Three pion nucleon coupling constants
NASA Astrophysics Data System (ADS)
Ruiz Arriola, E.; Amaro, J. E.; Navarro Pérez, R.
2016-08-01
There exist four pion nucleon coupling constants, fπ0pp, - fπ0nn, fπ+pn/2 and fπ-np/2 which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination fp2 = 0.0759(4),f 02 = 0.079(1),f c2 = 0.0763(6), based on a partial wave analysis of the 3σ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Backward pion-nucleon scattering
F. Huang; Sibirtsev, Alex; Haidenbauer, Johann; Meissner, Ulf-G.
2010-02-01
A global analysis of the world data on differential cross sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3 GeV is performed in a Regge model. Including the $N_\\alpha$, $N_\\gamma$, $\\Delta_\\delta$ and $\\Delta_\\beta$ trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable $u$, in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3 GeV. Our analysis suggests a $G_{39}$ resonance with a mass of 2.83 GeV as member of the $\\Delta_{\\beta}$ trajectory from the corresponding Chew-Frautschi plot.
Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations
NASA Astrophysics Data System (ADS)
Kubis, Bastian; Hoferichter, Martin; de Elvira, Jacobo Ruiz; Meißner, Ulf-G.
2016-11-01
Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. The scattering lengths or the pion-nucleon σ-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon-nucleon potentials, and hence has a far-reaching impact on nuclear physics. We discuss the fruitful combination of dispersion-theoretical methods, in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.
Covariant formulation of pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Lahiff, A. D.; Afnan, I. R.
A covariant model of elastic pion-nucleon scattering based on the Bethe-Salpeter equation is presented. The kernel consists of s- and u-channel nucleon and delta poles, along with rho and sigma exchange in the t-channel. A good fit is obtained to the s- and p-wave phase shifts up to the two-pion production threshold.
Low-energy pion-nucleon scattering
Gibbs, W.R.; Ai, L.; Kaufmann, W.B.
1998-02-01
An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}
Low-energy pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Gibbs, W. R.; Ai, Li; Kaufmann, W. B.
1998-02-01
An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.
Skyrmion recoil in pion-nucleon scattering
Hughes, J. Physics Department, University of California at Davis, Davis, California 95616 ); Mathews, G.J. )
1992-08-01
We calculate the lowest-order recoil corrections to the pion-nucleon scattering matrix in the SU(2) Skyrme model. The corrections result from a direct semiclassical evaluation of path-integral expressions for relevant finite-time transition amplitudes. The {ital S} matrix for pion-nucleon scattering is extracted from these amplitudes by using a configuration-space representation for the asymptotic nucleons; the quanta are treated just as in the vacuum sector. The recoil corrections result from the Skyrmion freely translating between initial and final positions, and are relevant to a kinematical regime opposite to that where the impulse approximation is valid. The form of the corrections is model independent, unchanged for any chiral model with hedgehog solitary wave solutions. Remarkably, new lowest-lying resonances emerge in the {ital p} channels, whereas the {ital s} and {ital d} waves are not noticeably improved.
Roy-Steiner-equation analysis of pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Meißner, U.-G.; Ruiz de Elvira, J.; Hoferichter, M.; Kubis, B.
2017-03-01
Low-energy pion-nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion-nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion-nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.
Quark dynamics and pion-nucleon coupling
NASA Astrophysics Data System (ADS)
Weise, W.; Werner, E.
1981-05-01
In the framework of nonperturbative QCD phenomenology we discuss: (1) The elementary process for the creation of color-singlet qq-pairs inside a hadron. (2) The interaction of the qq-pair with the surrounding quark-gluon medium. An important consequence of these discussions is that meson emission takes place preferentially, if the primary qq-pair is created in the surface region of the hadron. For the case of pseudoscalar coupling we employ PCAC to obtain the coupling of the qq-pair to the pion. The resulting form and coupling strength of the πNN vertex is consistent with the phenomenological OPEP.
Roy-Steiner-equation analysis of pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2016-04-01
We review the structure of Roy-Steiner equations for pion-nucleon scattering, the solution for the partial waves of the t-channel process ππ → N ¯ N, as well as the high-accuracy extraction of the pion-nucleon S-wave scattering lengths from data on pionic hydrogen and deuterium. We then proceed to construct solutions for the lowest partial waves of the s-channel process πN → πN and demonstrate that accurate solutions can be found if the scattering lengths are imposed as constraints. Detailed error estimates of all input quantities in the solution procedure are performed and explicit parameterizations for the resulting low-energy phase shifts as well as results for subthreshold parameters and higher threshold parameters are presented. Furthermore, we discuss the extraction of the pion-nucleon σ-term via the Cheng-Dashen low-energy theorem, including the role of isospin-breaking corrections, to obtain a precision determination consistent with all constraints from analyticity, unitarity, crossing symmetry, and pionic-atom data. We perform the matching to chiral perturbation theory in the subthreshold region and detail the consequences for the chiral convergence of the threshold parameters and the nucleon mass.
Roy-Steiner equations for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meissner, U. G.
Starting from hyperbolic dispersion relations for the invariant amplitudes of pion-nucleon scattering together with crossing symmetry and unitarity, one can derive a closed system of integral equations for the partial waves of both the s-channel (pi N --> pi N) and the t-channel (pi pi --> Nbar N) reaction, called Roy-Steiner equations. After giving a brief overview of the Roy-Steiner system for pi N scattering, we demonstrate that the solution of the t-channel subsystem, which represents the first step in solving the full system, can be achieved by means of Muskhelishvili-Omn\\`es techniques. In particular, we present results for the P-waves featuring in the dispersive analysis of the electromagnetic form factors of the nucleon.
A New Pion-Nucleon Partial Wave Analysis
NASA Astrophysics Data System (ADS)
Sadler, Michael; Watson, Shon; Stahov, Jugoslav
2006-10-01
Existing determinations of the masses, widths and decay modes of low-lying excited states of the nucleon, as compiled in the Review of Particle Physics, are determined from energy-independent partial wave analyses of pion-nucleon scattering data. For the N*(1440) and most other resonances under 2 GeV, the analyses cited are the Karlsruhe-Helsinki, Carnegie Mellon-Berkeley and Kent State analyses, the latter of which used the elastic amplitudes from the other two. The data included in these analyses were published before 1980. Other analyses, notably the recent ones from George Washington University and the Pittsburgh-Argonne group, are ``not used for averages, fits, limits, etc.'' Complete sets of measurements (differential cross sections, analyzing powers and spin rotation parameters) have been measured in the N*(1440) resonance region since 1980, culminating in the Crystal Ball program at BNL to measure all-neutral final states (charge exchange, multiple pi-zero final states, and inverse photoproduction). A new partial wave analysis of the Karlsruhe-Helsinki type has been started by Abilene Christian University, University of Tuzla, and Rudjer Boskovic Institute. The analysis is constrained by fixed-t and interior hyperbolic dispersion relations. Comparisons of the new analysis to modern experimental data and to previous analyses will be presented.
Reconciling threshold and subthreshold expansions for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Siemens, D.; Ruiz de Elvira, J.; Epelbaum, E.; Hoferichter, M.; Krebs, H.; Kubis, B.; Meißner, U.-G.
2017-07-01
Heavy-baryon chiral perturbation theory (ChPT) at one loop fails in relating the pion-nucleon amplitude in the physical region and for subthreshold kinematics due to loop effects enhanced by large low-energy constants. Studying the chiral convergence of threshold and subthreshold parameters up to fourth order in the small-scale expansion, we address the question to what extent this tension can be mitigated by including the Δ (1232) as an explicit degree of freedom and/or using a covariant formulation of baryon ChPT. We find that the inclusion of the Δ indeed reduces the low-energy constants to more natural values and thereby improves consistency between threshold and subthreshold kinematics. In addition, even in the Δ-less theory the resummation of 1 /mN corrections in the covariant scheme improves the results markedly over the heavy-baryon formulation, in line with previous observations in the single-baryon sector of ChPT that so far have evaded a profound theoretical explanation.
Roy-Steiner equations for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.
2012-06-01
Starting from hyperbolic dispersion relations, we derive a closed system of Roy-Steiner equations for pion-nucleon scattering that respects analyticity, unitarity, and crossing symmetry. We work out analytically all kernel functions and unitarity relations required for the lowest partial waves. In order to suppress the dependence on the high energy regime we also consider once- and twice-subtracted versions of the equations, where we identify the subtraction constants with subthreshold parameters. Assuming Mandelstam analyticity we determine the maximal range of validity of these equations. As a first step towards the solution of the full system we cast the equations for the π π to overline N N partial waves into the form of a Muskhelishvili-Omnès problem with finite matching point, which we solve numerically in the single-channel approximation. We investigate in detail the role of individual contributions to our solutions and discuss some consequences for the spectral functions of the nucleon electromagnetic form factors.
NASA Astrophysics Data System (ADS)
Yao, De-Liang; Siemens, D.; Bernard, V.; Epelbaum, E.; Gasparyan, A. M.; Gegelia, J.; Krebs, H.; Meißner, Ulf-G.
2016-05-01
We present the results of a third order calculation of the pion-nucleon scattering amplitude in a chiral effective field theory with pions, nucleons and delta resonances as explicit degrees of freedom. We work in a manifestly Lorentz invariant formulation of baryon chiral perturbation theory using dimensional regularization and the extended on-mass-shell renormalization scheme. In the delta resonance sector, the on mass-shell renormalization is realized as a complex-mass scheme. By fitting the low-energy constants of the effective Lagrangian to the S- and P -partial waves a satisfactory description of the phase shifts from the analysis of the Roy-Steiner equations is obtained. We predict the phase shifts for the D and F waves and compare them with the results of the analysis of the George Washington University group. The threshold parameters are calculated both in the delta-less and delta-full cases. Based on the determined low-energy constants, we discuss the pion-nucleon sigma term. Additionally, in order to determine the strangeness content of the nucleon, we calculate the octet baryon masses in the presence of decuplet resonances up to next-to-next-to-leading order in SU(3) baryon chiral perturbation theory. The octet baryon sigma terms are predicted as a byproduct of this calculation.
a Phenomenological Determination of the Pion-Nucleon Scattering Lengths from Pionic Hydrogen
NASA Astrophysics Data System (ADS)
Ericson, T. E. O.; Loiseau, B.; Wycech, S.
A model independent expression for the electromagnetic corrections to a phenomenological hadronic pion-nucleon (πN) scattering length ah, extracted from pionic hydrogen, is obtained. In a non-relativistic approach and using an extended charge distribution, these corrections are derived up to terms of order α2 log α in the limit of a short-range hadronic interaction. We infer ahπ ^-p=0.0870(5)m-1π which gives for the πNN coupling through the GMO relation g2π ^± pn/(4π )=14.04(17).
Solution of the Bethe-Salpeter equation for pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Lahiff, A. D.; Afnan, I. R.
1999-08-01
A relativistic description of pion-nucleon scattering based on the four-dimensional Bethe-Salpeter equation is presented. The kernel of the equation consists of s- and u-channel nucleon and Δ(1232) pole diagrams, as well as ρ and σ exchange in the t channel. The Bethe-Salpeter equation is solved by means of a Wick rotation, and good fits are obtained to the s- and p-wave πN phase shifts up to 360 MeV pion laboratory energy. The coupling constants determined by the fits are consistent with the commonly accepted values in the literature.
Elastic pion-nucleon scattering in chiral perturbation theory: A fresh look
NASA Astrophysics Data System (ADS)
Siemens, D.; Bernard, V.; Epelbaum, E.; Gasparyan, A.; Krebs, H.; Meißner, Ulf-G.
2016-07-01
Elastic pion-nucleon scattering is analyzed in the framework of chiral perturbation theory up to fourth order within the heavy-baryon expansion and a covariant approach based on an extended on-mass-shell renormalization scheme. We discuss in detail the renormalization of the various low-energy constants and provide explicit expressions for the relevant β functions and the finite subtractions of the power-counting breaking terms within the covariant formulation. To estimate the theoretical uncertainty from the truncation of the chiral expansion, we employ an approach which has been successfully applied in the most recent analysis of the nuclear forces. This allows us to reliably extract the relevant low-energy constants from the available scattering data at low energy. The obtained results provide clear evidence that the breakdown scale of the chiral expansion for this reaction is related to the Δ resonance. The explicit inclusion of the leading contributions of the Δ isobar is demonstrated to substantially increase the range of applicability of the effective field theory. The resulting predictions for the phase shifts are in an excellent agreement with the predictions from the recent Roy-Steiner-equation analysis of pion-nucleon scattering.
A relativistic meson-exchange model of pion-nucleon scattering
Lee, T.S.H.; Hung, C.T.; Yang, S.N.
1995-08-01
Pion-nucleon scattering is investigated using the Kadshevsky three-dimensional reduction of the Bethe-Salpeter equation. The resulting potential includes the direct and crossed N and {Delta} terms, and the t-channel {sigma}- and {rho}-exchange terms. The nucleon-pole condition is imposed to define the renormalization of the nucleon mass and the {pi}NN coupling constant. A mixture of the scalar and vector {sigma}{pi}{pi} couplings is introduced to simulate the broad width of the s-wave correlated two-pion exchange mechanism. Good descriptions of the {pi}N phase shifts up to 400 MeV have been obtained in all S- and P-waves. The off-shell behavior for our model differs significantly from that obtained using different reductions. A paper describing our results was published.
Matching Pion-Nucleon Roy-Steiner Equations to Chiral Perturbation Theory
NASA Astrophysics Data System (ADS)
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2015-11-01
We match the results for the subthreshold parameters of pion-nucleon scattering obtained from a solution of Roy-Steiner equations to chiral perturbation theory up to next-to-next-to-next-to-leading order, to extract the pertinent low-energy constants including a comprehensive analysis of systematic uncertainties and correlations. We study the convergence of the chiral series by investigating the chiral expansion of threshold parameters up to the same order and discuss the role of the Δ (1232 ) resonance in this context. Results for the low-energy constants are also presented in the counting scheme usually applied in chiral nuclear effective field theory, where they serve as crucial input to determine the long-range part of the nucleon-nucleon potential as well as three-nucleon forces.
High-Precision Determination of the Pion-Nucleon σ Term from Roy-Steiner Equations
NASA Astrophysics Data System (ADS)
Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.
2015-08-01
We present a determination of the pion-nucleon (π N ) σ term σπ N based on the Cheng-Dashen low-energy theorem (LET), taking advantage of the recent high-precision data from pionic atoms to pin down the π N scattering lengths as well as of constraints from analyticity, unitarity, and crossing symmetry in the form of Roy-Steiner equations to perform the extrapolation to the Cheng-Dashen point in a reliable manner. With isospin-violating corrections included both in the scattering lengths and the LET, we obtain σπ N=(59.1 ±1.9 ±3.0 ) MeV =(59.1 ±3.5 ) MeV , where the first error refers to uncertainties in the π N amplitude and the second to the LET. Consequences for the scalar nucleon couplings relevant for the direct detection of dark matter are discussed.
Temporal Dynamic Controllability Revisited
NASA Technical Reports Server (NTRS)
Morris, Paul H.; Muscettola, Nicola
2005-01-01
An important issue for temporal planners is the ability to handle temporal uncertainty. We revisit the question of how to determine whether a given set of temporal requirements are feasible in the light of uncertain durations of some processes. In particular, we consider how best to determine whether a network is Dynamically Controllable, i.e., whether a dynamic strategy exists for executing the network that is guaranteed to satisfy the requirements. Previous work has shown the existence of a pseudo-polynomial algorithm for testing Dynamic Controllability. Here, we greatly simplify the previous framework, and present a true polynomial algorithm with a cutoff based only on the number of nodes.
Determination of the pion-nucleon coupling constant and scattering lengths
NASA Astrophysics Data System (ADS)
Ericson, T. E.; Loiseau, B.; Thomas, A. W.
2002-07-01
We critically evaluate the isovector Goldberger-Miyazawa-Oehme (GMO) sum rule for forward πN scattering using the recent precision measurements of π-p and π-d scattering lengths from pionic atoms. We deduce the charged-pion-nucleon coupling constant, with careful attention to systematic and statistical uncertainties. This determination gives, directly from data, g2c(GMO)/ 4π=14.11+/-0.05(statistical)+/-0.19(systematic) or f2c/4π=0.0783(11). This value is intermediate between that of indirect methods and the direct determination from backward np differential scattering cross sections. We also use the pionic atom data to deduce the coherent symmetric and antisymmetric sums of the pion-proton and pion-neutron scattering lengths with high precision, namely, (aπ-p+aπ-n)/2=[- 12+/-2(statistical)+/-8(systematic)]×10-4 m-1π and (aπ-p-aπ- n)/2=[895+/-3(statistical)+/-13 (systematic)]×10-4 m-1π. For the need of the present analysis, we improve the theoretical description of the pion-deuteron scattering length.
Dynamic causal modelling revisited.
Friston, K J; Preller, Katrin H; Mathys, Chris; Cagnan, Hayriye; Heinzle, Jakob; Razi, Adeel; Zeidman, Peter
2017-02-17
This paper revisits the dynamic causal modelling of fMRI timeseries by replacing the usual (Taylor) approximation to neuronal dynamics with a neural mass model of the canonical microcircuit. This provides a generative or dynamic causal model of laminar specific responses that can generate haemodynamic and electrophysiological measurements. In principle, this allows the fusion of haemodynamic and (event related or induced) electrophysiological responses. Furthermore, it enables Bayesian model comparison of competing hypotheses about physiologically plausible synaptic effects; for example, does attentional modulation act on superficial or deep pyramidal cells - or both? In this technical note, we describe the resulting dynamic causal model and provide an illustrative application to the attention to visual motion dataset used in previous papers. Our focus here is on how to answer long-standing questions in fMRI; for example, do haemodynamic responses reflect extrinsic (afferent) input from distant cortical regions, or do they reflect intrinsic (recurrent) neuronal activity? To what extent do inhibitory interneurons contribute to neurovascular coupling? What is the relationship between haemodynamic responses and the frequency of induced neuronal activity? This paper does not pretend to answer these questions; rather it shows how they can be addressed using neural mass models of fMRI timeseries.
NASA Astrophysics Data System (ADS)
Moresi, Louis
2015-04-01
Dynamic Topography Revisited Dynamic topography is usually considered to be one of the trinity of contributing causes to the Earth's non-hydrostatic topography along with the long-term elastic strength of the lithosphere and isostatic responses to density anomalies within the lithosphere. Dynamic topography, thought of this way, is what is left over when other sources of support have been eliminated. An alternate and explicit definition of dynamic topography is that deflection of the surface which is attributable to creeping viscous flow. The problem with the first definition of dynamic topography is 1) that the lithosphere is almost certainly a visco-elastic / brittle layer with no absolute boundary between flowing and static regions, and 2) the lithosphere is, a thermal / compositional boundary layer in which some buoyancy is attributable to immutable, intrinsic density variations and some is due to thermal anomalies which are coupled to the flow. In each case, it is difficult to draw a sharp line between each contribution to the overall topography. The second definition of dynamic topography does seem cleaner / more precise but it suffers from the problem that it is not measurable in practice. On the other hand, this approach has resulted in a rich literature concerning the analysis of large scale geoid and topography and the relation to buoyancy and mechanical properties of the Earth [e.g. refs 1,2,3] In convection models with viscous, elastic, brittle rheology and compositional buoyancy, however, it is possible to examine how the surface topography (and geoid) are supported and how different ways of interpreting the "observable" fields introduce different biases. This is what we will do. References (a.k.a. homework) [1] Hager, B. H., R. W. Clayton, M. A. Richards, R. P. Comer, and A. M. Dziewonski (1985), Lower mantle heterogeneity, dynamic topography and the geoid, Nature, 313(6003), 541-545, doi:10.1038/313541a0. [2] Parsons, B., and S. Daly (1983), The
Sadler, M.E.; Isenhower, L.D.
1992-02-15
This report discusses research on the following topics: pion-nucleon interactions; detector tomography facility; nuclear dependence of charm and beauty quark production and a study of two-prong decays of neutral D and B mesons; N* collaboration at CEBAF; and pilac experiments. (LSP)
Pion-nucleon scattering in the Roper channel from lattice QCD
Lang, Christian B.; Leskovec, L.; Padmanath, M.; ...
2017-01-31
We present a lattice QCD study ofmore » $$N\\pi$$ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance $N^*(1440)$ resides in experiment. The study is based on the PACS-CS ensemble of gauge configurations with $$N_f=2+1$$ Wilson-clover dynamical fermions, $$m_\\pi \\simeq 156~$$MeV and $$L\\simeq 2.9~$$fm. In addition to a number of $qqq$ interpolating fields, we implement operators for $$N\\pi$$ in $p$-wave and $$N\\sigma$$ in $s$-wave. In the center-of-momentum frame we find three eigenstates below 1.65 GeV. They are dominated by $N(0)$, $$N(0)\\pi(0)\\pi(0)$$ (mixed with $$N(0)\\sigma(0)$$) and $$N(p)\\pi(-p)$$ with $$p\\simeq 2\\pi/L$$, where momenta are given in parentheses. This is the first simulation where the expected multi-hadron states are found in this channel. The experimental $$N\\pi$$ phase-shift would -- in the approximation of purely elastic $$N\\pi$$ scattering -- imply an additional eigenstate near the Roper mass $$m_R\\simeq 1.43~$$GeV for our lattice size. We do not observe any such additional eigenstate, which indicates that $$N\\pi$$ elastic scattering alone does not render a low-lying Roper. Coupling with other channels, most notably with $$N\\pi\\pi$$, seems to be important for generating the Roper resonance, reinforcing the notion that this state could be a dynamically generated resonance. Our results are in line with most of previous lattice studies based just on $qqq$ interpolators, that did not find a Roper eigenstate below $1.65~$GeV. As a result, the study of the coupled-channel scattering including a three-particle decay $$N\\pi\\pi$$ remains a challenge.« less
Pion-nucleon scattering in the Roper channel from lattice QCD
NASA Astrophysics Data System (ADS)
Lang, C. B.; Leskovec, L.; Padmanath, M.; Prelovsek, S.
2017-01-01
We present a lattice QCD study of N π scattering in the positive-parity nucleon channel, where the puzzling Roper resonance N*(1440 ) resides in experiment. The study is based on the PACS-CS ensemble of gauge configurations with Nf=2 +1 Wilson-clover dynamical fermions, mπ≃156 MeV and L ≃2.9 fm . In addition to a number of q q q interpolating fields, we implement operators for N π in p -wave and N σ in s -wave. In the center-of-momentum frame we find three eigenstates below 1.65 GeV. They are dominated by N (0 ), N (0 )π (0 )π (0 ) [mixed with N (0 )σ (0 )] and N (p )π (-p ) with p ≃2 π /L , where momenta are given in parentheses. This is the first simulation where the expected multi-hadron states are found in this channel. The experimental N π phase shift would—in the approximation of purely elastic N π scattering—imply an additional eigenstate near the Roper mass mR≃1.43 GeV for our lattice size. We do not observe any such additional eigenstate, which indicates that N π elastic scattering alone does not render a low-lying Roper. Coupling with other channels, most notably with N π π , seems to be important for generating the Roper resonance, reinforcing the notion that this state could be a dynamically generated resonance. Our results are in line with most of the previous lattice studies based just on q q q interpolators, which did not find a Roper eigenstate below 1.65 GeV. The study of the coupled-channel scattering including a three-particle decay N π π remains a challenge.
NASA Astrophysics Data System (ADS)
Lukyanov, V. K.; Zemlyanaya, E. V.; Lukyanov, K. V.; Abdul-Magead, I. A. M.
2016-11-01
The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π ±-mesons on 28Si, 40Ca, 58Ni, and 208Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2+ and 3- collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion-nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole ( β 2) and octupole ( β 3) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion-nucleon amplitude is emphasized.
Sadler, M.E.; Isenhower, L.D.
1992-02-15
This report discusses research on the following topics: pion-nucleon interactions; detector tomography facility; nuclear dependence of charm and beauty quark production and a study of two-prong decays of neutral D and B mesons; N* collaboration at CEBAF; and pilac experiments. (LSP)
Suleiman, R
2003-05-01
The longest range weak pion-nucleon coupling constant, h^{1}/_{n} is important for nuclear parity violation. However, after considerable effort in the past two decades, its value is still poorly known largely due to many-body theoretical uncertainties. Prospects of a new measurement of h^{1}/_{n} in a theoretically clean process are presented. A measurement of the parity-violating asymmetry in pion photoproduction off the proton is related to h^{1}/_{n} in a low-energy theorem for the photon polarization asymmetry at threshold in the chiral limit. At present two completed experiments - photon circular polarization for ^{18}F and the anapole moment of ^{133}Cs - have been interpreted to give very different values of h^{1}/_{n}. This experiment will be the first attempt to measure h^{1}/_{n} in the single nucleon system. A reliable measurement of h^{1}/_{n} provides a crucial test of the meson-exchange picture of the weak NN interaction. Such a test of the meson-exchange picture will shed light on low energy QCD.
Spin effects in pion-nucleon and nucleon-nucleon scattering at high energies and fixed angles
NASA Astrophysics Data System (ADS)
Chavleishvili, M. P.
1989-05-01
Based on the study of the general structure of helicity amplitudes, obligatory kinematic factors are separated and the so-called dynamic amplitudes are introduced. These factors make conservation laws fulfill and contain all the kinematic singularities of helicity amplitudes. Via the dynamic amplitudes, the observable quantities are expressed in a simple form. Kinematic factors play the role of weighting functions. At high energies and fixed angles these factors turn into small parameters which suppress contributions of some helicity amplitudes, and enhance contributions of others. So we get the kinematic hierarchy for binary processes. As an example we consider πN- and NN-scattering. Predictions are given for some asymmetry parameters which do not coincide with the helicity conservation rules, predicted by QCD.
The beauty and charm production cross-sections in 250-GeV/C pion - nucleon interactions
Darling, Christopher Lynn
1993-01-01
By determining the production cross sections for heavy flavor hadrons, we test the theoretical predictions from perturhative quantum chroma-dynamics (QCD). In the case of pion induced beauty production, the few published results do not resolve the issue of the applicability of perturbative QCD. This analysis is undertaken in order to help resolve this situation. We determine the total beauty and charm production cross sections using an analysis of single electron decay products. We extract the cross sections per nucleon from the two-dimensional distribution of electron p versus impact parameter ( d) to the primary vertex. We place an upper limit on the beauty production cross section of σ_{b$\\bar{b}$} < 105 nb at the 90% confidence level, where the limit includes both statistical and systematic errors. The charm production cross section is determined to be σ_{c}c = 13.9$+2.4/atop{-2.3}$ (stat) ± 1.8 (syst) μ.b, which is in good agreement with next-to-leading order QCD predictions and other measurements.
Exclusive measurements of pion nucleon going to pion pion nucleon
NASA Astrophysics Data System (ADS)
Kermani, Mohammad Arjomand
The pion induced pion production reactions π±p/toπ±π+n were studied at projectile incident energies of 223, 243, 264, 284, and 305 MeV. The Canadian High Acceptance Orbit Spectrometer (CHAOS) was used to detected the charged particles, which originated from the interaction of the incident pion beam with a cryogenic liquid hydrogen target. The experimental results are presented in the form of single, double and triple differential cross sections. Total cross sections obtained by integrating the differential quantities are also reported. The experimental data, namely the π-p/toπ-π+n double differential cross sections, were used as input to the Chew-Low extrapolation procedure which was utilized to determine on-shell π+π- elastic scattering cross sections in the near threshold region. The Chew-Low results (the extrapolated πpi cross sections) were then used in a dispersion analysis (Roy equations) to obtain the πpi isospin zero S-wave scattering length. We find a00=0.209/pm 0.011μ-1. In addition, the invariant mass distributions from the (π+π-) channel were fitted to determine the model parameters for the extended model of Oset and Vicente-Vacas. We find that the model parameters obtained from fitting the (π+π-) data do not describe the invariant mass distributions in the (π+π+) channel.
Toward complete pion nucleon amplitudes
Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; ...
2015-10-05
We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.
Toward complete pion nucleon amplitudes
Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; Pennington, Michael R.; Schott, Diane M.; Szczepaniak, Adam P.; Fox, G.
2015-10-05
We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.
Chiral dynamics with (non)strange quarks
NASA Astrophysics Data System (ADS)
Kubis, Bastian; Meißner, Ulf-G.
2017-01-01
We review the results and achievements of the project B.3. Topics addressed include pion photoproduction off the proton and off deuterium, three-flavor chiral perturbation theory studies, chiral symmetry tests in Goldstone boson decays, the development of unitarized chiral perturbation theory to next-to-leading order, the two-pole structure of the Λ(1405), the dynamical generation of the lowest S11 resonances, the theory of hadronic atoms and its application to various systems, precision studies in light-meson decays based on dispersion theory, the Roy-Steiner analysis of pion-nucleon scattering, a high-precision extraction of the elusive pion-nucleon σ-term, and aspects of chiral dynamics in few-nucleon systems.
Factorizable Language Revisited from Dynamics to Biology
NASA Astrophysics Data System (ADS)
Hao, Bailin; Xie, Huimin
A formal language is called factorizable if any substring of a word in it also belongs to the language. Symbolic sequences from symbolic dynamics make factorizable languages by definition. In studying avoided and under-represented strings in bacterial genomes we have defined a factorizable language for each complete genome. Recently, in studying the problem of uniqueness of reconstruction of a protein sequence from its constituent K-peptides we encounter again factorizable language which helps to build a finite state automaton to recognize the uniqueness of reconstruction. We present a brief review of these applications of factorizable languages from dynamics to biology.
Dynamic properties of liquid Ni revisited
NASA Astrophysics Data System (ADS)
del Rio, B. G.; González, L. E.; González, D. J.
2017-08-01
Liquid Ni has previously been studied by different approaches such as molecular dynamics simulations and experimental techniques including inelastic neutron and X-ray scattering. Although some puzzling results, such as the shape of the sound dispersion curve for q ≤ 1.0 Å-1, have already been sorted out, there still persist some discrepancies, among different studies, for greater q-values. We have performed ab initio simulation calculations which show how those differences can be reconciled. Moreover, we have found that the transverse current spectral functions have some features which, so far, had previously been shown by high pressure liquid metals.
Revisiting approximate dynamic programming and its convergence.
Heydari, Ali
2014-12-01
Value iteration-based approximate/adaptive dynamic programming (ADP) as an approximate solution to infinite-horizon optimal control problems with deterministic dynamics and continuous state and action spaces is investigated. The learning iterations are decomposed into an outer loop and an inner loop. A relatively simple proof for the convergence of the outer-loop iterations to the optimal solution is provided using a novel idea with some new features. It presents an analogy between the value function during the iterations and the value function of a fixed-final-time optimal control problem. The inner loop is utilized to avoid the need for solving a set of nonlinear equations or a nonlinear optimization problem numerically, at each iteration of ADP for the policy update. Sufficient conditions for the uniqueness of the solution to the policy update equation and for the convergence of the inner-loop iterations to the solution are obtained. Afterwards, the results are formed as a learning algorithm for training a neurocontroller or creating a look-up table to be used for optimal control of nonlinear systems with different initial conditions. Finally, some of the features of the investigated method are numerically analyzed.
Dynamical Properties of Internal Shocks Revisited
NASA Astrophysics Data System (ADS)
Pe’er, Asaf; Long, Killian; Casella, Piergiorgio
2017-09-01
Internal shocks between propagating plasma shells, originally ejected at different times with different velocities, are believed to play a major role in dissipating the kinetic energy, thereby explaining the observed light curves and spectra in a large range of transient objects. Even if initially the colliding plasmas are cold, following the first collision, the plasma shells are substantially heated, implying that in a scenario of multiple collisions, most collisions take place between plasmas of non-zero temperatures. Here, we calculate the dynamical properties of plasmas resulting from a collision between arbitrarily hot plasma shells, moving at arbitrary speeds. We provide simple analytical expressions valid for both ultrarelativistic and Newtonian velocities for both hot and cold plasmas. We derive the minimum criteria required for the formation of the two-shock wave system, and show that in the relativistic limit, the minimum Lorentz factor is proportional to the square root of the ratio of the initial plasmas enthalpies. We provide basic scaling laws of synchrotron emission from both the forward and reverse-shock waves, and show how these can be used to deduce the properties of the colliding shells. Finally, we discuss the implications of these results in the study of several astronomical transients, such as X-ray binaries, radio-loud quasars, and gamma-ray bursts.
The dynamics of three vortices revisited
NASA Technical Reports Server (NTRS)
Tavantzis, John; Ting, LU
1988-01-01
The dynamics of three vortices was studied by Synge (1949) using the length of the sides of the triangle formed by the vortices as prime variables. The critical states at which the lengths of the sides remain fixed throughout the motion were found to be either equilateral triangles or collinear configurations. The equilateral configurations were either stable or unstable depending on whether the sum of the products of strengths K was greater or less than zero, respectively. In the case of K = 0, a one-parameter family of solutions of contracting and another of expanding similar triangles were found. It is shown here that, for this special case, the family of contracting similar solutions is always unstable while the family of expanding ones is stable. The critical states for collinear configurations in the general case are studied where K is greater than or less than zero. It is shown that there are either six or four critical states depending on the strengths of the vortices. The properties of these states are discussed.
The dynamics of three vortices revisited
NASA Technical Reports Server (NTRS)
Tavantzis, John; Ting, LU
1988-01-01
The dynamics of three vortices was studied by Synge (1949) using the length of the sides of the triangle formed by the vortices as prime variables. The critical states at which the lengths of the sides remain fixed throughout the motion were found to be either equilateral triangles or collinear configurations. The equilateral configurations were either stable or unstable depending on whether the sum of the products of strengths K was greater or less than zero, respectively. In the case of K = 0, a one-parameter family of solutions of contracting and another of expanding similar triangles were found. It is shown here that, for this special case, the family of contracting similar solutions is always unstable while the family of expanding ones is stable. The critical states for collinear configurations in the general case are studied where K is greater than or less than zero. It is shown that there are either six or four critical states depending on the strengths of the vortices. The properties of these states are discussed.
Fast dynamics in glass-forming polymers revisited
Colmenero, J.; Arbe, A.; Mijangos, C.; Reinecke, H.
1997-12-31
The so called fast-dynamics of glass-forming systems as observed by time of flight (TOF) neutron scattering techniques is revisited. TOF-results corresponding to several glass-forming polymers with different chemical microstructure and glass-transition temperature are presented together with the theoretical framework proposed by the authors to interpret these results. The main conclusion is that the TOF-data can be explained in terms of quasiharmonic vibrations and the particular short time behavior of the segmental dynamics. The segmental dynamics display in the very short time range (t {approx} 2 ps) a crossover from a simple exponential behavior towards a non-exponential regime. The first exponential decay, which is controlled by C-C rotational barriers, can be understood as a trace of the behavior of the system in absence of the effects (correlations, cooperativity, memory effects {hor_ellipsis}) which characterize the dense supercooled liquid like state against the normal liquid state. The non-exponential regime at t > 2 ps corresponds to what is usually understood as {alpha} and {beta} relaxations. Some implications of these results are also discussed.
Dynamics of personality test responses: the empiricist's manifesto revisited.
Butcher, J N
2000-03-01
This article revisits the classic empirical manifesto written by Meehl in 1945, and examines subsequent developments in structured personality assessment. The current status of personality assessment from an empirical-scale-development perspective is presented, with examples drawn from recent work on the MMPI-2. Meehl's heuristic defense of empirically based personality-scale construction was reexamined and the lasting influences of these views were highlighted. Meehl's early conceptualization of the relative unimportance of item content in personality-test construction and several alternative views were summarized, and Meehl's modified position was described. The role that test-taking attitudes can play in personality assessment was discussed in the 1945 article, and Meehl's views on the need for appraisal of invalidating conditions have been reaffirmed in contemporary test development. Finally, the so-called "dynamics" of a structured personality item response were discussed from a contemporary perspective, and some recent research was included to illustrate the continued importance of anchoring test interpretation in empirical correlates.
Quantum-mechanical picture of peripheral chiral dynamics
NASA Astrophysics Data System (ADS)
Granados, C.; Weiss, C.
2015-08-01
The nucleon's peripheral transverse charge and magnetization densities are computed in chiral effective field theory. The densities are represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft pion-nucleon intermediate states. The orbital motion of the pion causes a large left-right asymmetry in a transversely polarized nucleon. The effect attests to the relativistic nature of chiral dynamics [pion momenta k =O (Mπ) ] and could be observed in form factor measurements at low momentum transfer.
Quantum-mechanical picture of peripheral chiral dynamics
Granados, Carlos; Weiss, Christian
2015-08-28
The nucleon's peripheral transverse charge and magnetization densities are computed in chiral effective field theory. The densities are represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft pion-nucleon intermediate states. The orbital motion of the pion causes a large left-right asymmetry in a transversely polarized nucleon. As a result, the effect attests to the relativistic nature of chiral dynamics [pion momenta k = O(M_{π})] and could be observed in form factor measurements at low momentum transfer.
Richards model revisited: validation by and application to infection dynamics.
Wang, Xiang-Sheng; Wu, Jianhong; Yang, Yong
2012-11-21
Ever since Richards proposed his flexible growth function more than half a century ago, it has been a mystery that this empirical function has made many incredible coincidences with real ecological or epidemic data even though one of its parameters (i.e., the exponential term) does not seem to have clear biological meaning. It is therefore a natural challenge to mathematical biologists to provide an explanation of the interesting coincidences and a biological interpretation of the parameter. Here we start from a simple epidemic SIR model to revisit Richards model via an intrinsic relation between both models. Especially, we prove that the exponential term in the Richards model has a one-to-one nonlinear correspondence to the basic reproduction number of the SIR model. This one-to-one relation provides us an explicit formula in calculating the basic reproduction number. Another biological significance of our study is the observation that the peak time is approximately just a serial interval after the turning point. Moreover, we provide an explicit relation between final outbreak size, basic reproduction number and the peak epidemic size which means that we can predict the final outbreak size shortly after the peak time. Finally, we introduce a constraint in Richards model to address over fitting problem observed in the existing studies and then apply our method with constraint to conduct some validation analysis using the data of recent outbreaks of prototype infectious diseases such as Canada 2009 H1N1 outbreak, GTA 2003 SARS outbreak, Singapore 2005 dengue outbreak, and Taiwan 2003 SARS outbreak. Our new formula gives much more stable and precise estimate of model parameters and key epidemic characteristics such as the final outbreak size, the basic reproduction number, and the turning point, compared with earlier simulations without constraints.
System identification based approach to dynamic weighing revisited
NASA Astrophysics Data System (ADS)
Niedźwiecki, Maciej; Meller, Michał; Pietrzak, Przemysław
2016-12-01
Dynamic weighing, i.e., weighing of objects in motion, without stopping them on the weighing platform, allows one to increase the rate of operation of automatic weighing systems, used in industrial production processes, without compromising their accuracy. Since the classical identification-based approach to dynamic weighing, based on the second-order mass-spring-damper model of the weighing system, does not yield satisfactory results when applied to conveyor belt type checkweighers, several extensions of this technique are examined. Experiments confirm that when appropriately modified the identification-based approach becomes a reliable tool for dynamic mass measurement in checkweighers.
Extensional channel flow revisited: a dynamical systems perspective
NASA Astrophysics Data System (ADS)
Marques, Francisco; Meseguer, Alvaro; Mellibovsky, Fernando; Weidman, Patrick D.
2017-06-01
Extensional self-similar flows in a channel are explored numerically for arbitrary stretching-shrinking rates of the confining parallel walls. The present analysis embraces time integrations, and continuations of steady and periodic solutions unfolded in the parameter space. Previous studies focused on the analysis of branches of steady solutions for particular stretching-shrinking rates, although recent studies focused also on the dynamical aspects of the problems. We have adopted a dynamical systems perspective, analysing the instabilities and bifurcations the base state undergoes when increasing the Reynolds number. It has been found that the base state becomes unstable for small Reynolds numbers, and a transitional region including complex dynamics takes place at intermediate Reynolds numbers, depending on the wall acceleration values. The base flow instabilities are constitutive parts of different codimension-two bifurcations that control the dynamics in parameter space. For large Reynolds numbers, the restriction to self-similarity results in simple flows with no realistic behaviour, but the flows obtained in the transition region can be a valuable tool for the understanding of the dynamics of realistic Navier-Stokes solutions.
Subpicosecond measurements of polar solvation dynamics: Coumarin 153 revisited
Horng, M.L.; Gardecki, J.A.; Papazyan, A.; Maroncelli, M.
1995-11-30
Time-resolved emission measurements of the solute coumarin 153 (C153) are used to probe the time dependence of solvation in 24 common solvents at room temperature. Significant improvements in experimental time resolution ({approx}100 fs instrument response) as well as corresponding improvements in analysis methods provide confidence that all of the spectral evolution (including both the inertial and the diffusive parts of the response) are observed in these measurements. Extensive data concerning the steady-state solvatochromism of C153, coupled to an examination of the effects of vibrational relaxation, further demonstrate that the spectral dynamics being observed accurately monitor the dynamics of nonspecific solvation. Comparisons to theoretical predictions show that models based on the dielectric response of the pure solvent provide a semiquantitative understanding of the dynamics observed. 156 refs., 26 figs., 5 tabs.
Revisiting r > g-The asymptotic dynamics of wealth inequality
NASA Astrophysics Data System (ADS)
Berman, Yonatan; Shapira, Yoash
2017-02-01
Studying the underlying mechanisms of wealth inequality dynamics is essential for its understanding and for policy aiming to regulate its level. We apply a heterogeneous non-interacting agent-based modeling approach, solved using iterated maps to model the dynamics of wealth inequality based on 3 parameters-the economic output growth rate g, the capital value change rate a and the personal savings rate s and show that for a < g the wealth distribution reaches an asymptotic shape and becomes close to the income distribution. If a > g, the wealth distribution constantly becomes more and more inegalitarian. We also show that when a < g, wealth is asymptotically accumulated at the same rate as the economic output, which also implies that the wealth-disposable income ratio asymptotically converges to s /(g - a) .
Quantum critical point revisited by dynamical mean-field theory
Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.
2017-03-31
Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations basedmore » on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.« less
The “anomalous” dynamics of decahyroisoquinoline revisited
Casalini, R.; Roland, C. M.
2016-01-14
Decahydroisoquinoline (DHIQ) appears to be a unique material—the only non-associated, simple liquid with dynamics deviating from density scaling. To examine whether this anomaly is real, the density, ρ, of DHIQ was measured at temperatures, T, as low as 214 K and pressures up to ∼1.2 GPa. This enabled the equation of state (EoS) to be determined, without extrapolation, over the range of thermodynamic conditions for which the relaxation times had been reported. Using this less ambiguous EoS, we find that within the precision of the available relaxation times, the latter are a function of T/ρ{sup 3.9}, contrary to previous reports. Thus, the behavior of DHIQ is unexceptional; similar to every non-associated liquid tested to date, its dynamics comply with density scaling.
Revisiting the S-Au(111) interaction: Static or Dynamic?
Biener, M M; Biener, J; Friend, C M
2004-08-17
The chemical inertness typically observed for Au does not imply a general inability to form stable bonds with non-metals but is rather a consequence of high reaction barriers. The Au-S interaction is probably the most intensively studied interaction of Au surfaces with non-metals as, for example, it plays an important role in Au ore formation, and controls the structure and dynamics of thiol-based self-assembled-monolayers (SAMs). In recent years a quite complex picture of the interaction of sulfur with Au(111) surfaces emerged, and a variety of S-induced surface structures was reported under different conditions. The majority of these structures were interpreted in terms of a static Au surface, where the positions of the Au atoms remain essentially unperturbed. Here we demonstrate that the Au(111) surface exhibits a very dynamic character upon interaction with adsorbed sulfur: low sulfur coverages modify the surface stress of the Au surface leading to lateral expansion of the surface layer; large-scale surface restructuring and incorporation of Au atoms into a growing two-dimensional AuS phase were observed with increasing sulfur coverage. These results provide new insight into the Au-S surface chemistry, and reveal the dynamic character of the Au(111) surface.
The dorsal visual stream revisited: Stable circuits or dynamic pathways?
Galletti, Claudio; Fattori, Patrizia
2017-01-23
In both macaque and human brain, information regarding visual motion flows from the extrastriate area V6 along two different paths: a dorsolateral one towards areas MT/V5, MST, V3A, and a dorsomedial one towards the visuomotor areas of the superior parietal lobule (V6A, MIP, VIP). The dorsolateral visual stream is involved in many aspects of visual motion analysis, including the recognition of object motion and self motion. The dorsomedial stream uses visual motion information to continuously monitor the spatial location of objects while we are looking and/or moving around, to allow skilled reaching for and grasping of the objects in structured, dynamically changing environments. Grasping activity is present in two areas of the dorsal stream, AIP and V6A. Area AIP is more involved than V6A in object recognition, V6A in encoding vision for action. We suggest that V6A is involved in the fast control of prehension and plays a critical role in biomechanically selecting appropriate postures during reach to grasp behaviors. In everyday life, numerous functional networks, often involving the same cortical areas, are continuously in action in the dorsal visual stream, with each network dynamically activated or inhibited according to the context. The dorsolateral and dorsomedial streams represent only two examples of these networks. Many others streams have been described in the literature, but it is worthwhile noting that the same cortical area, and even the same neurons within an area, are not specific for just one functional property, being part of networks that encode multiple functional aspects. Our proposal is to conceive the cortical streams not as fixed series of interconnected cortical areas in which each area belongs univocally to one stream and is strictly involved in only one function, but as interconnected neuronal networks, often involving the same neurons, that are involved in a number of functional processes and whose activation changes dynamically according
Diagnosing erectile dysfunction: the penile dynamic colour duplex ultrasound revisited.
Aversa, A; Bruzziches, R; Spera, G
2005-12-01
A number of disease processes of the penis including Peyronie's disease, priapism, penile fractures and tumors are clearly visualized with ultrasound. Diagnostic evaluation of erectile dysfunction (ED) by penile dynamic colour-duplex Doppler ultrasonography (D-CDDU) is actually considered a second level approach to ED patients because of the fact that intracavernous injections test IV with prostaglandin-E(1) may provide important information about the patients' erectile capacity. However, no direct vascular imaging and a high percentage of false negative diagnoses of vasculogenic ED are its major pitfalls and subsequent treatment decisions remain quite limited. The occurrence of ED and its sentinel relationship to cardiovascular disease has prompted more accurate vascular screening in all patients even in the absence of cardiovascular risk factors. The sonographic evaluation of the intima-media thickness of the carotid arteries may sometimes represent an early manifestation of diffuse atherosclerotic disease and endothelial damage. This latter finding is often the cause of failure to oral agents, i.e. phosphodiesterase inhibitors, because of inability of the dysfunctional endothelium to release nitric oxide. D-CDDU represents an accurate tool to investigate cavernous artery inflow and venous leakage when compared with more invasive diagnostic techniques i.e. selective arteriography and dynamic infusion cavernosometry along with cavernosography.
Autonomic neural control of heart rate during dynamic exercise: revisited
White, Daniel W; Raven, Peter B
2014-01-01
The accepted model of autonomic control of heart rate (HR) during dynamic exercise indicates that the initial increase is entirely attributable to the withdrawal of parasympathetic nervous system (PSNS) activity and that subsequent increases in HR are entirely attributable to increases in cardiac sympathetic activity. In the present review, we sought to re-evaluate the model of autonomic neural control of HR in humans during progressive increases in dynamic exercise workload. We analysed data from both new and previously published studies involving baroreflex stimulation and pharmacological blockade of the autonomic nervous system. Results indicate that the PSNS remains functionally active throughout exercise and that increases in HR from rest to maximal exercise result from an increasing workload-related transition from a 4 : 1 vagal–sympathetic balance to a 4 : 1 sympatho–vagal balance. Furthermore, the beat-to-beat autonomic reflex control of HR was found to be dependent on the ability of the PSNS to modulate the HR as it was progressively restrained by increasing workload-related sympathetic nerve activity. In conclusion: (i) increases in exercise workload-related HR are not caused by a total withdrawal of the PSNS followed by an increase in sympathetic tone; (ii) reciprocal antagonism is key to the transition from vagal to sympathetic dominance, and (iii) resetting of the arterial baroreflex causes immediate exercise-onset reflexive increases in HR, which are parasympathetically mediated, followed by slower increases in sympathetic tone as workloads are increased. PMID:24756637
Autonomic neural control of heart rate during dynamic exercise: revisited.
White, Daniel W; Raven, Peter B
2014-06-15
The accepted model of autonomic control of heart rate (HR) during dynamic exercise indicates that the initial increase is entirely attributable to the withdrawal of parasympathetic nervous system (PSNS) activity and that subsequent increases in HR are entirely attributable to increases in cardiac sympathetic activity. In the present review, we sought to re-evaluate the model of autonomic neural control of HR in humans during progressive increases in dynamic exercise workload. We analysed data from both new and previously published studies involving baroreflex stimulation and pharmacological blockade of the autonomic nervous system. Results indicate that the PSNS remains functionally active throughout exercise and that increases in HR from rest to maximal exercise result from an increasing workload-related transition from a 4 : 1 vagal-sympathetic balance to a 4 : 1 sympatho-vagal balance. Furthermore, the beat-to-beat autonomic reflex control of HR was found to be dependent on the ability of the PSNS to modulate the HR as it was progressively restrained by increasing workload-related sympathetic nerve activity. (i) increases in exercise workload-related HR are not caused by a total withdrawal of the PSNS followed by an increase in sympathetic tone; (ii) reciprocal antagonism is key to the transition from vagal to sympathetic dominance, and (iii) resetting of the arterial baroreflex causes immediate exercise-onset reflexive increases in HR, which are parasympathetically mediated, followed by slower increases in sympathetic tone as workloads are increased. © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.
Benzophenone Ultrafast Triplet Population: Revisiting the Kinetic Model by Surface-Hopping Dynamics.
Marazzi, Marco; Mai, Sebastian; Roca-Sanjuán, Daniel; Delcey, Mickaël G; Lindh, Roland; González, Leticia; Monari, Antonio
2016-02-18
The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation; the long-debated direct (S1 → T1) and indirect (S1 → T2 → T1) mechanisms for population of the low-lying triplet state are both possible, with the latter being prevalent. Moreover, we established the existence of a kinetic equilibrium between the two triplet states, never observed before. This fact implies that a significant fraction of the overall population resides in T2, eventually allowing one to revisit the usual spectroscopic assignment proposed by transient absorption spectroscopy. This finding is of particular interest for photocatalysis as well as for DNA damages studies because both T1 and T2 channels are, in principle, available for benzophenone-mediated photoinduced energy transfer toward DNA.
Benzophenone Ultrafast Triplet Population: Revisiting the Kinetic Model by Surface-Hopping Dynamics
2016-01-01
The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation; the long-debated direct (S1 → T1) and indirect (S1 → T2 → T1) mechanisms for population of the low-lying triplet state are both possible, with the latter being prevalent. Moreover, we established the existence of a kinetic equilibrium between the two triplet states, never observed before. This fact implies that a significant fraction of the overall population resides in T2, eventually allowing one to revisit the usual spectroscopic assignment proposed by transient absorption spectroscopy. This finding is of particular interest for photocatalysis as well as for DNA damages studies because both T1 and T2 channels are, in principle, available for benzophenone-mediated photoinduced energy transfer toward DNA. PMID:26821061
Polarization and dilepton anisotropy in pion-nucleon collisions
NASA Astrophysics Data System (ADS)
Speranza, Enrico; Zétényi, Miklós; Friman, Bengt
2017-01-01
Hadronic polarization and the related anisotropy of the dilepton angular distribution are studied for the reaction πN → Ne+e-. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the N (1520) and N (1440) resonances, which are essential at the collision energy of the recent data obtained by the HADES Collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unraveling the resonance contributions to this process.
Pion-nucleon {sigma} term in lattice QCD
Fukugita, M.; Kuramashi, Y.; Okawa, M.; Ukawa, A.
1995-05-01
We calculate both the connected and disconnected contributions to the {pi}-{ital N} {sigma} term in quenched lattice QCD with the Wilson quark action on a 12{sup 3}{times}20 lattice at {beta}=5.7 with the lattice spacing {ital a}{approx}0.14 fm. The latter is evaluated with the variant wall source method, previously applied successfully for {pi}-{pi} scattering lengths and the {eta}{prime} meson mass. We found the disconnected contribution to be about twice as large as the connected one. The value for the full {pi}-{ital N} {sigma} term {sigma}=40--60 MeV is consistent with the experimental estimates. The nucleon matrix element of the strange quark density {ital {bar s}s} is fairly large in our result.
Delta: the First Pion Nucleon Resonance - Its Discovery and Applications
DOE R&D Accomplishments Database
Nagle, D. E.
1984-07-01
It is attempted to recapture some of the fun and excitement of the pion-scattering work that led to the discovery of what is now called the delta particle. How significant this discovery was became apparent only gradually. That the delta is alive today and thriving at Los Alamos (as well as other places) is described.
Analyzing power reduction in quasifree pion-nucleon knockout reactions
NASA Astrophysics Data System (ADS)
Khayat, Mohammad G.; Roos, P. G.; Chant, N. S.; Dvoredsky, A. P.; Breuer, H.; Kelly, J. J.; Flanders, B. S.; Payerle, T. M.; Adimi, F.; Gu, T.; Huffman, J.; Klein, A.; Dooling, T.; Greco, T.; Kyle, G. S.; Chang, T.; Lin, Z.; Wang, M.; Meier, R.; Ritt, S.; Koch, K.; Konter, J.; Kovalev, S.; Mango, S.; van den Brandt, B.; Lawrie, J.
2001-12-01
Unpolarized cross sections and vector target analyzing powers for the 7Li-->(π+,π+'p) proton knockout reaction were measured using a vector polarized 7LiH target and a 240 MeV π+ beam at the πM1 channel of PSI. Typical target polarizations were >30% for 7Li. Coincident π+-p data are presented for three emitted pion angles (60°, 85°, and 108°). For each π+ angle coincident data with adequate statistics were obtained for three proton angles near the quasifree π+-p angle. The π+ angles were chosen to emphasize and isolate contributions to the target analyzing powers from the two-body π-nucleon interaction with a polarized nucleon whose polarization resulted from either the target polarization or from the distortion-induced effective polarization. The data are compared with factorized-amplitude distorted-wave impulse approximation (DWIA) calculations. The unpolarized cross sections are rather well described by these calculations. However, for all three angles the target analyzing powers are substantially reduced from predictions of conventional DWIA calculations. This result suggests a rather strong spin dependence in the Δ-nucleus spreading potential.
The pion nucleon scattering lengths from pionic hydrogen and deuterium
NASA Astrophysics Data System (ADS)
Schröder, H.-Ch.; Badertscher, A.; Goudsmit, P. F. A.; Janousch, M.; Leisi, H. J.; Matsinos, E.; Sigg, D.; Zhao, Z. G.; Chatellard, D.; Egger, J.-P.; Gabathuler, K.; Hauser, P.; Simons, L. M.; Rusi El Hassani, A. J.
