WorldWideScience

Sample records for arcab two-component system

  1. Feedback Control of Two-Component Regulatory Systems.

    Science.gov (United States)

    Groisman, Eduardo A

    2016-09-01

    Two-component systems are a dominant form of bacterial signal transduction. The prototypical two-component system consists of a sensor that responds to a specific input(s) by modifying the output of a cognate regulator. Because the output of a two-component system is the amount of phosphorylated regulator, feedback mechanisms may alter the amount of regulator, and/or modify the ability of a sensor or other proteins to alter the phosphorylation state of the regulator. Two-component systems may display intrinsic feedback whereby the amount of phosphorylated regulator changes under constant inducing conditions and without the participation of additional proteins. Feedback control allows a two-component system to achieve particular steady-state levels, to reach a given steady state with distinct dynamics, to express coregulated genes in a given order, and to activate a regulator to different extents, depending on the signal acting on the sensor. PMID:27607549

  2. Theory of Ostwald ripening in a two-component system

    Science.gov (United States)

    Baird, J. K.; Lee, L. K.; Frazier, D. O.; Naumann, R. J.

    1986-01-01

    When a two-component system is cooled below the minimum temperature for its stability, it separates into two or more immiscible phases. The initial nucleation produces grains (if solid) or droplets (if liquid) of one of the phases dispersed in the other. The dynamics by which these nuclei proceed toward equilibrium is called Ostwald ripening. The dynamics of growth of the droplets depends upon the following factors: (1) The solubility of the droplet depends upon its radius and the interfacial energy between it and the surrounding (continuous) phase. There is a critical radius determined by the supersaturation in the continuous phase. Droplets with radii smaller than critical dissolve, while droplets with radii larger grow. (2) The droplets concentrate one component and reject the other. The rate at which this occurs is assumed to be determined by the interdiffusion of the two components in the continuous phase. (3) The Ostwald ripening is constrained by conservation of mass; e.g., the amount of materials in the droplet phase plus the remaining supersaturation in the continuous phase must equal the supersaturation available at the start. (4) There is a distribution of droplet sizes associated with a mean droplet radius, which grows continuously with time. This distribution function satisfies a continuity equation, which is solved asymptotically by a similarity transformation method.

  3. Efficient two-component relativistic method for large systems

    International Nuclear Information System (INIS)

    This paper reviews a series of theoretical studies to develop efficient two-component (2c) relativistic method for large systems by the author’s group. The basic theory is the infinite-order Douglas-Kroll-Hess (IODKH) method for many-electron Dirac-Coulomb Hamiltonian. The local unitary transformation (LUT) scheme can effectively produce the 2c relativistic Hamiltonian, and the divide-and-conquer (DC) method can achieve linear-scaling of Hartree-Fock and electron correlation methods. The frozen core potential (FCP) theoretically connects model potential calculations with the all-electron ones. The accompanying coordinate expansion with a transfer recurrence relation (ACE-TRR) scheme accelerates the computations of electron repulsion integrals with high angular momenta and long contractions

  4. Efficient two-component relativistic method for large systems

    Energy Technology Data Exchange (ETDEWEB)

    Nakai, Hiromi [Department of Chemitsry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Elements Strategy Initiative for Catalysts and Batteries (ESICB), Kyoto University, Katsura, Kyoto 615-8520 (Japan)

    2015-12-31

    This paper reviews a series of theoretical studies to develop efficient two-component (2c) relativistic method for large systems by the author’s group. The basic theory is the infinite-order Douglas-Kroll-Hess (IODKH) method for many-electron Dirac-Coulomb Hamiltonian. The local unitary transformation (LUT) scheme can effectively produce the 2c relativistic Hamiltonian, and the divide-and-conquer (DC) method can achieve linear-scaling of Hartree-Fock and electron correlation methods. The frozen core potential (FCP) theoretically connects model potential calculations with the all-electron ones. The accompanying coordinate expansion with a transfer recurrence relation (ACE-TRR) scheme accelerates the computations of electron repulsion integrals with high angular momenta and long contractions.

  5. Two component systems: physiological effect of a third component.

    Directory of Open Access Journals (Sweden)

    Baldiri Salvado

    Full Text Available Signal transduction systems mediate the response and adaptation of organisms to environmental changes. In prokaryotes, this signal transduction is often done through Two Component Systems (TCS. These TCS are phosphotransfer protein cascades, and in their prototypical form they are composed by a kinase that senses the environmental signals (SK and by a response regulator (RR that regulates the cellular response. This basic motif can be modified by the addition of a third protein that interacts either with the SK or the RR in a way that could change the dynamic response of the TCS module. In this work we aim at understanding the effect of such an additional protein (which we call "third component" on the functional properties of a prototypical TCS. To do so we build mathematical models of TCS with alternative designs for their interaction with that third component. These mathematical models are analyzed in order to identify the differences in dynamic behavior inherent to each design, with respect to functionally relevant properties such as sensitivity to changes in either the parameter values or the molecular concentrations, temporal responsiveness, possibility of multiple steady states, or stochastic fluctuations in the system. The differences are then correlated to the physiological requirements that impinge on the functioning of the TCS. This analysis sheds light on both, the dynamic behavior of synthetically designed TCS, and the conditions under which natural selection might favor each of the designs. We find that a third component that modulates SK activity increases the parameter space where a bistable response of the TCS module to signals is possible, if SK is monofunctional, but decreases it when the SK is bifunctional. The presence of a third component that modulates RR activity decreases the parameter space where a bistable response of the TCS module to signals is possible.

  6. Brazilian two-component TLD albedo neutron individual monitoring system

    International Nuclear Information System (INIS)

    Since 1983, Instituto de Radioprotecao e Dosimetria, Brazil, uses a TLD one-component albedo neutron monitor, which has a single different calibration factor specifically for each installation type. In order to improve its energy response, a two-component albedo monitor was developed, which measure the thermal neutron component besides the albedo one. The two-component monitor has been calibrated in reference neutron fields: thermal, five accelerator-produced monoenergetic beams (70, 144, 565, 1200 and 5000 keV) and five radionuclide sources (252Cf, 252Cf(D2O), 241Am-Be, 241Am-B and 238Pu-Be) at several distances. Since January 2008, mainly Brazilian workers who handle neutron sources at different distances and moderation, such as in well logging and calibration facilities are using it routinely.

  7. The Fractional Virial Potential Energy in Two-Component Systems

    Directory of Open Access Journals (Sweden)

    Caimmi, R.

    2008-12-01

    Full Text Available Two-component systems are conceived as macrogases, and the related equation of state is expressed using the virial theorem for subsystems, under the restriction of homeoidally striated density profiles. Explicit calculations are performed for a useful reference case and a few cases of astrophysical interest, both with and without truncation radius. Shallower density profiles are found to yield an equation of state, $phi=phi(y,m$, characterized (for assigned values of the fractional mass, $m=M_j/ M_i$ by the occurrence of two extremum points, a minimum and a maximum, as found in an earlier attempt. Steeper density profiles produce a similar equation of state, which implies that a special value of $m$ is related to a critical curve where the above mentioned extremum points reduce to a single horizontal inflexion point, and curves below the critical one show no extremum points. The similarity of the isofractional mass curves to van der Waals' isothermal curves, suggests the possibility of a phase transition in a bell-shaped region of the $({sf O}yphi$ plane, where the fractional truncation radius along a selected direction is $y=R_j/R_i$, and the fractional virial potential energy is $phi=(E_{ji}_mathrm{vir}/(E_{ij}_mathrm{vir}$. Further investigation is devoted to mass distributions described by Hernquist (1990 density profiles, for which an additional relation can be used to represent a sample of $N=16$ elliptical galaxies (EGs on the $({sf O}yphi$ plane. Even if the evolution of elliptical galaxies and their hosting dark matter (DM haloes, in the light of the model, has been characterized by equal fractional mass, $m$, and equal scaled truncation radius, or concentration, $Xi_u=R_u/r_u^dagger$, $u=i,j$, still it cannot be considered as strictly homologous, due to different values of fractional truncation radii, $y$, or fractional scaling radii, $y^dagger=r_j^dagger/r_i^dagger$, deduced from sample objects.

  8. Methods of producing epoxides from alkenes using a two-component catalyst system

    Science.gov (United States)

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

    2013-07-09

    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  9. Crystallographic characterization of a multidomain histidine protein kinase from an essential two-component regulatory system

    OpenAIRE

    Zhao, Haiyan; Tang, Liang

    2009-01-01

    The multidomain cytoplasmic portion of the histidine protein kinase from an essential two-component signal transduction system has been crystallized and X-ray data have been collected to 2.8 Å resolution.

  10. Two-Component Signal Transduction Systems in the Cyanobacterium Synechocystis sp. PCC 6803

    Institute of Scientific and Technical Information of China (English)

    LIU Xingguo; HUANG Wei; WU Qingyu

    2006-01-01

    Two-component systems are signal transduction systems which enable bacteria to regulate cellular functions in response to changing environmental conditions. The unicellular Synechocystis sp. PCC 6803 has become a model organism for a range of biochemical and molecular biology studies aiming at investigating environmental stress response. The publication of the complete genome sequence of the cyanobacterium Synechocystis sp. PCC 6803 provided a tremendous stimulus for research in this field, and at least 80 open reading frames were identified as members of the two-component signal transduction systems in this single species of cyanobacteria. To date, functional roles have been determined for only a limited number of such proteins. This review summarizes our current knowledge about the two-component signal transduction systems in Synechocystis sp. PCC 6803 and describes recent achievements in elucidating the functional roles of these systems.

  11. The Qualitative Analysis of a Solution of a Series Maintenance System with Two Components

    Institute of Scientific and Technical Information of China (English)

    GUOWei-hua; YANGMing-zeng

    2003-01-01

    In this paper, firstly we study the series maintenance system with two components, obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operators theory. Then we prove that 0 is the eigenvalue of the system's host operators, and finally we study the eigenvector of the eigenvalue 0.

  12. The essential YycFG two-component system controls cell wall metabolism in Bacillus subtilis

    DEFF Research Database (Denmark)

    Bisicchia, Paola; Noone, David; Lioliou, Efthimia;

    2007-01-01

    Adaptation of bacteria to the prevailing environmental and nutritional conditions is often mediated by two-component signal transduction systems (TCS). The Bacillus subtilis YycFG TCS has attracted special attention as it is essential for viability and its regulon is poorly defined. Here we show...

  13. A novel two-component system found in Mycobacterium tuberculosis

    DEFF Research Database (Denmark)

    Morth, J. P.; Gosmann, S.; Nowak, E.;

    2005-01-01

    We report the identification of a novel two-component system in Mycobacterium tuberculosis. We show that the putative histidine kinase with the genomic locus tag Rv3220c is able to self-phosphorylate in the presence of Mg2+/ATP and subsequently transfer the phosphoryl group to a novel response...

  14. The CpxRA two-component system is essential for Citrobacter rodentium virulence.

    Science.gov (United States)

    Thomassin, Jenny-Lee; Giannakopoulou, Natalia; Zhu, Lei; Gross, Jeremy; Salmon, Kristiana; Leclerc, Jean-Mathieu; Daigle, France; Le Moual, Hervé; Gruenheid, Samantha

    2015-05-01

    Citrobacter rodentium is a murine intestinal pathogen used as a model for the foodborne human pathogens enterohemorrhagic Escherichia coli and enteropathogenic E. coli. During infection, these pathogens use two-component signal transduction systems to detect and adapt to changing environmental conditions. In E. coli, the CpxRA two-component signal transduction system responds to envelope stress by modulating the expression of a myriad of genes. Quantitative real-time PCR showed that cpxRA was expressed in the colon of C57BL/6J mice infected with C. rodentium. To determine whether CpxRA plays a role during C. rodentium infection, a cpxRA deletion strain was generated and found to have a colonization defect during infection. This defect was independent of an altered growth rate or a defective type III secretion system, and single-copy chromosomal complementation of cpxRA restored virulence. The C. rodentium strains were then tested in C3H/HeJ mice, a lethal intestinal infection model. Mice infected with the ΔcpxRA strain survived infection, whereas mice infected with the wild-type or complemented strains succumbed to infection. Furthermore, we found that the cpxRA expression level was higher during early infection than at a later time point. Taken together, these data demonstrate that the CpxRA two-component signal transduction system is essential for the in vivo virulence of C. rodentium. In addition, these data suggest that fine-tuned cpxRA expression is important for infection. This is the first study that identifies a C. rodentium two-component transduction system required for pathogenesis. This study further indicates that CpxRA is an interesting target for therapeutics against enteric pathogens.

  15. Bioinformatics analysis of two-component regulatory systems in Staphylococcus epidermidis

    Institute of Scientific and Technical Information of China (English)

    QIN Zhiqiang; ZHONG Yang; ZHANG Jian; HE Youyu; WU Yang; JIANG Juan; CHEN Jiemin; LUO Xiaomin; QU Di

    2004-01-01

    Sixteen pairs of two-component regulatory systems are identified in the genome of Staphylococcus epidermidis ATCC12228 strain, which is newly sequenced by our laboratory for Medical Molecular Virology and Chinese National Human Genome Center at Shanghai, by using bioinformatics analysis. Comparative analysis of the twocomponent regulatory systems in S. epidermidis and that of S.aureus and Bacillus subtilis shows that these systems may regulate some important biological functions, e.g. growth,biofilm formation, and expression of virulence factors in S.epidermidis. Two conserved domains, i.e. HATPase_c and REC domains, are found in all 16 pairs of two-component proteins.Homologous modelling analysis indicates that there are 4similar HATPase_c domain structures of histidine kinases and 13 similar REC domain structures of response regulators,and there is one AMP-PNP binding pocket in the HATPase_c domain and three active aspartate residues in the REC domain. Preliminary experiment reveals that the bioinformatics analysis of the conserved domain structures in the two-component regulatory systems in S. epidermidis may provide useful information for discovery of potential drug target.

  16. Periodic and Solitary Wave Solutions of Two Component Zakharov-Yajima-Oikawa System, Using Madelung's Approach

    Directory of Open Access Journals (Sweden)

    Anca Visinescu

    2011-04-01

    Full Text Available Using the multiple scales method, the interaction between two bright and one dark solitons is studied. Provided that a long wave-short wave resonance condition is satisfied, the two-component Zakharov-Yajima-Oikawa (ZYO completely integrable system is obtained. By using a Madelung fluid description, the one-soliton solutions of the corresponding ZYO system are determined. Furthermore, a discussion on the interaction between one bright and two dark solitons is presented. In particular, this problem is reduced to solve a one-component ZYO system in the resonance conditions.

  17. On the inspection policy of a two-component parallel system with failure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Zequeira, Romulo I. [ISTIT, Equipe Modelisation et Surete des Systemes, Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes Cedex (France)]. E-mail: romulo.zequeira@utt.fr; Berenguer, Christophe [ISTIT, Equipe Modelisation et Surete des Systemes, Universite de Technologie de Troyes, 12 Rue Marie Curie, BP 2060, 10010 Troyes Cedex (France)]. E-mail: christophe.berenguer@utt.fr

    2005-04-01

    In this paper we study a two-component standby system which can successfully operate upon a demand if at least one component is not failed. We assume that failures can be detected only by periodic inspections. We consider that the failure of one component can modify the (conditional) failure probability of the component still alive with probability p and do not interact with probability 1-p. For that failure interaction scheme we obtain the system reliability function for the case of staggered inspections. We compare staggered and non-staggered inspections through numerical examples considering constant hazard rates.

  18. The Two-Component Virial Theorem and the Physical Properties of Stellar Systems.

    Science.gov (United States)

    Dantas; Ribeiro; Capelato; de Carvalho RR

    2000-01-01

    Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem that explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the baryonic or luminous component. Our analysis shows that the application of such a "two-component virial theorem" not only accounts for the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters. PMID:10587482

  19. The Two-Component Virial Theorem and the Physical Properties of Stellar Systems.

    Science.gov (United States)

    Dantas; Ribeiro; Capelato; de Carvalho RR

    2000-01-01

    Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem that explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the baryonic or luminous component. Our analysis shows that the application of such a "two-component virial theorem" not only accounts for the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters.

  20. Collective degrees of freedom of the two-component nuclear system

    International Nuclear Information System (INIS)

    A microscopic proton-neutron symplectic model of collective motions, based on the non-compact symplectic group Sp(12, R), is introduced by considering the symplectic geometry of the two-component many-particle nuclear system. The dynamical group of the whole many-particle system allows the separation of the nuclear variables into kinematical (internal) and dynamical (collective) ones. Then, the number and type of collective degrees of freedom, related to the dynamical variables, are determined properly by the group-theoretical consideration of the coordinate transformation of the microscopic configuration space, spanned by the m = A-1 translationally invariant Jacobi vectors, to the collective and intrinsic submanifolds. As a result the nuclear wave functions are represented as a product of collective and intrinsic parts. Dynamical content of the Sp(12,R) model is revealed by considering its GCM(6) submodel, which appears as an irrotational flow collective model of the two-component nuclear system augmented by the SO(6) intrinsic vortex degrees of freedom. Consequently, the Sp(12,R) model appears therefore as a hydrodynamic collective model of the proton-neutron nuclear system which include 21 collective irrotational flow degrees of freedom and an U(6) intrinsic structure associated with the vortex degrees of freedom. The latter play an important role in the construction of the microscopic wave functions because they allow to ensure the full antisymmetry of the total wave function and are responsible for the appearance of the low-lying collective bands. (orig.)

  1. Coexistence of superfluid and metallic-like state in two-component fermionic systems

    Energy Technology Data Exchange (ETDEWEB)

    Continentino, M.A., E-mail: mucio@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ (Brazil); Padilha, Igor T. [Universidade Federal do Amazonas, Departamento de Física, Av. Gal. Rodrigo Octávio Jordão Ramos, 3000 Setor Sul e Norte, Coroado I, Manaus (Brazil)

    2012-01-09

    We study the possibility of coexistence in a two component fermionic system of a superfluid state with a metallic-like state with gapless excitations at a Fermi surface. We consider a two-component system with mixing (hybridization) between them and attractive interactions between only one type of quasi-particles. Besides a conventional BCS regime, we find for sufficiently strong interactions a superfluid state of Bose condensed pairs at zero temperature. We investigate whether these pairs can coexist with a metallic-like state characterized by gapless electronic excitations. The zero temperature phase diagram as a function of the strength of the attractive interaction and the mixing is obtained. For simplicity and to clarify the nature of the quantum phase diagram we consider the case of s-wave pairing. -- Highlights: ► We study superconductivity in a multi-component system along the BCS–BEC crossover. ► The T=0 phase diagram exhibits different regimes for the superfluid phases. ► We find a new metallic phase with fermions coexisting with preformed pairs. ► Superconductivity is destroyed from the BEC-like regime.

  2. Two-Component Signal Transduction System SaeRS Positively Regulates Staphylococcus epidermidis Glucose Metabolism

    Directory of Open Access Journals (Sweden)

    Qiang Lou

    2014-01-01

    Full Text Available Staphylococcus epidermidis, which is a causative pathogen of nosocomial infection, expresses its virulent traits such as biofilm and autolysis regulated by two-component signal transduction system SaeRS. In this study, we performed a proteomic analysis of differences in expression between the S. epidermidis 1457 wild-type and saeRS mutant to identify candidates regulated by saeRS using two-dimensional gel electrophoresis (2-DE combined with matrix-assisted laser desorption/lonization mass spectrometry (MALDI-TOF-MS. Of 55 identified proteins that significantly differed in expression between the two strains, 15 were upregulated and 40 were downregulated. The downregulated proteins included enzymes related to glycolysis and TCA cycle, suggesting that glucose is not properly utilized in S. epidermidis when saeRS was deleted. The study will be helpful for treatment of S. epidermidis infection from the viewpoint of metabolic modulation dependent on two-component signal transduction system SaeRS.

  3. Global solutions for the two-component Camassa-Holm system

    CERN Document Server

    Grunert, K; Raynaud, X

    2011-01-01

    We prove existence of a global conservative solution of the Cauchy problem for the two-component Camassa-Holm (2CH) system on the line, allowing for nonvanishing and distinct asymptotics at plus and minus infinity. The solution is proven to be smooth as long as the density is bounded away from zero. Furthermore, we show that by taking the limit of vanishing density in the 2CH system, we obtain the global conservative solution of the (scalar) Camassa-Holm equation, which provides a novel way to define and obtain these solutions. Finally, it is shown that while solutions of the 2CH system have infinite speed of propagation, singularities travel with finite speed.

  4. Novel two-component systems implied in antibiotic production in Streptomyces coelicolor.

    Directory of Open Access Journals (Sweden)

    Ana Yepes

    Full Text Available The abundance of two-component systems (TCSs in Streptomyces coelicolor A3(2 genome indicates their importance in the physiology of this soil bacteria. Currently, several TCSs have been related to antibiotic regulation, and the purpose in this study was the characterization of five TCSs, selected by sequence homology with the well-known absA1A2 system, that could also be associated with this important process. Null mutants of the five TCSs were obtained and two mutants (ΔSCO1744/1745 and ΔSCO4596/4597/4598 showed significant differences in both antibiotic production and morphological differentiation, and have been renamed as abr (antibiotic regulator. No detectable changes in antibiotic production were found in the mutants in the systems that include the ORFs SCO3638/3639, SCO3640/3641 and SCO2165/2166 in any of the culture conditions assayed. The system SCO1744/1745 (AbrA1/A2 was involved in negative regulation of antibiotic production, and acted also as a negative regulator of the morphological differentiation. By contrast, the system SCO4596/4597/4598 (AbrC1/C2/C3, composed of two histidine kinases and one response regulator, had positive effects on both morphological development and antibiotic production. Microarray analyses of the ΔabrC1/C2/C3 and wild-type transcriptomes revealed downregulation of actII-ORF4 and cdaR genes, the actinorhodin and calcium-dependent antibiotic pathway-specific regulators respectively. These results demonstrated the involvement of these new two-component systems in antibiotic production and morphological differentiation by different approaches. One is a pleiotropic negative regulator: abrA1/A2. The other one is a positive regulator composed of three elements, two histidine kinases and one response regulator: abrC1/C2/C3.

  5. Wave-breaking phenomena and global solutions for periodic two-component Dullin-Gottwald-Holm systems

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    Min Zhu

    2013-02-01

    Full Text Available In this article we study the initial-value problem for the periodic two-component b-family system, including a special case, when b = 2, which is referred to as the two-component Dullin-Gottwald-Holm (DGH system. We first show that the two-component b-family system can be derived from the theory of shallow-water waves moving over a linear shear flow. Then we establish several results of blow-up solutions corresponding to only wave breaking with certain initial profiles for the periodic two-component DGH system. Moreover, we determine the exact blow-up rate and lower bound of the lifespan for the system. Finally, we give a sufficient condition for the existence of the strong global solution to the periodic two-component DGH system.

  6. Addition Formulae of Discrete KP, q-KP and Two-Component BKP Systems

    Science.gov (United States)

    Gao, Xu; Li, Chuan-Zhong; He, Jing-Song

    2016-04-01

    In this paper, we construct the addition formulae for several integrable hierarchies, including the discrete KP, the q-deformed KP, the two-component BKP and the D type Drinfeld-Sokolov hierarchies. With the help of the Hirota bilinear equations and τ functions of different kinds of KP hierarchies, we prove that these addition formulae are equivalent to these hierarchies. These studies show that the addition formula in the research of the integrable systems has good universality. Supported by the Zhejiang Provincial Natural Science Foundation under Grant No. LY15A010004, the National Natural Science Foundation of China under Grant Nos. 11201251, 11571192 and the Natural Science Foundation of Ningbo under Grant No. 2015A610157. Jingsong He is supported by the National Natural Science Foundation of China under Grant No. 11271210, K.C. Wong Magna Fund in Ningbo University

  7. The SaeRS Two-Component System of Staphylococcus aureus

    Science.gov (United States)

    Liu, Qian; Yeo, Won-Sik; Bae, Taeok

    2016-01-01

    In the Gram-positive pathogenic bacterium Staphylococcus aureus, the SaeRS two-component system (TCS) plays a major role in controlling the production of over 20 virulence factors including hemolysins, leukocidins, superantigens, surface proteins, and proteases. The SaeRS TCS is composed of the sensor histidine kinase SaeS, response regulator SaeR, and two auxiliary proteins SaeP and SaeQ. Since its discovery in 1994, the sae locus has been studied extensively, and its contributions to staphylococcal virulence and pathogenesis have been well documented and understood; however, the molecular mechanism by which the SaeRS TCS receives and processes cognate signals is not. In this article, therefore, we review the literature focusing on the signaling mechanism and its interaction with other global regulators. PMID:27706107

  8. Development and characterization of two-component albedo based neutron individual monitoring system using thermoluminescent detectors

    International Nuclear Information System (INIS)

    A TLD-albedo based two-component neutron individual monitoring system was developed and characterized in this work. The monitor consists of a black plastic holder, an incident neutron boron loaded shield, a moderator polyethylene body (to increase its response), two pairs of TLD-600 and TLD-700 (one pair to each component) and an adjustable belt. This monitoring system was calibrated in thermal neutron fields and in 70 keV, 144 keV, 565 keV, 1.2 MeV and 5 MeV monoenergetic neutron fields. In addition, it was calibrated in 252Cf(D2O), 252Cf, 241Am-B, 241Am-Be and 238Pu-Be source fields. For the latter, the lower detection levels are, respectively, 0.009 mSv, 0.06 mSv, 0.12 mSv, 0.09 mSv and 0.08 mSv. The participation in an international intercomparison sponsored by IAEA with simulated workplace fields validated the system. The monitoring system was successfully characterized in the ISO 21909 standard and in an IRD - the Brazilian Institute for Radioprotection and Dosimetry - technical regulation draft. Nowadays, the neutron individual system is in use by IRD for whole body individual monitoring of five institutions, which comprehend several activities. (author)

  9. The CpxRA two-component system contributes to Legionella pneumophila virulence.

    Science.gov (United States)

    Tanner, Jennifer R; Li, Laam; Faucher, Sébastien P; Brassinga, Ann Karen C

    2016-06-01

    The bacterium Legionella pneumophila is capable of intracellular replication within freshwater protozoa as well as human macrophages, the latter of which results in the serious pneumonia Legionnaires' disease. A primary factor involved in these host cell interactions is the Dot/Icm Type IV secretion system responsible for translocating effector proteins needed to establish and maintain the bacterial replicative niche. Several regulatory factors have been identified to control the expression of the Dot/Icm system and effectors, one of which is the CpxRA two-component system, suggesting essentiality for virulence. In this study, we generated cpxR, cpxA and cpxRA in-frame null mutant strains to further delineate the role of the CpxRA system in bacterial survival and virulence. We found that cpxR is essential for intracellular replication within Acanthamoeba castellanii, but not in U937-derived macrophages. Transcriptome analysis revealed that CpxRA regulates a large number of virulence-associated proteins including Dot/Icm effectors as well as Type II secreted substrates. Furthermore, the cpxR and cpxRA mutant strains were more sodium resistant than the parental strain Lp02, and cpxRA expression reaches maximal levels during postexponential phase. Taken together, our findings suggest the CpxRA system is a key contributor to L. pneumophila virulence in protozoa via virulence factor regulation. PMID:26934669

  10. P2CS: a two-component system resource for prokaryotic signal transduction research

    Directory of Open Access Journals (Sweden)

    Méjean Vincent

    2009-07-01

    Full Text Available Abstract Background With the escalation of high throughput prokaryotic genome sequencing, there is an ever-increasing need for databases that characterise, catalogue and present data relating to particular gene sets and genomes/metagenomes. Two-component system (TCS signal transduction pathways are the dominant mechanisms by which micro-organisms sense and respond to external as well as internal environmental changes. These systems respond to a wide range of stimuli by triggering diverse physiological adjustments, including alterations in gene expression, enzymatic reactions, or protein-protein interactions. Description We present P2CS (Prokaryotic 2-Component Systems, an integrated and comprehensive database of TCS signal transduction proteins, which contains a compilation of the TCS genes within 755 completely sequenced prokaryotic genomes and 39 metagenomes. P2CS provides detailed annotation of each TCS gene including family classification, sequence features, functional domains, as well as genomic context visualization. To bypass the generic problem of gene underestimation during genome annotation, we also constituted and searched an ORFeome, which improves the recovery of TCS proteins compared to searches on the equivalent proteomes. Conclusion P2CS has been developed for computational analysis of the modular TCSs of prokaryotic genomes and metagenomes. It provides a complete overview of information on TCSs, including predicted candidate proteins and probable proteins, which need further curation/validation. The database can be browsed and queried with a user-friendly web interface at http://www.p2cs.org/.

  11. Photoisomerization-induced morphology and transparency transition in an azobenzene based two-component organogel system.

    Science.gov (United States)

    Cao, Xinhua; Liu, Xue; Chen, Liming; Mao, Yueyuan; Lan, Haichuang; Yi, Tao

    2015-11-15

    A two-component gel containing long chain alkylated gallic acid (GA) and photochromic phenazopyridine (PAP) was prepared. The gel was thoroughly characterized by UV-visible and IR spectra, SEM and POM images, XRD diffraction and dynamic oscillatory measurements. The structure and transparency of the two-component gel can be reversibly changed by alternative UV light irradiation and warming in the palm of the hand. This kind of soft material has potential application in upscale surface functional materials. PMID:26218198

  12. A hybrid two-component system protein from Azospirillum brasilense Sp7 was involved in chemotaxis.

    Science.gov (United States)

    Cui, Yanhua; Tu, Ran; Wu, Lixian; Hong, Yuanyuan; Chen, Sanfeng

    2011-09-20

    We here report the sequence and functional analysis of org35 of Azospirillum brasilense Sp7, which was originally identified to be able to interact with NifA in yeast-two-hybrid system. The org35 encodes a hybrid two-component system protein, including N-terminal PAS domains, a histidine kinase (HPK) domain and a response regulator (RR) domain in C-terminal. To determine the function of the Org35, a deletion-insertion mutant in PAS domain [named Sp7353] and a complemental strain Sp7353C were constructed. The mutant had reduced chemotaxis ability compared to that of wild-type, and the complemental strain was similar to the wild-type strain. These data suggested that the A. brasilense org35 played a key role in chemotaxis. Variants containing different domains of the org35 were expressed, and the functions of these domains were studied in vitro. Phosphorylation assays in vitro demonstrated that the HPK domain of Org35 possessed the autokinase activity and that the phosphorylated HPK was able to transfer phosphate groups to the RR domain. The result indicated Org35 was a phosphorylation-communicating protein.

  13. A two component system is involved in acid adaptation of Lactobacillus delbrueckii subsp. bulgaricus.

    Science.gov (United States)

    Cui, Yanhua; Liu, Wei; Qu, Xiaojun; Chen, Zhangting; Zhang, Xu; Liu, Tong; Zhang, Lanwei

    2012-05-20

    The Gram-positive bacterium Lactobacillus delbrueckii subsp. bulgaricus is of vital importance to the food industry, especially to the dairy industry. Two component systems (TCSs) are one of the most important mechanisms for environmental sensing and signal transduction in the majority of Gram-positive and Gram-negative bacteria. A typical TCS consists of a histidine protein kinase (HPK) and a cytoplasmic response regulator (RR). To investigate the functions of TCSs during acid adaptation in L. bulgaricus, we used quantitative PCR to reveal how TCSs expression changes during acid adaptation. Two TCSs (JN675228/JN675229 and JN675230/JN675231) and two HPKs (JN675236 and JN675240) were induced during acid adaptation. These TCSs were speculated to be related with the acid adaptation ability of L. bulgaricus. The mutants of JN675228/JN675229 were constructed in order to investigate the functions of JN675228/JN675229. The mutants showed reduced acid adaptation compared to that of wild type, and the complemented strains were similar to the wild-type strain. These observations suggested that JN675228 and JN675229 were involved in acid adaptation in L. bulgaricus. The interaction between JN675228 and JN675229 was identified by means of yeast two-hybrid system. The results indicated there is interaction between JN675228 and JN675229.

  14. The Evolution of Two-Component Systems in Bacteria RevealsDifferent Strategies for Niche Adaptation

    Energy Technology Data Exchange (ETDEWEB)

    Alm, Eric; Huang, Katherine; Arkin, Adam

    2006-09-13

    Two-component systems including histidine protein kinasesrepresent the primary signal transduction paradigm in prokaryoticorganisms. To understand how these systems adapt to allow organisms todetect niche-specific signals, we analyzed the phylogenetic distributionof nearly 5000 histidine protein kinases from 207 sequenced prokaryoticgenomes. We found that many genomes carry a large repertoire of recentlyevolved signaling genes, which may reflect selective pressure to adapt tonew environmental conditions. Both lineage-specific gene family expansionand horizontal gene transfer play major roles in the introduction of newhistidine kinases into genomes; however, there are differences in howthese two evolutionary forces act. Genes imported via horizontal transferare more likely to retain their original functionality as inferred from asimilar complement of signaling domains, while gene family expansionaccompanied by domain shuffling appears to be a major source of novelgenetic diversity. Family expansion is the dominantsource of newhistidine kinase genes in the genomes most enriched in signalingproteins, and detailed analysis reveals that divergence in domainstructure and changes in expression patterns are hallmarks of recentexpansions. Finally, while these two modes of gene acquisition arewidespread across bacterial taxa, there are clear species-specificpreferences for which mode is used.

  15. Transcriptome analysis of the Brucella abortus BvrR/BvrS two-component regulatory system.

    Directory of Open Access Journals (Sweden)

    Cristina Viadas

    Full Text Available BACKGROUND: The two-component BvrR/BvrS system is essential for Brucella abortus virulence. It was shown previously that its dysfunction alters the expression of some major outer membrane proteins and the pattern of lipid A acylation. To determine the genes regulated by BvrR/BvrS, we performed a whole-genome microarray analysis using B. abortus RNA obtained from wild type and bvrR mutant cells grown in the same conditions. METHODOLOGY/PRINCIPAL FINDINGS: A total of 127 differentially expressed genes were found: 83 were over expressed and 44 were less expressed in the bvrR mutant. Two operons, the phosphotransferase system and the maltose transport system, were down-regulated. Several genes involved in cell envelope or outer membrane biogenesis were differentially expressed: genes for outer membrane proteins (omp25a, omp25d, lipoproteins, LPS and fatty acid biosynthesis, stress response proteins, chaperones, flagellar genes, and twelve genes encoding ABC transport systems. Ten genes related with carbon metabolism (pckA and fumB among others were up-regulated in the bvrR mutant, and denitrification genes (nirK, norC and nosZ were also regulated. Notably, seven transcriptional regulators were affected, including VjbR, ExoR and OmpR that were less expressed in the bvrR mutant. Finally, the expression of eleven genes which have been previously related with Brucella virulence was also altered. CONCLUSIONS/SIGNIFICANCE: All these data corroborate the impact of BvrR/BvrS on cell envelope modulation, confirm that this system controls the carbon and nitrogen metabolism, and suggest a cross-talk among some regulators to adjust the Brucella physiology to the shift expected to occur during the transit from the extracellular to the intracellular niche.

  16. Genome-Wide Identification and Expression Analysis of Two-Component System Genes in Tomato

    Science.gov (United States)

    He, Yanjun; Liu, Xue; Ye, Lei; Pan, Changtian; Chen, Lifei; Zou, Tao; Lu, Gang

    2016-01-01

    The two-component system (TCS), which comprises histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays pivotal roles in regulating plant growth, development, and responses to biotic and abiotic stresses. TCS genes have been comprehensively identified and investigated in various crops but poorly characterized in tomato. In this work, a total of 65 TCS genes consisting of 20 HK(L)s, six HPs, and 39 RRs were identified from tomato genome. The classification, gene structures, conserved domains, chromosome distribution, phylogenetic relationship, gene duplication events, and subcellular localization of the TCS gene family were predicted and analyzed in detail. The amino acid sequences of tomato TCS family members, except those of type-B RRs, are highly conserved. The gene duplication events of the TCS family mainly occurred in the RR family. Furthermore, the expansion of RRs was attributed to both segment and tandem duplication. The subcellular localizations of the selected green fluorescent protein (GFP) fusion proteins exhibited a diverse subcellular targeting, thereby confirming their predicted divergent functionality. The majority of TCS family members showed distinct organ- or development-specific expression patterns. In addition, most of TCS genes were induced by abiotic stresses and exogenous phytohormones. The full elucidation of TCS elements will be helpful for comprehensive analysis of the molecular biology and physiological role of the TCS superfamily. PMID:27472316

  17. Relating gene expression data on two-component systems to functional annotations in Escherichia coli

    Directory of Open Access Journals (Sweden)

    Sule Preeti

    2008-06-01

    Full Text Available Abstract Background Obtaining physiological insights from microarray experiments requires computational techniques that relate gene expression data to functional information. Traditionally, this has been done in two consecutive steps. The first step identifies important genes through clustering or statistical techniques, while the second step assigns biological functions to the identified groups. Recently, techniques have been developed that identify such relationships in a single step. Results We have developed an algorithm that relates patterns of gene expression in a set of microarray experiments to functional groups in one step. Our only assumption is that patterns co-occur frequently. The effectiveness of the algorithm is demonstrated as part of a study of regulation by two-component systems in Escherichia coli. The significance of the relationships between expression data and functional annotations is evaluated based on density histograms that are constructed using product similarity among expression vectors. We present a biological analysis of three of the resulting functional groups of proteins, develop hypotheses for further biological studies, and test one of these hypotheses experimentally. A comparison with other algorithms and a different data set is presented. Conclusion Our new algorithm is able to find interesting and biologically meaningful relationships, not found by other algorithms, in previously analyzed data sets. Scaling of the algorithm to large data sets can be achieved based on a theoretical model.

  18. Functional characterization of WalRK: A two-component signal transduction system from Bacillus anthracis

    Directory of Open Access Journals (Sweden)

    Alisha Dhiman

    2014-01-01

    Full Text Available Two-component signal transduction systems (TCS, consisting of a sensor histidine protein kinase and its cognate response regulator, are an important mode of environmental sensing in bacteria. Additionally, they have been found to regulate virulence determinants in several pathogens. Bacillus anthracis, the causative agent of anthrax and a bioterrorism agent, harbours 41 pairs of TCS. However, their role in its pathogenicity has remained largely unexplored. Here, we show that WalRK of B. anthracis forms a functional TCS which exhibits some species-specific functions. Biochemical studies showed that domain variants of WalK, the histidine kinase, exhibit classical properties of autophosphorylation and phosphotransfer to its cognate response regulator WalR. Interestingly, these domain variants also show phosphatase activity towards phosphorylated WalR, thereby making WalK a bifunctional histidine kinase/phosphatase. An in silico regulon determination approach, using a consensus binding sequence from Bacillus subtilis, provided a list of 30 genes that could form a putative WalR regulon in B. anthracis. Further, electrophoretic mobility shift assay was used to show direct binding of purified WalR to the upstream regions of three putative regulon candidates, an S-layer protein EA1, a cell division ABC transporter FtsE and a sporulation histidine kinase KinB3. Our work lends insight into the species-specific functions and mode of action of B. anthracis WalRK.

  19. Evolutionary tuning of protein expression levels of a positively autoregulated two-component system.

    Directory of Open Access Journals (Sweden)

    Rong Gao

    2013-10-01

    Full Text Available Cellular adaptation relies on the development of proper regulatory schemes for accurate control of gene expression levels in response to environmental cues. Over- or under-expression can lead to diminished cell fitness due to increased costs or insufficient benefits. Positive autoregulation is a common regulatory scheme that controls protein expression levels and gives rise to essential features in diverse signaling systems, yet its roles in cell fitness are less understood. It remains largely unknown how much protein expression is 'appropriate' for optimal cell fitness under specific extracellular conditions and how the dynamic environment shapes the regulatory scheme to reach appropriate expression levels. Here, we investigate the correlation of cell fitness and output response with protein expression levels of the E. coli PhoB/PhoR two-component system (TCS. In response to phosphate (Pi-depletion, the PhoB/PhoR system activates genes involved in phosphorus assimilation as well as genes encoding themselves, similarly to many other positively autoregulated TCSs. We developed a bacteria competition assay in continuous cultures and discovered that different Pi conditions have conflicting requirements of protein expression levels for optimal cell fitness. Pi-replete conditions favored cells with low levels of PhoB/PhoR while Pi-deplete conditions selected for cells with high levels of PhoB/PhoR. These two levels matched PhoB/PhoR concentrations achieved via positive autoregulation in wild-type cells under Pi-replete and -deplete conditions, respectively. The fitness optimum correlates with the wild-type expression level, above which the phosphorylation output saturates, thus further increase in expression presumably provides no additional benefits. Laboratory evolution experiments further indicate that cells with non-ideal protein levels can evolve toward the optimal levels with diverse mutational strategies. Our results suggest that the natural

  20. Characterization of an archaeal two-component system that regulates methanogenesis in Methanosaeta harundinacea.

    Directory of Open Access Journals (Sweden)

    Jie Li

    Full Text Available Two-component signal transduction systems (TCSs are a major mechanism used by bacteria in response to environmental changes. Although many sequenced archaeal genomes encode TCSs, they remain poorly understood. Previously, we reported that a methanogenic archaeon, Methanosaeta harundinacea, encodes FilI, which synthesizes carboxyl-acyl homoserine lactones, to regulate transitions of cellular morphology and carbon metabolic fluxes. Here, we report that filI, the cotranscribed filR2, and the adjacent filR1 constitute an archaeal TCS. FilI possesses a cytoplasmic kinase domain (histidine kinase A and histidine kinase-like ATPase and its cognate response regulator. FilR1 carries a receiver (REC domain coupled with an ArsR-related domain with potential DNA-binding ability, while FilR2 carries only a REC domain. In a phosphorelay assay, FilI was autophosphorylated and specifically transferred the phosphoryl group to FilR1 and FilR2, confirming that the three formed a cognate TCS. Through chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR using an anti-FilR1 antibody, FilR1 was shown to form in vivo associations with its own promoter and the promoter of the filI-filR2 operon, demonstrating a regulatory pattern common among TCSs. ChIP-qPCR also detected FilR1 associations with key genes involved in acetoclastic methanogenesis, acs4 and acs1. Electrophoretic mobility shift assays confirmed the in vitro tight binding of FilR1 to its own promoter and those of filI-filR2, acs4, and mtrABC. This also proves the DNA-binding ability of the ArsR-related domain, which is found primarily in Archaea. The archaeal promoters of acs4, filI, acs1, and mtrABC also initiated FilR1-modulated expression in an Escherichia coli lux reporter system, suggesting that FilR1 can up-regulate both archaeal and bacterial transcription. In conclusion, this work identifies an archaeal FilI/FilRs TCS that regulates the methanogenesis of M. harundinacea.

  1. The Two-Component Virial Theorem and the Physical Properties of Stellar Systems

    OpenAIRE

    Dantas, Christine C.; Ribeiro, Andre L. B.; Capelato, Hugo V.; de Carvalho, Reinaldo R.

    1999-01-01

    Motivated by present indirect evidences that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem which explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the barionic or luminous component. Our analysis shows that the application of such a ``two-component virial theorem'' not only accounts for the scaling relations displayed, in part...

  2. Cloning of a two-component signal transduction system of Xanthomonas campestris pv. phaseoli var. fuscans strain BXPF65

    DEFF Research Database (Denmark)

    Chan, JWYF; Maynard, Scott; Goodwin, PH

    1998-01-01

    A putative two-component signal transduction system was amplified and cloned from the plant pathogenic bacterium Xanthomonas campestris pv. phaseoli var. fuscans isolate BXPF65. The 620 bp amplified fragment was sequenced and analyzed with the BLAST Enhanced Alignment Utility (BEAUTY). BEAUTY...... analysis indicates that the putative xanthomonad response regulator contains regions which matched to an ATP phosphorylation site, a s54-factor interaction domain, and the “receiver” domains of various transcriptional regulators of the two-component signal transduction systems. Similar analysis indicates...... that the putative histidine kinase has homology with conserved “transmitter” domains of sensor proteins in two-component signal transduction systems. RFLP analysis using the putative signal transduction system showed polymorphisms among the strains....

  3. Rosen-Zener Transition in a Nonlinear System for Two-Component Bose-Einstein Condensates in Optical Lattices

    Institute of Scientific and Technical Information of China (English)

    JIANG Xin; LIN Mai-Mai; LI Sheng-Chang; DUAN Wen-Shan

    2009-01-01

    We study the Rosen-Zener transition (RZT) in a nonlinear system for two-component Bose-Einstein condensates in optical lattices. It is found that the percentage of the components could affect the quantum transition dra-matically. For the component with large percentage it is equivalent that the effect of the nonlinearity is stronger, whereas for the component with small percentage the effect is weaker. We also find that the nonlinearity C11 can affect the quantum transition dramatically. This is similar to that reported from Ref. [14]. Compared with one-component systems, however, the effect of the nonlinearity is decreased due to the two components of the BECs in optical lattices. Furthermore, the effect of the coupling nonlinearity between two components c12 is stud-ied. The component with large percentage is more affected by the nonlinearity than that with small-percentage component.

  4. Phenotype microarray analysis of Escherichia coli K-12 mutants with deletions of all two-component systems.

    Science.gov (United States)

    Zhou, Lu; Lei, Xiang-He; Bochner, Barry R; Wanner, Barry L

    2003-08-01

    Two-component systems are the most common mechanism of transmembrane signal transduction in bacteria. A typical system consists of a histidine kinase and a partner response regulator. The histidine kinase senses an environmental signal, which it transmits to its partner response regulator via a series of autophosphorylation, phosphotransfer, and dephosphorylation reactions. Much work has been done on particular systems, including several systems with regulatory roles in cellular physiology, communication, development, and, in the case of bacterial pathogens, the expression of genes important for virulence. We used two methods to investigate two-component regulatory systems in Escherichia coli K-12. First, we systematically constructed mutants with deletions of all two-component systems by using a now-standard technique of gene disruption (K. A. Datsenko and B. L. Wanner, Proc. Natl. Acad. Sci. USA 97:6640-6645, 2000). We then analyzed these deletion mutants with a new technology called Phenotype MicroArrays, which permits assays of nearly 2,000 growth phenotypes simultaneously. In this study we tested 100 mutants, including mutants with individual deletions of all two-component systems and several related genes, including creBC-regulated genes (cbrA and cbrBC), phoBR-regulated genes (phoA, phoH, phnCDEFGHIJKLMNOP, psiE, and ugpBAECQ), csgD, luxS, and rpoS. The results of this battery of nearly 200,000 tests provided a wealth of new information concerning many of these systems. Of 37 different two-component mutants, 22 showed altered phenotypes. Many phenotypes were expected, and several new phenotypes were also revealed. The results are discussed in terms of the biological roles and other information concerning these systems, including DNA microarray data for a large number of the same mutants. Other mutational effects are also discussed. PMID:12897016

  5. Bacillus subtilis Two-Component System Sensory Kinase DegS Is Regulated by Serine Phosphorylation in Its Input Domain

    DEFF Research Database (Denmark)

    Jers, Carsten; Kobir, Ahasanul; Søndergaard, Elsebeth Oline;

    2011-01-01

    Bacillus subtilis two-component system DegS/U is well known for the complexity of its regulation. The cytosolic sensory kinase DegS does not receive a single predominant input signal like most two-component kinases, instead it integrates a wide array of metabolic inputs that modulate its activity...... demonstrate that DegS phosphorylation can be carried out by at least two B. subtilis Hanks-type kinases in vitro, and this stimulates the phosphate transfer towards DegU. The consequences of this process were studied in vivo, using phosphomimetic (Ser76Asp) and non-phosphorylatable (Ser76Ala) mutants of Deg...

  6. Comparative analysis of two-component signal transduction systems of Bacillus cereus, Bacillus thuringiensis and Bacillus anthracis

    NARCIS (Netherlands)

    Been, M.W.H.J. de; Francke, C.; Moezelaar, R.; Abee, T.; Siezen, R.J.

    2006-01-01

    Members of the Bacillus cereus group are ubiquitously present in the environment and can adapt to a wide range of environmental fluctuations. In bacteria, these adaptive responses are generally mediated by two-component signal transduction systems (TCSs), which consist of a histidine kinase (HK) and

  7. Vortices with scalar condensates in two-component Ginzburg-Landau systems

    CERN Document Server

    Forgacs, Peter

    2016-01-01

    In a class of two-component Ginzburg-Landau models (TCGL) with a U(1)$\\times$U(1) symmetric potential, vortices with a condensate at their core may have significantly lower energies than the Abrikosov-Nielsen-Olesen (ANO) ones. On the example of liquid metallic hydrogen (LMH) above the critical temperature for protons we show that the ANO vortices become unstable against core-condensation, while condensate-core (CC) vortices are stable. For LMH the ratio of the masses of the two types of condensates, $M=m_2/m_1$ is large, and then as a consequence the energy per flux quantum of the vortices, $E_n/n$ becomes a non-monotonous function of the number of flux quanta, $n$. This leads to yet another manifestation of neither type 1 nor type 2, (type 1.5) superconductivity: superconducting and normal domains coexist while various "giant" vortices form. We note that LMH provides a particularly clean example of type 1.5 state as the interband coupling between electronic and protonic Cooper-pairs is forbidden.

  8. Some new integrable systems of two-component fifth order equations

    OpenAIRE

    Talati, Daryoush; Wazwaz, Abdul-Majid

    2016-01-01

    In this work we develop some fifth-order integrable coupled systems of weight $0$ and $1$ which possess seventh-order symmetry. We establish four new systems, where in some cases, related recursion operator and bi-Hamiltonian formulations are given. We also investigate the integrability of the developed systems.

  9. The BaeSR Two-Component Regulatory System Mediates Resistance to Condensed Tannins in Escherichia coli▿ †

    OpenAIRE

    Zoetendal, E.G.; Smith, A H; Sundset, M.A.; Mackie, R. I.

    2007-01-01

    The gene expression profiles of Escherichia coli strains grown anaerobically with or without Acacia mearnsii (black wattle) extract were compared to identify tannin resistance strategies. The cell envelope stress protein gene spy and the multidrug transporter-encoding operon mdtABCD, both under the control of the BaeSR two-component regulatory system, were significantly up-regulated in the presence of tannins. BaeSR mutants were more tannin sensitive than their wild-type counterparts.

  10. Two-component signal transduction pathways regulating growth and cell cycle progression in a bacterium: a system-level analysis.

    Directory of Open Access Journals (Sweden)

    Jeffrey M Skerker

    2005-10-01

    Full Text Available Two-component signal transduction systems, comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein-protein interactions. These signaling pathways have also been demonstrated to play a role in coordinating bacterial cell cycle progression and development. Here we report a system-level investigation of two-component pathways in the model organism Caulobacter crescentus. First, by a comprehensive deletion analysis we show that at least 39 of the 106 two-component genes are required for cell cycle progression, growth, or morphogenesis. These include nine genes essential for growth or viability of the organism. We then use a systematic biochemical approach, called phosphotransfer profiling, to map the connectivity of histidine kinases and response regulators. Combining these genetic and biochemical approaches, we identify a new, highly conserved essential signaling pathway from the histidine kinase CenK to the response regulator CenR, which plays a critical role in controlling cell envelope biogenesis and structure. Depletion of either cenK or cenR leads to an unusual, severe blebbing of cell envelope material, whereas constitutive activation of the pathway compromises cell envelope integrity, resulting in cell lysis and death. We propose that the CenK-CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. Finally, the ability of our in vitro phosphotransfer profiling method to identify signaling pathways that operate in vivo takes advantage of an observation that histidine kinases are endowed with a global kinetic preference for their cognate response regulators. We propose that this

  11. Solution of thermal neutron diffusion equation for the two-component system by perturbation calculation

    International Nuclear Information System (INIS)

    A method of solving the diffusion equation for the th ermal neutron flux in a heterogeneous medium is presented. Perturbation calculation is successfully applied for the cylindrical concentric system after testing this method for the spherical concentric geometry analytically solved by Czubek (1981). The method permits to calculate the t hermal neutron decay constant and the space distribution of the thermal neutron flux in a heterogeneous geom etry. The condition of the constant value of the neutron flux in the inner part of the system has to be m et. This method has an application in the measurement of the thermal neutron absorption cross section, presented by Czubek (1981). (author)

  12. Phosphate sink containing two-component signaling systems as tunable threshold devices

    DEFF Research Database (Denmark)

    Amin, Munia; Kothamachu, Varun B; Feliu, Elisenda;

    2014-01-01

    rapid signal termination, whereby one of the RRs acts as a phosphate sink towards the other RR (i.e. the output RR), but also implements a sigmoidal signal-response relationship. We identify two mathematical conditions on system parameters that are necessary for sigmoidal signal-response relationships...

  13. Reciprocal regulation as a source of ultrasensitivity in two-component systems with a bifunctional sensor kinase.

    Directory of Open Access Journals (Sweden)

    Ronny Straube

    2014-05-01

    Full Text Available Two-component signal transduction systems, where the phosphorylation state of a regulator protein is modulated by a sensor kinase, are common in bacteria and other microbes. In many of these systems, the sensor kinase is bifunctional catalyzing both, the phosphorylation and the dephosphorylation of the regulator protein in response to input signals. Previous studies have shown that systems with a bifunctional enzyme can adjust the phosphorylation level of the regulator protein independently of the total protein concentrations--a property known as concentration robustness. Here, I argue that two-component systems with a bifunctional enzyme may also exhibit ultrasensitivity if the input signal reciprocally affects multiple activities of the sensor kinase. To this end, I consider the case where an allosteric effector inhibits autophosphorylation and, concomitantly, activates the enzyme's phosphatase activity, as observed experimentally in the PhoQ/PhoP and NRII/NRI systems. A theoretical analysis reveals two operating regimes under steady state conditions depending on the effector affinity: If the affinity is low the system produces a graded response with respect to input signals and exhibits stimulus-dependent concentration robustness--consistent with previous experiments. In contrast, a high-affinity effector may generate ultrasensitivity by a similar mechanism as phosphorylation-dephosphorylation cycles with distinct converter enzymes. The occurrence of ultrasensitivity requires saturation of the sensor kinase's phosphatase activity, but is restricted to low effector concentrations, which suggests that this mode of operation might be employed for the detection and amplification of low abundant input signals. Interestingly, the same mechanism also applies to covalent modification cycles with a bifunctional converter enzyme, which suggests that reciprocal regulation, as a mechanism to generate ultrasensitivity, is not restricted to two-component

  14. Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap

    DEFF Research Database (Denmark)

    J. Lindgren, E.; Rotureau, J.; Forssén, C.;

    2014-01-01

    The nature of strongly interacting Fermi gases and magnetism is one of the most important and studied topics in condensed-matter physics. Still, there are many open questions. A central issue is under what circumstances strong short-range repulsive interactions are enough to drive magnetic...... correlations. Recent progress in the field of cold atomic gases allows to address this question in very clean systems where both particle numbers, interactions and dimensionality can be tuned. Here we study fermionic few-body systems in a one dimensional harmonic trap using a new rapidly converging effective......-interaction technique, plus a novel analytical approach. This allows us to calculate the properties of a single spin-down atom interacting with a number of spin-up particles, a case of much recent experimental interest. Our findings indicate that, in the strongly interacting limit, spin-up and spin-down particles want...

  15. Mean-square radii of two-component three-body systems in two spatial dimensions

    Science.gov (United States)

    Sandoval, J. H.; Bellotti, F. F.; Jensen, A. S.; Yamashita, M. T.

    2016-08-01

    We calculate root-mean-square radii for a three-body system confined to two spatial dimensions and consisting of two identical bosons (A ) and one distinguishable particle (B ). We use zero-range two-body interactions between each of the pairs, and focus thereby directly on universal properties. We solve the Faddeev equations in momentum space and express the mean-square radii in terms of first-order derivatives of the Fourier transforms of densities. The strengths of the interactions are adjusted for each set of masses to produce equal two-body bound-state energies between different pairs. The mass ratio, A =mB/mA , between particles B and A are varied from 0.01 to 100, providing a number of bound states decreasing from 8 to 2. Energies and mean-square radii of these states are analyzed for small A by use of the Born-Oppenheimer potential between the two heavy A particles. For large A the radii of the two bound states are consistent with a slightly asymmetric three-body structure. When A approaches thresholds for binding of the three-body excited states, the corresponding mean-square radii diverge inversely proportional to the deviation of the three-body energy from the two-body thresholds. The structures at these three-body thresholds correspond to bound A B dimers and one loosely bound A particle.

  16. SELF-SIMILAR SOLUTIONS AND BLOW-UP PHENOMENA FOR A TWO-COMPONENT SHALLOW WATER SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Shouming ZHOU; Chunlai MU; Liangchen WANG

    2013-01-01

    In this article,we consider a two-component nonlinear shallow water system,which includes the famous 2-component Camassa-Holm and Degasperis-Procesi equations as special cases.The local well-posedess for this equations is established.Some sufficient conditions for blow-up of the solutions in finite time are given.Moreover,by separation method,the self-similar solutions for the nonlinear shallow water equations are obtained,and which local or global behavior can be determined by the corresponding Emden equation.

  17. The CsrR/CsrS two-component system of group A Streptococcus responds to environmental Mg2+

    OpenAIRE

    Gryllos, Ioannis; Levin, James C.; Wessels, Michael R.

    2003-01-01

    Group A streptococci control expression of key virulence determinants via the two-component sensor/regulator system CsrR/CsrS. The membrane-bound sensor CsrS is thought to respond to previously unknown environmental signal(s) by controlling phosphorylation of its cognate regulator component CsrR. Phosphorylation of CsrR increases its affinity for binding to the promoter regions of Csr-regulated genes to repress transcription. Here we show that environmental Mg2+ concentration is a potent and ...

  18. Identification and characterization of the two-component NtrY/NtrX regulatory system in Azospirillum brasilense

    Directory of Open Access Journals (Sweden)

    M.L. Ishida

    2002-06-01

    Full Text Available Two Azospirillum brasilense open reading frames (ORFs exhibited homology with the two-component NtrY/NtrX regulatory system from Azorhizobium caulinodans. These A. brasilense ORFs, located downstream to the nifR3ntrBC operon, were isolated, sequenced and characterized. The present study suggests that ORF1 and ORF2 correspond to the A. brasilense ntrY and ntrX genes, respectively. The amino acid sequences of A. brasilense NtrY and NtrX proteins showed high similarity to sensor/kinase and regulatory proteins, respectively. Analysis of lacZ transcriptional fusions by the ß-galactosidase assay in Escherichia coli ntrC mutants showed that the NtrY/NtrX proteins failed to activate transcription of the nifA promoter of A. brasilense. The ntrYX operon complemented a nifR3ntrBC deletion mutant of A. brasilense for nitrate-dependent growth, suggesting a possible cross-talk between the NtrY/X and NtrB/C sensor/regulator pairs. Our data support the existence of another two-component regulatory system in A. brasilense, the NtrY/NtrX system, probably involved in the regulation of nitrate assimilation.

  19. Two-Component Regulatory Systems – implication in the quorum sensing mechanisms and bacteriocin production in lactic acid bacteria

    Directory of Open Access Journals (Sweden)

    Lia–Mara Ditu

    2014-08-01

    Full Text Available For lactic acid bacteria, the mechanisms of quorum sensing and response are mediated by peptides or pheromones that interfere with the synthesis of antimicrobial peptides (AMP called bacteriocins, when these molecules reach a certain critical level of concentration. Generally, the synthesis and activity of pheromones is adjusted by means of a two-component regulatory system. The observation that some microorganisms, in particular lactic acid bacteria, produce bacteriocins according to the cell density, has led to the discovery of the involvement of QS mechanisms in the synthesis of these peptides. Bacteriocins synthesis is inducible, the process requiring the extracellular accumulation of peptides that functions as chemical messengers activators of bacteriocins synthesis. This minireview presents the molecular architecture and functions of two-component regulatory systems and ABC transporters implicated in the synthesis and secretion of nisin, one of the most studied bacteriocin. The elucidation of the intimate mechanisms of bacteriocins synthesis is equally of biotechnological and medical importance, opening interesting perspectives for the development of improved technologies for the production of bacteriocins with good yields, and also, for increasing the beneficial anti-infective roles of probiotic bacteria when administered in vivo.

  20. Origin and evolution of two-component debris discs and an application to the q1 Eridani system

    Science.gov (United States)

    Schüppler, Christian; Krivov, Alexander V.; Löhne, Torsten; Booth, Mark; Kirchschlager, Florian; Wolf, Sebastian

    2016-09-01

    Many debris discs reveal a two-component structure, with an outer Kuiper-belt analogue and a warm inner component whose origin is still a matter of debate. One possibility is that warm emission stems from an `asteroid belt' closer in to the star. We consider a scenario in which a set of giant planets is formed in an initially extended planetesimal disc. These planets carve a broad gap around their orbits, splitting up the disc into the outer and the inner belts. After the gas dispersal, both belts undergo collisional evolution in a steady-state regime. This scenario is explored with detailed collisional simulations involving realistic physics to describe a long-term collisional depletion of the two-component disc. We find that the inner disc may be able to retain larger amounts of material at older ages than thought before on the basis of simplified analytic models. We show that the proposed scenario is consistent with a suite of thermal emission and scattered light observational data for a bright two-temperature debris disc around a nearby solar-type star q1 Eridani. This implies a Solar system-like architecture of the system, with an outer massive `Kuiper belt', an inner `asteroid belt', and a few Neptune- to Jupiter-mass planets in between.

  1. A two-component system regulates the expression of an ABC transporter for xylo-oligosaccharides in Geobacillus stearothermophilus.

    Science.gov (United States)

    Shulami, Smadar; Zaide, Galia; Zolotnitsky, Gennady; Langut, Yael; Feld, Geoff; Sonenshein, Abraham L; Shoham, Yuval

    2007-02-01

    Geobacillus stearothermophilus T-6 utilizes an extensive and highly regulated hemicellulolytic system. The genes comprising the xylanolytic system are clustered in a 39.7-kb chromosomal segment. This segment contains a 6-kb transcriptional unit (xynDCEFG) coding for a potential two-component system (xynDC) and an ATP-binding cassette (ABC) transport system (xynEFG). The xynD promoter region contains a 16-bp inverted repeat resembling the operator site for the xylose repressor, XylR. XylR was found to bind specifically to this sequence, and binding was efficiently prevented in vitro in the presence of xylose. The ABC transport system was shown to comprise an operon of three genes (xynEFG) that is transcribed from its own promoter. The nonphosphorylated fused response regulator, His6-XynC, bound to a 220-bp fragment corresponding to the xynE operator. DNase I footprinting analysis showed four protected zones that cover the -53 and the +34 regions and revealed direct repeat sequences of a GAAA-like motif. In vitro transcriptional assays and quantitative reverse transcription-PCR demonstrated that xynE transcription is activated 140-fold in the presence of 1.5 microM XynC. The His6-tagged sugar-binding lipoprotein (XynE) of the ABC transporter interacted with different xylosaccharides, as demonstrated by isothermal titration calorimetry. The change in the heat capacity of binding (DeltaCp) for XynE with xylotriose suggests a stacking interaction in the binding site that can be provided by a single Trp residue and a sugar moiety. Taken together, our data show that XynEFG constitutes an ABC transport system for xylo-oligosaccharides and that its transcription is negatively regulated by XylR and activated by the response regulator XynC, which is part of a two-component sensing system. PMID:17142383

  2. Two-Component Signal Transduction Systems of Desulfovibrio Vulgaris: Structural and Phylogenetic Analysis and Deduction of Putative Cognate Pairs

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Weiwen; Culley, David E.; Wu, Gang; Brockman, Fred J.

    2006-01-20

    ABSTRACT-Two-component signal transduction systems (TCSTS) composed of sensory histidine kinases (HK) and response regulators (RR), constitute a key element of the mechanism by which bacteria sense and respond to changes in environments. A large number of TCSTSs including 59 putative HKs and 55 RRs were identified from the Desulfovibrio vulgaris genome, indicating their important roles in regulation of cellular metabolism. In this study, the structural and phylogenetic analysis of all putative TCSTSs in D. vulgaris was performed. The results showed D. vulgaris contained an unexpectedly large number of hybrid-type HKs, implying that multiple-step phosphorelay may be a common signal transduction mechanism in D. vulgaris. Most TCSTS components of D. vulgaris were found clustered into several subfamilies previously recognized in other bacteria and extensive co-evolution between D. vulgaris HKs and RRs was observed, suggesting that the concordance of HKs and RRs in cognate phylogenetic groups could be indicative of cognate TCSTSs...

  3. Effects of the global regulator CsrA on the BarA/UvrY two-component signaling system.

    Science.gov (United States)

    Camacho, Martha I; Alvarez, Adrian F; Chavez, Ricardo Gonzalez; Romeo, Tony; Merino, Enrique; Georgellis, Dimitris

    2015-03-01

    The hybrid sensor kinase BarA and its cognate response regulator UvrY, members of the two-component signal transduction family, activate transcription of CsrB and CsrC noncoding RNAs. These two small RNAs act by sequestering the RNA binding protein CsrA, which posttranscriptionally regulates translation and/or stability of its target mRNAs. Here, we provide evidence that CsrA positively affects, although indirectly, uvrY expression, at both the transcriptional and translational levels. We also demonstrate that CsrA is required for properly switching BarA from its phosphatase to its kinase activity. Thus, the existence of a feedback loop mechanism that involves the Csr and BarA/UvrY global regulatory systems is exposed. PMID:25535275

  4. Identification of two-component system elements downstream of AHK5 in the stomatal closure response of Arabidopsis thaliana.

    Science.gov (United States)

    Mira-Rodado, Virtudes; Veerabagu, Manikandan; Witthöft, Janika; Teply, Julia; Harter, Klaus; Desikan, Radhika

    2012-11-01

    To optimize water use efficiency, plants regulate stomatal closure through a complex signaling process. Hydrogen peroxide (H₂O₂) is produced in response to several environmental stimuli, and has been identified as a key second messenger involved in the regulation of stomatal aperture. The Arabidopsis histidine kinase 5 (AHK5) has been shown to regulate stomatal closure in response to H₂O₂ and other stimuli that depend on H₂O₂. AHK5 is a member of the two-component system (TCS) in Arabidopsis. The plant TCS comprises three different protein types: the hybrid histidine kinases (HKs), the phosphotransfer proteins (HPs) and the response regulators (RRs). Here we determined TCS elements involved in H₂O₂- and ethylene-dependent stomatal closure downstream of AHK5. By yeast and in planta interaction assays and functional studies, AHP1, 2 and 5 as well as the response regulators ARR4 and ARR7 were identified acting downstream of AHK5 in the ethylene and H₂O₂ response pathways of guard cells. Furthermore, we demonstrate that aspartate phosphorylation of ARR4 is only required for the H₂O₂- but not for the ethylene-induced stomatal closure response. Our data suggest the presence of a complex TCS signaling network comprising of at least AHK5, several AHPs and response regulators, which modulate stomatal closure in response to H₂O₂ and ethylene.

