresh nutrients 5 or 24 hours after that infection. An unexpected new mode of response has been identified. Hibernation mode is a persistent but reversible dormant state in which the infected cells make at least some phage enzymes, but halt phage development until appropriate nutrients become available before producing phage particles. Our evidence indicates that the block in hibernation mode occurs after the middle-mode stage of phage development; host DNA breakdown and the incorporation of the released nucleotides into phage DNA indicate that the enzymes of the nucleotide synthesizing complex, under middle-mode control, have been made and assembled into a functional state. Once fresh glucose and amino acids become available, the standard lytic infection process rapidly resumes and concentrations of up to 1011 progeny phage (an average of about 40 phage per initially-present cell are produced. All evidence is consistent with the hibernation-mode control point lying between middle mode and late mode T4 gene expression. We have also observed a scavenger response, where the infecting phage takes advantage of whatever few nutrients are available to produce small quantities of progeny within 2 to 5 hours after infection. The scavenger

  11. Characterization of bonded stationary phase performance as a function of qualitative and quantitative chromatographic factors in chaotropic chromatography with risperidone and its impurities as model substances.

    Science.gov (United States)

    Čolović, Jelena; Rmandić, Milena; Malenović, Anđelija

    2018-05-17

    Numerous stationary phases have been developed with the aim to provide desired performances during chromatographic analysis of the basic solutes in their protonated form. In this work, the procedure for the characterization of bonded stationary phase performance, when both qualitative and quantitative chromatographic factors were varied in chaotropic chromatography, was proposed. Risperidone and its three impurities were selected as model substances, while acetonitrile content in the mobile phase (20-30%), the pH of the aqueous phase (3.00-5.00), the content of chaotropic agents in the aqueous phase (10-100 mM), type of chaotropic agent (NaClO 4 , CF 3 COONa), and stationary phase type (Zorbax Eclipse XDB, Zorbax Extend) were studied as chromatographic factors. The proposed procedure implies the combination of D-optimal experimental design, indirect modeling, and polynomial-modified Gaussian model, while grid point search method was selected for the final choice of the experimental conditions which lead to the best possible stationary phase performance for basic solutes. Good agreement between experimentally obtained chromatogram and simulated chromatogram for chosen experimental conditions (25% acetonitrile, 75 mM of NaClO 4 , pH 4.00 on Zorbax Eclipse XDB column) confirmed the applicability of the proposed procedure. The additional point was selected for the verification of proposed procedure ability to distinguish changes in solutes' elution order. Simulated chromatogram for 21.5% acetonitrile, 85 mM of NaClO 4 , pH 5.00 on Zorbax Eclipse XDB column was in line with experimental data. Furthermore, the values of left and right peak half-widths obtained from indirect modeling were used in order to evaluate performances of differently modified stationary phases applying a half-width plots approach. The results from half-width plot approach as well as from the proposed procedure indicate higher efficiency and better separation performance of the stationary phase

  12. Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure.

    Science.gov (United States)

    Yui, Yuko; Miyazaki, Shota; Ma, Yan; Ohira, Masayoshi; Fiehn, Oliver; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

    2016-06-10

    Separation of diastereomers of dl-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3mmID, 20cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic dl-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0°C, 536bar, while three peaks were observed when the separation was carried out either at 12.0°C at low pressure or at 20°C at 488bar. Higher temperature (30.0°C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0°C and 441bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0°C and 463bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of dl-α-tocopherol. Copyright © 2016. Published by Elsevier B.V.

  13. Preparation of a novel dual-function strong cation exchange/hydrophobic interaction chromatography stationary phase for protein separation.

    Science.gov (United States)

    Zhao, Kailou; Yang, Li; Wang, Xuejiao; Bai, Quan; Yang, Fan; Wang, Fei

    2012-08-30

    We have explored a novel dual-function stationary phase which combines both strong cation exchange (SCX) and hydrophobic interaction chromatography (HIC) characteristics. The novel dual-function stationary phase is based on porous and spherical silica gel functionalized with ligand containing sulfonic and benzyl groups capable of electrostatic and hydrophobic interaction functionalities, which displays HIC character in a high salt concentration, and IEC character in a low salt concentration in mobile phase employed. As a result, it can be employed to separate proteins with SCX and HIC modes, respectively. The resolution and selectivity of the dual-function stationary phase were evaluated under both HIC and SCX modes with standard proteins and can be comparable to that of conventional IEC and HIC columns. More than 96% of mass and bioactivity recoveries of proteins can be achieved in both HIC and SCX modes, respectively. The results indicated that the novel dual-function column could replace two individual SCX and HIC columns for protein separation. Mixed retention mechanism of proteins on this dual-function column based on stoichiometric displacement theory (SDT) in LC was investigated to find the optimal balance of the magnitude of electrostatic and hydrophobic interactions between protein and the ligand on the silica surface in order to obtain high resolution and selectivity for protein separation. In addition, the effects of the hydrophobicity of the ligand of the dual-function packings and pH of the mobile phase used on protein separation were also investigated in detail. The results show that the ligand with suitable hydrophobicity to match the electrostatic interaction is very important to prepare the dual-function stationary phase, and a better resolution and selectivity can be obtained at pH 6.5 in SCX mode. Therefore, the dual-function column can replace two individual SCX and HIC columns for protein separation and be used to set up two-dimensional liquid

  14. Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure.

    Science.gov (United States)

    Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

    2014-04-25

    A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Retention behavior of resorcinarene-based cavitands on C8 and C18 stationary phases.

    Science.gov (United States)

    Bartó, Endre; Prauda, Ibolya; Kilár, Ferenc; Kiss, Ibolya; Felinger, Attila

    2015-09-01

    The understanding of the retention behavior of large molecules is an area of interest in liquid chromatography. Resorcinarene-based cavitands are cavity-shaped cyclic oligomers that can create host-guest interactions. We have investigated the chromatographic behavior of two types of cyclic tetramers as analytes in high-performance liquid chromatography. The experiments were performed at four different temperatures (15, 25, 35, 45°C) on two types of reversed stationary phases (C8 and C18 ) from two different manufacturers. We have found a huge difference between the retention of resorcinarenes and cavitands. In some cases, the retention factor of cavitands was even a hundred times larger than the retention factor of resorcinarenes. The retention of methylated derivates was two to four times larger compared to that of demethylated compounds on every column. The opposite retention behavior of the resorcinarenes and cavitands on the two types of stationary phases showed well the difference of the selectivity of the XTerra and BDS Hypersil columns. The retention mechanism was studied by the thermodynamic parameters calculated from the van't Hoff equation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Preparation and evaluation of surface-bonded tricationic ionic liquid silica as stationary phases for high-performance liquid chromatography.

    Science.gov (United States)

    Qiao, Lizhen; Shi, Xianzhe; Lu, Xin; Xu, Guowang

    2015-05-29

    Two tricationic ionic liquids were prepared and then bonded onto the surface of supporting silica materials through "thiol-ene" click chemistry as new stationary phases for high-performance liquid chromatography. The obtained columns of tricationic ionic liquids were evaluated respectively in the reversed-phase liquid chromatography (RPLC) mode and hydrophilic interaction liquid chromatography (HILIC) mode, and possess ideal column efficiency of 80,000 plates/m in the RPLC mode with naphthalene as the test solute. The tricationic ionic liquid stationary phases exhibit good hydrophobic and shape selectivity to hydrophobic compounds, and RPLC retention behavior with multiple interactions. In the HILIC mode, the retention and selectivity were evaluated through the efficient separation of nucleosides and bases as well as flavonoids, and the typical HILIC retention behavior was demonstrated by investigating retention changes of hydrophilic solutes with water volume fraction in mobile phase. The results show that the tricationic ionic liquid columns possess great prospect for applications in analysis of hydrophobic and hydrophilic samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Molecular theory of chromatography for blocklike solutes in isotropic stationary phases and its application to supercritical fluid chromatographic retention of PAHs

    International Nuclear Information System (INIS)

    Chao Yan; Martire, D.E.

    1992-01-01

    This report discusses a molecular theory of chromatography for blocklike solutes in isotropic stationary phases as an extension to the anisotopic phase approach. Its it applied to gas, liquid, and supercritical fluid chromatography

  18. Synthesis and characterization of a novel stationary phase, Si-Zr/Ti(PMTDS), based upon ternary oxide support for high performance liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Amparo, Maura R.; Marques, Fabiana A.; Faria, Anizio M., E-mail: anizio@pontal.ufu.br [Universidade Federal de Uberlandia (FACIP/UFU), Ituiutaba, MG (Brazil). Faculdade de Ciencias Integradas do Pontal

    2013-09-15

    A new stationary phase based on the thermal immobilization of poly(methyltetradecylsiloxane) (PMTDS) on silica particles coated with a mixture of zirconia and titania was prepared and evaluated for the chromatographic separation of test mixtures. The spherical particles were characterized by elemental analysis, SEM, FTIR and {sup 29}Si NMR. The physicochemical properties of PMTDS phase supported on Si-Zr/Ti were intermediate between PMTDS phases supported on titanized silica and zirconized silica. The chromatographic performance of Si-Zr/Ti(PMTDS) phase was similar to PMTDS phases based on metal oxide coated silica having only one metal oxide and the preparation of a Si-Zr/Ti(PMTDS) phase allowed evaluation of the effect of each oxide, zirconia and titania, on the separation process and on the stability of the immobilized polymer phase. The hydrolytic stability of Si-Zr/Ti(PMTDS) stationary phase was similar to the Si-Ti(PMTDS) phase, improving the chemical stability of the silica-based PMTDS phase by about 100%. (author)

  19. Determination of carbofuran on hydrophilic interaction liquid chromatography using TSK gel amide 80 as stationary phase

    International Nuclear Information System (INIS)

    A Kurnia; LW Lim; T Takeuchi

    2016-01-01

    The hydrophilic interaction liquid chromatography (HILIC) coupled to environmental friendly capillary liquid chromatography was employed to investigate retention behavior of carbofuran. Aim of this research is to investigate retention behavior of carbofuran using TSK gel amide 80 as stationary phase. Several condition was conducted to investigate retention behavior of carbofuran such as comparison study of TSK gel amide 80 with other polar column, comparison study retention behavior of carbofuran on various system wavelength, water content effect in HILIC mode, effect of buffer concentration on HILIC mode, and analytical performance. Results showed that TSK gel imidazole was superior compare to other polar stationary phase on determine carbofuran, wavelength 251 and 254 nm was resulting higher absorbance for carbofuran than others, increase of water content on mobile phase was decrease the retention time, also increase buffer salt concentration was decrease the retention time and according to analysis performance that is the accuracy was 101±10,1, the LOD 0.66 ppm while LOQ 2.22 ppm. As conclusions that TSK gel amide 80 was offering good determine on carbofuran even using capillary liquid chromatography with 10 cm length of column. (author)

  20. Heat-shock induction of ionizing radiation resistance in Saccharomyces cerevisiae, and the correlation with stationary growth phase

    International Nuclear Information System (INIS)

    Mitchel, R.E.J.; Morrison, D.P.

    1982-01-01

    Radiation resistance and thermal resistance vary as a function of culture temperature in logarithmically growing Saccharomyces cerevisiae and are related to the optimum temperature for growth. Radiation resistance and thermal resistance were also induced when cells grown at low temperatures were subjected to a heat shock at or above the optimum growth temperature. Exposure to ionizing radiation followed by a short incubation at low temperature also induced resistance to killing by heat. Heat-shocked cells are induced to a level of thermal and radioresistance much greater than the characteristic resistance level of cells grown continuously at the shock temperature. This high level of resistance, which resembles that of stationary-phase cells, decays to the characteristic log-phase level within one doubling of cell number after the heat shock. Both induction of resistance and decay of that induction require protein synthesis. It is postulated that induction of resistance by heat shock or ionizing radiation is a response of the cells to stress and represents a preparation to enter stationary phase

  1. Changes in pyridine metabolism profile during growth of trigonelline-forming Lotus japonicus cell cultures.

    Science.gov (United States)

    Yin, Yuling; Matsui, Ayu; Sakuta, Masaaki; Ashihara, Hiroshi

    2008-12-01

    Changes in the profile of pyridine metabolism during growth of cells were investigated using trigonelline-forming suspension-cultured cells of Lotus japonicus. Activity of the de novo and salvage pathways of NAD biosynthesis was estimated from the in situ metabolism of [(3)H] quinolinic acid and [(14)C] nicotinamide. Maximum activity of the de novo pathway for NAD synthesis was found in the exponential growth phase, whereas activity of the salvage pathway was increased in the lag phase of cell growth. Expression profiles of some genes related to pyridine metabolism were examined using the expression sequence tags obtained from the L. japonicus database. Transcript levels of NaPRT and NIC, encoding salvage enzymes, were enhanced in the lag phase of cell growth, whereas the maximum expression of NADS was found in the exponential growth phase. Correspondingly, the activities of the salvage enzymes, nicotinate phosphoribosyltransferase (EC 2.4.2.11) and nicotinamidase (EC 3.5.1.19), increased one day after transfer of the stationary phase cells to the fresh medium. The greatest in situ trigonelline synthesis, both from [(3)H] quinolinic acid and [(14)C] nicotinamide, was found in the stationary phase of cell growth. The role of trigonelline in leguminous plants is discussed.

  2. Phase 0 and phase III transport in various organs: combined concept of phases in xenobiotic transport and metabolism.

    Science.gov (United States)

    Döring, Barbara; Petzinger, Ernst

    2014-08-01

    The historical phasing concept of drug metabolism and elimination was introduced to comprise the two phases of metabolism: phase I metabolism for oxidations, reductions and hydrolyses, and phase II metabolism for synthesis. With this concept, biological membrane barriers obstructing the accessibility of metabolism sites in the cells for drugs were not considered. The concept of two phases was extended to a concept of four phases when drug transporters were detected that guided drugs and drug metabolites in and out of the cells. In particular, water soluble or charged drugs are virtually not able to overcome the phospholipid membrane barrier. Drug transporters belong to two main clusters of transporter families: the solute carrier (SLC) families and the ATP binding cassette (ABC) carriers. The ABC transporters comprise seven families with about 20 carriers involved in drug transport. All of them operate as pumps at the expense of ATP splitting. Embedded in the former phase concept, the term "phase III" was introduced by Ishikawa in 1992 for drug export by ABC efflux pumps. SLC comprise 52 families, from which many carriers are drug uptake transporters. Later on, this uptake process was referred to as the "phase 0 transport" of drugs. Transporters for xenobiotics in man and animal are most expressed in liver, but they are also present in extra-hepatic tissues such as in the kidney, the adrenal gland and lung. This review deals with the function of drug carriers in various organs and their impact on drug metabolism and elimination.

  3. Morphological and quantitative changes in mitochondria, plastids, and peroxisomes during the log-to-stationary transition of the growth phase in cultured tobacco BY-2 cells.

    Science.gov (United States)

    Toyooka, Kiminori; Sato, Mayuko; Wakazaki, Mayumi; Matsuoka, Ken

    2016-01-01

    We developed a wide-range and high-resolution transmission electron microscope acquisition system and obtained giga-pixel images of tobacco BY-2 cells during the log and stationary phases of cell growth. We demonstrated that the distribution and ultrastructure of compartments involved in membrane traffic (i.e., Golgi apparatus, multivesicular body, and vesicle cluster) change during the log-to-stationary transition. Mitochondria, peroxisomes, and plastids were also enumerated. Electron densities of mitochondria and peroxisomes were altered during the growth-phase shift, while their numbers were reduced by nearly half. Plastid structure dramatically changed from atypical to spherical with starch granules. Nearly the same number of plastids was observed in both log and stationary phases. These results indicate that mechanisms regulating organelle populations differ from organelle to organelle.

  4. Chiral stationary phase optimized selectivity liquid chromatography: A strategy for the separation of chiral isomers.

    Science.gov (United States)

    Hegade, Ravindra Suryakant; De Beer, Maarten; Lynen, Frederic

    2017-09-15

    Chiral Stationary-Phase Optimized Selectivity Liquid Chromatography (SOSLC) is proposed as a tool to optimally separate mixtures of enantiomers on a set of commercially available coupled chiral columns. This approach allows for the prediction of the separation profiles on any possible combination of the chiral stationary phases based on a limited number of preliminary analyses, followed by automated selection of the optimal column combination. Both the isocratic and gradient SOSLC approach were implemented for prediction of the retention times for a mixture of 4 chiral pairs on all possible combinations of the 5 commercial chiral columns. Predictions in isocratic and gradient mode were performed with a commercially available and with an in-house developed Microsoft visual basic algorithm, respectively. Optimal predictions in the isocratic mode required the coupling of 4 columns whereby relative deviations between the predicted and experimental retention times ranged between 2 and 7%. Gradient predictions led to the coupling of 3 chiral columns allowing baseline separation of all solutes, whereby differences between predictions and experiments ranged between 0 and 12%. The methodology is a novel tool allowing optimizing the separation of mixtures of optical isomers. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Capillary electrochromatography of inorganic cations in open tubular columns with a controllable capacity multilayered stationary phase architecture.

    Science.gov (United States)

    Kubán, Pavel; Kubán, Petr; Kubán, Vlastimil; Hauser, Peter C; Bocek, Petr

    2008-05-09

    In this paper capillary electrochromatography of alkali and alkaline-earth metal cations in open tubular capillary columns is described. Capillary columns are prepared by coating fused silica capillaries of 75 microm I.D. with poly(butadiene-maleic acid) copolymer (PBMA) in multiple layers. Thermally initiated radical polymerization is used to crosslink the stationary phase. Capillary columns with different number of stationary phase layers can be prepared and allow for the adjustment of separation selectivity in the electrochromatographic mode. Fast and sensitive separations of common inorganic cations are achieved in less than 6 min in a 60 cm capillary column with on-column capacitively coupled contactless conductivity detector. Limits of detection (S/N=3) for the determination of alkali and alkaline-earth metal cations range from 0.3 to 2.5 microM and repeatability is better than 0.5, 4.5 and 6.1% for migration times, peak heights and peak areas, respectively.

  6. Poly(butylene terephthalate) based novel achiral stationary phase investigated under supercritical fluid chromatography conditions.

    Science.gov (United States)

    Nagai, Kanji; Shibata, Tohru; Shinkura, Satoshi; Ohnishi, Atsushi

    2018-05-11

    Poly(butylene terephthalate) based novel stationary phase (SP), composed of planar aromatic phenyl group together with ester group monomer units, was designed for supercritical fluid chromatography (SFC) use. As expected from its structure, this phase shows planarity recognition of isomeric aromatics and closely similar compounds. Interestingly, for most analytes, the retention behavior of this SP is significantly distinct from that of the 2-ethylpyridine based SPs which is among the most well-known SFC dedicated phases. Although the poly(butylene terephthalate) is coated on silica gel, the performance of the column did not change by using extended range modifiers such as THF, dichloromethane or ethyl acetate and column robustness was confirmed by cycle durability testing. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Comparison of a polymeric pseudostationary phase in EKC with ODS stationary phase in RP-HPLC.

    Science.gov (United States)

    Ni, Xinjiong; Zhang, Min; Xing, Xiaoping; Cao, Yuhua; Cao, Guangqun

    2018-01-01

    Poly(stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) was induced as pseudostationary phase (PSP) in electrokinetic chromatography (EKC). The n-octadecyl groups in SMA were the same as that in octadecylsilane (ODS) C18 column. Thus, the present work focused on the comparison of selectivity between polymeric PSP and ODS stationary phase (SP), and the effect of organic modifiers on the selectivity of polymeric PSP and ODS SP. 1-butanol could directly interacted with PSP as a Class I modifier, and improved both of the methylene selectivity and polar group selectivity. When the analysis times were similar, the polymeric PSP exhibited better methylene selectivity and polar group selectivity. Although the hydrophobic groups were similar, the substituted benzenes elution order was different between polymeric PSP and ODS SP. Linear solvation energy relationships (LSER) model analysis found that polymeric PSP and ODS SP exhibited two same key factors in selectivity: hydrophobic interaction and hydrogen bonding acidity. But polymeric PSP exhibited relatively strong n- and π-electrons interaction to the analytes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Optimising reversed-phase liquid chromatographic separation of an acidic mixture on a monolithic stationary phase with the aid of response surface methodology and experimental design.

    Science.gov (United States)

    Wang, Y; Harrison, M; Clark, B J

    2006-02-10

    An optimization strategy for the separation of an acidic mixture by employing a monolithic stationary phase is presented, with the aid of experimental design and response surface methodology (RSM). An orthogonal array design (OAD) OA(16) (2(15)) was used to choose the significant parameters for the optimization. The significant factors were optimized by using a central composite design (CCD) and the quadratic models between the dependent and the independent parameters were built. The mathematical models were tested on a number of simulated data set and had a coefficient of R(2) > 0.97 (n = 16). On applying the optimization strategy, the factor effects were visualized as three-dimensional (3D) response surfaces and contour plots. The optimal condition was achieved in less than 40 min by using the monolithic packing with the mobile phase of methanol/20 mM phosphate buffer pH 2.7 (25.5/74.5, v/v). The method showed good agreement between the experimental data and predictive value throughout the studied parameter space and were suitable for optimization studies on the monolithic stationary phase for acidic compounds.

  9. Sequential metabolic phases as a means to optimize cellular output in a constant environment.

    Science.gov (United States)

    Palinkas, Aljoscha; Bulik, Sascha; Bockmayr, Alexander; Holzhütter, Hermann-Georg

    2015-01-01

    Temporal changes of gene expression are a well-known regulatory feature of all cells, which is commonly perceived as a strategy to adapt the proteome to varying external conditions. However, temporal (rhythmic and non-rhythmic) changes of gene expression are also observed under virtually constant external conditions. Here we hypothesize that such changes are a means to render the synthesis of the metabolic output more efficient than under conditions of constant gene activities. In order to substantiate this hypothesis, we used a flux-balance model of the cellular metabolism. The total time span spent on the production of a given set of target metabolites was split into a series of shorter time intervals (metabolic phases) during which only selected groups of metabolic genes are active. The related flux distributions were calculated under the constraint that genes can be either active or inactive whereby the amount of protein related to an active gene is only controlled by the number of active genes: the lower the number of active genes the more protein can be allocated to the enzymes carrying non-zero fluxes. This concept of a predominantly protein-limited efficiency of gene expression clearly differs from other concepts resting on the assumption of an optimal gene regulation capable of allocating to all enzymes and transporters just that fraction of protein necessary to prevent rate limitation. Applying this concept to a simplified metabolic network of the central carbon metabolism with glucose or lactate as alternative substrates, we demonstrate that switching between optimally chosen stationary flux modes comprising different sets of active genes allows producing a demanded amount of target metabolites in a significantly shorter time than by a single optimal flux mode at fixed gene activities. Our model-based findings suggest that temporal expression of metabolic genes can be advantageous even under conditions of constant external substrate supply.

  10. Carbon nanoparticles from corn stalk soot and its novel application as stationary phase of hydrophilic interaction chromatography and per aqueous liquid chromatography

    International Nuclear Information System (INIS)

    Li Yuanyuan; Xu Luan; Chen Tong; Liu Xiaoyan; Xu Zhigang; Zhang Haixia

    2012-01-01

    Highlights: ► Carbon nanoparticles (6–18 nm in size) were prepared from corn stalk soot. ► CNPs-based silica were used as novel chromatography stationary phase. ► The new phase shows good separation selectivity for polar compounds. ► The new phase had the similar retention for polar probes in HILIC and PALC modes. ► In contrast to PALC, under HILIC conditions high efficiencies were achieved. - Abstract: Carbon nanoparticles (CNPs) (6–18 nm in size) were prepared by refluxing corn stalk soot in nitric acid. The obtained acid-oxidized CNPs are soluble in water due to the existence of carboxylic and hydroxyl groups. 13 C NMR measurement shows the CNPs are mainly of sp 2 and sp 3 carbon structure different from CNPs obtained from candle soot and natural gas soot. Furthermore, these CNPs exhibit unique photoluminescence properties. Interestingly, the CNPs might be exploited to immobilize on the surface of porous silica particles as chromatographic stationary phase. The resultant packing material was evaluated by high-performance liquid chromatography, indicating that the new stationary phase could be used in hydrophilic interaction liquid chromatography (HILIC) and per aqueous liquid chromatography (PALC) modes. The separation of five nucleosides, four sulfa compounds and safflower injection was achieved by using the new column in the HILIC and PALC modes, respectively.

  11. Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2016-05-01

    Full Text Available Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material.

  12. The PaPsr1 and PaWhi2 genes are members of the regulatory network that connect stationary phase to mycelium differentiation and reproduction in Podospora anserina.

    Science.gov (United States)

    Timpano, Hélène; Chan Ho Tong, Laetitia; Gautier, Valérie; Lalucque, Hervé; Silar, Philippe

    2016-09-01

    In filamentous fungi, entrance into stationary phase is complex as it is accompanied by several differentiation and developmental processes, including the synthesis of pigments, aerial hyphae, anastomoses and sporophores. The regulatory networks that control these processes are still incompletely known. The analysis of the "Impaired in the development of Crippled Growth (IDC)" mutants of the model filamentous ascomycete Podospora anserina has already yielded important information regarding the pathway regulating entrance into stationary phase. Here, the genes affected in two additional IDC mutants are identified as orthologues of the Saccharomyces cerevisiae WHI2 and PSR1 genes, known to regulate stationary phase in this yeast, arguing for a conserved role of these proteins throughout the evolution of ascomycetes. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. New poly(styrene/divinylbenzene) based stationary phases for the solid phase extraction of pesticides and the chromatography of carbohydrates

    International Nuclear Information System (INIS)

    Wartusch, I.

    2002-02-01

    The introduced sorbents based on poly(styrene/divinylbenzene) are studied regarding their extraction behavior of pesticides out of water. The sorbents are prepared with different porogens like n-octanol, n-decanol, n-dodecanol and acetone. The comparison of the extraction properties of these substances shows that the use of n-octanol as a porogen leads to the best recoveries. Furthermore this sorbent is compared to a stationary phase prepared via ring opening metathesis polymerization (ROMP) and to commercially available silica-C18. It is shown that the poly(styrene/divinylbenzene) based material on average yields higher recoveries as the other materials. Only the extraction of relatively polar pesticides works better with the ROMP based sorbent. For the chromatography of carbohydrates nonporous particles with diameters of about 3 μm were synthesized via poly(styrene/divinylbenzene) using the activated swelling method. Quaternary ammonia functional groups were introduced into the poly(styrene/divinylbenzene) particles via their nitration, reduction and quaternization. The applicability of these stationary phases for anion exchange chromatography is shown by separation of different kinds of sugars using a pulsed amperometric detection system. Monosaccharides are isocratically separated using an eluent containing sodium hydroxide, separations of disaccharides and oligosaccharides are performed using sodium acetate gradients. Linearity, detection limits and reproducibility of the system are investigated by the analysis of glucose, sucrose and fructose out of the real samples Coca Cola and apple juice. (author)

  14. A phase angle based diagnostic scheme to planetary gear faults diagnostics under non-stationary operational conditions

    Science.gov (United States)

    Feng, Ke; Wang, Kesheng; Ni, Qing; Zuo, Ming J.; Wei, Dongdong

    2017-11-01

    Planetary gearbox is a critical component for rotating machinery. It is widely used in wind turbines, aerospace and transmission systems in heavy industry. Thus, it is important to monitor planetary gearboxes, especially for fault diagnostics, during its operational conditions. However, in practice, operational conditions of planetary gearbox are often characterized by variations of rotational speeds and loads, which may bring difficulties for fault diagnosis through the measured vibrations. In this paper, phase angle data extracted from measured planetary gearbox vibrations is used for fault detection under non-stationary operational conditions. Together with sample entropy, fault diagnosis on planetary gearbox is implemented. The proposed scheme is explained and demonstrated in both simulation and experimental studies. The scheme proves to be effective and features advantages on fault diagnosis of planetary gearboxes under non-stationary operational conditions.

  15. Characterizing the selectivity of stationary phases and organic modifiers in reversed-phase high-performance liquid chromatographic systems by a general solvation equation using gradient elution.

    Science.gov (United States)

    Du, C M; Valko, K; Bevan, C; Reynolds, D; Abraham, M H

    2000-11-01

    Retention data for a set of 69 compounds using rapid gradient elution are obtained on a wide range of reversed-phase stationary phases and organic modifiers. The chromatographic stationary phases studied are Inertsil (IN)-ODS, pentafluorophenyl, fluoro-octyl, n-propylcyano, Polymer (PLRP-S 100), and hexylphenyl. The organic solvent modifiers are 2,2,2-trifluoroethanol (TFE); 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP); isopropanol; methanol (MeOH); acetonitrile (AcN); tetrahydrofuran; 1,4-dioxane; N,N-dimethylformamide; and mixed solvents of dimethylsulfoxide (DMSO) with AcN and DMSO with MeOH (1:1). A total of 25 chromatographic systems are analyzed using a solvation equation. In general, most of the systems give reasonable statistics. The selectivity of the reversed phase-high-performance liquid chromatographic (HPLC) systems with respect to the solute's dipolarity-polarity, hydrogen-bond acidity, and basicity are reflected in correspondingly large coefficients in the solvation equation. We wanted to find the most orthogonal HPLC systems, showing the highest possible selectivity difference in order to derive molecular descriptors using the gradient retention times of a compound. We selected eight chromatographic systems that have a large range of coefficients of interest (s, a, and b) similar to those found in water-solvent partitions used previously to derive molecular descriptors. The systems selected are IN-ODS phases with AcN, MeOH, TFE, and HFIP as mobile phase, PLRP-S 100 phase with AcN, propylcyano phase with AcN and MeOH, and fluorooctyl phase with TFE. Using the retention data obtained for a compound in the selected chromatographic systems, we can estimate the molecular descriptors with the faster and simpler gradient elution method.

  16. The Trypanosoma cruzi nucleolus: a morphometrical analysis of cultured epimastigotes in the exponential and stationary phases.

    Science.gov (United States)

    Nepomuceno-Mejía, Tomás; Lara-Martínez, Reyna; Cevallos, Ana María; López-Villaseñor, Imelda; Jiménez-García, Luis Felipe; Hernández, Roberto

    2010-12-01

    Our group is interested in rRNA and ribosome biogenesis in the parasitic protozoan Trypanosoma cruzi. Epimastigotes represent an extracellular replicative stage of T. cruzi and can be cultured in axenic media. The growth curve of epimastigotes allows assessment of potential differences in the nucleoli of cells undergoing growth-rate transitions. To establish cellular parameters for studying ribosome biogenesis in T. cruzi, a morphometric analysis of the nucleoli of cultured cells in the exponential and stationary phases was conducted. Electron micrograph-based measurements of nuclear sections from independent cells demonstrated that the nucleolar area is over twofold higher in exponentially growing cells, as compared with epimastigotes in the stationary phase. The granular component of the nucleoli of actively growing cells was the main structural element. Cycloheximide moderately reduced the apparent size of the nucleoli without an apparent disruption of their architecture. Our results provide a firm basis for the establishment of an experimental model to study the organization of the nucleolus during the growth and development of T. cruzi. © 2010 Federation of European Microbiological Societies Published by Blackwell Publishing Ltd. All rights reserved.

  17. A 3-D open-framework material with intrinsic chiral topology used as a stationary phase in gas chromatography.

    Science.gov (United States)

    Xie, Sheng-Ming; Zhang, Xin-Huan; Zhang, Ze-Jun; Zhang, Mei; Jia, Jia; Yuan, Li-Ming

    2013-04-01

    Compared with liquid chromatography and capillary electrophoresis, the diversity of gas chromatography chiral stationary phases is rather limited. Here, we report the fabrication of Co(D-Cam)1/2(bdc)1/2(tmdpy) (D-Cam = D-camphoric acid; bdc = 1,4-benzenedicarboxylate; tmdpy = 4,4'-trimethylenedipyridine)-coated open tubular columns for high-resolution gas chromatographic separation of compounds. The Co(D-Cam)1/2(bdc)1/2(tmdpy) compound possesses a 3-D framework containing enantiopure building blocks embedded in intrinsically chiral topological nets. In this study, two fused-silica open tubular columns with different inner diameters and lengths, including column A (30 m × 530 μm i.d.) and column B (2 m × 75 μm i.d.), were prepared by a dynamic coating method using Co-(D-Cam)1/2(bdc)1/2(tmdpy) as the stationary phase. The chromatographic properties of the two columns were investigated using n-dodecane as the test compound at 120 °C. The number of theoretical plates (plates/m) of the two metal-organic framework columns was 1,450 and 3,100, respectively. The separation properties were evaluated using racemates, isomers, alkanes, alcohols, and Grob's test mixture. The limit of detection and limit of quantification were found to be 0.125 and 0.417 ng for citronellal enantiomers, respectively. Repeatability (n = 6) showed lower than 0.25 % relative standard deviation (RSD) for retention times and lower than 2.2 % RSD for corrected peak areas. The experimental results showed that the stationary phase has excellent selectivity and also possesses good recognition ability toward these organic compounds, especially chiral compounds.

  18. High-performance liquid chromatography using reversed-phase stationary phases dynamically modified with organophosphorus compound for the separation and determination of lanthanoid elements

    International Nuclear Information System (INIS)

    Tsuyoshi, Akira; Akiba, Kenichi

    2000-01-01

    An acidic organophosphorus compound, 2-ethylhexylphosphonic acid mono-2-ethlhexyl ester (EHPA), has been applied to reversed-phase high-performance liquid chromatography (RP-HPLC). The reversed-phase stationary phase was dynamically modified with EHPA by flowing the mobile phase of an acetone-water mixture containing the extracting regent. The retention of lanthanoid elements was widely varied by changing the conditions of the mobile phase, i.e., the pH, the EHPA concentration and the acetone content. The selectivity of EHPA is well reflected to the chromatographic systems, and a precise separation of lanthanoid elements was achieved with sufficient resolution. The determination of Sm was examined in the presence of a large amount of Nd. A linear calibration graph was obtained for Sm at the level of 10 -7 mol dm -3 , in the presence of 1x10 -4 mol dm -3 of Nd. (author)

  19. Comparison of liquid and supercritical fluid chromatography mobile phases for enantioselective separations on polysaccharide stationary phases.

    Science.gov (United States)

    Khater, Syame; Lozac'h, Marie-Anne; Adam, Isabelle; Francotte, Eric; West, Caroline

    2016-10-07

    Analysis and production of enantiomerically pure compounds is a major topic of interest when active pharmaceutical ingredients are concerned. Enantioselective chromatography has become a favourite both at the analytical and preparative scales. High-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) are dominating the scene and are often seen as complementary techniques. Nowadays, for economic and ecologic reasons, SFC may be preferred over normal-phase HPLC (NPLC) as it allows significant reductions in solvent consumption. However, the transfer of NPLC methods to SFC is not always straightforward. In this study, we compare the retention of achiral molecules and separation of enantiomers under supercritical fluid (carbon dioxide with ethanol or isopropanol) and liquid normal-phase (heptane with ethanol or isopropanol) elution modes with polysaccharide stationary phases in order to explore the differences between the retention and enantioseparation properties between the two modes. Chemometric methods (namely quantitative structure-retention relationships and discriminant analysis) are employed to compare the results obtained on a large set of analytes (171 achiral probes and 97 racemates) and gain some understanding on the retention and separation mechanisms. The results indicate that, contrary to popular belief, carbon dioxide - solvent SFC mobile phases are often weaker eluents than liquid mobile phases. It appears that SFC and NPLC elution modes provide different retention mechanisms. While some enantioseparations are unaffected, facilitating the transfer between the two elution modes, other enantioseparations may be drastically different due to different types and strength of interactions contributing to enantioselectivity. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Application of the zeta potential for stationary phase characterization in ion chromatography.

    Science.gov (United States)

    Buszewski, Bogusław; Jaćkowska, Magdalena; Bocian, Szymon; Dziubakiewicz, Ewelina

    2013-01-01

    Two series of homemade stationary bonded phases for ion chromatography were investigated according to their zeta potential. One set of dendrimer anion exchanger was synthesized on the polymer support whereas the second material was prepared on the silica gel. The zeta potential data in water environment as well as buffered water solution were obtained. The influence of the length of anion-exchanger chains, the type of the support of the modified surface, and charge distribution on these data was investigated. Additionally, the zeta potential was correlated with retention factor of inorganic ions to describe their influence on the retention mechanism in ion chromatography. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. A high-throughput method for quantifying metabolically active yeast cells

    DEFF Research Database (Denmark)

    Nandy, Subir Kumar; Knudsen, Peter Boldsen; Rosenkjær, Alexander

    2015-01-01

    By redesigning the established methylene blue reduction test for bacteria and yeast, we present a cheap and efficient methodology for quantitative physiology of eukaryotic cells applicable for high-throughput systems. Validation of themethod in fermenters and highthroughput systems proved....... The drop in metabolic activity associated with the diauxic shift in yeast proved more pronounced for the MBRT-derived curve compared with OD curves, consistent with a dramatic shift in the ratio between live and dead cells at this metabolic event. This method provides a tool with numerous applications, e.......g. characterizing the death phase of stationary phase cultures, or in drug screens with pathogenic yeasts....

  2. Solvation molar enthalpies and heat capacities of n-alkanes and n-alkylbenzenes on stationary phases of wide-ranging polarity.

    Science.gov (United States)

    Lebrón-Aguilar, Rosa; Quintanilla-López, Jesús Eduardo; Santiuste, José María

    2010-12-03

    A comparison of the most usual gas chromatographic methods for the calculation of partial molar enthalpies of solvation (Δ(sol)H(o)) has been carried out. Those methods based on the fitting of lnV(g) or ln(k/T) vs. 1/T and ln(k/T) vs. (1/T and the temperature arrangement, T(a)) are the most adequate ones for obtaining Δ(sol)H(o) values. However, the latter is the only reliable option for Δ(sol)H(o) estimation when commercial WCOT capillary columns are used, since in this case the estimation of some variables involved in the V(g) determination is less accurate or even impossible. Consequently, in this paper, Δ(sol)H(o) obtained from ln(k/T) vs. (1/T+T(a)) fitting at 373.15 and 298.15K for n-alkanes and n-alkylbenzenes on 12 commercial capillary columns coated with stationary phases covering the 203-3608 McReynolds polarity range are reported. Moreover, molar heat capacities of solvation at constant pressure (Δ(sol)C(p)(o)) have also been calculated using this method. A clear influence on Δ(sol)H(o) of the type and content of the substitution group in the stationary phase was observed. In addition, a linear relationship of Δ(sol)C(p)(o) with the van der Waals volume of the n-alkanes and the temperature gradient of density of the stationary phase was found. The effect of the size of the hydrocarbon on both thermodynamic variables was also investigated. Copyright © 2010 Elsevier B.V. All rights reserved.

  3. Comparison of the peak resolution and the stationary phase retention between the satellite and the planetary motions using the coil satellite centrifuge with counter-current chromatographic separation of 4-methylumbelliferyl sugar derivatives.

    Science.gov (United States)

    Shinomiya, Kazufusa; Zaima, Kazumasa; Harada, Yukina; Yasue, Miho; Harikai, Naoki; Tokura, Koji; Ito, Yoichiro

    2017-01-20

    Coil satellite centrifuge (CSC) produces the complex satellite motion consisting of the triplicate rotation of the coiled column around three axes including the sun axis (the angular velocity, ω 1 ), the planet axis (ω 2 ) and the satellite axis (the central axis of the column) (ω 3 ) according to the following formula: ω 1 =ω 2 +ω 3 . Improved peak resolution in the separation of 4-methylumbelliferyl sugar derivatives was achieved using the conventional multilayer coiled columns with ethyl acetate/1-butanol/water (3: 2: 5, v/v) for the lower mobile phase at the combination of the rotation speeds (ω 1 , ω 2 , ω 3 )=(300, 150, 150rpm), and (1:4:5, v/v) for the upper mobile phase at (300:100:200rpm). The effect of the satellite motion on the peak resolution and the stationary phase retention was evaluated by each CSC separation with the different rotation speeds of ω 2 and ω 3 under the constant revolution speed at ω 1 =300rpm. With the lower mobile phase, almost constant peak resolution and stationary phase retention were yielded regardless of the change of ω 2 and ω 3 , while with the upper mobile phase these two values were sensitively varied according to the different combination of ω 2 and ω 3 . For example, when ω 2 =147 or 200rpm is used, no stationary phase was retained in the coiled column while ω 2 =150rpm could retain enough volume of stationary phase for separation. On the other hand, the combined rotation speeds at (ω 1 , ω 2 , ω 3 )=(300, 300, 0rpm) or (300, 0, 300rpm) produced insufficient peak resolution regardless of the choice of the mobile phase apparently due to the lack of rotation speed except at (300, 0, 300rpm) with the upper mobile phase. At lower rotation speed of ω 1 =300rpm, better peak resolution and stationary phase retention were obtained by the satellite motion (ω 3 ) than by the planetary motion (ω 2 ), or ω 3 >ω 2 . The effect of the hydrophobicity of the two-phase solvent systems on the stationary phase

  4. High performance liquid chromatographic separation of thirteen drugs collected in Chinese Pharmacopoeia 2010(Ch.P2010 on cellulose ramification chiral stationary phase

    Directory of Open Access Journals (Sweden)

    Ying Zhou

    2012-02-01

    Full Text Available The enantiomers separation of thirteen drugs collected in Ch.P2010 was performed on chiral stationary phase of cellulose ramification (chiralpak OD and chiralpak OJ by high performance liquid chromatographic (HPLC methods, which included ibuprofen (C1, ketoprofen (C2, nitrendipine (C3, nimodipine (C4, felodipine (C5, omeprazole (C6, praziquantel (C7, propranolol hydrochloride (C8, atenolol (C9, sulpiride (C10, clenbuterol hydrochloride (C11, verapamil hydrochloride (C12, and chlorphenamine maleate (C13. The mobile phase consisted of isopropanol and n-hexane. The detection wavelength was set at 254 nm and the flow rate was 0.7 mL/min. The enantiomers separation of these thirteen racemates on chiralpak OD column and chiralpak OJ column was studied, while the effects of proportion of organic additives, alcohol displacer and temperature on the separation were studied. And the mechanism of some of racemates was discussed. The results indicated that thirteen chiral drugs could be separated on chiral stationary phase of cellulose ramification in normal phase chromatographic system. The chromatographic retention and resolution of enantiomers could be adjusted by factors including column temperature and the concentration of alcohol displacer and organic alkaline modifier in mobile phase. It was shown that the resolution was improved with reducing concentration of alcohol displacer. When concentration of organic alkaline modifier was 0.2% (v/v, the resolution and the peak shape were fairly good. Most racemates mentioned above had better resolution at column temperature of 25 °C. When racemates were separated, the temperature should be kept so as to obtain stable separation results. Keywords: HPLC, Chiral stationary phase, Optical enantiomers, Cellulose ramification

  5. Determination of nitrosamines and caffeine metabolites in wastewaters using gas chromatography mass spectrometry and ionic liquid stationary phases.

    Science.gov (United States)

    Reyes-Contreras, Carolina; Domínguez, Carmen; Bayona, Josep M

    2012-10-26

    Recently, the interest to assess the environmental and human health effects of a wide group of emerging contaminants is growing worldwide. However, one of the main problems associated to their exposure is their determination in environmental matrices. It is hindered by the high polarity of most of these analytes, the poor selectivity obtained with low polarity stationary phases and the high background obtained with polar columns commonly used in GC-MS. Accordingly, this study examines the suitability of ionic liquid (IL) (e.g. SLB-IL59, SLB-IL61, SLB-IL82 and SLB-IL111) as stationary phases for GC-MS and their application to the determination of nitrosamines and caffeine metabolites in wastewater samples. Different chromatographic conditions were evaluated and results discussed in terms of resolution and peak symmetry. The SLB-IL111 column enabled the baseline separation and quantification of 7 nitrosamines in a shorter analysis time compared with cyanopropylphenyl polysiloxane commonly used. On the other hand, the SLB-IL59 column provided the best results for caffeine metabolites. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Growth Phase-Dependent Proteomes of the Malaysian Isolated Lactococcus lactis Dairy Strain M4 Using Label-Free Qualitative Shotgun Proteomics Analysis

    Directory of Open Access Journals (Sweden)

    Theresa Wan Chen Yap

    2014-01-01

    Full Text Available Lactococcus lactis is the most studied mesophilic fermentative lactic acid bacterium. It is used extensively in the food industry and plays a pivotal role as a cell factory and also as vaccine delivery platforms. The proteome of the Malaysian isolated L. lactis M4 dairy strain, obtained from the milk of locally bred cows, was studied to elucidate the physiological changes occurring between the growth phases of this bacterium. In this study, ultraperformance liquid chromatography nanoflow electrospray ionization tandem mass spectrometry (UPLC- nano-ESI-MSE approach was used for qualitative proteomic analysis. A total of 100 and 121 proteins were identified from the midexponential and early stationary growth phases, respectively, of the L. lactis strain M4. During the exponential phase, the most important reaction was the generation of sufficient energy, whereas, in the early stationary phase, the metabolic energy pathways decreased and the biosynthesis of proteins became more important. Thus, the metabolism of the cells shifted from energy production in the exponential phase to the synthesis of macromolecules in the stationary phase. The resultant proteomes are essential in providing an improved view of the cellular machinery of L. lactis during the transition of growth phases and hence provide insight into various biotechnological applications.

  7. Growth phase-dependent proteomes of the Malaysian isolated Lactococcus lactis dairy strain M4 using label-free qualitative shotgun proteomics analysis.

    Science.gov (United States)

    Yap, Theresa Wan Chen; Rabu, Amir; Abu Bakar, Farah Diba; Rahim, Raha Abdul; Mahadi, Nor Muhammad; Illias, Rosli Md; Murad, Abdul Munir Abdul

    2014-01-01

    Lactococcus lactis is the most studied mesophilic fermentative lactic acid bacterium. It is used extensively in the food industry and plays a pivotal role as a cell factory and also as vaccine delivery platforms. The proteome of the Malaysian isolated L. lactis M4 dairy strain, obtained from the milk of locally bred cows, was studied to elucidate the physiological changes occurring between the growth phases of this bacterium. In this study, ultraperformance liquid chromatography nanoflow electrospray ionization tandem mass spectrometry (UPLC- nano-ESI-MS(E)) approach was used for qualitative proteomic analysis. A total of 100 and 121 proteins were identified from the midexponential and early stationary growth phases, respectively, of the L. lactis strain M4. During the exponential phase, the most important reaction was the generation of sufficient energy, whereas, in the early stationary phase, the metabolic energy pathways decreased and the biosynthesis of proteins became more important. Thus, the metabolism of the cells shifted from energy production in the exponential phase to the synthesis of macromolecules in the stationary phase. The resultant proteomes are essential in providing an improved view of the cellular machinery of L. lactis during the transition of growth phases and hence provide insight into various biotechnological applications.

  8. Growth Phase-Dependent Proteomes of the Malaysian Isolated Lactococcus lactis Dairy Strain M4 Using Label-Free Qualitative Shotgun Proteomics Analysis

    Science.gov (United States)

    Yap, Theresa Wan Chen; Rabu, Amir; Abu Bakar, Farah Diba; Abdul Rahim, Raha; Mahadi, Nor Muhammad; Illias, Rosli Md.

    2014-01-01

    Lactococcus lactis is the most studied mesophilic fermentative lactic acid bacterium. It is used extensively in the food industry and plays a pivotal role as a cell factory and also as vaccine delivery platforms. The proteome of the Malaysian isolated L. lactis M4 dairy strain, obtained from the milk of locally bred cows, was studied to elucidate the physiological changes occurring between the growth phases of this bacterium. In this study, ultraperformance liquid chromatography nanoflow electrospray ionization tandem mass spectrometry (UPLC- nano-ESI-MSE) approach was used for qualitative proteomic analysis. A total of 100 and 121 proteins were identified from the midexponential and early stationary growth phases, respectively, of the L. lactis strain M4. During the exponential phase, the most important reaction was the generation of sufficient energy, whereas, in the early stationary phase, the metabolic energy pathways decreased and the biosynthesis of proteins became more important. Thus, the metabolism of the cells shifted from energy production in the exponential phase to the synthesis of macromolecules in the stationary phase. The resultant proteomes are essential in providing an improved view of the cellular machinery of L. lactis during the transition of growth phases and hence provide insight into various biotechnological applications. PMID:24982972

  9. New method for evaluating irreversible adsorption and stationary phase bleed in gas chromatographic capillary columns.

    Science.gov (United States)

    Wright, Bob W; Wright, Cherylyn W

    2012-10-26

    A novel method is described for the evaluation of irreversible adsorption and column bleed in gas chromatographic (GC) columns using a tandem GC approach. This work specifically determined the degree of irreversible adsorption behavior of specific sulfur and phosphorous containing test probe compounds at levels ranging from approximately 50 picograms (pg) to 1 nanogram (ng) on selected gas chromatographic columns. This method does not replace existing evaluation methods that characterize reversible adsorption but provides an additional tool. The test compounds were selected due to their ease of adsorption and their importance in the specific trace analytical detection methodology being developed. Replicate chromatographic columns with 5% phenylmethylpolysiloxane (PMS), polyethylene glycol (wax), trifluoropropylpolysiloxane (TFP), or 78% cyanopropylpolysiloxane stationary phases from a variety of vendors were evaluated. As expected, the results demonstrate that the different chromatographic phases exhibit differing degrees of irreversible adsorption behavior. The results also indicate that all manufacturers do not produce equally inert columns nor are columns from a given manufacturer identical. The wax-coated columns for the test probes used were more inert as a group than 5% PMS coated columns, and they were more reproducibly manufactured. Both TFP and 78% cyanopropylpolysiloxane columns displayed superior inertness to the test compounds compared to either 5% PMS- or wax-coated columns. Irreversible adsorption behavior was characterized for a limited range of stationary phase film thicknesses. In addition, the method was shown effective for characterizing column bleed and methods to remove bleed components. This method is useful in screening columns for demanding applications and to obtain diagnostic information related to improved preparation methods. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Preparation, characterization and application of N-methylene phosphonic acid chitosan grafted magnesia–zirconia stationary phase

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qing; Chen, Jie; Huang, Kun; Zhang, Xin; Xu, Li [Tongji School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030 (China); Shi, Zhi-guo, E-mail: shizg@whu.edu.cn [Department of Chemistry, Wuhan University, Wuhan 430072 (China)

    2015-01-07

    Highlights: • N-methylene phosphonic acid chitosan grafted MgO–ZrO{sub 2} was prepared. • It exhibited superior HILIC chromatographic performance to the bare MgO–ZrO{sub 2}. • Monosaccharides, phospholipids and peptides were successfully separated. • It was a promising HILIC stationary phase. - Abstract: A hydrophilic stationary phase (SP) was prepared through grafting N-methylene phosphonic acid chitosan on magnesia–zirconia particles (P-CTS-MgO–ZrO{sub 2}) via Lewis acid–base interaction. The resulting material was characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope and nitrogen adsorption analysis. The chromatographic performance of P-CTS-MgO–ZrO{sub 2} was systemically evaluated by studying effect of acetonitrile content, pH and buffer concentration in the mobile phase. The results demonstrated that the novel SP provided hydrophilic, electrostatic-repulsion and ion-exchange interactions. Compared to the bare MgO–ZrO{sub 2}, P-CTS-MgO–ZrO{sub 2} exhibited superior peak shape, reasonable resolution and reduced analysis time in separation of basic analytes. Besides, remarkable resolving power of acids, i.e. six non-steroidal anti-inflammatory drugs which failed to be eluted from the bare MgO–ZrO{sub 2}, was obtained with the theoretical plate number (N/m) of 4653–31313, asymmetry factor <1.21 and the resolution of 1.6–3.4. Finally, P-CTS-MgO–ZrO{sub 2} SP was applied to separate monosaccharides, phospholipids and peptides. P-CTS-MgO–ZrO{sub 2} was a promising hydrophilic SP for wide applications.

  11. Comparison of Various Types of Stationary Phases in Non-Aqueous Reversed-Phase High-Performance Liquid Chromatography–Mass Spectrometry of Glycerolipids in Blackcurrant Oil and Its Enzymatic Hydrolysis Mixture

    Czech Academy of Sciences Publication Activity Database

    Lísa, M.; Holčapek, M.; Sovová, Helena

    2009-01-01

    Roč. 1216, č. 47 (2009), s. 8371-8378 ISSN 0021-9673 Institutional research plan: CEZ:AV0Z40720504 Keywords : ultra high-performance liquid chromatography * C30 stationary phase * triacylglycerols Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.101, year: 2009

  12. Forensic relevance of glucuronidation in phase-II-metabolism of alcohols and drugs.

    Science.gov (United States)

    Kaeferstein, Herbert

    2009-04-01

    Forensic toxicology means detecting toxic or pharmacologically active substances in body fluids and organs and the evaluation and judgement of the respective results. In the legal judgement, not only the taken in active drugs, but also their metabolites are to be included. Regarding metabolism one distinguishes phase-I- and phase-II-metabolism. In the phase-I-metabolism, active substances are converted by oxidation, reduction or hydrolysis, but influencing the polarity of more lipophilic substances often not decisively. The pharmacological activity is often preserved or even increased. In phase-II-metabolism a highly hydrophilic substance--mostly glucuronic acid--is coupled to the active substances or the respective phase-I-metabolites. This reaction step decisively increases hydrophilicity of lipophilic substances, thus enhancing renal elimination and often also abolishing pharmacologically and/or toxicologically effects. Nevertheless the interaction of different drugs and alcohols in glucuronidation and the glucuronides of phase-II-metabolism still do not play a substantial role in the forensic-toxicological analysis and interpretation of results so far. However, in vitro investigations since 1999 in our lab show that such interactions are not unlikely. For valid interpretation of complex cases in the future it may become necessary not only to quantify drugs and the phase-I-metabolites but also the phase-II-metabolites and discuss possible interactions in the metabolism.

  13. Physiological Status Drives Metabolic Rate in Mediterranean Geckos Infected with Pentastomes.

    Directory of Open Access Journals (Sweden)

    Isabel C Caballero

    Full Text Available Negative effects of parasites on their hosts are well documented, but the proximate mechanisms by which parasites reduce their host's fitness are poorly understood. For example, it has been suggested that parasites might be energetically demanding. However, a recent meta-analysis suggests that they have statistically insignificant effects on host resting metabolic rate (RMR. It is possible, though, that energetic costs associated with parasites are only manifested during and/or following periods of activity. Here, we measured CO2 production (a surrogate for metabolism in Mediterranean geckos (Hemidactylus turcicus infected with a lung parasite, the pentastome Raillietiella indica, under two physiological conditions: rested and recently active. In rested geckos, there was a negative, but non-significant association between the number of pentastomes (i.e., infection intensity and CO2 production. In recently active geckos (chased for 3 minutes, we recorded CO2 production from its maximum value until it declined to a stationary phase. We analyzed this decline as a 3 phase function (initial decline, secondary decline, stationary. Geckos that were recently active showed, in the secondary phase, a significant decrease in CO2 production as pentastome intensity increased. Moreover, duration of the secondary phase showed a significant positive association with the number of pentastomes. These results suggest that the intensity of pentastome load exerts a weak effect on the metabolism of resting geckos, but a strong physiological effect on geckos that have recently been active; we speculate this occurs via mechanical constraints on breathing. Our results provide a potential mechanism by which pentastomes can reduce gecko fitness.

  14. Physiological Status Drives Metabolic Rate in Mediterranean Geckos Infected with Pentastomes.

    Science.gov (United States)

    Caballero, Isabel C; Sakla, Andrew J; Detwiler, Jillian T; Le Gall, Marion; Behmer, Spencer T; Criscione, Charles D

    2015-01-01

    Negative effects of parasites on their hosts are well documented, but the proximate mechanisms by which parasites reduce their host's fitness are poorly understood. For example, it has been suggested that parasites might be energetically demanding. However, a recent meta-analysis suggests that they have statistically insignificant effects on host resting metabolic rate (RMR). It is possible, though, that energetic costs associated with parasites are only manifested during and/or following periods of activity. Here, we measured CO2 production (a surrogate for metabolism) in Mediterranean geckos (Hemidactylus turcicus) infected with a lung parasite, the pentastome Raillietiella indica, under two physiological conditions: rested and recently active. In rested geckos, there was a negative, but non-significant association between the number of pentastomes (i.e., infection intensity) and CO2 production. In recently active geckos (chased for 3 minutes), we recorded CO2 production from its maximum value until it declined to a stationary phase. We analyzed this decline as a 3 phase function (initial decline, secondary decline, stationary). Geckos that were recently active showed, in the secondary phase, a significant decrease in CO2 production as pentastome intensity increased. Moreover, duration of the secondary phase showed a significant positive association with the number of pentastomes. These results suggest that the intensity of pentastome load exerts a weak effect on the metabolism of resting geckos, but a strong physiological effect on geckos that have recently been active; we speculate this occurs via mechanical constraints on breathing. Our results provide a potential mechanism by which pentastomes can reduce gecko fitness.

