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.
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)
Unstable particles in non-relativistic quantum mechanics?
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.
A Fundamental Theorem on Particle Acceleration
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.
Factorization method in the model of unstable particles with a smeared mass
Kuksa, V. I.
2009-06-15
The method of factorization, based on the model of unstable particles with a smeared mass, is applied to the processes with an unstable particle in the intermediate state. It was shown, that in the framework of the method suggested, the decay rate and cross section can be represented in the universal factorized form for an arbitrary set of particles. An exact factorization is caused by the specific structure of unstable particles propagators. We performed the phenomenological analysis of the factorization effect.
Unstable particles and the large- and small-scale dark-matter problems
Dicus, D.A.; Teplitz, V.L.
1986-08-15
We consider cosmological models in which the mass of the Universe is dominated by unstable weakly interacting particles (X-italic) with lifetime on the order of the age of the Universe. In our picture the mass of galaxies and clusters is dominated by undecayed X-italic particles while the Universe is closed in the large by their relativistic decay products. Quantitative results are given based on Turner's equations for evolution in the presence of dominant unstable particles. Several possibilities for the X-italic particle are considered. Lifetimes are calculated within these scenarios and shown to be close to those required.
Particle acceleration by magnetic reconnection in unstable twisted coronal loop
NASA Astrophysics Data System (ADS)
Gordovskyy, Mykola; Browning, Philippa; Vekstein, Grigory
Photospheric motions may result in twisting of a coronal loop magnetic field. Such a field configuration contains free energy that may be released by reconnection with the magnetic field relaxing to the linear force-free configuration. Browning & Van der Linden (2003) suggested that such a relaxation event may be triggered by onset of ideal kink instability. In the present work we study the evolution of a twisted magnetic fluxtube with zero net ax-ial current following Browning et al. (2008). Further, proton and electron trajectories are investigated using the test-particle approach consistently with the time-dependent reconnec-tion model. We discuss temporal evolution of proton and electron energy spectra and possible observational implications.
Relativistic Gamow vectors: State vectors for unstable particles
NASA Astrophysics Data System (ADS)
Kaldas, Hany Kamel Halim
The relativistic Gamow vectors are derived from the analytic continuation of the angular momentum velocity kets to the resonance pole of the S- matrix. This construction is justifiable within a Rigged Hilbert Space of Hardy class functions. The kets obtained | p j3[
Unstable states in quantum theory
NASA Astrophysics Data System (ADS)
Kuksa, V. I.
2014-05-01
Various approaches to the problem of describing unstable particles are reviewed. Fundamental problems that arise in quantum field description of these particles and the ways of their solution are considered. Among them, there is an approach related to the notion of the smeared (continuous) mass, which originates from the finite lifetime of unstable particles. The quantum field model of unstable particles with smeared mass, which is built upon two basic axiomatic elements, is considered in detail. The basic processes with unstable particles (decay and scattering) are considered within the framework of the model and the formalism for describing physical characteristics of those processes is developed. The model is successfully applied to describing the processes of pair and triple boson production at the linear collider, top quark pair production, and certain hadronic decays. Based on this model, the factorization method is developed, which allows a description of complicated and multistep scattering and decay processes with unstable particles to be considerably simplified.
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…
Fundamentals of relativistic particle beam optics
Cornacchia, M.
1995-12-01
This lecture introduces the nonaccelerator-specialist to the motion of charged particles in a Storage Ring. The topics of discussion are restricted to the linear and nonlinear dynamics of a single particle in the transverse plane, i.e., the plane perpendicular to the direction of motion. The major omissions for a complete review of accelerator theory, for which a considerable literature exists, are the energy and phase oscillations (1). Other important accelerator physics aspects not treated here are the collective instabilities (2), the role of synchrotron radiation in electron storage rings (3), scattering processes (4), and beam-beam effects in colliding beam facilities (5). Much of the discussion that follows applies equally well to relativistic electron, proton, or ion synchrotrons. In this narrative, we refer to the particle as electron. After a broad overview, the magnetic forces acting on the electrons and the associated differential equations of motion are discussed. Solutions of the equations are given without derivation; the method of solution is outlined. and references for deeper studies are given. In this paper, the word electron is used to signify electron or positron. The dynamics of a single particle are not affected by the sign of its charge when the magnetic field direction is changed accordingly.
Microwaves and particle accelerators: a fundamental link
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)
Geometric representation of fundamental particles' inertial mass
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 θ_{ν} of the masses on the Sphere, satisfy the symmetry θ_{ν} + θ_{N+1-ν} = π within less than 1% relative error. In addition, these pair correlations include the pairs θ_{γ} + θ_{top} ≃ π and θ_{gluon} + θ_{H} ≃ π as well as pairing the weak gauge bosons with the three neutrinos.
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.
Near-threshold boson pair production in the model of smeared-mass unstable particles
Kuksa, V. I.; Pasechnik, R. S.
2010-09-15
Near-threshold production of boson pairs is considered within the framework of the model of unstable particles with smeared mass. We describe the principal aspects of the model and consider the strategy of calculations including the radiative corrections. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations. Suggested approach significantly simplifies calculations with respect to the standard perturbative one.
Fundamental Particles and Interactions. A Wall Chart of Modern Physics.
ERIC Educational Resources Information Center
Achor, William T.; And Others
1988-01-01
Discusses a wall chart, "The Standard Model of Fundamental Particles and Interactions," for use in introductory physics courses at either high school or college level. Describes the chart development process, introduction and terminology of particle physics, components of the chart, and suggestions for using the chart, booklet, and software. (YP)
Non-factorizable photonic corrections to resonant production and decay of many unstable particles
NASA Astrophysics Data System (ADS)
Dittmaier, Stefan; Schwan, Christopher
2016-03-01
Electroweak radiative corrections to the production of high-multiplicity final states with several intermediate resonances in most cases can be sufficiently well described by the leading contribution of an expansion about the resonance poles. In this approach, also known as pole approximation, corrections are classified into separately gauge-invariant factorizable and non-factorizable corrections, where the former can be attributed to the production and decay of the unstable particles on their mass shell. The remaining non-factorizable corrections are induced by the exchange of soft photons between different production and decay subprocesses. We give explicit analytical results for the non-factorizable photonic virtual corrections to the production of an arbitrary number of unstable particles at the one-loop level and, thus, present an essential building block in the calculation of next-to-leading-order electroweak corrections in pole approximation. The remaining virtual factorizable corrections can be obtained with modern automated one-loop matrix-element generators, while the evaluation of the corresponding real photonic corrections can be evaluated with full matrix elements by multi-purpose Monte Carlo generators. Our results can be easily modified to non-factorizable QCD corrections, which are induced by soft-gluon exchange.
NASA Astrophysics Data System (ADS)
Giannini, Judith
2016-03-01
The object of this work was to study the feasibility of identifying a minimum set of fundamental particles that could be used to build up composite fermions and bosons that exhibit the same properties and behavior as the Standard Model (SM) fundamental particles. The spontaneous decay of most of the SM fermions suggests the possibility that they are composite in nature. The results of this arithmetically-based conceptual model identify a minimum set of only two fundamental particles (with equal and opposite mass) that combine in fractal-like configurations to form Intermediate Building Blocks (IMB). The IMBs then combine to form all of the SM fundamental particles and their anti-counterparts. These composite (bright universe) particles agree with the SM particles in mass, spin, electric charge, decay products and maximum classical radius (indicated by the scattering cross-section). Further, FRACEP identifies an equal set of dark universe particles, based primarily on its negative fundamental particle, which could represent the dark matter and energy understood to be the cause of the expansion of our (bright) universe.
Simulation of Unstable Fault Slip in Granite Using a Bonded-particle Model
NASA Astrophysics Data System (ADS)
Hazzard, J. F.; Collins, D. S.; Pettitt, W. S.; Young, R. P.
- A bonded-particle model is used to simulate shear-type microseismic events induced by tunnel excavation in granite. The model represents a volume of granite by an assembly of 50,000 individual particles bonded together at points of contact. A plane of weakness is included in the model and this plane is subjected to increasing shear load while the normal load across the plane is held constant. As shear stress in the model increases, bonds begin to break and small acoustic emissions (AE) result. After enough bonds have broken, macro-slip occurs across the large portions of the fault in an unstable manner. Since the model is run dynamically, seismic source information can be calculated for the simulated AE and macro-slip events. This information is compared with actual results obtained from seismic monitoring around an underground excavation. Although the modelled events exhibit larger magnitudes than the actual recorded events, there are many similarities between the model and the actual results, namely the presence of foreshocks before the macro-slip events and the patterns of energy release during loading. In particular, the model provides the ability to examine the complexity of the slip events in detail.
Fundamental theories of waves and particles formulated without classical mass
Fry, J.L.; Musielak, Z.E.
2010-12-15
Quantum and classical mechanics are two conceptually and mathematically different theories of physics, and yet they do use the same concept of classical mass that was originally introduced by Newton in his formulation of the laws of dynamics. In this paper, physical consequences of using the classical mass by both theories are explored, and a novel approach that allows formulating fundamental (Galilean invariant) theories of waves and particles without formally introducing the classical mass is presented. In this new formulation, the theories depend only on one common parameter called 'wave mass', which is deduced from experiments for selected elementary particles and for the classical mass of one kilogram. It is shown that quantum theory with the wave mass is independent of the Planck constant and that higher accuracy of performing calculations can be attained by such theory. Natural units in connection with the presented approach are also discussed and justification beyond dimensional analysis is given for the particular choice of such units.
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)].
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.
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.
Fundamental Constants as Monitors of Particle Physics and Dark Energy
NASA Astrophysics Data System (ADS)
Thompson, Rodger
2016-03-01
This contribution considers the constraints on particle physics and dark energy parameter space imposed by the astronomical observational constraints on the variation of the proton to electron mass ratio μ and the fine structure constant α. These constraints impose limits on the temporal variation of these parameters on a time scale greater than half the age of the universe, a time scale inaccessible by laboratory facilities such as the Large Hadron Collider. The limits on the variance of μ and α constrain combinations of the QCD Scale, the Higgs VEV and the Yukawa coupling on the particle physics side and a combination of the temporal variation of rolling scalar field and its coupling to the constants on the dark energy side.
... Braunwald E. Unstable angina and non-ST elevation myocardial infarction In: Mann DL, Zipes DP, Libby P, et ... coronary syndrome: unstable angina and non-ST elevation myocardial infarction. In: Goldman L, Schafer AI, eds. Goldman's Cecil ...
On the Masses of the Fundamental Particles in the Bound State
NASA Astrophysics Data System (ADS)
Subramanium, R.; Goh, N. K.; Chia, L. S.
1996-07-01
A simple computational approach is presented to show that the masses of the fundamental particles are not only lower in the elements but are also different for the various elements. Only basic concepts relating to an atom such as mass number, atomic number, relative isotopic mass, and Avogadro's Number are required. The mass values of the fundamental particles are not needed in the proposed treatment, except for comparison. Some pedagogical elements of interest are also addressed.
Smoothed Particle Hydrodynamics pore-scale simulations of unstable immiscible flow in porous media
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.
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.
... to the ER. You could be having a heart attack which puts you at increased risk for severe cardiac arrhythmias or cardiac arrest , which could lead to sudden death. Learn about an unstable form of angina called ...
Research on fundamental aspects of inorganic vapor and particle deposition in coal-fired systems
Rosner, D.E.
1992-06-01
Parallel research studies are underway on the following interrelated and fundamental subjects; Geometrical Approach to Determining the Sticking Probability of Particles Impacting on Convex Solid Surfaces; Correlations for High Schmidt Number Particle Deposition From Dilute Flowing Rational Engineering Suspensions; Average Capture Probability of Arriving Particles Which Are Distributed With ResPect to ImPact VelocitY and Incidence Angle (Relative to Deposit Substrate); Experimental and Theoretical Studies of Vapor Infiltration of Non-isothermal Granular Deposits; Effective Area/Volume of Populations of 'MicroPorous' Aerosol Particles (Compact and 'Fractal' Quasispherical Aggregates); Effects of Radiative Heat Transfer on the Coagulation Rates of Combustion-Generated Particles; Structure-Sensitivity of Total Mass Deposition Rates from Combustion Product Streams containing Coagulation-Aged Populations of Aggregated Primary Particles; and Na[sub 2]SO[sub 4] Chemical Vapor Deposition From Chlorine-containing Coal-Derived Gases.
Possibilities for fundamental particle/astrophysics experiments at a lunar base
NASA Astrophysics Data System (ADS)
Rudaz, S.
1990-03-01
It is suggested that some experiments such as the search for proton decay and for cosmic ray signatures of dark matter particles should be seriously considered in planning the scientific program of a Lunar Base Laboratory. Such experiments could elucidate many of the most fundamental unanswered questions of cosmology and particle physics, but face eventual basic limitations on earth and in earth orbit, respectively. Some of these limitations may be circumvented at a Lunar Base due to the lack of atmosphere and stable environment of the moon.
NASA Astrophysics Data System (ADS)
Krasnoselskikh, V.; Artemyev, A.; Agapitov, O. V.; Mourenas, D.
2013-12-01
We present selected THEMIS observations of highly-oblique and large amplitude chorus waves at medium latitudes. The major part of observed waves propagates at nearly-electrostatic mode with normal angles close to resonance cone. We use test particle simulations and analytical theory to estimate efficiency of nonlinear particle acceleration by these waves via Landau and fundamental cyclotron resonances. We show that trapping into the Landau resonance corresponds to a decrease of electron equatorial pitch-angles, while trapping into the first cyclotron resonance increases electron equatorial pitch-angles. For 100 keV electrons, the energy gain is larger for the trapping due to Landau resonance. Moreover, trapping into the Landau resonance is accessible for a wider range of initial pitch-angles in comparison with the fundamental resonance.
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.
NASA Astrophysics Data System (ADS)
Wittmann, René; Marechal, Matthieu; Mecke, Klaus
2016-06-01
Density functional theory (DFT) for hard bodies provides a theoretical description of the effect of particle shape on inhomogeneous fluids. We present improvements of the DFT framework fundamental measure theory (FMT) for hard bodies and validate these improvements for hard spherocylinders. To keep the paper self-contained, we first discuss the recent advances in FMT for hard bodies that lead to the introduction of fundamental mixed measure theory (FMMT) in our previous paper (2015 Europhys. Lett. 109 26003). Subsequently, we provide an efficient semi-empirical alternative to FMMT and show that the phase diagram for spherocylinders is described with similar accuracy in both versions of the theory. Finally, we present a semi-empirical modification of FMMT whose predictions for the phase diagram for spherocylinders are in excellent quantitative agreement with computer simulation results.