  5. Two-component system response regulators involved in virulence of Streptococcus pneumoniae TIGR4 in infective endocarditis.

    Science.gov (United States)

    Trihn, My; Ge, Xiuchun; Dobson, Alleson; Kitten, Todd; Munro, Cindy L; Xu, Ping

    2013-01-01

    Streptococci resident in the oral cavity have been linked to infective endocarditis (IE). While other viridans streptococci are commonly studied in relation to IE, less research has been focused on Streptococcus pneumoniae. We established for the first time an animal model of S. pneumoniae IE, and examined the virulence of the TIGR4 strain in this model. We hypothesized that two-component systems (TCS) may mediate S. pneumoniae TIGR4 strain virulence in IE and examined TCS response regulator (RR) mutants of TIGR4 in vivo with the IE model. Thirteen of the 14 RR protein genes were mutagenized, excluding only the essential gene SP_1227. The requirement of the 13 RRs for S. pneumoniae competitiveness in the IE model was assessed in vivo through use of quantitative real-time PCR (qPCR) and competitive index assays. Using real-time PCR, several RR mutants were detected at significantly lower levels in infected heart valves compared with a control strain suggesting the respective RRs are candidate virulence factors for IE. The virulence reduction of the ΔciaR mutant was further confirmed by competitive index assay. Our data suggest that CiaR is a virulence factor of S. pneumoniae strain TIGR4 for IE. PMID:23342132

  6. The two-component signal transduction system YvcPQ regulates the bacterial resistance to bacitracin in Bacillus thuringiensis.

    Science.gov (United States)

    Zhang, Shumeng; Li, Xinfeng; Wang, Xun; Li, Zhou; He, Jin

    2016-10-01

    YvcPQ is one of the two-component signal transduction systems that respond to specific stimuli and enable cells to adjust multiple cellular functions. It consists of a histidine kinase YvcQ and a response regulator YvcP. In this study, through searching the consensus sequence recognized by YvcP, we found four YvcP-binding motifs in the promoter regions of genes yvcR (BMB171_C4100), BMB171_C4385, kapD (BMB171_C4525) and BMB171_C4835 in Bacillus thuringiensis BMB171 which is a representative of Bacillus cereus group, and confirmed that these genes are regulated by YvcP. We compared the sequence of yvcPQ and its downstream genes in genus Bacillus, and found two different kinds of yvc locus, one was the yvcPQ-RS in B. subtilis species and the other was the yvcPQ-R-S1S2 in B. cereus group. Furthermore, we found that YvcP activates the transcription of yvcS1S2 (downstream of yvcR) to promote bacterial resistance to bacitracin and deletion of either yvcPQ operon or yvcS1S2 operon renders the bacterial cells more sensitive to bacitracin. This study enriched our understanding of both the YvcPQ's function and the mechanism of bacterial resistance to bacitracin.

  7. The Role of CzcRS Two-Component Systems in the Heavy Metal Resistance of Pseudomonas putida X4

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    Pulin Liu

    2015-07-01

    Full Text Available The role of different czcRS genes in metal resistance and the cross-link between czcRS and czcCBA in Pseudomonas putida X4 were studied to advance understanding of the mechanisms by which P. putida copes with metal stress. Similar to P. putida KT2440, two complete czcRS1 and czcRS2 two-component systems, as well as a czcR3 without the corresponding sensing component were amplified in P. putida X4. The histidine kinase genes czcS1 and czcS2 were inactivated and fused to lacZ by homologous recombination. The lacZ fusion assay revealed that Cd2+ and Zn2+ caused a decrease in the transcription of czcRS1, whereas Cd2+ treatment enhanced the transcription of czcRS2. The mutation of different czcRSs showed that all czcRSs are necessary to facilitate full metal resistance in P. putida X4. A putative gene just downstream of czcR3 is related to metal ion resistance, and its transcription was activated by Zn2+. Data from quantitative real-time polymerase chain reaction (qRT-PCR strongly suggested that czcRSs regulate the expression of czcCBA, and a cross-link exists between different czcRSs.

  8. Analysis of the virulence-associated RevSR two-component signal transduction system of Clostridium perfringens.

    Science.gov (United States)

    Cheung, Jackie K; Wisniewski, Jessica A; Adams, Vicki M; Quinsey, Noelene S; Rood, Julian I

    2016-09-01

    Clostridium perfringens is a Gram-positive, anaerobic, spore-forming bacterium that causes human gas gangrene (clostridial myonecrosis) and food poisoning. Early studies showed that virulence was regulated by the VirSR two-component signal transduction system. However, our identification of the RevR orphan response regulator indicated that more than one system was involved in controlling virulence. To further characterize this virulence-associated regulator, gel mobility shift experiments, coupled with DNase I footprinting, were used to identify the RevR DNA binding sequence. Bioinformatics analysis suggested that an orphan sensor histidine kinase, CPE1757 (renamed RevS), was the cognate sensor of RevR. Interaction between RevS and RevR was demonstrated by use of a bacterial two-hybrid system and validated by protein-protein interaction studies using biolayer interferometry. To assess the involvement of RevS in virulence regulation, the revS gene was inactivated by Targetron insertion. When isogenic wild-type, revS and complemented revS strains were tested in a mouse myonecrosis model, the revS mutant was found to be attenuated in virulence, which was similar to the attenuation observed previously with the revR mutant. However, transcriptional analysis of selected RevR-regulated genes in the revS mutant revealed a different pattern of expression to a revR mutant, suggesting that the RevSR system is more complex than originally thought. Taken together, the results have led to the identification and characterization of the two essential parts of a new regulatory network that is involved in the regulation of virulence in C. perfringens.

  9. Diversity of two-component systems: insights into the signal transduction mechanism by the Staphylococcus aureus two-component system GraSR [v2; ref status: indexed, http://f1000r.es/4qf

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    Uzma Muzamal

    2014-11-01

    Full Text Available The response to cationic antimicrobial peptides (CAMPs in Staphylococcus aureus relies on a two-component system (TCS, GraSR, an auxiliary protein GraX and an ATP-binding cassette (ABC transporter, VraF/G. To understand the signal transduction mechanism by GraSR, we investigated the kinase activity of the cytoplasmic domain of histidine kinase GraS and the interaction with its cognate response regulator GraR. We also investigated interactions among the auxiliary protein GraX, GraS/R and the ATPase protein of the ABC transporter, VraF. We found that GraS lacks autophosphorylation activity, unlike a similar histidine kinase, BceS, of Bacillus subtilis. In addition, the interaction between GraS and GraR is very weak in comparison to the stronger interaction observed between BceS and its conjugated response regulator, BceR, suggesting that CAMP signaling may not flow directly from GraS to GraR. We found that the auxiliary protein GraX interacts with VraF and GraR, and requires the histidine phosphotransfer and dimerization domain of GraS to interact with this protein. Further, VraF requires the GraS region that connects the membrane-bound domain with the cytoplasmic domain of this protein for interaction with GraS. The interactions of GraX with GraS/R and VraF indicate that GraX may serve as a scaffold to bring these proteins in close proximity to GraS, plausibly to facilitate activation of GraS to ultimately transduce the signal to GraR.

  10. A two-component system regulates gene expression of the type IX secretion component proteins via an ECF sigma factor.

    Science.gov (United States)

    Kadowaki, Tomoko; Yukitake, Hideharu; Naito, Mariko; Sato, Keiko; Kikuchi, Yuichiro; Kondo, Yoshio; Shoji, Mikio; Nakayama, Koji

    2016-01-01

    The periodontopathogen Porphyromonas gingivalis secretes potent pathogenic proteases, gingipains, via the type IX secretion system (T9SS). This system comprises at least 11 components; however, the regulatory mechanism of their expression has not yet been elucidated. Here, we found that the PorY (PGN_2001)-PorX (PGN_1019)-SigP (PGN_0274) cascade is involved in the regulation of T9SS. Surface plasmon resonance (SPR) analysis revealed a direct interaction between a recombinant PorY (rPorY) and a recombinant PorX (rPorX). rPorY autophosphorylated and transferred a phosphoryl group to rPorX in the presence of Mn(2+). These results demonstrate that PorX and PorY act as a response regulator and a histidine kinase, respectively, of a two component system (TCS), although they are separately encoded on the chromosome. T9SS component-encoding genes were down-regulated in a mutant deficient in a putative extracytoplasmic function (ECF) sigma factor, PGN_0274 (SigP), similar to the porX mutant. Electrophoretic gel shift assays showed that rSigP bound to the putative promoter regions of T9SS component-encoding genes. The SigP protein was lacking in the porX mutant. Co-immunoprecipitation and SPR analysis revealed the direct interaction between SigP and PorX. Together, these results indicate that the PorXY TCS regulates T9SS-mediated protein secretion via the SigP ECF sigma factor. PMID:26996145

  11. Two-component system cross-regulation integrates Bacillus anthracis response to heme and cell envelope stress.

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    Laura A Mike

    2014-03-01

    Full Text Available Two-component signaling systems (TCSs are one of the mechanisms that bacteria employ to sense and adapt to changes in the environment. A prototypical TCS functions as a phosphorelay from a membrane-bound sensor histidine kinase (HK to a cytoplasmic response regulator (RR that controls target gene expression. Despite significant homology in the signaling domains of HKs and RRs, TCSs are thought to typically function as linear systems with little to no cross-talk between non-cognate HK-RR pairs. Here we have identified several cell envelope acting compounds that stimulate a previously uncharacterized Bacillus anthracis TCS. Furthermore, this TCS cross-signals with the heme sensing TCS HssRS; therefore, we have named it HssRS interfacing TCS (HitRS. HssRS reciprocates cross-talk to HitRS, suggesting a link between heme toxicity and cell envelope stress. The signaling between HssRS and HitRS occurs in the parental B. anthracis strain; therefore, we classify HssRS-HitRS interactions as cross-regulation. Cross-talk between HssRS and HitRS occurs at both HK-RR and post-RR signaling junctions. Finally, HitRS also regulates a previously unstudied ABC transporter implicating this transporter in the response to cell envelope stress. This chemical biology approach to probing TCS signaling provides a new model for understanding how bacterial signaling networks are integrated to enable adaptation to complex environments such as those encountered during colonization of the vertebrate host.

  12. The KdpD/KdpE two-component system: integrating K⁺ homeostasis and virulence.

    Science.gov (United States)

    Freeman, Zoë N; Dorus, Steve; Waterfield, Nicholas R

    2013-03-01

    The two-component system (TCS) KdpD/KdpE, extensively studied for its regulatory role in potassium (K(+)) transport, has more recently been identified as an adaptive regulator involved in the virulence and intracellular survival of pathogenic bacteria, including Staphylococcus aureus, entero-haemorrhagic Escherichia coli, Salmonella typhimurium, Yersinia pestis, Francisella species, Photorhabdus asymbiotica, and mycobacteria. Key homeostasis requirements monitored by KdpD/KdpE and other TCSs such as PhoP/PhoQ are critical to survival in the stressful conditions encountered by pathogens during host interactions. It follows these TCSs may therefore acquire adaptive roles in response to selective pressures associated with adopting a pathogenic lifestyle. Given the central role of K(+) in virulence, we propose that KdpD/KdpE, as a regulator of a high-affinity K(+) pump, has evolved virulence-related regulatory functions. In support of this hypothesis, we review the role of KdpD/KdpE in bacterial infection and summarize evidence that (i) KdpD/KdpE production is correlated with enhanced virulence and survival, (ii) KdpE regulates a range of virulence loci through direct promoter binding, and (iii) KdpD/KdpE regulation responds to virulence-related conditions including phagocytosis, exposure to microbicides, quorum sensing signals, and host hormones. Furthermore, antimicrobial stress, osmotic stress, and oxidative stress are associated with KdpD/KdpE activity, and the system's accessory components (which allow TCS fine-tuning or crosstalk) provide links to stress response pathways. KdpD/KdpE therefore appears to be an important adaptive TCS employed during host infection, promoting bacterial virulence and survival through mechanisms both related to and distinct from its conserved role in K(+) regulation.

  13. The KdpD/KdpE two-component system: integrating K⁺ homeostasis and virulence.

    Directory of Open Access Journals (Sweden)

    Zoë N Freeman

    2013-03-01

    Full Text Available The two-component system (TCS KdpD/KdpE, extensively studied for its regulatory role in potassium (K(+ transport, has more recently been identified as an adaptive regulator involved in the virulence and intracellular survival of pathogenic bacteria, including Staphylococcus aureus, entero-haemorrhagic Escherichia coli, Salmonella typhimurium, Yersinia pestis, Francisella species, Photorhabdus asymbiotica, and mycobacteria. Key homeostasis requirements monitored by KdpD/KdpE and other TCSs such as PhoP/PhoQ are critical to survival in the stressful conditions encountered by pathogens during host interactions. It follows these TCSs may therefore acquire adaptive roles in response to selective pressures associated with adopting a pathogenic lifestyle. Given the central role of K(+ in virulence, we propose that KdpD/KdpE, as a regulator of a high-affinity K(+ pump, has evolved virulence-related regulatory functions. In support of this hypothesis, we review the role of KdpD/KdpE in bacterial infection and summarize evidence that (i KdpD/KdpE production is correlated with enhanced virulence and survival, (ii KdpE regulates a range of virulence loci through direct promoter binding, and (iii KdpD/KdpE regulation responds to virulence-related conditions including phagocytosis, exposure to microbicides, quorum sensing signals, and host hormones. Furthermore, antimicrobial stress, osmotic stress, and oxidative stress are associated with KdpD/KdpE activity, and the system's accessory components (which allow TCS fine-tuning or crosstalk provide links to stress response pathways. KdpD/KdpE therefore appears to be an important adaptive TCS employed during host infection, promoting bacterial virulence and survival through mechanisms both related to and distinct from its conserved role in K(+ regulation.

  14. Regulation of Arsenite Oxidation by the Phosphate Two-Component System PhoBR in Halomonas sp. HAL1

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    Fang eChen

    2015-09-01

    Full Text Available Previously, the expression of arsenite [As(III] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR931 and HAL1-△phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi acquisition and assimilation. Both of the mutants showed negative As(III-oxidation phenotypes in low Pi condition (0.1 mM but not under normal Pi condition (1 mM. The phoBR complementation strain HAL1-△phoB-C reversed the mutants’ null phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III but were not induced in HAL1-phoR931 and HAL1-△phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection and in vitro (electrophoretic mobility gel shift assay, and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi.

  15. Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1.

    Science.gov (United States)

    Chen, Fang; Cao, Yajing; Wei, Sha; Li, Yanzhi; Li, Xiangyang; Wang, Qian; Wang, Gejiao

    2015-01-01

    Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR 931 and HAL1-▵phoB, were obtained in strain HAL1. The phoR and phoB constitute a two-component system which is responsible for phosphate (Pi) acquisition and assimilation. Both of the mutants showed negative As(III)-oxidation phenotypes in low Pi condition (0.1 mM) but not under normal Pi condition (1 mM). The phoBR complementation strain HAL1-▵phoB-C reversed the mutants' null phenotypes back to wild type status. Meanwhile, lacZ reporter fusions using pCM-lacZ showed that the expression of phoBR and aioBA were both induced by As(III) but were not induced in HAL1-phoR 931 and HAL1-▵phoB. Using 15 consensus Pho box sequences, a putative Pho box was found in the aioBA regulation region. PhoB was able to bind to the putative Pho box in vivo (bacterial one-hybrid detection) and in vitro (electrophoretic mobility gel shift assay), and an 18-bp binding sequence containing nine conserved bases were determined. This study provided the evidence that PhoBR regulates the expression of aioBA in Halomonas sp. HAL1 under low Pi condition. The new regulation model further implies the close metabolic connection between As and Pi. PMID:26441863

  16. Evolutionary history of the OmpR/IIIA family of signal transduction two component systems in Lactobacillaceae and Leuconostocaceae

    Directory of Open Access Journals (Sweden)

    González-Candelas Fernando

    2011-02-01

    Full Text Available Abstract Background Two component systems (TCS are signal transduction pathways which typically consist of a sensor histidine kinase (HK and a response regulator (RR. In this study, we have analyzed the evolution of TCS of the OmpR/IIIA family in Lactobacillaceae and Leuconostocaceae, two families belonging to the group of lactic acid bacteria (LAB. LAB colonize nutrient-rich environments such as foodstuffs, plant materials and the gastrointestinal tract of animals thus driving the study of this group of both basic and applied interest. Results The genomes of 19 strains belonging to 16 different species have been analyzed. The number of TCS encoded by the strains considered in this study varied between 4 in Lactobacillus helveticus and 17 in Lactobacillus casei. The OmpR/IIIA family was the most prevalent in Lactobacillaceae accounting for 71% of the TCS present in this group. The phylogenetic analysis shows that no new TCS of this family has recently evolved in these Lactobacillaceae by either lineage-specific gene expansion or domain shuffling. Furthermore, no clear evidence of non-orthologous replacements of either RR or HK partners has been obtained, thus indicating that coevolution of cognate RR and HKs has been prevalent in Lactobacillaceae. Conclusions The results obtained suggest that vertical inheritance of TCS present in the last common ancestor and lineage-specific gene losses appear as the main evolutionary forces involved in their evolution in Lactobacillaceae, although some HGT events cannot be ruled out. This would agree with the genomic analyses of Lactobacillales which show that gene losses have been a major trend in the evolution of this group.

  17. Extrusion foaming of thermoplastic cellulose acetate from renewable resources using a two-component physical blowing agent system

    Science.gov (United States)

    Hopmann, Ch.; Windeck, C.; Hendriks, S.; Zepnik, S.; Wodke, T.

    2014-05-01

    Thermoplastic cellulose acetate (CA) is a bio-based polymer with optical, mechanical and thermal properties comparable to those of polystyrene (PS). The substitution of the predominant petrol-based PS in applications like foamed food trays can lead to a more sustainable economic practice. However, CA is also suitable for more durable applications as the biodegradability rate can be controlled by adjusting the degree of substitutions. The extrusion foaming of CA still has to overcome certain challenges. CA is highly hydrophilic and can suffer from hydrolytic degradation if not dried properly. Therefore, the influence of residual moisture on the melt viscosity is rather high. Beyond, the surface quality of foam CA sheets is below those of PS due to the particular foaming behaviour. This paper presents results of a recent study on extrusion foamed CA, using a two-component physical blowing agent system compromising HFO 1234ze as blowing agent and organic solvents as co-propellant. Samples with different co-propellants are processed on a laboratory single screw extruder at IKV. Morphology and surface topography are investigated with respect to the blowing agent composition and the die pressure. In addition, relationships between foam density, foam morphology and the propellants are analysed. The choice of the co-propellant has a significant influence on melt-strength, foaming behaviour and the possible blow-up ratio of the sheet. Furthermore, a positive influence of the co-propellant on the surface quality can be observed. In addition, the focus is laid on the effect of external contact cooling of the foamed sheets after the die exit.

  18. A novel two-component signaling system facilitates uropathogenic Escherichia coli's ability to exploit abundant host metabolites.

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    Wentong Cai

    Full Text Available Two-component signaling systems (TCSs are major mechanisms by which bacteria adapt to environmental conditions. It follows then that TCSs would play important roles in the adaptation of pathogenic bacteria to host environments. However, no pathogen-associated TCS has been identified in uropathogenic Escherichia coli (UPEC. Here, we identified a novel TCS, which we termed KguS/KguR (KguS: α-ketoglutarate utilization sensor; KguR: α-ketoglutarate utilization regulator in UPEC CFT073, a strain isolated from human pyelonephritis. kguS/kguR was strongly associated with UPEC but was found only rarely among other E. coli including commensal and intestinal pathogenic strains. An in vivo competition assay in a mouse UTI model showed that deletion of kguS/kguR in UPEC CFT073 resulted in a significant reduction in its colonization of the bladders and kidneys of mice, suggesting that KguS/KguR contributed to UPEC fitness in vivo. Comparative proteomics identified the target gene products of KguS/KguR, and sequence analysis showed that TCS KguS/KguR and its targeted-genes, c5032 to c5039, are encoded on a genomic island, which is not present in intestinal pathogenic E. coli. Expression of the target genes was induced by α-ketoglutarate (α-KG. These genes were further shown to be involved in utilization of α-KG as a sole carbon source under anaerobic conditions. KguS/KguR contributed to the regulation of the target genes with the direct regulation by KguR verified using an electrophoretic mobility shift assay. In addition, oxygen deficiency positively modulated expression of kguS/kguR and its target genes. Taken altogether, this study describes the first UPEC-associated TCS that functions in controlling the utilization of α-ketoglutarate in vivo thereby facilitating UPEC adaptation to life inside the urinary tract.

  19. A novel two-component signaling system facilitates uropathogenic Escherichia coli's ability to exploit abundant host metabolites.

    Science.gov (United States)

    Cai, Wentong; Wannemuehler, Yvonne; Dell'anna, Giuseppe; Nicholson, Bryon; Barbieri, Nicolle L; Kariyawasam, Subhashinie; Feng, Yaping; Logue, Catherine M; Nolan, Lisa K; Li, Ganwu

    2013-01-01

    Two-component signaling systems (TCSs) are major mechanisms by which bacteria adapt to environmental conditions. It follows then that TCSs would play important roles in the adaptation of pathogenic bacteria to host environments. However, no pathogen-associated TCS has been identified in uropathogenic Escherichia coli (UPEC). Here, we identified a novel TCS, which we termed KguS/KguR (KguS: α-ketoglutarate utilization sensor; KguR: α-ketoglutarate utilization regulator) in UPEC CFT073, a strain isolated from human pyelonephritis. kguS/kguR was strongly associated with UPEC but was found only rarely among other E. coli including commensal and intestinal pathogenic strains. An in vivo competition assay in a mouse UTI model showed that deletion of kguS/kguR in UPEC CFT073 resulted in a significant reduction in its colonization of the bladders and kidneys of mice, suggesting that KguS/KguR contributed to UPEC fitness in vivo. Comparative proteomics identified the target gene products of KguS/KguR, and sequence analysis showed that TCS KguS/KguR and its targeted-genes, c5032 to c5039, are encoded on a genomic island, which is not present in intestinal pathogenic E. coli. Expression of the target genes was induced by α-ketoglutarate (α-KG). These genes were further shown to be involved in utilization of α-KG as a sole carbon source under anaerobic conditions. KguS/KguR contributed to the regulation of the target genes with the direct regulation by KguR verified using an electrophoretic mobility shift assay. In addition, oxygen deficiency positively modulated expression of kguS/kguR and its target genes. Taken altogether, this study describes the first UPEC-associated TCS that functions in controlling the utilization of α-ketoglutarate in vivo thereby facilitating UPEC adaptation to life inside the urinary tract.

  20. BarA-UvrY two-component system regulates virulence of uropathogenic E. coli CFT073.

    Science.gov (United States)

    Palaniyandi, Senthilkumar; Mitra, Arindam; Herren, Christopher D; Lockatell, C Virginia; Johnson, David E; Zhu, Xiaoping; Mukhopadhyay, Suman

    2012-01-01

    Uropathogenic Escherichia coli (UPEC), a member of extraintestinal pathogenic E. coli, cause ∼80% of community-acquired urinary tract infections (UTI) in humans. UPEC initiates its colonization in epithelial cells lining the urinary tract with a complicated life cycle, replicating and persisting in intracellular and extracellular niches. Consequently, UPEC causes cystitis and more severe form of pyelonephritis. To further understand the virulence characteristics of UPEC, we investigated the roles of BarA-UvrY two-component system (TCS) in regulating UPEC virulence. Our results showed that mutation of BarA-UvrY TCS significantly decreased the virulence of UPEC CFT073, as assessed by mouse urinary tract infection, chicken embryo killing assay, and cytotoxicity assay on human kidney and uroepithelial cell lines. Furthermore, mutation of either barA or uvrY gene reduced the production of hemolysin, lipopolysaccharide (LPS), proinflammatory cytokines (TNF-α and IL-6) and chemokine (IL-8). The virulence phenotype was restored similar to that of wild-type by complementation of either barA or uvrY gene in trans. In addition, we discussed a possible link between the BarA-UvrY TCS and CsrA in positively and negatively controlling virulence in UPEC. Overall, this study provides the evidences for BarA-UvrY TCS regulates the virulence of UPEC CFT073 and may point to mechanisms by which virulence regulations are observed in different ways may control the long-term survival of UPEC in the urinary tract.

  1. Role of the LytSR two-component regulatory system in adaptation to cationic antimicrobial peptides in Staphylococcus aureus.

    Science.gov (United States)

    Yang, Soo-Jin; Xiong, Yan Q; Yeaman, Michael R; Bayles, Kenneth W; Abdelhady, Wessam; Bayer, Arnold S

    2013-08-01

    Many host defense cationic antimicrobial peptides (HDPs) perturb the staphylococcal cell membrane (CM) and alter transmembrane potential (ΔΨ) as key parts of their lethal mechanism. Thus, a sense-response system for detecting and mediating adaptive responses to such stresses could impact organism survival; the Staphylococcus aureus LytSR two-component regulatory system (TCRS) may serve as such a ΔΨ sensor. One well-known target of this system is the lrgAB operon, which, along with the related cidABC operon, has been shown to be a regulator in the control of programmed cell death and lysis. We used an isogenic set of S. aureus strains: (i) UAMS-1, (ii) its isogenic ΔlytS and ΔlrgAB mutants, and (iii) plasmid-complemented ΔlytSR and ΔlrgAB mutants. The ΔlytS strain displayed significantly increased in vitro susceptibilities to all HDPs tested (neutrophil-derived human neutrophil peptide 1 [hNP-1], platelet-derived thrombin-induced platelet microbicidal proteins [tPMPs], and the tPMP-mimetic peptide RP-1), as well as to calcium-daptomycin (DAP), a cationic antimicrobial peptide (CAP). In contrast, the ΔlrgAB strain exhibited no significant changes in susceptibilities to these cationic peptides, indicating that although lytSR positively regulates transcription of lrgAB, increased HDP/CAP susceptibilities in the ΔlytS mutant were lrgAB independent. Further, parental UAMS-1 (but not the ΔlytS mutant) became more resistant to hNP-1 and DAP following pretreatment with carbonyl cyanide m-chlorophenylhydrazone (CCCP) (a CM-depolarizing agent). Of note, lytSR-dependent survival against CAP/HDP killing was not associated with changes in either surface positive charge, expression of mprF and dlt, or CM fluidity. The ΔlytS strain (but not the ΔlrgAB mutant) displayed a significant reduction in target tissue survival in an endocarditis model during DAP treatment. Collectively, these results suggest that the lytSR TCRS plays an important role in adaptive responses of

  2. Molecular evolution of the two-component system BvgAS involved in virulence regulation in Bordetella.

    Directory of Open Access Journals (Sweden)

    Julien Herrou

    Full Text Available The whooping cough agent Bordetella pertussis is closely related to Bordetella bronchiseptica, which is responsible for chronic respiratory infections in various mammals and is occasionally found in humans, and to Bordetella parapertussis, one lineage of which causes mild whooping cough in humans and the other ovine respiratory infections. All three species produce similar sets of virulence factors that are co-regulated by the two-component system BvgAS. We characterized the molecular diversity of BvgAS in Bordetella by sequencing the two genes from a large number of diverse isolates. The response regulator BvgA is virtually invariant, indicating strong functional constraints. In contrast, the multi-domain sensor kinase BvgS has evolved into two different types. The pertussis type is found in B. pertussis and in a lineage of essentially human-associated B. bronchiseptica, while the bronchiseptica type is associated with the majority of B. bronchiseptica and both ovine and human B. parapertussis. BvgS is monomorphic in B. pertussis, suggesting optimal adaptation or a recent population bottleneck. The degree of diversity of the bronchiseptica type BvgS is markedly different between domains, indicating distinct evolutionary pressures. Thus, absolute conservation of the putative solute-binding cavities of the two periplasmic Venus Fly Trap (VFT domains suggests that common signals are perceived in all three species, while the external surfaces of these domains vary more extensively. Co-evolution of the surfaces of the two VFT domains in each type and domain swapping experiments indicate that signal transduction in the periplasmic region may be type-specific. The two distinct evolutionary solutions for BvgS confirm that B. pertussis has emerged from a specific B. bronchiseptica lineage. The invariant regions of BvgS point to essential parts for its molecular mechanism, while the variable regions may indicate adaptations to different lifestyles. The

  3. Identification, Functional Characterization and Regulon Prediction of a Novel Two Component System Comprising BAS0540-BAS0541 of Bacillus anthracis

    Science.gov (United States)

    Gopalani, Monisha; Kandari, Divya; Bhatnagar, Rakesh

    2016-01-01

    Two component systems (TCSs) can be envisaged as complex molecular devices that help the bacteria to sense its environment and respond aptly. 41 TCSs are predicted in Bacillus anthracis, a potential bioterrorism agent, of which only four have been studied so far. Thus, the intricate signaling network contributed by TCSs remains largely unmapped in B. anthracis and needs comprehensive exploration. In this study, we functionally characterized one such system composed of BAS0540 (Response regulator) and BAS0541 (Histidine kinase). BAS0540-BAS0541, the closest homolog of CiaRH of Streptococcus in B. anthracis, forms a functional TCS with BAS0541 displaying autophosphorylation and subsequent phosphotransfer to BAS0540. BAS0540 was also found to accept phosphate from physiologically relevant small molecule phosphodonors like acetyl phosphate and carbamoyl phosphate. Results of qRT-PCR and immunoblotting demonstrated that BAS0540 exhibits a constitutive expression throughout the growth of B. anthracis. Regulon prediction for BAS0540 in B. anthracis was done in silico using the consensus DNA binding sequence of CiaR of Streptococcus. The predicted regulon of BAS0540 comprised of 23 genes, which could be classified into 8 functionally diverse categories. None of the proven virulence factors were a part of the predicted regulon, an observation contrasting with the regulon of CiaRH in Streptococci. Electrophoretic mobility shift assay was used to show direct binding of purified BAS0540 to the upstream regions of 5 putative regulon candidates- BAS0540 gene itself; a gene predicted to encode cell division protein FtsA; a self–immunity gene; a RND family transporter gene and a gene encoding stress (heat) responsive protein. A significant enhancement in the DNA binding ability of BAS0540 was observed upon phosphorylation. Overexpression of response regulator BAS0540 in B. anthracis led to a prodigious increase of ~6 folds in the cell length, thereby conferring it a filamentous

  4. Pseudomonas aeruginosa MifS-MifR Two-Component System Is Specific for α-Ketoglutarate Utilization.

    Directory of Open Access Journals (Sweden)

    Gorakh Tatke

    Full Text Available Pseudomonas aeruginosa is a Gram-negative, metabolically versatile opportunistic pathogen that elaborates a multitude of virulence factors, and is extraordinarily resistant to a gamut of clinically significant antibiotics. This ability, in part, is mediated by two-component regulatory systems (TCS that play a crucial role in modulating virulence mechanisms and metabolism. MifS (PA5512 and MifR (PA5511 form one such TCS implicated in biofilm formation. MifS is a sensor kinase whereas MifR belongs to the NtrC superfamily of transcriptional regulators that interact with RpoN (σ54. In this study we demonstrate that the mifS and mifR genes form a two-gene operon. The close proximity of mifSR operon to poxB (PA5514 encoding a ß-lactamase hinted at the role of MifSR TCS in regulating antibiotic resistance. To better understand this TCS, clean in-frame deletions were made in P. aeruginosa PAO1 creating PAO∆mifS, PAO∆mifR and PAO∆mifSR. The loss of mifSR had no effect on the antibiotic resistance profile. Phenotypic microarray (BioLOG analyses of PAO∆mifS and PAO∆mifR revealed that these mutants were unable to utilize C5-dicarboxylate α-ketoglutarate (α-KG, a key tricarboxylic acid cycle intermediate. This finding was confirmed using growth analyses, and the defect can be rescued by mifR or mifSR expressed in trans. These mifSR mutants were able to utilize all the other TCA cycle intermediates (citrate, succinate, fumarate, oxaloacetate or malate and sugars (glucose or sucrose except α-KG as the sole carbon source. We confirmed that the mifSR mutants have functional dehydrogenase complex suggesting a possible defect in α-KG transport. The inability of the mutants to utilize α-KG was rescued by expressing PA5530, encoding C5-dicarboxylate transporter, under a regulatable promoter. In addition, we demonstrate that besides MifSR and PA5530, α-KG utilization requires functional RpoN. These data clearly suggests that P. aeruginosa MifSR TCS

  5. Origin and evolution of two-component debris discs and an application to the q$^1$ Eridani system

    CERN Document Server

    Schüppler, Christian; Löhne, Torsten; Booth, Mark; Kirchschlager, Florian; Wolf, Sebastian

    2016-01-01

    Many debris discs reveal a two-component structure, with an outer Kuiper-belt analogue and a warm inner component whose origin is still a matter of debate. One possibility is that warm emission stems from an "asteroid belt" closer in to the star. We consider a scenario in which a set of giant planets is formed in an initially extended planetesimal disc. These planets carve a broad gap around their orbits, splitting up the disc into the outer and the inner belts. After the gas dispersal, both belts undergo collisional evolution in a steady-state regime. This scenario is explored with detailed collisional simulations involving realistic physics to describe a long-term collisional depletion of the two-component disc. We find that the inner disc may be able to retain larger amounts of material at older ages than thought before on the basis of simplified analytic models. We show that the proposed scenario is consistent with a suite of thermal emission and scattered light observational data for a bright two-tempera...

  6. Phosphorelay of non-orthodox two component systems functions through a bi-molecular mechanism in vivo

    DEFF Research Database (Denmark)

    Jovanovic, Goran; Sheng, Xia; Ale, Angelique;

    2015-01-01

    functional relevance of the dimerization of a non-orthodox or hybrid histidine kinase along which the phosphorelay takes place has been a subject of debate. We use a combination of molecular and genetic approaches, coupled to mathematical and statistical modelling, to demonstrate that the different possible...... intra- and inter-molecular mechanisms of phosphotransfer are formally non-identifiable in Escherichia coli expressing the ArcB non-orthodox histidine kinase used in anoxic redox control. In order to resolve this issue we further analyse the mathematical model in order to identify discriminatory...... histidine kinase. This is the first detailed mechanistic analysis of the molecular processes involved in non-orthodox two-component signalling and our results suggest strongly that dimerization facilitates more discriminatory proof-reading of external signals, via these allosteric reactions, prior to them...

  7. The impact of ColRS two-component system and TtgABC efflux pump on phenol tolerance of Pseudomonas putida becomes evident only in growing bacteria

    OpenAIRE

    Kivisaar Maia; Lilje Liisa; Ilves Heili; Putrinš Marta; Hõrak Rita

    2010-01-01

    Abstract Background We have recently found that Pseudomonas putida deficient in ColRS two-component system is sensitive to phenol and displays a serious defect on solid glucose medium where subpopulation of bacteria lyses. The latter phenotype is significantly enhanced by the presence of phenol in growth medium. Here, we focused on identification of factors affecting phenol tolerance of the colR-deficient P. putida. Results By using transposon mutagenesis approach we identified a set of pheno...

  8. Crystal Structure of the Response Regulator 02 Receiver Domain, the Essential YycF Two-Component System of Streptococcus pneumoniae in both Complexed and Native States†

    OpenAIRE

    Bent, Colin J.; Isaacs, Neil W.; Mitchell, Timothy J.; Riboldi-Tunnicliffe, Alan

    2004-01-01

    A variety of bacterial cellular responses to environmental signals are mediated by two-component signal transduction systems comprising a membrane-associated histidine protein kinase and a cytoplasmic response regulator (RR), which interpret specific stimuli and produce a measured physiological response. In RR activation, transient phosphorylation of a highly conserved aspartic acid residue drives the conformation changes needed for full activation of the protein. Sequence homology reveals th...

  9. The development of a two-component force dynamometer and tool control system for dynamic machine tool research

    Science.gov (United States)

    Sutherland, I. A.

    1973-01-01

    The development is presented of a tooling system that makes a controlled sinusoidal oscillation simulating a dynamic chip removal condition. It also measures the machining forces in two mutually perpendicular directions without any cross sensitivity.

  10. Elliptic waves in two-component long-wave–short-wave resonance interaction system in one and two dimensions

    International Nuclear Information System (INIS)

    We consider (2+1)- and (1+1)-dimensional long-wave–short-wave resonance interaction systems. We construct an extensive set of exact periodic solutions of these systems in terms of Lamé polynomials of order one and two. The periodic solutions are classified into three categories as similar, mixed, superposed elliptic solutions. We also discuss the hyperbolic solutions as limiting cases. - Highlights: • Jacobi elliptic solutions for (1+1)D and (2+1)D LSRI system in terms of Lamé polynomials order 1 and 2. • Three types of Jacobi elliptic solutions: similar, mixed, superposed solutions. • Identified special in-phase and out-of-phase periodic wave train solutions. • Demonstrated the appearance of various types of solitons in the hyperbolic limit. • Identified special solitary waves: bi-soliton and anti-dark soliton wave at the order 2

  11. Pattern formation in a two-component reaction-diffusion system with delayed processes on a network

    Science.gov (United States)

    Petit, Julien; Asllani, Malbor; Fanelli, Duccio; Lauwens, Ben; Carletti, Timoteo

    2016-11-01

    Reaction-diffusion systems with time-delay defined on complex networks have been studied in the framework of the emergence of Turing instabilities. The use of the Lambert W-function allowed us to get explicit analytic conditions for the onset of patterns as a function of the main involved parameters, the time-delay, the network topology and the diffusion coefficients. Depending on these parameters, the analysis predicts whether the system will evolve towards a stationary Turing pattern or rather to a wave pattern associated to a Hopf bifurcation. The possible outcomes of the linear analysis overcome the respective limitations of the single-species case with delay, and that of the classical activator-inhibitor variant without delay. Numerical results gained from the Mimura-Murray model support the theoretical approach.

  12. Regulation of Arsenite Oxidation by the Phosphate Two-Component System PhoBR in Halomonas sp. HAL1

    OpenAIRE

    Fang eChen; Yajing eCao; Sha eWei; Yanzhi eLi; Xiangyang eLi; Qian eWang; Gejiao eWang

    2015-01-01

    Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR931 and HAL1-△phoB, were obtained i...

  13. Regulation of arsenite oxidation by the phosphate two-component system PhoBR in Halomonas sp. HAL1

    OpenAIRE

    Chen, Fang; Cao, Yajing; Wei, Sha; Li, Yanzhi; Li, Xiangyang; Wang, Qian; Wang, Gejiao

    2015-01-01

    Previously, the expression of arsenite [As(III)] oxidase genes aioBA was reported to be regulated by a three-component regulatory system, AioXSR, in a number of As(III)-oxidizing bacterial strains. However, the regulation mechanism is still unknown when aioXSR genes are absent in some As(III)-oxidizing bacterial genomes, such as in Halomonas sp. HAL1. In this study, transposon mutagenesis and gene knock-out mutation were performed, and two mutants, HAL1-phoR 931 and HAL1-▵phoB, were obtained ...

  14. A model system for pathogen detection using a two-component bacteriophage/bioluminescent signal amplification assay

    Science.gov (United States)

    Bright, Nathan G.; Carroll, Richard J.; Applegate, Bruce M.

    2004-03-01

    Microbial contamination has become a mounting concern the last decade due to an increased emphasis of minimally processed food products specifically produce, and the recognition of foodborne pathogens such as Campylobacter jejuni, Escherichia coli O157:H7, and Listeria monocytogenes. This research investigates a detection approach utilizing bacteriophage pathogen specificity coupled with a bacterial bioluminescent bioreporter utilizing the quorum sensing molecule from Vibrio fischeri, N-(3-oxohexanoyl)-homoserine lactone (3-oxo-C6-HSL). The 3-oxo-C6-HSL molecules diffuse out of the target cell after infection and induce bioluminescence from a population of 3-oxo-C6-HSL bioreporters (ROLux). E. coli phage M13, a well-characterized bacteriophage, offers a model system testing the use of bacteriophage for pathogen detection through cell-to-cell communication via a LuxR/3-oxo-C6-HSL system. Simulated temperate phage assays tested functionality of the ROLux reporter and production of 3-oxo-C6-HSL by various test strains. These assays showed detection limits of 102cfu after 24 hours in a varietry of detection formats. Assays incorporating the bacteriophage M13-luxI with the ROLux reporter and a known population of target cells were subsequently developed and have shown consistent detection limits of 105cfu target organisms. Measurable light response from high concentrations of target cells was almost immediate, suggesting an enrichment step to further improve detection limits and reduce assay time.

  15. A novel outer-membrane anion channel (porin) as part of a putatively two-component transport system for 4-toluenesulphonate in Comamonas testosteroni T-2

    OpenAIRE

    Mampel, Jörg; Maier, Elke; Tralau, Tewes; Ruff, Jürgen; Benz, Roland; Cook, Alasdair M.

    2004-01-01

    Inducible mineralization of TSA (4-toluenesulphonate) by Comamonas testosteroni T-2 is initiated by a secondary transport system, followed by oxygenation and oxidation by TsaMBCD to 4-sulphobenzoate under the regulation of TsaR and TsaQ. Evidence is presented for a novel, presumably two-component transport system (TsaST). It is proposed that TsaT, an outer-membrane porin, formed an anion-selective channel that works in co-operation with the putative secondary transporter, TsaS, located in the...

  16. Polymyxin resistance of Pseudomonas aeruginosa phoQ mutants is dependent on additional two-component regulatory systems

    DEFF Research Database (Denmark)

    Gutu, Alina D; Sgambati, Nicole; Strasbourger, Pnina;

    2013-01-01

    systems, ColRS and CprRS. Deletion of the colRS genes, individually or in tandem, abrogated the polymyxin resistance of a ΔphoQ mutant, as did individual or tandem deletion of cprRS. Individual deletion of colR or colS in a ΔphoQ mutant also suppressed 4-amino-L-arabinose addition to lipid A, consistent...... with the known role of this modification in polymyxin resistance. Surprisingly, tandem deletion of colRS or cprRS in the ΔphoQ mutant or individual deletion of cprR or cprS failed to suppress 4-amino-L-arabinose addition to lipid A, indicating that this modification alone is not sufficient for Pho......PQ-mediated polymyxin resistance in P. aeruginosa. Episomal expression of colRS or cprRS in tandem or of cprR individually complemented the Pm resistance phenotype in the ΔphoQ mutant, while episomal expression of colR, colS, or cprS individually did not. Highly polymyxin-resistant phoQ mutants of P. aeruginosa...

  17. On Mechanics and Thermodynamics of a stellar galaxy in a two-component virial system and the Fundamental Plane

    CERN Document Server

    Secco, L

    2005-01-01

    The paper confirms the existence of a special configuration (among the infinite number of virial states) which a B stellar(Baryonic) component may assume inside a given D dark halo potential well.This satisfies the d'Alembert Principle of virtual works and its typical dimension works as a scale length (tidal radius)induced on the gravitational field of the bright component by the dark one.Its dynamic and thermodynamic properties are here analyzed in connection with the physical reason for the existence of the Fundamental Plane (FP) for ellipticals.The analysis is performed by using 2-component models with two power-law density profiles and two homogeneous cores and compared with some observable scaling relations for pressure supported ellipticals.The virial equilibrium stages of the 2-component system have to occur after a previous violent relaxation phase. If the stellar B component is allowed to cool slowly its virial evolution consists of a sequence of contractions with enough time to rearrange the virial ...

  18. The two-component regulatory systems in Pseudomonas aeruginosa%铜绿假单胞菌的双组分系统

    Institute of Scientific and Technical Information of China (English)

    陈利达; 黄彬

    2011-01-01

    双组分系统是存在于原核和少部分真核生物细胞中的信号转导系统,主要由组氨酸蛋白激酶和反应调节蛋白组成,通过感应外界环境信号、信号输入、磷酸基团传递、信号输出等环节调节基因表达,使细胞能更加适应环境变化.铜绿假单胞菌为条件致病菌,其双组分系统构成多样、功能复杂且参与介导耐药性产生,因此铜绿假单胞菌的双组分系统日益引起人们关注.本文对铜绿假单胞菌双组分系统的组成、信号转导机制、种类、研究方法及其临床意义进行了综述.%Two-component regulatory system exists in both Prokaryotes and eukaryotes, which is mainly composed with HPK and RR. By means of the signal input, phosphorylation, and output, it can regulate the adaptability of cells to the environment. As a major opportunistic pathogen, Pseudomonas aeruginosa is one of the main pathogens of nosocomial infection. Its drug-resistant strains increase year by year, the two-component system of which involved in the generation of drug resistance. Since the two-component system is essentially different from the system in human cells in signal transduc-tion, finding a new antibiotic target has great potential.

  19. Signaling mechanism by the Staphylococcus aureus two-component system LytSR: role of acetyl phosphate in bypassing the cell membrane electrical potential sensor LytS

    OpenAIRE

    Kevin Patel; Dasantila Golemi-Kotra

    2016-01-01

    The two-component system LytSR has been linked to the signal transduction of cell membrane electrical potential perturbation and is involved in the adaptation of Staphylococcus aureus to cationic antimicrobial peptides. It consists of a membrane-bound histidine kinase, LytS, which belongs to the family of multiple transmembrane-spanning domains receptors, and a response regulator, LytR, which belongs to the novel family of non-helix-turn-helix DNA-binding domain proteins. LytR regulates the e...

  20. The Role of the Two-Component System BaeSR in Disposing Chemicals through Regulating Transporter Systems in Acinetobacter baumannii.

    Directory of Open Access Journals (Sweden)

    Ming-Feng Lin

    Full Text Available Bacterial two-component regulatory systems (TCSs facilitate changes in gene expression in response to environmental stimuli. TCS BaeR regulons influence tigecycline susceptibility in Acinetobacter baumannii through positively regulating the pump genes adeA and adeB. In this study, we demonstrate that an additional two transport systems, AdeIJK and MacAB-TolC, are also regulated by BaeSR. In the wild type and clinical tigecycline-resistant A. baumannii strains, gene expression of AdeIJK and MacAB-TolC increased after tigecycline induction, implicating their importance to tigecycline resistance in addition to AdeABC. Phenotypic microarray results showed that A. baumannii is vulnerable to certain chemicals, especially tannic acid, after deleting baeR, which was confirmed using the spot assay. The wild-type strain of A. baumannii also exhibited 1.6-fold and 4.4-fold increase in gene expression of adeJ and macB in the medium with 100 μg/mL tannic acid, but the increase was fully inhibited by baeR deletion. An electrophoretic motility shift assay based on an interaction between His-BaeR and the adeA, adeI and macA promoter regions did not demonstrate direct binding. In conclusion, A. baumannii can use the TCS BaeSR in disposing chemicals, such as tannic acid and tigecycline, through regulating the efflux pumps.

  1. Searching for Potential Drug Targets in Two-component and Phosphorelay Signal-transduction Systems using Three-dimensional Cluster Analysis

    Institute of Scientific and Technical Information of China (English)

    Xiao-Hui CAI; Qing ZHANG; Shuo-Yong SHI; Da-Fu DING

    2005-01-01

    Two-component and phosphorelay signal transduction systems are central components in the virulence and antimicrobial resistance responses of a number of bacterial and fungal pathogens; in some cases, these systems are essential for bacterial growth and viability. Herein, we analyze in detail the conserved surface residue clusters in the phosphotransferase domain of histidine kinases and the regulatory domain of response regulators by using complex structure-based three-dimensional cluster analysis. We also investigatethe protein-protein interactions that these residue clusters participate in. The Spo0B-SpoOF complex structure was used as the reference structure, and the multiple aligned sequences of phosphotransferases and response regulators were paired correspondingly. The results show that a contiguous conserved residue cluster is formed around the active site, which crosses the interface of histidine kinases and response regulators. The conserved residue clusters of phosphotransferase and the regulatory domains are directly involved in the functional implementation of two-component signal transduction systems and are good targets for the development of novel antimicrobial agents.

  2. Systems level analysis of two-component signal transduction systems in Erwinia amylovora: Role in virulence, regulation of amylovoran biosynthesis and swarming motility

    Directory of Open Access Journals (Sweden)

    Sundin George W

    2009-05-01

    Full Text Available Abstract Background Two-component signal transduction systems (TCSTs, consisting of a histidine kinase (HK and a response regulator (RR, represent a major paradigm for signal transduction in prokaryotes. TCSTs play critical roles in sensing and responding to environmental conditions, and in bacterial pathogenesis. Most TCSTs in Erwinia amylovora have either not been identified or have not yet been studied. Results We used a systems approach to identify TCST and related signal transduction genes in the genome of E. amylovora. Comparative genomic analysis of TCSTs indicated that E. amylovora TCSTs were closely related to those of Erwinia tasmaniensis, a saprophytic enterobacterium isolated from apple flowers, and to other enterobacteria. Forty-six TCST genes in E. amylovora including 17 sensor kinases, three hybrid kinases, 20 DNA- or ligand-binding RRs, four RRs with enzymatic output domain (EAL-GGDEF proteins, and two kinases were characterized in this study. A systematic TCST gene-knockout experiment was conducted, generating a total of 59 single-, double-, and triple-mutants. Virulence assays revealed that five of these mutants were non-pathogenic on immature pear fruits. Results from phenotypic characterization and gene expression experiments indicated that several groups of TCST systems in E. amylovora control amylovoran biosynthesis, one of two major virulence factors in E. amylovora. Both negative and positive regulators of amylovoran biosynthesis were identified, indicating a complex network may control this important feature of pathogenesis. Positive (non-motile, EnvZ/OmpR, negative (hypermotile, GrrS/GrrA, and intermediate regulators for swarming motility in E. amylovora were also identified. Conclusion Our results demonstrated that TCSTs in E. amylovora played major roles in virulence on immature pear fruit and in regulating amylovoran biosynthesis and swarming motility. This suggested presence of regulatory networks governing

  3. A connecter-like factor, CacA, links RssB/RpoS and the CpxR/CpxA two-component system in Salmonella

    Directory of Open Access Journals (Sweden)

    Kato Akinori

    2012-10-01

    Full Text Available Abstract Background Bacteria integrate numerous environmental stimuli when generating cellular responses. Increasing numbers of examples describe how one two-component system (TCS responds to signals detected by the sensor of another TCS. However, the molecular mechanisms underlying this phenomenon remain poorly defined. Results Here, we report a connector-like factor that affects the activity of the CpxR/CpxA two-component system in Salmonella enterica serovar Typhimurium. We isolated a clone that induced the expression of a cpxP-lac gene fusion from a high-copy-number plasmid pool of random Salmonella genomic fragments. A 63-amino acid protein, CacA, was responsible for the CpxA/CpxR-dependent activation of the cpxP gene. The CpxR-activated genes cpxP and spy exhibited approximately 30% and 50% reductions in transcription, respectively, in a clean cacA deletion mutant strain in comparison to wild-type. From 33 response regulator (RR deletion mutants, we identified that the RssB regulator represses cacA transcription. Substitution mutations in a conserved -10 region harboring the RNA polymerase recognition sequence, which is well conserved with a known RpoS -10 region consensus sequence, rendered the cacA promoter RpoS-independent. The CacA-mediated induction of cpxP transcription was affected in a trxA deletion mutant, which encodes thioredoxin 1, suggesting a role for cysteine thiol-disulfide exchange(s in CacA-dependent Cpx activation. Conclusions We identified CacA as an activator of the CpxR/CpxA system in the plasmid clone. We propose that CacA may integrate the regulatory status of RssB/RpoS into the CpxR/CpxA system. Future investigations are necessary to thoroughly elucidate how CacA activates the CpxR/CpxA system.

  4. Contributions of Two-Component Regulatory Systems, Alternative σ Factors, and Negative Regulators to Listeria monocytogenes Cold Adaptation and Cold Growth

    Science.gov (United States)

    Chan, Yvonne C.; Hu, Yuewei; Chaturongakul, Soraya; Files, Kali D.; Bowen, Barbara M.; Boor, Kathryn J.; Wiedmann, Martin

    2011-01-01

    The ability of Listeria monocytogenes to grow at refrigeration temperatures is critical for transmission of this foodborne pathogen. We evaluated the contributions of different transcriptional regulators and two-component regulatory systems to L. monocytogenes cold adaptation and cold growth. L. monocytogenes parent strain 10403S and selected isogenic null mutants in genes encoding four alternative σ factors (sigB, sigH, sigC, and sigL), two regulators of σB (rsbT and rsbV), two negative regulators (ctsR and hrcA), and 15 two-component response regulators were grown in brain heart infusion broth at 4°C with (i) a high-concentration starting inoculum (108 CFU/ml), (ii) a low-concentration starting inoculum (102 CFU/ml), and (iii) a high-concentration starting inoculum of cold-adapted cells. With a starting inoculum of 108 CFU/ml, null mutants in genes encoding selected alternative σ factors (ΔsigH, ΔsigC, and ΔsigL), a negative regulator (ΔctsR), regulators of σB (ΔrsbT and ΔrsbV), and selected two-component response regulators (ΔlisR, Δlmo1172, and Δlmo1060) had significantly reduced growth (P < 0.05) compared with the parent strain after 12 days at 4°C. The growth defect for ΔsigL was limited and was not confirmed by optical density (OD600) measurement data. With a starting inoculum of 102 CFU/ml and after monitoring growth at 4°C over 84 days, only the ΔctsR strain had a consistent but limited growth defect; the other mutant strains had either no growth defects or limited growth defects apparent at only one or two of the nine sampling points evaluated during the 84-day growth period (ΔsigB, ΔsigC, and Δlmo1172). With a 108 CFU/ml starting inoculum of cold-adapted cells, none of the mutant strains that had a growth defect when inoculation was performed with cells pregrown at 37°C had reduced growth as compared with the parent strain after 12 days at 4°C, suggesting a specific defect in the ability of these mutant strains to adapt to 4

  5. The Two-Component System CprRS Senses Cationic Peptides and Triggers Adaptive Resistance in Pseudomonas aeruginosa Independently of ParRS

    DEFF Research Database (Denmark)

    Fernandez, Luca; Jenssen, Håvard; Bains, Manjeet;

    2012-01-01

    through ParRS. Here, we report the identification of a new two-component system, CprRS, which, upon exposure to a wide range of antimicrobial peptides, triggered the expression of the LPS modification operon. Thus, mutations in the cprRS operon blocked the induction of the arn operon in response to...... several antimicrobial peptides independently of ParRS but did not affect the response to low Mg2+. Distinct patterns of arn induction were identified. Thus, the responses to polymyxins were abrogated by either parR or cprR mutations, while responses to other peptides, including indolicidin, showed...... differential dependency on the CprRS and ParRS systems in a concentration-dependent manner. It was further demonstrated that, following exposure to inducing antimicrobial peptides, cprRS mutants did not become adaptively resistant to polymyxins as was observed for wild-type cells. Our microarray studies...

  6. The Eukaryotic-Like Ser/Thr Kinase PrkC Regulates the Essential WalRK Two-Component System in Bacillus subtilis.

    Science.gov (United States)

    Libby, Elizabeth A; Goss, Lindsie A; Dworkin, Jonathan

    2015-06-01

    Most bacteria contain both eukaryotic-like Ser/Thr kinases (eSTKs) and eukaryotic-like Ser/Thr phosphatases (eSTPs). Their role in bacterial physiology is not currently well understood in large part because the conditions where the eSTKs are active are generally not known. However, all sequenced Gram-positive bacteria have a highly conserved eSTK with extracellular PASTA repeats that bind cell wall derived muropeptides. Here, we report that in the Gram-positive bacterium Bacillus subtilis, the PASTA-containing eSTK PrkC and its cognate eSTP PrpC converge with the essential WalRK two-component system to regulate WalR regulon genes involved in cell wall metabolism. By continuously monitoring gene expression throughout growth, we consistently find a large PrkC-dependent effect on expression of several different WalR regulon genes in early stationary phase, including both those that are activated by WalR (yocH) as well as those that are repressed (iseA, pdaC). We demonstrate that PrkC phosphorylates WalR in vitro and in vivo on a single Thr residue located in the receiver domain. Although the phosphorylated region of the receiver domain is highly conserved among several B. subtilis response regulators, PrkC displays specificity for WalR in vitro. Consistently, strains expressing a nonphosphorylatable WalR point mutant strongly reduce both PrkC dependent activation and repression of yocH, iseA, and pdaC. This suggests a model where the eSTK PrkC regulates the essential WalRK two-component signaling system by direct phosphorylation of WalR Thr101, resulting in the regulation of WalR regulon genes involved in cell wall metabolism in stationary phase. As both the eSTK PrkC and the essential WalRK two-component system are highly conserved in Gram-positive bacteria, these results may be applicable to further understanding the role of eSTKs in Gram-positive physiology and cell wall metabolism. PMID:26102633

  7. The Eukaryotic-Like Ser/Thr Kinase PrkC Regulates the Essential WalRK Two-Component System in Bacillus subtilis.

    Directory of Open Access Journals (Sweden)

    Elizabeth A Libby

    2015-06-01

    Full Text Available Most bacteria contain both eukaryotic-like Ser/Thr kinases (eSTKs and eukaryotic-like Ser/Thr phosphatases (eSTPs. Their role in bacterial physiology is not currently well understood in large part because the conditions where the eSTKs are active are generally not known. However, all sequenced Gram-positive bacteria have a highly conserved eSTK with extracellular PASTA repeats that bind cell wall derived muropeptides. Here, we report that in the Gram-positive bacterium Bacillus subtilis, the PASTA-containing eSTK PrkC and its cognate eSTP PrpC converge with the essential WalRK two-component system to regulate WalR regulon genes involved in cell wall metabolism. By continuously monitoring gene expression throughout growth, we consistently find a large PrkC-dependent effect on expression of several different WalR regulon genes in early stationary phase, including both those that are activated by WalR (yocH as well as those that are repressed (iseA, pdaC. We demonstrate that PrkC phosphorylates WalR in vitro and in vivo on a single Thr residue located in the receiver domain. Although the phosphorylated region of the receiver domain is highly conserved among several B. subtilis response regulators, PrkC displays specificity for WalR in vitro. Consistently, strains expressing a nonphosphorylatable WalR point mutant strongly reduce both PrkC dependent activation and repression of yocH, iseA, and pdaC. This suggests a model where the eSTK PrkC regulates the essential WalRK two-component signaling system by direct phosphorylation of WalR Thr101, resulting in the regulation of WalR regulon genes involved in cell wall metabolism in stationary phase. As both the eSTK PrkC and the essential WalRK two-component system are highly conserved in Gram-positive bacteria, these results may be applicable to further understanding the role of eSTKs in Gram-positive physiology and cell wall metabolism.

  8. Quantum theory for the dynamic microstructure in correlated two-component systems far from equilibrium -- Application to x-ray scattering

    CERN Document Server

    Vorberger, J

    2016-01-01

    We present a quantum theory for the dynamic structure factors in non-equilibrium, correlated, two-component systems such as plasmas or warm dense matter. Using this general framework, we derive expressions for effective local field corrections to the random phase approximation. The polarization function, which is needed as the input for the calculation of the structure factors, is calculated in non-equilibrium based on a perturbation expansion in the interaction strength. To make our theory applicable for x-ray scattering, a generalized Chihara decomposition for the total electron structure factor in non-equilibrium is derived. Examples are given for the special case of equilibrium and for a model bump-on-hot-tail distribution, as often encountered during laser heating of materials.

  9. The LovK-LovR two-component system is a regulator of the general stress pathway in Caulobacter crescentus.

    Science.gov (United States)

    Foreman, Robert; Fiebig, Aretha; Crosson, Sean

    2012-06-01

    A conserved set of regulators control the general stress response in Caulobacter crescentus, including σ(T), its anti-σ factor NepR, the anti-anti-σ factor PhyR, and the transmembrane sensor kinase PhyK. We report that the soluble histidine kinase LovK and the single-domain response regulator LovR also function within the C. crescentus general stress pathway. Our genetic data support a model in which LovK-LovR functions upstream of σ(T) by controlling the phosphorylation state and thus anti-anti-σ activity of PhyR. Transcription of lovK and lovR is independently activated by stress through a mechanism that requires sigT and phyR. Conversely, lovK and lovR function together to repress transcription of the general stress regulon. Concordant with a functional role of the LovK-LovR two-component system as a negative regulator of the general stress pathway, lovK-lovR-null mutants exhibit increased cell survival after osmotic stress, while coordinate overexpression of lovK and lovR attenuates cell survival relative to that of the wild type. Notably, lovK can complement the transcriptional and cell survival defects of a phyK-null mutant when lovR is deleted. Moreover, in this same genetic background, σ(T)-dependent transcription is activated in response to osmotic stress. This result suggests that flavin-binding LOV (light, oxygen, or voltage) histidine kinases are competent to perceive cytoplasmic signals in addition to the environmental signal blue light. We conclude that the PhyK-PhyR and LovK-LovR two-component signaling systems coordinately regulate stress physiology in C. crescentus.

  10. Impact of the Staphylococcus epidermidis LytSR two-component regulatory system on murein hydrolase activity, pyruvate utilization and global transcriptional profile

    Directory of Open Access Journals (Sweden)

    Yu Fangyou

    2010-11-01

    Full Text Available Abstract Background Staphylococcus epidermidis has emerged as one of the most important nosocomial pathogens, mainly because of its ability to colonize implanted biomaterials by forming a biofilm. Extensive studies are focused on the molecular mechanisms involved in biofilm formation. The LytSR two-component regulatory system regulates autolysis and biofilm formation in Staphylococcus aureus. However, the role of LytSR played in S. epidermidis remained unknown. Results In the present study, we demonstrated that lytSR knock-out in S. epidermidis did not alter susceptibility to Triton X-100 induced autolysis. Quantitative murein hydrolase assay indicated that disruption of lytSR in S. epidermidis resulted in decreased activities of extracellular murein hydrolases, although zymogram showed no apparent differences in murein hydrolase patterns between S. epidermidis strain 1457 and its lytSR mutant. Compared to the wild-type counterpart, 1457ΔlytSR produced slightly more biofilm, with significantly decreased dead cells inside. Microarray analysis showed that lytSR mutation affected the transcription of 164 genes (123 genes were upregulated and 41 genes were downregulated. Specifically, genes encoding proteins responsible for protein synthesis, energy metabolism were downregulated, while genes involved in amino acid and nucleotide biosynthesis, amino acid transporters were upregulated. Impaired ability to utilize pyruvate and reduced activity of arginine deiminase was observed in 1457ΔlytSR, which is consistent with the microarray data. Conclusions The preliminary results suggest that in S. epidermidis LytSR two-component system regulates extracellular murein hydrolase activity, bacterial cell death and pyruvate utilization. Based on the microarray data, it appears that lytSR inactivation induces a stringent response. In addition, LytSR may indirectly enhance biofilm formation by altering the metabolic status of the bacteria.

  11. The Hybrid Histidine Kinase LadS Forms a Multicomponent Signal Transduction System with the GacS/GacA Two-Component System in Pseudomonas aeruginosa

    Science.gov (United States)

    Redelberger, David; Fadel, Firas; Filloux, Alain; Sivaneson, Melissa; de Bentzmann, Sophie; Bordi, Christophe

    2016-01-01

    In response to environmental changes, Pseudomonas aeruginosa is able to switch from a planktonic (free swimming) to a sessile (biofilm) lifestyle. The two-component system (TCS) GacS/GacA activates the production of two small non-coding RNAs, RsmY and RsmZ, but four histidine kinases (HKs), RetS, GacS, LadS and PA1611, are instrumental in this process. RetS hybrid HK blocks GacS unorthodox HK autophosphorylation through the formation of a heterodimer. PA1611 hybrid HK, which is structurally related to GacS, interacts with RetS in P. aeruginosa in a very similar manner to GacS. LadS hybrid HK phenotypically antagonizes the function of RetS by a mechanism that has never been investigated. The four sensors are found in most Pseudomonas species but their characteristics and mode of signaling may differ from one species to another. Here, we demonstrated in P. aeruginosa that LadS controls both rsmY and rsmZ gene expression and that this regulation occurs through the GacS/GacA TCS. We additionally evidenced that in contrast to RetS, LadS signals through GacS/GacA without forming heterodimers, either with GacS or with RetS. Instead, we demonstrated that LadS is involved in a genuine phosphorelay, which requires both transmitter and receiver LadS domains. LadS signaling ultimately requires the alternative histidine-phosphotransfer domain of GacS, which is here used as an Hpt relay by the hybrid kinase. LadS HK thus forms, with the GacS/GacA TCS, a multicomponent signal transduction system with an original phosphorelay cascade, i.e. H1LadS→D1LadS→H2GacS→D2GacA. This highlights an original strategy in which a unique output, i.e. the modulation of sRNA levels, is controlled by a complex multi-sensing network to fine-tune an adapted biofilm and virulence response. PMID:27176226

  12. Two-component Dirac equation

    OpenAIRE

    Luo, Da-Wei; Pyshkin, P. V.; Yu, Ting; Lin, Hai-Qing; You, J. Q.; Wu, Lian-Ao

    2016-01-01

    We provide an alternative approach to relativistic dynamics based on the Feshbach projection technique. Instead of directly studying the Dirac equation, we derive a two-component equation for the upper spinor. This approach allows one to investigate the underlying physics in a different perspective. For particles with small mass such as the neutrino, the leading order equation has a Hermitian effective Hamiltonian, implying there is no leakage between the upper and lower spinors. In the weak ...

  13. The Pseudomonas aeruginosa CreBC two-component system plays a major role in the response to β-lactams, fitness, biofilm growth, and global regulation.