  15. Integrated Time and Phase Synchronization Strategy for a Multichannel Spaceborne-Stationary Bistatic SAR System

    Directory of Open Access Journals (Sweden)

    Feng Hong

    2016-07-01

    Full Text Available The spatial separation of the transmitter and receiver in Bistatic Synthetic Aperture Radar (BiSAR makes it a promising and useful supplement to a classical Monostatic SAR system (MonoSAR. This paper proposes a novel integrated time and phase synchronization strategy for a multichannel spaceborne-stationary BiSAR system. Firstly, the time synchronization strategy is proposed, which includes Pulse Repetition Frequency (PRF generation under noisy conditions, multichannel calibration and the alignment of the recorded data with the orbital data. Furthermore, the phase synchronization strategy, which fully considers the deteriorative factors in the BiSAR configuration, is well studied. The contribution of the phase synchronization strategy includes two aspects: it not only compensates the phase error, but also improves the Signal to Noise Ratio (SNR of the obtained signals. Specifically, all direct signals on different PRF time can be reconstructed with the shift and phase compensation operation using a reference signal. Besides, since the parameters of the reference signal can be estimated only once using the selected practical direct signal and a priori information, the processing complexity is well reduced. Final imaging results with and without compensation for real data are presented to validate the proposed synchronization strategy.

  16. Improved Procedure for Preparation of Covalently Bonded Cellulose Tris-phenylcarbamate Chiral Stationary Phases

    Institute of Scientific and Technical Information of China (English)

    秦峰; 陈小明; 刘月启; 邹汉法; 王俊德

    2005-01-01

    The classical method for preparation of covalently boned cellulose derivative chiral stationary phases (CSP) with diisocyanate as spacer was improved. Diisocyanate was firstly allowed to react with 3-aminopropyltriethoxysilane, and the resulting product was then applied as the spacer reagent to immobilize cellulose derivatives onto silica gel. Influences of the amount and the length of the spacer on the optical resolution ability of the CSP were investigated. Comparing improved procedure to classical diisocyanate method, the cross-linking between the glucose units of the cellulose derivatives was avoided to the most extent. With the improved procedure, regio-nonselective ways could be adooted to prepare covalently bonded CSP, which showed an advantage for the rapid preparation.

  17. The Optical Resolution of Chiral Tetrahedrone-type Clusters Contai- ning SCoFeM (M=Mo or W) Using High Performance Liquid Chromatography Chiral Stationary Phase

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Amylose tris (phenylcarbamate) chiral stationary phase (ATPC-CSP) was prepared and used for optical resolution of clusters 1 and 2. n-Hexane/2-propanol ( 99/1; v/v) were found to be the most suitable mobile phase on ATPC-CSP.

  18. The effect of charged groups on hydrophilic monolithic stationary phases on their chromatographic properties.

    Science.gov (United States)

    Li, Haibin; Liu, Chusheng; Wang, Qiqin; Zhou, Haibo; Jiang, Zhengjin

    2016-10-21

    In order to investigate the effect of charged groups present in hydrophilic monolithic stationary phases on their chromatographic properties, three charged hydrophilic monomers, i.e. N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA), [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETA), and 3-sulfopropyl acrylate potassium salt (SPA) were co-polymerized with the crosslinker N,N'-methylenebisacrylamide (MBA), respectively. The physicochemical properties of the three resulting charged hydrophilic monolithic columns were evaluated using scanning electron microscopy, ζ-potential analysis and micro-HPLC. High column efficiency was obtained on the three monolithic columns at a linear velocity of 1mm/s using thiourea as test compound. Comparative characterization of the three charged HILIC phases was then carried out using a set of model compounds, including nucleobases, nucleosides, benzoic acid derivatives, phenols, β-blockers and small peptides. Depending on the combination of stationary phase/mobile phase/solute, both hydrophilic interaction and other potential secondary interactions, including electrostatic interaction, hydrogen-bonding interaction, molecular shape selectivity, could contribute to the over-all retention of the analytes. Because of the strong electrostatic interaction provided by the quaternary ammonium groups in the poly (AETA-co-MBA) monolith, this cationic HILIC monolith exhibited the strongest retention for benzoic acid derivatives and small peptides with distorted peak shapes and the weakest retention for basic β-blockers. The sulfonyl groups on the poly (SPA-co-MBA) hydrophilic monolith could provide strong electrostatic attraction and hydrogen bonding for positively charged analytes and hydrogen-donor/acceptor containing analytes, respectively. Therefore, basic drugs, nucleobases and nucleotides exhibited the strongest retention on this anionic monolith. Because of the weak but distinct cation exchange properties of

  19. Selective Essential Oils from Spice or Culinary Herbs Have High Activity against Stationary Phase and Biofilm Borrelia burgdorferi.

    Science.gov (United States)

    Feng, Jie; Zhang, Shuo; Shi, Wanliang; Zubcevik, Nevena; Miklossy, Judith; Zhang, Ying

    2017-01-01

    Although the majority of patients with acute Lyme disease can be cured with the standard 2-4 week antibiotic treatment, about 10-20% of patients continue suffering from chronic symptoms described as posttreatment Lyme disease syndrome. While the cause for this is debated, one possibility is that persister bacteria are not killed by the current Lyme antibiotics and remain active in the system. It has been reported that essential oils have antimicrobial activities and some have been used by patients with persisting Lyme disease symptoms. However, the activity of essential oils against the causative agent Borrelia burgdorferi ( B. burgdorferi ) has not been well studied. Here, we evaluated the activity of 34 essential oils against B. burgdorferi stationary phase culture as a model for persister bacteria. We found that not all essential oils had activity against the B. burgdorferi stationary phase culture, with top five essential oils (oregano, cinnamon bark, clove bud, citronella, and wintergreen) at a low concentration of 0.25% showing high anti-persister activity that is more active than the known persister drug daptomycin. Interestingly, some highly active essential oils were found to have excellent anti-biofilm ability as shown by their ability to dissolve the aggregated biofilm-like structures. The top three hits, oregano, cinnamon bark, and clove bud completely eradicated all viable cells without any regrowth in subculture in fresh medium, whereas but not citronella and wintergreen did not have this effect. Carvacrol was found to be the most active ingredient of oregano oil showing excellent activity against B. burgdorferi stationary phase cells, while other ingredients of oregano oil p-cymene and α-terpinene had no apparent activity. Future studies are needed to characterize and optimize the active essential oils in drug combination studies in vitro and in vivo and to address their safety and pharmacokinetic properties before they can be considered as a

  20. Selective Essential Oils from Spice or Culinary Herbs Have High Activity against Stationary Phase and Biofilm Borrelia burgdorferi

    Science.gov (United States)

    Feng, Jie; Zhang, Shuo; Shi, Wanliang; Zubcevik, Nevena; Miklossy, Judith; Zhang, Ying

    2017-01-01

    Although the majority of patients with acute Lyme disease can be cured with the standard 2–4 week antibiotic treatment, about 10–20% of patients continue suffering from chronic symptoms described as posttreatment Lyme disease syndrome. While the cause for this is debated, one possibility is that persister bacteria are not killed by the current Lyme antibiotics and remain active in the system. It has been reported that essential oils have antimicrobial activities and some have been used by patients with persisting Lyme disease symptoms. However, the activity of essential oils against the causative agent Borrelia burgdorferi (B. burgdorferi) has not been well studied. Here, we evaluated the activity of 34 essential oils against B. burgdorferi stationary phase culture as a model for persister bacteria. We found that not all essential oils had activity against the B. burgdorferi stationary phase culture, with top five essential oils (oregano, cinnamon bark, clove bud, citronella, and wintergreen) at a low concentration of 0.25% showing high anti-persister activity that is more active than the known persister drug daptomycin. Interestingly, some highly active essential oils were found to have excellent anti-biofilm ability as shown by their ability to dissolve the aggregated biofilm-like structures. The top three hits, oregano, cinnamon bark, and clove bud completely eradicated all viable cells without any regrowth in subculture in fresh medium, whereas but not citronella and wintergreen did not have this effect. Carvacrol was found to be the most active ingredient of oregano oil showing excellent activity against B. burgdorferi stationary phase cells, while other ingredients of oregano oil p-cymene and α-terpinene had no apparent activity. Future studies are needed to characterize and optimize the active essential oils in drug combination studies in vitro and in vivo and to address their safety and pharmacokinetic properties before they can be considered as a

  1. Silica, alumina and aluminosilicates as solid stationary phases in gas chromatography

    Directory of Open Access Journals (Sweden)

    S. Faramawy

    2016-09-01

    Full Text Available Silica, alumina and Aluminosilicates of different Si/Al ratios were prepared by conventional precipitation or co-precipitation methods and then subjected to thermal treatment at 800 °C. The parent and thermally treated materials were characterized by means of FTIR, SEM and thermal analysis (DTA and TGA in order to elucidate the main structural properties. Surface textural characteristics were investigated by means of nitrogen adsorption–desorption isotherms at −196 °C. Pore size distribution curves indicated the presence of mesopores (10–150 Å exhibiting maxima at 35 Å. The maxima were shifted toward higher values by increasing the alumina content. Thermodynamic parameters, ΔH, ΔG and ΔS, were determined by means of inverse gas chromatography using n-hexane as a probe. The untreated and thermally treated materials were tested as solid stationary phases in gas chromatography. The separation efficiency of various non polar and polar compounds was explained in terms of surface texture and thermodynamic parameters.

  2. Enantioseparation of novel chiral sulfoxides on chlorinated polysaccharide stationary phases in supercritical fluid chromatography.

    Science.gov (United States)

    West, Caroline; Konjaria, Mari-Luiza; Shashviashvili, Natia; Lemasson, Elise; Bonnet, Pascal; Kakava, Rusudan; Volonterio, Alessandro; Chankvetadze, Bezhan

    2017-05-26

    Asymmetric sulfoxides is a particular case of chirality that may be found in natural as well as synthetic products. Twenty-four original molecules containing a sulfur atom as a centre of chirality were analyzed in supercritical fluid chromatography on seven polysaccharide-based chiral stationary phases (CSP) with carbon dioxide - methanol mobile phases. While all the tested CSP provided enantioseparation for a large part of the racemates, chlorinated cellulosic phases proved to be both highly retentive and highly enantioselective towards these species. Favourable structural features were determined by careful comparison of the enantioseparation of the probe molecules. Molecular modelling studies indicate that U-shaped (folded) conformations were most favorable to achieve high enantioresolution on these CSP, while linear (extended) conformations were not so clearly discriminated. For a subset of these species adopting different conformations, a broad range of mobile phase compositions, ranging from 20 to 100% methanol in carbon dioxide, were investigated. While retention decreased continuously in this range, enantioseparation varied in a non-monotonous fashion. Abrupt changes in the tendency curves of retention and selectivity were observed when methanol proportion reaches about 60%, suggesting that a change in the conformation of the analytes and/or chiral selector is occurring at this point. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase for the enantioseparation of drugs in supercritical fluid chromatography: comparison with HPLC.

    Science.gov (United States)

    Kalíková, Květa; Martínková, Monika; Schmid, Martin G; Tesařová, Eva

    2018-03-01

    A cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase was studied as a tool for the enantioselective separation of 21 selected analytes with different pharmaceutical and physicochemical properties. The enantioseparations were performed using supercritical fluid chromatography. The effect of the mobile phase composition was studied. Four different additives (diethylamine, triethylamine, isopropylamine, and trifluoroacetic acid) and isopropylamine combined with trifluoroacetic acid were tested and their influence on enantioseparation was compared. The influence of two different mobile phase co-solvents (methanol and propan-2-ol) combined with all the additives was also evaluated. The best mobile phase compositions for the separation of the majority of enantiomers were CO 2 /methanol/isopropylamine 80:20:0.1 v/v/v or CO 2 /propan-2-ol/isopropylamine/trifluoroacetic acid 80:20:0.05:0.05 v/v/v/v. The best results were obtained from the group of basic β-blockers. A high-performance liquid chromatography separation system composed of the same stationary phase and mobile phase of similar properties prepared as a mixture of hexane/propan-2-ol/additive 80:20:0.1 v/v/v was considered for comparison. Supercritical fluid chromatography was found to yield better results, i.e. better enantioresolution for shorter analysis times than high-performance liquid chromatography. However, examples of enantiomers better resolved under the optimized conditions in high-performance liquid chromatography were also found. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Evaluation of innovative stationary phase ligand chemistries and analytical conditions for the analysis of basic drugs by supercritical fluid chromatography.

    Science.gov (United States)

    Desfontaine, Vincent; Veuthey, Jean-Luc; Guillarme, Davy

    2016-03-18

    Similar to reversed phase liquid chromatography, basic compounds can be highly challenging to analyze by supercritical fluid chromatography (SFC), as they tend to exhibit poor peak shape, especially those with high pKa values. In this study, three new stationary phase ligand chemistries available in sub -2 μm particle sizes, namely 2-picolylamine (2-PIC), 1-aminoanthracene (1-AA) and diethylamine (DEA), were tested in SFC conditions for the analysis of basic drugs. Due to the basic properties of these ligands, it is expected that the repulsive forces may improve peak shape of basic substances, similarly to the widely used 2-ethypyridine (2-EP) phase. However, among the 38 tested basic drugs, less of 10% displayed Gaussian peaks (asymmetry between 0.8 and 1.4) using pure CO2/methanol on these phases. The addition of 10mM ammonium formate as mobile phase additive, drastically improved peak shapes and increased this proportion to 67% on 2-PIC. Introducing the additive in the injection solvent rather than in the organic modifier, gave acceptable results for 2-PIC only, with 31% of Gaussian peaks with an average asymmetry of 1.89 for the 38 selected basic drugs. These columns were also compared to hybrid silica (BEH), DIOL and 2-EP stationary phases, commonly employed in SFC. These phases commonly exhibit alternative retention and selectivity. In the end, the two most interesting ligands used as complementary columns were 2-PIC and BEH, as they provided suitable peak shapes for the basic drugs and almost orthogonal selectivities. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Ceramic stationary gas turbine development. Final report, Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1994-09-01

    This report summarizes work performed by Solar Turbines Inc. and its subcontractors during the period September 25, 1992 through April 30, 1993. The objective of the work is to improve the performance of stationary gas turbines in cogeneration through implementation of selected ceramic components.

  6. Deteriorated stress response in stationary-phase yeast: Sir2 and Yap1 are essential for Hsf1 activation by heat shock and oxidative stress, respectively.

    Directory of Open Access Journals (Sweden)

    Inbal Nussbaum

    Full Text Available Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response.

  7. Deteriorated stress response in stationary-phase yeast: Sir2 and Yap1 are essential for Hsf1 activation by heat shock and oxidative stress, respectively.

    Science.gov (United States)

    Nussbaum, Inbal; Weindling, Esther; Jubran, Ritta; Cohen, Aviv; Bar-Nun, Shoshana

    2014-01-01

    Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response.

  8. A 2H nuclear magnetic resonance study of the state of water in neat silica and zwitterionic stationary phases and its influence on the chromatographic retention characteristics in hydrophilic interaction high-performance liquid chromatography.

    Science.gov (United States)

    Wikberg, Erika; Sparrman, Tobias; Viklund, Camilla; Jonsson, Tobias; Irgum, Knut

    2011-09-23

    2H NMR has been used as a tool for probing the state of water in hydrophilic stationary phases for liquid chromatography at temperatures between -80 and +4 °C. The fraction of water that remained unfrozen in four different neat silicas with nominal pore sizes between 60 and 300 Å, and in silicas with polymeric sulfobetaine zwitterionic functionalities prepared in different ways, could be determined by measurements of the line widths and temperature-corrected integrals of the 2H signals. The phase transitions detected during thawing made it possible to estimate the amount of non-freezable water in each phase. A distinct difference was seen between the neat and modified silicas tested. For the neat silicas, the relationship between the freezing point depression and their pore size followed the expected Gibbs-Thomson relationship. The polymeric stationary phases were found to contain considerably higher amounts of non-freezable water compared to the neat silica, which is attributed to the structural effect that the sulfobetaine polymers have on the water layer close to the stationary phase surface. The sulfobetaine stationary phases were used alongside the 100 Å silica to separate a number of polar compounds in hydrophilic interaction (HILIC) mode, and the retention characteristics could be explained in terms of the surface water structure, as well as by the porous properties of the stationary phases. This provides solid evidence supporting a partitioning mechanism, or at least of the existence of an immobilized layer of water into which partitioning could be occurring. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Bacterial metabolism of human polymorphonuclear leukocyte-derived arachidonic acid.

    Science.gov (United States)

    Sorrell, T C; Muller, M; Sztelma, K

    1992-05-01

    Evidence for transcellular bacterial metabolism of phagocyte-derived arachidonic acid was sought by exposing human blood polymorphonuclear leukocytes, prelabelled with [3H]arachidonic acid, to opsonized, stationary-phase Pseudomonas aeruginosa (bacteria-to-phagocyte ratio of 50:1) for 90 min at 37 degrees C. Control leukocytes were stimulated with the calcium ionophore A23187 (5 microM) for 5 min. Radiochromatograms of arachidonic acid metabolites, extracted from A23187-stimulated cultures and then separated by reverse-phase high-performance liquid chromatography, revealed leukotriene B4, its omega-oxidation products, and 5-hydroxy-eicosatetraenoic acid. In contrast, two major metabolite peaks, distinct from known polymorphonuclear leukocyte arachidonic acid products by high-performance liquid chromatography or by thin-layer chromatography, were identified in cultures of P. aeruginosa with [3H]arachidonic acid-labelled polymorphonuclear leukocytes. Respective chromatographic characteristics of these novel products were identical to those of two major metabolite peaks produced by incubation of stationary-phase P. aeruginosa with [3H]arachidonic acid. Production of the metabolites was dependent upon pseudomonal viability. UV spectral data were consistent with a conjugated diene structure. Metabolism of arachidonic acid by P. aeruginosa was not influenced by the presence of catalase, superoxide dismutase, nordihydroguaiaretic acid, ethanol, dimethyl sulfoxide, or ferrous ions but was inhibited by carbon monoxide, ketoconazole, and 1,2-epoxy-3,3,3-trichloropropane. Our data suggest that pseudomonal metabolism of polymorphonuclear leukocyte-derived arachidonic acid occurs during phagocytosis, probably by enzymatic epoxidation and hydroxylation via an oxygenase. By this means, potential proinflammatory effects of arachidonic acid or its metabolites may be modulated by P. aeruginosa at sites of infection in vivo.

  10. Synthesis of a stationary phase based on silica modified with branched octadecyl groups by Michael addition and photoinduced thiol-yne click chemistry for the separation of basic compounds.

    Science.gov (United States)

    Huang, Guang; Ou, Junjie; Wang, Hongwei; Ji, Yongsheng; Wan, Hao; Zhang, Zhang; Peng, Xiaojun; Zou, Hanfa

    2016-04-01

    A novel silica-based stationary phase with branched octadecyl groups was prepared by the sequential employment of the Michael addition reaction and photoinduced thiol-yne click chemistry with 3-aminopropyl-functionalized silica microspheres as the initial material. The resulting stationary phase denoted as SiO2 -N(C18)4 was characterized by elemental analysis, FTIR spectroscopy and Raman spectroscopy, demonstrating the existence of branched octadecyl groups in silica microspheres. The separations of benzene homologous compounds, acid compounds and amine analogues were conducted, demonstrating mixed-mode separation mechanism on SiO2 -N(C18)4 . Baseline separation of basic drugs mixture was acquired with the mobile phase of acetonitrile/H2 O (5%, v/v). SiO2 -N(C18)4 was further applied to separate Corydalis yanhusuo Wang water extracts, and more baseline separation peaks were obtained for SiO2 -N(C18)4 than those on Atlantis dC18 column. It can be expected that this new silica-based stationary phase will exhibit great potential in the analysis of basic compounds. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Two-dimensional high-performance thin-layer chromatography of tryptic bovine albumin digest using normal- and reverse-phase systems with silanized silica stationary phase.

    Science.gov (United States)

    Gwarda, Radosław Łukasz; Dzido, Tadeusz Henryk

    2013-10-18

    Among many advantages of planar techniques, two-dimensional (2D) separation seems to be the most important for analysis of complex samples. Here we present quick, simple and efficient two-dimensional high-performance thin-layer chromatography (2D HPTLC) of bovine albumin digest using commercial HPTLC RP-18W plates (silica based stationary phase with chemically bonded octadecyl ligands of coverage density 0.5μmol/m(2) from Merck, Darmstadt). We show, that at low or high concentration of water in the mobile phase comprised methanol and some additives the chromatographic systems with the plates mentioned demonstrate normal- or reversed-phase liquid chromatography properties, respectively, for separation of peptides obtained. These two systems show quite different separation selectivity and their combination into 2D HPTLC process provides excellent separation of peptides of the bovine albumin digest. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Application of a cholesterol stationary phase in the analysis of phosphorothioate oligonucleotides by means of ion pair chromatography coupled with tandem mass spectrometry.

    Science.gov (United States)

    Studzińska, Sylwia; Krzemińska, Katarzyna; Szumski, Michał; Buszewski, Bogusław

    2016-07-01

    The main aim of this study was the investigation of the influence of several ion pair reagents towards both the retention and the mass spectrometry sensitivity of phosphorothioate oligonucleotides. A cholesterol stationary phase was applied for the first time in the analysis of this group of compounds. The mobile phase composition was modified by changing the concentration and the type of amines and acetates or 1,1,1,3,3,3-hexafluoroisopropanol. It has been shown that the increase of amines concentration results in the retention factor increase for each oligonucleotide, on each adsorbent. The only exception was the mobile phase composed of triethylamine and 1,1,1,3,3,3-hexafluoroisopropanol. This is a consequence of interactions taking place between a cholesterol molecule and an alcohol. This effect was convenient when the mass spectrometry detection was applied, since it allowed an increase in the sensitivity. Moreover, optimization of the mobile phase composition and its impact on the efficiency of ionization process and on the sensitivity in mass spectrometry were also presented. The optimization of this new method, based on cholesterol stationary phase coupled with mass spectrometry detection, was finally applied for the determination of phosphorothioate oligonucleotides impurity in a real sample. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Rapid purification of diastereoisomers from Piper kadsura using supercritical fluid chromatography with chiral stationary phases.

    Science.gov (United States)

    Xin, Huaxia; Dai, Zhuoshun; Cai, Jianfeng; Ke, Yanxiong; Shi, Hui; Fu, Qing; Jin, Yu; Liang, Xinmiao

    2017-08-04

    Supercritical fluid chromatography (SFC) with chiral stationary phases (CSPs) is an advanced solution for the separation of achiral compounds in Piper kadsura. Analogues and stereoisomers are abundant in natural products, but there are obstacles in separation using conventional method. In this paper, four lignan diastereoisomers, (-)-Galbelgin, (-)-Ganschisandrin, Galgravin and (-)-Veraguensin, from Piper kadsura were separated and purified by chiral SFC. Purification strategy was designed, considering of the compound enrichment, sample purity and purification throughput. Two-step achiral purification method on chiral preparative columns with stacked automated injections was developed. Unconventional mobile phase modifier dichloromethane (DCM) was applied to improve the sample solubility. Four diastereoisomers was prepared at the respective weight of 103.1mg, 10.0mg, 152.3mg and 178.6mg from 710mg extract with the purity of greater than 98%. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Rerouting of carbon flux in a glycogen mutant of cyanobacteria assessed via isotopically non-stationary 13 C metabolic flux analysis.

    Science.gov (United States)

    Hendry, John I; Prasannan, Charulata; Ma, Fangfang; Möllers, K Benedikt; Jaiswal, Damini; Digmurti, Madhuri; Allen, Doug K; Frigaard, Niels-Ulrik; Dasgupta, Santanu; Wangikar, Pramod P

    2017-10-01

    Cyanobacteria, which constitute a quantitatively dominant phylum, have attracted attention in biofuel applications due to favorable physiological characteristics, high photosynthetic efficiency and amenability to genetic manipulations. However, quantitative aspects of cyanobacterial metabolism have received limited attention. In the present study, we have performed isotopically non-stationary 13 C metabolic flux analysis (INST- 13 C-MFA) to analyze rerouting of carbon in a glycogen synthase deficient mutant strain (glgA-I glgA-II) of the model cyanobacterium Synechococcus sp. PCC 7002. During balanced photoautotrophic growth, 10-20% of the fixed carbon is stored in the form of glycogen via a pathway that is conserved across the cyanobacterial phylum. Our results show that deletion of glycogen synthase gene orchestrates cascading effects on carbon distribution in various parts of the metabolic network. Carbon that was originally destined to be incorporated into glycogen gets partially diverted toward alternate storage molecules such as glucosylglycerol and sucrose. The rest is partitioned within the metabolic network, primarily via glycolysis and tricarboxylic acid cycle. A lowered flux toward carbohydrate synthesis and an altered distribution at the glucose-1-phosphate node indicate flexibility in the network. Further, reversibility of glycogen biosynthesis reactions points toward the presence of futile cycles. Similar redistribution of carbon was also predicted by Flux Balance Analysis. The results are significant to metabolic engineering efforts with cyanobacteria where fixed carbon needs to be re-routed to products of interest. Biotechnol. Bioeng. 2017;114: 2298-2308. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Wide-range high-resolution transmission electron microscopy reveals morphological and distributional changes of endomembrane compartments during log to stationary transition of growth phase in tobacco BY-2 cells.

    Science.gov (United States)

    Toyooka, Kiminori; Sato, Mayuko; Kutsuna, Natsumaro; Higaki, Takumi; Sawaki, Fumie; Wakazaki, Mayumi; Goto, Yumi; Hasezawa, Seiichiro; Nagata, Noriko; Matsuoka, Ken

    2014-09-01

    Rapid growth of plant cells by cell division and expansion requires an endomembrane trafficking system. The endomembrane compartments, such as the Golgi stacks, endosome and vesicles, are important in the synthesis and trafficking of cell wall materials during cell elongation. However, changes in the morphology, distribution and number of these compartments during the different stages of cell proliferation and differentiation have not yet been clarified. In this study, we examined these changes at the ultrastructural level in tobacco Bright yellow 2 (BY-2) cells during the log and stationary phases of growth. We analyzed images of the BY-2 cells prepared by the high-pressure freezing/freeze substitution technique with the aid of an auto-acquisition transmission electron microscope system. We quantified the distribution of secretory and endosomal compartments in longitudinal sections of whole cells by using wide-range gigapixel-class images obtained by merging thousands of transmission electron micrographs. During the log phase, all Golgi stacks were composed of several thick cisternae. Approximately 20 vesicle clusters (VCs), including the trans-Golgi network and secretory vesicle cluster, were observed throughout the cell. In the stationary-phase cells, Golgi stacks were thin with small cisternae, and only a few VCs were observed. Nearly the same number of multivesicular body and small high-density vesicles were observed in both the stationary and log phases. Results from electron microscopy and live fluorescence imaging indicate that the morphology and distribution of secretory-related compartments dramatically change when cells transition from log to stationary phases of growth. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  16. Stereoelectronic model to explain the resolution of enantiomeric ibuprofen amides on the Pirkle chiral stationary phase.

    Science.gov (United States)

    Nicoll-Griffith, D A

    1987-07-31

    A chiral recognition model is proposed which incorporates the electronic and steric interactions between amide derivatives of ibuprofen and the (R)-N-(3,5-dinitrobenzoyl)phenylglycine-derived Pirkle chiral stationary phase during high-performance liquid chromatography. Based on this rationale, amide derivatives of ibuprofen were prepared using 4-chloroaniline, 4-bromoaniline, aniline, 4-methoxyaniline and 1-aminonaphthylene to improve the enantiomer separation over previously reported results with this column. The amides prepared gave separation values of 1.16, 1.16, 1.19, 1.21 and 1.23, respectively. These high separation values are consistent with the proposed model.

  17. Alkali Metal Modification of Silica Gel-Based Stationary Phase in Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Ashraf Yehia El-Naggar

    2013-01-01

    Full Text Available Modification of the precipitated silica gel was done by treatment with alkali metal (NaCl before and after calcination. The silica surfaces before and after modification were confirmed by infrared spectroscopy in order to observe the strength and abundance of the acidic surface OH group bands which play an important role in the adsorption properties of polar and nonpolar solutes. The surface-modified silica gels were tested as GC solid stationary phases in terms of the separation efficiency for various groups of non-polar and polar solutes. Also, thermodynamic parameters (ΔH, ΔG, and ΔS were determined using n-hexane as a probe in order to show the adsorbate-adsorbent interaction. It was observed that the non-polar solutes could be separated Independent on the reactivity and porosity of the silica surfaces. The efficiency of the surface-modified silica gels to separate the aromatic hydrocarbons seemed to be strongly influenced by the density of the surface hydroxyls.

  18. Recent Advances in Understanding of Kinetic Interplay Between Phase II Metabolism and Efflux Transport.

    Science.gov (United States)

    Wang, Shuai; Xing, Huijie; Zhao, Mengjing; Lu, Danyi; Li, Zhijie; Dong, Dong; Wu, Baojian

    2016-01-01

    Mechanistic understanding of the metabolism-transport interplay assumes great importance in pharmaceutical fields because the knowledge can help to interpret drug/xenobiotic metabolism and disposition studies as well as the drug-drug interactions in vivo. About 10 years ago, it started to recognize that cellular phase II metabolism is strongly influenced by the excretion (efflux transport) of generated metabolites, a kinetic phenomenon termed "phase II metabolism-transport interplay". This interplay is believed to have significant effects on the pharmacokinetics (bioavailability) of drugs/chemicals undergoing phase II metabolism. In this article, we review the studies investigating the phase II metabolism-transport interplay using cell models, perfused rat intestine, and intact rats. The potential confounding factors in exploring such interplay is also summarized. Moreover, the mechanism underlying the phase II metabolism-transport interplay is discussed. Various studies with engineered cells and rodents have demonstrated that there is an interaction (interplay) between phase II enzymes and efflux transporters. This type of interplay mainly refers to the dependence of phase II (conjugative) metabolism on the activities of efflux transporters. In general, inhibiting efflux transporters or decreasing their expression causes the reductions in metabolite excretion, apparent excretion clearance (CLapp) and total metabolism (fmet), as well as an increase in the intracellular level of metabolite (Ci). The deconjugation mediated by hydrolase (acting as a "bridge") is essential for the interplay to play out based on pharmacokinetic modeling/simulations, cell and animal studies. The hydrolases bridge the two processes (i.e., metabolite formation and excretion) and enable the interplay thereof (a bridging effect). Without the bridge, metabolite formation is independent on its downstream process excretion, thus impact of metabolite excretion on its formation is impossible

  19. Probing Gamma-ray Emission of Geminga & Vela with Non-stationary Models

    Directory of Open Access Journals (Sweden)

    Yating Chai

    2016-06-01

    Full Text Available It is generally believed that the high energy emissions from isolated pulsars are emitted from relativistic electrons/positrons accelerated in outer magnetospheric accelerators (outergaps via a curvature radiation mechanism, which has a simple exponential cut-off spectrum. However, many gamma-ray pulsars detected by the Fermi LAT (Large Area Telescope cannot be fitted by simple exponential cut-off spectrum, and instead a sub-exponential is more appropriate. It is proposed that the realistic outergaps are non-stationary, and that the observed spectrum is a superposition of different stationary states that are controlled by the currents injected from the inner and outer boundaries. The Vela and Geminga pulsars have the largest fluxes among all targets observed, which allows us to carry out very detailed phase-resolved spectral analysis. We have divided the Vela and Geminga pulsars into 19 (the off pulse of Vela was not included and 33 phase bins, respectively. We find that most phase resolved spectra still cannot be fitted by a simple exponential spectrum: in fact, a sub-exponential spectrum is necessary. We conclude that non-stationary states exist even down to the very fine phase bins.

  20. Impact of the updating scheme on stationary states of networks

    International Nuclear Information System (INIS)

    Radicchi, F; Ahn, Y Y; Meyer-Ortmanns, H

    2008-01-01

    From Boolean networks it is well known that the number of attractors as a function of the system size depends on the updating scheme which is chosen either synchronously or asynchronously. In this contribution, we report on a systematic interpolation between synchronous and asynchronous updating in a one-dimensional chain of Ising spins. The stationary state for fully synchronous updating is antiferromagnetic. The interpolation allows us to locate a phase transition between phases with an absorbing and a fluctuating stationary state. The associated universality class is that of parity conservation. We also report on a more recent study of asynchronous updates applied to the yeast cell-cycle network. Compared to the synchronous update, the basin of attraction of the largest attractor considerably shrinks and the convergence to the biological pathway slows down and is less dominant. Both examples illustrate how sensitively the stationary states and the properties of attractors can depend on the updating mode of the algorithm

  1. On necessary resonance criteria in the stationary one-channel case

    International Nuclear Information System (INIS)

    Szasz, G.I.

    1975-01-01

    First we will exhibit for the stationary case, a connection between the probability to find a particle in the region of interaction and the derivative of the scattering phase shift for the momentum. From the idea that in stationary scattering a resonance is linked with an appreciable increase of this probability, one obtains new and quantitative criteria for the behaviour of the scattering phase. The maximum probability for the particle to be in the region of interaction is considered in accordance with the criterium of maximal change of the phase shift as a function of k. This characterizes the location of the resonance. Wigner's lower limit for the derivate of the scattering phase allows the formulation of a resonance condition directly for the cross section. Furthermore, some connections with the pole approximations of the S-matrix and the 'collision lifetime' of Smith will be discussed. (orig./BJ) [de

  2. Enantiomeric separation of type I and type II pyrethroid insecticides with different chiral stationary phases by reversed-phase high-performance liquid chromatography.

    Science.gov (United States)

    Zhang, Ping; Yu, Qian; He, Xiulong; Qian, Kun; Xiao, Wei; Xu, Zhifeng; Li, Tian; He, Lin

    2018-04-01

    The enantiomeric separation of type I (bifenthrin, BF) and type II (lambda-cyhalothrin, LCT) pyrethroid insecticides on Lux Cellulose-1, Lux Cellulose-3, and Chiralpak IC chiral columns was investigated by reversed-phase high-performance liquid chromatography. Methanol/water or acetonitrile/water was used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase composition, column temperature, and thermodynamic parameters on enantiomer separation were carefully studied. Bifenthrin got a partial separation on Lux Cellulose-1 column and baseline separation on Lux Cellulose-3 column, while LCT enantiomers could be completely separated on both Lux Cellulose-1 and Lux Cellulose-3 columns. Chiralpak IC provided no separation ability for both BF and LCT. Retention factor (k) and selectivity factor (α) decreased with the column temperature increasing from 10°C to 40°C for both BF and LCT enantiomers. Thermodynamic parameters including ∆H and ∆S were also calculated, and the maximum R s were not always obtained at lowest temperature. Furthermore, the quantitative analysis methods for BF and LCT enantiomers in soil and water were also established. Such results provide a new approach for pyrethroid separation under reversed-phase condition and contribute to environmental risk assessment of pyrethroids at enantiomer level. © 2017 Wiley Periodicals, Inc.

  3. A Stationary Reference Frame Grid Synchronization System for Three-Phase Grid-Connected Power Converters Under Adverse Grid Conditions

    DEFF Research Database (Denmark)

    Rodríguez, P.; Luna, A.; Muñoz-Aguilar, R. S.

    2012-01-01

    synchronization method for three-phase three-wire networks, namely dual second-order generalized integrator (SOGI) frequency-locked loop. The method is based on two adaptive filters, implemented by using a SOGI on the stationary αβ reference frame, and it is able to perform an excellent estimation......Grid synchronization algorithms are of great importance in the control of grid-connected power converters, as fast and accurate detection of the grid voltage parameters is crucial in order to implement stable control strategies under generic grid conditions. This paper presents a new grid...

  4. Enantioseparation and chiral recognition mechanism of new chiral derivatives of xanthones on macrocyclic antibiotic stationary phases.

    Science.gov (United States)

    Fernandes, Carla; Tiritan, Maria Elizabeth; Cass, Quezia; Kairys, Visvaldas; Fernandes, Miguel Xavier; Pinto, Madalena

    2012-06-08

    A chiral HPLC method using four macrocyclic antibiotic chiral stationary phases (CSPs) has been investigated for determination of the enantiomeric purity of fourteen new chiral derivatives of xanthones (CDXs). The separations were performed with the CSPs Chirobiotic T, Chirobiotic TAG, Chirobiotic V and Chirobiotic R under multimodal elution conditions (normal-phase, reversed-phase and polar ionic mode). The analyses were performed at room temperature in isocratic mode and UV and CD detection at a wavelength of 254 nm. The best enantioselectivity and resolution were achieved on Chirobiotic R and Chirobiotic T CSPs, under normal elution conditions, with R(S) ranging from 1.25 to 2.50 and from 0.78 to 2.06, respectively. The optimized chromatographic conditions allowed the determination of the enantiomeric ratio of eight CDXs, always higher than 99%. In order to better understand the chromatographic behavior at a molecular level, and the structural features associated with the chiral recognition mechanism, computational studies by molecular docking were carried out using VDock. These studies shed light on the mechanisms involved in the enantioseparation for this important class of chiral compounds. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Normal-phase liquid chromatography retention behavior of polycyclic aromatic sulfur heterocycles and alkyl-substituted polycyclic aromatic sulfur heterocycle isomers on an aminopropyl stationary phase.

    Science.gov (United States)

    Wilson, Walter B; Hayes, Hugh V; Sander, Lane C; Campiglia, Andres D; Wise, Stephen A

    2018-02-01

    Retention indices for 67 polycyclic aromatic sulfur heterocycles (PASHs) and 80 alkyl-substituted PASHs were determined using normal-phase liquid chromatography (NPLC) on an aminopropyl (NH 2 ) stationary phase. The retention behavior of PASH on the NH 2 phase is correlated with the number of aromatic carbon atoms and two structural characteristics have a significant influence on their retention: non-planarity (thickness, T) and the position of the sulfur atom in the bay-region of the structure. Correlations between solute retention on the NH 2 phase and T of PASHs were investigated for three cata-condensed (cata-) PASH isomer groups: (a) 13 four-ring molecular mass (MM) 234 Da cata-PASHs, (b) 20 five-ring MM 284 Da cata-PASHs, and (c) 12 six-ring MM 334 Da cata-PASHs. Correlation coefficients ranged from r = -0.49 (MM 234 Da) to r = -0.65 (MM 334 Da), which were significantly lower than structurally similar PAH isomer groups (r = -0.70 to r = -0.99). The NPLC retention behavior of the PASHs are compared to similar results for PAHs.

  6. Stationary and non-stationary occurrences of miniature end plate potentials are well described as stationary and non-stationary Poisson processes in the mollusc Navanax inermis.

    Science.gov (United States)

    Cappell, M S; Spray, D C; Bennett, M V

    1988-06-28

    Protractor muscles in the gastropod mollusc Navanax inermis exhibit typical spontaneous miniature end plate potentials with mean amplitude 1.71 +/- 1.19 (standard deviation) mV. The evoked end plate potential is quantized, with a quantum equal to the miniature end plate potential amplitude. When their rate is stationary, occurrence of miniature end plate potentials is a random, Poisson process. When non-stationary, spontaneous miniature end plate potential occurrence is a non-stationary Poisson process, a Poisson process with the mean frequency changing with time. This extends the random Poisson model for miniature end plate potentials to the frequently observed non-stationary occurrence. Reported deviations from a Poisson process can sometimes be accounted for by the non-stationary Poisson process and more complex models, such as clustered release, are not always needed.

  7. Normal-phase liquid chromatography retention behavior of polycyclic aromatic hydrocarbon and their methyl-substituted derivatives on an aminopropyl stationary phase.

    Science.gov (United States)

    Wilson, Walter B; Hayes, Hugh V; Sander, Lane C; Campiglia, Andres D; Wise, Stephen A

    2017-09-01

    Retention indices for 124 polycyclic aromatic hydrocarbons (PAHs) and 62 methyl-substituted (Me-) PAHs were determined using normal-phase liquid chromatography (NPLC) on a aminopropyl (NH 2 ) stationary phase. PAH retention behavior on the NH 2 phase is correlated to the total number of aromatic carbons in the PAH structure. Within an isomer group, non-planar isomers generally elute earlier than planar isomers. MePAHs generally elute slightly later but in the same region as the parent PAHs. Correlations between PAH retention behavior on the NH 2 phase and PAH thickness (T) values were investigated to determine the influence of non-planarity for isomeric PAHs with four to seven aromatic rings. Correlation coefficients ranged from r = 0.19 (five-ring peri-condensed molecular mass (MM) 252 Da) to r = -0.99 (five-ring cata-condensed MM 278 Da). In the case of the smaller PAHs (MM ≤ 252 Da), most of the PAHs had a planar structure and provided a low correlation. In the case of larger PAHs (MM ≥ 278 Da), nonplanarity had a significant influence on the retention behavior and good correlation between retention and T was obtained for the MM 278 Da, MM 302 Da, MM 328 Da, and MM 378 Da isomer sets. Graphical abstract NPLC separation of the three-, four-, five-, and six-ring PAH isomers with different number of aromatic carbon atoms and degrees of non-planarity (Thickness, T). The inserted figure plots the number of aromatic carbon atoms vs. the log I value for the 124 parent PAHs.

  8. Chaotic Bohmian trajectories for stationary states

    International Nuclear Information System (INIS)

    Cesa, Alexandre; Martin, John; Struyve, Ward

    2016-01-01

    In Bohmian mechanics, the nodes of the wave function play an important role in the generation of chaos. However, so far, most of the attention has been on moving nodes; little is known about the possibility of chaos in the case of stationary nodes. We address this question by considering stationary states, which provide the simplest examples of wave functions with stationary nodes. We provide examples of stationary wave functions for which there is chaos, as demonstrated by numerical computations, for one particle moving in three spatial dimensions and for two and three entangled particles in two dimensions. Our conclusion is that the motion of the nodes is not necessary for the generation of chaos. What is important is the overall complexity of the wave function. That is, if the wave function, or rather its phase, has a complex spatial variation, it will lead to complex Bohmian trajectories and hence to chaos. Another aspect of our work concerns the average Lyapunov exponent, which quantifies the overall amount of chaos. Since it is very hard to evaluate the average Lyapunov exponent analytically, which is often computed numerically, it is useful to have simple quantities that agree well with the average Lyapunov exponent. We investigate possible correlations with quantities such as the participation ratio and different measures of entanglement, for different systems and different families of stationary wave functions. We find that these quantities often tend to correlate to the amount of chaos. However, the correlation is not perfect, because, in particular, these measures do not depend on the form of the basis states used to expand the wave function, while the amount of chaos does. (paper)

  9. Learning Markov models for stationary system behaviors

    DEFF Research Database (Denmark)

    Chen, Yingke; Mao, Hua; Jaeger, Manfred

    2012-01-01

    to a single long observation sequence, and in these situations existing automatic learning methods cannot be applied. In this paper, we adapt algorithms for learning variable order Markov chains from a single observation sequence of a target system, so that stationary system properties can be verified using......Establishing an accurate model for formal verification of an existing hardware or software system is often a manual process that is both time consuming and resource demanding. In order to ease the model construction phase, methods have recently been proposed for automatically learning accurate...... the learned model. Experiments demonstrate that system properties (formulated as stationary probabilities of LTL formulas) can be reliably identified using the learned model....

  10. High-performance liquid chromatographic enantioseparation of unusual isoxazoline-fused 2-aminocyclopentanecarboxylic acids on macrocyclic glycopeptide-based chiral stationary phases.

    Science.gov (United States)

    Sipos, László; Ilisz, István; Nonn, Melinda; Fülöp, Ferenc; Pataj, Zoltán; Armstrong, Daniel W; Péter, Antal

    2012-04-06

    The enantiomers of four unusual isoxazoline-fused 2-aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing macrocyclic glycopeptide antibiotics teicoplanin (Astec Chirobiotic T and T2), teicoplanin aglycone (Chirobiotic TAG), vancomycin (Chirobiotic V) and vancomycin aglycone (Chirobiotic VAG) as chiral selectors. The effects of the mobile phase composition, the structure of the analytes and temperature on the separations were investigated. Experiments were performed at constant mobile phase compositions in the temperature range 5-45 °C to study the effects of temperature, and thermodynamic parameters were calculated from plots of lnk or lnα versus 1/T. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. It was found that the enantiomeric separations were in most cases enthalpy-driven. The sequence of elution of the enantiomers was determined in all cases. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. In vitro phase I metabolism of gamabufotalin and arenobufagin: Reveal the effect of substituent group on metabolic stability.

    Science.gov (United States)

    Feng, Yujie; Wang, Chao; Tian, Xiangge; Huo, Xiaokui; Feng, Lei; Sun, Chengpeng; Ge, Guangbo; Yang, Ling; Ning, Jing; Ma, Xiaochi

    2017-09-01

    Bufadienolides are a major class of bioactive compounds derived from amphibian skin secretion. Gamabufotalin (GB) and arenobufagin (AB) are among the top of the intensively investigated natural bufadienolides for their outstanding biological activities. This study aimed to characterize the phase I metabolism of GB and AB with respect to the metabolic profiles, enzymes involved, and catalytic efficacy, thereafter tried to reveal substituent effects on metabolism. Two mono-hydroxylated products of GB and AB were detected in the incubation mixtures, and they were accurately identified as 1- and 5-hydroxylated bufadienolides by NMR and HPLC-MS techniques. Reaction phenotyping studies demonstrated that CYP3A mediated the metabolism of the two bufadienolides with a high specific selectivity. Further kinetic evaluation demonstrated that the metabolism stability of GB and AB were better than other reported bufadienolides. Additionally, the CYP3A5 preference for hydroxylation of AB was observed, which was different to the selectivity of CYP3As for bufadienolides suggested by our previous report. This study can provide important data for elucidating the phase I metabolism of GB and AB and can lead to a better understanding of the bufadienolide-CYP3A interaction which is helpful for preclinical development and rational use of bufadienolides. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Thermal and Hydrothermal Treatment of Silica Gels as Solid Stationary Phases in Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Ashraf Yehia El-Naggar

    2013-01-01

    Full Text Available Silica gel was prepared and treated thermally and hydrothermally and was characterized as solid stationary phase in gas chromatography. The characteristics have been evaluated in terms of polarity, selectivity, and separation efficiencies. These parameters were used to assess the outer silica surface contributions and the degree of surface deactivation brought about by different treatment techniques. The parent silica elutes the paraffinic hydrocarbons with high efficiency of separation and elutes aromatic hydrocarbons with nearly good separation and has bad separation of alcohols. The calcined silica at 500°C and 1000°C has a pronounced effect on the separation of aromatic hydrocarbons compared with the parent silica and hydrothermal treatment of silica. With respect to alcohols separation, the obtained bad separations using treated and untreated silica reflect the little effect of the thermal and hydrothermal treatment on the silica surface deactivation.

  13. Role of microorganism growth phase in the accumulation and characteristics of biomacromolecules (BMM) in a membrane bioreactor

    DEFF Research Database (Denmark)

    Zhou, Zhongbo; Meng, Fangang; Liang, Shuang

    2012-01-01

    The objective of this study was to highlight the significance of microorganism growth on the production of biomacromolecules (BMM) in a membrane bioreactor (MBR). During the MBR operation, both polysaccharides and proteins in the sludge supernatant were found to increase steadily in exponential...... growth phase (EGP) due to higher organic loading rates and microbial primary metabolism. Subsequently, both increased continuously and then decreased sharply in the following deceleration growth phase (DGP). Finally, the BMM maintained a low and steady level as the sludge reached stationary growth phase...

  14. On structural identifiability analysis of the cascaded linear dynamic systems in isotopically non-stationary 13C labelling experiments.

    Science.gov (United States)

    Lin, Weilu; Wang, Zejian; Huang, Mingzhi; Zhuang, Yingping; Zhang, Siliang

    2018-06-01

    The isotopically non-stationary 13C labelling experiments, as an emerging experimental technique, can estimate the intracellular fluxes of the cell culture under an isotopic transient period. However, to the best of our knowledge, the issue of the structural identifiability analysis of non-stationary isotope experiments is not well addressed in the literature. In this work, the local structural identifiability analysis for non-stationary cumomer balance equations is conducted based on the Taylor series approach. The numerical rank of the Jacobian matrices of the finite extended time derivatives of the measured fractions with respect to the free parameters is taken as the criterion. It turns out that only one single time point is necessary to achieve the structural identifiability analysis of the cascaded linear dynamic system of non-stationary isotope experiments. The equivalence between the local structural identifiability of the cascaded linear dynamic systems and the local optimum condition of the nonlinear least squares problem is elucidated in the work. Optimal measurements sets can then be determined for the metabolic network. Two simulated metabolic networks are adopted to demonstrate the utility of the proposed method. Copyright © 2018 Elsevier Inc. All rights reserved.

  15. Metabolism of ferulic acid during growth of Lactobacillus plantarum and Lactobacillus collinoides.

    Science.gov (United States)

    Knockaert, Dries; Raes, Katleen; Wille, Christophe; Struijs, Karin; Van Camp, John

    2012-08-30

    Food-isolated lactic acid bacteria can transform ferulic acid (FA) into several products. Since quantification of these metabolites during the different bacterial growth phases is lacking, the aim of this study was to identify and quantify conversion products of FA and to follow the kinetics of FA metabolism during growth of Lactobacillus plantarum and Lactobacillus collinoides. Lactobacillus plantarum and Lactobacillus collinoides were incubated in MRS broth, to which different amounts of FA were added (final concentrations of 0, 0.5, 1.5 and 3 mmol L⁻¹), at 30 °C until the late stationary phase. Lactobacillus plantarum metabolised FA into 4-vinylguaiacol (4-VG) and hydroferulic acid (HFA). Conversion to 4-VG started simultaneously with the degradation of FA, while formation of HFA started in the mid-exponential phase. Lactobacillus collinoides only formed 4-VG, mainly in the stationary phase. No significant effect of the different amounts of FA was seen on the growth and fermentation characteristics of both bacteria. The results demonstrate that both bacteria are able to convert FA. However, start of conversion differs between the two strains. The different amounts of FA had no influence on the growth and fermentation characteristics of both bacteria. Copyright © 2012 Society of Chemical Industry.

  16. Significance and challenges of stereoselectivity assessing methods in drug metabolism

    Directory of Open Access Journals (Sweden)

    Zhuowei Shen

    2016-02-01

    Full Text Available Stereoselectivity in drug metabolism can not only influence the pharmacological activities, tolerability, safety, and bioavailability of drugs directly, but also cause different kinds of drug–drug interactions. Thus, assessing stereoselectivity in drug metabolism is of great significance for pharmaceutical research and development (R&D and rational use in clinic. Although there are various methods available for assessing stereoselectivity in drug metabolism, many of them have shortcomings. The indirect method of chromatographic methods can only be applicable to specific samples with functional groups to be derivatized or form complex with a chiral selector, while the direct method achieved by chiral stationary phases (CSPs is expensive. As a detector of chromatographic methods, mass spectrometry (MS is highly sensitive and specific, whereas the matrix interference is still a challenge to overcome. In addition, the use of nuclear magnetic resonance (NMR and immunoassay in chiral analysis are worth noting. This review presents several typical examples of drug stereoselective metabolism and provides a literature-based evaluation on current chiral analytical techniques to show the significance and challenges of stereoselectivity assessing methods in drug metabolism.

  17. Stationary analysis of signals and ratio decay determination in BWR type reactors by neuronal network

    International Nuclear Information System (INIS)

    Sanchis, R.; Palomo, M. J.; Munoz-Cobo, J. L.

    1998-01-01

    The signals registered in the nuclear plants have non stationary characteristics, in numerous times. This made difficult the application of the methods of analysis. There are determinate temporal intervals in that the signal is stationary with determinate mean, value together of zones with corrupt registers, and other zones with mean value distinct, but stationary during a temporal interval. The methodology consist in a stationary analysis to the signal received of the nuclear plant. With the Gabor Transformation are determined the temporal intervals of the stationary signals, synthesised it, as previous phase to the application of the methods of the analysis of stability parameters with methods ARMA, SVD, Neural Net,... to the reconstructed signal. 4 refs. (Author)

  18. In situ synthesis of metal-organic frameworks in a porous polymer monolith as the stationary phase for capillary liquid chromatography.

    Science.gov (United States)

    Yang, Shengchao; Ye, Fanggui; Zhang, Cong; Shen, Shufen; Zhao, Shulin

    2015-04-21

    In this study, HKUST-1 was synthesized in situ on the porous polymer monolith as the stationary phase for capillary liquid chromatography (cLC). The unique carboxyl functionalized poly(methacrylic acid-co-ethylene dimethacrylate) (poly(MAA-co-EDMA)) monolith was used as a support to directly grow HKUST-1 by a controlled layer-by-layer self-assembly strategy. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, and Fourier transform infrared spectroscopy of the resulting HKUST-1-poly(MAA-co-EDMA) monoliths indicated that HKUST-1 was successfully grafted onto the pore surface of the poly(MAA-co-EDMA) monolith. The column performance of HKUST-1-poly(MAA-co-EDMA) monoliths for the separation of various small molecules, such as benzenediols, xylenes, ethylbenzenes, and styrenes, was evaluated. The chromatographic performance was found to improve with increasing HKUST-1 density, and the column efficiencies and resolutions of HKUST-1-poly(MAA-co-EDMA) monoliths were 18 320-19 890 plates m(-1) and 1.62-6.42, respectively, for benzenediols. The HKUST-1-poly(MAA-co-EDMA) monolith displayed enhanced resolution for the separation of positional isomers when compared to the traditional C18 and HKUST-1 incorporated polymer monoliths. Hydrophobic, π-π, and hydrogen bonding interactions within the HKUST-1-poly(MAA-co-EDMA) monolith were observed in the separation of small molecules. The results showed that the HKUST-1-poly(MAA-co-EDMA) monoliths are promising stationary phases for cLC.

  19. Influence of stationary and non-stationary conditions on drying time and mechanical properties of a porcelain slab

    Science.gov (United States)

    Hammouda, Imen; Mihoubi, Daoued

    2017-12-01

    This work deals with a numerical study of the response of a porcelain slab when subjected to convective drying in stationary and non-stationary conditions. The used model describes heat, mass, and momentum transfers is applied to an unsaturated viscoelastic medium described by a Maxwell model. The numerical code allows us to determine the effect of the surrounding air temperature on drying kinetics and on mechanical stress intensities. Von Mises stresses are analysed in order to foresee an eventual damage that may occur during drying. Simulation results for several temperatures in the range of [30 °C, 90 °C] shows that for the temperature from 30 °C to 60 °C, Von Mises stresses are always lower than the yield strength. But above 70 °C, Von Mises stresses are higher than the ultimate strength, and consequently there is a risk of crack at the end of the constant drying rate period. The idea proposed in this work is to integrate a reducing temperature phase when the predicted Von Mises stress intensity exceeds the admissible stress. Simulation results shows that a non-stationary convective drying (90-60 °C) allows us to optimize costs and quality by reducing the drying time and maintaining Von Mises stress values under the admissible stress.

  20. [Preparation and evaluation of stationary phase of high performance liquid chromatography for the separation of basic solutes].

    Science.gov (United States)

    Wang, P; Wang, J; Cong, R; Dong, B

    1997-05-01

    A bonded phase for high performance liquid chromatography (HPLC) has been prepared by the new reaction between silica and silicon ether. The ether was synthesized from alkylchlorosilane and pentane-2,4-dione in the presence of imidazole under inert conditions by using anhydrous tetrahydrofuran as solvent. The bonded phase thus obtained was characterized by elemental analysis, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and HPLC evaluation. The carbon content was 9.4% and the surface coverage almost attained 3.0micromol/m2 without end-capping. The silanol absorption peaks of the product cannot be observed from the DRIFT spectrum, which revealed that the silanization reaction proceeded thoroughly. The basic solutes, such as aniline, o-toluidine, p-toluidine, N,N-dimethylaniline and pyridine were used as the probe solutes to examine their interaction with the residual silanols on the surface of the products. No buffer or salt was used in the mobile phase for these experiments. In comparison with an acidic solute, such as, phenol, basic aniline eluted in front of phenol, and the ratio of asymmetry of aniline peak to that of the phenol peak was 1.1. Furthermore the relative k' value of p-toluidine to that of o-toluidine was also 1.1. All the results showed that the stationary phase has better quality and reproducibility and can be used for the separation of basic solutes efficiently.

  1. Fases estacionárias quirais para cromatografia líquida de alta eficiência Chiral stationary phases for high-performance liquid chromatography

    OpenAIRE

    Tiago de Campos Lourenço; Neila Maria Cassiano; Quezia B. Cass

    2010-01-01

    The development of Chiral Stationary Phases (CSPs) for high performance liquid chromatography has been studied by various researches around the world, especially, since 1980. This simple interest has been transformed into a tool of great technological value for the industrial community and scholars in general providing the existence of several CSPs, which act through different mechanisms of chiral discrimination. This paper describes the main types of CSPs that are used for the resolution of ...