Wittmann, René; Marechal, Matthieu; Mecke, Klaus
2016-06-22
Density functional theory (DFT) for hard bodies provides a theoretical description of the effect of particle shape on inhomogeneous fluids. We present improvements of the DFT framework fundamental measure theory (FMT) for hard bodies and validate these improvements for hard spherocylinders. To keep the paper self-contained, we first discuss the recent advances in FMT for hard bodies that lead to the introduction of fundamental mixed measure theory (FMMT) in our previous paper (2015 Europhys. Lett. 109 26003). Subsequently, we provide an efficient semi-empirical alternative to FMMT and show that the phase diagram for spherocylinders is described with similar accuracy in both versions of the theory. Finally, we present a semi-empirical modification of FMMT whose predictions for the phase diagram for spherocylinders are in excellent quantitative agreement with computer simulation results. PMID:27115987
Fundamentals and Application of Magnetic Particles in Cell Isolation and Enrichment
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
Interactive Multimedia Software on Fundamental Particles and Forces. Final Technical Report
Jack Sculley
1999-04-27
Research in the SBIR Phase 2 grant number 95 ER 81944 centered on creating interactive multimedia software for teaching basic concepts in particle physics on fundamental particles and forces. The work was undertaken from February 1997 through July 1998. Overall the project has produced some very encouraging results in terms of product development, interest from the general public and interest from potential Phase 3 funders. Although the original Phase 3 publisher, McGraw Hill Home Interactive, was dissolved by its parent company, and other changes in the CD-ROM industry forced them to change their focus from CD-ROM to the Internet, there has been substantial interest from software publishers and online content providers in the content developed in the course of the Phase 2 research. Results are summarized.
Testing Fundamental Particle Physics with the Galactic White Dwarf Luminosity Function
NASA Astrophysics Data System (ADS)
Miller Bertolami, M. M.; Melendez, B. E.; Althaus, L. G.; Isern, J.
2015-06-01
Recent determinations of the white dwarf luminosity function (WDLF) from very large surveys have extended our knowledge of the WDLF to very high luminosities. It has been shown that the shape of the luminosity function of white dwarfs (WDLF) is a powerful tool to test the possible properties and existence of fundamental weakly interacting subelectronvolt particles. This, together with the availability of new full evolutionary white dwarf models that are reliable at high luminosities, have opened the possibility of testing particle emission in the core of very hot white dwarfs. We use the available WDLFs from the Sloan Digital Sky Survey and the SuperCOSMOS Sky Survey to constrain the values of the neutrino magnetic dipole moment (μν) and the axion-electron coupling constant (gae) of DFSZ-axions.
A new fundamental model of moving particle for reinterpreting Schroedinger equation
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.
NASA Astrophysics Data System (ADS)
Bürger, Hans; Betzel, Martina
1985-10-01
Fourier Transform far infrared spectra of unstable stannyl chloride, bromide and iodide have been measured in the gas phase with a resolution of 0.04 cm-1. At pressures below 10 mbar, their lifetimes at 0 °C in preconditioned cells were found to be 10-30 min. The v3 fundamentals and hot bands of the series (n + 1)v3 - nv3 have been observed. Rotational J structure has been resolved for monoisotopic samples, and band origins v30, anharmonicity constants x33, ɑ3B and DJ0 values have been determined from the rovibrational analyses. The following v30 values were obtained: H3116Sn35Cl 375.470 (5), H3116Sn37Cl 367.689 (6), H3116Sn79Br 263.566 (5) and H3116SnI 209.759 (6) cm-1.
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.
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
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
Greene, G.
2001-08-24
Low-energy neutrons from reactor and spallation neutron sources have been employed in a wide variety of investigations that shed light on important issues in nuclear, particle, and astrophysics; in the elucidation of quantum mechanics; in the determination of fundamental constants; and in the study of fundamental symmetry violation (Appendix A, Glossary). In many cases, these experiments provide important information that is not otherwise available from accelerator-based nuclear physics facilities or high energy accelerators. An energetic research community in the United States is engaged in ''fundamental'' neutron physics. With exciting recent results, the possibility of new and upgraded sources, and a number of new experimental ideas, there is an important opportunity for outstanding science in the next decade. ''Fundamental'' neutron physics experiments are usually intensity limited. Researchers require the highest flux neutron sources available, which are either high-flux reactors (continuous sources) or spallation neutron sources (pulsed sources). The primary mission of these major facilities is neutron scattering for materials science research. Notwithstanding this condensed matter focus, essentially all neutron scattering facilities have accepted the value of an on-site fundamental physics program and have typically allocated 5 to 10% of their capabilities (i.e., beam lines) toward nuclear and particle physics research activities.
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
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.
Fundamentals of elasto-inertial particle focusing in curved microfluidic channels.
Xiang, Nan; Zhang, Xinjie; Dai, Qing; Cheng, Jie; Chen, Ke; Ni, Zhonghua
2016-07-01
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. PMID:27300118
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,…
NASA Astrophysics Data System (ADS)
Oechsner, Hans
1995-05-01
Recent instrumental developments of the conventional secondary neutral mass spectrometry (SNMS) technique based on electron gas post-ionization are described with regard to its application to non-conducting samples and its implementation in a novel secondary neutral microprobe. The use of molecular SNMS signals for quantitative surface analysis, and a standard free technique for absolute depth calibration from the mass spectrometric signals are discussed and elucidated by appropriate examples. Finally, some applications of electron gas SNMS to fundamental studies on low energy particle/surface interaction are presented.
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.
NASA Astrophysics Data System (ADS)
Coupland, Jeremy M.; Lobera Salazar, Julia; Halliwell, Neil A.
2000-08-01
We have recently proposed a variant of holographic particle image velocimetry (HPIV) to measure three-component measurements of fluid velocity throughout an extended flow volume. In essence the technique uses double exposure holography to record the positions of seeding particles at two, close spaced constants in time. Analysis of the resulting record is achieved by computing the auto (or cross) correlation of the complex amplitude distributions transmitted by a sampling aperture placed within a real, reconstruction of the holographic image. IN the case of sparsely seeded flows, it is straightforward to show that the field transmitted by the aperture is dominated by the particle images reconstructed close to the aperture itself and the measurement is therefore attributed to the instantaneous flow velocity at the centre of the aperture. As the seeding concentration is increased, however, a significant contribution of the transmitted field is due to light scattered from more distant particles. If significant velocity gradients exist, the contribution due to distant particles is largely un- correlated and the local particle displacement can be extracted even if the field is dominated by this component. If a significant proportion of the scattered light that passes from the aperture is collected from areas in the flow with similar velocity (for example from stagnant regions or light scattered from the flow vessel) then spurious peaks can occur in the correlation signal. This paper examines the limitations on the flow volume that can be mapped at a given seeding concentration and hence the fundamental limits on the number of velocity measurements that can be retrieved from a single recording.
NASA Astrophysics Data System (ADS)
Burikham, Piyabut; Cheamsawat, Krai; Harko, Tiberiu; Lake, Matthew J.
2016-03-01
We obtain bounds for the minimum and maximum mass/radius ratio of a stable, charged, spherically symmetric compact object in a D-dimensional space-time in the framework of general relativity, and in the presence of dark energy. The total energy, including the gravitational component, and the stability of objects with minimum mass/radius ratio is also investigated. The minimum energy condition leads to a representation of the mass and radius of the charged objects with minimum mass/radius ratio in terms of the charge and vacuum energy only. As applied to the electron in the four-dimensional case, this procedure allows one to re-obtain the classical electron radius from purely general relativistic considerations. By combining the lower mass bound, in four space-time dimensions, with minimum length uncertainty relations (MLUR) motivated by quantum gravity, we obtain an alternative bound for the maximum charge/mass ratio of a stable, gravitating, charged quantum mechanical object, expressed in terms of fundamental constants. Evaluating this limit numerically, we obtain again the correct order of magnitude value for the charge/mass ratio of the electron, as required by the stability conditions. This suggests that, if the electron were either less massive (with the same charge) or if its charge were any higher (for fixed mass), a combination of electrostatic and dark energy repulsion would destabilize the Compton radius. In other words, the electron would blow itself apart. Our results suggest the existence of a deep connection between gravity, the presence of the cosmological constant, and the stability of fundamental particles.
NASA Astrophysics Data System (ADS)
Epstein, R.; Delettrez, J. A.; Goncharov, V. N.; McKenty, P. W.; Radha, P. B.; Skupsky, S.
1999-11-01
The effects of Rayleigh--Taylor flow in recent laser-driven implosion experiments are simulated in one dimension by the hydrocode LILAC. Mix is modeled as a diffusive transport process affecting material constituents, thermal energy, and turbulent mix-motion energy within a growing mix region whose boundaries are derived from a saturable, linear multimode model of the Rayleigh--Taylor instability. The linear growth rates and the feedthrough coupling between perturbations of different unstable interfaces are obtained analytically in terms of the one- dimensional fluid profiles. Mode evolution proceeds according to equations applicable to all phases of acceleration, and the effects of geometrically converging, compressible flow are taken into account. Simulated mix-diagnostic signals include time-resolved energy spectra of neutrons from core fuel and/or embedded deuterium shell layers and the energy spectra of charged primary and secondary products of nuclear reactions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority.
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.
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
Rosner, D.E.
1992-06-01
Parallel research studies are underway on the following interrelated and fundamental subjects; Geometrical Approach to Determining the Sticking Probability of Particles Impacting on Convex Solid Surfaces; Correlations for High Schmidt Number Particle Deposition From Dilute Flowing Rational Engineering Suspensions; Average Capture Probability of Arriving Particles Which Are Distributed With ResPect to ImPact VelocitY and Incidence Angle (Relative to Deposit Substrate); Experimental and Theoretical Studies of Vapor Infiltration of Non-isothermal Granular Deposits; Effective Area/Volume of Populations of `MicroPorous` Aerosol Particles (Compact and `Fractal` Quasispherical Aggregates); Effects of Radiative Heat Transfer on the Coagulation Rates of Combustion-Generated Particles; Structure-Sensitivity of Total Mass Deposition Rates from Combustion Product Streams containing Coagulation-Aged Populations of Aggregated Primary Particles; and Na{sub 2}SO{sub 4} Chemical Vapor Deposition From Chlorine-containing Coal-Derived Gases.
Kahn, W K
1966-03-01
A technique, firmly based on a development from ray optics, is presented for calculating the loss due to the finite sizes of curved mirrors when these form an unstable optical resonator. If paraxial rays launched within such a resonator are confined near the resonator axis, the resonator is termed stable; otherwise it is termed unstable, and is known to have high losses. Siegman has recently presented a geometrical method, brilliantly constructed ad hoc, for calculating these losses in unstable resonators, and indicated where these might be advantageous in laser application. The ray optical theory presented here, which employs the concept of ray modes in an equivalent beam waveguide, is shown to yield results equivalent to those of Siegman for all cases considered by him. However, being derived from conventional ray optics, the validity of the formulas is independently established, and these formulas are immediately applicable to re-entrant resonators and resonators containing inhomogeneous media. The fractional loss per resonator pass is equal to 1-|lambda(2)|, where |lambda(2)| < this 1 is an eigenvalue of the transfer matrix T, representing the corresponding ray transformation. PMID:20048863
Unstable nonlocal interface dynamics.
Nicoli, Matteo; Cuerno, Rodolfo; Castro, Mario
2009-06-26
Nonlocal effects occur in many nonequilibrium interfaces, due to diverse physical mechanisms like diffusive, ballistic, or anomalous transport, with examples from flame fronts to thin films. While dimensional analysis describes stable nonlocal interfaces, we show the morphologically unstable condition to be nontrivial. This is the case for a family of stochastic equations of experimental relevance, paradigmatically including the Michelson-Sivashinsky system. For a whole parameter range, the asymptotic dynamics is scale invariant with dimension-independent exponents reflecting a hidden Galilean symmetry. The usual Kardar-Parisi-Zhang nonlinearity, albeit irrelevant in that parameter range, plays a key role in this behavior. PMID:19659099
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.
Romatschke, Paul; Venugopalan, Raju
2006-08-15
We discuss results from 3+1-D numerical simulations of SU(2) Yang-Mills equations for an unstable glasma expanding into the vacuum after a high energy heavy-ion collision. We expand on our earlier work on a non-Abelian Weibel instability in such a system and study the behavior of the instability in greater detail on significantly larger lattices than previously. We establish the time scale for the onset of the instability and demonstrate that the growth rate is robust as one approaches the continuum limit. For large violations of boost invariance, non-Abelian effects cause the growth of soft modes to saturate. At late times, we observe significant creation of longitudinal pressure and a systematic trend towards isotropy. These time scales however are significantly larger than those required for early thermalization in heavy-ion collisions. We discuss additional effects in the produced glasma that may speed up thermalization.
Unstable resonator diode laser
Clark, G.L.
1988-04-19
In a semiconductor diode laser, a structure is described comprising: a generally planar active layer, across which a forward bias voltage is applied, cladding layers adjacent to the active layer, to confine light in a direction perpendicular to the active layer, and first and second facets; in which the first facet is curved to present a concave part-cylindrical reflective surface toward the active layer, and in which the second facet includes a curved portion presenting a convex part-cylindrical reflective surface toward the active layer and a planar portion that is non-reflective. The curvatures of the two curved surfaces have axes of curvature that are approximately perpendicular to the active layer, the curvatures being selected to form an unstable resonator, in which light is confined in a particular sense by the cladding layers and from which energy is out-coupled through the planar portion of the second facet.
Sriranjan, Rouchelle S; Tarkin, Jason M; Evans, Nicholas R; Chowdhury, Mohammed M; Rudd, James H
2016-09-01
Recent advances in imaging technology have enabled us to utilise a range of diagnostic approaches to better characterise high-risk atherosclerotic plaque. The aim of this article is to review current and emerging techniques used to detect and quantify unstable plaque in the context of large and small arterial systems and will focus on both invasive and non-invasive imaging techniques. While the diagnosis of clinically relevant atherosclerosis still relies heavily on anatomical assessment of arterial luminal stenosis, evolving multimodal cross-sectional imaging techniques that encompass novel molecular probes can provide added information with regard to plaque composition and overall disease burden. Novel molecular probes currently being developed to track precursors of plaque rupture such as inflammation, micro-calcification, hypoxia and neoangiogenesis are likely to have translational applications beyond diagnostics and have the potential to play a part in quantifying early responses to therapeutic interventions and more accurate cardiovascular risk stratification. PMID:27273430
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.
