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Sample records for continuum state cellular

  1. Continuum representations of cellular solids

    SciTech Connect

    Neilsen, M.K.

    1993-09-01

    Cellular materials consist of interconnected struts or plates which form cells. The struts or plates are constructed from a variety of metals, polymers, ceramics and wood products. Cellular materials are often used in impact limiters for shipping containers to protect the contents from accidental impact events. These materials exhibit a variety of complex behavior when subjected to crushing loads. This research focuses on the development of continuum representations of cellular solids that can be used in the finite element analysis of shipping container accidents. A significant portion of this work is the development of a new methodology to relate localized deformations to appropriate constitutive descriptions. This methodology provides the insight needed to select constitutive descriptions for cellular solids that capture the localized deformations that are observed experimentally. Constitutive relations are developed for two different cellular materials, aluminum honeycomb and polyurethane foam. These constitutive relations are based on plasticity and continuum damage theories. Plasticity is used to describe the permanent deformation exhibited by both aluminum honeycomb and polyurethane foam. Continuum damage is needed to capture the change in elastic parameters due to cracking of the polyurethane cell wall materials. The new constitutive description of polyurethane foam is implemented in both static and dynamic finite element codes, and analytical and numerical predictions are compared with available experimental data.

  2. Floquet bound states in the continuum

    PubMed Central

    Longhi, Stefano; Valle, Giuseppe Della

    2013-01-01

    Quantum mechanics predicts that certain stationary potentials can sustain bound states with an energy buried in the continuous spectrum of scattered states, the so-called bound states in the continuum (BIC). Originally regarded as mathematical curiosities, BIC have found an increasing interest in recent years, particularly in quantum and classical transport of matter and optical waves in mesoscopic and photonic systems where the underlying potential can be judiciously tailored. Most of our knowledge of BIC is so far restricted to static potentials. Here we introduce a new kind of BIC, referred to as Floquet BIC, which corresponds to a normalizable Floquet state of a time-periodic Hamiltonian with a quasienergy embedded into the spectrum of Floquet scattered states. We discuss the appearance of Floquet BIC states in a tight-binding lattice model driven by an ac field in the proximity of the dynamic localization regime. PMID:23860625

  3. Towards a continuum theory of movement in interacting cellular systems

    NASA Astrophysics Data System (ADS)

    Newman, Timothy

    2003-10-01

    Interacting cellular systems form the basis of all higher organisms, and are fundamental to the understanding of embryogenesis, organ function, and neoplasms. I will describe a stochastic model of cell interactions which can be applied to these problems, and present some of our recent results on chemotactic response.

  4. Cellular automaton for chimera states

    NASA Astrophysics Data System (ADS)

    García-Morales, Vladimir

    2016-04-01

    A minimalistic model for chimera states is presented. The model is a cellular automaton (CA) which depends on only one adjustable parameter, the range of the nonlocal coupling, and is built from elementary cellular automata and the majority (voting) rule. This suggests the universality of chimera-like behavior from a new point of view: Already simple CA rules based on the majority rule exhibit this behavior. After a short transient, we find chimera states for arbitrary initial conditions, the system spontaneously splitting into stable domains separated by static boundaries, some synchronously oscillating and the others incoherent. When the coupling range is local, nontrivial coherent structures with different periodicities are formed.

  5. A new micromechanical approach of micropolar continuum modeling for 2-D periodic cellular material

    NASA Astrophysics Data System (ADS)

    Niu, Bin; Yan, Jun

    2016-06-01

    In this paper, we present a new united approach to formulate the equivalent micropolar constitutive relation of two-dimensional (2-D) periodic cellular material to capture its non-local properties and to explain the size effects in its structural analysis. The new united approach takes both the displacement compatibility and the equilibrium of forces and moments into consideration, where Taylor series expansion of the displacement and rotation fields and the extended averaging procedure with an explicit enforcement of equilibrium are adopted in the micromechanical analysis of a unit cell. In numerical examples, the effective micropolar constants obtained in this paper and others derived in the literature are used for the equivalent micropolar continuum simulation of cellular solids. The solutions from the equivalent analysis are compared with the discrete simulation solutions of the cellular solids. It is found that the micropolar constants developed in this paper give satisfying results of equivalent analysis for the periodic cellular material.

  6. Quantum state transfer by time reversal in the continuum

    NASA Astrophysics Data System (ADS)

    Longhi, S.

    2016-03-01

    A method for high-fidelity quantum state transfer in a quantum network coupled to a continuum, based on time reversal in the continuum after decay, is theoretically suggested. Provided that the energy spectrum of the network is symmetric around a reference energy and symmetric energy states are coupled the same way to the common continuum, ideal perfect state transfer can be obtained after time reversal. In particular, it is shown that in a linear tight-binding chain a quantum state can be transformed into its mirror image with respect to the center of the chain after a controllable time. As compared to a quantum mirror image based on coherent transport in a static chain with properly tailored inhomogeneous hopping rates, our method does not require hopping rate engineering and is less sensitive to disorder for long transfer times.

  7. Regulation of cellular chromatin state

    PubMed Central

    Mishra, Rakesh K; Dhawan, Jyotsna

    2010-01-01

    The identity and functionality of eukaryotic cells is defined not just by their genomic sequence which remains constant between cell types, but by their gene expression profiles governed by epigenetic mechanisms. Epigenetic controls maintain and change the chromatin state throughout development, as exemplified by the setting up of cellular memory for the regulation and maintenance of homeotic genes in proliferating progenitors during embryonic development. Higher order chromatin structure in reversibly arrested adult stem cells also involves epigenetic regulation and in this review we highlight common trends governing chromatin states, focusing on quiescence and differentiation during myogenesis. Together, these diverse developmental modules reveal the dynamic nature of chromatin regulation providing fresh insights into the role of epigenetic mechanisms in potentiating development and differentiation. PMID:20592864

  8. Bound states in continuum: Quantum dots in a quantum well

    NASA Astrophysics Data System (ADS)

    Prodanović, Nikola; Milanović, Vitomir; Ikonić, Zoran; Indjin, Dragan; Harrison, Paul

    2013-11-01

    We report on the existence of a bound state in the continuum (BIC) of quantum rods (QR). QRs are novel elongated InGaAs quantum dot nanostructures embedded in the shallower InGaAs quantum well. BIC appears as an excited confined dot state and energetically above the bottom of a well subband continuum. We prove that high height-to-diameter QR aspect ratio and the presence of a quantum well are indispensable conditions for accommodating the BIC. QRs are unique semiconductor nanostructures, exhibiting this mathematical curiosity predicted 83 years ago by Wigner and von Neumann.

  9. Bound States in the Continuum in double layer structures

    PubMed Central

    Li, LiangSheng; Yin, Hongcheng

    2016-01-01

    We have theoretically investigated the reflectivity spectrums of single- and double-layer photonic crystal slabs and the dielectric multilayer stack. It is shown that light can be perfectly confined in a single-layer photonic crystal slab at a given incident angle by changing the thickness, permittivity or hole radius of the structure. With a tunable double-layer photonic crystal slab, we demonstrate that the occurrence of tunable bound states in the continuum is dependent on the spacing between two slabs. Moreover, by analytically investigating the Drude lossless multilayer stack model, the spacing dependence of bound states in the continuum is characterized as the phase matching condition that illuminates these states can occur at any nonzero incident angles by adjusting the spacing. PMID:27245435

  10. Bound States in the Continuum in double layer structures.

    PubMed

    Li, LiangSheng; Yin, Hongcheng

    2016-01-01

    We have theoretically investigated the reflectivity spectrums of single- and double-layer photonic crystal slabs and the dielectric multilayer stack. It is shown that light can be perfectly confined in a single-layer photonic crystal slab at a given incident angle by changing the thickness, permittivity or hole radius of the structure. With a tunable double-layer photonic crystal slab, we demonstrate that the occurrence of tunable bound states in the continuum is dependent on the spacing between two slabs. Moreover, by analytically investigating the Drude lossless multilayer stack model, the spacing dependence of bound states in the continuum is characterized as the phase matching condition that illuminates these states can occur at any nonzero incident angles by adjusting the spacing. PMID:27245435

  11. Bound States in the Continuum in double layer structures

    NASA Astrophysics Data System (ADS)

    Li, Liangsheng; Yin, Hongcheng

    2016-06-01

    We have theoretically investigated the reflectivity spectrums of single- and double-layer photonic crystal slabs and the dielectric multilayer stack. It is shown that light can be perfectly confined in a single-layer photonic crystal slab at a given incident angle by changing the thickness, permittivity or hole radius of the structure. With a tunable double-layer photonic crystal slab, we demonstrate that the occurrence of tunable bound states in the continuum is dependent on the spacing between two slabs. Moreover, by analytically investigating the Drude lossless multilayer stack model, the spacing dependence of bound states in the continuum is characterized as the phase matching condition that illuminates these states can occur at any nonzero incident angles by adjusting the spacing.

  12. Analytic continuation as a bridge between continuum and bound states

    NASA Astrophysics Data System (ADS)

    Blokhintsev, Leonid; Savin, Dmitry

    2015-05-01

    The problem of obtaining characteristics of bound nuclear states from continuum states data is discussed. It is shown that the ambiguities due to the existence of phase-equivalent potentials can be resolved by using the analytic properties of scattering amplitudes. The methods of determination of asymptotic normalization coefficients and vertex constants are considered. The asymptotic normalization coefficients for 6Li in the α + d channel are found by analytic continuation of the two-channel effective range expansion. The account of inelastic channels within the effective range approach is discussed.

  13. Mechanical bound state in the continuum for optomechanical microresonators

    NASA Astrophysics Data System (ADS)

    Chen, Yuan; Shen, Zhen; Xiong, Xiao; Dong, Chun-Hua; Zou, Chang-Ling; Guo, Guang-Can

    2016-06-01

    Clamping loss limits the quality factor of mechanical mode in the optomechanical resonators supported with the supporting stem. Using the mechanical bound state in the continuum (BIC), we have found that the mechanical clamping loss can be avoided. The mechanical quality factor of a microsphere could be achieved up to 108 for a specific radius of the stem, which forms a mechanical BIC with the combination of the symmetry protected mechanism and the single resonance mechanism. Such a mechanism is proved to be universal for different geometries and materials, thus can also be generalized to design high quality mechanical resonators.

  14. Block versus continuum deformation in the Western United States

    USGS Publications Warehouse

    King, G.; Oppenheimer, D.; Amelung, F.

    1994-01-01

    The relative role of block versus continuum deformation of continental lithosphere is a current subject of debate. Continuous deformation is suggested by distributed seismicity at continental plate margins and by cumulative seismic moment sums which yield slip estimates that are less than estimates from plate motion studies. In contrast, block models are favored by geologic studies of displacement in places like Asia. A problem in this debate is a lack of data from which unequivocal conclusions may be reached. In this paper we apply the techniques of study used in regions such as the Alpine-Himalayan belt to an area with a wealth of instrumental data-the Western United States. By comparing plate rates to seismic moment release rates and assuming a typical seismogenic layer thickness of 15 km it appears that since 1850 about 60% of the Pacific-North America motion across the plate boundary in California and Nevada has occurred seismically and 40% aseismically. The San Francisco Bay area shows similar partitioning between seismic and aseismic deformation, and it can be shown that within the seismogenic depth range aseismic deformation is concentrated near the surface and at depth. In some cases this deformation can be located on creeping surface faults, but elsewhere it is spread over a several kilometer wide zone adjacent to the fault. These superficial creeping deformation zones may be responsible for the palaeomagnetic rotations that have been ascribed elsewhere to the surface expression of continuum deformation in the lithosphere. Our results support the dominant role of non-continuum deformation processes with the implication that deformation localization by strain softening must occur in the lower crust and probably the upper mantle. Our conclusions apply only to the regions where the data are good, and even within the Western United States (i.e., the Basin and Range) deformation styles remain poorly resolved. Nonetheless, we maintain that block motion is the

  15. Bound states at exceptional points in the continuum

    NASA Astrophysics Data System (ADS)

    Fernández-García, N.; Hernández, E.; Jáuregui, A.; Mondragón, A.

    2014-05-01

    In this work, an example of exceptional points in the continuous spectrum of a Hamiltonian of von Neumann-Wigner type is presented and discussed. Remarkably, these exceptional points are not associated with a double pole in the scattering matrix but with a double pole in the normalization factor of the Jost eigenfunctions normalized to unit flux. At the exceptional points the two unnormalized Jost eigenfunctions are no longer linearly independent but coalesce to give rise to two Jordan cycles of generalized bound state energy eigenfunctions in the continuum and a Jordan block representation of the Hamiltonian. The regular scattering eigenfunction vanishes at the exceptional points and the irregular scattering eigenfunction has a double pole at the exceptional points. The scattering matrix is a regular analytical function of the wave number k for all k real including the exceptional points.

  16. Continuum-state and bound-state β--decay rates of the neutron

    NASA Astrophysics Data System (ADS)

    Faber, M.; Ivanov, A. N.; Ivanova, V. A.; Marton, J.; Pitschmann, M.; Serebrov, A. P.; Troitskaya, N. I.; Wellenzohn, M.

    2009-09-01

    For the β--decay of the neutron we analyze the continuum-state and bound-state decay modes. We calculate the decay rates, the electron energy spectrum for the continuum-state decay mode, and angular distributions of the decay probabilities for the continuum-state and bound-state decay modes. The theoretical results are obtained for the new value for the axial coupling constant gA=1.2750(9), obtained recently by H. Abele [Prog. Part. Nucl. Phys. 60, 1 (2008)] from the fit of the experimental data on the coefficient of the correlation of the neutron spin and the electron momentum of the electron energy spectrum of the continuum-state decay mode. We take into account the contribution of radiative corrections and the scalar and tensor weak couplings. The calculated angular distributions of the probabilities of the bound-state decay modes of the polarized neutron can be used for the experimental measurements of the bound-state β--decays into the hyperfine states with total angular momentum F=1 and scalar and tensor weak coupling constants.

  17. Proton capture to continuum states of {sup 209}Bi

    SciTech Connect

    Likar, A.; Lipoglavsek, M.; Vencelj, M.; Vidmar, T.; Bark, R.A.; Gueorguieva, E.; Komati, F.; Lawrie, J.J.; Maliage, S.M.; Mullins, S.M.; Murray, S.H.T.; Ramashidzha, T.M.

    2006-04-15

    High resolution spectra from fast proton radiative capture in {sup 208}Pb are presented for three energies of the incident protons: 14.8, 15.7, and 16.9 MeV. The collected spectra were analyzed with emphasis on the region of capture to unbound states in order to search for possible structure and to study the competition between two basically different phenomena: the statistical process versus the fluctuation effects in radiative capture to unbound final states. In the energy region of incoming protons considered in our experiment, the statistical processes modeled with a Hauser-Feshbach calculation dominate. The spectra of primary {gamma} rays, coincident with the low energy one from the decay of the f{sub 7/2} single-particle state, show a prominent structure which is predominantly of g{sub 9/2} character. The calculations of continuum spectra based on the extended direct-semidirect model and the Hauser-Feshbach statistical approach successfully reproduce the experimental data.

  18. Strain-Induced Localized States Within the Matrix Continuum of Self-Assembled Quantum Dots

    SciTech Connect

    Popescu, V.; Bester, G.; Zunger, A.

    2009-07-01

    Quantum dot-based infrared detectors often involve transitions from confined states of the dot to states above the minimum of the conduction band continuum of the matrix. We discuss the existence of two types of resonant states within this continuum in self-assembled dots: (i) virtual bound states, which characterize square wells even without strain and (ii) strain-induced localized states. The latter emerge due to the appearance of 'potential wings' near the dot, related to the curvature of the dots. While states (i) do couple to the continuum, states (ii) are sheltered by the wings, giving rise to sharp absorption peaks.

  19. Construction of a state evolution for Kawasaki dynamics in continuum

    NASA Astrophysics Data System (ADS)

    Berns, Christoph; Kondratiev, Yuri; Kutoviy, Oleksandr

    2013-06-01

    We consider conservative, non-equilibrium stochastic jump dynamics of interacting particles in continuum. These dynamics have a (grand canonical) Gibbs measure as invariant measure. The problem of existence of these dynamics is studied. The corresponding time evolution of correlation functions is constructed.

  20. Bound-state eigenenergy outside and inside the continuum for unstable multilevel systems

    NASA Astrophysics Data System (ADS)

    Miyamoto, Manabu

    2005-12-01

    The eigenvalue problem for the dressed bound state of unstable multilevel systems is examined both outside and inside the continuum, based on the N -level Friedrichs model, which describes the couplings between the discrete levels and the continuous spectrum. It is shown that a bound-state eigenenergy always exists below each of the discrete levels that lie outside the continuum. Furthermore, by strengthening the couplings gradually, the eigenenergy corresponding to each of the discrete levels inside the continuum finally emerges. On the other hand, the absence of the eigenenergy inside the continuum is proved in weak but finite coupling regimes, provided that each of the form factors that determine the transition between some definite level and the continuum does not vanish at that energy level. An application to the spontaneous emission process for the hydrogen atom interacting with the electromagnetic field is demonstrated.

  1. Low-lying continuum states of drip-line oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Tsukiyama, Koshiroh; Otsuka, Takaharu; Fujimoto, Rintaro

    2015-09-01

    Low-lying continuum states of exotic oxygen isotopes with A=23-26 are studied, by introducing the continuum-coupled shell model (CCSM) characterized by an infinite wall placed very far away and by an interaction for continuum coupling constructed in a close relation to the realistic shell-model Hamiltonian. Neutron-emission spectra from exotic oxygen isotopes are calculated by the doorway-state approach in heavy-ion multi-nucleon transfer reactions. The results agree with experiment remarkably well, providing evidence that the continuum effects are stronger than ˜ 1 MeV, consistent with the shell evolution in exotic nuclei. The peaks in the neutron spectra are understood as doorway-state resonances. The results by this CCSM doorway-state approach are compared with calculations on neutron-scattering resonance peaks made within the CCSM phase-shift approach and also with those obtained in the Gamow shell model, by taking the same Hamiltonian.

  2. Continuum limit of lattice models with Laughlin-like ground states containing quasiholes

    NASA Astrophysics Data System (ADS)

    Rodríguez, Iván D.; Nielsen, Anne E. B.

    2015-09-01

    There has been significant interest in recent years in finding fractional quantum Hall physics in lattice models, but it is not always clear how these models connect to the corresponding models in continuum systems. Here we introduce a family of models that is able to interpolate between a recently proposed set of lattice models with Laughlin-like ground states constructed from conformal field theory and models with ground states that are practically the usual bosonic/fermionic Laughlin states in the continuum. Both the ground state and the Hamiltonian are known analytically, and we find that the Hamiltonian in the continuum limit does not coincide with the usual delta interaction Hamiltonian for the Laughlin states. We introduce quasiholes into the models and show analytically that their braiding properties are as expected if the quasiholes are screened. We demonstrate screening numerically for the 1/3 Laughlin model and find that the quasiholes are slightly smaller in the continuum than in the lattice. Finally, we compute the effective magnetic field felt by the quasiholes and show that it is close to uniform when approaching the continuum limit. The techniques presented here to interpolate between the lattice and the continuum can also be applied to other fractional quantum Hall states that are constructed from conformal field theory.

  3. Multi-scale continuum modeling of biological processes: from molecular electro-diffusion to sub-cellular signaling transduction

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; Kekenes-Huskey, P.; Hake, J. E.; Holst, M. J.; McCammon, J. A.; Michailova, A. P.

    2012-01-01

    This paper presents a brief review of multi-scale modeling at the molecular to cellular scale, with new results for heart muscle cells. A finite element-based simulation package (SMOL) was used to investigate the signaling transduction at molecular and sub-cellular scales (http://mccammon.ucsd.edu/smol/, http://FETK.org) by numerical solution of the time-dependent Smoluchowski equations and a reaction-diffusion system. At the molecular scale, SMOL has yielded experimentally validated estimates of the diffusion-limited association rates for the binding of acetylcholine to mouse acetylcholinesterase using crystallographic structural data. The predicted rate constants exhibit increasingly delayed steady-state times, with increasing ionic strength, and demonstrate the role of an enzyme's electrostatic potential in influencing ligand binding. At the sub-cellular scale, an extension of SMOL solves a nonlinear, reaction-diffusion system describing Ca2+ ligand buffering and diffusion in experimentally derived rodent ventricular myocyte geometries. Results reveal the important role of mobile and stationary Ca2+ buffers, including Ca2+ indicator dye. We found that alterations in Ca2+-binding and dissociation rates of troponin C (TnC) and total TnC concentration modulate sub-cellular Ca2+ signals. The model predicts that reduced off-rate in the whole troponin complex (TnC, TnI, TnT) versus reconstructed thin filaments (Tn, Tm, actin) alters cytosolic Ca2+ dynamics under control conditions or in disease-linked TnC mutations. The ultimate goal of these studies is to develop scalable methods and theories for the integration of molecular-scale information into simulations of cellular-scale systems.

  4. Unified calculation of generalized oscillator strength of argon ranging from bound to continuum states

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Jin, Rui; Zeng, De-Ling; Han, Xiao-Ying; Yan, Jun; Li, Jia-Ming

    2015-11-01

    The electron and photon scattering data of an atom are crucial for many scientific fields, including plasma physics, astrophysics, and so on. For high enough but nonrelativistic incident energies, the first Born approximation is applicable for calculating these data, in which the key physics quantity is the generalized oscillator strength (GOS). In high-energy electron impact excitation processes, atoms will be excited into various excited states including strongly perturbed Rydberg and adjacent continuum states. How to calculate these quantities of a nontrivial many-electron atom rapidly and accurately is still a great challenge. Based on our eigenchannel R -matrix method R -eigen, we further extend it to calculate the GOS of a whole channel in an atom, which includes all Rydberg and adjacent continuum states. The Jπ=1- states of argon are chosen as an illustrating example. The calculation results are in good agreement with the available benchmark absolute experimental measurements. The calculated eigenchannel GOS matrix elements are smooth functions of the excitation energy and momentum transfer. From such smooth eigenchannel GOS matrix elements, we can obtain the GOS of any specific excited state through multichannel quantum defect theory, e.g., infinite Rydberg (including a strongly perturbed one), autoionization, and continuum states.

  5. Treatment of continuum in nuclear reactions involving weakly bound systems. A simple model to test different prescriptions describing the coupling to continuum states

    SciTech Connect

    Dasso, C. H.; Vitturi, A.

    2009-03-04

    We exploit a model describing the break-up of weakly-bound nuclei that can be used as a laboratory for testing different prescriptions that have been advanced in the literature to take into account the near-by presence of continuum states. In the model we follow the evolution of a single particle wave function in one dimension, initially bound by a Woods-Saxon type potential and then perturbed by a time- and position-dependent external field. Proper choices of this potential can simulate the effect of the interaction between reaction partners in a nuclear collision. These processes generate inelastic excitation probabilities that--distributed over the bound and continuum states of the system--lead to either a partial or a total fragmentation of the final wave function. The comparison with the exact calculations shows that standard coupled channel descriptions based on discretization of the continuum can be accurate only when a proper choice is made of the number of discrete states, of the energy mesh and of the energy cutoff. This may imply, even in simplified cases, the use of a rather large (and unpracticable) number of channels. The use of a more restricted number of channels may lead to misleading results.

  6. Critical field enhancement of asymptotic optical bound states in the continuum

    PubMed Central

    Yoon, Jae Woong; Song, Seok Ho; Magnusson, Robert

    2015-01-01

    We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 108 are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications. PMID:26673548

  7. Critical field enhancement of asymptotic optical bound states in the continuum.

    PubMed

    Yoon, Jae Woong; Song, Seok Ho; Magnusson, Robert

    2015-01-01

    We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 10(8) are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications. PMID:26673548

  8. Critical field enhancement of asymptotic optical bound states in the continuum

    NASA Astrophysics Data System (ADS)

    Yoon, Jae Woong; Song, Seok Ho; Magnusson, Robert

    2015-12-01

    We study spectral singularities and critical field enhancement factors associated with embedded photonic bound states in subwavelength periodic Si films. Ultrahigh-Q resonances supporting field enhancement factor exceeding 108 are obtained in the spectral vicinity of exact embedded eigenvalues in spite of deep surface modulation and vertical asymmetry of the given structure. Treating relations between the partial resonance Q and field enhancement factors with an analytical coupled-mode model, we derive a general strategy to maximize the field enhancement associated with these photonic bound states in the presence of material dissipation. The analytical expression for the field enhancement quantitatively agrees with rigorous numerical calculations. Therefore, our results provide a general knowledge for designing practical resonance elements based on optical bound states in the continuum in various applications.

  9. Imaging of continuum states of the He{sub 2}{sup 2+} quasimolecule

    SciTech Connect

    Schmidt, L. Ph. H.; Schoeffler, M. S.; Stiebing, K. E.; Schmidt-Boecking, H.; Doerner, R.; Afaneh, F.; Weber, Th.

    2007-07-15

    Using cold target recoil ion momentum spectroscopy (COLTRIMS) we have investigated the production of one free electron in slow He{sup 2+}+He(1s{sup 2}) collisions. At projectile velocities between 0.6 and 1.06 a.u. (9-28 keV/u), the fully differential cross section was measured state selective with respect to the second electron, which is bound either at the target or the projectile. We provide a comprehensive data set comprising state selective total cross section, scattering angle dependent single differential cross sections, and fully differential cross section. We show that the momentum distribution of the electron in the continuum image the relevant molecular orbitals for the reaction channel under consideration. By choosing the bound electron final state at the target or projectile and the impact parameter we can select these orbitals and manipulate their relative phase.

  10. Types or States? Cellular Dynamics and Regenerative Potential.

    PubMed

    Adler, Carolyn E; Sánchez Alvarado, Alejandro

    2015-11-01

    Many of our organs can maintain and repair themselves during homeostasis and injury, as a result of the action of tissue-specific, multipotent stem cells. However, recent evidence from mammalian systems suggests that injury stimulates dramatic plasticity, or transient changes in cell potential, in both stem cells and more differentiated cells. Planarian flatworms possess abundant stem cells, making them an exceptional model for understanding the cellular behavior underlying homeostasis and regeneration. Recent discoveries of cell lineages and regeneration-specific events provide an initial framework for unraveling the complex cellular contributions to regeneration. In this review, we discuss the concept of cellular plasticity in the context of planarian regeneration, and consider the possibility that pluripotency may be a transient, probabilistic state exhibited by stem cells. PMID:26437587

  11. Catching the bound states in the continuum of a phantom atom in graphene

    NASA Astrophysics Data System (ADS)

    Guessi, L. H.; Machado, R. S.; Marques, Y.; Ricco, L. S.; Kristinsson, K.; Yoshida, M.; Shelykh, I. A.; de Souza, M.; Seridonio, A. C.

    2015-07-01

    We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states near the Dirac points exhibits two characteristic features: (i) a cubic dependence on energy instead of a linear one for graphene as found in New J. Phys. 16, 013045 (2014), 10.1088/1367-2630/16/1/013045, and (ii) the formation of BICs as an aftermath of a Fano destructive interference assisted by the Coulomb correlations in the adatoms. For the geometry where adatoms are collinear to carbon atoms, we report an absence of BICs.

  12. Formation mechanism of guided resonances and bound states in the continuum in photonic crystal slabs

    PubMed Central

    Gao, Xingwei; Hsu, Chia Wei; Zhen, Bo; Lin, Xiao; Joannopoulos, John D.; Soljačić, Marin; Chen, Hongsheng

    2016-01-01

    We develop a formalism, based on the mode expansion method, to describe the guided resonances and bound states in the continuum (BICs) in photonic crystal slabs with one-dimensional periodicity. This approach provides analytic insights to the formation mechanisms of these states: the guided resonances arise from the transverse Fabry–Pérot condition, and the divergence of the resonance lifetimes at the BICs is explained by a destructive interference of radiation from different propagating components inside the slab. We show BICs at the center and on the edge of the Brillouin zone protected by symmetry, BICs at generic wave vectors not protected by symmetry, and the annihilation of BICs at low-symmetry wave vectors. PMID:27557882

  13. Formation mechanism of guided resonances and bound states in the continuum in photonic crystal slabs.

    PubMed

    Gao, Xingwei; Hsu, Chia Wei; Zhen, Bo; Lin, Xiao; Joannopoulos, John D; Soljačić, Marin; Chen, Hongsheng

    2016-01-01

    We develop a formalism, based on the mode expansion method, to describe the guided resonances and bound states in the continuum (BICs) in photonic crystal slabs with one-dimensional periodicity. This approach provides analytic insights to the formation mechanisms of these states: the guided resonances arise from the transverse Fabry-Pérot condition, and the divergence of the resonance lifetimes at the BICs is explained by a destructive interference of radiation from different propagating components inside the slab. We show BICs at the center and on the edge of the Brillouin zone protected by symmetry, BICs at generic wave vectors not protected by symmetry, and the annihilation of BICs at low-symmetry wave vectors. PMID:27557882

  14. Friedel phase discontinuity and bound states in the continuum in quantum dot systems

    NASA Astrophysics Data System (ADS)

    Solís, B.; Ladrón de Guevara, M. L.; Orellana, P. A.

    2008-06-01

    In this Letter we study the Friedel phase of the electron transport in two different systems of quantum dots which exhibit bound states in the continuum (BIC). The Friedel phase jumps abruptly in the energies of the BICs, which is associated to the vanishing width of these states, as shown by Friedrich and Wintgen in [H. Friedrich, D. Wintgen, Phys. Rev. A 31 (1985) 3964]. This odd behavior of the Friedel phase has consequences in the charge through the Friedel sum rule. Namely, if the energy of the BIC drops under the Fermi energy the charge changes abruptly in a unity. We show that this behavior closely relates to discontinuities in the conductance predicted for interacting quantum dot systems.

  15. Ultrasensitive optical absorption in graphene based on bound states in the continuum

    PubMed Central

    Zhang, Mingda; Zhang, Xiangdong

    2015-01-01

    We have designed a sphere-graphene-slab structure so that the electromagnetic wave can be well confined in the graphene due to the formation of a bound state in a continuum (BIC) of radiation modes. Based on such a bound state, we have realized strong optical absorption in the monolayer graphene. Such a strong optical absorption exhibits many advantages. It is ultrasensitive to the wavelength because the Q factor of the absorption peak can be more than 2000. By taking suitable BICs, the selective absorption for S and P waves has not only been realized, but also all-angle absorption for the S and P waves at the same time has been demonstrated. We have also found that ultrasensitive strong absorptions can appear at any wavelength from mid-infrared to far-infrared band. These phenomena are very beneficial to biosensing, perfect filters and waveguides. PMID:25652437

  16. Resonances and continuum states of drip-line nuclei using the complex scaling method

    NASA Astrophysics Data System (ADS)

    Myo, Takayuki; Katō, Kiyoshi

    2011-09-01

    Resonances and continuum states of He isotopes are investigated using the cluster orbital shell model (COSM) with the complex scaling method (CSM). We discuss the following subjects: 1) Spectroscopic factors of the unbound nucleus 7He into the 6He-n components and their relation to the one-neutron removal strengths of 7He. The importance of the 6He(2+) resonance is shown. 2) Structure of five-body 0+ resonance of 8He from the viewpoint of the two-neutron pair coupling. The monopole strengths into five-body unbound states are also investigated. It is found that the sequential breakup process of 8He → 7He+n → 6He+n+n is dominant in the monopole excitation, while the contribution of 8He(0+2) is negligible.