  2. STATIONARY HIGH-PERFORMANCE DISCHARGES IN THE DIII-D TOKAMAK

    International Nuclear Information System (INIS)

    LUCE, TC; WADE, MR; FERRON, JR; HYATT, AW; KELLMAN, AG; KINSEY, JE; LAHAYE, RJ; LASNIER, CJ; MURAKAMI, M; POLITZER, PA; SCOVILLE, JT

    2002-01-01

    A271 STATIONARY HIGH-PERFORMANCE DISCHARGES IN THE DII-D TOKAMAK. Discharges which can satisfy the high gain goals of burning plasma experiments have been demonstrated in the DIII-D tokamak under stationary conditions at relatively low plasma current (q 95 > 4). A figure of merit for fusion gain (β N H 89 /q 95 2 ) has been maintained at values corresponding to | = 10 operation in a burning plasma for > 6 s or 36τ E and 2τ R . The key element is the relaxation of the current profile to a stationary state with q min > 1. In the absence of sawteeth and fishbones, stable operation has been achieved up to the estimated no-wall β limit. Feedback control of the energy content and particle inventory allow reproducible, stationary operation. The particle inventory is controlled by gas fueling and active pumping; the wall plays only a small role in the particle balance. The reduced current lessens significantly the potential for structural damage in the event of a major disruption. In addition, the pulse length capability is greatly increased, which is essential for a technology testing phase of a burning plasma experiment where fluence (duty cycle) is important

  3. Novas fases estacionárias à base de sílica para cromatografia líquida de alta eficiência New stationary phases based on silica for high performance liquid chromatography

    Directory of Open Access Journals (Sweden)

    César R. Silva

    2004-04-01

    Full Text Available The present work reviews recent advances in the preparation of new reversed phase packing materials such as sterically protected, bidentate, hybrid organic-inorganic and monolithic phases and phases containing embedded polar groups. The bonding chemistry involved in the preparation of these phases as well as their advantages over conventional C8 and C18 reversed phases are discussed. Understanding the reasons behind the development of these newer column packings helps analysts select the best stationary phase for a given application.

  4. One-Pot Click Access to a Cyclodextrin Dimer-Based Novel Aggregation Induced Emission Sensor and Monomer-Based Chiral Stationary Phase

    Directory of Open Access Journals (Sweden)

    Xiaoli Li

    2016-11-01

    Full Text Available A ‘two birds, one stone’ strategy was developed via a one-pot click reaction to simultaneously prepare a novel cyclodextrin (CD dimer based aggregation induced emission (AIE sensor (AIE-DCD and a monomer based chiral stationary phase (CSP-MCD for chiral high performance liquid chromatography (CHPLC. AIE-DCD was found to afford satisfactory AIE response for specific detection of Zn2+ with a detection limit of 50 nM. CSP-MCD exhibits excellent enantioseparation ability toward dansyl amino acids, where the resolution of dansyl amino leucine reaches 5.43.

  5. Effect of Secondary Equilibria on the Adsorption of Ibuprofen Enantiomers on a Chiral Stationary Phase with a Grafted Antibiotic Eremomycin

    Science.gov (United States)

    Reshetova, E. N.; Asnin, L. D.; Kachmarsky, K.

    2018-02-01

    The chromatographic separation of ibuprofen enantiomers on a Nautilus-E chiral stationary phase with a grafted eremomycin antibiotic at high column loading is accompanied by distortion of the shape of chromatographic peaks. A model is proposed to explain this phenomenon. A number of factors are considered in the model: the ionization of ibuprofen in the mobile phase, the pH change in the mass transfer zone caused by ionization, and competitive adsorption involving buffer components. Simulations performed using this model within the theory of nonequilibrium chromatography allow the shape of chromatograms for large amounts of S- and R-ibuprofen samples to be predicted. The adsorption mechanism is found to be mainly ion-exchange. The contribution from the molecular adsorption of ibuprofen to the total retention is shown to be several percent.

  6. Pharmacokinetic interplay of phase II metabolism and transport: a theoretical study.

    Science.gov (United States)

    Wu, Baojian

    2012-01-01

    Understanding of the interdependence of cytochrome P450 enzymes and P-glycoprotein in disposition of drugs (also termed "transport-metabolism interplay") has been significantly advanced in recent years. However, whether such "interplay" exists between phase II metabolic enzymes and efflux transporters remains largely unknown. The objective of this article is to explore the role of efflux transporters (acting on the phase II metabolites) in disposition of the parent drug in Caco-2 cells, liver, and intestine via simulations utilizing a catenary model (for Caco-2 system) and physiologically based pharmacokinetic (PBPK) models (for the liver and intestine). In all three models, "transport-metabolism interplay" (i.e., inhibition of metabolite efflux decreases the metabolism) can be observed only when futile recycling (or deconjugation) occurred. Futile recycling appeared to bridge the two processes (i.e., metabolite formation and excretion) and enable the interplay thereof. Without futile recycling, metabolite formation was independent on its downstream process excretion, thus impact of metabolite excretion on its formation was impossible. Moreover, in liver PBPK model with futile recycling, impact of biliary metabolite excretion on the exposure of parent drug [(systemic (reservoir) area under the concentration-time curve (AUC(R1))] was limited; a complete inhibition of efflux resulted in AUC(R1) increases of less than 1-fold only. In intestine PBPK model with futile recycling, even though a complete inhibition of efflux could result in large elevations (e.g., 3.5-6.0-fold) in AUC(R1), an incomplete inhibition of efflux (e.g., with a residual activity of ≥ 20% metabolic clearance) saw negligible increases (interplay between phase II enzymes and efflux transporters. Those studying such "interplay" are encouraged to adequately consider potential consequences of inhibition of efflux transporters in humans. Copyright © 2011 Wiley-Liss, Inc.

  7. Effects of Long-Term Cultivation on Medium with Alpha-Ketoglutarate Supplementation on Metabolic Processes of Saccharomyces cerevisiae

    Directory of Open Access Journals (Sweden)

    Nadia Burdyliuk

    2017-01-01

    Full Text Available During last years, alpha-ketoglutarate (AKG, an important intermediate in the Krebs cycle, has been intensively studied as a dietary supplement with stress-protective and potential antiaging effects. Here, we examined the effects of exogenous AKG on metabolic processes and survival of yeast Saccharomyces cerevisiae during long-term cultivation. Growth on AKG had no effect on the total cell number but increased the number of reproductively active cells at the late days of cultivation (from day 7 to day 15. A gradual increase in levels of total protein, glycogen, and trehalose was found over 7-day cultivation with more pronounced effects in AKG-grown cells. In control cells, metabolic activity and the activities of superoxide dismutase and catalase decreased, whereas levels of carbonyl proteins and low-molecular-mass thiols increased during 7-day cultivation. This suggests development of oxidative stress in stationary phase cells. Meanwhile, stationary phase cells cultured on AKG possessed higher levels of low-molecular-mass thiols and lower levels of carbonyl proteins and α-dicarbonyl compounds when compared to control ones. Collectively, higher levels of storage carbohydrates and an activation of antioxidant defense with diminishing oxidative protein damage can prevent a loss of reproductive ability in yeast cells during long-term cultivation on AKG-supplemented medium.

  8. The nutritional status of Methanosarcina acetivorans regulates glycogen metabolism and gluconeogenesis and glycolysis fluxes.

    Science.gov (United States)

    Santiago-Martínez, Michel Geovanni; Encalada, Rusely; Lira-Silva, Elizabeth; Pineda, Erika; Gallardo-Pérez, Juan Carlos; Reyes-García, Marco Antonio; Saavedra, Emma; Moreno-Sánchez, Rafael; Marín-Hernández, Alvaro; Jasso-Chávez, Ricardo

    2016-05-01

    Gluconeogenesis is an essential pathway in methanogens because they are unable to use exogenous hexoses as carbon source for cell growth. With the aim of understanding the regulatory mechanisms of central carbon metabolism in Methanosarcina acetivorans, the present study investigated gene expression, the activities and metabolic regulation of key enzymes, metabolite contents and fluxes of gluconeogenesis, as well as glycolysis and glycogen synthesis/degradation pathways. Cells were grown with methanol as a carbon source. Key enzymes were kinetically characterized at physiological pH/temperature. Active consumption of methanol during exponential cell growth correlated with significant methanogenesis, gluconeogenic flux and steady glycogen synthesis. After methanol exhaustion, cells reached the stationary growth phase, which correlated with the rise in glycogen consumption and glycolytic flux, decreased methanogenesis, negligible acetate production and an absence of gluconeogenesis. Elevated activities of carbon monoxide dehydrogenase/acetyl-CoA synthetase complex and pyruvate: ferredoxin oxidoreductase suggested the generation of acetyl-CoA and pyruvate for glycogen synthesis. In the early stationary growth phase, the transcript contents and activities of pyruvate phosphate dikinase, fructose 1,6-bisphosphatase and glycogen synthase decreased, whereas those of glycogen phosphorylase, ADP-phosphofructokinase and pyruvate kinase increased. Therefore, glycogen and gluconeogenic metabolites were synthesized when an external carbon source was provided. Once such a carbon source became depleted, glycolysis and methanogenesis fed by glycogen degradation provided the ATP supply. Weak inhibition of key enzymes by metabolites suggested that the pathways evaluated were mainly transcriptionally regulated. Because glycogen metabolism and glycolysis/gluconeogenesis are not present in all methanogens, the overall data suggest that glycogen storage might represent an environmental

  9. Fragment-based approach to calculate hydrophobicity of anionic and nonionic surfactants derived from chromatographic retention on a C18 stationary phase.

    Science.gov (United States)

    Hammer, Jort; Haftka, Joris J-H; Scherpenisse, Peter; Hermens, Joop L M; de Voogt, Pim W P

    2017-02-01

    To predict the fate and potential effects of organic contaminants, information about their hydrophobicity is required. However, common parameters to describe the hydrophobicity of organic compounds (e.g., octanol-water partition constant [K OW ]) proved to be inadequate for ionic and nonionic surfactants because of their surface-active properties. As an alternative approach to determine their hydrophobicity, the aim of the present study was therefore to measure the retention of a wide range of surfactants on a C 18 stationary phase. Capacity factors in pure water (k' 0 ) increased linearly with increasing number of carbon atoms in the surfactant structure. Fragment contribution values were determined for each structural unit with multilinear regression, and the results were consistent with the expected influence of these fragments on the hydrophobicity of surfactants. Capacity factors of reference compounds and log K OW values from the literature were used to estimate log K OW values for surfactants (log KOWHPLC). These log KOWHPLC values were also compared to log K OW values calculated with 4 computational programs: KOWWIN, Marvin calculator, SPARC, and COSMOThermX. In conclusion, capacity factors from a C 18 stationary phase are found to better reflect hydrophobicity of surfactants than their K OW values. Environ Toxicol Chem 2017;36:329-336. © 2016 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC. © 2016 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc. on behalf of SETAC.

  10. [[Chiral separation of five arylpropionic acid drugs and determination of their enantiomers in pharmaceutical preparations by reversed-phase high performance liquid chromatography with cellulose-tris-(4-methylbenzoate) stationary phase

    Science.gov (United States)

    Luo, An; Wan, Qiang; Fan, Huajun; Chen, Zhi; Wu, Xuehao; Huang, Xiaowen; Zang, Linquan

    2014-09-01

    Chromatographic behaviors for enantiomeric separation of arylpropionic acid drugs were systematically developed by reversed phase-high performance liquid chromatography (RP-HPLC) using cellulose-tris-(4-methylbenzoate) (CTMB) as chiral stationary phase (CSP). The effects of the composition of the mobile phase, additives and temperature on chiral separation of flurbiprofen, pranoprofen, naproxen, ibuprofen and loxoprofen were further investigated. The enantiomers had been successfully separated on CSP of CTMB by the mobile phase of methanol-0.1% (v/v) formic acid except naproxen by acetonitrile-0.1% (v/v) formic acid at 25 °C. The mechanisms of the racemic resolution for the above mentioned five drugs are discussed thermodynamically and structurally. The resolutions between respective enantiomers for arylpropionic acid drugs on CTMB had significant differences due to their chromatographic behaviors. The order of resolutions ranked pranoprofen, loxoprofen, flurbiprofen, ibuprofen and naproxen. The method established has been successfully applied to the determination of the enantiomers of the five drugs in commercial preparations under the optimized conditions. It proved that the method is simple, reliable and accurate.

  11. Retention prediction of highly polar ionizable solutes under gradient conditions on a mixed-mode reversed-phase and weak anion-exchange stationary phase.

    Science.gov (United States)

    Balkatzopoulou, P; Fasoula, S; Gika, H; Nikitas, P; Pappa-Louisi, A

    2015-05-29

    In the present work the retention of three highly polar and ionizable solutes - uric acid, nicotinic acid and ascorbic acid - was investigated on a mixed-mode reversed-phase and weak anion-exchange (RP/WAX) stationary phase in buffered aqueous acetonitrile (ACN) mobile phases. A U-shaped retention behavior was observed for all solutes with respect to the eluent organic modifier content studied in a range of 5-95% (v/v). This retention behavior clearly demonstrates the presence of a HILIC-type retention mechanism at ACN-rich hydro-organic eluents and an RP-like retention at aqueous-rich hydro-organic eluents. Hence, this column should be promising for application under both RP and HILIC gradient elution modes. For this reason, a series of programmed elution runs were carried out with increasing (RP) and decreasing (HILIC) organic solvent concentration in the mobile phase. This dual gradient process was successfully modeled by two retention models exhibiting a quadratic or a cubic dependence of the logarithm of the solute retention factor (lnk) upon the organic modifier volume fraction (φ). It was found that both models produced by gradient retention data allow the prediction of solute retention times for both types of programmed elution on the mixed-mode column. Four, in the case of the quadratic model, or five, in the case of the cubic model, initial HILIC- and RP-type gradient runs gave satisfactory retention predictions of any similar kind elution program, even with different flow rate, with an overall error of only 2.5 or 1.7%, respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Adsorptive removal of Methylene blue and Methyl orange from aqueous media by carboxylated diaminoethane sporopollenin: On the usability of an aminocarboxilic acid functionality-bearing solid-stationary phase in column techniques

    International Nuclear Information System (INIS)

    Ayar, Ahmet; Gezici, Orhan; Kuecuekosmanoglu, Muhittin

    2007-01-01

    The adsorption phenomena of Methylene blue (MB) and Methyl orange (MO) on a carboxylated diaminoethane sporopollenin (CDAE-S) solid phase were investigated in a column arrangement by using breakthrough technique. The adsorption phenomena were evaluated using some common adsorption isotherm models and Scatchard plot analysis, and obtained results were interpreted for evaluating the usability of CDAE-S for removal, recovery and preconcentration of the studied dyes both at the laboratory and industrial scales. On the basis of Scatchard plot analysis, the interaction types between the CDAE-S and the studied dyes were criticized in terms of affinity phenomena. Thus, the usability of a biomacromolecule-derived material, CDAE-S, as a cheap, environmentally-friendly and effective solid-stationary phase exhibiting both cation-exchange and anion-exchange characteristics at the same time, is discussed through the present study. Besides, from the obtained results, the protonated CDAE-S, which functionally resembles an amino acid structure, are presented as a two-in-one solid-stationary phase, and its adaptability to common processes performed under column conditions is also drawn in detail

  13. Theory and applications of a novel ion exchange chromatographic technology using controlled pH gradients for separating proteins on anionic and cationic stationary phases.

    Science.gov (United States)

    Tsonev, Latchezar I; Hirsh, Allen G

    2008-07-25

    pISep is a major new advance in low ionic strength ion exchange chromatography. It enables the formation of externally controlled pH gradients over the very broad pH range from 2 to 12. The gradients can be generated on either cationic or anionic exchangers over arbitrary pH ranges wherein the stationary phases remain totally charged. Associated pISep software makes possible the calculation of either linear, nonlinear or combined, multi-step, multi-slope pH gradients. These highly reproducible pH gradients, while separating proteins and glycoproteins in the order of their electrophoretic pIs, provide superior chromatographic resolution compared to salt. This paper also presents a statistical mechanical model for protein binding to ion exchange stationary phases enhancing the electrostatic interaction theory for the general dependence of retention factor k, on both salt and pH simultaneously. It is shown that the retention factors computed from short time isocratic salt elution data of a model protein can be used to accurately predict its salt elution concentration in varying slope salt elution gradients formed at varying isocratic pH as well as the pH at which it will be eluted from an anionic exchange column by a pISep pH gradient in the absence of salt.

  14. Capillary gas chromatographic separation of organic bases using a pH-adjusted basic water stationary phase.

    Science.gov (United States)

    Darko, Ernest; Thurbide, Kevin B

    2016-09-23

    The use of a pH-adjusted water stationary phase for analyzing organic bases in capillary gas chromatography (GC) is demonstrated. Through modifying the phase to typical values near pH 11.5, it is found that various organic bases are readily eluted and separated. Conversely, at the normal pH 7 operating level, they are not. Sodium hydroxide is found to be a much more stable base than ammonium hydroxide for altering the pH due to the higher volatility and evaporation of the latter. In the basic condition, such analytes are not ionized and are observed to produce good peak shapes even for injected masses down to about 20ng. By comparison, analyses on a conventional non-polar capillary GC column yield more peak tailing and only analyte masses of 1μg or higher are normally observed. Through carefully altering the pH, it is also found that the selectivity between analytes can be potentially further enhanced if their respective pKa values differ sufficiently. The analysis of different pharmaceutical and petroleum samples containing organic bases is demonstrated. Results indicate that this approach can potentially offer unique and beneficial selectivity in such analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Preferential Ty1 retromobility in mother cells and nonquiescent stationary phase cells is associated with increased concentrations of total Gag or processed Gag and is inhibited by exposure to a high concentration of calcium.

    Science.gov (United States)

    Peifer, Andrew C; Maxwell, Patrick H

    2018-03-21

    Retrotransposons are abundant mobile DNA elements in eukaryotic genomes that are more active with age in diverse species. Details of the regulation and consequences of retrotransposon activity during aging remain to be determined. Ty1 retromobility in Saccharomyces cerevisiae is more frequent in mother cells compared to daughter cells, and we found that Ty1 was more mobile in nonquiescent compared to quiescent subpopulations of stationary phase cells. This retromobility asymmetry was absent in mutant strains lacking BRP1 that have reduced expression of the essential Pma1p plasma membrane proton pump, lacking the mRNA decay gene LSM1 , and in cells exposed to a high concentration of calcium. Mother cells had higher levels of Ty1 Gag protein than daughters. The proportion of protease-processed Gag decreased as cells transitioned to stationary phase, processed Gag was the dominant form in nonquiescent cells, but was virtually absent from quiescent cells. Treatment with calcium reduced total Gag levels and the proportion of processed Gag, particularly in mother cells. We also found that Ty1 reduced the fitness of proliferating but not stationary phase cells. These findings may be relevant to understanding regulation and consequences of retrotransposons during aging in other organisms, due to conserved impacts and regulation of retrotransposons.

  16. The use of Stationary Phase Optimized Selectivity Liquid Chromatography for the development of herbal fingerprints to detect targeted plants in plant food supplements.

    Science.gov (United States)

    Deconinck, E; Djiogo, C A Sokeng; Kamugisha, A; Courselle, P

    2017-08-01

    The consumption of plant food supplements is increasing steadily and more and more, these products are bought through internet. Often the products sold through internet are not registered or declared with a national authority, meaning that no or minimal quality control is performed and that they could contain herbs or plants that are regulated. Stationary Phase Optimized Selectivity Liquid Chromatography (SOS-LC) was evaluated for the development of specific fingerprints, to be used for the detection of targeted plants in plant food supplements. Three commonly used plants in plant food supplements and two regulated plants were used to develop fingerprints with SOS-LC. It was shown that for all plants specific fingerprints could be obtained, allowing the detection of these targeted plants in triturations with different herbal matrices as well as in real samples of suspicious supplements seized by the authorities. For three of the five plants a more specific fingerprint was obtained, compared to the ones developed on traditional columns described in literature. It could therefore be concluded that the combination of segments of different types of stationary phases, as used in SOS-LC, has the potential of becoming a valuable tool in the quality control and the identification of crude herbal or plant material and in the detection of regulated plants in plant food supplements or other herbal preparations. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Acute Phase Proteins and Variables of Protein Metabolism in Dairy Cows during the Pre- and Postpartal Period

    Directory of Open Access Journals (Sweden)

    Cs. Tóthová

    2008-01-01

    Full Text Available The objective of the present study was to compare the concentrations of acute phase proteins and selected variables of protein metabolism in dairy cows of the Slovak Spotted breed from 4 weeks before parturition to 10 weeks after parturition. Acute phase proteins - haptoglobin (Hp and serum amyloid A (SAA - and variables of protein metabolism - total proteins, albumin, urea, creatinine, total immunoglobulins - were evaluated in blood serum. Significant differences were found in average values of the Hp and SAA concentrations in several groups during the monitored period (P P P P P P P P P < 0.001. The above mentioned results indicate that in the time around parturition there are significant changes in concentrations of acute phase proteins, as well as in the whole protein metabolism of dairy cows. These facts suggest that the postparturient period is a critical biological phase, throughout which there is the highest incidence of metabolic disorders.

  18. Stationary rotary force waves on the liquid-air core interface of a swirl atomizer

    Science.gov (United States)

    Chinn, J. J.; Cooper, D.; Yule, A. J.; Nasr, G. G.

    2016-10-01

    A one-dimensional wave equation, applicable to the waves on the surface of the air-core of a swirl atomizer is derived analytically, by analogy to the similar one-dimensional wave equation derivation for shallow-water gravity waves. In addition an analogy to the flow of water over a weir is used to produce an analytical derivation of the flow over the lip of the outlet of a swirl atomizer using the principle of maximum flow. The principle of maximum flow is substantiated by reference to continuity of the discharge in the direction of streaming. For shallow-water gravity waves, the phase velocity is the same expression as for the critical velocity over the weir. Similarly, in the present work, the wave phase velocity on the surface of the air-core is shown to be the same expression as for the critical velocity for the flow at the outlet. In addition, this wave phase velocity is shown to be the square root of the product of the radial acceleration and the liquid thickness, as analogous with the wave phase velocity for shallow water gravity waves, which is the square root of the product of the acceleration due to gravity and the water depth. The work revisits the weirs and flumes work of Binnie et al. but using a different methodology. The results corroborate with the work of Binnie. High speed video, Laser Doppler Anemometry and deflected laser beam experimental work has been carried out on an oversize Perspex (Plexiglas) swirl atomizer. Three distinctive types of waves were detected: helical striations, low amplitude random ripples and low frequency stationary waves. It is the latter wave type that is considered further in this article. The experimentally observed waves appear to be stationary upon the axially moving flow. The mathematical analysis allows for the possibility of a negative value for the phase velocity expression. Therefore the critical velocity and the wave phase velocity do indeed lead to stationary waves in the atomizer. A quantitative comparison

  19. Evaluation and application of a mixed-mode chromatographic stationary phase in two-dimensional liquid chromatography for the separation of traditional Chinese medicine.

    Science.gov (United States)

    Wei, Zhishen; Fu, Qing; Cai, Jianfeng; Huan, Liyun; Zhao, Jianchao; Shi, Hui; Jin, Yu; Liang, Xinmiao

    2016-06-01

    In this study, two mixed-mode chromatography stationary phases (C8SAX and C8SCX) were evaluated and used to establish a two-dimensional liquid chromatography system for the separation of traditional Chinese medicine. The chromatographic properties of the mixed-mode columns were systematically evaluated by comparing with other three columns of C8, strong anion exchanger, and strong cation exchanger. The result showed that C8SAX and C8SCX had a mixed-mode retention mechanism including electrostatic interaction and hydrophobic interaction. Especially, they were suitable for separating acidic and/or basic compounds and their separation selectivities could be easily adjusted by changing pH value. Then, several off-line 2D-LC systems based on the C8SAX in the first dimension and C8SAX, C8SCX, or C8 columns in the second dimension were developed to analyze a traditional Chinese medicine-Uncaria rhynchophylla. The two-dimensional liquid chromatography system of C8SAX (pH 3.0) × C8SAX (pH 6.0) exhibited the most effective peak distribution. Finally, fractions of U. rhynchophylla prepared from the first dimension were successfully separated on the C8SAX column with a gradient pH. Thus, the mixed-mode stationary phase could provide a platform to separate the traditional Chinese medicine in practical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Entropy production and thermodynamics of nonequilibrium stationary states: a point of view.

    Science.gov (United States)

    Gallavotti, Giovanni

    2004-09-01

    Entropy might be a not well defined concept if the system can undergo transformations involving stationary nonequilibria. It might be analogous to the heat content (once called "caloric") in transformations that are not isochoric (i.e., which involve mechanical work): it could be just a quantity that can be transferred or created, like heat in equilibrium. The text first reviews the philosophy behind a recently proposed definition of entropy production in nonequilibrium stationary systems. A detailed technical attempt at defining the entropy of a stationary states via their variational properties follows: the unsatisfactory aspects of the results add arguments in favor of the nonexistence of a function of state to be identified with entropy; at the same time new aspects and properties of the phase space contraction emerge. Copyright 2004 American Institute of Physics

  1. Diversity oriented high-throughput screening of 1,3,4-oxadiazole modified chlorophenylureas and halogenobenzamides by HPLC with peptidomimetic calixarene-bonded stationary phases.

    Science.gov (United States)

    Bazylak, Grzegorz; Malak, Anna; Ali, Imran; Borowiak, Teresa; Dutkiewicz, Grzegorz

    2008-06-01

    Retention profiles in series of the neutral and highly hydrophobic 1,3,4-oxadiazoles containing chlorophenylurea and halogenobenzamide moiety and indicating analgesic activity were determined in the isocratic standard- and narrow-bore HPLC systems employing, respectively, various octadecylsilica and different calixarene bonded stationary phases. When acetonitrile - 2.65 mM phosphoric acid (55 : 45, %, v/v), pH* 3.25, mobile phase was applied retention of these compounds increased with decline of their overall hydrophobicity according to the general preference of more polar compounds by calixarene cavity in time of its non-specific host-guest supramolecular interactions with halogenated substances. The size of calixarene nanocavity and its upper-rim substitution did not change the observed retention order, resolution and selectivity of separation for oxadiazoles. Compared to the retention on the non-end-capped and the highly-end-capped octadecylsilica HPLC column a most improved separation of some regioisomers of halogenated 1,3,4-oxadiazoles were observed on both used calixarene-type HPLC supports. In addition, preliminary data on the self-assembled supramolecular crystal structure of exemplary 1,3,4-oxadiazolchlorophenylurea with cis-elongated conformation was reported and formation of the monovalent inclusion host-guest complexes between 1,3,4-oxadiazoles and each calixarene-type stationary phase was studied with molecular modelling MM+ and AM1 methods. The structural, isomeric and energetic factors leading to the hydrogen bond stabilized inclusion complexes between these species were considered and used for explanation of observed retention sequence and selectivity of 1,3,4-oxadiazoles separation in applied calixarene-based HPLC systems. All these data would be useful in future development of optimized procedures enabling encapsulation of 1,3,4-oxadiazolurea-type drugs with calixarenes.

  2. Determinação da espessura da camada polimérica de fases estacionárias imobilizadas para cromatografia líquida de alta eficiência por termogravimetria Determination of polymeric layer thickness on immobilized stationary phases for high-performance liquid chromatography using thermogravimetric analyses

    Directory of Open Access Journals (Sweden)

    Anizio M. Faria

    2008-01-01

    Full Text Available This paper presents a simple and practical thermogravimetric method for determining the layer thickness of immobilized polymer stationary phases used in reversed-phase high-performance liquid chromatography. In this method, the weight loss of different polysiloxanes immobilized onto chromatographic supports, determined over the temperature range 150-650 ºC, demonstrated excellent agreement with the sum of carbon and hydrogen content obtained by elemental analysis. The results presented here suggest that the thermogravimetric procedure is an accurate and precise method to determine the polymeric material content on polymer-coated stationary phases.

  3. Preparation of chitosan-graft-(β-cyclodextrin) based sol-gel stationary phase for open-tubular capillary electrochromatography.

    Science.gov (United States)

    Lü, Haixia; Li, Qingyin; Yu, Xiaowei; Yi, Jiaojiao; Xie, Zenghong

    2013-07-01

    A novel open-tubular CEC column coated with chitosan-graft-(β-CD) (CDCS) was prepared using sol-gel technique. In the sol-gel approach, owing to the 3D network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. The column efficiencies of 55,000∼163,000 plates/m for the isomeric xanthopterin and phenoxy acid herbicides using the sol-gel-derived CDCS columns were achieved. Good stabilities were demonstrated that the RSD values for the retention time of thiourea and isoxanthopterin were 1.3 and 1.4% (run to run, n = 5), 1.6 and 2.0% (day to day, n = 3), 2.9 and 3.1% (column to column, n = 3), respectively. The sol-gel-coated CDCS columns have shown improved separations of isomeric xanthopterin in comparison with CDCS-bonded capillary column. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Microstructure-based analysis and simulation of flow and mass transfer in chromatographic stationary phases

    Science.gov (United States)

    Koku, Harun

    Limitations of mass transfer in chromatographic bioseparations employing traditional packed particles have fuelled the inception and development of alternative stationary phases with improved performance characteristics. This work investigates case studies in two categories of these alternative media, namely polymer-modified packed particles and continuous monolithic phases, for insight into their enhanced properties. Specifically, high-resolution microscopy techniques and image-based analysis algorithms were implemented to extract morphology information for these materials, in an attempt to elucidate the relation between microstructure and performance. For the monolith, mesoscopic simulation methods were also employed for a more rigorous analysis of the flow and dispersion behavior. Scanning and transmission electron microscopy images of the commercial polymer-modified, agarose-based particle Sepharose XL were compared to those for its unmodified counterpart, Sepharose FF. Local regions in the composite dextran-agarose Sepharose XL particles were noted to exhibit a denser network of fibers and smaller pore sizes overall, compared to those in the traditional Sepharose FF particles. Images of particles equilibrated with high concentrations of protein revealed a significant difference in protein localization patterns, with the stained protein in XL occupying a markedly higher area fraction of the images. This suggests a higher volume available for adsorption and provides visual clues into how the consistently higher static capacity of these polymer-modified particles is manifested. Treatment of the XL particles with dextranase, an enzyme that breaks down dextran, resulted in a reduction of protein coverage, providing evidence that it is indeed the dextran that is responsible for the improved static capacity in this polymer-modified stationary phase. Imaging and image analysis techniques were also used to analyze the commercial CIM(TM) disk monolith. Two- and three

  5. Non-stationary dynamics in the bouncing ball: A wavelet perspective

    Energy Technology Data Exchange (ETDEWEB)

    Behera, Abhinna K., E-mail: abhinna@iiserkol.ac.in; Panigrahi, Prasanta K., E-mail: pprasanta@iiserkol.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246 (India); Sekar Iyengar, A. N., E-mail: ansekar.iyengar@saha.ac.in [Plasma Physics Division, Saha Institute of Nuclear Physics (SINP), Sector 1, Block-AF, Bidhannagar, Kolkata 700064 (India)

    2014-12-01

    The non-stationary dynamics of a bouncing ball, comprising both periodic as well as chaotic behavior, is studied through wavelet transform. The multi-scale characterization of the time series displays clear signatures of self-similarity, complex scaling behavior, and periodicity. Self-similar behavior is quantified by the generalized Hurst exponent, obtained through both wavelet based multi-fractal detrended fluctuation analysis and Fourier methods. The scale dependent variable window size of the wavelets aptly captures both the transients and non-stationary periodic behavior, including the phase synchronization of different modes. The optimal time-frequency localization of the continuous Morlet wavelet is found to delineate the scales corresponding to neutral turbulence, viscous dissipation regions, and different time varying periodic modulations.

  6. Calcium and Magnesium Ions Are Membrane-Active against Stationary-Phase Staphylococcus aureus with High Specificity

    Science.gov (United States)

    Xie, Yuntao; Yang, Lihua

    2016-02-01

    Staphylococcus aureus (S. aureus) is notorious for its ability to acquire antibiotic-resistance, and antibiotic-resistant S. aureus has become a wide-spread cause of high mortality rate. Novel antimicrobials capable of eradicating S. aureus cells including antibiotic-resistant ones are thus highly desired. Membrane-active bactericides and species-specific antimicrobials are two promising sources of novel anti-infective agents for fighting against bacterial antibiotic-resistance. We herein show that Ca2+ and Mg2+, two alkaline-earth-metal ions physiologically essential for diverse living organisms, both disrupt model S. aureus membranes and kill stationary-phase S. aureus cells, indicative of membrane-activity. In contrast to S. aureus, Escherichia coli and Bacillus subtilis exhibit unaffected survival after similar treatment with these two cations, indicative of species-specific activity against S. aureus. Moreover, neither Ca2+ nor Mg2+ lyses mouse red blood cells, indicative of hemo-compatibility. This works suggests that Ca2+ and Mg2+ may have implications in targeted eradication of S. aureus pathogen including the antibiotic-resistant ones.

  7. Enantioseparation and impurity determination of the enantiomers of novel phenylethanolamine derivatives by high performance liquid chromatography on amylose stationary phase

    International Nuclear Information System (INIS)

    Yang Jing; Guan Jin; Pan Li; Jiang Kun; Cheng Maosheng; Li Famei

    2008-01-01

    Simple and efficient analytical HPLC methods using Chiralpak AS-H as chiral stationary phase were developed for direct enantioseparation of 11 novel phenylethanolamine derivatives. The chromatographic experiments were performed in normal phase mode with n-hexane-ethanol-triethylamine (TEA) as mobile phase. Excellent baseline enantioseparation was obtained for most of compounds. The effects of the concentration of organic modifiers and column temperature were studied for the enantiomeric separation. The mechanism of chiral recognition was discussed based on the relationship between the thermodynamic parameters and structures of compounds. It was found that the enantioseparations were all enthalpy driven, and the tert-butyl groups of compounds had significant influence on the chiral recognition. Trantinterol enantiomers were resolved (R s = 2.73) within 14 min using n-hexane-ethanol-TEA (98:2:0.1, v/v/v) as mobile phase with a flow rate of 0.8 mL min -1 at 30 deg. C. The optimized method was validated for linearity, precision, accuracy and stability in solution and proved to be robust. The limits of detection (LOD) and quantification (LOQ) for (+)-trantinterol were 0.15 and 0.46 μg mL -1 . The method was applied for enantiomeric impurity determination of (-)-trantinterol bulk samples

  8. Ion chromatography of transition metals: specific alteration of retention by complexation reactions in the mobile and on the stationary phase

    International Nuclear Information System (INIS)

    Baumgartner, S.

    1992-05-01

    Ion chromatography of mono- and bivalent cations was performed on a conventional cation exchanger. The pH influence of an ethylene-diamine/citrate eluent was significant for the retention of alkaline earth and transition metals, but negligible for alkali ions. This was dealt with from a mechanistic point of view. Mobile phase optimization allowed fast isocratic analysis of mono- and bivalent cations and the separation of the radionuclides Cs-137 and Sr-90. A newly synthesized stationary phase containing iminodiacetate (IDA) function was investigated for cation chromatography using ethylenediamine/citrate eluents, polyhydroxy acid and dipicolinic acid. The column's high selectivity for transition metal ions in comparison to alkali and alkaline earth metals may be governed by the choice of complexing ability and pH of the eluent. Applications verified by atomic absorption spectroscopy include alkaline earth metals in beverages and the determination of Co, Cd and Zn in solutions containing more than 10 14 -fold excess of Na and Mg, such as sea water

  9. Groebner Basis Methods for Stationary Solutions of a Low-Dimensional Model for a Shear Flow

    Science.gov (United States)

    Pausch, Marina; Grossmann, Florian; Eckhardt, Bruno; Romanovski, Valery G.

    2014-10-01

    We use Groebner basis methods to extract all stationary solutions for the nine-mode shear flow model described in Moehlis et al. (New J Phys 6:56, 2004). Using rational approximations to irrational wave numbers and algebraic manipulation techniques we reduce the problem of determining all stationary states to finding roots of a polynomial of order 30. The coefficients differ by 30 powers of 10, so that algorithms for extended precision are needed to extract the roots reliably. We find that there are eight stationary solutions consisting of two distinct states, each of which appears in four symmetry-related phases. We discuss extensions of these results for other flows.

  10. Thiol-ene click chemistry derived cationic cyclodextrin chiral stationary phase and its enhanced separation performance in liquid chromatography.

    Science.gov (United States)

    Yao, Xiaobin; Tan, Timothy Thatt Yang; Wang, Yong

    2014-01-24

    This work is the first demonstration of a simple thiol-ene click chemistry to anchor vinyl imidazolium β-CD onto thiol silica to form a novel cationic native cyclodextrin (CD) chiral stationary phase (CSP). The CSP afforded high enantioseparation ability towards dansyl (Dns) amino acids, carboxylic aryl compounds and flavonoids in chiral HPLC. The current CSP demonstrates the highest resolving ability (selectivity >1.1, resolution >1.5) towards Dns amino acids in a mobile phase buffered at pH=6.5, with the resolution of Dns-dl-leucine as high as 6.97. 2,4-dichloride propionic acid (2,4-ClPOPA) was well resolved with the selectivity and resolution of 1.37 and 4.88, respectively. Compared to a previously reported native CD-CSP based on a triazole linkage, the current cationic CD-CSP shows a stronger retention and higher resolution towards acidic chiral compounds, ascribed to the propitious strong electrostatic attraction. Stability evaluation results indicated that thiol-ene reaction can provide a facile and robust approach for the preparation of positively charged CD CSPs. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Stationary and non-stationary extreme value modeling of extreme temperature in Malaysia

    Science.gov (United States)

    Hasan, Husna; Salleh, Nur Hanim Mohd; Kassim, Suraiya

    2014-09-01

    Extreme annual temperature of eighteen stations in Malaysia is fitted to the Generalized Extreme Value distribution. Stationary and non-stationary models with trend are considered for each station and the Likelihood Ratio test is used to determine the best-fitting model. Results show that three out of eighteen stations i.e. Bayan Lepas, Labuan and Subang favor a model which is linear in the location parameter. A hierarchical cluster analysis is employed to investigate the existence of similar behavior among the stations. Three distinct clusters are found in which one of them consists of the stations that favor the non-stationary model. T-year estimated return levels of the extreme temperature are provided based on the chosen models.

  12. Carbon isotopic patterns of amino acids associated with various microbial metabolic pathways and physiological conditions

    Science.gov (United States)

    Wang, P. L.; Hsiao, K. T.; Lin, L. H.

    2017-12-01

    Amino acids represent one of the most important categories of biomolecule. Their abundance and isotopic patterns have been broadly used to address issues related to biochemical processes and elemental cycling in natural environments. Previous studies have shown that various carbon assimilative pathways of microorganisms (e.g. autotrophy, heterotrophy and acetotrophy) could be distinguished by carbon isotopic patterns of amino acids. However, the taxonomic and catabolic coverage are limited in previous examination. This study aims to uncover the carbon isotopic patterns of amino acids for microorganisms remaining uncharacterized but bearing biogeochemical and ecological significance in anoxic environments. To fulfill the purpose, two anaerobic strains were isolated from riverine wetland and mud volcano in Taiwan. One strain is a sulfate reducing bacterium (related to Desulfovibrio marrakechensis), which is capable of utilizing either H2 or lactate, and the other is a methanogen (related to Methanolobus profundi), which grows solely with methyl-group compounds. Carbon isotope analyses of amino acids were performed on cells grown in exponential and stationary phase. The isotopic patterns were similar for all examined cultures, showing successive 13C depletion along synthetic pathways. No significant difference was observed for the methanogen and lactate-utilizing sulfate reducer harvested in exponential and stationary phases. In contrast, the H2-utilizing sulfate reducer harvested in stationary phase depleted and enriched 13C in aspartic acid and glycine, respectively when compared with that harvested in exponential phase. Such variations might infer the change of carbon flux during synthesis of these two amino acids in the reverse TCA cycle. In addition, the discriminant function analysis for all available data from culture studies further attests the capability of using carbon isotope patterns of amino acids in identifying microbial metabolisms.

  13. Climatic feedbacks between stationary and transient eddies

    International Nuclear Information System (INIS)

    Branscome, L.E.

    1994-01-01

    Stationary eddies make a significant contribution to poleward heat transport during Northern Hemisphere winter, equaling the transport by transient eddies. On the other hand, stationary eddy transport during the summer is negligible. The effect of topography on time-mean stationary waves and low-frequency variability has been widely studied. In contrast, little attention has been given to the climatic feedbacks associated with stationary eddies. Furthermore, the relationship between stationary and transient eddies in the context of global and regional climate is not well understood. The response of the climate system to anthropogenic forcing is likely to have some dependence on stationary wave transport and its interaction with transient eddies. Some early GCM simulations and observational analyses indicate a strong feedback between the meridional heat fluxes of stationary and transient eddies

  14. Impact of metabolism and growth phase on the hydrogen isotopic composition of microbial fatty acids

    Science.gov (United States)

    Heinzelmann, Sandra M.; Villanueva, Laura; Sinke-Schoen, Danielle; Sinninghe Damsté, Jaap S.; Schouten, Stefan; van der Meer, Marcel T. J.

    2015-01-01

    Microorganisms are involved in all elemental cycles and therefore it is important to study their metabolism in the natural environment. A recent technique to investigate this is the hydrogen isotopic composition of microbial fatty acids, i.e., heterotrophic microorganisms produce fatty acids enriched in deuterium (D) while photoautotrophic and chemoautotrophic microorganisms produce fatty acids depleted in D compared to the water in the culture medium (growth water). However, the impact of factors other than metabolism have not been investigated. Here, we evaluate the impact of growth phase compared to metabolism on the hydrogen isotopic composition of fatty acids of different environmentally relevant microorganisms with heterotrophic, photoautotrophic and chemoautotrophic metabolisms. Fatty acids produced by heterotrophs are enriched in D compared to growth water with εlipid/water between 82 and 359‰ when grown on glucose or acetate, respectively. Photoautotrophs (εlipid/water between −149 and −264‰) and chemoautotrophs (εlipid/water between −217 and −275‰) produce fatty acids depleted in D. Fatty acids become, in general, enriched by between 4 and 46‰ with growth phase which is minor compared to the influence of metabolisms. Therefore, the D/H ratio of fatty acids is a promising tool to investigate community metabolisms in nature. PMID:26005437

  15. Non-stationary and relaxation phenomena in cavity-assisted quantum memories

    Science.gov (United States)

    Veselkova, N. G.; Sokolov, I. V.

    2017-12-01

    We investigate the non-stationary and relaxation phenomena in cavity-assisted quantum memories for light. As a storage medium we consider an ensemble of cold atoms with standard Lambda-scheme of working levels. Some theoretical aspects of the problem were treated previously by many authors, and recent experiments stimulate more deep insight into the ultimate ability and limitations of the device. Since quantum memories can be used not only for the storage of quantum information, but also for a substantial manipulation of ensembles of quantum states, the speed of such manipulation and hence the ability to write and retrieve the signals of relatively short duration becomes important. In our research we do not apply the so-called bad cavity limit, and consider the memory operation of the signals whose duration is not much larger than the cavity field lifetime, accounting also for the finite lifetime of atomic coherence. In our paper we present an effective approach that makes it possible to find the non-stationary amplitude and phase behavior of strong classical control field, that matches the desirable time profile of both the envelope and the phase of the retrieved quantized signal. The phase properties of the retrieved quantized signals are of importance for the detection and manipulation of squeezing, entanglement, etc by means of optical mixing and homodyning.

  16. Diastereo- and enantioseparation of a Nα-Boc amino acid with a zwitterionic quinine-based stationary phase: Focus on the stereorecognition mechanism

    International Nuclear Information System (INIS)

    Ianni, Federica; Carotti, Andrea; Marinozzi, Maura; Marcelli, Gloria; Di Michele, Alessandro; Sardella, Roccaldo; Lindner, Wolfgang; Natalini, Benedetto

    2015-01-01

    Highlights: • The ZWIX(+) column allowed getting the Boc-Aph(Hor)-OH (1) isomeric peaks resolved. • ECD studies and molecular dynamic simulations allowed to assign the elution order. • Molecular descriptors revealed the active role of achiral elements of the CSP. - Abstract: A chiral chromatography method enabling the simultaneous diastereo- and enantioseparation of N α -Boc-N 4 -(hydroorotyl)-4-aminophenylalanine [Boc-Aph(Hor)-OH, 1] was optimized with a quinine-based zwitterionic stationary phase. The polar-ionic eluent system consisting of ACN:MeOH:water—49.7:49.7:0.6 (v/v/v) with formic acid (4.0 mM) and diethylamine (2.5 mM), allowed the successful separation of the four acid stereoisomers: α D,D-/D,L-1 = 1.08; α D,L-/L,D-1 = 1.08; α L,D-/L,L-1 = 1.40. According to the in-house developed synthetic procedure and the recorded electronic circular dichroism spectra, the following stereoisomeric elution order was readily established in the optimal chromatographic conditions: D,D-1 < D,L-1 < L,D-1 < L,L-1. With the aim of better understanding the molecular basis of the retention behaviour of the four stereoisomers in the employed chromatographic system and conditions, a computational protocol consisting in molecular dynamics simulations was applied. The use of the three descriptors INTER (in kcal mol −1 , encoding for the interaction energy between the selector SO unit and the whole system), INTER-SA (in kcal mol −1 , encoding for the interaction energy between SO and the sole selectand SA), and SELF (in kcal mol −1 , encoding for the conformational energy of SA relative to its minimum energy registered by the collected snapshots) revealed the active role of achiral sub-structural elements of the chiral stationary phase and eluent components in the overall stereorecognition mechanism

  17. Identification of IbeR as a Stationary-Phase Regulator in Meningitic Escherichia coli K1 that Carries a Loss-of-Function Mutation in rpoS

    Directory of Open Access Journals (Sweden)

    Feng Chi

    2009-01-01

    Full Text Available IbeR is a regulator present in meningitic Escherichia coli strain E44 that carries a loss-of-function mutation in the stationary-phase (SP regulatory gene rpoS. In order to determine whether IbeR is an SP regulator in E44, two-dimensional gel electrophoresis and LC-MS were used to compare the proteomes of a noninvasive ibeR deletion mutant BR2 and its parent strain E44 in the SP. Four up-regulated (TufB, GapA, OmpA, AhpC and three down-regulated (LpdA, TnaA, OpmC proteins in BR2 were identified when compared to E44. All these proteins contribute to energy metabolism or stress resistance, which is related to SP regulation. One of the down-regulated proteins, tryptophanase (TnaA, which is regulated by RpoS in other E. coli strains, is associated with SP regulation via production of a signal molecule indole. Our studies demonstrated that TnaA was required for E44 invasion, and that indole was able to restore the noninvasive phenotype of the tnaA mutant. The production of indole was significantly reduced in BR2, indicating that ibeR is required for the indole production via tnaA. Survival studies under different stress conditions indicated that IbeR contributed to bacteria stress resistance in the SP. Taken together, IbeR is a novel regulator contributing to the SP regulation.

  18. Analytical and semipreparative chiral separation of cis-itraconazole on cellulose stationary phases by high-performance liquid chromatography.

    Science.gov (United States)

    Kurka, Ondřej; Kučera, Lukáš; Bednář, Petr

    2016-07-01

    cis-Itraconazole is a chiral antifungal drug administered as a racemate. The knowledge of properties of individual cis-itraconazole stereoisomers is vital information for medicine and biosciences as different stereoisomers of cis-itraconazole may possess different affinity to certain biological pathways in the human body. For this purpose, either chiral synthesis of enantiomers or chiral separation of racemate can be used. This paper presents a two-step high-performance liquid chromatography approach for the semipreparative isolation of four stereoisomers (two enantiomeric pairs) of itraconazole using polysaccharide stationary phases and volatile organic mobile phases without additives in isocratic mode. The approach used involves the separation of the racemate into three fractions (i.e. two pure stereoisomers and one mixed fraction containing the remaining two stereoisomers) in the first run and consequent separation of the collected mixed fraction in the second one. For this purpose, combination of cellulose tris-(4-methylbenzoate) and cellulose tris-(3,5-dimehylphenylcarbamate) columns with complementary selectivity for cis-itraconazole provided full separation of all four stereoisomers (with purity of each isomer > 97%). The stereoisomers were collected, their optical rotation determined and their identity confirmed based on the results of a previously published study. Pure separated stereoisomers are subjected to further biological studies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. An ER Protein Functionally Couples Neutral Lipid Metabolism on Lipid Droplets to Membrane Lipid Synthesis in the ER

    DEFF Research Database (Denmark)

    Markgraf, Daniel F; Klemm, Robin W; Junker, Mirco

    2014-01-01

    Eukaryotic cells store neutral lipids such as triacylglycerol (TAG) in lipid droplets (LDs). Here, we have addressed how LDs are functionally linked to the endoplasmic reticulum (ER). We show that, in S. cerevisiae, LD growth is sustained by LD-localized enzymes. When LDs grow in early stationary...... phase, the diacylglycerol acyl-transferase Dga1p moves from the ER to LDs and is responsible for all TAG synthesis from diacylglycerol (DAG). During LD breakdown in early exponential phase, an ER membrane protein (Ice2p) facilitates TAG utilization for membrane-lipid synthesis. Ice2p has a cytosolic...... and explain how cells switch neutral lipid metabolism from storage to consumption....

  20. Silica particles encapsulated poly(styrene-divinylbenzene) monolithic stationary phases for micro-high performance liquid chromatography.

    Science.gov (United States)

    Bakry, R; Stöggl, W M; Hochleitner, E O; Stecher, G; Huck, C W; Bonn, G K

    2006-11-03

    In the paper we demonstrate a new approach for the preparation and application of continuous silica bed columns that involve encapsulation (entrapment) of functionalized silica microparticles, which can be used as packing material in micro high performance liquid chromatography (micro-HPLC) and capillary electrochromatography (CEC). Like traditional packed columns, these capillaries possess characterized silica particles that offer high phase ratio and narrow pore size distribution leading to high retention and separation efficiency, respectively. More importantly, immobilization of the microparticles stabilizes the separation bed and eliminates the need for retaining frits. The developed capillary columns were fabricated in exactly the same way as a packed capillary column (slurry packing) but with an additional entrapment step. This immobilization of the packed bed was achieved by in situ polymerization of styrene and divinylbenzene in presence of decanol as a porogen and azobisisobutyronitrile as thermal initiator. Silica particles with different particle sizes and pore sizes ranging from 60 to 4000 A were studied. In addition different modified silica was used, including C-18 reversed phase, anion exchange and chiral stationary phases. Efficient separation of polyphenolic compounds, peptides, proteins and even DNA mutation were achieved using the developed technique depending on the properties of the silica particles used (particles pore size). For example, using 3 microm ProntoSIL C-18 particles with 300 A pore size, separation efficiencies in the range of 120,000-200,000 plates/m were obtained for protein separation, in a 6 cm x 200 microm i.d. capillary column. Using encapsulated silica C-18 with 1000 A pore size, separation of DNA homo and hetero duplexes were achieved under denaturing HPLC conditions for mutation detection. In addition, nucleotides were separated using anion exchange material encapsulated with poly(styrene-divinylbenzene) (PS/DVB), which

  1. Identification of metabolic pathways expressed by Pichia anomala Kh6 in the presence of the pathogen Botrytis cinerea on apple: new possible targets for biocontrol improvement.

    Directory of Open Access Journals (Sweden)

    Anthony Kwasiborski

    Full Text Available Yeast Pichia anomala strain Kh6 Kurtzman (Saccharomycetales: Endomycetaceae exhibits biological control properties that provide an alternative to the chemical fungicides currently used by fruit or vegetable producers against main post-harvest pathogens, such as Botrytis cinerea (Helotiales: Sclerotiniaceae. Using an in situ model that takes into account interactions between organisms and a proteomic approach, we aimed to identify P. anomala metabolic pathways influenced by the presence of B. cinerea. A total of 105 and 60 P. anomala proteins were differentially represented in the exponential and stationary growth phases, respectively. In the exponential phase and in the presence of B. cinerea, the pentose phosphate pathway seems to be enhanced and would provide P. anomala with the needed nucleic acids and energy for the wound colonisation. In the stationary phase, P. anomala would use alcoholic fermentation both in the absence and presence of the pathogen. These results would suggest that the competitive colonisation of apple wounds could be implicated in the mode of action of P. anomala against B. cinerea.

  2. Pilots' Attention Distributions Between Chasing a Moving Target and a Stationary Target.

    Science.gov (United States)

    Li, Wen-Chin; Yu, Chung-San; Braithwaite, Graham; Greaves, Matthew

    2016-12-01

    Attention plays a central role in cognitive processing; ineffective attention may induce accidents in flight operations. The objective of the current research was to examine military pilots' attention distributions between chasing a moving target and a stationary target. In the current research, 37 mission-ready F-16 pilots participated. Subjects' eye movements were collected by a portable head-mounted eye-tracker during tactical training in a flight simulator. The scenarios of chasing a moving target (air-to-air) and a stationary target (air-to-surface) consist of three operational phases: searching, aiming, and lock-on to the targets. The findings demonstrated significant differences in pilots' percentage of fixation during the searching phase between air-to-air (M = 37.57, SD = 5.72) and air-to-surface (M = 33.54, SD = 4.68). Fixation duration can indicate pilots' sustained attention to the trajectory of a dynamic target during air combat maneuvers. Aiming at the stationary target resulted in larger pupil size (M = 27,105, SD = 6565), reflecting higher cognitive loading than aiming at the dynamic target (M = 23,864, SD = 8762). Pilots' visual behavior is not only closely related to attention distribution, but also significantly associated with task characteristics. Military pilots demonstrated various visual scan patterns for searching and aiming at different types of targets based on the research settings of a flight simulator. The findings will facilitate system designers' understanding of military pilots' cognitive processes during tactical operations. They will assist human-centered interface design to improve pilots' situational awareness. The application of an eye-tracking device integrated with a flight simulator is a feasible and cost-effective intervention to improve the efficiency and safety of tactical training.Li W-C, Yu C-S, Braithwaite G, Greaves M. Pilots' attention distributions between chasing a moving target and a stationary target. Aerosp Med

  3. Development of an achiral supercritical fluid chromatography method with ultraviolet absorbance and mass spectrometric detection for impurity profiling of drug candidates. Part II. Selection of an orthogonal set of stationary phases.

    Science.gov (United States)

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

    2015-08-21

    Impurity profiling of organic products that are synthesized as possible drug candidates requires complementary analytical methods to ensure that all impurities are identified. Supercritical fluid chromatography (SFC) is a very useful tool to achieve this objective, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. In this series of papers, we have developed a method for achiral SFC-MS profiling of drug candidates, based on a selection of 160 analytes issued from Servier Research Laboratories. In the first part of this study, focusing on mobile phase selection, a gradient elution with carbon dioxide and methanol comprising 2% water and 20mM ammonium acetate proved to be the best in terms of chromatographic performance, while also providing good MS response [1]. The objective of this second part was the selection of an orthogonal set of ultra-high performance stationary phases, that was carried out in two steps. Firstly, a reduced set of analytes (20) was used to screen 23 columns. The columns selected were all 1.7-2.5μm fully porous or 2.6-2.7μm superficially porous particles, with a variety of stationary phase chemistries. Derringer desirability functions were used to rank the columns according to retention window, column efficiency evaluated with peak width of selected analytes, and the proportion of analytes successfully eluted with good peak shapes. The columns providing the worst performances were thus eliminated and a shorter selection of columns (11) was obtained. Secondly, based on 160 tested analytes, the 11 columns were ranked again. The retention data obtained on these columns were then compared to define a reduced set of the best columns providing the greatest orthogonality, to maximize the chances to see all impurities within a limited number of runs. Two high-performance columns were thus selected: ACQUITY UPC(2) HSS C18 SB and Nucleoshell HILIC. Copyright © 2015

  4. Quantitative Tools for Dissection of Hydrogen-Producing Metabolic Networks-Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rabinowitz, Joshua D.; Dismukes, G.Charles.; Rabitz, Herschel A.; Amador-Noguez, Daniel

    2012-10-19

    During this project we have pioneered the development of integrated experimental-computational technologies for the quantitative dissection of metabolism in hydrogen and biofuel producing microorganisms (i.e. C. acetobutylicum and various cyanobacteria species). The application of these new methodologies resulted in many significant advances in the understanding of the metabolic networks and metabolism of these organisms, and has provided new strategies to enhance their hydrogen or biofuel producing capabilities. As an example, using mass spectrometry, isotope tracers, and quantitative flux-modeling we mapped the metabolic network structure in C. acetobutylicum. This resulted in a comprehensive and quantitative understanding of central carbon metabolism that could not have been obtained using genomic data alone. We discovered that biofuel production in this bacterium, which only occurs during stationary phase, requires a global remodeling of central metabolism (involving large changes in metabolite concentrations and fluxes) that has the effect of redirecting resources (carbon and reducing power) from biomass production into solvent production. This new holistic, quantitative understanding of metabolism is now being used as the basis for metabolic engineering strategies to improve solvent production in this bacterium. In another example, making use of newly developed technologies for monitoring hydrogen and NAD(P)H levels in vivo, we dissected the metabolic pathways for photobiological hydrogen production by cyanobacteria Cyanothece sp. This investigation led to the identification of multiple targets for improving hydrogen production. Importantly, the quantitative tools and approaches that we have developed are broadly applicable and we are now using them to investigate other important biofuel producers, such as cellulolytic bacteria.

