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Sample records for fundamental unstable particles

  1. Unstable particles near threshold

    NASA Astrophysics Data System (ADS)

    Chway, Dongjin; Jung, Tae Hyun; Kim, Hyung Do

    2016-07-01

    We explore the physics of unstable particles when the mother particle's mass is approximately the sum of the masses of its daughter particles. In this case, the conventional wave function renormalization factor used for the narrow width approximation is ill-defined. We propose a simple resolution of the problem that allows the use of the narrow width approximation by defining the wave function renormalization factor and the branching ratio in terms of the spectral density. We test new definitions by calculating the cross section in the Higgs portal model and a significant improvement is obtained. Meanwhile, no single decay width can be assigned to the unstable particles and non-exponential decay occurs at all time scales.

  2. Fundamental principles of particle detectors

    SciTech Connect

    Fernow, R.C.

    1988-01-01

    This paper goes through the fundamental physics of particles-matter interactions which is necessary for the detection of these particles with detectors. A listing of 41 concepts and detector principles are given. 14 refs., 11 figs.

  3. Light as a Fundamental Particle

    ERIC Educational Resources Information Center

    Weinberg, Steven

    1975-01-01

    Presents two arguments concerning the role of the photon. One states that the photon is just another particle distinguished by a particular value of charge, spin, mass, lifetime, and interaction properties. The second states that the photon plays a fundamental role with a deep relation to ultimate formulas of physics. (GS)

  4. Towards pair production near threshold with unstable particle effective theory

    SciTech Connect

    Beneke, M.; Kauer, N.; Signer, A.; Zanderighi, G.; /Fermilab

    2004-10-01

    We illustrate the use of effective theory techniques to describe processes involving unstable particles close to resonance. First, we present the main ideas in the context of a scalar resonance in an Abelian gauge-Yukawa model. We then outline the necessary modifications to describe W-pair production close to threshold in electron-positron collisions.

  5. CP violation in correlated production and decay of unstable particles

    NASA Astrophysics Data System (ADS)

    Kittel, Olaf; Pilaftsis, Apostolos

    2012-03-01

    We study resonant CP-violating Einstein-Podolsky-Rosen correlations that may take place in the production and decay of unstable scalar particles at high-energy colliders. We show that as a consequence of unitarity and CPT invariance of the S-matrix, in 2→2 scatterings mediated by mixed scalar particles, at least three linearly independent decay matrices associated with the unstable scalar states are needed to obtain non-zero CP-odd observables that are also odd under C-conjugation. Instead, for the correlated production and decay of two unstable particle systems in 2→4 processes, we find that only two independent decay matrices are sufficient to induce a net non-vanishing CP-violating phenomenon. As an application of this theorem, we present numerical estimates of CP asymmetries for the correlated production and decay of supersymmetric scalar top-anti-top pairs at the LHC, and demonstrate that these could reach values of order one. As a byproduct of our analysis, we develop a novel spinorial trace technique, which enables us to efficiently evaluate lengthy expressions of squared amplitudes describing the resonant scalar transitions.

  6. Unstable particles in non-relativistic quantum mechanics?

    SciTech Connect

    Hernandez-Coronado, H.

    2011-10-14

    The Schroedinger equation is up-to-a-phase invariant under the Galilei group. This phase leads to the Bargmann's superselection rule, which forbids the existence of the superposition of states with different mass and implies that unstable particles cannot be described consistently in non-relativistic quantum mechanics (NRQM). In this paper we claim that Bargmann's rule neglects physical effects and that a proper description of non-relativistic quantum mechanics requires to take into account this phase through the Extended Galilei group and the definition of its action on spacetime coordinates.

  7. Nonlinear particle-wave kinetics in weakly unstable plasmas

    SciTech Connect

    Breizman, B.N.; Berk, H.L.; Pekker, M.S.

    1996-12-31

    With the motivation to address the behavior of the fusion produced alpha particles in a thermonuclear reactor, a theory is developed for predicting the wave saturation levels and particle transport in weakly unstable systems with a discrete number of modes in the presence of energetic particle sources and sinks. Conditions are established for either steady state or bursting nonlinear scenarios when several modes are excited for cases where there is and there is not resonance overlap. Depending on parameters, the particles can undergo benign relaxation, with only a small fraction of the available free energy released to waves and with no global transport, or the particles can experience rapid global transport caused by a substantial conversion of their free energy into wave energy. When the resonance condition of the particle-wave interaction is varied adiabatically, the particles trapped in a wave are found to form phase space holes or clumps that enhance the particle-wave energy exchange. This mechanism, which has been experimentally observed when there is frequency chirping, causes increased saturation levels of instabilities. If resonance sweeping is imposed externally, the particle free energy can even be tapped in stable systems where background dissipation suppresses linear instability. Externally applied resonance sweeping can be important for alpha particle energy channeling, as well as for understanding fishbone and some Alfven wave instability experiments. Near instability threshold, that is when the destabilizing drive just exceeds the background dissipation, a more sophisticated analysis is developed to predict the correct saturation. To leading order, this problem reduces to an integral equation for the wave amplitude with a temporally non local cubic term. This equation has a self-similar solution that blows-up in a finite time.

  8. A Fundamental Theorem on Particle Acceleration

    SciTech Connect

    Xie, Ming

    2003-05-01

    A fundamental theorem on particle acceleration is derived from the reciprocity principle of electromagnetism and a rigorous proof of the theorem is presented. The theorem establishes a relation between acceleration and radiation, which is particularly useful for insightful understanding of and practical calculation about the first order acceleration in which energy gain of the accelerated particle is linearly proportional to the accelerating field.

  9. How do classical particle-field systems become unstable? - The last physics problem that Ronald Davidson studied

    NASA Astrophysics Data System (ADS)

    Qin, Hong

    2016-10-01

    Many of the classical particle-field systems in (neutral and nonneutral) plasma physics and accelerator physics become unstable when the system parameters vary. How do these instabilities happen? It turns out, very interestingly, that all conservative systems become unstable by the same mechanism, i.e, the resonance between a positive- and a negative-action modes. And this is the only route that a stable system can become unstable. In this talk, I will use several examples in plasma physics and accelerator physics with finite and infinite degrees of freedom to illustrate the basic physical picture and the rigorous theoretical structure of the process. The features at the transition between stable and unstable regions in the parameter space are the fundamental characteristics of the underlying real Hamiltonian system and complex G-Hamiltonian system. The resonance between a positive- and a negative-action modes at the transition is the Krein collision well-known to mathematicians. Research supported by the U.S. Department of Energy (DE-AC02-09CH11466).

  10. Lightest Visible-Sector Supersymmetric Particle is Likely to be Unstable

    NASA Astrophysics Data System (ADS)

    Acharya, Bobby S.; Ellis, Sebastian A. R.; Kane, Gordon L.; Nelson, Brent D.; Perry, Malcolm J.

    2016-10-01

    We argue, based on typical properties of known solutions of string or M theory, that the lightest supersymmetric particle of the visible sector is likely to be unstable. In other words, dark matter is probably not a particle with standard model quantum numbers, such as a weakly interacting massive particle. The argument is simple and based on the typical occurrence of (a) hidden sectors, (b) interactions between the standard model (visible) sector and these hidden sectors, and (c) the lack of an argument against massive neutral hidden sector particles being lighter than the lightest visible supersymmetric particle. These conclusions do not rely on arguments such as R -parity violation.

  11. Particles as Fundaments of Discourse Structuring.

    ERIC Educational Resources Information Center

    Fernandez-Vest, M. M. Jocelyne

    A serious study of discourse particles (DIPs) must be founded on the analysis of orality in its two main dimensions: oral communication in its ordinary functioning (i.e., discourse, conversation, enunciation), but also in expression ritualized by the oral tradition of cultures that do not have a writing system. The association of the two…

  12. Fundamentals and applications of magnetic particle imaging.

    PubMed

    Borgert, Jörn; Schmidt, Joachim D; Schmale, Ingo; Rahmer, Jürgen; Bontus, Claas; Gleich, Bernhard; David, Bernd; Eckart, Rainer; Woywode, Oliver; Weizenecker, Jürgen; Schnorr, Jörg; Taupitz, Matthias; Haegele, Julian; Vogt, Florian M; Barkhausen, Jörg

    2012-01-01

    Magnetic particle imaging (MPI) is a new medical imaging technique which performs a direct measurement of magnetic nanoparticles, also known as superparamagnetic iron oxide. MPI can acquire quantitative images of the local distribution of the magnetic material with high spatial and temporal resolution. Its sensitivity is well above that of other methods used for the detection and quantification of magnetic materials, for example, magnetic resonance imaging. On the basis of an intravenous injection of magnetic particles, MPI has the potential to play an important role in medical application areas such as cardiovascular, oncology, and also in exploratory fields such as cell labeling and tracking. Here, we present an introduction to the basic function principle of MPI, together with an estimation of the spatial resolution and the detection limit. Furthermore, the above-mentioned medical applications are discussed with respect to an applicability of MPI.

  13. Microwaves and particle accelerators: a fundamental link

    SciTech Connect

    Chattopadhyay, Swapan

    2011-07-01

    John Cockcroft's splitting of the atom and Ernest Lawrence's invention of the cyclotron in the first half of the twentieth century ushered in the grand era of ever higher energy particle accelerators to probe deeper into matter. It also forged a link, bonding scientific discovery with technological innovation that continues today in the twenty first century. The development of radar and high power vacuum electronics, especially microwave power tubes like the magnetrons and the klystrons in the pre-second world war era, was instrumental in the rapid development of circular and linear charged particle accelerators in the second half of the twentieth century. We had harnessed the powerful microwave radio-frequency sources from few tens of MHz to up to 90 GHz spanning L-band to W-band frequencies. Simultaneously in the second half of the twentieth century, lasers began to offer very first opportunities of controlling charged particles at smaller resolutions on the scale of wavelengths of visible light. We also witnessed in this period the emergence of the photon and neutron sciences driven by accelerators built-by-design producing tailored and ultra-bright pulses of bright photons and neutrons to probe structure and function of matter from aggregate to individual molecular and atomic scales in unexplored territories in material and life sciences. As we enter the twenty first century, the race for ever higher energies, brightness and luminosity to probe atto-metric and atto-second domains of the ultra-small structures and ultra-fast processes continues. These developments depend crucially on yet further advancements in the production and control of high power and high frequency microwaves and light sources, often intricately coupled in their operation to the high energy beams themselves. We give a glimpse of the recent developments and innovations in the electromagnetic production and control of charged particle beams in the service of science and society. (author)

  14. Geometric representation of fundamental particles' inertial mass

    SciTech Connect

    Schachter, L.; Spencer, James

    2015-07-22

    A geometric representation of the (N = 279) masses of quarks, leptons, hadrons and gauge bosons was introduced by employing a Riemann Sphere facilitating the interpretation of the N masses in terms of a single particle, the Masson, which might be in one of the N eigen-states. Geometrically, its mass is the radius of the Riemann Sphere. Dynamically, its derived mass is near the mass of the nucleon regardless of whether it is determined from all N particles of only the hadrons, the mesons or the baryons separately. Ignoring all the other properties of these particles, it is shown that the eigen-values, the polar representation θν of the masses on the Sphere, satisfy the symmetry θν + θN+1-ν = π within less than 1% relative error. In addition, these pair correlations include the pairs θγ + θtop ≃ π and θgluon + θH ≃ π as well as pairing the weak gauge bosons with the three neutrinos.

  15. Characterization of the structural collapse undergone by an unstable system of ultrasoft particles

    NASA Astrophysics Data System (ADS)

    Prestipino, Santi; Malescio, Gianpietro

    2016-09-01

    The effective repulsion between macromolecules such as polymer chains or dendrimers is everywhere finite, implying that interaction centers can even coincide. If, in addition, the large-distance attraction is sufficiently strong, then the system is driven unstable. An unstable system lacks a conventional thermodynamics since, in the infinite-size limit, it eventually collapses to a finite-size cluster (for instance, a polymer dispersion undergoes irreversible coagulation when increasing the amount of dissolved salt beyond a certain limit). Using a double-Gaussian (DG) potential for demonstration, we study the phase behavior of a system of ultrasoft particles as a function of the attraction strength η. Above a critical threshold ηc, the DG system is unstable but its collective behavior is far from trivial since two separate regions of the thermodynamic plane can be identified, based on the value taken by the average waiting time for collapse: this is finite and small on one side of the boundary, while presumably infinite in the other region. In order to make sense of this evidence, we consider a stable system of particles interacting through a DG potential augmented with a hard core (stabilized DG, or SDG potential). We provide arguments supporting the view that the boundary line of the unstable DG model is the remnant of the spinodal line of a fluid-fluid phase transition occurring in the SDG model when the hard-core diameter is sent to zero.

  16. Fundamentals of chemistry modeling applicable to a vectorized particle simulation

    NASA Technical Reports Server (NTRS)

    Haas, Brian L.

    1990-01-01

    This paper describes the fundamentals of extending the vectorized particle simulation method derived by Baganoff and McDonald (1990), McDonald and Baganoff (1988), and McDonald (1989) for modeling chemically reacting flows. Details of reaction mechanics per reaction are presented, with particular attention given to the quantum nature of the vibrational mode. The models of reactive flows developed here were verified through a simulation of a superheated diatomic gas relaxing thermochemically to equilibrium in a reservoir.

  17. Fundamental Particle Structure in the Cosmological Dark Matter

    NASA Astrophysics Data System (ADS)

    Khlopov, Maxim

    2013-11-01

    The nonbaryonic dark matter of the universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of noninteracting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for superhigh energy physics in the early universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP-violation in the unique framework of models of horizontal unification. Dark matter candidates can also appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, hidden in elusive "dark atoms." Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms," maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. In the context of cosmoparticle physics, studying

  18. The unstable ice nucleation properties of Snomax® bacterial particles

    NASA Astrophysics Data System (ADS)

    Polen, Michael; Lawlis, Emily; Sullivan, Ryan C.

    2016-10-01

    Snomax® is often used as a surrogate for biological ice nucleating particles (INPs) and has recently been proposed as an INP standard for evaluating ice nucleation methods. We have found the immersion freezing properties of Snomax particles to be substantially unstable, observing a loss of ice nucleation ability over months of repeated droplet freezing measurements of the same batch of Snomax stored as dry pellets in a freezer. This reflects the fragility of the most ice active large protein aggregates and presents issues for the use of Snomax as an INP standard. The ice nucleation properties we determined using a fresh Snomax batch agreed well with the recent method intercomparison from the Ice Nucleation UnIT (UNIT) project, while an older batch did not. Using an oil immersion droplet freezing technique, repeated freezes of Snomax droplets resulted in a decrease in ice nucleation ability after successive refreezes. We attribute this to the disruption or displacement of the most ice active protein aggregates that are thought to contain the ice nucleants. Partitioning of the protein aggregates from the droplet into the immersion oil that is accelerated by droplet freezing events could explain the observed decrease in freezing ability. Droplets in mineral oil or low viscosity silicone oil experienced a smaller reduction in freezing temperature than when squalene oil was used. The effect of the immersion oil may be specific to proteinaceous biological particles, and we have not observed it in nonproteinaceous materials. Caution is warranted in the use of oil immersion droplet freezing methods to determine immersion freezing properties.

  19. Fundamental Study of Emulsions Stabilized by Soft and Rigid Particles.

    PubMed

    Li, Zifu; Harbottle, David; Pensini, Erica; Ngai, To; Richtering, Walter; Xu, Zhenghe

    2015-06-16

    Two distinct uniform hybrid particles, with similar hydrodynamic diameters and comparable zeta potentials, were prepared by copolymerizing N-isopropylacrylamide (NIPAM) and styrene. These particles differed in their styrene to NIPAM (S/N) mass ratios of 1 and 8 and are referred to as S/N 1 and S/N 8, respectively. Particle S/N 1 exhibited a typical behavior of soft particles; that is, the particles shrank in bulk aqueous solutions when the temperature was increased. As a result, S/N 1 particles were interfacially active. In contrast, particle S/N 8 appeared to be rigid in response to temperature changes. In this case, the particles showed a negligible interfacial activity. Interfacial shear rheology tests revealed the increased rigidity of the particle-stabilized film formed at the heptane-water interface by S/N 1 than S/N 8 particles. As a result, S/N 1 particles were shown to be better emulsion stabilizers and emulsify a larger amount of heptane, as compared with S/N 8 particles. The current investigation confirmed a better performance of emulsion stabilization by soft particles (S/N 1) than by rigid particles (S/N 8), reinforcing the importance of controlling softness or deformability of particles for the purpose of stabilizing emulsions.

  20. Fundamentals of particle beam dynamics and phase space

    SciTech Connect

    Weng, W.T.; Mane, S.R.

    1991-09-04

    This report discusses the following topics on synchrotron accelerators: Transverse motion---betatron oscillations; machine lattice; representation of a particle beam; and longitudinal motion---synchrotron oscillations.

  1. One-particle spectroscopic intensities as a signature of shape phase transition: The {gamma}-unstable case

    SciTech Connect

    Alonso, C. E.; Arias, J. M.; Vitturi, A.

    2006-08-15

    We investigate the evolution of one-particle spectroscopic intensities as a possible signature of shape phase transitions. The study describes the odd systems in terms of the interacting boson-fermion model. We consider the particular case of an odd j=3/2 particle coupled to an even-even boson core that undergoes a phase transition from spherical U(5) to {gamma}-unstable O(6) situation. At the critical point, our findings are compared with the one-particle spectroscopic intensities that can be obtained within the E(5/4) model proposed by[F. Iachello, Phys. Rev. Lett. 95, 052503 (2005); F. Iachello, in Symmetries and Low-Energy Phase Transitions in Nuclear Structure Physics, edited by G. Lo Bianco (University of Camerino Press, Camerino, Italy, in press)].

  2. The Relation between Fundamental Constants and Particle Physics Parameters

    NASA Astrophysics Data System (ADS)

    Thompson, Rodger

    2017-01-01

    The observed constraints on the variability of the proton to electron mass ratio $\\mu$ and the fine structure constant $\\alpha$ are used to establish constraints on the variability of the Quantum Chromodynamic Scale and a combination of the Higgs Vacuum Expectation Value and the Yukawa couplings. Further model dependent assumptions provide constraints on the Higgs VEV and the Yukawa couplings separately. A primary conclusion is that limits on the variability of dimensionless fundamental constants such as $\\mu$ and $\\alpha$ provide important constraints on the parameter space of new physics and cosmologies.

  3. Fundamental studies of the solid-particle erosion of silicon

    NASA Technical Reports Server (NTRS)

    Routbort, J. L.; Scattergood, R. O.

    1982-01-01

    The predictions of the theories of solid-particle erosion of brittle materials are compared to experimental results of studies in which angular Al2O3 particles with mean diameters D of 23 to 270 microns are used to erode (111) surfaces of silicon single crystals at impact angles alpha from 20 to 90 deg and velocities v from 30 to 150 m/s. The description of the steady state erosion rate by a power law, delta W varies directly as (v sin alpha)(n)D(m) must be modified to include threshold and plasticity effects. Furthermore the velocity exponent n depends on D. Results using abrasives of different sizes mixed together can be explained using a logarithmic-normal distribution. The results of transient experiments can be used to explain the synergistic effects which are observed using a biomodal distribution of abrasives.

  4. Kinetic Study of Radiation-reaction-limited Particle Acceleration During the Relaxation of Unstable Force-free Equilibria

    NASA Astrophysics Data System (ADS)

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-01

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The “flares” are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. Higher magnetization studies are promising and will be carried out in the future.

  5. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    DOE PAGES

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; ...

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focusmore » on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less

  6. Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

    SciTech Connect

    Yuan, Yajie; Nalewajko, Krzysztof; Zrake, Jonathan; East, William E.; Blandford, Roger D.

    2016-09-07

    Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model. Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.

  7. Smoothed Particle Hydrodynamics pore-scale simulations of unstable immiscible flow in porous media

    SciTech Connect

    Bandara, Dunusinghe Mudiyanselage Uditha C.; Tartakovsky, Alexandre M.; Oostrom, Martinus; Palmer, Bruce J.; Grate, Jay W.; Zhang, Changyong

    2013-12-01

    We have conducted a series of high-resolution numerical experiments using the Pair-Wise Force Smoothed Particle Hydrodynamics (PF-SPH) multiphase flow model. First, we derived analytical expressions relating parameters in the PF-SPH model to the surface tension and static contact angle. Next, we used the model to study viscous fingering, capillary fingering, and stable displacement of immiscible fluids in porous media for a wide range of capillary numbers and viscosity ratios. We demonstrated that the steady state saturation profiles and the boundaries of viscous fingering, capillary fingering, and stable displacement regions compare favorably with micromodel laboratory experimental results. For displacing fluid with low viscosity, we observed that the displacement pattern changes from viscous fingering to stable displacement with increasing injection rate. When a high viscosity fluid is injected, transition behavior from capillary fingering to stable displacement occurred as the flow rate was increased. These observation also agree with the results of the micromodel laboratory experiments.

  8. Fundamental equations of a mixture of gas and small spherical solid particles from simple kinetic theory.

    NASA Technical Reports Server (NTRS)

    Pai, S. I.

    1973-01-01

    The fundamental equations of a mixture of a gas and pseudofluid of small spherical solid particles are derived from the Boltzmann equation of two-fluid theory. The distribution function of the gas molecules is defined in the same manner as in the ordinary kinetic theory of gases, but the distribution function for the solid particles is different from that of the gas molecules, because it is necessary to take into account the different size and physical properties of solid particles. In the proposed simple kinetic theory, two additional parameters are introduced: one is the radius of the spheres and the other is the instantaneous temperature of the solid particles in the distribution of the solid particles. The Boltzmann equation for each species of the mixture is formally written, and the transfer equations of these Boltzmann equations are derived and compared to the well-known fundamental equations of the mixture of a gas and small solid particles from continuum theory. The equations obtained reveal some insight into various terms in the fundamental equations. For instance, the partial pressure of the pseudofluid of solid particles is not negligible if the volume fraction of solid particles is not negligible as in the case of lunar ash flow.

  9. Measurement of fundamental illite particle thicknesses by X-ray diffraction using PVP-10 intercalation

    USGS Publications Warehouse

    Eberl, D.D.; Nuesch, R.; Sucha, V.; Tsipursky, S.

    1998-01-01

    The thicknesses of fundamental illite particles that compose mixed-layer illite-smectite (I-S) crystals can be measured by X-ray diffraction (XRD) peak broadening techniques (Bertaut-Warren-Averbach [BWA] method and integral peak-width method) if the effects of swellinf and XRD background noise are eliminated from XRD patterns of the clays. Swelling is eliminated by intercalating Na-saturated I-S with polyvinylpyrrolidone having a molecular weightof 10,000 (PVP-10). Background is minimized by using polished metallic silicon wafers cut perpendicular to (100) as a substrate for XRD specimens, and by using a single-crystal monochromator. XRD measurements of PVP-intercalated diagenetic, hydro-thermal and low-grade metamorphic I-S indicate that there at least 2 type of crystallite thickness distribution shapes for illite fundamental particles, lognormal and asymptotic; that measurements of mean fundamental illite particle thicknesses made by various techniques (Bertaut-Warren-Averbach, integral peak width, fixed cation content, and transmission electron microscopy [TEM]) give comparable results; and that strain (small difference in layer thicknesses) generally has a Gaussian distribution in the lognormal-type illites, but is often absent in the asymptotic-type illites.

  10. Core-shell particles: preparation, fundamentals and applications in high performance liquid chromatography.

    PubMed

    Hayes, Richard; Ahmed, Adham; Edge, Tony; Zhang, Haifei

    2014-08-29

    The challenges in HPLC are fast and efficient separation for a wide range of samples. Fast separation often results in very high operating pressure, which places a huge burden on HPLC instrumentation. In recent years, core-shell silica microspheres (with a solid core and a porous shell, also known as fused-core or superficially porous microspheres) have been widely investigated and used for highly efficient and fast separation with reasonably low pressure for separation of small molecules, large molecules and complex samples. In this review, we firstly show the types of core-shell particles and how they are generally prepared, focusing on the methods used to produce core-shell silica particles for chromatographic applications. The fundamentals are discussed on why core-shell particles can perform better with low back pressure, in terms of van Deemter equation and kinetic plots. The core-shell particles are compared with totally porous silica particles and also monolithic columns. The use of columns packed with core-shell particles in different types of liquid chromatography is then discussed, followed by illustrating example applications of such columns for separation of various types of samples. The review is completed with conclusion and a brief perspective on future development of core-shell particles in chromatography.

  11. Fundamentals and application of magnetic particles in cell isolation and enrichment: a review

    NASA Astrophysics Data System (ADS)

    Plouffe, Brian D.; Murthy, Shashi K.; Lewis, Laura H.

    2015-01-01

    Magnetic sorting using magnetic beads has become a routine methodology for the separation of key cell populations from biological suspensions. Due to the inherent ability of magnets to provide forces at a distance, magnetic cell manipulation is now a standardized process step in numerous processes in tissue engineering, medicine, and in fundamental biological research. Herein we review the current status of magnetic particles to enable isolation and separation of cells, with a strong focus on the fundamental governing physical phenomena, properties and syntheses of magnetic particles and on current applications of magnet-based cell separation in laboratory and clinical settings. We highlight the contribution of cell separation to biomedical research and medicine and detail modern cell-separation methods (both magnetic and non-magnetic). In addition to a review of the current state-of-the-art in magnet-based cell sorting, we discuss current challenges and available opportunities for further research, development and commercialization of magnetic particle-based cell-separation systems.

  12. Fundamentals and Application of Magnetic Particles in Cell Isolation and Enrichment

    PubMed Central

    Plouffe, Brian D.; Murthy, Shashi K.; Lewis, Laura H.

    2014-01-01

    Magnetic sorting using magnetic beads has become a routine methodology for the separation of key cell populations from biological suspensions. Due to the inherent ability of magnets to provide forces at a distance, magnetic cell manipulation is now a standardized process step in numerous processes in tissue engineering, medicine, and in fundamental biological research. Herein we review the current status of magnetic particles to enable isolation and separation of cells, with a strong focus on the fundamental governing physical phenomena, properties and syntheses of magnetic particles and on current applications of magnet-based cell separation in laboratory and clinical settings. We highlight the contribution of cell separation to biomedical research and medicine and detail modern cell separation methods (both magnetic and non-magnetic). In addition to a review of the current state-of-the-art in magnet-based cell sorting, we discuss current challenges and available opportunities for further research, development and commercialization of magnetic particle-based cell separation systems. PMID:25471081

  13. A new fundamental model of moving particle for reinterpreting Schroedinger equation

    SciTech Connect

    Umar, Muhamad Darwis

    2012-06-20

    The study of Schroedinger equation based on a hypothesis that every particle must move randomly in a quantum-sized volume has been done. In addition to random motion, every particle can do relative motion through the movement of its quantum-sized volume. On the other way these motions can coincide. In this proposed model, the random motion is one kind of intrinsic properties of the particle. The every change of both speed of randomly intrinsic motion and or the velocity of translational motion of a quantum-sized volume will represent a transition between two states, and the change of speed of randomly intrinsic motion will generate diffusion process or Brownian motion perspectives. Diffusion process can take place in backward and forward processes and will represent a dissipative system. To derive Schroedinger equation from our hypothesis we use time operator introduced by Nelson. From a fundamental analysis, we find out that, naturally, we should view the means of Newton's Law F(vector sign) = ma(vector sign) as no an external force, but it is just to describe both the presence of intrinsic random motion and the change of the particle energy.

  14. Modeling fundamental plasma transport and particle-induced emission in a simplified Test Cell

    NASA Astrophysics Data System (ADS)

    Giuliano, Paul Nicholas

    This work involves the modeling of fundamental plasma physics processes occurring within environments that are similar to that of the discharge and plume regions of electric propulsion devices such as Hall effect thrusters. The research is conducted as a collaborative effort with the Plasma & Space Propulsion Laboratory at the University of California, Los Angeles (UCLA), as part of the University of Michigan/AFRL Center for Excellence in Electric Propulsion (MACEEP). Transport physics, such as particle-particle collisions and particle-induced electron emission, are simulated within the UCLA experimental facility and its representative electric propulsion environment. Simulation methods employed include the direct simulation Monte Carlo (DSMC) and particle-in-cell (PIC) techniques for the kinetic simulation of charged, rarefied species on high-performance computing architectures. Momentum- (MEX) and charge-exchange (CEX) collision cross-section models for Xe and Xe+, both total and differential, are successfully validated at collision energies of ˜1.5 keV within the novel facility. Heavy-species collisional transport models are validated and the importance of scattering anisotropy in this collision-dominated environment is shown. The theory of particle-induced electron emission (PIE) is then investigated in the context of the relevant energies and environments of the UCLA facility and electric propulsion devices and diagnostics. Reduced, semi-empirical models for total yield and emitted electron energy distribution functions that are easily implemented in a DSMC-PIC code are developed for the simulation of secondary-electron emission due to low-energy ions and high-energy atoms, even in the case of incomplete target-material information. These models are important for the characterization of electric propulsion devices due to the problematic nature of low-temperature plasma diagnostic techniques in which the emission of electrons is physically indistinguishable

  15. Lifetime of Cosmic-Ray Muons and the Standard Model of Fundamental Particles

    NASA Astrophysics Data System (ADS)

    Mukherji, Sahansha; Shevde, Yash; Majewski, Walerian

    2015-04-01

    Muon is one of the twelve fundamental particles of matter, having the longest free-particle lifetime. It decays into three other leptons through an exchange of the weak vector bosons W+/W-. Muons are present in the secondary cosmic ray showers in the atmosphere, reaching the sea level. By detecting time delay between arrival of the muon and an appearance of the decay electron in our single scintillation detector (donated by the Thomas Jefferson National Accelerator Facility, Newport News, VA), we measured muon's lifetime at rest. It compares well with the value predicted by the Standard Model of Particles. From the lifetime we were able to calculate the ratio gw /MW of the weak coupling constant gw (an analog of the electric charge) to the mass of the W-boson MW. Using further Standard Model relations and an experimental value for MW, we calculated the weak coupling constant, the electric charge of the muon, and the vacuum expectation value of the Higgs field. We determined the sea-level flux of cosmic muons.

  16. Parametrically Unstable Alfven-cyclotron Waves and Wave--Particle Interactions in the Solar Corona and Solar Wind

    SciTech Connect

    Maneva, Y. G.; Marsch, E.; Araneda, J. A.

    2009-04-26

    We consider the parametric instabilities of large-amplitude Alfven/ion-cyclotron waves and the consequent wave-particle interactions, and discuss their importance for modelling the evolution of ion velocity distribution functions in the tenuous and collisionless plasma of a coronal hole and the fast solar wind. We perform 1D hybrid simulations to study the nonlinear evolution of the parametric instabilities by analyzing the simulation results in terms of microinstabilities and discussing the influence of both Landau and cyclotron resonances on the evolution of the ion distributions. We demonstrate the origin of a relative drift between the protons and alpha particles, show the related anisotropic ion heating and follow the simultaneous proton beam formation. Finally, we focus on the development and evolution of both electromagnetic and acoustic micro-turbulence and present indications for an inverse energy cascade from shorter to longer wavelengths.

  17. Self-consistent particle-in-cell simulations of fundamental and harmonic radio plasma emission mechanisms

    NASA Astrophysics Data System (ADS)

    Tsiklauri, D.; Thurgood, J. O.

    2015-12-01

    first co-author Jonathan O. Thurgood (QMUL) The simulation of three-wave interaction based plasma emission, an underlying mechanism for type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some authors report that no such processes occur and others draw conflicting conclusions, by using 2D, fully kinetic, particle-in-cell simulations of relaxing electron beams. Here we present the results of particle-in-cell simulations which for different physical parameters permit or prohibit the plasma emission. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to the frequency beat requirements. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses the emission. Comparison of our results indicates that, contrary to the suggestions of previous authors, a plasma emission mechanism based on two counter-propagating beams is unnecessary in astrophysical context. Finally, we also consider the action of the Weibel instability, which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that evidence of plasma emission in simulations must disentangle the two contributions and not simply interpret changes in total electromagnetic energy as the evidence of plasma emission. In summary, we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. Pre-print can be found at http://astro.qmul.ac.uk/~tsiklauri/jtdt1

  18. COST Action MP0806 'Particles in Turbulence': International Conference on Fundamentals, Experiments, Numeric and Applications

    NASA Astrophysics Data System (ADS)

    Abel, Markus; Bodenschatz, Eberhard; Toschi, Federico

    2011-12-01

    Turbulent flows are ubiquitous in nature and technology. Turbulent flows govern the transport of particulate matter in nature. For example, in atmospheric flows turbulence impacts the dynamics of aerosols, droplets, spores and of the living world by either chemo-attractant transport or transport of the insects themselves. In marine flows examples include the bubble dynamics that governs the uptake of oxygen and carbon dioxide at the ocean air interface, or the impact of turbulence on the life of phyto- and zoo-plankton, or the spread of pollutants in the oceans and estuaries. Turbulence is equally important for technology from process engineering in chemical and pharmaceutical industries to energy transport and energy generation. The COST Action MP0806 'Particles in Turbulence' has as the primary objective the support of the fundamental research on the statistical properties of particle transport in turbulent flows. The Action provides excellent opportunities for the exchange of ideas by bringing together scientists from different areas of research and applications, or different views on the problem. The COST Action MP0806 organizes several events annually. The conference held at the University of Potsdam from 16 to 18 March 2011 was the main meeting of the Action in 2011. In total 87 researchers from 18 countries (of which 12 were European) met and presented their work, discussed new ideas on theoretical, numerical and experimental approaches, as well as on applications to various scientific domains. The conference attracted also a number of participants from outside the COST Action. The scientific presentations focused on inertial and finite-size particles, particle collisions, as well as advection and reaction in simple and complex flow geometries. Very interesting results were presented at the forefront of the field: the increasing computational power combined with novel numerical techniques now allows for the first time simulation of the dynamics of finites

  19. Number of Packages of Information which are processed in a Second by the Fundamental Particles (strings) of a Human Body

    NASA Astrophysics Data System (ADS)

    Gholibeigian, Hassan; Gholibeigian, Ghasem; Gholibeigian, Kazem

    2016-11-01

    The fundamental particle (string) gets a package of complete information of its quantum state via inside of its sub-particle (sub-string) from dimension of information. This package is processed by sub-particle in each Planck time [Gholibeigian, APS 2015, abstract #L1.027]. On the other hand, a 70 kg human's body would have approximately 7*1027 atoms. Of that, 4.7*1027 would be hydrogen atoms. Another 1.8*1027 would be oxygen and there are 7.0*1026 carbon atoms. If we add that all up, total is 2.3*1028 protons, 1.8*1028 neutrons, and 2.3*1028 electrons. Each proton and neutron has 6 fundamental particles. So the total number of packages of information which are processed by each of us in a second becomes: I = [ 6 × (2 . 3 + 1 . 8) ×1028 + 2 . 3 ×1028 ] ×1044 = 2 . 69 ×1073 The processed information carry by fundamental particles. Based on Shanon equation, I = - S , this number can be equal to the increased entropy of each of us per second too. AmirKabir University of Technology, Tehran, Iran.

  20. Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms

    NASA Astrophysics Data System (ADS)

    Thurgood, J. O.; Tsiklauri, D.

    2015-12-01

    Aims: The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some studies indicate that no such processes occur. Methods: We self-consistently simulate three-wave based plasma emission through all stages by using 2D, fully kinetic, electromagnetic particle-in-cell simulations of relaxing electron beams using the EPOCH2D code. Results: Here we present the results of two simulations; Run 1 (nb/n0 = 0.0057, vb/ Δvb = vb/Ve = 16) and Run 2 (nb/n0 = 0.05, vb/ Δvb = vb/Ve = 8), which we find to permit and prohibit plasma emission respectively. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to frequency conservation requirements. In resolving this apparent contradiction through a comprehensive analysis, in this paper we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses emission. Comparison of our results also indicates that, contrary to the suggestions of previous authors, an alternative plasma emission mechanism based on two counter-propagating beams is unnecessary in an astrophysical context. Finally, we also consider the action of the Weibel instability which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that

  1. Inductively Coupled Plasma: Fundamental Particle Investigations with Laser Ablation and Applications in Magnetic Sector Mass Spectrometry

    SciTech Connect

    Saetveit, Nathan Joe

    2008-01-01

    Particle size effects and elemental fractionation in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are investigated with nanosecond and femtosecond laser ablation, differential mobility analysis, and magnetic sector ICP-MS. Laser pulse width was found to have a significant influence on the LA particle size distribution and the elemental composition of the aerosol and thus fractionation. Emission from individual particles from solution nebulization, glass, and a pressed powder pellet are observed with high speed digital photography. The presence of intact particles in an ICP is shown to be a likely source of fractionation. A technique for the online detection of stimulated elemental release from neural tissue using magnetic sector ICP-MS is described. Detection limits of 1 μg L-1 or better were found for P, Mn, Fe, Cu, and Zn in a 60 μL injection in a physiological saline matrix.

  2. Fundamental Particle Combustion Kinetics Measurement in the Shock Tube in Support of Enhanced Blast Weapons Development

    DTIC Science & Technology

    2012-07-01

    detonation wave on the reactivity of aluminum particles in aluminized explosives. These to research thrust were conducted in parallel. 1S. SUBJECT TERMS... Aluminized Explosives VII. Optical Depth of Fireballs from Aluminized Explosives VIII. Emissivity of Aluminum Oxide at High Temperature IX...passage of the detonation wave on the reactivity of aluminum particles in aluminized explosives. These two research thrusts were conducted in parallel

  3. Fundamentals of elasto-inertial particle focusing in curved microfluidic channels.

    PubMed

    Xiang, Nan; Zhang, Xinjie; Dai, Qing; Cheng, Jie; Chen, Ke; Ni, Zhonghua

    2016-07-05

    Elasto-inertial focusing in viscoelastic fluids has attracted increasing interest in recent years due to its potential applications in particle counting and sorting. However, current investigations of the elasto-inertial focusing mechanisms have mainly been focused on simple straight channels with little attention being paid to curved channels. Herein, we experimentally explore the elasto-inertial focusing behaviors of particles in spiral microfluidic channels over a wide range of flow rates, channel aspect ratios and channel radii. As compared with those observed in inertial microfluidics without viscoelasticity, the particle focusing pattern in our spiral elasto-inertial microfluidic system appears in a more interesting manner due to the complex coupling of elasticity, inertia and Dean flow effects. On the basis of the obtained data, the underlying mechanics and force competition behind the focusing behaviors are analyzed. In addition, for the first time, we propose a six-stage process model illustrating the particle focusing process in Dean-coupled elasto-inertial flows with increasing flow rate. It is interesting to find that the Dean drag force makes a significant contribution to particle focusing only at high flow rates and finally shifts the particle focusing positions into the outer channel region. Through carefully balancing the forces acting on particles, single-line 3D focusing can also be achieved at a throughput level of ∼100 μl min(-1), which is much higher than those in most existing studies. We envision that this improved understanding of the particle focusing mechanisms would provide helpful insights into the design and operation of spiral elasto-inertial microfluidic systems.

  4. Assessment of Airborne Particles. Fundamentals, Applications, and Implications to Inhalation Toxicity.

    ERIC Educational Resources Information Center

    Mercer, Thomas T., Ed.; And Others

    Concern over chemical and radioactive particulate matter in industry and over rapidly increasing air pollution has stimulated research both on the properties of airborne particles and methods for assessing them and on their biological effects following inhalation. The Third Rochester International Conference on Environmental Toxicity was,…

  5. Time of flight of ultra-relativistic particles in a realistic Universe: A viable tool for fundamental physics?

    NASA Astrophysics Data System (ADS)

    Fanizza, G.; Gasperini, M.; Marozzi, G.; Veneziano, G.

    2016-06-01

    Including the metric fluctuations of a realistic cosmological geometry we reconsider an earlier suggestion that measuring the relative time-of-flight of ultra-relativistic particles can provide interesting constraints on fundamental cosmological and/or particle parameters. Using convenient properties of the geodetic light-cone coordinates we first compute, to leading order in the Lorentz factor and for a generic (inhomogeneous, anisotropic) space-time, the relative arrival times of two ultra-relativistic particles as a function of their masses and energies as well as of the details of the large-scale geometry. Remarkably, the result can be written as an integral over the unperturbed line-of-sight of a simple function of the local, inhomogeneous redshift. We then evaluate the irreducible scatter of the expected data-points due to first-order metric perturbations, and discuss, for an ideal source of ultra-relativistic particles, the resulting attainable precision on the determination of different physical parameters.

  6. Practical experience with unstable compressors

    NASA Technical Reports Server (NTRS)

    Malanoski, S. B.

    1980-01-01

    Using analytical mathematical modeling techniques for the system components, an attempt is made to gauge the destabilizing effects in a number of compressor designs. In particular the overhung (or cantilevered) compressor designs and the straddle-mounted (or simply supported) compressor designs are examined. Recommendations are made, based on experiences with stable and unstable compressors, which can be used as guides in future designs. High and low pressure compressors which operate well above their fundamental rotor-bearing lateral natural frequencies can suffer from destructive subsynchronous vibration. Usually the elements in the system design which contribute to this vibration, other than the shafting and the bearings, are the seals (both gas labyrinth and oil breakdown bushings) and the aerodynamic components.

  7. Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Khoa, Dao Tien; Egelhof, Peter; Gales, Sydney; Giai, Nguyen Van; Motobayashi, Tohru

    2008-04-01

    Studies at the RIKEN RI beam factory / T. Motobayashi -- Dilute nuclear states / M. Freer -- Studies of exotic systems using transfer reactions at GANIL / D. Beaumel et al. -- First results from the Magnex large-acceptance spectrometer / A. Cunsolo et al. -- The ICHOR project and spin-isospin physics with unstable beams / H. Sakai -- Structure and low-lying states of the [symbol]He exotic nucleus via direct reactions on proton / V. Lapoux et al. -- Shell gap below [symbol]Sn based on the excited states in [symbol]Cd and [symbol]In / M. Górska -- Heavy neutron-rich nuclei produced in the fragmentation of a [symbol]Pb beam / Zs. Podolyák et al. -- Breakup and incomplete fusion in reactions of weakly-bound nuclei / D.J. Hinde et al. -- Excited states of [symbol]B and [symbol]He and their cluster aspect / Y. Kanada-En'yo et al. -- Nuclear reactions with weakly-bound systems: the treatment of the continuum / C. H. Dasso, A. Vitturi -- Dynamic evolution of three-body decaying resonances / A. S. Jensen et al. -- Prerainbow oscillations in [symbol]He scattering from the Hoyle state of [symbol]C and alpha particle condensation / S. Ohkubo, Y. Hirabayashi -- Angular dispersion behavior in heavy ion elastic scattering / Q. Wang et al. -- Microscopic optical potential in relativistic approach / Z.Yu. Ma et al. -- Exotic nuclei studied in direct reactions at low momentum transfer - recent results and future perspectives at fair / P. Egelhof -- Isotopic temperatures and symmetry energy in spectator fragmentation / M. De Napoli et al. -- Multi-channel algebraic scattering theory and the structure of exotic compound nuclei / K. Amos et al. -- Results for the first feasibility study for the EXL project at the experimental storage ring at GSI / N. Kalantar-Nayestanaki et al. -- Coulomb excitation of ISOLDE neutron-rich beams along the Z = 28 chain / P. Van Duppen -- The gamma decay of the pygmy resonance far from stability and the GDR at finite temperature / G. Benzoni et al

  8. Fundamental ecology is fundamental.

    PubMed

    Courchamp, Franck; Dunne, Jennifer A; Le Maho, Yvon; May, Robert M; Thébaud, Christophe; Hochberg, Michael E

    2015-01-01

    The primary reasons for conducting fundamental research are satisfying curiosity, acquiring knowledge, and achieving understanding. Here we develop why we believe it is essential to promote basic ecological research, despite increased impetus for ecologists to conduct and present their research in the light of potential applications. This includes the understanding of our environment, for intellectual, economical, social, and political reasons, and as a major source of innovation. We contend that we should focus less on short-term, objective-driven research and more on creativity and exploratory analyses, quantitatively estimate the benefits of fundamental research for society, and better explain the nature and importance of fundamental ecology to students, politicians, decision makers, and the general public. Our perspective and underlying arguments should also apply to evolutionary biology and to many of the other biological and physical sciences.

  9. Gas-Grain Simulation Facility: Fundamental studies of particle formation and interactions. Volume 1: Executive summary and overview

    NASA Technical Reports Server (NTRS)

    Fogleman, Guy (Editor); Huntington, Judith L. (Editor); Schwartz, Deborah E. (Editor); Fonda, Mark L. (Editor)

    1989-01-01

    An overview of the Gas-Grain Simulation Facility (GGSF) project and its current status is provided. The proceedings of the Gas-Grain Simulation Facility Experiments Workshop are recorded. The goal of the workshop was to define experiments for the GGSF--a small particle microgravity research facility. The workshop addressed the opportunity for performing, in Earth orbit, a wide variety of experiments that involve single small particles (grains) or clouds of particles. The first volume includes the executive summary, overview, scientific justification, history, and planned development of the Facility.

  10. Fundamental Study of Direct Contact Cold Energy Release by Flowing Hot Air through Ice Particles Packed Layer

    NASA Astrophysics Data System (ADS)

    Aoyama, Sigeo; Inaba, Hideo

    This paper has dealt with the direct contact heat exchange characteristics between ice particles (average ice particle diameter : 3.10mm) packed in the rectangular cold energy storage vessel and flowing hot air as a heat transfer medium. The hot air bubbles ascended in the fluidized ice particles layer, and they were cooled down directly by melting ice particles. The temperature efficiency increased as Reynolds number Re increased because the hot air flowing in the layer became active. The dehumidity efficiency increased with an increase in modified Stefan number and Re, since the heat capacity of inlet air and heat transfer coefficient increased. Finally, some empirical correlations for temperature efficiency, dehumidity efficiency and the completion time of cold energy release were derived in terms of various nondimensional parameters.

  11. False vacuum as an unstable state

    NASA Astrophysics Data System (ADS)

    Urbanowski, K.

    2016-11-01

    Calculations performed within the Standard Model suggest that the electroweak vacuum is unstable if MH < 126 GeV, (MH is the mass of the Higgs particle). LHC discovery of the Higgs boson indicates that MH ≃ 125 GeV. So the vacuum in our Universe may be unstable. We analyze properties of unstable vacuum states from the point of view of the quantum theory. At asymptotically late times the survival probability as a function of time t has an inverse power-like form. We show that at this time region the energy of the false vacuum states tends to the energy of the true vacuum state as 1/t2 for t → ∞. This means that the energy density in the unstable vacuum state should have analogous properties and hence the cosmological constant Λ = Λ(t) too. So Λ in the Universe with the unstable vacuum should have a form of the sum of the "bare" cosmological constant and of the term of a type 1/t^2:Λ (t) ≡ Λbare + d/t^2, (where Λbare is the cosmological constant for the Universe with the true vacuum).

  12. Unstable giant gravitons

    SciTech Connect

    Mello Koch, Robert de; Ives, Norman; Smolic, Jelena; Smolic, Milena

    2006-03-15

    We find giant graviton solutions in Frolov's three parameter generalization of the Lunin-Maldacena background. The background we study has {gamma}-tilde{sub 1}=0 and {gamma}-tilde{sub 2}={gamma}-tilde{sub 3}={gamma}-tilde. This class of backgrounds provides a nonsupersymmetric example of the gauge theory/gravity correspondence that can be tested quantitatively, as recently shown by Frolov, Roiban, and Tseytlin. The giant graviton solutions we find have a greater energy than the point gravitons, making them unstable states. Despite this, we find striking quantitative agreement between the gauge theory and gravity descriptions of open strings attached to the giant.

  13. Communication of Information with Sub-particles (Sub-strings) from Fifth Dimension of the Universe (Information) as the ``Fundamental Symmetry'' in the Nature

    NASA Astrophysics Data System (ADS)

    Gholibeigian, Hassan; Gholibeigian, Ghasem; Amirshahkarami, Abdolazim; Gholibeigian, Kazem

    2016-10-01

    Fundamental particles (strings) getting processed information from their four animated sub-particles (sub-strings) for their motion [Gholibeigian, APS, 2015, abstract #L1.027]. It seems that the source of information which particles and dark mater/energy are floating in it and whispering to its communication for getting order may be ``fifth dimension'' of the nature in addition of space-time dimensions. In other words, space-time can be the universe's hardware and information's dimension can be dynamic software of the universe which has always become up to date. Communication of information which has a vital role in creation and evolution of the universe, may be as the ``fundamental symmetry'' in the nature, which sparked to B.B. (Convection Bang). Communication of information leads other symmetries and supersymmetry as well as other phenomena in Universe. Before Planck time, from 0 ->10-44 second, and its correspondence space needed communication of information for preparing the B.B. So, this fifth dimension has appeared for leading the processes before and after Planck time. AmirKabir University of Technology, Tehran, Iran.

  14. Communication of Information with Sub-particles (Sub-strings) from Fifth Dimension of the Universe (Information) as the "Fundamental Symmetry" in the Nature

    NASA Astrophysics Data System (ADS)

    Gholibeigian, Hassan; Gholibeigian, Ghsem; Amirshahkarami, Abdolazim; Gholibeigian, Kazem

    2016-11-01

    All fundamental particles (strings) getting information from their four animated sub-particles (sub-strings) after processing by them for motion. It seems that the source of information which particles and dark mater/energy are floating in it and whispering to its communication may be "fifth dimension" of the nature after space-time dimensions. In other words, the space-time can be the universe's hardware and information's dimension can be dynamic software of the universe which has always become up to date. Communication of information has a vital role in creation and evolution of the universe, may be as the "fundamental symmetry" in the nature, which began before the spark to B.B. (Convection Bang), and leads other symmetries and supersymmetry as well as other phenomena. Duration of the before Planck time, from 0 ->10-44 second, and its correspondence space which its result was generation of the very hot and energetic point for the B.B. / C.B. needed to communication of information. It seems that this fifth dimension has appeared for leading the processes before and after Planck time. How this dimension of the nature appeared and has always become up to date? AmirKabir University of Technology, Tehran, Iran.

  15. Discovery of particle unstable 69Br

    NASA Astrophysics Data System (ADS)

    Lynch, William

    2011-04-01

    Two-proton capture on 68Se through 69Br provides a possible mechanism to bypass the waiting point at 68Se during explosive hydrogen burning processes on neutron stars. This two-proton capture rate, however, depends exponentially on the 69Br proton separation energy. We have determined the proton separation energy for 69Br to be -785+34-40 keV by a direct measurement of the p+68Se decay products., This extracted value is less bound than that obtained from Coulomb displacement energy calculations and the known masses for 69Se and 68Se. The influence of our value for the proton separation energy for 69Br on rp-process occurring in Type 1 X-ray bursts is examined in a one-zone burst model. A M Rogers, W G Lynch, M A Famiano, M S Wallace, F Amorini, D Bazin, R J Charity, F Delaunay, R T de Souza, J Elson, A Gade, D Galaviz, S Hudan, J Lee, S Lobostov, S Lukyanov, M Matos, M Mocko, M B Tsang, D Shapira, L G Sobotka, G Verde, arXiv:1009.2950.

  16. Gas-Grain Simulation Facility: Fundamental studies of particle formation and interactions. Volume 2: Abstracts, candidate experiments and feasibility study

    NASA Technical Reports Server (NTRS)

    Fogleman, Guy (Editor); Huntington, Judith L. (Editor); Schwartz, Deborah E. (Editor); Fonda, Mark L. (Editor)

    1989-01-01

    An overview of the Gas-Grain Simulation Facility (GGSF) project and its current status is provided. The proceedings of the Gas-Grain Simulation Facility Experiments Workshop are recorded. The goal of the workshop was to define experiments for the GGSF--a small particle microgravity research facility. The workshop addressed the opportunity for performing, in Earth orbit, a wide variety of experiments that involve single small particles (grains) or clouds of particles. Twenty experiments from the fields of exobiology, planetary science, astrophysics, atmospheric science, biology, physics, and chemistry were described at the workshop and are outlined in Volume 2. Each experiment description included specific scientific objectives, an outline of the experimental procedure, and the anticipated GGSF performance requirements. Since these experiments represent the types of studies that will ultimately be proposed for the facility, they will be used to define the general science requirements of the GGSF. Also included in the second volume is a physics feasibility study and abstracts of example Gas-Grain Simulation Facility experiments and related experiments in progress.

  17. Astrophysical data on 5 eV to 1 keV radiation from the radiative decay of fundamental particles - Current limits and prospects for improvement

    NASA Technical Reports Server (NTRS)

    Bowyer, Stuart; Malina, Roger F.

    1986-01-01

    Line emission from the decay of fundamental particles, integrated over cosmological distances, can give rise to detectable spectral features in the diffuse astronomical background between 5 eV and 1 keV. Spectroscopic observations may allow these features to be separated from line emission from the numerous local sources of radiation. The current observational status and existing evidence for such features are reviewed. No definitive detections of nongalactic line features have been made. Several local sources of background mask the features at many wavelengths and confuse the interpretation of the data. No systematic spectral observations have been carried out to date. Upcoming experiments which can be expected to provide significantly better constraints on the presence of spectral features in the diffuse background from 5 eV to 1 keV are reviewed.

  18. Fundamental study on transient bubble (slug) behavior by characterizing transient forces of solid particles in fluidized beds. Topical report, January 1991--June 1992

    SciTech Connect

    Kono, H.

    1992-10-01

    The objective of this work is to recognize and interpret the signals of transient motion of bubbles (slugs) in fluidized beds (METC/DOE) by measuring and utilizing the signals of transient gas phase pressure fluctuation, and also by taking the video pictures of transient motions of the bubbles and emulsion phase in fluidized beds. The two signals were measured simultaneously in a three dimensional fluidized bed. Correlation study on the voidage signal and pressure fluctuation was carried out. A domain concept was introduced and new bubble classification was suggested. A video recording approach was also developed to record the transient bubble motion in a two dimensional fluidized bed with a special consideration. This new approach enhances the understanding of bubble image and the physical meaning of transient particle forces. The fundamental mechanism of bubble flow was experimentally investigated and interesting new findings of the transient bubble flow were obtained.

  19. Information as the Fifth Dimension of the Universe which Fundamental Particles (strings), Dark Matter/Energy and Space-time are Floating in it While they are Listening to its Whispering for Getting Order

    NASA Astrophysics Data System (ADS)

    Gholibeigian, Hassan; Gholibeigian, Ghasem; Amirshahkarami, Azim; Gholibeigian, Kazem

    2017-01-01

    Four animated sub-particles (sub-strings) as origin of the life and generator of momentum (vibration) of elementary particles (strings) are communicated for transferring information for processing and preparing fundamental particles for the next step. It means that information may be a ``dimension'' of the nature which fundamental particles, dark matter/energy and space-time are floating in it and listening to its whispering and getting quantum information packages about their conditions and laws. So, communication of information which began before the spark to B.B. (Convection Bang), may be a ``Fundamental symmetry'' in the nature because leads other symmetries and supersymmetry as well as other phenomena. The processed information are always carried by fundamental particles as the preserved history and entropy of Universe. So, information wouldn't be destroyed, lost or released by black hole. But the involved fundamental particles of thermal radiation, electromagnetic and gravitational fields carry processed information during emitting from black hole, while they are communicated from fifth dimension for their new movement. AmirKabir University of Technology, Tehran, Iran.

  20. Two dimensional unstable scar statistics.

    SciTech Connect

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Kotulski, Joseph Daniel; Lee, Kelvin S. H. (ITT Industries/AES Los Angeles, CA)

    2006-12-01

    This report examines the localization of time harmonic high frequency modal fields in two dimensional cavities along periodic paths between opposing sides of the cavity. The cases where these orbits lead to unstable localized modes are known as scars. This paper examines the enhancements for these unstable orbits when the opposing mirrors are both convex and concave. In the latter case the construction includes the treatment of interior foci.

  1. Tether fundamentals

    NASA Technical Reports Server (NTRS)

    Carroll, J. A.

    1986-01-01

    Some fundamental aspects of tethers are presented and briefly discussed. The effects of gravity gradients, dumbbell libration in circular orbits, tether control strategies and impact hazards for tethers are among those fundamentals. Also considered are aerodynamic drag, constraints in momentum transfer applications and constraints with permanently deployed tethers. The theoretical feasibility of these concepts are reviewed.

  2. Manual control of unstable systems

    NASA Technical Reports Server (NTRS)

    Allen, R. W.; Hogue, J. R.; Parseghian, Z.

    1986-01-01

    Under certain operational regimes and failure modes, air and ground vehicles can present the human operator with a dynamically unstable or divergent control task. Research conducted over the last two decades has explored the ability of the human operator to control unstable systems under a variety of circumstances. Past research is reviewed and human operator control capabilities are summarized. A current example of automobile directional control under rear brake lockup conditions is also reviewed. A control system model analysis of the driver's steering control task is summarized, based on a generic driver/vehicle model presented at last year's Annual Manual. Results from closed course braking tests are presented that confirm the difficulty the average driver has in controlling the unstable directional dynamics arising from rear wheel lockup.

  3. Width adjustment: relative dominance in unstable alluvial streams

    USGS Publications Warehouse

    Simon, Andrew

    1994-01-01

    The mechanisms that control the relative dominance of width adjustment in unstable streams are described. Specifically, the role of the following factors affecting the fluvial environment were investigated: vertical processes and fluvial action, bed-material particle, cohesive strength of bank material, and riparian vegetation.