NASA Astrophysics Data System (ADS)
Bürger, Hans; Betzel, Martina; Schulz, Petra
1987-01-01
The IR fundamentals {ν 1}/{ν 4} near 1900 cm -1 and {ν 2}/{ν 5} near 700 cm -1 of the unstable stannyl halides H 3116Sn 35Cl, H 3116Sn 79Br, and H 3116SnI have been studied as monoisotopic species by FT spectroscopy. With a resolution of ˜0.04 cm -1, rotational J and K structure has been resolved at least in part, and rovibrational analyses have been performed. Typically, 500 data of each {a 1}/{e} band have been fitted with σ = 5 × 10 -3 cm -1. Excited state rovibrational parameters complete to second order have been determined. A HOFF-based harmonic force field has been computed, and ground state parameters and ground state geometries have been deduced by combining all presently available data. A strong Coriolis interaction between ν2 and ν5 is revealed, while the interaction between ν1 and ν4 was found to be weak. Perturbations by multiply excited rovibrational levels are important for ν4 of H 3116Sn 79Br, while all other bands (with the exception of a weak local perturbation of ν5 by 2 ν3 in H 3116Sn 35CL) appeared to be unperturbed.
ERIC Educational Resources Information Center
Groseclose, Richard
This third in a series of six modules for a course titled Nondestructive Examination (NDE) Techniques II explains the principles of magnets and magnetic fields and how they are applied in magnetic particle testing, describes the theory and methods of magnetizing test specimens, describes the test equipment used, discusses the principles and…
Kono, H.O.
1991-01-01
The objective of this work is to recognize and interpret the signals of transient motion of bubbles (slugs) in fluidized beds by measuring and utilizing the signals of transient motion of solid particles. The two signals were measured simultaneously and also synchronized by using the TTL signal technique in the same fluidized beds. Also, a simultaneous study of video bubble image, transient force and pressure signals was initiated in a two dimensional fluidized bed. we successfully synchronized three signals so that the relationship of bubble behavior and force pressure signals can be identified and characterized. It has been found that bubble image can well be correlated to the transient force signal of solid particles under certain conditions in three dimensional fluidized beds. Accordingly, it seems that the transient force signals can significantly help understanding the transient motion of bubbles (slugs), which is important to design the fluidized beds.
Kono, H.O.
1991-01-01
The objective of this work is to recognize and interpret the signals of transient motion of bubbles (slugs) in fluidized beds by measuring and utilizing the signals of transient motion of solid particles. The two signals were measured simultaneously and also synchronized by using the TTL signal technique in the same fluidized beds. Also, a simultaneous study of video bubble image, transient force and pressure signals was initiated in a two dimensional fluidized bed. we successfully synchronized three signals so that the relationship of bubble behavior and force pressure signals can be identified and characterized. It has been found that bubble image can well be correlated to the transient force signal of solid particles under certain conditions in three dimensional fluidized beds. Accordingly, it seems that the transient force signals can significantly help understanding the transient motion of bubbles (slugs), which is important to design the fluidized beds.
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.
How fundamental are fundamental constants?
NASA Astrophysics Data System (ADS)
Duff, M. J.
2015-01-01
I argue that the laws of physics should be independent of one's choice of units or measuring apparatus. This is the case if they are framed in terms of dimensionless numbers such as the fine structure constant, ?. For example, the standard model of particle physics has 19 such dimensionless parameters whose values all observers can agree on, irrespective of what clock, rulers or scales? they use to measure them. Dimensional constants, on the other hand, such as ?, c, G, e and k ?, are merely human constructs whose number and values differ from one choice of units to the next. In this sense, only dimensionless constants are 'fundamental'. Similarly, the possible time variation of dimensionless fundamental 'constants' of nature is operationally well defined and a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants such as ? or ? on which a good many (in my opinion, confusing) papers have been written, is a unit-dependent phenomenon on which different observers might disagree depending on their apparatus. All these confusions disappear if one asks only unit-independent questions. We provide a selection of opposing opinions in the literature and respond accordingly.
Two dimensional unstable scar statistics.
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.
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.
Unstable infinite nuclear matter in stochastic mean field approach
Colonna, M.; Chomaz, P. Laboratorio Nazionale del Sud, Viale Andrea Doria, Catania )
1994-04-01
In this article, we consider a semiclassical stochastic mean-field approach. In the case of unstable infinite nuclear matter, we calculate the characteristic time of the exponential growing of fluctuations and the diffusion coefficients associated to the unstable modes, in the framework of the Boltzmann-Langevin theory. These two quantities are essential to describe the dynamics of fluctuations and instabilities since, in the unstable regions, the evolution of the system will be dominated by the amplification of fluctuations. In order to make realistic 3D calculations feasible, we suggest to replace the complicated Boltzmann-Langevin theory by a simpler stochastic mean-field approach corresponding to a standard Boltzmann evolution, complemented by a simple noise chosen to reproduce the dynamics of the most unstable modes. Finally we explain how to approximately implement this method by simply tuning the noise associated to the use of a finite number of test particles in Boltzman-like calculations.
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.
Stabilization Strategies for Unstable Dynamics
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
Finite-aperture tapered unstable resonator lasers
NASA Astrophysics Data System (ADS)
Bedford, Robert George
The development of high power, high brightness semiconductor lasers is important for applications such as efficient pumping of fiber amplifiers and free space communication. The ability to couple directly into the core of a single-mode fiber can vastly increase the absorption of pump light. Further, the high mode-selectivity provided by unstable resonators accommodates single-mode operation to many times the threshold current level. The objective of this dissertation is to investigate a more efficient semiconductor-based unstable resonator design. The tapered unstable resonator laser consists of a single-mode ridge coupled to a tapered gain region. The ridge, aided by spoiling grooves, provides essential preparation of the fundamental mode, while the taper provides significant amplification and a large output mode. It is shown a laterally finite taper-side mirror (making the laser a "finite-aperture tapered unstable resonator laser") serves to significantly improve differential quantum efficiency. This results in the possibility for higher optical powers while still maintaining single-mode operation. Additionally, the advent of a detuned second order grating allows for a low divergent, quasicircular output beam emitted from the semiconductor surface, easing packaging tolerances, and making two dimensional integrated arrays possible. In this dissertation, theory, design, fabrication, and characterization are presented. Material theory is introduced, reviewing gain, carrier, and temperature effects on field propagation. Coupled-mode and coupled wave theory is reviewed to allow simulation of the passive grating. A numerical model is used to investigate laser design and optimization, and effects of finite-apertures are explored. A microfabrication method is introduced to create the FATURL in InAlGaAs/-InGaAsP/InP material emitting at about 1410 nm. Fabrication consists of photolithography, electron-beam lithography, wet etch and dry etching processes, metal and
Logarithmic decays of unstable states
NASA Astrophysics Data System (ADS)
Giraldi, Filippo
2015-01-01
It is known that the survival amplitude of unstable quantum states deviates from exponential relaxations and exhibits decays that depend on the integral and analytic properties of the energy distribution density. In the same scenario, model independent dominant logarithmic decays t -1- α0log t of the survival amplitude are induced over long times by special conditions on the energy distribution density. While the instantaneous decay rate exhibits the dominant long time relaxation 1 / t, the instantaneous energy tends to the minimum value of the energy spectrum with the dominant logarithmic decay 1/( tlog 2 t) over long times. Similar logarithmic relaxations have already been found in the dynamics of short range potential systems with even dimensional space or in the Weisskopf-Wigner model of spontaneous emission from a two-level atom. Here, logarithmic decays are obtained as a pure model independent quantum effect in general unstable states.
Unstable semiclassical trajectories in tunneling.
Levkov, D G; Panin, A G; Sibiryakov, S M
2007-10-26
Some tunneling phenomena are described, in the semiclassical approximation, by unstable complex trajectories. We develop a systematic procedure to stabilize the trajectories and to calculate the tunneling probability, including both the suppression exponent and prefactor. We find that the instability of tunneling solutions modifies the power-law dependence of the prefactor on Planck's variant as compared to the case of stable solutions. PMID:17995308
NASA Astrophysics Data System (ADS)
Murdin, P.
2000-11-01
Term that is sometimes used to describe a helium nucleus, a positively charged particle that consists of two protons and two neutrons, bound together. Alpha particles, which were discovered by Ernest Rutherford (1871-1937) in 1898, are emitted by atomic nuclei that are undergoing alpha radioactivity. During this process, an unstable heavy nucleus spontaneously emits an alpha particle and transmut...
Constraints on the mass of unstable neutrinos from the supernova
NASA Astrophysics Data System (ADS)
Liu, Jiang
1987-11-01
The cosmological constraint together with the information obtained from the supernova could be used to give a lower bound on the mass of unstable neutrinos. It is shown that if the only viable channel for the unstable neutrino decay is through three lighter neutrinos, the mass of this particle should be heavier than about 500 eV. I wish to thank Professor Ling-Fong Li and Professor Lincoln Wolfenstein for valuable discussions. This work was supported in part by the US Department of Energy.
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.
Stabilization strategies for unstable dynamics.
Morasso, Pietro; Casadio, Maura; De Santis, Dalia; Nomura, Taishin; Rea, Francesco; Zenzeri, Jacopo
2014-12-01
The stabilization of the human standing posture was originally attributed to the stiffness of the ankle muscles but direct measurements of the ankle stiffness ruled out this hypothesis, leaving open the possibility for a feedback stabilization strategy driven by proprioceptive signals. This solution, however, could be implemented with two different kinds of control mechanisms, namely continuous or intermittent feedback. The debate is now settled and the latter solution seems to be the most plausible one. Moreover, stabilization of unstable dynamics is not limited to bipedal standing. Indeed many manipulation tasks can be described in the same framework and thus a very general protocol for addressing this kind of problems is the use of haptic virtual reality where instability is generated by some kind of divergent or saddle-like force field. Several studies demonstrated that human subjects can choose to adopt a stiffness or feedback strategy as a combination of biomechanical and task constraints and can learn to switch from one strategy to the other if it is feasible or to use one or the other is infeasible. Understanding such mechanisms is relevant, for example, for the design of novel ergonomic man-machine interfaces in difficult, unstable tasks. PMID:25453479
Fundamental Mechanisms of Interface Roughness
Randall L. Headrick
2009-01-06
Publication quality results were obtained for several experiments and materials systems including: (i) Patterning and smoothening of sapphire surfaces by energetic Ar+ ions. Grazing Incidence Small Angle X-ray Scattering (GISAXS) experiments were performed in the system at the National Synchrotron Light Source (NSLS) X21 beamline. Ar+ ions in the energy range from 300 eV to 1000 eV were used to produce ripples on the surfaces of single-crystal sapphire. It was found that the ripple wavelength varies strongly with the angle of incidence of the ions, which increase significantly as the angle from normal is varied from 55° to 35°. A smooth region was found for ion incidence less than 35° away from normal incidence. In this region a strong smoothening mechanism with strength proportional to the second derivative of the height of the surface was found to be responsible for the effect. The discovery of this phase transition between stable and unstable regimes as the angle of incidence is varied has also stimulated new work by other groups in the field. (ii) Growth of Ge quantum dots on Si(100) and (111). We discovered the formation of quantum wires on 4° misoriented Si(111) using real-time GISAXS during the deposition of Ge. The results represent the first time-resolved GISAXS study of Ge quantum dot formation. (iii) Sputter deposition of amorphous thin films and multilayers composed of WSi2 and Si. Our in-situ GISAXS experiments reveal fundamental roughening and smoothing phenomena on surfaces during film deposition. The main results of this work is that the WSi2 layers actually become smoother during deposition due to the smoothening effect of energetic particles in the sputter deposition process.
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. PMID:27108987
Stable processing with unstable plasmas?
NASA Astrophysics Data System (ADS)
Benjamin, Neil
2004-09-01
Plasmas are employed for materials processing over a very wide range of conditions. For typical etch applications, these include plasmas generated in various ways with RF at various frequencies and power levels ranging from 100W up to 10000W. Mixed gas chemistries are used, at pressures ranging from mTorr to Torr, with multiple, often electron-attaching species present in significant proportions. These complex conditions are typically produced in production reactors that are hardly optimal for diagnostic access, so this is not a recipe for a quiescent lab plasma that may be conveniently studied. Inevitably a range of plasma instabilities and other unstable conditions may be encountered, often without immediate detection, as one spans the operating space. These unstable conditions may range from internal well known linear and quasi-linear plasma instabilities1, 2 to gross non-linear relaxation oscillations3, 4, 5, parametric drifts and even plasma extinguishment. Many of these phenomena involve strong interactions with the materials being processed and the external hardware that supports the reactor module operation. We will discuss certain questions: how may one observe such conditions (if you can't see it, does it matter from the processing perspective?); is it advisable to continue processing regardless; what might the consequences be, good or bad, and how they may be controlled6? 1) T. H. Stix, Waves in Plasmas, American Institute of Physics, New York (1992), and The Theory of Plasma Waves, McGraw-Hill (1962). 2) N. Krall and A. Trivelpiece, Principles of Plasma Physics, McGraw-Hill (1973). 3) M. Tuszewski, J. App. Phys., 79 8967 (1996) 4) M. A. Lieberman et. al., Appl. Phys. Lett. 75, 3617 (1999) 5) A. M. Marakhtanov et..al., J. Vac. Sci. Tech. A, 21 1864 (2003) and references therein. 6) D.L.Goodman and N. M. P. Benjamin, J. Phys. D, 36 2845 (2003).
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. PMID:11401791
Intervention Research in Highly Unstable Environments
Buckwalter, Kathleen C.; Grey, Margaret; Bowers, Barbara; McCarthy, Ann Marie; Gross, Deborah; Funk, Marjorie; Beck, Cornelia
2010-01-01
This article highlights issues and presents strategies for conducting intervention research in highly unstable environments such as schools, critical care units, and long-term care facilities. The authors draw on their own experiences to discuss the challenges that may be encountered in highly unstable settings. The concept of validity provides a framework for understanding the value of addressing the many methodological issues that can emerge in settings characterized by instability. We explain unstable environments by elaborating on knowable elements that contribute to instability. Strategies are provided for improving success of intervention research in unstable settings by carrying out an environmental assessment prior to beginning a study. PMID:19035619
Osteoporosis in unstable adult scoliosis
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.
Unstable supercritical discontinuous percolation transitions
NASA Astrophysics Data System (ADS)
Chen, Wei; Cheng, Xueqi; Zheng, Zhiming; Chung, Ning Ning; D'Souza, Raissa M.; Nagler, Jan
2013-10-01
The location and nature of the percolation transition in random networks is a subject of intense interest. Recently, a series of graph evolution processes have been introduced that lead to discontinuous percolation transitions where the addition of a single edge causes the size of the largest component to exhibit a significant macroscopic jump in the thermodynamic limit. These processes can have additional exotic behaviors, such as displaying a “Devil's staircase” of discrete jumps in the supercritical regime. Here we investigate whether the location of the largest jump coincides with the percolation threshold for a range of processes, such as Erdős-Rényipercolation, percolation via edge competition and via growth by overtaking. We find that the largest jump asymptotically occurs at the percolation transition for Erdős-Rényiand other processes exhibiting global continuity, including models exhibiting an “explosive” transition. However, for percolation processes exhibiting genuine discontinuities, the behavior is substantially richer. In percolation models where the order parameter exhibits a staircase, the largest discontinuity generically does not coincide with the percolation transition. For the generalized Bohman-Frieze-Wormald model, it depends on the model parameter. Distinct parameter regimes well in the supercritical regime feature unstable discontinuous transitions—a novel and unexpected phenomenon in percolation. We thus demonstrate that seemingly and genuinely discontinuous percolation transitions can involve a rich behavior in supercriticality, a regime that has been largely ignored in percolation.