  5. Imitation of phase I oxidative metabolism of anabolic steroids by titanium dioxide photocatalysis.

    Science.gov (United States)

    Ruokolainen, Miina; Valkonen, Minna; Sikanen, Tiina; Kotiaho, Tapio; Kostiainen, Risto

    2014-12-18

    The aim of this study was to investigate the feasibility of titanium dioxide (TiO2) photocatalysis for oxidation of anabolic steroids and for imitation of their phase I metabolism. The photocatalytic reaction products of five anabolic steroids were compared to their phase I in vitro metabolites produced by human liver microsomes (HLM). The same main reaction types - hydroxylation, dehydrogenation and combination of these two - were observed both in TiO2 photocatalysis and in microsomal incubations. Several isomers of each product type were formed in both systems. Based on the same mass, retention time and similarity of the product ion spectra, many of the products observed in HLM reactions were also formed in TiO2 photocatalytic reactions. However, products characteristic to only either one of the systems were also formed. In conclusion, TiO2 photocatalysis is a rapid, simple and inexpensive method for imitation of phase I metabolism of anabolic steroids and production of metabolite standards. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Stationary and Transient Response Statistics

    DEFF Research Database (Denmark)

    Madsen, Peter Hauge; Krenk, Steen

    1982-01-01

    The covariance functions for the transient response of a linear MDOF-system due to stationary time limited excitation with an arbitrary frequency content are related directly to the covariance functions of the stationary response. For rational spectral density functions closed form expressions fo...

  7. Metabolic cartography: experimental quantification of metabolic fluxes from isotopic labelling studies.

    Science.gov (United States)

    O'Grady, John; Schwender, Jörg; Shachar-Hill, Yair; Morgan, John A

    2012-03-01

    For the past decade, flux maps have provided researchers with an in-depth perspective on plant metabolism. As a rapidly developing field, significant headway has been made recently in computation, experimentation, and overall understanding of metabolic flux analysis. These advances are particularly applicable to the study of plant metabolism. New dynamic computational methods such as non-stationary metabolic flux analysis are finding their place in the toolbox of metabolic engineering, allowing more organisms to be studied and decreasing the time necessary for experimentation, thereby opening new avenues by which to explore the vast diversity of plant metabolism. Also, improved methods of metabolite detection and measurement have been developed, enabling increasingly greater resolution of flux measurements and the analysis of a greater number of the multitude of plant metabolic pathways. Methods to deconvolute organelle-specific metabolism are employed with increasing effectiveness, elucidating the compartmental specificity inherent in plant metabolism. Advances in metabolite measurements have also enabled new types of experiments, such as the calculation of metabolic fluxes based on (13)CO(2) dynamic labelling data, and will continue to direct plant metabolic engineering. Newly calculated metabolic flux maps reveal surprising and useful information about plant metabolism, guiding future genetic engineering of crops to higher yields. Due to the significant level of complexity in plants, these methods in combination with other systems biology measurements are necessary to guide plant metabolic engineering in the future.

  8. Salmonella Modulates Metabolism During Growth under Conditions that Induce Expression of Virulence Genes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Young-Mo; Schmidt, Brian; Kidwai, Afshan S.; Jones, Marcus B.; Deatherage, Brooke L.; Brewer, Heather M.; Mitchell, Hugh D.; Palsson, Bernhard O.; McDermott, Jason E.; Heffron, Fred; Smith, Richard D.; Peterson, Scott N.; Ansong, Charles; Hyduke, Daniel R.; Metz, Thomas O.; Adkins, Joshua N.

    2013-04-05

    Salmonella enterica serovar Typhimurium (S. Typhimurium) is a facultative pathogen that uses complex mechanisms to invade and proliferate within mammalian host cells. To investigate possible contributions of metabolic processes in S. Typhimurium grown under conditions known to induce expression of virulence genes, we used a metabolomics-driven systems biology approach coupled with genome scale modeling. First, we identified distinct metabolite profiles associated with bacteria grown in either rich or virulence-inducing media and report the most comprehensive coverage of the S. Typhimurium metabolome to date. Second, we applied an omics-informed genome scale modeling analysis of the functional consequences of adaptive alterations in S. Typhimurium metabolism during growth under our conditions. Excitingly, we observed possible sequestration of metabolites recently suggested to have immune modulating roles. Modeling efforts highlighted a decreased cellular capability to both produce and utilize intracellular amino acids during stationary phase culture in virulence conditions, despite significant abundance increases for these molecules as observed by our metabolomics measurements. Model-guided analysis suggested that alterations in metabolism prioritized other activities necessary for pathogenesis instead, such as lipopolysaccharide biosynthesis.

  9. New Non-Stationary Gradient Model of Heat-Mass-Electric Charge Transfer in Thin Porous Media

    Directory of Open Access Journals (Sweden)

    V. Rogankov

    2017-10-01

    Full Text Available The well-known complicated system of non-equilibrium balance equations for a continuous fluid (f medium needs the new non-Gibbsian model of f-phase to be applicable for description of the heterogeneous porous media (PMs. It should be supplemented by the respective coupled thermal and caloric equations of state (EOS developed specially for PMs to become adequate and solvable for the irreversible transport f-processes. The set of standard assumptions adopted by the linear (or quasi-linear non-equilibrium thermodynamics are based on the empirical gradient-caused correlations between flows and forces. It leads, in particular, to the oversimplified stationary solutions for PMs. The most questionable but typical modeling suppositions of the stationary gradient (SG theory are: 1 the assumption of incompressibility accepted, as a rule, for f-flows; 2 the ignorance of distinctions between the hydrophilic and hydrophobic influence of a porous matrix on the properties; 3 the omission of effects arising due to the concomitant phase intra-porous transitions between the neighboring f-fragments with the sharp differences in densities; 4 the use of exclusively Gibbsian (i.e. homogeneous and everywhere differentiable description of any f-phase in PM; 5 the very restrictive reduction of the mechanical velocity field to its specific potential form in the balance equation of f-motion as well as of the heat velocity field in the balance equation of internal energy; 6 the neglect of the new specific peculiarities arising due to the study of any non-equilibrium PM in the meso- and nano-scales of a finite-size macroscopic (N,V-system of discrete particles. This work is an attempt to develop the alternative non-stationary gradient (NSG model of real irreversible processes in PM. Another aim is to apply it without the above restrictions 1-6 to the description of f-flows through the obviously non-Gibbsian thin porous medium (TPM. We will suppose that it is composed by two

  10. Effect of algal growth phase on Aureococcus anophagefferens susceptibility to hydrogen peroxide

    International Nuclear Information System (INIS)

    Randhawa, Varunpreet; Thakkar, Megha; Wei, Liping

    2013-01-01

    Highlights: •Brown tide alga's susceptibility to H 2 O 2 was examined via growth and physiology responses. •The study was designed equalizing the influence of the media and cell density in test cultures. •Stationary cells was more sensitive to H 2 O 2 than exponential cells. •Stationary cells showed weaker non-protein thiol up-regulation than exponential cells. •Stationary cells mediated greater H 2 O 2 decomposition than exponential cells did. -- Abstract: A cell's growth phase could affect its susceptibility to a biocide in microbial control. This study examines the growth phase dependent susceptibility of a brown tide bloom alga Aureococcus anophagefferens to microbial biocide hydrogen peroxide (H 2 O 2 ). Test cultures of A. anophagefferens cells in exponential and stationary growth phase and similar initial cell density (1.6 × 10 6 cells mL −1 ) were exposed to 0.4–1.6 mg L −1 H 2 O 2 . Changes in algal growth (in vivo fluorescence, total chlorophyll a, and cell density), cell physiology (maximum quantum yield of photosystem II, and total intracellular non-protein thiols), and H 2 O 2 decomposition were quantified. Results show that the stationary phase cells are more susceptible to H 2 O 2 than the exponential phase cells, and this is attributed to the weaker ROS (reactive oxygen species) scavenging system and consequently greater cell damage in stationary phase cells. The stationary phase cells potentially require 30–40% less H 2 O 2 to reach 90% removal within 12 h of treatment as compared to the exponential phase cells. The results have practical implications in brown tide bloom control with respect to the timing and the dosage of H 2 O 2 application

  11. Stationary nonlinear Airy beams

    International Nuclear Information System (INIS)

    Lotti, A.; Faccio, D.; Couairon, A.; Papazoglou, D. G.; Panagiotopoulos, P.; Tzortzakis, S.; Abdollahpour, D.

    2011-01-01

    We demonstrate the existence of an additional class of stationary accelerating Airy wave forms that exist in the presence of third-order (Kerr) nonlinearity and nonlinear losses. Numerical simulations and experiments, in agreement with the analytical model, highlight how these stationary solutions sustain the nonlinear evolution of Airy beams. The generic nature of the Airy solution allows extension of these results to other settings, and a variety of applications are suggested.

  12. 30 CFR 57.14115 - Stationary grinding machines.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Stationary grinding machines. 57.14115 Section... and Equipment Safety Devices and Maintenance Requirements § 57.14115 Stationary grinding machines. Stationary grinding machines, other than special bit grinders, shall be equipped with— (a) Peripheral hoods...

  13. Application of Homochiral Alkylated Organic Cages as Chiral Stationary Phases for Molecular Separations by Capillary Gas Chromatography.

    Science.gov (United States)

    Xie, Shengming; Zhang, Junhui; Fu, Nan; Wang, Bangjin; Hu, Cong; Yuan, Liming

    2016-11-08

    Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of ( S , S )-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.

  14. Application of Homochiral Alkylated Organic Cages as Chiral Stationary Phases for Molecular Separations by Capillary Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Shengming Xie

    2016-11-01

    Full Text Available Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701 was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.

  15. Phenotypic and metabolic traits of commercial Saccharomyces cerevisiae yeasts.

    Science.gov (United States)

    Barbosa, Catarina; Lage, Patrícia; Vilela, Alice; Mendes-Faia, Arlete; Mendes-Ferreira, Ana

    2014-01-01

    Currently, pursuing yeast strains that display both a high potential fitness for alcoholic fermentation and a favorable impact on quality is a major goal in the alcoholic beverage industry. This considerable industrial interest has led to many studies characterizing the phenotypic and metabolic traits of commercial yeast populations. In this study, 20 Saccharomyces cerevisiae strains from different geographical origins exhibited high phenotypic diversity when their response to nine biotechnologically relevant conditions was examined. Next, the fermentation fitness and metabolic traits of eight selected strains with a unique phenotypic profile were evaluated in a high-sugar synthetic medium under two nitrogen regimes. Although the strains exhibited significant differences in nitrogen requirements and utilization rates, a direct relationship between nitrogen consumption, specific growth rate, cell biomass, cell viability, acetic acid and glycerol formation was only observed under high-nitrogen conditions. In contrast, the strains produced more succinic acid under the low-nitrogen regime, and a direct relationship with the final cell biomass was established. Glucose and fructose utilization patterns depended on both yeast strain and nitrogen availability. For low-nitrogen fermentation, three strains did not fully degrade the fructose. This study validates phenotypic and metabolic diversity among commercial wine yeasts and contributes new findings on the relationship between nitrogen availability, yeast cell growth and sugar utilization. We suggest that measuring nitrogen during the stationary growth phase is important because yeast cells fermentative activity is not exclusively related to population size, as previously assumed, but it is also related to the quantity of nitrogen consumed during this growth phase.

  16. Asymptotic Theory for the QMLE in GARCH-X Models with Stationary and Non-Stationary Covariates

    DEFF Research Database (Denmark)

    Han, Heejoon; Kristensen, Dennis

    as captured by its long-memory parameter dx; in particular, we allow for both stationary and non-stationary covariates. We show that the QMLE'’s of the regression coefficients entering the volatility equation are consistent and normally distributed in large samples independently of the degree of persistence....... This implies that standard inferential tools, such as t-statistics, do not have to be adjusted to the level of persistence. On the other hand, the intercept in the volatility equation is not identifi…ed when the covariate is non-stationary which is akin to the results of Jensen and Rahbek (2004, Econometric...

  17. Real-time metabolome profiling of the metabolic switch between starvation and growth.

    Science.gov (United States)

    Link, Hannes; Fuhrer, Tobias; Gerosa, Luca; Zamboni, Nicola; Sauer, Uwe

    2015-11-01

    Metabolic systems are often the first networks to respond to environmental changes, and the ability to monitor metabolite dynamics is key for understanding these cellular responses. Because monitoring metabolome changes is experimentally tedious and demanding, dynamic data on time scales from seconds to hours are scarce. Here we describe real-time metabolome profiling by direct injection of living bacteria, yeast or mammalian cells into a high-resolution mass spectrometer, which enables automated monitoring of about 300 compounds in 15-30-s cycles over several hours. We observed accumulation of energetically costly biomass metabolites in Escherichia coli in carbon starvation-induced stationary phase, as well as the rapid use of these metabolites upon growth resumption. By combining real-time metabolome profiling with modeling and inhibitor experiments, we obtained evidence for switch-like feedback inhibition in amino acid biosynthesis and for control of substrate availability through the preferential use of the metabolically cheaper one-step salvaging pathway over costly ten-step de novo purine biosynthesis during growth resumption.

  18. 30 CFR 56.14115 - Stationary grinding machines.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Stationary grinding machines. 56.14115 Section... Equipment Safety Devices and Maintenance Requirements § 56.14115 Stationary grinding machines. Stationary grinding machines, other than special bit grinders, shall be equipped with— (a) Peripheral hoods capable of...

  19. [Preparation and performance characterization of gold nanoparticles modified chiral capillary electrochromatography stationary phase].

    Science.gov (United States)

    Xiong, Lele; Li, Ruijun; Ji, Yibing

    2017-07-08

    Gold nanoparticles (GNPs, 15 nm) were prepared and introduced to amino groups derived silica monolithic column. Bovine serum albumin (BSA) was immobilized via covalent modification method onto the carboxylic functionalized GNPs to afford chiral stationary phase (CSP) for enantioseparation. GNPs were well dispersed and successfully incorporated onto the columns with the contents as high as 17.18% by characterization method such as transmission electron microscopy (TEM), ultraviolet (UV)-visible absorption spectra and scanning electron microscopy (SEM). The preparation conditions of the BSA modified CSP were optimized and 10% (v/v) 3-aminopropyltriethoxysilane (APTES) and 15 g/L BSA were selected as appropriate reaction conditions. The enantioseparation performance of the BSA modified CSP has been investigated by capillary electrochromatography (CEC). Enantiomers of tryptophan, ephedrine and atenolol were resolved, and the baseline separation of tryptophan was achieved. Meanwhile, the influences of pH value, buffer concentrations and applied voltages used on the chiral separation were studied, and the optimal separation conditions were 10 mmol/L phosphate buffer at pH 7.4 and 15 kV applied voltages. In comparison with the BSA modified CSP prepared by physical adsorption, the CSP prepared by covalent modification method had better separation results, and the analytes could be separated directly without pre-column derivatization. In addition, the prepared BSA modified CSP exhibited good run to run repeatability with relative standard deviations (RSDs) of the migration times and selectivity factors not more than 2.3% and 0.96%, respectively. This work offers a good thinking for modification with other proteins or other types of chiral selectors.

  20. Virtual Stationary Automata for Mobile Networks

    National Research Council Canada - National Science Library

    Dolev, Shlomi; Gilbert, Seth; Lahiani, Limor; Lynch, Nancy; Nolte, Tina

    2005-01-01

    We define a programming abstraction for mobile networks called the Virtual Stationary Automata programming layer, consisting of real mobile clients, virtual timed I/O automata called virtual stationary automata (VSAs...

  1. Mixed-mode reversed phase/positively charged repulsion chromatography for intact protein separation.

    Science.gov (United States)

    Ding, Ling; Guo, Zhimou; Hu, Zhuo; Liang, Xinmiao

    2017-05-10

    A mixed-mode reversed phase/positively charged repulsion stationary phase C8PN composed of octyl and amino group has been developed for separation of intact protein. Before the separation of proteins, a set of probe compounds were employed to evaluate the chromatographic properties of C8PN, demonstrating typical reversed phase/positively charged repulsion interaction on this stationary phase as estimated. Then the new C8PN stationary phase was used to separate a standard protein mixture on the reversed phase mode. Compared with a commercial C4 stationary phase, it showed different selectivity for some proteins. In order to better understand the properties of C8PN, the effect of acetonitrile content was investigated based on retention equation. Higher values of the equation parameters on C8PN demonstrated that the protein retentions were more sensitive to the change of acetonitrile content. Besides, the influences of buffer salt additives on the protein retentions were also studied. The retention factors of the proteins got larger with the increase of buffer salt concentration, which confirmed the positively charged repulsion interaction on the column. Finally, the C8PN was further applied to separate oxidized- and reduced- forms of Recombinant Human Growth Hormone. Our study indicated the advantages and application potential of mixed-mode reversed phase/positively charged repulsion stationary phase for intact protein separation. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. The stationary phase sigma factor, RpoS, regulates the production of a carbapenem antibiotic, a bioactive prodigiosin and virulence in the enterobacterial pathogen Serratia sp. ATCC 39006.

    Science.gov (United States)

    Wilf, Nabil M; Salmond, George P C

    2012-03-01

    Serratia sp. ATCC 39006 (S39006) is a Gram-negative bacterium that is virulent in plant (potato) and invertebrate animal (Caenorhabditis elegans) models. It produces two secondary metabolite antibiotics, a prodigiosin and a carbapenem, and the exoenzymes pectate lyase and cellulase. We showed previously that deletion of the RNA chaperone Hfq abolished antibiotic production and attenuated virulence in both animal and plant hosts. Hfq and dependent small RNAs (sRNAs) are known to regulate the post-transcriptional expression of rpoS, which encodes σ(S), the stationary phase sigma factor subunit of RNA polymerase. An S39006 hfq deletion mutant showed decreased transcript levels of rpoS. Therefore, in this study we investigated whether the phenotypes regulated by Hfq were mediated through its control of rpoS. Whereas loss of Hfq abolished prodigiosin and carbapenem production and attenuated virulence in both C. elegans and potato, characterization of an S39006 rpoS mutant showed unexpectedly elevated prodigiosin and carbapenem production. Furthermore, the rpoS mutant exhibited attenuated animal pathogenesis, but not plant pathogenesis. Additionally, a homologue of the Hfq-dependent sRNA, RprA, was identified and shown to regulate prodigiosin production in a manner consistent with its role in positively regulating translation of rpoS mRNA. Combined, these results demonstrate that Hfq regulation of secondary metabolism and plant pathogenesis is independent of RpoS and establishes RpoS and RprA as regulators of antibiotic production.

  3. Stationary Josephson effect in a weak-link between nonunitary triplet superconductors

    International Nuclear Information System (INIS)

    Rashedi, G; Kolesnichenko, Yu.A.

    2005-01-01

    A stationary Josephson effect in a weak-link between misorientated nonunitary triplet superconductors is investigated theoretically. The non-self-consistent quasiclassical Eilenberger equation for this system has been solved analytically. As an application of this analytical calculation, the current-phase diagrams are plotted for the junction between two nonunitary bipolar f-wave superconducting banks. A spontaneous current parallel to the interface between superconductors has been observed. Also, the effect of misorientation between crystals on the Josephson and spontaneous currents is studied. Such experimental investigations of the current-phase diagrams can be used to test the pairing symmetry in the above-mentioned superconductors

  4. Thin Layer Chromatographic Resolution of Some β-adrenolytics and a β2-Agonist Using Bovine Serum Albumin as Chiral Additive in Stationary Phase.

    Science.gov (United States)

    Malik, Poonam; Bhushan, Ravi

    2018-01-01

    Direct enantiomeric resolution of commonly used five racemic β-adrenolytics, namely, bisoprolol, atenolol, propranolol, salbutamol and carvedilol has been achieved by thin layer chromatography using bovine serum albumin (BSA) as chiral additive in stationary phase. Successful resolution of the enantiomers of all racemic β-adrenolytics was achieved by use of different composition of simple organic solvents having no buffer or inorganic ions. The effect of variation in pH, temperature, amount of BSA as the additive, and composition of mobile phase on resolution was systematically studied. Spots were visualized in iodine vapors. Native enantiomers for each of the five analytes were isolated and identified and their elution order was determined. The limit of detection was found to be 0.7, 1.2, 0.84, 1.6 and 0.9 μg (per spot) for each enantiomer of bisoprolol, atenolol, propranolol, salbutamol and carvedilol, respectively. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  5. Oxygen-enriched fermentation of sodium gluconate by Aspergillus niger and its impact on intracellular metabolic flux distributions.

    Science.gov (United States)

    Shen, Yuting; Tian, Xiwei; Zhao, Wei; Hang, Haifeng; Chu, Ju

    2018-01-01

    Different concentrations of oxygen-enriched air were utilized for sodium gluconate (SG) fermentation by Aspergillus niger. The fermentation time shortened from 20 to 15.5 h due to the increase of volumetric oxygen transfer coefficient (K L a) and the formation of more dispersed mycelia when inlet oxygen concentration ascended from 21 to 32%. According to metabolic flux analysis, during the growth phase, extracellular glucose for SG synthesis accounted for 79.0 and 85.3% with air and oxygen-enriched air (25%), respectively, whereas the proportions were 89.4 and 93.0% in the stationary phase. Intracellular glucose consumption decreased in oxygen-enriched fermentation, as cell respiration was more high-efficiently performed. Metabolic profiling indicated that most intermediates in TCA cycle and EMP pathway had smaller pool sizes in oxygen-enriched fermentations. Moreover, the main by-product of citric acid dramatically decreased from 1.36 to 0.34 g L -1 in oxygen-enriched fermentation. And the sodium gluconate yield increased from 0.856 to 0.903 mol mol -1 .

  6. Strong Stationary Duality for Diffusion Processes

    OpenAIRE

    Fill, James Allen; Lyzinski, Vince

    2014-01-01

    We develop the theory of strong stationary duality for diffusion processes on compact intervals. We analytically derive the generator and boundary behavior of the dual process and recover a central tenet of the classical Markov chain theory in the diffusion setting by linking the separation distance in the primal diffusion to the absorption time in the dual diffusion. We also exhibit our strong stationary dual as the natural limiting process of the strong stationary dual sequence of a well ch...

  7. Impact of column and stationary phase properties on the productivity in chiral preparative LC.

    Science.gov (United States)

    Forssén, Patrik; Fornstedt, Torgny

    2018-03-01

    By generating 1500 random chiral separation systems, assuming two-site Langmuir interactions, we investigated numerically how the maximal productivity (P R,max ) was affected by changes in stationary phase adsorption properties. The relative change in P R,max , when one adsorption property changed 10%, was determined for each system and for each studied parameter the corresponding productivity change distribution of the systems was analyzed. We could conclude that there is no reason to have columns with more than 500 theoretical plates and larger selectivity than 3. More specifically, we found that changes in selectivity have a major impact on P R,max if it is below ∼2 and, interestingly, increasing selectivity when it is above ∼3 decreases P R,max . Increase in relative saturation capacity will have a major impact on P R,max if it is below ∼40%, but only modest above this percent. Increasing total monolayer saturation capacity, or decreasing the first eluting enantiomer's retention factor, will have a modest effect on P R,max and increased efficiency will have almost no effect at all on P R,max unless it is below ∼500 theoretical plates. Finally, we showed that chiral columns with superior analytic performance might have inferior preparative performance, or vice versa. It is, therefore, not possible to assess columns based on their analytical performance alone. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Effect of Various Diets on the Expression of Phase-I Drug Metabolizing Enzymes in Livers of Mice

    Science.gov (United States)

    Guo, Ying; Cui, Julia Yue; Lu, Hong; Klaassen, Curtis D.

    2017-01-01

    Previous studies have shown that diets can alter the metabolism of drugs; however, it is difficult to compare the effects of multiple diets on drug metabolism among different experimental settings. Phase-I related genes play a major role in the biotransformation of pro-drugs and drugs.In the current study, effects of nine diets on the mRNA expression of phase-I drug-metabolizing enzymes in livers of mice were simultaneously investigated. Compared to the AIN-93M purified diet (control), 73 of the 132 critical phase-I drug metabolizing genes were differentially regulated by at least one diet. Diet restriction produced the most number of changed genes (51), followed by the atherogenic diet (27), high-fat diet (25), standard rodent chow (21), western diet (20), high-fructose diet (5), EFA deficient diet (3), and low n-3 FA diet (1). The mRNAs of the Fmo family changed most, followed by Cyp2b and 4a subfamilies, as well as Por (From 1121 to 21-fold increase of theses mRNAs). There were 59 genes not altered by any of these diets.The present results may improve the interpretation of studies with mice and aid in determining effective and safe doses for individuals with different nutritional diets. PMID:25733028

  9. Enantioseparation of angiotensin II receptor type 1 blockers: evaluation of 6-substituted carbamoyl benzimidazoles on immobilized polysaccharide-based chiral stationary phases. Unusual temperature behavior.

    Science.gov (United States)

    Su, Ran; Hou, Zhun; Sang, Lihong; Zhou, Zhi-Ming; Fang, Hao; Yang, Xinying

    2017-09-15

    Enantioseparation of thirteen 6-substituted carbamoyl benzimidazoles by high-performance liquid chromatography (HPLC) was investigated using two immobilized polysaccharide-based chiral stationary phases (CSPs), Chiralpak IC and Chiralpak IA, in normal-phase mode. Most of the examined compounds were completely resolved. The effects of a polar alcohol modifier, analyte structure, and column temperature on the chiral recognition were investigated. Furthermore, the structure-retention relationship was evaluated, and thermodynamic parameters were calculated from plots of ln k' or ln α versus 1/T. The thermodynamic parameters indicated that the separations were enthalpy-driven. Moreover, nonlinear van't Hoff plots were obtained on Chiralpak IA. However, two unusual phenomena were observed: (1) an unusual increase in retention with increasing temperature with linear van't Hoff plots on Chiralpak IC and (2) an extremely high T iso value (i.e., several thousand degrees centigrade). Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Determination of melatonin in wine and plant extracts by capillary electrochromatography with immobilized carboxylic multi-walled carbon nanotubes as stationary phase.

    Science.gov (United States)

    Stege, Patricia W; Sombra, Lorena L; Messina, Germán; Martinez, Luis D; Silva, María F

    2010-07-01

    The finding of melatonin, the often called "hormone of darkness" in plants opens an interesting perspective associated to the plethora of health benefits related to the moderate consumption of red wine. In this study, the implementation of a new method for the determination of melatonin in complex food matrices by CEC with immobilized carboxylic multi-walled carbon nanotubes as stationary phase is demonstrated. The results indicated high electrochromatographic resolution, good capillary efficiencies and improved sensitivity respect to those obtained with conventional capillaries. In addition, it was demonstrated highly reproducible results between runs, days and columns. The LOD for melatonin was 0.01 ng/mL. The method was successfully applied to the determination of melatonin in red and white wine, grape skin and plant extracts of Salvia officinalis L.

  11. [Separation of purines, pyrimidines, pterins and flavonoids on magnolol-bonded silica gel stationary phase by high performance liquid chromatography].

    Science.gov (United States)

    Chen, Hong; Li, Laishen; Zhang, Yang; Zhou, Rendan

    2012-10-01

    A new magnolol-bonded silica gel stationary phase (MSP) was used to separate the basic drugs including four purines, eight pyrimidines, four pterins and five flavonoids as polar representative samples by high performance liquid chromatography (HPLC). To clarify the separation mechanism, a commercial ODS column was also tested under the same chromatographic conditions. The high selectivities and fast baseline separations of the above drugs were achieved by using simple mobile phases on MSP. Although there is no end-caped treatment, the peak shapes of basic drugs containing nitrogen such as purines, pyrimidines and pterins were rather symmetrical on MSP, which indicated the the magnolol as ligand with multi-sites could shield the side effect of residual silanol groups on the surface of silica gel. Although somewhat different in the separation resolution, it was found that the elution orders of some drugs were generally similar on both MSP and ODS. The hydrophobic interaction should play a significant role in the separations of the above basic drugs, which was attributed to their reversed-phase property in the nature. However, MSP could provide the additional sites for many polar solutes, which was a rational explanation for the high selectivity of MSP. For example, in the separation of purines, pyrimidines and pterins on MSP, hydrogen-bonding and dipole-dipole interactions played leading roles besides hydrophobic interaction. Some solute molecules (such as mercaptopurine, vitexicarpin) and MSP can form the strong pi-pi stacking in the separation process. All enhanced the retention and improved the separation selectivity of MSP, which facilitated the separation of the basic drugs.

  12. Effect of algal growth phase on Aureococcus anophagefferens susceptibility to hydrogen peroxide

    Energy Technology Data Exchange (ETDEWEB)

    Randhawa, Varunpreet; Thakkar, Megha; Wei, Liping, E-mail: liping.wei@njit.edu

    2013-10-15

    Highlights: •Brown tide alga's susceptibility to H{sub 2}O{sub 2} was examined via growth and physiology responses. •The study was designed equalizing the influence of the media and cell density in test cultures. •Stationary cells was more sensitive to H{sub 2}O{sub 2} than exponential cells. •Stationary cells showed weaker non-protein thiol up-regulation than exponential cells. •Stationary cells mediated greater H{sub 2}O{sub 2} decomposition than exponential cells did. -- Abstract: A cell's growth phase could affect its susceptibility to a biocide in microbial control. This study examines the growth phase dependent susceptibility of a brown tide bloom alga Aureococcus anophagefferens to microbial biocide hydrogen peroxide (H{sub 2}O{sub 2}). Test cultures of A. anophagefferens cells in exponential and stationary growth phase and similar initial cell density (1.6 × 10{sup 6} cells mL{sup −1}) were exposed to 0.4–1.6 mg L{sup −1} H{sub 2}O{sub 2}. Changes in algal growth (in vivo fluorescence, total chlorophyll a, and cell density), cell physiology (maximum quantum yield of photosystem II, and total intracellular non-protein thiols), and H{sub 2}O{sub 2} decomposition were quantified. Results show that the stationary phase cells are more susceptible to H{sub 2}O{sub 2} than the exponential phase cells, and this is attributed to the weaker ROS (reactive oxygen species) scavenging system and consequently greater cell damage in stationary phase cells. The stationary phase cells potentially require 30–40% less H{sub 2}O{sub 2} to reach 90% removal within 12 h of treatment as compared to the exponential phase cells. The results have practical implications in brown tide bloom control with respect to the timing and the dosage of H{sub 2}O{sub 2} application.

  13. Gene expression of transporters and phase I/II metabolic enzymes in murine small intestine during fasting

    Directory of Open Access Journals (Sweden)

    van der Meijde Jolanda

    2007-08-01

    Full Text Available Abstract Background Fasting has dramatic effects on small intestinal transport function. However, little is known on expression of intestinal transport and phase I/II metabolism genes during fasting and the role the fatty acid-activated transcription factor PPARα may play herein. We therefore investigated the effects of fasting on expression of these genes using Affymetrix GeneChip MOE430A arrays and quantitative RT-PCR. Results After 24 hours of fasting, expression levels of 33 of the 253 analyzed transporter and phase I/II metabolism genes were changed. Upregulated genes were involved in transport of energy-yielding molecules in processes such as glycogenolysis (G6pt1 and mitochondrial and peroxisomal oxidation of fatty acids (Cact, Mrs3/4, Fatp2, Cyp4a10, Cyp4b1. Other induced genes were responsible for the inactivation of the neurotransmitter serotonin (Sert, Sult1d1, Dtd, Papst2, formation of eicosanoids (Cyp2j6, Cyp4a10, Cyp4b1, or for secretion of cholesterol (Abca1 and Abcg8. Cyp3a11, typically known because of its drug metabolizing capacity, was also increased. Fasting had no pronounced effect on expression of phase II metabolic enzymes, except for glutathione S-transferases which were down-regulated. Time course studies revealed that some genes were acutely regulated, whereas expression of other genes was only affected after prolonged fasting. Finally, we identified 8 genes that were PPARα-dependently upregulated upon fasting. Conclusion We have characterized the response to fasting on expression of transporters and phase I/II metabolic enzymes in murine small intestine. Differentially expressed genes are involved in a variety of processes, which functionally can be summarized as a increased oxidation of fat and xenobiotics, b increased cholesterol secretion, c increased susceptibility to electrophilic stressors, and d reduced intestinal motility. This knowledge increases our understanding of gut physiology, and may be of relevance

  14. Shift work or food intake during the rest phase promotes metabolic disruption and desynchrony of liver genes in male rats.

    Science.gov (United States)

    Salgado-Delgado, Roberto C; Saderi, Nadia; Basualdo, María del Carmen; Guerrero-Vargas, Natali N; Escobar, Carolina; Buijs, Ruud M

    2013-01-01

    In the liver, clock genes are proposed to drive metabolic rhythms. These gene rhythms are driven by the suprachiasmatic nucleus (SCN) mainly by food intake and via autonomic and hormonal pathways. Forced activity during the normal rest phase, induces also food intake, thus neglecting the signals of the SCN, leading to conflicting time signals to target tissues of the SCN. The present study explored in a rodent model of night-work the influence of food during the normal sleep period on the synchrony of gene expression between clock genes and metabolic genes in the liver. Male Wistar rats were exposed to forced activity for 8 h either during the rest phase (day) or during the active phase (night) by using a slow rotating wheel. In this shift work model food intake shifts spontaneously to the forced activity period, therefore the influence of food alone without induced activity was tested in other groups of animals that were fed ad libitum, or fed during their rest or active phase. Rats forced to be active and/or eating during their rest phase, inverted their daily peak of Per1, Bmal1 and Clock and lost the rhythm of Per2 in the liver, moreover NAMPT and metabolic genes such as Pparα lost their rhythm and thus their synchrony with clock genes. We conclude that shift work or food intake in the rest phase leads to desynchronization within the liver, characterized by misaligned temporal patterns of clock genes and metabolic genes. This may be the cause of the development of the metabolic syndrome and obesity in individuals engaged in shift work.

  15. Stationary scattering theory

    International Nuclear Information System (INIS)

    Combes, J.M.

    1980-10-01

    A complementary approach to the time dependent scattering theory for one-body Schroedinger operators is presented. The stationary theory is concerned with objects of quantum theory like scattering waves and amplitudes. In the more recent abstract stationary theory some generalized form of the Lippman-Schwinger equation plays the basic role. Solving this equation leads to a linear map between generalized eigenfunctions of the perturbed and unperturbed operators. This map is the section at fixed energy of the wave-operator from the time dependent theory. Although the radiation condition does not appears explicitely in this formulation it can be shown to hold a posteriori in a variety of situations thus restoring the link with physical theories

  16. Solid phase extraction and metabolic profiling of exudates from living copepods

    DEFF Research Database (Denmark)

    Selander, Erik; Heuschele, Jan; Nylund, Göran M.

    2016-01-01

    describe the development of a closed loop solid phase extraction setup that allows for extraction of exuded metabolites from live copepods. We captured exudates from male and female Temora longicornis and analyzed the content with high resolution LC-MS. Chemometric methods revealed 87 compounds...... that solid phase extraction in combination with metabolic profiling of exudates is a useful tool to develop our understanding of the chemical interplay between pelagic organisms....... Copepodamide G, known to induce defensive responses in phytoplankton, was among the ten compounds of highest relative abundance in both male and female extracts. The presence of copepodamide G shows that the method can be used to capture and analyze chemical signals from living source organisms. We conclude...

  17. High enantioselective Novozym 435-catalyzed esterification of (R,S)-flurbiprofen monitored with a chiral stationary phase.

    Science.gov (United States)

    Siódmiak, Tomasz; Mangelings, Debby; Vander Heyden, Yvan; Ziegler-Borowska, Marta; Marszałł, Michał Piotr

    2015-03-01

    Lipases form Candida rugosa and Candida antarctica were tested for their application in the enzymatic kinetic resolution of (R,S)-flurbiprofen by enantioselective esterification. Successful chromatographic separation with well-resolved peaks of (R)- and (S)-flurbiprofen and their esters was achieved in one run on chiral stationary phases by high-performance liquid chromatography (HPLC). In this study screening of enzymes was performed, and Novozym 435 was selected as an optimal catalyst for obtaining products with high enantiopurity. Additionally, the influence of organic solvents (dichloromethane, dichloroethane, dichloropropane, and methyl tert-butyl ether), primary alcohols (methanol, ethanol, n-propanol, and n-butanol), reaction time, and temperature on the enantiomeric ratio and conversion was tested. The high values of enantiomeric ratio (E in the range of 51.3-90.5) of the esterification of (R,S)-flurbiprofen were obtained for all tested alcohols using Novozym 435, which have a great significance in the field of biotechnological synthesis of drugs. The optimal temperature range for the performed reactions was from 37 to 45 °C. As a result of the optimization, (R)-flurbiprofen methyl ester was obtained with a high optical purity, eep = 96.3 %, after 96 h of incubation. The enantiomeric ratio of the reaction was E = 90.5 and conversion was C = 35.7 %.

  18. Preparation and evaluation of a hydrophilic interaction and cation-exchange chromatography stationary phase modified with 2-methacryloyloxyethyl phosphorylcholine.

    Science.gov (United States)

    Xiong, Caifeng; Yuan, Jie; Wang, Zhiying; Wang, Siyao; Yuan, Chenchen; Wang, Lili

    2018-04-20

    In this work, 2-methacryloyloxyethyl phosphorylcholine (MPC) was used as a ligand to prepare a novel mixed-mode chromatography (MMC) stationary phase by the thiol-ene click reaction onto silica (MPC-silica). It was found that this MPC-silica showed the retention characteristics of hydrophilic interaction chromatography (HILIC) and weak cation exchange chromatography (WCX) under suitable mobile phase conditions. In detail, acidic and basic hydrophilic compounds and puerarin from pueraria were separated quickly with HILIC mode. Meanwhile, six standard proteins were allowed to reach baseline separation in WCX mode, and protein separation from egg white was also achieved with this mode. In addition, reduced/denatured lysozyme could be refolded with the MPC-silica column. In the meantime, the MPC-silica has been applied for refolding with simultaneous purification of recombinant human Delta-like1-RGD (rhDll1-RGD) expressed in Escherichia coli. The results show that the mass recovery and purity of rhDll1-RGD could reach 63.4% and 97% by one step, respectively. Furthermore, the reporter assay results demonstrated that refolded with simultaneously purified rhDll1-RGD could efficiently activate the signalling pathway in a dose-dependent manner. In general, this MPC-silica has good resolution and selectivity in the separation of polar compounds and protein samples in different high-performance liquid chromatography (HPLC) modes, and it successfully achieved refolding with simultaneous purification of denatured protein. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Stationary infinitely divisible processes

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole E.

    Several recent strands of work has led to the consideration of various types of continuous time stationary and infinitely divisible processes. A review of these types, with some new results, is presented.......Several recent strands of work has led to the consideration of various types of continuous time stationary and infinitely divisible processes. A review of these types, with some new results, is presented....

  20. Flood frequency analysis of historical flood data under stationary and non-stationary modelling

    Science.gov (United States)

    Machado, M. J.; Botero, B. A.; López, J.; Francés, F.; Díez-Herrero, A.; Benito, G.

    2015-06-01

    Historical records are an important source of information on extreme and rare floods and fundamental to establish a reliable flood return frequency. The use of long historical records for flood frequency analysis brings in the question of flood stationarity, since climatic and land-use conditions can affect the relevance of past flooding as a predictor of future flooding. In this paper, a detailed 400 yr flood record from the Tagus River in Aranjuez (central Spain) was analysed under stationary and non-stationary flood frequency approaches, to assess their contribution within hazard studies. Historical flood records in Aranjuez were obtained from documents (Proceedings of the City Council, diaries, chronicles, memoirs, etc.), epigraphic marks, and indirect historical sources and reports. The water levels associated with different floods (derived from descriptions or epigraphic marks) were computed into discharge values using a one-dimensional hydraulic model. Secular variations in flood magnitude and frequency, found to respond to climate and environmental drivers, showed a good correlation between high values of historical flood discharges and a negative mode of the North Atlantic Oscillation (NAO) index. Over the systematic gauge record (1913-2008), an abrupt change on flood magnitude was produced in 1957 due to constructions of three major reservoirs in the Tagus headwaters (Bolarque, Entrepeñas and Buendia) controlling 80% of the watershed surface draining to Aranjuez. Two different models were used for the flood frequency analysis: (a) a stationary model estimating statistical distributions incorporating imprecise and categorical data based on maximum likelihood estimators, and (b) a time-varying model based on "generalized additive models for location, scale and shape" (GAMLSS) modelling, which incorporates external covariates related to climate variability (NAO index) and catchment hydrology factors (in this paper a reservoir index; RI). Flood frequency

  1. Avalanche consumption and the stationary regions of the density profile around the droplets in the theory of condensation

    OpenAIRE

    Kurasov, V.

    1998-01-01

    The contradiction between the stationary aproach to the density profile and the avalanche character of the metastable phase consumption is investigated. The exact solution for the metastable phase profile is obtained. The reconsidered value for the special parameter responsible for the hierarchy in the structure of the density profile around the droplet is presented.

  2. Nonlinear stationary solutions of the Wigner and Wigner-Poisson equations

    OpenAIRE

    Haas, F.; Shukla, P. K.

    2008-01-01

    Exact nonlinear stationary solutions of the one-dimensional Wigner and Wigner-Poisson equations in the terms of the Wigner functions that depend not only on the energy but also on position are presented. In this way, the Bernstein-Greene-Kruskal modes of the classical plasma are adapted for the quantum formalism in the phase space. The solutions are constructed for the case of a quartic oscillator potential, as well as for the self-consistent Wigner-Poisson case. Conditions for well-behaved p...

  3. Stationary solutions and asymptotic flatness I

    International Nuclear Information System (INIS)

    Reiris, Martin

    2014-01-01

    In general relativity, a stationary isolated system is defined as an asymptotically flat (AF) stationary spacetime with compact material sources. Other definitions that are less restrictive on the type of asymptotic could in principle be possible. Between this article and its sequel, we show that under basic assumptions, asymptotic flatness indeed follows as a consequence of Einstein's theory. In particular, it is proved that any vacuum stationary spacetime-end whose (quotient) manifold is diffeomorphic to R 3 minus a ball and whose Killing field has its norm bounded away from zero, is necessarily AF with Schwarzschildian fall off. The ‘excised’ ball would contain (if any) the actual material body, but this information is unnecessary to reach the conclusion. In this first article, we work with weakly asymptotically flat (WAF) stationary ends, a notion that generalizes as much as possible that of the AF end, and prove that WAF ends are AF with Schwarzschildian fall off. Physical and mathematical implications are also discussed. (paper)

  4. Analyzing Non Stationary Processes in Radiometers

    Science.gov (United States)

    Racette, Paul

    2010-01-01

    The lack of well-developed techniques for modeling changing statistical moments in our observations has stymied the application of stochastic process theory for many scientific and engineering applications. Non linear effects of the observation methodology is one of the most perplexing aspects to modeling non stationary processes. This perplexing problem was encountered when modeling the effect of non stationary receiver fluctuations on the performance of radiometer calibration architectures. Existing modeling approaches were found not applicable; particularly problematic is modeling processes across scales over which they begin to exhibit non stationary behavior within the time interval of the calibration algorithm. Alternatively, the radiometer output is modeled as samples from a sequence random variables; the random variables are treated using a conditional probability distribution function conditioned on the use of the variable in the calibration algorithm. This approach of treating a process as a sequence of random variables with non stationary stochastic moments produce sensible predictions of temporal effects of calibration algorithms. To test these model predictions, an experiment using the Millimeter wave Imaging Radiometer (MIR) was conducted. The MIR with its two black body calibration references was configured in a laboratory setting to observe a third ultra-stable reference (CryoTarget). The MIR was programmed to sequentially sample each of the three references in approximately a 1 second cycle. Data were collected over a six-hour interval. The sequence of reference measurements form an ensemble sample set comprised of a series of three reference measurements. Two references are required to estimate the receiver response. A third reference is used to estimate the uncertainty in the estimate. Typically, calibration algorithms are designed to suppress the non stationary effects of receiver fluctuations. By treating the data sequence as an ensemble

  5. Strong cation exchange-type chiral stationary phase for enantioseparation of chiral amines in subcritical fluid chromatography.

    Science.gov (United States)

    Wolrab, Denise; Kohout, Michal; Boras, Mario; Lindner, Wolfgang

    2013-05-10

    A new strong cation exchange type chiral stationary phase (SCX CSP) based on a syringic acid amide derivative of trans-(R, R)-2-aminocyclohexanesulfonic acid was applied to subcritical fluid chromatography (SFC) for separation of various chiral basic drugs and their analogues. Mobile phase systems consisting of aliphatic alcohols as polar modifiers and a broad range of amines with different substitution patterns and lipophilicity were employed to evaluate the impact on the SFC retention and selectivity characteristics. The observed results point to the existence of carbonic and carbamic acid salts formed as a consequence of reactions occurring between carbon dioxide, the alcoholic modifiers and the amine species present in the sub/supercritical fluid medium, respectively. Evidence is provided that these species are essential for affecting ion exchange between the strongly acidic chiral selector units and the basic analytes, following the well-established stoichiometric displacement mechanisms. Specific trends were observed when different types of amines were used as basic additives. While ammonia gave rise to the formation of the most strongly eluting carbonic and carbamic salt species, simple tertiary amines consistently provided superior levels of enantioselectivity. Furthermore, trends in the chiral SFC separation characteristics were investigated by the systematic variation of the modifier content and temperature. Different effects of additives are interpreted in terms of changes in the relative concentration of the transient ionic species contributing to analyte elution, with ammonia-derived carbamic salts being depleted at elevated temperatures by decomposition. Additionally, in an effort to optimize SFC enantiomer separation conditions for selected analytes, the impact of the type of the organic modifier, temperature, flow rate and active back pressure were also investigated. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Application of Ionic Liquids in High Performance Reversed-Phase Chromatography

    Directory of Open Access Journals (Sweden)

    Wentao Bi

    2009-06-01

    Full Text Available Ionic liquids, considered “green” chemicals, are widely used in many areas of analytical chemistry due to their unique properties. Recently, ionic liquids have been used as a kind of novel additive in separation and combined with silica to synthesize new stationary phase as separation media. This review will focus on the properties and mechanisms of ionic liquids and their potential applications as mobile phase modifier and surface-bonded stationary phase in reversed-phase high performance liquid chromatography (RP-HPLC. Ionic liquids demonstrate advantages and potential in chromatographic field.

  7. Synthesis and Evaluation of Molecularly Imprinted Polymeric Microspheres for Chloramphenicol by Aqueous Suspension Polymerization as a High Performance Liquid Chromatography Stationary Phase

    International Nuclear Information System (INIS)

    Zhang, Yan; Lei, Jiandu

    2013-01-01

    Molecularly imprinted microsphere for chloramphenicol (CAP) with high adsorption capacity and excellent selectivity is prepared by aqueous suspension polymerization, in which chloramphenicol is used as template molecule and ethyl acetate as porogen. The CAP-imprinted microspheres are used as high performance liquid chromatography (HPLC) stationary phase and packed into stainless steel column (150 mm Χ 4.6 mm i. d.) for selective separation of chloramphenicol. HPLC analysis suggests that chloramphenicol can be distinguished from not only its structural analogs but also other broad-spectrum antibiotic such as erythromycin and tetracycline. In addition, the binding experiments of CAP-imprinted microspheres are carried out in ethanol/water (1:4, V:V), the results indicate that the maximum apparent static binding capacity of molecularly imprinted microspheres is up to 66.64 mg g -1 according to scatchard model

  8. Phenotypic diversity of diploid and haploid Emiliania huxleyi cells and of cells in different growth phases revealed by comparative metabolomics.

    Science.gov (United States)

    Mausz, Michaela A; Pohnert, Georg

    2015-01-01

    In phytoplankton a high species diversity of microalgae co-exists at a given time. But diversity is not only reflected by the species composition. Within these species different life phases as well as different metabolic states can cause additional diversity. One important example is the coccolithophore Emiliania huxleyi. Diploid cells play an important role in marine ecosystems since they can form massively abundant algal blooms but in addition the less abundant haploid life phase of E. huxleyi occurs in lower quantities. Both life phases may fulfill different functions in the plankton. We hypothesize that in addition to the functional diversity caused by this life phase transition the growth stage of cells can also influence the metabolic composition and thus the ecological impact of E. huxleyi. Here we introduce a metabolomic survey in dependence of life phases as well as different growth phases to reveal such changes. The comparative metabolomic approach is based on the extraction of intracellular metabolites from intact microalgae, derivatization and analysis by gas chromatography coupled to mass spectrometry (GC-MS). Automated data processing and statistical analysis using canonical analysis of principal coordinates (CAP) revealed unique metabolic profiles for each life phase. Concerning the correlations of metabolites to growth phases, complex patterns were observed. As for example the saccharide mannitol showed its highest concentration in the exponential phase, whereas fatty acids were correlated to stationary and sterols to declining phase. These results are indicative for specific ecological roles of these stages of E. huxleyi and are discussed in the context of previous physiological and ecological studies. Copyright © 2014 Elsevier GmbH. All rights reserved.

  9. Frequency Analysis of Extreme Sub-Daily Precipitation under Stationary and Non-Stationary Conditions across Two Contrasting Hydroclimatic Environments

    Science.gov (United States)

    Demaria, E. M.; Goodrich, D. C.; Keefer, T.

    2017-12-01

    Observed sub-daily precipitation intensities from contrasting hydroclimatic environments in the USA are used to evaluate temporal trends and to develop Intensity-Duration Frequency (IDF) curves under stationary and nonstationary climatic conditions. Analyses are based on observations from two United States Department of Agriculture (USDA)-Agricultural Research Service (ARS) experimental watersheds located in a semi-arid and a temperate environment. We use an Annual Maximum Series (AMS) and a Partial Duration Series (PDS) approach to identify temporal trends in maximum intensities for durations ranging from 5- to 1440-minutes. A Bayesian approach with Monte Carlo techniques is used to incorporate the effect of non-stationary climatic assumptions in the IDF curves. The results show increasing trends in observed AMS sub-daily intensities in both watersheds whereas trends in the PDS observations are mostly positive in the semi-arid site and a mix of positive and negative in the temperate site. Stationary climate assumptions lead to much lower estimated sub-daily intensities than those under non-stationary assumptions with larger absolute differences found for shorter durations and smaller return periods. The risk of failure (R) of a hydraulic structure is increased for non-stationary effects over those of stationary effects, with absolute differences of 25% for a 100-year return period (T) and a project life (n) of 100 years. The study highlights the importance of considering non-stationarity, due to natural variability or to climate change, in storm design.

  10. Yinchenhao Decoction Ameliorates Alpha-Naphthylisothiocyanate Induced Intrahepatic Cholestasis in Rats by Regulating Phase II Metabolic Enzymes and Transporters

    Directory of Open Access Journals (Sweden)

    Ya-Xiong Yi

    2018-05-01

    Full Text Available Yinchenhao Decoction (YCHD, a famous traditional Chinese formula, has been used for treating cholestasis for 1000s of years. The cholagogic effect of YCHD has been widely reported, but its pharmacodynamic material and underlying therapeutic mechanism remain unclear. By using ultra-high-performance liquid chromatography (UHPLC-quadrupole time-of-flight mass spectrometry, 11 original active components and eight phase II metabolites were detected in rats after oral administration of YCHD, including three new phase II metabolites. And it indicated that phase II metabolism was one of the major metabolic pathway for most active components in YCHD, which was similar to the metabolism process of bilirubin. It arouses our curiosity that whether the metabolism process of YCHD has any relationship with its cholagogic effects. So, a new method for simultaneous quantitation of eight active components and four phase II metabolites of rhein, emodin, genipin, and capillarisin has been developed and applied for their pharmacokinetic study in both normal and alpha-naphthylisothiocyanate (ANIT-induced intrahepatic cholestasis rats. The results indicated the pharmacokinetic behaviors of most components of YCHD were inhibited, which was hypothesized to be related to different levels of metabolic enzymes and transporters in rat liver. So dynamic changes of intrahepatic enzyme expression in cholestasis and YCHD treated rats have been monitored by an UHPLC-tandem mass spectrometry method. The results showed expression levels of UDP-glucuronosyltransferase 1-1 (UGT1A1, organic anion-transporting polypeptide 1A4 (OATP1A4, multidrug resistance-associated protein 2 (MRP2, multidrug resistance protein 1, sodium-dependent taurocholate cotransporter, and organic anion-transporting polypeptide 1A2 were significantly inhibited in cholestasis rats, which would account for reducing the drug absorption and the metabolic process of YCHD in cholestatic rats. A high dose (12 g/kg of

  11. Differentiating the growth phases of single bacteria using Raman spectroscopy

    Science.gov (United States)

    Strola, S. A.; Marcoux, P. R.; Schultz, E.; Perenon, R.; Simon, A.-C.; Espagnon, I.; Allier, C. P.; Dinten, J.-M.

    2014-03-01

    In this paper we present a longitudinal study of bacteria metabolism performed with a novel Raman spectrometer system. Longitudinal study is possible with our Raman setup since the overall procedure to localize a single bacterium and collect a Raman spectrum lasts only 1 minute. Localization and detection of single bacteria are performed by means of lensfree imaging, whereas Raman signal (from 600 to 3200 cm-1) is collected into a prototype spectrometer that allows high light throughput (HTVS technology, Tornado Spectral System). Accomplishing time-lapse Raman spectrometry during growth of bacteria, we observed variation in the net intensities for some band groups, e.g. amides and proteins. The obtained results on two different bacteria species, i.e. Escherichia coli and Bacillus subtilis clearly indicate that growth affects the Raman chemical signature. We performed a first analysis to check spectral differences and similarities. It allows distinguishing between lag, exponential and stationary growth phases. And the assignment of interest bands to vibration modes of covalent bonds enables the monitoring of metabolic changes in bacteria caused by growth and aging. Following the spectra analysis, a SVM (support vector machine) classification of the different growth phases is presented. In sum this longitudinal study by means of a compact and low-cost Raman setup is a proof of principle for routine analysis of bacteria, in a real-time and non-destructive way. Real-time Raman studies on metabolism and viability of bacteria pave the way for future antibiotic susceptibility testing.

  12. Contributions to reversed-phase column selectivity: III. Column hydrogen-bond basicity.

    Science.gov (United States)

    Carr, P W; Dolan, J W; Dorsey, J G; Snyder, L R; Kirkland, J J

    2015-05-22

    Column selectivity in reversed-phase chromatography (RPC) can be described in terms of the hydrophobic-subtraction model, which recognizes five solute-column interactions that together determine solute retention and column selectivity: hydrophobic, steric, hydrogen bonding of an acceptor solute (i.e., a hydrogen-bond base) by a stationary-phase donor group (i.e., a silanol), hydrogen bonding of a donor solute (e.g., a carboxylic acid) by a stationary-phase acceptor group, and ionic. Of these five interactions, hydrogen bonding between donor solutes (acids) and stationary-phase acceptor groups is the least well understood; the present study aims at resolving this uncertainty, so far as possible. Previous work suggests that there are three distinct stationary-phase sites for hydrogen-bond interaction with carboxylic acids, which we will refer to as column basicity I, II, and III. All RPC columns exhibit a selective retention of carboxylic acids (column basicity I) in varying degree. This now appears to involve an interaction of the solute with a pair of vicinal silanols in the stationary phase. For some type-A columns, an additional basic site (column basicity II) is similar to that for column basicity I in primarily affecting the retention of carboxylic acids. The latter site appears to be associated with metal contamination of the silica. Finally, for embedded-polar-group (EPG) columns, the polar group can serve as a proton acceptor (column basicity III) for acids, phenols, and other donor solutes. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Metabolic Flux Analysis in Isotope Labeling Experiments Using the Adjoint Approach.

    Science.gov (United States)

    Mottelet, Stephane; Gaullier, Gil; Sadaka, Georges

    2017-01-01

    Comprehension of metabolic pathways is considerably enhanced by metabolic flux analysis (MFA-ILE) in isotope labeling experiments. The balance equations are given by hundreds of algebraic (stationary MFA) or ordinary differential equations (nonstationary MFA), and reducing the number of operations is therefore a crucial part of reducing the computation cost. The main bottleneck for deterministic algorithms is the computation of derivatives, particularly for nonstationary MFA. In this article, we explain how the overall identification process may be speeded up by using the adjoint approach to compute the gradient of the residual sum of squares. The proposed approach shows significant improvements in terms of complexity and computation time when it is compared with the usual (direct) approach. Numerical results are obtained for the central metabolic pathways of Escherichia coli and are validated against reference software in the stationary case. The methods and algorithms described in this paper are included in the sysmetab software package distributed under an Open Source license at http://forge.scilab.org/index.php/p/sysmetab/.

  14. Stationary closed strings in five-dimensional flat spacetime

    Science.gov (United States)

    Igata, Takahisa; Ishihara, Hideki; Nishiwaki, Keisuke

    2012-11-01

    We investigate stationary rotating closed Nambu-Goto strings in five-dimensional flat spacetime. The stationary string is defined as a world sheet that is tangent to a timelike Killing vector. The Nambu-Goto equation of motion for the stationary string is reduced to the geodesic equation on the orbit space of the isometry group action generated by the Killing vector. We take a linear combination of a time-translation vector and space-rotation vectors as the Killing vector, and explicitly construct general solutions of stationary rotating closed strings in five-dimensional flat spacetime. We show a variety of their configurations and properties.