  4. Stabilization Strategies for Unstable Dynamics

    PubMed Central

    Saha, Devjani J.; Morasso, Pietro

    2012-01-01

    Background When humans are faced with an unstable task, two different stabilization mechanisms are possible: a high-stiffness strategy, based on the inherent elastic properties of muscles/tools/manipulated objects, or a low-stiffness strategy, based on an explicit positional feedback mechanism. Specific constraints related to the dynamics of the task and/or the neuromuscular system often force people to adopt one of these two strategies. Methodology/Findings This experiment was designed such that subjects could achieve stability using either strategy, with a marked difference in terms of effort and control requirements between the two strategies. The task was to balance a virtual mass in an unstable environment via two elastic linkages that connected the mass to each hand. The dynamics of the mass under the influence of the unstable force field and the forces applied through the linkages were simulated using a bimanual, planar robot. The two linkages were non-linear, with a stiffness that increased with the amount of stretch. The mass could be stabilized by stretching the linkages to achieve a stiffness that was greater than the instability coefficient of the unstable field (high-stiffness), or by balancing the mass with sequences of small force impulses (low-stiffness). The results showed that 62% of the subjects quickly adopted the high-stiffness strategy, with stiffness ellipses that were aligned along the direction of instability. The remaining subjects applied the low-stiffness strategy, with no clear preference for the orientation of the stiffness ellipse. Conclusions The choice of a strategy was based on the bimanual coordination of the hands: high-stiffness subjects achieved stability quickly by separating the hands to stretch the linkages, while the low-stiffness subjects kept the hands close together and took longer to achieve stability but with lower effort. We suggest that the existence of multiple solutions leads to different types of skilled behavior

  5. Influence of an Additive-Free Particle Spreading Method on Interactions between Charged Colloidal Particles at an Oil/Water Interface.

    PubMed

    Gao, Peng; Yi, Zonglin; Xing, Xiaochen; Ngai, To; Jin, Fan

    2016-05-17

    The assembly and manipulation of charged colloidal particles at oil/water interfaces represent active areas of fundamental and applied research. Previously, we have shown that colloidal particles can spontaneously generate unstable residual charges at the particle/oil interface when spreading solvent is used to disperse them at an oil/water interface. These residual charges in turn affect the long-ranged electrostatic repulsive forces and packing of particles at the interface. To further uncover the influence arising from the spreading solvents on interfacial particle interactions, in the present study we utilize pure buoyancy to drive the particles onto an oil/water interface and compare the differences between such a spontaneously adsorbed particle monolayer to the spread monolayer based on solvent spreading techniques. Our results show that the solvent-free method could also lead particles to spread well at the interface, but it does not result in violent sliding of particles along the interface. More importantly, this additive-free spreading method can avoid the formation of unstable residual charges at the particle/oil interface. These findings agree well with our previous hypothesis; namely, those unstable residual charges are triboelectric charges that arise from the violently rubbing of particles on oil at the interface. Therefore, if the spreading solvents could be avoided, then we would be able to get rid of the formation of residual charges at interfaces. This finding will provide insight for precisely controlling the interactions among colloidal particles trapped at fluid/fluid interfaces.

  6. Aberration correction of unstable resonators

    NASA Technical Reports Server (NTRS)

    Lang, Robert J. (Inventor)

    1994-01-01

    Construction of aspheric reflectors for unstable resonator lasers to provide an arbitrary laser mode inside the resonator to correct aberrations of an output beam by the construction of the shape of an end reflector opposite the output reflector of the resonator cavity, such as aberrations resulting from refraction of a beam exiting the solid of the resonator having an index of refraction greater than 1 or to produce an aberration in the output beam that will precisely compensate for the aberration of an optical train into which the resonator beam is coupled.

  7. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes.

    PubMed

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-07-25

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface.

  8. Nonlinear force dependence on optically bound micro-particle arrays in the evanescent fields of fundamental and higher order microfibre modes

    PubMed Central

    Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle

    2016-01-01

    Particles trapped in the evanescent field of an ultrathin optical fibre interact over very long distances via multiple scattering of the fibre-guided fields. In ultrathin fibres that support higher order modes, these interactions are stronger and exhibit qualitatively new behaviour due to the coupling of different fibre modes, which have different propagation wave-vectors, by the particles. Here, we study one dimensional longitudinal optical binding interactions of chains of 3 μm polystyrene spheres under the influence of the evanescent fields of a two-mode microfibre. The observation of long-range interactions, self-ordering and speed variation of particle chains reveals strong optical binding effects between the particles that can be modelled well by a tritter scattering-matrix approach. The optical forces, optical binding interactions and the velocity of bounded particle chains are calculated using this method. Results show good agreement with finite element numerical simulations. Experimental data and theoretical analysis show that higher order modes in a microfibre offer a promising method to not only obtain stable, multiple particle trapping or faster particle propulsion speeds, but that they also allow for better control over each individual trapped object in particle ensembles near the microfibre surface. PMID:27451935

  9. Marketing fundamentals.

    PubMed

    Redmond, W H

    2001-01-01

    This chapter outlines current marketing practice from a managerial perspective. The role of marketing within an organization is discussed in relation to efficiency and adaptation to changing environments. Fundamental terms and concepts are presented in an applied context. The implementation of marketing plans is organized around the four P's of marketing: product (or service), promotion (including advertising), place of delivery, and pricing. These are the tools with which marketers seek to better serve their clients and form the basis for competing with other organizations. Basic concepts of strategic relationship management are outlined. Lastly, alternate viewpoints on the role of advertising in healthcare markets are examined.

  10. Inherently Unstable Internal Gravity Waves

    NASA Astrophysics Data System (ADS)

    Alam, Reza

    2016-11-01

    Here we show that there exist internal gravity waves that are inherently unstable, that is, they cannot exist in nature for a long time. The instability mechanism is a one-way (irreversible) harmonic-generation resonance that permanently transfers the energy of an internal wave to its higher harmonics. We show that, in fact, there are countably infinite number of such unstable waves. For the harmonic-generation resonance to take place, nonlinear terms in the free surface boundary condition play a pivotal role, and the instability does not obtain for a linearly-stratified fluid if a simplified boundary condition such as rigid lid or linear form is employed. Harmonic-generation resonance discussed here also provides a mechanism for the transfer of the energy of the internal waves to the higher-frequency part of the spectrum where internal waves are more prone to breaking, hence losing energy to turbulence and heat and contributing to oceanic mixing. Yong Liang (yong.liang@berkeley.edu).

  11. Unstable extension of Enceladus' lithosphere

    NASA Astrophysics Data System (ADS)

    Bland, Michael T.; Beyer, Ross A.; Showman, Adam P.

    2007-12-01

    Regions near Enceladus' equator, Sarandib and Diyar Planitia, contain extensive sets of parallel ridges and troughs that may be diagnostic of the region's formation conditions. We present photoclinometry profiles across these ridges and troughs, which indicate that they are periodic, low-slope features with dominant wavelengths of 3 to 4 km and amplitudes between 100 and 400 m. The morphology of these terrains is consistent with formation via unstable extension of the lithosphere. Our numerical modeling demonstrates that unstable extension can generate large-scale topography under Enceladus-like conditions. Comparison of our photoclinometry profiles with the dominant wavelengths produced by our numerical model permits estimation of the background heat flow at the time the Sarandib-Diyar province formed. We estimate heat flows of 110 to 220mWm, suggesting that resurfacing of the planitiae was accompanied by strong, localized heating. The extension necessary to produce the ridges and troughs may have been caused by now-inactive diapirs, internal phase changes, or other mechanisms. Our heat flux estimates imply elastic thickness at the time of resurfacing of 0.4 to 1.4 km, which are sufficient to have allowed satellite reorientation if the province was underlain by a low-density region. It is therefore plausible that Enceladus has experienced multiple heating events, each leading to localized resurfacing and global reorientation.

  12. Fundamentals of Monte Carlo

    SciTech Connect

    Wollaber, Allan Benton

    2016-06-16

    This is a powerpoint presentation which serves as lecture material for the Parallel Computing summer school. It goes over the fundamentals of the Monte Carlo calculation method. The material is presented according to the following outline: Introduction (background, a simple example: estimating π), Why does this even work? (The Law of Large Numbers, The Central Limit Theorem), How to sample (inverse transform sampling, rejection), and An example from particle transport.

  13. Research on fundamental aspects of inorganic particle deposition on coal-fired equipment. Final technical report, 6 September 1990--31 October 1994

    SciTech Connect

    Rosner, D.E.

    1995-01-01

    We review results of our recent DOE-PETC research program on the deposition dynamics of combustion-generated particles in power production technologies. We outline and illustrate the results of recently developed methods to predict total surface deposition rates and associated convective heat transfer reductions for targets exposed to a distribution of particles suspended in a mainstream. Our methods combine the essential features of recently developed single particle sticking probability laws with correlations of the inertial impaction of particles on targets in high Reynolds number cross-flow, to develop formulae and ``universal`` graphs which provide the dependence of particle deposition rates, and associated reductions in convective heat transfer, on such system parameters as mainstream velocity, mean suspended particle size and target size. The deposition rate/deposit microstructue/properties prediction and correlation procedures illustrated be incorporated into improved ``fouling propensity indices,`` to motivate, evaluate and implement ``ruggedization`` and/or fouling reduction strategies, and/or incorporated (as subroutines) into more ``comprehensive`` CFD models of an entire power plant.

  14. Arthroscopic treatment of unstable total hip replacement.

    PubMed

    Cuéllar, Ricardo; Aguinaga, Iñaki; Corcuera, Irene; Ponte, Juan; Usabiaga, Jaime

    2010-06-01

    Hip arthroscopy may be useful in the diagnosis and treatment of apparently well-implanted but unstable total hip replacement prostheses. We present 2 cases of arthroscopically assisted capsular tightening in unstable total hip replacements. Both cases had significant capsular laxity. Case 2 had impingement of the lower part of the acetabulum with the lesser trochanter that caused hip dislocation. Early revision surgery can be avoided with the use of this technique in selected cases of unstable total hip replacements.

  15. Correlations of Decay Times of Entangled Composite Unstable Systems

    NASA Astrophysics Data System (ADS)

    Durt, Thomas

    2013-01-01

    The role played by time in the quantum theory is still mysterious by many aspects. In particular it is not clear today whether the distribution of decay times of unstable particles could be described by a time operator (TO). As we shall discuss, different approaches to this problem (one could say interpretations) can be found in the literature on the subject. As we shall show, it is possible to conceive crucial experiments aimed at distinguishing the different approaches, by measuring with accuracy the statistical distribution of decay times of entangled particles. Such experiments can be realized in principle with entangled kaon pairs.

  16. Correlations of Decay Times of Entangled Composite Unstable Systems

    NASA Astrophysics Data System (ADS)

    Durt, Thomas

    2012-05-01

    The role played by time in the quantum theory is still mysterious by many aspects. In particular it is not clear today whether the distribution of decay times of unstable particles could be described by a time operator (TO). As we shall discuss, different approaches to this problem (one could say interpretations) can be found in the literature on the subject. As we shall show, it is possible to conceive crucial experiments aimed at distinguishing the different approaches, by measuring with accuracy the statistical distribution of decay times of entangled particles. Such experiments can be realized in principle with entangled kaon pairs.

  17. Neutrons and Fundamental Symmetries

    SciTech Connect

    Plaster, Bradley

    2016-01-11

    The research supported by this project addressed fundamental open physics questions via experiments with subatomic particles. In particular, neutrons constitute an especially ideal “laboratory” for fundamental physics tests, as their sensitivities to the four known forces of nature permit a broad range of tests of the so-called “Standard Model”, our current best physics model for the interactions of subatomic particles. Although the Standard Model has been a triumphant success for physics, it does not provide satisfactory answers to some of the most fundamental open questions in physics, such as: are there additional forces of nature beyond the gravitational, electromagnetic, weak nuclear, and strong nuclear forces?, or why does our universe consist of more matter than anti-matter? This project also contributed significantly to the training of the next generation of scientists, of considerable value to the public. Young scientists, ranging from undergraduate students to graduate students to post-doctoral researchers, made significant contributions to the work carried out under this project.

  18. Osteoporosis in unstable adult scoliosis

    SciTech Connect

    Velis, K.P.; Healey, J.H.; Schneider, R.

    1988-12-01

    New noninvasive techniques as well as conventional methods were used to evaluate skeletal mass in the following three populations of adult white women as follows: (1) 79 subjects with preexisting idiopathic scoliosis designated as unstable (US) because of the associated presence in the lumbar spine of lateral spondylolisthesis with segmental instability; (2) 67 subjects with preexisting idiopathic scoliosis without lateral spondylolisthesis designated as stable (SS); and (3) 248 age-matched nonscoliotic controls. Ages in all three groups were categorized into premenopausal (25-44 years), perimenopausal (45-54 years), and postmenopausal (55-84 years). The results showed higher scoliosis morbidity in the US compared to the SS populations. The prevalence and severity of osteoporosis were markedly increased in US versus SS populations. Femoral neck density determined by dual-photon absorptiometry techniques averaged 26% to 48% lower in all age categories of US patients compared to controls. These changes were found in the youngest age groups, indicating reductions in bone mineral content earlier in the adult life of white women with a specific type of high-morbidity US characterized by the marker of lateral spondylolisthesis.

  19. Fundamental properties of resonances.

    PubMed

    Ceci, S; Hadžimehmedović, M; Osmanović, H; Percan, A; Zauner, B

    2017-03-27

    All resonances, from hydrogen nuclei excited by the high-energy gamma rays in deep space to newly discovered particles produced in Large Hadron Collider, should be described by the same fundamental physical quantities. However, two distinct sets of properties are used to describe resonances: the pole parameters (complex pole position and residue) and the Breit-Wigner parameters (mass, width, and branching fractions). There is an ongoing decades-old debate on which one of them should be abandoned. In this study of nucleon resonances appearing in the elastic pion-nucleon scattering we discover an intricate interplay of the parameters from both sets, and realize that neither set is completely independent or fundamental on its own.

  20. Fundamental properties of resonances

    PubMed Central

    Ceci, S.; Hadžimehmedović, M.; Osmanović, H.; Percan, A.; Zauner, B.

    2017-01-01

    All resonances, from hydrogen nuclei excited by the high-energy gamma rays in deep space to newly discovered particles produced in Large Hadron Collider, should be described by the same fundamental physical quantities. However, two distinct sets of properties are used to describe resonances: the pole parameters (complex pole position and residue) and the Breit-Wigner parameters (mass, width, and branching fractions). There is an ongoing decades-old debate on which one of them should be abandoned. In this study of nucleon resonances appearing in the elastic pion-nucleon scattering we discover an intricate interplay of the parameters from both sets, and realize that neither set is completely independent or fundamental on its own. PMID:28345595

  1. Fundamentals of Polarized Light

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael

    2003-01-01

    The analytical and numerical basis for describing scattering properties of media composed of small discrete particles is formed by the classical electromagnetic theory. Although there are several excellent textbooks outlining the fundamentals of this theory, it is convenient for our purposes to begin with a summary of those concepts and equations that are central to the subject of this book and will be used extensively in the following chapters. We start by formulating Maxwell's equations and constitutive relations for time- harmonic macroscopic electromagnetic fields and derive the simplest plane-wave solution that underlies the basic optical idea of a monochromatic parallel beam of light. This solution naturally leads to the introduction of such fundamental quantities as the refractive index and the Stokes parameters. Finally, we define the concept of a quasi-monochromatic beam of light and discuss its implications.

  2. 30 CFR 56.9304 - Unstable ground.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Unstable ground. 56.9304 Section 56.9304... § 56.9304 Unstable ground. (a) Dumping locations shall be visually inspected prior to work commencing and as ground conditions warrant. (b) Where there is evidence that the ground at a dumping...

  3. 30 CFR 56.9304 - Unstable ground.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Unstable ground. 56.9304 Section 56.9304... § 56.9304 Unstable ground. (a) Dumping locations shall be visually inspected prior to work commencing and as ground conditions warrant. (b) Where there is evidence that the ground at a dumping...

  4. 30 CFR 56.9304 - Unstable ground.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Unstable ground. 56.9304 Section 56.9304... § 56.9304 Unstable ground. (a) Dumping locations shall be visually inspected prior to work commencing and as ground conditions warrant. (b) Where there is evidence that the ground at a dumping...

  5. 30 CFR 56.9304 - Unstable ground.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Unstable ground. 56.9304 Section 56.9304... § 56.9304 Unstable ground. (a) Dumping locations shall be visually inspected prior to work commencing and as ground conditions warrant. (b) Where there is evidence that the ground at a dumping...

  6. 30 CFR 56.9304 - Unstable ground.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Unstable ground. 56.9304 Section 56.9304... § 56.9304 Unstable ground. (a) Dumping locations shall be visually inspected prior to work commencing and as ground conditions warrant. (b) Where there is evidence that the ground at a dumping...

  7. Survival of the structures in the universe dominated by unstable dark matter

    NASA Astrophysics Data System (ADS)

    Suto, Y.; Noguchi, M.

    1986-04-01

    Dynamical evolution of non-linear structures in the universe dominated by unstable particles is studied by the numerical integration of the Vlasov equation. Their dynamical behaviour is determined by two parameters; one is the ratio of energy densities of baryons and unstable particles β and the other is the ratio of the lifetime of unstable particles τX to the initial free-fall time-scale tff,i. Non-linear structures satisfying the survival condition - τX/tff,i > 1/(2β2) - remains as bound systems irrespective of the decay of unstable particles. As long as one considers the cosmologically restricted range of τX and β, galaxies satisfy the survival condition and their evolution is well understood in terms of adiabatic behaviour. On the other hand, clusters of galaxies may be disrupted in future due to decay of unstable particles. A possible restriction to the formation of structures and the consequence of this scenario to the observed angular size of galaxies are discussed quantitatively.

  8. Investigating Unstable Water Infiltration into Alcohol Contaminated Soils

    NASA Astrophysics Data System (ADS)

    McLeod, H. C.; Smith, J. E.; Henry, E. J.; Brodsky, Y.

    2009-05-01

    A new mechanism causing highly focused, unstable flow exists in soils contaminated with alcohols due to their surface-activity. For example, surface-active compounds can significantly decrease the interfacial tension of the air-water interface and change the pressure-head of the soil water; directly affecting water flow and solute transport in the vadose zone. This study evaluated the fundamental effects of surface-active alcohols on water infiltration into contaminated soils under controlled laboratory conditions. A small scale 3-D glass flow cell and a mini disk tension infiltrometer were used to monitor the rates and physical characteristics of water infiltration from a constant head point source into sands of various textures contaminated with a butanol solution. The results confirmed that water infiltration into these soils is fundamentally and substantially different than the current understanding of infiltration patterns, including previously described mechanisms of wetting front instability. In butanol-contaminated soils, the wetting fronts exhibited highly focused flow with smaller wetted soil volumes, deeper penetration and substantially higher infiltration rates. In addition, the extent of fingered focused flow was confirmed to be texturally dependent, decreasing with grain size and dependent on the constant head boundary. This study characterized a new mechanism of focused, unstable flow with significant implications for groundwater management and solute transport in alcohol contaminated soils.

  9. Unstable Binocular Control in Dyslexic Children.

    ERIC Educational Resources Information Center

    Stein, J. F.; Fowler, M. S.

    1993-01-01

    Offers evidence for four propositions that demonstrate a strong association between binocular instability and dyslexic reading difficulties. Discusses two propositions designed to prove that it is unstable binocular control that causes reading difficulties, rather than vice versa. (RS)

  10. Unstable attractors induce perpetual synchronization and desynchronization.

    PubMed

    Timme, Marc; Wolf, Fred; Geisel, Theo

    2003-03-01

    Common experience suggests that attracting invariant sets in nonlinear dynamical systems are generally stable. Contrary to this intuition, we present a dynamical system, a network of pulse-coupled oscillators, in which unstable attractors arise naturally. From random initial conditions, groups of synchronized oscillators (clusters) are formed that send pulses alternately, resulting in a periodic dynamics of the network. Under the influence of arbitrarily weak noise, this synchronization is followed by a desynchronization of clusters, a phenomenon induced by attractors that are unstable. Perpetual synchronization and desynchronization lead to a switching among attractors. This is explained by the geometrical fact, that these unstable attractors are surrounded by basins of attraction of other attractors, whereas the full measure of their own basin is located remote from the attractor. Unstable attractors do not only exist in these systems, but moreover dominate the dynamics for large networks and a wide range of parameters.

  11. From stable to unstable anomaly-induced inflation

    NASA Astrophysics Data System (ADS)

    Netto, Tibério de Paula; Pelinson, Ana M.; Shapiro, Ilya L.; Starobinsky, Alexei A.

    2016-10-01

    Quantum effects derived through conformal anomaly lead to an inflationary model that can be either stable or unstable. The unstable version requires a large dimensionless coefficient of about 5× {10}^8 in front of the {R}^2 term that results in the inflationary regime in the R+{R}^2 ("Starobinsky") model being a generic intermediate attractor. In this case the non-local terms in the effective action are practically irrelevant, and there is a `graceful exit' to a low curvature matter-like dominated stage driven by high-frequency oscillations of R - scalarons, which later decay to pairs of all particles and antiparticles, with the amount of primordial scalar (density) perturbations required by observations. The stable version is a genuine generic attractor, so there is no exit from it. We discuss a possible transition from stable to unstable phases of inflation. It is shown that this transition is automatic if the sharp cut-off approximation is assumed for quantum corrections in the period of transition. Furthermore, we describe two different quantum mechanisms that may provide a required large {R}^2-term in the transition period.

  12. Fundamental neutron physics at LANSCE

    SciTech Connect

    Greene, G.

    1995-10-01

    Modern neutron sources and science share a common origin in mid-20th-century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for studying condensed matter with modern neutron sources being primarily used (and justified) as tools for neutron scattering and materials science research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities performed at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high-flux neutron facilities. Future sources, particularly high-power spallation sources, offer exciting possibilities for continuing this research.

  13. Testing Our Fundamental Assumptions

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-06-01

    Science is all about testing the things we take for granted including some of the most fundamental aspects of how we understand our universe. Is the speed of light in a vacuum the same for all photons regardless of their energy? Is the rest mass of a photon actually zero? A series of recent studies explore the possibility of using transient astrophysical sources for tests!Explaining Different Arrival TimesArtists illustration of a gamma-ray burst, another extragalactic transient, in a star-forming region. [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]Suppose you observe a distant transient astrophysical source like a gamma-ray burst, or a flare from an active nucleus and two photons of different energies arrive at your telescope at different times. This difference in arrival times could be due to several different factors, depending on how deeply you want to question some of our fundamental assumptions about physics:Intrinsic delayThe photons may simply have been emitted at two different times by the astrophysical source.Delay due to Lorentz invariance violationPerhaps the assumption that all massless particles (even two photons with different energies) move at the exact same velocity in a vacuum is incorrect.Special-relativistic delayMaybe there is a universal speed for massless particles, but the assumption that photons have zero rest mass is wrong. This, too, would cause photon velocities to be energy-dependent.Delay due to gravitational potentialPerhaps our understanding of the gravitational potential that the photons experience as they travel is incorrect, also causing different flight times for photons of different energies. This would mean that Einsteins equivalence principle, a fundamental tenet of general relativity (GR), is incorrect.If we now turn this problem around, then by measuring the arrival time delay between photons of different energies from various astrophysical sources the further away, the better we can provide constraints on these

  14. Unstable solar lentigo: A defined separate entity.

    PubMed

    Byrom, Lisa; Barksdale, Sarah; Weedon, David; Muir, Jim

    2016-08-01

    An unstable solar lentigo is a solar lentigo with areas of melanocytic hyperplasia not extending past the margin of the lesion. They are discrete, macular, pigmented lesions arising on sun-damaged skin and a subset of typical solar lentigos. Clinically they differ from usual solar lentigines in often being solitary or larger and darker than adjacent solar lentigines. These lesions are of clinical importance as they can arise in close proximity to lentigo maligna and in a single lesion there can be demonstrated changes of solar lentigo, unstable solar lentigo and lentigo maligna. These observations led us to conjecture that unstable solar lentigos could be a precursor lesion to lentigo maligna. In this article we examine the possibility that lentigo maligna can arise within a solar lentigo through an intermediate lesion, the unstable solar lentigo. We propose that the histopathological recognition of this entity will allow for future research into its behaviour and thus management. We review difficulties in the diagnosis of single cell predominant melanocytic proliferations and the concept of unstable lentigo in view of the literature and clinical experience supporting the proposal of its recognition as a separate entity.

  15. NOVA SCIENCE UNIT 15, FUNDAMENTAL PARTICLES 4.

    ERIC Educational Resources Information Center

    1964

    THE PRINCIPLES OF ATOMIC STRUCTURE WHICH ARE STRESSED ARE THAT ATOMS ARE MADE UP OF A NUCLEUS WITH A POSITIVE CHARGE, SURROUNDED BY ELECTRONS WITH A NEGATIVE CHARGE, AND THAT THERE IS NO CHANGE IN THE ATOM WHEN THE POSITIVE AND NEGATIVE CHARGES ARE EQUAL. EXPERIMENTS ILLUSTRATE THAT CURRENT ELECTRICITY IS ACTUALLY ELECTRONS IN MOTION, THAT THERE…

  16. Inferring unstable equilibrium configurations from experimental data

    NASA Astrophysics Data System (ADS)

    Virgin, L. N.; Wiebe, R.; Spottswood, S. M.; Beberniss, T.

    2016-09-01

    This research considers the structural behavior of slender, mechanically buckled beams and panels of the type commonly found in aerospace structures. The specimens were deflected and then clamped in a rigid frame in order to exhibit snap-through. That is, the initial equilibrium and the buckled (snapped-through) equilibrium configurations both co-existed for the given clamped conditions. In order to transit between these two stable equilibrium configurations (for example, under the action of an externally applied load), it is necessary for the structural component to pass through an intermediate unstable equilibrium configuration. A sequence of sudden impacts was imparted to the system, of various strengths and at various locations. The goal of this impact force was to induce relatively intermediate-sized transients that effectively slowed-down in the vicinity of the unstable equilibrium configuration. Thus, monitoring the velocity of the motion, and specifically its slowing down, should give an indication of the presence of an equilibrium configuration, even though it is unstable and not amenable to direct experimental observation. A digital image correlation (DIC) system was used in conjunction with an instrumented impact hammer to track trajectories and statistical methods used to infer the presence of unstable equilibria in both a beam and a panel.

  17. The Fate of Unstable Circumbinary Planets

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-03-01

    What happens to Tattooine-like planets that are instead in unstable orbits around their binary star system? A new study examines whether such planets will crash into a host star, get ejected from the system, or become captured into orbit around one of their hosts.Orbit Around a DuoAt this point we have unambiguously detected multiple circumbinary planets, raising questions about these planets formation and evolution. Current models suggest that it is unlikely that circumbinary planets would be able to form in the perturbed environment close their host stars. Instead, its thought that the planets formed at a distance and then migrated inwards.One danger such planets face when migrating is encountering ranges of radii where their orbits become unstable. Two scientists at the University of Chicago, Adam Sutherland and Daniel Fabrycky, have studied what happens when circumbinary planets migrate into such a region and develop unstable orbits.Producing Rogue PlanetsTime for planets to either be ejected or collide with one of the two stars, as a function of the planets starting distance (in AU) from the binary barycenter. Colors represent different planetary eccentricities. [Sutherland Fabrycky 2016]Sutherland and Fabrycky used N-body simulations to determine the fates of planets orbiting around a star system consisting of two stars a primary like our Sun and a secondary roughly a tenth of its size that are separated by 1 AU.The authors find that the most common fate for a circumbinary planet with an unstable orbit is ejection from the system; over 80% of unstable planets were ejected. This has interesting implications: if the formation of circumbinary planets is common, this mechanism could be filling the Milky Way with a population of free-floating, rogue planets that no longer are associated with their host star.The next most common outcome for unstable planets is collision with one of their host stars (most often the secondary), resulting inaccretion of the planet

  18. Review of management of unstable elbow fractures

    PubMed Central

    Ozel, Omer; Demircay, Emre

    2016-01-01

    Stable and painless elbow motion is essential for activities of daily living. The elbow joint is the second most commonly dislocated joint in adults. The goals of treatment are to perform a stable fixation of all fractures, to achieve concentric and stable reduction of the elbow and to provide early motion. The treatment modality for complex elbow instability is almost always surgical. The treatment objectives are anatomic reduction, stable fixation, and early rehabilitation of the elbow. The common complications of these unstable fractures include recurrent instability, stiffness, myositis ossifications, heterotopic calcification, and neurovascular dysfunction. We analyzed the management of complex elbow fractures and instabilities on the basis of recent literature and suggested possible guidelines for the treatment in this paper. In conclusion, recognition of the injury pattern and restoration of the joint stability are the prerequisites for any successful treatment of an unstable elbow injury. PMID:26807356

  19. Unstable resonators with excited converging wave

    SciTech Connect

    Hodgson, N. ); Weber, H. )

    1990-04-01

    This paper reports the properties of unstable resonators with an additional mirror inside or outside the resonator investigated, both experimentally and theoretically. The additional mirror excites the converging wave, and by this, output coupling is decreased without affecting beam quality. Experiments were performed with a pulsed Nd:YAG system. The theoretical model was based on the coupled Kirchhoff integrals and solved numerically. Agreement between theory and experiments indicates that this kind of resonator provides high focusability and maximum extraction efficiency simultaneously, even with low-gain media. This enables one to apply unstable resonators to solid-state lasers with low small-signal gain, like alexandrite or CW-pumped Nd:YAG.

  20. "Explosively growing" vortices of unstably stratified atmosphere

    NASA Astrophysics Data System (ADS)

    Onishchenko, O. G.; Horton, W.; Pokhotelov, O. A.; Fedun, V.

    2016-10-01

    A new type of "explosively growing" vortex structure is investigated theoretically in the framework of ideal fluid hydrodynamics. It is shown that vortex structures may arise in convectively unstable atmospheric layers containing background vorticity. From an exact analytical vortex solution the vertical vorticity structure and toroidal speed are derived and analyzed. The assumption that vorticity is constant with height leads to a solution that grows explosively when the flow is inviscid. The results shown are in agreement with observations and laboratory experiments

  1. Unstable resonators with a distributed focusing gain.

    PubMed

    Ferguson, T R

    1994-08-20

    The geometrical optics approximation is used to form a model of axisymmetric unstable resonators having distributed focus, gain, and loss. A tapered reflectivity feedback mirror is included. The rate equations for propagation through the focusing gain medium are derived. A unique grid is found for propagation without interpolation along eigenrays in each direction. Numerical examples show the effects of distributed gain and focus on the axial and transverse intensity distributions.

  2. Special Relativity and Reactions with Unstable Nuclei

    SciTech Connect

    Bertulani, C.A.

    2005-10-14

    Dynamical relativistic effects are often neglected in the description of reactions with unstable nuclear beams at intermediate energies (ELab {approx_equal} 100 MeV/nucleon). Evidently, this introduces sizable errors in experimental analysis and theoretical descriptions of these reactions. This is particularly important for the experiments held in GANIL/France, MSU/USA, RIKEN/Japan and GSI/Germany. I review a few examples where relativistic effects have been studied in nucleus-nucleus scattering at intermediate energies.

  3. Combustion Fundamentals Research

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

  4. Exchange Rates and Fundamentals.

    ERIC Educational Resources Information Center

    Engel, Charles; West, Kenneth D.

    2005-01-01

    We show analytically that in a rational expectations present-value model, an asset price manifests near-random walk behavior if fundamentals are I (1) and the factor for discounting future fundamentals is near one. We argue that this result helps explain the well-known puzzle that fundamental variables such as relative money supplies, outputs,…

  5. Exploring the Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Volya, Alexander

    In this presentation the Continuum Shell Model (CSM) approach is advertised as a powerful theoretical tool for studying physics of unstable nuclei. The approach is illustrated using 17O as an example, which is followed by a brief presentation of the general CSM formalism. The successes of the CSM are highlighted and references are provided throughout the text. As an example, the CSM is applied perturbatively to 20O allowing one to explore the effects of continuum on positions of weakly bound states and low-lying resonances, as well as to discern some effects of threshold discontinuity.

  6. Confocal unstable optical resonator with asymmetrical magnification

    SciTech Connect

    Hoffmann, P.

    1981-12-01

    The appropriate combination of spherical and cylindrical mirrors allows one to arrange an unstable laser cavity with asymmetrical magnification and to generate collimated output as well. By introducing two additional cylindrical mirrors into the cavity the aberration problems of tilted mirror systems are avoided. On the other hand, this modification is a low-cost alternative to cavities with diamond-turned mirrors with ellipsoidal surface curvature. In the geometrical-optics limit there exists a unique combination of mirror radii of curvature for a given ratio of magnification at fixed distances between the mirrors.

  7. Confocal unstable optical resonator with asymmetrical magnification.

    PubMed

    Hoffmann, P

    1981-12-01

    The appropriate combination of spherical and cylindrical mirrors allows one to arrange an unstable laser cavity with asymmetrical magnification and to generate collimated output as well. By introducing two additional cylindrical mirrors into the cavity the aberration problems of tilted mirror systems are avoided. On the other hand, this modification is a low-cost alternative to cavities with diamond-turned mirrors with ellipsoidal surface curvature. In the geometrical-optics limit there exists a unique combination of mirror radii of curvature for a given ratio of magnification at fixed distances between the mirrors.

  8. Particle physics: Axions exposed

    NASA Astrophysics Data System (ADS)

    Lombardo, Maria Paola

    2016-11-01

    Physicists are hunting for a particle called the axion that could solve two major puzzles in fundamental physics. An ambitious study calculates the expected mass of this particle, which might reshape the experimental searches. See Letter p.69

  9. Boundary between stable and unstable regimes of accretion. Ordered and chaotic unstable regimes

    NASA Astrophysics Data System (ADS)

    Blinova, A. A.; Romanova, M. M.; Lovelace, R. V. E.

    2016-07-01

    We present a new study of the Rayleigh-Taylor unstable regime of accretion on to rotating magnetized stars in a set of high grid resolution three-dimensional magnetohydrodynamic simulations performed in low-viscosity discs. We find that the boundary between the stable and unstable regimes is determined almost entirely by the fastness parameter ωs = Ω⋆/ΩK(rm), where Ω⋆ is the angular velocity of the star and ΩK(rm) is the angular velocity of the Keplerian disc at the disc-magnetosphere boundary r = rm. We found that accretion is unstable if ωs ≲ 0.6. Accretion through instabilities is present in stars with different magnetospheric sizes. However, only in stars with relatively small magnetospheres, rm/R⋆ ≲ 7, do the unstable tongues produce chaotic hotspots on the stellar surface and irregular light curves. At even smaller values of the fastness parameter, ωs ≲ 0.45, multiple irregular tongues merge, forming one or two ordered unstable tongues that rotate with the angular frequency of the inner disc. This transition occurs in stars with even smaller magnetospheres, rm/R⋆ ≲ 4.2. Most of our simulations were performed at a small tilt of the dipole magnetosphere, Θ = 5°, and a small viscosity parameter α = 0.02. Test simulations at higher α values show that many more cases become unstable, and the light curves become even more irregular. Test simulations at larger tilts of the dipole Θ show that instability is present, however, accretion in two funnel streams dominates if Θ ≳ 15°. The results of these simulations can be applied to accreting magnetized stars with relatively small magnetospheres: Classical T Tauri stars, accreting millisecond X-ray pulsars, and cataclysmic variables.

  10. Black holes and fundamental fields in numerical relativity: Initial data construction and evolution of bound states

    NASA Astrophysics Data System (ADS)

    Okawa, Hirotada; Witek, Helvi; Cardoso, Vitor

    2014-05-01

    Fundamental fields are a natural outcome in cosmology and particle physics and might therefore serve as a proxy for more complex interactions. The equivalence principle implies that all forms of matter gravitate, and one therefore expects relevant, universal imprints of new physics in strong field gravity, such as that encountered close to black holes. Fundamental fields in the vicinities of supermassive black holes give rise to extremely long-lived, or even unstable, configurations, which slowly extract angular momentum from the black hole or simply evolve nonlinearly over long time scales, with important implications for particle physics and gravitational-wave physics. Here, we perform a fully nonlinear study of scalar-field condensates around rotating black holes. We provide novel ways to specify initial data for the Einstein—Klein—Gordon system, with potential applications in a variety of scenarios. Our numerical results confirm the existence of long-lived bar modes, which act as lighthouses for gravitational wave emission: the scalar field condenses outside the black hole geometry and acts as a constant frequency gravitational-wave source for very long time scales. This effect could turn out to be a potential signature of beyond standard model physics and also a promising source of gravitational waves for future gravitational-wave detectors.

  11. Multijoint error compensation mediates unstable object control.

    PubMed

    Cluff, Tyler; Manos, Aspasia; Lee, Timothy D; Balasubramaniam, Ramesh

    2012-08-01

    A key feature of skilled object control is the ability to correct performance errors. This process is not straightforward for unstable objects (e.g., inverted pendulum or "stick" balancing) because the mechanics of the object are sensitive to small control errors, which can lead to rapid performance changes. In this study, we have characterized joint recruitment and coordination processes in an unstable object control task. Our objective was to determine whether skill acquisition involves changes in the recruitment of individual joints or distributed error compensation. To address this problem, we monitored stick-balancing performance across four experimental sessions. We confirmed that subjects learned the task by showing an increase in the stability and length of balancing trials across training sessions. We demonstrated that motor learning led to the development of a multijoint error compensation strategy such that after training, subjects preferentially constrained joint angle variance that jeopardized task performance. The selective constraint of destabilizing joint angle variance was an important metric of motor learning. Finally, we performed a combined uncontrolled manifold-permutation analysis to ensure the variance structure was not confounded by differences in the variance of individual joint angles. We showed that reliance on multijoint error compensation increased, whereas individual joint variation (primarily at the wrist joint) decreased systematically with training. We propose a learning mechanism that is based on the accurate estimation of sensory states.

  12. Unstable Planetary Systems Around White Dwarfs

    NASA Astrophysics Data System (ADS)

    Sigurdsson, S.; Debes, J. H.

    2001-12-01

    The presence of planets around solar-type stars suggests that many white dwarfs should have planetary systems. While planets closer than ~5 AU will most likely not survive the post-main sequence lifetime of their parent star, any planet > 5 AU will survive and its semimajor axis will increase as the central star loses mass. Since the stability of adjacent orbits to mutual perturbations depends on the ratio of the planet mass to the central star's mass, some planets in previously stable orbits around a star undergoing mass loss will become unstable. We show that when mass loss is slow, systems of two planets that are marginally stable can become unstable to close encounters, while for three planets the timescale for close approaches decreases with increasing mass ratio. These processes could explain the presence of anomalous IR excesses around white dwarfs that cannot be explained by close companions, such as G29-38. We find that this should also be an effect for planetary embryos gaining mass in protoplanetary disks.

  13. 2001 QR322: a dynamically unstable Neptune Trojan?

    NASA Astrophysics Data System (ADS)

    Horner, J.; Lykawka, P. S.

    2010-06-01

    Since early work on the stability of the first Neptunian Trojan, 2001 QR322, suggested that it was a dynamically stable, primordial body, it has been assumed that this applies to both that object and its more recently discovered brethren. However, it seems that things are no longer so clear-cut. In this work, we present the results of detailed dynamical simulations of the orbital behaviour of 2001 QR322. Using an ephemeris for the object that has significantly improved since earlier works, we follow the evolution of 19683 test particles, placed on orbits within the observational error ellipse of 2001 QR322's orbit, for a period of 1Gyr. We find that majority of these `clones' of 2001 QR322 are dynamically unstable, exhibiting a near-exponential decay from both the Neptunian Trojan cloud (decay half-life of ~550Myr) and the Solar system (decay half-life of ~590Myr). The stability of the object within Neptune's Trojan cloud is found to be strongly dependent on the initial semimajor axis used, with these objects located at a >= 30.30au being significantly less stable than those interior to this value, as a result of their having initial libration amplitudes very close to a critical threshold dividing regular and irregular motion, located at ~70°-75° (full extent of angular motion). This result suggests that if 2001 QR322 is a primordial Neptunian Trojan, it must be a representative of a population that was once significantly larger than that we see today and adds weight to the idea that the Neptune Trojans may represent a significant source of objects moving on unstable orbits between the giant planets (the Centaurs).

  14. Fundamental Physical Constants

    National Institute of Standards and Technology Data Gateway

    SRD 121 CODATA Fundamental Physical Constants (Web, free access)   This site, developed in the Physics Laboratory at NIST, addresses three topics: fundamental physical constants, the International System of Units (SI), which is the modern metric system, and expressing the uncertainty of measurement results.

  15. Fundamentals of Physics

    NASA Astrophysics Data System (ADS)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2003-01-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.

  16. Phase Transformation Behavior at Low Temperature in Hydrothermal Treatment of Stable and Unstable Titania Sol

    PubMed

    So; Park; Kim; Moon

    1997-07-15

    Nanosize titania sol was prepared from titanium tetraisopropoxide (TTIP) and conditions for the formation of stable sol were identified. As the H+/TTIP mole ratio decreased and H2O/TTIP mole ratio increased, stable sol was likely to be formed. The size and crystallinity remained unchanged after hydrothermal treatment of the stable sol at between 160 and 240°C. However, hydrothermal treatment of unstable sol produced rod-like particles and crystallinity of particles was changed from anatase to rutile. This difference in phase transformation at low hydrothermal treatment temperature was likely to be caused by the fact that stable sol remained to be stable even after hydrothermal treatment, while unstable sol had a tendency to be aggregated.

  17. Self-collimated unstable resonator semiconductor laser

    NASA Technical Reports Server (NTRS)

    Lang, Robert J. (Inventor)

    1993-01-01

    Self-collimation of the output is achieved in an unstable resonator semiconductor laser by providing a large concave mirror M sub 1 and a small convex mirror M sub 2 on opposite surfaces of a semiconductor body of a material having an effective index of refraction denoted by n, where the respective mirror radii R sub 1, R sub 2 and beam radii r sub 1, r sub 2 are chosen to satisfy a condition (R sub 2)/(1 + r sub 1) = (n - 1)/n, with a value of geometric magnification 1 less than or equal to M less than or equal to (n + 1)/(n - 1) where r sub 1 and r sub 2 are the radii of counterpropagating beams at respective mirrors of radii R sub 1 and R sub 2.

  18. Unstable avoided crossing in coupled spinor condensates.

    PubMed

    Bernier, Nathan R; Dalla Torre, Emanuele G; Demler, Eugene

    2014-08-08

    We consider the dynamics of a Bose-Einstein condensate with two internal states, coupled through a coherent drive. We focus on a specific quench protocol, in which the sign of the coupling field is suddenly changed. At a mean-field level, the system is transferred from a minimum to a maximum of the coupling energy and can remain dynamically stable, in spite of the development of negative-frequency modes. In the presence of a nonzero detuning between the two states, the "charge" and "spin" modes couple, giving rise to an unstable avoided crossing. This phenomenon is generic to systems with two dispersing modes away from equilibrium and constitutes an example of class-I(o) nonequilibrium pattern formation in quantum systems.

  19. The free energy of mechanically unstable phases

    PubMed Central

    van de Walle, A.; Hong, Q.; Kadkhodaei, S.; Sun, R.

    2015-01-01

    Phase diagrams provide ‘roadmaps' to the possible states of matter. Their determination traditionally rests on the assumption that all phases, even unstable ones, have well-defined free energies under all conditions. However, this assumption is commonly violated in condensed phases due to mechanical instabilities. This long-standing problem impedes thermodynamic database development, as pragmatic attempts at solving this problem involve delicate extrapolations that are highly nonunique and that lack an underlying theoretical justification. Here we propose an efficient computational solution to this problem that has a simple interpretation, both as a topological partitioning of atomic configuration space and as a minimally constrained physical system. Our natural scheme smoothly extends the free energy of stable phases, without relying on extrapolation, thus enabling a formal assessment of widely used extrapolation schemes. PMID:26130613

  20. Reverse wave suppression in unstable ring resonator

    NASA Astrophysics Data System (ADS)

    Mirels, H.; Chodzko, R. A.; Bernard, J. M.; Giedt, R. R.; Coffer, J. G.

    1984-12-01

    Criteria for effective reverse-wave suppression (RWS) in CW and pulsed unstable ring lasers with inhomogeneously broadened media are determined theoretically, and the performance of a CW HF linear ring resonator (Chodzko et al., 1976) and of two configurations of a pulsed CO2 annular beam-rotation/internal-axicon (BRIA) resonator (Bullock et al., 1979) without and with an RWS mirror is evaluated experimentally. In the CW laser, the average forward-wave (FW) and RW power values are shown to be 61 and 39 W without RWS and 110 and 2.7 W with RWS, corresponding to a FW/RW power ratio of 41; in the pulsed BRIA lasers, power ratios of about 20 are achieved, but the RWS effectiveness is found to be highly sensitive to RWS-mirror and cavity misalignment. Graphs, drawings, tables, and photographs of typical waveforms are included.

  1. Astrophysical quests for neutron capture data of unstable nuclei

    NASA Astrophysics Data System (ADS)

    Käppeler, F.

    2016-11-01

    The abundances of the chemical elements heavier than iron can be attributed in about equal parts to the r and to the s process, which are taking place in supernova explosions and during the He and C burning phases of stellar evolution, respectively. So far, quantitative studies on the extremely short-lived neutron-rich nuclei constituting the ( n, γ) network of the r process are out of reach. On the contrary, the situation for the s -process is far advanced, as the reaction path of the s process from 12C to the Pb/Bi region is located within the valley of stability. Accordingly, a comprehensive database of experimental ( n, γ) cross sections has been established. While for many stable isotopes the necessary accuracy is still to be reached, reliable cross sections for the involved unstable isotopes are almost completely missing. Because of the intrinsic γ background of radioactive samples, successful time-of-flight measurements are depending on intense pulsed neutron sources. Such data are fundamental for our understanding of branchings in the s -process reaction path, which carry important model-independent information on neutron flux and temperature in the deep stellar interior.

  2. Thermodynamics fundamentals of energy conversion

    NASA Astrophysics Data System (ADS)

    Dan, Nicolae

    The work reported in the chapters 1-5 focuses on the fundamentals of heat transfer, fluid dynamics, thermodynamics and electrical phenomena related to the conversion of one form of energy to another. Chapter 6 is a re-examination of the fundamental heat transfer problem of how to connect a finite-size heat generating volume to a concentrated sink. Chapter 1 extends to electrical machines the combined thermodynamics and heat transfer optimization approach that has been developed for heat engines. The conversion efficiency at maximum power is 1/2. When, as in specific applications, the operating temperature of windings must not exceed a specified level, the power output is lower and efficiency higher. Chapter 2 addresses the fundamental problem of determining the optimal history (regime of operation) of a battery so that the work output is maximum. Chapters 3 and 4 report the energy conversion aspects of an expanding mixture of hot particles, steam and liquid water. At the elemental level, steam annuli develop around the spherical drops as time increases. At the mixture level, the density decreases while the pressure and velocity increases. Chapter 4 describes numerically, based on the finite element method, the time evolution of the expanding mixture of hot spherical particles, steam and water. The fluid particles are moved in time in a Lagrangian manner to simulate the change of the domain configuration. Chapter 5 describes the process of thermal interaction between the molten material and water. In the second part of the chapter the model accounts for the irreversibility due to the flow of the mixture through the cracks of the mixing vessel. The approach presented in this chapter is based on exergy analysis and represents a departure from the line of inquiry that was followed in chapters 3-4. Chapter 6 shows that the geometry of the heat flow path between a volume and one point can be optimized in two fundamentally different ways. In the "growth" method the

  3. Unstable whistlers and Bernstein waves within the front of supercritical perpendicular shocks

    NASA Astrophysics Data System (ADS)

    Muschietti, Laurent; Lembege, Bertrand

    2016-04-01

    In supercritical shocks a significant fraction of ions is reflected at the steep shock ramp and carries a considerable amount of energy. The existence of reflected ions enables streaming instabilities to develop which are excited by the relative drifts between the populations of incoming ions, reflected ions, and electrons. The processes are fundamental to the transformation of directed kinetic energy into thermal energy, a tenet of shock physics. We model the particle distributions as a broad electron population and two ion populations, namely a core and a beam (representing the reflected ions) in order to investigate the kinetic instabilities possible under various wave propagation angles. Recently, assuming the ion beam is directed along the shock normal at 90° to the magnetic field Bo, we analyzed the linear dispersion properties by computing the full electromagnetic dielectric tensor [Muschietti and Lembege, AGU Fall meeting 2015]. Three types of waves were shown to be unstable: (1) Oblique whistlers with wavelengths about the ion inertia length which propagate toward upstream at angles about 50° to the magnetic field. Frequencies are a few times the lower-hybrid. The waves share many similarities to the obliquely propagating whistlers measured in detail by Polar [Hull et al., JGR 117, 2012]. (2) Quasi-perpendicular whistlers with wavelength covering a fraction of the electron inertia length which propagate toward downstream at angles larger than 80° to Bo. Frequencies are close to the lower-hybrid. (3) Bernstein waves with wavelengths close to the electron gyroradius which propagate toward upstream at angles within 5° of perpendicular to the magnetic field. Frequencies are close to the electron cyclotron. The waves have similarities to those reported by Wind and Stereo [Breneman et al., JGR 118, 2013; Wilson et al., JGR 115, 2010]. We will present electromagnetic 1D3V PIC simulations with predetermined propagation angles which illustrate the three types

  4. Levitated Optomechanics for Fundamental Physics

    NASA Astrophysics Data System (ADS)

    Rashid, Muddassar; Bateman, James; Vovrosh, Jamie; Hempston, David; Ulbricht, Hendrik

    2015-05-01

    Optomechanics with levitated nano- and microparticles is believed to form a platform for testing fundamental principles of quantum physics, as well as find applications in sensing. We will report on a new scheme to trap nanoparticles, which is based on a parabolic mirror with a numerical aperture of 1. Combined with achromatic focussing, the setup is a cheap and readily straightforward solution to trapping nanoparticles for further study. Here, we report on the latest progress made in experimentation with levitated nanoparticles; these include the trapping of 100 nm nanodiamonds (with NV-centres) down to 1 mbar as well as the trapping of 50 nm Silica spheres down to 10?4 mbar without any form of feedback cooling. We will also report on the progress to implement feedback stabilisation of the centre of mass motion of the trapped particle using digital electronics. Finally, we argue that such a stabilised particle trap can be the particle source for a nanoparticle matterwave interferometer. We will present our Talbot interferometer scheme, which holds promise to test the quantum superposition principle in the new mass range of 106 amu. EPSRC, John Templeton Foundation.

  5. Grating tuned unstable resonator laser cavity

    DOEpatents

    Johnson, Larry C.

    1982-01-01

    An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

  6. Pulse dynamics in an unstable medium

    SciTech Connect

    Balmforth, N.J.; Ierley, G.R.; Worthing, R.

    1995-05-01

    A study is presented of a one-dimensional, nonlinear partial differential equation that describes evolution of dispersive, long-wave instability. The solutions, under certain specific conditions, take the form of trains of well-separated pulses. The dynamics of such patterns of pulses is investigated using singular perturbation theory and with numerical simulation. These tools permit the formulation of a theory of pulse interaction, and enable the mapping out of the range of behavior in parameter space. There are regimes in which steady trains form; such states can be studied with the asymptotic, pulse-interaction theory. In other regimes, pulse trains are unstable to global, wave-like modes or its radiation. This can precipitate more violent phenomena involving pulse creation, or generate periodic states which may follow Shil`nikov`s route to temporal chaos. The asymptotic theory is generalized lo take some account of radiative dynamics. In the limit of small dispersion, steady trains largely cease to exist; the system follows various pathways to temporal complexity and typical-bifurcation sequences are sketched out. The investigation guides us to a critical appraisal of the asymptotic theory and uncovers the wealth of different types of behavior present in the system.

  7. Order-parameter model for unstable multilane traffic flow

    NASA Astrophysics Data System (ADS)

    Lubashevsky, Ihor A.; Mahnke, Reinhard

    2000-11-01

    We discuss a phenomenological approach to the description of unstable vehicle motion on multilane highways that explains in a simple way the observed sequence of the ``free flow <--> synchronized mode <--> jam'' phase transitions as well as the hysteresis in these transitions. We introduce a variable called an order parameter that accounts for possible correlations in the vehicle motion at different lanes. So, it is principally due to the ``many-body'' effects in the car interaction in contrast to such variables as the mean car density and velocity being actually the zeroth and first moments of the ``one-particle'' distribution function. Therefore, we regard the order parameter as an additional independent state variable of traffic flow. We assume that these correlations are due to a small group of ``fast'' drivers and by taking into account the general properties of the driver behavior we formulate a governing equation for the order parameter. In this context we analyze the instability of homogeneous traffic flow that manifested itself in the above-mentioned phase transitions and gave rise to the hysteresis in both of them. Besides, the jam is characterized by the vehicle flows at different lanes which are independent of one another. We specify a certain simplified model in order to study the general features of the car cluster self-formation under the ``free flow <--> synchronized motion'' phase transition. In particular, we show that the main local parameters of the developed cluster are determined by the state characteristics of vehicle motion only.

  8. Arguing against fundamentality

    NASA Astrophysics Data System (ADS)

    McKenzie, Kerry

    This paper aims to open up discussion on the relationship between fundamentality and naturalism, and in particular on the question of whether fundamentality may be denied on naturalistic grounds. A historico-inductive argument for an anti-fundamentalist conclusion, prominent within the contemporary metaphysical literature, is examined; finding it wanting, an alternative 'internal' strategy is proposed. By means of an example from the history of modern physics - namely S-matrix theory - it is demonstrated that (1) this strategy can generate similar (though not identical) anti-fundamentalist conclusions on more defensible naturalistic grounds, and (2) that fundamentality questions can be empirical questions. Some implications and limitations of the proposed approach are discussed.

  9. Monte Carlo fundamentals

    SciTech Connect

    Brown, F.B.; Sutton, T.M.

    1996-02-01

    This report is composed of the lecture notes from the first half of a 32-hour graduate-level course on Monte Carlo methods offered at KAPL. These notes, prepared by two of the principle developers of KAPL`s RACER Monte Carlo code, cover the fundamental theory, concepts, and practices for Monte Carlo analysis. In particular, a thorough grounding in the basic fundamentals of Monte Carlo methods is presented, including random number generation, random sampling, the Monte Carlo approach to solving transport problems, computational geometry, collision physics, tallies, and eigenvalue calculations. Furthermore, modern computational algorithms for vector and parallel approaches to Monte Carlo calculations are covered in detail, including fundamental parallel and vector concepts, the event-based algorithm, master/slave schemes, parallel scaling laws, and portability issues.

  10. Fundamentals of fluid sealing

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1976-01-01

    The fundamentals of fluid sealing, including seal operating regimes, are discussed and the general fluid-flow equations for fluid sealing are developed. Seal performance parameters such as leakage and power loss are presented. Included in the discussion are the effects of geometry, surface deformations, rotation, and both laminar and turbulent flows. The concept of pressure balancing is presented, as are differences between liquid and gas sealing. Mechanisms of seal surface separation, fundamental friction and wear concepts applicable to seals, seal materials, and pressure-velocity (PV) criteria are discussed.

  11. Fundamentals of fluid lubrication

    NASA Technical Reports Server (NTRS)

    Hamrock, Bernard J.

    1991-01-01

    The aim is to coordinate the topics of design, engineering dynamics, and fluid dynamics in order to aid researchers in the area of fluid film lubrication. The lubrication principles that are covered can serve as a basis for the engineering design of machine elements. The fundamentals of fluid film lubrication are presented clearly so that students that use the book will have confidence in their ability to apply these principles to a wide range of lubrication situations. Some guidance on applying these fundamentals to the solution of engineering problems is also provided.

  12. Unstable trajectories and the quantum mechanical uncertainty

    SciTech Connect

    Moser, Hans R.

    2008-08-15

    There is still an ongoing discussion about various seemingly contradictory aspects of classical particle motion and its quantum mechanical counterpart. One of the best accepted viewpoints that intend to bridge the gap is the so-called Copenhagen Interpretation. A major issue there is to regard wave functions as probability amplitudes (usually for the position of a particle). However, the literature also reports on approaches that claim a trajectory for any quantum mechanical particle, Bohmian mechanics probably being the most prominent one among these ideas. We introduce a way to calculate trajectories as well, but our crucial ingredient is their well controlled local (thus also momentaneous) degree of instability. By construction, at every moment their unpredictability, i.e., their local separation rates of neighboring trajectories, is governed by the local value of the given modulus square of a wave function. We present extensive numerical simulations of the H and He atom, and for some velocity-related quantities, namely angular momentum and total energy, we inspect their agreement with the values appearing in wave mechanics. Further, we interpret the archetypal double slit interference experiment in the spirit of our findings. We also discuss many-particle problems far beyond He, which guides us to a variety of possible applications.