  17. Modeling electron dynamics coupled to continuum states in finite volumes with absorbing boundaries

    NASA Astrophysics Data System (ADS)

    De Giovannini, Umberto; Larsen, Ask Hjorth; Rubio, Angel

    2015-03-01

    Absorbing boundaries are frequently employed in real-time propagation of the Schrödinger equation to remove spurious reflections and efficiently emulate outgoing boundary conditions. These conditions are a fundamental ingredient for the calculation of observables involving infinitely extended continuum states in finite volumes. In the literature, several boundary absorbers have been proposed. They mostly fall into three main families: mask function absorbers, complex absorbing potentials, and exterior complex-scaled potentials. To date none of the proposed absorbers is perfect, and all present a certain degree of reflections. Characterization of such reflections is thus a critical task with strong implications for time-dependent simulations of atoms and molecules. We introduce a method to evaluate the reflection properties of a given absorber and present a comparison of selected samples for each family of absorbers. Further, we discuss the connections between members of each family and show how the same reflection curves can be obtained with very different absorption schemes.

  18. Self-localized states for electron transfer in nonlocal continuum deformable media

    NASA Astrophysics Data System (ADS)

    Cisneros-Ake, Luis A.

    2016-08-01

    We consider the problem of electron transport in a deformable continuum medium subjected to an external harmonic substrate potential. We then consider the quasi-stationary state of the full problem to find a Gross-Pitaevskii type equation with a nonlocal external potential, which is solved by variational and numerical means (considered as the exact solution) to find the parameter conditions for the existence of self-localized solutions. The variational approach predicts a threshold on the on-site or nonlocality parameter where localized solutions cease to exist from the Non-Linear Schrödinger soliton limit. A numerical continuation of stationary state solutions in the corresponding discrete system is used to confirm the prediction of the turning value in the on-site term. We finally study the full stationary state and make use of an approximation, proposed by Briedis et al. [17], for the nonlocal term, corresponding to strong nonlocalities, to find analytic expressions for self-localized states in terms of the series solutions of a nonlinear modified Bessel equation.

  19. Cellular immunity in semistarved states in hospitalized adults.

    PubMed

    Bistrian, B R; Blackburn, G L; Scrimshaw, N S; Flatt, J P

    1975-10-01

    Adult protein-calorie malnutrition, as reflected by decreased levels of serum albumin and transferrin, was studied in 21 hospitalized patients. This malnutrition state was a consequence of a catabolic response to stress and also use of standard parenteral fluid maintenance with 5% dextrose and water. Associated findings included a significant reduction in both total lymphocytes and cellular immunity, as measured by dinitrochlorobenzene and Candida skin testing. This state of visceral attrition, resembling kwashiorkor, occurs commonly in hospitalized patients, and may account for significant morbidity and mortality. Alternatives to the 5% dextrose and water in the nutritional support of the semistarved state may allow better preservation of visceral protein status and immune function. PMID:810018

  20. Renormalisation of 2D Cellular Automata with an Absorbing State

    NASA Astrophysics Data System (ADS)

    Weaver, Iain S.; Prügel-Bennett, Adam

    2015-04-01

    We describe a real-space renormalisation scheme for non-equilibrium probabilistic cellular automata (PCA) models, and apply it to a two-dimensional binary PCA. An exact renormalisation scheme is rare, and therefore we provide a method for computing the stationary probability distribution of states for such models with which to weight the renormalisation, effectively minimising the error in the scale transformation. While a mean-field approximation is trivial, we use the principle of maximum entropy to incorporate nearest-neighbour spin-correlations in the steady-state probability distribution. In doing so we find the fixed point of the renormalisation is modified by the steady-state approximation order.

  1. Quantum phase transition triggering magnetic bound states in the continuum in graphene

    NASA Astrophysics Data System (ADS)

    Guessi, L. H.; Marques, Y.; Machado, R. S.; Kristinsson, K.; Ricco, L. S.; Shelykh, I. A.; Figueira, M. S.; de Souza, M.; Seridonio, A. C.

    2015-12-01

    Graphene hosting a pair of collinear adatoms in the phantom atom configuration has density of states vanishing in the vicinity of the Dirac point which can be described in terms of the pseudogap scaling as cube of the energy, Δ ∝|ɛ| 3 , which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015), 10.1103/PhysRevB.92.045409]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. Here, we explore the effects of nonlocal coupling characterized by the Fano factor of interference q0, tunable by changing the slope of the Dirac cones in the graphene band structure. We demonstrate that three distinct regimes can be identified: (i) for q0qc 2 the cubic scaling of the pseudogap with energy Δ ∝|ɛ| 3 characteristic to the phantom atom configuration is restored and the phase with nonmagnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of QPT resulting from the competition between two ground states, respectively characterized by spin-degenerate and magnetic BICs.

  2. Lifetime measurements of 17C excited states and three-body and continuum effects

    DOE PAGESBeta

    Smalley, D.; Iwasaki, H.; Navratil, P.; Roth, R.; Langhammer, J.; Bader, V. M.; Bazin, D.; Barryman, J. S.; Campbell, C. M.; Dohet-Eraly, J.; et al

    2015-12-18

    We studied transition rates for the lowest 1/2+ and 5/2+ excited states of 17C through lifetime measurements with the GRETINA array using the recoil-distance method. The present measurements provide a model-independent determination of transition strengths giving the values of B(M1;1/2+ → 3/2+g.s.) = 1.04+0.03–0.12 × 10–2μ2N and B(M1;5/2+ → 3/2+g.s.) = 7.12+1.27–0.96 × 10–2μ2N. The quenched M1 transition strength for the 1/2+ → 3/2+g.s. transition, with respect to the 5/2+ → 3/2+g.s. transition, has been confirmed with greater precision. Furthermore, the current data are compared to importance-truncated no-core shell model calculations addressing effects due to continuum and three-body forces.

  3. Continuum electrodynamics of type-II superconductors in the mixed state: The dc and ac response

    SciTech Connect

    Placais, B.; Mathieu, P.; Simon, Y.; Sonin, E.B.; Traito, K.B.

    1996-11-01

    The dc and ac response of the ideal type-II superconductor in the mixed state is analyzed in the frame of a continuum electrodynamics, in which all fields are averaged on a scale exceeding the intervortex distance. The results of previous calculations are brought together and compared, while paying special attention to the role of the vortex line tension and the normal current. The electromagnetic response is studied in the whole range of magnetic fields and frequencies. The possible effect of the normal current on vortex motion is discussed. We argue in this respect that existing theories, where the Lorentz force involves the normal current, are not consistent with Onsager relations. Due to vortex line tension the external fields penetrate into a superconductor as a superposition of two modes with different complex wave numbers (the two-mode electrodynamics). Obtained expressions for the surface impedance should permit one to determine the parameters of the theory from the experiment and to discriminate different models of vortex motion. {copyright} {ital 1996 The American Physical Society.}

  4. Continuum emission in Nd3+/Yb3+ co-doped Ca12Al14O33 phosphor: Charge transfer state luminescence versus induced optical heating

    NASA Astrophysics Data System (ADS)

    Verma, R. K.; Rai, S. B.

    2013-02-01

    An unusual phenomenon of local heating and associated emission of continuum in lanthanide doped material has attracted much interest currently because of its use in white light generation and in localized heating. In the present work, Nd3+/Yb3+ co-doped Ca12Al14O33 phosphor has been synthesized, which gives broad continuum emission both by downconversion (DC) and upconversion (UC) processes. On 266 nm excitation, broad continuum emission is achieved through charge transfer state (CTS) luminescence of Yb3+ ion. On the other hand on 976 nm excitation, UC emission is observed from Nd3+ ion, which at higher pump power gives continuum emission.

  5. Doubling of states, quantum anomalies, and possible cosmological consequences in the continuum limit of the theory of discrete quantum gravity

    SciTech Connect

    Vergeles, S. N.

    2008-01-15

    The problem of the doubling of states is investigated in the framework of the theory of discrete quantum gravity under the assumption that the theory has a continuum (macroscopic) limit. It is demonstrated that irregular (in some sense) modes of fields (i.e., modes that change abruptly on scales of a lattice step and have a finite energy when the lattice step tends to zero) are separated from the normal modes. Some cosmological consequences of this finding are discussed.

  6. Exogenous antioxidants—Double-edged swords in cellular redox state

    PubMed Central

    Bohn, Torsten

    2010-01-01

    The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O2.-), hydroxyl radicals (OH.), alkoxyl radicals (RO.) and peroxyradicals (ROO.). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects. PMID:20972369

  7. Fano effect and bound state in continuum in electron transport through an armchair graphene nanoribbon with line defect

    PubMed Central

    2013-01-01

    Electron transport properties in an armchair graphene nanoribbon are theoretically investigated by considering the presence of line defect. It is found that the line defect causes the abundant Fano effects and bound state in continuum (BIC) in the electron transport process, which are tightly dependent on the width of the nanoribbon. By plotting the spectra of the density of electron states of the line defect, we see that the line defect induces some localized quantum states around the Dirac point and that the different localizations of these states lead to these two kinds of transport results. Next, the Fano effect and BIC phenomenon are detailedly described via the analysis about the influence of the structure parameters. According to the numerical results, we propose such a structure to be a promising candidate for graphene nanoswitch. PACS 81.05.Uw, 71.55.-i, 73.23.-b, 73.25.+i PMID:23870061

  8. Inhomogeneous ordered states and translational nature of the gauge group in the landau continuum theory: I. General analysis

    SciTech Connect

    Braginsky, A. Ya.

    2007-07-15

    A phenomenological continuum theory of phase transitions to a global inhomogeneous state of a crystal must take into account the compensating fields that represent the fields of stresses caused by dislocations appearing at the boundaries between local homogeneous regions. These compensating fields, which are introduced in order to satisfy the condition of invariance of the Landau potential with respect to the operation of translation, enter into the theory via extended derivatives of the local order parameters with respect to macroscopic coordinates of the local homogeneous regions in the crystal. Because of this extension of derivatives, the theory of phase transitions to an inhomogeneous state must include the theory of elasticity, in which a potential of the stress field induced by the phase transition is proportional to the compensating field magnitude. The Kroener equation, which describes the state of dislocations induced by spatially inhomogeneous ordering, appears in this theory as a result of minimization of the Landau potential with respect to the compensating fields.

  9. Decay of bound states in the continuum of Majorana fermions induced by vacuum fluctuations: Proposal of qubit technology

    NASA Astrophysics Data System (ADS)

    Ricco, L. S.; Marques, Y.; Dessotti, F. A.; Machado, R. S.; de Souza, M.; Seridonio, A. C.

    2016-04-01

    We report on a theoretical investigation of the interplay between vacuum fluctuations, Majorana quasiparticles (MQPs), and bound states in the continuum (BICs) by proposing a new venue for qubit storage. BICs emerge due to quantum interference processes as the Fano effect and, since such a mechanism is unbalanced, these states decay as regular into the continuum. Such fingerprints identify BICs in graphene as we have discussed in detail in Phys. Rev. B 92, 245107 (2015), 10.1103/PhysRevB.92.245107 and Phys. Rev. B, 92, 045409 (2015), 10.1103/PhysRevB.92.045409. Here, by considering two semi-infinite Kitaev chains within the topological phase, coupled to a quantum dot (QD) hybridized with leads, we show the emergence of a novel type of BICs, in which MQPs are trapped. As the MQPs of these chains far apart build a delocalized fermion and qubit, we identify that the decay of these BICs is not connected to Fano and it occurs when finite fluctuations are observed in the vacuum composed by electron pairs for this qubit. From the experimental point of view, we also show that vacuum fluctuations can be induced just by changing the chain-dot couplings from symmetric to asymmetric. Hence, we show how to perform the qubit storage within two delocalized BICs of MQPs and to access it when the vacuum fluctuates by means of a complete controllable way in quantum transport experiments.

  10. Measuring the redox state of cellular peroxiredoxins by immunoblotting.

    PubMed

    Cox, Andrew G; Winterbourn, Christine C; Hampton, Mark B

    2010-01-01

    The peroxiredoxins (Prxs) are a family of thiol peroxidases that scavenge hydroperoxides and peroxynitrite. The abundance and reactivity of these proteins makes them primary targets for cellular H(2)O(2). The catalytic cycle of typical 2-Cys Prxs involves formation of an intermolecular disulfide bond between peroxidatic and resolving cysteines on opposing subunits. Rapid alterations in the ratio of reduced monomer and oxidized dimer have been detected in the cytoplasm and mitochondria of cultured cells exposed to various exogenous and endogenous sources of oxidative stress. Here we describe immunoblot methods to monitor the interconversion of individual 2-Cys Prxs in cultured cells. We also outline an adaptation of this method to measure the extent to which individual 2-Cys Prxs become hyper oxidized in treated cells. Together, these methods enable the redox status of cellular Prxs to be assessed and quantified in a rapid and robust manner. PMID:20609904

  11. Combining the GW formalism with the polarizable continuum model: A state-specific non-equilibrium approach

    NASA Astrophysics Data System (ADS)

    Duchemin, Ivan; Jacquemin, Denis; Blase, Xavier

    2016-04-01

    We have implemented the polarizable continuum model within the framework of the many-body Green's function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology.

  12. Photoelectron circular dichroism of chiral molecules studied with a continuum-state-corrected strong-field approximation

    NASA Astrophysics Data System (ADS)

    Dreissigacker, Ingo; Lein, Manfred

    2014-05-01

    Motivated by recent experiments on circular dichroism in the photoelectron momentum distributions from strong-field ionization of chiral molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012), 10.1002/anie.201109035; C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013), 10.1063/1.4844295], we investigate the origin of this effect theoretically. We show that it is not possible to describe photoelectron circular dichroism with the commonly used strong-field approximation due to its plane-wave nature. We therefore apply the Born approximation to the scattering state and use this as a continuum-state correction in the strong-field approximation. We obtain electron distributions for the molecules camphor and fenchone. In order to gain physical insight into the process, we study the contributions of individual molecular orientations.

  13. Combining the GW formalism with the polarizable continuum model: A state-specific non-equilibrium approach.

    PubMed

    Duchemin, Ivan; Jacquemin, Denis; Blase, Xavier

    2016-04-28

    We have implemented the polarizable continuum model within the framework of the many-body Green's function GW formalism for the calculation of electron addition and removal energies in solution. The present formalism includes both ground-state and non-equilibrium polarization effects. In addition, the polarization energies are state-specific, allowing to obtain the bath-induced renormalisation energy of all occupied and virtual energy levels. Our implementation is validated by comparisons with ΔSCF calculations performed at both the density functional theory and coupled-cluster single and double levels for solvated nucleobases. The present study opens the way to GW and Bethe-Salpeter calculations in disordered condensed phases of interest in organic optoelectronics, wet chemistry, and biology. PMID:27131530

  14. Photoionization microscopy of the lithium atom: Wave-function imaging of quasibound and continuum Stark states

    NASA Astrophysics Data System (ADS)

    Cohen, S.; Harb, M. M.; Ollagnier, A.; Robicheaux, F.; Vrakking, M. J. J.; Barillot, T.; Lépine, F.; Bordas, C.

    2016-07-01

    Photoionization of an atom in the presence of a uniform static electric field provides the unique opportunity to expand and visualize the atomic wave function at a macroscopic scale. In a number of seminal publications dating back to the 1980s, Fabrikant, Demkov, Kondratovich, and Ostrovsky showed that this goal could be achieved by projecting slow (meV) photoionized electrons onto a position-sensitive detector and underlined the distinction between continuum and resonant contributions. The uncovering of resonant signatures was achieved fairly recently in experiments on the nonhydrogenic lithium atoms [Cohen et al., Phys. Rev. Lett. 110, 183001 (2013)], 10.1103/PhysRevLett.110.183001. The purpose of the present article is the general description of these findings, with emphasis on the various manifestations of resonant character. From this point of view, lithium has been chosen as an illustrative example between the two limiting cases of hydrogen, where resonance effects are more easily identified, and heavy atoms like xenon, where resonant effects were not observed.

  15. The characteristics of four ratcheting states in cellular flames.

    PubMed

    Gorman, M; el-Hamdi, M; Pearson, B

    2009-09-01

    A premixed flat flame on a circular porous plug burner can form patterns of one or two concentric rings of cells in which brighter, hotter regions are separated by darker, cooler cusps and folds. Dynamic states are found at parameter values that are interleaved between those of the ordered states. Rotating states, modulated rotating states, hopping states, and intermittently ordered states have all been observed with motions of approximately 100 degrees/s. These states have been described using the ideas of dynamical systems. Their characteristics have been analyzed using modal decomposition techniques. Ratcheting states are qualitatively and quantitatively different from these other dynamic states. In ratcheting states one or both of the concentric rings rotate very slowly, approximately 0.8 degrees/s, each speeding up and slowing down in a manner unique to that state. Measurements of the angular displacement and computed values of the angular velocity are presented for four ratcheting states. The experimental results are discussed in the context of the physical characteristics of the flame front and in terms of bifurcations of systems with symmetry. Many of the principal features of ratcheting motion are not yet understood. PMID:19792020

  16. Spin polarized bound states in the continuum in open Aharonov–Bohm rings with the Rashba spin–orbit interaction

    NASA Astrophysics Data System (ADS)

    Bulgakov, Evgeny N.; Sadreev, Almas F.

    2016-07-01

    We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov–Bohm rings in the presence of the Rashba spin–orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase.

  17. Spin polarized bound states in the continuum in open Aharonov-Bohm rings with the Rashba spin-orbit interaction.

    PubMed

    Bulgakov, Evgeny N; Sadreev, Almas F

    2016-07-01

    We consider the trapping of electrons with a definite spin polarization by bound states in the continuum (BSC) in the open Aharonov-Bohm rings in the presence of the Rashba spin-orbit interaction (RSOI). Neglecting the Zeeman term we show the existence of BSCs in the one-dimensional ring when the eigenstates of the closed ring are doubly degenerate. With account of the Zeeman term BSCs occur only at the points of threefold degeneracy. The BSCs are found in the parametric space of flux and RSOI strength in close pairs with opposite spin polarization. Thereby the spin polarization of electrons transmitted through the ring can be altered by minor variation of magnetic or electric field at the vicinity of these pairs. Numerical simulations of the two-dimensional open ring show similar results for the BSCs. Encircling the BSC points in the parametric space of the flux and the RSOI constant gives rise to a geometric phase. PMID:27165662

  18. Reciprocal Control of the Circadian Clock and Cellular Redox State - a Critical Appraisal

    PubMed Central

    Putker, Marrit; O’Neill, John Stuart

    2016-01-01

    Redox signalling comprises the biology of molecular signal transduction mediated by reactive oxygen (or nitrogen) species. By specific and reversible oxidation of redox-sensitive cysteines, many biological processes sense and respond to signals from the intracellular redox environment. Redox signals are therefore important regulators of cellular homeostasis. Recently, it has become apparent that the cellular redox state oscillates in vivo and in vitro, with a period of about one day (circadian). Circadian time-keeping allows cells and organisms to adapt their biology to resonate with the 24-hour cycle of day/night. The importance of this innate biological time-keeping is illustrated by the association of clock disruption with the early onset of several diseases (e.g. type II diabetes, stroke and several forms of cancer). Circadian regulation of cellular redox balance suggests potentially two distinct roles for redox signalling in relation to the cellular clock: one where it is regulated by the clock, and one where it regulates the clock. Here, we introduce the concepts of redox signalling and cellular timekeeping, and then critically appraise the evidence for the reciprocal regulation between cellular redox state and the circadian clock. We conclude there is a substantial body of evidence supporting circadian regulation of cellular redox state, but that it would be premature to conclude that the converse is also true. We therefore propose some approaches that might yield more insight into redox control of cellular timekeeping. PMID:26810072

  19. Studies of continuum states in 16 Ne using three-body correlation techniques

    NASA Astrophysics Data System (ADS)

    Marganiec, J.; Wamers, F.; Aksouh, F.; Aksyutina, Yu.; Álvarez-Pol, H.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Borge, M. J. G.; Chartier, M.; Chatillon, A.; Chulkov, L. V.; Cortina-Gil, D.; Emling, H.; Ershova, O.; Fraile, L. M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Heil, M.; Hoffmann, D. H. H.; Hoffmann, J.; Johansson, H. T.; Jonson, B.; Karagiannis, C.; Kiselev, O. A.; Kratz, J. V.; Kulessa, R.; Kurz, N.; Langer, C.; Lantz, M.; Le Bleis, T.; Lemmon, R.; Litvinov, Yu. A.; Mahata, K.; Müntz, C.; Nilsson, T.; Nociforo, C.; Nyman, G.; Ott, W.; Panin, V.; Paschalis, S.; Perea, A.; Plag, R.; Reifarth, R.; Richter, A.; Rodriguez-Tajes, C.; Rossi, D.; Riisager, K.; Savran, D.; Schrieder, G.; Simon, H.; Stroth, J.; Sümmerer, K.; Tengblad, O.; Weick, H.; Wiescher, M.; Wimmer, C.; Zhukov, M. V.

    2015-01-01

    Two-proton decay of the unbound nucleus 16Ne , produced in one-neutron knockout from a 500 MeV/u 17Ne beam, has been studied at GSI. The ground state, at a resonance energy 1.388(15) MeV, ( MeV) above the 14O +p+p threshold, and two narrow resonances at MeV and 7.57(6) MeV have been investigated. A comparison of the energy difference between the first excited 2+ state and the 0+ ground state in 16Ne with its mirror nucleus 16C reveals a small Thomas-Ehrman shift (TES) of keV. A trend of the TES for the T = 2 quintet is obtained by completing the known data with a prediction for 16F obtained from an IMME analysis. The decay mechanisms of the observed three resonances were revealed from an analysis of the energy and angular correlations of the 14O +p+p decay products. The ground state decay can be considered as a genuine three-body (democratic) mode and the excited states decay sequentially via states in the intermediate nucleus 15F , the 3.22 MeV state predominantly via the 15F ground-state resonance, while the 7.57 MeV state decays via the 5/2+ resonance in 15F at 2.8 MeV above the 14O +p+p threshold. Further, from an analysis of angular correlations, the spin-parity of the 7.57 MeV state has been determined as and assigned as the third 2+ state in 16Ne based on a comparison with 16C.

  20. Live cell tracking based on cellular state recognition from microscopic images.

    PubMed

    Sun, Y-N; Lin, C-H; Kuo, C-C; Ho, C-L; Lin, C-J

    2009-07-01

    The analysis of cell motion is an essential process in fundamental medical studies because most active cellular functions involve motion. In this paper, a computer-assisted motion analysis system is proposed for cell tracking. In the proposed tracking process, unlike in conventional tracking methods, cellular states referring to the cellular life cycle are defined and appropriate strategies are adopted for cells at different states. The use of cellular state recognition allows detection of possible cell division and hence can improve the robustness of cell tracking. Experimental results show that cells can be successfully segmented and tracked over a long period of time, and the proposed system is found to be as accurate as manual tracking. Various quantitative analyses and visualizations are used to represent cell motion, which demonstrates the usefulness of the proposed system in the study of cell dynamics. PMID:19566631

  1. MEASURING BLACK HOLE SPIN VIA THE X-RAY CONTINUUM-FITTING METHOD: BEYOND THE THERMAL DOMINANT STATE

    SciTech Connect

    Steiner, James F.; McClintock, Jeffrey E.; Narayan, Ramesh; Gou Lijun; Remillard, Ronald A.

    2009-08-20

    All prior work on measuring the spins of stellar-mass black holes (BHs) via the X-ray continuum-fitting (CF) method has relied on the use of weakly Comptonized spectra obtained in the thermal dominant (TD) state. Using a self-consistent Comptonization model, we show that one can analyze spectra that exhibit strong power-law components and obtain values of the inner disk radius, and hence spin, that are consistent with those obtained in the TD state. Specifically, we analyze many RXTE spectra of two BH transients, H1743-322 and XTE J1550-564, and we demonstrate that the radius of the inner edge of the accretion disk remains constant to within a few percent as the strength of the Comptonized component increases by an order of magnitude, i.e., as the fraction of the thermal seed photons that are scattered approaches 25%. We conclude that the CF method can be applied to a much wider body of data than previously thought possible, and to sources that have never been observed to enter the TD state (e.g., Cyg X-1)

  2. Photoluminescence of a quantum dot hybridized with a continuum of extended states.

    PubMed

    León Hilario, L M; Aligia, A A

    2009-10-01

    We calculate the intensity of photon emission from a trion in a single quantum dot, as a function of energy and gate voltage, using the impurity Anderson model and variational wave functions. Assuming a flat density of conduction states and constant hybridization energy, the results agree with the main features observed in recent experiments: nonmonotonic dependence of the energy on gate voltage, non-Lorentzian line shapes, and a linewidth that increases near the regions of instability of the single electron final state to occupations zero or two. PMID:19905656

  3. The Teacher Development Continuum in the United States and China: Summary of a Workshop

    ERIC Educational Resources Information Center

    Ferreras, Ana; Olson, Steve

    2010-01-01

    In 1999, Liping Ma published her book "Knowing and Teaching Elementary Mathematics: Teachers' Understanding of Fundamental Mathematics in the United States and China," which probed the kinds of knowledge that elementary school teachers need to convey mathematical concepts and procedures effectively to their students. Later that year, Roger Howe, a…

  4. Coherent-state path integrals in the continuum: The SU(2) case

    NASA Astrophysics Data System (ADS)

    Kordas, G.; Kalantzis, D.; Karanikas, A. I.

    2016-09-01

    We define the time-continuous spin coherent-state path integral in a way that is free from inconsistencies. The proposed definition is used to reproduce known exact results. Such a formalism opens new possibilities for applying approximations with improved accuracy and can be proven useful in a great variety of problems where spin Hamiltonians are used.

  5. Studies of yrast and continuum states in A = 140 - 160 nuclei. Progress report for 1985

    SciTech Connect

    Daly, P.J.

    1986-02-01

    The results of nuclear structure investigations by in-beam ..gamma..-ray spectroscopy following heavy ion reactions are summarized. Detailed information is given for the proton-rich nuclei /sup 151/Tm, /sup 152/Tm and /sup 150/Ho, and for nuh/sub 11/2//sup n/ states in heavy tin isotopes. The first experiments performed with the new Compton-suppressed detector array at ATLAS are outlined.

  6. Bound and continuum states of molecular anions C2H- and C3N-

    NASA Astrophysics Data System (ADS)

    Harrison, Stephen; Tennyson, Jonathan

    2011-02-01

    Recently a number of molecular anions, closed-shell linear carbon chains of the form CnH- and CnN-, have been detected in space. The molecules C2H- and C3N- are investigated by using the R-matrix method to consider electron scattering from the corresponding neutral targets. Initial target calculations are conducted and refined in order to produce target state characteristics similar to the experimental data. A number of different scattering models are tested including static exchange and close-coupling models, and the use of Hartree-Fock or natural orbitals in the close-coupling calculations. The calculations concentrate on bound and resonances states for the anions as well as eigenphase sums, elastic cross-sections and electronic excitation cross-sections for electron collisions with the neutral. It is found that electronic resonances are all too high in energy to be important for anion formation in the interstellar medium. However, C3N-, unlike C2H-, supports a number of very weakly bound excited states, which may well provide the route to electron attachment for this system.

  7. [Effect of gentamicin on the state of cellular resistance].

    PubMed

    Shcherbakova, E G; Rastunova, G A; Medvedeva, M M; Zhuravleva, T P; Kuchushev, Sh A

    1977-05-01

    The effect of gentamicin on the functional state of the cells of the reticuloendothelial system (RES) of the abdominal cavity of mouse macrophages and the cell culture of the rabbit embryon kidneys was studied. Gentamicin administered intramuscularly in multiple doses of I and 10 mg/kg for 6--14 days did not induce significant changes in the absorptive activity of the RES. In doses of 20 and 40 mg/kg gentamicin induced some inhibition of the absorptive activity of the abdominal cavity macrophages, which was accompanied by a decrease in the content of the total protein and an increase in the activity of the acid phosphatase in the cell cytoplasm. The changes were reversible and persisted for not more than 48 hours after the last administration of the antibiotic. Gentamicin inhibited the cell growth in the culture of the rabbit embryon kidneys in concentrations higher than 1000 mg/kg, LD50 of gentamicin for mice weighing 20--22 gm being 244 mg/kg. Preliminary administration of amigluracyl provided a decrease in the toxic effect of gentamicin in both the cell culture and the host, which was possibly associated with the anabolyzing effect of amigluracyl. PMID:879726

  8. A Ground State Method for Continuum Systems Using Random Walks in the Space of Slater Determinants.^

    NASA Astrophysics Data System (ADS)

    Zhang, Shiwei; Krakauer, Henry

    2001-03-01

    We study a ground state quantum Monte Carlo method for electronic systems. The method is based on the constrained path Monte Carlo approach(S. Zhang, J. Carlson, and J. E. Gubernatis, Phys. Rev. B 55), 7464 (1997). developed for lattice models of correlated electrons. It works in second-quantized form and uses random walks involving full Slater determinants rather than individual real-space configurations. The method allows easy calculation of expectation values and also makes it straightforward to import standard techniques (e.g., pseudopotentials) used in density functional and quantum chemistry calculations. In general, Slater determinants will acquire overall complex phases, due to the Hubbard-Stratonovich transformation of the two-body potential. In order to control the sign decay, an approximation is developed for the propagation of complex Slater determinants by random walks. We test the method in a homogeneous 3-D electron gas (jellium) using a planewave basis. ^ Supported by NSF, ONR and Research Corporation.

  9. Studies of yrast and continuum states in A = 140 - 160 nuclei. Progress report for 1984

    SciTech Connect

    Daly, P.J.

    1985-02-01

    Proton-rich nuclei in the mass region around A = 150 have been studied by in-beam ..gamma..-ray spectroscopy using /sup 58/Ni and /sup 60/Ni beams from the Argonne Superconducting Linac. New structural information was obtained for the N = 81 nuclei /sup 146/Tb, /sup 147/Dy, /sup 148/Ho, /sup 149/Er, /sup 150/Tm and /sup 151/Yb, for the N = 82 nuclei /sup 150/Er and /sup 151/Tm, and for the N = 83 nuclei /sup 150/Ho and /sup 152/Tm. Collaborative studies of feeding patterns and feeding times of yrast states in A approx. 150 nuclei were also completed. Publications and talks are listed.

  10. Continuum {gamma} rays feeding normal and superdeformed states in Gd nuclei

    SciTech Connect

    Zhu, L.H.; Cinausero, M.; de Angelis, G.; De Poli, M.; Gadea, A.; Napoli, D.R.; Bazzacco, D.; Lunardi, S.; Viesti, G.; Petrache, C.M.; Rossi Alvarez, C.

    1997-03-01

    The feeding mechanism of the superdeformed bands in {sup 147}Gd and {sup 148}Gd has been studied via the {sup 124}Sn + {sup 29}Si reaction at a beam energy of 157 MeV. Using the BGO inner ball of the GASP array, high-energy {gamma} rays have been detected in coincidence with discrete transitions deexciting normal-deformed (ND) and superdeformed (SD) states in the final product nuclei. The slope of the measured high-energy {gamma}-ray spectra depends strongly on the number of emitted neutrons and is somewhat lower for spectra in coincidence with SD bands than for those in coincidence with ND structures. Both observations are qualitatively reproduced by statistical model Monte Carlo calculations, which point out the importance of angular momentum effects in the emission of energetic {gamma} rays. The present data exclude the enhanced population of SD bands when fed through high-energy E1 transitions. {copyright} {ital 1997} {ital The American Physical Society}

  11. Lifetime measurements of 17C excited states and three-body and continuum effects

    SciTech Connect

    Smalley, D.; Iwasaki, H.; Navratil, P.; Roth, R.; Langhammer, J.; Bader, V. M.; Bazin, D.; Barryman, J. S.; Campbell, C. M.; Dohet-Eraly, J.; Fallon, P.; Gade, A.; Langer, C.; Lemasson, A.; Macchiavelli, A. O.; Morse, C.; Parker, J.; Quaglioni, S.; Recchia, F.; Stroberg, S. R.; Wiesshaar, D.; Whitmore, K.; Wimmer, K.; Brown, B. A.