    Science.gov (United States)

    Zamorano, Laura; Moyà, Bartolomé; Juan, Carlos; Mulet, Xavier; Blázquez, Jesús; Oliver, Antonio

    2014-09-01

    Pseudomonas aeruginosa is a ubiquitous versatile environmental microorganism with a remarkable ability to grow under diverse environmental conditions. Moreover, P. aeruginosa is responsible for life-threatening infections in immunocompromised and cystic fibrosis patients, as the extraordinary capacity of this pathogen to develop antimicrobial resistance dramatically limits our therapeutic arsenal. Its large genome carries an outstanding number of genes belonging to regulatory systems, including multiple two-component sensor-regulator systems that modulate the response to the different environmental stimuli. Here, we show that one of two systems, designated CreBC (carbon source responsive) and BlrAB (β-lactam resistance), might be of particular relevance. We first identified the stimuli triggering the activation of the CreBC system, which specifically responds to penicillin-binding protein 4 (PBP4) inhibition by certain β-lactam antibiotics. Second, through an analysis of a large comprehensive collection of mutants, we demonstrate an intricate interconnection between the CreBC system, the peptidoglycan recycling pathway, and the expression of the concerning chromosomal β-lactamase AmpC. Third, we show that the CreBC system, and particularly its effector inner membrane protein CreD, plays a major role in bacterial fitness and biofilm development, especially in the presence of subinhibitory concentrations of β-lactams. Finally, global transcriptomics reveals broad regulatory functions of CreBC in basic physiological aspects, particularly anaerobic respiration, in both the presence and absence of antibiotics. Therefore, the CreBC system is envisaged as a potentially interesting target for improving the efficacy of β-lactams against P. aeruginosa infections. PMID:24936599

  14. The Campylobacter jejuni RacRS two-component system activates the glutamate synthesis by directly upregulating γ-glutamyltranspeptidase (GGT

    Directory of Open Access Journals (Sweden)

    Anne-Xander evan der Stel

    2015-06-01

    Full Text Available The highly conserved enzyme γ-glutamyltranspeptidase (GGT plays an important role in metabolism of glutathione and glutamine. Yet, the regulation of ggt transcription in prokaryotes is poorly understood. In the human pathogen Campylobacter jejuni, GGT is important as it contributes to persistent colonization of the gut. Here we show that the GGT activity in C. jejuni is dependent on a functional RacRS (reduced ability to colonize two-component system. Electrophoretic mobility shift and luciferase reporter assays indicate that the response regulator RacR binds to a promoter region ~80 bp upstream of the ggt transcriptional start site, which contains a recently identified RacR DNA binding consensus sequence. RacR needs to be phosphorylated to activate the transcription of the ggt gene, which is the case under low oxygen conditions in presence of alternative electron acceptors. A functional GGT and RacR are needed to allow C. jejuni to grow optimally on glutamine as sole carbon source under RacR inducing conditions. However, when additional carbon sources are present C. jejuni is capable of utilizing glutamine independently of GGT. RacR is the first prokaryotic transcription factor known to directly upregulate both the cytoplasmic (glutamine-2-oxoglutarate aminotransferase (GOGAT as well as the periplasmic (GGT production of glutamate.

  15. Regulation of natural competence by the orphan two-component system sensor kinase ChiS involves a non-canonical transmembrane regulator in Vibrio cholerae.

    Science.gov (United States)

    Yamamoto, Shouji; Mitobe, Jiro; Ishikawa, Takahiko; Wai, Sun Nyunt; Ohnishi, Makoto; Watanabe, Haruo; Izumiya, Hidemasa

    2014-01-01

    In Vibrio cholerae, 41 chitin-inducible genes, including the genes involved in natural competence for DNA uptake, are governed by the orphan two-component system (TCS) sensor kinase ChiS. However, the mechanism by which ChiS controls the expression of these genes is currently unknown. Here, we report the involvement of a novel transcription factor termed 'TfoS' in this process. TfoS is a transmembrane protein that contains a large periplasmic domain and a cytoplasmic AraC-type DNA-binding domain, but lacks TCS signature domains. Inactivation of tfoS abolished natural competence as well as transcription of the tfoR gene encoding a chitin-induced small RNA essential for competence gene expression. A TfoS fragment containing the DNA-binding domain specifically bound to and activated transcription from the tfoR promoter. Intracellular TfoS levels were unaffected by disruption of chiS and coexpression of TfoS and ChiS in Escherichia coli recovered transcription of the chromosomally integrated tfoR::lacZ gene, suggesting that TfoS is post-translationally modulated by ChiS during transcriptional activation; however, this regulation persisted when the canonical phosphorelay residues of ChiS were mutated. The results presented here suggest that ChiS operates a chitin-induced non-canonical signal transduction cascade through TfoS, leading to transcriptional activation of tfoR. PMID:24236404

  16. Expression of the genes encoding the CasK/R two-component system and the DesA desaturase during Bacillus cereus cold adaptation.

    Science.gov (United States)

    Diomandé, Sara Esther; Doublet, Bénédicte; Vasaï, Florian; Guinebretière, Marie-Hélène; Broussolle, Véronique; Brillard, Julien

    2016-08-01

    Two-component systems (TCS) allow a cell to elaborate a variety of adaptive responses to environment changes. The recently discovered CasK/R TCS plays a role in the optimal unsaturation of fatty acids necessary for cold adaptation of the foodborne-pathogen Bacillus cereus Here, we showed that the promoter activity of the operon encoding this TCS was repressed during growth at low temperature in the stationary phase in the parental strain when compared to the casK/R mutant, suggesting that CasR negatively regulates the activity of its own promoter in these conditions. The promoter activity of the desA gene encoding the Δ5 fatty acid desaturase, providing unsaturated fatty acids (UFAs) required for low temperature adaptation, was repressed in the casK/R mutant grown at 12°C versus 37°C. This result suggests that CasK/R activates desA expression during B. cereus growth at low temperature, allowing an optimal unsaturation of the fatty acids. In contrast, desA expression was repressed during the lag phase at low temperature in presence of UFAs, in a CasK/R-independent manner. Our findings confirm that the involvement of this major TCS in B. cereus cold adaptation is linked to the upregulation of a fatty acid desaturase. PMID:27435329

  17. Novel photosensory two-component system (PixA-NixB-NixC) involved in the regulation of positive and negative phototaxis of cyanobacterium Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Narikawa, Rei; Suzuki, Fumiko; Yoshihara, Shizue; Higashi, Sho-ichi; Watanabe, Masakatsu; Ikeuchi, Masahiko

    2011-12-01

    Two wild-type substrains of a motile cyanobacterium Synechocystis sp. PCC 6803 show positive phototaxis toward a light source (PCC-P) and negative phototaxis away from light (PCC-N). In this study, we found that a novel two-component system of photoresponse is involved in the phototactic regulation. Inactivation of slr1212 (pixA), which encodes a photoreceptor histidine kinase, reverted the positive phototaxis of PCC-P to negative phototaxis, and inactivation of the downstream slr1213 (nixB) and slr1214 (nixC), which encode AraC-like transcription factor-type and PatA-type response regulators, respectively, reverted the negative phototaxis of PCC-N to positive phototaxis. Opposite effects of pixA and nixBC disruption implies an unexpected signal transduction pathway in the switching of positive and negative phototaxis. The blue/green-type cyanobacteriochrome GAF domain of PixA was expressed in Synechocystis and phycocyanobilin-producing Escherichia coli. The holoprotein covalently bound a chromophore phycoviolobilin and showed reversible photoconversion between the violet- (Pv, λ(peak) = 396 nm) and green-absorbing (Pg, λ(peak) = 533 nm) forms, although the protein from E. coli partially bound a precursor phycocyanobilin. These results were discussed with regard to an idea that PixA serves as a violet light receptor for switching of positive and negative phototaxis by transcriptional and functional regulation. PMID:22065076

  18. Biophysical and physiological characterization of ZraP from Escherichia coli, the periplasmic accessory protein of the atypical ZraSR two-component system.

    Science.gov (United States)

    Petit-Härtlein, Isabelle; Rome, Kevin; de Rosny, Eve; Molton, Florian; Duboc, Carole; Gueguen, Erwan; Rodrigue, Agnès; Covès, Jacques

    2015-12-01

    The ZraSR system belongs to the family of TCSs (two-component signal transduction systems). In Escherichia coli, it was proposed to participate in zinc balance and to protect cytoplasmic zinc overload by sequestering this metal ion into the periplasm. This system controls the expression of the accessory protein ZraP that would be a periplasmic zinc scavenger. ZraPSR is functionally homologous with CpxPAR that integrates signals of envelope perturbation, including misfolded periplasmic proteins. The auxiliary periplasmic regulator CpxP inhibits the Cpx pathway by interacting with CpxA. Upon envelope stress sensing, the inhibitory function of CpxP is relieved, resulting in CpxR activation. Similarly to CpxPAR, ZraPSR probably plays a role in envelope stress response as a zinc-dependent chaperone activity was demonstrated for ZraP in Salmonella. We have purified ZraP from E. coli and shown that it is an octamer containing four interfacial metal-binding sites contributing to dimer stability. These sites are located close to the N-terminus, whereas the C-terminus is involved in polymerization of the protein to form a tetramer of dimers. In vitro, ZraP binds copper with a higher affinity than zinc and displays chaperone properties partially dependent on zinc binding. In vivo, zinc-bound ZraP is a repressor of the expression of the zraPSR operon. However, we have demonstrated that none of the Zra proteins are involved in zinc or copper resistance. We propose an integrated mechanism in which zinc is a marker of envelope stress perturbation and ZraPSR TCS is a sentinel sensing and responding to zinc entry into the periplasm.

  19. Regulation of hrp genes and type III protein secretion in Erwinia amylovora by HrpX/HrpY, a novel two-component system, and HrpS.

    Science.gov (United States)

    Wei, Z; Kim, J F; Beer, S V

    2000-11-01

    Two novel regulatory components, hrpX and hrpY, of the hrp system of Erwinia amylovora were identified. The hrpXY operon is expressed in rich media, but its transcription is increased threefold by low pH, nutrient, and temperature levels--conditions that mimic the plant apoplast. hrpXY is autoregulated and directs the expression of hrpL; hrpL, in turn, activates transcription of other loci in the hrp gene cluster (Z.-M. Wei and S. V. Beer, J. Bacteriol. 177:6201-6210, 1995). The deduced amino -acid sequences of hrpX and hrpY are similar to bacterial two-component regulators including VsrA/VsrD of Pseudomonas (Ralstonia) solanacearum, DegS/DegU of Bacillus subtilis, and UhpB/UhpA and NarX/NarP, NarL of Escherichia coli. The N-terminal signal-input domain of HrpX contains PAS domain repeats. hrpS, located downstream of hrpXY, encodes a protein with homology to WtsA (HrpS) of Erwinia (Pantoea) stewartii, HrpR and HrpS of Pseudomonas syringae, and other delta54-dependent, enhancer-binding proteins. Transcription of hrpS also is induced under conditions that mimic the plant apoplast. However, hrpS is not autoregulated, and its expression is not affected by hrpXY. When hrpS or hrpL were provided on multicopy plasmids, both hrpX and hrpY mutants recovered the ability to elicit the hypersensitive reaction in tobacco. This confirms that hrpS and hrpL are not epistatic to hrpXY. A model of the regulatory cascades leading to the induction of the E. amylovora type III system is proposed. PMID:11059492

  20. The essential yhcSR two-component signal transduction system directly regulates the lac and opuCABCD operons of Staphylococcus aureus.

    Directory of Open Access Journals (Sweden)

    Meiying Yan

    Full Text Available Our previous studies suggested that the essential two-component signal transduction system, YhcSR, regulates the opuCABCD operon at the transcriptional level, and the Pspac-driven opuCABCD partially complements the lethal effects of yhcS antisense RNA expression in Staphylococcus aureus. However, the reason why yhcSR regulon is required for growth is still unclear. In this report, we present that the lac and opuC operons are directly transcriptionally regulated by YhcSR. Using real-time RT-PCR we showed that the down-regulation of yhcSR expression affected the transcription of lacA encoding galactose-6-phosphotase isomerase subunit LacA, and opuCA encoding a subunit of a glycine betaine/carnitine/choline ABC transporter. Promoter-lux reporter fusion studies further confirmed the transcriptional regulation of lac by YhcSR. Gel shift assays revealed that YhcR binds to the promoter regions of the lac and opuC operons. Moreover, the Pspac-driven lacABC expression in trans was able to partially complement the lethal effect of induced yhcS antisense RNA. Likewise, the Pspac-driven opuCABCD expression in trans complemented the growth defect of S. aureus in a high osmotic strength medium during the depletion of YhcSR. Taken together, the above data indicate that the yhcSR system directly regulates the expression of lac and opuC operons, which, in turn, may be partially associated with the essentiality of yhcSR in S. aureus. These results provide a new insight into the biological functions of the yhcSR, a global regulator.

  1. Two-component signal transduction system CBO0787/CBO0786 represses transcription from botulinum neurotoxin promoters in Clostridium botulinum ATCC 3502.

    Directory of Open Access Journals (Sweden)

    Zhen Zhang

    2013-03-01

    Full Text Available Blocking neurotransmission, botulinum neurotoxin is the most poisonous biological substance known to mankind. Despite its infamy as the scourge of the food industry, the neurotoxin is increasingly used as a pharmaceutical to treat an expanding range of muscle disorders. Whilst neurotoxin expression by the spore-forming bacterium Clostridium botulinum appears tightly regulated, to date only positive regulatory elements, such as the alternative sigma factor BotR, have been implicated in this control. The identification of negative regulators has proven to be elusive. Here, we show that the two-component signal transduction system CBO0787/CBO0786 negatively regulates botulinum neurotoxin expression. Single insertional inactivation of cbo0787 encoding a sensor histidine kinase, or of cbo0786 encoding a response regulator, resulted in significantly elevated neurotoxin gene expression levels and increased neurotoxin production. Recombinant CBO0786 regulator was shown to bind to the conserved -10 site of the core promoters of the ha and ntnh-botA operons, which encode the toxin structural and accessory proteins. Increasing concentration of CBO0786 inhibited BotR-directed transcription from the ha and ntnh-botA promoters, demonstrating direct transcriptional repression of the ha and ntnh-botA operons by CBO0786. Thus, we propose that CBO0786 represses neurotoxin gene expression by blocking BotR-directed transcription from the neurotoxin promoters. This is the first evidence of a negative regulator controlling botulinum neurotoxin production. Understanding the neurotoxin regulatory mechanisms is a major target of the food and pharmaceutical industries alike.

  2. The two-component signal transduction system ArlRS regulates Staphylococcus epidermidis biofilm formation in an ica-dependent manner.

    Directory of Open Access Journals (Sweden)

    Yang Wu

    Full Text Available Due to its ability to form biofilms on medical devices, Staphylococcus epidermidis has emerged as a major pathogen of nosocomial infections. In this study, we investigated the role of the two-component signal transduction system ArlRS in regulating S. epidermidis biofilm formation. An ArlRS-deficient mutant, WW06, was constructed using S. epidermidis strain 1457 as a parental strain. Although the growth curve of WW06 was similar to that of SE1457, the mutant strain was unable to form biofilms in vitro. In a rabbit subcutaneous infection model, sterile disks made of polymeric materials were implanted subcutaneously followed with inoculation of WW06 or SE1457. The viable bacteria cells of WW06 recovered from biofilms on the embedded disks were much lower than that of SE1457. Complementation of arlRS genes expression from plasmid in WW06 restored biofilm-forming phenotype both in vivo and in vitro. WW06 maintained the ability to undergo initial attachment. Transcription levels of several genes involved in biofilm formation, including icaADBC, sigB, and sarA, were decreased in WW06, compared to SE1457; and icaR expression was increased in WW06, detected by real-time reverse-transcription PCR. The biofilm-forming phenotype was restored by overexpressing icaADBC in WW06 but not by overexpressing sigB, indicating that ArlRS regulates biofilm formation through the regulation of icaADBC. Gel shift assay showed that ArlR can bind to the promoter region of the ica operon. In conclusion, ArlRS regulates S. epidermidis biofilm formation in an ica-dependent manner, distinct from its role in S. aureus.

  3. Three distinct two-component systems are involved in resistance to the class I bacteriocins, Nukacin ISK-1 and nisin A, in Staphylococcus aureus.

    Directory of Open Access Journals (Sweden)

    Miki Kawada-Matsuo

    Full Text Available Staphylococcus aureus uses two-component systems (TCSs to adapt to stressful environmental conditions. To colonize a host, S. aureus must resist bacteriocins produced by commensal bacteria. In a comprehensive analysis using individual TCS inactivation mutants, the inactivation of two TCSs, graRS and braRS, significantly increased the susceptibility to the class I bacteriocins, nukacin ISK-1 and nisin A, and inactivation of vraSR slightly increased the susceptibility to nukacin ISK-1. In addition, two ABC transporters (BraAB and VraDE regulated by BraRS and one transporter (VraFG regulated by GraRS were associated with resistance to nukacin ISK-1 and nisin A. We investigated the role of these three TCSs of S. aureus in co-culture with S. warneri, which produces nukacin ISK-1, and Lactococcus lactis, which produces nisin A. When co-cultured with S. warneri or L. lactis, the braRS mutant showed a significant decrease in its population compared with the wild-type, whereas the graRS and vraSR mutants showed slight decreases. Expression of vraDE was elevated significantly in S. aureus co-cultured with nisin A/nukacin ISK-1-producing strains. These results suggest that three distinct TCSs are involved in the resistance to nisin A and nukacin ISK-1. Additionally, braRS and its related transporters played a central role in S. aureus survival in co-culture with the strains producing nisin A and nukacin ISK-1.

  4. Signaling mechanism by the Staphylococcus aureus two-component system LytSR: role of acetyl phosphate in bypassing the cell membrane electrical potential sensor LytS.

    Science.gov (United States)

    Patel, Kevin; Golemi-Kotra, Dasantila

    2015-01-01

    The two-component system LytSR has been linked to the signal transduction of cell membrane electrical potential perturbation and is involved in the adaptation of Staphylococcus aureus to cationic antimicrobial peptides. It consists of a membrane-bound histidine kinase, LytS, which belongs to the family of multiple transmembrane-spanning domains receptors, and a response regulator, LytR, which belongs to the novel family of non-helix-turn-helix DNA-binding domain proteins. LytR regulates the expression of cidABC and lrgAB operons, the gene products of which are involved in programmed cell death and lysis. In vivo studies have demonstrated involvement of two overlapping regulatory networks in regulating the lrgAB operon, both depending on LytR. One regulatory network responds to glucose metabolism and the other responds to changes in the cell membrane potential. Herein, we show that LytS has autokinase activity and can catalyze a fast phosphotransfer reaction, with 50% of its phosphoryl group lost within 1 minute of incubation with LytR. LytS has also phosphatase activity. Notably, LytR undergoes phosphorylation by acetyl phosphate at a rate that is 2-fold faster than the phosphorylation by LytS. This observation is significant in lieu of the in vivo observations that regulation of the lrgAB operon is LytR-dependent in the presence of excess glucose in the medium. The latter condition does not lead to perturbation of the cell membrane potential but rather to the accumulation of acetate in the cell. Our study provides insights into the molecular basis for regulation of lrgAB in a LytR-dependent manner under conditions that do not involve sensing by LytS. PMID:27127614

  5. Peptidoglycan metabolism is controlled by the WalRK (YycFG) and PhoPR two-component systems in phosphate-limited Bacillus subtilis cells.

    Science.gov (United States)

    Bisicchia, Paola; Lioliou, Efthimia; Noone, David; Salzberg, Letal I; Botella, Eric; Hübner, Sebastian; Devine, Kevin M

    2010-02-01

    In Bacillus subtilis, the WalRK (YycFG) two-component system controls peptidoglycan metabolism in exponentially growing cells while PhoPR controls the response to phosphate limitation. Here we examine the roles of WalRK and PhoPR in peptidoglycan metabolism in phosphate-limited cells. We show that B. subtilis cells remain viable in a phosphate-limited state for an extended period and resume growth rapidly upon phosphate addition, even in the absence of a PhoPR-mediated response. Peptidoglycan synthesis occurs in phosphate-limited wild-type cells at approximately 27% the rate of exponentially growing cells, and at approximately 18% the rate of exponentially growing cells in the absence of PhoPR. In phosphate-limited cells, the WalRK regulon genes yocH, cwlO(yvcE), lytE and ydjM are expressed in a manner that is dependent on the WalR recognition sequence and deleting these genes individually reduces the rate of peptidoglycan synthesis. We show that ydjM expression can be activated by PhoP approximately P in vitro and that PhoP occupies its promoter in phosphate-limited cells. However, iseA(yoeB) expression cannot be repressed by PhoP approximately P in vitro, but can be repressed by non-phosphorylated WalR in vitro. Therefore, we conclude that peptidoglycan metabolism is controlled by both WalRK and PhoPR in phosphate-limited B. subtilis cells. PMID:20487291

  6. Role of the two component signal transduction system CpxAR in conferring cefepime and chloramphenicol resistance in Klebsiella pneumoniae NTUH-K2044.

    Directory of Open Access Journals (Sweden)

    Vijaya Bharathi Srinivasan

    Full Text Available BACKGROUND: Klebsiella pneumoniae is a gram-negative, non-motile, facultative anaerobe belonging to the Enterobacteriaceae family of the γ-Proteobacteria class in the phylum Proteobacteria. Multidrug resistant K. pneumoniae have caused major therapeutic problems worldwide due to emergence of extended-spectrum β-lactamase producing strains. Two-component systems serve as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions including antibiotic stress. PRINCIPAL FINDINGS: In the present study, we investigated the role of an uncharacterized cpxAR operon in bacterial physiology and antimicrobial resistance by generating isogenic mutant (ΔcpxAR deficient in the CpxA/CpxR component derived from the hyper mucoidal K1 strain K. pneumoniae NTUH-K2044. The behaviour of ΔcpxAR was determined under hostile conditions, reproducing stresses encountered in the gastrointestinal environment and deletion resulted in higher sensitivity to bile, osmotic and acid stresses. The ΔcpxAR was more susceptible to β-lactams and chloramphenicol than the wild-type strain, and complementation restored the altered phenotypes. The relative change in expression of acrB, acrD, eefB efflux genes were decreased in cpxAR mutant as evidenced by qRT-PCR. Comparison of outer membrane protein profiles indicated a conspicuous difference in the knock out background. Gel shift assays demonstrated direct binding of CpxR(KP to promoter region of ompC(KP in a concentration dependent manner. CONCLUSIONS AND SIGNIFICANCE: The Cpx envelope stress response system is known to be activated by alterations in pH, membrane composition and misfolded proteins, and this systematic investigation reveals its direct involvement in conferring antimicrobial resistance against clinically significant antibiotics for the very first time. Overall results displayed in this report reflect the pleiotropic role of the Cpx

  7. The impact of ColRS two-component system and TtgABC efflux pump on phenol tolerance of Pseudomonas putida becomes evident only in growing bacteria

    Directory of Open Access Journals (Sweden)

    Kivisaar Maia

    2010-04-01

    Full Text Available Abstract Background We have recently found that Pseudomonas putida deficient in ColRS two-component system is sensitive to phenol and displays a serious defect on solid glucose medium where subpopulation of bacteria lyses. The latter phenotype is significantly enhanced by the presence of phenol in growth medium. Here, we focused on identification of factors affecting phenol tolerance of the colR-deficient P. putida. Results By using transposon mutagenesis approach we identified a set of phenol-tolerant derivatives of colR-deficient strain. Surprisingly, half of independent phenol tolerant clones possessed miniTn5 insertion in the ttgABC operon. However, though inactivation of TtgABC efflux pump significantly enhanced phenol tolerance, it did not affect phenol-enhanced autolysis of the colR mutant on glucose medium indicating that phenol- and glucose-caused stresses experienced by the colR-deficient P. putida are not coupled. Inactivation of TtgABC pump significantly increased the phenol tolerance of the wild-type P. putida as well. Comparison of phenol tolerance of growing versus starving bacteria revealed that both ColRS and TtgABC systems affect phenol tolerance only under growth conditions and not under starvation. Flow cytometry analysis showed that phenol strongly inhibited cell division and to some extent also caused cell membrane permeabilization to propidium iodide. Single cell analysis of populations of the ttgC- and colRttgC-deficient strains revealed that their membrane permeabilization by phenol resembles that of the wild-type and the colR mutant, respectively. However, cell division of P. putida with inactivated TtgABC pump seemed to be less sensitive to phenol than that of the parental strain. At the same time, cell division appeared to be more inhibited in the colR-mutant strain than in the wild-type P. putida. Conclusions ColRS signal system and TtgABC efflux pump are involved in the phenol tolerance of P. putida. However, as

  8. The two-component system CpxR/A represses the expression of Salmonella virulence genes by affecting the stability of the transcriptional regulator HilD

    Science.gov (United States)

    De la Cruz, Miguel A.; Pérez-Morales, Deyanira; Palacios, Irene J.; Fernández-Mora, Marcos; Calva, Edmundo; Bustamante, Víctor H.

    2015-01-01

    Salmonella enterica can cause intestinal or systemic infections in humans and animals mainly by the presence of pathogenicity islands SPI-1 and SPI-2, containing 39 and 44 genes, respectively. The AraC-like regulator HilD positively controls the expression of the SPI-1 genes, as well as many other Salmonella virulence genes including those located in SPI-2. A previous report indicates that the two-component system CpxR/A regulates the SPI-1 genes: the absence of the sensor kinase CpxA, but not the absence of its cognate response regulator CpxR, reduces their expression. The presence and absence of cell envelope stress activates kinase and phosphatase activities of CpxA, respectively, which in turn controls the level of phosphorylated CpxR (CpxR-P). In this work, we further define the mechanism for the CpxR/A-mediated regulation of SPI-1 genes. The negative effect exerted by the absence of CpxA on the expression of SPI-1 genes was counteracted by the absence of CpxR or by the absence of the two enzymes, AckA and Pta, which render acetyl-phosphate that phosphorylates CpxR. Furthermore, overexpression of the lipoprotein NlpE, which activates CpxA kinase activity on CpxR, or overexpression of CpxR, repressed the expression of SPI-1 genes. Thus, our results provide several lines of evidence strongly supporting that the absence of CpxA leads to the phosphorylation of CpxR via the AckA/Pta enzymes, which represses both the SPI-1 and SPI-2 genes. Additionally, we show that in the absence of the Lon protease, which degrades HilD, the CpxR-P-mediated repression of the SPI-1 genes is mostly lost; moreover, we demonstrate that CpxR-P negatively affects the stability of HilD and thus decreases the expression of HilD-target genes, such as hilD itself and hilA, located in SPI-1. Our data further expand the insight on the different regulatory pathways for gene expression involving CpxR/A and on the complex regulatory network governing virulence in Salmonella. PMID:26300871

  9. The Two-Component System CpxRA Negatively Regulates the Locus of Enterocyte Effacement of Enterohemorrhagic Escherichia coli Involving σ32 and Lon protease

    Science.gov (United States)

    De la Cruz, Miguel A.; Morgan, Jason K.; Ares, Miguel A.; Yáñez-Santos, Jorge A.; Riordan, James T.; Girón, Jorge A.

    2016-01-01

    Enterohemorrhagic Escherichia coli (EHEC) is a significant cause of serious human gastrointestinal disease worldwide. EHEC strains contain a pathogenicity island called the locus of enterocyte effacement (LEE), which encodes virulence factors responsible for damaging the gut mucosa. The Cpx envelope stress response of E. coli is controlled by a two-component system (TCS) consisting of a sensor histidine kinase (CpxA) and a cytoplasmic response regulator (CpxR). In this study, we investigated the role of CpxRA in the expression of LEE-encoded virulence factors of EHEC. We found that a mutation in cpxA significantly affected adherence of EHEC to human epithelial cells. Analysis of this mutant revealed the presence of high levels of CpxR which repressed transcription of grlA and ler, the main positive virulence regulators of the LEE, and influenced negatively the production of the type 3 secretion system–associated EspABD translocator proteins. It is known that CpxR activates rpoH (Sigma factor 32), which in turns activates transcription of the lon protease gene. We found that transcription levels of ler and grlA were significantly increased in the lon and cpxA lon mutants suggesting that lon is involved in down-regulating LEE genes. In addition, the Galleria mellonella model of infection was used to analyze the effect of the loss of the cpx and lon genes in EHEC's ability to kill the larvae. We found that the cpxA mutant was significantly deficient at killing the larvae however, the cpxA lon mutant which overexpresses LEE genes in vitro, was unable to kill the larvae, suggesting that virulence in the G. mellonella model is T3SS independent and that CpxA modulates virulence through a yet unknown EHEC-specific factor. Our data provides new insights and broadens our scope into the complex regulatory network of the LEE in which the CpxA sensor kinase plays an important role in a cascade involving both global and virulence regulators. PMID:26904510

  10. 两部件串联维修系统解的定性分析%The Qualitative Analysis of a Solution of a Series Maintenance System with Two Components

    Institute of Scientific and Technical Information of China (English)

    郭卫华; 杨明增

    2003-01-01

    In this paper, firstly we study the series maintenance system with two components, obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operators theory. Then we prove that 0 is the eigenvalue of the system's host operators, and finally we study the eigenvector of the eigenvalue 0.

  11. Two component theory and electron magnetic moment

    NARCIS (Netherlands)

    Veltman, M.J.G.

    1998-01-01

    The two-component formulation of quantum electrodynamics is studied. The relation with the usual Dirac formulation is exhibited, and the Feynman rules for the two-component form of the theory are presented in terms of familiar objects. The transformation from the Dirac theory to the two-component th

  12. Vancomycin susceptibility in methicillin-resistant Staphylococcus aureus is mediated by YycHI activation of the WalRK essential two-component regulatory system.

    Science.gov (United States)

    Cameron, David R; Jiang, Jhih-Hang; Kostoulias, Xenia; Foxwell, Daniel J; Peleg, Anton Y

    2016-01-01

    The treatment of infections caused by methicillin-resistant Staphylococcus aureus is complicated by the emergence of strains with intermediate-level resistance to vancomycin (termed VISA). We have characterised a molecular pathway involved in the in vivo evolution of VISA mediated by the regulatory proteins YycH and YycI. In contrast to their function in other bacterial species, we report a positive role for these auxiliary proteins in regulation of the two-component regulator WalRK. Transcriptional profiling of yycH and yycI deletion mutants revealed downregulation of the 'WalRK regulon' including cell wall hydrolase genes atlA and sle1, with functional autolysis assays supporting these data by showing an impaired autolytic phenotype for each deletion strain. Using bacterial-two hybrid assays, we showed that YycH and YycI interact, and that YycHI also interacts with the sensor kinase WalK, forming a ternary protein complex. Mutation to YycH or YycI associated with clinical VISA strains had a deleterious impact on the YycHI/WalK complex, suggesting that the interaction is important for the regulation of WalRK. Taken together, we have described a novel antibiotic resistance strategy for the human pathogen S. aureus, whereby YycHI mutations are selected for in vivo leading to reduced WalRK activation, impaired cell wall turnover and ultimately reduced vancomycin efficacy. PMID:27600558

  13. Two Component Signal Transduction in Desulfovibrio Species

    Energy Technology Data Exchange (ETDEWEB)

    Luning, Eric; Rajeev, Lara; Ray, Jayashree; Mukhopadhyay, Aindrila

    2010-05-17

    The environmentally relevant Desulfovibrio species are sulfate-reducing bacteria that are of interest in the bioremediation of heavy metal contaminated water. Among these, the genome of D. vulgaris Hildenborough encodes a large number of two component systems consisting of 72 putative response regulators (RR) and 64 putative histidinekinases (HK), the majority of which are uncharacterized. We classified the D. vulgaris Hildenborough RRs based on their output domains and compared the distribution of RRs in other sequenced Desulfovibrio species. We have successfully purified most RRs and several HKs as His-tagged proteins. We performed phospho-transfer experiments to verify relationships between cognate pairs of HK and RR, and we have also mapped a few non-cognate HK-RR pairs. Presented here are our discoveries from the Desulfovibrio RR categorization and results from the in vitro studies using purified His tagged D. vulgaris HKs and RRs.

  14. Two-component Duality and Strings

    CERN Document Server

    Freund, Peter G O

    2007-01-01

    A phenomenologically successful two-component hadronic duality picture led to Veneziano's amplitude, the fundamental first step to string theory. This picture is briefly recalled and its two components are identified as the open strings (mesons and baryons) and closed strings (Pomeron).

  15. An aromatic hydroxylation reaction catalyzed by a two-component FMN-dependent Monooxygenase. The ActVA-ActVB system from Streptomyces coelicolor.

    OpenAIRE

    Valton, Julien; Fontecave, Marc; Douki, Thierry; Kendrew, Steven G; Nivière, Vincent

    2006-01-01

    International audience The ActVA-ActVB system from Streptomyces coelicolor isatwo-component flavin-dependent monooxygenase that belongs to an emerging class of enzymes involved in various oxidation reactions in microorganisms. The ActVB component is a NADH:flavin oxidoreductase that provides a reduced FMN to the second component, ActVA the proper monooxygenase. In this work, we demonstrate that the ActVA-ActVB system catalyzes the aromatic monohydroxylation of dihydrokalafungin by molecula...

  16. The Pseudomonas aeruginosa CreBC Two-Component System Plays a Major Role in the Response to β-Lactams, Fitness, Biofilm Growth, and Global Regulation

    OpenAIRE

    Zamorano, Laura; Moyà, Bartolomé; Juan, Carlos; Mulet, Xavier; Blázquez, Jesús; Oliver, Antonio

    2014-01-01

    Pseudomonas aeruginosa is a ubiquitous versatile environmental microorganism with a remarkable ability to grow under diverse environmental conditions. Moreover, P. aeruginosa is responsible for life-threatening infections in immunocompromised and cystic fibrosis patients, as the extraordinary capacity of this pathogen to develop antimicrobial resistance dramatically limits our therapeutic arsenal. Its large genome carries an outstanding number of genes belonging to regulatory systems, includi...

  17. The Clostridium difficile cpr Locus Is Regulated by a Noncontiguous Two-Component System in Response to Type A and B Lantibiotics

    OpenAIRE

    Suárez, Jose M.; Edwards, Adrianne N.; McBride, Shonna M

    2013-01-01

    The intestinal pathogen Clostridium difficile is known to grow only within the intestines of mammals, yet little is known about how the bacterium subsists in this environment. In the intestine, C. difficile must contend with innate defenses within the host, such as cationic antimicrobial peptides (CAMPs) produced by the host and the indigenous microbiota. In this study, we investigated the mechanism of activation and regulation of the CprABC transporter system, which provides resistance to mu...

  18. The BatR/BatS two-component regulatory system controls the adaptive response of Bartonella henselae during human endothelial cell infection

    OpenAIRE

    Quebatte, Maxime; Dehio, Michaela; Tropel, David; Basler, Andrea; Toller, Isabella; Raddatz, Guenter; Engel, Philipp; Huser, Sonja; Schein, Hermine; Lindroos, Hillevi L.; Andersson, Siv G. E.; Dehio, Christoph

    2010-01-01

    Here, we report the first comprehensive study of Bartonella henselae gene expression during infection of human endothelial cells. Expression of the main cluster of upregulated genes, comprising the VirB type IV secretion system and its secreted protein substrates, is shown to be under the positive control of the transcriptional regulator BatR. We demonstrate binding of BatR to the promoters of the virB operon and a substrate-encoding gene and provide biochemical evidence that BatR and BatS co...

  19. Preliminary Crystallographic Studies of the Regulatory Domain of Response Regulator YycF from an Essential Two-Component Signal Transduction System

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, H.; Heroux, A; Sequeira, R; Tang, L

    2009-01-01

    YycGF is a crucial signal transduction system for the regulation of cell-wall metabolism in low-G+C Gram-positive bacteria, which include many important human pathogens. The response regulator YycF receives signals from its cognate histidine kinase YycG through a phosphotransfer reaction and elicits responses through regulation of gene expression. The N-terminal regulatory domain of YycF from Bacillus subtilis was overproduced and purified. The protein was crystallized and X-ray data were collected to 1.95 A resolution with a completeness of 97.7% and an overall Rmerge of 7.7%. The crystals belonged to space group P3121, with unit-cell parameters a = b = 59.50, c = 79.06 A.

  20. Normal solution and transport coefficients to the Enskog-Landau kinetic equation for a two-component system of charged hard spheres The Chapman-Enskog method

    CERN Document Server

    Kobryn, A E; Tokarchuk, M V

    1999-01-01

    An Enskog-Landau kinetic equation for a many-component system of charged hard spheres is proposed. It has been obtained from the Liouville equation with modified boundary conditions by the method of nonequilibrium statistical operator. On the basis of this equation the normal solutions and transport coefficients such as bulk kappa and shear eta viscosities, thermal conductivity lambda, mutual diffusion D^{\\alpha\\beta} and thermal diffusion D_T^\\alpha have been obtained for a binary mixture in the first approximation using the Chapman-Enskog method. Numerical calculations of all transport coefficients for mixtures Ar-Kr, Ar-Xe, Kr-Xe with different concentrations of compounds have been evaluated for the cases of absence and presence of long-range Coulomb interactions. The results are compared with those obtained from other theories and experiment.

  1. Two-component abelian sandpile models

    OpenAIRE

    Alcaraz, F. C.; Pyatov, P.; Rittenberg, V.

    2008-01-01

    In one-component abelian sandpile models, the toppling probabilities are independent quantities. This is not the case in multi-component models. The condition of associativity of the underlying abelian algebras impose nonlinear relations among the toppling probabilities. These relations are derived for the case of two-component quadratic abelian algebras. We show that abelian sandpile models with two conservation laws have only trivial avalanches.

  2. Two-component Abelian sandpile models.

    Science.gov (United States)

    Alcaraz, F C; Pyatov, P; Rittenberg, V

    2009-04-01

    In one-component Abelian sandpile models, the toppling probabilities are independent quantities. This is not the case in multicomponent models. The condition of associativity of the underlying Abelian algebras imposes nonlinear relations among the toppling probabilities. These relations are derived for the case of two-component quadratic Abelian algebras. We show that Abelian sandpile models with two conservation laws have only trivial avalanches. PMID:19518280

  3. Two-component PhoB-PhoR regulatory system and ferric uptake regulator sense phosphate and iron to control virulence genes in type III and VI secretion systems of Edwardsiella tarda.

    Science.gov (United States)

    Chakraborty, Smarajit; Sivaraman, J; Leung, Ka Yin; Mok, Yu-Keung

    2011-11-11

    Inorganic phosphate (P(i)) and iron are essential nutrients that are depleted by vertebrates as a protective mechanism against bacterial infection. This depletion, however, is sensed by some pathogens as a signal to turn on the expression of virulence genes. Here, we show that the PhoB-PhoR two-component system senses changes in P(i) concentration, whereas the ferric uptake regulator (Fur) senses changes in iron concentration in Edwardsiella tarda PPD130/91 to regulate the expression of type III and VI secretion systems (T3SS and T6SS) through an E. tarda secretion regulator, EsrC. In sensing low P(i) concentration, PhoB-PhoR autoregulates and activates the phosphate-specific transport operon, pstSCAB-phoU, by binding directly to the Pho box in the promoters of phoB and pstS. PhoB also binds with EsrC simultaneously on the promoter of an E. tarda virulence protein, evpA, to regulate directly the transcription of genes from T6SS. In addition, PhoB requires and interacts with PhoU to activate esrC and suppress fur indirectly through unidentified regulators. Fur, on the other hand, senses high iron concentration and binds directly to the Fur box in the promoter of evpP to inhibit EsrC binding to the same region. In addition, Fur suppresses transcription of phoB, pstSCAB-phoU, and esrC indirectly via unidentified regulators, suggesting negative cross-talk with the Pho regulon. Physical interactions exist between Fur and PhoU and between Fur and EsrC. Our findings suggest that T3SS and T6SS may carry out distinct roles in the pathogenicity of E. tarda by responding to different environmental factors.

  4. Exposure of a 23F Serotype Strain of Streptococcus pneumoniae to Cigarette Smoke Condensate Is Associated with Selective Upregulation of Genes Encoding the Two-Component Regulatory System 11 (TCS11

    Directory of Open Access Journals (Sweden)

    Riana Cockeran

    2014-01-01

    Full Text Available Alterations in whole genome expression profiles following exposure of the pneumococcus (strain 172, serotype 23F to cigarette smoke condensate (160 μg/mL for 15 and 60 min have been determined using the TIGR4 DNA microarray chip. Exposure to CSC resulted in the significant (P<0.014–0.0006 upregulation of the genes encoding the two-component regulatory system 11 (TCS11, consisting of the sensor kinase, hk11, and its cognate response regulator, rr11, in the setting of increased biofilm formation. These effects of cigarette smoke on the pneumococcus may contribute to colonization of the airways by this microbial pathogen.

  5. Exposure of a 23F Serotype Strain of Streptococcus pneumoniae to Cigarette Smoke Condensate Is Associated with Selective Upregulation of Genes Encoding the Two-Component Regulatory System 11 (TCS11)

    Science.gov (United States)

    Herbert, Jenny A.; Mitchell, Timothy J.; Dix-Peek, Thérèse; Dickens, Caroline; Anderson, Ronald; Feldman, Charles

    2014-01-01

    Alterations in whole genome expression profiles following exposure of the pneumococcus (strain 172, serotype 23F) to cigarette smoke condensate (160 μg/mL) for 15 and 60 min have been determined using the TIGR4 DNA microarray chip. Exposure to CSC resulted in the significant (P < 0.014–0.0006) upregulation of the genes encoding the two-component regulatory system 11 (TCS11), consisting of the sensor kinase, hk11, and its cognate response regulator, rr11, in the setting of increased biofilm formation. These effects of cigarette smoke on the pneumococcus may contribute to colonization of the airways by this microbial pathogen. PMID:25013815

  6. Temporal and evolutionary dynamics of two-component signaling pathways.

    Science.gov (United States)

    Salazar, Michael E; Laub, Michael T

    2015-04-01

    Bacteria sense and respond to numerous environmental signals through two-component signaling pathways. Typically, a given stimulus will activate a sensor histidine kinase to autophosphorylate and then phosphotransfer to a cognate response regulator, which can mount an appropriate response. Although these signaling pathways often appear to be simple switches, they can also orchestrate surprisingly sophisticated and complex responses. These temporal dynamics arise from several key regulatory features, including the bifunctionality of histidine kinases as well as positive and negative feedback loops. Two-component signaling pathways are also dynamic on evolutionary time-scales, expanding dramatically in many species through gene duplication and divergence. Here, we review recent work probing the temporal and evolutionary dynamics of two-component signaling systems. PMID:25589045

  7. Development and characterization of two-component albedo based neutron individual monitoring system using thermoluminescent detectors; Desenvolvimento e caracterizacao de um sistema de monitoracao individual de neutrons tipo albedo de duas componentes usando detectores termoluminescentes

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcelo Marques

    2008-07-01

    A TLD-albedo based two-component neutron individual monitoring system was developed and characterized in this work. The monitor consists of a black plastic holder, an incident neutron boron loaded shield, a moderator polyethylene body (to increase its response), two pairs of TLD-600 and TLD-700 (one pair to each component) and an adjustable belt. This monitoring system was calibrated in thermal neutron fields and in 70 keV, 144 keV, 565 keV, 1.2 MeV and 5 MeV monoenergetic neutron fields. In addition, it was calibrated in {sup 252C}f(D{sub 2}O), {sup 252}Cf, {sup 241}Am-B, {sup 241}Am-Be and {sup 238}Pu-Be source fields. For the latter, the lower detection levels are, respectively, 0.009 mSv, 0.06 mSv, 0.12 mSv, 0.09 mSv and 0.08 mSv. The participation in an international intercomparison sponsored by IAEA with simulated workplace fields validated the system. The monitoring system was successfully characterized in the ISO 21909 standard and in an IRD - the Brazilian Institute for Radioprotection and Dosimetry - technical regulation draft. Nowadays, the neutron individual system is in use by IRD for whole body individual monitoring of five institutions, which comprehend several activities. (author)

  8. Two-component model of solar plages

    Institute of Scientific and Technical Information of China (English)

    LI; Jianping(李建平); DING; Mingde(丁明德); FANG; Cheng(方成)

    2002-01-01

    By use of the 2-m Mcmath-Pierce telescope at Kitt Peak, the high-quality spectra of a plage with moderate brightness near the center of solar disk were obtained. The data include seven spectral lines, which are Hα, Hβ, CaII H and K lines and the infrared triplet. With the consideration of fine structures of solar plages, a two-component atmospheric model is constructed by keeping the cool component to be the quiet atmosphere. Three cases of the hot component are given for different filling factors where the temperature and density distribution are adjusted in order to reproduce the seven observed spectral profiles. We also briefly discuss the influence of the column density at the base of the corona, m0, and the macro-turbulent velocity on the required filling factor and computed profiles. The two-component model is compared with precious one-component semi-empirical models. The limitation of the model is pointed out and further improvement is indicated.

  9. The Legionella pneumophila CpxRA two-component regulatory system: new insights into CpxR's function as a dual regulator and its connection to the effectors regulatory network.

    Science.gov (United States)

    Feldheim, Yaron S; Zusman, Tal; Speiser, Yariv; Segal, Gil

    2016-03-01

    Legionella pneumophila utilizes the Icm/Dot type-IV secretion system to translocate approximately 300 effector proteins into host cells, and the CpxRA two-component system (TCS) was previously shown to regulate the expression of several of these effectors. In this study, we expanded the pool of L. pneumophila CpxR-regulated genes to 38, including 27 effector-encoding genes. Our study demonstrates for the first time that the CpxR dual regulator has different requirements for activation and repression of target genes. These differences include the positioning of the CpxR regulatory element relative to the promoter element, and the effect of CpxR phosphate donors on the expression of CpxR target genes. In addition, unlike most response regulators, a mutant form of the L. pneumophila CpxR which cannot be phosphorylated was found to self-interact, and to repress gene expression similarly to wild-type CpxR, even though its ability to activate gene expression was reduced. Moreover, the CpxRA TCS was found to activate the expression of LetE which was found to function as a connector protein between the CpxRA TCS and the LetAS-RsmYZ-CsrA regulatory cascade. Our results show that CpxR plays a major role in L. pneumophila pathogenesis gene expression and functions as part of a regulatory network. PMID:26713766

  10. The HrpX/HrpY two-component system activates hrpS expression, the first step in the regulatory cascade controlling the Hrp regulon in Pantoea stewartii subsp. stewartii.

    Science.gov (United States)

    Merighi, Massimo; Majerczak, Doris R; Stover, Elizabeth H; Coplin, David L

    2003-03-01

    A regulatory cascade activating hrp/hrc type III secretion and effector genes was delineated in Pantoea stewartii subsp. stewartii, a bacterial pathogen of corn. Four hrp regulatory genes were characterized: hrpX and hrpY encode the sensor kinase and response regulator, respectively, of a two-component signal transduction system; hrpS encodes an NtrC-like transcriptional enhancer; and hrpL encodes an alternative sigma factor. Epistasis analysis, expression studies using gene fusions, and genetic reconstruction of each step in Escherichia coli were used to delineate the following pathway: HrpY activates hrpS and also positively autoregulates the hrpXY operon. In turn, HrpS is required for full activation of the sigma54-dependent hrpL promoter. Finally, HrpL controls expression of all known hrp and wts genes. In vitro, hrpS and all downstream hrp genes were regulated by pH and salt concentration. Mutants with in-frame deletions in hrpX were still partially virulent on corn but were unable to sense the chemical or metabolic signals that induce hrp genes in vitro. Site-directed mutagenesis of HrpY indicated that aspartate 57 is the probable phosphorylation site and that it is needed for activity. These findings suggest that both HrpX and an alternate mechanism are involved in the activation of HrpY in planta. PMID:12650455

  11. VicRK two-component signal transduction system of Streptococcus mutans%变异链球菌的VicRK双组分信号传导系统

    Institute of Scientific and Technical Information of China (English)

    田媛媛

    2012-01-01

    Streptococcus mutans(S.nuaans), which is considered as the chief pathogen of human caries, possesses the ability to form biofilm via sucrose-dependent adhesion, genesis and endure acids in the biofilm that may ultimately lead to dental caries. VicRK is one of the 13 putative two-component signal transduction systems of S.mutans that modulate the expression of cariogeneisis related virulence factors. This review summarized the mechanism, structural organization, physiological characteristics and the impact on the cariogenesis capabilities of VicRK, as well as the correlation between VicRK and VicX in S.mutans.%变异链球菌是人类龋病的主要病原菌,它通过蔗糖依赖性黏附形成生物膜并在其中产酸耐酸,最终导致龋病.VicRK是变异链球菌13种双组分信号传导系统之一,可调节变异链球菌致龋性毒力相关因子的表达.本文就VicRK的作用机制、结构组成、生理特性,及其对变异链球菌致龋性的影响,VicRK和VicX间的关系等研究进展作一综述.

  12. Two-component signal transduction system and the virulence-related characteristics of Streptococcus mutans%双组分信号传导系统与变异链球菌的致病相关特性

    Institute of Scientific and Technical Information of China (English)

    陈娇

    2011-01-01

    Two-component signal transduction system (TCSTS) plays an important role in the expression of virulence factors of Streptococcus mutans, such as the competence development, the formation of biofilm, the stability of structure, the production of bacteriocin, and the properties of acid production and resistance. It provides many ecological advantages to compete and survive in the dental plaque. This article is a review about the composition of TCSTS of Streptococcus mutans, the effect of TCSTS on the virulence-related characteristics of Streptococcus mutans, and the application significance of TCSTS.%双组分信号传导系统(TCSTS)在变异链球菌感受态形成、生物膜形成、结构稳定、菌素产生、产酸耐酸特性等毒力因子表达方面起着重要的作用,为其在菌斑生物膜中的竞争和生存提供了诸多生态性优势.本文就变异链球菌TCSTS的组成、TCSTS对变异链球菌致病相关特性的影响、TCSTS的应用意义等作一综述.

  13. The β-propeller gene Rv1057 of Mycobacterium tuberculosis has a complex promoter directly regulated by both the MprAB and TrcRS two-component systems

    Science.gov (United States)

    Pang, Xiuhua; Cao, Guangxiang; Neuenschwander, Pierre F.; Haydel, Shelley E.; Hou, Guihua; Howard, Susan T.

    2011-01-01

    SUMMARY The β-propeller gene Rv1057 of Mycobacterium tuberculosis is activated by envelope stress and was first characterized as a regulatory target of the TrcRS two-component system (TCS). Rv1057 expression is repressed by TrcRS, and the Rv1057 proximal promoter contains a TrcR binding site. In this study, we determined that Rv1057 is also directly regulated by MprAB, a TCS associated with envelope stress. Multiple potential MprA binding sites (MprA boxes) were identified in the 1 kb intergenic region upstream of Rv1057, and four sites were shown to bind MprA. Although MprA boxes were found in the proximal promoter, analyses suggest that MprA and TrcR do not compete for binding in this region. An MprAB-dependent, detergent-inducible transcriptional start point for Rv1057 was identified downstream of the MprA boxes, and a second TrcR binding site and small ORF of the 13E12 family were discovered in the distal promoter. MprAB was required for activation of Rv1057 during growth in macrophages and under detergent stress, and lacZ promoter constructs suggest the entire intergenic region is utilized during MprAB-dependent activation of Rv1057. These findings indicate that Rv1057 has an extensive and complex promoter, and provide evidence for coordinated regulation of stress response genes by TCSs. PMID:22099420

  14. Hemolysin EthA in Edwardsiella tarda is essential for fish invasion in vivo and in vitro and regulated by two-component system EsrA-EsrB and nucleoid protein HhaEt.

    Science.gov (United States)

    Wang, Xin; Wang, Qiyao; Xiao, Jingfan; Liu, Qin; Wu, Haizhen; Zhang, Yuanxing

    2010-12-01

    Edwardsiella tarda is a Gram-negative pathogen for hemorrhagic septicemia in fish. Recently, two-component system (TCS) EsrA-EsrB in E. tarda has been found to play key roles in regulating type III secretion system (TTSS) and type VI secretion system (T6SS). In this study, a markedly attenuated ΔesrB mutant was investigated to exhibit enhanced cell-invasion capability, as well as the increased cytotoxicity of its extracellular products (ECPs). Compared with the parental strain, the ΔesrB mutant unexpectedly displayed the significantly increased hemolytic activity, and the restoration of hemolysin production was observed in the complemented strain esrB(+). A hemolysis-associated 147 kDa protein, EthA, was found to be up-regulated in the ECPs of ΔesrB. The deletion of ethA gene in E. tarda wild type and ΔesrB strains drastically decreased their capacities in internalization of epithelial papilloma of carp (EPC) cells. These results indicated that the increased production of EthA was responsible for the enhanced cell-invasion related capabilities in ΔesrB. Furthermore, the expression of EthA in ΔesrB exhibited a temperature-induced manner, and a nucleoid protein Hha(Et) was identified to mediate ethA expression by directly binding to its promoter. These results demonstrated that the virulence determinant EthA was fully required for invasion abilities of E. tarda and was subjected to the control of a complicated and precisely regulated network primed for its invasion, colonization and infection process in fish. PMID:20832475

  15. Tobacco two-component gene NTHK2

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By using a previously isolated tobacco two- component gene NTHK1 as a probe, we screened a cDNA library and obtained a homologous gene designated NTHK2. Sequencing analysis revealed that NTHK2 encoded a putative ethylene receptor homolog and contained a histidine kinase domain and a receiver domain. In the histidine kinase domain, the histidine at the phosphorylation site was replaced by an asparagine. Southern analysis indicated that NTHK2 was present at low copies in tobacco genome. The expression of NTHK2 was studied using a competitive RT-PCR method. It was found that, in young flower buds, NTHK2 was expressed abundantly, while in other organs or tissues, it was expressed in a low level. When leaf was subjected to wounding (cutting) treatment, NTHK2 expression was increased. When tobacco seedlings were stressed with PEG and heat shock, NTHK2 transcription was also enhanced. Other treatments showed little effects. These results indicated that NTHK2 might be involved in the developmental processes and in plant responses to some environmental stresses.

  16. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit.

    Science.gov (United States)

    Vincent, Maxence S; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  17. The PorX response regulator of the Porphyromonas gingivalis PorXY two-component system does not directly regulate the Type IX secretion genes but binds the PorL subunit.

    Directory of Open Access Journals (Sweden)

    Maxence S Vincent

    2016-08-01

    Full Text Available The Type IX secretion system (T9SS is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion of surface attachment of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY and PorX encode typical two-component system (TCS sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of the porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we showed that PorX does not bind and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  18. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit

    Science.gov (United States)

    Vincent, Maxence S.; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  19. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit.

    Science.gov (United States)

    Vincent, Maxence S; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS. PMID:27630829

  20. Relaxation times hierarchy in two-component quasiparticle gas

    OpenAIRE

    Alexander V. Zhukov

    2001-01-01

    A quasiparticle description of various condensed media is a very popular tool in study of their transport and thermodynamic properties. I present here a microscopic theory for the description of diffusion processes in two-component gas of quasiparticles with arbitrary dispersion law and statistics. Particularly, I analyze the role of interaction within each subsystem (i.e. between identical quasiparticles) in relaxation of the whole system. The approach for solution of such kinetic problem al...

  1. Effects of the two-component system comprising GacA and GacS of Erwinia carotovora subsp. carotovora on the production of global regulatory rsmB RNA, extracellular enzymes, and harpinEcc.

    Science.gov (United States)

    Cui, Y; Chatterjee, A; Chatterjee, A K

    2001-04-01

    Posttranscriptional regulation mediated by the regulator of secondary metabolites (RSM) RsmA-rsmB pair is the most important factor in the expression of genes for extracellular enzymes and HarpinEcc in Erwinia carotovora subsp. carotovora. RsmA is a small RNA-binding protein, which acts by lowering the half-life of a mRNA species. rsmB specifies an untranslated regulatory RNA and neutralizes the RsmA effect. It has been speculated that GacA-GacS, members of a two-component system, may affect gene expression via RsmA. Because expA, a gacA homolog, and expS (or rpfA), a gacS homolog, have been identified in E. carotovora subsp. carotovora, we examined the effects of these gacA and gacS homologs on the expression of rsmA, rsmB, and an assortment of exoprotein genes. The gacA gene of E. carotovora subsp. carotovora strain 71 stimulated transcription of genes for several extracellular enzymes (pel-1, a pectate lyase gene; peh-1, a polygalacturonase gene; and celV, a cellulase gene), hrpNEcc (an E. carotovora subsp. carotovora gene specifying the elicitor of hypersensitive reaction), and rsmB in GacA+ and GacS+ E. carotovora subsp. carotovora strains. Similarly, the E. carotovora subsp. carotovora gacA gene stimulated csrB (rsmB) transcription in Escherichia coli. A GacS- mutant of E. carotovora subsp. carotovora strain AH2 and a GacA- mutant of E. carotovora subsp. carotovora strain Ecc71 compared with their parent strains produced very low levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts but produced similar levels of rsmA RNA and RsmA protein as well as transcripts of hyperproduction of extracellular enzymes (Hex) hexA, kdgR (repressor of genes for uronate and pectate catabolism), rsmC, and rpoS (gene for Sigma-S, an alternate Sigma factor). The levels of rsmB, pel-1, peh-1, celV, and hrpNEcc transcripts as well as production of pectate lyase, polygalacturonase, cellulase, protease, and HarpinEcc proteins were stimulated in GacS- and GacA- mutants by Gac

  2. Signaling mechanism by the Staphylococcus aureus two-component system LytSR: role of acetyl phosphate in bypassing the cell membrane electrical potential sensor LytS [version 2; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Kevin Patel

    2016-03-01

    Full Text Available The two-component system LytSR has been linked to the signal transduction of cell membrane electrical potential perturbation and is involved in the adaptation of Staphylococcus aureus to cationic antimicrobial peptides. It consists of a membrane-bound histidine kinase, LytS, which belongs to the family of multiple transmembrane-spanning domains receptors, and a response regulator, LytR, which belongs to the novel family of non-helix-turn-helix DNA-binding domain proteins. LytR regulates the expression of cidABC and lrgAB operons, the gene products of which are involved in programmed cell death and lysis. In vivo studies have demonstrated involvement of two overlapping regulatory networks in regulating the lrgAB operon, both depending on LytR. One regulatory network responds to glucose metabolism and the other responds to changes in the cell membrane potential. Herein, we show that LytS has autokinase activity and can catalyze a fast phosphotransfer reaction, with 50% of its phosphoryl group lost within 1 minute of incubation with LytR. LytS has also phosphatase activity. Notably, LytR undergoes phosphorylation by acetyl phosphate at a rate that is 2-fold faster than the phosphorylation by LytS. This observation is significant in lieu of the in vivo observations that regulation of the lrgAB operon is LytR-dependent in the presence of excess glucose in the medium. The latter condition does not lead to perturbation of the cell membrane potential but rather to the accumulation of acetate in the cell. Our study provides insights into the molecular basis for regulation of lrgAB in a LytR-dependent manner under conditions that do not involve sensing by LytS.

  3. Dispersionless Hirota Equations of Two-Component BKP Hierarchy

    Directory of Open Access Journals (Sweden)

    Kanehisa Takasaki

    2006-05-01

    Full Text Available The BKP hierarchy has a two-component analogue (the 2-BKP hierarchy. Dispersionless limit of this multi-component hierarchy is considered on the level of the τ-function. The so called dispersionless Hirota equations are obtained from the Hirota equations of the τ-function. These dispersionless Hirota equations turn out to be equivalent to a system of Hamilton-Jacobi equations. Other relevant equations, in particular, dispersionless Lax equations, can be derived from these fundamental equations. For comparison, another approach based on auxiliary linear equations is also presented.

  4. Molecular Mechanisms of Two-Component Signal Transduction.

    Science.gov (United States)

    Zschiedrich, Christopher P; Keidel, Victoria; Szurmant, Hendrik

    2016-09-25

    Two-component systems (TCS) comprising sensor histidine kinases and response regulator proteins are among the most important players in bacterial and archaeal signal transduction and also occur in reduced numbers in some eukaryotic organisms. Given their importance to cellular survival, virulence, and cellular development, these systems are among the most scrutinized bacterial proteins. In the recent years, a flurry of bioinformatics, genetic, biochemical, and structural studies have provided detailed insights into many molecular mechanisms that underlie the detection of signals and the generation of the appropriate response by TCS. Importantly, it has become clear that there is significant diversity in the mechanisms employed by individual systems. This review discusses the current knowledge on common themes and divergences from the paradigm of TCS signaling. An emphasis is on the information gained by a flurry of recent structural and bioinformatics studies.

  5. Topological Objects in Two-component Bose-Einstein Condensates

    OpenAIRE

    Cho, Y. M.; Khim, Hyojoong; Zhang, Pengming

    2005-01-01

    We study the topological objects in two-component Bose-Einstein condensates. We compare two competing theories of two-component Bose-Einstein condensate, the popular Gross-Pitaevskii theory and the recently proposed gauge theory of two-component Bose-Einstein condensate which has an induced vorticity interaction. We show that two theories produce very similar topological objects, in spite of the obvious differences in dynamics. Furthermore we show that the gauge theory of two-component Bose-E...

  6. Two-Component Wadati-Konno-Ichikawa Equation and Its Symmetry Reductions

    Institute of Scientific and Technical Information of China (English)

    QU Chang-Zheng; YAO Ruo-Xia; LI Zhi-Bin

    2004-01-01

    @@ It is shown that two-component Wadati-Konno-Ichikawa (WKI) equation, i.e. a generalization of the well-known WKI equation, is obtained from the motion of space curves in Euclidean geometry, and it is exactly a system for the graph of the curves when the curve motion is governed by the two-component modified Korteweg-de Vries flow. Group-invariant solutions of the two-component WKI equation which corresponds to an optimal system of its Lie point symmetry groups are obtained, and its similarity reductions to systems of ordinary differential equations are also given.

  7. Determinants of specificity in two-component signal transduction.

    Science.gov (United States)

    Podgornaia, Anna I; Laub, Michael T

    2013-04-01

    Maintaining the faithful flow of information through signal transduction pathways is critical to the survival and proliferation of organisms. This problem is particularly challenging as many signaling proteins are part of large, paralogous families that are highly similar at the sequence and structural levels, increasing the risk of unwanted cross-talk. To detect environmental signals and process information, bacteria rely heavily on two-component signaling systems comprised of sensor histidine kinases and their cognate response regulators. Although most species encode dozens of these signaling pathways, there is relatively little cross-talk, indicating that individual pathways are well insulated and highly specific. Here, we review the molecular mechanisms that enforce this specificity. Further, we highlight recent studies that have revealed how these mechanisms evolve to accommodate the introduction of new pathways by gene duplication. PMID:23352354

  8. Exact two-component relativistic energy band theory and application

    International Nuclear Information System (INIS)

    An exact two-component (X2C) relativistic density functional theory in terms of atom-centered basis functions is proposed for relativistic calculations of band structures and structural properties of periodic systems containing heavy elements. Due to finite radial extensions of the local basis functions, the periodic calculation is very much the same as a molecular calculation, except only for an Ewald summation for the Coulomb potential of fluctuating periodic monopoles. For comparison, the nonrelativistic and spin-free X2C counterparts are also implemented in parallel. As a first and pilot application, the band gaps, lattice constants, cohesive energies, and bulk moduli of AgX (X = Cl, Br, I) are calculated to compare with other theoretical results

  9. Exact two-component relativistic energy band theory and application

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Rundong; Zhang, Yong; Xiao, Yunlong; Liu, Wenjian, E-mail: liuwj@pku.edu.cn [Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, and Center for Computational Science and Engineering, Peking University, Beijing 100871 (China)

    2016-01-28

    An exact two-component (X2C) relativistic density functional theory in terms of atom-centered basis functions is proposed for relativistic calculations of band structures and structural properties of periodic systems containing heavy elements. Due to finite radial extensions of the local basis functions, the periodic calculation is very much the same as a molecular calculation, except only for an Ewald summation for the Coulomb potential of fluctuating periodic monopoles. For comparison, the nonrelativistic and spin-free X2C counterparts are also implemented in parallel. As a first and pilot application, the band gaps, lattice constants, cohesive energies, and bulk moduli of AgX (X = Cl, Br, I) are calculated to compare with other theoretical results.

  10. Budding Transition of Asymmetric Two-component Lipid Domains

    CERN Document Server

    Wolff, Jean; Andelman, David

    2016-01-01

    We propose a model that accounts for the budding transition of asymmetric two-component lipid domains, where the two monolayers (leaflets) have different average compositions controlled by independent chemical potentials. Assuming a coupling between the local curvature and local lipid composition in each of the leaflets, we discuss the morphology and thermodynamic behavior of asymmetric lipid domains. The membrane free-energy contains three contributions: the bending energy, the line tension, and a Landau free-energy for a lateral phase separation. Within a mean-field treatment, we obtain various phase diagrams containing fully budded, dimpled, and flat states as a function of the two leaflet compositions. The global phase behavior is analyzed, and depending on system parameters, the phase diagrams include one-phase, two-phase and three-phase regions. In particular, we predict various phase coexistence regions between different morphologies of domains, which may be observed in multi-component membranes or ves...

  11. Stability of Two-Component Bose-Einstein Condensates in Bessel Optical Lattices

    Institute of Scientific and Technical Information of China (English)

    FU Hong-Zhi; CHEN Hai-Jun; LI De-Hua; LI Hao-Cai; PENG Feng; XUE Ju-Kui; GAO Tao; CHENG Xin-Lu

    2008-01-01

    The stability of the ground state of two-component Bose-Einstein condensates (BECs) loaded into the central well of an axially symmetric Bessel lattices (BLs) potential with attractive or repulsive atoms interactions is studied using the time-dependent Gross-Pitaevskii equation (GPE). By using the variational method, we find that stable ground state of two-component BECs can exist in BLs. The BLs's depth and the intra-species atom interaction play an important role in the stability of ground state. The collapse of two-component BECs in BLs is also studied and a collapse condition for trapped two-component BECs is obtained. It is shown that the two-component BECs exhibit rich collapse dynamics. That is, the two-component BECs can collapse in the system with both intra- and inter-attractive, or with intra-attractive and inter-repulsive, or with intra-repulsive and inter-attractive atom interactions. Furthermore, the control of the collapse of the two-component BECs in BLs is discussed in detail The stability diagram of the ground state in parameter space is obtained. The results show that the collapse of two-component BECs can be controlled by temporal modulation of the atom interaction.

  12. Two-component micro injection moulding for hearing aid applications

    DEFF Research Database (Denmark)

    Islam, Aminul; Hansen, Hans Nørgaard; Marhöfer, David Maximilian;

    2012-01-01

    Two-component (2k) injection moulding is an important process technique at the present state of technology, and it is growing rapidly in the field of precision micro moulding. Besides combining different material properties in the same product, two-component moulding can eliminate many assembly s...

  13. Role of functionality in two-component signal transduction: A stochastic study

    Science.gov (United States)

    Maity, Alok Kumar; Bandyopadhyay, Arnab; Chaudhury, Pinaki; Banik, Suman K.

    2014-03-01

    We present a stochastic formalism for signal transduction processes in a bacterial two-component system. Using elementary mass action kinetics, the proposed model takes care of signal transduction in terms of a phosphotransfer mechanism between the cognate partners of a two-component system, viz., the sensor kinase and the response regulator. Based on the difference in functionality of the sensor kinase, the noisy phosphotransfer mechanism has been studied for monofunctional and bifunctional two-component systems using the formalism of the linear noise approximation. Steady-state analysis of both models quantifies different physically realizable quantities, e.g., the variance, the Fano factor (variance/mean), and mutual information. The resultant data reveal that both systems reliably transfer information of extracellular environment under low external stimulus and in a high-kinase-and-phosphatase regime. We extend our analysis further by studying the role of the two-component system in downstream gene regulation.