  13. Managing risk in an unstable world.

    PubMed

    Bremmer, Ian

    2005-06-01

    With emerging markets like China and politically unstable countries like Saudi Arabia figuring more than ever into companies' investment calculations, business leaders are turning to political risk analysis to measure the impact of politics on potential markets, minimize risks, and make the most of global opportunities. But political risk is more subjective than its economic counterpart. It is influenced by the passage of laws, the foibles of government leaders, and the rise of popular movements. So corporate leaders must grapple not just with broad, easily observable trends but also with nuances of society and even quirks of personality. And those hard-to-quantify factors must constantly be pieced together into an ongoing narrative within historical and regional contexts. As goods, services, information, ideas, and people cross borders today with unprecedented velocity, corporations debating operational or infrastructural investments abroad increasingly need objective, rigorous assessments. One tool for measuring and presenting stability data, for example, incorporates 20 composite indicators of risk in emerging markets and scores risk variables according to both their structural and their temporal components. The indicators are then organized into four equally weighted subcategories whose ratings are aggregated into a single stability score. Countries are ranked on a scale of zero (a failed state) to100 (a fully institutionalized, stable democracy). Companies can buy political risk analyses from consultants or, as some large energy and financial services organizations have done, develop them in-house. Either way, a complete and accurate picture of any country's risk requires analysts with strong reportorial skills; timely, accurate data on a variety of social and political trends; and a framework for evaluating the impact of individual risks on stability.

  14. Unstable ground in western North Dakota

    USGS Publications Warehouse

    Trimble, Donald E.

    1979-01-01

    Unstable ground in western North Dakota is mainly the result of mass-wasting processes. The units most affected are mudstones, siltstones, and sandstones of the Fort Union Formation. Ground instability generally is indicated by landslides, soil slides, or subsidence. Landslides are mostly of the slump-earthflow type and are localized along the flanks of the high buttes in southwestern North Dakota, including HT (Black) Butte, Chalky Buttes, Sentinel Butte, and East and West Rainy Buttes, and along parts of the valleys of the Des Lacs, Missouri, Little Missouri, and Heart Rivers. Landslides are sparse elsewhere. Soil slides are common in the areas south and southwest of the maximum position of the Pleistocene glacial ice margin on slopes of 15 degrees or more, and have taken place on some slopes as gentle as five degrees. The weathered, exposed surface of the Fort Union Formation seems to be especially susceptible to soil slides. Soil slides constitute the major type of ground instability in southwestern North Dakota. Subsidence is of two types: (1) subsidence over old underground mine workings, and (2) subsidence over naturally ignited and burned underground coal beds. Major subsidence has taken place over old, underground workings near Beulah, Wilton, Lehigh, Haynes, and Belfield, and lesser subsidence near Scranton, and west and north of Bowman. Thickness of overburden above the coal in all these areas is believed to be less than 30 m (100 ft). Subsidence has not taken place over old underground workings along the Des Lacs and-Souris valleys northwest of Minot, where the thickness of overburden is more than 60 m (200 ft). Spectacular subsidence has occurred over a burning underground coal bed at Burning Coal Vein Park near the Little Missouri River, northwest of Amidon.

  15. Food Service Fundamentals.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on food service fundamentals is designed to provide a general background in the basic aspects of the food service program in the Marine Corps; it is adaptable for nonmilitary instruction. Introductory materials include specific information for MCI…

  16. Unification of Fundamental Forces

    NASA Astrophysics Data System (ADS)

    Salam, Abdus; Taylor, Foreword by John C.

    2005-10-01

    Foreword John C. Taylor; 1. Unification of fundamental forces Abdus Salam; 2. History unfolding: an introduction to the two 1968 lectures by W. Heisenberg and P. A. M. Dirac Abdus Salam; 3. Theory, criticism, and a philosophy Werner Heisenberg; 4. Methods in theoretical physics Paul Adrian Maurice Dirac.

  17. Basic Publication Fundamentals.

    ERIC Educational Resources Information Center

    Savedge, Charles E., Ed.

    Designed for students who produce newspapers and newsmagazines in junior high, middle, and elementary schools, this booklet is both a scorebook and a fundamentals text. The scorebook provides realistic criteria for judging publication excellence at these educational levels. All the basics for good publications are included in the text of the…

  18. Reading Is Fundamental, 1977.

    ERIC Educational Resources Information Center

    Smithsonian Institution, Washington, DC. National Reading is Fun-damental Program.

    Reading Is Fundamental (RIF) is a national, nonprofit organization designed to motivate children to read by making a wide variety of inexpensive books available to them and allowing the children to choose and keep books that interest them. This annual report for 1977 contains the following information on the RIF project: an account of the…

  19. Laser Fundamentals and Experiments.

    ERIC Educational Resources Information Center

    Van Pelt, W. F.; And Others

    As a result of work performed at the Southwestern Radiological Health Laboratory with respect to lasers, this manual was prepared in response to the increasing use of lasers in high schools and colleges. It is directed primarily toward the high school instructor who may use the text for a short course in laser fundamentals. The definition of the…

  20. Homeschooling and Religious Fundamentalism

    ERIC Educational Resources Information Center

    Kunzman, Robert

    2010-01-01

    This article considers the relationship between homeschooling and religious fundamentalism by focusing on their intersection in the philosophies and practices of conservative Christian homeschoolers in the United States. Homeschooling provides an ideal educational setting to support several core fundamentalist principles: resistance to…

  1. The Fundamental Property Relation.

    ERIC Educational Resources Information Center

    Martin, Joseph J.

    1983-01-01

    Discusses a basic equation in thermodynamics (the fundamental property relation), focusing on a logical approach to the development of the relation where effects other than thermal, compression, and exchange of matter with the surroundings are considered. Also demonstrates erroneous treatments of the relation in three well-known textbooks. (JN)

  2. Fundamentals of Library Instruction

    ERIC Educational Resources Information Center

    McAdoo, Monty L.

    2012-01-01

    Being a great teacher is part and parcel of being a great librarian. In this book, veteran instruction services librarian McAdoo lays out the fundamentals of the discipline in easily accessible language. Succinctly covering the topic from top to bottom, he: (1) Offers an overview of the historical context of library instruction, drawing on recent…

  3. Fundamentals of soil science

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study guide provides comments and references for professional soil scientists who are studying for the soil science fundamentals exam needed as the first step for certification. The performance objectives were determined by the Soil Science Society of America's Council of Soil Science Examiners...

  4. Fundamentals of Electromagnetic Phenomena

    NASA Astrophysics Data System (ADS)

    Lorrain, Paul; Corson, Dale R.; Lorrain, Francois

    Based on the classic Electromagnetic Fields and Waves by the same authors, Fundamentals of Electromagnetic Phenomena capitalizes on the older text's traditional strengths--solid physics, inventive problems, and an experimental approach--while offering a briefer, more accessible introduction to the basic principles of electromagnetism.

  5. Fundamentals of Solid Lubrication

    DTIC Science & Technology

    2012-03-01

    NOTES 14. ABSTRACT During this program, we have worked to develop a fundamental understanding of the chemical and tribological issues related to...approach, tribological measurements performed over a range of length scales, and the correlation of the two classes of information. Research activities...correlated measurements of surface composition and environmentally specific tribological performance of thin film solid lubricants. • Correlate shear

  6. Fundamentals of Diesel Engines.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

    This student guide, one of a series of correspondence training courses designed to improve the job performance of members of the Marine Corps, deals with the fundamentals of diesel engine mechanics. Addressed in the three individual units of the course are the following topics: basic principles of diesel mechanics; principles, mechanics, and…

  7. Phase transitions in the interacting boson fermion model: The {gamma}-unstable case

    SciTech Connect

    Alonso, C.E.; Arias, J.M.; Fortunato, L.; Vitturi, A.

    2005-12-15

    The phase transition around the critical point in the evolution from spherical to deformed {gamma}-unstable shapes is investigated in odd nuclei within the interacting boson fermion model. We consider the particular case of an odd j=3/2 particle coupled to an even-even boson core that undergoes a transition from spherical U(5) to {gamma}-unstable O(6) situation. The particular choice of the j=3/2 orbital preserves in the odd case the condition of {gamma}-instability of the system. As a consequence, energy spectrum and electromagnetic transitions, in correspondence of the critical point, display behaviors qualitatively similar to those of the even core. The results are also in qualitative agreement with the recently proposed E(5/4) model, although few differences are present, due to the different nature of the two schemes.

  8. Accumulation of unstable periodic orbits and the stickiness in the two-dimensional piecewise linear map.

    PubMed

    Akaishi, A; Shudo, A

    2009-12-01

    We investigate the stickiness of the two-dimensional piecewise linear map with a family of marginal unstable periodic orbits (FMUPOs), and show that a series of unstable periodic orbits accumulating to FMUPOs plays a significant role to give rise to the power law correlation of trajectories. We can explicitly specify the sticky zone in which unstable periodic orbits whose stability increases algebraically exist, and find that there exists a hierarchy in accumulating periodic orbits. In particular, the periodic orbits with linearly increasing stability play the role of fundamental cycles as in the hyperbolic systems, which allows us to apply the method of cycle expansion. We also study the recurrence time distribution, especially discussing the position and size of the recurrence region. Following the definition adopted in one-dimensional maps, we show that the recurrence time distribution has an exponential part in the short time regime and an asymptotic power law part. The analysis on the crossover time T(c)(*) between these two regimes implies T(c)(*) approximately -log[micro(R)] where micro(R) denotes the area of the recurrence region.

  9. Noncommutative Tachyon Kinks as D(p-1)-branes from Unstable Dp-brane

    NASA Astrophysics Data System (ADS)

    Banerjee, Rabin; Kim, Yoonbai; Kwon, O.-Kab

    2005-01-01

    We study noncommutative (NC) field theory of a real NC tachyon and NC U(1) gauge field, describing the dynamics of an unstable Dp-brane. For every given set of diagonal component of open string metric G 0 , NC parameter θ0 , and interpolating electric field hat E, we find all possible static NC kinks as exact solutions, in spite of complicated NC terms, which are classified by an array of NC kink-antikink and topological NC kinks. By computing their tensions and charges, those configurations are identified as an array of D0bar D0 and single stable D0 from the unstable D1, respectively. When the interpolating electric field has critical value as G 0 2 = hat E2 , the obtained topological kink becomes a BPS object with nonzero thickness and is identified as BPS D0 in the fluid of fundamental strings. Particularly in the scaling limit of infinite θ0 and vanishing G 0 and hat E, while keeping G 0θ0 = hat Eθ0 = 1, finiteness of the tension of NC kink corresponds to tensionless kink in ordinary effective field theory. An extension to stable D(p-1) from unstable Dp is straightforward for pure electric cases with parallel NC parameter and interpolating two-form field.

  10. 2008 LC18: a potentially unstable Neptune Trojan

    NASA Astrophysics Data System (ADS)

    Horner, J.; Lykawka, P. S.; Bannister, M. T.; Francis, P.

    2012-05-01

    The recent discovery of the first Neptune Trojan at the planet's trailing (L5) Lagrange point, 2008 LC18, offers an opportunity to confirm the formation mechanism of a member of this important tracer population for the Solar system's dynamical history. We tested the stability of 2008 LC18's orbit through a detailed dynamical study, using test particles spread across the ±3σ range of orbital uncertainties in a, e, i and Ω. This showed that the wide uncertainties of the published orbit span regions of both extreme dynamical instability, with lifetimes <100 Myr, and significant stability, with lifetimes >1 Gyr. The stability of 2008 LC18's clones is greatly dependent on their semimajor axis and only weakly correlated with their orbital eccentricity. Test particles on orbits with an initial semimajor axis of less than 29.91 au have dynamical half-lives shorter than 100 Myr; in contrast, particles with an initial semimajor axis of greater than 29.91 au exhibit such strong dynamical stability that almost all are retained over the 1 Gyr of our simulations. More observations of this object are necessary to improve the orbit. If 2008 LC18 is in the unstable region, then our simulations imply that it is either a temporary Trojan capture or a representative of a slowly decaying Trojan population (like its sibling the L4 Neptunian Trojan 2001 QR322), and that it may not be primordial. Alternatively, if the orbit falls into the larger, stable region, then 2008 LC18 is a primordial member of the highly stable and highly inclined component of the Neptune Trojan population, joining 2005 TN53 and 2007 VL305. We attempted to recover 2008 LC18 using the 2.3-m telescope at Siding Spring Observatory to provide this astrometry, but were unsuccessful due to the high stellar density of its current sky location near the Galactic centre. The recovery of this object will require a telescope in the 8-m class.

  11. Universality classes for unstable crystal growth.

    PubMed

    Biagi, Sofia; Misbah, Chaouqi; Politi, Paolo

    2014-06-01

    Universality has been a key concept for the classification of equilibrium critical phenomena, allowing associations among different physical processes and models. When dealing with nonequilibrium problems, however, the distinction in universality classes is not as clear and few are the examples, such as phase separation and kinetic roughening, for which universality has allowed to classify results in a general spirit. Here we focus on an out-of-equilibrium case, unstable crystal growth, lying in between phase ordering and pattern formation. We consider a well-established 2+1-dimensional family of continuum nonlinear equations for the local height h(x,t) of a crystal surface having the general form ∂_{t}h(x,t)=-∇·[j(∇h)+∇(∇^{2}h)]: j(∇h) is an arbitrary function, which is linear for small ∇h, and whose structure expresses instabilities which lead to the formation of pyramidlike structures of planar size L and height H. Our task is the choice and calculation of the quantities that can operate as critical exponents, together with the discussion of what is relevant or not to the definition of our universality class. These aims are achieved by means of a perturbative, multiscale analysis of our model, leading to phase diffusion equations whose diffusion coefficients encapsulate all relevant information on dynamics. We identify two critical exponents: (i) the coarsening exponent, n, controlling the increase in time of the typical size of the pattern, L∼t^{n}; (ii) the exponent β, controlling the increase in time of the typical slope of the pattern, M∼t^{β}, where M≈H/L. Our study reveals that there are only two different universality classes, according to the presence (n=1/3, β=0) or the absence (n=1/4, β>0) of faceting. The symmetry of the pattern, as well as the symmetry of the surface mass current j(∇h) and its precise functional form, is irrelevant. Our analysis seems to support the idea that also space dimensionality is irrelevant.

  12. Projection-free approximate balanced truncation of large unstable systems

    NASA Astrophysics Data System (ADS)

    Flinois, Thibault L. B.; Morgans, Aimee S.; Schmid, Peter J.

    2015-08-01

    In this article, we show that the projection-free, snapshot-based, balanced truncation method can be applied directly to unstable systems. We prove that even for unstable systems, the unmodified balanced proper orthogonal decomposition algorithm theoretically yields a converged transformation that balances the Gramians (including the unstable subspace). We then apply the method to a spatially developing unstable system and show that it results in reduced-order models of similar quality to the ones obtained with existing methods. Due to the unbounded growth of unstable modes, a practical restriction on the final impulse response simulation time appears, which can be adjusted depending on the desired order of the reduced-order model. Recommendations are given to further reduce the cost of the method if the system is large and to improve the performance of the method if it does not yield acceptable results in its unmodified form. Finally, the method is applied to the linearized flow around a cylinder at Re = 100 to show that it actually is able to accurately reproduce impulse responses for more realistic unstable large-scale systems in practice. The well-established approximate balanced truncation numerical framework therefore can be safely applied to unstable systems without any modifications. Additionally, balanced reduced-order models can readily be obtained even for large systems, where the computational cost of existing methods is prohibitive.

  13. Neutron Capture Experiments on Unstable Nuclei

    SciTech Connect

    Schwantes, Jon M.; Sudowe, Ralf; Folden, Charles M., III; Nitsche, Heino; Hoffman, Darleane C.

    2005-01-15

    The overall objective of this project is the measurement of neutron capture cross sections of importance to stewardship science and astrophysical modeling of nucleosynthesis, while at the same time helping to train the next generation of scientists with expertise relevant to U.S. national nuclear security missions and to stewardship science. A primary objective of this project is to study neutron capture cross sections for various stable and unstable isotopes that will contribute to the Science Based Stockpile Stewardship (SBSS) program by providing improved data for modeling and interpretation of nuclear device performance. Much of the information obtained will also be important in astrophysical modeling of nucleosynthesis. Measurements of these neutron capture cross sections are being conducted in collaboration with researchers at the Los Alamos Neutron Science Center (LANSCE) facility using the unique Detector for Advanced Neutron Capture Experiments (DANCE). In our early discussions with the DANCE group, decisions were made on the first cross sections to be measured and how our expertise in target preparation, radiochemical separations chemistry, and data analysis could best be applied. The initial emphasis of the project was on preparing suitable targets of both natural and separated stable europium isotopes in preparation for the ultimate goal of preparing a sufficiently large target of radioactive 155Eu (t1/2 = 4.7 years) and other radioactive and stable species for neutron cross-section measurements at DANCE. Our Annual Report, ''Neutron Capture Experiments on Unstable Nuclei'' by J. M. Schwantes, R. Sudowe, C. M. Folden III, H. Nitsche, and D. C. Hoffman, submitted to NNSA in December 2003, gives details about the initial considerations and scope of the project. During the current reporting period, electroplated targets of natural Eu together with valuable, stable, and isotopically pure 151Eu and 153Eu, and isotopically separated 154Sm were measured for

  14. Fundamentals of neurobiology.

    PubMed

    Greg Hall, D

    2011-01-01

    Session 1 of the 2010 STP/IFSTP Joint Symposium on Toxicologic Neuropathology, titled "Fundamentals of Neurobiology," was organized to provide a foundation for subsequent sessions by presenting essential elements of neuroanatomy and nervous system function. A brief introduction to the session titled "Introduction to Correlative Neurobiology" was provided by Dr. Greg Hall (Eli Lilly and Company, Indianapolis, IN). Correlative neurobiology refers to considerations of the relationships between the highly organized and compartmentalized structure of nervous tissues and the functioning within this system.

  15. Fundamental studies in geodynamics

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.; Hager, B. H.; Kanamori, H.

    1981-01-01

    Research in fundamental studies in geodynamics continued in a number of fields including seismic observations and analysis, synthesis of geochemical data, theoretical investigation of geoid anomalies, extensive numerical experiments in a number of geodynamical contexts, and a new field seismic volcanology. Summaries of work in progress or completed during this report period are given. Abstracts of publications submitted from work in progress during this report period are attached as an appendix.

  16. Fundamentals of petroleum maps

    SciTech Connect

    Mc Elroy, D.P.

    1986-01-01

    It's a complete guide to the fundamentals of reading, using, and making petroleum maps. The topics covered are well spotting, lease posting, contouring, hanging cross sections, and ink drafting. This book not only tells the how of petroleum mapping, but it also tells the why to better understand the principles and techniques. The books does not teach ''drafting,'' but does describe the proper care and use of drafting equipment for those who are totally new to the task.

  17. Value of Fundamental Science

    NASA Astrophysics Data System (ADS)

    Burov, Alexey

    Fundamental science is a hard, long-term human adventure that has required high devotion and social support, especially significant in our epoch of Mega-science. The measure of this devotion and this support expresses the real value of the fundamental science in public opinion. Why does fundamental science have value? What determines its strength and what endangers it? The dominant answer is that the value of science arises out of curiosity and is supported by the technological progress. Is this really a good, astute answer? When trying to attract public support, we talk about the ``mystery of the universe''. Why do these words sound so attractive? What is implied by and what is incompatible with them? More than two centuries ago, Immanuel Kant asserted an inseparable entanglement between ethics and metaphysics. Thus, we may ask: which metaphysics supports the value of scientific cognition, and which does not? Should we continue to neglect the dependence of value of pure science on metaphysics? If not, how can this issue be addressed in the public outreach? Is the public alienated by one or another message coming from the face of science? What does it mean to be politically correct in this sort of discussion?

  18. The Unstable Repeats - Three Evolving Faces of Neurological Disease

    PubMed Central

    Nelson, David L.; Orr, Harry T.; Warren, Stephen T.

    2013-01-01

    Disorders characterized by expansion of an unstable nucleotide repeat account for a number of inherited neurological diseases. Here, we review examples of unstable repeat disorders that nicely illustrate the three of the major pathogenic mechanisms associated with these diseases: loss-of-function typically by disrupting transcription of the mutated gene, RNA toxic gain-of-function, and protein toxic gain-of-function. In addition to providing insight into the mechanisms underlying these devastating neurological disorders, the study of these unstable microsatellite repeat disorders has provided insight into very basic aspects of neuroscience. PMID:23473314

  19. Fundamental space radiobiology

    NASA Technical Reports Server (NTRS)

    Nelson, Gregory A.

    2003-01-01

    The unique feature of the space radiation environment is the dominance of high-energy charged particles (HZE or high LET radiation) emitted by the Sun and galactic sources, or trapped in the Van Allen radiation belts. These charged particles present a significant hazard to space flight crews, and accelerator-based experiments are underway to quantify the health risks due to unavoidable radiation exposure. There are three principal properties of charged particles that distinguish them from conventional radiation, i.e. gamma rays and x-rays. First, they have a defined range in matter rather than an exponential absorption profile. Second, they undergo nuclear reactions to produce secondary particles. Third, and most important, they deposit their energy along well-defined linear paths or tracks rather than diffuse fields. The structured energy deposition pattern interacts on multiple scales with the biological structures of DNA, cells and tissues to produce correlated patterns of damage that evade repair systems. Traditional concepts of dose and its associated normalization parameter, RBE (relative biological effectiveness), break down under experimental scrutiny, and probabilistic models of risk based on the number of particle traversals per cell may be more appropriate. Unique patterns of DNA damage, gene expression, mobilization of repair proteins, activation of cytokines and remodeling of cellular microenvironment are observed following exposure to high LET radiation. At low levels of exposure the communication of bioactive substances from irradiated to unirradiated "bystander" cells can amplify the damage and cause a significant deviation from linearity in dose vs. response relations. Under some circumstances, there is even a multigenerational delay in the expression of radiation-induced genetic damage (genomic instability) which is not strictly dose dependent. These issues and the experimental evidence derived from ground based experiments at particle

  20. Fundamental space radiobiology.

    PubMed

    Nelson, Gregory A

    2003-06-01

    The unique feature of the space radiation environment is the dominance of high-energy charged particles (HZE or high LET radiation) emitted by the Sun and galactic sources, or trapped in the Van Allen radiation belts. These charged particles present a significant hazard to space flight crews, and accelerator-based experiments are underway to quantify the health risks due to unavoidable radiation exposure. There are three principal properties of charged particles that distinguish them from conventional radiation, i.e. gamma rays and x-rays. First, they have a defined range in matter rather than an exponential absorption profile. Second, they undergo nuclear reactions to produce secondary particles. Third, and most important, they deposit their energy along well-defined linear paths or tracks rather than diffuse fields. The structured energy deposition pattern interacts on multiple scales with the biological structures of DNA, cells and tissues to produce correlated patterns of damage that evade repair systems. Traditional concepts of dose and its associated normalization parameter, RBE (relative biological effectiveness), break down under experimental scrutiny, and probabilistic models of risk based on the number of particle traversals per cell may be more appropriate. Unique patterns of DNA damage, gene expression, mobilization of repair proteins, activation of cytokines and remodeling of cellular microenvironment are observed following exposure to high LET radiation. At low levels of exposure the communication of bioactive substances from irradiated to unirradiated "bystander" cells can amplify the damage and cause a significant deviation from linearity in dose vs. response relations. Under some circumstances, there is even a multigenerational delay in the expression of radiation-induced genetic damage (genomic instability) which is not strictly dose dependent. These issues and the experimental evidence derived from ground based experiments at particle

  1. Fundamental limits of optical force and torque

    NASA Astrophysics Data System (ADS)

    Rahimzadegan, A.; Alaee, R.; Fernandez-Corbaton, I.; Rockstuhl, C.

    2017-01-01

    Optical force and torque provide unprecedented control on the spatial motion of small particles. A valid scientific question, that has many practical implications, concerns the existence of fundamental upper bounds for the achievable force and torque exerted by a plane wave illumination with a given intensity. Here, while studying isotropic particles, we show that different light-matter interaction channels contribute to the exerted force and torque, and analytically derive upper bounds for each of the contributions. Specific examples for particles that achieve those upper bounds are provided. We study how and to which extent different contributions can add up to result in the maximum optical force and torque. Our insights are important for applications ranging from molecular sorting, particle manipulation, and nanorobotics up to ambitious projects such as laser-propelled spaceships.

  2. The effect of nonlinearity on unstable zones of Mathieu equation

    NASA Astrophysics Data System (ADS)

    Saryazdi, M. Gh

    2017-03-01

    Mathieu equation is a well-known ordinary differential equation in which the excitation term appears as the non-constant coefficient. The mathematical modelling of many dynamic systems leads to Mathieu equation. The determination of the locus of unstable zone is important for the control of dynamic systems. In this paper, the stable and unstable regions of Mathieu equation are determined for three cases of linear and nonlinear equations using the homotopy perturbation method. The effect of nonlinearity is examined in the unstable zone. The results show that the transition curves of linear Mathieu equation depend on the frequency of the excitation term. However, for nonlinear equations, the curves depend also on initial conditions. In addition, increasing the amplitude of response leads to an increase in the unstable zone.

  3. Fundamental experiments in velocimetry

    SciTech Connect

    Briggs, Matthew Ellsworth; Hull, Larry; Shinas, Michael

    2009-01-01

    One can understand what velocimetry does and does not measure by understanding a few fundamental experiments. Photon Doppler Velocimetry (PDV) is an interferometer that will produce fringe shifts when the length of one of the legs changes, so we might expect the fringes to change whenever the distance from the probe to the target changes. However, by making PDV measurements of tilted moving surfaces, we have shown that fringe shifts from diffuse surfaces are actually measured only from the changes caused by the component of velocity along the beam. This is an important simplification in the interpretation of PDV results, arising because surface roughness randomizes the scattered phases.

  4. Active Control of Linear Periodic System with Two Unstable Modes.

    DTIC Science & Technology

    1982-12-01

    tV;;;.~II.~9 - B ~ZV ~- p1 . ,,~ >. ~ ACTIVE CONTROL OF LINEAR PERIODIC SYSTEM WITH TWO UNSTABLE MODES THESIS by Gregory E. Myers, B.S.E. 2nd Lt...PERIODIC SYSTEM WITH TWO UNSTABLE MODES THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute of Technology Air University...December 1982 Approved for public release; distribution unlimited -ow PREFACE This thesis is a continuation of the work done by Yeakel in the control of

  5. Unstable laser resonators with super-Gaussian mirrors

    SciTech Connect

    De Silvestri, S.; Laporta, P.; Magni, V.; Svelto, O.; Majocchi, B.

    1988-03-01

    A new class of tapered reflectivity mirrors with a super-Gaussian profile R atmI exp(-kr/sup n/) is introduced, and a geometrical-optics approach for analysis and design of unstable resonators made with these mirrors is presented. A super-Gaussian mirror, built by a special evaporation technique, has been tested in an unstable resonator of a pulsed Nd:YAG laser, demonstrating its effectiveness in generating diffraction-limited beams.

  6. The stabilization of unstable detonation waves for the mixture of nitromethane/methanol

    NASA Astrophysics Data System (ADS)

    Utkin, A. V.; Koldunov, S. A.; Mochalova, V. M.; Torunov, S. I.; Lapin, S. M.

    2015-11-01

    Using a laser interferometer VISAR the measurements of the particle velocity profiles in detonation waves for nitromethane/methanol mixtures with additions of a sensitizer diethylenetriamine were conducted. It is shown that the detonation front in a mixture of nitromethane/methanol is unstable and sensitizer is an effective method for the flow stabilization. If the diluent concentration is less than 10%, the detonation front is stabilized by adding of 1% diethylenetriamine. At higher concentrations of methanol, the sensitizer does not reject instability, but the amplitude of oscillations decreases in several times. An increase of the limit concentration of methanol at the addition of diethylenetriamine to the mixture was found.

  7. Fundamentals of Space Systems

    NASA Astrophysics Data System (ADS)

    Pisacane, Vincent L.

    2005-06-01

    Fundamentals of Space Systems was developed to satisfy two objectives: the first is to provide a text suitable for use in an advanced undergraduate or beginning graduate course in both space systems engineering and space system design. The second is to be a primer and reference book for space professionals wishing to broaden their capabilities to develop, manage the development, or operate space systems. The authors of the individual chapters are practicing engineers that have had extensive experience in developing sophisticated experimental and operational spacecraft systems in addition to having experience teaching the subject material. The text presents the fundamentals of all the subsystems of a spacecraft missions and includes illustrative examples drawn from actual experience to enhance the learning experience. It included a chapter on each of the relevant major disciplines and subsystems including space systems engineering, space environment, astrodynamics, propulsion and flight mechanics, attitude determination and control, power systems, thermal control, configuration management and structures, communications, command and telemetry, data processing, embedded flight software, survuvability and reliability, integration and test, mission operations, and the initial conceptual design of a typical small spacecraft mission.

  8. Auroral particles

    NASA Astrophysics Data System (ADS)

    Evans, David S.

    1987-06-01

    The problems concerning the aurora posed prior to the war are now either solved in principle or were restated in a more fundamental form. The pre-war hypothesis concerning the nature of the auroral particles and their energies was fully confirmed, with the exception that helium and oxygen ions were identified as participating in the auroral particle precipitation in addition to the protons. The nature of the near-Earth energization processes affecting auroral particles was clarified. Charged particle trajectories in various electric field geometries were modeled. The physical problems have now moved from determining the nature and geometry of the electric fields, which accelerate charged particles near the Earth, to accounting for the existence of these electric fields as a natural consequence of the solar wind's interaction with Earth. Ultimately the reward in continuing the work in auroral and magnetospheric particle dynamics will be a deeper understanding of the subtleties of classical electricity and magnetism as applied to situations not blessed with well-defined and invariant geometries.

  9. Auroral particles

    NASA Technical Reports Server (NTRS)

    Evans, David S.

    1987-01-01

    The problems concerning the aurora posed prior to the war are now either solved in principle or were restated in a more fundamental form. The pre-war hypothesis concerning the nature of the auroral particles and their energies was fully confirmed, with the exception that helium and oxygen ions were identified as participating in the auroral particle precipitation in addition to the protons. The nature of the near-Earth energization processes affecting auroral particles was clarified. Charged particle trajectories in various electric field geometries were modeled. The physical problems have now moved from determining the nature and geometry of the electric fields, which accelerate charged particles near the Earth, to accounting for the existence of these electric fields as a natural consequence of the solar wind's interaction with Earth. Ultimately the reward in continuing the work in auroral and magnetospheric particle dynamics will be a deeper understanding of the subtleties of classical electricity and magnetism as applied to situations not blessed with well-defined and invariant geometries.

  10. Neutron Capture Experiments on Unstable Nuclei

    SciTech Connect

    Jon M. Schwantes; Ralf Sudowe; Heino Nitsche; Darleane C. Hoffman

    2003-12-16

    A primary objective of this project is to study neutron capture cross sections for various stable and unstable isotopes that will contribute to the Science Based Stockpile Stewardship (SBSS) program by providing improved data for modeling and interpretation of nuclear device performance. The information obtained will also be important in astrophysical modeling of nucleosynthesis. During this reporting period, the emphasis has been on preparing a radioactive target of {sup 155}Eu (half-life = 4.7 years), and several stable targets, including isotopically separated {sup 154}Sm, {sup 151}Eu, and {sup 153}Eu. Measurements of their neutron capture cross sections will be conducted in collaboration with researchers at the Los Alamos Neutron Science Center (LANSCE) facility using the Detector for Advanced Neutron Capture Experiments (DANCE). A suitable backing material (beryllium) for the targets has been selected after careful calculations of its contribution to the background of the measurements. In addition, a high voltage plating procedure has been developed and optimized. Stable targets of {sup 151}Eu and {sup 153}Eu and a target of natural Eu ({approx}50% {sup 151}Eu and {approx}50% {sup 153}Eu) have each been plated to a mass thickness of >1 mg/cm{sup 2} and delivered to the DANCE collaboration at Los Alamos National Laboratory (LANL). Natural Eu targets will be tested first to confirm that the target dimensions and backing are appropriate prior to performing measurements on the extremely valuable targets of separated isotopes. In order to prepare a target of the radioactive {sup 155}Eu, it must first be separated from the {sup 154}Sm target material that was irradiated in a very high neutron flux of 1.5x1015 neutrons/cm{sup 2}/s for 50 days. The reaction is {sup 154}Sm (n,f){sup 155}Sm (half-life = 22 minutes) {sup 155}Eu. Considerable progress has been made in developing a suitable high-yield and high-purity separation method for separating Eu from targets

  11. Fundamentals of zoological scaling

    NASA Astrophysics Data System (ADS)

    Lin, Herbert

    1982-01-01

    Most introductory physics courses emphasize highly idealized problems with unique well-defined answers. Though many textbooks complement these problems with estimation problems, few books present anything more than an elementary discussion of scaling. This paper presents some fundamentals of scaling in the zoological domain—a domain complex by any standard, but one also well suited to illustrate the power of very simple physical ideas. We consider the following animal characteristics: skeletal weight, speed of running, height and range of jumping, food consumption, heart rate, lifetime, locomotive efficiency, frequency of wing flapping, and maximum sizes of animals that fly and hover. These relationships are compared to zoological data and everyday experience, and match reasonably well.

  12. Nuclei and Fundamental Symmetries

    NASA Astrophysics Data System (ADS)

    Haxton, Wick

    2016-09-01

    Nuclei provide marvelous laboratories for testing fundamental interactions, often enhancing weak processes through accidental degeneracies among states, and providing selection rules that can be exploited to isolate selected interactions. I will give an overview of current work, including the use of parity violation to probe unknown aspects of the hadronic weak interaction; nuclear electric dipole moment searches that may shed light on new sources of CP violation; and tests of lepton number violation made possible by the fact that many nuclei can only decay by rare second-order weak interactions. I will point to opportunities in both theory and experiment to advance the field. Based upon work supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics and SciDAC under Awards DE-SC00046548 (Berkeley), DE-AC02-05CH11231 (LBNL), and KB0301052 (LBNL).

  13. Wall of fundamental constants

    SciTech Connect

    Olive, Keith A.; Peloso, Marco; Uzan, Jean-Philippe

    2011-02-15

    We consider the signatures of a domain wall produced in the spontaneous symmetry breaking involving a dilatonlike scalar field coupled to electromagnetism. Domains on either side of the wall exhibit slight differences in their respective values of the fine-structure constant, {alpha}. If such a wall is present within our Hubble volume, absorption spectra at large redshifts may or may not provide a variation in {alpha} relative to the terrestrial value, depending on our relative position with respect to the wall. This wall could resolve the contradiction between claims of a variation of {alpha} based on Keck/Hires data and of the constancy of {alpha} based on Very Large Telescope data. We derive the properties of the wall and the parameters of the underlying microscopic model required to reproduce the possible spatial variation of {alpha}. We discuss the constraints on the existence of the low-energy domain wall and describe its observational implications concerning the variation of the fundamental constants.

  14. Fundamentals of gel dosimeters

    NASA Astrophysics Data System (ADS)

    McAuley, K. B.; Nasr, A. T.

    2013-06-01

    Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

  15. Gas cell neutralizers (Fundamental principles)

    SciTech Connect

    Fuehrer, B.

    1985-06-01

    Neutralizing an ion-beam of the size and energy levels involved in the neutral-particle-beam program represents a considerable extension of the state-of-the-art of neutralizer technology. Many different mediums (e.g., solid, liquid, gas, plasma, photons) can be used to strip the hydrogen ion of its extra electron. A large, multidisciplinary R and D effort will no doubt be required to sort out all of the ''pros and cons'' of these various techniques. The purpose of this particular presentation is to discuss some basic configurations and fundamental principles of the gas type of neutralizer cell. Particular emphasis is placed on the ''Gasdynamic Free-Jet'' neutralizer since this configuration has the potential of being much shorter than other type of gas cells (in the beam direction) and it could operate in nearly a continuous mode (CW) if necessary. These were important considerations in the ATSU design which is discussed in some detail in the second presentation entitled ''ATSU Point Design''.

  16. Unstable genes unstable mind: beyond the central dogma of molecular biology.

    PubMed

    Hegde, Mahabaleshwar V; Saraph, Arundhati A

    2011-08-01

    Schizophrenia has a polygenic mode of inheritance and an estimated heritability of over 80%, but success in understanding its genetic underpinnings to date has been modest. Unlike in trinucleotide neurodegenerative disorders, the phenomenon of genetic anticipation observed in schizophrenia or bipolar disorder has not been explained. For the first time, we provide a plausible molecular explanation of genetic anticipation and pathophysiology of schizophrenia, at least in part, with supporting evidence. We postulate that abnormally increased numbers of CAG repeats in many genes being expressed in the brain, coding for glutamine, cumulatively press for higher demand of glutamine in the respective brain cells, resulting in a metabolic crisis and dysregulation of the glutamate-glutamine cycle. This can adversely affect the functioning of both glutamate and GABA receptors, which are known to be involved in psychosis, and may also affect glutathione levels, increasing oxidative stress. The resulting psychosis (gain in function), originating from unstable genes, is described as an effect "beyond the central dogma of molecular biology". The hypothesis explains genetic anticipation, as further expansions in subsequent generations may result in increased severity and earlier occurrence. Many other well described findings provide proof of concept. This is a testable hypothesis, does not deny any known facts and opens up new avenues of research.

  17. Hysteresis and Wavenumber Vacillation in Unstable Baroclinic Flows

    NASA Technical Reports Server (NTRS)

    Chou, Shih-Hung; Goodman, H. Michael (Technical Monitor)

    2001-01-01

    Hysteresis and wavenumber vacillation are studied numerically in a weakly stratified quasigeostrophic model. In general, the amplitude of the most unstable wave increases, as the flow becomes more unstable. When the wave becomes saturated, the next longer wave will grow at the expanse of the most unstable wave and becomes the dominant wave. However, once the longwave state is established, it may remain in that regime even as the instability is decreased beyond the threshold where it first developed, thus constituting a hysteresis loop. In a highly unstable case, the flow may not show a preference for any single wave. Instead, the dominant wave aperiodically varies among several long waves. This phenomenon is known as wavenumber vacillation. Hysteresis is further examined in terms of eddy heat flux. It is shown that total eddy heat flux increases as the flow becomes more unstable, but displays a sharp drop when transition to a longer wave occurs. However, in a longwave state, the heat flux always decreases with decreasing instability even pass the threshold when wave transition first occurs.

  18. Gait biomechanics of a second generation unstable shoe.

    PubMed

    Gardner, Jacob K; Zhang, Songning; Paquette, Max R; Milner, Clare E; Brock, Elizabeth

    2014-08-01

    The recent popularity of unstable shoes has sparked much interest in the efficacy of the shoe design. Anecdotal evidence suggests that earlier designs appear bulky and less aesthetically appealing for everyday use. The purpose of this study was to examine effects of a second generation unstable shoe on center of pressure (COP), ground reaction force (GRF), kinematics, and kinetics of the ankle joint during level walking at normal and fast speeds. In addition, findings were compared with results from the first generation shoe. Fourteen healthy males performed five successful level walking trials in four testing conditions: walking in unstable and control shoes at normal (1.3 m/s) and fast (1.8 m/s) speeds. The unstable shoe resulted in an increase in mediolateral COP displacement, first peak vertical GRF loading rate, braking GRF, ankle eversion range of motion (ROM), and inversion moment; as well as a decrease in anteroposterior COP displacement, second peak vertical GRF, ankle plantarflexion ROM, and dorsiflexion moment. Only minor differences were found between the shoe generations. Results of the generational comparisons suggest that the lower-profile second generation shoe may be as effective at achieving the desired unstable effects while promoting a smoother transition from heel contact through toe off compared with the first generation shoe.

  19. GRBs and Fundamental Physics

    NASA Astrophysics Data System (ADS)

    Petitjean, Patrick; Wang, F. Y.; Wu, X. F.; Wei, J. J.

    2016-12-01

    Gamma-ray bursts (GRBs) are short and intense flashes at the cosmological distances, which are the most luminous explosions in the Universe. The high luminosities of GRBs make them detectable out to the edge of the visible universe. So, they are unique tools to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal evolution of the Universe. First, they can be used to constrain the history of cosmic acceleration and the evolution of dark energy in a redshift range hardly achievable by other cosmological probes. Second, long GRBs are believed to be formed by collapse of massive stars. So they can be used to derive the high-redshift star formation rate, which can not be probed by current observations. Moreover, the use of GRBs as cosmological tools could unveil the reionization history and metal evolution of the Universe, the intergalactic medium (IGM) properties and the nature of first stars in the early universe. But beyond that, the GRB high-energy photons can be applied to constrain Lorentz invariance violation (LIV) and to test Einstein's Equivalence Principle (EEP). In this paper, we review the progress on the GRB cosmology and fundamental physics probed by GRBs.

  20. Overlay accuracy fundamentals

    NASA Astrophysics Data System (ADS)

    Kandel, Daniel; Levinski, Vladimir; Sapiens, Noam; Cohen, Guy; Amit, Eran; Klein, Dana; Vakshtein, Irina

    2012-03-01

    Currently, the performance of overlay metrology is evaluated mainly based on random error contributions such as precision and TIS variability. With the expected shrinkage of the overlay metrology budget to < 0.5nm, it becomes crucial to include also systematic error contributions which affect the accuracy of the metrology. Here we discuss fundamental aspects of overlay accuracy and a methodology to improve accuracy significantly. We identify overlay mark imperfections and their interaction with the metrology technology, as the main source of overlay inaccuracy. The most important type of mark imperfection is mark asymmetry. Overlay mark asymmetry leads to a geometrical ambiguity in the definition of overlay, which can be ~1nm or less. It is shown theoretically and in simulations that the metrology may enhance the effect of overlay mark asymmetry significantly and lead to metrology inaccuracy ~10nm, much larger than the geometrical ambiguity. The analysis is carried out for two different overlay metrology technologies: Imaging overlay and DBO (1st order diffraction based overlay). It is demonstrated that the sensitivity of DBO to overlay mark asymmetry is larger than the sensitivity of imaging overlay. Finally, we show that a recently developed measurement quality metric serves as a valuable tool for improving overlay metrology accuracy. Simulation results demonstrate that the accuracy of imaging overlay can be improved significantly by recipe setup optimized using the quality metric. We conclude that imaging overlay metrology, complemented by appropriate use of measurement quality metric, results in optimal overlay accuracy.

  1. Fundamentals of Radiation Dosimetry

    SciTech Connect

    Bos, Adrie J. J.

    2011-05-05

    The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

  2. Fundamentals of Radiation Dosimetry

    NASA Astrophysics Data System (ADS)

    Bos, Adrie J. J.

    2011-05-01

    The basic concepts of radiation dosimetry are reviewed on basis of ICRU reports and text books. The radiation field is described with, among others, the particle fluence. Cross sections for indirectly ionizing radiation are defined and indicated is how they are related to the mass energy transfer and mass energy absorption coefficients. Definitions of total and restricted mass stopping powers of directly ionizing radiation are given. The dosimetric quantities, kerma, absorbed dose and exposure together with the relations between them are discussed in depth. Finally it is indicated how the absorbed dose can be measured with a calorimeter by measuring the temperature increase and with an ionisation chamber measuring the charge produced by the ionizing radiation and making use of the Bragg-Gray relation.

  3. Buoyancy effects in an unstably stratified turbulent boundary layer flow

    NASA Astrophysics Data System (ADS)

    Li, Dong; Luo, Kun; Fan, Jianren

    2017-01-01

    Direct numerical simulation has been performed to investigate the effect of buoyancy on an unstably stratified turbulent boundary layer with the Oberbeck-Boussinesq approximation. The simulation results show that the mean values of the streamwise velocity and scalar fields are increased in the near-wall region but decreased in the outer layer under the effect of buoyancy, which leads to significant increases in the skin-friction drag and heat transfer. In addition, it is found that the unstable thermal stratification results in large increases in the intensities of the near-wall streamwise vortices and high- and low-speed streaks, and a reduction in the mean diameter of the vortical structures. Moreover, the turbulent coherent structures become less organized due to the stratification effect. With respect to the neutral boundary layer flow, the outer vortical structures tend to bias the direction of the principal extensional strain towards the vertical plane in the unstably stratified flow.

  4. Mathematical modeling of transformation process of structurally unstable magnetic configurations into structurally stable ones in two-dimensional and three-dimensional geometry

    NASA Astrophysics Data System (ADS)

    Inovenkov, Igor; Echkina, Eugenia; Ponomarenko, Loubov

    Magnetic reconnection is a fundamental process in astrophysical, space and laboratory plasma. In essence, it represents a change of topology of the magnetic field caused by readjustment of the structure of the magnetic field lines. This change leads to release of energy accumulated in the field. We consider transformation process of structurally unstable magnetic configurations into the structurally steady ones from the point of view of the сatastrophe theory. Special attention is paid to modeling of evolution of the structurally unstable three-dimensional magnetic fields.

  5. Detecting unstable periodic orbits from transient chaotic time series

    PubMed

    Dhamala; Lai; Kostelich

    2000-06-01

    We address the detection of unstable periodic orbits from experimentally measured transient chaotic time series. In particular, we examine recurrence times of trajectories in the vector space reconstructed from an ensemble of such time series. Numerical experiments demonstrate that this strategy can yield periodic orbits of low periods even when noise is present. We analyze the probability of finding periodic orbits from transient chaotic time series and derive a scaling law for this probability. The scaling law implies that unstable periodic orbits of high periods are practically undetectable from transient chaos.

  6. Ultrastructural studies of unstable angina in living man

    SciTech Connect

    Gotlieb, A.I.; Freeman, M.R.; Salerno, T.A.; Lichtenstein, S.V.; Armstrong, P.W. )

    1991-01-01

    Nineteen patients with refractory unstable angina who were undergoing aortocoronary bypass were studied to assess the extent of platelet aggregation present in the microvasculature. Ultrastructural findings on the morphology of cardiac muscle and microvasculature were correlated with the findings on coronary angiograms and thallium scans. There were no significant correlations. The presence of platelet aggregates was identified in four biopsies, two of which had thrombus by angiographic criteria. Biopsy in areas with thallium defects revealed an increased prevalence of white blood cells without acute myocardial infarction. This study confirms the presence of platelet aggregates in patients with unstable angina, albeit at a reduced frequency when compared with autopsy studies.

  7. Kinetic Simulations of the Lowest-order Unstable Mode of Relativistic Magnetostatic Equilibria

    NASA Astrophysics Data System (ADS)

    Nalewajko, Krzysztof; Zrake, Jonathan; Yuan, Yajie; East, William E.; Blandford, Roger D.

    2016-08-01

    We present the results of particle-in-cell numerical pair plasma simulations of relativistic two-dimensional magnetostatic equilibria known as the “Arnold-Beltrami-Childress” fields. In particular, we focus on the lowest-order unstable configuration consisting of two minima and two maxima of the magnetic vector potential. Breaking of the initial symmetry leads to exponential growth of the electric energy and to the formation of two current layers, which is consistent with the picture of “X-point collapse” first described by Syrovatskii. Magnetic reconnection within the layers heats a fraction of particles to very high energies. After the saturation of the linear instability, the current layers are disrupted and the system evolves chaotically, diffusing the particle energies in a stochastic second-order Fermi process, leading to the formation of power-law energy distributions. The power-law slopes harden with the increasing mean magnetization, but they are significantly softer than those produced in simulations initiated from Harris-type layers. The maximum particle energy is proportional to the mean magnetization, which is attributed partly to the increase of the effective electric field and partly to the increase of the acceleration timescale. We describe in detail the evolving structure of the dynamical current layers and report on the conservation of magnetic helicity. These results can be applied to highly magnetized astrophysical environments, where ideal plasma instabilities trigger rapid magnetic dissipation with efficient particle acceleration and flares of high-energy radiation.

  8. Fundamentals of Space Medicine

    NASA Astrophysics Data System (ADS)

    Clément, Gilles

    2005-03-01

    A total of more than 240 human space flights have been completed to date, involving about 450 astronauts from various countries, for a combined total presence in space of more than 70 years. The seventh long-duration expedition crew is currently in residence aboard the International Space Station, continuing a permanent presence in space that began in October 2000. During that time, investigations have been conducted on both humans and animal models to study the bone demineralization and muscle deconditioning, space motion sickness, the causes and possible treatment of postflight orthostatic intolerance, the changes in immune function, crew and crew-ground interactions, and the medical issues of living in a space environment, such as the effects of radiation or the risk of developing kidney stones. Some results of these investigations have led to fundamental discoveries about the adaptation of the human body to the space environment. Gilles Clément has been active in this research. This readable text presents the findings from the life science experiments conducted during and after space missions. Topics discussed in this book include: adaptation of sensory-motor, cardio-vascular, bone, and muscle systems to the microgravity of spaceflight; psychological and sociological issues of living in a confined, isolated, and stressful environment; operational space medicine, such as crew selection, training and in-flight health monitoring, countermeasures and support; results of space biology experiments on individual cells, plants, and animal models; and the impact of long-duration missions such as the human mission to Mars. The author also provides a detailed description of how to fly a space experiment, based on his own experience with research projects conducted onboard Salyut-7, Mir, Spacelab, and the Space Shuttle. Now is the time to look at the future of human spaceflight and what comes next. The future human exploration of Mars captures the imagination of both the

  9. Fundamentals of Space Medicine

    NASA Astrophysics Data System (ADS)

    Clément, G.

    2003-10-01

    As of today, a total of more than 240 human space flights have been completed, involving about 450 astronauts from various countries, for a combined total presence in space of more than 70 years. The seventh long-duration expedition crew is currently in residence aboard the International Space Station, continuing a permanent presence in space that began in October 2000. During that time, investigations have been conducted on both humans and animal models to study the bone demineralization and muscle deconditioning, space motion sickness, the causes and possible treatment of postflight orthostatic intolerance, the changes in immune function, crew and crew-ground interactions, and the medical issues of living in a space environment, such as the effects of radiation or the risk of developing kidney stones. Some results of these investigations have led to fundamental discoveries about the adaptation of the human body to the space environment. Gilles Clément has been active in this research. This book presents in a readable text the findings from the life science experiments conducted during and after space missions. Topics discussed in this book include: adaptation of sensory-motor, cardiovascular, bone and muscle systems to the microgravity of spaceflight; psychological and sociological issues of living in a confined, isolated and stressful environment; operational space medicine, such as crew selection, training and in-flight health monitoring, countermeasures and support; results of space biology experiments on individual cells, plants, and animal models; and the impact of long-duration missions such as the human mission to Mars. The author also provides a detailed description of how to fly a space experiment, based on his own experience with research projects conducted onboard Salyut-7, Mir, Spacelab, and the Space Shuttle. Now is the time to look at the future of human spaceflight and what comes next. The future human exploration of Mars captures the imagination

  10. Stabilizing control for a class of delay unstable processes.

    PubMed

    Lee, See Chek; Wang, Qing-Guo; Nguyen, Le Binh

    2010-07-01

    The stabilization of unstable first-order plus time-delay processes with a zero by means of simple controllers is investigated in detail. Explicit stabilizability conditions are established. And the computational methods for determining stabilizing controller parameters are also presented with illustrative examples.

  11. Shearing box simulations in the Rayleigh unstable regime

    NASA Astrophysics Data System (ADS)

    Nauman, Farrukh; Blackman, Eric G.

    2017-01-01

    We study the stability properties of Rayleigh unstable flows both in the purely hydrodynamic and magnetohydrodynamic (MHD) regimes for two different values of the shear q = 2.1, 4.2 (q = -dln Ω/dln r) and compare it with the Keplerian case q = 1.5. We find that the q > 2 regime is unstable both in the hydrodynamic and in the MHD limit (with an initially weak magnetic field). In this regime, the velocity fluctuations dominate the magnetic fluctuations. In contrast, in the q < 2 (magnetorotational instability (MRI)) regime the magnetic fluctuations dominate. This highlights two different paths to MHD turbulence implied by the two regimes, suggesting that in the q > 2 regime the instability produces primarily velocity fluctuations that cause magnetic fluctuations, with the causality reversed for the q < 2 MRI unstable regime. We also find that the magnetic field correlation is increasingly localized as the shear is increased in the Rayleigh unstable regime. In calculating the time evolution of spatial averages of different terms in the MHD equations, we find that the q > 2 regime is dominated by terms which are nonlinear in the fluctuations, whereas for q < 2, the linear terms play a more significant role.

  12. Assessment and treatment of patients with acute unstable bradycardia.

    PubMed

    Swift, Jennie

    Bradycardia is a slow heart rate that can lead to cardiac arrest or occur after initial resuscitation following cardiac arrest. This article provides information on acute unstable bradycardia and common arrhythmias. It focuses on the assessment of patients with acute bradycardia and how the presence or absence of adverse clinical features, in conjunction with an arrhythmia, dictates the necessity and choice of treatment.

  13. Mirage cosmology with an unstable probe D3-brane

    SciTech Connect

    Jeong, Dong Hyeok; Kim, Jin Young

    2005-10-15

    We consider the mirage cosmology by an unstable probe brane whose action is represented by Dirac-Born-Infeld action with tachyon. We study how the presence of tachyon affects the evolution of the brane inflation. At the early stage of the brane inflation, the tachyon kinetic term can play an important role in curing the superluminal expansion in mirage cosmology.

  14. Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

    NASA Astrophysics Data System (ADS)

    Kleinbrod, U.; Burjanek, J.; Fäh, D.

    2014-12-01

    Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. An analysis of ambient vibrations of unstable rock slopes might be a new alternative to the already existing methods, e.g. geotechnical displacement measurements. Systematic measurements have been performed recently in Switzerland to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. Each measurement setup included a reference station, which was installed on a stable part close to the instability. Recorded ground motion is highly directional in the unstable parts of the rock slope, and significantly amplified with respect to stable areas. These effects are strongest at certain frequencies, which were identified as eigenfrequencies of the unstable rock mass. In most cases the directions of maximum amplification are perpendicular to open cracks and in good agreement with the deformation directions obtained by geodetic measurements. Such unique signatures might improve our understanding of slope structure and stability. Thus we link observed vibration characteristics with available results of detailed geological characterization. This is supported by numerical modeling of seismic wave propagation in fractured media with complex topography.For example, a potential relation between eigenfrequencies and unstable rock mass volume is investigated.

  15. Neuromuscular adjustments of gait associated with unstable conditions

    PubMed Central

    Ivanenko, Y. P.; d'Avella, A.; Serrao, M.; Ranavolo, A.; Draicchio, F.; Cappellini, G.; Casali, C.; Lacquaniti, F.

    2015-01-01

    A compact description of coordinated muscle activity is provided by the factorization of electromyographic (EMG) signals. With the use of this approach, it has consistently been shown that multimuscle activity during human locomotion can be accounted for by four to five modules, each one comprised of a basic pattern timed at a different phase of gait cycle and the weighting coefficients of synergistic muscle activations. These modules are flexible, in so far as the timing of patterns and the amplitude of weightings can change as a function of gait speed and mode. Here we consider the adjustments of the locomotor modules related to unstable walking conditions. We compared three different conditions, i.e., locomotion of healthy subjects on slippery ground (SL) and on narrow beam (NB) and of cerebellar ataxic (CA) patients on normal ground. Motor modules were computed from the EMG signals of 12 muscles of the right lower limb using non-negative matrix factorization. The unstable gait of SL, NB, and CA showed significant changes compared with controls in the stride length, stride width, range of angular motion, and trunk oscillations. In most subjects of all three unstable conditions, >70% of the overall variation of EMG waveforms was accounted for by four modules that were characterized by a widening of muscle activity patterns. This suggests that the nervous system adopts the strategy of prolonging the duration of basic muscle activity patterns to cope with unstable conditions resulting from either slippery ground, reduced support surface, or pathology. PMID:26378199

  16. RAYLEIGH–TAYLOR UNSTABLE FLAMES—FAST OR FASTER?

    SciTech Connect

    Hicks, E. P.

    2015-04-20

    Rayleigh–Taylor (RT) unstable flames play a key role in the explosions of supernovae Ia. However, the dynamics of these flames are still not well understood. RT unstable flames are affected by both the RT instability of the flame front and by RT-generated turbulence. The coexistence of these factors complicates the choice of flame speed subgrid models for full-star Type Ia simulations. Both processes can stretch and wrinkle the flame surface, increasing its area and, therefore, the burning rate. In past research, subgrid models have been based on either the RT instability or turbulence setting the flame speed. We evaluate both models, checking their assumptions and their ability to correctly predict the turbulent flame speed. Specifically, we analyze a large parameter study of 3D direct numerical simulations of RT unstable model flames. This study varies both the simulation domain width and the gravity in order to probe a wide range of flame behaviors. We show that RT unstable flames are different from traditional turbulent flames: they are thinner rather than thicker when turbulence is stronger. We also show that none of the several different types of turbulent flame speed models accurately predicts measured flame speeds. In addition, we find that the RT flame speed model only correctly predicts the measured flame speed in a certain parameter regime. Finally, we propose that the formation of cusps may be the factor causing the flame to propagate more quickly than predicted by the RT model.

  17. Unstable oscillatory Pierce modes of neutralized electron beams

    SciTech Connect

    Cary, J.R.; Lemons, D.S.

    1982-04-01

    Oscillatory modes of the Pierce system have been calculated. These modes are found to have growth rates comparable to the previously investigated purely growing modes. When these modes are included, it is found that the Pierce system is unstable for most values of ..omega../sub p/ L/V/sub 0/>..pi...