    2015-12-18

    We studied transition rates for the lowest 1/2+ and 5/2+ excited states of 17C through lifetime measurements with the GRETINA array using the recoil-distance method. The present measurements provide a model-independent determination of transition strengths giving the values of B(M1;1/2+ → 3/2+g.s.) = 1.04+0.03–0.12 × 10–2μ2N and B(M1;5/2+ → 3/2+g.s.) = 7.12+1.27–0.96 × 10–2μ2N. The quenched M1 transition strength for the 1/2+ → 3/2+g.s. transition, with respect to the 5/2+ → 3/2+g.s. transition, has been confirmed with greater precision. Furthermore, the current data are compared to importance-truncated no-core shell model calculations addressing effects due to continuum and three-body forces.

  12. Continuum Nanofluidics.

    PubMed

    Hansen, Jesper S; Dyre, Jeppe C; Daivis, Peter; Todd, Billy D; Bruus, Henrik

    2015-12-15

    This paper introduces the fundamental continuum theory governing momentum transport in isotropic nanofluidic systems. The theory is an extension of the classical Navier-Stokes equation, and includes coupling between translational and rotational degrees of freedom as well as nonlocal response functions that incorporate spatial correlations. The continuum theory is compared with molecular dynamics simulation data for both relaxation processes and fluid flows, showing excellent agreement on the nanometer length scale. We also present practical tools to estimate when the extended theory should be used. It is shown that in the wall-fluid region the fluid molecules align with the wall, and in this region the isotropic model may fail and a full anisotropic description is necessary. PMID:26457405

  13. Feed-forward regulation ensures stability and rapid reversibility of a cellular state

    PubMed Central

    Doncic, Andreas; Skotheim, Jan M.

    2013-01-01

    Cellular transitions are important for all life. Such transitions, including cell fate decisions, often employ positive feedback regulation to establish and stabilize new cellular states. However, positive feedback is unlikely to underlie stable cell cycle arrest in yeast exposed to mating pheromone because the signaling pathway is linear, rather than bistable, over a broad range of extracellular pheromone concentration. We show that the stability of the pheromone arrested state results from coherent feed-forward regulation of the cell cycle inhibitor Far1. This network motif is effectively isolated from the more complex regulatory network in which it is embedded. Fast regulation of Far1 by phosphorylation allows rapid cell cycle arrest and reentry, whereas slow Far1 synthesis reinforces arrest. We thus expect coherent feed-forward regulation to be frequently implemented at reversible cellular transitions because this network motif can achieve the ostensibly conflicting aims of arrest stability and rapid reversibility without loss of signaling information. PMID:23685071

  14. A Ubiquitiformal One-Dimensional Steady-State Conduction Model for a Cellular Material Rod

    NASA Astrophysics Data System (ADS)

    Li, Guan-Ying; Ou, Zhuo-Cheng; Xie, Ran; Duan, Zhuo-Ping; Huang, Feng-Lei

    2016-04-01

    A ubiquitiformal model for the one-dimensional steady-state heat transfer of a cellular material rod is developed in this paper, and the explicit analytical expressions for both the temperature distribution and the equivalent thermal conductivity are obtained. The calculated results for two kinds of dry soil are found to be in good agreement with previous experimental data. Moreover, it is demonstrated that the ubiquitiformal model is more reasonable for describing such a cellular material than the fractal one, and hence a ubiquitiformal rather than a fractal model should be considered in practical applications whenever the integral dimensional measure of a real physical object must be taken into account.

  15. A Study of the Density of Unfilled States in Yttrium Barium Copper Oxide by means of Soft X-ray Continuum Isochromats

    NASA Astrophysics Data System (ADS)

    Rajaram, Ramya; Liefeld, Robert

    2002-10-01

    The New Mexico State University two-crystal X-ray spectrometer is designed for spectroscopy in the soft X-ray region. It has a demountable ultra-high vacuum X-ray tube and is equipped with Potassium Acid Phthalate (KAP) crystals and a flowing gas proportional counter. The KAP crystals provide a unique and sensitive spectral window at a photon energy of 530 eV. The high signal to background available makes it possible to record continuum limit spectra as continuum isochromats. We intend to obtain continuum isochromats at 530 eV from Yttrium Barium Copper Oxide, a high temperature superconductor. Such spectra are convolutions of the energy spectrum of the incident electrons in the target with the product of the density of unfilled states and a matrix element for the transition. The spectrum of initially mono-energetic electrons in the target can be derived from equivalent photoemission experiments and used to obtain a representation of the density of unfilled states above the Fermi level of the target material from the isochromat spectra.

  16. Numerical Study of Rarefied Hypersonic Flow Interacting with a Continuum Jet. Degree awarded by Pennsylvania State Univ., Aug. 1999

    NASA Technical Reports Server (NTRS)

    Glass, Christopher E.

    2000-01-01

    An uncoupled Computational Fluid Dynamics-Direct Simulation Monte Carlo (CFD-DSMC) technique is developed and applied to provide solutions for continuum jets interacting with rarefied external flows. The technique is based on a correlation of the appropriate Bird breakdown parameter for a transitional-rarefied condition that defines a surface within which the continuum solution is unaffected by the external flow-jet interaction. The method is applied to two problems to assess and demonstrate its validity; one of a jet interaction in the transitional-rarefied flow regime and the other in the moderately rarefied regime. Results show that the appropriate Bird breakdown surface for uncoupling the continuum and non-continuum solutions is a function of a non-dimensional parameter relating the momentum flux and collisionality between the two interacting flows. The correlation is exploited for the simulation of a jet interaction modeled for an experimental condition in the transitional-rarefied flow regime and the validity of the correlation is demonstrated. The uncoupled technique is also applied to an aerobraking flight condition for the Mars Global Surveyor spacecraft with attitude control system jet interaction. Aerodynamic yawing moment coefficients for cases without and with jet interaction at various angles-of-attack were predicted, and results from the present method compare well with values published previously. The flow field and surface properties are analyzed in some detail to describe the mechanism by which the jet interaction affects the aerodynamics.

  17. Aurora Borealis: stochastic cellular automata simulations of the excited-state dynamics of oxygen atoms.

    NASA Astrophysics Data System (ADS)

    Seybold, P. G.; Kier, L. B.; Cheng, C.-K.

    1999-12-01

    Emissions from the 1S and 1D excited states of atomic oxygen play a prominent role in creating the dramatic light displays (aurora borealis) seen in the skies over polar regions of the Northern Hemisphere. A probabilistic asynchronous cellular automaton model described previously has been applied to the excited-state dynamics of atomic oxygen. The model simulates the time-dependent variations in ground (3P) and excited-state populations that occur under user-defined probabilistic transition rules for both pulse and steady-state conditions. Although each trial simulation is itself an independent "experiment", deterministic values for the excited-state emission lifetimes and quantum yields emerge as limiting cases for large numbers of cells or large numbers of trials. Stochastic variations in the lifetimes and emission yields can be estimated from repeated trials.

  18. Unified ab initio approach to bound and unbound states: No-core shell model with continuum and its application to 7He

    DOE PAGESBeta

    Baroni, Simone; Navratil, Petr; Quaglioni, Sofia

    2013-03-26

    In this study, we introduce a unified approach to nuclear bound and continuum states based on the coupling of the no-core shell model (NCSM), a bound-state technique, with the no-core shell model/resonating group method (NCSM/RGM), a nuclear scattering technique. This new ab initio method, no-core shell model with continuum (NCSMC), leads to convergence properties superior to either NCSM or NCSM/RGM while providing a balanced approach to different classes of states. In the NCSMC, the ansatz for the many-nucleon wave function includes (i) a square-integrable A-nucleon component expanded in a complete harmonic oscillator basis and (ii) a binary-cluster component with asymptoticmore » boundary conditions that can properly describe weakly bound states, resonances, and scattering. The Schrödinger equation is transformed into a system of coupled-channel integral-differential equations that we solve using a modified microscopic R-matrix formalism within a Lagrange mesh basis. We demonstrate the usefulness of the approach by investigating the unbound 7He nucleus.« less

  19. Efficient cellular solid-state NMR of membrane proteins by targeted protein labeling.

    PubMed

    Baker, Lindsay A; Daniëls, Mark; van der Cruijsen, Elwin A W; Folkers, Gert E; Baldus, Marc

    2015-06-01

    Solid-state NMR spectroscopy (ssNMR) has made significant progress towards the study of membrane proteins in their native cellular membranes. However, reduced spectroscopic sensitivity and high background signal levels can complicate these experiments. Here, we describe a method for ssNMR to specifically label a single protein by repressing endogenous protein expression with rifampicin. Our results demonstrate that treatment of E. coli with rifampicin during induction of recombinant membrane protein expression reduces background signals for different expression levels and improves sensitivity in cellular membrane samples. Further, the method reduces the amount of time and resources needed to produce membrane protein samples, enabling new strategies for studying challenging membrane proteins by ssNMR. PMID:25956570

  20. 76 FR 17652 - Wireline Competition Bureau Seeks Comment on the Cellular South Licenses, Inc. and United States...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-30

    ... of Documents in Rulemaking Proceedings, 63 FR 24121, May 1, 1998. Electronic Filers: Comments may be... COMMISSION Wireline Competition Bureau Seeks Comment on the Cellular South Licenses, Inc. and United States..., the Wireline Competition Bureau seeks comment on a joint petition filed by Cellular South...

  1. Influence of higher-order dispersion coefficients on near-threshold bound and continuum states: Application to {sup 88}Sr{sub 2}

    SciTech Connect

    Kaiser, Alexander; Mueller, Tim-Oliver; Friedrich, Harald

    2011-12-07

    We give a simple description of quantum states near the dissociation threshold of deep interatomic potentials. The influence of the potential tail is separated from effects due to the interaction at short distances. We present a general formalism which is valid for weakly bound and low-energy continuum states, both for vanishing and non-vanishing angular momentum. Its applicability is demonstrated for the example of the electronic ground state of the strontium dimer {sup 88}Sr{sub 2}. With an appropriate choice of the potential tail that includes higher-order dispersion coefficients, all short-range effects are incorporated via the threshold quantum number v{sub D} and one further parameter accounting for residual short-range effects.

  2. In vitro chemical and cellular tests applied to uranium trioxide with different hydration states.

    PubMed Central

    Ansoborlo, E; Chalabreysse, J; Hengé-Napoli, M H; Pujol, E

    1992-01-01

    A simple and rapid in vitro chemical solubility test applicable to industrial uranium trioxide (UO3) was developed together with two in vitro cellular tests using rat alveolar macrophages maintained either in gas phase or in alginate beads at 37 degrees C. Industrial UO3 was characterized by particle size, X-ray, and IR spectra, and chemical transformation (e.g., aging and hydration of the dust) was also studied. Solvents used for the in vitro chemical solubility study included carbonates, citrates, phosphates, water, Eagle's basal medium, and Gamble's solution (simulated lung fluid), alone, with oxygen, or with superoxide ions. Results, expressed in terms of the half-time of dissolution, according to International Commission on Radiological Protection (ICRP) classification (D,W,Y), varied for different hydration states of UO3, showing a lower solubility of hydrated UO3 in solvents compared to basic UO3 or UO3 heated at 450 degrees C. Two in vitro cellular tests on cultured rat alveolar macrophages (cells maintained in gas phase and cells immobilized in alginate beads) were used on the same UO3 samples and generally showed a lower solution transfer rate in the presence of macrophages than in the culture medium alone. The results of in vitro chemical and cellular tests were compared, with four main conclusions: a good reproducibility of the three tests in Eagle's basal medium the effect of hydration state on solubility, the classification of UO3 in terms of ICRP solubility criteria, and the ability of macrophages to decrease uranium solubility in medium. PMID:1396449

  3. On the evolution of the cellular automaton of rule 150 from some simple initial states

    NASA Astrophysics Data System (ADS)

    Macfarlane, A. J.

    2009-06-01

    The evolution Eα in discrete time t of the cellular automaton CA150 of Wolfram rule 150 is studied for certain initial states ψα. The values of the cell variables in any state ψα considered are all zero outside a principal sequence (PS) of length k within which they take on values 1a2a3⋯ak -2ak -11, where a2=1,0,…. Powerful algebraic methods are used to develop formulas for the weight, Ωα(t), i.e., the total number of cell variables with value equal to 1 at time t, of the state of Eα at time t ≥0, and of the sum Wα(N)=∑t =02N-1Ωα(t) of the weights of the first 2N states of the evolution of Eα in discrete time. The methods are described carefully. A selection of results, new here, is stated and proved for several initial states ψα with simple PSs of increasing lengths k >1. Many of them feature numbers in the Fibonacci, Lucas, and Jacobsthal sequences.

  4. [Motivation and Emotional States: Structural Systemic, Neurochemical, Molecular and Cellular Mechanisms].

    PubMed

    Bazyan, A S

    2016-01-01

    The structural, systemic, neurochemical, molecular and cellular mechanisms of organization and coding motivation and emotional states are describe. The GABA and glutamatergic synaptic systems of basal ganglia form a neural network and participate in the implementation of voluntary behavior. Neuropeptides, neurohormones and paracrine neuromodulators involved in the organization of motivation and emotional states, integrated with synaptic systems, controlled by neural networks and organizing goal-directed behavior. Structural centers for united and integrated of information in voluntary and goal-directed behavior are globus pallidus. Substantia nigra pars reticulata switches the information from corticobasal networks to thalamocortical networks, induces global dopaminergic (DA) signal and organize interaction of mesolimbic and nigostriatnoy DA systems controlled by prefrontal and motor cortex. Together with the motor cortex, substantia nigra displays information in the brainstem and spinal cord to implementation of behavior. Motivation states are formed in the interaction of neurohormonal and neuropeptide systems by monoaminergic systems of brain. Emotional states are formed by monoaminergic systems of the mid-brain, where the leading role belongs to the mesolimbic DA system. The emotional and motivation state of the encoded specific epigenetic molecular and chemical pattern of neuron. PMID:27149821

  5. Integrated Stress Response Modulates Cellular Redox State via Induction of Cystathionine γ-Lyase

    PubMed Central

    Dickhout, Jeffrey G.; Carlisle, Rachel E.; Jerome, Danielle E.; Mohammed-Ali, Zahraa; Jiang, Hua; Yang, Guangdong; Mani, Sarathi; Garg, Sanjay K.; Banerjee, Ruma; Kaufman, Randal J.; Maclean, Kenneth N.; Wang, Rui; Austin, Richard C.

    2012-01-01

    The integrated stress response mediated by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation maintains cellular homeostasis under endoplasmic reticulum (ER) stress. eIF2α phosphorylation induces activating transcription factor 4 (ATF4), a basic leucine zipper transcription factor that regulates the expression of genes responsible for amino acid metabolism, cellular redox state, and anti-stress responses. Cystathionine γ-lyase (CSE) and cystathionine β-synthase are critical enzymes in the transsulfuration pathway, which also regulate cellular redox status by modulating glutathione (GSH) levels. To determine the link between the integrated stress response and the transsulfuration pathway, we used homocysteine (Hcy) as an inducer of eIF2α phosphorylation and ATF4 gene induction. Mouse embryonic fibroblasts (MEFs) lacking ATF4 (ATF4−/−) had reduced GSH levels and increased reactive oxygen species and were susceptible to apoptotic cell death under normal culture conditions. Further, ATF4−/− MEFs were more sensitive to Hcy-induced cytotoxicity and showed significantly reduced intracellular GSH levels associated with apoptosis. ATF4−/− MEFs could be rescued from l-Hcy-induced apoptosis by β-mercaptoethanol medium supplementation that increases cysteine levels and restores GSH synthesis. ATF4−/− MEFs showed little or no CSE protein but did express cystathionine β-synthase. Further, ER stress-inducing agents, including tunicamycin and thapsigargin, induced the expression of CSE in ATF4+/+ MEFs. Consistent with ATF4−/− MEFs, CSE−/− MEFs showed significantly greater apoptosis when treated with tunicamycin, thapsigargin, and l-Hcy, compared with CSE+/+ MEFs. Liver and kidney GSH levels were also reduced in CSE−/− mice, suggesting that CSE is a critical factor in GSH synthesis and may act to protect the liver and kidney from a variety of conditions that cause ER stress. PMID:22215680

  6. Cellular Solid-State NMR Investigation of a Membrane Protein Using Dynamic Nuclear Polarization

    PubMed Central

    Yamamoto, Kazutoshi; Caporini, Marc A.; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2014-01-01

    While an increasing number of structural biology studies successfully demonstrate the power of high-resolution structures and dynamics of membrane proteins in fully understanding their function, there is considerable interest in developing NMR approaches to obtain such information in a cellular setting. As long as the proteins inside the living cell tumble rapidly in the NMR timescale, recently developed in-cell solution NMR approaches can be applied towards the determination of 3D structural information. However, there are numerous challenges that need to be overcome to study membrane proteins inside a cell. Research in our laboratory is focused on developing a combination of solid-state NMR and biological approaches to overcome these challenges with a specific emphasis on obtaining high-resolution structural insights into electron transfer biological processes mediated by membrane-bound proteins like mammalian cytochrome b5, cytochrome P450 and cytochrome P450 reductase. In this study, we demonstrate the feasibility of using the signal-enhancement rendered by dynamic nuclear polarization (DNP) magic angle spinning (MAS) NMR spectroscopy for in-cell studies on a membrane-anchored protein. Our experimental results obtained from 13C-labeled membrane-anchored cytochrome b5 in native Escherichia coli cells show a ~16-fold DNP signal enhancement (ε). Further, results obtained from a 2D 13C/13C chemical shift correlation MAS experiment demonstrates that it is highly possible to suppress the background signals from other cellular contents for high-resolution structural studies on membrane proteins. We believe that this study would pave new avenues for high-resolution 3D structural studies on a variety of membrane-associated proteins and their complexes in the cellular context to fully understand their functional roles in physiological processes. PMID:25017802

  7. Cellular and circuit models of increased resting-state network gamma activity in schizophrenia.

    PubMed

    White, R S; Siegel, S J

    2016-05-01

    Schizophrenia (SCZ) is a disorder characterized by positive symptoms (hallucinations, delusions), negative symptoms (blunted affect, alogia, reduced sociability, and anhedonia), as well as persistent cognitive deficits (memory, concentration, and learning). While the biology underlying subjective experiences is difficult to study, abnormalities in electroencephalographic (EEG) measures offer a means to dissect potential circuit and cellular changes in brain function. EEG is indispensable for studying cerebral information processing due to the introduction of techniques for the decomposition of event-related activity into its frequency components. Specifically, brain activity in the gamma frequency range (30-80Hz) is thought to underlie cognitive function and may be used as an endophenotype to aid in diagnosis and treatment of SCZ. In this review we address evidence indicating that there is increased resting-state gamma power in SCZ. We address how modeling this aspect of the illness in animals may help treatment development as well as providing insights into the etiology of SCZ. PMID:26577758

  8. Description of the Charge Transfer States at the Pentacene/C60 Interface: Combining Range-Separated Hybrid Functionals with the Polarizable Continuum Model.

    PubMed

    Zheng, Zilong; Brédas, Jean-Luc; Coropceanu, Veaceslav

    2016-07-01

    Density functional theory (DFT) approaches based on range-separated hybrid functionals are currently methods of choice for the description of the charge-transfer (CT) states in organic donor/acceptor solar cells. However, these calculations are usually performed on small-size donor/acceptor complexes and as result do not account for electronic polarization effects. Here, using a pentacene/C60 complex as a model system, we discuss the ability of long-range corrected (LCR) hybrid functionals in combination with the polarizable continuum model (PCM) to determine the impact of the solid-state environment on the CT states. The CT energies are found to be insensitive to the interactions with the dielectric medium when a conventional time-dependent DFT/PCM (TDDFT/PCM) approach is used. However, a decrease in the energy of the CT state in the framework of LRC functionals can be obtained by using a smaller range-separated parameter when going from an isolated donor/acceptor complex to the solid-state case. PMID:27338105

  9. Modelling chronotaxicity of cellular energy metabolism to facilitate the identification of altered metabolic states.

    PubMed

    Lancaster, Gemma; Suprunenko, Yevhen F; Jenkins, Kirsten; Stefanovska, Aneta

    2016-01-01

    Altered cellular energy metabolism is a hallmark of many diseases, one notable example being cancer. Here, we focus on the identification of the transition from healthy to abnormal metabolic states. To do this, we study the dynamics of energy production in a cell. Due to the thermodynamic openness of a living cell, the inability to instantaneously match fluctuating supply and demand in energy metabolism results in nonautonomous time-varying oscillatory dynamics. However, such oscillatory dynamics is often neglected and treated as stochastic. Based on experimental evidence of metabolic oscillations, we show that changes in metabolic state can be described robustly by alterations in the chronotaxicity of the corresponding metabolic oscillations, i.e. the ability of an oscillator to resist external perturbations. We also present a method for the identification of chronotaxicity, applicable to general oscillatory signals and, importantly, apply this to real experimental data. Evidence of chronotaxicity was found in glycolytic oscillations in real yeast cells, verifying that chronotaxicity could be used to study transitions between metabolic states. PMID:27483987

  10. Open boundaries in a cellular automaton model for traffic flow with metastable states

    NASA Astrophysics Data System (ADS)

    Barlovic, Robert; Huisinga, Torsten; Schadschneider, Andreas; Schreckenberg, Michael

    2002-10-01

    The effects of open boundaries in the velocity-dependent randomization (VDR) model, a modified version of the well-known Nagel-Schreckenberg (NaSch) cellular automaton model for traffic flow, are investigated. In contrast to the NaSch model, the VDR model exhibits metastable states and phase separation in a certain density regime. A proper insertion strategy allows us to investigate the whole spectrum of possible system states and the structure of the phase diagram by Monte Carlo simulations. We observe an interesting microscopic structure of the jammed phases, which is different from the one of the NaSch model. For finite systems, the existence of high flow states in a certain parameter regime leads to a special structure of the fundamental diagram measured in the open system. Apart from that, the results are in agreement with an extremal principle for the flow, which has been introduced for models with a unique flow-density relation. Finally, we discuss the application of our findings for a systematic flow optimization. Here some surprising results are obtained, e.g., a restriction of the inflow can lead to an improvement of the total flow through a bottleneck.

  11. Cellular Nonlinear Networks for the emergence of perceptual states: application to robot navigation control.

    PubMed

    Arena, Paolo; De Fiore, Sebastiano; Patané, Luca

    2009-01-01

    In this paper a new general purpose perceptual control architecture, based on nonlinear neural lattices, is presented and applied to solve robot navigation tasks. Insects show the ability to react to certain stimuli with simple reflexes, using direct sensory-motor pathways, which can be considered as basic behaviors, inherited and pre-wired. Relevant brain centres, known as Mushroom Bodies (MB) and Central Complex (CX) were recently identified in insects: though their functional details are not yet fully understood, it is known that they provide secondary pathways allowing the emergence of cognitive behaviors. These are gained through the coordination of the basic abilities to satisfy the insect's needs. Taking inspiration from this evidence, our architecture modulates, through a reinforcement learning, a set of competitive and concurrent basic behaviors in order to accomplish the task assigned through a reward function. The core of the architecture is constituted by the so-called Representation layer, used to create a concise picture of the current environment situation, fusing together different stimuli for the emergence of perceptual states. These perceptual states are steady state solutions of lattices of Reaction-Diffusion Cellular Nonlinear Networks (RD-CNN), designed to show Turing patterns. The exploitation of the dynamics of the multiple equilibria of the network is emphasized through the adaptive shaping of the basins of attraction for each emerged pattern. New experimental campaigns on standard robotic platforms are reported to demonstrate the potentiality and the effectiveness of the approach. PMID:19596552

  12. Modelling chronotaxicity of cellular energy metabolism to facilitate the identification of altered metabolic states

    PubMed Central

    Lancaster, Gemma; Suprunenko, Yevhen F.; Jenkins, Kirsten; Stefanovska, Aneta

    2016-01-01

    Altered cellular energy metabolism is a hallmark of many diseases, one notable example being cancer. Here, we focus on the identification of the transition from healthy to abnormal metabolic states. To do this, we study the dynamics of energy production in a cell. Due to the thermodynamic openness of a living cell, the inability to instantaneously match fluctuating supply and demand in energy metabolism results in nonautonomous time-varying oscillatory dynamics. However, such oscillatory dynamics is often neglected and treated as stochastic. Based on experimental evidence of metabolic oscillations, we show that changes in metabolic state can be described robustly by alterations in the chronotaxicity of the corresponding metabolic oscillations, i.e. the ability of an oscillator to resist external perturbations. We also present a method for the identification of chronotaxicity, applicable to general oscillatory signals and, importantly, apply this to real experimental data. Evidence of chronotaxicity was found in glycolytic oscillations in real yeast cells, verifying that chronotaxicity could be used to study transitions between metabolic states. PMID:27483987

  13. Analytical second derivatives of excited-state energy within the time-dependent density functional theory coupled with a conductor-like polarizable continuum model

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Liang, WanZhen

    2013-01-01

    This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011), 10.1063/1.3605504; J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)], 10.1063/1.3659312 on analytical excited-state Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with a conductor-like polarizable continuum model (CPCM). The formalism, implementation, and application of analytical first and second energy derivatives of TDDFT/CPCM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of excitation energies, excited-state geometries, and harmonic vibrational frequencies for a number of benchmark systems. The calculated results are in good agreement with the corresponding experimental data or other theoretical calculations, indicating the reliability of the current computer implementation of the developed algorithms. Then we made some preliminary applications to calculate the resonant Raman spectrum of 4-hydroxybenzylidene-2,3-dimethyl-imidazolinone in ethanol solution and the infrared spectra of ground and excited states of 9-fluorenone in methanol solution.

  14. Population transfer through the continuum

    SciTech Connect

    Nakajima, T.; Elk, M.; Zhang, J.; Lambropoulos, P. Foundation of Research and Technology Hellas, Institute of Electronic Structure and Laser and Department of Physics, University of Crete, P.O. Box 1527, Heraklion 711 10, Crete Department of Physics, University of Southern California, Los Angeles, California 90089-0484 )

    1994-08-01

    We show that complete population transfer is not in general possible through continuum intermediate states. We present a formal theoretical argument and supporting numerical results. In addition, the behavior of the system is compared with the well-known [Lambda] system.

  15. Parameter identification in continuum models

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Crowley, J. M.

    1983-01-01

    Approximation techniques for use in numerical schemes for estimating spatially varying coefficients in continuum models such as those for Euler-Bernoulli beams are discussed. The techniques are based on quintic spline state approximations and cubic spline parameter approximations. Both theoretical and numerical results are presented.

  16. Cellular Mechanisms Underlying Behavioral State-Dependent Bidirectional Modulation of Motor Cortex Output

    PubMed Central

    Schiemann, Julia; Puggioni, Paolo; Dacre, Joshua; Pelko, Miha; Domanski, Aleksander; van Rossum, Mark C.W.; Duguid, Ian

    2015-01-01

    Summary Neuronal activity in primary motor cortex (M1) correlates with behavioral state, but the cellular mechanisms underpinning behavioral state-dependent modulation of M1 output remain largely unresolved. Here, we performed in vivo patch-clamp recordings from layer 5B (L5B) pyramidal neurons in awake mice during quiet wakefulness and self-paced, voluntary movement. We show that L5B output neurons display bidirectional (i.e., enhanced or suppressed) firing rate changes during movement, mediated via two opposing subthreshold mechanisms: (1) a global decrease in membrane potential variability that reduced L5B firing rates (L5Bsuppressed neurons), and (2) a coincident noradrenaline-mediated increase in excitatory drive to a subpopulation of L5B neurons (L5Benhanced neurons) that elevated firing rates. Blocking noradrenergic receptors in forelimb M1 abolished the bidirectional modulation of M1 output during movement and selectively impaired contralateral forelimb motor coordination. Together, our results provide a mechanism for how noradrenergic neuromodulation and network-driven input changes bidirectionally modulate M1 output during motor behavior. PMID:25981037

  17. Quasi-bound states and continuum absorption background of polar Al{sub 0.5}Ga{sub 0.5}N/GaN quantum dots

    SciTech Connect

    Elmaghraoui, D. Triki, M.; Jaziri, S.; Leroux, M.; Brault, J.

    2014-07-07

    A theoretical interpretation of the photoluminescence excitation spectra of self-organized polar GaN/(Al,Ga)N quantum dots is presented. A numerical method assuming a realistic shape of the dots and including the built-in electric field effects is developed to calculate their energy structure and hence their optical absorption. The electron and hole spectra show the existence of a set of quasi-bound states that does not originate from the wetting layer and plays a crucial role in the observed absorption spectrum of the GaN/(Al,Ga)N dots. Transitions involving these quasi-bound states and wetting layer states give a sufficient explanation for the observed continuum absorption background. The properties of this absorption band, especially its extension, depend strongly on the dot's size. Our simulation provides a natural explanation of the experimental luminescence excitation spectra of ensembles of dots of different heights. Our theoretical model can be convenient for future optical studies including systems with more complicated potentials.

  18. Resonance and non-resonance effect of continuum states of 6Li on elastic scattering angular distributions

    NASA Astrophysics Data System (ADS)

    Gómez Camacho, A.

    2016-07-01

    CDCC calculations of elastic scattering angular distributions for reactions of the weakly bound projectile 6Li with targets 28Si and 58Ni at energies around the Coulomb barrier are presented. Special emphasis is given to account for the effect of couplings from 6Li resonance states l = 2, J π = 3+, 2+, 1+. Similarly, the effect produced by non-resonant state couplings is studied. The convergent calculations are carried out with global α-target and d-target interactions. The calculated elastic scattering angular distributions are in general in good agreement with the measurements for the systems considered in this work. It is found that the calculations with only resonance states are very similar to that with all couplings (resonance+non-resonance). So, the absence of these states have a strong effect on elastic scattering (non-resonance states calculation). It is shown that the effects increase as the collision energy increases. An interpretation of the strength of the different effects is given in terms of the polarization potentials that emerge from the different couplings.