  14. Travelling wave solutions for some two-component shallow water models

    Science.gov (United States)

    Dutykh, Denys; Ionescu-Kruse, Delia

    2016-07-01

    In the present study we perform a unified analysis of travelling wave solutions to three different two-component systems which appear in shallow water theory. Namely, we analyze the celebrated Green-Naghdi equations, the integrable two-component Camassa-Holm equations and a new two-component system of Green-Naghdi type. In particular, we are interested in solitary and cnoidal-type solutions, as two most important classes of travelling waves that we encounter in applications. We provide a complete phase-plane analysis of all possible travelling wave solutions which may arise in these models. In particular, we show the existence of new type of solutions.

  15. Preparation and frictional investigation of the two-components silanes deposited on alumina surface

    International Nuclear Information System (INIS)

    Highlights: • The two-component silane films on the alumina surface were obtained by a combination of soft lithography and vapor phase deposition method. • The effectiveness of modification procedure was monitored by AFM topography images. • By using gas phase deposition method succeeded in obtaining a good reproduction of pattern. • Silane films with low surface free energy and coefficient of friction values were obtained. • The frictional performance in milli-Newton load range of one- and two-component films was investigated by microtribometry. - Abstract: Functionalization and pattering technique that permits two-component pattern-specific modification of alumina surface with silanes molecules are reported. The method relies on a two-component molecular system that simultaneously decreases coefficient of friction of the alumina surface and provides uniform chemical functionality suitable for further elaboration. Pattern/two-component modification is achieved via gas-phase deposition of the silanes using polydimethylsiloxane stamp. The frictional behaviors of the two-component films of the silane molecules with different chain length covalently absorbed on alumina surfaces, were characterized by the ball-disk (microtribometer) tester. The surfaces of the substrate modified by two-component molecular films were examined by atomic force microscopy (AFM). The measured tribological results showed that the mixing of the fluoroalkylsilane and alkylsilane enhance the lubrication and decrease the friction compared to the one-component thin films

  16. Local-field effect in atom optics of two-component Bose-Einstein condensates

    OpenAIRE

    K.V.Krutitsky; Marzlin, K. -P.; Audretsch, J.

    2000-01-01

    Starting from the first principles of nonrelativistic QED we have developed the quantum theory of the interaction of a two-component ultracold atomic ensemble with the electromagnetic field of vacuum and laser photons. The main attention has been paid to the consistent consideration of dynamical dipole-dipole interactions in the radiation field. Taking into account local-field effects we have derived the system of Maxwell-Bloch equations. Optical properties of the two-component Bose gas are i...

  17. Circulation Condition of Two-component Bose-Einstein Condensate

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In the report we point out that there exists an intrinsic difference in the internal symmetry of the two components spin-1/2 Bose condensates from that of spinor Bose condensates of the atoms with hyperfine states of nonzero integer-spins,which gives rise to a new topological constrain on the circulation for this two-component spin-1/2 Bose condensates.It is shown that the SU(2) symmetry of the spin-1/2 Bose condensate implies a

  18. Phase separation and dynamics of two-component Bose-Einstein condensates

    DEFF Research Database (Denmark)

    Lee, Kean Loon; Jørgensen, Nils Byg; Liu, I-Kang;

    2016-01-01

    The miscibility of two interacting quantum systems is an important testing ground for the understanding of complex quantum systems. Two-component Bose-Einstein condensates enable the investigation of this scenario in a particularly well controlled setting. In a homogeneous system, the transition ...

  19. Two component permeation through thin zeolite MFI membranes

    NARCIS (Netherlands)

    Keizer, K.; Burggraaf, A.J.; Vroon, Z.A.E.P.; Verweij, H.

    1998-01-01

    Two component permeation measurements have been performed by the Wicke-Kallenbach method on a thin (3 μm) zeolite MFI (Silicalite-1) membrane with molecules of different kinetic diameters, d(k). The membrane was supported by a flat porous α-Al2O3 substrate. The results obtained could be classified i

  20. Entanglement Properties in Two-Component Bose-Einstein Condensate

    Science.gov (United States)

    Jiang, Di-You

    2016-05-01

    We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.

  1. Entanglement Properties in Two-Component Bose-Einstein Condensate

    Science.gov (United States)

    Jiang, Di-You

    2016-10-01

    We investigate entanglement inseparability and bipartite entanglement of in two-component Bose-Einstein condensate in the presence of the nonlinear interatomic interaction, interspecies interaction. Entanglement inseparability and bipartite entanglement have the similar properties. More entanglement can be generated by adjusting the nonlinear interatomic interaction and control the time interval of the entanglement by adjusting interspecies interaction.

  2. Two component injection moulding: Present and future perspectives

    DEFF Research Database (Denmark)

    Islam, Aminul; Hansen, Hans Nørgaard

    2009-01-01

    Two component injection moulding has widespread industrial applications. Still the technology is yet to gain its full potential in highly demanding and technically challenging applications areas. The smart use of this technology can open the doors for cost effective and convergent manufacturing...

  3. Two component micro injection moulding for moulded interconnect devices

    DEFF Research Database (Denmark)

    Islam, Aminul

    2008-01-01

    moulding and laser direct structuring process), present a comparative analysis of the two processes and find the factors which are important for successful selective metallization. The demonstrator MID fabricated at the final stage of the project proves that the multidisciplinary knowledge gained from...... untraditional material pairs have been proven successful in the experiments. The experimental results find the factors which can effectively control the adhesion and interface quality between two polymers. Investigations on the selective metallization process, by two different methods (two component injection...... the project about materials, tooling and process optimization can be linked for successful fabrication of the MIDs in precision applications. In conclusion, it can be stated that the main results of the Ph.D. project is the documented knowledge presented in the current thesis about two component injection...

  4. Temporal and Evolutionary Dynamics of Two-Component Signaling Pathways

    OpenAIRE

    Salazar, Michael E.; Laub, Michael T.

    2015-01-01

    Bacteria sense and respond to numerous environmental signals through two-component signaling pathways. Typically, a given stimulus will activate a sensor histidine kinase to autophosphorylate and then phosphotransfer to a cognate response regulator, which can mount an appropriate response. Although these signaling pathways often appear to be simple switches, they can also orchestrate surprisingly sophisticated and complex responses. These temporal dynamics arise from several key regulatory fe...

  5. Numerical investigation of the evaporation of two-component droplets

    OpenAIRE

    Strotos, G.; Gavaises, M.; Theodorakakos, A.; Bergeles, G.

    2011-01-01

    A numerical model for the complete thermo-fluid-dynamic and phase-change transport processes of two-component hydrocarbon liquid droplets consisting of n-heptane, n-decane and mixture of the two in various compositions is presented and validated against experimental data. The Navier–Stokes equations are solved numerically together with the VOF methodology for tracking the droplet interface, using an adaptive local grid refinement technique. The energy and concentration equations inside the li...

  6. Parallel TREE code for two-component ultracold plasma analysis

    OpenAIRE

    Jeon, Byoungseon; Kress, Joel D.; Collins, Lee A.; Grønbech-Jensen, Niels

    2007-01-01

    The TREE method has been widely used for long-range interaction {\\it N}-body problems. We have developed a parallel TREE code for two-component classical plasmas with open boundary conditions and highly non-uniform charge distributions. The program efficiently handles millions of particles evolved over long relaxation times requiring millions of time steps. Appropriate domain decomposition and dynamic data management were employed, and large-scale parallel processing was achieved using an int...

  7. Itinerant Ferromagnetism in a Polarized Two-Component Fermi Gas

    DEFF Research Database (Denmark)

    Massignan, Pietro; Yu, Zhenhua; Bruun, Georg

    2013-01-01

    We analyze when a repulsively interacting two-component Fermi gas becomes thermodynamically unstable against phase separation. We focus on the strongly polarized limit, where the free energy of the homogeneous mixture can be calculated accurately in terms of well-defined quasiparticles, the repul...... of the minority atoms, raising the prospects of detecting the transition to the elusive itinerant ferromagnetic state with ultracold atoms....

  8. Dynamics of Two-Component Bose-Einstein Condensates

    Science.gov (United States)

    Baik, Eunsil

    I explored the vortex dynamics in homonuclear species two-component Bose-Einstein condensates (BECs) based on the knowledge of vortex dynamics in one-component BECs. The vortex dynamics in BECs depends on the background fields induced by different external potentials and other vortices. The motion of vortices is numerically computed and the numerical results are compared to the theoretical formulas where possible. In the study of the vortex-vortex interaction dynamics in one-component BECs, a power law relationship between the motion of the vortices and their separation distance is depicted. In addition to that, the relationship between the linear and the angular velocities of the vortices is found to be similar to the relationship between the tangential and the angular velocities of classical fluid vortices. In the case of two-component BEC dynamics, two different cases are studied: one without atomic inter-conversion between the two components and the other with atomic inter-conversion. The stability analysis of the two-component BECs is conducted to identify the stable regions as well as the regions of mixed and separated states. When a vortex is seeded in one component, this vortex induces a hump in the other component at the same location as the vortex, which leads to the vortex-hump dynamics. The vortex-hump-vortex-hump interaction dynamics without atomic inter-conversion depicts a power law relation between the motion of vortex-humps and the separation distance; whereas, the vortex-hump-vortex-hump interaction dynamics with atomic inter-conversion reveals a more complex relation between the motion of vortex-humps and the separation distance.

  9. A two-component rain model for the prediction of attenuation statistics

    Science.gov (United States)

    Crane, R. K.

    1982-01-01

    A two-component rain model has been developed for calculating attenuation statistics. In contrast to most other attenuation prediction models, the two-component model calculates the occurrence probability for volume cells or debris attenuation events. The model performed significantly better than the International Radio Consultative Committee model when used for predictions on earth-satellite paths. It is expected that the model will have applications in modeling the joint statistics required for space diversity system design, the statistics of interference due to rain scatter at attenuating frequencies, and the duration statistics for attenuation events.

  10. Domain Walls and Textured Vortices in a Two-Component Ginzburg-Landau Model

    DEFF Research Database (Denmark)

    Madsen, Søren Peder; Gaididei, Yu. B.; Christiansen, Peter Leth;

    2005-01-01

    We look for domain wall and textured vortex solutions in a two-component Ginzburg-Landau model inspired by two-band superconductivity. The two-dimensional two-component model, with equal coherence lengths and no magnetic field, shows some interesting properties. In the absence of a Josephson type...... coupling between the two order parameters a ''textured vortex'' is found by analytical and numerical solution of the Ginzburg-Landau equations. With a Josephson type coupling between the two order parameters we find the system to split up in two domains separated by a domain wall, where the order parameter...... is depressed to zero....

  11. Block algebra in two-component BKP and D type Drinfeld-Sokolov hierarchies

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chuanzhong, E-mail: lichuanzhong@nbu.edu.cn; He, Jingsong, E-mail: hejingsong@nbu.edu.cn [Department of Mathematics, Ningbo University, Ningbo 315211 (China)

    2013-11-15

    We construct generalized additional symmetries of a two-component BKP hierarchy defined by two pseudo-differential Lax operators. These additional symmetry flows form a Block type algebra with some modified (or additional) terms because of a B type reduction condition of this integrable hierarchy. Further we show that the D type Drinfeld-Sokolov hierarchy, which is a reduction of the two-component BKP hierarchy, possess a complete Block type additional symmetry algebra. That D type Drinfeld-Sokolov hierarchy has a similar algebraic structure as the bigraded Toda hierarchy which is a differential-discrete integrable system.

  12. Genomic Analysis of Two-Component Signal Transduction Proteins in Basidiomycetes

    DEFF Research Database (Denmark)

    Ussery, David; Lavín, JL; Binnewies, Tim Terence;

    2010-01-01

    Two-component system (TCS) proteins are components of complex signal transduction pathways in fungi, and play essential roles in the regulation of several cellular functions and responses. Species of basidiomycetes have a marked variation in their specific physiological traits, morphological...

  13. Instabilities on crystal surfaces: The two-component body-centered solid-on-solid model

    NARCIS (Netherlands)

    Carlon, E.; van Beijeren, H.; Mazzeo, G.

    1996-01-01

    The free energy of crystal surfaces that can be described by the two-component body-centered solid-on-solid model has been calculated in a mean-field approximation. The system may model ionic crystals with a bcc lattice structure (for instance CsCl). Crossings between steps are energetically favored

  14. Light Responsive Two-Component Supramolecular Hydrogel: A Sensitive Platform for Humidity Sensors

    KAUST Repository

    Samai, Suman

    2016-02-15

    The supramolecular assembly of anionic azobenzene dicarboxylate and cationic cetyltrimethylammonium bromide (CTAB) formed a stimuli responsive hydrogel with a critical gelation concentration (CGC) of 0.33 wt%. This self-sustainable two-component system was able to repair damage upon light irradiation. Moreover, it was successfully employed in the fabrication of highly sensitive humidity sensors for the first time.

  15. Two component micro injection molding for MID fabrication

    DEFF Research Database (Denmark)

    Islam, Mohammad Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben

    2009-01-01

    Molded Interconnect Devices (MIDs) are plastic substrates with electrical infrastructure. The fabrication of MIDs is usually based on injection molding and different process chains may be identified from this starting point. The use of MIDs has been driven primarily by the automotive sector......, but recently the medical sector seems more and more interested. In particular the possibility of miniaturization of 3D components with electrical infrastructure is attractive. The paper describes possible manufacturing routes and challenges of miniaturized MIDs based on two component micro injection molding...

  16. Measurement of two-component flow using ultrasonic flowmeters

    Science.gov (United States)

    Whitehouse, J. C.; Eghbali, D. A.; Flitton, V. E.; Anderson, D. G.

    Calibration of transit-time and Doppler ultrasonic flowmeters under two-component flow conditions has been conducted on 400 mm (16-in.) pipe. Testing covered total flows of 0.19 to 1.89 m(exp 3)/s (3000 to 30,000 gpm) and void fractions up to 40 percent. Both flowmeter types accurately measured total volumetric flow over a portion of their ranges. Pipe average void fraction, based on a three-beam gamma densitometer, was used to determine water component flow under stratified flow conditions, with similar results.

  17. Bond strength of two component injection moulded MID

    DEFF Research Database (Denmark)

    Islam, Mohammad Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben;

    2006-01-01

    Most products of the future will require industrially adapted, cost effective production processes and on this issue two-component (2K) injection moulding is a potential candidate for MID manufacturing. MID based on 2k injection moulded plastic part with selectively metallised circuit tracks allows...... the integration of electrical and mechanical functionalities in a real 3D structure. If 2k injection moulding is applied with two polymers, of which one is plateable and the other is not, it will be possible to make 3D electrical structures directly on the component. To be applicable in the real engineering field...... the two different plastic materials in the MID structure require good bonding between them. This paper finds suitable combinations of materials for MIDs from both bond strength and metallisation view-point. Plastic parts were made by two-shot injection moulding and the effects of some important process...

  18. Dynamics of two-component membranes surrounded by viscoelastic media

    International Nuclear Information System (INIS)

    We discuss the dynamics of two-component fluid membranes which are surrounded by viscoelastic media. We assume that membrane-embedded proteins can diffuse laterally and induce a local membrane curvature. The mean squared displacement of a tagged membrane segment is obtained as a generalized Einstein relation. When the elasticity of the surrounding media obeys a power-law behavior in frequency, an anomalous diffusion of the membrane segment is predicted. We also consider the situation where the proteins generate active non-equilibrium forces. The generalized Einstein relation is further modified by an effective temperature that depends on the force dipole energy. The obtained generalized Einstein relations are useful for membrane microrheology experiments. (fast track communication)

  19. Chemical evolution of two-component galaxies. II

    International Nuclear Information System (INIS)

    In order to confirm and refine the results obtained in a previous paper the chemical evolution of two-component (spheroid + disk) galaxies is derived rejecting the instantaneous recycling approximation, by means of numerical computations, accounting for (i) the collapse phase of the gas, assumed to be uniform in density and composition, and (ii) a birth-rate stellar function. Computations are performed relatively to the solar neighbourhood and to model galaxies which closely resemble the real morphological sequence: in both cases, numerical results are compared with analytical ones. The numerical models of this paper constitute a first-order approximation, while higher order approximations could be made by rejecting the hypothesis of uniform density and composition, and making use of detailed dynamical models. (Auth.)

  20. Bounds to the conductivity of some two-component composites

    Science.gov (United States)

    Helsing, Johan

    1993-02-01

    Calculation of third-order bounds to the conductivity of isotropic two-component composites is discussed. Coincidence of the Beran bounds and bounds derived using trial fields based on the solution of a single-body electrostatic boundary-value problem is demonstrated for a random distribution of impenetrable ellipsoids. This extends a proof of Beasley and Torquato [J. Appl. Phys. 60, 3576 (1986)]. A structural parameter related to third-order bounds is calculated for a face-centered cubic array of cubes in a matrix. For an array of rectangular blocks an upper bound in one direction is derived. This bound, and its two-dimensional analogs, become very sharp in the limit of strong inhomogeneity. Improved third- and fourth-order bounds for the three-dimensional checkerboard are presented.

  1. How insects overcome two-component plant chemical defence

    DEFF Research Database (Denmark)

    Pentzold, Stefan; Zagrobelny, Mika; Rook, Frederik;

    2014-01-01

    Insect herbivory is often restricted by glucosylated plant chemical defence compounds that are activated by plant β-glucosidases to release toxic aglucones upon plant tissue damage. Such two-component plant defences are widespread in the plant kingdom and examples of these classes of compounds...... are alkaloid, benzoxazinoid, cyanogenic and iridoid glucosides as well as glucosinolates and salicinoids. Conversely, many insects have evolved a diversity of counteradaptations to overcome this type of constitutive chemical defence. Here we discuss that such counter-adaptations occur at different time points......, before and during feeding as well as during digestion, and at several levels such as the insects’ feeding behaviour, physiology and metabolism. Insect adaptations frequently circumvent or counteract the activity of the plant β-glucosidases, bioactivating enzymes that are a key element in the plant’s two...

  2. Dynamics of two-component membranes surrounded by viscoelastic media.

    Science.gov (United States)

    Komura, Shigeyuki; Yasuda, Kento; Okamoto, Ryuichi

    2015-11-01

    We discuss the dynamics of two-component fluid membranes which are surrounded by viscoelastic media. We assume that membrane-embedded proteins can diffuse laterally and induce a local membrane curvature. The mean squared displacement of a tagged membrane segment is obtained as a generalized Einstein relation. When the elasticity of the surrounding media obeys a power-law behavior in frequency, an anomalous diffusion of the membrane segment is predicted. We also consider the situation where the proteins generate active non-equilibrium forces. The generalized Einstein relation is further modified by an effective temperature that depends on the force dipole energy. The obtained generalized Einstein relations are useful for membrane microrheology experiments.

  3. No electrostatic supersolitons in two-component plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Verheest, Frank, E-mail: frank.verheest@ugent.be [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, B–9000 Gent (Belgium); School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa); Lakhina, Gurbax S., E-mail: lakhina@iigm.iigs.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India); Hellberg, Manfred A., E-mail: hellberg@ukzn.ac.za [School of Chemistry and Physics, University of KwaZulu-Natal, Durban 4000 (South Africa)

    2014-06-15

    The concept of acoustic supersolitons was introduced for a very specific plasma with five constituents, and discussed only for a single set of plasma parameters. Supersolitons are characterized by having subsidiary extrema on the sides of a typical bipolar electric field signature, or by association with a root beyond double layers in the fully nonlinear Sagdeev pseudopotential description. It was subsequently found that supersolitons could exist in several plasma models having three constituent species, rather than four or five. In the present paper, it is proved that standard two-component plasma models cannot generate supersolitons, by recalling and extending results already in the literature, and by establishing the necessary properties of a more recent model.

  4. Two-component Brownian coagulation: Monte Carlo simulation and process characterization

    Institute of Scientific and Technical Information of China (English)

    Haibo Zhao; Chu guang Zheng

    2011-01-01

    The compositional distribution within aggregates of a given size is essential to the functionality of composite aggregates that are usually enlarged by rapid Brownian coagulation.There is no analytical solution for the process of such two-component systems.Monte Carlo method is an effective numerical approach for two-component coagulation.In this paper,the differentially weighted Monte Carlo method is used to investigate two-component Brownian coagulation,respectively,in the continuum regime,the freemolecular regime and the transition regime.It is found that ( 1 ) for Brownian coagulation in the continuum regime and in the free-molecular regime,the mono-variate compositional distribution,i.e.,the number density distribution function of one component amount (in the form of volume of the component in aggregates) satisfies self-preserving form the same as particle size distribution in mono-component Brownian coagulation; (2) however,for Brownian coagulation in the transition regime the mono-variate compositional distribution cannot reach self-similarity; and (3) the bivariate compositional distribution,i.e.,the combined number density distribution function of two component amounts in the three regimes satisfies a semi self-preserving form.Moreover,other new features inherent to aggregative mixing are also demonstrated; e.g.,the degree of mixing between components,which is largely controlled by the initial compositional mass fraction,improves as aggregate size increases.

  5. Two-component coupled KdV equations and its connection with the generalized Harry Dym equations

    Science.gov (United States)

    Popowicz, Ziemowit

    2014-01-01

    It is shown that three different Lax operators in the Dym hierarchy produce three generalized coupled Harry Dym equations. These equations transform, via the reciprocal link, to the coupled two-component Korteweg de Vries (KdV) system. The first equation gives us known integrable two-component KdV system, while the second reduces to the known symmetrical two-component KdV equation. The last one reduces to the Drienfeld-Sokolov equation. This approach gives us new Lax representation for these equations.

  6. Bloch Oscillations of Two-Component Bose-Einstein Condensates in Optical Lattices

    Institute of Scientific and Technical Information of China (English)

    GU Huai-Qiang; WANG Zhi-Cheng; JIN Kang; TAN Lei

    2006-01-01

    @@ We study the Bloch oscillations of two-component Bose-Einstein condensates trapped in spin-dependent optical lattices. The influence of the intercomponent atom interaction on the system is discussed in detail Accelerated breakdown of the Bloch oscillations and revival phenomena are found respectively for the repulsive and attractive case. For both the cases, the system will finally be set in a quantum self-trapping state due to dynamical instability.

  7. Mapping the Two-Component Atomic Fermi Gas to the Nuclear Shell-Model

    DEFF Research Database (Denmark)

    Özen, C.; Zinner, Nikolaj Thomas

    2014-01-01

    The physics of a two-component cold fermi gas is now frequently addressed in laboratories. Usually this is done for large samples of tens to hundreds of thousands of particles. However, it is now possible to produce few-body systems (1-100 particles) in very tight traps where the shell structure...... of the external potential becomes important. A system of two-species fermionic cold atoms with an attractive zero-range interaction is analogous to a simple model of nucleus in which neutrons and protons interact only through a residual pairing interaction. In this article, we discuss how the problem of a two......-component atomic fermi gas in a tight external trap can be mapped to the nuclear shell model so that readily available many-body techniques in nuclear physics, such as the Shell Model Monte Carlo (SMMC) method, can be directly applied to the study of these systems. We demonstrate an application of the SMMC method...

  8. Implementation of Two Component Advective Flow Solution in XSPEC

    CERN Document Server

    Debnath, Dipak; Mondal, Santanu

    2014-01-01

    Spectral and Temporal properties of black hole candidates can be explained reasonably well using Chakrabarti-Titarchuk solution of two component advective flow (TCAF). This model requires two accretion rates, namely, the Keplerian disk accretion rate and the halo accretion rate, the latter being composed of a sub-Keplerian, low angular momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disk rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for the first time, we made it user friendly by implementing it into XSPEC software of GSFC/NASA. This enables any user to extract physical parameters of the accretion flows, such as two accretion rates, the shock location, the shock strength etc. for any black hole candidate. We provide some examples of fitting a few cases usin...

  9. Two-component perfect fluid in FRW universe

    CERN Document Server

    ,

    2012-01-01

    We propose the cosmological model which allows to describe on equal footing the evolution of matter in the universe on the time interval from the inflation till the domination of dark energy. The matter is considered as a two-component perfect fluid imitated by homogeneous scalar fields between which there is energy exchange. Dark energy is represented by the cosmological constant, which is supposed invariable during the whole evolution of the universe. The matter changes its equation of state with time, so that the era of radiation domination in the early universe smoothly passes into the era of a pressureless gas, which then passes into the late-time epoch, when the matter is represented by a gas of low-velocity cosmic strings. The inflationary phase is described as an analytic continuation of the energy density in the very early universe into the region of small negative values of the parameter which characterizes typical time of energy transfer from one matter component to another. The Hubble expansion ra...

  10. A minimal model for two-component dark matter

    International Nuclear Information System (INIS)

    We propose and study a new minimal model for two-component dark matter. The model contains only three additional fields, one fermion and two scalars, all singlets under the Standard Model gauge group. Two of these fields, one fermion and one scalar, are odd under a Z2 symmetry that renders them simultaneously stable. Thus, both particles contribute to the observed dark matter density. This model resembles the union of the singlet scalar and the singlet fermionic models but it contains some new features of its own. We analyze in some detail its dark matter phenomenology. Regarding the relic density, the main novelty is the possible annihilation of one dark matter particle into the other, which can affect the predicted relic density in a significant way. Regarding dark matter detection, we identify a new contribution that can lead either to an enhancement or to a suppression of the spin-independent cross section for the scalar dark matter particle. Finally, we define a set of five benchmarks models compatible with all present bounds and examine their direct detection prospects at planned experiments. A generic feature of this model is that both particles give rise to observable signals in 1-ton direct detection experiments. In fact, such experiments will be able to probe even a subdominant dark matter component at the percent level.

  11. The Bound of Entanglement of Superpositions with More Than Two Components

    OpenAIRE

    Xiang, Yang; Xiong, Shi-Jie; Hong, Fang-Yu

    2007-01-01

    A bipartite quantum state (for two systems in any dimensions) can be decomposed as a superposition of many components. For a superposition of more than two components we prove that there is a bound of the entanglement of the superposition state which can be expressed according to entanglements of its component states. Especially, if the component states are mutually bi-orthogonal, the entanglement of the superposition state can be exactly given in terms of the entanglements of the states bein...

  12. Two-component Fermi gas in a one-dimensional harmonic trap

    OpenAIRE

    Xianlong, Gao; Wonneberger, W.

    2001-01-01

    A many body theory for a two-component system of spin polarized interacting fermions in a one-dimensional harmonic trap is developed. The model considers two different states of the same fermionic species and treats the dominant interactions between the two using the bosonization method for forward scattering. Asymptotically exact results for the one-particle matrix elements at zero temperature are given. Using them, occupation probabilities of oscillator states are discussed. Particle and mo...

  13. Analysis of proteins regulated by two-component signal transduction system saeRS in Staphylococcus epidermidis%表皮葡萄球菌双组分信号转导系统saeRS对相关蛋白调控的研究

    Institute of Scientific and Technical Information of China (English)

    娄强; 王艳歌; 瞿涤

    2012-01-01

    目的 利用双向电泳技术对表皮葡萄球菌菌体蛋白进行蛋白质组学分析,寻找双组分信号转导系统saeRS的调控网络.方法 对表皮葡萄球菌1457双组分信号转导系统saeRS删除株与野生株菌体蛋白进行双向电泳差异比较;电泳图谱采用Image Master 2D Platinum软件分析;免疫印迹法验证saeRS调控的差异蛋白.结果 在表皮葡萄球菌1457双组分信号转导系统saeRS删除株与野生株蛋白质图谱中共发现23个差异表达的蛋白点(10个下调,13个上调).结论 蛋白质双向电泳技术可以成功应用于分析表皮葡萄球菌双组分信号转导系统saeRS的调控网络;此图谱为进一步研究saeRS在表皮葡萄球菌中的调控机制奠定了基础.%Objective To search for new proteins regulated by two-component signal transduction system saeRS, the proteomics of whole cellular proteins between saeRS deletion mutant and wild-type strain of Staphylococcus epidermidis ( S. epidermidis) using two-dimensional electrophoresis. Methods Immobilized pH gradient (IPG) two-dimensional electrophoresis was adopted and the gels were analyzed with Image Master 2D Platinum software. Western blot was used to analyze the differentially expressed proteins. Results We found 23 differentially expressed protein spots (10 down-regulated and 13 up-regulated) in 2-DE gels of saeRS deletion mutant and wild-type strain of S. epidermidis. Conclusion Two-dimensional electrophoresis of protein can be used to analyze the regulation network of two-component signal transduction system saeRS in S. epidermidis, and this provides basis for further study on saeRS regulation mechanism.

  14. Real time propagation of the exact two component time-dependent density functional theory

    Science.gov (United States)

    Goings, Joshua J.; Kasper, Joseph M.; Egidi, Franco; Sun, Shichao; Li, Xiaosong

    2016-09-01

    We report the development of a real time propagation method for solving the time-dependent relativistic exact two-component density functional theory equations (RT-X2C-TDDFT). The method is fundamentally non-perturbative and may be employed to study nonlinear responses for heavy elements which require a relativistic Hamiltonian. We apply the method to several group 12 atoms as well as heavy-element hydrides, comparing with the extensive theoretical and experimental studies on this system, which demonstrates the correctness of our approach. Because the exact two-component Hamiltonian contains spin-orbit operators, the method is able to describe the non-zero transition moment of otherwise spin-forbidden processes in non-relativistic theory. Furthermore, the two-component approach is more cost effective than the full four-component approach, with similar accuracy. The RT-X2C-TDDFT will be useful in future studies of systems containing heavy elements interacting with strong external fields.

  15. Real time propagation of the exact two component time-dependent density functional theory.

    Science.gov (United States)

    Goings, Joshua J; Kasper, Joseph M; Egidi, Franco; Sun, Shichao; Li, Xiaosong

    2016-09-14

    We report the development of a real time propagation method for solving the time-dependent relativistic exact two-component density functional theory equations (RT-X2C-TDDFT). The method is fundamentally non-perturbative and may be employed to study nonlinear responses for heavy elements which require a relativistic Hamiltonian. We apply the method to several group 12 atoms as well as heavy-element hydrides, comparing with the extensive theoretical and experimental studies on this system, which demonstrates the correctness of our approach. Because the exact two-component Hamiltonian contains spin-orbit operators, the method is able to describe the non-zero transition moment of otherwise spin-forbidden processes in non-relativistic theory. Furthermore, the two-component approach is more cost effective than the full four-component approach, with similar accuracy. The RT-X2C-TDDFT will be useful in future studies of systems containing heavy elements interacting with strong external fields. PMID:27634251

  16. Two-component Fermions in Optical Lattice with Spatially Alternating Interactions

    Science.gov (United States)

    Hoang, Anh-Tuan; Nguyen, Thi-Hai-Yen; Tran, Thi-Thu-Trang; Le, Duc-Anh

    2016-10-01

    We investigate two-component mass-imbalanced fermions in an optical lattice with spatially modulated interactions by using two-site dynamical mean field theory. At half-filling and zero temperature, the phase diagram of the system is analytically obtained, in which the metallic region is reduced with increasing the mass imbalance. The ground-state properties of the fermionic system are discussed from the behaviors of both the spin-dependent quasi-particle weight at the Fermi level and the double occupancy for each sublattice as functions of the local interaction strengths for various values of the mass imbalance.

  17. High-temperature superfluidity of the two-component Bose gas in a transition metal dichalcogenide bilayer

    Science.gov (United States)

    Berman, Oleg L.; Kezerashvili, Roman Ya.

    2016-06-01

    The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel transition metal dichalcogenide (TMDC) layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity, and critical temperature are obtained for different TMDC materials. It is shown that in the Bogoliubov approximation, the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component exciton system. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for a two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the two-component exciton system in a TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.

  18. Topological phases of two-component bosons in species-dependent artificial gauge potentials

    Science.gov (United States)

    Wu, Ying-Hai; Shi, Tao

    2016-08-01

    We study bosonic atoms with two internal states in artificial gauge potentials whose strengths are different for the two components. A series of topological phases for such systems is proposed using the composite fermion theory and the parton construction. It is found in exact diagonalization that some of the proposed states may be realized for simple contact interaction between bosons. The ground states and low-energy excitations of these states are modeled using trial wave functions. The effective field theories for these states are also constructed and reveal some interesting properties.

  19. Two-component Bose-Hubbard model with higher-angular-momentum states

    Science.gov (United States)

    Pietraszewicz, Joanna; Sowiński, Tomasz; Brewczyk, Mirosław; Zakrzewski, Jakub; Lewenstein, Maciej; Gajda, Mariusz

    2012-05-01

    Bose-Hubbard Hamiltonian of cold two-component Bose gas of spinor chromium atoms is studied. Dipolar interactions of magnetic moments while tuned resonantly by an ultralow magnetic field can lead to a transfer of atoms from the ground to excited Wannier states with a nonvanishing angular orbital momentum. Hence we propose the way of creating Px+iPy orbital superfluid. The spin introduces an additional degree of control and leads to a variety of different stable phases of the system. The Mott insulator of atoms in a superposition of the ground and vortex Wannier states as well as a superposition of the Mott insulator with orbital superfluid are predicted.

  20. Two Component Injection Moulding for Moulded Interconnect Devices

    DEFF Research Database (Denmark)

    Islam, Aminul

    The moulded interconnect devices (MIDs) contain huge possibilities for many applications in micro electro-mechanical-systems because of their potential in reducing the number of components, process steps and finally in miniaturization of the product. Among the available MID process chains, two...

  1. Instabilities in relativistic two-component (super)fluids

    CERN Document Server

    Haber, Alexander; Stetina, Stephan

    2016-01-01

    We study two-fluid systems with nonzero fluid velocities and compute their sound modes, which indicate various instabilities. For the case of two zero-temperature superfluids we employ a microscopic field-theoretical model of two coupled bosonic fields, including an entrainment coupling and a non-entrainment coupling. We analyse the onset of the various instabilities systematically and point out that the dynamical two-stream instability can only occur beyond Landau's critical velocity, i.e., in an already energetically unstable regime. A qualitative difference is found for the case of two normal fluids, where certain transverse modes suffer a two-stream instability in an energetically stable regime if there is entrainment between the fluids. Since we work in a fully relativistic setup, our results are very general and of potential relevance for (super)fluids in neutron stars and, in the non-relativistic limit of our results, in the laboratory.

  2. Two-component dual-scatter laser Doppler velocimeter with frequency burst signal readout.

    Science.gov (United States)

    Brayton, D B; Kalb, H T; Crosswy, F L

    1973-06-01

    A dual-scatter laser Doppler velocimeter (LDV) system designed for measuring wind tunnel flow velocity is described. The system simultaneously measures two orthogonal velocity components of a flowing fluid at a common point in the flow. Essential single-velocity component dual-scatter concepts are presented to simplify the description of the more sophisticated two-component system. To implement the two-component system three laser beams with a 0 degrees , 45 degrees , and 90 degrees polarization plane relationship are focused to a common point in the flow by the system-transmitting optics. The beams interfere to form two perpendicular sets of interference fringe planes that are orthogonally polarized. The system-receiving optics collect and separate the orthogonally polarized components of laser radiation scattered from micron-size particles moving with the flowing fluid through the ringes. The system requires no artificial seeding, since intrinsic test section aerosols are utilized for radiation scattering. The passage of each scatter particle through the interference fringes simultaneously produces two frequency-burst-type photodetected signals, the frequencies of which are directly proportional to two perpendicular components of particle velocity. The system photodetection, signal-conditioning, and data acquisition instrumentation is specifically designed to process the frequency burst information in the time domain as opposed to spectrum analysis or frequency domain processing. The system was initially evaluated in an AEDC wind tunnel operating over a Mach number range from 0.6 to 1.5. The LDV and calculated wind tunnel mean velocity data agreed to within 1.25%; flow direction deviations of a few milliradians were resolved. PMID:20125494

  3. Analytical solution and meaning of feasible regions in two-component three-way arrays.

    Science.gov (United States)

    Omidikia, Nematollah; Abdollahi, Hamid; Kompany-Zareh, Mohsen; Rajkó, Róbert

    2016-10-01

    Although many efforts have been directed to the development of approximation methods for determining the extent of feasible regions in two- and three-way data sets; analytical determination (i.e. using only finite-step direct calculation(s) instead of the less exact numerical ones) of feasible regions in three-way arrays has remained unexplored. In this contribution, an analytical solution of trilinear decomposition is introduced which can be considered as a new direct method for the resolution of three-way two-component systems. The proposed analytical calculation method is applied to the full rank three-way data array and arrays with rank overlap (a type of rank deficiency) loadings in a mode. Close inspections of the analytically calculated feasible regions of rank deficient cases help us to make clearer the information gathered from multi-way problems frequently emerged in physics, chemistry, biology, agricultural, environmental and clinical sciences, etc. These examinations can also help to answer, e.g., the following practical question: "Is two-component three-way data with proportional loading in a mode actually a three-way data array?" By the aid of the additional information resulted from the investigated feasible regions of two-component three-way data arrays with proportional profile in a mode, reasons for the inadequacy of the seemingly trilinear data treatment methods published in the literature (e.g., U-PLS/RBL-LD that was used for extraction of quantitative and qualitative information reported by Olivieri et al. (Anal. Chem. 82 (2010) 4510-4519)) could be completely understood.

  4. Arabidopsis ethylene-response gene ETR1: Similiarity of product to two-component regulators

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Kwok, S.F.; Bleecker, A.B.; Meyerowitz, E.M. (California Institute of Technology, Pasadena, CA (United States))

    1993-10-22

    Ethylene behaves as a hormone in plants, regulating such aspects of growth and development as fruit ripening, flower senescence, and abscission. Ethylene insensitivity is conferred by dominant mutations in the ETR1 gene early in the ethylene signal transduction pathway of Arabidopsis thaliana. The ETR1 gene was cloned by the method of chromosome walking. Each of the four known etr1 mutant alleles contains a missense mutation near the amino terminus of the predicted protein. Although the sequence of the amino-terminal half of the deduced ETR1 protein appears to be novel, the carboxyl-terminal half is similar in sequence to both components of the prokaryotic family of signal transducers known as the two-component systems. Thus, an early step in ethylene signal transduction in plants may involve transfer of phosphate as in prokaryotic two-component systems. The dominant etr1-1 mutant gene conferred ethylene insensitivity to wild-type Arabidopsis plants when introduced by transformation.

  5. Phase Separation and Dynamics of two-component Bose-Einstein condensates

    CERN Document Server

    Lee, Kean Loon; Liu, I-Kang; Wacker, Lars; Arlt, Jan J; Proukakis, Nick P

    2016-01-01

    The miscibility of two interacting quantum systems is an important testing ground for the understanding of complex quantum systems. Two-component Bose-Einstein condensates enable the investigation of this scenario in a particularly well controlled setting. In a homogeneous system, the transition between mixed and separated phases is fully characterised by a `miscibility parameter', based on the ratio of intra- to inter-species interaction strengths. Here we show, however, that this parameter is no longer the optimal one for trapped gases, for which the location of the phase boundary depends critically on atom numbers. We demonstrate how monitoring of damping rates and frequencies of dipole oscillations enables the experimental mapping of the phase diagram by numerical implementation of a fully self-consistent finite-temperature kinetic theory for binary condensates. The change in damping rate is explained in terms of surface oscillation in the immiscible regime, and counterflow instability in the miscible reg...

  6. Small two-component Fermi gases in a cubic box with periodic boundary conditions

    Science.gov (United States)

    Yin, X. Y.; Blume, D.

    2013-06-01

    The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length as and the average interparticle spacing are much larger than the range of the underlying two-body potential. Using an explicitly correlated Gaussian basis set expansion approach, we determine the eigenenergies of two-component Fermi gases in a cubic box with periodic boundary conditions as functions of the interspecies s-wave scattering length and the effective range of the two-body potential. The universal properties of systems consisting of up to four particles are determined by extrapolating the finite-range energies to the zero-range limit. We determine the eigenenergies of states with vanishing and finite momenta. In the weakly attractive BCS regime, we analyze the energy spectra and degeneracies using first-order degenerate perturbation theory. Excellent agreement between the perturbative energy shifts and the numerically determined energies is obtained. For the infinitely large scattering length case, we compare our results—where available—with those presented in the literature.

  7. Universal properties of a trapped two-component fermi gas at unitarity.

    Science.gov (United States)

    Blume, D; von Stecher, J; Greene, Chris H

    2007-12-01

    We treat the trapped two-component Fermi system, in which unlike fermions interact through a two-body short-range potential having no bound state but an infinite scattering length. By accurately solving the Schrödinger equation for up to N=6 fermions, we show that no many-body bound states exist other than those bound by the trapping potential, and we demonstrate unique universal properties of the system: Certain excitation frequencies are separated by 2variant Planck's over 2piomega, the wave functions agree with analytical predictions and a virial theorem is fulfilled. Further calculations up to N=30 determine the excitation gap, an experimentally accessible universal quantity, and it agrees with recent predictions based on a density functional approach. PMID:18233361

  8. Universal properties of a trapped two-component fermi gas at unitarity.

    Science.gov (United States)

    Blume, D; von Stecher, J; Greene, Chris H

    2007-12-01

    We treat the trapped two-component Fermi system, in which unlike fermions interact through a two-body short-range potential having no bound state but an infinite scattering length. By accurately solving the Schrödinger equation for up to N=6 fermions, we show that no many-body bound states exist other than those bound by the trapping potential, and we demonstrate unique universal properties of the system: Certain excitation frequencies are separated by 2variant Planck's over 2piomega, the wave functions agree with analytical predictions and a virial theorem is fulfilled. Further calculations up to N=30 determine the excitation gap, an experimentally accessible universal quantity, and it agrees with recent predictions based on a density functional approach.

  9. Modulational instability for a self-attractive two-component Bose–Einstein condensate

    International Nuclear Information System (INIS)

    By means of the multiple-scale expansion method, the coupled nonlinear Schrödinger equations without an explicit external potential are obtained in two-dimensional geometry for a self-attractive Bose–Einstein condensate composed of different hyperfine states. The modulational instability of two-component condensate is investigated by using a simple technique. Based on the discussion about two typical cases, the explicit expression of the growth rate for a purely growing modulational instability and the optimum stable conditions are given and analysed analytically. The results show that the modulational instability of this two-dimensional system is quite different from that in a one-dimensional system. (general)

  10. 生防荧光假单胞菌2 P24中EnvZ/OmpR双因子系统克隆与OmpR原核表达%Cloning of EnvZ/OmpR Two-component System from Pseudomonas fluorescens 2 P24 and Prokaryotic Expression of OmpR

    Institute of Scientific and Technical Information of China (English)

    孙冰冰; 张伟; 段红英; 李伟; 田涛; 张力群

    2014-01-01

    用Mini-Tn5转座子随机突变荧光假单胞菌野生型菌株2P24,得到抗生素2,4二乙酰基间苯三酚(2,4-di-acetylphloroglucinol,2,4-DAPG)产量提高的突变体Sesu-25。对转座子侧翼序列分析表明,转座子插入到EnvZ/OmpR双因子系统的反应调节因子ompR基因。克隆得到包含完整EnvZ/OmpR系统,全长约为5.9 kb的DNA片段。该双因子系统中的envZ基因和ompR基因与P. fluorescens F113的envZ基因和ompR基因同源性分别为93%和96%。将ompR基因克隆到表达载体pET-22b(+)中,得到重组表达载体pET-ompR。将pET-ompR转入Escherichia coli BL21中得到重组菌株BL21-ompR,用IPTG诱导表达和亲和柱层析法纯化的OmpR蛋白,经SDS-PAGE电泳分析表明ompR基因得到成功表达和纯化。%Using the colour of colony as the selective marker, the random mutagenesis of mini-Tn5 was per-formed to wild-type biocontrol strain Pseudomonas fluorescens 2P24 for the screening of mutants,which might have altered yields of polyketide metabolite 2,4-diacetylphloroglucinol(2,4-DAPG). The strain Sesu-25 with a increased yield of 2,4-DAPG was screened from the mutant pool. The analysis of flank sequence of transposon implied that the response regulator OmpR of EnvZ/OmpR two-component regulatory system ( TCS ) was disrupted in mutant strain Sesu-25. A DNA fragment harbouring a intact EnvZ/OmpR TCS was obtained by subcloning. The envZ and ompR of P. fluorescens 2P24 shared a identity of 93% and 96% with P. fluorescens F113,respectively. The ompR was ligated into the expression vector pET-22b( +) to obtain the recombinated plasmid pET-ompR,and the plasmid pET-ompR was transformed into E. coli BL21 to generate the strain BL21-ompR. The His-taged OmpR was purified by affinity chromatography and verified by SDS-PAGE electrophoresis analysis.

  11. Relativistic two-component jet evolutions in 2D and 3D

    NARCIS (Netherlands)

    Meliani, Z.; Keppens, R.

    2009-01-01

    Observations of astrophysical jets and theoretical arguments suggest a transverse stratification with two components induced by intrinsic features of the central engine (accretion disk + black hole). We study two-component jet dynamics for an inner fast low density jet, surrounded by a slower, dense

  12. Comparison of Dynamical Behaviors Between Monofunctional and Bifunctional Two-Component Signaling Modules

    Science.gov (United States)

    Yang, Xiyan; Wu, Yahao; Yuan, Zhanjiang

    2015-06-01

    Two-component signaling modules exist extensively in bacteria and microbes. These modules can be, based on their distinct network structures, divided into two types: the monofunctional system (denoted by MFS) where the sensor kinase (SK) modulates only phosphorylation of the response regulator (RR), and the bifunctional system (denoted by BFS) where the SK catalyzes both phosphorylation and dephosphorylation of the RR. Here, we analyze dynamical behaviors of these two systems based on stability theory, focusing on differences between them. The analysis of the deterministic behavior indicates that there is no difference between the two modules, that is, each system has the unique stable steady state. However, there are significant differences in stochastic behavior between them. Specifically, if the mean phosphorylated SK level is kept the same for the two modules, then the variance and the Fano factor for the phosphorylated RR in the BFS are always no less than those in the MFS, indicating that bifunctionality always enhances fluctuations. The correlation between the phosphorylated SK and the phosphorylated RR in the BFS is always positive mainly due to competition between system components, but this correlation in the MFS may be positive, almost zero, or negative, depending on the ratio between two rate constants. Our overall analysis indicates that differences between dynamical behaviors of monofunctional and bifunctional signaling modules are mainly in the stochastic rather than deterministic aspect.

  13. Bioorthogonal two-component drug delivery in HER2(+) breast cancer mouse models

    Science.gov (United States)

    Hapuarachchige, Sudath; Kato, Yoshinori; Artemov, Dmitri

    2016-04-01

    The HER2 receptor is overexpressed in approximately 20% of breast cancers and is associated with tumorigenesis, metastasis, and a poor prognosis. Trastuzumab is a first-line targeted drug used against HER2(+) breast cancers; however, at least 50% of HER2(+) tumors develop resistance to trastuzumab. To treat these patients, trastuzumab-based antibody-drug conjugates (ACDs) have been developed and are currently used in the clinic. Despite their high efficacy, the long circulation half-life and non-specific binding of cytotoxic ADCs can result in systemic toxicity. In addition, standard ADCs do not provide an image-guided mode of administration. Here, we have developed a two-component, two-step, pre-targeting drug delivery system integrated with image guidance to circumvent these issues. In this strategy, HER2 receptors are pre-labeled with a functionalized trastuzumab antibody followed by the delivery of drug-loaded nanocarriers. Both components are cross-linked by multiple bioorthogonal click reactions in situ on the surface of the target cell and internalized as nanoclusters. We have explored the efficacy of this delivery strategy in HER2(+) human breast cancer models. Our therapeutic study confirms the high therapeutic efficacy of the new delivery system, with no significant toxicity.

  14. Viscous Growth in Spinodal Decomposition of the Two-component Lennard-Jones Model in Two Dimensions

    DEFF Research Database (Denmark)

    Laradji, M.; Toxvaerd, S.; Mouritsen, Ole G.

    1997-01-01

    The dynamics of phase separation of a two-component Lennard-Jones model in three dimensions is investigated by means of large scale molecular dynamics simulation. A systematic study over a wide range of quench temperatures within the coexistence region shows that the binary system reaches a dynam...... a dynamical scaling regime at late times during which the average domain size grows linearly with time in agreement with Siggia's theoretical prediction and dimensional analyses of model H.......The dynamics of phase separation of a two-component Lennard-Jones model in three dimensions is investigated by means of large scale molecular dynamics simulation. A systematic study over a wide range of quench temperatures within the coexistence region shows that the binary system reaches...

  15. Phase separation and near-critical fluctuations in two-component lipid membranes: Monte Carlo simulations on experimentally relevant scales

    OpenAIRE

    Ehrig, Jens; Petrov, Eugene P.; Schwille, Petra

    2010-01-01

    By means of lattice-based Monte Carlo simulations, we address properties of two-component lipid membranes on the experimentally relevant spatial scales of order of a micrometer and time intervals of order of a second, using DMPC/DSPC lipid mixtures as a model system. Our large-scale simulations allowed us to obtain important results previously not reported in simulation studies of lipid membranes. We find that, within a certain range of lipid compositions, the phase transition from the fluid ...

  16. Mechanism and regulation of the Two-component FMN-dependent monooxygenase ActVA-ActVB from Streptomyces coelicolor.

    OpenAIRE

    Valton, Julien; Mathevon, Carole; Fontecave, Marc; Nivière, Vincent; Ballou, David P.

    2008-01-01

    International audience The ActVA-ActVB system from Streptomyces coelicolor is a two-component flavin-dependent monooxygenase involved in the antibiotic actinorhodin biosynthesis. ActVB is a NADH:flavin oxidoreductase that provides a reduced FMN to ActVA, the monooxygenase that catalyzes the hydroxylation of dihydrokalafungin, the precursor of actinorhodin. In this work, using stopped-flow spectrophotometry, we investigated the mechanism of hydroxylation of dihydrokalafungin catalyzed by Ac...

  17. Laser controlling chaotic region of a two-component Bose-Einstein condensate

    Institute of Scientific and Technical Information of China (English)

    Boli Xia; Wenhua Hai

    2005-01-01

    @@ For a weakly and periodically driven two-component Bose-Einstein condensate (BEC) the Melnikov chaotic solution and boundedness conditions are derived from a direct perturbation theory that leads to the chaotic regions in the parameter space.

  18. Two-component spinor techniques and Feynman rules for quantum field theory and supersymmetry

    CERN Document Server

    Dreiner, Herbi K; Martin, Stephen P

    2008-01-01

    Two-component spinors are the basic ingredients for describing fermions in quantum field theory in four space-time dimensions. We develop and review the techniques of the two-component spinor formalism and provide a complete set of Feynman rules for fermions using two-component spinor notation. These rules are suitable for practical calculations of cross-sections, decay rates, and radiative corrections in the Standard Model and its extensions, including supersymmetry, and many explicit examples are provided. The unified treatment presented in this review applies to massless Weyl fermions and massive Dirac and Majorana fermions. We exhibit the relation between the two-component spinor formalism and the more traditional four-component spinor formalism, and indicate their connections to the spinor helicity method and techniques for the computation of helicity amplitudes.

  19. Non-equilibrium dynamics around integrability in a one-dimensional two-component Bose gas

    Science.gov (United States)

    van Druten, Nicolaas; Wicke, Philipp; Whitlock, Shannon

    2011-05-01

    We investigate a one-dimensional two-component Bose gas near the point of state-independent interactions. At this specific point the system is integrable, in the sense that exact (thermodynamic) Bethe Ansatz solutions can be applied locally. In the experiments, we employ an atom chip and the magnetically trappable clock states in 87Rb. State-dependent potentials are generated by using the polarization dependence of radio-frequency dressing. We show that this allows us to continuously and dynamically tune both the local interactions and the global trapping potential. The experimentally accessible range in interactions includes the region around the integrability point. We study the spin motion that follows upon a sudden change in the system, a quantum quench. When starting from a low-temperature, quantum-degenerate gas in the weakly interacting regime, good agreement with a Gross-Pitaevskii description is found. The experiment allows exploring regimes that go beyond such a description and opens up a novel route to the study of the relation between non-equilibrium dynamics, thermalization and the making and breaking of integrability in quantum many-body physics. Supported by FOM, NWO and EU

  20. Impact of backmixing of the aqueous phase on two-component rare earth separation process

    Institute of Scientific and Technical Information of China (English)

    WU Sheng; CHENG Fuxiang; LIAO Chunsheng; YAN Chunhua

    2013-01-01

    Solvent extraction based on mixer-settler is the major industrial method of rare earth (RE) separation.In the mixer-settler extraction process,due to the insufficient settling time in normal circumstances,backmixing of the aqueous phase could have significant impact on the process of RE extraction separation.Therefore on the basis of the extraction equilibrium and mass balance of the mixer-settler extraction process,here we developed a mathematic expression of the aqueous phase backmixing in a two-component separation process,and obtained a quantitative analysis of the backmixing effect on the purification process by the approximations according to certain hypotheses.Two extraction systems of La/Ce and Pr/Nd separation were chosen as the examples to analyze the backmixing effect,and the results showed that the aqueous backmixing had greater influence in the scrubbing segment than in the extraction segment,especially in the system with a high separation factor such as La/Ce separation.Therefore it was suggested that the aqueous backmixing effect should be well attended in the design and application of RE extraction separation.

  1. Surfactant effect on cloud condensation nuclei for two-component internally mixed aerosols

    Science.gov (United States)

    Petters, Sarah Suda; Petters, Markus Dirk

    2016-02-01

    This work presents experimental data on the cloud condensation nuclei (CCN) activity of two-component mixtures containing surfactants. Nine binary systems were tested combining strong ionic (sodium dodecyl sulfate) and nonionic surfactants (Zonyl FS-300 and Triton X-100) with nonsurfactant compounds (glucose, ammonium sulfate, or sodium chloride). Control tests were performed for systems combining organic (glucose) and inorganic compounds (ammonium sulfate or sodium chloride). Results show that CCN activity deviates strongly relative to predictions made from measurements of bulk surface tension. Köhler theory accounting for surface tension reduction and surface partitioning underpredicts the CCN activity of particles containing Zonyl FS-300 and Triton X-100. Partitioning theory better describes data for Zonyl FS-300 and Triton X-100 when limiting surface adsorption to 1.5 monolayers of the growing drop. Deviations from predictions were observed. Likely explanations include solute-solute interactions and nonspherical particle shape. The findings presented here examine in detail the perturbation of CCN activity by surfactants and may offer insight into both the success and limitations of physical models describing CCN activity of surface active molecules.

  2. Note on a tetrad composed of a two-component spinor and a time-like vector

    International Nuclear Information System (INIS)

    In order to describe and extended object in conformity with relativity, it is useful to introduce a tetrad which is composed of four orthonormal vectors and moves in a similar way as the motion of the object. The tetrad is a kind of relativistic generalization of a body fixed triad which is often employed to describe the non-relativistic motion of a rigid body. In this paper, the study of a tetrad constructed in terms of a two-component spinor and a time-like vector is presented. Three vectors orthogonal to P sub(μ), which is a time-like four-momentum of a closed system, are defined in terms of a two-component spinor Xi sub(α). With a conjugate spinor sup(α) various variables and operators can be introduced, and constraints are described. By using the transformation introduced in this study, the Poincare generators can be rewritten. (Kato, T.)

  3. Energy spectra of small two-component Fermi gases in a cubic box with periodic boundary conditions

    Science.gov (United States)

    Yin, X. Y.; Blume, D.

    2013-05-01

    The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length and the average interparticle spacing are much larger than the range of the underlying two-body potential. Using an explicitly correlated Gaussian basis set expansion approach, we determine the eigenenergies of two-component Fermi gases in a cubic box with periodic boundary conditions as functions of the interspecies s-wave scattering length and the effective range of the two-body potential. The universal properties of systems consisting of up to five particles are determined by extrapolating the finite-range energies to the zero-range limit. We determine the eigenenergies of states with vanishing and finite momentum. For the infinitely large scattering length case, we compare our results with those presented in the literature. Support by the ARO is gratefully acknowledged.

  4. Interference of Two-Component Bose-Einstein Condensates with a Coupling Drive in Presence of Dissipation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The interference of the two-component Bose-Einstein condensates with a coupling drive in the presence of the dissipation is studied. We find that when the two-component Bose-Einstein condensates are initially in the coherent states, for the smaller dissipation parameters compared with that of the rf frequency ωrf, the interference intensity exhibits damply oscillation behavior, whereas when the dissipation parameters are larger than that of the ωrf, the interference intensity exhibits a fast attenuation behavior. As a comparison, the interference intensity in the absence of the dissipation is also studied. We conclude that the dissipation of the system can be evaluated by selecting the ωrf experimentally.

  5. Stenotrophomonas maltophilia PhoP, a Two-Component Response Regulator, Involved in Antimicrobial Susceptibilities.

    Directory of Open Access Journals (Sweden)

    Ming-Che Liu

    Full Text Available Stenotrophomonas maltophilia, a gram-negative bacterium, has increasingly emerged as an important nosocomial pathogen. It is well-known for resistance to a variety of antimicrobial agents including cationic antimicrobial polypeptides (CAPs. Resistance to polymyxin B, a kind of CAPs, is known to be controlled by the two-component system PhoPQ. To unravel the role of PhoPQ in polymyxin B resistance of S. maltophilia, a phoP mutant was constructed. We found MICs of polymyxin B, chloramphenicol, ampicillin, gentamicin, kanamycin, streptomycin and spectinomycin decreased 2-64 fold in the phoP mutant. Complementation of the phoP mutant by the wild-type phoP gene restored all of the MICs to the wild type levels. Expression of PhoP was shown to be autoregulated and responsive to Mg2+ levels. The polymyxin B and gentamicin killing tests indicated that pretreatment of low Mg2+ can protect the wild-type S. maltophilia from killing but not phoP mutant. Interestingly, we found phoP mutant had a decrease in expression of SmeZ, an efflux transporter protein for aminoglycosides in S. maltophilia. Moreover, phoP mutant showed increased permeability in the cell membrane relative to the wild-type. In summary, we demonstrated the two-component regulator PhoP of S. maltophilia is involved in antimicrobial susceptibilities and low Mg2+ serves as a signal for triggering the pathway. Both the alteration in membrane permeability and downregulation of SmeZ efflux transporter in the phoP mutant contributed to the increased drug susceptibilities of S. maltophilia, in particular for aminoglycosides. This is the first report to describe the role of the Mg2+-sensing PhoP signaling pathway of S. maltophilia in regulation of the SmeZ efflux transporter and in antimicrobial susceptibilities. This study suggests PhoPQ TCS may serve as a target for development of antimicrobial agents against multidrug-resistant S. maltophilia.

  6. Dynamics of coupled simplest chaotic two-component electronic circuits and its potential application to random bit generation

    Energy Technology Data Exchange (ETDEWEB)

    Modeste Nguimdo, Romain, E-mail: Romain.Nguimdo@vub.ac.be [Applied Physics Research Group, APHY, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussel (Belgium); Tchitnga, Robert [Laboratory of Electronics, Automation and Signal Processing, Department of Physics, University of Dschang, P.O. Box 67, Dschang (Cameroon); Woafo, Paul [Laboratory of Modelling and Simulation in Engineering and Biological Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812, Yaoundé (Cameroon)

    2013-12-15

    We numerically investigate the possibility of using a coupling to increase the complexity in simplest chaotic two-component electronic circuits operating at high frequency. We subsequently show that complex behaviors generated in such coupled systems, together with the post-processing are suitable for generating bit-streams which pass all the NIST tests for randomness. The electronic circuit is built up by unidirectionally coupling three two-component (one active and one passive) oscillators in a ring configuration through resistances. It turns out that, with such a coupling, high chaotic signals can be obtained. By extracting points at fixed interval of 10 ns (corresponding to a bit rate of 100 Mb/s) on such chaotic signals, each point being simultaneously converted in 16-bits (or 8-bits), we find that the binary sequence constructed by including the 10(or 2) least significant bits pass statistical tests of randomness, meaning that bit-streams with random properties can be achieved with an overall bit rate up to 10×100 Mb/s =1Gbit/s (or 2×100 Mb/s =200 Megabit/s). Moreover, by varying the bias voltages, we also investigate the parameter range for which more complex signals can be obtained. Besides being simple to implement, the two-component electronic circuit setup is very cheap as compared to optical and electro-optical systems.

  7. Transcriptional and proteomic analyses of two-component response regulators in multidrug-resistant Mycobacterium tuberculosis.

    Science.gov (United States)

    Zhou, Lei; Yang, Liu; Zeng, Xianfei; Danzheng, Jiacuo; Zheng, Qing; Liu, Jiayun; Liu, Feng; Xin, Yijuan; Cheng, Xiaodong; Su, Mingquan; Ma, Yueyun; Hao, Xiaoke

    2015-07-01

    Two-component systems (TCSs) have been reported to exhibit a sensing and responding role under drug stress that induces drug resistance in several bacterial species. However, the relationship between TCSs and multidrug resistance in Mycobacterium tuberculosis has not been comprehensively analysed to date. In this study, 90 M. tuberculosis clinical isolates were analysed using 15-loci mycobacterial interspersed repetitive unit (MIRU)-variable number tandem repeat (VNTR) typing and repetitive extragenic palindromic (rep)-PCR-based DNA fingerprinting. The results showed that all of the isolates were of the Beijing lineage, and strains with a drug-susceptible phenotype had not diverged into similar genotype clusters. Expression analysis of 13 response regulators of TCSs using real-time PCR and tandem mass spectrometry (MS/MS) proteomic analysis demonstrated that four response regulator genes (devR, mtrA, regX3 and Rv3143) were significantly upregulated in multidrug-resistant (MDR) strains compared with the laboratory strain H37Rv as well as drug-susceptible and isoniazid-monoresistant strains (PMycobacterium bovis BCG did not alter its sensitivity to the four antitubercular drugs. This suggests that upregulation of devR, which is common in MDR-TB strains, might be induced by drug stress and hypoxic adaptation following the acquisition of multidrug resistance.

  8. Modelling elliptical galaxies phase-space constraints on two-component (gamma1,gamma2) models

    CERN Document Server

    Ciotti, L

    1999-01-01

    In the context of the study of the properties of the mutual mass distribution of the bright and dark matter in elliptical galaxies, present a family of two-component, spherical, self-consistent galaxy models, where one density distribution follows a gamma_1 profile, and the other a gamma_2 profile [(gamma_1,gamma_2) models], with different total masses and ``core'' radii. A variable amount of Osipkov-Merritt (radial) orbital anisotropy is allowed in both components. For these models, I derive analytically the necessary and sufficient conditions that the model parameters must satisfy in order to correspond to a physical system. Moreover, the possibility of adding a black hole at the center of radially anisotropic gamma models is discussed, determining analytically a lower limit of the anisotropy radius as a function of gamma. The analytical phase-space distribution function for (1,0) models is presented, together with the solution of the Jeans equations and the quantities entering the scalar virial theorem. It...

  9. Ferromagnetism in Two-component Fermi gases: Variational and Green's Function Monte Carlo Studies

    Science.gov (United States)

    Trivedi, Nandini; Chang, Soon-Yong; Randeria, Mohit

    2010-03-01

    We study the possibility of a ferromagnetic instability in both repulsive and attractive two-component Fermi gases using lowest-order constrained variational (LOCV), variational Monte Carlo (VMC), and fixed-node Green's function Monte Carlo (GFMC) methods. For repulsive interactions, where the range r0 is of order the scattering length a >0 , we find clear evidence for a ferromagnetic Stoner instability at kFa ˜O(1). The occurrence of ferromagnetism is robust though the precise value of kFa at the instability is not universal and depends upon the shape of the potential. To model the recent experiments [1], where the underlying interactions are attractive with |a| r0, one must be on the repulsive excited branch on the a>0 side of the Feshbach resonance. We write the many-body wavefunction as a suitable Jastrow factor times a fermionic determinant, with a nodal structure that ensures the system is on the excited branch. We will report on the possible ferromagnetic instability in this Fermi-liquid state and its implications for experiments. [1] G-B. Jo et al., Science 325, 1521 (2009).

  10. Two-component Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H9OH).

    Science.gov (United States)

    Nakahara, Hiromichi; Hirano, Chikayo; Shibata, Osamu

    2013-01-01

    The interaction of (perfluorooctyl)nonanol (F8H9OH) with dipalmitoylphosphatidylcholine (DPPC) was systematically studied in two-component monolayers at air-water interface. The thermodynamic property and phase morphology of the monolayers were investigated by isotherm measurements and several microscopic methods such as Brewster angle microscopy, fluorescence microscopy, and atomic force microscopy (AFM). The AFM topographies for Langmuir-Blodgett films of F8H9OH exhibit the formation of monodispersed surface micelles. In the two-component system, the incorporation of F8H9OH induces condensation (or solidification) of DPPC monolayers. The excess Gibbs free energy and interaction parameter (or energy) of the two components were calculated from the isotherm data. Both the phase transition pressure for the coexistence of ordered and disordered phases and collapse pressure of monolayers vary with the mole fraction of F8H9OH, indicating binary miscibility between F8H9OH and DPPC within a monolayer state. The miscibility is also confirmed visually by in situ and ex situ microscopy at micro- and nanometer scales.

  11. Systematic dissection and trajectory-scanning mutagenesis of the molecular interface that ensures specificity of two-component signaling pathways.

    Directory of Open Access Journals (Sweden)

    Emily J Capra

    2010-11-01

    Full Text Available Two-component signal transduction systems enable bacteria to sense and respond to a wide range of environmental stimuli. Sensor histidine kinases transmit signals to their cognate response regulators via phosphorylation. The faithful transmission of information through two-component pathways and the avoidance of unwanted cross-talk require exquisite specificity of histidine kinase-response regulator interactions to ensure that cells mount the appropriate response to external signals. To identify putative specificity-determining residues, we have analyzed amino acid coevolution in two-component proteins and identified a set of residues that can be used to rationally rewire a model signaling pathway, EnvZ-OmpR. To explore how a relatively small set of residues can dictate partner selectivity, we combined alanine-scanning mutagenesis with an approach we call trajectory-scanning mutagenesis, in which all mutational intermediates between the specificity residues of EnvZ and another kinase, RstB, were systematically examined for phosphotransfer specificity. The same approach was used for the response regulators OmpR and RstA. Collectively, the results begin to reveal the molecular mechanism by which a small set of amino acids enables an individual kinase to discriminate amongst a large set of highly-related response regulators and vice versa. Our results also suggest that the mutational trajectories taken by two-component signaling proteins following gene or pathway duplication may be constrained and subject to differential selective pressures. Only some trajectories allow both the maintenance of phosphotransfer and the avoidance of unwanted cross-talk.