  18. Fundamental physics at the threshold of discovery

    NASA Astrophysics Data System (ADS)

    Toro, Natalia

    This thesis is divided into two parts: one driven by theory, the other by experiment. The first two chapters consider two model-building challenges: the little hierarchy of supersymmetry and the slowness of confinement in Randall-Sundrum models. In the third chapter, we turn to the question of determining the nature of fundamental physics at the TeV scale from LHC data. Crucial to this venture is a characterization for models of new physics. We present On-Shell Effective Theories (OSETs), a characterization of hadron collider data in terms of masses, production cross sections, and decay modes of new particles. We argue that such a description can likely be obtained from ≲ 1 year of LHC data, and in many scenarios is an essential intermediate step in describing fundamental physics at the TeV scale.

  19. Matter and Interactions: A Particle Physics Perspective

    ERIC Educational Resources Information Center

    Organtini, Giovanni

    2011-01-01

    In classical mechanics, matter and fields are completely separated; matter interacts with fields. For particle physicists this is not the case; both matter and fields are represented by particles. Fundamental interactions are mediated by particles exchanged between matter particles. In this article we explain why particle physicists believe in…

  20. A novel approach to modeling unstable EOR displacements. Final report

    SciTech Connect

    Peters, E.J.

    1994-04-01

    Most enhanced oil recovery schemes involve the displacement of a more dense and more viscous oil by a less dense and less viscous fluid in a heterogeneous porous medium. The interaction of heterogeneity with the several competing forces, namely, viscous, capillary, gravitational, and dispersive forces, can conspire to make the displacements unstable and difficult to model and to predict. The objective of this research was to develop a systematic methodology for modeling unstable fluid displacements in heterogeneous media. Flow visualization experiments were conducted using X-ray computed tomography imaging and a video imaging workstation to gain insights into the dynamics of unstable displacements, acquire detailed quantitative experimental image data for calibrating numerical models of unstable displacements, and image and characterize heterogeneities in laboratory cores geostatistically. High-resolution numerical models modified for use on vector-architecture supercomputers were used to replicate the image data. Geostatistical models of reservoir heterogeneity were incorporated in order to study the interaction of hydrodynamic instability and heterogeneity in reservoir displacements. Finally, a systematic methodology for matching the experimental data with the numerical models and scaling the laboratory results to other systems were developed. The result is a new method for predicting the performance of unstable EOR displacements in the field based on small-scale displacements in the laboratory. The methodology is general and can be applied to forecast the performance of most processes that involve fluid flow and transport in porous media. Therefore, this research should be of interest to those involved in forecasting the performance of enhanced oil recovery processes and the spreading of contaminants in heterogeneous aquifers.

  1. Fundamentals of ICF Hohlraums

    SciTech Connect

    Rosen, M D

    2005-09-30

    On the Nova Laser at LLNL, we demonstrated many of the key elements required for assuring that the next laser, the National Ignition Facility (NIF) will drive an Inertial Confinement Fusion (ICF) target to ignition. The indirect drive (sometimes referred to as ''radiation drive'') approach converts laser light to x-rays inside a gold cylinder, which then acts as an x-ray ''oven'' (called a hohlraum) to drive the fusion capsule in its center. On Nova we've demonstrated good understanding of the temperatures reached in hohlraums and of the ways to control the uniformity with which the x-rays drive the spherical fusion capsules. In these lectures we will be reviewing the physics of these laser heated hohlraums, recent attempts at optimizing their performance, and then return to the ICF problem in particular to discuss scaling of ICF gain with scale size, and to compare indirect vs. direct drive gains. In ICF, spherical capsules containing Deuterium and Tritium (DT)--the heavy isotopes of hydrogen--are imploded, creating conditions of high temperature and density similar to those in the cores of stars required for initiating the fusion reaction. When DT fuses an alpha particle (the nucleus of a helium atom) and a neutron are created releasing large amount amounts of energy. If the surrounding fuel is sufficiently dense, the alpha particles are stopped and can heat it, allowing a self-sustaining fusion burn to propagate radially outward and a high gain fusion micro-explosion ensues. To create those conditions the outer surface of the capsule is heated (either directly by a laser or indirectly by laser produced x-rays) to cause rapid ablation and outward expansion of the capsule material. A rocket-like reaction to that outward flowing heated material leads to an inward implosion of the remaining part of the capsule shell. The pressure generated on the outside of the capsule can reach nearly 100 megabar (100 million times atmospheric pressure [1b = 10{sup 6} cgs

  2. Piecewise - Parabolic Methods for Parallel Computation with Applications to Unstable Fluid Flow in 2 and 3 Dimensions

    SciTech Connect

    Woodward, P. R.

    2003-03-26

    This report summarizes the results of the project entitled, ''Piecewise-Parabolic Methods for Parallel Computation with Applications to Unstable Fluid Flow in 2 and 3 Dimensions'' This project covers a span of many years, beginning in early 1987. It has provided over that considerable period the core funding to my research activities in scientific computation at the University of Minnesota. It has supported numerical algorithm development, application of those algorithms to fundamental fluid dynamics problems in order to demonstrate their effectiveness, and the development of scientific visualization software and systems to extract scientific understanding from those applications.

  3. An Evaluation of Fundamental Schools.

    ERIC Educational Resources Information Center

    Weber, Larry J.; And Others

    1984-01-01

    When compared with regular schools in the same district, fundamental school students performed as well as or better than regular school students; fundamental schools rated better on learning climate, discipline, and suspensions; and there were no differences in student self-concept. (Author/BW)

  4. Strain Wave during the Transient Process of Fault Unstable Slip

    NASA Astrophysics Data System (ADS)

    Guo, L.; Liu, L.

    2011-12-01

    The "stick-slip" model was proposed as an important mechanism for shallow-focus earthquakes. The study on the transient process of fault unstable slip failure is helpful for understanding the earthquake preparatory process, the mechanism of energy released, the precursor and after shake effect. Double shear frictional experiments are conducted for simulating "stick-slip" phenomenon, and a specially designed multi-channel super dynamic strain field observation system is employed to acquire dada continuously with the sample rate of 3,400 samples/second. The rock deformation process can be recorded in detail, especially in the moment of unstable slip (The unstable slip duration is less than two second in experiments). The strain results from super dynamic strain field observation system show that multi-frequency components and tremendous amplitude fluctuation are included in strain signals along the fault. There are three clear phases during the unstable slip progress: pre-slip (phase I), high-frequency strain vibration (phase II) and strain regulating to stop (phase III). Each phase has its own characteristics on duration, strain rate, frequency, amplitude and energy release. There are strong fluctuations in duration of approximately 70ms in phase II. The frequency and maximum amplitude are 300-400Hz and 150~300μɛ respectively. Main strain energy release takes place at phase II, less than one-tenth of the total slip time, so that the whole course of dislocation or stress drop would not be taken as earthquake simply at least in laboratory. The phase characteristic of the strain wave is probably its inherent attribute of unstable slip process and independent of dynamical loading conditions. The elastic rebound phenomena, considered as one classic earthquake generation model, can be observed clearly by analyzing the rotation of the principal strain axis with strain variation. The rotated angle ranges from 5° to 15° typically. The value and location of precursor slip

  5. Extension of the CPT theorem to non-Hermitian Hamiltonians and unstable states

    NASA Astrophysics Data System (ADS)

    Mannheim, Philip D.

    2016-02-01

    We extend the CPT theorem to quantum field theories with non-Hermitian Hamiltonians and unstable states. Our derivation is a quite minimal one as it requires only the time-independent evolution of scalar products, invariance under complex Lorentz transformations, and a non-standard but nonetheless perfectly legitimate interpretation of charge conjugation as an antilinear operator. The first of these requirements does not force the Hamiltonian to be Hermitian. Rather, it forces its eigenvalues to either be real or to appear in complex conjugate pairs, forces the eigenvectors of such conjugate pairs to be conjugates of each other, and forces the Hamiltonian to admit of an antilinear symmetry. The latter two requirements then force this antilinear symmetry to be CPT, while forcing the Hamiltonian to be real rather than Hermitian. Our work justifies the use of the CPT theorem in establishing the equality of the lifetimes of unstable particles that are charge conjugates of each other. We show that the Euclidean time path integrals of a CPT-symmetric theory must always be real. In the quantum-mechanical limit the key results of the PT symmetry program of Bender and collaborators are recovered, with the C-operator of the PT symmetry program being identified with the linear component of the charge conjugation operator.

  6. Shape phase transition in odd-even nuclei: From spherical to deformed gamma-unstable shapes

    SciTech Connect

    Boeyuekata, M.; Alonso, C. E.; Arias, J. M.; Fortunato, L.; Vitturi, A.

    2010-07-15

    Shape phase transitions in odd-A nuclei are investigated within the framework of the interacting boson-fermion model. The case of a single j=9/2 fermion coupled to an even-even boson core is considered. This boson core transits from spherical to gamma-unstable shapes depending on the value of a control parameter in the boson Hamiltonian. The effect of the coupling of the odd particle to this core along the shape transition and, in particular, at the critical point is discussed. For that purpose, the ground-state energy surface in terms of the beta and gamma shape variables for the even core and odd-even energy surfaces for the different K states coming from j=9/2 are constructed. The evolution of each individual coupled state along the transition from the spherical [U(5)] to the gamma-unstable [O(6)] situation is investigated. One finds that the core-fermion coupling gives rise to a smoother transition than in the even-core case.

  7. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  8. Is the magnetopause Rayleigh-Taylor unstable sometimes?

    SciTech Connect

    Gratton, F.T.; Farrugia, C.J.; Cowley, S.W.H.

    1996-03-01

    The authors examine the question of whether the magnetopause is Rayleigh-Taylor stable. The magnetopause tends to be in continuous motion because of the effect of the dyanmic pressure from the solar wind. When there is a sudden drop in solar wind pressure, and the magnetopause tends to accelerate sunward, a situation is created where the magnetopause may go unstable. The authors look at two possible stabilizing effects, first the magnetic shear which exists across the magnetopause, and then the viscous nature of the magnetosheath plasma. They find that large shear leads to stability for the Rayleigh-Taylor mode. When there is a strong northward component in the magnetosheath field, they find that the magnetopause may be unstable to this mode for both global and internal modes. They also discuss the effect of such instabilities on observations.

  9. Thermally unstable hydrides of titanium aluminide Ti3Al

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Popov, A. G.; Mushnikov, N. V.; Skripov, A. V.; Soloninin, A. V.; Aleksashin, B. A.; Novozhenov, V. I.; Sazonova, V. A.; Kharisova, A. G.

    2011-04-01

    The hydrogen capacity of (Ti, Nb)3Al titanium aluminides subjected to mechanical activation in a hydrogen atmosphere has been studied. It has been shown that the application of this procedure allows one to prepare thermally unstable titanium aluminide (Ti3Al) hydrides with a high hydrogen content (to 2.6 wt %) at room temperature and normal pressure; in this case, no special requirements for the hydrogen purity are placed. The thermally unstable nanostructured Ti3Al hydrides were found to exhibit a higher hydrogen mobility as compared to that of the microcrystalline hydrides. Low niobium additions (to 2.1 at %) have been found to decrease the hydrogen capacity. Experiments on the preparation of bulk samples from the hydride powders obtained were performed.

  10. Cancer stem cells as the engine of unstable tumor progression.

    PubMed

    Solé, Ricard V; Rodríguez-Caso, Carlos; Deisboeck, Thomas S; Saldaña, Joan

    2008-08-21

    Genomic instability is considered by many authors the key engine of tumorigenesis. However, mounting evidence indicates that a small population of drug resistant cancer cells can also be a key component of tumor progression. Such cancer stem cells would define a compartment effectively acting as the source of most tumor cells. Here we study the interplay between these two conflicting components of cancer dynamics using two types of tissue architecture. Both mean field and multicompartment models are studied. It is shown that tissue architecture affects the pattern of cancer dynamics and that unstable cancers spontaneously organize into a heterogeneous population of highly unstable cells. This dominant population is in fact separated from the low-mutation compartment by an instability gap, where almost no cancer cells are observed. The possible implications of this prediction are discussed.

  11. Inherently unstable internal gravity waves due to resonant harmonic generation

    NASA Astrophysics Data System (ADS)

    Liang, Yong; Zareei, Ahmad; Alam, Mohammad-Reza

    2017-01-01

    Here we show that there exist internal gravity waves that are inherently unstable, that is, they cannot exist in nature for a long time. The instability mechanism is a one-way (irreversible) harmonic-generation resonance that permanently transfers the energy of an internal wave to its higher harmonics. We show that, in fact, there are countably infinite number of such unstable waves. For the harmonic-generation resonance to take place, nonlinear terms in the free surface boundary condition play a pivotal role, and the instability does not obtain for a linearly-stratified fluid if a simplified boundary condition such as rigid lid or linear form is employed. Harmonic-generation resonance presented here also provides a mechanism for the transfer of the energy of the internal waves to the higher-frequency part of the spectrum where internal waves are more prone to breaking, hence losing energy to turbulence and heat and contributing to oceanic mixing.

  12. [The efficacy of emoxipin and neoton in unstable stenocardia].

    PubMed

    Golikov, A P; Riabinin, V A; Golikov, P P; Davydov, B V; Polumiskov, V Iu; Rudnev, D V; Taranova, Z V

    1996-01-01

    55 patients with unstable angina pectoris (group 1) received conventional treatment and neoton infusions (30 g/day for 3 days). Emoxipin was injected intramuscularly to 20 patients of group 2 (3 mg/kg for 20 days) and intravenously to 38 patients of group 3 (10 mg/kg). Control group consisted of 100 patients. Stabilization occurred in 89.2, 80 and 86.8% of group 1, 2 and 3 patients, respectively, versus 78% in controls. Holter ECG monitoring provided evidence on decline of myocardial ischemia for group 1 patients. Diene conjugates in group 1 decreased by 37%, ceruloplasmin level was higher by 30% compared to controls. Respective indices for emoxipin reached 52 and 37%, respectively. It is concluded that emoxipin and neoton produced a beneficial effect on unstable angina pectoris through correction of lipid peroxidation.

  13. Note about unstable D-branes with dynamical tension

    NASA Astrophysics Data System (ADS)

    KlusoÅ, J.

    2016-08-01

    We propose an action for an unstable Dp-brane with dynamical tension. We show that the equations of motion are equivalent to the equations of motion derived from Dirac-Born-Infeld and Wess-Zumino actions for a non-Bogomol'nyi-Prasad-Sommerfield Dp-brane. We also find the Hamiltonian formulation of this action and analyze the properties of the solutions corresponding to the tachyon vacuum and zero-tension solution.

  14. Is the Milky Way's hot halo convectively unstable?

    SciTech Connect

    Henley, David B.; Shelton, Robin L.

    2014-03-20

    We investigate the convective stability of two popular types of model of the gas distribution in the hot Galactic halo. We first consider models in which the halo density and temperature decrease exponentially with height above the disk. These halo models were created to account for the fact that, on some sight lines, the halo's X-ray emission lines and absorption lines yield different temperatures, implying that the halo is non-isothermal. We show that the hot gas in these exponential models is convectively unstable if γ < 3/2, where γ is the ratio of the temperature and density scale heights. Using published measurements of γ and its uncertainty, we use Bayes' theorem to infer posterior probability distributions for γ, and hence the probability that the halo is convectively unstable for different sight lines. We find that, if these exponential models are good descriptions of the hot halo gas, at least in the first few kiloparsecs from the plane, the hot halo is reasonably likely to be convectively unstable on two of the three sight lines for which scale height information is available. We also consider more extended models of the halo. While isothermal halo models are convectively stable if the density decreases with distance from the Galaxy, a model of an extended adiabatic halo in hydrostatic equilibrium with the Galaxy's dark matter is on the boundary between stability and instability. However, we find that radiative cooling may perturb this model in the direction of convective instability. If the Galactic halo is indeed convectively unstable, this would argue in favor of supernova activity in the Galactic disk contributing to the heating of the hot halo gas.

  15. Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

    NASA Astrophysics Data System (ADS)

    Kleinbrod, Ulrike; Burjánek, Jan; Fäh, Donat

    2014-05-01

    Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. Analysing unstable rock slopes by means of ambient vibrations might be a new alternative to the already existing methods as for example geotechnical displacement measurements. A systematic measurement campaign has been initiated recently in Switzerland in order to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. First results are presented in this contribution. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. During each measurement a reference station was installed on a stable part close to the instability. The total number of stations used varies from 16 down to 2, depending on the site scope and resource availability. Instable rock slopes show a highly directional ground motion which is significantly amplified with respect to stable areas. These effects are strongest at certain frequencies which are identified as eigenfrequencies of the unstable rock mass. The eigenfrequencies and predominant directions have been estimated by frequency dependent polarization analysis. Site-to-reference spectral ratios have been calculated as well in order to estimate the relative amplification of ground motion at unstable parts. The retrieved results were compared with independent in-situ observations and other available data. The directions of maximum amplification are in most cases perpendicular to open cracks mapped on the surface and in good agreement with the deformation directions obtained by geodetic measurements. The interpretation of the observed wave field is done through numerical modelling of seismic wave propagation in fractured media with complex

  16. Thermally-sustained structure in convectively unstable systems

    NASA Technical Reports Server (NTRS)

    Deissler, Robert J.

    1993-01-01

    The complex Ginzburg-Landau equation with a thermal noise term is studied under conditions when the system is convectively unstable. Under these conditions, the noise is selectively and spatially amplified giving rise to a noise-sustained structure. Analytical results, applicable to a wide range of physical systems, are derived for the variance, and the coefficients and thermal noise term are determined for Taylor-Couette flow with an axial through-flow. Comparison is made to recent experiments.

  17. Calcar Preservation Arthroplasty for Unstable Intertrochanteric Femoral Fractures in Elderly

    PubMed Central

    Togrul, Emre; Kose, Ozkan

    2015-01-01

    Background The treatment of unstable intertrochanteric fractures in elderly is still controversial. The purpose of this study is to present treatment strategies for unstable intertrochanteric fractures with hemiarthroplasty using standard uncemented collared femoral stems and at the same time preserving the fractured calcar fragment. Methods Fifty-four patients aged 75 years or older with unstable intertrochanteric fractures were included in this prospective cohort study. All patients were treated with calcar preserving hemiarthroplasty using cementless collored femoral stems. Fractured calcar fragment was stabilized either by compaction between the implant and femur or fixed with cable grip system. Follow-up evaluations were performed at least 24 months and later. Palmer and Parker mobility score and visual analogue scale (VAS) pain score were assessed. We also analyzed radiographs of the operated hip at each follow-up visit. Results The patients were 15 males and 39 females with a mean age of 81.3 years (range, 75 to 93 years). The average operative time was 86.6 minutes. The mean transfused blood units were 1.2 units. The average duration of hospital stay was 5.3 days. The preoperative mean mobility score was 6.20. This score was found to be 4.96 on postoperative third day and 5.90 at 24 months postoperatively. The results of the statistical analysis revealed significant increase in the mobility scores at each follow-up after three days. Radiological interpretation revealed no loosening in the cable-grip systems, and no significant subsidence (> 5 mm) of prosthesis was observed. Conclusions Calcar preservation arthroplasty is a good option for elderly patients with severe osteoporosis, frail constitution and the patients who are at higher risk for second operation due to unstable intertrochanteric fractures. PMID:26640625

  18. Fluorination utilizing thermodynamically unstable fluorides and fluoride salts thereof

    DOEpatents

    Bartlett, Neil; Whalen, J. Marc; Chacon, Lisa

    2000-12-12

    A method for fluorinating a carbon compound or cationic carbon compound utilizes a fluorination agent selected from thermodynamically unstable nickel fluorides and salts thereof in liquid anhydrous hydrogen fluoride. The desired carbon compound or cationic organic compound to undergo fluorination is selected and reacted with the fluorination agent by contacting the selected organic or cationic organic compound and the chosen fluorination agent in a reaction vessel for a desired reaction time period at room temperature or less.

  19. Inherently unstable networks collapse to a critical point.

    PubMed

    Sheinman, M; Sharma, A; Alvarado, J; Koenderink, G H; MacKintosh, F C

    2015-07-01

    Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.

  20. A fundamental study of liquid phase particle breakup. Revision

    NASA Astrophysics Data System (ADS)

    1984-12-01

    Combustion efficiency of aluminized propellants in solid rocket motors is reduced by incomplete aluminum combustion and two-phase nozzle flow losses. Combustion of these propellants can produce large Al/Al2O3 agglomerates. As a direct result of agglomerate breakup, the aluminum combustion rate is increased, and the thermal energy released is more efficiently transferred into exhaust kinetic energy. This research sought to obtain physical data to characterize the mechanisms of aerodynamic droplet breakup. Experiments have been completed in which conventional liquids and a liquid metal (mercury) was studied. The primary goal of the conventional liquid experiments was to examine the effect of liquid properties (viscosity and surface tension) on the breakup mechanism, time scale, and fragment size distribution. The goal of the mercury experiments was to examine the effect of the much higher surface tension more characteristic of liquid aluminum. A key element of the experimental effort is the use of nonintrusive laser diagnostics including pulsed laser holography (PLH) and laser Doppler velocimetry (LDV). The exceptional temporal and spatial resolution of PLH provided the ability to resolve the mechanism of breakup and the size distribution of the fragments. LDV was used to determine drop velocity distributions along the nozzle revealing the rapid acceleration of the flattened droplets and then, surprisingly, the milder acceleration of the fragments.

  1. Adaptive control of unknown unstable steady states of dynamical systems.

    PubMed

    Pyragas, K; Pyragas, V; Kiss, I Z; Hudson, J L

    2004-08-01

    A simple adaptive controller based on a low-pass filter to stabilize unstable steady states of dynamical systems is considered. The controller is reference-free; it does not require knowledge of the location of the fixed point in the phase space. A topological limitation similar to that of the delayed feedback controller is discussed. We show that the saddle-type steady states cannot be stabilized by using the conventional low-pass filter. The limitation can be overcome by using an unstable low-pass filter. The use of the controller is demonstrated for several physical models, including the pendulum driven by a constant torque, the Lorenz system, and an electrochemical oscillator. Linear and nonlinear analyses of the models are performed and the problem of the basins of attraction of the stabilized steady states is discussed. The robustness of the controller is demonstrated in experiments and numerical simulations with an electrochemical oscillator, the dissolution of nickel in sulfuric acid; a comparison of the effect of using direct and indirect variables in the control is made. With the use of the controller, all unstable phase-space objects are successfully reconstructed experimentally.

  2. Metastability in plyometric training on unstable surfaces: a pilot study

    PubMed Central

    2014-01-01

    Background In the past, plyometric training (PT) has been predominantly performed on stable surfaces. The purpose of this pilot study was to examine effects of a 7-week lower body PT on stable vs. unstable surfaces. This type of exercise condition may be denoted as metastable equilibrium. Methods Thirty-three physically active male sport science students (age: 24.1 ± 3.8 years) were randomly assigned to a PT group (n = 13) exercising on stable (STAB) and a PT group (n = 20) on unstable surfaces (INST). Both groups trained countermovement jumps, drop jumps, and practiced a hurdle jump course. In addition, high bar squats were performed. Physical fitness tests on stable surfaces (hexagonal obstacle test, countermovement jump, hurdle drop jump, left-right hop, dynamic and static balance tests, and leg extension strength) were used to examine the training effects. Results Significant main effects of time (ANOVA) were found for the countermovement jump, hurdle drop jump, hexagonal test, dynamic balance, and leg extension strength. A significant interaction of time and training mode was detected for the countermovement jump in favor of the INST group. No significant improvements were evident for either group in the left-right hop and in the static balance test. Conclusions These results show that lower body PT on unstable surfaces is a safe and efficient way to improve physical performance on stable surfaces. PMID:25089202

  3. Self-aggregation of clouds in conditionally unstable moist convection.

    PubMed

    Pauluis, Olivier; Schumacher, Jörg

    2011-08-02

    The behavior of moist Rayleigh-Bénard convection is investigated using a Boussinesq model with a simplified thermodynamics for phase transitions. This idealized configuration makes the problem accessible to high-resolution three-dimensional direct numerical simulations without small-scale parameterizations of the turbulence for extended layers with aspect ratios up to 64. Our study is focused on the frequently observed conditionally unstable environment that is stably stratified for unsaturated air, but is unstable for cloudy air. We find that no sharp threshold for the transition to convective turbulence exists, a situation similar to wall-bounded shear flows. Rather, the transition depends on the amplitude of the initial perturbation of the quiescent equilibrium and on the aspect ratio of the convective domain. In contrast to the classical dry Rayleigh-Bénard case, convection is highly asymmetric with respect to the vertical direction. Moist upwelling air inside turbulent cloud aggregates is surrounded by ambient regions of slowly descending unsaturated air. It is also found that conditionally unstable moist convection is inefficient at transporting energy. Our study suggests that there is an upper bound on the Nusselt number in moist convection that is lower than that of the classical dry case.

  4. Momentum broadening in unstable quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Carrington, M. E.; Mrówczyński, St.; Schenke, B.

    2017-02-01

    Quark-gluon plasma produced at the early stage of ultrarelativistic heavy-ion collisions is unstable, if weakly coupled, due to the anisotropy of its momentum distribution. Chromomagnetic fields are spontaneously generated and can reach magnitudes much exceeding typical values of the fields in equilibrated plasma. We consider a high-energy test parton traversing an unstable plasma that is populated with strong fields. We study the momentum broadening parameter q ̂ which determines the radiative energy loss of the test parton. We develop a formalism which gives q ̂ as the solution of an initial value problem, and we focus on extremely oblate plasmas which are physically relevant for relativistic heavy-ion collisions. The parameter q ̂ is found to be strongly dependent on time. For short times it is of the order of the equilibrium value, but at later times q ̂ grows exponentially due to the interaction of the test parton with unstable modes and becomes much bigger than the value in equilibrium. The momentum broadening is also strongly directionally dependent and is largest when the test parton velocity is transverse to the beam axis. Consequences of our findings for the phenomenology of jet quenching in relativistic heavy-ion collisions are briefly discussed.

  5. Unstable periodic orbits and noise in chaos computing.

    PubMed

    Kia, Behnam; Dari, Anna; Ditto, William L; Spano, Mark L

    2011-12-01

    Different methods to utilize the rich library of patterns and behaviors of a chaotic system have been proposed for doing computation or communication. Since a chaotic system is intrinsically unstable and its nearby orbits diverge exponentially from each other, special attention needs to be paid to the robustness against noise of chaos-based approaches to computation. In this paper unstable periodic orbits, which form the skeleton of any chaotic system, are employed to build a model for the chaotic system to measure the sensitivity of each orbit to noise, and to select the orbits whose symbolic representations are relatively robust against the existence of noise. Furthermore, since unstable periodic orbits are extractable from time series, periodic orbit-based models can be extracted from time series too. Chaos computing can be and has been implemented on different platforms, including biological systems. In biology noise is always present; as a result having a clear model for the effects of noise on any given biological implementation has profound importance. Also, since in biology it is hard to obtain exact dynamical equations of the system under study, the time series techniques we introduce here are of critical importance.

  6. Treatment of unstable fractures of the pelvic ring in pregnancy.

    PubMed

    Loegters, Tim; Briem, Daniel; Gatzka, Christian; Linhart, Wolfgang; Begemann, Phillip G; Rueger, Johannes M; Windolf, Joachim

    2005-04-01

    Unstable fractures of the posterior pelvic ring during pregnancy are rare. Pregnancy increases the high demands on the therapy of these types of fractures. The aim of the therapeutic strategy in such a situation is a good functional outcome of the mother without influencing the fetal health. Some osteosynthetic techniques result in good functional outcomes, but they are associated with high amounts of ionizing radiation. We report the case of a pregnant woman who sustained a vertical unstable fracture of the posterior pelvic ring as a result of a traffic accident. The fracture was treated surgically by open reduction and internal fixation with two transiliac reconstruction plates with minimal radiographic exposure to the fetus. One year later, a good functional result concerning the mother was shown. The child was healthy without any signs of prenatal impairment. Surgical treatment of an unstable fracture of the pelvic ring during pregnancy is possible with a justifiable risk to the mother and the child. Consideration of the expected fetal radiation exposure in the course of the therapy is particularly recommended. Using minimal doses of ionizing radiation, the described method results in a good clinical outcome of the mother while simultaneously reducing the radiation exposure of the fetus to an acceptable level.

  7. Investigation of the unstable flow phenomenon in a pump turbine

    NASA Astrophysics Data System (ADS)

    Yin, JunLian; Wang, DeZhong; Walters, D. Keith; Wei, XianZhu

    2014-06-01

    Instability of pump turbine with S-shaped curve is characterized by large fluctuations of rotational speed during the transient processes. For investigating this phenomenon, a numerical model based on the dynamic sliding mesh method (DSSM) is presented and used to numerically solve the 3D transient flow which is characterized by the variable rotation speed of runner. The method is validated by comparison with measured data for a load rejection process in a prototype pump turbine. The results show that the calculated rotation speed agrees well with the experimental data. Based on the validated model, simulations were performed for the runaway process using an artificially assumed operating condition under which the unstable rotation speed is expected to appear. The results confirm that the instability of runner rotational speed can be effectively captured with the proposed method. Presented results include the time history profiles of unit flow rate and unit rotating speed. The internal flow characteristics in a typical unstable period are discussed in detail and the mechanism of the unstable hydraulic phenomenon is explained. Overall, the results suggest that the method presented here can be a viable alternative to predict the dynamic characteristics of pump turbines during transient processes.

  8. Soft-Sphere Packings at Finite Pressure but Unstable to Shear

    NASA Astrophysics Data System (ADS)

    Dagois-Bohy, Simon; Tighe, Brian P.; Simon, Johannes; Henkes, Silke; van Hecke, Martin

    2012-08-01

    When are athermal soft-sphere packings jammed? Any experimentally relevant definition must, at the very least, require a jammed packing to resist shear. We demonstrate that widely used (numerical) protocols, in which particles are compressed together, can and do produce packings that are unstable to shear—and that the probability of generating such packings reaches one near jamming. We introduce a new protocol which, by allowing the system to explore different box shapes as it equilibrates, generates truly jammed packings with strictly positive shear moduli G. For these packings, the scaling of the average of G is consistent with earlier results, while the probability distribution P(G) exhibits novel and rich scalings.

  9. Particles, Quarks, Leptons and Coloured Glue.

    ERIC Educational Resources Information Center

    Ryder, Lewis

    1980-01-01

    Explains the current situation in particle physics by reviewing the three major periods in the development of atomic theory. Outlines the current picture of fundamental particles and identifies five major problems with this model. (GS)

  10. Reactive Ion Etched Unstable and Stable Semiconductor Lasers

    NASA Astrophysics Data System (ADS)

    Biellak, Stephen Alexander

    1995-01-01

    High power, diffraction-limited semiconductor laser diodes are desirable for numerous applications such as efficient solid state laser pumping, nonlinear frequency conversion, and free-space communication. In the past several years, wide-stripe diode lasers and laser arrays with powers of up to several watts have become commercially available, but the beam quality of these devices is generally poor due to filamentation, a nonlinear material effect that aberrates the output beam profile. An attractive alternative to these simple Fabry-Perot lasers is offered by unstable resonators, which have inherently large gain volumes and a cavity geometry that inhibits filamentation. Prototype unstable resonators with dry-etched cavity mirrors have recently been demonstrated to achieve near diffraction -limited operation at moderately high output powers. However, the lateral mode properties of unstable resonators have heretofore not been examined in detail, nor has a reliable, high-throughput mirror etch process been developed for these devices. In this work, we have developed a GaAs RIE etching technique using common process equipment that yields mirrors with RMS surface roughness of 3 to 5 nm. We have fabricated unstable resonators and have measured lateral M ^2 beam quality values as low as 1.25 at 300 mW single facet output power in high magnification devices. The impact of cavity geometry and processing techniques on device performance was studied, and the optimal parameters for high-brightness applications were determined. Nearly concentric stable-resonator diode lasers were also fabricated for the first time using this etching technique. These stable-resonators were observed to operate in lateral modes determined primarily by the physical resonator structure up to several times threshold, after which nonlinear effects dominated the cavity modes. Based on these measurements, a description of stable device behavior in terms of gain saturation was developed. Finally, a

  11. Outcomes of Short Segment Posterior Instrumentation in Unstable Thoracolumbar Fractures

    PubMed Central

    Gajjar, Sharvil H; Chaudhari, Nitin; Chaudhari, Vipul

    2016-01-01

    Introduction The spinal traumas are common and leading problem in orthopaedics practice. The individuals are at a risk of high energy trauma in modern era. Unstable thoracolumbar burst fractures are serious injuries of concern, if left untreated may result in marked morbidity and disability to the patient. Thoracolumbar is the second most common segment involved in the spinal cord following spinal injuries followed by cervical segment. The goal of treatment of any spinal injury is restoration of the patient to maximum possible function with disability free life. Aim To analyse the outcomes of unstable thoracolumbar burst fractures stabilized with short segment posterior instrumentation with transpedicular screws. Materials and Methods This prospective interventional study consisted of 32 patients with unstable thoracolumbar burst fractures carried out at Department of Orthopaedics, New Civil Hospital, Surat during Jan 2014 to Dec 2015. We stabilized the patients with unstable thoracolumbar spinal fractures with short segment posterior instrumentation by using the intermediate screw option in the fractured vertebra level as a method of augmentation. Patients were evaluated for maintenance of spinal correction and neurological improvement after short segment posterior instrumentation in unstable thoracolumbar burst fractures. Results The mean age for males was 35.57 ± 11.62 years and for females was 33.56 ± 11.2 years. The most common vertebra involved in the study group was T12 (31.25%). In the study, about 66% patients had a fall from height as the mode of injury, whereas 34% injuries were due to road traffic accident. In the study group, the mean regional angle observed during pre-operative stages was 16.0°±5.1°. There was a statistically significant (p<0.05) difference between pre-op and post-operative regional angles as well as anterior wedge angles. There was a statistically significant difference (p<0.05) in the vertebral height between pre-operative and

  12. Planetesimal Formation in Zonal Flows Arising in Magneto-Rotationally-Unstable Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Dittrich, Karsten; Klahr, Hubert; Johansen, Anders

    2014-04-01

    Recent simulations show long -lived sub- and super-Keplerian flows in protoplanetary disks. These so-called zonal flows are found in local as well as global simulations of magneto-rotationally unstable disks. We investigate the strength and life-time of the resulting long-lived gas over- and under-densities as well as particle concentrations function of the azimuthal and radial size of the local shearing box. Changes in the azimuthal extent do not affect the zonal flow features. However, strength and life-time of zonal flows increase with increasing radial box sizes. Our simulations show indications, and support earlier results, that zonal flows have a natural length scale of approximately 5 pressure scale heights. For the first time, the reaction of dust particles in boxes with zonal flows are studied. We show that particles of some centimeters in size reach a hundred-fold higher density than initially, without any self-gravitating forces acting on the point masses. We further investigate collision velocities of dust grains in a turbulent medium.

  13. Ablative Thermal Protection System Fundamentals

    NASA Technical Reports Server (NTRS)

    Beck, Robin A. S.

    2013-01-01

    This is the presentation for a short course on the fundamentals of ablative thermal protection systems. It covers the definition of ablation, description of ablative materials, how they work, how to analyze them and how to model them.

  14. Atom Interferometry for Fundamental Physics and Gravity Measurements in Space

    NASA Technical Reports Server (NTRS)

    Kohel, James M.

    2012-01-01

    Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.

  15. Unstable Roche-Lobe Overflow of Gaseous Planets

    NASA Astrophysics Data System (ADS)

    Jackson, Brian

    The discoveries of more than 100 roughly Earth-sized bodies with orbital periods less than 1 day, ultra-short-period planets or candidates (USPs), have challenged planet formation theories, and evidence suggests USPs may be the remnants of gaseous planets that shed their atmospheres. Indeed, many hot Jupiters are near Roche-Lobe overflow (RLO), and tidal decay can push them the rest of the way in. Recent work has shown stable RLO (atmospheres lost via a steady outflow and thin accretion disk) probably cannot produce USPs on its own but suggested unstable RLO (atmospheres quickly shed on dynamical timescales) may. In fact, stable RLO may drive overflowing hot Jupiters into unstable RLO, and by analogy with the common-envelope binaries, the core that remains can drive off the gaseous envelope at the cost of its orbital energy. Wellestablished mass-radius relations for gaseous planets, coupled to simple energy and angular momentum considerations, provide a connection between the observed masses and periods for USPs and their putative progenitor gaseous planets, with few free parameters. We propose to investigate the hypothesis that USPs originate through tidal decay and a combination of stable and unstable Roche-lobe overflow of short-period gaseous planets through the following studies: -We will explore the planetary masses, orbital periods, etc. that produce unstable RLO using the Modules for Experiments in Stellar Astrophysics (MESA) suite. -We will relate the observed periods and masses of USPs to their putative progenitor masses and periods to see whether they are consistent with the unstable RLO hypothesis. This proposal is directly relevant to the Exoplanets Research Program since it seeks to "understand the ... physical processes of exoplanets" and "improve understanding of [their] origins" through "theoretical studies ... and modeling'". We also expect that it will have broad impacts on a variety of astrophysical topics: -Ultra-short period planets could

  16. Unstable Distal Radius Fractures Treated by Volar Locking Anatomical Plates

    PubMed Central

    Jose, Anto; Deniese, Pascal Noel; Babu, Abey Thomas; Rengasamy, Kanagasabai; Najimudeen, Syed

    2017-01-01

    Introduction Fracture of the distal end of radius represents the most common fracture of the upper extremity accounting for 16-20% of all fractures. Plating is now emerging as the gold standard for management of distal radius fractures due to increased rate of complications such as malunion, subluxation/dislocation of distal radio-ulnar joint or late collapse of fracture. Procedures such as closed reduction and cast immobilization, ligamentotaxis with external fixator and percutaneous pin fixation are no longer acceptable. Aim The purpose of the study was to evaluate the functional and radiological outcome of unstable distal radius fractures treated with the volar locking plate. Materials and Methods We reviewed 53 patients from January 2011 to December 2015, treated for unstable distal radius fractures using a volar locking compression plate. Standard radiographic and clinical assessment after 12 months (range 12-16 months) were measured and final functional and radiological outcome were assessed using the Modified Mayo wrist scoring system and Sarmiento’s modification of Lindstorm criteria respectively. Results There were 42 males and 11 females with an average age of 39.12±31.78 years (18-71 years). At the end of 12 months, 36 patients had an excellent radiological outcome and 10 patients had good radiological outcome as per Sarmiento’s modification of Lindstorm criteria. Eleven patients had an excellent functional outcome and 26 patients had a good functional outcome as per modified Mayo wrist scoring system. There was one case of superficial wound infection which subsided with intravenous antibiotics. Conclusion The volar locking plate fixation helps in early mobilization of the wrist, restores anatomy, allows early return to function, prevents secondary loss of reduction and hence is an effective treatment for unstable fractures of the distal radius. PMID:28274009

  17. Strategy Switching in the Stabilization of Unstable Dynamics

    PubMed Central

    Zenzeri, Jacopo; De Santis, Dalia; Morasso, Pietro

    2014-01-01

    In order to understand mechanisms of strategy switching in the stabilization of unstable dynamics, this work investigates how human subjects learn to become skilled users of an underactuated bimanual tool in an unstable environment. The tool, which consists of a mass and two hand-held non-linear springs, is affected by a saddle-like force-field. The non-linearity of the springs allows the users to determine size and orientation of the tool stiffness ellipse, by using different patterns of bimanual coordination: minimal stiffness occurs when the two spring terminals are aligned and stiffness size grows by stretching them apart. Tool parameters were set such that minimal stiffness is insufficient to provide stable equilibrium whereas asymptotic stability can be achieved with sufficient stretching, although at the expense of greater effort. As a consequence, tool users have two possible strategies for stabilizing the mass in different regions of the workspace: 1) high stiffness feedforward strategy, aiming at asymptotic stability and 2) low stiffness positional feedback strategy aiming at bounded stability. The tool was simulated by a bimanual haptic robot with direct torque control of the motors. In a previous study we analyzed the behavior of naïve users and we found that they spontaneously clustered into two groups of approximately equal size. In this study we trained subjects to become expert users of both strategies in a discrete reaching task. Then we tested generalization capabilities and mechanism of strategy-switching by means of stabilization tasks which consist of tracking moving targets in the workspace. The uniqueness of the experimental setup is that it addresses the general problem of strategy-switching in an unstable environment, suggesting that complex behaviors cannot be explained in terms of a global optimization criterion but rather require the ability to switch between different sub-optimal mechanisms. PMID:24921254

  18. A novel approach to modeling unstable EOR displacements

    SciTech Connect

    Peters, E.J.

    1991-01-01

    This research is aimed at developing a methodology for predicting the performance of unstable displacements in heterogeneous porous media. A performance prediction approach that integrates numerical modeling with laboratory experiments will be developed. Flow visualization experiments will be performed on laboratory corefloods using X-ray computed tomography (CT) and other imaging technologies to map the in situ fluid saturations in time and space. A systematic procedure will be developed to replicate the experimental image data with high-resolution numerical models of the displacements. 2 refs., 3 figs., 1 tab.

  19. Stabilizing unstable steady states using multiple delay feedback control.

    PubMed

    Ahlborn, Alexander; Parlitz, Ulrich

    2004-12-31

    Feedback control with different and independent delay times is introduced and shown to be an efficient method for stabilizing fixed points (equilibria) of dynamical systems. In comparison to other delay based chaos control methods multiple delay feedback control is superior for controlling steady states and works also for relatively large delay times (sometimes unavoidable in experiments due to system dead times). To demonstrate this approach for stabilizing unstable fixed points we present numerical simulations of Chua's circuit and a successful experimental application for stabilizing a chaotic frequency doubled Nd-doped yttrium aluminum garnet laser.

  20. Unstable evolution of pointwise trajectory solutions to chaotic maps.

    PubMed

    Fox, Ronald F.

    1995-12-01

    Simple chaotic maps are used to illustrate the inherent instability of trajectory solutions to the Frobenius-Perron equation. This is demonstrated by the difference in the behavior of delta-function solutions and of extended densities. Extended densities evolve asymptotically and irreversibly into invariant measures on stationary attractors. Pointwise trajectories chaotically roam over these attractors forever. Periodic Gaussian distributions on the unit interval are used to provide insight. Viewing evolving densities as ensembles of unstable pointwise trajectories gives densities a stochastic interpretation. (c) 1995 American Institute of Physics.

  1. Photoneutron cross sections for unstable neutron-rich oxygen isotopes.

    PubMed

    Leistenschneider, A; Aumann, T; Boretzky, K; Cortina, D; Cub, J; Datta Pramanik, U; Dostal, W; Elze, T W; Emling, H; Geissel, H; Grünschloss, A; Hellstr, M; Holzmann, R; Ilievski, S; Iwasa, N; Kaspar, M; Kleinböhl, A; Kratz, J V; Kulessa, R; Leifels, Y; Lubkiewicz, E; Münzenberg, G; Reiter, P; Rejmund, M; Scheidenberger, C; Schlegel, C; Simon, H; Stroth, J; Sümmerer, K; Wajda, E; Walús, W; Wan, S

    2001-06-11

    The dipole response of stable and unstable neutron-rich oxygen nuclei of masses A = 17 to A = 22 has been investigated experimentally utilizing electromagnetic excitation in heavy-ion collisions at beam energies about 600 MeV/nucleon. A kinematically complete measurement of the neutron decay channel in inelastic scattering of the secondary beam projectiles from a Pb target was performed. Differential electromagnetic excitation cross sections d sigma/dE were derived up to 30 MeV excitation energy. In contrast to stable nuclei, the deduced dipole strength distribution appears to be strongly fragmented and systematically exhibits a considerable fraction of low-lying strength.

  2. Quantum field theory of classically unstable Hamiltonian dynamics

    SciTech Connect

    Strauss, Y.; Horwitz, L. P.; Levitan, J.; Yahalom, A.

    2015-07-15

    We study a class of dynamical systems for which the motions can be described in terms of geodesics on a manifold (ordinary potential models can be cast into this form by means of a conformal map). It is rigorously proven that the geodesic deviation equation of Jacobi, constructed with a second covariant derivative, is unitarily equivalent to that of a parametric harmonic oscillator, and we study the second quantization of this oscillator. The excitations of the Fock space modes correspond to the emission and absorption of quanta into the dynamical medium, thus associating unstable behavior of the dynamical system with calculable fluctuations in an ensemble with possible thermodynamic consequences.

  3. Stable/unstable slow integral manifolds in critical cases

    NASA Astrophysics Data System (ADS)

    Shchepakina, Elena

    2017-02-01

    The paper deals with the problem of a construction of global stable/unstable slow integral manifolds of the singularly perturbed systems in critical cases. In addition to the well-known critical cases a novel scenario of the stability change of the slow integral manifold is considered. All three critical cases leading to the change of the stability are discussed via the Hindmarsh-Rose dynamic model. It is shown that the suitable choice of the additional parameters of the system yields the slow integral manifold with multiple change of its stability.

  4. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    DOE PAGES

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  5. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    SciTech Connect

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  6. Elementary Particles and Forces.

    ERIC Educational Resources Information Center

    Quigg, Chris

    1985-01-01

    Discusses subatomic particles (quarks, leptons, and others) revealed by higher accelerator energies. A connection between forces at this subatomic level has been established, and prospects are good for a description of forces that encompass binding atomic nuclei. Colors, fundamental interactions, screening, camouflage, electroweak symmetry, and…

  7. Nucleosome Core Particle

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Nucleosome Core Particle grown on STS-81. The fundamental structural unit of chromatin and is the basis for organization within the genome by compaction of DNA within the nucleus of the cell and by making selected regions of chromosomes available for transcription and replication. Principal Investigator's are Dr. Dan Carter and Dr. Gerard Bunick of New Century Pharmaceuticals.

  8. Astrophysical probes of fundamental physics

    NASA Astrophysics Data System (ADS)

    Martins, C. J. A. P.

    2009-10-01

    I review the motivation for varying fundamental couplings and discuss how these measurements can be used to constrain fundamental physics scenarios that would otherwise be inaccessible to experiment. I highlight the current controversial evidence for varying couplings and present some new results. Finally I focus on the relation between varying couplings and dark energy, and explain how varying coupling measurements might be used to probe the nature of dark energy, with some advantages over standard methods. In particular I discuss what can be achieved with future spectrographs such as ESPRESSO and CODEX.

  9. Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media

    SciTech Connect

    Franciscis, S. de; Torres, J. J.; Marro, J.

    2010-10-15

    Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a ''critical state'' during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.

  10. Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media.

    PubMed

    de Franciscis, S; Torres, J J; Marro, J

    2010-10-01

    Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a "critical state" during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.

  11. Are There Unstable Planetary Systems around White Dwarfs?

    NASA Astrophysics Data System (ADS)

    Debes, John H.; Sigurdsson, Steinn

    2002-06-01

    The presence of planets around solar-type stars suggests that many white dwarfs should have relic planetary systems. While planets closer than ~5 AU will most likely not survive the post-main-sequence lifetime of their parent star, any planet with semimajor axis greater than 5 AU will survive, and its semimajor axis will increase as the central star loses mass. Since the stability of adjacent orbits to mutual planet-planet perturbations depends on the ratio of the planet mass to the central star's mass, some planets in previously stable orbits around a star undergoing mass loss will become unstable. We show that when mass loss is slow, systems of two planets that are marginally stable can become unstable to close encounters, while for three planets the timescale for close approaches decreases significantly with increasing mass ratio. These processes could explain the presence of anomalous IR excesses around white dwarfs that cannot be explained by close companions, such as G29-38, and may also be an important factor in explaining the existence of DAZ white dwarfs. The onset of instability through changing mass ratios will also be a significant effect for planetary embryos gaining mass in protoplanetary disks.

  12. Finding and Scaling Unstable Periodic Orbits in Biological Systems

    NASA Astrophysics Data System (ADS)

    Moss, Frank

    1998-03-01

    Unstable periodic orbits (UPOs) of low order can be detected in noisy physical(D. Pierson and F. Moss, Phys. Rev. Lett.) 75, 2124 (1995)and biological(X. Pei and F. Moss, Nature) 379, 618 (1996) systems. The statistically based detection method extracts the number of encounters with UPOs of period p, and compares that with findings from surrogate files. UPOs can be distinguished from stable orbits. The results are expressed as a time evolving statistical measure, useful for analyzing short files from non-stationary systems. We show bifurcations between stable and unstable behavior in peripheral cold receptors, neurosecretory hypothalamic cells (both in rat) and electroreceptors in catfish(H.A. Braun, et al., J. Comp. Neurosci.), in press. Since only orbits of the lowest orders (p < 4) can be detected, a scaling is necessary to connect the experimentally observable orbits to the infinite set of UPOs which characterize dissipative chaos. A scaling due to C.-Y. Lai is calculated for the Henon map. Data from crayfish photoreceptor cells for p = 1 to 3 are consistent with this scaling.

  13. Identifying Unstable Regions of Proteins Involved in Misfolding Diseases

    NASA Astrophysics Data System (ADS)

    Guest, Will; Cashman, Neil; Plotkin, Steven

    2009-05-01

    Protein misfolding is a necessary step in the pathogenesis of many diseases, including Creutzfeldt-Jakob disease (CJD) and familial amyotrophic lateral sclerosis (fALS). Identifying unstable structural elements in their causative proteins elucidates the early events of misfolding and presents targets for inhibition of the disease process. An algorithm was developed to calculate the Gibbs free energy of unfolding for all sequence-contiguous regions of a protein using three methods to parameterize energy changes: a modified G=o model, changes in solvent-accessible surface area, and all-atoms molecular dynamics. The entropic effects of disulfide bonds and post-translational modifications are treated analytically. It incorporates a novel method for finding local dielectric constants inside a protein to accurately handle charge effects. We have predicted the unstable parts of prion protein and superoxide dismutase 1, the proteins involved in CJD and fALS respectively, and have used these regions as epitopes to prepare antibodies that are specific to the misfolded conformation and show promise as therapeutic agents.

  14. A Mouse Model for Human Unstable Hemoglobin Santa Ana.

    PubMed

    Miyashiro, Samantha I; Massironi, Silvia M G; Mori, Claudia M C; Cruz, Carolina C; Hagiwara, Mitika K; Maiorka, Paulo C

    2016-12-01

    In the present study, we described the phenotype, histologic morphology, and molecular etiology of a mouse model of unstable hemoglobin Santa Ana. Hematologic evaluation of anemic mice (Anem/+) discovered after N-ethyl-N-nitrosourea mutagenesis revealed moderate anemia with intense reticulocytosis and polychromasia, followed by anisocytosis, macrocytosis, hypochromia, and intraerythrocytic inclusion and Heinz bodies. The mice also demonstrated hemoglobinuria, bilirubinemia, and erythrocytic populations with differing resistance to osmotic lysis. Splenomegaly (particularly in older mutant mice) and jaundice were apparent at necropsy. Histopathologic examination revealed dramatically increased hematopoiesis and hemosiderosis in hematopoietic organs and intracellular iron deposition in tubular renal cells. These data are characteristic of a congenital hemolytic regenerative anemia, similar to human anemias due to unstable hemoglobin. Genetic mapping assigned the affected gene to mouse chromosome 7, approximately 50 cM from the Hbb locus. The sequence of the mutant Hbb gene exhibited a T→C transversion at nucleotide 179 in Hbb-b1, leading to the substitution of proline for leucine at amino acid residue 88 and thus homologous to the genetic defect underlying Santa Ana anemia in humans.

  15. Unstable Behavior of Anodic Arc Discharge for Synthesis of Nanomaterials

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia; Raitses, Yevgeny

    2016-09-01

    Fast imaging and electrical current measurements reveal unstable behavior of the carbon arc discharge for synthesis of nanomaterials. The arc column and the arc attachment region to the anode move in a somewhat sporadic way with a characteristic time in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. A physical mechanism is proposed based on the thermal processes in the arc plasma region interacting with the ablating anode which leads to the shift of the arc to a new anode region. According to the transient heat transfer analysis, the time needed to heat a new anode region is also in a 10-3 sec range. For a 0.6 cm diameter anode used in our experiments, this time yields a frequency of about 200-300 Hz, comparable to the measured frequency of the arc motion. The voltage and current measurements show oscillations with a similar characteristic frequency. The thermal model is indirectly supported by the measured negative differential resistance of the arc discharge during arc oscillations. The observed unstable behavior of the arc may be responsible for the mixing of the flow of nanoparticles during the synthesis of nanoparticles leading to poor selectivity typical for the arc synthesis. The work was supported by US DOE under Contract No. DE-AC02-09CH11466.

  16. Excess quantum noise fluctuations in unstable-resonator lasers

    NASA Astrophysics Data System (ADS)

    Cheng, Yuh-Jen; Mussche, Paul; Fanning, Geoff; Siegman, A. E.

    1996-12-01

    Experiments completed during the past year confirm the existence of a sizable excess quantum noise factor in lasers using unstable optical resonators or, more generally, resonators with nonorthogonal oscillation modes. Schawlow and Townes predicted in 1958, before the first laser was built, that even an ideal laser should exhibit a finite linewidth resulting from spontaneous emission by the laser atoms.1 Lamb and others, using standard techniques of cavity mode expansion and second quantization, then showed that the spontaneous emission in any laser should have a magnitude equal to the downward stimulated emission due to one additional quantum of signal energy acting on the inverted laser medium.2 This "one extra noise photon" approach to quantum noise has since become conventional wisdom in the field. Petermann noted in 1979, however, that spontaneous emission into the oscillating mode of a gain-guided semiconductor laser could be significantly larger than one photon per mode, leading to potentially measurable consequences for such lasers.3 In 1985, Haus and Kawakami showed that there would be partial coherence between the excess noise emission into different cavity modes, thus avoiding apparent conflicts between this excess emission and basic concepts of thermal equilibrium.4 One of us then showed in 1989 that this excess quantum noise was actually associated with the nonhermitian or biorthogonal character of the modes in certain laser structures rather than with gain guiding per se, so that large excess quantum noise effects should be observed in unstable resonator lasers in particular.5

  17. Designing capture trajectories to unstable periodic orbits around Europa

    NASA Technical Reports Server (NTRS)

    Russell, Ryan P.; Lam, Try

    2006-01-01

    The hostile environment of third body perturbations restricts a mission designer's ability to find well-behaved reproducible capture trajectories when dealing with limited control authority as is typical with low-thrust missions. The approach outlined in this paper confronts this shortcoming by utilizing dynamical systems theory and an extensive preexisting database of Restricted Three Body Problem (RTBP) periodic orbits. The stable manifolds of unstable periodic orbits are utilized to attract a spacecraft towards Europa. By selecting an appropriate periodic orbit, a mission designer can control important characteristics of the captured state including stability, minimum altitudes, characteristic inclinations, and characteristic radii among others. Several free parameters are optimized in the non-trivial mapping from the RTBP to a more realistic model. Although the ephemeris capture orbit is ballistic by design, low-thrust is used to target the state that leads to the capture orbit, control the spacecraft after arriving on the unstable quasi-periodic orbit, and begin the spiral down towards the science orbit. The approach allows a mission designer to directly target fuel efficient captures at Europa in an ephemeris model. Furthermore, it provides structure and controllability to the design of capture trajectories that reside in a chaotic environment.

  18. Brake Fundamentals. Automotive Articulation Project.

    ERIC Educational Resources Information Center

    Cunningham, Larry; And Others

    Designed for secondary and postsecondary auto mechanics programs, this curriculum guide contains learning exercises in seven areas: (1) brake fundamentals; (2) brake lines, fluid, and hoses; (3) drum brakes; (4) disc brake system and service; (5) master cylinder, power boost, and control valves; (6) parking brakes; and (7) trouble shooting. Each…

  19. Environmental Law: Fundamentals for Schools.

    ERIC Educational Resources Information Center

    Day, David R.

    This booklet outlines the environmental problems most likely to arise in schools. An overview provides a fundamental analysis of environmental issues rather than comprehensive analysis and advice. The text examines the concerns that surround superfund cleanups, focusing on the legal framework, and furnishes some practical pointers, such as what to…

  20. Fundamentals of the Slide Library.

    ERIC Educational Resources Information Center

    Boerner, Susan Zee

    This paper is an introduction to the fundamentals of the art (including architecture) slide library, with some emphasis on basic procedures of the science slide library. Information in this paper is particularly relevant to the college, university, and museum slide library. Topics addressed include: (1) history of the slide library; (2) duties of…

  1. Fundamentals of Environmental Education. Report.

    ERIC Educational Resources Information Center

    1976

    An outline of fundamental definitions, relationships, and human responsibilities related to environment provides a basis from which a variety of materials, programs, and activities can be developed. The outline can be used in elementary, secondary, higher education, or adult education programs. The framework is based on principles of the science…

  2. Fundamentals of Welding. Teacher Edition.

    ERIC Educational Resources Information Center

    Fortney, Clarence; And Others

    These instructional materials assist teachers in improving instruction on the fundamentals of welding. The following introductory information is included: use of this publication; competency profile; instructional/task analysis; related academic and workplace skills list; tools, materials, and equipment list; and 27 references. Seven units of…

  3. Fundamentals of Microelectronics Processing (VLSI).

    ERIC Educational Resources Information Center

    Takoudis, Christos G.

    1987-01-01

    Describes a 15-week course in the fundamentals of microelectronics processing in chemical engineering, which emphasizes the use of very large scale integration (VLSI). Provides a listing of the topics covered in the course outline, along with a sample of some of the final projects done by students. (TW)

  4. FUNdamental Movement in Early Childhood.

    ERIC Educational Resources Information Center

    Campbell, Linley

    2001-01-01

    Noting that the development of fundamental movement skills is basic to children's motor development, this booklet provides a guide for early childhood educators in planning movement experiences for children between 4 and 8 years. The booklet introduces a wide variety of appropriate practices to promote movement skill acquisition and increased…

  5. The Fundamental Manifold of Spheroids

    NASA Astrophysics Data System (ADS)

    Zaritsky, Dennis; Gonzalez, Anthony H.; Zabludoff, Ann I.