  19. The Early Childhood and Elementary Education Continuum: Constructing an Understanding of P-3 as State-Level Policy Reform

    ERIC Educational Resources Information Center

    Kauerz, Kristie Anne

    2009-01-01

    State-level policy attention to young children's early learning opportunities burgeons; a sense of urgency exists to identify reform agendas that are both effective and sustainable. "P-3" often is used as the term for the first level of a seamless P-20 system that stretches from early childhood through post-secondary education. While it is…

  20. FANTOM5 transcriptome catalog of cellular states based on Semantic MediaWiki

    PubMed Central

    Abugessaisa, Imad; Shimoji, Hisashi; Sahin, Serkan; Kondo, Atsushi; Harshbarger, Jayson; Lizio, Marina; Hayashizaki, Yoshihide; Carninci, Piero; Forrest, Alistair; Kasukawa, Takeya; Kawaji, Hideya

    2016-01-01

    The Functional Annotation of the Mammalian Genome project (FANTOM5) mapped transcription start sites (TSSs) and measured their activities in a diverse range of biological samples. The FANTOM5 project generated a large data set; including detailed information about the profiled samples, the uncovered TSSs at high base-pair resolution on the genome, their transcriptional initiation activities, and further information of transcriptional regulation. Data sets to explore transcriptome in individual cellular states encoded in the mammalian genomes have been enriched by a series of additional analysis, based on the raw experimental data, along with the progress of the research activities. To make the heterogeneous data set accessible and useful for investigators, we developed a web-based database called Semantic catalog of Samples, Transcription initiation And Regulators (SSTAR). SSTAR utilizes the open source wiki software MediaWiki along with the Semantic MediaWiki (SMW) extension, which provides flexibility to model, store, and display a series of data sets produced during the course of the FANTOM5 project. Our use of SMW demonstrates the utility of the framework for dissemination of large-scale analysis results. SSTAR is a case study in handling biological data generated from a large-scale research project in terms of maintenance and growth alongside research activities. Database URL: http://fantom.gsc.riken.jp/5/sstar/ PMID:27402679

  1. FANTOM5 transcriptome catalog of cellular states based on Semantic MediaWiki.

    PubMed

    Abugessaisa, Imad; Shimoji, Hisashi; Sahin, Serkan; Kondo, Atsushi; Harshbarger, Jayson; Lizio, Marina; Hayashizaki, Yoshihide; Carninci, Piero; Forrest, Alistair; Kasukawa, Takeya; Kawaji, Hideya

    2016-01-01

    The Functional Annotation of the Mammalian Genome project (FANTOM5) mapped transcription start sites (TSSs) and measured their activities in a diverse range of biological samples. The FANTOM5 project generated a large data set; including detailed information about the profiled samples, the uncovered TSSs at high base-pair resolution on the genome, their transcriptional initiation activities, and further information of transcriptional regulation. Data sets to explore transcriptome in individual cellular states encoded in the mammalian genomes have been enriched by a series of additional analysis, based on the raw experimental data, along with the progress of the research activities. To make the heterogeneous data set accessible and useful for investigators, we developed a web-based database called Semantic catalog of Samples, Transcription initiation And Regulators (SSTAR). SSTAR utilizes the open source wiki software MediaWiki along with the Semantic MediaWiki (SMW) extension, which provides flexibility to model, store, and display a series of data sets produced during the course of the FANTOM5 project. Our use of SMW demonstrates the utility of the framework for dissemination of large-scale analysis results. SSTAR is a case study in handling biological data generated from a large-scale research project in terms of maintenance and growth alongside research activities.Database URL: http://fantom.gsc.riken.jp/5/sstar/. PMID:27402679

  2. Quantitative metric profiles capture three-dimensional temporospatial architecture to discriminate cellular functional states

    PubMed Central

    2011-01-01

    Background Computational analysis of tissue structure reveals sub-visual differences in tissue functional states by extracting quantitative signature features that establish a diagnostic profile. Incomplete and/or inaccurate profiles contribute to misdiagnosis. Methods In order to create more complete tissue structure profiles, we adapted our cell-graph method for extracting quantitative features from histopathology images to now capture temporospatial traits of three-dimensional collagen hydrogel cell cultures. Cell-graphs were proposed to characterize the spatial organization between the cells in tissues by exploiting graph theory wherein the nuclei of the cells constitute the nodes and the approximate adjacency of cells are represented with edges. We chose 11 different cell types representing non-tumorigenic, pre-cancerous, and malignant states from multiple tissue origins. Results We built cell-graphs from the cellular hydrogel images and computed a large set of features describing the structural characteristics captured by the graphs over time. Using three-mode tensor analysis, we identified the five most significant features (metrics) that capture the compactness, clustering, and spatial uniformity of the 3D architectural changes for each cell type throughout the time course. Importantly, four of these metrics are also the discriminative features for our histopathology data from our previous studies. Conclusions Together, these descriptive metrics provide rigorous quantitative representations of image information that other image analysis methods do not. Examining the changes in these five metrics allowed us to easily discriminate between all 11 cell types, whereas differences from visual examination of the images are not as apparent. These results demonstrate that application of the cell-graph technique to 3D image data yields discriminative metrics that have the potential to improve the accuracy of image-based tissue profiles, and thus improve the detection

  3. Functional Divergence of Hsp90 Genetic Interactions in Biofilm and Planktonic Cellular States

    PubMed Central

    Cowen, Leah E.

    2015-01-01

    Candida albicans is among the most prevalent opportunistic fungal pathogens. Its capacity to cause life-threatening bloodstream infections is associated with the ability to form biofilms, which are intrinsically drug resistant reservoirs for dispersal. A key regulator of biofilm drug resistance and dispersal is the molecular chaperone Hsp90, which stabilizes many signal transducers. We previously identified 226 C. albicans Hsp90 genetic interactors under planktonic conditions, of which 56 are involved in transcriptional regulation. Six of these transcriptional regulators have previously been implicated in biofilm formation, suggesting that Hsp90 genetic interactions identified in planktonic conditions may have functional significance in biofilms. Here, we explored the relationship between Hsp90 and five of these transcription factor genetic interactors: BCR1, MIG1, TEC1, TUP1, and UPC2. We deleted each transcription factor gene in an Hsp90 conditional expression strain, and assessed biofilm formation and morphogenesis. Strikingly, depletion of Hsp90 conferred no additional biofilm defect in the mutants. An interaction was observed in which deletion of BCR1 enhanced filamentation upon reduction of Hsp90 levels. Further, although Hsp90 modulates expression of TEC1, TUP1, and UPC2 in planktonic conditions, it has no impact in biofilms. Lastly, we probed for physical interactions between Hsp90 and Tup1, whose WD40 domain suggests that it might interact with Hsp90 directly. Hsp90 and Tup1 formed a stable complex, independent of temperature or developmental state. Our results illuminate a physical interaction between Hsp90 and a key transcriptional regulator of filamentation and biofilm formation, and suggest that Hsp90 has distinct genetic interactions in planktonic and biofilm cellular states. PMID:26367740

  4. Satellite Retrieval of Marine Stratocumulus Surface Coupling State and its Effect on the Clouds Cellular Organization

    NASA Astrophysics Data System (ADS)

    Goren, T.; Rosenfeld, D.

    2014-12-01

    A methodology for a complete description of the marine stratocumulus clouds geometrical and microphysical properties was developed and tested. These include, among others, coupling state and cloud geometrical depth. The methodology combines simultaneous observations from several A-TRAIN instruments (CALIPSO, CloudSat and MODIS) and re-analysis data. Analysis of different types of Marine Stratocumulus (MSC) scenes revealed interesting features. While most of the MSC that we have analyzed existed within a coupled Marine Boundary Layer (MBL), those that existed in a de-coupled MBL, i.e., cloud layer that is de-coupled from the ocean surface, lacked the typical spatial cellular organization. It was found that the occurrence of rain within closed cells breaks and organizes them into open cells only when the clouds are coupled with the surface. Otherwise the closed cells remain as thin lightly precipitating stratiform clouds having low cloud water. The coupling state was also found to affect the ability of drizzle to break closed cells, so that closed cells in a de-coupled MBL tend to produce stronger drizzle before breaking up. We hypothesize that rain driven downdrafts hit the surface and form gust fronts that trigger convective elements, which break the cloud deck, only when the clouds are coupled to the surface. Among the other problems that can be answered by using the presented methodology is disentangling the role of large scale meteorology and aerosols on the development of precipitation (i.e., cloud depth versus droplet concentrations as a limiting factor for drizzle initiation). Examples will be shown together with their physical interpretation.

  5. The Suicide Prevention Continuum

    PubMed Central

    Caldwell, Dawn

    2010-01-01

    The suicide prevention continuum illustrates a practical approach to the complex issue of suicide prevention. The continuum evolved from discussions with two Aboriginal communities in Atlantic Canada about suicide and the different types of interventions available. The continuum offers a framework and reference tool to differentiate between the different stages of suicide risk. It illustrates where the Aboriginal Community Youth Resilience Network (ACYRN) fits into suicide prevention and how it contributes to prevention knowledge, capacity building, and policy development. PMID:20835376

  6. [Cellular immunity state assessed in bronchial and alveolar lavage for experimental animals exposed to the rubber dust].

    PubMed

    Zhumabekova, B K; Karabalin, S K; Bakirova, R E

    2004-01-01

    Experiments on 21 rats helped to study influence of mechanical rubber dust on cellular immunity state in bronchial and alveolar lavage, efficiency of Ruvimine for prophylaxis. Findings are that mechanical rubber dust is strongly cytotoxic. Ruvimine administration during the whole experiment demonstrates therapeutic and prophylactic effect and normalizes local pulmonary phagocytosis. PMID:15318451

  7. The plastic cellular states of liver cells: Are EpCAM and Lgr5 fit for purpose?

    PubMed

    Huch, Meritxell; Dollé, Laurent

    2016-08-01

    Adult liver cells have been considered restricted regarding their fate and lineage potential. That is, hepatocytes have been thought able only to generate hepatocytes and duct cells, only duct cells. While this may be the case for the majority of scenarios in a state of quiescence or homeostasis, evidence suggests that liver cells are capable of interconverting between cellular states of distinct phenotypic traits. This interconversion or plasticity had been suggested by classical studies using cellular markers, but recently lineage tracing approaches have proven that cells are highly plastic and retain an extraordinary ability to respond differently to normal tissue homeostasis, to tissue repair, or when challenged to expand ex vivo or to differentiate upon transplantation. Stemness, as "self-renewal and multipotency," seems not to be limited to a particular cell type but rather to a cellular state in which cells exhibit a high degree of plasticity and can move back and forth in different phenotypic states. For instance, upon damage cells can dedifferentiate to acquire stem cell potential that allows them to self-renew, repopulate a damaged tissue, and then undergo differentiation. In this review, we will discuss the evidence on cellular plasticity in the liver, focusing our attention on two markers, epithelial cell adhesion molecule and leucine-rich repeat-containing G protein-coupled receptor 5, which identify cells with stem cell potential. (Hepatology 2016;64:652-662). PMID:26799921

  8. The plastic cellular states of liver cells: Are EpCAM and Lgr5 fit for purpose?

    PubMed Central

    2016-01-01

    Adult liver cells have been considered restricted regarding their fate and lineage potential. That is, hepatocytes have been thought able only to generate hepatocytes and duct cells, only duct cells. While this may be the case for the majority of scenarios in a state of quiescence or homeostasis, evidence suggests that liver cells are capable of interconverting between cellular states of distinct phenotypic traits. This interconversion or plasticity had been suggested by classical studies using cellular markers, but recently lineage tracing approaches have proven that cells are highly plastic and retain an extraordinary ability to respond differently to normal tissue homeostasis, to tissue repair, or when challenged to expand ex vivo or to differentiate upon transplantation. Stemness, as “self‐renewal and multipotency,” seems not to be limited to a particular cell type but rather to a cellular state in which cells exhibit a high degree of plasticity and can move back and forth in different phenotypic states. For instance, upon damage cells can dedifferentiate to acquire stem cell potential that allows them to self‐renew, repopulate a damaged tissue, and then undergo differentiation. In this review, we will discuss the evidence on cellular plasticity in the liver, focusing our attention on two markers, epithelial cell adhesion molecule and leucine‐rich repeat‐containing G protein‐coupled receptor 5, which identify cells with stem cell potential. (Hepatology 2016;64:652‐662) PMID:26799921

  9. QCD equation of state at nonzero chemical potential: continuum results with physical quark masses at order μ 2

    NASA Astrophysics Data System (ADS)

    Borsányi, Sz.; Endrődi, G.; Fodor, Z.; Katz, S. D.; Krieg, S.; Ratti, C.; Szabó, K. K.

    2012-08-01

    We determine the equation of state of QCD for nonzero chemical potentials via a Taylor expansion of the pressure. The results are obtained for N f = 2 + 1 flavors of quarks with physical masses, on various lattice spacings. We present results for the pressure, interaction measure, energy density, entropy density, and the speed of sound for small chemical potentials. At low temperatures we compare our results with the Hadron Resonance Gas model. We also express our observables along trajectories of constant entropy over particle number. A simple parameterization is given (the Matlab/Octave script parameterization.m, submitted to the arXiv along with the paper), which can be used to reconstruct the observables as functions of T and μ, or as functions of T and S/N.

  10. "Caught in the Continuum"

    ERIC Educational Resources Information Center

    Nisbet, Jan

    2004-01-01

    This article presents a critical review of Steve Taylor's Caught in the Continuum. Steve Taylor describes the flawed thinking associated with the "least restrictive environment" (LRE) principle and the related continuum model of human services that linked severity of disability with segregation, and required improvements in skills as a…

  11. Studies of yrast and continuum states in A=140-160 nuclei. Progress report, January 1, 1980-December 31, 1980. [Purdue Univ. , 1/1/80-12/31/80

    SciTech Connect

    Daly, P.J.

    1981-01-01

    The structure of nuclei in the A approx. 150 region was investigated by in-beam ..gamma..-ray spectroscopy using heavy-ion beams, mostly from the Argonne Tandem-Linac. Results for the nuclei /sup 148/Dy, /sup 149/Dy, /sup 153/Dy, /sup 154/Dy, /sup 149/Ho, and /sup 150/Ho are summarized. The feeding of yrast states in these nuclei and the link between the highest known yrast states and the continuum region were also studied. 6 figures.

  12. Continuum radiation at Uranus

    SciTech Connect

    Kurth, W.S.; Gurnett, D.A. ); Desch, M.D. )

    1990-02-01

    Uranus has proven to be a radio source of remarkable complexity with as many as six distinctly different types of emission. One Uranian radio emission which has thus far escaped attention is an analog of continuum radiation at Earth, Jupiter, and Saturn. The emission is found to be propagating in the ordinary mode in the range of one to a few kHz on the inbound leg of the Voyager 2 encounter, shortly after the magnetopause crossing. The continuum radiation spectrum at Uranus also includes bands with frequencies as high as 12 kHz or greater on both the inbound and outbound legs. The Uranian continuum radiation is notably weak, making it more like that detected at Saturn than the extremely intense Jovian continuum radiation. The Uranian emission shows some evidence for narrow-band components lying in the same frequency regime as the continuum, completing the analogy with the other planets, which also show narrow-band components superimposed on the continuum spectrum. The authors argue that the low intensity of the Uranian continuum is most likely related to the lack of a density cavity within the Uranian magnetosphere that is deep relative to the solar wind plasma density.

  13. Boundary-corrected four-body continuum-intermediate-state method: Single-electron capture from heliumlike atomic systems by fast nuclei

    NASA Astrophysics Data System (ADS)

    Mančev, Ivan; Milojević, Nenad; Belkić, Dževad

    2015-06-01

    Single charge exchange in collisions between bare projectiles and heliumlike atomic systems at intermediate and high incident energies is examined by using the four-body formalism of the first- and second-order theories. The main purpose of the present study is to investigate the relative importance of the intermediate ionization continua of the captured electron compared to the usual direct path of the single electron transfer from a target to a projectile. In order to achieve this goal, comprehensive comparisons are made between the four-body boundary-corrected continuum-intermediate-states (BCIS-4B) method and the four-body boundary-corrected first Born (CB1-4B) method. The perturbation potential is the same in the CB1-4B and BCIS-4B methods. Both methods satisfy the correct boundary conditions in the entrance and exit channels. However, unlike the CB1-4B method, the second-order BCIS-4B method takes into account the electronic Coulomb continuum-intermediate states in either the entrance or the exit channel depending on whether the post or the prior version of the transition amplitude is used. Hence, by comparing the results from these two theories, the relative importance of the intermediate ionization electronic continua can be assessed within the four-body formalism of scattering theory. The BCIS-4B method predicts the usual second-order effect through double scattering of the captured electron on two nuclei as a quantum-mechanical counterpart of the Thomas classical two-step, billiard-type collision. The physical mechanism for this effect in the BCIS-4B method is also comprised of two steps such that ionization occurs first. This is followed by capture of the electron by the projectile with both processes taking place on the energy shell. Moreover, the role of the second, noncaptured electron in a heliumlike target is revisited. To this end, the BCIS-4B method describes the effect of capture of one electron by the interaction of the projectile nucleus with

  14. Kernel Continuum Regression.

    PubMed

    Lee, Myung Hee; Liu, Yufeng

    2013-12-01

    The continuum regression technique provides an appealing regression framework connecting ordinary least squares, partial least squares and principal component regression in one family. It offers some insight on the underlying regression model for a given application. Moreover, it helps to provide deep understanding of various regression techniques. Despite the useful framework, however, the current development on continuum regression is only for linear regression. In many applications, nonlinear regression is necessary. The extension of continuum regression from linear models to nonlinear models using kernel learning is considered. The proposed kernel continuum regression technique is quite general and can handle very flexible regression model estimation. An efficient algorithm is developed for fast implementation. Numerical examples have demonstrated the usefulness of the proposed technique. PMID:24058224

  15. Rapid induction and persistence of paracrine-induced cellular antiviral states arrest viral infection spread in A549 cells.

    PubMed

    Voigt, Emily A; Swick, Adam; Yin, John

    2016-09-01

    The virus/host interaction is a complex interplay between pro- and anti-viral factors that ultimately determines the spread or halt of virus infections in tissues. This interplay develops over multiple rounds of infection. The purpose of this study was to determine how cellular-level processes combine to impact the spatial spread of infection. We measured the kinetics of virus replication (VSV), antiviral paracrine signal upregulation and secretion, spatial spread of virus and paracrine antiviral signaling, and inhibition of virus production in antiviral-exposed A549 human lung epithelial cells. We found that initially infected cells released antiviral signals 4-to-7h following production of virus. However, the subsequent rapid dissemination of signal and fast induction of a robust and persistent antiviral state ultimately led to a suppression of infection spread. This work shows how cellular responses to infection and activation of antiviral responses can integrate to ultimately control infection spread across host cell populations. PMID:27254596

  16. The Aquatic Systems Continuum

    NASA Astrophysics Data System (ADS)

    Winter, T. C.

    2004-12-01

    The Aquatic Systems Continuum is a proposed framework for interrelating the physical, chemical, and biological characteristics of aquatic ecosystems. The continuum can be represented by a three-dimensional matrix that relates aquatic ecosystems to their position within hydrologic flow paths (x-axis, a spatial dimension) and their response to climate variability (y-axis). The z-axis describes the structure of biological communities as they relate to the hydrological conditions defined by the x and y axes. The concept is an extension of the Wetland Continuum that was derived from field studies of a prairie pothole wetland complex in North Dakota. At that site, the hydrologic continuum in space is defined by ground-water flow systems. The wetlands are surface-water expressions of larger ground-water watersheds, in which wetlands serve recharge, flow-through, and discharge functions with respect to ground water. The water balance of the wetlands is dominated by precipitation and evaporation. However, the interaction of the wetlands with ground water, although a small part of their water budget, provides the primary control on delivery of major solutes to and from the wetlands. Having monitored these wetlands for more than 25 years, during which time the site had a complete range of climate conditions from drought to deluge, the response of the aquatic communities to a wide variety of climate conditions has been well documented. The Aquatic Systems Continuum extends the model provided by the Wetland Continuum to include rivers and their interaction with ground water. As a result, both ground water and surface water are used to describe terrestrial water flows for all types of aquatic ecosystems. By using the Aquatic Systems Continuum to describe the hydrologic flow paths in all types of terrain, including exchange with atmospheric water, it is possible to design studies, monitoring programs, and management plans for nearly any type of aquatic ecosystem.

  17. Diversification of importin-α isoforms in cellular trafficking and disease states

    PubMed Central

    Pumroy, Ruth A.; Cingolani, Gino

    2015-01-01

    The human genome encodes seven isoforms of importin α which are grouped into three subfamilies known as α1, α2 and α3. All isoforms share a fundamentally conserved architecture that consists of an N-terminal, autoinhibitory, importin-β-binding (IBB) domain and a C-terminal Arm (Armadillo)-core that associates with nuclear localization signal (NLS) cargoes. Despite striking similarity in amino acid sequence and 3D structure, importin-α isoforms display remarkable substrate specificity in vivo. In the present review, we look at key differences among importin-α isoforms and provide a comprehensive inventory of known viral and cellular cargoes that have been shown to associate preferentially with specific isoforms. We illustrate how the diversification of the adaptor importin α into seven isoforms expands the dynamic range and regulatory control of nucleocytoplasmic transport, offering unexpected opportunities for pharmacological intervention. The emerging view of importin α is that of a key signalling molecule, with isoforms that confer preferential nuclear entry and spatiotemporal specificity on viral and cellular cargoes directly linked to human diseases. PMID:25656054

  18. Perturbation of cellular oxidative state induced by dichloroacetate and arsenic trioxide for treatment of acute myeloid leukemia.

    PubMed

    Emadi, Ashkan; Sadowska, Mariola; Carter-Cooper, Brandon; Bhatnagar, Vishal; van der Merwe, Isabella; Levis, Mark J; Sausville, Edward A; Lapidus, Rena G

    2015-07-01

    The incidence of acute myeloid leukemia (AML) is rising and the outcome of current therapy, which has not changed significantly in the last 40 years, is suboptimal. Cellular oxidative state is a credible target to selectively eradicate AML cells, because it is a fundamental property of each cell that is sufficiently different between leukemic and normal cells, yet its aberrancy shared among different AML cells. To this end, we tested whether a short-time treatment of AML cells, including cells with FLT3-ITD mutation, with sub-lethal dose of dichloroacetate (DCA) (priming) followed by pharmacologic dose of arsenic trioxide (ATO) in presence of low-dose DCA could produce insurmountable level of oxidative damage that kill AML cells. Using cellular cytotoxicity, apoptotic and metabolic assays with both established AML cell lines and primary AML cells, we found that priming with DCA significantly potentiated the cytotoxicity of ATO in AML cells in a synergistic manner. The combination decreased the mitochondrial membrane potential as well as expression of Mcl-1 and GPx in primary AML cells more than either drug alone. One patient with AML whose disease was refractory to several lines of prior treatments was treated with this combination, and tolerated it well. These data suggest that targeting cellular redox balance in leukemia may provide a therapeutic option for AML patients with relapsed/refractory disease. PMID:25982179

  19. A cellular automaton model of the steady-state free'' growth of a non-isothermal dendrite

    SciTech Connect

    Brown, S.G.R.; Williams, T.; Spittle, J.A. . Dept. of Materials Engineering)

    1994-08-01

    A 2D cellular automaton model has been developed to study the steady-state free'' growth of a non-isothermal dendrite. The model incorporates rules to account for heat diffusion, the influence of curvature on the equilibrium freezing temperature and latent heat evolution. The model predicts a V [proportional to] [Delta]T[sup b] growth rate-undercooling relationship for the various dendrite tip growth temperatures selected. The prediction of the values of b accords reasonably with analytical models and reported experimental observations.

  20. A study of high-temperature heat pipes with multiple heat sources and sinks. I - Experimental methodology and frozen startup profiles. II - Analysis of continuum transient and steady-state experimental data with numerical predictions

    NASA Technical Reports Server (NTRS)

    Faghri, A.; Cao, Y.; Buchko, M.

    1991-01-01

    Experimental profiles for heat pipe startup from the frozen state were obtained, using a high-temperature sodium/stainless steel pipe with multiple heat sources and sinks to investigate the startup behavior of the heat pipe for various heat loads and input locations, with both low and high heat rejection rates at the condensor. The experimental results of the performance characteristics for the continuum transient and steady-state operation of the heat pipe were analyzed, and the performance limits for operation with varying heat fluxes and location are determined.

  1. Examining the Psychosis Continuum

    PubMed Central

    DeRosse, Pamela; Karlsgodt, Katherine H.

    2015-01-01

    The notion that psychosis may exist on a continuum with normal experience has been proposed in multiple forms throughout the history of psychiatry. However, in recent years there has been an exponential increase in efforts aimed at elucidating what has been termed the ‘psychosis continuum’. The present review seeks to summarize some of the more basic characteristics of this continuum and to present some of the recent findings that provide support for its validity. While there is still considerable work to be done, the emerging data holds considerable promise for advancing our understanding of both risk and resilience to psychiatric disorders characterized by psychosis. PMID:26052479

  2. Disordered cellular automaton traffic flow model: phase separated state, density waves and self organized criticality

    NASA Astrophysics Data System (ADS)

    Fourrate, K.; Loulidi, M.

    2006-01-01

    We suggest a disordered traffic flow model that captures many features of traffic flow. It is an extension of the Nagel-Schreckenberg (NaSch) stochastic cellular automata for single line vehicular traffic model. It incorporates random acceleration and deceleration terms that may be greater than one unit. Our model leads under its intrinsic dynamics, for high values of braking probability pr, to a constant flow at intermediate densities without introducing any spatial inhomogeneities. For a system of fast drivers pr→0, the model exhibits a density wave behavior that was observed in car following models with optimal velocity. The gap of the disordered model we present exhibits, for high values of pr and random deceleration, at a critical density, a power law distribution which is a hall mark of a self organized criticality phenomena.

  3. A cellular and molecular mosaic establishes growth and differentiation states for cranial sensory neurons.

    PubMed

    Karpinski, Beverly A; A Bryan, Corey; Paronett, Elizabeth M; Baker, Jennifer L; Fernandez, Alejandra; Horvath, Anelia; Maynard, Thomas M; Moody, Sally A; LaMantia, Anthony-S

    2016-07-15

    We compared apparent origins, cellular diversity and regulation of initial axon growth for differentiating cranial sensory neurons. We assessed the molecular and cellular composition of the developing olfactory and otic placodes, and cranial sensory ganglia to evaluate contributions of ectodermal placode versus neural crest at each site. Special sensory neuron populations-the olfactory and otic placodes, as well as those in vestibulo-acoustic ganglion- are entirely populated with cells expressing cranial placode-associated, rather than neural crest-associated markers. The remaining cranial sensory ganglia are a mosaic of cells that express placode-associated as well as neural crest-associated markers. We found two distinct populations of neural crest in the cranial ganglia: the first, as expected, is labeled by Wnt1:Cre mediated recombination. The second is not labeled by Wnt1:Cre recombination, and expresses both Sox10 and FoxD3. These populations-Wnt1:Cre recombined, and Sox10/Foxd3-expressing- are proliferatively distinct from one another. Together, the two neural crest-associated populations are substantially more proliferative than their placode-associated counterparts. Nevertheless, the apparently placode- and neural crest-associated populations are similarly sensitive to altered signaling that compromises cranial morphogenesis and differentiation. Acute disruption of either Fibroblast growth factor (Fgf) or Retinoic acid (RA) signaling alters axon growth and cell death, but does not preferentially target any of the three distinct populations. Apparently, mosaic derivation and diversity of precursors and early differentiating neurons, modulated uniformly by local signals, supports early cranial sensory neuron differentiation and growth. PMID:26988119

  4. A computational model of skeletal muscle metabolism linking cellular adaptations induced by altered loading states to metabolic responses during exercise

    PubMed Central

    Dash, Ranjan K; DiBella, John A; Cabrera, Marco E

    2007-01-01

    Background The alterations in skeletal muscle structure and function after prolonged periods of unloading are initiated by the chronic lack of mechanical stimulus of sufficient intensity, which is the result of a series of biochemical and metabolic interactions spanning from cellular to tissue/organ level. Reduced activation of skeletal muscle alters the gene expression of myosin heavy chain isoforms to meet the functional demands of reduced mechanical load, which results in muscle atrophy and reduced capacity to process fatty acids. In contrast, chronic loading results in the opposite pattern of adaptations. Methods To quantify interactions among cellular and skeletal muscle metabolic adaptations, and to predict metabolic responses to exercise after periods of altered loading states, we develop a computational model of skeletal muscle metabolism. The governing model equations – with parameters characterizing chronic loading/unloading states- were solved numerically to simulate metabolic responses to moderate intensity exercise (WR ≤ 40% VO2 max). Results Model simulations showed that carbohydrate oxidation was 8.5% greater in chronically unloaded muscle compared with the loaded muscle (0.69 vs. 0.63 mmol/min), while fat oxidation was 7% higher in chronically loaded muscle (0.14 vs. 0.13 mmol/min), during exercise. Muscle oxygen uptake (VO2) and blood flow (Q) response times were 29% and 44% shorter in chronically loaded muscle (0.4 vs. 0.56 min for VO2 and 0.25 vs. 0.45 min for Q). Conclusion The present model can be applied to test complex hypotheses during exercise involving the integration and control of metabolic processes at various organizational levels (cellular to tissue) in individuals who have undergone periods of chronic loading or unloading. PMID:17448235

  5. The Continuum of Listening

    ERIC Educational Resources Information Center

    Rud, A. G.; Garrison, Jim

    2007-01-01

    The distinction between "apophatic" and "cataphatic" listening is defined and analyzed. "Apophatic" listening is more or less devoid of cognitivist claims, whereas "cataphatic" listening involves cognition and questioning. Many of the papers in this volume are discussed along the continuum determined by these two types of listening.…

  6. Teacher Education: A Continuum.

    ERIC Educational Resources Information Center

    Momentum, 1990

    1990-01-01

    This document is a theme issue of the journal "Momentum", devoted to the topic "Teacher Education: A Continuum." It contains 15 articles in the central section and 7 articles in a special section subtitled "The Multicultural Challenge." The following articles on the central theme are presented: (1) "Closing the Gap" concerns fusing the college and…

  7. The Creativity Continuum

    ERIC Educational Resources Information Center

    Walling, Donovan R.

    2009-01-01

    Children are innately creative, and the youngest often are the most original because they have yet to be influenced by the creativity of others. One way to think of creative expression is as a continuum. At one end is originality, or the creation of something wholly new, "original." At the other end is replication, or the re-creation of something…

  8. Extragalactic continuum sources.

    NASA Astrophysics Data System (ADS)

    Valtaoja, E.

    1989-09-01

    As with most other high-frequency radio telescopes, continuum work occupies only a small fraction - currently about 5% - of SEST's total time. The importance of these observations in increasing our understanding of quasars and other extragalactic sources is, however, large.

  9. Chemical tagging and customizing of cellular chromatin states using ultrafast trans-splicing inteins

    NASA Astrophysics Data System (ADS)

    David, Yael; Vila-Perelló, Miquel; Verma, Shivam; Muir, Tom W.

    2015-05-01

    Post-translational modification of the histone proteins in chromatin plays a central role in the epigenetic control of DNA-templated processes in eukaryotic cells. Developing methods that enable the structure of histones to be manipulated is, therefore, essential to understand the biochemical mechanisms that underlie genomic regulation. Here we present a synthetic biology method to engineer histones that bear site-specific modifications on cellular chromatin using protein trans-splicing (PTS). We genetically fused the N-terminal fragment of ultrafast split intein to the C terminus of histone H2B, which, on reaction with a complementary synthetic C intein, generated labelled histone. Using this approach, we incorporated various non-native chemical modifications into chromatin in vivo with temporal control. Furthermore, the time and concentration dependence of PTS performed in nucleo enabled us to examine differences in the accessibility of the euchromatin and heterochromatin regions of the epigenome. Finally, we used PTS to semisynthesize a native histone modification, H2BK120 ubiquitination, in isolated nuclei and showed that this can trigger downstream epigenetic crosstalk of H3K79 methylation.

  10. Chemical Fluxes in Cellular Steady States Measured by Fluorescence Correlation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Qian, Hong; Elson, Elliot L.

    Genetically, identical cells adopt phenotypes that have different structures, functions, and metabolic properties. In multi-cellular organisms, for example, tissue-specific phenotypes distinguish muscle cells, liver cells, fibroblasts, and blood cells that differ in biochemical functions, geometric forms, and interactions with extracellular environments. Tissue-specific cells usually have different metabolic functions such as synthesis of distinct spectra of secreted proteins, e.g., by liver or pancreatic cells, or of structural proteins, e.g., muscle vs. epithelial cells. But more importantly, a phenotype should include a dynamic aspect: different phenotypes can have distinctly different dynamic functions such as contraction of muscle cells and locomotion of leukocytes. The phenotypes of differentiated tissue cells are typically stable, but they can respond to changes in external conditions, e.g., as in the hypertrophy of muscle cells in response to extra load [1] or the phenotypic shift of fibroblasts to myofibroblasts as part of the wound healing response [2]. Cells pass through sequences of phenotypes during development and also undergo malignant phenotypic transformations as occur in cancer and heart disease.

  11. Multiplexed mass cytometry profiling of cellular states perturbed by small-molecule regulators

    PubMed Central

    Bodenmiller, Bernd; Zunder, Eli R.; Finck, Rachel; Chen, Tiffany J.; Savig, Erica S.; Bruggner, Robert V.; Simonds, Erin F.; Bendall, Sean C.; Sachs, Karen; Krutzik, Peter O.; Nolan, Garry P.