2001-07-01
This is the final publication of the ETH Zurich Neuchâtel PSI collaboration on the pionic hydrogen and deuterium precision X-ray experiments. We describe the recent hydrogen 3 p 1 s measurement, report on the determination of the Doppler effect correction to the transition line width, analyze the deuterium shift measurement and discuss implications of the combined hydrogen and deuterium results. From the pionic hydrogen 3 p 1 s transition experiments we obtain the strong-interaction energy level shift \\varepsilon_{1s} = -7.108±0.013 (stat.)±0.034 (syst.) eV and the total decay width Γ_{1s} = 0.868±0.040 (stat.)±0.038 (syst.) eV of the 1s state. Taking into account the electromagnetic corrections we find the hadronic π N s-wave scattering amplitude a_{π-prightarrowπ-p} = 0.0883±0.0008 m_{π}^{-1} for elastic scattering and a_{π-prightarrowπ0n} = -0.128±0.006 m_{π} ^{-1} for single charge exchange, respectively. We then combine the pionic hydrogen results with the 1 s level shift measurement on pionic deuterium and test isospin symmetry of the strong interaction: our data are still compatible with isospin symmetry. The isoscalar and isovector π N scattering lengths (within the framework of isospin symmetry) are found to be b_0 = -0.0001^{+0.0009}_{-0.0021} m_{π}^{-1} and b1 = -0.0885^{+0.0010}_{-0.0021} m_{π} ^{-1}, respectively. Using the GMO sum rule, we obtain from b_1 a new value of the π N coupling constant (g_{π N} = 13.21_{-0.05}^{+0.11}) from which follows the Goldberger Treiman discrepancy Δ_{{GT}} =0.027_{-0.008}^{+0.012}. The new values of b_0 and g_{π N} imply an increase of the nucleon sigma term by at least 9 MeV.
Pion-nucleon scattering in the P11 channel
NASA Astrophysics Data System (ADS)
Morioka, S.; Afnan, I. R.
1982-09-01
We present a parametrization of the π-N interaction in the P11 channel in which the amplitude is the sum of a pole part and a non-pole part (t=tpole+tnp) and satisfies two-body unitarity. Here tpole has both the nucleon propagator and the πNN vertex dressed. The final amplitude fits the scattering length and low energy π-N phase shifts (Tlabπ<300 MeV). We study the effect of a resonance in tnp on the phase shifts, πNN coupling constant, and the off-shell behavior of the amplitude. NUCLEAR REACTIONS πN scattering in P11 channel, renormalization, resonance effect.
Delta: the first pion nucleon resonance - its discovery and applications
Nagle, D.E.
1984-07-01
It is attempted to recapture some of the fun and excitement of the pion-scattering work that led to the discovery of what is now called the delta particle. How significant this discovery was became apparent only gradually. That the delta is alive today and thriving at Los Alamos (as well as other places) is described.
Pion-Nucleon Scattering Experiments at Low Energies:
NASA Astrophysics Data System (ADS)
Breitschopf, J.; Bauer, M.; Clement, H.; Cröni, M.; Denz, H.; Meier, R.; Wagner, G. J.; Friedman, E.; Gibson, E.
Total cross sections of the single charge exchange reaction π-p→π0n have been measured at PSI from about 40 to 250 MeV using a transmission technique. Preliminary results show an excellent agreement with predictions from the SAID FA02 phase shift analysis for energies above 70 MeV.
Geostationary secular dynamics revisited: application to high area-to-mass ratio objects
NASA Astrophysics Data System (ADS)
Gachet, Fabien; Celletti, Alessandra; Pucacco, Giuseppe; Efthymiopoulos, Christos
2017-06-01
The long-term dynamics of the geostationary Earth orbits (GEO) is revisited through the application of canonical perturbation theory. We consider a Hamiltonian model accounting for all major perturbations: geopotential at order and degree two, lunisolar perturbations with a realistic model for the Sun and Moon orbits, and solar radiation pressure. The long-term dynamics of the GEO region has been studied both numerically and analytically, in view of the relevance of such studies to the issue of space debris or to the disposal of GEO satellites. Past studies focused on the orbital evolution of objects around a nominal solution, hereafter called the forced equilibrium solution, which shows a particularly strong dependence on the area-to-mass ratio. Here, we (i) give theoretical estimates for the long-term behavior of such orbits, and (ii) we examine the nature of the forced equilibrium itself. In the lowest approximation, the forced equilibrium implies motion with a constant non-zero average `forced eccentricity', as well as a constant non-zero average inclination, otherwise known in satellite dynamics as the inclination of the invariant `Laplace plane'. Using a higher order normal form, we demonstrate that this equilibrium actually represents not a point in phase space, but a trajectory taking place on a lower-dimensional torus. We give analytical expressions for this special trajectory, and we compare our results to those found by numerical orbit propagation. We finally discuss the use of proper elements, i.e., approximate integrals of motion for the GEO orbits.
Geostationary secular dynamics revisited: application to high area-to-mass ratio objects
NASA Astrophysics Data System (ADS)
Gachet, Fabien; Celletti, Alessandra; Pucacco, Giuseppe; Efthymiopoulos, Christos
2016-12-01
The long-term dynamics of the geostationary Earth orbits (GEO) is revisited through the application of canonical perturbation theory. We consider a Hamiltonian model accounting for all major perturbations: geopotential at order and degree two, lunisolar perturbations with a realistic model for the Sun and Moon orbits, and solar radiation pressure. The long-term dynamics of the GEO region has been studied both numerically and analytically, in view of the relevance of such studies to the issue of space debris or to the disposal of GEO satellites. Past studies focused on the orbital evolution of objects around a nominal solution, hereafter called the forced equilibrium solution, which shows a particularly strong dependence on the area-to-mass ratio. Here, we (i) give theoretical estimates for the long-term behavior of such orbits, and (ii) we examine the nature of the forced equilibrium itself. In the lowest approximation, the forced equilibrium implies motion with a constant non-zero average `forced eccentricity', as well as a constant non-zero average inclination, otherwise known in satellite dynamics as the inclination of the invariant `Laplace plane'. Using a higher order normal form, we demonstrate that this equilibrium actually represents not a point in phase space, but a trajectory taking place on a lower-dimensional torus. We give analytical expressions for this special trajectory, and we compare our results to those found by numerical orbit propagation. We finally discuss the use of proper elements, i.e., approximate integrals of motion for the GEO orbits.
NASA Technical Reports Server (NTRS)
Nguyen, Nhan
2013-01-01
This paper presents the optimal control modification for linear uncertain plants. The Lyapunov analysis shows that the modification parameter has a limiting value depending on the nature of the uncertainty. The optimal control modification exhibits a linear asymptotic property that enables it to be analyzed in a linear time invariant framework for linear uncertain plants. The linear asymptotic property shows that the closed-loop plants in the limit possess a scaled input-output mapping. Using this property, we can derive an analytical closed-loop transfer function in the limit as the adaptive gain tends to infinity. The paper revisits the Rohrs counterexample problem that illustrates the nature of non-robustness of model-reference adaptive control in the presence of unmodeled dynamics. An analytical approach is developed to compute exactly the modification parameter for the optimal control modification that stabilizes the plant in the Rohrs counterexample. The linear asymptotic property is also used to address output feedback adaptive control for non-minimum phase plants with a relative degree 1.
Barros, Wilson; Gochberg, Daniel F; Gore, John C
2009-05-07
The description of the nuclear magnetic resonance magnetization dynamics in the presence of long-range dipolar interactions, which is based upon approximate solutions of Bloch-Torrey equations including the effect of a distant dipolar field, has been revisited. New experiments show that approximate analytic solutions have a broader regime of validity as well as dependencies on pulse-sequence parameters that seem to have been overlooked. In order to explain these experimental results, we developed a new method consisting of calculating the magnetization via an iterative formalism where both diffusion and distant dipolar field contributions are treated as integral operators incorporated into the Bloch-Torrey equations. The solution can be organized as a perturbative series, whereby access to higher order terms allows one to set better boundaries on validity regimes for analytic first-order approximations. Finally, the method legitimizes the use of simple analytic first-order approximations under less demanding experimental conditions, it predicts new pulse-sequence parameter dependencies for the range of validity, and clarifies weak points in previous calculations.
Dynamics of Cl + propane, butanes revisited: a crossed beam slice imaging study.
Joalland, Baptiste; Shi, Yuanyuan; Patel, Nitin; Van Camp, Richard; Suits, Arthur G
2014-01-14
We report velocity-flux contour maps for H-D abstraction in selected Cl + alkane reactions measured by means of crossed beam scattering combined with universal DC slice imaging. The studied hydrocarbons are propane and its two selectively deuterated isotopologues, namely 1,1,1,3,3,3-propane-d6 and 2,2-propane-d2, n-butane and isobutane (2-methyl-propane), with detection of the hydrocarbon radical product by 157 nm single photon ionization. Data are obtained at collision energies of 12-13 kcal mol(-1) using a high-density atomic chlorine radical source combining Cl2 photolysis with ablation. All presented scattering distributions involving secondary and tertiary abstractions show distinct differences. Their comparisons allow for revisiting the dynamical picture of these reactions in terms of the nature of the abstraction sites, radical product energy disposal, and H vs. D abstraction. Results are discussed in the light of previous work and ab initio thermochemical calculations, along with proposals to future directions for investigation.
Delta-nucleus dynamics: proceedings of symposium
Lee, T.S.H.; Geesaman, D.F.; Schiffer, J.P.
1983-10-01
The appreciation of the role in nuclear physics of the first excited state of the nucleon, the delta ..delta..(1232), has grown rapidly in the past decade. The delta resonance dominates nuclear reactions induced by intermediate energy pions, nucleons, and electromagnetic probes. It is also the most important non-nucleonic degree of freedom needed to resolve many fundamental problems encountered in the study of low-energy nuclear phenomena. Clearly, a new phase of nuclear physics has emerged and conventional thinking must be extended to account for this new dimension of nuclear dynamics. The most challenging problem we are facing is how a unified theory can be developed to describe ..delta..-nucleus dynamics at all energies. In exploring this new direction, it is important to have direct discussions among researchers with different viewpoints. Separate entries were prepared for the 49 papers presented. (WHK)
Kessler, Jan; Elgabarty, Hossam; Spura, Thomas; Karhan, Kristof; Partovi-Azar, Pouya; Hassanali, Ali A; Kühne, Thomas D
2015-08-06
The structure and dynamics of the water/vapor interface is revisited by means of path-integral and second-generation Car-Parrinello ab initio molecular dynamics simulations in conjunction with an instantaneous surface definition [Willard, A. P.; Chandler, D. J. Phys. Chem. B 2010, 114, 1954]. In agreement with previous studies, we find that one of the OH bonds of the water molecules in the topmost layer is pointing out of the water into the vapor phase, while the orientation of the underlying layer is reversed. Therebetween, an additional water layer is detected, where the molecules are aligned parallel to the instantaneous water surface.
Revisiting the body-schema concept in the context of whole-body postural-focal dynamics.
Morasso, Pietro; Casadio, Maura; Mohan, Vishwanathan; Rea, Francesco; Zenzeri, Jacopo
2015-01-01
The body-schema concept is revisited in the context of embodied cognition, further developing the theory formulated by Marc Jeannerod that the motor system is part of a simulation network related to action, whose function is not only to shape the motor system for preparing an action (either overt or covert) but also to provide the self with information on the feasibility and the meaning of potential actions. The proposed computational formulation is based on a dynamical system approach, which is linked to an extension of the equilibrium-point hypothesis, called Passive Motor Paradigm: this dynamical system generates goal-oriented, spatio-temporal, sensorimotor patterns, integrating a direct and inverse internal model in a multi-referential framework. The purpose of such computational model is to operate at the same time as a general synergy formation machinery for planning whole-body actions in humanoid robots and/or for predicting coordinated sensory-motor patterns in human movements. In order to illustrate the computational approach, the integration of simultaneous, even partially conflicting tasks will be analyzed in some detail with regard to postural-focal dynamics, which can be defined as the fusion of a focal task, namely reaching a target with the whole-body, and a postural task, namely maintaining overall stability.
NASA Astrophysics Data System (ADS)
Habasaki, Junko; Ueda, Akira
2011-02-01
Molecular dynamics simulations have been performed to study the glass transition for the soft core system with a pair potential ϕn(r) = ɛ(σ/r)n of n = 12. Using the compressibility factor, PV/Nk_B T = tilde P(ρ ^*), its phase diagram can be represented as a function of a reduced density, ρ* = ρ(ɛ/kBT)3/n, where ρ = Nσ3/V. In the present work, NVE relaxations to the glassy or crystalline states starting from the unstable states in the phase diagram have been revisited in details and compared with other processes. Relaxation processes can be characterized by the time dependence of the dynamical compressibility factor (PV/Nk_B T)_t ( equiv g(ρ _t^*)) on the phase diagram. In some cases, g(ρ _t^*) reached a crystal branch in the phase diagram; however, metastable states are found in many cases. With connecting points for the metastable states in the phase diagram, we can define a glass branch where the dynamics of particles are almost frozen. The structures observed there have common properties characterized as glasses. Although overlaps of glass forming process and nanocrystallization process are observed in some cases, these behaviors are distinguishable to each other by the characteristics of structures. There are several routes to the glass branch and we suggest that all of them are the glass transition.
Revisiting the Body-Schema Concept in the Context of Whole-Body Postural-Focal Dynamics
Morasso, Pietro; Casadio, Maura; Mohan, Vishwanathan; Rea, Francesco; Zenzeri, Jacopo
2015-01-01
The body-schema concept is revisited in the context of embodied cognition, further developing the theory formulated by Marc Jeannerod that the motor system is part of a simulation network related to action, whose function is not only to shape the motor system for preparing an action (either overt or covert) but also to provide the self with information on the feasibility and the meaning of potential actions. The proposed computational formulation is based on a dynamical system approach, which is linked to an extension of the equilibrium-point hypothesis, called Passive Motor Paradigm: this dynamical system generates goal-oriented, spatio-temporal, sensorimotor patterns, integrating a direct and inverse internal model in a multi-referential framework. The purpose of such computational model is to operate at the same time as a general synergy formation machinery for planning whole-body actions in humanoid robots and/or for predicting coordinated sensory–motor patterns in human movements. In order to illustrate the computational approach, the integration of simultaneous, even partially conflicting tasks will be analyzed in some detail with regard to postural-focal dynamics, which can be defined as the fusion of a focal task, namely reaching a target with the whole-body, and a postural task, namely maintaining overall stability. PMID:25741274
Density fluctuation dynamics in a dissipative self-gravitating dilute gas revisited
NASA Astrophysics Data System (ADS)
Méndez, A. R.; García-Perciante, A. L.
2016-11-01
The analysis of the behavior of density fluctuations in a dissipative self gravitating gas in the linear regime is revisited. A factorization for the dispersion relation given by approximate roots is proposed, which is analogous to the one introduced in the case without gravitational field. The threshold for the onset of a gravitational instability, namely Jeans wavenumber, is found to be unaltered by the presence of thermal and viscous dissipation. However, the behavior of damped modes does not correspond to the usual Rayleigh-Brillouin spectrum when the gravitational field is taken into account. Additional to the usual central Rayleigh peak and Brillouin doublet, both corrected due to the presence of the field, non-Lorentizan terms are included in the structure factor. These terms are larger in the presence of the gravitational field and may lead in principle to relevant differences in the general properties of the spectrum. The possible mathematical origin of these modifications is briefly discussed.
Chemical Kinetics, Heat Transfer, and Sensor Dynamics Revisited in a Simple Experiment
ERIC Educational Resources Information Center
Sad, Maria E.; Sad, Mario R.; Castro, Alberto A.; Garetto, Teresita F.
2008-01-01
A simple experiment about thermal effects in chemical reactors is described, which can be used to illustrate chemical reactor models, the determination and validation of their parameters, and some simple principles of heat transfer and sensor dynamics. It is based in the exothermic reaction between aqueous solutions of sodium thiosulfate and…
Chemical Kinetics, Heat Transfer, and Sensor Dynamics Revisited in a Simple Experiment
ERIC Educational Resources Information Center
Sad, Maria E.; Sad, Mario R.; Castro, Alberto A.; Garetto, Teresita F.
2008-01-01
A simple experiment about thermal effects in chemical reactors is described, which can be used to illustrate chemical reactor models, the determination and validation of their parameters, and some simple principles of heat transfer and sensor dynamics. It is based in the exothermic reaction between aqueous solutions of sodium thiosulfate and…
The auditory dynamic attending theory revisited: A closer look at the pitch comparison task.
Bauer, Anna-Katharina R; Jaeger, Manuela; Thorne, Jeremy D; Bendixen, Alexandra; Debener, Stefan
2015-11-11
The dynamic attending theory as originally proposed by Jones, 1976. Psychol. Rev. 83(5), 323-355 posits that tone sequences presented at a regular rhythm entrain attentional oscillations and thereby facilitate the processing of sounds presented in phase with this rhythm. The increased interest in neural correlates of dynamic attending requires robust behavioral indicators of the phenomenon. Here we aimed to replicate and complement the most prominent experimental implementation of dynamic attending (Jones et al., 2002. Psychol. Sci. 13(4), 313-319). The paradigm uses a pitch comparison task in which two tones, the initial and the last of a longer series, have to be compared. In-between the two, distractor tones with variable pitch are presented, at a regular pace. A comparison tone presented in phase with the entrained rhythm is hypothesized to lead to better behavioral performance. Aiming for a conceptual replication, four different variations of the original paradigm were created which were followed by an exact replication attempt. Across all five experiments, only 40 of the 140 tested participants showed the hypothesized pattern of an inverted U-shaped profile in task accuracy, and the group average effects did not replicate the pattern reported by Jones et al., 2002. Psychol. Sci. 13(4), 313-319 in any of the five experiments. However, clear evidence for a relationship between musicality and overall behavioral performance was found. This study casts doubt on the suitability of the pitch comparison task for demonstrating auditory dynamic attending. We discuss alternative tasks that have been shown to support dynamic attending theory, thus lending themselves more readily to studying its neural correlates. This article is part of a Special Issue entitled SI: Prediction and Attention.
Lerner, Itamar; Bentin, Shlomo; Shriki, Oren
2012-01-01
Localist models of spreading activation (SA) and models assuming distributed-representations offer very different takes on semantic priming, a widely investigated paradigm in word recognition and semantic memory research. In the present study we implemented SA in an attractor neural network model with distributed representations and created a unified framework for the two approaches. Our models assumes a synaptic depression mechanism leading to autonomous transitions between encoded memory patterns (latching dynamics), which account for the major characteristics of automatic semantic priming in humans. Using computer simulations we demonstrated how findings that challenged attractor-based networks in the past, such as mediated and asymmetric priming, are a natural consequence of our present model’s dynamics. Puzzling results regarding backward priming were also given a straightforward explanation. In addition, the current model addresses some of the differences between semantic and associative relatedness and explains how these differences interact with stimulus onset asynchrony in priming experiments. PMID:23094718
Critical Dynamics of the Dirty Boson Problem: Revisiting the Equality z=d
Weichman, Peter B.; Mukhopadhyay, Ranjan
2007-06-15
It is shown that previous arguments, leading to the equality z=d for the dynamical exponent describing the Bose glass to superfluid transition in d dimensions, may break down, as apparently seen in recent simulations. The key observation is that the major contribution to the compressibility, which remains finite through the transition and was predicted to scale as {kappa}{approx} vertical bar {delta} vertical bar{sup (d-z){nu}} (where {delta} is the deviation from criticality and {nu} is the correlation length exponent) comes from the analytic, not the singular part of the free energy, and is not restricted by any conventional scaling hypothesis.
Revisiting nonlinearity in meandering river planform dynamics using Gradual Wavelet Reconstruction
NASA Astrophysics Data System (ADS)
Schwenk, J.; Foufoula-Georgiou, E.; Lanzoni, S.
2014-12-01
Characterizing the intrinsic nonlinearity in meandering river dynamics is important because it dictates river evolution response to perturbations such as bank armoring or channel straightening. Meandering river dynamics have been described in terms of chaos or self-organized criticality—characterizations predicated on the presence of nonlinearity—yet recent studies have found only limited evidence for its existence. Standard nonlinearity tests are performed by generating a number of linearized surrogate series from a signal of interest. Inherent nonlinearities in the original signal are destroyed in the surrogates via phase randomization in the Fourier domain. Nonlinearity is inferred if a significant difference exists between the original and the surrogates in an appropriately determined phase space. These tests detect the presence or absence of nonlinearity but cannot identify which scales and locations are contributing most to the signal's nonlinearity. A new surrogate generation method called Gradual Wavelet Reconstruction (GWR) has two key advantages over the standard methodology. First, GWR quantifies the degree of nonlinearity rather than simply detecting its presence or absence, providing a basis for comparisons between river planforms and models of meander migration. Second, because the GWR methodology relies on localized transformations, it can determine the scales and locations primarily contributing to the observed complexity. As a result of those advantages too, GWR has been shown to detect the presence of nonlinearity in signals where standard tests have failed. We apply GWR methodology to time series of channel sinuosity predicted by two established models of long-time meander migration: a HIPS-type model and that of Zolezzi and Seminara (2001). Although the former model has been shown to capture first-order meander dynamics, it fails to fully couple sediment and flow dynamics; nor does it account for the resonance phenomenon. Using GWR, we show
The structure and dynamics of the AC114 galaxy cluster revisited
NASA Astrophysics Data System (ADS)
Proust, Dominique; Yegorova, Irina; Saviane, Ivo; Ivanov, Valentin D.; Bresolin, Fabio; Salzer, John J.; Capelato, Hugo V.
2015-10-01
We present a dynamical analysis of the galaxy cluster AC114 based on a catalogue of 524 velocities. Of these, 169 (32 per cent) are newly obtained at European Southern Observatory (Chile) with the Very Large Telescope and the VIsible MultiObject spectrograph. Data on individual galaxies are presented and the accuracy of the measured velocities is discussed. Dynamical properties of the cluster are derived. We obtain an improved mean redshift value z = 0.31665 ± 0.0008 and velocity dispersion σ = 1893^{+73}_{-82} km s^{-1}. A large velocity dispersion within the core radius and the shape of the infall pattern suggests that this part of the cluster is in a radial phase of relaxation with a very elongated radial filament spanning 12 000 km s-1. A radial foreground structure is detected within the central 0.5 h-1 Mpc radius, recognizable as a redshift group at the same central redshift value. We analyse the colour distribution for this archetype Butcher-Oemler galaxy cluster and identify the separate red and blue galaxy sequences. The latter subset contains 44 per cent of confirmed members of the cluster, reaching magnitudes as faint as Rf= 21.1 (1.0 mag fainter than previous studies). We derive a mass M200 = (4.3 ± 0.7) × 1015 M⊙ h-1. In a subsequent paper, we will utilize the spectral data presented here to explore the mass-metallicity relation for this intermediate redshift cluster.
Pion scattering and nuclear dynamics
Johnson, M.B.
1988-01-01
A phenomenological optical-model analysis of pion elastic scattering and single- and double-charge-exchange scattering to isobaric-analog states is reviewed. Interpretation of the optical-model parameters is briefly discussed, and several applications and extensions are considered. The applications include the study of various nuclear properties, including neutron deformation and surface-fluctuation contributions to the density. One promising extension for the near future would be to develop a microscopic approach based on powerful momentum-space methods brought to existence over the last decade. In this, the lowest-order optical potential as well as specific higher-order pieces would be worked out in terms of microscopic pion-nucleon and delta-nucleon interactions that can be determined within modern meson-theoretical frameworks. A second extension, of a more phenomenological nature, would use coupled-channel methods and shell-model wave functions to study dynamical nuclear correlations in pion double charge exchange. 35 refs., 11 figs., 1 tab.
Parker, Andrew; Dagnall, Neil
2009-05-01
Two experiments are presented that investigate the effects of dynamic visual noise (DVN) on memory for concrete and abstract words. Memory for concrete words is typically superior to that of abstract words and is referred to as the concreteness effect. DVN is a procedure that has been demonstrated to interfere selectively with visual working memory and the generation of images from long-term memory. It was reasoned that if concreteness effects arise because of the ability of the latter to activate visual representations, then DVN should selectively impair memory for concrete words. Experiment 1 found DVN to selectively reduce free recall of concrete words. Experiment 2 investigated recognition memory and found DVN to reduce memory accuracy and remember responses, while increasing know responses to concrete words.
Dispositional envy revisited: unraveling the motivational dynamics of benign and malicious envy.
Lange, Jens; Crusius, Jan
2015-02-01
Previous research has conceptualized dispositional envy as a unitary construct. Recently however, episodic envy has been shown to emerge in two qualitatively different forms. Benign envy is related to the motivation to move upward, whereas malicious envy is related to pulling superior others down. In four studies (N = 1,094)--using the newly developed Benign and Malicious Envy Scale (BeMaS)--we show that dispositional envy is also characterized by two independent dimensions related to distinct motivational dynamics and behavioral consequences. Dispositional benign and malicious envy uniquely predict envious responding following upward social comparisons. Furthermore, they are differentially connected to hope for success and fear of failure. Corresponding to these links, dispositional benign envy predicted faster race performance of marathon runners mediated via higher goal setting. In contrast, dispositional malicious envy predicted race goal disengagement. The findings highlight that disentangling the two sides of envy opens up numerous research avenues.
Revisiting Molecular Dynamics on a CPU/GPU system: Water Kernel and SHAKE Parallelization.
Ruymgaart, A Peter; Elber, Ron
2012-11-13
We report Graphics Processing Unit (GPU) and Open-MP parallel implementations of water-specific force calculations and of bond constraints for use in Molecular Dynamics simulations. We focus on a typical laboratory computing-environment in which a CPU with a few cores is attached to a GPU. We discuss in detail the design of the code and we illustrate performance comparable to highly optimized codes such as GROMACS. Beside speed our code shows excellent energy conservation. Utilization of water-specific lists allows the efficient calculations of non-bonded interactions that include water molecules and results in a speed-up factor of more than 40 on the GPU compared to code optimized on a single CPU core for systems larger than 20,000 atoms. This is up four-fold from a factor of 10 reported in our initial GPU implementation that did not include a water-specific code. Another optimization is the implementation of constrained dynamics entirely on the GPU. The routine, which enforces constraints of all bonds, runs in parallel on multiple Open-MP cores or entirely on the GPU. It is based on Conjugate Gradient solution of the Lagrange multipliers (CG SHAKE). The GPU implementation is partially in double precision and requires no communication with the CPU during the execution of the SHAKE algorithm. The (parallel) implementation of SHAKE allows an increase of the time step to 2.0fs while maintaining excellent energy conservation. Interestingly, CG SHAKE is faster than the usual bond relaxation algorithm even on a single core if high accuracy is expected. The significant speedup of the optimized components transfers the computational bottleneck of the MD calculation to the reciprocal part of Particle Mesh Ewald (PME).
Dworkin’s argument revisited: Point processes, dynamics, diffraction, and correlations
NASA Astrophysics Data System (ADS)
Deng, Xinghua; Moody, Robert V.
2008-04-01
The setting is an ergodic dynamical system (X,μ) whose points are themselves uniformly discrete point sets Λ in some space Rd and whose group action is that of translation of these point sets by the vectors of Rd. Steven Dworkin's argument relates the diffraction of the typical point sets comprising X to the dynamical spectrum of X. In this paper we look more deeply at this relationship, particularly in the context of point processes. We show that there is an Rd-equivariant, isometric embedding, depending on the scattering strengths (weights) that are assigned to the points of Λ∈X, that takes the L2-space of Rd under the diffraction measure into L2(X,μ). We examine the image of this embedding and give a number of examples that show how it fails to be surjective. We show that full information on the measure μ is available from the weights and set of all the correlations (that is, the two-point, three-point, …, correlations) of the typical point set Λ∈X. We develop a formalism in the setting of random point measures that includes multi-colour point sets, and arbitrary real-valued weightings for the scattering from the different colour types of points, in the context of Palm measures and weighted versions of them. As an application we give a simple proof of a square-mean version of the Bombieri-Taylor conjecture, and from that we obtain an inequality that gives a quantitative relationship between the autocorrelation, the diffraction, and the ɛ-dual characters of typical element of X. The paper ends with a discussion of the Palm measure in the context of defining pattern frequencies.
Revisiting Molecular Dynamics on a CPU/GPU system: Water Kernel and SHAKE Parallelization
Ruymgaart, A. Peter; Elber, Ron
2012-01-01
We report Graphics Processing Unit (GPU) and Open-MP parallel implementations of water-specific force calculations and of bond constraints for use in Molecular Dynamics simulations. We focus on a typical laboratory computing-environment in which a CPU with a few cores is attached to a GPU. We discuss in detail the design of the code and we illustrate performance comparable to highly optimized codes such as GROMACS. Beside speed our code shows excellent energy conservation. Utilization of water-specific lists allows the efficient calculations of non-bonded interactions that include water molecules and results in a speed-up factor of more than 40 on the GPU compared to code optimized on a single CPU core for systems larger than 20,000 atoms. This is up four-fold from a factor of 10 reported in our initial GPU implementation that did not include a water-specific code. Another optimization is the implementation of constrained dynamics entirely on the GPU. The routine, which enforces constraints of all bonds, runs in parallel on multiple Open-MP cores or entirely on the GPU. It is based on Conjugate Gradient solution of the Lagrange multipliers (CG SHAKE). The GPU implementation is partially in double precision and requires no communication with the CPU during the execution of the SHAKE algorithm. The (parallel) implementation of SHAKE allows an increase of the time step to 2.0fs while maintaining excellent energy conservation. Interestingly, CG SHAKE is faster than the usual bond relaxation algorithm even on a single core if high accuracy is expected. The significant speedup of the optimized components transfers the computational bottleneck of the MD calculation to the reciprocal part of Particle Mesh Ewald (PME). PMID:23264758
NASA Astrophysics Data System (ADS)
Assouline, Shmuel; Or, Dani
2014-06-01
Across many soil types and conditions, post wetting soil internal drainage exhibits predictable dynamics that lead to a stable and repeatable hydration state termed "field capacity" (FC). Soil regulation of internal drainage toward FC has long been recognized as producing a useful hydrologic benchmark for modeling and for estimation of plant available soil water. To overcome ambiguities and inconsistencies in various ad hoc definitions of FC, we propose using a soil intrinsic characteristic length (a matric potential value derived from drainable soil pore size distribution) to characterize the loss of hydraulic continuity associated with the attainment of FC. The resulting static criterion for FC was extended to formulate a self-consistent dynamic criterion based on soil internal drainage dynamics. A systematic evaluation of the proposed definitions of FC using numerical simulations and experimental data reveals remarkable consistency and predictability across a wide range of soil types. The new metrics add definitiveness and robustness of this widely used concept with potential expansion to additional agronomic, hydrologic, ecological, and climatic applications.
Energy corrugation in atomic-scale friction on graphite revisited by molecular dynamics simulations
NASA Astrophysics Data System (ADS)
Sun, Xiao-Yu; Qi, Yi-Zhou; Ouyang, Wengen; Feng, Xi-Qiao; Li, Qunyang
2016-08-01
Although atomic stick-slip friction has been extensively studied since its first demonstration on graphite, the physical understanding of this dissipation-dominated phenomenon is still very limited. In this work, we perform molecular dynamics (MD) simulations to study the frictional behavior of a diamond tip sliding over a graphite surface. In contrast to the common wisdom, our MD results suggest that the energy barrier associated lateral sliding (known as energy corrugation) comes not only from interaction between the tip and the top layer of graphite but also from interactions among the deformed atomic layers of graphite. Due to the competition of these two subentries, friction on graphite can be tuned by controlling the relative adhesion of different interfaces. For relatively low tip-graphite adhesion, friction behaves normally and increases with increasing normal load. However, for relatively high tip-graphite adhesion, friction increases unusually with decreasing normal load leading to an effectively negative coefficient of friction, which is consistent with the recent experimental observations on chemically modified graphite. Our results provide a new insight into the physical origins of energy corrugation in atomic scale friction.
On the Characterization of Revisitation Patterns in Complex Human Dynamics - A Data Science Approach
NASA Astrophysics Data System (ADS)
Barbosa Filho, Hugo Serrano
When it comes to visitation patterns, humans beings are extremely regular and predictable, with recurrent activities responsible for most of our movements. In recent years, we have seen scientists attempt to model and explain human dynamics and in particular human movement. Akin to other human behaviors, traveling patterns evolve from the convolution between internal and external factors. A better understanding on the mechanisms responsible for transforming and incorporating individual events into regular patterns is of fundamental importance. Many aspects of our complex lives are affected by human movements such as disease spread and epidemics modeling, city planning, wireless network development, and disaster relief, to name a few. Given the myriad of applications, it is clear that a complete understanding of how people move in space can lead to considerable benefits to our society. In most of the recent works, scientists have focused on the idea that people movements are biased towards frequently-visited locations. According to them, human movement is based on a exploration/exploitation dichotomy in which individuals choose new locations (exploration) or return to frequently-visited locations (exploitation). In this dissertation we present some of our contributions to the field, such as the presence of a recency effect in human mobility and Web browsing behaviors as well as the Returner vs. Explorers dichotomy in Web browsing trajectories.
NASA Astrophysics Data System (ADS)
Yamamoto, Takashi
2013-08-01
Molecular mechanisms of the steady-state growth of the chain folded lamella and the cold crystallization across the glass transition temperature Tg are investigated by molecular dynamics simulation for a system of long polyethylene (PE)-like polymers made of 512 united atoms C512. The present paper aims to reconsider results of our previous simulations for short PE-like polymers C100 by carrying out very long simulations up to 1 μs for more realistic systems of much longer chains, thereby to establish the firm molecular image of chain-folded crystallization and clarify the specific molecular process of cold crystallization. We observe that the chain-folded lamella shows fast thickening-growth keeping marked tapered growth front. Despite the fast growth in much longer chains, the fold-surface is found to be predominantly of adjacent-reentry. Detailed inspections of the molecular pathway give an insightful image that can explain the apparently contradicting results. In addition, the fold-structure with specific spatial heterogeneity is found to give rise to heterogeneous mobility within the crystalline region. On the other hand, investigations of the cold crystallization during slow heating of the glassy film across Tg is found to give a granular texture made of small crystallites. The crystallites are found to nucleate preferentially near the free surfaces having lower Tg, and to be dominantly edge-on showing a definite tendency to orient their chain axes parallel to the free surface.
Revisit of Rotational Dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby
NASA Astrophysics Data System (ADS)
Zhao, Yuhui; Hu, Shoucun; Ji, Jianghui
2015-08-01
In this work we investigate the rotational dynamics of Toutatis based on the derived results from Chang'e-2's close flyby to the asteroid (Huang et al. 2013). Toutatis' non-principal axis rotation (NPA) was revealed by radar observations captured from its Earth approaches in the past two decades. Matrix of inertia calculated from radar derived shape model are inconsistent with observations, which may indicate an uneven density distribution of the asteroid. We perform numerical simulations of rotational evolution of Toutatis and figure out the relative rotational parameters of Euler angles, rotational velocities and matrix of inertia. According to the major morphological feature of the ginger-shaped asteroid, we suggest a density ratio of the two lobes. On the basis of these results, we will evaluate the magnitude of the bias of mass center and figure center, which may have slight effects in the momentum variation calculation. These results are in good agreements with the previous radar observation derived results (Takahashi et al. 2013).
ERIC Educational Resources Information Center
Court, Deborah
1999-01-01
Revisits and reviews Imre Lakatos' ideas on "Falsification and the Methodology of Scientific Research Programmes." Suggests that Lakatos' framework offers an insightful way of looking at the relationship between theory and research that is relevant not only for evaluating research programs in theoretical physics, but in the social…
ERIC Educational Resources Information Center
Court, Deborah
1999-01-01
Revisits and reviews Imre Lakatos' ideas on "Falsification and the Methodology of Scientific Research Programmes." Suggests that Lakatos' framework offers an insightful way of looking at the relationship between theory and research that is relevant not only for evaluating research programs in theoretical physics, but in the social…
Tasali, N; Cubuk, R; Aricak, M; Ozarar, M; Saydam, B; Nur, H; Tuncbilek, N
2012-03-01
We aimed to assess the contrast enhancement patterns of the retrodiscal tissue with dynamic contrast-enhanced MR imaging (DCE-MRI) with respect to different temporomandibular joint disc pathologies. Additionally, we questioned the relationship between the temporomandibular joint (TMJ) pain and the contrast enhancement pattern of the retrodiscal tissue regardless of the TMJ disc position. 52 joints of 26 patients (4 males and 22 females) who have pain in at least at one of their TMJ were included in this study. For the qualitative analysis, the joints were divided into four groups in terms of their disc positions: normal (1), partially displaced with or without reduction (2), totally dislocated with reduction (3) and totally dislocated without reduction (4). Besides, two different joint groups were constituted, namely the painful group and painless group according to the clinical findings without taking the TMJ disc positions into account. Quantitative analyses were made by means of measuring signal intensity ratios (SI) ratio at the retrodiscal tissue (from internal side and external side of the each joint) using DCE-MRI and these measurements were analyzed with paired samples t test to define the difference between the measurements. At the second stage, the time-dependent arithmetical mean values of the SI ratios were calculated for each joint group and significant differences between the groups were questioned using analysis of variance (ANOVA) test. Besides, painful and painless groups which were classified on the basis of the clinical data were compared according to the mean SI ratios found for each joint and the significant differences between these two groups were assessed by means of Student's T test. The results were assessed in 95% confidence interval where the significance level was p<0.05. A significant difference was observed between the internal and external contrast enhancement of the joints with partial displacement. Another significant difference
NASA Astrophysics Data System (ADS)
Crifo, J.-F.; Loukianov, G. A.; Rodionov, A. V.; Zakharov, V. V.
2005-07-01
This paper describes the first computations of dust distributions in the vicinity of an active cometary nucleus, using a multidimensional Direct Simulation Monte Carlo Method (DSMC). The physical model is simplistic: spherical grains of a broad range of sizes are liberated by H 2O sublimation from a selection of nonrotating sunlit spherical nuclei, and submitted to the nucleus gravity, the gas drag, and the solar radiation pressure. The results are compared to those obtained by the previously described Dust Multi-Fluid Method (DMF) and demonstrate an excellent agreement in the regions where the DMF is usable. Most importantly, the DSMC allows the discovery of hitherto unsuspected dust coma properties in those cases which cannot be treated by the DMF. This leads to a thorough reconsideration of the properties of the near-nucleus dust dynamics. In particular, the results show that (1) none of the three forces considered here can be neglected a priori, in particular not the radiation pressure; (2) hitherto unsuspected new families of grain trajectories exist, for instance trajectories leading from the nightside surface to the dayside coma; (3) a wealth of balistic-like trajectories leading from one point of the surface to another point exist; on the dayside, such trajectories lead to the formation of "mini-volcanoes." The present model and results are discussed carefully. It is shown that (1) the neglected forces (inertia associated with a nucleus rotation, solar tidal force) are, in general, not negligible everywhere, and (2) when allowing for these additional forces, a time-dependent model will, in general, have to be used. The future steps of development of the model are outlined.
REVISITING THE ROLE OF M31 IN THE DYNAMICAL HISTORY OF THE MAGELLANIC CLOUDS
Kallivayalil, Nitya; Sanderson, Robyn; Besla, Gurtina; Alcock, Charles
2009-08-01
We study the dynamics of the Magellanic Clouds in a model for the Local Group whose mass is constrained using the timing argument/two-body limit of the action principle. The goal is to evaluate the role of M31 in generating the high angular momentum orbit of the Clouds, a puzzle that has only been exacerbated by the latest Hubble Space Telescope proper motion measurements. We study the effects of varying the total Local Group mass, the relative mass of the Milky Way (MW) and M31, the proper motion of M31, and the proper motion of the Large Magellanic Cloud (LMC) on this problem. Over a large part of this parameter space, we find that tides from M31 are insignificant. For a range of LMC proper motions approximately 3{sigma} higher than the mean and total Local Group mass >3.5 x 10{sup 12} M{sub sun}, M31 can provide a significant torque to the LMC orbit. However, if the LMC is bound to the MW, then M31 is found to have negligible effect on its motion, and the origin of the high angular momentum of the system remains a puzzle. Finally, we use the timing argument to calculate the total mass of the MW-LMC system based on the assumption that they are encountering each other for the first time, their previous perigalacticon being a Hubble time ago, obtaining M{sub MW} + M{sub LMC} = (8.7 {+-} 0.8) x 10{sup 11} M{sub sun}.
McNamara, Andrew R; Boudreau, John A; Moed, Berton R
2015-08-01
Performing an examination under general anesthesia (EUA) using dynamic stress fluoroscopy of patients with posterior wall acetabular fractures has been used as a tool to determine hip stability and the need for surgical intervention. The purpose of this study was to further evaluate the effectiveness of this technique, from a source other than its primary advocates, in patients with posterior wall acetabular fractures less than or equal to 50% who were stable on EUA and treated nonoperatively. Retrospective case series. University Level 1 Trauma Center. Seventeen patients with a posterior wall acetabular fracture stable on EUA treated nonoperatively. The patients were treated nonoperatively as guided by an EUA negative for instability. Patient follow-up averaged 30 months (range, 6-64 months). Outcome evaluation included the modified Merle d'Aubigné clinical score and the Short Musculoskeletal Function Assessment Questionnaire. Radiographic evaluation for subluxation or arthritis consisted of the 3 standard pelvic radiographs. Radiographic evaluation showed all hips to be congruent with a normal joint space. Sixteen of the 17 patients had radiographic outcomes rated as "excellent"; 1 patient was rated "good." The modified Merle d'Aubigné score (obtained in 12 patients) averaged very good, with only 1 having less than a good (graded as fair) clinical outcome. The Short Musculoskeletal Function Assessment Questionnaire scores (from 11 patients) were not significantly different from normal and were within the normal reported values for all indices and categories. There was no correlation between fracture fragment size and outcome. This study further supports the contention that a stable hip joint, as determined by EUA, after posterior wall acetabular fracture treated nonoperatively is predictive of continued joint congruity, an excellent radiographic outcome, and good-to-excellent early clinical and functional outcomes. Therapeutic Level IV. See Instructions for
Dynamic reciprocity revisited.
Kaul, Himanshu; Ventikos, Yiannis
2015-04-07
The cellular microenvironment - which includes the cells, extracellular matrix (ECM), and local transport processes - affects the cell which in turn responds by synthetic or degradative processes causing the composition and the structure of ECM, and the local transport processes, to change which in a coupled manner influence the cell, and so forth. Copyright © 2015 Elsevier Ltd. All rights reserved.
Improved input for multi-reaction hadronic analyses from elastic pion-nucleon scattering
NASA Astrophysics Data System (ADS)
Revier, Joseph; Roenchen, Deborah; Doering, Michael; Workman`, Ronald
2017-01-01
In the search for missing baryonic resonances, many analyses include data from a variety of pion and photon induced reactions. For elastic πN scattering, however, usually the partial waves of the SAID or other groups are fitted, instead of data. We provide the partial-wave covariance matrices needed to perform correlated χ2 fits, in which the obtained χ2 equals the actual χ2 up to non-linear and normalization corrections. For any analysis relying on partial waves extracted from elastic pion scattering, this is a prerequisite to assess the significance of resonance signals and to assign any uncertainty on results. The compilation of the necessary data to improve hadronic analyses is presented in detail. Supported by the U.S. Department of Energy Grant DE-SC0014133, contract DE-AC05-06OR23177, and by the National Science Foundation (CAREER grant No. 1452055, PIF Grant No. 1415459).
Pion-nucleon scattering and pion production in nucleon-nucleon and nucleus-nucleus collisions
Dover, C.B.
1982-01-01
Lecture notes are presented on the following: (1) basic aspects of ..pi..N interactions (properties of pions and nucleons, SU(3) and SU(6) classification phenomenology of ..pi..N scattering ((3.3) resonance; phase shift analysis, and bag model approach to ..pi..N); (2) pion production and absorption in the two nucleon system (NN ..-->.. NN..pi.. (isobar model) and ..pi..d reversible NN (existence of dibaryon resonances)); (3) pion absorption in complex nuclei (multiparticle aspects and cascade calculations); and (4) pion production with nuclear targets including (a) nucleon-nucleus, (b) nucleus-nucleus (Fermi-averaged 2-body vs thermodynamic models), and (c) ..pi pi.. interoferometry.
New Aspects of Experimental Study of the Pion-Nucleon Interaction in the Resonance Region
Sumachev, V.V.
2005-06-01
New experimental data that were obtained by the PNPI-ITEP Collaboration have resolved some discrete ambiguities in the partial-wave analysis (PWA). These results were used in the new FA02 PWA performed at George Washington University. At the same time, the FA02 PWA has revealed considerable fewer N* and {delta} resonances than those listed in the RPP tables. This circumstance aggravated the known problem of so-called missing resonances. The program for further measurements of the spin rotation parameters in elastic {pi}N scattering that are required to eliminate the remaining discrete PWA ambiguities is discussed.
PHOTOPRODUCTION OF PI O FROM HYDROGEN NEAR THE SECOND PION NUCLEON RESONANCE,
state interaction between emitted pion and recoil nucleon. There has remained, however, a noticeable lack of data at high momentum transfer in the...positions is not due to the photo-electric term, and also establish the possibility of a high momentum transfer enhancement of pi o photoproduction caused by
Renormdynamics, discrete dynamics and quanputers
NASA Astrophysics Data System (ADS)
Makhaldiani, Nugzar
2017-03-01
In the Standard Model of Particle Physics (SM), the values of the coupling constants and masses of particles evolve according to the Renormdynamic motion equations. In SM, minimal supersymmetric extension of the SM, standard pion-nucleon field theory and other models is shown how to define the values of coupling constants and masses. Why supersymmetry is So universal?
Light-front representation of chiral dynamics in peripheral transverse densities
Granados, Carlos G.; Weiss, Christian
2015-07-31
The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances b = O(M_pi^{-1}) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independentmore » and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantized, quantum-mechanical view of chiral dynamics that is fully relativistic and exactly equivalent to the second-quantized, field-theoretical formulation. It relates the charge and magnetization densities measured in low-energy elastic scattering to the generalized parton distributions probed in peripheral high-energy scattering processes. The method can be applied to nucleon form factors of other operators, e.g. the energy-momentum tensor.« less
Light-front representation of chiral dynamics in peripheral transverse densities
Granados, Carlos G.; Weiss, Christian
2015-07-31
The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances b = O(M_pi^{-1}) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independent and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantized, quantum-mechanical view of chiral dynamics that is fully relativistic and exactly equivalent to the second-quantized, field-theoretical formulation. It relates the charge and magnetization densities measured in low-energy elastic scattering to the generalized parton distributions probed in peripheral high-energy scattering processes. The method can be applied to nucleon form factors of other operators, e.g. the energy-momentum tensor.
NASA Astrophysics Data System (ADS)
Ngo, N. H.; Tran, H.; Gamache, R. R.; Bermejo, D.; Domenech, J.-L.
2012-08-01
The modeling of the shape of H2O lines perturbed by N2 (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], 10.1016/j.jqsrt.2007.03.009, the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H2O broadened by N2 (and air) in the ν3 and 2ν1 + ν2 + ν3 bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.
Ngo, N H; Tran, H; Gamache, R R; Bermejo, D; Domenech, J-L
2012-08-14
The modeling of the shape of H(2)O lines perturbed by N(2) (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H(2)O broadened by N(2) (and air) in the ν(3) and 2ν(1) + ν(2) + ν(3) bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.
NASA Astrophysics Data System (ADS)
Prasetyo, Niko; Armunanto, Ria
2016-05-01
Structures and dynamics of Ag+ in 18.6% aqueous ammonia have been studied using Quantum Mechanical Charge Field Molecular Dynamics (QMCF-MD) simulation at the Hartree-Fock (HF) level theory employing LANL2DZ ECP basis set for Ag+ and Dunning DZP for solvent molecules. Structural properties are in excellent agreement with previous QM/MM and experiments studies. [Ag(NH3)2(H2O)3]+ was found as dominant species during simulation time. For 20 ps of simulation time, a labile first solvation shell was observed with both fast ammonia and water ligands exchanges. QMCF-MD framework describes first solvation shell more labile than conventional QM/MM MD simulation.
Cats protecting birds revisited.
Fan, Meng; Kuang, Yang; Feng, Zhilan
2005-09-01
In this paper, we revisit the dynamical interaction among prey (bird), mesopredator (rat), and superpredator (cat) discussed in [Courchamp, F., Langlais, M., Sugihara, G., 1999. Cats protecting birds: modelling the mesopredator release effect. Journal of Animal Ecology 68, 282-292]. First, we develop a prey-mesopredator-superpredator (i.e., bird-rat-cat, briefly, BRC) model, where the predator's functional responses are derived based on the classical Holling's time budget arguments. Our BRC model overcomes several model construction problems in Courchamp et al. (1999), and admits richer, reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rat or the cat when the bird is endangered. We establish the existence of two types of mesopredator release phenomena: severe mesopredator release, where once superpredators are suppressed, a burst of mesopredators follows which leads their shared prey to extinction; and mild mesopredator release, where the mesopredator release could assert more negative impact on the endemic prey but does not lead the endemic prey to extinction. A sharp sufficient criterion is established for the occurrence of severe mesopredator release. We also show that, in a prey-mesopredator-superpredator trophic food web, eradication of introduced superpredators such as feral domestic cats in the BRC model, is not always the best solution to protect endemic insular prey. The presence of a superpredator may have a beneficial effect in such systems.
NASA Astrophysics Data System (ADS)
Cheung, Y. L.; Wong, W. O.
2011-08-01
The H∞ optimum parameters of a dynamic vibration absorber (DVA) with ground-support are derived to minimize the resonant vibration amplitude of a single degree-of-freedom (sdof) system under harmonic force excitation. The optimum parameters which are derived based on the classical fixed-points theory and reported in literature for this non-traditional DVA are shown to be not leading to the minimum resonant vibration amplitude of the controlled mass. A new procedure is proposed for the H∞ optimization of such a dynamic vibration absorber. A new set of optimum tuning frequency and damping of the absorber is derived, thereby resulting in lower maximum amplitude responses than those reported in the literature. The proposed optimized variant DVA is also compared to a ground-hooked damper of the same damping capacity of the damper in the DVA. It is proved that the proposed optimized DVA has better suppression of the resonant vibration amplitude of the controlled system than both the traditional DVA and also the ground-hooked damper if the proposed design procedure of the variant DVA is followed.
Salzer, Yael; de Hollander, Gilles; Forstmann, Birte U
2017-02-24
The Simon task is one of the most prominent interference tasks and has been extensively studied in experimental psychology and cognitive neuroscience. Despite years of research, the underlying mechanism driving the phenomenon and its temporal dynamics are still disputed. Within the framework of the review, we adopt a model-based cognitive neuroscience approach. We first go over key findings in the literature of the Simon task, discuss competing qualitative cognitive theories and the difficulty of testing them empirically. We then introduce sequential sampling models, a particular class of mathematical cognitive process models. Finally, we argue that the brain architecture accountable for the processing of spatial ('where') and non-spatial ('what') information, could constrain these models. We conclude that there is a clear need to bridge neural and behavioral measures, and that mathematical cognitive models may facilitate the construction of this bridge and work towards revealing the underlying mechanisms of the Simon effect.
NASA Astrophysics Data System (ADS)
Zheng, Yue; Bian, Yukun; Zhao, Nanrong; Hou, Zhonghuai
2014-03-01
A theoretical framework based on a generalized Langevin equation (GLE) with fractional Gaussian noise (fGn) and a power-law memory kernel is presented to describe the non-exponential kinetics of the unfolding of a single poly-ubiquitin molecule under a constant force [T.-L. Kuo, S. Garcia-Manyes, J. Li, I. Barel, H. Lu, B. J. Berne, M. Urbakh, J. Klafter, and J. M. Fernández, Proc. Natl. Acad. Sci. U.S.A. 107, 11336 (2010)]. Such a GLE-fGn strategy is made on the basis that the pulling coordinate variable x undergoes subdiffusion, usually resulting from conformational fluctuations, over a one-dimensional force-modified free-energy surface U(x, F). By using the Kramers' rate theory, we have obtained analytical formulae for the time-dependent rate coefficient k(t, F), the survival probability S(t, F) as well as the waiting time distribution function f(t, F) as functions of time t and force F. We find that our results can fit the experimental data of f(t, F) perfectly in the whole time range with a power-law exponent γ = 1/2, the characteristic of typical anomalous subdiffusion. In addition, the fitting of the survival probabilities for different forces facilitates us to reach rather reasonable estimations for intrinsic properties of the system, such as the free-energy barrier and the distance between the native conformation and the transition state conformation along the reaction coordinate, which are in good agreements with molecular dynamics simulations in the literatures. Although static disorder has been implicated in the original work of Kuo et al., our work suggests a sound and plausible alternative interpretation for the non-exponential kinetics in the stretching of poly-ubiquitin molecules, associated with dynamic disorder.
NASA Astrophysics Data System (ADS)
Ohkitani, Koji
2012-11-01
The celebrated Beale-Kato-Majda (BKM) criterion for the 3D Euler equations has been updated by Kozono and Taniuchi by replacing the supremum with the bounded mean oscillation norm. We consider this generalized criterion in an attempt to understand it more intuitively by giving an alternative explanation. For simplicity, we first treat the Constantin-Lax-Majda (CLM) equation dfrac{partial ω }{partial t}=H(ω )ω for the vorticity ω in one-dimension and identify a mechanism underlying the update of such an estimate. We consider a Fefferman-Stein (FS) decomposition for the initial vorticity ω = ω0 + H[ω1] and how it propagates under the dynamics of the CLM equation. In particular, we obtain a set of dynamical equations for it, which reads in its simplest case dfrac{partial ω _0}{partial t} =ω _0 H[ω _0]-{ω _1} H[{ω _1}] and dfrac{partial {ω _1}}{partial t} =ω _0 H[{ω _1}]+{ω _1} H[ω _0]. The equation for the second component ω1, responsible for a possible logarithmic blow-up, is linear and homogeneous; hence it remains zero if it is so initially until a stronger blow-up takes place. This rules out a logarithmic blow-up on its own and underlies the generalized BKM criterion. Numerical results are also presented to illustrate how each component of the FS decomposition evolves in time. Higher dimensional cases are also discussed. Without knowing fully explicit FS decompositions for the 3D Euler equations, we show that the second component of the FS decomposition will not appear if it is zero initially, thereby precluding a logarithmic blow-up.
Nasiri, Rasoul
2016-05-24
The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn't always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process.
Nasiri, Rasoul
2016-01-01
The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn’t always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process. PMID:27215897
Lewis, Tanza; Winter, Berndt; Stern, Abraham C.; Baer, Marcel D.; Mundy, Christopher J.; Tobias, Douglas J.; Hemminger, J. C.