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
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
NASA Astrophysics Data System (ADS)
Maimaiti, Aili; Holzmann, Daniela; Truong, Viet Giang; Ritsch, Helmut; Nic Chormaic, Síle
2016-07-01
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.
Unstable vicinal crystal growth from cellular automata
NASA Astrophysics Data System (ADS)
Krasteva, A.; Popova, H.; KrzyŻewski, F.; Załuska-Kotur, M.; Tonchev, V.
2016-03-01
In order to study the unstable step motion on vicinal crystal surfaces we devise vicinal Cellular Automata. Each cell from the colony has value equal to its height in the vicinal, initially the steps are regularly distributed. Another array keeps the adatoms, initially distributed randomly over the surface. The growth rule defines that each adatom at right nearest neighbor position to a (multi-) step attaches to it. The update of whole colony is performed at once and then time increases. This execution of the growth rule is followed by compensation of the consumed particles and by diffusional update(s) of the adatom population. Two principal sources of instability are employed - biased diffusion and infinite inverse Ehrlich-Schwoebel barrier (iiSE). Since these factors are not opposed by step-step repulsion the formation of multi-steps is observed but in general the step bunches preserve a finite width. We monitor the developing surface patterns and quantify the observations by scaling laws with focus on the eventual transition from diffusion-limited to kinetics-limited phenomenon. The time-scaling exponent of the bunch size N is 1/2 for the case of biased diffusion and 1/3 for the case of iiSE. Additional distinction is possible based on the time-scaling exponents of the sizes of multi-step Nmulti, these are 0.36÷0.4 (for biased diffusion) and 1/4 (iiSE).
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...
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...
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...
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...
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...
Unification of Fundamental Forces
NASA Astrophysics Data System (ADS)
Salam, Abdus
1990-05-01
This is an expanded version of the third Dirac Memorial Lecture, given in 1988 by the Nobel Laureate Abdus Salam. Salam's lecture presents an overview of the developments in modern particle physics from its inception at the turn of the century to the present theories seeking to unify all the fundamental forces. In addition, two previously unpublished lectures by Paul Dirac, and Werner Heisenberg are included. These lectures provide a fascinating insight into their approach to research and the developments in particle physics at that time. Nonspecialists, undergraduates and researchers will find this a fascinating book. It contains a clear introduction to the major themes of particle physics and cosmology by one of the most distinguished contemporary physicists.
NASA Astrophysics Data System (ADS)
Trubnikov, B. A.; Zhdanov, S. K.
1987-11-01
The present work shows that in the long-wave approximation many-about 30-unstable media are described by the equations >ϱdot;=-ϱ divoverlineν, overline∸ =c 20m∇ϱ {1}/{m}which differ from the equations of ideal gas motion only in the sign on the right-hand side. Various quantities can be taken as an “effective density” ϱ and the parameter m, referred to as the “azimuthal number”, is generally an integer or half-integer varying as m=-2, -1, {-1}/{2}, {1}/{2}, 1, {3}/{2}. Historically, the earliest example of the systems under consideration is the hypothetical “Chaplygin gas”, i.e. a gas with the adiabetic exponent γ=-1, which corresponds to the azimuthal number m= {-1}/{2} (it was studied by S.A. Chaplygin in 1896-1902). That is why the authors refer to such media as “quasi-gas” or “quasi-Chaplygin” media. They include, in particular, the “overturned shallow water”, constrictions on current-carrying pinches, self-focusing of light, the Buneman, modulation and tearing instabilities in plasmas, as well as many other instabilities. Similar “quasi-Chaplygin” equations describe perturbations of various solitons, such as the Korteweg-de Vries and Kadomtsev-Petviashvili solitons, those of the non-linear Schrödinger equations, as well as cnoidal waves. These equations are shown to have particular self-similar solutions of the form ν∼ r/ t in the multi-dimensional case. Of greater interest, however, is the possibility of their complete integrability under any initial conditions either in a one-dimensional unsteady-state case when ϱ= ϱ( t, x) or in a two-dimensional steady-state case when ϱ= ϱ( x, y). In these cases, the original non-linear equations are reduced by hodograph transformations to two linear equations and then to the classical Laplace equation ∇ 2ψ( r, ϕ, z)=0 in a certain three-dimensional “phase” space. The two simplest “electrostatic” solutions-the Coulomb and dipole ones-give four forms of the most
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.
Database on unstable rock slopes in Norway
NASA Astrophysics Data System (ADS)
Oppikofer, Thierry; Nordahl, Bo; Bunkholt, Halvor; Nicolaisen, Magnus; Hermanns, Reginald L.; Böhme, Martina; Yugsi Molina, Freddy X.
2014-05-01
Several large rockslides have occurred in historic times in Norway causing many casualties. Most of these casualties are due to displacement waves triggered by a rock avalanche and affecting coast lines of entire lakes and fjords. The Geological Survey of Norway performs systematic mapping of unstable rock slopes in Norway and has detected up to now more than 230 unstable slopes with significant postglacial deformation. This systematic mapping aims to detect future rock avalanches before they occur. The registered unstable rock slopes are stored in a database on unstable rock slopes developed and maintained by the Geological Survey of Norway. The main aims of this 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, hazard and risk classification and so on. Feature classes and tables linked to the main feature class include the run-out area, the area effected by secondary effects, the hazard and risk classification, subareas and scenarios of an unstable rock slope, field observation points, displacement measurement stations, URL links for further documentation and references. The database on unstable rock slopes in Norway will be publicly consultable through the online map service on www.skrednett.no in 2014. Only publicly relevant parts of
Quantifying mixing in viscously unstable porous media flows.
Jha, Birendra; Cueto-Felgueroso, Luis; Juanes, Ruben
2011-12-01
Viscous fingering is a well-known hydrodynamic instability that sets in when a less viscous fluid displaces a more viscous fluid. When the two fluids are miscible, viscous fingering introduces disorder in the velocity field and exerts a fundamental control on the rate at which the fluids mix. Here we analyze the characteristic signature of the mixing process in viscously unstable flows, by means of high-resolution numerical simulations using a computational strategy that is stable for arbitrary viscosity ratios. We propose a reduced-order model of mixing, which, in the spirit of turbulence modeling and in contrast with previous approaches, recognizes the fundamental role played by the mechanical dissipation rate. The proposed model captures the nontrivial interplay between channeling and creation of interfacial area as a result of viscous fingering. PMID:22304195
Intracavity CH4 Raman laser using negative-branch unstable resonator
NASA Astrophysics Data System (ADS)
Zhou, Dongjian; Guo, Jingwei; Zhou, Canhua; Liu, Jinbo; Liu, Dong; Jin, Yuqi
2015-12-01
An intracavity Q-switched Nd:YAG/CH4 Raman laser is realized based on the configuration of a negative-branch confocal unstable resonator. A numerical model of the bare resonator was introduced to simulate the fundamental transverse mode and calculate the loss of the fundamental resonator. With different magnifications of the fundamental resonator, the first Stokes output energy was presented as a function of the discharge voltage. The influence of the Stokes resonator on Raman conversion was analyzed. With a fundamental resonator magnification of 1.1, a maximum output energy of 58 mJ was obtained, and the corresponding photon conversion efficiency was 48%.
Unstable attractors induce perpetual synchronization and desynchronization.
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. PMID:12675444
[Nonlinear magnetohydrodynamics]. [Threshold unstable MHD activity
Not Available
1992-01-01
Theoretical predictions were compared with available data from JET on the threshold unstable MHD activity in toroidal confinement devices. In particular, questions arising as to Hartmans number and the selection of a kinematic viscosity are discussed.
Treatment of Unstable Pelvic Ring Injuries
2014-01-01
Pelvic fractures are classified according to the stability of the pelvic ring. Unlike stable pelvic fractures, which heal without complications, unstable fractures may lead to pelvic ring deformities, which cause severe complications. An orthopedic surgeon must determine the stability of the pelvic ring by radiography and physical examination of the patient in order to ensure early, prompt treatment. This article includes anatomy of the pelvic ring, classification of pelvic ring injuries, its treatment algorithm, and corresponding cases involving unstable pelvic ring injury.
Reaction cross sections of unstable nuclei
Ozawa, Akira
2006-11-02
Experimental studies on reaction cross sections are reviewed. The recent developments of radioactive nuclear beams have enabled us to measure reaction cross-sections for unstable nuclei. Using Glauber-model analysis, effective nuclear matter density distributions of unstable nuclei can be studied. Recent measurements in RIBLL at IMP and RIPS at RIKEN are introduced. The effective matter density distributions for 14-18C are also mentioned.
Porter-Thomas distribution in unstable many-body systems
Volya, Alexander
2011-04-15
We use the continuum shell model approach to explore the resonance width distribution in unstable many-body systems. The single-particle nature of a decay, the few-body character of the interaction Hamiltonian, and the collectivity that emerges in nonstationary systems due to the coupling to the continuum of reaction states are discussed. Correlations between the structures of the parent and daughter nuclear systems in the common Fock space are found to result in deviations of decay width statistics from the Porter-Thomas distribution.
Unstable solar lentigo: A defined separate entity.
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. PMID:26832231
Observation of the particle-unstable nucleus 10N
NASA Astrophysics Data System (ADS)
Lépine-Szily, A.; Oliveira, J. M.; Vanin, V. R.; Ostrowski, A. N.; Lichtenthäler, R.; di Pietro, A.; Guimarães, V.; Laird, A. M.; Maunoury, L.; Lima, G. F.; de Oliveira Santos, F.; Roussel-Chomaz, P.; Savajols, H.; Trinder, W.; Villari, A. C.; de Vismes, A.
2002-05-01
For the first time evidence of the ground state of the proton-rich, unbound nucleus 10N has been found in the multinucleon transfer reaction 10B(14N,14B)10N. The observed resonance of 10N has a mass excess of 38.8(4) MeV and a width of Γ=2.3(16) MeV, close to the Audi-Wapstra estimation of 38.5(4) MeV. 10N is the last missing A=10 multiplet partner.
Fundamental neutron physics at LANSCE
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.
30 CFR 57.9304 - Unstable ground.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Unstable ground. 57.9304 Section 57.9304 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling,...
30 CFR 57.9304 - Unstable ground.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Unstable ground. 57.9304 Section 57.9304 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling,...
30 CFR 57.9304 - Unstable ground.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Unstable ground. 57.9304 Section 57.9304 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling,...
30 CFR 57.9304 - Unstable ground.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Unstable ground. 57.9304 Section 57.9304 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling,...
30 CFR 57.9304 - Unstable ground.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Unstable ground. 57.9304 Section 57.9304 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Loading, Hauling,...
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
Modal control of an unstable periodic orbit
NASA Astrophysics Data System (ADS)
Wiesel, W.; Shelton, W.
1983-03-01
Floquet theory is applied to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time-periodic linear system, which is augmented by a time-periodic control term. It is shown that this can be done such that (1) the application of control produces only inertial accelerations, (2) positive real Poincareexponents are shifted into the left half-plane, and (3) the shift of the exponent is linear with control gain. These developments are applied to an unstable orbit near the earth-moon L(3) point pertubed by the sun. Finally, it is shown that the control theory can be extended to include first order perturbations about the periodic orbit without increase in control cost.
Unstable resonators with excited converging wave
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.
Modal control of an unstable periodic orbit
NASA Technical Reports Server (NTRS)
Wiesel, W.; Shelton, W.
1983-01-01
Floquet theory is applied to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time-periodic linear system, which is augmented by a time-periodic control term. It is shown that this can be done such that (1) the application of control produces only inertial accelerations, (2) positive real Poincareexponents are shifted into the left half-plane, and (3) the shift of the exponent is linear with control gain. These developments are applied to an unstable orbit near the earth-moon L(3) point pertubed by the sun. Finally, it is shown that the control theory can be extended to include first order perturbations about the periodic orbit without increase in control cost.
Review of management of unstable elbow fractures
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
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
On unstable periodic regime of small HAWT
NASA Astrophysics Data System (ADS)
Dosaev, Marat Z.; Klimina, Liubov A.; Selyutskiy, Yury D.; Tsai, Mi-Ching; Yang, Hong-Tzer
2012-11-01
Dynamics of a small HAWT is studied. The closed mathematical model involving phenomenological description of both aerodynamic load upon turbine blades and permanent magnet electric generator is developed, in order to take into account the inductive reactance of the electric circuit. A series of experiments is performed in the subsonic wind tunnel of the LMSU Institute of Mechanics that allowed verifying the model and identifying its parameters. Parameters of dynamic model are identified, such as the coefficient of electromechanical interaction, the active internal resistance of generator, the circuit reactance. Parametric analysis of steady regimes is performed. The model prediction that HAWT operating dynamic system has two stable steady regimes (high speed regime and low speed one) is confirmed by experiments. Transient regimes are registered depending on parameters of the system, which allows estimating the unstable steady regime. The characteristics of the unstable regime are experimentally determined. Obtained results are used for estimation of aerodynamic moment acting on HAWT blades.
Is the earth's magnetotail balloon unstable?
NASA Technical Reports Server (NTRS)
Lee, D.-Y.; Wolf, R. A.
1992-01-01
In the past, the onset of magnetospheric substorms has been attributed to the plasma tearing mode instabilities. This paper investigates the ideal MHD ballooning instability of the near-and middle-tail magnetosphere region, as a first step toward determining whether it could trigger the tearing mode, by using the energy principle to investigate whether standard 2D tail models with the 'hard' ionospheric boundary condition are unstable to ballooning instability. Numerical results are presented for compressible ballooning modes that are symmetric about the center of the current sheet. It is shown that, for such a hard boundary condition, no reasonable magnetotail configuration exists that would be unstable to compressible symmetric ballooning but stable against interchange.
Special Relativity and Reactions with Unstable Nuclei
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.
Confocal unstable-resonator semiconductor laser
NASA Technical Reports Server (NTRS)
Salzman, J.; Lang, R.; Yariv, A.; Larson, A.
1986-01-01
GaAs/GaAlAs heterostructure lasers with a monolithic confocal unstable resonator were demonstrated. The curved mirrors satisfying the confocal condition were fabricated by etching. Close to threshold, the lasers operate in a single lateral mode with a nearly collimated output beam. A single-lobe far-field intensity distribution as narrow as 1.9-deg full width at half maximum was measured.