    2013-01-01

    The ability to comprehensively explore the impact of bio-active molecules on human samples at the single-cell level can provide great insight for biomedical research. Mass cytometry enables quantitative single-cell analysis with deep dimensionality, but currently lacks high-throughput capability. Here we report a method termed mass-tag cellular barcoding (MCB) that increases mass cytometry throughput by sample multiplexing. 96-well format MCB was used to characterize human peripheral blood mononuclear cell (PBMC) signaling dynamics, cell-to-cell communication, the signaling variability between 8 donors, and to define the impact of 27 inhibitors on this system. For each compound, 14 phosphorylation sites were measured in 14 PBMC types, resulting in 18,816 quantified phosphorylation levels from each multiplexed sample. This high-dimensional systems-level inquiry allowed analysis across cell-type and signaling space, reclassified inhibitors, and revealed off-target effects. MCB enables high-content, high-throughput screening, with potential applications for drug discovery, pre-clinical testing, and mechanistic investigation of human disease. PMID:22902532

  12. Cellular and biochemical mechanisms, risk factors and management of preterm birth: state of the art.

    PubMed

    Vitale, S G; Marilli, I; Rapisarda, A M; Rossetti, D; Belluomo, G; Iapichino, V; Stancanelli, F; Cianci, A

    2014-12-01

    Preterm birth (PTB) is usually defined as a delivery before 37 completed weeks or 259 days of gestation. World Health Organization estimates a worldwide incidence of PTB of 9.6%. Infants born preterm are at higher risks than infants born at term for mortality, and acute and chronic morbidity. Major causes of PTB are the following: spontaneous preterm labor with intact membranes (50%), labor induction or caesarean delivery for maternal or fetal indications (30%), and preterm premature rupture of membranes or PPROM (20%). The aim of this review is to analyze this medical condition, focusing on cellular and biochemical mechanisms, maternal risk factors and role of inflammation and infections in preterm premature rupture of membranes (PPROM) and PTB. Moreover we will discuss about the proper therapeutic strategies for its management. Although different methods have been introduced to predict the advent of preterm labour in asymptomatic women, possibilities for real primary prevention are rare. An early estimation of potential risk factors is pivotal in the secondary prevention of PTB. Finally most efforts so far have been tertiary interventions. These measures have reduced perinatal morbidity and mortality. Advances in primary and secondary care will be needed to prevent prematurity-related illness in infants and children. PMID:25373016

  13. Mitoplasticity: adaptation biology of the mitochondrion to the cellular redox state in physiology and carcinogenesis.

    PubMed

    Jose, Caroline; Melser, Su; Benard, Giovanni; Rossignol, Rodrigue

    2013-03-01

    Adaptation and transformation biology of the mitochondrion to redox status is an emerging domain of physiology and pathophysiology. Mitochondrial adaptations occur in response to accidental changes in cellular energy demand or supply while mitochondrial transformations are a part of greater program of cell metamorphosis. The possible role of mitochondrial adaptations and transformations in pathogenesis remains unexplored, and it has become critical to decipher the stimuli and the underlying molecular pathways. Immediate activation of mitochondrial function was described during acute exercise, respiratory chain injury, Endoplasmic Reticulum stress, genotoxic stress, or environmental toxic insults. Delayed adaptations of mitochondrial form, composition, and functions were evidenced for persistent changes in redox status as observed in endurance training, in fibroblasts grown in presence of respiratory chain inhibitors or in absence of glucose, in the smooth muscle of patients with severe asthma, or in the skeletal muscle of patients with a mitochondrial disease. Besides, mitochondrial transformations were observed in the course of human cell differentiation, during immune response activation, or in cells undergoing carcinogenesis. Little is known on the signals and downstream pathways that govern mitochondrial adaptations and transformations. Few adaptative loops, including redox sensors, kinases, and transcription factors were deciphered, but their implication in physiology and pathology remains elusive. Mitoplasticity could play a protective role against aging, diabetes, cancer, or neurodegenerative diseases. Research on adaptation and transformation could allow the design of innovative therapies, notably in cancer. PMID:22989324

  14. Correlating two-photon excited fluorescence imaging of breast cancer cellular redox state with seahorse flux analysis of normalized cellular oxygen consumption

    NASA Astrophysics Data System (ADS)

    Hou, Jue; Wright, Heather J.; Chan, Nicole; Tran, Richard; Razorenova, Olga V.; Potma, Eric O.; Tromberg, Bruce J.

    2016-06-01

    Two-photon excited fluorescence (TPEF) imaging of the cellular cofactors nicotinamide adenine dinucleotide and oxidized flavin adenine dinucleotide is widely used to measure cellular metabolism, both in normal and pathological cells and tissues. When dual-wavelength excitation is used, ratiometric TPEF imaging of the intrinsic cofactor fluorescence provides a metabolic index of cells-the "optical redox ratio" (ORR). With increased interest in understanding and controlling cellular metabolism in cancer, there is a need to evaluate the performance of ORR in malignant cells. We compare TPEF metabolic imaging with seahorse flux analysis of cellular oxygen consumption in two different breast cancer cell lines (MCF-7 and MDA-MB-231). We monitor metabolic index in living cells under both normal culture conditions and, for MCF-7, in response to cell respiration inhibitors and uncouplers. We observe a significant correlation between the TPEF-derived ORR and the flux analyzer measurements (R=0.7901, p<0.001). Our results confirm that the ORR is a valid dynamic index of cell metabolism under a range of oxygen consumption conditions relevant for cancer imaging.

  15. Optical and near-infrared spectroscopy of the black hole GX 339-4 - I. A focus on the continuum in the low/hard and high/soft states

    NASA Astrophysics Data System (ADS)

    Rahoui, F.; Coriat, M.; Corbel, S.; Cadolle Bel, M.; Tomsick, J. A.; Lee, J. C.; Rodriguez, J.; Russell, D. M.; Migliari, S.

    2012-05-01

    The microquasar GX 339-4, known to exhibit powerful compact jets that dominate its radio to near-infrared emission, entered an outburst in 2010 for the fifth time in about 15 yr. An extensive radio to X-ray multiwavelength campaign was immediately triggered, and we report here on European Southern Observatory/FORS2+ISAAC optical and near-infrared spectroscopic observations, supported by Australia Telescope Compact Array radio and Rossi X-ray Timing Experiment/Swift X-ray quasi-simultaneous data. GX 339-4 was observed at three different epochs, once in the soft state and twice in the hard state. In the soft state, the optical and near-infrared continuum is largely consistent with the Raleigh-Jeans tail of a thermal process. As an explanation, we favour irradiation of the outer accretion disc by its inner regions, enhanced by disc warping. An excess is also present at low frequencies, likely due to an M subgiant companion star. During the first hard state, the optical/near-infrared continuum is well described by the optically thin synchrotron emission of the compact jet combined with disc irradiation and perhaps another component peaking in the ultraviolet. The spectral break where the jet transits from the optically thick to thin regimes, located below 1.20 × 1014 Hz, is not detected and the extension of the optically thin synchrotron is consistent with the 3-50 keV spectrum. In contrast, the emission during the second hard state is more difficult to understand and points towards a more complex jet continuum. In both cases, the near-infrared continuum is found to be variable at time-scales at least as short as 20 s, although these variabilities are smoothed out beyond a few hundred seconds. This implies rapid variations - in flux and frequency - of the location of the spectral break, i.e. dramatic short time-scale changes of the physical conditions at the base of the jet, such as the magnetic field and/or the base radius. a Same as DISKBB.

  16. Unified ab initio approach to bound and unbound states: No-core shell model with continuum and its application to 7He

    SciTech Connect

    Baroni, Simone; Navratil, Petr; Quaglioni, Sofia

    2013-03-26

    In this study, we introduce a unified approach to nuclear bound and continuum states based on the coupling of the no-core shell model (NCSM), a bound-state technique, with the no-core shell model/resonating group method (NCSM/RGM), a nuclear scattering technique. This new ab initio method, no-core shell model with continuum (NCSMC), leads to convergence properties superior to either NCSM or NCSM/RGM while providing a balanced approach to different classes of states. In the NCSMC, the ansatz for the many-nucleon wave function includes (i) a square-integrable A-nucleon component expanded in a complete harmonic oscillator basis and (ii) a binary-cluster component with asymptotic boundary conditions that can properly describe weakly bound states, resonances, and scattering. The Schrödinger equation is transformed into a system of coupled-channel integral-differential equations that we solve using a modified microscopic R-matrix formalism within a Lagrange mesh basis. We demonstrate the usefulness of the approach by investigating the unbound 7He nucleus.

  17. [Toxicological assessment of nanostructured silica. III. Microecological, hematological indices, state of cellular immunity].

    PubMed

    Shumakova, A A; Efimochkina, N R; Minaeva, L P; Bykova, I B; Batishchava, S Yu; Markova, Yu M; Trushina, E N; Mustafina, O K; Sharanova, N E; Gmoshinsky, I V; Khanferyan, R A; Khotimchenko, S A; Sheveleva, S A; Tutelyan, V A

    2015-01-01

    This paper is the third in a series of publications on the experimental study of subacute oral toxicity of nanostructured silicon dioxide (SiO2). We used commercial nanostructured SiO2, obtained by hydrolysis of tetrachlorosilane in the gaseous phase, with the size of the primary nanoparticles (NPs) of 5-30 nm. The aqueous dispersion of SiO2 after treatment with ultrasound was administered to rats with initial weight of 80 +/- 5 g for the first 30 days by intragastric gavage and further for 60 days with diets in doses of 0.1; 1.0; 10 and 100 mg/kg body weight per day. Animals of the control group were treated with deionized water. The amount of basic and transient populations of gut microbiocenosis, hematological indexes were measured using standard methods. Specific content of the B-lymphocytes (CD45RA+), total T-lymphocytes (CD3+), T-helper cells (CD4+), T-cytotoxic cells (CD8+), NK-cells (CD161a+) in general population of lymphocytes was evaluated byflow cytometry; serum cytokine levels of TNF-alpha, IL-6, IL-10 were determined by ELISA. No significant changes in the qualitative and quantitative composition of the intestinal microbiota populations regardless of the dose of administered nanomaterial have been found. This gave reason to believe that the postulated mechanism of the toxic effects of the NPs of SiO2, mediated by modification of the composition of the intestinal microflora and the corresponding changes in its functional activity, apparently, is not realized. The main target of nanostructured SiO2 was the T-cellular system of the immune system of animals, that was manifested in the significant decrease of the number of leukocytes (33%), number of T-helper cells (13%), CD4/CD8 ratio (27%) and increasing the number of cytotoxic lymphocytes (19%) and the level of TNF-alpha (590%). The value of the maximum dose (NOAEL) of nanostructured SiO2, has no effect on T-cell immunity was not more than 100 mg/kg body weight per day. PMID:26852532

  18. Evidence for transcriptional and post-translational regulation of sucrose synthase in pea nodules by the cellular redox state.

    PubMed

    Marino, Daniel; Hohnjec, Natalija; Küster, Helge; Moran, Jose F; González, Esther M; Arrese-Igor, Cesar

    2008-05-01

    Nitrogen fixation (NF) in legume nodules is very sensitive to environmental constraints. Nodule sucrose synthase (SS; EC 2.4.1.13) has been suggested to play a crucial role in those circumstances because its downregulation leads to an impaired glycolytic carbon flux and, therefore, a depletion of carbon substrates for bacteroids. In the present study, the likelihood of SS being regulated by oxidative signaling has been addressed by the in vivo supply of paraquat (PQ) to nodulated pea plants and the in vitro effects of oxidizing and reducing agents on nodule SS. PQ produced cellular redox imbalance leading to an inhibition of NF. This was preceded by the downregulation of SS gene expression, protein content, and activity. In vitro, oxidizing agents were able to inhibit SS activity and this inhibition was completely reversed by the addition of dithiothreitol. The overall results are consistent with a regulation model of nodule SS exerted by the cellular redox state at both the transcriptional and post-translational levels. The importance of such mechanisms for the regulation of NF in response to environmental stresses are discussed. PMID:18393622

  19. Delayed effects of low-dose radiation on cellular immunity in atomic bomb survivors residing in the United States.

    PubMed

    Bloom, E T; Akiyama, M; Kusunoki, Y; Makinodan, T

    1987-05-01

    Several parameters of cellular immune function were assessed among persons who survived the 1945 atomic bombs in Hiroshima and Nagasaki but who now reside in the United States. The subjects in this study were exposed to various low doses (T65D) of radiation at the time of the bomb. More than half received an estimated 0 Gy (S0 group). Of those exposed to more radiation (S+ group), nearly 90% received less than 0.50 Gy (50 rad). Lymphocytes were isolated from the peripheral blood of these individuals and were assessed for the following parameters of cellular immunity: mitogenic response to phytohemagglutinin, mitogenic response to allogeneic lymphocytes, natural cell-mediated cytotoxicity (NCMC), and interferon production. In every case, the response of the S+ group was greater than that of the S0 group, although only the difference for NCMC was statistically significant. Results of studies presently being performed on A-bomb survivors residing in Hiroshima do not confirm this difference. Therefore, it is difficult to say whether the increase in natural cytotoxicity observed among the American and not the Japanese A-bomb survivors exposed to very low doses of radiation is a hormetic effect which was modulated by post-radiation environmental conditions or a result of selective migration. PMID:3570796

  20. Conway's game of life is a near-critical metastable state in the multiverse of cellular automata

    NASA Astrophysics Data System (ADS)

    Reia, Sandro M.; Kinouchi, Osame

    2014-05-01

    Conway's cellular automaton Game of Life has been conjectured to be a critical (or quasicritical) dynamical system. This criticality is generally seen as a continuous order-disorder transition in cellular automata (CA) rule space. Life's mean-field return map predicts an absorbing vacuum phase (ρ =0) and an active phase density, with ρ =0.37, which contrasts with Life's absorbing states in a square lattice, which have a stationary density of ρ2D≈0.03. Here, we study and classify mean-field maps for 6144 outer-totalistic CA and compare them with the corresponding behavior found in the square lattice. We show that the single-site mean-field approach gives qualitative (and even quantitative) predictions for most of them. The transition region in rule space seems to correspond to a nonequilibrium discontinuous absorbing phase transition instead of a continuous order-disorder one. We claim that Life is a quasicritical nucleation process where vacuum phase domains invade the alive phase. Therefore, Life is not at the "border of chaos," but thrives on the "border of extinction."

  1. Conway's Game of Life is a near-critical metastable state in the multiverse of cellular automata.

    PubMed

    Reia, Sandro M; Kinouchi, Osame

    2014-05-01

    Conway's cellular automaton Game of Life has been conjectured to be a critical (or quasicritical) dynamical system. This criticality is generally seen as a continuous order-disorder transition in cellular automata (CA) rule space. Life's mean-field return map predicts an absorbing vacuum phase (ρ = 0) and an active phase density, with ρ = 0.37, which contrasts with Life's absorbing states in a square lattice, which have a stationary density of ρ(2D) ≈ 0.03. Here, we study and classify mean-field maps for 6144 outer-totalistic CA and compare them with the corresponding behavior found in the square lattice. We show that the single-site mean-field approach gives qualitative (and even quantitative) predictions for most of them. The transition region in rule space seems to correspond to a nonequilibrium discontinuous absorbing phase transition instead of a continuous order-disorder one. We claim that Life is a quasicritical nucleation process where vacuum phase domains invade the alive phase. Therefore, Life is not at the "border of chaos," but thrives on the "border of extinction." PMID:25353755

  2. A continuum model of transcriptional bursting

    PubMed Central

    Corrigan, Adam M; Tunnacliffe, Edward; Cannon, Danielle; Chubb, Jonathan R

    2016-01-01

    Transcription occurs in stochastic bursts. Early models based upon RNA hybridisation studies suggest bursting dynamics arise from alternating inactive and permissive states. Here we investigate bursting mechanism in live cells by quantitative imaging of actin gene transcription, combined with molecular genetics, stochastic simulation and probabilistic modelling. In contrast to early models, our data indicate a continuum of transcriptional states, with a slowly fluctuating initiation rate converting the gene between different levels of activity, interspersed with extended periods of inactivity. We place an upper limit of 40 s on the lifetime of fluctuations in elongation rate, with initiation rate variations persisting an order of magnitude longer. TATA mutations reduce the accessibility of high activity states, leaving the lifetime of on- and off-states unchanged. A continuum or spectrum of gene states potentially enables a wide dynamic range for cell responses to stimuli. DOI: http://dx.doi.org/10.7554/eLife.13051.001 PMID:26896676

  3. Preformed Soluble Chemoreceptor Trimers That Mimic Cellular Assembly States and Activate CheA Autophosphorylation

    PubMed Central

    2015-01-01

    Bacterial chemoreceptors associate with the histidine kinase CheA and coupling protein CheW to form extended membrane arrays that receive and transduce environmental signals. A receptor trimers-of-dimers resides at each vertex of the hexagonal protein lattice. CheA is fully activated and regulated when it is integrated into the receptor assembly. To mimic these states in solution, we have engineered chemoreceptor cytoplasmic kinase-control modules (KCMs) based on the Escherichia coli aspartate receptor Tar that are covalently fused and trimerized by a foldon domain (TarFO). Small-angle X-ray scattering, multi-angle light scattering, and pulsed-dipolar electron spin resonance spectroscopy of spin-labeled proteins indicate that the TarFO modules assemble into homogeneous trimers wherein the protein interaction regions closely associate at the end opposite to the foldon domains. The TarFO variants greatly increase the saturation levels of phosphorylated CheA (CheA-P), indicating that the association with a trimer of receptor dimers changes the fraction of active kinase. However, the rate constants for CheA-P formation with the Tar variants are low compared to those for autophosphorylation by free CheA, and net phosphotransfer from CheA to CheY does not increase commensurately with CheA autophosphorylation. Thus, the Tar variants facilitate slow conversion to an active form of CheA that then undergoes stable autophosphorylation and is capable of subsequent phosphotransfer to CheY. Free CheA is largely incapable of phosphorylation but contains a small active fraction. Addition of TarFO to CheA promotes a planar conformation of the regulatory domains consistent with array models for the assembly state of the ternary complex and different from that observed with a single inhibitory receptor. Introduction of TarFO into E. coli cells activates endogenous CheA to produce increased clockwise flagellar rotation, with the effects increasing in the presence of the chemotaxis

  4. Ionization states, cellular toxicity and molecular modeling studies of midazolam complexed with trimethyl-β-cyclodextrin.

    PubMed

    Shityakov, Sergey; Sohajda, Tamás; Puskás, István; Roewer, Norbert; Förster, Carola; Broscheit, Jens-Albert

    2014-01-01

    We investigated the ionization profiles for open-ring (OR) and closed-ring (CR) forms of midazolam and drug-binding modes with heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (trimethyl-β-cyclodextrin; TRIMEB) using molecular modeling techniques and quantum mechanics methods. The results indicated that the total net charges for different molecular forms of midazolam tend to be cationic for OR and neutral for CR at physiological pH levels. The thermodynamic calculations demonstrated that CR is less water-soluble than OR, mainly due to the maximal solvation energy (ΔG(CR)(solv = -9.98 kcal·mol ⁻¹), which has a minimal ΔG(OR)(solv) of -67.01 kcal·mol⁻¹. A cell viability assay did not detect any signs of TRIMEB and OR/CR-TRIMEB complex toxicity on the cEND cells after 24 h of incubation in either Dulbecco's Modified Eagles Medium or in heat-inactivated human serum. The molecular docking studies identified the more flexible OR form of midazolam as being a better binder to TRIMEB with the fluorophenyl ring introduced inside the amphiphilic cavity of the host molecule. The OR binding affinity was confirmed by a minimal Gibbs free energy of binding (ΔG(bind)) value of -5.57 ± 0.02 kcal·mol⁻¹, an equilibrium binding constant (K(b)) of 79.89 ± 2.706 μM, and a ligand efficiency index (LE(lig)) of -0.21 ± 0.001. Our current data suggest that in order to improve the clinical applications of midazolam via its complexation with trimethyl-β-cyclodextrin to increase drug's overall aqueous solubility, it is important to concern the different forms and ionization states of this anesthetic. All mean values are indicated with their standard deviations. PMID:25338177

  5. The Response Continuum

    SciTech Connect

    Caltagirone, Sergio; Frincke, Deborah A.

    2005-06-17

    Active response is a sequence of actions per- formed speci¯cally to mitigate a detected threat. Response decisions always follow detection: a decision to take `no ac- tion' remains a response decision. However, active response is a complex subject that has received insu±cient formal attention. To facilitate discussion, this paper provides a framework that proposes a common de¯nition, describes the role of response and the major issues surrounding response choices, and ¯nally, provides a model for the process of re- sponse. This provides a common starting point for discus- sion of the full response continuum as an integral part of contemporary computer security.

  6. Role of the cellular oxidation-reduction state in methotrexate binding to dihydrofolate reductase and dissociation induced by reduced folates.

    PubMed

    Matherly, L H; Anderson, L A; Goldman, I D

    1984-06-01

    5-Formyltetrahydrofolate promotes the net dissociation of methotrexate bound to dihydrofolate reductase in the Ehrlich ascites tumor (L. H. Matherly et al., Cancer Res., 43: 2694-2699, 1983). Treatment of Ehrlich tumor cells with glucose or inhibitors of electron transfer stabilized the association of the antifolate with dihydrofolate reductase as reflected by a 2-fold increased fraction of dihydrofolate reductase-bound methotrexate and an abolition of the 5-formyltetrahydrofolate-induced dissociation of the inhibitor-enzyme complex. Glucose and azide were also found to increase the intracellular ratio of reduced nicotinamide adenine dinucleotide phosphate (NADPH) to oxidized nicotinamide adenine dinucleotide phosphate (NADP+) in the tumor approximately 8- and 11-fold, respectively. However, other agents which enhanced the association between methotrexate and its target enzyme were less effective in increasing the intracellular level of NADPH relative to NADP+. Micromolar concentrations of NADPH promoted methotrexate binding to the purified Ehrlich tumor dihydrofolate reductase. Bound methotrexate could be dissociated from the purified enzyme by 5-methyltetrahydrofolate but less readily by 5-formyltetrahydrofolate and only in the presence of reduced levels of NADPH relative to NADP+. The tetraglutamate derivative of 5-methyltetrahydrofolate was even more effective than the underivatized compound in dissociating methotrexate from dihydrofolate reductase. These findings suggest a critical role for the cellular oxidation-reduction state in determining the affinity of dihydrofolate reductase for methotrexate and thus the cellular sensitivity to the antifolate. In addition, the data are consistent with the possibility that dihydrofolate reductase is a key locus for intracellular competitive interactions between reduced folates and methotrexate during leucovorin rescue from the pharmacological effects of the antifolate. PMID:6609765

  7. Micropolar continuum in spatial description

    NASA Astrophysics Data System (ADS)

    Ivanova, Elena A.; Vilchevskaya, Elena N.

    2016-06-01

    Within the spatial description, it is customary to refer thermodynamic state quantities to an elementary volume fixed in space containing an ensemble of particles. During its evolution, the elementary volume is occupied by different particles, each having its own mass, tensor of inertia, angular and linear velocities. The aim of the present paper is to answer the question of how to determine the inertial and kinematic characteristics of the elementary volume. In order to model structural transformations due to the consolidation or defragmentation of particles or anisotropic changes, one should consider the fact that the tensor of inertia of the elementary volume may change. This means that an additional constitutive equation must be formulated. The paper suggests kinetic equations for the tensor of inertia of the elementary volume. It also discusses the specificity of the inelastic polar continuum description within the framework of the spatial description.

  8. Kilometric Continuum Radiation

    NASA Technical Reports Server (NTRS)

    Green, James L.; Boardsen, Scott

    2006-01-01

    Kilometric continuum (KC) is the high frequency component (approximately 100 kHz to approximately 800 kHz) of nonthermal continuum (NTC). Unlike the lower frequency portion of NTC (approximately 5 kHz to approximately 100 kHz) whose source is around the dawn sector, the source of KC occurs at all magnetic local times. The latitudinal beaming of KC as observed by GEOTAIL is, for most events, restricted to plus or minus 15 degrees magnetic latitude. KC has been observed during periods of both low and strong geomagnetic activity, with no significant correlation of wave intensity with K(sub p), index. However statistically the maximum observed frequency of KC emission tends to increase with K(sub p) index, the effect is more pronounced around solar maximum, but is also detected near solar minimum. There is strong evidence that the source region of KC is from the equatorial plasmapause during periods when a portion of the plasmapause moves significantly inwards from its nominal position. Case studies have shown that KC emissions are nearly always associated with plasmaspheric notches, shoulders, and tails. There is a recent focus on trying to understand the banded frequency structure of this emission and its relationship to plasmaspheric density ducts and irregularities in the source region.

  9. Continuum lowering - A new perspective

    NASA Astrophysics Data System (ADS)

    Crowley, B. J. B.

    2014-12-01

    What is meant by continuum lowering and ionization potential depression (IPD) in a Coulomb system depends very much upon precisely what question is being asked. It is shown that equilibrium (equation of state) phenomena and non-equilibrium dynamical processes like photoionization are characterized by different values of the IPD. In the former, the ionization potential of an atom embedded in matter is the difference in the free energy of the many-body system between states of thermodynamic equilibrium differing by the ionization state of just one atom. Typically, this energy is less than that required to ionize the same atom in vacuo. Probably, the best known example of this is the IPD given by Stewart and Pyatt (SP). However, it is a common misconception that this formula should apply directly to the energy of a photon causing photoionization, since this is a local adiabatic process that occurs in the absence of a response from the surrounding plasma. To achieve the prescribed final equilibrium state, in general, additional energy, in the form of heat and work, is transferred between the atom and its surroundings. This additional relaxation energy is sufficient to explain the discrepancy between recent spectroscopic measurements of IPD in dense plasmas and the predictions of the SP formula. This paper provides a detailed account of an analytical approach, based on SP, to calculating thermodynamic and spectroscopic (adiabatic) IPDs in multicomponent Coulomb systems of arbitrary coupling strength with Te ≠ Ti. The ramifications for equilibrium Coulomb systems are examined in order to elucidate the roles of the various forms of the IPD and any possible connection with the plasma microfield. The formulation embodies an analytical equation of state (EoS) that is thermodynamically self-consistent, provided that the bound and free electrons are dynamically separable, meaning that the system is not undergoing pressure ionization. Apart from this restriction, the model is

  10. Some Continuum Aspects of Data Assimilation

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Menard, Richard

    1999-01-01

    A long-sought goal in data assimilation is to build more fully the time dimension into the data assimilation process. Truly four-dimensional data assimilation requires evolving second-moment information, namely the estimation error covariance, along with the state estimate itself. The continuum evolution equations for the estimation error covariance constitute a system of partial differential equations in six space dimensions, forced by a model error covariance and by the observations themselves. The high dimensionality of this system poses a difficult computational problem. Numerous methods have been proposed for approximate, discrete solution of this system of equations. Four-dimensional variational schemes solve these equations indirectly, while schemes based on Kalman filtering solve the equations more directly, usually on a small subspace of the full six-dimensional space. In both cases, most proposed solution methods are not derived from the continuum covariance evolution equations themselves. Instead, most methods simply inherit the discretization used for evolving the state estimate, either in the form of a discrete tangent linear model or, in the case of ensemble schemes, in the form of a fully nonlinear discrete model. In this lecture we show that solutions of the continuum covariance evolution equations possess simple properties that are not readily satisfied upon discretization of the equations. we give numerical examples illustrating that "inherited" discretizations sometimes fail to produce meaningfully accurate solutions. Finally, we suggest alternative discretization methods that may yield more faithful approximate solutions of the continuum problem.

  11. Cellular resilience.

    PubMed

    Smirnova, Lena; Harris, Georgina; Leist, Marcel; Hartung, Thomas

    2015-01-01

    Cellular resilience describes the ability of a cell to cope with environmental changes such as toxicant exposure. If cellular metabolism does not collapse directly after the hit or end in programmed cell death, the ensuing stress responses promote a new homeostasis under stress. The processes of reverting "back to normal" and reversal of apoptosis ("anastasis") have been studied little at the cellular level. Cell types show astonishingly similar vulnerability to most toxicants, except for those that require a very specific target, metabolism or mechanism present only in specific cell types. The majority of chemicals triggers "general cytotoxicity" in any cell at similar concentrations. We hypothesize that cells differ less in their vulnerability to a given toxicant than in their resilience (coping with the "hit"). In many cases, cells do not return to the naive state after a toxic insult. The phenomena of "pre-conditioning", "tolerance" and "hormesis" describe this for low-dose exposures to toxicants that render the cell more resistant to subsequent hits. The defense and resilience programs include epigenetic changes that leave a "memory/scar" - an alteration as a consequence of the stress the cell has experienced. These memories might have long-term consequences, both positive (resistance) and negative, that contribute to chronic and delayed manifestations of hazard and, ultimately, disease. This article calls for more systematic analyses of how cells cope with toxic perturbations in the long-term after stressor withdrawal. A technical prerequisite for these are stable (organotypic) cultures and a characterization of stress response molecular networks. PMID:26536287

  12. Negative-continuum dielectronic recombination for heavy ions

    SciTech Connect

    Artemyev, A.N.; Yerokhin, V.A.; Beier, T.; Kozhuharov, C.; Eichler, J.; Klasnikov, A.E.; Shabaev, V.M.; Stoehlker, T.

    2003-05-01

    The process of recombination of an electron with a bare heavy nucleus via the creation of a free-positron-bound-electron pair is considered. This process is denoted as 'negative-continuum dielectronic recombination' because it results in the capture of an incident electron into a bound state accompanied by a transition of a negative-continuum electron into a bound state. The calculations are performed for a wide range of incident electron energies for Z=82 and 92.

  13. Internal photopumping of Nd3+ (2H9/2, 4F5/2) states in yttrium aluminum garnet by excitation transfer from oxygen deficiency centers and Fe3+ continuum emission

    NASA Astrophysics Data System (ADS)

    Hewitt, J. D.; Spinka, T. M.; Senin, A. A.; Eden, J. G.

    2011-07-01

    Photoexcitation of Nd3+ (2H9/2, 4F5/2) states by the broad (˜70 nm FWHM), near-infrared continuum provided by Fe3+ has been observed at 300 K in bulk yttrium aluminum garnet (YAG) crystals doped with trace concentrations (<50 ppm) of Fe, Cr, and Eu. Irradiation of YAG at 248 nm with a KrF laser, which excites the oxygen deficiency center (ODC) in YAG having peak absorption at ˜240 nm, culminates in ODC→Fe3+ excitation transfer and subsequent Fe3+ emission. This internal optical pumping mechanism for rare earth ions is unencumbered by the requirement for donor-acceptor proximity that constrains conventional Förster-Dexter excitation transfer in co-doped crystals.

  14. Structured photoionization continuum of superheated cesium vapor

    NASA Astrophysics Data System (ADS)

    Pichler, G.; Makdisi, Y.; Kokaj, J.; Thomas, N.; Mathew, J.

    2015-08-01

    We studied the absorption spectrum of dense cesium vapor in an all-sapphire cell with a special emphasis on the highly structured photoionization continuum. This continuum appears to be composed of atomic and molecular contributions which can be separated by means of additional superheating of the cesium vapor in the sapphire cell. This was possible due to the small amount of cesium filling which completely evaporated at a temperature of around 450 °C. This enabled the overheating of cesium dimers which greatly reduced its concentration at a temperature of 900 °C, leaving almost pure atomic Cs vapor. The analysis of the thermal destruction indicated that the highly structured molecular component of the photoionization continuum can be entirely attributed to cesium dimers. We discuss the possible origin of the structured photoionization continuum as stemming from the absorption process from the ground state of the Cs2 molecule to the doubly excited Cs2** molecule located above Cs2+ molecular ionization limit. The corresponding potential curves are subjected to mutual interactions and autoionization.

  15. Defining the Molecular-Cellular-Field Continuum of Mercury Detoxification

    SciTech Connect

    Miller, Susan M.