2011-08-04
Molecular-level insight into the dissociation of nitric acid in water is obtained from photoelectron X-ray spectroscopy and first-principles molecular dynamics (MD) simulations. Our combined studies reveal surprisingly abrupt changes in solvation configurations of undissociated nitric acid at approximately 4 M concentration. Experimentally, this is inferred from N1s binding energy shifts of HNO3(aq) as a function of concentration, and is associated with variations in the local electronic structure of the nitrogen atom. It also shows up as a discontinuity in the degree of dissociation as a function of concentration, determined here from the N1s photoelectron signal intensity, which can be separately quantified for undissociated HNO3(aq) and dissociated NO3-(aq). Intermolecular interactions within the nitric acid solution are discussed on the basis of MD simulations, which reveal that molecular HNO3 interacts remarkably weakly with solvating water molecules at low concentration; around 4 M there is a turnover to a more structured solvation shell, accompanied by an increase in hydrogen bonding between HNO3 and water. We suggest that the driving force behind the more structured solvent configuration of HNO3 is the overlap of nitric acid solvent shells that sets in around 4 M concentration. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
Lewis, Tanza; Winter, Bernd; Stern, Abraham C; Baer, Marcel D; Mundy, Christopher J; Tobias, Douglas J; Hemminger, John C
2011-08-04
Molecular-level insight into the dissociation of nitric acid in water is obtained from X-ray photoelectron spectroscopy and first-principles molecular dynamics (MD) simulations. Our combined studies reveal surprisingly abrupt changes in solvation configurations of undissociated nitric acid at approximately 4 M concentration. Experimentally, this is inferred from shifts of the N1s binding energy of HNO(3)(aq) as a function of concentration and is associated with variations in the local electronic structure of the nitrogen atom. It also shows up as a discontinuity in the degree of dissociation as a function of concentration, determined here from the N1s photoelectron signal intensity, which can be separately quantified for undissociated HNO(3)(aq) and dissociated NO(3)(-)(aq). Intermolecular interactions within the nitric acid solution are discussed on the basis of MD simulations, which reveal that molecular HNO(3) interacts remarkably weakly with solvating water molecules at low concentration; around 4 M there is a turnover to a more structured solvation shell, accompanied by an increase in hydrogen bonding between HNO(3) and water. We suggest that the driving force behind the more structured solvent configuration of HNO(3) is the overlap of nitric acid solvent shells that sets in around 4 M concentration.
NASA Astrophysics Data System (ADS)
Nasiri, Rasoul
2016-05-01
The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn’t always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process.
Vellela, Melissa; Qian, Hong
2009-10-06
Schlögl's model is the canonical example of a chemical reaction system that exhibits bistability. Because the biological examples of bistability and switching behaviour are increasingly numerous, this paper presents an integrated deterministic, stochastic and thermodynamic analysis of the model. After a brief review of the deterministic and stochastic modelling frameworks, the concepts of chemical and mathematical detailed balances are discussed and non-equilibrium conditions are shown to be necessary for bistability. Thermodynamic quantities such as the flux, chemical potential and entropy production rate are defined and compared across the two models. In the bistable region, the stochastic model exhibits an exchange of the global stability between the two stable states under changes in the pump parameters and volume size. The stochastic entropy production rate shows a sharp transition that mirrors this exchange. A new hybrid model that includes continuous diffusion and discrete jumps is suggested to deal with the multiscale dynamics of the bistable system. Accurate approximations of the exponentially small eigenvalue associated with the time scale of this switching and the full time-dependent solution are calculated using Matlab. A breakdown of previously known asymptotic approximations on small volume scales is observed through comparison with these and Monte Carlo results. Finally, in the appendix section is an illustration of how the diffusion approximation of the chemical master equation can fail to represent correctly the mesoscopically interesting steady-state behaviour of the system.
Kaiser, Alexander; Ismailova, Oksana; Koskela, Antti; Huber, Stefan E.; Ritter, Marcel; Cosenza, Biagio; Benger, Werner; Nazmutdinov, Renat; Probst, Michael
2014-01-01
Molecular dynamics simulations of liquid ethylene glycol described by the OPLS-AA force field were performed to gain insight into its hydrogen-bond structure. We use the population correlation function as a statistical measure for the hydrogen-bond lifetime. In an attempt to understand the complicated hydrogen-bonding, we developed new molecular visualization tools within the Vish Visualization shell and used it to visualize the life of each individual hydrogen-bond. With this tool hydrogen-bond formation and breaking as well as clustering and chain formation in hydrogen-bonded liquids can be observed directly. Liquid ethylene glycol at room temperature does not show significant clustering or chain building. The hydrogen-bonds break often due to the rotational and vibrational motions of the molecules leading to an H-bond half-life time of approximately 1.5 ps. However, most of the H-bonds are reformed again so that after 50 ps only 40% of these H-bonds are irreversibly broken due to diffusional motion. This hydrogen-bond half-life time due to diffusional motion is 80.3 ps. The work was preceded by a careful check of various OPLS-based force fields used in the literature. It was found that they lead to quite different angular and H-bond distributions. PMID:24748697
Jain, Ashish R.; Venkat Prasad, M. K.; Ariga, Padma
2014-01-01
It is the responsibility of the dentist to fabricate a denture that is fully functional and perfectly esthetic. One prime oral function that has always been overlooked in this regard is speech. It has been thought that speech will follow mere replacement of teeth and that it is the patient's duty to fine tune this function with practice. Phonetics, esthetics, function and comfort form the foundation of a successful prosthodontic treatment. Accurate approximation of palatal contours of a maxillary complete denture to a patient's tongue can improve speech intelligibility, if other factors such as tooth position, occlusal plane and occlusal vertical dimension are satisfactory. Customizing palatal contours of a maxillary complete denture can be accomplished by using tissue-conditioning material, which provides sufficient working time for a patient to pronounce a series of sibilant sounds while recording dynamic impression of the tongue. This article describes a technique of obtaining palatogram and customizing palatal contours of a maxillary complete denture with autopolymerizing acrylic resin to improve the intelligibility of speech. PMID:24808716
NASA Astrophysics Data System (ADS)
Wucknitz, O.
2004-03-01
We discuss the LENSCLEAN algorithm which for a given gravitational lens model fits a source brightness distribution to interferometric radio data in a similar way as standard CLEAN does in the unlensed case. The lens model parameters can then be varied in order to minimize the residuals and determine the best model for the lens mass distribution. Our variant of this method is improved in order to be useful and stable even for high dynamic range systems with nearly degenerated lens model parameters. Our test case B0218+357 is dominated by two bright images but the information needed to constrain the unknown parameters is provided only by the relatively smooth and weak Einstein ring. The new variant of LENSCLEAN is able to fit lens models even in this difficult case. In order to allow the use of general mass models with LENSCLEAN, we develop the new method LENTIL which inverts the lens equation much more reliably than any other method. This high reliability is essential for the use as part of LENSCLEAN. Finally a new method is developed to produce source plane maps of the unlensed source from the best LENSCLEAN brightness models. This method is based on the new concept of `dirty beams' in the source plane. The application to the lens B0218+357 leads to the first useful constraints for the lens position and thus to a result for the Hubble constant. These results are presented in the accompanying Paper II, together with a discussion of classical lens modelling for this system.
NASA Astrophysics Data System (ADS)
Deau, E.
2007-12-01
In the Solar system, the planetary rings represent a fantastic opportunity of studying a majority of phenomena taking place in the thin discs. One can find discs at all redshifts and on all scales of the Universe. Planetary discs are very different~: among the jovian rings, one finds a halo of fine and diffuse dust; the rings of Uranus are very compact, like radially confined strings and the system of rings of Neptune consists of azimuthally stable arcs. However our interest goes on Saturn which has the most complex and widest system of rings known to date~: 484.000 km and a vertical extension which increases with the distance to Saturn (typically less than 1km to 10.000 km). The interest of such a matter organization around Saturn plus its many moons (more than one forty including 8 of a size of several hundreds kilometers) gave birth to the exploration mission CASSINI, supposed to allow the development and the refinement of models set up at the flybies of the two interplanetary probes VOYAGER. The CASSINI Mission began its nominal tour on january, 15th 2005 after the orbital insertion the 1st july 2004 and the dropping of HUYGENS probe on january, 14th 2005 on Titan's surface. The purpose of this thesis consists to revisite two subjects unsolved of long date in the photometric and dynamic behaviours of the Saturn's rings. In a first part, we try to solve the problem of accretion of matter within the Roche limit by studying the F ring. This ring, since its discovery in 1979 by Pioneer 11, is involved in a most various dynamic theories to explain its complex multi-radial structure and its variable azimuthal structure. We showed that the multi-radial structure of this ring can be understood by the existence of a spiral which is rolled up around a central area, bright, eccentric and inclined~: the core. The lifespan of this spiral is not the same one as the core, suggesting that the processes which create the spiral are periodic. Moreover, we showed that the
NASA Astrophysics Data System (ADS)
Burns, J. A.; Sharma, I.
2000-10-01
Motivated by the recent detection of complex rotational states for several asteroids and comets, as well as by the ongoing and planned spacecraft missions to such bodies, which should allow their rotational states to be accurately determined, we revisit the problem of the nutational damping of small solar system bodies. The nutational damping of asteroids has been approximately analyzed by Prendergast (1958), Burns and Safronov (1973), and Efroimsky and Lazarian (2000). Many other similar dynamical studies concern planetary wobble decay (e.g., Peale 1973; Yoder and Ward 1979), interstellar dust grain alignment (e.g., Purcell 1979; Lazarian and Efroimsky 1999) and damping of Earth's Chandler wobble (Lambeck 1980). Recall that rotational energy loss for an isolated body aligns the body's angular momentum vector with its axis of maximum inertia. Assuming anelastic dissipation, simple dimensional analysis determines a functional form of the damping timescale, on which all the above authors agree. However, the numerical coefficients of published results are claimed to differ by orders of magnitude. Differences have been ascribed to absent physics, to solutions that fail to satisfy boundary conditions perfectly, and to unphysical choices for the Q parameter. The true reasons for the discrepancy are unclear since, despite contrary claims, the full 3D problem (nutational damping of an anelastic ellipsoid) is analytically intractable so far. To move the debate forward, we compare the solution of a related 2D problem to the expressions found previously, and we present results from a finite element model. On this basis, we feel that previous rates for the decay of asteroidal tumbling (Harris 1994), derived from Burns and Safronov (1973), are likely to be accurate, at least to a factor of a few. Funded by NASA.
Revisiting Curriculum Potential
ERIC Educational Resources Information Center
Deng, Zongyi
2011-01-01
This article analyzes the notion of curriculum potential by revisiting the ideas of Miriam Ben-Peretz and Joseph Schwab. Invoking the German "Didaktik" tradition and by way of a curriculum-making framework, the paper argues that interpreting curriculum materials for curriculum potential requires a careful analysis and unpacking of the meanings and…
The Linguistic Repertoire Revisited
ERIC Educational Resources Information Center
Busch, Brigitta
2012-01-01
This article argues for the relevance of poststructuralist approaches to the notion of a linguistic repertoire and introduces the notion of language portraits as a basis for empirical study of the way in which speakers conceive and represent their heteroglossic repertoires. The first part of the article revisits Gumperz's notion of a linguistic…
ERIC Educational Resources Information Center
Bingolbali, Erhan; Monaghan, John
2008-01-01
Concept image and concept definition is an important construct in mathematics education. Its use, however, has been limited to cognitive studies. This article revisits concept image in the context of research on undergraduate students' understanding of the derivative which regards the context of learning as paramount. The literature, mainly on…
Colloquial Hebrew Imperatives Revisited
ERIC Educational Resources Information Center
Bolozky, Shmuel
2009-01-01
In revisiting Bolozky's [Bolozky, Shmuel, 1979. "On the new imperative in colloquial Hebrew." "Hebrew Annual Review" 3, 17-24] and Bat-El's [Bat-El, Outi, 2002. "True truncation in colloquial Hebrew imperatives." "Language" 78(4), 651-683] analyses of colloquial Hebrew imperatives, the article argues for restricting Imperative Truncation to the…
Swedish Successful Schools Revisited
ERIC Educational Resources Information Center
Hoog, Jonas; Johansson, Olof; Olofsson, Anders
2009-01-01
Purpose: The purpose of this paper is to describe the results of a follow-up study of two Swedish schools in which, five years previously, the principals had been successful leaders. Had this success been maintained? Design/methodology/approach: Two schools were revisited to enable the authors to interview principals and teachers as well as…
Parametric Resonance Revisited
NASA Astrophysics Data System (ADS)
van den Broeck, C.; Bena, I.
The phenomenon of parametric resonance is revisited. Several physical examples are reviewed and an exactly solvable model is discussed. A mean field theory is presented for globally coupled parametric oscillators with randomly distributed phases. A new type of collective instability appears, which is similar in nature to that of noise induced phase transitions.
A Hydrostatic Paradox Revisited
ERIC Educational Resources Information Center
Ganci, Salvatore
2012-01-01
This paper revisits a well-known hydrostatic paradox, observed when turning upside down a glass partially filled with water and covered with a sheet of light material. The phenomenon is studied in its most general form by including the mass of the cover. A historical survey of this experiment shows that a common misunderstanding of the phenomenon…
Revisiting Bioaccumulation Criteria
The objective of workgroup 5 was to revisit the B(ioaccumulation) criteria that are currently being used to identify POPs under the Stockholm Convention and PBTs under CEPA, TSCA, REACh and other programs. Despite the lack of a recognized definition for a B substance, we defined ...
A Hydrostatic Paradox Revisited
ERIC Educational Resources Information Center
Ganci, Salvatore
2012-01-01
This paper revisits a well-known hydrostatic paradox, observed when turning upside down a glass partially filled with water and covered with a sheet of light material. The phenomenon is studied in its most general form by including the mass of the cover. A historical survey of this experiment shows that a common misunderstanding of the phenomenon…
Anodic Polarization Curves Revisited
ERIC Educational Resources Information Center
Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin
2013-01-01
An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into…
Revisiting Bioaccumulation Criteria
The objective of workgroup 5 was to revisit the B(ioaccumulation) criteria that are currently being used to identify POPs under the Stockholm Convention and PBTs under CEPA, TSCA, REACh and other programs. Despite the lack of a recognized definition for a B substance, we defined ...
Revisiting Teachers as Learners
ERIC Educational Resources Information Center
Thomson, Liz
2008-01-01
This article revisits the concept of teachers as learners within the context of radical changes that have taken place within the education system in England over the past 25 years. The concept of "professional courage" is discussed and examined in relation to questions and issues raised by Paulo Freire in a series of letters to teachers…
Colloquial Hebrew Imperatives Revisited
ERIC Educational Resources Information Center
Bolozky, Shmuel
2009-01-01
In revisiting Bolozky's [Bolozky, Shmuel, 1979. "On the new imperative in colloquial Hebrew." "Hebrew Annual Review" 3, 17-24] and Bat-El's [Bat-El, Outi, 2002. "True truncation in colloquial Hebrew imperatives." "Language" 78(4), 651-683] analyses of colloquial Hebrew imperatives, the article argues for restricting Imperative Truncation to the…
A Multi-Level Model of Moral Functioning Revisited
ERIC Educational Resources Information Center
Reed, Don Collins
2009-01-01
The model of moral functioning scaffolded in the 2008 "JME" Special Issue is here revisited in response to three papers criticising that volume. As guest editor of that Special Issue I have formulated the main body of this response, concerning the dynamic systems approach to moral development, the problem of moral relativism and the role of…
Mass Spectrometric Immunoassay Revisited
Nelson, Randall W.; Borges, Chad R.
2013-01-01
The progressive understanding and improvement of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), realized over the years through the considerable efforts of Dr. Marvin Vestal, have made possible numerous comparable efforts involving its application in the biological sciences. Here we revisit the concepts behind one such analytical approach, Mass Spectrometric Immunoassay, which is designed to selectively detect and quantify proteins present in biological milieu. PMID:21953037
Singer, Peter A; Pellegrino, Edmund D; Siegler, Mark
2001-01-01
A decade ago, we reviewed the field of clinical ethics; assessed its progress in research, education, and ethics committees and consultation; and made predictions about the future of the field. In this article, we revisit clinical ethics to examine our earlier observations, highlight key developments, and discuss remaining challenges for clinical ethics, including the need to develop a global perspective on clinical ethics problems. PMID:11346456
NASA Astrophysics Data System (ADS)
Schultz, Colin
2011-12-01
Published in 2000, the original Mountain Rivers was written to provide a concise summary of the scientific understanding of the distinct subset of rivers that gave the book its name. Spurred by developments in the field in the past decade, the book's author, Ellen Wohl, produced Mountain Rivers Revisited, an updated edition aimed at graduate students and professional researchers. In this interview, Eos talks to Wohl about steep channels, climate change, and opportunities for future research.
Revisiting Dialogues and Monologues
ERIC Educational Resources Information Center
Kvernbekk, Tone
2012-01-01
In educational discourse dialogue tends to be viewed as being (morally) superior to monologue. When we look at them as basic forms of communication, we find that dialogue is a two-way, one-to-one form and monologue is a one-way, one-to-many form. In this paper I revisit the alleged (moral) superiority of dialogue. First, I problematize certain…
Revisiting Dialogues and Monologues
ERIC Educational Resources Information Center
Kvernbekk, Tone
2012-01-01
In educational discourse dialogue tends to be viewed as being (morally) superior to monologue. When we look at them as basic forms of communication, we find that dialogue is a two-way, one-to-one form and monologue is a one-way, one-to-many form. In this paper I revisit the alleged (moral) superiority of dialogue. First, I problematize certain…
Light-front representation of chiral dynamics with Δ isobar and large-Nc relations
Granados, C.; Weiss, C.
2016-06-13
Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O(Mπ–1) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). Recent work has shown that the EFT results can be represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft-pion-nucleon intermediate states, resulting in a quantum-mechanical picture of the peripheral transverse densities. We now extend this representation to include intermediate states with Δ isobars and implement relations based on themore » large-Nc limit of QCD. We derive the wave function overlap formulas for the Δ contributions to the peripheral transverse densities by way of a three-dimensional reduction of relativistic chiral EFT expressions. Our procedure effectively maintains rotational invariance and avoids the ambiguities with higher-spin particles in the light-front time-ordered approach. We study the interplay of πN and πΔ intermediate states in the quantum-mechanical picture of the densities in a transversely polarized nucleon. We show that the correct Nc-scaling of the charge and magnetization densities emerges as the result of the particular combination of currents generated by intermediate states with degenerate N and Δ. The off-shell behavior of the chiral EFT is summarized in contact terms and can be studied easily. As a result, the methods developed here can be applied to other peripheral densities and to moments of the nucleon's generalized parton distributions.« less
Light-front representation of chiral dynamics with Δ isobar and large- N c relations
NASA Astrophysics Data System (ADS)
Granados, C.; Weiss, C.
2016-06-01
Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O( M π - 1 ) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). Recent work has shown that the EFT results can be represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft-pion-nucleon intermediate states, resulting in a quantum-mechanical picture of the peripheral transverse densities. We now extend this representation to include intermediate states with Δ isobars and implement relations based on the large- N c limit of QCD. We derive the wave function overlap formulas for the Δ contributions to the peripheral transverse densities by way of a three-dimensional reduction of relativistic chiral EFT expressions. Our procedure effectively maintains rotational invariance and avoids the ambiguities with higher-spin particles in the light-front time-ordered approach. We study the interplay of π N and πΔ intermediate states in the quantum-mechanical picture of the densities in a transversely polarized nucleon. We show that the correct N c -scaling of the charge and magnetization densities emerges as the result of the particular combination of currents generated by intermediate states with degenerate N and Δ. The off-shell behavior of the chiral EFT is summarized in contact terms and can be studied easily. The methods developed here can be applied to other peripheral densities and to moments of the nucleon's generalized parton distributions.
NASA Astrophysics Data System (ADS)
Olivares-Rivas, Wilmer; Colmenares, Pedro J.
2016-09-01
The non-static generalized Langevin equation and its corresponding Fokker-Planck equation for the position of a viscous fluid particle were solved in closed form for a time dependent external force. Its solution for a constant external force was obtained analytically. The non-Markovian stochastic differential equation, associated to the dynamics of the position under a colored noise, was then applied to the description of the dynamics and persistence time of particles constrained within absorbing barriers. Comparisons with molecular dynamics were very satisfactory.
Al-Bassam, Jawdat
2017-02-01
Soluble αβ-tubulin heterodimers are maintained at high concentration inside eukaryotic cells, forming pools that fundamentally drive microtubule dynamics. Five conserved tubulin cofactors and ADP ribosylation factor-like 2 regulate the biogenesis and degradation of αβ-tubulins to maintain concentrated soluble pools. Here I describe a revised model for the function of three tubulin cofactors and Arl2 as a multisubunit GTP-hydrolyzing catalytic chaperone that cycles to promote αβ-tubulin biogenesis and degradation. This model helps explain old and new data indicating these activities enhance microtubule dynamics in vivo via repair or removal of αβ-tubulins from the soluble pools.
Light-front representation of chiral dynamics with Δ isobar and large-N_{c} relations
Granados, C.; Weiss, C.
2016-06-13
Transverse densities describe the spatial distribution of electromagnetic current in the nucleon at fixed light-front time. At peripheral distances b = O(M_{π}^{–1}) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). Recent work has shown that the EFT results can be represented in first-quantized form, as overlap integrals of chiral light-front wave functions describing the transition of the nucleon to soft-pion-nucleon intermediate states, resulting in a quantum-mechanical picture of the peripheral transverse densities. We now extend this representation to include intermediate states with Δ isobars and implement relations based on the large-N_{c} limit of QCD. We derive the wave function overlap formulas for the Δ contributions to the peripheral transverse densities by way of a three-dimensional reduction of relativistic chiral EFT expressions. Our procedure effectively maintains rotational invariance and avoids the ambiguities with higher-spin particles in the light-front time-ordered approach. We study the interplay of πN and πΔ intermediate states in the quantum-mechanical picture of the densities in a transversely polarized nucleon. We show that the correct N_{c}-scaling of the charge and magnetization densities emerges as the result of the particular combination of currents generated by intermediate states with degenerate N and Δ. The off-shell behavior of the chiral EFT is summarized in contact terms and can be studied easily. As a result, the methods developed here can be applied to other peripheral densities and to moments of the nucleon's generalized parton distributions.
Storch, Laura S; Pringle, James M; Alexander, Karen E; Jones, David O
2017-04-01
There is an ongoing debate about the applicability of chaotic and nonlinear models to ecological systems. Initial introduction of chaotic population models to the ecological literature was largely theoretical in nature and difficult to apply to real-world systems. Here, we build upon and expand prior work by performing an in-depth examination of the dynamical complexities of a spatially explicit chaotic population, within an ecologically applicable modeling framework. We pair a classic chaotic growth model (the logistic map) with explicit dispersal length scale and shape via a Gaussian dispersal kernel. Spatio-temporal heterogeneity is incorporated by applying stochastic perturbations throughout the spatial domain. We witness a variety of population dynamics dependent on the growth rate, dispersal distance, and domain size. Dispersal serves to eliminate chaotic population behavior for many of the parameter combinations tested. The model displays extreme sensitivity to changes in growth rate, dispersal distance, or domain size, but is robust to low-level stochastic population perturbations. Large and temporally consistent perturbations can lead to a change in population dynamics. Frequent switching occurs between chaotic/non-chaotic behaviors as dispersal distance, domain size, or growth rate increases. Small changes in these parameters are easy to imagine in real populations, and understanding or anticipating the abrupt resulting shifts in population dynamics is important for population management and conservation. Copyright © 2016 Elsevier Inc. All rights reserved.
NASA Astrophysics Data System (ADS)
Charles, Alexandre; Ballard, Patrick
2016-08-01
The dynamics of mechanical systems with a finite number of degrees of freedom (discrete mechanical systems) is governed by the Lagrange equation which is a second-order differential equation on a Riemannian manifold (the configuration manifold). The handling of perfect (frictionless) unilateral constraints in this framework (that of Lagrange's analytical dynamics) was undertaken by Schatzman and Moreau at the beginning of the 1980s. A mathematically sound and consistent evolution problem was obtained, paving the road for many subsequent theoretical investigations. In this general evolution problem, the only reaction force which is involved is a generalized reaction force, consistently with the virtual power philosophy of Lagrange. Surprisingly, such a general formulation was never derived in the case of frictional unilateral multibody dynamics. Instead, the paradigm of the Coulomb law applying to reaction forces in the real world is generally invoked. So far, this paradigm has only enabled to obtain a consistent evolution problem in only some very few specific examples and to suggest numerical algorithms to produce computational examples (numerical modeling). In particular, it is not clear what is the evolution problem underlying the computational examples. Moreover, some of the few specific cases in which this paradigm enables to write down a precise evolution problem are known to show paradoxes: the Painlevé paradox (indeterminacy) and the Kane paradox (increase in kinetic energy due to friction). In this paper, we follow Lagrange's philosophy and formulate the frictional unilateral multibody dynamics in terms of the generalized reaction force and not in terms of the real-world reaction force. A general evolution problem that governs the dynamics is obtained for the first time. We prove that all the solutions are dissipative; that is, this new formulation is free of Kane paradox. We also prove that some indeterminacy of the Painlevé paradox is fixed in this
Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go
2016-05-10
It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle's Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas.
Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go
2016-01-01
It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle’s Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas. PMID:27160346
NASA Astrophysics Data System (ADS)
Campbell, D. M.; Mackowiak, M.; Jonas, J.
1992-02-01
The main goal of this study is to extend the dynamic range of isomerization rates for cyclohexane in order to determine with high accuracy whether the barrier height to isomerization is pressure dependent. Therefore, the effect of pressure and temperature on the conformational isomerization of cyclohexane in carbon disulfide solvent has been investigated using the NMR (nuclear magnetic resonance) rotating frame relaxation technique. This technique, used for the first time in pressure studies of chemical exchange, allows the measurement of isomerization dynamics over a wide range of pressures and temperatures. By combining the rotating frame and NMR line shape techniques and generating the isoviscosity plots, it is shown that the barrier height to isomerization is independent of pressure. Since the experimental isomerization rate is accelerated by pressure, the viscosity dependence of the reduced transmission coefficient shows that the isomerization falls into the energy controlled (inertial) regime of the Kramers model in agreement with our earlier experimental findings. These experimental results, as interpreted in terms of stochastic models of isomerization reactions, indicate a strong collisional coupling and the presence of dynamical solvent effects.
``Robinson's sum rule'' revisited
NASA Astrophysics Data System (ADS)
Orlov, Yuri F.
2010-02-01
This discussion revisits two articles on synchrotron radiation damping published in 1958, one by this author and Evgeny K. Tarasov [Zh. Eksp. Teor. Fiz. 34, 651 (1958)ZETFA70044-4510; Sov. Phys. JETP 34, 449 (1958)SPHJAR0038-5646], and one by Kenneth W. Robinson [Phys. Rev. 111, 373 (1958)PHRVAO0031-899X10.1103/PhysRev.111.373]. The latter is the source of what is known as “Robinson’s sum rule.” Both present the familiar rule, but with very different proofs and calculations of concrete damping decrements. Comparative analysis of these differences reveals serious flaws in Robinson’s proof and calculations.
NASA Astrophysics Data System (ADS)
Schmidt, Alexandre G. M.; Paiva, Milena M.
2012-03-01
We revisit the quantum two-person duel. In this problem, both Alice and Bob each possess a spin-1/2 particle which models dead and alive states for each player. We review the Abbott and Flitney result—now considering non-zero α1 and α2 in order to decide if it is better for Alice to shoot or not the second time—and we also consider a duel where players do not necessarily start alive. This simple assumption allows us to explore several interesting special cases, namely how a dead player can win the duel shooting just once, or how can Bob revive Alice after one shot, and the better strategy for Alice—being either alive or in a superposition of alive and dead states—fighting a dead opponent.
Effective string theory revisited
NASA Astrophysics Data System (ADS)
Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor
2012-09-01
We revisit the effective field theory of long relativistic strings such as confining flux tubes in QCD. We derive the Polchinski-Strominger interaction by a calculation in static gauge. This interaction implies that a non-critical string which initially oscillates in one direction gets excited in orthogonal directions as well. In static gauge no additional term in the effective action is needed to obtain this effect. It results from a one-loop calculation using the Nambu-Goto action. Non-linearly realized Lorentz symmetry is manifest at all stages in dimensional regularization. We also explain that independent of the number of dimensions non-covariant counterterms have to be added to the action in the commonly used zeta-function regularization.
NASA Astrophysics Data System (ADS)
Jovanović, Dejan; Barrett, Clark
The classic method of Nelson and Oppen for combining decision procedures requires the theories to be stably-infinite. Unfortunately, some important theories do not fall into this category (e.g. the theory of bit-vectors). To remedy this problem, previous work introduced the notion of polite theories. Polite theories can be combined with any other theory using an extension of the Nelson-Oppen approach. In this paper we revisit the notion of polite theories, fixing a subtle flaw in the original definition. We give a new combination theorem which specifies the degree to which politeness is preserved when combining polite theories. We also give conditions under which politeness is preserved when instantiating theories by identifying two sorts. These results lead to a more general variant of the theorem for combining multiple polite theories.
Alakent, Burak; Camurdan, Mehmet C; Doruker, Pemra
2005-10-08
Time series models, which are constructed from the projections of the molecular-dynamics (MD) runs on principal components (modes), are used to mimic the dynamics of two proteins: tendamistat and immunity protein of colicin E7 (ImmE7). Four independent MD runs of tendamistat and three independent runs of ImmE7 protein in vacuum are used to investigate the energy landscapes of these proteins. It is found that mean-square displacements of residues along the modes in different time scales can be mimicked by time series models, which are utilized in dividing protein dynamics into different regimes with respect to the dominating motion type. The first two regimes constitute the dominance of intraminimum motions during the first 5 ps and the random walk motion in a hierarchically higher-level energy minimum, which comprise the initial time period of the trajectories up to 20-40 ps for tendamistat and 80-120 ps for ImmE7. These are also the time ranges within which the linear nonstationary time series are completely satisfactory in explaining protein dynamics. Encountering energy barriers enclosing higher-level energy minima constrains the random walk motion of the proteins, and pseudorelaxation processes at different levels of minima are detected in tendamistat, depending on the sampling window size. Correlation (relaxation) times of 30-40 ps and 150-200 ps are detected for two energy envelopes of successive levels for tendamistat, which gives an overall idea about the hierarchical structure of the energy landscape. However, it should be stressed that correlation times of the modes are highly variable with respect to conformational subspaces and sampling window sizes, indicating the absence of an actual relaxation. The random-walk step sizes and the time length of the second regime are used to illuminate an important difference between the dynamics of the two proteins, which cannot be clarified by the investigation of relaxation times alone: ImmE7 has lower
Visser's massive graviton bimetric theory revisited
Roany, Alain de; Chauvineau, Bertrand; Freitas Pacheco, Jose A. de
2011-10-15
A massive gravity theory was proposed by Visser in the late 1990s. This theory, based on a background metric b{sub {alpha}{beta}} and on an usual dynamical metric g{sub {alpha}{beta}} has the advantage of being free of ghosts as well as discontinuities present in other massive theories proposed in the past. In the present investigation, the equations of Visser's theory are revisited with particular care on the related conservation laws. It will be shown that a multiplicative factor is missing in the graviton tensor originally derived by Visser, which has no incidence on the weak field approach but becomes important in the strong field regime when, for instance, cosmological applications are considered. In this case, contrary to some previous claims found in the literature, we conclude that a nonstatic background metric is required in order to obtain a solution able to mimic the {Lambda}CDM cosmology.
NASA Astrophysics Data System (ADS)
Dimitrov, I. K.
2005-03-01
In-situ SANS and ac-susceptibility measurements have provided evidence for a first-order Bragg glass transition into a disordered vortex state in a Nb single crystal. This transition manifests itself in the peak effect (PE) in the critical current density, widely believed to be associated with the sudden softening of the vortex lattice. Subsequent studies mapping the full phase diagram in the same sample have suggested the existence of four distinct phase boundaries meeting at a single multicritical point (MCP). The natures of the transition lines combined with simple thermodynamic requirements suggest that the MCP is a bicritical point. This would rule out either the bulk transition line Tc2(T) or the surface superconducting transition Hc3(T) as being related to the MCP. Mutual inductance magnetic ac-susceptibility and ultrasonic attenuation measurements in V-21at.%Ti have unequivocally established the presence of a PE in this alloy. The H-T phase diagram for this sample will be presented and vortex dynamics in the vicinity of the PE will be discussed. We are indebted to Prof. Shapira of Tufts University for providing us with the sample. This work was supported by the NSF under Grant No. DMR-0406626.
Millau, Jean-François; Bastien, Nathalie; Bouchard, Eric F; Drouin, Régen
2009-11-01
p53 is a master transcription factor that prevents neoplasia and genomic instability. It is an important target for anticancer drug design. Understanding the molecular mechanisms behind its transcriptional activities in normal cells is a prerequisite to further understand the deregulation effected by mutant p53 in cancerous cells. Currently, how p53 coordinates transcription programs in response to stress remains unclear. One theory proposes that stresses induce pre-binding events that direct p53 to bind to specific response elements, whereas a second posits that, in response to stress, p53 binds most response elements and post-binding events then regulate transcription initiation. It is critical to establish the relevance of both theories and investigate whether stresses induce specific p53-binding patterns correlated with effector gene induction. Using unique in cellulo genomic footprinting experiments, we studied p53 binding to the five response elements of p21 in response to stresses and monitored p21 mRNA variant transcription. We show clear footprints of p53 bound to response elements in living cells and reveal that the binding of p53 to response elements is transient, subject to dynamic changes during stress responses, and influenced by response element pentamer orientations. We show further that stresses lead to specific p53-binding patterns correlated with particular p21 mRNA variant transcription profiles and that p53 binding is necessary but not sufficient to induce p21 transcription. Our results indicate that pre- and post-binding events act together to regulate adapted stress responses; this paves the way to the unification of pre- and post-binding event theories.
Twin Signature Schemes, Revisited
NASA Astrophysics Data System (ADS)
Schäge, Sven
In this paper, we revisit the twin signature scheme by Naccache, Pointcheval and Stern from CCS 2001 that is secure under the Strong RSA (SRSA) assumption and improve its efficiency in several ways. First, we present a new twin signature scheme that is based on the Strong Diffie-Hellman (SDH) assumption in bilinear groups and allows for very short signatures and key material. A big advantage of this scheme is that, in contrast to the original scheme, it does not require a computationally expensive function for mapping messages to primes. We prove this new scheme secure under adaptive chosen message attacks. Second, we present a modification that allows to significantly increase efficiency when signing long messages. This construction uses collision-resistant hash functions as its basis. As a result, our improvements make the signature length independent of the message size. Our construction deviates from the standard hash-and-sign approach in which the hash value of the message is signed in place of the message itself. We show that in the case of twin signatures, one can exploit the properties of the hash function as an integral part of the signature scheme. This improvement can be applied to both the SRSA based and SDH based twin signature scheme.
NASA Astrophysics Data System (ADS)
Pagani, L.; Pardo-Carrion, J. R.; Stepnik, B.
2001-07-01
L134N (also known as L183) is a very cold, starless and nearby dark cloud which has attracted much attention from the astrochemists in the past. They have been using it as an oxygen-rich reference to test their models in parallel with TMC-1, the other, but carbon-rich, reference. However, our knowledge of the cloud temperature, structure, and various species abundances has relied for a long time largely on the work by Swade (1987a, 1987b) which suffers from low signal-to-noise C18O and CS maps and limited excitation analysis. This work has been recently repeated and improved by Dickens et al. (2000) but they still lack adequate surface coverage, higher rotational lines of important species and comparison with the dust. While FIRST will probably find many new species in this cloud, it is time to revisit completely this source in order to interpret correctly the FIRST results to come. We have thus made a complete survey of several transitions of CO, 13CO, C18O, C17O, CS, C34S, SO and 34SO species with the NRAO 12-m and CSO 10-m together with maps of the dust from ISO and SCUBA to assess the fundamental properties of this cloud. Preliminary results are reported here.
Aziz, M; Jacob, A; Wang, P
2014-01-01
Sepsis is a life-threatening illness that occurs due to an abnormal host immune network which extends through the initial widespread and overwhelming inflammation, and culminates at the late stage of immunosupression. Recently, interest has been shifted toward therapies aimed at reversing the accompanying periods of immune suppression. Studies in experimental animals and critically ill patients have demonstrated that increased apoptosis of lymphoid organs and some parenchymal tissues contributes to this immune suppression, anergy and organ dysfunction. Immediate to the discoveries of the intracellular proteases, caspases for the induction of apoptosis and inflammation, and their striking roles in sepsis have been focused elaborately in a number of original and review articles. Here we revisited the different aspects of caspases in terms of apoptosis, pyroptosis, necroptosis and inflammation and focused their links in sepsis by reviewing several recent findings. In addition, we have documented striking perspectives which not only rewrite the pathophysiology, but also modernize our understanding for developing novel therapeutics against sepsis. PMID:25412304
P., Henry
2008-11-20
A recent article in which John Searle claims to refute dualism is examined from a scientific perspective. John Searle begins his recent article 'Dualism Revisited' by stating his belief that the philosophical problem of consciousness has a scientific solution. He then claims to refute dualism. It is therefore appropriate to examine his arguments against dualism from a scientific perspective. Scientific physical theories contain two kinds of descriptions: (1) Descriptions of our empirical findings, expressed in an every-day language that allows us communicate to each other our sensory experiences pertaining to what we have done and what we have learned; and (2) Descriptions of a theoretical model, expressed in a mathematical language that allows us to communicate to each other certain ideas that exist in our mathematical imaginations, and that are believed to represent, within our streams of consciousness, certain aspects of reality that we deem to exist independently of their being perceived by any human observer. These two parts of our scientific description correspond to the two aspects of our general contemporary dualistic understanding of the total reality in which we are imbedded, namely the empirical-mental aspect and the theoretical-physical aspect. The duality question is whether this general dualistic understanding of ourselves should be regarded as false in some important philosophical or scientific sense.
Hunana, P.; Zank, G. P.; Webb, G. M.; Adhikari, L.; Goldstein, M. L.
2016-03-25
Solar wind observational studies have emphasized that the solar wind plasma data is bounded by the mirror and firehose instabilities, and it is often believed that these instabilities are of a purely kinetic nature. The simplest fluid model that generalizes magnetohydrodynamics with anisotropic temperatures is the Chew-Goldberger-Low model (CGL). Here we briefly revisit the CGL description and discuss its (otherwise well-documented) linear firehose and mirror instability thresholds; namely that the firehose instability threshold is identical to the one found from linear kinetic theory and that the mirror threshold contains a factor of 6 error. We consider a simple higher-order fluid model with time dependent heat flux equations and show that the mirror instability threshold is correctly reproduced. We also present fully nonlinear three-dimensional simulations of freely decaying turbulence for the Hall-CGL model with isothermal electrons. The spatial resolution of these simulations is 512{sup 3} and the formation of a spectral break in magnetic and velocity field spectra around the proton inertial length is found.
Multinomial pattern matching revisited
NASA Astrophysics Data System (ADS)
Horvath, Matthew S.; Rigling, Brian D.
2015-05-01
Multinomial pattern matching (MPM) is an automatic target recognition algorithm developed for specifically radar data at Sandia National Laboratories. The algorithm is in a family of algorithms that first quantizes pixel value into Nq bins based on pixel amplitude before training and classification. This quantization step reduces the sensitivity of algorithm performance to absolute intensity variation in the data, typical of radar data where signatures exhibit high variation for even small changes in aspect angle. Our previous work has focused on performance analysis of peaky template matching, a special case of MPM where binary quantization is used (Nq = 2). Unfortunately references on these algorithms are generally difficult to locate and here we revisit the MPM algorithm and illustrate the underlying statistical model and decision rules for two algorithm interpretations: the 1-of-K vector form and the scalar. MPM can also be used as a detector and specific attention is given to algorithm tuning where "peak pixels" are chosen based on their underlying empirical probabilities according to a reward minimization strategy aimed at reducing false alarms in the detection scenario and false positives in a classification capacity. The algorithms are demonstrated using Monte Carlo simulations on the AFRL civilian vehicle dataset for variety of choices of Nq.
Reif, Maria M; Hünenberger, Philippe H
2016-08-25
The asymmetric solvation of ions can be defined as the tendency of a solvent to preferentially solvate anions over cations or cations over anions, at identical ionic charge magnitudes and effective sizes. Taking water as a reference, these effects are quantified experimentally for many solvents by the relative acity (A) and basity (B) parameters of the Swain scale. The goal of the present study is to investigate the asymmetric solvation of ions using molecular dynamics simulations, and to connect the results to this empirical scale. To this purpose, the charging free energies of alkali and halide ions, and of their hypothetical oppositely charged counterparts, are calculated in a variety of solvents. In a first set of calculations, artificial solvent models are considered that present either a charge or a shape asymmetry at the molecular level. The solvation asymmetry, probed by the difference in charging free energy between the two oppositely charged ions, is found to encompass a term quadratic in the ion charge, related to the different solvation structures around the anion and cation, and a term linear in the ion charge, related to the solvation structure around the uncharged ion-sized cavity. For these simple solvent models, the two terms are systematically counteracting each other, and it is argued that only the quadratic term should be retained when comparing the results of simulations involving physical solvents to experimental data. In a second set of calculations, 16 physical solvents are considered. The theoretical estimates for the acity A are found to correlate very well with the Swain parameters, whereas the correlation for B is very poor. Based on this observation, the Swain scale is reformulated into a new scale involving an asymmetry parameter Σ, positive for acitic solvents and negative for basitic ones, and a polarity parameter Π. This revised scale has the same predictive power as the original scale, but it characterizes asymmetry in an
The "Mushroom Cloud" Demonstration Revisited
ERIC Educational Resources Information Center
Panzarasa, Guido; Sparnacci, Katia
2013-01-01
A revisitation of the classical "mushroom cloud" demonstration is described. Instead of aniline and benzoyl peroxide, the proposed reaction involves household chemicals such as alpha-pinene (turpentine oil) and trichloroisocyanuric acid ("Trichlor") giving an impressive demonstration of oxidation and combustion reactions that…
Cultural Warping of Childbirth, Revisited
Budin, Wendy C.
2007-01-01
In this column, the editor of The Journal of Perinatal Education revisits Doris Haire's classic 1972 article, “The Cultural Warping of Childbirth,” and describes the birth culture of today. The editor also describes the contents of this issue, which offer a broad range of resources, research, and inspiration for childbirth educators in their efforts to promote normal birth.
The "Mushroom Cloud" Demonstration Revisited
ERIC Educational Resources Information Center
Panzarasa, Guido; Sparnacci, Katia
2013-01-01
A revisitation of the classical "mushroom cloud" demonstration is described. Instead of aniline and benzoyl peroxide, the proposed reaction involves household chemicals such as alpha-pinene (turpentine oil) and trichloroisocyanuric acid ("Trichlor") giving an impressive demonstration of oxidation and combustion reactions that…
Benjamin Franklin and Mesmerism, revisited.
McConkey, Kevin M; Perry, Campbell
2002-10-01
The authors revisit and update their previous historiographical note (McConkey & Perry, 1985) on Benjamin Franklin's involvement with and investigation of animal magnetism or mesmerism. They incorporate more recent literature and offer additional comment about Franklin's role in and views about mesmerism. Franklin had a higher degree of personal involvement with and a more detailed opinion of mesmerism than has been previously appreciated.
Revisiting the Schoolwide Enrichment Model--An Approach to Gifted Programming.
ERIC Educational Resources Information Center
Gibson, Sherry; Efinger, Joan
2001-01-01
This article provides a consistent framework through which educators may better identify and serve gifted and talented students by revisiting the dynamics of the Schoolwide Enrichment Model (SEM) in relation to student achievement. Delivery and structural and organizational components of SEM are discussed, along with research supporting the model.…
Quasicycles revisited: apparent sensitivity to initial conditions.
Pascual, Mercedes; Mazzega, Pierre
2003-11-01
Environmental noise is known to sustain cycles by perturbing a deterministic approach to equilibrium that is itself oscillatory. Quasicycles produced in this way display a regular period but varied amplitude. They were proposed by Nisbet and Gurney (Nature 263 (1976) 319) as one possible explanation for population fluctuations in nature. Here, we revisit quasicyclic dynamics from the perspective of nonlinear time series analysis. Time series are generated with a predator-prey model whose prey's growth rate is driven by environmental noise. A method for the analysis of short and noisy data provides evidence for sensitivity to initial conditions, with a global Lyapunov exponent often close to zero characteristic of populations 'at the edge of chaos'. Results with methods restricted to long time series are consistent with a finite-dimensional attractor on which dynamics are sensitive to initial conditions. These results are compared with those previously obtained for quasicycles in an individual-based model with heterogeneous spatial distributions. Patterns of sensitivity to initial conditions are shown to differentiate phase-forgetting from phase-remembering quasicycles involving a periodic driver. The previously reported mode at zero of Lyapunov exponents in field and laboratory populations may reflect, in part, quasicyclic dynamics.
Sea quark matrix elements and flavor singlet spectroscopy on the lattice
Lagae, J.F.
1996-12-31
I summarize the results of three recent lattice studies which use stochastic estimator techniques in order to investigate the flavor singlet dynamics in QCD. These include a measurement of the pion-nucleon {sigma}-term, the computation of the flavor singlet axial coupling constant of the nucleon and a determination of flavor singlet meson screening lengths in finite temperature QCD.
BHQ revisited (2): Texture development
NASA Astrophysics Data System (ADS)
Kilian, Rüdiger; Heilbronner, Renée
2016-04-01
appears that grains can be unfavourably oriented for glide despite their c-axis direction falling in those positions which were used in the "classical" interpretation. Additionally, it turns out that grain-scale dispersion axes can be used to describe the kinematic behaviour in a more consistent way compared to the rotations axes obtained from intragranular misorientations in the range of 2-10°. The implications derived from the experimental data set will be compared to data obtained from natural quartz mylonites which formed in a comparable recrystallization regime. This is the companion poster to "BHQ revisited (I) looking at grain size" where the development of the dynamically recrystallized grain size is addressed. Reference cited: Heilbronner, R., and J. Tullis (2006), Evolution of c axis pole figures and grain size during dynamic recrystallization: Results from experimentally sheared quartzite, J. Geophys. Res., 111, B10202, doi:10.1029/2005JB004194.
Parallel Dynamics of Continuous Hopfield Model Revisited
NASA Astrophysics Data System (ADS)
Mimura, Kazushi
2009-03-01
We have applied the generating functional analysis (GFA) to the continuous Hopfield model. We have also confirmed that the GFA predictions in some typical cases exhibit good consistency with computer simulation results. When a retarded self-interaction term is omitted, the GFA result becomes identical to that obtained using the statistical neurodynamics as well as the case of the sequential binary Hopfield model.
Enceladus' tidal dissipation revisited
NASA Astrophysics Data System (ADS)
Tobie, Gabriel; Behounkova, Marie; Choblet, Gael; Cadek, Ondrej; Soucek, Ondrej
2016-10-01
A series of chemical and physical evidence indicates that the intense activity at Enceladus' South Pole is related to a subsurface salty water reservoir underneath the tectonically active ice shell. The detection of a significant libration implies that this water reservoir is global and that the average ice shell thickness is about 20-25km (Thomas et al. 2016). The interpretation of gravity and topography data further predicts large variations in ice shell thickness, resulting in a shell potentially thinner than 5 km in the South Polar Terrain (SPT) (Cadek et al. 2016). Such an ice shell structure requires a very strong heat source in the interior, with a focusing mechanism at the SPT. Thermal diffusion through the ice shell implies that at least 25-30 GW is lost into space by passive diffusion, implying a very efficient dissipation mechanism in Enceladus' interior to maintain such an ocean/ice configuration thermally stable.In order to determine in which conditions such a large dissipation power may be generated, we model the tidal response of Enceladus including variable ice shell thickness. For the rock core, we consider a wide range of rheological parameters representative of water-saturated porous rock materials. We demonstrate that the thinning toward the South Pole leads to a strong increase in heat production in the ice shell, with a optimal thickness obtained between 1.5 and 3 km, depending on the assumed ice viscosity. Our results imply that the heat production in the ice shell within the SPT may be sufficient to counterbalance the heat loss by diffusion and to power eruption activity. However, outside the SPT, a strong dissipation in the porous core is required to counterbalance the diffusive heat loss. We show that about 20 GW can be generated in the core, for an effective viscosity of 1012 Pa.s, which is comparable to the effective viscosity estimated in water-saturated glacial tills on Earth. We will discuss the implications of this revisited tidal
First Grade Writers Revisit Their Work
ERIC Educational Resources Information Center
Hansen, Jane A.
2007-01-01
In this article, the author focuses on first grade readers and writers who revisit their work and describes what first-graders do when they revisit their writing about science and literature and review collections of their work. The first-graders discussed here are in Elaine O'Connor's classroom at Clark Elementary School in Charlottesville. In a…
The Battle of Britain Revisited
1989-05-01
In any European war, it is likely that the United Kingdom would be a lucrative target for the WP air forces. A considerable proportion of NATO...Winston. The Second World War. Vols I and II, Cassell, London, 1948. 2. Collier, Basil. The Defence of the United Kingdom . HMSO London, 1952. 3...DTIC tiLE COPY,0 AIR WAS COLLEGEL I4 RESEARCH REPORT Lfl THE BATTLE OF BRITAIN REVISITED GROUP CAPTAIN JOHN H. SPENCER ROYAL AIR FORCE DTIC
Asymptotic structure of electrodynamics revisited
NASA Astrophysics Data System (ADS)
Herdegen, Andrzej
2017-03-01
We point out that recently published analyses of null and timelike infinity and long-range structures in electrodynamics to large extent rediscover results present in the literature. At the same time, some of the conclusions these recent works put forward may prove controversial. In view of these facts, we find it desirable to revisit the analysis taken up more than two decades ago, starting from earlier works on null infinity by other authors.
Revisiting and computing reaction coordinates with Directional Milestoning.
Kirmizialtin, Serdal; Elber, Ron
2011-06-16
The method of Directional Milestoning is revisited. We start from an exact and more general expression and state the conditions and validity of the memory-loss approximation. An algorithm to compute a reaction coordinate from Directional Milestoning data is presented. The reaction coordinate is calculated as a set of discrete jumps between Milestones that maximizes the flux between two stable states. As an application we consider a conformational transition in solvated adenosine. We compare a long molecular dynamic trajectory with Directional Milestoning and discuss the differences between the maximum flux path and minimum energy coordinates. © 2011 American Chemical Society
Radiolytic Cryovolcanism Revisited
NASA Astrophysics Data System (ADS)
Cooper, J. F.; Cooper, P. D.; Sittler, E. C.; Wesenberg, R. P.
2013-12-01
Active geysers of water vapor and ice grains from the south pole of Enceladus are not yet definitively explained in terms of energy sources and processes. Other instances of hot (Io) and cold (Mars, Triton) volcanism beyond Earth are known if not fully understood. We revisit, in comparison to other models, the 'Old Faithful' theory of radiolytic gas-driven cryovolcanism first proposed by Cooper et al. [Plan. Sp. Sci. 2009]. In the energetic electron irradiation environment of Enceladus within Saturn's magnetosphere, a 10-percent duty cycle could be maintained for current geyser activity driven by gases from oxidation of ammonia to N2 and methane to CO2 in the thermal margins of a south polar sea. Much shorter duty cycles down to 0.01 percent would be required to account for thermal power output up to 16 GW, Steady accumulation of oxidant energy over four billion years could have powered all Enceladus emissions over the past four hundred thousand to four hundred million years. There could be separate energy sources driving mass flow and thermal emission over vastly different time scales. Since episodic tidal dissipation on 10 Myr time scales at 0.1 - 1 Gyr intervals [O'Neill and Nimmo, Nature 2010], and thus duty cycles 1 - 10 percent, could heat the polar sea to the current level, the radiolytic energy source could easily power and modulate the geyser mass flow on million-year time scales. Maximum thermal emission temperature 223 K [Abramov and Spencer, Icarus 2009] hints at thermal buffering in the basal and vent wall layers by a 1:1 H2O:H2O2 radiolytic eutectic, assuming deep ice crust saturation with H2O2 from long cumulative surface irradiation and downward ice convection. Due to density stratification the peroxide eutectic and salt water layers could separate, so that the denser peroxide layer (1.2 g/cc) descends to the polar sea while the lighter salt water (1.05 g/cc) rises along separate channels. Methane reservoirs could be found dissolved into the polar
Friston, Karl J; Bastos, André M; Oswal, Ashwini; van Wijk, Bernadette; Richter, Craig; Litvak, Vladimir
2014-11-01
This technical paper offers a critical re-evaluation of (spectral) Granger causality measures in the analysis of biological timeseries. Using realistic (neural mass) models of coupled neuronal dynamics, we evaluate the robustness of parametric and nonparametric Granger causality. Starting from a broad class of generative (state-space) models of neuronal dynamics, we show how their Volterra kernels prescribe the second-order statistics of their response to random fluctuations; characterised in terms of cross-spectral density, cross-covariance, autoregressive coefficients and directed transfer functions. These quantities in turn specify Granger causality - providing a direct (analytic) link between the parameters of a generative model and the expected Granger causality. We use this link to show that Granger causality measures based upon autoregressive models can become unreliable when the underlying dynamics is dominated by slow (unstable) modes - as quantified by the principal Lyapunov exponent. However, nonparametric measures based on causal spectral factors are robust to dynamical instability. We then demonstrate how both parametric and nonparametric spectral causality measures can become unreliable in the presence of measurement noise. Finally, we show that this problem can be finessed by deriving spectral causality measures from Volterra kernels, estimated using dynamic causal modelling.
Friston, Karl J.; Bastos, André M.; Oswal, Ashwini; van Wijk, Bernadette; Richter, Craig; Litvak, Vladimir
2014-01-01
This technical paper offers a critical re-evaluation of (spectral) Granger causality measures in the analysis of biological timeseries. Using realistic (neural mass) models of coupled neuronal dynamics, we evaluate the robustness of parametric and nonparametric Granger causality. Starting from a broad class of generative (state-space) models of neuronal dynamics, we show how their Volterra kernels prescribe the second-order statistics of their response to random fluctuations; characterised in terms of cross-spectral density, cross-covariance, autoregressive coefficients and directed transfer functions. These quantities in turn specify Granger causality — providing a direct (analytic) link between the parameters of a generative model and the expected Granger causality. We use this link to show that Granger causality measures based upon autoregressive models can become unreliable when the underlying dynamics is dominated by slow (unstable) modes — as quantified by the principal Lyapunov exponent. However, nonparametric measures based on causal spectral factors are robust to dynamical instability. We then demonstrate how both parametric and nonparametric spectral causality measures can become unreliable in the presence of measurement noise. Finally, we show that this problem can be finessed by deriving spectral causality measures from Volterra kernels, estimated using dynamic causal modelling. PMID:25003817
NASA Astrophysics Data System (ADS)
Álvarez, Enrique; González-Martín, Sergio
2017-02-01
The on shell equivalence of first order and second order formalisms for the Einstein-Hilbert action does not hold for those actions quadratic in curvature. It would seem that by considering the connection and the metric as independent dynamical variables, there are no quartic propagators for any dynamical variable. This suggests that it is possible to get both renormalizability and unitarity along these lines. We have studied a particular instance of those theories, namely Weyl gravity. In this first paper we show that it is not possible to implement this program with the Weyl connection alone.
NASA Astrophysics Data System (ADS)
Casdagli, M. C.
1997-09-01
We show that recurrence plots (RPs) give detailed characterizations of time series generated by dynamical systems driven by slowly varying external forces. For deterministic systems we show that RPs of the time series can be used to reconstruct the RP of the driving force if it varies sufficiently slowly. If the driving force is one-dimensional, its functional form can then be inferred up to an invertible coordinate transformation. The same results hold for stochastic systems if the RP of the time series is suitably averaged and transformed. These results are used to investigate the nonlinear prediction of time series generated by dynamical systems driven by slowly varying external forces. We also consider the problem of detecting a small change in the driving force, and propose a surrogate data technique for assessing statistical significance. Numerically simulated time series and a time series of respiration rates recorded from a subject with sleep apnea are used as illustrative examples.
Revisiting and parallelizing SHAKE
NASA Astrophysics Data System (ADS)
Weinbach, Yael; Elber, Ron
2005-10-01
An algorithm is presented for running SHAKE in parallel. SHAKE is a widely used approach to compute molecular dynamics trajectories with constraints. An essential step in SHAKE is the solution of a sparse linear problem of the type Ax = b, where x is a vector of unknowns. Conjugate gradient minimization (that can be done in parallel) replaces the widely used iteration process that is inherently serial. Numerical examples present good load balancing and are limited only by communication time.