  12. Two components in charged particle production in heavy-ion collisions

    Science.gov (United States)

    Bylinkin, A. A.; Chernyavskaya, N. S.; Rostovtsev, A. A.

    2016-02-01

    Transverse momentum spectra of charged particle production in heavy-ion collisions are considered in terms of a recently introduced Two Component parameterization combining exponential ("soft") and power-law ("hard") functional forms. The charged hadron densities calculated separately for them are plotted versus number of participating nucleons, Npart. The obtained dependences are discussed and the possible link between the two component parameterization introduced by the authors and the two component model historically used for the case of heavy-ion collisions is established. Next, the variations of the parameters of the introduced approach with the center of mass energy and centrality are studied using the available data from RHIC and LHC experiments. The spectra shapes are found to show universal dependences on Npart for all investigated collision energies.

  13. Stochastic simulation of prokaryotic two-component signalling indicates stochasticity-induced active-state locking and growth-rate dependent bistability.

    Science.gov (United States)

    Wei, Katy; Moinat, Maxim; Maarleveld, Timo R; Bruggeman, Frank J

    2014-07-29

    Signal transduction by prokaryotes almost exclusively relies on two-component systems for sensing and responding to (extracellular) signals. Here, we use stochastic models of two-component systems to better understand the impact of stochasticity on the fidelity and robustness of signal transmission, the outcome of autoregulatory gene expression and the influence of cell growth and division. We report that two-component systems are remarkably robust against copy number fluctuations of the signalling proteins they are composed of, which enhances signal transmission fidelity. Furthermore, we find that due to stochasticity these systems can get locked in an active state for extended time periods when (initially high) signal levels drop to zero. This behaviour can contribute to a bet-hedging adaptation strategy, aiding survival in fluctuating environments. Additionally, autoregulatory gene expression can cause two-component systems to become bistable at realistic parameter values. As a result, two sub-populations of cells can co-exist-active and inactive cells, which contributes to fitness in unpredictable environments. Bistability proved robust with respect to cell growth and division, and is tunable by the growth rate. In conclusion, our results indicate how single cells can cope with the inevitable stochasticity occurring in the activity of their two-component systems. They are robust to disadvantageous fluctuations that scramble signal transduction and they exploit beneficial stochasticity that generates fitness-enhancing heterogeneity across an isogenic population of cells.

  14. Generating ring dark solitons in two-component Bose–Einstein condensates

    International Nuclear Information System (INIS)

    The dynamical evolution of two-component Bose–Einstein condensates trapped in cylindrical well is numerically investigated by solving the coupled Gross–Pitaevskii equations. We illustrate that, due to intercomponent interaction and different initial component populations (n12), different numbers of ring dark (gray) solitons are generated in two components at same time. These solitons have density zeros (minima) accompanied with phase jumps, which cause large superfluid velocities. We also illustrate that at phase jump points ring dark solitons have zero superfluid currents, while ring gray solitons have large superfluid currents. They are unstable and will evolve into other soliton states after a brief time.

  15. Rabi Oscillations in Two-Component Bose-Einstein Condensates with a Coupling Drive

    Institute of Scientific and Technical Information of China (English)

    LI Wei-Dong; FAN Wen-Bing; ZHOU Xiao-Ji; WANG Yi-Qiu; LIANG Jiu-Qing

    2002-01-01

    The Rabi oscillations in two-component Bose-Einstein condensates with a coupling drive are studiedby means of a pair of bosonic operators. The coupling drive and initial phase difference will affect the amplitudeand the period of the Rabi oscillations. The Rabi oscillations will vanish in the evolution of the condensate densityfor some special initial phase differences (ψ = 0 or π). Our theory provides not only an analytical framework forquantitative predictions for two-component condensates, but also gives an intuitive understanding of some mysteriousfeatures observed in experiments and numerical. simulations.

  16. Small two-component Fermi gases in a cubic box with periodic boundary conditions

    OpenAIRE

    Yin, X. Y.; Blume, D.

    2013-01-01

    The properties of two-component Fermi gases become universal if the interspecies s-wave scattering length $a_s$ and the average interparticle spacing are much larger than the range of the underlying two-body potential. Using an explicitly correlated Gaussian basis set expansion approach, we determine the eigen energies of two-component Fermi gases in a cubic box with periodic boundary conditions as functions of the interspecies s-wave scattering length and the effective range of the two-body ...

  17. Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population

    Science.gov (United States)

    Darsheshdar, E.; Yavari, H.; Zangeneh, Z.

    2016-07-01

    By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.

  18. Comparative genomic analysis of two-component regulatory proteins in Pseudomonas syringae

    Directory of Open Access Journals (Sweden)

    Ussery David W

    2007-10-01

    Full Text Available Abstract Background Pseudomonas syringae is a widespread bacterial plant pathogen, and strains of P. syringae may be assigned to different pathovars based on host specificity among different plant species. The genomes of P. syringae pv. syringae (Psy B728a, pv. tomato (Pto DC3000 and pv. phaseolicola (Pph 1448A have been recently sequenced providing a major resource for comparative genomic analysis. A mechanism commonly found in bacteria for signal transduction is the two-component system (TCS, which typically consists of a sensor histidine kinase (HK and a response regulator (RR. P. syringae requires a complex array of TCS proteins to cope with diverse plant hosts, host responses, and environmental conditions. Results Based on the genomic data, pattern searches with Hidden Markov Model (HMM profiles have been used to identify putative HKs and RRs. The genomes of Psy B728a, Pto DC3000 and Pph 1448A were found to contain a large number of genes encoding TCS proteins, and a core of complete TCS proteins were shared between these genomes: 30 putative TCS clusters, 11 orphan HKs, 33 orphan RRs, and 16 hybrid HKs. A close analysis of the distribution of genes encoding TCS proteins revealed important differences in TCS proteins among the three P. syringae pathovars. Conclusion In this article we present a thorough analysis of the identification and distribution of TCS proteins among the sequenced genomes of P. syringae. We have identified differences in TCS proteins among the three P. syringae pathovars that may contribute to their diverse host ranges and association with plant hosts. The identification and analysis of the repertoire of TCS proteins in the genomes of P. syringae pathovars constitute a basis for future functional genomic studies of the signal transduction pathways in this important bacterial phytopathogen.

  19. Structural studies of the activation of the two component receiver domain NTRC by multidimensional heteronuclear NMR

    Energy Technology Data Exchange (ETDEWEB)

    Nohaile, M J [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1996-05-01

    Multidimensional heteronuclear NMR spectroscopy was used to investigate the N-terminal domain of the transcriptional enhancer NTRC (NiTrogen Regulatory protein C). This domain belongs to the family of receiver domains of two-component regulatory systems involved in signal transduction. Phosphorylation of NTRC at D54 leads to an activated form of the molecule which stimulates transcription of genes involved in nitrogen regulation. Three and four dimensional NMR techniques were used to determine an intermediate resolution structure of the unphosphorylated, inactive form of the N-terminal domain of NTRC. The structure is comprised of five {alpha}-helices and a five-stranded {beta}-sheet in a ({beta}/{alpha}){sub 5} topology. Analysis of the backbone dynamics of NTRC indicate that helix 4 and strand 5 are significantly more flexible than the rest of the secondary structure of the protein and that the loops making up the active site are flexible. The short lifetime of phospho-NTRC hampers the study of this form. However, conditions for determining the resonance assignments and, possibly, the three dimensional structure of phosphorylated NTRC have been obtained. Tentative assignments of the phosphorylated form indicate that the majority of the changes that NTRC experiences upon phosphorylation occur in helix 3, strand 4, helix 4, strand 5, and the loop between strand 5 and helix 5 (the 3445 face of NTRC) as well as near the site of phosphorylation. In order to examine a stable, activated form of the protein, constitutively active mutants of NTRC were investigated.

  20. Temporal Variability from the Two-Component Advective Flow Solution and Its Observational Evidence

    Science.gov (United States)

    Dutta, Broja G.; Chakrabarti, Sandip K.

    2016-09-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν c) of ˜3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.

  1. On bi-Hamiltonian structure of two-component Novikov equation

    Energy Technology Data Exchange (ETDEWEB)

    Li, Nianhua [Department of Mathematics, China University of Mining and Technology, Beijing 100083 (China); Liu, Q.P., E-mail: qpl@cumtb.edu.cn [Department of Mathematics, China University of Mining and Technology, Beijing 100083 (China)

    2013-01-03

    In this Letter, we present a bi-Hamiltonian structure for the two-component Novikov equation. We also show that proper reduction of this bi-Hamiltonian structure leads to the Hamiltonian operators found by Hone and Wang for the Novikov equation.

  2. Two-Component Horizontal Motion Vectors from Scanning Eye-Safe Aerosol Lidar

    OpenAIRE

    Mayor, Shane; Dérian, Pierre; Héas, Patrick; Memin, Etienne

    2011-01-01

    This poster was presented at the 19th Symposium on Boundary Layers and Turbulence, August 2010, Keystone, CO. Session P1.4. Derive the two-component vector motion field from pairs of aerosol backscatter lidar images and compare results with observations from a co-located sonic anemometer. Two methods will be tested: correlations and dense estimation.

  3. Kink-Like Wave and Compacton-Like Wave Solutions for a Two-Component Fornberg-Whitham Equation

    Directory of Open Access Journals (Sweden)

    Shaoyong Li

    2014-01-01

    systems, we study a two-component Fornberg-Whitham equation. Two types of bounded traveling wave solutions are found, that is, the kink-like wave and compacton-like wave solutions. The planar graphs of these solutions are simulated by using software Mathematica; meanwhile, two new phenomena are revealed; that is, the periodic wave solution can become the kink-like wave or compacton-like wave solution under some conditions, respectively. Exact implicit or parameter expressions of these solutions are given.

  4. Correlations of the metastable branch of harmonically-trapped one-dimensional two-component Fermi gases

    Science.gov (United States)

    Gharashi, Seyed; Blume, D.

    2013-05-01

    We present highly-accurate energy spectra and eigen functions of small harmonically-trapped one-dimensional two-component Fermi gases with interspecies δ-function interactions, and analyze the correlations of the metastable crossover branch with effectively repulsive and attractive interactions. Structural expectation values are presented as a function of the interspecies coupling strength and related to cold atom tunneling experiments. Moreover, we show that the eigenstate ψadia of the infinitely strongly-interacting system with n1 +n2 > 2 and | n1 -n2 | eigen function of the non-interacting single-component Fermi gas. We gratefully acknowledge support by the ARO.

  5. The dynamics of a slider-crank mechanism with an initially curved coupler under two-component parametric resonance

    Science.gov (United States)

    Wang, Yi-Ming

    2005-02-01

    The objective of this paper is to study the dynamics and dynamic instability of a slider-crank mechanism with an initially curved coupler under parametric resonance. An attention is given to the phenomena arising due to initial curvature, geometric imperfection, of a connecting rod and modal interactions produced by the existence of two-component parametric resonance. The two-component parametric resonance can occur, for example, when the fundamental frequency of the flexible part of a slider-crank mechanism is close to one-half of the excitation frequency and simultaneously the difference between the first and the second natural frequencies is near the frequency of excitation. It is known that for the case of one-component parametric resonance, an initially curved connecting rod enlarges the amplitude of fundamental mode of vibration significantly only if the motion is in the vicinity of the secondary region of instability. In other words, the initial curvature of a coupler plays no effects to the fundamental response of the system if the oscillation is near the primary region of instability. However, result of present study shows that under the condition of two-component parametric resonance, unlike the case of one-component parametric resonance, an initially curved linkage can result significant effects to the vibration of the system even if the motion is close to the primary region of instability. In addition, the result also indicates that the growth of small amplitude vibration into large motion regime occurs if vibrations arise near the boundary of stable region.

  6. Dissecting the specificity of protein-protein interaction in bacterial two-component signaling: orphans and crosstalks.

    Directory of Open Access Journals (Sweden)

    Andrea Procaccini

    Full Text Available Predictive understanding of the myriads of signal transduction pathways in a cell is an outstanding challenge of systems biology. Such pathways are primarily mediated by specific but transient protein-protein interactions, which are difficult to study experimentally. In this study, we dissect the specificity of protein-protein interactions governing two-component signaling (TCS systems ubiquitously used in bacteria. Exploiting the large number of sequenced bacterial genomes and an operon structure which packages many pairs of interacting TCS proteins together, we developed a computational approach to extract a molecular interaction code capturing the preferences of a small but critical number of directly interacting residue pairs. This code is found to reflect physical interaction mechanisms, with the strongest signal coming from charged amino acids. It is used to predict the specificity of TCS interaction: Our results compare favorably to most available experimental results, including the prediction of 7 (out of 8 known interaction partners of orphan signaling proteins in Caulobacter crescentus. Surveying among the available bacterial genomes, our results suggest 15∼25% of the TCS proteins could participate in out-of-operon "crosstalks". Additionally, we predict clusters of crosstalking candidates, expanding from the anecdotally known examples in model organisms. The tools and results presented here can be used to guide experimental studies towards a system-level understanding of two-component signaling.

  7. Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive

    Institute of Scientific and Technical Information of China (English)

    JIAOZhi-Yong; YUZhao-Xian; YANGXin-Jian

    2004-01-01

    In this paper, we have studied the atomic population difference and the atomic tunneling current of two-component Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of 10-10 ~ 10-9 second.

  8. Formation of combined solitons in two-component Bose–Einstein condensates

    International Nuclear Information System (INIS)

    We investigate the combined soliton solutions of two-component Bose–Einstein condensates with external potential. The “phase diagram” is obtained for the formation regions of different combined solitons. Our results show that the intraspecies (interspecies) interaction strengths and the external trapped potential clearly affect the formation of dark-dark, bright-bright, and dark–bright soliton solutions in different regions. Especially, we find that the bright–bright (dark–dark) soliton can exist in the case of both repulsive (attractive) intraspecies interaction strengths in the presence of external potential. This novel phenomenon is completely different from the formation of soliton solution of one-component Bose–Einstein condensates without external potential, and it will be useful for the study of two-component Bose–Einstein condensates. (general)

  9. An efficient implementation of two-component relativistic exact-decoupling methods for large molecules

    CERN Document Server

    Peng, Daoling; Weigend, Florian; Reiher, Markus

    2013-01-01

    We present an efficient algorithm for one- and two-component relativistic exact-decoupling calculations. The spin-orbit coupling was taken into account for the evaluation of relativistically transformed Hamiltonian. The relativistic decoupling transformation has to be evaluated with primitive functions so that the construction of the relativistic one-electron Hamiltonian becomes the bottleneck of the whole calculation for large molecules. We apply our recently developed local DLU scheme [J. Chem. Phys. 136 (2012) 244108] to accelerate this step. With our new implementation two-component relativistic density functional calculations can be performed invoking the resolution-of-identity density-fitting approximation and (Abelian as well as non-Abelian) point group symmetries to accelerate both the exact-decoupling and the two-electron part. The capability of our implementation is illustrated at the example of silver clusters with up to 309 atoms, for which the cohesive energy is calculated and extrapolated to the...

  10. Error Propagation in Equations for Geochemical Modeling of Radiogenic Isotopes in Two-Component Mixing

    Indian Academy of Sciences (India)

    Surendra P Verma

    2000-03-01

    This paper presents error propagation equations for modeling of radiogenic isotopes during mixing of two components or end-members. These equations can be used to estimate errors on an isotopic ratio in the mixture of two components, as a function of the analytical errors or the total errors of geological field sampling and analytical errors. Two typical cases (``Small errors'' and ``Large errors'') are illustrated for mixing of Sr isotopes. Similar examples can be formulated for the other radiogenic isotopic ratios. Actual isotopic data for sediment and basalt samples from the Cocos plate are also included to further illustrate the use of these equations. The isotopic compositions of the predicted mixtures can be used to constrain the origin of magmas in the central part of the Mexican Volcanic Belt. These examples show the need of high quality experimental data for them to be useful in geochemical modeling of magmatic processes.

  11. Three-dimensional solitons in two-component Bose—Einstein condensates

    International Nuclear Information System (INIS)

    We investigate a kind of solitons in the two-component Bose—Einstein condensates with axisymmetric configurations in the R2 × S1 space. The corresponding topological structure is referred to as Hopfion. The spin texture differs from the conventional three-dimensional (3D) skyrmion and knot, which is characterized by two homotopy invariants. The stability of the Hopfion is verified numerically by evolving the Gross—Pitaevskii equations in imaginary time. (general)

  12. Quantum phase transition and engineering in two-component BEC in optical lattices

    OpenAIRE

    Wu, Yong-Shi

    2003-01-01

    In this paper we review recent progress in studying quantum phase transitions in one- and two-component Bose-Einstein condensates (BEC) in optical lattices. These phase transitions involve the emergence and disappearance of quantum coherence over whole optical lattice and of linear superposition of macroscopic quantum states. The latter may provide new means to engineer and to manipulate novel macroscopic quantum states and novel coherent atomic beams for quantum information processing, quant...

  13. Two-component model of the interaction of an interstellar cloud with surrounding hot plasma

    OpenAIRE

    Provornikova, E. A.; Izmodenov, V. V.; Lallement, R.

    2011-01-01

    We present a two-component gasdynamic model of an interstellar cloud embedded in a hot plasma. It is assumed that the cloud consists of atomic hydrogen gas, interstellar plasma is quasineutral. Hydrogen atoms and plasma protons interact through a charge exchange process. Magnetic felds and radiative processes are ignored in the model. The influence of heat conduction within plasma on the interaction between a cloud and plasma is studied. We consider the extreme case and assume that hot plasma...

  14. On the spin separation of algebraic two-component relativistic Hamiltonians

    International Nuclear Information System (INIS)

    The separation of the spin-free and spin-dependent terms of a given relativistic Hamiltonian is usually facilitated by the Dirac identity. However, this is no longer possible for the recently developed exact two-component relativistic Hamiltonians derived from the matrix representation of the Dirac equation in a kinetically balanced basis. This stems from the fact that the decoupling matrix does not have an explicit form. To resolve this formal difficulty, we first define the spin-dependent term as the difference between a two-component Hamiltonian corresponding to the full Dirac equation and its one-component counterpart corresponding to the spin-free Dirac equation. The series expansion of the spin-dependent term is then developed in two different ways. One is in the spirit of the Douglas-Kroll-Hess (DKH) transformation and the other is based on the perturbative expansion of a two-component Hamiltonian of fixed structure, either the two-step Barysz-Sadlej-Snijders (BSS) or the one-step exact two-component (X2C) form. The algorithms for constructing arbitrary order terms are proposed for both schemes and their convergence patterns are assessed numerically. Truncating the expansions to finite orders leads naturally to a sequence of novel spin-dependent Hamiltonians. In particular, the order-by-order distinctions among the DKH, BSS, and X2C approaches can nicely be revealed. The well-known Pauli, zeroth-order regular approximation, and DKH1 spin-dependent Hamiltonians can also be recovered naturally by appropriately approximating the decoupling and renormalization matrices. On the practical side, the sf-X2C+so-DKH3 Hamiltonian, together with appropriately constructed generally contracted basis sets, is most promising for accounting for relativistic effects in two steps, first spin-free and then spin-dependent, with the latter applied either perturbatively or variationally.

  15. Magnetic Richtmyer-Meshkov instability in a two-component Bose-Einstein condensate

    OpenAIRE

    Bezett, Alice; Bychkov, Vitaly; Lundh, Emil; Kobyakov, Dmitry; Marklund, Mattias

    2010-01-01

    The magnetically induced Richtmyer-Meshkov instability in a two-component Bose-Einstein condensate is investigated. We construct and study analytical models describing the development of the instability at both the linear and nonlinear stages. The models indicate new features of the instability: the influence of quantum capillary waves and the separation of droplets, which are qualitatively different from the classical case. We perform numerical simulations of the instability in a trapped Bos...

  16. Stability properties of vector solitons in two-component Bose—Einstein condensates with tunable interactions

    International Nuclear Information System (INIS)

    By using a unified theory of the formation of various types of vector-solitons in two-component Bose—Einstein condensates with tunable interactions, we obtain a family of exact vector-soliton solutions for the coupled nonlinear Schrödinger equations. Moreover, the Bogoliubov equation shows that there exists stable dark soliton in specific situations. Our results open up new ways in considerable experimental interest for the quantum control of multi-component Bose—Einstein condensates. (general)

  17. Composite structure of vortices in two-component Bose-Einstein condensate

    OpenAIRE

    Ivashin Anatoly P.; Poluektov Yuri M.

    2015-01-01

    In contrast to one-component Bose-Einstein condensate case, the vortices in two-component condensate can have various complicated structures. The vortices in a space-homogeneous Bose-Einstein condensate have been studied in this paper. It is shown that the vortex structure is described by three dimensionless parameters. This is totally different from the usual one-component condensate case,where an isolated vortex is described by a parameterless dimensionless equation....

  18. Ordinary Chondrite Formation from two Components: Implied Connection to Planet Mercury

    OpenAIRE

    Herndon, J. Marvin

    2004-01-01

    Major element fractionation among chondrites has been discussed for decades as ratios relative to Si or Mg. Expressing ratios relative to Fe leads to a new relationship admitting the possibility that ordinary chondrite meteorites are derived from two components: one is a relatively undifferentiated, primitive component, oxidized like the CI or C1 chondrites; the other is a somewhat differentiated, planetary component, with oxidation state like the reduced enstatite chondrites. Such a picture ...

  19. On the spin separation of algebraic two-component relativistic Hamiltonians.

    Science.gov (United States)

    Li, Zhendong; Xiao, Yunlong; Liu, Wenjian

    2012-10-21

    The separation of the spin-free and spin-dependent terms of a given relativistic Hamiltonian is usually facilitated by the Dirac identity. However, this is no longer possible for the recently developed exact two-component relativistic Hamiltonians derived from the matrix representation of the Dirac equation in a kinetically balanced basis. This stems from the fact that the decoupling matrix does not have an explicit form. To resolve this formal difficulty, we first define the spin-dependent term as the difference between a two-component Hamiltonian corresponding to the full Dirac equation and its one-component counterpart corresponding to the spin-free Dirac equation. The series expansion of the spin-dependent term is then developed in two different ways. One is in the spirit of the Douglas-Kroll-Hess (DKH) transformation and the other is based on the perturbative expansion of a two-component Hamiltonian of fixed structure, either the two-step Barysz-Sadlej-Snijders (BSS) or the one-step exact two-component (X2C) form. The algorithms for constructing arbitrary order terms are proposed for both schemes and their convergence patterns are assessed numerically. Truncating the expansions to finite orders leads naturally to a sequence of novel spin-dependent Hamiltonians. In particular, the order-by-order distinctions among the DKH, BSS, and X2C approaches can nicely be revealed. The well-known Pauli, zeroth-order regular approximation, and DKH1 spin-dependent Hamiltonians can also be recovered naturally by appropriately approximating the decoupling and renormalization matrices. On the practical side, the sf-X2C+so-DKH3 Hamiltonian, together with appropriately constructed generally contracted basis sets, is most promising for accounting for relativistic effects in two steps, first spin-free and then spin-dependent, with the latter applied either perturbatively or variationally. PMID:23083155

  20. A Possible Two-Component Structure of the Non-Perturbative Pomeron

    OpenAIRE

    Gauron, Pierre; Nicolescu, Basarab

    2000-01-01

    We propose a QCD-inspired two-component Pomeron form which gives an excellent description of the proton-proton, pi-proton, kaon-proton, gamma-proton and gamma-gamma total cross sections. Our fit has a better CHI2/dof for a smaller number of parameters as compared with the PDG fit. Our 2-Pomeron form is fully compatible with weak Regge exchange-degeneracy, universality, Regge factorization and the generalized vector dominance model.

  1. Analytic second derivatives for the spin-free exact two-component theory.

    Science.gov (United States)

    Cheng, Lan; Gauss, Jürgen

    2011-12-28

    The formulation and implementation of the spin-free (SF) exact two-component (X2c) theory at the one-electron level (SFX2c-1e) is extended in the present work to the analytic evaluation of second derivatives of the energy. In the X2c-1e scheme, the four-component one-electron Dirac Hamiltonian is block diagonalized in its matrix representation and the resulting "electrons-only" two-component Hamiltonian is then used together with untransformed two-electron interactions. The derivatives of the two-component Hamiltonian can thus be obtained by means of simple manipulations of the parent four-component Hamiltonian integrals and derivative integrals. The SF version of X2c-1e can furthermore exploit available nonrelativistic quantum-chemical codes in a straightforward manner. As a first application of analytic SFX2c-1e second derivatives, we report a systematic study of the equilibrium geometry and vibrational frequencies for the bent ground state of the copper hydroxide (CuOH) molecule. Scalar-relativistic, electron-correlation, and basis-set effects on these properties are carefully assessed. PMID:22225141

  2. Sub classification and targeted characterization of prophage-encoded two-component cell lysis cassette

    Indian Academy of Sciences (India)

    K V Srividhya; S Krishnaswamy

    2007-08-01

    Bacteriophage induced lysis of host bacterial cell is mediated by a two component cell lysis cassette comprised of holin and lysozyme. Prophages are integrated forms of bacteriophages in bacterial genomes providing a repertoire for bacterial evolution. Analysis using the prophage database (http://bicmku.in:8082) constructed by us showed 47 prophages were associated with putative two component cell lysis genes. These proteins cluster into four different subgroups. In this process, a putative holin (essd) and endolysin (ybcS), encoded by the defective lambdoid prophage DLP12 was found to be similar to two component cell lysis genes in functional bacteriophages like p21 and P1. The holin essd was found to have a characteristic dual start motif with two transmembrane regions and C-terminal charged residues as in class II holins. Expression of a fusion construct of essd in Escherichia coli showed slow growth. However, under appropriate conditions, this protein could be over expressed and purified for structure function studies. The second component of the cell lysis cassette, ybcS, was found to have an N-terminal SAR (Signal Arrest Release) transmembrane domain. The construct of ybcS has been over expressed in E. coli and the purified protein was functional, exhibiting lytic activity against E. coli and Salmonella typhi cell wall substrate. Such targeted sequence-structure-function characterization of proteins encoded by cryptic prophages will help understand the contribution of prophage proteins to bacterial evolution.

  3. Turbulent Burning Velocities of Two-Component Fuel Mixtures of Methane, Propane and Hydrogen

    Science.gov (United States)

    Kido, Hiroyuki; Nakahara, Masaya; Hashimoto, Jun; Barat, Dilmurat

    In order to clarify the turbulent burning velocity of multi-component fuel mixtures, both lean and rich two-component fuel mixtures, in which methane, propane and hydrogen were used as fuels, were prepared while maintaining the laminar burning velocity approximately constant. A distinct difference in the measured turbulent burning velocity at the same turbulence intensity is observed for two-component fuel mixtures having different addition rates of fuel, even the laminar burning velocities are approximately the same. The burning velocities of lean mixtures change almost constantly as the rate of addition changes, whereas the burning velocities of the rich mixtures show no such tendency. This trend can be explained qualitatively based on the mean local burning velocity, which is estimated by taking into account the preferential diffusion effect for each fuel component. In addition, a model of turbulent burning velocity proposed for single-component fuel mixtures may be applied to two-component fuel mixtures by considering the estimated mean local burning velocity of each fuel.

  4. Evaluation of the operational parameters for NBI-driven fusion in low-gain tokamaks with two-component plasma

    Science.gov (United States)

    Chirkov, A. Yu.

    2015-09-01

    Low gain (Q ~ 1) fusion plasma systems are of interest for concepts of fusion-fission hybrid reactors. Operational regimes of large modern tokamaks are close to Q  ≈  1. Therefore, they can be considered as prototypes of neutron sources for fusion-fission hybrids. Powerful neutral beam injection (NBI) can support the essential population of fast particles compared with the Maxwellial population. In such two-component plasma, fusion reaction rate is higher than for Maxwellian plasma. Increased reaction rate allows the development of relatively small-size and relatively inexpensive neutron sources. Possible operating regimes of the NBI-heated tokamak neutron source are discussed. In a relatively compact device, the predictions of physics of two-component fusion plasma have some volatility that causes taking into account variations of the operational parameters. Consequent parameter ranges are studied. The feasibility of regimes with Q  ≈  1 is shown for the relatively small and low-power system. The effect of NBI fraction in total heating power is analyzed.

  5. Localized nonlinear vector matter waves in two-component Bose–Einstein condensates with spatially modulated nonlinearities

    International Nuclear Information System (INIS)

    Exact localized nonlinear vector matter waves in the form of soliton–soliton and vortex–vortex pairs in two-component Bose–Einstein condensates with spatially modulated nonlinearity coefficients and harmonic trapping potentials are reported. It is shown that there exists an infinite number of exact vector pairs sharing the same chemical potential with soliton–soliton ones for odd integer n while vortex–vortex ones for even integer n. The stability of the vector pairs found is investigated by means of direct numerical simulations and a linear stability analysis; the results show that the stable vortex–vortex pairs (±l,±l) with large topological charges can be supported by the spatially modulated interaction when the harmonic trapping potential is presented in this system. -- Highlights: ► Exact localized nonlinear vector matter waves in two-component Bose–Einstein condensates with spatially modulated nonlinearities are reported. ► An infinite number of exact vector pairs sharing the same chemical potential are presented. ► The stable vortex–vortex pairs (±l,±l) with large topological charges can be supported in this system.

  6. Vortices in a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiao-Fei, E-mail: xfzhang@ntsc.ac.cn [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi’an 710600 (China); Du, Zhi-Jing [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi’an 710600 (China); Tan, Ren-Bing [Department of Physics, School of Mathematics and Physics, Chongqing University of Science and Technology, Chongqing 401331 (China); Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi’an 710600 (China)

    2014-07-15

    We consider a pair of coupled nonlinear Schrödinger equations modeling a rotating two-component Bose–Einstein condensate with tunable interactions and harmonic potential, with emphasis on the structure of vortex states by varying the strength of inter-component interaction, rotational frequency, and the aspect ratio of the harmonic potential. Our results show that the inter-component interaction greatly enhances the effect of rotation. For the case of isotropic harmonic potential and small inter-component interaction, the initial vortex structure remains unchanged. As the ratio of inter- to intra-component interactions increases, each component undergoes a transition from a vortex lattice (vortex line) in an isotropic (anisotropic) harmonic potential to an alternatively arranged stripe pattern, and eventually to the interwoven “serpentine” vortex sheets. Moreover, in the case of anisotropic harmonic potential the system can develop to a rotating droplet structure. -- Highlights: •Different vortex structures are obtained within the full parameter space. •Effects of system parameters on the ground state structure are discussed. •Phase transition between different vortex structures is also examined. •Present one possible way to obtain the rotating droplet structure. •Provide many possibilities to manipulate vortex in two-component BEC.

  7. Phase behaviour of two-component bottle-brush polymers with flexible backbones under poor solvent conditions

    International Nuclear Information System (INIS)

    The phase behaviour of two-component bottle-brush polymers with fully flexible backbones under poor solvent conditions is studied via molecular-dynamics simulations, using a coarse-grained bead-spring model and side chains of up to N = 40 effective monomers. We consider a symmetric model where side chains of type A and B are grafted alternately onto a flexible backbone. The aim of this study is to explore the phase behaviour of two-component bottle-brushes depending on parameters, such as as the grafting density σ, the backbone length Nb, the side-chain length N, and the temperature T. Based on a cluster analysis, we identify for our range of parameters the regimes of fully phase separated systems, i.e., A-type side chains form one cluster and B-type chains another, while the interface that separates these two clusters contains the backbone monomers. We find that pearl-necklace or Janus-like structures, which normally occur for bottle-brush polymers with rigid backbones under poor solvent conditions, are fully attributed to the backbone rigidity, and, therefore, such structures are unlikely in the case of bottle brushes with fully flexible backbones. Also, a comparative discussion with earlier work on the phase behaviour of single-component bottle-brush polymers with flexible backbones is performed. (paper)

  8. rgf Encodes a Novel Two-Component Signal Transduction System of Streptococcus agalactiae

    OpenAIRE

    Spellerberg, Barbara; Rozdzinski, Eva; Martin, Simone; Weber-Heynemann, Josefine; Lütticken, Rudolf

    2002-01-01

    The adhesion of gram-positive bacteria to extracellular matrix (ECM) proteins is regarded as an important determinant of pathogenicity. A comparison of the adhesion of Streptococcus agalactiae strain O90R to different ECM proteins showed that the most pronounced binding could be observed for immobilized fibrinogen. To investigate the genetic determinants of S. agalactiae fibrinogen binding, a pGhost9:ISS1 mutant library was screened for mutants displaying reduced agglutination of fibrinogen-c...

  9. Lipase expression in Pseudomonas alcaligenes is under the control of a two-component regulatory system

    NARCIS (Netherlands)

    Krzeslak, Joanna; Gerritse, Gijs; van Merkerk, Ronald; Cool, Robbert H.; Quax, Wim J.

    2008-01-01

    Preliminary observations in a large-scale fermentation process suggested that the lipase expression of Pseudomonas alcaligenes can be switched on by the addition of certain medium components, such as soybean oil. In an attempt to elucidate the mechanism of induction of lipase expression, we have set

  10. Regulation of Virulence by a Two-Component System in Group B Streptococcus†

    OpenAIRE

    Jiang, Sheng-Mei; Cieslewicz, Michael J.; Kasper, Dennis L.; Wessels, Michael R.

    2005-01-01

    Group B Streptococcus (GBS) is frequently carried in the gastrointestinal or genitourinary tract as a commensal organism, yet it has the potential to cause life-threatening infection in newborn infants, pregnant women, and individuals with chronic illness. Regulation of virulence factor expression may affect whether GBS behaves as an asymptomatic colonizer or an invasive pathogen, but little is known about how such factors are controlled in GBS. We now report the characterization of a GBS loc...

  11. Numerical simulation of two-component flow fluid - fluid in the microchannel T- type

    Directory of Open Access Journals (Sweden)

    Shebeleva A.A.

    2015-01-01

    Full Text Available Results of testing methodology for calculating two-phase flows based on the method of fluid in the cells (VOF method, and the procedure for CSF accounting of surface tension forces in the microchannel are considered in the work. Mathematical modeling of two-component flow fluid -fluid in the T- microchannel conducted using this methodology. The following flow regimes studied slug flow, rivulet flow, parallel flow, dispersed (droplet flow, plug flow. Comparison of numerical results with experimental data done. Satisfactory agreement between the calculated values with the experimental data obtained.

  12. Optimization and control of two-component radially self-accelerating beams

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, Christian; Eichelkraut, Toni; Ornigotti, Marco; Szameit, Alexander [Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Albert-Einstein-Str. 15, 07745 Jena (Germany)

    2015-11-23

    We report on the properties of radially self-accelerating intensity distributions consisting of two components in the angular frequency domain. We show how this subset of solutions, in literature also known as helicon beams, possesses peculiar characteristics that enable a better control over its properties. In this work, we present a step-by-step optimization procedure to achieve the best possible intensity contrast, a distinct rotation rate and long propagation lengths. All points are discussed on a theoretical basis and are experimentally verified.

  13. Anisotropic pair superfluidity of trapped two-component Bose gases in an optical lattice

    Science.gov (United States)

    Li, Yongqiang; He, Liang; Hofstetter, Walter

    2013-09-01

    We theoretically investigate the pair-superfluid phase of two-component ultracold gases with attractive inter-species interactions in an optical lattice. We establish the phase diagram for filling n = 1 at zero and finite temperatures, by applying bosonic dynamical mean-field theory, and observe stable pair-superfluid and charge-density wave quantum phases for asymmetric hopping of the two species. While the pair superfluid is found to be robust in the presence of a harmonic trap, we observe that it is destroyed already by a small population imbalance of the two species.

  14. Two-component model of strong Langmuir turbulence - Scalings, spectra, and statistics of Langmuir waves

    Science.gov (United States)

    Robinson, P. A.; Newman, D. L.

    1990-01-01

    A simple two-component model of strong turbulence that makes clear predictions for the scalings, spectra, and statistics of Langmuir waves is developed. Scalings of quantities such as energy density, power input, dissipation power wave collapse, and number density of collapsing objects are investigated in detail and found to agree well with model predictions. The nucleation model of wave-packet formation is strongly supported by the results. Nucleation proceeds with energy flowing from background to localized states even in the absence of a driver. Modulational instabilities play little or no role in maintaining the turbulent state when significant density nonuniformities are present.

  15. Three-wave interaction in two-component quadratic nonlinear lattices

    DEFF Research Database (Denmark)

    Konotop, V. V.; Cunha, M. D.; Christiansen, Peter Leth;

    1999-01-01

    We investigate a two-component lattice with a quadratic nonlinearity and find with the multiple scale technique that integrable three-wave interaction takes place between plane wave solutions when these fulfill resonance conditions. We demonstrate that. energy conversion and pulse propagation known...... from three-wave interaction is reproduced in the lattice and that exact phase matching of parametric processes can be obtained in non-phase-matched lattices by tilting the interacting plane waves with respect to each other. [S1063-651X(99)15110-9]....

  16. Investigation of the adhesion interface obtained through two-component injection molding

    Science.gov (United States)

    Fetecau, Catalin; Stan, Felicia; Dobrea, Daniel

    2011-01-01

    In this paper we study the interface strength obtained through two-component (2C) injection molding of LDPE-HDPE polymers. First, numerical simulation of the over-molding process is carried out using Moldflow technology. Second, butt-joint specimens were produced by over-molding under different process condition, and tested. Two injection sequences were considered, injection of LDPE on HDPE polymer, and HDLE on LDPE, respectively. To investigate the effects of the mold surface roughness on the polymers adhesion at interface, different inserts with different roughness are employed.

  17. Two-component vector solitons in defocusing Kerr-type media with spatially modulated nonlinearity

    International Nuclear Information System (INIS)

    We present a class of exact solutions to the coupled (2+1)-dimensional nonlinear Schrödinger equation with spatially modulated nonlinearity and a special external potential, which describe the evolution of two-component vector solitons in defocusing Kerr-type media. We find a robust soliton solution, constructed with the help of Whittaker functions. For specific choices of the topological charge, the radial mode number and the modulation depth, the solitons may exist in various forms, such as the half-moon, necklace-ring, and sawtooth vortex-ring patterns. Our results show that the profile of such solitons can be effectively controlled by the topological charge, the radial mode number, and the modulation depth. - Highlights: • Two-component vector soliton clusters in defocusing Kerr-type media are reported. • These soliton clusters are constructed with the help of Whittaker functions. • The half-moon, necklace-ring and vortex-ring patterns are found. • The profile of these solitons can be effectively controlled by three soliton parameters

  18. Two-component superconductivity. II. Copper oxide high-Tc superconductors

    International Nuclear Information System (INIS)

    A systematic relationship between the Cu-O-based high-Tc materials and a two-component theory is developed. The two components are mobile-single-particle states associated with Cu-O planes and localized paired (negative-U) states associated with oxygen vacancies. The focus is on identification of the relevant electronic states in theoretical calculations and experimental observations. The family of Cu-O-based materials is discussed and an understanding is developed of the implications of layering and dimensionality, oxygenation, and doping. The relationship to superconducting properties is developed through the pair-density dependence and single-particle-density dependence of superconductivity. Comparisons with existing experimental data are made, distinctive experimental results are predicted. New directions for finding high-Tc materials are suggested both within the Cu-O-based family and in the more general class of materials which share with the Cu-O-based family the structure of metal-semiconductor layering and can be formed with off-stoichiometric compositions

  19. Modeling and Simulation of Two-Phase Two-Component Flow with Disappearing Nonwetting Phase

    CERN Document Server

    Neumann, Rebecca; Ippisch, Olaf

    2012-01-01

    Carbon Capture and Storage (CCS) is a recently discussed new technology, aimed at allowing an ongoing use of fossil fuels while preventing the produced CO2 to be released to the atmosphere. CSS can be modeled with two components (water and CO2) in two phases (liquid and CO2). To simulate the process, a multiphase flow equation with equilibrium phase exchange is used. One of the big problems arising in two-phase two-component flow simulations is the disappearance of the nonwetting phase, which leads to a degeneration of the equations satisfied by the saturation. A standard choice of primary variables, which is the pressure of one phase and the saturation of the other phase, cannot be applied here. We developed a new approach using the pressure of the nonwetting phase and the capillary pressure as primary variables. One important advantage of this approach is the fact that we have only one set of primary variables that can be used for the biphasic as well as the monophasic case. We implemented this new choice o...

  20. Analytical energy gradient for the two-component normalized elimination of the small component method

    Science.gov (United States)

    Zou, Wenli; Filatov, Michael; Cremer, Dieter

    2015-06-01

    The analytical gradient for the two-component Normalized Elimination of the Small Component (2c-NESC) method is presented. The 2c-NESC is a Dirac-exact method that employs the exact two-component one-electron Hamiltonian and thus leads to exact Dirac spin-orbit (SO) splittings for one-electron atoms. For many-electron atoms and molecules, the effect of the two-electron SO interaction is modeled by a screened nucleus potential using effective nuclear charges as proposed by Boettger [Phys. Rev. B 62, 7809 (2000)]. The effect of spin-orbit coupling (SOC) on molecular geometries is analyzed utilizing the properties of the frontier orbitals and calculated SO couplings. It is shown that bond lengths can either be lengthened or shortened under the impact of SOC where in the first case the influence of low lying excited states with occupied antibonding orbitals plays a role and in the second case the jj-coupling between occupied antibonding and unoccupied bonding orbitals dominates. In general, the effect of SOC on bond lengths is relatively small (≤5% of the scalar relativistic changes in the bond length). However, large effects are found for van der Waals complexes Hg2 and Cn2, which are due to the admixture of more bonding character to the highest occupied spinors.

  1. An efficient implementation of two-component relativistic exact-decoupling methods for large molecules.

    Science.gov (United States)

    Peng, Daoling; Middendorf, Nils; Weigend, Florian; Reiher, Markus

    2013-05-14

    We present an efficient algorithm for one- and two-component relativistic exact-decoupling calculations. Spin-orbit coupling is thus taken into account for the evaluation of relativistically transformed (one-electron) Hamiltonian. As the relativistic decoupling transformation has to be evaluated with primitive functions, the construction of the relativistic one-electron Hamiltonian becomes the bottleneck of the whole calculation for large molecules. For the established exact-decoupling protocols, a minimal matrix operation count is established and discussed in detail. Furthermore, we apply our recently developed local DLU scheme [D. Peng and M. Reiher, J. Chem. Phys. 136, 244108 (2012)] to accelerate this step. With our new implementation two-component relativistic density functional calculations can be performed invoking the resolution-of-identity density-fitting approximation and (Abelian as well as non-Abelian) point group symmetry to accelerate both the exact-decoupling and the two-electron part. The capability of our implementation is illustrated at the example of silver clusters with up to 309 atoms, for which the cohesive energy is calculated and extrapolated to the bulk. PMID:23676027

  2. Two-component model of the interaction of an interstellar cloud with surrounding hot plasma

    CERN Document Server

    Provornikova, E A; Lallement, R

    2011-01-01

    We present a two-component gasdynamic model of an interstellar cloud embedded in a hot plasma. It is assumed that the cloud consists of atomic hydrogen gas, interstellar plasma is quasineutral. Hydrogen atoms and plasma protons interact through a charge exchange process. Magnetic felds and radiative processes are ignored in the model. The influence of heat conduction within plasma on the interaction between a cloud and plasma is studied. We consider the extreme case and assume that hot plasma electrons instantly heat the plasma in the interaction region and that plasma flow can be described as isothermal. Using the two-component model of the interaction of cold neutral cloud and hot plasma, we estimate the lifetime of interstellar clouds. We focus on the clouds typical for the cluster of local interstellar clouds embedded in the hot Local Bubble and give an estimate of the lifetime of the Local interstellar cloud where the Sun currently travels. The charge transfer between highly charged plasma ions and neutr...

  3. A theory of scintillation for two-component power law irregularity spectra: Overview and numerical results

    Science.gov (United States)

    Carrano, Charles S.; Rino, Charles L.

    2016-06-01

    We extend the power law phase screen theory for ionospheric scintillation to account for the case where the refractive index irregularities follow a two-component inverse power law spectrum. The two-component model includes, as special cases, an unmodified power law and a modified power law with spectral break that may assume the role of an outer scale, intermediate break scale, or inner scale. As such, it provides a framework for investigating the effects of a spectral break on the scintillation statistics. Using this spectral model, we solve the fourth moment equation governing intensity variations following propagation through two-dimensional field-aligned irregularities in the ionosphere. A specific normalization is invoked that exploits self-similar properties of the structure to achieve a universal scaling, such that different combinations of perturbation strength, propagation distance, and frequency produce the same results. The numerical algorithm is validated using new theoretical predictions for the behavior of the scintillation index and intensity correlation length under strong scatter conditions. A series of numerical experiments are conducted to investigate the morphologies of the intensity spectrum, scintillation index, and intensity correlation length as functions of the spectral indices and strength of scatter; retrieve phase screen parameters from intensity scintillation observations; explore the relative contributions to the scintillation due to large- and small-scale ionospheric structures; and quantify the conditions under which a general spectral break will influence the scintillation statistics.

  4. Numerical analysis of a non equilibrium two-component two-compressible flow in porous media

    KAUST Repository

    Saad, Bilal Mohammed

    2013-09-01

    We propose and analyze a finite volume scheme to simulate a non equilibrium two components (water and hydrogen) two phase flow (liquid and gas) model. In this model, the assumption of local mass non equilibrium is ensured and thus the velocity of the mass exchange between dissolved hydrogen and hydrogen in the gas phase is supposed finite. The proposed finite volume scheme is fully implicit in time together with a phase-by-phase upwind approach in space and it is discretize the equations in their general form with gravity and capillary terms We show that the proposed scheme satisfies the maximum principle for the saturation and the concentration of the dissolved hydrogen. We establish stability results on the velocity of each phase and on the discrete gradient of the concentration. We show the convergence of a subsequence to a weak solution of the continuous equations as the size of the discretization tends to zero. At our knowledge, this is the first convergence result of finite volume scheme in the case of two component two phase compressible flow in several space dimensions.

  5. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    International Nuclear Information System (INIS)

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ε parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ε and γ = βe2n1/3 (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ε and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of εcrit≈13(Tcrit*≈0.076),γcrit≈1.8(vcrit*≈0.17),Pcrit*≈0.39, where specific volume v* = 1/γ3 and reduced temperature T* = ε−1

  6. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    Science.gov (United States)

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1). PMID:25028031

  7. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model

    Energy Technology Data Exchange (ETDEWEB)

    Butlitsky, M. A.; Zelener, B. V. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Zelener, B. B. [Joint Institute for High Temperature of Russian Academy of Science, 125412, Russia, Moscow, Izhorskaya str. 13/2 (Russian Federation); Moscow Engineering Physics Institute, 115409, Russia, Moscow, Kashirskoe sh. 31 (Russian Federation)

    2014-07-14

    A two-component plasma model, which we called a “shelf Coulomb” model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The “shelf Coulomb” model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ε parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ε and γ = βe{sup 2}n{sup 1/3} (where β = 1/k{sub B}T, n is the particle's density, k{sub B} is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ε and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ε{sub crit}≈13(T{sub crit}{sup *}≈0.076),γ{sub crit}≈1.8(v{sub crit}{sup *}≈0.17),P{sub crit}{sup *}≈0.39, where specific volume v* = 1/γ{sup 3} and reduced temperature T{sup *} = ε{sup −1}.

  8. Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

    Science.gov (United States)

    Butlitsky, M A; Zelener, B B; Zelener, B V

    2014-07-14

    A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1).

  9. Differences in two-component signal transduction proteins among the genus Brucella: implications for host preference and pathogenesis

    DEFF Research Database (Denmark)

    Binnewies, Tim Terence; Ussery, David; Lavín, JL;

    2010-01-01

    Two-component systems (TCSs) are the predominant bacterial signal transduction mechanisms. Species of the genus Brucella are genetically highly related and differ mainly in mammalian host adaptation and pathogenesis. In this study, TCS proteins encoded in the available genome sequences of Brucella...... species have been identified using bioinformatic methods. All the Brucella species share an identical set of TCS proteins, and the number of TCS proteins in the closely related opportunistic human pathogen Ochrobactrum anthropi was higher than in Brucella species as expected from its lifestyle. O....... anthropi lacks orthologs of the Brucella TCSs NodVW, TceSR and TcfSR, suggesting that these TCS proteins could be necessary for the adaptation of Brucella as an intracellular pathogen. This genomic analysis revealed the presence of a differential distribution of TCS pseudogenes among Brucella species...

  10. Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive

    Institute of Scientific and Technical Information of China (English)

    JIAO Zhi-Yong; YU Zhao-Xian; YANG Xin-Jian

    2004-01-01

    In this paper, we have studied the atomic population difference and the atomic tunneling current of twocomponent Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose-Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of 10-10 ~ 10-9 second.

  11. A two component model describing nucleon structure functions in the low-x region

    Energy Technology Data Exchange (ETDEWEB)

    Bugaev, E.V. [Institute for Nuclear Research of the Russian Academy of Sciences, 7a, 60th October Anniversary prospect, Moscow 117312 (Russian Federation); Mangazeev, B.V. [Irkutsk State University, 1, Karl Marx Street, Irkutsk 664003 (Russian Federation)

    2009-12-15

    A two component model describing the electromagnetic nucleon structure functions in the low-x region, based on generalized vector dominance and color dipole approaches is briefly described. The model operates with the mesons of rho-family having the mass spectrum of the form m{sub n}{sup 2}=m{sub r}ho{sup 2}(1+2n) and takes into account the nondiagonal transitions in meson-nucleon scattering. The special cut-off factors are introduced in the model, to exclude the gamma-qq-bar-V transitions in the case of narrow qq-bar-pairs. For the color dipole part of the model the well known FKS-parameterization is used.

  12. Output Rate of Atomic Four-Wave Mixing in Two-Component Bose-Einstein Condensate

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Hua; LI Wei-Bing; PENG Ju-Cun

    2004-01-01

    In this letter, following the proposal of Heurich et al. [Phys. Rev. A63 (2001) 033605], we analyze and discuss output rate of atomic four-wave mixing in the two-component Bose-Einstein condensate under the condition of the steady state. The results show that the magnitude of the signal beam increases with the increase of the intensity of the probe beam, up to a saturated value, then it decreases as the probe beam increases. The influence of the interaction range on the signal beam is also predicted. In particular, it is worth while pointing out that in contrast to the previous solutions, our obtained analytical solutions are of very simple and explicit forms, which open the door for further investigating the related physical mechanisms.

  13. A two-component model for fitting light-curves of core-collapse supernovae

    CERN Document Server

    Nagy, Andrea P

    2016-01-01

    We present an improved version of a light curve model, which is able to estimate the physical properties of different types of core-collapse supernovae having double-peaked light curves, in a quick and efficient way. The model is based on a two-component configuration consisting of a dense, inner region and an extended, low-mass envelope. Using this configuration, we estimate the initial parameters of the progenitor via fitting the shape of the quasi-bolometric light curves of 10 SNe, including Type IIP and IIb events, with model light curves. In each case we compare the fitting results with available hydrodynamic calculations, and also match the derived expansion velocities with the observed ones. Furthermore, we also compare our calculations with hydrodynamic models derived by the SNEC code, and examine the uncertainties of the estimated physical parameters caused by the assumption of constant opacity and the inaccurate knowledge of the moment of explosion.

  14. Phase diagram of two-component bosons on an optical lattice

    Energy Technology Data Exchange (ETDEWEB)

    Altman, Ehud; Hofstetter, Walter; Demler, Eugene; Lukin, Mikhail D [Department of Physics, Harvard University, Cambridge, MA 02138 (United States)

    2003-09-01

    We present a theoretical analysis of the phase diagram of two-component bosons on an optical lattice. A new formalism is developed which treats the effective spin interactions in the Mott and superfluid phases on the same footing. Using this new approach we chart the phase boundaries of the broken spin symmetry states up to the Mott to superfluid transition and beyond. Near the transition point, the magnitude of spin exchange can be very large, which facilitates the experimental realization of spin-ordered states. We find that spin and quantum fluctuations have a dramatic effect on the transition, making it first order in extended regions of the phase diagram. When each species is at integer filling, an additional phase transition may occur, from a spin-ordered insulator to a Mott insulator with no broken symmetries. We determine the phase boundaries in this regime and show that this is essentially a Mott transition in the spin sector.

  15. Evidence of a two-component jet in the afterglow of GRB 070419A

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A two-component jet model is proposed to explain the unusual afterglow of GRB 070419A.Regarding the optical light curve,a wide "jet" with an opening angle of >30-40 degrees is assumed to produce the late shallow decay,while the three early power-law segments must be caused by a narrow jet with an opening angle of-2-4 degrees.Additional energy injections to both components are required.Late X-ray emission may come from either the wide jet or the narrow one.If the latter is correct,the jets may run into an ISM environment and the temporal index of the late energy injection may be q-0.65.

  16. Two-component mixture model: Application to palm oil and exchange rate

    Science.gov (United States)

    Phoong, Seuk-Yen; Ismail, Mohd Tahir; Hamzah, Firdaus Mohamad

    2014-12-01

    Palm oil is a seed crop which is widely adopt for food and non-food products such as cookie, vegetable oil, cosmetics, household products and others. Palm oil is majority growth in Malaysia and Indonesia. However, the demand for palm oil is getting growth and rapidly running out over the years. This phenomenal cause illegal logging of trees and destroy the natural habitat. Hence, the present paper investigates the relationship between exchange rate and palm oil price in Malaysia by using Maximum Likelihood Estimation via Newton-Raphson algorithm to fit a two components mixture model. Besides, this paper proposes a mixture of normal distribution to accommodate with asymmetry characteristics and platykurtic time series data.

  17. Energy Spectrum of Two-Component Bose-Einstein Condensates in Optical Lattices

    Institute of Scientific and Technical Information of China (English)

    HAN Jiu-Rong; LIU Jin-Ming; JING Hui; WANG Yu-Zhu

    2005-01-01

    With the method of Green's function, we investigate the energy spectra of two-component ultracold bosonic atoms in optical lattices. We find that there are two energy bands for each component. The critical condition of the superfluid-Mott insulator phase transition is determined by the energy band structure. We also find that the nearest neighboring and on-site interactions fail to change the structure of energy bands, but shift the energy bands only.According to the conditions of the phase transitions, three stable superfluid and Mott insulating phases can be found by adjusting the experiment parameters. We also discuss the possibility of observing these new phases and their transitions in further experiments.

  18. [Acute cholangitis in interstenosis space accompanied by two-component unit of the main bile duct].

    Science.gov (United States)

    Yurchenko, V V

    2016-02-01

    Palliative treatment of obstructive jaundice with the help of biliary endoprosthesis due to the possible complication of post-intervention in the form of insolvency stent deformation or dislocation. The study features in the postoperative period of the main bile duct endoprosthesis about their two-component unit, described the syndrome of the closed space of the bile ducts. On the basis of observation of 14 patients with the given anatomical feature of endoscopic, who were underwent stenting, was assessed frequency of the syndrome and possibilities of its prevention. Interstenosis space expansion of the main bile duct can be a reason for local cholangitis. For the prevention of cholangitis, it should be carried out a separate drainage of interstenosis space with the help of endoprosthesis or by proximal supra-stenotic extension of two or more stents. PMID:27263209

  19. Communication: Two-component ring-coupled-cluster computation of the correlation energy in the random-phase approximation

    Science.gov (United States)

    Krause, Katharina; Klopper, Wim

    2013-11-01

    Within the framework of density-functional theory, the correlation energy is computed in the random-phase approximation (RPA) using spinors obtained from a two-component relativistic Kohn-Sham calculation accounting for spin-orbit interactions. Ring-coupled-cluster equations are solved to obtain the two-component RPA correlation energy. Results are presented for the hydrides of the halogens Br, I, and At as well as of the coinage metals Cu, Ag, and Au, based on two-component relativistic exact-decoupling Kohn-Sham calculations.

  20. Calibration of the IRD two-component TLD albedo neutron dosemeter in some moderated neutron fields

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, Bruno M.; Silva, Ademir X. da, E-mail: bfreitas@nuclear.ufrj.br, E-mail: ademir@nuclear.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear; Martins, Marcelo M.; Pereira, Walsan W.; Mauricio, Claudia L.P., E-mail: marcelo@ird.gov.br, E-mail: walsan@ird.gov.br, E-mail: claudia@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    In some stray neutron fields, like those found in practices involving the handling of radionuclide sources, the neutron calibration factor for albedo neutron dosemeter can vary widely compared to the factor for bare sources. This is the case for well logging, which is the area with the largest number of workers exposed to neutrons in Brazil. The companies employ routinely {sup 241}Am-Be neutron sources. The albedo response variation is mainly due to the presence of scattered and moderated neutrons. This paper studies the response variation of the two-component TLD albedo neutron dosemeter used in the neutron individual monitoring service of Instituto de Radioprotecao e Dosimetria, in different radionuclide neutron source beams. The neutron spectra were evaluated applying a Bonner sphere spectrometer with a {sup 6}LiI(Eu) detector in the Brazilian National Metrology Neutron Laboratory. Standard neutron sources of {sup 241}Am-Be and {sup 252}Cf were employed, besides {sup 238}Pu-Be. Measurements were also made with scattered and moderated neutron beams, including {sup 252}Cf(D{sub 2}O) reference spectrum, {sup 241}Am-Be moderated with paraffin and silicone and a thermal neutron flux facility. New neutron calibration factors, as a function of the incident to albedo neutron ratio, were proposed for use in the albedo algorithm for occupational fields where the primary neutron beam is one of those studied sources. (author)

  1. A feasibility study of using two-component polyurethane adhesive in constructing wooden structures

    Institute of Scientific and Technical Information of China (English)

    Mohammad Derikvand; Ghanbar Ebrahimi; Mehdi Tajvidi

    2014-01-01

    This investigation was conducted to determine the feasibility of using a two-component polyurethane (PUR) adhesive, with special waterproof properties, in constructing wooden structures. We designed and conducted tests to compare the shear strength and adhesion per-formance of PUR with polyvinyl acetate (PVAc) adhesive on block-shear specimens constructed of oriental beech (Fagus orientalis L.), fir (Abies alba Mill.), poplar (Populus deltoides Bartr.), white oak (Quercus alba L.), sycamore (Platanus orientalis L.) and white walnut (Juglans cinerea L.). The values of the percentage of wood failure were also determined in specimens constructed with each adhesive. The highest shear strength values of both adhesives were obtained in specimens constructed of beech, while the lowest shear strength values were obtained in fir and poplar specimens. Average shear strength of the PUR adhesive was 16.5%higher than that of the PVAc adhesive. Specimens constructed of fir, poplar and sycamore were characterised by the highest percentages of wood failure, whereas the lowest average percentages of wood failure were obtained in beech and oak specimens. With the exception of oak specimens, there was no statistically significant difference between per-centage of wood failure among the PUR and PVAc adhesives. Generally, the PUR adhesive showed an acceptable adhesion performance on wood materials used in our study.

  2. Gradients for two-component quasirelativistic methods. Application to dihalogenides of element 116.

    Science.gov (United States)

    van Wüllen, Christoph; Langermann, Norbert

    2007-03-21

    The authors report the implementation of geometry gradients for quasirelativistic two-component Hartree-Fock and density functional methods using either the zero-order regular approximation Hamiltonian or spin-dependent effective core potentials. The computational effort of the resulting program is comparable to that of corresponding nonrelativistic calculations, as it is dominated by the evaluation of derivative two-electron integrals, which is the same for both types of calculations. Besides the implementation of derivatives of matrix elements of the one-particle Hamiltonian with respect to nuclear displacements, the calculation of the derivative exchange-correlation energy for the open shell case involves complicated expressions because of the noncollinear approach chosen to define the spin density. A pilot application to dihalogenides of element 116 shows how spin-orbit coupling strongly affects the chemistry of the superheavy p-block elements. While these molecules are bent at a scalar-relativistic level, spin-orbit coupling is so strong that only the 7p3/2 atomic orbitals of element 116 are involved in bonding, which favors linear molecular geometries for dihalogenides with heavy terminal halogen atoms. PMID:17381195

  3. Probing bilayer-cytoskeletal interactions in erythrocytes using a two-component dissipative particle dynamics model

    Science.gov (United States)

    Peng, Zhangli; Li, Xuejin; Pivkin, Igor; Dao, Ming; Karniadakis, George

    2013-11-01

    We develop a two-component dissipative particle dynamics (DPD) model of the red blood cell (RBC) membrane by modeling the lipid bilayer and the cytoskeleton separately. By applying this model to simulate four different experiments on RBCs, including micropipette aspiration, membrane fluctuations, tank-treading motions in shear flow and bilayer tethering in a flow channel, we validated our model and studied the mechanical properties of the bilayer-cytoskeletal interaction in a systematic and controlled manner, such as its elastic stiffness, viscous friction and strength. In the same time, we also resolved several controversies in RBC mechanics, e.g., the dependence of tank-treading frequency on shear rates and the possibility of bilayer-cytoskeletal slip. Furthermore, to investigate RBC dynamics in the microcirculation, we simulated the passages of RBCs through narrow channels of the flow cytometer in vitro and their passages through the splenic inter-endothelial slits in vivo. The effects of RBC geometry and membrane stiffness on the critical pressure gradient of passage were studied, and the simulation results agree well with experimental measurements. This work was supported by National Institutes of Health Grant R01HL094270 and the new Department of Energy Collaboratory on Mathematics for Mesoscopic Modeling of Materials (CM4).

  4. The two-component model of memory development, and its potential implications for educational settings.

    Science.gov (United States)

    Sander, Myriam C; Werkle-Bergner, Markus; Gerjets, Peter; Shing, Yee Lee; Lindenberger, Ulman

    2012-02-15

    We recently introduced a two-component model of the mechanisms underlying age differences in memory functioning across the lifespan. According to this model, memory performance is based on associative and strategic components. The associative component is relatively mature by middle childhood, whereas the strategic component shows a maturational lag and continues to develop until young adulthood. Focusing on work from our own lab, we review studies from the domains of episodic and working memory informed by this model, and discuss their potential implications for educational settings. The episodic memory studies uncover the latent potential of the associative component in childhood by documenting children's ability to greatly improve their memory performance following mnemonic instruction and training. The studies on working memory also point to an immature strategic component in children whose operation is enhanced under supportive conditions. Educational settings may aim at fostering the interplay between associative and strategic components. We explore possible routes towards this goal by linking our findings to recent trends in research on instructional design. PMID:22682913

  5. Accurate design of megadalton-scale two-component icosahedral protein complexes.

    Science.gov (United States)

    Bale, Jacob B; Gonen, Shane; Liu, Yuxi; Sheffler, William; Ellis, Daniel; Thomas, Chantz; Cascio, Duilio; Yeates, Todd O; Gonen, Tamir; King, Neil P; Baker, David

    2016-07-22

    Nature provides many examples of self- and co-assembling protein-based molecular machines, including icosahedral protein cages that serve as scaffolds, enzymes, and compartments for essential biochemical reactions and icosahedral virus capsids, which encapsidate and protect viral genomes and mediate entry into host cells. Inspired by these natural materials, we report the computational design and experimental characterization of co-assembling, two-component, 120-subunit icosahedral protein nanostructures with molecular weights (1.8 to 2.8 megadaltons) and dimensions (24 to 40 nanometers in diameter) comparable to those of small viral capsids. Electron microscopy, small-angle x-ray scattering, and x-ray crystallography show that 10 designs spanning three distinct icosahedral architectures form materials closely matching the design models. In vitro assembly of icosahedral complexes from independently purified components occurs rapidly, at rates comparable to those of viral capsids, and enables controlled packaging of molecular cargo through charge complementarity. The ability to design megadalton-scale materials with atomic-level accuracy and controllable assembly opens the door to a new generation of genetically programmable protein-based molecular machines. PMID:27463675

  6. Analysis of water hammer in two-component two-phase flows

    International Nuclear Information System (INIS)

    The water hammer phenomena caused by a sudden valve closure in air-water two-phase flows must be clarified for the safety analysis of LOCA in reactors and further for the safety of boilers, chemical plants, pipe transport of fluids such as petroleum and natural gas. In the present paper water hammer phenomena caused by a sudden valve closure in two-component two-phase flow are investigated theoretically and experimentally. The phenomena are more complicated that in single phase-flow due to the fact of the presence of compressible component. Basic partial differential equations based on a one-dimensional homogeneous flow model are solved by the method of characteristic. The analysis is extended to include friction in a two-phase mixture depending on the local flow pattern. The profiles of the pressure transients, the propagation velocity of pressure waves and the effect of valve closure on the transient pressure are found. Different two-phase flow pattern and frictional pressure drop correlations were used including Baker, Chesholm and Beggs ampersand Bril correlations

  7. On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties

    International Nuclear Information System (INIS)

    The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α2 in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the O(α2) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections

  8. The Formation of Bulges, Discs and Two Component Galaxies in the CANDELS Survey at z < 3

    CERN Document Server

    Margalef-Bentabol, Berta; Mortlock, Alice; Hartley, Will; Duncan, Kenneth; Ferguson, Harry C; Koekemoer, Anton M; Dekel, Avishai; Primack, Joel R

    2016-01-01

    We examine a sample of 1495 galaxies in the CANDELS fields to determine the evolution of two component galaxies, including bulges and discs, within massive galaxies at the epoch 1 < z < 3 when the Hubble sequence forms. We fit all of our galaxies' light profiles with a single S\\'ersic fit, as well as with a combination of exponential and S\\'ersic profiles. The latter is done in order to describe a galaxy with an inner and an outer component, or bulge and disc component. We develop and use three classification methods (visual, F-test and the RFF) to separate our sample into 1-component galaxies (disc/spheroids-like galaxies) and 2-component galaxies (galaxies formed by an 'inner part' or bulge and an 'outer part' or disc). We then compare the results from using these three different ways to classify our galaxies. We find that the fraction of galaxies selected as 2-component galaxies increases on average 50 per cent from the lowest mass bin to the most massive galaxies, and decreases with redshift by a fa...