    2014-09-04

    Hg is of special interest to DOE due to past use at the Oak Ridge Reservation (ORR). Its facile redox [Hg2+/0] chemistry, bonding to carbon [e.g. MeHg+] and unique physical properties [e.g., Hg0 volatility] underlie a complex global Hg cycle involving biotic and abiotic chemical and physical transport and transformations in soils, sediments, waterways and the atmosphere. Facultative and anaerobic bacteria make MeHg+, which is neurotoxic to wildlife and humans. Sustainable stewardship requires eliminating both MeHg+ and even more toxic Hg2+, which is also the substrate for methylation. The proteins encoded by the mer locus in aerobic and facultative mercury resistant (HgR) bacteria convert soil or waterborne Hg2+ or MeHg+ to less toxic, gaseous Hg0. HgR microbes live in highly Hg-contaminated sites and depress MeHg+ formation >500-fold in such zones. So, enhancing the capacity of natural HgR microbes to remove Hg2+/MeHg+ from wetlands and waterways is a logical component of contaminated site stewardship. To apply enhancement in the field requires knowing how the HgR pathway works including the metabolic demands it makes on the cell, i.e., the entire cell is the relevant catalytic unit. HgR loci occur in metabolically diverse bacteria and unique mer-host co-evolution has been found. In this project we extended our previous studies of mer enzymes in γ-proteobacteria, which are abundant in high Hg areas of the ORR to include studies of mer enzymes from HgR α-proteobacteria and HgR actinobacteria, which also increase in the high Hg regions of the ORR. Specifically, we (1) examined interactions between structural compoenents of MerA and MerB enzymes from γ-proteobacteria, (2) investigated effects of mutations on kinetic efficiency of Hg2+ reduction by γ-proteobacterial MerA, (3) cloned and performed initital characterization of MerA and MerB enzymes from Streptomyces lividans, an actinobacterium, (4) cloned and performed initial characterization of a fused MerB-MerA protein from Ochrobactrum anthropi, an α-proteobacterium, (5) investigate the extent of Hg isotope fractionation that occurs with purified γ-proteobacterial MerA.

  16. Cellular growth in biofilms

    SciTech Connect

    Wood, B.D.; Whitaker, S.

    1999-09-20

    In this paper the authors develop a macroscopic evolutionary equation for the growth of the cellular phase starting from a microscopic description of mass transport and a simple structured model for product formation. The methods of continuum mechanics and volume averaging are used to develop the macroscopic representation by carefully considering the fluxes of chemical species that pertain to cell growth. The concept of structured models is extended to include the transport of reacting chemical species at the microscopic scale. The resulting macroscopic growth model is similar in form to previously published models for the transport of a single substrate and electron donor and for the production of cellular mass and exopolymer. The method of volume averaging indicated under what conditions the developed growth model is valid and provides an explicit connection between the relevant microscopic model parameters and their corresponding macroscopic counterparts.

  17. Relativistic Continuum Shell Model

    NASA Astrophysics Data System (ADS)

    Grineviciute, Janina; Halderson, Dean

    2011-04-01

    The R-matrix formalism of Lane and Thomas has been extended to the relativistic case so that the many-coupled channels problem may be solved for systems in which binary breakup channels satisfy a relative Dirac equation. The formalism was previously applied to the relativistic impulse approximation RIA and now we applied it to Quantum Hadrodynamics QHD in the continuum Tamm-Dancoff approximation TDA with the classical meson fields replaced by one-meson exchange potentials. None of the published QHD parameters provide a decent fit to the 15 N + p elastic cross section. The deficiency is also evident in inability of the QHD parameters with the one meson exchange potentials to reproduce the QHD single particle energies. Results with alternate parameters sets are presented. A. M. Lane and R. G. Thomas, R-Matrix Theory of Nuclear Reactions, Reviews of Modern Physics, 30 (1958) 257

  18. Electron-ion continuum-continuum mixing in dissociative recombination

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1993-01-01

    In recent calculations on the dissociative recombination (DR) of the v=1 vibrational level of the ground state of N2(+), N2(+)(v=1) + e(-) yields N + N, we have observed an important continuun-continuum mixing process involving the open channels on both sides of N2(+)(v=1) + e(-) yields N2(+)(v=0) + e(-). In vibrational relaxation by electron impact (immediately above) the magnitude of the cross section depends upon the strength of the interaction between these continua. In DR of the v=1 ion level, these continua can also interact in the entrance channel, and the mixing can have a profound effect upon the DR cross section from v=1, as we illustrate in this paper. In our theoretical calculations of N2(+) DR using multichannel quantum defect theory (MQDT), the reactants and products in the two above equations are described simultaneously. This allows us to calculate vibrational relaxation and excitation cross sections as well as DR cross sections. In order to understand the mixing described above, we first present a brief review of the prior results for DR of the v=0 level of N2(+).

  19. The Paranoid-Depressive Continuum

    ERIC Educational Resources Information Center

    Johnson, Betty J.

    1977-01-01

    Few investigators have attempted to lay a conceptual base for comparative studies of paranoia and depression within a single general framework. The paranoid-depressive continuum is an attempt to develop such a framework. (Author)

  20. Stem cell-like ALDHbright cellular states in EGFR-mutant non-small cell lung cancer

    PubMed Central

    Corominas-Faja, Bruna; Oliveras-Ferraros, Cristina; Cuyàs, Elisabet; Segura-Carretero, Antonio; Joven, Jorge; Martin-Castillo, Begoña; Barrajón-Catalán, Enrique; Micol, Vicente; Bosch-Barrera, Joaquim; Menendez, Javier A

    2013-01-01

    The enrichment of cancer stem cell (CSC)-like cellular states has not previously been considered to be a causative mechanism in the generalized progression of EGFR-mutant non-small cell lung carcinomas (NSCLC) after an initial response to the EGFR tyrosine kinase inhibitor erlotinib. To explore this possibility, we utilized a pre-clinical model of acquired erlotinib resistance established by growing NSCLC cells containing a TKI-sensitizing EGFR exon 19 deletion (ΔE746-A750) in the continuous presence of high doses of erlotinib. Genome-wide analyses using Agilent 44K Whole Human Genome Arrays were evaluated via bioinformatics analyses through GSEA-based screening of the KEGG pathway database to identify the molecular circuitries that were over-represented in the transcriptomic signatures of erlotinib-refractory cells. The genomic spaces related to erlotinib resistance included a preponderance of cell cycle genes (E2F1, -2, CDC2, -6) and DNA replication-related genes (MCM4, -5, -6, -7), most of which are associated with early lung development and poor prognosis. In addition, metabolic genes such as ALDH1A3 (a candidate marker for lung cancer cells with CSC-like properties) were identified. Thus, we measured the proportion of erlotinib-resistant cells expressing very high levels of aldehyde dehydrogenase (ALDH) activity attributed to ALDH1/3 isoforms. Using flow cytometry and the ALDEFLUOR® reagent, we confirmed that erlotinib-refractory cell populations contained drastically higher percentages (>4500%) of ALDHbright cells than the parental erlotinib-responsive cells. Notably, strong decreases in the percentages of ALDHbright cells were observed following incubation with silibinin, a bioactive flavonolignan that can circumvent erlotinib resistance in vivo. The number of lung cancer spheres was drastically suppressed by silibinin in a dose-dependent manner, thus confirming the ability of this agent to inhibit the self-renewal of erlotinib-refractory CSC-like cells

  1. Uses of continuum radiation in the AXAF calibration

    NASA Technical Reports Server (NTRS)

    Kolodziejczak, J. J.; Austin, R. A.; Elsner, R. F.; O'Dell, S. L.; Sulkanen, M. E.; Swartz, D. A.; Tennant, A. F.; Weisskopf, M. C.; Zirnstein, G.; McDermott, W. C.

    1997-01-01

    X-ray calibration of the Advanced X-ray Astrophysics Facility (AXAF) observatory at the MSFC X-Ray Calibration Facility (XRCF) made novel use of the x-ray continuum from a conventional electron-impact source. Taking advantage of the good spectral resolution of solid-state detectors, continuum measurements proved advantageous in calibrating the effective area of AXAF's High-Resolution Mirror Assembly (HRMA) and in verifying its alignment to the XRCF's optical axis.

  2. Uses of Continuum Radiation in the AXAF Calibration

    NASA Technical Reports Server (NTRS)

    Kolodziejczak, J. J.; Austin, R. A.; Eisner, R. F.; ODell, S. L.; Sulkanen, M. E.; Swartz, D. A.; Tennant, A. F.; Weisskopf, M. C.; Zirnstein, G.; McDermott, W. C.

    1997-01-01

    X-ray calibration of the Advanced X-ray Astrophysics Facility (AXAF) observatory at the MSFC X-Ray Calibration Facility (XRCF) made novel use of the x-ray continuum from a conventional electron-impact source. Taking advantage of the good spectral resolution of solid-state detectors, continuum measurements proved advantageous in calibrating the effective area of AXAF's High-Resolution Mirror Assembly (HRMA) and in verifying its alignment to the XRCF's optical axis.

  3. Progress in Using Continuum radiation for AXAF Calibration

    NASA Technical Reports Server (NTRS)

    Kolodziejczak, J. J.; Austin, R. A.; Elsner, R. F.; O'Dell, S. L.; Sulkanen, M. E.; Swartz, D. A.; Tennant, A. F.; Weisskopf, M. C.; Zirnstein, G.; McDermott, W. C.; Zhao, P.

    1998-01-01

    X-ray calibration of the AXAF observatory at MSFC's X-Ray Calibration Facility (XRCF) made novel use of the x-ray continuum from a conventional electron-impact source. Taking advantage of the good spectral resolution of solid-state detectors, continuum measurements proved advantageous in calibrating the effective area of AXAF's High-Resolution Mirror Assembly (HRMA) and in verifying its alignment to the XRCF's optical axis. Further verification of AXAF response models will be presented.

  4. The Intraprofessional Continuum and Cleft.

    PubMed

    Jensen, Clyde B

    2016-08-01

    The continuum cleft is a costly and precarious gap that divides professions on the health professions' continuum. It is an interprofessional phenomenon that is encouraged because health care professions protect their members in professional silos and isolate competing professions in professional cysts. This article uses case studies of the allopathic, osteopathic, naturopathic, and chiropractic professions to contemplate the existence, consequences, and possible mitigation of intraprofessional silos, cysts, and clefts. PMID:27574493

  5. Multiscale modeling of cellular epigenetic states: stochasticity in molecular networks, chromatin folding in cell nuclei, and tissue pattern formation of cells

    PubMed Central

    Liang, Jie; Cao, Youfang; Gürsoy, Gamze; Naveed, Hammad; Terebus, Anna; Zhao, Jieling

    2016-01-01

    Genome sequences provide the overall genetic blueprint of cells, but cells possessing the same genome can exhibit diverse phenotypes. There is a multitude of mechanisms controlling cellular epigenetic states and that dictate the behavior of cells. Among these, networks of interacting molecules, often under stochastic control, depending on the specific wirings of molecular components and the physiological conditions, can have a different landscape of cellular states. In addition, chromosome folding in three-dimensional space provides another important control mechanism for selective activation and repression of gene expression. Fully differentiated cells with different properties grow, divide, and interact through mechanical forces and communicate through signal transduction, resulting in the formation of complex tissue patterns. Developing quantitative models to study these multi-scale phenomena and to identify opportunities for improving human health requires development of theoretical models, algorithms, and computational tools. Here we review recent progress made in these important directions. PMID:27480462

  6. Radiation from charges in the continuum limit

    SciTech Connect

    Ianconescu, Reuven

    2013-06-15

    It is known that an accelerating charge radiates according to Larmor formula. On the other hand, any DC current following a curvilinear path, consists of accelerating charges, but in such case the radiated power is 0. The scope of this paper is to analyze and quantify how a system of charges goes from a radiating state to a non radiating state when the charges distribution goes to the continuum limit. Understanding this is important from the theoretical point of view and the results of this work are applicable to particle accelerator, cyclotron and other high energy devices.

  7. Atomistic to continuum modeling of solidification microstructures

    SciTech Connect

    Karma, Alain; Tourret, Damien

    2015-09-26

    We summarize recent advances in modeling of solidification microstructures using computational methods that bridge atomistic to continuum scales. We first discuss progress in atomistic modeling of equilibrium and non-equilibrium solid–liquid interface properties influencing microstructure formation, as well as interface coalescence phenomena influencing the late stages of solidification. The latter is relevant in the context of hot tearing reviewed in the article by M. Rappaz in this issue. We then discuss progress to model microstructures on a continuum scale using phase-field methods. We focus on selected examples in which modeling of 3D cellular and dendritic microstructures has been directly linked to experimental observations. Finally, we discuss a recently introduced coarse-grained dendritic needle network approach to simulate the formation of well-developed dendritic microstructures. The approach reliably bridges the well-separated scales traditionally simulated by phase-field and grain structure models, hence opening new avenues for quantitative modeling of complex intra- and inter-grain dynamical interactions on a grain scale.

  8. Atomistic to continuum modeling of solidification microstructures

    DOE PAGESBeta

    Karma, Alain; Tourret, Damien

    2015-09-26

    We summarize recent advances in modeling of solidification microstructures using computational methods that bridge atomistic to continuum scales. We first discuss progress in atomistic modeling of equilibrium and non-equilibrium solid–liquid interface properties influencing microstructure formation, as well as interface coalescence phenomena influencing the late stages of solidification. The latter is relevant in the context of hot tearing reviewed in the article by M. Rappaz in this issue. We then discuss progress to model microstructures on a continuum scale using phase-field methods. We focus on selected examples in which modeling of 3D cellular and dendritic microstructures has been directly linked tomore » experimental observations. Finally, we discuss a recently introduced coarse-grained dendritic needle network approach to simulate the formation of well-developed dendritic microstructures. The approach reliably bridges the well-separated scales traditionally simulated by phase-field and grain structure models, hence opening new avenues for quantitative modeling of complex intra- and inter-grain dynamical interactions on a grain scale.« less

  9. Quantitative X-ray - UV Line and Continuum Spectroscopy with Application to AGN: State-Specific Hydrogenic Recombination Cooling Coefficients for a Wide Range of Conditions

    NASA Technical Reports Server (NTRS)

    LaMothe, J.; Ferland, Gary J.

    2002-01-01

    Recombination cooling, in which a free electron emits light while being captured to an ion, is an important cooling process in photoionized clouds that are optically thick or have low metallicity. State specific rather than total recombination cooling rates are needed since the hydrogen atom tends to become optically thick in high-density regimes such as Active Galactic Nuclei. This paper builds upon previous work to derive the cooling rate over the full temperature range where the process can be a significant contributor in a photoionized plasma. We exploit the fact that the recombination and cooling rates are given by intrinsically similar formulae to express the cooling rate in terms of the closely related radiative recombination rate. We give an especially simple but accurate approximation that works for any high hydrogenic level and can be conveniently employed in large-scale numerical simulations.

  10. Continuum ionization transition probabilities of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Samson, J. R.; Petrosky, V. E.

    1973-01-01

    The technique of photoelectron spectroscopy was used to obtain the relative continuum transition probabilities of atomic oxygen at 584 A for transitions from 3P ground state into the 4S, D2, and P2 states of the ion. Transition probability ratios for the D2 and P2 states relative to the S4 state of the ion are 1.57 + or - 0.14 and 0.82 + or - 0.07, respectively. In addition, transitions from excited O2(a 1 Delta g) state into the O2(+)(2 Phi u and 2 Delta g) were observed. The adiabatic ionization potential of O2(+)(2 Delta g) was measured as 18.803 + or - 0.006 eV.

  11. Continuum modeling of deformation and aggregation of red blood cells.

    PubMed

    Yoon, Daegeun; You, Donghyun

    2016-07-26

    In order to gain better understanding for rheology of an isolated red blood cell (RBC) and a group of multiple RBCs, new continuum models for describing mechanical properties of cellular structures of an RBC and inter-cellular interactions among multiple RBCs are developed. The viscous property of an RBC membrane, which characterizes dynamic behaviors of an RBC under stress loading and unloading processes, is determined using a generalized Maxwell model. The present model is capable of predicting stress relaxation and stress-strain hysteresis, of which prediction is not possible using the commonly used Kelvin-Voigt model. Nonlinear elasticity of an RBC is determined using the Yeoh hyperelastic material model in a framework of continuum mechanics using finite-element approximation. A novel method to model inter-cellular interactions among multiple adjacent RBCs is also developed. Unlike the previous modeling approaches for aggregation of RBCs, where interaction energy for aggregation is curve-fitted using a Morse-type potential function, the interaction energy is analytically determined. The present aggregation model, therefore, allows us to predict various effects of physical parameters such as the osmotic pressure, the thickness of a glycocalyx layer, the penetration depth, and the permittivity, on the depletion and electrostatic energy among RBCs. Simulations for elongation and recovery deformation of an RBC and for aggregation of multiple RBCs are conducted to evaluate the efficacy of the present continuum modeling methods. PMID:26706720

  12. Thermodynamically consistent continuum dislocation dynamics

    NASA Astrophysics Data System (ADS)

    Hochrainer, Thomas

    2016-03-01

    Dislocation based modeling of plasticity is one of the central challenges at the crossover of materials science and continuum mechanics. Developing a continuum theory of dislocations requires the solution of two long standing problems: (i) to represent dislocation kinematics in terms of a reasonable number of variables and (ii) to derive averaged descriptions of the dislocation dynamics (i.e. material laws) in terms of these variables. The kinematic problem (i) was recently solved through the introduction of continuum dislocation dynamics (CDD), which provides kinematically consistent evolution equations of dislocation alignment tensors, presuming a given average dislocation velocity (Hochrainer, T., 2015, Multipole expansion of continuum dislocations dynamics in terms of alignment tensors. Philos. Mag. 95 (12), 1321-1367). In the current paper we demonstrate how a free energy formulation may be used to solve the dynamic closure problem (ii) in CDD. We do so exemplarily for the lowest order CDD variant for curved dislocations in a single slip situation. In this case, a thermodynamically consistent average dislocation velocity is found to comprise five mesoscopic shear stress contributions. For a postulated free energy expression we identify among these stress contributions a back-stress term and a line-tension term, both of which have already been postulated for CDD. A new stress contribution occurs which is missing in earlier CDD models including the statistical continuum theory of straight parallel edge dislocations (Groma, I., Csikor, F.F., Zaiser, M., 2003. Spatial correlations and higher-order gradient terms in a continuum description of dislocation dynamics. Acta Mater. 51, 1271-1281). Furthermore, two entirely new stress contributions arise from the curvature of dislocations.

  13. Submillimeter Continuum Observations of Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

    The aim of this proposal was to study the submillimeter continuum emission from comets. The study was based mainly on the exploitation of the world's leading submillimeter telescope, the JCMT (James Clerk Maxwell Telescope) on Mauna Kea. Submillimeter wavelengths provide a unique view of cometary physics for one main reason. The cometary size distribution is such that the scattering cross-section is dominated by small dust grains, while the mass is dominated by the largest particles. Submillimeter continuum radiation samples cometary particles much larger than those sampled by more common observations at shorter (optical and infrared) wavelengths and therefore provides a nearly direct measure of the cometary dust mass.

  14. Lagrangian continuum dynamics in ALEGRA.

    SciTech Connect

    Wong, Michael K. W.; Love, Edward

    2007-12-01

    Alegra is an ALE (Arbitrary Lagrangian-Eulerian) multi-material finite element code that emphasizes large deformations and strong shock physics. The Lagrangian continuum dynamics package in Alegra uses a Galerkin finite element spatial discretization and an explicit central-difference stepping method in time. The goal of this report is to describe in detail the characteristics of this algorithm, including the conservation and stability properties. The details provided should help both researchers and analysts understand the underlying theory and numerical implementation of the Alegra continuum hydrodynamics algorithm.

  15. Quasiparticle-continuum level repulsion in a quantum magnet

    SciTech Connect

    Plumb, K. W.; Hwang, Kyusung; Qiu, Y.; Harriger, Leland W.; Granroth, G.  E.; Kolesnikov, Alexander I.; Shu, G. J.; Chou, F. C.; Rüegg, Ch.; Kim, Yong Baek; Kim, Young-June

    2015-11-30

    When the energy eigenvalues of two coupled quantum states approach each other in a certain parameter space, their energy levels repel each other and level crossing is avoided. Such level repulsion, or avoided level crossing, is commonly used to describe the dispersion relation of quasiparticles in solids. But, little is known about the level repulsion when more than two quasiparticles are present; for example, in a strongly interacting quantum system where a quasiparticle can spontaneously decay into a many-particle continuum. Here we show that even in this case level repulsion exists between a long-lived quasiparticle state and a continuum. Here, we observe a renormalization of the quasiparticle dispersion relation due to the presence of the continuum of multi-quasiparticle states, in our fine-resolution neutron spectroscopy study of magnetic quasiparticles in the frustrated quantum magnet BiCu2PO6.

  16. Quasiparticle-continuum level repulsion in a quantum magnet

    DOE PAGESBeta

    Plumb, K. W.; Hwang, Kyusung; Qiu, Y.; Harriger, Leland W.; Granroth, G.  E.; Kolesnikov, Alexander I.; Shu, G. J.; Chou, F. C.; Rüegg, Ch.; Kim, Yong Baek; et al

    2015-11-30

    When the energy eigenvalues of two coupled quantum states approach each other in a certain parameter space, their energy levels repel each other and level crossing is avoided. Such level repulsion, or avoided level crossing, is commonly used to describe the dispersion relation of quasiparticles in solids. But, little is known about the level repulsion when more than two quasiparticles are present; for example, in a strongly interacting quantum system where a quasiparticle can spontaneously decay into a many-particle continuum. Here we show that even in this case level repulsion exists between a long-lived quasiparticle state and a continuum. Here,more » we observe a renormalization of the quasiparticle dispersion relation due to the presence of the continuum of multi-quasiparticle states, in our fine-resolution neutron spectroscopy study of magnetic quasiparticles in the frustrated quantum magnet BiCu2PO6.« less

  17. Quasiparticle-continuum level repulsion in a quantum magnet

    NASA Astrophysics Data System (ADS)

    Plumb, K. W.; Hwang, Kyusung; Qiu, Y.; Harriger, Leland W.; Granroth, G. E.; Kolesnikov, Alexander I.; Shu, G. J.; Chou, F. C.; Rüegg, Ch.; Kim, Yong Baek; Kim, Young-June

    2016-03-01

    When the energy eigenvalues of two coupled quantum states approach each other in a certain parameter space, their energy levels repel each other and level crossing is avoided. Such level repulsion, or avoided level crossing, is commonly used to describe the dispersion relation of quasiparticles in solids. However, little is known about the level repulsion when more than two quasiparticles are present; for example, in a strongly interacting quantum system where a quasiparticle can spontaneously decay into a many-particle continuum. Here we show that even in this case level repulsion exists between a long-lived quasiparticle state and a continuum. In our fine-resolution neutron spectroscopy study of magnetic quasiparticles in the frustrated quantum magnet BiCu2PO6, we observe a renormalization of the quasiparticle dispersion relation due to the presence of the continuum of multi-quasiparticle states.

  18. Map of fluid flow in fractal porous medium into fractal continuum flow.

    PubMed

    Balankin, Alexander S; Elizarraraz, Benjamin Espinoza

    2012-05-01

    This paper is devoted to fractal continuum hydrodynamics and its application to model fluid flows in fractally permeable reservoirs. Hydrodynamics of fractal continuum flow is developed on the basis of a self-consistent model of fractal continuum employing vector local fractional differential operators allied with the Hausdorff derivative. The generalized forms of Green-Gauss and Kelvin-Stokes theorems for fractional calculus are proved. The Hausdorff material derivative is defined and the form of Reynolds transport theorem for fractal continuum flow is obtained. The fundamental conservation laws for a fractal continuum flow are established. The Stokes law and the analog of Darcy's law for fractal continuum flow are suggested. The pressure-transient equation accounting the fractal metric of fractal continuum flow is derived. The generalization of the pressure-transient equation accounting the fractal topology of fractal continuum flow is proposed. The mapping of fluid flow in a fractally permeable medium into a fractal continuum flow is discussed. It is stated that the spectral dimension of the fractal continuum flow d(s) is equal to its mass fractal dimension D, even when the spectral dimension of the fractally porous or fissured medium is less than D. A comparison of the fractal continuum flow approach with other models of fluid flow in fractally permeable media and the experimental field data for reservoir tests are provided. PMID:23004869

  19. Map of fluid flow in fractal porous medium into fractal continuum flow

    NASA Astrophysics Data System (ADS)

    Balankin, Alexander S.; Elizarraraz, Benjamin Espinoza

    2012-05-01

    This paper is devoted to fractal continuum hydrodynamics and its application to model fluid flows in fractally permeable reservoirs. Hydrodynamics of fractal continuum flow is developed on the basis of a self-consistent model of fractal continuum employing vector local fractional differential operators allied with the Hausdorff derivative. The generalized forms of Green-Gauss and Kelvin-Stokes theorems for fractional calculus are proved. The Hausdorff material derivative is defined and the form of Reynolds transport theorem for fractal continuum flow is obtained. The fundamental conservation laws for a fractal continuum flow are established. The Stokes law and the analog of Darcy's law for fractal continuum flow are suggested. The pressure-transient equation accounting the fractal metric of fractal continuum flow is derived. The generalization of the pressure-transient equation accounting the fractal topology of fractal continuum flow is proposed. The mapping of fluid flow in a fractally permeable medium into a fractal continuum flow is discussed. It is stated that the spectral dimension of the fractal continuum flow ds is equal to its mass fractal dimension D, even when the spectral dimension of the fractally porous or fissured medium is less than D. A comparison of the fractal continuum flow approach with other models of fluid flow in fractally permeable media and the experimental field data for reservoir tests are provided.

  20. The Influence of Metal Stress on the Availability and Redox State of Ascorbate, and Possible Interference with Its Cellular Functions

    PubMed Central

    Bielen, An; Remans, Tony; Vangronsveld, Jaco; Cuypers, Ann

    2013-01-01

    Worldwide, metals have been distributed to excessive levels in the environment due to industrial and agricultural activities. Plants growing on soils contaminated with excess levels of metals experience a disturbance of the cellular redox balance, which leads to an augmentation of reactive oxygen species (ROS). Even though the increased ROS levels can cause cellular damage, controlled levels play an important role in modulating signaling networks that control physiological processes and stress responses. Plants control ROS levels using their antioxidative defense system both under non-stress conditions, as well as under stress conditions such as exposure to excess metals. Ascorbate (AsA) is a well-known and important component of the plant’s antioxidative system. As primary antioxidant, it can reduce ROS directly and indirectly via ascorbate peroxidase in the ascorbate–glutathione cycle. Furthermore, AsA fulfills an essential role in physiological processes, some of which are disturbed by excess metals. In this review, known direct effects of excess metals on AsA biosynthesis and functioning will be discussed, as well as the possible interference of metals with the role of AsA in physiological and biochemical processes. PMID:23519107

  1. A Math Continuum, Part D.

    ERIC Educational Resources Information Center

    Zander, Del; And Others

    Evaluation sheets and developmental checklists, prepared by three special education departments, are provided to facilitate continuous measurement of student progress in elementary school mathematics. One hundred forty-three objectives are given, and each is followed by a continuum-oriented set of worksheet-type pages on mathematics skills. The…

  2. Learner Continuums and Speech Communities.

    ERIC Educational Resources Information Center

    Amastae, Jon

    1981-01-01

    A method for analyzing acquisition-like patterns in the English consonants used by Spanish-English bilinguals is presented which allows a distinction to be made between individual and group phenomena. An analysis of a bilingual community in southern Texas shows that there is a continuum of use of the standard English consonants not occurring in…

  3. Steady-state and time-resolved two-photon fluorescence microscopy: a versatile tool for probing cellular environment and function

    NASA Astrophysics Data System (ADS)

    Denicke, Stefan; Ehlers, Jan-Eric; Niesner, Raluca; Quentmeier, Stefan; Gericke, Karl-Heinz

    2007-09-01

    In the last decade, the two-photon fluorescence laser-scanning microscopy (TPLSM) has become an indispensable tool for the bioscientific and biomedical research. TPLSM techniques as well as their applications are currently experiencing a dramatic evolution and represent the focus of many biophysical research projects. In this work, we compare in detail two steady-state TPLSM techniques, i.e. single-beam scanning microscopy combined with point-detection (SB-PMT) and multi-beam scanning microscopy combined with synchronous detection (MB-CCD), as far as their technical characteristics relevant for the bioscientific research are concerned, i.e. optical performance and imaging speed. We demonstrate that the SB-PMT technique is more adequate for deep-tissue imaging (few 100 μm depth) than the MB-CCD technique, whereas only the MB-CCD technique enables high-speed imaging for characterizing the dynamics of fast biological phenomena. Novel applications of these techniques are additionally discussed. Moreover, we employ a time-resolved TPLSM technique, i.e. biexponential fluorescence lifetime imaging based on the cellular fluorescence of the nicotinamide pyridine dinucleotides NADH and NADPH, which allows us to probe for the first time the redox cellular metabolism of MIN6 cells (mutated insulin producing pancreatic β-cells) as well as to show the potential of this method for the specific and dynamic investigation of NADH- and NADPH-dependent cellular processes.

  4. The climate continuum revisited

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Wang, J.; Partin, J. W.

    2015-12-01

    A grand challenge of climate science is to quantify the extent of natural variability on adaptation-relevant timescales (10-100y). Since the instrumental record is too short to adequately estimate the spectra of climate measures, this information must be derived from paleoclimate proxies, which may harbor a many-to-one, non-linear (e.g. thresholded) and non-stationary relationship to climate. In this talk, I will touch upon the estimation of climate scaling behavior from climate proxies. Two case studies will be presented: an investigation of scaling behavior in a reconstruction of global surface temperature using state-of- the-art data [PAGES2K Consortium, in prep] and methods [Guillot et al., 2015]. Estimating the scaling exponent β in spectra derived from this reconstruction, we find that 0 < β < 1 in most regions, suggesting long-term memory. Overall, the reconstruction-based spectra are steeper than the ones based on an instrumental dataset [HadCRUT4.2, Morice et al., 2012], and those estimated from PMIP3/CMIP5 models, suggesting the climate system is more energetic at multidecadal to centennial timescales than can be inferred from the short instrumental record or from the models developed to reproduce it [Laepple and Huybers, 2014]. an investigation of scaling behavior in speleothems records of tropical hydroclimate. We will make use of recent advances in proxy system modeling [Dee et al., 2015] and investigate how various aspects of the speleothem system (karst dynamics, age uncertainties) may conspire to bias the estimate of scaling behavior from speleothem timeseries. The results suggest that ignoring such complications leads to erroneous inferences about hydroclimate scaling. References Dee, S. G., J. Emile-Geay, M. N. Evans, Allam, A., D. M. Thompson, and E. J. Steig (2015), J. Adv. Mod. Earth Sys., 07, doi:10.1002/2015MS000447. Guillot, D., B. Rajaratnam, and J. Emile-Geay (2015), Ann. Applied. Statist., pp. 324-352, doi:10.1214/14-AOAS794. Laepple, T

  5. The importance of antioxidants which play the role in cellular response against oxidative/nitrosative stress: current state.