Revisiting large neutrino magnetic moments
NASA Astrophysics Data System (ADS)
Lindner, Manfred; Radovčić, Branimir; Welter, Johannes
2017-07-01
Current experimental sensitivity on neutrino magnetic moments is many orders of magnitude above the Standard Model prediction. A potential measurement of next-generation experiments would therefore strongly request new physics beyond the Standard Model. However, large neutrino magnetic moments generically tend to induce large corrections to the neutrino masses and lead to fine-tuning. We show that in a model where neutrino masses are proportional to neutrino magnetic moments. We revisit, discuss and propose mechanisms that still provide theoretical consistent explanations for a potential measurement of large neutrino magnetic moments. We find only two viable mechanisms to realize large transition magnetic moments for Majorana neutrinos only.
Lithium in the Pleiades Revisited
NASA Astrophysics Data System (ADS)
King, J. R.; Hobbs, L. M.; Schuler, S. C.; Pinsonneault, M. H.
2003-12-01
New Li abundances have been derived for some 15-20 Pleiades dwarfs using new high-resolution and high S/N spectroscopy from HET/HRS. Previous studies suggested that our objects, all modest (projected) rotators, evinced considerable scatter in their Li abundances. We revisit the question of this scatter and its origin. This work has been supported by NSF grants AST 00-86576 and 02-39518, a South Carolina Space Grant Scholarship award, a generous donation from the Curry Foundation of Seneca, SC, and the NOAO Public Access Program.
Chao, Alex; /SLAC
2008-07-25
An early, but at the time illuminating, piece of work on how to deal with a general, linearly coupled accelerator lattice is revisited. This work is based on the SLIM formalism developed in 1979-1981.
McLean's second variation formula revisited
NASA Astrophysics Data System (ADS)
Lê, Hông Vân; Vanžura, Jiří
2017-03-01
We revisit McLean's second variation formulas for calibrated submanifolds in exceptional geometries, and correct his formulas concerning associative submanifolds and Cayley submanifolds, using a unified treatment based on the (relative) calibration method and Harvey-Lawson's identities.
Rabbits killing birds revisited.
Zhang, Jimin; Fan, Meng; Kuang, Yang
2006-09-01
We formulate and study a three-species population model consisting of an endemic prey (bird), an alien prey (rabbit) and an alien predator (cat). Our model overcomes several model construction problems in existing models. Moreover, our model generates richer, more reasonable and realistic dynamics. We explore the possible control strategies to save or restore the bird by controlling or eliminating the rabbit or the cat when the bird is endangered. We confirm the existence of the hyperpredation phenomenon, which is a big potential threat to most endemic prey. Specifically, we show that, in an endemic prey-alien prey-alien predator system, eradication of introduced predators such as the cat alone is not always the best solution to protect endemic insular prey since predator control may fail to protect the indigenous prey when the control of the introduced prey is not carried out simultaneously.
2013-01-01
The overhead pitching motion is described as a coordinated sequence of body movements and muscular forces that have an ultimate goal of achieving high ball velocity and target accuracy. An understanding of the dynamic overhead throwing motion outlined in this clinical commentary can assist the clinician in addressing the unique injuries experienced by the pitcher. The potential biomechanical sources for injury have been studied utilizing videography and electromyographic techniques due to the rapid pace with which the pitching motion occurs. This clinical comentary will describe what is widely accepted as the six phases of the pitching motion and the relationship to the kinetic chain theory as well as outline the common mechanical faults that can lead to increased tissue stress and potential injury. Level of Evidence: 5 PMID:24175144
Revisiting the conundrum of trehalose stabilization.
Katyal, Nidhi; Deep, Shashank
2014-12-28
Protein aggregation and loss of protein's biological functionality are manifestations of protein instability. Cosolvents, in particular trehalose, are widely accepted antidotes against such destabilization. Although numerous theories have been promulgated in the literature with regard to its mechanism of stabilization, the present scenario is still elusive in view of the discrepancies existing in them. To this end, we have revisited the conundrum and attempted to rationalize the mechanism by conducting thorough investigation of the effect of trehalose on the native, partially unfolded and denatured states of protein "Lysozyme" by means of molecular dynamic (MD) simulations under different temperature and concentration regimes. Two-dimensional contour plots along with principal component analysis suggest that trehalose molecules offer on-pathway stabilization unaltering the principal direction of protein's motion, although it slows down protein dynamics so that the protein gets trapped in the homogeneous ensemble of conformations closer to the native state. Free energy landscape reveals higher population of native compared to intermediate and denatured states. Delphi results and calculation of the preferential interaction parameter demonstrate that this relative stabilization of the native state can be ascribed to be the consequence of favourable interactions of trehalose with side chains of certain loci on the protein surface encompassing polar flexible residues. Stability of protein results from the observed difference in binding affinity of trehalose for native and denatured states of protein. Our findings are at variance with the common conception of relative destabilization of the denatured state. Rather, we provide evidence for relative stabilization of the native state. This stabilization is due to interplay of protein-trehalose, water-trehalose, water-water, protein-water and trehalose-trehalose interactions.
Revisiting the destiny compulsion.
Potamianou, Anna
2017-02-01
This paper is an attempt to deal with some questions raised by the so-called 'compulsion of destiny' constellation. In presenting the standpoints of Freud and of psychoanalysts who after him were concerned with this problematic, the author takes the view that several aspects of the configuration merit further discussion. Accordingly, the dynamics of repetition compulsion, the complexity of the projective strategy, the coexistence of passive and omnipotent trends are considered. Concerning compulsive repetitions the dimension of drive intrication is underlined, thus moderating the understanding of this clinical entity as mainly related to death drive trends. Projection is understood as serving complex psychic demands. The coexistence of passive and omnipotent trends is envisaged, as manifested in phantasies of submission / participation of patients to a force that exceeds human limitations. For certain cases the consonance of somatic and psychic experiences is noted. Finally, elements from the material of two cases are presented which pertain to the problematic of the compulsion of destiny in which random events are submitted to heavy psychic necessities.
The bacterial nucleoid revisited.
Robinow, C; Kellenberger, E
1994-01-01
This review compares the results of different methods of investigating the morphology of nucleoids of bacteria grown under conditions favoring short generation times. We consider the evidence from fixed and stained specimens, from phase-contrast and fluorescence microscopy of growing bacteria, and from electron microscopy of whole as well as thinly sectioned ones. It is concluded that the nucleoid of growing cells is in a dynamic state: part of the chromatin is "pulled out" of the bulk of the nucleoid in order to be transcribed. This activity is performed by excrescences which extend far into the cytoplasm so as to reach the maximum of available ribosomes. Different means of fixation provide markedly different views of the texture of the DNA-containing plasm of the bulk of the nucleoid. Conventional chemical fixatives stabilize the cytoplasm of bacteria but not their protein-low chromatin. Uranyl acetate does cross-link the latter well but only if the cytoplasm has first been fixed conventionally. In the interval between the two fixations, the DNA arranges itself in liquid-crystalline form, supposedly because of loss of supercoiling. In stark contrast, cryofixation preserves bacterial chromatin in a finely granular form, believed to reflect its native strongly negatively supercoiled state. In dinoflagellates the DNA of their permanently visible chromosomes (also low in histone-like protein) is natively present as a liquid crystal. The arrangement of chromatin in Epulocystis fishelsoni, one of the largest known prokaryotes, is briefly described. Images PMID:7521510
NASA Astrophysics Data System (ADS)
Urrutxua, Hodei; Sanjurjo-Rivo, Manuel; Peláez, Jesús
2016-01-01
In the year 2000 an in-house orbital propagator called DROMO (Peláez et al. in Celest Mech Dyn Astron 97:131-150, 2007. doi: 10.1007/s10569-006-9056-3) was developed by the Space Dynamics Group of the Technical University of Madrid, based in a set of redundant variables including Euler-Rodrigues parameters. An original deduction of the DROMO propagator is carried out, underlining its close relation with the ideal frame concept introduced by Hansen (Abh der Math-Phys Cl der Kon Sachs Ges der Wissensch 5:41-218, 1857). Based on the very same concept, Deprit (J Res Natl Bur Stand Sect B Math Sci 79B(1-2):1-15, 1975) proposed a formulation for orbit propagation. In this paper, similarities and differences with the theory carried out by Deprit are analyzed. Simultaneously, some improvements are introduced in the formulation, that lead to a more synthetic and better performing propagator. Also, the long-term effect of the oblateness of the primary is studied in terms of DROMO variables, and new numerical results are presented to evaluate the performance of the method.
Multiscale Fluctuation Analysis Revisited
NASA Astrophysics Data System (ADS)
Struzik, Zbigniew R.; Kiyono, Ken; Yamamoto, Yoshiharu
2007-07-01
Ubiquitous non-Gaussianity of the probability density of (time-series) fluctuations in many real world phenomena has been known and modelled extensively in recent years. Similarly, the analysis of (multi)scaling properties of (fluctuations in) complex systems has become a standard way of addressing unknown complexity. Yet the combined analysis and modelling of multiscale behaviour of probability density — multiscale PDF analysis — has only recently been proposed for the analysis of time series arising in complex systems, such as the cardiac neuro-regulatory system, financial markets or hydrodynamic turbulence. This relatively new technique has helped significantly to expand the previously obtained insights into the phenomena addressed. In particular, it has helped to identify a novel class of scale invariant behaviour of the multiscale PDF in healthy heart rate regulation during daily activity and in a market system undergoing crash dynamics. This kind of invariance reflects invariance of the system under renormalisation and resembles behaviour at criticality of a system undergoing continuous phase transition — indeed in both phenomena, such phase transition behaviour has been revealed. While the precise mechanism underlying invariance of the PDF under system renormalisation of both systems discussed is not to date understood, there is an intimate link between the non-Gaussian PDF characteristics and the persistent invariant correlation structure emerging between fluctuations across scale and time.
Radiolytic Cryovolcanism Revisited
NASA Technical Reports Server (NTRS)
Cooper, John F.
2011-01-01
Location of Enceladus within the inner magnetosphere of Saturn makes it likely that energetic electron irradiation, ion-neutral chemistry of the emergent cryovolcanic plume gas, and resultant radiolytic modification of surface ice composition could impact long-term evolution of molecular composition in the global ice crust. Thermally-driven convection of ice in the south polar terrain would bring radiolytic oxidant products into contact with subsurface reservoirs of primordial organics on million-year time scales. The chemical reactions leading to CO2 gas production as a primary gas-piston driver of cryovolcanic activity would be exponentially elevated in the warm-ice margins of a heated fluid. The fluid temperature is typically assumed to be below 273 K but could be much higher in a gas-pressurized deep subsurface environment. The Perrier Ocean model has demonstrated how a CO2-loaded fluid could account for the observed jets, while the heat content of the fluid arising from the moon's deeper interior could support high levels of chemical reactivity in the thermal margins. Since mass loss and tidal dissipation arguments do not support continuous activity over billions of years, the activity is likely very episodic so that even low-level energy sources including irradiation-driven radiolysis of surface ices could substantially contribute to the chemical dynamics of the activity apparently now in high phase. A multi-phase thermochemical model, and supporting laboratory measurements of temperature-dependent reaction rates, are needed to investigate these potentially complex processes.
NASA Astrophysics Data System (ADS)
Sahni, Varun
2016-07-01
The Phantom brane is based on the normal branch of the DGP braneworld. It possesses a phantom-like equation of state at late times, but no big-rip future singularity. In this braneworld, the cosmological constant is dynamically screened at late times. Consequently it provides a good fit to SDSS DR11 measurements of H(z) at high redshifts. We obtain a closed system of equations for scalar perturbations on the brane. Perturbations of radiation, matter and the Weyl fluid are self-consistently evolved until the present epoch. We find that the late time growth of density perturbations on the brane proceeds at a faster rate than in ΛCDM. Additionally, the gravitational potentials φ, Ψ evolve differently on the brane than in ΛCDM, for which φ = Ψ. On the Brane, by contrast, the ratio φ/Ψ exceeds unity during the late matter dominated epoch (z ≤ 50). These features emerge as smoking gun tests of phantom brane cosmology and allow predictions of this scenario to be tested against observations of galaxy clustering and large scale structure. The phantom brane also displays a pole in its equation of state, which provides a key test of this dark energy model.
Conformal Lorentz geometry revisited
NASA Astrophysics Data System (ADS)
Teleman, Kostake
1996-02-01
. We also show that Mach's principle on inertial motions receives an explanation in our theory by considering the particular geodesic paths, for which one of the partners of an interacting pair is fixed and sent to infinity. In fact we study a dynamical system (W,L) which presents some formal and topological similarities with a system of two particles interacting gravitationally. (W,L) is the only conformally invariant relativistic two-point dynamical system. At the end we show that W can be naturally regarded as the base of a principal GL(2,C)-bundle which comes with a natural connection. We study this bundle from differential geometric point of view. Physical interpretations will be discussed in a future paper. This text is an improvement of a previous version, which was submitted under the title ``Hypertwistor Geometry.'' [See, K. Teleman, ``Hypertwistor Geometry (abstract),'' 14th International Conference on General Relativity and Gravitation, Florence, Italy, 1995.] The change of the title and many other improvements are due to the valuable comments of the referee, who also suggested the author to avoid hazardous interpretations.
Collisional Cascades Revisited
NASA Astrophysics Data System (ADS)
Schlichting, Hilke; Pan, M.
2013-01-01
Collisional cascades are believed to be the primary mechanism operating in circumstellar dusty debris disks, and are thought to be important in the Kuiper and Asteroid belt. Collisional cascades transfer mass via destructive collisions from larger bodies to smaller ones. Their widespread occurrence and potential importance in understanding planet formation and planet-disk interactions have motivated detailed studies of collisional cascades. The standard theoretical treatment of collisional cascades derives a steady-state size distribution assuming a single constant velocity dispersion for all bodies regardless of size. We relax this assumption and solve self-consistently for the bodies' steady-state size and size-dependent velocity distributions. Specifically, we account for viscous stirring, dynamical friction, and collisional damping of the bodies' random velocities in addition to the mass conservation requirement typically applied to find the size distribution in a steady-state cascade. The resulting size distributions are significantly steeper than those derived without velocity evolution. For example, accounting self-consistently for the velocities can change the standard q = 3.5 power-law index of the Dohnanyi differential size spectrum to an index as large as q = 4. Similarly, for bodies held together by their own gravity, the corresponding power-law index range 2.88 < q < 3.14 of Pan & Sari (2005) can steepen to values as large as q = 3.26. These differences in the size distribution power law index are very important when estimating the total disk mass, including larger bodies, by extrapolating from the observed dust masses. Our velocity results allow quantitative predictions of the bodies' scale heights as a function of size. Together with our predictions, observations of the scale heights for different-sized bodies in, for example, extrasolar debris disks may constrain the total mass in large bodies stirring the cascade as well as the colliding bodies
NASA Technical Reports Server (NTRS)
Contopoulos, Ioannis; Kazanas, Demosthenes; Christodoulos, Dimistris M.
2007-01-01
We reinvestigate the generation and accumulation of magnetic flux in optically thin accretion flows around active gravitating objects. The source of the magnetic field is the azimuthal electric current associated with the Poynting-Robertson drag on the electrons of the accreting plasma. This current generates magnetic field loops which open up because of the differential rotation of the flow. We show through simple numerical simulations that what regulates the generation and accumulation of magnetic flux near the center is the value of the plasma conductivity. Although the conductivity is usually considered to be effectively infinite for the fully ionized plasmas expected near the inner edge of accretion disks, the turbulence of those plasmas may actually render them much less conducting due to the presence of anomalous resistivity. We have discovered that if the resistivity is sufficiently high throughout the turbulent disk while it is suppressed interior to its inner edge, an interesting steady-state process is established: accretion carries and accumulates magnetic flux of one polarity inside the inner edge of the disk, whereas magnetic diffusion releases magnetic flux of the opposite polarity to large distances. In this scenario, magnetic flux of one polarity grows and accumulates at a steady rate in the region inside the inner edge and up to the point of equipartition when it becomes dynamically important. We argue that this inward growth and outward expulsion of oppositely-directed magnetic fields that we propose may account for the approx. 30 min cyclic variability observed in the galactic microquasar GRS1915+105.
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
Orthopaedic service lines-revisited.
Patterson, Cheryl
2008-01-01
This article revisits the application of orthopaedic service lines from early introduction and growth of this organizational approach in the 1980s, through the 1990s, and into the current decade. The author has experienced and worked in various service-line structures through these three decades, as well as the preservice-line era of 1970s orthopaedics. Past lessons learned during earlier phases and then current trends and analysis by industry experts are summarized briefly, with indication given of the future for service lines. Variation versus consistency of certain elements in service-line definitions and in operational models is discussed. Main components of service-line structures and typical processes are described briefly, along with a more detailed section on the service-line director/manager role. Current knowledge contained here will help guide the reader to more "out-of-the-box" thinking toward comprehensive orthopaedic centers of excellence.
Acute Kidney Injury: Controversies Revisited
Yong, Kenneth; Dogra, Gursharan; Boudville, Neil; Pinder, Mary; Lim, Wai
2011-01-01
This paper addresses the epidemiology of AKI specifically in relation to recent changes in AKI classification and revisits the controversies regarding the timing of initiation of dialysis and the use of peritoneal dialysis as a renal replacement therapy for AKI. In summary, the new RIFLE/AKIN classifications of AKI have facilitated more uniform diagnosis of AKI and clinically significant risk stratification. Regardless, the issue of timing of dialysis initiation still remains unanswered and warrants further examination. Furthermore, peritoneal dialysis as a treatment modality for AKI remains underutilised in spite of potential beneficial effects. Future research should be directed at identifying early reliable biomarkers of AKI, which in conjunction with RIFLE/AKIN classifications of AKI could facilitate well-designed large randomised controlled trials of early versus late initiation of dialysis in AKI. In addition, further studies of peritoneal dialysis in AKI addressing dialysis dose and associated complications are required for this therapy to be accepted more widely by clinicians. PMID:21660314
Revisiting the method of characteristics via a convex hull algorithm
NASA Astrophysics Data System (ADS)
LeFloch, Philippe G.; Mercier, Jean-Marc
2015-10-01
We revisit the method of characteristics for shock wave solutions to nonlinear hyperbolic problems and we propose a novel numerical algorithm-the convex hull algorithm (CHA)-which allows us to compute both entropy dissipative solutions (satisfying all entropy inequalities) and entropy conservative (or multi-valued) solutions. From the multi-valued solutions determined by the method of characteristics, our algorithm "extracts" the entropy dissipative solutions, even after the formation of shocks. It applies to both convex and non-convex flux/Hamiltonians. We demonstrate the relevance of the proposed method with a variety of numerical tests, including conservation laws in one or two spatial dimensions and problem arising in fluid dynamics.
Shuttle entry guidance revisited using nonlinear geometric methods
NASA Astrophysics Data System (ADS)
Mease, Kenneth D.; Kremer, Jean-Paul
1994-11-01
The entry guidance law for the space shuttle orbiter is revisited using nonlinear geometric methods. The shuttle guidance concept is to track a reference drag trajectory that has been designed to lead a specified range and velocity. It is shown that the approach taken in the original derivation of the shuttle entry guidance has much in common with the more recently developed feedback linearization method of differential geometric control. Using the feedback linearization method, however, an alternative, potentially superior, guidance law was formulated. Comparing the two guidance laws based performance domains in state space, taking into account the nonlinear dynamics, the alternative guidance law achieves the desired performance over larger domains in state space; the stability domain of the laws are similar. With larger operating domain for the shuttle or some other entry vehicle, the alternative guidance law should be considered.
Recollision revisited: How far can we push the classical picture?
NASA Astrophysics Data System (ADS)
Staudte, André
2007-06-01
The double ionization probability of nobel gases in strong laser fields at intermediate intensities exceeds the probability that can be expected on grounds of an independent electron picture by several orders of magnitude. Electron-electron correlation is the well-known origin for this dramatic effect. We have revisited this so called nonsequential double ionization in the simplest 2-electron system, the Helium atom, and, using very high resolution coincidence techniques, we observe a surprising structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process, taking the analogy to the classical (e,2e) processes one step further. This interpretation is supported by inspecting the solution of the 2-body 3-dimensional time-dependent Schr"odinger equation.
Pharmacy school survey standards revisited.
Mészáros, Károly; Barnett, Mitchell J; Lenth, Russell V; Knapp, Katherine K
2013-02-12
In a series of 3 papers on survey practices published from 2008 to 2009, the editors of the American Journal of Pharmaceutical Education presented guidelines for reporting survey research, and these criteria are reflected in the Author Instructions provided on the Journal's Web site. This paper discusses the relevance of these criteria for publication of survey research regarding pharmacy colleges and schools. In addition, observations are offered about surveying of small "universes" like that comprised of US colleges and schools of pharmacy. The reason for revisiting this issue is the authors' concern that, despite the best of intentions, overly constraining publication standards might discourage research on US colleges and schools of pharmacy at a time when the interest in the growth of colleges and schools, curricular content, clinical education, competence at graduation, and other areas is historically high. In the best traditions of academia, the authors share these observations with the community of pharmacy educators in the hope that the publication standards for survey research about US pharmacy schools will encourage investigators to collect and disseminate valuable information.
Revisiting Bohr's semiclassical quantum theory.
Ben-Amotz, Dor
2006-10-12
Bohr's atomic theory is widely viewed as remarkable, both for its accuracy in predicting the observed optical transitions of one-electron atoms and for its failure to fully correspond with current electronic structure theory. What is not generally appreciated is that Bohr's original semiclassical conception differed significantly from the Bohr-Sommerfeld theory and offers an alternative semiclassical approximation scheme with remarkable attributes. More specifically, Bohr's original method did not impose action quantization constraints but rather obtained these as predictions by simply matching photon and classical orbital frequencies. In other words, the hydrogen atom was treated entirely classically and orbital quantized emerged directly from the Planck-Einstein photon quantization condition, E = h nu. Here, we revisit this early history of quantum theory and demonstrate the application of Bohr's original strategy to the three quintessential quantum systems: an electron in a box, an electron in a ring, and a dipolar harmonic oscillator. The usual energy-level spectra, and optical selection rules, emerge by solving an algebraic (quadratic) equation, rather than a Bohr-Sommerfeld integral (or Schroedinger) equation. However, the new predictions include a frozen (zero-kinetic-energy) state which in some (but not all) cases lies below the usual zero-point energy. In addition to raising provocative questions concerning the origin of quantum-chemical phenomena, the results may prove to be of pedagogical value in introducing students to quantum mechanics.
Pharmacy School Survey Standards Revisited
Barnett, Mitchell J.; Lenth, Russell V.; Knapp, Katherine K.
2013-01-01
In a series of 3 papers on survey practices published from 2008 to 2009, the editors of the American Journal of Pharmaceutical Education presented guidelines for reporting survey research, and these criteria are reflected in the Author Instructions provided on the Journal’s Web site. This paper discusses the relevance of these criteria for publication of survey research regarding pharmacy colleges and schools. In addition, observations are offered about surveying of small "universes" like that comprised of US colleges and schools of pharmacy. The reason for revisiting this issue is the authors’ concern that, despite the best of intentions, overly constraining publication standards might discourage research on US colleges and schools of pharmacy at a time when the interest in the growth of colleges and schools, curricular content, clinical education, competence at graduation, and other areas is historically high. In the best traditions of academia, the authors share these observations with the community of pharmacy educators in the hope that the publication standards for survey research about US pharmacy schools will encourage investigators to collect and disseminate valuable information. PMID:23459404
Revisiting intracellular calcium signaling semantics.
Haiech, Jacques; Audran, Emilie; Fève, Marie; Ranjeva, Raoul; Kilhoffer, Marie-Claude
2011-12-01
Cells use intracellular free calcium concentration changes for signaling. Signal encoding occurs through both spatial and temporal modulation of the free calcium concentration. The encoded message is detected by an ensemble of intracellular sensors forming the family of calcium-binding proteins (CaBPs) which must faithfully translate the message using a new syntax that is recognized by the cell. The cell is home to a significant although limited number of genes coding for proteins involved in the signal encoding and decoding processes. In a cell, only a subset of this ensemble of genes is expressed, leading to a genetic regulation of the calcium signal pathways. Calmodulin (CaM), the most ubiquitous expressed intracellular calcium-binding protein, plays a major role in calcium signal translation. Similar to a hub, it is central to a large and finely tuned network, receiving information, integrating it and dispatching the cognate response. In this review, we examine the different steps starting with an external stimulus up to a cellular response, with special emphasis on CaM and the mechanism by which it decodes calcium signals and translates it into exquisitely coordinated cellular events. By this means, we will revisit the calcium signaling semantics, hoping that we will ease communication between scientists dealing with calcium signals in different biological systems and different domains.
Revisiting the safety of aspartame.
Choudhary, Arbind Kumar; Pretorius, Etheresia
2017-09-01
Aspartame is a synthetic dipeptide artificial sweetener, frequently used in foods, medications, and beverages, notably carbonated and powdered soft drinks. Since 1981, when aspartame was first approved by the US Food and Drug Administration, researchers have debated both its recommended safe dosage (40 mg/kg/d) and its general safety to organ systems. This review examines papers published between 2000 and 2016 on both the safe dosage and higher-than-recommended dosages and presents a concise synthesis of current trends. Data on the safe aspartame dosage are controversial, and the literature suggests there are potential side effects associated with aspartame consumption. Since aspartame consumption is on the rise, the safety of this sweetener should be revisited. Most of the literature available on the safety of aspartame is included in this review. Safety studies are based primarily on animal models, as data from human studies are limited. The existing animal studies and the limited human studies suggest that aspartame and its metabolites, whether consumed in quantities significantly higher than the recommended safe dosage or within recommended safe levels, may disrupt the oxidant/antioxidant balance, induce oxidative stress, and damage cell membrane integrity, potentially affecting a variety of cells and tissues and causing a deregulation of cellular function, ultimately leading to systemic inflammation. © The Author(s) 2017. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Gravity current jump conditions, revisited
NASA Astrophysics Data System (ADS)
Ungarish, Marius; Hogg, Andrew J.
2016-11-01
Consider the flow of a high-Reynolds-number gravity current of density ρc in an ambient fluid of density ρa in a horizontal channel z ∈ [ 0 , H ] , with gravity in - z direction. The motion is often modeled by a two-layer formulation which displays jumps (shocks) in the height of the interface, in particular at the leading front of the dense layer. Various theoretical models have been advanced to predict the dimensionless speed of the jump, Fr = U /√{g' h } ; g' , h are reduced gravity and jump height. We revisit this problem and using the Navier-Stokes equations, integrated over a control volume embedding the jump, derive balances of mass and momentum fluxes. We focus on understanding the closures needed to complete this model and we show the vital need to understand the pressure head losses over the jump, which we show can be related to the vorticity fluxes at the boundaries of the control volume. Our formulation leads to two governing equations for three dimensionless quantities. Closure requires one further assumption, depending on which we demonstrate that previous models for gravity current fronts and internal bores can be recovered. This analysis yield new insights into existing results, and also provides constraints for potential new formulae.
Revisiting the Regenerative Possibilities of Ortiz
ERIC Educational Resources Information Center
Duques, Matthew
2004-01-01
The author of this article revisits Simon Ortiz's poem, "From Sand Creek," in which the latter can in so few words convey both the horrific tragedy of conquest and colonization, while at the same time find a space for possibility, a means for recovery that is never about forgetting but always occurs as a kind of recuperative remembering. Ortiz…
The Rotating Morse-Pekeris Oscillator Revisited
ERIC Educational Resources Information Center
Zuniga, Jose; Bastida, Adolfo; Requena, Alberto
2008-01-01
The Morse-Pekeris oscillator model for the calculation of the vibration-rotation energy levels of diatomic molecules is revisited. This model is based on the realization of a second-order exponential expansion of the centrifugal term about the minimum of the vibrational Morse oscillator and the subsequent analytical resolution of the resulting…
Revisiting Basic Counseling Skills with Children
ERIC Educational Resources Information Center
Van Velsor, Patricia
2004-01-01
Counseling with children can be challenging for counselors whose training focused on adult clients. The purpose of this article is to offer information to counselors seeking to improve their skills with children, revisiting a topic discussed in an earlier Journal of Counseling & Development article by P. Erdman and R. Lampe (1996). Examples of…
The Rotating Morse-Pekeris Oscillator Revisited
ERIC Educational Resources Information Center
Zuniga, Jose; Bastida, Adolfo; Requena, Alberto
2008-01-01
The Morse-Pekeris oscillator model for the calculation of the vibration-rotation energy levels of diatomic molecules is revisited. This model is based on the realization of a second-order exponential expansion of the centrifugal term about the minimum of the vibrational Morse oscillator and the subsequent analytical resolution of the resulting…
The Future of Engineering Education--Revisited
ERIC Educational Resources Information Center
Wankat, Phillip C.; Bullard, Lisa G.
2016-01-01
This paper revisits the landmark CEE series, "The Future of Engineering Education," published in 2000 (available free in the CEE archives on the internet) to examine the predictions made in the original paper as well as the tools and approaches documented. Most of the advice offered in the original series remains current. Despite new…
Topological string theory revisited I: The stage
NASA Astrophysics Data System (ADS)
Jia, Bei
2016-08-01
In this paper, we reformulate topological string theory using supermanifolds and supermoduli spaces, following the approach worked out by Witten (Superstring perturbation theory revisited, arXiv:1209.5461). We intend to make the construction geometrical in nature, by using supergeometry techniques extensively. The goal is to establish the foundation of studying topological string amplitudes in terms of integration over appropriate supermoduli spaces.
Revisiting separation properties of convex fuzzy sets
USDA-ARS?s Scientific Manuscript database
Separation of convex sets by hyperplanes has been extensively studied on crisp sets. In a seminal paper separability and convexity are investigated, however there is a flaw on the definition of degree of separation. We revisited separation on convex fuzzy sets that have level-wise (crisp) disjointne...
The Future of Engineering Education--Revisited
ERIC Educational Resources Information Center
Wankat, Phillip C.; Bullard, Lisa G.
2016-01-01
This paper revisits the landmark CEE series, "The Future of Engineering Education," published in 2000 (available free in the CEE archives on the internet) to examine the predictions made in the original paper as well as the tools and approaches documented. Most of the advice offered in the original series remains current. Despite new…
Revisiting the Paradigms of Instructional Technology.
ERIC Educational Resources Information Center
Koschmann, Timothy
This paper revisits a previously published analysis of paradigm shifts within research on instructional technology (IT). Following Kuhn, the author uses the term "paradigm" to denote an actual scientific achievement. Used in this way, a particular experiment or research study must meet two criteria to qualify as a paradigm: it must be…
"Student Personnel: All Hail and Farewell!" Revisited.
ERIC Educational Resources Information Center
Bucci, Frank A.
1993-01-01
Revisits Crookston's (1976) article advocating to expunge term "student personnel," arguing that it is inappropriate and no longer descriptive of student affairs. Presents background of term to determine whether it continues to be used to identify chief student affairs officers and graduate programs that prepare sstudent affairs practitioners or…
Revisiting Basic Counseling Skills with Children
ERIC Educational Resources Information Center
Van Velsor, Patricia
2004-01-01
Counseling with children can be challenging for counselors whose training focused on adult clients. The purpose of this article is to offer information to counselors seeking to improve their skills with children, revisiting a topic discussed in an earlier Journal of Counseling & Development article by P. Erdman and R. Lampe (1996). Examples of…
Phenomenology of n - n ¯ oscillations revisited
Gardner, S.; Jafari, E.
2015-05-22
We revisit the phenomenology of n-n¯ oscillations in the presence of external magnetic fields, highlighting the role of spin. We show, contrary to long-held belief, that the n-n¯ transition rate need not be suppressed, opening new opportunities for its empirical study.
Nuclear fragmentation and charge-exchange reactions induced by pions in the Δ -resonance region
NASA Astrophysics Data System (ADS)
Feng, Zhao-Qing
2016-11-01
The dynamics of the nuclear fragmentations and the charge exchange reactions in pion-nucleus collisions near the Δ (1232) resonance energies has been investigated within the Lanzhou quantum molecular dynamics transport model. An isospin-, momentum-, and density-dependent pion-nucleon potential is implemented in the model, which influences the pion dynamics, in particular the kinetic energy spectra, but weakly impacts the fragmentation mechanism. The absorption process in pion-nucleon collisions to form the Δ (1232) resonance dominates the heating mechanism of the target nucleus. The excitation energy transferred to the target nucleus increases with the pion kinetic energy and is similar for both π-- and π+-induced reactions. The magnitude of fragmentation of the target nucleus weakly depends on the pion energy. The isospin ratio in the pion double-charge exchange is influenced by the isospin ingredient of target nucleus.
Revisiting the 1761 Transatlantic Tsunami
NASA Astrophysics Data System (ADS)
Baptista, Maria Ana; Wronna, Martin; Miranda, Jorge Miguel
2016-04-01
The tsunami catalogs of the Atlantic include two transatlantic tsunamis in the 18th century the well known 1st November 1755 and the 31st March 1761. The 31st March 1761 earthquake struck Portugal, Spain, and Morocco. The earthquake occurred around noontime in Lisbon alarming the inhabitants and throwing down ruins of the past 1st November 1755 earthquake. According to several sources, the earthquake was followed by a tsunami observed as far as Cornwall (United Kingdom), Cork (Ireland) and Barbados (Caribbean). The analysis of macroseismic information and its compatibility with tsunami travel time information led to a source area close to the Ampere Seamount with an estimated epicenter circa 34.5°N 13°W. The estimated magnitude of the earthquake was 8.5. In this study, we revisit the tsunami observations, and we include a report from Cadiz not used before. We use the results of the compilation of the multi-beam bathymetric data, that covers the area between 34°N - 38°N and 12.5°W - 5.5°W and use the recent tectonic map published for the Southwest Iberian Margin to select among possible source scenarios. Finally, we use a non-linear shallow water model that includes the discretization and explicit leap-frog finite difference scheme to solve the shallow water equations in the spherical or Cartesian coordinate to compute tsunami waveforms and tsunami inundation and check the results against the historical descriptions to infer the source of the event. This study received funding from project ASTARTE- Assessment Strategy and Risk Reduction for Tsunamis in Europe a collaborative project Grant 603839, FP7-ENV2013 6.4-3
Spataro, Emily; Branham, Gregory H; Kallogjeri, Dorina; Piccirillo, Jay F; Desai, Shaun C
2016-12-01
Estimates of the 30-day hospital revisit rate following septorhinoplasty and the risk factors associated with revisits are unknown in the current literature. Surgical 30-day readmission rates are important to establish, as they are increasingly used as a quality care metric and can incur future financial penalties from third-party payers and government agencies. To determine the rate of 30-day hospital revisits following septorhinoplasty and the risk factors associated with revisits. A retrospective cohort analysis was conducted of 175 842 patients undergoing septorhinoplasty between January 1, 2005, and December 31, 2009, using data from the Healthcare Cost and Utilization Project state inpatient database, state ambulatory surgery database, and state emergency department database from California, Florida, and New York. Information on revisits for these patients was collected from the 3 databases between January 1, 2005, and December 31, 2012. Data analysis was conducted from September 1, 2014, to May 1, 2015. Hospital revisits within 30 days after an index septorhinoplasty and the primary diagnosis at the time of the revisit were the main outcome measures. The revisit rate was calculated within subgroups of patients based on different demographic and clinical characteristics. A multivariable model was then used to determine independent risk factors for the occurrence of a hospital revisit within 30 days of the septorhinoplasty procedure. In total, 11 456 of 175 842 patients (6.5%) who underwent septorhinoplasty procedures revisited the hospital within 30 days of the procedure. Most of these revisits (6353 [55.5%]) were to the emergency department. The most common primary diagnosis was bleeding or epistaxis, occurring in 2150 patients (1.2%). Multivariable logistic regression showed that patients aged 41 to 65 years (adjusted odds ratio [aOR], 1.09; 99% CI, 1.02-1.16) or older than 65 years (aOR, 1.23; 99% CI, 1.06-1.43) had an increased revisit rate, as did
Spataro, Emily; Branham, Gregory H.; Kallogjeri, Dorina; Piccirillo, Jay F.; Desai, Shaun C.
2017-01-01
IMPORTANCE Estimates of the 30-day hospital revisit rate following septorhinoplasty and the risk factors associated with revisits are unknown in the current literature. Surgical 30-day readmission rates are important to establish, as they are increasingly used as a quality care metric and can incur future financial penalties from third-party payers and government agencies. OBJECTIVE To determine the rate of 30-day hospital revisits following septorhinoplasty and the risk factors associated with revisits. DESIGN, SETTING, AND PARTICIPANTS A retrospective cohort analysis was conducted of 175 842 patients undergoing septorhinoplasty between January 1, 2005, and December 31, 2009, using data from the Healthcare Cost and Utilization Project state inpatient database, state ambulatory surgery database, and state emergency department database from California, Florida, and New York. Information on revisits for these patients was collected from the 3 databases between January 1, 2005, and December 31, 2012. Data analysis was conducted from September 1, 2014, to May 1, 2015. MAIN OUTCOMES AND MEASURES Hospital revisits within 30 days after an index septorhinoplasty and the primary diagnosis at the time of the revisit were the main outcome measures. The revisit rate was calculated within subgroups of patients based on different demographic and clinical characteristics. A multivariable model was then used to determine independent risk factors for the occurrence of a hospital revisit within 30 days of the septorhinoplasty procedure. RESULTS In total, 11 456 of 175 842 patients (6.5%) who underwent septorhinoplasty procedures revisited the hospital within 30 days of the procedure. Most of these revisits (6353 [55.5%]) were to the emergency department. The most common primary diagnosis was bleeding or epistaxis, occurring in 2150 patients (1.2%). Multivariable logistic regression showed that patients aged 41 to 65 years (adjusted odds ratio [aOR], 1.09; 99% CI, 1.02–1.16) or
The flow along an external corner revisited
NASA Astrophysics Data System (ADS)
Denier, Jim; Jewell, Nathaniel
2013-11-01
We revisit the problem of the flow of an almost inviscid fluid along an external corner made from the junction of two quarter infinite plates joined at an angle 0 < α < π / 2 . The structure of the boundary layer which develops along the corner is explored using a computational approach based upon a spectral element discretisation of the steady two-dimensional boundary-layer equations. We pay particular attention to the case when the angle α is small, thus approximating the semi-infinte quarter plate problem considered by Stewartson (1961) and recently revisited by Duck & Hewitt (2012). Our results, which demonstrate a thickening of the boundary-layer near the sharp corner, will be discussed in the context of the asymptotic theory developed in the aforementioned papers.
Revisiting the definition of homo sapiens.
Loike, John D; Tendler, Moshe D
2002-12-01
Research in genomics, human cloning, and transgenic technology has challenged bioethicists and scientists to rethink the definition of human beings as a species. For example, should the definition incorporate a genetic criterion and how does the capacity to genetically engineer human beings affect the definition of our species? In considering these contemporary bioethical dilemmas, we revisit an ancient source, the Talmud, and highlight how it provides specific biological, cultural, and genetic criteria to define the human species.
Revisiting Cementoblastoma with a Rare Case Presentation.
Subramani, Vijayanirmala; Narasimhan, Malathi; Ramalingam, Suganya; Anandan, Soumya; Ranganathan, Subhashini
2017-01-01
Cementoblastoma is a rare benign odontogenic neoplasm which is characterized by the proliferation of cellular cementum. Diagnosis of cementoblastoma is challenging because of its protracted clinical, radiographic features, and bland histological appearance; most often cementoblastoma is often confused with other cementum and bone originated lesions. The aim of this article is to overview/revisit, approach the diagnosis of cementoblastoma, and also present a unique radiographic appearance of a cementoblastoma lesion associated with an impacted tooth.
Careers in paediatrics: Community paediatrics revisited
Tonkin, Roger Sherriff
2012-01-01
The concept of ‘community paediatrics’, as enunciated by Robert Haggerty in 1968, has informed and shaped many paediatric careers. The principle tenets of inclusiveness: attention to unmet needs; addressing common health problems of children and youth; using and applying preventive and harm-reduction strategies; and securing community input and control, were part of the Haggerty model. The present article revisits Haggerty’s model and describes how the concepts have shaped contemporary paediatrics in North America. PMID:23277752
Revisiting Cementoblastoma with a Rare Case Presentation
Narasimhan, Malathi; Ramalingam, Suganya; Anandan, Soumya; Ranganathan, Subhashini
2017-01-01
Cementoblastoma is a rare benign odontogenic neoplasm which is characterized by the proliferation of cellular cementum. Diagnosis of cementoblastoma is challenging because of its protracted clinical, radiographic features, and bland histological appearance; most often cementoblastoma is often confused with other cementum and bone originated lesions. The aim of this article is to overview/revisit, approach the diagnosis of cementoblastoma, and also present a unique radiographic appearance of a cementoblastoma lesion associated with an impacted tooth. PMID:28337352
How to infer gene networks from expression profiles, revisited
Penfold, Christopher A.; Wild, David L.
2011-01-01
Inferring the topology of a gene-regulatory network (GRN) from genome-scale time-series measurements of transcriptional change has proved useful for disentangling complex biological processes. To address the challenges associated with this inference, a number of competing approaches have previously been used, including examples from information theory, Bayesian and dynamic Bayesian networks (DBNs), and ordinary differential equation (ODE) or stochastic differential equation. The performance of these competing approaches have previously been assessed using a variety of in silico and in vivo datasets. Here, we revisit this work by assessing the performance of more recent network inference algorithms, including a novel non-parametric learning approach based upon nonlinear dynamical systems. For larger GRNs, containing hundreds of genes, these non-parametric approaches more accurately infer network structures than do traditional approaches, but at significant computational cost. For smaller systems, DBNs are competitive with the non-parametric approaches with respect to computational time and accuracy, and both of these approaches appear to be more accurate than Granger causality-based methods and those using simple ODEs models. PMID:23226586
Revisiting the observed surface climate response to large volcanic eruptions
NASA Astrophysics Data System (ADS)
Wunderlich, Fabian; Mitchell, Daniel M.
2017-01-01
In light of the range in presently available observational, reanalysis and model data, we revisit the surface climate response to large tropical volcanic eruptions from the end of the 19th century until present. We focus on the dynamically driven response of the North Atlantic Oscillation (NAO) and the radiative-driven tropical temperature response. Using 10 different reanalysis products and the Hadley Centre Sea Level Pressure observational dataset (HadSLP2) we confirm a positive tendency in the phase of the NAO during boreal winters following large volcanic eruptions, although we conclude that it is not as clear cut as the current literature suggests. While different reanalyses agree well on the sign of the surface volcanic NAO response for individual volcanoes, the spread in the response is often large (˜ 1/2 standard deviation). This inter-reanalysis spread is actually larger for the more recent volcanic eruptions, and in one case does not encompass observations (El Chichón). These are all in the satellite era and therefore assimilate more atmospheric data that may lead to a more complex interaction for the surface response. The phase of the NAO leads to a dynamically driven warm anomaly over northern Europe in winter, which is present in all datasets considered. The general cooling of the surface temperature due to reduced incoming shortwave radiation is therefore disturbed by dynamical impacts. In the tropics, where less dynamically driven influences are present, we confirm a predominant cooling after most but not all eruptions. All datasets agree well on the strength of the tropical response, with the observed and reanalysis response being statistically significant but the modelled response not being significant due to the high variability across models.
Revisiting the Master-Signifier, or, Mandela and Repression
Hook, Derek; Vanheule, Stijn
2016-01-01
The concept of the master-signifier has been subject to a variety of applications in Lacanian forms of political discourse theory and ideology critique. While there is much to be commended in literature of this sort, it often neglects salient issues pertaining to the role of master signifiers in the clinical domain of (individual) psychical economy. The popularity of the concept of the master (or “empty”) signifier in political discourse analysis has thus proved a double-edged sword. On the one hand it demonstrates how crucial psychical processes are performed via the operations of the signifier, extending thus the Lacanian thesis that identification is the outcome of linguistic and symbolic as opposed to merely psychological processes. On the other, the use of the master signifier concept within the political realm to track discursive formations tends to distance the term from the dynamics of the unconscious and operation of repression. Accordingly, this paper revisits the master signifier concept, and does so within the socio-political domain, yet while paying particular attention to the functioning of unconscious processes of fantasy and repression. More specifically, it investigates how Nelson Mandela operates as a master signifier in contemporary South Africa, as a vital means of knitting together diverse elements of post-apartheid society, enabling the fantasy of the post-apartheid nation, and holding at bay a whole series of repressed and negated undercurrents. PMID:26834664
The flux qubit revisited to enhance coherence and reproducibility
NASA Astrophysics Data System (ADS)
Yan, Fei; Gustavsson, Simon; Kamal, Archana; Birenbaum, Jeffrey; Sears, Adam P.; Hover, David; Gudmundsen, Ted J.; Rosenberg, Danna; Samach, Gabriel; Weber, S.; Yoder, Jonilyn L.; Orlando, Terry P.; Clarke, John; Kerman, Andrew J.; Oliver, William D.
2016-11-01
The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). Here, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad-frequency tunability, strong anharmonicity, high reproducibility and relaxation times in excess of 40 μs at its flux-insensitive point. Qubit relaxation times T1 across 22 qubits are consistently matched with a single model involving resonator loss, ohmic charge noise and 1/f-flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal-photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2~85 μs, approximately the 2T1 limit. In addition to realizing an improved flux qubit, our results uniquely identify photon shot noise as limiting T2 in contemporary qubits based on transverse qubit-resonator interaction.
Liquid drop spreading on surfaces: Initial regimes revisited
NASA Astrophysics Data System (ADS)
Mitra, Surjyasish; Mitra, Sushanta
2016-11-01
Liquid drop spreading on a given surface is fundamental towards technological processes like coating and paints, inkjet printing, surface characterization, etc. Though, the underlying dynamics is well understood, we have revisited this problem through experiments conducted on surfaces kept in air as well as immersed in water. It was found that the two key parameters that dictated the spreading process were drop-surrounding medium viscosity ratio and the characteristic viscous length scale. It was observed that irrespective of the drop liquid and surrounding liquid medium (air and water in this case), spreading always began in a regime dominated by drop viscosity, where the spreading radius scales as r t . However, the prefactor of the scaling observed was different for air (of the order of unity) and under-water (much less than unity). Following this initial regime, a second intermediate regime dominated by drop inertia (typically found for water drops spreading in air) was observed only when the characteristic viscous length scale favored such a transition. In this regime as well, a non-universal prefactor was noted for the scaling law, i.e., r t1/2. In all cases considered, the spreading process terminated in the Tanner's regime where the spreading radius scaled as r t1/10.
The flux qubit revisited to enhance coherence and reproducibility
Yan, Fei; Gustavsson, Simon; Kamal, Archana; Birenbaum, Jeffrey; Sears, Adam P; Hover, David; Gudmundsen, Ted J.; Rosenberg, Danna; Samach, Gabriel; Weber, S; Yoder, Jonilyn L.; Orlando, Terry P.; Clarke, John; Kerman, Andrew J.; Oliver, William D.
2016-01-01
The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). Here, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad-frequency tunability, strong anharmonicity, high reproducibility and relaxation times in excess of 40 μs at its flux-insensitive point. Qubit relaxation times T1 across 22 qubits are consistently matched with a single model involving resonator loss, ohmic charge noise and 1/f-flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal-photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2≈85 μs, approximately the 2T1 limit. In addition to realizing an improved flux qubit, our results uniquely identify photon shot noise as limiting T2 in contemporary qubits based on transverse qubit–resonator interaction. PMID:27808092
Revisiting the Master-Signifier, or, Mandela and Repression.
Hook, Derek; Vanheule, Stijn
2015-01-01
The concept of the master-signifier has been subject to a variety of applications in Lacanian forms of political discourse theory and ideology critique. While there is much to be commended in literature of this sort, it often neglects salient issues pertaining to the role of master signifiers in the clinical domain of (individual) psychical economy. The popularity of the concept of the master (or "empty") signifier in political discourse analysis has thus proved a double-edged sword. On the one hand it demonstrates how crucial psychical processes are performed via the operations of the signifier, extending thus the Lacanian thesis that identification is the outcome of linguistic and symbolic as opposed to merely psychological processes. On the other, the use of the master signifier concept within the political realm to track discursive formations tends to distance the term from the dynamics of the unconscious and operation of repression. Accordingly, this paper revisits the master signifier concept, and does so within the socio-political domain, yet while paying particular attention to the functioning of unconscious processes of fantasy and repression. More specifically, it investigates how Nelson Mandela operates as a master signifier in contemporary South Africa, as a vital means of knitting together diverse elements of post-apartheid society, enabling the fantasy of the post-apartheid nation, and holding at bay a whole series of repressed and negated undercurrents.
Revisiting the texture zero neutrino mass matrices
NASA Astrophysics Data System (ADS)
Singh, Madan; Ahuja, Gulsheen; Gupta, Manmohan
2016-12-01
In the light of refined and large measurements of the reactor mixing angle θ, we have revisited the texture three- and two-zero neutrino mass matrices in the flavor basis. For Majorana neutrinos, it has been explicitly shown that all the texture three-zero mass matrices remain ruled out. Further, for both normal and inverted mass ordering, for the texture two-zero neutrino mass matrices one finds interesting constraints on the Dirac-like CP-violating phase δ and Majorana phases ρ and σ.
Sloan Digital Sky Survey Photometric Calibration Revisited
Marriner, John; /Fermilab
2012-06-29
The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.
Quantum scattering on a cone revisited
NASA Astrophysics Data System (ADS)
Barroso, V. S.; Pitelli, J. P. M.
2017-07-01
We revisit the scattering of quantum test particles on the conical (2 +1 )-dimensional spacetime and find the scattering amplitude as a function of the boundary conditions imposed at the apex of the cone. We show that the boundary condition is responsible for a purely analytical term in the scattering amplitude, in addition to those coming from purely topological effects. Since it is possible to have nonequivalent physical evolutions for the wave packet (each one corresponding to a different boundary condition), it seems crucial to have an observable quantity specifying which evolution has been prescribed.
Chiral corrections to nucleon two- and three-point correlation functions
NASA Astrophysics Data System (ADS)
Tiburzi, Brian C.
2015-05-01
We consider multiparticle contributions to nucleon two- and three-point functions from the perspective of chiral dynamics. Lattice nucleon interpolating operators, which have definite chiral transformation properties, can be mapped into chiral perturbation theory. Using the most common of such operators, we determine pion-nucleon and pion-delta couplings to nucleon two- and three-point correlation functions at leading order in the low-energy expansion. The couplings of pions to nucleons and deltas in two-point functions are consistent with simple phase-space considerations, in accordance with the Lehmann spectral representation. An argument based on available phase space on a torus is utilized to derive the scaling of multiple-pion couplings. While multipion states are indeed suppressed, this suppression scales differently with particle number compared to that in infinite volume. For nucleon three-point correlation functions, we investigate the axial-vector current at vanishing momentum transfer. The effect of pion-nucleon and pion-delta states on the extraction of the nucleon axial charge is assessed. We show that couplings to finite volume multiparticle states could potentially lead to overestimation of the axial charge. Hence pion-nucleon excited states cannot explain the trend seen in lattice QCD calculations of the nucleon axial charge.
Soft two-pion-exchange nucleon-nucleon potentials
Rijken, Th.A. )
1991-06-01
Two-pion-exchange nucleon-nucleon potentials are derived for the pseudo-vector pion-nucleon interaction, assuming strong dynamical pair-suppression. At the pion-nucleon vertices the authors include Gaussian form factors, which are incorporated into the relativistic two-body framework by using a dispersion representation for the one-pion-exchange amplitude. The Fourier transformations are performed using a factorization technique for the energy denominators. This leads to analytic expressions for the TPE-potentials containing at most one-dimensional integrals. The TPE-potentials are calculated up to orders {line integral}{sup 4} and (m/M){line integral}{sup 4}. The terms of order {line integral}{sup 4} come from the adiabatic contributions of the parallel and crossed three-dimensional momentum-space TPE-diagrams, and from the non-adiabatic contributions of the OPE-iteration. The (m/M)-corrections are due to the 1/M-terms in the non-adiabatic expansion of the nucleon energies in the intermediate states, and the 1/M-terms in the pion-nucleon vertices. The latter are typical for the PV-coupling and would be absent for the PS-coupling. The Gaussian form factors lead to soft TPE-potentials. These potentials can readily be exploited in NN-calculations in combination with, e.g., the Nijmegen soft-core OBE-model, and in nuclear (matter) calculations.
Military Gay Ban Revisited: Is our Military Ready for Change?
2009-02-20
Military gay ban revisited: Is our military ready for change? Captain LS...2009 4. TITLE AND SUBTITLE Military gay ban revisited: Is our military ready for change? 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...Lesbian, Gay, Bi-sexual, Transgender ] (LGBT) rights is exploited by those seeking to divide us. But at its core, this issue is about who we are as
Hershfield factor revisited: Correcting annual maximum precipitation
NASA Astrophysics Data System (ADS)
Papalexiou, Simon Michael; Dialynas, Yannis G.; Grimaldi, Salvatore
2016-11-01
The Hershfield factor (H) is a multiplier aiming to correct the error between fixed time interval maxima (F-maxima) and sliding maxima (S-maxima) as a direct consequence of temporal discretization of hydrometeorological time series. Rainfall is typically recorded over discrete intervals, e.g., over fixed 24-h intervals, and the historical series express average values over these intervals. This temporal discretization introduces an important systematic error on rainfall characteristics such as the annual maxima. Research to date suggests that our understanding of this error across different time scales is limited. In this study we revisit the probabilistic nature of the H-factor in an unprecedentedly large analysis comprising thousands of up-to-date hourly records across the US. We study the probabilistic behavior of F- and S-maxima of the historical records. We quantify the discretization error of the rainfall maxima and its statistical properties at different time scales. We revisit the classical definitions of the H-factor and we investigate the exact probability distribution of H-factor. We introduce a bounded exponential distribution with an atom at one, which closely depicts the empirical distribution of the H-factor. Notable is the result that the proposed mixed-type distribution is invariant across a range of time scales. This work clarifies the probabilistic nature of the rainfall maxima correction. The results may have wide use across a range of hydrological applications.
Revisit rates and diagnoses following pediatric tonsillectomy in a large multistate population.
Shay, Sophie; Shapiro, Nina L; Bhattacharyya, Neil
2015-02-01
Investigate the incidence and characteristics of revisits following ambulatory pediatric tonsillectomy/adenotonsillectomy. Cross-sectional study using national databases. Ambulatory pediatric (age <18.0 years) tonsillectomy or adenotonsillectomy cases were extracted from the 2010 State Ambulatory Surgery, Emergency Department, and Inpatient databases for New York, Florida, Iowa, and California. First and second revisits within the 14-day postoperative period were tabulated. Diagnoses, procedure codes, and mortality were examined. There were 36,221 pediatric tonsillectomies/adenotonsillectomies (mean age 7.4 years, 51.4% male). Overall, 2,740 patients (7.6%) had a revisit after pediatric tonsillectomy; 402 patients (1.1%) had a second revisit. Among revisits, 6.3% revisited the ambulatory surgery center, 77.5% revisited the emergency department, and 16.2% were readmitted as an inpatient. Among all tonsillectomies, bleeding occurred in 2.0% and 0.5% within the first and second revisits, respectively. A second revisit had a statistically higher association with a primary bleeding diagnosis than the first revisit (P < .001). Among all cases, 0.75% underwent a surgical procedure for bleeding at a first revisit compared to 0.25% during a second revisit. Acute pain was the primary diagnosis in 18.4% and 11.2% of first and second revisits; fever/vomiting/dehydration were primary diagnoses in 28.2% and 17.9%, respectively. There were two mortalities (0.0055%) within the 14-day postoperative interval. This large-scale analysis describes the current rates and diagnoses of revisits, hospital readmission, and surgical intervention following ambulatory pediatric tonsillectomy. Many revisits centered on pain control and dehydration, suggesting that more adequate symptom control may prevent a large proportion of revisits. 2b. © 2014 The American Laryngological, Rhinological and Otological Society, Inc.