  15. A Stationary North-Finding Scheme for an Azimuth Rotational IMU Utilizing a Linear State Equality Constraint

    Directory of Open Access Journals (Sweden)

    Huapeng Yu

    2015-02-01

    Full Text Available The Kalman filter (KF has always been used to improve north-finding performance under practical conditions. By analyzing the characteristics of the azimuth rotational inertial measurement unit (ARIMU on a stationary base, a linear state equality constraint for the conventional KF used in the fine north-finding filtering phase is derived. Then, a constrained KF using the state equality constraint is proposed and studied in depth. Estimation behaviors of the concerned navigation errors when implementing the conventional KF scheme and the constrained KF scheme during stationary north-finding are investigated analytically by the stochastic observability approach, which can provide explicit formulations of the navigation errors with influencing variables. Finally, multiple practical experimental tests at a fixed position are done on a postulate system to compare the stationary north-finding performance of the two filtering schemes. In conclusion, this study has successfully extended the utilization of the stochastic observability approach for analytic descriptions of estimation behaviors of the concerned navigation errors, and the constrained KF scheme has demonstrated its superiority over the conventional KF scheme for ARIMU stationary north-finding both theoretically and practically.

  16. Solutions without phase-slip for the Ginsburg-Landau equation

    International Nuclear Information System (INIS)

    Collet, P.; Eckmann, J.P.

    1992-01-01

    We consider the Ginsburg-Landau equation for a complex scalar field in one dimension and consider initial data which have two different stationary solutions as their limits in space as x→±∞. If these solutions are not very different, then we show that the initial data will evolve to a stationary solution by a 'phase melting' process which avoids 'phase slips,' i.e., which does not go through zero amplitude. (orig.)

  17. No improvement of neuronal metabolism in the reperfusion phase with melatonin treatment after hypoxic-ischemic brain injury in the neonatal rat.

    Science.gov (United States)

    Berger, Hester R; Morken, Tora Sund; Vettukattil, Riyas; Brubakk, Ann-Mari; Sonnewald, Ursula; Widerøe, Marius

    2016-01-01

    Mitochondrial impairment is a key feature underlying neonatal hypoxic-ischemic (HI) brain injury and melatonin is potentially neuroprotective through its effects on mitochondria. In this study, we have used (1) H and (13) C NMR spectroscopy after injection of [1-(13) C]glucose and [1,2-(13) C]acetate to examine neuronal and astrocytic metabolism in the early reperfusion phase after unilateral HI brain injury in 7-day-old rat pups, exploring the effects of HI on mitochondrial function and the potential protective effects of melatonin on brain metabolism. One hour after hypoxia-ischemia, astrocytic metabolism was recovered and glycolysis was normalized, whereas mitochondrial metabolism in neurons was clearly impaired. Pyruvate carboxylation was also lower in both hemispheres after HI. The transfer of glutamate from neurons to astrocytes was higher whereas the transfer of glutamine from astrocytes to neurons was lower 1 h after HI in the contralateral hemisphere. Neuronal metabolism was equally affected in pups treated with melatonin (10 mg/kg) immediately after HI as in vehicle treated pups indicating that the given dose of melatonin was not capable of protecting the neuronal mitochondria in this early phase after HI brain injury. However, any beneficial effects of melatonin might have been masked by modulatory effects of the solvent dimethyl sulfoxide on cerebral metabolism. Neuronal and astrocytic metabolism was examined by (13) C and (1) H NMR spectroscopy in the early reperfusion phase after unilateral hypoxic-ischemic brain injury and melatonin treatment in neonatal rats. One hour after hypoxia-ischemia astrocytic mitochondrial metabolism had recovered and glycolysis was normalized, whereas mitochondrial metabolism in neurons was impaired. Melatonin treatment did not show a protective effect on neuronal metabolism. © 2015 International Society for Neurochemistry.

  18. Behavior of neutral solutes in pressurized flow driven electrochromatography using a mixed stationary phase of ODS and anion-exchange.

    Science.gov (United States)

    Kitagawa, Shinya; Tsuda, Takao

    2003-05-02

    The behavior of neutral sample solutes in pressurized flow driven electrochromatography using a mixed stationary phase, which consisted of ODS and anion-exchange (ODS-SAX), was studied. Applications of both positive and negative voltage on a column induced increases in retention factors of sample solutes. The direction of an electroosmotic flow under applications of positive and negative voltage were the same, therefore, the sign of the surface charge density under positive and negative voltage was opposite. We proposed a new equation for the relationship between applied voltage and surface charge density, and the practical electroosmotic flow conformed to this equation. Studying the electroosmotic flow using our proposed equation revealed that the applied negative voltage accelerates the protonation of the quaternary ammonium group and dissociation of the silanol group on packing materials. The retention behavior of a neutral solute was affected by the existence of the charged functional groups. We propose that this phenomenon is applicable to the control of the retention behavior of a sample solute using an electric field.

  19. The Fourier decomposition method for nonlinear and non-stationary time series analysis.

    Science.gov (United States)

    Singh, Pushpendra; Joshi, Shiv Dutt; Patney, Rakesh Kumar; Saha, Kaushik

    2017-03-01

    for many decades, there has been a general perception in the literature that Fourier methods are not suitable for the analysis of nonlinear and non-stationary data. In this paper, we propose a novel and adaptive Fourier decomposition method (FDM), based on the Fourier theory, and demonstrate its efficacy for the analysis of nonlinear and non-stationary time series. The proposed FDM decomposes any data into a small number of 'Fourier intrinsic band functions' (FIBFs). The FDM presents a generalized Fourier expansion with variable amplitudes and variable frequencies of a time series by the Fourier method itself. We propose an idea of zero-phase filter bank-based multivariate FDM (MFDM), for the analysis of multivariate nonlinear and non-stationary time series, using the FDM. We also present an algorithm to obtain cut-off frequencies for MFDM. The proposed MFDM generates a finite number of band-limited multivariate FIBFs (MFIBFs). The MFDM preserves some intrinsic physical properties of the multivariate data, such as scale alignment, trend and instantaneous frequency. The proposed methods provide a time-frequency-energy (TFE) distribution that reveals the intrinsic structure of a data. Numerical computations and simulations have been carried out and comparison is made with the empirical mode decomposition algorithms.

  20. Cationic amino acid uptake constitutes a metabolic regulation mechanism and occurs in the flagellar pocket of Trypanosoma cruzi.

    Directory of Open Access Journals (Sweden)

    Mariana R Miranda

    Full Text Available Trypanosomatids' amino acid permeases are key proteins in parasite metabolism since they participate in the adaptation of parasites to different environments. Here, we report that TcAAP3, a member of a Trypanosoma cruzi multigene family of permeases, is a bona fide arginine transporter. Most higher eukaryotic cells incorporate cationic amino acids through a single transporter. In contrast, T. cruzi can recognize and transport cationic amino acids by mono-specific permeases since a 100-fold molar excess of lysine could not affect the arginine transport in parasites that over-express the arginine permease (TcAAP3 epimastigotes. In order to test if the permease activity regulates downstream processes of the arginine metabolism, the expression of the single T. cruzi enzyme that uses arginine as substrate, arginine kinase, was evaluated in TcAAP3 epimastigotes. In this parasite model, intracellular arginine concentration increases 4-folds and ATP level remains constant until cultures reach the stationary phase of growth, with decreases of about 6-folds in respect to the controls. Interestingly, Western Blot analysis demonstrated that arginine kinase is significantly down-regulated during the stationary phase of growth in TcAAP3 epimastigotes. This decrease could represent a compensatory mechanism for the increase in ATP consumption as a consequence of the displacement of the reaction equilibrium of arginine kinase, when the intracellular arginine concentration augments and the glucose from the medium is exhausted. Using immunofluorescence techniques we also determined that TcAAP3 and the specific lysine transporter TcAAP7 co-localize in a specialized region of the plasma membrane named flagellar pocket, staining a single locus close to the flagellar pocket collar. Taken together these data suggest that arginine transport is closely related to arginine metabolism and cell energy balance. The clinical relevance of studying trypanosomatids' permeases

  1. Estimation of reproduction number and non stationary spectral analysis of dengue epidemic.

    Science.gov (United States)

    Enduri, Murali Krishna; Jolad, Shivakumar

    2017-06-01

    In this work we analyze the post monsoon Dengue outbreaks by analyzing the transient and long term dynamics of Dengue incidences and its environmental correlates in Ahmedabad city in western India from 2005 to 2012. We calculate the reproduction number R p using the growth rate of post monsoon Dengue outbreaks and biological parameters like host and vector incubation periods and vector mortality rate, and its uncertainties are estimated through Monte-Carlo simulations by sampling parameters from their respective probability distributions. Reduction in Female Aedes mosquito density required for an effective prevention of Dengue outbreaks is also calculated. The non stationary pattern of Dengue incidences and its climatic correlates like rainfall temperature is analyzed through Wavelet based methods. We find that the mean time lag between peak of monsoon and Dengue is 9 weeks. Monsoon and Dengue cases are phase locked from 2008 to 2012 in the 16 to maintain consistency make it "16 to 32" 32 weeks band. The duration of post monsoon outbreak has been increasing every year, especially post 2008, even though the intensity and duration of monsoon has been decreasing. Temperature and Dengue incidences show correlations in the same band, but phase lock is not stationary. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Stationary shear flows in CGL anisotropic toroidal plasmas

    International Nuclear Information System (INIS)

    Pastukhov, V.P.; Ilgisonis, V.I.

    1996-01-01

    Recently a general structure of stationary shear flows in toroidal plasmas was obtained in the frame of ideal isotropic-pressure MHD model. The structure of the stationary plasma flows was shown to be determined by a hidden symmetry of MHD equations inherent in the toroidal systems with nested magnetic surfaces. However, the characteristic frequencies of the stationary plasma motion can considerably exceed the collisional frequencies in real plasma experiments. In this case the CGL collisionless MHD model seems to be more adequate than the simplified isotropic-pressure MHD model to describe the stationary plasma flows. In this paper we have generalized our approach to analyze the stationary plasma flows in the frame of the collisionless CGL model. We have found again that the hidden symmetry inherent in the toroidal topology results in two integral invariants which depend on two independent surface functions. The structure of stationary flows for CGL model is still the same as for isotropic MHD, however, the pressure tensor components satisfy a appreciably modifies the steady state force-balance equation. These results are applied to analyze the generalized equilibrium in axisymmetric (tokamak-like) magnetic confinement systems

  3. 30 CFR 75.1723 - Stationary grinding machines; protective devices.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Stationary grinding machines; protective....1723 Stationary grinding machines; protective devices. (a) Stationary grinding machines other than... the wheel. (3) Safety washers. (b) Grinding wheels shall be operated within the specifications of the...

  4. Two-Scale 13C Metabolic Flux Analysis for Metabolic Engineering.

    Science.gov (United States)

    Ando, David; Garcia Martin, Hector

    2018-01-01

    Accelerating the Design-Build-Test-Learn (DBTL) cycle in synthetic biology is critical to achieving rapid and facile bioengineering of organisms for the production of, e.g., biofuels and other chemicals. The Learn phase involves using data obtained from the Test phase to inform the next Design phase. As part of the Learn phase, mathematical models of metabolic fluxes give a mechanistic level of comprehension to cellular metabolism, isolating the principle drivers of metabolic behavior from the peripheral ones, and directing future experimental designs and engineering methodologies. Furthermore, the measurement of intracellular metabolic fluxes is specifically noteworthy as providing a rapid and easy-to-understand picture of how carbon and energy flow throughout the cell. Here, we present a detailed guide to performing metabolic flux analysis in the Learn phase of the DBTL cycle, where we show how one can take the isotope labeling data from a 13 C labeling experiment and immediately turn it into a determination of cellular fluxes that points in the direction of genetic engineering strategies that will advance the metabolic engineering process.For our modeling purposes we use the Joint BioEnergy Institute (JBEI) Quantitative Metabolic Modeling (jQMM) library, which provides an open-source, python-based framework for modeling internal metabolic fluxes and making actionable predictions on how to modify cellular metabolism for specific bioengineering goals. It presents a complete toolbox for performing different types of flux analysis such as Flux Balance Analysis, 13 C Metabolic Flux Analysis, and it introduces the capability to use 13 C labeling experimental data to constrain comprehensive genome-scale models through a technique called two-scale 13 C Metabolic Flux Analysis (2S- 13 C MFA) [1]. In addition to several other capabilities, the jQMM is also able to predict the effects of knockouts using the MoMA and ROOM methodologies. The use of the jQMM library is

  5. The application of unattended ground sensors to stationary targets

    International Nuclear Information System (INIS)

    Sleefe, G.E.; Peglow, S.; Hamrick, R.

    1997-01-01

    The unattended sensing of stationary (i.e. non-mobile) targets is important in applications ranging from counter-proliferation to law enforcement. With stationary targets, sources of seismic, acoustic, and electro-magnetic emissions can potentially be used to detect, identify, and locate the target. Stationary targets have considerably different sensing requirements than the traditional mobile-target unattended ground sensor applications. This paper presents the novel features and requirements of a system for sensing stationary targets. In particular, issues associated with long-listen time signal processing for signal detection, and array processing techniques for signal localization are presented. Example data and signal processing outputs from a stationary target will be used to illustrate these issues. The impact on sensor, electronic signal processing, battery subsystem, and communication requirements will also be discussed. The paper will conclude with a detailed comparison between mobile-target and stationary-target unattended ground sensor architectures

  6. Stability and instability of stationary solutions for sublinear parabolic equations

    Science.gov (United States)

    Kajikiya, Ryuji

    2018-01-01

    In the present paper, we study the initial boundary value problem of the sublinear parabolic equation. We prove the existence of solutions and investigate the stability and instability of stationary solutions. We show that a unique positive and a unique negative stationary solutions are exponentially stable and give the exact exponent. We prove that small stationary solutions are unstable. For one space dimensional autonomous equations, we elucidate the structure of stationary solutions and study the stability of all stationary solutions.

  7. Direct imaging of slow, stored and stationary EIT polaritons

    Science.gov (United States)

    Campbell, Geoff T.; Cho, Young-Wook; Su, Jian; Everett, Jesse; Robins, Nicholas; Lam, Ping Koy; Buchler, Ben

    2017-09-01

    Stationary and slow light effects are of great interest for quantum information applications. Using laser-cooled Rb87 atoms, we performed side imaging of our atomic ensemble under slow and stationary light conditions, which allows direct comparison with numerical models. The polaritons were generated using electromagnetically induced transparency (EIT), with stationary light generated using counter-propagating control fields. By controlling the power ratio of the two control fields, we show fine control of the group velocity of the stationary light. We also compare the dynamics of stationary light using monochromatic and bichromatic control fields. Our results show negligible difference between the two situations, in contrast to previous work in EIT-based systems.

  8. Nonlinear stationary solutions of the Wigner and Wigner-Poisson equations

    International Nuclear Information System (INIS)

    Haas, F.; Shukla, P. K.

    2008-01-01

    Exact nonlinear stationary solutions of the one-dimensional Wigner and Wigner-Poisson equations in the terms of the Wigner functions that depend not only on the energy but also on position are presented. In this way, the Bernstein-Greene-Kruskal modes of the classical plasma are adapted for the quantum formalism in the phase space. The solutions are constructed for the case of a quartic oscillator potential, as well as for the self-consistent Wigner-Poisson case. Conditions for well-behaved physically meaningful equilibrium Wigner functions are discussed.

  9. 30 CFR 77.401 - Stationary grinding machines; protective devices.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Stationary grinding machines; protective... OF UNDERGROUND COAL MINES Safeguards for Mechanical Equipment § 77.401 Stationary grinding machines; protective devices. (a) Stationary grinding machines other than special bit grinders shall be equipped with...

  10. Sleep deprivation decreases phase-shift responses of circadian rhythms to light in the mouse: role of serotonergic and metabolic signals.

    Science.gov (United States)

    Challet, E; Turek, F W; Laute, M; Van Reeth, O

    2001-08-03

    The circadian pacemaker in the suprachiasmatic nuclei is primarily synchronized to the daily light-dark cycle. The phase-shifting and synchronizing effects of light can be modulated by non-photic factors, such as behavioral, metabolic or serotonergic cues. The present experiments examine the effects of sleep deprivation on the response of the circadian pacemaker to light and test the possible involvement of serotonergic and/or metabolic cues in mediating the effects of sleep deprivation. Photic phase-shifting of the locomotor activity rhythm was analyzed in mice transferred from a light-dark cycle to constant darkness, and sleep-deprived for 8 h from Zeitgeber Time 6 to Zeitgeber Time 14. Phase-delays in response to a 10-min light pulse at Zeitgeber Time 14 were reduced by 30% in sleep-deprived mice compared to control mice, while sleep deprivation without light exposure induced no significant phase-shifts. Stimulation of serotonin neurotransmission by fluoxetine (10 mg/kg), a serotonin reuptake inhibitor that decreases light-induced phase-delays in non-deprived mice, did not further reduce light-induced phase-delays in sleep-deprived mice. Impairment of serotonin neurotransmission with p-chloroamphetamine (three injections of 10 mg/kg), which did not increase light-induced phase-delays in non-deprived mice significantly, partially normalized light-induced phase-delays in sleep-deprived mice. Injections of glucose increased light-induced phase-delays in control and sleep-deprived mice. Chemical damage of the ventromedial hypothalamus by gold-thioglucose (600 mg/kg) prevented the reduction of light-induced phase-delays in sleep-deprived mice, without altering phase-delays in control mice. Taken together, the present results indicate that sleep deprivation can reduce the light-induced phase-shifts of the mouse suprachiasmatic pacemaker, due to serotonergic and metabolic changes associated with the loss of sleep.

  11. Stationary axisymmetric Einstein--Maxwell field equations

    International Nuclear Information System (INIS)

    Catenacci, R.; Diaz Alonso, J.

    1976-01-01

    We show the existence of a formal identity between Einstein's and Ernst's stationary axisymmetric gravitational field equations and the Einstein--Maxwell and the Ernst equations for the electrostatic and magnetostatic axisymmetric cases. Our equations are invariant under very simple internal symmetry groups, and one of them appears to be new. We also obtain a method for associating two stationary axisymmetric vacuum solutions with every electrostatic known

  12. Recovery and deformation substructures of zircaloy-4 in high temperature plasticity under stationary or non-stationary stress

    International Nuclear Information System (INIS)

    Bocek, M.; Armas, I.

    1982-01-01

    It was the aim of the present investigation to examine how the recovery rate in creep is influenced by a non-stationary stress. For purposes of phenomenological analysis it is postulated that, irrespective of whether the applied stress is stationary or not, for large strains the mean internal stress sigmasub(i) approaches a stationary value sigmasub(i,s). The stationary recovery rate Rsub(s) for constant load creep turns out be governed by the applied stress indicating that the recovery mechanism is dynamic in nature. For sigma-ramp loading, Rsub(s) is dependent on the stress rate sigma. In tensional stress cycling, Rsub(s) is governed by the maximum stress sigmasub(M) and is also dependent on the ratio of sigmasub(M) to the minimum stress sigma 0 . TEM examination of Zircaloy-4 specimens crept at 800 0 C at constant and cycling load respectively could not reveal any differences in the deformation substructure for the two loading types. Subgrain formation did not appear, individual dislocations were observed only rarely. However, typical networks were formed as well as pileups which perhaps are responsible for the back stress in high temperature plasticity (HTP). (orig.)

  13. Stationary stochastic processes theory and applications

    CERN Document Server

    Lindgren, Georg

    2012-01-01

    Some Probability and Process BackgroundSample space, sample function, and observablesRandom variables and stochastic processesStationary processes and fieldsGaussian processesFour historical landmarksSample Function PropertiesQuadratic mean propertiesSample function continuityDerivatives, tangents, and other characteristicsStochastic integrationAn ergodic resultExercisesSpectral RepresentationsComplex-valued stochastic processesBochner's theorem and the spectral distributionSpectral representation of a stationary processGaussian processesStationary counting processesExercisesLinear Filters - General PropertiesLinear time invariant filtersLinear filters and differential equationsWhite noise in linear systemsLong range dependence, non-integrable spectra, and unstable systemsThe ARMA-familyLinear Filters - Special TopicsThe Hilbert transform and the envelopeThe sampling theoremKarhunen-Loève expansionClassical Ergodic Theory and MixingThe basic ergodic theorem in L2Stationarity and transformationsThe ergodic th...

  14. Considerations of stationary-phase interactions in groundwater pollution studies

    International Nuclear Information System (INIS)

    Hall, E.S.

    1980-01-01

    Studies of groundwater pollution are complicated by retention of both pollutant and tracers as static phases associated with the rock matrix. Three types of static phase are considered: (1) immobile pore water, (2) equilibrium adsorbed layers and (3) bulk precipitates, including biological systems. A brief discussion of the systems is given with examples from the work of the Water Research Centre on the problems encountered in quantifying groundwater pollution where static contamination may occur. (author)

  15. Stationary radiation of objects with scattering media

    International Nuclear Information System (INIS)

    Vasil'eva, Inna A

    2001-01-01

    The radiation observed inside or outside a stationary radiator with a scattering medium is a sum of components, each being determined by, first, the primary radiation from some part of the radiator and, second, the probability of this radiation reaching the region where it is observed. In this review, general and rather simple relations between these components are discussed. These relations, unlike the components themselves, are independent of the specific optical characteristics of the object as well as of its geometry, inhomogeneity, etc. In deriving the relations, the situations in which geometrical optics is either applicable or inapplicable to radiation in a scattering medium are considered. For the case where geometrical optics does apply, stationary relations are derived from the probabilistic stationarity condition for radiation passing through the medium, i.e., from the fact that all radiation emitted in a stationary regime disappears with probability unity. Equilibrium relations are derived from the stationary relations in the particular case of a thermal radiator in an isothermal cavity. To derive the stationary relations in the geometrical optics approximation, we obtain general solutions of the linear equation of transfer using the Green function approach. If geometrical optics cannot be applied to a scattering and radiating medium, only relations for the components of outgoing thermal radiation are obtained, and the generalized Kirchhoff law, obtained by Levin and Rytov using statistical radio-physics methods, is employed. In this case, stationary relations are also derived from a probabilistic stationarity condition; the equilibrium relations follow from the stationary ones as well as from the equilibrium condition for radiation in the isothermal cavity. The quantities involved in all the relations obtained are a subject of experimental and computational spectroscopic studies. Examples of current and potential applications are given. The relations

  16. Optimization of o-phtaldialdehyde/2-mercaptoethanol postcolumn reaction for the hydrophilic interaction liquid chromatography determination of memantine utilizing a silica hydride stationary phase.

    Science.gov (United States)

    Douša, Michal; Pivoňková, Veronika; Sýkora, David

    2016-08-01

    A rapid procedure for the determination of memantine based on hydrophilic interaction chromatography with fluorescence detection was developed. Fluorescence detection after postcolumn derivatization with o-phtaldialdehyde/2-mercaptoethanol was performed at excitation and emission wavelengths of 345 and 450 nm, respectively. The postcolumn reaction conditions such as reaction temperature, derivatization reagent flow rate, and reagents concentration were studied due to steric hindrance of amino group of memantine. The derivatization reaction was applied for the hydrophilic interaction liquid chromatography method which was based on Cogent Silica-C stationary phase with a mobile phase consisting of a mixture of 10 mmol/L citric acid and 10 mmol/L o-phosphoric acid (pH 6.0) with acetonitrile using an isocratic composition of 2:8 v/v. The benefit of the reported approach consists in a simple sample pretreatment and a quick and sensitive hydrophilic interaction chromatography method. The developed method was validated in terms of linearity, accuracy, precision, and selectivity according to the International Conference on Harmonisation guidelines. The developed method was successfully applied for the analysis of commercial memantine tablets. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Conformational variability of the stationary phase survival protein E from Xylella fastidiosa revealed by X-ray crystallography, small-angle X-ray scattering studies, and normal mode analysis.

    Science.gov (United States)

    Machado, Agnes Thiane Pereira; Fonseca, Emanuella Maria Barreto; Reis, Marcelo Augusto Dos; Saraiva, Antonio Marcos; Santos, Clelton Aparecido Dos; de Toledo, Marcelo Augusto Szymanski; Polikarpov, Igor; de Souza, Anete Pereira; Aparicio, Ricardo; Iulek, Jorge

    2017-10-01

    Xylella fastidiosa is a xylem-limited bacterium that infects a wide variety of plants. Stationary phase survival protein E is classified as a nucleotidase, which is expressed when bacterial cells are in the stationary growth phase and subjected to environmental stresses. Here, we report four refined X-ray structures of this protein from X. fastidiosa in four different crystal forms in the presence and/or absence of the substrate 3'-AMP. In all chains, the conserved loop verified in family members assumes a closed conformation in either condition. Therefore, the enzymatic mechanism for the target protein might be different of its homologs. Two crystal forms exhibit two monomers whereas the other two show four monomers in the asymmetric unit. While the biological unit has been characterized as a tetramer, differences of their sizes and symmetry are remarkable. Four conformers identified by Small-Angle X-ray Scattering (SAXS) in a ligand-free solution are related to the low frequency normal modes of the crystallographic structures associated with rigid body-like protomer arrangements responsible for the longitudinal and symmetric adjustments between tetramers. When the substrate is present in solution, only two conformers are selected. The most prominent conformer for each case is associated to a normal mode able to elongate the protein by moving apart two dimers. To our knowledge, this work was the first investigation based on the normal modes that analyzed the quaternary structure variability for an enzyme of the SurE family followed by crystallography and SAXS validation. The combined results raise new directions to study allosteric features of XfSurE protein. © 2017 Wiley Periodicals, Inc.

  18. Detection of hidden stationary deformations of vibrating surfaces by use of time-averaged digital holographic interferometry.

    Science.gov (United States)

    Demoli, Nazif; Vukicevic, Dalibor

    2004-10-15

    A method of detecting displacements of a surface from its steady-state position to its equilibrium position while it is vibrating has been developed by use of time-average digital holographic interferometry. This method permits extraction of such a hidden deformation by creating two separated systems of interferogram fringes: one corresponding to a time-varying resonantly oscillating optical phase, the other to the stationary phase modification. A mathematical description of the method and illustrative results of experimental verification are presented.

  19. 4. Workshop - Measurement techniques of stationary and transient multiphase flow

    International Nuclear Information System (INIS)

    Prasser, H.M.

    2001-05-01

    In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture ''Ultrasonic doppler method for bubbly flow measurement'' of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. (orig.)

  20. The stationary neutron radiography system

    International Nuclear Information System (INIS)

    Weeks, A.A.; Newell, D.L.; Heidel, C.C.

    1990-01-01

    To provide the high intensity neutron beam and support systems necessary for radiography, the Stationary Neutron Radiography System was constructed at McClellan Air Force Base. The Stationary Neutron Radiography System utilizes a one megawatt TRIGA reactor contained in an Aluminium tank surrounded by eight foot thick concrete walls. There are four neutron beam tubes at inclined angles from the reactor core to separate radiography bays. In three of the bays, robotic systems manipulate aircraft components in the neutron beam, while real-time imaging systems provide images concurrent with the irradiation. Film radiography of smaller components is performed in the remaining bay

  1. Enantiomeric Separation of 1-(Benzofuran-2-yl)alkylamines on Chiral Stationary Phases Based on Chiral Crown Ethers

    International Nuclear Information System (INIS)

    Park, Soohyun; Kim, Sang Jun; Hyun, Myung Ho

    2012-01-01

    Optically active chiral amines are important as building blocks for pharmaceuticals and as scaffolds for chiral ligands and, consequently, many efforts have been devoted to the development of efficient methods for their preparation. For example, reduction of amine precursors with chiral catalysts, enzymatic kinetic resolution or dynamic kinetic resolution of racemic amines and the direct amination of ketones with transaminases have been developed as the efficient methods for the preparation of optically active chiral amines. During the process of developing or utilizing optically active chiral amines, the methods for the determination of their enantiomeric composition are essential. Among various methods, liquid chromatographic resolution of enantiomers on chiral stationary phases (CSPs) have been known to be one of the most accurate and economic means for the determination of the enantiomeric composition of optically active chiral compounds. Especially, CSPs based on chiral crown ethers have been successfully used for the resolution of racemic primary amines. For example, CSPs based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (CSP 1, Figure 1) or (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 (CSP 2 and CSP 3, Figure 1) have been known to be quite effective for the resolution of cyclic and non-cyclic amines, various fluoroquinolone antibacterials containing a primary amino group, tocainide (antiarrhythmic agent) and its analogues, aryl-a-amino ketones and 3-amino-1,4-benzodiazepin-2-ones

  2. Heterodyne laser Doppler distance sensor with phase coding measuring stationary as well as laterally and axially moving objects

    International Nuclear Information System (INIS)

    Pfister, T; Günther, P; Nöthen, M; Czarske, J

    2010-01-01

    Both in production engineering and process control, multidirectional displacements, deformations and vibrations of moving or rotating components have to be measured dynamically, contactlessly and with high precision. Optical sensors would be predestined for this task, but their measurement rate is often fundamentally limited. Furthermore, almost all conventional sensors measure only one measurand, i.e. either out-of-plane or in-plane distance or velocity. To solve this problem, we present a novel phase coded heterodyne laser Doppler distance sensor (PH-LDDS), which is able to determine out-of-plane (axial) position and in-plane (lateral) velocity of rough solid-state objects simultaneously and independently with a single sensor. Due to the applied heterodyne technique, stationary or purely axially moving objects can also be measured. In addition, it is shown theoretically as well as experimentally that this sensor offers concurrently high temporal resolution and high position resolution since its position uncertainty is in principle independent of the lateral object velocity in contrast to conventional distance sensors. This is a unique feature of the PH-LDDS enabling precise and dynamic position and shape measurements also of fast moving objects. With an optimized sensor setup, an average position resolution of 240 nm was obtained

  3. Breathing multichimera states in nonlocally coupled phase oscillators

    Science.gov (United States)

    Suda, Yusuke; Okuda, Koji

    2018-04-01

    Chimera states for the one-dimensional array of nonlocally coupled phase oscillators in the continuum limit are assumed to be stationary states in most studies, but a few studies report the existence of breathing chimera states. We focus on multichimera states with two coherent and incoherent regions and numerically demonstrate that breathing multichimera states, whose global order parameter oscillates temporally, can appear. Moreover, we show that the system exhibits a Hopf bifurcation from a stationary multichimera to a breathing one by the linear stability analysis for the stationary multichimera.

  4. Non-stationary covariance function modelling in 2D least-squares collocation

    Science.gov (United States)

    Darbeheshti, N.; Featherstone, W. E.

    2009-06-01

    Standard least-squares collocation (LSC) assumes 2D stationarity and 3D isotropy, and relies on a covariance function to account for spatial dependence in the observed data. However, the assumption that the spatial dependence is constant throughout the region of interest may sometimes be violated. Assuming a stationary covariance structure can result in over-smoothing of, e.g., the gravity field in mountains and under-smoothing in great plains. We introduce the kernel convolution method from spatial statistics for non-stationary covariance structures, and demonstrate its advantage for dealing with non-stationarity in geodetic data. We then compared stationary and non- stationary covariance functions in 2D LSC to the empirical example of gravity anomaly interpolation near the Darling Fault, Western Australia, where the field is anisotropic and non-stationary. The results with non-stationary covariance functions are better than standard LSC in terms of formal errors and cross-validation against data not used in the interpolation, demonstrating that the use of non-stationary covariance functions can improve upon standard (stationary) LSC.

  5. Numerical Control Machine Tool Fault Diagnosis Using Hybrid Stationary Subspace Analysis and Least Squares Support Vector Machine with a Single Sensor

    Directory of Open Access Journals (Sweden)

    Chen Gao

    2017-03-01

    Full Text Available Tool fault diagnosis in numerical control (NC machines plays a significant role in ensuring manufacturing quality. However, current methods of tool fault diagnosis lack accuracy. Therefore, in the present paper, a fault diagnosis method was proposed based on stationary subspace analysis (SSA and least squares support vector machine (LS-SVM using only a single sensor. First, SSA was used to extract stationary and non-stationary sources from multi-dimensional signals without the need for independency and without prior information of the source signals, after the dimensionality of the vibration signal observed by a single sensor was expanded by phase space reconstruction technique. Subsequently, 10 dimensionless parameters in the time-frequency domain for non-stationary sources were calculated to generate samples to train the LS-SVM. Finally, the measured vibration signals from tools of an unknown state and their non-stationary sources were separated by SSA to serve as test samples for the trained SVM. The experimental validation demonstrated that the proposed method has better diagnosis accuracy than three previous methods based on LS-SVM alone, Principal component analysis and LS-SVM or on SSA and Linear discriminant analysis.

  6. Changes in Microbial Energy Metabolism Measured by Nanocalorimetry during Growth Phase Transitions

    Science.gov (United States)

    Robador, Alberto; LaRowe, Douglas E.; Finkel, Steven E.; Amend, Jan P.; Nealson, Kenneth H.

    2018-01-01

    Calorimetric measurements of the change in heat due to microbial metabolic activity convey information about the kinetics, as well as the thermodynamics, of all chemical reactions taking place in a cell. Calorimetric measurements of heat production made on bacterial cultures have recorded the energy yields of all co-occurring microbial metabolic reactions, but this is a complex, composite signal that is difficult to interpret. Here we show that nanocalorimetry can be used in combination with enumeration of viable cell counts, oxygen consumption rates, cellular protein content, and thermodynamic calculations to assess catabolic rates of an isolate of Shewanella oneidensis MR-1 and infer what fraction of the chemical energy is assimilated by the culture into biomass and what fraction is dissipated in the form of heat under different limiting conditions. In particular, our results demonstrate that catabolic rates are not necessarily coupled to rates of cell division, but rather, to physiological rearrangements of S. oneidensis MR-1 upon growth phase transitions. In addition, we conclude that the heat released by growing microorganisms can be measured in order to understand the physiochemical nature of the energy transformation and dissipation associated with microbial metabolic activity in conditions approaching those found in natural systems. PMID:29449836

  7. Network analysis of the transcriptional pattern of young and old cells of Escherichia coli during lag phase

    Directory of Open Access Journals (Sweden)

    Hinton Jay CD

    2009-11-01

    Full Text Available Abstract Background The aging process of bacteria in stationary phase is halted if cells are subcultured and enter lag phase and it is then followed by cellular division. Network science has been applied to analyse the transcriptional response, during lag phase, of bacterial cells starved previously in stationary phase for 1 day (young cells and 16 days (old cells. Results A genome scale network was constructed for E. coli K-12 by connecting genes with operons, transcription and sigma factors, metabolic pathways and cell functional categories. Most of the transcriptional changes were detected immediately upon entering lag phase and were maintained throughout this period. The lag period was longer for older cells and the analysis of the transcriptome revealed different intracellular activity in young and old cells. The number of genes differentially expressed was smaller in old cells (186 than in young cells (467. Relatively, few genes (62 were up- or down-regulated in both cultures. Transcription of genes related to osmotolerance, acid resistance, oxidative stress and adaptation to other stresses was down-regulated in both young and old cells. Regarding carbohydrate metabolism, genes related to the citrate cycle were up-regulated in young cells while old cells up-regulated the Entner Doudoroff and gluconate pathways and down-regulated the pentose phosphate pathway. In both old and young cells, anaerobic respiration and fermentation pathways were down-regulated, but only young cells up-regulated aerobic respiration while there was no evidence of aerobic respiration in old cells. Numerous genes related to DNA maintenance and replication, translation, ribosomal biosynthesis and RNA processing as well as biosynthesis of the cell envelope and flagellum and several components of the chemotaxis signal transduction complex were up-regulated only in young cells. The genes for several transport proteins for iron compounds were up-regulated in both young

  8. Network analysis of the transcriptional pattern of young and old cells of Escherichia coli during lag phase

    LENUS (Irish Health Repository)

    Pin, Carmen

    2009-11-16

    Abstract Background The aging process of bacteria in stationary phase is halted if cells are subcultured and enter lag phase and it is then followed by cellular division. Network science has been applied to analyse the transcriptional response, during lag phase, of bacterial cells starved previously in stationary phase for 1 day (young cells) and 16 days (old cells). Results A genome scale network was constructed for E. coli K-12 by connecting genes with operons, transcription and sigma factors, metabolic pathways and cell functional categories. Most of the transcriptional changes were detected immediately upon entering lag phase and were maintained throughout this period. The lag period was longer for older cells and the analysis of the transcriptome revealed different intracellular activity in young and old cells. The number of genes differentially expressed was smaller in old cells (186) than in young cells (467). Relatively, few genes (62) were up- or down-regulated in both cultures. Transcription of genes related to osmotolerance, acid resistance, oxidative stress and adaptation to other stresses was down-regulated in both young and old cells. Regarding carbohydrate metabolism, genes related to the citrate cycle were up-regulated in young cells while old cells up-regulated the Entner Doudoroff and gluconate pathways and down-regulated the pentose phosphate pathway. In both old and young cells, anaerobic respiration and fermentation pathways were down-regulated, but only young cells up-regulated aerobic respiration while there was no evidence of aerobic respiration in old cells. Numerous genes related to DNA maintenance and replication, translation, ribosomal biosynthesis and RNA processing as well as biosynthesis of the cell envelope and flagellum and several components of the chemotaxis signal transduction complex were up-regulated only in young cells. The genes for several transport proteins for iron compounds were up-regulated in both young and old cells

  9. Enantiomeric separation of iridium (III) complexes using HPLC chiral stationary phases based on amylose derivatives

    International Nuclear Information System (INIS)

    Kim, Hee Eun; Seo, Na Hyeon; Hyun, Myung Ho

    2016-01-01

    Cyclometalated iridium (III) complexes formed with three identical cyclometalating (C-N) ligands (homoleptic) or formed with two cyclometalating (C-N) ligands and one ancillary (LX) ligand (heteroleptic) have been known as highly phosphorescent materials and, thus, they have been utilized as efficient phosphorescent dopants in organic light emitting diodes (OLEDs) 1–3 or as effective phosphorescent chemosensors. 4–7 Cylometalated iridium (III) complexes are chiral compounds consisting of lambda (Λ, left-handed) and delta (Δ, right-handed) isomers. Racemic cyclometa- lated iridium (III) complexes emit light with no net polarization, but optically active cyclometalated iridium (III) complexes emit circularly polarized light. 8,9 Circularly polarized light can be used in various fields including highly efficient three dimensional electronic devices, photo nic devices for optical data storage, biological assays, and others. 8,9 In order to obtain optically active cylometalated iridium (III) complexes and to determine the enantiomeric composition of optically active cylometalated iridium (III) complexes, liquid chromatogr aphic enantiomer separation method on chiral stationary phases (CSPs) has been used. For example, Okamoto and coworkers first reported the high performance liquid chromatographic (HPLC) direct enantiomeric separation of two homoleptic cylometalated iridium (III) complexes on immobilized amylose tris(3,5- dimethylphenylcarbamate) (Chiralpak IA), coated cellulose tris(3,5-dimethylphenylcarbamate) (Chiralc el OD), and coated cellulose tris(4-methylbenzoate) (Chiralce l OJ). 10 Supercritical fluid chromatography (SFC) was also used by Bernhard and coworkers for the enantiomeric separation of cylometalated iridium (III) complexes on coated amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H). 8 However, the general use of the HPLC method for the direct enantiomeric separation of homoleptic

  10. Enantiomeric separation of iridium (III) complexes using HPLC chiral stationary phases based on amylose derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hee Eun; Seo, Na Hyeon; Hyun, Myung Ho [Dept. of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan (Korea, Republic of)

    2016-12-15

    Cyclometalated iridium (III) complexes formed with three identical cyclometalating (C-N) ligands (homoleptic) or formed with two cyclometalating (C-N) ligands and one ancillary (LX) ligand (heteroleptic) have been known as highly phosphorescent materials and, thus, they have been utilized as efficient phosphorescent dopants in organic light emitting diodes (OLEDs) 1–3 or as effective phosphorescent chemosensors. 4–7 Cylometalated iridium (III) complexes are chiral compounds consisting of lambda (Λ, left-handed) and delta (Δ, right-handed) isomers. Racemic cyclometa- lated iridium (III) complexes emit light with no net polarization, but optically active cyclometalated iridium (III) complexes emit circularly polarized light. 8,9 Circularly polarized light can be used in various fields including highly efficient three dimensional electronic devices, photo nic devices for optical data storage, biological assays, and others. 8,9 In order to obtain optically active cylometalated iridium (III) complexes and to determine the enantiomeric composition of optically active cylometalated iridium (III) complexes, liquid chromatogr aphic enantiomer separation method on chiral stationary phases (CSPs) has been used. For example, Okamoto and coworkers first reported the high performance liquid chromatographic (HPLC) direct enantiomeric separation of two homoleptic cylometalated iridium (III) complexes on immobilized amylose tris(3,5- dimethylphenylcarbamate) (Chiralpak IA), coated cellulose tris(3,5-dimethylphenylcarbamate) (Chiralc el OD), and coated cellulose tris(4-methylbenzoate) (Chiralce l OJ). 10 Supercritical fluid chromatography (SFC) was also used by Bernhard and coworkers for the enantiomeric separation of cylometalated iridium (III) complexes on coated amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD-H). 8 However, the general use of the HPLC method for the direct enantiomeric separation of homoleptic.

  11. Investigation of the stationary state of parametric spin waves in antiferromagnetics by the modulation technique

    International Nuclear Information System (INIS)

    Andrienko, A.V.; Safonov, V.L.; Yakubovskij, A.Yu.

    1987-01-01

    The response of parametric electron and nuclear spin waves to weak modulation of a stationary magnetic field is investigated in the antiferromagnetics MnCO 3 and CsMnF 3 . The modulation response is calculated by taking into accout the phase mechanism of restriction of the parametric wave amplitude and positive nonlinear attenuation of the waves. Some characteristics of the stationary state of parametric electron and nuclear magnons are determined within the framework of the model by analysis of the experimental results: the nonlinear magnon interaction coefficient S k and the parameter κ which characterizes the relative contribution from positive nonlinear attenuation and the phase mechanism to the restriction of the number of parametric magnons. An anomaly in the behavior of the modulation response of the parametric nuclear magnons is observed in CsMnF 3 ; this is manifest in asubstantial decrease of the modulation response in a narrow supercriticality and modulation frequency range. A giant hexagonal anisotropy of the modulation response and nonlinear dynamic susceptibility of the nuclear magnons is observed in the same crystal. This may indicate a nonisotropic distribution of the magnons in k-space

  12. Imaginary geometric phases of quantum trajectories in high-order terahertz sideband generation

    Science.gov (United States)

    Yang, Fan; Liu, Ren-Bao

    2014-03-01

    Quantum evolution of particles under strong fields can be described by a small number of quantum trajectories that satisfy the stationary phase condition in the Dirac-Feynmann path integral. The quantum trajectories are the key concept to understand the high-order terahertz siedeband generation (HSG) in semiconductors. Due to the nontrivial ``vacuum'' states of band materials, the quantum trajectories of optically excited electron-hole pairs in semiconductors can accumulate geometric phases under the driving of an elliptically polarized THz field. We find that the geometric phase of the stationary trajectory is generally complex with both real and imaginary parts. In monolayer MoS2, the imaginary parts of the geometric phase leads to a changing of the polarization ellipticity of the sideband. We further show that the imaginary part originates from the quantum interference of many trajectories with different phases. Thus the observation of the polarization ellipticity of the sideband shall be a good indication of the quantum nature of the stationary trajectory. This work is supported by Hong Kong RGC/GRF 401512 and the CUHK Focused Investments Scheme.

  13. The staphylococcal accessory regulator, SarA, is an RNA-binding protein that modulates the mRNA turnover properties of late-exponential and stationary phase Staphylococcus aureus cells

    Directory of Open Access Journals (Sweden)

    John M Morrison

    2012-03-01

    Full Text Available The modulation of mRNA turnover is gaining recognition as a mechanism by which Staphylococcus aureus regulates gene expression, but the factors that orchestrate alterations in transcript degradation are poorly understood. In that regard, we previously found that 138 mRNA species, including the virulence factors protein A (spa and collagen binding protein (cna, are stabilized in a sarA-dependent manner during exponential phase growth, suggesting that SarA protein may directly or indirectly effect the RNA turnover properties of these transcripts. Herein, we expanded our characterization of the effects of sarA on mRNA turnover during late exponential and stationary phases of growth. Results revealed that the locus affects the RNA degradation properties of cells during both growth phases. Further, using gel mobility shift assays and RIP-ChIP, it was found that SarA protein is capable of binding mRNA species that it stabilizes both in vitro and within bacterial cells. Taken together, these results suggest that SarA post-transcriptionally regulates S. aureus gene expression in a manner that involves binding to and consequently altering the mRNA turnover properties of target transcripts.

  14. Non-stationary condition monitoring through event alignment

    DEFF Research Database (Denmark)

    Pontoppidan, Niels Henrik; Larsen, Jan

    2004-01-01

    We present an event alignment framework which enables change detection in non-stationary signals. change detection. Classical condition monitoring frameworks have been restrained to laboratory settings with stationary operating conditions, which are not resembling real world operation....... In this paper we apply the technique for non-stationary condition monitoring of large diesel engines based on acoustical emission sensor signals. The performance of the event alignment is analyzed in an unsupervised probabilistic detection framework based on outlier detection with either Principal Component...... Analysis or Gaussian Processes modeling. We are especially interested in the true performance of the condition monitoring performance with mixed aligned and unaligned data, e.g. detection of fault condition of unaligned examples versus false alarms of aligned normal condition data. Further, we expect...

  15. In Vivo Exposure of Kaempferol Is Driven by Phase II Metabolic Enzymes and Efflux Transporters.

    Science.gov (United States)

    Zheng, Liang; Zhu, Lijun; Zhao, Min; Shi, Jian; Li, Yuhuan; Yu, Jia; Jiang, Huangyu; Wu, Jinjun; Tong, Yunli; Liu, Yuting; Hu, Ming; Lu, Linlin; Liu, Zhongqiu

    2016-09-01

    Kaempferol is a well-known flavonoid; however, it lacks extensive pharmacokinetic studies. Phase II metabolic enzymes and efflux transporters play an important role in the disposition of flavonoids. This study aimed to investigate the mechanism by which phase II metabolic enzymes and efflux transporters determine the in vivo exposure of kaempferol. Pharmacokinetic analysis in Sprague-Dawley rats revealed that kaempferol was mostly biotransformed to conjugates, namely, kaempferol-3-glucuronide (K-3-G), kaempferol-7-glucuronide (K-7-G), and kaempferol-7-sulfate, in plasma. K-3-G represented the major metabolite. Compared with that in wild-type mice, pharmacokinetics in knockout FVB mice demonstrated that the absence of multidrug resistance protein 2 (MRP2) and breast cancer resistance protein (BCRP) significantly increased the area under the curve (AUC) of the conjugates. The lack of MRP1 resulted in a much lower AUC of the conjugates. Intestinal perfusion in rats revealed that the glucuronide conjugates were mainly excreted in the small intestine, but 7-sulfate was mainly excreted in the colon. In Caco-2 monolayers, K-7-G efflux toward the apical (AP) side was significantly higher than K-3-G efflux. In contrast, K-3-G efflux toward the basolateral (BL) side was significantly higher than K-7-G efflux. The BL-to-AP efflux was significantly reduced in the presence of the MRP2 inhibitor LTC4. The AP-to-BL efflux was significantly decreased in the presence of the BL-side MRPs inhibitor MK571. The BCRP inhibitor Ko143 decreased the glucuronide conjugate efflux. Therefore, kaempferol is mainly exposed as K-3-G in vivo, which is driven by phase II metabolic enzymes and efflux transporters (i.e., BCRP and MRPs).

  16. Evaluation of stationary and non-stationary geostatistical models for inferring hydraulic conductivity values at Aespoe

    International Nuclear Information System (INIS)

    La Pointe, P.R.

    1994-11-01

    This report describes the comparison of stationary and non-stationary geostatistical models for the purpose of inferring block-scale hydraulic conductivity values from packer tests at Aespoe. The comparison between models is made through the evaluation of cross-validation statistics for three experimental designs. The first experiment consisted of a 'Delete-1' test previously used at Finnsjoen. The second test consisted of 'Delete-10%' and the third test was a 'Delete-50%' test. Preliminary data analysis showed that the 3 m and 30 m packer test data can be treated as a sample from a single population for the purposes of geostatistical analyses. Analysis of the 3 m data does not indicate that there are any systematic statistical changes with depth, rock type, fracture zone vs non-fracture zone or other mappable factor. Directional variograms are ambiguous to interpret due to the clustered nature of the data, but do not show any obvious anisotropy that should be accounted for in geostatistical analysis. Stationary analysis suggested that there exists a sizeable spatially uncorrelated component ('Nugget Effect') in the 3 m data, on the order of 60% of the observed variance for the various models fitted. Four different nested models were automatically fit to the data. Results for all models in terms of cross-validation statistics were very similar for the first set of validation tests. Non-stationary analysis established that both the order of drift and the order of the intrinsic random functions is low. This study also suggests that conventional cross-validation studies and automatic variogram fitting are not necessarily evaluating how well a model will infer block scale hydraulic conductivity values. 20 refs, 20 figs, 14 tabs

  17. Influence of Stationary Crossflow Modulation on Secondary Instability

    Science.gov (United States)

    Choudhari, Meelan M.; Li, Fei; Paredes, Pedro

    2016-01-01

    A likely scenario for swept wing transition on subsonic aircraft with natural laminar flow involves the breakdown of stationary crossflow vortices via high frequency secondary instability. A majority of the prior research on this secondary instability has focused on crossflow vortices with a single dominant spanwise wavelength. This paper investigates the effects of the spanwise modulation of stationary crossflow vortices at a specified wavelength by a subharmonic stationary mode. Secondary instability of the modulated crossflow pattern is studied using planar, partial-differential-equation based eigenvalue analysis. Computations reveal that weak modulation by the first subharmonic of the input stationary mode leads to mode splitting that is particularly obvious for Y-type secondary modes that are driven by the wall-normal shear of the basic state. Thus, for each Y mode corresponding to the fundamental wavelength of results in unmodulated train of crossflow vortices, the modulated flow supports a pair of secondary modes with somewhat different amplification rates. The mode splitting phenomenon suggests that a more complex stationary modulation such as that induced by natural surface roughness would yield a considerably richer spectrum of secondary instability modes. Even modest levels of subharmonic modulation are shown to have a strong effect on the overall amplification of secondary disturbances, particularly the Z-modes driven by the spanwise shear of the basic state. Preliminary computations related to the nonlinear breakdown of these secondary disturbances provide interesting insights into the process of crossflow transition in the presence of the first subharmonic of the dominant stationary vortex.

  18. Response surface methodology for the determination of the design space of enantiomeric separations on cinchona-based zwitterionic chiral stationary phases by high performance liquid chromatography.

    Science.gov (United States)

    Hanafi, Rasha Sayed; Lämmerhofer, Michael

    2018-01-26

    Quality-by-Design approach for enantioselective HPLC method development surpasses Quality-by-Testing in offering the optimal separation conditions with the least number of experiments and in its ability to describe the method's Design Space visually which helps to determine enantiorecognition to a significant extent. Although some schemes exist for enantiomeric separations on Cinchona-based zwitterionic stationary phases, the exact design space and the weights by which each of the chromatographic parameters influences the separation have not yet been statistically studied. In the current work, a screening design followed by a Response Surface Methodology optimization design were adopted for enantioseparation optimization of 3 model drugs namely the acidic Fmoc leucine, the amphoteric tryptophan and the basic salbutamol. The screening design proved that the acid/base additives are of utmost importance for the 3 chiral drugs, and that among 3 different pairs of acids and bases, acetic acid and diethylamine is the couple able to provide acceptable resolution at variable conditions. Visualization of the response surface of the retention factor, separation factor and resolution helped describe accurately the magnitude by which each chromatographic factor (% MeOH, concentration and ratio of acid base modifiers) affects the separation while interacting with other parameters. The global optima compromising highest enantioresolution with the least run time for the 3 chiral model drugs varied extremely, where it was best to set low % methanol with equal ratio of acid-base modifiers for the acidic drug, very high % methanol and 10-fold higher concentration of the acid for the amphoteric drug while 20 folds of the base modifier with moderate %methanol were needed for the basic drug. Considering the selected drugs as models for many series of structurally related compounds, the design space defined and the optimum conditions computed are the key for method development on

  19. 4. Workshop - Measurement techniques of stationary and transient multiphase flow

    Energy Technology Data Exchange (ETDEWEB)

    Prasser, H.M. (ed.)

    2001-05-01

    In November 2000, the 4th Workshop on Measurement Techniques for Stationary and Transient Multiphase Flows took place in Rossendorf. Three previous workshops of this series were national meetings; this time participants from different countries took part. The programme comprised 14 oral presentations, 9 of which are included in these proceedings in full length. A special highlight of the meeting was the main lecture ''Ultrasonic doppler method for bubbly flow measurement'' of Professor Masanori Aritomi, Dr. Hiroshige Kikura and Dr. Yumiko Suzuki. The workshop again dealt with high-resolution phase distribution and phase velocity measurement techniques based on electrical conductivity, ultrasound, laser light and high-speed cinematography. A number of presentations were dedicated to the application of wire-mesh sensors developed by FZR for different applications used by the Technical Universities of Delft and Munich and the Tokyo Institute of Technology. (orig.)

  20. MID Max: LC–MS/MS Method for Measuring the Precursor and Product Mass Isotopomer Distributions of Metabolic Intermediates and Cofactors for Metabolic Flux Analysis Applications

    DEFF Research Database (Denmark)

    McCloskey, Douglas; Young, Jamey D.; Xu, Sibei

    2016-01-01

    The analytical challenges to acquire accurate isotopic data of intracellular metabolic intermediates for stationary, nonstationary, and dynamic metabolic flux analysis (MFA) are numerous. This work presents MID Max, a novel LC–MS/MS workflow, acquisition, and isotopomer deconvolution method for MFA...... that takes advantage of additional scan types that maximizes the number of mass isotopomer distributions (MIDs) that can be acquired in a given experiment. The analytical method was found to measure the MIDs of 97 metabolites, corresponding to 74 unique metabolite-fragment pairs (32 precursor spectra and 42...

  1. Kinesiological Analysis of Stationary Running Performed in Aquatic and Dry Land Environments

    Directory of Open Access Journals (Sweden)

    Lima Alberton Cristine

    2015-12-01

    Full Text Available The purpose of the present study was to analyze the electromyographic (EMG signals of the rectus femoris (RF, vastus lateralis (VL, semitendinosus (ST and short head of the biceps femoris (BF during the performance of stationary running at different intensities in aquatic and dry land environments. The sample consisted of 12 female volunteers who performed the stationary running exercise in aquatic and dry land environments at a submaximal cadence (80 beats·min-1 controlled by a metronome and at maximal velocity, with EMG signal measurements from the RF, VL, ST and BF muscles. The results showed a distinct pattern between environments for each muscle examined. For the submaximal cadence of 80 beats·min-1, there was a reduced magnitude of the EMG signal in the aquatic environment, except for the ST muscle, the pattern of which was similar in both environments. In contrast to the submaximal cadence, the pattern of the EMG signal from all of the muscles showed similar magnitudes for both environments and phases of movement at maximal velocity, except for the VL muscle. Therefore, the EMG signals from the RF, VL, ST and BF muscles of women during stationary running had different patterns of activation over the range of motion between aquatic and dry land environments for different intensities. Moreover, the neuromuscular responses of the lower limbs were optimized by an increase in intensity from submaximal cadence to maximal velocity.

  2. C18, C8, and perfluoro reversed phases on diamond for solid-phase extraction.

    Science.gov (United States)

    Saini, Gaurav; Wiest, Landon A; Herbert, David; Biggs, Katherine N; Dadson, Andrew; Vail, Michael A; Linford, Matthew R

    2009-04-17

    In spite of advances in solid-phase extraction (SPE) technology there are certain disadvantages to current SPE silica-based, column packings. The pH range over which extraction can occur is limited and each column is generally only used once. New diamond-based reversed SPE phases (C(18), C(8), and perfluorinated) were developed in our laboratories. Studies were done which show that these phases do not have the same limitations as traditional silica-based stationary phases. The synthesis and properties of these diamond-based phases are presented, and the stability, percent recovery, and column capacity are given for the C(18) phase.

  3. STABLE STATIONARY STATES OF NON-LOCAL INTERACTION EQUATIONS

    KAUST Repository

    FELLNER, KLEMENS

    2010-12-01

    In this paper, we are interested in the large-time behaviour of a solution to a non-local interaction equation, where a density of particles/individuals evolves subject to an interaction potential and an external potential. It is known that for regular interaction potentials, stable stationary states of these equations are generically finite sums of Dirac masses. For a finite sum of Dirac masses, we give (i) a condition to be a stationary state, (ii) two necessary conditions of linear stability w.r.t. shifts and reallocations of individual Dirac masses, and (iii) show that these linear stability conditions imply local non-linear stability. Finally, we show that for regular repulsive interaction potential Wε converging to a singular repulsive interaction potential W, the Dirac-type stationary states ρ̄ ε approximate weakly a unique stationary state ρ̄ ∈ L∞. We illustrate our results with numerical examples. © 2010 World Scientific Publishing Company.