    2006-02-01

    We present a unifying empirical description of the structural and kinematic properties of all spheroids embedded in dark matter halos. We find that the intracluster stellar spheroidal components of galaxy clusters, which we call cluster spheroids (CSphs) and which are typically 100 times the size of normal elliptical galaxies, lie on a ``fundamental plane'' as tight as that defined by elliptical galaxies (rms in effective radius of ~0.07) but having a different slope. The slope, as measured by the coefficient of the logσ term, declines significantly and systematically between the fundamental planes of ellipticals, brightest cluster galaxies (BCGs), and CSphs. We attribute this decline primarily to a continuous change in Me/Le, the mass-to-light ratio within the effective radius re, with spheroid scale. The magnitude of the slope change requires that it arise principally from differences in the relative distributions of luminous and dark matter, rather than from stellar population differences such as in age and metallicity. By expressing the Me/Le term as a function of σ in the simple derivation of the fundamental plane and requiring the behavior of that term to mimic the observed nonlinear relationship between logMe/Le and logσ, we simultaneously fit a two-dimensional manifold to the measured properties of dwarf elliptical and elliptical galaxies, BCGs, and CSphs. The combined data have an rms scatter in logre of 0.114 (0.099 for the combination of ellipticals, BCGs, and CSphs), which is modestly larger than each fundamental plane has alone, but which includes the scatter introduced by merging different studies done in different filters by different investigators. This ``fundamental manifold'' fits the structural and kinematic properties of spheroids that span a factor of 100 in σ and 1000 in re. While our mathematical form is neither unique nor derived from physical principles, the tightness of the fit leaves little room for improvement by other unification

  6. Unstable Pore-Water Flow in Intertidal Wetlands

    NASA Astrophysics Data System (ADS)

    Barry, D. A.; Shen, C.; Li, L.

    2014-12-01

    Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and

  7. Unstable dynamics and population limitation in mountain hares.

    PubMed

    Newey, Scott; Dahl, Fredrik; Willebrand, Tomas; Thirgood, Simon

    2007-11-01

    The regular large-scale population fluctuations that characterize many species of northern vertebrates have fascinated ecologists since the time of Charles Elton. There is still, however, no clear consensus on what drives these fluctuations. Throughout their circumpolar distribution, mountain hares Lepus timidus show regular and at times dramatic changes in density. There are distinct differences in the nature, amplitude and periodicity of these fluctuations between regions and the reasons for these population fluctuations and the geographic differences remain largely unknown. In this review we synthesize knowledge on the factors that limit or regulate mountain hare populations across their range in an attempt to identify the drivers of unstable dynamics. Current knowledge of mountain hare population dynamics indicates that trophic interactions--either predator-prey or host-parasite--appear to be the major factor limiting populations and these interactions may contribute to the observed unstable dynamics. There is correlative and experimental evidence that some mountain hare populations in Fennoscandia are limited by predation and that predation may link hare and grouse cycles to microtine cycles. Predation is unlikely to be important in mountain hare populations in Scotland as most hares occur on sporting estates where predators are controlled, but this hypothesis remains to be experimentally tested. There is, however, emerging experimental evidence that some Scottish mountain hare populations are limited by parasites and that host-parasite interactions contribute to unstable dynamics. By contrast, there is little evidence from Fennoscandia that parasitism is of any importance to mountain hare population dynamics, although disease may cause periodic declines. Although severe weather and food limitation may interact to cause periodic high winter mortality there is little evidence that food availability limits mountain hare populations. There is a paucity of

  8. Chiroptical signatures of life and fundamental physics.

    PubMed

    Macdermott, Alexandra J

    2012-09-01

    This paper aims to inspire experimentalists to carry out proposed new chiroptical experiments springing from the theoretical study of the role of parity violation in the origin of biomolecular homochirality and to provide a brief update on the current status of calculations of the electroweak parity-violating energy difference (PVED) between enantiomers. If the PVED did select life's handedness, we would expect to find life on other planets consistently using the same hand as terrestrial biochemistry. Much more importantly, even finding the "wrong" hand (rather than a racemic mixture) on another planet could be the homochiral signature of life, and we discuss our proposal for chiroptical detection of life on extra-solar planets. The PVED may also have an exciting future as a "molecular footprint" of fundamental physics: comparison of calculated PVEDs with measured values could one day allow chemists to do "table-top particle physics" more cheaply with improved chiroptical techniques instead of ever larger particle accelerators. We discuss our proposed chiroptical method to measure the PVED by using molecular beams. To our knowledge, optical rotation has not yet been measured in molecular beams, but the rewards of doing so include a host of other "first ever" results in addition to measurement of the PVED.

  9. Postural control responses sitting on unstable board during visual stimulation

    NASA Astrophysics Data System (ADS)

    Mizuno, Y.; Shindo, M.; Kuno, S.; Kawakita, T.; Watanabe, S.

    2001-08-01

    Concerning with the relation of vection induced by the optokinetic stimulation and the body movement, especially we attended to the neck joint movement, which counteracted to the shoulder movement. Then, we analyzed the mechanisms of the sitting postural control by using the seesaw board. By the optokinetic stimulation through the head mounted display (H.M.D.), the vection was leaded, and it affected to the sway of the body on the seesaw board. In this experiment, we found that the movement of upper part of body except for the head was the same direction to the seesaw board but the head moved out of phase to the seesaw board. This phenomenon will be suggested that the unstable condition of sway is balanced by the counter swing of head and the neck muscle tonus is controlled by acting of the vestiburo-collic reflex.

  10. Neuromuscular control and rehabilitation of the unstable ankle

    PubMed Central

    Hung, You-jou

    2015-01-01

    Lateral ankle sprain is a common orthopedic injury with a very high recurrence rate in athletes. After decades of research, it is still unclear what contributes to the high recurrence rate of ankle sprain, and what is the most effective intervention to reduce the incident of initial and recurrent injuries. In addition, clinicians often implement balance training as part of the rehabilitation protocol in hopes of enhancing the neuromuscular control and proprioception of the ankle joint. However, there is no consensus on whether the neuromuscular control and proprioception are compromised in unstable ankles. To reduce the prevalence of ankle sprains, the effectiveness of engaging balance training to enhance the neuromuscular control and proprioception of the ankle joint is also questionable. PMID:26085985

  11. Wetting reversal at gelation transition freezes thermodynamically unstable states.

    PubMed

    Hirayama, Shinya; Sano, Masahito

    2013-07-23

    The contact angle of a drop of gelling solution on a flat, solid surface was monitored as the hot solution was allowed to cool. When a solvent with a high cohesive energy and a wettable solid surface was used, a wetting solution turned into a dewetting solid at the gelation transition. The density profiles in gel as probed by confocal Raman microscopy reveal that the adsorption of both gelator and solvent shifts at the transition and the solvent is severely depleted from the interfacial region. Thus, the wetting reversal is accompanied by the interfacial desolvation. As a result of the adsorption shift during the gelation process in progress, a locally concentrated region of the gelator is frozen in space far away from the surface. This is a thermodynamically unstable state but can be realized reproducibly. The profile analysis also shows that the effect of the surface extends out to a few hundred micrometers, 2 orders of magnitude larger than the bulk correlation length.

  12. Unstable periodic orbits in human epileptic hippocampal slices.

    PubMed

    Pen-Ning Yu; Min-Chi Hsiao; Dong Song; Liu, Charles Y; Heck, Christi N; Millett, David; Berger, Theodore W

    2014-01-01

    Inter-ictal activity is studied in hippocampal slices resected from patients with epilepsy using local field potential recording. Inter-ictal activity in the dentate gyrus (DG) is induced by high-potassium (8 mM), low-magnesium (0.25 mM) aCSF with additional 100 μM 4-aminopyridine(4-AP). The dynamics of the inter-ictal activity is investigated by developing the first return map with inter-pulse intervals. Unstable periodic orbits (UPOs) are detected in the hippocampal slice at the DG area according to both the topological recurrence method and the periodic orbit transform method. Surrogate analysis suggests the presence of UPOs in hippocampal slices from patients with epilepsy. This finding also suggests that inter-ictal activity is a chaotic system and will allow us to apply chaos control techniques to manipulate inter-ictal activity.

  13. Unstable, self-limiting thermochemical temperature oscillations in Macrozamia cycads.

    PubMed

    Roemer, Robert B; Terry, L Irene; Walter, Gimme H

    2008-06-01

    Field measurements and laboratory experiments on the Australian cycads Macrozamia lucida and Macrozamia macleayi demonstrate that their cones' diel peak thermogenic temperature increase varies systematically with cone stage, with single thermogenic temperature peaks occurring daily for up to 2 weeks and reaching 12 degrees C above ambient at midstage. The initiation, magnitude and timing of those peaks are strongly modulated by ambient temperature; the period between successive thermogenic temperature peaks is not circadian, and light is neither necessary nor sufficient to initiate a thermogenic event. A mathematical analysis is developed that provides a unified explanation of the experimental results. It describes these unstable, self-limiting thermogenic events in terms of conservation of energy and a first-order chemical reaction rate model that includes an Arrhenius equation dependence of the cone's metabolic heating rate on the cone temperature.

  14. Oscillation structure of localized perturbations in modulationally unstable media.

    PubMed

    Biondini, Gino; Li, Sitai; Mantzavinos, Dionyssios

    2016-12-01

    We characterize the properties of the asymptotic stage of modulational instability arising from localized perturbations of a constant background, including the number and location of the individual peaks in the oscillation region. We show that, for long times, the solution tends to an ensemble of classical (i.e., sech-shaped) solitons of the focusing nonlinear Schrödinger equation (as opposed to the various breatherlike solutions of the same equation with a nonzero background). We also confirm the robustness of the theoretical results by comparing the analytical predictions with careful numerical simulations with a variety of initial conditions, which confirm that the evolution of modulationally unstable media in the presence of localized initial perturbations is indeed described by the same asymptotic state.

  15. Oscillation structure of localized perturbations in modulationally unstable media

    NASA Astrophysics Data System (ADS)

    Biondini, Gino; Li, Sitai; Mantzavinos, Dionyssios

    2016-12-01

    We characterize the properties of the asymptotic stage of modulational instability arising from localized perturbations of a constant background, including the number and location of the individual peaks in the oscillation region. We show that, for long times, the solution tends to an ensemble of classical (i.e., sech-shaped) solitons of the focusing nonlinear Schrödinger equation (as opposed to the various breatherlike solutions of the same equation with a nonzero background). We also confirm the robustness of the theoretical results by comparing the analytical predictions with careful numerical simulations with a variety of initial conditions, which confirm that the evolution of modulationally unstable media in the presence of localized initial perturbations is indeed described by the same asymptotic state.

  16. Unstable transition properties of the driven magnetohydrodynamic sheet pinch

    NASA Technical Reports Server (NTRS)

    Dahlburg, R. B.; Zang, T. A.; Montgomery, D.

    1986-01-01

    The unstable transition behavior of a bounded current-carrying two-dimensional magnetofluid is explored, using the hydrodynamic theory developed for parallel shear flows as a guide. Nonlinear excitation of the higher wavenumbers results in the development of electric current sheets of finite extent, as well as the formation of 'attraction currents' centered at the magnetic O-points. A secondary instability mechanism, the dynamic tearing of the electric current sheet, is also observed. This dynamic tearing leads to sawtoothlike temporal oscillations in certain global quantities. The long-time state of the system resembles a nonlinearly saturated state with significant excitation of many wavenumbers. Some features of this state can be understood by means of a Landau nonlinear stability theory based on certain assumptions about the perturbation energy balance.

  17. Unstable behavior of lasers and other optical systems

    NASA Astrophysics Data System (ADS)

    Narducci, L. N.; Tredicce, J. R.; Yuan, J. M.; Abraham, N. B.

    1987-11-01

    This final report summarizes the theoretical and experimental activities carried out jointly by the Qauntum Optics Group at Drexel University and the Nonlinear Dynamics and Laser Physics Group at Bryn Mawr College during the period October 15, 1985 to August 31, 1987. The report includes detailed reviews of our major findings in the study of laser dynamics, especially theoretically, but also experimentally, and summaries of other parallel studies on Stimulated Raman Scattering (SRS) and nonlinear dynamics. Our emphasis has been on the formulation of a generalized version of the Maxwell-Bloch equations for the laser to include transverse degrees of freedom. We have succeeded in developing this model and have investigated in detail its steady state and linear stability properties. Our main result is the discovery of low threshold unstable behaviors and the identification of their physical origin.

  18. Neutron capture measurements on unstable nuclei at LANSCE

    SciTech Connect

    Ullmann, J. L.; Haight, R. C.; Fowler, M. M.; Miller, G. G.; Rundberg, R. S.; Wilhelmy, J. B.

    1999-06-10

    Although neutron capture by stable isotopes has been extensively measured, there are very few measurements on unstable isotopes. The intense neutron flux at the Manual Lujan Jr. Neutron Scattering Center at LANSCE enables us to measure capture on targets with masses of about 1 mg over the energy range from 1 eV to 100 keV. These measurements are important not only for understanding the basic physics, but also for calculations of stellar nucleosynthesis and Science-Based Stockpile Stewardship. Preliminary measurements on {sup 169}Tm and {sup 171}Tm have been made with deuterated benzene detectors. A new detector array at the Lujan center and a new radioactive isotope separator will combine to give Los Alamos a unique capability for making these measurements.

  19. Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

    DOEpatents

    Horwitz, Earl Philip; Gatrone, Ralph Carl; Nash, Kenneth LaVerne

    1997-01-01

    Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described.

  20. Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

    DOEpatents

    Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

    1997-10-14

    Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

  1. Antisocial personality disorder--stable and unstable subtypes.

    PubMed

    Ullrich, Simone; Coid, Jeremy

    2010-04-01

    There have been criticisms that the criteria for antisocial personality disorder (ASPD) are over-dependent on criminal behavior. This study aimed to identify unrelated criteria of social and behavioral problems and instability, and to investigate their associations in a representative household sample of adults in the UK. Approximately one third of adults with ASPD did not fulfill any of the criteria for instability. They were less aggressive and involved in illegal activities but expressed less remorse for their behaviors. Instability in ASPD was mediated primarily through comorbid anxiety disorders and borderline personality disorder. The concept of Secondary Psychopathy, which has not generally been applied to ASPD, demonstrated many similarities to the unstable subtype.

  2. Acetabular augmentation for the treatment of unstable total hip arthroplasties.

    PubMed Central

    Nicholl, J. E.; Koka, S. R.; Bintcliffe, I. W.; Addison, A. K.

    1999-01-01

    Twenty-eight unstable total hip arthroplasties were treated with an acetabular augmentation wedge. Of the hips, 23 have had no further dislocations at a mean follow-up of 26 months. Five patients continued to dislocate and have needed further surgery. To our knowledge this is the largest reported series of acetabular augmentation with as good results as those of the most successful reported series of this technique, and a success rate comparable to other methods of treating recurrent dislocation. Careful patient selection, and using a thin augmentation wedge to avoid impingement, are important to the success of a technique which is a useful option in the management of recurrent dislocation. Images Figure 1 PMID:10364973

  3. Augmentation of proximal femoral nail in unstable trochanteric fractures

    PubMed Central

    Gadegone, Wasudeo M.; Shivashankar, Bhaskaran; Lokhande, Vijayanad; Salphale, Yogesh

    2017-01-01

    Introduction: Biomechanically proximal femoral nail (PFN) is a better choice of implant, still it is associated with screw breakage, cut out of screw through femoral head, Z effect, reverse Z effect, and lateral migration of screws. The purpose of this study is to evaluate the results of augmented PFN in terms of prevention of postoperative complications and failure rates in unstable trochanteric fractures. Material and methods: We carried out a prospective study of 82 cases with unstable trochanteric femoral fractures from April 2010 to December 2015. Forty-two females and 40 males in the age group between 58 and 81 years were included in this study. There were 45 cases of AO 31 A2 (2.2, 2.3) and 37 cases of AO 31 A3 (3.1, 3.2, 3.3). Fractures were fixed by PFN with augmentation by an additional screw from trochanter to inferior quadrant of femoral head or cerclage wire to strengthen the lateral trochanteric wall. Results: The bone healing is observed in all the cases in the mean period of 14.2 weeks. Nine patients developed complications, including lateral migration of neck screws (n = 5), Z effect (n = 1), infection (n = 2), and breakage of distal interlocking bolt in one case. Removal of screws was required in five cases. Patients were followed up for a mean of 8.4 months. At the end of follow-up the Salvati and Wilson hip function was 32 (out of 40) in 88% of patients. Conclusion: The stabilization of lateral trochanteric wall with additional screw or cerclage wire increases the stability of construct. PMID:28186871

  4. Migration of Gas Giant Planets in a Gravitationally Unstable Disk

    NASA Astrophysics Data System (ADS)

    Desai, Karna Mahadev; Steiman-Cameron, Thomas Y.; Michael, Scott; Durisen, Richard H.

    2017-01-01

    Understanding the migration of giant planets in gravitationally unstable protoplanetary disks is important for understanding planetary system architecture, especially the existence of planets orbiting close to and at large distances from their stars. Migration rates can determine the efficiency of planet formation and survival rates of planets. We present results from simulations of 0.3, 1, and 3 Jupiter-mass planets in a 0.14 M⊙ protoplanetary disk around a 1 M⊙ star, where the disk is marginally unstable to gravitational instabilities (GIs). Each planet is simulated separately. We use CHYMERA, a radiative 3D hydrodynamics code developed by the Indiana University Hydrodynamics Group. The simulations include radiative cooling governed by realistic dust opacities. The planets are inserted into the disk, once the disk has settled into its quasi-steady GI-active phase. We simulate each of the 0.3, 1, and 3 Jupiter-mass planets by inserting it at three different locations in the disk, at the corotation radius and at the inner and outer Lindblad resonances. No matter where placed, the 3 Jupiter-mass planets tend to drift inexorably inward but with a rate that slows after many orbital periods. The 1 Jupiter-mass planets migrate mostly inward, but their motion can be delayed or reversed near the corotation of the two-armed wave. The 0.3 Jupiter-mass planets are much less predictable and frequently migrate outward. We analyze how the density of matter and waves in the disk at different azimuthal locations affect the migration.

  5. MIGRATION OF GAS GIANT PLANETS IN GRAVITATIONALLY UNSTABLE DISKS

    SciTech Connect

    Michael, Scott; Durisen, Richard H.; Boley, Aaron C. E-mail: durisen@astro.indiana.edu

    2011-08-20

    Characterization of migration in gravitationally unstable disks is necessary to understand the fate of protoplanets formed by disk instability. As part of a larger study, we are using a three-dimensional radiative hydrodynamics code to investigate how an embedded gas giant planet interacts with a gas disk that undergoes gravitational instabilities (GIs). This Letter presents results from simulations with a Jupiter-mass planet placed in orbit at 25 AU within a 0.14 M{sub sun} disk. The disk spans 5-40 AU around a 1 M{sub sun} star and is initially marginally unstable. In one simulation, the planet is inserted prior to the eruption of GIs; in another, it is inserted only after the disk has settled into a quasi-steady GI-active state, where heating by GIs roughly balances radiative cooling. When the planet is present from the beginning, its own wake stimulates growth of a particular global mode with which it strongly interacts, and the planet plunges inward 6 AU in about 10{sup 3} years. In both cases with embedded planets, there are times when the planet's radial motion is slow and varies in direction. At other times, when the planet appears to be interacting with strong spiral modes, migration both inward and outward can be relatively rapid, covering several AUs over hundreds of years. Migration in both cases appears to stall near the inner Lindblad resonance of a dominant low-order mode. Planet orbit eccentricities fluctuate rapidly between about 0.02 and 0.1 throughout the GI-active phases of the simulations.

  6. Astrophysical Probes of Fundamental Physics

    NASA Astrophysics Data System (ADS)

    Martins, C. J. A. P.

    I review the theoretical motivation for varying fundamental couplings and discuss how these measurements can be used to constrain a number of fundamental physics scenarios that would otherwise be inacessible to experiment. As a case study I will focus on the relation between varying couplings and dark energy, and explain how varying coupling measurements can be used to probe the nature of dark energy, with important advantages over the standard methods. Assuming that the current observational evidence for varying α. and μ is correct, a several-sigma detection of dynamical dark energy is feasible within a few years, using currently operational ground-based facilities. With forthcoming instruments like CODEX, a high-accuracy reconstruction of the equation of state may be possible all the way up to redshift z ˜ 4.

  7. DOE Fundamentals Handbook: Classical Physics

    SciTech Connect

    Not Available

    1992-06-01

    The Classical Physics Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of physical forces and their properties. The handbook includes information on the units used to measure physical properties; vectors, and how they are used to show the net effect of various forces; Newton's Laws of motion, and how to use these laws in force and motion applications; and the concepts of energy, work, and power, and how to measure and calculate the energy involved in various applications. This information will provide personnel with a foundation for understanding the basic operation of various types of DOE nuclear facility systems and equipment.

  8. Nonlinear dispersive evolution of coherent trapped particle structures in collisionless plasmas

    NASA Astrophysics Data System (ADS)

    Mandal, Debraj; Sharma, Devendra

    2016-10-01

    The nonlinear limit of the collective perturbations in plasma is characterized by the onset of amplitude dependence in the wave dispersion. In a special class of nonlinear effects having origin in plasma kinetic theory, this amplitude dependence is removed only by collisions such that perturbations have no linear counterpart in collisionless limit and must follow a nonlinear dispersion relation (NDR). Exploring whether these fundamentally nonlinear perturbations can be driven unstable without entropy production might transform the character of the linear threshold based operating mechanism of the plasma turbulence that relies on well defined discrete spectrum prescribed by the linear plasma dispersion. In our multiscale, exact mass ratio, kinetic simulations the evolution of fundamentally nonlinear trapped particle structures is explored on both fast and slow ion and electron acoustic branches of the associated Nonlinear dispersion relation, respectively. The propagating structures that mutually interact exhibit a near continuum of the phase velocities and show microscopic evolution of the separatrix between streaming and trapped particle regions in the phase space, describing the subtle continuity between discrete and continuum bases of the plasma turbulence.

  9. Microplasmas: from applications to fundamentals

    NASA Astrophysics Data System (ADS)

    Nguon, Olivier; Huang, Sisi; Gauthier, Mario; Karanassios, Vassili

    2014-05-01

    Microplasmas are receiving increasing attention in the scientific literature and in recent conferences. Yet, few analytical applications of microplasmas for elemental analysis using liquid samples have been described in the literature. To address this, we describe two applications: one involves the determination of Zn in microsamples of the metallo-enzyme Super Oxide Dismutase. The other involves determination of Pd-concentration in microsamples of Pd nanocatalysts. These applications demonstrate the potential of microplasmas and point to the need for future fundamental studies.

  10. Radiation Belt Storm Probes: Resolving Fundamental Physics with Practical Consequences

    NASA Technical Reports Server (NTRS)

    Ukhorskiy, Aleksandr Y.; Mauk, Barry H.; Fox, Nicola J.; Sibeck, David G.; Grebowsky, Joseph M.

    2011-01-01

    The fundamental processes that energize, transport, and cause the loss of charged particles operate throughout the universe at locations as diverse as magnetized planets, the solar wind, our Sun, and other stars. The same processes operate within our immediate environment, the Earth's radiation belts. The Radiation Belt Storm Probes (RBSP) mission will provide coordinated two-spacecraft observations to obtain understanding of these fundamental processes controlling the dynamic variability of the near-Earth radiation environment. In this paper we discuss some of the profound mysteries of the radiation belt physics that will be addressed by RBSP and briefly describe the mission and its goals.

  11. BOOK REVIEWS: Quantum Mechanics: Fundamentals

    NASA Astrophysics Data System (ADS)

    Whitaker, A.

    2004-02-01

    This review is of three books, all published by Springer, all on quantum theory at a level above introductory, but very different in content, style and intended audience. That of Gottfried and Yan is of exceptional interest, historical and otherwise. It is a second edition of Gottfried’s well-known book published by Benjamin in 1966. This was written as a text for a graduate quantum mechanics course, and has become one of the most used and respected accounts of quantum theory, at a level mathematically respectable but not rigorous. Quantum mechanics was already solidly established by 1966, but this second edition gives an indication of progress made and changes in perspective over the last thirty-five years, and also recognises the very substantial increase in knowledge of quantum theory obtained at the undergraduate level. Topics absent from the first edition but included in the second include the Feynman path integral, seen in 1966 as an imaginative but not very useful formulation of quantum theory. Feynman methods were given only a cursory mention by Gottfried. Their practical importance has now been fully recognised, and a substantial account of them is provided in the new book. Other new topics include semiclassical quantum mechanics, motion in a magnetic field, the S matrix and inelastic collisions, radiation and scattering of light, identical particle systems and the Dirac equation. A topic that was all but totally neglected in 1966, but which has flourished increasingly since, is that of the foundations of quantum theory. John Bell’s work of the mid-1960s has led to genuine theoretical and experimental achievement, which has facilitated the development of quantum optics and quantum information theory. Gottfried’s 1966 book played a modest part in this development. When Bell became increasingly irritated with the standard theoretical approach to quantum measurement, Viki Weisskopf repeatedly directed him to Gottfried’s book. Gottfried had devoted a

  12. Case report: nonoperative treatment of an unstable Jefferson fracture using a cervical collar.

    PubMed

    Haus, Brian M; Harris, Mitchel B

    2008-05-01

    The treatment of unstable burst fractures of the atlas (Jefferson fractures) is controversial. Unstable Jefferson fractures have been managed successfully with either immobilization, typically halo traction or halo vest, or surgery. We report a patient with an unstable Jefferson fracture treated nonoperatively with a cervical collar, frequent clinical examinations, and flexion-extension radiographs. Twelve months after treatment, the patient achieved painless union of his fracture. The successful treatment confirms prior studies reporting unstable Jefferson fractures have been treated nonoperatively. The outcome challenges the clinical relevance of treatment algorithms that rely on the "rules of Spence" to guide treatment of unstable Jefferson fractures and illustrates instability may not necessarily be present in patients with considerable lateral mass widening. Additionally, it emphasizes a more reliable way of assessing C1-C2 stability in unstable Jefferson fractures is by measuring the presence and extent of anterior subluxation on lateral flexion and extension views.

  13. Fundamental studies of coal liquefaction

    SciTech Connect

    Not Available

    1995-01-01

    The authors have examined the pyrolysis of Argonne samples of Wyodak and Illinois No. 6 coal in argon, undecane, Tetralin, and water. The effects of the pyrolysis on individual particles of coal were monitored visually in a cell with diamond windows capable of operation to temperature and pressures in excess of 500{degrees}C and 3000 psi. The changes in the particles from ambient to 460{degrees}C were recorded in real time on video tape, and images were then taken from the tape record and analyzed. The study showed that in argon both coals developed tars at 350{degrees}-370{degrees}C. The tars then quickly evaporated, leaving core particles remarkably similar in size and shape to the initial particles. These observations suggest that coal does not melt nor become fully liquid when heated. Nor does the softened coal undergo crosslinking to generate coke. Rather the simple loss of volatiles leaves behind the core residue as coke. Contrary to the common view, there appears to be no link between the bond-breaking processes yielding tar and the interaction of the coal with H-donors leading to liquefaction. Water as a medium was surprising in its effect. Both coals began to shrink at 300{degrees}-350{degrees}C, with the effect appearing to be more of an erosion rather than a uniform loss of substance as seen in Tetralin. The Wyodak continued to shrink to 460{degrees}C to about half its initial size. With the Illinois No. 6 coal, however, the process reversed at around 420{degrees}C, and the particles appeared to grow with the evolution of a tar, continuing to 460{degrees}C. The authors submit that this final observation is evidence for hydrothermal synthesis of hydrocarbons at these conditions.

  14. Fundamental Limits to Cellular Sensing

    NASA Astrophysics Data System (ADS)

    ten Wolde, Pieter Rein; Becker, Nils B.; Ouldridge, Thomas E.; Mugler, Andrew

    2016-03-01

    In recent years experiments have demonstrated that living cells can measure low chemical concentrations with high precision, and much progress has been made in understanding what sets the fundamental limit to the precision of chemical sensing. Chemical concentration measurements start with the binding of ligand molecules to receptor proteins, which is an inherently noisy process, especially at low concentrations. The signaling networks that transmit the information on the ligand concentration from the receptors into the cell have to filter this receptor input noise as much as possible. These networks, however, are also intrinsically stochastic in nature, which means that they will also add noise to the transmitted signal. In this review, we will first discuss how the diffusive transport and binding of ligand to the receptor sets the receptor correlation time, which is the timescale over which fluctuations in the state of the receptor, arising from the stochastic receptor-ligand binding, decay. We then describe how downstream signaling pathways integrate these receptor-state fluctuations, and how the number of receptors, the receptor correlation time, and the effective integration time set by the downstream network, together impose a fundamental limit on the precision of sensing. We then discuss how cells can remove the receptor input noise while simultaneously suppressing the intrinsic noise in the signaling network. We describe why this mechanism of time integration requires three classes (groups) of resources—receptors and their integration time, readout molecules, energy—and how each resource class sets a fundamental sensing limit. We also briefly discuss the scheme of maximum-likelihood estimation, the role of receptor cooperativity, and how cellular copy protocols differ from canonical copy protocols typically considered in the computational literature, explaining why cellular sensing systems can never reach the Landauer limit on the optimal trade

  15. Short-range Fundamental forces

    SciTech Connect

    Antoniadis, I; Baessler, Stefan; Buechner, M; Fedorov, General Victor; Hoedl, S.; Lambrecht, A; Nesvizhevsky, V.; Pignol, G; Reynaud, S.; Sobolev, Yu.

    2011-01-01

    We consider theoretical motivations to search for extra short-range fundamental forces as well as experiments constraining their parameters. The forces could be of two types: (1) spin-independent forces; and (2) spin-dependent axion-like forces. Different experimental techniques are sensitive in respective ranges of characteristic distances. The techniques include measurements of gravity at short distances, searches for extra interactions on top of the Casimir force, precision atomic and neutron experiments. We focus on neutron constraints, thus the range of characteristic distances considered here corresponds to the range accessible for neutron experiments.

  16. Fundamental Characteristics of Breather Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Chabchoub, Amin

    2014-05-01

    The formation of oceanic rogue waves can be explained by the modulation instability of deep-water Stokes waves. In particular, being doubly-localized and amplifying the background wave amplitude by a factor of three or higher, the class of Peregrine-type breather solutions of the nonlinear Schrödinger equation (NLS) are considered to be appropriate models to describe extreme ocean wave dynamics. Here, we present an experimental validation of fundamental properties of the NLS within the context of Peregrine breather dynamics and we discuss the long-term behavior of such in time and space localized structures.

  17. Reconstruction of fundamental SUSY parameters

    SciTech Connect

    P. M. Zerwas et al.

    2003-09-25

    We summarize methods and expected accuracies in determining the basic low-energy SUSY parameters from experiments at future e{sup +}e{sup -} linear colliders in the TeV energy range, combined with results from LHC. In a second step we demonstrate how, based on this set of parameters, the fundamental supersymmetric theory can be reconstructed at high scales near the grand unification or Planck scale. These analyses have been carried out for minimal supergravity [confronted with GMSB for comparison], and for a string effective theory.

  18. Solid Lubrication Fundamentals and Applications

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    2001-01-01

    Solid Lubrication Fundamentals and Applications description of the adhesion, friction, abrasion, and wear behavior of solid film lubricants and related tribological materials, including diamond and diamond-like solid films. The book details the properties of solid surfaces, clean surfaces, and contaminated surfaces as well as discussing the structures and mechanical properties of natural and synthetic diamonds; chemical-vapor-deposited diamond film; surface design and engineering toward wear-resistant, self-lubricating diamond films and coatings. The author provides selection and design criteria as well as applications for synthetic and natural coatings in the commercial, industrial and aerospace industries..

  19. Size limit for particle-stabilized emulsion droplets under gravity.

    PubMed

    Tavacoli, J W; Katgert, G; Kim, E G; Cates, M E; Clegg, P S

    2012-06-29

    We demonstrate that emulsion droplets stabilized by interfacial particles become unstable beyond a size threshold set by gravity. This holds not only for colloids but also for supracolloidal glass beads, using which we directly observe the ejection of particles near the droplet base. The number of particles acting together in these ejection events decreases with time until a stable acornlike configuration is reached. Stability occurs when the weight of all remaining particles is less than the interfacial binding force of one particle. We also show the importance of the curvature of the droplet surface in promoting particle ejection.

  20. Micronization processes with supercritical fluids: fundamentals and mechanisms.

    PubMed

    Martín, A; Cocero, M J

    2008-02-14

    Supercritical fluid techniques for materials precipitation have been proposed as an alternative to conventional precipitation processes as they allow to improve the performance of these processes in terms of reduction of particle size and control of morphology and particle size distribution, without degradation or contamination of the product. These techniques have received much attention during the last years, and their feasibility and performance have been experimentally demonstrated for many substances. One of the main pending tasks is the development of a systematic procedure for the design and scale-up of these processes. This requires not only empirical knowledge, but also information about the fundamentals of the process. This work aims to review the published literature dealing with a fundamental investigation or modeling of supercritical fluid precipitation processes.

  1. Anisotropic Particles in Turbulence

    NASA Astrophysics Data System (ADS)

    Voth, Greg A.; Soldati, Alfredo

    2017-01-01

    Anisotropic particles are common in many industrial and natural turbulent flows. When these particles are small and neutrally buoyant, they follow Lagrangian trajectories while exhibiting rich orientational dynamics from the coupling of their rotation to the velocity gradients of the turbulence field. This system has proven to be a fascinating application of the fundamental properties of velocity gradients in turbulence. When particles are not neutrally buoyant, they experience preferential concentration and very different preferential alignment than neutrally buoyant tracer particles. A vast proportion of the parameter range of anisotropic particles in turbulence is still unexplored, with most existing research focusing on the simple foundational cases of axisymmetric ellipsoids at low concentrations in homogeneous isotropic turbulence and in turbulent channel flow. Numerical simulations and experiments have recently developed a fairly comprehensive picture of alignment and rotation in these cases, and they provide an essential foundation for addressing more complex problems of practical importance. Macroscopic effects of nonspherical particle dynamics include preferential concentration in coherent structures and drag reduction by fiber suspensions. We review the models used to describe nonspherical particle motion, along with numerical and experimental methods for measuring particle dynamics.

  2. Field Theory of Fundamental Interactions

    NASA Astrophysics Data System (ADS)

    Wang, Shouhong; Ma, Tian

    2017-01-01

    First, we present two basic principles, the principle of interaction dynamics (PID) and the principle of representation invariance (PRI). Intuitively, PID takes the variation of the action under energy-momentum conservation constraint. We show that the PID is the requirement of the presence of dark matter and dark energy, the Higgs field and the quark confinement. PRI requires that the SU(N) gauge theory be independent of representations of SU(N). It is clear that PRI is the logic requirement of any gauge theory. With PRI, we demonstrate that the coupling constants for the strong and the weak interactions are the main sources of these two interactions, reminiscent of the electric charge. Second, we emphasize that symmetry principles-the principle of general relativity and the principle of Lorentz invariance and gauge invariance-together with the simplicity of laws of nature, dictate the actions for the four fundamental interactions. Finally, we show that the PID and the PRI, together with the symmetry principles give rise to a unified field model for the fundamental interactions, which is consistent with current experimental observations and offers some new physical predictions. The research is supported in part by the National Science Foundation (NSF) grant DMS-1515024, and by the Office of Naval Research (ONR) grant N00014-15-1-2662.

  3. Astronomers Gain Clues About Fundamental Physics

    NASA Astrophysics Data System (ADS)

    2005-12-01

    An international team of astronomers has looked at something very big -- a distant galaxy -- to study the behavior of things very small -- atoms and molecules -- to gain vital clues about the fundamental nature of our entire Universe. The team used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to test whether the laws of nature have changed over vast spans of cosmic time. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF (Click on image for GBT gallery) "The fundamental constants of physics are expected to remain fixed across space and time; that's why they're called constants! Now, however, new theoretical models for the basic structure of matter indicate that they may change. We're testing these predictions." said Nissim Kanekar, an astronomer at the National Radio Astronomy Observatory (NRAO), in Socorro, New Mexico. So far, the scientists' measurements show no change in the constants. "We've put the most stringent limits yet on some changes in these constants, but that's not the end of the story," said Christopher Carilli, another NRAO astronomer. "This is the exciting frontier where astronomy meets particle physics," Carilli explained. The research can help answer fundamental questions about whether the basic components of matter are tiny particles or tiny vibrating strings, how many dimensions the Universe has, and the nature of "dark energy." The astronomers were looking for changes in two quantities: the ratio of the masses of the electron and the proton, and a number physicists call the fine structure constant, a combination of the electron charge, the speed of light and the Planck constant. These values, considered fundamental physical constants, once were "taken as time independent, with values given once and forever" said German particle physicist Christof Wetterich. However, Wetterich explained, "the viewpoint of modern particle theory has changed in recent years," with ideas such as

  4. About the method of investigation of applied unstable process

    NASA Astrophysics Data System (ADS)

    Romanova, O. V.; Sapega, V. F.

    2003-04-01

    ABOUT THE METHOD OF INVESTIGATION OF APPLIED UNSTABLE PROCESS O.V. Romanova (1), V.F. Sapega (1) (1) All-russian geological institute (VSEGEI) zapgeo@mail.wpus.net (mark: for Romanova)/Fax: +7-812-3289283 Samples of Late Proterosoic (Rephean) rocks from Arkhangelsk, Jaroslav and Leningrad regions were prepared by the developed method of sample preparation and researched by X-ray analysis. The presence of mantle fluid process had been previously estabished in some of the samples (injecting tuffizites) (Kazak, Jakobsson, 1999). It appears that unchanged rephean rocks contain the set of low-temperature minerals as illite, chlorite, vermiculite, goethite, indicates conditions of diagenesis with temperature less than 300° C. Presense of corrensite, rectorite, illite-montmorillonite indicates application of the post-diagenesis low-temperature process to the original sediment rock. At the same time the rocks involved in the fluid process, contain such minerals as olivine, pyrope, graphite and indicate application of the high-temperature process not less than 650-800°C. Within these samples a set of low-temperature minerals occur also, this demonstrates the short-timing and disequilibrium of the applied high-temperature process. Therefore implementation of the x-ray method provides unambiguous criterion to the establishment of the fluid process which as a rule is coupled with the development of kimberlite rock fields.

  5. Differential rotation of the unstable nonlinear r -modes

    NASA Astrophysics Data System (ADS)

    Friedman, John L.; Lindblom, Lee; Lockitch, Keith H.

    2016-01-01

    At second order in perturbation theory, the r -modes of uniformly rotating stars include an axisymmetric part that can be identified with differential rotation of the background star. If one does not include radiation reaction, the differential rotation is constant in time and has been computed by Sá. It has a gauge dependence associated with the family of time-independent perturbations that add differential rotation to the unperturbed equilibrium star: For stars with a barotropic equation of state, one can add to the time-independent second-order solution arbitrary differential rotation that is stratified on cylinders (that is a function of distance ϖ to the axis of rotation). We show here that the gravitational radiation-reaction force that drives the r -mode instability removes this gauge freedom; the exponentially growing differential rotation of the unstable second-order r -mode is unique. We derive a general expression for this rotation law for Newtonian models and evaluate it explicitly for slowly rotating models with polytropic equations of state.

  6. Foraging and farming as niche construction: stable and unstable adaptations.

    PubMed

    Rowley-Conwy, Peter; Layton, Robert

    2011-03-27

    All forager (or hunter-gatherer) societies construct niches, many of them actively by the concentration of wild plants into useful stands, small-scale cultivation, burning of natural vegetation to encourage useful species, and various forms of hunting, collectively termed 'low-level food production'. Many such niches are stable and can continue indefinitely, because forager populations are usually stable. Some are unstable, but these usually transform into other foraging niches, not geographically expansive farming niches. The Epipalaeolithic (final hunter-gatherer) niche in the Near East was complex but stable, with a relatively high population density, until destabilized by an abrupt climatic change. The niche was unintentionally transformed into an agricultural one, due to chance genetic and behavioural attributes of some wild plant and animal species. The agricultural niche could be exported with modifications over much of the Old World. This was driven by massive population increase and had huge impacts on local people, animals and plants wherever the farming niche was carried. Farming niches in some areas may temporarily come close to stability, but the history of the last 11,000 years does not suggest that agriculture is an effective strategy for achieving demographic and political stability in the world's farming populations.

  7. Big bang nucleosynthesis constraints on massive, unstable neutrinos.

    NASA Astrophysics Data System (ADS)

    Steigman, G.

    1995-01-01

    The tau-neutrino, if sufficiently massive, must be unstable. Big bang nucleosynthesis (BBN) can provide constraints on the ντ mass and lifetime. The modification to the energy density of the early universe in the case of a massive τ-neutrino which decays via ντ→νμ+φ (where φ is a weakly coupled massless scalar) is described and the results of BBN production of the light elements is presented. Consistency with the primordial abundances of D, 3He, 7Li and, especially, 4He leads to constraints on the mass (mντ) and lifetime (τντ) of the tau-neutrino. Very massive ντ (mντ ≥ 5 - 10 MeV), up to the ARGUS bound of 31 MeV, are only allowed for short lifetimes (≤40 sec). Much lighter (mντ ≤ 0.01 MeV) ντ are permitted for lifetimes longer than ≡0.01 sec but, mντ(MeV) ≤ 10 τν(sec) for shorter lifetimes.

  8. Gamma camera intrinsic uniformity in an unstable power supply environment.

    PubMed

    Ejeh, John E; Adedapo, Kayode S; Akinlade, Bidemi I; Osifo, Bola O A

    2011-01-01

    The main objective of this work was to show that a gamma camera in a developing country could perform efficiently despite electricity outages using intrinsic flood uniformity tests as an index of performance. A total of 143 intrinsic uniformity test results for a new gamma camera in use in an environment with unstable power supply are presented. The integral uniformity for the central field of view (CFOV) was found to be between 3.43% and 1.49% (3.29% for acceptance test) while the integral uniformity for the useful field of view (UFOV) was between 4.51% and 1.9% (5.21% for acceptance test). The differential uniformity for the CFOV was between 1.99% and 1.04% (2.25% for acceptance test) while that of the UFOV was between 2.84% and 1.23% (2.63% for acceptance test). In conclusion, these results show that the uniformity of the gamma camera under this condition is within an acceptable range for both planar and SPET imaging.

  9. Unstable Air-Sea Interaction in the Extratropical North Atlantic

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1999-01-01

    The possibility of coupled modes in the extratropical North Atlantic has fascinated the climate community since 1960's. A significant aspect of such modes is an unstable air-sea interaction, also called positive feedback, where disturbances between the atmosphere and ocean grow unbound. If a delayed response exists before the negative feedback takes effect, an oscillatory behaviour will develop. Here we explore the relationship between heat flux (positive upward) and sea surface temperature (SST). Positive feedback is characterized by a cross-correlation between the two where correlation maintains a negative sign whether SST or heat flux leads. We use model results and observations to argue that in the North Atlantic there exist regions with positive feedback. The two main locations coincide with the well-known north-south SST dipole where anomalies of opposite sign occupy areas east of Florida and north-east of Newfoundland. We show that oceanic dynamics, wave propagation and advection, give rise to oceanic anomalies in these regions. Subsequently these anomalies are amplified by atmosphere- ocean interaction: thus a positive feedback.

  10. Unstable and stable periodicities in thermally sensitive electroreceptors of catfish

    NASA Astrophysics Data System (ADS)

    Moss, Frank; Pei, Xing; Braun, Hans; Schafer, Klaus; Peters, Rob

    1997-03-01

    A statistical technique for distinguishing and counting unstable periodic orbits (UPOs) and stable limit cycles (LCs), based on their differing phase space topologies, has recently been developed(D. Pierson and F. Moss, Phys. Rev. Lett. 75, 2124 (1995)). Because the method is able to operate effectively on data files from noisy dynamical sources, it is uniquely effective when operating on data from biological sources, for example, weakly stimulated sensory neurons(X. Pei and F. Moss, Nature 379, 618 (1996)). Here we report the results of a study of bifurcations between UPOs and LCs in the electroreceptor organs of the catfish with the surface temperature of the receptors used as the bifurcation parameter. These organs have previously been shown to exhibit an internal near sub threshold oscillator which may account for the spontaneous appearance of the UPOs for certain values of the temperature. In previous experiments on different sensory systems (possibly of lower dimension) external periodic forcing was necessary for the appearance of UPOs.

  11. Thermal conduction in a mirror-unstable plasma

    NASA Astrophysics Data System (ADS)

    Komarov, S. V.; Churazov, E. M.; Kunz, M. W.; Schekochihin, A. A.

    2016-07-01

    The plasma of galaxy clusters is subject to firehose and mirror instabilities at scales of order the ion Larmor radius. The mirror instability generates fluctuations of magnetic-field strength δB/B ˜ 1. These fluctuations act as magnetic traps for the heat-conducting electrons, suppressing their transport. We calculate the effective parallel thermal conductivity in the ICM in the presence of the mirror fluctuations for different stages of the evolution of the instability. The mirror fluctuations are limited in amplitude by the maximum and minimum values of the field strength, with no large deviations from the mean value. This key property leads to a finite suppression of thermal conduction at large scales. We find suppression down to ≈0.2 of the Spitzer value for the secular phase of the perturbations' growth, and ≈0.3 for their saturated phase. The effect operates in addition to other suppression mechanisms and independently of them. Globally, fluctuations δB/B ˜ 1 can be present on much larger scales, of the order of the scale of turbulent motions. However, we do not expect large suppression of thermal conduction by these, because their scale is considerably larger than the collisional mean free path of the ICM electrons. The obtained suppression of thermal conduction by a factor of ˜5 appears to be characteristic and potentially universal for a weakly collisional mirror-unstable plasma.

  12. Richtmyer-Meshkov unstable dynamics influenced by pressure fluctuations

    NASA Astrophysics Data System (ADS)

    Bhowmick, A. K.; Abarzhi, S. I.

    2016-11-01

    We theoretically study the effect of pressure fluctuations on the Richtmyer-Meshkov (RM) unstable interface in approximation of ideal incompressible immiscible fluids and two-dimensional flow. Pressure fluctuations are treated as an effective acceleration directed from the heavy to light fluid with inverse square time dependence. The group theory approach is applied to analyze large-scale coherent dynamics, solve the complete set of the governing equations, and find regular asymptotic solutions describing RM bubbles. A strong effect is found, for the first time to our knowledge, of pressure fluctuations on the interface morphology and dynamics. In the linear regime, a nearly flat bubble gets more curved, and its velocity increases for strong pressure fluctuations and decreases otherwise. In the nonlinear regime, solutions form a one-parameter family parameterized by the bubble front curvature. For the fastest stable solution in the family, the RM bubble is curved for strong pressure fluctuations and is flattened otherwise. The flow is characterized by the intense motion of the fluids in the vicinity of the interface, effectively no motion away from the interface, and presence of shear at the interface leading to formation of smaller scale vortical structures. Our theoretical results agree with and explain existing experiments and simulations and identify new qualitative and quantitative characteristics to evaluate the strength of pressure fluctuations in experiments and simulations.

  13. Direct Numerical Simulation of Multiphase Flows with Unstable Interfaces

    NASA Astrophysics Data System (ADS)

    Schillaci, Eugenio; Lehmkuhl, Oriol; Antepara, Oscar; Oliva, Assensi

    2016-09-01

    This paper presents a numerical model that intends to simulate efficiently the surface instability that arise in multiphase flows, typically liquid-gas, both for laminar or turbulent regimes. The model is developed on the in-house computing platform TermoFluids, and operates the finite-volume, direct numerical simulation (DNS) of multiphase flows by means of a conservative level-set method for the interface-capturing. The mesh size is optimized by means of an adaptive mesh refinement (AMR) strategy, that allows the dynamic re-concentration of the mesh in the vicinity of the interfaces between fluids, in order to correctly represent the diverse structures (as ligaments and droplets) that may rise from unstable phenomena. In addition, special attention is given to the discretization of the various terms of the momentum equations, to ensure stability of the flow and correct representation of turbulent vortices. As shown, the method is capable of truthfully simulate the interface phenomena as the Kelvin-Helmholtz instability and the Plateau-Rayleigh instability, both in the case of 2-D and 3-D configurations. Therefore it is suitable for the simulation of complex phenomena such as simulation of air-blast atomization, with several important application in the field of automotive and aerospace engines. A prove is given by our preliminary study of the 3-D coaxial liquid-gas jet.

  14. [Correlations between clinical picture and coronary angiography in unstable angina].

    PubMed

    Zöllei, E; Halmai, L; Horváth, T; Pap, I; Törk, T; Verzár, Z; Rudas, L; Gaál, T

    1996-03-10

    In a one year period (from 01.07. 1993 to 30. 06. 1994) 103 patients were admitted to the Central Intensive Care Unit of the Albert Szent-Györgyi Medical University with the diagnosis of unstable angina. In this cohort of patients the authors assessed the correlation of clinical and angiographic data. Significant coronary artery disease was found in 84% (85 patients), single-vessel disease in 23% (24 patients), double-vessel disease in 38% (29 patients), triple-vessel disease in 20% (21 patients), left main stenosis in 8% (8 patients). The culprit lesion was determined in 73 cases. The distribution of the culprit lesion severity was the following: 50-70% in 17% (12 cases), 70-90% in 27% (20 cases), greater than 90% in 44% (32 cases), 100% in 12% (9 cases). Simplex lesions were seen in 43 cases, complex lesions in 9 cases, diffuse irregularities in 5 cases and total occlusions in 9 cases. Abnormalities indicating intracoronary thrombin-us were seen on 5 coronarograms. No correlation could be demonstrated between the clinical classes according to Braunwald and the angiographic morphology.

  15. The Unstable Elbow: Current Concepts in Diagnosis and Treatment.

    PubMed

    Tashjian, Robert Z; Wolf, Brian R; van Riet, Roger P; Steinmann, Scott P

    2016-01-01

    Elbow instability is common and may occur after a variety of injuries, including falls or direct blows. Instability can be classified as either acute or chronic. Acute instability is classified as simple (without fracture) or complex (with associated fracture). Chronic instability is classified as a chronically dislocated or recurrently unstable elbow. Recurrent instability commonly presents as isolated medial or lateral collateral ligament insufficiency. A chronically dislocated elbow is often more complex, involving both osseous and ligamentous injuries. The treatment of simple dislocations typically involves closed reduction and nonsurgical management. Chronic recurrent lateral and medial collateral ligament insufficiencies have very different clinical characteristics, but definitive treatment frequently involves ligament reconstruction. Complex instability usually requires surgery, which includes open reduction and internal fixation of coronoid and olecranon fractures, repair or replacement of radial head fractures, and lateral collateral ligament repair. Medial collateral ligament repair and/or external fixation are rarely required to restore stability. It is important for surgeons to understand current concepts in the diagnosis and management of acute and chronic elbow instability as well as the preferred surgical treatments and techniques for the management of these injuries.

  16. Secondary Students' Stable and Unstable Optics Conceptions Using Contextualized Questions

    NASA Astrophysics Data System (ADS)

    Chu, Hye-Eun; Treagust, David F.

    2014-04-01

    This study focuses on elucidating and explaining reasons for the stability of and interrelationships between students' conceptions about Light Propagation and Visibility of Objects using contextualized questions across 3 years of secondary schooling from Years 7 to 9. In a large-scale quantitative study involving 1,233 Korean students and 1,149 Singaporean students, data were analyzed from responses to the Light Propagation Diagnostic Instrument consisting of four pairs of items, each of which evaluated the same concept in two different problem situations. Findings show that only about 10-45 % of students could apply their conceptions of basic optics in contextualized problem situations giving rise to both stable and unstable alternative conceptions. Students' understanding of Light Propagation concepts compared with Visibility of Objects concepts was more stable in different problem situations. The concepts of Light Propagation and Visibility of Objects were only moderately correlated. School grade was not a strong predictive variable, but students' school achievement correlated strongly with their conceptual understanding in optics. The teaching and learning approach and education systems in the two countries may have had some influence on students' conceptual understanding.

  17. Numerical investigations on unstable direct contact condensation of cryogenic fluids

    NASA Astrophysics Data System (ADS)

    Jayachandran, K. N.; Arnab, Roy; Parthasarathi, Ghosh

    2017-02-01

    A typical problem of Direct Contact Condensation (DCC) occurs at the liquid oxygen (LOX) booster turbopump exit of oxidiser rich staged combustion cycle based semi-cryogenic rocket engines, where the hot gas mixture (predominantly oxygen and small amounts of combustion products) that runs the turbine mixes with LOX from the pump exit. This complex multiphase phenomena leads to the formation of solid CO2 & H2O, which is undesirable for the functioning of the main LOX turbopump. As a starting point for solving this complex problem, in this study, the hot gas mixture is taken as pure oxygen and hence, DCC of pure oxygen vapour jets in subcooled liquid oxygen is simulated using the commercial CFD package ANSYS CFX®. A two fluid model along with the thermal phase change model is employed for capturing the heat and mass transfer effects. The study mainly focuses on the subsonic DCC bubbling regime, which is reported as unstable with bubble formation, elongation, necking and collapsing effects. The heat transfer coefficients over a period of time have been computed and the various stages of bubbling have been analysed with the help of vapour volume fraction and pressure profiles. The results obtained for DCC of oxygen vapour-liquid mixtures is in qualitative agreement with the experimental results on DCC of steam-water mixtures.

  18. Foraging and farming as niche construction: stable and unstable adaptations

    PubMed Central

    Rowley-Conwy, Peter; Layton, Robert

    2011-01-01

    All forager (or hunter–gatherer) societies construct niches, many of them actively by the concentration of wild plants into useful stands, small-scale cultivation, burning of natural vegetation to encourage useful species, and various forms of hunting, collectively termed ‘low-level food production’. Many such niches are stable and can continue indefinitely, because forager populations are usually stable. Some are unstable, but these usually transform into other foraging niches, not geographically expansive farming niches. The Epipalaeolithic (final hunter–gatherer) niche in the Near East was complex but stable, with a relatively high population density, until destabilized by an abrupt climatic change. The niche was unintentionally transformed into an agricultural one, due to chance genetic and behavioural attributes of some wild plant and animal species. The agricultural niche could be exported with modifications over much of the Old World. This was driven by massive population increase and had huge impacts on local people, animals and plants wherever the farming niche was carried. Farming niches in some areas may temporarily come close to stability, but the history of the last 11 000 years does not suggest that agriculture is an effective strategy for achieving demographic and political stability in the world's farming populations. PMID:21320899

  19. Unstable minisatellite expansion causing recessively inherited myoclonus epilepsy, EPM1.

    PubMed

    Virtaneva, K; D'Amato, E; Miao, J; Koskiniemi, M; Norio, R; Avanzini, G; Franceschetti, S; Michelucci, R; Tassinari, C A; Omer, S; Pennacchio, L A; Myers, R M; Dieguez-Lucena, J L; Krahe, R; de la Chapelle, A; Lehesjoki, A E

    1997-04-01

    Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1; MIM 254800) is an autosomal recessive disorder that occurs with a low frequency in many populations but is more common in Finland and the Mediterranean region. It is characterized by stimulus-sensitive myoclonus and tonic-clonic seizures with onset at age 6-15 years, typical electroencephalographic abnormalities and a variable rate of progression between and within families. Following the initial mapping of the EPM1 gene to chromosome 21 (ref. 6) and the refinement of the critical region to a small interval, positional cloning identified the gene encoding cystatin B (CST6), a cysteine protease inhibitor, as the gene underlying EPM1 (ref. 10). Levels of messenger RNA encoded by CST6 were dramatically decreased in patients. A 3' splice site and a stop codon mutation were identified in three families, leaving most mutations uncharacterized. In this study, we report a novel type of disease-causing mutation, an unstable 15- to 18-mer minisatellite repeat expansion in the putative promoter region of the CST6 gene. The mutation accounts for the majority of EPM1 patients worldwide. Haplotype data are compatible with a single ancestral founder mutation. The length of the repeat array differs between chromosomes and families, but changes in repeat number seem to be comparatively rare events.

  20. Some properties of unstable slip on rough surfaces

    NASA Astrophysics Data System (ADS)

    Spetzler, Hartmut; Sobolev, Guennadi; Koltsov, Anatoli; Zang, Arno; Getting, Ivan C.

    1991-03-01

    In this paper we report results obtained from various friction experiments under direct and oblique shear loading conditions. We used four rock types of varying brittleness (quartzite, anhydrite, limestone, pyrophyllite) with different surface roughness. The observations concentrate on the time span several milliseconds before dynamic failure occurs. During this period a premonitory, unstable phase of slip (slip 2) occurs. This differs importantly from a premonitory, stable process (slip 1) with durations of hundreds of seconds. On smooth surfaces slip 2 is usually observed with ductile rocks and less reliably with brittle rocks. Slip 2 is mostly accompanied by acoustic emissions, which increase in rate of occurrence and in magnitude until the stick-slip event. Foreshocks are observed during approximately 50% of the slip 2 events on rough surfaces. Foreshocks far exceed the “acoustic noise level”, which is also prevalent before stick-slip events on rough surfaces. In the direct shear experiment, where two faults are being loaded simultaneously, in about 20% of the cases precursory slip 2 was observed on the opposite side on which the final stick-slip event occurred.