The Mathematics of Dispatchability, Revisited
NASA Technical Reports Server (NTRS)
Morris, Paul
2016-01-01
Dispatchability is an important property for the efficient execution of temporal plans where the temporal constraints are represented as a Simple Temporal Network (STN). It has been shown that every STN may be reformulated as a dispatchable STN, and dispatchability ensures that the temporal constraints need only be satisfied locally during execution. Recently, it has also been shown that Simple Temporal Networks with Uncertainty, augmented with wait edges, are Dynamically Controllable provided every projection is dispatchable. Thus, dispatchability has considerable theoretical as well as practical significance. One thing that hampers further work in this area is the underdeveloped theory. Moreover, the existing foundation is inadequate in certain respects. In this paper, we develop a new mathematical theory of dispatchability and its relationship to execution. We also provide several characterizations of dispatchability, including characterizations in terms of the structural properties of the STN graph. This facilitates the potential application of the theory to other areas.
The Mathematics of Dispatchability Revisited
NASA Technical Reports Server (NTRS)
Morris, Paul
2016-01-01
Dispatchability is an important property for the efficient execution of temporal plans where the temporal constraints are represented as a Simple Temporal Network (STN). It has been shown that every STN may be reformulated as a dispatchable STN, and dispatchability ensures that the temporal constraints need only be satisfied locally during execution. Recently it has also been shown that Simple Temporal Networks with Uncertainty, augmented with wait edges, are Dynamically Controllable provided every projection is dispatchable. Thus, the dispatchability property has both theoretical and practical interest. One thing that hampers further work in this area is the underdeveloped theory. The existing definitions are expressed in terms of algorithms, and are less suitable for mathematical proofs. In this paper, we develop a new formal theory of dispatchability in terms of execution sequences. We exploit this to prove a characterization of dispatchability involving the structural properties of the STN graph. This facilitates the potential application of the theory to uncertainty reasoning.
Proteome Dynamics: Revisiting Turnover with a Global Perspective*
Claydon, Amy J.; Beynon, Robert
2012-01-01
Although bulk protein turnover has been measured with the use of stable isotope labeled tracers for over half a century, it is only recently that the same approach has become applicable to the level of the proteome, permitting analysis of the turnover of many proteins instead of single proteins or an aggregated protein pool. The optimal experimental design for turnover studies is dependent on the nature of the biological system under study, which dictates the choice of precursor label, protein pool sampling strategy, and treatment of data. In this review we discuss different approaches and, in particular, explore how complexity in experimental design and data processing increases as we shift from unicellular to multicellular systems, in particular animals. PMID:23125033
Oscillatory dynamics of Gestalt perception in schizophrenia revisited.
Spencer, Kevin M; Ghorashi, Shahab
2014-01-01
Abnormalities in γ oscillations (30-100 Hz) in the scalp-recorded electroencephalogram (EEG) have been proposed to reflect neural circuitry abnormalities in schizophrenia. Oscillations in the γ band are thought to play an important role in visual perception, mediating the binding of visual features into coherent objects. However, there is relatively little evidence to date of deficits in γ-mediated processes associated with Gestalt perception in schizophrenia. Fourteen healthy control subjects (HC) and 17 chronic schizophrenia patients (SZ) discriminated between illusory Kanisza Squares and No-Square control stimuli, indicating their judgment with a manual button press. Time-frequency decomposition of the EEG was computed with the Morlet wavelet transform. Time-frequency maps of phase locking factor (PLF) values were calculated for stimulus- and response-locked oscillations. HC and SZ did not differ in reaction time, error rate, an early ERP effect associated with Gestalt processing, nor an early visual-evoked γ oscillation. Two response-locked high γ effects had greater PLF for Square than No-Square stimuli in HC, and the reverse pattern in SZ. One of these effects was correlated with thought disorder symptom ratings in SZ. SZ demonstrated abnormalities in γ oscillations associated with the perception of Gestalt objects, while their early visual-evoked γ activity was mostly normal, contrary to previous results. This study supports the hypothesis that high-frequency oscillations are sensitive to aspects of psychosis.
Oscillatory dynamics of Gestalt perception in schizophrenia revisited
Spencer, Kevin M.; Ghorashi, Shahab
2014-01-01
Background: Abnormalities in γ oscillations (30–100 Hz) in the scalp-recorded electroencephalogram (EEG) have been proposed to reflect neural circuitry abnormalities in schizophrenia. Oscillations in the γ band are thought to play an important role in visual perception, mediating the binding of visual features into coherent objects. However, there is relatively little evidence to date of deficits in γ-mediated processes associated with Gestalt perception in schizophrenia. Methods: Fourteen healthy control subjects (HC) and 17 chronic schizophrenia patients (SZ) discriminated between illusory Kanisza Squares and No-Square control stimuli, indicating their judgment with a manual button press. Time-frequency decomposition of the EEG was computed with the Morlet wavelet transform. Time-frequency maps of phase locking factor (PLF) values were calculated for stimulus- and response-locked oscillations. Results: HC and SZ did not differ in reaction time, error rate, an early ERP effect associated with Gestalt processing, nor an early visual-evoked γ oscillation. Two response-locked high γ effects had greater PLF for Square than No-Square stimuli in HC, and the reverse pattern in SZ. One of these effects was correlated with thought disorder symptom ratings in SZ. Conclusions: SZ demonstrated abnormalities in γ oscillations associated with the perception of Gestalt objects, while their early visual-evoked γ activity was mostly normal, contrary to previous results. This study supports the hypothesis that high-frequency oscillations are sensitive to aspects of psychosis. PMID:24550878
NetDyn Revisited: A Replicated Study of Network Dynamics
1996-10-01
experiment were in one location (UC-Berkeley).Our experiments di er from these studies in that we wanted to observe user level performance ofend -to-end...and B. Jain. Experimental assessment ofend -to-end behavior on Internet. Technical Report CS-TR-2909, University of Maryland,Computer Science Department
Radical Change Revisited: Dynamic Digital Age Books for Youth
ERIC Educational Resources Information Center
Dresang, Eliza T.
2008-01-01
Radical change, a theory described in Eliza Dresang's 1999 book, "Radical Change: Books for Youth in a Digital Age," was developed in the mid-1990s. It serves as a lens through which to examine, explain, and ultimately, use contemporary literature for youth growing up in the Digital Age. It identifies changes in forms and formats,…
Origins of Hot Jupiters, Revisited
NASA Astrophysics Data System (ADS)
Batygin, Konstantin; Bodenheimer, Peter; Laughlin, Greg
2015-12-01
Hot Jupiters, giant extrasolar planets with orbital periods less than ~10 days, have long been thought to form at large radial distances (a > 2AU) in protostellar disks, only to subsequently experience large-scale inward migration to the small orbital radii at which they are observed. Here, we propose that a substantial fraction of the hot Jupiter population forms in situ, with the Galactically prevalent short-period super-Earths acting as the source population. Our calculations suggest that under conditions appropriate to the inner regions of protostellar disks, rapid gas accretion can be initiated for solid cores of 10-20 Earth masses, in line with the conventional picture of core-nucleated accretion. This formation scenario leads to testable consequences, including the expectation that hot Jupiters should frequently be accompanied by additional planets, reminiscent of those observed in large numbers by NASA’s Kepler Mission and Doppler velocity surveys. However, dynamical interactions during the early stages of planetary systems' evolutionary lifetimes tend to increase the mutual inclinations of exterior, low-mass companions to hot Jupiters, making transits rare. High-precision radial velocity monitoring provides the best prospect for their detection.
Astrosociological Implications of Astrobiology (Revisited)
NASA Astrophysics Data System (ADS)
Pass, Jim
2010-01-01
Supporters of astrobiology continue to organize the field around formalized associations and organizations under the guise of the so-called ``hard'' sciences (e.g., biology and the related physical/natural sciences). The so-called ``soft'' sciences-including sociology and the other social sciences, the behavioral sciences, and the humanities-remain largely separated from this dynamically growing field. However, as argued in this paper, space exploration involving the search for extraterrestrial life should be viewed as consisting of two interrelated parts (i.e., two sides of the same coin): astrobiology and astrosociology. Together, these two fields broadly combine the two major branches of science as they relate to the relationship between human life and alien life, as appropriate. Moreover, with a formalized system of collaboration, these two complimentary fields would also focus on the implications of their research to human beings as well as their cultures and social structures. By placing the astrosociological implications of astrobiology at a high enough priority, scientists interested in the search for alien life can augment their focus to include the social, cultural, and behavioral implications that were always associated with their work (yet previously overlooked or understated, and too often misunderstood). Recognition of the astrosociological implications expands our perception about alien life by creating a new emphasis on their ramifications to human life on Earth.
Lower hybrid wavepacket stochasticity revisited
Fuchs, V.; Krlín, L.; Pánek, R.; Preinhaelter, J.; Seidl, J.; Urban, J.
2014-02-12
Analysis is presented in support of the explanation in Ref. [1] for the observation of relativistic electrons during Lower Hybrid (LH) operation in EC pre-heated plasma at the WEGA stellarator [1,2]. LH power from the WEGA TE11 circular waveguide, 9 cm diameter, un-phased, 2.45 GHz antenna, is radiated into a B≅0.5 T, Ðœ„n{sub e}≅5×10{sup 17} 1/m{sup 3} plasma at T{sub e}≅10 eV bulk temperature with an EC generated 50 keV component [1]. The fast electrons cycle around flux or drift surfaces with few collisions, sufficient for randomizing phases but insufficient for slowing fast electrons down, and thus repeatedly interact with the rf field close to the antenna mouth, gaining energy in the process. Our antenna calculations reveal a standing electric field pattern at the antenna mouth, with which we formulate the electron dynamics via a relativistic Hamiltonian. A simple approximation of the equations of motion leads to a relativistic generalization of the area-preserving Fermi-Ulam (F-U) map [3], allowing phase-space global stochasticity analysis. At typical WEGA plasma and antenna conditions, the F-U map predicts an LH driven current of about 230 A, at about 225 W of dissipated power, in good agreement with the measurements and analysis reported in [1].
Healthier times?: revisiting Indigenous Australian health history.
Blyton, Greg
2009-01-01
The perception that Indigenous Australians were primitive hunters and gatherers who lived in a nomadic 'Stone Age' culture resonates through most narratives found on Indigenous people in pre-colonial times. This narrative is better placed in the realm of myth; I contest claims that the life expectancy of Indigenous Australians was only forty years in pre-colonial times, by providing suggestive evidence that there is a strong probability that longevity favoured Indigenous Australians in comparison to many poorer sectors of the European population living in slum habitats. As well, I will challenge notions that Indigenous Australians were more violent than supposedly 'civilised' nations. Finally I express the hope that future researchers will revisit archival sources to develop a more nuanced perspective on the past.
Revisiting Lepton Flavour Universality in B Decays
NASA Astrophysics Data System (ADS)
Paradisi, Paride
2017-04-01
Lepton flavour universality (LFU) in B-decays is revisited by considering a class of semileptonic operators defined at a scale Λ above the electroweak scale v. The importance of quantum effects is emphasised [F. Feruglio, P. Paradisi and A. Pattori, arxiv:arXiv:1606.00524 [hep-ph], to appear in PRL]. We construct the low-energy effective Lagrangian taking into account the running effects from Λ down to v through the one-loop renormalization group equations (RGE) in the limit of exact electroweak symmetry and QED RGEs from v down to the 1 GeV scale. The most important quantum effects turn out to be the modification of the leptonic couplings of the vector boson Z and the generation of a purely leptonic effective Lagrangian. Large LFU breaking effects in Z and τ decays as well as visible lepton flavour violating (LFV) effects in τ decays are induced.
Revisiting kaon physics in general Z scenario
NASA Astrophysics Data System (ADS)
Endo, Motoi; Kitahara, Teppei; Mishima, Satoshi; Yamamoto, Kei
2017-08-01
New physics contributions to the Z penguin are revisited in the light of the recently-reported discrepancy of the direct CP violation in K → ππ. Interference effects between the standard model and new physics contributions to ΔS = 2 observables are taken into account. Although the effects are overlooked in the literature, they make experimental bounds significantly severer. It is shown that the new physics contributions must be tuned to enhance B (KL →π0 ν ν bar), if the discrepancy of the direct CP violation is explained with satisfying the experimental constraints. The branching ratio can be as large as 6 ×10-10 when the contributions are tuned at the 10% level.
Revisiting Hafemeister's science and society tests
NASA Astrophysics Data System (ADS)
Brecha, R. J.; Berney, R.; Craver, B.
2007-10-01
We revisit a series of papers on science and society issues by David Hafemeister in the 1970s and 1980s. The emphasis in the present work is on world oil production limits and some consequences of various possible scenarios for the near future. Some of the data and scenarios used by Hafemeister are updated for U.S. oil production in the past two decades, and extended to an analysis of a peak in world oil production in the future. We discuss some simple scenarios for future energy use patterns and look at the consequence of these scenarios as world oil production begins to decline. We also provide a list of resources for critical investigations of natural resource extraction and depletion patterns.
NASA Astrophysics Data System (ADS)
Cai, Yi; Schmidt, Michael A.
2016-05-01
Combining neutrino mass generation and a dark matter candidate in a unified model has always been intriguing. We revisit the class of R νMDM models, which incorporate minimal dark matter in radiative neutrino mass models based on the one-loop ultraviolet completions of the Weinberg operator. The possibility of an exact accidental Z 2 is completely ruled out in this scenario. We study the phenomenology of one of the models with an approximate Z 2 symmetry. In addition to the Standard Model particles, it contains two real scalar quintuplets, one vector-like quadruplet fermion and a fermionic quintuplet. The neutral component of the fermionic quintuplet serves as a good dark matter candidate which can be tested by the future direct and indirect detection experiments. The constraints from flavor physics and electroweak-scale naturalness are also discussed.
Re-visiting the electrophysiology of language.
Obleser, Jonas
2015-09-01
This editorial accompanies a special issue of Brain and Language re-visiting old themes and new leads in the electrophysiology of language. The event-related potential (ERP) as a series of characteristic deflections ("components") over time and their distribution on the scalp has been exploited by speech and language researchers over decades to find support for diverse psycholinguistic models. Fortunately, methodological and statistical advances have allowed human neuroscience to move beyond some of the limitations imposed when looking at the ERP only. Most importantly, we currently witness a refined and refreshed look at "event-related" (in the literal sense) brain activity that relates itself more closely to the actual neurobiology of speech and language processes. It is this imminent change in handling and interpreting electrophysiological data of speech and language experiments that this special issue intends to capture. Copyright © 2015 Elsevier Inc. All rights reserved.
Revisiting gravitino dark matter in thermal leptogenesis
NASA Astrophysics Data System (ADS)
Ibe, Masahiro; Suzuki, Motoo; Yanagida, Tsutomu T.
2017-02-01
In this paper, we revisit the gravitino dark matter scenario in the presence of the bilinear R-parity violating interaction. In particular, we discuss a consistency with the thermal leptogenesis. For a high reheating temperature required for the thermal leptogenesis, the gravitino dark matter tends to be overproduced, which puts a severe upper limit on the gluino mass. As we will show, a large portion of parameter space of the gravitino dark matter scenario has been excluded by combining the constraints from the gravitino abundance and the null results of the searches for the superparticles at the LHC experiments. In particular, the models with the stau (and other charged slepton) NLSP has been almost excluded by the searches for the long-lived charged particles at the LHC unless the required reheating temperature is somewhat lowered by assuming, for example, a degenerated right-handed neutrino mass spectrum.
Revisiting Lepton Flavor Universality in B Decays
NASA Astrophysics Data System (ADS)
Feruglio, Ferruccio; Paradisi, Paride; Pattori, Andrea
2017-01-01
Lepton flavor universality (LFU) in B decays is revisited by considering a class of semileptonic operators defined at a scale Λ above the electroweak scale v . The importance of quantum effects, so far neglected in the literature, is emphasized. We construct the low-energy effective Lagrangian taking into account the running effects from Λ down to v through the one-loop renormalization group equations (RGEs) in the limit of exact electroweak symmetry and QED RGEs from v down to the 1 GeV scale. The most important quantum effects turn out to be the modification of the leptonic couplings of the vector boson Z and the generation of a purely leptonic effective Lagrangian. Large LFU breaking effects in Z and τ decays and visible lepton flavor violating effects in the processes τ →μ ℓℓ, τ →μ ρ , τ →μ π , and τ →μ η(') are induced.
Olfactory pathogenesis of idiopathic Parkinson disease revisited.
Lerner, Alicja; Bagic, Anto
2008-06-15
Idiopathic Parkinson disease (PD) is traditionally considered a movement disorder with hallmark lesions located in the substantia nigra pars compacta (SNpc). However, recent histopathological studies of some PD cases suggest the possibility of a multisystem disorder which progresses in a predictable sequence as described in Braak's staging criteria. The disease process starts in the dorsal motor nucleus of the vagus (dmX) and anterior olfactory nucleus and bulb, and from there, spreads through the brainstem nuclei to ultimately reach the SNpc, which then presents as symptomatic PD. In this article, we would like to revisit the olfactory pathogenesis of PD based on Braak's staging system and review anatomical pathways supporting such a possibility. We also suggest some biomarkers for early stages of PD. Additionally, we present and discuss the possibility that a prion-like process underlies the neurodegenerative changes in PD.
The Species Problem in Myxomycetes Revisited.
Walker, Laura M; Stephenson, Steven L
2016-08-01
Species identification in the myxomycetes (plasmodial slime molds or myxogastrids) poses particular challenges to researchers as a result of their morphological plasticity and frequent alteration between sexual and asexual life strategies. Traditionally, myxomycete morphology has been used as the primary method of species delimitation. However, with the increasing availability of genetic information, traditional myxomycete taxonomy is being increasingly challenged, and new hypotheses continue to emerge. Due to conflicts that sometimes occur between traditional and more modern species concepts that are based largely on molecular data, there is a pressing need to revisit the discussion surrounding the species concept used for myxomycetes. Biological diversity is being increasingly studied with molecular methods and data accumulates at ever-faster rates, making resolution of this matter urgent. In this review, currently used and potentially useful species concepts (biological, morphological, phylogenetic and ecological) are reviewed, and an integrated approach to resolve the myxomycete species problem is discussed. Copyright © 2016 Elsevier GmbH. All rights reserved.
Revisiting instanton corrections to the Konishi multiplet
NASA Astrophysics Data System (ADS)
Alday, Luis F.; Korchemsky, Gregory P.
2016-12-01
We revisit the calculation of instanton effects in correlation functions in N=4 SYM involving the Konishi operator and operators of twist two. Previous studies revealed that the scaling dimensions and the OPE coefficients of these operators do not receive instanton corrections in the semiclassical approximation. We go beyond this approximation and demonstrate that, while operators belonging to the same N=4 supermultiplet ought to have the same conformal data, the evaluation of quantum instanton corrections for one operator can be mapped into a semiclassical computation for another operator in the same supermultiplet. This observation allows us to compute explicitly the leading instanton correction to the scaling dimension of operators in the Konishi supermultiplet as well as to their structure constants in the OPE of two half-BPS scalar operators. We then use these results, together with crossing symmetry, to determine instanton corrections to scaling dimensions of twist-four operators with large spin.
Revisiting Lepton Flavor Universality in B Decays.
Feruglio, Ferruccio; Paradisi, Paride; Pattori, Andrea
2017-01-06
Lepton flavor universality (LFU) in B decays is revisited by considering a class of semileptonic operators defined at a scale Λ above the electroweak scale v. The importance of quantum effects, so far neglected in the literature, is emphasized. We construct the low-energy effective Lagrangian taking into account the running effects from Λ down to v through the one-loop renormalization group equations (RGEs) in the limit of exact electroweak symmetry and QED RGEs from v down to the 1 GeV scale. The most important quantum effects turn out to be the modification of the leptonic couplings of the vector boson Z and the generation of a purely leptonic effective Lagrangian. Large LFU breaking effects in Z and τ decays and visible lepton flavor violating effects in the processes τ→μℓℓ, τ→μρ, τ→μπ, and τ→μη^{(')} are induced.
C-Nucleosides To Be Revisited.
De Clercq, Erik
2016-03-24
Two new C-nucleoside analogues, BCX4430, an imino-C-nucleoside, and GS-6620, a phosphoramidate derivative of 1'-cyano-2'-C-methyl-4-aza-7,9-dideazaadenosine C-nucleoside, have been recently described as effective against filovirus infections (Marburg) and hepatitis C virus (HCV), respectively. The first C-nucleoside analogues were described about half a century ago. The C-nucleoside pseudouridine is a natural component of RNA, and various other C-nucleoside analogues have been reported previously for their antiviral and/or anticancer potential, the most prominent being pyrazofurin, tiazofurin, and selenazofurin. In the meantime, showdomycin, formycin, and various triazole, pyrazine, pyridine, dihydroxyphenyl, thienopyrimidine, pyrazolotriazine, and porphyrin C-nucleoside analogues have been described. It would be worth revisiting these C-nucleosides and derivatives thereof, including their phosphoramidates, for their therapeutic potential in the treatment of virus infections and, where appropriate, cancer as well.
Seasonal dating of Sappho's 'Midnight Poem' revisited
NASA Astrophysics Data System (ADS)
Cuntz, Manfred; Gurdemir, Levent; George, Martin
2016-04-01
Sappho was a Greek lyric poet who composed a significant array of pristine poetry. Although much of it has been lost, her reputation has endured thanks to numerous surviving fragments. One of her contributions includes the so-called 'Midnight Poem', which contains a line about the Pleiades, setting sometime before midnight, and supposedly observed from the island of Lesbos. This poem also refers to the setting of the Moon. Sappho's Midnight Poem thus represents a prime example of where ancient poetry and astronomy merge, and it also offers the possibility of seasonal dating. Previously, Herschberg and Mebius (1990) estimated that the poem was composed in late winter/early spring, a time frame that is not unusual for lyrics of an amorous nature. The aim of our paper is to revisit this earlier finding by using modern-day software. Our study confirms Herschberg and Mebius' result, but also conveys further information.
Peckarsky, Barbara L; Abrams, Peter A; Bolnick, Daniel I; Dill, Lawrence M; Grabowski, Jonathan H; Luttbeg, Barney; Orrock, John L; Peacor, Scott D; Preisser, Evan L; Schmitz, Oswald J; Trussell, Geoffrey C
2008-09-01
Predator effects on prey dynamics are conventionally studied by measuring changes in prey abundance attributed to consumption by predators. We revisit four classic examples of predator-prey systems often cited in textbooks and incorporate subsequent studies of nonconsumptive effects of predators (NCE), defined as changes in prey traits (e.g., behavior, growth, development) measured on an ecological time scale. Our review revealed that NCE were integral to explaining lynx-hare population dynamics in boreal forests, cascading effects of top predators in Wisconsin lakes, and cascading effects of killer whales and sea otters on kelp forests in nearshore marine habitats. The relative roles of consumption and NCE of wolves on moose and consequent indirect effects on plant communities of Isle Royale depended on climate oscillations. Nonconsumptive effects have not been explicitly tested to explain the link between planktonic alewives and the size structure of the zooplankton, nor have they been invoked to attribute keystone predator status in intertidal communities or elsewhere. We argue that both consumption and intimidation contribute to the total effects of keystone predators, and that characteristics of keystone consumers may differ from those of predators having predominantly NCE. Nonconsumptive effects are often considered as an afterthought to explain observations inconsistent with consumption-based theory. Consequently, NCE with the same sign as consumptive effects may be overlooked, even though they can affect the magnitude, rate, or scale of a prey response to predation and can have important management or conservation implications. Nonconsumptive effects may underlie other classic paradigms in ecology, such as delayed density dependence and predator-mediated prey coexistence. Revisiting classic studies enriches our understanding of predator-prey dynamics and provides compelling rationale for ramping up efforts to consider how NCE affect traditional predator
The "frontal syndrome" revisited: lessons from electrostimulation mapping studies.
Duffau, Hugues
2012-01-01
For a long time, in a localizationist view of brain functioning, a combination of symptoms called "frontal syndrome" has been interpreted as the direct result of damages involving the frontal lobe(s). The goal of this review is to challenge this view, that is, to move to a hodotopical approach to lesion mapping, on the basis of new insights provided by intraoperative electrostimulation mapping investigations in patients who underwent awake surgery for cerebral tumors. These original data reported in the last decade break with the traditional dogma of a modular and fixed organization of the central nervous system, by switching to the concepts of cerebral connectivity and plasticity - i.e., a brain organization based on dynamic interrelationships between parallel distributed networks. According to this revisited model, "frontal symptoms" can be generated by tumor or electrostimulation not only of the frontal lobes, but also of cortical and subcortical (white matter pathways/deep gray nuclei) structures outside the frontal lobes: especially, stimulation of the superior longitudinal fascicle may elicit speech production disorders, syntactic disturbances, involuntary language switching or phonemic paraphasia (arcuate fascicle), stimulation of the inferior fronto-occipital fascicle can generate semantic paraphasia or deficit of cross-modal judgment, stimulation of the subcallosal fasciculus may elicit transcortical motor aphasia, while stimulation of the striatum induces preservations. On the other hand, it is also possible to perform extensive right or left frontal lobectomy in patients who continue to have a normal familial, social and professional life, without "frontal syndrome". Therefore, this provocative approach may open the door to a renewal in the modeling of brain processing as well as in its clinical applications, especially in the fields of cerebral surgery and functional rehabilitation. These findings illustrate well the need to reinforce links between
Standing and travelling waves in a spherical brain model: The Nunez model revisited.
Visser, S; Nicks, R; Faugeras, O; Coombes, S
2017-06-15
The Nunez model for the generation of electroencephalogram (EEG) signals is naturally described as a neural field model on a sphere with space-dependent delays. For simplicity, dynamical realisations of this model either as a damped wave equation or an integro-differential equation, have typically been studied in idealised one dimensional or planar settings. Here we revisit the original Nunez model to specifically address the role of spherical topology on spatio-temporal pattern generation. We do this using a mixture of Turing instability analysis, symmetric bifurcation theory, centre manifold reduction and direct simulations with a bespoke numerical scheme. In particular we examine standing and travelling wave solutions using normal form computation of primary and secondary bifurcations from a steady state. Interestingly, we observe spatio-temporal patterns which have counterparts seen in the EEG patterns of both epileptic and schizophrenic brain conditions.
Standing and travelling waves in a spherical brain model: The Nunez model revisited
NASA Astrophysics Data System (ADS)
Visser, S.; Nicks, R.; Faugeras, O.; Coombes, S.
2017-06-01
The Nunez model for the generation of electroencephalogram (EEG) signals is naturally described as a neural field model on a sphere with space-dependent delays. For simplicity, dynamical realisations of this model either as a damped wave equation or an integro-differential equation, have typically been studied in idealised one dimensional or planar settings. Here we revisit the original Nunez model to specifically address the role of spherical topology on spatio-temporal pattern generation. We do this using a mixture of Turing instability analysis, symmetric bifurcation theory, centre manifold reduction and direct simulations with a bespoke numerical scheme. In particular we examine standing and travelling wave solutions using normal form computation of primary and secondary bifurcations from a steady state. Interestingly, we observe spatio-temporal patterns which have counterparts seen in the EEG patterns of both epileptic and schizophrenic brain conditions.
Predator-prey interactions, resource depression and patch revisitation
Erwin, R.M.
1989-01-01
Generalist predators may be confronted by different types of prey in different patches: sedentary and conspicuous, cryptic (with or without refugia), conspicuous and nonsocial, or conspicuous and social. I argue that, where encounter rates with prey are of most importance, patch revisitation should be a profitable tactic where prey have short 'recovery' times (conspicuous, nonsocial prey), or where anti-predator response (e.g. shoaling) may increase conspicuousness. Predictions are made for how temporal changes in prey encounter rates should affect revisit schedules and feeding rates for the 4 different prey types.
Revisiting scalar quark hidden sector in light of 750-GeV diphoton resonance
NASA Astrophysics Data System (ADS)
Chiang, Cheng-Wei; Ibe, Masahiro; Yanagida, Tsutomu T.
2016-05-01
We revisit the model of a CP -even singlet scalar resonance proposed in
Role of iron in synthetic tetrahedrites revisited
NASA Astrophysics Data System (ADS)
Nasonova, Daria I.; Presniakov, Igor A.; Sobolev, Alexei V.; Verchenko, Valeriy Yu.; Tsirlin, Alexander A.; Wei, Zheng; Dikarev, Evgeny V.; Shevelkov, Andrei V.
2016-03-01
The valence state of iron in Cu12-xFexSb4S13 tetrahedrites have been revisited by the combination of the crystallographic results, Mössbauer spectroscopy, and magnetization measurements. The crystal structure solution for Cu11.0Fe1.0Sb4S13 (space group I 4 bar 3m, a=10.3253(12), z=2, R=0.011) proved that iron substitutes for copper only in the Cu1 position. At the iron content of x=0.8, 1.0, and 1.2, the presence of two nonequivalent and non-interacting Fe3+ cations was inferred from Mössbauer spectra. At higher levels of substitution (x=1.5 and 2.0), room-temperature Mössbauer spectra indicate the electron hopping between part of Fe3+ and Fe2+ centers, whereas the rest of iron atoms exists as valence-localized Fe3+ and Fe2+ cations. Electron transfer is frozen out at 77 K, where a combination of two Fe3+ sites and one high-spin Fe2+ site is observed. Paramagnetic effective moments extracted from the magnetic susceptibility data point at the Fe3+ state of iron at x=0.8, while a mixture of Fe2+ and Fe3+ is presumed in the samples with higher Fe content.
Role of iron in synthetic tetrahedrites revisited
NASA Astrophysics Data System (ADS)
Nasonova, Daria I.; Presniakov, Igor A.; Sobolev, Alexei V.; Verchenko, Valeriy Yu.; Tsirlin, Alexander A.; Wei, Zheng; Dikarev, Evgeny V.; Shevelkov, Andrei V.
2016-10-01
The valence state of iron in Cu12-xFexSb4S13 tetrahedrites have been revisited by the combination of the crystallographic results, Mössbauer spectroscopy, and magnetization measurements. The crystal structure solution for Cu11.0Fe1.0Sb4S13 (space group I 4 bar 3m, a=10.3253(12), z=2, R=0.011) proved that iron substitutes for copper only in the Cu1 position. At the iron content of x=0.8, 1.0, and 1.2, the presence of two nonequivalent and non-interacting Fe3+ cations was inferred from Mössbauer spectra. At higher levels of substitution (x=1.5 and 2.0), room-temperature Mössbauer spectra indicate the electron hopping between part of Fe3+ and Fe2+ centers, whereas the rest of iron atoms exists as valence-localized Fe3+ and Fe2+ cations. Electron transfer is frozen out at 77 K, where a combination of two Fe3+ sites and one high-spin Fe2+ site is observed. Paramagnetic effective moments extracted from the magnetic susceptibility data point at the Fe3+ state of iron at x=0.8, while a mixture of Fe2+ and Fe3+ is presumed in the samples with higher Fe content.
The problem Of muscle hypertrophy: Revisited.
Buckner, Samuel L; Dankel, Scott J; Mattocks, Kevin T; Jessee, Matthew B; Mouser, J Grant; Counts, Brittany R; Loenneke, Jeremy P
2016-12-01
In this paper we revisit a topic originally discussed in 1955, namely the lack of direct evidence that muscle hypertrophy from exercise plays an important role in increasing strength. To this day, long-term adaptations in strength are thought to be primarily contingent on changes in muscle size. Given this assumption, there has been considerable attention placed on programs designed to allow for maximization of both muscle size and strength. However, the conclusion that a change in muscle size affects a change in strength is surprisingly based on little evidence. We suggest that these changes may be completely separate phenomena based on: (1) the weak correlation between the change in muscle size and the change in muscle strength after training; (2) the loss of muscle mass with detraining, yet a maintenance of muscle strength; and (3) the similar muscle growth between low-load and high-load resistance training, yet divergent results in strength. Muscle Nerve 54: 1012-1014, 2016. © 2016 Wiley Periodicals, Inc.
Ellis, John; Evans, Jason L.; Mustafayev, Azar; ...
2016-10-28
Here, we revisit minimal supersymmetric SU(5) grand unification (GUT) models in which the soft supersymmetry-breaking parameters of the minimal supersymmetric Standard Model (MSSM) are universal at some input scale, Min, above the supersymmetric gauge-coupling unification scale, MGUT. As in the constrained MSSM (CMSSM), we assume that the scalar masses and gaugino masses have common values, m0 and m1/2, respectively, at Min, as do the trilinear soft supersymmetry-breaking parameters A0. Going beyond previous studies of such a super-GUT CMSSM scenario, we explore the constraints imposed by the lower limit on the proton lifetime and the LHC measurement of the Higgs mass,more » mh. We find regions of m0, m1/2 A0 and the parameters of the SU(5) superpotential that are compatible with these and other phenomenological constraints such as the density of cold dark matter, which we assume to be provided by the lightest neutralino. Typically, these allowed regions appear for m0 and m1/2 in the multi-TeV region, for suitable values of the unknown SU(5) GUT-scale phases and superpotential couplings, and with the ratio of supersymmetric Higgs vacuum expectation values tan β≲6.« less
Carbon emission from global hydroelectric reservoirs revisited.
Li, Siyue; Zhang, Quanfa
2014-12-01
Substantial greenhouse gas (GHG) emissions from hydropower reservoirs have been of great concerns recently, yet the significant carbon emitters of drawdown area and reservoir downstream (including spillways and turbines as well as river reaches below dams) have not been included in global carbon budget. Here, we revisit GHG emission from hydropower reservoirs by considering reservoir surface area, drawdown zone and reservoir downstream. Our estimates demonstrate around 301.3 Tg carbon dioxide (CO2)/year and 18.7 Tg methane (CH4)/year from global hydroelectric reservoirs, which are much higher than recent observations. The sum of drawdown and downstream emission, which is generally overlooked, represents 42 % CO2 and 67 % CH4 of the total emissions from hydropower reservoirs. Accordingly, the global average emissions from hydropower are estimated to be 92 g CO2/kWh and 5.7 g CH4/kWh. Nonetheless, global hydroelectricity could currently reduce approximate 2,351 Tg CO2eq/year with respect to fuel fossil plant alternative. The new findings show a substantial revision of carbon emission from the global hydropower reservoirs.
The Einstein-Boltzmann equations revisited
NASA Astrophysics Data System (ADS)
Nadkarni-Ghosh, Sharvari; Refregier, Alexandre
2017-10-01
The linear Einstein-Boltzmann (E-B) equations describe the evolution of perturbations in the universe and its numerical solutions play a central role in cosmology. We revisit this system of differential equations and present a detailed investigation of its mathematical properties. For this purpose, we focus on a simplified set of equations aimed at describing the broad features of the matter power spectrum. We first perform an eigenvalue analysis and study the onset of oscillations in the system signalled by the transition from real to complex eigenvalues. We then provide a stability criterion of different numerical schemes for this linear system and estimate the associated step size. We elucidate the stiffness property of the E-B system and show how it can be characterized in terms of the eigenvalues. While the parameters of the system are time dependent making it non-autonomous, we define an adiabatic regime where the parameters vary slowly enough for the system to be quasi-autonomous. We summarize the different regimes of the system for these different criteria as function of wavenumber k and scalefactor a. We also provide a compendium of analytic solutions for all perturbation variables in six limits on the k-a plane and express them explicitly in terms of initial conditions. These results are aimed to help the further development and testing of numerical cosmological Boltzmann solvers.
Computational Electrocardiography: Revisiting Holter ECG Monitoring.
Deserno, Thomas M; Marx, Nikolaus
2016-08-05
Since 1942, when Goldberger introduced the 12-lead electrocardiography (ECG), this diagnostic method has not been changed. After 70 years of technologic developments, we revisit Holter ECG from recording to understanding. A fundamental change is fore-seen towards "computational ECG" (CECG), where continuous monitoring is producing big data volumes that are impossible to be inspected conventionally but require efficient computational methods. We draw parallels between CECG and computational biology, in particular with respect to computed tomography, computed radiology, and computed photography. From that, we identify technology and methodology needed for CECG. Real-time transfer of raw data into meaningful parameters that are tracked over time will allow prediction of serious events, such as sudden cardiac death. Evolved from Holter's technology, portable smartphones with Bluetooth-connected textile-embedded sensors will capture noisy raw data (recording), process meaningful parameters over time (analysis), and transfer them to cloud services for sharing (handling), predicting serious events, and alarming (understanding). To make this happen, the following fields need more research: i) signal processing, ii) cycle decomposition; iii) cycle normalization, iv) cycle modeling, v) clinical parameter computation, vi) physiological modeling, and vii) event prediction. We shall start immediately developing methodology for CECG analysis and understanding.
Revisiting the phase diagram of hard ellipsoids
NASA Astrophysics Data System (ADS)
Odriozola, Gerardo
2012-04-01
In this work, the well-known Frenkel-Mulder phase diagram of hard ellipsoids of revolution [D. Frenkel and B. M. Mulder, Mol. Phys. 55, 1171 (1985), 10.1080/00268978500101971] is revisited by means of replica exchange Monte Carlo simulations. The method provides good sampling of dense systems and so, solid phases can be accessed without the need of imposing a given structure. At high densities, we found plastic solids and fcc-like crystals for semi-spherical ellipsoids (prolates and oblates), and SM2 structures [P. Pfleiderer and T. Schilling, Phys. Rev. E 75, 020402 (2007)] for x : 1-prolates and 1 : x-oblates with x ≥ 3. The revised fluid-crystal and isotropic-nematic transitions reasonably agree with those presented in the Frenkel-Mulder diagram. An interesting result is that, for small system sizes (100 particles), we obtained 2:1- and 1.5:1-prolate equations of state without transitions, while some order is developed at large densities. Furthermore, the symmetric oblate cases are also reluctant to form ordered phases.
Pair Production Constraints on Superluminal Neutrinos Revisited
Brodsky, Stanley J.; Gardner, Susan; /Kentucky U.
2012-02-16
We revisit the pair creation constraint on superluminal neutrinos considered by Cohen and Glashow in order to clarify which types of superluminal models are constrained. We show that a model in which the superluminal neutrino is effectively light-like can evade the Cohen-Glashow constraint. In summary, any model for which the CG pair production process operates is excluded because such timelike neutrinos would not be detected by OPERA or other experiments. However, a superluminal neutrino which is effectively lightlike with fixed p{sup 2} can evade the Cohen-Glashow constraint because of energy-momentum conservation. The coincidence involved in explaining the SN1987A constraint certainly makes such a picture improbable - but it is still intrinsically possible. The lightlike model is appealing in that it does not violate Lorentz symmetry in particle interactions, although one would expect Hughes-Drever tests to turn up a violation eventually. Other evasions of the CG constraints are also possible; perhaps, e.g., the neutrino takes a 'short cut' through extra dimensions or suffers anomalous acceleration in matter. Irrespective of the OPERA result, Lorentz-violating interactions remain possible, and ongoing experimental investigation of such possibilities should continue.
Post-inflationary gravitino production revisited
Ellis, John; Garcia, Marcos A.G.; Olive, Keith A.; Nanopoulos, Dimitri V.; Peloso, Marco E-mail: garciagarcia@physics.umn.edu E-mail: olive@physics.umn.edu
2016-03-01
We revisit gravitino production following inflation. As a first step, we review the standard calculation of gravitino production in the thermal plasma formed at the end of post-inflationary reheating when the inflaton has completely decayed. Next we consider gravitino production prior to the completion of reheating, assuming that the inflaton decay products thermalize instantaneously while they are still dilute. We then argue that instantaneous thermalization is in general a good approximation, and also show that the contribution of non-thermal gravitino production via the collisions of inflaton decay products prior to thermalization is relatively small. Our final estimate of the gravitino-to-entropy ratio is approximated well by a standard calculation of gravitino production in the post-inflationary thermal plasma assuming total instantaneous decay and thermalization at a time t ≅ 1.2/Γ{sub φ}. Finally, in light of our calculations, we consider potential implications of upper limits on the gravitino abundance for models of inflation, with particular attention to scenarios for inflaton decays in supersymmetric Starobinsky-like models.
NASA Astrophysics Data System (ADS)
Ellis, John; Evans, Jason L.; Mustafayev, Azar; Nagata, Natsumi; Olive, Keith A.
2016-11-01
We revisit minimal supersymmetric SU(5) grand unification (GUT) models in which the soft supersymmetry-breaking parameters of the minimal supersymmetric Standard Model (MSSM) are universal at some input scale, M_in, above the supersymmetric gauge-coupling unification scale, M_GUT. As in the constrained MSSM (CMSSM), we assume that the scalar masses and gaugino masses have common values, m_0 and m_{1/2}, respectively, at M_in, as do the trilinear soft supersymmetry-breaking parameters A_0. Going beyond previous studies of such a super-GUT CMSSM scenario, we explore the constraints imposed by the lower limit on the proton lifetime and the LHC measurement of the Higgs mass, m_h. We find regions of m_0, m_{1/2}, A_0 and the parameters of the SU(5) superpotential that are compatible with these and other phenomenological constraints such as the density of cold dark matter, which we assume to be provided by the lightest neutralino. Typically, these allowed regions appear for m_0 and m_{1/2} in the multi-TeV region, for suitable values of the unknown SU(5) GUT-scale phases and superpotential couplings, and with the ratio of supersymmetric Higgs vacuum expectation values tan β ≲ 6.
Revisiting the phase diagram of hard ellipsoids.
Odriozola, Gerardo
2012-04-07
In this work, the well-known Frenkel-Mulder phase diagram of hard ellipsoids of revolution [D. Frenkel and B. M. Mulder, Mol. Phys. 55, 1171 (1985)] is revisited by means of replica exchange Monte Carlo simulations. The method provides good sampling of dense systems and so, solid phases can be accessed without the need of imposing a given structure. At high densities, we found plastic solids and fcc-like crystals for semi-spherical ellipsoids (prolates and oblates), and SM2 structures [P. Pfleiderer and T. Schilling, Phys. Rev. E 75, 020402 (2007)] for x : 1-prolates and 1 : x-oblates with x ≥ 3. The revised fluid-crystal and isotropic-nematic transitions reasonably agree with those presented in the Frenkel-Mulder diagram. An interesting result is that, for small system sizes (100 particles), we obtained 2:1- and 1.5:1-prolate equations of state without transitions, while some order is developed at large densities. Furthermore, the symmetric oblate cases are also reluctant to form ordered phases.
Meta-Analysis in Clinical Trials Revisited
Laird, Nan
2015-01-01
In this paper, we revisit a 1986 article we published in this Journal, Meta-Analysis in Clinical Trials, where we introduced a random-effect model to summarize the evidence about treatment efficacy from a number of related clinical trials. Because of its simplicity and ease of implementation, our approach has been widely used (with more than 12,000 citations to date) and the “DerSimonian and Laird method” is now often referred to as the ‘standard approach’ or a ‘popular’ method for meta-analysis in medical and clinical research. The method is especially useful for providing an overall effect estimate and for characterizing the heterogeneity of effects across a series of studies. Here, we review the background that led to the original 1986 article, briefly describe the random-effects approach for meta-analysis, explore its use in various settings and trends over time and recommend a refinement to the method using a robust variance estimator for testing overall effect. We conclude with a discussion of repurposing the method for Big Data meta-analysis and Genome Wide Association Studies for studying the importance of genetic variants in complex diseases. PMID:26343745
Critical boundary sine-Gordon revisited
Hasselfield, M.; Lee, Taejin; Semenoff, G.W. . E-mail: gordonws@phas.ubc.ca; Stamp, P.C.E.
2006-12-15
We revisit the exact solution of the two space-time dimensional quantum field theory of a free massless boson with a periodic boundary interaction and self-dual period. We analyze the model by using a mapping to free fermions with a boundary mass term originally suggested in Ref. [J. Polchinski, L. Thorlacius, Phys. Rev. D 50 (1994) 622]. We find that the entire SL (2, C) family of boundary states of a single boson are boundary sine-Gordon states and we derive a simple explicit expression for the boundary state in fermion variables and as a function of sine-Gordon coupling constants. We use this expression to compute the partition function. We observe that the solution of the model has a strong-weak coupling generalization of T-duality. We then examine a class of recently discovered conformal boundary states for compact bosons with radii which are rational numbers times the self-dual radius. These have simple expression in fermion variables. We postulate sine-Gordon-like field theories with discrete gauge symmetries for which they are the appropriate boundary states.
No-scale ripple inflation revisited
Li, Tianjun; Li, Zhijin; Nanopoulos, Dimitri V. E-mail: lizhijin@physics.tamu.edu
2014-04-01
We revisit the no-scale ripple inflation model, where no-scale supergravity is modified by an additional term for the inflaton field in the Kähler potential. This term not only breaks one SU(N,1) symmetry explicitly, but also plays an important role for inflation. We generalize the superpotential in the no-scale ripple inflation model slightly. There exists a discrete Z{sub 2} symmetry/parity in the scalar potential in general, which can be preserved or violated by the non-canonical nomalized inflaton kinetic term. Thus, there are three inflation paths: one parity invariant path, and the left and right paths for parity violating scenario. We show that the inflations along the parity invariant path and right path are consistent with the Planck results. However, the gavitino mass for the parity invariant path is so large that the inflation results will be invalid if we consider the inflaton supersymmetry breaking soft mass term. Thus, only the inflation along the right path gives the correct and consistent results. Notably, the tensor-to-scalar ratio in such case can be large, with a value around 0.05, which may be probed by the future Planck experiment.
Targeting Cancer Metabolism - Revisiting the Warburg Effects
Tran, Quangdon; Lee, Hyunji; Park, Jisoo; Kim, Seon-Hwan; Park, Jongsun
2016-01-01
After more than half of century since the Warburg effect was described, this atypical metabolism has been standing true for almost every type of cancer, exhibiting higher glycolysis and lactate metabolism and defective mitochondrial ATP production. This phenomenon had attracted many scientists to the problem of elucidating the mechanism of, and reason for, this effect. Several models based on oncogenic studies have been proposed, such as the accumulation of mitochondrial gene mutations, the switch from oxidative phosphorylation respiration to glycolysis, the enhancement of lactate metabolism, and the alteration of glycolytic genes. Whether the Warburg phenomenon is the consequence of genetic dysregulation in cancer or the cause of cancer remains unknown. Moreover, the exact reasons and physiological values of this peculiar metabolism in cancer remain unclear. Although there are some pharmacological compounds, such as 2-deoxy-D-glucose, dichloroacetic acid, and 3-bromopyruvate, therapeutic strategies, including diet, have been developed based on targeting the Warburg effect. In this review, we will revisit the Warburg effect to determine how much scientists currently understand about this phenomenon and how we can treat the cancer based on targeting metabolism. PMID:27437085
Revisiting the argument from fetal potential.
Manninen, Bertha Alvarez
2007-05-17
One of the most famous, and most derided, arguments against the morality of abortion is the argument from potential, which maintains that the fetus' potential to become a person and enjoy the valuable life common to persons, entails that its destruction is prima facie morally impermissible. In this paper, I will revisit and offer a defense of the argument from potential.First, I will criticize the classical arguments proffered against the importance of fetal potential, specifically the arguments put forth by philosophers Peter Singer and David Boonin, by carefully unpacking the claims made in these arguments and illustrating why they are flawed.Secondly, I will maintain that fetal potential is morally relevant when it comes to the morality of abortion, but that it must be accorded a proper place in the argument. This proper place, however, cannot be found until we first answer a very important and complex question: we must first address the issue of personal identity, and when the fetus becomes the type of being who is relevantly identical to a future person. I will illustrate why the question of fetal potential can only be meaningfully addressed after we have first answered the question of personal identity and how it relates to the human fetus.
Binocularity and visual search-Revisited.
Zou, Bochao; Utochkin, Igor S; Liu, Yue; Wolfe, Jeremy M
2017-02-01
Binocular rivalry is a phenomenon of visual competition in which perception alternates between two monocular images. When two eye's images only differ in luminance, observers may perceive shininess, a form of rivalry called binocular luster. Does dichoptic information guide attention in visual search? Wolfe and Franzel (Perception & Psychophysics, 44(1), 81-93, 1988) reported that rivalry could guide attention only weakly, but that luster (shininess) "popped out," producing very shallow Reaction Time (RT) × Set Size functions. In this study, we have revisited the topic with new and improved stimuli. By using a checkerboard pattern in rivalry experiments, we found that search for rivalry can be more efficient (16 ms/item) than standard, rivalrous grating (30 ms/item). The checkerboard may reduce distracting orientation signals that masked the salience of rivalry between simple orthogonal gratings. Lustrous stimuli did not pop out when potential contrast and luminance artifacts were reduced. However, search efficiency was substantially improved when luster was added to the search target. Both rivalry and luster tasks can produce search asymmetries, as is characteristic of guiding features in search. These results suggest that interocular differences that produce rivalry or luster can guide attention, but these effects are relatively weak and can be hidden by other features like luminance and orientation in visual search tasks.
[What mirror neurons have revealed: revisited].
Murata, Akira; Maeda, Kazutaka
2014-06-01
The first paper on mirror neurons was published in 1992. In the span of over two decades since then, much knowledge about the relationship between social cognitive function and the motor control system has been accumulated. Direct matching of visual actions and their corresponding motor representations is the most important functional property of mirror neuron. Many studies have emphasized intrinsic simulation as a core concept for mirror neurons. Mirror neurons are thought to play a role in social cognitive function. However, the function of mirror neurons in the macaque remains unclear, because such cognitive functions are limited or lacking in macaque monkeys. It is therefore important to discuss these neurons in the context of motor function. Rizzolatti and colleagues have stressed that the most important function of mirror neurons in macaques is recognition of actions performed by other individuals. I suggest that mirror neurons in the Macaque inferior pariental lobule might be correlated with body schema. In the parieto-premotor network, matching of corollary discharge and actual sensory feedback is an essential neuronal operation. Recently, neurons showing mirror properties were found in some cortical areas outside the mirror neuron system. The current work would revisit the outcomes of mirror neuron studies to discuss the function of mirror neurons in the monkey.
THE CONCEPT OF REFERENCE CONDITION, REVISITED ...
Ecological assessments of aquatic ecosystems depend on the ability to compare current conditions against some expectation of how they could be in the absence of significant human disturbance. The concept of a ‘‘reference condition’’ is often used to describe the standard or benchmark against which current condition is compared. If assessments are to be conducted consistently, then a common understanding of the definitions and complications of reference condition is necessary. A 2006 paper (Stoddard et al., 2006, Ecological Applications 16:1267-1276) made an early attempt at codifying the reference condition concept; in this presentation we will revisit the points raised in that paper (and others) and examine how our thinking has changed in a little over 10 years.Among the issues to be discussed: (1) the “moving target” created when reference site data are used to set thresholds in large scale assessments; (2) natural vs. human disturbance and their effects on reference site distributions; (3) circularity and the use of biological data to assist in reference site identification; (4) using site-scale (in-stream or in-lake) measurements vs. landscape-level human activity to identify reference conditions. Ecological assessments of aquatic ecosystems depend on the ability to compare current conditions against some expectation of how they could be in the absence of significant human disturbance. The concept of a ‘‘reference condition’’ is often use
Hyperinflation in Brazil, Israel, and Nicaragua revisited
NASA Astrophysics Data System (ADS)
Szybisz, Martín A.; Szybisz, Leszek
2017-01-01
The aim of the present work is to address the description of hyperinflation regimens in economy. The spirals of hyperinflation developed in Brazil, Israel, and Nicaragua are revisited. This new analysis of data indicates that the episodes occurred in Brazil and Nicaragua can be understood within the frame of the model available in the literature, which is based on a nonlinear feedback (NLF) characterized by an exponent β > 0. In the NLF model the accumulated consumer price index carries a finite time singularity of the type 1 /(tc - t) (1 - β) / β determining a critical time tc at which the economy would crash. It is shown that in the case of Brazil the entire episode cannot be described with a unique set of parameters because the time series was strongly affected by a change of policy. This fact gives support to the ;so called; Lucas critique, who stated that model's parameters usually change once policy changes. On the other hand, such a model is not able to provide any tc in the case of the weaker hyperinflation occurred in Israel. It is shown that in this case the fit of data yields β → 0. This limit leads to the linear feedback formulation which does not predict any tc. An extension for the NLF model is suggested.
Educational Administration and the Management of Knowledge: 1980 Revisited
ERIC Educational Resources Information Center
Bates, Richard
2013-01-01
This paper revisits the thesis of a 1980 paper that suggested a new approach to educational administration based upon the New Sociology of Education. In particular it updates answers to the six key questions asked by that paper: what counts as knowledge; how is what counts as knowledge organised; how is what counts as knowledge transmitted; how is…
Antidote for Zero Tolerance: Revisiting a "Reclaiming" School.
ERIC Educational Resources Information Center
Farner, Conrad D.
2002-01-01
Reports on a revisit to the Frank Lloyd Wright Middle School, which implemented strategies to deal with disciplinary problems. The school continues to progress towards creating the type of reclaiming environment necessary to ensure the needs of all students. Strategies used include alternatives to zero tolerance policy; smaller teams of students;…
Language Transmission Revisited: Family Type, Linguistic Environment and Language Attitudes
ERIC Educational Resources Information Center
Schupbach, Doris
2009-01-01
This article revisits factors in intergenerational language maintenance and shift within the family. It does so through an in-depth analysis of what 14 migrants to Australia from German-speaking Switzerland reported in written life stories and subsequent life story interviews. The participants represent four family types and a wide age range, and…
Threshold Concepts and Student Engagement: Revisiting Pedagogical Content Knowledge
ERIC Educational Resources Information Center
Zepke, Nick
2013-01-01
This article revisits the notion that to facilitate quality learning requires teachers in higher education to have pedagogical content knowledge. It constructs pedagogical content knowledge as a teaching and learning space that brings content and pedagogy together. On the content knowledge side, it suggests that threshold concepts, akin to a…
Revisiting the quantum harmonic oscillator via unilateral Fourier transforms
NASA Astrophysics Data System (ADS)
Nogueira, Pedro H. F.; de Castro, Antonio S.
2016-01-01
The literature on the exponential Fourier approach to the one-dimensional quantum harmonic oscillator problem is revised and criticized. It is shown that the solution of this problem has been built on faulty premises. The problem is revisited via the Fourier sine and cosine transform method and the stationary states are properly determined by requiring definite parity and square-integrable eigenfunctions.
Bohr’s ‘Light and Life’ revisited
NASA Astrophysics Data System (ADS)
Nussenzveig, H. M.
2015-11-01
I revisit Niels Bohr’s famous 1932 ‘Light and Life’ lecture, confronting it with current knowledge. Topics covered include: life origin and evolution, quantum mechanics and life, brain and mind, consciousness and free will, and light as a tool for biology, with special emphasis on optical tweezers and their contributions to biophysics. Specialized knowledge of biology is not assumed.