  9. Modified Baryonic Dynamics: two-component cosmological simulations with light sterile neutrinos

    Energy Technology Data Exchange (ETDEWEB)

    Angus, G.W.; Gentile, G. [Department of Physics and Astrophysics, Vrije Universiteit Brussel, Pleinlaan 2, Brussels, 1050 Belgium (Belgium); Diaferio, A. [Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, Torino, I-10125 Italy (Italy); Famaey, B. [Observatoire astronomique de Strasbourg, CNRS UMR 7550, Université de Strasbourg, 11 rue de l' Université, Strasbourg, F-67000 France (France); Heyden, K.J. van der, E-mail: garry.angus@vub.ac.be, E-mail: diaferio@ph.unito.it, E-mail: benoit.famaey@astro.unistra.fr, E-mail: gianfranco.gentile@ugent.be, E-mail: heyden@ast.uct.ac.za [Astrophysics, Cosmology and Gravity Centre, Dept. of Astronomy, University of Cape Town, Private Bag X3, Rondebosch, 7701 South Africa (South Africa)

    2014-10-01

    In this article we continue to test cosmological models centred on Modified Newtonian Dynamics (MOND) with light sterile neutrinos, which could in principle be a way to solve the fine-tuning problems of the standard model on galaxy scales while preserving successful predictions on larger scales. Due to previous failures of the simple MOND cosmological model, here we test a speculative model where the modified gravitational field is produced only by the baryons and the sterile neutrinos produce a purely Newtonian field (hence Modified Baryonic Dynamics). We use two-component cosmological simulations to separate the baryonic N-body particles from the sterile neutrino ones. The premise is to attenuate the over-production of massive galaxy cluster halos which were prevalent in the original MOND plus light sterile neutrinos scenario. Theoretical issues with such a formulation notwithstanding, the Modified Baryonic Dynamics model fails to produce the correct amplitude for the galaxy cluster mass function for any reasonable value of the primordial power spectrum normalisation.

  10. Devil's crevasse and macroscopic entanglement in two-component Bose-Einstein condensates

    CERN Document Server

    Byrnes, Tim

    2013-01-01

    Spin coherent states are the matter equivalent of optical coherent states, where a large number of two component particles form a macroscopic state displaying quantum coherence. Here we give a detailed study of entanglement generated between two spin-1/2 BECs due to an Sz1 Sz2 interaction. The states that are generated show a remarkably rich structure showing fractal characteristics. In the limit of large particle number N, the entanglement shows a strong dependence upon whether the entangling gate times are a rational or irrational multiple of pi/4. We discuss the robustness of various states under decoherence and show that despite the large number of particles in a typical BEC, entanglement on a macroscopic scale should be observable as long as the gate times are less than hbar/J sqrt[N], where J is the effective BEC-BEC coupling energy. Such states are anticipated to be useful for various quantum information applications such as quantum teleportation and quantum algorithms.

  11. Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps.

    Science.gov (United States)

    Zhang, Xiao-Fei; Han, Wei; Wen, Lin; Zhang, Peng; Dong, Rui-Fang; Chang, Hong; Zhang, Shou-Gang

    2015-01-01

    Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is found that various ground-state phases and the related vortex structures, such as polygonal vortex clusters and vortex necklaces, can be obtained via a proper choice of the dipolar interaction and rotational frequency. Finally, we also study and discuss the formation process of such vortex structures. PMID:25731962

  12. A principle of corresponding states for two-component, self-gravitating fluids

    CERN Document Server

    Caimmi, R

    2009-01-01

    Macrogases are defined as two-component, large-scale celestial objects where the subsystems interact only via gravitation. The macrogas equation of state is formulated and compared to the van der Waals equation of state for ordinary gases. By analogy, it is assumed that real macroisothermal curves in macrogases occur as real isothermal curves in ordinary gases, where a phase transition takes place along a horisontal line in the macrovolume-macropressure (Mv-Mp) plane. A simple guidance case and two density profiles which satisfactorily fit to observations or simulations, are studied in detail. For sufficiently steep density profiles, a critical macroisothermal curve exists as shown by ordinary gases, where the critical point coincides with the horisontal inflexion point. By analogy with ordinary gases, the first quadrant of the (Mv-Mp) plane may be divided into three parts, namely (i) the G region, where only gas exists; (ii) the S region, where only stars exist; (iii) the GS region, where both gas and stars ...

  13. Competing interactions in population-imbalanced two-component Bose-Einstein condensates

    Science.gov (United States)

    Galteland, Peder Notto; Sudbø, Asle

    2016-08-01

    We consider a two-component Bose-Einstein condensate with and without synthetic "spin-orbit" interactions in two dimensions. Density and phase fluctuations of the condensate are included, allowing us to study the impact of thermal fluctuations and density-density interactions on the physics originating with spin-orbit interactions. In the absence of spin-orbit interactions, we find that intercomponent density interactions deplete the minority condensate. The thermally driven phase transition is driven by coupled density and phase-fluctuations, but is nevertheless shown to be a phase-transition in the Kosterlitz-Thouless universality class with close to universal amplitude ratios irrespective of whether both the minority- and majority condensates exist in the ground state, or only one condensate exists. In the presence of spin-orbit interactions we observe three separate phases, depending on the strength of the spin-orbit coupling and intercomponent density-density interactions: a phase-modulated phase with uniform amplitudes for small intercomponent interactions, a completely imbalanced, effectively single-component condensate for intermediate spin-orbit coupling strength and sufficiently large intercomponent interactions, and a phase-modulated and amplitude-modulated phase for sufficiently large values of both the spin-orbit coupling and the intercomponent density-density interactions. The phase that is modulated by a single q -vector only is observed to transition into an isotropic liquid through a strong depinning transition with periodic boundary conditions, which weakens with open boundaries.

  14. Effects of external magnetic trap on two dark solitons of a two-component Bose-Einstein condensate

    Institute of Scientific and Technical Information of China (English)

    Hong Li; D. N. Wang

    2008-01-01

    Two dark solitons are considered in a two-component Bose-Einstein condensate with an external magnetic trap, and effects of the trap potential on their dynamics are investigated by the numerical simulation. The results show that the dark solitons attract, collide and repel periodically in two components as time changes, the time period depends strictly on the initial condition and the potential, and there are obvious self-trapping effects on the two dark solitons.

  15. Beats and expansion of two-component Bose–Einstein condensates in the Thomas–Fermi limit

    International Nuclear Information System (INIS)

    A unique feature of multi-component Bose–Einstein condensates (BECs) is the possibility of beating frequencies in collective oscillations. We analytically determine this beating frequency for the two-component BEC in one-dimension. We also show that the Thomas–Fermi approximation, where the quantum pressure is neglected, describes well the expansion of the two-component condensate released from an harmonic trap. (paper)

  16. Phase separation and near-critical fluctuations in two-component lipid membranes: Monte Carlo simulations on experimentally relevant scales

    Science.gov (United States)

    Ehrig, Jens; Petrov, Eugene P.; Schwille, Petra

    2011-04-01

    By means of lattice-based Monte Carlo simulations, we address the properties of two-component lipid membranes on the experimentally relevant spatial scales of the order of a micrometer and time intervals of the order of 1 s, using DMPC/DSPC lipid mixtures as a model system. Our large-scale simulations allowed us to obtain important results not reported previously in simulation studies of lipid membranes. We find that, for a certain range of lipid compositions, the phase transition from the fluid phase to the fluid-gel phase coexistence proceeds via near-critical fluctuations, whereas for other lipid compositions this phase transition has a quasi-abrupt character. In the presence of near-critical fluctuations, transient subdiffusion of lipid molecules is observed. These features of the system are stable with respect to perturbations in lipid interaction parameters used in our simulations. The line tension characterizing lipid domains in the fluid-gel coexistence region is found to be in the pN range. On approaching the critical point, the line tension, the inverse correlation length of fluid-gel spatial fluctuations and the corresponding inverse order parameter susceptibility of the membrane vanish. All these results are in agreement with recent experimental findings for model lipid membranes. Our analysis of the domain coarsening dynamics after an abrupt quench of the membrane to the fluid-gel coexistence region reveals that lateral diffusion of lipids plays an important role in the fluid-gel phase separation process.

  17. Analysis of water hammer in two-component two-phase flows

    International Nuclear Information System (INIS)

    The water hammer phenomena caused by a sudden valve closure in air-water two-phase flows must be clarified for the safety analysis of LOCA in reactors and further for the safety of boilers, chemical plants, pipe transport of fluids such as petroleum and natural gas. In the present work water hammer phenomena caused by sudden valve closure in two-component two-phase flows are investigated theoretically and experimentally. The phenomena are more complicated than in single phase-flows due to the fact of the presence of compressible component. Basic partial differential equations based on a one-dimensional homogeneous flow model are solved by the method of characteristic. The analysis is extended to include friction in a two-phase mixture depending on the local flow pattern. The profiles of the pressure transients, the propagation velocity of pressure waves and the effect of valve closure on the transient pressure are found. Different two-phase flow pattern and frictional pressure drop correlations were used including Baker, Chesholm and Beggs and Bril correlations. The effect of the flow pattern on the characteristic of wave propagation is discussed primarily to indicate the effect of void fraction on the velocity of wave propagation and on the attenuation of pressure waves. Transient pressure in the mixture were recorded at different air void fractions, rates of uniform valve closure and liquid flow velocities with the aid of pressure transducers, transient wave form recorders interfaced with an on-line pc computer. The results are compared with computation, and good agreement was obtained within experimental accuracy

  18. Large-scale Models Reveal the Two-component Mechanics of Striated Muscle

    Directory of Open Access Journals (Sweden)

    Robert Jarosch

    2008-12-01

    Full Text Available This paper provides a comprehensive explanation of striated muscle mechanics and contraction on the basis of filament rotations. Helical proteins, particularly the coiled-coils of tropomyosin, myosin and α-actinin, shorten their H-bonds cooperatively and produce torque and filament rotations when the Coulombic net-charge repulsion of their highly charged side-chains is diminished by interaction with ions. The classical “two-component model” of active muscle differentiated a “contractile component” which stretches the “series elastic component” during force production. The contractile components are the helically shaped thin filaments of muscle that shorten the sarcomeres by clockwise drilling into the myosin cross-bridges with torque decrease (= force-deficit. Muscle stretch means drawing out the thin filament helices off the cross-bridges under passive counterclockwise rotation with torque increase (= stretch activation. Since each thin filament is anchored by four elastic α-actinin Z-filaments (provided with forceregulating sites for Ca2+ binding, the thin filament rotations change the torsional twist of the four Z-filaments as the “series elastic components”. Large scale models simulate the changes of structure and force in the Z-band by the different Z-filament twisting stages A, B, C, D, E, F and G. Stage D corresponds to the isometric state. The basic phenomena of muscle physiology, i. e. latency relaxation, Fenn-effect, the force-velocity relation, the length-tension relation, unexplained energy, shortening heat, the Huxley-Simmons phases, etc. are explained and interpreted with the help of the model experiments.

  19. Characterization of GX 339-4 outburst of 2010-11: analysis by XSPEC using two component advective flow model

    Science.gov (United States)

    Debnath, Dipak; Mondal, Santanu; Chakrabarti, Sandip K.

    2015-02-01

    We study spectral properties of GX 339-4 during its 2010-11 outburst with two component advective flow (TCAF) model after its inclusion in XSPEC as a table model. We compare results fitted by TCAF model with combined disc blackbody and power-law model. For a spectral fit, we use 2.5-25 keV spectral data of the Proportional Counter Array instrument onboard RXTE satellite. From our fit, accretion flow parameters such as Keplerian (disc) rate, sub-Keplerian (halo) rate, location and strength of shock are extracted. We quantify how the disc and the halo rates vary during the entire outburst. We study how the halo to disc accretion rate ratio (ARR), quasi-periodic oscillations (QPOs), shock locations and its strength vary when the system passes through hard, hard-intermediate, soft-intermediate and soft states. We find pieces of evidence of monotonically increasing and decreasing nature of QPO frequencies depending on the variation of ARR during rising and declining phases. Interestingly, on days of transition from hard state to hard-intermediate spectral state (during the rising phase) or vice-versa (during decline phase), ARR is observed to be locally maximum. Non-constancy of ARR while obtaining reasonable fits points to the presence of two independent components in the flow.

  20. Laplace-transformed atomic orbital-based Møller-Plesset perturbation theory for relativistic two-component Hamiltonians

    Science.gov (United States)

    Helmich-Paris, Benjamin; Repisky, Michal; Visscher, Lucas

    2016-07-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order Møller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy contributions, which show the same long-range decay with the inter-electronic/atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the proper distance behavior is introduced to the quaternion Schwarz-type estimates as for non-relativistic MP2.

  1. Phase separation and near-critical fluctuations in two-component lipid membranes: Monte Carlo simulations on experimentally relevant scales

    CERN Document Server

    Ehrig, Jens; Schwille, Petra

    2010-01-01

    By means of lattice-based Monte Carlo simulations, we address properties of two-component lipid membranes on the experimentally relevant spatial scales of order of a micrometer and time intervals of order of a second, using DMPC/DSPC lipid mixtures as a model system. Our large-scale simulations allowed us to obtain important results previously not reported in simulation studies of lipid membranes. We find that, within a certain range of lipid compositions, the phase transition from the fluid phase to the fluid-gel phase coexistence proceeds via near-critical fluctuations, while for other lipid compositions this phase transition has a quasi-abrupt character. The line tension characterizing lipid domains in the fluid-gel coexistence region is found to be ~2 pN. When approaching the critical point, the line tension, the inverse correlation length of fluid-gel spatial fluctuations, and the corresponding inverse order parameter susceptibility of the membrane vanish. All these results are in agreement with recent e...

  2. Laplace-transformed atomic orbital-based M{\\o}ller-Plesset perturbation theory for relativistic two-component Hamiltonians

    CERN Document Server

    Helmich-Paris, Benjamin; Visscher, Lucas

    2016-01-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order M{\\o}ller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy con- tributions, which show the same long-range decay with the inter-electronic / atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the pro...

  3. MECHANICAL RELAXATION TIME OF A TWO-COMPONENT EPOXY NETWORK-LiClO4 POLYMER ELECTROLYTE

    Institute of Scientific and Technical Information of China (English)

    PENG Xinsheng; WU Shuyun; CHEN Donglin

    1993-01-01

    The mechanical relaxation time of a two-component epoxy network-LiClO4 system as a polymer electrolyte was investigated.The network is composed of diglycidyl ether of polyethylene glycol (DGEPEG) and triglycidyl ether of glycerol (TGEG),wherein LiClO4 was incorporated and acts as both the ionic carrier and the curing catalyst.As the relaxation time is informative to the segmental mobility,which is known to be essential for ionic conductivity,the average relaxation times of the specimens were determined through master curve construction.Experimental results showed that the salt concentration,molecular weight of PEG in DGEPEG and DGEPEG/TGEG ratio have profound effect on the relaxation time of the specimen.Among these factors,the former reinforces the network hains,leading to lengthen the relaxation time,whereas the latter two are in favour of the chain flexibility and show an opposite effect.The findings was rationalized in terms of the free volume concept.

  4. Laplace-transformed atomic orbital-based Møller-Plesset perturbation theory for relativistic two-component Hamiltonians.

    Science.gov (United States)

    Helmich-Paris, Benjamin; Repisky, Michal; Visscher, Lucas

    2016-07-01

    We present a formulation of Laplace-transformed atomic orbital-based second-order Møller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy contributions, which show the same long-range decay with the inter-electronic/atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the proper distance behavior is introduced to the quaternion Schwarz-type estimates as for non-relativistic MP2. PMID:27394099

  5. 454 Transcriptome sequencing suggests a role for two-component signalling in cellularization and differentiation of barley endosperm transfer cells.

    Directory of Open Access Journals (Sweden)

    Johannes Thiel

    Full Text Available BACKGROUND: Cell specification and differentiation in the endosperm of cereals starts at the maternal-filial boundary and generates the endosperm transfer cells (ETCs. Besides the importance in assimilate transfer, ETCs are proposed to play an essential role in the regulation of endosperm differentiation by affecting development of proximate endosperm tissues. We attempted to identify signalling elements involved in early endosperm differentiation by using a combination of laser-assisted microdissection and 454 transcriptome sequencing. PRINCIPAL FINDINGS: 454 sequencing of the differentiating ETC region from the syncytial state until functionality in transfer processes captured a high proportion of novel transcripts which are not available in existing barley EST databases. Intriguingly, the ETC-transcriptome showed a high abundance of elements of the two-component signalling (TCS system suggesting an outstanding role in ETC differentiation. All components and subfamilies of the TCS, including distinct kinds of membrane-bound receptors, have been identified to be expressed in ETCs. The TCS system represents an ancient signal transduction system firstly discovered in bacteria and has previously been shown to be co-opted by eukaryotes, like fungi and plants, whereas in animals and humans this signalling route does not exist. Transcript profiling of TCS elements by qRT-PCR suggested pivotal roles for specific phosphorelays activated in a coordinated time flow during ETC cellularization and differentiation. ETC-specificity of transcriptionally activated TCS phosphorelays was assessed for early differentiation and cellularization contrasting to an extension of expression to other grain tissues at the beginning of ETC maturation. Features of candidate genes of distinct phosphorelays and transcriptional activation of genes putatively implicated in hormone signalling pathways hint at a crosstalk of hormonal influences, putatively ABA and ethylene, and

  6. Atomic resolution imaging of the two-component Dirac-Landau levels in a gapped graphene monolayer

    Science.gov (United States)

    Wang, Wen-Xiao; Yin, Long-Jing; Qiao, Jia-Bin; Cai, Tuocheng; Li, Si-Yu; Dou, Rui-Fen; Nie, Jia-Cai; Wu, Xiaosong; He, Lin

    2015-10-01

    The wave function of Dirac fermions is a two-component spinor. In graphene, a one-atom-thick film showing two-dimensional Dirac-like electronic excitations, the two-component representation, reflects the amplitude of the electron wave function on the A and B sublattices. This unique property provides unprecedented opportunities to image the two components of Dirac fermions spatially. Here, we report atomic resolution imaging of two-component Dirac-Landau levels in gapped graphene monolayers by scanning tunneling microscopy and spectroscopy. A gap of about 20 meV, driven by inversion symmetry breaking by the substrate potential, is observed in the graphene sheets on both SiC and graphite substrates. Such a gap splits the n =0 Landau level (LL) into two levels, 0+ and 0-. We demonstrate that the amplitude of the wave function of the 0+ LL is mainly on the A sites and that of the 0- LL is mainly on the B sites of graphene, characterizing the internal structure of the spinor of the n =0 LL. This provides direct evidence of the two-component nature of Dirac fermions.

  7. Mixing process by molecular diffusion and natural circulation of two component gases in a reversed U-shaped channel

    International Nuclear Information System (INIS)

    This study is to investigate an effect of natural convection (or natural circulation) on a mixing process by molecular diffusion in a reverse U-shaped channel consisting of two component gases. It is confirmed that these phenomena appear when the depressurization accident occurs in the very high temperature reactor (VHTR). The experiment has been performed regarding the combined phenomena of molecular diffusion and natural circulation in a two parallel vertical slots filled with two component gases. The experimental results show that the transport phenomena by the molecular diffusion are influenced by the natural circulation of the gas mixture in the reverse U-shaped channel. (author)

  8. Experimental investigation of the factors influencing the polymer-polymer bond strength during two component injection moulding

    DEFF Research Database (Denmark)

    Islam, Mohammad Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben

    2007-01-01

    effectively control the adhesion between two polymers. The effects of environmental conditions on the bond strength after moulding are also investigated. The material selections and environmental conditions were chosen based on the suitability of MID production, but the results and discussion presented in......Two component injection moulding is a commercially important manufacturing process and a key technology for Moulded Interconnect Devices (MIDs). Many fascinating applications of two component or multi component polymer parts are restricted due to the weak interfacial adhesion of the polymers. A...

  9. A Principle of Corresponding States for Two-Component, Self-Gravitating Fluids

    Directory of Open Access Journals (Sweden)

    Caimmi, R.

    2010-06-01

    Full Text Available Macrogases are defined as two-component,large-scale celestial objects where the subsystems interact only via gravitation.The macrogas equation of state is formulated and compared to the van der Waals (VDWequation of state for ordinary gases.By analogy, it is assumed that real macroisothermal curves in macrogases occur as real isothermal curves in ordinary gases, where a phase transition(vapour-liquid observed in ordinary gases and gas-stars assumed in macrogases takesplace along a horizontal linein the macrovolume-macropressure{small $({sf O}sX_mathrm{V}sX_mathrm{p}$} plane.The intersections between real and theoretical(deduced from the equation of state macro isothermalcurves, make two regions of equal surface as for ordinary gases obeying the VDW equation of state.A numerical algorithm is developed for determining the following points of a selected theoretical macroisothermal curve on the {small $({sf O}sX_mathrm{V}sX_mathrm{p}$} plane:the three intersections with the related real macroisothermal curve,and the two extremum points (one maximum and one minimum. Different kinds of macrogases are studied in detail: UU, where U density profiles are flat, to be conceived as a simple guidance case; HH, where H density profiles obey the Hernquist (1990 law, which satisfactorily fits the observed spheroidal components of galaxies; HN/NH, where N density profiles obey the Navarro-Frenk-White (1995,1996, 1997 law, which satisfactorily fits the simulated nonbaryonic dark matter haloes.A different trend is shown by theoretical macroisothermal curves on the{small $({sf O}sX_mathrm{V}sX_mathrm{p}$} plane,according to whether density profiles are sufficiently mild (UU or sufficiently steep (HH, HN/NH.In the former alternative, no critical macroisothermal curve exists, below or above which the trend is monotonous. In the latter alternative, a critical macroisothermal curve exists, as shown by VDW gases, where the critical point may be defined as the horizontal

  10. Experimental investigation of the factors influencing the polymer-polymer bond strength during two-component injection moulding

    DEFF Research Database (Denmark)

    Islam, Aminul; Hansen, Hans Nørgaard; Bondo, Martin

    2010-01-01

    Two-component injection moulding is a commercially important manufacturing process and a key technology for combining different material properties in a single plastic product. It is also one of most industrially adaptive process chain for manufacturing so-called moulded interconnect devices (MID...

  11. Rebrightening of XRF 030723: further evidence for a two-component jet in gamma-ray burst

    CERN Document Server

    Huang, Y F; Dai, Z G; Ma, H T; Lu, T

    2004-01-01

    Optical afterglows from two-component jets under various configurations are investigated numerically. Generally, the light curve is characterized by a rapid rebrightening when the observer is off-axis with respect to the narrow component, with the amplitude and peak time depending on detailed parameters. We further show that the optical afterglow of XRF 030723, especially its notable and rapid rebrightening, can be well explained by a typical two-component jet. This X-ray flash, together with GRB 030329, strongly hints the two-component jet model as a unified picture for X-ray flashes and gamma-ray bursts. With a narrow but ultra-relativistic inner outflow and a wide but less energetic outer ejecta, a two-component jet will be observed as a typical gamma-ray burst if our line of sight is within the angular scope of the narrow outflow. Otherwise, if the line of sight is within or slightly beyond the cone of the wide component, an X-ray flash will be detected.

  12. Bose–Einstein condensation in a two-component Bose gas with harmonic oscillator interaction

    Science.gov (United States)

    Abulseoud, A. A.; Abbas, A. H.; Galal, A. A.; El-Sherbini, Th M.

    2016-07-01

    In this article a system containing two species of identical bosons interacting via a harmonic oscillator potential is considered. It is assumed that the number of bosons of each species is the same and that bosons belonging to the same species repel each other while those belonging to different species attract. The Hamiltonian is diagonalized and the energy spectrum of the system is written down. The behaviour of the system in the thermodynamic limit is studied within the framework of the grand canonical ensemble, and thermodynamic parameters, such as the internal energy, entropy and specific heat capacity are calculated. It is shown that the system exhibits a single species Bose–Einstein condensation when the coupling strengths are equal and a dual species condensation when they are different.

  13. A Scheme of Generating and Spatially Separating Two-Component Entangled Atom Lasers

    OpenAIRE

    Liu, Xiong-Jun; Jing, Hui; Liu, Xin; Zhan, Ming-sheng; Ge, Mo-Lin

    2005-01-01

    Entanglement of remote atom lasers is obtained via quantum state transfer technique from lights to matter waves in a five-level $M$-type system. The considered atom-atom collisions can yield an effective Kerr susceptibility for this system and lead to the self- and cross- phase modulation between the two output atom lasers. This effect results in generation of entangled states of output fields. Particularly, under different conditions of space-dependent control fields, the entanglement of ato...

  14. Two-Component Signaling Regulates Osmotic Stress Adaptation via SskA and the High-Osmolarity Glycerol MAPK Pathway in the Human Pathogen Talaromyces marneffei.

    Science.gov (United States)

    Boyce, Kylie J; Cao, Cunwei; Andrianopoulos, Alex

    2016-01-01

    For successful infection to occur, a pathogen must be able to evade or tolerate the host's defense systems. This requires the pathogen to first recognize the host environment and then signal this response to elicit a complex adaptive program in order to activate its own defense strategies. In both prokaryotes and eukaryotes, two-component signaling systems are utilized to sense and respond to changes in the external environment. The hybrid histidine kinases (HHKs) at the start of the two-component signaling pathway have been well characterized in human pathogens. However, how these HHKs regulate processes downstream currently remains unclear. This study describes the role of a response regulator downstream of these HHKs, sskA, in Talaromyces marneffei, a dimorphic human pathogen. sskA is required for asexual reproduction, hyphal morphogenesis, cell wall integrity, osmotic adaptation, and the morphogenesis of yeast cells both in vitro at 37°C and during macrophage infection, but not during dimorphic switching. Comparison of the ΔsskA mutant with a strain in which the mitogen-activated protein kinase (MAPK) of the high-osmolarity glycerol pathway (SakA) has been deleted suggests that SskA acts upstream of this pathway in T. marneffei to regulate these morphogenetic processes. This was confirmed by assessing the amount of phosphorylated SakA in the ΔsskA mutant, antifungal resistance due to a lack of SakA activation, and the ability of a constitutively active sakA allele (sakA(F316L) ) to suppress the ΔsskA mutant phenotypes. We conclude that SskA regulates morphogenesis and osmotic stress adaptation in T. marneffei via phosphorylation of the SakA MAPK of the high-osmolarity glycerol pathway. IMPORTANCE This is the first study in a dimorphic fungal pathogen to investigate the role of a response regulator downstream of two-component signaling systems and its connection to the high-osmolarity glycerol pathway. This study will inspire further research into the

  15. Exact periodic wave and soliton solutions in two-component Bose-Einstein condensates

    Institute of Scientific and Technical Information of China (English)

    Li Hua-Mei

    2007-01-01

    We present several families of exact solutions to a system of coupled nonlinear Schr(o)dinger equations. The model describes a binary mixture of two Bose-Einstein condensates in a magnetic trap potential. Using a mapping deformation method, we find exact periodic wave and soliton solutions, including bright and dark soliton pairs.

  16. VISCOELASTICITY AND IONIC CONDUCTIVITY OF TWO-COMPONENT EPOXY NETWORK CONTAINING LITHIUM PERCHLORATE

    Institute of Scientific and Technical Information of China (English)

    PENG Xinsheng; BA Hengfei; QIAO Ziwen; CHEN Donglin; WANG Fosong

    1991-01-01

    Polymeric solid electrolyte system composed of triglycidyl ether of glycerol (TGEG), diglycidyl ether of polyethylene glycol (DGEPEG)and LiClO4 salt were synthesized. In this system the electrolyte has a pecularity that not merely can the LiClO4 provide ionic carriers, but also catalyze the crosslinking reaction without adding an usual curing agent. The effect of salt content and degree of crosslinking on the viscoelasticity and ionic conductivity were studied. Both WLF and VTF equations were used to treat the experimental data in order to elucidate the mechanism of ionic conduction. It was found that the ionic conductivity of the system is carried out through the segmental motion mechanism. However, the data must be treated with care. For example, in evaluating WLF parameters, the contribution concerned with ionic carrier generation with temperature to the conductivity must be differentiated from that concerned with segmental motion. Besides, the temperature range suitable to WLF equation must also be considered. For VTF equation, it might be inapplicable if the temperature is too low and close to the glass transition temperature of the specimen. Further study is needed in order to have a quantitative information on the limitation of these equations.

  17. Spatially resolved imaging of the two-component eta Crv debris disk with Herschel

    CERN Document Server

    Duchene, G; Wyatt, M; Kennedy, G; Sibthorpe, B; Lisse, C; Holland, W; Wisniewski, J; Clampin, M; Kalas, P; Pinte, C; Wilner, D; Booth, M; Horner, J; Matthews, B; Greaves, J

    2014-01-01

    We present far-infrared and sub-millimeter images of the eta Crv debris disk system obtained with Herschel and SCUBA-2, as well as Hubble Space Telescope visible and near-infrared coronagraphic images. In the 70 micron Herschel image, we clearly separate the thermal emission from the warm and cold belts in the system, find no evidence for a putative dust population located between them, and precisely determine the geometry of the outer belt. We also find marginal evidence for azimuthal asymmetries and a global offset of the outer debris ring relative to the central star. Finally, we place stringent upper limits on the scattered light surface brightness of the outer ring. Using radiative transfer modeling, we find that it is impossible to account for all observed properties of the system under the assumption that both rings contain dust populations with the same properties. While the outer belt is in reasonable agreement with the expectations of steady-state collisional cascade models, albeit with a minimum gr...

  18. A high-resolution study of surfactant partitioning and kinetic limitations for two-component internally mixed aerosols

    Science.gov (United States)

    Suda, S. R.; Petters, M. D.

    2013-12-01

    Atmospheric aerosols serve as cloud condensation nuclei (CCN), altering cloud properties and ultimately affecting climate through their effect on the radiative balance. Aerosol CCN activity depends in part on aerosol composition and surfactant compounds are of particular interest because surfactants are enriched at the water/air interface, resulting in a radial concentration gradient within the aqueous droplet. Accurate treatment of the surfactant concentration gradient complicates the otherwise straightforward predictions of CCN activity for aerosols of known composition. To accurately evaluate predictions made by theory, laboratory studies investigating the relationship between critical supersaturation and dry diameter of particles that include surfactants require significant reduction in measurement uncertainty for both water-uptake and CCN measurements. Furthermore, uncertainties remain regarding kinetic limitations to surfactant partitioning that could result in deviation from predictions based on equilibrium thermodynamics. This study attempts to address some of these issues through high-resolution analysis of CCN activity of two-component mixed surfactant/non-surfactant aerosols at different internal mixing ratios performed with and without a water-uptake time delay to ascertain whether or not the observed effects are kinetically limited. We present new data for the aerosols consisting of 1) the ionic surfactant sodium dodecyl sulfate (SDS) with ammonium sulfate, 2) SDS with sodium chloride and 3) the strong non-ionic fluorosurfactant Zonyl with an organic proxy glucose. As a point of reference we also evaluated the mixture of ammonium sulfate with glucose. Aerosol activation diameters were determined using CCN analysis in conjunction with scanning mobility size classification and high sheath-to-aerosol flow ratios. This resulted in CCN-derived kappa values that could be determined within +/-5% relative error. To test whether dynamic surfactant partitioning

  19. Spatially resolved imaging of the two-component η Crv debris disk with Herschel

    Energy Technology Data Exchange (ETDEWEB)

    Duchêne, G.; Arriaga, P.; Kalas, P. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Wyatt, M.; Kennedy, G. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Sibthorpe, B. [SRON Netherlands Institute for Space Research, P.O. Box 800, 9700 AV Groningen (Netherlands); Lisse, C. [JHU-APL, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Holland, W. [UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Wisniewski, J. [H.L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019 (United States); Clampin, M. [NASA Goddard Space Flight Center, Code 681, Greenbelt, MD 20771 (United States); Pinte, C. [UMI-FCA, CNRS/INSU, France (UMI 3386) (France); Wilner, D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Booth, M. [Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Horner, J. [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Matthews, B. [National Research Council of Canada Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Greaves, J. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom)

    2014-04-01

    We present far-infrared and submillimeter images of the η Crv debris disk system obtained with Herschel and SCUBA-2, as well as Hubble Space Telescope visible and near-infrared coronagraphic images. In the 70 μm Herschel image, we clearly separate the thermal emission from the warm and cold belts in the system, find no evidence for a putative dust population located between them, and precisely determine the geometry of the outer belt. We also find marginal evidence for azimuthal asymmetries and a global offset of the outer debris ring relative to the central star. Finally, we place stringent upper limits on the scattered light surface brightness of the outer ring. Using radiative transfer modeling, we find that it is impossible to account for all observed properties of the system under the assumption that both rings contain dust populations with the same properties. While the outer belt is in reasonable agreement with the expectations of steady-state collisional cascade models, albeit with a minimum grain size that is four times larger than the blow-out size, the inner belt appears to contain copious amounts of small dust grains, possibly below the blow-out size. This suggests that the inner belt cannot result from a simple transport of grains from the outer belt and rather supports a more violent phenomenon as its origin. We also find that the emission from the inner belt has not declined over three decades, a much longer timescale than its dynamical timescale, which indicates that the belt is efficiently replenished.

  20. Direct MD simulation of liquid-solid phase equilibria for two-component plasmas

    OpenAIRE

    Schneider, A. S.; Hughto, J.; Horowitz, C. J.; Berry, D. K.

    2011-01-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase MD simulations. We identified liquid, solid, and interface regions using a bond angle metric. To study finite size effects, we perform 27648 and 55296 ion simulations. To help monitor non-equilibrium effects, we calculate diffusion constants $D_i$. For the carbon-oxygen system we find that $D_O$ for oxygen ions in the solid is much smaller than $D_C$ for carbon ions and that both ...

  1. Unstaggered-staggered solitons in two-component discrete nonlinear Schr\\"{o}dinger lattices

    CERN Document Server

    Malomed, Boris A; Van Gorder, Robert A

    2012-01-01

    We present stable bright solitons built of coupled unstaggered and staggered components in a symmetric system of two discrete nonlinear Schr\\"{o}dinger (DNLS) equations with the attractive self-phase-modulation (SPM) nonlinearity, coupled by the repulsive cross-phase-modulation (XPM) interaction. These mixed modes are of a "symbiotic" type, as each component in isolation may only carry ordinary unstaggered solitons. The results are obtained in an analytical form, using the variational and Thomas-Fermi approximations (VA and TFA), and the generalized Vakhitov-Kolokolov (VK) criterion for the evaluation of the stability. The analytical predictions are verified against numerical results. Almost all the symbiotic solitons are predicted by the VA quite accurately, and are stable. Close to a boundary of the existence region of the solitons (which may feature several connected branches), there are broad solitons which are not well approximated by the VA, and are unstable.

  2. The implicit contribution of slab modes to the perpendicular diffusion coefficient of particles interacting with two-component turbulence

    CERN Document Server

    Shalchi, Andreas

    2016-01-01

    We explore the transport of energetic particles in two-component turbulence in which the stochastic magnetic field is assumed to be a superposition of slab and two-dimensional modes. It is known that in magnetostatic slab turbulence, the motion of particles across the mean magnetic field is subdiffusive. If a two-dimensional component is added, diffusion is recovered. It was also shown before that in two-component turbulence, the slab modes do not explicitly contribute to the perpendicular diffusion coefficient. In the current paper the implicit contribution of slab modes is explored and it is shown that this contribution leads to a reduction of the perpendicular diffusion coefficient. This effect improves the agreement between simulations and analytical theory. Furthermore, the obtained results are relevant for investigations of diffusive shock acceleration.

  3. A new pair of hard-soft plastic combination for precision manufacturing of two component plastic parts

    DEFF Research Database (Denmark)

    Islam, Aminul; Hansen, Hans Nørgaard; Marhöfer, David Maximilian;

    2011-01-01

    challenges associated with 2k moulding is the unavailability of suitable two component material combinations which can meet the diverse requirement from product and process point of view. This paper presents a new pair of commercial polymer materials (BASF Ultramid A3EG10 and Kraiburg TPE Thermolast K TC5PCZ...... of sealing between the Plug-Socket combination so, corrosive agents like human sweat, oil and dirt could corrode the contact pins inside the Socket house. The new design of the Socket is an improvement of the old design which contains a micro sealing ring. This 2k micro part was moulded by the use of State...... the pressure developed inside the socket house and finally could detect the leak of the fluid due to the sealing ring leakage. All the test procedures and results presented in this paper can be a valuable source of information for researchers and scientists who work with two component micro injection moulding....

  4. Transient two-phase two-component flow in NPP with WWER premises during loss-of coolant-accident

    International Nuclear Information System (INIS)

    The work objective was the development of a model describing processes in the premises of a NPP with water cooled reactor within the first second during lost-of-coolant-accident with the main circulation pipeline rupture. Two-phase two-component flow of water-steam-air mixture has been studied. An attempt has been made to obtain a hyperbolic set of partial differential equations in a canonical form suitable for application of the method of charakteristics in any modification. The two-phase two-component critical flow theory is considered as well as the sonic velocity corresponding to the calculated sonic velocity value as a function of the true volumetric gas contant. A calculation example is presented of the pressure history in a 1000 m3 box wherein the NPP with WWER primary circulating loop coolant is flowing (the main circulation pipeline cold branch rupture)

  5. Excitation spectrum and structure factor of a two-component Bose—Einstein condensate in different hyperfine states

    International Nuclear Information System (INIS)

    The elementary excitation spectrum of a two-component Bose—Einstein condensate in different hyperfine states is obtained by Green's function method. It is found to have two branches. In the long wave-length limit, the two branches of the excitation spectrum are reduced to one phonon excitation and one single-particle excitation. The single-particle one has an energy gap. When the energy gap exists, we study the Landau critical velocity and the depletion of the condensate. With the obtained Green's functions, we calculate the structure factor of a two-component condensate. It is found that the static structure factor comprises only the branch of the phonon excitation and the single-particle excitation makes no contribution to the structure factor. (general)

  6. Localization of a two-component Bose–Einstein condensate in a two-dimensional bichromatic optical lattice

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Kui-Tian, E-mail: kuitianxi@gmail.com; Li, Jinbin, E-mail: jinbin@nuaa.edu.cn; Shi, Da-Ning, E-mail: shi@nuaa.edu.cn

    2014-03-01

    We consider a weakly interacting two-component Bose–Einstein condensate (BEC) in a two-dimensional (2D) quasi-periodic bichromatic optical lattice (BOL). The problem is studied by means of split-step Crank–Nicolson method. The effects of weak intra- and inter-component interactions on localization of a two-component BEC are investigated. It is shown that in the quasi-2D regime, due to the enhanced disorder, there is no symmetry breaking like that in the one-dimensional (1D) case under a sine-typed potential, while configurations of density profiles are also quite different from that in the 1D case. By modulating interactions, the interplay of disorder and weak repulsive or attractive interactions is studied in detail. The cases with sine- and cosine-typed potentials acting on components 1 and 2 respectively are also discussed.

  7. Excitation spectrum and structure factor of a two-component Bose-Einstein condensate in different hyperfine states

    Institute of Scientific and Technical Information of China (English)

    Han Yu-Feng; Chen Liang; Liu Hou-Tong; Huang Xian-Shan

    2013-01-01

    The elementary excitation spectrum of a two-component Bose-Einstein condensate in different hyperfine states is obtained by Green's function method.It is found to have two branches.In the long wave-length limit,the two branches of the excitation spectrum are reduced to one phonon excitation and one single-particle excitation.The single-particle one has an energy gap.When the energy gap exists,we study the Landau critical velocity and the depletion of the condensate.With the obtained Green's functions,we calculate the structure factor of a two-component condensate.It is found that the static structure factor comprises only the branch of the phonon excitation and the single-particle excitation makes no contribution to the structure factor.

  8. Nonautonomous dark soliton solutions in two-component Bose—Einstein condensates with a linear time-dependent potential

    International Nuclear Information System (INIS)

    We report the analytical nonautonomous soliton solutions (NSSs) for two-component Bose—Einstein condensates with the presence of a time-dependent potential. These solutions show that the time-dependent potential can affect the velocity of NSS. The velocity shows the characteristic of both increasing and oscillation with time. A detailed analysis for the asymptotic behavior of NSSs demonstrates that the collision of two NSSs of each component is elastic

  9. Comparing Response Inhibition and Flexibility for Two Components of Executive Functioning in Children with Autism Spectrum Disorder and Normal Children

    OpenAIRE

    Seyed-Mousa Kafi; Seyed-omid Sotodeh; Fatemeh Pooragha

    2013-01-01

    Objective: The aim of this study was investigating and comparing two components of executive functioning in children with high function autism with normal children.Methods: this study was correlation descriptive (causal-comparative). There were two groups, one consisted of 15 participants of children with high function autism disorder (Intelligence quotient [IQ]>80) and the other consisted of 15 normal children, all age and education matched. They were compared with two neuro-cognitive tests,...

  10. Two-component wave equation for particles of spin 1/2 and nonzero rest mass. Pt. 1

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, T. (Leeds Univ. (UK). School of Mathematics)

    1984-03-21

    Spin-1/2 particles with nonzero rest mass have hitherto been described by the field equation of Dirac, i.e. by a four-component wave function. ''Why must the wave function have four components.'' was a question posed by Feynman and Gell-Mann which they answered by using the second-order equation ((inablasub(..mu..)-Asub(..mu..))/sup 2/+sigmax(B+iE))phi=m/sup 2/phi with phi a two-component spinor. The same equation - sometimes called the relativistic Pauli equation - was studied further by Brown, Tonin and Pietschmann with specific ends in view. However, a two-component wave equation which is essentially a Schroedinger equation insomuch as it retains the form i(h/2..pi..)(dphi/dt)=Hphi and is, therefore, first order in d/dt has been considered impossible, which it certainly is, if the operators used are confined to the type ..cap alpha..d, where ..cap alpha..'s are matrices with complex elements and d's are differential operators. Biedenharn and collaborators in 1971-1972 presented a two-component alternative to Dirac's equation which was of the Schroedinger type: their approach, however, is completely different from ours. We drop all the above restrictions but one, in these papers, and discuss, in part I, the qualifications of the equation (d/sub 0/+sigmasup(k)dsub(k))psi=-kappaTpsi, where dsub(..mu..)identicald/dchisup(..mu..), sigmasup(k) are the Pauli matrices, T is the linear operator which changes the sign of t, kappa=m/sub 0/c/(h/2..pi..) and psi a two-component wave function. The equation of the particle interacting with an electromagnetic field is dealt with in part II.

  11. Rabi-coupled two-component Bose-Einstein condensates: Classification of the ground states, defects, and energy estimates

    Science.gov (United States)

    Aftalion, Amandine; Mason, Peter

    2016-08-01

    We classify the ground states and topological defects of two-component Bose-Einstein condensates under the effect of internal coherent Rabi coupling. We present numerical phase diagrams which show the boundaries between symmetry-breaking components and various vortex patterns (triangular, square, bound state between vortices). We estimate the Rabi energy in the Thomas-Fermi limit which allows us to have an analytical description of the point energy leading to the formation of the various vortex patterns.

  12. A comparative experimental evaluation of uncertainty estimation methods for two-component PIV

    Science.gov (United States)

    Boomsma, Aaron; Bhattacharya, Sayantan; Troolin, Dan; Pothos, Stamatios; Vlachos, Pavlos

    2016-09-01

    Uncertainty quantification in planar particle image velocimetry (PIV) measurement is critical for proper assessment of the quality and significance of reported results. New uncertainty estimation methods have been recently introduced generating interest about their applicability and utility. The present study compares and contrasts current methods, across two separate experiments and three software packages in order to provide a diversified assessment of the methods. We evaluated the performance of four uncertainty estimation methods, primary peak ratio (PPR), mutual information (MI), image matching (IM) and correlation statistics (CS). The PPR method was implemented and tested in two processing codes, using in-house open source PIV processing software (PRANA, Purdue University) and Insight4G (TSI, Inc.). The MI method was evaluated in PRANA, as was the IM method. The CS method was evaluated using DaVis (LaVision, GmbH). Utilizing two PIV systems for high and low-resolution measurements and a laser doppler velocimetry (LDV) system, data were acquired in a total of three cases: a jet flow and a cylinder in cross flow at two Reynolds numbers. LDV measurements were used to establish a point validation against which the high-resolution PIV measurements were validated. Subsequently, the high-resolution PIV measurements were used as a reference against which the low-resolution PIV data were assessed for error and uncertainty. We compared error and uncertainty distributions, spatially varying RMS error and RMS uncertainty, and standard uncertainty coverages. We observed that qualitatively, each method responded to spatially varying error (i.e. higher error regions resulted in higher uncertainty predictions in that region). However, the PPR and MI methods demonstrated reduced uncertainty dynamic range response. In contrast, the IM and CS methods showed better response, but under-predicted the uncertainty ranges. The standard coverages (68% confidence interval) ranged from

  13. A comparative experimental evaluation of uncertainty estimation methods for two-component PIV

    Science.gov (United States)

    Boomsma, Aaron; Bhattacharya, Sayantan; Troolin, Dan; Pothos, Stamatios; Vlachos, Pavlos

    2016-09-01

    Uncertainty quantification in planar particle image velocimetry (PIV) measurement is critical for proper assessment of the quality and significance of reported results. New uncertainty estimation methods have been recently introduced generating interest about their applicability and utility. The present study compares and contrasts current methods, across two separate experiments and three software packages in order to provide a diversified assessment of the methods. We evaluated the performance of four uncertainty estimation methods, primary peak ratio (PPR), mutual information (MI), image matching (IM) and correlation statistics (CS). The PPR method was implemented and tested in two processing codes, using in-house open source PIV processing software (PRANA, Purdue University) and Insight4G (TSI, Inc.). The MI method was evaluated in PRANA, as was the IM method. The CS method was evaluated using DaVis (LaVision, GmbH). Utilizing two PIV systems for high and low-resolution measurements and a laser doppler velocimetry (LDV) system, data were acquired in a total of three cases: a jet flow and a cylinder in cross flow at two Reynolds numbers. LDV measurements were used to establish a point validation against which the high-resolution PIV measurements were validated. Subsequently, the high-resolution PIV measurements were used as a reference against which the low-resolution PIV data were assessed for error and uncertainty. We compared error and uncertainty distributions, spatially varying RMS error and RMS uncertainty, and standard uncertainty coverages. We observed that qualitatively, each method responded to spatially varying error (i.e. higher error regions resulted in higher uncertainty predictions in that region). However, the PPR and MI methods demonstrated reduced uncertainty dynamic range response. In contrast, the IM and CS methods showed better response, but under-predicted the uncertainty ranges. The standard coverages (68% confidence interval) ranged from

  14. Localization of a two-component Bose–Einstein condensate in a one-dimensional random potential

    International Nuclear Information System (INIS)

    We consider a weakly interacting two-component Bose–Einstein condensate (BEC) in a one-dimensional random speckle potential. The problem is studied with solutions of Gross–Pitaevskii (GP) equations by means of numerical method in Crank–Nicolson scheme. Properties of various cases owing to the competition of disorder and repulsive interactions of a cigar-shaped two-component BEC are discussed in detail. It is shown that in the central region, phase separation of a two-component BEC is not only affected by the intra- and inter-component interactions, but also influenced by the strength of the random speckle potential. Due to the strong disorder of the potential, the criterion of phase separation which is independent of the trap strength in an ordered potential, such as a harmonic potential, is no longer available. The influence of different random numbers generated by distinct processes on localization of BEC in the random potential is also investigated, as well as the configurations of the density profiles in the tail regions

  15. Five new Fast Radio Bursts from the HTRU high latitude survey: first evidence for two-component bursts

    CERN Document Server

    Champion, D J; Kramer, M; Keith, M J; Bailes, M; Barr, E D; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Flynn, C M L; Jameson, A; Johnston, S; Ng, C; Levin, L; Possenti, A; Stappers, B W; van Straten, W; Tiburzi, C; Lyne, A G

    2015-01-01

    The detection of five new fast radio bursts (FRBs) found in the High Time Resolution Universe high latitude survey is presented. The rate implied is 6$^{+4}_{-3}\\times~10^3$ (95%) FRBs sky$^{-1}$ day$^{-1}$ above a fluence of between 0.13 and 5.9 Jy ms for FRBs between 0.128 and 262 ms in duration. One of these FRBs has a clear two-component profile, each component is similar to the known population of single component FRBs and are separated by 2.4(4) ms. All the FRB components appear to be unresolved following deconvolution with a scattering tail and accounting for intra-channel smearing. The two-component FRB also has the highest dispersion measure (1629 pc cm$^{-3}$) of any FRB to-date. Many of the proposed models to explain FRBs use a single high energy event involving compact objects (such as neutron star mergers) and therefore cannot easily explain a two-component FRB. Models that are based on extreme versions of flaring, pulsing or orbital events however could produce multiple component profiles. The c...

  16. Localization of a two-component Bose–Einstein condensate in a one-dimensional random potential

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Kui-Tian; Li, Jinbin, E-mail: jinbin@nuaa.edu.cn; Shi, Da-Ning, E-mail: shi@nuaa.edu.cn

    2015-02-15

    We consider a weakly interacting two-component Bose–Einstein condensate (BEC) in a one-dimensional random speckle potential. The problem is studied with solutions of Gross–Pitaevskii (GP) equations by means of numerical method in Crank–Nicolson scheme. Properties of various cases owing to the competition of disorder and repulsive interactions of a cigar-shaped two-component BEC are discussed in detail. It is shown that in the central region, phase separation of a two-component BEC is not only affected by the intra- and inter-component interactions, but also influenced by the strength of the random speckle potential. Due to the strong disorder of the potential, the criterion of phase separation which is independent of the trap strength in an ordered potential, such as a harmonic potential, is no longer available. The influence of different random numbers generated by distinct processes on localization of BEC in the random potential is also investigated, as well as the configurations of the density profiles in the tail regions.

  17. A two-component volatile atmosphere for Pluto. I. The bulk hydrodynamic escape regime

    International Nuclear Information System (INIS)

    The seasonal effects on Pluto's atmosphere of a simplified system of CH4 and N2 saturated over a solid solution are investigated, and the results are compared with previous CH4 models. It is found that bulk escape occurs for CH4 mole fractions less than 0.7 of Pluto's volatile reservoir. Greater CH4 abundance leads to diffusive separation during the escape of both species and an atmospheric mixing ratio of about Xc(0). If Xc(0) is in the range 0.02-0.10, Pluto's atmosphere remains largely intact at aphelion rather than virtually freezing out as it does for Xc(0) greater than 0.3 or less than 0.001, or form an atmosphere with only a single volatile gas. An upper limit for the CH4 mixing ratio is about 0.07 if N2 is the second gas. On the other hand, CH4 is the dominant surface constituent of the volatile deposit if Xc(0) is greater than 0.0001. 29 refs

  18. VLT spectroscopy of XTE J2123-058 during quiescence: the masses of the two components

    Science.gov (United States)

    Casares, J.; Dubus, G.; Shahbaz, T.; Zurita, C.; Charles, P. A.

    2002-01-01

    We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ6300 and orbits the neutron star at K2=287+/-12kms-1. Contrary to other soft X-ray transients (SXTs), the Hα emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain K1=140+/-27kms-1 and hence q=K1/K2=M2/M1=0.49+/-0.10. This, combined with a previous determination of the inclination angle (i=73°+/-4°) yields M1=1.55+/-0.31Msolar and M2=0.76+/-0.22Msolar. M2 agrees well with the observed spectral type. Doppler tomography of the Hα emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of - 110+/-8kms-1 this value is consistent with the galactic rotation velocity at the position of J2123-058, and hence a halo origin. The formation scenario of J2123-058 is still unresolved.

  19. Effect of FLR and rotation on the Rayleigh-Taylor instability of two component plasma

    International Nuclear Information System (INIS)

    The problem of Rayleigh-Taylor (R-T) instability of superposed magnetized fluids is investigated in a partially ionized medium. The fluid has ionized and neutralized particles components interacting with each other by collisions. The effect of rotation in the horizontal directions also included in this R-T problem. The usual magnetohydrodynamic equations are modified for finite Larmor radius corrections which is in the form of tensor. The permeability of medium is also included in the equation. The relevant linearized perturbation equation are taken and using normal mode analysis the general relation is obtained. The dispersion relation for two superimposed fluids of different densities is derived. The dispersion relation shows that the growth rate of unstable system is reduced due to FLR corrections, rotation and collisional frequency of the neutrals. The dispersions relation gives no effect of magnetic field because horizontal magnetic field has no role in the R-T instability. The condition of instability remains unaffected by the permeability of porous medium, pressure of neutral particles in the fluids and rotation. (author)

  20. Temporal variability from the two-component advective flow solution and its observational evidence

    CERN Document Server

    Dutta, Broja G

    2016-01-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of energy-dependent temporal properties in different variability time scales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase the time lag increase...

  1. The transport co-efficients of two component hot hadronic matter

    International Nuclear Information System (INIS)

    Heavy ion collision experiments at RHIC showed large elliptic flow of emitted hadrons. This lead to the conclusion that the quark gluon plasma behaves as a nearly perfect fluid. This interpretation is based on the small but finite value of shear viscosity to entropy density ratio η/s. This gave rise to a great interest in transport coefficients of both partonic as well as hadronic matter. Hydrodynamic equations may be derived from entropy considerations using the second law of thermodynamics, a microscopic approach is necessary in order to determine the parameters, e.g., the coefficients of shear and bulk viscosity, thermal conductivity. The Boltzmann transport equation has been used extensively to estimate the transport coefficients of relativistic imperfect fluids. Pions form the most significant part of hadronic system, and quite a few estimations of the transport coefficients of pion gas are available. Nucleons also form a significant bulk of the hadronic matter produced in heavy ion collision. We aim to find the medium effect on the transport coefficients of this hadronic matter composed of mainly pions and nucleons. Here we try to find an estimation of the medium effect on the transport coefficient by employing relaxation time formalism

  2. Fitting a Two- Component Scattering Model to Polarimetric SAR Data from Forests

    Science.gov (United States)

    Freeman, A.

    2007-03-01

    Two simple scattering mechanisms are f itted to polarimetric SAR observations of forests. The mechanisms are canopy scatter from a reciprocal medium with azimuthal symmetry, and a ground scatter term, which can represent double-bounce scatter from a pair of orthogonal surfaces with different d ielectric constants or Bragg scatter from a moderately rough surface, seen through a layer of vertically oriented scatterers. The model is shown to represent the behavior of polarimetric backscatter from a tropical forest and two temperate forest sites, by applying it to data from NASA/JPL's AIRSAR system. Scattering contributions from the two basic scattering mechanisms are estimated for clusters of pixels in polarimetric SAR images. The solution involves the estimation of four parameters from four separate equations. This model fit approach is justified as a simplification of more complicated scattering models, which require many inputs to solve the forward scattering problem. The model is used to develop an understanding of the ground-trunk, double-bounce scattering present in the data, which is seen to vary considerably as a function of incidence angle. Two parameters in the model fit appear to exhibit sensitivity to vegetation canopy structure, which is worth further exploration. Results from the model fit for the ground scattering term are compared with estimates from a forward model and shown to be in good agreement. The behavior of the scattering from the ground-trunk interaction is consistent with the presence of a pseudo-Brewster angle effect for the air- trunk scattering interface. If the Brewster angle is known, it is possible to directly estimate the real part of the dielectric constant of the trunks, a key variable in forward modeling of backscatter from forests. It is also shown how, with a priori knowledge of the forest height, an estimate for the attenuation coefficient of the canopy can be obtained directly from the multi-incidence angle, polarimetric

  3. Quasi-analytical determination of noise-induced error limits in lidar retrieval of aerosol backscatter coefficient by the elastic, two-component algorithm.

    Science.gov (United States)

    Sicard, Michaël; Comerón, Adolfo; Rocadenbosch, Francisco; Rodríguez, Alejandro; Muñoz, Constantino

    2009-01-10

    The elastic, two-component algorithm is the most common inversion method for retrieving the aerosol backscatter coefficient from ground- or space-based backscatter lidar systems. A quasi-analytical formulation of the statistical error associated to the aerosol backscatter coefficient caused by the use of real, noise-corrupted lidar signals in the two-component algorithm is presented. The error expression depends on the signal-to-noise ratio along the inversion path and takes into account "instantaneous" effects, the effect of the signal-to-noise ratio at the range where the aerosol backscatter coefficient is being computed, as well as "memory" effects, namely, both the effect of the signal-to-noise ratio in the cell where the inversion is started and the cumulative effect of the noise between that cell and the actual cell where the aerosol backscatter coefficient is evaluated. An example is shown to illustrate how the "instantaneous" effect is reduced when averaging the noise-contaminated signal over a number of cells around the range where the inversion is started. PMID:19137026

  4. A two-component monooxygenase catalyzes both the hydroxylation of p-nitrophenol and the oxidative release of nitrite from 4-nitrocatechol in Bacillus sphaericus JS905.

    Science.gov (United States)

    Kadiyala, V; Spain, J C

    1998-07-01

    Bacteria that metabolize p-nitrophenol (PNP) oxidize the substrate to 3-ketoadipic acid via either hydroquinone or 1,2,4-trihydroxybenzene (THB); however, initial steps in the pathway for PNP biodegradation via THB are unclear. The product of initial hydroxylation of PNP could be either 4-nitrocatechol or 4-nitroresorcinol. Here we describe the complete pathway for aerobic PNP degradation by Bacillus sphaericus JS905 that was isolated by selective enrichment from an agricultural soil in India. Washed cells of PNP-grown JS905 released nitrite in stoichiometric amounts from PNP and 4-nitrocatechol. Experiments with extracts obtained from PNP-grown cells revealed that the initial reaction is a hydroxylation of PNP to yield 4-nitrocatechol. 4-Nitrocatechol is subsequently oxidized to THB with the concomitant removal of the nitro group as nitrite. The enzyme that catalyzed the two sequential monooxygenations of PNP was partially purified and separated into two components by anion-exchange chromatography and size exclusion chromatography. Both components were required for NADH-dependent oxidative release of nitrite from PNP or 4-nitrocatechol. One of the components was identified as a reductase based on its ability to catalyze the NAD(P)H-dependent reduction of 2,6-dichlorophenolindophenol and nitroblue tetrazolium. Nitrite release from either PNP or 4-nitrocatechol was inhibited by the flavoprotein inhibitor methimazole. Our results indicate that the two monooxygenations of PNP to THB are catalyzed by a single two-component enzyme system comprising a flavoprotein reductase and an oxygenase.

  5. A two-component monooxygenase catalyzes both the hydroxylation of p-nirophenol and the oxidative release of nitrite from 4-nitrocatechol in Bacillus sphaericus JS905

    Energy Technology Data Exchange (ETDEWEB)

    Kadiyala, V.; Spain, J.C. [Air Force Research Lab., Tyndall AFB, FL (United States)

    1998-07-01

    Bacteria that metabolize p-nitrophenol (PNP) oxidize the substrate to 3-ketoadipic acid via either hydroquinone or 1,2,4-trihydroxybenzene (THB); however, initial steps in the pathway for PNP biodegradation via THB are unclear. The product of initial hydroxylation of PNP could be either 4-nitrocatechol or 4-nitroresorcinol. Here the authors describe the complete pathway for aerobic PNP degradation by Bacillus sphaericus JS905 that was isolated by selective enrichment from an agricultural soil in India. Washed cells of PNP-grown JS905 released nitrite in stoichiometric amounts from PNP and 4-nitrocatechol. Experiments with extracts obtained from PNP-grown cells revealed that the initial reaction is a hydroxylation of PNP to yield 4-nitrocatechol. 4-nitrocatechol is subsequently oxidized to THB with the concomitant removal of the nitro group as nitrite. The enzyme that catalyzed the two sequential monooxygenations of PNP was partially purified and separated into two components by anion-exchange chromatography and size exclusion chromatography. Both components were required for NADH-dependent oxidative release of nitrite from PNP or 4-nitrocatechol. One of the components was identified as a reductase based on its ability to catalyze the NAD(P)H-dependent reduction of 2,6-dichlorophenolindophenol and nitroblue tetrazolium. Nitrite release from either PNP or 4-nitrocatechol was inhibited by the flavoprotein inhibitor methimazole. Their results indicate that the two monooxygenations of PNP to THB are catalyzed by a single two-component enzyme system comprising a flavoprotein reductase and an oxygenase.

  6. A novel two-component response regulator links rpf with biofilm formation and virulence of Xanthomonas axonopodis pv. citri.

    Directory of Open Access Journals (Sweden)

    Tzu-Pi Huang

    Full Text Available Citrus bacterial canker caused by Xanthomonas axonopodis pv. citri is a serious disease that impacts citrus production worldwide, and X. axonopodis pv. citri is listed as a quarantine pest in certain countries. Biofilm formation is important for the successful development of a pathogenic relationship between various bacteria and their host(s. To understand the mechanisms of biofilm formation by X. axonopodis pv. citri strain XW19, the strain was subjected to transposon mutagenesis. One mutant with a mutation in a two-component response regulator gene that was deficient in biofilm formation on a polystyrene microplate was selected for further study. The protein was designated as BfdR for biofilm formation defective regulator. BfdR from strain XW19 shares 100% amino acid sequence identity with XAC1284 of X. axonopodis pv. citri strain 306 and 30-100% identity with two-component response regulators in various pathogens and environmental microorganisms. The bfdR mutant strain exhibited significantly decreased biofilm formation on the leaf surfaces of Mexican lime compared with the wild type strain. The bfdR mutant was also compromised in its ability to cause canker lesions. The wild-type phenotype was restored by providing pbfdR in trans in the bfdR mutant. Our data indicated that BfdR did not regulate the production of virulence-related extracellular enzymes including amylase, lipase, protease, and lecithinase or the expression of hrpG, rfbC, and katE; however, BfdR controlled the expression of rpfF in XVM2 medium, which mimics cytoplasmic fluids in planta. In conclusion, biofilm formation on leaf surfaces of citrus is important for canker development in X. axonopodis pv. citri XW19. The process is controlled by the two-component response regulator BfdR via regulation of rpfF, which is required for the biosynthesis of a diffusible signal factor.

  7. Matter-Wave Solitons in Two-Component Bose-Einstein Condensates with Tunable Interactions and Time Varying Potential

    Institute of Scientific and Technical Information of China (English)

    宣恒农; 左苗

    2011-01-01

    We present three families of exact matter-wave soliton solutions for an effective one-dimension two- component Bose-Einstein condensates (BECs) with tunable interactions, harmonic potential and gain or loss term. We investigate the dynamics of bright-bright solitons, bright-dark solitons and dark-dark solitons for the time-dependent expulsive harmonic trap potential, periodically modulated harmonic trap potential, and kinklike modulated harmonic trap potential. Through the Feshbach resonance, these dynamics can be realized in experiments by suitable control of time-dependent trap parameters, atomic interactions, and interaction with thermal cloud.

  8. Switching and Self-trapping Dynamics of Dark Solitons in a Two-Component Bose-Einstein Condensate

    Institute of Scientific and Technical Information of China (English)

    LI Hong; WANG D.N.

    2007-01-01

    Two coupled dark solitons are considered in a two-component Bose-Einstein condensate.and their dynamics are investigated by the variational approach based the renormalized integrals of motion.The stationary states as physical solutions to the describing equations are obtained,and the dynamic mechanism is demonstrated by performing a coordinate of a classical particle moving in an effective potential field.The switching and selftrapping dynamics of the coupled dark vector solitons are discussed by the evolution of the atom population transferring ratio.

  9. A two-component wave equation for particles of spin 1/2 and nonzero rest mass: Pt. 1

    International Nuclear Information System (INIS)

    Spin-1/2 particles with nonzero rest mass have hitherto been described by the field equation of Dirac, i.e. by a four component wave function. 'Why must the wave function have four components' was a question posed by Feynman and Gell-Mann which they answered by using the second-order equation [(inablasub(μ) - Asub(μ))2 + sigma.(B + iE)]phi = m2phi with phi a two-component spinor. The same equation-sometimes called the relativistic Pauli equation-was studied further by Brown, Tonin and Pietschmann with specific ends in view. However, a two-component wave equation which is essentially a Schroedinger equation insomuch as it retains the form i(h/2π)(deltaphi/deltat) = Hphi and is, therefore, first order in delta/deltat has been considered impossible, which it certainly is, if the operators used are confined to the type αdelta, where α's are matrices with complex elements and delta's are differential operators. Biedenharn and collaborators in 1971-1972 presented a two-component alternative to Dirac's equation which was of the Schroedinger type: their approach, however, is completely different from ours. They are dropped all the above restrictions but one, in these papers, and discussed, in part I, the qualifications of the equation (delta0 + sigmasup(k)deltasub(k))psi = -xTpsi, where deltasub(μ) identical delta/deltaxsup(μ), sigmasup(k) are the Pauli matrices, T is the linear operator which changes the sign of t, x = m0c/(h/2π) and psi a two-component wave function. The equation of the particle interacting with an electromagnetic field is dealt with in part II. In part I it has been established that both components of all the solutions of the above equation satisfy the Klein-Gordon equation and that a 1-1 correspondence can be set up between its solutions and the positive-energy solutions of the Dirac equation which preserves inner products (when suitably defined for our case). Covariance under the proper Lorentz group followed by covariance under space and time

  10. Controlling of Fusion of Two Solitons in a Two-Component Condensate by an Anharmonic External Potential

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Qiang; WANG Deng-Long; LUO Xiao-Qing; HE Zhang-Ming; DING Jian-Wen

    2011-01-01

    By using the multiple-scale method, we analytically study dynamical properties of two-component Bose-Einstein condensates trapped in a harmonic plus quartic anharmonic potential.It is shown that the anharmonic potential has an important effect on the dark solitons of the condensates.In particular, when the strength of the anharmonic external potential increases, the fusion of the two solitons becomes faster.This implies that the fusion of the two solitons can be controlled by an anharmonic potential.%@@ By using the multiple-scale method,we analytically study dynamical properties of two-component Bose-Einstein condensates trapped in a harmonic plus quartic anharmonic potential.It is shown that the anharmonic potential has an important effect on the dark solitons of the condensates.In particular,when the strength of the anharmonic external potential increases,the fusion of the two solitons becomes faster.This implies that the fusion of the two solitons can be controlled by an anharmonic potential.

  11. Stable and unstable vector dark solitons of coupled nonlinear Schroedinger equations: Application to two-component Bose-Einstein condensates

    International Nuclear Information System (INIS)

    The dynamics of vector dark solitons in two-component Bose-Einstein condensates is studied within the framework of coupled one-dimensional nonlinear Schroedinger (NLS) equations. We consider the small-amplitude limit in which the coupled NLS equations are reduced to coupled Korteweg-de Vries (KdV) equations. For a specific choice of the parameters the obtained coupled KdV equations are exactly integrable. We find that there exist two branches of (slow and fast) dark solitons corresponding to the two branches of the sound waves. Slow solitons, corresponding to the lower branch of the acoustic wave, appear to be unstable and transform during the evolution into stable fast solitons (corresponding to the upper branch of the dispersion law). Vector dark solitons of arbitrary depths are studied numerically. It is shown that effectively different parabolic traps, to which the two components are subjected, cause an instability of the solitons, leading to a splitting of their components and subsequent decay. A simple phenomenological theory, describing the oscillations of vector dark solitons in a magnetic trap, is proposed

  12. A two wavelength holographic technique for simultaneous measurement of temperature and concentration during the solidification of two component systems

    Science.gov (United States)

    Ecker, A.

    1987-01-01

    Simultaneous measurement of the temperature and concentration distribution within a fluid can be made using a 'two wavelength holographic' setup. The technique is successfully applied to the study of temperature, concentration, and flow fields in the melt of a transparent 'model alloy' during solidification.