  1. Unstable shear flows in two dimensional strongly correlated liquids - a hydrodynamic and molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Gupta, Akanksha; Ganesh, Rajaraman; Joy, Ashwin

    2016-11-01

    In Navier-Stokes fluids, shear flows are known to become unstable leading to instability and eventually to turbulence. A class of flow namely, Kolmogorov Flows (K-Flows) exhibit such transition at low Reynolds number. Using fluid and molecular dynamics, we address the physics of transition from laminar to turbulent regime in strongly correlated-liquids such as in multi-species plasmas and also in naturally occurring plasmas with K-Flows as initial condition. A 2D phenomenological generalized hydrodynamic model is invoked wherein the effect of strong correlations is incorporated via a viscoelastic memory. To study the stability of K-Flows or in general any shear flow, a generalized eigenvalue solver has been developed along with a spectral solver for the full nonlinear set of fluid equations. A study of the linear and nonlinear features of K-Flow in incompressible and compressible limit exhibits cyclicity and nonlinear pattern formation in vorticity. A first principles based molecular dynamics simulation of particles interacting via Yukawa potential is performed with features such as configurational and kinetic thermostats for K-Flows. This work reveals several interesting similarities and differences between hydrodynamics and molecular dynamics studies.

  2. The Unstable Distal Radius Fracture—How Do We Define It? A Systematic Review

    PubMed Central

    Walenkamp, Monique M. J.; Vos, Lara M.; Strackee, Simon D.; Goslings, J. Carel; Schep, Niels W. L.

    2015-01-01

    Background Unstable distal radius fractures are a popular research subject. However, to appreciate the findings of studies that enrolled patients with unstable distal radius fractures, it should be clear how the authors defined an unstable distal radius fracture. Questions In what percentage of studies involving patients with unstable distal radius fractures did the authors define unstable distal radius fracture? What are the most common descriptions of an unstable distal radius fracture? And is there one preferred evidence-based definition for future authors? Methods A systematic search of literature was performed to identify any type of study with the term unstable distal radius fracture. We assessed whether a definition was provided and determined the level of evidence for the most common definitions. Results The search yielded 2,489 citations, of which 479 were included. In 149 studies, it was explicitly stated that patients with unstable distal radius fractures were enrolled. In 54% (81/149) of these studies, the authors defined an unstable distal radius fracture. Overall, we found 143 different definitions. The seven most common definitions were: displacement following adequate reduction; Lafontaine's definition; irreducibility; an AO type C2 fracture; a volarly displaced fracture; Poigenfürst's criteria; and Cooney's criteria. Only Lafontaine's definition originated from a clinical study (level IIIb). Conclusion In only half of the studies involving patients with an unstable distal radius fracture did the authors defined what they considered an unstable distal radius fracture. None of the definitions stood out as the preferred choice. A general consensus definition could help to standardize future research. PMID:26649263

  3. A study of unstable rock failures using finite difference and discrete element methods

    NASA Astrophysics Data System (ADS)

    Garvey, Ryan J.

    Case histories in mining have long described pillars or faces of rock failing violently with an accompanying rapid ejection of debris and broken material into the working areas of the mine. These unstable failures have resulted in large losses of life and collapses of entire mine panels. Modern mining operations take significant steps to reduce the likelihood of unstable failure, however eliminating their occurrence is difficult in practice. Researchers over several decades have supplemented studies of unstable failures through the application of various numerical methods. The direction of the current research is to extend these methods and to develop improved numerical tools with which to study unstable failures in underground mining layouts. An extensive study is first conducted on the expression of unstable failure in discrete element and finite difference methods. Simulated uniaxial compressive strength tests are run on brittle rock specimens. Stable or unstable loading conditions are applied onto the brittle specimens by a pair of elastic platens with ranging stiffnesses. Determinations of instability are established through stress and strain histories taken for the specimen and the system. Additional numerical tools are then developed for the finite difference method to analyze unstable failure in larger mine models. Instability identifiers are established for assessing the locations and relative magnitudes of unstable failure through measures of rapid dynamic motion. An energy balance is developed which calculates the excess energy released as a result of unstable equilibria in rock systems. These tools are validated through uniaxial and triaxial compressive strength tests and are extended to models of coal pillars and a simplified mining layout. The results of the finite difference simulations reveal that the instability identifiers and excess energy calculations provide a generalized methodology for assessing unstable failures within potentially complex

  4. Quantum repeaters: fundamental and future

    NASA Astrophysics Data System (ADS)

    Li, Yue; Hua, Sha; Liu, Yu; Ye, Jun; Zhou, Quan

    2007-04-01

    An overview of the Quantum Repeater techniques based on Entanglement Distillation and Swapping is provided. Beginning with a brief history and the basic concepts of the quantum repeaters, the article primarily focuses on the communication model based on the quantum repeater techniques, which mainly consists of two fundamental modules --- the Entanglement Distillation module and the Swapping module. The realizations of Entanglement Distillation are discussed, including the Bernstein's Procrustean method, the Entanglement Concentration and the CNOT-purification method, etc. The schemes of implementing Swapping, which include the Swapping based on Bell-state measurement and the Swapping in Cavity QED, are also introduced. Then a comparison between these realizations and evaluations on them are presented. At last, the article discusses the experimental schemes of quantum repeaters at present, documents some remaining problems and emerging trends in this field.

  5. Astronomical reach of fundamental physics

    NASA Astrophysics Data System (ADS)

    Burrows, Adam S.; Ostriker, Jeremiah P.

    2014-02-01

    Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.

  6. Astronomical reach of fundamental physics.

    PubMed

    Burrows, Adam S; Ostriker, Jeremiah P

    2014-02-18

    Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law.

  7. Fundamentals of Condensed Matter Physics

    NASA Astrophysics Data System (ADS)

    Cohen, Marvin L.; Louie, Steven G.

    2016-05-01

    Part I. Basic Concepts: Electrons and Phonons: 1. Concept of a solid: qualitative introduction and overview; 2. Electrons in crystals; 3. Electronic energy bands; 4. Lattice vibrations and phonons; Part II. Electron Intercations, Dynamics and Responses: 5. Electron dynamics in crystals; 6. Many-electron interactions: the interacting electron gas and beyond; 7. Density functional theory; 8. The dielectric function for solids; Part III. Optical and Transport Phenomena: 9. Electronic transitions and optical properties of solids; 10. Electron-phonon interactions; 11. Dynamics of crystal electrons in a magnetic field; 12. Fundamentals of transport phenomena in solids; Part IV. Superconductivity, Magnetism, and Lower Dimensional Systems: 13. Using many-body techniques; 14. Superconductivity; 15. Magnetism; 16. Reduced-dimensional systems and nanostructures; Index.

  8. Fundamentals of Acoustic Backscatter Imagery

    DTIC Science & Technology

    2011-09-20

    pressure, I,, of 1 /iPa, corresponds to 0.67 x 10- 8 Wim2. Assuming spherical spreading, the one meter distance reference frame, and the definition of dB (Eq...then be approximated by an infinite series Fundamentals ofAcoustic Backscatter Imagery 11 W(r) = Wm (r) + X Fjsc (r) j=O where "tic(r) is the incident...f( x ,y, Z)Iz=h(xy) = 0 f( x , y, z)I z=h( x ,y)= f( x , y, Z) I z o + h di+ h 2 d2f +zz z= The function ftx,y,z) can represent, for example, the stress

  9. Fundamental Travel Demand Model Example

    NASA Technical Reports Server (NTRS)

    Hanssen, Joel

    2010-01-01

    Instances of transportation models are abundant and detailed "how to" instruction is available in the form of transportation software help documentation. The purpose of this paper is to look at the fundamental inputs required to build a transportation model by developing an example passenger travel demand model. The example model reduces the scale to a manageable size for the purpose of illustrating the data collection and analysis required before the first step of the model begins. This aspect of the model development would not reasonably be discussed in software help documentation (it is assumed the model developer comes prepared). Recommendations are derived from the example passenger travel demand model to suggest future work regarding the data collection and analysis required for a freight travel demand model.

  10. Fundamental studies of polymer filtration

    SciTech Connect

    Smith, B.F.; Lu, M.T.; Robison, T.W.; Rogers, Y.C.; Wilson, K.V.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objectives of this project were (1) to develop an enhanced fundamental understanding of the coordination chemistry of hazardous-metal-ion complexation with water-soluble metal-binding polymers, and (2) to exploit this knowledge to develop improved separations for analytical methods, metals processing, and waste treatment. We investigated features of water-soluble metal-binding polymers that affect their binding constants and selectivity for selected transition metal ions. We evaluated backbone polymers using light scattering and ultrafiltration techniques to determine the effect of pH and ionic strength on the molecular volume of the polymers. The backbone polymers were incrementally functionalized with a metal-binding ligand. A procedure and analytical method to determine the absolute level of functionalization was developed and the results correlated with the elemental analysis, viscosity, and molecular size.

  11. Fundamental concepts of quantum chaos

    NASA Astrophysics Data System (ADS)

    Robnik, M.

    2016-09-01

    We review the fundamental concepts of quantum chaos in Hamiltonian systems. The quantum evolution of bound systems does not possess the sensitive dependence on initial conditions, and thus no chaotic behaviour occurs, whereas the study of the stationary solutions of the Schrödinger equation in the quantum phase space (Wigner functions) reveals precise analogy of the structure of the classical phase portrait. We analyze the regular eigenstates associated with invariant tori in the classical phase space, and the chaotic eigenstates associated with the classically chaotic regions, and the corresponding energy spectra. The effects of quantum localization of the chaotic eigenstates are treated phenomenologically, resulting in Brody-like level statistics, which can be found also at very high-lying levels, while the coupling between the regular and the irregular eigenstates due to tunneling, and of the corresponding levels, manifests itself only in low-lying levels.

  12. Cognition is … Fundamentally Cultural

    PubMed Central

    Bender, Andrea; Beller, Sieghard

    2013-01-01

    A prevailing concept of cognition in psychology is inspired by the computer metaphor. Its focus on mental states that are generated and altered by information input, processing, storage and transmission invites a disregard for the cultural dimension of cognition, based on three (implicit) assumptions: cognition is internal, processing can be distinguished from content, and processing is independent of cultural background. Arguing against each of these assumptions, we point out how culture may affect cognitive processes in various ways, drawing on instances from numerical cognition, ethnobiological reasoning, and theory of mind. Given the pervasive cultural modulation of cognition—on all of Marr’s levels of description—we conclude that cognition is indeed fundamentally cultural, and that consideration of its cultural dimension is essential for a comprehensive understanding. PMID:25379225

  13. Fundamental reaction pathways during coprocessing

    SciTech Connect

    Stock, L.M.; Gatsis, J.G. . Dept. of Chemistry)

    1992-12-01

    The objective of this research was to investigate the fundamental reaction pathways in coal petroleum residuum coprocessing. Once the reaction pathways are defined, further efforts can be directed at improving those aspects of the chemistry of coprocessing that are responsible for the desired results such as high oil yields, low dihydrogen consumption, and mild reaction conditions. We decided to carry out this investigation by looking at four basic aspects of coprocessing: (1) the effect of fossil fuel materials on promoting reactions essential to coprocessing such as hydrogen atom transfer, carbon-carbon bond scission, and hydrodemethylation; (2) the effect of varied mild conditions on the coprocessing reactions; (3) determination of dihydrogen uptake and utilization under severe conditions as a function of the coal or petroleum residuum employed; and (4) the effect of varied dihydrogen pressure, temperature, and residence time on the uptake and utilization of dihydrogen and on the distribution of the coprocessed products. Accomplishments are described.

  14. Astronomical reach of fundamental physics

    PubMed Central

    Burrows, Adam S.; Ostriker, Jeremiah P.

    2014-01-01

    Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law. PMID:24477692

  15. Rare Isotopes and Fundamental Symmetries

    NASA Astrophysics Data System (ADS)

    Brown, B. Alex; Engel, Jonathan; Haxton, Wick; Ramsey-Musolf, Michael; Romalis, Michael; Savard, Guy

    2009-01-01

    Experiments searching for new interactions in nuclear beta decay / Klaus P. Jungmann -- The beta-neutrino correlation in sodium-21 and other nuclei / P. A. Vetter ... [et al.] -- Nuclear structure and fundamental symmetries/ B. Alex Brown -- Schiff moments and nuclear structure / J. Engel -- Superallowed nuclear beta decay: recent results and their impact on V[symbol] / J. C. Hardy and I. S. Towner -- New calculation of the isospin-symmetry breaking correlation to superallowed Fermi beta decay / I. S. Towner and J. C. Hardy -- Precise measurement of the [symbol]H to [symbol]He mass difference / D. E. Pinegar ... [et al.] -- Limits on scalar currents from the 0+ to 0+ decay of [symbol]Ar and isospin breaking in [symbol]Cl and [symbol]Cl / A. Garcia -- Nuclear constraints on the weak nucleon-nucleon interaction / W. C. Haxton -- Atomic PNC theory: current status and future prospects / M. S. Safronova -- Parity-violating nucleon-nucleon interactions: what can we learn from nuclear anapole moments? / B. Desplanques -- Proposed experiment for the measurement of the anapole moment in francium / A. Perez Galvan ... [et al.] -- The Radon-EDM experiment / Tim Chupp for the Radon-EDM collaboration -- The lead radius Eexperiment (PREX) and parity violating measurements of neutron densities / C. J. Horowitz -- Nuclear structure aspects of Schiff moment and search for collective enhancements / Naftali Auerbach and Vladimir Zelevinsky -- The interpretation of atomic electric dipole moments: Schiff theorem and its corrections / C. -P. Liu -- T-violation and the search for a permanent electric dipole moment of the mercury atom / M. D. Swallows ... [et al.] -- The new concept for FRIB and its potential for fundamental interactions studies / Guy Savard -- Collinear laser spectroscopy and polarized exotic nuclei at NSCL / K. Minamisono -- Environmental dependence of masses and coupling constants / M. Pospelov.

  16. Quantum electrodynamics and fundamental constants

    NASA Astrophysics Data System (ADS)

    Wundt, Benedikt Johannes Wilhelm

    The unprecedented precision achieved both in the experimental measurements as well as in the theoretical description of atomic bound states make them an ideal study object for fundamental physics and the determination of fundamental constants. This requires a careful study of the effects from quantum electrodynamics (QED) on the interaction between the electron and the nucleus. The two theoretical approaches for the evaluation of QED corrections are presented and discussed. Due to the presence of two energy scales from the binding potential and the radiation field, an overlapping parameter has to be used in both approaches in order to separate the energy scales. The different choices for the overlapping parameter in the two methods are further illustrated in a model example. With the nonrelativistic theory, relativistic corrections in order ( Zalpha)2 to the two-photon decay rate of ionic states are calculated, as well as the leading radiative corrections of alpha( Zalpha)2ln[(Zalpha)-2 ]. It is shown that the corrections is gauge-invariant under a "hybrid" gauge transformation between Coulomb and Yennie gauge. Furthermore, QED corrections for Rydberg states in one-electron ions are investigated. The smallness of the corrections and the absence of nuclear size corrections enable very accurate theoretical predictions. Measuring transition frequencies and comparing them to the theoretical predictions, QED theory can be tested more precisely. In turn, this could yield a more accurate value for the Rydberg constant. Using a transition in a nucleus with a well determined mass, acting as a reference, a comparison to transition in other nuclei can even allow to determined nuclear masses. Finally, in order to avoid an additional uncertainty in nuclei with non zero nuclear spin, QED self-energy corrections to the hyperfine structure up to order alpha(Zalpha)2Delta EHFS are determined for highly excited Rydberg states.

  17. Fundamental enabling issues in nanotechnology :

    SciTech Connect

    Floro, Jerrold Anthony; Foiles, Stephen Martin; Hearne, Sean Joseph; Hoyt, Jeffrey John; Seel, Steven Craig; Webb III, Edmund Blackburn; Morales, Alfredo Martin; Zimmerman, Jonathan A.

    2007-10-01

    To effectively integrate nanotechnology into functional devices, fundamental aspects of material behavior at the nanometer scale must be understood. Stresses generated during thin film growth strongly influence component lifetime and performance; stress has also been proposed as a mechanism for stabilizing supported nanoscale structures. Yet the intrinsic connections between the evolving morphology of supported nanostructures and stress generation are still a matter of debate. This report presents results from a combined experiment and modeling approach to study stress evolution during thin film growth. Fully atomistic simulations are presented predicting stress generation mechanisms and magnitudes during all growth stages, from island nucleation to coalescence and film thickening. Simulations are validated by electrodeposition growth experiments, which establish the dependence of microstructure and growth stresses on process conditions and deposition geometry. Sandia is one of the few facilities with the resources to combine experiments and modeling/theory in this close a fashion. Experiments predicted an ongoing coalescence process that generates signficant tensile stress. Data from deposition experiments also supports the existence of a kinetically limited compressive stress generation mechanism. Atomistic simulations explored island coalescence and deposition onto surfaces intersected by grain boundary structures to permit investigation of stress evolution during later growth stages, e.g. continual island coalescence and adatom incorporation into grain boundaries. The predictive capabilities of simulation permit direct determination of fundamental processes active in stress generation at the nanometer scale while connecting those processes, via new theory, to continuum models for much larger island and film structures. Our combined experiment and simulation results reveal the necessary materials science to tailor stress, and therefore performance, in

  18. Fundamental Physics and Precision Measurements

    NASA Astrophysics Data System (ADS)

    Hänsch, T. W.

    2006-11-01

    "Very high precision physics has always appealed to me. The steady improvement in technologies that afford higher and higher precision has been a regular source of excitement and challenge during my career. In science, as in most things, whenever one looks at something more closely, new aspects almost always come into play …" With these word from the book "How the Laser happened", Charles H. Townes expresses a passion for precision that is now shared by many scientists. Masers and lasers have become indispensible tools for precision measurements. During the past few years, the advent of femtosecond laser frequency comb synthesizers has revolutionized the art of directly comparing optical and microwave frequencies. Inspired by the needs of precision laser spectroscopy of the simple hydrogen atom, such frequency combs are now enabling ultra-precise spectroscopy over wide spectral ranges. Recent laboratory experiments are already setting stringent limits for possible slow variations of fundamental constants. Laser frequency combs also provide the long missing clockwork for optical atomic clocks that may ultimately reach a precision of parts in 1018 and beyond. Such tools will open intriguing new opportunities for fundamental experiments including new tests of special and general relativity. In the future, frequency comb techniques may be extended into the extreme ultraviolet and soft xray regime, opening a vast new spectral territory to precision measurements. Frequency combs have also become a key tool for the emerging new field of attosecond science, since they can control the electric field of ultrashort laser pulses on an unprecedented time scale. The biggest surprise in these endeavours would be if we found no surprise.

  19. Fundamentals of figure control and fracture-'free' finishing for high aspect ratio laser optics

    SciTech Connect

    Suratwala, Tayyab

    2014-10-01

    The high level objectives of the this work were to: 1) scientifically understand critical phenomena affecting the surface figure during full aperture finishing; 2) utilize these fundamentals to more deterministically control the surface figure during finishing; 3) successfully polish under rogue particle-‘free’ environments during polishing by understanding/preventing key sources of rogue particles.

  20. Survival of habitable planets in unstable planetary systems

    NASA Astrophysics Data System (ADS)

    Carrera, Daniel; Davies, Melvyn B.; Johansen, Anders

    2016-12-01

    Many observed giant planets lie on eccentric orbits. Such orbits could be the result of strong scatterings with other giant planets. The same dynamical instability that produces these scatterings may also cause habitable planets in interior orbits to become ejected, destroyed, or be transported out of the habitable zone. We say that a habitable planet has resilient habitability if it is able to avoid ejections and collisions and its orbit remains inside the habitable zone. Here we model the orbital evolution of rocky planets in planetary systems where giant planets become dynamically unstable. We measure the resilience of habitable planets as a function of the observed, present-day masses and orbits of the giant planets. We find that the survival rate of habitable planets depends strongly on the giant planet architecture. Equal-mass planetary systems are far more destructive than systems with giant planets of unequal masses. We also establish a link with observation; we find that giant planets with present-day eccentricities higher than 0.4 almost never have a habitable interior planet. For a giant planet with a present-day eccentricity of 0.2 and semimajor axis of 5 au orbiting a Sun-like star, 50 per cent of the orbits in the habitable zone are resilient to the instability. As semimajor axis increases and eccentricity decreases, a higher fraction of habitable planets survive and remain habitable. However, if the habitable planet has rocky siblings, there is a significant risk of rocky planet collisions that would sterilize the planet.

  1. Salvianolate injection in the treatment of unstable angina pectoris

    PubMed Central

    Zhang, Dan; Wu, Jiarui; Liu, Shi; Zhang, Xiaomeng; Zhang, Bing

    2016-01-01

    Abstract Background: To systematically evaluate the clinical efficacy and safety of Salvianolate injection in the treatment of unstable angina pectoris (UAP). Methods: Using literature databases, we conducted a thorough and systematic retrieval of randomized controlled trials (RCTs) that using Salvianolate injection for treating UAP. The Cochrane Risk of Bias Assessment Tool was used to evaluate the methodological quality of the RCTs, and then the data were extracted and meta-analyzed by RevMan5.2 software. Results: A total of 22 RCTs with 2050 participants were included. The meta-analysis indicated that the combined use of Salvianolate injection and western medicine (WM) in the treatment of UAP can achieve a superior effect in angina pectoris total effective rate (risk ratio [RR] = 1.22, 95% confidence interval [CI] (1.17, 1.27), Z = 10.15, P < 0.00001], and the total effectiveness rate of electrocardiogram [RR = 1.26, 95% CI (1.19,1.34), Z = 7.77, P < 0.00001]. In addition, Salvianolate injection can improve the nitroglycerin withdrawal rate and the serum level of NO, decrease high-sensitivity C-reactive protein. Adverse drug reactions (ADRs) or adverse drug events (ADEs) were reported in 6 RCTs involving 15 cases; however, there were no serious ADRs/ADEs. Conclusion: Based on the systematic review, the combined use of Salvianolate injection and WM in the treatment of UAP can achieve a better effect; however, there was no definitive conclusion about its safety. More the large-sample and multicenter RCTs are needed to support its clinical usage. PMID:28002341

  2. ORBITAL MIGRATION OF PROTOPLANETS IN A MARGINALLY GRAVITATIONALLY UNSTABLE DISK

    SciTech Connect

    Boss, Alan P.

    2013-02-20

    Core accretion and disk instability require giant protoplanets to form in the presence of disk gas. Protoplanet migration models generally assume disk masses low enough that the disk's self-gravity can be neglected. However, disk instability requires a disk massive enough to be marginally gravitationally unstable (MGU). Even for core accretion, an FU Orionis outburst may require a brief MGU disk phase. We present a new set of three-dimensional, gravitational radiation hydrodynamics models of MGU disks with multiple protoplanets, which interact gravitationally with the disk and with each other, including disk gas mass accretion. Initial protoplanet masses are 0.01 to 10 M {sub Circled-Plus} for core accretion models, and 0.1 to 3 M {sub Jup} for Nice scenario models, starting on circular orbits with radii of 6, 8, 10, or 12 AU, inside a 0.091 M {sub Sun} disk extending from 4 to 20 AU around a 1 M {sub Sun} protostar. Evolutions are followed for up to {approx}4000 yr and involve phases of relative stability (e {approx} 0.1) interspersed with chaotic phases (e {approx} 0.4) of orbital interchanges. The 0.01 to 10 M {sub Circled-Plus} cores can orbit stably for {approx}1000 yr: monotonic inward or outward orbital migration of the type seen in low mass disks does not occur. A system with giant planet masses similar to our solar system (1.0, 0.33, 0.1, 0.1 M {sub Jup}) was stable for over 1000 yr, and a Jupiter-Saturn-like system was stable for over 3800 yr, implying that our giant planets might well survive an MGU disk phase.

  3. UNSTABLE PLANETARY SYSTEMS EMERGING OUT OF GAS DISKS

    SciTech Connect

    Matsumura, Soko; Thommes, Edward W.; Chatterjee, Sourav; Rasio, Frederic A.

    2010-05-01

    The discovery of over 400 extrasolar planets allows us to statistically test our understanding of the formation and dynamics of planetary systems via numerical simulations. Traditional N-body simulations of multiple-planet systems without gas disks have successfully reproduced the eccentricity (e) distribution of the observed systems by assuming that the planetary systems are relatively closely packed when the gas disk dissipates, so that they become dynamically unstable within the stellar lifetime. However, such studies cannot explain the small semimajor axes a of extrasolar planetary systems, if planets are formed, as the standard planet formation theory suggests, beyond the ice line. In this paper, we numerically study the evolution of three-planet systems in dissipating gas disks, and constrain the initial conditions that reproduce the observed a and e distributions simultaneously. We adopt initial conditions that are motivated by the standard planet formation theory, and self-consistently simulate the disk evolution and planet migration, by using a hybrid N-body and one-dimensional gas disk code. We also take into account eccentricity damping, and investigate the effect of saturation of corotation resonances on the evolution of planetary systems. We find that the a distribution is largely determined in a gas disk, while the e distribution is determined after the disk dissipation. We also find that there may be an optimum disk mass which leads to the observed a-e distribution. Our simulations generate a larger fraction of planetary systems trapped in mean-motion resonances (MMRs) than the observations, indicating that the disk's perturbation to the planetary orbits may be important to explain the observed rate of MMRs. We also find a much lower occurrence of planets on retrograde orbits than the current observations of close-in planets suggest.

  4. How Do Fundamental Christians Deal with Depression?

    ERIC Educational Resources Information Center

    Spinney, Douglas Harvey

    1991-01-01

    Provides explanation of developmental dynamics in experience of fundamental Christians that provoke reactive depression. Describes depressant retardant defenses against depression that have been observed in Christian fundamental subculture. Suggests four counseling strategies for helping fundamentalists. (Author/ABL)

  5. Fundamentals and Techniques of Nonimaging

    SciTech Connect

    O'Gallagher, J. J.; Winston, R.

    2003-07-10

    This is the final report describing a long term basic research program in nonimaging optics that has led to major advances in important areas, including solar energy, fiber optics, illumination techniques, light detectors, and a great many other applications. The term ''nonimaging optics'' refers to the optics of extended sources in systems for which image forming is not important, but effective and efficient collection, concentration, transport, and distribution of light energy is. Although some of the most widely known developments of the early concepts have been in the field of solar energy, a broad variety of other uses have emerged. Most important, under the auspices of this program in fundamental research in nonimaging optics established at the University of Chicago with support from the Office of Basic Energy Sciences at the Department of Energy, the field has become very dynamic, with new ideas and concepts continuing to develop, while applications of the early concepts continue to be pursued. While the subject began as part of classical geometrical optics, it has been extended subsequently to the wave optics domain. Particularly relevant to potential new research directions are recent developments in the formalism of statistical and wave optics, which may be important in understanding energy transport on the nanoscale. Nonimaging optics permits the design of optical systems that achieve the maximum possible concentration allowed by physical conservation laws. The earliest designs were constructed by optimizing the collection of the extreme rays from a source to the desired target: the so-called ''edge-ray'' principle. Later, new concentrator types were generated by placing reflectors along the flow lines of the ''vector flux'' emanating from lambertian emitters in various geometries. A few years ago, a new development occurred with the discovery that making the design edge-ray a functional of some other system parameter permits the construction of whole

  6. A generalized twistor dynamics of relativistic particles and strings

    SciTech Connect

    Soroka, V.A.; Sorokin, D.P.; Tkach, V.I.; Volkov, D.V. )

    1992-09-30

    In this paper, a generalization of relativistic particle and sting dynamics based on a notion of twistor shift and containing a fundamental length constant is considered, which results in a modification of particle (or string) interactions with background fields.

  7. Future Fundamental Combustion Research for Aeropropulsion Systems.

    DTIC Science & Technology

    1985-01-01

    AD-MISS 771 FUTURE FUNDAMENTAL COMBUSTION RESEARCH FOR I AEROPROPULSION SYSTEMS(U) NATIONAL AERONAUTICS AND I SPACE ADMINISTRATION CLEVELAND OH LEWIS... Future Fundamental Combustion Research for Aeropropulsion Systems u. Edward J. Mularz V Propulsion Laboratory A VSCOM Research and Technology Laboratories... FUTURE FUNDAMENTAL COMBUSTION RESEARCH FOR AEROPROPULSION SYSTEMS Edward J. Mularz

  8. Fundamental Scaling Laws in Nanophotonics

    PubMed Central

    Liu, Ke; Sun, Shuai; Majumdar, Arka; Sorger, Volker J.

    2016-01-01

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of “smaller-is-better” has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors. PMID:27869159

  9. Fundamental Scaling Laws in Nanophotonics

    NASA Astrophysics Data System (ADS)

    Liu, Ke; Sun, Shuai; Majumdar, Arka; Sorger, Volker J.

    2016-11-01

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of “smaller-is-better” has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors.

  10. Fundamental studies of fusion plasmas

    SciTech Connect

    Aamodt, R.E.; Catto, P.J.; D'Ippolito, D.A.; Myra, J.R.; Russell, D.A.

    1992-05-26

    The major portion of this program is devoted to critical ICH phenomena. The topics include edge physics, fast wave propagation, ICH induced high frequency instabilities, and a preliminary antenna design for Ignitor. This research was strongly coordinated with the world's experimental and design teams at JET, Culham, ORNL, and Ignitor. The results have been widely publicized at both general scientific meetings and topical workshops including the speciality workshop on ICRF design and physics sponsored by Lodestar in April 1992. The combination of theory, empirical modeling, and engineering design in this program makes this research particularly important for the design of future devices and for the understanding and performance projections of present tokamak devices. Additionally, the development of a diagnostic of runaway electrons on TEXT has proven particularly useful for the fundamental understanding of energetic electron confinement. This work has led to a better quantitative basis for quasilinear theory and the role of magnetic vs. electrostatic field fluctuations on electron transport. An APS invited talk was given on this subject and collaboration with PPPL personnel was also initiated. Ongoing research on these topics will continue for the remainder fo the contract period and the strong collaborations are expected to continue, enhancing both the relevance of the work and its immediate impact on areas needing critical understanding.

  11. Fundamental Scaling Laws in Nanophotonics.

    PubMed

    Liu, Ke; Sun, Shuai; Majumdar, Arka; Sorger, Volker J

    2016-11-21

    The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of "smaller-is-better" has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors.

  12. Information physics fundamentals of nanophotonics.

    PubMed

    Naruse, Makoto; Tate, Naoya; Aono, Masashi; Ohtsu, Motoichi

    2013-05-01

    Nanophotonics has been extensively studied with the aim of unveiling and exploiting light-matter interactions that occur at a scale below the diffraction limit of light, and recent progress made in experimental technologies--both in nanomaterial fabrication and characterization--is driving further advancements in the field. From the viewpoint of information, on the other hand, novel architectures, design and analysis principles, and even novel computing paradigms should be considered so that we can fully benefit from the potential of nanophotonics. This paper examines the information physics aspects of nanophotonics. More specifically, we present some fundamental and emergent information properties that stem from optical excitation transfer mediated by optical near-field interactions and the hierarchical properties inherent in optical near-fields. We theoretically and experimentally investigate aspects such as unidirectional signal transfer, energy efficiency and networking effects, among others, and we present their basic theoretical formalisms and describe demonstrations of practical applications. A stochastic analysis of light-assisted material formation is also presented, where an information-based approach provides a deeper understanding of the phenomena involved, such as self-organization. Furthermore, the spatio-temporal dynamics of optical excitation transfer and its inherent stochastic attributes are utilized for solution searching, paving the way to a novel computing paradigm that exploits coherent and dissipative processes in nanophotonics.

  13. Hyperbolic metamaterials: fundamentals and applications.

    PubMed

    Shekhar, Prashant; Atkinson, Jonathan; Jacob, Zubin

    2014-01-01

    Metamaterials are nano-engineered media with designed properties beyond those available in nature with applications in all aspects of materials science. In particular, metamaterials have shown promise for next generation optical materials with electromagnetic responses that cannot be obtained from conventional media. We review the fundamental properties of metamaterials with hyperbolic dispersion and present the various applications where such media offer potential for transformative impact. These artificial materials support unique bulk electromagnetic states which can tailor light-matter interaction at the nanoscale. We present a unified view of practical approaches to achieve hyperbolic dispersion using thin film and nanowire structures. We also review current research in the field of hyperbolic metamaterials such as sub-wavelength imaging and broadband photonic density of states engineering. The review introduces the concepts central to the theory of hyperbolic media as well as nanofabrication and characterization details essential to experimentalists. Finally, we outline the challenges in the area and offer a set of directions for future work.

  14. Unstable reshaping of gold nanorods prepared by a wet chemical method in the presence of silver nitrate.

    PubMed

    Iqbal, Muhammad; Tae, Giyoong

    2006-11-01

    We characterized the stability of the gold nanorods synthesized by means of a seed mediated growth approach in the presence of AgNO3, which consists of synthesis of small diameter seed particles (approximately 4 nm) and subsequent growth of these nanoparticles into nanorods by addition to gold salt solution containing cetyltrimethylammonium bromide (CTAB) in the presence of ascorbic acid. The presence of silver nitrate significantly enhanced the nanorod synthesis as previously reported. However, the synthesized nanorods were unstable and reshaped in aqueous environment; the continuous blue-shift of the 2nd plasmon bands was monitored and the changes in the nanorod morphologies were also observed by electron microscopy with increasing storage time. This reshaping was observed at wide CTAB concentration range regardless of the removal of the unreacted gold or silver ions.

  15. Particle separation

    DOEpatents

    Moosmuller, Hans [Reno, NV; Chakrabarty, Rajan K [Reno, NV; Arnott, W Patrick [Reno, NV

    2011-04-26

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  16. Particle separation

    NASA Technical Reports Server (NTRS)

    Moosmuller, Hans (Inventor); Chakrabarty, Rajan K. (Inventor); Arnott, W. Patrick (Inventor)

    2011-01-01

    Embodiments of a method for selecting particles, such as based on their morphology, is disclosed. In a particular example, the particles are charged and acquire different amounts of charge, or have different charge distributions, based on their morphology. The particles are then sorted based on their flow properties. In a specific example, the particles are sorted using a differential mobility analyzer, which sorts particles, at least in part, based on their electrical mobility. Given a population of particles with similar electrical mobilities, the disclosed process can be used to sort particles based on the net charge carried by the particle, and thus, given the relationship between charge and morphology, separate the particles based on their morphology.

  17. Diagnostics of the unstable envelopes of Wolf-Rayet stars

    NASA Astrophysics Data System (ADS)

    Grassitelli, L.; Chené, A.-N.; Sanyal, D.; Langer, N.; St-Louis, N.; Bestenlehner, J. M.; Fossati, L.

    2016-05-01

    Context. The envelopes of stars near the Eddington limit are prone to various instabilities. A high Eddington factor in connection with the iron opacity peak leads to convective instability, and a corresponding envelope inflation may induce pulsational instability. Here, we investigate the occurrence and consequences of both instabilities in models of Wolf-Rayet stars. Aims: We determine the convective velocities in the sub-surface convective zones to estimate the amplitude of the turbulent velocity at the base of the wind that potentially leads to the formation of small-scale wind structures, as observed in several Wolf-Rayet stars. We also investigate the effect of stellar wind mass loss on the pulsations of our stellar models. Methods: We approximated solar metallicity Wolf-Rayet stars in the range 2-17 M⊙ by models of mass-losing helium stars, computed with the Bonn stellar evolution code. We characterized the properties of convection in the envelope of these stars adopting the standard mixing length theory. Results: Our results show the occurrence of sub-surface convective regions in all studied models. Small (≈1 km s-1) surface velocity amplitudes are predicted for models with masses below ≈10 M⊙. For models with M ≳ 10 M⊙, the surface velocity amplitudes are of the order of 10 km s-1. Moreover we find the occurrence of pulsations for stars in the mass range 9-14 M⊙, while mass loss appears to stabilize the more massive Wolf-Rayet stars. We confront our results with observationally derived line variabilities of 17 WN stars, of which we analysed eight here for the first time. The data suggest variability to occur for stars above 10 M⊙, which is increasing linearly with mass above this value, in agreement with our results. We further find our models in the mass range 9-14M⊙ to be unstable to radial pulsations, and predict local magnetic fields of the order of hundreds of gauss in Wolf-Rayet stars more massive than ≈10 M⊙. Conclusions: Our

  18. Fundamental mechanisms of micromachine reliability

    SciTech Connect

    DE BOER,MAARTEN P.; SNIEGOWSKI,JEFFRY J.; KNAPP,JAMES A.; REDMOND,JAMES M.; MICHALSKE,TERRY A.; MAYER,THOMAS K.

    2000-01-01

    Due to extreme surface to volume ratios, adhesion and friction are critical properties for reliability of Microelectromechanical Systems (MEMS), but are not well understood. In this LDRD the authors established test structures, metrology and numerical modeling to conduct studies on adhesion and friction in MEMS. They then concentrated on measuring the effect of environment on MEMS adhesion. Polycrystalline silicon (polysilicon) is the primary material of interest in MEMS because of its integrated circuit process compatibility, low stress, high strength and conformal deposition nature. A plethora of useful micromachined device concepts have been demonstrated using Sandia National Laboratories' sophisticated in-house capabilities. One drawback to polysilicon is that in air the surface oxidizes, is high energy and is hydrophilic (i.e., it wets easily). This can lead to catastrophic failure because surface forces can cause MEMS parts that are brought into contact to adhere rather than perform their intended function. A fundamental concern is how environmental constituents such as water will affect adhesion energies in MEMS. The authors first demonstrated an accurate method to measure adhesion as reported in Chapter 1. In Chapter 2 through 5, they then studied the effect of water on adhesion depending on the surface condition (hydrophilic or hydrophobic). As described in Chapter 2, they find that adhesion energy of hydrophilic MEMS surfaces is high and increases exponentially with relative humidity (RH). Surface roughness is the controlling mechanism for this relationship. Adhesion can be reduced by several orders of magnitude by silane coupling agents applied via solution processing. They decrease the surface energy and render the surface hydrophobic (i.e. does not wet easily). However, only a molecular monolayer coats the surface. In Chapters 3-5 the authors map out the extent to which the monolayer reduces adhesion versus RH. They find that adhesion is independent of

  19. Research on the unstable operating region of axial-flow and mixed flow pump

    NASA Astrophysics Data System (ADS)

    Cheng, L.; Liu, C.; Luo, C.; Zhou, J. R.; Jin, Y.

    2012-11-01

    The unstable operating region affected safety of pump start-up and limited the range of stable operating. When there are three flowrates points matching along with one lift, the hydraulic unstable operating region happened. The range region of unstable operation region is from peak to bottom of performance curve when the axial flow pump was test on the closed test rig. There are two factors, rotating stall and bad inlet condition, which cause the unstable operating region. The unstable operating regions of different pumping system are presented. The unsteady CFD calculations were done to present the internal flow pattern and hydraulic pressure when axial flow pump and mixed flow pump were operated on the unstable operating region. The frequency spectrum is given of one of the force components in radial direction, as measured in the whriling frame of reference. It is important to prevent and avoid unstable operating region along with the construction of South to North water transfer of China and reconstruction of large scale pumping station.

  20. Particle transport and deposition: basic physics of particle kinetics.

    PubMed

    Tsuda, Akira; Henry, Frank S; Butler, James P

    2013-10-01

    The human body interacts with the environment in many different ways. The lungs interact with the external environment through breathing. The enormously large surface area of the lung with its extremely thin air-blood barrier is exposed to particles suspended in the inhaled air. The particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic. Conversely, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drugs. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental to understanding subsequent biological response, and the basic physics of particle motion and engineering knowledge needed to understand these subjects is the topic of this article. A large portion of this article deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: (i) the physical characteristics of particles, (ii) particle behavior in gas flow, and (iii) gas-flow patterns in the respiratory tract. Other areas, such as particle transport in the developing lung and in the diseased lung are also considered. The article concludes with a summary and a brief discussion of areas of future research.

  1. Particle transport and deposition: basic physics of particle kinetics

    PubMed Central

    Tsuda, Akira; Henry, Frank S.; Butler, James P.

    2015-01-01

    The human body interacts with the environment in many different ways. The lungs interact with the external environment through breathing. The enormously large surface area of the lung with its extremely thin air-blood barrier is exposed to particles suspended in the inhaled air. Whereas the particle-lung interaction may cause deleterious effects on health if the inhaled pollutant aerosols are toxic, this interaction can be beneficial for disease treatment if the inhaled particles are therapeutic aerosolized drug. In either case, an accurate estimation of dose and sites of deposition in the respiratory tract is fundamental to understanding subsequent biological response, and the basic physics of particle motion and engineering knowledge needed to understand these subjects is the topic of this chapter. A large portion of this chapter deals with three fundamental areas necessary to the understanding of particle transport and deposition in the respiratory tract. These are: 1) the physical characteristics of particles, 2) particle behavior in gas flow, and 3) gas flow patterns in the respiratory tract. Other areas, such as particle transport in the developing lung and in the diseased lung are also considered. The chapter concludes with a summary and a brief discussion of areas of future research. PMID:24265235

  2. Fundamental Investigations of Airframe Noise

    NASA Technical Reports Server (NTRS)

    Macaraeg, M. G.

    2004-01-01

    An extensive numerical and experimental study of airframe noise mechanisms associated with a subsonic high-lift system has been performed at NASA Langley Research Center (LaRC). Investigations involving both steady and unsteady computations and experiments on a small-scale, part-span flap model are presented. Both surface (steady and unsteady pressure measurements, hot films, oil flows, pressure sensitive paint) and off surface (5 hole-probe, particle-imaged velocimetry, laser velocimetry, laser light sheet measurements) were taken in the LaRC Quiet Flow Facility (QFF) and several hard-wall tunnels up to flight Reynolds number. Successful microphone array measurements were also taken providing both acoustic source maps on the model, and quantitative spectra. Critical directivity measurements were obtained in the QFF. NASA Langley unstructured and structured Reynolds- Averaged Navier-Stokes codes modeled the flap geometries excellent comparisons with surface and offsurface experimental data were obtained. Subsequently, these meanflow calculations were utilized in both linear stability and direct numerical simulations of the flap-edge flow field to calculate unsteady surface pressures and farfield acoustic spectra. Accurate calculations were critical in obtaining not only noise source characteristics, but shear layer correction data as well. Techniques utilized in these investigations as well as brief overviews of results will be given.

  3. Forces and Particles: Concepts Again in Conflict

    ERIC Educational Resources Information Center

    Gale, George

    1973-01-01

    Traces the historical developments in physics leading to the present conflict of fundamental beliefs about the nature of the physical world. It has been recently proposed that the concept of fundamental particles (corpuscularianism) be replaced with a full-blown field dynamical theory. (JR)

  4. Preliminary Measurement of Lunar Particle Shapes.

    NASA Technical Reports Server (NTRS)

    Rickman, Doug

    2013-01-01

    Particle shape is a basic parameter and essential for many engineering applications. Very little data is published on the shape of lunar particles. An unpublished review found that even where the same samples were studied the results were contradictory, probably because of extremely small sample sizes. Other workers have made fundamental errors in algorithms. There are many ways to measure particle shape. One common approach is to examine the particles as intersected by a plain, such as a thin section. If discrete particles can be segmented from the image, programs such as ImageJ can readily obtain shape measurements for each particle.

  5. Astronomia Motivadora no Ensino Fundamental

    NASA Astrophysics Data System (ADS)

    Melo, J.; Voelzke, M. R.

    2008-09-01

    O objetivo principal deste trabalho é procurar desenvolver o interesse dos alunos pelas ciências através da Astronomia. Uma pesquisa com perguntas sobre Astronomia foi realizada junto a 161 alunos do Ensino Fundamental, com o intuito de descobrir conhecimentos prévios dos alunos sobre o assunto. Constatou-se, por exemplo, que 29,3% da 6ª série responderam corretamente o que é eclipse, 30,0% da 8ª série acertaram o que a Astronomia estuda, enquanto 42,3% dos alunos da 5ª série souberam definir o Sol. Pretende-se ampliar as turmas participantes e trabalhar, principalmente de forma prática com: dimensões e escalas no Sistema Solar, construção de luneta, questões como dia e noite, estações do ano e eclipses. Busca-se abordar, também, outros conteúdos de Física tais como a óptica na construção da luneta, e a mecânica no trabalho com escalas e medidas, e ao utilizar uma luminária para representar o Sol na questão do eclipse, e de outras disciplinas como a Matemática na transformação de unidades, regras de três; Artes na modelagem ou desenho dos planetas; a própria História com relação à busca pela origem do universo, e a Informática que possibilita a busca mais rápida por informações, além de permitir simulações e visualizações de imagens importantes. Acredita-se que a Astronomia é importante no processo ensino aprendizagem, pois permite a discussão de temas curiosos como, por exemplo, a origem do universo, viagens espaciais a existência ou não de vida em outros planetas, além de temas atuais como as novas tecnologias.

  6. Unstable nuclei in dissociation of light stable and radioactive nuclei in nuclear track emulsion

    NASA Astrophysics Data System (ADS)

    Artemenkov, D. A.; Zaitsev, A. A.; Zarubin, P. I.

    2017-01-01

    A role of the unstable nuclei 6Be, 8Be and 9B in the dissociation of relativistic nuclei 7,9Be, 10B and 10,11C is under study on the basis of nuclear track emulsion exposed to secondary beams of the JINR Nuclotron. Contribution of the configuration 6Be + n to the 7Be nucleus structure is 8 ± 1% which is near the value for the configuration 6Li + p. Distributions over the opening angle of α-particle pairs indicate to a simultaneous presence of virtual 8Beg.s. and 8Be2+ states in the ground states of the 9Be and 10C nuclei. The core 9B is manifested in the 10C nucleus with a probability of 30 ± 4%. Selection of the 10C "white" stars accompanied by 8Beg.s. (9B) leads to appearance in the excitation energy distribution of 2α2 p "quartets" of the distinct peak with a maximum at 4.1 ± 0.3 MeV. 8Beg.s. decays are presented in 24 ± 7% of 2He + 2H events of the 11C coherent dissociation and 27 ± 11% of the 3He ones. The channel 9B + H amounts 14 ± 3%. The 8Bg.s. nucleus is manifested in the coherent dissociation 10B → 2He + H with a probability of 25 ± 5% including 13 ± 3% of 9B decays. A probability ratio of the mirror channels 9B + n and 9Be + p is estimated to be 10 ± 1.

  7. Consequences of an unstable chemical stratification on mantle dynamics

    NASA Astrophysics Data System (ADS)

    Plesa, Ana-Catalina; Tosi, Nicola; Breuer, Doris

    2013-04-01

    Early in the history of terrestrial planets, the fractional crystallization of primordial magma oceans may have led to the formation of large scale chemical heterogeneities. These may have been preserved over the entire planetary evolution as suggested for Mars by the isotopic analysis of the so-called SNC meteorites. The fractional crystallization of a magma ocean leads to a chemical stratification characterized by a progressive enrichment in heavy elements from the core-mantle boundary to the surface. This results in an unstable configuration that causes the overturn of the mantle and the subsequent formation of a stable chemical layering. Assuming scaling parameters appropriate for Mars, we first performed simulations of 2D thermo-chemical convection in Cartesian geometry with the numerical code YACC [1]. We investigated systems heated either solely from below or from within by varying systematically the buoyancy ratio B, which measures the relative importance of chemical to thermal buoyancy, and the mantle rheology, by considering systems with constant, strongly temperature-dependent and plastic viscosity. We ran a large set of simulations spanning a wide parameter space in order to understand the basic physics governing the magma ocean cumulate overturn and its consequence on mantle dynamics. Moreover, we derived scaling laws that relate the time over which chemical heterogeneities can be preserved (mixing time) and the critical yield stress (maximal yield stress that allows the lithosphere to undergo brittle failure) to the buoyancy ratio. We have found that the mixing time increases exponentially with B, while the critical yield stress shows a linear dependence. We investigated then Mars' early thermo-chemical evolution using the code GAIA in a 2D cylindrical geometry [2] and assuming a detailed magma ocean crystallization sequence as obtained from geochemical modeling [3]. We used an initial composition profile adapted from [3], accounted for an exothermic

  8. Unstable Nuclei in Astrophysics - Proceedings of the International Workshop

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Kajino, T.

    1992-01-01

    Kinematics Reaction Yields at 0° * Astrophysical Information for Capture Reactions by Coulomb Dissociation (Contributed) * VI. Electroweak Processes in Astrophysics * The Neutrino Process and Neutrino r-Process * Diffusion of Neutrinos in a Presupernova Star and the Effect of Electron Screening of Nuclei * Multigroup Simulation of Protoneutron Star Cooling and Neutrino Spectra * VII. Neutron Stars and Equations of State * Properties of Dense Supernova Matter and Hot Neutron Stars at the Birth * Impact of the Nuclear Equation of State on Models of Rotating Neutron Stars * Supernova and Neutron Stars with Equations of State in Relativistic Many Body Theory Constrained by Unstable Nuclei * Nuclear Shapes in the Crust of Neutron Stars and in the Core of Supernovae (Contributed) * List of Contributed Papers * List of Participants * Author Index

  9. UNSTABLE MUTATIONS IN THE FMR1 GENE AND THE PHENOTYPES

    PubMed Central

    Loesch, Danuta; Hagerman, Randi

    2014-01-01

    Fragile X syndrome (FXS), a severe neurodevelopmental anomaly, and one of the earliest disorders linked to an unstable (‘dynamic’) mutation, is caused by the large (>200) CGG repeat expansions in the noncoding portion of the FMR1 (Fragile X Mental Retardation-1) gene. These expansions, termed full mutations, normally silence this gene's promoter through methylation, leading to a gross deficit of the Fragile X Mental Retardation Protein (FMRP) that is essential for normal brain development. Rare individuals with the expansion but with an unmethylated promoter (and thus, FMRP production), present a much less severe form of FXS. However, a unique feature of the relationship between the different sizes of CGG expanded tract and phenotypic changes is that smaller expansions (<200) generate a series of different clinical manifestations and/or neuropsychological changes. The major part of this chapter is devoted to those FMR1 alleles with small (55-200) CGG expansions, termed ‘premutations’, which have the potential for generating the full mutation alleles on mother-offspring transmission, on the one hand, and are associated with some phenotypic changes, on the other. Thus, the role of several factors known to determine the rate of CGG expansion in the premutation alleles is discussed first. Then, an account of various neurodevelopmental, congnitive, behavioural and physical changes reported in carriers of these small expansions is given, and possible association of these conditions with a toxicity of the elevated FMR1 gene's transcript (mRNA) is discussed. The next two sections are devoted to major and well defined clinical conditions associated with the premutation alleles. The first one is the late onset neurodegenerative disorder termed fragile X-associated tremor ataxia syndrome (FXTAS). The wide range of clinical and neuropsychological manifestations of this syndrome, and their relevance to elevated levels of the FMR1 mRNA, are described. Another distinct

  10. Particle generator

    DOEpatents

    Hess, Wayne P.; Joly, Alan G.; Gerrity, Daniel P.; Beck, Kenneth M.; Sushko, Peter V.; Shlyuger, Alexander L.

    2005-06-28

    Energy tunable solid state sources of neutral particles are described. In a disclosed embodiment, a halogen particle source includes a solid halide sample, a photon source positioned to deliver photons to a surface of the halide, and a collimating means positioned to accept a spatially defined plume of hyperthermal halogen particles emitted from the sample surface.

  11. Fundamental Principles of Proper Space Kinematics

    NASA Astrophysics Data System (ADS)

    Wade, Sean

    It is desirable to understand the movement of both matter and energy in the universe based upon fundamental principles of space and time. Time dilation and length contraction are features of Special Relativity derived from the observed constancy of the speed of light. Quantum Mechanics asserts that motion in the universe is probabilistic and not deterministic. While the practicality of these dissimilar theories is well established through widespread application inconsistencies in their marriage persist, marring their utility, and preventing their full expression. After identifying an error in perspective the current theories are tested by modifying logical assumptions to eliminate paradoxical contradictions. Analysis of simultaneous frames of reference leads to a new formulation of space and time that predicts the motion of both kinds of particles. Proper Space is a real, three-dimensional space clocked by proper time that is undergoing a densification at the rate of c. Coordinate transformations to a familiar object space and a mathematical stationary space clarify the counterintuitive aspects of Special Relativity. These symmetries demonstrate that within the local universe stationary observers are a forbidden frame of reference; all is in motion. In lieu of Quantum Mechanics and Uncertainty the use of the imaginary number i is restricted for application to the labeling of mass as either material or immaterial. This material phase difference accounts for both the perceived constant velocity of light and its apparent statistical nature. The application of Proper Space Kinematics will advance more accurate representations of microscopic, oscopic, and cosmological processes and serve as a foundation for further study and reflection thereafter leading to greater insight.

  12. Neutrino properties and fundamental symmetries

    SciTech Connect

    Bowles, T.J.

    1996-07-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). There are two components to this work. The first is a development of a new detection scheme for neutrinos. The observed deficit of neutrinos from the Sun may be due to either a lack of understanding of physical processes in the Sun or may be due to neutrinos oscillating from one type to another during their transit from the Sun to the Earth. The Sudbury Neutrino Observatory (SNO) is designed to use a water Cerenkov detector employing one thousand tonnes of heavy water to resolve this question. The ability to distinguish muon and tau neutrinos from electron neutrinos is crucial in order to carry out a model-independent test of neutrino oscillations. We describe a developmental exploration of a novel technique to do this using {sup 3}He proportional counters. Such a method offers considerable advantages over the initially proposed method of using Cerenkov light from capture on NaCl in the SNO. The second component of this work is an exploration of optimal detector geometry for a time-reversal invariance experiment. The question of why time moves only in the forward direction is one of the most puzzling problems in modern physics. We know from particle physics measurements of the decay of kaons that there is a charge-parity symmetry that is violated in nature, implying time-reversal invariance violation. Yet, we do not understand the origin of the violation of this symmetry. To promote such an understanding, we are developing concepts and prototype apparatus for a new, highly sensitive technique to search for time-reversal-invariance violation in the beta decay of the free neutron. The optimized detector geometry is seven times more sensitive than that in previous experiments. 15 refs.

  13. Energetic particle physics issues for ITER

    SciTech Connect

    Cheng, C.Z.; Budny, R.; Fu, G.Y.

    1996-12-31

    This paper summarizes our present understanding of the following energetic/alpha particle physics issues for the 21 MA, 20 TF coil ITER Interim Design configuration and operational scenarios: (a) toroidal field ripple effects on alpha particle confinement, (b) energetic particle interaction with low frequency MHD modes, (c) energetic particle excitation of toroidal Alfven eigenmodes, and (d) energetic particle transport due to MHD modes. TF ripple effects on alpha loss in ITER under a number of different operating conditions are found to be small with a maximum loss of 1%. With careful plasma control in ITER reversed-shear operation, TF ripple induced alpha loss can be reduced to below the nominal ITER design limit of 5%. Fishbone modes are expected to be unstable for {beta}{sub {alpha}} > 1%, and sawtooth stabilization is lost if the ideal kink growth rate exceeds 10% of the deeply trapped alpha precessional drift frequency evaluated at the q = 1 surface. However, it is expected that the fishbone modes will lead only to a local flattening of the alpha profile due to small banana size. MHD modes observed during slow decrease of stored energy after fast partial electron temperature collapse in JT-60U reversed-shear experiments may be resonant type instabilities; they may have implications on the energetic particle confinement in ITER reversed-shear operation. From the results of various TAE stability code calculations, ITER equilibria appear to lie close to TAE linear stability thresholds. However, the prognosis depends strongly on q profile and profiles of alpha and other high energy particles species. If TAE modes are unstable in ITER, the stochastic diffusion is the main loss mechanism, which scales with ({delta}B{sub r}/B){sup 2}, because of the relatively small alpha particle banana orbit size. For isolated TAE modes the particle loss is very small, and TAE modes saturate via the resonant wave-particle trapping process at very small amplitude.