Revisiting the Role of Communication in Adolescent Intimate Partner Violence
ERIC Educational Resources Information Center
Messinger, Adam M.; Rickert, Vaughn I.; Fry, Deborah A.; Lessel, Harriet; Davidson, Leslie L.
2012-01-01
A growing literature suggests that communication strategies can promote or inhibit intimate partner violence (IPV). Research on communication is still needed on a group ripe for early IPV intervention: high school-aged adolescents. This article revisits our previous analyses of young female reproductive clinic patients (Messinger, Davidson, &…
Revisiting Jack Goody to Rethink Determinisms in Literacy Studies
ERIC Educational Resources Information Center
Collin, Ross
2013-01-01
This article revisits Goody's arguments about literacy's influence on social arrangements, culture, cognition, economics, and other domains of existence. Whereas some of his arguments tend toward technological determinism (i.e., literacy causes change in the world), other of his arguments construe literacy as a force that shapes and is shaped by…
Antidote for Zero Tolerance: Revisiting a "Reclaiming" School.
ERIC Educational Resources Information Center
Farner, Conrad D.
2002-01-01
Reports on a revisit to the Frank Lloyd Wright Middle School, which implemented strategies to deal with disciplinary problems. The school continues to progress towards creating the type of reclaiming environment necessary to ensure the needs of all students. Strategies used include alternatives to zero tolerance policy; smaller teams of students;…
Instructional Efficiency: Revisiting the Original Construct in Educational Research
ERIC Educational Resources Information Center
van Gog, Tamara; Paas, Fred
2008-01-01
This article revisits Paas and Van Merrienboer's (1993) measure of instructional efficiency, which can be applied by educational researchers to compare the effects of different instructional conditions on learning. This measure relied on performance and mental effort on the test, and as such gave an indication of the quality of learning outcomes.…
Revisiting Constructivist Teaching Methods in Ontario Colleges Preparing for Accreditation
ERIC Educational Resources Information Center
Schultz, Rachel A.
2015-01-01
At the time of writing, the first community colleges in Ontario were preparing for transition to an accreditation model from an audit system. This paper revisits constructivist literature, arguing that a more pragmatic definition of constructivism effectively blends positivist and interactionist philosophies to achieve both student centred…
College-Level Sheltered Instruction: Revisiting the Issue of Effectiveness
ERIC Educational Resources Information Center
Knoblock, Natalia; Youngquist, Judy
2016-01-01
Finding an effective instruction mode for ESL students in the US educational system has not been an easy task. The country's secondary and tertiary institutions continue to struggle to meet the needs of their large non-native student populations. The article revisits the debate whether sheltered instruction is an effective model to follow. In our…
Revisiting Methodological Issues in Transcript Analysis: Negotiated Coding and Reliability
ERIC Educational Resources Information Center
Garrison, D. R.; Cleveland-Innes, M.; Koole, Marguerite; Kappelman, James
2006-01-01
Transcript analysis is an important methodology to study asynchronous online educational discourse. The purpose of this study is to revisit reliability and validity issues associated with transcript analysis. The goal is to provide researchers with guidance in coding transcripts. For validity reasons, it is suggested that the first step is to…
The Importance of Being a Complement: CED Effects Revisited
ERIC Educational Resources Information Center
Jurka, Johannes
2010-01-01
This dissertation revisits subject island effects (Ross 1967, Chomsky 1973) cross-linguistically. Controlled acceptability judgment studies in German, English, Japanese and Serbian show that extraction out of specifiers is consistently degraded compared to extraction out of complements, indicating that the Condition on Extraction domains (CED,…
Decay of the neutron deficient 32Ar, revisited.
NASA Astrophysics Data System (ADS)
Domínguez-Reyes, R.; Borge, M. J. G.; Blank, B.; Matea, I.; Adimi, N.; Thomas, J. C.
2007-11-01
The aim of this work is to revisit the decay of Argon 32Ar with special emphasis in the p-γ coincidences. The study was motivated by the increase in granularity and sensitivity of the charged particle detectors and by the high sensitivity and large angular coverage obtained by the use of CLOVER detectors.
Facilitating Grade Acceleration: Revisiting the Wisdom of John Feldhusen
ERIC Educational Resources Information Center
Culross, Rita R.; Jolly, Jennifer L.; Winkler, Daniel
2013-01-01
This article revisits the 1986 Feldhusen, Proctor, and Black recommendations on grade skipping. These recommendations originally appeared as 12 guidelines. In this article, the guidelines are grouped into three general categories: how to screen accelerant candidates, how to engage with the adults in the acceleration process (e.g., teachers,…
Facilitating Grade Acceleration: Revisiting the Wisdom of John Feldhusen
ERIC Educational Resources Information Center
Culross, Rita R.; Jolly, Jennifer L.; Winkler, Daniel
2013-01-01
This article revisits the 1986 Feldhusen, Proctor, and Black recommendations on grade skipping. These recommendations originally appeared as 12 guidelines. In this article, the guidelines are grouped into three general categories: how to screen accelerant candidates, how to engage with the adults in the acceleration process (e.g., teachers,…
Pockets of Participation: Revisiting Child-Centred Participation Research
ERIC Educational Resources Information Center
Franks, Myfanwy
2011-01-01
This article revisits the theme of the clash of interests and power relations at work in participatory research which is prescribed from above. It offers a possible route toward solving conflict between adult-led research carried out by young researchers, funding requirements and organisational constraints. The article explores issues of…
Closing Achievement Gaps: Revisiting Benjamin S. Bloom's "Learning for Mastery"
ERIC Educational Resources Information Center
Guskey, Thomas R.
2007-01-01
The problem of achievement gaps among different subgroups of students has been evident in education for many years. This manuscript revisits the work of renowned educator Benjamin S. Bloom, who saw reducing gaps in the achievement of various groups of students as a simple problem of reducing variation in student learning outcomes. Bloom observed…
Moral Judgment Development across Cultures: Revisiting Kohlberg's Universality Claims
ERIC Educational Resources Information Center
Gibbs, John C.; Basinger, Karen S.; Grime, Rebecca L.; Snarey, John R.
2007-01-01
This article revisits Kohlberg's cognitive developmental claims that stages of moral judgment, facilitative processes of social perspective-taking, and moral values are commonly identifiable across cultures. Snarey [Snarey, J. (1985). "The cross-cultural universality of social-moral development: A critical review of Kohlbergian research."…
Literary Origins of the Term "School Psychologist" Revisited
ERIC Educational Resources Information Center
Fagan, Thomas K.
2005-01-01
Previous research on the literary origins of the term "school psychologist" is revisited, and conclusions are revised in light of new evidence. It appears that the origin of the term in the American literature occurred as early as 1898 in an article by Hugo Munsterberg, predating the usage by Wilhelm Stern in 1911. The early references to the…
Girl Number 20 Revisited: Feminist Literacies in New Hard Times
ERIC Educational Resources Information Center
Gonick, Marnina
2007-01-01
This paper revisits the question of "voice" in the context of neo-liberal social and educational reform. "Voice" has been one of the key concepts of feminist and critical pedagogies in the theory and practice of producing social transformation. I argue in this paper, that the political effectiveness of this concept needs to be…
Moral Judgment Development across Cultures: Revisiting Kohlberg's Universality Claims
ERIC Educational Resources Information Center
Gibbs, John C.; Basinger, Karen S.; Grime, Rebecca L.; Snarey, John R.
2007-01-01
This article revisits Kohlberg's cognitive developmental claims that stages of moral judgment, facilitative processes of social perspective-taking, and moral values are commonly identifiable across cultures. Snarey [Snarey, J. (1985). "The cross-cultural universality of social-moral development: A critical review of Kohlbergian research."…
[Factors associated with emergency department revisits for acute bacterial prostatitis].
Ferré Losa, Carles; Llopis Roca, Ferran; Jacob Rodríguez, Javier; Cabello Zamora, Irene; Martínez Muñoz, Concepción; Bardés Robles, Ignasi
2017-01-01
To analyze factors associated with revisits by patients with acute bacterial prostatitis treated in a hospital emergency department. Descriptive analysis and prospective follow-up of a cohort of patients with acute bacterial prostatitis treated in an emergency department. We included 241 episodes of acute bacterial prostatitis. The mean (SD) age was 63 (16) years. Seventy-three percent reported dysuria, 64% had fever, and between 15.4% and 22.4% had medical histories of cancer, urethral/bladder catheterization, or prostate adenoma. Positive urine cultures were obtained for 48.1% and positive blood cultures for 17.6%. Escherichia coli was the bacterium isolated most often, and 27.7% of the cultures showed resistance to ciprofloxacin and amoxicillin-clavulanic acid. Twenty-nine patients (12%) revisited within 30 days. The only factors associated with revisiting were performance of a rectal examination (odds ratio [OR], 9.23; 95% CI, 1.12-75.82) and bacteremia (OR, 3.81; 95% CI, 1.31-11.04) (P<.05). Factors associated with revisiting for acute bacterial prostatitis were bacteremia and performance of a rectal examination.
Educational Administration and the Management of Knowledge: 1980 Revisited
ERIC Educational Resources Information Center
Bates, Richard
2013-01-01
This paper revisits the thesis of a 1980 paper that suggested a new approach to educational administration based upon the New Sociology of Education. In particular it updates answers to the six key questions asked by that paper: what counts as knowledge; how is what counts as knowledge organised; how is what counts as knowledge transmitted; how is…
The Importance of Being a Complement: CED Effects Revisited
ERIC Educational Resources Information Center
Jurka, Johannes
2010-01-01
This dissertation revisits subject island effects (Ross 1967, Chomsky 1973) cross-linguistically. Controlled acceptability judgment studies in German, English, Japanese and Serbian show that extraction out of specifiers is consistently degraded compared to extraction out of complements, indicating that the Condition on Extraction domains (CED,…
Magnetic Braking Revisited: Activities for the Undergraduate Laboratory
ERIC Educational Resources Information Center
Ireson, Gren; Twidle, John
2008-01-01
This paper revisits the demonstration of Lenz by dropping magnets down a non-magnetic tube. Recent publications are reviewed and ideas for undergraduate laboratory investigations are suggested. Finally, an example of matching theory to observation is presented. (Contains 4 tables, 5 figures and 3 footnotes.)
Girl Number 20 Revisited: Feminist Literacies in New Hard Times
ERIC Educational Resources Information Center
Gonick, Marnina
2007-01-01
This paper revisits the question of "voice" in the context of neo-liberal social and educational reform. "Voice" has been one of the key concepts of feminist and critical pedagogies in the theory and practice of producing social transformation. I argue in this paper, that the political effectiveness of this concept needs to be…
Revisiting the Role of Communication in Adolescent Intimate Partner Violence
ERIC Educational Resources Information Center
Messinger, Adam M.; Rickert, Vaughn I.; Fry, Deborah A.; Lessel, Harriet; Davidson, Leslie L.
2012-01-01
A growing literature suggests that communication strategies can promote or inhibit intimate partner violence (IPV). Research on communication is still needed on a group ripe for early IPV intervention: high school-aged adolescents. This article revisits our previous analyses of young female reproductive clinic patients (Messinger, Davidson, &…
Revisiting the Trust Effect in Urban Elementary Schools
ERIC Educational Resources Information Center
Adams, Curt M.; Forsyth, Patrick B.
2013-01-01
More than a decade after Goddard, Tschannen-Moran, and Hoy (2001) found that collective faculty trust in clients predicts student achievement in urban elementary schools, we sought to identify a plausible link for this relationship. Our purpose in revisiting the trust effect was twofold: (1) to test the main effect of collective faculty trust on…
Literary Origins of the Term "School Psychologist" Revisited
ERIC Educational Resources Information Center
Fagan, Thomas K.
2005-01-01
Previous research on the literary origins of the term "school psychologist" is revisited, and conclusions are revised in light of new evidence. It appears that the origin of the term in the American literature occurred as early as 1898 in an article by Hugo Munsterberg, predating the usage by Wilhelm Stern in 1911. The early references to the…
High Resolution Rapid Revisits Insar Monitoring of Surface Deformation
NASA Astrophysics Data System (ADS)
Singhroy, V.; Li, J.; Charbonneau, F.
2014-12-01
Monitoring surface deformation on strategic energy and transportation corridors requires high resolution spatial and temporal InSAR images for mitigation and safety purposes. High resolution air photos, lidar and other satellite images are very useful in areas where the landslides can be fatal. Recently, radar interferometry (InSAR) techniques using more rapid revisit images from several radar satellites are increasingly being used in active deformation monitoring. The Canadian RADARSAT Constellation (RCM) is a three-satellite mission that will provide rapid revisits of four days interferometric (InSAR) capabilities that will be very useful for complex deformation monitoring. For instance, the monitoring of surface deformation due to permafrost activity, complex rock slide motion and steam assisted oil extraction will benefit from this new rapid revisit capability. This paper provide examples of how the high resolution (1-3 m) rapid revisit InSAR capabilities will improve our monitoring of surface deformation and provide insights in understanding triggering mechanisms. We analysed over a hundred high resolution InSAR images over a two year period on three geologically different sites with various configurations of topography, geomorphology, and geology conditions. We show from our analysis that the more frequent InSAR acquisitions are providing more information in understanding the rates of movement and failure process of permafrost triggered retrogressive thaw flows; the complex motion of an asymmetrical wedge failure of an active rock slide and the identification of over pressure zones related to oil extraction using steam injection. Keywords: High resolution, InSAR, rapid revisits, triggering mechanisms, oil extraction.
Active Nuclear Import of Membrane Proteins Revisited
Laba, Justyna K.; Steen, Anton; Popken, Petra; Chernova, Alina; Poolman, Bert; Veenhoff, Liesbeth M.
2015-01-01
It is poorly understood how membrane proteins destined for the inner nuclear membrane pass the crowded environment of the Nuclear Pore Complex (NPC). For the Saccharomyces cerevisiae proteins Src1/Heh1 and Heh2, a transport mechanism was proposed where the transmembrane domains diffuse through the membrane while the extralumenal domains encoding a nuclear localization signal (NLS) and intrinsically disordered linker (L) are accompanied by transport factors and travel through the NPC. Here, we validate the proposed mechanism and explore and discuss alternative interpretations of the data. First, to disprove an interpretation where the membrane proteins become membrane embedded only after nuclear import, we present biochemical and localization data to support that the previously used, as well as newly designed reporter proteins are membrane-embedded irrespective of the presence of the sorting signals, the specific transmembrane domain (multipass or tail anchored), independent of GET, and also under conditions that the proteins are trapped in the NPC. Second, using the recently established size limit for passive diffusion of membrane proteins in yeast, and using an improved assay, we confirm active import of polytopic membrane protein with extralumenal soluble domains larger than those that can pass by diffusion on similar timescales. This reinforces that NLS-L dependent active transport is distinct from passive diffusion. Thirdly, we revisit the proposed route through the center of the NPC and conclude that the previously used trapping assay is, unfortunately, poorly suited to address the route through the NPC, and the route thus remains unresolved. Apart from the uncertainty about the route through the NPC, the data confirm active, transport factor dependent, nuclear transport of membrane-embedded mono- and polytopic membrane proteins in baker’s yeast. PMID:26473931
Machining as a mechanical property test revisited
NASA Astrophysics Data System (ADS)
Smith, David L.
There is much need for data on mechanical behavior of metals at high strains and strain rates. This need is dictated by modeling of processes like forming and machining, wherein the material in the deformation zone is subjected to severe deformation conditions atypical of conventional material property tests such as tension and torsion. Accurate flow stress data is an essential input for robust prediction of process outputs. Similar requirements arise from applications in high speed ballistic penetration and design of materials for armor. Since the deformation zone in cutting of metals is characterized by unique and extreme combinations of strain, strain rate and temperature, an opportunity exists for using plane-strain cutting as a mechanical property test for measuring flow properties of metals. The feasibility of using plane-strain cutting to measure flow properties of metals is revisited in the light of recent data showing controllability of the deformation conditions in chip formation by systematic variation of process input parameters. A method is outlined as to how the deformation conditions can be varied by changing the process parameters. The method is applied to cutting of commercially pure copper (FCC), iron (BCC) and zinc (HCP). Forces and chip geometries are measured, in conjunction with particle image velocimetry characterization of the deformation using high speed image sequences. The flow stresses are estimated from these measurements. The measured flow stress and its dependence on strain are shown to agree well with prior measurements of these parameters using conventional tests, and flow stress inferred from hardness characterization. The method is also demonstrated to be able to measure properties of metals that recrystallize at room temperature (zinc), wherein quasi-static tests predict much lower strength. Sources of variability and uncertainty in the application of this measurement technique are discussed. Future work in the context of further
The coordinate coherent states approach revisited
Miao, Yan-Gang Zhang, Shao-Jun
2013-02-15
We revisit the coordinate coherent states approach through two different quantization procedures in the quantum field theory on the noncommutative Minkowski plane. The first procedure, which is based on the normal commutation relation between an annihilation and creation operators, deduces that a point mass can be described by a Gaussian function instead of the usual Dirac delta function. However, we argue this specific quantization by adopting the canonical one (based on the canonical commutation relation between a field and its conjugate momentum) and show that a point mass should still be described by the Dirac delta function, which implies that the concept of point particles is still valid when we deal with the noncommutativity by following the coordinate coherent states approach. In order to investigate the dependence on quantization procedures, we apply the two quantization procedures to the Unruh effect and Hawking radiation and find that they give rise to significantly different results. Under the first quantization procedure, the Unruh temperature and Unruh spectrum are not deformed by noncommutativity, but the Hawking temperature is deformed by noncommutativity while the radiation specturm is untack. However, under the second quantization procedure, the Unruh temperature and Hawking temperature are untack but the both spectra are modified by an effective greybody (deformed) factor. - Highlights: Black-Right-Pointing-Pointer Suggest a canonical quantization in the coordinate coherent states approach. Black-Right-Pointing-Pointer Prove the validity of the concept of point particles. Black-Right-Pointing-Pointer Apply the canonical quantization to the Unruh effect and Hawking radiation. Black-Right-Pointing-Pointer Find no deformations in the Unruh temperature and Hawking temperature. Black-Right-Pointing-Pointer Provide the modified spectra of the Unruh effect and Hawking radiation.
Revisiting mu suppression in autism spectrum disorder.
Dumas, Guillaume; Soussignan, Robert; Hugueville, Laurent; Martinerie, Jacques; Nadel, Jacqueline
2014-10-17
Two aspects of the EEG literature lead us to revisit mu suppression in Autism Spectrum Disorder (ASD). First and despite the fact that the mu rhythm can be functionally segregated in two discrete sub-bands, 8-10 Hz and 10-12/13 Hz, mu-suppression in ASD has been analyzed as a homogeneous phenomenon covering the 8-13 Hz frequency. Second and although alpha-like activity is usually found across the entire scalp, ASD studies of action observation have focused on the central electrodes (C3/C4). The present study was aimed at testing on the whole brain the hypothesis of a functional dissociation of mu and alpha responses to the observation of human actions in ASD according to bandwidths. Electroencephalographic (EEG) mu and alpha responses to execution and observation of hand gestures were recorded on the whole scalp in high functioning subjects with ASD and typical subjects. When two bandwidths of the alpha-mu 8-13 Hz were distinguished, a different mu response to observation appeared for subjects with ASD in the upper sub-band over the sensorimotor cortex, whilst the lower sub-band responded similarly in the two groups. Source reconstructions demonstrated that this effect was related to a joint mu-suppression deficit over the occipito-parietal regions and an increase over the frontal regions. These findings suggest peculiarities in top-down response modulation in ASD and question the claim of a global dysfunction of the MNS in autism. This research also advocates for the use of finer grained analyses at both spatial and spectral levels for future directions in neurophysiological accounts of autism.
Primaquine revisited six decades after its discovery.
Vale, Nuno; Moreira, Rui; Gomes, Paula
2009-03-01
Primaquine was firstly synthesized in 1946 in the USA, and is the most representative member of the anti-malarial 8-aminoquinolines. Six decades have passed and primaquine is still the only transmission-blocking anti-malarial clinically available, displaying a marked activity against gametocytes of all species of human malaria, including multi-resistant Plasmodium falciparum strains. Primaquine is also effective against all exoerythrocytic forms of the parasite and is used in conjunction with other anti-malarials for the treatment of vivax and ovale malaria. However, primaquine is often associated with serious adverse effects, in consequence of its toxic metabolites. 5-Hydroxyprimaquine or 6-methoxy-8-aminoquinoline has been considered to be directly responsible for complications such as hemolytic anemia. Primaquine toxicity is aggravated in people deficient of 6-glucose phosphate dehydrogenase or glutathione synthetase. Adverse effects are further amplified by the fact that primaquine must be repeatedly administered at high doses, due to its limited oral bioavailability. Over the last two decades, Medicinal Chemists have battled against primaquine's disadvantages, while keeping or even improving its unequalled performance as an anti-malarial. The present text revisits primaquine and its properties on the occasion of its 60th anniversary and aims to give a general overview of what has been the path towards the development of effective and safe primaquine-based anti-malarials. Presently, aablaquine and tafenoquine the two most promising primaquine analogues are already in the final stages of clinical trials against Plasmodium vivax and P. falciparum. Both compounds are a new hope against malaria and other primaquine-sensitive illnesses, such as Pneumocystis Pneumonia or the Chagas disease.
Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters
NASA Technical Reports Server (NTRS)
Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, Maxim L.
2013-01-01
Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R(sub 500) as P(sub 1.4) approx. L(2.1+/-0.2) - 500). Our bigger and more homogenous sample confirms that the X-ray luminous (L(sub 500) > 5 × 10(exp 44) erg/s)) clusters branch into two populations-radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P(sub 1.4) scales with the cluster integrated SZ signal within R(sub 500), measured by Planck, as P(sub 1.4) approx. Y(2.05+/-0.28) - 500), in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y(sub 500) > 6×10(exp -5) Mpc(exp 2) clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.
Consensus Paper: Revisiting the Symptoms and Signs of Cerebellar Syndrome
Bodranghien, Florian; Bastian, Amy; Casali, Carlo; Hallett, Mark; Louis, Elan D.; Mariën, Peter; Nowak, Dennis A.; Schmahmann, Jeremy D.; Serrao, Mariano; Steiner, Katharina Marie; Strupp, Michael; Tilikete, Caroline; Timmann, Dagmar; van Dun, Kim
2017-01-01
The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann’s syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor
REVISITING SCALING RELATIONS FOR GIANT RADIO HALOS IN GALAXY CLUSTERS
Cassano, R.; Brunetti, G.; Venturi, T.; Kale, R.; Pratt, G. W.; Markevitch, M.
2013-11-10
Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R{sub 500} as P{sub 1.4}∼L{sup 2.1±0.2}{sub 500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L{sub 500} > 5 × 10{sup 44} erg s{sup –1}) clusters branch into two populations—radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P{sub 1.4} scales with the cluster integrated SZ signal within R{sub 500}, measured by Planck, as P{sub 1.4}∼Y{sup 2.05±0.28}{sub 500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that 'SZ-luminous' Y{sub 500} > 6 × 10{sup –5} Mpc{sup 2} clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle
Distant future of the Sun and Earth revisited
NASA Astrophysics Data System (ADS)
Schröder, K.-P.; Connon Smith, Robert
2008-05-01
We revisit the distant future of the Sun and the Solar system, based on stellar models computed with a thoroughly tested evolution code. For the solar giant stages, mass loss by the cool (but not dust-driven) wind is considered in detail. Using the new and well-calibrated mass-loss formula of Schröder & Cuntz, we find that the mass lost by the Sun as a red giant branch (RGB) giant (0.332Msolar, 7.59 Gyr from now) potentially gives planet Earth a significant orbital expansion, inversely proportional to the remaining solar mass. According to these solar evolution models, the closest encounter of planet Earth with the solar cool giant photosphere will occur during the tip-RGB phase. During this critical episode, for each time-step of the evolution model, we consider the loss of orbital angular momentum suffered by planet Earth from tidal interaction with the giant Sun, as well as dynamical drag in the lower chromosphere. As a result of this, we find that planet Earth will not be able to escape engulfment, despite the positive effect of solar mass loss. In order to survive the solar tip-RGB phase, any hypothetical planet would require a present-day minimum orbital radius of about 1.15 au. The latter result may help to estimate the chances of finding planets around white dwarfs. Furthermore, our solar evolution models with detailed mass-loss description predict that the resulting tip-AGB (asymptotic giant branch) giant will not reach its tip-RGB size. Compared to other solar evolution models, the main reason is the more significant amount of mass lost already in the RGB phase of the Sun. Hence, the tip-AGB luminosity will come short of driving a final, dust-driven superwind, and there will be no regular solar planetary nebula (PN). The tip-AGB is marked by a last thermal pulse, and the final mass loss of the giant may produce a circumstellar (CS) shell similar to, but rather smaller than, that of the peculiar PN IC 2149 with an estimated total CS shell mass of just a
Revisiting Scaling Relations for Giant Radio Halos in Galaxy Clusters
NASA Astrophysics Data System (ADS)
Cassano, R.; Ettori, S.; Brunetti, G.; Giacintucci, S.; Pratt, G. W.; Venturi, T.; Kale, R.; Dolag, K.; Markevitch, M.
2013-11-01
Many galaxy clusters host megaparsec-scale radio halos, generated by ultrarelativistic electrons in the magnetized intracluster medium. Correlations between the synchrotron power of radio halos and the thermal properties of the hosting clusters were established in the last decade, including the connection between the presence of a halo and cluster mergers. The X-ray luminosity and redshift-limited Extended GMRT Radio Halo Survey provides a rich and unique dataset for statistical studies of the halos. We uniformly analyze the radio and X-ray data for the GMRT cluster sample, and use the new Planck Sunyaev-Zel'dovich (SZ) catalog to revisit the correlations between the power of radio halos and the thermal properties of galaxy clusters. We find that the radio power at 1.4 GHz scales with the cluster X-ray (0.1-2.4 keV) luminosity computed within R 500 as P_{1.4} \\sim L^{2.1+/- 0.2}_{500}. Our bigger and more homogenous sample confirms that the X-ray luminous (L 500 > 5 × 1044 erg s-1) clusters branch into two populations—radio halos lie on the correlation, while clusters without radio halos have their radio upper limits well below that correlation. This bimodality remains if we excise cool cores from the X-ray luminosities. We also find that P 1.4 scales with the cluster integrated SZ signal within R 500, measured by Planck, as P_{1.4}\\sim Y^{2.05+/- 0.28}_{500}, in line with previous findings. However, contrary to previous studies that were limited by incompleteness and small sample size, we find that "SZ-luminous" Y 500 > 6 × 10-5 Mpc2 clusters show a bimodal behavior for the presence of radio halos, similar to that in the radio-X-ray diagram. Bimodality of both correlations can be traced to clusters dynamics, with radio halos found exclusively in merging clusters. These results confirm the key role of mergers for the origin of giant radio halos, suggesting that they trigger the relativistic particle acceleration.
Consensus Paper: Revisiting the Symptoms and Signs of Cerebellar Syndrome.
Bodranghien, Florian; Bastian, Amy; Casali, Carlo; Hallett, Mark; Louis, Elan D; Manto, Mario; Mariën, Peter; Nowak, Dennis A; Schmahmann, Jeremy D; Serrao, Mariano; Steiner, Katharina Marie; Strupp, Michael; Tilikete, Caroline; Timmann, Dagmar; van Dun, Kim
2016-06-01
The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann's syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor
Partial Dynamical Symmetry in Molecules
NASA Astrophysics Data System (ADS)
Ping, Jia-Lun; Chen, Jin-Quan
1997-03-01
It is shown that any Hamiltonian involving only one- and two-bond interactions for a molecule withnbonds and having a point groupPas its symmetry group may have theSn⊃Ppartial dynamical symmetry, i.e., the Hamiltonian can be solved analytically for a part of the states, called the unique states. For example, theXY6molecule has theS6⊃Ohpartial dynamical symmetry. The model of Iachello and Oss forncoupled anharmonic oscillators is revisited in terms of the partial dynamical symmetry. The energies are obtained analytically for the nine unique levels of theXY6molecule and the structures of the eigenstates are disclosed for the first time, while for non-unique states they are obtained by diagonalizing the Hamiltonian in theS6⊃Ohsymmetry adapted basis with greatly reduced dimension.
Conditional dynamics driving financial markets
NASA Astrophysics Data System (ADS)
Boguñá, M.; Masoliver, J.
2004-08-01
We revisit the problem of daily correlations in speculative prices and report empirical evidences on the existence of what we term a conditional or dual dynamics driving the evolution of financial assets. This dynamics is detected in several markets around the world and for different historical periods. In particular, we have analyzed the DJIA database from 1900 to 2002 as well as 65 companies trading in the LIFFE market of futures and 12 of the major European and American treasury bonds. In all cases, we find a twofold dynamics driving the financial evolution depending on whether the previous price went up or down. We conjecture that this effect is universal and intrinsic to all markets.
Revisiting the CALIOP Mineral Dust Optical Model
NASA Astrophysics Data System (ADS)
Winker, D. M.; Omar, A. H.; Liu, Z.
2013-12-01
The standard aerosol extinction retrieval applied to CALIOP observations relies heavily on a priori values of the lidar ratio (the ratio of extinction to 180-degree backscatter) for each of several aerosol types. The original CALIOP aerosol models were developed over 10 years ago, based on a combination of Aeronet retrievals, measurements from ground-based lidars, and theoretical scattering calculations. Both prior to and since the launch of CALIPSO, a number of studies using a variety of approaches have shown lidar ratios of around 40 sr for mineral dust. Ground-based Raman lidar measurements in Europe and Morroco, on the other hand, have consistently shown higher values of 50 to 60 sr. Reasons for this inconsistency have not been clearly identified, but may be due to geographical variability, mixtures of dust with fine-mode aerosol, multiple scattering effects on the CALIOP retrieval, other retrieval artifacts, or a combination of these. The simplest explanation for the difference between ground-based Raman and space-based retrievals of dust lidar ratio would be multiple scattering effects on the CALIOP signals. We have taken advantage of improvements in scattering codes and of recent field campaigns to re-evaluate the CALIOP optical model for mineral dust and to revisit multiple scattering effects. The original scattering phase functions used to predict multiple scattering were based on Dipole-Dipole Approximation (DDA) calculations of size-shape mixtures of irregular dust particles. At the time, the DDA calculations were limited to particles of less than 2 um diameter. Using current T-matrix codes, we are now able to compute scattering from particles as large as 10 um diameter. Applying T-matrix scattering calculations to spheroidal particles with size distributions consistent with those measured during the SAMUM campaign in Morroco, we find multiple scattering effects are similar to those predicted from the original DDA calculations. Thus multiple scattering
Alkaline phosphatase revisited: hydrolysis of alkyl phosphates.
O'Brien, Patrick J; Herschlag, Daniel
2002-03-05
Escherichia coli alkaline phosphatase (AP) is the prototypical two metal ion catalyst with two divalent zinc ions bound approximately 4 A apart in the active site. Studies spanning half a century have elucidated many structural and mechanistic features of this enzyme, rendering it an attractive model for investigating the potent catalytic power of bimetallic centers. Unfortunately, fundamental mechanistic features have been obscured by limitations with the standard assays. These assays generate concentrations of inorganic phosphate (P(i)) in excess of its inhibition constant (K(i) approximately 1 muM). This tight binding by P(i) has affected the majority of published kinetic constants. Furthermore, binding limits k(cat)/K(m) for reaction of p-nitrophenyl phosphate, the most commonly employed substrate. We describe a sensitive (32)P-based assay for hydrolysis of alkyl phosphates that avoids the complication of product inhibition. We have revisited basic mechanistic features of AP with these alkyl phosphate substrates. The results suggest that the chemical step for phosphorylation of the enzyme limits k(cat)/K(m). The pH-rate profile and additional results suggest that the serine nucleophile is active in its anionic form and has a pK(a) of < or = 5.5 in the free enzyme. An inactivating pK(a) of 8.0 is observed for binding of both substrates and inhibitors, and we suggest that this corresponds to ionization of a zinc-coordinated water molecule. Counter to previous suggestions, inorganic phosphate dianion appears to bind to the highly charged AP active site at least as strongly as the trianion. The dependence of k(cat)/K(m) on the pK(a) of the leaving group follows a Brønsted correlation with a slope of beta(lg) = -0.85 +/- 0.1, differing substantially from the previously reported value of -0.2 obtained from data with a less sensitive assay. This steep leaving group dependence is consistent with a largely dissociative transition state for AP-catalyzed hydrolysis of
Five years on: Revisiting GSN data quality
NASA Astrophysics Data System (ADS)
Gee, L. S.; Nettles, M.; Ekstrom, G.; Davis, J. P.; Ringler, A. T.; Storm, T. L.; Wilson, D.; Anderson, K. R.
2014-12-01
In 2010, the Lamont Waveform Quality Center (WQC) conducted an in-depth review of ten stations in the Global Seismographic Network (GSN). IU stations (CASY, DAV, KIP, KONO, WCI), IC stations (SSE, XAN), and II stations (ALE, DGAR, RPN) were analyzed using a scaling analysis based on data-synthetic comparisons, evaluation of noise levels, assessment of inter-sensor coherence, and polarization analysis. These reports (available from http://www.ldeo.columbia.edu/~ekstrom/Projects/WQC.html) highlighted a number of significant problems in GSN data quality, including the frequency-dependent loss of gain in the STS-1 seismometer (Ekström et al., 2006) that has been attributed to the presence of humidity in the electronics, cables, and connectors (Yuki and Ishihara, 2002; Hutt and Ringler, 2011). The reports from the WQC spurred a number of changes in the operation of the GSN, including the adoption of the policy of annual calibrations and the development of new tools and metrics to monitor, evaluate, and communicate data quality. In parallel, the USGS' Albuquerque Seismological Laboratory (ASL) and UCSD's Project IDA worked with the IRIS Consortium to upgrade GSN stations with new data acquisition systems, to refurbish the STS-1 seismometers with new electronics, and to expand the deployment of secondary broadband sensors. We revisit the 2010 reports, using the tools of the WQC as well as a number of newly developed tools such as the USGS' Data Quality Analyzer and IRIS' MUSTANG, and provide an update on GSN data quality. Our initial focus is on CASY and KIP, the first two stations reviewed by the WQC. Our goal is to evaluate progress in the last five years and assess our ability to quantify data quality as well as to identify potential problems that could compromise data quality in the future. Ekström, G., C. A. Dalton, and M. Nettles (2006). Observations of time-dependent errors in long-period instrument gain at global seismic stations. Seismological Research Letters
The Stern-Gerlach experiment revisited
NASA Astrophysics Data System (ADS)
Schmidt-Böcking, Horst; Schmidt, Lothar; Lüdde, Hans Jürgen; Trageser, Wolfgang; Templeton, Alan; Sauer, Tilman
2016-12-01
experimental example for such directional quantization in scattering processes is shown. Last not least, the early history of the "almost" discovery of the electron spin in the SGE is revisited.
14 CFR 1214.205 - Revisit and/or retrieval services.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 14 Aeronautics and Space 5 2012-01-01 2012-01-01 false Revisit and/or retrieval services. 1214.205 Section 1214.205 Aeronautics and Space NATIONAL AERONAUTICS AND SPACE ADMINISTRATION SPACE FLIGHT..., time on orbit, and other extra costs incurred by the revisit. ...
14 CFR 1214.205 - Revisit and/or retrieval services.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 5 2011-01-01 2010-01-01 true Revisit and/or retrieval services. 1214.205... Substantial Investment in the STS Program § 1214.205 Revisit and/or retrieval services. These services will be... dedicated price will be charged. If the user's retrieval requirement is such that it can be accomplished...
14 CFR 1214.205 - Revisit and/or retrieval services.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 5 2010-01-01 2010-01-01 false Revisit and/or retrieval services. 1214.205... Substantial Investment in the STS Program § 1214.205 Revisit and/or retrieval services. These services will be... dedicated price will be charged. If the user's retrieval requirement is such that it can be accomplished...
14 CFR § 1214.205 - Revisit and/or retrieval services.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 14 Aeronautics and Space 5 2014-01-01 2014-01-01 false Revisit and/or retrieval services. Â§ 1214... Have Made Substantial Investment in the STS Program § 1214.205 Revisit and/or retrieval services. These..., the full dedicated price will be charged. If the user's retrieval requirement is such that it can...
14 CFR 1214.205 - Revisit and/or retrieval services.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 14 Aeronautics and Space 5 2013-01-01 2013-01-01 false Revisit and/or retrieval services. 1214.205... Substantial Investment in the STS Program § 1214.205 Revisit and/or retrieval services. These services will be... dedicated price will be charged. If the user's retrieval requirement is such that it can be accomplished...
Unwarranted Return: A Response to McVee, Dunsmore, and Gavelek's (2005) "Schema Theory Revisited"
ERIC Educational Resources Information Center
Krasny, Karen A.; Sadoski, Mark; Paivio, Allan
2007-01-01
This article presents the authors' response to McVee, Dunsmore, and Gavelek's "Schema Theory Revisited." In "Schema Theory Revisited," McVee, Dunsmore, and Gavelek (2005) proposed a rearticulation of schema theory intended to encompass the ideas that schemata and other cognitive processes are embodied, that knowledge is situated in the transaction…
Enthalpy-Entropy Compensation (EEC) Effect: A Revisit.
Pan, Animesh; Biswas, Tapas; Rakshit, Animesh K; Moulik, Satya P
2015-12-31
A short account of the developments and perspectives of IKR (iso-kinetic relation) and EEC (enthalpy (H) - entropy (S) compensation) has been presented. The IKR and EEC are known to be extra thermodynamic or empirical correlations though linear H-S correlation can be thermodynamically deduced. Attempt has also been made to explain the phenomena in terms of statistical thermodynamics. In this study, we have briefly revisited the fundamentals of both IKR and EEC from kinetic and thermodynamic grounds. A detailed revisit of the EEC phenomenon on varied kinetic and equilibrium processes has been also presented. Possible correlations among the free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes of different similar and nonsimilar chemical processes under varied conditions have been discussed with possible future projections.
Hospital revisit rate after a diagnosis of conversion disorder.
Merkler, Alexander E; Parikh, Neal S; Chaudhry, Simriti; Chait, Alanna; Allen, Nicole C; Navi, Babak B; Kamel, Hooman
2016-04-01
To estimate the hospital revisit rate of patients diagnosed with conversion disorder (CD). Using administrative data, we identified all patients discharged from California, Florida and New York emergency departments (EDs) and acute care hospitals between 2005 and 2011 with a primary discharge diagnosis of CD. Patients discharged with a primary diagnosis of seizure or transient global amnesia (TGA) served as control groups. Our primary outcome was the rate of repeat ED visits and hospital admissions after initial presentation. Poisson regression was used to compare rates between diagnosis groups while adjusting for demographic characteristics. We identified 7946 patients discharged with a primary diagnosis of CD. During a mean follow-up of 3.0 (±1.6) years, patients with CD had a median of three (IQR, 1-9) ED or inpatient revisits, compared with 0 (IQR, 0-2) in patients with TGA and 3 (IQR, 1-7) in those with seizures. Revisit rates were 18.25 (95% CI, 18.10 to 18.40) visits per 100 patients per month in those with CD, 3.90 (95% CI, 3.84 to 3.95) in those with TGA and 17.78 (95% CI, 17.75 to 17.81) in those with seizures. As compared to CD, the incidence rate ratio for repeat ED visits or hospitalisations was 0.89 (95% CI, 0.86 to 0.93) for seizure disorder and 0.32 (95% CI 0.31 to 0.34) for TGA. CD is associated with a substantial hospital revisit rate. Our findings suggest that CD is not an acute, time-limited response to stress, but rather that CD is a manifestation of a broader pattern of chronic neuropsychiatric disease. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/
Discussion of "Computational Electrocardiography: Revisiting Holter ECG Monitoring".
Baumgartner, Christian; Caiani, Enrico G; Dickhaus, Hartmut; Kulikowski, Casimir A; Schiecke, Karin; van Bemmel, Jan H; Witte, Herbert
2016-08-05
This article is part of a For-Discussion-Section of Methods of Information in Medicine about the paper "Computational Electrocardiography: Revisiting Holter ECG Monitoring" written by Thomas M. Deserno and Nikolaus Marx. It is introduced by an editorial. This article contains the combined commentaries invited to independently comment on the paper of Deserno and Marx. In subsequent issues the discussion can continue through letters to the editor.
Non linear evolution: revisiting the solution in the saturation region
NASA Astrophysics Data System (ADS)
Contreras, Carlos; Levin, Eugene; Meneses, Rodrigo
2014-10-01
In this paper we revisit the problem of the solution to Balitsky-Kovchegov equation deeply in the saturation domain. We find that solution has the form given in ref. [23] but it depends on variable and the value of Const is calculated in this paper. We propose the solution for full BFKL kernel at large in the entire kinematic region that satisfies the McLerran-Venugopalan-type [3-7] initial condition.
Mesenchymal stem cells: revisiting history, concepts, and assays.
Bianco, Paolo; Robey, Pamela Gehron; Simmons, Paul J
2008-04-10
The concept of mesenchymal stem cells has gained wide popularity. Despite the rapid growth of the field, uncertainties remain with respect to the defining characteristics of these cells, including their potency and self-renewal. These uncertainties are reflected in a growing tendency to question the very use of the term. This commentary revisits the experimental origin of the concept of the population(s) referred to as mesenchymal stem cells and the experimental framework required to assess their stemness and function.
Indoor air and human health revisited: A recent IAQ symposium
Gammage, R.B.
1994-12-31
Indoor Air and Human Health Revisited was a speciality symposium examining the scientific underpinnings of sensory and sensitivity effects, allergy and respiratory disease, neurotoxicity and cancer. An organizing committee selected four persons to chain the sessions and invite experts to give state-of-the-art presentations that will be published as a book. A summary of the presentations is made and some critical issues identified.
Revisiting the velocity-dependent one-scale model for monopoles
NASA Astrophysics Data System (ADS)
Sousa, L.; Avelino, P. P.
2017-07-01
We revisit the physical properties of global and local monopoles and discuss their implications in the dynamics of monopole networks. In particular, we review the velocity-dependent one-scale (VOS) model for global and local monopoles and propose physically motivated changes to its equations. We suggest a new form for the acceleration term of the evolution equation of the root-mean-squared velocity and show that, with this change, the VOS model is able to describe the results of radiation and matter era numerical simulations of global monopole networks with a single value of the acceleration parameter k , thus resolving the tension previously found in the literature. We also show that the fact that the energy of global monopoles is not localized within their cores affects their dynamics and thus the Hubble damping terms in the VOS equations. We study the ultrarelativistic linear scaling regime predicted by the VOS equations and demonstrate that it cannot be attained either on radiation or matter eras and thus cannot arise from the cosmological evolution of a global monopole network. We also briefly discuss the implications of our findings for the VOS model for local monopoles.
Cameron, Danielle B; Graham, Dionne A; Milliren, Carly E; Serres, Stephanie; Glass, Charity C; Goldin, Adam B; Rangel, Shawn J
2017-06-01
The purpose of this study was to compare the relatedness of revisits to the index surgical encounter across different pediatric surgical procedures and to explore whether all-cause revisit rates are an accurate surrogate measure for related revisits in this cohort of children. We reviewed all-cause revisits occurring within ninety days of the thirty most commonly performed pediatric surgical procedures at 44 children's hospitals between 1/1/2012 and 3/31/2015. For each condition, a team of four surgeons reviewed revisit diagnoses and reached consensus around relatedness to the index surgical encounter. Chi-squared tests were used to test for variation in all-cause and related revisits among procedures. Spearman's correlation coefficient was used to measure the association between rankings of procedures by their all-cause and related revisit rates. 144,535 index encounters were analyzed with an overall revisit rate of 15.0% (21,732). Significant variation was found in both the rates of all-cause revisits among procedures (ranges: 7.6-68.4%, p<0.0001), and in the relative proportions of revisits related the index surgical encounter (range: 0% to 77%, p<0.0001). Poor correlation was found between procedure rankings based on all-cause revisit rates and revisit rates related to the index admission (r=0.33, p=0.07). The relative proportion of revisits related to the index encounter varies significantly across pediatric surgical conditions, and poor correlation exists at the procedure-level between all-cause and related revisits rates. IV. Copyright © 2017 Elsevier Inc. All rights reserved.
Revisiting the revisit: added evidence for a social chemosignal in human emotional tears.
Sobel, Noam
2017-01-01
In a study by Gelstein et al., we found that human emotional tears act as a social chemosignal. In the first of three different experiments in that study we observed that sniffing women's emotional tears reduced the sexual attractiveness attributed by men to pictures of women's faces. In a study partly titled "Chemosignaling effects of human tears revisited", Gračanin et al. claim failed replication of this effect in a series of experiments, one they described as "exactly the same procedure" as Gelstein. Given that Gračanin et al. refused our extended offer to jointly replicate the experiment at our expense, we can merely comment on their effort. We find that Gračanin, who are not a chemosignaling laboratory, used methodology that falls short of standards typically applied in chemosignaling research. Thus, their experiments were profoundly different from Gelstein. Finally, we found that in reanalysing their raw data we could in fact replicate the effect from Gelstein. Thus, we conclude that the failed replication in Gračanin is neither a replication nor failed.
Emergency Department Revisits for Patients with Kidney Stones in California
Scales, Charles D.; Lin, Li; Saigal, Christopher S.; Bennett, Carol J.; Ponce, Ninez A.; Mangione, Carol M.; Litwin, Mark S.
2015-01-01
Objectives Kidney stones affect nearly one in 11 persons in the United States, and among those experiencing symptoms, emergency care is common. In this population, little is known about the incidence of and factors associated with repeat emergency department (ED) visits. The objective was to identify associations between potentially mutable factors and the risk of an ED revisit for patients with kidney stones in a large, all-payer cohort. Methods This was a retrospective cohort study of all patients in California initially treated and released from EDs for kidney stones between February 2008 and November 2009. A multivariable regression model was created to identify associations between patient-level characteristics, area health care resources, processes of care, and the risk of repeat ED visits. The primary outcome was a second ED visit within 30 days of the initial discharge from emergent care. Results Among 128,564 patients discharged from emergent care, 13,684 (11%) had at least one additional emergent visit for treatment of their kidney stone. In these patients, nearly one in three required hospitalization or an urgent temporizing procedure at the second visit. On multivariable analysis, the risk of an ED revisit was associated with insurance status (e.g., Medicaid vs. private insurance, OR 1.52, 95% CI = 1.43 to 1.61; P < 0.001). Greater access to urologic care was associated with lower odds of an ED revisit (highest quartile OR 0.88, 95% CI = 0.80 to 0.97; P < 0.01, vs. lowest quartile). In exploratory models, performance of a complete blood count was associated with a decreased odds of revisit (OR = 0.86, 95% CI = 0.75 to 0.97; P = 0.02). Conclusions Repeat high-acuity care affects one in nine patients discharged from initial emergent evaluations for kidney stones. Access to urologic care and processes of care are associated with lower risk of repeat emergent encounters. Efforts are indicated to identify preventable causes of ED revisits for kidney stone
Summary and Findings of the ARL Dynamic Failure Forum
2016-09-29
Johnson and Cook 1985). Originally introduced to the computational modeling community in a 1985 publication, the Johnson-Cook damage model (Johnson... community should revisit more complex models Approved for public release; distribution is unlimited. 12 that were viewed as too complex or...that will yield improvements in researchers’ ability to understand and model dynamic failure. The discussion revolved around 2 common scenarios where
Behavioral Objectives and Standards Movement Revisited
ERIC Educational Resources Information Center
Shakouri, Nima; Mirzaee, Sepideh
2014-01-01
The present paper sparks a complementary argument that the development of standards movement must not be at the expense of sacrificing the achievement of behavioral objectives. Furthermore, due to the systemic and dynamic nature of standards, standards need to be revised off and on. Besides, the present writers taking a more or less relativist…
Liberal Arts Catch-Up Revisited
ERIC Educational Resources Information Center
Goyder, John
2014-01-01
This paper replicates the work of Giles and Drewes from the 1990s. They showed a catch-up effect whereby graduates of liberal arts undergraduate programs, although at an early-career disadvantage compared with graduates of applied programs, had higher incomes by mid-career. Working with the Panel 5 Survey of Labour and Income Dynamics (2005-2010),…
Revisiting a Problem of Two Freezers
ERIC Educational Resources Information Center
Easton, Don
2014-01-01
The January 2013 Physics Challenge for Teachers and Students has some features that are surprising and worth a closer look. The problem concerns a Carnot-cycle refrigeration unit operating inside a tent. It achieves dynamic equilibrium with a freezer ("cold") compartment temperature of T[subscript C] = 13°C, tent temperature of…
Charitable Giving by Married Couples Revisited
ERIC Educational Resources Information Center
Yoruk, Baris K.
2010-01-01
This paper investigates the effect of gender differences and household bargaining on charitable giving. I replicate the study of Andreoni, Brown, and Rischall (2003) using a different data set--the recently available Panel Study of Income Dynamics (PSID) supplement on charitable giving--and test the sensitivity of their results to inclusion of…
The effect of time ordering revisited
Rosato, J.; Boland, D.; Capes, H.; Marandet, Y.; Stamm, R.
2008-10-22
The effects of time ordering on line shapes are investigated for the dynamic ionic broadening of the Lyman alpha line in hydrogen plasmas. The difference between calculations with and without time ordering is calculated for an electric field created by a single particle, and for a thermal average over plasma configurations with moderate temperature and density.
Topological entropy of catalytic sets: Hypercycles revisited
NASA Astrophysics Data System (ADS)
Sardanyés, Josep; Duarte, Jorge; Januário, Cristina; Martins, Nuno
2012-02-01
The dynamics of catalytic networks have been widely studied over the last decades because of their implications in several fields like prebiotic evolution, virology, neural networks, immunology or ecology. One of the most studied mathematical bodies for catalytic networks was initially formulated in the context of prebiotic evolution, by means of the hypercycle theory. The hypercycle is a set of self-replicating species able to catalyze other replicator species within a cyclic architecture. Hypercyclic organization might arise from a quasispecies as a way to increase the informational containt surpassing the so-called error threshold. The catalytic coupling between replicators makes all the species to behave like a single and coherent evolutionary multimolecular unit. The inherent nonlinearities of catalytic interactions are responsible for the emergence of several types of dynamics, among them, chaos. In this article we begin with a brief review of the hypercycle theory focusing on its evolutionary implications as well as on different dynamics associated to different types of small catalytic networks. Then we study the properties of chaotic hypercycles with error-prone replication with symbolic dynamics theory, characterizing, by means of the theory of topological Markov chains, the topological entropy and the periods of the orbits of unimodal-like iterated maps obtained from the strange attractor. We will focus our study on some key parameters responsible for the structure of the catalytic network: mutation rates, autocatalytic and cross-catalytic interactions.
Revisiting the Gulf Coast after Katrina
ERIC Educational Resources Information Center
Principal, 2009
2009-01-01
In August 2005, the world witnessed one of the most destructive natural disasters on America's mainland. Hurricane Katrina, followed a month later by Hurricane Rita, brought more than broken levees, flooded streets and homes, and destroyed businesses. It caused changes in the dynamics and the demographic and cultural makeup of the region. One of…
Revisiting the Gulf Coast after Katrina
ERIC Educational Resources Information Center
Principal, 2009
2009-01-01
In August 2005, the world witnessed one of the most destructive natural disasters on America's mainland. Hurricane Katrina, followed a month later by Hurricane Rita, brought more than broken levees, flooded streets and homes, and destroyed businesses. It caused changes in the dynamics and the demographic and cultural makeup of the region. One of…
Revisiting a Problem of Two Freezers
ERIC Educational Resources Information Center
Easton, Don
2014-01-01
The January 2013 Physics Challenge for Teachers and Students has some features that are surprising and worth a closer look. The problem concerns a Carnot-cycle refrigeration unit operating inside a tent. It achieves dynamic equilibrium with a freezer ("cold") compartment temperature of T[subscript C] = 13°C, tent temperature of…
Parameter Estimation in Epidemiology: from Simple to Complex Dynamics
NASA Astrophysics Data System (ADS)
Aguiar, Maíra; Ballesteros, Sebastién; Boto, João Pedro; Kooi, Bob W.; Mateus, Luís; Stollenwerk, Nico
2011-09-01
We revisit the parameter estimation framework for population biological dynamical systems, and apply it to calibrate various models in epidemiology with empirical time series, namely influenza and dengue fever. When it comes to more complex models like multi-strain dynamics to describe the virus-host interaction in dengue fever, even most recently developed parameter estimation techniques, like maximum likelihood iterated filtering, come to their computational limits. However, the first results of parameter estimation with data on dengue fever from Thailand indicate a subtle interplay between stochasticity and deterministic skeleton. The deterministic system on its own already displays complex dynamics up to deterministic chaos and coexistence of multiple attractors.
Risk of hospitalisation after early-revisit in the emergency department.
Cozzi, Giorgio; Ghirardo, Sergio; Fiorese, Ilaria; Proietti, Ilaria; Monasta, Lorenzo; Minute, Marta; Barbi, Egidio; Calligaris, Lorenzo
2017-09-01
Early-revisits are frequent in the paediatric emergency department (ED) setting, but few data are available about early-revisited patients. The aim of this study was to investigate the hospitalisation rate of a population of early-revisited patients and to detect if an early-revisited patient was at risk of a more severe disease. Between June 2014 and January 2015, we conducted a retrospective cohort study, considering all patients presented to the ED of a tertiary level children's hospital in Italy. We selected all patients who were revisited within 72 h from the initial visit (study cohort), while all other patients accessed in the same period were considered the control cohort. The two cohorts were compared for age, gender, triage category, hospitalisation rate, diagnosis at admission and hospital length of stay. In the study period, we reviewed 10 750 visits, of which 430 (4%) were unplanned revisits for the same chief complaint within 72 h from the initial visit. Hospitalisation rate of early-revisited patients was significantly higher compared to control patients (8.4 vs. 2.9%). Hospitalisation rate increases in parallel with the number of revisits, but in many cases, it was not directly related to a worst triage category, neither to a longer hospital length of stay. Early revisited patients in the ED had a significantly higher risk of hospitalisation, but this risk was only partially related to their clinical conditions. © 2017 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).
Circular revisit orbits design for responsive mission over a single target
NASA Astrophysics Data System (ADS)
Li, Taibo; Xiang, Junhua; Wang, Zhaokui; Zhang, Yulin
2016-10-01
The responsive orbits play a key role in addressing the mission of Operationally Responsive Space (ORS) because of their capabilities. These capabilities are usually focused on supporting specific targets as opposed to providing global coverage. One subtype of responsive orbits is repeat coverage orbit which is nearly circular in most remote sensing applications. This paper deals with a special kind of repeating ground track orbit, referred to as circular revisit orbit. Different from traditional repeat coverage orbits, a satellite on circular revisit orbit can visit a target site at both the ascending and descending stages in one revisit cycle. This typology of trajectory allows a halving of the traditional revisit time and does a favor to get useful information for responsive applications. However the previous reported numerical methods in some references often cost lots of computation or fail to obtain such orbits. To overcome this difficulty, an analytical method to determine the existence conditions of the solutions to revisit orbits is presented in this paper. To this end, the mathematical model of circular revisit orbit is established under the central gravity model and the J2 perturbation. A constraint function of the circular revisit orbit is introduced, and the monotonicity of that function has been studied. The existent conditions and the number of such orbits are naturally worked out. Taking the launch cost into consideration, optimal design model of circular revisit orbit is established to achieve a best orbit which visits a target twice a day in the morning and in the afternoon respectively for several days. The result shows that it is effective to apply circular revisit orbits in responsive application such as reconnoiter of natural disaster.