  4. The spectral analysis of cyclo-non-stationary signals

    Science.gov (United States)

    Abboud, D.; Baudin, S.; Antoni, J.; Rémond, D.; Eltabach, M.; Sauvage, O.

    2016-06-01

    Condition monitoring of rotating machines in speed-varying conditions remains a challenging task and an active field of research. Specifically, the produced vibrations belong to a particular class of non-stationary signals called cyclo-non-stationary: although highly non-stationary, they contain hidden periodicities related to the shaft angle; the phenomenon of long term modulations is what makes them different from cyclostationary signals which are encountered under constant speed regimes. In this paper, it is shown that the optimal way of describing cyclo-non-stationary signals is jointly in the time and the angular domains. While the first domain describes the waveform characteristics related to the system dynamics, the second one reveals existing periodicities linked to the system kinematics. Therefore, a specific class of signals - coined angle-time cyclostationary is considered, expressing the angle-time interaction. Accordingly, the related spectral representations, the order-frequency spectral correlation and coherence functions are proposed and their efficiency is demonstrated on two industrial cases.

  5. Noise Diagnostics of Stationary and Non-Stationary Reactor Processes

    Energy Technology Data Exchange (ETDEWEB)

    Sunde, Carl

    2007-04-15

    This thesis concerns the application of noise diagnostics on different problems in the area of reactor physics involving both stationary and non-stationary core processes. Five different problems are treated, divided into three different parts. The first problem treated in the first part is the classification of two-phase flow regimes from neutron radiographic and visible light images with a neuro-wavelet algorithm. The algorithm consists of wavelet pre-processing and of an artificial neural network. The result indicates that the wavelet pre-processing is improving the training of the neural network. Next, detector tubes which are suspected of impacting on nearby fuel-assemblies in a boiling water reactor (BWR) are identified by both a classical spectral method and wavelet-based methods. It was found that there is good agreement between the different methods as well as with visual inspections of detector tube and fuel assembly damage made during the outage at the plant. The third problem addresses the determination of the decay ratio of a BWR from the auto-correlation function (ACF). Here wavelets are used, with some success, both for de-trending and de-nosing of the ACF and also for direct estimation of the decay ratio from the ACF. The second part deals with the analysis of beam-mode and shell-mode core-barrel vibrations in pressurised water reactors (PWRs). The beam-mode vibrations are analysed by using parameters of the vibration peaks, in spectra from ex core detectors. A trend analysis of the peak amplitude shows that the peak amplitude is changing during the fuel cycle. When it comes to the analysis of the shell-mode vibration, 1-D analytical and numerical calculations are performed in order to calculate the neutron noise induced in the core. The two calculations are in agreement and show that a large local noise component is present in the core which could be used to classify the shell-mode vibrations. However, a measurement made in the PWR Ringhals-3 shows

  6. Noise Diagnostics of Stationary and Non-Stationary Reactor Processes

    International Nuclear Information System (INIS)

    Sunde, Carl

    2007-01-01

    This thesis concerns the application of noise diagnostics on different problems in the area of reactor physics involving both stationary and non-stationary core processes. Five different problems are treated, divided into three different parts. The first problem treated in the first part is the classification of two-phase flow regimes from neutron radiographic and visible light images with a neuro-wavelet algorithm. The algorithm consists of wavelet pre-processing and of an artificial neural network. The result indicates that the wavelet pre-processing is improving the training of the neural network. Next, detector tubes which are suspected of impacting on nearby fuel-assemblies in a boiling water reactor (BWR) are identified by both a classical spectral method and wavelet-based methods. It was found that there is good agreement between the different methods as well as with visual inspections of detector tube and fuel assembly damage made during the outage at the plant. The third problem addresses the determination of the decay ratio of a BWR from the auto-correlation function (ACF). Here wavelets are used, with some success, both for de-trending and de-nosing of the ACF and also for direct estimation of the decay ratio from the ACF. The second part deals with the analysis of beam-mode and shell-mode core-barrel vibrations in pressurised water reactors (PWRs). The beam-mode vibrations are analysed by using parameters of the vibration peaks, in spectra from ex core detectors. A trend analysis of the peak amplitude shows that the peak amplitude is changing during the fuel cycle. When it comes to the analysis of the shell-mode vibration, 1-D analytical and numerical calculations are performed in order to calculate the neutron noise induced in the core. The two calculations are in agreement and show that a large local noise component is present in the core which could be used to classify the shell-mode vibrations. However, a measurement made in the PWR Ringhals-3 shows

  7. Exponentially Stable Stationary Solutions for Stochastic Evolution Equations and Their Perturbation

    International Nuclear Information System (INIS)

    Caraballo, Tomas; Kloeden, Peter E.; Schmalfuss, Bjoern

    2004-01-01

    We consider the exponential stability of stochastic evolution equations with Lipschitz continuous non-linearities when zero is not a solution for these equations. We prove the existence of anon-trivial stationary solution which is exponentially stable, where the stationary solution is generated by the composition of a random variable and the Wiener shift. We also construct stationary solutions with the stronger property of attracting bounded sets uniformly. The existence of these stationary solutions follows from the theory of random dynamical systems and their attractors. In addition, we prove some perturbation results and formulate conditions for the existence of stationary solutions for semilinear stochastic partial differential equations with Lipschitz continuous non-linearities

  8. Comparison of TiO2 photocatalysis, electrochemically assisted Fenton reaction and direct electrochemistry for simulation of phase I metabolism reactions of drugs.

    Science.gov (United States)

    Ruokolainen, Miina; Gul, Turan; Permentier, Hjalmar; Sikanen, Tiina; Kostiainen, Risto; Kotiaho, Tapio

    2016-02-15

    The feasibility of titanium dioxide (TiO2) photocatalysis, electrochemically assisted Fenton reaction (EC-Fenton) and direct electrochemical oxidation (EC) for simulation of phase I metabolism of drugs was studied by comparing the reaction products of buspirone, promazine, testosterone and 7-ethoxycoumarin with phase I metabolites of the same compounds produced in vitro by human liver microsomes (HLM). Reaction products were analysed by UHPLC-MS. TiO2 photocatalysis simulated the in vitro phase I metabolism in HLM more comprehensively than did EC-Fenton or EC. Even though TiO2 photocatalysis, EC-Fenton and EC do not allow comprehensive prediction of phase I metabolism, all three methods produce several important metabolites without the need for demanding purification steps to remove the biological matrix. Importantly, TiO2 photocatalysis produces aliphatic and aromatic hydroxylation products where direct EC fails. Furthermore, TiO2 photocatalysis is an extremely rapid, simple and inexpensive way to generate oxidation products in a clean matrix and the reaction can be simply initiated and quenched by switching the UV lamp on/off. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Carbon nanotube-based benzyl polymethacrylate composite monolith as a solid phase extraction adsorbent and a stationary phase material for simultaneous extraction and analysis of polycyclic aromatic hydrocarbon in water.

    Science.gov (United States)

    Al-Rifai, Asma'a; Aqel, Ahmad; Wahibi, Lamya Al; ALOthman, Zeid A; Badjah-Hadj-Ahmed, Ahmed-Yacine

    2018-02-02

    A composite of multi-walled carbon nanotubes incorporated into a benzyl methacrylate-co-ethylene dimethacrylate porous monolith was prepared, characterized and used as solid phase adsorbent and as stationary phase for simultaneous extraction and separation of ten polycyclic aromatic hydrocarbons, followed by nano-liquid chromatography analysis. The extraction and chromatographic parameters were optimized with regard to the extraction efficiency and the quality of chromatographic analytes separation. Under the optimized conditions, all PAHs were separated in 13 min with suitable resolution values (Rs = 1.74-3.98). Addition of a small amount of carbon nanotubes (0.1% with respect to monomers) to the polymerization mixture increased the efficiency for the separation column to over 41,700 plates m -1 for chrysene at flow rate of 0.5 μL min -1 . The method showed a wide linear range (1-500 μg L -1 with R 2 more than 0.9938), acceptable extraction repeatability (RSDs extraction cartridges) and satisfactory detection limits (0.02-0.22 μg L -1 ). Finally, the proposed method was successfully applied to the detection of polycyclic aromatic hydrocarbons in environmental water samples. After a simple extraction procedure with preconcentration factor equal to 100, the average recovery values in ultra-pure, tap and sea water samples were found to be in the range 81.3-95.4% with %RSD less than 6.4. Again, the presence of carbon nanotubes (0.3% relatively to monomers) in native polymer enhanced the extraction performance for the solid phase adsorbent up to 78.4%. The application of the monoliths modified with CNTs in extraction and nano-scale liquid chromatography for analysis of environmental samples offered several advantages; it demonstrated an acceptable precision, low detection limits, good reproducibility, satisfying recoveries and wide dynamic linear ranges. Copyright © 2018. Published by Elsevier B.V.

  10. Solid-phase extraction sorbent consisting of alkyltrimethylammonium surfactants immobilized onto strong cation-exchange polystyrene resin.

    Science.gov (United States)

    Reid, Kendra R; Kennedy, Lonnie J; Crick, Eric W; Conte, Eric D

    2002-10-25

    Presented is a solid-phase extraction sorbent material composed of cationic alkyltrimethylammonium surfactants attached to a strong cation-exchange resin via ion-exchange. The original hydrophilic cation-exchange resin is made hydrophobic by covering the surface with alkyl chains from the hydrophobic portion of the surfactant. The sorbent material now has a better ability to extract hydrophobic molecules from aqueous samples. The entire stationary phase (alkyltrimethylammonium surfactant) is removed along with the analyte during the elution step. The elution step requires a mild elution solvent consisting of 0.25 M Mg2+ in a 50% 2-propanol solution. The main advantage of using a removable stationary phase is that traditionally utilized toxic elution solvents such as methylene chloride, which are necessary to efficiently release strongly hydrophobic species from SPE stationary phases, may now be avoided. Also, the final extract is directly compatible with reversed-phase liquid chromatography. The performance of this procedure is presented using pyrene as a test molecule.

  11. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak’s extracts

    International Nuclear Information System (INIS)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat,; Suzery, Meiny

    2015-01-01

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak’s extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r 2 =0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak’s extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel

  12. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak’s extracts

    Energy Technology Data Exchange (ETDEWEB)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat,; Suzery, Meiny [Organic Chemistry Laboratory, Departement of Chemistry, Diponegoro University Jln Prof. Soedharto SH, Tembalang, Semarang 50275, Indonesia Tel / Fax: (024) 7460058 (Indonesia)

    2015-12-29

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak’s extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r{sup 2}=0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak’s extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel.

  13. A functional glycogen biosynthesis pathway in Lactobacillus acidophilus: expression and analysis of the glg operon

    Science.gov (United States)

    Goh, Yong Jun; Klaenhammer, Todd R

    2013-01-01

    Glycogen metabolism contributes to energy storage and various physiological functions in some prokaryotes, including colonization persistence. A role for glycogen metabolism is proposed on the survival and fitness of Lactobacillus acidophilus, a probiotic microbe, in the human gastrointestinal environment. L. acidophilus NCFM possesses a glycogen metabolism (glg) operon consisting of glgBCDAP-amy-pgm genes. Expression of the glg operon and glycogen accumulation were carbon source- and growth phase-dependent, and were repressed by glucose. The highest intracellular glycogen content was observed in early log-phase cells grown on trehalose, which was followed by a drastic decrease of glycogen content prior to entering stationary phase. In raffinose-grown cells, however, glycogen accumulation gradually declined following early log phase and was maintained at stable levels throughout stationary phase. Raffinose also induced an overall higher temporal glg expression throughout growth compared with trehalose. Isogenic ΔglgA (glycogen synthase) and ΔglgB (glycogen-branching enzyme) mutants are glycogen-deficient and exhibited growth defects on raffinose. The latter observation suggests a reciprocal relationship between glycogen synthesis and raffinose metabolism. Deletion of glgB or glgP (glycogen phosphorylase) resulted in defective growth and increased bile sensitivity. The data indicate that glycogen metabolism is involved in growth maintenance, bile tolerance and complex carbohydrate utilization in L. acidophilus. PMID:23879596

  14. Non-Stationary Dependence Structures for Spatial Extremes

    KAUST Repository

    Huser, Raphaël

    2016-03-03

    Max-stable processes are natural models for spatial extremes because they provide suitable asymptotic approximations to the distribution of maxima of random fields. In the recent past, several parametric families of stationary max-stable models have been developed, and fitted to various types of data. However, a recurrent problem is the modeling of non-stationarity. In this paper, we develop non-stationary max-stable dependence structures in which covariates can be easily incorporated. Inference is performed using pairwise likelihoods, and its performance is assessed by an extensive simulation study based on a non-stationary locally isotropic extremal t model. Evidence that unknown parameters are well estimated is provided, and estimation of spatial return level curves is discussed. The methodology is demonstrated with temperature maxima recorded over a complex topography. Models are shown to satisfactorily capture extremal dependence.

  15. Fluctuation relations in non-equilibrium stationary states of Ising models

    Energy Technology Data Exchange (ETDEWEB)

    Piscitelli, A; Gonnella, G [Dipartimento di Fisica, Universita di Bari and Istituto Nazionale di Fisica Nucleare, Sezione di Bari, via Amendola 173, 70126 Bari (Italy); Corberi, F [Dipartimento di Matematica ed Informatica, via Ponte don Melillo, Universita di Salerno, 84084 Fisciano (Italy); Pelizzola, A [Dipartimento di Fisica and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, and CNISM, Politecnico di Torino, c. Duca degli Abruzzi 24, 10129 Torino (Italy)

    2009-01-15

    Fluctuation relations for the entropy production in non-equilibrium stationary states of Ising models are investigated by means of Monte Carlo simulations. Systems in contact with heat baths at two different temperatures or subject to external driving will be studied. In the first case, considering different kinetic rules and couplings with the baths, the behaviors of the probability distributions of the heat exchanged in time {tau} with the thermostats, both in the disordered phase and in the low temperature phase, are discussed. The fluctuation relation is always followed in the large {tau} limit and deviations from linear response theory are observed. Finite {tau} corrections are shown to obey a scaling behavior. In the other case the system is in contact with a single heat bath, but work is done by shearing it. Also for this system, using the statistics collected for the mechanical work we show the validity of the fluctuation relation and the preasymptotic corrections behave analogously to those for the case with two baths.

  16. Cosmological red shift in the Seeliger-Einstein stationary Universe

    International Nuclear Information System (INIS)

    Kropotkin, P.N.

    1988-01-01

    A problem of Seeliger-Einstein stationary Universe is considered. Simple empirical relations between cosmological and physical constants to which attention was paid by Stanukovich K., Dikke R., Dirac P. testify to the supposition on stationary Universe. The Universe expansion being absent, a hypothesis of ''photon aging'' suggested in 1929 by Belopolskij A. and Zwicky F. must be accepted for explanation of Hubble effect. It is stated that abandon the Seeliger-Einstein stationary cosmological model would be premature. Study and comparison of different mechanisms suggested for validation of photon aging hypothesis is necessary

  17. Bi-spectrum based-EMD applied to the non-stationary vibration signals for bearing faults diagnosis.

    Science.gov (United States)

    Saidi, Lotfi; Ali, Jaouher Ben; Fnaiech, Farhat

    2014-09-01

    Empirical mode decomposition (EMD) has been widely applied to analyze vibration signals behavior for bearing failures detection. Vibration signals are almost always non-stationary since bearings are inherently dynamic (e.g., speed and load condition change over time). By using EMD, the complicated non-stationary vibration signal is decomposed into a number of stationary intrinsic mode functions (IMFs) based on the local characteristic time scale of the signal. Bi-spectrum, a third-order statistic, helps to identify phase coupling effects, the bi-spectrum is theoretically zero for Gaussian noise and it is flat for non-Gaussian white noise, consequently the bi-spectrum analysis is insensitive to random noise, which are useful for detecting faults in induction machines. Utilizing the advantages of EMD and bi-spectrum, this article proposes a joint method for detecting such faults, called bi-spectrum based EMD (BSEMD). First, original vibration signals collected from accelerometers are decomposed by EMD and a set of IMFs is produced. Then, the IMF signals are analyzed via bi-spectrum to detect outer race bearing defects. The procedure is illustrated with the experimental bearing vibration data. The experimental results show that BSEMD techniques can effectively diagnosis bearing failures. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  18. Stationary states of two-level open quantum systems

    International Nuclear Information System (INIS)

    Gardas, Bartlomiej; Puchala, Zbigniew

    2011-01-01

    A problem of finding stationary states of open quantum systems is addressed. We focus our attention on a generic type of open system: a qubit coupled to its environment. We apply the theory of block operator matrices and find stationary states of two-level open quantum systems under certain conditions applied on both the qubit and the surrounding.

  19. Modeling stationary and moving pebbles in a pebble bed reactor

    International Nuclear Information System (INIS)

    Zhao, Xiang; Montgomery, Trent; Zhang, Sijun

    2015-01-01

    Highlights: • The stationary and moving pebbles in a PBR are numerically studied by DEM. • The packing structure of stationary pebbles is simulated by a filling process. • The packing structural properties are obtained and analyzed. • The dynamic behavior of pebbles is predicted and discussed. - Abstract: This paper presents a numerical study of the stationary and moving pebbles in a pebble bed reactor (PBR) by means of discrete element method (DEM). The packing structure of stationary pebbles is simulated by a filling process that terminates with the settling of the pebbles into a PBR. The packing structural properties are obtained and analyzed. Subsequently, when the outlet of the PBR is opened during the operation of the PBR, the stationary pebbles start to flow downward and are removed at the bottom of the PBR. The dynamic behavior of pebbles is predicted and discussed. Our results indicate the DEM can offer both macroscopic and microscopic information for PBR design calculations and safety assessment

  20. Towards Gravitating Discs around Stationary Black Holes

    Science.gov (United States)

    Semerák, Oldřich

    This article outlines the search for an exact general relativistic description of the exterior(vacuum) gravitational field of a rotating spheroidal black hole surrounded by a realistic axially symmetric disc of matter. The problem of multi-body stationary spacetimes is first exposed from the perspective of the relativity theory (section 1) and astrophysics (section 2), listing the basic methods employed and results obtained. Then (in section 3) basic formulas for stationary axisymmetric solutions are summarized. Sections 4 and 5 review what we have learnt with Miroslav Žáček and Tomáš Zellerin about certain static and stationary situations recently. Concluding remarks are given in section 6. Although the survey part is quite general, the list of references cannot be complete.Our main desideratum was the informative value rather than originality — novelties have been preferred, mainly reviews and those with detailed introductions.

  1. Quantum manipulation of two-color stationary light: Quantum wavelength conversion

    International Nuclear Information System (INIS)

    Moiseev, S. A.; Ham, B. S.

    2006-01-01

    We present a quantum manipulation of a traveling light pulse using electromagnetically induced transparency-based slow light phenomenon for the generation of two-color stationary light. We theoretically discuss the two-color stationary light for the quantum wavelength conversion process in terms of pulse area, energy transfer, and propagation directions. The condition of the two-color stationary light pulse generation has been found and the quantum light dynamics has been studied analytically in the adiabatic limit. The quantum frequency conversion rate of the traveling light is dependent on the spatial spreading of the two-color stationary light pulse and can be near unity in an optically dense medium for the optimal frequencies of the control laser fields

  2. High-frequency instabilities of stationary crossflow vortices in a hypersonic boundary layer

    Science.gov (United States)

    Li, Fei; Choudhari, Meelan; Paredes, Pedro; Duan, Lian

    2016-09-01

    Hypersonic boundary layer flows over a circular cone at moderate incidence angle can support strong crossflow instability in between the windward and leeward rays on the plane of symmetry. Due to more efficient excitation of stationary crossflow vortices by surface roughness, such boundary layer flows may transition to turbulence via rapid amplification of the high-frequency secondary instabilities of finite-amplitude stationary crossflow vortices. The amplification characteristics of these secondary instabilities are investigated for crossflow vortices generated by an azimuthally periodic array of roughness elements over a 7° half-angle circular cone in a Mach 6 free stream. The analysis is based on both quasiparallel stability theory in the form of a partial-differential-equation-based eigenvalue analysis and plane marching parabolized stability equations that account for the effects of the nonparallel basic state on the growth of secondary disturbances. Depending on the local amplitude of the stationary crossflow mode, the most unstable high-frequency disturbances either originate from the second (i.e., Mack) mode instabilities of the unperturbed boundary layer or correspond to genuine secondary instabilities that reduce to stable disturbances at sufficiently small amplitudes of the stationary crossflow vortex. The predicted frequencies of the dominant secondary disturbances of either type are similar to those measured during wind tunnel experiments at Purdue University and the Technical University of Braunschweig, Germany. Including transverse surface curvature within the quasiparallel predictions does not alter the topology of the unstable modes; however, the resulting changes in both mode shape and disturbance growth rate are rather significant and curvature can be either stabilizing or destabilizing depending on the disturbance frequency and mode type. Nonparallel effects are shown to be strongly destabilizing for secondary instabilities originating from

  3. Supercritical fluid chromatography versus high performance liquid chromatography for enantiomeric and diastereoisomeric separations on coated polysaccharides-based stationary phases: Application to dihydropyridone derivatives.

    Science.gov (United States)

    Hoguet, Vanessa; Charton, Julie; Hecquet, Paul-Emile; Lakhmi, Chahinaze; Lipka, Emmanuelle

    2018-05-11

    For analytical applications, SFC has always remained in the shadow of LC. Analytical enantioseparation of eight dihydropyridone derivatives, was run in both High Performance Liquid Chromatography and Supercritical Fluid Chromatography. Four polysaccharide based chiral stationary phases namely amylose and cellulose tris(3, 5-dimethylphenylcarbamate), amylose tris((S)-α-phenylethylcarbamate) and cellulose tris(4-methylbenzoate) with four mobile phases consisted of either n-hexane/ethanol or propan-2-ol (80:20 v:v) or carbon dioxide/ethanol or propan-2-ol (80:20 v:v) mixtures were investigated under same operatory conditions (temperature and flow-rate). The elution strength, enantioselectivity and resolution were compared in the two methodologies. For these compounds, for most of the conditions, HPLC afforded shorter retention times and a higher resolution than SFC. HPLC appears particularly suitable for the separation of the compounds bearing two chiral centers. For instance compound 7 was baseline resolved on OD-H CSP under n-Hex/EtOH 80/20, with resolution values equal to 2.98, 1.55, 4.52, between the four stereoisomers in less than 17 min, whereas in SFC, this latter is not fully separated in 23 min under similar eluting conditions. After analytical screenings, the best conditions were transposed to semi-preparative scale. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Design, preparation and application of a Pirkle-type chiral stationary phase for enantioseparation of some racemic organic acids and molecular dynamics studies

    Directory of Open Access Journals (Sweden)

    Reşit Çakmak

    2017-08-01

    Full Text Available This study consists of two parts. In the first part of the study; a Pirkle-type chiral stationary phase was prepared by synthesizing an aromatic amine derivative of (R-2-amino-1-butanol as a chiral selectorand binding to L- tyrosine -modified cyanogen bromide (CNBr-activated Sepharose 4B and then, packed into the separation column. T he chromatographic performance of the separation column was evaluated w ith racemic mandelic acid and 2-phenylpropionic acid by using phosphate buffers at three different pHs as mobile phase. In the resolution processes, t he prepared solutions were loaded onto the separation column at two different concentrations and at three different pHs for each racemic organic acid, separately. Enantiomeric excess (ee % of the eluates was determined on CHIRALPAK AD-H chiral analytical column by HPLC. The maximum ee% for mandelic acid and 2-phenylpropionic acid was determined to be 60.84 and 27.4, respectively. Separation factors (k 1 ’, k 2 ’, α, and Rs were calculated for each acid. The structures of the obtained compounds were characterized using the spectroscopic methods (NMR, and elemental analysis. In the second part of the study; enantioselective interactions between the prepared CSP and the analytes have been widely studied by docking, molecular dynamics simulation and quantum mechanical computation methods. The reason of column eluation of rac-2-phenylpropionic acid with lower enantiomeric yield was explained by these techniques.

  5. Stationary black holes: large D analysis

    International Nuclear Information System (INIS)

    Suzuki, Ryotaku; Tanabe, Kentaro

    2015-01-01

    We consider the effective theory of large D stationary black holes. By solving the Einstein equations with a cosmological constant using the 1/D expansion in near zone of the black hole we obtain the effective equation for the stationary black hole. The effective equation describes the Myers-Perry black hole, bumpy black holes and, possibly, the black ring solution as its solutions. In this effective theory the black hole is represented as an embedded membrane in the background, e.g., Minkowski or Anti-de Sitter spacetime and its mean curvature is given by the surface gravity redshifted by the background gravitational field and the local Lorentz boost. The local Lorentz boost property of the effective equation is observed also in the metric itself. In fact we show that the leading order metric of the Einstein equation in the 1/D expansion is generically regarded as a Lorentz boosted Schwarzschild black hole. We apply this Lorentz boost property of the stationary black hole solution to solve perturbation equations. As a result we obtain an analytic formula for quasinormal modes of the singly rotating Myers-Perry black hole in the 1/D expansion.

  6. Evaluation of the chiral recognition properties and the column performances of three chiral stationary phases based on cellulose for the enantioseparation of six dihydropyridines by high-performance liquid chromatography.

    Science.gov (United States)

    Yu, Jia; Tang, Jing; Yuan, Xiaowei; Guo, Xingjie; Zhao, Longshan

    2017-03-01

    Separations of six dihydropyridine enantiomers on three commercially available cellulose-based chiral stationary phases (Chiralcel OD-RH, Chiralpak IB, and Chiralpak IC) were evaluated with high-performance liquid chromatography (HPLC). The best enantioseparation of the six chiral drugs was obtained with a Chiralpak IC (250 × 4.6 mm i.d., 5 μm) column. Then the influence of the mobile phase including an alcohol-modifying agent and alkaline additive on the enantioseparation were investigated and optimized. The optimal mobile phase conditions and maximum resolution for every analyte were as follows respectively: n-hexane/isopropanol (85:15, v/v) for nimodipine (R = 5.80) and cinildilpine (R = 5.65); n-hexane/isopropanol (92:8, v/v) for nicardipine (R = 1.76) and nisoldipine (R = 1.92); and n-hexane/isopropanol/ethanol (97:2:1, v/v/v) for felodipine (R = 1.84) and lercanidipine (R = 1.47). Relative separation mechanisms are discussed based on the separation results, and indicate that the achiral parts in the analytes' structure showed an important influence on the separation of the chiral column. © 2017 Wiley Periodicals, Inc.

  7. Selectivity of calixarene-bonded silica phases in HPLC: Description of special characteristics with a multiple term linear equation at different methanol concentrations.

    Science.gov (United States)

    Schneider, Christian; Jira, Thomas

    2010-10-01

    Retention and selectivity characteristics of different calixarene-, resorcinarene- and alkyl-bonded stationary phases are examined by analyzing a set of test solutes covering the main interactions (hydrophobic, steric, ionic, polar) that apply in HPLC. Therefore Dolan and Snyder's multiple term linear equation has been adapted to fit the properties of calixarene-bonded columns. The obtained parameters are used to describe retention and selectivity of the novel Caltrex(®) phases and to elucidate underlying mechanisms of retention. Here, differences of stationary phase characteristics at different methanol concentrations in the mobile phases are examined. Both selectivity and retention were found to depend on the methanol content. Differences of these dependencies were found for different stationary phases and interactions. The differences between common alkyl-bonded and novel calixarene-bonded phases increase with increasing methanol content.

  8. The Stationary SQUID

    Science.gov (United States)

    Berger, Jorge

    2018-06-01

    In the customary mode of operation of a SQUID, the electromagnetic field in the SQUID is an oscillatory function of time. In this situation, electromagnetic radiation is emitted and couples to the sample. This is a back action that can alter the state that we intend to measure. A circuit that could perform as a stationary SQUID consists of a loop of superconducting material that encloses the magnetic flux, connected to a superconducting and to a normal electrode. This circuit does not contain Josephson junctions, or any other miniature feature. We study the evolution of the order parameter and of the electrochemical potential in this circuit; they converge to a stationary regime, and the voltage between the electrodes depends on the enclosed flux. We obtain expressions for the power dissipation and for the heat transported by the electric current; the validity of these expressions does not rely on a particular evolution model for the order parameter. We evaluate the influence of fluctuations. For a SQUID perimeter of the order of 1μ m and temperature 0.9T_c, we obtain a flux resolution of the order of 10^{-5}Φ _0/Hz^{1/2}; the resolution is expected to improve as the temperature is lowered.

  9. Investigation of the stationary-thermonuclear-reaction realization possibility in a tokamak device

    International Nuclear Information System (INIS)

    Kolesnichenko, Ya.I.; Reznik, S.N.; Fursa, A.D.

    1976-01-01

    The stationary (quasistationary) selfsustaining thermonuclear D-T reaction is shown to be possible in a toroidal device such as 'Tokamak' with large enough plasma radius. The stationary temperature of the plasma can be quite high. Thus when the transport processes are assumed to be neoclassical the temperature of the central part of a plasma colomn of radius approximately 10-200 cm in the stationary state is 70 keV.The stationary temperature distribution is reached spontaneously as a result of the thermal instability development if plasma is preheated to 10 keV. The stationary thermonuclear burning is also possible at lower temperatures if plasma energy balance is controlled

  10. Analysis of stress and deformation in non-stationary creep

    International Nuclear Information System (INIS)

    Feijoo, R.A.; Taroco, E.; Guerreiro, J.N.C.

    1980-12-01

    A variational method and its algorithm are presented; they permit the analysis of stress and deformation in non-stationary creep. This algorithm is applied to an infinite cylinder submitted to an internal pressure. The solution obtained is compared with the solution of non-stationary creep problems [pt

  11. Stability of Bifurcating Stationary Solutions of the Artificial Compressible System

    Science.gov (United States)

    Teramoto, Yuka

    2018-02-01

    The artificial compressible system gives a compressible approximation of the incompressible Navier-Stokes system. The latter system is obtained from the former one in the zero limit of the artificial Mach number ɛ which is a singular limit. The sets of stationary solutions of both systems coincide with each other. It is known that if a stationary solution of the incompressible system is asymptotically stable and the velocity field of the stationary solution satisfies an energy-type stability criterion, then it is also stable as a solution of the artificial compressible one for sufficiently small ɛ . In general, the range of ɛ shrinks when the spectrum of the linearized operator for the incompressible system approaches to the imaginary axis. This can happen when a stationary bifurcation occurs. It is proved that when a stationary bifurcation from a simple eigenvalue occurs, the range of ɛ can be taken uniformly near the bifurcation point to conclude the stability of the bifurcating solution as a solution of the artificial compressible system.

  12. Characterisation of the maternal response to chronic phase shifts during gestation in the rat: implications for fetal metabolic programming.

    Directory of Open Access Journals (Sweden)

    Tamara J Varcoe

    Full Text Available Disrupting maternal circadian rhythms through exposure to chronic phase shifts of the photoperiod has lifelong consequences for the metabolic homeostasis of the fetus, such that offspring develop increased adiposity, hyperinsulinaemia and poor glucose and insulin tolerance. In an attempt to determine the mechanisms by which these poor metabolic outcomes arise, we investigated the impact of chronic phase shifts (CPS on maternal and fetal hormonal, metabolic and circadian rhythms. We assessed weight gain and food consumption of dams exposed to either CPS or control lighting conditions throughout gestation. At day 20, dams were assessed for plasma hormone and metabolite concentrations and glucose and insulin tolerance. Additionally, the expression of a range of circadian and metabolic genes was assessed in maternal, placental and fetal tissue. Control and CPS dams consumed the same amount of food, yet CPS dams gained 70% less weight during the first week of gestation. At day 20, CPS dams had reduced retroperitoneal fat pad weight (-15%, and time-of-day dependent decreases in liver weight, whereas fetal and placental weight was not affected. Melatonin secretion was not altered, yet the timing of corticosterone, leptin, glucose, insulin, free fatty acids, triglycerides and cholesterol concentrations were profoundly disrupted. The expression of gluconeogenic and circadian clock genes in maternal and fetal liver became either arrhythmic or were in antiphase to the controls. These results demonstrate that disruptions of the photoperiod can severely disrupt normal circadian profiles of plasma hormones and metabolites, as well as gene expression in maternal and fetal tissues. Disruptions in the timing of food consumption and the downstream metabolic processes required to utilise that food, may lead to reduced efficiency of growth such that maternal weight gain is reduced during early embryonic development. It is these perturbations that may contribute to

  13. Characterisation of the maternal response to chronic phase shifts during gestation in the rat: implications for fetal metabolic programming.

    Science.gov (United States)

    Varcoe, Tamara J; Boden, Michael J; Voultsios, Athena; Salkeld, Mark D; Rattanatray, Leewen; Kennaway, David J

    2013-01-01

    Disrupting maternal circadian rhythms through exposure to chronic phase shifts of the photoperiod has lifelong consequences for the metabolic homeostasis of the fetus, such that offspring develop increased adiposity, hyperinsulinaemia and poor glucose and insulin tolerance. In an attempt to determine the mechanisms by which these poor metabolic outcomes arise, we investigated the impact of chronic phase shifts (CPS) on maternal and fetal hormonal, metabolic and circadian rhythms. We assessed weight gain and food consumption of dams exposed to either CPS or control lighting conditions throughout gestation. At day 20, dams were assessed for plasma hormone and metabolite concentrations and glucose and insulin tolerance. Additionally, the expression of a range of circadian and metabolic genes was assessed in maternal, placental and fetal tissue. Control and CPS dams consumed the same amount of food, yet CPS dams gained 70% less weight during the first week of gestation. At day 20, CPS dams had reduced retroperitoneal fat pad weight (-15%), and time-of-day dependent decreases in liver weight, whereas fetal and placental weight was not affected. Melatonin secretion was not altered, yet the timing of corticosterone, leptin, glucose, insulin, free fatty acids, triglycerides and cholesterol concentrations were profoundly disrupted. The expression of gluconeogenic and circadian clock genes in maternal and fetal liver became either arrhythmic or were in antiphase to the controls. These results demonstrate that disruptions of the photoperiod can severely disrupt normal circadian profiles of plasma hormones and metabolites, as well as gene expression in maternal and fetal tissues. Disruptions in the timing of food consumption and the downstream metabolic processes required to utilise that food, may lead to reduced efficiency of growth such that maternal weight gain is reduced during early embryonic development. It is these perturbations that may contribute to the programming of

  14. Synergistic effects on enantioselectivity of zwitterionic chiral stationary phases for separations of chiral acids, bases, and amino acids by HPLC.

    Science.gov (United States)

    Hoffmann, Christian V; Pell, Reinhard; Lämmerhofer, Michael; Lindner, Wolfgang

    2008-11-15

    In an attempt to overcome the limited applicability scope of earlier proposed Cinchona alkaloid-based chiral weak anion exchangers (WAX) and recently reported aminosulfonic acid-based chiral strong cation exchangers (SCX), which are conceptionally restricted to oppositely charged solutes, their individual chiral selector (SO) subunits have been fused in a combinatorial synthesis approach into single, now zwitterionic, chiral SO motifs. The corresponding zwitterionic ion-exchange-type chiral stationary phases (CSPs) in fact combined the applicability spectra of the parent chiral ion exchangers allowing for enantioseparations of chiral acids and amine-type solutes in liquid chromatography using polar organic mode with largely rivaling separation factors as compared to the parent WAX and SCX CSPs. Furthermore, the application spectrum could be remarkably expanded to various zwitterionic analytes such as alpha- and beta-amino acids and peptides. A set of structurally related yet different CSPs consisting of either a quinine or quinidine alkaloid moiety as anion-exchange subunit and various chiral or achiral amino acids as cation-exchange subunits enabled us to derive structure-enantioselectivity relationships, which clearly provided strong unequivocal evidence for synergistic effects of the two oppositely charged ion-exchange subunits being involved in molecular recognition of zwitterionic analytes by zwitterionic SOs driven by double ionic coordination.

  15. Non-Stationary Internal Tides Observed with Satellite Altimetry

    Science.gov (United States)

    Ray, Richard D.; Zaron, E. D.

    2011-01-01

    Temporal variability of the internal tide is inferred from a 17-year combined record of Topex/Poseidon and Jason satellite altimeters. A global sampling of along-track sea-surface height wavenumber spectra finds that non-stationary variance is generally 25% or less of the average variance at wavenumbers characteristic of mode-l tidal internal waves. With some exceptions the non-stationary variance does not exceed 0.25 sq cm. The mode-2 signal, where detectable, contains a larger fraction of non-stationary variance, typically 50% or more. Temporal subsetting of the data reveals interannual variability barely significant compared with tidal estimation error from 3-year records. Comparison of summer vs. winter conditions shows only one region of noteworthy seasonal changes, the northern South China Sea. Implications for the anticipated SWOT altimeter mission are briefly discussed.

  16. Azithromycin blocks quorum sensing and alginate polymer formation and increases the sensitivity to serum and stationary growth phase killing of P. aeruginosa and attenuates chronic P. aeruginosa lung infection in Cftr -/--mice

    DEFF Research Database (Denmark)

    Hoffmann, N.; Lee, Bao le ri; Hentzer, Morten

    2007-01-01

    The consequences of O-acetylated alginate-producing Pseudomonas aeruginosa biofilms in the lungs of chronically infected cystic fibrosis (CF) patients are tolerance to both antibiotic treatments and effects on the innate and the adaptive defense mechanisms. In clinical trials, azithromycin (AZM...... and the complement system. Moreover, we show that AZM may affect the polymerization of P. aeruginosa alginate by the incomplete precipitation of polymerized alginate and high levels of readily dialyzable uronic acids. In addition, we find that mucoid bacteria in the stationary growth phase became sensitive to AZM......, whereas cells in the exponential phase did not. Interestingly, AZM-treated P. aeruginosa lasI mutants appeared to be particularly resistant to serum, whereas bacteria with a functional QS system did not. We show in a CF mouse model of chronic P. aeruginosa lung infection that AZM treatment results...

  17. Evaluation of the Methods for Response Analysis under Non-Stationary Excitation

    Directory of Open Access Journals (Sweden)

    R.S. Jangid

    1999-01-01

    Full Text Available Response of structures to non-stationary ground motion can be obtained either by the evolutionary spectral analysis or by the Markov approach. In certain conditions, a quasi-stationary analysis can also be performed. The first two methods of analysis are difficult to apply for complex situations such as problems involving soil-structure interaction, non-classical damping and primary-secondary structure interaction. The quasi-stationary analysis, on the other hand, provides an easier solution procedure for such cases. Here-in, the effectiveness of the quasi-stationary analysis is examined with the help of the analysis of a single degree-of-freedom (SDOF system under a set of parametric variations. For this purpose, responses of the SDOF system to uniformly modulated non-stationary random ground excitation are obtained by the three methods and they are compared. In addition, the relative computational efforts for different methods are also investigated.

  18. Large-Deviation Results for Discriminant Statistics of Gaussian Locally Stationary Processes

    Directory of Open Access Journals (Sweden)

    Junichi Hirukawa

    2012-01-01

    Full Text Available This paper discusses the large-deviation principle of discriminant statistics for Gaussian locally stationary processes. First, large-deviation theorems for quadratic forms and the log-likelihood ratio for a Gaussian locally stationary process with a mean function are proved. Their asymptotics are described by the large deviation rate functions. Second, we consider the situations where processes are misspecified to be stationary. In these misspecified cases, we formally make the log-likelihood ratio discriminant statistics and derive the large deviation theorems of them. Since they are complicated, they are evaluated and illustrated by numerical examples. We realize the misspecification of the process to be stationary seriously affecting our discrimination.

  19. Stationary Double Layers in a Collisionless Magnetoplasma

    DEFF Research Database (Denmark)

    Noriyoshi, Sato; Mieno, Tetsu; Hatakeyama, Rikizo

    1983-01-01

    of the plate on the low-potential side, being accompanied with current limitation. This localized potential drop moves along the plasma column, but finally stops and results in the formation of the stationary double layer in the presence of sufficient plasma supply from the plate on the high-potential side.......Stationary double layers are generated in a magnetoplasma by applying potential differences between two heated plates on which the plasma is produced by surface ionization. By measuring the double-layer formation process, a localized potential drop is found to be formed initially in front...

  20. Relativistic elasticity of stationary fluid branes

    Science.gov (United States)

    Armas, Jay; Obers, Niels A.

    2013-02-01

    Fluid mechanics can be formulated on dynamical surfaces of arbitrary codimension embedded in a background space-time. This has been the main object of study of the blackfold approach in which the emphasis has primarily been on stationary fluid configurations. Motivated by this approach we show under certain conditions that a given stationary fluid configuration living on a dynamical surface of vanishing thickness and satisfying locally the first law of thermodynamics will behave like an elastic brane when the surface is subject to small deformations. These results, which are independent of the number of space-time dimensions and of the fluid arising from a gravitational dual, reveal the (electro)elastic character of (charged) black branes when considering extrinsic perturbations.

  1. Variational analysis of topological stationary barotropic MHD in the case of single-valued magnetic surfaces

    International Nuclear Information System (INIS)

    Yahalom, A

    2014-01-01

    Variational principles for magnetohydrodynamics have been introduced by previous authors both in Lagrangian and Eulerian form. Yahalom and Lynden-Bell (2008) have previously introduced simpler Eulerian variational principles from which all the relevant equations of barotropic magnetohydrodynamics can be derived. These variational principles were given in terms of six independent functions for non-stationary barotropic flows with given topologies and three independent functions for stationary barotropic flows. This is less then the seven variables which appear in the standard equations of barotropic magnetohydrodynamics which are the magnetic field B-vector the velocity field v-vector and the density ρ. Later, Yahalom (2010) introduced a simpler variational principle in terms of four functions for non-stationary barotropic magnetohydrodynamics. It was shown that the above variational principles are also relevant for flows of non-trivial topologies and in fact using those variational variables one arrives at additional topological conservation laws in terms of cuts of variables which have close resemblance to the Aharonov- Bohm phase (Yahalom (2013)). In previous examples (Yahalom and Lynden-Bell (2008); Yahalom (2013)) the magnetic field lines with non-trivial topology were at the intersection of two surface one of which was always multivalued; in this paper an example is introduced in which the magnetic helicity is not zero yet both surfaces are single-valued

  2. Inference for local autocorrelations in locally stationary models.

    Science.gov (United States)

    Zhao, Zhibiao

    2015-04-01

    For non-stationary processes, the time-varying correlation structure provides useful insights into the underlying model dynamics. We study estimation and inferences for local autocorrelation process in locally stationary time series. Our constructed simultaneous confidence band can be used to address important hypothesis testing problems, such as whether the local autocorrelation process is indeed time-varying and whether the local autocorrelation is zero. In particular, our result provides an important generalization of the R function acf() to locally stationary Gaussian processes. Simulation studies and two empirical applications are developed. For the global temperature series, we find that the local autocorrelations are time-varying and have a "V" shape during 1910-1960. For the S&P 500 index, we conclude that the returns satisfy the efficient-market hypothesis whereas the magnitudes of returns show significant local autocorrelations.

  3. The stationary storage of energy. Available technologies and CEA researches

    International Nuclear Information System (INIS)

    2012-01-01

    After a discussion of the main challenges related to the stationary storage of energy, this publication proposes an overview of the different available technologies: plant for transfer of energy by pumping, compressed air, energy flywheels, hydrogen, lithium-ion battery, redox-flow battery, thermal storage by sensitive heat, thermal-chemical storage coupled to a thermal solar system, thermal storage by phase change, superconductive inductance storage, super-capacitors. It discusses the criteria of choice of storage technology, either for electric energy storage or for heat storage. It proposes an overview of researches performed within the CEA on storage systems: electrochemical, thermal, and hydrogen-based storages. The final chapter addresses current fundamental researches on storage in the field of lithium-ion batteries, hydrogen as a fuel, and thermoelectricity

  4. Stability of interfacial waves in two-phase flows

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W S [Ontario Hydro, Toronto, ON (Canada)

    1996-12-31

    The influence of the interfacial pressure and the flow distribution in the one-dimensional two-fluid model on the stability problems of interfacial waves is discussed. With a proper formulation of the interfacial pressure, the following two-phase phenomena can be predicted from the stability and stationary criteria of the interfacial waves: onset of slug flow, stationary hydraulic jump in a stratified flow, flooding in a vertical pipe, and the critical void fraction of a bubbly flow. It can be concluded that the interfacial pressure plays an important role in the interfacial wave propagation of the two-fluid model. The flow distribution parameter may enhance the flow stability range, but only plays a minor role in the two-phase characteristics. (author). 20 refs., 3 tabs., 4 figs.

  5. A Generalized Framework for Non-Stationary Extreme Value Analysis

    Science.gov (United States)

    Ragno, E.; Cheng, L.; Sadegh, M.; AghaKouchak, A.

    2017-12-01

    Empirical trends in climate variables including precipitation, temperature, snow-water equivalent at regional to continental scales are evidence of changes in climate over time. The evolving climate conditions and human activity-related factors such as urbanization and population growth can exert further changes in weather and climate extremes. As a result, the scientific community faces an increasing demand for updated appraisal of the time-varying climate extremes. The purpose of this study is to offer a robust and flexible statistical tool for non-stationary extreme value analysis which can better characterize the severity and likelihood of extreme climatic variables. This is critical to ensure a more resilient environment in a changing climate. Following the positive feedback on the first version of Non-Stationary Extreme Value Analysis (NEVA) Toolbox by Cheng at al. 2014, we present an improved version, i.e. NEVA2.0. The upgraded version herein builds upon a newly-developed hybrid evolution Markov Chain Monte Carlo (MCMC) approach for numerical parameters estimation and uncertainty assessment. This addition leads to a more robust uncertainty estimates of return levels, return periods, and risks of climatic extremes under both stationary and non-stationary assumptions. Moreover, NEVA2.0 is flexible in incorporating any user-specified covariate other than the default time-covariate (e.g., CO2 emissions, large scale climatic oscillation patterns). The new feature will allow users to examine non-stationarity of extremes induced by physical conditions that underlie the extreme events (e.g. antecedent soil moisture deficit, large-scale climatic teleconnections, urbanization). In addition, the new version offers an option to generate stationary and/or non-stationary rainfall Intensity - Duration - Frequency (IDF) curves that are widely used for risk assessment and infrastructure design. Finally, a Graphical User Interface (GUI) of the package is provided, making NEVA

  6. Membrane oscillations in the channel of a stationary plasma motor

    International Nuclear Information System (INIS)

    Bugrova, A.I.; Lipatov, A.S.; Morozov, A.I.; Kharchevnikov, V.K.

    1999-01-01

    Results of measuring the ion flux density in the channel of the stationary plasma drive are presented. Two plane easters move both along and transverse to the plasma flux. During the experiment, the strong low-frequency oscillations (∼ 35 kHz) are observed in the channel of the stationary plasma drive. It is found that membrane oscillations are accompanied by oscillations of the electron temperature. These membrane oscillations affect the divergence of the output plasma jet and the erosion of the output part of the channel of the stationary plasma drive [ru

  7. Generating stationary entangled states in superconducting qubits

    International Nuclear Information System (INIS)

    Zhang Jing; Liu Yuxi; Li Chunwen; Tarn, T.-J.; Nori, Franco

    2009-01-01

    When a two-qubit system is initially maximally entangled, two independent decoherence channels, one per qubit, would greatly reduce the entanglement of the two-qubit system when it reaches its stationary state. We propose a method on how to minimize such a loss of entanglement in open quantum systems. We find that the quantum entanglement of general two-qubit systems with controllable parameters can be controlled by tuning both the single-qubit parameters and the two-qubit coupling strengths. Indeed, the maximum fidelity F max between the stationary entangled state, ρ ∞ , and the maximally entangled state, ρ m , can be about 2/3≅max(tr(ρ ∞ ρ m ))=F max , corresponding to a maximum stationary concurrence, C max , of about 1/3≅C(ρ ∞ )=C max . This is significant because the quantum entanglement of the two-qubit system can be produced and kept, even for a long time. We apply our proposal to several types of two-qubit superconducting circuits and show how the entanglement of these two-qubit circuits can be optimized by varying experimentally controllable parameters.

  8. Propagation of Boundary-Induced Discontinuity in Stationary Radiative Transfer

    Science.gov (United States)

    Kawagoe, Daisuke; Chen, I.-Kun

    2018-01-01

    We consider the boundary value problem of the stationary transport equation in the slab domain of general dimensions. In this paper, we discuss the relation between discontinuity of the incoming boundary data and that of the solution to the stationary transport equation. We introduce two conditions posed on the boundary data so that discontinuity of the boundary data propagates along positive characteristic lines as that of the solution to the stationary transport equation. Our analysis does not depend on the celebrated velocity averaging lemma, which is different from previous works. We also introduce an example in two dimensional case which shows that piecewise continuity of the boundary data is not a sufficient condition for the main result.

  9. Investigation of the statistical distance to reach stationary distributions

    International Nuclear Information System (INIS)

    Nicholson, S.B.; Kim, Eun-jin

    2015-01-01

    The thermodynamic length gives a Riemannian metric to a system's phase space. Here we extend the traditional thermodynamic length to the information length (L) out of equilibrium and examine its properties. We utilise L as a useful methodology of analysing non-equilibrium systems without evoking conventional assumptions such as Gaussian statistics, detailed balance, priori-known constraints, or ergodicity and numerically examine how L evolves in time for the logistic map in the chaotic regime depending on initial conditions. To this end, we propose a discrete version of L which is mathematically well defined by taking a set theoretic approach. We identify the areas of phase space where the loss of information of the system takes place most rapidly. In particular, we present an interesting result that the unstable fixed points turn out to most efficiently drive the logistic map towards a stationary distribution through L. - Highlights: • Define a set theoretic version of the discrete thermodynamic length. • These sets allow one to analyse systems having zero probabilities in their evolution. • Numerically analyse the Logistic map using the thermodynamic length. • Show how the unstable fixed points most efficiently lead the system to equilibrium

  10. Framework for Assessing Biogenic CO2 Emissions from Stationary Sources

    Science.gov (United States)

    This revision of the 2011 report, Accounting Framework for Biogenic CO2 Emissions from Stationary Sources, evaluates biogenic CO2 emissions from stationary sources, including a detailed study of the scientific and technical issues associated with assessing biogenic carbon dioxide...

  11. Modeling of electron cyclotron resonance acceleration in a stationary inhomogeneous magnetic field

    Directory of Open Access Journals (Sweden)

    Valeri D. Dougar-Jabon

    2008-04-01

    Full Text Available In this paper, the cyclotron autoresonance acceleration of electrons in a stationary inhomogeneous magnetic field is studied. The trajectory and energy of electrons are found through a numerical solution of the relativistic Newton-Lorentz equation by a finite difference method. The electrons move along a TE_{112} cylinder cavity in a steady-state magnetic field whose axis coincides with the cavity axis. The magnetic field profile is such that it keeps the phase difference between the electric microwave field and the electron velocity vector within the acceleration phase band. The microwaves amplitude of 6  kV/cm is used for numerical calculations. It is shown that an electron with an initial longitudinal energy of 8 keV can be accelerated up to 260 keV by 2.45 GHz microwaves at a distance of 17 cm.

  12. Energy metabolism after U.V.-irradiation in a sensitive yeast strain

    International Nuclear Information System (INIS)

    Kiefer, J.

    1976-01-01

    Stationary-phase cells of an excision-repair deficient diploid yeast (strain 2094) were UV-irradiated at exposures of up to 440 erg mm -2 and then resuspended in fresh medium. Measurements of energy metabolism per cell at periods of up to 6 hours after irradiation showed that cellular respiration was increased for all doses tested from about 3 hours after exposure, whereas fermentation did not start before about 2 hours after irradiation, never significantly exceeded control values and was markedly inhibited by the higher doses. The results suggest that respiration is under nuclear control, since a mutation in one gene is thought to be the only difference between this strain and the wild-type. The D 0 value of about 360 erg mm -2 found for the relative cellular fermentation at 2 hours after irradiation was used to give an estimate of the size of the structural gene involved, of about 3000 nucleotides, or a protein with 1000 amino-acid residues, compatible with the molecular weight of alcohol dehydrogenase. Fermentation can therefore be inhibited in this sensitive strain by lesions in the structural gene of a key enzyme. Since respiration was increased even more in repair-deficient than in repair-proficient strains, it must be assumed that higher energy metabolism is not linked to the repair process, but rather reflects a general disturbance in cellular regulation. (U.K.)

  13. A Novel Vehicle Stationary Detection Utilizing Map Matching and IMU Sensors

    Directory of Open Access Journals (Sweden)

    Md. Syedul Amin

    2014-01-01

    Full Text Available Precise navigation is a vital need for many modern vehicular applications. The global positioning system (GPS cannot provide continuous navigation information in urban areas. The widely used inertial navigation system (INS can provide full vehicle state at high rates. However, the accuracy diverges quickly in low cost microelectromechanical systems (MEMS based INS due to bias, drift, noise, and other errors. These errors can be corrected in a stationary state. But detecting stationary state is a challenging task. A novel stationary state detection technique from the variation of acceleration, heading, and pitch and roll of an attitude heading reference system (AHRS built from the inertial measurement unit (IMU sensors is proposed. Besides, the map matching (MM algorithm detects the intersections where the vehicle is likely to stop. Combining these two results, the stationary state is detected with a smaller timing window of 3 s. A longer timing window of 5 s is used when the stationary state is detected only from the AHRS. The experimental results show that the stationary state is correctly identified and the position error is reduced to 90% and outperforms previously reported work. The proposed algorithm would help to reduce INS errors and enhance the performance of the navigation system.

  14. Generation of an intense stationary wave in modulated beam-plasma systems

    International Nuclear Information System (INIS)

    Jungwirth, K.; Krlin, L.

    1974-03-01

    Basic equations and numerical results describing nonlinear interaction of a weakly modulated electron beam with a single stationary one-dimensional wave excited in a cold plasma without the magnetic field, are presented and discussed. The effect of all possible irreversible processes (e.g., plasma turbulence) accompanying this interaction is simulated by the constant effective collision frequency νsub(eff) of plasma electrons. Starting from the nonlinear Poisson equation, the expression for the amplitude and the phase of the beam-excited wave are derived and solved numerically together with the equations of the beam electron motion. The results are compared with those of a time model. Significant, experimentally detectable differences are established. (author)

  15. Vacillations induced by interference of stationary and traveling planetary waves

    Science.gov (United States)

    Salby, Murry L.; Garcia, Rolando R.

    1987-01-01

    The interference pattern produced when a traveling planetary wave propagates over a stationary forced wave is explored, examining the interference signature in a variety of diagnostics. The wave field is first restricted to a diatomic spectrum consisting of two components: a single stationary wave and a single monochromatic traveling wave. A simple barotropic normal mode propagating over a simple stationary plane wave is considered, and closed form solutions are obtained. The wave fields are then restricted spatially, providing more realistic structures without sacrificing the advantages of an analytical solution. Both stationary and traveling wave fields are calculated numerically with the linearized Primitive Equations in a realistic basic state. The mean flow reaction to the fluctuating eddy forcing which results from interference is derived. Synoptic geopotential behavior corresponding to the combined wave and mean flow fields is presented, and the synoptic signature in potential vorticity on isentropic surfaces is examined.

  16. Costationarity of Locally Stationary Time Series Using costat

    OpenAIRE

    Cardinali, Alessandro; Nason, Guy P.

    2013-01-01

    This article describes the R package costat. This package enables a user to (i) perform a test for time series stationarity; (ii) compute and plot time-localized autocovariances, and (iii) to determine and explore any costationary relationship between two locally stationary time series. Two locally stationary time series are said to be costationary if there exists two time-varying combination functions such that the linear combination of the two series with the functions produces another time...

  17. Wrapped and unwrapped phase of radiation scattered by a discrete number of particles

    International Nuclear Information System (INIS)

    Watson, Stephen M; Ridley, Kevin D

    2007-01-01

    This paper investigates wrapped and unwrapped phase differences generated by a non-Gaussian scattering model: the two-dimensional random walk. Mean square values for these quantities are obtained for one and two scatterers, as well as the large scatterer limit when the field constitutes a circular complex Gaussian process. Numerical simulation is used to investigate the phase under more general fluctuation conditions, and reveals that the wrapped phase difference correlation converges rapidly to that result predicted for a Gaussian speckle field. Analytical results for the unwrapped phase indicate that this quantity transitions from a stationary process for one and two scatterers to a non-stationary process in the large scatterer limit. The nature of this transition is examined using numerical simulation for arbitrary scatterer number. Phase correlations are of consequence in various phase sensitive detection systems, and this paper examines both Gaussian and non-Gaussian fields

  18. Phase diagrams and switching of voltage and magnetic field in dilute magnetic semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo, R. [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, M.; Bonilla, L.L. [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Maths., Universidad Carlos III de Madrid, 28911 Leganes (Spain); Unidad Asociada al Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain)

    2010-04-15

    The response of an n-doped dc voltage biased II-VI multi-quantum well dilute magnetic semiconductor nanostructure having its first well doped with magnetic (Mn) impurities is analyzed by sweeping wide ranges of both the voltage and the Zeeman level splitting induced by an external magnetic field. The level splitting versus voltage phase diagram shows regions of stable self-sustained current oscillations immersed in a region of stable stationary states. Transitions between stationary states and self-sustained current oscillations are systematically analyzed by both voltage and level splitting abrupt switching. Sudden voltage or/and magnetic field changes may switch on current oscillations from an initial stationary state, and reciprocally, current oscillations may disappear after sudden changes of voltage or/and magnetic field changes into the stable stationary states region. The results show how to design such a device to operate as a spin injector and a spin oscillator by tuning the Zeeman splitting (through the applied external magnetic field), the applied voltage and the sample configuration parameters (doping density, barrier and well widths, etc.) to select the desired stationary or oscillatory behavior. Phase diagram of Zeeman level splitting {delta} vs. dimensionless applied voltage {phi} for N = 10 QWs. White region: stable stationary states; black: stable self-sustained current oscillations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Construção de câmara de luz ultravioleta para fotopolimerização de fases estacionárias monolíticas Coinstruction of ultraviolet-light chamber for monolithic stationary phases photo-polymerization

    Directory of Open Access Journals (Sweden)

    Fernando Antonio Simas Vaz

    2008-01-01

    Full Text Available The assembly of a photochemical reactor with six fluorescent lamps, used for photopolymerizations is described. This chamber presents a mobile support, allowing the placement of samples at different heights and a safety lock that interrupts the radiation, if it is opened during operation. The mirrored internal walls avoid the dispersion and non-uniform distribution of light. There is no high heating because the own character of the used lamps. All parts could be purchased in commerce with less than U$ 150,00. This reactor was successfully used for monolithic stationary phase photopolymerization.