    PubMed

    Kurutas, Ergul Belge

    2016-01-01

    Remarkable interest has risen in the idea that oxidative/nitrosative stress is mediated in the etiology of numerous human diseases. Oxidative/Nitrosative stress is the result of an disequilibrium in oxidant/antioxidant which reveals from continuous increase of Reactive Oxygen and Reactive Nitrogen Species production. The aim of this review is to emphasize with current information the importance of antioxidants which play the role in cellular responce against oxidative/nitrosative stress, which would be helpful in enhancing the knowledge of any biochemist, pathophysiologist, or medical personnel regarding this important issue. Products of lipid peroxidation have commonly been used as biomarkers of oxidative/nitrosative stress damage. Lipid peroxidation generates a variety of relatively stable decomposition end products, mainly α, β-unsaturated reactive aldehydes, such as malondialdehyde, 4-hydroxy-2-nonenal, 2-propenal (acrolein) and isoprostanes, which can be measured in plasma and urine as an indirect index of oxidative/nitrosative stress. Antioxidants are exogenous or endogenous molecules that mitigate any form of oxidative/nitrosative stress or its consequences. They may act from directly scavenging free radicals to increasing antioxidative defences. Antioxidant deficiencies can develop as a result of decreased antioxidant intake, synthesis of endogenous enzymes or increased antioxidant utilization. Antioxidant supplementation has become an increasingly popular practice to maintain optimal body function. However, antoxidants exhibit pro-oxidant activity depending on the specific set of conditions. Of particular importance are their dosage and redox conditions in the cell. PMID:27456681

  6. Continuum descriptions of cytoskeletal dynamics

    PubMed Central

    2013-01-01

    This tutorial presents an introduction into continuum descriptions of cytoskeletal dynamics. In contrast to discrete models in which each molecule keeps its identity, such descriptions are given in terms of averaged quantities per unit volume like the number density of a certain molecule. Starting with a discrete description for the assembly dynamics of cytoskeletal filaments, we derive the continuity equation, which serves as the basis of many continuum theories. We illustrate the use of this approach with an investigation of spontaneous cytoskeletal polymerization waves. Such waves have by now been observed in various cell types and might help to orchestrate cytoskeletal dynamics during cell spreading and locomotion. Our analysis shows how processes at the scale of single molecules, namely, the nucleation of new filaments and filament treadmilling, can lead to the spontaneous appearance of coherent traveling waves on scales spanning many filament lengths. For readers less familiar with calculus, we include an informal introduction to the Taylor expansion. PMID:24565412

  7. Differential Complexes in Continuum Mechanics

    NASA Astrophysics Data System (ADS)

    Angoshtari, Arzhang; Yavari, Arash

    2015-04-01

    We study some differential complexes in continuum mechanics that involve both symmetric and non-symmetric second-order tensors. In particular, we show that the tensorial analogue of the standard grad-curl-div complex can simultaneously describe the kinematics and the kinetics of motion of a continuum. The relation between this complex and the de Rham complex allows one to readily derive the necessary and sufficient conditions for the compatibility of displacement gradient and the existence of stress functions on non-contractible bodies.We also derive the local compatibility equations in terms of the Green deformation tensor for motions of 2D and 3D bodies, and shells in curved ambient spaces with constant curvatures.

  8. Continuum radiation in planetary magnetospheres

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    1991-01-01

    With the completion of the Voyager tour of the outer planets, radio and plasma wave instruments have executed the first survey of the wave spectra of Earth, Jupiter, Saturn, Uranus, and Neptune. One of the most notable conclusions of this survey is that there is a great deal of qualitative similarity in both the plasma wave and radio wave spectra from one magnetosphere to the next. In particular, in spite of detailed differences, most of the radio emissions at each of the planets have been tentatively classified into two primary categories. First, the most intense emissions are generally associated with the cyclotron maser instability. Second, a class of weaker emissions can be found at each of the magnetospheres which appears to be the result of conversion from intense electrostatic emissions at the upper hybrid resonance frequency into (primarily) ordinary mode radio emission. It is this second category, often referred to as nonthermal continuum radiation, which we will discuss in this review. We review the characteristics of the continuum spectrum at each of the planets, discuss the source region and direct observations of the generation of the emissions where available, and briefly describe the theories for the generation of the emissions. Over the past few years evidence has increased that the linear mode conversion of electrostatic waves into the ordinary mode can account for at least some of the continuum radiation observed. There is no definitive evidence which precludes the possibility that a nonlinear mechanism may also be important.

  9. 77 FR 45367 - Continuum of Care Homeless Assistance Grant Application; Continuum of Care Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-31

    ... URBAN DEVELOPMENT Continuum of Care Homeless Assistance Grant Application; Continuum of Care Application... subject proposal. Pre-established communities, called Continuums of Care (CoC), will complete the Exhibit 1 of the Continuum of Care Homeless Assistance application which collects data about the...

  10. Reconstructing and analysing cellular states, space and time from gene expression profiles of many cells and single cells.

    PubMed

    Francesconi, Mirko; Lehner, Ben

    2015-10-01

    Genome-wide gene expression profiling is a fast, cheap and standardised analysis that provides a high dimensional measurement of the state of a biological sample. In this review we describe computational methods that can be applied to identify and interpret sources of variance in gene expression in whole organisms, organs, tissues or single cells. This allows the identification of constituent cell types and states in complex mixtures, the reconstruction of temporal trajectories of development, differentiation and progression, and the reconstruction of spatial patterning. When applied to genetically variable samples, these methods allow the efficient investigation of how genetic variation influences gene expression and biological processes in space and time. PMID:26273952

  11. Divergent cellular responses during asymptomatic subclinical and clinical states of disease in cows naturally infected with Mycobacterium avium subsp. paratuberculosis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Infection of the host with Mycobacterium avium subsp. paratuberculosis (MAP) results in a chronic and progressive enteritis that traverses both subclinical and clinical stages. The mechanism(s) for the shift from asymptomatic subclinical disease state to advanced clinical disease are not fully under...

  12. The Continuum and Current Controversies in the USA.

    ERIC Educational Resources Information Center

    Taylor, Steven J.

    2001-01-01

    This article reviews policy developments in deinstitutionalization and community inclusion in North America, specifically the United States. It begins with a critique of the continuum concept and the associated principle of the least restrictive environment. Past and current controversies surrounding deinstitutionalization are then examined.…

  13. The New Cellular Immunology

    ERIC Educational Resources Information Center

    Claman, Henry N.

    1973-01-01

    Discusses the nature of the immune response and traces many of the discoveries that have led to the present state of knowledge in immunology. The new cellular immunology is directing its efforts toward improving health by proper manipulation of the immune mechanisms of the body. (JR)

  14. A continuum model of protrusion of pseudopod in leukocytes.

    PubMed Central

    Zhu, C; Skalak, R

    1988-01-01

    The morphology of human leukocytes, the biochemistry of actin polymerization, and the theory of continuum mechanics are used to model the pseudopod protrusion process of leukocytes. In the proposed model, the pseudopod is considered as a porous solid of F-actin network, the pores of which are full of aqueous solution. G-actin is considered as a "solute" transported by convection and diffusion in the fluid phase. The pseudopod grows as actin filaments elongate at their barbed ends at the tip of the pseudopod. The driving force of extension is hypothesized as being provided by the actin polymerization. It is assumed that elongation of actin filaments, powered by chemical energy liberated from the polymerization reaction, does mechanical work against opposing pressure on the membrane. This also gives rise to a pressure drop in the fluid phase at the tip of the pseudopod, which is formulated by an equation relating the work done by actin polymerization to the local state of pressure. The pressure gradient along the pseudopod drives the fluid filtration through the porous pseudopod according to Darcy's Law, which in turn brings more actin monomers to the growing tip. The main cell body serves as a reservoir of G-actin. A modified first-order equation is used to describe the kinetics of polymerization. The rate of pseudopod growth is modulated by regulatory proteins. A one-dimensional moving boundary problem based on the proposed mechanism has been constructed and approximate solutions have been obtained. Comparison of the solutions with experimental data shows that the model is compatible with available observations. The model is also applicable to growth of other cellular systems such as elongation of acrosomal process in sperm cells. Images FIGURE 1 FIGURE 4 PMID:3233268

  15. Modeling continuum of epithelial mesenchymal transition plasticity.

    PubMed

    Mandal, Mousumi; Ghosh, Biswajoy; Anura, Anji; Mitra, Pabitra; Pathak, Tanmaya; Chatterjee, Jyotirmoy

    2016-02-01

    Living systems respond to ambient pathophysiological changes by altering their phenotype, a phenomenon called 'phenotypic plasticity'. This program contains information about adaptive biological dynamism. Epithelial-mesenchymal transition (EMT) is one such process found to be crucial in development, wound healing, and cancer wherein the epithelial cells with restricted migratory potential develop motile functions by acquiring mesenchymal characteristics. In the present study, phase contrast microscopy images of EMT induced HaCaT cells were acquired at 24 h intervals for 96 h. The expression study of relevant pivotal molecules viz. F-actin, vimentin, fibronectin and N-cadherin was carried out to confirm the EMT process. Cells were intuitively categorized into five distinct morphological phenotypes. A population of 500 cells for each temporal point was selected to quantify their frequency of occurrence. The plastic interplay of cell phenotypes from the observations was described as a Markovian process. A model was formulated empirically using simple linear algebra, to depict the possible mechanisms of cellular transformation among the five phenotypes. This work employed qualitative, semi-quantitative and quantitative tools towards illustration and establishment of the EMT continuum. Thus, it provides a newer perspective to understand the embedded plasticity across the EMT spectrum. PMID:26762753

  16. Continuum Theory of Retroviral Capsids

    NASA Astrophysics Data System (ADS)

    Nguyen, T. T.; Bruinsma, R. F.; Gelbart, W. M.

    2006-02-01

    We present a self-assembly phase diagram for the shape of retroviral capsids, based on continuum elasticity theory. The spontaneous curvature of the capsid proteins drives a weakly first-order transition from spherical to spherocylindrical shapes. The conical capsid shape which characterizes the HIV-1 retrovirus is never stable under unconstrained energy minimization. Only under conditions of fixed volume and/or fixed spanning length can the conical shape be a minimum energy structure. Our results indicate that, unlike the capsids of small viruses, retrovirus capsids are not uniquely determined by the molecular structure of the constituent proteins but depend in an essential way on physical constraints present during assembly.

  17. The Continuum of Pharmacist Prescriptive Authority.

    PubMed

    Adams, Alex J; Weaver, Krystalyn K

    2016-09-01

    Recently momentum has been building behind pharmacist prescriptive authority for certain products such as oral contraceptives or naloxone. To some, prescriptive authority by pharmacists represents a departure from the traditional role of pharmacists in dispensing medications. Nearly all states, however, currently enable pharmacist prescriptive authority in some form or fashion. The variety of different state approaches makes it difficult for pharmacists to ascertain the pros and cons of different models. We leverage data available from the National Alliance of State Pharmacy Associations (NASPA), a trade association that tracks pharmacy legislation and regulations across all states, to characterize models of pharmacist prescriptive authority along a continuum from most restrictive to least restrictive. We identify 2 primary categories of current pharmacist prescriptive authority: (1) collaborative prescribing and (2) autonomous prescribing. Collaborative prescribing models provide a broad framework for the treatment of acute or chronic disease. Current autonomous prescribing models have focused on a limited range of medications for which a specific diagnosis is not needed. Approaches to pharmacist prescriptive authority are not mutually exclusive. We anticipate that more states will pursue the less-restrictive approaches in the years ahead. PMID:27307413

  18. Human Mobility in a Continuum Approach

    PubMed Central

    Simini, Filippo; Maritan, Amos; Néda, Zoltán

    2013-01-01

    Human mobility is investigated using a continuum approach that allows to calculate the probability to observe a trip to any arbitrary region, and the fluxes between any two regions. The considered description offers a general and unified framework, in which previously proposed mobility models like the gravity model, the intervening opportunities model, and the recently introduced radiation model are naturally resulting as special cases. A new form of radiation model is derived and its validity is investigated using observational data offered by commuting trips obtained from the United States census data set, and the mobility fluxes extracted from mobile phone data collected in a western European country. The new modeling paradigm offered by this description suggests that the complex topological features observed in large mobility and transportation networks may be the result of a simple stochastic process taking place on an inhomogeneous landscape. PMID:23555885

  19. The Nuclear Three-Body Continuum

    NASA Astrophysics Data System (ADS)

    Brune, Carl R.

    2001-04-01

    Experiments in the three-nucleon (3N) continuum provide important insights into the underlying nuclear forces, as theoretical calculations of 3N systems using realistic nucleon-nucleon (NN) and 3N interactions are now routinely possible. This talk will focus on experimental results at low energies, below ≈ 50 MeV. Measurements of p-d and n-d elastic scattering are generally in agreement with theoretical predictions, with the exception of large discrepancies found for the polarization observables Ay and iT_11. Studies of breakup reactions, such as n+darrow n+n+p, offer greater flexibility in the final state kinematics, providing additional sensitivity to quantities such as NN scattering lengths and perhaps to 3N forces. Some possibilities for future experiments will also be discussed.

  20. Irregular Cellular Learning Automata.

    PubMed

    Esnaashari, Mehdi; Meybodi, Mohammad Reza

    2015-08-01

    Cellular learning automaton (CLA) is a recently introduced model that combines cellular automaton (CA) and learning automaton (LA). The basic idea of CLA is to use LA to adjust the state transition probability of stochastic CA. This model has been used to solve problems in areas such as channel assignment in cellular networks, call admission control, image processing, and very large scale integration placement. In this paper, an extension of CLA called irregular CLA (ICLA) is introduced. This extension is obtained by removing the structure regularity assumption in CLA. Irregularity in the structure of ICLA is needed in some applications, such as computer networks, web mining, and grid computing. The concept of expediency has been introduced for ICLA and then, conditions under which an ICLA becomes expedient are analytically found. PMID:25291810

  1. Cellular Contraction and Polarization Drive Collective Cellular Motion.

    PubMed

    Notbohm, Jacob; Banerjee, Shiladitya; Utuje, Kazage J C; Gweon, Bomi; Jang, Hwanseok; Park, Yongdoo; Shin, Jennifer; Butler, James P; Fredberg, Jeffrey J; Marchetti, M Cristina

    2016-06-21

    Coordinated motions of close-packed multicellular systems typically generate cooperative packs, swirls, and clusters. These cooperative motions are driven by active cellular forces, but the physical nature of these forces and how they generate collective cellular motion remain poorly understood. Here, we study forces and motions in a confined epithelial monolayer and make two experimental observations: 1) the direction of local cellular motion deviates systematically from the direction of the local traction exerted by each cell upon its substrate; and 2) oscillating waves of cellular motion arise spontaneously. Based on these observations, we propose a theory that connects forces and motions using two internal state variables, one of which generates an effective cellular polarization, and the other, through contractile forces, an effective cellular inertia. In agreement with theoretical predictions, drugs that inhibit contractility reduce both the cellular effective elastic modulus and the frequency of oscillations. Together, theory and experiment provide evidence suggesting that collective cellular motion is driven by at least two internal variables that serve to sustain waves and to polarize local cellular traction in a direction that deviates systematically from local cellular velocity. PMID:27332131

  2. Epimedium koreanum Nakai displays broad spectrum of antiviral activity in vitro and in vivo by inducing cellular antiviral state.

    PubMed

    Cho, Won-Kyung; Weeratunga, Prasanna; Lee, Byeong-Hoon; Park, Jun-Seol; Kim, Chul-Joong; Ma, Jin Yeul; Lee, Jong-Soo

    2015-01-01

    Epimedium koreanum Nakai has been extensively used in traditional Korean and Chinese medicine to treat a variety of diseases. Despite the plant's known immune modulatory potential and chemical make-up, scientific information on its antiviral properties and mode of action have not been completely investigated. In this study, the broad antiviral spectrum and mode of action of an aqueous extract from Epimedium koreanum Nakai was evaluated in vitro, and moreover, the protective effect against divergent influenza A subtypes was determined in BALB/c mice. An effective dose of Epimedium koreanum Nakai markedly reduced the replication of Influenza A Virus (PR8), Vesicular Stomatitis Virus (VSV), Herpes Simplex Virus (HSV) and Newcastle Disease Virus (NDV) in RAW264.7 and HEK293T cells. Mechanically, we found that an aqueous extract from Epimedium koreanum Nakai induced the secretion of type I IFN and pro-inflammatory cytokines and the subsequent stimulation of the antiviral state in cells. Among various components present in the extract, quercetin was confirmed to have striking antiviral properties. The oral administration of Epimedium koreanum Nakai exhibited preventive effects on BALB/c mice against lethal doses of highly pathogenic influenza A subtypes (H1N1, H5N2, H7N3 and H9N2). Therefore, an extract of Epimedium koreanum Nakai and its components play roles as immunomodulators in the innate immune response, and may be potential candidates for prophylactic or therapeutic treatments against diverse viruses in animal and humans. PMID:25609307

  3. Epimedium koreanum Nakai Displays Broad Spectrum of Antiviral Activity in Vitro and in Vivo by Inducing Cellular Antiviral State

    PubMed Central

    Cho, Won-Kyung; Weeratunga, Prasanna; Lee, Byeong-Hoon; Park, Jun-Seol; Kim, Chul-Joong; Ma, Jin Yeul; Lee, Jong-Soo

    2015-01-01

    Epimedium koreanum Nakai has been extensively used in traditional Korean and Chinese medicine to treat a variety of diseases. Despite the plant’s known immune modulatory potential and chemical make-up, scientific information on its antiviral properties and mode of action have not been completely investigated. In this study, the broad antiviral spectrum and mode of action of an aqueous extract from Epimedium koreanum Nakai was evaluated in vitro, and moreover, the protective effect against divergent influenza A subtypes was determined in BALB/c mice. An effective dose of Epimedium koreanum Nakaimarkedly reduced the replication of Influenza A Virus (PR8), Vesicular Stomatitis Virus (VSV), Herpes Simplex Virus (HSV) and Newcastle Disease Virus (NDV) in RAW264.7 and HEK293T cells. Mechanically, we found that an aqueous extract from Epimedium koreanum Nakai induced the secretion of type I IFN and pro-inflammatory cytokines and the subsequent stimulation of the antiviral state in cells. Among various components present in the extract, quercetin was confirmed to have striking antiviral properties. The oral administration of Epimedium koreanum Nakai exhibited preventive effects on BALB/c mice against lethal doses of highly pathogenic influenza A subtypes (H1N1, H5N2, H7N3 and H9N2). Therefore, an extract of Epimedium koreanum Nakai and its components play roles as immunomodulators in the innate immune response, and may be potential candidates for prophylactic or therapeutic treatments against diverse viruses in animal and humans. PMID:25609307

  4. Quantum features of natural cellular automata

    NASA Astrophysics Data System (ADS)

    Elze, Hans-Thomas

    2016-03-01

    Cellular automata can show well known features of quantum mechanics, such as a linear rule according to which they evolve and which resembles a discretized version of the Schrödinger equation. This includes corresponding conservation laws. The class of “natural” Hamiltonian cellular automata is based exclusively on integer-valued variables and couplings and their dynamics derives from an Action Principle. They can be mapped reversibly to continuum models by applying Sampling Theory. Thus, “deformed” quantum mechanical models with a finite discreteness scale l are obtained, which for l → 0 reproduce familiar continuum results. We have recently demonstrated that such automata can form “multipartite” systems consistently with the tensor product structures of nonrelativistic many-body quantum mechanics, while interacting and maintaining the linear evolution. Consequently, the Superposition Principle fully applies for such primitive discrete deterministic automata and their composites and can produce the essential quantum effects of interference and entanglement.

  5. Teaching cellular engineering.

    PubMed

    Hammer, Daniel A; Waugh, Richard E

    2006-02-01

    Cellular engineering is one of the fastest growing subdisciplines in the field of Biomedical Engineering. It involves the application of engineering analysis to understand and control cellular behavior, with the ultimate objective of developing novel therapeutic or diagnostic approaches for the clinic or harnessing cellular function for commercial applications. Well-educated students in this area need strong foundational knowledge in engineering science, chemistry, and cell and molecular biology. In undergraduate curricula, the challenge is to include essential engineering skills plus appropriate levels of training in chemistry and biology while satisfying accreditation-mandated breadth in engineering training. At the graduate level, educators must accommodate students with diverse backgrounds and provide them with both a state-of-the-art understanding of the life sciences and the most advanced engineering skills. Engineering curricular content should include mechanics and materials, physical chemistry, transport phenomena, and control theory. Training from faculty with appointments and research programs in the life sciences is generally recommended, and additional life science content should also be integrated within the engineering curriculum. A capstone course in cellular engineering that includes opportunities for students to have hands-on experiences with state-of-the-art laboratory techniques is highly recommended. PMID:16450196

  6. Dispersal state of multiwalled carbon nanotubes elicits profibrogenic cellular responses that correlate with fibrogenesis biomarkers and fibrosis in the murine lung.

    PubMed

    Wang, Xiang; Xia, Tian; Ntim, Susana Addo; Ji, Zhaoxia; Lin, Sijie; Meng, Huan; Chung, Choong-Heui; George, Saji; Zhang, Haiyuan; Wang, Meiying; Li, Ning; Yang, Yang; Castranova, Vincent; Mitra, Somenath; Bonner, James C; Nel, André E

    2011-12-27

    We developed a dispersal method for multiwalled carbon nanotubes (MWCNTs) that allows quantitative assessment of dispersion on profibrogenic responses in tissue culture cells and in mouse lung. We demonstrate that the dispersal of as-prepared (AP), purified (PD), and carboxylated (COOH) MWCNTs by bovine serum albumin (BSA) and dipalmitoylphosphatidylcholine (DPPC) influences TGF-β1, PDGF-AA, and IL-1β production in vitro and in vivo. These biomarkers were chosen based on their synergy in promoting fibrogenesis and cellular communication in the epithelial-mesenchymal cell trophic unit in the lung. The effect of dispersal was most noticeable in AP- and PD-MWCNTs, which are more hydrophobic and unstable in aqueous buffers than hydrophilic COOH-MWCNTs. Well-dispersed AP- and PD-MWCNTs were readily taken up by BEAS-2B, THP-1 cells, and alveolar macrophages (AM) and induced more prominent TGF-β1 and IL-1β production in vitro and TGF-β1, IL-1β, and PDGF-AA production in vivo than nondispersed tubes. Moreover, there was good agreement between the profibrogenic responses in vitro and in vivo as well as the ability of dispersed tubes to generate granulomatous inflammation and fibrosis in airways. Tube dispersal also elicited more robust IL-1β production in THP-1 cells. While COOH-MWCNTs were poorly taken up in BEAS-2B and induced little TGF-β1 production, they were bioprocessed by AM and induced less prominent collagen deposition at sites of nongranulomatous inflammation in the alveolar region. Taken together, these results indicate that the dispersal state of MWCNTs affects profibrogenic cellular responses that correlate with the extent of pulmonary fibrosis and are of potential use to predict pulmonary toxicity. PMID:22047207

  7. Cellular Barcoding Links B-1a B Cell Potential to a Fetal Hematopoietic Stem Cell State at the Single-Cell Level.

    PubMed

    Kristiansen, Trine A; Jaensson Gyllenbäck, Elin; Zriwil, Alya; Björklund, Tomas; Daniel, Jeremy A; Sitnicka, Ewa; Soneji, Shamit; Bryder, David; Yuan, Joan

    2016-08-16

    Hematopoietic stem cells (HSCs) undergo a functional switch in neonatal mice hallmarked by a decrease in self-renewing divisions and entry into quiescence. Here, we investigated whether the developmental attenuation of B-1a cell output is a consequence of a shift in stem cell state during ontogeny. Using cellular barcoding for in vivo single-cell fate analyses, we found that fetal liver definitive HSCs gave rise to both B-1a and B-2 cells. Whereas B-1a potential diminished in all HSCs with time, B-2 output was maintained. B-1a and B-2 plasticity could be reinitiated in a subset of adult HSCs by ectopic expression of the RNA binding protein LIN28B, a key regulator of fetal hematopoiesis, and this coincided with the clonal reversal to fetal-like elevated self-renewal and repopulation potential. These results anchor the attenuation of B-1a cell output to fetal HSC behavior and demonstrate that the developmental decline in regenerative potential represents a reversible HSC state. PMID:27533015

  8. Hybrid discrete/continuum algorithms for stochastic reaction networks

    NASA Astrophysics Data System (ADS)

    Safta, Cosmin; Sargsyan, Khachik; Debusschere, Bert; Najm, Habib N.

    2015-01-01

    Direct solutions of the Chemical Master Equation (CME) governing Stochastic Reaction Networks (SRNs) are generally prohibitively expensive due to excessive numbers of possible discrete states in such systems. To enhance computational efficiency we develop a hybrid approach where the evolution of states with low molecule counts is treated with the discrete CME model while that of states with large molecule counts is modeled by the continuum Fokker-Planck equation. The Fokker-Planck equation is discretized using a 2nd order finite volume approach with appropriate treatment of flux components. The numerical construction at the interface between the discrete and continuum regions implements the transfer of probability reaction by reaction according to the stoichiometry of the system. The performance of this novel hybrid approach is explored for a two-species circadian model with computational efficiency gains of about one order of magnitude.

  9. Hybrid discrete/continuum algorithms for stochastic reaction networks

    SciTech Connect

    Safta, Cosmin; Sargsyan, Khachik; Debusschere, Bert; Najm, Habib N.

    2014-10-22

    Direct solutions of the Chemical Master Equation (CME) governing Stochastic Reaction Networks (SRNs) are generally prohibitively expensive due to excessive numbers of possible discrete states in such systems. To enhance computational efficiency we develop a hybrid approach where the evolution of states with low molecule counts is treated with the discrete CME model while that of states with large molecule counts is modeled by the continuum Fokker-Planck equation. The Fokker-Planck equation is discretized using a 2nd order finite volume approach with appropriate treatment of flux components to avoid negative probability values. The numerical construction at the interface between the discrete and continuum regions implements the transfer of probability reaction by reaction according to the stoichiometry of the system. As a result, the performance of this novel hybrid approach is explored for a two-species circadian model with computational efficiency gains of about one order of magnitude.

  10. Hybrid discrete/continuum algorithms for stochastic reaction networks

    SciTech Connect

    Safta, Cosmin Sargsyan, Khachik Debusschere, Bert Najm, Habib N.

    2015-01-15

    Direct solutions of the Chemical Master Equation (CME) governing Stochastic Reaction Networks (SRNs) are generally prohibitively expensive due to excessive numbers of possible discrete states in such systems. To enhance computational efficiency we develop a hybrid approach where the evolution of states with low molecule counts is treated with the discrete CME model while that of states with large molecule counts is modeled by the continuum Fokker–Planck equation. The Fokker–Planck equation is discretized using a 2nd order finite volume approach with appropriate treatment of flux components. The numerical construction at the interface between the discrete and continuum regions implements the transfer of probability reaction by reaction according to the stoichiometry of the system. The performance of this novel hybrid approach is explored for a two-species circadian model with computational efficiency gains of about one order of magnitude.

  11. Hybrid discrete/continuum algorithms for stochastic reaction networks

    DOE PAGESBeta

    Safta, Cosmin; Sargsyan, Khachik; Debusschere, Bert; Najm, Habib N.

    2014-10-22

    Direct solutions of the Chemical Master Equation (CME) governing Stochastic Reaction Networks (SRNs) are generally prohibitively expensive due to excessive numbers of possible discrete states in such systems. To enhance computational efficiency we develop a hybrid approach where the evolution of states with low molecule counts is treated with the discrete CME model while that of states with large molecule counts is modeled by the continuum Fokker-Planck equation. The Fokker-Planck equation is discretized using a 2nd order finite volume approach with appropriate treatment of flux components to avoid negative probability values. The numerical construction at the interface between the discretemore » and continuum regions implements the transfer of probability reaction by reaction according to the stoichiometry of the system. As a result, the performance of this novel hybrid approach is explored for a two-species circadian model with computational efficiency gains of about one order of magnitude.« less

  12. Conductivity of continuum percolating systems

    NASA Astrophysics Data System (ADS)

    Stenull, Olaf; Janssen, Hans-Karl

    2001-11-01

    We study the conductivity of a class of disordered continuum systems represented by the Swiss-cheese model, where the conducting medium is the space between randomly placed spherical holes, near the percolation threshold. This model can be mapped onto a bond percolation model where the conductance σ of randomly occupied bonds is drawn from a probability distribution of the form σ-a. Employing the methods of renormalized field theory we show to arbitrary order in ɛ expansion that the critical conductivity exponent of the Swiss-cheese model is given by tSC(a)=(d-2)ν+max[φ,(1-a)-1], where d is the spatial dimension and ν and φ denote the critical exponents for the percolation correlation length and resistance, respectively. Our result confirms a conjecture that is based on the ``nodes, links, and blobs'' picture of percolation clusters.

  13. Continuum Fitting HST QSO Spectra

    NASA Technical Reports Server (NTRS)

    Tytler, David; Oliversen, Ronald J. (Technical Monitor)

    2002-01-01

    The Principal Component Analysis (PCA) method which we are using to fit and describe QSO spectra relies upon the fact that QSO continuum are generally very smooth and simple except for emission and absorption lines. To see this we need high signal-to-noise (S/N) spectra of QSOs at low redshift which have relatively few absorption lines in the Lyman-a forest. We need a large number of such spectra to use as the basis set for the PCA analysis which will find the set of principal component spectra which describe the QSO family as a whole. We have found that too few HST spectra have the required S/N and hence we need to supplement them with ground based spectra of QSOs at higher redshift. We have many such spectra and we have been working to make them suitable for this analysis. We have concentrated on this topic since 12/15/01.

  14. A Health Services Research Agenda for Cellular, Molecular and Genomic Technologies in Cancer Care

    PubMed Central

    Wideroff, Louise; Phillips, Kathryn A.; Randhawa, Gurvaneet; Ambs, Anita; Armstrong, Katrina; Bennett, Charles L.; Brown, Martin L.; Donaldson, Molla S.; Follen, Michele; Goldie, Sue J.; Hiatt, Robert A.; Khoury, Muin J.; Lewis, Graham; McLeod, Howard L.; Piper, Margaret; Powell, Isaac; Schrag, Deborah; Schulman, Kevin A.; Scott, Joan

    2009-01-01

    Background In recent decades, extensive resources have been invested to develop cellular, molecular and genomic technologies with clinical applications that span the continuum of cancer care. Methods In December 2006, the National Cancer Institute sponsored the first workshop to uniquely examine the state of health services research on cancer-related cellular, molecular and genomic technologies and identify challenges and priorities for expanding the evidence base on their effectiveness in routine care. Results This article summarizes the workshop outcomes, which included development of a comprehensive research agenda that incorporates health and safety endpoints, utilization patterns, patient and provider preferences, quality of care and access, disparities, economics and decision modeling, trends in cancer outcomes, and health-related quality of life among target populations. Conclusions Ultimately, the successful adoption of useful technologies will depend on understanding and influencing the patient, provider, health care system and societal factors that contribute to their uptake and effectiveness in ‘real-world’ settings. PMID:19367091

  15. Single attosecond pulse generation via continuum wave packet interference

    NASA Astrophysics Data System (ADS)

    Zhou, Shengpeng; Yang, Yujun; Ding, Dajun

    2016-07-01

    A single attosecond pulse generation via continuum-continuum interference is investigated theoretically by exposing a single-electron atom in a femtosecond laser field with the intensity in over-the-barrier ionization regime. We show that the ground state of the atom is depleted in such intense laser field and the high-order harmonics (HHG) via continuum to continuum coherence are generated. In a few-cycle monochromatic laser field (5 fs/800 nm, 1.2×1016 W cm-2), a single attosecond pulse with duration of 49 as is obtained from the HHG. With a two-color laser field combined by 1200 nm (8 fs/7.5×1015 W cm-2) and 800 nm (5 fs/1.0×1016 W cm-2), a shorter single pulse with duration of 29 as can further be produced by changing the relative carrier envelope phase of two laser pulses as a result of controlling the electronic quantum path in the intense electric field. Our results also show that a short single attosecond pulse can be generated in a wide range of the relative carrier envelope phase of the two laser pulses.

  16. A continuum model for interconnected lattice trusses

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.

    1992-01-01

    A continuum model for interconnected lattice trusses based on the 1D Timoshenko beam approximation is developed using the NASA-LRC Phase Zero Evolutionary Model. The continuum model dynamics is presented in the canonical wave-equation form in a Hilbert space.

  17. Turbulent fluid motion 3: Basic continuum equations

    NASA Technical Reports Server (NTRS)

    Deissler, Robert G.

    1991-01-01

    A derivation of the continuum equations used for the analysis of turbulence is given. These equations include the continuity equation, the Navier-Stokes equations, and the heat transfer or energy equation. An experimental justification for using a continuum approach for the study of turbulence is given.