Further studies of gravitationally unstable protostellar disks
NASA Technical Reports Server (NTRS)
Tomley, Leslie; Steiman-Cameron, Thomas Y.; Cassen, Patrick
1994-01-01
Models of the solar nebula reveal that it might have been gravitationally unstable, both early and later in its evolution. Such instabilities produce density waves and associated gravitational torques, which are potent agents of angular momentum transport. In previous work, we conducted a series of numerical simulations designed to quantify the effects of gravitational instabilities in a generalizable way (Tomley, Cassen, & Steiman-Cameron 1991). Here we present a second series of simulations in which we examine disks of greater size, increased star/disk mass ratio, and flatter surface density distribution than those in our initial study. The purpose is to represent disks at a later stage of evolution than those already studied, to test the quantitative relations derived in our earlier work and to explore the effects of mass ratio on the results. The new results indicate that the tendencies for unstable, uncooled disks to heat to stability and for dynamical evolution rates to be proportional to cooling rates are general characteristics of the behavior of gravitationally unstable disks. Nevertheless, there are quantitative, and (for strong cooling) even qualitative differences that are revealed in the new simulations, particularly with regard to the cooling rates at which clumping tends to occur.
Unstable resonator with reduced output coupling.
Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Grünewald, Karin Maria; Handke, Jürgen
2012-06-20
The properties of a laser beam coupled out of a standard unstable laser resonator are heavily dependent on the chosen resonator magnification. A higher magnification results in a higher output coupling and a better beam quality. But in some configurations, an unstable resonator with a low output coupling in combination with a good beam quality is desirable. In order to reduce the output coupling for a particular resonator, magnification fractions of the outcoupled radiation are reflected back into the cavity. In the confocal case, the output mirror consists of a spherical inner section with a high reflectivity and a flat outer section with a partial reflectivity coating. With the application of the unstable resonator with reduced output coupling (URROC), magnification and output coupling can be adjusted independently from each other and it is possible to get a good beam quality and a high power extraction for lasers with a large low gain medium. The feasibility of this resonator design is examined numerically and experimentally with the help of a chemical oxygen iodine laser. PMID:22722301
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…
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
Quantization of black hole entropy from unstable circular null geodesics
NASA Astrophysics Data System (ADS)
Wei, Shao-Wen; Liu, Yu-Xiao; Fu, Chun-E.
2016-04-01
The quasinormal mode frequencies can be understood from the massless particles trapped at the unstable circular null geodesics and slowly leaking out to infinity. Based on this viewpoint, in this paper, we semiclassically construct the entropy spectrum of the static and stationary black holes from the null geodesics. The result shows that the spacing of the entropy spectrum only depends on the property of the black hole in the eikonal limit. Moreover, for a black hole far from the extremal case, the spacing is found to be smaller than 2πħ for any dimension, which is very different from the result of the previous work by using the usual quasinormal mode frequencies.
Fundamentals of Atmospheric Radiation
NASA Astrophysics Data System (ADS)
Bohren, Craig F.; Clothiaux, Eugene E.
2006-02-01
This textbook fills a gap in the literature for teaching material suitable for students of atmospheric science and courses on atmospheric radiation. It covers the fundamentals of emission, absorption, and scattering of electromagnetic radiation from ultraviolet to infrared and beyond. Much of the book applies to planetary atmosphere. The authors are physicists and teach at the largest meteorology department of the US at Penn State. Craig T. Bohren has taught the atmospheric radiation course there for the past 20 years with no book. Eugene Clothiaux has taken over and added to the course notes. Problems given in the text come from students, colleagues, and correspondents. The design of the figures especially for this book is meant to ease comprehension. Discussions have a graded approach with a thorough treatment of subjects, such as single scattering by particles, at different levels of complexity. The discussion of the multiple scattering theory begins with piles of plates. This simple theory introduces concepts in more advanced theories, i.e. optical thickness, single-scattering albedo, asymmetry parameter. The more complicated theory, the two-stream theory, then takes the reader beyond the pile-of-plates theory. Ideal for advanced undergraduate and graduate students of atmospheric science.
Neutral Black Rings in Five Dimensions are Unstable
NASA Astrophysics Data System (ADS)
Santos, Jorge E.; Way, Benson
2015-06-01
We study nonaxisymmetric linearized gravitational perturbations of the Emparan-Reall black ring using numerical methods. We find an unstable mode whose onset lies within the "fat" branch of the black ring and continues into the "thin" branch. Together with previous results using Penrose inequalities that fat black rings are unstable, this provides numerical evidence that the entire black ring family is unstable.
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.
Nuclear data on unstable nuclei for astrophysics
NASA Astrophysics Data System (ADS)
Smith, Michael S.; Meyer, Richard A.; Bardayan, Daniel W.; Blackmon, Jeffery C.; Chae, Kyungyuk; Guidry, Michael W.; Hix, W. Raphael; Kozub, R. L.; Lingerfelt, Eric J.; Ma, Zhanwen; Scott, Jason P.
2004-12-01
Recent measurements with radioactive beams at ORNL's Holifield Radioactive Ion Beam Facility (HRIBF) have prompted the evaluation of a number of reactions involving unstable nuclei needed for stellar explosion studies. We discuss these evaluations, as well as the development of a new computational infrastructure to enable the rapid incorporation of the latest nuclear physics results in astrophysics models. This infrastructure includes programs that simplify the generation of reaction rates, manage rate databases, and visualize reaction rates, all hosted at a new website http://www.nucastrodata.org.
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.
Entangling unstable optically active matter qubits
Matsuzaki, Yuichiro; Fitzsimons, Joseph; Benjamin, Simon C.
2011-06-15
In distributed quantum computation, small devices composed of a single or a few qubits are networked together to achieve a scalable machine. Typically, there is an optically active matter qubit at each node, so that photons are exploited to achieve remote entanglement. However, in many systems the optically active states are unstable or poorly defined. We report a scheme to perform a high-fidelity entanglement operation even given severe instability. The protocol exploits the existence of optically excited states for phase acquisition without actually exciting those states; it functions with or without cavities and does not require number-resolving detectors.
Unstable periodic orbits in the Lorenz attractor.
Boghosian, Bruce M; Brown, Aaron; Lätt, Jonas; Tang, Hui; Fazendeiro, Luis M; Coveney, Peter V
2011-06-13
We apply a new method for the determination of periodic orbits of general dynamical systems to the Lorenz equations. The accuracy of the expectation values obtained using this approach is shown to be much larger and have better convergence properties than the more traditional approach of time averaging over a generic orbit. Finally, we discuss the relevance of the present work to the computation of unstable periodic orbits of the driven Navier-Stokes equations, which can be simulated using the lattice Boltzmann method. PMID:21536582
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,…
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.
Transition phenomena in unstably stratified turbulent flows.
Bukai, M; Eidelman, A; Elperin, T; Kleeorin, N; Rogachevskii, I; Sapir-Katiraie, I
2011-03-01
We study experimentally and theoretically the transition phenomena caused by external forcing from Rayleigh-Bénard convection with large-scale circulation (LSC) to the limiting regime of unstably stratified turbulent flow without LSC, where the temperature field behaves like a passive scalar. In the experiments we use the Rayleigh-Bénard apparatus with an additional source of turbulence produced by two oscillating grids located near the sidewalls of the chamber. When the frequency of the grid oscillations is larger than 2 Hz, the LSC in turbulent convection is destroyed, and the destruction of the LSC is accompanied by a strong change of the mean temperature distribution. However, in all regimes of the unstably stratified turbulent flow the ratio [(ℓ{x}∇{x}T)²+(ℓ{y}∇{y}T)² + (ℓ{z}∇{z}T)²]/<θ²> varies slightly (even in the range of parameters where the behavior of the temperature field is different from that of the passive scalar). Here ℓ{i} are the integral scales of turbulence along the x,y,z directions, and T and θ are the mean and fluctuating parts of the fluid temperature. At all frequencies of the grid oscillations we have detected long-term nonlinear oscillations of the mean temperature. The theoretical predictions based on the budget equations for turbulent kinetic energy, turbulent temperature fluctuations, and turbulent heat flux, are in agreement with the experimental results. PMID:21517582
Multijoint error compensation mediates unstable object control.
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. PMID:22623491
Dynamics and statistics of unstable quantum states
NASA Astrophysics Data System (ADS)
Sokolov, V. V.; Zelevinsky, V. G.
1989-11-01
The statistical theory of spectra formulated in terms of random matrices is extended to unstable states. The energies and widths of these states are treated as real and imaginary parts of complex eigenvalues for an effective non-hermitian hamiltonian. Eigenvalue statistics are investigated under simple assumptions. If the coupling through common decay channels is weak we obtain a Wigner distribution for the level spacings and a Porter-Thomas one for the widths, with the only exception for spacings less than widths where level repulsion fades out. Meanwhile in the complex energy plane the repulsion of eigenvalues is quadratic in accordance with the T-noninvariant character of decaying systems. In the opposite case of strong coupling with the continuum, k short-lived states are formed ( k is the number of open decay channels). These states accumulate almost the whole total width, the rest of the states becoming long-lived. Such a perestroika corresponds to separation of direct processes (a nuclear analogue of Dicke coherent superradiance). At small channel number, Ericson fluctuations of the cross sections are found to be suppressed. The one-channel case is considered in detail. The joint distribution of energies and widths is obtained. The average cross sections and density of unstable states are calculated.
Lang, R J
1991-09-01
A new set of design parameters for unstable resonators is presented that yields simpler expressions for the mirror and beam radii and magnification than those given by the usual g parameters. The new formalism is applied to determine the design of a solid unstable resonator of index n with a self-collimated output beam, applicable to unstable-resonator diode lasers. PMID:19776957
Analytical puff modelling of light-wind dispersion in stable and unstable conditions
NASA Astrophysics Data System (ADS)
Luhar, Ashok K.
2011-01-01
The puff modelling technique can describe dispersion in light winds by accounting for streamwise diffusion. A simple analytical puff model is formulated for stable as well as unstable stratification. In the stable case, the model is a slight generalisation of the Gaussian puff model of Thomson and Manning (2001), whereas in the unstable case it incorporates a probability density function approach to account for the observed skewness of the vertical turbulent velocities. An evaluation conducted using a well-known dataset collected under stable conditions suggests that the performance of the model is comparable to some of the top-performing models based on more complex techniques. However, it is apparent that some of the observed complex dispersion behaviour that arises due to the non-Gaussian characteristics of the wind direction distribution cannot be properly modelled by using the hourly-averaged meteorology. Since there are no suitable datasets for evaluation under unstable conditions, the puff model is benchmarked against a full three-dimensional Lagrangian particle model. The results show that the puff model is capable of describing most of the well-known features of convective dispersion observed under moderate winds, and that it simulates light-wind dispersion characteristics that are in good agreement with the particle model predictions. The results also highlight that the time since the start of tracer release is an important parameter in light winds. Quantitative estimates as to when the effects of streamwise diffusion in unstable flows can be neglected are also given.
Reaction-Transport Fronts Propagating into Unstable States
NASA Astrophysics Data System (ADS)
Méndez, Vicenç; Fedotov, Sergei; Horsthemke, Werner
In this chapter we consider the problem of propagating fronts traveling into an unstable state of a reaction-transport system. The purpose is to present the general formalism for the asymptotic analysis of traveling fronts. The method relies on the hyperbolic scaling procedure, the theory of large deviations, and the Hamilton-Jacobi technique. A generic model that describes phenomena of this type is the RD equation (2.3) with appropriate kinetics, such as the FKPP equation (4.1). The propagation velocity of fronts of this equation has been studied in Chap.4. The RD equation involves implicitly a long-time large-scale parabolic scaling, while as far as propagating fronts are concerned, the appropriate scaling must be a hyperbolic one. The macroscopic transport process arises from the overall effect of many particles performing complex random movements. Classical diffusion is simply an approximation for this transport in the long-time large-scale parabolic limit. In general, this approximation is not appropriate for problems involving propagating fronts. The basic idea is that the kinetic term in the RD equation with KPP kinetics is very sensitive to the tails of a density profile. These tails are typically "non-universal," "non-diffusional," and dependent on the microscopic details of the underlying random walk. The purpose of this chapter is to demonstrate that the macroscopic dynamics of the front for a reaction-transport system are dependent on the choice of the underlying random walk model for the transport process. To illustrate the idea of an alternative description of front propagation into an unstable state of reaction-transport system, we consider several models including discrete-in-time or continuous-in-time Markov models with long-distance dispersal kernels, non-Markovian models with memory effects, etc., instead of the RD equation. Let us give a few examples of such models.
The free energy of mechanically unstable phases
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
Unstable periodic orbits in human cardiac rhythms
NASA Astrophysics Data System (ADS)
Narayanan, K.; Govindan, R. B.; Gopinathan, M. S.
1998-04-01
Unstable periodic orbits (UPOs) extracted from experimental electrocardiograph signals are reported for normal and pathological human cardiac rhythms. The periodicity and distribution of the orbits on the chaotic attractor are found to be indicative of the state of health of the cardiac system. The normal cardiac system is characterized by three to four UPOs with typical periodicities and intensities. However, pathological conditions such as premature ventricular contraction, atrio ventricular block, ventricular tachy arrhythmia, and ventricular fibrillation have UPOs whose periodicity and intensity distribution are quite distinct from those of the healthy cases and are characteristic of the pathological conditions. Eigenvalues and the largest positive Lyapunov exponent value for the UPOs are also reported. The UPOs are shown to be insensitive to the embedding dimension and the present UPO analysis is demonstrated to be reliable by the method of surrogate analysis.
The oxidative cost of unstable social dominance.
Beaulieu, Michaël; Mboumba, Sylvère; Willaume, Eric; Kappeler, Peter M; Charpentier, Marie J E
2014-08-01
High social rank is expected to incur fitness costs under unstable social conditions. A disruption of the oxidative balance may underlie such effects, but how markers of oxidative stress vary in relation to social rank and stability is unknown. We examined in mandrills whether the mating season characterized by social instability between males (but not between females) affected their oxidative balance differently according to their social rank. Outside the mating season, high-ranking males showed the lowest levels of oxidative damage, while during the mating season, they were the only males to experience increased oxidative damage. In contrast, the mating season increased oxidative stress in all females, irrespective of their social rank. These results support the hypothesis that the coupling between social rank and social stability is responsible for differential costs in terms of oxidative stress, which may explain inter-individual differences in susceptibility to socially induced health issues. PMID:24902748
Unstable avoided crossing in coupled spinor condensates.
Bernier, Nathan R; Dalla Torre, Emanuele G; Demler, Eugene
2014-08-01
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. PMID:25148334
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.