A practical method of predicting client revisit intention in a hospital setting.
Lee, Kyun Jick
2005-01-01
Data mining (DM) models are an alternative to traditional statistical methods for examining whether higher customer satisfaction leads to higher revisit intention. This study used a total of 906 outpatients' satisfaction data collected from a nationwide survey interviews conducted by professional interviewers on a face-to-face basis in South Korea, 1998. Analyses showed that the relationship between overall satisfaction with hospital services and outpatients' revisit intention, along with word-of-mouth recommendation as intermediate variables, developed into a nonlinear relationship. The five strongest predictors of revisit intention were overall satisfaction, intention to recommend to others, awareness of hospital promotion, satisfaction with physician's kindness, and satisfaction with treatment level.
High-level Behavior Representation Languages Revisited
2016-06-07
efficiency of the development of user models. In Proceedings of the IEEE System Information and Engineering Design Symposium. Ritter, F. E., Morgan, G. P...languages agimap agimap (Urbas & Leuchter, 2005) is a tool chain approach that makes cognitive modelling of operator performance in dynamic systems more...cognitive architecture / physical world communication layer, (d) a system state to internal GUI representation mapper, and (e) an extendable library of part
Nonlinear time-series analysis revisited.
Bradley, Elizabeth; Kantz, Holger
2015-09-01
In 1980 and 1981, two pioneering papers laid the foundation for what became known as nonlinear time-series analysis: the analysis of observed data-typically univariate-via dynamical systems theory. Based on the concept of state-space reconstruction, this set of methods allows us to compute characteristic quantities such as Lyapunov exponents and fractal dimensions, to predict the future course of the time series, and even to reconstruct the equations of motion in some cases. In practice, however, there are a number of issues that restrict the power of this approach: whether the signal accurately and thoroughly samples the dynamics, for instance, and whether it contains noise. Moreover, the numerical algorithms that we use to instantiate these ideas are not perfect; they involve approximations, scale parameters, and finite-precision arithmetic, among other things. Even so, nonlinear time-series analysis has been used to great advantage on thousands of real and synthetic data sets from a wide variety of systems ranging from roulette wheels to lasers to the human heart. Even in cases where the data do not meet the mathematical or algorithmic requirements to assure full topological conjugacy, the results of nonlinear time-series analysis can be helpful in understanding, characterizing, and predicting dynamical systems.
Nonlinear time-series analysis revisited
NASA Astrophysics Data System (ADS)
Bradley, Elizabeth; Kantz, Holger
2015-09-01
In 1980 and 1981, two pioneering papers laid the foundation for what became known as nonlinear time-series analysis: the analysis of observed data—typically univariate—via dynamical systems theory. Based on the concept of state-space reconstruction, this set of methods allows us to compute characteristic quantities such as Lyapunov exponents and fractal dimensions, to predict the future course of the time series, and even to reconstruct the equations of motion in some cases. In practice, however, there are a number of issues that restrict the power of this approach: whether the signal accurately and thoroughly samples the dynamics, for instance, and whether it contains noise. Moreover, the numerical algorithms that we use to instantiate these ideas are not perfect; they involve approximations, scale parameters, and finite-precision arithmetic, among other things. Even so, nonlinear time-series analysis has been used to great advantage on thousands of real and synthetic data sets from a wide variety of systems ranging from roulette wheels to lasers to the human heart. Even in cases where the data do not meet the mathematical or algorithmic requirements to assure full topological conjugacy, the results of nonlinear time-series analysis can be helpful in understanding, characterizing, and predicting dynamical systems.
NASA Astrophysics Data System (ADS)
Tian, Yong; Ko, Chung-Ming
2015-08-01
Planetary nebulae (PNe) at large distances from the centre of a galaxy provide us a tool to study its dynamics there. Romanowsky et al. (2003) reported the dynamics of three luminous elliptical galaxies up to 6 effective radii, and all of them can be explained by Newtonian dynamics without dark matter. Milgrom & Sanders (2003) deem that the result can be understood in the framework of MOND (MOdified Newtonian dynamics). We revisit this problem as more measurements are available in the past decade. In this contribution, we present our result on 7 elliptical galaxies with PNe data up to 6-8 effective radii and also stellar data from SAURON. We conclude that MOND can well explain the dynamics of all these galaxies.
Dynamics of elliptical galaxies with planetary nebulae in modified Newtonian dynamics
NASA Astrophysics Data System (ADS)
Tian, Yong; Ko, Chung-Ming
2016-10-01
The dynamics of an elliptical galaxy within a couple of effective radii can be probed effectively by stars. However, at larger distances planetary nebulae (PNe) replace stars as the tracer of the dynamics. Making use of the motion of PNe, Romanowsky et al. measured the dynamics of three luminous elliptical galaxies (NGC821, NGC3379 and NGC4494) at large distances from the galactic centre. They found that little dark matter is needed up to six effective radii. Milgrom & Sanders showed that this result can be understood in the framework of MOdified Newtonian Dynamics (MOND). As more data are available in the past decade, we revisit this problem. We combine PNe data (up to six to eight effective radii) and stellar data from SAURON of seven elliptical galaxies, including those three galaxies in Romanowsky et al. with updated data and four other galaxies which have not been analysed before. We conclude that the dynamics of these galaxies can be well explained by MOND.
REVISITING THE FIRST GALAXIES: THE EFFECTS OF POPULATION III STARS ON THEIR HOST GALAXIES
Muratov, Alexander L.; Gnedin, Oleg Y.; Zemp, Marcel; Gnedin, Nickolay Y.
2013-08-01
We revisit the formation and evolution of the first galaxies using new hydrodynamic cosmological simulations with the adaptive refinement tree code. Our simulations feature a recently developed model for H{sub 2} formation and dissociation, and a star formation recipe that is based on molecular rather than atomic gas. Here, we develop and implement a recipe for the formation of metal-free Population III (Pop III) stars in galaxy-scale simulations that resolve primordial clouds with sufficiently high density. We base our recipe on the results of prior zoom-in simulations that resolved the protostellar collapse in pre-galactic objects. We find the epoch during which Pop III stars dominated the energy and metal budget of the first galaxies to be short-lived. Galaxies that host Pop III stars do not retain dynamical signatures of their thermal and radiative feedback for more than 10{sup 8} years after the lives of the stars end in pair-instability supernovae, even when we consider the maximum reasonable efficiency of the feedback. Though metals ejected by the supernovae can travel well beyond the virial radius of the host galaxy, they typically begin to fall back quickly, and do not enrich a large fraction of the intergalactic medium. Galaxies with a total mass in excess of 3 Multiplication-Sign 10{sup 6} M{sub Sun} re-accrete most of their baryons and transition to metal-enriched Pop II star formation.
Mo, Qifeng; Li, Zhi'an; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming
2016-01-22
Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China.
Revisiting with Chandra the X-ray Scaling Relations of Early-Type Galaxies
NASA Astrophysics Data System (ADS)
Kim, Dong-Woo
2011-09-01
The scaling relations of early-type galaxies are key observables which can be directly compared with theoretical models to better understand the evolution of the galaxies and their hot ISM. We revisit the scaling relations, using high spatial resolution Chandra observations of optical and X-ray selected early type galaxies, including a large fraction of gas-poor galaxies. We have accurately measured the X-ray properties of hot ISM, after carefully removing other individual emission components. In particular, we find a positive correlation between the luminosity and temperature of the hot ISM, significantly tighter than reported by earlier studies. This relation is particularly well defined in the subsample with σ>240 km/s, where it may be related to the analogous correlation found in cD galaxies and groups/clusters. However, the gas-poor galaxies with the shallowest potentials (σ < 200 km/s) also follow this relation, contrary to the expected anti-correlation in a simple outflow/wind scenario. Galaxies with intermediate values of σ instead tend to have the same kT, while Lx(gas) spans a factor of 20. We address the implications of our results in terms of theoretical predictions of the dynamical states of hot halos.
NASA Astrophysics Data System (ADS)
Mo, Qifeng; Li, Zhi'An; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming
2016-01-01
Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China.
Reaction Hg+I/sub 2/. -->. HgI+I revisited
Oprysko, M.M.; Aoiz, F.J.; McMahan, M.A.; Bernstein, R.B.
1983-03-15
The crossed molecular beam study of Mayer et al. (1977) on the subject reaction is revisited. The present work employs a different beam configuration and thus kinematic framework, and a larger range of relative translational energies is covered (i.e., from the threshold of 1.15 to 3.75 eV). Measurements include in-plane angular distributions and relative values of integral reaction cross sections as a function of energy. At low energies, the results of the present experiments are in good agreement with the previous work. Starting at the threshold, the reaction proceeds through the formation of a long-lived complex, presumed to be IHgI. At higher energies, the c.m. angular distributions show a gradual increase of the so-called ''backscattered component.'' This is interpreted as the opening of a new reaction path: the direct-mode abstraction of I via collinear approach of the Hg atom to the I/sub 2/ molecule. The overall dynamics of this reaction are interpreted in the context of the semiempirical potential energy surfaces and electronic state correlation diagrams of Muckerman et al. (1977). From the present experimental results, the height of the barrier in the exit channel for the collinear configuration can be estimated to be in the range 2.0--2.3 eV. The excitation function rises from threshold and reaches a maximum at collision energy of 2.6 eV, falling off monotonically thereafter.
Mo, Qifeng; Li, Zhi’an; Zhu, Weixing; Zou, Bi; Li, Yingwen; Yu, Shiqin; Ding, Yongzhen; Chen, Yao; Li, Xiaobo; Wang, Faming
2016-01-01
Nitrogen availability and tree species selection play important roles in reforestation. However, long-term field studies on the effects and mechanisms of tree species composition on N transformation are very limited. Eight years after tree seedlings were planted in a field experiment, we revisited the site and tested how tree species composition affects the dynamics of N mineralization and nitrification. Both tree species composition and season significantly influenced the soil dissolved organic carbon (DOC) and nitrogen (DON). N-fixing Acacia crassicarpa monoculture had the highest DON, and 10-mixed species plantation had the highest DOC. The lowest DOC and DON concentrations were both observed in Eucalyptus urophylla monoculture. The tree species composition also significantly affected net N mineralization rates. The highest rate of net N mineralization was found in A. crassicarpa monoculture, which was over twice than that in Castanopsis hystrix monoculture. The annual net N mineralization rates of 10-mixed and 30-mixed plantations were similar as that of N-fixing monoculture. Since mixed plantations have good performance in increasing soil DOC, DON, N mineralization and plant biodiversity, we recommend that mixed species plantations should be used as a sustainable approach for the restoration of degraded land in southern China. PMID:26794649
Revisiting the Lissajous figure as a tool to study bistable perception.
Weilnhammer, V A; Ludwig, K; Sterzer, P; Hesselmann, G
2014-05-01
During bistable vision perception spontaneously "switches" between two mutually exclusive percepts despite constant sensory input. The endogenous nature of these perceptual transitions has motivated extensive research aimed at the underlying mechanisms, since spontaneous perceptual transitions of bistable stimuli should in principle allow for a dissociation of processes related to sensory stimulation from those related to conscious perception. However, transitions from one conscious percept to another are often not instantaneous, and participants usually report a considerable amount of mixed or unclear percepts. This feature of bistable vision makes it difficult to isolate transition-related visual processes. Here, we revisited an ambiguous depth-from-motion stimulus which was first introduced to experimental psychology more than 80 years ago. This rotating Lissajous figure might prove useful in complementing other bistable stimuli, since its perceptual transitions only occur at critical stimulus configurations and are virtually instantaneous, thus facilitating the construction of a perceptually equivalent replay condition. We found that three parameters of the Lissajous figure - complexity, line width, and rotational speed - differentially modulated its perceptual dominance durations and transition probabilities, thus providing experimenters with a versatile tool to study the perceptual dynamics of bistable vision. Copyright © 2014 Elsevier B.V. All rights reserved.
"Perception of the speech code" revisited: Speech is alphabetic after all.
Fowler, Carol A; Shankweiler, Donald; Studdert-Kennedy, Michael
2016-03-01
We revisit an article, "Perception of the Speech Code" (PSC), published in this journal 50 years ago (Liberman, Cooper, Shankweiler, & Studdert-Kennedy, 1967) and address one of its legacies concerning the status of phonetic segments, which persists in theories of speech today. In the perspective of PSC, segments both exist (in language as known) and do not exist (in articulation or the acoustic speech signal). Findings interpreted as showing that speech is not a sound alphabet, but, rather, phonemes are encoded in the signal, coupled with findings that listeners perceive articulation, led to the motor theory of speech perception, a highly controversial legacy of PSC. However, a second legacy, the paradoxical perspective on segments has been mostly unquestioned. We remove the paradox by offering an alternative supported by converging evidence that segments exist in language both as known and as used. We support the existence of segments in both language knowledge and in production by showing that phonetic segments are articulatory and dynamic and that coarticulation does not eliminate them. We show that segments leave an acoustic signature that listeners can track. This suggests that speech is well-adapted to public communication in facilitating, not creating a barrier to, exchange of language forms.
Snow-(N)AO relationship revisited over the whole twentieth century
NASA Astrophysics Data System (ADS)
Douville, H.; Peings, Y.; Saint-Martin, D.
2017-01-01
Several studies suggest that the Siberian snow cover in fall is a source of predictability of the Arctic Oscillation (AO) in winter. Although a plausible dynamical mechanism was proposed, the robustness of this relationship was recently challenged. Here we use two atmospheric reanalyses to revisit the snow-AO relationship and its modulation across the whole twentieth century. While our results support a stratospheric pathway mechanism, they show that the snow-AO relationship has only emerged in the 1970s and should be rather analyzed as a contrasted multidecadal behavior of the North Atlantic Oscillation (NAO) and Pacific North America pattern. They confirm that the quasi-biennial oscillation is a plausible candidate for the modulation of the snow-(N)AO relationship across the twentieth century, but they further show that this modulation might be a purely stochastic effect. Therefore, they emphasize the limitations of any empirical prediction of the (N)AO only based on snow and/or sea ice predictors.
'The Ethiopian famine' revisited: band aid and the antipolitics of celebrity humanitarian action.
Müller, Tanja R
2013-01-01
In many ways the Ethiopian famine of 1983-85 has served as a watershed with respect to humanitarian action. One of its lasting legacies has been the emergence of Band Aid and the subsequent increase in celebrity humanitarianism. A revisiting of the events of 1983-85 occurred in 2010 during a dispute in which it was alleged that a portion of the donations of Band Aid were spent on arms purchases. This paper takes this controversy as its starting point. It goes on to use the theoretical reflections of Giorgio Agamben to consider the dynamics that unfolded during the Ethiopian famine of 1983-85 and to analyse the underlying conceptualisation behind the emergence of Band Aid-type celebrity humanitarianism. The paper concludes with some wider thoughts on how the in essence antipolitical agenda of celebrity humanitarian action is transported into the everyday understanding of 'African disaster', resulting ultimately in the perpetuation of hegemonic control by the global North. © 2013 The Author(s). Journal compilation © Overseas Development Institute, 2013.
Nonlinear realization of spontaneously broken N = 1 supersymmetry revisited
NASA Astrophysics Data System (ADS)
Luo, Hui; Luo, Mingxing; Wang, Liucheng
2010-02-01
This paper revisits the nonlinear realization of spontaneously broken N = 1 supersymmetry. It is shown that the constrained superfield formalism as proposed in [6] can be reinterpreted in the language of standard realization of nonlinear supersymmetry via a new and simpler route. Explicit formulas of actions are presented for general renormalizable theories with or without gauge interactions. The nonlinearWess-Zumino gauge is discussed and relations are pointed out for different definitions of gauge fields. In addition, a general procedure is provided to deal with theories of arbitrary Kahler potentials.
The Floor in the Solar Wind Magnetic Field Revisited
2012-05-07
Paper 3 . DATES COVERED (From - To) 1 Oct 2007 – 10 Nov 2010 4. TITLE AND SUBTITLE The Floor in the Solar Wind Magnetic Field Revisited...magnitude [B] had a floor of ≈ 4.6 nT in yearly averages, a value which the interplanetary magnetic - field [IMF] strength returned to, or approached, at...is implicit in the work of Owens and Crooker (2006, 2007) who simulated the interplanetary magnetic - field strength in terms of a constant open-flux
The Atlanta Campaign: Principle of the Objective Revisited
1975-06-06
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Premises, principles, and practices in qualitative research: revisiting the foundations.
Charmaz, Kathy
2004-09-01
In this keynote address, the author focuses on what we bring to qualitative inquiry and how we conduct our research. What we do, why we do it, and how we do it remain contested issues. She proposes that we look at our methodological premises anew, revisit our principles, and revise our practices. Throughout this address, she draws on Goffman's methodological insights to provide a foundation for reassessing qualitative inquiry. She argues that researchers can build on Goffman's ideas to strengthen their methodological practices and research products. Last, she counters current institutional scrutiny of qualitative inquiry and suggests unacknowledged benefits of this work.
Rural-Nonrural Disparities in Postsecondary Educational Attainment Revisited
Byun, Soo-yong; Meece, Judith L.; Irvin, Matthew J.
2013-01-01
Using data from the National Educational Longitudinal Study, this study revisited rural-nonrural disparities in educational attainment by considering a comprehensive set of factors that constrain and support youth's college enrollment and degree completion. Results showed that rural students were more advantaged in community social resources compared to nonrural students, and these resources were associated with a significant increase in the likelihood of bachelor's degree attainment. Yet results confirmed that rural students lagged behind nonrural students in attaining a bachelor's degree largely due to their lower socioeconomic background. The findings present a more comprehensive picture of the complexity of geographic residence in shaping college enrollment and degree attainment. PMID:24285873
Revisiting a Constructive Classic: Wright's Physical Disability: A Psychosocial Approach
Dunn, Dana S.; Elliott, Timothy R.
2008-01-01
Beatrice A. Wright's (1960) classic book, Physical Disability: A Psychological Approach is a landmark publication in rehabilitation psychology. The authors believe that Division 22's forthcoming 50th anniversary, the results of a recent survey on essential readings in rehabilitation psychology, and a public critique concerning the relevance of individuating language in psychology are compelling reasons for revisiting the influence of Physical Disability. After discussing these catalysts, the authors review the book's history, scholarly impact, and link to positive disciplinary directions. The authors conclude by encouraging rehabilitation psychologists and other members of the discipline to (re)acquaint themselves with this important book and the timeless concepts it espouses. PMID:19079791
Revisiting the deific-decree doctrine in Washington state.
Leong, Gregory B
2008-01-01
The deific-decree exception to Washington's M'Naughten insanity standard first appeared in case law a quarter century ago in State v. Crenshaw. A few subsequent cases have attempted to refine the contours of the deific decree; however, the deific-decree doctrine has had only limited utility as a basis for the insanity defense. After about a decade of no activity in this area, the Washington courts have recently revisited the deific-decree doctrine in a case involving two defendants.
Revisiting the vanishing refuge model of diversification.
Damasceno, Roberta; Strangas, Maria L; Carnaval, Ana C; Rodrigues, Miguel T; Moritz, Craig
2014-01-01
Much of the debate around speciation and historical biogeography has focused on the role of stabilizing selection on the physiological (abiotic) niche, emphasizing how isolation and vicariance, when associated with niche conservatism, may drive tropical speciation. Yet, recent re-emphasis on the ecological dimensions of speciation points to a more prominent role of divergent selection in driving genetic, phenotypic, and niche divergence. The vanishing refuge model (VRM), first described by Vanzolini and Williams (1981), describes a process of diversification through climate-driven habitat fragmentation and exposure to new environments, integrating both vicariance and divergent selection. This model suggests that dynamic climates and peripheral isolates can lead to genetic and functional (i.e., ecological and phenotypic) diversity, resulting in sister taxa that occupy contrasting habitats with abutting distributions. Here, we provide predictions for populations undergoing divergence according to the VRM that encompass habitat dynamics, phylogeography, and phenotypic differentiation across populations. Such integrative analyses can, in principle, differentiate the operation of the VRM from other speciation models. We applied these principles to a lizard species, Coleodactylus meridionalis, which was used to illustrate the model in the original paper. We incorporate data on inferred historic habitat dynamics, phylogeography and thermal physiology to test for divergence between coastal and inland populations in the Atlantic Forest of Brazil. Environmental and genetic analyses are concordant with divergence through the VRM, yet physiological data are not. We emphasize the importance of multidisciplinary approaches to test this and alternative speciation models while seeking to explain the extraordinarily high genetic and phenotypic diversity of tropical biomes.
Revisiting the vanishing refuge model of diversification
Damasceno, Roberta; Strangas, Maria L.; Carnaval, Ana C.; Rodrigues, Miguel T.; Moritz, Craig
2014-01-01
Much of the debate around speciation and historical biogeography has focused on the role of stabilizing selection on the physiological (abiotic) niche, emphasizing how isolation and vicariance, when associated with niche conservatism, may drive tropical speciation. Yet, recent re-emphasis on the ecological dimensions of speciation points to a more prominent role of divergent selection in driving genetic, phenotypic, and niche divergence. The vanishing refuge model (VRM), first described by Vanzolini and Williams (1981), describes a process of diversification through climate-driven habitat fragmentation and exposure to new environments, integrating both vicariance and divergent selection. This model suggests that dynamic climates and peripheral isolates can lead to genetic and functional (i.e., ecological and phenotypic) diversity, resulting in sister taxa that occupy contrasting habitats with abutting distributions. Here, we provide predictions for populations undergoing divergence according to the VRM that encompass habitat dynamics, phylogeography, and phenotypic differentiation across populations. Such integrative analyses can, in principle, differentiate the operation of the VRM from other speciation models. We applied these principles to a lizard species, Coleodactylus meridionalis, which was used to illustrate the model in the original paper. We incorporate data on inferred historic habitat dynamics, phylogeography and thermal physiology to test for divergence between coastal and inland populations in the Atlantic Forest of Brazil. Environmental and genetic analyses are concordant with divergence through the VRM, yet physiological data are not. We emphasize the importance of multidisciplinary approaches to test this and alternative speciation models while seeking to explain the extraordinarily high genetic and phenotypic diversity of tropical biomes. PMID:25374581
Nonclassical 21-Homododecahedryl Cation Rearrangement Revisited.
Jalife, Said; Mondal, Sukanta; Osorio, Edison; Cabellos, José Luis; Martínez-Guajardo, Gerardo; Fernández-Herrera, María A; Merino, Gabriel
2016-03-04
The degenerate rearrangement in the 21-homododecahedryl cation (1) has been studied via density functional theory computations and Born-Oppenheimer Molecular Dynamics simulations. Compound 1 can be described as a highly fluxional hyperconjugated carbocation. Complete scrambling of 1 can be achieved by the combination of two unveiled barrierless processes. The first one is a "rotation" of one of the six-membered rings via a 0.8 kcal·mol(-1) barrier, and the second one is a slower interconvertion between two hyperconjomers via an out-of-plane methine bending (ΔG(⧧) = 4.0 kcal·mol(-1)).
Revisiting the social cost of carbon
Nordhaus, William D.
2017-01-01
The social cost of carbon (SCC) is a central concept for understanding and implementing climate change policies. This term represents the economic cost caused by an additional ton of carbon dioxide emissions or its equivalent. The present study presents updated estimates based on a revised DICE model (Dynamic Integrated model of Climate and the Economy). The study estimates that the SCC is $31 per ton of CO2 in 2010 US$ for the current period (2015). For the central case, the real SCC grows at 3% per year over the period to 2050. The paper also compares the estimates with those from other sources. PMID:28143934
Revisiting the social cost of carbon
NASA Astrophysics Data System (ADS)
Nordhaus, William D.
2017-02-01
The social cost of carbon (SCC) is a central concept for understanding and implementing climate change policies. This term represents the economic cost caused by an additional ton of carbon dioxide emissions or its equivalent. The present study presents updated estimates based on a revised DICE model (Dynamic Integrated model of Climate and the Economy). The study estimates that the SCC is 31 per ton of CO2 in 2010 US for the current period (2015). For the central case, the real SCC grows at 3% per year over the period to 2050. The paper also compares the estimates with those from other sources.
Vaporisation of a dicationic ionic liquid revisited.
Vitorino, Joana; Leal, João P; Licence, Peter; Lovelock, Kevin R J; Gooden, Peter N; Minas da Piedade, Manuel E; Shimizu, Karina; Rebelo, Luís P N; Canongia Lopes, José N
2010-12-03
The vaporization of a dicationic ionic liquid at moderate temperatures and under reduced pressures--recently studied by line-of-sight mass spectrometry--was further analyzed using an ion-cyclotron resonance mass spectroscopy technique that allows the monitoring of the different species present in the gas phase through the implementation of controlled ion-molecule reactions. The results support the view that the vapour phase of an aprotic dicationic ionic liquid is composed of neutral ion triplets (one dication attached to two anions). Molecular dynamics simulations were also performed in order to explain the magnitude of the vaporization enthalpies of dicationic ionic liquids vis-à-vis their monocationic counterparts.
Revisiting a Problem of Two Freezers
NASA Astrophysics Data System (ADS)
Easton, Don
2014-02-01
The January 2013 Physics Challenge for Teachers and Students has some features that are surprising and worth a closer look. The problem concerns a Carnot-cycle refrigeration unit operating inside a tent. It achieves dynamic equilibrium with a freezer ("cold") compartment temperature of TC=13°C, tent temperature of TH=1°C (the "hot" waste side of the freezer), and temperature "outside" the tent of TO=0°C. The problem is to find the equilibrium temperature inside the tent if an identical freezer is brought in and run simultaneously. As explained here, what constitutes an identical freezer is open to interpretation.
Revisiting the social cost of carbon.
Nordhaus, William D
2017-02-14
The social cost of carbon (SCC) is a central concept for understanding and implementing climate change policies. This term represents the economic cost caused by an additional ton of carbon dioxide emissions or its equivalent. The present study presents updated estimates based on a revised DICE model (Dynamic Integrated model of Climate and the Economy). The study estimates that the SCC is $31 per ton of CO2 in 2010 US$ for the current period (2015). For the central case, the real SCC grows at 3% per year over the period to 2050. The paper also compares the estimates with those from other sources.
Revisiting the block method for evaluating thermal conductivities of clay and granite
USDA-ARS?s Scientific Manuscript database
Determination of thermal conductivities of porous media using the contact method is revisited and revalidated with consideration of thermal contact resistance. Problems that limit the accuracy of determination of thermal conductivities of porous media are discussed. Thermal conductivities of granite...
Molecular ring rotation in solid ferrocene revisited
NASA Astrophysics Data System (ADS)
Appel, Markus; Frick, Bernhard; Spehr, Tinka Luise; Stühn, Bernd
2015-03-01
We report on quasielastic neutron spectroscopy experiments on ferrocene (bis(η5-cyclopentadienyl)iron) in its three different crystalline phases: the disordered monoclinic crystalline phase (T > 164 K), the metastable triclinic phase (T < 164 K), and the stable orthorhombic phase (T < 250 K). The cyclopentadienyl rings in ferrocene are known to undergo rotational reorientations for which the analysis of our large data set suggests partially a revision of the known picture of the dynamics and allows for an extension and completion of previous studies. In the monoclinic phase, guided by structural information, we propose a model for rotational jumps among non-equivalent sites in contrast to the established 5-fold jump rotation model. The new model takes the dynamical disorder into account and allows the cyclopentadienyl rings to reside in two different configurations which are found to be twisted by an angle of approximately 30°. In the triclinic phase, our analysis demands the use of a 2-ring model accounting for crystallographically independent sites with different barriers to rotation. For the orthorhombic phase of ferrocene, we confirm a significantly increased barrier of rotation using neutron backscattering spectroscopy. Our data analysis includes multiple scattering corrections and presents a novel approach of simultaneous analysis of different neutron scattering data by combining elastic and inelastic fixed window temperature scans with energy spectra, providing a very robust and reliable mean of extracting the individual activation energies of overlapping processes.
Molecular ring rotation in solid ferrocene revisited
Appel, Markus; Frick, Bernhard; Spehr, Tinka Luise; Stühn, Bernd
2015-03-21
We report on quasielastic neutron spectroscopy experiments on ferrocene (bis(η{sup 5}-cyclopentadienyl)iron) in its three different crystalline phases: the disordered monoclinic crystalline phase (T > 164 K), the metastable triclinic phase (T < 164 K), and the stable orthorhombic phase (T < 250 K). The cyclopentadienyl rings in ferrocene are known to undergo rotational reorientations for which the analysis of our large data set suggests partially a revision of the known picture of the dynamics and allows for an extension and completion of previous studies. In the monoclinic phase, guided by structural information, we propose a model for rotational jumps among non-equivalent sites in contrast to the established 5-fold jump rotation model. The new model takes the dynamical disorder into account and allows the cyclopentadienyl rings to reside in two different configurations which are found to be twisted by an angle of approximately 30°. In the triclinic phase, our analysis demands the use of a 2-ring model accounting for crystallographically independent sites with different barriers to rotation. For the orthorhombic phase of ferrocene, we confirm a significantly increased barrier of rotation using neutron backscattering spectroscopy. Our data analysis includes multiple scattering corrections and presents a novel approach of simultaneous analysis of different neutron scattering data by combining elastic and inelastic fixed window temperature scans with energy spectra, providing a very robust and reliable mean of extracting the individual activation energies of overlapping processes.
Hall, A Brad; Novotny, April; Bhisitkul, Donna M; Melton, James; Regan, Tim; Leckie, Maureen
2017-06-01
Although pediatric asthma continues to be a highly studied disease, data to suggest clear strategies to decrease asthma related revisits or readmissions is lacking. The purpose of our study was to assess the effect of emergency department (ED) direct dispensing of beta-agonist metered dose inhalers on pediatric asthma ED revisit and readmission rates. We conducted a retrospective cohort study of pediatric patients discharged from the pediatric ED with a diagnosis of asthma. Our primary outcome measured the rate of asthma revisits to the ED or admissions to the hospital within 28 days. Logistic regression analysis was used to assess ED beta-agonist MDI dispensing and revisit and/or readmission as the outcome. A total of 853 patients met eligibility for inclusion in the study, with 657 enrolled in the Baseline group and 196 enrolled in the ED-MDI group. The Baseline group experienced a revisit and readmission rate of 7.0% (46/657) versus 2.6% (5/196) in the ED-MDI group, (p = 0.026). ED direct dispensing of MDIs was found to be independently associated with a decreased risk of revisit or readmission (odds ratio 0.37; 95% confidence interval 0.14-0.95). In our study, ED direct dispensing of beta-agonist MDIs resulted in a reduction in 28-day revisit and readmission to the hospital. Further studies should be performed to evaluate the economic impact of reducing these revisits and readmissions against the costs of maintaining a dispensing program. Our findings may support modification of asthma programs to include dispensing MDIs from the emergency department.
Revisiting the Capture of Mercury into Its 3:2 Spin-orbit Resonance
2014-01-01
well before differentiation. Keywords. celestial mechanics, planets and satellites: individual ( Mercury ) 1. Previous studies In the literature hitherto...2014 2. REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Revisiting the capture of Mercury into its 3:2 spin-orbit...Astronomical Union 2014 doi:10.1017/S1743921314007765 Revisiting the capture of Mercury into its 3:2 spin-orbit resonance Benôıt Noyelles1, Julien
Revisiting the Decision of Death in Hurst v. Florida.
Cooke, Brian K; Ginory, Almari; Zedalis, Jennifer
2016-12-01
The United States Supreme Court has considered the question of whether a judge or a jury must make the findings necessary to support imposition of the death penalty in several notable cases, including Spaziano v. Florida (1984), Hildwin v. Florida (1989), and Ring v. Arizona (2002). In 2016, the U.S. Supreme Court revisited the subject in Hurst v. Florida Florida Statute § 921.141 allows the judge, after weighing aggravating and mitigating circumstances, to enter a sentence of life imprisonment or death. Before Hurst, Florida's bifurcated sentencing proceedings included an advisory sentence from jurors and a separate judicial hearing without juror involvement. In Hurst, the Court revisited the question of whether Florida's capital sentencing scheme violates the Sixth Amendment, which requires a jury, not a judge, to find each fact necessary to impose a sentence of death in light of Ring In an eight-to-one decision, the Court reversed the judgment of the Florida Supreme Court, holding that the Sixth Amendment requires a jury to find the aggravating factors necessary for imposing the death penalty. The role of Florida juries in capital sentencing proceedings was thereby elevated from advisory to determinative. We examine the Court's decision and offer commentary regarding this shift from judge to jury in the final imposition of the death penalty and the overall effect of this landmark case. © 2016 American Academy of Psychiatry and the Law.
Engineered nanoparticles: Revisiting safety concerns in light of ethno medicine.
Palkhiwala, Suhani; Bakshi, Sonal R
2014-01-01
The nanoparticles are a miracle invention of the century that has opened novel avenues of applications in various fields. The safety aspect of exposure to nanoparticles for humans, plants, animals, soil micro-flora, and ecosystem at large has been questioned. The safety concern can be addressed by laboratory studies to assess the actual risk and recommend exposure limits and related regulation. There is also a suggestion for considering the nanoparticle form of conventional compounds as a new chemical and subject it to safety assessment in line with the chemical regulatory agencies. In the light of the current scenario of popularity and safety concerns regarding nanoparticles, the use of ancient metal based forms like, Bhasma is revisited in the present article. The current approach of green synthesis of nanoparticles is compared with the Ayurveda Rasayana Shastra guidelines of Bhasma preparation and modern preparation of engineered nanoparticles. Since the benefits of nanotechnology are undeniable, and safety concerns are also not ungrounded, there is a pressing need to revisit the ways nanoparticles are manufactured, and to carry out safety assessment by the techniques specially adapted for this novel compound.
Engineered nanoparticles: Revisiting safety concerns in light of ethno medicine
Palkhiwala, Suhani; Bakshi, Sonal R.
2014-01-01
The nanoparticles are a miracle invention of the century that has opened novel avenues of applications in various fields. The safety aspect of exposure to nanoparticles for humans, plants, animals, soil micro-flora, and ecosystem at large has been questioned. The safety concern can be addressed by laboratory studies to assess the actual risk and recommend exposure limits and related regulation. There is also a suggestion for considering the nanoparticle form of conventional compounds as a new chemical and subject it to safety assessment in line with the chemical regulatory agencies. In the light of the current scenario of popularity and safety concerns regarding nanoparticles, the use of ancient metal based forms like, Bhasma is revisited in the present article. The current approach of green synthesis of nanoparticles is compared with the Ayurveda Rasayana Shastra guidelines of Bhasma preparation and modern preparation of engineered nanoparticles. Since the benefits of nanotechnology are undeniable, and safety concerns are also not ungrounded, there is a pressing need to revisit the ways nanoparticles are manufactured, and to carry out safety assessment by the techniques specially adapted for this novel compound. PMID:26664232
Revisiting Parametric Types and Virtual Classes
NASA Astrophysics Data System (ADS)
Madsen, Anders Bach; Ernst, Erik
This paper presents a conceptually oriented updated view on the relationship between parametric types and virtual classes. The traditional view is that parametric types excel at structurally oriented composition and decomposition, and virtual classes excel at specifying mutually recursive families of classes whose relationships are preserved in derived families. Conversely, while class families can be specified using a large number of F-bounded type parameters, this approach is complex and fragile; and it is difficult to use traditional virtual classes to specify object composition in a structural manner, because virtual classes are closely tied to nominal typing. This paper adds new insight about the dichotomy between these two approaches; it illustrates how virtual constraints and type refinements, as recently introduced in gbeta and Scala, enable structural treatment of virtual types; finally, it shows how a novel kind of dynamic type check can detect compatibility among entire families of classes.
Revisiting perturbations in extended quasidilaton massive gravity
NASA Astrophysics Data System (ADS)
Heisenberg, Lavinia
2015-04-01
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Regulation of adipose tissue lipolysis revisited.
Bézaire, Véronic; Langin, Dominique
2009-11-01
Human obesity and its complications are an increasing burden in developed and underdeveloped countries. Adipose tissue mass and the mechanisms that control it are central to elucidating the aetiology of obesity and insulin resistance. Over the past 15 years tremendous progress has been made in several avenues relating to adipose tissue. Knowledge of the lipolytic machinery has grown with the identification of new lipases, cofactors and interactions between proteins and lipids that are central to the regulation of basal and stimulated lipolysis. The dated idea of an inert lipid droplet has been appropriately revamped to that of a dynamic and highly-structured organelle that in itself offers regulatory control over lipolysis. The present review provides an overview of the numerous partners and pathways involved in adipose tissue lipolysis and their interaction under various metabolic states. Integration of these findings into whole adipose tissue metabolism and its systemic effects is also presented in the context of inflammation and insulin resistance.
H-bonding in protein hydration revisited
Petukhov, Michael; Rychkov, Georgy; Firsov, Leonid; Serrano, Luis
2004-01-01
H-bonding between protein surface polar/charged groups and water is one of the key factors of protein hydration. Here, we introduce an Accessible Surface Area (ASA) model for computationally efficient estimation of a free energy of water–protein H-bonding at any given protein conformation. The free energy of water–protein H-bonds is estimated using empirical formulas describing probabilities of hydrogen bond formation that were derived from molecular dynamics simulations of water molecules at the surface of a small protein, Crambin, from the Abyssinian cabbage (Crambe abyssinica) seed. The results suggest that atomic solvation parameters (ASP) widely used in continuum hydration models might be dependent on ASA for polar/charged atoms under consideration. The predictions of the model are found to be in qualitative agreement with the available experimental data on model compounds. This model combines the computational speed of ASA potential, with the high resolution of more sophisticated solvation methods. PMID:15238635
H-bonding in protein hydration revisited.
Petukhov, Michael; Rychkov, Georgy; Firsov, Leonid; Serrano, Luis
2004-08-01
H-bonding between protein surface polar/charged groups and water is one of the key factors of protein hydration. Here, we introduce an Accessible Surface Area (ASA) model for computationally efficient estimation of a free energy of water-protein H-bonding at any given protein conformation. The free energy of water-protein H-bonds is estimated using empirical formulas describing probabilities of hydrogen bond formation that were derived from molecular dynamics simulations of water molecules at the surface of a small protein, Crambin, from the Abyssinian cabbage (Crambe abyssinica) seed. The results suggest that atomic solvation parameters (ASP) widely used in continuum hydration models might be dependent on ASA for polar/charged atoms under consideration. The predictions of the model are found to be in qualitative agreement with the available experimental data on model compounds. This model combines the computational speed of ASA potential, with the high resolution of more sophisticated solvation methods.
Revisiting perturbations in extended quasidilaton massive gravity
Heisenberg, Lavinia
2015-04-01
In this work we study the theory of extended quasidilaton massive gravity together with the presence of matter fields. After discussing the homogeneous and isotropic fully dynamical background equations, which governs the exact expansion history of the universe, we consider small cosmological perturbations around these general FLRW solutions. The stability of tensor, vector and scalar perturbations on top of these general background solutions give rise to slightly different constraints on the parameters of the theory than those obtained in the approximative assumption of the late-time asymptotic form of the expansion history, which does not correspond to our current epoch. This opens up the possibility of stable FLRW solutions to be compared with current data on cosmic expansion with the restricted parameter space based on theoretical ground.
Loop quantization of Schwarzschild interior revisited
NASA Astrophysics Data System (ADS)
Singh, Parampreet; Corichi, Alejandro
2016-03-01
Several studies of different inequivalent loop quantizations have shown, that there exists no fully satisfactory quantum theory for the Schwarzschild interior. Existing quantizations fail either on dependence on the fiducial structure or on the lack of the classical limit. Here we put forward a novel viewpoint to construct the quantum theory that overcomes all of the known problems of the existing quantizations. It is shown that the quantum gravitational constraint is well defined past the singularity and that its effective dynamics possesses a bounce into an expanding regime. The classical singularity is avoided, and a semiclassical spacetime satisfying vacuum Einstein's equations is recovered on the ``other side'' of the bounce. We argue that such metric represents the interior region of a white-hole spacetime, but for which the corresponding ``white-hole mass'' differs from the original black hole mass. We compare the differences in physical implications with other quantizations.
Cell repair: Revisiting the patch hypothesis
Davenport, Nicholas R.
2016-01-01
ABSTRACT Plasma membrane damage elicits a complex and dynamic cellular response. A vital component of this response, membrane resealing, is thought to arise from fusion of intracellular membranous compartments to form a temporary, impermeant patch at the site of damage; however, this hypothesis has been difficult to confirm visually. By utilizing advanced microscopy technologies with high spatiotemporal resolution in wounded Xenopus laevis oocytes, we provide the first direct visualization of the membrane fusion events predicted by the patch hypothesis; we show the barrier formed by patching is capable of abating exchange of material across the plasma membrane within seconds. Profound changes also occur to the plasma membrane surrounding wounds; lipid remodeling is accompanied by membrane fusion events, both conventional (e.g., exocytosis) and novel (e.g., “explodosis”). Further, we reveal additional complexity in wound-induced subcellular patterning, supporting existing evidence that extensive interactions between lipid, protein, and ionic signaling pathways shape the cellular wound response. PMID:28042380
Revisiting anomalous structures in liquid Ga.
Tsai, K H; Wu, Ten-Ming; Tsay, Shiow-Fon
2010-01-21
In terms of an interatomic pair potential, which well characterizes the dynamic properties of liquid Ga, we investigate again the origin of the well known high-q shoulder in the static structure factor of the liquid. Similar to the results of Gong's simulation at high temperature, dimers with extremely short bond lengths are indeed found in our model just above the melting point, but our results indicate that it is unlikely for the high-q shoulder to be produced by these dimers. Instead, based on our model, the high-q shoulder is resulted from some medium-range order, which is related to the structures beyond the first shell of the radial distribution function, caused by Friedel oscillations within a nanoscale range.
Minimal Model of Plankton Systems Revisited with Spatial Diffusion and Maturation Delay.
Zhao, Jiantao; Tian, Jianjun Paul; Wei, Junjie
2016-03-01
This study revisits the minimal model for a plankton ecosystem proposed by Scheffer with spatial diffusion of plankton and the delay of the maturation period of herbivorous zooplankton. It deepens our understanding of effects of the nutrients and the predation of fish upon zooplankton on the dynamical patterns of the plankton system and also presents new phenomena induced by the delay with spatial diffusion. When the nutrient level is sufficient low, the zooplankton population collapses and the phytoplankton population reaches its carrying capacity. Mathematically, the global stability of the boundary equilibrium is proved. As the nutrient level increases, the system switches to coexistent equilibria or oscillations depending on the maturation period of zooplankton and the predation rate of fish on herbivorous zooplankton. Under an eutrophic condition, there is a unique coexistent homogeneous equilibrium, and the equilibrium density of phytoplankton increases, while the equilibrium density of herbivorous zooplankton decreases as the fish predation rate on herbivorous zooplankton is increasing. The study shows that the system will never collapses under the eutrophic condition unless the fish predation rate approaches infinite. The study also finds a functional bifurcation relation between the delay parameter of the maturation period of herbivorous zooplankton and the fish predation rate on herbivorous zooplankton that, above a critical value of the fish predation rate, the system stays at the coexistent equilibrium, and below that value, the system switches its dynamical patterns among stable and unstable equilibria and oscillations. The oscillations emerge from Hopf bifurcations, and a detailed mathematical analysis about the Hopf bifurcations is carried out to give relevant ecological predications.
Revisiting sea level changes in the North Sea during the Anthropocene
NASA Astrophysics Data System (ADS)
Jensen, Jürgen; Dangendorf, Sönke; Wahl, Thomas; Niehüser, Sebastian
2016-04-01
The North Sea is one of the best instrumented ocean basins in the world. Here we revisit sea level changes in the North Sea region from tide gauges, satellite altimetry, hydrographic profiles and ocean reanalysis data from the beginning of the 19th century to present. This includes an overview of the sea level chapter of the North Sea Climate Change Assessment (NOSCCA) complemented by results from more recent investigations. The estimates of long-term changes from tide gauge records are significantly affected by vertical land motion (VLM), which is related to both the large-scale viscoelastic response of the solid earth to ice melting since the last deglaciation and local effects. Removing VLM (estimated from various data sources such as GPS, tide gauge minus altimetry and GIA) significantly reduces the spatial variability of long-term trends in the basin. VLM corrected tide gauge records suggest a transition from relatively moderate changes in the 19th century towards modern trends of roughly 1.5 mm/yr during the 20th century. Superimposed on the long-term changes there is a considerable inter-annual to multi-decadal variability. On inter-annual timescales this variability mainly reflects the barotropic response of the ocean to atmospheric forcing with the inverted barometer effect dominating along the UK and Norwegian coastlines and wind forcing controlling the southeastern part of the basin. The decadal variability is mostly remotely forced and dynamically linked to the North Atlantic via boundary waves in response to long-shore winds along the continental slope. These findings give valuable information about the required horizontal resolution of ocean models and the necessary boundary conditions and are therefore important for the dynamical downscaling of sea level projections for the North Sea coastlines.
Biologically inspired dynamic material systems.
Studart, André R
2015-03-09
Numerous examples of material systems that dynamically interact with and adapt to the surrounding environment are found in nature, from hair-based mechanoreceptors in animals to self-shaping seed dispersal units in plants to remodeling bone in vertebrates. Inspired by such fascinating biological structures, a wide range of synthetic material systems have been created to replicate the design concepts of dynamic natural architectures. Examples of biological structures and their man-made counterparts are herein revisited to illustrate how dynamic and adaptive responses emerge from the intimate microscale combination of building blocks with intrinsic nanoscale properties. By using top-down photolithographic methods and bottom-up assembly approaches, biologically inspired dynamic material systems have been created 1) to sense liquid flow with hair-inspired microelectromechanical systems, 2) to autonomously change shape by utilizing plantlike heterogeneous architectures, 3) to homeostatically influence the surrounding environment through self-regulating adaptive surfaces, and 4) to spatially concentrate chemical species by using synthetic microcompartments. The ever-increasing complexity and remarkable functionalities of such synthetic systems offer an encouraging perspective to the rich set of dynamic and adaptive properties that can potentially be implemented in future man-made material systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Loop quantization of the Schwarzschild interior revisited
NASA Astrophysics Data System (ADS)
Corichi, Alejandro; Singh, Parampreet
2016-03-01
The loop quantization of the Schwarzschild interior region, as described by a homogeneous anisotropic Kantowski-Sachs model, is re-examined. As several studies of different—inequivalent—loop quantizations have shown, to date there exists no fully satisfactory quantum theory for this model. This fact poses challenges to the validity of some scenarios to address the black hole information problem. Here we put forward a novel viewpoint to construct the quantum theory that builds from some of the models available in the literature. The final picture is a quantum theory that is both independent of any auxiliary structure and possesses a correct low curvature limit. It represents a subtle but non-trivial modification of the original prescription given by Ashtekar and Bojowald. It is shown that the quantum gravitational constraint is well defined past the singularity and that its effective dynamics possesses a bounce into an expanding regime. The classical singularity is avoided, and a semiclassical spacetime satisfying vacuum Einstein’s equations is recovered on the ‘other side’ of the bounce. We argue that such a metric represents the interior region of a white-hole spacetime, but for which the corresponding ‘white hole mass’ differs from the original black hole mass. Furthermore, we find that the value of the white hole mass is proportional to the third power of the starting black hole mass.
Revisiting tolerance from the endogenous morphine perspective.
Stefano, George B; Kream, Richard M; Esch, Tobias
2009-09-01
Tolerance represents a dynamic mechanism that can be used to temper various regulatory processes regardless of whether they mediate excitation or inhibition. Tolerance operationally directs state-dependent attenuation of the action of endogenous and exogenous morphine. For example, tolerance ensures that immuno-inhibition induced by morphine does not compromise a requisite functional system over an extended period of time. In the nervous system, tolerance to inhibitory action insures that excitatory tone is resumed. Thus, desensitization sets in and allows various essential processes to be operational once again. Clearly, the temporal rebound of diverse immune and nervous processes involved with opiate actions provides a self-contained operational mechanism to ensure survival of the organism. Furthermore, love and/or pleasure, and satiety, are complex neurobiological phenomena linked to limbic brain reward circuitry. These processes are critically dependent on oxytocin, vasopressin, dopamine, endogenous morphine and serotoninergic signaling. Naturally rewarding and/or pleasurable activities are usually governed by beneficial biological behaviors like eating, sex, and reproduction. It is our contention that critically important tolerance mechanisms extend to behaviors mediated by CNS reward systems. In other words, we become satisfied with sex, food, pleasure for the moment and disinterest creeps in until the "urges" return.
Regular Language Constrained Sequence Alignment Revisited
NASA Astrophysics Data System (ADS)
Kucherov, Gregory; Pinhas, Tamar; Ziv-Ukelson, Michal
Imposing constraints in the form of a finite automaton or a regular expression is an effective way to incorporate additional a priori knowledge into sequence alignment procedures. With this motivation, Arslan [1] introduced the Regular Language Constrained Sequence Alignment Problem and proposed an O(n 2 t 4) time and O(n 2 t 2) space algorithm for solving it, where n is the length of the input strings and t is the number of states in the non-deterministic automaton, which is given as input. Chung et al. [2] proposed a faster O(n 2 t 3) time algorithm for the same problem. In this paper, we further speed up the algorithms for Regular Language Constrained Sequence Alignment by reducing their worst case time complexity bound to O(n 2 t 3/logt). This is done by establishing an optimal bound on the size of Straight-Line Programs solving the maxima computation subproblem of the basic dynamic programming algorithm. We also study another solution based on a Steiner Tree computation. While it does not improve the run time complexity in the worst case, our simulations show that both approaches are efficient in practice, especially when the input automata are dense.
Wheeler & Feynman's Response of the Universe, revisited
NASA Astrophysics Data System (ADS)
Wolff, Milo
2003-04-01
In a famous 1945 paper Wheeler and Feynman (1) sought the cause of radiation from an accelerated electron. They assumed that acceleration produced an electromagnetic wave pulse from the electron that caused responding waves from static point-particle absorbers in the universe. Problems arose with possible violation of causality by waves that begin before their cause. This paper points out that a rigorous logical solution is obtained (2) when the electron is a dynamic structure of two scalar quantum waves. The scalar wave equation produces two such inward and outward spherical waves. The two waves combined have complete properties of positrons and electrons and the natural laws. Thus the problem is resolved by replacing the point particle with a scalar quantum wave structure (3). ... The conclusion: The universe and the laws of nature are inter-connected by co-mingled matter waves. Thus if the stars did not exist, it would be meaningless to think that we could exist. 1) Wheeler & Feynman, RMP, 17, 157 (1945). 2) Wolff, Gravition and Cosmology, Kluwer Acad. Publ. (2002). 3) www.QuantumMatter.com
NEC violation in mimetic cosmology revisited
NASA Astrophysics Data System (ADS)
Ijjas, Anna; Ripley, Justin; Steinhardt, Paul J.
2016-09-01
In the context of Einstein gravity, if the null energy condition (NEC) is satisfied, the energy density in expanding space-times always decreases while in contracting space-times the energy density grows and the universe eventually collapses into a singularity. In particular, no non-singular bounce is possible. It is, though, an open question if this energy condition can be violated in a controlled way, i.e., without introducing pathologies, such as unstable negative-energy states or an imaginary speed of sound. In this letter, we will re-examine the claim that the recently proposed mimetic scenario can violate the NEC without pathologies. We show that mimetic cosmology is prone to gradient instabilities even in cases when the NEC is satisfied (except for trivial examples). Most interestingly, the source of the instability is always the Einstein-Hilbert term in the action. The matter stress-energy component does not contribute spatial gradient terms but instead makes the problematic curvature modes dynamical. We also show that mimetic cosmology can be understood as a singular limit of known, well-behaved theories involving higher-derivative kinetic terms and discuss ways of removing the instability.
Dynamical modelling of meteoroid streams
NASA Astrophysics Data System (ADS)
Clark, D. L.; Wiegert, P. A.
2014-07-01
Accurate simulations of meteoroid streams permit the prediction of stream interaction with Earth, and provide a measure of risk to Earth satellites and interplanetary spacecraft. Current cometary ejecta and meteoroid stream models have been somewhat successful in predicting some stream observations, but have required significant assumptions and simplifications. Extending on the approach of Vaubaillon et al. 2005, we model dust ejection from the cometary nucleus, and generate sample particles representing bins of distinct dynamical evolution-regulating characteristics (size, density, direction, albedo). Ephemerides of the sample particles are integrated and recorded for later assignment of weights based on model parameter changes. To assist in model analysis we are developing interactive software to permit the "turning of knobs" of model parameters, allowing for near-real-time 3D visualization of resulting stream structure. Using the tool, we will revisit prior assumptions made, and will observe the impact of introducing non-uniform and time-variant cometary surface attributes and processes.
Revisiting static modulation in pyramid wavefront sensing
NASA Astrophysics Data System (ADS)
Marafatto, L.; Ragazzoni, R.; Vassallo, D.; Bergomi, M.; Biondi, F.; Farinato, J.; Greggio, D.; Magrin, D.; Viotto, V.
2016-07-01
The Pyramid Sensor (PS) is based on the Focault knife-edge test, yielding then, in geometrical approximation, only the sign of the wavefront slope. To provide linear measurements of the wavefront slopes the PS relies on a technique known as modulation, which also plays a central role to improve the linear range of the pyramid WFS, very small in the nonmodulated case. In the main PS using modulation so far, this task is achieved by moving optical components in the WFS, increasing the complexity of the system. An attractive idea to simplify the optical and mechanical design of a pyramid WFS is to work without any dynamic modulation. This concept was only merely described and functionally tested in the framework of MAD, and subsequently, with a holographic diffuser. The latter produce a sort of random distribution of the light coming out from the pupil plane, leading to sort of inefficient modulation, as most of the rays are focused in the central region of the light diffused by such device. The bi-dimensional original grating is, in contrast, producing a well defined deterministic distribution of the light onto a specifically shaped pattern. A crude option has been already discussed as a possibility, and it is here generalized to holographic plates leading to various distribution of lights, including a circle whose diameter would match the required modulation pattern, or more cost effective approaches like the one of a square pattern. These holographic diffusers would exhibit also zero-th and high order patterns and the actual size of the equivalent modulation would be linearly wavelength dependent, leading to colour effects that requires a careful handling in order to properly choose the right amount of equivalent modulation.
Orbital anisotropy in cosmological haloes revisited
NASA Astrophysics Data System (ADS)
Wojtak, Radosław; Gottlöber, Stefan; Klypin, Anatoly
2013-09-01
The velocity anisotropy of particles inside dark matter (DM) haloes is an important physical quantity, which is required for the accurate modelling of mass profiles of galaxies and clusters of galaxies. It is typically measured using the ratio of the radial to tangential velocity dispersions at a given distance from the halo centre. However, this measure is insufficient to describe the dynamics of realistic haloes, which are not spherical and are typically quite elongated. Studying the velocity distribution in massive DM haloes in cosmological simulations, we find that in the inner parts of the haloes, the local velocity ellipsoids are strongly aligned with the major axis of the halo, the alignment being stronger for more relaxed haloes. In the outer regions of the haloes, the alignment becomes gradually weaker and the orientation is more random. These two distinct regions of different degree of the alignment coincide with two characteristic regimes of the DM density profile: a shallow inner cusp and a steep outer profile that are separated by a characteristic radius at which the density declines as ρ ∝ r-2. This alignment of the local velocity ellipsoids requires reinterpretation of features found in measurements based on the spherically averaged ratio of the radial to tangential velocity dispersions. In particular, we show that the velocity distribution in the central halo regions is highly anisotropic. For cluster-size haloes with mass 1014-1015 h-1 M⊙, the velocity anisotropy along the major axis is nearly independent of radius and is equal to β = 1 - σ ^2_perp/σ ^2_radial≈ 0.4, which is significantly larger than the previously estimated spherically averaged velocity anisotropy. The alignment of density and velocity anisotropies and the radial trends may also have some implications for the mass modelling based on kinematical data of objects such as galaxy clusters or dwarf spheroidals, where the orbital anisotropy is a key element in an unbiased mass
Revisiting Feynman's ratchet with thermoelectric transport theory.