  20. Non-stationary pre-envelope covariances of non-classically damped systems

    Science.gov (United States)

    Muscolino, G.

    1991-08-01

    A new formulation is given to evaluate the stationary and non-stationary response of linear non-classically damped systems subjected to multi-correlated non-separable Gaussian input processes. This formulation is based on a new and more suitable definition of the impulse response function matrix for such systems. It is shown that, when using this definition, the stochastic response of non-classically damped systems involves the evaluation of quantities similar to those of classically damped ones. Furthermore, considerations about non-stationary cross-covariances, spectral moments and pre-envelope cross-covariances are presented for a monocorrelated input process.

  1. Two-phase flow characterisation by nuclear magnetic resonance

    International Nuclear Information System (INIS)

    Leblond, J.; Javelot, S.; Lebrun, D.; Lebon, L.

    1998-01-01

    The results presented in this paper demonstrate the performance of the PFGSE-NMR to obtain a complete characterisation of two-phase flows. Different methods are proposed to characterise air-water flows in different regimes: stationary two-phase flows and flows in transient condition. Finally a modified PFGSE is proposed to analyse the turbulence of air-water bubbly flow. (author)

  2. An ER protein functionally couples neutral lipid metabolism on lipid droplets to membrane lipid synthesis in the ER.

    Science.gov (United States)

    Markgraf, Daniel F; Klemm, Robin W; Junker, Mirco; Hannibal-Bach, Hans K; Ejsing, Christer S; Rapoport, Tom A

    2014-01-16

    Eukaryotic cells store neutral lipids such as triacylglycerol (TAG) in lipid droplets (LDs). Here, we have addressed how LDs are functionally linked to the endoplasmic reticulum (ER). We show that, in S. cerevisiae, LD growth is sustained by LD-localized enzymes. When LDs grow in early stationary phase, the diacylglycerol acyl-transferase Dga1p moves from the ER to LDs and is responsible for all TAG synthesis from diacylglycerol (DAG). During LD breakdown in early exponential phase, an ER membrane protein (Ice2p) facilitates TAG utilization for membrane-lipid synthesis. Ice2p has a cytosolic domain with affinity for LDs and is required for the efficient utilization of LD-derived DAG in the ER. Ice2p breaks a futile cycle on LDs between TAG degradation and synthesis, promoting the rapid relocalization of Dga1p to the ER. Our results show that Ice2p functionally links LDs with the ER and explain how cells switch neutral lipid metabolism from storage to consumption. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  3. An ER Protein Functionally Couples Neutral Lipid Metabolism on Lipid Droplets to Membrane Lipid Synthesis in the ER

    Directory of Open Access Journals (Sweden)

    Daniel F. Markgraf

    2014-01-01

    Full Text Available Eukaryotic cells store neutral lipids such as triacylglycerol (TAG in lipid droplets (LDs. Here, we have addressed how LDs are functionally linked to the endoplasmic reticulum (ER. We show that, in S. cerevisiae, LD growth is sustained by LD-localized enzymes. When LDs grow in early stationary phase, the diacylglycerol acyl-transferase Dga1p moves from the ER to LDs and is responsible for all TAG synthesis from diacylglycerol (DAG. During LD breakdown in early exponential phase, an ER membrane protein (Ice2p facilitates TAG utilization for membrane-lipid synthesis. Ice2p has a cytosolic domain with affinity for LDs and is required for the efficient utilization of LD-derived DAG in the ER. Ice2p breaks a futile cycle on LDs between TAG degradation and synthesis, promoting the rapid relocalization of Dga1p to the ER. Our results show that Ice2p functionally links LDs with the ER and explain how cells switch neutral lipid metabolism from storage to consumption.

  4. Hydrogen Fuel Cell Analysis: Lessons Learned from Stationary Power Generation Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Scott E. Grasman; John W. Sheffield; Fatih Dogan; Sunggyu Lee; Umit O. Koylu; Angie Rolufs

    2010-04-30

    This study considered opportunities for hydrogen in stationary applications in order to make recommendations related to RD&D strategies that incorporate lessons learned and best practices from relevant national and international stationary power efforts, as well as cost and environmental modeling of pathways. The study analyzed the different strategies utilized in power generation systems and identified the different challenges and opportunities for producing and using hydrogen as an energy carrier. Specific objectives included both a synopsis/critical analysis of lessons learned from previous stationary power programs and recommendations for a strategy for hydrogen infrastructure deployment. This strategy incorporates all hydrogen pathways and a combination of distributed power generating stations, and provides an overview of stationary power markets, benefits of hydrogen-based stationary power systems, and competitive and technological challenges. The motivation for this project was to identify the lessons learned from prior stationary power programs, including the most significant obstacles, how these obstacles have been approached, outcomes of the programs, and how this information can be used by the Hydrogen, Fuel Cells & Infrastructure Technologies Program to meet program objectives primarily related to hydrogen pathway technologies (production, storage, and delivery) and implementation of fuel cell technologies for distributed stationary power. In addition, the lessons learned address environmental and safety concerns, including codes and standards, and education of key stakeholders.

  5. Genetic variation in eleven phase I drug metabolism genes in an ethnically diverse population.

    Science.gov (United States)

    Solus, Joseph F; Arietta, Brenda J; Harris, James R; Sexton, David P; Steward, John Q; McMunn, Chara; Ihrie, Patrick; Mehall, Janelle M; Edwards, Todd L; Dawson, Elliott P

    2004-10-01

    The extent of genetic variation found in drug metabolism genes and its contribution to interindividual variation in response to medication remains incompletely understood. To better determine the identity and frequency of variation in 11 phase I drug metabolism genes, the exons and flanking intronic regions of the cytochrome P450 (CYP) isoenzyme genes CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP3A5 were amplified from genomic DNA and sequenced. A total of 60 kb of bi-directional sequence was generated from each of 93 human DNAs, which included Caucasian, African-American and Asian samples. There were 388 different polymorphisms identified. These included 269 non-coding, 45 synonymous and 74 non-synonymous polymorphisms. Of these, 54% were novel and included 176 non-coding, 14 synonymous and 21 non-synonymous polymorphisms. Of the novel variants observed, 85 were represented by single occurrences of the minor allele in the sample set. Much of the variation observed was from low-frequency alleles. Comparatively, these genes are variation-rich. Calculations measuring genetic diversity revealed that while the values for the individual genes are widely variable, the overall nucleotide diversity of 7.7 x 10(-4) and polymorphism parameter of 11.5 x 10(-4) are higher than those previously reported for other gene sets. Several independent measurements indicate that these genes are under selective pressure, particularly for polymorphisms corresponding to non-synonymous amino acid changes. There is relatively little difference in measurements of diversity among the ethnic groups, but there are large differences among the genes and gene subfamilies themselves. Of the three CYP subfamilies involved in phase I drug metabolism (1, 2, and 3), subfamily 2 displays the highest levels of genetic diversity.

  6. Stationary strings near a higher-dimensional rotating black hole

    International Nuclear Information System (INIS)

    Frolov, Valeri P.; Stevens, Kory A.

    2004-01-01

    We study stationary string configurations in a space-time of a higher-dimensional rotating black hole. We demonstrate that the Nambu-Goto equations for a stationary string in the 5D (five-dimensional) Myers-Perry metric allow a separation of variables. We present these equations in the first-order form and study their properties. We prove that the only stationary string configuration that crosses the infinite redshift surface and remains regular there is a principal Killing string. A worldsheet of such a string is generated by a principal null geodesic and a timelike at infinity Killing vector field. We obtain principal Killing string solutions in the Myers-Perry metrics with an arbitrary number of dimensions. It is shown that due to the interaction of a string with a rotating black hole, there is an angular momentum transfer from the black hole to the string. We calculate the rate of this transfer in a space-time with an arbitrary number of dimensions. This effect slows down the rotation of the black hole. We discuss possible final stationary configurations of a rotating black hole interacting with a string

  7. Identification of QRS complex in non-stationary electrocardiogram of sick infants.

    Science.gov (United States)

    Kota, S; Swisher, C B; Al-Shargabi, T; Andescavage, N; du Plessis, A; Govindan, R B

    2017-08-01

    Due to the high-frequency of routine interventions in an intensive care setting, electrocardiogram (ECG) recordings from sick infants are highly non-stationary, with recurrent changes in the baseline, alterations in the morphology of the waveform, and attenuations of the signal strength. Current methods lack reliability in identifying QRS complexes (a marker of individual cardiac cycles) in the non-stationary ECG. In the current study we address this problem by proposing a novel approach to QRS complex identification. Our approach employs lowpass filtering, half-wave rectification, and the use of instantaneous Hilbert phase to identify QRS complexes in the ECG. We demonstrate the application of this method using ECG recordings from eight preterm infants undergoing intensive care, as well as from 18 normal adult volunteers available via a public database. We compared our approach to the commonly used approaches including Pan and Tompkins (PT), gqrs, wavedet, and wqrs for identifying QRS complexes and then compared each with manually identified QRS complexes. For preterm infants, a comparison between the QRS complexes identified by our approach and those identified through manual annotations yielded sensitivity and positive predictive values of 99% and 99.91%, respectively. The comparison metrics for each method are as follows: PT (sensitivity: 84.49%, positive predictive value: 99.88%), gqrs (85.25%, 99.49%), wavedet (95.24%, 99.86%), and wqrs (96.99%, 96.55%). Thus, the sensitivity values of the four methods previously described, are lower than the sensitivity of the method we propose; however, the positive predictive values of these other approaches is comparable to those of our method, with the exception of the wqrs approach, which yielded a slightly lower value. For adult ECG, our approach yielded a sensitivity of 99.78%, whereas PT yielded 99.79%. The positive predictive value was 99.42% for both our approach as well as for PT. We propose a novel method for

  8. Quantum field theory in stationary coordinate systems

    International Nuclear Information System (INIS)

    Pfautsch, J.D.

    1981-01-01

    Quantum field theory is examined in stationary coordinate systems in Minkowski space. Preliminary to quantization of the scalar field, all of the possible stationary coordinate systems in flat spacetime are classified and explicitly constructed. Six distinct classes of such systems are found. Of these six, three have (identical) event horizons associated with them and five have Killing horizons. Two classes have distinct Killing and event horizons, with an intervening region analogous to the ergosphere in rotating black holes. Particular representatives of each class are selected for subsequent use in the quantum field theory. The scalar field is canonically quantized and a vacuum defined in each of the particular coordinate systems chosen. The vacuum states can be regarded as adapted to the six classes of stationary motions. There are only two vacuum states found, the Minkowski vacuum in those coordinate systems without event horizons and the Fulling vacuum in those with event horizons. The responses of monopole detectors traveling along stationary world lines are calculated in both the Minkowski and Fulling vacuums. The responses for each class of motions are distinct from those for every other class. A vacuum defined by the response of a detector must therefore not be equivalent in general to a vacuum defined by canonical quantization. Quantization of the scalar field within a rotating wedge is examined. It has not been possible to construct mode functions satisfying appropriate boundary conditions on the surface of the wedge. The asymptotic form of the renormalized stress tensor near the surfaces had been calculated and is found to include momentum terms which represent a circulation of energy within the wedge

  9. Expansions of general stationary stochastic optical fields: general formalism

    International Nuclear Information System (INIS)

    Martinez-Herrero, R.; Mejias, P.M.

    1985-01-01

    A new expansion of a general stationary stochastic optical field is derived. Each term of the series is seen to represent a recently defined new class of optical fields, the so-called spectrally quasi-factorizable fields. Alternative expansion in terms of nonstationary fields that obey the wave equation is also shown. A relationship between temporal and spatial features of stationary free optical fields is discussed

  10. Geophysics-based method of locating a stationary earth object

    Science.gov (United States)

    Daily, Michael R [Albuquerque, NM; Rohde, Steven B [Corrales, NM; Novak, James L [Albuquerque, NM

    2008-05-20

    A geophysics-based method for determining the position of a stationary earth object uses the periodic changes in the gravity vector of the earth caused by the sun- and moon-orbits. Because the local gravity field is highly irregular over a global scale, a model of local tidal accelerations can be compared to actual accelerometer measurements to determine the latitude and longitude of the stationary object.

  11. Chapter 5: Modeling and Control of Three-Phase AC/DC Converter Including Phase-Locked Loop

    DEFF Research Database (Denmark)

    Zhou, Dao; Song, Yipeng; Blaabjerg, Frede

    2018-01-01

    In this chapter, a mathematical model of the power circuit of a three-phase AC/DC converter is developed in the stationary and synchronous reference frames. Then, the operation principle of the phasor locked loop is addressed to exact the angle information of the power grid to realize the accurat...

  12. Stationary nonimaging lenses for solar concentration.

    Science.gov (United States)

    Kotsidas, Panagiotis; Chatzi, Eleni; Modi, Vijay

    2010-09-20

    A novel approach for the design of refractive lenses is presented, where the lens is mounted on a stationary aperture and the Sun is tracked by a moving solar cell. The purpose of this work is to design a quasi-stationary concentrator by replacing the two-axis tracking of the Sun with internal motion of the miniaturized solar cell inside the module. Families of lenses are designed with a variation of the simultaneous multiple surface technique in which the sawtooth genetic algorithm is implemented to optimize the geometric variables of the optic in order to produce high fluxes for a range of incidence angles. Finally, we show examples of the technique for lenses with 60° and 30° acceptance half-angles, with low to medium attainable concentrations.

  13. Modeling stationary and dynamic pebbles in a pebble bed reactor

    International Nuclear Information System (INIS)

    Zhao, Xiang; Montgomery, Trent; Zhang, Sijun

    2011-01-01

    This paper presents a numerical study of the stationary and dynamic pebbles in a pebble bed reactor (PBR) by means of discrete element method (DEM). At first, the packing structure of stationary pebbles is simulated by filling process until the settling of pebbles into PBR. The packing structural properties are obtained and analyzed. Subsequently, when the outlet of PBR is open during the operational maintenance of PBR, the stationary pebbles start to flow downward and are removed at the bottom of PBR. The dynamic behavior of pebbles is predicted and discussed. Our results indicate the DEM can offer both macroscopic and microscopic information for PBR design calculations and safety assessment. (author)

  14. Couplings in Phase Domain Impedance Modelling of Grid-Connected Converters

    DEFF Research Database (Denmark)

    Dowlatabadi, Mohammadkazem Bakhshizadeh; Wang, Xiongfei; Blaabjerg, Frede

    2016-01-01

    The output impedance of a power converter plays an important role in the stability assessment of the converter. The impedance can be expressed in different frames such as the stationary frame (phase domain) or in the synchronous frame (dq domain). To treat the three-phase system like a single...

  15. Characterisation of two-phase horizontal flow regime transition by the application of time-frequency analysis methods

    International Nuclear Information System (INIS)

    Seleghim, Paulo

    1996-01-01

    This work concerns the development of a methodology which objective is to characterize and diagnose two-phase flow regime transitions. The approach is based on the fundamental assumption that a transition flow is less stationary than a flow with an established regime. In a first time, the efforts focused on: 1) the design and construction of an experimental loop, allowing to reproduce the main horizontal two-phase flow patterns, in a stable and controlled way, 2) the design and construction of an electrical impedance probe, providing an imaged information of the spatial phase distribution in the pipe, the systematic study of the joint time-frequency and time-scale analysis methods, which permitted to define an adequate parameter quantifying the un-stationary degree. In a second time, in order to verify the fundamental assumption, a series of experiments were conducted, which objective was to demonstrate the correlation between un-stationary and regime transition. The un-stationary degree was quantified by calculating the Gabor's transform time-frequency covariance of the impedance probe signals. Furthermore, the phenomenology of each transition was characterized by the joint moments and entropy. The results clearly show that the regime transitions are correlated with local-time frequency covariance peaks, which demonstrates that these regime transitions are characterized by a loss of stationarity. Consequently, the time-frequency covariance constitutes an objective two-phase flow regime transition indicator. (author) [fr

  16. Evaluation of the chiral recognition properties as well as the column performance of four chiral stationary phases based on cellulose (3,5-dimethylphenylcarbamate) by parallel HPLC and SFC.

    Science.gov (United States)

    Nelander, Hanna; Andersson, Shalini; Ohlén, Kristina

    2011-12-30

    The performance of four commercially available cellulose tris(3,5-dimethylphenylcarbamate) based chiral stationary phases (CSPs) was evaluated with parallel high performance liquid chromatography (HPLC) and super critical fluid chromatography (SFC). Retention, enantioselectivity, resolution and efficiency were compared for a set of neutral, basic and acidic compounds having different physico-chemical properties by using different mobile phase conditions. Although the chiral selector is the same in all the four CSPs, a large difference in the ability to retain and resolve enantiomers was observed under the same chromatographic conditions. We believe that this is mainly due to differences in the silica matrix and immobilization techniques used by the different vendors. An extended study of metoprolol and structure analogues gave a deeper understanding of the accessibility of the chiral discriminating interactions and its impact on the resolution of the racemic compounds on the four CSPs studied. Also, a clear difference in enantioselectivity is observed between SFC and LC mode, hydrogen bonding was found to play an important role in the differential binding of the enantiomers to the CSPs. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Stationary theory of scattering

    International Nuclear Information System (INIS)

    Kato, T.

    1977-01-01

    A variant of the stationary methods is described, and it is shown that it is useful in a wide range of problems, including scattering, by long-range potentials, two-space scattering, and multichannel scattering. The method is based on the notion of spectral forms. The paper is restricted to the simplest case of continuous spectral forms defined on a Banach space embedded in the basic Hilbert space. (P.D.)

  18. Carbon nanotube based stationary phases for microchip chromatography

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo; Kutter, Jörg Peter

    2012-01-01

    already been demonstrated in more classical formats, for improved separation performance in gas and liquid chromatography, and for unique applications in solid phase extraction. Carbon nanotubes are now also entering the field of microfluidics, where there is a large potential to be able to provide......The objective of this article is to provide an overview and critical evaluation of the use of carbon nanotubes and related carbon-based nanomaterials for microchip chromatography. The unique properties of carbon nanotubes, such as a very high surface area and intriguing adsorptive behaviour, have...... integrated, tailor-made nanotube columns by means of catalytic growth of the nanotubes inside the fluidic channels. An evaluation of the different implementations of carbon nanotubes and related carbon-based nanomaterials for microfluidic chromatography devices is given in terms of separation performance...

  19. Radio-Oxidation in Polyolefins: Non-Stationary Kinetic Conditions

    International Nuclear Information System (INIS)

    Dely, N.

    2006-01-01

    In the last fifty years, many authors have been interested in the radio-oxidation processes occurring in polymers. The polymer degradation under ionising radiations in presence of dioxygen is well described by a radical chemistry. The radio-oxidation process occurs in three steps: the first one is the production of radicals P degree by interaction between the polymer and the ionising radiations; then radicals P degree react spontaneously with O 2 solved in the polymer giving a peroxy radical POO degree which attacks the polymer forming a hydroperoxide POOH and a new radical P degree (propagation). The third step corresponds to the termination step, that is bimolecular reactions between radicals. It is generally assumed that the stationary state is rapidly reached and consequently that the oxidation induced during the built-up period of the radical concentration can be neglected. However, to our best knowledge, the temporal evolution of radical concentrations before reaching the steady state regime has never been studied in details. We recently performed a complete study of oxygen consumption under electron irradiation for an EPDM elastomer. An analysis, as function of dose rate and oxygen pressure, and assuming steady state conditions, allowed extracting all the kinetic constants. Starting for these experimental data, we calculated the build-up of the radical concentration by solving numerically the differential equations with help of the Minichem code. We conclude that, in fact, the oxidation induced during the built-up period is negligible. In this paper we show that [P degree] could present a quasi-stationary plateau before reaching its stationary level. Consequently, the full radical time evolution is essentially determined by two characteristic times for reaching the quasi and stationary levels and three concentrations: [P degree] and [POO degree] at the stationary level and [P degree] at the quasi-stationary plateau. We show that realistic approximations can

  20. On the GI/M/1 Queue with Vacations and Multiple Service Phases

    Directory of Open Access Journals (Sweden)

    Jianjun Li

    2017-01-01

    Full Text Available This paper considers a GI/M/1 queue with vacations and multiple service phases. Whenever the system becomes empty, the server takes a vacation, causing the system to move to vacation phase 0. If the server returns from a vacation to find no customer waiting, another vacation begins. Otherwise, the system jumps from phase 0 to some service phase i with probability qi,  i=1,2,…,N. Using the matrix geometric solution method and semi-Markov process, we obtain the distributions of the stationary system size at both arrival and arbitrary epochs. The distribution of the stationary waiting time of an arbitrary customer is also derived. In addition, we present some performance measures such as mean waiting time of an arbitrary customer, mean length of the type-i cycle, and mean number of customers in the system at the end of phase 0. Finally, some numerical examples are presented.

  1. A direct HPLC method for the resolution and quantitation of the R-(-)- and S-(+)-enantiomers of vigabatrin (gamma-vinyl-GABA) in pharmaceutical dosage forms using teicoplanin aglycone chiral stationary phase.

    Science.gov (United States)

    Al-Majed, Abdulrahman A

    2009-08-15

    A direct chiral high-performance liquid chromatography (HPLC) method was developed and validated for the resolution and quantification of antiepileptic drug enantiomers, R-(-)- and S-(+)-vigabatrin (gamma-vinyl-gamma-aminobutyric acid) in pharmaceutical products. The separation was optimized on a macrocyclic glycopeptide antibiotic chiral stationary phase (CSP) based on teicoplanin aglycone, chirobiotic (TAG), using a mobile phase system containing ethanol-water (80:20, v/v), at a flow rate of 0.4ml/min and UV detection set at 210nm. The stability of vigabatrin enantiomers under different degrees of temperature was also studied. The enantiomers of vigabatrin were separated from each other. The calibration curves were linear over a range of 100-1600microg/ml (r=0.999) for both enantiomers. The overall recoveries of R-(-)- and S-(+)-vigabatrin enantiomers from pharmaceutical products were in the range of 98.3-99.8% with %RSD ranged from 0.48 to 0.52%. The limit of quantification (LOQ) and limit of detection (LOD) for each enantiomer were 100 and 25microg/ml, respectively. No interferences were found from commonly co-formulated excipients.

  2. Stationary neoclassical profiles of plasma parameters in stellarators

    International Nuclear Information System (INIS)

    Danilkin, I.S.; Mineev, A.B.

    1991-01-01

    Peculiarities of neoclassical model of heat and particle transfer, occuring by calculations of plasma stationary profile parameters in stellarators are considered. The main peculiarity out of all consists in ineadequate compatibility with real physical conditions on the boundary, requiring application of supplementary 'anomalous' transfer or special (but technically possible) adjustment of particle and heat sources to achieve solution in form of 'correct' monotonically sloping profile. It is stated, that neoclassical theory does not provide for well-known ambiguity of solutions for ambipolar electrical field by search of monotonous stationary profiles supported by outside sources

  3. Spin in stationary gravitational fields and rotating frames

    International Nuclear Information System (INIS)

    Obukhov, Yuri N.; Silenko, Alexander J.; Teryaev, Oleg V.

    2010-01-01

    A spin motion of particles in stationary spacetimes is investigated in the framework of the classical gravity and relativistic quantum mechanics. We bring the Dirac equation for relativistic particles in nonstatic spacetimes to the Hamiltonian form and perform the Foldy-Wouthuysen transformation. We show the importance of the choice of tetrads for description of spin dynamics in the classical gravity. We derive classical and quantum mechanical equations of motion of the spin for relativistic particles in stationary gravitational fields and rotating frames and establish the full agreement between the classical and quantum mechanical approaches.

  4. Backset-stationary and during car driving.

    Science.gov (United States)

    Jonsson, Bertil; Stenlund, Hans; Björnstig, Ulf

    2008-12-01

    The aim of the study was to measure and analyze backset, defined as the horizontal distance between the back of the occupant's head and a point located on the ventral/top aspect of the sewn rim of the head restraint, with the car stationary and during driving, in the driver's position in a modern car. A population of 65 subjects, 35 males and 30 females, was studied in a Volvo V70 car, model year 2007. The subjects were studied in the driver's position, in a self-selected posture. Stationary backset was measured with the technique described by Jonsson et al. (2007) and backset during driving with video analysis. Descriptive data were calculated, and variability and correlation analyses were performed. A t-test was used to test differences of means. Significance level was set to 0.05. In comparison to stationary backset, mean backset during driving was 43 mm greater in males and 41 mm greater in females. Driving backset was 44 mm larger in males than in females. Driving backset was moderately correlated (0.37-0.43) to stature, seated height, and seat back angle in males and moderately correlated (0.44-0.52) to hip width, waist circumference, and weight in females. The overall intraclass correlation coefficient for backset during driving was 0.81 (CI: 0.75-0.86). These results may be of use in designing future updates of test protocols/routines for geometric backset, such as RCAR and RCAR-IIWPG.

  5. Stationary flywheel energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Gilhaus, A; Hau, E; Gassner, G; Huss, G; Schauberger, H

    1981-01-01

    The aim of this system study is to find out industrial applications of stationary flywheel energy accumulators. The economic value for the consumer and the effects on the power supply grid are investigated. Up to now, stationary flywheel energy accumulators have only been used in a small range. The main reason for thinking of the application in a wider range was the hope that those could be used economically for lowering the maximum output demand of the power supply grid. The possible savings in energy costs, however, proved to be too small for paying back the investment costs. Further benefits are necessary for advantageous application. As to overall economy, compensation of short time maximum power output seems to be more favorable at the power stations. An additional possibility for energy storage by flywheels is given where otherwise lost energy can be used effectively, according to the successful brake energy storage in vehicles. Under this aspect the future use of flywheels in wind-power-plants seems to be promising. Attractive savings of energy can be obtained by introducing modern flywheel technology for emergency power supply units which are employed for instance in telecommunication systems. Especially the application for emergency power supply, in power stations and in combustion with wind energy converters need further investigation.

  6. Removal of Pyrimethanil and Fenhexamid from Saccharomyces cerevisiae Liquid Cultures

    Directory of Open Access Journals (Sweden)

    Etjen Bizaj

    2011-01-01

    Full Text Available The capacity for the removal of pyrimethanil and fenhexamid, two fungicides commonly used for the control of Botrytis cinerea in vineyards, has been evaluated during an alcoholic fermentation process in batch system. Commercial and wild strains of Saccharomyces cerevisiae were used. Batch fermentations were carried out in yeast extract-malt extract medium (YM with 18.0 % (by mass glucose, and the fungicides were added separately at three concentrations: 0.1, 1.0 and 10.0 mg/L. The removal capacity of yeast strains was also examined in stationary phase cultures of Saccharomyces cerevisiae. Stationary assays were performed with yeast biomass harvested from the stationary phase of an anaerobic fermentation process, with separate additions of 0.1, 1.0 and 10.0 mg/L of both fungicides. Removal studies with stationary phase cells were performed with viable and non-viable cells inactivated with sodium azide. This study clearly shows that both Saccharomyces cerevisiae strains were able to remove fenhexamid and pyrimethanil in stationary and fermentative assays. The removal potential is shown to be strain dependent in stationary but not in fermentative assays. However, the removal potential is dependent on the type of fungicide in both stationary and fermentative assays. In stationary phase cultures no significant difference in fungicide removal potential between viable and non-viable cells was observed, indicating that both pesticides were not degraded by metabolically active cells. However, the presence of both pesticides influenced fermentation kinetics and only pyrimethanil at 10.0 mg/L increased the production of volatile acidity of both strains.

  7. Distinguishing Stationary/Nonstationary Scaling Processes Using Wavelet Tsallis q-Entropies

    Directory of Open Access Journals (Sweden)

    Julio Ramirez Pacheco

    2012-01-01

    Full Text Available Classification of processes as stationary or nonstationary has been recognized as an important and unresolved problem in the analysis of scaling signals. Stationarity or nonstationarity determines not only the form of autocorrelations and moments but also the selection of estimators. In this paper, a methodology for classifying scaling processes as stationary or nonstationary is proposed. The method is based on wavelet Tsallis q-entropies and particularly on the behaviour of these entropies for scaling signals. It is demonstrated that the observed wavelet Tsallis q-entropies of 1/f signals can be modeled by sum-cosh apodizing functions which allocates constant entropies to a set of scaling signals and varying entropies to the rest and that this allocation is controlled by q. The proposed methodology, therefore, differentiates stationary signals from non-stationary ones based on the observed wavelet Tsallis entropies for 1/f signals. Experimental studies using synthesized signals confirm that the proposed method not only achieves satisfactorily classifications but also outperforms current methods proposed in the literature.

  8. Determination and theoretical analysis of supercritical fluid chromatographic retention of polycyclic aromatic hydrocarbons in a polymeric smectic phase

    International Nuclear Information System (INIS)

    Chao Yan; Martire, D.E.

    1992-01-01

    A mean-field lattice model is used to describe the partitioning of blocklike molecules between an isotropic mobile phase and an anisotropic stationary phase in chromatography by applying it to supercritical fluid retention of polycyclic aromatic hydrocarbons in a polymeric smectic phase. This concludes that the logarithm of the capacity factor (1) increases linearly with increasing reciprocal temperature, (2) decreases with increasing mobile phase density more rapidly for solute molecules with a relatively larger contact area with the mobile phase, and (3) is a linear function of the minimum area. The van't Hoff plot slope is also determined to be more negative for solute molecules with a relatively larger ratio of contact area with the stationary phase versus the mobile phase. 18 refs., 9 figs., 5 tabs

  9. Stationary Density Variation Produced by a Standing Plasma Wave

    DEFF Research Database (Denmark)

    Michelsen, Poul; Pécseli, Hans; Juul Rasmussen, Jens

    1977-01-01

    Measurements are presented of a stationary density modulation produced by a standing electron plasma wave. The experimental results are well explained by taking into account the ponderomotive forces on the electrons exerted by the high frequency field.......Measurements are presented of a stationary density modulation produced by a standing electron plasma wave. The experimental results are well explained by taking into account the ponderomotive forces on the electrons exerted by the high frequency field....

  10. Pushing concentration of stationary solar concentrators to the limit.

    Science.gov (United States)

    Winston, Roland; Zhang, Weiya

    2010-04-26

    We give the theoretical limit of concentration allowed by nonimaging optics for stationary solar concentrators after reviewing sun- earth geometry in direction cosine space. We then discuss the design principles that we follow to approach the maximum concentration along with examples including a hollow CPC trough, a dielectric CPC trough, and a 3D dielectric stationary solar concentrator which concentrates sun light four times (4x), eight hours per day year around.

  11. Tightly localized stationary pulses in a multilevel atomic system

    International Nuclear Information System (INIS)

    Liu, Xiong-Jun; Oh, C. H.; Liu, Xin; Liu, Zheng-Xin; Kwek, L. C.

    2007-01-01

    We show that the pulse matching phenomenon can be obtained in the general multilevel system with electromagnetically induced transparency. For this we find a different way to create tightly localized stationary pulses by using counterpropagating pump fields. The present process is a spatial compression of excitation so that it allows us to shape and further intensify the localized stationary pulses, without using standing waves of pump fields or spatially modulated pump fields

  12. Non-stationary Markov chains

    OpenAIRE

    Mallak, Saed

    1996-01-01

    Ankara : Department of Mathematics and Institute of Engineering and Sciences of Bilkent University, 1996. Thesis (Master's) -- Bilkent University, 1996. Includes bibliographical references leaves leaf 29 In thi.s work, we studierl the Ergodicilv of Non-Stationary .Markov chains. We gave several e.xainples with different cases. We proved that given a sec[uence of Markov chains such that the limit of this sec|uence is an Ergodic Markov chain, then the limit of the combination ...

  13. Stationary fuel cell systems. Danish strategy for maturing micro- combined power and heat generation for the market. To make the house owners environmentally conscious prosumers; Stationaere braendselscellesystemer. Dansk plan for markedsmodning af mikrokraftvarme. Goer boligejerne til miljoevenlige prosumenter

    Energy Technology Data Exchange (ETDEWEB)

    2011-04-15

    The aim of this new market maturing plan is to show how innovative technologies for micro stationary fuel cell cogeneration systems can enter both the Danish and the international markets. The report first presents a general description of all types of stationary plants. Not all of them are yet ready for commercialization - some are still in the research and development phase. The plan documents that there is a need for incentives for maturing the technologies for the market after the demonstration phase, and it presents methods for market introduction in Denmark and internationally. (ln)

  14. The Changes of Energy Interactions between Nucleus Function and Mitochondria Functions Causing Transmutation of Chronic Inflammation into Cancer Metabolism.

    Science.gov (United States)

    Ponizovskiy, Michail R

    2016-01-01

    Interactions between nucleus and mitochondria functions induce the mechanism of maintenance stability of cellular internal energy according to the first law of thermodynamics in able-bodied cells and changes the mechanisms of maintenance stability of cellular internal energy creating a transition stationary state of ablebodied cells into quasi-stationary pathologic states of acute inflammation transiting then into chronic inflammation and then transmuting into cancer metabolism. The mechanisms' influences of intruding etiologic pathologic agents (microbe, virus, etc.) lead to these changes of energy interactions between nucleus and mitochondria functions causing general acute inflammation, then passing into local chronic inflammation, and reversing into cancer metabolism transmutation. Interactions between biochemical processes and biophysical processes of cellular capacitors' operations create a supplementary mechanism of maintenance stability of cellular internal energy in the norm and in pathology. Discussion of some scientific works eliminates doubts of the authors of these works.

  15. Ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography.

    Science.gov (United States)

    Pesek, Joseph J; Matyska, Maria T

    2015-07-03

    The use of ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography with silica hydride-based stationary phases and mass spectrometry detection is evaluated. Retention times, peak shape, efficiency and peak intensity are compared to the more standard additives formic acid and ammonium formate. The test solutes were NAD, 3-hydroxyglutaric acid, α-ketoglutaric acid, p-aminohippuric acid, AMP, ATP, aconitic acid, threonine, N-acetyl carnitine, and 3-methyladipic acid. The column parameters are assessed in both the positive and negative ion detection modes. Ammonium fluoride is potentially an aggressive mobile phase additive that could have detrimental effects on column lifetime. Column reproducibility is measured and the effects of switching between different additives are also tested. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Phase I to II cross-induction of xenobiotic metabolizing enzymes: A feedforward control mechanism for potential hormetic responses

    International Nuclear Information System (INIS)

    Zhang Qiang; Pi Jingbo; Woods, Courtney G.; Andersen, Melvin E.

    2009-01-01

    Hormetic responses to xenobiotic exposure likely occur as a result of overcompensation by the homeostatic control systems operating in biological organisms. However, the mechanisms underlying overcompensation that leads to hormesis are still unclear. A well-known homeostatic circuit in the cell is the gene induction network comprising phase I, II and III metabolizing enzymes, which are responsible for xenobiotic detoxification, and in many cases, bioactivation. By formulating a differential equation-based computational model, we investigated in this study whether hormesis can arise from the operation of this gene/enzyme network. The model consists of two feedback and one feedforward controls. With the phase I negative feedback control, xenobiotic X activates nuclear receptors to induce cytochrome P450 enzyme, which bioactivates X into a reactive metabolite X'. With the phase II negative feedback control, X' activates transcription factor Nrf2 to induce phase II enzymes such as glutathione S-transferase and glutamate cysteine ligase, etc., which participate in a set of reactions that lead to the metabolism of X' into a less toxic conjugate X''. The feedforward control involves phase I to II cross-induction, in which the parent chemical X can also induce phase II enzymes directly through the nuclear receptor and indirectly through transcriptionally upregulating Nrf2. As a result of the active feedforward control, a steady-state hormetic relationship readily arises between the concentrations of the reactive metabolite X' and the extracellular parent chemical X to which the cell is exposed. The shape of dose-response evolves over time from initially monotonically increasing to J-shaped at the final steady state-a temporal sequence consistent with adaptation-mediated hormesis. The magnitude of the hormetic response is enhanced by increases in the feedforward gain, but attenuated by increases in the bioactivation or phase II feedback loop gains. Our study suggests a

  17. Phase I to II cross-induction of xenobiotic metabolizing enzymes: a feedforward control mechanism for potential hormetic responses.

    Science.gov (United States)

    Zhang, Qiang; Pi, Jingbo; Woods, Courtney G; Andersen, Melvin E

    2009-06-15

    Hormetic responses to xenobiotic exposure likely occur as a result of overcompensation by the homeostatic control systems operating in biological organisms. However, the mechanisms underlying overcompensation that leads to hormesis are still unclear. A well-known homeostatic circuit in the cell is the gene induction network comprising phase I, II and III metabolizing enzymes, which are responsible for xenobiotic detoxification, and in many cases, bioactivation. By formulating a differential equation-based computational model, we investigated in this study whether hormesis can arise from the operation of this gene/enzyme network. The model consists of two feedback and one feedforward controls. With the phase I negative feedback control, xenobiotic X activates nuclear receptors to induce cytochrome P450 enzyme, which bioactivates X into a reactive metabolite X'. With the phase II negative feedback control, X' activates transcription factor Nrf2 to induce phase II enzymes such as glutathione S-transferase and glutamate cysteine ligase, etc., which participate in a set of reactions that lead to the metabolism of X' into a less toxic conjugate X''. The feedforward control involves phase I to II cross-induction, in which the parent chemical X can also induce phase II enzymes directly through the nuclear receptor and indirectly through transcriptionally upregulating Nrf2. As a result of the active feedforward control, a steady-state hormetic relationship readily arises between the concentrations of the reactive metabolite X' and the extracellular parent chemical X to which the cell is exposed. The shape of dose-response evolves over time from initially monotonically increasing to J-shaped at the final steady state-a temporal sequence consistent with adaptation-mediated hormesis. The magnitude of the hormetic response is enhanced by increases in the feedforward gain, but attenuated by increases in the bioactivation or phase II feedback loop gains. Our study suggests a

  18. The Pathwise Numerical Approximation of Stationary Solutions of Semilinear Stochastic Evolution Equations

    International Nuclear Information System (INIS)

    Caraballo, T.; Kloeden, P.E.

    2006-01-01

    Under a one-sided dissipative Lipschitz condition on its drift, a stochastic evolution equation with additive noise of the reaction-diffusion type is shown to have a unique stochastic stationary solution which pathwise attracts all other solutions. A similar situation holds for each Galerkin approximation and each implicit Euler scheme applied to these Galerkin approximations. Moreover, the stationary solution of the Euler scheme converges pathwise to that of the Galerkin system as the stepsize tends to zero and the stationary solutions of the Galerkin systems converge pathwise to that of the evolution equation as the dimension increases. The analysis is carried out on random partial and ordinary differential equations obtained from their stochastic counterparts by subtraction of appropriate Ornstein-Uhlenbeck stationary solutions

  19. Direct Power Control for Three-Phase Two-Level Voltage-Source Rectifiers Based on Extended-State Observation

    DEFF Research Database (Denmark)

    Song, Zhanfeng; Tian, Yanjun; Yan, Zhuo

    2016-01-01

    This paper proposed a direct power control strategy for three-phase two-level voltage-source rectifiers based on extended-state observation. Active and reactive powers are directly regulated in the stationary reference frame. Similar to the family of predictive controllers whose inherent characte......This paper proposed a direct power control strategy for three-phase two-level voltage-source rectifiers based on extended-state observation. Active and reactive powers are directly regulated in the stationary reference frame. Similar to the family of predictive controllers whose inherent...

  20. Nonparametric estimation of the stationary M/G/1 workload distribution function

    DEFF Research Database (Denmark)

    Hansen, Martin Bøgsted

    2005-01-01

    In this paper it is demonstrated how a nonparametric estimator of the stationary workload distribution function of the M/G/1-queue can be obtained by systematic sampling the workload process. Weak convergence results and bootstrap methods for empirical distribution functions for stationary associ...

  1. Similarity flows between a rotating and a stationary disk

    International Nuclear Information System (INIS)

    Buchmann, J.H.; Qassim, R.Y.

    1981-07-01

    The radial distribution of fluid pressure on a stationary disk coaxial with a rotating disk is determined experimentally for various inter-disc spacings. The results show that similarity flows are only possible for both small and large values of this distance. In the former case, the flow faraway from the stationary disk appears to be that suggested by Batchelor, while in the latter case, the flow turns out to be in accordance with the assumption of Stewartson. (Author) [pt

  2. Metabolic flux analysis during the exponential growth phase of Saccharomyces cerevisiae in wine fermentations.

    Directory of Open Access Journals (Sweden)

    Manuel Quirós

    Full Text Available As a consequence of the increase in global average temperature, grapes with the adequate phenolic and aromatic maturity tend to be overripe by the time of harvest, resulting in increased sugar concentrations and imbalanced C/N ratios in fermenting musts. This fact sets obvious additional hurdles in the challenge of obtaining wines with reduced alcohols levels, a new trend in consumer demands. It would therefore be interesting to understand Saccharomyces cerevisiae physiology during the fermentation of must with these altered characteristics. The present study aims to determine the distribution of metabolic fluxes during the yeast exponential growth phase, when both carbon and nitrogen sources are in excess, using continuous cultures. Two different sugar concentrations were studied under two different winemaking temperature conditions. Although consumption and production rates for key metabolites were severely affected by the different experimental conditions studied, the general distribution of fluxes in central carbon metabolism was basically conserved in all cases. It was also observed that temperature and sugar concentration exerted a higher effect on the pentose phosphate pathway and glycerol formation than on glycolysis and ethanol production. Additionally, nitrogen uptake, both quantitatively and qualitatively, was strongly influenced by environmental conditions. This work provides the most complete stoichiometric model used for Metabolic Flux Analysis of S. cerevisiae in wine fermentations employed so far, including the synthesis and release of relevant aroma compounds and could be used in the design of optimal nitrogen supplementation of wine fermentations.

  3. On Maximal Hard-Core Thinnings of Stationary Particle Processes

    Science.gov (United States)

    Hirsch, Christian; Last, Günter

    2018-02-01

    The present paper studies existence and distributional uniqueness of subclasses of stationary hard-core particle systems arising as thinnings of stationary particle processes. These subclasses are defined by natural maximality criteria. We investigate two specific criteria, one related to the intensity of the hard-core particle process, the other one being a local optimality criterion on the level of realizations. In fact, the criteria are equivalent under suitable moment conditions. We show that stationary hard-core thinnings satisfying such criteria exist and are frequently distributionally unique. More precisely, distributional uniqueness holds in subcritical and barely supercritical regimes of continuum percolation. Additionally, based on the analysis of a specific example, we argue that fluctuations in grain sizes can play an important role for establishing distributional uniqueness at high intensities. Finally, we provide a family of algorithmically constructible approximations whose volume fractions are arbitrarily close to the maximum.

  4. Only adding stationary storage to vaccine supply chains may create and worsen transport bottlenecks.

    Science.gov (United States)

    Haidari, Leila A; Connor, Diana L; Wateska, Angela R; Brown, Shawn T; Mueller, Leslie E; Norman, Bryan A; Schmitz, Michelle M; Paul, Proma; Rajgopal, Jayant; Welling, Joel S; Leonard, Jim; Claypool, Erin G; Weng, Yu-Ting; Chen, Sheng-I; Lee, Bruce Y

    2013-01-01

    Although vaccine supply chains in many countries require additional stationary storage and transport capacity to meet current and future needs, international donors tend to donate stationary storage devices far more often than transport equipment. To investigate the impact of only adding stationary storage equipment on the capacity requirements of transport devices and vehicles, we used HERMES (Highly Extensible Resource for Modeling Supply Chains) to construct a discrete event simulation model of the Niger vaccine supply chain. We measured the transport capacity requirement for each mode of transport used in the Niger vaccine cold chain, both before and after adding cold rooms and refrigerators to relieve all stationary storage constraints in the system. With the addition of necessary stationary storage, the average transport capacity requirement increased from 88% to 144% for cold trucks, from 101% to 197% for pickup trucks, and from 366% to 420% for vaccine carriers. Therefore, adding stationary storage alone may worsen or create new transport bottlenecks as more vaccines flow through the system, preventing many vaccines from reaching their target populations. Dynamic modeling can reveal such relationships between stationary storage capacity and transport constraints.

  5. Power variation for Gaussian processes with stationary increments

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Corcuera, J.M.; Podolskij, Mark

    2009-01-01

    We develop the asymptotic theory for the realised power variation of the processes X=•G, where G is a Gaussian process with stationary increments. More specifically, under some mild assumptions on the variance function of the increments of G and certain regularity conditions on the path of the pr......We develop the asymptotic theory for the realised power variation of the processes X=•G, where G is a Gaussian process with stationary increments. More specifically, under some mild assumptions on the variance function of the increments of G and certain regularity conditions on the path...... a chaos representation....

  6. Income dynamics with a stationary double Pareto distribution.

    Science.gov (United States)

    Toda, Alexis Akira

    2011-04-01

    Once controlled for the trend, the distribution of personal income appears to be double Pareto, a distribution that obeys the power law exactly in both the upper and the lower tails. I propose a model of income dynamics with a stationary distribution that is consistent with this fact. Using US male wage data for 1970-1993, I estimate the power law exponent in two ways--(i) from each cross section, assuming that the distribution has converged to the stationary distribution, and (ii) from a panel directly estimating the parameters of the income dynamics model--and obtain the same value of 8.4.

  7. Interaction of storage carbohydrates and other cyclic fluxes with central metabolism: A quantitative approach by non-stationary 13C metabolic flux analysis

    Directory of Open Access Journals (Sweden)

    C.A. Suarez-Mendez

    2016-12-01

    Full Text Available 13C labeling experiments in aerobic glucose limited cultures of Saccharomyces cerevisiae at four different growth rates (0.054; 0.101, 0.207, 0.307 h−1 are used for calculating fluxes that include intracellular cycles (e.g., storage carbohydrate cycles, exchange fluxes with amino acids, which are rearranged depending on the growth rate. At low growth rates the impact of the storage carbohydrate recycle is relatively more significant than at high growth rates due to a higher concentration of these materials in the cell (up to 560-fold and higher fluxes relative to the glucose uptake rate (up to 16%. Experimental observations suggest that glucose can be exported to the extracellular space, and that its source is related to storage carbohydrates, most likely via the export and subsequent extracellular breakdown of trehalose. This hypothesis is strongly supported by 13C-labeling experimental data, measured extracellular trehalose, and the corresponding flux estimations. Keywords: Non-stationary 13C labeling, Flux estimation, Trehalose, Glycogen, Amino acids

  8. [Sampling methods for PM2.5 from stationary sources: a review].

    Science.gov (United States)

    Jiang, Jing-Kun; Deng, Jian-Guo; Li, Zhen; Li, Xing-Hua; Duan, Lei; Hao, Ji-Ming

    2014-05-01

    The new China national ambient air quality standard has been published in 2012 and will be implemented in 2016. To meet the requirements in this new standard, monitoring and controlling PM2,,5 emission from stationary sources are very important. However, so far there is no national standard method on sampling PM2.5 from stationary sources. Different sampling methods for PM2.5 from stationary sources and relevant international standards were reviewed in this study. It includes the methods for PM2.5 sampling in flue gas and the methods for PM2.5 sampling after dilution. Both advantages and disadvantages of these sampling methods were discussed. For environmental management, the method for PM2.5 sampling in flue gas such as impactor and virtual impactor was suggested as a standard to determine filterable PM2.5. To evaluate environmental and health effects of PM2.5 from stationary sources, standard dilution method for sampling of total PM2.5 should be established.

  9. Nanomaterials as stationary phases and supports in liquid chromatography.

    Science.gov (United States)

    Beeram, Sandya R; Rodriguez, Elliott; Doddavenkatanna, Suresh; Li, Zhao; Pekarek, Allegra; Peev, Darin; Goerl, Kathryn; Trovato, Gianfranco; Hofmann, Tino; Hage, David S

    2017-10-01

    The development of various nanomaterials over the last few decades has led to many applications for these materials in liquid chromatography (LC). This review will look at the types of nanomaterials that have been incorporated into LC systems and the applications that have been explored for such systems. A number of carbon-based nanomaterials and inorganic nanomaterials have been considered for use in LC, ranging from carbon nanotubes, fullerenes and nanodiamonds to metal nanoparticles and nanostructures based on silica, alumina, zirconia and titanium dioxide. Many ways have been described for incorporating these nanomaterials into LC systems. These methods have included covalent immobilization, adsorption, entrapment, and the synthesis or direct development of nanomaterials as part of a chromatographic support. Nanomaterials have been used in many types of LC. These applications have included the reversed-phase, normal-phase, ion-exchange, and affinity modes of LC, as well as related methods such as chiral separations, ion-pair chromatography and hydrophilic interaction liquid chromatography. Both small and large analytes (e.g., dyes, drugs, amino acids, peptides and proteins) have been used to evaluate possible applications for these nanomaterial-based methods. The use of nanomaterials in columns, capillaries and planar chromatography has been considered as part of these efforts. Potential advantages of nanomaterials in these applications have included their good chemical and physical stabilities, the variety of interactions many nanomaterials can have with analytes, and their unique retention properties in some separation formats. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Segmented slant hole collimator for stationary cardiac SPECT: Monte Carlo simulations.

    Science.gov (United States)

    Mao, Yanfei; Yu, Zhicong; Zeng, Gengsheng L

    2015-09-01

    This work is a preliminary study of a stationary cardiac SPECT system. The goal of this research is to propose a stationary cardiac SPECT system using segmented slant-hole collimators and to perform computer simulations to test the feasibility. Compared to the rotational SPECT, a stationary system has a benefit of acquiring temporally consistent projections. The most challenging issue in building a stationary system is to provide sufficient projection view-angles. A GATE (GEANT4 application for tomographic emission) Monte Carlo model was developed to simulate a two-detector stationary cardiac SPECT that uses segmented slant-hole collimators. Each detector contains seven segmented slant-hole sections that slant to a common volume at the rotation center. Consequently, 14 view-angles over 180° were acquired without any gantry rotation. The NCAT phantom was used for data generation and a tailored maximum-likelihood expectation-maximization algorithm was used for image reconstruction. Effects of limited number of view-angles and data truncation were carefully evaluated in the paper. Simulation results indicated that the proposed segmented slant-hole stationary cardiac SPECT system is able to acquire sufficient data for cardiac imaging without a loss of image quality, even when the uptakes in the liver and kidneys are high. Seven views are acquired simultaneously at each detector, leading to 5-fold sensitivity gain over the conventional dual-head system at the same total acquisition time, which in turn increases the signal-to-noise ratio by 19%. The segmented slant-hole SPECT system also showed a good performance in lesion detection. In our prototype system, a short hole-length was used to reduce the dead zone between neighboring collimator segments. The measured sensitivity gain is about 17-fold over the conventional dual-head system. The gate Monte Carlo simulations confirm the feasibility of the proposed stationary cardiac SPECT system with segmented slant

  11. Segmented slant hole collimator for stationary cardiac SPECT: Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Yanfei, E-mail: ymao@ucair.med.utah.edu [Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108 and Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 (United States); Yu, Zhicong [Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905 (United States); Zeng, Gengsheng L. [Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108 and Department of Engineering, Weber State University, Ogden, Utah 84408 (United States)

    2015-09-15

    Purpose: This work is a preliminary study of a stationary cardiac SPECT system. The goal of this research is to propose a stationary cardiac SPECT system using segmented slant-hole collimators and to perform computer simulations to test the feasibility. Compared to the rotational SPECT, a stationary system has a benefit of acquiring temporally consistent projections. The most challenging issue in building a stationary system is to provide sufficient projection view-angles. Methods: A GATE (GEANT4 application for tomographic emission) Monte Carlo model was developed to simulate a two-detector stationary cardiac SPECT that uses segmented slant-hole collimators. Each detector contains seven segmented slant-hole sections that slant to a common volume at the rotation center. Consequently, 14 view-angles over 180° were acquired without any gantry rotation. The NCAT phantom was used for data generation and a tailored maximum-likelihood expectation-maximization algorithm was used for image reconstruction. Effects of limited number of view-angles and data truncation were carefully evaluated in the paper. Results: Simulation results indicated that the proposed segmented slant-hole stationary cardiac SPECT system is able to acquire sufficient data for cardiac imaging without a loss of image quality, even when the uptakes in the liver and kidneys are high. Seven views are acquired simultaneously at each detector, leading to 5-fold sensitivity gain over the conventional dual-head system at the same total acquisition time, which in turn increases the signal-to-noise ratio by 19%. The segmented slant-hole SPECT system also showed a good performance in lesion detection. In our prototype system, a short hole-length was used to reduce the dead zone between neighboring collimator segments. The measured sensitivity gain is about 17-fold over the conventional dual-head system. Conclusions: The GATE Monte Carlo simulations confirm the feasibility of the proposed stationary cardiac

  12. Effects of low-level α radiation on intracellular energy metabolism

    International Nuclear Information System (INIS)

    Steinhaeusler, F.; Schaffer, S.; Lee, C.C.; O'Connor, J.; Wrenn, M.E.

    1980-01-01

    The effect on the adenosine triphosphate (ATP) content of cell samples irradiated with α particles of a mean LET of 135 to 141 keV/μm is described. Cells in logarithmic growth phase showed an ATP content about 50% below the unirradiated control value 5 to 15 sec after receiving a mean cellular dose of 25 rad (0.25 Gy). This was followed by a slow recovery up to control values after about 30 sec. Stationary cells responded with an increase in ATP content about threefold over that of the controls 20 sec after irradiation. Within the following 20 sec these elevated ATP values decreased to control levels. Additional measurements of 14 C uptake also showed pronounced differentiated changes in carbon uptake after irradiation for cells in logarithmic and stationary growth phase. The possible importance of these effects on bioenergetic processes as a compensatory reaction of the cellular system to an increased demand for energy is discussed

  13. Detection of Multiple Stationary Humans Using UWB MIMO Radar

    Directory of Open Access Journals (Sweden)

    Fulai Liang

    2016-11-01

    Full Text Available Remarkable progress has been achieved in the detection of single stationary human. However, restricted by the mutual interference of multiple humans (e.g., strong sidelobes of the torsos and the shadow effect, detection and localization of the multiple stationary humans remains a huge challenge. In this paper, ultra-wideband (UWB multiple-input and multiple-output (MIMO radar is exploited to improve the detection performance of multiple stationary humans for its multiple sight angles and high-resolution two-dimensional imaging capacity. A signal model of the vital sign considering both bi-static angles and attitude angle of the human body is firstly developed, and then a novel detection method is proposed to detect and localize multiple stationary humans. In this method, preprocessing is firstly implemented to improve the signal-to-noise ratio (SNR of the vital signs, and then a vital-sign-enhanced imaging algorithm is presented to suppress the environmental clutters and mutual affection of multiple humans. Finally, an automatic detection algorithm including constant false alarm rate (CFAR, morphological filtering and clustering is implemented to improve the detection performance of weak human targets affected by heavy clutters and shadow effect. The simulation and experimental results show that the proposed method can get a high-quality image of multiple humans and we can use it to discriminate and localize multiple adjacent human targets behind brick walls.

  14. Danish emission inventories for stationary combustion plants

    DEFF Research Database (Denmark)

    Nielsen, M.; Illerup, J. B.

    Emission inventories for stationary combustion plants are presented and the methodologies and assumptions used for the inventories are described. The pollutants considered are: SO2, NOx, NMVOC, CH4, CO, CO2, N2O, particulate matter, heavy metals, dioxins and PAH. Since 1990 the fuel consumption...... in stationary combustion has increased by 12% - the fossil fuel consumption however only by 6%. Despite the increased fuel consumption the emission of several pollutants have decreased due to the improved flue gas cleaning technology, improved burner technology and the change of fuel type used. A considerable...... plants. The emission of PAH increased as a result of the increased combustion of wood in residential boilers and stoves. Uncertainties for the emissions and trends have been estimated....

  15. Danish emission inventories for stationary combustion plants

    DEFF Research Database (Denmark)

    Nielsen, M.; Illerup, J. B.