Dissolution Patterns and Mixing Dynamics in Unstable Reactive Flow
NASA Astrophysics Data System (ADS)
Hidalgo, Juan J.; Dentz, Marco; Cabeza, Yoar; Carrera, Jesus
2015-04-01
We study the fundamental problem of mixing and chemical reactions under a Rayleigh-Bénard-type hydrodynamic instability in a two miscible fluids system. The dense fluid mixture, which is generated at the fluids interface, leads to the onset of a convective instability. At the same time, a fast chemical dissolution reaction produces a characteristic porosity pattern that follows the regions of maximum mixing. Contrary to intuition, the dissolution pattern does not map out the finger geometry of the unstable flow. Instead, it displays a dome-like, hierarchical structure that reflects the positions of the ascending fluid interface. We find that this behavior is caused by stagnation points along the deformed interface, which act as mixing and reaction hotspots due to a strong compression of the interfacial boundary layer. We develop a model for mixing and reaction around the stagnation points of the deformed fluids interface that captures the evolution of the global scalar dissipation and reaction rates and predicts their independence of the Rayleigh number.
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.
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. PMID:9268523
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.
Mechanical analogy of the nonlinear dynamics of a driven unstable mode near marginal stability
NASA Astrophysics Data System (ADS)
Zaleśny, J.; Marczyński, S.; Lisak, M.; Anderson, D.; Gałkowski, A.; Berczyński, P.; Berczyński, S.; Rogowski, R.
2009-02-01
The universal integrodifferential model equation derived by Berk et al. [Phys. Rev. Lett. 76, 1256 (1996)] for studying the nonlinear evolution of unstable modes driven by kinetic wave particle resonances near the instability threshold is reduced to a differential equation and next as a further simplification to a nonlinear oscillator equation. This mechanical analogy properly reproduces most of the essential physics of the system and allows an understanding of the qualitative features of the theory of Berk et al.
Fundamentals of air quality systems
Noll, K.E.
1999-08-01
The book uses numerous examples to demonstrate how basic design concepts can be applied to the control of air emissions from industrial sources. It focuses on the design of air pollution control devices for the removal of gases and particles from industrial sources, and provides detailed, specific design methods for each major air pollution control system. Individual chapters provide design methods that include both theory and practice with emphasis on the practical aspect by providing numerous examples that demonstrate how air pollution control devices are designed. Contents include air pollution laws, air pollution control devices; physical properties of air, gas laws, energy concepts, pressure; motion of airborne particles, filter and water drop collection efficiency; fundamentals of particulate emission control; cyclones; fabric filters; wet scrubbers; electrostatic precipitators; control of volatile organic compounds; adsorption; incineration; absorption; control of gaseous emissions from motor vehicles; practice problems (with solutions) for the P.E. examination in environmental engineering. Design applications are featured throughout.
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
Thermally unstable perturbations in stratified conducting atmospheres
NASA Astrophysics Data System (ADS)
Reale, Fabio; Serio, Salvatore; Peres, Giovanni
1994-10-01
We investigate the thermal stability of isobaric perturbations in a stratified isothermal background atmosphere with solar abundances, as resulting from the competition of optically thin plasma radiative cooling and of heating conducted from the surrounding atmosphere. We have analyzed the threshold line between stable and unstable perturbations, in the plane of the two important control parameters: the initial size of the perturbation and the temperature of the unperturbed medium; this line changes with the pressure of the unperturbed atmosphere. We have extended the results of linear perturbation analysis by means of numerical calculations of the evolution of spherical isobaric perturbations, using a two-dimensional hydrodynamic code including Spitzer heat conduction. We explore a wide range of the parameters appropriate to the solar and stellar upper atmospheres: the background uniform temperature is between 105 K and 107 K, the initial pressure betweeen 0.1 and 10 dyn/sq cm, and the perturbation size between 105 and 1010 cm. The numerical results are in substantial agreement with the linear analysis. We discuss possible implications of our results also in terms of observable effects, especially concerning plasma downflows, and propose thermal instability as a possible candidate to explain the observed redshifts in solar and stellar transition region lines.
Nuclear Data on Unstable Nuclei for Astrophysics
NASA Astrophysics Data System (ADS)
Smith, Michael; Bardayan, Daniel; Blackmon, Jeffery; Nesaraja, Caroline; Lingerfelt, Eric; Scott, Jason; Hix, W. Raphael; Chae, Kyungyuk; Ma, Zhanwen; Guidry, Michael; Kozub, Raymond; Sharp, Jacob; Meyer, Richard
2004-10-01
The sequence of nuclear reactions occurring in supernova explosions is believed to involve thousands of neutron-rich nuclei, and a knowledge of the properties of these nuclei is essential to calculating the element synthesis in these cataclysmic events. Similarly, information on proton-rich nuclei is needed to understand nova explosions occurring on the surfaces of white dwarf stars and X-ray bursts occurring on the surfaces of neutron stars. Recent measurements with radioactive beams at ORNL's Holifield Radioactive Ion Beam Facility (HRIBF) and elsewhere have prompted the evaluation of a number of reactions involving unstable nuclei needed for stellar explosion studies. Recent evaluation efforts will be presented. To ensure that the latest relevant experimental and theoretical nuclear physics results are rapidly incorporated into astrophysical models, we have created a new computational infrastructure for nuclear astrophysics data. Available on-line at www.nucastrodata.org, a simple point-and-click interface guides users to convert evaluated nuclear reaction and structure information as input into thermonuclear reaction rates in a variety of output formats. It also enables users to combine a new reaction rate with an existing library, as well as to create, merge, store, document, and share custom libraries. Future capabilities will include tools to carry out data evaluations and to calculate and visualize the synthesis of elements in astrophysical environments. The site www.nucastrodata.org also features a comprehensive set of links (over 60 so far) to nuclear datasets around the world which are important for nuclear astrophysics studies.
Slinky Mechanics: Static Shapes and Unstable States
NASA Astrophysics Data System (ADS)
Holmes, Douglas; Borum, Andy; Moore, Billy; Plaut, Raymond; Dillard, David
2014-03-01
The floppy nature of a tumbling Slinky has captivated children and adults alike for over half a century. Highly flexible, the spring will walk down stairs, turn over in your hands, and-much to the chagrin of children everywhere-become easily entangled. The Slinky is an educational tool for demonstrating standing waves, and a structural inspiration due to its ability to extend to many times beyond its initial length without imparting plastic strain on the material. In this work, we provide a mechanical model that captures the static equilibrium configurations of the Slinky in terms of its geometric and material properties. We present both continuous and discrete models to capture a Slinky's static equilibria and unstable transitions. We compare these with experimental results obtained for the Slinky's static equilibrium shapes. We emphasize the importance of modeling coil contact, and determine the critical criteria for the Slinky to topple over in terms of a tilt angle, and the vertical displacement of one bale of coils. Finally, we provide a general description of highly flexible helical springs by considering the nondimensional potential energy of the spring, which characterizes the ``Slinkiness'' of a spring.
Grating tuned unstable resonator laser cavity
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.
Unstable equilibrium behaviour in collapsible tubes.
Bertram, C D
1986-01-01
Thick-walled silicone rubber tube connected to rigid pipes upstream and downstream was externally pressurised (pe) to cause collapse while aqueous fluid flowed through propelled by a constant upstream head. Three types of equilibrium were found: stable equilibria (steady flow) at high downstream flow resistance R2, self-excited oscillations at low R2, and 'unattainable' (by varying external pressure) or exponentially unstable equilibria at intermediate R2. The self-excited oscillations were highly non-linear and appeared in four, apparently discrete, frequency bands: 2.7 Hz, 3.8-5.0 Hz, 12-16 Hz and 60-63 Hz, suggesting that the possible oscillation modes may be harmonically related. Stable, intermediate 'two-in-every-three-beats' oscillation was also observed, with a repetition frequency in the 3.8-5.0 Hz band. As pe was increased, self-excited oscillations were eventually suppressed, leaving internal fluid pressure varying with no single dominant frequency as a result of turbulent jet dissipation at the downstream rigid pipe connection. Comparison of pressure-wave velocity calculated from the local pressure-area relation for the tube with fluid velocity indicated that supercritical velocities were attained in the course of the self-excited oscillations. PMID:2936743
Pulse dynamics in an unstable medium
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.
Fundamental symmetries and interactions—selected topics
NASA Astrophysics Data System (ADS)
Jungmann, Klaus P.
2015-11-01
In the field of fundamental interactions and symmetries numerous experiments are underway or planned in order to verify the standard model in particle physics, to search for possible extensions to it or to exploit the standard model for extracting most precise values for fundamental constants. We cover selected recent developments, in particular such which exploit stored and confined particles. Emphasis is on experiments with transformative character, i.e. such which may be able to guide and steer theoretical model building into new but defined directions. Among those are projects with antiprotons, muons and certain selected atoms and atomic nuclei.
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.
Jet broadening in unstable non-Abelian plasmas
Dumitru, Adrian; Schenke, Bjoern; Strickland, Michael; Nara, Yasushi
2008-08-15
We perform numerical simulations of the SU(2) Boltzmann-Vlasov equation including both hard elastic particle collisions and soft interactions mediated by classical Yang-Mills fields. Using this technique we calculate the momentum-space broadening of high-energy jets in real time for both locally isotropic and anisotropic plasmas. In both cases we introduce a separation scale that separates hard and soft interactions and demonstrate that our results for jet broadening are independent of the precise separation scale chosen. For an isotropic plasma this allows us to calculate the jet transport coefficient q-circumflex including hard and soft nonequilibrium dynamics. For an anisotropic plasma the jet transport coefficient becomes a tensor with q-circumflex{sub L}{ne}q-circumflex{sub perpendicular}. We find that for weakly coupled anisotropic plasmas the fields develop unstable modes, forming configurations where B{sub perpendicular}>E{sub perpendicular} and E{sub z}>B{sub z}, which lead to q-circumflex{sub L}>q-circumflex{sub perpendicular}. We study whether the effect is strong enough to explain the experimental observation that high-energy jets traversing the plasma perpendicular to the beam axis experience much stronger broadening in rapidity, {delta}{eta}, than in azimuth, {delta}{phi}.
Neutron Capture Experiments on Unstable Nuclei
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
Unstable ground in western North Dakota
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.
Managing risk in an unstable world.
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. PMID:15938438
Unstable trajectories and the quantum mechanical uncertainty
NASA Astrophysics Data System (ADS)
Moser, Hans R.
2008-08-01
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.
Universality classes for unstable crystal growth
NASA Astrophysics Data System (ADS)
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 ∂th(x,t)=-∇.[j(∇h)+∇(∇2h)]: 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 ˜tn; (ii) the exponent β, controlling the increase in time of the typical slope of the pattern, M ˜tβ, 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.
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.
Phase transitions in the interacting boson fermion model: The {gamma}-unstable case
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.
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.
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.
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.
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.
The Unstable Repeats - Three Evolving Faces of Neurological Disease
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
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…
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...
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…
Suh, N.P.; Saka, N.
1980-01-01
This book presents the proceedings of the June 1978 International Conference on the Fundamentals of Tribology. The papers discuss the effects of surface topography and of the properties of materials on wear; friction, wear, and thermomechanical effects; wear mechanisms in metal processing; polymer wear; wear monitoring and prevention; and lubrication. (LCL)
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…
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.
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…
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…
Fundamental electrode kinetics
NASA Technical Reports Server (NTRS)
Elder, J. P.
1968-01-01
Report presents the fundamentals of electrode kinetics and the methods used in evaluating the characteristic parameters of rapid-charge transfer processes at electrode-electrolyte interfaces. The concept of electrode kinetics is outlined, followed by the principles underlying the experimental techniques for the investigation of electrode kinetics.
Fundamental research data base
NASA Technical Reports Server (NTRS)
1983-01-01
A fundamental research data base containing ground truth, image, and Badhwar profile feature data for 17 North Dakota, South Dakota, and Minnesota agricultural sites is described. Image data was provided for a minimum of four acquisition dates for each site and all four images were registered to one another.
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…
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)
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…
Ma, Huanfei; Lin, Wei; Lai, Ying-Cheng
2013-05-01
Detecting unstable periodic orbits (UPOs) in chaotic systems based solely on time series is a fundamental but extremely challenging problem in nonlinear dynamics. Previous approaches were applicable but mostly for low-dimensional chaotic systems. We develop a framework, integrating approximation theory of neural networks and adaptive synchronization, to address the problem of time-series-based detection of UPOs in high-dimensional chaotic systems. An example of finding UPOs from the classic Mackey-Glass equation is presented. PMID:23767476
Nonlinear Unstable Wave Disturbances in Fluidized Beds
NASA Astrophysics Data System (ADS)
Liu, J. T. C.
1983-10-01
Instabilities in fluidized beds are interpreted from the two-phase continuum theory of linearized hydrodynamic stability as the result of interactions between wave hierarchies for which the stability condition is violated; that is, in which the lower-order waves propagate at speeds exceeding those of the higher-order waves. For weak nonlinearities a hierarchy of Burgers-like equations is obtained. The nonlinear modifications to the wave speeds point towards the restoration of the stability condition in the linearized sense. A weakly nonlinear hydrodynamic stability analysis yields an amplitude equation that is of second order. It is argued, however, that the major history of the disturbance development may be expressed by a simpler first-order amplitude equation. The Landau-Stuart constant obtained is intimately related to the nonlinear modifications of the wave speeds of the higher- and lower-order wave operators. It is shown that for supercritical disturbances, amplitude and phase velocity equilibration is possible, and that the levels of the equilibration depend on the initial amplification rate, in agreement with observations. The equilibration occurs by cascades of the fundamental wave disturbance into its harmonics.
Small Kerr-anti-de Sitter black holes are unstable
Cardoso, Vitor; Dias, Oscar J.C.
2004-10-15
Superradiance in black hole spacetimes can trigger instabilities. Here we show that, due to superradiance, small Kerr-anti-de Sitter black holes are unstable. Our demonstration uses a matching procedure, in a long wavelength approximation.
Dental Occlusion Influences the Standing Balance on an Unstable Platform.
Julià-Sánchez, Sonia; Álvarez-Herms, Jesús; Gatterer, Hannes; Burtscher, Martin; Pagès, Teresa; Viscor, Ginés
2015-10-01
Contradictory results are still reported on the influence of dental occlusion on the balance control. We attempted to determine whether there are differences in balance between opposed dental occlusion (Intercuspal position (ICP)/"Cotton rolls" mandibular position [CR]) for two extreme levels of stability (stable/ unstable). Twenty-five subjects were monitored under both dental occlusion and level of stability conditions using an unstable platform Balance System SD. The resulting stability index suggests that body balance is significantly better when dental occlusion is set in CR (p < .001) in unstable but not in stable conditions. Occlusal traits significantly influencing postural control were Angle Class (p < .001), crowding (p = .006), midline deviation (p < .001), crossbite (p < .001), anterior open bite (p = .05), and overjet (p = .01). It could be concluded that the sensory information linked to the dental occlusion for the balance control comes strongly into effect in unstable conditions. PMID:25674772
Stability of neuronal pulses composed of concatenated unstable kinks
NASA Astrophysics Data System (ADS)
Romeo, Mónica M.; Jones, Christopher K.