  14. Percutaneous pedicle screw for unstable spine fractures in polytraumatized patients: A report of two cases

    PubMed Central

    Tan, Boon Beng; Chan, Chris Yin Wei; Saw, Lim Beng; Kwan, Mun Keong

    2012-01-01

    Unstable spine fractures commonly occur in the setting of a polytraumatized patient. The aim of management is to balance the need for early operative stabilization and prevent additional trauma due to the surgery. Recent published literature has demonstrated the benefits of early stabilization of an unstable spine fracture particularly in patients with higher injury severity score (ISS). We report two cases of polytrauma with unstable spine fractures stabilized with a minimally invasive percutaneous pedicle screw instrumentation system as a form of damage control surgery. The patients had good recovery from the polytrauma injuries. These two cases illustrate the role of minimally invasive stabilization, its limitations and technical pitfalls in the management of unstable spine fractures in the polytrauma setting as a form of damage control surgery. PMID:23325978

  15. Incarceration and Unstable Housing Interact to Predict Sexual Risk Behaviors among African American STD Clinic Patients

    PubMed Central

    Widman, Laura; Noar, Seth M.; Golin, Carol E.; Willoughby, Jessica Fitts; Crosby, Richard

    2014-01-01

    Given dramatic racial disparities in rates of HIV/STDs among African Americans, understanding broader structural factors that increase the risk for HIV/STDs is crucial. This study investigated incarceration history and unstable housing as two structural predictors of HIV risk behavior among 293 African Americans (159 men/134 women, Mage=27). Participants were recruited from an urban STD clinic in the southeastern U.S. Approximately half the sample had been incarcerated in their lifetime (54%), and 43% had been unstably housed in the past 6 months. Incarceration was independently associated with number of sex partners and the frequency of unprotected sex. Unstable housing was independently associated with the frequency of unprotected sex. However, these main effects were qualified by significant interactions: individuals with a history of incarceration and more unstable housing had more sex partners and more unprotected sex in the past three months than individuals without these structural barriers. Implications for structural-level interventions are discussed. PMID:24060677

  16. Delayed feedback control and phase reduction of unstable quasi-periodic orbits.

    PubMed

    Ichinose, Natsuhiro; Komuro, Motomasa

    2014-09-01

    The delayed feedback control (DFC) is applied to stabilize unstable quasi-periodic orbits (QPOs) in discrete-time systems. The feedback input is given by the difference between the current state and a time-delayed state in the DFC. However, there is an inevitable time-delay mismatch in QPOs. To evaluate the influence of the time-delay mismatch on the DFC, we propose a phase reduction method for QPOs and construct a phase response curve (PRC) from unstable QPOs directly. Using the PRC, we estimate the rotation number of QPO stabilized by the DFC. We show that the orbit of the DFC is consistent with the unstable QPO perturbed by a small state difference resulting from the time-delay mismatch, implying that the DFC can certainly stabilize the unstable QPO.

  17. Delayed feedback control and phase reduction of unstable quasi-periodic orbits

    NASA Astrophysics Data System (ADS)

    Ichinose, Natsuhiro; Komuro, Motomasa

    2014-09-01

    The delayed feedback control (DFC) is applied to stabilize unstable quasi-periodic orbits (QPOs) in discrete-time systems. The feedback input is given by the difference between the current state and a time-delayed state in the DFC. However, there is an inevitable time-delay mismatch in QPOs. To evaluate the influence of the time-delay mismatch on the DFC, we propose a phase reduction method for QPOs and construct a phase response curve (PRC) from unstable QPOs directly. Using the PRC, we estimate the rotation number of QPO stabilized by the DFC. We show that the orbit of the DFC is consistent with the unstable QPO perturbed by a small state difference resulting from the time-delay mismatch, implying that the DFC can certainly stabilize the unstable QPO.

  18. Stabilization and PID tuning algorithms for second-order unstable processes with time-delays.

    PubMed

    Seer, Qiu Han; Nandong, Jobrun

    2017-03-01

    Open-loop unstable systems with time-delays are often encountered in process industry, which are often more difficult to control than stable processes. In this paper, the stabilization by PID controller of second-order unstable processes, which can be represented as second-order deadtime with an unstable pole (SODUP) and second-order deadtime with two unstable poles (SODTUP), is performed via the necessary and sufficient criteria of Routh-Hurwitz stability analysis. The stability analysis provides improved understanding on the existence of a stabilizing range of each PID parameter. Three simple PID tuning algorithms are proposed to provide desired closed-loop performance-robustness within the stable regions of controller parameters obtained via the stability analysis. The proposed PID controllers show improved performance over those derived via some existing methods.

  19. The unstable CO2 feedback cycle on ocean planets

    NASA Astrophysics Data System (ADS)

    Kitzmann, D.; Alibert, Y.; Godolt, M.; Grenfell, J. L.; Heng, K.; Patzer, A. B. C.; Rauer, H.; Stracke, B.; von Paris, P.

    2015-10-01

    Ocean planets are volatile-rich planets, not present in our Solar system, which are thought to be dominated by deep, global oceans. This results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. Therefore, instead of a carbonate-silicate cycle like on the Earth, the atmospheric carbon dioxide concentration is governed by the capability of the ocean to dissolve carbon dioxide (CO2). In our study, we focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a fundamental quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree. In contrast to the stabilizing carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle feedback on ocean planets is negative and has strong destabilizing effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle can severely limit the extension of the habitable zone for ocean planets.

  20. The unstable CO2 feedback cycle on ocean planets

    NASA Astrophysics Data System (ADS)

    Kitzmann, Daniel; Alibert, Yann; Godolt, Mareike; Grenfell, John Lee; Heng, Kevin; Patzer, Beate; Rauer, Heike; Stracke, Barbara; von Paris, Philip

    2015-12-01

    Ocean planets are volatile rich planets, not present in our Solar System, which are dominated by deep, global oceans. Theoretical considerations and planet formation modeling studies suggest that extrasolar ocean planets should be a very common type of planet. One might therefore expect that low-mass ocean planets would be ideal candidates when searching for habitable exoplanets, since water is considered to be an essential requirement for life. However, a very large global ocean can also strongly influence the climate.The high pressure at the oceans bottom results in the formation of high-pressure water ice, separating the planetary crust from the liquid ocean and, thus, also from the atmosphere. In our study we, therefore, focus on the CO2 cycle between the atmosphere and the ocean which determines the atmospheric CO2 content. The atmospheric amount of CO2 is a fundamental quantity for assessing the potential habitability of the planet's surface because of its strong greenhouse effect, which determines the planetary surface temperature to a large degree.In contrast to the stabilising carbonate-silicate cycle regulating the long-term CO2 inventory of the Earth atmosphere, we find that the CO2 cycle on ocean planets is positive and has strong destabilising effects on the planetary climate. By using a chemistry model for oceanic CO2 dissolution and an atmospheric model for exoplanets, we show that the CO2 feedback cycle is severely limiting the potential habitability of ocean planets.

  1. Low-energy dipole modes in unstable nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Sagawa, H.

    2001-01-01

    Enhancement of electric dipole (E1) strength at low energy is investigated in light neutron and proton drip-line nuclei with halo or skin by large scale shell model calculations. Large E1 strength are found in low excitation energy region below 5 MeV in 11Li, 12Be and 13O. Both the effects of extended halo or skin wave functions and the coherence in the transition amplitudes are important to enhance the E1 strength. The particle (hole)- vibration coupling model is shown to explain the splitting of the low energy E1 strength in 11Li and 13O. Melting of the shell magicity at N=8 and Z=8 is pointed out. Pigmy resonances in oxygen isotopes are also studied. The pigmy strength below E x = 15 MeV are shown to have about 10 % of the Thomas- Reiche-Kuhn (TRK) sum rule and more than 40 % of the cluster sum rule.

  2. Material instability in granular assemblies from fundamentally different models

    NASA Astrophysics Data System (ADS)

    Sibille, L.; Nicot, F.; Donzé, F. V.; Darve, F.

    2007-03-01

    Three fundamentally different models: a phenomenological constitutive relation, a micro-mechanical model and direct numerical simulations by Distinct Element Method (DEM) are compared in this paper. In addition, the local form of Hill's sufficient condition of stability (i.e. the vanishing of the second-order work d2W) is considered to describe material instabilities in granular assemblies. Stress probes in the axisymmetric plane of stress increments are achieved with all three models to check whether d2W vanishes at different stress-strain states. For all the models, cones of unstable stress directions (cones of stress probe directions for which d2W = 0) are found and they appear for stress states strictly inside the plastic limit condition. Thus, independently of the model, a bifurcation domain exists inside the plastic limit condition which can describe the sudden collapses of sand samples observed in laboratory tests before reaching the Mohr-Coulomb criterion. Taking advantage of the different models considered, the vanishing of the second-order work is linked to the existence of non-associated plastic strains and to micro-mechanical bases. Copyright

  3. Chaotic attractors based on unstable dissipative systems via third-order differential equation

    NASA Astrophysics Data System (ADS)

    Campos-Cantón, E.

    2016-07-01

    In this paper, we present an approach how to yield 1D, 2D and 3D-grid multi-scroll chaotic systems in R3 based on unstable dissipative systems via third-order differential equation. This class of systems is constructed by a switching control law(SCL) changing the equilibrium point of an unstable dissipative system. The switching control law that governs the position of the equilibrium point varies according to the number of scrolls displayed in the attractor.

  4. Transfer Maneuvers Between Periodic Earth-Moon Orbits Using Stable an Unstable Manifolds

    NASA Astrophysics Data System (ADS)

    Marcuzzi, J. P.; Leiva, A. M.; Briozzo, C. B.

    In this paper we have determined the stable and unstable manifold of six unstable periodic orbits (h=-1,586656) in an appropriate surface of section in the Earth-Moon coplanar circular restricted three body problem. The cost diagrams give account of a low transfer tax on using this technique and they would allow to determine the lower cost regions in order to apply the required propellent in each maneuver. FULL TEXT IN SPANISH

  5. Implementing fundamental care in clinical practice.

    PubMed

    Feo, Rebecca; Conroy, Tiffany; Alderman, Jan; Kitson, Alison

    2017-04-05

    Modern healthcare environments are becoming increasingly complex. Delivering high-quality fundamental care in these environments is challenging for nurses and has been the focus of recent media, policy, academic and public scrutiny. Much of this attention arises from evidence that fundamental care is being neglected or delivered inadequately. There are an increasing number of standards and approaches to the delivery of fundamental care, which may result in confusion and additional documentation for nurses to complete. This article provides nurses with an approach to reframe their thinking about fundamental care, to ensure they meet patients' care needs and deliver holistic, person-centred care.

  6. Ontogeny of Unstable Chromosomes Generated by Telomere Error in Budding Yeast.

    PubMed

    Beyer, Tracey; Weinert, Ted

    2016-10-01

    DNA replication errors at certain sites in the genome initiate chromosome instability that ultimately leads to stable genomic rearrangements. Where instability begins is often unclear. And, early instability may form unstable chromosome intermediates whose transient nature also hinders mechanistic understanding. We report here a budding yeast model that reveals the genetic ontogeny of genome rearrangements, from initial replication error to unstable chromosome formation to their resolution. Remarkably, the initial error often arises in or near the telomere, and frequently forms unstable chromosomes. Early unstable chromosomes may then resolve to an internal "collection site" where a dicentric forms and resolves to an isochromosome (other outcomes are possible at each step). The initial telomere-proximal unstable chromosome is increased in mutants in telomerase subunits, Tel1, and even Rad9, with no known telomere-specific function. Defects in Tel1 and in Rrm3, a checkpoint protein kinase with a role in telomere maintenance and a DNA helicase, respectively, synergize dramatically to generate unstable chromosomes, further illustrating the consequence of replication error in the telomere. Collectively, our results suggest telomeric replication errors may be a common cause of seemingly unrelated genomic rearrangements located hundreds of kilobases away.

  7. Azimuthally unstable resonators for high-power CO[sub 2] lasers with annular gain media

    SciTech Connect

    Ehrlichmann, D.; Habich, U.; Plum, H.D.; Loosen, P.; Herziger, G. )

    1994-06-01

    Stable-unstable resonators have proved suitable for the extraction of a high-quality beam from a gain area that consists of a rectangular slab. Such gain areas have two substantially different transverse dimensions, and the resonators are stable in the small dimension while unstable in the larger one. Using off-axis unstable resonators avoids a central beam obscuration and improves beam quality. The adaptation of stable-unstable resonators to annular gain areas is described in this paper. The resulting resonators are stable in the radial direction and unstable in the azimuthal direction. Different unstable resonators, wound to match the annular geometry, are presented. The resonator modes are calculated numerically using a 3D-diffraction code that considers gain and misalignment. Resonator design parameters are obtained from a geometrical description of the resonator. Experimental results from a diffusion-cooled CO[sub 2] laser confirm theoretical predictions and show that the resonators are capable of extracting beams that are nearly diffraction-limited with high efficiency from an annular gain medium. Output powers of 2 kW have been obtained from a gain length of 1.8 m.

  8. Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

    NASA Astrophysics Data System (ADS)

    Han, Jian; Jiang, Nan; Tian, Yan

    2011-08-01

    Experimental investigation of hypersonic boundary layer instability on a cone is performed at Mach number 6 in a hypersonic wind tunnel. Time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface in the streamwise direction to investigate the development of the unstable disturbance. Wavelet transform is employed as a mathematical tool to obtain the multi-scale characteristics of fluctuating surface-thermal-flux both in the temporal and spectrum space. The conditional sampling algorithm using wavelet coefficient as an index is put forward to extract the unstable disturbance waveform from the fluctuating surface-thermal-flux signals. The generic waveform for the second mode unstable disturbance is obtained by a phase-averaging technique. The development of the unstable disturbance in the streamwise direction is assessed both in the temporal and spectrum space. Our study shows that the local unstable disturbance detection method based on wavelet transformation offers an alternative powerful tool in studying the hypersonic unstable mode of laminar-turbulent transition. It is demonstrated that, at hypersonic speeds, the dominant flow instability is the second mode, which governs the course of laminar-turbulent transition of sharp cone boundary layer.

  9. Ontogeny of Unstable Chromosomes Generated by Telomere Error in Budding Yeast

    PubMed Central

    Weinert, Ted

    2016-01-01

    DNA replication errors at certain sites in the genome initiate chromosome instability that ultimately leads to stable genomic rearrangements. Where instability begins is often unclear. And, early instability may form unstable chromosome intermediates whose transient nature also hinders mechanistic understanding. We report here a budding yeast model that reveals the genetic ontogeny of genome rearrangements, from initial replication error to unstable chromosome formation to their resolution. Remarkably, the initial error often arises in or near the telomere, and frequently forms unstable chromosomes. Early unstable chromosomes may then resolve to an internal "collection site" where a dicentric forms and resolves to an isochromosome (other outcomes are possible at each step). The initial telomere-proximal unstable chromosome is increased in mutants in telomerase subunits, Tel1, and even Rad9, with no known telomere-specific function. Defects in Tel1 and in Rrm3, a checkpoint protein kinase with a role in telomere maintenance and a DNA helicase, respectively, synergize dramatically to generate unstable chromosomes, further illustrating the consequence of replication error in the telomere. Collectively, our results suggest telomeric replication errors may be a common cause of seemingly unrelated genomic rearrangements located hundreds of kilobases away. PMID:27716774

  10. Far-field beam quality evaluation of high-power unstable resonators TEA CO2 Laser

    NASA Astrophysics Data System (ADS)

    Guo, Ruhai; Chen, Ning; Shi, Kui; Wang, Bing

    2013-05-01

    High average power pulsed TEA CO2 lasers have many important applications, such as laser manufacturing, military applications, but there rarely have reports about the theoretical and experimental studies on the virtual confocus resonator of pulsed TEA CO2 laser, especially its far field optical quality. Based on the real date of the unstable resonator modified by the stable resonator of high power TEA CO2, three common theoretical evaluations and analyzes were conducted and compared with the measured results of far field light intensity distribution with 2 kW designed unstable resonator laser with the block ratio is ɛ=0.404. The results show that the unstable resonator can obtain near diffraction limitation and high optical quality beam. The β factor is smaller than 4 times than the stable resonator. Furthermore, the smaller block factor can make higher power in bucket for the unstable resonator. The comprehensive prediction and evaluation of designed unstable resonator need to synthetically use these three theoretical methods of the evaluations. The simulation results, with considering the optical aberration, heat distortion and atmospheric effect, agree well with the real recording image by the infrared imaging system in the distance of 300m. The research of this paper has very important reference value for evaluating the tactical effectiveness and optimization design of high power TEA CO2 laser system with different unstable resonators.

  11. Particle accelerators inside spinning black holes.

    PubMed

    Lake, Kayll

    2010-05-28

    On the basis of the Kerr metric as a model for a spinning black hole accreting test particles from rest at infinity, I show that the center-of-mass energy for a pair of colliding particles is generically divergent at the inner horizon. This shows not only that classical black holes are internally unstable, but also that Planck-scale physics is a characteristic feature within black holes at scales much larger that the Planck length. The novel feature of the divergence discussed here is that the phenomenon is present only for black holes with rotation, and in this sense it is distinct from the well-known Cauchy horizon instability.

  12. Fundamental cosmology in the E-ELT era: the status and future role of tests of fundamental coupling stability

    NASA Astrophysics Data System (ADS)

    Martins, C. J. A. P.

    2015-01-01

    The observational evidence for the recent acceleration of the universe demonstrates that canonical theories of cosmology and particle physics are incomplete—if not incorrect—and that new physics is out there, waiting to be discovered. The most fundamental task for the next generation of astrophysical facilities is therefore to search for, identify and ultimately characterise this new physics. Here we highlight recent efforts along these lines, mostly focusing on ongoing work by CAUP's Dark Side Team aiming to develop some of the science case and optimise observational strategies for forthcoming facilities. The discussion is centred on tests of the stability of fundamental couplings (since the provide a direct handle on new physics), but synergies with other probes are also briefly considered. The goal is to show how a new generation of precision consistency tests of the standard paradigm will soon become possible.

  13. Unstable infiltration fronts in porous media on laboratory scale

    NASA Astrophysics Data System (ADS)

    Schuetz, Cindi; Neuweiler, Insa

    2014-05-01

    Water flow and transport of substances in the unsaturated zone are important processes for the quality and quantity of water in the hydrologic cycle. The water movement through preferential paths is often much faster than standard models (e. g. Richards equation in homogeneous porous media) predict. One type/phenomenon of preferential flow can occur during water infiltration into coarse and/or dry porous media: the so-called gravity-driven fingering flow. To upscale the water content and to describe the averaged water fluxes in order to couple models of different spheres it is necessary to understand and to quantify the behavior of flow instabilities. We present different experiments of unstable infiltration in homogeneous and heterogeneous structures to analyze development and morphology of gravity-driven fingering flow on the laboratory scale. Experiments were carried out in two-dimensional and three-dimensional sand tanks as well as in larger two-dimensional sand tanks with homogeneous and heterogeneous filling of sand and glass beads. In the small systems, water content in the medium was measured at different times. We compare the experiments to prediction of theoretical approaches (e.g. Saffman and Taylor, 1958; Chuoke et al., 1959; Philip 1975a; White et al., 1976; Parlange and Hill, 1976a; Glass et al., 1989a; Glass et al., 1991; Wang et al., 1998c) that quantify properties of the gravity-driven fingers. We use hydraulic parameters needed for the theoretical predictions (the water-entry value (hwe), van Genuchten parameter (Wang et al., 1997, Wang et al., 2000) and saturated conductivity (Ks), van Genuchten parameter (Guarracino, 2007) to simplify the prediction of the finger properties and if necessary to identify a constant correction factor. We find in general that the finger properties correspond well to theoretical predictions. In heterogeneous settings, where fine inclusions are embedded into a coarse material, the finger properties do not change much

  14. Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles

    NASA Technical Reports Server (NTRS)

    Evans, Helen H.; Horng, Min-Fen; Ricanati, Marlene; Diaz-Insua, M.; Jordan, Robert; Schwartz, Jeffrey L.

    2003-01-01

    The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.

  15. Fundamental modes in waveguide pipe twisted by saturated double-well potential

    NASA Astrophysics Data System (ADS)

    Chen, Gui-Hua; Wang, Hong-Cheng; Chen, Zhao-Pin; Liu, Yan

    2017-02-01

    We study fundamental modes trapped in a rotating ring with a saturated nonlinear double-well potential. This model, which is based on the nonlinear Schrödinger equation, can be constructed in a twisted waveguide pipe in terms of light propagation, or in a Bose-Einstein condensate (BEC) loaded into a toroidal trap under a combination of a rotating π-out-of-phase linear potential and nonlinear pseudopotential induced by means of a rotating optical field and the Feshbach resonance. Three types of fundamental modes are identified in this model, one symmetric and the other two asymmetric. The shape and stability of the modes and the transitions between different modes are investigated in the first rotational Brillouin zone. A similar model used a Kerr medium to build its nonlinear potential, but we replace it with a saturated nonlinear medium. The model exhibits not only symmetry breaking, but also symmetry recovery. A specific type of unstable asymmetric mode is also found, and the evolution of the unstable asymmetric mode features Josephson oscillation between two linear wells. By considering the model as a configuration of a BEC system, the ground state mode is identified among these three types, which characterize a specific distribution of the BEC atoms around the trap.

  16. Direct reactions for nuclear structure required for fundamental symmetry tests

    NASA Astrophysics Data System (ADS)

    Garrett, P. E.; Rand, E. T.; Diaz Varela, A.; Ball, G. C.; Bildstein, V.; Faestermann, T.; Hadinia, B.; Hertenberger, R.; Jamieson, D. S.; Jigmeddorj, B.; Leach, K. G.; Svensson, C. E.; Wirth, H.-F.

    2016-09-01

    A program of nuclear structure studies to support fundamental symmetry tests has been initiated. Motivated by the search for an electric dipole moment in 199Hg, the structure in the vicinity has been explored via direct reaction studies. To date, these have included the 198,200Hg(d, d') inelastic scattering reactions, with the aim to obtain information on the E2 and E3 strength distributions, and the 198Hg(d, p) and 200Hg(d, t) reactions to obtain information on the single-particle states in 199Hg. The studies using the 200Hg targets have been fully analyzed using the FRESCO reaction code yielding the E2 and E3 strength distribution to 4 MeV in excitation energy, and the (d, t) single- particle strength to over 3 MeV in excitation energy.

  17. Global stability of trajectories of inertial particles within domains of instability

    NASA Astrophysics Data System (ADS)

    Sudarsanam, Senbagaraman; Tallapragada, Phanindra

    2017-01-01

    Finite sized particles exhibit complex dynamics that differ from that of the underlying fluid flow. These dynamics such as chaotic motion, size dependent clustering and separation can have important consequences in many natural and engineered settings. Though fluid streamlines are global attractors for the inertial particles, regions of local instability can exist where the inertial particle can move away from the fluid streamlines. Identifying and manipulating the location of the so called stable and unstable regions in the fluid flow can find important applications in microfluidics. Research in the last two decades has identified analytical criteria that can partition the fluid domain into locally stable and unstable regions. In this paper, we identify two new mechanisms by which neutrally buoyant inertial particles could exhibit globally stable dynamics in the regions of the fluid flow that are thought to be locally unstable and demonstrate this with examples. The examples we use are restricted to the simpler case of time independent fluid flows.

  18. Global stability of inertial particle trajectories in a two dimensional flow

    NASA Astrophysics Data System (ADS)

    Sudarsanam, Senbagaraman; Tallapragada, Phanindra

    2016-11-01

    The trajectories of inertial particles moving even in a two dimensional fluid flow exhibit complex dynamics, in particular preferential clustering in some sub domains of the fluid. This preferential clustering is influenced by the vorticity field. Based on the Maxey-Riley equation, several Eulerian criteria have been proposed in the past that classify the fluid region into local stable and unstable regions which roughly act as attracting and repelling regions for inertial particles. We demonstrate through examples that the locally unstable regions of the fluid domain can nevertheless act as global attractors. This global stability of unstable regions can partly explain the experimental evidence that particle clustering in fluids is more robust than usually predicted. The example relies on fluid flow generated by point vortices. Such vortex fields are often encountered in several microfluidic flows where the manipulation of the motion of inertial particles has several important applications.

  19. Quantum Particles From Quantum Information

    NASA Astrophysics Data System (ADS)

    Görnitz, T.; Schomäcker, U.

    2012-08-01

    Many problems in modern physics demonstrate that for a fundamental entity a more general conception than quantum particles or quantum fields are necessary. These concepts cannot explain the phenomena of dark energy or the mind-body-interaction. Instead of any kind of "small elementary building bricks", the Protyposis, an abstract and absolute quantum information, free of special denotation and open for some purport, gives the solution in the search for a fundamental substance. However, as long as at least relativistic particles are not constructed from the Protyposis, such an idea would remain in the range of natural philosophy. Therefore, the construction of relativistic particles without and with rest mass from quantum information is shown.

  20. Electron Heating in a Relativistic, Weibel-unstable Plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Rahul; Eichler, David; Gedalin, Michael

    2015-06-01

    The dynamics of two initially unmagnetized relativistic counter-streaming homogeneous ion-electron plasma beams are simulated in two dimensions (2D) using the particle-in-cell (PIC) method. It is shown that current filaments, which form due to the Weibel instability, develop a large-scale longitudinal electric field in the direction opposite to the current carried by the filaments as predicted by theory. This field, which is partially inductive and partially electrostatic, is identified as the main source of net electron acceleration, greatly exceeding that due to magnetic field decay at later stages. The transverse electric field, although larger than the longitudinal field, is shown to play a smaller role in heating electrons, contrary to previous claims. It is found that in one dimension, the electrons become strongly magnetized and are not accelerated beyond their initial kinetic energy. Rather, the heating of the electrons is enhanced by the bending and break up of the filaments, which releases electrons that would otherwise be trapped within a single filament and slow the development of the Weibel instability (i.e., the magnetic field growth) via induction as per Lenz’s law. In 2D simulations, electrons are heated to about one quarter of the initial kinetic energy of ions. The magnetic energy at maximum is about 4%, decaying to less than 1% by the end of the simulation. The ions are found to gradually decelerate until the end of the simulation, by which time they retain a residual anisotropy of less than 10%.

  1. ELECTRON HEATING IN A RELATIVISTIC, WEIBEL-UNSTABLE PLASMA

    SciTech Connect

    Kumar, Rahul; Eichler, David; Gedalin, Michael

    2015-06-20

    The dynamics of two initially unmagnetized relativistic counter-streaming homogeneous ion–electron plasma beams are simulated in two dimensions (2D) using the particle-in-cell (PIC) method. It is shown that current filaments, which form due to the Weibel instability, develop a large-scale longitudinal electric field in the direction opposite to the current carried by the filaments as predicted by theory. This field, which is partially inductive and partially electrostatic, is identified as the main source of net electron acceleration, greatly exceeding that due to magnetic field decay at later stages. The transverse electric field, although larger than the longitudinal field, is shown to play a smaller role in heating electrons, contrary to previous claims. It is found that in one dimension, the electrons become strongly magnetized and are not accelerated beyond their initial kinetic energy. Rather, the heating of the electrons is enhanced by the bending and break up of the filaments, which releases electrons that would otherwise be trapped within a single filament and slow the development of the Weibel instability (i.e., the magnetic field growth) via induction as per Lenz’s law. In 2D simulations, electrons are heated to about one quarter of the initial kinetic energy of ions. The magnetic energy at maximum is about 4%, decaying to less than 1% by the end of the simulation. The ions are found to gradually decelerate until the end of the simulation, by which time they retain a residual anisotropy of less than 10%.

  2. Individual differences in fundamental social motives.

    PubMed

    Neel, Rebecca; Kenrick, Douglas T; White, Andrew Edward; Neuberg, Steven L

    2016-06-01

    Motivation has long been recognized as an important component of how people both differ from, and are similar to, each other. The current research applies the biologically grounded fundamental social motives framework, which assumes that human motivational systems are functionally shaped to manage the major costs and benefits of social life, to understand individual differences in social motives. Using the Fundamental Social Motives Inventory, we explore the relations among the different fundamental social motives of Self-Protection, Disease Avoidance, Affiliation, Status, Mate Seeking, Mate Retention, and Kin Care; the relationships of the fundamental social motives to other individual difference and personality measures including the Big Five personality traits; the extent to which fundamental social motives are linked to recent life experiences; and the extent to which life history variables (e.g., age, sex, childhood environment) predict individual differences in the fundamental social motives. Results suggest that the fundamental social motives are a powerful lens through which to examine individual differences: They are grounded in theory, have explanatory value beyond that of the Big Five personality traits, and vary meaningfully with a number of life history variables. A fundamental social motives approach provides a generative framework for considering the meaning and implications of individual differences in social motivation. (PsycINFO Database Record

  3. Fundamentals of Physics, Problem Supplement No. 1

    NASA Astrophysics Data System (ADS)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2000-05-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.

  4. Fundamentals of Physics, Student's Solutions Manual

    NASA Astrophysics Data System (ADS)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2000-07-01

    No other book on the market today can match the success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving.

  5. Fundamentals of Physics, 7th Edition

    NASA Astrophysics Data System (ADS)

    Halliday, David; Resnick, Robert; Walker, Jearl

    2004-05-01

    No other book on the market today can match the 30-year success of Halliday, Resnick and Walker's Fundamentals of Physics! In a breezy, easy-to-understand style the book offers a solid understanding of fundamental physics concepts, and helps readers apply this conceptual understanding to quantitative problem solving. This book offers a unique combination of authoritative content and stimulating applications.

  6. Particle astrophysics

    NASA Technical Reports Server (NTRS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    1991-01-01

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  7. Particle astrophysics

    NASA Astrophysics Data System (ADS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  8. Particle separator

    DOEpatents

    Hendricks, Charles D.

    1990-01-01

    Method and apparatus (10) are provided for separating and classifying particles (48,50,56) by dispersing the particles within a fluid (52) that is upwardly flowing within a cone-shaped pipe (12) that has its large end (20) above its small end (18). Particles of similar size and shape (48,50) migrate to individual levels (A,B) within the flowing fluid. As the fluid is deflected by a plate (42) at the top end of the pipe (12), the smallest particles are collected on a shelf-like flange (40). Ever larger particles are collected as the flow rate of the fluid is increased. To prevent particle sticking on the walls (14) of the pipe (12), additional fluid is caused to flow into the pipe (12) through holes (68) that are specifically provided for that purpose. Sticking is further prevented by high frequency vibrators (70) that are positioned on the apparatus (10).

  9. Particle therapy

    SciTech Connect

    Raju, M.R.

    1993-09-01

    Particle therapy has a long history. The experimentation with particles for their therapeutic application got started soon after they were produced in the laboratory. Physicists played a major role in proposing the potential applications in radiotherapy as well as in the development of particle therapy. A brief review of the current status of particle radiotherapy with some historical perspective is presented and specific contributions made by physicists will be pointed out wherever appropriate. The rationale of using particles in cancer treatment is to reduce the treatment volume to the target volume by using precise dose distributions in three dimensions by using particles such as protons and to improve the differential effects on tumors compared to normal tissues by using high-LET radiations such as neutrons. Pions and heavy ions combine the above two characteristics.

  10. Supergranular-scale magnetic flux emergence beneath an unstable filament

    NASA Astrophysics Data System (ADS)

    Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato, Y.

    2015-11-01

    may play a fundamental role, which is helped by the emergence. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  11. Particle-Charge Spectrometer

    NASA Technical Reports Server (NTRS)

    Fuerstenau, Stephen; Wilson, Gregory R.

    2008-01-01

    An instrument for rapidly measuring the electric charges and sizes (from approximately 1 to approximately 100 micrometers) of airborne particles is undergoing development. Conceived for monitoring atmospheric dust particles on Mars, instruments like this one could also be used on Earth to monitor natural and artificial aerosols in diverse indoor and outdoor settings for example, volcanic regions, clean rooms, powder-processing machinery, and spray-coating facilities. The instrument incorporates a commercially available, low-noise, ultrasensitive charge-sensing preamplifier circuit. The input terminal of this circuit--the gate of a field-effect transistor--is connected to a Faraday-cage cylindrical electrode. The charged particles of interest are suspended in air or other suitable gas that is made to flow along the axis of the cylindrical electrode without touching the electrode. The flow can be channeled and generated by any of several alternative means; in the prototype of this instrument, the gas is drawn along a glass capillary tube (see upper part of figure) coaxial with the electrode. The size of a particle affects its rate of acceleration in the flow and thus affects the timing and shape of the corresponding signal peak generated by the charge-sensing amplifier. The charge affects the magnitude (and thus also the shape) of the signal peak. Thus, the signal peak (see figure) conveys information on both the size and electric charge of a sensed particle. In experiments thus far, the instrument has been found to be capable of measuring individual aerosol particle charges of magnitude greater than 350 e (where e is the fundamental unit of electric charge) with a precision of +/- 150 e. The instrument can sample particles at a rate as high as several thousand per second.

  12. Motion of spheroidal particles in vertical shear flows

    NASA Astrophysics Data System (ADS)

    Broday, David; Fichman, Mati; Shapiro, Michael; Gutfinger, Chaim

    1998-01-01

    The motion of non-neutrally buoyant prolate spheroidal particles in vertical shear flows is investigated. Using the generalized Faxen law, we calculate the hydrodynamic forces and moments acting on such inertial and inertialess particles, and their trajectories. The calculations are done for (i) freely rotating particles, and (ii) particles with orientations fixed by means of an external torque exerted by a strong orienting field. Inertial particles are found to migrate across the streamlines, and their trajectories differ considerably from those calculated for inertialess particles. Neutrally buoyant spheroids, inertial or not, which either freely rotate or have fixed orientations in shear flows, translate along the streamlines. Non-neutrally buoyant inertialess spheroids freely moving in simple shear flow translate along periodic trajectories with no net lateral drift. In contrast, inertial particles under similar flow conditions drift laterally toward locations characterized by higher local velocities in a direction opposing gravity. The motion of non-neutrally buoyant inertial particles with fixed orientations may be unstable with the drift velocity growing exponentially with time. Conditions for the occurrence of this unstable motion are formulated analytically in terms of particle and flow parameters. In general, the rate of drift depends on particle shape, via its aspect ratio, and its inertia.

  13. Magnetic particles

    NASA Technical Reports Server (NTRS)

    Chang, Manchium (Inventor); Colvin, Michael S. (Inventor)

    1989-01-01

    Magnetic polymer particles are formed by swelling porous, polymer particles and impregnating the particles with an aqueous solution of precursor magnetic metal salt such as an equimolar mixture of ferrous chloride and ferric chloride. On addition of a basic reagent such as dilute sodium hydroxide, the metal salts are converted to crystals of magnetite which are uniformly contained througout the pores of the polymer particle. The magnetite content can be increased and neutral buoyancy achieved by repetition of the impregnaton and neutralization steps to adjust the magnetite content to a desired level.

  14. Physics of windblown particles

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Leach, Rodman; Marshall, John R.; White, Bruce; Iversen, James D.; Nickling, William G.; Gillette, Dale; Sorensen, Michael

    1987-01-01

    A laboratory facility proposed for the Space Station to investigate fundamental aspects of windblown particles is described. The experiments would take advantage of the environment afforded in earth orbit and would be an extension of research currently being conducted on the geology and physics of windblown sediments on earth, Mars, and Venus. Aeolian (wind) processes are reviewed in the planetary context, the scientific rational is given for specific experiments to be conducted, the experiment apparatus (the Carousel Wind Tunnel, or CWT) is described, and a plan presented for implementing the proposed research program.

  15. Effect of an Unstable Load on Primary and Stabilizing Muscles During the Bench Press.

    PubMed

    Ostrowski, Stephanie J; Carlson, Lara A; Lawrence, Michael A

    2017-02-01

    Ostrowski, SJ, Carlson, LA, and Lawrence, MA. Effect of an unstable load on primary and stabilizing muscles during the bench press. J Strength Cond Res 31(2): 430-434, 2017-Unstable resistance exercises are performed to increase activity of stabilizing muscles. The premise is that this increase in activity will yield greater strength gains than traditional resistance exercises. The purpose of this study was to determine if an unstable load increases muscle activity of stabilizing muscles during a bench press as compared with a standard bench press with a typical load. Fifteen resistance-trained males (age 24.2 ± 2.7 years, mass 84.8 ± 12.0 kg, height 1.77 ± 0.05 m, weight lifting experience 9.9 ± 3.4 years, and bench press 1 repetition maximum [1RM] 107.5 ± 25.9 kg) volunteered for this study. Subjects pressed 2 sets of 5 repetitions in both stable (75% 1RM) and unstable (60% 1RM) conditions using a standard barbell and a flexible Earthquake bar, respectively. Surface electromyography was used to detect muscle activity of primary movers (pectoralis major, anterior deltoid, and triceps) and stabilizing musculature (latissimus dorsi, middle and posterior deltoid, biceps brachii, and upper trapezius). Muscle activity was compared using a multivariate analysis of variance to determine significant (p ≤ 0.05) phase and condition differences. The right and left biceps and the left middle deltoid were significantly more active in the unstable condition. Some of the stabilizing muscles were found to be significantly more active in the unstable condition with 15% less weight. Therefore, bench pressing with an unstable load appears promising in activating stabilizing musculature compared with pressing a typical barbell.

  16. Cosmology and particle physics

    NASA Technical Reports Server (NTRS)

    Turner, Michael S.

    1988-01-01

    The interplay between cosmology and elementary particle physics is discussed. The standard cosmology is reviewed, concentrating on primordial nucleosynthesis and discussing how the standard cosmology has been used to place constraints on the properties of various particles. Baryogenesis is discussed, showing how a scenario in which the B-, C-, and CP-violating interactions in GUTs provide a dynamical explanation for the predominance of matter over antimatter and for the present baryon-to-photon ratio. It is shown how the very early dynamical evolution of a very weakly coupled scalar field which is initially displaced from the minimum of its potential may explain a handful of very fundamental cosmological facts which are not explained by the standard cosmology.

  17. Particle preconcentrator

    DOEpatents

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    2000-01-01

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  18. Particle preconcentrator

    SciTech Connect

    Linker, K.L.; Conrad, F.J.; Custer, C.A.; Rhykerd, C.L. Jr.

    1998-12-29

    An apparatus and method are disclosed for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents. 3 figs.

  19. Particle preconcentrator

    SciTech Connect

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    1998-01-01

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  20. Particle preconcentrator

    SciTech Connect

    Linker, Kevin L.; Conrad, Frank J.; Custer, Chad A.; Rhykerd, Jr., Charles L.

    2005-09-20

    An apparatus and method for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a pervious screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  1. Particle preconcentrator

    SciTech Connect

    Linker, K.L.; Conrad, F.J.; Custer, C.A.; Rhykerd, C.L. Jr

    2000-07-11

    An apparatus and method are disclosed for preconcentrating particles and vapors. The preconcentrator apparatus permits detection of highly diluted amounts of particles in a main gas stream, such as a stream of ambient air. A main gas stream having airborne particles entrained therein is passed through a previous screen. The particles accumulate upon the screen, as the screen acts as a sort of selective particle filter. The flow of the main gas stream is then interrupted by diaphragm shutter valves, whereupon a cross-flow of carrier gas stream is blown parallel past the faces of the screen to dislodge the accumulated particles and carry them to a particle or vapor detector, such as an ion mobility spectrometer. The screen may be heated, such as by passing an electrical current there through, to promote desorption of particles therefrom during the flow of the carrier gas. Various types of screens are disclosed. The apparatus and method of the invention may find particular utility in the fields of narcotics, explosives detection and chemical agents.

  2. Fundamental and harmonic radiation in type III solar radio bursts

    NASA Technical Reports Server (NTRS)

    Robinson, P. A.; Cairns, I. H.

    1994-01-01

    Type III solar radio bursts are investigated by modeling the propagation of the electron beam and the generation and subsequent propagation of waves to the observer. Predictions from this model are compared in detail with particle, Langmuir wave, and radio data from the International Sun Earth Explorer-3 (ISSE-3) spacecraft and with other observations to clarify the roles of fundamental and harmonic emission in type III radio bursts. Langmuir waves are seen only after the arrival of the beam, in accord with the standard theory. These waves persist after a positive beam slope is last resolved, implying that sporadic positive slopes persist for some time, unresolved but in accord with the predictions of stochastic growth theory. Local electromagnetic emission sets in only after Langmuir waves are seen, in accord with the standard theory, which relies on nonlinear processes involving Langmuir waves. In the events investigated here, fundamental radiation appears to dominate early in the event, followed and/or accompanied by harmonic radiation after the peak, with a long-lived tail of multiply scattered fundamental or harmonic emission extending long afterwards. These results are largely independent of, but generally consistent with, the conclusions of earlier works.

  3. Atomically Precise Colloidal Metal Nanoclusters and Nanoparticles: Fundamentals and Opportunities.

    PubMed

    Jin, Rongchao; Zeng, Chenjie; Zhou, Meng; Chen, Yuxiang

    2016-09-28

    Colloidal nanoparticles are being intensely pursued in current nanoscience research. Nanochemists are often frustrated by the well-known fact that no two nanoparticles are the same, which precludes the deep understanding of many fundamental properties of colloidal nanoparticles in which the total structures (core plus surface) must be known. Therefore, controlling nanoparticles with atomic precision and solving their total structures have long been major dreams for nanochemists. Recently, these goals are partially fulfilled in the case of gold nanoparticles, at least in the ultrasmall size regime (1-3 nm in diameter, often called nanoclusters). This review summarizes the major progress in the field, including the principles that permit atomically precise synthesis, new types of atomic structures, and unique physical and chemical properties of atomically precise nanoparticles, as well as exciting opportunities for nanochemists to understand very fundamental science of colloidal nanoparticles (such as the stability, metal-ligand interfacial bonding, ligand assembly on particle surfaces, aesthetic structural patterns, periodicities, and emergence of the metallic state) and to develop a range of potential applications such as in catalysis, biomedicine, sensing, imaging, optics, and energy conversion. Although most of the research activity currently focuses on thiolate-protected gold nanoclusters, important progress has also been achieved in other ligand-protected gold, silver, and bimetal (or alloy) nanoclusters. All of these types of unique nanoparticles will bring unprecedented opportunities, not only in understanding the fundamental questions of nanoparticles but also in opening up new horizons for scientific studies of nanoparticles.

  4. High-accuracy mass spectrometry for fundamental studies.

    PubMed

    Kluge, H-Jürgen

    2010-01-01

    Mass spectrometry for fundamental studies in metrology and atomic, nuclear and particle physics requires extreme sensitivity and efficiency as well as ultimate resolving power and accuracy. An overview will be given on the global status of high-accuracy mass spectrometry for fundamental physics and metrology. Three quite different examples of modern mass spectrometric experiments in physics are presented: (i) the retardation spectrometer KATRIN at the Forschungszentrum Karlsruhe, employing electrostatic filtering in combination with magnetic-adiabatic collimation-the biggest mass spectrometer for determining the smallest mass, i.e. the mass of the electron anti-neutrino, (ii) the Experimental Cooler-Storage Ring at GSI-a mass spectrometer of medium size, relative to other accelerators, for determining medium-heavy masses and (iii) the Penning trap facility, SHIPTRAP, at GSI-the smallest mass spectrometer for determining the heaviest masses, those of super-heavy elements. Finally, a short view into the future will address the GSI project HITRAP at GSI for fundamental studies with highly-charged ions.

  5. [Internal Fixation of Sacro-iliac Joint in Unstable Fractures of the Pelvic Ring.].

    PubMed

    Soukup, B

    1999-01-01

    Unstable fractures of the pelvic ring are always serious injuries posing problems from many aspects. Among the most serious are definitely unstable fractures of the pelvic ring with both vertical and rotational instability, i. e. type C fractures according to AO classification scheme. The recent therapeutic concept recommends in case of these fractures an active reconstruction on the dorsal SI complex which evidently improves the final perspective of patients with such a severe injury. The author presents his own clinical experience and literary data relating to the treatment of 11 patients who underwent reconstruction in the region of dorsal sacro-iliac complex due to type C unstable fracture. Clinical results achieved on the basis of the evaluation of a group of 11 patients are favourable and promising despite a significant complexity of the problems of unstable pelvic fractures. In 9 patients the anatomical result on radiograph was excellent, 9 patients regained full mobility after the proper physiotherapy, 10 patients resumed their work and 6 patients resumed even professional sports activity. In the conclusion the author states that in suitable, mainly young and fully stabilized patients the reconstruction surgery on the dorsal pelvic SI segment is fully justified which is documented both by the literary data and his own experience. Key words: unstable pelvic fractures.

  6. Stable and unstable physicochemical hydrodynamic flows in thin-layer cell electrodeposition

    NASA Astrophysics Data System (ADS)

    Marshall, Guillermo; Mocskos, Esteban; Molina, Fernando V.; Dengra, Silvina

    2003-03-01

    Electrodeposition in thin cells of different orientations relative to gravity leads to stable and unstable flows. A vertical cell with the cathode (and low density fluid) at the top of the cell and the anode (and high density fluid) at the bottom give rise to a stable flow as long as there is no dendrite growth, while a vertical cell with the cathode (and low density fluid) at the bottom of the cell and high density fluid at the top, leads to unstable flows in the form of plumes. As a consequence, growth pattern formation is strongly inhibited in the unstable case. In the stable case, when growth starts, the concentration in a zone adjacent to the downwards growing finger is lowered giving rise to a gravity driven convective vortex ring wrapped to the finger. In the unstable case, the cathodic and anodic gravity driven rolls break into tongues expanding toward one another and mixing. Consequently, concentration gradients are strongly attenuated, resulting in little or none dendrite growth. For both cases, when dendrites grow, an electrically driven vortex ring exists at the dendrite tip; it allows fluid to penetrate the dendrite tip and to be ejected from its side. The interaction among vortex roll, vortex rings and dendrite growth is a complex three-dimensional problem, its complexity further enhanced in the unstable case. Here we elucidate their behavior through three-dimensional computational modeling.

  7. Force production during squats performed with a rotational resistance device under stable versus unstable conditions

    PubMed Central

    Moras, Gerard; Vázquez-Guerrero, Jairo

    2015-01-01

    [Purpose] Force production during a squat action on a rotational resistance device (RRD) under stable and unstable conditions. [Subjects and Methods] Twenty-one healthy males were asked to perform six sets of six repetitions of squats on an RRD on either stable or unstable surfaces. The stable and unstable sets were performed on different days. Muscular outputs were obtained from a linear encoder and a strain gauge fixed to a vest. [Results] Overall, the results showed no significant differences for any of the dependent variables across exercise modes. Forcemean outputs were higher in the concentric phase than in the eccentric phase for each condition, but there were no differences in velocity, time or displacement. The forcepeak was similar in the eccentric and concentric phases of movement under both stable and unstable conditions. There were no significant differences in forcemean between sets per condition or between conditions. [Conclusion] These results suggest that performing squats with a RRD achieves similar forcemean and forcepeak under stable and unstable conditions. The forcepeak produced is also similar in concentric and eccentric phases. PMID:26696707

  8. Unstable normal modes of low T /W dynamical instabilities in differentially rotating stars

    NASA Astrophysics Data System (ADS)

    Saijo, Motoyuki; Yoshida, Shin'ichirou

    2016-10-01

    We investigate the nature of low T /W dynamical instabilities in differentially rotating stars by means of linear perturbation. Here, T and W represent rotational kinetic energy and the gravitational binding energy of the star. This is the first attempt to investigate low T /W dynamical instabilities as a complete set of the eigenvalue problem. Our equilibrium configuration has "constant" specific angular momentum distribution, which potentially contains a singular solution in the perturbed enthalpy at a corotation radius in linear perturbation. We find the unstable normal modes of differentially rotating stars by solving the eigenvalue problem along the equatorial plane of the star, imposing the regularity condition on the center and the vanished enthalpy at the oscillating equatorial surface. We find that the existing pulsation modes become unstable due to the existence of the corotation radius inside the star. The feature of the unstable mode eigenfrequency and its eigenfunction in the linear analysis roughly agrees with that in three-dimensional hydrodynamical simulations in Newtonian gravity. Therefore, our normal mode analysis in the equatorial motion proves valid to find the unstable equilibrium stars efficiently. Moreover, the nature of the eigenfunction that oscillates between corotation and the surface radius for unstable stars requires reinterpretation of the pulsation modes in differentially rotating stars.

  9. Muscle co-contraction around the knee when walking with unstable shoes.

    PubMed

    Horsak, Brian; Heller, Mario; Baca, Arnold

    2015-02-01

    Walking with unstable shoes has been discussed to decrease joint loading. Typical estimates of joint loading using an inverse dynamic approach only account for net joint moments, not considering the potential role of muscular co-contraction. Therefore, the purpose of this study was to compare muscular co-contraction levels when walking with two different unstable shoe constructions (rocker-bottom and toning shoes) compared to walking with regular shoes. For each shoe condition, 12 healthy subjects walked with both, a regular shoe and with an unstable shoe at self-selected walking speed at a 10-m walkway. Surface EMG data of selected muscles were recorded and time normalized for calculating co-contraction indices (CCI) for opposing muscle groups. Results showed an increase of co-contraction primarily for vastii and gastrocnemius muscles for the first and second half of stance when walking with an unstable shoe construction. Therefore, when using an inverse dynamic approach to analyze joint loading differences between regular shoes and unstable shoes, one should be cautious in interpreting the data, as these methods base their estimates of joint moments upon the net joint torque.

  10. A new instability index for unstable mode selection in squeal prediction by complex eigenvalue analysis

    NASA Astrophysics Data System (ADS)

    Brunetti, J.; Massi, F.; D`Ambrogio, W.; Berthier, Y.

    2016-09-01

    During these last decades the modal instability of systems, generated by frictional contact forces, has been the subject of a huge amount of works in friction induced vibration literature. Linear and nonlinear numerical analyses have been largely investigated to predict and reproduce squeal vibrations. While nonlinear transient analysis needs large computational efforts, results of Complex Eigenvalue Analysis (CEA) suffer from an over-prediction issue and it is not able to predict correctly the mode that will become effectively unstable in case of several unstable eigenvalues. Because the CEA has been adopted as an efficient tool for brake design, a more reliable index is here proposed, from the CEA outputs and energetic considerations, to identify the mode that will become effectively unstable. A modular lumped model is developed to reproduce friction induced vibrations. The use of the eigenvalue real part, as discriminant of the system instability, is here combined with information coming from the eigenvectors, projected on the equilibrium position, to account for the energy flows involved in the squeal phenomena. This approach allows to define a Modal Absorption Index (MAI). The MAI allows for comparing unstable modes of the same system and is applied in this paper to predict, by CEA outputs, the unstable mode that will effectively result in squeal vibrations.

  11. Kinetics of an enzyme reaction in which both the enzyme-substrate complex and the product are unstable or only the product is unstable.

    PubMed Central

    Garrido-del Solo, C; García-Cánovas, F; Havsteen, B H; Valero, E; Varón, R

    1994-01-01

    A kinetic analysis of the Michaelis-Menten mechanism has been made for the case in which both the enzyme-substrate complex and the product are unstable or only the product is unstable, either spontaneously or as the result of the addition of a reagent. This analysis allows the derivation of equations which under conditions of limiting enzyme concentration relate the concentration of all of the species to the time. A kinetic data analysis is suggested, which leads to the evaluation of the kinetic parameters involved in the reaction. The analysis is based on the equation which describes the formation of products with time and one's experimental progress curves. We demonstrate the method numerically by computer simulation of the reaction with added experimental errors and experimentally by the use of data from the kinetic study of the action of tyrosinase on dopamine. PMID:7980401

  12. Fundamentals of preparative and nonlinear chromatography

    SciTech Connect

    Guiochon, Georges A; Felinger, Attila; Katti, Anita; Shirazi, Dean G

    2006-02-01

    The second edition of Fundamentals of Preparative and Nonlinear Chromatography is devoted to the fundamentals of a new process of purification or extraction of chemicals or proteins widely used in the pharmaceutical industry and in preparative chromatography. This process permits the preparation of extremely pure compounds satisfying the requests of the US Food and Drug Administration. The book describes the fundamentals of thermodynamics, mass transfer kinetics, and flow through porous media that are relevant to chromatography. It presents the models used in chromatography and their solutions, discusses the applications made, describes the different processes used, their numerous applications, and the methods of optimization of the experimental conditions of this process.

  13. Particle Astrophysics Using Balloons

    NASA Astrophysics Data System (ADS)

    Seo, E. S.

    Cosmic rays, energetic particles coming from outer space, bring us information about the physical processes that accelerate particles to relativistic energies, about the effects of those particles in driving dynamical processes in our Galaxy, and about the distribution of matter and fields in interstellar space. Cosmic rays were discovered in the early twentieth century using a balloon-borne electroscope. Balloons are currently being used for answering fundamental questions about the cosmos: (1) Is the Universe symmetric, and if so where is the antimatter? (2) What is the dark matter? (3) How do cosmic rays get their enormous energies? (4) Can the entire energy spectrum of cosmic rays result from a single acceleration mechanism? (5) Are supernovae really the sources of cosmic rays? (6) What is the history of cosmic rays in the Galaxy? (7) What is the origin of the "knee" in the cosmic ray energy spectrum? etc. The status of results from past balloon-borne measurements and expected results from ongoing and planned future balloon-borne particle astrophysics experiments will be reviewed.

  14. Relation of the diffuse reflectance remission function to the fundamental optical parameters.

    NASA Technical Reports Server (NTRS)

    Simmons, E. L.

    1972-01-01

    The Kubelka-Munk equations describing the diffuse reflectance of a powdered sample were compared to equations obtained using a uniformly-sized rough-surfaced spherical particle model. The comparison resulted in equations relating the remission function and the Kubelka-Munk constants to the index of refraction, the absorption coefficient, and the average particle diameter of a powdered sample. Published experimental results were used to test the equation relating to the remission function to the fundamental optical parameters.

  15. Strategic Information Resources Management: Fundamental Practices.

    ERIC Educational Resources Information Center

    Caudle, Sharon L.

    1996-01-01

    Discusses six fundamental information resources management (IRM) practices in successful organizations that can improve government service delivery performance. Highlights include directing changes, integrating IRM decision making into a strategic management process, performance management, maintaining an investment philosophy, using business…

  16. Instructor Special Report: RIF (Reading Is FUNdamental)

    ERIC Educational Resources Information Center

    Instructor, 1976

    1976-01-01

    At a time when innovative programs of the sixties are quickly falling out of the picture, Reading Is FUNdamental, after ten years and five million free paperbacks, continues to expand and show results. (Editor)

  17. Language Policy and Planning: Fundamental Issues.

    ERIC Educational Resources Information Center

    Kaplan, Robert B.

    1994-01-01

    Fundamental issues in language policy and planning are discussed: language death, language survival, language change, language revival, language shift and expansion, language contact and pidginization or creolization, and literacy development. (Contains 21 references.) (LB)

  18. Accounting Fundamentals for Non-Accountants

    EPA Pesticide Factsheets

    The purpose of this module is to provide an introduction and overview of accounting fundamentals for non-accountants. The module also covers important topics such as communication, internal controls, documentation and recordkeeping.

  19. Fundamentals of Indoor Air Quality in Buildings

    EPA Pesticide Factsheets

    This module provides the fundamentals to understanding indoor air quality. It provides a rudimentary framework for understanding how indoor and outdoor sources of pollution affect the indoor air quality of buildings.

  20. Unstable Domain-Wall Solution in the Metal-Mott Insulator Coexisting Regime

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Han; Dobrosavljevic, Vladimir; Vucicevic, Jaksa; Tanaskovic, Darko; Miranda, Eduardo

    2015-03-01

    We employ Dynamical Mean Field Theory (DMFT) with multidimensional optimization (Conjugate Gradient and Broyden method) to investigate the transport properties of the unstable solution in the Mott metal-insulator coexisting regime. Physically, this solution is expected to describe the properties of the domain wall separating the metallic and the Mott-insulating regions in a spatially inhomogeneous case. We show that the multidimensional optimization can efficiently converge not only to the local minima of the free energy, describing the two coexisting phases, but also to the saddle-point describing the unstable solution. This unstable solution represents a new phase of matter: its low temperature transport properties differ qualitatively from both the metal and the insulator, displaying incoherent metallic behavior down to lowest temperatures.

  1. Effects of Unstable Conditions on Kinematics and Performance Variables in Young Handball Players.

    PubMed

    Urbán, Tomás; Gutiérrez, Óscar; Moreno, Francisco J

    2015-06-27

    The execution variability and outcomes found in throwing actions have received special attention in numerous studies in recent years. The aim of this study was to analyze the effect of an unstable condition on velocity, accuracy and kinematics of movement in the seven metres throw in handball. Twenty-five young handball players took part in an experiment, throwing towards a target on a stable and an unstable surface. Each participant performed 32 throws, 16 for each situation. Linear variability of the dominant hand was assessed by 3D Motion Tracking. A radar sports gun was used to record the velocity of the ball and the throws were video recorded to establish their accuracy. Results showed significant decreases in throwing velocity in unstable conditions, but these did not significantly affect the accuracy achieved in performance. Differences were also found in movement kinematics between the two throwing conditions and relationships were found between kinematics, velocity and accuracy.

  2. Energy harvesting by dynamic unstability and internal resonance for piezoelectric beam

    SciTech Connect

    Lan, Chunbo; Qin, Weiyang Deng, Wangzheng

    2015-08-31

    We investigated the energy harvesting of a vertical beam with tip mass under vertical excitations. We applied dynamic unstability and internal resonance to improve the efficiency of harvesting. The experiments of harmonic excitation were carried out. Results show that for the beam there exist internal resonances in the dynamically unstable and the buckling bistable cases. The dynamic unstability is a determinant for strong internal resonance or mode coupling, which can be used to create a large output from piezoelectric patches. Then, the experiments of stochastic excitation were carried out. Results prove that the internal resonance or mode coupling can transfer the excitation energy to the low order modes, mainly the first and the second one. This can bring about a large output voltage. For a stochastic excitation, it is proved that there is an optimal weight of tip mass for realizing internal resonance and producing large outputs.

  3. Effects of Unstable Conditions on Kinematics and Performance Variables in Young Handball Players

    PubMed Central

    Urbán, Tomás; Gutiérrez, Óscar; Moreno, Francisco J.