    Emission inventories for stationary combustion plants are presented and the methodologies and assumptions used for the inventories are described. The pollutants considered are SO2, NOX, NMVOC, CH4, CO, CO2, N2O, particulate matter, heavy metals, dioxins and PAH. Since 1990 the fuel consumption...... in stationary combustion has increased by 14% - the fossil fuel consumption however only by 8%. Despite the increased fuel consumption the emission of several pollutants has decreased due to the improved flue gas cleaning technology, improved burner technology and the change of fuel type used. A considerable...... plants. The emission of PAH increased as a result of the increased combustion of wood in residential boilers and stoves. Uncertainties for the emissions and trends have been estimated...

  16. Stationary distribution and ergodicity of a stochastic food-chain model with Lévy jumps

    Science.gov (United States)

    Yu, Jingyi; Liu, Meng

    2017-09-01

    In this paper, a three-species stochastic food-chain model with Lévy jumps is proposed and analyzed. Sharp sufficient criteria for the existence and uniqueness of an ergodic stationary distribution are established. The effects of Lévy jumps on the existence of the stationary distribution are revealed: in some cases, the Lévy jumps could make the stationary distribution appear, while in some cases, the Lévy jumps could make the stationary distribution disappear. Some numerical simulations are introduced to illustrate the theoretical results.

  17. Stone Stability under Stationary Nonuniform Flows

    NARCIS (Netherlands)

    Steenstra, Remco; Hofland, B.; Paarlberg, Andries; Smale, Alfons; Huthoff, Fredrik; Uijttewaal, W.S.J.

    2016-01-01

    A stability parameter for rock in bed protections under nonuniform stationary flow is derived. The influence of the mean flow velocity, turbulence, and mean acceleration of the flow are included explicitly in the parameter. The relatively new notion of explicitly incorporating the mean acceleration

  18. Relativistic elasticity of stationary fluid branes

    DEFF Research Database (Denmark)

    Armas, J.; Obers, N.A.

    2013-01-01

    under certain conditions that a given stationary fluid configuration living on a dynamical surface of vanishing thickness and satisfying locally the first law of thermodynamics will behave like an elastic brane when the surface is subject to small deformations. These results, which are independent...

  19. EDITORIAL: CAMOP: Quantum Non-Stationary Systems CAMOP: Quantum Non-Stationary Systems

    Science.gov (United States)

    Dodonov, Victor V.; Man'ko, Margarita A.

    2010-09-01

    Although time-dependent quantum systems have been studied since the very beginning of quantum mechanics, they continue to attract the attention of many researchers, and almost every decade new important discoveries or new fields of application are made. Among the impressive results or by-products of these studies, one should note the discovery of the path integral method in the 1940s, coherent and squeezed states in the 1960-70s, quantum tunneling in Josephson contacts and SQUIDs in the 1960s, the theory of time-dependent quantum invariants in the 1960-70s, different forms of quantum master equations in the 1960-70s, the Zeno effect in the 1970s, the concept of geometric phase in the 1980s, decoherence of macroscopic superpositions in the 1980s, quantum non-demolition measurements in the 1980s, dynamics of particles in quantum traps and cavity QED in the 1980-90s, and time-dependent processes in mesoscopic quantum devices in the 1990s. All these topics continue to be the subject of many publications. Now we are witnessing a new wave of interest in quantum non-stationary systems in different areas, from cosmology (the very first moments of the Universe) and quantum field theory (particle pair creation in ultra-strong fields) to elementary particle physics (neutrino oscillations). A rapid increase in the number of theoretical and experimental works on time-dependent phenomena is also observed in quantum optics, quantum information theory and condensed matter physics. Time-dependent tunneling and time-dependent transport in nano-structures are examples of such phenomena. Another emerging direction of study, stimulated by impressive progress in experimental techniques, is related to attempts to observe the quantum behavior of macroscopic objects, such as mirrors interacting with quantum fields in nano-resonators. Quantum effects manifest themselves in the dynamics of nano-electromechanical systems; they are dominant in the quite new and very promising field of circuit

  20. Stationary measure in the multiverse

    International Nuclear Information System (INIS)

    Linde, Andrei; Vanchurin, Vitaly; Winitzki, Sergei

    2009-01-01

    We study the recently proposed ''stationary measure'' in the context of the string landscape scenario. We show that it suffers neither from the ''Boltzmann brain'' problem nor from the ''youngness'' paradox that makes some other measures predict a high CMB temperature at present. We also demonstrate a good performance of this measure in predicting the results of local experiments, such as proton decay

  1. Stationary magnetic shear reversal during Lower Hybrid experiments in Tore Supra

    International Nuclear Information System (INIS)

    Litaudon, X.; Arslanbekov, R.; Hoang, G.T.; Joffrin, E.; Kazarian-Vibert, F.; Moreau, D.; Peysson, Y.; Bibet, P.

    1996-01-01

    Stable and stationary states with hollow current density profiles have been achieved with Lower Hybrid Current Drive (LHCD) during Lower Hybrid (LH) wave accessibility experiments. By analysing the bounded propagation domain in phase space which naturally limits the central penetration and absorption of the waves, off-axis LH power deposition has been realized in a reproducible manner. The resulting current density profile modifications have led to a global confinement enhancement attributed to the formation of an internal 'transport barrier' in the central reversed shear region where the electron thermal diffusivity is reduced to its neoclassical collisional level. The multiple-pass LH wave propagation in the weak Landau damping and reversed magnetic shear regime is also investigated in the framework of a statistical theory and the experimental validation of this theory is discussed. (author)

  2. Moment distributions of phase-type

    DEFF Research Database (Denmark)

    Bladt, Mogens; Nielsen, Bo Friis

    2012-01-01

    Both matrix-exponential and phase-type distributions have a number of important closure properties. Among those are the distributions of the age and residual life-time of a stationary renewal process with inter-arrivals of either type. In this talk we show that the spread, which is the sum of the...... with phase-type distributions. For the first order distribution we present an explicit formula for the related Lorenz curve and Gini index. Moment distributions of orders one, two and three have been extensively used in areas such as economy, physics, demography and civil engineering....

  3. High-frequency stock linkage and multi-dimensional stationary processes

    Science.gov (United States)

    Wang, Xi; Bao, Si; Chen, Jingchao

    2017-02-01

    In recent years, China's stock market has experienced dramatic fluctuations; in particular, in the second half of 2014 and 2015, the market rose sharply and fell quickly. Many classical financial phenomena, such as stock plate linkage, appeared repeatedly during this period. In general, these phenomena have usually been studied using daily-level data or minute-level data. Our paper focuses on the linkage phenomenon in Chinese stock 5-second-level data during this extremely volatile period. The method used to select the linkage points and the arbitrage strategy are both based on multi-dimensional stationary processes. A new program method for testing the multi-dimensional stationary process is proposed in our paper, and the detailed program is presented in the paper's appendix. Because of the existence of the stationary process, the strategy's logarithmic cumulative average return will converge under the condition of the strong ergodic theorem, and this ensures the effectiveness of the stocks' linkage points and the more stable statistical arbitrage strategy.

  4. Comparison of high-accuracy numerical simulations of black-hole binaries with stationary-phase post-Newtonian template waveforms for initial and advanced LIGO

    International Nuclear Information System (INIS)

    Boyle, Michael; Brown, Duncan A; Pekowsky, Larne

    2009-01-01

    We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the initial- and advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both initial and advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 post-Newtonian (pN) order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass (M ≤ 35 M o-dot ) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass η above this. This strategy always achieves overlaps within 0.3% of the optimum, for the data used here. For advanced LIGO we recommend a strategy using 3.5 pN templates up to M = 12 M o-dot , 2.0 pN templates up to M = 21 M o-dot , pseudo-4.0 pN templates up to 65 M o-dot , and 3.5 pN templates with unphysical η for higher masses. This strategy always achieves overlaps within 0.7% of the optimum for advanced LIGO.

  5. On the non-stationary generalized Langevin equation

    Science.gov (United States)

    Meyer, Hugues; Voigtmann, Thomas; Schilling, Tanja

    2017-12-01

    In molecular dynamics simulations and single molecule experiments, observables are usually measured along dynamic trajectories and then averaged over an ensemble ("bundle") of trajectories. Under stationary conditions, the time-evolution of such averages is described by the generalized Langevin equation. By contrast, if the dynamics is not stationary, it is not a priori clear which form the equation of motion for an averaged observable has. We employ the formalism of time-dependent projection operator techniques to derive the equation of motion for a non-equilibrium trajectory-averaged observable as well as for its non-stationary auto-correlation function. The equation is similar in structure to the generalized Langevin equation but exhibits a time-dependent memory kernel as well as a fluctuating force that implicitly depends on the initial conditions of the process. We also derive a relation between this memory kernel and the autocorrelation function of the fluctuating force that has a structure similar to a fluctuation-dissipation relation. In addition, we show how the choice of the projection operator allows us to relate the Taylor expansion of the memory kernel to data that are accessible in MD simulations and experiments, thus allowing us to construct the equation of motion. As a numerical example, the procedure is applied to Brownian motion initialized in non-equilibrium conditions and is shown to be consistent with direct measurements from simulations.

  6. Integrity assessment of stationary blade ring for nuclear power plant

    International Nuclear Information System (INIS)

    Park, Jung Yong; Chung, Yong Keun; Park, Jong Jin; Kang, Yong Ho

    2004-01-01

    The inner side between HP stationary blades in no.1 turbine of nuclear power plant A is damaged by the FAC(Flow Assisted Corrosion) which is exposed to moisture. For many years the inner side is repaired by welding the damaged part, however, the FAC continues to deteriorate the original material of the welded blade ring. In this study, we have two stages to verify the integrity of stationary blade ring in nuclear power plant A. In the stage I, replication of blade ring is performed to survey the microstructure of blade ring. In the stage II, the stress analysis of blade ring is performed to verify the structural safety of blade ring. Throughout the two stages analysis of blade ring, the stationary blade ring had remained undamaged

  7. The stationary states of interacting fields

    NARCIS (Netherlands)

    Frazer, W.R.; Hove, Léon van

    1958-01-01

    As an application of a time-independent perturbation formalism developed earlier for systems with many degrees of freedom, we give in terms of diagrams the general perturbation expressions for the exact stationary states of interacting fields. The physical vacuum is obtained by applying to the bare

  8. Collaborative Area Monitoring Using Wireless Sensor Networks with Stationary and Mobile Nodes

    Directory of Open Access Journals (Sweden)

    Theofanis P. Lambrou

    2009-01-01

    Full Text Available Monitoring a large area with stationary sensor networks requires a very large number of nodes which with current technology implies a prohibitive cost. The motivation of this work is to develop an architecture where a set of mobile sensors will collaborate with the stationary sensors in order to reliably detect and locate an event. The main idea of this collaborative architecture is that the mobile sensors should sample the areas that are least covered (monitored by the stationary sensors. Furthermore, when stationary sensors have a “suspicion” that an event may have occurred, they report it to a mobile sensor that can move closer to the suspected area and can confirm whether the event has occurred or not. An important component of the proposed architecture is that the mobile nodes autonomously decide their path based on local information (their own beliefs and measurements as well as information collected from the stationary sensors in a neighborhood around them. We believe that this approach is appropriate in the context of wireless sensor networks since it is not feasible to have an accurate global view of the state of the environment.

  9. Poisson-Nernst-Planck equations with steric effects - non-convexity and multiple stationary solutions

    Science.gov (United States)

    Gavish, Nir

    2018-04-01

    We study the existence and stability of stationary solutions of Poisson-Nernst-Planck equations with steric effects (PNP-steric equations) with two counter-charged species. We show that within a range of parameters, steric effects give rise to multiple solutions of the corresponding stationary equation that are smooth. The PNP-steric equation, however, is found to be ill-posed at the parameter regime where multiple solutions arise. Following these findings, we introduce a novel PNP-Cahn-Hilliard model, show that it is well-posed and that it admits multiple stationary solutions that are smooth and stable. The various branches of stationary solutions and their stability are mapped utilizing bifurcation analysis and numerical continuation methods.

  10. Halo formation in three-dimensional bunches with various phase space distributions

    Directory of Open Access Journals (Sweden)

    A. V. Fedotov

    1999-01-01

    Full Text Available A realistic treatment of halo formation must take into account 3D beam bunches and 6D phase space distributions. We recently constructed, analytically and numerically, a new class of self-consistent 6D phase space stationary distributions, which allowed us to study the halo development mechanism without being obscured by the effect of beam redistribution. In this paper we consider nonstationary distributions and study how the halo characteristics compare with those obtained using the stationary distribution. We then discuss the effect of redistribution on the halo development mechanism. In contrast to bunches with a large aspect ratio, we find that the effect of coupling between the r and z planes is especially important as the bunch shape becomes more spherical.

  11. Discretization of Stationary Solutions of Stochastic Systems Driven by Fractional Brownian Motion

    International Nuclear Information System (INIS)

    Garrido-Atienza, Maria J.; Kloeden, Peter E.; Neuenkirch, Andreas

    2009-01-01

    In this article we study the behavior of dissipative systems with additive fractional noise of any Hurst parameter. Under a one-sided dissipative Lipschitz condition on the drift the continuous stochastic system is shown to have a unique stationary solution, which pathwise attracts all other solutions. The same holds for the discretized stochastic system, if the drift-implicit Euler method is used for the discretization. Moreover, the unique stationary solution of the drift-implicit Euler scheme converges to the unique stationary solution of the original system as the stepsize of the discretization decreases

  12. Transcription factor levels enable metabolic diversification of single cells of environmental bacteria.

    Science.gov (United States)

    Guantes, Raúl; Benedetti, Ilaria; Silva-Rocha, Rafael; de Lorenzo, Víctor

    2016-05-01

    Transcriptional noise is a necessary consequence of the molecular events that drive gene expression in prokaryotes. However, some environmental microorganisms that inhabit polluted sites, for example, the m-xylene degrading soil bacterium Pseudomonas putida mt-2 seem to have co-opted evolutionarily such a noise for deploying a metabolic diversification strategy that allows a cautious exploration of new chemical landscapes. We have examined this phenomenon under the light of deterministic and stochastic models for activation of the main promoter of the master m-xylene responsive promoter of the system (Pu) by its cognate transcriptional factor (XylR). These analyses consider the role of co-factors for Pu activation and determinants of xylR mRNA translation. The model traces the onset and eventual disappearance of the bimodal distribution of Pu activity along time to the growth-phase dependent abundance of XylR itself, that is, very low in exponentially growing cells and high in stationary. This tenet was validated by examining the behaviour of a Pu-GFP fusion in a P. putida strain in which xylR expression was engineered under the control of an IPTG-inducible system. This work shows how a relatively simple regulatory scenario (for example, growth-phase dependent expression of a limiting transcription factor) originates a regime of phenotypic diversity likely to be advantageous in competitive environmental settings.

  13. Equilibrium positions on stationary orbits and planetary principal inertia axis orientations for the Solar System

    Science.gov (United States)

    Romero, Pilar; Barderas, Gonzalo; Mejuto, Javier

    2018-05-01

    We present a qualitative analysis in a phase space to determine the longitudinal equilibrium positions on the planetary stationary orbits by applying an analytical model that considers linear gravitational perturbations. We discuss how these longitudes are related with the orientation of the planetary principal inertia axes with respect to their Prime Meridians, and then we use this determination to derive their positions with respect to the International Celestial Reference Frame. Finally, a numerical analysis of the non-linear effects of the gravitational fields on the equilibrium point locations is developed and their correlation with gravity field anomalies shown.

  14. TOWARD A MAGNETOHYDRODYNAMIC THEORY OF THE STATIONARY ACCRETION SHOCK INSTABILITY: TOY MODEL OF THE ADVECTIVE-ACOUSTIC CYCLE IN A MAGNETIZED FLOW

    International Nuclear Information System (INIS)

    Guilet, Jerome; Foglizzo, Thierry

    2010-01-01

    The effect of a magnetic field on the linear phase of the advective-acoustic instability is investigated as a first step toward a magnetohydrodynamic (MHD) theory of the stationary accretion shock instability taking place during stellar core collapse. We study a toy model where the flow behind a planar stationary accretion shock is adiabatically decelerated by an external potential. Two magnetic field geometries are considered: parallel or perpendicular to the shock. The entropy-vorticity wave, which is simply advected in the unmagnetized limit, separates into five different waves: the entropy perturbations are advected, while the vorticity can propagate along the field lines through two Alfven waves and two slow magnetosonic waves. The two cycles existing in the unmagnetized limit, advective-acoustic and purely acoustic, are replaced by up to six distinct MHD cycles. The phase differences among the cycles play an important role in determining the total cycle efficiency and hence the growth rate. Oscillations in the growth rate as a function of the magnetic field strength are due to this varying phase shift. A vertical magnetic field hardly affects the cycle efficiency in the regime of super-Alfvenic accretion that is considered. In contrast, we find that a horizontal magnetic field strongly increases the efficiencies of the vorticity cycles that bend the field lines, resulting in a significant increase of the growth rate if the different cycles are in phase. These magnetic effects are significant for large-scale modes if the Alfven velocity is a sizable fraction of the flow velocity.

  15. Effect of non-stationary climate on infectious gastroenteritis transmission in Japan

    Science.gov (United States)

    Onozuka, Daisuke

    2014-06-01

    Local weather factors are widely considered to influence the transmission of infectious gastroenteritis. Few studies, however, have examined the non-stationary relationships between global climatic factors and transmission of infectious gastroenteritis. We analyzed monthly data for cases of infectious gastroenteritis in Fukuoka, Japan from 2000 to 2012 using cross-wavelet coherency analysis to assess the pattern of associations between indices for the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Infectious gastroenteritis cases were non-stationary and significantly associated with the IOD and ENSO (Multivariate ENSO Index [MEI], Niño 1 + 2, Niño 3, Niño 4, and Niño 3.4) for a period of approximately 1 to 2 years. This association was non-stationary and appeared to have a major influence on the synchrony of infectious gastroenteritis transmission. Our results suggest that non-stationary patterns of association between global climate factors and incidence of infectious gastroenteritis should be considered when developing early warning systems for epidemics of infectious gastroenteritis.

  16. The RNA chaperone Hfq impacts growth, metabolism and production of virulence factors in Yersinia enterocolitica.

    Directory of Open Access Journals (Sweden)

    Tamara Kakoschke

    Full Text Available To adapt to changes in environmental conditions, bacteria regulate their gene expression at the transcriptional but also at the post-transcriptional level, e.g. by small RNAs (sRNAs which modulate mRNA stability and translation. The conserved RNA chaperone Hfq mediates the interaction of many sRNAs with their target mRNAs, thereby playing a global role in fine-tuning protein production. In this study, we investigated the significance of Hfq for the enteropathogen Yersina enterocolitica serotype O:8. Hfq facilitated optimal growth in complex and minimal media. Our comparative protein analysis of parental and hfq-negative strains suggested that Hfq promotes lipid metabolism and transport, cell redox homeostasis, mRNA translation and ATP synthesis, and negatively affects carbon and nitrogen metabolism, transport of siderophore and peptides and tRNA synthesis. Accordingly, biochemical tests indicated that Hfq represses ornithine decarboxylase activity, indole production and utilization of glucose, mannitol, inositol and 1,2-propanediol. Moreover, Hfq repressed production of the siderophore yersiniabactin and its outer membrane receptor FyuA. In contrast, hfq mutants exhibited reduced urease production. Finally, strains lacking hfq were more susceptible to acidic pH and oxidative stress. Unlike previous reports in other Gram-negative bacteria, Hfq was dispensable for type III secretion encoded by the virulence plasmid. Using a chromosomally encoded FLAG-tagged Hfq, we observed increased production of Hfq-FLAG in late exponential and stationary phases. Overall, Hfq has a profound effect on metabolism, resistance to stress and modulates the production of two virulence factors in Y. enterocolitica, namely urease and yersiniabactin.

  17. Comparison of TiO2 photocatalysis, electrochemically assisted Fenton reaction and direct electrochemistry for simulation of phase I metabolism reactions of drugs

    NARCIS (Netherlands)

    Ruokolainen, Miina; Gül, Turan; Permentier, Hjalmar; Sikanen, Tiina; Kostiainen, Risto; Kotiaho, Tapio

    2016-01-01

    The feasibility of titanium dioxide (TiO2) photocatalysis, electrochemically assisted Fenton reaction (EC-Fenton) and direct electrochemical oxidation (EC) for simulation of phase I metabolism of drugs was studied by comparing the reaction products of buspirone, promazine, testosterone and

  18. Non-stationary flow of hydraulic oil in long pipe

    Directory of Open Access Journals (Sweden)

    Hružík Lumír

    2014-03-01

    Full Text Available The paper deals with experimental evaluation and numerical simulation of non-stationary flow of hydraulic oil in a long hydraulic line. Non-stationary flow is caused by a quick closing of valves at the beginning and the end of the pipe. Time dependence of pressure is measured by means of pressure sensors at the beginning and the end of the pipe. A mathematical model of a given circuit is created using Matlab SimHydraulics software. The long line is simulated by means of segmented pipe. The simulation is verified by experiment.

  19. Evaluation of different hydrophilic stationary phases for the simultaneous determination of iminosugars and other low molecular weight carbohydrates in vegetable extracts by liquid chromatography tandem mass spectrometry.

    Science.gov (United States)

    Rodríguez-Sánchez, S; Quintanilla-López, J E; Soria, A C; Sanz, M L

    2014-11-01

    Iminosugars are considered potential drug candidates for the treatment of several diseases, mainly as a result of their α-glycosidase inhibition properties. A method by hydrophilic interaction liquid chromatography tandem mass spectrometry has been optimized for the first time for the simultaneous determination of complex mixtures of bioactive iminosugars and other low molecular weight carbohydrates (LMWC) in vegetable extracts. Three hydrophilic stationary phases (sulfoalkylbetaine zwitterionic, polyhydroxyethyl aspartamide and ethylene bridge hybrid (BEH) with trifunctionally bonded amide) were compared under both basic and acidic conditions. The best sensitivity (limits of detection between 0.025 and 0.28ngmL -1 ) and overall chromatographic performance in terms of resolution, peak width and analysis time were obtained with the BEH amide column using 0.1% ammonium hydroxide as a mobile phase additive. The optimized method was applied to the analysis of extracts of hyacinth bulbs, buckwheat seeds and mulberry leaves. Iminosugar and other LMWC structures were tentatively assigned by their high resolution daughter ions mass spectra. Several iminosugars such as glycosyl-fagomine in mulberry extract were also described for the first time. Among the extracts analysed, mulberry showed the widest diversity of iminosugars, whereas the highest content of them was found in hyacinth bulb (2.5mgg -1 ) followed by mulberry (1.95 mgg -1 ). Copyright © 2014 Elsevier B.V. All rights reserved.

  20. The computation of stationary distributions of Markov chains through perturbations

    Directory of Open Access Journals (Sweden)

    Jeffery J. Hunter

    1991-01-01

    Full Text Available An algorithmic procedure for the determination of the stationary distribution of a finite, m-state, irreducible Markov chain, that does not require the use of methods for solving systems of linear equations, is presented. The technique is based upon a succession of m, rank one, perturbations of the trivial doubly stochastic matrix whose known steady state vector is updated at each stage to yield the required stationary probability vector.

  1. Regulatory design governing progression of population growth phases in bacteria.

    Directory of Open Access Journals (Sweden)

    Agustino Martínez-Antonio

    Full Text Available It has long been noted that batch cultures inoculated with resting bacteria exhibit a progression of growth phases traditionally labeled lag, exponential, pre-stationary and stationary. However, a detailed molecular description of the mechanisms controlling the transitions between these phases is lacking. A core circuit, formed by a subset of regulatory interactions involving five global transcription factors (FIS, HNS, IHF, RpoS and GadX, has been identified by correlating information from the well- established transcriptional regulatory network of Escherichia coli and genome-wide expression data from cultures in these different growth phases. We propose a functional role for this circuit in controlling progression through these phases. Two alternative hypotheses for controlling the transition between the growth phases are first, a continuous graded adjustment to changing environmental conditions, and second, a discontinuous hysteretic switch at critical thresholds between growth phases. We formulate a simple mathematical model of the core circuit, consisting of differential equations based on the power-law formalism, and show by mathematical and computer-assisted analysis that there are critical conditions among the parameters of the model that can lead to hysteretic switch behavior, which--if validated experimentally--would suggest that the transitions between different growth phases might be analogous to cellular differentiation. Based on these provocative results, we propose experiments to test the alternative hypotheses.

  2. Regulatory design governing progression of population growth phases in bacteria.

    Science.gov (United States)

    Martínez-Antonio, Agustino; Lomnitz, Jason G; Sandoval, Santiago; Aldana, Maximino; Savageau, Michael A

    2012-01-01

    It has long been noted that batch cultures inoculated with resting bacteria exhibit a progression of growth phases traditionally labeled lag, exponential, pre-stationary and stationary. However, a detailed molecular description of the mechanisms controlling the transitions between these phases is lacking. A core circuit, formed by a subset of regulatory interactions involving five global transcription factors (FIS, HNS, IHF, RpoS and GadX), has been identified by correlating information from the well- established transcriptional regulatory network of Escherichia coli and genome-wide expression data from cultures in these different growth phases. We propose a functional role for this circuit in controlling progression through these phases. Two alternative hypotheses for controlling the transition between the growth phases are first, a continuous graded adjustment to changing environmental conditions, and second, a discontinuous hysteretic switch at critical thresholds between growth phases. We formulate a simple mathematical model of the core circuit, consisting of differential equations based on the power-law formalism, and show by mathematical and computer-assisted analysis that there are critical conditions among the parameters of the model that can lead to hysteretic switch behavior, which--if validated experimentally--would suggest that the transitions between different growth phases might be analogous to cellular differentiation. Based on these provocative results, we propose experiments to test the alternative hypotheses.

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

    Science.gov (United States)

    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. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. A new derivation of the conformally flat stationary cyclic non-circular spacetimes

    International Nuclear Information System (INIS)

    Ayon-Beato, Eloy; Campuzano, Cuauhtemoc; GarcIa, Alberto

    2007-01-01

    We present an alternative way to derive the conformally flat stationary cyclic non-circular spacetimes. We show that there is no room for stationary axisymmetric non-circular axisymmetric spacetimes. We reproduce the well know results for this sort of spacetimes recently reported in [1

  5. A new derivation of the conformally flat stationary cyclic non-circular spacetimes

    Energy Technology Data Exchange (ETDEWEB)

    Ayon-Beato, Eloy [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico); Campuzano, Cuauhtemoc [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico); GarcIa, Alberto [Department of Physics, University of California, Davis, CA 95616 (United States)

    2007-11-15

    We present an alternative way to derive the conformally flat stationary cyclic non-circular spacetimes. We show that there is no room for stationary axisymmetric non-circular axisymmetric spacetimes. We reproduce the well know results for this sort of spacetimes recently reported in [1].

  6. Non-Stationary Dependence Structures for Spatial Extremes

    KAUST Repository

    Huser, Raphaë l; Genton, Marc G.

    2016-01-01

    been developed, and fitted to various types of data. However, a recurrent problem is the modeling of non-stationarity. In this paper, we develop non-stationary max-stable dependence structures in which covariates can be easily incorporated. Inference

  7. Stationary neoclassical profiles of plasma parameters in stellarators

    International Nuclear Information System (INIS)

    Danilkin, I.S.; Mineev, A.B.

    1991-01-01

    The properties of the neoclassical model of heat and particle transport are considered in connection with calculations of stationary profiles of the plasma parameters in stellarators. The most important feature is the poor agreement with real physical conditions of the boundary, which imposes the necessity of invoking either an additional anomalous transport or a special (although technically possible) consistency between the particle and heat sources in order to obtain a solution in the form of a correct monotonically decreasing profile. In search for monotonic stationary profiles maintained by external sources, it is ascertained that the neoclassical theory does not give rise to the well-known multivalued solutions for the ambipolar electric field

  8. HIGH PERFORMANCE STATIONARY DISCHARGES IN THE DIII-D TOKAMAK

    International Nuclear Information System (INIS)

    Luce, T.C.; Wade, M.R.; Ferron, J.R.; Politzer, P.A.; Hyatt, A.W.; Sips, A.C.C.; Murakami, M.

    2003-01-01

    Recent experiments in the DIII-D tokamak [J.L. Luxon, Nucl. Fusion 42,614 (2002)] have demonstrated high β with good confinement quality under stationary conditions. Two classes of stationary discharges are observed--low q 95 discharges with sawteeth and higher q 95 without sawteeth. The discharges are deemed stationary when the plasma conditions are maintained for times greater than the current profile relaxation time. In both cases the normalized fusion performance (β N H 89P /q 95 2 ) reaches or exceeds the value of this parameter projected for Q fus = 10 in the International Thermonuclear Experimental Reactor (ITER) design [R. Aymar, et al., Plasma Phys. Control. Fusion 44, 519 (2002)]. The presence of sawteeth reduces the maximum achievable normalized β, while confinement quality (confinement time relative to scalings) is largely independent of q 95 . Even with the reduced β limit, the normalized fusion performance maximizes at the lowest q 95 . Projections to burning plasma conditions are discussed, including the methodology of the projection and the key physics issues which still require investigation

  9. Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.

    Science.gov (United States)

    Jiang, Hua; Dou, Nannan; Fan, Guoqiang; Yang, Zhaohui; Zhang, Xiaohua

    2013-09-28

    We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.

  10. A simple stationary semi-analytical wake model

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.

    We present an idealized simple, but fast, semi-analytical algorithm for computation of stationary wind farm wind fields with a possible potential within a multi-fidelity strategy for wind farm topology optimization. Basically, the model considers wakes as linear perturbations on the ambient non......-linear. With each of these approached, a parabolic system are described, which is initiated by first considering the most upwind located turbines and subsequently successively solved in the downstream direction. Algorithms for the resulting wind farm flow fields are proposed, and it is shown that in the limit......-uniform mean wind field, although the modelling of the individual stationary wake flow fields includes non-linear terms. The simulation of the individual wake contributions are based on an analytical solution of the thin shear layer approximation of the NS equations. The wake flow fields are assumed...

  11. Information theory explanation of the fluctuation theorem, maximum entropy production and self-organized criticality in non-equilibrium stationary states

    CERN Document Server

    Dewar, R

    2003-01-01

    Jaynes' information theory formalism of statistical mechanics is applied to the stationary states of open, non-equilibrium systems. First, it is shown that the probability distribution p subGAMMA of the underlying microscopic phase space trajectories GAMMA over a time interval of length tau satisfies p subGAMMA propor to exp(tau sigma subGAMMA/2k sub B) where sigma subGAMMA is the time-averaged rate of entropy production of GAMMA. Three consequences of this result are then derived: (1) the fluctuation theorem, which describes the exponentially declining probability of deviations from the second law of thermodynamics as tau -> infinity; (2) the selection principle of maximum entropy production for non-equilibrium stationary states, empirical support for which has been found in studies of phenomena as diverse as the Earth's climate and crystal growth morphology; and (3) the emergence of self-organized criticality for flux-driven systems in the slowly-driven limit. The explanation of these results on general inf...

  12. Plasma oscillations in a stationary external magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ciulli, S [Joint Institute for Nuclear Research, Dubna, Moscow (USSR); Micu, M [Institute of Atomic Physics, Bucharest (Romania)

    1958-07-01

    The stationary distribution function as well as the small deviations from the stationary state of a gas discharge using the Boltzmann equation is studied as a basis for the calculations. The stationary problem which is discussed corresponds to plasma with cylindrical symmetry. It leads to a Maxwell velocity distribution and to a spatial distribution function which has the asymptotic form 1/r{sup 4}. The plasma perturbations are estimated by the deviations of the first order moments from their Maxwell values. A homogeneous system of differential equations is derived for the Fourier amplitudes of the magnetic field and their asymptotic form is studied. The dispersion relation is obtained by joining smoothly a solution regular at the origin with the regular asymptotic one.A number of idealizations and approximations have been made in the present analysis which limit the utility of the formulae obtained. For example, if the collision term is included in the Boltzmann equation additional quantities appear in the final results, i.e., viscosity, thermal and electrical conductivity, etc. Furthermore, the finite dimensions of linear discharge tubes or the toroidal form of some discharges strongly modify the present results. Taking into account these additional effects, exact solutions are to be obtained numerically for different values of the experimental parameters.

  13. A Model for Solving the Maxwell Quasi Stationary Equations in a 3-Phase Electric Reduction Furnace

    Directory of Open Access Journals (Sweden)

    S. Ekrann

    1982-10-01

    Full Text Available A computer code has been developed for the approximate computation of electric and magnetic fields within an electric reduction furnace. The paper describes the numerical methods used to solve Maxwell's quasi-stationary equations, which are the governing equations for this problem. The equations are discretized by a staggered grid finite difference technique. The resulting algebraic equations are solved by iterating between computations of electric and magnetic quantities. This 'outer' iteration converges only when the skin depth is larger or of about the same magnitude as the linear dimensions of the computational domain. In solving for electric quantities with magnetic quantities being regarded as known, and vice versa, the central computational task is the solution of a Poisson equation for a scalar potential. These equations are solved by line successive overrelaxation combined with a rebalancing technique.

  14. Non-stationary dynamics of climate variability in synchronous influenza epidemics in Japan

    Science.gov (United States)

    Onozuka, Daisuke; Hagihara, Akihito

    2015-09-01

    Seasonal variation in the incidence of influenza is widely assumed. However, few studies have examined non-stationary relationships between global climate factors and influenza epidemics. We examined the monthly incidence of influenza in Fukuoka, Japan, from 2000 to 2012 using cross-wavelet coherency analysis to assess the patterns of associations between indices for the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). The monthly incidence of influenza showed cycles of 1 year with the IOD and 2 years with ENSO indices (Multivariate, Niño 4, and Niño 3.4). These associations were non-stationary and appeared to have major influences on the synchrony of influenza epidemics. Our study provides quantitative evidence that non-stationary associations have major influences on synchrony between the monthly incidence of influenza and the dynamics of the IOD and ENSO. Our results call for the consideration of non-stationary patterns of association between influenza cases and climatic factors in early warning systems.

  15. Condensation in models with factorized and pair-factorized stationary states

    International Nuclear Information System (INIS)

    Evans, M R; Waclaw, B

    2015-01-01

    Non-equilibrium real-space condensation is a phenomenon in which a finite fraction of some conserved quantity (mass, particles, etc) becomes spatially localized. We review two popular stochastic models of hopping particles that lead to condensation and whose stationary states assume a factorized form: the zero-range process and the misanthrope process, and their various generalizations. We also introduce a new model—a misanthrope process with parallel dynamics—that exhibits condensation and has a pair-factorized stationary state

  16. A dissipative model of solar system and stability of stationary rotations

    Science.gov (United States)

    Vilke, V. G.

    2009-04-01

    receives the equations describing movements of the centers of mass of planets and their own rotations. In the offered model takes place a dissipation of the energy which source are internally viscous forces of each planet. The system supposes the first integral - the law of preservation of the kinetic moment concerning the centre of mass of system. As a result of deformations of planets in the law of the universal gravitation which has been written down for material points, there are small conservative amendments. The equations of motion describe motions of the centers of mass of planets and their rotation around of the centers of mass in view of the tidal phenomena and the dissipative forces. The connected system of the equations consists of 3 the vector equations of the second order representing the theorems of motion of the center of mass of planets, and the vector equations of the first order determining changes of the own kinetic moments of each planet. Stationary values of full mechanical energy on the variety set in integral of the kinetic moment, correspond to stationary motions - to rotations of system as rigid body with constant angular velocity around of the centre of mass of all system. Angular velocity of stationary rotation is directed along a constant vector of the kinetic moment, and the axis of rotation is the principal central axis of inertia of system. We shall notice, that deformations of planets in stationary motion are constant, as in system of coordinates rotating with constant angular velocity centrifugal forces and forces of gravitational interaction of planets are constant. Stationary configurations of system are determined according to Routh`s technique as stationary points of the changed potential energy submitted by the sum potential energies of centrifugal and gravitational forces. The first variation of the changed potential energy addresses in zero on a stationary configuration. The judgment about stability stationary configurations is based

  17. Uniqueness of solution to a stationary boundary kinetic problem

    International Nuclear Information System (INIS)

    Zhykharsky, A.V.

    1992-01-01

    The paper treats the question of uniqueness of solution to the boundary kinetic problem. This analysis is based on the accurate solutions to the stationary one-dimensional boundary kinetic problem for the limited plasma system. In the paper a simplified problem statement is used (no account is taken of the external magnetic field, a simplest form of boundary conditions is accepted) which, however, covers all features of the problem considered. Omitting the details of the conclusion we will write a set of Vlasov stationary kinetic equations for the cases of plane, cylindrical and spherical geometry of the problem. (author) 1 ref

  18. Stationary striations due to interaction of two ionization waves in xenon glow discharge

    International Nuclear Information System (INIS)

    Maruyama, T.; Nishina, S.; Kitamura, H.; Itagaki, K.; Mizuochi, H.

    1990-01-01

    Experimental observations on stationary striations in the positive column of xenon discharge are reported. Stationary striations are observed when two ionization waves exist simultaneously in the positive column at low pressure and high current region. These stationary striations are caused by nonlinear interference of two backward ionization waves of which frequencies are either equal or are in the ratio 1:2. The spatial intervals for the striated pattern are equal to the reciprocal of the difference between the wave-numbers of two ionization waves. (orig.)

  19. On the Existence of Solutions for Stationary Mean-Field Games with Congestion

    KAUST Repository

    Evangelista, David; Gomes, Diogo A.

    2017-01-01

    Mean-field games (MFGs) are models of large populations of rational agents who seek to optimize an objective function that takes into account their location and the distribution of the remaining agents. Here, we consider stationary MFGs with congestion and prove the existence of stationary solutions. Because moving in congested areas is difficult, agents prefer to move in non-congested areas. As a consequence, the model becomes singular near the zero density. The existence of stationary solutions was previously obtained for MFGs with quadratic Hamiltonians thanks to a very particular identity. Here, we develop robust estimates that give the existence of a solution for general subquadratic Hamiltonians.

  20. An inversion-relaxation approach for sampling stationary points of spin model Hamiltonians

    International Nuclear Information System (INIS)

    Hughes, Ciaran; Mehta, Dhagash; Wales, David J.

    2014-01-01

    Sampling the stationary points of a complicated potential energy landscape is a challenging problem. Here, we introduce a sampling method based on relaxation from stationary points of the highest index of the Hessian matrix. We illustrate how this approach can find all the stationary points for potentials or Hamiltonians bounded from above, which includes a large class of important spin models, and we show that it is far more efficient than previous methods. For potentials unbounded from above, the relaxation part of the method is still efficient in finding minima and transition states, which are usually the primary focus of attention for atomistic systems

  1. On the Existence of Solutions for Stationary Mean-Field Games with Congestion

    KAUST Repository

    Evangelista, David

    2017-09-11

    Mean-field games (MFGs) are models of large populations of rational agents who seek to optimize an objective function that takes into account their location and the distribution of the remaining agents. Here, we consider stationary MFGs with congestion and prove the existence of stationary solutions. Because moving in congested areas is difficult, agents prefer to move in non-congested areas. As a consequence, the model becomes singular near the zero density. The existence of stationary solutions was previously obtained for MFGs with quadratic Hamiltonians thanks to a very particular identity. Here, we develop robust estimates that give the existence of a solution for general subquadratic Hamiltonians.

  2. Stationary measure in the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Linde, Andrei [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Vanchurin, Vitaly; Winitzki, Sergei, E-mail: alinde@stanford.edu, E-mail: vitaly@cosmos2.phy.tufts.edu, E-mail: winitzki@physik.uni-muenchen.de [Department of Physics, Ludwig-Maximilians University, Munich (Germany)

    2009-01-15

    We study the recently proposed ''stationary measure'' in the context of the string landscape scenario. We show that it suffers neither from the ''Boltzmann brain'' problem nor from the ''youngness'' paradox that makes some other measures predict a high CMB temperature at present. We also demonstrate a good performance of this measure in predicting the results of local experiments, such as proton decay.

  3. Bridging the gap between a stationary point process and its Palm distribution

    NARCIS (Netherlands)

    Nieuwenhuis, G.

    1994-01-01

    In the context of stationary point processes measurements are usually made from a time point chosen at random or from an occurrence chosen at random. That is, either the stationary distribution P or its Palm distribution P° is the ruling probability measure. In this paper an approach is presented to

  4. METHOD OF CALCULATION OF THE NON-STATIONARY TEMPERATURE FIELD INSIDE OF THERMAL PACKED BED ENERGY STORAGE

    Directory of Open Access Journals (Sweden)

    Ermuratschii V.V.

    2014-04-01

    Full Text Available e paper presents a method of the approximate calculation of the non-stationary temperature field inside of thermal packed bed energy storages with feasible and latent heat. Applying thermoelectric models and computational methods in electrical engineering, the task of computing non-stationary heat transfer is resolved with respect to third type boundary conditions without applying differential equations of the heat transfer. For sub-volumes of the energy storage the method is executed iteratively in spatiotemporal domain. Single-body heating is modeled for each sub-volume, and modeling conditions are assumed to be identical for remained bod-ies, located in the same sub-volume. For each iteration step the boundary conditions will be represented by re-sults at the previous step. The fulfillment of the first law of thermodynamics for system “energy storage - body” is obtained by the iterative search of the mean temperature of the energy storage. Under variable boundary con-ditions the proposed method maybe applied to calculating temperature field inside of energy storages with packed beds consisted of solid material, liquid and phase-change material. The method may also be employed to compute transient, power and performance characteristics of packed bed energy storages.

  5. Cross-beam energy transfer: On the accuracy of linear stationary models in the linear kinetic regime

    Science.gov (United States)

    Debayle, A.; Masson-Laborde, P.-E.; Ruyer, C.; Casanova, M.; Loiseau, P.

    2018-05-01

    We present an extensive numerical study by means of particle-in-cell simulations of the energy transfer that occurs during the crossing of two laser beams. In the linear regime, when ions are not trapped in the potential well induced by the laser interference pattern, a very good agreement is obtained with a simple linear stationary model, provided the laser intensity is sufficiently smooth. These comparisons include different plasma compositions to cover the strong and weak Landau damping regimes as well as the multispecies case. The correct evaluation of the linear Landau damping at the phase velocity imposed by the laser interference pattern is essential to estimate the energy transfer rate between the laser beams, once the stationary regime is reached. The transient evolution obtained in kinetic simulations is also analysed by means of a full analytical formula that includes 3D beam energy exchange coupled with the ion acoustic wave response. Specific attention is paid to the energy transfer when the laser presents small-scale inhomogeneities. In particular, the energy transfer is reduced when the laser inhomogeneities are comparable with the Landau damping characteristic length of the ion acoustic wave.

  6. Characterization of Stationary Distributions of Reflected Diffusions

    Science.gov (United States)

    2014-01-01

    operations research to finance and mathemat- ical physics , and their stationary distributions often serve to characterize or approximate important...REFERENCES [1] Atar , R., Budhiraja, A. and Dupuis, P. (2001). On positive recurrence of constrained diffusion processes. Ann. Probab., 29 No. 2, 979-1000

  7. Robust Forecasting of Non-Stationary Time Series

    NARCIS (Netherlands)

    Croux, C.; Fried, R.; Gijbels, I.; Mahieu, K.

    2010-01-01

    This paper proposes a robust forecasting method for non-stationary time series. The time series is modelled using non-parametric heteroscedastic regression, and fitted by a localized MM-estimator, combining high robustness and large efficiency. The proposed method is shown to produce reliable

  8. Linear simulation of the stationary eddies in a GCM. II - The 'Mountain' model

    Science.gov (United States)

    Nigam, Sumant; Held, Isaac M.; Lyons, Steven W.

    1988-01-01

    Linear stationary wave theory is used to account for zonal asymmetries of the winter-averaged tropospheric circulation obtained in a GCM. The eddy zonal velocity field in the upper troposphere indicates that the orographic and thermal plus transient contributions are nearly equal in amplitude, while the eddy meridional velocity field (which is dominated by shorter zonal scales) shows the orographic contribution to be dominant. The two contributions are found to be roughly in phase over the east Asian coast, and they contribute roughly equal amounts to the low level Siberian high. Results indicate that the 300 mb extratropical response to tropical forcing reaches 50 gpm over Alaska, and that the responses to sensible heating and lower tropospheric transients are strongly anticorrelated.

  9. Drug discovery strategies in the field of tumor energy metabolism: Limitations by metabolic flexibility and metabolic resistance to chemotherapy.

    Science.gov (United States)

    Amoedo, N D; Obre, E; Rossignol, R

    2017-08-01

    The search for new drugs capable of blocking the metabolic vulnerabilities of human tumors has now entered the clinical evaluation stage, but several projects already failed in phase I or phase II. In particular, very promising in vitro studies could not be translated in vivo at preclinical stage and beyond. This was the case for most glycolysis inhibitors that demonstrated systemic toxicity. A more recent example is the inhibition of glutamine catabolism in lung adenocarcinoma that failed in vivo despite a strong addiction of several cancer cell lines to glutamine in vitro. Such contradictory findings raised several questions concerning the optimization of drug discovery strategies in the field of cancer metabolism. For instance, the cell culture models in 2D or 3D might already show strong limitations to mimic the tumor micro- and macro-environment. The microenvironment of tumors is composed of cancer cells of variegated metabolic profiles, supporting local metabolic exchanges and symbiosis, but also of immune cells and stroma that further interact with and reshape cancer cell metabolism. The macroenvironment includes the different tissues of the organism, capable of exchanging signals and fueling the tumor 'a distance'. Moreover, most metabolic targets were identified from their increased expression in tumor transcriptomic studies, or from targeted analyses looking at the metabolic impact of particular oncogenes or tumor suppressors on selected metabolic pathways. Still, very few targets were identified from in vivo analyses of tumor metabolism in patients because such studies are difficult and adequate imaging methods are only currently being developed for that purpose. For instance, perfusion of patients with [ 13 C]-glucose allows deciphering the metabolomics of tumors and opens a new area in the search for effective targets. Metabolic imaging with positron emission tomography and other techniques that do not involve [ 13 C] can also be used to evaluate tumor

  10. Dynamics of the two-dimensional directed Ising model in the paramagnetic phase

    Science.gov (United States)

    Godrèche, C.; Pleimling, M.

    2014-05-01

    We consider the nonconserved dynamics of the Ising model on the two-dimensional square lattice, where each spin is influenced preferentially by its east and north neighbours. The single-spin flip rates are such that the stationary state is Gibbsian with respect to the usual ferromagnetic Ising Hamiltonian. We show the existence, in the paramagnetic phase, of a dynamical transition between two regimes of violation of the fluctuation-dissipation theorem in the nonequilibrium stationary state: a regime of weak violation where the stationary fluctuation-dissipation ratio is finite, when the asymmetry parameter is less than a threshold value, and a regime of strong violation where this ratio vanishes asymptotically above the threshold. This study suggests that this novel kind of dynamical transition in nonequilibrium stationary states, already found for the directed Ising chain and the spherical model with asymmetric dynamics, might be quite general. In contrast with the latter models, the equal-time correlation function for the two-dimensional directed Ising model depends on the asymmetry.

  11. Heat-transfer characteristics of flowing and stationary particle-bed-type fusion-reactor blankets

    International Nuclear Information System (INIS)

    Nietert, R.E.

    1983-02-01

    The following five appendices are included: (1) physical properties of materials, (2) thermal entrance length Nusselt number variations, (3) stationary particle bed temperature variations, (4) falling bed experimental data and calculations, and (5) stationary bed experimental data and calculations

  12. Pool boiling from rotating and stationary spheres in liquid nitrogen

    Science.gov (United States)

    Cuan, Winston M.; Schwartz, Sidney H.

    1988-01-01

    Results are presented for a preliminary experiment involving saturated pool boiling at 1 atm from rotating 2 and 3 in. diameter spheres which were immersed in liquid nitrogen (LN2). Additional results are presented for a stationary, 2 inch diameter sphere, quenched in LN2, which were obtained utilizing a more versatile and complete experimental apparatus that will eventually be used for additional rotating sphere experiments. The speed for the rotational tests was varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere. The average Nusselt number over the cooling period was plotted against the rotational Reynolds number. Stationary sphere results included local boiling heat transfer coefficients at different latitudinal locations, for various pressure and subcooling levels.

  13. Acoustic Characterization of a Stationary Field Synchronous Motor

    National Research Council Canada - National Science Library

    Woodward, E

    2001-01-01

    .... We investigate the gross acoustic signature of a notional stationary field synchronous motor utilized as a marine propulsion motor in a naval combatant using the following methodology: (1) model the forces...

  14. On the Oracle Property of the Adaptive LASSO in Stationary and Nonstationary Autoregressions

    DEFF Research Database (Denmark)

    Kock, Anders Bredahl

    We show that the Adaptive LASSO is oracle efficient in stationary and non-stationary autoregressions. This means that it estimates parameters consistently, selects the correct sparsity pattern, and estimates the coefficients belonging to the relevant variables at the same asymptotic efficiency...

  15. Analysis of expression profile of mce operon genes (mce1, mce2, mce3 operon) in different Mycobacterium tuberculosis isolates at different growth phases.

    Science.gov (United States)

    Singh, Pratibha; Katoch, V M; Mohanty, K K; Chauhan, Devendra Singh

    2016-04-01

    Mycobacterium tuberculosis (M. tuberculosis) has four homologous mammalian cell entry (mce) operons (mce1-4) that encode exported proteins and have a possible role in the virulence mechanism of this pathogen. The expression of mce operon is considered to be complex and not completely understood. Although expression of mce operon at different in vitro growth phases has been studied earlier, its expression in different M. tuberculosis isolates under different growth phases is not yet studied. The present preliminary study was conducted on a limited number of isolates to know the trend of expression pattern of mce operon genes in different M. tuberculosis isolates under different growth stages. In this study, we monitored the transcriptional profile of selected mce operon genes (mce1A, mce1D, mce2A, mce2D, mce3A, mce3C) in different M.tuberculosis isolates (MDR1, MDR2, and sensitive isolate) at early exponential and stationary phases using real-time quantitative PCR. The expression ratio of all selected mce operon genes in all M. tuberculosis isolates was reduced at the initial phase and increased substantially at a later phase of growth. Higher expression of mce1 operon genes was found in all M. tuberculosis isolates as compared to other mce operon genes (mce2 and mce3 operons) at stationary growth phase. the higher expression of mce operon genes at stationary phase (as compared to early exponential phase) suggested growth phase dependent expression of mce operon genes. This indicated that the mce operon genes might have a role in M. tuberculosis survival and adaptation on the onset of adverse condition like stationary phase. Identification of differentially expressed genes will add to our understanding of the bacilli involved in adaptation to different growth conditions.

  16. Intake of Hydrolyzed Casein is Associated with Reduced Body Fat Accretion and Enhanced Phase II Metabolism in Obesity Prone C57BL/6J Mice

    Science.gov (United States)

    Clausen, Morten Rahr; Zhang, Xumin; Yde, Christian C.; Ditlev, Ditte B.; Lillefosse, Haldis H.; Madsen, Lise; Kristiansen, Karsten; Liaset, Bjørn; Bertram, Hanne C.

    2015-01-01

    The amount and form of dietary casein have been shown to affect energy metabolism and lipid accumulation in mice, but the underlying mechanisms are not fully understood. We investigated 48 hrs urinary metabolome, hepatic lipid composition and gene expression in male C57BL/6J mice fed Western diets with 16 or 32 energy% protein in the form of extensively hydrolyzed or intact casein. LC-MS based metabolomics revealed a very strong impact of casein form on the urinary metabolome. Evaluation of the discriminatory metabolites using tandem mass spectrometry indicated that intake of extensively hydrolyzed casein modulated Phase II metabolism associated with an elevated urinary excretion of glucuronic acid- and sulphate conjugated molecules, whereas glycine conjugated molecules were more abundant in urine from mice fed the intact casein diets. Despite the differences in the urinary metabolome, we observed no differences in hepatic expression of genes involved in Phase II metabolism, but it was observed that expression of Abcc3 encoding ATP binding cassette c3 (transporter of glucuronic acid conjugates) was increased in livers of mice fed hydrolyzed casein. As glucuronic acid is derived from glucose and sulphate is derived from cysteine, our metabolomic data provided evidence for changes in carbohydrate and amino acid metabolism and we propose that this modulation of metabolism was associated with the reduced glucose and lipid levels observed in mice fed the extensively hydrolyzed casein diets. PMID:25738501

  17. Removal of Stationary Sinusoidal Noise from Random Vibration Signals.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Brian; Cap, Jerome S.

    2018-02-01

    In random vibration environments, sinusoidal line noise may appear in the vibration signal and can affect analysis of the resulting data. We studied two methods which remove stationary sine tones from random noise: a matrix inversion algorithm and a chirp-z transform algorithm. In addition, we developed new methods to determine the frequency of the tonal noise. The results show that both of the removal methods can eliminate sine tones in prefabricated random vibration data when the sine-to-random ratio is at least 0.25. For smaller ratios down to 0.02 only the matrix inversion technique can remove the tones, but the metrics to evaluate its effectiveness also degrade. We also found that using fast Fourier transforms best identified the tonal noise, and determined that band-pass-filtering the signals prior to the process improved sine removal. When applied to actual vibration test data, the methods were not as effective at removing harmonic tones, which we believe to be a result of mixed-phase sinusoidal noise.

  18. Stationary flow near fronts

    Directory of Open Access Journals (Sweden)

    Reinhold Steinacker

    2016-12-01

    Full Text Available In 1906, the Austrian scientist Max Margules published a paper on temperature stratification in resting and non-accelerated moving air. The paper derives conditions for stationary slopes of air mass boundaries and was an important forerunner of frontal theories. Its formulation of relations between changes in density and geostrophic wind across the front is basically a discrete version of the thermal wind balance equation. The paper was highly influential and is still being cited to the present day. This paper accompanies an English translation of Margules’ seminal paper. We conclude here our “Classic Papers” series of the Meteorologische Zeitschrift.

  19. Metabolic response of Pseudomonas putida during redox biocatalysis in the presence of a second octanol phase.

    Science.gov (United States)

    Blank, Lars M; Ionidis, Georgios; Ebert, Birgitta E; Bühler, Bruno; Schmid, Andreas

    2008-10-01

    A key limitation of whole-cell redox biocatalysis for the production of valuable, specifically functionalized products is substrate/product toxicity, which can potentially be overcome by using solvent-tolerant micro-organisms. To investigate the inter-relationship of solvent tolerance and energy-dependent biocatalysis, we established a model system for biocatalysis in the presence of toxic low logP(ow) solvents: recombinant solvent-tolerant Pseudomonas putida DOT-T1E catalyzing the stereospecific epoxidation of styrene in an aqueous/octanol two-liquid phase reaction medium. Using (13)C tracer based metabolic flux analysis, we investigated the central carbon and energy metabolism and quantified the NAD(P)H regeneration rate in the presence of toxic solvents and during redox biocatalysis, which both drastically increased the energy demands of solvent-tolerant P. putida. According to the driven by demand concept, the NAD(P)H regeneration rate was increased up to eightfold by two mechanisms: (a) an increase in glucose uptake rate without secretion of metabolic side products, and (b) reduced biomass formation. However, in the presence of octanol, only approximately 1% of the maximally observed NAD(P)H regeneration rate could be exploited for styrene epoxidation, of which the rate was more than threefold lower compared with operation with a non-toxic solvent. This points to a high energy and redox cofactor demand for cell maintenance, which limits redox biocatalysis in the presence of octanol. An estimated upper bound for the NAD(P)H regeneration rate available for biocatalysis suggests that cofactor availability does not limit redox biocatalysis under optimized conditions, for example, in the absence of toxic solvent, and illustrates the high metabolic capacity of solvent-tolerant P. putida. This study shows that solvent-tolerant P. putida have the remarkable ability to compensate for high energy demands by boosting their energy metabolism to levels up to an order of

  20. A Yeast Mutant Deleted of GPH1 Bears Defects in Lipid Metabolism.

    Directory of Open Access Journals (Sweden)

    Martina Gsell

    Full Text Available In a previous study we demonstrated up-regulation of the yeast GPH1 gene under conditions of phosphatidylethanolamine (PE depletion caused by deletion of the mitochondrial (M phosphatidylserine decarboxylase 1 (PSD1 (Gsell et al., 2013, PLoS One. 8(10:e77380. doi: 10.1371/journal.pone.0077380. Gph1p has originally been identified as a glycogen phosphorylase catalyzing degradation of glycogen to glucose in the stationary growth phase of the yeast. Here we show that deletion of this gene also causes decreased levels of phosphatidylcholine (PC, triacylglycerols and steryl esters. Depletion of the two non-polar lipids in a Δgph1 strain leads to lack of lipid droplets, and decrease of the PC level results in instability of the plasma membrane. In vivo labeling experiments revealed that formation of PC via both pathways of biosynthesis, the cytidine diphosphate (CDP-choline and the methylation route, is negatively affected by a Δgph1 mutation, although expression of genes involved is not down regulated. Altogether, Gph1p besides its function as a glycogen mobilizing enzyme appears to play a regulatory role in yeast lipid metabolism.