2001-01-01
We demonstrate that a traveling pulse solution, emerging from the concatenation of two unstable kinks, can be stable. By means of stability analysis and numerical simulations, we show the stability of neuronal pulses (action potentials) with increasing refractory periods, which decompose into two (radiationally) unstable kinks in the limit. These action potentials are solutions of an ultrarefractory version of the FitzHugh-Nagumo system.
Unstable-Resonator Oscillator/Amplifier Diode Laser
NASA Technical Reports Server (NTRS)
Lang, Robert J.; Mittelstein, Michael; Tiberio, Richard C.; Forouhar, Siamak; Crawford, Deborah
1994-01-01
Fabricated as single-chip integrated circuit. Device based partly on concept proved in commercial solid-state lasers: using unstable-resonator oscillator to define electromagnetic mode and, following oscillator, traveling-wave amplifier to generate high power. Mode-definition and power-amplification functions optimized separately. Hyperbolic-grating, unstable-resonator oscillator/amplifier diode laser produces single-longitudinal-mode, broad, laterally coherent, diffraction-limited, high-power beam.
NASA Astrophysics Data System (ADS)
Frohlich, Cliff
Choosing an intermediate-level geophysics text is always problematic: What should we teach students after they have had introductory courses in geology, math, and physics, but little else? Fundamentals of Geophysics is aimed specifically at these intermediate-level students, and the author's stated approach is to construct a text “using abundant diagrams, a simplified mathematical treatment, and equations in which the student can follow each derivation step-by-step.” Moreover, for Lowrie, the Earth is round, not flat—the “fundamentals of geophysics” here are the essential properties of our Earth the planet, rather than useful techniques for finding oil and minerals. Thus this book is comparable in both level and approach to C. M. R. Fowler's The Solid Earth (Cambridge University Press, 1990).
NASA Astrophysics Data System (ADS)
Showers, R. M.; Lin, S.-Y.; Schulz, R. B.
1981-02-01
Both fundamental and state-of-the-art limits are treated with emphasis on the former. Fundamental limits result from both natural and man-made electromagnetic noise which then affect two basic ratios, signal-to-noise (S/N) and extraneous-input-to-noise (I/N). Tolerable S/N values are discussed for both digital and analog communications systems. These lead to tolerable signal-to-extraneous-input (S/I) ratios, again for digital and analog communications systems, as well as radar and sonar. State-of-the-art limits for transmitters include RF noise emission, spurious emissions, and intermodulation. Receiver limits include adjacent-channel interactions, image, IF, and other spurious responses, including cross modulation, intermodulation, and desensitization. Unintentional emitters and receivers are also discussed. Coupling limitations between undesired sources and receptors are considered from mechanisms including radiation, induction, and conduction.
Neutron Capture Experiments on Unstable Nuclei
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
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.
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?
Fundamentals of Structural Geology
NASA Astrophysics Data System (ADS)
Pollard, David D.; Fletcher, Raymond C.
2005-09-01
Fundamentals of Structural Geology provides a new framework for the investigation of geological structures by integrating field mapping and mechanical analysis. Assuming a basic knowledge of physical geology, introductory calculus and physics, it emphasizes the observational data, modern mapping technology, principles of continuum mechanics, and the mathematical and computational skills, necessary to quantitatively map, describe, model, and explain deformation in Earth's lithosphere. By starting from the fundamental conservation laws of mass and momentum, the constitutive laws of material behavior, and the kinematic relationships for strain and rate of deformation, the authors demonstrate the relevance of solid and fluid mechanics to structural geology. This book offers a modern quantitative approach to structural geology for advanced students and researchers in structural geology and tectonics. It is supported by a website hosting images from the book, additional colour images, student exercises and MATLAB scripts. Solutions to the exercises are available to instructors. The book integrates field mapping using modern technology with the analysis of structures based on a complete mechanics MATLAB is used to visualize physical fields and analytical results and MATLAB scripts can be downloaded from the website to recreate textbook graphics and enable students to explore their choice of parameters and boundary conditions The supplementary website hosts color images of outcrop photographs used in the text, supplementary color images, and images of textbook figures for classroom presentations The textbook website also includes student exercises designed to instill the fundamental relationships, and to encourage the visualization of the evolution of geological structures; solutions are available to instructors
Nucleosynthesis and the variation of fundamental couplings
Mueller, Christian M.; Schaefer, Gregor; Wetterich, Christof
2004-10-15
We determine the influence of a variation of the fundamental 'constants' on the predicted helium abundance in Big Bang Nucleosynthesis. The analytic estimate is performed in two parts: the first step determines the dependence of the helium abundance on the nuclear physics parameters, while the second step relates those parameters to the fundamental couplings of particle physics. This procedure can incorporate in a flexible way the time variation of several couplings within a grand unified theory while keeping the nuclear physics computation separate from any GUT model dependence.
Laser Wakefield Acceleration and Fundamental Physics
Tajima, Toshiki
2011-06-20
The laser wakefield acceleration (LWFA) along with the now available laser technology allows us to look at TeV physics both in leptons and hadrons. Near future proof-of-principle experiments for a collider as well as high energy frontier experiments without a collider paradigm are suggested. The intense laser can also contribute to other fundamental physics explorations such as those of dark matter and dark energy candidates. Finally the combination of intense laser and laser-accelerated particles (electrons, hadrons, gammas) provides a further avenue of fundamental research.
Fundamentals of plasma simulation
Forslund, D.W.
1985-01-01
With the increasing size and speed of modern computers, the incredibly complex nonlinear properties of plasmas in the laboratory and in space are being successfully explored in increasing depth. Of particular importance have been numerical simulation techniques involving finite size particles on a discrete mesh. After discussing the importance of this means of understanding a variety of nonlinear plasma phenomena, we describe the basic elements of particle-in-cell simulation and their limitations and advantages. The differencing techniques, stability and accuracy issues, data management and optimization issues are discussed by means of a simple example of a particle-in-cell code. Recent advances in simulation methods allowing large space and time scales to be treated with minimal sacrifice in physics are reviewed. Various examples of nonlinear processes successfully studied by plasma simulation will be given.
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
Fundamental experiments in velocimetry
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.
Fundamental research data base
NASA Technical Reports Server (NTRS)
1983-01-01
A fundamental research data base was created on a single 9-track 1600 BPI tape containing ground truth, image, and Badhwar profile feature data for 17 North Dakota, South Dakota, and Minnesota agricultural sites. Each site is 5x6 nm in area. Image data has been provided for a minimum of four acquisition dates for each site. All four images have been registered to one another. A list of the order of the files on tape and the dates of acquisition is provided.
NASA Astrophysics Data System (ADS)
Muxworthy, Adrian R.; Williams, Wyn; Roberts, Andrew P.; Winklhofer, Michael; Chang, Liao; Pósfai, Mihály
2013-12-01
Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosomes), which aid navigation (magnetotaxis). To improve the efficiency of magnetotaxis, magnetosome crystals (which can consist of magnetite or greigite) should be magnetically stable single domain (SD) particles. Larger particles subdivide into nonuniform multidomain (MD) magnetic structures that produce weaker magnetic signals, while small SD particles become magnetically unstable due to thermal fluctuations and exhibit superparamagnetic (SP) behavior. In this study, we determined the stable SD range as a function of grain elongation and interparticle separation for chains of identical greigite grains using fundamental parameters recently determined for greigite. Interactions significantly increase the stable SD range. For example, for cube-shaped greigite grains the upper stable SD threshold size is increased from 107 nm for isolated grains to 204 nm for touching grains arranged in chains. The larger critical SD grain size for greigite means that, compared to magnetite magnetosomes, greigite magnetosomes can produce larger magnetic signals without the need for intergrain interactions.
Fundamental Atomtronic Circuit Elements
NASA Astrophysics Data System (ADS)
Lee, Jeffrey; McIlvain, Brian; Lobb, Christopher; Hill, Wendell T., III
2012-06-01
Recent experiments with neutral superfluid gases have shown that it is possible to create atomtronic circuits analogous to existing superconducting circuits. The goals of these experiments are to create complex systems such as Josephson junctions. In addition, there are theoretical models for active atomtronic components analogous to diodes, transistors and oscillators. In order for any of these devices to function, an understanding of the more fundamental atomtronic elements is needed. Here we describe the first experimental realization of these more fundamental elements. We have created an atomtronic capacitor that is discharged through a resistance and inductance. We will discuss a theoretical description of the system that allows us to determine values for the capacitance, resistance and inductance. The resistance is shown to be analogous to the Sharvin resistance, and the inductance analogous to kinetic inductance in electronics. This atomtronic circuit is implemented with a thermal sample of laser cooled rubidium atoms. The atoms are confined using what we call free-space atom chips, a novel optical dipole trap produced using a generalized phase-contrast imaging technique. We will also discuss progress toward implementing this atomtronic system in a degenerate Bose gas.
Fundamentals of electrokinetics
NASA Astrophysics Data System (ADS)
Kozak, M. W.
The study of electrokinetics is a very mature field. Experimental studies date from the early 1800s, and acceptable theoretical analyses have existed since the early 1900s. The use of electrokinetics in practical field problems is more recent, but it is still quite mature. Most developments in the fundamental understanding of electrokinetics are in the colloid science literature. A significant and increasing divergence between the theoretical understanding of electrokinetics found in the colloid science literature and the theoretical analyses used in interpreting applied experimental studies in soil science and waste remediation has developed. The soil science literature has to date restricted itself to the use of very early theories, with their associated limitations. The purpose of this contribution is to review fundamental aspects of electrokinetic phenomena from a colloid science viewpoint. It is hoped that a bridge can be built between the two branches of the literature, from which both will benefit. Attention is paid to special topics such as the effects of overlapping double layers, applications in unsaturated soils, the influence of dispersivity, and the differences between electrokinetic theory and conductivity theory.
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.
Fundamentals of Plasma Physics
NASA Astrophysics Data System (ADS)
Bellan, Paul M.
2008-07-01
Preface; 1. Basic concepts; 2. The Vlasov, two-fluid, and MHD models of plasma dynamics; 3. Motion of a single plasma particle; 4. Elementary plasma waves; 5. Streaming instabilities and the Landau problem; 6. Cold plasma waves in a magnetized plasma; 7. Waves in inhomogeneous plasmas and wave energy relations; 8. Vlasov theory of warm electrostatic waves in a magnetized plasma; 9. MHD equilibria; 10. Stability of static MHD equilibria; 11. Magnetic helicity interpreted and Woltjer-Taylor relaxation; 12. Magnetic reconnection; 13. Fokker-Planck theory of collisions; 14. Wave-particle nonlinearities; 15. Wave-wave nonlinearities; 16. Non-neutral plasmas; 17. Dusty plasmas; Appendix A. Intuitive method for vector calculus identities; Appendix B. Vector calculus in orthogonal curvilinear coordinates; Appendix C. Frequently used physical constants and formulae; Bibliography; References; Index.
Connecting Fundamental Constants
Di Mario, D.
2008-05-29
A model for a black hole electron is built from three basic constants only: h, c and G. The result is a description of the electron with its mass and charge. The nature of this black hole seems to fit the properties of the Planck particle and new relationships among basic constants are possible. The time dilation factor in a black hole associated with a variable gravitational field would appear to us as a charge; on the other hand the Planck time is acting as a time gap drastically limiting what we are able to measure and its dimension will appear in some quantities. This is why the Planck time is numerically very close to the gravitational/electric force ratio in an electron: its difference, disregarding a {pi}{radical}(2) factor, is only 0.2%. This is not a coincidence, it is always the same particle and the small difference is between a rotating and a non-rotating particle. The determination of its rotational speed yields accurate numbers for many quantities, including the fine structure constant and the electron magnetic moment.
Three fundamental problems of molecular statistics
NASA Astrophysics Data System (ADS)
Bubenchikov, M. A.; Potekaev, A. I.; Bubenchikov, A. M.
2013-08-01
Three fundamental problems of molecular statistics can be identified using the shape of a nanoparticle and the curvature of a λ-layer surrounding it, which correspond to the polar, axial, and plane symmetry. Within the framework of a single-velocity approximation, solutions to these problems are constructed and formulas for coefficients of average resistance to motion of variously-shaped particles are found.
Relevant signs of stable and unstable thoracolumbar vertebral column trauma
Gehweiler, J.A.; Daffner, R.H.; Osborne, R.L.
1981-12-01
One-hundred and seventeen patients with acute thoracolumbar vertebral column fracture or fracture-dislocations were analyzed and classified into stable (36%) and unstable (64%). Eight helpful roentgen signs were observed that may serve to direct attention to serious underlying, often occult, fractures and dislocations. The changes fall into four principal groups: abnormal soft tissues, abnormal vertebral alignment, abnormal joints, and widened vertebral canal. All stable and unstable lesions showed abnormal soft tissues, while 70% demonstrated kyphosis and/or scoliosis, and an abnormal adjacent intervertebral disk space. All unstable lesions showed one or more of the following signs: displaced vertebra, widened interspinous space, abnormal apophyseal joint(s), and widened vertebral canal.
Unstable manifolds for the MacKay approximate renormalisation
NASA Astrophysics Data System (ADS)
Stark, Jaroslav
1989-01-01
For a renormalisation of a critical phenomenon in some class of dynamical systems, it is the unstable manifolds of the critical set which give the universal families which describe the critical transition. In this paper, we study such manifolds for the MacKay [1988] approximate renormalisation scheme which models the breakup of invariant circles of arbitrary rotation number in area-preserving twist maps. We derive a number of properties of the unstable manifolds and then discuss the implications of these to the full renormalisation. In particular a) we suggest the importance of continuity in the definition of unstable manifolds, and b) show that their structure is similar to that observed numerically by MacKay and Percival [1987] in a related renormalisation. Finally we show that the residues of approximating periodic orbits are bounded above on the critical set.
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.
Fundamentals in Nuclear Physics
NASA Astrophysics Data System (ADS)
Basdevant, Jean-Louis, Rich, James, Spiro, Michael
This course on nuclear physics leads the reader to the exploration of the field from nuclei to astrophysical issues. Much nuclear phenomenology can be understood from simple arguments such as those based on the Pauli principle and the Coulomb barrier. This book is concerned with extrapolating from such arguments and illustrating nuclear systematics with experimental data. Starting with the basic concepts in nuclear physics, nuclear models, and reactions, the book covers nuclear decays and the fundamental electro-weak interactions, radioactivity, and nuclear energy. After the discussions of fission and fusion leading into nuclear astrophysics, there is a presentation of the latest ideas about cosmology. As a primer this course will lay the foundations for more specialized subjects. This book emerged from a series of topical courses the authors delivered at the Ecole Polytechnique and will be useful for graduate students and for scientists in a variety of fields.