  18. Cellular Morphogenesis In Silico

    PubMed Central

    Shinbrot, Troy; Chun, Young; Caicedo-Carvajal, Carlos; Foty, Ramsey

    2009-01-01

    Abstract We describe a model that simulates spherical cells of different types that can migrate and interact either attractively or repulsively. We find that both expected morphologies and previously unreported patterns spontaneously self-assemble. Among the newly discovered patterns are a segmented state of alternating discs, and a “shish-kebab” state, in which one cell type forms a ring around a second type. We show that these unique states result from cellular attraction that increases with distance (e.g., as membranes stretch viscoelastically), and would not be seen in traditional, e.g., molecular, potentials that diminish with distance. Most of the states found computationally have been observed in vitro, and it remains to be established what role these self-assembled states may play in in vivo morphogenesis. PMID:19686642

  19. Non compact continuum limit of two coupled Potts models

    NASA Astrophysics Data System (ADS)

    Vernier, Éric; Lykke Jacobsen, Jesper; Saleur, Hubert

    2014-10-01

    We study two Q-state Potts models coupled by the product of their energy operators, in the regime 2 < Q ⩽ 4 where the coupling is relevant. A particular choice of weights for the square lattice is shown to be equivalent to the integrable a_3(2) vertex model. It corresponds to a selfdual system of two antiferromagnetic Potts models, coupled ferromagnetically. We derive the Bethe ansatz equations and study them numerically for two arbitrary twist angles. The continuum limit is shown to involve two compact bosons and one non compact boson, with discrete states emerging from the continuum at appropriate twists. The non compact boson entails strong logarithmic corrections to the finite-size behaviour of the scaling levels, an understanding of which allows us to correct an earlier proposal for some of the critical exponents. In particular, we infer the full set of magnetic scaling dimensions (watermelon operators) of the Potts model.

  20. Electron-pair excitations and the molecular Coulomb continuum

    SciTech Connect

    Colgan, James

    2009-01-01

    Electron-pair excitations in the molecular hydrogen continuum are described by quantizing rotations of the momentum plane of the electron pair about by the pair's relative momentum. A helium-like description of the molecular pi.Joto double ionization is thus extended to higher angular momenta of the electron pair. A simple three-state superposition is found to account surprisingly well for recent observations of noncoplanar electron-pair, molecular-axis angular distributions.

  1. Continuum methods in lattice perturbation theory

    SciTech Connect

    Becher, Thomas G

    2002-11-15

    We show how methods of continuum perturbation theory can be used to simplify perturbative lattice calculations. We use the technique of asymptotic expansions to expand lattice loop integrals around the continuum limit. After the expansion, all nontrivial dependence on momenta and masses is encoded in continuum loop integrals and the only genuine lattice integrals left are tadpole integrals. Using integration-by-parts relations all of these can be expressed in terms of a small number of master integrals. Four master integrals are needed for bosonic one loop integrals, sixteen in QCD with Wilson or staggered fermions.

  2. Analysis of an optimization-based atomistic-to-continuum coupling method for point defects

    DOE PAGESBeta

    Olson, Derek; Shapeev, Alexander V.; Bochev, Pavel B.; Luskin, Mitchell

    2015-11-16

    Here, we formulate and analyze an optimization-based Atomistic-to-Continuum (AtC) coupling method for problems with point defects. Application of a potential-based atomistic model near the defect core enables accurate simulation of the defect. Away from the core, where site energies become nearly independent of the lattice position, the method switches to a more efficient continuum model. The two models are merged by minimizing the mismatch of their states on an overlap region, subject to the atomistic and continuum force balance equations acting independently in their domains. We prove that the optimization problem is well-posed and establish error estimates.

  3. Self-consistent continuum random-phase approximation calculations of {sup 4}He electromagnetic responses

    SciTech Connect

    De Donno, V.; Co', G.; Anguiano, M.; Lallena, A. M.

    2011-09-15

    We study the electromagnetic responses of {sup 4}He within the framework of the self-consistent continuum random-phase approximation theory. In this approach, the ground-state properties are described by a Hartree-Fock calculation. The single-particle basis constructed in this manner is used in the calculations of the continuum responses of the system. Finite-range interactions are considered in the calculations. We compare our results with photon-absorption cross sections and electron-scattering quasielastic data. From this comparison, and also from the comparison with the results of microscopic calculations, we deduce that our approach describes well the continuum excitation.

  4. Azide vs Alkyne Functionalization in Pt(II) Complexes for Post-treatment Click Modification: Solid-State Structure, Fluorescent Labeling, and Cellular Fate.

    PubMed

    Wirth, Regina; White, Jonathan D; Moghaddam, Alan D; Ginzburg, Aurora L; Zakharov, Lev N; Haley, Michael M; DeRose, Victoria J

    2015-12-01

    Tracking of Pt(II) complexes is of crucial importance toward understanding Pt interactions with cellular biomolecules. Post-treatment fluorescent labeling of functionalized Pt(II)-based agents using the bioorthogonal Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has recently been reported as a promising approach. Here we describe an azide-functionalized Pt(II) complex, cis-[Pt(2-azidobutyl)amido-1,3-propanediamine)Cl2] (1), containing the cis geometry and difunctional reactivity of cisplatin, and present a comparative study with its previously described alkyne-functionalized congener. Single-crystal X-ray diffraction reveals a dramatic change in the solid-state arrangement with exchange of the alkyne for an azide moiety wherein 1 is dominated by a pseudo-chain of Pt-Pt dimers and antiparallel alignment of the azide substituents, in comparison with a circular arrangement supported by CH/π(C≡C) interactions in the alkyne version. In vitro studies indicate similar DNA binding and click reactivity of both congeners observed by fluorescent labeling. Interestingly, complex 1 shows in vitro enhanced click reactivity in comparison to a previously reported azide-appended Pt(II) complex. Despite their similar behavior in vitro, preliminary in cellulo HeLa studies indicate a superior imaging potential of azide-functionalized 1. Post-treatment fluorescent labeling of 1 observed by confocal fluorescence microscopy shows nuclear and intense nucleolar localization. These results demonstrate the potential of 1 in different cell line localization studies and for future isolation and purification of Pt-bound targets. PMID:26512733

  5. Continuum source tungsten coil atomic fluorescence spectrometry.

    PubMed

    Gu, Jiyan; Donati, George L; Young, Carl G; Jones, Bradley T

    2011-04-01

    A simple continuum source tungsten coil atomic fluorescence spectrometer is constructed and evaluated. The heart of the system is the atomizer: a low-cost tungsten filament extracted from a 150 W light bulb. The filament is resistively heated with a small, solid-state, constant-current power supply. The atomizer is housed in a glass chamber and purged with a 1 L/min flow of a conventional welding gas mixture: 10% H(2)/Ar. A 25 μL sample aliquot is pipetted onto the tungsten coil, the liquid is dried at low current, and then the atomic vapor is produced by applying a current in the range 3.5-5.5 A. The atomization current does not produce temperatures high enough to excite atomic emission. Radiation from a 300 W xenon lamp is focused through the atomic vapor, exciting atomic fluorescence. Fluorescence signals are collected using a hand-held charge-coupled device (CCD) spectrometer. Simultaneous determination of ten elements (Ag, Bi, Cr, Cu, Ga, In, Mg, Mn, and Tl) results in detection limits in the range 0.3 to 10 ng. The application of higher atomization currents (10 A) leads to straightforward detection of atomic emission signals with no modifications to the instrument. PMID:21396184

  6. Diagnostic Reasoning across the Medical Education Continuum

    PubMed Central

    Smith, C. Scott; Hill, William; Francovich, Chris; Morris, Magdalena; Robbins, Bruce; Robins, Lynne; Turner, Andrew

    2014-01-01

    We aimed to study linguistic and non-linguistic elements of diagnostic reasoning across the continuum of medical education. We performed semi-structured interviews of premedical students, first year medical students, third year medical students, second year internal medicine residents, and experienced faculty (ten each) as they diagnosed three common causes of dyspnea. A second observer recorded emotional tone. All interviews were digitally recorded and blinded transcripts were created. Propositional analysis and concept mapping were performed. Grounded theory was used to identify salient categories and transcripts were scored with these categories. Transcripts were then unblinded. Systematic differences in propositional structure, number of concept connections, distribution of grounded theory categories, episodic and semantic memories, and emotional tone were identified. Summary concept maps were created and grounded theory concepts were explored for each learning level. We identified three major findings: (1) The “apprentice effect” in novices (high stress and low narrative competence); (2) logistic concept growth in intermediates; and (3) a cognitive state transition (between analytical and intuitive approaches) in experts. These findings warrant further study and comparison.

  7. A continuum three-zone model for swarms.

    PubMed

    Miller, Jennifer M; Kolpas, Allison; Juchem Neto, Joao Plinio; Rossi, Louis F

    2012-03-01

    We present a progression of three distinct three-zone, continuum models for swarm behavior based on social interactions with neighbors in order to explain simple coherent structures in popular biological models of aggregations. In continuum models, individuals are replaced with density and velocity functions. Individual behavior is modeled with convolutions acting within three interaction zones corresponding to repulsion, orientation, and attraction, respectively. We begin with a variable-speed first-order model in which the velocity depends directly on the interactions. Next, we present a variable-speed second-order model. Finally, we present a constant-speed second-order model that is coordinated with popular individual-based models. For all three models, linear stability analysis shows that the growth or decay of perturbations in an infinite, uniform swarm depends on the strength of attraction relative to repulsion and orientation. We verify that the continuum models predict the behavior of a swarm of individuals by comparing the linear stability results with an individual-based model that uses the same social interaction kernels. In some unstable regimes, we observe that the uniform state will evolve toward a radially symmetric attractor with a variable density. In other unstable regimes, we observe an incoherent swarming state. PMID:21800229

  8. Commitment to Quality throughout the Continuum.

    ERIC Educational Resources Information Center

    Gillet, Pamela

    1995-01-01

    This editorial by the president of the Council for Exceptional Children indicates the organization's support of a continuum of special education placements for students with special needs and calls for improving transition of students from one placement to another. (JDD)

  9. Periodic amplitude variations in Jovian continuum radiation

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1986-12-01

    An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both 5 and 10 horus. Contrary to a plausible initial idea, the continuum amplitudes are not organized by the position of the observer relative to the dense plasma sheet. Instead, there seem to be perferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clocklike modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude solar wind alignment to the amplitude of the continuum radiation implies that the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

  10. Cellular automatons applied to gas dynamic problems

    NASA Astrophysics Data System (ADS)

    Long, Lyle N.; Coopersmith, Robert M.; McLachlan, B. G.

    1987-06-01

    This paper compares the results of a relatively new computational fluid dynamics method, cellular automatons, with experimental data and analytical results. This technique has been shown to qualitatively predict fluidlike behavior; however, there have been few published comparisons with experiment or other theories. Comparisons are made for a one-dimensional supersonic piston problem, Stokes first problem, and the flow past a normal flat plate. These comparisons are used to assess the ability of the method to accurately model fluid dynamic behavior and to point out its limitations. Reasonable results were obtained for all three test cases, but the fundamental limitations of cellular automatons are numerous. It may be misleading, at this time, to say that cellular automatons are a computationally efficient technique. Other methods, based on continuum or kinetic theory, would also be very efficient if as little of the physics were included.

  11. Cellular automatons applied to gas dynamic problems

    NASA Technical Reports Server (NTRS)

    Long, Lyle N.; Coopersmith, Robert M.; Mclachlan, B. G.

    1987-01-01

    This paper compares the results of a relatively new computational fluid dynamics method, cellular automatons, with experimental data and analytical results. This technique has been shown to qualitatively predict fluidlike behavior; however, there have been few published comparisons with experiment or other theories. Comparisons are made for a one-dimensional supersonic piston problem, Stokes first problem, and the flow past a normal flat plate. These comparisons are used to assess the ability of the method to accurately model fluid dynamic behavior and to point out its limitations. Reasonable results were obtained for all three test cases, but the fundamental limitations of cellular automatons are numerous. It may be misleading, at this time, to say that cellular automatons are a computationally efficient technique. Other methods, based on continuum or kinetic theory, would also be very efficient if as little of the physics were included.

  12. Geometric continuum regularization of quantum field theory

    SciTech Connect

    Halpern, M.B. . Dept. of Physics)

    1989-11-08

    An overview of the continuum regularization program is given. The program is traced from its roots in stochastic quantization, with emphasis on the examples of regularized gauge theory, the regularized general nonlinear sigma model and regularized quantum gravity. In its coordinate-invariant form, the regularization is seen as entirely geometric: only the supermetric on field deformations is regularized, and the prescription provides universal nonperturbative invariant continuum regularization across all quantum field theory. 54 refs.

  13. Noise scaling in continuum percolating films

    NASA Astrophysics Data System (ADS)

    Garfunkel, G. A.; Weissman, M. B.

    1985-07-01

    Measurements of the scaling of 1/f noise magnitude versus resistance were made in metal films as the metal was removed by sandblasting. This procedure gives an approximate experimental realization of a Swiss-cheese continuum-percolation model, for which theory indicates some scaling properties very different from lattice percolation. The ratio of the resistance and noise exponents was in strong disagreement with lattice-percolation predictions and agreed approximately with simple continuum predictions.

  14. Nuclear reprogramming of luminal-like breast cancer cells generates Sox2-overexpressing cancer stem-like cellular states harboring transcriptional activation of the mTOR pathway.

    PubMed

    Corominas-Faja, Bruna; Cufí, Sílvia; Oliveras-Ferraros, Cristina; Cuyàs, Elisabet; López-Bonet, Eugeni; Lupu, Ruth; Alarcón, Tomás; Vellon, Luciano; Iglesias, Juan Manuel; Leis, Olatz; Martín, Ángel G; Vazquez-Martin, Alejandro; Menendez, Javier A

    2013-09-15

    Energy metabolism plasticity enables stemness programs during the reprogramming of somatic cells to an induced pluripotent stem cell (iPSC) state. This relationship may introduce a new era in the understanding of Warburg's theory on the metabolic origin of cancer at the level of cancer stem cells (CSCs). Here, we used Yamanaka's stem cell technology in an attempt to create stable CSC research lines in which to dissect the transcriptional control of mTOR--the master switch of cellular catabolism and anabolism--in CSC-like states. The rare colonies with iPSC-like morphology, obtained following the viral transduction of the Oct4, Sox2, Klf4, and c-Myc (OSKM) stemness factors into MCF-7 luminal-like breast cancer cells (MCF-7/Rep), demonstrated an intermediate state between cancer cells and bona fide iPSCs. MCF-7/Rep cells notably overexpressed SOX2 and stage-specific embryonic antigen (SSEA)-4 proteins; however, other stemness-related markers (OCT4, NANOG, SSEA-1, TRA-1-60, and TRA-1-81) were found at low to moderate levels. The transcriptional analyses of OSKM factors confirmed the strong but unique reactivation of the endogenous Sox2 stemness gene accompanied by the silencing of the exogenous Sox2 transgene in MCF-7/Rep cells. Some but not all MCF-7/Rep cells acquired strong alkaline phosphatase (AP) activity compared with MCF-7 parental cells. SOX2-overexpressing MCF-7/Rep cells contained drastically higher percentages of CD44(+) and ALDEFLUOR-stained ALDH(bright) cells than MCF-7 parental cells. The overlap between differentially expressed mTOR signaling-related genes in 3 different SOX2-overexpressing CSC-like cell lines revealed a notable downregulation of 3 genes, PRKAA1 (which codes for the catalytic α 1 subunit of AMPK), DDIT4/REDD1 (a stress response gene that operates as a negative regulator of mTOR), and DEPTOR (a naturally occurring endogenous inhibitor of mTOR activity). The insulin-receptor gene (INSR) was differentially upregulated in MCF-7/Rep cells

  15. Angular correlation in the two-electron continuum

    SciTech Connect

    Kheifets, A. S.; Bray, I.

    2006-02-15

    Following absorption of a single photon, angles of simultaneous emission of two electrons from a He(n {sup 1}S) atom become more correlated with increasing n. We find that the strength of this correlation is due to the two-electron continuum of the electron-impact ionization of the He{sup +}(ns) ion. The strength is determined by the width of the momentum profile of the ionic ns state but not the strength of the electron correlation in the He initial state. This can explain the increasing (over He) angular correlation strength found in double photoionization of targets such as Be, Ne, and H{sub 2}.

  16. Coherent population trapping via a continuum with a train of ultrashort pulses

    SciTech Connect

    Kuznetsova, Elena; Kolesov, Roman; Kocharovskaya, Olga

    2006-09-15

    We consider the coherent population trapping effect with a train of ultrashort pulses in a {lambda}-type system with two bound states and a continuum replacing the upper state. Population transfer to the continuum can be totally suppressed provided that the splitting between the bound states is a multiple of the pulse repetition rate. Compared to the traditional case with only two laser fields coupling the bound states to the continuum, CPT with a pulse train allows one to avoid incoherent population losses due to interaction of the fields with 'wrong' transitions, which results in only partial suppression of ionization. A method of suppression of excited-state absorption of pumping radiation in laser crystals, with pumping in the form of the pulse train, is proposed. As a particular example pumping dynamics of a Ti{sup 3+}:YAlO{sub 3} crystal using this technique is numerically analyzed.

  17. Continuum physics: Correlation and fluctuation analysis

    SciTech Connect

    Herskind, B.

    1993-10-01

    It is well known that the main flow of the {gamma}-decay from high spin states passes through the regions of high level density several MeV above the yrast line. Nevertheless, only very limited information about the nuclear structure in this region is available, due to the extremely high complexity of the decay patterns. The new highly efficient {gamma}-spectrometer arrays, GASP, EUROGAM and GAMMASPHERE coming into operation these years, with several orders of magnitude higher selectivity for studying weakly populated states, offers new exiting possibilities also for a much more detailed study of the high spin quasi-continuum. It is of special interest to study the phase transition from the region of discrete regular rotational band structures found close to the yrast line, into the region of damped rotational motion at higher excitation energies and investigate the interactions responsible for the damping phenomena. Some of the first large data-sets to be analyzed are made on residues around e.g. {sup 152}Dy and {sup 168}Yb produced with EUROGAM in Daresbury, UK, in addition to {sup 143}Eu and {sup 182}Pt produced with GASP in Legnaro, Italy. These data-sets will for the first time contain enough counts to allow for a fluctuation analysis of 3-fold coincidence matrixes. The high spatial resolution in a cube of triples make it possible to select transitions from specific configurations using 2 of the detectors and measure the fluctuations caused by the simplicity of feeding the selected configuration by the 3. detector. Thus, weakly mixed structures in the damped region as e.g. superdeformed- or high-K bands are expected to show large fluctuations. Results from these experiments will be discussed.

  18. The John F. Maher Award Recipient Lecture 2006. The continuum of chronic kidney disease and end-stage renal disease: challenges and opportunities for chronic peritoneal dialysis in the United States.

    PubMed

    Mehrotra, Rajnish

    2007-01-01

    End-stage renal disease (ESRD) patients undergoing renal replacement therapy have a high mortality rate and suffer from considerable morbidity. Degree of nutritional decline, disordered mineral metabolism, and vascular calcification are some of the abnormalities that predict an adverse outcome for ESRD patients. All these abnormalities begin early during the course of chronic kidney disease (CKD), long before the need for maintenance dialysis. Thus, CKD represents a continuum of metabolic and vascular abnormalities. Treatment of these abnormalities early during the course of CKD and a timely initiation of dialysis have the potential of improving patient outcomes. However, the thesis that successful management of these abnormalities will favorably modify the outcomes of dialysis patients remains untested. The proportion of incident USA ESRD patients starting chronic peritoneal dialysis (CPD) has historically been low. Limited physician training and inadequate predialysis patient education appear to underlie the low CPD take-on in the USA. Furthermore, two key changes have occurred in the USA: steep decline in CPD take-on and progressive increase in the use of automated peritoneal dialysis. The decline in CPD take-on has afflicted virtually every subgroup examined and has occurred, paradoxically, when the CPD outcomes in the country have improved. Understanding the reasons for historically low CPD take-on and recent steep declines in utilization may allow the development of plans to reverse these trends. PMID:17299144

  19. Theories of elastoplasticity coupled with continuum damage mechanics

    NASA Astrophysics Data System (ADS)

    Hansen, N. R.

    1993-01-01

    Inelastic material constitutive relations for elastoplasticity coupled with continuum damage mechanics are investigated. For elastoplasticity, continuum damage mechanics, and the coupled formulations, rigorous thermodynamic frameworks are derived. The elastoplasticity framework is shown to be sufficiently general to encompass J(sub 2) plasticity theories including general isotropic and kinematic hardening relations. The concepts of an intermediate undamaged configuration and a fictitious deformation gradient are used to develop a damage representation theory. An empirically-based, damage evolution theory is proposed to overcome some observed deficiencies. Damage deactivation, which is the negation of the effects of damage under certain loading conditions, is investigated. An improved deactivation algorithm is developed for both damaged elasticity and coupled elastoplasticity formulations. The applicability of coupled formulations is validated by comparing theoretical predictions to experimental data for a spectrum of materials and loads paths. The pressure-dependent brittle-to-ductile transitional behavior of concrete is replicated. The deactivation algorithm is validated using tensile and compression data for concrete. For a ductile material, the behavior of an aluminum alloy is simulated including the temperature-dependent ductile-to-brittle behavior features. The direct application of a coupled model to fatigue is introduced. In addition, the deactivation algorithm in conjunction with an assumed initial damage and strain is introduced as a novel method of simulating the densification phenomenon in cellular solids.

  20. Cancer communication and informatics research across the cancer continuum.

    PubMed

    Hesse, Bradford W; Beckjord, Ellen; Rutten, Lila J Finney; Fagerlin, Angela; Cameron, Linda D

    2015-01-01

    Over the past decade, dramatic changes brought about by a rapid diffusion of Internet technologies, cellular telephones, mobile devices, personal digital assistants, electronic health records, and data visualization have helped to create a revolution in health communication. To understand the implications of this communication revolution for cancer care, the National Cancer Institute launched an ambitious set of research priorities under its "extraordinary opportunities" program. We present an overview of some of the relevant behavioral research being conducted within the perspective of this extraordinary opportunity in cancer communication research. We begin by tracing the implications of this research for behavioral scientists across the continuum of cancer care from primary prevention (e.g., tobacco control, diet, exercise, sun protection, and immunization against human papilloma virus), to secondary prevention (e.g., screening for polyps, lesions, and early stage neoplasms), to diagnosis and treatment, posttreatment survivorship, and end of life. Along each point of the continuum, we describe a natural evolution of knowledge from studies on the traditional role of media to research on the changing role of new media and informatics, and we carefully highlight the role that psychological research has played in improving communication- and health-related outcomes along the way. We conclude with an appeal to psychologists of many different backgrounds to join with biomedical researchers, engineers, clinical practitioners, and others to accelerate progress against cancer. PMID:25730725

  1. Ensuring Congruency in Multiscale Modeling: Towards Linking Agent Based and Continuum Biomechanical Models of Arterial Adaptation

    PubMed Central

    Hayenga, Heather N.; Thorne, Bryan C.; Peirce, Shayn M.; Humphrey, Jay D.

    2011-01-01

    There is a need to develop multiscale models of vascular adaptations to understand tissue level manifestations of cellular level mechanisms. Continuum based biomechanical models are well suited for relating blood pressures and flows to stress-mediated changes in geometry and properties, but less so for describing underlying mechanobiological processes. Discrete stochastic agent based models are well suited for representing biological processes at a cellular level, but not for describing tissue level mechanical changes. We present here a conceptually new approach to facilitate the coupling of continuum and agent based models. Because of ubiquitous limitations in both the tissue- and cell-level data from which one derives constitutive relations for continuum models and rule-sets for agent based models, we suggest that model verification should enforce congruency across scales. That is, multiscale model parameters initially determined from data sets representing different scales should be refined, when possible, to ensure that common outputs are consistent. Potential advantages of this approach are illustrated by comparing simulated aortic responses to a sustained increase in blood pressure predicted by continuum and agent based models both before and after instituting a genetic algorithm to refine 16 objectively bounded model parameters. We show that congruency-based parameter refinement not only yielded increased consistency across scales, it also yielded predictions that are closer to in vivo observations. PMID:21809144

  2. 34 CFR 300.115 - Continuum of alternative placements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 2 2012-07-01 2012-07-01 false Continuum of alternative placements. 300.115 Section... Continuum of alternative placements. (a) Each public agency must ensure that a continuum of alternative... services. (b) The continuum required in paragraph (a) of this section must— (1) Include the...

  3. Sacrifice Along the Energy Continuum: A Call for Energy Justice

    PubMed Central

    Hernández, Diana

    2016-01-01

    The confluence of energy supply- and demand-side dynamics links vulnerable communities along the spectrum of energy production and consumption. The disproportionate burden borne by vulnerable communities along the energy continuum are seldom examined simultaneously. Yet, from a justice perspective there are important parallels that merit further exploration in the United States and beyond. A first step is to understand links to vulnerability and justice along the energy continuum by way of theoretical constructs and practical applications. The present article posits energy as a social and environmental justice issue and advances our current understanding of the links between energy and vulnerability, particularly in the U.S. context. Drawing on several emerging concepts including, “energy sacrifice zones,” “energy insecurity” and “energy justice,” this article lays a foundation for examining critical sacrifices along the energy continuum. To conclude, four basic rights are proposed as a starting point to achieve recognition and equity for vulnerable populations in the realm of energy. PMID:27053980

  4. Control of density fluctuations in atomistic-continuum simulations of dense liquids.

    PubMed

    Kotsalis, E M; Walther, J H; Koumoutsakos, P

    2007-07-01

    We present a control algorithm to eliminate spurious density fluctuations associated with the coupling of atomistic and continuum descriptions for dense liquids. A Schwartz domain decomposition algorithm is employed to couple molecular dynamics for the simulation of the atomistic system with a continuum solver for the simulation of the Navier-Stokes equations. The lack of periodic boundary conditions in the molecular dynamics simulations hinders the proper accounting for the virial pressure leading to spurious density fluctuations at the continuum-atomistic interface. An ad hoc boundary force is usually employed to remedy this situation. We propose the calculation of this boundary force using a control algorithm that explicitly cancels the density fluctuations. The results demonstrate that the present approach outperforms state-of-the-art algorithms. The conceptual and algorithmic simplicity of the method makes it suitable for any type of coupling between atomistic and continuum descriptions of dense fluids. PMID:17677596

  5. Observations of continuum depression in warm dense matter with x-ray Thomson scattering.

    PubMed

    Fletcher, L B; Kritcher, A L; Pak, A; Ma, T; Döppner, T; Fortmann, C; Divol, L; Jones, O S; Landen, O L; Scott, H A; Vorberger, J; Chapman, D A; Gericke, D O; Mattern, B A; Seidler, G T; Gregori, G; Falcone, R W; Glenzer, S H

    2014-04-11

    Detailed measurements of the electron densities, temperatures, and ionization states of compressed CH shells approaching pressures of 50 Mbar are achieved with spectrally resolved x-ray scattering. Laser-produced 9 keV x-rays probe the plasma during the transient state of three-shock coalescence. High signal-to-noise x-ray scattering spectra show direct evidence of continuum depression in highly degenerate warm dense matter states with electron densities ne>1024  cm-3. The measured densities and temperatures agree well with radiation-hydrodynamic modeling when accounting for continuum lowering in calculations that employ detailed configuration accounting. PMID:24765979

  6. Semianalytic continuum spectra of Type 2 supernovae

    NASA Technical Reports Server (NTRS)

    Montes, Marcos J.; Wagoner, Robert V.

    1995-01-01

    We extend the approximate radiative transfer analysis of Hershkowitz, Linder, & Wagoner (1986) to a more general class of supernova model atmospheres, using a simple fit to the effective continuum opacity produced by lines (Wagoner, Perez, & Vasu 1991). At the low densities considered, the populations of the excited states of hydrogen are governed mainly by photoionization and recombination, and scattering dominates absorptive opacity. We match the asymptotic expressions for the spectral energy density J(sub nu) at the photosphere, whose location at each frequency is determined by a first-order calculation of the deviation of J(sub nu) from the Planck function B(sub nu). The emergent spectral luminosity then assumes the form L(sub nu) = 4 pi(squared)r(squared)(sub *) zeta(squared)B(sub nu)(T(sub p)), where T(sub p)(nu) is the photospheric temperature zeta is the dilution factor, and r(sub *) is a fiducial radius (ultimately taken to be the photospheric radius r(sub p)(nu)). The atmosphere is characterized by an effective temperature T(sub e) (varies as L(sup 1/4)r(sup -1/2)(sub *)) and hydrogen density n(sub H) = dependence of zeta on frequency nu and the parameters T(sub p), r(sub p), and alpha. The resulting understanding of the dependence of the spectral luminosity on observable parameters which characterize the relevant physical conditions will be of particular use in assessing the reliability of the expanding photosphere method of distance determination. This is particularly important at cosmological distances, where no information about the progenitor star will be available. This technique can also be applied to other low-density photosphere.

  7. Continuum Absorption Coefficient of Atoms and Ions

    NASA Technical Reports Server (NTRS)

    Armaly, B. F.

    1979-01-01

    The rate of heat transfer to the heat shield of a Jupiter probe has been estimated to be one order of magnitude higher than any previously experienced in an outer space exploration program. More than one-third of this heat load is due to an emission of continuum radiation from atoms and ions. The existing computer code for calculating the continuum contribution to the total load utilizes a modified version of Biberman's approximate method. The continuum radiation absorption cross sections of a C - H - O - N ablation system were examined in detail. The present computer code was evaluated and updated by being compared with available exact and approximate calculations and correlations of experimental data. A detailed calculation procedure, which can be applied to other atomic species, is presented. The approximate correlations can be made to agree with the available exact and experimental data.

  8. Defining and testing a granular continuum element

    SciTech Connect

    Rycroft, Chris H.; Kamrin, Ken; Bazant, Martin Z.

    2007-12-03

    Continuum mechanics relies on the fundamental notion of amesoscopic volume "element" in which properties averaged over discreteparticles obey deterministic relationships. Recent work on granularmaterials suggests a continuum law may be inapplicable, revealinginhomogeneities at the particle level, such as force chains and slow cagebreaking. Here, we analyze large-scale Discrete-Element Method (DEM)simulations of different granular flows and show that a "granularelement" can indeed be defined at the scale of dynamical correlations,roughly three to five particle diameters. Its rheology is rather subtle,combining liquid-like dependence on deformation rate and solid-likedependence on strain. Our results confirm some aspects of classicalplasticity theory (e.g., coaxiality of stress and deformation rate),while contradicting others (i.e., incipient yield), and can guide thedevelopment of more realistic continuum models.

  9. Hadron resonances with a quark core embedded in the continuum

    SciTech Connect

    Shimizu, Kiyotaka; Takeuchi, Sachiko; Takizawa, Makoto

    2011-05-06

    We investigate the excited baryons and mesons which cannot be described in terms of a simple constituent quark model, such as {Lambda}(1405) and X(3872) as a resonance in a coupled channel hadron-hadron (baryon-meson or meson-meson) scattering with a 'bound state embedded in the continuum' (BSEC). For this purpose, we solve the Lippmann-Schwinger equation including a BSEC in the momentum space. This BSEC is introduced by hand, as a state not originated from a simple baryon-meson or meson-meson system. We assume it comes from the three-quark state or quark-anti quark state and show such a picture can describe the {Lambda}(1405) and X(3872) resonances.

  10. Continuum damping of ideal toroidal Alfven eigenmodes

    SciTech Connect

    Zhang, X.D.; Zhang, Y.Z.; Mahajan, S.M.

    1993-08-01

    A perturbation theory based on the two dimensional (2D) ballooning transform is systematically developed for ideal toroidal Alfven eigenmodes (TAEs). A formula, similar to the Fermi golden rule for decaying systems in quantum mechanics, is derived for the continuum damping rate of the TAE; the decay (damping) rate is expressed explicitly in terms of the coupling of the TAE to the continuum spectrum. Numerical results are compared with previous calculations. It is found that in some narrow intervals of the parameter m{cflx {epsilon}} the damping rate varies very rapidly. These regions correspond precisely to the root missing intervals of the numerical solution by Rosenbluth et al.