  13. Quorum sensing by peptide pheromones and two-component signal-transduction systems in Gram-positive bacteria

    NARCIS (Netherlands)

    Kleerebezem, Michiel; Quadri, Luis E.N.; Kuipers, Oscar P.; Vos, Willem M. de

    1997-01-01

    Cell-density-dependent gene expression appears to be widely spread in bacteria. This quorum-sensing phenomenon has been well established in Gram-negative bacteria, where N-acyl homoserine lactones are the diffusible communication molecules that modulate cell-density-dependent phenotypes. Similarly,

  14. Interfacial dynamic and dilational rheology of polyelectrolyte/surfactant two-component nanoparticle systems at air–water interface

    Energy Technology Data Exchange (ETDEWEB)

    Tong, L.J.; Bao, M.T.; Li, Y.M., E-mail: liym@ouc.edu.cn; Gong, H.Y.

    2014-10-15

    Graphical abstract: - Highlights: • DTAB/PSS mixture can self-assemble nanoparticles in bulk solution. • The nanoparticles can adsorb at the interface forming a nanoparticle monolayer. • The nanoparticles spread at the interface undergo a disassembly process with time. • The nanoparticle monolayer presents peculiar dilational viscoelastic behavior. - Abstract: The interfacial characteristics of nanoparticles and consequent inter-particle interactions at the interface are poorly understood. In this work, the interfacial dynamic and corresponding dilational surface rheology of self-assembled polyelectrolyte/surfactant nanoparticles at the air–water interface are characterized. The nanoparticles are prepared from dodecyltrimethylammonium (DTAB) and poly (sodium 4-styrene-sulfonate) (PSS) by mixing them in aqueous solution. The interfacial dynamic characteristics have been carried out by comparing the surface pressure with the dilational rheological response of these nanoparticles at interface. The results indicate that this type of nanoparticles can adsorb at the interface forming a nanoparticle monolayer, which leads to the surface tension decreased markedly. The dependence of surface pressure on time shows the instability and disassembly process of nanoparticles at the interface. On the basis of these observations, it is proposed that the nanoparticles undergo a dynamic process that interface induced nanoparticles disassembly into DTAB/PSS complexes. The presence of PSS in the subphase can promote the process of nanoparticles disassembly. A transition point in dilational elasticity and viscosity response of the nanoparticles versus oscillation frequency further validate the micro dynamic process of nanoparticles and the formation of polyelectrolyte/surfactant complex monolayer at the interface.

  15. Interfacial dynamic and dilational rheology of polyelectrolyte/surfactant two-component nanoparticle systems at air–water interface

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • DTAB/PSS mixture can self-assemble nanoparticles in bulk solution. • The nanoparticles can adsorb at the interface forming a nanoparticle monolayer. • The nanoparticles spread at the interface undergo a disassembly process with time. • The nanoparticle monolayer presents peculiar dilational viscoelastic behavior. - Abstract: The interfacial characteristics of nanoparticles and consequent inter-particle interactions at the interface are poorly understood. In this work, the interfacial dynamic and corresponding dilational surface rheology of self-assembled polyelectrolyte/surfactant nanoparticles at the air–water interface are characterized. The nanoparticles are prepared from dodecyltrimethylammonium (DTAB) and poly (sodium 4-styrene-sulfonate) (PSS) by mixing them in aqueous solution. The interfacial dynamic characteristics have been carried out by comparing the surface pressure with the dilational rheological response of these nanoparticles at interface. The results indicate that this type of nanoparticles can adsorb at the interface forming a nanoparticle monolayer, which leads to the surface tension decreased markedly. The dependence of surface pressure on time shows the instability and disassembly process of nanoparticles at the interface. On the basis of these observations, it is proposed that the nanoparticles undergo a dynamic process that interface induced nanoparticles disassembly into DTAB/PSS complexes. The presence of PSS in the subphase can promote the process of nanoparticles disassembly. A transition point in dilational elasticity and viscosity response of the nanoparticles versus oscillation frequency further validate the micro dynamic process of nanoparticles and the formation of polyelectrolyte/surfactant complex monolayer at the interface

  16. The CssRS two-component regulatory system controls a general secretion stress response in Bacillus subtilis

    NARCIS (Netherlands)

    Westers, Helga; Westers, L; Darmon, E.; van Dijl, Jan Maarten; Quax, Wim; Zanen, Geeske

    2006-01-01

    Bacillus species are valuable producers of industrial enzymes and biopharmaceuticals, because they can secrete large quantities of high-quality proteins directly into the growth medium. This requires the concerted action of quality control factors, such as folding catalysts and 'cleaning proteases'.

  17. Temperature-controlled structure and kinetics of ripple phases in one- and two-component supported lipid bilayers

    DEFF Research Database (Denmark)

    Kaasgaard, Thomas; Leidy, Chad; Crowe, J.H.;

    2003-01-01

    Temperature-controlled atomic force microscopy (AFM) has been used to visualize and study the structure and kinetics of ripple phases in one-component dipalmitoylphosphaticlylcholine (DPPC) and two-component dimyristoylphosphatidylcholine-distearoylphosphatidylcholine (DMPC-DSPC) lipid bilayers....... The lipid bilayers are mica-supported double bilayers in which ripple-phase formation occurs in the top bilayer. In one-component DPPC lipid bilayers, the stable and metastable ripple phases were observed. In addition, a third ripple structure with approximately twice the wavelength of the metastable...... ripples was seen. From height profiles of the AFM images, estimates of the amplitudes of the different ripple phases are reported. To elucidate the processes of ripple formation and disappearance, a ripple-phase DPPC lipid bilayer was taken through the pretransition in the cooling and the heating...

  18. Characterization of GX 339-4 outburst of 2010-11: Analysis by XSPEC using Two Component Advective Flow model

    CERN Document Server

    Debnath, Dipak; Chakrabarti, Sandip K

    2013-01-01

    We study the spectral properties of the Galactic transient black hole candidate (BHC) GX 339-4 during its 2010-11 outburst with Two Component (Keplerian and sub-Keplerian) Advective Flow (TCAF) model after its inclusion in XSPEC as a local model. We also compare our TCAF model fitted results with combined disk black body (DBB) and power-law (PL) model fitted spectral results and find similar types of smooth variation in thermal (Keplerian or disk black body) as well as non-thermal (power-law or sub-Keplerian) fluxes. For spectral fit, we use 2.5-25 keV spectral data of PCA instrument onboard RXTE satellite. From the TCAF model fit, accretion flow parameters, such as the Keplerian (disk) rate, sub-Keplerian (halo) rate, location of the shock and strength of the shock are extracted. Our study provides a comprehensive understanding of the mass accretion processes and properties of the accretion disk around the BHC during the outburst phases. Based on the comparison of the halo to disk accretion rate ratio (ARR) ...

  19. A Cyclic di-GMP-binding Adaptor Protein Interacts with Histidine Kinase to Regulate Two-component Signaling.

    Science.gov (United States)

    Xu, Linghui; Venkataramani, Prabhadevi; Ding, Yichen; Liu, Yang; Deng, Yinyue; Yong, Grace Lisi; Xin, Lingyi; Ye, Ruijuan; Zhang, Lianhui; Yang, Liang; Liang, Zhao-Xun

    2016-07-29

    The bacterial messenger cyclic di-GMP (c-di-GMP) binds to a diverse range of effectors to exert its biological effect. Despite the fact that free-standing PilZ proteins are by far the most prevalent c-di-GMP effectors known to date, their physiological function and mechanism of action remain largely unknown. Here we report that the free-standing PilZ protein PA2799 from the opportunistic pathogen Pseudomonas aeruginosa interacts directly with the hybrid histidine kinase SagS. We show that PA2799 (named as HapZ: histidine kinase associated PilZ) binds directly to the phosphoreceiver (REC) domain of SagS, and that the SagS-HapZ interaction is further enhanced at elevated c-di-GMP concentration. We demonstrate that binding of HapZ to SagS inhibits the phosphotransfer between SagS and the downstream protein HptB in a c-di-GMP-dependent manner. In accordance with the role of SagS as a motile-sessile switch and biofilm growth factor, we show that HapZ impacts surface attachment and biofilm formation most likely by regulating the expression of a large number of genes. The observations suggest a previously unknown mechanism whereby c-di-GMP mediates two-component signaling through a PilZ adaptor protein.

  20. Maladaptive correlates of the failure to forgive self and others: further evidence for a two-component model of forgiveness.

    Science.gov (United States)

    Ross, Scott R; Hertenstein, Matthew J; Wrobel, Thomas A

    2007-04-01

    In a sample composed of 162 young adults, we examined the generalizability of an orthogonal, 2-component model of forgiveness previously reported by Ross, Kendall, Matters, Rye, and Wrobel (2004). Furthermore, we examined the relationship of these two components with maladaptive personality characteristics as measured by the Schedule for Nonadaptive and Adaptive Personality (SNAP; Clark, 1993), with an emphasis on Five-factor model markers of personality. Using multiple measures of forgiveness, principal components analysis supported a 2-component model representing self-forgiveness and other forgiveness. Despite the independence of self-forgiveness and other forgiveness, zero order correlations with SNAP scales supported convergent more than discriminant validity. In contrast, hierarchical multiple regression analyses emphasized the discriminant validity of self-forgiveness and other forgiveness. Among indices of Neuroticism, Extraversion, and Agreeableness, Negative Temperament (+) was the sole predictor of self-forgiveness. In contrast, Positive Temperament (+), Aggression (-), and Histrionic PD (-) were most associated with other forgiveness. Overall, these findings support the validity of these factors and highlight the importance of self-forgiveness in clinical assessment.

  1. Probing red blood cell mechanics, rheology and dynamics with a two-component multi-scale model

    Science.gov (United States)

    Li, Xuejin; Peng, Zhangli; Lei, Huan; Dao, Ming; Karniadakis, George Em

    2014-01-01

    This study is partially motivated by the validation of a new two-component multi-scale cell model we developed recently that treats the lipid bilayer and the cytoskeleton as two distinct components. Here, the whole cell model is validated and compared against several available experiments that examine red blood cell (RBC) mechanics, rheology and dynamics. First, we investigated RBC deformability in a microfluidic channel with a very small cross-sectional area and quantified the mechanical properties of the RBC membrane. Second, we simulated twisting torque cytometry and compared predicted rheological properties of the RBC membrane with experimental measurements. Finally, we modelled the tank-treading (TT) motion of a RBC in a shear flow and explored the effect of channel width variation on the TT frequency. We also investigated the effects of bilayer–cytoskeletal interactions on these experiments and our simulations clearly indicated that they play key roles in the determination of cell membrane mechanical, rheological and dynamical properties. These simulations serve as validation tests and moreover reveal the capabilities and limitations of the new whole cell model. PMID:24982252

  2. A two-component histidine kinase Shk1 controls stress response, sclerotial formation and fungicide resistance in Sclerotinia sclerotiorum.

    Science.gov (United States)

    Duan, Yabing; Ge, Changyan; Liu, Shengming; Wang, Jianxin; Zhou, Mingguo

    2013-09-01

    Fungal histidine kinases (HKs) are involved in osmotic and oxidative stress responses, hyphal development, fungicide sensitivity and virulence. Members of HK class III are known to signal through the high-osmolarity glycerol mitogen-activated protein kinase (HOG MAPK). In this study, we characterized the Shk1 gene (SS1G_12694.3), which encodes a putative class III HK, from the plant pathogen Sclerotinia sclerotiorum. Disruption of Shk1 resulted in resistance to phenylpyrrole and dicarboximide fungicides and increased sensitivity to hyperosmotic stress and H2 O2 -induced oxidative stress. The Shk1 mutant showed a significant reduction in vegetative hyphal growth and was unable to produce sclerotia. Quantitative real-time polymerase chain reaction (qRT-PCR and glycerol determination assays showed that the expression of SsHOG1 (the last kinase of the Hog pathway) and glycerol accumulation were regulated by the Shk1 gene, but PAK (p21-activated kinase) was not. In addition, the Shk1 mutant showed no change in virulence. All the defects were restored by genetic complementation of the Shk1 deletion mutant with the wild-type Shk1 gene. These findings indicate that Shk1 is involved in vegetative differentiation, sclerotial formation, glycerol accumulation and adaption to hyperosmotic and oxidative stresses, and to fungicides, in S. sclerotiorum. Taken together, our results demonstrate, for the first time, the role of two-component HKs in Sclerotinia.

  3. HST-Scale 3D simulations of MHD disc winds : A rotating two-component jet structure

    CERN Document Server

    Staff, Jan; Ouyed, Rachid; Thompson, Adam; Pudritz, Ralph

    2014-01-01

    We present the results of large scale, three-dimensional magneto-hydrodynamics simulations of disc-winds for different initial magnetic field configurations. The jets are followed from the source to 90 AU scale, which covers several pixels of HST images of nearby protostellar jets. Our simulations show that jets are heated along their length by many shocks. We compute the emission lines that are produced, and find excellent agreement with observations. The jet width is found to be between 20 and 30 AU while the maximum velocities perpendicular to the jet is found to be up to above 100 km/s. The initially less open magnetic field configuration simulations results in a wider, two-component jet; a cylindrically shaped outer jet surrounding a narrow and much faster, inner jet. These simulations preserve the underlying Keplerian rotation profile of the inner jet to large distances from the source. However, for the initially most open magnetic field configuration the kink mode creates a narrow corkscrew-like jet wi...

  4. A two-component histidine kinase Shk1 controls stress response, sclerotial formation and fungicide resistance in Sclerotinia sclerotiorum.

    Science.gov (United States)

    Duan, Yabing; Ge, Changyan; Liu, Shengming; Wang, Jianxin; Zhou, Mingguo

    2013-09-01

    Fungal histidine kinases (HKs) are involved in osmotic and oxidative stress responses, hyphal development, fungicide sensitivity and virulence. Members of HK class III are known to signal through the high-osmolarity glycerol mitogen-activated protein kinase (HOG MAPK). In this study, we characterized the Shk1 gene (SS1G_12694.3), which encodes a putative class III HK, from the plant pathogen Sclerotinia sclerotiorum. Disruption of Shk1 resulted in resistance to phenylpyrrole and dicarboximide fungicides and increased sensitivity to hyperosmotic stress and H2 O2 -induced oxidative stress. The Shk1 mutant showed a significant reduction in vegetative hyphal growth and was unable to produce sclerotia. Quantitative real-time polymerase chain reaction (qRT-PCR and glycerol determination assays showed that the expression of SsHOG1 (the last kinase of the Hog pathway) and glycerol accumulation were regulated by the Shk1 gene, but PAK (p21-activated kinase) was not. In addition, the Shk1 mutant showed no change in virulence. All the defects were restored by genetic complementation of the Shk1 deletion mutant with the wild-type Shk1 gene. These findings indicate that Shk1 is involved in vegetative differentiation, sclerotial formation, glycerol accumulation and adaption to hyperosmotic and oxidative stresses, and to fungicides, in S. sclerotiorum. Taken together, our results demonstrate, for the first time, the role of two-component HKs in Sclerotinia. PMID:23724858

  5. A Cyclic di-GMP-binding Adaptor Protein Interacts with Histidine Kinase to Regulate Two-component Signaling.

    Science.gov (United States)

    Xu, Linghui; Venkataramani, Prabhadevi; Ding, Yichen; Liu, Yang; Deng, Yinyue; Yong, Grace Lisi; Xin, Lingyi; Ye, Ruijuan; Zhang, Lianhui; Yang, Liang; Liang, Zhao-Xun

    2016-07-29

    The bacterial messenger cyclic di-GMP (c-di-GMP) binds to a diverse range of effectors to exert its biological effect. Despite the fact that free-standing PilZ proteins are by far the most prevalent c-di-GMP effectors known to date, their physiological function and mechanism of action remain largely unknown. Here we report that the free-standing PilZ protein PA2799 from the opportunistic pathogen Pseudomonas aeruginosa interacts directly with the hybrid histidine kinase SagS. We show that PA2799 (named as HapZ: histidine kinase associated PilZ) binds directly to the phosphoreceiver (REC) domain of SagS, and that the SagS-HapZ interaction is further enhanced at elevated c-di-GMP concentration. We demonstrate that binding of HapZ to SagS inhibits the phosphotransfer between SagS and the downstream protein HptB in a c-di-GMP-dependent manner. In accordance with the role of SagS as a motile-sessile switch and biofilm growth factor, we show that HapZ impacts surface attachment and biofilm formation most likely by regulating the expression of a large number of genes. The observations suggest a previously unknown mechanism whereby c-di-GMP mediates two-component signaling through a PilZ adaptor protein. PMID:27231351

  6. Diagnostics for the structure of AGNs’broad line regions with reverberation mapping data:confirmation of the two-component broad line region model

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We re-examine the ten Reverberation Mapping(RM) sources with public data based on the two-component model of the Broad Line Region(BLR).In fitting their broad Hβ Mlines,six of them only need one Gaussian component,one of them has a double-peak profile,one has an irregular profile,and only two of them need two components,i.e.,a Very Broad Gaussian Component(VBGC) and an Inter-Mediate Gaussian Component(IMGC).The Gaussian components are assumed to come from two distinct regions in the two-component model;they are the Very Broad Line Region(VBLR) and the Inter-Mediate Line region(IMLR).The two sources with a two-component profile are Mrk 509 and NGC 4051.The time lags of the two components of both sources satisfy tIMLR/tVBLR=V 2VBLR/V 2IMLR,where tIMLR and tVBLR are the lags of the two components while VIMLR and VVBLR represent the mean gas velocities of the two regions,supporting the two-component model of the BLR of Active Galactic Nuclei(AGNs).The fact that most of these ten sources only have the VBGC confirms the assumption that RM mainly measures the radius of the VBLR;consequently,the radius obtained from the R-L relationship mainly represents the radius of VBLR.Moreover,NGC 4051,with a lag of about 5 days in the one component model,is an outlier on the R-L relationship as shown in Kaspi et al.(2005);however this problem disappears in our two-component model with lags of about 2 and 6 days for the VBGC and IMGC,respectively.

  7. Ground-state and rotational properties of a two-component Bose–Einstein condensate in a harmonic plus quartic trap

    International Nuclear Information System (INIS)

    We consider a two-component Bose–Einstein condensate under extreme elongation in a harmonic plus quartic trap. The ground-state and rotational properties of such a system are numerically studied as a function of intra- and inter-component contact interactions, and of the rotational frequency. For the nonrotational case, we obtain the exact phase diagram showing the ground-state density distributions as contact-interactions varied. For both slowly and ultrarapidly rotational cases, we demonstrate that the vortex configurations depend strongly on the relative strength of the contact interactions, as well as on the rotational frequency. The controllable system may be used to investigate the interplay of interaction and rotation, and to explore more exotic quantum phases. - Highlights: • Quartic trap extends the parameter space to a fast rotating region. • Different ground state density distributions and novel vortex structures are obtained within the full parameter space. • Effects of the contact interactions and rotation are discussed in detail

  8. Ground-state and rotational properties of a two-component Bose–Einstein condensate in a harmonic plus quartic trap

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Guang-Ping [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Zhang, Zhi-Yuan [The School of Physics and Mech-tronic Engineering, Sichuan University of Art and Science, DaZhou 635000 (China); Dong, Biao [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Lin-Xue [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Zhang, Xiao-Fei, E-mail: xfzhang@ntsc.ac.cn [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China); Zhang, Shou-Gang, E-mail: szhang@ntsc.ac.cn [Key Laboratory of Time and Frequency Primary Standards, National Time Service Center, Chinese Academy of Sciences, Xi' an 710600 (China)

    2015-10-02

    We consider a two-component Bose–Einstein condensate under extreme elongation in a harmonic plus quartic trap. The ground-state and rotational properties of such a system are numerically studied as a function of intra- and inter-component contact interactions, and of the rotational frequency. For the nonrotational case, we obtain the exact phase diagram showing the ground-state density distributions as contact-interactions varied. For both slowly and ultrarapidly rotational cases, we demonstrate that the vortex configurations depend strongly on the relative strength of the contact interactions, as well as on the rotational frequency. The controllable system may be used to investigate the interplay of interaction and rotation, and to explore more exotic quantum phases. - Highlights: • Quartic trap extends the parameter space to a fast rotating region. • Different ground state density distributions and novel vortex structures are obtained within the full parameter space. • Effects of the contact interactions and rotation are discussed in detail.

  9. Explaining low energy γ-ray excess from the galactic centre using a two-component dark matter model

    Science.gov (United States)

    Biswas, Anirban

    2016-06-01

    Over the past few years, there has been a hint of the γ-ray excess observed by the Fermi-LAT satellite-borne telescope from the regions surrounding the galactic centre (GC) at an energy range of ˜1-3 GeV. The nature of this excess γ-ray spectrum is found to be consistent with the γ-ray emission expected from dark matter (DM) annihilation at the GC while disfavouring other known astrophysical sources as the possible origin of this phenomena. It is also reported that the spectrum and morphology of this excess γ-rays can well be explained by the DM particles having mass in the range 30{--}40 {{GeV}} annihilating significantly into b\\bar{b} final state with an annihilation cross section σ v˜ (1.4-2.0)× {10}-26 cm{}3 {{{s}}}-1 at the GC. In this work, we propose a two-component DM model where two different types of DM particles, namely a complex scalar and a Dirac fermion are considered. The stability of both the dark sector particles are maintained by virtue of an additional local {{U}}{(1)}X gauge symmetry. We find that our proposed scenario can provide a viable explanation for this anomalous excess γ-rays besides satisfying all the existing relevant theoretical as well as experimental and observational bounds from LHC, PLANCK and LUX collaborations. The allowed range of ‘effective annihilation cross section’ of lighter DM particle for the b\\bar{b} annihilation channel thus obtained is finally compared with the limits reported by the Fermi-LAT and DES collaborations using data from various dwarf spheroidal galaxies.

  10. Remote sensing of particle dynamics: a two-component unmixing model in a western UK shelf sea.

    Science.gov (United States)

    Mitchell, Catherine; Cunningham, Alex

    2014-05-01

    The relationship between the backscattering and absorption coefficients, in particular the backscattering to absorption ratio, is mediated by the type of particles present in the water column. By considering the optical signals to be driven by phytoplankton and suspended minerals, with a relatively constant influence from CDOM, radiative transfer modelling is used to propose a method for retrieving the optical contribution of phytoplankton and suspended minerals to the total absorption coefficient with mean percentage errors of below 5% for both components. These contributions can be converted to constituent concentrations if the appropriate specific inherent optical properties are known or can be determined from the maximum and minimum backscattering to absorption ratios of the data. Remotely sensed absorption and backscattering coefficients from eight years of MODIS data for the Irish Sea reveal maximum backscattering to absorption coefficient ratios over the winter (with an average for the region of 0.27), which then decrease to a minimum over the summer months (with an average of 0.06) before increasing again through to winter, indicating a change in the particles present in the water column. Application of the two-component unmixing model to this data showed seasonal cycles of both phytoplankton and suspended mineral concentrations which vary in both amplitude and periodicity depending on their location. For example, in the Bristol Channel the amplitude of the suspended mineral concentration throughout one cycle is approximately 75% greater than a yearly cycle in the eastern Irish Sea. These seasonal cycles give an insight into the complex dynamics of particles in the water column, indicating the suspension of sediment throughout the winter months and the loss of sediments from the surface layer over the summer during stratification. The relationship between the timing of the phytoplankton spring bloom and changes in the availability of light in the water

  11. Evolution of multidrug resistance during Staphylococcus aureus infection involves mutation of the essential two component regulator WalKR.

    Directory of Open Access Journals (Sweden)

    Benjamin P Howden

    2011-11-01

    Full Text Available Antimicrobial resistance in Staphylococcus aureus is a major public health threat, compounded by emergence of strains with resistance to vancomycin and daptomycin, both last line antimicrobials. Here we have performed high throughput DNA sequencing and comparative genomics for five clinical pairs of vancomycin-susceptible (VSSA and vancomycin-intermediate ST239 S. aureus (VISA; each pair isolated before and after vancomycin treatment failure. These comparisons revealed a frequent pattern of mutation among the VISA strains within the essential walKR two-component regulatory locus involved in control of cell wall metabolism. We then conducted bi-directional allelic exchange experiments in our clinical VSSA and VISA strains and showed that single nucleotide substitutions within either walK or walR lead to co-resistance to vancomycin and daptomycin, and caused the typical cell wall thickening observed in resistant clinical isolates. Ion Torrent genome sequencing confirmed no additional regulatory mutations had been introduced into either the walR or walK VISA mutants during the allelic exchange process. However, two potential compensatory mutations were detected within putative transport genes for the walK mutant. The minimal genetic changes in either walK or walR also attenuated virulence, reduced biofilm formation, and led to consistent transcriptional changes that suggest an important role for this regulator in control of central metabolism. This study highlights the dramatic impacts of single mutations that arise during persistent S. aureus infections and demonstrates the role played by walKR to increase drug resistance, control metabolism and alter the virulence potential of this pathogen.

  12. Two-component mantle melting-mixing model for the generation of mid-ocean ridge basalts: Implications for the volatile content of the Pacific upper mantle

    Science.gov (United States)

    Shimizu, Kei; Saal, Alberto E.; Myers, Corinne E.; Nagle, Ashley N.; Hauri, Erik H.; Forsyth, Donald W.; Kamenetsky, Vadim S.; Niu, Yaoling

    2016-03-01

    We report major, trace, and volatile element (CO2, H2O, F, Cl, S) contents and Sr, Nd, and Pb isotopes of mid-ocean ridge basalt (MORB) glasses from the Northern East Pacific Rise (NEPR) off-axis seamounts, the Quebrada-Discovery-GoFar (QDG) transform fault system, and the Macquarie Island. The incompatible trace element (ITE) contents of the samples range from highly depleted (DMORB, Th/La ⩽ 0.035) to enriched (EMORB, Th/La ⩾ 0.07), and the isotopic composition spans the entire range observed in EPR MORB. Our data suggest that at the time of melt generation, the source that generated the EMORB was essentially peridotitic, and that the composition of NMORB might not represent melting of a single upper mantle source (DMM), but rather mixing of melts from a two-component mantle (depleted and enriched DMM or D-DMM and E-DMM, respectively). After filtering the volatile element data for secondary processes (degassing, sulfide saturation, assimilation of seawater-derived component, and fractional crystallization), we use the volatiles to ITE ratios of our samples and a two-component mantle melting-mixing model to estimate the volatile content of the D-DMM (CO2 = 22 ppm, H2O = 59 ppm, F = 8 ppm, Cl = 0.4 ppm, and S = 100 ppm) and the E-DMM (CO2 = 990 ppm, H2O = 660 ppm, F = 31 ppm, Cl = 22 ppm, and S = 165 ppm). Our two-component mantle melting-mixing model reproduces the kernel density estimates (KDE) of Th/La and 143Nd/144Nd ratios for our samples and for EPR axial MORB compiled from the literature. This model suggests that: (1) 78% of the Pacific upper mantle is highly depleted (D-DMM) while 22% is enriched (E-DMM) in volatile and refractory ITE, (2) the melts produced during variable degrees of melting of the E-DMM controls most of the MORB geochemical variation, and (3) a fraction (∼65% to 80%) of the low degree EMORB melts (produced by ∼1.3% melting) may escape melt aggregation by freezing at the base of the oceanic lithosphere, significantly enriching it in

  13. Two-component density functional theory within the projector augmented-wave approach: Accurate and self-consistent computations of positron lifetimes and momentum distributions

    Science.gov (United States)

    Wiktor, Julia; Jomard, Gérald; Torrent, Marc

    2015-09-01

    Many techniques have been developed in the past in order to compute positron lifetimes in materials from first principles. However, there is still a lack of a fast and accurate self-consistent scheme that could handle accurately the forces acting on the ions induced by the presence of the positron. We will show in this paper that we have reached this goal by developing the two-component density functional theory within the projector augmented-wave (PAW) method in the open-source code abinit. This tool offers the accuracy of the all-electron methods with the computational efficiency of the plane-wave ones. We can thus deal with supercells that contain few hundreds to thousands of atoms to study point defects as well as more extended defects clusters. Moreover, using the PAW basis set allows us to use techniques able to, for instance, treat strongly correlated systems or spin-orbit coupling, which are necessary to study heavy elements, such as the actinides or their compounds.

  14. Heat transfer, pressure drop and void fraction in two- phase, two-component flow in a vertical tube

    Science.gov (United States)

    Sujumnong, Manit

    1998-09-01

    There are very few data existing in two-phase, two- component flow where heat transfer, pressure drop and void fraction have all been measured under the same conditions. Such data are very valuable for two-phase heat-transfer model development and for testing existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction. An experiment was performed which adds markedly to the available data of the type described in terms of the range of gas and liquid flow rates and liquid Prandtl number. Heat transfer and pressure drop measurements were taken in a vertical 11.68-mm i.d. tube for two-phase (gas-liquid) flows covering a wide range of conditions. Mean void fraction measurements were taken, using quick- closing valves, in a 12.7-mm i.d. tube matching very closely pressures, temperatures, gas-phase superficial velocities and liquid-phase superficial velocities to those used in the heat-transfer and pressure-drop experiments. The gas phase was air while water and two aqueous solutions of glycerine (59 and 82% by mass) were used as the liquid phase. In the two-phase experiments the liquid Prandtl number varied from 6 to 766, the superficial liquid velocity from 0.05 to 8.5 m/s, and the superficial gas velocity from 0.02 to 119 m/s. The measured two-phase heat-transfer coefficients varied by a factor of approximately 1000, the two-phase frictional pressure drop ranged from small negative values (in slug flow) to 93 kPa and the void fraction ranged from 0.01 to 0.99; the flow patterns observed included bubble, slug, churn, annular, froth, the various transitions and annular-mist. Existing heat-transfer models or correlations requiring frictional pressure drop (or wall shear stress) and/or void fraction were: tested against the present data for mean heat-transfer coefficients. It was found that the methods with more restrictions (in terms of the applicable range of void fraction, liquid Prandtl number or liquid

  15. Metabolic flux analysis of Escherichia coli creB and arcA mutants reveals shared control of carbon catabolism under microaerobic growth conditions.

    Science.gov (United States)

    Nikel, Pablo I; Zhu, Jiangfeng; San, Ka-Yiu; Méndez, Beatriz S; Bennett, George N

    2009-09-01

    Escherichia coli has several elaborate sensing mechanisms for response to availability of oxygen and other electron acceptors, as well as the carbon source in the surrounding environment. Among them, the CreBC and ArcAB two-component signal transduction systems are responsible for regulation of carbon source utilization and redox control in response to oxygen availability, respectively. We assessed the role of CreBC and ArcAB in regulating the central carbon metabolism of E. coli under microaerobic conditions by means of (13)C-labeling experiments in chemostat cultures of a wild-type strain, DeltacreB and DeltaarcA single mutants, and a DeltacreB DeltaarcA double mutant. Continuous cultures were conducted at D = 0.1 h(-1) under carbon-limited conditions with restricted oxygen supply. Although all experimental strains metabolized glucose mainly through the Embden-Meyerhof-Parnas pathway, mutant strains had significantly lower fluxes in both the oxidative and the nonoxidative pentose phosphate pathways. Significant differences were also found at the pyruvate branching point. Both pyruvate-formate lyase and the pyruvate dehydrogenase complex contributed to acetyl-coenzyme A synthesis from pyruvate, and their activity seemed to be modulated by both ArcAB and CreBC. Strains carrying the creB deletion showed a higher biomass yield on glucose compared to the wild-type strain and its DeltaarcA derivative, which also correlated with higher fluxes from building blocks to biomass. Glyoxylate shunt and lactate dehydrogenase were active mainly in the DeltaarcA strain. Finally, it was observed that the tricarboxylic acid cycle reactions operated in a rather cyclic fashion under our experimental conditions, with reduced activity in the mutant strains.

  16. Dynamics of matrix-free Ca2+ in cardiac mitochondria: two components of Ca2+ uptake and role of phosphate buffering.

    Science.gov (United States)

    Wei, An-Chi; Liu, Ting; Winslow, Raimond L; O'Rourke, Brian

    2012-06-01

    Mitochondrial Ca(2+) uptake is thought to provide an important signal to increase energy production to meet demand but, in excess, can also trigger cell death. The mechanisms defining the relationship between total Ca(2+) uptake, changes in mitochondrial matrix free Ca(2+), and the activation of the mitochondrial permeability transition pore (PTP) are not well understood. We quantitatively measure changes in [Ca(2+)](out) and [Ca(2+)](mito) during Ca(2+) uptake in isolated cardiac mitochondria and identify two components of Ca(2+) influx. [Ca(2+)](mito) recordings revealed that the first, MCU(mode1), required at least 1 µM Ru360 to be completely inhibited, and responded to small Ca(2+) additions in the range of 0.1 to 2 µM with rapid and large changes in [Ca(2+)](mito). The second component, MCU(mode2), was blocked by 100 nM Ru360 and was responsible for the bulk of total Ca(2+) uptake for large Ca(2+) additions in the range of 2 to 10 µM; however, it had little effect on steady-state [Ca(2+)](mito). MCU(mode1) mediates changes in [Ca(2+)](mito) of 10s of μM, even in the presence of 100 nM Ru360, indicating that there is a finite degree of Ca(2+) buffering in the matrix associated with this pathway. In contrast, the much higher Ca(2+) loads evoked by MCU(mode2) activate a secondary dynamic Ca(2+) buffering system consistent with calcium-phosphate complex formation. Increasing P(i) potentiated [Ca(2+)](mito) increases via MCU(mode1) but suppressed [Ca(2+)](mito) changes via MCU(mode2). The results suggest that the role of MCU(mode1) might be to modulate oxidative phosphorylation in response to intracellular Ca(2+) signaling, whereas MCU(mode2) and the dynamic high-capacity Ca(2+) buffering system constitute a Ca(2+) sink function. Interestingly, the trigger for PTP activation is unlikely to be [Ca(2+)](mito) itself but rather a downstream byproduct of total mitochondrial Ca(2+) loading.

  17. Phase separation of a two-component dipolar Bose-Einstein condensate in the quasi-one-dimensional and quasi-two-dimensional regime

    International Nuclear Information System (INIS)

    We consider a two-component Bose-Einstein condensate, which contains atoms with magnetic dipole moments aligned along the z direction (labeled as component 1) and nonmagnetic atoms (labeled as component 2). The problem is studied by means of exact numerical simulations. The effects of dipole-dipole interaction on phase separations are investigated. It is shown that, in the quasi-one-dimensional regime, the atoms in component 2 are squeezed out when the dimensionless dipolar strength parameter is small, whereas the atoms in component 1 are pushed out instead when the parameter is large. This is in contrast to the phenomena in the quasi-two-dimensional regime. These two components are each kicked out by the other in the quasi-one-dimensional regime and this phenomenon is discussed as well.

  18. Two-component injection mould for automobile ventilation cover plate%汽车通风盖板双色注射模设计

    Institute of Scientific and Technical Information of China (English)

    董磊磊; 张惠敏

    2014-01-01

    以汽车通风盖板为例介绍一种新型双色注射模,模具采用封刀片结构可以避免传统的双色注射动模旋转带来的不便,同时能使模具尺寸减少、加工制造简单。实际生产证明,模具生产的塑件外观精致,硬塑料和软塑料结合的部位满足客户要求。%A new two-component injection mould for an automobile ventilation cover plate was developed in which sealing blade structure was adopted that can avoid the inconve-nience of traditional two-component injection mould in rotating; the mould size is reduced and the processing and manufacturing are simplified.

  19. Role of Streptococcus pyogenes Two-Component Response Regulators in the Temporal Control of Mga and the Mga-Regulated Virulence Gene emm

    OpenAIRE

    Ribardo, Deborah A.; Lambert, Thomas J.; McIver, Kevin S.

    2004-01-01

    We examined the role of Streptococcus pyogenes two-component response regulators (SptR) in expression of Mga and the Mga-regulated gene emm. Both serotype M6 and serotype M1 mutants in 12 of the 13 identified sptR genes exhibited levels of emm transcripts and Mga protein comparable to those of the wild type during exponential and stationary phases of growth. Thus, temporal control of these virulence genes does not require Spt response regulators.

  20. Boundary-induced bulk phase transition and violation of Fick's law in two-component single-file diffusion with open boundaries

    OpenAIRE

    Brzank, Andreas; Schütz, Gunter M.

    2006-01-01

    We study two-component single-file diffusion inside a narrow channel that at its ends is open and connected with particle reservoirs. Using a two-species version of the symmetric simple exclusion process as a model, we propose a hydrodynamic description of the coarse-grained dynamics with a self-diffusion coefficient that is inversely proportional to the length of the channel. The theory predicts an unexpected nonequilibrium phase transition for the bulk particle density as the external total...

  1. Internal Josephson-like tunnelling in two-component Bose-Einstein condensates affected by sign of the atomic interaction and external trapping potential

    Institute of Scientific and Technical Information of China (English)

    Xiong Bo; Liu Xun-Xu

    2007-01-01

    This paper studies the Josephson-like tunnelling in two-component Bose-Einstein condensates coupled with microwave field, which is in respond to various attractive and repulsive atomic interaction under the various aspect ratio of trapping potential. It is very interesting to find that the dynamic of Josephson-like tunnelling can be controlled from fast damped oscillations to nondamped oscillation, and relative number of atoms changes from asymmetric occupation to symmetric occupation correspondingly.

  2. A two-component dark matter model with real singlet scalars confronting GeV -ray excess from galactic centre and Fermi bubble

    Indian Academy of Sciences (India)

    Debasish Majumdar; Kamakshya Prasad Modak; Subhendu Rakshit

    2016-02-01

    We propose a two-component dark matter (DM) model, each component of which is a real singlet scalar, to explain results from both direct and indirect detection experiments. We put the constraints on the model parameters from theoretical bounds, PLANCK relic density results and direct DM experiments. The -ray flux is computed from DM annihilation in this framework and is then compared with the Fermi-LAT observations from galactic centre region and Fermi bubble.

  3. Phase diffusion of a two-component Bose–Einstein condensates: exact and short-time solutions for arbitrary coherent spin state

    International Nuclear Information System (INIS)

    We investigate phase diffusion of a two-component Bose–Einstein condensates prepared initially in arbitrary coherent spin state |θ0, φ0). Analytical expression of the phase-diffusion time is presented for θ0 ≠ π/2 case. In comparison with the symmetrical case (i.e., θ0 = π/2), we find that the diffusion process becomes slow due to the reduced atom number variance. (general)

  4. 双组分聚氨酯道桥密封膏的研制%The Research of Two-Component Polyurethane Sealant for Road and Bridge

    Institute of Scientific and Technical Information of China (English)

    孙金梅; 段文锋; 王小雪

    2011-01-01

    以聚醚多元醇、甲苯二异氰酸酯(TDI)、扩链剂、填料、复合催化剂、增塑剂、触变剂为主要原料,制备了一种低模量、高弹性、高粘接力的双组分聚氨酯道桥密封膏,讨论了影响该密封膏性能的因素.结果表明,当异氰酸酯指数在1.0~1.35、复合催化剂用量在0.9% ~1.1%、触变剂用量为10%~12%、活性轻钙用量为18% ~21%时,制备的密封膏的拉伸模量、下垂度、可施工时间、表干时间、弹性等性能较佳.同时通过采用自制的复合催化剂体系,利用化学增稠的方法解决了搅拌速度低对生产设备带来的问题,获得了性能优异的产品.%A low modulus, high elasticity, high bonding of two-component polyurethane sealant which were applied to road and bridge was prepared mainly from polyether polyol, toluene isocyanate, chain extender, padding, plasticizer and thixotropic agent. The affecting factors on the sealant performances were discussed. The results showed that the performance of sealant including tensile modulus, sag, construction time, dry time and flexibility were better when the isocyanate index (R) was from 1.0 to 1.35, the composite catalyst dosage was 0.9% to 1. 1% , the thixotropic agent dosage was 10% to 12% , the activity light calcium dosage was 18% to 21%. At the same time, the problems of production and performance that were caused by low speed mixing equipment were solved and excellent performance of product was obtained by using self-made compound catalyst system and chemical thickening.

  5. Magnetization damping in two-component metal oxide micropowder and nanopowder compacts by broadband ferromagnetic resonance measurements

    Science.gov (United States)

    Youssef, Jamal Ben; Brosseau, Christian

    2006-12-01

    The microwave damping mechanisms in magnetic inhomogeneous systems have displayed a richness of phenomenology that has attracted widespread interest over the years. Motivated by recent experiments, we report an extensive experimental study of the Gilbert damping parameter of multicomponent metal oxides micro- and nanophases. We label the former by M samples, and the latter by N samples. The main thrust of this examination is the magnetization dynamics in systems composed of mixtures of magnetic (γ-Fe2O3) and nonmagnetic (ZnO and epoxy resin) materials fabricated via powder processing. Detailed ferromagnetic resonance (FMR) measurements on N and M samples are described so to determine changes in the microwave absorption over the 6-18GHz frequency range as a function of composition and static magnetic field. The FMR linewidth and the field dependent resonance were measured for the M and N samples, at a given volume fraction of the magnetic phase. The asymmetry in the form and change in the linewidth for the M samples are caused by the orientation distribution of the local anisotropy fields, whereas the results for the N samples suggest that the linewidth is very sensitive to details of the spatial magnetic inhomogeneities. For N samples, the peak-to-peak linewidth increases continuously with the volume content of magnetic material. The influence of the volume fraction of the magnetic phase on the static internal field was also investigated. Furthermore, important insights are gleaned through analysis of the interrelationship between effective permeability and Gilbert damping constant. Different mechanisms have been considered to explain the FMR linewidth: the intrinsic Gilbert damping, the broadening induced by the magnetic inhomogeneities, and the extrinsic magnetic relaxation. We observed that the effective Gilbert damping constant of the series of N samples are found to be substantially smaller in comparison to M samples. This effect is attributed to the surface

  6. The ground states and pseudospin textures of rotating two-component Bose–Einstein condensates trapped in harmonic plus quartic potential

    Science.gov (United States)

    Liu, Yan; Zhang, Su-Ying

    2016-09-01

    The ground states of two-component miscible Bose–Einstein condensates (BECs) confined in a rotating annular trap are obtained by using the Thomas–Fermi (TF) approximation method. The ground state density distribution of the condensates experiences a transition from a disc shape to an annulus shape either when the angular frequency increases and the width and the center height of the trap are fixed, or when the width and the center height of the trap increase and the angular frequency is fixed. Meantime the numerical solutions of the ground states of the trapped two-component miscible BECs with the same condition are obtained by using imaginary-time propagation method. They are in good agreement with the solutions obtained by the TF approximation method. The ground states of the trapped two-component immiscible BECs are also given by using the imaginary-time propagation method. Furthermore, by introducing a normalized complex-valued spinor, three kinds of pseudospin textures of the BECs, i.e., giant skyrmion, coaxial double-annulus skyrmion, and coaxial three-annulus skyrmion, are found. Project supported by the National Natural Science Foundation of China (Grant Nos. 91430109 and 11404198), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).

  7. Effects of the Acrylic Polyol Structure and the Selectivity of the Employed Catalyst on the Performance of Two-component Aqueous Polyurethane Coatings

    Directory of Open Access Journals (Sweden)

    Miladin Gligoric

    2007-03-01

    Full Text Available Two kinds of aqueous acrylic polyols (single step and multi step synthesis typehave been investigated for their performance in the two-component aqueous polyurethaneapplication, by using more selective catalysts. The aliphatic polyfunctional isocyanatesbased on hexamethylen diisocyanates have been employed as suitable hardeners. Thecomplex of zirconium, commercially known as K-KAT®XC-6212, and manganese (IIIcomplexes with mixed ligands based on the derivative of maleic acid have been used ascatalysts in this study. Both of the aqueous polyols give good results, in terms of applicationand hardness, when elevated temperatures and more selective catalysts are applied. A moreselective catalyst promotes the reaction between the isocyanate and polyol component. Thisincreases the percentage of urethane bonds and the degree of hardness in the films formedfrom the two components of aqueous polyurethane lacquers. The polyol based on the singlestep synthesis route is favourable concerning potlife and hardness. The obtained resultsshow that the performance of the two-component aqueous polyurethane coatings depends onthe polymer structure of the polyols as well as on the selectivity of the employed catalyst.

  8. 双组份涂料机理及其防水效果探究%Mechanism of Two-component Coatings and Its Waterproofing Effect

    Institute of Scientific and Technical Information of China (English)

    许荣章

    2011-01-01

    目前公路建设、公路养护等普遍采用新型的双组份涂料,双组份涂料以其施工简便、干燥迅速、防水效果好等优点备受各涂料消耗行业青睐.但是随着我国经济的发展,涂料业也如雨后春笋般迅速成长,大大小小的涂料品牌,多种多样的涂料品种混杂在一起使消费者难以辨别.而在众多涂料种类中消费者最常用到的就是防水双组份涂料,由于市场的双组份防水涂料种类繁多,消费者对其作用机理又不是很了解,所以在选购时很难着手.本文就将就这一问题做深入细致的讨论,一方面阐述双足分涂料的作用机理,另一方面分析一下市场状况,为消费这或者企业在选购时提供一些参考.%Current road construction and road maintenance widely use new two-component coatings. For its advantages of simple construction, quick drying, good waterproof effect, two-component coating get much favor of paint industry consumes. But as China's economic development, paint industry has grew rapidly, large and small paint brands and kinds of paint make consumers be difficult to distinguish. In many types of paint, two-component coating is most common kind. Because there are varieties of two-component waterproof coating in market, the consumers do not very understand its role,so it is difficult to purchase. This paper will discuss this issue in depth, on the one hand describes the role mechanism of two-component waterproof coating, on the other hand analyzes the market situation, to provide some reference for the consumer and business.

  9. Miscibility of Two Components in a Binary Mixture of 9-Phenyl Anthracene Mixed with Stearic Acid or Polymethyl Methacrylate at Air-Water Interface

    Institute of Scientific and Technical Information of China (English)

    P. K. Paul; Md. N. Islam; D. Bhattacharjee; S. A. Hussain

    2007-01-01

    We report the miscibility characteristics of two components in a binary mixture of 9-phenyl anthracene (PA) mixed with stearic acid (SA) or polymethyl methacrylate (PMMA). The behaviour of surface pressure versus area per molecule isotherms reveal that the area per molecule decreases systematically with increasing molefractions of PA. The characteristics of areas per molecule versus molefractions and collapse pressure vs molefraction indicate that various interactions involved among the sample and matrix molecules. The interaction scheme is found to change with the change in surface pressure and molefraction of mixing. Scanning electron microscopic study confirms the aggregation of PA molecules in the mixed films.

  10. Theoretical study on spin-forbidden transitions of osmium complexes by two-component relativistic time-dependent density functional theory

    Science.gov (United States)

    Imamura, Yutaka; Kamiya, Muneaki; Nakajima, Takahito

    2016-03-01

    We study spin-forbidden transitions of Os polypyridyl sensitizers by two-component relativistic time-dependent density functional theory with the spin-orbit interaction based on Tamm-Dancoff approximation. The absorption spectra, including spin-forbidden-transition peaks, for the Os complexes are reasonably reproduced in comparison with the experimental ones. The extension of the conjugated lengths in the Os complexes is investigated and found to be effective to enhance photo absorption for spin-allowed transitions as well as spin-forbidden ones. This study provides fruitful information for a design of new dyes in terms of conjugation lengths.

  11. A Two-Component DNA-Prime/Protein-Boost Vaccination Strategy for Eliciting Long-Term, Protective T Cell Immunity against Trypanosoma cruzi

    OpenAIRE

    Shivali Gupta; Garg, Nisha J.

    2015-01-01

    In this study, we evaluated the long-term efficacy of a two-component subunit vaccine against Trypanosoma cruzi infection. C57BL/6 mice were immunized with TcG2/TcG4 vaccine delivered by a DNA-prime/Protein-boost (D/P) approach and challenged with T. cruzi at 120 or 180 days post-vaccination (dpv). We examined whether vaccine-primed T cell immunity was capable of rapid expansion and intercepting the infecting T. cruzi. Our data showed that D/P vaccine elicited CD4+ (30-38%) and CD8+ (22-42%) ...

  12. AN ENTROPIC ORDER QUANTITY MODEL WITH FUZZY HOLDING COST AND FUZZY DISPOSAL COST FOR PERISHABLE ITEMS UNDER TWO COMPONENT DEMAND AND DISCOUNTED SELLING PRICE

    Directory of Open Access Journals (Sweden)

    P.K. Tripathy

    2008-07-01

    Full Text Available A new type of replenishment policy is suggested in an entropy order quantity model for a perishable product possessing fuzzy holding cost and fuzzy disposal cost. This model represents an appropriate combination of two component demand with discounted selling price, particularly over a finite time horizon. Its main aim lies in the need for an entropic cost of the cycle time is a key feature of specific perishable product like fruits, vegetables, food stuffs, fishes etc. To handle this multiplicity of objectives in a pragmatic approach, entropic ordering quantity model with discounted selling price during pre and post deterioration of perishable items to optimize its payoff is proposed. It has been imperative to demonstrate this model by analysis, which reveals some important characteristics of discounted structure. Furthermore, numerical experiments are conducted to evaluate the difference between the crisp and fuzzy cases in EOQ and EnOQ separately. This paper explores the economy of investing in economics of lot sizing in Fuzzy EOQ, Crisp EOQ and Crisp EnOQ models. The proposed paper reveals itself as a pragmatic alternative to other approaches based on two component demand function with very sound theoretical underpinnings but with few possibilities of actually being put into practice. The results indicate that this can become a good model and can be replicated by researchers in neighbourhood of its possible extensions.

  13. Determination of Bisphenol A and Bisphenol AF in Vinegar samples by two-component mixed ionic liquid dispersive liquid-phase microextraction coupled with high performance liquid chromatography

    International Nuclear Information System (INIS)

    This paper describes a sensitive and simple method for the determination of bisphenol A (BPA) and bisphenol AF (BPAF) in vinegar samples using two-component mixed ionic liquid dispersive liquid-phase microextraction coupled with high performance liquid chromatography. In this work, BPA and BPAF were selected as the model analytes, and two-component mixed ionic liquid included 1-butyl-3-methylimidazolium hexafluorophosphate ((C4Mim)PF6) and 1-hexyl-3-methyl-imidazolium hexafluorophosphate ((C6Mim)PF6) was used as the extraction solvent for the first time here. Parameters that affect the extraction efficiency were investigated. Under the optimum conditions, good linear relationships were discovered in the range of 1.0-100 micro g/L for BPA and 2.0-150 micro g/L for BPAF, respectively. Detection limits of proposed method based on the signal-to-noise ratio (S/N=3) were in the range of 0.15-0.38 micro g/L. The efficiencies of proposed method have also been demonstrated with spiked real vinegar samples. The result show this method/ procedure to be a more efficient approach for the determination of BPA and BPAF in real vinegar, presenting average recovery rate of 89.3-112 % and precision values of 0.9-13.5% (RSDs, n = 6). In comparison with traditional solid phase extraction procedures this method results in lower solvent consumption, low pollution levels, and faster sample preparation. (author)

  14. 滑动型芯式双色注射模设计%Design of two-component injection mould with sliding core

    Institute of Scientific and Technical Information of China (English)

    董磊磊; 杜龙女

    2014-01-01

    介绍了一种滑动型芯式双色注射模,阐述了模具设计要点。模具采用第1次注射硬塑料熔体,第2次注射软塑料熔体的方式进行生产,相比传统旋转型芯式双色注射模,能在生产大型双色塑件时减少模具外形尺寸,降低对注塑机空间的要求,节省模具制造成本,提高塑件生产效率。%The design points of a two-component injection mould with sliding core for a scroll-shaped cover was presented. The rigid and flexible plastic melt was injected respec-tively in the first and second run which can reduce the mould outline dimensions and de-mands for the space of injection moulding machine in manufacturing large scale two-compo-nent plastic parts, compared to traditional two-component injection mould with rotating core.

  15. Fabrication and Investigation of Two-Component Film of 2,5-Diphenyloxazole and Octafluoronaphthalene Exhibiting Tunable Blue/Bluish Violet Fluorescence Based on Low Vacuum Physical Vapor Deposition Method

    Directory of Open Access Journals (Sweden)

    Xiaoyu Zhai

    2016-01-01

    Full Text Available Organic luminescent materials play an important role in the fields of light-emitting diodes and fluorescent imaging. Moreover, new synthetic approaches towards π-conjugated molecular systems with high fluorescence quantum efficiency are highly desired. Herein, different 2,5-diphenyloxazole-octafluoronaphthalene (DPO-OFN films with tunable fluorescence have been prepared by Low Vacuum Physical Vapor Deposition (LVPVD method. DPO-OFN films showed some changed properties, such as molecular vibration and fluorescence. All films exhibited blue/bluish violet fluorescence and showed blue shift, in comparison with pristine DPO. This work introduced a new method to fabricate two-component molecular materials with tunable blue/bluish violet luminescence properties and provided a new perspective to prepare organic luminescent film materials, layer film materials, cocrystal materials, and cocrystal film materials. Importantly, these materials have potential applications in the fields of next generation of photofunctional materials.

  16. Dose- and time-dependent changes of micronucleus frequency and gene expression in the progeny of irradiated cells: Two components in radiation-induced genomic instability?

    Energy Technology Data Exchange (ETDEWEB)

    Huumonen, Katriina [University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, 70211 Kuopio (Finland); Korkalainen, Merja [National Institute for Health and Welfare, Department of Environmental Health, P.O. Box 95, 70701 Kuopio (Finland); Boman, Eeva; Heikkilä, Janne [Kuopio University Hospital, Cancer Center, P.O. Box 1777, 70211 Kuopio (Finland); Höytö, Anne [University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, 70211 Kuopio (Finland); Lahtinen, Tapani [Kuopio University Hospital, Cancer Center, P.O. Box 1777, 70211 Kuopio (Finland); Luukkonen, Jukka [University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, 70211 Kuopio (Finland); Viluksela, Matti [National Institute for Health and Welfare, Department of Environmental Health, P.O. Box 95, 70701 Kuopio (Finland); Naarala, Jonne [University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, 70211 Kuopio (Finland); Juutilainen, Jukka, E-mail: jukka.juutilainen@uef.fi [University of Eastern Finland, Department of Environmental Science, P.O. Box 1627, 70211 Kuopio (Finland)

    2014-07-15

    Highlights: • Development with time of radiation-induced genomic instability (RIGI) was studied. • Dose–response of micronuclei showed marked time-dependent changes. • A new model assuming two components in RIGI was found to fit with the data. • The persisting component of RIGI seems to be independent of dose above a threshold. • Increasing heterogeneity was characteristic to delayed gene expression changes. - Abstract: Murine embryonic C3H/10T½ fibroblasts were exposed to X-rays at doses of 0.2, 0.5, 1, 2 or 5 Gy. To follow the development of radiation-induced genomic instability (RIGI), the frequency of micronuclei was measured with flow cytometry at 2 days after exposure and in the progeny of the irradiated cells at 8 and 15 days after exposure. Gene expression was measured at the same points in time by PCR arrays profiling the expression of 84 cancer-relevant genes. The micronucleus results showed a gradual decrease in the slope of the dose–response curve between days 2 and 15. The data were consistent with a model assuming two components in RIGI. The first component is characterized by dose-dependent increase in micronuclei. It may persist more than ten cell generations depending on dose, but eventually disappears. The second component is more persistent and independent of dose above a threshold higher than 0.2 Gy. Gene expression analysis 2 days after irradiation at 5 Gy showed consistent changes in genes that typically respond to DNA damage. However, the consistency of changes decreased with time, suggesting that non-specificity and increased heterogeneity of gene expression are characteristic to the second, more persistent component of RIGI.

  17. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to {radical}(s)=7 TeV

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Premomoy, E-mail: prem@vecc.gov.in [Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata 700 064 (India)

    2011-11-17

    Proton-proton collisions at new high energies ({radical}(s)=2.36 and 7 TeV) at LHC resulted into greater mean multiplicities (Left-Pointing-Angle-Bracket n Right-Pointing-Angle-Bracket) of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval |{eta}|<2.4. The change is most prominent with data at {radical}(s)=7 TeV. These new observations merit further studies. We consider a two-component model of particle production to analyze multiplicity distributions of charged hadrons from proton-proton collisions at centre-of-mass energies {radical}(s)=0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals |{eta}| of increasing width around the centre-of-mass pseudorapidity {eta}{sub cm}=0. The model, based on Quantum Statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a chaotic component, and a Poisson Distribution (PD), representing a coherent component of particle productions. The behaviour of characteristic parameters of the model is followed by the LHC data, while a scaling law, involving information entropy in quantum statistical viewpoint and derived as a function of chaotic multiplicity obtained from the two-component model, is not obeyed by the data, satisfactorily. An attempt to match the measured multiplicity distributions and suggested convolutions with values of characteristic parameters extracted from the data confirms disagreement between the data and the model.

  18. A two-component system, an anti-sigma factor and two paralogous ECF sigma factors are involved in the control of general stress response in Caulobacter crescentus.

    Science.gov (United States)

    Lourenço, Rogério F; Kohler, Christian; Gomes, Suely L

    2011-06-01

    The extracytoplasmic function sigma factor σ(T) is the master regulator of general stress response in Caulobacter crescentus and controls the expression of its paralogue σ(U). In this work we showed that PhyR and NepR act, respectively, as positive and negative regulators of σ(T) expression and function. Biochemical data also demonstrated that NepR directly binds σ(T) and the phosphorylated form of PhyR. We also described the essential role of the histidine kinase gene CC3474, here denominated phyK, for expression of σ(T)-dependent genes and for resistance to stress conditions. Additionally, in vivo evidence of PhyK-dependent phosphorylation of PhyR is presented. This study also identified a conserved cysteine residue (C95) located in the periplasmic portion of PhyK that is crucial for the function of the protein. Furthermore, we showed that PhyK, PhyR and σ(T) regulate the same set of genes and that σ(T) apparently directly controls most of its regulon. In contrast, σ(U) seems to have a very modest contribution to the expression of a subset of σ(T)-dependent genes. In conclusion, this report describes the molecular mechanism involved in the control of general stress response in C. crescentus.

  19. Development, Evaluation, and Validation of a Paper-and-Pencil Test for Measuring Two Components of Biology Teachers' Pedagogical Content Knowledge Concerning the "Cardiovascular System"

    Science.gov (United States)

    Schmelzing, Stephan; van Driel, Jan H.; Jüttner, Melanie; Brandenbusch, Stefanie; Sandmann, Angela; Neuhaus, Birgit J.

    2013-01-01

    One main focus of teacher education research concentrates on teachers' pedagogical content knowledge (PCK). It has been shown that teachers' PCK correlates with teaching effectiveness as well as with students' achievement gains. Teachers' PCK should be analyzed as one of the main important components to evaluate professional…

  20. The Campylobacter jejuni RacRS two-component system activates the glutamate synthesis by directly upregulating γ-glutamyltranspeptidase (GGT)

    NARCIS (Netherlands)

    van der Stel, Anne-Xander; van Mourik, Andries; Łaniewski, Paweł; van Putten, Jos P M; Jagusztyn-Krynicka, Elżbieta K; Wosten, Marc

    2015-01-01

    The highly conserved enzyme γ-glutamyltranspeptidase (GGT) plays an important role in metabolism of glutathione and glutamine. Yet, the regulation of ggt transcription in prokaryotes is poorly understood. In the human pathogen Campylobacter jejuni, GGT is important as it contributes to persistent co

  1. The Eukaryotic-Like Ser/Thr Kinase PrkC Regulates the Essential WalRK Two-Component System in Bacillus subtilis

    OpenAIRE

    Libby, Elizabeth A.; Goss, Lindsie A.; Jonathan Dworkin

    2015-01-01

    Most bacteria contain both eukaryotic-like Ser/Thr kinases (eSTKs) and eukaryotic-like Ser/Thr phosphatases (eSTPs). Their role in bacterial physiology is not currently well understood in large part because the conditions where the eSTKs are active are generally not known. However, all sequenced Gram-positive bacteria have a highly conserved eSTK with extracellular PASTA repeats that bind cell wall derived muropeptides. Here, we report that in the Gram-positive bacterium Bacillus subtilis, th...

  2. Quasi-Periodic Variations in X-ray Emission and Long-Term Radio Observations: Evidence for a Two-Component Jet in Sw J1644+57

    CERN Document Server

    Wang, Jiu-Zhou; Wang, Ding-Xiong; Zou, Yuan-Chuan; Zhang, Bing; Gao, He; Huang, Chang-Yin

    2014-01-01

    The continued observations of Sw J1644+57 in X-ray and radio bands accumulated a rich data set to study the relativistic jet launched in this tidal disruption event. The X-ray light curve of Sw J1644+57 from 5-30 days presents two kinds of quasi-periodic variations: a 200 second quasi-periodic oscillation (QPO) and a 2.7-day quasi-periodic variation. The latter has been interpreted by a precessing jet launched near the Bardeen-Petterson radius of a warped disk. Here we suggest that the $\\sim$ 200s QPO could be associated with a second, narrower jet sweeping the observer line-of-sight periodically, which is launched from a spinning black hole in the misaligned direction with respect to the black hole's angular momentum. In addition, we show that this two-component jet model can interpret the radio light curve of the event, especially the re-brightening feature starting $\\sim 100$ days after the trigger. From the data we infer that inner jet may have a Lorentz factor of $\\Gamma_{\\rm j} \\sim 5.5$ and a kinetic e...

  3. Two component silicone modified epoxy foul release coatings: Effect of modulus, surface energy and surface restructuring on pseudobarnacle and macrofouling behavior

    Energy Technology Data Exchange (ETDEWEB)

    Rath, S.K.; Chavan, J.G.; Sasane, Savita [Naval Materials Research Laboratory, Shil-Badlapur Road, Addl. Ambernath, Ambernath 421506, Maharashtra (India); Jagannath [Mod Lab, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra (India); Patri, M. [Naval Materials Research Laboratory, Shil-Badlapur Road, Addl. Ambernath, Ambernath 421506, Maharashtra (India); Samui, A.B., E-mail: absamui@rediffmail.com [Naval Materials Research Laboratory, Shil-Badlapur Road, Addl. Ambernath, Ambernath 421506, Maharashtra (India); Chakraborty, B.C. [Naval Materials Research Laboratory, Shil-Badlapur Road, Addl. Ambernath, Ambernath 421506, Maharashtra (India)

    2010-02-01

    Two component silicone modified epoxy resin based low surface energy and non-toxic foul release coatings were developed. Silicone modified epoxy resin with 15 and 30% silicone content was used as component A and a polyether diamine (Jeffamine-500) was used as the component B. Free standing films were prepared by casting a mixture of components A and B in stoichiometric proportions. The surface composition, surface topography and wetting properties of the coatings were studied by angle resolved X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometry respectively. The mechanical properties of the cured films were evaluated by tensile measurements as well as dynamic mechanical analysis. Pseudobarnacles made of aluminium studs were attached to the coated panels and adhesion tests were carried out by a pseudobarnacle tester. Coated panels were exposed in Mumbai harbor for fouling studies for a period of 90 days. Surface restructuring studies of the coatings upon immersion in seawater were carried out by measuring the changes in advancing and receding contact angles by contact angle goniometry. The effect of surface energy, modulus and surface restructuring of the coatings on the macrofouling and pseudobarnacle adhesion properties has been discussed in detail.

  4. A robust and efficient numerical method to compute the dynamics of the rotating two-component dipolar Bose-Einstein condensates

    CERN Document Server

    Tang, Qinglin; Mauser, Norbert

    2016-01-01

    In this paper, we propose a robust and efficient numerical method to compute the dynamics of the rotating two-component dipolar Bose-Einstein condensates (BEC). Using the rotating Lagrangian coordinates transform \\cite{BMTZ2013}, we reformulate the original coupled Gross-Pitaevskii equations (CGPE) into new equations where the rotating term vanishes and the potential becomes time-dependent. A time-splitting Fourier pseudospectral method is proposed to simulate the new equations where the nonlocal Dipole-Dipole Interactions (DDI) are computed by a newly-developed Gaussian-sum (GauSum) solver \\cite{EMZ2015} which helps achieve spectral accuracy in space within $O(N\\log N)$ operations ($N$ is the total number of grid points). The new method is spectrally accurate in space and second order accurate in time, and the accuracies are confirmed numerically. Dynamical properties of some physical quantities, including the total mass, energy, center of mass and angular momentum expectation, are presented and confirmed nu...

  5. Effects of Compton Cooling on the Hydrodynamic and the Spectral Properties of a Two Component Accretion Flow around a Black Hole

    CERN Document Server

    Ghosh, Himadri; Giri, Kinsuk; Chakrabarti, Sandip K

    2011-01-01

    We carry out a time dependent numerical simulation where both the hydrodynamics and the radiative transfer are coupled together. We consider a two-component accretion flow in which the Keplerian disk is immersed inside an accreting low angular momentum flow (halo) around a black hole. The injected soft photons from the Keplerian disk are reprocessed by the electrons in the halo. We show that in presence of an axisymmetric soft-photon source, the spherically symmetric Bondi flow losses its symmetry and becomes axisymmetric. The low angular momentum flow was observed to slow down close to the axis and formed a centrifugal barrier which added new features into the spectrum. Using the Monte Carlo method, we generated the radiated spectra as functions of the accretion rates. We find that the transitions from a hard state to a soft state is determined by the mass accretion rates of the disk and the halo. We separate out the signature of the bulk motion Comptonization and discuss its significance. We study how the n...

  6. Two component silicone modified epoxy foul release coatings: Effect of modulus, surface energy and surface restructuring on pseudobarnacle and macrofouling behavior

    International Nuclear Information System (INIS)

    Two component silicone modified epoxy resin based low surface energy and non-toxic foul release coatings were developed. Silicone modified epoxy resin with 15 and 30% silicone content was used as component A and a polyether diamine (Jeffamine-500) was used as the component B. Free standing films were prepared by casting a mixture of components A and B in stoichiometric proportions. The surface composition, surface topography and wetting properties of the coatings were studied by angle resolved X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometry respectively. The mechanical properties of the cured films were evaluated by tensile measurements as well as dynamic mechanical analysis. Pseudobarnacles made of aluminium studs were attached to the coated panels and adhesion tests were carried out by a pseudobarnacle tester. Coated panels were exposed in Mumbai harbor for fouling studies for a period of 90 days. Surface restructuring studies of the coatings upon immersion in seawater were carried out by measuring the changes in advancing and receding contact angles by contact angle goniometry. The effect of surface energy, modulus and surface restructuring of the coatings on the macrofouling and pseudobarnacle adhesion properties has been discussed in detail.