Fundamentals of battery dynamics
NASA Astrophysics Data System (ADS)
Jossen, Andreas
Modern applications, such as wireless communication systems or hybrid electric vehicles operate at high power fluctuations. For some applications, where the power frequencies are high (above some 10 or 100 Hz) it is possible to filter the high frequencies using passive components; yet this results in additional costs. In other applications, where the dynamic time constants are in the range up to some seconds, filtering cannot be done. Batteries are hence operated with the dynamic loads. But what happens under these dynamic operation conditions? This paper describes the fundamentals of the dynamic characteristics of batteries in a frequency range from some MHz down to the mHz range. As the dynamic behaviour depends on the actual state of charge (SOC) and the state of health (SOH), it is possible to gain information on the battery state by analysing the dynamic behaviour. High dynamic loads can influence the battery temperature, the battery performance and the battery lifetime.
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.
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.
Negative expansion of the myotonic dystrophy unstable sequence.
Abeliovich, D; Lerer, I; Pashut-Lavon, I; Shmueli, E; Raas-Rothschild, A; Frydman, M
1993-01-01
We have analyzed the unstable fragment of the myotonic dystrophy (DM) gene in a pregnancy at 50% risk for DM. The affected father in this family had a 3.0-kb expansion of the DM unstable region. The fetus inherited the mutated gene, but with an expansion of 0.5 kb. This case represented a counseling problem in light of the absence of data concerning "negative expansion." Analysis of the DM gene in 17 families with 72 affected individuals revealed four more cases of negative expansions, all of them in paternal transmissions. The possible significance of this finding is discussed. Images Figure 2 PMID:8503449
Error behaviour of multistep methods applied to unstable differential systems
NASA Technical Reports Server (NTRS)
Brown, R. L.
1978-01-01
The problem of modelling a dynamic system described by a system of ordinary differential equations which has unstable components for limited periods of time is discussed. It is shown that the global error in a multistep numerical method is the solution to a difference equation initial value problem, and the approximate solution is given for several popular multistep integration formulae. Inspection of the solution leads to the formulation of four criteria for integrators appropriate to unstable problems. A sample problem is solved numerically using three popular formulae and two different stepsizes to illustrate the appropriateness of the criteria.
Ultrastructural studies of unstable angina in living man
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.
Quasi-stadium laser diodes with an unstable resonator condition.
Fukushima, Takehiro; Harayama, Takahisa; Davis, Peter; Vaccaro, Pablo O; Nishimura, Takehiro; Aida, Tahito
2003-03-15
We have observed lasing in a complicated eigenmode of a quasi-stadium laser diode with an unstable resonator consisting of two curved end mirrors obeying an unstable resonator condition and two straight sidewall mirrors. The laser was fabricated by application of a reactive-ion-etching technique to a molecular beam epitaxy-grown graded-index separate-confinement heterostructure single-quantum-well GaAs/AlGaAs structure. The far-field pattern shows that the lasing mode corresponds to the complicated lowest-loss mode obtained numerically by an extended Fox-Li method. PMID:12659262
Tracking and controlling unstable steady states of dynamical systems
NASA Astrophysics Data System (ADS)
Tamaševičiūtė, Elena; Mykolaitis, Gytis; Bumelienė, Skaidra; Tamaševičius, Arūnas
2014-03-01
An adaptive controller for stabilization of unknown unstable steady states (spirals, nodes and saddles) of nonlinear dynamical systems is considered and its robustness under the changes of the location of the fixed point in the phase space is demonstrated. An analog electronic controller, based on a low-pass filter technique, is described. It can be easily switched between a stable and an unstable mode of operation for stabilizing either spirals/nodes or saddles, respectively. Numerical and experimental results for two autonomous systems, the damped Duffing-Holmes oscillator and the chaotic Lorenz system, are presented.
Ray-wave correspondence in an unstable quasistadium laser resonator
Fukushima, Takehiro; Harayama, Takahisa; Wiersig, Jan
2006-02-15
The relation between unstable periodic orbits and resonator modes in a fully chaotic open-sided two-dimensional laser resonator is theoretically investigated in the short wavelength limit. We derive a periodic-orbit-sum formula for eigenvalues of the resonator modes by applying the semiclassical approximation to the extended Fox-Li mode calculation method. With this formula, we show that the complicated wavelength dependence of the power-coupling coefficients of the fully chaotic quasi-stadium laser resonator can be explained by a few kinds of unstable periodic orbits.
Gas cell neutralizers (Fundamental principles)
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''.
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.
Fundamental Physics Explored with High Intensity Laser
NASA Astrophysics Data System (ADS)
Tajima, T.; Homma, K.
2012-10-01
Over the last century the method of particle acceleration to high energies has become the prime approach to explore the fundamental nature of matter in laboratory. It appears that the latest search of the contemporary accelerator based on the colliders shows a sign of saturation (or at least a slow-down) in increasing its energy and other necessary parameters to extend this frontier. We suggest two pronged approach enabled by the recent progress in high intensity lasers. First we envision the laser-driven plasma accelerator may be able to extend the reach of the collider. For this approach to bear fruit, we need to develop the technology of high averaged power laser in addition to the high intensity. For this we mention that the latest research effort of ICAN is an encouraging sign. In addition to this, we now introduce the concept of the noncollider paradigm in exploring fundamental physics with high intensity (and large energy) lasers. One of the examples we mention is the laser wakefield acceleration (LWFA) far beyond TeV without large luminosity. If we relax or do not require the large luminosity necessary for colliders, but solely in ultrahigh energy frontier, we are still capable of exploring such a fundamental issue. Given such a high energetic particle source and high-intensity laser fields simultaneously, we expect to be able to access new aspects on the matter and the vacuum structure from fundamental physical point of views. LWFA naturally exploits the nonlinear optical effects in the plasma when it becomes of relativistic intensity. Normally nonlinear optical effects are discussed based upon polarization susceptibility of matter to external fields. We suggest application of this concept even to the vacuum structure as a new kind of order parameter to discuss vacuum-originating phenomena at semimacroscopic scales. This viewpoint unifies the following observables with the unprecedented experimental environment we envision; the dispersion relation of
Log-Law scaling of a convective boundary layer in an unstably stratified turbulent channel flow
NASA Astrophysics Data System (ADS)
Scagliarini, Andrea; Einarsson, Halldor; Gylfason, Armann; Toschi, Federico
2014-11-01
Turbulent convection is ubiquitous in a variety of natural and industrial flows. In particular, convective motions may play a role in sheared flows. In this work, we are concerned with the interplay of buoyancy and shear in the dynamical boundary layer structure. The lattice Boltzmann Method (LBM) is applied to study numerically an unstably-stratified, fully developed, turbulent channel flow, driven by a longitudinal pressure gradient and with an imposed transverse wall temperature difference along the direction of gravity. Spanning the friction Reynolds (Retau <= 205) and Rayleigh numbers (Ra <= 1 . 3 ×107) we could systematically study the influence of the convection on the boundary layer structure and mean profiles of flow quantities in the channel. Our focus is on providing physical understanding of the deviations observed from the logarithmic law of the wall due to the buoyant motions as well as providing a model of this behavior, and link with fundamental quantities of heat transfer in the convective channel flow. Our findings show that the introduction of an unstably stratified thermal field results in an effective drag increase in the channel flow, quantified in the logarithmic region by a modified log-law, with model parameters dependent on Ra , Retau .
Fundamentals of Quantum Mechanics
NASA Astrophysics Data System (ADS)
Tang, C. L.
2005-06-01
Quantum mechanics has evolved from a subject of study in pure physics to one with a wide range of applications in many diverse fields. The basic concepts of quantum mechanics are explained in this book in a concise and easy-to-read manner emphasising applications in solid state electronics and modern optics. Following a logical sequence, the book is focused on the key ideas and is conceptually and mathematically self-contained. The fundamental principles of quantum mechanics are illustrated by showing their application to systems such as the hydrogen atom, multi-electron ions and atoms, the formation of simple organic molecules and crystalline solids of practical importance. It leads on from these basic concepts to discuss some of the most important applications in modern semiconductor electronics and optics. Containing many homework problems and worked examples, the book is suitable for senior-level undergraduate and graduate level students in electrical engineering, materials science and applied physics. Clear exposition of quantum mechanics written in a concise and accessible style Precise physical interpretation of the mathematical foundations of quantum mechanics Illustrates the important concepts and results by reference to real-world examples in electronics and optoelectronics Contains homeworks and worked examples, with solutions available for instructors
NASA Astrophysics Data System (ADS)
Petitjean, Patrick; Wang, F. Y.; Wu, X. F.; Wei, J. J.
2016-02-01
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.
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.
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.
Mirage cosmology with an unstable probe D3-brane
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.
Rayleigh-Taylor Unstable Flames -- Fast or Faster?
NASA Astrophysics Data System (ADS)
Hicks, E. P.
2015-04-01
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.
On unstable cohomology classes of SLn(Z)
Lee, Ronnie
1978-01-01
From algebraic K-theory, we show that there exists a spectral sequence that has real cohomology of SLn(Z) as its E1-terms and converges to the tensor product of a polynomial algebra and an exterior algebra. On the basis of this spectral sequence, we discovered several families of real unstable cohomology classes of SLn(Z). PMID:16592485
On unstable cohomology classes of SL(Z).
Lee, R
1978-01-01
From algebraic K-theory, we show that there exists a spectral sequence that has real cohomology of SL(n)(Z) as its E(1)-terms and converges to the tensor product of a polynomial algebra and an exterior algebra. On the basis of this spectral sequence, we discovered several families of real unstable cohomology classes of SL(n)(Z). PMID:16592485
Energy loss in unstable quark-gluon plasma
NASA Astrophysics Data System (ADS)
Carrington, Margaret E.; Deja, Katarzyna; Mrówczyński, Stanisław
2015-10-01
The momentum distribution of quark-gluon plasma at the early stage of a relativistic heavy-ion collision is anisotropic; consequently, the system, which is assumed to be weakly coupled, is unstable owing to chromomagnetic plasma modes. We consider a high-energy parton which flies across such an unstable plasma, and the energy transfer between the parton and the medium is studied as an initial value problem. In the case of equilibrium plasmas, the well-known formula of collisional energy loss is reproduced. The unstable plasma case is much more complex, and the parton can lose or gain energy depending on the initial conditions. The extremely prolate and extremely oblate systems are considered as examples of unstable plasmas, and two classes of initial conditions are discussed. When the initial chromodynamic field is uncorrelated with the color state of the parton, it typically looses energy, and the magnitude of the energy loss is comparable to that in an equilibrium plasma of the same density. When the initial chromodynamic field is induced by the parton, it can be either accelerated or decelerated depending on the relative phase factor. With a correlated initial condition, the energy transfer grows exponentially in time and its magnitude can much exceed the absolute value of energy loss in an equilibrium plasma. The energy transfer is also strongly directionally dependent. Consequences of our findings for the phenomenology of jet quenching in relativistic heavy-ion collisions are briefly discussed.
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.
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.
Fundamentals of Radiation Dosimetry
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.
A novel approach to modeling unstable EOR displacements. Final report
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.
Solar astrophysical fundamental parameters
NASA Astrophysics Data System (ADS)
Meftah, M.; Irbah, A.; Hauchecorne, A.
2014-08-01
The accurate determination of the solar photospheric radius has been an important problem in astronomy for many centuries. From the measurements made by the PICARD spacecraft during the transit of Venus in 2012, we obtained a solar radius of 696,156±145 kilometres. This value is consistent with recent measurements carried out atmosphere. This observation leads us to propose a change of the canonical value obtained by Arthur Auwers in 1891. An accurate value for total solar irradiance (TSI) is crucial for the Sun-Earth connection, and represents another solar astrophysical fundamental parameter. Based on measurements collected from different space instruments over the past 35 years, the absolute value of the TSI, representative of a quiet Sun, has gradually decreased from 1,371W.m-2 in 1978 to around 1,362W.m-2 in 2013, mainly due to the radiometers calibration differences. Based on the PICARD data and in agreement with Total Irradiance Monitor measurements, we predicted the TSI input at the top of the Earth's atmosphere at a distance of one astronomical unit (149,597,870 kilometres) from the Sun to be 1,362±2.4W.m-2, which may be proposed as a reference value. To conclude, from the measurements made by the PICARD spacecraft, we obtained a solar photospheric equator-to-pole radius difference value of 5.9±0.5 kilometres. This value is consistent with measurements made by different space instruments, and can be given as a reference value.
Exotic particles with four or more quarks
Olsen, Stephen Lars
2014-09-01
The familiar denizens of the particle zoo are made of two or three quarks, but particle theory allows for states comprising any number of those fundamental particles. Finally, after decades of searching, tetraquarks seem to have been spotted.
Fundamentals of phosphate transfer.
Kirby, Anthony J; Nome, Faruk
2015-07-21
Historically, the chemistry of phosphate transfer-a class of reactions fundamental to the chemistry of Life-has been discussed almost exclusively in terms of the nucleophile and the leaving group. Reactivity always depends significantly on both factors; but recent results for reactions of phosphate triesters have shown that it can also depend strongly on the nature of the nonleaving or "spectator" groups. The extreme stabilities of fully ionised mono- and dialkyl phosphate esters can be seen as extensions of the same effect, with one or two triester OR groups replaced by O(-). Our chosen lead reaction is hydrolysis-phosphate transfer to water: because water is the medium in which biological chemistry takes place; because the half-life of a system in water is an accepted basic index of stability; and because the typical mechanisms of hydrolysis, with solvent H2O providing specific molecules to act as nucleophiles and as general acids or bases, are models for reactions involving better nucleophiles and stronger general species catalysts. Not least those available in enzyme active sites. Alkyl monoester dianions compete with alkyl diester monoanions for the slowest estimated rates of spontaneous hydrolysis. High stability at physiological pH is a vital factor in the biological roles of organic phosphates, but a significant limitation for experimental investigations. Almost all kinetic measurements of phosphate transfer reactions involving mono- and diesters have been followed by UV-visible spectroscopy using activated systems, conveniently compounds with good leaving groups. (A "good leaving group" OR* is electron-withdrawing, and can be displaced to generate an anion R*O(-) in water near pH 7.) Reactivities at normal temperatures of P-O-alkyl derivatives-better models for typical biological substrates-have typically had to be estimated: by extended extrapolation from linear free energy relationships, or from rate measurements at high temperatures. Calculation is free