    2015-01-01

    The execution variability and outcomes found in throwing actions have received special attention in numerous studies in recent years. The aim of this study was to analyze the effect of an unstable condition on velocity, accuracy and kinematics of movement in the seven metres throw in handball. Twenty-five young handball players took part in an experiment, throwing towards a target on a stable and an unstable surface. Each participant performed 32 throws, 16 for each situation. Linear variability of the dominant hand was assessed by 3D Motion Tracking. A radar sports gun was used to record the velocity of the ball and the throws were video recorded to establish their accuracy. Results showed significant decreases in throwing velocity in unstable conditions, but these did not significantly affect the accuracy achieved in performance. Differences were also found in movement kinematics between the two throwing conditions and relationships were found between kinematics, velocity and accuracy. PMID:26240647

  4. The unstable distal radial fracture one year post Kapandji intrafocal pinning.

    PubMed

    Brady, O; Rice, J; Nicholson, P; Kelly, E; O'Rourke, S K

    1999-05-01

    Kapandji pinning has been proposed as the treatment of choice for unstable Colles' fractures. The aim of this paper is to evaluate our experience treating unstable Colles' type fractures using this technique. Over a nine month period, 36 patients with Colles' type fractures were treated operatively at St. Vincent's Hospital. 22 of these fractures were deemed unstable and were treated using percutaneous intrafocal Kapandji pinning. 20 of these patients were recalled for review at a mean of 11.3 month post injury. At this stage the wrist was examined clinically and radiologically. Initial satisfactory correction of deformity was achieved by this technique. Between the time of wire removal and final review, however, there was significant recurrence of dorsal angulation (P < 0.05), but no significant radial shortening on radiographs. The patients had a satisfactory clinical result in spite of these radiological parameters.

  5. Interaction effects on the unstable discharge-energy characteristic of pump-turbine in pump mode

    NASA Astrophysics Data System (ADS)

    Tao, R.; Xiao, R. F.; Yang, W.; Liu, W. C.

    2013-12-01

    For a pump-turbine, unstable discharge-energy characteristic is an important factor for operating stability. In this study, the rotor-stator interaction effects on the pump-turbine which has the unstable discharge-energy characteristic has been studied. A series of transient CFD simulations under different discharge conditions have been conducted. Through the contrast between the simulations and experiments, it is found out that the energy decline is strongly affected by the flow loss in the adjustable vane. More importantly, the magnitude and direction of fluid flowing into the adjustable vane are varying with the impeller rotating. Disordered flow structure occurs in the adjustable vane and causes the energy losses due to the interaction effects. Based on this study, improvements on the flow uniformity at impeller outlet will help us to solve the unstable discharge-energy problem.

  6. A novel double loop control model design for chemical unstable processes.

    PubMed

    Cong, Er-Ding; Hu, Ming-Hui; Tu, Shan-Tung; Xuan, Fu-Zhen; Shao, Hui-He

    2014-03-01

    In this manuscript, based on Smith predictor control scheme for unstable process in industry, an improved double loop control model is proposed for chemical unstable processes. Inner loop is to stabilize integrating the unstable process and transform the original process to first-order plus pure dead-time dynamic stable process. Outer loop is to enhance the performance of set point response. Disturbance controller is designed to enhance the performance of disturbance response. The improved control system is simple with exact physical meaning. The characteristic equation is easy to realize stabilization. Three controllers are separately design in the improved scheme. It is easy to design each controller and good control performance for the respective closed-loop transfer function separately. The robust stability of the proposed control scheme is analyzed. Finally, case studies illustrate that the improved method can give better system performance than existing design methods.

  7. Does logic moderate the fundamental attribution error?

    PubMed

    Stalder, D R

    2000-06-01

    The fundamental attribution error was investigated from an individual difference perspective. Mathematicians were compared with nonmathematicians (Exp. 1; n: 84), and undergraduates who scored high on a test of logical reasoning ability were compared with those who scored low (Exp. 2; n: 62). The mathematicians and those participants scoring higher on logic appeared less prone to the fundamental attribution error, primarily using a measure of confidence in attributions.

  8. Particle size effects in particle-particle triboelectric charging studied with an integrated fluidized bed and electrostatic separator system

    NASA Astrophysics Data System (ADS)

    Bilici, Mihai A.; Toth, Joseph R.; Sankaran, R. Mohan; Lacks, Daniel J.

    2014-10-01

    Fundamental studies of triboelectric charging of granular materials via particle-particle contact are challenging to control and interpret because of foreign material surfaces that are difficult to avoid during contacting and measurement. The measurement of particle charge itself can also induce charging, altering results. Here, we introduce a completely integrated fluidized bed and electrostatic separator system that charges particles solely by interparticle interactions and characterizes their charge on line. Particles are contacted in a free-surface fluidized bed (no reactor walls) with a well-controlled fountain-like flow to regulate particle-particle contact. The charged particles in the fountain are transferred by a pulsed jet of air to the top of a vertically-oriented electrostatic separator consisting of two electrodes at oppositely biased high voltage. The free-falling particles migrate towards the electrodes of opposite charge and are collected by an array of cups where their charge and size can be determined. We carried out experiments on a bidisperse size mixture of soda lime glass particles with systematically varying ratios of concentration. Results show that larger particles fall close to the negative electrode and smaller particles fall close to the positive electrode, consistent with theory and prior experiments that larger particles charge positively and smaller particles charge negatively. The segregation of particles by charge for one of the size components is strongest when its collisions are mostly with particles of the other size component; thus, small particles segregate most strongly to the negative sample when their concentration in the mixture is small (and analogous results occur for the large particles). Furthermore, we find additional size segregation due to granular flow, whereby the fountain becomes enriched in larger particles as the smaller particles are preferentially expelled from the fountain.

  9. Particle size effects in particle-particle triboelectric charging studied with an integrated fluidized bed and electrostatic separator system

    SciTech Connect

    Bilici, Mihai A.; Toth, Joseph R.; Sankaran, R. Mohan; Lacks, Daniel J.

    2014-10-15

    Fundamental studies of triboelectric charging of granular materials via particle-particle contact are challenging to control and interpret because of foreign material surfaces that are difficult to avoid during contacting and measurement. The measurement of particle charge itself can also induce charging, altering results. Here, we introduce a completely integrated fluidized bed and electrostatic separator system that charges particles solely by interparticle interactions and characterizes their charge on line. Particles are contacted in a free-surface fluidized bed (no reactor walls) with a well-controlled fountain-like flow to regulate particle-particle contact. The charged particles in the fountain are transferred by a pulsed jet of air to the top of a vertically-oriented electrostatic separator consisting of two electrodes at oppositely biased high voltage. The free-falling particles migrate towards the electrodes of opposite charge and are collected by an array of cups where their charge and size can be determined. We carried out experiments on a bidisperse size mixture of soda lime glass particles with systematically varying ratios of concentration. Results show that larger particles fall close to the negative electrode and smaller particles fall close to the positive electrode, consistent with theory and prior experiments that larger particles charge positively and smaller particles charge negatively. The segregation of particles by charge for one of the size components is strongest when its collisions are mostly with particles of the other size component; thus, small particles segregate most strongly to the negative sample when their concentration in the mixture is small (and analogous results occur for the large particles). Furthermore, we find additional size segregation due to granular flow, whereby the fountain becomes enriched in larger particles as the smaller particles are preferentially expelled from the fountain.

  10. High mode volume self filtering unstable resonator applied to a short pulse XeCl laser

    NASA Astrophysics Data System (ADS)

    Luches, A.; Nassisi, V.; Perrone, M. R.; Radiotis, E.

    1989-05-01

    A high mode volume non confocal self filtering unstable resonator has been applied to a short pulse XeCl laser. Such a resonator made up of a concave mirror (focal length is 25 cm) and a convex mirror (focal length is -25 cm), has a magnification | M|=34 and a cavity length of 151 cm. A nearly diffraction limited laser beam of 5.5 mJ, 10 ns duration and with a brightness of 2.5×10 13 W cm -2 sr -1 has been obtained. These results are compared to those obtained with another self-filtering unstable resonator having the same resonator length but | M|=10.

  11. Compact-beam stable-unstable resonator for free-electron laser. Phase 2, Final report

    SciTech Connect

    Paxton, A.H.; White, C.J.; Boyd, T.L.; Schmitt, M.J.; Aldrich, C.H.

    1991-10-01

    A significant problem in the design of high-energy free-electron lasers (FELs) centers on the technique for outcoupling the output beam. FELs with currently achievable output power usually include a conventional stable resonator with output through a partially transmitting mirror which will not work for arbitrarily high average power. An alternate scheme must be found for high-energy FELs. A high- efficiency grating outcoupler is an attractive possibility, but it is difficult to manufacture. Other suggestions include unstable resonators with an intracavity focus and unstable resonators with an intracavity focus and beam rotation. The intensity distribution at the intracavity focus of a negative-branch unstable resonator has side-lobes that would be scraped off by the faces of the wiggler magnets or by the beam tube through the wiggler. The resulting power loss would be significant. Therefore, it is desirable to develop another type of resonator for use with FELs. The resonator that we have developed is the compact-beam stable-unstable ring resonator. It is a stable resonator in one transverse dimension and an unstable resonator with an intracavity focus in the orthogonal transverse dimension. A scraper mirror outcouples the output beam from one side of the mode only. The resonator can be configured so that it has a small beam waist at the center of the wiggler in the stable direction and has an intracavity focus in the unstable direction. The half- width of the central lobe of the focus is approximately the size of the stable beam waist. In the stable direction, the Gaussian amplitude distribution results in a small loss on the wiggler magnets, or on a beam tube that will fit within the wiggler, if one is used. The beam tube can have an elliptical shape to permit the passage of several side lobes in the unstable dimension. A mode of the CBSUR is a product of the mode of a strip stable resonator with a strip compact-beam negative-branch unstable resonator.

  12. Broad Search for Unstable Resonant Orbits in the Planar Circular Restricted Three-Body Problem

    NASA Technical Reports Server (NTRS)

    Anderson, Rodney L.; Campagnola, Stefano; Lantoine, Gregory

    2013-01-01

    Unstable resonant orbits in the circular restricted three-body problem have increasingly been used for trajectory design using optimization and invariant manifold techniques.In this study, several methods for computing these unstable resonant orbits are explored including flyby maps, continuation from two-body models, and grid searches. Families of orbits are computed focusing on the Jupiter-Europa system, and their characteristics are explored. Different parameters such as period and stability are examined for each set of resonantor bits, and the continuation of several specific orbits is explored in more detail.

  13. First-principles calculations of free energies of unstable phases: the case of fcc W.

    PubMed

    Ozolins, V

    2009-02-13

    Ab initio molecular dynamics simulations are used to solve the long-standing problem of calculating the free energies of unstable phases, such as fcc W. We find that fcc W is mechanically unstable with respect to long-wavelength shear at all temperatures considered (T>2500 K), while the short-wavelength phonon modes are anharmonically stabilized. The calculated fcc-bcc enthalpy and entropy differences at T=3500 K (308 meV and 0.74k_{B} per atom, respectively) agree well with the recent values derived from analysis of experimental data.

  14. Asymmetric and persistent responses in price volatility of fertilizers through stable and unstable periods

    NASA Astrophysics Data System (ADS)

    Lahmiri, Salim

    2017-01-01

    Fertilizers are important to improve agricultural productivity growth. The purpose of this study is to investigate asymmetry, leverage, and persistence of shocks on price volatility of five fertilizers using EGARCH model during stable and unstable time periods, corresponding to before and after 2007 international financial crisis, respectively. Using price data of rock phosphate, triple super phosphate, diammonium phosphate (DAP), urea, and potassium chloride, it is found that fertilizers price volatilities display an apparent asymmetric response to shocks which have much pronounced and permanent effect during unstable period than in during stable period. Such effects should be taken into account whenever volatility modeling of fertilizers is considered, particularly during periods of volatile price.

  15. Magnetic particles

    NASA Technical Reports Server (NTRS)

    Chang, Manchium (Inventor); Colvin, Michael S. (Inventor); Rembaum, Alan (Inventor); Richards, Gil F. (Inventor)

    1987-01-01

    Metal oxide containing polymers and particularly styrene, acrylic or protein polymers containing fine, magnetic iron oxide particles are formed by combining a NO.sub.2 -substituted polymer with an acid such as hydrochloric acid in the presence of metal, particularly iron particles. The iron is oxidized to fine, black Fe.sub.3 O.sub.4 particles which deposit selectively on the polymer particles. Nitrated polymers are formed by reacting functionally substituted, nitrated organic compounds such as trinitrobenzene sulfonate or dinitrofluoro benzene with a functionally coreactive polymer such as an amine modified acrylic polymer or a protein. Other transition metals such as cobalt can also be incorporated into polymers using this method.

  16. Practical implications of some recent studies in electrospray ionization fundamentals.

    PubMed

    Cech, N B; Enke, C G

    2001-01-01

    In accomplishing successful electrospray ionization analyses, it is imperative to have an understanding of the effects of variables such as analyte structure, instrumental parameters, and solution composition. Here, we review some fundamental studies of the ESI process that are relevant to these issues. We discuss how analyte chargeability and surface activity are related to ESI response, and how accessible parameters such as nonpolar surface area and reversed phase HPLC retention time can be used to predict relative ESI response. Also presented is a description of how derivitizing agents can be used to maximize or enable ESI response by improving the chargeability or hydrophobicity of ESI analytes. Limiting factors in the ESI calibration curve are discussed. At high concentrations, these factors include droplet surface area and excess charge concentration, whereas at low concentrations ion transmission becomes an issue, and chemical interference can also be limiting. Stable and reproducible non-pneumatic ESI operation depends on the ability to balance a number of parameters, including applied voltage and solution surface tension, flow rate, and conductivity. We discuss how changing these parameters can shift the mode of ESI operation from stable to unstable, and how current-voltage curves can be used to characterize the mode of ESI operation. Finally, the characteristics of the ideal ESI solvent, including surface tension and conductivity requirements, are discussed. Analysis in the positive ion mode can be accomplished with acidified methanol/water solutions, but negative ion mode analysis necessitates special constituents that suppress corona discharge and facilitate the production of stable negative ions.

  17. Coronary artery compliance and adaptive vessel remodelling in patients with stable and unstable coronary artery disease

    PubMed Central

    Jeremias, A; Spies, C; Herity, N; Pomerantsev, E; Yock, P; Fitzgerald, P; Yeung, A

    2000-01-01

    OBJECTIVE—To test the hypothesis that patients with unstable coronary syndromes show accentuated compensatory vessel enlargement compared with patients with stable angina, and that this may in part be related to increased coronary artery distensibility.
DESIGN AND PATIENTS—In 23 patients with unstable coronary syndromes (10 with non-Q wave myocardial infarction and 13 with unstable angina), the culprit lesion was investigated by intravascular ultrasound before intervention. The vessel cross sectional area (VA), lumen area (LA), and plaque area (VA minus LA) were measured at end diastole and end systole at the lesion site and at the proximal and distal reference segments. Similar measurements were made in 23 patients with stable angina admitted during the same period and matched for age, sex, and target vessel. Calculations were made of remodelling index (VA at lesion site ÷ VA at reference site), distensibility index ([(ΔA/A)/ΔP] × 103, where ΔA is the luminal area change in systole and diastole and ΔP the difference in systolic and diastolic blood pressure measured at the tip of the guiding catheter during a cardiac cycle), and stiffness index β ([ln(Psys/Pdias)]/(ΔD/D), where Psys is systolic pressure, Pdias is diastolic pressure, and ΔD is the difference between systolic and diastolic lumen diameters). Positive remodelling was defined as when the VA at the lesion was > 1.05 times larger than at the proximal reference site, and negative remodelling when the VA at the lesion was < 0.95 of the reference site.
RESULTS—Mean (SD) LA at the lesion site was similar in both groups (4.03 (1.8) v 4.01 (1.93) mm2), while plaque area was larger in the unstable group (13.29 (4.04) v 8.34 (3.6) mm2, p < 0.001). Remodelling index was greater in the unstable group (1.14 (0.18) v 0.83 (0.15), p < 0.001). Positive remodelling was observed in 15 patients in the unstable group (65%) but in only two (9%) in the stable group (p < 0

  18. Analysis of unstable periodic orbits and chaotic orbits in the one-dimensional linear piecewise-smooth discontinuous map

    SciTech Connect

    Rajpathak, Bhooshan Pillai, Harish K.; Bandyopadhyay, Santanu

    2015-10-15

    In this paper, we analytically examine the unstable periodic orbits and chaotic orbits of the 1-D linear piecewise-smooth discontinuous map. We explore the existence of unstable orbits and the effect of variation in parameters on the coexistence of unstable orbits. Further, we show that this structuring is different from the well known period adding cascade structure associated with the stable periodic orbits of the same map. Further, we analytically prove the existence of chaotic orbit for this map.

  19. A rigorous proof for impossibility of a direct application of unstable delayed feedback control for continuous-time systems

    NASA Astrophysics Data System (ADS)

    Nakajima, Hiroyuki

    2003-04-01

    Unstable DFC (UDFC), which utilizes an unstable parameter of the EDFC, can overcome the odd-number limitation for discrete-time systems. However, it has been shown that a direct application of the UDFC for stabilizing unstable equilibrium points of continuous-time systems fails. In this Letter, we rigorously prove this impossibility of the direct application of UDFC for continuous-time systems.

  20. Database and online map service on unstable rock slopes in Norway - From data perpetuation to public information

    NASA Astrophysics Data System (ADS)

    Oppikofer, Thierry; Nordahl, Bobo; Bunkholt, Halvor; Nicolaisen, Magnus; Jarna, Alexandra; Iversen, Sverre; Hermanns, Reginald L.; Böhme, Martina; Yugsi Molina, Freddy X.

    2015-11-01

    The unstable rock slope database is developed and maintained by the Geological Survey of Norway as part of the systematic mapping of unstable rock slopes in Norway. This mapping aims to detect catastrophic rock slope failures before they occur. More than 250 unstable slopes with post-glacial deformation are detected up to now. The main aims of the unstable rock slope database are (1) to serve as a national archive for unstable rock slopes in Norway; (2) to serve for data collection and storage during field mapping; (3) to provide decision-makers with hazard zones and other necessary information on unstable rock slopes for land-use planning and mitigation; and (4) to inform the public through an online map service. The database is organized hierarchically with a main point for each unstable rock slope to which several feature classes and tables are linked. This main point feature class includes several general attributes of the unstable rock slopes, such as site name, general and geological descriptions, executed works, recommendations, technical parameters (volume, lithology, mechanism and others), displacement rates, possible consequences, as well as hazard and risk classification. Feature classes and tables linked to the main feature class include different scenarios of an unstable rock slope, field observation points, sampling points for dating, displacement measurement stations, lineaments, unstable areas, run-out areas, areas affected by secondary effects, along with tables for hazard and risk classification and URL links to further documentation and references. The database on unstable rock slopes in Norway will be publicly consultable through an online map service. Factsheets with key information on unstable rock slopes can be automatically generated and downloaded for each site. Areas of possible rock avalanche run-out and their secondary effects displayed in the online map service, along with hazard and risk assessments, will become important tools for

  1. Selective particle capture by asynchronously beating cilia

    NASA Astrophysics Data System (ADS)

    Ding, Yang; Kanso, Eva

    2015-12-01

    Selective particle filtration is fundamental in many engineering and biological systems. For example, many aquatic microorganisms use filter feeding to capture food particles from the surrounding fluid, using motile cilia. One of the capture strategies is to use the same cilia to generate feeding currents and to intercept particles when the particles are on the downstream side of the cilia. Here, we develop a 3D computational model of ciliary bands interacting with flow suspended particles and calculate particle trajectories for a range of particle sizes. Consistent with experimental observations, we find optimal particle sizes that maximize capture rate. The optimal size depends nonlinearly on cilia spacing and cilia coordination, synchronous vs. asynchronous. These parameters affect the cilia-generated flow field, which in turn affects particle trajectories. The low capture rate of smaller particles is due to the particles' inability to cross the flow streamlines of neighboring cilia. Meanwhile, large particles have difficulty entering the sub-ciliary region once advected downstream, also resulting in low capture rates. The optimal range of particle sizes is enhanced when cilia beat asynchronously. These findings have potentially important implications on the design and use of biomimetic cilia in processes such as particle sorting in microfluidic devices.

  2. Plasmon assisted optical trapping: fundamentals and biomedical applications

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexandros A.; Makropoulou, Mersini; Tsigaridas, Georgios N.; Gousetis, Anastasios

    2015-01-01

    The field of optical trapping has dramatically grown due to implementation in various arenas including physics, biology, medicine and nanotechnology. Certainly, optical tweezers are an invaluable tool to manipulate a variation of particles, such as small dielectric spheres, cells, bacteria, chromosomes and even genes, by highly focused laser beams through microscope. As the main disadvantage of the conventional optical trapping systems is the diffraction limit of the incident light, plasmon assisted nanotrapping is reported as a suitable technique for trapping sub-wavelength metallic or dielectric particles. In this work, firstly, we report briefly on the basic theory of plasmon excitation, focusing on the interaction of nanoscale metallic structures with laser light. Secondly, experimental and numerical simulation results are also presented, demonstrating enhancement of the trapping efficiency of glass or SiO2 substrates, coated with Au and Ag nanostructures, with or without nanoparticles. The optical forces were calculated by measuring the particle's escape velocity calibration method. Finally, representative applications of plasmon assisted optical trapping are reviewed, from cancer therapeutics to fundamental biology and cell nanosurgery.

  3. Fundamentals and applications of inertial microfluidics: a review.

    PubMed

    Zhang, Jun; Yan, Sheng; Yuan, Dan; Alici, Gursel; Nguyen, Nam-Trung; Ebrahimi Warkiani, Majid; Li, Weihua

    2016-01-07

    In the last decade, inertial microfluidics has attracted significant attention and a wide variety of channel designs that focus, concentrate and separate particles and fluids have been demonstrated. In contrast to conventional microfluidic technologies, where fluid inertia is negligible and flow remains almost within the Stokes flow region with very low Reynolds number (Re ≪ 1), inertial microfluidics works in the intermediate Reynolds number range (~1 < Re < ~100) between Stokes and turbulent regimes. In this intermediate range, both inertia and fluid viscosity are finite and bring about several intriguing effects that form the basis of inertial microfluidics including (i) inertial migration and (ii) secondary flow. Due to the superior features of high-throughput, simplicity, precise manipulation and low cost, inertial microfluidics is a very promising candidate for cellular sample processing, especially for samples with low abundant targets. In this review, we first discuss the fundamental kinematics of particles in microchannels to familiarise readers with the mechanisms and underlying physics in inertial microfluidic systems. We then present a comprehensive review of recent developments and key applications of inertial microfluidic systems according to their microchannel structures. Finally, we discuss the perspective of employing fluid inertia in microfluidics for particle manipulation. Due to the superior benefits of inertial microfluidics, this promising technology will still be an attractive topic in the near future, with more novel designs and further applications in biology, medicine and industry on the horizon.

  4. Spatial and temporal variations of fundamental constants

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Agafonova, I. I.; Molaro, P.; Reimers, D.

    2010-11-01

    Spatial and temporal variations in the electron-to-proton mass ratio, μ, and in the fine-structure constant, α, are not present in the Standard Model of particle physics but they arise quite naturally in grant unification theories, multidimensional theories and in general when a coupling of light scalar fields to baryonic matter is considered. The light scalar fields are usually attributed to a negative pressure substance permeating the entire visible Universe and known as dark energy. This substance is thought to be responsible for a cosmic acceleration at low redshifts, z < 1. A strong dependence of μ and α on the ambient matter density is predicted by chameleon-like scalar field models. Calculations of atomic and molecular spectra show that different transitions have different sensitivities to changes in fundamental constants. Thus, measuring the relative line positions, Δ V, between such transitions one can probe the hypothetical variability of physical constants. In particular, interstellar molecular clouds can be used to test the matter density dependence of μ, since gas density in these clouds is ~15 orders of magnitude lower than that in terrestrial environment. We use the best quality radio spectra of the inversion transition of NH3 (J,K)=(1,1) and rotational transitions of other molecules to estimate the radial velocity offsets, Δ V ≡ Vrot - Vinv. The obtained value of Δ V shows a statistically significant positive shift of 23±4stat±3sys m s-1 (1σ). Being interpreted in terms of the electron-to-proton mass ratio variation, this gives Δμ/μ = (22±4stat±3sys)×10-9. A strong constraint on variation of the quantity F = α2/μ in the Milky Way is found from comparison of the fine-structure transition J=1-0 in atomic carbon C i with the low-J rotational lines in carbon monoxide 13CO arising in the interstellar molecular clouds: |Δ F/F| < 3×10-7. This yields |Δ α/α| < 1.5×10-7 at z = 0. Since extragalactic absorbers have gas densities

  5. A Fundamental Equation of State for Ethanol

    NASA Astrophysics Data System (ADS)

    Schroeder, J. A.; Penoncello, S. G.; Schroeder, J. S.

    2014-12-01

    The existing fundamental equation for ethanol demonstrates undesirable behavior in several areas and especially in the critical region. In addition, new experimental data have become available in the open literature since the publication of the current correlation. The development of a new fundamental equation for ethanol, in the form of Helmholtz energy as a function of temperature and density, is presented. New, nonlinear fitting techniques, along with the new experimental data, are shown to improve the behavior of the fundamental equation. Ancillary equations are developed, including equations for vapor pressure, saturated liquid density, saturated vapor density, and ideal gas heat capacity. Both the fundamental and ancillary equations are compared to experimental data. The fundamental equation can compute densities to within ±0.2%, heat capacities to within ±1%-2%, and speed of sound to within ±1%. Values of the vapor pressure and saturated vapor densities are represented to within ±1% at temperatures of 300 K and above, while saturated liquid densities are represented to within ±0.3% at temperatures of 200 K and above. The uncertainty of all properties is higher in the critical region and near the triple point. The equation is valid for pressures up to 280 MPa and temperatures from 160 to 650 K.

  6. Fundamental frequency from classical molecular dynamics.

    PubMed

    Yamada, Tomonori; Aida, Misako

    2015-02-07

    We give a theoretical validation for calculating fundamental frequencies of a molecule from classical molecular dynamics (MD) when its anharmonicity is small enough to be treated by perturbation theory. We specifically give concrete answers to the following questions: (1) What is the appropriate initial condition of classical MD to calculate the fundamental frequency? (2) From that condition, how accurately can we extract fundamental frequencies of a molecule? (3) What is the benefit of using ab initio MD for frequency calculations? Our analytical approaches to those questions are classical and quantum normal form theories. As numerical examples we perform two types of MD to calculate fundamental frequencies of H2O with MP2/aug-cc-pVTZ: one is based on the quartic force field and the other one is direct ab initio MD, where the potential energies and the gradients are calculated on the fly. From those calculations, we show comparisons of the frequencies from MD with the post vibrational self-consistent field calculations, second- and fourth-order perturbation theories, and experiments. We also apply direct ab initio MD to frequency calculations of C-H vibrational modes of tetracene and naphthalene. We conclude that MD can give the same accuracy in fundamental frequency calculation as second-order perturbation theory but the computational cost is lower for large molecules.

  7. Bertotti-Robinson thin-shell wormhole is physical but unstable

    NASA Astrophysics Data System (ADS)

    Amirabi, Z.

    2016-08-01

    I construct a thin-shell wormhole in the spherically symmetric, static Bertotti-Robinson magnetic universe which is supported by normal matter in the sense that the energy conditions are all satisfied. Using the so called small velocity perturbation it is shown that this thin-shell wormhole is basically physical but unstable against radial perturbation.

  8. Wind tunnel simulation of a wind turbine wake in neutral, stable and unstable wind flow

    NASA Astrophysics Data System (ADS)

    Hancock, P. E.; Zhang, S.; Pascheke, F.; Hayden, P.

    2014-12-01

    Measurements of mean velocity, Reynolds stresses, temperature and heat flux have been made in the wake of a model wind turbine in the EnFlo meteorology wind tunnel, for three atmospheric boundary layer states: the base-line neutral case, stable and unstable. The full-to-model scale is approximately 300:1. Primary instrumentation is two-component LDA combine with cold-wire thermometry to measure heat flux. In terms of surface conditions, the stratified cases are weak, but there is a strong 'imposed' condition in the stable case. The measurements were made between 0.5D and 10D, where D is the turbine disk diameter. In the stable case the velocity deficit decreases more slowly; more quickly in the unstable case. Heights at which quantities are maximum or minimum are greater in the unstable case and smaller in the stable case. In the stable case the wake height is suppressed but the width is increased, while in the unstable case the height is increased and the width (at hub height) reaches a maximum and then decreases. The turbulence in the wake behaves in a complex way. Further work needs to be done, to cover stronger levels of surface condition, requiring more extensive measurements to properly capture the wake development.

  9. Greek University Candidates' Targets in a Changing, Unstable and Unpredictable Economic Environment

    ERIC Educational Resources Information Center

    Kalerante, E.; Mormory, P.; Mormoris, M.

    2013-01-01

    The topic of the present study is concerned with the university candidates' educational and career choices against an unstable economic background that may necessitate the reformulation and readjustment of choices to innovative concepts of advancement and future development as they may apply to youngsters of different social class and gender. The…

  10. Modeling diseases of noncoding unstable repeat expansions using mutant pluripotent stem cells

    PubMed Central

    Yanovsky-Dagan, Shira; Mor-Shaked, Hagar; Eiges, Rachel

    2015-01-01

    Pathogenic mutations involving DNA repeat expansions are responsible for over 20 different neuronal and neuromuscular diseases. All result from expanded tracts of repetitive DNA sequences (mostly microsatellites) that become unstable beyond a critical length when transmitted across generations. Nearly all are inherited as autosomal dominant conditions and are typically associated with anticipation. Pathologic unstable repeat expansions can be classified according to their length, repeat sequence, gene location and underlying pathologic mechanisms. This review summarizes the current contribution of mutant pluripotent stem cells (diseased human embryonic stem cells and patient-derived induced pluripotent stem cells) to the research of unstable repeat pathologies by focusing on particularly large unstable noncoding expansions. Among this class of disorders are Fragile X syndrome and Fragile X-associated tremor/ataxia syndrome, myotonic dystrophy type 1 and myotonic dystrophy type 2, Friedreich ataxia and C9 related amyotrophic lateral sclerosis and/or frontotemporal dementia, Facioscapulohumeral Muscular Dystrophy and potentially more. Common features that are typical to this subclass of conditions are RNA toxic gain-of-function, epigenetic loss-of-function, toxic repeat-associated non-ATG translation and somatic instability. For each mechanism we summarize the currently available stem cell based models, highlight how they contributed to better understanding of the related mechanism, and discuss how they may be utilized in future investigations. PMID:26131313

  11. The use of invariant manifolds for transfers between unstable periodic orbits of different energies

    NASA Astrophysics Data System (ADS)

    Davis, Kathryn E.; Anderson, Rodney L.; Scheeres, Daniel J.; Born, George H.

    2010-08-01

    Techniques from dynamical systems theory have been applied to the construction of transfers between unstable periodic orbits that have different energies. Invariant manifolds, trajectories that asymptotically depart or approach unstable periodic orbits, are used to connect the initial and final orbits. The transfer asymptotically departs the initial orbit on a trajectory contained within the initial orbit’s unstable manifold and later asymptotically approaches the final orbit on a trajectory contained within the stable manifold of the final orbit. The manifold trajectories are connected by the execution of impulsive maneuvers. Two-body parameters dictate the selection of the individual manifold trajectories used to construct efficient transfers. A bounding sphere centered on the secondary, with a radius less than the sphere of influence of the secondary, is used to study the manifold trajectories. A two-body parameter, κ, is computed within the bounding sphere, where the gravitational effects of the secondary dominate. The parameter κ is defined as the sum of two quantities: the difference in the normalized angular momentum vectors and eccentricity vectors between a point on the unstable manifold and a point on the stable manifold. It is numerically demonstrated that as the κ parameter decreases, the total cost to complete the transfer decreases. Preliminary results indicate that this method of constructing transfers produces a significant cost savings over methods that do not employ the use of invariant manifolds.

  12. A finite element exploration of cartilage stress near an articular incongruity during unstable motion.

    PubMed

    Goreham-Voss, Curtis M; McKinley, Todd O; Brown, Thomas D

    2007-01-01

    Both instability and residual articular incongruity are implicated in the development of post-traumatic osteoarthritis (OA) following intra-articular fracture, but currently no information exists regarding cartilage stresses for unstable residual incongruities. In this study, a transversely isotropic poroelastic cartilage finite element model was implemented and validated within physiologically relevant loading ranges. This material model was then used to simulate the loading of cartilage during stable and unstable motion accompanying a step-off incongruity residual from intra-articular fracture, using load data from previous cadaver tests of ankle instability. Peak solid-phase stresses and fluid pressure were found to increase markedly in the presence of instability. Solid-phase transients of normal stress increased from 2.00 to 13.8 MPa/s for stable compared to unstable motion, and tangential stress transients increased from 17.1 to 118.1 MPa/s. Corresponding fluid pressure transients increased from 15.1 to 117.9 MPa/s for unstable motion. In the most rapidly loaded sections of cartilage, the fluid was found to carry nearly all of the normal load, with the pressurization of the fluid resulting in high solid matrix tangential stresses.

  13. Isometric squat force output and muscle activity in stable and unstable conditions.

    PubMed

    McBride, Jeffrey M; Cormie, Prue; Deane, Russell

    2006-11-01

    The purpose of this study was to assess the effect of stable vs. unstable conditions on force output and muscle activity during an isometric squat. Nine men involved in recreational resistance training participated in the investigation by completing a single testing session. Within this session subjects performed isometric squats either while standing directly on the force plate (stable condition, S) or while standing on inflatable balls placed on top of the force plate (unstable condition, U). Electromyography (EMG) was recorded during both conditions from the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and medial gastrocnemius (G) muscles. Results indicated peak force (PF) and rate of force development (RFD) were significantly lower, 45.6% and 40.5% respectively, in the U vs. S condition (p < or = 0.05). Average integrated EMG values for the VL and VM were significantly higher in the S vs. U condition. VL and VM muscle activity was 37.3% and 34.4% less in U in comparison to S. No significant differences were observed in muscle activity of the BF or G between U and S. The primary finding in this investigation is that isometric squatting in an unstable condition significantly reduces peak force, rate of force development, and agonist muscle activity with no change in antagonist or synergist muscle activity. In terms of providing a stimulus for strength gain no discernable benefit of performing a resistance exercise in an unstable condition was observed in the current study.

  14. On the transfer of energy to an unstable liquid jet in a coflowing compressible airstream

    NASA Technical Reports Server (NTRS)

    Li, Hsi-Shang; Kelly, Robert E.

    1993-01-01

    The transfer of energy from a compressible airstream to a coflowing unstable liquid jet via the pressure perturbation at the interface is studied as the Mach number varies continuously from subsonic to supersonic values. The 'lift' component of the pressure perturbation has been demonstrated to predominate up to slightly supersonic free-stream Mach numbers, after which the 'drag' component predominates.

  15. UNSTABLE FEMORAL FRACTURES TREATED WITH TITANIUM ELASTIC INTRAMEDULLARY NAILS, IN CHILDREN

    PubMed Central

    Soni, Jamil Faissal; Schelle, Gisele; Valenza, Weverley; Pavelec, Anna Carolina; Souza, Camila Deneka Arantes

    2015-01-01

    Objective: To evaluate the indications, epidemiology, associated lesions, complications and prognosis among children with unstable femoral diaphysis fractures who were treated with titanium elastic intramedullary nails. Method: This was a retrospective analysis on 24 patients aged 5-12 years with unstable femoral diaphysis fractures who underwent surgical treatment with elastic titanium intramedullary nails at the Cajuru University Hospital, Curitiba-PR, between April 2002 and March 2008, with a minimum follow-up of 36 months. The epidemiological data, angular deviations, leg shortening and bone consolidation were evaluated. Results: The medical files of 113 cases operated between April 2002 and March 2008 were reassessed. From these, 24 cases of unstable femoral diaphysis fractures treated with elastic titanium intramedullary nails with retrograde insertion were included in the study. There were two bilateral fractures and two exposed fractures. Seven patients were female and 17 were male, and the mean age was 8.3 years. The following were presented at the end of the study: shortening, varus or valgus displacement, final retrocurvatum or antecurvatum of zero, and absence of delayed consolidation or pseudarthrosis. Conclusions: The elastic titanium intramedullary nails were easily placed and removed. We believe that using elastic titanium intramedullary nails is a good option for fixation of unstable femoral fractures in children. PMID:27047868

  16. Magnetic resonance imaging in patients with unstable angina: comparison with acute myocardial infarction and normals

    SciTech Connect

    Ahmad, M.; Johnson, R.F. Jr.; Fawcett, H.D.; Schreiber, M.H.

    1988-09-01

    The role of magnetic resonance imaging in characterizing normal, ischemic and infarcted segments of myocardium was examined in 8 patients with unstable angina, 11 patients with acute myocardial infarction, and 7 patients with stable angina. Eleven normal volunteers were imaged for comparison. Myocardial segments in short axis magnetic resonance images were classified as normal or abnormal on the basis of perfusion changes observed in thallium-201 images in 22 patients and according to the electrocariographic localization of infarction in 4 patients. T2 relaxation time was measured in 57 myocardial segments with abnormal perfusion (24 with reversible and 33 with irreversible perfusion changes) and in 25 normally perfused segments. T2 measurements in normally perfused segments of patients with acute myocardial infarction, unstable angina and stable angina were within normal range derived from T2 measurements in 48 myocardial segments of 11 normal volunteers (42 +/- 10 ms). T2 in abnormal myocardial segments of patients with stable angina also was not significantly different from normal. T2 of abnormal segments in patients with unstable angina (64 +/- 14 in reversibly ischemic and 67 +/- 21 in the irreversibly ischemic segments) was prolonged when compared to normal (p less than 0.0001) and was not significantly different from T2 in abnormal segments of patients with acute myocardial infarction (62 +/- 18 for reversibly and 66 +/- 11 for irreversibly ischemic segments). The data indicate that T2 prolongation is not specific for acute myocardial infarction and may be observed in abnormally perfused segments of patients with unstable angina.

  17. Watershed Scale Shear Stress From Tethersonde Wind Profile Measurements Under Near Neutral and Unstable Atmospheric Stability

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Katul, G. G.

    1995-04-01

    Mean wind speed profiles were measured in the atmospheric surface layer, using a tethersonde system, above the Ojai Valley Watershed in southern California. The valley is mainly planted with mature avocado and orange trees. The surface shear stress and latent and sensible heat fluxes were measured above the trees which are up to 9 m in height. Near-neutral wind speed profile measurements allowed the determination of the watershed surface roughness (z0 = 1.4 m) and the momentum displacement height (d0 = 7.0 m). The wind speed measurements obtained under unstable atmospheric stability were analyzed using Monin-Obukhov similarity theory. New stability correction functions proposed based on theory and experiments of Kader-Yaglom as well as the now classic Businger-Dyer type functions were tested. The watershed shear stress values calculated using the surface layer wind speed profiles with the new Monin-Obukhov stability functions were found to be improved in comparison with the values obtained with the Businger-Dyer functions under strongly unstable stability conditions. The Monin-Obukhov model with the Businger-Dyer stability correction function underpredicted the momentum flux by 25% under strongly unstable stability conditions, while the new Kader-Yaglom formulation compared well on average (R2 = 0.77) with the surface eddy correlation measurements for all atmospheric stability conditions. The unstable 100-m drag coefficient was found to be u*2/V1002 = 0.0182.

  18. Ankle proprioception is not targeted by exercises on an unstable surface.

    PubMed

    Kiers, Henri; Brumagne, Simon; van Dieën, Jaap; van der Wees, Philip; Vanhees, Luc

    2012-04-01

    Laboratory study using a repeated measures design. The aim of this study was to determine if ankle proprioception is targeted in exercises on unstable surfaces. Lateral ankle sprain (LAS) has recurrence rates over 70%, which are believed to be due to a reduced accuracy of proprioceptive signals from the ankle. Proprioceptive exercises in rehabilitation of LAS mostly consist of balancing activities on an unstable surface. The methods include 100 healthy adults stood barefoot on a solid surface and a foam pad over a force plate, with occluded vision. Mechanical vibration was used to stimulate proprioceptive output of muscle spindles of triceps surae and lumbar paraspinal musculature. Each trial lasted for 60 s; vibration was applied from the 15th till the 30th second. Changes in mean velocity and mean position of the center of pressure (CoP) as a result of muscle vibration were calculated. Results show that on foam, the effect of triceps surae vibration on mean CoP velocity was significantly smaller than on a solid surface, while for paraspinal musculature vibration the effect was bigger on foam than on solid surface. Similar effects were seen for mean CoP displacement as outcome. Exercises on unstable surfaces appear not to target peripheral ankle proprioception. Exercises on an unstable surface may challenge the capacity of the central nervous system to shift the weighting of sources of proprioceptive signals on balance.

  19. The influence of unstable modified wall squat exercises on the posture of female university students.

    PubMed

    Lee, Yoonmi

    2015-08-01

    [Purpose] The purpose of this study was to examine the effect of unstable modified wall squat exercises on the posture of female university students. [Subjects] The subjects of this study were 30 female university students who were equally and randomly allocated to an unstable modified wall squat exercises group the experimental group and a stable modified wall squat exercises group the control group. [Methods] Both groups performed their respective exercises for 30 minutes three times per week over a six-week period. Using BackMapper, trunk inclination, trunk imbalance, pelvic position, pelvic torsion, pelvic rotation, and position of the scapulae were evaluated. [Results] The unstable modified wall squat exercises group obtained significant results for trunk inclination, trunk imbalance, pelvic position, pelvic torsion, position of the scapulae, while the stable modified wall squat exercises group obtained significant results for trunk imbalance and pelvic position. [Conclusion] Unstable modified wall squat exercises may be applied as a method to correct the posture of average adults.

  20. How Unstable Are "School Effects" Assessed by a Value-Added Technique?

    ERIC Educational Resources Information Center

    Gorad, Stephen; Hordosy, Rita; Siddiqui, Nadia

    2013-01-01

    This paper re-considers the widespread use of value-added approaches to estimate school "effects", and shows the results to be very unstable over time. The paper uses as an example the contextualised value-added scores of all secondary schools in England. The study asks how many schools with at least 99% of their pupils included in the…

  1. A sliding mode control proposal for open-loop unstable processes.

    PubMed

    Rojas, Rubén; Camacho, Oscar; González, Luis

    2004-04-01

    This papers presents a sliding mode controller based on a first-order-plus-dead-time model of the process for controlling open-loop unstable systems. The proposed controller has a simple and fixed structure with a set of tuning equations as a function of the desired performance. Both linear and nonlinear models were used to study the controller performance by computer simulations.

  2. Sensors, Volume 1, Fundamentals and General Aspects

    NASA Astrophysics Data System (ADS)

    Grandke, Thomas; Ko, Wen H.

    1996-12-01

    'Sensors' is the first self-contained series to deal with the whole area of sensors. It describes general aspects, technical and physical fundamentals, construction, function, applications and developments of the various types of sensors. This volume deals with the fundamentals and common principles of sensors and covers the wide areas of principles, technologies, signal processing, and applications. Contents include: Sensor Fundamentals, e.g. Sensor Parameters, Modeling, Design and Packaging; Basic Sensor Technologies, e.g. Thin and Thick Films, Integrated Magnetic Sensors, Optical Fibres and Intergrated Optics, Ceramics and Oxides; Sensor Interfaces, e.g. Signal Processing, Multisensor Signal Processing, Smart Sensors, Interface Systems; Sensor Applications, e.g. Automotive: On-board Sensors, Traffic Surveillance and Control, Home Appliances, Environmental Monitoring, etc. This volume is an indispensable reference work and text book for both specialits and newcomers, researchers and developers.

  3. The Fundamental Neutron Physics Facilities at NIST.

    PubMed

    Nico, J S; Arif, M; Dewey, M S; Gentile, T R; Gilliam, D M; Huffman, P R; Jacobson, D L; Thompson, A K

    2005-01-01

    The program in fundamental neutron physics at the National Institute of Standards and Technology (NIST) began nearly two decades ago. The Neutron Interactions and Dosimetry Group currently maintains four neutron beam lines dedicated to studies of fundamental neutron interactions. The neutrons are provided by the NIST Center for Neutron Research, a national user facility for studies that include condensed matter physics, materials science, nuclear chemistry, and biological science. The beam lines for fundamental physics experiments include a high-intensity polychromatic beam, a 0.496 nm monochromatic beam, a 0.89 nm monochromatic beam, and a neutron interferometer and optics facility. This paper discusses some of the parameters of the beam lines along with brief presentations of some of the experiments performed at the facilities.

  4. Fundamental understanding of matter: an engineering viewpoint

    SciTech Connect

    Cullingford, H.S.; Cort, G.E.

    1980-01-01

    Fundamental understanding of matter is a continuous process that should produce physical data for use by engineers and scientists in their work. Lack of fundamental property data in any engineering endeavor cannot be mitigated by theoretical work that is not confirmed by physical experiments. An engineering viewpoint will be presented to justify the need for understanding of matter. Examples will be given in the energy engineering field to outline the importance of further understanding of material and fluid properties and behavior. Cases will be cited to show the effects of various data bases in energy, mass, and momentum transfer. The status of fundamental data sources will be discussed in terms of data centers, new areas of engineering, and the progress in measurement techniques. Conclusions and recommendations will be outlined to improve the current situation faced by engineers in carrying out their work. 4 figures.

  5. Fundamental Interventions: How Clinicians Can Address the Fundamental Causes of Disease.

    PubMed

    Reich, Adam D; Hansen, Helena B; Link, Bruce G

    2016-06-01

    In order to enhance the "structural competency" of medicine-the capability of clinicians to address social and institutional determinants of their patients' health-physicians need a theoretical lens to see how social conditions influence health and how they might address them. We consider one such theoretical lens, fundamental cause theory, and propose how it might contribute to a more structurally competent medical profession. We first describe fundamental cause theory and how it makes the social causes of disease and health visible. We then outline the sorts of "fundamental interventions" that physicians might make in order to address the fundamental causes.

  6. The Multiverse and Particle Physics

    NASA Astrophysics Data System (ADS)

    Donoghue, John F.

    2016-10-01

    The possibility of fundamental theories with very many ground states, each with different physical parameters, changes the way that we approach the major questions of particle physics. Most importantly, it raises the possibility that these different parameters could be realized in different domains in the larger universe. In this review, I survey the motivations for the multiverse and the impact of the idea of the multiverse on the search for new physics beyond the Standard Model.

  7. Double layers acting as particles accelerators

    SciTech Connect

    Sanduloviciu, M.; Lozneanu, E.

    1995-12-31

    It is shown that self-consistent stable and unstable double layers generated in plasma after a self-organisation process are able to accelerate charged particles. The implication of cosmic double layers (Dls) in the acceleration of electrical charged particles long been advocated by Alfven and his Stockholm school is today disputed by argument that static electric fields associated with Dls are conservative and consequently the line integral of the electric field outside the DL balances the line integral inside it. Related with this dispute we will evidence some, so far not considered, facts which are in our opinion arguments that aurora Dls are able to energize particles. For justifying this assertion we start from recent experimental results concerning the phenomenology of self-consistent Dls whose generation involve beside ionisations the neutrals excitations which are at tile origin of the light phenomena as those observed in auroras.

  8. Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes

    NASA Astrophysics Data System (ADS)

    Böhme, Martina; Hermanns, Reginald L.; Oppikofer, Thierry; Penna, Ivanna

    2016-04-01

    Unstable rock slopes that can cause large failures of the rock-avalanche type have been mapped in Norway for almost two decades. Four sites have earlier been characterized as high-risk objects based on expertise of few researchers. This resulted in installing continuous monitoring systems and set-up of an early-warning system for those four sites. Other unstable rock slopes have not been ranked related to their hazard or risk. There are ca. 300 other sites known of which 70 sites were installed for periodic deformation measurements using multiple techniques (Global Navigation Satellite Systems, extensometers, measurement bolts, and others). In 2012 a systematic hazard and risk classification system for unstable rock slopes was established in Norway and the mapping approach adapted to that in 2013. Now, the first 22 sites were classified for hazard, consequences and risk using this classification system. The selection of the first group of sites to be classified was based on an assumed high hazard or risk and importance given to the sites by Norwegian media and the public. Nine of the classified 22 unstable rock slopes are large sites that deform inhomogeneously or are strongly broken up in individual blocks. This suggests that different failure scenarios are possible that need to be analyzed individually. A total of 35 failure scenarios for those nine unstable rock slopes were considered. The hazard analyses were based on 9 geological parameters defined in the classification system. The classification system will be presented based on the Gamanjunni unstable rock slope. This slope has a well developed back scarp that exposes 150 m preceding displacement. The lateral limits of the unstable slope are clearly visible in the morphology and InSAR displacement data. There have been no single structures observed that allow sliding kinematically. The lower extend of the displacing rock mass is clearly defined in InSAR data and by a zone of higher rock fall activity. Yearly

  9. Particle sizing by measurement of forward-scattered light at two angles

    NASA Technical Reports Server (NTRS)

    Buchele, D. R.

    1983-01-01

    Fundamental and practical limitations to particle sizing by measurement of forward scattered light are presented. Methods to minimize the limitations are described. Two types of instruments are compared.

  10. Particle theory and cosmology

    SciTech Connect

    Not Available

    1990-01-01

    The overall objective of the research supported by this contract is to further our understanding of the basic building blocks of matter as well as the role fundamental interactions play in cosmology and astrophysics. Astrophysical data, such as from high energy cosmic rays and large scale structure of the universe, are employed to constrain particle physics theories. Particle collisions at Tevatron and higher (SSC) energies are also under investigation. During the past year a systematic reanalysis of the correlation between solar activity and the solar neutrino flux was undertaken. The conclusion seems to be that the Homestake experimental data show a correlation at a significant level, supporting the hypothesis that the neutrino possesses a magnetic moment. A separate, but related, theoretical investigation of electromagnetic properties of elementary particles has led to the discovery of a class of models in which the neutrino is endowed with an appreciable magnetic moment while its remains small. Altogether members of the group have been co-authors of 28 papers during the grant year on topics ranging from fermion masses to the role of ultra-high energy hadronic interactions in cosmic ray physics.

  11. Particle-drop Impact in Midair

    NASA Astrophysics Data System (ADS)

    Amirfazli, Alidad; Strzebin, Stefan; Peise, Oliver; Chevrollier, David

    2011-11-01

    For the first time the impact of a drop and particle in the mid-air is studied, which is a fundamental physical phenomenon relevant to many applications involving a fluidized bed and a liquid jet, e.g. drug particle coating, and upgrading of heavy oil. To date it has not been clear what happens when a particle and drop collide in midair. An apparatus was build to allow deterministic impact of a particle and drop to occur in midair. Using high speed imaging the impact of three different particles with water drops is studied at different relative velocities. Possible collision outcomes are elucidated in terms of particle-drop diameter ratio, Weber number, and particle wettability. Three distinct regimes of bonding, ripping and coating, and shattering are identified and discussed in this novel study. The differences between on-axis versus off-axis impact is also briefly discussed. NSERC & Canada Research Chairs.

  12. Improving Tidal Measurements about Europa Using the Properties of Unstable Periodic Orbits

    NASA Astrophysics Data System (ADS)

    Boone, Dylan; Scheeres, D. J.

    2012-10-01

    The NASA Jupiter Europa Orbiter mission requires a circular, near-polar orbit to measure Europa's Love numbers, geophysical coefficients which give insight into whether a liquid ocean exists. This type of orbit about planetary satellites is known to be unstable. The effects of Jupiter's tidal gravity are seen in changes in Europa's gravity field and surface deformation, which are sensed through doppler tracking over time and altimetry measurements respectively. These two measurement types separately determine the h and k Love numbers, a combination of which bounds how thick the ice shell of Europa is and whether liquid water is present. This work shows how the properties of an unstable periodic orbit about Europa generate preferred measurement directions in the orbit determination process for estimating science parameters. We generate an error covariance over seven days for the orbiter state and science parameters and then disperse the orbit initial conditions in a Monte Carlo simulation according to this covariance. The dispersed orbits are shown to have a bias toward longer lifetimes and we discuss this as an effect of the stable and unstable manifolds of the periodic orbit. The stable manifold represents contraction forward in time and the unstable manifold represents expansion forward in time. However, using an epoch formulation of a square-root information filter, measurements aligned with the unstable manifold mapped back in time add more information to the orbit determination process than measurements aligned with the stable manifold. This corresponds to a contraction in the uncertainty of the estimate of the desired parameters, including the Love numbers. Low altitude, near-polar periodic orbits with these characteristics are discussed along with the estimation results for the Love numbers, orbiter state, and orbit lifetime. These results are applicable to other measurements and planetary satellites since the mathematical model is the same.

  13. DOE Fundamentals Handbook: Mathematics, Volume 2

    SciTech Connect

    Not Available

    1992-06-01

    The Mathematics Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of mathematics and its application to facility operation. The handbook includes a review of introductory mathematics and the concepts and functional use of algebra, geometry, trigonometry, and calculus. Word problems, equations, calculations, and practical exercises that require the use of each of the mathematical concepts are also presented. This information will provide personnel with a foundation for understanding and performing basic mathematical calculations that are associated with various DOE nuclear facility operations.

  14. DOE Fundamentals Handbook: Mathematics, Volume 1

    SciTech Connect

    Not Available

    1992-06-01

    The Mathematics Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of mathematics and its application to facility operation. The handbook includes a review of introductory mathematics and the concepts and functional use of algebra, geometry, trigonometry, and calculus. Word problems, equations, calculations, and practical exercises that require the use of each of the mathematical concepts are also presented. This information will provide personnel with a foundation for understanding and performing basic mathematical calculations that are associated with various DOE nuclear facility operations.

  15. DOE Fundamentals Handbook: Electrical Science, Volume 1

    SciTech Connect

    Not Available

    1992-06-01

    The Electrical Science Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of electrical theory, terminology, and application. The handbook includes information on alternating current (AC) and direct current (DC) theory, circuits, motors, and generators; AC power and reactive components; batteries; AC and DC voltage regulators; transformers; and electrical test instruments and measuring devices. This information will provide personnel with a foundation for understanding the basic operation of various types of DOE nuclear facility electrical equipment.

  16. DOE Fundamentals Handbook: Electrical Science, Volume 2

    SciTech Connect

    Not Available

    1992-06-01

    The Electrical Science Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding terminology, and application. The handbook includes information on alternating current (AC) and direct current (DC) theory, circuits, motors, and generators; AC power and reactive components; batteries; AC and DC voltage regulators; transformers; and electrical test instruments and measuring devices. This information will provide personnel with a foundation for understanding the basic operation of various types of DOE nuclear facility electrical equipment.

  17. Dark Energy: A Crisis for Fundamental Physics

    ScienceCinema

    Stubbs, Christopher [Harvard University, Cambridge, Massachusetts, USA

    2016-07-12

    Astrophysical observations provide robust evidence that our current picture of fundamental physics is incomplete. The discovery in 1998 that the expansion of the Universe is accelerating (apparently due to gravitational repulsion between regions of empty space!) presents us with a profound challenge, at the interface between gravity and quantum mechanics. This "Dark Energy" problem is arguably the most pressing open question in modern fundamental physics. The first talk will describe why the Dark Energy problem constitutes a crisis, with wide-reaching ramifications. One consequence is that we should probe our understanding of gravity at all accessible scales, and the second talk will present experiments and observations that are exploring this issue.

  18. DOE Fundamentals Handbook: Electrical Science, Volume 4

    SciTech Connect

    Not Available

    1992-06-01

    The Electrical Science Fundamentals Handbook was developed to assist nuclear facility operating contractors provide operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of electrical theory, terminology, and application. The handbook includes information on alternating current (AC) and direct current (DC) theory, circuits, motors, and generators; AC power and reactive transformers; and electrical test components; batteries; AC and DC voltage regulators; instruments and measuring devices. This information will provide personnel with a foundation for understanding the basic operation of various types of DOE nuclear facility electrical equipment.

  19. Escape through an unstable limit cycle driven by multiplicative colored non-Gaussian and additive white Gaussian noises.

    PubMed

    Bag, Bidhan Chandra; Hu, Chin-Kun

    2007-04-01

    In a previous paper [Bag and Hu, Phys. Rev. E 73, 061107 (2006)], we studied the mean lifetime (MLT) for the escape of a Brownian particle through an unstable limit cycle driven by multiplicative colored Gaussian and additive Gaussian white noises and found resonant activation (RA) behavior. In the present paper we switch from Gaussian to non-Gaussian multiplicative colored noise. We find that in the RA phenomenon, the minimum appears at a smaller noise correlation time (tau) for non-Gaussian noises compared to Gaussian noises in the plot of MLT vs tau for a fixed noise variance; the same plot for a given noise strength increases linearly and the increasing rate is smaller for non-Gaussian noises than for the Gaussian noises; the plot of logarithm of inverse of MLT vs inverse of the strength of additive noise is Arrhenius-like for Gaussian colored noise and it becomes similar to the quantum-Kramers rate if the multiplicative noise is non-Gaussian.

  20. Particle Sizer

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Microspheres are tiny plastic beads that represent the first commercial products manufactured in orbit. An example of how they are used is a new aerodynamic particle sizer designated APS 33B produced by TSI Incorporated. TSI purchased the microspheres from the National Bureau of Standards which certified their exact size and the company uses them in calibration of the APS 33B* instrument, latest in a line of TSI systems for generating counting and weighing minute particles of submicron size. Instruments are used for evaluating air pollution control devices, quantifying environments, meteorological research, testing filters, inhalation, toxicology and other areas where generation or analysis of small airborne particles is required. * The APS 33B is no longer being manufactured. An improved version, APS 3320, is now being manufactured. 2/28/97