  7. Effects of Compton Cooling on Outflow in a Two Component Accretion Flow around a Black Hole: Results of a Coupled Monte Carlo-TVD Simulation

    CERN Document Server

    Garain, Sudip K; Chakrabarti, Sandip K; 10.1088/0004-637X/758/2/114

    2012-01-01

    We wish to investigate the effects of cooling of the Compton cloud on the outflow formation rate in an accretion disk around a black hole. We carry out a time dependent numerical simulation where both the hydrodynamics and the radiative transfer processes are coupled together. We consider a two-component accretion flow in which the Keplerian disk is immersed into an accreting low-angular momentum flow (halo) around a black hole. The soft photons which originate from the Keplerian disk are inverse-Comptonized by the electrons in the halo and the region between the centrifugal pressure supported shocks and the horizon. We run several cases by changing the rate of the Keplerian disk and see the effects on the shock location and properties of the outflow and the spectrum. We show that as a result of Comptonization of the Compton cloud, the cloud becomes cooler with the increase in the Keplerian disk rate. As the resultant thermal pressure is reduced, the post-shock region collapses and the outflow rate is also re...

  8. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to $\\sqrt {s}$ = 7 TeV

    CERN Document Server

    Ghosh, Premomoy

    2012-01-01

    Proton-proton collisions at new high energies ($\\sqrt {s} =$ 2.36 and 7 TeV) at LHC resulted into greater mean multiplicities ($$) of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval $|\\eta|<$2.4. The change is most prominent with data at $\\sqrt{s} = 7$ TeV. These new observations merit further studies. We consider a two-component model of particle production to analyze multiplicity distributions of charged hadrons from proton-proton collisions at centre-of-mass energies $\\sqrt{s} = $ 0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals $|\\eta|$ of increasing width around the centre-of-mass pseudorapidity $\\eta_{cm} = 0$. The model, based on quantum statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a cha...

  9. Two-component model in quantum statistical framework compared with multiplicity distributions in proton-proton collisions at energies up to √{ s} = 7 TeV

    Science.gov (United States)

    Ghosh, Premomoy

    2011-11-01

    Proton-proton collisions at new high energies (√{ s} = 2.36 and 7 TeV) at LHC resulted into greater mean multiplicities () of charged particles in the mid-rapidity region than estimated ones by different models and event generators. Another significant observation in multiplicity data is the change in slope in the distribution of primary charged hadrons in symmetric pseudorapidity interval | η | distributions of charged hadrons from proton-proton collisions at centre-of-mass energies √{ s} = 0.9, 2.36 and 7 TeV in symmetric pseudorapidity intervals | η | of increasing width around the centre-of-mass pseudorapidity ηcm = 0. The model, based on Quantum Statistical (QS) formalism, describes multiplicity distribution by convolution of a Negative Binomial Distribution (NBD), representing a chaotic component, and a Poisson Distribution (PD), representing a coherent component of particle productions. The behaviour of characteristic parameters of the model is followed by the LHC data, while a scaling law, involving information entropy in quantum statistical viewpoint and derived as a function of chaotic multiplicity obtained from the two-component model, is not obeyed by the data, satisfactorily. An attempt to match the measured multiplicity distributions and suggested convolutions with values of characteristic parameters extracted from the data confirms disagreement between the data and the model.

  10. Quasiparticle density of states of 2H-NbSe2 single crystals revealed by low-temperature specific heat measurements according to a two-component model

    Institute of Scientific and Technical Information of China (English)

    Yan Jing; Shan Lei; Wang Yue; Xiao Zhi-Li; Wen Hai-Hu

    2008-01-01

    Low-temperature specific heat in a dichalcogenide superconductor 2H-NbSe2 is measured in various magnetic fields. It is found that the specific heat can be described very well by a simple model concerning two components corresponding to vortex normal core and ambient superconducting region, separately. For calculating the specific heat outside the vortex core region, we use the Bardeen-Cooper-Schrieffer (BCS) formalism under the assumption of a narrow distribution of the superconducting gaps. The field-dependent vortex core size in the mixed state of 2H-NbSe2, determined by using this model, can explain the nonlinear field dependence of specific heat coefficient γ(H), which is in good agreement with the previous experimental results and more formal calculations. With the high-temperature specific heat data, we can find that, in the multi-band superconductor 2H-NbSe2, the recovered density of states (or Fermi surface) below Tc under a magnetic field seems not to be gapped again by the charge density wave (CDW) gap, which suggests that the superconducting gap and the CDW gap may open on different Fermi surface sheets.

  11. Re-growth of stellar disks in mature galaxies: The two component nature of NGC 7217 revisited with VIRUS-W

    CERN Document Server

    Fabricius, Maximilian H; Bender, Ralf; Drory, Niv; Goessl, Claus; Landriau, Martin; Saglia, Roberto P; Thomas, Jens; Williams, Michael J

    2014-01-01

    Previous studies have reported the existence of two counter-rotating stellar disks in the early-type spiral galaxy NGC7217. We have obtained high-resolution optical spectroscopic data (R ~ 9000) with the new fiber-based Integral Field Unit instrument VIRUS-W at the 2.7m telescope of the McDonald Observatory in Texas. Our analysis confirms the existence of two components. However, we find them to be co-rotating. The first component is the more luminous (~ 77% of the total light), has the higher velocity dispersion (~ 170 km/s) and rotates relatively slowly (projected $v_{max}$ = 50 km/s). The lower luminosity second component, (~ 23% of the total light), has a low velocity dispersion (~ 20 km/s) and rotates quickly (projected $v_{max}$ = 150 km/s). The difference in the kinematics of the two stellar components allows us to perform a kinematic decomposition and to measure the strengths of their Mg and Fe Lick indices separately. The rotational velocities and dispersions of the less luminous and faster component...

  12. A generalized two-component model of solar wind turbulence and ab initio diffusion mean free paths and drift lengthscales of cosmic rays

    CERN Document Server

    Wiengarten, Tobias; Engelbrecht, Eugene; Fichtner, Horst; Kleimann, Jens; Scherer, Klaus

    2016-01-01

    We extend a two-component model for the evolution of fluctuations in the solar wind plasma so that it is fully three-dimensional (3D) and also coupled self-consistently to the large-scale magnetohydrodynamic (MHD) equations describing the background solar wind. The two classes of fluctuations considered are a high-frequency parallel-propagating wave-like piece and a low-frequency quasi-two-dimensional component. For both components, the nonlinear dynamics is dominanted by quasi-perpendicular spectral cascades of energy. Driving of the fluctuations, by, for example, velocity shear and pickup ions, is included. Numerical solutions to the new model are obtained using the Cronos framework, and validated against previous simpler models. Comparing results from the new model with spacecraft measurements, we find improved agreement relative to earlier models that employ prescribed background solar wind fields. Finally, the new results for the wave-like and quasi-two-dimensional fluctuations are used to calculate ab i...

  13. Sequencing of leucocidin R from Staphylococcus aureus P83 suggests that staphylococcal leucocidins and gamma-hemolysin are members of a single, two-component family of toxins.

    Science.gov (United States)

    Supersac, G; Prevost, G; Piemont, Y

    1993-02-01

    A 2,813-bp HincII-ClaI DNA fragment encodes the two S and F components (LukS-R and LukF-R) of leucocidin R (Luk-R) which are secreted by Staphylococcus aureus P83. The two genes (lukS-R and lukF-R) belong to a single operon. Two peptidic sequences were deduced: LukS-R is a 35,721-Da polypeptide of 315 amino acids, including a signal sequence of 29 residues, and LukF-R is a 36,838-Da polypeptide of 325 amino acids, including a signal sequence of 25 residues. LukS-R and LukF-R were expressed in Escherichia coli and purified from the periplasmic space. Luk-R exerts biological activities on polymorphonuclear cells and on erythrocytes from various animals. Comparison of the amino acid sequence of LukF-R with that of the B component of gamma-hemolysin (HlgB), those of the F and S components of another recently sequenced staphylococcal leucocidin, and those of a few peptides of the F component from Panton-Valentine leucocidin suggests that all four toxins belong to a single, two-component family of toxins.

  14. The two-component adjuvant IC31® boosts type i interferon production of human monocyte-derived dendritic cells via ligation of endosomal TLRs.

    Directory of Open Access Journals (Sweden)

    Attila Szabo

    Full Text Available The aim of this study was to characterize and identify the mode of action of IC31®, a two-component vaccine adjuvant. We found that IC31® was accumulated in human peripheral blood monocytes, MHC class II positive cells and monocyte-derived DCs (moDCs but not in plasmacytoid DCs (pDCs. In the presence of IC31® the differentiation of inflammatory CD1a(+ moDCs and the secretion of chemokines, TNF-α and IL-6 cytokines was inhibited but the production of IFNβ was increased. Sustained addition of IC31® to differentiating moDCs interfered with IκBα phosphorylation, while the level of phospho-IRF3 increased. We also showed that both IC31® and its KLK component exhibited a booster effect on type I IFN responses induced by the specific ligands of TLR3 or TLR7/8, whereas TLR9 ligand induces type I IFN production only in the presence of IC31® or ODN1. Furthermore, long term incubation of moDCs with IC31® caused significantly higher expression of IRF and IFN genes than a single 24 hr treatment. The adjuvant activity of IC31® on the IFN response was shown to be exerted through TLRs residing in the vesicular compartment of moDCs. Based on these results IC31® was identified as a moDC modulatory adjuvant that sets the balance of the NF-κB and IRF3 mediated signaling pathways to the production of IFNβ. Thus IC31® is emerging as a potent adjuvant to increase immune responses against intracellular pathogens and cancer in future vaccination strategies.

  15. Theoretical modelling of the adsorption of thallium and element 113 atoms on gold using two-component density functional methods with effective core potentials

    International Nuclear Information System (INIS)

    Highlights: ► In this study we model the adsorption of the superheavy element 113 on gold surfaces. ► The binding energy of element 113 and thallium is calculated for cluster models. ► For many different binding sites, element 113 binds weaker by 90 ± 15 kJ/mol. - Abstract: The adsorption of thallium and element 113 atoms on a gold surface has been modelled by cluster calculations. Quasirelativistic two-component density functional calculations that include spin–orbit coupling self-consistently have been used together with spin-dependent effective core potentials. The validity of this method is demonstrated by comparisons with high-level wave function based calculations on the hetero-dimers AuTl and Au(113). New basis sets had to be generated because standard basis sets optimized for scalar-relativistic calculations are too inflexible to describe the different behaviour of the atomic sub-shells that result from the spin–orbit interaction. The topmost layer of gold atoms within the cluster was allowed to fully relax upon adsorption, and different adsorption sites (on-top, hollow, and bridge) on the (1 0 0) and (1 1 1) surfaces were considered. Spin–orbit coupling reduces the surface binding energies of an element 113 atom much more than it does for Tl, such that the binding energy of element 113 to the gold cluster, as compared to Tl, is reduced by 90 ± 15 kJ/mol in most cases. Together with the experimental result for thallium, this allows an estimate of the adsorption temperature of element 113 in thermochromatography experiments.

  16. Flame-Retarding of Cotton/Polyester Blended Yarn Fabrics Using Two-Component Sequential Treatment; Nidankai shori ni yoru men/poriesuteru konboshifu no nannenka

    Energy Technology Data Exchange (ETDEWEB)

    Kubokawa, Hiroo. [Textile Research Institute of Gunma Prefecture, Gunma (Japan)

    1999-01-10

    Cotton/polyester (C/P) blended yarn fabrics were treated with several flame retardants used for poly (ethylene terephthalate)(PET) using pad-dry-cure method. The relationships between the chemical structures of the flame retardants and their partition into PET fibers were investigated. When tetrabromobisphenol A (TBP-A) was tested, the amount of sorption increased with increasing concentration of TBP-A in treating acetone solution, and reached 4.0%o.w.f. (% on the weight of the fibre) at 10 wt%. THis treated fabric was again treated with a flame retardant for cotton, Pyrovatex CP New, which contains dimethyl 2-(N-hydroxymethylcarbamovl)ethylphosphonate as a main component. However, sufficient flame retardancy was not obtained. The second partition of TBP-A to cotton during heating was thought to lower the sorption efficiency of Pyrovatex CP New. Based on this assumption, for the case of the two-component sequential treatment, the Pyrovatex CP New treatment, which generates covalent bonds with hydroxy groups of cellulose, should be carried out prior to the TBP-A treatment. When a C/P blended yarn fabric was treated with Pyrovatex CP New and then with TBP-A, the amount of sorption of Pyrovatex CP New was 9.6%o.w.f. and the amount of sorption of TBP-A was 4.6%o.w.f. The limiting oxygen index of the treated fabric was 27.2%, a sufficient value for flame retardancy. Fromthis result, it was concluded that the practica flame-retardant finishing of c/p blended yarn fabrics could be carried out by using a simple finishing machine. (author)

  17. Synthesis and characterization of two-component waterborne acrylic-polyurethane%水性双组分丙烯酸-聚氨酯的合成与表征

    Institute of Scientific and Technical Information of China (English)

    周新华; 张灵娟; 涂伟萍; 胡剑青

    2005-01-01

    A two-component waterborne polyurethane(2K-WPU) was prepared by mixing water soluble acrylic resin and HDI biuret, and then diluting it to phase inversion with water. The effect of formula of acrylic resin on the performance of 2K-WPU was studied and the cured film of 2K-WPU was characterized by FTIR. It is shown that, ponent polyurethane emulsion with fine particle size can be achieved. When the film dried at room temperature for12 h, curing reaction can complete and the film has high crosslinking density.%使用相转化法,即将水溶性丙烯酸树脂和HDI缩二脲混合,然后加水稀释转相,制备了水性双组分丙烯酸聚氨酯.研究了丙烯酸树脂配方对双组分聚氨酯性能的影响,并用红外光谱(FTIR)对涂膜固化进行了表征.结果表明,以丙二醇甲醚醋酸酯为溶剂,在羟值为120 mgKOH·g-1、酸值为30 mgKOH·g-1的水溶性丙烯酸树脂中,添加10%的甲基丙烯酸异冰片酯,获得的双组分聚氨酯乳液粒径小.室温干燥12 h,固化反应完成,涂膜交联密度高.

  18. Study on Azeotropic Point of Azeotrope with Two Components%对二元溶液体系共沸溶液共沸点的再探究

    Institute of Scientific and Technical Information of China (English)

    曲金华; 杨旭

    2014-01-01

    共沸溶液很早就被人们所发现并取得了大量的实验数据,然而,这种现象的理论研究却很少。本文从理论上推导出二元体系共沸液的共沸点与外压、组成和组分沸点的定量关系式,并据此计算了二元体系共沸溶液常压下的共沸点,结果与文献的实验数据有相当好的一致性。本文还对二元体系共沸溶液的存在范围,共沸点相对单组分沸点高低的定性判定作了分析,从而为共沸溶液的研究和应用提供了理论依据。%Azeotropic solution soon discovered by the people and made the experimental data, a lot of however, theoretical study of this phenomenon is rarely. Quantitative relationship between the theoretically deduced two azeotropic distillation liquid boiling point and external pressure, composition and component boiling point, two component azeotropic solution under atmospheric pressure boiling point was calculated accordingly, the result of experimental data and literature are quite agreement. This paper also points the existence range azeotropic solution of the two group, boiling point to determine relative single component boiling point of qualitative analysis is made, which provides a theoretical basis for the research and application of azeotropic solution.

  19. Computer studies of the surface mechanism of preferential sputtering of two-component solids. Ion beam analysis of surface composition in low dose regime

    Science.gov (United States)

    Samoilov, Vladimir N.; Tatur, Andrei E.; Yastrzhembsky, Vladimir I.

    1996-09-01

    We investigated the process of collision cascade propagation through the solid-vacuum boundary for two-component targets: WSi, MoSi and VSi. The surface mechanism of preferential sputtering of atoms of light component based on stronger deflection of light atoms towards surface normal when scattering by heavy neighbouring surface atoms during ejection was studied. Simulations for ejection of 450 000 Si or W atoms from the surface of WSi for cos {ϑ 0}/{E 02} and {1}/{E 02} initial distributions gave {Si}/{W} sputtering ratio equal to 1.29-1.55 (for 1:1 {Si}/{W} concentration ratio at the surface) giving necessary addition to the Andersen-Sigmund formula which underestimated that ratio in comparison with available experimental data. Analysis of integral energy distributions of atoms of the components gave {Si}/{W} ratio maximum equal to 3.18-5.00 for energy interval 0.0-0.4 eV. Maxima of integral energy distributions of sputtered atoms were observed at 1.8 eV for Si and 3.4 eV for W in calculations with equal binding energies for atoms of light and heavy components in good agreement with experiment. The surface mechanism was shown to be the alternative mechanism in formation of observed maxima difference with respect to nonidentity of binding energy values for atoms of components proposed by Szymonski [Phys. Lett. A 82 (1981) 203]. The two-cone structure of ejection vs. initial polar angle for Si atoms sputtered was revealed and explained. Results obtained gave the new approach to solve the inverse problem of reconstruction of surface composition in low dose SNMS and showed that the surface mechanism of preferential sputtering is to be accounted for in analytical calculations of surface composition. Ejection was simulated in the plane containing the neighbouring surface atom.

  20. Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model

    Directory of Open Access Journals (Sweden)

    J. P. Kochendorfer

    2008-03-01

    Full Text Available The statistical-dynamical annual water balance model of Eagleson (1978 is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985 canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM. The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green Leaf Area Index (LAI suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration. Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends

  1. Catalytic Oxidation of Two-component VOCs and Kinetic Analysis%双组分VOCs的催化氧化及动力学分析

    Institute of Scientific and Technical Information of China (English)

    卜龙利; 杨力; 孙剑宇; 梁欣欣; 虎雪姣; 孟海龙

    2014-01-01

    考察了微波加热与管式炉加热下挥发性有机化合物( VOCs)甲苯与氯苯的催化氧化性能,并对双组分VOCs的反应动力学进行了分析。结果表明,VOCs的竞争吸附使得双组分中甲苯和氯苯的转化率比单组分降低3℅~12℅;微波的“热点效应”与“非热效应”使得VOCs转化效率明显优于管式炉加热,尤其是氯苯的转化率提高了31℅~38℅;微波加热降低了氧化反应温度和处理能耗。动力学分析表明,微波加热下甲苯和氯苯的反应活化能比管式炉加热下减少了2146 J•mol-1和1450 J•mol-1,微波加热下氯苯的化学反应速率常数是管式炉加热的35倍,甲苯的反应速率常数提高了6倍。%Catalytic oxidations of two-component volatile organic compounds ( VOCs) toluene and chlorobenzene were investigated under microwave heating and tube furnace heating, respectively, and reaction kinetics were analyzed in this paper. The research indicated that competitive adsorption between toluene and chlorobenzene reduced their removal efficiencies by 3℅-12℅ as compared to single component. ‘Hot spot effect' and ‘non-thermal effect' under microwave irradiation obviously enhanced conversion efficiencies of VOCs, especially, the chlorobenzene removal was increased by 31℅-38℅. Moreover, reaction temperature and energy consumption were both reduced under microwave heating. The dynamic calculations showed that microwave heating decreased the activation energies by 2 146 J•mol-1 and 1 450 J•mol-1 for toluene and chlorobenzene, respectively, as compared with tube furnace heating. Meanwhile, microwave heating enhanced the reaction rate constants of chlorobenzene and toluene to about 35 times and 6 times of that of tube furnace heating.

  2. Petrogenetic evaluation of the Laohutai basalts from North China Craton: Melting of a two-component source during lithospheric thinning in the late Cretaceous-early Cenozoic

    Science.gov (United States)

    Kuang, Y. S.; Wei, X.; Hong, L. B.; Ma, J. L.; Pang, C. J.; Zhong, Y. T.; Zhao, J.-X.; Xu, Y.-G.

    2012-12-01

    While the consensus has been reached as to the lithospheric thinning beneath the North China Craton, the timing of this event remains controversial. Whether it took place during the Early Cretaceous or it extended over a period from late Triassic to early Cenozoic is a matter of hot debate. With aims of contributing to this issue, we performed geochronological and geochemical analyses on basalts of the Laohutai Formation which were emplaced in the Fushun basin at 60-70 Ma. The Laohutai Formation consists of Ne- or Hy-normative alkali basalts in the lower part and Q-normative tholeiitic basalts in the upper part. The tholeiites are characterized by positive Eu and Sr anomalies and show higher ɛNd(t) (3.2-5.3) than the co-existing alkali basalts (1.8-2.4), opposite to the common observation made in other occurrences. Depletion of highly incompatible elements, positive Nbsbnd Ta and negative Pb anomalies in the Laohutai basalts are indicative of oceanic crustal components (likely in form of pyroxenite/eclogite) in their magma source. Since Eu and Sr anomalies are not related to magmatic differentiation, the negative correlation between 87Sr/86Sri and Eu/Eu* suggests that the melting process and sampling of source heterogeneity are intrinsically related. We propose a differential melting of a two-component source in association with lithospheric thinning to account for the temporal variation of the Laohutai basalts. Specifically, earlier alkali basalts were formed by low degree of melting of a source at a greater depth, modified by melts derived from a hydrothermally altered, upper oceanic crust; whereas the later tholeiitic basalts were generated by high degree of melting of a gabbroic lower oceanic crust and minor peridotite at a shallower depth. When the lithospheric lid effect is applied, this petrogenetic model suggests the late Cretaceous-early Cenozoic as an important period of lithospheric thinning, therefore leaning support to the idea of the protracted

  3. Modeling the monthly mean soil-water balance with a statistical-dynamical ecohydrology model as coupled to a two-component canopy model

    Directory of Open Access Journals (Sweden)

    J. P. Kochendorfer

    2010-10-01

    Full Text Available The statistical-dynamical annual water balance model of Eagleson (1978 is a pioneering work in the analysis of climate, soil and vegetation interactions. This paper describes several enhancements and modifications to the model that improve its physical realism at the expense of its mathematical elegance and analytical tractability. In particular, the analytical solutions for the root zone fluxes are re-derived using separate potential rates of transpiration and bare-soil evaporation. Those potential rates, along with the rate of evaporation from canopy interception, are calculated using the two-component Shuttleworth-Wallace (1985 canopy model. In addition, the soil column is divided into two layers, with the upper layer representing the dynamic root zone. The resulting ability to account for changes in root-zone water storage allows for implementation at the monthly timescale. This new version of the Eagleson model is coined the Statistical-Dynamical Ecohydrology Model (SDEM. The ability of the SDEM to capture the seasonal dynamics of the local-scale soil-water balance is demonstrated for two grassland sites in the US Great Plains. Sensitivity of the results to variations in peak green leaf area index (LAI suggests that the mean peak green LAI is determined by some minimum in root zone soil moisture during the growing season. That minimum appears to be close to the soil matric potential at which the dominant grass species begins to experience water stress and well above the wilting point, thereby suggesting an ecological optimality hypothesis in which the need to avoid water-stress-induced leaf abscission is balanced by the maximization of carbon assimilation (and associated transpiration. Finally, analysis of the sensitivity of model-determined peak green LAI to soil texture shows that the coupled model is able to reproduce the so-called "inverse texture effect", which consists of the observation that natural vegetation in dry climates tends

  4. Path integral Monte Carlo determination of the fourth-order virial coefficient for unitary two-component Fermi gas with zero-range interactions

    Science.gov (United States)

    Yan, Yangqian; Blume, D.

    2016-05-01

    The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astro physics. This work determines the fourth-order virial coefficient b4 of such a strongly-interacting Fermi gas using a customized ab inito path integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b4, our b4 agrees with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly anti-symmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions. We gratefully acknowledge support by the NSF.

  5. Path-Integral Monte Carlo Determination of the Fourth-Order Virial Coefficient for a Unitary Two-Component Fermi Gas with Zero-Range Interactions.

    Science.gov (United States)

    Yan, Yangqian; Blume, D

    2016-06-10

    The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astrophysics. This work determines the fourth-order virial coefficient b_{4} of such a strongly interacting Fermi gas using a customized ab initio path-integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b_{4}, our b_{4} agrees within error bars with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly antisymmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions. PMID:27341213

  6. Path-Integral Monte Carlo Determination of the Fourth-Order Virial Coefficient for a Unitary Two-Component Fermi Gas with Zero-Range Interactions

    Science.gov (United States)

    Yan, Yangqian; Blume, D.

    2016-06-01

    The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astrophysics. This work determines the fourth-order virial coefficient b4 of such a strongly interacting Fermi gas using a customized ab initio path-integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b4 , our b4 agrees within error bars with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly antisymmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions.

  7. Nonautonomous vector matter waves in two-component Bose-Einstein condensates with combined time-dependent harmonic-lattice potential

    International Nuclear Information System (INIS)

    We construct exact self-similar soliton solutions of three-dimensional coupled Gross–Pitaevskii equations for two-species Bose–Einstein condensates (BECs) in a combined time-dependent harmonic-lattice potential. Based on these solutions, we investigate the control and manipulation of solitary waves for three kinds of BECs with changing diffraction and nonlinearity coefficients; the solutions include Ma breathers and Peregrine and Akhmediev soliton solutions. Our results indicate that matter waves readily propagate in this system. It is shown that diffraction and lattice potential factors play important roles in the beam evolution characteristics, such as the peak, the phase offset, the linear phase, and the chirp. (paper)

  8. Ripples and the formation of anisotropic lipid domains: Imaging two-component double bilayers by atomic force microscopy_copy_03

    DEFF Research Database (Denmark)

    Leidy, C.; Kaasgaard, Thomas; Crowe, J.H.;

    2002-01-01

    Direct visualization of the fluid-phase/ordered-phase domain structure in mica-supported bilayers composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-distearoyl-sn-glycero-3-phosphocholine mixtures is performed with atomic force microscopy. The system studied is a double bilayer supported...... on a mica surface in which the top bilayer (which is not in direct contact with the mica) is visualized as a function of temperature. Because the top bilayer is not as restricted by the interactions with the surface as single supported bilayers, its behavior is more similar to a free-standing bilayer...

  9. Crosscap Numbers of Two-component Links

    OpenAIRE

    Zhang, Gengyu

    2006-01-01

    We define the crosscap number of a 2-component link as the minimum of the first Betti numbers of connected, non-orientable surfaces bounding the link. We discuss some properties of the crosscap numbers of 2-component links.

  10. Decelerating relativistc two-component jets

    OpenAIRE

    Meliani, Z.; Keppens, R.

    2009-01-01

    Transverse stratification is a common intrinsic feature of astrophysical jets. There is growing evidence that jets in radio galaxies consist of a fast low-density outflow at the jet axis, surrounded by a slower, denser, extended jet. The inner and outer jet components then have a different origin and launching mechanism, making their effective inertia, magnetization, associated energy flux, and angular momentum content different as well. Their interface will develop differential rotation, whe...

  11. Measures on two-component configuration spaces

    CERN Document Server

    Finkelshtein, D L

    2007-01-01

    We study measures on the configuration spaces of two type particles. Gibbs measures on the such spaces are described. Main properties of corresponding relative energies densities and correlation functions are considered. In particular, we show that a support set for the such Gibbs measure is the set of pairs of non-intersected configurations.

  12. Measures on two-component configuration spaces

    Directory of Open Access Journals (Sweden)

    D.L. Finkelshtein

    2009-01-01

    Full Text Available We study the measures on the configuration spaces of particles of two types. Gibbs measures on such spaces are described. Main properties of corresponding relative energy densities and correlation functions are considered. In particular, we show that a support set for such Gibbs measure is the set of pairs of non-intersected configurations.

  13. Two component-three dimensional catalysis

    Science.gov (United States)

    Schwartz, Michael; White, James H.; Sammells, Anthony F.

    2002-01-01

    This invention relates to catalytic reactor membranes having a gas-impermeable membrane for transport of oxygen anions. The membrane has an oxidation surface and a reduction surface. The membrane is coated on its oxidation surface with an adherent catalyst layer and is optionally coated on its reduction surface with a catalyst that promotes reduction of an oxygen-containing species (e.g., O.sub.2, NO.sub.2, SO.sub.2, etc.) to generate oxygen anions on the membrane. The reactor has an oxidation zone and a reduction zone separated by the membrane. A component of an oxygen containing gas in the reduction zone is reduced at the membrane and a reduced species in a reactant gas in the oxidation zone of the reactor is oxidized. The reactor optionally contains a three-dimensional catalyst in the oxidation zone. The adherent catalyst layer and the three-dimensional catalyst are selected to promote a desired oxidation reaction, particularly a partial oxidation of a hydrocarbon.

  14. Two-component multi-configurational second-order perturbation theory with Kramers restricted complete active space self-consistent field reference function and spin-orbit relativistic effective core potential

    Science.gov (United States)

    Kim, Inkoo; Lee, Yoon Sup

    2014-10-01

    We report the formulation and implementation of KRCASPT2, a two-component multi-configurational second-order perturbation theory based on Kramers restricted complete active space self-consistent field (KRCASSCF) reference function, in the framework of the spin-orbit relativistic effective core potential. The zeroth-order Hamiltonian is defined as the sum of nondiagonal one-electron operators with generalized two-component Fock matrix elements as scalar factors. The Kramers symmetry within the zeroth-order Hamiltonian is maintained via the use of a state-averaged density, allowing a consistent treatment of degenerate states. The explicit expressions are derived for the matrix elements of the zeroth-order Hamiltonian as well as for the perturbation vector. The use of a fully variational reference function and nondiagonal operators in relativistic multi-configurational perturbation theory is reported for the first time. A series of initial calculations are performed on the ionization potential and excitation energies of the atoms of the 6p-block; the results display a significant improvement over those from KRCASSCF, showing a closer agreement with experimental results. Accurate atomic properties of the superheavy elements of the 7p-block are also presented, and the electronic structures of the low-lying excited states are compared with those of their lighter homologues.

  15. High-power gas-discharge excimer ArF, KrCl, KrF and XeCl lasers utilising two-component gas mixtures without a buffer gas

    Science.gov (United States)

    Razhev, A. M.; Kargapol'tsev, E. S.; Churkin, D. S.

    2016-03-01

    Results of an experimental study of the influence of a gas mixture (laser active medium) composition on an output energy and total efficiency of gas-discharge excimer lasers on ArF* (193 nm), KrCl* (222 nm), KrF* (248 nm) and XeCl* (308 nm) molecules operating without a buffer gas are presented. The optimal ratios of gas components (from the viewpoint of a maximum output energy) of an active medium are found, which provide an efficient operation of laser sources. It is experimentally confirmed that for gas-discharge excimer lasers on halogenides of inert gases the presence of a buffer gas in an active medium is not a necessary condition for efficient operation. For the first time, in two-component gas mixtures of repetitively pulsed gas-discharge excimer lasers on electron transitions of excimer molecules ArF*, KrCl*, KrF* and XeCl*, the pulsed energy of laser radiation obtained under pumping by a transverse volume electric discharge in a low-pressure gas mixture without a buffer gas reached up to 170 mJ and a high pulsed output power (of up to 24 MW) was obtained at a FWHM duration of the KrF-laser pulse of 7 ns. The maximal total efficiency obtained in the experiment with two-component gas mixtures of KrF and XeCl lasers was 0.8%.

  16. Preparation and Characterization of Two-component Waterborne Polyurethane Comprised of Water-soluble Acrylic Resin and HDI Biuret%水性双组份丙烯酸聚氨酯的合成与表征

    Institute of Scientific and Technical Information of China (English)

    周新华; 涂伟萍; 胡剑青

    2006-01-01

    A two-component waterborne polyurethane (2K-WPU) was prepared by mixing water-soluble acrylic resin and hexamethylene diisocyanate biuret, and then diluted for phase inversion with water. Compared with water-soluble acrylic resin, the phase inversion of 2K-WPU occurs at lower water content. It is indicated by TEM that 2K-WPU particles show a core-shell structure, in which HDI biuret is encapsulated by hydrophilic acrylic resin. 2K-WPU emulsion with HDI biuret has larger particle size and narrower distribution index, while for 2K-WPU emulsion with HDI isocyanurate, the latex not only has large particle size, but also has two-peak distribution. FTIR shows that the reaction between HDI biuret and acrylic resin can complete in 12h. In addition, studies on effect of composition of acrylic resin on pefformance of 2K-WPU show that narrowing the polar difference between water-soluble acrylic resin and HDI biuret and improving the miscibility of two components are the key to prepare the transparent and high gloss films with high crosslinking density.

  17. Characterization of the two-component, FAD-dependent monooxygenase SgcC that requires carrier protein-tethered substrates for the biosynthesis of the enediyne antitumor antibiotic C-1027.

    Science.gov (United States)

    Lin, Shuangjun; Van Lanen, Steven G; Shen, Ben

    2008-05-21

    C-1027 is a potent antitumor antibiotic composed of an apoprotein (CagA) and a reactive enediyne chromophore. The chromophore has four distinct chemical moieties, including an ( S)-3-chloro-5-hydroxy-beta-tyrosine moiety, the biosynthesis of which from l-alpha-tyrosine requires five proteins: SgcC, SgcC1, SgcC2, SgcC3, and SgcC4; a sixth protein, SgcC5, catalyzes the incorporation of this beta-amino acid moiety into C-1027. Biochemical characterization of SgcC has now revealed that (i) SgcC is a two-component, flavin adenine dinucleotide (FAD)-dependent monooxygenase, (ii) SgcC is only active with SgcC2 (peptidyl carrier protein)-tethered substrates, (iii) SgcC-catalyzed hydroxylation requires O 2 and FADH 2, the latter supplied by the C-1027 pathway-specific flavin reductase SgcE6 or Escherichia coli flavin reductase Fre, and (iv) SgcC efficiently catalyzes regioselective hydroxylation of 3-substituted beta-tyrosyl-S-SgcC2 analogues, including the chloro-, bromo-, iodo-, fluoro-, and methyl-substituted analogues, but does not accept 3-hydroxy-beta-tyrosyl-S-SgcC2 as a substrate. Together with the in vitro data for SgcC4, SgcC1, and SgcC3, the results establish that SgcC catalyzes the hydroxylation of ( S)-3-chloro-beta-tyrosyl-S-SgcC2 as the final step in the biosynthesis of the ( S)-3-chloro-5-hydroxy-beta-tyrosine moiety prior to incorporation into C-1027. SgcC now represents the first biochemically characterized two-component, FAD-dependent monooxygenase that acts on a carrier-protein-tethered aromatic substrate. PMID:18426211

  18. 非焦油型双组分聚氨酯防水涂料的研制%Preparation of Non-tar-type Two-component Polyurethane Waterproof Coating

    Institute of Scientific and Technical Information of China (English)

    马俊

    2012-01-01

    通过一定比例合成含有NCO的聚氨酯预聚体为A组分,将粉料、聚醚、MOCA、助剂等制成B组分,将A、B组分按质量比1:2混合成膜制得非焦油型双组分聚氨酯涂料。探讨了NCO含量、MOCA、催化助剂、消泡荆对双组分聚氨酯涂料的影响,结果表明:NCO含量在4.O%。4.6%、MOCA含量在2.5%~4.0%、催化剂在0.08%~0.12%、消泡剂在013%~0.7%,可以制得性能优异的双组分聚氨酯涂料。%Polyurethane prepolymer with NCO groups was synthesized by proportional mixing as A component, B component was made of powder, polyether, MOCA and additives, and non-tar polyurethane coating was prepared by A, B components according to the mass ratio of 1 : 2. Influencing factors of two components polyurethane coating that caused by content of NCO, MOCA, catalytic agent, defoaming agent were discussed. The results showed that: high performance two-component polyurethane coating can be prepared when the content of NCO is 4.0%- 4.6%, MOCA content is 2.5% -4.0%, catalyst is 0.08% 0.12% and defoaming agent is 0.3%- 0.7%.

  19. Formulation and Characterization of Two Component Waterborne Acrylic Wood Coatings%水性双组分丙烯酸木器涂料的配制与表征

    Institute of Scientific and Technical Information of China (English)

    李慧; 张一帆

    2014-01-01

    以水性羟基丙烯酸为主要成膜物质,脂肪族异氰酸酯为交联剂,添加其它助剂制备了性能优良的水性双组分丙烯酸木器漆;研究了丙烯酸种类和不同的n(-NCO)∶n(-OH)对漆膜性能的影响,最佳的n(-NCO)∶n(-OH)=1.3。这种双组分水性木器漆在常温下能够固化成膜。性能测试表明,该水性涂料具有良好的耐醇性、耐碱性、耐污染性、耐干热和耐湿热性,以及较高的硬度。最后,用FTIR对固化前后丙烯酸结构的改变进行了表征。%Hydroxyl-functional acrylic aqueous dispersion is the main film forming substance , aliphatic isocyanate is the curing agent, and some coating additives are contained in the formula.The performance of two-component wood coating is excel-lence.Acrylic types and -NCO/-OH molar ratio have influences on the performance of cured coating.The best -NCO/-OH molar ratio is 1.3.This two-component waterborne wood coating can cure at room temperature.The tests show that performance properties of cured coating, induding alcohol resistance, alkaline resistance, dry resistance, wet heat resist-ance, and pencil hardness, are excellence.The change of coating structure during the curing process was studied by using Fourier transform infrared ( FTIR) spectroscopy .

  20. 一种低成本室温固化双组分环氧密封胶的研制%Preparation of a low-cost room temperature curable two-component epoxy sealant

    Institute of Scientific and Technical Information of China (English)

    李吉明; 薛纪东; 钟汉荣

    2013-01-01

    A low-cost room temperature curable two-component epoxy sealant was prepared with liquid bisphenol A type epoxy resin and modified amines.Its curing mechanism was discussed in this paper.The effect of temperature and two component weight ratio on the working life and the effect of the amounts of silica powder and dioctyl phthalate on the bonding strength were also studied.The experimental results showed that the change of temperature could affect the working life obviously.The working life of product got shorter while its reaction rate speeded up due to the elevation of temperature.When the silica powder amount was 30~75 phrs,the wettability of sealant got poor,the defects in cured sealant layer increased,amd the tensile shear strength decreased with increasing the silica powder amount.The adding of dioctyl phthalate decreased the cross-linking desity of cured sealant and the bonding strength of modified resin.%采用低分子质量双酚A型环氧树脂及改性胺类固化剂研制了一种低成本室温固化双组分环氧胶粘剂。探讨了其固化机理,考查了温度、配比对适用期的影响,以及硅微粉、邻苯二甲酸二辛酯的用量对胶接强度的影响。结果表明,温度变化对该产品的适用期影响较大。温度升高,适用期变短。硅微粉加入量在30~75份时,胶的湿润性变差,固化后的胶层缺陷增多,拉伸剪切强度随硅微粉用量的增大而下降。邻苯二甲酸二辛酯的加入降低固化后的交联密度,使环氧胶的胶接强度下降。

  1. 双组分聚氨酯涂料用改性醇酸树脂的研究%Research of Modified Alkyd Resin for Two-Component Polyurethane Coatings

    Institute of Scientific and Technical Information of China (English)

    刘清福; 徐朝华; 夏德慧

    2012-01-01

    The two-component polyurethane coatings were compounded with modified short oil alkyd resin as A component and isocyanate prepolymers as B component. The effect of A component on two-component polyurethane coatings were investigated. The results showed that coconut oil modification short oil alkyd resin could be used as gloss paint, yellowing resistance finish for its pure white color, yellowing resistance properties and good fullness. Castor oil modification short oil alkyd resin could be used as ordinary finish painted resin for its deep color, good fullness, lower drying rate and excellent flexility. Soybean oil modification short oil alkyd resin could be used as primer and matte paint for its fast drying rate. Synthetic fatty acid modification short oil alkyd resin could be used as high-grade finish painted resin for the pure while color, good level ability, slow-speeded drying, nice fullness and high hardness.%采用不同改性的短油度醇酸树脂作甲组分,异氰酸酯预聚物作乙组分,配制双组分聚氨酯涂料,探讨甲组分对双组分聚氨酯涂料性能的影响.结果表明,椰子油改性短油度醇酸树脂,颜色水白、耐黄变性能和丰满度好,可以作为高档的亮光清面漆、耐黄变的面漆用树脂;蓖麻油改性短油度醇酸树脂,颜色较深、丰满度较好、干燥速度慢及柔韧性好,可以作为普通的亮光面漆用树脂;豆油改性短油度醇酸树脂,干燥速度较快,应用于底漆和哑光面漆;合成脂肪酸改性短油度醇酸树脂,颜色水白、流平好、干燥速度慢、丰满度高及硬度高,可以作为高档的亮光面漆用树脂.

  2. Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostics

    CERN Document Server

    Sundqvist, J O; Owocki, S P

    2014-01-01

    [Abridged] We develop and benchmark a fast and easy-to-use effective-opacity formalism for line and continuum radiative transfer in an accelerating two-component clumpy medium. The formalism bridges the limits of optically thin and thick clumps, and is here used to i) design a simple vorosity-modified Sobolev with exact integration (vmSEI) method for analyzing UV wind resonance lines in hot, massive stars, and ii) derive simple correction factors to the line force driving the outflows of such stars. We show that (for a given ionization factor) UV resonance doublets may be used to analytically predict the upward corrections in empirically inferred mass-loss rates associated with porosity in velocity space (a.k.a. velocity-porosity, or vorosity), but that severe solution degeneracies exist. For an inter-clump density set to 1 % of the mean density, we for O and B supergiants derive upward empirical mass-loss corrections of typically factors of either ~5 or ~50, depending on which of the two applicable solutions...

  3. 液体古马隆改性双组分聚氨酯涂料的制备和性能%Preparation and properties of liquid coumarone modified two-component polyurethane coating

    Institute of Scientific and Technical Information of China (English)

    冯涛; 韩胜利; 杨足明; 周柳

    2012-01-01

    The liquid coumarone modified two-component polyurethane coating was prepared,among which the component A is the prepolymcr containing NCO groups and the component B is the curing agent containing mixed diamine and liquid coumarone.The effects of ratio of triol and diol,NCO group content,liquid coumarone amount etc.,on the film properties were discussed and the optimal formulation was obtained.The tensile strength is 2.5 MPa.the elongation at break is 750% and the solid content is over 99%,that can achieve the requirements,in standard GB/T 19250-2003.%制备了液体古马隆改性的双组分聚氨酯涂料,其中A组分为含-NCO的预聚物,B组分为含混合二元胺和液体古马隆的固化剂.分别讨论了三元醇和二元醇的比例、-NCO含量、液体古马隆添加量等对涂膜性能的影响,得到最优化的配方.胶膜强度为2.5 MPa,断裂伸长率为750%.涂料固含量大于99%,可以达到《GB/T 19250-2003聚氨酯防水涂料》规定的指标要求.

  4. Simultaneous Determination of two Components in Compound Tinidazole Gargles by Multiply Factor Method%用乘子法同时测定复方替硝唑含漱液中二组分的含量

    Institute of Scientific and Technical Information of China (English)

    魏得良; 郭皖北; 周明达; 王曼娟; 刘建华

    2006-01-01

    In this paper, the basic principle and computing of multiply factor method applied to multicomponent analysis were discussed. The method was applied to simultaneous determination of two components in compound tinidazole gargles. The average recovery of Chlorhexidine and tinidazole in simulation samples was 99.75%、100.17% and relative standard deviations for them were 0.73%、0.42% respectively (n=10). The results of determination for three batches of actual samples were agreed with those by standard method. This method promises well to be adopted as an official assay method for compound tinidazole gargles.%用乘子法处理多波长吸光度数据,同时测定复方替硝唑含漱液中二组分的含量.简要介绍了乘子法的原理和计算步骤,模拟样品中醋酸氯已定、替硝唑的平均回收率分别为99.75%,100.17%,标准偏差分别为0.73%,0.42%(n=10),对三个批号实际样品的测定结果与标准方法吻合.与标准方法相比,该方法具有简便、快速、易于实现自动分析的优点.

  5. Dam methylation participates in the regulation of PmrA/PmrB and RcsC/RcsD/RcsB two component regulatory systems in Salmonella enterica serovar Enteritidis.

    Directory of Open Access Journals (Sweden)

    Sebastián Hernán Sarnacki

    Full Text Available The absence of Dam in Salmonella enterica serovar Enteritidis causes a defect in lipopolysaccharide (LPS pattern associated to a reduced expression of wzz gene. Wzz is the chain length regulator of the LPS O-antigen. Here we investigated whether Dam regulates wzz gene expression through its two known regulators, PmrA and RcsB. Thus, the expression of rcsB and pmrA was monitored by quantitative real-time RT-PCR and Western blotting using fusions with 3×FLAG tag in wild type (wt and dam strains of S. Enteritidis. Dam regulated the expression of both rcsB and pmrA genes; nevertheless, the defect in LPS pattern was only related to a diminished expression of RcsB. Interestingly, regulation of wzz in serovar Enteritidis differed from that reported earlier for serovar Typhimurium; RcsB induces wzz expression in both serovars, whereas PmrA induces wzz in S. Typhimurium but represses it in serovar Enteritidis. Moreover, we found that in S. Enteritidis there is an interaction between both wzz regulators: RcsB stimulates the expression of pmrA and PmrA represses the expression of rcsB. Our results would be an example of differential regulation of orthologous genes expression, providing differences in phenotypic traits between closely related bacterial serovars.

  6. Final report of research supported by DOE Grant No. DE-FG02-96ER14635: Photochemical studies of two component systems within the restricted spaces of zeolites.

    Energy Technology Data Exchange (ETDEWEB)

    Ramamurthy, V.

    2002-05-05

    Most chemistry in nature occurs within a closed and confined space. In contrast to this time-evolved [m?] organic chemists have focused their interests in developing reaction methods in solution. The price for this is paid in terms of non-selectivity in product formation, expensive reagents, and enormous wastes. Eventually 'man-developed' solution methods to make molecules have to be replaced by more selective, more environmentally friendly, and less expensive strategies. One approach in this direction would be to use controlled environments. The project focused towards developing energy efficient methods to prepare energy rich molecules that were useful to the public. In this context synthetic zeolites, the counterpart of naturally occurring minerals, were explored as the reaction media.

  7. CesRK, a two-component signal transduction system in Listeria monocytogenes, responds to the presence of cell wall-acting antibiotics and affects beta-lactam resistance

    DEFF Research Database (Denmark)

    Kallipolitis, Birgitte H; Ingmer, Hanne; Gahan, Cormac G;

    2003-01-01

    Listeria monocytogenes is a food-borne pathogen that can cause a variety of illnesses ranging from gastroenteritis to life-threatening septicemia. The beta-lactam antibiotic ampicillin remains the drug of choice for the treatment of listeriosis. We have previously identified a response regulator ...

  8. Study on preparation and properties of two-components PU adhesive for PP or PE%PP或PE用双组分PU胶粘剂的制备与性能研究

    Institute of Scientific and Technical Information of China (English)

    林星; 胡佳; 蔡海元; 崔爱玲; 林中祥

    2012-01-01

    以聚酯多元醇、混合异氰酸酯(MDI/TDI)、扩链剂(1,2-丙二醇)、异氰酸酯固化剂(TMP-TDI)和溶剂(乙酸乙酯)等为主要原料,制备了PP(聚丙烯)、PE(聚乙烯)粘接用双组分PU(聚氨酯)胶粘剂.研究结果表明:当m(结晶性聚酯多元醇)∶m(非结晶性聚酯多元醇)=80∶20~60∶40、R=n(-NCO)/n(-OH)=0.95~0.97、m(MDI)∶m(TDI)=90∶10~60∶40和w(功能性聚酯多元醇XCP-2325)=2%时,PU预聚体的相对分子质量为(9~11)×104,其常温固化12h后的邵A硬度(76)有利于PU预聚体的破碎;当PU预聚体/乙酸乙酯溶液的固含量为12%时,双组分PU胶粘剂的操作性能(黏度为22 mPa·s)、180°剥离强度(初始2.3 N/25 mm、最终41.0 N/25 mm)俱佳.%With polyester polyol, hybrid isocyanate (MDI/TDI), chain extender (1 , 2-propylene glycol), isocyanate curing agent (TMP-TDI ) and solvent (ethyl acetate) as main raw materials , a two - components PU (polyurethane) adhesive for bonding polypropylene (PP) and polyethylene (PE) was prepared. The research results showed that the molecular weight of PU prepolymer was(9-11 )×104,its Shao A hardness(76) after room temperature curing 12 h was favorable for fragmentation of PU prepolymers when mass fractions of m (crystalline polyester polyol):m(noncrystalline polyester polyol) and m(MDI)-m(TDI) were 80:20-6040 and 90:10-6040 respectively,/? Value or molar ratio of n(-NCO)/n(-OH) was 0.95-0.97,and mass fraction of functional polyester polyol(XCP-2325) was 2%. The two-components PU adhesive had both good operation properties(viscosity at 22 mPa·s) and good 180° peeling strength (initial peeling strength at 2.3 N/25 mm,and final peeling strength at 41.0 N/25 mm) when solid content of PU prepolymers/ethyl acetate solution was 12%.

  9. Simulation of Mixing Eveness of Two - component Polyurethane Borehole Sealing Material by CFD Technique%聚氨酯封孔材料双液混合均匀度CFD模拟

    Institute of Scientific and Technical Information of China (English)

    成艳英; 林柏泉; 郝志勇; 高亚斌; 李飞; 代华明; 于俊洋

    2012-01-01

    Polyurethane is one of the most widely used material in borehole sealing. The two - component polyurethane must be mixed first in the static mixer before pumping into the drill hole. There. is no doubt that the mixing quality of polyurethane is very important to the sealing quality of various drillings. A mixing effect evaluation of uneven degree and sample variance through the mathematical meth- ods was established. Based on the previous studies, this paper designed a kind of special static mixer for mixing polyurethane, and car- ried on the optimization of the static mixer's structure by investigating the mixing effect of polyurethane through Fluent numerical simula- tion software.%聚氨酯材料是目前煤矿钻孔密封应用最广泛的材料之一。双液聚氨酯在用封孔泵注入钻孔前,先要在静态混合器中混合,其混合效果对于聚氨酯的封孔质量来说非常重要。利用数学方法建立了基于混合不均匀度和样本方差的混合效果评价指标,在前人研究的基础上,设计了一种适合聚氨酯封孔材料混合的静态混合器。同时运用Fluent数值模拟软件,考察聚氨酯在混合器内的混合效果,进而对静态混合器的结构参数进行优化。

  10. 简谐势+四次势阱中两组分自旋轨道耦合旋转玻色爱因斯坦凝聚体%Two-component Bose-Einstein Condensates in Harmonic Plus Quartic Potential with Spin-orbit-coupled and Rotation

    Institute of Scientific and Technical Information of China (English)

    陈光平

    2015-01-01

    采用中心差分和虚时演化数值实验方法研究了简谐势+四次势阱中自旋轨道耦合作用下的两分量旋转玻色爱因斯坦凝聚体。发现自旋轨道作用强度和原子种间相互作用对系统基态结构有着重要的影响,原子种间相互作用强度的增加可使系统从相混合变化成相分离;而自旋轨道耦合作用强度的增加,可使系统从相分离的状态变化成相混合,并产生涡旋、形成分块边界。%The two-component Bose-Einstein condensates in harmonic plus quartic potential with spin-orbit-coupled and rotation have been studied by the finite difference and image-time propagating numerical method. It is found that the inter-component interaction and the strength of the spin-orbit-coupled play an important role in the system’ s ground states. The system can transform from the phase co-exist to the phase separation with the increase of the inter-component interaction;with the increase of the strength of spin-orbit-coupled, the system can trans⁃form from phase separation to phase co-exist, at the same time, there are vortex and domain in the ground state of the system.

  11. Development of Waterborne Two-component Polyurethane Drawable and Anti-graffiti Wall Coatings%水性双组分聚氨酯可绘画和抗涂鸦涂料的研制

    Institute of Scientific and Technical Information of China (English)

    唐英; 蔡伟; 危春阳

    2015-01-01

    Waterborne drawable interior and exterior wall coatings were developed with excellent graffiti removal ability, scrub-resistance and application properties by using waterborne two-component polyurethane and curing agent as film-forming substances. The effect of the binder types and the mixing ratios of waterborne polyurethane and curing agent were discussed, including the dosage of water on the graffiti removal ability of the coatings. The marks of this drawable coatings by a water mark pen, water color pen, dustless chalk, shoe polish, ink, tomato juice, coffee and black tea can be easily cleaned. The compositions in this paint meet the requirements of all the related environment standards. In particular, VOC content is only 11 g/L, which is much lower than the VOC limit 20 g/L in T31/01002-C001—2014 for waterborne interior coatings. This product was environmentally friendly and suitable for kids' rooms, kindergarten, schools, hospitals, hotels and public places.%使用水性双组分聚氨酯乳液及固化剂技术开发出具有优异的耐涂鸦性能,和高度环境友好的水性内外墙可擦洗的绘画涂料.研究了水性聚氨酯乳液/固化剂种类、比例、稀释剂水添加量等因素对绘画涂料涂层上涂鸦物质清除性能等的影响,并对比测试了涂料的综合性能,制备出了兼具优异涂鸦清除性能、环保性能、耐擦洗性能、施工性能等综合性能优异的水性内墙绘画涂料.经试验测试,涂层表面能够轻松清除水性白板笔、水彩笔、无尘粉笔等涂鸦物质以及鞋油、墨水、番茄酱、咖啡、红茶等多种生活污渍,涂料的组分达到所有相关的环保标准要求,尤其是挥发性有机化合物(VOC)含量仅为11 g/L,远低于T31/01002-C001—2014《儿童水性内墙涂料》标准中VOC的限制20 g/L,特别适合家居儿童房、幼儿园、学校、医院、宾馆等场所的内外墙涂装.

  12. 氟改性双组分水性丙烯酸聚氨酯涂料性能研究%Research of Fluorine-Modified Two Component Waterborne Acrylic Polyurethane Coating Performance

    Institute of Scientific and Technical Information of China (English)

    许海燕; 张兴元; 戴家兵; 许飞; 李治; 周静

    2012-01-01

    A series of waterborne hydroxyl polyacrylate resin with different fluorine content were successfully prepared by solution polymerization, using dodecafluoroheptyl methacrylate (DFMA) , acrylate acid (AA) , hydroxyethyl methacrylate (HEMA) , methyl methacrylate (MMA) and butyl acrylate (BA) as monomers. Furthermore , the hydroxyl acrylic resins were cured with hydrophilically modified polyisocyanate curing agent (Bay-hydur XP 2655) to obtain two-component waterborne acrylic polyurethane (2K-WPU) coatings. FT-IR was employed to investigate the structure of the resin and cured films. The contact angle, water swelling ratio and varnish properties of the cured films were tested, respectively. The test result showed that the resins had an average particle size ranging from 28. 2 nm to 68. 1 ran and exhibited unimodal size distributions. The experiment revealed that the contact angle of 2K-WPU films increased from 70. 3° to 97. 6° and the water swelling ratio decreased from 11. 4% to 6. 31% with the DFMA content in hydroxyl polyacrylate resin increasing from 0 to 20% , indicating that the water resistance of 2K-WPU was greatly improved by the incorporation of fluorine-containing component. In addition, varnish test showed that the fluorine-modified 2K-WPU exhibited excellent properties.%以甲基丙烯酸十二氟庚酯(DFMA)、丙烯酸(AA)、甲基丙烯酸羟乙酯(HEMA)、甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)为原料,采用溶液聚合法合成了一系列氟含量不同的水性羟基丙烯酸树脂.将含氟水性羟基丙烯酸树脂、亲水性异氰酸酯固化剂和助剂混合制备氟改性双组分水性丙烯酸聚氨酯(2K-WPU)涂料.利用傅里叶变换红外光谱(FT-IR)对其结构进行了表征,并对涂料的接触角、吸水率和清漆性能分别进行了测试.结果表明,该水性树脂粒径在28.2~68.1 nm之间,粒径分布均匀.当水性羟基丙烯酸树脂组成中DFMA质量分数从0增加至20%时,所制备氟改性2K

  13. Development of Waterborne Two-component Polyurethane Drawable and Anti-graffiti Wall Coatings%水性双组分聚氨酯可绘画和抗涂鸦涂料的研制

    Institute of Scientific and Technical Information of China (English)

    唐英; 蔡伟; 危春阳

    2015-01-01

    使用水性双组分聚氨酯乳液及固化剂技术开发出具有优异的耐涂鸦性能,和高度环境友好的水性内外墙可擦洗的绘画涂料.研究了水性聚氨酯乳液/固化剂种类、比例、稀释剂水添加量等因素对绘画涂料涂层上涂鸦物质清除性能等的影响,并对比测试了涂料的综合性能,制备出了兼具优异涂鸦清除性能、环保性能、耐擦洗性能、施工性能等综合性能优异的水性内墙绘画涂料.经试验测试,涂层表面能够轻松清除水性白板笔、水彩笔、无尘粉笔等涂鸦物质以及鞋油、墨水、番茄酱、咖啡、红茶等多种生活污渍,涂料的组分达到所有相关的环保标准要求,尤其是挥发性有机化合物(VOC)含量仅为11 g/L,远低于T31/01002-C001—2014《儿童水性内墙涂料》标准中VOC的限制20 g/L,特别适合家居儿童房、幼儿园、学校、医院、宾馆等场所的内外墙涂装.%Waterborne drawable interior and exterior wall coatings were developed with excellent graffiti removal ability, scrub-resistance and application properties by using waterborne two-component polyurethane and curing agent as film-forming substances. The effect of the binder types and the mixing ratios of waterborne polyurethane and curing agent were discussed, including the dosage of water on the graffiti removal ability of the coatings. The marks of this drawable coatings by a water mark pen, water color pen, dustless chalk, shoe polish, ink, tomato juice, coffee and black tea can be easily cleaned. The compositions in this paint meet the requirements of all the related environment standards. In particular, VOC content is only 11 g/L, which is much lower than the VOC limit 20 g/L in T31/01002-C001—2014 for waterborne interior coatings. This product was environmentally friendly and suitable for kids' rooms, kindergarten, schools, hospitals, hotels and public places.

  14. Preparation and properties of a new type alcohol-soluble PUA laminating adhesive with two-components%新型醇溶性双组分PUA复膜胶的制备与性能

    Institute of Scientific and Technical Information of China (English)

    黄丹丹; 季永新

    2012-01-01

    With allyl glycidyl ether (AGE), hydroxypropyl acrylate (HPA), ethyl acrylate(EA) and vinyl acetate(Vac) as comonomers,a main agent for laminating adhesive(epoxy-polyacrylate) was prepared. Then,with TDI (toluene diisocyanate) and PPG2000( poly ether diols) as main raw materials, and diethylene triamine as end capping agent,a curing agent for laminating adhesive(amino-terminated polyurethane) was prepared. Finally,a new type alcohol-soluble laminating adhesive with two-components was made by blend between main agent and curing agent with a certain proportion. The research results showed that the main agent had reversely best alcohol-soluble property when reaction temperature and reaction time were 75℃ and 8 h respectively, mass fraction of initiator was 1.8%,and mass ratio of m(EA):m(Vac):m(AGE):m(HPA) was 41:14:35:10. The curing agent had reversely best properties when reaction temperature and reaction time were 70 ℃ and 2 h respectively, and R or molar ratio of n(-NCO)/n(-OH) was 1.25. The properties between laminating adhesive and like import product were adjacent when molar ratio of n(amino):n(epoxy group) was 20:3,curing temperature and curing time were 50℃ and 24 h respectively.%以烯丙基缩水甘油醚(AGE)、丙烯酸羟丙酯(HPA)、丙烯酸乙酯(EA)和醋酸乙烯酯(VAc)作为共聚单体,合成了复膜胶的主剂——环氧基聚丙烯酸酯;以TDI(甲苯二异氰酸酯)、PPG2000(聚醚二元醇)为主要原料,二乙烯三胺为封端剂,合成了复膜胶的固化剂——端氨基PU(聚氨酯);将主剂和固化剂按一定比例共混后,制得新型双组分醇溶性复膜胶.研究结果表明:当反应温度为75℃、反应时间为8h、w(引发剂)=1.8%和m(EA )∶m(VAc )∶m( AGE )∶m(HPA )=41∶14∶35∶10时,主剂的醇溶性相对最好;当反应温度为70℃、反应时间为2h和R=n(-NCO )/n(-OH)=1.25时,固化剂的性能相对最好;当n(氨基)∶n(环氧基)=20∶3、固化温度为50

  15. NADPH-dependent reductive biotransformation with Escherichia coli and its pfkA deletion mutant: influence on global gene expression and role of oxygen supply.

    Science.gov (United States)

    Siedler, Solvej; Bringer, Stephanie; Polen, Tino; Bott, Michael

    2014-10-01

    An Escherichia coli ΔpfkA mutant lacking the major phosphofructokinase possesses a partially cyclized pentose phosphate pathway leading to an increased NADPH per glucose ratio. This effect decreases the amount of glucose required for NADPH regeneration in reductive biotransformations, such as the conversion of methyl acetoacetate (MAA) to (R)-methyl 3-hydroxybutyrate (MHB) by an alcohol dehydrogenase from Lactobacillus brevis. Here, global transcriptional analyses were performed to study regulatory responses during reductive biotransformation. DNA microarray analysis revealed amongst other things increased expression of soxS, supporting previous results indicating that a high NADPH demand contributes to the activation of SoxR, the transcriptional activator of soxS. Furthermore, several target genes of the ArcAB two-component system showed a lower mRNA level in the reference strain than in the ΔpfkA mutant, pointing to an increased QH2 /Q ratio in the reference strain. This prompted us to analyze yields and productivities of MAA reduction to MHB under different oxygen regimes in a bioreactor. Under anaerobic conditions, the specific MHB production rates of both strains were comparable (7.4 ± 0.2 mmolMHB  h(-1)  gcdw (-1) ) and lower than under conditions of 15% dissolved oxygen, where those of the reference strain (12.8 mmol h(-1)  gcdw (-1) ) and of the ΔpfkA mutant (11.0 mmol h(-1)  gcdw (-1) ) were 73% and 49% higher. While the oxygen transfer rate (OTR) of the reference strain increased after the addition of MAA, presumably due to the oxidation of the acetate accumulated before MAA addition, the OTR of the ΔpfkA strain strongly decreased, indicating a very low respiration rate despite sufficient oxygen supply. The latter effect can likely be attributed to a restricted conversion of NADPH into NADH via the soluble transhydrogenase SthA, as the enzyme is outcompeted in the presence of MAA by the recombinant NADPH-dependent alcohol

  16. Dynamic structure factors and sum rules in two-component quantum gases with spin-orbit coupling%自旋-轨道耦合作用下双组分量子气体中的动力学结构因子与求和规则

    Institute of Scientific and Technical Information of China (English)

    贺丽; 余增强

    2016-01-01

    Sum rules for the dynamic structure factors are powerful tools to explore the collective behaviors in many-body systems at zero temperature as well as at finite temperatures. The recent remarkable realization of synthetic spin-orbit (SO) coupling in quantum gases is opening up new perspective to study the intriguing SO effects with ultracold atoms. So far, a specific type of SO coupling, which is generated by a pair of Raman laser beams, has been experimentally achieved in Bose-Einstein condensates of 87Rb and degenerate Fermi gases of 40K and 6Li. In the presence of SO coupling, the dynamic structure factors for the density fluctuation and spin fluctuation satisfy different sum rules. In particular, in the two-component quantum gases with inter-species Raman coupling, the f-sum rule for the spin fluctuation has an additional term proportional to the transverse spin polarization. Due to the coupling between the momentum and spin, the first moment of the dynamic structure factor does not necessarily possess the inversion symmetry, which is in strong contrast to the conventional system without SO coupling. Such an asymmetric behavior could be observed in both Fermi gases and Bose gases with Raman coupling. As a demonstration, we focus on the uniform case at zero temperature in this work. For the non-interacting Fermi gases, the asymmetric first moment appears only when the Raman detuning is finite. The asymmetric amplitude is quite limited, and it vanishes at both zero detuning and infinite detuning. For the weakly interacting Bose gases, the first moment is asymmetric in momentum space even at zero detuning, when the ground state spontaneously breaks the Z2 symmetry in the plane-wave condensation phase. Using the Bogoliubov method, the dynamic structure factor and its first moment are explicitly calculated for various interaction parameters. We find that the asymmetric behavior in the spin channel could be much more significant than in the density channel, and the

  17. Two-component microinjection moulding for MID fabrication

    DEFF Research Database (Denmark)

    Islam, Aminul; Hansen, Hans Nørgaard; Tang, Peter Torben;

    2010-01-01

    Moulded interconnect devices (MIDs) are plastic substrates with electrical infrastructure. The fabrication of MIDs is usually based on injection moulding, and different process chains may be identified from this starting point. The use of MIDs has been driven primarily by the automotive sector......, but recently, the medical sector seems more and more interested. In particular, the possibility of miniaturisation of three-dimensional components with electrical infrastructure is attractive. The present paper describes possible manufacturing routes and challenges of miniaturised MIDs based on two...

  18. Quantum melting of two-component Rydberg crystals

    CERN Document Server

    Lan, Zhihao; Lesanovsky, Igor

    2016-01-01

    We investigate the quantum melting of one dimensional crystals that are realized in an atomic lattice in which ground state atoms are laser excited to two Rydberg states. We focus on a regime where both, intra- and inter-state density-density interactions as well as coherent exchange interactions contribute. We determine stable crystalline phases in the classical limit and explore their melting under quantum fluctuations introduced by the excitation laser as well as two-body exchange. We find that quantum fluctuations introduced by the laser give rise to a devil's staircase structure which one might associate with transitions in the classical limit. The melting through exchange interactions is shown to also proceed in a step-like fashion, in case of mesoscopic crystals, due to the proliferation of Rydberg spinwaves.

  19. Characteristics of two-component epoxy modified bitumen

    NARCIS (Netherlands)

    Xiao, Y.; Van de Ven, M.F.C.; Molenaar, A.A.A.; Su, Z.; Zandvoort, F.

    2010-01-01

    Coal tar bearing emulsions were used in the Netherlands as binder in anti-skid surfaces for runways because of their perfect adhesion and fuel resistance properties. They are however toxic and will not be allowed anymore after 2010. Therefore alternatives need to be developed. As one of the alternat

  20. PHASE TRANSITION PROPERTIES OF A TWO COMPONENT FINITE MAGNETIC SUPERLATTICE

    Institute of Scientific and Technical Information of China (English)

    WANG XIAO-GUANG; LIU NING-NING; PAN SHAO-HUA; YANG GUO-ZHEN

    2000-01-01

    We study an (l, n) finite superlattice, which consists of two alternative magnetic materials(components) of l and n atomic layers, respectively. Based on the Ising model, we examine the phase transition properties of the magnetic superlattice. By transfer matrix method we derive the equation for Curie temperature of the superlattice. Numerical results are obtained for the dependence of Curie temperature on the thickness and exchange constants of the superlattice.