Apertet, Y; Ouerdane, H; Goupil, C; Lecoeur, Ph
2014-07-01
We show how the formalism used for thermoelectric transport may be adapted to Smoluchowski's seminal thought experiment, also known as Feynman's ratchet and pawl system. Our analysis rests on the notion of useful flux, which for a thermoelectric system is the electrical current and for Feynman's ratchet is the effective jump frequency. Our approach yields original insight into the derivation and analysis of the system's properties. In particular we define an entropy per tooth in analogy with the entropy per carrier or Seebeck coefficient, and we derive the analog to Kelvin's second relation for Feynman's ratchet. Owing to the formal similarity between the heat fluxes balance equations for a thermoelectric generator (TEG) and those for Feynman's ratchet, we introduce a distribution parameter γ that quantifies the amount of heat that flows through the cold and hot sides of both heat engines. While it is well established that γ = 1/2 for a TEG, it is equal to 1 for Feynman's ratchet. This implies that no heat may be rejected in the cold reservoir for the latter case. Further, the analysis of the efficiency at maximum power shows that the so-called Feynman efficiency corresponds to that of an exoreversible engine, with γ = 1. Then, turning to the nonlinear regime, we generalize the approach based on the convection picture and introduce two different types of resistance to distinguish the dynamical behavior of the considered system from its ability to dissipate energy. We finally put forth the strong similarity between the original Feynman ratchet and a mesoscopic thermoelectric generator with a single conducting channel.
Time Variability of Titan's Ionosphere Revisited
NASA Astrophysics Data System (ADS)
Hsu, Jen-Kai; Ip, Wing-Huen; Perryman, Rebecca; Waite, Hunter
2015-04-01
Since the Saturn Orbital Insertion in 2004, the Ion Neutral Mass Spectrometer (INMS) experiment aboard the Cassini-Huygens spacecraft has acquired an extensive data set. The decadal coverage of the measurements during numerous close encounters with Titan allows the study of spatial and temporal variations of Titan's nitrogen-rich atmosphere above 1000-km altitude. Titan's ionosphere is quite different to that of Earth's ionosphere. Due to Titan's thick (hundreds of kilometers) and dense atmosphere, the measurable ion density of Titan's nightside ionosphere extends well beyond the terminator. The diurnal variation of the ion density profiles and compositional changes are the result of photoionization and magnetospheric electron ionization (important at the night side). The different time evolutions of the light and heavy species from day to night could be indicative of the effects of flow dynamics and ion-molecule chemistry. From the observations, we can determine the ion content in Titan's night-side and the asymmetry between the dawn and dusk ion density profiles. We have also found in the long term data base the signature of the equatorial expansion of Titan's atmosphere during solar maximum. In addition the global distributions of the major compound N2 and minor species like CH4 and H2 all exhibit significant changes over a solar cycle as the closest approach points of Cassini moved from the northern hemisphere to the southern hemisphere. In this work, we will first compare the diurnal variations between different ion species and simulate the ion densities to study the possible contributing factors. Then we will compare the results of our analysis to those reported by other groups to construct a comprehensive model of Titan's neutral atmosphere and ionosphere under different solar conditions.
Topological analysis of chaotic orbits: Revisiting Hyperion
NASA Technical Reports Server (NTRS)
Boyd, Patricia T.; Mindlin, Gabriel B.; Gilmore, Robert; Solari, Hernan G.
1994-01-01
There is emerging interest in the possibility of chaotic evolution in astrophysical systems. To mention just one example, recent well-sampled ground-based observations of the Saturian satellite Hyperion strongly suggest that it is exhibiting chaotic behavior. We present a general technique, the method of close returns, for the analysis of data from astronomical objects believed to be exhibiting chaotic motion. The method is based on the extraction of pieces of the evolution that exhibit nearly periodic behavior-episodes during which the object stays near in phase space to some unstable periodic orbit. Such orbits generally act as skeletal features, tracing the topological organization of the manifold on which the chaotic dynamics takes place. This method does not require data sets as lengthy as other nonlinear analysis techniques do and is therefore well suited to many astronomical observing programs. Well sampled data covering between twenty and forty characteristic periods of the system have been found to be sufficient for the application of this technique. Additional strengths of this method are its robustness in the presence of noise and the ability for a user to clearly distinguish between periodic, random, and chaotic behavior by inspection of the resulting two-dimensional image. As an example of its power, we analyze close returns in a numerically generated data set, based on a model for Hyperion extensively studied in the literature, corresponding to nightly observations of the satellite. We show that with a small data set, embedded unstable periodic orbits can be extracted and that these orbits can be responsible for nearly periodic behavior lasting a substantial fraction of the observing run.
Conductivity Cell Thermal Inertia Correction Revisited
NASA Astrophysics Data System (ADS)
Eriksen, C. C.
2012-12-01
Salinity measurements made with a CTD (conductivity-temperature-depth instrument) rely on accurate estimation of water temperature within their conductivity cell. Lueck (1990) developed a theoretical framework for heat transfer between the cell body and water passing through it. Based on this model, Lueck and Picklo (1990) introduced the practice of correcting for cell thermal inertia by filtering a temperature time series using two parameters, an amplitude α and a decay time constant τ, a practice now widely used. Typically these two parameters are chosen for a given cell configuration and internal flushing speed by a statistical method applied to a particular data set. Here, thermal inertia correction theory has been extended to apply to flow speeds spanning well over an order of magnitude, both within and outside a conductivity cell, to provide predictions of α and τ from cell geometry and composition. The extended model enables thermal inertia correction for the variable flows encountered by conductivity cells on autonomous gliders and floats, as well as tethered platforms. The length scale formed as the product of cell encounter speed of isotherms, α, and τ can be used to gauge the size of the temperature correction for a given thermal stratification. For cells flushed by dynamic pressure variation induced by platform motion, this length varies by less than a factor of 2 over more than a decade of speed variation. The magnitude of correction for free-flow flushed sensors is comparable to that of pumped cells, but at an order of magnitude in energy savings. Flow conditions around a cell's exterior are found to be of comparable importance to thermal inertia response as flushing speed. Simplification of cell thermal response to a single normal mode is most valid at slow speed. Error in thermal inertia estimation arises from both neglect of higher modes and numerical discretization of the correction scheme, both of which can be easily quantified
The spectroscopic orbit of Capella revisited
NASA Astrophysics Data System (ADS)
Weber, M.; Strassmeier, K. G.
2011-07-01
Context. Capella is among the few binary stars with two evolved giant components. The hotter component is a chromospherically active star within the Hertzsprung gap, while the cooler star is possibly helium-core burning. Aims: The known inclination of the orbital plane from astrometry in combination with precise radial velocities will allow very accurate masses to be determined for the individual Capella stars. This will constrain their evolutionary stage and possibly the role of the active star's magnetic field on the dynamical evolution of the binary system. Methods: We obtained a total of 438 high-resolution échelle spectra during the years 2007-2010 and used the measured velocities to recompute the orbital elements. Our double-lined orbital solution yields average residuals of 64 m s-1 for the cool component and 297 m s-1 for the more rapidly rotating hotter component. Results: The semi-amplitude of the cool component is smaller by 0.045 km s-1 than the orbit determination of Torres et al. from data taken during 1996-1999 but more precise by a factor of 5.5, while for the hotter component it is larger by 0.580 km s-1 and more precise by a factor of 3.6. This corresponds to masses of 2.573 ± 0.009 M⊙ and 2.488 ± 0.008 M⊙ for the cool and hot component, respectively. Their relative errors of 0.34% and 0.30% are about half of the values given in Torres et al. for a combined literature-data solution but with absolute values different by 4% and 2% for the two components, respectively. The mass ratio of the system is therefore q = MA/MB = 0.9673 ± 0.0020. Conclusions: Our orbit is the most precise and also likely to be the most accurate ever obtained for Capella. Based on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC.Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A89
Response variance in functional maps: neural darwinism revisited.
Takahashi, Hirokazu; Yokota, Ryo; Kanzaki, Ryohei
2013-01-01
The mechanisms by which functional maps and map plasticity contribute to cortical computation remain controversial. Recent studies have revisited the theory of neural Darwinism to interpret the learning-induced map plasticity and neuronal heterogeneity observed in the cortex. Here, we hypothesize that the Darwinian principle provides a substrate to explain the relationship between neuron heterogeneity and cortical functional maps. We demonstrate in the rat auditory cortex that the degree of response variance is closely correlated with the size of its representational area. Further, we show that the response variance within a given population is altered through training. These results suggest that larger representational areas may help to accommodate heterogeneous populations of neurons. Thus, functional maps and map plasticity are likely to play essential roles in Darwinian computation, serving as effective, but not absolutely necessary, structures to generate diverse response properties within a neural population.
Response Variance in Functional Maps: Neural Darwinism Revisited
Takahashi, Hirokazu; Yokota, Ryo; Kanzaki, Ryohei
2013-01-01
The mechanisms by which functional maps and map plasticity contribute to cortical computation remain controversial. Recent studies have revisited the theory of neural Darwinism to interpret the learning-induced map plasticity and neuronal heterogeneity observed in the cortex. Here, we hypothesize that the Darwinian principle provides a substrate to explain the relationship between neuron heterogeneity and cortical functional maps. We demonstrate in the rat auditory cortex that the degree of response variance is closely correlated with the size of its representational area. Further, we show that the response variance within a given population is altered through training. These results suggest that larger representational areas may help to accommodate heterogeneous populations of neurons. Thus, functional maps and map plasticity are likely to play essential roles in Darwinian computation, serving as effective, but not absolutely necessary, structures to generate diverse response properties within a neural population. PMID:23874733
Revisiting the Sch önbein ozone measurement methodology
NASA Astrophysics Data System (ADS)
Ramírez-González, Ignacio A.; Añel, Juan A.; Saiz-López, Alfonso; García-Feal, Orlando; Cid, Antonio; Mejuto, Juan Carlos; Gimeno, Luis
2017-04-01
Trough the XIX century the Schönbein method gained a lot of popularity by its easy way to measure tropospheric ozone. Traditionally it has been considered that Schönbein measurements are not accurate enough to be useful. Detractors of this method argue that it is sensitive to meteorological conditions, being the most important the influence of relative humidity. As a consequence the data obtained by this method have usually been discarded. Here we revisit this method taking into account that values measured during the 19th century were taken using different measurement papers. We explore several concentrations of starch and potassium iodide, the basis for this measurement method. Our results are compared with the previous ones existing in the literature. The validity of the Schönbein methodology is discussed having into account humidity and other meteorological variables.
Revisiting the Interaction between the Chaperone Skp and Lipopolysaccharide
Burmann, Björn M.; Holdbrook, Daniel A.; Callon, Morgane; Bond, Peter J.; Hiller, Sebastian
2015-01-01
The bacterial outer membrane comprises two main classes of components, lipids and membrane proteins. These nonsoluble compounds are conveyed across the aqueous periplasm along specific molecular transport routes: the lipid lipopolysaccharide (LPS) is shuttled by the Lpt system, whereas outer membrane proteins (Omps) are transported by chaperones, including the periplasmic Skp. In this study, we revisit the specificity of the chaperone-lipid interaction of Skp and LPS. High-resolution NMR spectroscopy measurements indicate that LPS interacts with Skp nonspecifically, accompanied by destabilization of the Skp trimer and similar to denaturation by the nonnatural detergent lauryldimethylamine-N-oxide (LDAO). Bioinformatic analysis of amino acid conservation, structural analysis of LPS-binding proteins, and MD simulations further confirm the absence of a specific LPS binding site on Skp, making a biological relevance of the interaction unlikely. Instead, our analysis reveals a highly conserved salt-bridge network, which likely has a role for Skp function. PMID:25809264
Revisiting the Scattering Greenhouse Effect of CO2 Ice Clouds
NASA Astrophysics Data System (ADS)
Kitzmann, D.
2016-02-01
Carbon dioxide ice clouds are thought to play an important role for cold terrestrial planets with thick CO2 dominated atmospheres. Various previous studies showed that a scattering greenhouse effect by carbon dioxide ice clouds could result in a massive warming of the planetary surface. However, all of these studies only employed simplified two-stream radiative transfer schemes to describe the anisotropic scattering. Using accurate radiative transfer models with a general discrete ordinate method, this study revisits this important effect and shows that the positive climatic impact of carbon dioxide clouds was strongly overestimated in the past. The revised scattering greenhouse effect can have important implications for the early Mars, but also for planets like the early Earth or the position of the outer boundary of the habitable zone.
Revisiting Johnson and Jackson boundary conditions for granular flows
Li, Tingwen; Benyahia, Sofiane
2012-07-01
In this article, we revisit Johnson and Jackson boundary conditions for granular flows. The oblique collision between a particle and a flat wall is analyzed by adopting the classic rigid-body theory and a more realistic semianalytical model. Based on the kinetic granular theory, the input parameter for the partial-slip boundary conditions, specularity coefficient, which is not measurable in experiments, is then interpreted as a function of the particle-wall restitution coefficient, the frictional coefficient, and the normalized slip velocity at the wall. An analytical expression for the specularity coefficient is suggested for a flat, frictional surface with a low frictional coefficient. The procedure for determining the specularity coefficient for a more general problem is outlined, and a working approximation is provided.
Energy in synthetic fertilizers and pesticides: Revisited. Final project report
Bhat, M.G.; English, B.C.; Turhollow, A.F.; Nyangito, H.O.
1994-01-01
Agricultural chemicals that are derived from fossil-fuels are the major energy intensive inputs in agriculture. Growing scarcity of the world`s fossil resources stimulated research and development of energy-efficient technology for manufacturing these chemicals in the last decade. The purpose of this study is to revisit the energy requirements of major plant nutrients and pesticides. The data from manufacturers energy survey conducted by The Fertilizer Institute are used to estimate energy requirements of fertilizers. Energy estimates for pesticides are developed from consulting previously published literature. The impact of technical innovation in the fertilizer industry to US corn, cotton, soybean and wheat producers is estimated in terms of energy-saving.
Kinetic theory of turbulence for parallel propagation revisited: Formal results
Yoon, Peter H.
2015-08-15
In a recent paper, Gaelzer et al. [Phys. Plasmas 22, 032310 (2015)] revisited the second-order nonlinear kinetic theory for turbulence propagating in directions parallel/anti-parallel to the ambient magnetic field. The original work was according to Yoon and Fang [Phys. Plasmas 15, 122312 (2008)], but Gaelzer et al. noted that the terms pertaining to discrete-particle effects in Yoon and Fang's theory did not enjoy proper dimensionality. The purpose of Gaelzer et al. was to restore the dimensional consistency associated with such terms. However, Gaelzer et al. was concerned only with linear wave-particle interaction terms. The present paper completes the analysis by considering the dimensional correction to nonlinear wave-particle interaction terms in the wave kinetic equation.
Revisiting vectorlike quark models with enhanced top Yukawa coupling
NASA Astrophysics Data System (ADS)
Hashimoto, Michio
2017-08-01
We revisit a scenario with an enhanced top Yukawa coupling in vectorlike quark (VLQ) models, where the top Yukawa coupling is larger than the standard model value and the lightest VLQ has a negative Yukawa coupling. We find that the parameter space satisfying the LHC bounds of the Higgs signal strengths consistently with the precision measurements is rather wide. Because the Lagrangian parameters of the Yukawa couplings are large, such scenario can be realized in some strongly interacting theories. It also turns out that there is a noticeable relation between the contributions of the triangle and box diagrams in the g g →h h process by using the lowest order of the 1 /M expansion where M is the heavy mass running in the loops.
Global Instability on Laminar Separation Bubbles-Revisited
NASA Technical Reports Server (NTRS)
Theofilis, Vassilis; Rodriquez, Daniel; Smith, Douglas
2010-01-01
In the last 3 years, global linear instability of LSB has been revisited, using state-of-the-art hardware and algorithms. Eigenspectra of LSB flows have been understood and classified in branches of known and newly-discovered eigenmodes. Major achievements: World-largest numerical solutions of global eigenvalue problems are routinely performed. Key aerodynamic phenomena have been explained via critical point theory, applied to our global mode results. Theoretical foundation for control of LSB flows has been laid. Global mode of LSB at the origin of observable phenomena. U-separation on semi-infinite plate. Stall cells on (stalled) airfoil. Receptivity/Sensitivity/AFC feasible (practical?) via: Adjoint EVP solution. Direct/adjoint coupling (the Crete connection). Minor effect of compressibility on global instability in the subsonic compressible regime. Global instability analysis of LSB in realistic supersonic flows apparently quite some way down the horizon.
Cardiovascular health in Canadian women: the bigger picture revisited.
Sawatzky, Jo-Ann V
2005-01-01
Cardiovascular disease (CVD) is the leading cause of death in Canadian women. Recent projections suggest that the number of cardiovascular-related deaths among women will continue to increase for at least another decade (Heart & Stroke Foundation of Canada, 2003). Nurses are in pivotal roles to facilitate the development of strategies to promote cardiovascular health and prevent CVD in this population. These strategies must move beyond the current focus on the individual, to encompass the bigger picture of population health promotion. This paper revisits the current state of knowledge of the population-based determinants of cardiovascular health in women, incorporates a Canadian perspective by including relevant epidemiological data, and recommends strategies that extend beyond the individual to the broader community, policy, health services and research domains.
A short revisit to Kuo-Brown effective interactions
NASA Astrophysics Data System (ADS)
Wang, XiaoBao; Dong, GuoXiang
2015-10-01
This paper is a short revisit to Kuo-Brown effective interaction derived from the Hamada-Johnston nucleon-nucleon potential, done by Gerry Brown and Tom Kuo. This effective interaction, derived in year 1966, is the first attempt to describe nuclear structure properties from the free nucleon-nucleon potential. Nowadays much progress has been achieved for the effective interactions in shell model. We would compare the effective interactions obtained in the 1966 paper with up-to-date shell-model interactions in sd-shell and pf-shell model space. Recent knowledge of effective interactions on nuclear structure, can also be traced in the Kuo- Brown effective interaction, i.e., the universal roles of central and tensor forces, which reminds us that such discovery should be noticed much earlier.
Feedback instability in the magnetosphere-ionosphere coupling system: Revisited
Watanabe, T.-H.
2010-02-15
A coupled set of the reduced magnetohydrodynamic and the two-fluid equations is applied to the magnetosphere-ionosphere (M-I) feedback interactions in relation to growth of quite auroral arcs. A theoretical analysis revisiting the linear feedback instability reveals asymptotic behaviors of the dispersion relation and a non-Hermite property in the M-I coupling. A nonlinear simulation of the feedback instability in the M-I coupling system manifests growth of the Kelvin-Helmholtz-like mode in the magnetosphere as the secondary instability. The distorted vortex and field-aligned current profiles propagating as the shear Alfven waves lead to spontaneous deformation of ionospheric density and current structures associated with auroral arcs.
How clonal are Neisseria species? The epidemic clonality model revisited.
Tibayrenc, Michel; Ayala, Francisco J
2015-07-21
The three species Neisseria meningitidis, Neisseria gonorrheae, and Neisseria lactamica are often regarded as highly recombining bacteria. N. meningitidis has been considered a paradigmatic case of the "semiclonal model" or of "epidemic clonality," demonstrating occasional bouts of clonal propagation in an otherwise recombining species. In this model, occasional clonality generates linkage disequilibrium in the short term. In the long run, however, the effects of clonality are countered by recombination. We show that many data are at odds with this proposal and that N. meningitidis fits the criteria that we have proposed for predominant clonal evolution (PCE). We point out that (i) the proposed way to distinguish epidemic clonality from PCE may be faulty and (ii) the evidence of deep phylogenies by microarrays and whole-genome sequencing is at odds with the predictions of the semiclonal model. Last, we revisit the species status of N. meningitidis, N. gonorrheae, and N. lactamica in the light of the PCE model.
Willis elastodynamic homogenization theory revisited for periodic media
NASA Astrophysics Data System (ADS)
Nassar, H.; He, Q.-C.; Auffray, N.
2015-04-01
The theory of elastodynamic homogenization initiated by J.R. Willis is revisited for periodically inhomogeneous media through a careful scrutiny of the main aspects of that theory in the 3D continuum context and by applying it to the thorough treatment of a simple 1D discrete periodic system. The Bloch theorem appears to be central to appropriately defining and interpreting effective fields. Based on some physical arguments, three necessary conditions are derived for the transition from the microscopic description to the macroscopic description of periodic media. The parameters involved in the Willis effective constitutive relation are expressed in terms of two localization tensors and specified with the help of the corresponding Green function in the spirit of micromechanics. These results are illustrated and discussed for the 1D discrete periodic system considered. In particular, inspired by Brillouin's study, the dependency of the effective constitutive parameters on the frequency is physically interpreted in terms of oscillation modes of the underlying microstructure.
Neuroticism and vigilance revisited: A transcranial doppler investigation.
Mandell, Arielle R; Becker, Alexandra; VanAndel, Aaron; Nelson, Andrew; Shaw, Tyler H
2015-11-01
Selecting for vigilance assignments remains an important factor in human performance research. The current study revisits the potential relationship between vigilance performance and trait neuroticism, in light of two possible theories. The first theory suggests that neuroticism impairs vigilance performance by competing for available resources. The second theory, attentional control theory, posits that high neuroticism can result in similar or superior performance levels due to the allocation of compensatory effort. In the present study, Transcranial Doppler Sonography was used to investigate the neurophysiological underpinnings of neuroticism during a 12-min abbreviated vigilance task. Performance results were not modified by level of neuroticism, but high neuroticism was associated with higher initial CBFV levels and a greater CBFV decrement over time. These findings indicate that participants higher in neuroticism recruited additional cognitive resources in order to achieve similar performance, suggesting that there is more of an effect on processing efficiency than effectiveness.
Feedback instability in the magnetosphere-ionosphere coupling system: Revisited
NASA Astrophysics Data System (ADS)
Watanabe, T.-H.
2010-02-01
A coupled set of the reduced magnetohydrodynamic and the two-fluid equations is applied to the magnetosphere-ionosphere (M-I) feedback interactions in relation to growth of quite auroral arcs. A theoretical analysis revisiting the linear feedback instability reveals asymptotic behaviors of the dispersion relation and a non-Hermite property in the M-I coupling. A nonlinear simulation of the feedback instability in the M-I coupling system manifests growth of the Kelvin-Helmholtz-like mode in the magnetosphere as the secondary instability. The distorted vortex and field-aligned current profiles propagating as the shear Alfvén waves lead to spontaneous deformation of ionospheric density and current structures associated with auroral arcs.
Revisiting the Design of a Fusion Development Facility
NASA Astrophysics Data System (ADS)
Chan, V. S.; Stambaugh, R. D.; Garofalo, A. M.; Smith, J. P.; Wong, C. P. C.
2009-11-01
A Fusion Development Facility (FDF) is proposed to make possible a DEMO of the ARIES-AT type as the next step after ITER. The mission of the FDF should be to carry forward advanced tokamak physics and enable development of fusion nuclear science and technology. We have added more realism to the initial FDF concept [1] including inner and outer gaps from the plasma to the first wall; an improved estimate of the inboard/outboard blanket/shield thickness to protect the magnets/insulators; control coil positions; and realistic divertor geometry. Optimizing the mix of heating and current drive power has high leverage on the operating power. We have also revisited the assumed impurity fraction and the density profile peakedness. 8pt [1] R.D. Stambaugh, et al., Bull. Am. Phys. Soc. 53, 259 (2008).
Brane inflation revisited after WMAP five-year results
Ma, Yin-Zhe; Zhang, Xin E-mail: zhangxin@mail.neu.edu.cn
2009-03-15
In this paper, we revisit brane inflation models with the WMAP five-year results. The WMAP five-year data favor a red-tilted power spectrum of primordial fluctuations at the level of two standard deviations, which is the same as the WMAP three-year result qualitatively, but quantitatively the spectral index is slightly greater than the three-year value. This result can bring impacts on brane inflation models. According to the WMAP five-year data, we find that the KKLMMT model can survive at the level of one standard deviation, and the fine-tuning of the parameter {beta} can be alleviated to a certain extent at the level of two standard deviations.
Axial Electron Heat Loss From Mirror Devices Revisited
Ryutov, D
2004-08-16
An issue of the axial electron heat loss is of a significant importance for mirror-based fusion devices. This problem has been considered in a number of publications but it is still shrouded in misconceptions. In this paper we revisit it once again. We discuss the following issues: (1) Formation of the electron distribution function in the end tank at large expansion ratios; (2) The secondary emission from the end plates and the ways of suppressing it (if needed); (3) Ionization and charge exchange in the presence of neutrals in the end tanks; (4) Instabilities caused by the peculiar shape of the electron distribution function and their possible impact on the electron heat losses; (5) Electron heat losses in the pulsed mode of operation of mirror devices.
Revisiting the thermodynamic relations in AdS /CMT models
NASA Astrophysics Data System (ADS)
Hyun, Seungjoon; Park, Sang-A.; Yi, Sang-Heon
2017-03-01
Motivated by the recent unified approach to the Smarr-like relation of anti-de Sitter (AdS) planar black holes in conjunction with the quasilocal formalism on conserved charges, we revisit the quantum statistical and thermodynamic relations of hairy AdS planar black holes. By extending the previous results, we identify the hairy contribution in the bulk and show that the holographic computation can be improved so that it is consistent with the bulk computation. We argue that the first law can be retained in its universal form and that the relation between the on-shell renormalized Euclidean action and its free energy interpretation in gravity may also be undeformed even with the hairy contribution in hairy AdS black holes.
Dark matter relic density in scalar-tensor gravity revisited
Meehan, Michael T.; Whittingham, Ian B. E-mail: Ian.Whittingham@jcu.edu.au
2015-12-01
We revisit the calculation of dark matter relic abundances in scalar-tensor gravity using a generic form A(φ{sub *}) = e{sup βφ{sub *}{sup 2/2}} for the coupling between the scalar field φ{sub *} and the metric, for which detailed Big Bang Nucleosynthesis constraints are available. We find that BBN constraints restrict the modified expansion rate in these models to be almost degenerate with the standard expansion history at the time of dark matter decoupling. In this case the maximum level of enhancement of the dark matter relic density was found to be a factor of ∼ 3, several orders of magnitude below that found in previous investigations.
Reduplication revisited: functions, constraints, repairs, and clinical implications.
Klein, Harriet B
2005-02-01
This case study considers the phonological forms of early lexical items produced by 1 normally developing boy, from 19 to 22 months of age, who began to produce all monosyllabic words as bisyllabic. In order to link this empirical data (the apparent creation of increased complexity) with universal tendencies (motivated by the reduction of complexity), the functions of reduplication were revisited. Phonological processes (i.e., reduplication and final consonant deletion) are viewed as repairs motivated by 2 interacting constraints (i.e., constraints on monosyllabic words and on word-final consonants). These longitudinal case study data provide further evidence for a relationship between final consonant deletion and reduplication. A possible treatment approach for similar patterns demonstrated clinically is recommended.
Revisiting mental simulation in language comprehension: six replication attempts.
Zwaan, Rolf A; Pecher, Diane
2012-01-01
The notion of language comprehension as mental simulation has become popular in cognitive science. We revisit some of the original empirical evidence for this. Specifically, we attempted to replicate the findings from earlier studies that examined the mental simulation of object orientation, shape, and color, respectively, in sentence-picture verification. For each of these sets of findings, we conducted two web-based replication attempts using Amazon's Mechanical Turk. Our results are mixed. Participants responded faster to pictures that matched the orientation or shape implied by the sentence, replicating the original findings. The effect was larger and stronger for shape than orientation. Participants also responded faster to pictures that matched the color implied by the sentence, whereas the original studies obtained mismatch advantages. We argue that these results support mental simulation theory, show the importance of replication studies, and show the viability of web-based data collection.
Revisiting Public Health Challenges in the New Millennium
Anish, TS; Sreelakshmi, PR
2013-01-01
Positive Health of the communities could only be brought out through the interrelationship between conventional health sector and other development sectors. It was a dream that came true when World Health Organization (WHO) accepted Primary Health Care (PHC) as the major tool to achieve its proposed goal of Health For All (HFA) by 2000 A.D., but we could not succeed as expected. Now we have the Millennium Development Goals (MDG), which place health at the heart of development but the achievements in health is still challenging. The literature search in this article has been conducted in Pub Med and Google scholar, with the aim to draw references to discuss the major health issues and ways to tackle them. The current article briefly narrates the burden and complexities of challenges faced by the present global health. Revisiting the concept of PHC and reaffirming our solidarity to this philosophy is the need of this hour. PMID:24116303
The roles of kisspeptin revisited: inside and outside the hypothalamus
UENOYAMA, Yoshihisa; PHENG, Vutha; TSUKAMURA, Hiroko; MAEDA, Kei-ichiro
2016-01-01
Kisspeptin, encoded by KISS1/Kiss1 gene, is now considered a master regulator of reproductive functions in mammals owing to its involvement in the direct activation of gonadotropin-releasing hormone (GnRH) neurons after binding to its cognate receptor, GPR54. Ever since the discovery of kisspeptin, intensive studies on hypothalamic expression of KISS1/Kiss1 and on physiological roles of hypothalamic kisspeptin neurons have provided clues as to how the brain controls sexual maturation at the onset of puberty and subsequent reproductive performance in mammals. Additionally, emerging evidence indicates the potential involvement of extra-hypothalamic kisspeptin in reproductive functions. Here, we summarize data regarding kisspeptin inside and outside the hypothalamus and revisit the physiological roles of central and peripheral kisspeptins in the reproductive functions of mammals. PMID:27478063
A revisited auditing of the analytical abstracts database
Diospatonyi; Horvai; Braun
2000-09-01
This paper is a follow-up of a previous one dealing with the "Image of Analytical Chemistry as Reflected in the Analytical Abstracts Database: Journal Coverage, Concentration and Dispersion of the Analytical Literature" (J. Chem. Inf. Comput. Sci. 1993, 33, 164-173). It deals with revisiting these topics. The results have shown that the database has substantially improved its coverage by editorial reorganizations in 1994. The only open problem which has been revealed is a somewhat excessive emphasis given to the coverage of the journals on the lower tail of the journal distribution. The suggestion is made to reduce this emphasis in favor of an even more complete coverage of some "titled" analytical journals.
The Safety of Adjuvanted Vaccines Revisited: Vaccine-Induced Narcolepsy.
Ahmed, S Sohail; Montomoli, Emanuele; Pasini, Franco Laghi; Steinman, Lawrence
2016-01-01
Despite the very high benefit-to-risk ratio of vaccines, the fear of negative side effects has discouraged many people from getting vaccinated, resulting in the reemergence of previously controlled diseases such as measles, pertussis and diphtheria. This fear has been amplified more recently by multiple epidemiologic studies that confirmed the link of an AS03-adjuvanted pandemic influenza vaccine (Pandemrix, GlaxoSmithKline Biologicals, Germany) used in Europe during the 2009 H1N1 influenza pandemic [A(H1N1) pdm09] with the development of narcolepsy, a chronic sleep disorder, in children and adolescents. However, public misperceptions of what adjuvants are and why they are used in vaccines has created in some individuals a closed "black box" attitude towards all vaccines. The focus of this review article is to revisit this "black box" using the example of narcolepsy associated with the European AS03-adjuvanted pandemic influenza vaccine.
Revisiting Mental Simulation in Language Comprehension: Six Replication Attempts
Zwaan, Rolf A.; Pecher, Diane
2012-01-01
The notion of language comprehension as mental simulation has become popular in cognitive science. We revisit some of the original empirical evidence for this. Specifically, we attempted to replicate the findings from earlier studies that examined the mental simulation of object orientation, shape, and color, respectively, in sentence-picture verification. For each of these sets of findings, we conducted two web-based replication attempts using Amazon's Mechanical Turk. Our results are mixed. Participants responded faster to pictures that matched the orientation or shape implied by the sentence, replicating the original findings. The effect was larger and stronger for shape than orientation. Participants also responded faster to pictures that matched the color implied by the sentence, whereas the original studies obtained mismatch advantages. We argue that these results support mental simulation theory, show the importance of replication studies, and show the viability of web-based data collection. PMID:23300547
Godwin, Hayward J; Reichle, Erik D; Menneer, Tamaryn
2016-06-20
An important question about eye-movement behavior is when the decision is made to terminate a fixation and program the following saccade. Different approaches have found converging evidence in favor of a mixed-control account, in which there is some overlap between processing information at fixation and planning the following saccade. We examined one interesting instance of mixed control in visual search: lag-2 revisits, during which observers fixate a stimulus, move to a different stimulus, and then revisit the first stimulus on the next fixation. Results show that the probability of lag-2 revisits occurring increased with the number of target-similar stimuli, and revisits were preceded by a brief fixation on the intervening distractor stimulus. We developed the Efficient Visual Sampling (EVS) computational model to simulate our findings (fixation durations and fixation locations) and to provide insight into mixed control of fixations and the perceptual, cognitive, and motor processes that produce lag-2 revisits.
Revisiting Black Holes as Dark Matter
NASA Astrophysics Data System (ADS)
Kohler, Susanna
2017-02-01
Could dark matter be made of intermediate-mass black holes formed in the beginning of the universe? A recent study takes a renewed look at this question.Galactic LurkersThe nature of dark matter has long been questioned, but the recent discovery of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) has renewed interest in the possibility that dark matter could consist of primordial black holes in the mass range of 101000 solar masses.The relative amounts of the different constituents of the universe. Dark matter makes up roughly 27%. [ESA/Planck]According to this model, the extreme density of matter present during the universes early expansion led to the formation of a large number of intermediate-mass black holes. These black holes now hide in the halos of galaxies, constituting the mass that weve measured dynamically but remains unseen.LIGOs first gravitational-wave detection revealed the merger of two black holes that were both tens of solar masses in size. If primordial black holes are indeed a major constituent of dark matter, then LIGOs detection is consistent with what we would expect to find: occasional mergers of the intermediate-mass black holes that formed in the early universe and now lurk in galactic halos.Quasar MicrolensingTheres a catch, however. If there truly were a large number of intermediate-mass primordial black holes hiding in galactic halos, they wouldnt go completely unnoticed: we would see signs of their presence in the gravitational microlensing of background quasars. Unseen primordial black holes in a foreground galaxy could cause an image of a background quasar to briefly brighten which would provide us with clear evidence of such black holes despite our not being able to detect them directly.A depiction of quasar microlensing (click for a closer look!). The microlensing object in the foreground galaxy could be a star (as depicted), a primordial black hole, or any other compact object. [NASA
The Primordial Abundance of 4He Revisited
NASA Astrophysics Data System (ADS)
Izotov, Yuri I.; Thuan, Trinh X.
1998-06-01
-forming dwarf galaxies that satisfy all the observational constraints. Our Yp gives Ωbh250=0.058+/-0.007, consistent with the lower limit set by dynamical measurements and X-ray observations of clusters of galaxies. It is also consistent, within the framework of standard big bang nucleosynthesis theory, with measurements of primordial 7Li in galactic halo stars, and at the 1 σ level with the D/H abundance measured in absorption systems toward quasars by Tytler & Burles.
BHQ revisited (1) - Looking at grain size
NASA Astrophysics Data System (ADS)
Heilbronner, Renée; Kilian, Rüdiger; Tullis, Jan
2016-04-01
microstructure and texture analysis of Heilbronner & Tullis (2006). Here, in poster (1), we focus on the recrystallized grain size with the aim of (a) comparing CIP- and EBSD derived grain size measurements, (b) of comparing the recrystallized grain size of coaxially deformed and sheared BHQ and (c) in order to confirm that the quartz piezometer indeed depends on texture, and (d) to test if it also depends on the type of deformation (irrotational versus rotational deformation). References cited: Heilbronner, R., and S.D. Barrett (2014) Image Analysis in Earth Sciences, Springer. Heilbronner, R., and J. Tullis (2002), The effect of static annealing on micro- structure and crystallographic preferred orientations of quartzites experimentally deformed in axial compression and shear, Geol. Soc. Spec. Publ., 200, 191 - 218. Heilbronner, R., and J. Tullis (2006), Evolution of c axis pole figures and grain size during dynamic recrystallization: Results from experimentally sheared quartzite. JGR, 111, B10202, doi:10.1029/2005JB004194, 2006 Hirth, G., and J. Tullis (1992), Dislocation creep regimes in quartz aggregates, JSG, 14, 145-159. Stipp, M., and J. Tullis (2003), The recrystallized grain size piezometer for quartz, Geophys. Res. Lett., 30(21), 2088, doi:10.1029/2003GL018444.
Sparse RNA folding revisited: space-efficient minimum free energy structure prediction.
Will, Sebastian; Jabbari, Hosna
2016-01-01
RNA secondary structure prediction by energy minimization is the central computational tool for the analysis of structural non-coding RNAs and their interactions. Sparsification has been successfully applied to improve the time efficiency of various structure prediction algorithms while guaranteeing the same result; however, for many such folding problems, space efficiency is of even greater concern, particularly for long RNA sequences. So far, space-efficient sparsified RNA folding with fold reconstruction was solved only for simple base-pair-based pseudo-energy models. Here, we revisit the problem of space-efficient free energy minimization. Whereas the space-efficient minimization of the free energy has been sketched before, the reconstruction of the optimum structure has not even been discussed. We show that this reconstruction is not possible in trivial extension of the method for simple energy models. Then, we present the time- and space-efficient sparsified free energy minimization algorithm SparseMFEFold that guarantees MFE structure prediction. In particular, this novel algorithm provides efficient fold reconstruction based on dynamically garbage-collected trace arrows. The complexity of our algorithm depends on two parameters, the number of candidates Z and the number of trace arrows T; both are bounded by [Formula: see text], but are typically much smaller. The time complexity of RNA folding is reduced from [Formula: see text] to [Formula: see text]; the space complexity, from [Formula: see text] to [Formula: see text]. Our empirical results show more than 80 % space savings over RNAfold [Vienna RNA package] on the long RNAs from the RNA STRAND database (≥2500 bases). The presented technique is intentionally generalizable to complex prediction algorithms; due to their high space demands, algorithms like pseudoknot prediction and RNA-RNA-interaction prediction are expected to profit even stronger than "standard" MFE folding. SparseMFEFold is free
Curvature perturbation and domain wall formation with pseudo scaling scalar dynamics
Ema, Yohei; Nakayama, Kazunori; Takimoto, Masahiro E-mail: kazunori@hep-th.phys.s.u-tokyo.ac.jp
2016-02-01
Cosmological dynamics of scalar field with a monomial potential φ{sup n} with a general background equation of state is revisited. It is known that if n is smaller than a critical value, the scalar field exhibits a coherent oscillation and if n is larger it obeys a scaling solution without oscillation. We study in detail the case where n is equal to the critical value, and find a peculiar scalar dynamics which is neither oscillating nor scaling solution, and we call it a pseudo scaling solution. We also discuss cosmological implications of a pseudo scaling scalar dynamics, such as the curvature perturbation and the domain wall problem.
Lee, Seoyoung; Kim, Eun-Kyung
2017-06-01
The purpose of this study was to investigate medical service quality, satisfaction and to examine factors influencing hospital revisit intention of the United Arab Emirates government sponsored patients in Korea. A total of 152 UAE government sponsored patients who visited Korean hospitals participated in the questionnaire survey from August to November 2016. Stepwise multiple regression was used to identify the factors that affected the revisit intention of the participants. The mean scores of medical service quality, satisfaction, and revisit intention were 5.72 out of 7, 88.88 out of 100, 4.59 out of 5, respectively. Medical service quality and satisfaction, Medical service quality and revisit intention, satisfaction and revisit intention were positively correlated. Medical service of physician, visiting routes and responsiveness of medical service quality explained about 23.8% of revisit intention. There are needs for physicians to communicate with patients while ensuring sufficient consultation time based on excellent medical skills and nurses to respond immediately for the patients' needs through an empathic encounter in order to improve medical service quality and patient satisfaction so that to increase the revisit intention of the United Arab Emirates government sponsored patients. Further, it is necessary for the hospitals to have support plans for providing country specialized services in consideration of the UAE culture to ensure that physicians' and nurses' competencies are not undervalued by non-medical service elements such as interpreters and meals. Copyright © 2017. Published by Elsevier B.V.
Asao, Keiko; McEwen, Laura N; Crosson, Jesse C; Waitzfelder, Beth; Herman, William H
2014-01-01
To describe patient and provider characteristics associated with outpatient revisit frequency and to examine the associations between the revisit frequency and the processes and intermediate outcomes of diabetes care. We analyzed data from Translating Research Into Action for Diabetes (TRIAD), a prospective, multicenter, observational study of diabetes care in managed care. Our analysis included 6040 eligible adult participants with type 2 diabetes (42.6% ≥65 years of age, 54.1% female) whose primary care providers were the main provider of the participants' diabetes care. The median (interquartile range) revisit frequency was 4.0 (3.7, 6.0) visits per year. Being female, having lower education, lower income, more complex diabetes treatment, cardiovascular disease, higher Charlson comorbidity index, and impaired mobility were associated with higher revisit frequency. The proportion of participants who had annual assessments of HbA1c and LDL-cholesterol, foot examinations, advised or documented aspirin use, and influenza immunizations were higher for those with higher revisit frequency. The proportion of participants who met HbA1c (<9.5%) and LDL-cholesterol (<130 mg/dL) treatment goals were higher for those with a higher revisit frequency. The predicted probabilities of achieving more aggressive goals, HbA1c <8.5%, LDL-cholesterol <100mg/dL, and blood pressure <130/85 or even <140/90 mmHg were not associated with higher revisit frequency. Revisit frequency was highly variable and was associated with both sociodemographic characteristics and disease severity. A higher revisit frequency was associated with better processes of diabetes care, but the association with intermediate outcomes was less clear. Copyright © 2014 Elsevier Inc. All rights reserved.
Asao, Keiko; McEwen, Laura N.; Crosson, Jesse C.; Waitzfelder, Beth; Herman, William H.
2014-01-01
Objective To describe patient and provider characteristics associated with outpatient revisit frequency and to examine the associations between the revisit frequency and the processes and intermediate outcomes of diabetes care. Research Design and Methods We analyzed data from Translating Research Into Action for Diabetes (TRIAD), a prospective, multicenter, observational study of diabetes care in managed care. Results Our analysis included 6,040 eligible adult participants with type 2 diabetes (42.6% ≥ 65 years of age, 54.1% female) whose primary care providers were the main provider of the participants’ diabetes care. The median (interquartile range) revisit frequency was 4.0 (3.7, 6.0) visits per year. Being female, having lower education, lower income, more complex diabetes treatment, cardiovascular disease, higher Charlson comorbidity index, and impaired mobility were associated with higher revisit frequency. The proportion of participants who had annual assessments of HbA1c and LDL-cholesterol, foot examinations, advised or documented aspirin use, and influenza immunizations were higher for those with higher revisit frequency. The proportion of participants who met HbA1c (<9.5%) and LDL-cholesterol (<130 mg/dL) treatment goals was higher for those with a higher revisit frequency. The predicted probabilities of achieving more aggressive goals, HbA1c <8.5%, LDL-cholesterol <100 mg/dL, and blood pressure <130/85 or even <140/90 mmHg were not associated with higher revisit frequency. Conclusions Revisit frequency was highly variable and was associated with both sociodemographic characteristics and disease severity. A higher revisit frequency was associated with better processes of diabetes care, but the association with intermediate outcomes was less clear. PMID:25044233
V838 Monocerotis revisited: Space phenomenon imitates art
NASA Astrophysics Data System (ADS)
2004-03-01
V838 Monocerotis revisited: Space phenomenon imitates art hi-res Size hi-res: 558 Kb Credits: NASA, the Hubble Heritage Team (AURA/STScI) and ESA V838 Monocerotis revisited: Space phenomenon imitates art "Starry Night", Vincent van Gogh's famous painting, is renowned for its bold whorls of light sweeping across a raging night sky. Although this image of the heavens came only from the artist's restless imagination, a new picture from the NASA/ESA Hubble Space Telescope bears remarkable similarities to the van Gogh work, complete with never-before-seen spirals of dust swirling across trillions of kilometres of interstellar space. This image, obtained with the Advanced Camera for Surveys on February 8, 2004, is Hubble's latest view of an expanding halo of light around a distant star, named V838 Monocerotis (V838 Mon). The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a flashbulb-like pulse of light two years ago. V838 Mon is located about 20,000 light-years away from Earth in the direction of the constellation Monoceros, placing the star at the outer edge of our Milky Way galaxy V838 Monocerotis revisited: Space phenomenon imitates art hi-res Size hi-res: 1989 kb Credits: NASA, the Hubble Heritage Team (AURA/STScI) and ESA V838 Monocerotis revisited: Space phenomenon imitates art "Starry Night", Vincent van Gogh's famous painting, is renowned for its bold whorls of light sweeping across a raging night sky. Although this image of the heavens came only from the artist's restless imagination, a new picture from the NASA/ESA Hubble Space Telescope bears remarkable similarities to the van Gogh work, complete with never-before-seen spirals of dust swirling across trillions of kilometres of interstellar space. This image, obtained with the Advanced Camera for Surveys on February 8, 2004, is Hubble's latest view of an expanding halo of light around a distant star, named V838 Monocerotis (V838 Mon). The
Advanced Single-Aisle Transport Propulsion Design Options Revisited
NASA Technical Reports Server (NTRS)
Guynn, Mark D.; Berton, Jeffrey J.; Tong, Michael T.; Haller, William J.
2013-01-01
Future propulsion options for advanced single-aisle transports have been investigated in a number of previous studies by the authors. These studies have examined the system level characteristics of aircraft incorporating ultra-high bypass ratio (UHB) turbofans (direct drive and geared) and open rotor engines. During the course of these prior studies, a number of potential refinements and enhancements to the analysis methodology and assumptions were identified. This paper revisits a previously conducted UHB turbofan fan pressure ratio trade study using updated analysis methodology and assumptions. The changes incorporated have decreased the optimum fan pressure ratio for minimum fuel consumption and reduced the engine design trade-offs between minimizing noise and minimizing fuel consumption. Nacelle drag and engine weight are found to be key drivers in determining the optimum fan pressure ratio from a fuel efficiency perspective. The revised noise analysis results in the study aircraft being 2 to 4 EPNdB (cumulative) quieter due to a variety of reasons explained in the paper. With equal core technology assumed, the geared engine architecture is found to be as good as or better than the direct drive architecture for most parameters investigated. However, the engine ultimately selected for a future advanced single-aisle aircraft will depend on factors beyond those considered here.
Automated Guidance for Thermodynamics Essays: Critiquing Versus Revisiting
NASA Astrophysics Data System (ADS)
Donnelly, Dermot F.; Vitale, Jonathan M.; Linn, Marcia C.
2015-12-01
Middle school students struggle to explain thermodynamics concepts. In this study, to help students succeed, we use a natural language processing program to analyze their essays explaining the aspects of thermodynamics and provide guidance based on the automated score. The 346 sixth-grade students were assigned to either the critique condition where they criticized an explanation or the revisit condition where they reviewed visualizations. Within each condition, the student was assigned one of two types of tailored guidance based on the sophistication of their original essay. Both forms of guidance led to significant improvement in student understanding on the posttest. Guidance was more effective for students with low prior knowledge than for those with high prior knowledge (consistent with regression toward the mean). However, analysis of student responses to the guidance illustrates the value of aligning guidance with prior knowledge. All students were required to revise their essay as an embedded assessment. While effective, teachers involved in this study reported that revising is resisted by students and does not align with typical, vocabulary-focused classroom writing activities.
Revisiting reflexology: Concept, evidence, current practice, and practitioner training
Embong, Nurul Haswani; Soh, Yee Chang; Ming, Long Chiau; Wong, Tin Wui
2015-01-01
Reflexology is basically a study of how one part of the human body relates to another part of the body. Reflexology practitioners rely on the reflexes map of the feet and hands to all the internal organs and other human body parts. They believe that by applying the appropriate pressure and massage certain spots on the feet and hands, all other body parts could be energized and rejuvenated. This review aimed to revisit the concept of reflexology and examine its effectiveness, practices, and the training for reflexology practitioners. PubMed, SCOPUS, Google Scholar, and SpringerLink databases were utilized to search the following medical subject headings or keywords: foot massage, reflexology, foot reflexotherapy, reflexological treatment, and zone therapy. The articles published for the last 10 years were included. Previous systematic reviews failed to show concrete evidence for any specific effect of reflexology in any conditions. Due to its non-invasive, non-pharmacological complementary nature, reflexology is widely accepted and anecdotal evidence of positive effect reflexology in a variety of health conditions are available. Adequate training for practitioners is necessary to ensure the consistency of service provided. PMID:26587391
Revisiting Supernova 1987A constraints on dark photons
Chang, Jae Hyeok; Essig, Rouven; McDermott, Samuel D.
2017-01-25
We revisit constraints on dark photons with masses below ~ 100 MeV from the observations of Supernova 1987A. If dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. For the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter,ϵ, in this environment. This causes the constraints on ϵ to weaken with the dark-photon mass below ~ 15 MeV. For large-enough values of ϵ, it is well known that dark photons can be reabsorbed within the supernova. Since the rates ofmore » reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the Wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. Furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. Finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. Finally, this work clarifies the bounds from SN1987A on the dark-photon parameter space.« less
Revisiting the first fluid interface experiment in space
NASA Astrophysics Data System (ADS)
Chen, Yongkang; Weislogel, Mark; Masica, William; Kohl, Fred; Green, Robert
2016-11-01
This year marks the 54th anniversary of the first fluid physics experiment performed aboard a spacecraft during the Mercury-Atlas 7 mission (MA7). The MA7 experiment test cell served as an early model for a spacecraft liquid fuel tank consisting of a circular standpipe mounted within a spherical container. The low-g free surface configuration was dependent on contact angle, fluid fill fraction, standpipe dimensions, and initial conditions. Well-behaved symmetric equilibrium interfaces in the symmetric tank were expected and observed during the historic flight. We revisit the problem here employing a modern numerical tool and discover a rich variety of asymmetric fluid interface configurations that were not observed during the experiment. Interestingly, experimental support for these newly-computed outcomes may be found in 54 year old drop tower data collected by the original NASA investigator team. In short, rotationally symmetric nodoidal surfaces are unstable in a certain domain giving rise to highly asymmetric surfaces with significant shifts in the mass center of the liquid. The NASA team selected a fluid fill level for MA7 that 'fortunately' fell outside this domain. NASA NNX12A047A.
Biogas from Macroalgae: is it time to revisit the idea?
2012-01-01
The economic and environmental viability of dedicated terrestrial energy crops is in doubt. The production of large scale biomass (macroalgae) for biofuels in the marine environment was first tested in the late 1960’s. The culture attempts failed due to the engineering challenges of farming offshore. However the energy conversion via anaerobic digestion was successful as the biochemical composition of macroalgae makes it an ideal feedstock. The technology for the mass production of macroalgae has developed principally in China and Asia over the last 50 years to such a degree that it is now the single largest product of aquaculture. There has also been significant technology transfer and macroalgal cultivation is now well tried and tested in Europe and America. The inherent advantage of production of biofuel feedstock in the marine environment is that it does not compete with food production for land or fresh water. Here we revisit the idea of the large scale cultivation of macroalgae at sea for subsequent anaerobic digestion to produce biogas as a source of renewable energy, using a European case study as an example. PMID:23186536
Revisiting Supernova 1987A constraints on dark photons
NASA Astrophysics Data System (ADS)
Chang, Jae Hyeok; Essig, Rouven; McDermott, Samuel D.
2017-01-01
We revisit constraints on dark photons with masses below ˜ 100 MeV from the observations of Supernova 1987A. If dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. For the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter, ɛ, in this environment. This causes the constraints on ɛ to weaken with the dark-photon mass below ˜ 15 MeV. For large-enough values of ɛ, it is well known that dark photons can be reabsorbed within the supernova. Since the rates of reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the Wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. Furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. Finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. This work clarifies the bounds from SN1987A on the dark-photon parameter space.
Cation dyshomeostasis and cardiomyocyte necrosis: the Fleckenstein hypothesis revisited
Borkowski, Brian J.; Cheema, Yaser; Shahbaz, Atta U.; Bhattacharya, Syamal K.; Weber, Karl T.
2011-01-01
An ongoing loss of cardiomyocytes to apoptotic and necrotic cell death pathways contributes to the progressive nature of heart failure. The pathophysiological origins of necrotic cell loss relate to the neurohormonal activation that accompanies acute and chronic stressor states and which includes effector hormones of the adrenergic nervous system. Fifty years ago, Albrecht Fleckenstein and coworkers hypothesized the hyperadrenergic state, which accompanies such stressors, causes cardiomyocyte necrosis based on catecholamine-initiated excessive intracellular Ca2+ accumulation (EICA), and mitochondrial Ca2+ overloading in particular, in which the ensuing dysfunction and structural degeneration of these organelles leads to necrosis. In recent years, two downstream factors have been identified which, together with EICA, constitute a signal–transducer–effector pathway: (i) mitochondria-based induction of oxidative stress, in which the rate of reactive oxygen metabolite generation exceeds their rate of detoxification by endogenous antioxidant defences; and (ii) the opening of the mitochondrial inner membrane permeability transition pore (mPTP) followed by organellar swelling and degeneration. The pathogenesis of stress-related cardiomyopathy syndromes is likely related to this pathway. Other factors which can account for cytotoxicity in stressor states include: hypokalaemia; ionized hypocalcaemia and hypomagnesaemia with resultant elevations in parathyroid hormone serving as a potent mediator of EICA; and hypozincaemia with hyposelenaemia, which compromise antioxidant defences. Herein, we revisit the Fleckenstein hypothesis of EICA in leading to cardiomyocyte necrosis and the central role played by mitochondria. PMID:21398641
Spectroscopic properties of photosystem II reaction center revisited.
Gelzinis, Andrius; Abramavicius, Darius; Ogilvie, Jennifer P; Valkunas, Leonas
2017-09-21
Photosystem II (PSII) is the only biological system capable of splitting water to molecular oxygen. Its reaction center (RC) is responsible for the primary charge separation that drives the water oxidation reaction. In this work, we revisit the spectroscopic properties of the PSII RC using the complex time-dependent Redfield (ctR) theory for optical lineshapes [A. Gelzinis et al., J. Chem. Phys. 142, 154107 (2015)]. We obtain the PSII RC model parameters (site energies, disorder, and reorganization energies) from the fits of several spectra and then further validate the model by calculating additional independent spectra. We obtain good to excellent agreement between theory and calculations. We find that overall our model is similar to some of the previous asymmetric exciton models of the PSII RC. On the other hand, our model displays differences from previous work based on the modified Redfield theory. We extend the ctR theory to describe the Stark spectrum and use its fit to obtain the parameters of a single charge transfer state included in our model. Our results suggest that ChlD1(+)PheoD1(-) is most likely the primary charge transfer state, but that the Stark spectrum of the PSII RC is probably also influenced by other states.